kernel/bpf/disasm.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   3  * Copyright (c) 2016 Facebook
   4  */
   5
   6 #include <linux/bpf.h>
   7
   8 #include "disasm.h"
   9
  10 #define __BPF_FUNC_STR_FN(x) [BPF_FUNC_ ## x] = __stringify(bpf_ ## x)
  11 static const char * const func_id_str[] = {
  12         __BPF_FUNC_MAPPER(__BPF_FUNC_STR_FN)
  13 };
  14 #undef __BPF_FUNC_STR_FN
  15
  16 static const char *__func_get_name(const struct bpf_insn_cbs *cbs,
  17                                    const struct bpf_insn *insn,
  18                                    char *buff, size_t len)
  19 {
  20         BUILD_BUG_ON(ARRAY_SIZE(func_id_str) != __BPF_FUNC_MAX_ID);
  21
  22         if (!insn->src_reg &&
  23             insn->imm >= 0 && insn->imm < __BPF_FUNC_MAX_ID &&
  24             func_id_str[insn->imm])
  25                 return func_id_str[insn->imm];
  26
  27         if (cbs && cbs->cb_call) {
  28                 const char *res;
  29
  30                 res = cbs->cb_call(cbs->private_data, insn);
  31                 if (res)
  32                         return res;
  33         }
  34
  35         if (insn->src_reg == BPF_PSEUDO_CALL)
  36                 snprintf(buff, len, "%+d", insn->imm);
  37         else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL)
  38                 snprintf(buff, len, "kernel-function");
  39
  40         return buff;
  41 }
  42
  43 static const char *__func_imm_name(const struct bpf_insn_cbs *cbs,
  44                                    const struct bpf_insn *insn,
  45                                    u64 full_imm, char *buff, size_t len)
  46 {
  47         if (cbs && cbs->cb_imm)
  48                 return cbs->cb_imm(cbs->private_data, insn, full_imm);
  49
  50         snprintf(buff, len, "0x%llx", (unsigned long long)full_imm);
  51         return buff;
  52 }
  53
  54 const char *func_id_name(int id)
  55 {
  56         if (id >= 0 && id < __BPF_FUNC_MAX_ID && func_id_str[id])
  57                 return func_id_str[id];
  58         else
  59                 return "unknown";
  60 }
  61
  62 const char *const bpf_class_string[8] = {
  63         [BPF_LD]    = "ld",
  64         [BPF_LDX]   = "ldx",
  65         [BPF_ST]    = "st",
  66         [BPF_STX]   = "stx",
  67         [BPF_ALU]   = "alu",
  68         [BPF_JMP]   = "jmp",
  69         [BPF_JMP32] = "jmp32",
  70         [BPF_ALU64] = "alu64",
  71 };
  72
  73 const char *const bpf_alu_string[16] = {
  74         [BPF_ADD >> 4]  = "+=",
  75         [BPF_SUB >> 4]  = "-=",
  76         [BPF_MUL >> 4]  = "*=",
  77         [BPF_DIV >> 4]  = "/=",
  78         [BPF_OR  >> 4]  = "|=",
  79         [BPF_AND >> 4]  = "&=",
  80         [BPF_LSH >> 4]  = "<<=",
  81         [BPF_RSH >> 4]  = ">>=",
  82         [BPF_NEG >> 4]  = "neg",
  83         [BPF_MOD >> 4]  = "%=",
  84         [BPF_XOR >> 4]  = "^=",
  85         [BPF_MOV >> 4]  = "=",
  86         [BPF_ARSH >> 4] = "s>>=",
  87         [BPF_END >> 4]  = "endian",
  88 };
  89
  90 static const char *const bpf_atomic_alu_string[16] = {
  91         [BPF_ADD >> 4]  = "add",
  92         [BPF_AND >> 4]  = "and",
  93         [BPF_OR >> 4]  = "or",
  94         [BPF_XOR >> 4]  = "xor",
  95 };
  96
  97 static const char *const bpf_ldst_string[] = {
  98         [BPF_W >> 3]  = "u32",
  99         [BPF_H >> 3]  = "u16",
 100         [BPF_B >> 3]  = "u8",
 101         [BPF_DW >> 3] = "u64",
 102 };
 103
 104 static const char *const bpf_jmp_string[16] = {
 105         [BPF_JA >> 4]   = "jmp",
 106         [BPF_JEQ >> 4]  = "==",
 107         [BPF_JGT >> 4]  = ">",
 108         [BPF_JLT >> 4]  = "<",
 109         [BPF_JGE >> 4]  = ">=",
 110         [BPF_JLE >> 4]  = "<=",
 111         [BPF_JSET >> 4] = "&",
 112         [BPF_JNE >> 4]  = "!=",
 113         [BPF_JSGT >> 4] = "s>",
 114         [BPF_JSLT >> 4] = "s<",
 115         [BPF_JSGE >> 4] = "s>=",
 116         [BPF_JSLE >> 4] = "s<=",
 117         [BPF_CALL >> 4] = "call",
 118         [BPF_EXIT >> 4] = "exit",
 119 };
 120
 121 static void print_bpf_end_insn(bpf_insn_print_t verbose,
 122                                void *private_data,
 123                                const struct bpf_insn *insn)
 124 {
 125         verbose(private_data, "(%02x) r%d = %s%d r%d\n",
 126                 insn->code, insn->dst_reg,
 127                 BPF_SRC(insn->code) == BPF_TO_BE ? "be" : "le",
 128                 insn->imm, insn->dst_reg);
 129 }
 130
 131 void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 132                     const struct bpf_insn *insn,
 133                     bool allow_ptr_leaks)
 134 {
 135         const bpf_insn_print_t verbose = cbs->cb_print;
 136         u8 class = BPF_CLASS(insn->code);
 137
 138         if (class == BPF_ALU || class == BPF_ALU64) {
 139                 if (BPF_OP(insn->code) == BPF_END) {
 140                         if (class == BPF_ALU64)
 141                                 verbose(cbs->private_data, "BUG_alu64_%02x\n", insn->code);
