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drgn/libdrgn/debug_info.c
Omar Sandoval 2d8aeacb30 Allow naming and configuring order of object finders 
This one doesn't need any changes to the callback signature, just the
new interface. We also keep add_object_finder() for compatibility.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2024-06-05 13:40:26 -07:00

2452 lines
68 KiB
C
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// Copyright (c) Meta Platforms, Inc. and affiliates.
// SPDX-License-Identifier: LGPL-2.1-or-later
#include <assert.h>
#include <byteswap.h>
#include <elf.h>
#include <elfutils/libdw.h>
#include <elfutils/libdwelf.h>
#include <elfutils/version.h>
#include <errno.h>
#include <fcntl.h>
#include <gelf.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "binary_buffer.h"
#include "cleanup.h"
#include "debug_info.h"
#include "elf_file.h"
#include "error.h"
#include "linux_kernel.h"
#include "openmp.h"
#include "platform.h"
#include "program.h"
#include "util.h"
static inline Dwarf *drgn_elf_file_dwarf_key(struct drgn_elf_file * const *entry)
{
return (*entry)->dwarf;
}
DEFINE_HASH_TABLE_FUNCTIONS(drgn_elf_file_dwarf_table, drgn_elf_file_dwarf_key,
ptr_key_hash_pair, scalar_key_eq);
DEFINE_VECTOR_FUNCTIONS(drgn_module_vector);
struct drgn_module_key {
const void *build_id;
size_t build_id_len;
uint64_t start, end;
};
static inline struct drgn_module_key
drgn_module_key(struct drgn_module * const *entry)
{
return (struct drgn_module_key){
.build_id = (*entry)->build_id,
.build_id_len = (*entry)->build_id_len,
.start = (*entry)->start,
.end = (*entry)->end,
};
}
static inline struct hash_pair
drgn_module_key_hash_pair(const struct drgn_module_key *key)
{
size_t hash = hash_bytes(key->build_id, key->build_id_len);
hash = hash_combine(hash, key->start);
hash = hash_combine(hash, key->end);
return hash_pair_from_avalanching_hash(hash);
}
static inline bool drgn_module_key_eq(const struct drgn_module_key *a,
const struct drgn_module_key *b)
{
return (a->build_id_len == b->build_id_len &&
memcmp(a->build_id, b->build_id, a->build_id_len) == 0 &&
a->start == b->start && a->end == b->end);
}
DEFINE_HASH_TABLE_FUNCTIONS(drgn_module_table, drgn_module_key,
drgn_module_key_hash_pair, drgn_module_key_eq);
DEFINE_HASH_SET_FUNCTIONS(c_string_set, c_string_key_hash_pair,
c_string_key_eq);
/**
* @c Dwfl_Callbacks::find_elf() implementation.
*
* If the ELF file was reported directly, this returns it. Otherwise, it falls
* back to an appropriate callback.
*
* Ideally we'd use @c dwfl_report_elf() instead, but that doesn't take an @c
* Elf handle, which we need for a couple of reasons:
*
* - We usually already have the @c Elf handle open in order to identify the
* file.
* - For kernel modules, we set the section addresses in the @c Elf handle
* ourselves instead of using @c Dwfl_Callbacks::section_address().
*
* Additionally, there's a special case for vmlinux. It is usually an @c ET_EXEC
* ELF file, but when KASLR is enabled, it needs to be handled like an @c ET_DYN
* file. libdwfl has a hack for this when @c dwfl_report_module() is used, but
* @ref dwfl_report_elf() bypasses this hack.
*
* So, we're stuck using @c dwfl_report_module() and this dummy callback.
*/
static int drgn_dwfl_find_elf(Dwfl_Module *dwfl_module, void **userdatap,
const char *name, Dwarf_Addr base,
char **file_name, Elf **elfp)
{
struct drgn_module *module = *userdatap;
if (module->elf) {
*file_name = module->path;
int fd = module->fd;
*elfp = module->elf;
// libdwfl consumes the returned path, file descriptor, and ELF
// handle, so clear the fields.
module->path = NULL;
module->fd = -1;
module->elf = NULL;
return fd;
}
if (module->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
*elfp = NULL;
return -1;
} else if (module->prog->flags & DRGN_PROGRAM_IS_LIVE) {
return dwfl_linux_proc_find_elf(dwfl_module, userdatap, name,
base, file_name, elfp);
} else {
return dwfl_build_id_find_elf(dwfl_module, userdatap, name,
base, file_name, elfp);
}
}
/**
* @c Dwfl_Callbacks::section_address() implementation.
*
* We set the section header @c sh_addr in memory instead of using this, but
* libdwfl requires the callback pointer to be non-@c NULL. It will be called
* for any sections that still have a zero @c sh_addr, meaning they are not
* present in memory.
