xref: /linux/tools/bpf/bpftool/btf.c (revision 44f57d78) 
1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 /* Copyright (C) 2019 Facebook */
3 
4 #include <errno.h>
5 #include <fcntl.h>
6 #include <linux/err.h>
7 #include <stdbool.h>
8 #include <stdio.h>
9 #include <string.h>
10 #include <unistd.h>
11 #include <gelf.h>
12 #include <bpf.h>
13 #include <linux/btf.h>
14 
15 #include "btf.h"
16 #include "json_writer.h"
17 #include "main.h"
18 
19 static const char * const btf_kind_str[NR_BTF_KINDS] = {
20 	[BTF_KIND_UNKN]		= "UNKNOWN",
21 	[BTF_KIND_INT]		= "INT",
22 	[BTF_KIND_PTR]		= "PTR",
23 	[BTF_KIND_ARRAY]	= "ARRAY",
24 	[BTF_KIND_STRUCT]	= "STRUCT",
25 	[BTF_KIND_UNION]	= "UNION",
26 	[BTF_KIND_ENUM]		= "ENUM",
27 	[BTF_KIND_FWD]		= "FWD",
28 	[BTF_KIND_TYPEDEF]	= "TYPEDEF",
29 	[BTF_KIND_VOLATILE]	= "VOLATILE",
30 	[BTF_KIND_CONST]	= "CONST",
31 	[BTF_KIND_RESTRICT]	= "RESTRICT",
32 	[BTF_KIND_FUNC]		= "FUNC",
33 	[BTF_KIND_FUNC_PROTO]	= "FUNC_PROTO",
34 	[BTF_KIND_VAR]		= "VAR",
35 	[BTF_KIND_DATASEC]	= "DATASEC",
36 };
37 
38 static const char *btf_int_enc_str(__u8 encoding)
39 {
40 	switch (encoding) {
41 	case 0:
42 		return "(none)";
43 	case BTF_INT_SIGNED:
44 		return "SIGNED";
45 	case BTF_INT_CHAR:
46 		return "CHAR";
47 	case BTF_INT_BOOL:
48 		return "BOOL";
49 	default:
50 		return "UNKN";
51 	}
52 }
53 
54 static const char *btf_var_linkage_str(__u32 linkage)
55 {
56 	switch (linkage) {
57 	case BTF_VAR_STATIC:
58 		return "static";
59 	case BTF_VAR_GLOBAL_ALLOCATED:
60 		return "global-alloc";
61 	default:
62 		return "(unknown)";
63 	}
64 }
65 
66 static const char *btf_str(const struct btf *btf, __u32 off)
67 {
68 	if (!off)
69 		return "(anon)";
70 	return btf__name_by_offset(btf, off) ? : "(invalid)";
71 }
72 
73 static int dump_btf_type(const struct btf *btf, __u32 id,
74 			 const struct btf_type *t)
75 {
76 	json_writer_t *w = json_wtr;
77 	int kind, safe_kind;
78 
79 	kind = BTF_INFO_KIND(t->info);
80 	safe_kind = kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
81 
82 	if (json_output) {
83 		jsonw_start_object(w);
84 		jsonw_uint_field(w, "id", id);
85 		jsonw_string_field(w, "kind", btf_kind_str[safe_kind]);
86 		jsonw_string_field(w, "name", btf_str(btf, t->name_off));
87 	} else {
88 		printf("[%u] %s '%s'", id, btf_kind_str[safe_kind],
89 		       btf_str(btf, t->name_off));
90 	}
91 
92 	switch (BTF_INFO_KIND(t->info)) {
93 	case BTF_KIND_INT: {
94 		__u32 v = *(__u32 *)(t + 1);
95 		const char *enc;
96 
97 		enc = btf_int_enc_str(BTF_INT_ENCODING(v));
98 
99 		if (json_output) {
100 			jsonw_uint_field(w, "size", t->size);
101 			jsonw_uint_field(w, "bits_offset", BTF_INT_OFFSET(v));
102 			jsonw_uint_field(w, "nr_bits", BTF_INT_BITS(v));
103 			jsonw_string_field(w, "encoding", enc);
104 		} else {
105 			printf(" size=%u bits_offset=%u nr_bits=%u encoding=%s",
106 			       t->size, BTF_INT_OFFSET(v), BTF_INT_BITS(v),
107 			       enc);
108 		}
109 		break;
110 	}
111 	case BTF_KIND_PTR:
112 	case BTF_KIND_CONST:
113 	case BTF_KIND_VOLATILE:
