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 */
41 REG_LIVE_DONE = 4, /* liveness won't be updating this register anymore */
44 struct bpf_reg_state {
45 /* Ordering of fields matters. See states_equal() */
46 enum bpf_reg_type type;
48 /* valid when type == PTR_TO_PACKET */
51 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
52 * PTR_TO_MAP_VALUE_OR_NULL
54 struct bpf_map *map_ptr;
56 /* Max size from any of the above. */
59 /* Fixed part of pointer offset, pointer types only */
61 /* For PTR_TO_PACKET, used to find other pointers with the same variable
62 * offset, so they can share range knowledge.
63 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
64 * came from, when one is tested for != NULL.
65 * For PTR_TO_SOCKET this is used to share which pointers retain the
66 * same reference to the socket, to determine proper reference freeing.
69 /* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned
70 * from a pointer-cast helper, bpf_sk_fullsock() and
73 * Consider the following where "sk" is a reference counted
74 * pointer returned from "sk = bpf_sk_lookup_tcp();":
76 * 1: sk = bpf_sk_lookup_tcp();
77 * 2: if (!sk) { return 0; }
78 * 3: fullsock = bpf_sk_fullsock(sk);
79 * 4: if (!fullsock) { bpf_sk_release(sk); return 0; }
80 * 5: tp = bpf_tcp_sock(fullsock);
81 * 6: if (!tp) { bpf_sk_release(sk); return 0; }
82 * 7: bpf_sk_release(sk);
83 * 8: snd_cwnd = tp->snd_cwnd; // verifier will complain
85 * After bpf_sk_release(sk) at line 7, both "fullsock" ptr and
86 * "tp" ptr should be invalidated also. In order to do that,
87 * the reg holding "fullsock" and "sk" need to remember
88 * the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id
89 * such that the verifier can reset all regs which have
90 * ref_obj_id matching the sk_reg->id.
92 * sk_reg->ref_obj_id is set to sk_reg->id at line 1.
93 * sk_reg->id will stay as NULL-marking purpose only.
94 * After NULL-marking is done, sk_reg->id can be reset to 0.
96 * After "fullsock = bpf_sk_fullsock(sk);" at line 3,
97 * fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id.
99 * After "tp = bpf_tcp_sock(fullsock);" at line 5,
100 * tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id
101 * which is the same as sk_reg->ref_obj_id.
103 * From the verifier perspective, if sk, fullsock and tp
104 * are not NULL, they are the same ptr with different
105 * reg->type. In particular, bpf_sk_release(tp) is also
106 * allowed and has the same effect as bpf_sk_release(sk).
109 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
111 * For pointer types, this represents the variable part of the offset
112 * from the pointed-to object, and is shared with all bpf_reg_states
113 * with the same id as us.
116 /* Used to determine if any memory access using this register will
117 * result in a bad access.
118 * These refer to the same value as var_off, not necessarily the actual
119 * contents of the register.
121 s64 smin_value; /* minimum possible (s64)value */
122 s64 smax_value; /* maximum possible (s64)value */
123 u64 umin_value; /* minimum possible (u64)value */
124 u64 umax_value; /* maximum possible (u64)value */
125 /* parentage chain for liveness checking */
126 struct bpf_reg_state *parent;
127 /* Inside the callee two registers can be both PTR_TO_STACK like
128 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
129 * while another to the caller's stack. To differentiate them 'frameno'
130 * is used which is an index in bpf_verifier_state->frame[] array
131 * pointing to bpf_func_state.
134 enum bpf_reg_liveness live;
137 enum bpf_stack_slot_type {
138 STACK_INVALID, /* nothing was stored in this stack slot */
139 STACK_SPILL, /* register spilled into stack */
140 STACK_MISC, /* BPF program wrote some data into this slot */
141 STACK_ZERO, /* BPF program wrote constant zero */
144 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
146 struct bpf_stack_state {
147 struct bpf_reg_state spilled_ptr;
148 u8 slot_type[BPF_REG_SIZE];
151 struct bpf_reference_state {
152 /* Track each reference created with a unique id, even if the same
153 * instruction creates the reference multiple times (eg, via CALL).
