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Fix: relayd: Dereference before null check
[lttng-tools.git] / src / common / lttng-elf.c
1 /*
2 * Copyright (C) 2015 Antoine Busque <abusque@efficios.com>
3 * Copyright (C) 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
4 * Copyright (C) 2017 Erica Bugden <erica.bugden@efficios.com>
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21 #include <common/compat/endian.h>
22 #include <common/error.h>
23 #include <common/lttng-elf.h>
24 #include <common/macros.h>
25 #include <common/readwrite.h>
26 #include <fcntl.h>
27 #include <stdbool.h>
28 #include <stdint.h>
29 #include <stdlib.h>
30 #include <string.h>
31 #include <sys/stat.h>
32 #include <sys/types.h>
33 #include <unistd.h>
34
35 #include <elf.h>
36
37 #define BUF_LEN 4096
38 #define TEXT_SECTION_NAME ".text"
39 #define SYMBOL_TAB_SECTION_NAME ".symtab"
40 #define STRING_TAB_SECTION_NAME ".strtab"
41 #define DYNAMIC_SYMBOL_TAB_SECTION_NAME ".dynsym"
42 #define DYNAMIC_STRING_TAB_SECTION_NAME ".dynstr"
43 #define NOTE_STAPSDT_SECTION_NAME ".note.stapsdt"
44 #define NOTE_STAPSDT_NAME "stapsdt"
45 #define NOTE_STAPSDT_TYPE 3
46
47 #if BYTE_ORDER == LITTLE_ENDIAN
48 #define NATIVE_ELF_ENDIANNESS ELFDATA2LSB
49 #else
50 #define NATIVE_ELF_ENDIANNESS ELFDATA2MSB
51 #endif
52
53 #define next_4bytes_boundary(x) (typeof(x)) ((((uint64_t)x) + 3) & ~0x03)
54
55 #define bswap(x) \
56 do { \
57 switch (sizeof(x)) { \
58 case 8: \
59 x = be64toh((uint64_t)x); \
60 break; \
61 case 4: \
62 x = be32toh((uint32_t)x); \
63 break; \
64 case 2: \
65 x = be16toh((uint16_t)x); \
66 break; \
67 case 1: \
68 break; \
69 default: \
70 abort(); \
71 } \
72 } while (0)
73
74 #define bswap_shdr(shdr) \
75 do { \
76 bswap((shdr).sh_name); \
77 bswap((shdr).sh_type); \
78 bswap((shdr).sh_flags); \
79 bswap((shdr).sh_addr); \
80 bswap((shdr).sh_offset); \
81 bswap((shdr).sh_size); \
82 bswap((shdr).sh_link); \
83 bswap((shdr).sh_info); \
84 bswap((shdr).sh_addralign); \
85 bswap((shdr).sh_entsize); \
86 } while (0)
87
88 #define bswap_ehdr(ehdr) \
89 do { \
90 bswap((ehdr).e_type); \
91 bswap((ehdr).e_machine); \
92 bswap((ehdr).e_version); \
93 bswap((ehdr).e_entry); \
94 bswap((ehdr).e_phoff); \
95 bswap((ehdr).e_shoff); \
96 bswap((ehdr).e_flags); \
97 bswap((ehdr).e_ehsize); \
98 bswap((ehdr).e_phentsize); \
99 bswap((ehdr).e_phnum); \
100 bswap((ehdr).e_shentsize); \
101 bswap((ehdr).e_shnum); \
102 bswap((ehdr).e_shstrndx); \
103 } while (0)
104
105 #define copy_shdr(src_shdr, dst_shdr) \
106 do { \
107 (dst_shdr).sh_name = (src_shdr).sh_name; \
108 (dst_shdr).sh_type = (src_shdr).sh_type; \
109 (dst_shdr).sh_flags = (src_shdr).sh_flags; \
110 (dst_shdr).sh_addr = (src_shdr).sh_addr; \
111 (dst_shdr).sh_offset = (src_shdr).sh_offset; \
112 (dst_shdr).sh_size = (src_shdr).sh_size; \
113 (dst_shdr).sh_link = (src_shdr).sh_link; \
114 (dst_shdr).sh_info = (src_shdr).sh_info; \
115 (dst_shdr).sh_addralign = (src_shdr).sh_addralign; \
116 (dst_shdr).sh_entsize = (src_shdr).sh_entsize; \
117 } while (0)
118
119 #define copy_ehdr(src_ehdr, dst_ehdr) \
120 do { \
121 (dst_ehdr).e_type = (src_ehdr).e_type; \
122 (dst_ehdr).e_machine = (src_ehdr).e_machine; \
123 (dst_ehdr).e_version = (src_ehdr).e_version; \
124 (dst_ehdr).e_entry = (src_ehdr).e_entry; \
125 (dst_ehdr).e_phoff = (src_ehdr).e_phoff; \
126 (dst_ehdr).e_shoff = (src_ehdr).e_shoff; \
127 (dst_ehdr).e_flags = (src_ehdr).e_flags; \
128 (dst_ehdr).e_ehsize = (src_ehdr).e_ehsize; \
129 (dst_ehdr).e_phentsize = (src_ehdr).e_phentsize; \
