Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[linux-2.6-microblaze.git] / kernel / bpf / btf.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018 Facebook */

#include <uapi/linux/btf.h>
#include <uapi/linux/bpf.h>
#include <uapi/linux/bpf_perf_event.h>
#include <uapi/linux/types.h>
#include <linux/seq_file.h>
#include <linux/compiler.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/sort.h>
#include <linux/bpf_verifier.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
#include <linux/skmsg.h>
#include <linux/perf_event.h>
#include <linux/bsearch.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <net/sock.h>
#include "../tools/lib/bpf/relo_core.h"

/* BTF (BPF Type Format) is the meta data format which describes
 * the data types of BPF program/map.  Hence, it basically focus
 * on the C programming language which the modern BPF is primary
 * using.
 *
 * ELF Section:
 * ~~~~~~~~~~~
 * The BTF data is stored under the ".BTF" ELF section
 *
 * struct btf_type:
 * ~~~~~~~~~~~~~~~
 * Each 'struct btf_type' object describes a C data type.
 * Depending on the type it is describing, a 'struct btf_type'
 * object may be followed by more data.  F.e.
 * To describe an array, 'struct btf_type' is followed by
 * 'struct btf_array'.
 *
 * 'struct btf_type' and any extra data following it are
 * 4 bytes aligned.
 *
 * Type section:
 * ~~~~~~~~~~~~~
 * The BTF type section contains a list of 'struct btf_type' objects.
 * Each one describes a C type.  Recall from the above section
 * that a 'struct btf_type' object could be immediately followed by extra
 * data in order to describe some particular C types.
 *
 * type_id:
 * ~~~~~~~
 * Each btf_type object is identified by a type_id.  The type_id
 * is implicitly implied by the location of the btf_type object in
 * the BTF type section.  The first one has type_id 1.  The second
 * one has type_id 2...etc.  Hence, an earlier btf_type has
 * a smaller type_id.
 *
 * A btf_type object may refer to another btf_type object by using
 * type_id (i.e. the "type" in the "struct btf_type").
 *
 * NOTE that we cannot assume any reference-order.
 * A btf_type object can refer to an earlier btf_type object
 * but it can also refer to a later btf_type object.
 *
 * For example, to describe "const void *".  A btf_type
 * object describing "const" may refer to another btf_type
 * object describing "void *".  This type-reference is done
 * by specifying type_id:
 *
 * [1] CONST (anon) type_id=2
 * [2] PTR (anon) type_id=0
 *
 * The above is the btf_verifier debug log:
 *   - Each line started with "[?]" is a btf_type object
 *   - [?] is the type_id of the btf_type object.
 *   - CONST/PTR is the BTF_KIND_XXX
 *   - "(anon)" is the name of the type.  It just
 *     happens that CONST and PTR has no name.
 *   - type_id=XXX is the 'u32 type' in btf_type
 *
 * NOTE: "void" has type_id 0
 *
 * String section:
 * ~~~~~~~~~~~~~~
 * The BTF string section contains the names used by the type section.
 * Each string is referred by an "offset" from the beginning of the
 * string section.
 *
 * Each string is '\0' terminated.
 *
 * The first character in the string section must be '\0'
 * which is used to mean 'anonymous'. Some btf_type may not
 * have a name.
 */

/* BTF verification:
 *
 * To verify BTF data, two passes are needed.
 *
 * Pass #1
 * ~~~~~~~
 * The first pass is to collect all btf_type objects to
 * an array: "btf->types".
 *
 * Depending on the C type that a btf_type is describing,
 * a btf_type may be followed by extra data.  We don't know
 * how many btf_type is there, and more importantly we don't
 * know where each btf_type is located in the type section.
 *
 * Without knowing the location of each type_id, most verifications
 * cannot be done.  e.g. an earlier btf_type may refer to a later
 * btf_type (recall the "const void *" above), so we cannot
 * check this type-reference in the first pass.
 *
 * In the first pass, it still does some verifications (e.g.
 * checking the name is a valid offset to the string section).
 *
 * Pass #2
 * ~~~~~~~
 * The main focus is to resolve a btf_type that is referring
 * to another type.
 *
 * We have to ensure the referring type:
 * 1) does exist in the BTF (i.e. in btf->types[])
 * 2) does not cause a loop:
 *      struct A {
 *              struct B b;
 *      };
 *
 *      struct B {
 *              struct A a;
 *      };
 *
 * btf_type_needs_resolve() decides if a btf_type needs
 * to be resolved.
 *
 * The needs_resolve type implements the "resolve()" ops which
 * essentially does a DFS and detects backedge.
 *
 * During resolve (or DFS), different C types have different
 * "RESOLVED" conditions.
 *
 * When resolving a BTF_KIND_STRUCT, we need to resolve all its
 * members because a member is always referring to another
 * type.  A struct's member can be treated as "RESOLVED" if
 * it is referring to a BTF_KIND_PTR.  Otherwise, the
 * following valid C struct would be rejected:
 *
 *      struct A {
 *              int m;
 *              struct A *a;
 *      };
 *
 * When resolving a BTF_KIND_PTR, it needs to keep resolving if
 * it is referring to another BTF_KIND_PTR.  Otherwise, we cannot
 * detect a pointer loop, e.g.:
 * BTF_KIND_CONST -> BTF_KIND_PTR -> BTF_KIND_CONST -> BTF_KIND_PTR +
 *                        ^                                         |
 *                        +-----------------------------------------+
 *
 */

#define BITS_PER_U128 (sizeof(u64) * BITS_PER_BYTE * 2)
#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1)
#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK)
#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3)
#define BITS_ROUNDUP_BYTES(bits) \
        (BITS_ROUNDDOWN_BYTES(bits) + !!BITS_PER_BYTE_MASKED(bits))

#define BTF_INFO_MASK 0x9f00ffff
#define BTF_INT_MASK 0x0fffffff
#define BTF_TYPE_ID_VALID(type_id) ((type_id) <= BTF_MAX_TYPE)
#define BTF_STR_OFFSET_VALID(name_off) ((name_off) <= BTF_MAX_NAME_OFFSET)

/* 16MB for 64k structs and each has 16 members and
 * a few MB spaces for the string section.
 * The hard limit is S32_MAX.
 */
#define BTF_MAX_SIZE (16 * 1024 * 1024)

#define for_each_member_from(i, from, struct_type, member)              \
        for (i = from, member = btf_type_member(struct_type) + from;    \
             i < btf_type_vlen(struct_type);                            \
             i++, member++)

#define for_each_vsi_from(i, from, struct_type, member)                         \
        for (i = from, member = btf_type_var_secinfo(struct_type) + from;       \
             i < btf_type_vlen(struct_type);                                    \
             i++, member++)

DEFINE_IDR(btf_idr);
DEFINE_SPINLOCK(btf_idr_lock);

enum btf_kfunc_hook {
        BTF_KFUNC_HOOK_XDP,
        BTF_KFUNC_HOOK_TC,
        BTF_KFUNC_HOOK_STRUCT_OPS,
        BTF_KFUNC_HOOK_TRACING,
        BTF_KFUNC_HOOK_SYSCALL,
        BTF_KFUNC_HOOK_MAX,
};

enum {
        BTF_KFUNC_SET_MAX_CNT = 32,
        BTF_DTOR_KFUNC_MAX_CNT = 256,
};

struct btf_kfunc_set_tab {
        struct btf_id_set *sets[BTF_KFUNC_HOOK_MAX][BTF_KFUNC_TYPE_MAX];
};

struct btf_id_dtor_kfunc_tab {
        u32 cnt;
        struct btf_id_dtor_kfunc dtors[];
};

struct btf {
        void *data;
        struct btf_type **types;
        u32 *resolved_ids;
        u32 *resolved_sizes;
        const char *strings;
        void *nohdr_data;
        struct btf_header hdr;
        u32 nr_types; /* includes VOID for base BTF */
        u32 types_size;
        u32 data_size;
        refcount_t refcnt;
        u32 id;
        struct rcu_head rcu;
        struct btf_kfunc_set_tab *kfunc_set_tab;
        struct btf_id_dtor_kfunc_tab *dtor_kfunc_tab;

        /* split BTF support */
        struct btf *base_btf;
        u32 start_id; /* first type ID in this BTF (0 for base BTF) */
        u32 start_str_off; /* first string offset (0 for base BTF) */
        char name[MODULE_NAME_LEN];
        bool kernel_btf;
};

enum verifier_phase {
        CHECK_META,
        CHECK_TYPE,
};

struct resolve_vertex {
        const struct btf_type *t;
        u32 type_id;
        u16 next_member;
};

enum visit_state {
        NOT_VISITED,
        VISITED,
        RESOLVED,
};

enum resolve_mode {
        RESOLVE_TBD,    /* To Be Determined */
        RESOLVE_PTR,    /* Resolving for Pointer */
        RESOLVE_STRUCT_OR_ARRAY,        /* Resolving for struct/union
                                         * or array
                                         */
};

#define MAX_RESOLVE_DEPTH 32

struct btf_sec_info {
        u32 off;
        u32 len;
};

struct btf_verifier_env {
        struct btf *btf;
        u8 *visit_states;
        struct resolve_vertex stack[MAX_RESOLVE_DEPTH];
        struct bpf_verifier_log log;
        u32 log_type_id;
        u32 top_stack;
        enum verifier_phase phase;
        enum resolve_mode resolve_mode;
};

static const char * const btf_kind_str[NR_BTF_KINDS] = {
        [BTF_KIND_UNKN]         = "UNKNOWN",
        [BTF_KIND_INT]          = "INT",
        [BTF_KIND_PTR]          = "PTR",
        [BTF_KIND_ARRAY]        = "ARRAY",
        [BTF_KIND_STRUCT]       = "STRUCT",
        [BTF_KIND_UNION]        = "UNION",
        [BTF_KIND_ENUM]         = "ENUM",
        [BTF_KIND_FWD]          = "FWD",
        [BTF_KIND_TYPEDEF]      = "TYPEDEF",
        [BTF_KIND_VOLATILE]     = "VOLATILE",
        [BTF_KIND_CONST]        = "CONST",
        [BTF_KIND_RESTRICT]     = "RESTRICT",
        [BTF_KIND_FUNC]         = "FUNC",
        [BTF_KIND_FUNC_PROTO]   = "FUNC_PROTO",
        [BTF_KIND_VAR]          = "VAR",
        [BTF_KIND_DATASEC]      = "DATASEC",
        [BTF_KIND_FLOAT]        = "FLOAT",
        [BTF_KIND_DECL_TAG]     = "DECL_TAG",
        [BTF_KIND_TYPE_TAG]     = "TYPE_TAG",
};

const char *btf_type_str(const struct btf_type *t)
{
        return btf_kind_str[BTF_INFO_KIND(t->info)];
}

/* Chunk size we use in safe copy of data to be shown. */
#define BTF_SHOW_OBJ_SAFE_SIZE          32

/*
 * This is the maximum size of a base type value (equivalent to a
 * 128-bit int); if we are at the end of our safe buffer and have
 * less than 16 bytes space we can't be assured of being able
 * to copy the next type safely, so in such cases we will initiate
 * a new copy.
 */
#define BTF_SHOW_OBJ_BASE_TYPE_SIZE     16

/* Type name size */
#define BTF_SHOW_NAME_SIZE              80

/*
 * Common data to all BTF show operations. Private show functions can add
 * their own data to a structure containing a struct btf_show and consult it
 * in the show callback.  See btf_type_show() below.
 *
 * One challenge with showing nested data is we want to skip 0-valued
 * data, but in order to figure out whether a nested object is all zeros
 * we need to walk through it.  As a result, we need to make two passes
 * when handling structs, unions and arrays; the first path simply looks
 * for nonzero data, while the second actually does the display.  The first
 * pass is signalled by show->state.depth_check being set, and if we
 * encounter a non-zero value we set show->state.depth_to_show to
 * the depth at which we encountered it.  When we have completed the
 * first pass, we will know if anything needs to be displayed if
 * depth_to_show > depth.  See btf_[struct,array]_show() for the
 * implementation of this.
 *
 * Another problem is we want to ensure the data for display is safe to
 * access.  To support this, the anonymous "struct {} obj" tracks the data
 * object and our safe copy of it.  We copy portions of the data needed
 * to the object "copy" buffer, but because its size is limited to
 * BTF_SHOW_OBJ_COPY_LEN bytes, multiple copies may be required as we
 * traverse larger objects for display.
 *
 * The various data type show functions all start with a call to
 * btf_show_start_type() which returns a pointer to the safe copy
 * of the data needed (or if BTF_SHOW_UNSAFE is specified, to the
 * raw data itself).  btf_show_obj_safe() is responsible for
 * using copy_from_kernel_nofault() to update the safe data if necessary
 * as we traverse the object's data.  skbuff-like semantics are
 * used:
 *
 * - obj.head points to the start of the toplevel object for display
 * - obj.size is the size of the toplevel object
 * - obj.data points to the current point in the original data at
 *   which our safe data starts.  obj.data will advance as we copy
 *   portions of the data.
 *
 * In most cases a single copy will suffice, but larger data structures
 * such as "struct task_struct" will require many copies.  The logic in
 * btf_show_obj_safe() handles the logic that determines if a new
 * copy_from_kernel_nofault() is needed.
 */
struct btf_show {
        u64 flags;
        void *target;   /* target of show operation (seq file, buffer) */
        void (*showfn)(struct btf_show *show, const char *fmt, va_list args);
        const struct btf *btf;
        /* below are used during iteration */
        struct {
                u8 depth;
                u8 depth_to_show;
                u8 depth_check;
                u8 array_member:1,
                   array_terminated:1;
                u16 array_encoding;
                u32 type_id;
                int status;                     /* non-zero for error */
                const struct btf_type *type;
                const struct btf_member *member;
                char name[BTF_SHOW_NAME_SIZE];  /* space for member name/type */
        } state;
        struct {
                u32 size;
                void *head;
                void *data;
                u8 safe[BTF_SHOW_OBJ_SAFE_SIZE];
        } obj;
};

struct btf_kind_operations {
        s32 (*check_meta)(struct btf_verifier_env *env,
                          const struct btf_type *t,
                          u32 meta_left);
        int (*resolve)(struct btf_verifier_env *env,
                       const struct resolve_vertex *v);
        int (*check_member)(struct btf_verifier_env *env,
                            const struct btf_type *struct_type,
                            const struct btf_member *member,
                            const struct btf_type *member_type);
        int (*check_kflag_member)(struct btf_verifier_env *env,
                                  const struct btf_type *struct_type,
                                  const struct btf_member *member,
                                  const struct btf_type *member_type);
        void (*log_details)(struct btf_verifier_env *env,
                            const struct btf_type *t);
        void (*show)(const struct btf *btf, const struct btf_type *t,
                         u32 type_id, void *data, u8 bits_offsets,
                         struct btf_show *show);
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
static struct btf_type btf_void;

static int btf_resolve(struct btf_verifier_env *env,
                       const struct btf_type *t, u32 type_id);

static int btf_func_check(struct btf_verifier_env *env,
                          const struct btf_type *t);

static bool btf_type_is_modifier(const struct btf_type *t)
{
        /* Some of them is not strictly a C modifier
         * but they are grouped into the same bucket
         * for BTF concern:
         *   A type (t) that refers to another
         *   type through t->type AND its size cannot
         *   be determined without following the t->type.
         *
         * ptr does not fall into this bucket
         * because its size is always sizeof(void *).
         */
        switch (BTF_INFO_KIND(t->info)) {
        case BTF_KIND_TYPEDEF:
        case BTF_KIND_VOLATILE:
        case BTF_KIND_CONST:
        case BTF_KIND_RESTRICT:
        case BTF_KIND_TYPE_TAG:
                return true;
        }

        return false;
}

bool btf_type_is_void(const struct btf_type *t)
{
        return t == &btf_void;
}

static bool btf_type_is_fwd(const struct btf_type *t)
{
        return BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
}

static bool btf_type_nosize(const struct btf_type *t)
{
        return btf_type_is_void(t) || btf_type_is_fwd(t) ||
               btf_type_is_func(t) || btf_type_is_func_proto(t);
}

static bool btf_type_nosize_or_null(const struct btf_type *t)
{
        return !t || btf_type_nosize(t);
}

static bool __btf_type_is_struct(const struct btf_type *t)
{
        return BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT;
}

static bool btf_type_is_array(const struct btf_type *t)
{
        return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
}

static bool btf_type_is_datasec(const struct btf_type *t)
{
        return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
}

static bool btf_type_is_decl_tag(const struct btf_type *t)
{
        return BTF_INFO_KIND(t->info) == BTF_KIND_DECL_TAG;
}

static bool btf_type_is_decl_tag_target(const struct btf_type *t)
{
        return btf_type_is_func(t) || btf_type_is_struct(t) ||
               btf_type_is_var(t) || btf_type_is_typedef(t);
}

u32 btf_nr_types(const struct btf *btf)
{
        u32 total = 0;

        while (btf) {
                total += btf->nr_types;
                btf = btf->base_btf;
        }

        return total;
}

s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
{
        const struct btf_type *t;
        const char *tname;
        u32 i, total;

        total = btf_nr_types(btf);
        for (i = 1; i < total; i++) {
                t = btf_type_by_id(btf, i);
                if (BTF_INFO_KIND(t->info) != kind)
                        continue;

                tname = btf_name_by_offset(btf, t->name_off);
                if (!strcmp(tname, name))
                        return i;
        }

        return -ENOENT;
}

static s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p)
{
        struct btf *btf;
        s32 ret;
        int id;

        btf = bpf_get_btf_vmlinux();
        if (IS_ERR(btf))
                return PTR_ERR(btf);
        if (!btf)
                return -EINVAL;

        ret = btf_find_by_name_kind(btf, name, kind);
        /* ret is never zero, since btf_find_by_name_kind returns
         * positive btf_id or negative error.
         */
        if (ret > 0) {
                btf_get(btf);
                *btf_p = btf;
                return ret;
        }

        /* If name is not found in vmlinux's BTF then search in module's BTFs */
        spin_lock_bh(&btf_idr_lock);
        idr_for_each_entry(&btf_idr, btf, id) {
                if (!btf_is_module(btf))
                        continue;
                /* linear search could be slow hence unlock/lock
                 * the IDR to avoiding holding it for too long
                 */
                btf_get(btf);
                spin_unlock_bh(&btf_idr_lock);
                ret = btf_find_by_name_kind(btf, name, kind);
                if (ret > 0) {
                        *btf_p = btf;
                        return ret;
                }
                spin_lock_bh(&btf_idr_lock);
                btf_put(btf);
        }
        spin_unlock_bh(&btf_idr_lock);
        return ret;
}

const struct btf_type *btf_type_skip_modifiers(const struct btf *btf,
                                               u32 id, u32 *res_id)
{
        const struct btf_type *t = btf_type_by_id(btf, id);

        while (btf_type_is_modifier(t)) {
                id = t->type;
                t = btf_type_by_id(btf, t->type);
        }

        if (res_id)
                *res_id = id;

        return t;
}

const struct btf_type *btf_type_resolve_ptr(const struct btf *btf,
                                            u32 id, u32 *res_id)
{
        const struct btf_type *t;

        t = btf_type_skip_modifiers(btf, id, NULL);
        if (!btf_type_is_ptr(t))
                return NULL;

        return btf_type_skip_modifiers(btf, t->type, res_id);
}

const struct btf_type *btf_type_resolve_func_ptr(const struct btf *btf,
                                                 u32 id, u32 *res_id)
{
        const struct btf_type *ptype;

        ptype = btf_type_resolve_ptr(btf, id, res_id);
        if (ptype && btf_type_is_func_proto(ptype))
                return ptype;

        return NULL;
}

/* Types that act only as a source, not sink or intermediate
 * type when resolving.
 */
static bool btf_type_is_resolve_source_only(const struct btf_type *t)
{
        return btf_type_is_var(t) ||
               btf_type_is_decl_tag(t) ||
               btf_type_is_datasec(t);
}

/* What types need to be resolved?
 *
 * btf_type_is_modifier() is an obvious one.
 *
 * btf_type_is_struct() because its member refers to
 * another type (through member->type).
 *
 * btf_type_is_var() because the variable refers to
 * another type. btf_type_is_datasec() holds multiple
 * btf_type_is_var() types that need resolving.
 *
 * btf_type_is_array() because its element (array->type)
 * refers to another type.  Array can be thought of a
 * special case of struct while array just has the same
 * member-type repeated by array->nelems of times.
 */
static bool btf_type_needs_resolve(const struct btf_type *t)
{
        return btf_type_is_modifier(t) ||
               btf_type_is_ptr(t) ||
               btf_type_is_struct(t) ||
               btf_type_is_array(t) ||
               btf_type_is_var(t) ||
               btf_type_is_func(t) ||
               btf_type_is_decl_tag(t) ||
               btf_type_is_datasec(t);
}

/* t->size can be used */
static bool btf_type_has_size(const struct btf_type *t)
{
        switch (BTF_INFO_KIND(t->info)) {
        case BTF_KIND_INT:
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION:
        case BTF_KIND_ENUM:
        case BTF_KIND_DATASEC:
        case BTF_KIND_FLOAT:
                return true;
        }

        return false;
}

static const char *btf_int_encoding_str(u8 encoding)
{
        if (encoding == 0)
                return "(none)";
        else if (encoding == BTF_INT_SIGNED)
                return "SIGNED";
        else if (encoding == BTF_INT_CHAR)
                return "CHAR";
        else if (encoding == BTF_INT_BOOL)
                return "BOOL";
        else
                return "UNKN";
}

static u32 btf_type_int(const struct btf_type *t)
{
        return *(u32 *)(t + 1);
}

static const struct btf_array *btf_type_array(const struct btf_type *t)
{
        return (const struct btf_array *)(t + 1);
}

static const struct btf_enum *btf_type_enum(const struct btf_type *t)
{
        return (const struct btf_enum *)(t + 1);
}

static const struct btf_var *btf_type_var(const struct btf_type *t)
{
        return (const struct btf_var *)(t + 1);
}

static const struct btf_decl_tag *btf_type_decl_tag(const struct btf_type *t)
{
        return (const struct btf_decl_tag *)(t + 1);
}

static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
{
        return kind_ops[BTF_INFO_KIND(t->info)];
}

static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
{
        if (!BTF_STR_OFFSET_VALID(offset))
                return false;

        while (offset < btf->start_str_off)
                btf = btf->base_btf;

        offset -= btf->start_str_off;
        return offset < btf->hdr.str_len;
}

static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
{
        if ((first ? !isalpha(c) :
                     !isalnum(c)) &&
            c != '_' &&
            ((c == '.' && !dot_ok) ||
              c != '.'))
                return false;
        return true;
}

static const char *btf_str_by_offset(const struct btf *btf, u32 offset)
{
        while (offset < btf->start_str_off)
                btf = btf->base_btf;

        offset -= btf->start_str_off;
        if (offset < btf->hdr.str_len)
                return &btf->strings[offset];

        return NULL;
}

static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
{
        /* offset must be valid */
        const char *src = btf_str_by_offset(btf, offset);
        const char *src_limit;

        if (!__btf_name_char_ok(*src, true, dot_ok))
                return false;

        /* set a limit on identifier length */
        src_limit = src + KSYM_NAME_LEN;
        src++;
        while (*src && src < src_limit) {
                if (!__btf_name_char_ok(*src, false, dot_ok))
                        return false;
                src++;
        }

        return !*src;
}

/* Only C-style identifier is permitted. This can be relaxed if
 * necessary.
 */
static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
{
        return __btf_name_valid(btf, offset, false);
}

static bool btf_name_valid_section(const struct btf *btf, u32 offset)
{
        return __btf_name_valid(btf, offset, true);
}

static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
{
        const char *name;

        if (!offset)
                return "(anon)";

        name = btf_str_by_offset(btf, offset);
        return name ?: "(invalid-name-offset)";
}

const char *btf_name_by_offset(const struct btf *btf, u32 offset)
{
        return btf_str_by_offset(btf, offset);
}

const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
{
        while (type_id < btf->start_id)
                btf = btf->base_btf;

        type_id -= btf->start_id;
        if (type_id >= btf->nr_types)
                return NULL;
        return btf->types[type_id];
}

/*
 * Regular int is not a bit field and it must be either
 * u8/u16/u32/u64 or __int128.
 */
static bool btf_type_int_is_regular(const struct btf_type *t)
{
        u8 nr_bits, nr_bytes;
        u32 int_data;

        int_data = btf_type_int(t);
        nr_bits = BTF_INT_BITS(int_data);
        nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);
        if (BITS_PER_BYTE_MASKED(nr_bits) ||
            BTF_INT_OFFSET(int_data) ||
            (nr_bytes != sizeof(u8) && nr_bytes != sizeof(u16) &&
             nr_bytes != sizeof(u32) && nr_bytes != sizeof(u64) &&
             nr_bytes != (2 * sizeof(u64)))) {
                return false;
        }

        return true;
}

/*
 * Check that given struct member is a regular int with expected
 * offset and size.
 */
bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
                           const struct btf_member *m,
                           u32 expected_offset, u32 expected_size)
{
        const struct btf_type *t;
        u32 id, int_data;
        u8 nr_bits;

        id = m->type;
        t = btf_type_id_size(btf, &id, NULL);
        if (!t || !btf_type_is_int(t))
                return false;

        int_data = btf_type_int(t);
        nr_bits = BTF_INT_BITS(int_data);
        if (btf_type_kflag(s)) {
                u32 bitfield_size = BTF_MEMBER_BITFIELD_SIZE(m->offset);
                u32 bit_offset = BTF_MEMBER_BIT_OFFSET(m->offset);

                /* if kflag set, int should be a regular int and
                 * bit offset should be at byte boundary.
                 */
                return !bitfield_size &&
                       BITS_ROUNDUP_BYTES(bit_offset) == expected_offset &&
                       BITS_ROUNDUP_BYTES(nr_bits) == expected_size;
        }

        if (BTF_INT_OFFSET(int_data) ||
            BITS_PER_BYTE_MASKED(m->offset) ||
            BITS_ROUNDUP_BYTES(m->offset) != expected_offset ||
            BITS_PER_BYTE_MASKED(nr_bits) ||
            BITS_ROUNDUP_BYTES(nr_bits) != expected_size)
                return false;

        return true;
}

/* Similar to btf_type_skip_modifiers() but does not skip typedefs. */
static const struct btf_type *btf_type_skip_qualifiers(const struct btf *btf,
                                                       u32 id)
{
        const struct btf_type *t = btf_type_by_id(btf, id);

        while (btf_type_is_modifier(t) &&
               BTF_INFO_KIND(t->info) != BTF_KIND_TYPEDEF) {
                t = btf_type_by_id(btf, t->type);
        }

        return t;
}

#define BTF_SHOW_MAX_ITER       10

#define BTF_KIND_BIT(kind)      (1ULL << kind)

/*
 * Populate show->state.name with type name information.
 * Format of type name is
 *
 * [.member_name = ] (type_name)
 */
static const char *btf_show_name(struct btf_show *show)
{
        /* BTF_MAX_ITER array suffixes "[]" */
        const char *array_suffixes = "[][][][][][][][][][]";
        const char *array_suffix = &array_suffixes[strlen(array_suffixes)];
        /* BTF_MAX_ITER pointer suffixes "*" */
        const char *ptr_suffixes = "**********";
        const char *ptr_suffix = &ptr_suffixes[strlen(ptr_suffixes)];
        const char *name = NULL, *prefix = "", *parens = "";
        const struct btf_member *m = show->state.member;
        const struct btf_type *t;
        const struct btf_array *array;
        u32 id = show->state.type_id;
        const char *member = NULL;
        bool show_member = false;
        u64 kinds = 0;
        int i;

        show->state.name[0] = '\0';

        /*
         * Don't show type name if we're showing an array member;
         * in that case we show the array type so don't need to repeat
         * ourselves for each member.
         */
        if (show->state.array_member)
                return "";

        /* Retrieve member name, if any. */
        if (m) {
                member = btf_name_by_offset(show->btf, m->name_off);
                show_member = strlen(member) > 0;
                id = m->type;
        }

        /*
         * Start with type_id, as we have resolved the struct btf_type *
         * via btf_modifier_show() past the parent typedef to the child
         * struct, int etc it is defined as.  In such cases, the type_id
         * still represents the starting type while the struct btf_type *
         * in our show->state points at the resolved type of the typedef.
         */
        t = btf_type_by_id(show->btf, id);
        if (!t)
                return "";

        /*
         * The goal here is to build up the right number of pointer and
         * array suffixes while ensuring the type name for a typedef
         * is represented.  Along the way we accumulate a list of
         * BTF kinds we have encountered, since these will inform later
         * display; for example, pointer types will not require an
         * opening "{" for struct, we will just display the pointer value.
         *
         * We also want to accumulate the right number of pointer or array
         * indices in the format string while iterating until we get to
         * the typedef/pointee/array member target type.
         *
         * We start by pointing at the end of pointer and array suffix
         * strings; as we accumulate pointers and arrays we move the pointer
         * or array string backwards so it will show the expected number of
         * '*' or '[]' for the type.  BTF_SHOW_MAX_ITER of nesting of pointers
         * and/or arrays and typedefs are supported as a precaution.
