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