*/
static int drgn_dwfl_section_address(Dwfl_Module *module, void **userdatap,
const char *name, Dwarf_Addr base,
const char *secname, Elf32_Word shndx,
const GElf_Shdr *shdr, Dwarf_Addr *addr)
{
*addr = -1;
return DWARF_CB_OK;
}
static const Dwfl_Callbacks drgn_dwfl_callbacks = {
.find_elf = drgn_dwfl_find_elf,
.find_debuginfo = dwfl_standard_find_debuginfo,
.section_address = drgn_dwfl_section_address,
};
static void drgn_module_destroy(struct drgn_module *module)
{
if (module) {
drgn_error_destroy(module->err);
drgn_module_orc_info_deinit(module);
drgn_module_dwarf_info_deinit(module);
elf_end(module->elf);
if (module->fd != -1)
close(module->fd);
free(module->path);
for (struct drgn_elf_file_dwarf_table_iterator it =
drgn_elf_file_dwarf_table_first(&module->split_dwarf_files);
it.entry;
it = drgn_elf_file_dwarf_table_next(it))
drgn_elf_file_destroy(*it.entry);
drgn_elf_file_dwarf_table_deinit(&module->split_dwarf_files);
if (module->debug_file != module->loaded_file)
drgn_elf_file_destroy(module->debug_file);
drgn_elf_file_destroy(module->loaded_file);
free(module->name);
free(module);
}
}
static void drgn_module_finish_indexing(struct drgn_debug_info *dbinfo,
struct drgn_module *module)
{
module->state = DRGN_DEBUG_INFO_MODULE_INDEXED;
if (module->name) {
int ret = c_string_set_insert(&dbinfo->module_names,
(const char **)&module->name,
NULL);
/* drgn_debug_info_update_index() should've reserved enough. */
assert(ret != -1);
}
}
/*
* Wrapper around dwfl_report_end() that works around a libdwfl bug which causes
* it to close stdin when it frees some modules that were reported by
* dwfl_core_file_report(). This was fixed in elfutils 0.177 by commit
* d37f6ea7e3e5 ("libdwfl: Fix fd leak/closing wrong fd after
* dwfl_core_file_report()"), but we support older versions.
*/
static int my_dwfl_report_end(struct drgn_debug_info *dbinfo,
int (*removed)(Dwfl_Module *, void *,
const char *, Dwarf_Addr, void *),
void *arg)
{
int fd = -1;
if ((dbinfo->prog->flags
& (DRGN_PROGRAM_IS_LINUX_KERNEL | DRGN_PROGRAM_IS_LIVE)) == 0)
fd = dup(0);
int ret = dwfl_report_end(dbinfo->dwfl, removed, arg);
if (fd != -1) {
dup2(fd, 0);
close(fd);
}
return ret;
}
struct drgn_dwfl_module_removed_arg {
struct drgn_debug_info *dbinfo;
bool finish_indexing;
bool free_all;
};
static int drgn_dwfl_module_removed(Dwfl_Module *dwfl_module, void *userdatap,
const char *name, Dwarf_Addr base,
void *_arg)
{
struct drgn_dwfl_module_removed_arg *arg = _arg;
/*
* userdatap is actually a void ** like for the other libdwfl callbacks,
* but dwfl_report_end() has the wrong signature for the removed
* callback.
*/
struct drgn_module *module = *(void **)userdatap;
if (arg->finish_indexing && module &&
module->state == DRGN_DEBUG_INFO_MODULE_INDEXING)
drgn_module_finish_indexing(arg->dbinfo, module);
if (arg->free_all || !module ||
module->state != DRGN_DEBUG_INFO_MODULE_INDEXED) {
drgn_module_destroy(module);
} else {
/*
* The module was already indexed. Report it again so libdwfl
* doesn't remove it.
*/
Dwarf_Addr end;
dwfl_module_info(dwfl_module, NULL, NULL, &end, NULL, NULL,
NULL, NULL);
dwfl_report_module(arg->dbinfo->dwfl, name, base, end);
}
return DWARF_CB_OK;
}
static void drgn_debug_info_free_modules(struct drgn_debug_info *dbinfo,
bool finish_indexing, bool free_all)
{
for (struct drgn_module_table_iterator it =
drgn_module_table_first(&dbinfo->modules); it.entry; ) {
struct drgn_module *module = *it.entry;
struct drgn_module **nextp = it.entry;
do {
struct drgn_module *next = module->next;
if (finish_indexing &&
module->state == DRGN_DEBUG_INFO_MODULE_INDEXING)
drgn_module_finish_indexing(dbinfo, module);
if (free_all ||
module->state != DRGN_DEBUG_INFO_MODULE_INDEXED) {
if (module == *nextp) {
if (nextp == it.entry && !next) {
it = drgn_module_table_delete_iterator(&dbinfo->modules,
it);
} else {
if (!next)
it = drgn_module_table_next(it);
*nextp = next;
}
}
void **userdatap;
dwfl_module_info(module->dwfl_module,
&userdatap, NULL, NULL, NULL,
NULL, NULL, NULL);
*userdatap = NULL;
drgn_module_destroy(module);
} else {
if (!next)
it = drgn_module_table_next(it);
nextp = &module->next;
}
module = next;
} while (module);
}
dwfl_report_begin(dbinfo->dwfl);
struct drgn_dwfl_module_removed_arg arg = {
.dbinfo = dbinfo,
.finish_indexing = finish_indexing,
.free_all = free_all,
};
my_dwfl_report_end(dbinfo, drgn_dwfl_module_removed, &arg);
}
struct drgn_error *
drgn_debug_info_report_error(struct drgn_debug_info_load_state *load,
const char *name, const char *message,
struct drgn_error *err)
{
if (err && err->code == DRGN_ERROR_NO_MEMORY) {