         *
         * We also want to get typedef name while proceeding to resolve
         * type it points to so that we can add parentheses if it is a
         * "typedef struct" etc.
         */
        for (i = 0; i < BTF_SHOW_MAX_ITER; i++) {

                switch (BTF_INFO_KIND(t->info)) {
                case BTF_KIND_TYPEDEF:
                        if (!name)
                                name = btf_name_by_offset(show->btf,
                                                               t->name_off);
                        kinds |= BTF_KIND_BIT(BTF_KIND_TYPEDEF);
                        id = t->type;
                        break;
                case BTF_KIND_ARRAY:
                        kinds |= BTF_KIND_BIT(BTF_KIND_ARRAY);
                        parens = "[";
                        if (!t)
                                return "";
                        array = btf_type_array(t);
                        if (array_suffix > array_suffixes)
                                array_suffix -= 2;
                        id = array->type;
                        break;
                case BTF_KIND_PTR:
                        kinds |= BTF_KIND_BIT(BTF_KIND_PTR);
                        if (ptr_suffix > ptr_suffixes)
                                ptr_suffix -= 1;
                        id = t->type;
                        break;
                default:
                        id = 0;
                        break;
                }
                if (!id)
                        break;
                t = btf_type_skip_qualifiers(show->btf, id);
        }
        /* We may not be able to represent this type; bail to be safe */
        if (i == BTF_SHOW_MAX_ITER)
                return "";

        if (!name)
                name = btf_name_by_offset(show->btf, t->name_off);

        switch (BTF_INFO_KIND(t->info)) {
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION:
                prefix = BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT ?
                         "struct" : "union";
                /* if it's an array of struct/union, parens is already set */
                if (!(kinds & (BTF_KIND_BIT(BTF_KIND_ARRAY))))
                        parens = "{";
                break;
        case BTF_KIND_ENUM:
                prefix = "enum";
                break;
        default:
                break;
        }

        /* pointer does not require parens */
        if (kinds & BTF_KIND_BIT(BTF_KIND_PTR))
                parens = "";
        /* typedef does not require struct/union/enum prefix */
        if (kinds & BTF_KIND_BIT(BTF_KIND_TYPEDEF))
                prefix = "";

        if (!name)
                name = "";

        /* Even if we don't want type name info, we want parentheses etc */
        if (show->flags & BTF_SHOW_NONAME)
                snprintf(show->state.name, sizeof(show->state.name), "%s",
                         parens);
        else
                snprintf(show->state.name, sizeof(show->state.name),
                         "%s%s%s(%s%s%s%s%s%s)%s",
                         /* first 3 strings comprise ".member = " */
                         show_member ? "." : "",
                         show_member ? member : "",
                         show_member ? " = " : "",
                         /* ...next is our prefix (struct, enum, etc) */
                         prefix,
                         strlen(prefix) > 0 && strlen(name) > 0 ? " " : "",
                         /* ...this is the type name itself */
                         name,
                         /* ...suffixed by the appropriate '*', '[]' suffixes */
                         strlen(ptr_suffix) > 0 ? " " : "", ptr_suffix,
                         array_suffix, parens);

        return show->state.name;
}

static const char *__btf_show_indent(struct btf_show *show)
{
        const char *indents = "                                ";
        const char *indent = &indents[strlen(indents)];

        if ((indent - show->state.depth) >= indents)
                return indent - show->state.depth;
        return indents;
}

static const char *btf_show_indent(struct btf_show *show)
{
        return show->flags & BTF_SHOW_COMPACT ? "" : __btf_show_indent(show);
}

static const char *btf_show_newline(struct btf_show *show)
{
        return show->flags & BTF_SHOW_COMPACT ? "" : "\n";
}

static const char *btf_show_delim(struct btf_show *show)
{
        if (show->state.depth == 0)
                return "";

        if ((show->flags & BTF_SHOW_COMPACT) && show->state.type &&
                BTF_INFO_KIND(show->state.type->info) == BTF_KIND_UNION)
                return "|";

        return ",";
}

__printf(2, 3) static void btf_show(struct btf_show *show, const char *fmt, ...)
{
        va_list args;

        if (!show->state.depth_check) {
                va_start(args, fmt);
                show->showfn(show, fmt, args);
                va_end(args);
        }
}

/* Macros are used here as btf_show_type_value[s]() prepends and appends
 * format specifiers to the format specifier passed in; these do the work of
 * adding indentation, delimiters etc while the caller simply has to specify
 * the type value(s) in the format specifier + value(s).
 */
#define btf_show_type_value(show, fmt, value)                                  \
        do {                                                                   \
                if ((value) != 0 || (show->flags & BTF_SHOW_ZERO) ||           \
                    show->state.depth == 0) {                                  \
                        btf_show(show, "%s%s" fmt "%s%s",                      \
                                 btf_show_indent(show),                        \
                                 btf_show_name(show),                          \
                                 value, btf_show_delim(show),                  \
                                 btf_show_newline(show));                      \
                        if (show->state.depth > show->state.depth_to_show)     \
                                show->state.depth_to_show = show->state.depth; \
                }                                                              \
        } while (0)

#define btf_show_type_values(show, fmt, ...)                                   \
        do {                                                                   \
                btf_show(show, "%s%s" fmt "%s%s", btf_show_indent(show),       \
                         btf_show_name(show),                                  \
                         __VA_ARGS__, btf_show_delim(show),                    \
                         btf_show_newline(show));                              \
                if (show->state.depth > show->state.depth_to_show)             \
                        show->state.depth_to_show = show->state.depth;         \
        } while (0)

/* How much is left to copy to safe buffer after @data? */
static int btf_show_obj_size_left(struct btf_show *show, void *data)
{
        return show->obj.head + show->obj.size - data;
}

/* Is object pointed to by @data of @size already copied to our safe buffer? */
static bool btf_show_obj_is_safe(struct btf_show *show, void *data, int size)
{
        return data >= show->obj.data &&
               (data + size) < (show->obj.data + BTF_SHOW_OBJ_SAFE_SIZE);
}

/*
 * If object pointed to by @data of @size falls within our safe buffer, return
 * the equivalent pointer to the same safe data.  Assumes
 * copy_from_kernel_nofault() has already happened and our safe buffer is
 * populated.
 */
static void *__btf_show_obj_safe(struct btf_show *show, void *data, int size)
{
        if (btf_show_obj_is_safe(show, data, size))
                return show->obj.safe + (data - show->obj.data);
        return NULL;
}

/*
 * Return a safe-to-access version of data pointed to by @data.
 * We do this by copying the relevant amount of information
 * to the struct btf_show obj.safe buffer using copy_from_kernel_nofault().
 *
 * If BTF_SHOW_UNSAFE is specified, just return data as-is; no
 * safe copy is needed.
 *
 * Otherwise we need to determine if we have the required amount
 * of data (determined by the @data pointer and the size of the
 * largest base type we can encounter (represented by
 * BTF_SHOW_OBJ_BASE_TYPE_SIZE). Having that much data ensures
 * that we will be able to print some of the current object,
 * and if more is needed a copy will be triggered.
 * Some objects such as structs will not fit into the buffer;
 * in such cases additional copies when we iterate over their
 * members may be needed.
 *
 * btf_show_obj_safe() is used to return a safe buffer for
 * btf_show_start_type(); this ensures that as we recurse into
 * nested types we always have safe data for the given type.
 * This approach is somewhat wasteful; it's possible for example
 * that when iterating over a large union we'll end up copying the
 * same data repeatedly, but the goal is safety not performance.
 * We use stack data as opposed to per-CPU buffers because the
 * iteration over a type can take some time, and preemption handling
 * would greatly complicate use of the safe buffer.
 */
static void *btf_show_obj_safe(struct btf_show *show,
                               const struct btf_type *t,
                               void *data)
{
        const struct btf_type *rt;
        int size_left, size;
        void *safe = NULL;

        if (show->flags & BTF_SHOW_UNSAFE)
                return data;

        rt = btf_resolve_size(show->btf, t, &size);
        if (IS_ERR(rt)) {
                show->state.status = PTR_ERR(rt);
                return NULL;
        }

        /*
         * Is this toplevel object? If so, set total object size and
         * initialize pointers.  Otherwise check if we still fall within
         * our safe object data.
         */
        if (show->state.depth == 0) {
                show->obj.size = size;
                show->obj.head = data;
        } else {
                /*
                 * If the size of the current object is > our remaining
                 * safe buffer we _may_ need to do a new copy.  However
                 * consider the case of a nested struct; it's size pushes
                 * us over the safe buffer limit, but showing any individual
                 * struct members does not.  In such cases, we don't need
                 * to initiate a fresh copy yet; however we definitely need
                 * at least BTF_SHOW_OBJ_BASE_TYPE_SIZE bytes left
                 * in our buffer, regardless of the current object size.
                 * The logic here is that as we resolve types we will
                 * hit a base type at some point, and we need to be sure
                 * the next chunk of data is safely available to display
                 * that type info safely.  We cannot rely on the size of
                 * the current object here because it may be much larger
                 * than our current buffer (e.g. task_struct is 8k).
                 * All we want to do here is ensure that we can print the
                 * next basic type, which we can if either
                 * - the current type size is within the safe buffer; or
                 * - at least BTF_SHOW_OBJ_BASE_TYPE_SIZE bytes are left in
                 *   the safe buffer.
                 */
                safe = __btf_show_obj_safe(show, data,
                                           min(size,
                                               BTF_SHOW_OBJ_BASE_TYPE_SIZE));
        }

        /*
         * We need a new copy to our safe object, either because we haven't
         * yet copied and are initializing safe data, or because the data
         * we want falls outside the boundaries of the safe object.
         */
        if (!safe) {
                size_left = btf_show_obj_size_left(show, data);
                if (size_left > BTF_SHOW_OBJ_SAFE_SIZE)
                        size_left = BTF_SHOW_OBJ_SAFE_SIZE;
                show->state.status = copy_from_kernel_nofault(show->obj.safe,
                                                              data, size_left);
                if (!show->state.status) {
                        show->obj.data = data;
                        safe = show->obj.safe;
                }
        }

        return safe;
}

/*
 * Set the type we are starting to show and return a safe data pointer
 * to be used for showing the associated data.
 */
static void *btf_show_start_type(struct btf_show *show,
                                 const struct btf_type *t,
                                 u32 type_id, void *data)
{
        show->state.type = t;
        show->state.type_id = type_id;
        show->state.name[0] = '\0';

        return btf_show_obj_safe(show, t, data);
}

static void btf_show_end_type(struct btf_show *show)
{
        show->state.type = NULL;
        show->state.type_id = 0;
        show->state.name[0] = '\0';
}

static void *btf_show_start_aggr_type(struct btf_show *show,
                                      const struct btf_type *t,
                                      u32 type_id, void *data)
{
        void *safe_data = btf_show_start_type(show, t, type_id, data);

        if (!safe_data)
                return safe_data;

        btf_show(show, "%s%s%s", btf_show_indent(show),
                 btf_show_name(show),
                 btf_show_newline(show));
        show->state.depth++;
        return safe_data;
}

static void btf_show_end_aggr_type(struct btf_show *show,
                                   const char *suffix)
{
        show->state.depth--;
        btf_show(show, "%s%s%s%s", btf_show_indent(show), suffix,
                 btf_show_delim(show), btf_show_newline(show));
        btf_show_end_type(show);
}

static void btf_show_start_member(struct btf_show *show,
                                  const struct btf_member *m)
{
        show->state.member = m;
}

static void btf_show_start_array_member(struct btf_show *show)
{
        show->state.array_member = 1;
        btf_show_start_member(show, NULL);
}

static void btf_show_end_member(struct btf_show *show)
{
        show->state.member = NULL;
}

static void btf_show_end_array_member(struct btf_show *show)
{
        show->state.array_member = 0;
        btf_show_end_member(show);
}

static void *btf_show_start_array_type(struct btf_show *show,
                                       const struct btf_type *t,
                                       u32 type_id,
                                       u16 array_encoding,
                                       void *data)
{
        show->state.array_encoding = array_encoding;
        show->state.array_terminated = 0;
        return btf_show_start_aggr_type(show, t, type_id, data);
}

static void btf_show_end_array_type(struct btf_show *show)
{
        show->state.array_encoding = 0;
        show->state.array_terminated = 0;
        btf_show_end_aggr_type(show, "]");
}

static void *btf_show_start_struct_type(struct btf_show *show,
                                        const struct btf_type *t,
                                        u32 type_id,
                                        void *data)
{
        return btf_show_start_aggr_type(show, t, type_id, data);
}

static void btf_show_end_struct_type(struct btf_show *show)
{
        btf_show_end_aggr_type(show, "}");
}

__printf(2, 3) static void __btf_verifier_log(struct bpf_verifier_log *log,
                                              const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        bpf_verifier_vlog(log, fmt, args);
        va_end(args);
}

__printf(2, 3) static void btf_verifier_log(struct btf_verifier_env *env,
                                            const char *fmt, ...)
{
        struct bpf_verifier_log *log = &env->log;
        va_list args;

        if (!bpf_verifier_log_needed(log))
                return;

        va_start(args, fmt);
        bpf_verifier_vlog(log, fmt, args);
        va_end(args);
}

__printf(4, 5) static void __btf_verifier_log_type(struct btf_verifier_env *env,
                                                   const struct btf_type *t,
                                                   bool log_details,
                                                   const char *fmt, ...)
{
        struct bpf_verifier_log *log = &env->log;
        u8 kind = BTF_INFO_KIND(t->info);
        struct btf *btf = env->btf;
        va_list args;

        if (!bpf_verifier_log_needed(log))
                return;

        /* btf verifier prints all types it is processing via
         * btf_verifier_log_type(..., fmt = NULL).
         * Skip those prints for in-kernel BTF verification.
         */
        if (log->level == BPF_LOG_KERNEL && !fmt)
                return;

        __btf_verifier_log(log, "[%u] %s %s%s",
                           env->log_type_id,
                           btf_kind_str[kind],
                           __btf_name_by_offset(btf, t->name_off),
                           log_details ? " " : "");

        if (log_details)
                btf_type_ops(t)->log_details(env, t);

        if (fmt && *fmt) {
                __btf_verifier_log(log, " ");
                va_start(args, fmt);
                bpf_verifier_vlog(log, fmt, args);
                va_end(args);
        }

        __btf_verifier_log(log, "\n");
}

#define btf_verifier_log_type(env, t, ...) \
        __btf_verifier_log_type((env), (t), true, __VA_ARGS__)
#define btf_verifier_log_basic(env, t, ...) \
        __btf_verifier_log_type((env), (t), false, __VA_ARGS__)

__printf(4, 5)
static void btf_verifier_log_member(struct btf_verifier_env *env,
                                    const struct btf_type *struct_type,
                                    const struct btf_member *member,
                                    const char *fmt, ...)
{
        struct bpf_verifier_log *log = &env->log;
        struct btf *btf = env->btf;
        va_list args;

        if (!bpf_verifier_log_needed(log))
                return;

        if (log->level == BPF_LOG_KERNEL && !fmt)
                return;
        /* The CHECK_META phase already did a btf dump.
         *
         * If member is logged again, it must hit an error in
         * parsing this member.  It is useful to print out which
         * struct this member belongs to.
         */
        if (env->phase != CHECK_META)
                btf_verifier_log_type(env, struct_type, NULL);

        if (btf_type_kflag(struct_type))
                __btf_verifier_log(log,
                                   "\t%s type_id=%u bitfield_size=%u bits_offset=%u",
                                   __btf_name_by_offset(btf, member->name_off),
                                   member->type,
                                   BTF_MEMBER_BITFIELD_SIZE(member->offset),
                                   BTF_MEMBER_BIT_OFFSET(member->offset));
        else
                __btf_verifier_log(log, "\t%s type_id=%u bits_offset=%u",
                                   __btf_name_by_offset(btf, member->name_off),
                                   member->type, member->offset);

        if (fmt && *fmt) {
                __btf_verifier_log(log, " ");
                va_start(args, fmt);
                bpf_verifier_vlog(log, fmt, args);
                va_end(args);
        }

        __btf_verifier_log(log, "\n");
}

__printf(4, 5)
static void btf_verifier_log_vsi(struct btf_verifier_env *env,
                                 const struct btf_type *datasec_type,
                                 const struct btf_var_secinfo *vsi,
                                 const char *fmt, ...)
{
        struct bpf_verifier_log *log = &env->log;
        va_list args;

        if (!bpf_verifier_log_needed(log))
                return;
        if (log->level == BPF_LOG_KERNEL && !fmt)
                return;
        if (env->phase != CHECK_META)
                btf_verifier_log_type(env, datasec_type, NULL);

        __btf_verifier_log(log, "\t type_id=%u offset=%u size=%u",
                           vsi->type, vsi->offset, vsi->size);
        if (fmt && *fmt) {
                __btf_verifier_log(log, " ");
                va_start(args, fmt);
                bpf_verifier_vlog(log, fmt, args);
                va_end(args);
        }

        __btf_verifier_log(log, "\n");
}

static void btf_verifier_log_hdr(struct btf_verifier_env *env,
                                 u32 btf_data_size)
{
        struct bpf_verifier_log *log = &env->log;
        const struct btf *btf = env->btf;
        const struct btf_header *hdr;

        if (!bpf_verifier_log_needed(log))
                return;

        if (log->level == BPF_LOG_KERNEL)
                return;
        hdr = &btf->hdr;
        __btf_verifier_log(log, "magic: 0x%x\n", hdr->magic);
        __btf_verifier_log(log, "version: %u\n", hdr->version);
        __btf_verifier_log(log, "flags: 0x%x\n", hdr->flags);
        __btf_verifier_log(log, "hdr_len: %u\n", hdr->hdr_len);
        __btf_verifier_log(log, "type_off: %u\n", hdr->type_off);
        __btf_verifier_log(log, "type_len: %u\n", hdr->type_len);
        __btf_verifier_log(log, "str_off: %u\n", hdr->str_off);
        __btf_verifier_log(log, "str_len: %u\n", hdr->str_len);
        __btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);
}

static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
{
        struct btf *btf = env->btf;

        if (btf->types_size == btf->nr_types) {
                /* Expand 'types' array */

                struct btf_type **new_types;
                u32 expand_by, new_size;

                if (btf->start_id + btf->types_size == BTF_MAX_TYPE) {
                        btf_verifier_log(env, "Exceeded max num of types");
                        return -E2BIG;
                }

                expand_by = max_t(u32, btf->types_size >> 2, 16);
                new_size = min_t(u32, BTF_MAX_TYPE,
                                 btf->types_size + expand_by);

                new_types = kvcalloc(new_size, sizeof(*new_types),
                                     GFP_KERNEL | __GFP_NOWARN);
                if (!new_types)
                        return -ENOMEM;

                if (btf->nr_types == 0) {
                        if (!btf->base_btf) {
                                /* lazily init VOID type */
                                new_types[0] = &btf_void;
                                btf->nr_types++;
                        }
                } else {
                        memcpy(new_types, btf->types,
                               sizeof(*btf->types) * btf->nr_types);
                }

                kvfree(btf->types);
                btf->types = new_types;
                btf->types_size = new_size;
        }

        btf->types[btf->nr_types++] = t;

        return 0;
}

static int btf_alloc_id(struct btf *btf)
{
        int id;

        idr_preload(GFP_KERNEL);
        spin_lock_bh(&btf_idr_lock);
        id = idr_alloc_cyclic(&btf_idr, btf, 1, INT_MAX, GFP_ATOMIC);
        if (id > 0)
                btf->id = id;
        spin_unlock_bh(&btf_idr_lock);
        idr_preload_end();

        if (WARN_ON_ONCE(!id))
                return -ENOSPC;

        return id > 0 ? 0 : id;
}

static void btf_free_id(struct btf *btf)
{
        unsigned long flags;

        /*
         * In map-in-map, calling map_delete_elem() on outer
         * map will call bpf_map_put on the inner map.
         * It will then eventually call btf_free_id()
         * on the inner map.  Some of the map_delete_elem()
         * implementation may have irq disabled, so
         * we need to use the _irqsave() version instead
         * of the _bh() version.
         */
        spin_lock_irqsave(&btf_idr_lock, flags);
        idr_remove(&btf_idr, btf->id);
        spin_unlock_irqrestore(&btf_idr_lock, flags);
}

static void btf_free_kfunc_set_tab(struct btf *btf)
{
        struct btf_kfunc_set_tab *tab = btf->kfunc_set_tab;
        int hook, type;

        if (!tab)
                return;
        /* For module BTF, we directly assign the sets being registered, so
         * there is nothing to free except kfunc_set_tab.
         */
        if (btf_is_module(btf))
                goto free_tab;
        for (hook = 0; hook < ARRAY_SIZE(tab->sets); hook++) {
                for (type = 0; type < ARRAY_SIZE(tab->sets[0]); type++)
                        kfree(tab->sets[hook][type]);
        }
free_tab:
        kfree(tab);
        btf->kfunc_set_tab = NULL;
}

static void btf_free_dtor_kfunc_tab(struct btf *btf)
{
        struct btf_id_dtor_kfunc_tab *tab = btf->dtor_kfunc_tab;

        if (!tab)
                return;
        kfree(tab);
        btf->dtor_kfunc_tab = NULL;
}

static void btf_free(struct btf *btf)
{
        btf_free_dtor_kfunc_tab(btf);
        btf_free_kfunc_set_tab(btf);
        kvfree(btf->types);
        kvfree(btf->resolved_sizes);
        kvfree(btf->resolved_ids);
        kvfree(btf->data);
        kfree(btf);
}

static void btf_free_rcu(struct rcu_head *rcu)
{
        struct btf *btf = container_of(rcu, struct btf, rcu);

        btf_free(btf);
}

void btf_get(struct btf *btf)
{
        refcount_inc(&btf->refcnt);
}

void btf_put(struct btf *btf)
{
        if (btf && refcount_dec_and_test(&btf->refcnt)) {
                btf_free_id(btf);
                call_rcu(&btf->rcu, btf_free_rcu);
        }
}

static int env_resolve_init(struct btf_verifier_env *env)
{
        struct btf *btf = env->btf;
        u32 nr_types = btf->nr_types;
        u32 *resolved_sizes = NULL;
        u32 *resolved_ids = NULL;
        u8 *visit_states = NULL;

        resolved_sizes = kvcalloc(nr_types, sizeof(*resolved_sizes),
                                  GFP_KERNEL | __GFP_NOWARN);
        if (!resolved_sizes)
                goto nomem;

        resolved_ids = kvcalloc(nr_types, sizeof(*resolved_ids),
                                GFP_KERNEL | __GFP_NOWARN);
        if (!resolved_ids)
                goto nomem;

        visit_states = kvcalloc(nr_types, sizeof(*visit_states),
                                GFP_KERNEL | __GFP_NOWARN);
        if (!visit_states)
                goto nomem;

        btf->resolved_sizes = resolved_sizes;
        btf->resolved_ids = resolved_ids;
        env->visit_states = visit_states;

        return 0;

nomem:
        kvfree(resolved_sizes);
        kvfree(resolved_ids);
        kvfree(visit_states);
        return -ENOMEM;
}

static void btf_verifier_env_free(struct btf_verifier_env *env)
{
        kvfree(env->visit_states);
        kfree(env);
}

static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
                                     const struct btf_type *next_type)
{
        switch (env->resolve_mode) {
        case RESOLVE_TBD:
                /* int, enum or void is a sink */
                return !btf_type_needs_resolve(next_type);
        case RESOLVE_PTR:
                /* int, enum, void, struct, array, func or func_proto is a sink
                 * for ptr
                 */
                return !btf_type_is_modifier(next_type) &&
                        !btf_type_is_ptr(next_type);
        case RESOLVE_STRUCT_OR_ARRAY:
                /* int, enum, void, ptr, func or func_proto is a sink
                 * for struct and array
                 */
                return !btf_type_is_modifier(next_type) &&
                        !btf_type_is_array(next_type) &&
                        !btf_type_is_struct(next_type);
        default:
                BUG();
        }
}

static bool env_type_is_resolved(const struct btf_verifier_env *env,
                                 u32 type_id)
{
        /* base BTF types should be resolved by now */
        if (type_id < env->btf->start_id)
                return true;

        return env->visit_states[type_id - env->btf->start_id] == RESOLVED;
}

static int env_stack_push(struct btf_verifier_env *env,
                          const struct btf_type *t, u32 type_id)
{
        const struct btf *btf = env->btf;
        struct resolve_vertex *v;

        if (env->top_stack == MAX_RESOLVE_DEPTH)
                return -E2BIG;

        if (type_id < btf->start_id
            || env->visit_states[type_id - btf->start_id] != NOT_VISITED)
                return -EEXIST;

        env->visit_states[type_id - btf->start_id] = VISITED;

        v = &env->stack[env->top_stack++];
        v->t = t;
        v->type_id = type_id;
        v->next_member = 0;

        if (env->resolve_mode == RESOLVE_TBD) {
                if (btf_type_is_ptr(t))
                        env->resolve_mode = RESOLVE_PTR;
                else if (btf_type_is_struct(t) || btf_type_is_array(t))
                        env->resolve_mode = RESOLVE_STRUCT_OR_ARRAY;
        }

        return 0;
}

static void env_stack_set_next_member(struct btf_verifier_env *env,
                                      u16 next_member)
{
        env->stack[env->top_stack - 1].next_member = next_member;
}

static void env_stack_pop_resolved(struct btf_verifier_env *env,
                                   u32 resolved_type_id,
                                   u32 resolved_size)
{
        u32 type_id = env->stack[--(env->top_stack)].type_id;
        struct btf *btf = env->btf;

        type_id -= btf->start_id; /* adjust to local type id */
        btf->resolved_sizes[type_id] = resolved_size;
        btf->resolved_ids[type_id] = resolved_type_id;
        env->visit_states[type_id] = RESOLVED;
}

static const struct resolve_vertex *env_stack_peak(struct btf_verifier_env *env)
{
        return env->top_stack ? &env->stack[env->top_stack - 1] : NULL;
}

/* Resolve the size of a passed-in "type"
 *
 * type: is an array (e.g. u32 array[x][y])
 * return type: type "u32[x][y]", i.e. BTF_KIND_ARRAY,
 * *type_size: (x * y * sizeof(u32)).  Hence, *type_size always
 *             corresponds to the return type.
 * *elem_type: u32
 * *elem_id: id of u32
 * *total_nelems: (x * y).  Hence, individual elem size is
 *                (*type_size / *total_nelems)
 * *type_id: id of type if it's changed within the function, 0 if not
 *
 * type: is not an array (e.g. const struct X)
 * return type: type "struct X"
 * *type_size: sizeof(struct X)
 * *elem_type: same as return type ("struct X")
 * *elem_id: 0
 * *total_nelems: 1
 * *type_id: id of type if it's changed within the function, 0 if not
 */
static const struct btf_type *
__btf_resolve_size(const struct btf *btf, const struct btf_type *type,
                   u32 *type_size, const struct btf_type **elem_type,
                   u32 *elem_id, u32 *total_nelems, u32 *type_id)
{
        const struct btf_type *array_type = NULL;
        const struct btf_array *array = NULL;
        u32 i, size, nelems = 1, id = 0;

        for (i = 0; i < MAX_RESOLVE_DEPTH; i++) {
                switch (BTF_INFO_KIND(type->info)) {
                /* type->size can be used */
                case BTF_KIND_INT:
                case BTF_KIND_STRUCT:
                case BTF_KIND_UNION:
                case BTF_KIND_ENUM:
                case BTF_KIND_FLOAT:
                        size = type->size;
                        goto resolved;

                case BTF_KIND_PTR:
                        size = sizeof(void *);
                        goto resolved;

                /* Modifiers */
                case BTF_KIND_TYPEDEF:
                case BTF_KIND_VOLATILE:
                case BTF_KIND_CONST:
                case BTF_KIND_RESTRICT:
                case BTF_KIND_TYPE_TAG:
                        id = type->type;
                        type = btf_type_by_id(btf, type->type);
                        break;

                case BTF_KIND_ARRAY:
                        if (!array_type)
                                array_type = type;
                        array = btf_type_array(type);
                        if (nelems && array->nelems > U32_MAX / nelems)
                                return ERR_PTR(-EINVAL);
                        nelems *= array->nelems;
                        type = btf_type_by_id(btf, array->type);
                        break;

                /* type without size */
                default:
                        return ERR_PTR(-EINVAL);
                }
        }

        return ERR_PTR(-EINVAL);

resolved:
        if (nelems && size > U32_MAX / nelems)
                return ERR_PTR(-EINVAL);

        *type_size = nelems * size;
        if (total_nelems)
                *total_nelems = nelems;
        if (elem_type)
                *elem_type = type;
        if (elem_id)
                *elem_id = array ? array->type : 0;
        if (type_id && id)
                *type_id = id;

        return array_type ? : type;
}

const struct btf_type *
btf_resolve_size(const struct btf *btf, const struct btf_type *type,
                 u32 *type_size)
{
        return __btf_resolve_size(btf, type, type_size, NULL, NULL, NULL, NULL);
}

static u32 btf_resolved_type_id(const struct btf *btf, u32 type_id)
{
        while (type_id < btf->start_id)
                btf = btf->base_btf;

        return btf->resolved_ids[type_id - btf->start_id];
}

/* The input param "type_id" must point to a needs_resolve type */
static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
                                                  u32 *type_id)
{
        *type_id = btf_resolved_type_id(btf, *type_id);
        return btf_type_by_id(btf, *type_id);
}

static u32 btf_resolved_type_size(const struct btf *btf, u32 type_id)
{
        while (type_id < btf->start_id)
                btf = btf->base_btf;

        return btf->resolved_sizes[type_id - btf->start_id];
}

const struct btf_type *btf_type_id_size(const struct btf *btf,
                                        u32 *type_id, u32 *ret_size)
{
        const struct btf_type *size_type;
        u32 size_type_id = *type_id;
        u32 size = 0;

        size_type = btf_type_by_id(btf, size_type_id);
        if (btf_type_nosize_or_null(size_type))
                return NULL;

        if (btf_type_has_size(size_type)) {
                size = size_type->size;
        } else if (btf_type_is_array(size_type)) {
                size = btf_resolved_type_size(btf, size_type_id);
        } else if (btf_type_is_ptr(size_type)) {
                size = sizeof(void *);
        } else {
                if (WARN_ON_ONCE(!btf_type_is_modifier(size_type) &&
                                 !btf_type_is_var(size_type)))
                        return NULL;

                size_type_id = btf_resolved_type_id(btf, size_type_id);
                size_type = btf_type_by_id(btf, size_type_id);
                if (btf_type_nosize_or_null(size_type))
                        return NULL;
                else if (btf_type_has_size(size_type))
                        size = size_type->size;
                else if (btf_type_is_array(size_type))
                        size = btf_resolved_type_size(btf, size_type_id);
                else if (btf_type_is_ptr(size_type))
                        size = sizeof(void *);
                else
                        return NULL;
        }

        *type_id = size_type_id;
        if (ret_size)
                *ret_size = size;

        return size_type;
}

static int btf_df_check_member(struct btf_verifier_env *env,
                               const struct btf_type *struct_type,
                               const struct btf_member *member,
                               const struct btf_type *member_type)
{
        btf_verifier_log_basic(env, struct_type,
                               "Unsupported check_member");
        return -EINVAL;
}

static int btf_df_check_kflag_member(struct btf_verifier_env *env,
                                     const struct btf_type *struct_type,
                                     const struct btf_member *member,
                                     const struct btf_type *member_type)
{
        btf_verifier_log_basic(env, struct_type,
                               "Unsupported check_kflag_member");
        return -EINVAL;
}

/* Used for ptr, array struct/union and float type members.
