Fix: flt.lttng-utils.debug-info: Dereference after null check

[babeltrace.git] / src / plugins / lttng-utils / debug-info / bin-info.c

/*
 * bin-info.c
 *
 * Babeltrace - Executable and Shared Object Debug Info Reader
 *
 * Copyright 2015 Antoine Busque <abusque@efficios.com>
 *
 * Author: Antoine Busque <abusque@efficios.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#define BT_COMP_LOG_SELF_COMP (bin->self_comp)
#define BT_LOG_OUTPUT_LEVEL (bin->log_level)
#define BT_LOG_TAG "PLUGIN/FLT.LTTNG-UTILS.DEBUG-INFO/BIN-INFO"
#include "logging/comp-logging.h"

#include <babeltrace2/logging.h>
#include <dwarf.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <libgen.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <glib.h>

#include "common/common.h"

#include "bin-info.h"
#include "crc32.h"
#include "dwarf.h"
#include "utils.h"

/*
 * An address printed in hex is at most 20 bytes (16 for 64-bits +
 * leading 0x + optional leading '+' if addr is an offset + null
 * character).
 */
#define ADDR_STR_LEN 20
#define BUILD_ID_NOTE_NAME "GNU"

BT_HIDDEN
int bin_info_init(bt_logging_level log_level, bt_self_component *self_comp)
{
        int ret = 0;

        if (elf_version(EV_CURRENT) == EV_NONE) {
                BT_COMP_LOG_CUR_LVL(BT_LOG_INFO, log_level, self_comp,
                        "ELF library initialization failed: %s.",
                        elf_errmsg(-1));
                ret = -1;
        }

        return ret;
}

BT_HIDDEN
struct bin_info *bin_info_create(struct bt_fd_cache *fdc, const char *path,
                uint64_t low_addr, uint64_t memsz, bool is_pic,
                const char *debug_info_dir, const char *target_prefix,
                bt_logging_level log_level, bt_self_component *self_comp)
{
        struct bin_info *bin = NULL;

        BT_ASSERT(fdc);

        if (!path) {
                goto error;
        }

        bin = g_new0(struct bin_info, 1);
        if (!bin) {
                goto error;
        }

        bin->log_level = log_level;
        bin->self_comp = self_comp;
        if (target_prefix) {
                bin->elf_path = g_build_filename(target_prefix, path, NULL);
        } else {
                bin->elf_path = g_strdup(path);
        }

        if (!bin->elf_path) {
                goto error;
        }

        if (debug_info_dir) {
                bin->debug_info_dir = g_strdup(debug_info_dir);
                if (!bin->debug_info_dir) {
                        goto error;
                }
        }

        bin->is_pic = is_pic;
        bin->memsz = memsz;
        bin->low_addr = low_addr;
        bin->high_addr = bin->low_addr + bin->memsz;
        bin->build_id = NULL;
        bin->build_id_len = 0;
        bin->file_build_id_matches = false;
        bin->fd_cache = fdc;

        return bin;

error:
        bin_info_destroy(bin);
        return NULL;
}

BT_HIDDEN
void bin_info_destroy(struct bin_info *bin)
{
        if (!bin) {
                return;
        }

        dwarf_end(bin->dwarf_info);

        g_free(bin->debug_info_dir);
        g_free(bin->elf_path);
        g_free(bin->dwarf_path);
        g_free(bin->build_id);
        g_free(bin->dbg_link_filename);

        elf_end(bin->elf_file);

        bt_fd_cache_put_handle(bin->fd_cache, bin->elf_handle);
        bt_fd_cache_put_handle(bin->fd_cache, bin->dwarf_handle);

        g_free(bin);
}

/**
 * Initialize the ELF file for a given executable.
 *
 * @param bin   bin_info instance
 * @returns     0 on success, negative value on error.
 */
static
int bin_info_set_elf_file(struct bin_info *bin)
{
        struct bt_fd_cache_handle *elf_handle = NULL;
        Elf *elf_file = NULL;
        int ret;

        BT_ASSERT(bin);

        elf_handle = bt_fd_cache_get_handle(bin->fd_cache, bin->elf_path);
        if (!elf_handle) {
                BT_COMP_LOGI("Failed to open %s", bin->elf_path);
                goto error;
        }
        bin->elf_handle = elf_handle;

        elf_file = elf_begin(bt_fd_cache_handle_get_fd(bin->elf_handle),
                ELF_C_READ, NULL);
        if (!elf_file) {
                BT_COMP_LOGE("elf_begin failed: %s", elf_errmsg(-1));
                goto error;
        }

        bin->elf_file = elf_file;

        if (elf_kind(elf_file) != ELF_K_ELF) {
                BT_COMP_LOGE("Error: %s is not an ELF object", bin->elf_path);
                goto error;
        }


        ret = 0;
        goto end;

error:
        bt_fd_cache_put_handle(bin->fd_cache, elf_handle);
        elf_end(elf_file);
        ret = -1;

end:
        return ret;
}

/**
 * From a note section data struct, check if it is a build id note.
 *
 * @param note_data             Pointer to a note section
 *
 * @returns                     1 on match, 0 if `buf` does not contain a
 *                              valid build id note
 */
static
int is_build_id_note_section(Elf_Data *note_data)
{
        size_t name_offset, desc_offset;
        GElf_Nhdr note_header;
        int ret = 0;