156 /* Instruction where the allocation of this reference occurred. This
157 * is used purely to inform the user of a reference leak.
162 /* state of the program:
163 * type of all registers and stack info
165 struct bpf_func_state {
166 struct bpf_reg_state regs[MAX_BPF_REG];
167 /* index of call instruction that called into this func */
169 /* stack frame number of this function state from pov of
170 * enclosing bpf_verifier_state.
171 * 0 = main function, 1 = first callee.
174 /* subprog number == index within subprog_stack_depth
175 * zero == main subprog
179 /* The following fields should be last. See copy_func_state() */
181 struct bpf_reference_state *refs;
183 struct bpf_stack_state *stack;
186 #define MAX_CALL_FRAMES 8
187 struct bpf_verifier_state {
188 /* call stack tracking */
189 struct bpf_func_state *frame[MAX_CALL_FRAMES];
191 u32 active_spin_lock;
195 #define bpf_get_spilled_reg(slot, frame) \
196 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \
197 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \
198 ? &frame->stack[slot].spilled_ptr : NULL)
200 /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
201 #define bpf_for_each_spilled_reg(iter, frame, reg) \
202 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
203 iter < frame->allocated_stack / BPF_REG_SIZE; \
204 iter++, reg = bpf_get_spilled_reg(iter, frame))
206 /* linked list of verifier states used to prune search */
207 struct bpf_verifier_state_list {
208 struct bpf_verifier_state state;
209 struct bpf_verifier_state_list *next;
212 /* Possible states for alu_state member. */
213 #define BPF_ALU_SANITIZE_SRC 1U
214 #define BPF_ALU_SANITIZE_DST 2U
215 #define BPF_ALU_NEG_VALUE (1U << 2)
216 #define BPF_ALU_NON_POINTER (1U << 3)
217 #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
218 BPF_ALU_SANITIZE_DST)
220 struct bpf_insn_aux_data {
222 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
223 unsigned long map_state; /* pointer/poison value for maps */
224 s32 call_imm; /* saved imm field of call insn */
225 u32 alu_limit; /* limit for add/sub register with pointer */
227 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
228 int sanitize_stack_off; /* stack slot to be cleared */
229 bool seen; /* this insn was processed by the verifier */
230 u8 alu_state; /* used in combination with alu_limit */
231 unsigned int orig_idx; /* original instruction index */
234 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
236 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
238 struct bpf_verifier_log {
240 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
246 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
248 return log->len_used >= log->len_total - 1;
251 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
253 return log->level && log->ubuf && !bpf_verifier_log_full(log);
256 #define BPF_MAX_SUBPROGS 256
258 struct bpf_subprog_info {
259 u32 start; /* insn idx of function entry point */
260 u32 linfo_idx; /* The idx to the main_prog->aux->linfo */
261 u16 stack_depth; /* max. stack depth used by this function */
264 /* single container for all structs
265 * one verifier_env per bpf_check() call
267 struct bpf_verifier_env {
270 struct bpf_prog *prog; /* eBPF program being verified */
271 const struct bpf_verifier_ops *ops;
272 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
273 int stack_size; /* number of states to be processed */
274 bool strict_alignment; /* perform strict pointer alignment checks */
275 struct bpf_verifier_state *cur_state; /* current verifier state */
276 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
277 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
278 u32 used_map_cnt; /* number of used maps */
279 u32 id_gen; /* used to generate unique reg IDs */
280 bool allow_ptr_leaks;
281 bool seen_direct_write;
282 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
283 const struct bpf_line_info *prev_linfo;
284 struct bpf_verifier_log log;
285 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
289 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
290 const char *fmt, va_list args);
291 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
292 const char *fmt, ...);
294 static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
296 struct bpf_verifier_state *cur = env->cur_state;
298 return cur->frame[cur->curframe];
301 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
303 return cur_func(env)->regs;
306 int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
307 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
308 int insn_idx, int prev_insn_idx);
309 int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
311 bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
312 struct bpf_insn *insn);
314 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
316 #endif /* _LINUX_BPF_VERIFIER_H */