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58e2af8b JK |
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 */ | |
f1174f77 | 12 | #include <linux/tnum.h> |
58e2af8b | 13 | |
b03c9f9f EC |
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 | */ | |
de31796c | 18 | #define BPF_MAX_VAR_OFF (1 << 29) |
b03c9f9f EC |
19 | /* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures |
20 | * that converting umax_value to int cannot overflow. | |
21 | */ | |
de31796c | 22 | #define BPF_MAX_VAR_SIZ (1 << 29) |
48461135 | 23 | |
8e9cd9ce EC |
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 | */ | |
dc503a8a EC |
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 | ||
58e2af8b JK |
43 | struct bpf_reg_state { |
44 | enum bpf_reg_type type; | |
45 | union { | |
f1174f77 EC |
46 | /* valid when type == PTR_TO_PACKET */ |
47 | u16 range; | |
58e2af8b JK |
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 | }; | |
f1174f77 EC |
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 | */ | |
d2a4dd37 | 61 | u32 id; |
dc503a8a | 62 | /* Ordering of fields matters. See states_equal() */ |
f1174f77 EC |
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; | |
d2a4dd37 | 70 | /* Used to determine if any memory access using this register will |
f1174f77 EC |
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. | |
d2a4dd37 | 74 | */ |
b03c9f9f EC |
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 */ | |
dc503a8a EC |
79 | /* This field must be last, for states_equal() reasons. */ |
80 | enum bpf_reg_liveness live; | |
58e2af8b JK |
81 | }; |
82 | ||
83 | enum bpf_stack_slot_type { | |
84 | STACK_INVALID, /* nothing was stored in this stack slot */ | |
85 | STACK_SPILL, /* register spilled into stack */ | |
86 | STACK_MISC /* BPF program wrote some data into this slot */ | |
87 | }; | |
88 | ||
89 | #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ | |
90 | ||
91 | /* state of the program: | |
92 | * type of all registers and stack info | |
93 | */ | |
94 | struct bpf_verifier_state { | |
95 | struct bpf_reg_state regs[MAX_BPF_REG]; | |
96 | u8 stack_slot_type[MAX_BPF_STACK]; | |
97 | struct bpf_reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE]; | |
dc503a8a | 98 | struct bpf_verifier_state *parent; |
58e2af8b JK |
99 | }; |
100 | ||
101 | /* linked list of verifier states used to prune search */ | |
102 | struct bpf_verifier_state_list { | |
103 | struct bpf_verifier_state state; | |
104 | struct bpf_verifier_state_list *next; | |
105 | }; | |
106 | ||
107 | struct bpf_insn_aux_data { | |
81ed18ab AS |
108 | union { |
109 | enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ | |
110 | struct bpf_map *map_ptr; /* pointer for call insn into lookup_elem */ | |
111 | }; | |
23994631 | 112 | int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ |
2b3ea8ce | 113 | bool seen; /* this insn was processed by the verifier */ |
58e2af8b JK |
114 | }; |
115 | ||
116 | #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ | |
117 | ||
13a27dfc JK |
118 | struct bpf_verifier_env; |
119 | struct bpf_ext_analyzer_ops { | |
120 | int (*insn_hook)(struct bpf_verifier_env *env, | |
121 | int insn_idx, int prev_insn_idx); | |
122 | }; | |
123 | ||
58e2af8b JK |
124 | /* single container for all structs |
125 | * one verifier_env per bpf_check() call | |
126 | */ | |
127 | struct bpf_verifier_env { | |
128 | struct bpf_prog *prog; /* eBPF program being verified */ | |
129 | struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ | |
130 | int stack_size; /* number of states to be processed */ | |
e07b98d9 | 131 | bool strict_alignment; /* perform strict pointer alignment checks */ |
58e2af8b JK |
132 | struct bpf_verifier_state cur_state; /* current verifier state */ |
133 | struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ | |
13a27dfc JK |
134 | const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */ |
135 | void *analyzer_priv; /* pointer to external analyzer's private data */ | |
58e2af8b JK |
136 | struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ |
137 | u32 used_map_cnt; /* number of used maps */ | |
138 | u32 id_gen; /* used to generate unique reg IDs */ | |
139 | bool allow_ptr_leaks; | |
140 | bool seen_direct_write; | |
141 | struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ | |
142 | }; | |
143 | ||
13a27dfc JK |
144 | int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, |
145 | void *priv); | |
146 | ||
58e2af8b | 147 | #endif /* _LINUX_BPF_VERIFIER_H */ |