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8e2aed3f AB |
1 | /* |
2 | * Copyright (C) 2015 Antoine Busque <abusque@efficios.com> | |
3 | * | |
4 | * This library is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU Lesser General Public | |
6 | * License as published by the Free Software Foundation; either | |
7 | * version 2.1 of the License, or (at your option) any later version. | |
8 | * | |
9 | * This library is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * Lesser General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU Lesser General Public | |
15 | * License along with this library; if not, write to the Free Software | |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
17 | */ | |
18 | ||
19 | #include <helper.h> | |
20 | #include <string.h> | |
21 | #include <lttng/align.h> | |
22 | #include <lttng/ust-elf.h> | |
23 | ||
24 | /* | |
25 | * Retrieve the nth (where n is the `index` argument) phdr (program | |
26 | * header) from the given elf instance. | |
27 | * | |
28 | * A pointer to the phdr is returned on success, NULL on failure. | |
29 | */ | |
30 | static | |
31 | struct lttng_ust_elf_phdr *lttng_ust_elf_get_phdr(struct lttng_ust_elf *elf, | |
32 | uint16_t index) | |
33 | { | |
34 | struct lttng_ust_elf_phdr *phdr = NULL; | |
35 | long offset; | |
36 | ||
37 | if (!elf) { | |
38 | goto error; | |
39 | } | |
40 | ||
41 | if (index >= elf->ehdr->e_phnum) { | |
42 | goto error; | |
43 | } | |
44 | ||
45 | phdr = zmalloc(sizeof(struct lttng_ust_elf_phdr)); | |
46 | if (!phdr) { | |
47 | goto error; | |
48 | } | |
49 | ||
50 | offset = elf->ehdr->e_phoff + index * elf->ehdr->e_phentsize; | |
51 | if (fseek(elf->file, offset, SEEK_SET)) { | |
52 | goto error; | |
53 | } | |
54 | ||
55 | if (is_elf_32_bit(elf)) { | |
56 | Elf32_Phdr elf_phdr; | |
57 | ||
58 | if (!fread(&elf_phdr, sizeof(elf_phdr), 1, elf->file)) { | |
59 | goto error; | |
60 | } | |
61 | if (!is_elf_native_endian(elf)) { | |
62 | bswap_phdr(elf_phdr); | |
63 | } | |
64 | copy_phdr(elf_phdr, *phdr); | |
65 | } else { | |
66 | Elf64_Phdr elf_phdr; | |
67 | ||
68 | if (!fread(&elf_phdr, sizeof(elf_phdr), 1, elf->file)) { | |
69 | goto error; | |
70 | } | |
71 | if (!is_elf_native_endian(elf)) { | |
72 | bswap_phdr(elf_phdr); | |
73 | } | |
74 | copy_phdr(elf_phdr, *phdr); | |
75 | } | |
76 | ||
77 | return phdr; | |
78 | ||
79 | error: | |
80 | free(phdr); | |
81 | return NULL; | |
82 | } | |
83 | ||
84 | /* | |
85 | * Retrieve the nth (where n is the `index` argument) shdr (section | |
86 | * header) from the given elf instance. | |
87 | * | |
88 | * A pointer to the shdr is returned on success, NULL on failure. | |
89 | */ | |
90 | static | |
91 | struct lttng_ust_elf_shdr *lttng_ust_elf_get_shdr(struct lttng_ust_elf *elf, | |
92 | uint16_t index) | |
93 | { | |
94 | struct lttng_ust_elf_shdr *shdr = NULL; | |
95 | long offset; | |
96 | ||
97 | if (!elf) { | |
98 | goto error; | |
99 | } | |
100 | ||
101 | if (index >= elf->ehdr->e_shnum) { | |
102 | goto error; | |
103 | } | |
104 | ||
105 | shdr = zmalloc(sizeof(struct lttng_ust_elf_shdr)); | |
106 | if (!shdr) { | |
107 | goto error; | |
108 | } | |