 * int, enum and modifier types have their specific callback functions.
 */
static int btf_generic_check_kflag_member(struct btf_verifier_env *env,
                                          const struct btf_type *struct_type,
                                          const struct btf_member *member,
                                          const struct btf_type *member_type)
{
        if (BTF_MEMBER_BITFIELD_SIZE(member->offset)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member bitfield_size");
                return -EINVAL;
        }

        /* bitfield size is 0, so member->offset represents bit offset only.
         * It is safe to call non kflag check_member variants.
         */
        return btf_type_ops(member_type)->check_member(env, struct_type,
                                                       member,
                                                       member_type);
}

static int btf_df_resolve(struct btf_verifier_env *env,
                          const struct resolve_vertex *v)
{
        btf_verifier_log_basic(env, v->t, "Unsupported resolve");
        return -EINVAL;
}

static void btf_df_show(const struct btf *btf, const struct btf_type *t,
                        u32 type_id, void *data, u8 bits_offsets,
                        struct btf_show *show)
{
        btf_show(show, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
}

static int btf_int_check_member(struct btf_verifier_env *env,
                                const struct btf_type *struct_type,
                                const struct btf_member *member,
                                const struct btf_type *member_type)
{
        u32 int_data = btf_type_int(member_type);
        u32 struct_bits_off = member->offset;
        u32 struct_size = struct_type->size;
        u32 nr_copy_bits;
        u32 bytes_offset;

        if (U32_MAX - struct_bits_off < BTF_INT_OFFSET(int_data)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "bits_offset exceeds U32_MAX");
                return -EINVAL;
        }

        struct_bits_off += BTF_INT_OFFSET(int_data);
        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
        nr_copy_bits = BTF_INT_BITS(int_data) +
                BITS_PER_BYTE_MASKED(struct_bits_off);

        if (nr_copy_bits > BITS_PER_U128) {
                btf_verifier_log_member(env, struct_type, member,
                                        "nr_copy_bits exceeds 128");
                return -EINVAL;
        }

        if (struct_size < bytes_offset ||
            struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static int btf_int_check_kflag_member(struct btf_verifier_env *env,
                                      const struct btf_type *struct_type,
                                      const struct btf_member *member,
                                      const struct btf_type *member_type)
{
        u32 struct_bits_off, nr_bits, nr_int_data_bits, bytes_offset;
        u32 int_data = btf_type_int(member_type);
        u32 struct_size = struct_type->size;
        u32 nr_copy_bits;

        /* a regular int type is required for the kflag int member */
        if (!btf_type_int_is_regular(member_type)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member base type");
                return -EINVAL;
        }

        /* check sanity of bitfield size */
        nr_bits = BTF_MEMBER_BITFIELD_SIZE(member->offset);
        struct_bits_off = BTF_MEMBER_BIT_OFFSET(member->offset);
        nr_int_data_bits = BTF_INT_BITS(int_data);
        if (!nr_bits) {
                /* Not a bitfield member, member offset must be at byte
                 * boundary.
                 */
                if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                        btf_verifier_log_member(env, struct_type, member,
                                                "Invalid member offset");
                        return -EINVAL;
                }

                nr_bits = nr_int_data_bits;
        } else if (nr_bits > nr_int_data_bits) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member bitfield_size");
                return -EINVAL;
        }

        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
        nr_copy_bits = nr_bits + BITS_PER_BYTE_MASKED(struct_bits_off);
        if (nr_copy_bits > BITS_PER_U128) {
                btf_verifier_log_member(env, struct_type, member,
                                        "nr_copy_bits exceeds 128");
                return -EINVAL;
        }

        if (struct_size < bytes_offset ||
            struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static s32 btf_int_check_meta(struct btf_verifier_env *env,
                              const struct btf_type *t,
                              u32 meta_left)
{
        u32 int_data, nr_bits, meta_needed = sizeof(int_data);
        u16 encoding;

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        int_data = btf_type_int(t);
        if (int_data & ~BTF_INT_MASK) {
                btf_verifier_log_basic(env, t, "Invalid int_data:%x",
                                       int_data);
                return -EINVAL;
        }

        nr_bits = BTF_INT_BITS(int_data) + BTF_INT_OFFSET(int_data);

        if (nr_bits > BITS_PER_U128) {
                btf_verifier_log_type(env, t, "nr_bits exceeds %zu",
                                      BITS_PER_U128);
                return -EINVAL;
        }

        if (BITS_ROUNDUP_BYTES(nr_bits) > t->size) {
                btf_verifier_log_type(env, t, "nr_bits exceeds type_size");
                return -EINVAL;
        }

        /*
         * Only one of the encoding bits is allowed and it
         * should be sufficient for the pretty print purpose (i.e. decoding).
         * Multiple bits can be allowed later if it is found
         * to be insufficient.
         */
        encoding = BTF_INT_ENCODING(int_data);
        if (encoding &&
            encoding != BTF_INT_SIGNED &&
            encoding != BTF_INT_CHAR &&
            encoding != BTF_INT_BOOL) {
                btf_verifier_log_type(env, t, "Unsupported encoding");
                return -ENOTSUPP;
        }

        btf_verifier_log_type(env, t, NULL);

        return meta_needed;
}

static void btf_int_log(struct btf_verifier_env *env,
                        const struct btf_type *t)
{
        int int_data = btf_type_int(t);

        btf_verifier_log(env,
                         "size=%u bits_offset=%u nr_bits=%u encoding=%s",
                         t->size, BTF_INT_OFFSET(int_data),
                         BTF_INT_BITS(int_data),
                         btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}

static void btf_int128_print(struct btf_show *show, void *data)
{
        /* data points to a __int128 number.
         * Suppose
         *     int128_num = *(__int128 *)data;
         * The below formulas shows what upper_num and lower_num represents:
         *     upper_num = int128_num >> 64;
         *     lower_num = int128_num & 0xffffffffFFFFFFFFULL;
         */
        u64 upper_num, lower_num;

#ifdef __BIG_ENDIAN_BITFIELD
        upper_num = *(u64 *)data;
        lower_num = *(u64 *)(data + 8);
#else
        upper_num = *(u64 *)(data + 8);
        lower_num = *(u64 *)data;
#endif
        if (upper_num == 0)
                btf_show_type_value(show, "0x%llx", lower_num);
        else
                btf_show_type_values(show, "0x%llx%016llx", upper_num,
                                     lower_num);
}

static void btf_int128_shift(u64 *print_num, u16 left_shift_bits,
                             u16 right_shift_bits)
{
        u64 upper_num, lower_num;

#ifdef __BIG_ENDIAN_BITFIELD
        upper_num = print_num[0];
        lower_num = print_num[1];
#else
        upper_num = print_num[1];
        lower_num = print_num[0];
#endif

        /* shake out un-needed bits by shift/or operations */
        if (left_shift_bits >= 64) {
                upper_num = lower_num << (left_shift_bits - 64);
                lower_num = 0;
        } else {
                upper_num = (upper_num << left_shift_bits) |
                            (lower_num >> (64 - left_shift_bits));
                lower_num = lower_num << left_shift_bits;
        }

        if (right_shift_bits >= 64) {
                lower_num = upper_num >> (right_shift_bits - 64);
                upper_num = 0;
        } else {
                lower_num = (lower_num >> right_shift_bits) |
                            (upper_num << (64 - right_shift_bits));
                upper_num = upper_num >> right_shift_bits;
        }

#ifdef __BIG_ENDIAN_BITFIELD
        print_num[0] = upper_num;
        print_num[1] = lower_num;
#else
        print_num[0] = lower_num;
        print_num[1] = upper_num;
#endif
}

static void btf_bitfield_show(void *data, u8 bits_offset,
                              u8 nr_bits, struct btf_show *show)
{
        u16 left_shift_bits, right_shift_bits;
        u8 nr_copy_bytes;
        u8 nr_copy_bits;
        u64 print_num[2] = {};

        nr_copy_bits = nr_bits + bits_offset;
        nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);

        memcpy(print_num, data, nr_copy_bytes);

#ifdef __BIG_ENDIAN_BITFIELD
        left_shift_bits = bits_offset;
#else
        left_shift_bits = BITS_PER_U128 - nr_copy_bits;
#endif
        right_shift_bits = BITS_PER_U128 - nr_bits;

        btf_int128_shift(print_num, left_shift_bits, right_shift_bits);
        btf_int128_print(show, print_num);
}


static void btf_int_bits_show(const struct btf *btf,
                              const struct btf_type *t,
                              void *data, u8 bits_offset,
                              struct btf_show *show)
{
        u32 int_data = btf_type_int(t);
        u8 nr_bits = BTF_INT_BITS(int_data);
        u8 total_bits_offset;

        /*
         * bits_offset is at most 7.
         * BTF_INT_OFFSET() cannot exceed 128 bits.
         */
        total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
        data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
        bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
        btf_bitfield_show(data, bits_offset, nr_bits, show);
}

static void btf_int_show(const struct btf *btf, const struct btf_type *t,
                         u32 type_id, void *data, u8 bits_offset,
                         struct btf_show *show)
{
        u32 int_data = btf_type_int(t);
        u8 encoding = BTF_INT_ENCODING(int_data);
        bool sign = encoding & BTF_INT_SIGNED;
        u8 nr_bits = BTF_INT_BITS(int_data);
        void *safe_data;

        safe_data = btf_show_start_type(show, t, type_id, data);
        if (!safe_data)
                return;

        if (bits_offset || BTF_INT_OFFSET(int_data) ||
            BITS_PER_BYTE_MASKED(nr_bits)) {
                btf_int_bits_show(btf, t, safe_data, bits_offset, show);
                goto out;
        }

        switch (nr_bits) {
        case 128:
                btf_int128_print(show, safe_data);
                break;
        case 64:
                if (sign)
                        btf_show_type_value(show, "%lld", *(s64 *)safe_data);
                else
                        btf_show_type_value(show, "%llu", *(u64 *)safe_data);
                break;
        case 32:
                if (sign)
                        btf_show_type_value(show, "%d", *(s32 *)safe_data);
                else
                        btf_show_type_value(show, "%u", *(u32 *)safe_data);
                break;
        case 16:
                if (sign)
                        btf_show_type_value(show, "%d", *(s16 *)safe_data);
                else
                        btf_show_type_value(show, "%u", *(u16 *)safe_data);
                break;
        case 8:
                if (show->state.array_encoding == BTF_INT_CHAR) {
                        /* check for null terminator */
                        if (show->state.array_terminated)
                                break;
                        if (*(char *)data == '\0') {
                                show->state.array_terminated = 1;
                                break;
                        }
                        if (isprint(*(char *)data)) {
                                btf_show_type_value(show, "'%c'",
                                                    *(char *)safe_data);
                                break;
                        }
                }
                if (sign)
                        btf_show_type_value(show, "%d", *(s8 *)safe_data);
                else
                        btf_show_type_value(show, "%u", *(u8 *)safe_data);
                break;
        default:
                btf_int_bits_show(btf, t, safe_data, bits_offset, show);
                break;
        }
out:
        btf_show_end_type(show);
}

static const struct btf_kind_operations int_ops = {
        .check_meta = btf_int_check_meta,
        .resolve = btf_df_resolve,
        .check_member = btf_int_check_member,
        .check_kflag_member = btf_int_check_kflag_member,
        .log_details = btf_int_log,
        .show = btf_int_show,
};

static int btf_modifier_check_member(struct btf_verifier_env *env,
                                     const struct btf_type *struct_type,
                                     const struct btf_member *member,
                                     const struct btf_type *member_type)
{
        const struct btf_type *resolved_type;
        u32 resolved_type_id = member->type;
        struct btf_member resolved_member;
        struct btf *btf = env->btf;

        resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
        if (!resolved_type) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member");
                return -EINVAL;
        }

        resolved_member = *member;
        resolved_member.type = resolved_type_id;

        return btf_type_ops(resolved_type)->check_member(env, struct_type,
                                                         &resolved_member,
                                                         resolved_type);
}

static int btf_modifier_check_kflag_member(struct btf_verifier_env *env,
                                           const struct btf_type *struct_type,
                                           const struct btf_member *member,
                                           const struct btf_type *member_type)
{
        const struct btf_type *resolved_type;
        u32 resolved_type_id = member->type;
        struct btf_member resolved_member;
        struct btf *btf = env->btf;

        resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
        if (!resolved_type) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member");
                return -EINVAL;
        }

        resolved_member = *member;
        resolved_member.type = resolved_type_id;

        return btf_type_ops(resolved_type)->check_kflag_member(env, struct_type,
                                                               &resolved_member,
                                                               resolved_type);
}

static int btf_ptr_check_member(struct btf_verifier_env *env,
                                const struct btf_type *struct_type,
                                const struct btf_member *member,
                                const struct btf_type *member_type)
{
        u32 struct_size, struct_bits_off, bytes_offset;

        struct_size = struct_type->size;
        struct_bits_off = member->offset;
        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);

        if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member is not byte aligned");
                return -EINVAL;
        }

        if (struct_size - bytes_offset < sizeof(void *)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static int btf_ref_type_check_meta(struct btf_verifier_env *env,
                                   const struct btf_type *t,
                                   u32 meta_left)
{
        const char *value;

        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (!BTF_TYPE_ID_VALID(t->type)) {
                btf_verifier_log_type(env, t, "Invalid type_id");
                return -EINVAL;
        }

        /* typedef/type_tag type must have a valid name, and other ref types,
         * volatile, const, restrict, should have a null name.
         */
        if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF) {
                if (!t->name_off ||
                    !btf_name_valid_identifier(env->btf, t->name_off)) {
                        btf_verifier_log_type(env, t, "Invalid name");
                        return -EINVAL;
                }
        } else if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPE_TAG) {
                value = btf_name_by_offset(env->btf, t->name_off);
                if (!value || !value[0]) {
                        btf_verifier_log_type(env, t, "Invalid name");
                        return -EINVAL;
                }
        } else {
                if (t->name_off) {
                        btf_verifier_log_type(env, t, "Invalid name");
                        return -EINVAL;
                }
        }

        btf_verifier_log_type(env, t, NULL);

        return 0;
}

static int btf_modifier_resolve(struct btf_verifier_env *env,
                                const struct resolve_vertex *v)
{
        const struct btf_type *t = v->t;
        const struct btf_type *next_type;
        u32 next_type_id = t->type;
        struct btf *btf = env->btf;

        next_type = btf_type_by_id(btf, next_type_id);
        if (!next_type || btf_type_is_resolve_source_only(next_type)) {
                btf_verifier_log_type(env, v->t, "Invalid type_id");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, next_type) &&
            !env_type_is_resolved(env, next_type_id))
                return env_stack_push(env, next_type, next_type_id);

        /* Figure out the resolved next_type_id with size.
         * They will be stored in the current modifier's
         * resolved_ids and resolved_sizes such that it can
         * save us a few type-following when we use it later (e.g. in
         * pretty print).
         */
        if (!btf_type_id_size(btf, &next_type_id, NULL)) {
                if (env_type_is_resolved(env, next_type_id))
                        next_type = btf_type_id_resolve(btf, &next_type_id);

                /* "typedef void new_void", "const void"...etc */
                if (!btf_type_is_void(next_type) &&
                    !btf_type_is_fwd(next_type) &&
                    !btf_type_is_func_proto(next_type)) {
                        btf_verifier_log_type(env, v->t, "Invalid type_id");
                        return -EINVAL;
                }
        }

        env_stack_pop_resolved(env, next_type_id, 0);

        return 0;
}

static int btf_var_resolve(struct btf_verifier_env *env,
                           const struct resolve_vertex *v)
{
        const struct btf_type *next_type;
        const struct btf_type *t = v->t;
        u32 next_type_id = t->type;
        struct btf *btf = env->btf;

        next_type = btf_type_by_id(btf, next_type_id);
        if (!next_type || btf_type_is_resolve_source_only(next_type)) {
                btf_verifier_log_type(env, v->t, "Invalid type_id");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, next_type) &&
            !env_type_is_resolved(env, next_type_id))
                return env_stack_push(env, next_type, next_type_id);

        if (btf_type_is_modifier(next_type)) {
                const struct btf_type *resolved_type;
                u32 resolved_type_id;

                resolved_type_id = next_type_id;
                resolved_type = btf_type_id_resolve(btf, &resolved_type_id);

                if (btf_type_is_ptr(resolved_type) &&
                    !env_type_is_resolve_sink(env, resolved_type) &&
                    !env_type_is_resolved(env, resolved_type_id))
                        return env_stack_push(env, resolved_type,
                                              resolved_type_id);
        }

        /* We must resolve to something concrete at this point, no
         * forward types or similar that would resolve to size of
         * zero is allowed.
         */
        if (!btf_type_id_size(btf, &next_type_id, NULL)) {
                btf_verifier_log_type(env, v->t, "Invalid type_id");
                return -EINVAL;
        }

        env_stack_pop_resolved(env, next_type_id, 0);

        return 0;
}

static int btf_ptr_resolve(struct btf_verifier_env *env,
                           const struct resolve_vertex *v)
{
        const struct btf_type *next_type;
        const struct btf_type *t = v->t;
        u32 next_type_id = t->type;
        struct btf *btf = env->btf;

        next_type = btf_type_by_id(btf, next_type_id);
        if (!next_type || btf_type_is_resolve_source_only(next_type)) {
                btf_verifier_log_type(env, v->t, "Invalid type_id");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, next_type) &&
            !env_type_is_resolved(env, next_type_id))
                return env_stack_push(env, next_type, next_type_id);

        /* If the modifier was RESOLVED during RESOLVE_STRUCT_OR_ARRAY,
         * the modifier may have stopped resolving when it was resolved
         * to a ptr (last-resolved-ptr).
         *
         * We now need to continue from the last-resolved-ptr to
         * ensure the last-resolved-ptr will not referring back to
         * the current ptr (t).
         */
        if (btf_type_is_modifier(next_type)) {
                const struct btf_type *resolved_type;
                u32 resolved_type_id;

                resolved_type_id = next_type_id;
                resolved_type = btf_type_id_resolve(btf, &resolved_type_id);

                if (btf_type_is_ptr(resolved_type) &&
                    !env_type_is_resolve_sink(env, resolved_type) &&
                    !env_type_is_resolved(env, resolved_type_id))
                        return env_stack_push(env, resolved_type,
                                              resolved_type_id);
        }

        if (!btf_type_id_size(btf, &next_type_id, NULL)) {
                if (env_type_is_resolved(env, next_type_id))
                        next_type = btf_type_id_resolve(btf, &next_type_id);

                if (!btf_type_is_void(next_type) &&
                    !btf_type_is_fwd(next_type) &&
                    !btf_type_is_func_proto(next_type)) {
                        btf_verifier_log_type(env, v->t, "Invalid type_id");
                        return -EINVAL;
                }
        }

        env_stack_pop_resolved(env, next_type_id, 0);

        return 0;
}

static void btf_modifier_show(const struct btf *btf,
                              const struct btf_type *t,
                              u32 type_id, void *data,
                              u8 bits_offset, struct btf_show *show)
{
        if (btf->resolved_ids)
                t = btf_type_id_resolve(btf, &type_id);
        else
                t = btf_type_skip_modifiers(btf, type_id, NULL);

        btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show);
}

static void btf_var_show(const struct btf *btf, const struct btf_type *t,
                         u32 type_id, void *data, u8 bits_offset,
                         struct btf_show *show)
{
        t = btf_type_id_resolve(btf, &type_id);

        btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show);
}

static void btf_ptr_show(const struct btf *btf, const struct btf_type *t,
                         u32 type_id, void *data, u8 bits_offset,
                         struct btf_show *show)
{
        void *safe_data;

        safe_data = btf_show_start_type(show, t, type_id, data);
        if (!safe_data)
                return;

        /* It is a hashed value unless BTF_SHOW_PTR_RAW is specified */
        if (show->flags & BTF_SHOW_PTR_RAW)
                btf_show_type_value(show, "0x%px", *(void **)safe_data);
        else
                btf_show_type_value(show, "0x%p", *(void **)safe_data);
        btf_show_end_type(show);
}

static void btf_ref_type_log(struct btf_verifier_env *env,
                             const struct btf_type *t)
{
        btf_verifier_log(env, "type_id=%u", t->type);
}

static struct btf_kind_operations modifier_ops = {
        .check_meta = btf_ref_type_check_meta,
        .resolve = btf_modifier_resolve,
        .check_member = btf_modifier_check_member,
        .check_kflag_member = btf_modifier_check_kflag_member,
        .log_details = btf_ref_type_log,
        .show = btf_modifier_show,
};

static struct btf_kind_operations ptr_ops = {
        .check_meta = btf_ref_type_check_meta,
        .resolve = btf_ptr_resolve,
        .check_member = btf_ptr_check_member,
        .check_kflag_member = btf_generic_check_kflag_member,
        .log_details = btf_ref_type_log,
        .show = btf_ptr_show,
};

static s32 btf_fwd_check_meta(struct btf_verifier_env *env,
                              const struct btf_type *t,
                              u32 meta_left)
{
        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (t->type) {
                btf_verifier_log_type(env, t, "type != 0");
                return -EINVAL;
        }

        /* fwd type must have a valid name */
        if (!t->name_off ||
            !btf_name_valid_identifier(env->btf, t->name_off)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return 0;
}

static void btf_fwd_type_log(struct btf_verifier_env *env,
                             const struct btf_type *t)
{
        btf_verifier_log(env, "%s", btf_type_kflag(t) ? "union" : "struct");
}

static struct btf_kind_operations fwd_ops = {
        .check_meta = btf_fwd_check_meta,
        .resolve = btf_df_resolve,
        .check_member = btf_df_check_member,
        .check_kflag_member = btf_df_check_kflag_member,
        .log_details = btf_fwd_type_log,
        .show = btf_df_show,
};

static int btf_array_check_member(struct btf_verifier_env *env,
                                  const struct btf_type *struct_type,
                                  const struct btf_member *member,
                                  const struct btf_type *member_type)
{
        u32 struct_bits_off = member->offset;
        u32 struct_size, bytes_offset;
        u32 array_type_id, array_size;
        struct btf *btf = env->btf;

        if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member is not byte aligned");
                return -EINVAL;
        }

        array_type_id = member->type;
        btf_type_id_size(btf, &array_type_id, &array_size);
        struct_size = struct_type->size;
        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
        if (struct_size - bytes_offset < array_size) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static s32 btf_array_check_meta(struct btf_verifier_env *env,
                                const struct btf_type *t,
                                u32 meta_left)
{
        const struct btf_array *array = btf_type_array(t);
        u32 meta_needed = sizeof(*array);

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        /* array type should not have a name */
        if (t->name_off) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (t->size) {
                btf_verifier_log_type(env, t, "size != 0");
                return -EINVAL;
        }

        /* Array elem type and index type cannot be in type void,
         * so !array->type and !array->index_type are not allowed.
         */
        if (!array->type || !BTF_TYPE_ID_VALID(array->type)) {
                btf_verifier_log_type(env, t, "Invalid elem");
                return -EINVAL;
        }

        if (!array->index_type || !BTF_TYPE_ID_VALID(array->index_type)) {
                btf_verifier_log_type(env, t, "Invalid index");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return meta_needed;
}

static int btf_array_resolve(struct btf_verifier_env *env,
                             const struct resolve_vertex *v)
{
        const struct btf_array *array = btf_type_array(v->t);
        const struct btf_type *elem_type, *index_type;
        u32 elem_type_id, index_type_id;
        struct btf *btf = env->btf;
        u32 elem_size;

        /* Check array->index_type */
        index_type_id = array->index_type;
        index_type = btf_type_by_id(btf, index_type_id);
        if (btf_type_nosize_or_null(index_type) ||
            btf_type_is_resolve_source_only(index_type)) {
                btf_verifier_log_type(env, v->t, "Invalid index");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, index_type) &&
            !env_type_is_resolved(env, index_type_id))
                return env_stack_push(env, index_type, index_type_id);

        index_type = btf_type_id_size(btf, &index_type_id, NULL);
        if (!index_type || !btf_type_is_int(index_type) ||
            !btf_type_int_is_regular(index_type)) {
                btf_verifier_log_type(env, v->t, "Invalid index");
                return -EINVAL;
        }

        /* Check array->type */
        elem_type_id = array->type;
        elem_type = btf_type_by_id(btf, elem_type_id);
        if (btf_type_nosize_or_null(elem_type) ||
            btf_type_is_resolve_source_only(elem_type)) {
                btf_verifier_log_type(env, v->t,
                                      "Invalid elem");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, elem_type) &&
            !env_type_is_resolved(env, elem_type_id))
                return env_stack_push(env, elem_type, elem_type_id);

        elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
        if (!elem_type) {
                btf_verifier_log_type(env, v->t, "Invalid elem");
                return -EINVAL;
        }

        if (btf_type_is_int(elem_type) && !btf_type_int_is_regular(elem_type)) {
                btf_verifier_log_type(env, v->t, "Invalid array of int");
                return -EINVAL;
        }

        if (array->nelems && elem_size > U32_MAX / array->nelems) {
                btf_verifier_log_type(env, v->t,
                                      "Array size overflows U32_MAX");
                return -EINVAL;
        }

        env_stack_pop_resolved(env, elem_type_id, elem_size * array->nelems);

        return 0;
}

static void btf_array_log(struct btf_verifier_env *env,
                          const struct btf_type *t)
{
        const struct btf_array *array = btf_type_array(t);

        btf_verifier_log(env, "type_id=%u index_type_id=%u nr_elems=%u",
                         array->type, array->index_type, array->nelems);
}

static void __btf_array_show(const struct btf *btf, const struct btf_type *t,
                             u32 type_id, void *data, u8 bits_offset,
                             struct btf_show *show)
{
        const struct btf_array *array = btf_type_array(t);
        const struct btf_kind_operations *elem_ops;
        const struct btf_type *elem_type;
        u32 i, elem_size = 0, elem_type_id;
        u16 encoding = 0;

        elem_type_id = array->type;
        elem_type = btf_type_skip_modifiers(btf, elem_type_id, NULL);
        if (elem_type && btf_type_has_size(elem_type))
                elem_size = elem_type->size;

        if (elem_type && btf_type_is_int(elem_type)) {
                u32 int_type = btf_type_int(elem_type);

                encoding = BTF_INT_ENCODING(int_type);

                /*
                 * BTF_INT_CHAR encoding never seems to be set for
                 * char arrays, so if size is 1 and element is
                 * printable as a char, we'll do that.