        /*
         * Discard the return value as it contains the size of the note section
         * and we don't need it.
         */
        (void) gelf_getnote(note_data, 0, &note_header, &name_offset,
                &desc_offset);

        /*
         * Check the note name length. The name_sz field includes the
         * terminating null byte.
         */
        if (note_header.n_namesz != sizeof(BUILD_ID_NOTE_NAME)) {
                goto invalid;
        }

        /* Check the note type. */
        if (note_header.n_type != NT_GNU_BUILD_ID) {
                goto invalid;
        }

        /* Check the note name. */
        if (memcmp(note_data->d_buf + name_offset, BUILD_ID_NOTE_NAME,
                        note_header.n_namesz) != 0) {
                goto invalid;
        }

        ret = 1;

invalid:
        return ret;
}

/**
 *  From a build id note section data struct, check if the build id it contains
 *  is identical to the build id passed as parameter.
 *
 * @param note_data             Pointer to the file build id note section.
 * @param build_id              Pointer to a build id to compare to.
 * @param build_id_len          length of the build id.
 *
 * @returns                     1 on match, 0 otherwise.
 */
static
int is_build_id_note_section_matching(Elf_Data *note_data,
                uint8_t *build_id, size_t build_id_len)
{
        size_t name_offset, desc_offset;
        GElf_Nhdr note_header;

        if (build_id_len <= 0) {
                goto end;
        }

        /*
         * Discard the return value as it contains the size of the note section
         * and we don't need it.
         */
        (void) gelf_getnote(note_data, 0, &note_header, &name_offset,
                &desc_offset);

        /*
         * Compare the binary build id with the supplied build id.
         */
        if (memcmp(build_id, note_data->d_buf + desc_offset,
                        build_id_len) == 0) {
                return 1;
        }
end:
        return 0;
}

/**
 * Checks if the build id stored in `bin` (bin->build_id) is matching the build
 * id of the ondisk file (bin->elf_file).
 *
 * @param bin                   bin_info instance
 * @param build_id              build id to compare ot the on disk file
 * @param build_id_len          length of the build id
 *
 * @returns                     1 on if the build id of stored in `bin` matches
 *                              the build id of the ondisk file.
 *                              0 on if they are different or an error occured.
 */
static
int is_build_id_matching(struct bin_info *bin)
{
        int ret, is_build_id, is_matching = 0;
        Elf_Scn *curr_section = NULL, *next_section = NULL;
        GElf_Shdr curr_section_hdr;

        if (!bin->build_id) {
                goto error;
        }

        /* Set ELF file if it hasn't been accessed yet. */
        if (!bin->elf_file) {
                ret = bin_info_set_elf_file(bin);
                if (ret) {
                        /* Failed to set ELF file. */
                        goto error;
                }
        }

        next_section = elf_nextscn(bin->elf_file, curr_section);
        if (!next_section) {
                goto error;
        }

        while (next_section) {
                Elf_Data *note_data = NULL;

                curr_section = next_section;
                next_section = elf_nextscn(bin->elf_file, curr_section);

                if (!gelf_getshdr(curr_section, &curr_section_hdr)) {
                        goto error;
                }

                if (curr_section_hdr.sh_type != SHT_NOTE) {
                        continue;
                }

                /*
                 * elf_getdata() translates the data to native byte order.
                 */
                note_data = elf_getdata(curr_section, NULL);
                if (!note_data) {
                        goto error;
                }

                /* Check if the note is of the build-id type. */
                is_build_id = is_build_id_note_section(note_data);
                if (!is_build_id) {
                        continue;
                }

                /*
                 * Compare the build id of the on-disk file and
                 * the build id recorded in the trace.
                 */
                is_matching = is_build_id_note_section_matching(
                        note_data, bin->build_id, bin->build_id_len);
                if (!is_matching) {
                        break;
                }
        }
error:
        return is_matching;
}

BT_HIDDEN
int bin_info_set_build_id(struct bin_info *bin, uint8_t *build_id,
                size_t build_id_len)
{
        if (!bin || !build_id) {
                goto error;
        }

        /* Set the build id. */
        bin->build_id = g_new0(uint8_t, build_id_len);
        if (!bin->build_id) {
                goto error;
        }

        memcpy(bin->build_id, build_id, build_id_len);
        bin->build_id_len = build_id_len;

        /*
         * Check if the file found on the file system has the same build id
         * that what was recorded in the trace.
         */
        bin->file_build_id_matches = is_build_id_matching(bin);
        if (!bin->file_build_id_matches) {
                BT_COMP_LOGI_STR("Supplied Build ID does not match Build ID of the "
                                "binary or library found on the file system.");
                goto error;
        }

