tools/bpf/bpftool/jit_disasm.c

   1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
   2 /*
   3  * Based on:
   4  *
   5  * Minimal BPF JIT image disassembler
   6  *
   7  * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
   8  * debugging or verification purposes.
   9  *
  10  * Copyright 2013 Daniel Borkmann <[email protected]>
  11  * Licensed under the GNU General Public License, version 2.0 (GPLv2)
  12  */
  13
  14 #ifndef _GNU_SOURCE
  15 #define _GNU_SOURCE
  16 #endif
  17 #include <stdio.h>
  18 #include <stdarg.h>
  19 #include <stdint.h>
  20 #include <stdlib.h>
  21 #include <unistd.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <limits.h>
  25 #include <bpf/libbpf.h>
  26
  27 #ifdef HAVE_LLVM_SUPPORT
  28 #include <llvm-c/Core.h>
  29 #include <llvm-c/Disassembler.h>
  30 #include <llvm-c/Target.h>
  31 #include <llvm-c/TargetMachine.h>
  32 #endif
  33
  34 #ifdef HAVE_LIBBFD_SUPPORT
  35 #include <bfd.h>
  36 #include <dis-asm.h>
  37 #include <tools/dis-asm-compat.h>
  38 #endif
  39
  40 #include "json_writer.h"
  41 #include "main.h"
  42
  43 static int oper_count;
  44
  45 #ifdef HAVE_LLVM_SUPPORT
  46 #define DISASM_SPACER
  47
  48 typedef LLVMDisasmContextRef disasm_ctx_t;
  49
  50 static int printf_json(char *s)
  51 {
  52         s = strtok(s, " \t");
  53         jsonw_string_field(json_wtr, "operation", s);
  54
  55         jsonw_name(json_wtr, "operands");
  56         jsonw_start_array(json_wtr);
  57         oper_count = 1;
  58
  59         while ((s = strtok(NULL, " \t,()")) != 0) {
  60                 jsonw_string(json_wtr, s);
  61                 oper_count++;
  62         }
  63         return 0;
  64 }
  65
  66 /* This callback to set the ref_type is necessary to have the LLVM disassembler
  67  * print PC-relative addresses instead of byte offsets for branch instruction
  68  * targets.
  69  */
  70 static const char *
  71 symbol_lookup_callback(__maybe_unused void *disasm_info,
  72                        __maybe_unused uint64_t ref_value,
  73                        uint64_t *ref_type, __maybe_unused uint64_t ref_PC,
  74                        __maybe_unused const char **ref_name)
  75 {
  76         *ref_type = LLVMDisassembler_ReferenceType_InOut_None;
  77         return NULL;
  78 }
  79
  80 static int
  81 init_context(disasm_ctx_t *ctx, const char *arch,
  82              __maybe_unused const char *disassembler_options,
  83              __maybe_unused unsigned char *image, __maybe_unused ssize_t len,
  84              __maybe_unused __u64 func_ksym)
  85 {
  86         char *triple;
  87
  88         if (arch)
  89                 triple = LLVMNormalizeTargetTriple(arch);
  90         else
  91                 triple = LLVMGetDefaultTargetTriple();
  92         if (!triple) {
  93                 p_err("Failed to retrieve triple");
  94                 return -1;
  95         }
  96         *ctx = LLVMCreateDisasm(triple, NULL, 0, NULL, symbol_lookup_callback);
  97         LLVMDisposeMessage(triple);
  98
  99         if (!*ctx) {
 100                 p_err("Failed to create disassembler");
 101                 return -1;
 102         }
 103
 104         return 0;
 105 }
 106
 107 static void destroy_context(disasm_ctx_t *ctx)
 108 {
 109         LLVMDisposeMessage(*ctx);
 110 }
 111
 112 static int
 113 disassemble_insn(disasm_ctx_t *ctx, unsigned char *image, ssize_t len, int pc,
 114                  __u64 func_ksym)
 115 {
 116         char buf[256];
 117         int count;
 118
 119         count = LLVMDisasmInstruction(*ctx, image + pc, len - pc, func_ksym + pc,
 120                                       buf, sizeof(buf));
 121         if (json_output)
 122                 printf_json(buf);
 123         else
 124                 printf("%s", buf);
 125
 126         return count;
 127 }
 128
 129 int disasm_init(void)
 130 {
 131         LLVMInitializeAllTargetInfos();
 132         LLVMInitializeAllTargetMCs();
 133         LLVMInitializeAllDisassemblers();
 134         return 0;
 135 }
 136 #endif /* HAVE_LLVM_SUPPORT */
 137
 138 #ifdef HAVE_LIBBFD_SUPPORT
 139 #define DISASM_SPACER "\t"
 140
 141 struct disasm_info {
 142         struct disassemble_info info;
 143         __u64 func_ksym;
 144 };
 145
 146 static void disasm_print_addr(bfd_vma addr, struct disassemble_info *info)
 147 {
 148         struct disasm_info *dinfo = container_of(info, struct disasm_info, info);
 149
 150         addr += dinfo->func_ksym;
 151         generic_print_address(addr, info);
 152 }
 153
 154 typedef struct {
 155         struct disasm_info *info;
 156         disassembler_ftype disassemble;
 157         bfd *bfdf;
 158 } disasm_ctx_t;
 159
 160 static int get_exec_path(char *tpath, size_t size)
