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/* Copyright (c) 2011-2014 PLUMgrid,
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
#include <linux/bpf.h> /* for enum bpf_reg_type */
#include <linux/filter.h> /* for MAX_BPF_STACK */
#include <linux/tnum.h>
/* Maximum variable offset umax_value permitted when resolving memory accesses.
* In practice this is far bigger than any realistic pointer offset; this limit
* ensures that umax_value + (int)off + (int)size cannot overflow a u64.
#define BPF_MAX_VAR_OFF (1 << 29)
/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO]. This ensures
* that converting umax_value to int cannot overflow.
#define BPF_MAX_VAR_SIZ (1 << 29)
/* Liveness marks, used for registers and spilled-regs (in stack slots).
* Read marks propagate upwards until they find a write mark; they record that
* "one of this state's descendants read this reg" (and therefore the reg is
* relevant for states_equal() checks).
* Write marks collect downwards and do not propagate; they record that "the
* straight-line code that reached this state (from its parent) wrote this reg"
* (and therefore that reads propagated from this state or its descendants
* should not propagate to its parent).
* A state with a write mark can receive read marks; it just won't propagate
* them to its parent, since the write mark is a property, not of the state,
* but of the link between it and its parent. See mark_reg_read() and
* mark_stack_slot_read() in kernel/bpf/verifier.c.
enum bpf_reg_liveness {
REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
struct bpf_reg_state {
enum bpf_reg_type type;
union {
/* valid when type == PTR_TO_PACKET */
u16 range;
/* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
struct bpf_map *map_ptr;
/* Fixed part of pointer offset, pointer types only */
s32 off;
/* For PTR_TO_PACKET, used to find other pointers with the same variable
* offset, so they can share range knowledge.
* For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
* came from, when one is tested for != NULL.
u32 id;
/* Ordering of fields matters. See states_equal() */
/* For scalar types (SCALAR_VALUE), this represents our knowledge of
* the actual value.
* For pointer types, this represents the variable part of the offset
* from the pointed-to object, and is shared with all bpf_reg_states
* with the same id as us.
struct tnum var_off;
/* Used to determine if any memory access using this register will
* result in a bad access.
* These refer to the same value as var_off, not necessarily the actual
* contents of the register.
s64 smin_value; /* minimum possible (s64)value */
s64 smax_value; /* maximum possible (s64)value */
u64 umin_value; /* minimum possible (u64)value */
u64 umax_value; /* maximum possible (u64)value */
/* Inside the callee two registers can be both PTR_TO_STACK like
* R1=fp-8 and R2=fp-8, but one of them points to this function stack
* while another to the caller's stack. To differentiate them 'frameno'
* is used which is an index in bpf_verifier_state->frame[] array
* pointing to bpf_func_state.
* This field must be second to last, for states_equal() reasons.
u32 frameno;
/* This field must be last, for states_equal() reasons. */
enum bpf_reg_liveness live;
enum bpf_stack_slot_type {
STACK_INVALID, /* nothing was stored in this stack slot */
STACK_SPILL, /* register spilled into stack */
STACK_MISC, /* BPF program wrote some data into this slot */
STACK_ZERO, /* BPF program wrote constant zero */
#define BPF_REG_SIZE 8 /* size of eBPF register in bytes */
struct bpf_stack_state {
struct bpf_reg_state spilled_ptr;
u8 slot_type[BPF_REG_SIZE];
/* state of the program:
* type of all registers and stack info
struct bpf_func_state {
struct bpf_reg_state regs[MAX_BPF_REG];
struct bpf_verifier_state *parent;
/* index of call instruction that called into this func */
int callsite;
/* stack frame number of this function state from pov of
* enclosing bpf_verifier_state.
* 0 = main function, 1 = first callee.
u32 frameno;
/* subprog number == index within subprog_stack_depth
* zero == main subprog
u32 subprogno;
/* should be second to last. See copy_func_state() */
int allocated_stack;
struct bpf_stack_state *stack;
struct bpf_verifier_state {
/* call stack tracking */
struct bpf_func_state *frame[MAX_CALL_FRAMES];
struct bpf_verifier_state *parent;
u32 curframe;
/* linked list of verifier states used to prune search */
struct bpf_verifier_state_list {
struct bpf_verifier_state state;
struct bpf_verifier_state_list *next;
struct bpf_insn_aux_data {
union {
enum bpf_reg_type ptr_type; /* pointer type for load/store insns */
unsigned long map_state; /* pointer/poison value for maps */
s32 call_imm; /* saved imm field of call insn */
int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
int sanitize_stack_off; /* stack slot to be cleared */
bool seen; /* this insn was processed by the verifier */
#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
struct bpf_verifier_log {
u32 level;
char __user *ubuf;
u32 len_used;
u32 len_total;
static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
return log->len_used >= log->len_total - 1;
static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
return log->level && log->ubuf && !bpf_verifier_log_full(log);
#define BPF_MAX_SUBPROGS 256
struct bpf_subprog_info {
u32 start; /* insn idx of function entry point */
u16 stack_depth; /* max. stack depth used by this function */
/* single container for all structs
* one verifier_env per bpf_check() call
struct bpf_verifier_env {
struct bpf_prog *prog; /* eBPF program being verified */
const struct bpf_verifier_ops *ops;
struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
int stack_size; /* number of states to be processed */
bool strict_alignment; /* perform strict pointer alignment checks */
struct bpf_verifier_state *cur_state; /* current verifier state */
struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
u32 used_map_cnt; /* number of used maps */
u32 id_gen; /* used to generate unique reg IDs */
bool allow_ptr_leaks;
bool seen_direct_write;
struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
struct bpf_verifier_log log;
struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
u32 subprog_cnt;
__printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log,
const char *fmt, va_list args);
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
const char *fmt, ...);
static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
struct bpf_verifier_state *cur = env->cur_state;
return cur->frame[cur->curframe]->regs;
int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx);
#endif /* _LINUX_BPF_VERIFIER_H */