                 */
                if (elem_size == 1)
                        encoding = BTF_INT_CHAR;
        }

        if (!btf_show_start_array_type(show, t, type_id, encoding, data))
                return;

        if (!elem_type)
                goto out;
        elem_ops = btf_type_ops(elem_type);

        for (i = 0; i < array->nelems; i++) {

                btf_show_start_array_member(show);

                elem_ops->show(btf, elem_type, elem_type_id, data,
                               bits_offset, show);
                data += elem_size;

                btf_show_end_array_member(show);

                if (show->state.array_terminated)
                        break;
        }
out:
        btf_show_end_array_type(show);
}

static void btf_array_show(const struct btf *btf, const struct btf_type *t,
                           u32 type_id, void *data, u8 bits_offset,
                           struct btf_show *show)
{
        const struct btf_member *m = show->state.member;

        /*
         * First check if any members would be shown (are non-zero).
         * See comments above "struct btf_show" definition for more
         * details on how this works at a high-level.
         */
        if (show->state.depth > 0 && !(show->flags & BTF_SHOW_ZERO)) {
                if (!show->state.depth_check) {
                        show->state.depth_check = show->state.depth + 1;
                        show->state.depth_to_show = 0;
                }
                __btf_array_show(btf, t, type_id, data, bits_offset, show);
                show->state.member = m;

                if (show->state.depth_check != show->state.depth + 1)
                        return;
                show->state.depth_check = 0;

                if (show->state.depth_to_show <= show->state.depth)
                        return;
                /*
                 * Reaching here indicates we have recursed and found
                 * non-zero array member(s).
                 */
        }
        __btf_array_show(btf, t, type_id, data, bits_offset, show);
}

static struct btf_kind_operations array_ops = {
        .check_meta = btf_array_check_meta,
        .resolve = btf_array_resolve,
        .check_member = btf_array_check_member,
        .check_kflag_member = btf_generic_check_kflag_member,
        .log_details = btf_array_log,
        .show = btf_array_show,
};

static int btf_struct_check_member(struct btf_verifier_env *env,
                                   const struct btf_type *struct_type,
                                   const struct btf_member *member,
                                   const struct btf_type *member_type)
{
        u32 struct_bits_off = member->offset;
        u32 struct_size, bytes_offset;

        if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member is not byte aligned");
                return -EINVAL;
        }

        struct_size = struct_type->size;
        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
        if (struct_size - bytes_offset < member_type->size) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static s32 btf_struct_check_meta(struct btf_verifier_env *env,
                                 const struct btf_type *t,
                                 u32 meta_left)
{
        bool is_union = BTF_INFO_KIND(t->info) == BTF_KIND_UNION;
        const struct btf_member *member;
        u32 meta_needed, last_offset;
        struct btf *btf = env->btf;
        u32 struct_size = t->size;
        u32 offset;
        u16 i;

        meta_needed = btf_type_vlen(t) * sizeof(*member);
        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        /* struct type either no name or a valid one */
        if (t->name_off &&
            !btf_name_valid_identifier(env->btf, t->name_off)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        last_offset = 0;
        for_each_member(i, t, member) {
                if (!btf_name_offset_valid(btf, member->name_off)) {
                        btf_verifier_log_member(env, t, member,
                                                "Invalid member name_offset:%u",
                                                member->name_off);
                        return -EINVAL;
                }

                /* struct member either no name or a valid one */
                if (member->name_off &&
                    !btf_name_valid_identifier(btf, member->name_off)) {
                        btf_verifier_log_member(env, t, member, "Invalid name");
                        return -EINVAL;
                }
                /* A member cannot be in type void */
                if (!member->type || !BTF_TYPE_ID_VALID(member->type)) {
                        btf_verifier_log_member(env, t, member,
                                                "Invalid type_id");
                        return -EINVAL;
                }

                offset = __btf_member_bit_offset(t, member);
                if (is_union && offset) {
                        btf_verifier_log_member(env, t, member,
                                                "Invalid member bits_offset");
                        return -EINVAL;
                }

                /*
                 * ">" instead of ">=" because the last member could be
                 * "char a[0];"
                 */
                if (last_offset > offset) {
                        btf_verifier_log_member(env, t, member,
                                                "Invalid member bits_offset");
                        return -EINVAL;
                }

                if (BITS_ROUNDUP_BYTES(offset) > struct_size) {
                        btf_verifier_log_member(env, t, member,
                                                "Member bits_offset exceeds its struct size");
                        return -EINVAL;
                }

                btf_verifier_log_member(env, t, member, NULL);
                last_offset = offset;
        }

        return meta_needed;
}

static int btf_struct_resolve(struct btf_verifier_env *env,
                              const struct resolve_vertex *v)
{
        const struct btf_member *member;
        int err;
        u16 i;

        /* Before continue resolving the next_member,
         * ensure the last member is indeed resolved to a
         * type with size info.
         */
        if (v->next_member) {
                const struct btf_type *last_member_type;
                const struct btf_member *last_member;
                u16 last_member_type_id;

                last_member = btf_type_member(v->t) + v->next_member - 1;
                last_member_type_id = last_member->type;
                if (WARN_ON_ONCE(!env_type_is_resolved(env,
                                                       last_member_type_id)))
                        return -EINVAL;

                last_member_type = btf_type_by_id(env->btf,
                                                  last_member_type_id);
                if (btf_type_kflag(v->t))
                        err = btf_type_ops(last_member_type)->check_kflag_member(env, v->t,
                                                                last_member,
                                                                last_member_type);
                else
                        err = btf_type_ops(last_member_type)->check_member(env, v->t,
                                                                last_member,
                                                                last_member_type);
                if (err)
                        return err;
        }

        for_each_member_from(i, v->next_member, v->t, member) {
                u32 member_type_id = member->type;
                const struct btf_type *member_type = btf_type_by_id(env->btf,
                                                                member_type_id);

                if (btf_type_nosize_or_null(member_type) ||
                    btf_type_is_resolve_source_only(member_type)) {
                        btf_verifier_log_member(env, v->t, member,
                                                "Invalid member");
                        return -EINVAL;
                }

                if (!env_type_is_resolve_sink(env, member_type) &&
                    !env_type_is_resolved(env, member_type_id)) {
                        env_stack_set_next_member(env, i + 1);
                        return env_stack_push(env, member_type, member_type_id);
                }

                if (btf_type_kflag(v->t))
                        err = btf_type_ops(member_type)->check_kflag_member(env, v->t,
                                                                            member,
                                                                            member_type);
                else
                        err = btf_type_ops(member_type)->check_member(env, v->t,
                                                                      member,
                                                                      member_type);
                if (err)
                        return err;
        }

        env_stack_pop_resolved(env, 0, 0);

        return 0;
}

static void btf_struct_log(struct btf_verifier_env *env,
                           const struct btf_type *t)
{
        btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

enum btf_field_type {
        BTF_FIELD_SPIN_LOCK,
        BTF_FIELD_TIMER,
        BTF_FIELD_KPTR,
};

enum {
        BTF_FIELD_IGNORE = 0,
        BTF_FIELD_FOUND  = 1,
};

struct btf_field_info {
        u32 type_id;
        u32 off;
        enum bpf_kptr_type type;
};

static int btf_find_struct(const struct btf *btf, const struct btf_type *t,
                           u32 off, int sz, struct btf_field_info *info)
{
        if (!__btf_type_is_struct(t))
                return BTF_FIELD_IGNORE;
        if (t->size != sz)
                return BTF_FIELD_IGNORE;
        info->off = off;
        return BTF_FIELD_FOUND;
}

static int btf_find_kptr(const struct btf *btf, const struct btf_type *t,
                         u32 off, int sz, struct btf_field_info *info)
{
        enum bpf_kptr_type type;
        u32 res_id;

        /* For PTR, sz is always == 8 */
        if (!btf_type_is_ptr(t))
                return BTF_FIELD_IGNORE;
        t = btf_type_by_id(btf, t->type);

        if (!btf_type_is_type_tag(t))
                return BTF_FIELD_IGNORE;
        /* Reject extra tags */
        if (btf_type_is_type_tag(btf_type_by_id(btf, t->type)))
                return -EINVAL;
        if (!strcmp("kptr", __btf_name_by_offset(btf, t->name_off)))
                type = BPF_KPTR_UNREF;
        else if (!strcmp("kptr_ref", __btf_name_by_offset(btf, t->name_off)))
                type = BPF_KPTR_REF;
        else
                return -EINVAL;

        /* Get the base type */
        t = btf_type_skip_modifiers(btf, t->type, &res_id);
        /* Only pointer to struct is allowed */
        if (!__btf_type_is_struct(t))
                return -EINVAL;

        info->type_id = res_id;
        info->off = off;
        info->type = type;
        return BTF_FIELD_FOUND;
}

static int btf_find_struct_field(const struct btf *btf, const struct btf_type *t,
                                 const char *name, int sz, int align,
                                 enum btf_field_type field_type,
                                 struct btf_field_info *info, int info_cnt)
{
        const struct btf_member *member;
        struct btf_field_info tmp;
        int ret, idx = 0;
        u32 i, off;

        for_each_member(i, t, member) {
                const struct btf_type *member_type = btf_type_by_id(btf,
                                                                    member->type);

                if (name && strcmp(__btf_name_by_offset(btf, member_type->name_off), name))
                        continue;

                off = __btf_member_bit_offset(t, member);
                if (off % 8)
                        /* valid C code cannot generate such BTF */
                        return -EINVAL;
                off /= 8;
                if (off % align)
                        return -EINVAL;

                switch (field_type) {
                case BTF_FIELD_SPIN_LOCK:
                case BTF_FIELD_TIMER:
                        ret = btf_find_struct(btf, member_type, off, sz,
                                              idx < info_cnt ? &info[idx] : &tmp);
                        if (ret < 0)
                                return ret;
                        break;
                case BTF_FIELD_KPTR:
                        ret = btf_find_kptr(btf, member_type, off, sz,
                                            idx < info_cnt ? &info[idx] : &tmp);
                        if (ret < 0)
                                return ret;
                        break;
                default:
                        return -EFAULT;
                }

                if (ret == BTF_FIELD_IGNORE)
                        continue;
                if (idx >= info_cnt)
                        return -E2BIG;
                ++idx;
        }
        return idx;
}

static int btf_find_datasec_var(const struct btf *btf, const struct btf_type *t,
                                const char *name, int sz, int align,
                                enum btf_field_type field_type,
                                struct btf_field_info *info, int info_cnt)
{
        const struct btf_var_secinfo *vsi;
        struct btf_field_info tmp;
        int ret, idx = 0;
        u32 i, off;

        for_each_vsi(i, t, vsi) {
                const struct btf_type *var = btf_type_by_id(btf, vsi->type);
                const struct btf_type *var_type = btf_type_by_id(btf, var->type);

                off = vsi->offset;

                if (name && strcmp(__btf_name_by_offset(btf, var_type->name_off), name))
                        continue;
                if (vsi->size != sz)
                        continue;
                if (off % align)
                        return -EINVAL;

                switch (field_type) {
                case BTF_FIELD_SPIN_LOCK:
                case BTF_FIELD_TIMER:
                        ret = btf_find_struct(btf, var_type, off, sz,
                                              idx < info_cnt ? &info[idx] : &tmp);
                        if (ret < 0)
                                return ret;
                        break;
                case BTF_FIELD_KPTR:
                        ret = btf_find_kptr(btf, var_type, off, sz,
                                            idx < info_cnt ? &info[idx] : &tmp);
                        if (ret < 0)
                                return ret;
                        break;
                default:
                        return -EFAULT;
                }

                if (ret == BTF_FIELD_IGNORE)
                        continue;
                if (idx >= info_cnt)
                        return -E2BIG;
                ++idx;
        }
        return idx;
}

static int btf_find_field(const struct btf *btf, const struct btf_type *t,
                          enum btf_field_type field_type,
                          struct btf_field_info *info, int info_cnt)
{
        const char *name;
        int sz, align;

        switch (field_type) {
        case BTF_FIELD_SPIN_LOCK:
                name = "bpf_spin_lock";
                sz = sizeof(struct bpf_spin_lock);
                align = __alignof__(struct bpf_spin_lock);
                break;
        case BTF_FIELD_TIMER:
                name = "bpf_timer";
                sz = sizeof(struct bpf_timer);
                align = __alignof__(struct bpf_timer);
                break;
        case BTF_FIELD_KPTR:
                name = NULL;
                sz = sizeof(u64);
                align = 8;
                break;
        default:
                return -EFAULT;
        }

        if (__btf_type_is_struct(t))
                return btf_find_struct_field(btf, t, name, sz, align, field_type, info, info_cnt);
        else if (btf_type_is_datasec(t))
                return btf_find_datasec_var(btf, t, name, sz, align, field_type, info, info_cnt);
        return -EINVAL;
}

/* find 'struct bpf_spin_lock' in map value.
 * return >= 0 offset if found
 * and < 0 in case of error
 */
int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
{
        struct btf_field_info info;
        int ret;

        ret = btf_find_field(btf, t, BTF_FIELD_SPIN_LOCK, &info, 1);
        if (ret < 0)
                return ret;
        if (!ret)
                return -ENOENT;
        return info.off;
}

int btf_find_timer(const struct btf *btf, const struct btf_type *t)
{
        struct btf_field_info info;
        int ret;

        ret = btf_find_field(btf, t, BTF_FIELD_TIMER, &info, 1);
        if (ret < 0)
                return ret;
        if (!ret)
                return -ENOENT;
        return info.off;
}

struct bpf_map_value_off *btf_parse_kptrs(const struct btf *btf,
                                          const struct btf_type *t)
{
        struct btf_field_info info_arr[BPF_MAP_VALUE_OFF_MAX];
        struct bpf_map_value_off *tab;
        struct btf *kernel_btf = NULL;
        struct module *mod = NULL;
        int ret, i, nr_off;

        ret = btf_find_field(btf, t, BTF_FIELD_KPTR, info_arr, ARRAY_SIZE(info_arr));
        if (ret < 0)
                return ERR_PTR(ret);
        if (!ret)
                return NULL;

        nr_off = ret;
        tab = kzalloc(offsetof(struct bpf_map_value_off, off[nr_off]), GFP_KERNEL | __GFP_NOWARN);
        if (!tab)
                return ERR_PTR(-ENOMEM);

        for (i = 0; i < nr_off; i++) {
                const struct btf_type *t;
                s32 id;

                /* Find type in map BTF, and use it to look up the matching type
                 * in vmlinux or module BTFs, by name and kind.
                 */
                t = btf_type_by_id(btf, info_arr[i].type_id);
                id = bpf_find_btf_id(__btf_name_by_offset(btf, t->name_off), BTF_INFO_KIND(t->info),
                                     &kernel_btf);
                if (id < 0) {
                        ret = id;
                        goto end;
                }

                /* Find and stash the function pointer for the destruction function that
                 * needs to be eventually invoked from the map free path.
                 */
                if (info_arr[i].type == BPF_KPTR_REF) {
                        const struct btf_type *dtor_func;
                        const char *dtor_func_name;
                        unsigned long addr;
                        s32 dtor_btf_id;

                        /* This call also serves as a whitelist of allowed objects that
                         * can be used as a referenced pointer and be stored in a map at
                         * the same time.
                         */
                        dtor_btf_id = btf_find_dtor_kfunc(kernel_btf, id);
                        if (dtor_btf_id < 0) {
                                ret = dtor_btf_id;
                                goto end_btf;
                        }

                        dtor_func = btf_type_by_id(kernel_btf, dtor_btf_id);
                        if (!dtor_func) {
                                ret = -ENOENT;
                                goto end_btf;
                        }

                        if (btf_is_module(kernel_btf)) {
                                mod = btf_try_get_module(kernel_btf);
                                if (!mod) {
                                        ret = -ENXIO;
                                        goto end_btf;
                                }
                        }

                        /* We already verified dtor_func to be btf_type_is_func
                         * in register_btf_id_dtor_kfuncs.
                         */
                        dtor_func_name = __btf_name_by_offset(kernel_btf, dtor_func->name_off);
                        addr = kallsyms_lookup_name(dtor_func_name);
                        if (!addr) {
                                ret = -EINVAL;
                                goto end_mod;
                        }
                        tab->off[i].kptr.dtor = (void *)addr;
                }

                tab->off[i].offset = info_arr[i].off;
                tab->off[i].type = info_arr[i].type;
                tab->off[i].kptr.btf_id = id;
                tab->off[i].kptr.btf = kernel_btf;
                tab->off[i].kptr.module = mod;
        }
        tab->nr_off = nr_off;
        return tab;
end_mod:
        module_put(mod);
end_btf:
        btf_put(kernel_btf);
end:
        while (i--) {
                btf_put(tab->off[i].kptr.btf);
                if (tab->off[i].kptr.module)
                        module_put(tab->off[i].kptr.module);
        }
        kfree(tab);
        return ERR_PTR(ret);
}

static void __btf_struct_show(const struct btf *btf, const struct btf_type *t,
                              u32 type_id, void *data, u8 bits_offset,
                              struct btf_show *show)
{
        const struct btf_member *member;
        void *safe_data;
        u32 i;

        safe_data = btf_show_start_struct_type(show, t, type_id, data);
        if (!safe_data)
                return;

        for_each_member(i, t, member) {
                const struct btf_type *member_type = btf_type_by_id(btf,
                                                                member->type);
                const struct btf_kind_operations *ops;
                u32 member_offset, bitfield_size;
                u32 bytes_offset;
                u8 bits8_offset;

                btf_show_start_member(show, member);

                member_offset = __btf_member_bit_offset(t, member);
                bitfield_size = __btf_member_bitfield_size(t, member);
                bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
                bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
                if (bitfield_size) {
                        safe_data = btf_show_start_type(show, member_type,
                                                        member->type,
                                                        data + bytes_offset);
                        if (safe_data)
                                btf_bitfield_show(safe_data,
                                                  bits8_offset,
                                                  bitfield_size, show);
                        btf_show_end_type(show);
                } else {
                        ops = btf_type_ops(member_type);
                        ops->show(btf, member_type, member->type,
                                  data + bytes_offset, bits8_offset, show);
                }

                btf_show_end_member(show);
        }

        btf_show_end_struct_type(show);
}

static void btf_struct_show(const struct btf *btf, const struct btf_type *t,
                            u32 type_id, void *data, u8 bits_offset,
                            struct btf_show *show)
{
        const struct btf_member *m = show->state.member;

        /*
         * First check if any members would be shown (are non-zero).
         * See comments above "struct btf_show" definition for more
         * details on how this works at a high-level.
         */
        if (show->state.depth > 0 && !(show->flags & BTF_SHOW_ZERO)) {
                if (!show->state.depth_check) {
                        show->state.depth_check = show->state.depth + 1;
                        show->state.depth_to_show = 0;
                }
                __btf_struct_show(btf, t, type_id, data, bits_offset, show);
                /* Restore saved member data here */
                show->state.member = m;
                if (show->state.depth_check != show->state.depth + 1)
                        return;
                show->state.depth_check = 0;

                if (show->state.depth_to_show <= show->state.depth)
                        return;
                /*
                 * Reaching here indicates we have recursed and found
                 * non-zero child values.
                 */
        }

        __btf_struct_show(btf, t, type_id, data, bits_offset, show);
}

static struct btf_kind_operations struct_ops = {
        .check_meta = btf_struct_check_meta,
        .resolve = btf_struct_resolve,
        .check_member = btf_struct_check_member,
        .check_kflag_member = btf_generic_check_kflag_member,
        .log_details = btf_struct_log,
        .show = btf_struct_show,
};

static int btf_enum_check_member(struct btf_verifier_env *env,
                                 const struct btf_type *struct_type,
                                 const struct btf_member *member,
                                 const struct btf_type *member_type)
{
        u32 struct_bits_off = member->offset;
        u32 struct_size, bytes_offset;

        if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member is not byte aligned");
                return -EINVAL;
        }

        struct_size = struct_type->size;
        bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
        if (struct_size - bytes_offset < member_type->size) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static int btf_enum_check_kflag_member(struct btf_verifier_env *env,
                                       const struct btf_type *struct_type,
                                       const struct btf_member *member,
                                       const struct btf_type *member_type)
{
        u32 struct_bits_off, nr_bits, bytes_end, struct_size;
        u32 int_bitsize = sizeof(int) * BITS_PER_BYTE;

        struct_bits_off = BTF_MEMBER_BIT_OFFSET(member->offset);
        nr_bits = BTF_MEMBER_BITFIELD_SIZE(member->offset);
        if (!nr_bits) {
                if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
                        btf_verifier_log_member(env, struct_type, member,
                                                "Member is not byte aligned");
                        return -EINVAL;
                }

                nr_bits = int_bitsize;
        } else if (nr_bits > int_bitsize) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Invalid member bitfield_size");
                return -EINVAL;
        }

        struct_size = struct_type->size;
        bytes_end = BITS_ROUNDUP_BYTES(struct_bits_off + nr_bits);
        if (struct_size < bytes_end) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static s32 btf_enum_check_meta(struct btf_verifier_env *env,
                               const struct btf_type *t,
                               u32 meta_left)
{
        const struct btf_enum *enums = btf_type_enum(t);
        struct btf *btf = env->btf;
        u16 i, nr_enums;
        u32 meta_needed;

        nr_enums = btf_type_vlen(t);
        meta_needed = nr_enums * sizeof(*enums);

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (t->size > 8 || !is_power_of_2(t->size)) {
                btf_verifier_log_type(env, t, "Unexpected size");
                return -EINVAL;
        }

        /* enum type either no name or a valid one */
        if (t->name_off &&
            !btf_name_valid_identifier(env->btf, t->name_off)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        for (i = 0; i < nr_enums; i++) {
                if (!btf_name_offset_valid(btf, enums[i].name_off)) {
                        btf_verifier_log(env, "\tInvalid name_offset:%u",
                                         enums[i].name_off);
                        return -EINVAL;
                }

                /* enum member must have a valid name */
                if (!enums[i].name_off ||
                    !btf_name_valid_identifier(btf, enums[i].name_off)) {
                        btf_verifier_log_type(env, t, "Invalid name");
                        return -EINVAL;
                }

                if (env->log.level == BPF_LOG_KERNEL)
                        continue;
                btf_verifier_log(env, "\t%s val=%d\n",
                                 __btf_name_by_offset(btf, enums[i].name_off),
                                 enums[i].val);
        }

        return meta_needed;
}

static void btf_enum_log(struct btf_verifier_env *env,
                         const struct btf_type *t)
{
        btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_enum_show(const struct btf *btf, const struct btf_type *t,
                          u32 type_id, void *data, u8 bits_offset,
                          struct btf_show *show)
{
        const struct btf_enum *enums = btf_type_enum(t);
        u32 i, nr_enums = btf_type_vlen(t);
        void *safe_data;
        int v;

        safe_data = btf_show_start_type(show, t, type_id, data);
        if (!safe_data)
                return;

        v = *(int *)safe_data;

        for (i = 0; i < nr_enums; i++) {
                if (v != enums[i].val)
                        continue;

                btf_show_type_value(show, "%s",
                                    __btf_name_by_offset(btf,
                                                         enums[i].name_off));

                btf_show_end_type(show);
                return;
        }

        btf_show_type_value(show, "%d", v);
        btf_show_end_type(show);
}

static struct btf_kind_operations enum_ops = {
        .check_meta = btf_enum_check_meta,
        .resolve = btf_df_resolve,
        .check_member = btf_enum_check_member,
        .check_kflag_member = btf_enum_check_kflag_member,
        .log_details = btf_enum_log,
        .show = btf_enum_show,
};

static s32 btf_func_proto_check_meta(struct btf_verifier_env *env,
                                     const struct btf_type *t,
                                     u32 meta_left)
{
        u32 meta_needed = btf_type_vlen(t) * sizeof(struct btf_param);

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        if (t->name_off) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return meta_needed;
}

static void btf_func_proto_log(struct btf_verifier_env *env,
                               const struct btf_type *t)
{
        const struct btf_param *args = (const struct btf_param *)(t + 1);
        u16 nr_args = btf_type_vlen(t), i;

        btf_verifier_log(env, "return=%u args=(", t->type);
        if (!nr_args) {
                btf_verifier_log(env, "void");
                goto done;
        }

        if (nr_args == 1 && !args[0].type) {
                /* Only one vararg */
                btf_verifier_log(env, "vararg");
                goto done;
        }

        btf_verifier_log(env, "%u %s", args[0].type,
                         __btf_name_by_offset(env->btf,
                                              args[0].name_off));
        for (i = 1; i < nr_args - 1; i++)
                btf_verifier_log(env, ", %u %s", args[i].type,
                                 __btf_name_by_offset(env->btf,
                                                      args[i].name_off));

        if (nr_args > 1) {
                const struct btf_param *last_arg = &args[nr_args - 1];

                if (last_arg->type)
                        btf_verifier_log(env, ", %u %s", last_arg->type,
                                         __btf_name_by_offset(env->btf,
                                                              last_arg->name_off));
                else
                        btf_verifier_log(env, ", vararg");
        }

done:
        btf_verifier_log(env, ")");
}

static struct btf_kind_operations func_proto_ops = {
        .check_meta = btf_func_proto_check_meta,
        .resolve = btf_df_resolve,
        /*
         * BTF_KIND_FUNC_PROTO cannot be directly referred by
         * a struct's member.
         *
         * It should be a function pointer instead.
         * (i.e. struct's member -> BTF_KIND_PTR -> BTF_KIND_FUNC_PROTO)
         *
         * Hence, there is no btf_func_check_member().
         */
        .check_member = btf_df_check_member,
        .check_kflag_member = btf_df_check_kflag_member,
        .log_details = btf_func_proto_log,
        .show = btf_df_show,
};

static s32 btf_func_check_meta(struct btf_verifier_env *env,
                               const struct btf_type *t,
                               u32 meta_left)
{
        if (!t->name_off ||
            !btf_name_valid_identifier(env->btf, t->name_off)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        if (btf_type_vlen(t) > BTF_FUNC_GLOBAL) {
                btf_verifier_log_type(env, t, "Invalid func linkage");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return 0;
}

static int btf_func_resolve(struct btf_verifier_env *env,
                            const struct resolve_vertex *v)
{
        const struct btf_type *t = v->t;
        u32 next_type_id = t->type;
        int err;

        err = btf_func_check(env, t);
        if (err)
                return err;

        env_stack_pop_resolved(env, next_type_id, 0);
        return 0;
}

static struct btf_kind_operations func_ops = {
        .check_meta = btf_func_check_meta,
        .resolve = btf_func_resolve,
        .check_member = btf_df_check_member,
        .check_kflag_member = btf_df_check_kflag_member,
        .log_details = btf_ref_type_log,
        .show = btf_df_show,
};

static s32 btf_var_check_meta(struct btf_verifier_env *env,
                              const struct btf_type *t,
                              u32 meta_left)
{
        const struct btf_var *var;
        u32 meta_needed = sizeof(*var);

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (!t->name_off ||
            !__btf_name_valid(env->btf, t->name_off, true)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        /* A var cannot be in type void */
        if (!t->type || !BTF_TYPE_ID_VALID(t->type)) {
                btf_verifier_log_type(env, t, "Invalid type_id");
                return -EINVAL;
        }

        var = btf_type_var(t);
        if (var->linkage != BTF_VAR_STATIC &&
            var->linkage != BTF_VAR_GLOBAL_ALLOCATED) {
                btf_verifier_log_type(env, t, "Linkage not supported");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return meta_needed;
}

static void btf_var_log(struct btf_verifier_env *env, const struct btf_type *t)
{
        const struct btf_var *var = btf_type_var(t);

        btf_verifier_log(env, "type_id=%u linkage=%u", t->type, var->linkage);
}

static const struct btf_kind_operations var_ops = {
        .check_meta             = btf_var_check_meta,
        .resolve                = btf_var_resolve,
        .check_member           = btf_df_check_member,
        .check_kflag_member     = btf_df_check_kflag_member,
        .log_details            = btf_var_log,
        .show                   = btf_var_show,
};

static s32 btf_datasec_check_meta(struct btf_verifier_env *env,
                                  const struct btf_type *t,
                                  u32 meta_left)
{
        const struct btf_var_secinfo *vsi;
        u64 last_vsi_end_off = 0, sum = 0;
        u32 i, meta_needed;

        meta_needed = btf_type_vlen(t) * sizeof(*vsi);
        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        if (!t->size) {
                btf_verifier_log_type(env, t, "size == 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (!t->name_off ||
            !btf_name_valid_section(env->btf, t->name_off)) {
                btf_verifier_log_type(env, t, "Invalid name");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        for_each_vsi(i, t, vsi) {
                /* A var cannot be in type void */
                if (!vsi->type || !BTF_TYPE_ID_VALID(vsi->type)) {
                        btf_verifier_log_vsi(env, t, vsi,
                                             "Invalid type_id");
                        return -EINVAL;
                }

                if (vsi->offset < last_vsi_end_off || vsi->offset >= t->size) {
                        btf_verifier_log_vsi(env, t, vsi,
                                             "Invalid offset");
                        return -EINVAL;
                }

                if (!vsi->size || vsi->size > t->size) {
                        btf_verifier_log_vsi(env, t, vsi,
                                             "Invalid size");
                        return -EINVAL;
                }

                last_vsi_end_off = vsi->offset + vsi->size;
                if (last_vsi_end_off > t->size) {
                        btf_verifier_log_vsi(env, t, vsi,
                                             "Invalid offset+size");
                        return -EINVAL;
                }

                btf_verifier_log_vsi(env, t, vsi, NULL);
                sum += vsi->size;
        }

        if (t->size < sum) {
                btf_verifier_log_type(env, t, "Invalid btf_info size");
                return -EINVAL;
        }

        return meta_needed;
}

static int btf_datasec_resolve(struct btf_verifier_env *env,
                               const struct resolve_vertex *v)
{
        const struct btf_var_secinfo *vsi;
        struct btf *btf = env->btf;
        u16 i;

        for_each_vsi_from(i, v->next_member, v->t, vsi) {
                u32 var_type_id = vsi->type, type_id, type_size = 0;
                const struct btf_type *var_type = btf_type_by_id(env->btf,
                                                                 var_type_id);
                if (!var_type || !btf_type_is_var(var_type)) {
                        btf_verifier_log_vsi(env, v->t, vsi,
                                             "Not a VAR kind member");
                        return -EINVAL;
                }

                if (!env_type_is_resolve_sink(env, var_type) &&
                    !env_type_is_resolved(env, var_type_id)) {
                        env_stack_set_next_member(env, i + 1);
                        return env_stack_push(env, var_type, var_type_id);
                }

                type_id = var_type->type;
                if (!btf_type_id_size(btf, &type_id, &type_size)) {
                        btf_verifier_log_vsi(env, v->t, vsi, "Invalid type");
                        return -EINVAL;
                }

                if (vsi->size < type_size) {
                        btf_verifier_log_vsi(env, v->t, vsi, "Invalid size");
                        return -EINVAL;
                }
        }

        env_stack_pop_resolved(env, 0, 0);
        return 0;
}

static void btf_datasec_log(struct btf_verifier_env *env,
                            const struct btf_type *t)
{
        btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_datasec_show(const struct btf *btf,
                             const struct btf_type *t, u32 type_id,
                             void *data, u8 bits_offset,
                             struct btf_show *show)
{
        const struct btf_var_secinfo *vsi;
        const struct btf_type *var;
        u32 i;

        if (!btf_show_start_type(show, t, type_id, data))
                return;

        btf_show_type_value(show, "section (\"%s\") = {",
                            __btf_name_by_offset(btf, t->name_off));
        for_each_vsi(i, t, vsi) {
                var = btf_type_by_id(btf, vsi->type);
                if (i)
                        btf_show(show, ",");
                btf_type_ops(var)->show(btf, var, vsi->type,
                                        data + vsi->offset, bits_offset, show);
        }
        btf_show_end_type(show);
}

static const struct btf_kind_operations datasec_ops = {
        .check_meta             = btf_datasec_check_meta,
        .resolve                = btf_datasec_resolve,
        .check_member           = btf_df_check_member,
        .check_kflag_member     = btf_df_check_kflag_member,
        .log_details            = btf_datasec_log,
        .show                   = btf_datasec_show,
};

static s32 btf_float_check_meta(struct btf_verifier_env *env,
                                const struct btf_type *t,
                                u32 meta_left)
{
        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        if (t->size != 2 && t->size != 4 && t->size != 8 && t->size != 12 &&
            t->size != 16) {
                btf_verifier_log_type(env, t, "Invalid type_size");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return 0;
}

static int btf_float_check_member(struct btf_verifier_env *env,
                                  const struct btf_type *struct_type,
                                  const struct btf_member *member,
                                  const struct btf_type *member_type)
{
        u64 start_offset_bytes;
        u64 end_offset_bytes;
        u64 misalign_bits;
        u64 align_bytes;
        u64 align_bits;

        /* Different architectures have different alignment requirements, so
         * here we check only for the reasonable minimum. This way we ensure
         * that types after CO-RE can pass the kernel BTF verifier.