109 | ||
110 | offset = elf->ehdr->e_shoff + index * elf->ehdr->e_shentsize; | |
111 | if (fseek(elf->file, offset, SEEK_SET)) { | |
112 | goto error; | |
113 | } | |
114 | ||
115 | if (is_elf_32_bit(elf)) { | |
116 | Elf32_Shdr elf_shdr; | |
117 | ||
118 | if (!fread(&elf_shdr, sizeof(elf_shdr), 1, elf->file)) { | |
119 | goto error; | |
120 | } | |
121 | if (!is_elf_native_endian(elf)) { | |
122 | bswap_shdr(elf_shdr); | |
123 | } | |
124 | copy_shdr(elf_shdr, *shdr); | |
125 | } else { | |
126 | Elf64_Shdr elf_shdr; | |
127 | ||
128 | if (!fread(&elf_shdr, sizeof(elf_shdr), 1, elf->file)) { | |
129 | goto error; | |
130 | } | |
131 | if (!is_elf_native_endian(elf)) { | |
132 | bswap_shdr(elf_shdr); | |
133 | } | |
134 | copy_shdr(elf_shdr, *shdr); | |
135 | } | |
136 | ||
137 | return shdr; | |
138 | ||
139 | error: | |
140 | free(shdr); | |
141 | return NULL; | |
142 | } | |
143 | ||
144 | /* | |
145 | * Lookup a section's name from a given offset (usually from an shdr's | |
146 | * sh_name value) in bytes relative to the beginning of the section | |
147 | * names string table. | |
148 | * | |
149 | * If no name is found, NULL is returned. | |
150 | */ | |
151 | static | |
152 | char *lttng_ust_elf_get_section_name(struct lttng_ust_elf *elf, uint32_t offset) | |
153 | { | |
154 | char *name = NULL; | |
155 | size_t len; | |
156 | ||
157 | if (!elf) { | |
158 | goto error; | |
159 | } | |
160 | ||
161 | if (offset >= elf->section_names_size) { | |
162 | goto error; | |
163 | } | |
164 | ||
165 | if (fseek(elf->file, elf->section_names_offset + offset, SEEK_SET)) { | |
166 | goto error; | |
167 | } | |
168 | /* Note that len starts at 1, it is not an index. */ | |
169 | for (len = 1; offset + len <= elf->section_names_size; ++len) { | |
170 | switch (fgetc(elf->file)) { | |
171 | case EOF: | |
172 | goto error; | |
173 | case '\0': | |
174 | goto end; | |
175 | default: | |
176 | break; | |
177 | } | |
178 | } | |
179 | ||
180 | /* No name was found before the end of the table. */ | |
181 | goto error; | |
182 | ||
183 | end: | |
184 | name = zmalloc(sizeof(char) * len); | |
185 | if (!name) { | |
186 | goto error; | |
187 | } | |
188 | if (fseek(elf->file, elf->section_names_offset + offset, | |
189 | SEEK_SET)) { | |
190 | goto error; | |
191 | } | |
192 | if (!fgets(name, len, elf->file)) { | |
193 | goto error; | |
194 | } | |
195 | ||
196 | return name; | |
197 | ||
198 | error: | |
199 | free(name); | |
200 | return NULL; | |
201 | } | |
202 | ||
203 | /* | |
204 | * Create an instance of lttng_ust_elf for the ELF file located at | |
205 | * `path`. | |
206 | * | |
207 | * Return a pointer to the instance on success, NULL on failure. | |
208 | */ | |
209 | struct lttng_ust_elf *lttng_ust_elf_create(const char *path) | |
210 | { | |
211 | uint8_t e_ident[EI_NIDENT]; | |
212 | struct lttng_ust_elf_shdr *section_names_shdr; | |
213 | struct lttng_ust_elf *elf; | |
214 | ||
215 | elf = zmalloc(sizeof(struct lttng_ust_elf)); | |
216 | if (!elf) { | |
217 | goto error; | |
218 | } | |
219 | ||
220 | elf->path = strdup(path); | |
221 | if (!elf->path) { | |
222 | goto error; | |
223 | } | |
224 | ||
