kernel/bpf/disasm.c

   1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
   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_alu_sign_string[16] = {
  91         [BPF_DIV >> 4]  = "s/=",
  92         [BPF_MOD >> 4]  = "s%=",
  93 };
  94
  95 static const char *const bpf_movsx_string[4] = {
  96         [0] = "(s8)",
  97         [1] = "(s16)",
  98         [3] = "(s32)",
  99 };
 100
 101 static const char *const bpf_atomic_alu_string[16] = {
 102         [BPF_ADD >> 4]  = "add",
 103         [BPF_AND >> 4]  = "and",
 104         [BPF_OR >> 4]  = "or",
 105         [BPF_XOR >> 4]  = "xor",
 106 };
 107
 108 static const char *const bpf_ldst_string[] = {
 109         [BPF_W >> 3]  = "u32",
 110         [BPF_H >> 3]  = "u16",
 111         [BPF_B >> 3]  = "u8",
 112         [BPF_DW >> 3] = "u64",
 113 };
 114
 115 static const char *const bpf_ldsx_string[] = {
 116         [BPF_W >> 3]  = "s32",
 117         [BPF_H >> 3]  = "s16",
 118         [BPF_B >> 3]  = "s8",
 119 };
 120
 121 static const char *const bpf_jmp_string[16] = {
 122         [BPF_JA >> 4]   = "jmp",
 123         [BPF_JEQ >> 4]  = "==",
 124         [BPF_JGT >> 4]  = ">",
 125         [BPF_JLT >> 4]  = "<",
 126         [BPF_JGE >> 4]  = ">=",
 127         [BPF_JLE >> 4]  = "<=",
 128         [BPF_JSET >> 4] = "&",
 129         [BPF_JNE >> 4]  = "!=",
 130         [BPF_JSGT >> 4] = "s>",
 131         [BPF_JSLT >> 4] = "s<",
 132         [BPF_JSGE >> 4] = "s>=",
 133         [BPF_JSLE >> 4] = "s<=",
 134         [BPF_CALL >> 4] = "call",
 135         [BPF_EXIT >> 4] = "exit",
 136 };
 137
 138 static void print_bpf_end_insn(bpf_insn_print_t verbose,
 139                                void *private_data,
 140                                const struct bpf_insn *insn)
 141 {
 142         verbose(private_data, "(%02x) r%d = %s%d r%d\n",
 143                 insn->code, insn->dst_reg,
 144                 BPF_SRC(insn->code) == BPF_TO_BE ? "be" : "le",
 145                 insn->imm, insn->dst_reg);
 146 }
 147
 148 static void print_bpf_bswap_insn(bpf_insn_print_t verbose,
 149                                void *private_data,
 150                                const struct bpf_insn *insn)
 151 {
 152         verbose(private_data, "(%02x) r%d = bswap%d r%d\n",
 153                 insn->code, insn->dst_reg,
 154                 insn->imm, insn->dst_reg);
 155 }
 156
 157 static bool is_sdiv_smod(const struct bpf_insn *insn)
 158 {
 159         return (BPF_OP(insn->code)  == BPF_DIV || BPF_OP(insn->code) == BPF_MOD) &&
 160                insn->off == 1;
 161 }
 162
 163 static bool is_movsx(const struct bpf_insn *insn)
 164 {
 165         return BPF_OP(insn->code) == BPF_MOV &&
 166                (insn->off == 8 || insn->off == 16 || insn->off == 32);
 167 }
 168
 169 static bool is_addr_space_cast(const struct bpf_insn *insn)
 170 {
 171         return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) &&
 172                 insn->off == BPF_ADDR_SPACE_CAST;
 173 }
 174
 175 /* Special (internal-only) form of mov, used to resolve per-CPU addrs:
 176  * dst_reg = src_reg + <percpu_base_off>
 177  * BPF_ADDR_PERCPU is used as a special insn->off value.
