[lttng-ust.git] / liblttng-ust / lttng-ust-elf.c

/*
 * Copyright (C) 2015  Antoine Busque <abusque@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
 */

#define _GNU_SOURCE
#define _LGPL_SOURCE
#include <fcntl.h>
#include <helper.h>
#include <lttng/align.h>
#include <lttng/ust-elf.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <ust-fd.h>

#include "lttng-tracer-core.h"

#define BUF_LEN	4096

#ifndef NT_GNU_BUILD_ID
# define NT_GNU_BUILD_ID	3
#endif

/*
 * Retrieve the nth (where n is the `index` argument) phdr (program
 * header) from the given elf instance.
 *
 * A pointer to the phdr is returned on success, NULL on failure.
 */
static
struct lttng_ust_elf_phdr *lttng_ust_elf_get_phdr(struct lttng_ust_elf *elf,
						uint16_t index)
{
	struct lttng_ust_elf_phdr *phdr = NULL;
	off_t offset;

	if (!elf) {
		goto error;
	}

	if (index >= elf->ehdr->e_phnum) {
		goto error;
	}

	phdr = zmalloc(sizeof(struct lttng_ust_elf_phdr));
	if (!phdr) {
		goto error;
	}

	offset = (off_t) elf->ehdr->e_phoff
			+ (off_t) index * elf->ehdr->e_phentsize;
	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
		goto error;
	}

	if (is_elf_32_bit(elf)) {
		Elf32_Phdr elf_phdr;

		if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
				< sizeof(elf_phdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_phdr(elf_phdr);
		}
		copy_phdr(elf_phdr, *phdr);
	} else {
		Elf64_Phdr elf_phdr;

		if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
				< sizeof(elf_phdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_phdr(elf_phdr);
		}
		copy_phdr(elf_phdr, *phdr);
	}

	return phdr;

error:
	free(phdr);
	return NULL;
}

/*
 * Retrieve the nth (where n is the `index` argument) shdr (section
 * header) from the given elf instance.
 *
 * A pointer to the shdr is returned on success, NULL on failure.
 */
static
struct lttng_ust_elf_shdr *lttng_ust_elf_get_shdr(struct lttng_ust_elf *elf,
						uint16_t index)
{
	struct lttng_ust_elf_shdr *shdr = NULL;
	off_t offset;

	if (!elf) {
		goto error;
	}

	if (index >= elf->ehdr->e_shnum) {
		goto error;
	}

	shdr = zmalloc(sizeof(struct lttng_ust_elf_shdr));
	if (!shdr) {
		goto error;
	}

	offset = (off_t) elf->ehdr->e_shoff
			+ (off_t) index * elf->ehdr->e_shentsize;
	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
		goto error;
	}

	if (is_elf_32_bit(elf)) {
		Elf32_Shdr elf_shdr;

		if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
				< sizeof(elf_shdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_shdr(elf_shdr);
		}
		copy_shdr(elf_shdr, *shdr);
	} else {
		Elf64_Shdr elf_shdr;

		if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
				< sizeof(elf_shdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_shdr(elf_shdr);
		}
		copy_shdr(elf_shdr, *shdr);
	}

	return shdr;

error:
	free(shdr);
	return NULL;
}

/*
 * Lookup a section's name from a given offset (usually from an shdr's
 * sh_name value) in bytes relative to the beginning of the section
 * names string table.
 *
 * If no name is found, NULL is returned.
 */
static
char *lttng_ust_elf_get_section_name(struct lttng_ust_elf *elf, off_t offset)
{
	char *name = NULL;
	size_t len = 0, to_read;	/* len does not include \0 */

	if (!elf) {
		goto error;
	}

	if (offset >= elf->section_names_size) {
		goto error;
	}

	if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
		goto error;
	}

	to_read = elf->section_names_size - offset;

	/* Find first \0 after or at current location, remember len. */
	for (;;) {
		char buf[BUF_LEN];
		ssize_t read_len;
		size_t i;

		if (!to_read) {
			goto error;
		}
		read_len = lttng_ust_read(elf->fd, buf,
			min_t(size_t, BUF_LEN, to_read));
		if (read_len <= 0) {
			goto error;
		}
		for (i = 0; i < read_len; i++) {
			if (buf[i] == '\0') {
				len += i;
				goto end;
			}
		}
		len += read_len;
		to_read -= read_len;
	}
end:
	name = zmalloc(sizeof(char) * (len + 1));	/* + 1 for \0 */
	if (!name) {
		goto error;
	}
	if (lseek(elf->fd, elf->section_names_offset + offset,
		SEEK_SET) < 0) {
		goto error;
	}
	if (lttng_ust_read(elf->fd, name, len + 1) < len + 1) {
		goto error;
	}

	return name;

error:
	free(name);
	return NULL;
}

/*
 * Create an instance of lttng_ust_elf for the ELF file located at
 * `path`.
 *
 * Return a pointer to the instance on success, NULL on failure.
 */
struct lttng_ust_elf *lttng_ust_elf_create(const char *path)
{
	uint8_t e_ident[EI_NIDENT];
	struct lttng_ust_elf_shdr *section_names_shdr;
	struct lttng_ust_elf *elf = NULL;
	int ret, fd;

	elf = zmalloc(sizeof(struct lttng_ust_elf));
	if (!elf) {
		goto error;
	}

	/* Initialize fd field to -1. 0 is a valid fd number */
	elf->fd = -1;

