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 */ 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 }; 42 43 struct 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 83 enum 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 struct bpf_stack_state { 92 struct bpf_reg_state spilled_ptr; 93 u8 slot_type[BPF_REG_SIZE]; 94 }; 95 96 /* state of the program: 97 * type of all registers and stack info 98 */ 99 struct bpf_verifier_state { 100 struct bpf_reg_state regs[MAX_BPF_REG]; 101 struct bpf_verifier_state *parent; 102 int allocated_stack; 103 struct bpf_stack_state *stack; 104 }; 105 106 /* linked list of verifier states used to prune search */ 107 struct bpf_verifier_state_list { 108 struct bpf_verifier_state state; 109 struct bpf_verifier_state_list *next; 110 }; 111 112 struct bpf_insn_aux_data { 113 union { 114 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ 115 struct bpf_map *map_ptr; /* pointer for call insn into lookup_elem */ 116 }; 117 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ 118 bool seen; /* this insn was processed by the verifier */ 119 }; 120 121 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 122 123 #define BPF_VERIFIER_TMP_LOG_SIZE 1024 124 125 struct bpf_verifer_log { 126 u32 level; 127 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE]; 128 char __user *ubuf; 129 u32 len_used; 130 u32 len_total; 131 }; 132 133 static inline bool bpf_verifier_log_full(const struct bpf_verifer_log *log) 134 { 135 return log->len_used >= log->len_total - 1; 136 } 137 138 struct bpf_verifier_env; 139 struct bpf_ext_analyzer_ops { 140 int (*insn_hook)(struct bpf_verifier_env *env, 141 int insn_idx, int prev_insn_idx); 142 }; 143 144 /* single container for all structs 145 * one verifier_env per bpf_check() call 146 */ 147 struct bpf_verifier_env { 148 struct bpf_prog *prog; /* eBPF program being verified */ 149 const struct bpf_verifier_ops *ops; 150 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ 151 int stack_size; /* number of states to be processed */ 152 bool strict_alignment; /* perform strict pointer alignment checks */ 153 struct bpf_verifier_state *cur_state; /* current verifier state */ 154 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ 155 const struct bpf_ext_analyzer_ops *dev_ops; /* device analyzer ops */ 156 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 157 u32 used_map_cnt; /* number of used maps */ 158 u32 id_gen; /* used to generate unique reg IDs */ 159 bool allow_ptr_leaks; 160 bool seen_direct_write; 161 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ 162 163 struct bpf_verifer_log log; 164 }; 165 166 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env) 167 { 168 return env->cur_state->regs; 169 } 170 171 #if defined(CONFIG_NET) && defined(CONFIG_BPF_SYSCALL) 172 int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env); 173 #else 174 static inline int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env) 175 { 176 return -EOPNOTSUPP; 177 } 178 #endif 179 180 #endif /* _LINUX_BPF_VERIFIER_H */ 181