225 | elf->file = fopen(elf->path, "rb"); | |
226 | if (!elf->file) { | |
227 | goto error; | |
228 | } | |
229 | ||
230 | if (!fread(e_ident, 1, EI_NIDENT, elf->file)) { | |
231 | goto error; | |
232 | } | |
233 | elf->bitness = e_ident[EI_CLASS]; | |
234 | elf->endianness = e_ident[EI_DATA]; | |
235 | rewind(elf->file); | |
236 | ||
237 | elf->ehdr = zmalloc(sizeof(struct lttng_ust_elf_ehdr)); | |
238 | if (!elf->ehdr) { | |
239 | goto error; | |
240 | } | |
241 | ||
242 | if (is_elf_32_bit(elf)) { | |
243 | Elf32_Ehdr elf_ehdr; | |
244 | ||
245 | if (!fread(&elf_ehdr, sizeof(elf_ehdr), 1, elf->file)) { | |
246 | goto error; | |
247 | } | |
248 | if (!is_elf_native_endian(elf)) { | |
249 | bswap_ehdr(elf_ehdr); | |
250 | } | |
251 | copy_ehdr(elf_ehdr, *(elf->ehdr)); | |
252 | } else { | |
253 | Elf64_Ehdr elf_ehdr; | |
254 | ||
255 | if (!fread(&elf_ehdr, sizeof(elf_ehdr), 1, elf->file)) { | |
256 | goto error; | |
257 | } | |
258 | if (!is_elf_native_endian(elf)) { | |
259 | bswap_ehdr(elf_ehdr); | |
260 | } | |
261 | copy_ehdr(elf_ehdr, *(elf->ehdr)); | |
262 | } | |
263 | ||
264 | section_names_shdr = lttng_ust_elf_get_shdr(elf, elf->ehdr->e_shstrndx); | |
265 | if (!section_names_shdr) { | |
266 | goto error; | |
267 | } | |
268 | ||
269 | elf->section_names_offset = section_names_shdr->sh_offset; | |
270 | elf->section_names_size = section_names_shdr->sh_size; | |
271 | ||
272 | free(section_names_shdr); | |
273 | ||
274 | return elf; | |
275 | ||
276 | error: | |
277 | if (elf) { | |
278 | free(elf->ehdr); | |
279 | fclose(elf->file); | |
280 | free(elf->path); | |
281 | } | |
282 | free(elf); | |
283 | return NULL; | |
284 | } | |
285 | ||
286 | /* | |
287 | * Destroy the given lttng_ust_elf instance. | |
288 | */ | |
289 | void lttng_ust_elf_destroy(struct lttng_ust_elf *elf) | |
290 | { | |
291 | if (!elf) { | |
292 | return; | |
293 | } | |
294 | ||
295 | free(elf->ehdr); | |
296 | fclose(elf->file); | |
297 | free(elf->path); | |
298 | free(elf); | |
299 | } | |
300 | ||
301 | /* | |
302 | * Compute the total in-memory size of the ELF file, in bytes. | |
303 | * | |
304 | * Returns 0 if successful, -1 if not. On success, the memory size is | |
305 | * returned through the out parameter `memsz`. | |
306 | */ | |
307 | int lttng_ust_elf_get_memsz(struct lttng_ust_elf *elf, uint64_t *memsz) | |
308 | { | |
309 | uint16_t i; | |
310 | uint64_t _memsz = 0; | |
311 | ||
312 | if (!elf || !memsz) { | |
313 | goto error; | |
314 | } | |
315 | ||
316 | for (i = 0; i < elf->ehdr->e_phnum; ++i) { | |
317 | struct lttng_ust_elf_phdr *phdr; | |
318 | uint64_t align; | |
319 | ||
320 | phdr = lttng_ust_elf_get_phdr(elf, i); | |
321 | if (!phdr) { | |
322 | goto error; | |
323 | } | |
324 | ||
325 | /* | |
326 | * Only PT_LOAD segments contribute to memsz. Skip | |
327 | * other segments. | |
328 | */ | |
329 | if (phdr->p_type != PT_LOAD) { | |
330 | goto next_loop; | |
331 | } | |
332 | ||
333 | /* | |
334 | * A p_align of 0 means no alignment, i.e. aligned to | |
335 | * 1 byte. | |
336 | */ | |
337 | align = phdr->p_align == 0 ? 1 : phdr->p_align; | |
338 | /* Align the start of the segment. */ | |