130 (dst_ehdr).e_phnum = (src_ehdr).e_phnum; \
131 (dst_ehdr).e_shentsize = (src_ehdr).e_shentsize; \
132 (dst_ehdr).e_shnum = (src_ehdr).e_shnum; \
133 (dst_ehdr).e_shstrndx = (src_ehdr).e_shstrndx; \
134 } while (0)
135
136 #define copy_sym(src_sym, dst_sym) \
137 do { \
138 dst_sym.st_name = src_sym.st_name; \
139 dst_sym.st_info = src_sym.st_info; \
140 dst_sym.st_other = src_sym.st_other; \
141 dst_sym.st_shndx = src_sym.st_shndx; \
142 dst_sym.st_value = src_sym.st_value; \
143 dst_sym.st_size = src_sym.st_size; \
144 } while (0)
145
146 /* Both 32bit and 64bit use the same 1 byte field for type. (See elf.h) */
147 #define ELF_ST_TYPE(val) ELF32_ST_TYPE(val)
148
149 struct lttng_elf_ehdr {
150 uint16_t e_type;
151 uint16_t e_machine;
152 uint32_t e_version;
153 uint64_t e_entry;
154 uint64_t e_phoff;
155 uint64_t e_shoff;
156 uint32_t e_flags;
157 uint16_t e_ehsize;
158 uint16_t e_phentsize;
159 uint16_t e_phnum;
160 uint16_t e_shentsize;
161 uint16_t e_shnum;
162 uint16_t e_shstrndx;
163 };
164
165 struct lttng_elf_shdr {
166 uint32_t sh_name;
167 uint32_t sh_type;
168 uint64_t sh_flags;
169 uint64_t sh_addr;
170 uint64_t sh_offset;
171 uint64_t sh_size;
172 uint32_t sh_link;
173 uint32_t sh_info;
174 uint64_t sh_addralign;
175 uint64_t sh_entsize;
176 };
177
178 /*
179 * This struct can hold both 32bit and 64bit symbol description. It's used with
180 * the copy_sym() macro. Using this abstraction, we can use the same code for
181 * both bitness.
182 */
183 struct lttng_elf_sym {
184 uint32_t st_name;
185 uint8_t st_info;
186 uint8_t st_other;
187 uint16_t st_shndx;
188 uint64_t st_value;
189 uint64_t st_size;
190 };
191
192 struct lttng_elf {
193 int fd;
194 uint8_t bitness;
195 uint8_t endianness;
196 /* Offset in bytes to start of section names string table. */
197 off_t section_names_offset;
198 /* Size in bytes of section names string table. */
199 size_t section_names_size;
200 struct lttng_elf_ehdr *ehdr;
201 };
202
203 static inline
204 int is_elf_32_bit(struct lttng_elf *elf)
205 {
206 return elf->bitness == ELFCLASS32;
207 }
208
209 static inline
210 int is_elf_native_endian(struct lttng_elf *elf)
211 {
212 return elf->endianness == NATIVE_ELF_ENDIANNESS;
213 }
214
215 static
216 int populate_section_header(struct lttng_elf * elf, struct lttng_elf_shdr *shdr,
217 uint32_t index)
218 {
219 int ret = 0;
220 off_t offset;
221
222 /* Compute the offset of the section in the file */
223 offset = (off_t) elf->ehdr->e_shoff
224 + (off_t) index * elf->ehdr->e_shentsize;
225
226 if (lseek(elf->fd, offset, SEEK_SET) < 0) {
227 PERROR("Error seeking to the beginning of ELF section header");
228 ret = -1;
229 goto error;
230 }
231
232 if (is_elf_32_bit(elf)) {
233 Elf32_Shdr elf_shdr;
234
235 if (lttng_read(elf->fd, &elf_shdr, sizeof(elf_shdr)) < sizeof(elf_shdr)) {
236 PERROR("Error reading ELF section header");
237 ret = -1;
238 goto error;
239 }
240 if (!is_elf_native_endian(elf)) {
241 bswap_shdr(elf_shdr);
242 }
243 copy_shdr(elf_shdr, *shdr);
244 } else {
245 Elf64_Shdr elf_shdr;
246
247 if (lttng_read(elf->fd, &elf_shdr, sizeof(elf_shdr)) < sizeof(elf_shdr)) {
248 PERROR("Error reading ELF section header");
249 ret = -1;
250 goto error;
251 }
252 if (!is_elf_native_endian(elf)) {
253 bswap_shdr(elf_shdr);
254 }
255 copy_shdr(elf_shdr, *shdr);
256 }
257
258 error:
259 return ret;
260 }
261
262 static
263 int populate_elf_header(struct lttng_elf *elf)
264 {
265 int ret = 0;
266
267 /*
268 * Move the read pointer back to the beginning to read the full header
269 * and copy it in our structure.