 161 {
 162         const char *path = "/proc/self/exe";
 163         ssize_t len;
 164
 165         len = readlink(path, tpath, size - 1);
 166         if (len <= 0)
 167                 return -1;
 168
 169         tpath[len] = 0;
 170
 171         return 0;
 172 }
 173
 174 static int printf_json(void *out, const char *fmt, va_list ap)
 175 {
 176         char *s;
 177         int err;
 178
 179         err = vasprintf(&s, fmt, ap);
 180         if (err < 0)
 181                 return -1;
 182
 183         if (!oper_count) {
 184                 int i;
 185
 186                 /* Strip trailing spaces */
 187                 i = strlen(s) - 1;
 188                 while (s[i] == ' ')
 189                         s[i--] = '\0';
 190
 191                 jsonw_string_field(json_wtr, "operation", s);
 192                 jsonw_name(json_wtr, "operands");
 193                 jsonw_start_array(json_wtr);
 194                 oper_count++;
 195         } else if (!strcmp(fmt, ",")) {
 196                    /* Skip */
 197         } else {
 198                 jsonw_string(json_wtr, s);
 199                 oper_count++;
 200         }
 201         free(s);
 202         return 0;
 203 }
 204
 205 static int fprintf_json(void *out, const char *fmt, ...)
 206 {
 207         va_list ap;
 208         int r;
 209
 210         va_start(ap, fmt);
 211         r = printf_json(out, fmt, ap);
 212         va_end(ap);
 213
 214         return r;
 215 }
 216
 217 static int fprintf_json_styled(void *out,
 218                                enum disassembler_style style __maybe_unused,
 219                                const char *fmt, ...)
 220 {
 221         va_list ap;
 222         int r;
 223
 224         va_start(ap, fmt);
 225         r = printf_json(out, fmt, ap);
 226         va_end(ap);
 227
 228         return r;
 229 }
 230
 231 static int init_context(disasm_ctx_t *ctx, const char *arch,
 232                         const char *disassembler_options,
 233                         unsigned char *image, ssize_t len, __u64 func_ksym)
 234 {
 235         struct disassemble_info *info;
 236         char tpath[PATH_MAX];
 237         bfd *bfdf;
 238
 239         memset(tpath, 0, sizeof(tpath));
 240         if (get_exec_path(tpath, sizeof(tpath))) {
 241                 p_err("failed to create disassembler (get_exec_path)");
 242                 return -1;
 243         }
 244
 245         ctx->bfdf = bfd_openr(tpath, NULL);
 246         if (!ctx->bfdf) {
 247                 p_err("failed to create disassembler (bfd_openr)");
 248                 return -1;
 249         }
 250         if (!bfd_check_format(ctx->bfdf, bfd_object)) {
 251                 p_err("failed to create disassembler (bfd_check_format)");
 252                 goto err_close;
 253         }
 254         bfdf = ctx->bfdf;
 255
 256         ctx->info = malloc(sizeof(struct disasm_info));
 257         if (!ctx->info) {
 258                 p_err("mem alloc failed");
 259                 goto err_close;
 260         }
 261         ctx->info->func_ksym = func_ksym;
 262         info = &ctx->info->info;
 263
 264         if (json_output)
 265                 init_disassemble_info_compat(info, stdout,
 266                                              (fprintf_ftype) fprintf_json,
 267                                              fprintf_json_styled);
 268         else
 269                 init_disassemble_info_compat(info, stdout,
 270                                              (fprintf_ftype) fprintf,
 271                                              fprintf_styled);
 272
 273         /* Update architecture info for offload. */
 274         if (arch) {
 275                 const bfd_arch_info_type *inf = bfd_scan_arch(arch);
 276
 277                 if (inf) {
 278                         bfdf->arch_info = inf;
 279                 } else {
 280                         p_err("No libbfd support for %s", arch);
 281                         goto err_free;
 282                 }
 283         }
 284
 285         info->arch = bfd_get_arch(bfdf);
 286         info->mach = bfd_get_mach(bfdf);
 287         if (disassembler_options)
 288                 info->disassembler_options = disassembler_options;
 289         info->buffer = image;
 290         info->buffer_length = len;
 291         info->print_address_func = disasm_print_addr;
 292
 293         disassemble_init_for_target(info);
 294
 295 #ifdef DISASM_FOUR_ARGS_SIGNATURE
 296         ctx->disassemble = disassembler(info->arch,
 297                                         bfd_big_endian(bfdf),
 298                                         info->mach,
 299                                         bfdf);
 300 #else