        /*
         * Reset the is_elf_only flag in case it had been set
         * previously, because we might find separate debug info using
         * the new build id information.
         */
        bin->is_elf_only = false;

        return 0;

error:
        return -1;
}

BT_HIDDEN
int bin_info_set_debug_link(struct bin_info *bin, const char *filename,
                uint32_t crc)
{
        if (!bin || !filename) {
                goto error;
        }

        bin->dbg_link_filename = g_strdup(filename);
        if (!bin->dbg_link_filename) {
                goto error;
        }

        bin->dbg_link_crc = crc;

        /*
         * Reset the is_elf_only flag in case it had been set
         * previously, because we might find separate debug info using
         * the new build id information.
         */
        bin->is_elf_only = false;

        return 0;

error:

        return -1;
}

/**
 * Tries to read DWARF info from the location given by path, and
 * attach it to the given bin_info instance if it exists.
 *
 * @param bin   bin_info instance for which to set DWARF info
 * @param path  Presumed location of the DWARF info
 * @returns     0 on success, negative value on failure
 */
static
int bin_info_set_dwarf_info_from_path(struct bin_info *bin, char *path)
{
        int ret = 0;
        struct bt_fd_cache_handle *dwarf_handle = NULL;
        struct bt_dwarf_cu *cu = NULL;
        Dwarf *dwarf_info = NULL;

        if (!bin || !path) {
                goto error;
        }

        dwarf_handle = bt_fd_cache_get_handle(bin->fd_cache, path);
        if (!dwarf_handle) {
                goto error;
        }

        dwarf_info = dwarf_begin(bt_fd_cache_handle_get_fd(dwarf_handle),
                DWARF_C_READ);
        if (!dwarf_info) {
                goto error;
        }

        /*
         * Check if the dwarf info has any CU. If not, the
         * executable's object file contains no DWARF info.
         */
        cu = bt_dwarf_cu_create(dwarf_info);
        if (!cu) {
                goto error;
        }

        ret = bt_dwarf_cu_next(cu);
        if (ret) {
                goto error;
        }

        bin->dwarf_handle = dwarf_handle;
        bin->dwarf_path = g_strdup(path);
        if (!bin->dwarf_path) {
                goto error;
        }
        bin->dwarf_info = dwarf_info;
        free(cu);

        return 0;

error:
        if (bin) {
                bt_fd_cache_put_handle(bin->fd_cache, dwarf_handle);
        }
        dwarf_end(dwarf_info);
        g_free(dwarf_info);
        free(cu);

        return -1;
}

/**
 * Try to set the dwarf_info for a given bin_info instance via the
 * build ID method.
 *
 * @param bin           bin_info instance for which to retrieve the
 *                      DWARF info via build ID
 * @returns             0 on success (i.e. dwarf_info set), -1 on failure
 */
static
int bin_info_set_dwarf_info_build_id(struct bin_info *bin)
{
        int i = 0, ret = 0;
        char *path = NULL, *build_id_prefix_dir = NULL, *build_id_file = NULL;
        const char *dbg_dir = NULL;
        size_t build_id_char_len, build_id_suffix_char_len, build_id_file_len;

        if (!bin || !bin->build_id) {
                goto error;
        }

        dbg_dir = bin->debug_info_dir ? bin->debug_info_dir : DEFAULT_DEBUG_DIR;

        /*
         * The prefix dir is the first byte of the build id, represented in
         * lowercase hex as two characters per byte, +1 for '\0'.
         */
        build_id_prefix_dir = g_new0(gchar, BUILD_ID_PREFIX_DIR_LEN + 1);
        if (!build_id_prefix_dir) {
                goto error;
        }
        g_snprintf(build_id_prefix_dir, BUILD_ID_PREFIX_DIR_LEN + 1, "%02x", bin->build_id[0]);

        /*
         * The build id file is the remaining bytes of the build id,
         * represented in lowercase hex, as two characters per byte.
         */
        build_id_char_len = (2 * (bin->build_id_len - 1));

        /* To which the build id suffix is added, +1 for '\0'. */
        build_id_suffix_char_len = strlen(BUILD_ID_SUFFIX) + 1;

        /*
         * The resulting filename string is the concatenation of the
         * hex build id and the suffix.
         */
        build_id_file_len =  build_id_char_len + build_id_suffix_char_len;
        build_id_file = g_new0(gchar, build_id_file_len);
        if (!build_id_file) {
                goto error;
        }