339 | _memsz += offset_align(_memsz, align); | |
340 | _memsz += phdr->p_memsz; | |
341 | /* | |
342 | * Add padding at the end of the segment, so it ends | |
343 | * on a multiple of the align value (which usually | |
344 | * means a page boundary). This makes the computation | |
345 | * valid even in cases where p_align would change from | |
346 | * one segment to the next. | |
347 | */ | |
348 | _memsz += offset_align(_memsz, align); | |
349 | next_loop: | |
350 | free(phdr); | |
351 | } | |
352 | ||
353 | *memsz = _memsz; | |
354 | return 0; | |
355 | error: | |
356 | return -1; | |
357 | } | |
358 | ||
359 | /* | |
360 | * Internal method used to try and get the build_id from a PT_NOTE | |
361 | * segment ranging from `offset` to `segment_end`. | |
362 | * | |
363 | * If the function returns successfully, the out parameter `found` | |
364 | * indicates whether the build id information was present in the | |
365 | * segment or not. If `found` is not 0, the out parameters `build_id` | |
366 | * and `length` will both have been set with the retrieved | |
367 | * information. | |
368 | * | |
369 | * Returns 0 on success, -1 if an error occurred. | |
370 | */ | |
371 | static | |
372 | int lttng_ust_elf_get_build_id_from_segment( | |
373 | struct lttng_ust_elf *elf, uint8_t **build_id, size_t *length, | |
374 | uint64_t offset, uint64_t segment_end, int *found) | |
375 | { | |
376 | uint8_t *_build_id; | |
377 | size_t _length; | |
378 | int _found = 0; | |
379 | ||
380 | while (offset < segment_end) { | |
381 | struct lttng_ust_elf_nhdr nhdr; | |
382 | ||
383 | /* Align start of note entry */ | |
384 | offset += offset_align(offset, ELF_NOTE_ENTRY_ALIGN); | |
385 | if (offset >= segment_end) { | |
386 | break; | |
387 | } | |
388 | /* | |
389 | * We seek manually because if the note isn't the | |
390 | * build id the data following the header will not | |
391 | * have been read. | |
392 | */ | |
393 | if (fseek(elf->file, offset, SEEK_SET)) { | |
394 | goto error; | |
395 | } | |
396 | if (!fread(&nhdr, sizeof(nhdr), 1, elf->file)) { | |
397 | goto error; | |
398 | } | |
399 | ||
400 | if (!is_elf_native_endian(elf)) { | |
401 | nhdr.n_namesz = bswap_32(nhdr.n_namesz); | |
402 | nhdr.n_descsz = bswap_32(nhdr.n_descsz); | |
403 | nhdr.n_type = bswap_32(nhdr.n_type); | |
404 | } | |
405 | ||
406 | offset += sizeof(nhdr) + nhdr.n_namesz; | |
407 | /* Align start of desc entry */ | |
408 | offset += offset_align(offset, ELF_NOTE_DESC_ALIGN); | |
409 | ||
410 | if (nhdr.n_type != NT_GNU_BUILD_ID) { | |
411 | /* | |
412 | * Ignore non build id notes but still | |
413 | * increase the offset. | |
414 | */ | |
415 | offset += nhdr.n_descsz; | |
416 | continue; | |
417 | } | |
418 | ||
419 | _length = nhdr.n_descsz; | |
420 | _build_id = zmalloc(sizeof(uint8_t) * _length); | |
421 | if (!build_id) { | |
422 | goto error; | |
423 | } | |
424 | ||
425 | if (fseek(elf->file, offset, SEEK_SET)) { | |
426 | goto error; | |
427 | } | |
428 | if (!fread(_build_id, sizeof(*_build_id), _length, elf->file)) { | |
429 | goto error; | |
430 | } | |
431 | ||
432 | _found = 1; | |
433 | break; | |
434 | } | |
435 | ||
