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
22 #include <lttng/align.h>
23 #include <lttng/ust-elf.h>
24 #include <sys/types.h>
28 #include "lttng-tracer-core.h"
32 #ifndef NT_GNU_BUILD_ID
33 # define NT_GNU_BUILD_ID 3
37 * Retrieve the nth (where n is the `index` argument) phdr (program
38 * header) from the given elf instance.
40 * A pointer to the phdr is returned on success, NULL on failure.
43 struct lttng_ust_elf_phdr
*lttng_ust_elf_get_phdr(struct lttng_ust_elf
*elf
,
46 struct lttng_ust_elf_phdr
*phdr
= NULL
;
53 if (index
>= elf
->ehdr
->e_phnum
) {
57 phdr
= zmalloc(sizeof(struct lttng_ust_elf_phdr
));
62 offset
= (off_t
) elf
->ehdr
->e_phoff
63 + (off_t
) index
* elf
->ehdr
->e_phentsize
;
64 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
68 if (is_elf_32_bit(elf
)) {
71 if (lttng_ust_read(elf
->fd
, &elf_phdr
, sizeof(elf_phdr
))
75 if (!is_elf_native_endian(elf
)) {
78 copy_phdr(elf_phdr
, *phdr
);
82 if (lttng_ust_read(elf
->fd
, &elf_phdr
, sizeof(elf_phdr
))
86 if (!is_elf_native_endian(elf
)) {
89 copy_phdr(elf_phdr
, *phdr
);
100 * Retrieve the nth (where n is the `index` argument) shdr (section
101 * header) from the given elf instance.
103 * A pointer to the shdr is returned on success, NULL on failure.
106 struct lttng_ust_elf_shdr
*lttng_ust_elf_get_shdr(struct lttng_ust_elf
*elf
,
109 struct lttng_ust_elf_shdr
*shdr
= NULL
;
116 if (index
>= elf
->ehdr
->e_shnum
) {
120 shdr
= zmalloc(sizeof(struct lttng_ust_elf_shdr
));
125 offset
= (off_t
) elf
->ehdr
->e_shoff
126 + (off_t
) index
* elf
->ehdr
->e_shentsize
;
127 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
131 if (is_elf_32_bit(elf
)) {
134 if (lttng_ust_read(elf
->fd
, &elf_shdr
, sizeof(elf_shdr
))
135 < sizeof(elf_shdr
)) {
138 if (!is_elf_native_endian(elf
)) {
139 bswap_shdr(elf_shdr
);
141 copy_shdr(elf_shdr
, *shdr
);
145 if (lttng_ust_read(elf
->fd
, &elf_shdr
, sizeof(elf_shdr
))
146 < sizeof(elf_shdr
)) {
149 if (!is_elf_native_endian(elf
)) {
150 bswap_shdr(elf_shdr
);
152 copy_shdr(elf_shdr
, *shdr
);
163 * Lookup a section's name from a given offset (usually from an shdr's
164 * sh_name value) in bytes relative to the beginning of the section
165 * names string table.
167 * If no name is found, NULL is returned.
170 char *lttng_ust_elf_get_section_name(struct lttng_ust_elf
*elf
, off_t offset
)
173 size_t len
= 0, to_read
; /* len does not include \0 */
179 if (offset
>= elf
->section_names_size
) {
183 if (lseek(elf
->fd
, elf
->section_names_offset
+ offset
, SEEK_SET
) < 0) {
187 to_read
= elf
->section_names_size
- offset
;
189 /* Find first \0 after or at current location, remember len. */
198 read_len
= lttng_ust_read(elf
->fd
, buf
,
199 min_t(size_t, BUF_LEN
, to_read
));
203 for (i
= 0; i
< read_len
; i
++) {
204 if (buf
[i
] == '\0') {
213 name
= zmalloc(sizeof(char) * (len
+ 1)); /* + 1 for \0 */
217 if (lseek(elf
->fd
, elf
->section_names_offset
+ offset
,
221 if (lttng_ust_read(elf
->fd
, name
, len
+ 1) < len
+ 1) {
233 * Create an instance of lttng_ust_elf for the ELF file located at
236 * Return a pointer to the instance on success, NULL on failure.
