2 * Copyright (C) 2015 Antoine Busque <abusque@efficios.com>
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.
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.
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
21 #include <lttng/align.h>
22 #include <lttng/ust-elf.h>
23 #include <sys/types.h>
27 #include "lttng-tracer-core.h"
32 * Retrieve the nth (where n is the `index` argument) phdr (program
33 * header) from the given elf instance.
35 * A pointer to the phdr is returned on success, NULL on failure.
38 struct lttng_ust_elf_phdr
*lttng_ust_elf_get_phdr(struct lttng_ust_elf
*elf
,
41 struct lttng_ust_elf_phdr
*phdr
= NULL
;
48 if (index
>= elf
->ehdr
->e_phnum
) {
52 phdr
= zmalloc(sizeof(struct lttng_ust_elf_phdr
));
57 offset
= elf
->ehdr
->e_phoff
+ index
* elf
->ehdr
->e_phentsize
;
58 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
62 if (is_elf_32_bit(elf
)) {
65 if (lttng_ust_read(elf
->fd
, &elf_phdr
, sizeof(elf_phdr
))
69 if (!is_elf_native_endian(elf
)) {
72 copy_phdr(elf_phdr
, *phdr
);
76 if (lttng_ust_read(elf
->fd
, &elf_phdr
, sizeof(elf_phdr
))
80 if (!is_elf_native_endian(elf
)) {
83 copy_phdr(elf_phdr
, *phdr
);
94 * Retrieve the nth (where n is the `index` argument) shdr (section
95 * header) from the given elf instance.
97 * A pointer to the shdr is returned on success, NULL on failure.
100 struct lttng_ust_elf_shdr
*lttng_ust_elf_get_shdr(struct lttng_ust_elf
*elf
,
103 struct lttng_ust_elf_shdr
*shdr
= NULL
;
110 if (index
>= elf
->ehdr
->e_shnum
) {
114 shdr
= zmalloc(sizeof(struct lttng_ust_elf_shdr
));
119 offset
= (off_t
) elf
->ehdr
->e_shoff
120 + (off_t
) index
* elf
->ehdr
->e_shentsize
;
121 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
125 if (is_elf_32_bit(elf
)) {
128 if (lttng_ust_read(elf
->fd
, &elf_shdr
, sizeof(elf_shdr
))
129 < sizeof(elf_shdr
)) {
132 if (!is_elf_native_endian(elf
)) {
133 bswap_shdr(elf_shdr
);
135 copy_shdr(elf_shdr
, *shdr
);
139 if (lttng_ust_read(elf
->fd
, &elf_shdr
, sizeof(elf_shdr
))
140 < sizeof(elf_shdr
)) {
143 if (!is_elf_native_endian(elf
)) {
144 bswap_shdr(elf_shdr
);
146 copy_shdr(elf_shdr
, *shdr
);
157 * Lookup a section's name from a given offset (usually from an shdr's
158 * sh_name value) in bytes relative to the beginning of the section
159 * names string table.
161 * If no name is found, NULL is returned.
164 char *lttng_ust_elf_get_section_name(struct lttng_ust_elf
*elf
, uint32_t offset
)
167 size_t len
= 0, to_read
; /* len does not include \0 */
173 if (offset
>= elf
->section_names_size
) {
177 if (lseek(elf
->fd
, elf
->section_names_offset
+ offset
, SEEK_SET
) < 0) {
181 to_read
= elf
->section_names_size
- offset
;
183 /* Find first \0 after or at current location, remember len. */
192 read_len
= lttng_ust_read(elf
->fd
, buf
,
193 min_t(size_t, BUF_LEN
, to_read
));
197 for (i
= 0; i
< read_len
; i
++) {
198 if (buf
[i
] == '\0') {
207 name
= zmalloc(sizeof(char) * (len
+ 1)); /* + 1 for \0 */
211 if (lseek(elf
->fd
, elf
->section_names_offset
+ offset
,
215 if (lttng_ust_read(elf
->fd
, name
, len
+ 1) < len
+ 1) {
227 * Create an instance of lttng_ust_elf for the ELF file located at
230 * Return a pointer to the instance on success, NULL on failure.
