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 */
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 REG_LIVE_DONE = 4, /* liveness won't be updating this register anymore */
42};
43
44struct bpf_reg_state {
45 /* Ordering of fields matters. See states_equal() */
46 enum bpf_reg_type type;
47 union {
48 /* valid when type == PTR_TO_PACKET */
49 u16 range;
50
51 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
52 * PTR_TO_MAP_VALUE_OR_NULL
53 */
54 struct bpf_map *map_ptr;
55
56 /* Max size from any of the above. */
57 unsigned long raw;
58 };
59 /* Fixed part of pointer offset, pointer types only */
60 s32 off;
61 /* For PTR_TO_PACKET, used to find other pointers with the same variable
62 * offset, so they can share range knowledge.
63 * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
64 * came from, when one is tested for != NULL.
65 * For PTR_TO_SOCKET this is used to share which pointers retain the
66 * same reference to the socket, to determine proper reference freeing.
67 */
68 u32 id;
69 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
70 * the actual value.
71 * For pointer types, this represents the variable part of the offset
72 * from the pointed-to object, and is shared with all bpf_reg_states
73 * with the same id as us.
74 */
75 struct tnum var_off;
76 /* Used to determine if any memory access using this register will
77 * result in a bad access.
78 * These refer to the same value as var_off, not necessarily the actual
79 * contents of the register.
80 */
81 s64 smin_value; /* minimum possible (s64)value */
82 s64 smax_value; /* maximum possible (s64)value */
83 u64 umin_value; /* minimum possible (u64)value */
84 u64 umax_value; /* maximum possible (u64)value */
85 /* parentage chain for liveness checking */
86 struct bpf_reg_state *parent;
87 /* Inside the callee two registers can be both PTR_TO_STACK like
88 * R1=fp-8 and R2=fp-8, but one of them points to this function stack
89 * while another to the caller's stack. To differentiate them 'frameno'
90 * is used which is an index in bpf_verifier_state->frame[] array
91 * pointing to bpf_func_state.
92 */
93 u32 frameno;
94 enum bpf_reg_liveness live;
95};
96
97enum bpf_stack_slot_type {
98 STACK_INVALID, /* nothing was stored in this stack slot */
99 STACK_SPILL, /* register spilled into stack */
100 STACK_MISC, /* BPF program wrote some data into this slot */
101 STACK_ZERO, /* BPF program wrote constant zero */
102};
103
104#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
105
106struct bpf_stack_state {
107 struct bpf_reg_state spilled_ptr;
108 u8 slot_type[BPF_REG_SIZE];
109};
110
111struct bpf_reference_state {
112 /* Track each reference created with a unique id, even if the same
113 * instruction creates the reference multiple times (eg, via CALL).
114 */
115 int id;
116 /* Instruction where the allocation of this reference occurred. This
117 * is used purely to inform the user of a reference leak.
118 */
119 int insn_idx;
120};
121
122/* state of the program:
123 * type of all registers and stack info
124 */
125struct bpf_func_state {
126 struct bpf_reg_state regs[MAX_BPF_REG];
127 /* index of call instruction that called into this func */
128 int callsite;
129 /* stack frame number of this function state from pov of
130 * enclosing bpf_verifier_state.
131 * 0 = main function, 1 = first callee.
132 */
133 u32 frameno;
134 /* subprog number == index within subprog_stack_depth
135 * zero == main subprog
136 */
137 u32 subprogno;
138
139 /* The following fields should be last. See copy_func_state() */
140 int acquired_refs;
141 struct bpf_reference_state *refs;
142 int allocated_stack;
143 struct bpf_stack_state *stack;
144};
145
146#define MAX_CALL_FRAMES 8
147struct bpf_verifier_state {
148 /* call stack tracking */
149 struct bpf_func_state *frame[MAX_CALL_FRAMES];
150 u32 curframe;
151 u32 active_spin_lock;
152 bool speculative;
153};
154
155#define bpf_get_spilled_reg(slot, frame) \
156 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \
157 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \
158 ? &frame->stack[slot].spilled_ptr : NULL)
159
160/* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
161#define bpf_for_each_spilled_reg(iter, frame, reg) \
162 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
163 iter < frame->allocated_stack / BPF_REG_SIZE; \
164 iter++, reg = bpf_get_spilled_reg(iter, frame))
165
166/* linked list of verifier states used to prune search */
167struct bpf_verifier_state_list {
168 struct bpf_verifier_state state;
169 struct bpf_verifier_state_list *next;
170};
171
172/* Possible states for alu_state member. */
173#define BPF_ALU_SANITIZE_SRC 1U
174#define BPF_ALU_SANITIZE_DST 2U
175#define BPF_ALU_NEG_VALUE (1U << 2)
176#define BPF_ALU_NON_POINTER (1U << 3)
177#define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
178 BPF_ALU_SANITIZE_DST)
179
180struct bpf_insn_aux_data {
181 union {
182 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
183 unsigned long map_state; /* pointer/poison value for maps */
184 s32 call_imm; /* saved imm field of call insn */
185 u32 alu_limit; /* limit for add/sub register with pointer */
186 };
187 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
188 int sanitize_stack_off; /* stack slot to be cleared */
189 bool seen; /* this insn was processed by the verifier */
190 u8 alu_state; /* used in combination with alu_limit */
191 unsigned int orig_idx; /* original instruction index */
192};
193
194#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
195
196#define BPF_VERIFIER_TMP_LOG_SIZE 1024
197
198struct bpf_verifier_log {
199 u32 level;
200 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
201 char __user *ubuf;
202 u32 len_used;
203 u32 len_total;
204};
205
206static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
207{
208 return log->len_used >= log->len_total - 1;
209}
210
211static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
212{
213 return log->level && log->ubuf && !bpf_verifier_log_full(log);
214}
215
216#define BPF_MAX_SUBPROGS 256
217
218struct bpf_subprog_info {
219 u32 start; /* insn idx of function entry point */
220 u32 linfo_idx; /* The idx to the main_prog->aux->linfo */
221 u16 stack_depth; /* max. stack depth used by this function */
222};
223
224/* single container for all structs
225 * one verifier_env per bpf_check() call
226 */
227struct bpf_verifier_env {
228 u32 insn_idx;
229 u32 prev_insn_idx;
230 struct bpf_prog *prog; /* eBPF program being verified */
231 const struct bpf_verifier_ops *ops;
232 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
233 int stack_size; /* number of states to be processed */
234 bool strict_alignment; /* perform strict pointer alignment checks */
235 struct bpf_verifier_state *cur_state; /* current verifier state */
236 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
237 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
238 u32 used_map_cnt; /* number of used maps */
239 u32 id_gen; /* used to generate unique reg IDs */
240 bool allow_ptr_leaks;
241 bool seen_direct_write;
242 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
243 const struct bpf_line_info *prev_linfo;
244 struct bpf_verifier_log log;
245 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
246 u32 subprog_cnt;
247};
248
249__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
250 const char *fmt, va_list args);
251__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
252 const char *fmt, ...);
253
254static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env)
255{
256 struct bpf_verifier_state *cur = env->cur_state;
257
258 return cur->frame[cur->curframe];
259}
260
261static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
262{
263 return cur_func(env)->regs;
264}
265
266int bpf_prog_offload_verifier_prep(struct bpf_prog *prog);
267int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
268 int insn_idx, int prev_insn_idx);
269int bpf_prog_offload_finalize(struct bpf_verifier_env *env);
270void
271bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
272 struct bpf_insn *insn);
273void
274bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
275
276#endif /* _LINUX_BPF_VERIFIER_H */
277