238 struct lttng_ust_elf
*lttng_ust_elf_create(const char *path
)
240 uint8_t e_ident
[EI_NIDENT
];
241 struct lttng_ust_elf_shdr
*section_names_shdr
;
242 struct lttng_ust_elf
*elf
= NULL
;
244 elf
= zmalloc(sizeof(struct lttng_ust_elf
));
249 elf
->path
= strdup(path
);
254 elf
->fd
= open(elf
->path
, O_RDONLY
| O_CLOEXEC
);
259 if (lttng_ust_read(elf
->fd
, e_ident
, EI_NIDENT
) < EI_NIDENT
) {
262 elf
->bitness
= e_ident
[EI_CLASS
];
263 elf
->endianness
= e_ident
[EI_DATA
];
265 if (lseek(elf
->fd
, 0, SEEK_SET
) < 0) {
269 elf
->ehdr
= zmalloc(sizeof(struct lttng_ust_elf_ehdr
));
274 if (is_elf_32_bit(elf
)) {
277 if (lttng_ust_read(elf
->fd
, &elf_ehdr
, sizeof(elf_ehdr
))
278 < sizeof(elf_ehdr
)) {
281 if (!is_elf_native_endian(elf
)) {
282 bswap_ehdr(elf_ehdr
);
284 copy_ehdr(elf_ehdr
, *(elf
->ehdr
));
288 if (lttng_ust_read(elf
->fd
, &elf_ehdr
, sizeof(elf_ehdr
))
289 < sizeof(elf_ehdr
)) {
292 if (!is_elf_native_endian(elf
)) {
293 bswap_ehdr(elf_ehdr
);
295 copy_ehdr(elf_ehdr
, *(elf
->ehdr
));
298 section_names_shdr
= lttng_ust_elf_get_shdr(elf
, elf
->ehdr
->e_shstrndx
);
299 if (!section_names_shdr
) {
303 elf
->section_names_offset
= section_names_shdr
->sh_offset
;
304 elf
->section_names_size
= section_names_shdr
->sh_size
;
306 free(section_names_shdr
);
313 if (close(elf
->fd
)) {
324 * Test whether the ELF file is position independent code (PIC)
326 uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf
*elf
)
329 * PIC has and e_type value of ET_DYN, see ELF specification
330 * version 1.1 p. 1-3.
332 return elf
->ehdr
->e_type
== ET_DYN
;
336 * Destroy the given lttng_ust_elf instance.
338 void lttng_ust_elf_destroy(struct lttng_ust_elf
*elf
)
345 if (close(elf
->fd
)) {
353 * Compute the total in-memory size of the ELF file, in bytes.
355 * Returns 0 if successful, -1 if not. On success, the memory size is
356 * returned through the out parameter `memsz`.
358 int lttng_ust_elf_get_memsz(struct lttng_ust_elf
*elf
, uint64_t *memsz
)
361 uint64_t low_addr
= UINT64_MAX
, high_addr
= 0;
363 if (!elf
|| !memsz
) {
367 for (i
= 0; i
< elf
->ehdr
->e_phnum
; ++i
) {
368 struct lttng_ust_elf_phdr
*phdr
;
370 phdr
= lttng_ust_elf_get_phdr(elf
, i
);
376 * Only PT_LOAD segments contribute to memsz. Skip
379 if (phdr
->p_type
!= PT_LOAD
) {
383 low_addr
= min_t(uint64_t, low_addr
, phdr
->p_vaddr
);
384 high_addr
= max_t(uint64_t, high_addr
,
385 phdr
->p_vaddr
+ phdr
->p_memsz
);
390 if (high_addr
< low_addr
) {
391 /* No PT_LOAD segments or corrupted data. */
395 *memsz
= high_addr
- low_addr
;
402 * Internal method used to try and get the build_id from a PT_NOTE
403 * segment ranging from `offset` to `segment_end`.
405 * If the function returns successfully, the out parameter `found`
406 * indicates whether the build id information was present in the
407 * segment or not. If `found` is not 0, the out parameters `build_id`
408 * and `length` will both have been set with the retrieved
411 * Returns 0 on success, -1 if an error occurred.
414 int lttng_ust_elf_get_build_id_from_segment(
415 struct lttng_ust_elf
*elf
, uint8_t **build_id
, size_t *length
,
416 off_t offset
, off_t segment_end
)
418 uint8_t *_build_id
= NULL
; /* Silence old gcc warning. */
419 size_t _length
= 0; /* Silence old gcc warning. */
421 while (offset
< segment_end
) {
422 struct lttng_ust_elf_nhdr nhdr
;
425 /* Align start of note entry */
426 offset
+= offset_align(offset
, ELF_NOTE_ENTRY_ALIGN
);
427 if (offset
>= segment_end
) {
431 * We seek manually because if the note isn't the
432 * build id the data following the header will not
435 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
438 if (lttng_ust_read(elf
->fd
, &nhdr
, sizeof(nhdr
))
443 if (!is_elf_native_endian(elf
)) {
444 nhdr
.n_namesz
= bswap_32(nhdr
.n_namesz
);
445 nhdr
.n_descsz
= bswap_32(nhdr
.n_descsz
);
446 nhdr
.n_type
= bswap_32(nhdr
.n_type
);
449 offset
+= sizeof(nhdr
) + nhdr
.n_namesz
;
450 /* Align start of desc entry */
451 offset
+= offset_align(offset
, ELF_NOTE_DESC_ALIGN
);
453 if (nhdr
.n_type
!= NT_GNU_BUILD_ID
) {
455 * Ignore non build id notes but still
456 * increase the offset.