        /*
         * For each byte, starting at offset 1, append two characters
         * in lowercase hex.
         */
        for (i = 1; i < bin->build_id_len; ++i) {
                int path_idx = 2 * (i - 1);

                g_snprintf(&build_id_file[path_idx], 3, "%02x", bin->build_id[i]);
        }
        /* Append the suffix to the generated string, including the '\0'. */
        g_snprintf(&build_id_file[build_id_char_len], build_id_suffix_char_len,
                BUILD_ID_SUFFIX);

        path = g_build_filename(dbg_dir, BUILD_ID_SUBDIR, build_id_prefix_dir, build_id_file, NULL);
        if (!path) {
                goto error;
        }

        ret = bin_info_set_dwarf_info_from_path(bin, path);
        if (ret) {
                goto error;
        }

        goto end;

error:
        ret = -1;
end:
        g_free(build_id_prefix_dir);
        g_free(build_id_file);
        g_free(path);

        return ret;
}

/**
 * Tests whether the file located at path exists and has the expected
 * checksum.
 *
 * This predicate is used when looking up separate debug info via the
 * GNU debuglink method. The expected crc can be found .gnu_debuglink
 * section in the original ELF file, along with the filename for the
 * file containing the debug info.
 *
 * @param path  Full path at which to look for the debug file
 * @param crc   Expected checksum for the debug file
 * @returns     1 if the file exists and has the correct checksum,
 *              0 otherwise
 */
static
int is_valid_debug_file(struct bin_info *bin, char *path, uint32_t crc)
{
        int ret = 0;
        struct bt_fd_cache_handle *debug_handle = NULL;
        uint32_t _crc = 0;

        if (!path) {
                goto end;
        }

        debug_handle = bt_fd_cache_get_handle(bin->fd_cache, path);
        if (!debug_handle) {
                goto end;
        }

        ret = crc32(bt_fd_cache_handle_get_fd(debug_handle), &_crc);
        if (ret) {
                ret = 0;
                goto end;
        }

        ret = (crc == _crc);

end:
        bt_fd_cache_put_handle(bin->fd_cache, debug_handle);
        return ret;
}

/**
 * Try to set the dwarf_info for a given bin_info instance via the
 * debug-link method.
 *
 * @param bin           bin_info instance for which to retrieve the
 *                      DWARF info via debug link
 * @returns             0 on success (i.e. dwarf_info set), -1 on failure
 */
static
int bin_info_set_dwarf_info_debug_link(struct bin_info *bin)
{
        int ret = 0;
        const gchar *dbg_dir = NULL;
        gchar *bin_dir = NULL, *path = NULL;

        if (!bin || !bin->dbg_link_filename) {
                goto error;
        }

        dbg_dir = bin->debug_info_dir ? bin->debug_info_dir : DEFAULT_DEBUG_DIR;
        bin_dir = g_path_get_dirname(bin->elf_path);

        /* First look in the executable's dir */
        path = g_build_filename(bin_dir, bin->dbg_link_filename, NULL);

        if (is_valid_debug_file(bin, path, bin->dbg_link_crc)) {
                goto found;
        }

        /* If not found, look in .debug subdir */
        g_free(path);
        path = g_build_filename(bin_dir, DEBUG_SUBDIR, bin->dbg_link_filename, NULL);

        if (is_valid_debug_file(bin, path, bin->dbg_link_crc)) {
                goto found;
        }

        /* Lastly, look under the global debug directory */
        g_free(path);

        path = g_build_filename(dbg_dir, bin_dir, bin->dbg_link_filename, NULL);
        if (is_valid_debug_file(bin, path, bin->dbg_link_crc)) {
                goto found;
        }

error:
        ret = -1;
end:
        g_free(bin_dir);
        g_free(path);

        return ret;

found:
        ret = bin_info_set_dwarf_info_from_path(bin, path);
        if (ret) {
                goto error;
        }

        goto end;
}

/**
 * Initialize the DWARF info for a given executable.
 *
 * @param bin   bin_info instance
 * @returns     0 on success, negative value on failure
 */
static
int bin_info_set_dwarf_info(struct bin_info *bin)
{
        int ret = 0;

        if (!bin) {
                ret = -1;
                goto end;
        }

        /* First try to set the DWARF info from the ELF file */
        ret = bin_info_set_dwarf_info_from_path(bin, bin->elf_path);
        if (!ret) {
                goto end;
        }

        /*
         * If that fails, try to find separate debug info via build ID
         * and debug link.
         */
        ret = bin_info_set_dwarf_info_build_id(bin);
        if (!ret) {
                goto end;
        }

        ret = bin_info_set_dwarf_info_debug_link(bin);
        if (!ret) {
                goto end;
        }

end:
        return ret;
}

BT_HIDDEN
void source_location_destroy(struct source_location *src_loc)
{
        if (!src_loc) {
                return;
        }

        free(src_loc->filename);
        g_free(src_loc);
}

/**
 * Append a string representation of an address offset to an existing
 * string.
 *
 * On success, the out parameter `result` will contain the base string
 * followed by the offset string of the form "+0x1234". On failure,
 * `result` remains unchanged.
 *
 * @param base_str      The string to which to append an offset string
 * @param low_addr      The lower virtual memory address, the base from
 *                      which the offset is computed
 * @param high_addr     The higher virtual memory address
 * @param result        Out parameter, the base string followed by the
 *                      offset string
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_append_offset_str(const char *base_str, uint64_t low_addr,
                                uint64_t high_addr, char **result)
{
        uint64_t offset;
        char *_result = NULL;

        if (!base_str || !result) {
                goto error;
        }

        offset = high_addr - low_addr;

