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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 (1ULL << 31)
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 INT_MAX
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 */
37enum 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
43struct 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 /* This field must be last, for states_equal() reasons. */
80 enum bpf_reg_liveness live;
81};
82
83enum 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 */
94struct 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];
98 struct bpf_verifier_state *parent;
99};
100
101/* linked list of verifier states used to prune search */
102struct bpf_verifier_state_list {
103 struct bpf_verifier_state state;
104 struct bpf_verifier_state_list *next;
105};
106
107struct bpf_insn_aux_data {
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 };
112 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
113 int converted_op_size; /* the valid value width after perceived conversion */
114};
115
116#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
117
118struct bpf_verifier_env;
119struct bpf_ext_analyzer_ops {
120 int (*insn_hook)(struct bpf_verifier_env *env,
121 int insn_idx, int prev_insn_idx);
122};
123
124/* single container for all structs
125 * one verifier_env per bpf_check() call
126 */
127struct 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 */
131 bool strict_alignment; /* perform strict pointer alignment checks */
132 struct bpf_verifier_state cur_state; /* current verifier state */
133 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
134 const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */
135 void *analyzer_priv; /* pointer to external analyzer's private data */
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
144int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
145 void *priv);
146
147#endif /* _LINUX_BPF_VERIFIER_H */