 178  */
 179 #define BPF_ADDR_PERCPU (-1)
 180
 181 static inline bool is_mov_percpu_addr(const struct bpf_insn *insn)
 182 {
 183         return insn->code == (BPF_ALU64 | BPF_MOV | BPF_X) && insn->off == BPF_ADDR_PERCPU;
 184 }
 185
 186 void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 187                     const struct bpf_insn *insn,
 188                     bool allow_ptr_leaks)
 189 {
 190         const bpf_insn_print_t verbose = cbs->cb_print;
 191         u8 class = BPF_CLASS(insn->code);
 192
 193         if (class == BPF_ALU || class == BPF_ALU64) {
 194                 if (BPF_OP(insn->code) == BPF_END) {
 195                         if (class == BPF_ALU64)
 196                                 print_bpf_bswap_insn(verbose, cbs->private_data, insn);
 197                         else
 198                                 print_bpf_end_insn(verbose, cbs->private_data, insn);
 199                 } else if (BPF_OP(insn->code) == BPF_NEG) {
 200                         verbose(cbs->private_data, "(%02x) %c%d = -%c%d\n",
 201                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 202                                 insn->dst_reg, class == BPF_ALU ? 'w' : 'r',
 203                                 insn->dst_reg);
 204                 } else if (is_addr_space_cast(insn)) {
 205                         verbose(cbs->private_data, "(%02x) r%d = addr_space_cast(r%d, %d, %d)\n",
 206                                 insn->code, insn->dst_reg,
 207                                 insn->src_reg, ((u32)insn->imm) >> 16, (u16)insn->imm);
 208                 } else if (is_mov_percpu_addr(insn)) {
 209                         verbose(cbs->private_data, "(%02x) r%d = &(void __percpu *)(r%d)\n",
 210                                 insn->code, insn->dst_reg, insn->src_reg);
 211                 } else if (BPF_SRC(insn->code) == BPF_X) {
 212                         verbose(cbs->private_data, "(%02x) %c%d %s %s%c%d\n",
 213                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 214                                 insn->dst_reg,
 215                                 is_sdiv_smod(insn) ? bpf_alu_sign_string[BPF_OP(insn->code) >> 4]
 216                                                    : bpf_alu_string[BPF_OP(insn->code) >> 4],
 217                                 is_movsx(insn) ? bpf_movsx_string[(insn->off >> 3) - 1] : "",
 218                                 class == BPF_ALU ? 'w' : 'r',
 219                                 insn->src_reg);
 220                 } else {
 221                         verbose(cbs->private_data, "(%02x) %c%d %s %d\n",
 222                                 insn->code, class == BPF_ALU ? 'w' : 'r',
 223                                 insn->dst_reg,
 224                                 is_sdiv_smod(insn) ? bpf_alu_sign_string[BPF_OP(insn->code) >> 4]
 225                                                    : bpf_alu_string[BPF_OP(insn->code) >> 4],
 226                                 insn->imm);
 227                 }
 228         } else if (class == BPF_STX) {
 229                 if (BPF_MODE(insn->code) == BPF_MEM)
 230                         verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = r%d\n",
 231                                 insn->code,
 232                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 233                                 insn->dst_reg,
 234                                 insn->off, insn->src_reg);
 235                 else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 236                          (insn->imm == BPF_ADD || insn->imm == BPF_AND ||
 237                           insn->imm == BPF_OR || insn->imm == BPF_XOR)) {
 238                         verbose(cbs->private_data, "(%02x) lock *(%s *)(r%d %+d) %s r%d\n",
 239                                 insn->code,
 240                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 241                                 insn->dst_reg, insn->off,
 242                                 bpf_alu_string[BPF_OP(insn->imm) >> 4],
 243                                 insn->src_reg);
 244                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 245                            (insn->imm == (BPF_ADD | BPF_FETCH) ||
 246                             insn->imm == (BPF_AND | BPF_FETCH) ||
 247                             insn->imm == (BPF_OR | BPF_FETCH) ||
 248                             insn->imm == (BPF_XOR | BPF_FETCH))) {
 249                         verbose(cbs->private_data, "(%02x) r%d = atomic%s_fetch_%s((%s *)(r%d %+d), r%d)\n",
 250                                 insn->code, insn->src_reg,
 251                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 252                                 bpf_atomic_alu_string[BPF_OP(insn->imm) >> 4],
 253                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 254                                 insn->dst_reg, insn->off, insn->src_reg);
 255                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 256                            insn->imm == BPF_CMPXCHG) {
 257                         verbose(cbs->private_data, "(%02x) r0 = atomic%s_cmpxchg((%s *)(r%d %+d), r0, r%d)\n",
 258                                 insn->code,
 259                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 260                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 261                                 insn->dst_reg, insn->off,
 262                                 insn->src_reg);
 263                 } else if (BPF_MODE(insn->code) == BPF_ATOMIC &&
 264                            insn->imm == BPF_XCHG) {
 265                         verbose(cbs->private_data, "(%02x) r%d = atomic%s_xchg((%s *)(r%d %+d), r%d)\n",
 266                                 insn->code, insn->src_reg,
 267                                 BPF_SIZE(insn->code) == BPF_DW ? "64" : "",
 268                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 269                                 insn->dst_reg, insn->off, insn->src_reg);
 270                 } else {
 271                         verbose(cbs->private_data, "BUG_%02x\n", insn->code);
 272                 }
 273         } else if (class == BPF_ST) {
 274                 if (BPF_MODE(insn->code) == BPF_MEM) {
 275                         verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n",
 276                                 insn->code,
 277                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 278                                 insn->dst_reg,
 279                                 insn->off, insn->imm);
 280                 } else if (BPF_MODE(insn->code) == 0xc0 /* BPF_NOSPEC, no UAPI */) {
 281                         verbose(cbs->private_data, "(%02x) nospec\n", insn->code);
 282                 } else {
 283                         verbose(cbs->private_data, "BUG_st_%02x\n", insn->code);
 284                 }
 285         } else if (class == BPF_LDX) {
 286                 if (BPF_MODE(insn->code) != BPF_MEM && BPF_MODE(insn->code) != BPF_MEMSX) {
 287                         verbose(cbs->private_data, "BUG_ldx_%02x\n", insn->code);
 288                         return;
 289                 }
 290                 verbose(cbs->private_data, "(%02x) r%d = *(%s *)(r%d %+d)\n",