436 | if (_found) { | |
437 | *build_id = _build_id; | |
438 | *length = _length; | |
439 | } | |
440 | ||
441 | *found = _found; | |
442 | return 0; | |
443 | error: | |
444 | return -1; | |
445 | } | |
446 | ||
447 | /* | |
448 | * Retrieve a build ID (an array of bytes) from the corresponding | |
449 | * section in the ELF file. The length of the build ID can be either | |
450 | * 16 or 20 bytes depending on the method used to generate it, hence | |
451 | * the length out parameter. | |
452 | * | |
453 | * If the function returns successfully, the out parameter `found` | |
454 | * indicates whether the build id information was present in the ELF | |
455 | * file or not. If `found` is not 0, the out parameters `build_id` and | |
456 | * `length` will both have been set with the retrieved information. | |
457 | * | |
458 | * Returns 0 on success, -1 if an error occurred. | |
459 | */ | |
460 | int lttng_ust_elf_get_build_id(struct lttng_ust_elf *elf, uint8_t **build_id, | |
461 | size_t *length, int *found) | |
462 | { | |
463 | uint16_t i; | |
464 | uint8_t *_build_id; | |
465 | size_t _length; | |
466 | int _found = 0; | |
467 | ||
468 | if (!elf || !build_id || !length || !found) { | |
469 | goto error; | |
470 | } | |
471 | ||
472 | for (i = 0; i < elf->ehdr->e_phnum; ++i) { | |
473 | uint64_t offset, segment_end; | |
474 | struct lttng_ust_elf_phdr *phdr; | |
475 | int ret; | |
476 | ||
477 | phdr = lttng_ust_elf_get_phdr(elf, i); | |
478 | if (!phdr) { | |
479 | goto error; | |
480 | } | |
481 | ||
482 | /* Build ID will be contained in a PT_NOTE segment. */ | |
483 | if (phdr->p_type != PT_NOTE) { | |
484 | goto next_loop; | |
485 | } | |
486 | ||
487 | offset = phdr->p_offset; | |
488 | segment_end = offset + phdr->p_filesz; | |
489 | ret = lttng_ust_elf_get_build_id_from_segment( | |
490 | elf, &_build_id, &_length, offset, segment_end, | |
491 | &_found); | |
492 | next_loop: | |
493 | free(phdr); | |
494 | if (ret) { | |
495 | goto error; | |
496 | } | |
497 | if (_found) { | |
498 | break; | |
499 | } | |
500 | } | |
501 | ||
502 | if (_found) { | |
503 | *build_id = _build_id; | |
504 | *length = _length; | |
505 | } | |
506 | ||
507 | *found = _found; | |
508 | return 0; | |
509 | error: | |
510 | return -1; | |
511 | } | |
512 | ||
513 | /* | |
514 | * Try to retrieve filename and CRC from given ELF section `shdr`. | |
515 | * | |
516 | * If the function returns successfully, the out parameter `found` | |
517 | * indicates whether the debug link information was present in the ELF | |
518 | * section or not. If `found` is not 0, the out parameters `filename` and | |
519 | * `crc` will both have been set with the retrieved information. | |
520 | * | |
521 | * Returns 0 on success, -1 if an error occurred. | |
522 | */ | |
523 | static | |
524 | int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf *elf, | |
525 | char **filename, uint32_t *crc, | |
526 | int *found, | |
527 | struct lttng_ust_elf_shdr *shdr) | |
528 | { | |
529 | int _found = 0; | |
530 | char *_filename; | |
531 | char *section_name = NULL; | |
532 | uint32_t _crc; | |
533 | ||
534 | if (!elf || !filename || !crc || !found || !shdr) { | |
