include/linux/bpf_verifier.h

   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 enum bpf_reg_liveness {
  25         REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
  26         REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
  27         REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
  28 };
  29
  30 struct bpf_reg_state {
  31         enum bpf_reg_type type;
  32         union {
  33                 /* valid when type == PTR_TO_PACKET */
  34                 u16 range;
  35
  36                 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
  37                  *   PTR_TO_MAP_VALUE_OR_NULL
  38                  */
  39                 struct bpf_map *map_ptr;
  40         };
  41         /* Fixed part of pointer offset, pointer types only */
  42         s32 off;
  43         /* For PTR_TO_PACKET, used to find other pointers with the same variable
  44          * offset, so they can share range knowledge.
  45          * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
  46          * came from, when one is tested for != NULL.
  47          */
  48         u32 id;
  49         /* Ordering of fields matters.  See states_equal() */
  50         /* For scalar types (SCALAR_VALUE), this represents our knowledge of
  51          * the actual value.
  52          * For pointer types, this represents the variable part of the offset
  53          * from the pointed-to object, and is shared with all bpf_reg_states
  54          * with the same id as us.
  55          */
  56         struct tnum var_off;
  57         /* Used to determine if any memory access using this register will
  58          * result in a bad access.
  59          * These refer to the same value as var_off, not necessarily the actual
  60          * contents of the register.
  61          */
  62         s64 smin_value; /* minimum possible (s64)value */
  63         s64 smax_value; /* maximum possible (s64)value */
  64         u64 umin_value; /* minimum possible (u64)value */
  65         u64 umax_value; /* maximum possible (u64)value */
  66         /* This field must be last, for states_equal() reasons. */
  67         enum bpf_reg_liveness live;
  68 };
  69
  70 enum bpf_stack_slot_type {
  71         STACK_INVALID,    /* nothing was stored in this stack slot */
  72         STACK_SPILL,      /* register spilled into stack */
  73         STACK_MISC        /* BPF program wrote some data into this slot */
  74 };
  75
  76 #define BPF_REG_SIZE 8  /* size of eBPF register in bytes */
  77
  78 /* state of the program:
  79  * type of all registers and stack info
  80  */
  81 struct bpf_verifier_state {
  82         struct bpf_reg_state regs[MAX_BPF_REG];
  83         u8 stack_slot_type[MAX_BPF_STACK];
  84         struct bpf_reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
  85         struct bpf_verifier_state *parent;
  86 };
  87
  88 /* linked list of verifier states used to prune search */
  89 struct bpf_verifier_state_list {
  90         struct bpf_verifier_state state;
  91         struct bpf_verifier_state_list *next;
  92 };
  93
  94 struct bpf_insn_aux_data {
  95         union {
  96                 enum bpf_reg_type ptr_type;     /* pointer type for load/store insns */
  97                 struct bpf_map *map_ptr;        /* pointer for call insn into lookup_elem */
  98         };
  99         int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
 100         int converted_op_size; /* the valid value width after perceived conversion */
 101 };
 102
 103 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */
 104
 105 struct bpf_verifier_env;
 106 struct bpf_ext_analyzer_ops {
 107         int (*insn_hook)(struct bpf_verifier_env *env,
 108                          int insn_idx, int prev_insn_idx);
 109 };
 110
 111 /* single container for all structs
 112  * one verifier_env per bpf_check() call
 113  */
 114 struct bpf_verifier_env {
 115         struct bpf_prog *prog;          /* eBPF program being verified */
 116         struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
 117         int stack_size;                 /* number of states to be processed */
 118         bool strict_alignment;          /* perform strict pointer alignment checks */
 119         struct bpf_verifier_state cur_state; /* current verifier state */
 120         struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
 121         const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */
 122         void *analyzer_priv; /* pointer to external analyzer's private data */
 123         struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
 124         u32 used_map_cnt;               /* number of used maps */
 125         u32 id_gen;                     /* used to generate unique reg IDs */
 126         bool allow_ptr_leaks;
 127         bool seen_direct_write;
 128         bool varlen_map_value_access;
 129         struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
 130 };
 131
 132 int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
 133                  void *priv);
 134
 135 #endif /* _LINUX_BPF_VERIFIER_H */