270 */
271 if (lseek(elf->fd, 0, SEEK_SET) < 0) {
272 PERROR("Error seeking to the beginning of the file");
273 ret = -1;
274 goto error;
275 }
276
277 /*
278 * Use macros to set fields in the ELF header struct for both 32bit and
279 * 64bit.
280 */
281 if (is_elf_32_bit(elf)) {
282 Elf32_Ehdr elf_ehdr;
283
284 if (lttng_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr)) < sizeof(elf_ehdr)) {
285 ret = -1;
286 goto error;
287 }
288 if (!is_elf_native_endian(elf)) {
289 bswap_ehdr(elf_ehdr);
290 }
291 copy_ehdr(elf_ehdr, *(elf->ehdr));
292 } else {
293 Elf64_Ehdr elf_ehdr;
294
295 if (lttng_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr)) < sizeof(elf_ehdr)) {
296 ret = -1;
297 goto error;
298 }
299 if (!is_elf_native_endian(elf)) {
300 bswap_ehdr(elf_ehdr);
301 }
302 copy_ehdr(elf_ehdr, *(elf->ehdr));
303 }
304 error:
305 return ret;
306 }
307
308 /*
309 * Retrieve the nth (where n is the `index` argument) shdr (section
310 * header) from the given elf instance.
311 *
312 * 0 is returned on succes, -1 on failure.
313 */
314 static
315 int lttng_elf_get_section_hdr(struct lttng_elf *elf,
316 uint16_t index, struct lttng_elf_shdr *out_header)
317 {
318 int ret = 0;
319
320 if (!elf) {
321 ret = -1;
322 goto error;
323 }
324
325 if (index >= elf->ehdr->e_shnum) {
326 ret = -1;
327 goto error;
328 }
329
330 ret = populate_section_header(elf, out_header, index);
331 if (ret) {
332 DBG("Error populating section header.");
333 goto error;
334 }
335
336 error:
337 return ret;
338 }
339
340 /*
341 * Lookup a section's name from a given offset (usually from an shdr's
342 * sh_name value) in bytes relative to the beginning of the section
343 * names string table.
344 *
345 * If no name is found, NULL is returned.
346 */
347 static
348 char *lttng_elf_get_section_name(struct lttng_elf *elf, off_t offset)
349 {
350 char *name = NULL;
351 size_t name_length = 0, to_read; /* name_length does not include \0 */
352
353 if (!elf) {
354 goto error;
355 }
356
357 if (offset >= elf->section_names_size) {
358 goto error;
359 }
360
361 if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
362 PERROR("Error seeking to the beginning of ELF string table section");
363 goto error;
364 }
365
366 to_read = elf->section_names_size - offset;
367
368 /* Find first \0 after or at current location, remember name_length. */
369 for (;;) {
370 char buf[BUF_LEN];
371 ssize_t read_len;
372 size_t i;
373
374 if (!to_read) {
375 goto error;
376 }
377 read_len = lttng_read(elf->fd, buf, min_t(size_t, BUF_LEN, to_read));
378 if (read_len <= 0) {
379 PERROR("Error reading ELF string table section");
380 goto error;
381 }
382 for (i = 0; i < read_len; i++) {
383 if (buf[i] == '\0') {
384 name_length += i;
385 goto end;
386 }
387 }
388 name_length += read_len;
389 to_read -= read_len;
390 }
391 end:
392 /*
393 * We found the length of the section name, now seek back to the
394 * beginning of the name and copy it in the newly allocated buffer.
