1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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.
7 #ifndef _LINUX_BPF_VERIFIER_H
8 #define _LINUX_BPF_VERIFIER_H 1
10 #include <linux/bpf.h> /* for enum bpf_reg_type */
11 #include <linux/filter.h> /* for MAX_BPF_STACK */
12 #include <linux/tnum.h>
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.
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.
22 #define BPF_MAX_VAR_SIZ (1 << 29)
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.
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 REG_LIVE_DONE
= 4, /* liveness won't be updating this register anymore */
44 struct bpf_reg_state
{
45 /* Ordering of fields matters. See states_equal() */
46 enum bpf_reg_type type
;
48 /* valid when type == PTR_TO_PACKET */
51 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
52 * PTR_TO_MAP_VALUE_OR_NULL
54 struct bpf_map
*map_ptr
;
56 /* Max size from any of the above. */
59 /* Fixed part of pointer offset, pointer types only */
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.
69 /* For scalar types (SCALAR_VALUE), this represents our knowledge of
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.
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.
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.
94 enum bpf_reg_liveness live
;
97 enum 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 */
104 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
106 struct bpf_stack_state
{
107 struct bpf_reg_state spilled_ptr
;
108 u8 slot_type
[BPF_REG_SIZE
];
111 struct 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).
116 /* Instruction where the allocation of this reference occurred. This
117 * is used purely to inform the user of a reference leak.
122 /* state of the program:
123 * type of all registers and stack info
125 struct bpf_func_state
{
126 struct bpf_reg_state regs
[MAX_BPF_REG
];
127 /* index of call instruction that called into this func */
129 /* stack frame number of this function state from pov of
130 * enclosing bpf_verifier_state.
131 * 0 = main function, 1 = first callee.
134 /* subprog number == index within subprog_stack_depth
135 * zero == main subprog
139 /* The following fields should be last. See copy_func_state() */
141 struct bpf_reference_state
*refs
;
143 struct bpf_stack_state
*stack
;
146 #define MAX_CALL_FRAMES 8
147 struct bpf_verifier_state
{
148 /* call stack tracking */
149 struct bpf_func_state
*frame
[MAX_CALL_FRAMES
];
154 #define bpf_get_spilled_reg(slot, frame) \
155 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \
156 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \
157 ? &frame->stack[slot].spilled_ptr : NULL)
159 /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */
160 #define bpf_for_each_spilled_reg(iter, frame, reg) \
161 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \
162 iter < frame->allocated_stack / BPF_REG_SIZE; \
163 iter++, reg = bpf_get_spilled_reg(iter, frame))
165 /* linked list of verifier states used to prune search */
166 struct bpf_verifier_state_list
{
167 struct bpf_verifier_state state
;
168 struct bpf_verifier_state_list
*next
;
171 /* Possible states for alu_state member. */
172 #define BPF_ALU_SANITIZE_SRC 1U
173 #define BPF_ALU_SANITIZE_DST 2U
174 #define BPF_ALU_NEG_VALUE (1U << 2)
175 #define BPF_ALU_NON_POINTER (1U << 3)
176 #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \
177 BPF_ALU_SANITIZE_DST)
179 struct bpf_insn_aux_data
{
181 enum bpf_reg_type ptr_type
; /* pointer type for load/store insns */
182 unsigned long map_state
; /* pointer/poison value for maps */
183 s32 call_imm
; /* saved imm field of call insn */
184 u32 alu_limit
; /* limit for add/sub register with pointer */
186 int ctx_field_size
; /* the ctx field size for load insn, maybe 0 */
187 int sanitize_stack_off
; /* stack slot to be cleared */
188 bool seen
; /* this insn was processed by the verifier */
189 u8 alu_state
; /* used in combination with alu_limit */
192 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
194 #define BPF_VERIFIER_TMP_LOG_SIZE 1024
196 struct bpf_verifier_log
{
198 char kbuf
[BPF_VERIFIER_TMP_LOG_SIZE
];
204 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log
*log
)
206 return log
->len_used
>= log
->len_total
- 1;
209 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log
*log
)
211 return log
->level
&& log
->ubuf
&& !bpf_verifier_log_full(log
);
214 #define BPF_MAX_SUBPROGS 256
216 struct bpf_subprog_info
{
217 u32 start
; /* insn idx of function entry point */
218 u32 linfo_idx
; /* The idx to the main_prog->aux->linfo */
219 u16 stack_depth
; /* max. stack depth used by this function */
222 /* single container for all structs
223 * one verifier_env per bpf_check() call
225 struct bpf_verifier_env
{
228 struct bpf_prog
*prog
; /* eBPF program being verified */
229 const struct bpf_verifier_ops
*ops
;
230 struct bpf_verifier_stack_elem
*head
; /* stack of verifier states to be processed */
231 int stack_size
; /* number of states to be processed */
232 bool strict_alignment
; /* perform strict pointer alignment checks */
233 struct bpf_verifier_state
*cur_state
; /* current verifier state */
234 struct bpf_verifier_state_list
**explored_states
; /* search pruning optimization */
235 struct bpf_map
*used_maps
[MAX_USED_MAPS
]; /* array of map's used by eBPF program */
236 u32 used_map_cnt
; /* number of used maps */
237 u32 id_gen
; /* used to generate unique reg IDs */
238 bool allow_ptr_leaks
;
239 bool seen_direct_write
;
240 struct bpf_insn_aux_data
*insn_aux_data
; /* array of per-insn state */
241 const struct bpf_line_info
*prev_linfo
;
242 struct bpf_verifier_log log
;
243 struct bpf_subprog_info subprog_info
[BPF_MAX_SUBPROGS
+ 1];
247 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log
*log
,
248 const char *fmt
, va_list args
);
249 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env
*env
,
250 const char *fmt
, ...);
252 static inline struct bpf_func_state
*cur_func(struct bpf_verifier_env
*env
)
254 struct bpf_verifier_state
*cur
= env
->cur_state
;
256 return cur
->frame
[cur
->curframe
];
259 static inline struct bpf_reg_state
*cur_regs(struct bpf_verifier_env
*env
)
261 return cur_func(env
)->regs
;
264 int bpf_prog_offload_verifier_prep(struct bpf_prog
*prog
);
265 int bpf_prog_offload_verify_insn(struct bpf_verifier_env
*env
,
266 int insn_idx
, int prev_insn_idx
);
267 int bpf_prog_offload_finalize(struct bpf_verifier_env
*env
);
269 #endif /* _LINUX_BPF_VERIFIER_H */