 301         ctx->disassemble = disassembler(bfdf);
 302 #endif
 303         if (!ctx->disassemble) {
 304                 p_err("failed to create disassembler");
 305                 goto err_free;
 306         }
 307         return 0;
 308
 309 err_free:
 310         free(info);
 311 err_close:
 312         bfd_close(ctx->bfdf);
 313         return -1;
 314 }
 315
 316 static void destroy_context(disasm_ctx_t *ctx)
 317 {
 318         free(ctx->info);
 319         bfd_close(ctx->bfdf);
 320 }
 321
 322 static int
 323 disassemble_insn(disasm_ctx_t *ctx, __maybe_unused unsigned char *image,
 324                  __maybe_unused ssize_t len, int pc,
 325                  __maybe_unused __u64 func_ksym)
 326 {
 327         return ctx->disassemble(pc, &ctx->info->info);
 328 }
 329
 330 int disasm_init(void)
 331 {
 332         bfd_init();
 333         return 0;
 334 }
 335 #endif /* HAVE_LIBBPFD_SUPPORT */
 336
 337 int disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
 338                       const char *arch, const char *disassembler_options,
 339                       const struct btf *btf,
 340                       const struct bpf_prog_linfo *prog_linfo,
 341                       __u64 func_ksym, unsigned int func_idx,
 342                       bool linum)
 343 {
 344         const struct bpf_line_info *linfo = NULL;
 345         unsigned int nr_skip = 0;
 346         int count, i, pc = 0;
 347         disasm_ctx_t ctx;
 348
 349         if (!len)
 350                 return -1;
 351
 352         if (init_context(&ctx, arch, disassembler_options, image, len, func_ksym))
 353                 return -1;
 354
 355         if (json_output)
 356                 jsonw_start_array(json_wtr);
 357         do {
 358                 if (prog_linfo) {
 359                         linfo = bpf_prog_linfo__lfind_addr_func(prog_linfo,
 360                                                                 func_ksym + pc,
 361                                                                 func_idx,
 362                                                                 nr_skip);
 363                         if (linfo)
 364                                 nr_skip++;
 365                 }
 366
 367                 if (json_output) {
 368                         jsonw_start_object(json_wtr);
 369                         oper_count = 0;
 370                         if (linfo)
 371                                 btf_dump_linfo_json(btf, linfo, linum);
 372                         jsonw_name(json_wtr, "pc");
 373                         jsonw_printf(json_wtr, "\"0x%x\"", pc);
 374                 } else {
 375                         if (linfo)
 376                                 btf_dump_linfo_plain(btf, linfo, "; ",
 377                                                      linum);
 378                         printf("%4x:" DISASM_SPACER, pc);
 379                 }
 380
 381                 count = disassemble_insn(&ctx, image, len, pc, func_ksym);
 382
 383                 if (json_output) {
 384                         /* Operand array, was started in fprintf_json. Before
 385                          * that, make sure we have a _null_ value if no operand
 386                          * other than operation code was present.
 387                          */
 388                         if (oper_count == 1)
 389                                 jsonw_null(json_wtr);
 390                         jsonw_end_array(json_wtr);
 391                 }
 392
 393                 if (opcodes) {
 394                         if (json_output) {
 395                                 jsonw_name(json_wtr, "opcodes");
 396                                 jsonw_start_array(json_wtr);
 397                                 for (i = 0; i < count; ++i)
 398                                         jsonw_printf(json_wtr, "\"0x%02hhx\"",
 399                                                      (uint8_t)image[pc + i]);
 400                                 jsonw_end_array(json_wtr);
 401                         } else {
 402                                 printf("\n\t");
 403                                 for (i = 0; i < count; ++i)
 404                                         printf("%02x ",
 405                                                (uint8_t)image[pc + i]);
 406                         }
 407                 }
 408                 if (json_output)
 409                         jsonw_end_object(json_wtr);
 410                 else
 411                         printf("\n");
 412
 413                 pc += count;
 414         } while (count > 0 && pc < len);
 415         if (json_output)
 416                 jsonw_end_array(json_wtr);
 417
 418         destroy_context(&ctx);
 419
 420         return 0;
 421 }