         */
        align_bytes = min_t(u64, sizeof(void *), member_type->size);
        align_bits = align_bytes * BITS_PER_BYTE;
        div64_u64_rem(member->offset, align_bits, &misalign_bits);
        if (misalign_bits) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member is not properly aligned");
                return -EINVAL;
        }

        start_offset_bytes = member->offset / BITS_PER_BYTE;
        end_offset_bytes = start_offset_bytes + member_type->size;
        if (end_offset_bytes > struct_type->size) {
                btf_verifier_log_member(env, struct_type, member,
                                        "Member exceeds struct_size");
                return -EINVAL;
        }

        return 0;
}

static void btf_float_log(struct btf_verifier_env *env,
                          const struct btf_type *t)
{
        btf_verifier_log(env, "size=%u", t->size);
}

static const struct btf_kind_operations float_ops = {
        .check_meta = btf_float_check_meta,
        .resolve = btf_df_resolve,
        .check_member = btf_float_check_member,
        .check_kflag_member = btf_generic_check_kflag_member,
        .log_details = btf_float_log,
        .show = btf_df_show,
};

static s32 btf_decl_tag_check_meta(struct btf_verifier_env *env,
                              const struct btf_type *t,
                              u32 meta_left)
{
        const struct btf_decl_tag *tag;
        u32 meta_needed = sizeof(*tag);
        s32 component_idx;
        const char *value;

        if (meta_left < meta_needed) {
                btf_verifier_log_basic(env, t,
                                       "meta_left:%u meta_needed:%u",
                                       meta_left, meta_needed);
                return -EINVAL;
        }

        value = btf_name_by_offset(env->btf, t->name_off);
        if (!value || !value[0]) {
                btf_verifier_log_type(env, t, "Invalid value");
                return -EINVAL;
        }

        if (btf_type_vlen(t)) {
                btf_verifier_log_type(env, t, "vlen != 0");
                return -EINVAL;
        }

        if (btf_type_kflag(t)) {
                btf_verifier_log_type(env, t, "Invalid btf_info kind_flag");
                return -EINVAL;
        }

        component_idx = btf_type_decl_tag(t)->component_idx;
        if (component_idx < -1) {
                btf_verifier_log_type(env, t, "Invalid component_idx");
                return -EINVAL;
        }

        btf_verifier_log_type(env, t, NULL);

        return meta_needed;
}

static int btf_decl_tag_resolve(struct btf_verifier_env *env,
                           const struct resolve_vertex *v)
{
        const struct btf_type *next_type;
        const struct btf_type *t = v->t;
        u32 next_type_id = t->type;
        struct btf *btf = env->btf;
        s32 component_idx;
        u32 vlen;

        next_type = btf_type_by_id(btf, next_type_id);
        if (!next_type || !btf_type_is_decl_tag_target(next_type)) {
                btf_verifier_log_type(env, v->t, "Invalid type_id");
                return -EINVAL;
        }

        if (!env_type_is_resolve_sink(env, next_type) &&
            !env_type_is_resolved(env, next_type_id))
                return env_stack_push(env, next_type, next_type_id);

        component_idx = btf_type_decl_tag(t)->component_idx;
        if (component_idx != -1) {
                if (btf_type_is_var(next_type) || btf_type_is_typedef(next_type)) {
                        btf_verifier_log_type(env, v->t, "Invalid component_idx");
                        return -EINVAL;
                }

                if (btf_type_is_struct(next_type)) {
                        vlen = btf_type_vlen(next_type);
                } else {
                        /* next_type should be a function */
                        next_type = btf_type_by_id(btf, next_type->type);
                        vlen = btf_type_vlen(next_type);
                }

                if ((u32)component_idx >= vlen) {
                        btf_verifier_log_type(env, v->t, "Invalid component_idx");
                        return -EINVAL;
                }
        }

        env_stack_pop_resolved(env, next_type_id, 0);

        return 0;
}

static void btf_decl_tag_log(struct btf_verifier_env *env, const struct btf_type *t)
{
        btf_verifier_log(env, "type=%u component_idx=%d", t->type,
                         btf_type_decl_tag(t)->component_idx);
}

static const struct btf_kind_operations decl_tag_ops = {
        .check_meta = btf_decl_tag_check_meta,
        .resolve = btf_decl_tag_resolve,
        .check_member = btf_df_check_member,
        .check_kflag_member = btf_df_check_kflag_member,
        .log_details = btf_decl_tag_log,
        .show = btf_df_show,
};

static int btf_func_proto_check(struct btf_verifier_env *env,
                                const struct btf_type *t)
{
        const struct btf_type *ret_type;
        const struct btf_param *args;
        const struct btf *btf;
        u16 nr_args, i;
        int err;

        btf = env->btf;
        args = (const struct btf_param *)(t + 1);
        nr_args = btf_type_vlen(t);

        /* Check func return type which could be "void" (t->type == 0) */
        if (t->type) {
                u32 ret_type_id = t->type;

                ret_type = btf_type_by_id(btf, ret_type_id);
                if (!ret_type) {
                        btf_verifier_log_type(env, t, "Invalid return type");
                        return -EINVAL;
                }

                if (btf_type_needs_resolve(ret_type) &&
                    !env_type_is_resolved(env, ret_type_id)) {
                        err = btf_resolve(env, ret_type, ret_type_id);
                        if (err)
                                return err;
                }

                /* Ensure the return type is a type that has a size */
                if (!btf_type_id_size(btf, &ret_type_id, NULL)) {
                        btf_verifier_log_type(env, t, "Invalid return type");
                        return -EINVAL;
                }
        }

        if (!nr_args)
                return 0;

        /* Last func arg type_id could be 0 if it is a vararg */
        if (!args[nr_args - 1].type) {
                if (args[nr_args - 1].name_off) {
                        btf_verifier_log_type(env, t, "Invalid arg#%u",
                                              nr_args);
                        return -EINVAL;
                }
                nr_args--;
        }

        err = 0;
        for (i = 0; i < nr_args; i++) {
                const struct btf_type *arg_type;
                u32 arg_type_id;

                arg_type_id = args[i].type;
                arg_type = btf_type_by_id(btf, arg_type_id);
                if (!arg_type) {
                        btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
                        err = -EINVAL;
                        break;
                }

                if (args[i].name_off &&
                    (!btf_name_offset_valid(btf, args[i].name_off) ||
                     !btf_name_valid_identifier(btf, args[i].name_off))) {
                        btf_verifier_log_type(env, t,
                                              "Invalid arg#%u", i + 1);
                        err = -EINVAL;
                        break;
                }

                if (btf_type_needs_resolve(arg_type) &&
                    !env_type_is_resolved(env, arg_type_id)) {
                        err = btf_resolve(env, arg_type, arg_type_id);
                        if (err)
                                break;
                }

                if (!btf_type_id_size(btf, &arg_type_id, NULL)) {
                        btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
                        err = -EINVAL;
                        break;
                }
        }

        return err;
}

static int btf_func_check(struct btf_verifier_env *env,
                          const struct btf_type *t)
{
        const struct btf_type *proto_type;
        const struct btf_param *args;
        const struct btf *btf;
        u16 nr_args, i;

        btf = env->btf;
        proto_type = btf_type_by_id(btf, t->type);

        if (!proto_type || !btf_type_is_func_proto(proto_type)) {
                btf_verifier_log_type(env, t, "Invalid type_id");
                return -EINVAL;
        }

        args = (const struct btf_param *)(proto_type + 1);
        nr_args = btf_type_vlen(proto_type);
        for (i = 0; i < nr_args; i++) {
                if (!args[i].name_off && args[i].type) {
                        btf_verifier_log_type(env, t, "Invalid arg#%u", i + 1);
                        return -EINVAL;
                }
        }

        return 0;
}

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
        [BTF_KIND_INT] = &int_ops,
        [BTF_KIND_PTR] = &ptr_ops,
        [BTF_KIND_ARRAY] = &array_ops,
        [BTF_KIND_STRUCT] = &struct_ops,
        [BTF_KIND_UNION] = &struct_ops,
        [BTF_KIND_ENUM] = &enum_ops,
        [BTF_KIND_FWD] = &fwd_ops,
        [BTF_KIND_TYPEDEF] = &modifier_ops,
        [BTF_KIND_VOLATILE] = &modifier_ops,
        [BTF_KIND_CONST] = &modifier_ops,
        [BTF_KIND_RESTRICT] = &modifier_ops,
        [BTF_KIND_FUNC] = &func_ops,
        [BTF_KIND_FUNC_PROTO] = &func_proto_ops,
        [BTF_KIND_VAR] = &var_ops,
        [BTF_KIND_DATASEC] = &datasec_ops,
        [BTF_KIND_FLOAT] = &float_ops,
        [BTF_KIND_DECL_TAG] = &decl_tag_ops,
        [BTF_KIND_TYPE_TAG] = &modifier_ops,
};

static s32 btf_check_meta(struct btf_verifier_env *env,
                          const struct btf_type *t,
                          u32 meta_left)
{
        u32 saved_meta_left = meta_left;
        s32 var_meta_size;

        if (meta_left < sizeof(*t)) {
                btf_verifier_log(env, "[%u] meta_left:%u meta_needed:%zu",
                                 env->log_type_id, meta_left, sizeof(*t));
                return -EINVAL;
        }
        meta_left -= sizeof(*t);

        if (t->info & ~BTF_INFO_MASK) {
                btf_verifier_log(env, "[%u] Invalid btf_info:%x",
                                 env->log_type_id, t->info);
                return -EINVAL;
        }

        if (BTF_INFO_KIND(t->info) > BTF_KIND_MAX ||
            BTF_INFO_KIND(t->info) == BTF_KIND_UNKN) {
                btf_verifier_log(env, "[%u] Invalid kind:%u",
                                 env->log_type_id, BTF_INFO_KIND(t->info));
                return -EINVAL;
        }

        if (!btf_name_offset_valid(env->btf, t->name_off)) {
                btf_verifier_log(env, "[%u] Invalid name_offset:%u",
                                 env->log_type_id, t->name_off);
                return -EINVAL;
        }

        var_meta_size = btf_type_ops(t)->check_meta(env, t, meta_left);
        if (var_meta_size < 0)
                return var_meta_size;

        meta_left -= var_meta_size;

        return saved_meta_left - meta_left;
}

static int btf_check_all_metas(struct btf_verifier_env *env)
{
        struct btf *btf = env->btf;
        struct btf_header *hdr;
        void *cur, *end;

        hdr = &btf->hdr;
        cur = btf->nohdr_data + hdr->type_off;
        end = cur + hdr->type_len;

        env->log_type_id = btf->base_btf ? btf->start_id : 1;
        while (cur < end) {
                struct btf_type *t = cur;
                s32 meta_size;

                meta_size = btf_check_meta(env, t, end - cur);
                if (meta_size < 0)
                        return meta_size;

                btf_add_type(env, t);
                cur += meta_size;
                env->log_type_id++;
        }

        return 0;
}

static bool btf_resolve_valid(struct btf_verifier_env *env,
                              const struct btf_type *t,
                              u32 type_id)
{
        struct btf *btf = env->btf;

        if (!env_type_is_resolved(env, type_id))
                return false;

        if (btf_type_is_struct(t) || btf_type_is_datasec(t))
                return !btf_resolved_type_id(btf, type_id) &&
                       !btf_resolved_type_size(btf, type_id);

        if (btf_type_is_decl_tag(t) || btf_type_is_func(t))
                return btf_resolved_type_id(btf, type_id) &&
                       !btf_resolved_type_size(btf, type_id);

        if (btf_type_is_modifier(t) || btf_type_is_ptr(t) ||
            btf_type_is_var(t)) {
                t = btf_type_id_resolve(btf, &type_id);
                return t &&
                       !btf_type_is_modifier(t) &&
                       !btf_type_is_var(t) &&
                       !btf_type_is_datasec(t);
        }

        if (btf_type_is_array(t)) {
                const struct btf_array *array = btf_type_array(t);
                const struct btf_type *elem_type;
                u32 elem_type_id = array->type;
                u32 elem_size;

                elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
                return elem_type && !btf_type_is_modifier(elem_type) &&
                        (array->nelems * elem_size ==
                         btf_resolved_type_size(btf, type_id));
        }

        return false;
}

static int btf_resolve(struct btf_verifier_env *env,
                       const struct btf_type *t, u32 type_id)
{
        u32 save_log_type_id = env->log_type_id;
        const struct resolve_vertex *v;
        int err = 0;

        env->resolve_mode = RESOLVE_TBD;
        env_stack_push(env, t, type_id);
        while (!err && (v = env_stack_peak(env))) {
                env->log_type_id = v->type_id;
                err = btf_type_ops(v->t)->resolve(env, v);
        }

        env->log_type_id = type_id;
        if (err == -E2BIG) {
                btf_verifier_log_type(env, t,
                                      "Exceeded max resolving depth:%u",
                                      MAX_RESOLVE_DEPTH);
        } else if (err == -EEXIST) {
                btf_verifier_log_type(env, t, "Loop detected");
        }

        /* Final sanity check */
        if (!err && !btf_resolve_valid(env, t, type_id)) {
                btf_verifier_log_type(env, t, "Invalid resolve state");
                err = -EINVAL;
        }

        env->log_type_id = save_log_type_id;
        return err;
}

static int btf_check_all_types(struct btf_verifier_env *env)
{
        struct btf *btf = env->btf;
        const struct btf_type *t;
        u32 type_id, i;
        int err;

        err = env_resolve_init(env);
        if (err)
                return err;

        env->phase++;
        for (i = btf->base_btf ? 0 : 1; i < btf->nr_types; i++) {
                type_id = btf->start_id + i;
                t = btf_type_by_id(btf, type_id);

                env->log_type_id = type_id;
                if (btf_type_needs_resolve(t) &&
                    !env_type_is_resolved(env, type_id)) {
                        err = btf_resolve(env, t, type_id);
                        if (err)
                                return err;
                }

                if (btf_type_is_func_proto(t)) {
                        err = btf_func_proto_check(env, t);
                        if (err)
                                return err;
                }
        }

        return 0;
}

static int btf_parse_type_sec(struct btf_verifier_env *env)
{
        const struct btf_header *hdr = &env->btf->hdr;
        int err;

        /* Type section must align to 4 bytes */
        if (hdr->type_off & (sizeof(u32) - 1)) {
                btf_verifier_log(env, "Unaligned type_off");
                return -EINVAL;
        }

        if (!env->btf->base_btf && !hdr->type_len) {
                btf_verifier_log(env, "No type found");
                return -EINVAL;
        }

        err = btf_check_all_metas(env);
        if (err)
                return err;

        return btf_check_all_types(env);
}

static int btf_parse_str_sec(struct btf_verifier_env *env)
{
        const struct btf_header *hdr;
        struct btf *btf = env->btf;
        const char *start, *end;

        hdr = &btf->hdr;
        start = btf->nohdr_data + hdr->str_off;
        end = start + hdr->str_len;

        if (end != btf->data + btf->data_size) {
                btf_verifier_log(env, "String section is not at the end");
                return -EINVAL;
        }

        btf->strings = start;

        if (btf->base_btf && !hdr->str_len)
                return 0;
        if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET || end[-1]) {
                btf_verifier_log(env, "Invalid string section");
                return -EINVAL;
        }
        if (!btf->base_btf && start[0]) {
                btf_verifier_log(env, "Invalid string section");
                return -EINVAL;
        }

        return 0;
}

static const size_t btf_sec_info_offset[] = {
        offsetof(struct btf_header, type_off),
        offsetof(struct btf_header, str_off),
};

static int btf_sec_info_cmp(const void *a, const void *b)
{
        const struct btf_sec_info *x = a;
        const struct btf_sec_info *y = b;

        return (int)(x->off - y->off) ? : (int)(x->len - y->len);
}

static int btf_check_sec_info(struct btf_verifier_env *env,
                              u32 btf_data_size)
{
        struct btf_sec_info secs[ARRAY_SIZE(btf_sec_info_offset)];
        u32 total, expected_total, i;
        const struct btf_header *hdr;
        const struct btf *btf;

        btf = env->btf;
        hdr = &btf->hdr;

        /* Populate the secs from hdr */
        for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++)
                secs[i] = *(struct btf_sec_info *)((void *)hdr +
                                                   btf_sec_info_offset[i]);

        sort(secs, ARRAY_SIZE(btf_sec_info_offset),
             sizeof(struct btf_sec_info), btf_sec_info_cmp, NULL);

        /* Check for gaps and overlap among sections */
        total = 0;
        expected_total = btf_data_size - hdr->hdr_len;
        for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++) {
                if (expected_total < secs[i].off) {
                        btf_verifier_log(env, "Invalid section offset");
                        return -EINVAL;
                }
                if (total < secs[i].off) {
                        /* gap */
                        btf_verifier_log(env, "Unsupported section found");
                        return -EINVAL;
                }
                if (total > secs[i].off) {
                        btf_verifier_log(env, "Section overlap found");
                        return -EINVAL;
                }
                if (expected_total - total < secs[i].len) {
                        btf_verifier_log(env,
                                         "Total section length too long");
                        return -EINVAL;
                }
                total += secs[i].len;
        }

        /* There is data other than hdr and known sections */
        if (expected_total != total) {
                btf_verifier_log(env, "Unsupported section found");
                return -EINVAL;
        }

        return 0;
}

static int btf_parse_hdr(struct btf_verifier_env *env)
{
        u32 hdr_len, hdr_copy, btf_data_size;
        const struct btf_header *hdr;
        struct btf *btf;
        int err;

        btf = env->btf;
        btf_data_size = btf->data_size;

        if (btf_data_size < offsetofend(struct btf_header, hdr_len)) {
                btf_verifier_log(env, "hdr_len not found");
                return -EINVAL;
        }

        hdr = btf->data;
        hdr_len = hdr->hdr_len;
        if (btf_data_size < hdr_len) {
                btf_verifier_log(env, "btf_header not found");
                return -EINVAL;
        }

        /* Ensure the unsupported header fields are zero */
        if (hdr_len > sizeof(btf->hdr)) {
                u8 *expected_zero = btf->data + sizeof(btf->hdr);
                u8 *end = btf->data + hdr_len;

                for (; expected_zero < end; expected_zero++) {
                        if (*expected_zero) {
                                btf_verifier_log(env, "Unsupported btf_header");
                                return -E2BIG;
                        }
                }
        }

        hdr_copy = min_t(u32, hdr_len, sizeof(btf->hdr));
        memcpy(&btf->hdr, btf->data, hdr_copy);

        hdr = &btf->hdr;

        btf_verifier_log_hdr(env, btf_data_size);

        if (hdr->magic != BTF_MAGIC) {
                btf_verifier_log(env, "Invalid magic");
                return -EINVAL;
        }

        if (hdr->version != BTF_VERSION) {
                btf_verifier_log(env, "Unsupported version");
                return -ENOTSUPP;
        }

        if (hdr->flags) {
                btf_verifier_log(env, "Unsupported flags");
                return -ENOTSUPP;
        }

        if (!btf->base_btf && btf_data_size == hdr->hdr_len) {
                btf_verifier_log(env, "No data");
                return -EINVAL;
        }

        err = btf_check_sec_info(env, btf_data_size);
        if (err)
                return err;

        return 0;
}

static int btf_check_type_tags(struct btf_verifier_env *env,
                               struct btf *btf, int start_id)
{
        int i, n, good_id = start_id - 1;
        bool in_tags;

        n = btf_nr_types(btf);
        for (i = start_id; i < n; i++) {
                const struct btf_type *t;
                u32 cur_id = i;

                t = btf_type_by_id(btf, i);
                if (!t)
                        return -EINVAL;
                if (!btf_type_is_modifier(t))
                        continue;

                cond_resched();

                in_tags = btf_type_is_type_tag(t);
                while (btf_type_is_modifier(t)) {
                        if (btf_type_is_type_tag(t)) {
                                if (!in_tags) {
                                        btf_verifier_log(env, "Type tags don't precede modifiers");
                                        return -EINVAL;
                                }
                        } else if (in_tags) {
                                in_tags = false;
                        }
                        if (cur_id <= good_id)
                                break;
                        /* Move to next type */
                        cur_id = t->type;
                        t = btf_type_by_id(btf, cur_id);
                        if (!t)
                                return -EINVAL;
                }
                good_id = i;
        }
        return 0;
}

static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
                             u32 log_level, char __user *log_ubuf, u32 log_size)
{
        struct btf_verifier_env *env = NULL;
        struct bpf_verifier_log *log;
        struct btf *btf = NULL;
        u8 *data;
        int err;

        if (btf_data_size > BTF_MAX_SIZE)
                return ERR_PTR(-E2BIG);

        env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
        if (!env)
                return ERR_PTR(-ENOMEM);

        log = &env->log;
        if (log_level || log_ubuf || log_size) {
                /* user requested verbose verifier output
                 * and supplied buffer to store the verification trace
                 */
                log->level = log_level;
                log->ubuf = log_ubuf;
                log->len_total = log_size;

                /* log attributes have to be sane */
                if (!bpf_verifier_log_attr_valid(log)) {
                        err = -EINVAL;
                        goto errout;
                }
        }

        btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
        if (!btf) {
                err = -ENOMEM;
                goto errout;
        }
        env->btf = btf;

        data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN);
        if (!data) {
                err = -ENOMEM;
                goto errout;
        }

        btf->data = data;
        btf->data_size = btf_data_size;

        if (copy_from_bpfptr(data, btf_data, btf_data_size)) {
                err = -EFAULT;
                goto errout;
        }

        err = btf_parse_hdr(env);
        if (err)
                goto errout;

        btf->nohdr_data = btf->data + btf->hdr.hdr_len;

        err = btf_parse_str_sec(env);
        if (err)
                goto errout;

        err = btf_parse_type_sec(env);
        if (err)
                goto errout;

        err = btf_check_type_tags(env, btf, 1);
        if (err)
                goto errout;

        if (log->level && bpf_verifier_log_full(log)) {
                err = -ENOSPC;
                goto errout;
        }

        btf_verifier_env_free(env);
        refcount_set(&btf->refcnt, 1);
        return btf;

errout:
        btf_verifier_env_free(env);
        if (btf)
                btf_free(btf);
        return ERR_PTR(err);
}

extern char __weak __start_BTF[];
extern char __weak __stop_BTF[];
extern struct btf *btf_vmlinux;

#define BPF_MAP_TYPE(_id, _ops)
#define BPF_LINK_TYPE(_id, _name)
static union {
        struct bpf_ctx_convert {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
        prog_ctx_type _id##_prog; \
        kern_ctx_type _id##_kern;
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
        } *__t;
        /* 't' is written once under lock. Read many times. */
        const struct btf_type *t;
} bpf_ctx_convert;
enum {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
        __ctx_convert##_id,
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
        __ctx_convert_unused, /* to avoid empty enum in extreme .config */
};
static u8 bpf_ctx_convert_map[] = {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
        [_id] = __ctx_convert##_id,
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
        0, /* avoid empty array */
};
#undef BPF_MAP_TYPE
#undef BPF_LINK_TYPE

static const struct btf_member *
btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
                      const struct btf_type *t, enum bpf_prog_type prog_type,
                      int arg)
{
        const struct btf_type *conv_struct;
        const struct btf_type *ctx_struct;
        const struct btf_member *ctx_type;
        const char *tname, *ctx_tname;

        conv_struct = bpf_ctx_convert.t;
        if (!conv_struct) {
                bpf_log(log, "btf_vmlinux is malformed\n");
                return NULL;
        }
        t = btf_type_by_id(btf, t->type);
        while (btf_type_is_modifier(t))
                t = btf_type_by_id(btf, t->type);
        if (!btf_type_is_struct(t)) {
                /* Only pointer to struct is supported for now.
                 * That means that BPF_PROG_TYPE_TRACEPOINT with BTF
                 * is not supported yet.
                 * BPF_PROG_TYPE_RAW_TRACEPOINT is fine.
                 */
                return NULL;
        }
        tname = btf_name_by_offset(btf, t->name_off);
        if (!tname) {
                bpf_log(log, "arg#%d struct doesn't have a name\n", arg);
                return NULL;
        }
        /* prog_type is valid bpf program type. No need for bounds check. */
        ctx_type = btf_type_member(conv_struct) + bpf_ctx_convert_map[prog_type] * 2;
        /* ctx_struct is a pointer to prog_ctx_type in vmlinux.
         * Like 'struct __sk_buff'
         */
        ctx_struct = btf_type_by_id(btf_vmlinux, ctx_type->type);
        if (!ctx_struct)
                /* should not happen */
                return NULL;
        ctx_tname = btf_name_by_offset(btf_vmlinux, ctx_struct->name_off);
        if (!ctx_tname) {
                /* should not happen */
                bpf_log(log, "Please fix kernel include/linux/bpf_types.h\n");
                return NULL;
        }
        /* only compare that prog's ctx type name is the same as
         * kernel expects. No need to compare field by field.
