1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
4 #ifndef _LINUX_BPF_VERIFIER_H
5 #define _LINUX_BPF_VERIFIER_H 1
7 #include <linux/bpf.h> /* for enum bpf_reg_type */
8 #include <linux/filter.h> /* for MAX_BPF_STACK */
9 #include <linux/tnum.h>
11 /* Maximum variable offset umax_value permitted when resolving memory accesses.
12 * In practice this is far bigger than any realistic pointer offset; this limit
13 * ensures that umax_value + (int)off + (int)size cannot overflow a u64.
15 #define BPF_MAX_VAR_OFF (1 << 29)
16 /* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures
17 * that converting umax_value to int cannot overflow.
19 #define BPF_MAX_VAR_SIZ (1 << 29)
21 /* Liveness marks, used for registers and spilled-regs (in stack slots).
22 * Read marks propagate upwards until they find a write mark; they record that
23 * "one of this state's descendants read this reg" (and therefore the reg is
24 * relevant for states_equal() checks).
25 * Write marks collect downwards and do not propagate; they record that "the
26 * straight-line code that reached this state (from its parent) wrote this reg"
27 * (and therefore that reads propagated from this state or its descendants
28 * should not propagate to its parent).
29 * A state with a write mark can receive read marks; it just won't propagate
30 * them to its parent, since the write mark is a property, not of the state,
31 * but of the link between it and its parent. See mark_reg_read() and
32 * mark_stack_slot_read() in kernel/bpf/verifier.c.
34 enum bpf_reg_liveness {
35 REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
36 REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
37 REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
38 REG_LIVE_DONE = 4, /* liveness won't be updating this register anymore */
41 struct bpf_reg_state {
42 /* Ordering of fields matters. See states_equal() */
43 enum bpf_reg_type type;
45 /* valid when type == PTR_TO_PACKET */
48 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
49 * PTR_TO_MAP_VALUE_OR_NULL
51 struct bpf_map *map_ptr;
53 /* Max size from any of the above. */
56 /* Fixed part of pointer offset, pointer types only */
58 /* For PTR_TO_PACKET, used to find other pointers with the same variable
59 * offset, so they can share range knowledge.
60 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
61 * came from, when one is tested for != NULL.
62 * For PTR_TO_SOCKET this is used to share which pointers retain the
63 * same reference to the socket, to determine proper reference freeing.
66 /* PTR_TO_SOCKET and PTR_TO_TCP_SOCK could be a ptr returned
67 * from a pointer-cast helper, bpf_sk_fullsock() and
70 * Consider the following where "sk" is a reference counted
71 * pointer returned from "sk = bpf_sk_lookup_tcp();":
73 * 1: sk = bpf_sk_lookup_tcp();
74 * 2: if (!sk) { return 0; }
75 * 3: fullsock = bpf_sk_fullsock(sk);
76 * 4: if (!fullsock) { bpf_sk_release(sk); return 0; }
77 * 5: tp = bpf_tcp_sock(fullsock);
78 * 6: if (!tp) { bpf_sk_release(sk); return 0; }
79 * 7: bpf_sk_release(sk);
80 * 8: snd_cwnd = tp->snd_cwnd; // verifier will complain
82 * After bpf_sk_release(sk) at line 7, both "fullsock" ptr and
83 * "tp" ptr should be invalidated also. In order to do that,
84 * the reg holding "fullsock" and "sk" need to remember
85 * the original refcounted ptr id (i.e. sk_reg->id) in ref_obj_id
86 * such that the verifier can reset all regs which have
87 * ref_obj_id matching the sk_reg->id.
89 * sk_reg->ref_obj_id is set to sk_reg->id at line 1.
90 * sk_reg->id will stay as NULL-marking purpose only.
91 * After NULL-marking is done, sk_reg->id can be reset to 0.
93 * After "fullsock = bpf_sk_fullsock(sk);" at line 3,
94 * fullsock_reg->ref_obj_id is set to sk_reg->ref_obj_id.
96 * After "tp = bpf_tcp_sock(fullsock);" at line 5,
97 * tp_reg->ref_obj_id is set to fullsock_reg->ref_obj_id
98 * which is the same as sk_reg->ref_obj_id.
100 * From the verifier perspective, if sk, fullsock and tp
101 * are not NULL, they are the same ptr with different
102 * reg->type. In particular, bpf_sk_release(tp) is also
103 * allowed and has the same effect as bpf_sk_release(sk).
106 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
108 * For pointer types, this represents the variable part of the offset
109 * from the pointed-to object, and is shared with all bpf_reg_states
110 * with the same id as us.
113 /* Used to determine if any memory access using this register will
114 * result in a bad access.
115 * These refer to the same value as var_off, not necessarily the actual
116 * contents of the register.
118 s64 smin_value; /* minimum possible (s64)value */
119 s64 smax_value; /* maximum possible (s64)value */
120 u64 umin_value; /* minimum possible (u64)value */
121 u64 umax_value; /* maximum possible (u64)value */
122 /* parentage chain for liveness checking */
123 struct bpf_reg_state *parent;
124 /* Inside the callee two registers can be both PTR_TO_STACK like
125 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
126 * while another to the caller's stack. To differentiate them 'frameno'
127 * is used which is an index in bpf_verifier_state->frame[] array
128 * pointing to bpf_func_state.