	elf->path = strdup(path);
	if (!elf->path) {
		goto error;
	}

	lttng_ust_lock_fd_tracker();
	fd = open(elf->path, O_RDONLY | O_CLOEXEC);
	if (fd < 0) {
		lttng_ust_unlock_fd_tracker();
		goto error;
	}

	ret = lttng_ust_add_fd_to_tracker(fd);
	if (ret < 0) {
		ret = close(fd);
		if (ret) {
			PERROR("close on elf->fd");
		}
		ret = -1;
		lttng_ust_unlock_fd_tracker();
		goto error;
	}
	elf->fd = ret;
	lttng_ust_unlock_fd_tracker();

	if (lttng_ust_read(elf->fd, e_ident, EI_NIDENT) < EI_NIDENT) {
		goto error;
	}
	elf->bitness = e_ident[EI_CLASS];
	elf->endianness = e_ident[EI_DATA];

	if (lseek(elf->fd, 0, SEEK_SET) < 0) {
		goto error;
	}

	elf->ehdr = zmalloc(sizeof(struct lttng_ust_elf_ehdr));
	if (!elf->ehdr) {
		goto error;
	}

	if (is_elf_32_bit(elf)) {
		Elf32_Ehdr elf_ehdr;

		if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
				< sizeof(elf_ehdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_ehdr(elf_ehdr);
		}
		copy_ehdr(elf_ehdr, *(elf->ehdr));
	} else {
		Elf64_Ehdr elf_ehdr;

		if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
				< sizeof(elf_ehdr)) {
			goto error;
		}
		if (!is_elf_native_endian(elf)) {
			bswap_ehdr(elf_ehdr);
		}
		copy_ehdr(elf_ehdr, *(elf->ehdr));
	}

	section_names_shdr = lttng_ust_elf_get_shdr(elf, elf->ehdr->e_shstrndx);
	if (!section_names_shdr) {
		goto error;
	}

	elf->section_names_offset = section_names_shdr->sh_offset;
	elf->section_names_size = section_names_shdr->sh_size;

	free(section_names_shdr);
	return elf;

error:
	lttng_ust_elf_destroy(elf);
	return NULL;
}

/*
 * Test whether the ELF file is position independent code (PIC)
 */
uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf *elf)
{
	/*
	 * PIC has and e_type value of ET_DYN, see ELF specification
	 * version 1.1 p. 1-3.
	 */
	return elf->ehdr->e_type == ET_DYN;
}

/*
 * Destroy the given lttng_ust_elf instance.
 */
void lttng_ust_elf_destroy(struct lttng_ust_elf *elf)
{
	int ret;

	if (!elf) {
		return;
	}

	if (elf->fd >= 0) {
		lttng_ust_lock_fd_tracker();
		ret = close(elf->fd);
		if (!ret) {
			lttng_ust_delete_fd_from_tracker(elf->fd);
		} else {
			PERROR("close");
			abort();
		}
		lttng_ust_unlock_fd_tracker();
	}

	free(elf->ehdr);
	free(elf->path);
	free(elf);
}

/*
 * Compute the total in-memory size of the ELF file, in bytes.
 *
 * Returns 0 if successful, -1 if not. On success, the memory size is
 * returned through the out parameter `memsz`.
 */
int lttng_ust_elf_get_memsz(struct lttng_ust_elf *elf, uint64_t *memsz)
{
	uint16_t i;
	uint64_t low_addr = UINT64_MAX, high_addr = 0;

	if (!elf || !memsz) {
		goto error;
	}

	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
		struct lttng_ust_elf_phdr *phdr;

		phdr = lttng_ust_elf_get_phdr(elf, i);
		if (!phdr) {
			goto error;
		}

		/*
		 * Only PT_LOAD segments contribute to memsz. Skip
		 * other segments.
		 */
		if (phdr->p_type != PT_LOAD) {
			goto next_loop;
		}

		low_addr = min_t(uint64_t, low_addr, phdr->p_vaddr);
		high_addr = max_t(uint64_t, high_addr,
				phdr->p_vaddr + phdr->p_memsz);
	next_loop:
		free(phdr);
	}

	if (high_addr < low_addr) {
		/* No PT_LOAD segments or corrupted data. */
		goto error;
	}

	*memsz = high_addr - low_addr;
	return 0;
error:
	return -1;
}

/*
 * Internal method used to try and get the build_id from a PT_NOTE
 * segment ranging from `offset` to `segment_end`.
 *
 * If the function returns successfully, the out parameter `found`
 * indicates whether the build id information was present in the
 * segment or not. If `found` is not 0, the out parameters `build_id`
 * and `length` will both have been set with the retrieved
 * information.
 *
 * Returns 0 on success, -1 if an error occurred.
 */
static
int lttng_ust_elf_get_build_id_from_segment(
	struct lttng_ust_elf *elf, uint8_t **build_id, size_t *length,
	off_t offset, off_t segment_end)
{
	uint8_t *_build_id = NULL;	/* Silence old gcc warning. */
	size_t _length = 0;		/* Silence old gcc warning. */

	while (offset < segment_end) {
		struct lttng_ust_elf_nhdr nhdr;
		size_t read_len;

