1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
3 * This program is free software; you can redistribute it and/or
4 * modify it under the terms of version 2 of the GNU General Public
5 * License as published by the Free Software Foundation.
7 #ifndef _LINUX_BPF_VERIFIER_H
8 #define _LINUX_BPF_VERIFIER_H 1
10 #include <linux/bpf.h> /* for enum bpf_reg_type */
11 #include <linux/filter.h> /* for MAX_BPF_STACK */
12 #include <linux/tnum.h>
14 /* Maximum variable offset umax_value permitted when resolving memory accesses.
15 * In practice this is far bigger than any realistic pointer offset; this limit
16 * ensures that umax_value + (int)off + (int)size cannot overflow a u64.
18 #define BPF_MAX_VAR_OFF (1 << 29)
19 /* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures
20 * that converting umax_value to int cannot overflow.
22 #define BPF_MAX_VAR_SIZ (1 << 29)
24 /* Liveness marks, used for registers and spilled-regs (in stack slots).
25 * Read marks propagate upwards until they find a write mark; they record that
26 * "one of this state's descendants read this reg" (and therefore the reg is
27 * relevant for states_equal() checks).
28 * Write marks collect downwards and do not propagate; they record that "the
29 * straight-line code that reached this state (from its parent) wrote this reg"
30 * (and therefore that reads propagated from this state or its descendants
31 * should not propagate to its parent).
32 * A state with a write mark can receive read marks; it just won't propagate
33 * them to its parent, since the write mark is a property, not of the state,
34 * but of the link between it and its parent. See mark_reg_read() and
35 * mark_stack_slot_read() in kernel/bpf/verifier.c.
37 enum bpf_reg_liveness {
38 REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
39 REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
40 REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
43 struct bpf_reg_state {
44 /* Ordering of fields matters. See states_equal() */
45 enum bpf_reg_type type;
47 /* valid when type == PTR_TO_PACKET */
50 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
51 * PTR_TO_MAP_VALUE_OR_NULL
53 struct bpf_map *map_ptr;
55 /* Max size from any of the above. */
58 /* Fixed part of pointer offset, pointer types only */
60 /* For PTR_TO_PACKET, used to find other pointers with the same variable
61 * offset, so they can share range knowledge.
62 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
63 * came from, when one is tested for != NULL.
64 * For PTR_TO_SOCKET this is used to share which pointers retain the
65 * same reference to the socket, to determine proper reference freeing.
68 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
70 * For pointer types, this represents the variable part of the offset
71 * from the pointed-to object, and is shared with all bpf_reg_states
72 * with the same id as us.
75 /* Used to determine if any memory access using this register will
76 * result in a bad access.
77 * These refer to the same value as var_off, not necessarily the actual
78 * contents of the register.
80 s64 smin_value; /* minimum possible (s64)value */
81 s64 smax_value; /* maximum possible (s64)value */
82 u64 umin_value; /* minimum possible (u64)value */
83 u64 umax_value; /* maximum possible (u64)value */
84 /* parentage chain for liveness checking */
85 struct bpf_reg_state *parent;
86 /* Inside the callee two registers can be both PTR_TO_STACK like
87 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
88 * while another to the caller's stack. To differentiate them 'frameno'
89 * is used which is an index in bpf_verifier_state->frame[] array
90 * pointing to bpf_func_state.
93 enum bpf_reg_liveness live;
96 enum bpf_stack_slot_type {
97 STACK_INVALID, /* nothing was stored in this stack slot */
98 STACK_SPILL, /* register spilled into stack */
99 STACK_MISC, /* BPF program wrote some data into this slot */
100 STACK_ZERO, /* BPF program wrote constant zero */
103 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
105 struct bpf_stack_state {
106 struct bpf_reg_state spilled_ptr;
107 u8 slot_type[BPF_REG_SIZE];
110 struct bpf_reference_state {
111 /* Track each reference created with a unique id, even if the same
112 * instruction creates the reference multiple times (eg, via CALL).
115 /* Instruction where the allocation of this reference occurred. This
116 * is used purely to inform the user of a reference leak.
121 /* state of the program:
122 * type of all registers and stack info
124 struct bpf_func_state {
125 struct bpf_reg_state regs[MAX_BPF_REG];
126 /* index of call instruction that called into this func */
128 /* stack frame number of this function state from pov of
129 * enclosing bpf_verifier_state.
130 * 0 = main function, 1 = first callee.
133 /* subprog number == index within subprog_stack_depth
134 * zero == main subprog
138 /* The following fields should be last. See copy_func_state() */
140 struct bpf_reference_state *refs;
142 struct bpf_stack_state *stack;
145 #define MAX_CALL_FRAMES 8
146 struct bpf_verifier_state {
147 /* call stack tracking */
148 struct bpf_func_state *frame[MAX_CALL_FRAMES];
152 #define bpf_get_spilled_reg(slot, frame) \
153 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \
154 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \
155 ? &frame->stack[slot].spilled_ptr : NULL)
157 /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
158 #define bpf_for_each_spilled_reg(iter, frame, reg) \
159 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
160 iter < frame->allocated_stack / BPF_REG_SIZE; \
161 iter++, reg = bpf_get_spilled_reg(iter, frame))
163 /* linked list of verifier states used to prune search */
164 struct bpf_verifier_state_list {
165 struct bpf_verifier_state state;
166 struct bpf_verifier_state_list *next;
169 struct bpf_insn_aux_data {
171 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
172 unsigned long map_state; /* pointer/poison value for maps */
173 s32 call_imm; /* saved imm field of call insn */
175 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
176 int sanitize_stack_off; /* stack slot to be cleared */
177 bool seen; /* this insn was processed by the verifier */
180 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
182 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
184 struct bpf_verifier_log {
186 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
192 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
194 return log->len_used >= log->len_total - 1;
197 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
199 return log->level && log->ubuf && !bpf_verifier_log_full(log);
202 #define BPF_MAX_SUBPROGS 256
204 struct bpf_subprog_info {
205 u32 start; /* insn idx of function entry point */
206 u16 stack_depth; /* max. stack depth used by this function */
209 /* single container for all structs
210 * one verifier_env per bpf_check() call
212 struct bpf_verifier_env {
213 struct bpf_prog *prog; /* eBPF program being verified */
214 const struct bpf_verifier_ops *ops;
215 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
216 int stack_size; /* number of states to be processed */
217 bool strict_alignment; /* perform strict pointer alignment checks */
218 struct bpf_verifier_state *cur_state; /* current verifier state */
219 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
220 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
221 u32 used_map_cnt; /* number of used maps */
222 u32 id_gen; /* used to generate unique reg IDs */
223 bool allow_ptr_leaks;
224 bool seen_direct_write;
225 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
226 struct bpf_verifier_log log;
227 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
231 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
232 const char *fmt, va_list args);
233 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
234 const char *fmt, ...);
236 static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
238 struct bpf_verifier_state *cur = env->cur_state;
240 return cur->frame[cur->curframe];
243 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
245 return cur_func(env)->regs;
248 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
249 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
250 int insn_idx, int prev_insn_idx);
251 int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
253 #endif /* _LINUX_BPF_VERIFIER_H */