/*

 * 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

#include <helper.h>

#include <string.h>

#include <lttng/align.h>

#include <lttng/ust-elf.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <unistd.h>

#include "lttng-tracer-core.h"

#define BUF_LEN	4096

/*

 * 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;

	elf = zmalloc(sizeof(struct lttng_ust_elf));

	if (!elf) {

		goto error;

	}

	elf->path = strdup(path);

	if (!elf->path) {

		goto error;

	}

	elf->fd = open(elf->path, O_RDONLY | O_CLOEXEC);

	if (elf->fd < 0) {

		goto error;

	}

	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:

	if (elf) {

		free(elf->ehdr);

		if (elf->fd >= 0) {

			if (close(elf->fd)) {

				abort();

			}

		}

		free(elf->path);

		free(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)

{

	if (!elf) {

		return;

	}

	free(elf->ehdr);

	if (close(elf->fd)) {

		abort();

	}

	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;

}