114 	case BTF_KIND_RESTRICT:
115 	case BTF_KIND_TYPEDEF:
116 		if (json_output)
117 			jsonw_uint_field(w, "type_id", t->type);
118 		else
119 			printf(" type_id=%u", t->type);
120 		break;
121 	case BTF_KIND_ARRAY: {
122 		const struct btf_array *arr = (const void *)(t + 1);
123 
124 		if (json_output) {
125 			jsonw_uint_field(w, "type_id", arr->type);
126 			jsonw_uint_field(w, "index_type_id", arr->index_type);
127 			jsonw_uint_field(w, "nr_elems", arr->nelems);
128 		} else {
129 			printf(" type_id=%u index_type_id=%u nr_elems=%u",
130 			       arr->type, arr->index_type, arr->nelems);
131 		}
132 		break;
133 	}
134 	case BTF_KIND_STRUCT:
135 	case BTF_KIND_UNION: {
136 		const struct btf_member *m = (const void *)(t + 1);
137 		__u16 vlen = BTF_INFO_VLEN(t->info);
138 		int i;
139 
140 		if (json_output) {
141 			jsonw_uint_field(w, "size", t->size);
142 			jsonw_uint_field(w, "vlen", vlen);
143 			jsonw_name(w, "members");
144 			jsonw_start_array(w);
145 		} else {
146 			printf(" size=%u vlen=%u", t->size, vlen);
147 		}
148 		for (i = 0; i < vlen; i++, m++) {
149 			const char *name = btf_str(btf, m->name_off);
150 			__u32 bit_off, bit_sz;
151 
152 			if (BTF_INFO_KFLAG(t->info)) {
153 				bit_off = BTF_MEMBER_BIT_OFFSET(m->offset);
154 				bit_sz = BTF_MEMBER_BITFIELD_SIZE(m->offset);
155 			} else {
156 				bit_off = m->offset;
157 				bit_sz = 0;
158 			}
159 
160 			if (json_output) {
161 				jsonw_start_object(w);
162 				jsonw_string_field(w, "name", name);
163 				jsonw_uint_field(w, "type_id", m->type);
164 				jsonw_uint_field(w, "bits_offset", bit_off);
165 				if (bit_sz) {
166 					jsonw_uint_field(w, "bitfield_size",
167 							 bit_sz);
168 				}
169 				jsonw_end_object(w);
170 			} else {
171 				printf("\n\t'%s' type_id=%u bits_offset=%u",
172 				       name, m->type, bit_off);
173 				if (bit_sz)
174 					printf(" bitfield_size=%u", bit_sz);
175 			}
176 		}
177 		if (json_output)
178 			jsonw_end_array(w);
179 		break;
180 	}
181 	case BTF_KIND_ENUM: {
182 		const struct btf_enum *v = (const void *)(t + 1);
183 		__u16 vlen = BTF_INFO_VLEN(t->info);
184 		int i;
185 
186 		if (json_output) {
187 			jsonw_uint_field(w, "size", t->size);
188 			jsonw_uint_field(w, "vlen", vlen);
189 			jsonw_name(w, "values");
190 			jsonw_start_array(w);
191 		} else {
192 			printf(" size=%u vlen=%u", t->size, vlen);
193 		}
194 		for (i = 0; i < vlen; i++, v++) {
195 			const char *name = btf_str(btf, v->name_off);
196 
197 			if (json_output) {
198 				jsonw_start_object(w);
199 				jsonw_string_field(w, "name", name);
200 				jsonw_uint_field(w, "val", v->val);
201 				jsonw_end_object(w);
202 			} else {
203 				printf("\n\t'%s' val=%u", name, v->val);
204 			}
205 		}
206 		if (json_output)
207 			jsonw_end_array(w);
208 		break;
209 	}
210 	case BTF_KIND_FWD: {
211 		const char *fwd_kind = BTF_INFO_KFLAG(t->info) ? "union"
212 							       : "struct";
213 
214 		if (json_output)
215 			jsonw_string_field(w, "fwd_kind", fwd_kind);
216 		else
217 			printf(" fwd_kind=%s", fwd_kind);
218 		break;