/* Always fail hard if we're out of memory. */
goto err;
}
if (load->num_errors == 0 &&
!string_builder_append(&load->errors,
"missing some debugging symbols (see https://drgn.readthedocs.io/en/latest/getting_debugging_symbols.html):"))
goto err;
if (load->num_errors < load->max_errors) {
if (!string_builder_line_break(&load->errors))
goto err;
if (!string_builder_append(&load->errors, " "))
goto err;
if (name && !string_builder_append(&load->errors, name))
goto err;
if (name && (message || err) &&
!string_builder_append(&load->errors, " ("))
goto err;
if (message && !string_builder_append(&load->errors, message))
goto err;
if (message && err &&
!string_builder_append(&load->errors, ": "))
goto err;
if (err && !string_builder_append_error(&load->errors, err))
goto err;
if (name && (message || err) &&
!string_builder_appendc(&load->errors, ')'))
goto err;
}
load->num_errors++;
drgn_error_destroy(err);
return NULL;
err:
drgn_error_destroy(err);
return &drgn_enomem;
}
static struct drgn_error *
drgn_debug_info_report_module(struct drgn_debug_info_load_state *load,
const void *build_id, size_t build_id_len,
uint64_t start, uint64_t end, const char *name,
Dwfl_Module *dwfl_module, const char *path,
int fd, Elf *elf, bool *new_ret)
{
struct drgn_debug_info *dbinfo = load->dbinfo;
struct drgn_error *err;
char *path_key = NULL;
if (new_ret)
*new_ret = false;
struct hash_pair hp;
// Silence -Wmaybe-uninitialized false positive last seen with GCC 12 on
// i386 and Arm.
struct drgn_module_table_iterator it = {};
if (build_id_len) {
struct drgn_module_key key = {
.build_id = build_id,
.build_id_len = build_id_len,
.start = start,
.end = end,
};
hp = drgn_module_table_hash(&key);
it = drgn_module_table_search_hashed(&dbinfo->modules, &key,
hp);
if (it.entry &&
(*it.entry)->state == DRGN_DEBUG_INFO_MODULE_INDEXED) {
/* We've already indexed this module. */
err = NULL;
goto free;
}
}
if (!dwfl_module) {
path_key = realpath(path, NULL);
if (!path_key) {
path_key = strdup(path);
if (!path_key) {
err = &drgn_enomem;
goto free;
}
}
dwfl_module = dwfl_report_module(dbinfo->dwfl, path_key, start,
end);
if (!dwfl_module) {
err = drgn_error_libdwfl();
goto free;
}
}
void **userdatap;
dwfl_module_info(dwfl_module, &userdatap, NULL, NULL, NULL, NULL, NULL,
NULL);
if (*userdatap) {
/* We've already reported this file at this offset. */
err = NULL;
goto free;
}
if (new_ret)
*new_ret = true;
struct drgn_module *module = calloc(1, sizeof(*module));
if (!module) {
err = &drgn_enomem;
goto free;
}
module->prog = load->dbinfo->prog;
module->state = DRGN_DEBUG_INFO_MODULE_NEW;
module->build_id = build_id;
module->build_id_len = build_id_len;
module->start = start;
module->end = end;
if (name) {
module->name = strdup(name);
if (!module->name) {
err = &drgn_enomem;
free(module);
goto free;
}
}
module->dwfl_module = dwfl_module;
module->path = path_key;
module->fd = fd;
module->elf = elf;
drgn_elf_file_dwarf_table_init(&module->split_dwarf_files);
/* path_key, fd and elf are owned by the module now. */
if (!drgn_module_vector_append(&load->new_modules, &module)) {
drgn_module_destroy(module);
return &drgn_enomem;
}
if (build_id_len) {
if (it.entry) {
/*
* The first module with this build ID is in
* new_modules, so insert it after in the list, not
* before.
*/
module->next = (*it.entry)->next;
(*it.entry)->next = module;
} else if (drgn_module_table_insert_searched(&dbinfo->modules,
&module, hp,
NULL) < 0) {
drgn_module_vector_pop(&load->new_modules);
drgn_module_destroy(module);
return &drgn_enomem;
}
}
*userdatap = module;
return NULL;
free:
elf_end(elf);
if (fd != -1)
close(fd);
free(path_key);
return err;
}
struct drgn_error *
drgn_debug_info_report_elf(struct drgn_debug_info_load_state *load,
const char *path, int fd, Elf *elf, uint64_t start,
uint64_t end, const char *name, bool *new_ret)
{
struct drgn_error *err;
const void *build_id;
ssize_t build_id_len = dwelf_elf_gnu_build_id(elf, &build_id);
if (build_id_len < 0) {
err = drgn_debug_info_report_error(load, path, NULL,
drgn_error_libelf());
elf_end(elf);
close(fd);
return err;
} else if (build_id_len == 0) {
build_id = NULL;
}
return drgn_debug_info_report_module(load, build_id, build_id_len,
start, end, name, NULL, path, fd,
elf, new_ret);
}
static int drgn_debug_info_report_dwfl_module(Dwfl_Module *dwfl_module,
void **userdatap,
const char *name, Dwarf_Addr base,
void *arg)
{
struct drgn_debug_info_load_state *load = arg;
struct drgn_error *err;
if (*userdatap) {
/*
* This was either reported from drgn_debug_info_report_elf() or
* already indexed.