		/* Align start of note entry */
		offset += offset_align(offset, ELF_NOTE_ENTRY_ALIGN);
		if (offset >= segment_end) {
			break;
		}
		/*
		 * We seek manually because if the note isn't the
		 * build id the data following the header will not
		 * have been read.
		 */
		if (lseek(elf->fd, offset, SEEK_SET) < 0) {
			goto error;
		}
		if (lttng_ust_read(elf->fd, &nhdr, sizeof(nhdr))
				< sizeof(nhdr)) {
			goto error;
		}

		if (!is_elf_native_endian(elf)) {
			nhdr.n_namesz = bswap_32(nhdr.n_namesz);
			nhdr.n_descsz = bswap_32(nhdr.n_descsz);
			nhdr.n_type = bswap_32(nhdr.n_type);
		}

		offset += sizeof(nhdr) + nhdr.n_namesz;
		/* Align start of desc entry */
		offset += offset_align(offset, ELF_NOTE_DESC_ALIGN);

		if (nhdr.n_type != NT_GNU_BUILD_ID) {
			/*
			 * Ignore non build id notes but still
			 * increase the offset.
			 */
			offset += nhdr.n_descsz;
			continue;
		}

		_length = nhdr.n_descsz;
		_build_id = zmalloc(sizeof(uint8_t) * _length);
		if (!_build_id) {
			goto error;
		}

		if (lseek(elf->fd, offset, SEEK_SET) < 0) {
			goto error;
		}
		read_len = sizeof(*_build_id) * _length;
		if (lttng_ust_read(elf->fd, _build_id, read_len) < read_len) {
			goto error;
		}

		break;
	}

	if (_build_id) {
		*build_id = _build_id;
		*length = _length;
	}

	return 0;
error:
	free(_build_id);
	return -1;
}

/*
 * Retrieve a build ID (an array of bytes) from the corresponding
 * section in the ELF file. The length of the build ID can be either
 * 16 or 20 bytes depending on the method used to generate it, hence
 * the length out parameter.
 *
 * If the function returns successfully, the out parameter `found`
 * indicates whether the build id information was present in the ELF
 * file or not. If `found` is not 0, the out parameters `build_id` and
 * `length` will both have been set with the retrieved information.
 *
 * Returns 0 on success, -1 if an error occurred.
 */
int lttng_ust_elf_get_build_id(struct lttng_ust_elf *elf, uint8_t **build_id,
			size_t *length, int *found)
{
	uint16_t i;
	uint8_t *_build_id = NULL;	/* Silence old gcc warning. */
	size_t _length = 0;		/* Silence old gcc warning. */

	if (!elf || !build_id || !length || !found) {
		goto error;
	}

	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
		off_t offset, segment_end;
		struct lttng_ust_elf_phdr *phdr;
		int ret = 0;

		phdr = lttng_ust_elf_get_phdr(elf, i);
		if (!phdr) {
			goto error;
		}

		/* Build ID will be contained in a PT_NOTE segment. */
		if (phdr->p_type != PT_NOTE) {
			goto next_loop;
		}

		offset = phdr->p_offset;
		segment_end = offset + phdr->p_filesz;
		ret = lttng_ust_elf_get_build_id_from_segment(
			elf, &_build_id, &_length, offset, segment_end);
	next_loop:
		free(phdr);
		if (ret) {
			goto error;
		}
		if (_build_id) {
			break;
		}
	}

	if (_build_id) {
		*build_id = _build_id;
		*length = _length;
		*found = 1;
	} else {
		*found = 0;
	}

	return 0;
error:
	free(_build_id);
	return -1;
}

/*
 * Try to retrieve filename and CRC from given ELF section `shdr`.
 *
 * If the function returns successfully, the out parameter `found`
 * indicates whether the debug link information was present in the ELF
 * section or not. If `found` is not 0, the out parameters `filename` and
 * `crc` will both have been set with the retrieved information.
 *
 * Returns 0 on success, -1 if an error occurred.
 */
int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf *elf,
					char **filename, uint32_t *crc,
					struct lttng_ust_elf_shdr *shdr)
{
	char *_filename = NULL;		/* Silence old gcc warning. */
	size_t filename_len;
	char *section_name = NULL;
	uint32_t _crc = 0;		/* Silence old gcc warning. */

	if (!elf || !filename || !crc || !shdr) {
		goto error;
	}

	/*
	 * The .gnu_debuglink section is of type SHT_PROGBITS,
	 * skip the other sections.
	 */
	if (shdr->sh_type != SHT_PROGBITS) {
		goto end;
	}

	section_name = lttng_ust_elf_get_section_name(elf,
						shdr->sh_name);
	if (!section_name) {
		goto end;
	}
	if (strcmp(section_name, ".gnu_debuglink")) {
		goto end;
	}

	/*
	 * The length of the filename is the sh_size excluding the CRC
	 * which comes after it in the section.
	 */
	_filename = zmalloc(sizeof(char) * (shdr->sh_size - ELF_CRC_SIZE));
	if (!_filename) {
		goto error;
	}
	if (lseek(elf->fd, shdr->sh_offset, SEEK_SET) < 0) {
		goto error;
	}
	filename_len = sizeof(*_filename) * (shdr->sh_size - ELF_CRC_SIZE);
	if (lttng_ust_read(elf->fd, _filename, filename_len) < filename_len) {
		goto error;
	}
	if (lttng_ust_read(elf->fd, &_crc, sizeof(_crc)) < sizeof(_crc)) {
		goto error;
	}
	if (!is_elf_native_endian(elf)) {
		_crc = bswap_32(_crc);
	}

end:
	free(section_name);
	if (_filename) {
		*filename = _filename;
		*crc = _crc;
	}

	return 0;