         * It's ok for bpf prog to do:
         * struct __sk_buff {};
         * int socket_filter_bpf_prog(struct __sk_buff *skb)
         * { // no fields of skb are ever used }
         */
        if (strcmp(ctx_tname, tname))
                return NULL;
        return ctx_type;
}

static int btf_translate_to_vmlinux(struct bpf_verifier_log *log,
                                     struct btf *btf,
                                     const struct btf_type *t,
                                     enum bpf_prog_type prog_type,
                                     int arg)
{
        const struct btf_member *prog_ctx_type, *kern_ctx_type;

        prog_ctx_type = btf_get_prog_ctx_type(log, btf, t, prog_type, arg);
        if (!prog_ctx_type)
                return -ENOENT;
        kern_ctx_type = prog_ctx_type + 1;
        return kern_ctx_type->type;
}

BTF_ID_LIST(bpf_ctx_convert_btf_id)
BTF_ID(struct, bpf_ctx_convert)

struct btf *btf_parse_vmlinux(void)
{
        struct btf_verifier_env *env = NULL;
        struct bpf_verifier_log *log;
        struct btf *btf = NULL;
        int err;

        env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
        if (!env)
                return ERR_PTR(-ENOMEM);

        log = &env->log;
        log->level = BPF_LOG_KERNEL;

        btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
        if (!btf) {
                err = -ENOMEM;
                goto errout;
        }
        env->btf = btf;

        btf->data = __start_BTF;
        btf->data_size = __stop_BTF - __start_BTF;
        btf->kernel_btf = true;
        snprintf(btf->name, sizeof(btf->name), "vmlinux");

        err = btf_parse_hdr(env);
        if (err)
                goto errout;

        btf->nohdr_data = btf->data + btf->hdr.hdr_len;

        err = btf_parse_str_sec(env);
        if (err)
                goto errout;

        err = btf_check_all_metas(env);
        if (err)
                goto errout;

        err = btf_check_type_tags(env, btf, 1);
        if (err)
                goto errout;

        /* btf_parse_vmlinux() runs under bpf_verifier_lock */
        bpf_ctx_convert.t = btf_type_by_id(btf, bpf_ctx_convert_btf_id[0]);

        bpf_struct_ops_init(btf, log);

        refcount_set(&btf->refcnt, 1);

        err = btf_alloc_id(btf);
        if (err)
                goto errout;

        btf_verifier_env_free(env);
        return btf;

errout:
        btf_verifier_env_free(env);
        if (btf) {
                kvfree(btf->types);
                kfree(btf);
        }
        return ERR_PTR(err);
}

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES

static struct btf *btf_parse_module(const char *module_name, const void *data, unsigned int data_size)
{
        struct btf_verifier_env *env = NULL;
        struct bpf_verifier_log *log;
        struct btf *btf = NULL, *base_btf;
        int err;

        base_btf = bpf_get_btf_vmlinux();
        if (IS_ERR(base_btf))
                return base_btf;
        if (!base_btf)
                return ERR_PTR(-EINVAL);

        env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
        if (!env)
                return ERR_PTR(-ENOMEM);

        log = &env->log;
        log->level = BPF_LOG_KERNEL;

        btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
        if (!btf) {
                err = -ENOMEM;
                goto errout;
        }
        env->btf = btf;

        btf->base_btf = base_btf;
        btf->start_id = base_btf->nr_types;
        btf->start_str_off = base_btf->hdr.str_len;
        btf->kernel_btf = true;
        snprintf(btf->name, sizeof(btf->name), "%s", module_name);

        btf->data = kvmalloc(data_size, GFP_KERNEL | __GFP_NOWARN);
        if (!btf->data) {
                err = -ENOMEM;
                goto errout;
        }
        memcpy(btf->data, data, data_size);
        btf->data_size = data_size;

        err = btf_parse_hdr(env);
        if (err)
                goto errout;

        btf->nohdr_data = btf->data + btf->hdr.hdr_len;

        err = btf_parse_str_sec(env);
        if (err)
                goto errout;

        err = btf_check_all_metas(env);
        if (err)
                goto errout;

        err = btf_check_type_tags(env, btf, btf_nr_types(base_btf));
        if (err)
                goto errout;

        btf_verifier_env_free(env);
        refcount_set(&btf->refcnt, 1);
        return btf;

errout:
        btf_verifier_env_free(env);
        if (btf) {
                kvfree(btf->data);
                kvfree(btf->types);
                kfree(btf);
        }
        return ERR_PTR(err);
}

#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */

struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
{
        struct bpf_prog *tgt_prog = prog->aux->dst_prog;

        if (tgt_prog)
                return tgt_prog->aux->btf;
        else
                return prog->aux->attach_btf;
}

static bool is_int_ptr(struct btf *btf, const struct btf_type *t)
{
        /* t comes in already as a pointer */
        t = btf_type_by_id(btf, t->type);

        /* allow const */
        if (BTF_INFO_KIND(t->info) == BTF_KIND_CONST)
                t = btf_type_by_id(btf, t->type);

        return btf_type_is_int(t);
}

bool btf_ctx_access(int off, int size, enum bpf_access_type type,
                    const struct bpf_prog *prog,
                    struct bpf_insn_access_aux *info)
{
        const struct btf_type *t = prog->aux->attach_func_proto;
        struct bpf_prog *tgt_prog = prog->aux->dst_prog;
        struct btf *btf = bpf_prog_get_target_btf(prog);
        const char *tname = prog->aux->attach_func_name;
        struct bpf_verifier_log *log = info->log;
        const struct btf_param *args;
        const char *tag_value;
        u32 nr_args, arg;
        int i, ret;

        if (off % 8) {
                bpf_log(log, "func '%s' offset %d is not multiple of 8\n",
                        tname, off);
                return false;
        }
        arg = off / 8;
        args = (const struct btf_param *)(t + 1);
        /* if (t == NULL) Fall back to default BPF prog with
         * MAX_BPF_FUNC_REG_ARGS u64 arguments.
         */
        nr_args = t ? btf_type_vlen(t) : MAX_BPF_FUNC_REG_ARGS;
        if (prog->aux->attach_btf_trace) {
                /* skip first 'void *__data' argument in btf_trace_##name typedef */
                args++;
                nr_args--;
        }

        if (arg > nr_args) {
                bpf_log(log, "func '%s' doesn't have %d-th argument\n",
                        tname, arg + 1);
                return false;
        }

        if (arg == nr_args) {
                switch (prog->expected_attach_type) {
                case BPF_LSM_MAC:
                case BPF_TRACE_FEXIT:
                        /* When LSM programs are attached to void LSM hooks
                         * they use FEXIT trampolines and when attached to
                         * int LSM hooks, they use MODIFY_RETURN trampolines.
                         *
                         * While the LSM programs are BPF_MODIFY_RETURN-like
                         * the check:
                         *
                         *      if (ret_type != 'int')
                         *              return -EINVAL;
                         *
                         * is _not_ done here. This is still safe as LSM hooks
                         * have only void and int return types.
                         */
                        if (!t)
                                return true;
                        t = btf_type_by_id(btf, t->type);
                        break;
                case BPF_MODIFY_RETURN:
                        /* For now the BPF_MODIFY_RETURN can only be attached to
                         * functions that return an int.
                         */
                        if (!t)
                                return false;

                        t = btf_type_skip_modifiers(btf, t->type, NULL);
                        if (!btf_type_is_small_int(t)) {
                                bpf_log(log,
                                        "ret type %s not allowed for fmod_ret\n",
                                        btf_kind_str[BTF_INFO_KIND(t->info)]);
                                return false;
                        }
                        break;
                default:
                        bpf_log(log, "func '%s' doesn't have %d-th argument\n",
                                tname, arg + 1);
                        return false;
                }
        } else {
                if (!t)
                        /* Default prog with MAX_BPF_FUNC_REG_ARGS args */
                        return true;
                t = btf_type_by_id(btf, args[arg].type);
        }

        /* skip modifiers */
        while (btf_type_is_modifier(t))
                t = btf_type_by_id(btf, t->type);
        if (btf_type_is_small_int(t) || btf_type_is_enum(t))
                /* accessing a scalar */
                return true;
        if (!btf_type_is_ptr(t)) {
                bpf_log(log,
                        "func '%s' arg%d '%s' has type %s. Only pointer access is allowed\n",
                        tname, arg,
                        __btf_name_by_offset(btf, t->name_off),
                        btf_kind_str[BTF_INFO_KIND(t->info)]);
                return false;
        }

        /* check for PTR_TO_RDONLY_BUF_OR_NULL or PTR_TO_RDWR_BUF_OR_NULL */
        for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {
                const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];
                u32 type, flag;

                type = base_type(ctx_arg_info->reg_type);
                flag = type_flag(ctx_arg_info->reg_type);
                if (ctx_arg_info->offset == off && type == PTR_TO_BUF &&
                    (flag & PTR_MAYBE_NULL)) {
                        info->reg_type = ctx_arg_info->reg_type;
                        return true;
                }
        }

        if (t->type == 0)
                /* This is a pointer to void.
                 * It is the same as scalar from the verifier safety pov.
                 * No further pointer walking is allowed.
                 */
                return true;

        if (is_int_ptr(btf, t))
                return true;

        /* this is a pointer to another type */
        for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {
                const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];

                if (ctx_arg_info->offset == off) {
                        if (!ctx_arg_info->btf_id) {
                                bpf_log(log,"invalid btf_id for context argument offset %u\n", off);
                                return false;
                        }

                        info->reg_type = ctx_arg_info->reg_type;
                        info->btf = btf_vmlinux;
                        info->btf_id = ctx_arg_info->btf_id;
                        return true;
                }
        }

        info->reg_type = PTR_TO_BTF_ID;
        if (tgt_prog) {
                enum bpf_prog_type tgt_type;

                if (tgt_prog->type == BPF_PROG_TYPE_EXT)
                        tgt_type = tgt_prog->aux->saved_dst_prog_type;
                else
                        tgt_type = tgt_prog->type;

                ret = btf_translate_to_vmlinux(log, btf, t, tgt_type, arg);
                if (ret > 0) {
                        info->btf = btf_vmlinux;
                        info->btf_id = ret;
                        return true;
                } else {
                        return false;
                }
        }

        info->btf = btf;
        info->btf_id = t->type;
        t = btf_type_by_id(btf, t->type);

        if (btf_type_is_type_tag(t)) {
                tag_value = __btf_name_by_offset(btf, t->name_off);
                if (strcmp(tag_value, "user") == 0)
                        info->reg_type |= MEM_USER;
                if (strcmp(tag_value, "percpu") == 0)
                        info->reg_type |= MEM_PERCPU;
        }

        /* skip modifiers */
        while (btf_type_is_modifier(t)) {
                info->btf_id = t->type;
                t = btf_type_by_id(btf, t->type);
        }
        if (!btf_type_is_struct(t)) {
                bpf_log(log,
                        "func '%s' arg%d type %s is not a struct\n",
                        tname, arg, btf_kind_str[BTF_INFO_KIND(t->info)]);
                return false;
        }
        bpf_log(log, "func '%s' arg%d has btf_id %d type %s '%s'\n",
                tname, arg, info->btf_id, btf_kind_str[BTF_INFO_KIND(t->info)],
                __btf_name_by_offset(btf, t->name_off));
        return true;
}

enum bpf_struct_walk_result {
        /* < 0 error */
        WALK_SCALAR = 0,
        WALK_PTR,
        WALK_STRUCT,
};

static int btf_struct_walk(struct bpf_verifier_log *log, const struct btf *btf,
                           const struct btf_type *t, int off, int size,
                           u32 *next_btf_id, enum bpf_type_flag *flag)
{
        u32 i, moff, mtrue_end, msize = 0, total_nelems = 0;
        const struct btf_type *mtype, *elem_type = NULL;
        const struct btf_member *member;
        const char *tname, *mname, *tag_value;
        u32 vlen, elem_id, mid;

again:
        tname = __btf_name_by_offset(btf, t->name_off);
        if (!btf_type_is_struct(t)) {
                bpf_log(log, "Type '%s' is not a struct\n", tname);
                return -EINVAL;
        }

        vlen = btf_type_vlen(t);
        if (off + size > t->size) {
                /* If the last element is a variable size array, we may
                 * need to relax the rule.
                 */
                struct btf_array *array_elem;

                if (vlen == 0)
                        goto error;

                member = btf_type_member(t) + vlen - 1;
                mtype = btf_type_skip_modifiers(btf, member->type,
                                                NULL);
                if (!btf_type_is_array(mtype))
                        goto error;

                array_elem = (struct btf_array *)(mtype + 1);
                if (array_elem->nelems != 0)
                        goto error;

                moff = __btf_member_bit_offset(t, member) / 8;
                if (off < moff)
                        goto error;

                /* Only allow structure for now, can be relaxed for
                 * other types later.
                 */
                t = btf_type_skip_modifiers(btf, array_elem->type,
                                            NULL);
                if (!btf_type_is_struct(t))
                        goto error;

                off = (off - moff) % t->size;
                goto again;

error:
                bpf_log(log, "access beyond struct %s at off %u size %u\n",
                        tname, off, size);
                return -EACCES;
        }

        for_each_member(i, t, member) {
                /* offset of the field in bytes */
                moff = __btf_member_bit_offset(t, member) / 8;
                if (off + size <= moff)
                        /* won't find anything, field is already too far */
                        break;

                if (__btf_member_bitfield_size(t, member)) {
                        u32 end_bit = __btf_member_bit_offset(t, member) +
                                __btf_member_bitfield_size(t, member);

                        /* off <= moff instead of off == moff because clang
                         * does not generate a BTF member for anonymous
                         * bitfield like the ":16" here:
                         * struct {
                         *      int :16;
                         *      int x:8;
                         * };
                         */
                        if (off <= moff &&
                            BITS_ROUNDUP_BYTES(end_bit) <= off + size)
                                return WALK_SCALAR;

                        /* off may be accessing a following member
                         *
                         * or
                         *
                         * Doing partial access at either end of this
                         * bitfield.  Continue on this case also to
                         * treat it as not accessing this bitfield
                         * and eventually error out as field not
                         * found to keep it simple.
                         * It could be relaxed if there was a legit
                         * partial access case later.
                         */
                        continue;
                }

                /* In case of "off" is pointing to holes of a struct */
                if (off < moff)
                        break;

                /* type of the field */
                mid = member->type;
                mtype = btf_type_by_id(btf, member->type);
                mname = __btf_name_by_offset(btf, member->name_off);

                mtype = __btf_resolve_size(btf, mtype, &msize,
                                           &elem_type, &elem_id, &total_nelems,
                                           &mid);
                if (IS_ERR(mtype)) {
                        bpf_log(log, "field %s doesn't have size\n", mname);
                        return -EFAULT;
                }

                mtrue_end = moff + msize;
                if (off >= mtrue_end)
                        /* no overlap with member, keep iterating */
                        continue;

                if (btf_type_is_array(mtype)) {
                        u32 elem_idx;

                        /* __btf_resolve_size() above helps to
                         * linearize a multi-dimensional array.
                         *
                         * The logic here is treating an array
                         * in a struct as the following way:
                         *
                         * struct outer {
                         *      struct inner array[2][2];
                         * };
                         *
                         * looks like:
                         *
                         * struct outer {
                         *      struct inner array_elem0;
                         *      struct inner array_elem1;
                         *      struct inner array_elem2;
                         *      struct inner array_elem3;
                         * };
                         *
                         * When accessing outer->array[1][0], it moves
                         * moff to "array_elem2", set mtype to
                         * "struct inner", and msize also becomes
                         * sizeof(struct inner).  Then most of the
                         * remaining logic will fall through without
                         * caring the current member is an array or
                         * not.
                         *
                         * Unlike mtype/msize/moff, mtrue_end does not
                         * change.  The naming difference ("_true") tells
                         * that it is not always corresponding to
                         * the current mtype/msize/moff.
                         * It is the true end of the current
                         * member (i.e. array in this case).  That
                         * will allow an int array to be accessed like
                         * a scratch space,
                         * i.e. allow access beyond the size of
                         *      the array's element as long as it is
                         *      within the mtrue_end boundary.
                         */

                        /* skip empty array */
                        if (moff == mtrue_end)
                                continue;

                        msize /= total_nelems;
                        elem_idx = (off - moff) / msize;
                        moff += elem_idx * msize;
                        mtype = elem_type;
                        mid = elem_id;
                }

                /* the 'off' we're looking for is either equal to start
                 * of this field or inside of this struct
                 */
                if (btf_type_is_struct(mtype)) {
                        /* our field must be inside that union or struct */
                        t = mtype;

                        /* return if the offset matches the member offset */
                        if (off == moff) {
                                *next_btf_id = mid;
                                return WALK_STRUCT;
                        }

                        /* adjust offset we're looking for */
                        off -= moff;
                        goto again;
                }

                if (btf_type_is_ptr(mtype)) {
                        const struct btf_type *stype, *t;
                        enum bpf_type_flag tmp_flag = 0;
                        u32 id;

                        if (msize != size || off != moff) {
                                bpf_log(log,
                                        "cannot access ptr member %s with moff %u in struct %s with off %u size %u\n",
                                        mname, moff, tname, off, size);
                                return -EACCES;
                        }

                        /* check type tag */
                        t = btf_type_by_id(btf, mtype->type);
                        if (btf_type_is_type_tag(t)) {
                                tag_value = __btf_name_by_offset(btf, t->name_off);
                                /* check __user tag */
                                if (strcmp(tag_value, "user") == 0)
                                        tmp_flag = MEM_USER;
                                /* check __percpu tag */
                                if (strcmp(tag_value, "percpu") == 0)
                                        tmp_flag = MEM_PERCPU;
                        }

                        stype = btf_type_skip_modifiers(btf, mtype->type, &id);
                        if (btf_type_is_struct(stype)) {
                                *next_btf_id = id;
                                *flag = tmp_flag;
                                return WALK_PTR;
                        }
                }

                /* Allow more flexible access within an int as long as
                 * it is within mtrue_end.
                 * Since mtrue_end could be the end of an array,
                 * that also allows using an array of int as a scratch
                 * space. e.g. skb->cb[].
                 */
                if (off + size > mtrue_end) {
                        bpf_log(log,
                                "access beyond the end of member %s (mend:%u) in struct %s with off %u size %u\n",
                                mname, mtrue_end, tname, off, size);
                        return -EACCES;
                }

                return WALK_SCALAR;
        }
        bpf_log(log, "struct %s doesn't have field at offset %d\n", tname, off);
        return -EINVAL;
}

int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
                      const struct btf_type *t, int off, int size,
                      enum bpf_access_type atype __maybe_unused,
                      u32 *next_btf_id, enum bpf_type_flag *flag)
{
        enum bpf_type_flag tmp_flag = 0;
        int err;
        u32 id;

        do {
                err = btf_struct_walk(log, btf, t, off, size, &id, &tmp_flag);

                switch (err) {
                case WALK_PTR:
                        /* If we found the pointer or scalar on t+off,
                         * we're done.
                         */
                        *next_btf_id = id;
                        *flag = tmp_flag;
                        return PTR_TO_BTF_ID;
                case WALK_SCALAR:
                        return SCALAR_VALUE;
                case WALK_STRUCT:
                        /* We found nested struct, so continue the search
                         * by diving in it. At this point the offset is
                         * aligned with the new type, so set it to 0.
                         */
                        t = btf_type_by_id(btf, id);
                        off = 0;
                        break;
                default:
                        /* It's either error or unknown return value..
                         * scream and leave.
                         */
                        if (WARN_ONCE(err > 0, "unknown btf_struct_walk return value"))
                                return -EINVAL;
                        return err;
                }
        } while (t);

        return -EINVAL;
}

/* Check that two BTF types, each specified as an BTF object + id, are exactly
 * the same. Trivial ID check is not enough due to module BTFs, because we can
 * end up with two different module BTFs, but IDs point to the common type in
 * vmlinux BTF.
 */
static bool btf_types_are_same(const struct btf *btf1, u32 id1,
                               const struct btf *btf2, u32 id2)
{
        if (id1 != id2)
                return false;
        if (btf1 == btf2)
                return true;
        return btf_type_by_id(btf1, id1) == btf_type_by_id(btf2, id2);
}

bool btf_struct_ids_match(struct bpf_verifier_log *log,
                          const struct btf *btf, u32 id, int off,
                          const struct btf *need_btf, u32 need_type_id,
                          bool strict)
{
        const struct btf_type *type;
        enum bpf_type_flag flag;
        int err;

        /* Are we already done? */
        if (off == 0 && btf_types_are_same(btf, id, need_btf, need_type_id))
                return true;
        /* In case of strict type match, we do not walk struct, the top level
         * type match must succeed. When strict is true, off should have already
         * been 0.
         */
        if (strict)
                return false;
again:
        type = btf_type_by_id(btf, id);
        if (!type)
                return false;
        err = btf_struct_walk(log, btf, type, off, 1, &id, &flag);
        if (err != WALK_STRUCT)
                return false;

        /* We found nested struct object. If it matches
         * the requested ID, we're done. Otherwise let's
         * continue the search with offset 0 in the new
         * type.
         */
        if (!btf_types_are_same(btf, id, need_btf, need_type_id)) {
                off = 0;
                goto again;
        }

        return true;
}

static int __get_type_size(struct btf *btf, u32 btf_id,
                           const struct btf_type **bad_type)
{
        const struct btf_type *t;

        if (!btf_id)
                /* void */
                return 0;
        t = btf_type_by_id(btf, btf_id);
        while (t && btf_type_is_modifier(t))
                t = btf_type_by_id(btf, t->type);
        if (!t) {
                *bad_type = btf_type_by_id(btf, 0);
                return -EINVAL;
        }
        if (btf_type_is_ptr(t))
                /* kernel size of pointer. Not BPF's size of pointer*/
                return sizeof(void *);
        if (btf_type_is_int(t) || btf_type_is_enum(t))
                return t->size;
        *bad_type = t;
        return -EINVAL;
}

int btf_distill_func_proto(struct bpf_verifier_log *log,
                           struct btf *btf,
                           const struct btf_type *func,
                           const char *tname,
                           struct btf_func_model *m)
{
        const struct btf_param *args;
        const struct btf_type *t;
        u32 i, nargs;
        int ret;

        if (!func) {
                /* BTF function prototype doesn't match the verifier types.
                 * Fall back to MAX_BPF_FUNC_REG_ARGS u64 args.
                 */
                for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++)
                        m->arg_size[i] = 8;
                m->ret_size = 8;
                m->nr_args = MAX_BPF_FUNC_REG_ARGS;
                return 0;
        }
        args = (const struct btf_param *)(func + 1);
        nargs = btf_type_vlen(func);
        if (nargs > MAX_BPF_FUNC_ARGS) {
                bpf_log(log,
                        "The function %s has %d arguments. Too many.\n",
                        tname, nargs);
                return -EINVAL;
        }
        ret = __get_type_size(btf, func->type, &t);
        if (ret < 0) {
                bpf_log(log,
                        "The function %s return type %s is unsupported.\n",
                        tname, btf_kind_str[BTF_INFO_KIND(t->info)]);
                return -EINVAL;
        }
        m->ret_size = ret;

        for (i = 0; i < nargs; i++) {
                if (i == nargs - 1 && args[i].type == 0) {
                        bpf_log(log,
                                "The function %s with variable args is unsupported.\n",
                                tname);
                        return -EINVAL;
                }
                ret = __get_type_size(btf, args[i].type, &t);
                if (ret < 0) {
                        bpf_log(log,
                                "The function %s arg%d type %s is unsupported.\n",
                                tname, i, btf_kind_str[BTF_INFO_KIND(t->info)]);
                        return -EINVAL;
                }
                if (ret == 0) {
                        bpf_log(log,
                                "The function %s has malformed void argument.\n",
                                tname);
                        return -EINVAL;
                }
                m->arg_size[i] = ret;
        }
        m->nr_args = nargs;
        return 0;
}

/* Compare BTFs of two functions assuming only scalars and pointers to context.
 * t1 points to BTF_KIND_FUNC in btf1
 * t2 points to BTF_KIND_FUNC in btf2
 * Returns:
 * EINVAL - function prototype mismatch
 * EFAULT - verifier bug
 * 0 - 99% match. The last 1% is validated by the verifier.
 */
static int btf_check_func_type_match(struct bpf_verifier_log *log,
                                     struct btf *btf1, const struct btf_type *t1,
                                     struct btf *btf2, const struct btf_type *t2)
{
        const struct btf_param *args1, *args2;
        const char *fn1, *fn2, *s1, *s2;
        u32 nargs1, nargs2, i;

        fn1 = btf_name_by_offset(btf1, t1->name_off);
        fn2 = btf_name_by_offset(btf2, t2->name_off);

        if (btf_func_linkage(t1) != BTF_FUNC_GLOBAL) {
                bpf_log(log, "%s() is not a global function\n", fn1);
                return -EINVAL;
        }
        if (btf_func_linkage(t2) != BTF_FUNC_GLOBAL) {
                bpf_log(log, "%s() is not a global function\n", fn2);
                return -EINVAL;
        }

        t1 = btf_type_by_id(btf1, t1->type);
        if (!t1 || !btf_type_is_func_proto(t1))
                return -EFAULT;
        t2 = btf_type_by_id(btf2, t2->type);
        if (!t2 || !btf_type_is_func_proto(t2))
                return -EFAULT;

        args1 = (const struct btf_param *)(t1 + 1);
        nargs1 = btf_type_vlen(t1);
        args2 = (const struct btf_param *)(t2 + 1);
        nargs2 = btf_type_vlen(t2);

        if (nargs1 != nargs2) {
                bpf_log(log, "%s() has %d args while %s() has %d args\n",
                        fn1, nargs1, fn2, nargs2);
                return -EINVAL;
        }

        t1 = btf_type_skip_modifiers(btf1, t1->type, NULL);
        t2 = btf_type_skip_modifiers(btf2, t2->type, NULL);
        if (t1->info != t2->info) {
                bpf_log(log,
                        "Return type %s of %s() doesn't match type %s of %s()\n",
                        btf_type_str(t1), fn1,
                        btf_type_str(t2), fn2);
                return -EINVAL;
        }

        for (i = 0; i < nargs1; i++) {
                t1 = btf_type_skip_modifiers(btf1, args1[i].type, NULL);
                t2 = btf_type_skip_modifiers(btf2, args2[i].type, NULL);

                if (t1->info != t2->info) {
                        bpf_log(log, "arg%d in %s() is %s while %s() has %s\n",
                                i, fn1, btf_type_str(t1),
                                fn2, btf_type_str(t2));
                        return -EINVAL;
                }
                if (btf_type_has_size(t1) && t1->size != t2->size) {
                        bpf_log(log,
                                "arg%d in %s() has size %d while %s() has %d\n",
                                i, fn1, t1->size,
                                fn2, t2->size);
                        return -EINVAL;
                }

                /* global functions are validated with scalars and pointers
                 * to context only. And only global functions can be replaced.
                 * Hence type check only those types.
                 */
                if (btf_type_is_int(t1) || btf_type_is_enum(t1))
                        continue;
                if (!btf_type_is_ptr(t1)) {
                        bpf_log(log,
                                "arg%d in %s() has unrecognized type\n",
                                i, fn1);
                        return -EINVAL;
                }
                t1 = btf_type_skip_modifiers(btf1, t1->type, NULL);
                t2 = btf_type_skip_modifiers(btf2, t2->type, NULL);
                if (!btf_type_is_struct(t1)) {
                        bpf_log(log,
                                "arg%d in %s() is not a pointer to context\n",
                                i, fn1);
                        return -EINVAL;
                }
                if (!btf_type_is_struct(t2)) {
                        bpf_log(log,
                                "arg%d in %s() is not a pointer to context\n",
                                i, fn2);
                        return -EINVAL;
                }
                /* This is an optional check to make program writing easier.
                 * Compare names of structs and report an error to the user.
                 * btf_prepare_func_args() already checked that t2 struct
                 * is a context type. btf_prepare_func_args() will check
                 * later that t1 struct is a context type as well.