395 */
396 name = zmalloc(sizeof(char) * (name_length + 1)); /* + 1 for \0 */
397 if (!name) {
398 PERROR("Error allocating ELF section name buffer");
399 goto error;
400 }
401 if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
402 PERROR("Error seeking to the offset of the ELF section name");
403 goto error;
404 }
405 if (lttng_read(elf->fd, name, name_length + 1) < name_length + 1) {
406 PERROR("Error reading the ELF section name");
407 goto error;
408 }
409
410 return name;
411
412 error:
413 free(name);
414 return NULL;
415 }
416
417 static
418 int lttng_elf_validate_and_populate(struct lttng_elf *elf)
419 {
420 uint8_t version;
421 uint8_t e_ident[EI_NIDENT];
422 uint8_t *magic_number = NULL;
423 int ret = 0;
424
425 if (elf->fd == -1) {
426 DBG("fd error");
427 ret = LTTNG_ERR_ELF_PARSING;
428 goto end;
429 }
430
431 /*
432 * First read the magic number, endianness and version to later populate
433 * the ELF header with the correct endianness and bitness.
434 * (see elf.h)
435 */
436
437 if (lseek(elf->fd, 0, SEEK_SET) < 0) {
438 PERROR("Error seeking the beginning of ELF file");
439 ret = LTTNG_ERR_ELF_PARSING;
440 goto end;
441 }
442 ret = lttng_read(elf->fd, e_ident, EI_NIDENT);
443 if (ret < EI_NIDENT) {
444 DBG("Error reading the ELF identification fields");
445 if (ret == -1) {
446 PERROR("Error reading the ELF identification fields");
447 }
448 ret = LTTNG_ERR_ELF_PARSING;
449 goto end;
450 }
451
452 /*
453 * Copy fields used to check that the target file is in fact a valid ELF
454 * file.
455 */
456 elf->bitness = e_ident[EI_CLASS];
457 elf->endianness = e_ident[EI_DATA];
458 version = e_ident[EI_VERSION];
459 magic_number = &e_ident[EI_MAG0];
460
461 /*
462 * Check the magic number.
463 */
464 if (memcmp(magic_number, ELFMAG, SELFMAG) != 0) {
465 DBG("Error check ELF magic number.");
466 ret = LTTNG_ERR_ELF_PARSING;
467 goto end;
468 }
469
470 /*
471 * Check the bitness is either ELFCLASS32 or ELFCLASS64.
472 */
473 if (elf->bitness <= ELFCLASSNONE || elf->bitness >= ELFCLASSNUM) {
474 DBG("ELF class error.");
475 ret = LTTNG_ERR_ELF_PARSING;
476 goto end;
477 }
478
479 /*
480 * Check the endianness is either ELFDATA2LSB or ELFDATA2MSB.
481 */
482 if (elf->endianness <= ELFDATANONE || elf->endianness >= ELFDATANUM) {
483 DBG("ELF endianness error.");
484 ret = LTTNG_ERR_ELF_PARSING;
485 goto end;
486 }
487
488 /*
489 * Check the version is ELF_CURRENT.
490 */
491 if (version <= EV_NONE || version >= EV_NUM) {
492 DBG("Wrong ELF version.");
493 ret = LTTNG_ERR_ELF_PARSING;
494 goto end;
495 }
496
497 elf->ehdr = zmalloc(sizeof(struct lttng_elf_ehdr));
498 if (!elf->ehdr) {
499 PERROR("Error allocation buffer for ELF header");
500 ret = LTTNG_ERR_NOMEM;
501 goto end;
502 }
503
504 /*
505 * Copy the content of the elf header.
506 */
507 ret = populate_elf_header(elf);
508 if (ret) {
509 DBG("Error reading ELF header,");
510 goto free_elf_error;
511 }
512
513 goto end;
514
515 free_elf_error:
516 free(elf->ehdr);
517 elf->ehdr = NULL;
518 end:
519 return ret;
520 }
521
522 /*
523 * Create an instance of lttng_elf for the ELF file located at
524 * `path`.
525 *
526 * Return a pointer to the instance on success, NULL on failure.