232 struct lttng_ust_elf
*lttng_ust_elf_create(const char *path
)
234 uint8_t e_ident
[EI_NIDENT
];
235 struct lttng_ust_elf_shdr
*section_names_shdr
;
236 struct lttng_ust_elf
*elf
= NULL
;
238 elf
= zmalloc(sizeof(struct lttng_ust_elf
));
243 elf
->path
= strdup(path
);
248 elf
->fd
= open(elf
->path
, O_RDONLY
| O_CLOEXEC
);
253 if (lttng_ust_read(elf
->fd
, e_ident
, EI_NIDENT
) < EI_NIDENT
) {
256 elf
->bitness
= e_ident
[EI_CLASS
];
257 elf
->endianness
= e_ident
[EI_DATA
];
259 if (lseek(elf
->fd
, 0, SEEK_SET
) < 0) {
263 elf
->ehdr
= zmalloc(sizeof(struct lttng_ust_elf_ehdr
));
268 if (is_elf_32_bit(elf
)) {
271 if (lttng_ust_read(elf
->fd
, &elf_ehdr
, sizeof(elf_ehdr
))
272 < sizeof(elf_ehdr
)) {
275 if (!is_elf_native_endian(elf
)) {
276 bswap_ehdr(elf_ehdr
);
278 copy_ehdr(elf_ehdr
, *(elf
->ehdr
));
282 if (lttng_ust_read(elf
->fd
, &elf_ehdr
, sizeof(elf_ehdr
))
283 < sizeof(elf_ehdr
)) {
286 if (!is_elf_native_endian(elf
)) {
287 bswap_ehdr(elf_ehdr
);
289 copy_ehdr(elf_ehdr
, *(elf
->ehdr
));
292 section_names_shdr
= lttng_ust_elf_get_shdr(elf
, elf
->ehdr
->e_shstrndx
);
293 if (!section_names_shdr
) {
297 elf
->section_names_offset
= section_names_shdr
->sh_offset
;
298 elf
->section_names_size
= section_names_shdr
->sh_size
;
300 free(section_names_shdr
);
307 if (close(elf
->fd
)) {
318 * Destroy the given lttng_ust_elf instance.
320 void lttng_ust_elf_destroy(struct lttng_ust_elf
*elf
)
327 if (close(elf
->fd
)) {
335 * Compute the total in-memory size of the ELF file, in bytes.
337 * Returns 0 if successful, -1 if not. On success, the memory size is
338 * returned through the out parameter `memsz`.
340 int lttng_ust_elf_get_memsz(struct lttng_ust_elf
*elf
, uint64_t *memsz
)
345 if (!elf
|| !memsz
) {
349 for (i
= 0; i
< elf
->ehdr
->e_phnum
; ++i
) {
350 struct lttng_ust_elf_phdr
*phdr
;
353 phdr
= lttng_ust_elf_get_phdr(elf
, i
);
359 * Only PT_LOAD segments contribute to memsz. Skip
362 if (phdr
->p_type
!= PT_LOAD
) {
367 * A p_align of 0 means no alignment, i.e. aligned to
370 align
= phdr
->p_align
== 0 ? 1 : phdr
->p_align
;
371 /* Align the start of the segment. */
372 _memsz
+= offset_align(_memsz
, align
);
373 _memsz
+= phdr
->p_memsz
;
375 * Add padding at the end of the segment, so it ends
376 * on a multiple of the align value (which usually
377 * means a page boundary). This makes the computation
378 * valid even in cases where p_align would change from
379 * one segment to the next.
381 _memsz
+= offset_align(_memsz
, align
);
393 * Internal method used to try and get the build_id from a PT_NOTE
394 * segment ranging from `offset` to `segment_end`.
396 * If the function returns successfully, the out parameter `found`
397 * indicates whether the build id information was present in the
398 * segment or not. If `found` is not 0, the out parameters `build_id`
399 * and `length` will both have been set with the retrieved
402 * Returns 0 on success, -1 if an error occurred.
405 int lttng_ust_elf_get_build_id_from_segment(
406 struct lttng_ust_elf
*elf
, uint8_t **build_id
, size_t *length
,
407 uint64_t offset
, uint64_t segment_end
, int *found
)
409 uint8_t *_build_id
= NULL
; /* Silence old gcc warning. */
410 size_t _length
= 0; /* Silence old gcc warning. */
413 while (offset
< segment_end
) {
414 struct lttng_ust_elf_nhdr nhdr
;
417 /* Align start of note entry */
418 offset
+= offset_align(offset
, ELF_NOTE_ENTRY_ALIGN
);
419 if (offset
>= segment_end
) {
423 * We seek manually because if the note isn't the
424 * build id the data following the header will not
427 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
430 if (lttng_ust_read(elf
->fd
, &nhdr
, sizeof(nhdr
))
435 if (!is_elf_native_endian(elf
)) {
436 nhdr
.n_namesz
= bswap_32(nhdr
.n_namesz
);
437 nhdr
.n_descsz
= bswap_32(nhdr
.n_descsz
);
438 nhdr
.n_type
= bswap_32(nhdr
.n_type
);
441 offset
+= sizeof(nhdr
) + nhdr
.n_namesz
;
442 /* Align start of desc entry */
443 offset
+= offset_align(offset
, ELF_NOTE_DESC_ALIGN
);
445 if (nhdr
.n_type
!= NT_GNU_BUILD_ID
) {
447 * Ignore non build id notes but still
448 * increase the offset.