                 */
                s1 = btf_name_by_offset(btf1, t1->name_off);
                s2 = btf_name_by_offset(btf2, t2->name_off);
                if (strcmp(s1, s2)) {
                        bpf_log(log,
                                "arg%d %s(struct %s *) doesn't match %s(struct %s *)\n",
                                i, fn1, s1, fn2, s2);
                        return -EINVAL;
                }
        }
        return 0;
}

/* Compare BTFs of given program with BTF of target program */
int btf_check_type_match(struct bpf_verifier_log *log, const struct bpf_prog *prog,
                         struct btf *btf2, const struct btf_type *t2)
{
        struct btf *btf1 = prog->aux->btf;
        const struct btf_type *t1;
        u32 btf_id = 0;

        if (!prog->aux->func_info) {
                bpf_log(log, "Program extension requires BTF\n");
                return -EINVAL;
        }

        btf_id = prog->aux->func_info[0].type_id;
        if (!btf_id)
                return -EFAULT;

        t1 = btf_type_by_id(btf1, btf_id);
        if (!t1 || !btf_type_is_func(t1))
                return -EFAULT;

        return btf_check_func_type_match(log, btf1, t1, btf2, t2);
}

static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
#ifdef CONFIG_NET
        [PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
        [PTR_TO_SOCK_COMMON] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
        [PTR_TO_TCP_SOCK] = &btf_sock_ids[BTF_SOCK_TYPE_TCP],
#endif
};

/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
                                        const struct btf *btf,
                                        const struct btf_type *t, int rec)
{
        const struct btf_type *member_type;
        const struct btf_member *member;
        u32 i;

        if (!btf_type_is_struct(t))
                return false;

        for_each_member(i, t, member) {
                const struct btf_array *array;

                member_type = btf_type_skip_modifiers(btf, member->type, NULL);
                if (btf_type_is_struct(member_type)) {
                        if (rec >= 3) {
                                bpf_log(log, "max struct nesting depth exceeded\n");
                                return false;
                        }
                        if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
                                return false;
                        continue;
                }
                if (btf_type_is_array(member_type)) {
                        array = btf_type_array(member_type);
                        if (!array->nelems)
                                return false;
                        member_type = btf_type_skip_modifiers(btf, array->type, NULL);
                        if (!btf_type_is_scalar(member_type))
                                return false;
                        continue;
                }
                if (!btf_type_is_scalar(member_type))
                        return false;
        }
        return true;
}

static bool is_kfunc_arg_mem_size(const struct btf *btf,
                                  const struct btf_param *arg,
                                  const struct bpf_reg_state *reg)
{
        int len, sfx_len = sizeof("__sz") - 1;
        const struct btf_type *t;
        const char *param_name;

        t = btf_type_skip_modifiers(btf, arg->type, NULL);
        if (!btf_type_is_scalar(t) || reg->type != SCALAR_VALUE)
                return false;

        /* In the future, this can be ported to use BTF tagging */
        param_name = btf_name_by_offset(btf, arg->name_off);
        if (str_is_empty(param_name))
                return false;
        len = strlen(param_name);
        if (len < sfx_len)
                return false;
        param_name += len - sfx_len;
        if (strncmp(param_name, "__sz", sfx_len))
                return false;

        return true;
}

static int btf_check_func_arg_match(struct bpf_verifier_env *env,
                                    const struct btf *btf, u32 func_id,
                                    struct bpf_reg_state *regs,
                                    bool ptr_to_mem_ok)
{
        struct bpf_verifier_log *log = &env->log;
        u32 i, nargs, ref_id, ref_obj_id = 0;
        bool is_kfunc = btf_is_kernel(btf);
        bool rel = false, kptr_get = false;
        const char *func_name, *ref_tname;
        const struct btf_type *t, *ref_t;
        const struct btf_param *args;
        int ref_regno = 0, ret;

        t = btf_type_by_id(btf, func_id);
        if (!t || !btf_type_is_func(t)) {
                /* These checks were already done by the verifier while loading
                 * struct bpf_func_info or in add_kfunc_call().
                 */
                bpf_log(log, "BTF of func_id %u doesn't point to KIND_FUNC\n",
                        func_id);
                return -EFAULT;
        }
        func_name = btf_name_by_offset(btf, t->name_off);

        t = btf_type_by_id(btf, t->type);
        if (!t || !btf_type_is_func_proto(t)) {
                bpf_log(log, "Invalid BTF of func %s\n", func_name);
                return -EFAULT;
        }
        args = (const struct btf_param *)(t + 1);
        nargs = btf_type_vlen(t);
        if (nargs > MAX_BPF_FUNC_REG_ARGS) {
                bpf_log(log, "Function %s has %d > %d args\n", func_name, nargs,
                        MAX_BPF_FUNC_REG_ARGS);
                return -EINVAL;
        }

        if (is_kfunc) {
                /* Only kfunc can be release func */
                rel = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
                                                BTF_KFUNC_TYPE_RELEASE, func_id);
                kptr_get = btf_kfunc_id_set_contains(btf, resolve_prog_type(env->prog),
                                                     BTF_KFUNC_TYPE_KPTR_ACQUIRE, func_id);
        }

        /* check that BTF function arguments match actual types that the
         * verifier sees.
         */
        for (i = 0; i < nargs; i++) {
                enum bpf_arg_type arg_type = ARG_DONTCARE;
                u32 regno = i + 1;
                struct bpf_reg_state *reg = &regs[regno];

                t = btf_type_skip_modifiers(btf, args[i].type, NULL);
                if (btf_type_is_scalar(t)) {
                        if (reg->type == SCALAR_VALUE)
                                continue;
                        bpf_log(log, "R%d is not a scalar\n", regno);
                        return -EINVAL;
                }

                if (!btf_type_is_ptr(t)) {
                        bpf_log(log, "Unrecognized arg#%d type %s\n",
                                i, btf_type_str(t));
                        return -EINVAL;
                }

                ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
                ref_tname = btf_name_by_offset(btf, ref_t->name_off);

                if (rel && reg->ref_obj_id)
                        arg_type |= OBJ_RELEASE;
                ret = check_func_arg_reg_off(env, reg, regno, arg_type);
                if (ret < 0)
                        return ret;

                /* kptr_get is only true for kfunc */
                if (i == 0 && kptr_get) {
                        struct bpf_map_value_off_desc *off_desc;

                        if (reg->type != PTR_TO_MAP_VALUE) {
                                bpf_log(log, "arg#0 expected pointer to map value\n");
                                return -EINVAL;
                        }

                        /* check_func_arg_reg_off allows var_off for
                         * PTR_TO_MAP_VALUE, but we need fixed offset to find
                         * off_desc.
                         */
                        if (!tnum_is_const(reg->var_off)) {
                                bpf_log(log, "arg#0 must have constant offset\n");
                                return -EINVAL;
                        }

                        off_desc = bpf_map_kptr_off_contains(reg->map_ptr, reg->off + reg->var_off.value);
                        if (!off_desc || off_desc->type != BPF_KPTR_REF) {
                                bpf_log(log, "arg#0 no referenced kptr at map value offset=%llu\n",
                                        reg->off + reg->var_off.value);
                                return -EINVAL;
                        }

                        if (!btf_type_is_ptr(ref_t)) {
                                bpf_log(log, "arg#0 BTF type must be a double pointer\n");
                                return -EINVAL;
                        }

                        ref_t = btf_type_skip_modifiers(btf, ref_t->type, &ref_id);
                        ref_tname = btf_name_by_offset(btf, ref_t->name_off);

                        if (!btf_type_is_struct(ref_t)) {
                                bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
                                        func_name, i, btf_type_str(ref_t), ref_tname);
                                return -EINVAL;
                        }
                        if (!btf_struct_ids_match(log, btf, ref_id, 0, off_desc->kptr.btf,
                                                  off_desc->kptr.btf_id, true)) {
                                bpf_log(log, "kernel function %s args#%d expected pointer to %s %s\n",
                                        func_name, i, btf_type_str(ref_t), ref_tname);
                                return -EINVAL;
                        }
                        /* rest of the arguments can be anything, like normal kfunc */
                } else if (btf_get_prog_ctx_type(log, btf, t, env->prog->type, i)) {
                        /* If function expects ctx type in BTF check that caller
                         * is passing PTR_TO_CTX.
                         */
                        if (reg->type != PTR_TO_CTX) {
                                bpf_log(log,
                                        "arg#%d expected pointer to ctx, but got %s\n",
                                        i, btf_type_str(t));
                                return -EINVAL;
                        }
                } else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
                           (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
                        const struct btf_type *reg_ref_t;
                        const struct btf *reg_btf;
                        const char *reg_ref_tname;
                        u32 reg_ref_id;

                        if (!btf_type_is_struct(ref_t)) {
                                bpf_log(log, "kernel function %s args#%d pointer type %s %s is not supported\n",
                                        func_name, i, btf_type_str(ref_t),
                                        ref_tname);
                                return -EINVAL;
                        }

                        if (reg->type == PTR_TO_BTF_ID) {
                                reg_btf = reg->btf;
                                reg_ref_id = reg->btf_id;
                                /* Ensure only one argument is referenced PTR_TO_BTF_ID */
                                if (reg->ref_obj_id) {
                                        if (ref_obj_id) {
                                                bpf_log(log, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
                                                        regno, reg->ref_obj_id, ref_obj_id);
                                                return -EFAULT;
                                        }
                                        ref_regno = regno;
                                        ref_obj_id = reg->ref_obj_id;
                                }
                        } else {
                                reg_btf = btf_vmlinux;
                                reg_ref_id = *reg2btf_ids[base_type(reg->type)];
                        }

                        reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
                                                            &reg_ref_id);
                        reg_ref_tname = btf_name_by_offset(reg_btf,
                                                           reg_ref_t->name_off);
                        if (!btf_struct_ids_match(log, reg_btf, reg_ref_id,
                                                  reg->off, btf, ref_id, rel && reg->ref_obj_id)) {
                                bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
                                        func_name, i,
                                        btf_type_str(ref_t), ref_tname,
                                        regno, btf_type_str(reg_ref_t),
                                        reg_ref_tname);
                                return -EINVAL;
                        }
                } else if (ptr_to_mem_ok) {
                        const struct btf_type *resolve_ret;
                        u32 type_size;

                        if (is_kfunc) {
                                bool arg_mem_size = i + 1 < nargs && is_kfunc_arg_mem_size(btf, &args[i + 1], &regs[regno + 1]);

                                /* Permit pointer to mem, but only when argument
                                 * type is pointer to scalar, or struct composed
                                 * (recursively) of scalars.
                                 * When arg_mem_size is true, the pointer can be
                                 * void *.
                                 */
                                if (!btf_type_is_scalar(ref_t) &&
                                    !__btf_type_is_scalar_struct(log, btf, ref_t, 0) &&
                                    (arg_mem_size ? !btf_type_is_void(ref_t) : 1)) {
                                        bpf_log(log,
                                                "arg#%d pointer type %s %s must point to %sscalar, or struct with scalar\n",
                                                i, btf_type_str(ref_t), ref_tname, arg_mem_size ? "void, " : "");
                                        return -EINVAL;
                                }

                                /* Check for mem, len pair */
                                if (arg_mem_size) {
                                        if (check_kfunc_mem_size_reg(env, &regs[regno + 1], regno + 1)) {
                                                bpf_log(log, "arg#%d arg#%d memory, len pair leads to invalid memory access\n",
                                                        i, i + 1);
                                                return -EINVAL;
                                        }
                                        i++;
                                        continue;
                                }
                        }

                        resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
                        if (IS_ERR(resolve_ret)) {
                                bpf_log(log,
                                        "arg#%d reference type('%s %s') size cannot be determined: %ld\n",
                                        i, btf_type_str(ref_t), ref_tname,
                                        PTR_ERR(resolve_ret));
                                return -EINVAL;
                        }

                        if (check_mem_reg(env, reg, regno, type_size))
                                return -EINVAL;
                } else {
                        bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
                                is_kfunc ? "kernel " : "", func_name, func_id);
                        return -EINVAL;
                }
        }

        /* Either both are set, or neither */
        WARN_ON_ONCE((ref_obj_id && !ref_regno) || (!ref_obj_id && ref_regno));
        /* We already made sure ref_obj_id is set only for one argument. We do
         * allow (!rel && ref_obj_id), so that passing such referenced
         * PTR_TO_BTF_ID to other kfuncs works. Note that rel is only true when
         * is_kfunc is true.
         */
        if (rel && !ref_obj_id) {
                bpf_log(log, "release kernel function %s expects refcounted PTR_TO_BTF_ID\n",
                        func_name);
                return -EINVAL;
        }
        /* returns argument register number > 0 in case of reference release kfunc */
        return rel ? ref_regno : 0;
}

/* Compare BTF of a function with given bpf_reg_state.
 * Returns:
 * EFAULT - there is a verifier bug. Abort verification.
 * EINVAL - there is a type mismatch or BTF is not available.
 * 0 - BTF matches with what bpf_reg_state expects.
 * Only PTR_TO_CTX and SCALAR_VALUE states are recognized.
 */
int btf_check_subprog_arg_match(struct bpf_verifier_env *env, int subprog,
                                struct bpf_reg_state *regs)
{
        struct bpf_prog *prog = env->prog;
        struct btf *btf = prog->aux->btf;
        bool is_global;
        u32 btf_id;
        int err;

        if (!prog->aux->func_info)
                return -EINVAL;

        btf_id = prog->aux->func_info[subprog].type_id;
        if (!btf_id)
                return -EFAULT;

        if (prog->aux->func_info_aux[subprog].unreliable)
                return -EINVAL;

        is_global = prog->aux->func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
        err = btf_check_func_arg_match(env, btf, btf_id, regs, is_global);

        /* Compiler optimizations can remove arguments from static functions
         * or mismatched type can be passed into a global function.
         * In such cases mark the function as unreliable from BTF point of view.
         */
        if (err)
                prog->aux->func_info_aux[subprog].unreliable = true;
        return err;
}

int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
                              const struct btf *btf, u32 func_id,
                              struct bpf_reg_state *regs)
{
        return btf_check_func_arg_match(env, btf, func_id, regs, true);
}

/* Convert BTF of a function into bpf_reg_state if possible
 * Returns:
 * EFAULT - there is a verifier bug. Abort verification.
 * EINVAL - cannot convert BTF.
 * 0 - Successfully converted BTF into bpf_reg_state
 * (either PTR_TO_CTX or SCALAR_VALUE).
 */
int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
                          struct bpf_reg_state *regs)
{
        struct bpf_verifier_log *log = &env->log;
        struct bpf_prog *prog = env->prog;
        enum bpf_prog_type prog_type = prog->type;
        struct btf *btf = prog->aux->btf;
        const struct btf_param *args;
        const struct btf_type *t, *ref_t;
        u32 i, nargs, btf_id;
        const char *tname;

        if (!prog->aux->func_info ||
            prog->aux->func_info_aux[subprog].linkage != BTF_FUNC_GLOBAL) {
                bpf_log(log, "Verifier bug\n");
                return -EFAULT;
        }

        btf_id = prog->aux->func_info[subprog].type_id;
        if (!btf_id) {
                bpf_log(log, "Global functions need valid BTF\n");
                return -EFAULT;
        }

        t = btf_type_by_id(btf, btf_id);
        if (!t || !btf_type_is_func(t)) {
                /* These checks were already done by the verifier while loading
                 * struct bpf_func_info
                 */
                bpf_log(log, "BTF of func#%d doesn't point to KIND_FUNC\n",
                        subprog);
                return -EFAULT;
        }
        tname = btf_name_by_offset(btf, t->name_off);

        if (log->level & BPF_LOG_LEVEL)
                bpf_log(log, "Validating %s() func#%d...\n",
                        tname, subprog);

        if (prog->aux->func_info_aux[subprog].unreliable) {
                bpf_log(log, "Verifier bug in function %s()\n", tname);
                return -EFAULT;
        }
        if (prog_type == BPF_PROG_TYPE_EXT)
                prog_type = prog->aux->dst_prog->type;

        t = btf_type_by_id(btf, t->type);
        if (!t || !btf_type_is_func_proto(t)) {
                bpf_log(log, "Invalid type of function %s()\n", tname);
                return -EFAULT;
        }
        args = (const struct btf_param *)(t + 1);
        nargs = btf_type_vlen(t);
        if (nargs > MAX_BPF_FUNC_REG_ARGS) {
                bpf_log(log, "Global function %s() with %d > %d args. Buggy compiler.\n",
                        tname, nargs, MAX_BPF_FUNC_REG_ARGS);
                return -EINVAL;
        }
        /* check that function returns int */
        t = btf_type_by_id(btf, t->type);
        while (btf_type_is_modifier(t))
                t = btf_type_by_id(btf, t->type);
        if (!btf_type_is_int(t) && !btf_type_is_enum(t)) {
                bpf_log(log,
                        "Global function %s() doesn't return scalar. Only those are supported.\n",
                        tname);
                return -EINVAL;
        }
        /* Convert BTF function arguments into verifier types.
         * Only PTR_TO_CTX and SCALAR are supported atm.
         */
        for (i = 0; i < nargs; i++) {
                struct bpf_reg_state *reg = &regs[i + 1];

                t = btf_type_by_id(btf, args[i].type);
                while (btf_type_is_modifier(t))
                        t = btf_type_by_id(btf, t->type);
                if (btf_type_is_int(t) || btf_type_is_enum(t)) {
                        reg->type = SCALAR_VALUE;
                        continue;
                }
                if (btf_type_is_ptr(t)) {
                        if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
                                reg->type = PTR_TO_CTX;
                                continue;
                        }

                        t = btf_type_skip_modifiers(btf, t->type, NULL);

                        ref_t = btf_resolve_size(btf, t, &reg->mem_size);
                        if (IS_ERR(ref_t)) {
                                bpf_log(log,
                                    "arg#%d reference type('%s %s') size cannot be determined: %ld\n",
                                    i, btf_type_str(t), btf_name_by_offset(btf, t->name_off),
                                        PTR_ERR(ref_t));
                                return -EINVAL;
                        }

                        reg->type = PTR_TO_MEM | PTR_MAYBE_NULL;
                        reg->id = ++env->id_gen;

                        continue;
                }
                bpf_log(log, "Arg#%d type %s in %s() is not supported yet.\n",
                        i, btf_kind_str[BTF_INFO_KIND(t->info)], tname);
                return -EINVAL;
        }
        return 0;
}

static void btf_type_show(const struct btf *btf, u32 type_id, void *obj,
                          struct btf_show *show)
{
        const struct btf_type *t = btf_type_by_id(btf, type_id);

        show->btf = btf;
        memset(&show->state, 0, sizeof(show->state));
        memset(&show->obj, 0, sizeof(show->obj));

        btf_type_ops(t)->show(btf, t, type_id, obj, 0, show);
}

static void btf_seq_show(struct btf_show *show, const char *fmt,
                         va_list args)
{
        seq_vprintf((struct seq_file *)show->target, fmt, args);
}

int btf_type_seq_show_flags(const struct btf *btf, u32 type_id,
                            void *obj, struct seq_file *m, u64 flags)
{
        struct btf_show sseq;

        sseq.target = m;
        sseq.showfn = btf_seq_show;
        sseq.flags = flags;

        btf_type_show(btf, type_id, obj, &sseq);

        return sseq.state.status;
}

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
                       struct seq_file *m)
{
        (void) btf_type_seq_show_flags(btf, type_id, obj, m,
                                       BTF_SHOW_NONAME | BTF_SHOW_COMPACT |
                                       BTF_SHOW_ZERO | BTF_SHOW_UNSAFE);
}

struct btf_show_snprintf {
        struct btf_show show;
        int len_left;           /* space left in string */
        int len;                /* length we would have written */
};

static void btf_snprintf_show(struct btf_show *show, const char *fmt,
                              va_list args)
{
        struct btf_show_snprintf *ssnprintf = (struct btf_show_snprintf *)show;
        int len;

        len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);

        if (len < 0) {
                ssnprintf->len_left = 0;
                ssnprintf->len = len;
        } else if (len > ssnprintf->len_left) {
                /* no space, drive on to get length we would have written */
                ssnprintf->len_left = 0;
                ssnprintf->len += len;
        } else {
                ssnprintf->len_left -= len;
                ssnprintf->len += len;
                show->target += len;
        }
}

int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
                           char *buf, int len, u64 flags)
{
        struct btf_show_snprintf ssnprintf;

        ssnprintf.show.target = buf;
        ssnprintf.show.flags = flags;
        ssnprintf.show.showfn = btf_snprintf_show;
        ssnprintf.len_left = len;
        ssnprintf.len = 0;

        btf_type_show(btf, type_id, obj, (struct btf_show *)&ssnprintf);

        /* If we encountered an error, return it. */
        if (ssnprintf.show.state.status)
                return ssnprintf.show.state.status;

        /* Otherwise return length we would have written */
        return ssnprintf.len;
}

#ifdef CONFIG_PROC_FS
static void bpf_btf_show_fdinfo(struct seq_file *m, struct file *filp)
{
        const struct btf *btf = filp->private_data;

        seq_printf(m, "btf_id:\t%u\n", btf->id);
}
#endif

static int btf_release(struct inode *inode, struct file *filp)
{
        btf_put(filp->private_data);
        return 0;
}

const struct file_operations btf_fops = {
#ifdef CONFIG_PROC_FS
        .show_fdinfo    = bpf_btf_show_fdinfo,
#endif
        .release        = btf_release,
};

static int __btf_new_fd(struct btf *btf)
{
        return anon_inode_getfd("btf", &btf_fops, btf, O_RDONLY | O_CLOEXEC);
}

int btf_new_fd(const union bpf_attr *attr, bpfptr_t uattr)
{
        struct btf *btf;
        int ret;

        btf = btf_parse(make_bpfptr(attr->btf, uattr.is_kernel),
                        attr->btf_size, attr->btf_log_level,
                        u64_to_user_ptr(attr->btf_log_buf),
                        attr->btf_log_size);
        if (IS_ERR(btf))
                return PTR_ERR(btf);

        ret = btf_alloc_id(btf);
        if (ret) {
                btf_free(btf);
                return ret;
        }

        /*
         * The BTF ID is published to the userspace.
         * All BTF free must go through call_rcu() from
         * now on (i.e. free by calling btf_put()).
         */

        ret = __btf_new_fd(btf);
        if (ret < 0)
                btf_put(btf);

        return ret;
}

struct btf *btf_get_by_fd(int fd)
{
        struct btf *btf;
        struct fd f;

        f = fdget(fd);

        if (!f.file)
                return ERR_PTR(-EBADF);

        if (f.file->f_op != &btf_fops) {
                fdput(f);
                return ERR_PTR(-EINVAL);
        }

        btf = f.file->private_data;
        refcount_inc(&btf->refcnt);
        fdput(f);

        return btf;
}

int btf_get_info_by_fd(const struct btf *btf,
                       const union bpf_attr *attr,
                       union bpf_attr __user *uattr)
{
        struct bpf_btf_info __user *uinfo;
        struct bpf_btf_info info;
        u32 info_copy, btf_copy;
        void __user *ubtf;
        char __user *uname;
        u32 uinfo_len, uname_len, name_len;
        int ret = 0;

        uinfo = u64_to_user_ptr(attr->info.info);
        uinfo_len = attr->info.info_len;

        info_copy = min_t(u32, uinfo_len, sizeof(info));
        memset(&info, 0, sizeof(info));
        if (copy_from_user(&info, uinfo, info_copy))
                return -EFAULT;

        info.id = btf->id;
        ubtf = u64_to_user_ptr(info.btf);
        btf_copy = min_t(u32, btf->data_size, info.btf_size);
        if (copy_to_user(ubtf, btf->data, btf_copy))
                return -EFAULT;
        info.btf_size = btf->data_size;

        info.kernel_btf = btf->kernel_btf;

        uname = u64_to_user_ptr(info.name);
        uname_len = info.name_len;
        if (!uname ^ !uname_len)
                return -EINVAL;

        name_len = strlen(btf->name);
        info.name_len = name_len;

        if (uname) {
                if (uname_len >= name_len + 1) {
                        if (copy_to_user(uname, btf->name, name_len + 1))
                                return -EFAULT;
                } else {
                        char zero = '\0';

                        if (copy_to_user(uname, btf->name, uname_len - 1))
                                return -EFAULT;
                        if (put_user(zero, uname + uname_len - 1))
                                return -EFAULT;
                        /* let user-space know about too short buffer */
                        ret = -ENOSPC;
                }
        }

        if (copy_to_user(uinfo, &info, info_copy) ||
            put_user(info_copy, &uattr->info.info_len))
                return -EFAULT;

        return ret;
}

int btf_get_fd_by_id(u32 id)
{
        struct btf *btf;
        int fd;

        rcu_read_lock();
        btf = idr_find(&btf_idr, id);
        if (!btf || !refcount_inc_not_zero(&btf->refcnt))
                btf = ERR_PTR(-ENOENT);
        rcu_read_unlock();

        if (IS_ERR(btf))
                return PTR_ERR(btf);

        fd = __btf_new_fd(btf);
        if (fd < 0)
                btf_put(btf);

        return fd;
}

u32 btf_obj_id(const struct btf *btf)
{
        return btf->id;
}

bool btf_is_kernel(const struct btf *btf)
{
        return btf->kernel_btf;
}

bool btf_is_module(const struct btf *btf)
{
        return btf->kernel_btf && strcmp(btf->name, "vmlinux") != 0;
}

static int btf_id_cmp_func(const void *a, const void *b)
{
        const int *pa = a, *pb = b;

        return *pa - *pb;
}

bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
{
        return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
}

enum {
        BTF_MODULE_F_LIVE = (1 << 0),
};

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
struct btf_module {
        struct list_head list;
        struct module *module;
        struct btf *btf;
        struct bin_attribute *sysfs_attr;
        int flags;
};

static LIST_HEAD(btf_modules);
static DEFINE_MUTEX(btf_module_mutex);

static ssize_t
btf_module_read(struct file *file, struct kobject *kobj,
                struct bin_attribute *bin_attr,
                char *buf, loff_t off, size_t len)
{
        const struct btf *btf = bin_attr->private;

        memcpy(buf, btf->data + off, len);
        return len;
}

static void purge_cand_cache(struct btf *btf);

static int btf_module_notify(struct notifier_block *nb, unsigned long op,
                             void *module)
{
        struct btf_module *btf_mod, *tmp;
        struct module *mod = module;
        struct btf *btf;
        int err = 0;

        if (mod->btf_data_size == 0 ||
            (op != MODULE_STATE_COMING && op != MODULE_STATE_LIVE &&
             op != MODULE_STATE_GOING))
                goto out;

        switch (op) {
        case MODULE_STATE_COMING:
                btf_mod = kzalloc(sizeof(*btf_mod), GFP_KERNEL);
                if (!btf_mod) {
                        err = -ENOMEM;
                        goto out;
                }
                btf = btf_parse_module(mod->name, mod->btf_data, mod->btf_data_size);
                if (IS_ERR(btf)) {
                        pr_warn("failed to validate module [%s] BTF: %ld\n",
                                mod->name, PTR_ERR(btf));
                        kfree(btf_mod);
                        if (!IS_ENABLED(CONFIG_MODULE_ALLOW_BTF_MISMATCH))
                                err = PTR_ERR(btf);
                        goto out;
                }
                err = btf_alloc_id(btf);
                if (err) {
                        btf_free(btf);
                        kfree(btf_mod);
                        goto out;
                }

                purge_cand_cache(NULL);
                mutex_lock(&btf_module_mutex);
                btf_mod->module = module;
                btf_mod->btf = btf;
                list_add(&btf_mod->list, &btf_modules);
                mutex_unlock(&btf_module_mutex);

                if (IS_ENABLED(CONFIG_SYSFS)) {
                        struct bin_attribute *attr;

                        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
                        if (!attr)
                                goto out;

                        sysfs_bin_attr_init(attr);
                        attr->attr.name = btf->name;
                        attr->attr.mode = 0444;
                        attr->size = btf->data_size;
                        attr->private = btf;
                        attr->read = btf_module_read;

                        err = sysfs_create_bin_file(btf_kobj, attr);
                        if (err) {
                                pr_warn("failed to register module [%s] BTF in sysfs: %d\n",
                                        mod->name, err);
                                kfree(attr);
                                err = 0;
                                goto out;
                        }

                        btf_mod->sysfs_attr = attr;
                }

                break;
        case MODULE_STATE_LIVE:
                mutex_lock(&btf_module_mutex);
                list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
                        if (btf_mod->module != module)
                                continue;

                        btf_mod->flags |= BTF_MODULE_F_LIVE;
                        break;
                }
                mutex_unlock(&btf_module_mutex);
                break;
        case MODULE_STATE_GOING:
                mutex_lock(&btf_module_mutex);
                list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
                        if (btf_mod->module != module)
                                continue;

                        list_del(&btf_mod->list);
                        if (btf_mod->sysfs_attr)
                                sysfs_remove_bin_file(btf_kobj, btf_mod->sysfs_attr);
                        purge_cand_cache(btf_mod->btf);
                        btf_put(btf_mod->btf);
                        kfree(btf_mod->sysfs_attr);
                        kfree(btf_mod);
                        break;
                }
                mutex_unlock(&btf_module_mutex);
                break;
        }
out:
        return notifier_from_errno(err);
}

static struct notifier_block btf_module_nb = {
        .notifier_call = btf_module_notify,
};

static int __init btf_module_init(void)
{
        register_module_notifier(&btf_module_nb);
        return 0;
}

fs_initcall(btf_module_init);
#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */

struct module *btf_try_get_module(const struct btf *btf)
{
        struct module *res = NULL;
#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
        struct btf_module *btf_mod, *tmp;

        mutex_lock(&btf_module_mutex);
        list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
                if (btf_mod->btf != btf)
                        continue;

                /* We must only consider module whose __init routine has
                 * finished, hence we must check for BTF_MODULE_F_LIVE flag,
                 * which is set from the notifier callback for
                 * MODULE_STATE_LIVE.
                 */
                if ((btf_mod->flags & BTF_MODULE_F_LIVE) && try_module_get(btf_mod->module))
                        res = btf_mod->module;

                break;
        }
        mutex_unlock(&btf_module_mutex);
#endif

        return res;
}

/* Returns struct btf corresponding to the struct module.
 * This function can return NULL or ERR_PTR.