535 | goto error; | |
536 | } | |
537 | ||
538 | /* | |
539 | * The .gnu_debuglink section is of type SHT_PROGBITS, | |
540 | * skip the other sections. | |
541 | */ | |
542 | if (shdr->sh_type != SHT_PROGBITS) { | |
543 | goto end; | |
544 | } | |
545 | ||
546 | section_name = lttng_ust_elf_get_section_name(elf, | |
547 | shdr->sh_name); | |
548 | if (!section_name) { | |
549 | goto end; | |
550 | } | |
551 | if (strcmp(section_name, ".gnu_debuglink")) { | |
552 | goto end; | |
553 | } | |
554 | ||
555 | /* | |
556 | * The length of the filename is the sh_size excluding the CRC | |
557 | * which comes after it in the section. | |
558 | */ | |
559 | _filename = zmalloc(sizeof(char) * (shdr->sh_size - ELF_CRC_SIZE)); | |
560 | if (!_filename) { | |
561 | goto error; | |
562 | } | |
563 | if (fseek(elf->file, shdr->sh_offset, SEEK_SET)) { | |
564 | goto error; | |
565 | } | |
566 | if (!fread(_filename, sizeof(*_filename), shdr->sh_size - ELF_CRC_SIZE, | |
567 | elf->file)) { | |
568 | goto error; | |
569 | } | |
570 | if (!fread(&_crc, sizeof(_crc), 1, elf->file)) { | |
571 | goto error; | |
572 | } | |
573 | if (!is_elf_native_endian(elf)) { | |
574 | _crc = bswap_32(_crc); | |
575 | } | |
576 | ||
577 | _found = 1; | |
578 | ||
579 | end: | |
580 | free(section_name); | |
581 | if (_found) { | |
582 | *filename = _filename; | |
583 | *crc = _crc; | |
584 | } | |
585 | *found = _found; | |
586 | ||
587 | return 0; | |
588 | ||
589 | error: | |
590 | if (section_name) { | |
591 | free(section_name); | |
592 | } | |
593 | ||
594 | return -1; | |
595 | } | |
596 | ||
597 | /* | |
598 | * Retrieve filename and CRC from ELF's .gnu_debuglink section, if any. | |
599 | * | |
600 | * If the function returns successfully, the out parameter `found` | |
601 | * indicates whether the debug link information was present in the ELF | |
602 | * file or not. If `found` is not 0, the out parameters `filename` and | |
603 | * `crc` will both have been set with the retrieved information. | |
604 | * | |
605 | * Returns 0 on success, -1 if an error occurred. | |
606 | */ | |
607 | int lttng_ust_elf_get_debug_link(struct lttng_ust_elf *elf, char **filename, | |
608 | uint32_t *crc, int *found) | |
609 | { | |
610 | int ret; | |
611 | uint16_t i; | |
612 | int _found = 0; | |
613 | char *_filename; | |
614 | uint32_t _crc; | |
615 | ||
616 | if (!elf || !filename || !crc || !found) { | |
617 | goto error; | |
618 | } | |
619 | ||
620 | for (i = 0; i < elf->ehdr->e_shnum; ++i) { | |
621 | struct lttng_ust_elf_shdr *shdr = NULL; | |
622 | ||
623 | shdr = lttng_ust_elf_get_shdr(elf, i); | |
624 | if (!shdr) { | |
625 | goto error; | |
626 | } | |
627 | ||
628 | ret = lttng_ust_elf_get_debug_link_from_section( | |
629 | elf, &_filename, &_crc, &_found, shdr); | |
630 | free(shdr); | |
631 | ||
632 | if (ret) { | |
633 | goto error; | |
634 | } | |
635 | if (_found) { | |
636 | break; | |
637 | } | |
638 | } | |
639 | ||
640 | if (_found) { | |
641 | *filename = _filename; | |
642 | *crc = _crc; | |
643 | } | |
644 | ||
645 | *found = _found; | |
646 | return 0; | |
647 | error: | |
648 | return -1; | |
649 | } |