*/
return DWARF_CB_OK;
}
const unsigned char *build_id;
GElf_Addr build_id_vaddr;
int build_id_len = dwfl_module_build_id(dwfl_module, &build_id,
&build_id_vaddr);
if (build_id_len < 0) {
err = drgn_debug_info_report_error(load, name, NULL,
drgn_error_libdwfl());
if (err)
goto err;
} else if (build_id_len == 0) {
build_id = NULL;
}
Dwarf_Addr end;
dwfl_module_info(dwfl_module, NULL, NULL, &end, NULL, NULL, NULL, NULL);
err = drgn_debug_info_report_module(load, build_id, build_id_len, base,
end, NULL, dwfl_module, name, -1,
NULL, NULL);
if (err)
goto err;
return DWARF_CB_OK;
err:
drgn_error_destroy(err);
return DWARF_CB_ABORT;
}
static struct drgn_error *drgn_get_nt_file(Elf *elf, const char **ret,
size_t *len_ret)
{
size_t phnum;
if (elf_getphdrnum(elf, &phnum) != 0)
return drgn_error_libelf();
for (size_t i = 0; i < phnum; i++) {
GElf_Phdr phdr_mem, *phdr = gelf_getphdr(elf, i, &phdr_mem);
if (!phdr)
return drgn_error_libelf();
if (phdr->p_type == PT_NOTE) {
Elf_Data *data = elf_getdata_rawchunk(elf,
phdr->p_offset,
phdr->p_filesz,
note_header_type(phdr->p_align));
if (!data)
return drgn_error_libelf();
GElf_Nhdr nhdr;
size_t offset = 0, name_offset, desc_offset;
while (offset < data->d_size &&
(offset = gelf_getnote(data, offset, &nhdr,
&name_offset,
&desc_offset))) {
const char *name =
(char *)data->d_buf + name_offset;
if (nhdr.n_namesz == sizeof("CORE") &&
memcmp(name, "CORE", sizeof("CORE")) == 0 &&
nhdr.n_type == NT_FILE) {
*ret = (char *)data->d_buf + desc_offset;
*len_ret = nhdr.n_descsz;
return NULL;
}
}
}
}
*ret = NULL;
*len_ret = 0;
return NULL;
}
struct drgn_mapped_file_segment {
uint64_t start;
uint64_t end;
uint64_t file_offset;
};
DEFINE_VECTOR(drgn_mapped_file_segment_vector, struct drgn_mapped_file_segment);
DEFINE_HASH_MAP(drgn_mapped_files, const char *,
struct drgn_mapped_file_segment_vector, c_string_key_hash_pair,
c_string_key_eq);
struct userspace_core_report_state {
struct drgn_mapped_files files;
void *phdr_buf;
size_t phdr_buf_capacity;
void *segment_buf;
size_t segment_buf_capacity;
};
static struct drgn_error *parse_nt_file_error(struct binary_buffer *bb,
const char *pos,
const char *message)
{
return drgn_error_create(DRGN_ERROR_OTHER, "couldn't parse NT_FILE");
}
static bool
drgn_mapped_file_segments_contiguous(const struct drgn_mapped_file_segment *segment1,
const struct drgn_mapped_file_segment *segment2)
{
if (segment1->end != segment2->start)
return false;
uint64_t size = segment1->end - segment1->start;
return segment1->file_offset + size == segment2->file_offset;
}
static struct drgn_error *
userspace_core_get_mapped_files(struct drgn_debug_info_load_state *load,
struct userspace_core_report_state *core,
const char *nt_file, size_t nt_file_len)
{
struct drgn_error *err;
GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr(load->dbinfo->prog->core,
&ehdr_mem);
if (!ehdr)
return drgn_error_libelf();
bool is_64_bit = ehdr->e_ident[EI_CLASS] == ELFCLASS64;
bool little_endian = ehdr->e_ident[EI_DATA] == ELFDATA2LSB;
struct binary_buffer bb;
binary_buffer_init(&bb, nt_file, nt_file_len, little_endian,
parse_nt_file_error);
/*
* fs/binfmt_elf.c in the Linux kernel source code documents the format
* of NT_FILE as:
*
* long count -- how many files are mapped
* long page_size -- units for file_ofs
* array of [COUNT] elements of
* long start
* long end
* long file_ofs
* followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL...