527 */
528 static
529 struct lttng_elf *lttng_elf_create(int fd)
530 {
531 struct lttng_elf_shdr section_names_shdr;
532 struct lttng_elf *elf = NULL;
533 int ret;
534
535 if (fd < 0) {
536 goto error;
537 }
538
539 elf = zmalloc(sizeof(struct lttng_elf));
540 if (!elf) {
541 PERROR("Error allocating struct lttng_elf");
542 goto error;
543 }
544
545 elf->fd = dup(fd);
546 if (elf->fd < 0) {
547 PERROR("Error duplicating file descriptor to binary");
548 goto error;
549 }
550
551 ret = lttng_elf_validate_and_populate(elf);
552 if (ret) {
553 goto error;
554 }
555
556 ret = lttng_elf_get_section_hdr(
557 elf, elf->ehdr->e_shstrndx, &section_names_shdr);
558 if (ret) {
559 goto error;
560 }
561
562 elf->section_names_offset = section_names_shdr.sh_offset;
563 elf->section_names_size = section_names_shdr.sh_size;
564 return elf;
565
566 error:
567 if (elf) {
568 if (elf->ehdr) {
569 free(elf->ehdr);
570 }
571 if (elf->fd >= 0) {
572 if (close(elf->fd)) {
573 PERROR("Error closing file descriptor in error path");
574 abort();
575 }
576 }
577 free(elf);
578 }
579 return NULL;
580 }
581
582 /*
583 * Destroy the given lttng_elf instance.
584 */
585 static
586 void lttng_elf_destroy(struct lttng_elf *elf)
587 {
588 if (!elf) {
589 return;
590 }
591
592 free(elf->ehdr);
593 if (close(elf->fd)) {
594 PERROR("Error closing file description in error path");
595 abort();
596 }
597 free(elf);
598 }
599
600 static
601 int lttng_elf_get_section_hdr_by_name(struct lttng_elf *elf,
602 const char *section_name, struct lttng_elf_shdr *section_hdr)
603 {
604 int i;
605 char *curr_section_name;
606
607 for (i = 0; i < elf->ehdr->e_shnum; ++i) {
608 bool name_equal;
609 int ret = lttng_elf_get_section_hdr(elf, i, section_hdr);
610
611 if (ret) {
612 break;
613 }
614 curr_section_name = lttng_elf_get_section_name(elf,
615 section_hdr->sh_name);
616 if (!curr_section_name) {
617 continue;
618 }
619 name_equal = strcmp(curr_section_name, section_name) == 0;
620 free(curr_section_name);
621 if (name_equal) {
622 return 0;
623 }
624 }
625 return LTTNG_ERR_ELF_PARSING;
626 }
627
628 static
629 char *lttng_elf_get_section_data(struct lttng_elf *elf,
630 struct lttng_elf_shdr *shdr)
631 {
632 int ret;
633 off_t section_offset;
634 char *data;
635
636 if (!elf || !shdr) {
637 goto error;
638 }
639
640 section_offset = shdr->sh_offset;
641 if (lseek(elf->fd, section_offset, SEEK_SET) < 0) {
642 PERROR("Error seeking to section offset");
643 goto error;
644 }
645
646 data = zmalloc(shdr->sh_size);
647 if (!data) {
648 PERROR("Error allocating buffer for ELF section data");
649 goto error;
650 }
651 ret = lttng_read(elf->fd, data, shdr->sh_size);
652 if (ret == -1) {
653 PERROR("Error reading ELF section data");
654 goto free_error;
655 }
656
657 return data;
658
659 free_error:
660 free(data);
661 error:
662 return NULL;
663 }
664
665 /*
666 * Convert the virtual address in a binary's mapping to the offset of
667 * the corresponding instruction in the binary file.
668 * This function assumes the address is in the text section.
669 *
670 * Returns the offset on success or non-zero in case of failure.
671 */
672 static
673 int lttng_elf_convert_addr_in_text_to_offset(struct lttng_elf *elf_handle,
674 size_t addr, uint64_t *offset)
675 {
676 int ret = 0;
677 off_t text_section_offset;
678 off_t text_section_addr_beg;
679 off_t text_section_addr_end;
680 off_t offset_in_section;
681 struct lttng_elf_shdr text_section_hdr;
682
683 if (!elf_handle) {
684 DBG("Invalid ELF handle.");
685 ret = LTTNG_ERR_ELF_PARSING;
686 goto error;
687 }
688
689 /* Get a pointer to the .text section header. */
690 ret = lttng_elf_get_section_hdr_by_name(elf_handle,
691 TEXT_SECTION_NAME, &text_section_hdr);
692 if (ret) {
693 DBG("Text section not found in binary.");
694 ret = LTTNG_ERR_ELF_PARSING;
695 goto error;
696 }
697
698 text_section_offset = text_section_hdr.sh_offset;
699 text_section_addr_beg = text_section_hdr.sh_addr;
700 text_section_addr_end =
701 text_section_addr_beg + text_section_hdr.sh_size;
702
703 /*
704 * Verify that the address is within the .text section boundaries.
