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 <daniel@iogearbox.net>
  11  * Licensed under the GNU General Public License, version 2.0 (GPLv2)
  12  */
  13
  14 #define _GNU_SOURCE
  15 #include <stdio.h>
  16 #include <stdarg.h>
  17 #include <stdint.h>
  18 #include <stdlib.h>
  19 #include <assert.h>
  20 #include <unistd.h>
  21 #include <string.h>
  22 #include <bfd.h>
  23 #include <dis-asm.h>
  24 #include <sys/stat.h>
  25 #include <limits.h>
  26 #include <bpf/libbpf.h>
  27
  28 #include "json_writer.h"
  29 #include "main.h"
  30
  31 static void get_exec_path(char *tpath, size_t size)
  32 {
  33         const char *path = "/proc/self/exe";
  34         ssize_t len;
  35
  36         len = readlink(path, tpath, size - 1);
  37         assert(len > 0);
  38         tpath[len] = 0;
  39 }
  40
  41 static int oper_count;
  42 static int fprintf_json(void *out, const char *fmt, ...)
  43 {
  44         va_list ap;
  45         char *s;
  46
  47         va_start(ap, fmt);
  48         if (vasprintf(&s, fmt, ap) < 0)
  49                 return -1;
  50         va_end(ap);
  51
  52         if (!oper_count) {
  53                 int i;
  54
  55                 /* Strip trailing spaces */
  56                 i = strlen(s) - 1;
  57                 while (s[i] == ' ')
  58                         s[i--] = '\0';
  59
  60                 jsonw_string_field(json_wtr, "operation", s);
  61                 jsonw_name(json_wtr, "operands");
  62                 jsonw_start_array(json_wtr);
  63                 oper_count++;
  64         } else if (!strcmp(fmt, ",")) {
  65                    /* Skip */
  66         } else {
  67                 jsonw_string(json_wtr, s);
  68                 oper_count++;
  69         }
  70         free(s);
  71         return 0;
  72 }
  73
  74 void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
  75                        const char *arch, const char *disassembler_options,
  76                        const struct btf *btf,
  77                        const struct bpf_prog_linfo *prog_linfo,
  78                        __u64 func_ksym, unsigned int func_idx,
  79                        bool linum)
  80 {
  81         const struct bpf_line_info *linfo = NULL;
  82         disassembler_ftype disassemble;
  83         struct disassemble_info info;
  84         unsigned int nr_skip = 0;
  85         int count, i, pc = 0;
  86         char tpath[PATH_MAX];
  87         bfd *bfdf;
  88
  89         if (!len)
  90                 return;
  91
  92         memset(tpath, 0, sizeof(tpath));
  93         get_exec_path(tpath, sizeof(tpath));
  94
  95         bfdf = bfd_openr(tpath, NULL);
  96         assert(bfdf);
  97         assert(bfd_check_format(bfdf, bfd_object));
  98
  99         if (json_output)
 100                 init_disassemble_info(&info, stdout,
 101                                       (fprintf_ftype) fprintf_json);
 102         else
 103                 init_disassemble_info(&info, stdout,
 104                                       (fprintf_ftype) fprintf);
 105
 106         /* Update architecture info for offload. */
 107         if (arch) {
 108                 const bfd_arch_info_type *inf = bfd_scan_arch(arch);
 109
 110                 if (inf) {
 111                         bfdf->arch_info = inf;
 112                 } else {
 113                         p_err("No libbfd support for %s", arch);
 114                         return;
 115                 }
 116         }
 117
 118         info.arch = bfd_get_arch(bfdf);
 119         info.mach = bfd_get_mach(bfdf);
 120         if (disassembler_options)
 121                 info.disassembler_options = disassembler_options;
 122         info.buffer = image;
 123         info.buffer_length = len;
 124
 125         disassemble_init_for_target(&info);
 126
 127 #ifdef DISASM_FOUR_ARGS_SIGNATURE
 128         disassemble = disassembler(info.arch,
 129                                    bfd_big_endian(bfdf),
 130                                    info.mach,
 131                                    bfdf);
 132 #else
 133         disassemble = disassembler(bfdf);
 134 #endif
 135         assert(disassemble);
 136
 137         if (json_output)
 138                 jsonw_start_array(json_wtr);
 139         do {
 140                 if (prog_linfo) {
 141                         linfo = bpf_prog_linfo__lfind_addr_func(prog_linfo,
 142                                                                 func_ksym + pc,
 143                                                                 func_idx,
 144                                                                 nr_skip);
 145                         if (linfo)
 146                                 nr_skip++;
 147                 }
 148
 149                 if (json_output) {
 150                         jsonw_start_object(json_wtr);
 151                         oper_count = 0;
 152                         if (linfo)
 153                                 btf_dump_linfo_json(btf, linfo, linum);
 154                         jsonw_name(json_wtr, "pc");
 155                         jsonw_printf(json_wtr, "\"0x%x\"", pc);
 156                 } else {
 157                         if (linfo)
 158                                 btf_dump_linfo_plain(btf, linfo, "; ",
 159                                                      linum);
 160                         printf("%4x:\t", pc);
 161                 }
 162
 163                 count = disassemble(pc, &info);
 164                 if (json_output) {
 165                         /* Operand array, was started in fprintf_json. Before
 166                          * that, make sure we have a _null_ value if no operand
 167                          * other than operation code was present.
 168                          */
 169                         if (oper_count == 1)
 170                                 jsonw_null(json_wtr);
 171                         jsonw_end_array(json_wtr);
 172                 }
 173
 174                 if (opcodes) {
 175                         if (json_output) {
 176                                 jsonw_name(json_wtr, "opcodes");
 177                                 jsonw_start_array(json_wtr);
 178                                 for (i = 0; i < count; ++i)
 179                                         jsonw_printf(json_wtr, "\"0x%02hhx\"",
 180                                                      (uint8_t)image[pc + i]);
 181                                 jsonw_end_array(json_wtr);
 182                         } else {
 183                                 printf("\n\t");
 184                                 for (i = 0; i < count; ++i)
 185                                         printf("%02x ",
 186                                                (uint8_t)image[pc + i]);
 187                         }
 188                 }
 189                 if (json_output)
 190                         jsonw_end_object(json_wtr);
 191                 else
 192                         printf("\n");
 193
 194                 pc += count;
 195         } while (count > 0 && pc < len);
 196         if (json_output)
 197                 jsonw_end_array(json_wtr);
 198
 199         bfd_close(bfdf);
 200 }
 201
 202 int disasm_init(void)
 203 {
 204         bfd_init();
 205         return 0;
 206 }