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 enum bpf_reg_type type;
45 union {
46 /* valid when type == PTR_TO_PACKET */
47 u16 range;
48
49 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
50 * PTR_TO_MAP_VALUE_OR_NULL
51 */
52 struct bpf_map *map_ptr;
53 };
54 /* Fixed part of pointer offset, pointer types only */
55 s32 off;
56 /* For PTR_TO_PACKET, used to find other pointers with the same variable
57 * offset, so they can share range knowledge.
58 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
59 * came from, when one is tested for != NULL.
60 */
61 u32 id;
62 /* Ordering of fields matters. See states_equal() */
63 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
64 * the actual value.
65 * For pointer types, this represents the variable part of the offset
66 * from the pointed-to object, and is shared with all bpf_reg_states
67 * with the same id as us.
68 */
69 struct tnum var_off;
70 /* Used to determine if any memory access using this register will
71 * result in a bad access.
72 * These refer to the same value as var_off, not necessarily the actual
73 * contents of the register.
74 */
75 s64 smin_value; /* minimum possible (s64)value */
76 s64 smax_value; /* maximum possible (s64)value */
77 u64 umin_value; /* minimum possible (u64)value */
78 u64 umax_value; /* maximum possible (u64)value */
79 /* Inside the callee two registers can be both PTR_TO_STACK like
80 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
81 * while another to the caller's stack. To differentiate them 'frameno'
82 * is used which is an index in bpf_verifier_state->frame[] array
83 * pointing to bpf_func_state.
84 * This field must be second to last, for states_equal() reasons.
85 */
86 u32 frameno;
87 /* This field must be last, for states_equal() reasons. */
88 enum bpf_reg_liveness live;
89 };
90
91 enum bpf_stack_slot_type {
92 STACK_INVALID, /* nothing was stored in this stack slot */
93 STACK_SPILL, /* register spilled into stack */
94 STACK_MISC, /* BPF program wrote some data into this slot */
95 STACK_ZERO, /* BPF program wrote constant zero */
96 };
97
98 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
99
100 struct bpf_stack_state {
101 struct bpf_reg_state spilled_ptr;
102 u8 slot_type[BPF_REG_SIZE];
103 };
104
105 /* state of the program:
106 * type of all registers and stack info
107 */
108 struct bpf_func_state {
109 struct bpf_reg_state regs[MAX_BPF_REG];
110 struct bpf_verifier_state *parent;
111 /* index of call instruction that called into this func */
112 int callsite;
113 /* stack frame number of this function state from pov of
114 * enclosing bpf_verifier_state.
115 * 0 = main function, 1 = first callee.
116 */
117 u32 frameno;
118 /* subprog number == index within subprog_stack_depth
119 * zero == main subprog
120 */
121 u32 subprogno;
122
123 /* should be second to last. See copy_func_state() */
124 int allocated_stack;
125 struct bpf_stack_state *stack;
126 };
127
128 #define MAX_CALL_FRAMES 8
129 struct bpf_verifier_state {
130 /* call stack tracking */
131 struct bpf_func_state *frame[MAX_CALL_FRAMES];
132 struct bpf_verifier_state *parent;
133 u32 curframe;
134 };
135
136 /* linked list of verifier states used to prune search */
137 struct bpf_verifier_state_list {
138 struct bpf_verifier_state state;
139 struct bpf_verifier_state_list *next;
140 };
141
142 struct bpf_insn_aux_data {
143 union {
144 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
145 unsigned long map_state; /* pointer/poison value for maps */
146 s32 call_imm; /* saved imm field of call insn */
147 };
148 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
149 int sanitize_stack_off; /* stack slot to be cleared */
150 bool seen; /* this insn was processed by the verifier */
151 };
152
153 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
154
155 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
156
157 struct bpf_verifier_log {
158 u32 level;
159 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
160 char __user *ubuf;
161 u32 len_used;
162 u32 len_total;
163 };
164
bpf_verifier_log_full(const struct bpf_verifier_log * log)165 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
166 {
167 return log->len_used >= log->len_total - 1;
168 }
169
bpf_verifier_log_needed(const struct bpf_verifier_log * log)170 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
171 {
172 return log->level && log->ubuf && !bpf_verifier_log_full(log);
173 }
174
175 #define BPF_MAX_SUBPROGS 256
176
177 struct bpf_subprog_info {
178 u32 start; /* insn idx of function entry point */
179 u16 stack_depth; /* max. stack depth used by this function */
180 };
181
182 /* single container for all structs
183 * one verifier_env per bpf_check() call
184 */
185 struct bpf_verifier_env {
186 struct bpf_prog *prog; /* eBPF program being verified */
187 const struct bpf_verifier_ops *ops;
188 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
189 int stack_size; /* number of states to be processed */
190 bool strict_alignment; /* perform strict pointer alignment checks */
191 struct bpf_verifier_state *cur_state; /* current verifier state */
192 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
193 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
194 u32 used_map_cnt; /* number of used maps */
195 u32 id_gen; /* used to generate unique reg IDs */
196 bool allow_ptr_leaks;
197 bool seen_direct_write;
198 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
199 struct bpf_verifier_log log;
200 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
201 u32 subprog_cnt;
202 };
203
204 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
205 const char *fmt, va_list args);
206 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
207 const char *fmt, ...);
208
cur_regs(struct bpf_verifier_env * env)209 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
210 {
211 struct bpf_verifier_state *cur = env->cur_state;
212
213 return cur->frame[cur->curframe]->regs;
214 }
215
216 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
217 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
218 int insn_idx, int prev_insn_idx);
219
220 #endif /* _LINUX_BPF_VERIFIER_H */
221
