1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
2 *
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.
6 */
7 #ifndef _LINUX_BPF_VERIFIER_H
8 #define _LINUX_BPF_VERIFIER_H 1
9
10 #include <linux/bpf.h> /* for enum bpf_reg_type */
11 #include <linux/filter.h> /* for MAX_BPF_STACK */
12 #include <linux/tnum.h>
13
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.
17 */
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.
21 */
22 #define BPF_MAX_VAR_SIZ (1 << 29)
23
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.
36 */
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 };
42
43 struct bpf_reg_state {
44 /* Ordering of fields matters. See states_equal() */
45 enum bpf_reg_type type;
46 union {
47 /* valid when type == PTR_TO_PACKET */
48 u16 range;
49
50 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
51 * PTR_TO_MAP_VALUE_OR_NULL
52 */
53 struct bpf_map *map_ptr;
54
55 /* Max size from any of the above. */
56 unsigned long raw;
57 };
58 /* Fixed part of pointer offset, pointer types only */
59 s32 off;
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 */
65 u32 id;
66 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
67 * the actual value.
68 * For pointer types, this represents the variable part of the offset
69 * from the pointed-to object, and is shared with all bpf_reg_states
70 * with the same id as us.
71 */
72 struct tnum var_off;
73 /* Used to determine if any memory access using this register will
74 * result in a bad access.
75 * These refer to the same value as var_off, not necessarily the actual
76 * contents of the register.
77 */
78 s64 smin_value; /* minimum possible (s64)value */
79 s64 smax_value; /* maximum possible (s64)value */
80 u64 umin_value; /* minimum possible (u64)value */
81 u64 umax_value; /* maximum possible (u64)value */
82 /* parentage chain for liveness checking */
83 struct bpf_reg_state *parent;
84 /* Inside the callee two registers can be both PTR_TO_STACK like
85 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
86 * while another to the caller's stack. To differentiate them 'frameno'
87 * is used which is an index in bpf_verifier_state->frame[] array
88 * pointing to bpf_func_state.
89 */
90 u32 frameno;
91 enum bpf_reg_liveness live;
92 };
93
94 enum bpf_stack_slot_type {
95 STACK_INVALID, /* nothing was stored in this stack slot */
96 STACK_SPILL, /* register spilled into stack */
97 STACK_MISC, /* BPF program wrote some data into this slot */
98 STACK_ZERO, /* BPF program wrote constant zero */
99 };
100
101 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
102
103 struct bpf_stack_state {
104 struct bpf_reg_state spilled_ptr;
105 u8 slot_type[BPF_REG_SIZE];
106 };
107
108 /* state of the program:
109 * type of all registers and stack info
110 */
111 struct bpf_func_state {
112 struct bpf_reg_state regs[MAX_BPF_REG];
113 /* index of call instruction that called into this func */
114 int callsite;
115 /* stack frame number of this function state from pov of
116 * enclosing bpf_verifier_state.
117 * 0 = main function, 1 = first callee.
118 */
119 u32 frameno;
120 /* subprog number == index within subprog_stack_depth
121 * zero == main subprog
122 */
123 u32 subprogno;
124
125 /* should be second to last. See copy_func_state() */
126 int allocated_stack;
127 struct bpf_stack_state *stack;
128 };
129
130 struct bpf_id_pair {
131 u32 old;
132 u32 cur;
133 };
134
135 /* Maximum number of register states that can exist at once */
136 #define BPF_ID_MAP_SIZE (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
137 #define MAX_CALL_FRAMES 8
138 struct bpf_verifier_state {
139 /* call stack tracking */
140 struct bpf_func_state *frame[MAX_CALL_FRAMES];
141 u32 curframe;
142 bool speculative;
143 };
144
145 /* linked list of verifier states used to prune search */
146 struct bpf_verifier_state_list {
147 struct bpf_verifier_state state;
148 struct bpf_verifier_state_list *next;
149 };
150
151 /* Possible states for alu_state member. */
152 #define BPF_ALU_SANITIZE_SRC (1U << 0)
153 #define BPF_ALU_SANITIZE_DST (1U << 1)
154 #define BPF_ALU_NEG_VALUE (1U << 2)
155 #define BPF_ALU_NON_POINTER (1U << 3)
156 #define BPF_ALU_IMMEDIATE (1U << 4)
157 #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
158 BPF_ALU_SANITIZE_DST)
159
160 struct bpf_insn_aux_data {
161 union {
162 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
163 unsigned long map_state; /* pointer/poison value for maps */
164 s32 call_imm; /* saved imm field of call insn */
165 u32 alu_limit; /* limit for add/sub register with pointer */
166 };
167 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
168 bool seen; /* this insn was processed by the verifier */
169 bool sanitize_stack_spill; /* subject to Spectre v4 sanitation */
170 u8 alu_state; /* used in combination with alu_limit */
171 };
172
173 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
174
175 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
176
177 struct bpf_verifier_log {
178 u32 level;
179 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
180 char __user *ubuf;
181 u32 len_used;
182 u32 len_total;
183 };
184
bpf_verifier_log_full(const struct bpf_verifier_log * log)185 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
186 {
187 return log->len_used >= log->len_total - 1;
188 }
189
bpf_verifier_log_needed(const struct bpf_verifier_log * log)190 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
191 {
192 return log->level && log->ubuf && !bpf_verifier_log_full(log);
193 }
194
195 #define BPF_MAX_SUBPROGS 256
196
197 struct bpf_subprog_info {
198 u32 start; /* insn idx of function entry point */
199 u16 stack_depth; /* max. stack depth used by this function */
200 };
201
202 /* single container for all structs
203 * one verifier_env per bpf_check() call
204 */
205 struct bpf_verifier_env {
206 u32 insn_idx;
207 u32 prev_insn_idx;
208 struct bpf_prog *prog; /* eBPF program being verified */
209 const struct bpf_verifier_ops *ops;
210 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
211 int stack_size; /* number of states to be processed */
212 bool strict_alignment; /* perform strict pointer alignment checks */
213 struct bpf_verifier_state *cur_state; /* current verifier state */
214 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
215 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
216 u32 used_map_cnt; /* number of used maps */
217 u32 id_gen; /* used to generate unique reg IDs */
218 bool explore_alu_limits;
219 bool allow_ptr_leaks;
220 bool seen_direct_write;
221 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
222 struct bpf_verifier_log log;
223 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
224 struct bpf_id_pair idmap_scratch[BPF_ID_MAP_SIZE];
225 u32 subprog_cnt;
226 };
227
228 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
229 const char *fmt, va_list args);
230 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
231 const char *fmt, ...);
232
cur_regs(struct bpf_verifier_env * env)233 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
234 {
235 struct bpf_verifier_state *cur = env->cur_state;
236
237 return cur->frame[cur->curframe]->regs;
238 }
239
240 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
241 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
242 int insn_idx, int prev_insn_idx);
243
244 #endif /* _LINUX_BPF_VERIFIER_H */
245