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