*/
uint64_t count, page_size;
if (is_64_bit) {
if ((err = binary_buffer_next_u64(&bb, &count)))
return err;
if (count > UINT64_MAX / 24)
return binary_buffer_error(&bb, "count is too large");
if ((err = binary_buffer_next_u64(&bb, &page_size)) ||
(err = binary_buffer_skip(&bb, count * 24)))
return err;
} else {
if ((err = binary_buffer_next_u32_into_u64(&bb, &count)))
return err;
if (count > UINT64_MAX / 12)
return binary_buffer_error(&bb, "count is too large");
if ((err = binary_buffer_next_u32_into_u64(&bb, &page_size)) ||
(err = binary_buffer_skip(&bb, count * 12)))
return err;
}
for (uint64_t i = 0; i < count; i++) {
struct drgn_mapped_file_segment segment;
if (is_64_bit) {
memcpy(&segment, nt_file + 16 + i * 24, 24);
if (bb.bswap) {
segment.start = bswap_64(segment.start);
segment.end = bswap_64(segment.end);
segment.file_offset = bswap_64(segment.file_offset);
}
} else {
struct {
uint32_t start;
uint32_t end;
uint32_t file_offset;
} segment32;
memcpy(&segment32, nt_file + 8 + i * 12, 12);
if (bb.bswap) {
segment.start = bswap_32(segment32.start);
segment.end = bswap_32(segment32.end);
segment.file_offset = bswap_32(segment32.file_offset);
} else {
segment.start = segment32.start;
segment.end = segment32.end;
segment.file_offset = segment32.file_offset;
}
}
segment.file_offset *= page_size;
struct drgn_mapped_files_entry entry = {
.key = bb.pos,
};
if ((err = binary_buffer_skip_string(&bb)))
return err;
struct drgn_mapped_files_iterator it;
int r = drgn_mapped_files_insert(&core->files, &entry, &it);
if (r < 0)
return &drgn_enomem;
if (r == 1)
drgn_mapped_file_segment_vector_init(&it.entry->value);
/*
* The Linux kernel creates separate entries for contiguous
* mappings with different memory protections even though the
* protection is not included in NT_FILE. Merge them if we can.
*/
if (!drgn_mapped_file_segment_vector_empty(&it.entry->value)
&& drgn_mapped_file_segments_contiguous(drgn_mapped_file_segment_vector_last(&it.entry->value),
&segment))
drgn_mapped_file_segment_vector_last(&it.entry->value)->end = segment.end;
else if (!drgn_mapped_file_segment_vector_append(&it.entry->value,
&segment))
return &drgn_enomem;
}
return NULL;
}
static bool build_id_matches(Elf *elf, const void *build_id,
size_t build_id_len)
{
const void *elf_build_id;
ssize_t elf_build_id_len = dwelf_elf_gnu_build_id(elf, &elf_build_id);
if (elf_build_id_len < 0)
return false;
return (elf_build_id_len == build_id_len &&
memcmp(elf_build_id, build_id, build_id_len) == 0);
}
static struct drgn_error *
userspace_core_elf_address_range(uint16_t e_type, size_t phnum,
struct drgn_error *(*get_phdr)(void *, size_t, GElf_Phdr *),
void *arg,
const struct drgn_mapped_file_segment *segments,
size_t num_segments,
const struct drgn_mapped_file_segment *ehdr_segment,
uint64_t *bias_ret, uint64_t *start_ret,
uint64_t *end_ret)
{
struct drgn_error *err;
/*
* First, find the virtual address of the ELF header so that we can
* calculate the bias.
*/
uint64_t ehdr_vaddr;
size_t i;
for (i = 0; i < phnum; i++) {
GElf_Phdr phdr;
err = get_phdr(arg, i, &phdr);
if (err)
return err;
if (phdr.p_type == PT_LOAD) {
uint64_t align = phdr.p_align ? phdr.p_align : 1;
if ((phdr.p_offset & -align) == 0) {
ehdr_vaddr = phdr.p_vaddr & -align;
break;
}
}
}
if (i >= phnum) {
/*
* No loadable segments contain the ELF header. This can't be
* our file.
*/
*bias_ret = 0;
not_loaded:
*start_ret = *end_ret = 0;
return NULL;
}
*bias_ret = ehdr_segment->start - ehdr_vaddr;
if (*bias_ret != 0 && e_type == ET_EXEC) {
/* The executable is not loaded at the correct address. */
goto not_loaded;
}
/*
* Now check all of the program headers to (1) get the module address
* range and (2) make sure that they are mapped as expected. If we're
* lucky, this can detect a file that was mmap'd and not actually loaded
* by the kernel or dynamic loader. This could also be the wrong file.
*/
const struct drgn_mapped_file_segment *segment = segments;
const struct drgn_mapped_file_segment *end_segment =
segments + num_segments;
uint64_t start = 0, end = 0;
bool first = true;
for (i = 0; i < phnum; i++) {
GElf_Phdr phdr;
err = get_phdr(arg, i, &phdr);
if (err)
return err;
if (phdr.p_type != PT_LOAD)
continue;
uint64_t vaddr = phdr.p_vaddr + *bias_ret;
if (phdr.p_filesz != 0) {
/*
* Advance to the mapped segment containing the start
* address.
*/
while (vaddr >= segment->end) {
if (++segment == end_segment)
goto not_loaded;
if (vaddr < segment->start)
goto not_loaded;
}
if (segment->file_offset + (vaddr - segment->start) !=
phdr.p_offset) {
/*
* The address in the core dump does not map to
* the segment's file offset.