        _result = g_strdup_printf("%s+%#0" PRIx64, base_str, offset);
        if (!_result) {
                goto error;
        }
        *result = _result;

        return 0;

error:
        free(_result);
        return -1;
}

/**
 * Try to find the symbol closest to an address within a given ELF
 * section.
 *
 * Only function symbols are taken into account. The symbol's address
 * must precede `addr`. A symbol with a closer address might exist
 * after `addr` but is irrelevant because it cannot encompass `addr`.
 *
 * On success, if found, the out parameters `sym` and `shdr` are
 * set. On failure or if none are found, they remain unchanged.
 *
 * @param scn           ELF section in which to look for the address
 * @param addr          Virtual memory address for which to find the
 *                      nearest function symbol
 * @param sym           Out parameter, the nearest function symbol
 * @param shdr          Out parameter, the section header for scn
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_get_nearest_symbol_from_section(Elf_Scn *scn, uint64_t addr,
                GElf_Sym **sym, GElf_Shdr **shdr)
{
        int i;
        size_t symbol_count;
        Elf_Data *data = NULL;
        GElf_Shdr *_shdr = NULL;
        GElf_Sym *nearest_sym = NULL;

        if (!scn || !sym || !shdr) {
                goto error;
        }

        _shdr = g_new0(GElf_Shdr, 1);
        if (!_shdr) {
                goto error;
        }

        _shdr = gelf_getshdr(scn, _shdr);
        if (!_shdr) {
                goto error;
        }

        if (_shdr->sh_type != SHT_SYMTAB) {
                /*
                 * We are only interested in symbol table (symtab)
                 * sections, skip this one.
                 */
                goto end;
        }

        data = elf_getdata(scn, NULL);
        if (!data) {
                goto error;
        }

        symbol_count = _shdr->sh_size / _shdr->sh_entsize;

        for (i = 0; i < symbol_count; ++i) {
                GElf_Sym *cur_sym = NULL;

                cur_sym = g_new0(GElf_Sym, 1);
                if (!cur_sym) {
                        goto error;
                }
                cur_sym = gelf_getsym(data, i, cur_sym);
                if (!cur_sym) {
                        goto error;
                }
                if (GELF_ST_TYPE(cur_sym->st_info) != STT_FUNC) {
                        /* We're only interested in the functions. */
                        g_free(cur_sym);
                        continue;
                }

                if (cur_sym->st_value <= addr &&
                                (!nearest_sym ||
                                cur_sym->st_value > nearest_sym->st_value)) {
                        g_free(nearest_sym);
                        nearest_sym = cur_sym;
                } else {
                        g_free(cur_sym);
                }
        }

end:
        if (nearest_sym) {
                *sym = nearest_sym;
                *shdr = _shdr;
        } else {
                g_free(_shdr);
        }

        return 0;

error:
        g_free(nearest_sym);
        g_free(_shdr);
        return -1;
}

/**
 * Get the name of the function containing a given address within an
 * executable using ELF symbols.
 *
 * The function name is in fact the name of the nearest ELF symbol,
 * followed by the offset in bytes between the address and the symbol
 * (in hex), separated by a '+' character.
 *
 * If found, the out parameter `func_name` is set on success. On failure,
 * it remains unchanged.
 *
 * @param bin           bin_info instance for the executable containing
 *                      the address
 * @param addr          Virtual memory address for which to find the
 *                      function name
 * @param func_name     Out parameter, the function name
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_elf_function_name(struct bin_info *bin, uint64_t addr,
                char **func_name)
{
        /*
         * TODO (possible optimisation): if an ELF has no symtab
         * section, it has been stripped. Therefore, it would be wise
         * to store a flag indicating the stripped status after the
         * first iteration to prevent subsequent ones.
         */
        int ret = 0;
        Elf_Scn *scn = NULL;
        GElf_Sym *sym = NULL;
        GElf_Shdr *shdr = NULL;
        char *sym_name = NULL;

        /* Set ELF file if it hasn't been accessed yet. */
        if (!bin->elf_file) {
                ret = bin_info_set_elf_file(bin);
                if (ret) {
                        /* Failed to set ELF file. */
                        goto error;
                }
        }

        scn = elf_nextscn(bin->elf_file, scn);
        if (!scn) {
                goto error;
        }

        while (scn && !sym) {
                ret = bin_info_get_nearest_symbol_from_section(
                                scn, addr, &sym, &shdr);
                if (ret) {
                        goto error;
                }

                scn = elf_nextscn(bin->elf_file, scn);
        }

        if (sym) {
                sym_name = elf_strptr(bin->elf_file, shdr->sh_link,
                                sym->st_name);
                if (!sym_name) {
                        goto error;
                }

                ret = bin_info_append_offset_str(sym_name, sym->st_value, addr,
                                                func_name);
                if (ret) {
                        goto error;
                }
        }

        g_free(shdr);
        g_free(sym);
        return 0;

