kernel/bpf/disasm.c

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