458 offset
+= nhdr
.n_descsz
;
462 _length
= nhdr
.n_descsz
;
463 _build_id
= zmalloc(sizeof(uint8_t) * _length
);
468 if (lseek(elf
->fd
, offset
, SEEK_SET
) < 0) {
471 read_len
= sizeof(*_build_id
) * _length
;
472 if (lttng_ust_read(elf
->fd
, _build_id
, read_len
) < read_len
) {
480 *build_id
= _build_id
;
491 * Retrieve a build ID (an array of bytes) from the corresponding
492 * section in the ELF file. The length of the build ID can be either
493 * 16 or 20 bytes depending on the method used to generate it, hence
494 * the length out parameter.
496 * If the function returns successfully, the out parameter `found`
497 * indicates whether the build id information was present in the ELF
498 * file or not. If `found` is not 0, the out parameters `build_id` and
499 * `length` will both have been set with the retrieved information.
501 * Returns 0 on success, -1 if an error occurred.
503 int lttng_ust_elf_get_build_id(struct lttng_ust_elf
*elf
, uint8_t **build_id
,
504 size_t *length
, int *found
)
507 uint8_t *_build_id
= NULL
; /* Silence old gcc warning. */
508 size_t _length
= 0; /* Silence old gcc warning. */
510 if (!elf
|| !build_id
|| !length
|| !found
) {
514 for (i
= 0; i
< elf
->ehdr
->e_phnum
; ++i
) {
515 off_t offset
, segment_end
;
516 struct lttng_ust_elf_phdr
*phdr
;
519 phdr
= lttng_ust_elf_get_phdr(elf
, i
);
524 /* Build ID will be contained in a PT_NOTE segment. */
525 if (phdr
->p_type
!= PT_NOTE
) {
529 offset
= phdr
->p_offset
;
530 segment_end
= offset
+ phdr
->p_filesz
;
531 ret
= lttng_ust_elf_get_build_id_from_segment(
532 elf
, &_build_id
, &_length
, offset
, segment_end
);
544 *build_id
= _build_id
;
558 * Try to retrieve filename and CRC from given ELF section `shdr`.
560 * If the function returns successfully, the out parameter `found`
561 * indicates whether the debug link information was present in the ELF
562 * section or not. If `found` is not 0, the out parameters `filename` and
563 * `crc` will both have been set with the retrieved information.
565 * Returns 0 on success, -1 if an error occurred.
567 int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf
*elf
,
568 char **filename
, uint32_t *crc
,
569 struct lttng_ust_elf_shdr
*shdr
)
571 char *_filename
= NULL
; /* Silence old gcc warning. */
573 char *section_name
= NULL
;
574 uint32_t _crc
= 0; /* Silence old gcc warning. */
576 if (!elf
|| !filename
|| !crc
|| !shdr
) {
581 * The .gnu_debuglink section is of type SHT_PROGBITS,
582 * skip the other sections.
584 if (shdr
->sh_type
!= SHT_PROGBITS
) {
588 section_name
= lttng_ust_elf_get_section_name(elf
,
593 if (strcmp(section_name
, ".gnu_debuglink")) {
598 * The length of the filename is the sh_size excluding the CRC
599 * which comes after it in the section.
601 _filename
= zmalloc(sizeof(char) * (shdr
->sh_size
- ELF_CRC_SIZE
));
605 if (lseek(elf
->fd
, shdr
->sh_offset
, SEEK_SET
) < 0) {
608 filename_len
= sizeof(*_filename
) * (shdr
->sh_size
- ELF_CRC_SIZE
);
609 if (lttng_ust_read(elf
->fd
, _filename
, filename_len
) < filename_len
) {
612 if (lttng_ust_read(elf
->fd
, &_crc
, sizeof(_crc
)) < sizeof(_crc
)) {
615 if (!is_elf_native_endian(elf
)) {
616 _crc
= bswap_32(_crc
);
622 *filename
= _filename
;
635 * Retrieve filename and CRC from ELF's .gnu_debuglink section, if any.
637 * If the function returns successfully, the out parameter `found`
638 * indicates whether the debug link information was present in the ELF
639 * file or not. If `found` is not 0, the out parameters `filename` and
640 * `crc` will both have been set with the retrieved information.
642 * Returns 0 on success, -1 if an error occurred.
644 int lttng_ust_elf_get_debug_link(struct lttng_ust_elf
*elf
, char **filename
,
645 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
, shdr
);
677 *filename
= _filename
;
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