705 */
706 if (addr < text_section_addr_beg || addr > text_section_addr_end) {
707 DBG("Address found is outside of the .text section addr=0x%zx, "
708 ".text section=[0x%jd - 0x%jd].", addr, (intmax_t)text_section_addr_beg,
709 (intmax_t)text_section_addr_end);
710 ret = LTTNG_ERR_ELF_PARSING;
711 goto error;
712 }
713
714 offset_in_section = addr - text_section_addr_beg;
715
716 /*
717 * Add the target offset in the text section to the offset of this text
718 * section from the beginning of the binary file.
719 */
720 *offset = text_section_offset + offset_in_section;
721
722 error:
723 return ret;
724 }
725
726 /*
727 * Compute the offset of a symbol from the begining of the ELF binary.
728 *
729 * On success, returns 0 offset parameter is set to the computed value
730 * On failure, returns -1.
731 */
732 int lttng_elf_get_symbol_offset(int fd, char *symbol, uint64_t *offset)
733 {
734 int ret = 0;
735 int sym_found = 0;
736 int sym_count = 0;
737 int sym_idx = 0;
738 uint64_t addr = 0;
739 char *curr_sym_str = NULL;
740 char *symbol_table_data = NULL;
741 char *string_table_data = NULL;
742 char *string_table_name = NULL;
743 struct lttng_elf_shdr symtab_hdr;
744 struct lttng_elf_shdr strtab_hdr;
745 struct lttng_elf *elf = NULL;
746
747 if (!symbol || !offset ) {
748 ret = LTTNG_ERR_ELF_PARSING;
749 goto end;
750 }
751
752 elf = lttng_elf_create(fd);
753 if (!elf) {
754 ret = LTTNG_ERR_ELF_PARSING;
755 goto end;
756 }
757
758 /*
759 * The .symtab section might not exist on stripped binaries.
760 * Try to get the symbol table section header first. If it's absent,
761 * try to get the dynamic symbol table. All symbols in the dynamic
762 * symbol tab are in the (normal) symbol table if it exists.
763 */
764 ret = lttng_elf_get_section_hdr_by_name(elf, SYMBOL_TAB_SECTION_NAME,
765 &symtab_hdr);
766 if (ret) {
767 DBG("Cannot get ELF Symbol Table section. Trying to get ELF Dynamic Symbol Table section.");
768 /* Get the dynamic symbol table section header. */
769 ret = lttng_elf_get_section_hdr_by_name(elf, DYNAMIC_SYMBOL_TAB_SECTION_NAME,
770 &symtab_hdr);
771 if (ret) {
772 DBG("Cannot get ELF Symbol Table nor Dynamic Symbol Table sections.");
773 ret = LTTNG_ERR_ELF_PARSING;
774 goto destroy_elf;
775 }
776 string_table_name = DYNAMIC_STRING_TAB_SECTION_NAME;
777 } else {
778 string_table_name = STRING_TAB_SECTION_NAME;
779 }
780
781 /* Get the data associated with the symbol table section. */
782 symbol_table_data = lttng_elf_get_section_data(elf, &symtab_hdr);
783 if (symbol_table_data == NULL) {
784 DBG("Cannot get ELF Symbol Table data.");
785 ret = LTTNG_ERR_ELF_PARSING;
786 goto destroy_elf;
787 }
788
789 /* Get the string table section header. */
790 ret = lttng_elf_get_section_hdr_by_name(elf, string_table_name,
791 &strtab_hdr);
792 if (ret) {
793 DBG("Cannot get ELF string table section.");
794 goto free_symbol_table_data;
795 }
796
797 /* Get the data associated with the string table section. */
798 string_table_data = lttng_elf_get_section_data(elf, &strtab_hdr);
799 if (string_table_data == NULL) {
800 DBG("Cannot get ELF string table section data.");
801 ret = LTTNG_ERR_ELF_PARSING;
802 goto free_symbol_table_data;
803 }
804
805 /* Get the number of symbol in the table for the iteration. */
806 sym_count = symtab_hdr.sh_size / symtab_hdr.sh_entsize;
807
808 /* Loop over all symbol. */
809 for (sym_idx = 0; sym_idx < sym_count; sym_idx++) {
810 struct lttng_elf_sym curr_sym;
811
812 /* Get the symbol at the current index. */
813 if (is_elf_32_bit(elf)) {
814 Elf32_Sym tmp = ((Elf32_Sym *) symbol_table_data)[sym_idx];
815 copy_sym(tmp, curr_sym);
816 } else {
817 Elf64_Sym tmp = ((Elf64_Sym *) symbol_table_data)[sym_idx];
818 copy_sym(tmp, curr_sym);
819 }
820
821 /*
822 * If the st_name field is zero, there is no string name for
823 * this symbol; skip to the next symbol.