219 	}
220 	case BTF_KIND_FUNC:
221 		if (json_output)
222 			jsonw_uint_field(w, "type_id", t->type);
223 		else
224 			printf(" type_id=%u", t->type);
225 		break;
226 	case BTF_KIND_FUNC_PROTO: {
227 		const struct btf_param *p = (const void *)(t + 1);
228 		__u16 vlen = BTF_INFO_VLEN(t->info);
229 		int i;
230 
231 		if (json_output) {
232 			jsonw_uint_field(w, "ret_type_id", t->type);
233 			jsonw_uint_field(w, "vlen", vlen);
234 			jsonw_name(w, "params");
235 			jsonw_start_array(w);
236 		} else {
237 			printf(" ret_type_id=%u vlen=%u", t->type, vlen);
238 		}
239 		for (i = 0; i < vlen; i++, p++) {
240 			const char *name = btf_str(btf, p->name_off);
241 
242 			if (json_output) {
243 				jsonw_start_object(w);
244 				jsonw_string_field(w, "name", name);
245 				jsonw_uint_field(w, "type_id", p->type);
246 				jsonw_end_object(w);
247 			} else {
248 				printf("\n\t'%s' type_id=%u", name, p->type);
249 			}
250 		}
251 		if (json_output)
252 			jsonw_end_array(w);
253 		break;
254 	}
255 	case BTF_KIND_VAR: {
256 		const struct btf_var *v = (const void *)(t + 1);
257 		const char *linkage;
258 
259 		linkage = btf_var_linkage_str(v->linkage);
260 
261 		if (json_output) {
262 			jsonw_uint_field(w, "type_id", t->type);
263 			jsonw_string_field(w, "linkage", linkage);
264 		} else {
265 			printf(" type_id=%u, linkage=%s", t->type, linkage);
266 		}
267 		break;
268 	}
269 	case BTF_KIND_DATASEC: {
270 		const struct btf_var_secinfo *v = (const void *)(t+1);
271 		__u16 vlen = BTF_INFO_VLEN(t->info);
272 		int i;
273 
274 		if (json_output) {
275 			jsonw_uint_field(w, "size", t->size);
276 			jsonw_uint_field(w, "vlen", vlen);
277 			jsonw_name(w, "vars");
278 			jsonw_start_array(w);
279 		} else {
280 			printf(" size=%u vlen=%u", t->size, vlen);
281 		}
282 		for (i = 0; i < vlen; i++, v++) {
283 			if (json_output) {
284 				jsonw_start_object(w);
285 				jsonw_uint_field(w, "type_id", v->type);
286 				jsonw_uint_field(w, "offset", v->offset);
287 				jsonw_uint_field(w, "size", v->size);
288 				jsonw_end_object(w);
289 			} else {
290 				printf("\n\ttype_id=%u offset=%u size=%u",
291 				       v->type, v->offset, v->size);
292 			}
293 		}
294 		if (json_output)
295 			jsonw_end_array(w);
296 		break;
297 	}
298 	default:
299 		break;
300 	}
301 
302 	if (json_output)
303 		jsonw_end_object(json_wtr);
304 	else
305 		printf("\n");
306 
307 	return 0;
308 }
309 
310 static int dump_btf_raw(const struct btf *btf,
311 			__u32 *root_type_ids, int root_type_cnt)
312 {
313 	const struct btf_type *t;
314 	int i;
315 
316 	if (json_output) {
317 		jsonw_start_object(json_wtr);
318 		jsonw_name(json_wtr, "types");
319 		jsonw_start_array(json_wtr);
320 	}
321 
322 	if (root_type_cnt) {
323 		for (i = 0; i < root_type_cnt; i++) {
324 			t = btf__type_by_id(btf, root_type_ids[i]);
325 			dump_btf_type(btf, root_type_ids[i], t);
326 		}
327 	} else {
328 		int cnt = btf__get_nr_types(btf);
329 
330 		for (i = 1; i <= cnt; i++) {
331 			t = btf__type_by_id(btf, i);
332 			dump_btf_type(btf, i, t);