131 enum bpf_reg_liveness live;
134 enum bpf_stack_slot_type {
135 STACK_INVALID, /* nothing was stored in this stack slot */
136 STACK_SPILL, /* register spilled into stack */
137 STACK_MISC, /* BPF program wrote some data into this slot */
138 STACK_ZERO, /* BPF program wrote constant zero */
141 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
143 struct bpf_stack_state {
144 struct bpf_reg_state spilled_ptr;
145 u8 slot_type[BPF_REG_SIZE];
148 struct bpf_reference_state {
149 /* Track each reference created with a unique id, even if the same
150 * instruction creates the reference multiple times (eg, via CALL).
153 /* Instruction where the allocation of this reference occurred. This
154 * is used purely to inform the user of a reference leak.
159 /* state of the program:
160 * type of all registers and stack info
162 struct bpf_func_state {
163 struct bpf_reg_state regs[MAX_BPF_REG];
164 /* index of call instruction that called into this func */
166 /* stack frame number of this function state from pov of
167 * enclosing bpf_verifier_state.
168 * 0 = main function, 1 = first callee.
171 /* subprog number == index within subprog_stack_depth
172 * zero == main subprog
176 /* The following fields should be last. See copy_func_state() */
178 struct bpf_reference_state *refs;
180 struct bpf_stack_state *stack;
183 #define MAX_CALL_FRAMES 8
184 struct bpf_verifier_state {
185 /* call stack tracking */
186 struct bpf_func_state *frame[MAX_CALL_FRAMES];
188 u32 active_spin_lock;
192 #define bpf_get_spilled_reg(slot, frame) \
193 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \
194 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \
195 ? &frame->stack[slot].spilled_ptr : NULL)
197 /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
198 #define bpf_for_each_spilled_reg(iter, frame, reg) \
199 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
200 iter < frame->allocated_stack / BPF_REG_SIZE; \
201 iter++, reg = bpf_get_spilled_reg(iter, frame))
203 /* linked list of verifier states used to prune search */
204 struct bpf_verifier_state_list {
205 struct bpf_verifier_state state;
206 struct bpf_verifier_state_list *next;
207 int miss_cnt, hit_cnt;
210 /* Possible states for alu_state member. */
211 #define BPF_ALU_SANITIZE_SRC 1U
212 #define BPF_ALU_SANITIZE_DST 2U
213 #define BPF_ALU_NEG_VALUE (1U << 2)
214 #define BPF_ALU_NON_POINTER (1U << 3)
215 #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
216 BPF_ALU_SANITIZE_DST)
218 struct bpf_insn_aux_data {
220 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
221 unsigned long map_state; /* pointer/poison value for maps */
222 s32 call_imm; /* saved imm field of call insn */
223 u32 alu_limit; /* limit for add/sub register with pointer */
225 u32 map_index; /* index into used_maps[] */
226 u32 map_off; /* offset from value base address */
229 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
230 int sanitize_stack_off; /* stack slot to be cleared */
231 bool seen; /* this insn was processed by the verifier */
232 u8 alu_state; /* used in combination with alu_limit */
233 unsigned int orig_idx; /* original instruction index */
236 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
238 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
240 struct bpf_verifier_log {
242 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
248 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
250 return log->len_used >= log->len_total - 1;
253 #define BPF_LOG_LEVEL1 1
254 #define BPF_LOG_LEVEL2 2
255 #define BPF_LOG_STATS 4
256 #define BPF_LOG_LEVEL (BPF_LOG_LEVEL1 | BPF_LOG_LEVEL2)
257 #define BPF_LOG_MASK (BPF_LOG_LEVEL | BPF_LOG_STATS)
259 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
261 return log->level && log->ubuf && !bpf_verifier_log_full(log);
264 #define BPF_MAX_SUBPROGS 256
266 struct bpf_subprog_info {
267 u32 start; /* insn idx of function entry point */
268 u32 linfo_idx; /* The idx to the main_prog->aux->linfo */
269 u16 stack_depth; /* max. stack depth used by this function */
272 /* single container for all structs
273 * one verifier_env per bpf_check() call
275 struct bpf_verifier_env {
278 struct bpf_prog *prog; /* eBPF program being verified */
279 const struct bpf_verifier_ops *ops;
280 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
281 int stack_size; /* number of states to be processed */
282 bool strict_alignment; /* perform strict pointer alignment checks */
283 struct bpf_verifier_state *cur_state; /* current verifier state */
284 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
285 struct bpf_verifier_state_list *free_list;
286 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
287 u32 used_map_cnt; /* number of used maps */
288 u32 id_gen; /* used to generate unique reg IDs */
289 bool allow_ptr_leaks;
290 bool seen_direct_write;
291 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
292 const struct bpf_line_info *prev_linfo;
293 struct bpf_verifier_log log;
294 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
301 /* number of instructions analyzed by the verifier */
303 /* total verification time */
304 u64 verification_time;
305 /* maximum number of verifier states kept in 'branching' instructions */
306 u32 max_states_per_insn;
307 /* total number of allocated verifier states */
309 /* some states are freed during program analysis.
310 * this is peak number of states. this number dominates kernel
311 * memory consumption during verification
314 /* longest register parentage chain walked for liveness marking */
315 u32 longest_mark_read_walk;
318 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
319 const char *fmt, va_list args);
320 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
321 const char *fmt, ...);
323 static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
325 struct bpf_verifier_state *cur = env->cur_state;
327 return cur->frame[cur->curframe];
330 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
332 return cur_func(env)->regs;
335 int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
336 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
337 int insn_idx, int prev_insn_idx);
338 int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
340 bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
341 struct bpf_insn *insn);
343 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
345 #endif /* _LINUX_BPF_VERIFIER_H */