450 offset
+= nhdr
.n_descsz
;
454 _length
= nhdr
.n_descsz
;
455 _build_id
= zmalloc(sizeof(uint8_t) * _length
);
460 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
463 read_len
= sizeof(*_build_id
) * _length
;
464 if (lttng_ust_read(elf
->fd
, _build_id
, read_len
) < read_len
) {
473 *build_id
= _build_id
;
484 * Retrieve a build ID (an array of bytes) from the corresponding
485 * section in the ELF file. The length of the build ID can be either
486 * 16 or 20 bytes depending on the method used to generate it, hence
487 * the length out parameter.
489 * If the function returns successfully, the out parameter `found`
490 * indicates whether the build id information was present in the ELF
491 * file or not. If `found` is not 0, the out parameters `build_id` and
492 * `length` will both have been set with the retrieved information.
494 * Returns 0 on success, -1 if an error occurred.
496 int lttng_ust_elf_get_build_id(struct lttng_ust_elf
*elf
, uint8_t **build_id
,
497 size_t *length
, int *found
)
500 uint8_t *_build_id
= NULL
; /* Silence old gcc warning. */
501 size_t _length
= 0; /* Silence old gcc warning. */
504 if (!elf
|| !build_id
|| !length
|| !found
) {
508 for (i
= 0; i
< elf
->ehdr
->e_phnum
; ++i
) {
509 uint64_t offset
, segment_end
;
510 struct lttng_ust_elf_phdr
*phdr
;
513 phdr
= lttng_ust_elf_get_phdr(elf
, i
);
518 /* Build ID will be contained in a PT_NOTE segment. */
519 if (phdr
->p_type
!= PT_NOTE
) {
523 offset
= phdr
->p_offset
;
524 segment_end
= offset
+ phdr
->p_filesz
;
525 ret
= lttng_ust_elf_get_build_id_from_segment(
526 elf
, &_build_id
, &_length
, offset
, segment_end
,
539 *build_id
= _build_id
;
550 * Try to retrieve filename and CRC from given ELF section `shdr`.
552 * If the function returns successfully, the out parameter `found`
553 * indicates whether the debug link information was present in the ELF
554 * section or not. If `found` is not 0, the out parameters `filename` and
555 * `crc` will both have been set with the retrieved information.
557 * Returns 0 on success, -1 if an error occurred.
559 int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf
*elf
,
560 char **filename
, uint32_t *crc
,
562 struct lttng_ust_elf_shdr
*shdr
)
565 char *_filename
= NULL
; /* Silence old gcc warning. */
567 char *section_name
= NULL
;
568 uint32_t _crc
= 0; /* Silence old gcc warning. */
570 if (!elf
|| !filename
|| !crc
|| !found
|| !shdr
) {
575 * The .gnu_debuglink section is of type SHT_PROGBITS,
576 * skip the other sections.
578 if (shdr
->sh_type
!= SHT_PROGBITS
) {
582 section_name
= lttng_ust_elf_get_section_name(elf
,
587 if (strcmp(section_name
, ".gnu_debuglink")) {
592 * The length of the filename is the sh_size excluding the CRC
593 * which comes after it in the section.
595 _filename
= zmalloc(sizeof(char) * (shdr
->sh_size
- ELF_CRC_SIZE
));
599 if (lseek(elf
->fd
, shdr
->sh_offset
, SEEK_SET
) < 0) {
602 filename_len
= sizeof(*_filename
) * (shdr
->sh_size
- ELF_CRC_SIZE
);
603 if (lttng_ust_read(elf
->fd
, _filename
, filename_len
) < filename_len
) {
606 if (lttng_ust_read(elf
->fd
, &_crc
, sizeof(_crc
)) < sizeof(_crc
)) {
609 if (!is_elf_native_endian(elf
)) {
610 _crc
= bswap_32(_crc
);
618 *filename
= _filename
;
634 * Retrieve filename and CRC from ELF's .gnu_debuglink section, if any.
636 * If the function returns successfully, the out parameter `found`
637 * indicates whether the debug link information was present in the ELF
638 * file or not. If `found` is not 0, the out parameters `filename` and
639 * `crc` will both have been set with the retrieved information.
641 * Returns 0 on success, -1 if an error occurred.
643 int lttng_ust_elf_get_debug_link(struct lttng_ust_elf
*elf
, char **filename
,
644 uint32_t *crc
, int *found
)
649 char *_filename
= NULL
; /* Silence old gcc warning. */
650 uint32_t _crc
= 0; /* Silence old gcc warning. */
652 if (!elf
|| !filename
|| !crc
|| !found
) {
656 for (i
= 0; i
< elf
->ehdr
->e_shnum
; ++i
) {
657 struct lttng_ust_elf_shdr
*shdr
= NULL
;
659 shdr
= lttng_ust_elf_get_shdr(elf
, i
);
664 ret
= lttng_ust_elf_get_debug_link_from_section(
665 elf
, &_filename
, &_crc
, &_found
, shdr
);
677 *filename
= _filename
;
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