error:
	free(_filename);
	free(section_name);
	return -1;
}

/*
 * Retrieve filename and CRC from ELF's .gnu_debuglink section, if any.
 *
 * If the function returns successfully, the out parameter `found`
 * indicates whether the debug link information was present in the ELF
 * file or not. If `found` is not 0, the out parameters `filename` and
 * `crc` will both have been set with the retrieved information.
 *
 * Returns 0 on success, -1 if an error occurred.
 */
int lttng_ust_elf_get_debug_link(struct lttng_ust_elf *elf, char **filename,
				uint32_t *crc, int *found)
{
	int ret;
	uint16_t i;
	char *_filename = NULL;		/* Silence old gcc warning. */
	uint32_t _crc = 0;		/* Silence old gcc warning. */

	if (!elf || !filename || !crc || !found) {
		goto error;
	}

	for (i = 0; i < elf->ehdr->e_shnum; ++i) {
		struct lttng_ust_elf_shdr *shdr = NULL;

		shdr = lttng_ust_elf_get_shdr(elf, i);
		if (!shdr) {
			goto error;
		}

		ret = lttng_ust_elf_get_debug_link_from_section(
			elf, &_filename, &_crc, shdr);
		free(shdr);

		if (ret) {
			goto error;
		}
		if (_filename) {
			break;
		}
	}

	if (_filename) {
		*filename = _filename;
		*crc = _crc;
		*found = 1;
	} else {
		*found = 0;
	}

	return 0;

