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