*/
goto not_loaded;
}
if (phdr.p_filesz > segment->end - vaddr) {
/* Part of the segment is not mapped. */
goto not_loaded;
}
}
if (first) {
uint64_t align = phdr.p_align ? phdr.p_align : 1;
start = vaddr & -align;
first = false;
}
end = vaddr + phdr.p_memsz;
}
if (start >= end)
goto not_loaded;
*start_ret = start;
*end_ret = end;
return NULL;
}
/* ehdr_buf must be aligned as Elf64_Ehdr. */
static void read_ehdr(const void *ehdr_buf, GElf_Ehdr *ret, bool *is_64_bit_ret,
bool *bswap_ret)
{
*is_64_bit_ret = ((unsigned char *)ehdr_buf)[EI_CLASS] == ELFCLASS64;
bool little_endian =
((unsigned char *)ehdr_buf)[EI_DATA] == ELFDATA2LSB;
*bswap_ret = little_endian != HOST_LITTLE_ENDIAN;
if (*is_64_bit_ret) {
const Elf64_Ehdr *ehdr64 = ehdr_buf;
if (*bswap_ret) {
memcpy(ret->e_ident, ehdr64->e_ident, EI_NIDENT);
ret->e_type = bswap_16(ehdr64->e_type);
ret->e_machine = bswap_16(ehdr64->e_machine);
ret->e_version = bswap_32(ehdr64->e_version);
ret->e_entry = bswap_64(ehdr64->e_entry);
ret->e_phoff = bswap_64(ehdr64->e_phoff);
ret->e_shoff = bswap_64(ehdr64->e_shoff);
ret->e_flags = bswap_32(ehdr64->e_flags);
ret->e_ehsize = bswap_16(ehdr64->e_ehsize);
ret->e_phentsize = bswap_16(ehdr64->e_phentsize);
ret->e_phnum = bswap_16(ehdr64->e_phnum);
ret->e_shentsize = bswap_16(ehdr64->e_shentsize);
ret->e_shnum = bswap_16(ehdr64->e_shnum);
ret->e_shstrndx = bswap_16(ehdr64->e_shstrndx);
} else {
*ret = *ehdr64;
}
} else {
const Elf32_Ehdr *ehdr32 = ehdr_buf;
memcpy(ret->e_ident, ehdr32->e_ident, EI_NIDENT);
if (*bswap_ret) {
ret->e_type = bswap_16(ehdr32->e_type);
ret->e_machine = bswap_16(ehdr32->e_machine);
ret->e_version = bswap_32(ehdr32->e_version);
ret->e_entry = bswap_32(ehdr32->e_entry);
ret->e_phoff = bswap_32(ehdr32->e_phoff);
ret->e_shoff = bswap_32(ehdr32->e_shoff);
ret->e_flags = bswap_32(ehdr32->e_flags);
ret->e_ehsize = bswap_16(ehdr32->e_ehsize);
ret->e_phentsize = bswap_16(ehdr32->e_phentsize);
ret->e_phnum = bswap_16(ehdr32->e_phnum);
ret->e_shentsize = bswap_16(ehdr32->e_shentsize);
ret->e_shnum = bswap_16(ehdr32->e_shnum);
ret->e_shstrndx = bswap_16(ehdr32->e_shstrndx);
} else {
ret->e_type = ehdr32->e_type;
ret->e_machine = ehdr32->e_machine;
ret->e_version = ehdr32->e_version;
ret->e_entry = ehdr32->e_entry;
ret->e_phoff = ehdr32->e_phoff;
ret->e_shoff = ehdr32->e_shoff;
ret->e_flags = ehdr32->e_flags;
ret->e_ehsize = ehdr32->e_ehsize;
ret->e_phentsize = ehdr32->e_phentsize;
ret->e_phnum = ehdr32->e_phnum;
ret->e_shentsize = ehdr32->e_shentsize;
ret->e_shnum = ehdr32->e_shnum;
ret->e_shstrndx = ehdr32->e_shstrndx;
}
}
}
/* phdr_buf must be aligned as Elf64_Phdr. */
static void read_phdr(const void *phdr_buf, size_t i, bool is_64_bit,
bool bswap, GElf_Phdr *ret)
{
if (is_64_bit) {
const Elf64_Phdr *phdr64 = (Elf64_Phdr *)phdr_buf + i;
if (bswap) {
ret->p_type = bswap_32(phdr64->p_type);
ret->p_flags = bswap_32(phdr64->p_flags);
ret->p_offset = bswap_64(phdr64->p_offset);
ret->p_vaddr = bswap_64(phdr64->p_vaddr);
ret->p_paddr = bswap_64(phdr64->p_paddr);
ret->p_filesz = bswap_64(phdr64->p_filesz);
ret->p_memsz = bswap_64(phdr64->p_memsz);
ret->p_align = bswap_64(phdr64->p_align);
} else {
*ret = *phdr64;
}
} else {
const Elf32_Phdr *phdr32 = (Elf32_Phdr *)phdr_buf + i;
if (bswap) {
ret->p_type = bswap_32(phdr32->p_type);
ret->p_offset = bswap_32(phdr32->p_offset);
ret->p_vaddr = bswap_32(phdr32->p_vaddr);
ret->p_paddr = bswap_32(phdr32->p_paddr);
ret->p_filesz = bswap_32(phdr32->p_filesz);
ret->p_memsz = bswap_32(phdr32->p_memsz);
ret->p_flags = bswap_32(phdr32->p_flags);
ret->p_align = bswap_32(phdr32->p_align);
} else {
ret->p_type = phdr32->p_type;
ret->p_offset = phdr32->p_offset;
ret->p_vaddr = phdr32->p_vaddr;
ret->p_paddr = phdr32->p_paddr;
ret->p_filesz = phdr32->p_filesz;
ret->p_memsz = phdr32->p_memsz;
ret->p_flags = phdr32->p_flags;
ret->p_align = phdr32->p_align;
}
}
}
static const char *read_build_id(const char *buf, size_t buf_len,
uint64_t align, bool bswap,
size_t *len_ret)
{
/*
* Build IDs are usually 16 or 20 bytes (MD5 or SHA-1, respectively), so
* these arbitrary limits are generous.