error:
	free(_filename);
	return -1;
}
Commit	Line	Data
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
aaf93c60	19	#define _GNU_SOURCE
3fbec7dc	20	#define _LGPL_SOURCE
fb31eb73	21	#include <fcntl.h>
8e2aed3f	22	#include <helper.h>
8e2aed3f AB	23	#include <lttng/align.h>
8e2aed3f AB	24	#include <lttng/ust-elf.h>
fb31eb73 FD	25	#include <stdbool.h>
	26	#include <stdint.h>
	27	#include <string.h>
405be658	28	#include <sys/stat.h>
fb31eb73	29	#include <sys/types.h>
405be658	30	#include <unistd.h>
fb31eb73	31
ba8dcc8c	32	#include <ust-fd.h>
fb31eb73	33
405be658 MD	34	#include "lttng-tracer-core.h"
	35
	36	#define BUF_LEN 4096
8e2aed3f	37
2df586a6 PP	38	#ifndef NT_GNU_BUILD_ID
	39	# define NT_GNU_BUILD_ID 3
	40	#endif
	41
8e2aed3f AB	42	/*
	43	* Retrieve the nth (where n is the `index` argument) phdr (program
	44	* header) from the given elf instance.
	45	*
	46	* A pointer to the phdr is returned on success, NULL on failure.
	47	*/
	48	static
	49	struct lttng_ust_elf_phdr lttng_ust_elf_get_phdr(struct lttng_ust_elf elf,
	50	uint16_t index)
	51	{
	52	struct lttng_ust_elf_phdr *phdr = NULL;
f5a6717a	53	off_t offset;
8e2aed3f AB	54
	55	if (!elf) {
	56	goto error;
	57	}
	58
	59	if (index >= elf->ehdr->e_phnum) {
	60	goto error;
	61	}
	62
	63	phdr = zmalloc(sizeof(struct lttng_ust_elf_phdr));
	64	if (!phdr) {
	65	goto error;
	66	}
	67
f5a6717a MD	68	offset = (off_t) elf->ehdr->e_phoff
f5a6717a MD	69	+ (off_t) index * elf->ehdr->e_phentsize;
405be658	70	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
8e2aed3f AB	71	goto error;
	72	}
	73
	74	if (is_elf_32_bit(elf)) {
	75	Elf32_Phdr elf_phdr;
	76
405be658 MD	77	if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
405be658 MD	78	< sizeof(elf_phdr)) {
8e2aed3f AB	79	goto error;
	80	}
	81	if (!is_elf_native_endian(elf)) {
	82	bswap_phdr(elf_phdr);
	83	}
	84	copy_phdr(elf_phdr, *phdr);
	85	} else {
	86	Elf64_Phdr elf_phdr;
	87
405be658 MD	88	if (lttng_ust_read(elf->fd, &elf_phdr, sizeof(elf_phdr))
405be658 MD	89	< sizeof(elf_phdr)) {
8e2aed3f AB	90	goto error;
	91	}
	92	if (!is_elf_native_endian(elf)) {
	93	bswap_phdr(elf_phdr);
	94	}
	95	copy_phdr(elf_phdr, *phdr);
	96	}
	97
	98	return phdr;
	99
	100	error:
	101	free(phdr);
	102	return NULL;
	103	}
	104
	105	/*
	106	* Retrieve the nth (where n is the `index` argument) shdr (section
	107	* header) from the given elf instance.
	108	*
	109	* A pointer to the shdr is returned on success, NULL on failure.
	110	*/
	111	static
	112	struct lttng_ust_elf_shdr lttng_ust_elf_get_shdr(struct lttng_ust_elf elf,
	113	uint16_t index)
	114	{
	115	struct lttng_ust_elf_shdr *shdr = NULL;
4c5dac0d	116	off_t offset;
8e2aed3f AB	117
	118	if (!elf) {
	119	goto error;
	120	}
	121
	122	if (index >= elf->ehdr->e_shnum) {
	123	goto error;
	124	}
	125
	126	shdr = zmalloc(sizeof(struct lttng_ust_elf_shdr));
	127	if (!shdr) {
	128	goto error;
	129	}
	130
4c5dac0d	131	offset = (off_t) elf->ehdr->e_shoff
5a26ac54	132	+ (off_t) index * elf->ehdr->e_shentsize;
405be658	133	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
8e2aed3f AB	134	goto error;
	135	}
	136
	137	if (is_elf_32_bit(elf)) {
	138	Elf32_Shdr elf_shdr;
	139
405be658 MD	140	if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
405be658 MD	141	< sizeof(elf_shdr)) {
8e2aed3f AB	142	goto error;
	143	}
	144	if (!is_elf_native_endian(elf)) {
	145	bswap_shdr(elf_shdr);
	146	}
	147	copy_shdr(elf_shdr, *shdr);
	148	} else {
	149	Elf64_Shdr elf_shdr;
	150
405be658 MD	151	if (lttng_ust_read(elf->fd, &elf_shdr, sizeof(elf_shdr))
405be658 MD	152	< sizeof(elf_shdr)) {
8e2aed3f AB	153	goto error;
	154	}
	155	if (!is_elf_native_endian(elf)) {
	156	bswap_shdr(elf_shdr);
	157	}
	158	copy_shdr(elf_shdr, *shdr);
	159	}
	160
	161	return shdr;
	162
	163	error:
	164	free(shdr);
	165	return NULL;
	166	}
	167
	168	/*
	169	* Lookup a section's name from a given offset (usually from an shdr's
	170	* sh_name value) in bytes relative to the beginning of the section
	171	* names string table.
	172	*
	173	* If no name is found, NULL is returned.
	174	*/
	175	static
f5a6717a	176	char lttng_ust_elf_get_section_name(struct lttng_ust_elf elf, off_t offset)
8e2aed3f AB	177	{
8e2aed3f AB	178	char *name = NULL;
405be658	179	size_t len = 0, to_read; /* len does not include \0 */
8e2aed3f AB	180
	181	if (!elf) {
	182	goto error;
	183	}
	184
	185	if (offset >= elf->section_names_size) {
	186	goto error;
	187	}
	188
405be658	189	if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
8e2aed3f AB	190	goto error;
8e2aed3f AB	191	}
405be658 MD	192
	193	to_read = elf->section_names_size - offset;
	194
	195	/* Find first \0 after or at current location, remember len. */
	196	for (;;) {
	197	char buf[BUF_LEN];
	198	ssize_t read_len;
	199	size_t i;
	200
	201	if (!to_read) {
8e2aed3f	202	goto error;
8e2aed3f	203	}
405be658 MD	204	read_len = lttng_ust_read(elf->fd, buf,
