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
get_exec_path(char * tpath,size_t size)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;
fprintf_json(void * out,const char * fmt,...)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
disasm_print_insn(unsigned char * image,ssize_t len,int opcodes,const char * arch,const char * disassembler_options,const struct btf * btf,const struct bpf_prog_linfo * prog_linfo,__u64 func_ksym,unsigned int func_idx,bool linum)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
disasm_init(void)202 int disasm_init(void)
203 {
204 bfd_init();
205 return 0;
206 }
207