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 REG_LIVE_DONE = 4, /* liveness won't be updating this register anymore */ 42 }; 43 44 struct bpf_reg_state { 45 /* Ordering of fields matters. See states_equal() */ 46 enum bpf_reg_type type; 47 union { 48 /* valid when type == PTR_TO_PACKET */ 49 u16 range; 50 51 /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE | 52 * PTR_TO_MAP_VALUE_OR_NULL 53 */ 54 struct bpf_map *map_ptr; 55 56 /* Max size from any of the above. */ 57 unsigned long raw; 58 }; 59 /* Fixed part of pointer offset, pointer types only */ 60 s32 off; 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. 67 */ 68 u32 id; 69 /* For scalar types (SCALAR_VALUE), this represents our knowledge of 70 * the actual value. 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. 74 */ 75 struct tnum var_off; 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. 80 */ 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. 92 */ 93 u32 frameno; 94 enum bpf_reg_liveness live; 95 }; 96 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 */ 102 }; 103 104 #define BPF_REG_SIZE 8 /* size of eBPF register in bytes */ 105 106 struct bpf_stack_state { 107 struct bpf_reg_state spilled_ptr; 108 u8 slot_type[BPF_REG_SIZE]; 109 }; 110 111 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). 114 */ 115 int id; 116 /* Instruction where the allocation of this reference occurred. This 117 * is used purely to inform the user of a reference leak. 118 */ 119 int insn_idx; 120 }; 121 122 /* state of the program: 123 * type of all registers and stack info 124 */ 125 struct bpf_func_state { 126 struct bpf_reg_state regs[MAX_BPF_REG]; 127 /* index of call instruction that called into this func */ 128 int callsite; 129 /* stack frame number of this function state from pov of 130 * enclosing bpf_verifier_state. 131 * 0 = main function, 1 = first callee. 132 */ 133 u32 frameno; 134 /* subprog number == index within subprog_stack_depth 135 * zero == main subprog 136 */ 137 u32 subprogno; 138 139 /* The following fields should be last. See copy_func_state() */ 140 int acquired_refs; 141 struct bpf_reference_state *refs; 142 int allocated_stack; 143 struct bpf_stack_state *stack; 144 }; 145 146 #define MAX_CALL_FRAMES 8 147 struct bpf_verifier_state { 148 /* call stack tracking */ 149 struct bpf_func_state *frame[MAX_CALL_FRAMES]; 150 u32 curframe; 151 u32 active_spin_lock; 152 bool speculative; 153 }; 154 155 #define bpf_get_spilled_reg(slot, frame) \ 156 (((slot < frame->allocated_stack / BPF_REG_SIZE) && \ 157 (frame->stack[slot].slot_type[0] == STACK_SPILL)) \ 158 ? &frame->stack[slot].spilled_ptr : NULL) 159 160 /* Iterate over 'frame', setting 'reg' to either NULL or a spilled register. */ 161 #define bpf_for_each_spilled_reg(iter, frame, reg) \ 162 for (iter = 0, reg = bpf_get_spilled_reg(iter, frame); \ 163 iter < frame->allocated_stack / BPF_REG_SIZE; \ 164 iter++, reg = bpf_get_spilled_reg(iter, frame)) 165 166 /* linked list of verifier states used to prune search */ 167 struct bpf_verifier_state_list { 168 struct bpf_verifier_state state; 169 struct bpf_verifier_state_list *next; 170 }; 171 172 /* Possible states for alu_state member. */ 173 #define BPF_ALU_SANITIZE_SRC 1U 174 #define BPF_ALU_SANITIZE_DST 2U 175 #define BPF_ALU_NEG_VALUE (1U << 2) 176 #define BPF_ALU_NON_POINTER (1U << 3) 177 #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \ 178 BPF_ALU_SANITIZE_DST) 179 180 struct bpf_insn_aux_data { 181 union { 182 enum bpf_reg_type ptr_type; /* pointer type for load/store insns */ 183 unsigned long map_state; /* pointer/poison value for maps */ 184 s32 call_imm; /* saved imm field of call insn */ 185 u32 alu_limit; /* limit for add/sub register with pointer */ 186 }; 187 int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ 188 int sanitize_stack_off; /* stack slot to be cleared */ 189 bool seen; /* this insn was processed by the verifier */ 190 u8 alu_state; /* used in combination with alu_limit */ 191 unsigned int orig_idx; /* original instruction index */ 192 }; 193 194 #define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */ 195 196 #define BPF_VERIFIER_TMP_LOG_SIZE 1024 197 198 struct bpf_verifier_log { 199 u32 level; 200 char kbuf[BPF_VERIFIER_TMP_LOG_SIZE]; 201 char __user *ubuf; 202 u32 len_used; 203 u32 len_total; 204 }; 205 206 static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log) 207 { 208 return log->len_used >= log->len_total - 1; 209 } 210 211 static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log) 212 { 213 return log->level && log->ubuf && !bpf_verifier_log_full(log); 214 } 215 216 #define BPF_MAX_SUBPROGS 256 217 218 struct bpf_subprog_info { 219 u32 start; /* insn idx of function entry point */ 220 u32 linfo_idx; /* The idx to the main_prog->aux->linfo */ 221 u16 stack_depth; /* max. stack depth used by this function */ 222 }; 223 224 /* single container for all structs 225 * one verifier_env per bpf_check() call 226 */ 227 struct bpf_verifier_env { 228 u32 insn_idx; 229 u32 prev_insn_idx; 230 struct bpf_prog *prog; /* eBPF program being verified */ 231 const struct bpf_verifier_ops *ops; 232 struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ 233 int stack_size; /* number of states to be processed */ 234 bool strict_alignment; /* perform strict pointer alignment checks */ 235 struct bpf_verifier_state *cur_state; /* current verifier state */ 236 struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ 237 struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */ 238 u32 used_map_cnt; /* number of used maps */ 239 u32 id_gen; /* used to generate unique reg IDs */ 240 bool allow_ptr_leaks; 241 bool seen_direct_write; 242 struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ 243 const struct bpf_line_info *prev_linfo; 244 struct bpf_verifier_log log; 245 struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1]; 246 u32 subprog_cnt; 247 }; 248 249 __printf(2, 0) void bpf_verifier_vlog(struct bpf_verifier_log *log, 250 const char *fmt, va_list args); 251 __printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env, 252 const char *fmt, ...); 253 254 static inline struct bpf_func_state *cur_func(struct bpf_verifier_env *env) 255 { 256 struct bpf_verifier_state *cur = env->cur_state; 257 258 return cur->frame[cur->curframe]; 259 } 260 261 static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env) 262 { 263 return cur_func(env)->regs; 264 } 265 266 int bpf_prog_offload_verifier_prep(struct bpf_prog *prog); 267 int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env, 268 int insn_idx, int prev_insn_idx); 269 int bpf_prog_offload_finalize(struct bpf_verifier_env *env); 270 void 271 bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off, 272 struct bpf_insn *insn); 273 void 274 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt); 275 276 #endif /* _LINUX_BPF_VERIFIER_H */ 277