	205	min_t(size_t, BUF_LEN, to_read));
	206	if (read_len <= 0) {
	207	goto error;
	208	}
	209	for (i = 0; i < read_len; i++) {
	210	if (buf[i] == '\0') {
	211	len += i;
	212	goto end;
	213	}
	214	}
	215	len += read_len;
	216	to_read -= read_len;
8e2aed3f	217	}
8e2aed3f	218	end:
405be658	219	name = zmalloc(sizeof(char) * (len + 1)); /* + 1 for \0 */
8e2aed3f AB	220	if (!name) {
	221	goto error;
	222	}
405be658 MD	223	if (lseek(elf->fd, elf->section_names_offset + offset,
405be658 MD	224	SEEK_SET) < 0) {
8e2aed3f AB	225	goto error;
8e2aed3f AB	226	}
405be658	227	if (lttng_ust_read(elf->fd, name, len + 1) < len + 1) {
8e2aed3f AB	228	goto error;
	229	}
	230
	231	return name;
	232
	233	error:
	234	free(name);
	235	return NULL;
	236	}
	237
	238	/*
	239	* Create an instance of lttng_ust_elf for the ELF file located at
	240	* `path`.
	241	*
	242	* Return a pointer to the instance on success, NULL on failure.
	243	*/
	244	struct lttng_ust_elf lttng_ust_elf_create(const char path)
	245	{
	246	uint8_t e_ident[EI_NIDENT];
	247	struct lttng_ust_elf_shdr *section_names_shdr;
405be658	248	struct lttng_ust_elf *elf = NULL;
f5c453e9	249	int ret, fd;
8e2aed3f AB	250
	251	elf = zmalloc(sizeof(struct lttng_ust_elf));
	252	if (!elf) {
	253	goto error;
	254	}
	255
1ac2e79c JR	256	/* Initialize fd field to -1. 0 is a valid fd number */
1ac2e79c JR	257	elf->fd = -1;
ba8dcc8c	258
8e2aed3f AB	259	elf->path = strdup(path);
	260	if (!elf->path) {
	261	goto error;
	262	}
	263
ba8dcc8c	264	lttng_ust_lock_fd_tracker();
f5c453e9 JR	265	fd = open(elf->path, O_RDONLY \| O_CLOEXEC);
f5c453e9 JR	266	if (fd < 0) {
ba8dcc8c	267	lttng_ust_unlock_fd_tracker();
8e2aed3f AB	268	goto error;
8e2aed3f AB	269	}
f5c453e9 JR	270
	271	ret = lttng_ust_add_fd_to_tracker(fd);
	272	if (ret < 0) {
	273	ret = close(fd);
	274	if (ret) {
	275	PERROR("close on elf->fd");
	276	}
	277	ret = -1;
	278	lttng_ust_unlock_fd_tracker();
	279	goto error;
	280	}
	281	elf->fd = ret;
ba8dcc8c	282	lttng_ust_unlock_fd_tracker();
8e2aed3f	283
405be658	284	if (lttng_ust_read(elf->fd, e_ident, EI_NIDENT) < EI_NIDENT) {
8e2aed3f AB	285	goto error;
	286	}
	287	elf->bitness = e_ident[EI_CLASS];
	288	elf->endianness = e_ident[EI_DATA];
405be658 MD	289
	290	if (lseek(elf->fd, 0, SEEK_SET) < 0) {
	291	goto error;
	292	}
8e2aed3f AB	293
	294	elf->ehdr = zmalloc(sizeof(struct lttng_ust_elf_ehdr));
	295	if (!elf->ehdr) {
	296	goto error;
	297	}
	298
	299	if (is_elf_32_bit(elf)) {
	300	Elf32_Ehdr elf_ehdr;
	301
405be658 MD	302	if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
405be658 MD	303	< sizeof(elf_ehdr)) {
8e2aed3f AB	304	goto error;
	305	}
	306	if (!is_elf_native_endian(elf)) {
	307	bswap_ehdr(elf_ehdr);
	308	}
	309	copy_ehdr(elf_ehdr, *(elf->ehdr));
	310	} else {
	311	Elf64_Ehdr elf_ehdr;
	312
405be658 MD	313	if (lttng_ust_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr))
405be658 MD	314	< sizeof(elf_ehdr)) {
8e2aed3f AB	315	goto error;
	316	}
	317	if (!is_elf_native_endian(elf)) {
	318	bswap_ehdr(elf_ehdr);
	319	}
	320	copy_ehdr(elf_ehdr, *(elf->ehdr));
	321	}
	322
	323	section_names_shdr = lttng_ust_elf_get_shdr(elf, elf->ehdr->e_shstrndx);
	324	if (!section_names_shdr) {
	325	goto error;
	326	}
	327
	328	elf->section_names_offset = section_names_shdr->sh_offset;
	329	elf->section_names_size = section_names_shdr->sh_size;
	330
	331	free(section_names_shdr);
8e2aed3f AB	332	return elf;
	333
	334	error:
ba8dcc8c	335	lttng_ust_elf_destroy(elf);
8e2aed3f AB	336	return NULL;
	337	}
	338
f5eb039d AB	339	/*
	340	* Test whether the ELF file is position independent code (PIC)
	341	*/
	342	uint8_t lttng_ust_elf_is_pic(struct lttng_ust_elf *elf)
	343	{
	344	/*
	345	* PIC has and e_type value of ET_DYN, see ELF specification
	346	* version 1.1 p. 1-3.
	347	*/
	348	return elf->ehdr->e_type == ET_DYN;
	349	}
	350
8e2aed3f AB	351	/*
	352	* Destroy the given lttng_ust_elf instance.
	353	*/
	354	void lttng_ust_elf_destroy(struct lttng_ust_elf *elf)
	355	{
ba8dcc8c JR	356	int ret;
ba8dcc8c JR	357
8e2aed3f AB	358	if (!elf) {
	359	return;
	360	}
	361
ba8dcc8c JR	362	if (elf->fd >= 0) {
	363	lttng_ust_lock_fd_tracker();
	364	ret = close(elf->fd);
	365	if (!ret) {
	366	lttng_ust_delete_fd_from_tracker(elf->fd);
	367	} else {
	368	PERROR("close");
	369	abort();
	370	}
	371	lttng_ust_unlock_fd_tracker();
405be658	372	}
ba8dcc8c JR	373
ba8dcc8c JR	374	free(elf->ehdr);
8e2aed3f AB	375	free(elf->path);
	376	free(elf);
	377	}
	378
	379	/*
	380	* Compute the total in-memory size of the ELF file, in bytes.
	381	*
	382	* Returns 0 if successful, -1 if not. On success, the memory size is
	383	* returned through the out parameter `memsz`.
	384	*/
	385	int lttng_ust_elf_get_memsz(struct lttng_ust_elf elf, uint64_t memsz)
	386	{
	387	uint16_t i;
e1f0c569	388	uint64_t low_addr = UINT64_MAX, high_addr = 0;