333 		}
334 	}
335 
336 	if (json_output) {
337 		jsonw_end_array(json_wtr);
338 		jsonw_end_object(json_wtr);
339 	}
340 	return 0;
341 }
342 
343 static bool check_btf_endianness(GElf_Ehdr *ehdr)
344 {
345 	static unsigned int const endian = 1;
346 
347 	switch (ehdr->e_ident[EI_DATA]) {
348 	case ELFDATA2LSB:
349 		return *(unsigned char const *)&endian == 1;
350 	case ELFDATA2MSB:
351 		return *(unsigned char const *)&endian == 0;
352 	default:
353 		return 0;
354 	}
355 }
356 
357 static int btf_load_from_elf(const char *path, struct btf **btf)
358 {
359 	int err = -1, fd = -1, idx = 0;
360 	Elf_Data *btf_data = NULL;
361 	Elf_Scn *scn = NULL;
362 	Elf *elf = NULL;
363 	GElf_Ehdr ehdr;
364 
365 	if (elf_version(EV_CURRENT) == EV_NONE) {
366 		p_err("failed to init libelf for %s", path);
367 		return -1;
368 	}
369 
370 	fd = open(path, O_RDONLY);
371 	if (fd < 0) {
372 		p_err("failed to open %s: %s", path, strerror(errno));
373 		return -1;
374 	}
375 
376 	elf = elf_begin(fd, ELF_C_READ, NULL);
377 	if (!elf) {
378 		p_err("failed to open %s as ELF file", path);
379 		goto done;
380 	}
381 	if (!gelf_getehdr(elf, &ehdr)) {
382 		p_err("failed to get EHDR from %s", path);
383 		goto done;
384 	}
385 	if (!check_btf_endianness(&ehdr)) {
386 		p_err("non-native ELF endianness is not supported");
387 		goto done;
388 	}
389 	if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
390 		p_err("failed to get e_shstrndx from %s\n", path);
391 		goto done;
392 	}
393 
394 	while ((scn = elf_nextscn(elf, scn)) != NULL) {
395 		GElf_Shdr sh;
396 		char *name;
397 
398 		idx++;
399 		if (gelf_getshdr(scn, &sh) != &sh) {
400 			p_err("failed to get section(%d) header from %s",
401 			      idx, path);
402 			goto done;
403 		}
404 		name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
405 		if (!name) {
406 			p_err("failed to get section(%d) name from %s",
407 			      idx, path);
408 			goto done;
409 		}
410 		if (strcmp(name, BTF_ELF_SEC) == 0) {
411 			btf_data = elf_getdata(scn, 0);
412 			if (!btf_data) {
413 				p_err("failed to get section(%d, %s) data from %s",
414 				      idx, name, path);
415 				goto done;
416 			}
417 			break;
418 		}
419 	}
420 
421 	if (!btf_data) {
422 		p_err("%s ELF section not found in %s", BTF_ELF_SEC, path);
423 		goto done;
424 	}
425 
426 	*btf = btf__new(btf_data->d_buf, btf_data->d_size);
427 	if (IS_ERR(*btf)) {
428 		err = PTR_ERR(*btf);
429 		*btf = NULL;
430 		p_err("failed to load BTF data from %s: %s",
431 		      path, strerror(err));
432 		goto done;
433 	}
434 
435 	err = 0;
436 done:
437 	if (err) {
438 		if (*btf) {
439 			btf__free(*btf);
440 			*btf = NULL;
441 		}
442 	}
443 	if (elf)
444 		elf_end(elf);
445 	close(fd);
446 	return err;
447 }
448 
449 static int do_dump(int argc, char **argv)
450 {
451 	struct btf *btf = NULL;
452 	__u32 root_type_ids[2];
453 	int root_type_cnt = 0;
454 	__u32 btf_id = -1;
455 	const char *src;
456 	int fd = -1;
457 	int err;
458 
459 	if (!REQ_ARGS(2)) {
460 		usage();
461 		return -1;
462 	}