*/
static const uint32_t build_id_min_size = 2;
static const uint32_t build_id_max_size = 1024;
/* Elf32_Nhdr is the same as Elf64_Nhdr. */
Elf64_Nhdr nhdr;
const char *p = buf;
while (buf + buf_len - p >= sizeof(nhdr)) {
memcpy(&nhdr, p, sizeof(nhdr));
if (bswap) {
nhdr.n_namesz = bswap_32(nhdr.n_namesz);
nhdr.n_descsz = bswap_32(nhdr.n_descsz);
nhdr.n_type = bswap_32(nhdr.n_type);
}
p += sizeof(nhdr);
uint64_t namesz = (nhdr.n_namesz + align - 1) & ~(align - 1);
if (namesz > buf + buf_len - p)
return NULL;
const char *name = p;
p += namesz;
if (nhdr.n_namesz == sizeof("GNU") &&
memcmp(name, "GNU", sizeof("GNU")) == 0 &&
nhdr.n_type == NT_GNU_BUILD_ID &&
nhdr.n_descsz >= build_id_min_size &&
nhdr.n_descsz <= build_id_max_size) {
if (nhdr.n_descsz > buf + buf_len - p)
return NULL;
*len_ret = nhdr.n_descsz;
return p;
}
uint64_t descsz = (nhdr.n_descsz + align - 1) & ~(align - 1);
if (descsz > buf + buf_len - p)
return NULL;
p += descsz;
}
return NULL;
}
struct core_get_phdr_arg {
const void *phdr_buf;
bool is_64_bit;
bool bswap;
};
static struct drgn_error *
core_get_phdr(void *arg_, size_t i, GElf_Phdr *ret)
{
struct core_get_phdr_arg *arg = arg_;
read_phdr(arg->phdr_buf, i, arg->is_64_bit, arg->bswap, ret);
return NULL;
}
struct userspace_core_identified_file {
const void *build_id;
size_t build_id_len;
uint64_t start, end;
bool ignore;
bool have_address_range;
};
static struct drgn_error *
userspace_core_identify_file(struct drgn_program *prog,
struct userspace_core_report_state *core,
const struct drgn_mapped_file_segment *segments,
size_t num_segments,
const struct drgn_mapped_file_segment *ehdr_segment,
struct userspace_core_identified_file *ret)
{
struct drgn_error *err;
Elf64_Ehdr ehdr_buf;
err = drgn_program_read_memory(prog, &ehdr_buf, ehdr_segment->start,
sizeof(ehdr_buf), false);
if (err) {
if (err->code == DRGN_ERROR_FAULT) {
drgn_error_destroy(err);
err = NULL;
}
return err;
}
if (memcmp(&ehdr_buf, ELFMAG, SELFMAG) != 0) {
ret->ignore = true;
return NULL;
}
GElf_Ehdr ehdr;
struct core_get_phdr_arg arg;
read_ehdr(&ehdr_buf, &ehdr, &arg.is_64_bit, &arg.bswap);
if (ehdr.e_type == ET_CORE ||
ehdr.e_phnum == 0 ||
ehdr.e_phentsize !=
(arg.is_64_bit ? sizeof(Elf64_Phdr) : sizeof(Elf32_Phdr))) {
ret->ignore = true;
return NULL;
}
if (ehdr.e_phnum > SIZE_MAX / ehdr.e_phentsize ||
!alloc_or_reuse(&core->phdr_buf, &core->phdr_buf_capacity,
ehdr.e_phnum * ehdr.e_phentsize))
return &drgn_enomem;
/*
* Check whether the mapped segment containing the file header also
* contains the program headers. This seems to be the case in practice.
*/
uint64_t ehdr_segment_file_end =
(ehdr_segment->file_offset +
(ehdr_segment->end - ehdr_segment->start));
if (ehdr_segment_file_end < ehdr.e_phoff ||
ehdr_segment_file_end - ehdr.e_phoff <
ehdr.e_phnum * ehdr.e_phentsize)
return NULL;
err = drgn_program_read_memory(prog, core->phdr_buf,
ehdr_segment->start + ehdr.e_phoff,
ehdr.e_phnum * ehdr.e_phentsize, false);
if (err) {
if (err->code == DRGN_ERROR_FAULT) {
drgn_error_destroy(err);
err = NULL;
}
return err;
}
arg.phdr_buf = core->phdr_buf;
/*
* In theory, if the program has a huge number of program headers, they
* may not all be dumped. However, the largest binary I was able to find
* still had all program headers within 1k.
*
* It'd be more reliable to determine the bias based on the headers that
* were saved, use that to read the build ID, use that to find the ELF
* file, and then determine the address range directly from the ELF
* file. However, we need the address range to report the build ID to
* libdwfl, so we do it this way.
