+/*
+ * 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
+ */
+
+#include <helper.h>
+#include <string.h>
+#include <lttng/align.h>
+#include <lttng/ust-elf.h>
+
+/*
+ * 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;
+ long 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 = elf->ehdr->e_phoff + index * elf->ehdr->e_phentsize;
+ if (fseek(elf->file, offset, SEEK_SET)) {
+ goto error;
+ }
+
+ if (is_elf_32_bit(elf)) {
+ Elf32_Phdr elf_phdr;
+
+ if (!fread(&elf_phdr, sizeof(elf_phdr), 1, elf->file)) {
+ goto error;
+ }
+ if (!is_elf_native_endian(elf)) {
+ bswap_phdr(elf_phdr);
+ }
+ copy_phdr(elf_phdr, *phdr);
+ } else {
+ Elf64_Phdr elf_phdr;
+
+ if (!fread(&elf_phdr, sizeof(elf_phdr), 1, elf->file)) {
+ 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;
+ long 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 = elf->ehdr->e_shoff + index * elf->ehdr->e_shentsize;
+ if (fseek(elf->file, offset, SEEK_SET)) {
+ goto error;
+ }
+
+ if (is_elf_32_bit(elf)) {
+ Elf32_Shdr elf_shdr;
+
+ if (!fread(&elf_shdr, sizeof(elf_shdr), 1, elf->file)) {
+ goto error;
+ }
+ if (!is_elf_native_endian(elf)) {
+ bswap_shdr(elf_shdr);
+ }
+ copy_shdr(elf_shdr, *shdr);
+ } else {
+ Elf64_Shdr elf_shdr;
+
+ if (!fread(&elf_shdr, sizeof(elf_shdr), 1, elf->file)) {
+ 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, uint32_t offset)
+{
+ char *name = NULL;
+ size_t len;
+
+ if (!elf) {
+ goto error;
+ }
+
+ if (offset >= elf->section_names_size) {
+ goto error;
+ }
+
+ if (fseek(elf->file, elf->section_names_offset + offset, SEEK_SET)) {
+ goto error;
+ }
+ /* Note that len starts at 1, it is not an index. */
+ for (len = 1; offset + len <= elf->section_names_size; ++len) {
+ switch (fgetc(elf->file)) {
+ case EOF:
+ goto error;
+ case '\0':
+ goto end;
+ default:
+ break;
+ }
+ }
+
+ /* No name was found before the end of the table. */
+ goto error;
+
+end:
+ name = zmalloc(sizeof(char) * len);
+ if (!name) {
+ goto error;
+ }
+ if (fseek(elf->file, elf->section_names_offset + offset,
+ SEEK_SET)) {
+ goto error;
+ }
+ if (!fgets(name, len, elf->file)) {
+ 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;
+
+ elf = zmalloc(sizeof(struct lttng_ust_elf));
+ if (!elf) {
+ goto error;
+ }
+
+ elf->path = strdup(path);
+ if (!elf->path) {
+ goto error;
+ }
+
+ elf->file = fopen(elf->path, "rb");
+ if (!elf->file) {
+ goto error;
+ }
+
+ if (!fread(e_ident, 1, EI_NIDENT, elf->file)) {
+ goto error;
+ }
+ elf->bitness = e_ident[EI_CLASS];
+ elf->endianness = e_ident[EI_DATA];
+ rewind(elf->file);
+
+ 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 (!fread(&elf_ehdr, sizeof(elf_ehdr), 1, elf->file)) {
+ goto error;
+ }
+ if (!is_elf_native_endian(elf)) {
+ bswap_ehdr(elf_ehdr);
+ }
+ copy_ehdr(elf_ehdr, *(elf->ehdr));
+ } else {
+ Elf64_Ehdr elf_ehdr;
+
+ if (!fread(&elf_ehdr, sizeof(elf_ehdr), 1, elf->file)) {
+ 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);
+ fclose(elf->file);
+ free(elf->path);
+ }
+ free(elf);
+ return NULL;
+}
+
+/*
+ * Destroy the given lttng_ust_elf instance.