463 	src = GET_ARG();
464 
465 	if (is_prefix(src, "map")) {
466 		struct bpf_map_info info = {};
467 		__u32 len = sizeof(info);
468 
469 		if (!REQ_ARGS(2)) {
470 			usage();
471 			return -1;
472 		}
473 
474 		fd = map_parse_fd_and_info(&argc, &argv, &info, &len);
475 		if (fd < 0)
476 			return -1;
477 
478 		btf_id = info.btf_id;
479 		if (argc && is_prefix(*argv, "key")) {
480 			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
481 			NEXT_ARG();
482 		} else if (argc && is_prefix(*argv, "value")) {
483 			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
484 			NEXT_ARG();
485 		} else if (argc && is_prefix(*argv, "all")) {
486 			NEXT_ARG();
487 		} else if (argc && is_prefix(*argv, "kv")) {
488 			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
489 			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
490 			NEXT_ARG();
491 		} else {
492 			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
493 			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
494 		}
495 	} else if (is_prefix(src, "prog")) {
496 		struct bpf_prog_info info = {};
497 		__u32 len = sizeof(info);
498 
499 		if (!REQ_ARGS(2)) {
500 			usage();
501 			return -1;
502 		}
503 
504 		fd = prog_parse_fd(&argc, &argv);
505 		if (fd < 0)
506 			return -1;
507 
508 		err = bpf_obj_get_info_by_fd(fd, &info, &len);
509 		if (err) {
510 			p_err("can't get prog info: %s", strerror(errno));
511 			goto done;
512 		}
513 
514 		btf_id = info.btf_id;
515 	} else if (is_prefix(src, "id")) {
516 		char *endptr;
517 
518 		btf_id = strtoul(*argv, &endptr, 0);
519 		if (*endptr) {
520 			p_err("can't parse %s as ID", **argv);
521 			return -1;
522 		}
523 		NEXT_ARG();
524 	} else if (is_prefix(src, "file")) {
525 		err = btf_load_from_elf(*argv, &btf);
526 		if (err)
527 			goto done;
528 		NEXT_ARG();
529 	} else {
530 		err = -1;
531 		p_err("unrecognized BTF source specifier: '%s'", src);
532 		goto done;
533 	}
534 
535 	if (!btf) {
536 		err = btf__get_from_id(btf_id, &btf);
537 		if (err) {
538 			p_err("get btf by id (%u): %s", btf_id, strerror(err));
539 			goto done;
540 		}
541 		if (!btf) {
542 			err = ENOENT;
543 			p_err("can't find btf with ID (%u)", btf_id);
544 			goto done;
545 		}
546 	}
547 
548 	dump_btf_raw(btf, root_type_ids, root_type_cnt);
549 
550 done:
551 	close(fd);
552 	btf__free(btf);
553 	return err;
554 }
555 
556 static int do_help(int argc, char **argv)
557 {
558 	if (json_output) {
559 		jsonw_null(json_wtr);
560 		return 0;
561 	}
562 
563 	fprintf(stderr,
564 		"Usage: %s btf dump BTF_SRC\n"
565 		"       %s btf help\n"
566 		"\n"
567 		"       BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"
568 		"       " HELP_SPEC_MAP "\n"
569 		"       " HELP_SPEC_PROGRAM "\n"
570 		"       " HELP_SPEC_OPTIONS "\n"
571 		"",
572 		bin_name, bin_name);
573 
574 	return 0;
575 }
576 
577 static const struct cmd cmds[] = {
578 	{ "help",	do_help },
579 	{ "dump",	do_dump },
580 	{ 0 }
581 };
582 
583 int do_btf(int argc, char **argv)
584 {
585 	return cmd_select(cmds, argc, argv, do_help);
586 }
587