8e2aed3f AB	389
	390	if (!elf \|\| !memsz) {
	391	goto error;
	392	}
	393
	394	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
	395	struct lttng_ust_elf_phdr *phdr;
8e2aed3f AB	396
	397	phdr = lttng_ust_elf_get_phdr(elf, i);
	398	if (!phdr) {
	399	goto error;
	400	}
	401
	402	/*
	403	* Only PT_LOAD segments contribute to memsz. Skip
	404	* other segments.
	405	*/
	406	if (phdr->p_type != PT_LOAD) {
	407	goto next_loop;
	408	}
	409
8886accb MD	410	low_addr = min_t(uint64_t, low_addr, phdr->p_vaddr);
	411	high_addr = max_t(uint64_t, high_addr,
	412	phdr->p_vaddr + phdr->p_memsz);
8e2aed3f AB	413	next_loop:
	414	free(phdr);
	415	}
	416
e1f0c569 AB	417	if (high_addr < low_addr) {
	418	/* No PT_LOAD segments or corrupted data. */
	419	goto error;
	420	}
	421
	422	*memsz = high_addr - low_addr;
8e2aed3f AB	423	return 0;
	424	error:
	425	return -1;
	426	}
	427
	428	/*
	429	* Internal method used to try and get the build_id from a PT_NOTE
	430	* segment ranging from `offset` to `segment_end`.
	431	*
	432	* If the function returns successfully, the out parameter `found`
	433	* indicates whether the build id information was present in the
	434	* segment or not. If `found` is not 0, the out parameters `build_id`
	435	* and `length` will both have been set with the retrieved
	436	* information.
	437	*
	438	* Returns 0 on success, -1 if an error occurred.
	439	*/
	440	static
	441	int lttng_ust_elf_get_build_id_from_segment(
	442	struct lttng_ust_elf elf, uint8_t build_id, size_t length,
82ee1ee4	443	off_t offset, off_t segment_end)
8e2aed3f	444	{
814d07b1 MD	445	uint8_t _build_id = NULL; / Silence old gcc warning. */
814d07b1 MD	446	size_t _length = 0; /* Silence old gcc warning. */
8e2aed3f AB	447
	448	while (offset < segment_end) {
	449	struct lttng_ust_elf_nhdr nhdr;
405be658	450	size_t read_len;
8e2aed3f AB	451
	452	/* Align start of note entry */
	453	offset += offset_align(offset, ELF_NOTE_ENTRY_ALIGN);
	454	if (offset >= segment_end) {
	455	break;
	456	}
	457	/*
	458	* We seek manually because if the note isn't the
	459	* build id the data following the header will not
	460	* have been read.
	461	*/
405be658	462	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
8e2aed3f AB	463	goto error;
8e2aed3f AB	464	}
405be658 MD	465	if (lttng_ust_read(elf->fd, &nhdr, sizeof(nhdr))
405be658 MD	466	< sizeof(nhdr)) {
8e2aed3f AB	467	goto error;
	468	}
	469
	470	if (!is_elf_native_endian(elf)) {
	471	nhdr.n_namesz = bswap_32(nhdr.n_namesz);
	472	nhdr.n_descsz = bswap_32(nhdr.n_descsz);
	473	nhdr.n_type = bswap_32(nhdr.n_type);
	474	}
	475
	476	offset += sizeof(nhdr) + nhdr.n_namesz;
	477	/* Align start of desc entry */
	478	offset += offset_align(offset, ELF_NOTE_DESC_ALIGN);
	479
	480	if (nhdr.n_type != NT_GNU_BUILD_ID) {
	481	/*
	482	* Ignore non build id notes but still
	483	* increase the offset.
	484	*/
	485	offset += nhdr.n_descsz;
	486	continue;
	487	}
	488
	489	_length = nhdr.n_descsz;
	490	_build_id = zmalloc(sizeof(uint8_t) * _length);
5ada26b4	491	if (!_build_id) {
8e2aed3f AB	492	goto error;
	493	}
	494
405be658	495	if (lseek(elf->fd, offset, SEEK_SET) < 0) {
8e2aed3f AB	496	goto error;
8e2aed3f AB	497	}
405be658 MD	498	read_len = sizeof(_build_id) _length;
405be658 MD	499	if (lttng_ust_read(elf->fd, _build_id, read_len) < read_len) {
8e2aed3f AB	500	goto error;
	501	}
	502
8e2aed3f AB	503	break;
	504	}
	505
82ee1ee4	506	if (_build_id) {
8e2aed3f AB	507	*build_id = _build_id;
	508	*length = _length;
	509	}
	510
8e2aed3f AB	511	return 0;
8e2aed3f AB	512	error:
83215d66	513	free(_build_id);
8e2aed3f AB	514	return -1;
	515	}
	516
	517	/*
	518	* Retrieve a build ID (an array of bytes) from the corresponding
	519	* section in the ELF file. The length of the build ID can be either
	520	* 16 or 20 bytes depending on the method used to generate it, hence
	521	* the length out parameter.
	522	*
	523	* If the function returns successfully, the out parameter `found`
	524	* indicates whether the build id information was present in the ELF
	525	* file or not. If `found` is not 0, the out parameters `build_id` and
	526	* `length` will both have been set with the retrieved information.
	527	*
	528	* Returns 0 on success, -1 if an error occurred.
	529	*/
	530	int lttng_ust_elf_get_build_id(struct lttng_ust_elf elf, uint8_t *build_id,
	531	size_t length, int found)
	532	{
	533	uint16_t i;
8c83dbda MD	534	uint8_t _build_id = NULL; / Silence old gcc warning. */
8c83dbda MD	535	size_t _length = 0; /* Silence old gcc warning. */
8e2aed3f AB	536
	537	if (!elf \|\| !build_id \|\| !length \|\| !found) {
	538	goto error;
	539	}
	540
	541	for (i = 0; i < elf->ehdr->e_phnum; ++i) {
f5a6717a	542	off_t offset, segment_end;
8e2aed3f	543	struct lttng_ust_elf_phdr *phdr;
5b3bbf98	544	int ret = 0;
8e2aed3f AB	545
	546	phdr = lttng_ust_elf_get_phdr(elf, i);
