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 #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
printf_json(char * s)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 *
symbol_lookup_callback(__maybe_unused void * disasm_info,__maybe_unused uint64_t ref_value,uint64_t * ref_type,__maybe_unused uint64_t ref_PC,__maybe_unused const char ** ref_name)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
init_context(disasm_ctx_t * ctx,const char * arch,__maybe_unused const char * disassembler_options,__maybe_unused unsigned char * image,__maybe_unused ssize_t len,__maybe_unused __u64 func_ksym)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
destroy_context(disasm_ctx_t * ctx)107 static void destroy_context(disasm_ctx_t *ctx)
108 {
109 LLVMDisposeMessage(*ctx);
110 }
111
112 static int
disassemble_insn(disasm_ctx_t * ctx,unsigned char * image,ssize_t len,int pc,__u64 func_ksym)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
disasm_init(void)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
disasm_print_addr(bfd_vma addr,struct disassemble_info * info)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
get_exec_path(char * tpath,size_t size)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
printf_json(void * out,const char * fmt,va_list ap)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
fprintf_json(void * out,const char * fmt,...)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
fprintf_json_styled(void * out,enum disassembler_style style __maybe_unused,const char * fmt,...)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
init_context(disasm_ctx_t * ctx,const char * arch,const char * disassembler_options,unsigned char * image,ssize_t len,__u64 func_ksym)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
destroy_context(disasm_ctx_t * ctx)316 static void destroy_context(disasm_ctx_t *ctx)
317 {
318 free(ctx->info);
319 bfd_close(ctx->bfdf);
320 }
321
322 static int
disassemble_insn(disasm_ctx_t * ctx,__maybe_unused unsigned char * image,__maybe_unused ssize_t len,int pc,__maybe_unused __u64 func_ksym)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
disasm_init(void)330 int disasm_init(void)
331 {
332 bfd_init();
333 return 0;
334 }
335 #endif /* HAVE_LIBBPFD_SUPPORT */
336
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)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 }
422