 291                         insn->code, insn->dst_reg,
 292                         BPF_MODE(insn->code) == BPF_MEM ?
 293                                  bpf_ldst_string[BPF_SIZE(insn->code) >> 3] :
 294                                  bpf_ldsx_string[BPF_SIZE(insn->code) >> 3],
 295                         insn->src_reg, insn->off);
 296         } else if (class == BPF_LD) {
 297                 if (BPF_MODE(insn->code) == BPF_ABS) {
 298                         verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[%d]\n",
 299                                 insn->code,
 300                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 301                                 insn->imm);
 302                 } else if (BPF_MODE(insn->code) == BPF_IND) {
 303                         verbose(cbs->private_data, "(%02x) r0 = *(%s *)skb[r%d + %d]\n",
 304                                 insn->code,
 305                                 bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 306                                 insn->src_reg, insn->imm);
 307                 } else if (BPF_MODE(insn->code) == BPF_IMM &&
 308                            BPF_SIZE(insn->code) == BPF_DW) {
 309                         /* At this point, we already made sure that the second
 310                          * part of the ldimm64 insn is accessible.
 311                          */
 312                         u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
 313                         bool is_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD ||
 314                                       insn->src_reg == BPF_PSEUDO_MAP_VALUE;
 315                         char tmp[64];
 316
 317                         if (is_ptr && !allow_ptr_leaks)
 318                                 imm = 0;
 319
 320                         verbose(cbs->private_data, "(%02x) r%d = %s\n",
 321                                 insn->code, insn->dst_reg,
 322                                 __func_imm_name(cbs, insn, imm,
 323                                                 tmp, sizeof(tmp)));
 324                 } else {
 325                         verbose(cbs->private_data, "BUG_ld_%02x\n", insn->code);
 326                         return;
 327                 }
 328         } else if (class == BPF_JMP32 || class == BPF_JMP) {
 329                 u8 opcode = BPF_OP(insn->code);
 330
 331                 if (opcode == BPF_CALL) {
 332                         char tmp[64];
 333
 334                         if (insn->src_reg == BPF_PSEUDO_CALL) {
 335                                 verbose(cbs->private_data, "(%02x) call pc%s\n",
 336                                         insn->code,
 337                                         __func_get_name(cbs, insn,
 338                                                         tmp, sizeof(tmp)));
 339                         } else {
 340                                 strcpy(tmp, "unknown");
 341                                 verbose(cbs->private_data, "(%02x) call %s#%d\n", insn->code,
 342                                         __func_get_name(cbs, insn,
 343                                                         tmp, sizeof(tmp)),
 344                                         insn->imm);
 345                         }
 346                 } else if (insn->code == (BPF_JMP | BPF_JA)) {
 347                         verbose(cbs->private_data, "(%02x) goto pc%+d\n",
 348                                 insn->code, insn->off);
 349                 } else if (insn->code == (BPF_JMP | BPF_JCOND) &&
 350                            insn->src_reg == BPF_MAY_GOTO) {
 351                         verbose(cbs->private_data, "(%02x) may_goto pc%+d\n",
 352                                 insn->code, insn->off);
 353                 } else if (insn->code == (BPF_JMP32 | BPF_JA)) {
 354                         verbose(cbs->private_data, "(%02x) gotol pc%+d\n",
 355                                 insn->code, insn->imm);
 356                 } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
 357                         verbose(cbs->private_data, "(%02x) exit\n", insn->code);
 358                 } else if (BPF_SRC(insn->code) == BPF_X) {
 359                         verbose(cbs->private_data,
 360                                 "(%02x) if %c%d %s %c%d goto pc%+d\n",
 361                                 insn->code, class == BPF_JMP32 ? 'w' : 'r',
 362                                 insn->dst_reg,
 363                                 bpf_jmp_string[BPF_OP(insn->code) >> 4],
 364                                 class == BPF_JMP32 ? 'w' : 'r',
 365                                 insn->src_reg, insn->off);
 366                 } else {
 367                         verbose(cbs->private_data,
 368                                 "(%02x) if %c%d %s 0x%x goto pc%+d\n",
 369                                 insn->code, class == BPF_JMP32 ? 'w' : 'r',
 370                                 insn->dst_reg,
 371                                 bpf_jmp_string[BPF_OP(insn->code) >> 4],
 372                                 insn->imm, insn->off);
 373                 }
 374         } else {
 375                 verbose(cbs->private_data, "(%02x) %s\n",
 376                         insn->code, bpf_class_string[class]);
 377         }
 378 }