error:
        g_free(shdr);
        g_free(sym);
        return ret;
}

/**
 * Get the name of the function containing a given address within a
 * given compile unit (CU).
 *
 * If found, the out parameter `func_name` is set on success. On
 * failure, it remains unchanged.
 *
 * @param cu            bt_dwarf_cu instance which may contain the address
 * @param addr          Virtual memory address for which to find the
 *                      function name
 * @param func_name     Out parameter, the function name
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_cu_function_name(struct bt_dwarf_cu *cu, uint64_t addr,
                char **func_name)
{
        int ret = 0;
        bool found = false;
        struct bt_dwarf_die *die = NULL;

        if (!cu || !func_name) {
                goto error;
        }

        die = bt_dwarf_die_create(cu);
        if (!die) {
                goto error;
        }

        while (bt_dwarf_die_next(die) == 0) {
                int tag;

                ret = bt_dwarf_die_get_tag(die, &tag);
                if (ret) {
                        goto error;
                }

                if (tag == DW_TAG_subprogram) {
                        ret = bt_dwarf_die_contains_addr(die, addr, &found);
                        if (ret) {
                                goto error;
                        }

                        if (found) {
                                break;
                        }
                }
        }

        if (found) {
                uint64_t low_addr = 0;
                char *die_name = NULL;

                ret = bt_dwarf_die_get_name(die, &die_name);
                if (ret) {
                        goto error;
                }

                ret = dwarf_lowpc(die->dwarf_die, &low_addr);
                if (ret) {
                        free(die_name);
                        goto error;
                }

                ret = bin_info_append_offset_str(die_name, low_addr, addr,
                                                func_name);
                free(die_name);
                if (ret) {
                        goto error;
                }
        }

        bt_dwarf_die_destroy(die);
        return 0;

error:
        bt_dwarf_die_destroy(die);
        return -1;
}

/**
 * Get the name of the function containing a given address within an
 * executable using DWARF debug info.
 *
 * If found, the out parameter `func_name` is set on success. On
 * failure, it remains unchanged.
 *
 * @param bin           bin_info instance for the executable containing
 *                      the address
 * @param addr          Virtual memory address for which to find the
 *                      function name
 * @param func_name     Out parameter, the function name
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_dwarf_function_name(struct bin_info *bin, uint64_t addr,
                char **func_name)
{
        int ret = 0;
        char *_func_name = NULL;
        struct bt_dwarf_cu *cu = NULL;

        if (!bin || !func_name) {
                goto error;
        }

        cu = bt_dwarf_cu_create(bin->dwarf_info);
        if (!cu) {
                goto error;
        }

        while (bt_dwarf_cu_next(cu) == 0) {
                ret = bin_info_lookup_cu_function_name(cu, addr, &_func_name);
                if (ret) {
                        goto error;
                }

                if (_func_name) {
                        break;
                }
        }

        if (_func_name) {
                *func_name = _func_name;
        } else {
                goto error;
        }

        bt_dwarf_cu_destroy(cu);
        return 0;

error:
        bt_dwarf_cu_destroy(cu);
        return -1;
}

BT_HIDDEN
int bin_info_lookup_function_name(struct bin_info *bin,
                uint64_t addr, char **func_name)
{
        int ret = 0;
        char *_func_name = NULL;

        if (!bin || !func_name) {
                goto error;
        }

        /*
         * If the bin_info has a build id but it does not match the build id
         * that was found on the file system, return an error.
         */
        if (bin->build_id && !bin->file_build_id_matches) {
                goto error;
        }

        /* Set DWARF info if it hasn't been accessed yet. */
        if (!bin->dwarf_info && !bin->is_elf_only) {
                ret = bin_info_set_dwarf_info(bin);
                if (ret) {
                        BT_COMP_LOGI_STR("Failed to set bin dwarf info, falling "
                                        "back to ELF lookup.");
                        /* Failed to set DWARF info, fallback to ELF. */
                        bin->is_elf_only = true;
                }
        }

        if (!bin_info_has_address(bin, addr)) {
                goto error;
        }

        /*
         * Addresses in ELF and DWARF are relative to base address for
         * PIC, so make the address argument relative too if needed.
         */
        if (bin->is_pic) {
                addr -= bin->low_addr;
        }

        if (bin->is_elf_only) {
                ret = bin_info_lookup_elf_function_name(bin, addr,
                                &_func_name);
                if (ret) {
                        BT_COMP_LOGI("Failed to lookup function name (ELF): "
                                "ret=%d", ret);
                }
        } else {
                ret = bin_info_lookup_dwarf_function_name(bin, addr,
                                &_func_name);
                if (ret) {
                        BT_COMP_LOGI("Failed to lookup function name (DWARF): "
                                "ret=%d", ret);
                }
        }