824 */
825 if (curr_sym.st_name == 0) {
826 continue;
827 }
828
829 /*
830 * Use the st_name field in the lttng_elf_sym struct to get offset of
831 * the symbol's name from the beginning of the string table.
832 */
833 curr_sym_str = string_table_data + curr_sym.st_name;
834
835 /*
836 * If the current symbol is not a function; skip to the next symbol.
837 */
838 if (ELF_ST_TYPE(curr_sym.st_info) != STT_FUNC) {
839 continue;
840 }
841
842 /*
843 * Compare with the search symbol. If there is a match set the address
844 * output parameter and return success.
845 */
846 if (strcmp(symbol, curr_sym_str) == 0 ) {
847 sym_found = 1;
848 addr = curr_sym.st_value;
849 break;
850 }
851 }
852
853 if (!sym_found) {
854 DBG("Symbol not found.");
855 ret = LTTNG_ERR_ELF_PARSING;
856 goto free_string_table_data;
857 }
858
859 /*
860 * Use the virtual address of the symbol to compute the offset of this
861 * symbol from the beginning of the executable file.
862 */
863 ret = lttng_elf_convert_addr_in_text_to_offset(elf, addr, offset);
864 if (ret) {
865 DBG("Cannot convert addr to offset.");
866 goto free_string_table_data;
867 }
868
869
870 free_string_table_data:
871 free(string_table_data);
872 free_symbol_table_data:
873 free(symbol_table_data);
874 destroy_elf:
875 lttng_elf_destroy(elf);
876 end:
877 return ret;
878 }
879
880 /*
881 * Compute the offsets of SDT probes from the begining of the ELF binary.
882 *
883 * On success, returns 0 and the nb_probes parameter is set to the number of
884 * offsets found and the offsets parameter points to an array of offsets where
885 * the SDT probes are.
886 * On failure, returns -1.
887 */
888 int lttng_elf_get_sdt_probe_offsets(int fd, const char *provider_name,
889 const char *probe_name, uint64_t **offsets, uint32_t *nb_probes)
890 {
891 int ret = 0, nb_match = 0;
892 struct lttng_elf_shdr stap_note_section_hdr;
893 struct lttng_elf *elf = NULL;
894 char *stap_note_section_data = NULL;
895 char *curr_note_section_begin, *curr_data_ptr, *curr_probe, *curr_provider;
896 char *next_note_ptr;
897 uint32_t name_size, desc_size, note_type;
898 uint64_t curr_probe_location, curr_probe_offset, curr_semaphore_location;
899 uint64_t *probe_locs = NULL, *new_probe_locs = NULL;
900
901 if (!provider_name || !probe_name || !nb_probes || !offsets) {
902 DBG("Invalid arguments.");
903 ret = LTTNG_ERR_ELF_PARSING;
904 goto error;
905 }
906
907 elf = lttng_elf_create(fd);
908 if (!elf) {
909 DBG("Error allocation ELF.");
910 ret = LTTNG_ERR_ELF_PARSING;
911 goto error;
912 }
913
914 /* Get the stap note section header. */
915 ret = lttng_elf_get_section_hdr_by_name(elf, NOTE_STAPSDT_SECTION_NAME,
916 &stap_note_section_hdr);
917 if (ret) {
918 DBG("Cannot get ELF stap note section.");
919 goto destroy_elf_error;
920 }
921
922 /* Get the data associated with the stap note section. */
923 stap_note_section_data =
924 lttng_elf_get_section_data(elf, &stap_note_section_hdr);
925 if (stap_note_section_data == NULL) {
926 DBG("Cannot get ELF stap note section data.");
927 ret = LTTNG_ERR_ELF_PARSING;
928 goto destroy_elf_error;
929 }
930
931 next_note_ptr = stap_note_section_data;
932 curr_note_section_begin = stap_note_section_data;
933
934 *offsets = NULL;
935 while (1) {
936 curr_data_ptr = next_note_ptr;
937 /* Check if we have reached the end of the note section. */
938 if (curr_data_ptr >=
939 curr_note_section_begin +
940 stap_note_section_hdr.sh_size) {
941 *nb_probes = nb_match;
942 *offsets = probe_locs;
943 ret = 0;
944 break;
945 }
946 /* Get name size field. */
947 name_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
948 curr_data_ptr += sizeof(uint32_t);
949
950 /* Sanity check; a zero name_size is reserved. */
951 if (name_size == 0) {
952 DBG("Invalid name size field in SDT probe descriptions"
953 "section.");
954 ret = -1;
955 goto realloc_error;
956 }
957
958 /* Get description size field. */
959 desc_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
960 curr_data_ptr += sizeof(uint32_t);
961
962 /* Get type field. */
963 note_type = *(uint32_t *) curr_data_ptr;
964 curr_data_ptr += sizeof(uint32_t);
965
966 /*
967 * Move the pointer to the next note to be ready for the next
968 * iteration. The current note is made of 3 unsigned 32bit
969 * integers (name size, descriptor size and note type), the
970 * name and the descriptor. To move to the next note, we move
971 * the pointer according to those values.