 */
static struct btf *btf_get_module_btf(const struct module *module)
{
#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
        struct btf_module *btf_mod, *tmp;
#endif
        struct btf *btf = NULL;

        if (!module) {
                btf = bpf_get_btf_vmlinux();
                if (!IS_ERR_OR_NULL(btf))
                        btf_get(btf);
                return btf;
        }

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
        mutex_lock(&btf_module_mutex);
        list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
                if (btf_mod->module != module)
                        continue;

                btf_get(btf_mod->btf);
                btf = btf_mod->btf;
                break;
        }
        mutex_unlock(&btf_module_mutex);
#endif

        return btf;
}

BPF_CALL_4(bpf_btf_find_by_name_kind, char *, name, int, name_sz, u32, kind, int, flags)
{
        struct btf *btf = NULL;
        int btf_obj_fd = 0;
        long ret;

        if (flags)
                return -EINVAL;

        if (name_sz <= 1 || name[name_sz - 1])
                return -EINVAL;

        ret = bpf_find_btf_id(name, kind, &btf);
        if (ret > 0 && btf_is_module(btf)) {
                btf_obj_fd = __btf_new_fd(btf);
                if (btf_obj_fd < 0) {
                        btf_put(btf);
                        return btf_obj_fd;
                }
                return ret | (((u64)btf_obj_fd) << 32);
        }
        if (ret > 0)
                btf_put(btf);
        return ret;
}

const struct bpf_func_proto bpf_btf_find_by_name_kind_proto = {
        .func           = bpf_btf_find_by_name_kind,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_MEM | MEM_RDONLY,
        .arg2_type      = ARG_CONST_SIZE,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_ANYTHING,
};

BTF_ID_LIST_GLOBAL(btf_tracing_ids, MAX_BTF_TRACING_TYPE)
#define BTF_TRACING_TYPE(name, type) BTF_ID(struct, type)
BTF_TRACING_TYPE_xxx
#undef BTF_TRACING_TYPE

/* Kernel Function (kfunc) BTF ID set registration API */

static int __btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook,
                                    enum btf_kfunc_type type,
                                    struct btf_id_set *add_set, bool vmlinux_set)
{
        struct btf_kfunc_set_tab *tab;
        struct btf_id_set *set;
        u32 set_cnt;
        int ret;

        if (hook >= BTF_KFUNC_HOOK_MAX || type >= BTF_KFUNC_TYPE_MAX) {
                ret = -EINVAL;
                goto end;
        }

        if (!add_set->cnt)
                return 0;

        tab = btf->kfunc_set_tab;
        if (!tab) {
                tab = kzalloc(sizeof(*tab), GFP_KERNEL | __GFP_NOWARN);
                if (!tab)
                        return -ENOMEM;
                btf->kfunc_set_tab = tab;
        }

        set = tab->sets[hook][type];
        /* Warn when register_btf_kfunc_id_set is called twice for the same hook
         * for module sets.
         */
        if (WARN_ON_ONCE(set && !vmlinux_set)) {
                ret = -EINVAL;
                goto end;
        }

        /* We don't need to allocate, concatenate, and sort module sets, because
         * only one is allowed per hook. Hence, we can directly assign the
         * pointer and return.
         */
        if (!vmlinux_set) {
                tab->sets[hook][type] = add_set;
                return 0;
        }

        /* In case of vmlinux sets, there may be more than one set being
         * registered per hook. To create a unified set, we allocate a new set
         * and concatenate all individual sets being registered. While each set
         * is individually sorted, they may become unsorted when concatenated,
         * hence re-sorting the final set again is required to make binary
         * searching the set using btf_id_set_contains function work.
         */
        set_cnt = set ? set->cnt : 0;

        if (set_cnt > U32_MAX - add_set->cnt) {
                ret = -EOVERFLOW;
                goto end;
        }

        if (set_cnt + add_set->cnt > BTF_KFUNC_SET_MAX_CNT) {
                ret = -E2BIG;
                goto end;
        }

        /* Grow set */
        set = krealloc(tab->sets[hook][type],
                       offsetof(struct btf_id_set, ids[set_cnt + add_set->cnt]),
                       GFP_KERNEL | __GFP_NOWARN);
        if (!set) {
                ret = -ENOMEM;
                goto end;
        }

        /* For newly allocated set, initialize set->cnt to 0 */
        if (!tab->sets[hook][type])
                set->cnt = 0;
        tab->sets[hook][type] = set;

        /* Concatenate the two sets */
        memcpy(set->ids + set->cnt, add_set->ids, add_set->cnt * sizeof(set->ids[0]));
        set->cnt += add_set->cnt;

        sort(set->ids, set->cnt, sizeof(set->ids[0]), btf_id_cmp_func, NULL);

        return 0;
end:
        btf_free_kfunc_set_tab(btf);
        return ret;
}

static int btf_populate_kfunc_set(struct btf *btf, enum btf_kfunc_hook hook,
                                  const struct btf_kfunc_id_set *kset)
{
        bool vmlinux_set = !btf_is_module(btf);
        int type, ret = 0;

        for (type = 0; type < ARRAY_SIZE(kset->sets); type++) {
                if (!kset->sets[type])
                        continue;

                ret = __btf_populate_kfunc_set(btf, hook, type, kset->sets[type], vmlinux_set);
                if (ret)
                        break;
        }
        return ret;
}

static bool __btf_kfunc_id_set_contains(const struct btf *btf,
                                        enum btf_kfunc_hook hook,
                                        enum btf_kfunc_type type,
                                        u32 kfunc_btf_id)
{
        struct btf_id_set *set;

        if (hook >= BTF_KFUNC_HOOK_MAX || type >= BTF_KFUNC_TYPE_MAX)
                return false;
        if (!btf->kfunc_set_tab)
                return false;
        set = btf->kfunc_set_tab->sets[hook][type];
        if (!set)
                return false;
        return btf_id_set_contains(set, kfunc_btf_id);
}

static int bpf_prog_type_to_kfunc_hook(enum bpf_prog_type prog_type)
{
        switch (prog_type) {
        case BPF_PROG_TYPE_XDP:
                return BTF_KFUNC_HOOK_XDP;
        case BPF_PROG_TYPE_SCHED_CLS:
                return BTF_KFUNC_HOOK_TC;
        case BPF_PROG_TYPE_STRUCT_OPS:
                return BTF_KFUNC_HOOK_STRUCT_OPS;
        case BPF_PROG_TYPE_TRACING:
                return BTF_KFUNC_HOOK_TRACING;
        case BPF_PROG_TYPE_SYSCALL:
                return BTF_KFUNC_HOOK_SYSCALL;
        default:
                return BTF_KFUNC_HOOK_MAX;
        }
}

/* Caution:
 * Reference to the module (obtained using btf_try_get_module) corresponding to
 * the struct btf *MUST* be held when calling this function from verifier
 * context. This is usually true as we stash references in prog's kfunc_btf_tab;
 * keeping the reference for the duration of the call provides the necessary
 * protection for looking up a well-formed btf->kfunc_set_tab.
 */
bool btf_kfunc_id_set_contains(const struct btf *btf,
                               enum bpf_prog_type prog_type,
                               enum btf_kfunc_type type, u32 kfunc_btf_id)
{
        enum btf_kfunc_hook hook;

        hook = bpf_prog_type_to_kfunc_hook(prog_type);
        return __btf_kfunc_id_set_contains(btf, hook, type, kfunc_btf_id);
}

/* This function must be invoked only from initcalls/module init functions */
int register_btf_kfunc_id_set(enum bpf_prog_type prog_type,
                              const struct btf_kfunc_id_set *kset)
{
        enum btf_kfunc_hook hook;
        struct btf *btf;
        int ret;

        btf = btf_get_module_btf(kset->owner);
        if (!btf) {
                if (!kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
                        pr_err("missing vmlinux BTF, cannot register kfuncs\n");
                        return -ENOENT;
                }
                if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
                        pr_err("missing module BTF, cannot register kfuncs\n");
                        return -ENOENT;
                }
                return 0;
        }
        if (IS_ERR(btf))
                return PTR_ERR(btf);

        hook = bpf_prog_type_to_kfunc_hook(prog_type);
        ret = btf_populate_kfunc_set(btf, hook, kset);
        btf_put(btf);
        return ret;
}
EXPORT_SYMBOL_GPL(register_btf_kfunc_id_set);

s32 btf_find_dtor_kfunc(struct btf *btf, u32 btf_id)
{
        struct btf_id_dtor_kfunc_tab *tab = btf->dtor_kfunc_tab;
        struct btf_id_dtor_kfunc *dtor;

        if (!tab)
                return -ENOENT;
        /* Even though the size of tab->dtors[0] is > sizeof(u32), we only need
         * to compare the first u32 with btf_id, so we can reuse btf_id_cmp_func.
         */
        BUILD_BUG_ON(offsetof(struct btf_id_dtor_kfunc, btf_id) != 0);
        dtor = bsearch(&btf_id, tab->dtors, tab->cnt, sizeof(tab->dtors[0]), btf_id_cmp_func);
        if (!dtor)
                return -ENOENT;
        return dtor->kfunc_btf_id;
}

static int btf_check_dtor_kfuncs(struct btf *btf, const struct btf_id_dtor_kfunc *dtors, u32 cnt)
{
        const struct btf_type *dtor_func, *dtor_func_proto, *t;
        const struct btf_param *args;
        s32 dtor_btf_id;
        u32 nr_args, i;

        for (i = 0; i < cnt; i++) {
                dtor_btf_id = dtors[i].kfunc_btf_id;

                dtor_func = btf_type_by_id(btf, dtor_btf_id);
                if (!dtor_func || !btf_type_is_func(dtor_func))
                        return -EINVAL;

                dtor_func_proto = btf_type_by_id(btf, dtor_func->type);
                if (!dtor_func_proto || !btf_type_is_func_proto(dtor_func_proto))
                        return -EINVAL;

                /* Make sure the prototype of the destructor kfunc is 'void func(type *)' */
                t = btf_type_by_id(btf, dtor_func_proto->type);
                if (!t || !btf_type_is_void(t))
                        return -EINVAL;

                nr_args = btf_type_vlen(dtor_func_proto);
                if (nr_args != 1)
                        return -EINVAL;
                args = btf_params(dtor_func_proto);
                t = btf_type_by_id(btf, args[0].type);
                /* Allow any pointer type, as width on targets Linux supports
                 * will be same for all pointer types (i.e. sizeof(void *))
                 */
                if (!t || !btf_type_is_ptr(t))
                        return -EINVAL;
        }
        return 0;
}

/* This function must be invoked only from initcalls/module init functions */
int register_btf_id_dtor_kfuncs(const struct btf_id_dtor_kfunc *dtors, u32 add_cnt,
                                struct module *owner)
{
        struct btf_id_dtor_kfunc_tab *tab;
        struct btf *btf;
        u32 tab_cnt;
        int ret;

        btf = btf_get_module_btf(owner);
        if (!btf) {
                if (!owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
                        pr_err("missing vmlinux BTF, cannot register dtor kfuncs\n");
                        return -ENOENT;
                }
                if (owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
                        pr_err("missing module BTF, cannot register dtor kfuncs\n");
                        return -ENOENT;
                }
                return 0;
        }
        if (IS_ERR(btf))
                return PTR_ERR(btf);

        if (add_cnt >= BTF_DTOR_KFUNC_MAX_CNT) {
                pr_err("cannot register more than %d kfunc destructors\n", BTF_DTOR_KFUNC_MAX_CNT);
                ret = -E2BIG;
                goto end;
        }

        /* Ensure that the prototype of dtor kfuncs being registered is sane */
        ret = btf_check_dtor_kfuncs(btf, dtors, add_cnt);
        if (ret < 0)
                goto end;

        tab = btf->dtor_kfunc_tab;
        /* Only one call allowed for modules */
        if (WARN_ON_ONCE(tab && btf_is_module(btf))) {
                ret = -EINVAL;
                goto end;
        }

        tab_cnt = tab ? tab->cnt : 0;
        if (tab_cnt > U32_MAX - add_cnt) {
                ret = -EOVERFLOW;
                goto end;
        }
        if (tab_cnt + add_cnt >= BTF_DTOR_KFUNC_MAX_CNT) {
                pr_err("cannot register more than %d kfunc destructors\n", BTF_DTOR_KFUNC_MAX_CNT);
                ret = -E2BIG;
                goto end;
        }

        tab = krealloc(btf->dtor_kfunc_tab,
                       offsetof(struct btf_id_dtor_kfunc_tab, dtors[tab_cnt + add_cnt]),
                       GFP_KERNEL | __GFP_NOWARN);
        if (!tab) {
                ret = -ENOMEM;
                goto end;
        }

        if (!btf->dtor_kfunc_tab)
                tab->cnt = 0;
        btf->dtor_kfunc_tab = tab;

        memcpy(tab->dtors + tab->cnt, dtors, add_cnt * sizeof(tab->dtors[0]));
        tab->cnt += add_cnt;

        sort(tab->dtors, tab->cnt, sizeof(tab->dtors[0]), btf_id_cmp_func, NULL);

        return 0;
end:
        btf_free_dtor_kfunc_tab(btf);
        btf_put(btf);
        return ret;
}
EXPORT_SYMBOL_GPL(register_btf_id_dtor_kfuncs);

#define MAX_TYPES_ARE_COMPAT_DEPTH 2

static
int __bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
                                const struct btf *targ_btf, __u32 targ_id,
                                int level)
{
        const struct btf_type *local_type, *targ_type;
        int depth = 32; /* max recursion depth */

        /* caller made sure that names match (ignoring flavor suffix) */
        local_type = btf_type_by_id(local_btf, local_id);
        targ_type = btf_type_by_id(targ_btf, targ_id);
        if (btf_kind(local_type) != btf_kind(targ_type))
                return 0;

recur:
        depth--;
        if (depth < 0)
                return -EINVAL;

        local_type = btf_type_skip_modifiers(local_btf, local_id, &local_id);
        targ_type = btf_type_skip_modifiers(targ_btf, targ_id, &targ_id);
        if (!local_type || !targ_type)
                return -EINVAL;

        if (btf_kind(local_type) != btf_kind(targ_type))
                return 0;

        switch (btf_kind(local_type)) {
        case BTF_KIND_UNKN:
        case BTF_KIND_STRUCT:
        case BTF_KIND_UNION:
        case BTF_KIND_ENUM:
        case BTF_KIND_FWD:
                return 1;
        case BTF_KIND_INT:
                /* just reject deprecated bitfield-like integers; all other
                 * integers are by default compatible between each other
                 */
                return btf_int_offset(local_type) == 0 && btf_int_offset(targ_type) == 0;
        case BTF_KIND_PTR:
                local_id = local_type->type;
                targ_id = targ_type->type;
                goto recur;
        case BTF_KIND_ARRAY:
                local_id = btf_array(local_type)->type;
                targ_id = btf_array(targ_type)->type;
                goto recur;
        case BTF_KIND_FUNC_PROTO: {
                struct btf_param *local_p = btf_params(local_type);
                struct btf_param *targ_p = btf_params(targ_type);
                __u16 local_vlen = btf_vlen(local_type);
                __u16 targ_vlen = btf_vlen(targ_type);
                int i, err;

                if (local_vlen != targ_vlen)
                        return 0;

                for (i = 0; i < local_vlen; i++, local_p++, targ_p++) {
                        if (level <= 0)
                                return -EINVAL;

                        btf_type_skip_modifiers(local_btf, local_p->type, &local_id);
                        btf_type_skip_modifiers(targ_btf, targ_p->type, &targ_id);
                        err = __bpf_core_types_are_compat(local_btf, local_id,
                                                          targ_btf, targ_id,
                                                          level - 1);
                        if (err <= 0)
                                return err;
                }

                /* tail recurse for return type check */
                btf_type_skip_modifiers(local_btf, local_type->type, &local_id);
                btf_type_skip_modifiers(targ_btf, targ_type->type, &targ_id);
                goto recur;
        }
        default:
                return 0;
        }
}

/* Check local and target types for compatibility. This check is used for
 * type-based CO-RE relocations and follow slightly different rules than
 * field-based relocations. This function assumes that root types were already
 * checked for name match. Beyond that initial root-level name check, names
 * are completely ignored. Compatibility rules are as follows:
 *   - any two STRUCTs/UNIONs/FWDs/ENUMs/INTs are considered compatible, but
 *     kind should match for local and target types (i.e., STRUCT is not
 *     compatible with UNION);
 *   - for ENUMs, the size is ignored;
 *   - for INT, size and signedness are ignored;
 *   - for ARRAY, dimensionality is ignored, element types are checked for
 *     compatibility recursively;
 *   - CONST/VOLATILE/RESTRICT modifiers are ignored;
 *   - TYPEDEFs/PTRs are compatible if types they pointing to are compatible;
 *   - FUNC_PROTOs are compatible if they have compatible signature: same
 *     number of input args and compatible return and argument types.
 * These rules are not set in stone and probably will be adjusted as we get
 * more experience with using BPF CO-RE relocations.
 */
int bpf_core_types_are_compat(const struct btf *local_btf, __u32 local_id,
                              const struct btf *targ_btf, __u32 targ_id)
{
        return __bpf_core_types_are_compat(local_btf, local_id,
                                           targ_btf, targ_id,
                                           MAX_TYPES_ARE_COMPAT_DEPTH);
}

static bool bpf_core_is_flavor_sep(const char *s)
{
        /* check X___Y name pattern, where X and Y are not underscores */
        return s[0] != '_' &&                                 /* X */
               s[1] == '_' && s[2] == '_' && s[3] == '_' &&   /* ___ */
               s[4] != '_';                                   /* Y */
}

size_t bpf_core_essential_name_len(const char *name)
{
        size_t n = strlen(name);
        int i;

        for (i = n - 5; i >= 0; i--) {
                if (bpf_core_is_flavor_sep(name + i))
                        return i + 1;
        }
        return n;
}

struct bpf_cand_cache {
        const char *name;
        u32 name_len;
        u16 kind;
        u16 cnt;
        struct {
                const struct btf *btf;
                u32 id;
        } cands[];
};

static void bpf_free_cands(struct bpf_cand_cache *cands)
{
        if (!cands->cnt)
                /* empty candidate array was allocated on stack */
                return;
        kfree(cands);
}

static void bpf_free_cands_from_cache(struct bpf_cand_cache *cands)
{
        kfree(cands->name);
        kfree(cands);
}

#define VMLINUX_CAND_CACHE_SIZE 31
static struct bpf_cand_cache *vmlinux_cand_cache[VMLINUX_CAND_CACHE_SIZE];

#define MODULE_CAND_CACHE_SIZE 31
static struct bpf_cand_cache *module_cand_cache[MODULE_CAND_CACHE_SIZE];

static DEFINE_MUTEX(cand_cache_mutex);

static void __print_cand_cache(struct bpf_verifier_log *log,
                               struct bpf_cand_cache **cache,
                               int cache_size)
{
        struct bpf_cand_cache *cc;
        int i, j;

        for (i = 0; i < cache_size; i++) {
                cc = cache[i];
                if (!cc)
                        continue;
                bpf_log(log, "[%d]%s(", i, cc->name);
                for (j = 0; j < cc->cnt; j++) {
                        bpf_log(log, "%d", cc->cands[j].id);
                        if (j < cc->cnt - 1)
                                bpf_log(log, " ");
                }
                bpf_log(log, "), ");
        }
}

static void print_cand_cache(struct bpf_verifier_log *log)
{
        mutex_lock(&cand_cache_mutex);
        bpf_log(log, "vmlinux_cand_cache:");
        __print_cand_cache(log, vmlinux_cand_cache, VMLINUX_CAND_CACHE_SIZE);
        bpf_log(log, "\nmodule_cand_cache:");
        __print_cand_cache(log, module_cand_cache, MODULE_CAND_CACHE_SIZE);
        bpf_log(log, "\n");
        mutex_unlock(&cand_cache_mutex);
}

static u32 hash_cands(struct bpf_cand_cache *cands)
{
        return jhash(cands->name, cands->name_len, 0);
}

static struct bpf_cand_cache *check_cand_cache(struct bpf_cand_cache *cands,
                                               struct bpf_cand_cache **cache,
                                               int cache_size)
{
        struct bpf_cand_cache *cc = cache[hash_cands(cands) % cache_size];

        if (cc && cc->name_len == cands->name_len &&
            !strncmp(cc->name, cands->name, cands->name_len))
                return cc;
        return NULL;
}

static size_t sizeof_cands(int cnt)
{
        return offsetof(struct bpf_cand_cache, cands[cnt]);
}

static struct bpf_cand_cache *populate_cand_cache(struct bpf_cand_cache *cands,
                                                  struct bpf_cand_cache **cache,
                                                  int cache_size)
{
        struct bpf_cand_cache **cc = &cache[hash_cands(cands) % cache_size], *new_cands;

        if (*cc) {
                bpf_free_cands_from_cache(*cc);
                *cc = NULL;
        }
        new_cands = kmemdup(cands, sizeof_cands(cands->cnt), GFP_KERNEL);
        if (!new_cands) {
                bpf_free_cands(cands);
                return ERR_PTR(-ENOMEM);
        }
        /* strdup the name, since it will stay in cache.
         * the cands->name points to strings in prog's BTF and the prog can be unloaded.
         */
        new_cands->name = kmemdup_nul(cands->name, cands->name_len, GFP_KERNEL);
        bpf_free_cands(cands);
        if (!new_cands->name) {
                kfree(new_cands);
                return ERR_PTR(-ENOMEM);
        }
        *cc = new_cands;
        return new_cands;
}

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
static void __purge_cand_cache(struct btf *btf, struct bpf_cand_cache **cache,
                               int cache_size)
{
        struct bpf_cand_cache *cc;
        int i, j;

        for (i = 0; i < cache_size; i++) {
                cc = cache[i];
                if (!cc)
                        continue;
                if (!btf) {
                        /* when new module is loaded purge all of module_cand_cache,
                         * since new module might have candidates with the name
                         * that matches cached cands.
                         */
                        bpf_free_cands_from_cache(cc);
                        cache[i] = NULL;
                        continue;
                }
                /* when module is unloaded purge cache entries
                 * that match module's btf
                 */
                for (j = 0; j < cc->cnt; j++)
                        if (cc->cands[j].btf == btf) {
                                bpf_free_cands_from_cache(cc);
                                cache[i] = NULL;
                                break;
                        }
        }

}

static void purge_cand_cache(struct btf *btf)
{
        mutex_lock(&cand_cache_mutex);
        __purge_cand_cache(btf, module_cand_cache, MODULE_CAND_CACHE_SIZE);
        mutex_unlock(&cand_cache_mutex);
}
#endif

static struct bpf_cand_cache *
bpf_core_add_cands(struct bpf_cand_cache *cands, const struct btf *targ_btf,
                   int targ_start_id)
{
        struct bpf_cand_cache *new_cands;
        const struct btf_type *t;
        const char *targ_name;
        size_t targ_essent_len;
        int n, i;

        n = btf_nr_types(targ_btf);
        for (i = targ_start_id; i < n; i++) {
                t = btf_type_by_id(targ_btf, i);
                if (btf_kind(t) != cands->kind)
                        continue;

                targ_name = btf_name_by_offset(targ_btf, t->name_off);
                if (!targ_name)
                        continue;

                /* the resched point is before strncmp to make sure that search
                 * for non-existing name will have a chance to schedule().
                 */
                cond_resched();

                if (strncmp(cands->name, targ_name, cands->name_len) != 0)
                        continue;

                targ_essent_len = bpf_core_essential_name_len(targ_name);
                if (targ_essent_len != cands->name_len)
                        continue;

                /* most of the time there is only one candidate for a given kind+name pair */
                new_cands = kmalloc(sizeof_cands(cands->cnt + 1), GFP_KERNEL);
                if (!new_cands) {
                        bpf_free_cands(cands);
                        return ERR_PTR(-ENOMEM);
                }

                memcpy(new_cands, cands, sizeof_cands(cands->cnt));
                bpf_free_cands(cands);
                cands = new_cands;
                cands->cands[cands->cnt].btf = targ_btf;
                cands->cands[cands->cnt].id = i;
                cands->cnt++;
        }
        return cands;
}

static struct bpf_cand_cache *
bpf_core_find_cands(struct bpf_core_ctx *ctx, u32 local_type_id)
{
        struct bpf_cand_cache *cands, *cc, local_cand = {};
        const struct btf *local_btf = ctx->btf;
        const struct btf_type *local_type;
        const struct btf *main_btf;
        size_t local_essent_len;
        struct btf *mod_btf;
        const char *name;
        int id;

        main_btf = bpf_get_btf_vmlinux();
        if (IS_ERR(main_btf))
                return ERR_CAST(main_btf);
        if (!main_btf)
                return ERR_PTR(-EINVAL);

        local_type = btf_type_by_id(local_btf, local_type_id);
        if (!local_type)
                return ERR_PTR(-EINVAL);

        name = btf_name_by_offset(local_btf, local_type->name_off);
        if (str_is_empty(name))
                return ERR_PTR(-EINVAL);
        local_essent_len = bpf_core_essential_name_len(name);

        cands = &local_cand;
        cands->name = name;
        cands->kind = btf_kind(local_type);
        cands->name_len = local_essent_len;

        cc = check_cand_cache(cands, vmlinux_cand_cache, VMLINUX_CAND_CACHE_SIZE);
        /* cands is a pointer to stack here */
        if (cc) {
                if (cc->cnt)
                        return cc;
                goto check_modules;
        }

        /* Attempt to find target candidates in vmlinux BTF first */
        cands = bpf_core_add_cands(cands, main_btf, 1);
        if (IS_ERR(cands))
                return ERR_CAST(cands);

        /* cands is a pointer to kmalloced memory here if cands->cnt > 0 */

        /* populate cache even when cands->cnt == 0 */
        cc = populate_cand_cache(cands, vmlinux_cand_cache, VMLINUX_CAND_CACHE_SIZE);
        if (IS_ERR(cc))
                return ERR_CAST(cc);

        /* if vmlinux BTF has any candidate, don't go for module BTFs */
        if (cc->cnt)
                return cc;

check_modules:
        /* cands is a pointer to stack here and cands->cnt == 0 */
        cc = check_cand_cache(cands, module_cand_cache, MODULE_CAND_CACHE_SIZE);
        if (cc)
                /* if cache has it return it even if cc->cnt == 0 */
                return cc;

        /* If candidate is not found in vmlinux's BTF then search in module's BTFs */
        spin_lock_bh(&btf_idr_lock);
        idr_for_each_entry(&btf_idr, mod_btf, id) {
                if (!btf_is_module(mod_btf))
                        continue;
                /* linear search could be slow hence unlock/lock
                 * the IDR to avoiding holding it for too long
                 */
                btf_get(mod_btf);
                spin_unlock_bh(&btf_idr_lock);
                cands = bpf_core_add_cands(cands, mod_btf, btf_nr_types(main_btf));
                if (IS_ERR(cands)) {
                        btf_put(mod_btf);
                        return ERR_CAST(cands);
                }
                spin_lock_bh(&btf_idr_lock);
                btf_put(mod_btf);
        }
        spin_unlock_bh(&btf_idr_lock);
        /* cands is a pointer to kmalloced memory here if cands->cnt > 0
         * or pointer to stack if cands->cnd == 0.
         * Copy it into the cache even when cands->cnt == 0 and
         * return the result.
         */
        return populate_cand_cache(cands, module_cand_cache, MODULE_CAND_CACHE_SIZE);
}

int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
                   int relo_idx, void *insn)
{
        bool need_cands = relo->kind != BPF_CORE_TYPE_ID_LOCAL;
        struct bpf_core_cand_list cands = {};
        struct bpf_core_relo_res targ_res;
        struct bpf_core_spec *specs;
        int err;

        /* ~4k of temp memory necessary to convert LLVM spec like "0:1:0:5"
         * into arrays of btf_ids of struct fields and array indices.
         */
        specs = kcalloc(3, sizeof(*specs), GFP_KERNEL);
        if (!specs)
                return -ENOMEM;

        if (need_cands) {
                struct bpf_cand_cache *cc;
                int i;

                mutex_lock(&cand_cache_mutex);
                cc = bpf_core_find_cands(ctx, relo->type_id);
                if (IS_ERR(cc)) {
                        bpf_log(ctx->log, "target candidate search failed for %d\n",
                                relo->type_id);
                        err = PTR_ERR(cc);
                        goto out;
                }
                if (cc->cnt) {
                        cands.cands = kcalloc(cc->cnt, sizeof(*cands.cands), GFP_KERNEL);
                        if (!cands.cands) {
                                err = -ENOMEM;
                                goto out;
                        }
                }
                for (i = 0; i < cc->cnt; i++) {
                        bpf_log(ctx->log,
                                "CO-RE relocating %s %s: found target candidate [%d]\n",
                                btf_kind_str[cc->kind], cc->name, cc->cands[i].id);
                        cands.cands[i].btf = cc->cands[i].btf;
                        cands.cands[i].id = cc->cands[i].id;
                }
                cands.len = cc->cnt;
                /* cand_cache_mutex needs to span the cache lookup and
                 * copy of btf pointer into bpf_core_cand_list,
                 * since module can be unloaded while bpf_core_calc_relo_insn
                 * is working with module's btf.
                 */
        }

        err = bpf_core_calc_relo_insn((void *)ctx->log, relo, relo_idx, ctx->btf, &cands, specs,
                                      &targ_res);
        if (err)
                goto out;

        err = bpf_core_patch_insn((void *)ctx->log, insn, relo->insn_off / 8, relo, relo_idx,
                                  &targ_res);

out:
        kfree(specs);
        if (need_cands) {
                kfree(cands.cands);
                mutex_unlock(&cand_cache_mutex);
                if (ctx->log->level & BPF_LOG_LEVEL2)
                        print_cand_cache(ctx->log);
        }
        return err;
}