 142                         else
 143                                 print_bpf_end_insn(verbose, cbs->private_data, insn);
 144                 } else if (BPF_OP(insn->code) == BPF_NEG) {
 145                         verbose(cbs->private_data, "(%02x) %c%d = -%c%d\n",
 146                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 147                                 insn->dst_reg, class == BPF_ALU ? 'w' : 'r',
 148                                 insn->dst_reg);
 149                 } else if (BPF_SRC(insn->code) == BPF_X) {
 150                         verbose(cbs->private_data, "(%02x) %c%d %s %c%d\n",
 151                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 152                                 insn->dst_reg,
 153                                 bpf_alu_string[BPF_OP(insn->code) >> 4],
 154                                 class == BPF_ALU ? 'w' : 'r',
 155                                 insn->src_reg);
 156                 } else {
 157                         verbose(cbs->private_data, "(%02x) %c%d %s %d\n",
 158                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 159                                 insn->dst_reg,
 160                                 bpf_alu_string[BPF_OP(insn->code) >> 4],
 161                                 insn->imm);
 162                 }
 163         } else if (class == BPF_STX) {
 164                 if (BPF_MODE(insn->code) == BPF_MEM)
 165                         verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = r%d\n",
 166                                 insn->code,
 167                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 168                                 insn->dst_reg,
 169                                 insn->off, insn->src_reg);
 170                 else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 171                          (insn->imm == BPF_ADD || insn->imm == BPF_AND ||
 172                           insn->imm == BPF_OR || insn->imm == BPF_XOR)) {
 173                         verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) %s r%d\n",
 174                                 insn->code,
 175                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 176                                 insn->dst_reg, insn->off,
 177                                 bpf_alu_string[BPF_OP(insn->imm) >> 4],
 178                                 insn->src_reg);
 179                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 180                            (insn->imm == (BPF_ADD | BPF_FETCH) ||
 181                             insn->imm == (BPF_AND | BPF_FETCH) ||
 182                             insn->imm == (BPF_OR | BPF_FETCH) ||
 183                             insn->imm == (BPF_XOR | BPF_FETCH))) {
 184                         verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_%s((%s *)(r%d %+d), r%d)\n",
 185                                 insn->code, insn->src_reg,
 186                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 187                                 bpf_atomic_alu_string[BPF_OP(insn->imm) >> 4],
 188                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 189                                 insn->dst_reg, insn->off, insn->src_reg);
 190                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 191                            insn->imm == BPF_CMPXCHG) {
 192                         verbose(cbs->private_data, "(%02x) r0 = atomic%s_cmpxchg((%s *)(r%d %+d), r0, r%d)\n",
 193                                 insn->code,
 194                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 195                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 196                                 insn->dst_reg, insn->off,
 197                                 insn->src_reg);
 198                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 199                            insn->imm == BPF_XCHG) {
 200                         verbose(cbs->private_data, "(%02x) r%d = atomic%s_xchg((%s *)(r%d %+d), r%d)\n",
 201                                 insn->code, insn->src_reg,
 202                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 203                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 204                                 insn->dst_reg, insn->off, insn->src_reg);
 205                 } else {
 206                         verbose(cbs->private_data, "BUG_%02x\n", insn->code);
 207                 }
 208         } else if (class == BPF_ST) {
 209                 if (BPF_MODE(insn->code) != BPF_MEM) {
 210                         verbose(cbs->private_data, "BUG_st_%02x\n", insn->code);
 211                         return;
 212                 }
 213                 verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n",
 214                         insn->code,
 215                         bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 216                         insn->dst_reg,
 217                         insn->off, insn->imm);