972 */
973 next_note_ptr = next_note_ptr +
974 (3 * sizeof(uint32_t)) + desc_size + name_size;
975
976 /*
977 * Move ptr to the end of the name string (we don't need it)
978 * and go to the next 4 byte alignement.
979 */
980 if (note_type != NOTE_STAPSDT_TYPE ||
981 strncmp(curr_data_ptr, NOTE_STAPSDT_NAME, name_size) != 0) {
982 continue;
983 }
984
985 curr_data_ptr += name_size;
986
987 /* Get probe location. */
988 curr_probe_location = *(uint64_t *) curr_data_ptr;
989 curr_data_ptr += sizeof(uint64_t);
990
991 /* Pass over the base. Not needed. */
992 curr_data_ptr += sizeof(uint64_t);
993
994 /* Get semaphore location. */
995 curr_semaphore_location = *(uint64_t *) curr_data_ptr;
996 curr_data_ptr += sizeof(uint64_t);
997 /* Get provider name. */
998 curr_provider = curr_data_ptr;
999 curr_data_ptr += strlen(curr_provider) + 1;
1000
1001 /* Get probe name. */
1002 curr_probe = curr_data_ptr;
1003
1004 /* Check if the provider and probe name match */
1005 if (strcmp(provider_name, curr_provider) == 0 &&
1006 strcmp(probe_name, curr_probe) == 0) {
1007 int new_size;
1008
1009 /*
1010 * We currently don't support SDT probes with semaphores. Return
1011 * success as we found a matching probe but it's guarded by a
1012 * semaphore.
1013 */
1014 if (curr_semaphore_location != 0) {
1015 ret = LTTNG_ERR_SDT_PROBE_SEMAPHORE;
1016 goto realloc_error;
1017 }
1018
1019 new_size = (++nb_match) * sizeof(uint64_t);
1020
1021 /*
1022 * Found a match with not semaphore, we need to copy the
1023 * probe_location to the output parameter.
1024 */
1025 new_probe_locs = realloc(probe_locs, new_size);
1026 if (!new_probe_locs) {
1027 /* Error allocating a larger buffer */
1028 DBG("Allocation error in SDT.");
1029 ret = LTTNG_ERR_NOMEM;
1030 goto realloc_error;
1031 }
1032 probe_locs = new_probe_locs;
1033 new_probe_locs = NULL;
1034
1035 /*
1036 * Use the virtual address of the probe to compute the offset of
1037 * this probe from the beginning of the executable file.
1038 */
1039 ret = lttng_elf_convert_addr_in_text_to_offset(elf,
1040 curr_probe_location, &curr_probe_offset);
1041 if (ret) {
1042 DBG("Conversion error in SDT.");
1043 goto realloc_error;
1044 }
1045
1046 probe_locs[nb_match - 1] = curr_probe_offset;
1047 }
1048 }
1049
1050 end:
1051 free(stap_note_section_data);
1052 destroy_elf_error:
1053 lttng_elf_destroy(elf);
1054 error:
1055 return ret;
1056 realloc_error:
1057 free(probe_locs);
1058 goto end;
1059 }
LTTng 2.0 tools and control repository
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