        *func_name = _func_name;
        return 0;

error:
        return -1;
}

BT_HIDDEN
int bin_info_get_bin_loc(struct bin_info *bin, uint64_t addr, char **bin_loc)
{
        gchar *_bin_loc = NULL;

        if (!bin || !bin_loc) {
                goto error;
        }

        /*
         * If the bin_info has a build id but it does not match the build id
         * that was found on the file system, return an error.
         */
        if (bin->build_id && !bin->file_build_id_matches) {
                goto error;
        }

        if (bin->is_pic) {
                addr -= bin->low_addr;
                _bin_loc = g_strdup_printf("+%#0" PRIx64, addr);
        } else {
                _bin_loc = g_strdup_printf("@%#0" PRIx64, addr);
        }

        if (!_bin_loc) {
                goto error;
        }

        *bin_loc = _bin_loc;
        return 0;

error:
        return -1;
}

/**
 * Predicate used to determine whether the children of a given DIE
 * contain a specific address.
 *
 * More specifically, the parameter `die` is expected to be a
 * subprogram (function) DIE, and this predicate tells whether any
 * subroutines are inlined within this function and would contain
 * `addr`.
 *
 * On success, the out parameter `contains` is set with the boolean
 * value indicating whether the DIE's range covers `addr`. On failure,
 * it remains unchanged.
 *
 * Do note that this function advances the position of `die`. If the
 * address is found within one of its children, `die` will be pointing
 * to that child upon returning from the function, allowing to extract
 * the information deemed necessary.
 *
 * @param die           The parent DIE in whose children the address will be
 *                      looked for
 * @param addr          The address for which to look for in the DIEs
 * @param contains      Out parameter, true if addr is contained,
 *                      false if not
 * @returns             Returns 0 on success, -1 on failure
 */
static
int bin_info_child_die_has_address(struct bt_dwarf_die *die, uint64_t addr, bool *contains)
{
        int ret = 0;
        bool _contains = false;

        if (!die) {
                goto error;
        }

        ret = bt_dwarf_die_child(die);
        if (ret) {
                goto error;
        }

        do {
                ret = bt_dwarf_die_contains_addr(die, addr, &_contains);
                if (ret) {
                        goto error;
                }

                if (_contains) {
                        /*
                         * The address is within the range of the current DIE
                         * or its children.
                         */
                        int tag;

                        ret = bt_dwarf_die_get_tag(die, &tag);
                        if (ret) {
                                goto error;
                        }

                        if (tag == DW_TAG_inlined_subroutine) {
                                /* Found the tracepoint. */
                                goto end;
                        }

                        if (bt_dwarf_die_has_children(die)) {
                                /*
                                 * Look for the address in the children DIEs.
                                 */
                                ret = bt_dwarf_die_child(die);
                                if (ret) {
                                        goto error;
                                }
                        }
                }
        } while (bt_dwarf_die_next(die) == 0);

end:
        *contains = _contains;
        return 0;

error:
        return -1;
}

/**
 * Lookup the source location for a given address within a CU, making
 * the assumption that it is contained within an inline routine in a
 * function.
 *
 * @param cu            bt_dwarf_cu instance in which to look for the address
 * @param addr          The address for which to look for
 * @param src_loc       Out parameter, the source location (filename and
 *                      line number) for the address
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_cu_src_loc_inl(struct bt_dwarf_cu *cu, uint64_t addr,
                struct source_location **src_loc)
{
        int ret = 0;
        bool found = false;
        struct bt_dwarf_die *die = NULL;
        struct source_location *_src_loc = NULL;

        if (!cu || !src_loc) {
                goto error;
        }

        die = bt_dwarf_die_create(cu);
        if (!die) {
                goto error;
        }

        while (bt_dwarf_die_next(die) == 0) {
                int tag;

                ret = bt_dwarf_die_get_tag(die, &tag);
                if (ret) {
                        goto error;
                }

                if (tag == DW_TAG_subprogram) {
                        bool contains = false;

                        ret = bt_dwarf_die_contains_addr(die, addr, &contains);
                        if (ret) {
                                goto error;
                        }

                        if (contains) {
                                /*
                                 * Try to find an inlined subroutine
                                 * child of this DIE containing addr.
                                 */
                                ret = bin_info_child_die_has_address(die, addr,
                                                &found);
                                if(ret) {
                                        goto error;
                                }

                                goto end;
                        }
                }
        }

end:
        if (found) {
                char *filename = NULL;
                uint64_t line_no;

                _src_loc = g_new0(struct source_location, 1);
                if (!_src_loc) {
                        goto error;
                }

                ret = bt_dwarf_die_get_call_file(die, &filename);
                if (ret) {
                        goto error;
                }
                ret = bt_dwarf_die_get_call_line(die, &line_no);
                if (ret) {
                        free(filename);
                        goto error;
                }

                _src_loc->filename = filename;
                _src_loc->line_no = line_no;
                *src_loc = _src_loc;
        }

        bt_dwarf_die_destroy(die);
        return 0;

error:
        source_location_destroy(_src_loc);
        bt_dwarf_die_destroy(die);
        return -1;
}