 218         } else if (class == BPF_LDX) {
 219                 if (BPF_MODE(insn->code) != BPF_MEM) {
 220                         verbose(cbs->private_data, "BUG_ldx_%02x\n", insn->code);
 221                         return;
 222                 }
 223                 verbose(cbs->private_data, "(%02x) r%d = *(%s *)(r%d %+d)\n",
 224                         insn->code, insn->dst_reg,
 225                         bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 226                         insn->src_reg, insn->off);
 227         } else if (class == BPF_LD) {
 228                 if (BPF_MODE(insn->code) == BPF_ABS) {
 229                         verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[%d]\n",
 230                                 insn->code,
 231                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 232                                 insn->imm);
 233                 } else if (BPF_MODE(insn->code) == BPF_IND) {
 234                         verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[r%d + %d]\n",
 235                                 insn->code,
 236                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 237                                 insn->src_reg, insn->imm);
 238                 } else if (BPF_MODE(insn->code) == BPF_IMM &&
 239                            BPF_SIZE(insn->code) == BPF_DW) {
 240                         /* At this point, we already made sure that the second
 241                          * part of the ldimm64 insn is accessible.
 242                          */
 243                         u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
 244                         bool is_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD ||
 245                                       insn->src_reg == BPF_PSEUDO_MAP_VALUE;
 246                         char tmp[64];
 247
 248                         if (is_ptr && !allow_ptr_leaks)
 249                                 imm = 0;
 250
 251                         verbose(cbs->private_data, "(%02x) r%d = %s\n",
 252                                 insn->code, insn->dst_reg,
 253                                 __func_imm_name(cbs, insn, imm,
 254                                                 tmp, sizeof(tmp)));
 255                 } else {
 256                         verbose(cbs->private_data, "BUG_ld_%02x\n", insn->code);
 257                         return;
 258                 }
 259         } else if (class == BPF_JMP32 || class == BPF_JMP) {
 260                 u8 opcode = BPF_OP(insn->code);
 261
 262                 if (opcode == BPF_CALL) {
 263                         char tmp[64];
 264
 265                         if (insn->src_reg == BPF_PSEUDO_CALL) {
 266                                 verbose(cbs->private_data, "(%02x) call pc%s\n",
 267                                         insn->code,
 268                                         __func_get_name(cbs, insn,
 269                                                         tmp, sizeof(tmp)));
 270                         } else {
 271                                 strcpy(tmp, "unknown");
 272                                 verbose(cbs->private_data, "(%02x) call %s#%d\n", insn->code,
 273                                         __func_get_name(cbs, insn,
 274                                                         tmp, sizeof(tmp)),
 275                                         insn->imm);
 276                         }
 277                 } else if (insn->code == (BPF_JMP | BPF_JA)) {
 278                         verbose(cbs->private_data, "(%02x) goto pc%+d\n",
 279                                 insn->code, insn->off);
 280                 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
 281                         verbose(cbs->private_data, "(%02x) exit\n", insn->code);
 282                 } else if (BPF_SRC(insn->code) == BPF_X) {
 283                         verbose(cbs->private_data,
 284                                 "(%02x) if %c%d %s %c%d goto pc%+d\n",
 285                                 insn->code, class == BPF_JMP32 ? 'w' : 'r',
 286                                 insn->dst_reg,
 287                                 bpf_jmp_string[BPF_OP(insn->code) >> 4],
 288                                 class == BPF_JMP32 ? 'w' : 'r',
 289                                 insn->src_reg, insn->off);
 290                 } else {
 291                         verbose(cbs->private_data,
 292                                 "(%02x) if %c%d %s 0x%x goto pc%+d\n",
 293                                 insn->code, class == BPF_JMP32 ? 'w' : 'r',
 294                                 insn->dst_reg,
 295                                 bpf_jmp_string[BPF_OP(insn->code) >> 4],
 296                                 insn->imm, insn->off);
 297                 }
 298         } else {
 299                 verbose(cbs->private_data, "(%02x) %s\n",
 300                         insn->code, bpf_class_string[class]);
 301         }
 302 }