+ */
+void lttng_ust_elf_destroy(struct lttng_ust_elf *elf)
+{
+ if (!elf) {
+ return;
+ }
+
+ free(elf->ehdr);
+ fclose(elf->file);
+ 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 _memsz = 0;
+
+ if (!elf || !memsz) {
+ goto error;
+ }
+
+ for (i = 0; i < elf->ehdr->e_phnum; ++i) {
+ struct lttng_ust_elf_phdr *phdr;
+ uint64_t align;
+
+ 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;
+ }
+
+ /*
+ * A p_align of 0 means no alignment, i.e. aligned to
+ * 1 byte.
+ */
+ align = phdr->p_align == 0 ? 1 : phdr->p_align;
+ /* Align the start of the segment. */
+ _memsz += offset_align(_memsz, align);
+ _memsz += phdr->p_memsz;
+ /*
+ * Add padding at the end of the segment, so it ends
+ * on a multiple of the align value (which usually
+ * means a page boundary). This makes the computation
+ * valid even in cases where p_align would change from
+ * one segment to the next.
+ */
+ _memsz += offset_align(_memsz, align);
+ next_loop:
+ free(phdr);
+ }
+
+ *memsz = _memsz;
+ 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,
+ uint64_t offset, uint64_t segment_end, int *found)
+{
+ uint8_t *_build_id;
+ size_t _length;
+ int _found = 0;
+
+ while (offset < segment_end) {
+ struct lttng_ust_elf_nhdr nhdr;
+
+ /* 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 (fseek(elf->file, offset, SEEK_SET)) {
+ goto error;
+ }
+ if (!fread(&nhdr, sizeof(nhdr), 1, elf->file)) {
+ 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 (fseek(elf->file, offset, SEEK_SET)) {
+ goto error;
+ }
+ if (!fread(_build_id, sizeof(*_build_id), _length, elf->file)) {
+ goto error;
+ }
+
+ _found = 1;
+ break;
+ }
+
+ if (_found) {
+ *build_id = _build_id;
+ *length = _length;
+ }
+
+ *found = _found;
+ return 0;
+error:
+ 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;
+ size_t _length;
+ int _found = 0;
+
+ if (!elf || !build_id || !length || !found) {
+ goto error;
+ }
+
+ for (i = 0; i < elf->ehdr->e_phnum; ++i) {
+ uint64_t offset, segment_end;
+ struct lttng_ust_elf_phdr *phdr;
+ int ret;
+
+ 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,
+ &_found);
+ next_loop:
+ free(phdr);
+ if (ret) {
+ goto error;
+ }
+ if (_found) {
+ break;
+ }
+ }
+
+ if (_found) {
+ *build_id = _build_id;
+ *length = _length;
+ }
+
+ *found = _found;
+ return 0;
+error:
+ 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.
+ */
+static
+int lttng_ust_elf_get_debug_link_from_section(struct lttng_ust_elf *elf,
+ char **filename, uint32_t *crc,
+ int *found,
+ struct lttng_ust_elf_shdr *shdr)
+{
+ int _found = 0;
+ char *_filename;
+ char *section_name = NULL;
+ uint32_t _crc;
+
+ if (!elf || !filename || !crc || !found || !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 (fseek(elf->file, shdr->sh_offset, SEEK_SET)) {
+ goto error;
+ }
+ if (!fread(_filename, sizeof(*_filename), shdr->sh_size - ELF_CRC_SIZE,
+ elf->file)) {
+ goto error;
+ }
+ if (!fread(&_crc, sizeof(_crc), 1, elf->file)) {
+ goto error;
+ }
+ if (!is_elf_native_endian(elf)) {
+ _crc = bswap_32(_crc);
+ }
+
+ _found = 1;
+
+end:
+ free(section_name);
+ if (_found) {
+ *filename = _filename;
+ *crc = _crc;
+ }
+ *found = _found;
+
+ return 0;
+
+error:
+ if (section_name) {
+ 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;
+ int _found = 0;
+ char *_filename;
+ uint32_t _crc;
+
+ 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, &_found, shdr);
+ free(shdr);
+
+ if (ret) {
+ goto error;
+ }
+ if (_found) {
+ break;
+ }
+ }
+
+ if (_found) {
+ *filename = _filename;
+ *crc = _crc;
+ }
+
+ *found = _found;
+ return 0;
+error:
+ return -1;
+}