/**
 * Lookup the source location for a given address within a CU,
 * assuming that it is contained within an inlined function.
 *
 * A source location can be found regardless of inlining status for
 * this method, but in the case of an inlined function, the returned
 * source location will point not to the callsite but rather to the
 * definition site of the inline function.
 *
 * @param cu            bt_dwarf_cu instance in which to look for the address
 * @param addr          The address for which to look for
 * @param src_loc       Out parameter, the source location (filename and
 *                      line number) for the address. Set only if the address
 *                      is found and resolved successfully
 *
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_cu_src_loc_no_inl(struct bt_dwarf_cu *cu, uint64_t addr,
                struct source_location **src_loc)
{
        struct source_location *_src_loc = NULL;
        struct bt_dwarf_die *die = NULL;
        const char *filename = NULL;
        Dwarf_Line *line = NULL;
        Dwarf_Addr line_addr;
        int ret = 0, line_no;

        if (!cu || !src_loc) {
                goto error;
        }

        die = bt_dwarf_die_create(cu);
        if (!die) {
                goto error;
        }

        line = dwarf_getsrc_die(die->dwarf_die, addr);
        if (!line) {
                /* This is not an error. The caller needs to keep looking. */
                goto end;
        }

        ret = dwarf_lineaddr(line, &line_addr);
        if (ret) {
                goto error;
        }

        filename = dwarf_linesrc(line, NULL, NULL);
        if (!filename) {
                goto error;
        }

        if (addr == line_addr) {
                _src_loc = g_new0(struct source_location, 1);
                if (!_src_loc) {
                        goto error;
                }

                ret = dwarf_lineno(line, &line_no);
                if (ret) {
                        goto error;
                }

                _src_loc->line_no = line_no;
                _src_loc->filename = g_strdup(filename);
        }

        if (_src_loc) {
                *src_loc = _src_loc;
        }

        goto end;

error:
        source_location_destroy(_src_loc);
        ret = -1;
end:
        bt_dwarf_die_destroy(die);
        return ret;
}

/**
 * Get the source location (file name and line number) for a given
 * address within a compile unit (CU).
 *
 * On success, the out parameter `src_loc` is set if found. On
 * failure, it remains unchanged.
 *
 * @param cu            bt_dwarf_cu instance for the compile unit which
 *                      may contain the address
 * @param addr          Virtual memory address for which to find the
 *                      source location
 * @param src_loc       Out parameter, the source location
 * @returns             0 on success, -1 on failure
 */
static
int bin_info_lookup_cu_src_loc(struct bt_dwarf_cu *cu, uint64_t addr,
                struct source_location **src_loc)
{
        int ret = 0;
        struct source_location *_src_loc = NULL;

        if (!cu || !src_loc) {
                goto error;
        }

        ret = bin_info_lookup_cu_src_loc_inl(cu, addr, &_src_loc);
        if (ret) {
                goto error;
        }

        if (_src_loc) {
                goto end;
        }

        ret = bin_info_lookup_cu_src_loc_no_inl(cu, addr, &_src_loc);
        if (ret) {
                goto error;
        }

        if (_src_loc) {
                goto end;
        }

end:
        if (_src_loc) {
                *src_loc = _src_loc;
        }

        return 0;

error:
        source_location_destroy(_src_loc);
        return -1;
}

BT_HIDDEN
int bin_info_lookup_source_location(struct bin_info *bin, uint64_t addr,
                struct source_location **src_loc)
{
        struct bt_dwarf_cu *cu = NULL;
        struct source_location *_src_loc = NULL;

        if (!bin || !src_loc) {
                goto error;
        }

        /*
         * If the bin_info has a build id but it does not match the build id
         * that was found on the file system, return an error.
         */
        if (bin->build_id && !bin->file_build_id_matches) {
                goto error;
        }

        /* Set DWARF info if it hasn't been accessed yet. */
        if (!bin->dwarf_info && !bin->is_elf_only) {
                if (bin_info_set_dwarf_info(bin)) {
                        /* Failed to set DWARF info. */
                        bin->is_elf_only = true;
                }
        }

        if (bin->is_elf_only) {
                /* We cannot lookup source location without DWARF info. */
                goto error;
        }

        if (!bin_info_has_address(bin, addr)) {
                goto error;
        }

        /*
         * Addresses in ELF and DWARF are relative to base address for
         * PIC, so make the address argument relative too if needed.
         */
        if (bin->is_pic) {
                addr -= bin->low_addr;
        }

        cu = bt_dwarf_cu_create(bin->dwarf_info);
        if (!cu) {
                goto error;
        }

        while (bt_dwarf_cu_next(cu) == 0) {
                int ret;

                ret = bin_info_lookup_cu_src_loc(cu, addr, &_src_loc);
                if (ret) {
                        goto error;
                }

                if (_src_loc) {
                        break;
                }
        }

        bt_dwarf_cu_destroy(cu);
        if (_src_loc) {
                *src_loc = _src_loc;
        }

        return 0;

error:
        source_location_destroy(_src_loc);
        bt_dwarf_cu_destroy(cu);
        return -1;
}