	547	if (!phdr) {
	548	goto error;
	549	}
	550
	551	/* Build ID will be contained in a PT_NOTE segment. */
	552	if (phdr->p_type != PT_NOTE) {
	553	goto next_loop;
	554	}
	555
	556	offset = phdr->p_offset;
	557	segment_end = offset + phdr->p_filesz;
	558	ret = lttng_ust_elf_get_build_id_from_segment(
82ee1ee4	559	elf, &_build_id, &_length, offset, segment_end);
8e2aed3f AB	560	next_loop:
	561	free(phdr);
	562	if (ret) {
	563	goto error;
	564	}
82ee1ee4	565	if (_build_id) {
8e2aed3f AB	566	break;
	567	}
	568	}
	569
82ee1ee4	570	if (_build_id) {
8e2aed3f AB	571	*build_id = _build_id;
8e2aed3f AB	572	*length = _length;
82ee1ee4 AB	573	*found = 1;
	574	} else {
	575	*found = 0;
8e2aed3f AB	576	}
8e2aed3f AB	577
8e2aed3f AB	578	return 0;
8e2aed3f AB	579	error:
99b7132d	580	free(_build_id);
8e2aed3f AB	581	return -1;
	582	}
	583
	584	/*
	585	* Try to retrieve filename and CRC from given ELF section `shdr`.
	586	*
	587	* If the function returns successfully, the out parameter `found`
	588	* indicates whether the debug link information was present in the ELF
	589	* section or not. If `found` is not 0, the out parameters `filename` and
	590	* `crc` will both have been set with the retrieved information.
	591	*
	592	* Returns 0 on success, -1 if an error occurred.
	593	*/
8e2aed3f AB	594	int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf *elf,
8e2aed3f AB	595	char *filename, uint32_t crc,
8e2aed3f AB	596	struct lttng_ust_elf_shdr *shdr)
8e2aed3f AB	597	{
8c83dbda	598	char _filename = NULL; / Silence old gcc warning. */
405be658	599	size_t filename_len;
8e2aed3f	600	char *section_name = NULL;
8c83dbda	601	uint32_t _crc = 0; /* Silence old gcc warning. */
8e2aed3f	602
82ee1ee4	603	if (!elf \|\| !filename \|\| !crc \|\| !shdr) {
8e2aed3f AB	604	goto error;
	605	}
	606
	607	/*
	608	* The .gnu_debuglink section is of type SHT_PROGBITS,
	609	* skip the other sections.
	610	*/
	611	if (shdr->sh_type != SHT_PROGBITS) {
	612	goto end;
	613	}
	614
	615	section_name = lttng_ust_elf_get_section_name(elf,
	616	shdr->sh_name);
	617	if (!section_name) {
	618	goto end;
	619	}
	620	if (strcmp(section_name, ".gnu_debuglink")) {
	621	goto end;
	622	}
	623
	624	/*
	625	* The length of the filename is the sh_size excluding the CRC
	626	* which comes after it in the section.
	627	*/
	628	_filename = zmalloc(sizeof(char) * (shdr->sh_size - ELF_CRC_SIZE));
	629	if (!_filename) {
	630	goto error;
	631	}
405be658	632	if (lseek(elf->fd, shdr->sh_offset, SEEK_SET) < 0) {
8e2aed3f AB	633	goto error;
8e2aed3f AB	634	}
405be658 MD	635	filename_len = sizeof(_filename) (shdr->sh_size - ELF_CRC_SIZE);
405be658 MD	636	if (lttng_ust_read(elf->fd, _filename, filename_len) < filename_len) {
8e2aed3f AB	637	goto error;
8e2aed3f AB	638	}
405be658	639	if (lttng_ust_read(elf->fd, &_crc, sizeof(_crc)) < sizeof(_crc)) {
8e2aed3f AB	640	goto error;
	641	}
	642	if (!is_elf_native_endian(elf)) {
	643	_crc = bswap_32(_crc);
	644	}
	645
8e2aed3f AB	646	end:
8e2aed3f AB	647	free(section_name);
82ee1ee4	648	if (_filename) {
8e2aed3f AB	649	*filename = _filename;
	650	*crc = _crc;
	651	}
8e2aed3f AB	652
	653	return 0;
	654
	655	error:
83215d66 MD	656	free(_filename);
83215d66 MD	657	free(section_name);
8e2aed3f AB	658	return -1;
	659	}
	660
	661	/*
	662	* Retrieve filename and CRC from ELF's .gnu_debuglink section, if any.
	663	*
	664	* If the function returns successfully, the out parameter `found`
	665	* indicates whether the debug link information was present in the ELF
	666	* file or not. If `found` is not 0, the out parameters `filename` and
	667	* `crc` will both have been set with the retrieved information.
	668	*
	669	* Returns 0 on success, -1 if an error occurred.
	670	*/
	671	int lttng_ust_elf_get_debug_link(struct lttng_ust_elf elf, char *filename,
	672	uint32_t crc, int found)
	673	{
	674	int ret;
	675	uint16_t i;
8c83dbda MD	676	char _filename = NULL; / Silence old gcc warning. */
8c83dbda MD	677	uint32_t _crc = 0; /* Silence old gcc warning. */
8e2aed3f AB	678
	679	if (!elf \|\| !filename \|\| !crc \|\| !found) {
	680	goto error;
	681	}
	682
	683	for (i = 0; i < elf->ehdr->e_shnum; ++i) {
	684	struct lttng_ust_elf_shdr *shdr = NULL;
	685
	686	shdr = lttng_ust_elf_get_shdr(elf, i);
	687	if (!shdr) {
	688	goto error;
	689	}
	690
	691	ret = lttng_ust_elf_get_debug_link_from_section(
82ee1ee4	692	elf, &_filename, &_crc, shdr);
8e2aed3f AB	693	free(shdr);
	694
	695	if (ret) {
	696	goto error;
	697	}
82ee1ee4	698	if (_filename) {
8e2aed3f AB	699	break;
	700	}
	701	}
	702
82ee1ee4	703	if (_filename) {
8e2aed3f AB	704	*filename = _filename;
8e2aed3f AB	705	*crc = _crc;
82ee1ee4 AB	706	*found = 1;
	707	} else {
	708	*found = 0;
8e2aed3f AB	709	}
8e2aed3f AB	710
8e2aed3f	711	return 0;
82ee1ee4	712
8e2aed3f	713	error:
99b7132d	714	free(_filename);
8e2aed3f AB	715	return -1;
8e2aed3f AB	716	}