*/
uint64_t bias;
err = userspace_core_elf_address_range(ehdr.e_type, ehdr.e_phnum,
core_get_phdr, &arg, segments,
num_segments, ehdr_segment,
&bias, &ret->start, &ret->end);
if (err)
return err;
if (ret->start >= ret->end) {
ret->ignore = true;
return NULL;
}
ret->have_address_range = true;
for (uint16_t i = 0; i < ehdr.e_phnum; i++) {
GElf_Phdr phdr;
core_get_phdr(&arg, i, &phdr);
if (phdr.p_type == PT_NOTE) {
if (phdr.p_filesz > SIZE_MAX ||
!alloc_or_reuse(&core->segment_buf,
&core->segment_buf_capacity,
phdr.p_filesz))
return &drgn_enomem;
err = drgn_program_read_memory(prog, core->segment_buf,
phdr.p_vaddr + bias,
phdr.p_filesz, false);
if (err) {
if (err->code == DRGN_ERROR_FAULT) {
drgn_error_destroy(err);
continue;
} else {
return err;
}
}
ret->build_id = read_build_id(core->segment_buf,
phdr.p_filesz,
phdr.p_align, arg.bswap,
&ret->build_id_len);
if (ret->build_id)
break;
}
}
return NULL;
}
static struct drgn_error *elf_file_get_phdr(void *arg, size_t i,
GElf_Phdr *phdr)
{
if (!gelf_getphdr(arg, i, phdr))
return drgn_error_libelf();
return NULL;
}
static struct drgn_error *
userspace_core_maybe_report_file(struct drgn_debug_info_load_state *load,
struct userspace_core_report_state *core,
const char *path,
const struct drgn_mapped_file_segment *segments,
size_t num_segments)
{
struct drgn_error *err;
struct drgn_program *prog = load->dbinfo->prog;
for (size_t ehdr_idx = 0; ehdr_idx < num_segments; ehdr_idx++) {
const struct drgn_mapped_file_segment *ehdr_segment =
&segments[ehdr_idx];
/*
* There should always be a full page mapped, so even if it's a
* 32-bit file, we can read the 64-bit size.
*/
if (ehdr_segment->file_offset != 0 ||
ehdr_segment->end - ehdr_segment->start < sizeof(Elf64_Ehdr))
continue;
/*
* This logic is complicated because we're dealing with two data
* sources that we can't completely trust: the memory in the
* core dump and the file at the path found in the core dump.
*
* First, we try to identify the mapped file contents in the
* core dump. Ideally, this will find a build ID. However, this
* can fail for a few reasons:
*
* 1. The file is not an ELF file.
* 2. The ELF file is not an executable or library.
* 3. The ELF file does not have a build ID.
* 4. The file header was not dumped to the core dump, in which
* case we can't tell whether this is an ELF file. Dumping
* the first page of an executable file has been the default
* behavior since Linux kernel commit 895021552d6f
* ("coredump: default
* CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS=y") (in v2.6.37), but
* it can be disabled at kernel build time or toggled at
* runtime.
* 5. The build ID or the necessary ELF metadata were not dumped
* in the core dump. This can happen if the necessary program
* headers or note segment were not in the first page of the
* file.
* 6. The file is mapped but not actually loaded into the
* program (e.g., if the program is a tool like a profiler or
* a debugger that mmaps binaries [like drgn itself!]).
*
* In cases 1 and 2, we can simply ignore the file. In cases
* 3-5, we blindly trust the path in the core dump. We can
* sometimes detect case 6 in
* userspace_core_elf_address_range().
*
* There is also the possibility that the program modified or
* corrupted the ELF metadata in memory (more likely if the file
* was explicitly mmap'd, since the metadata will usually be
* read-only if it was loaded properly). We don't deal with that
* yet.
*/
struct userspace_core_identified_file identity = {};
err = userspace_core_identify_file(prog, core, segments,
num_segments, ehdr_segment,
&identity);
if (err)
return err;
if (identity.ignore)
continue;
#define CLEAR_ELF() do { \
elf = NULL; \
fd = -1; \
} while (0)
#define CLOSE_ELF() do { \
elf_end(elf); \
close(fd); \
CLEAR_ELF(); \
} while (0)
int fd;
Elf *elf;
/*
* There are a few things that can go wrong here:
*
* 1. The path no longer exists.
* 2. The path refers to a different ELF file than was in the
* core dump.
* 3. The path refers to something which isn't a valid ELF file.
*/
err = open_elf_file(path, &fd, &elf);
if (err) {
drgn_error_destroy(err);
CLEAR_ELF();
} else if (identity.build_id_len > 0) {
if (!build_id_matches(elf, identity.build_id,
identity.build_id_len))
CLOSE_ELF();
}
if (elf && !identity.have_address_range) {
GElf_Ehdr ehdr_mem, *ehdr;
size_t phnum;
if ((ehdr = gelf_getehdr(elf, &ehdr_mem)) &&
(elf_getphdrnum(elf, &phnum) == 0)) {
uint64_t bias;
err = userspace_core_elf_address_range(ehdr->e_type,
phnum,
elf_file_get_phdr,
elf,
segments,
num_segments,
ehdr_segment,
&bias,
&identity.start,
&identity.end);
if (err || identity.start >= identity.end) {
drgn_error_destroy(err);
CLOSE_ELF();
} else {
identity.have_address_range = true;
}
} else {
CLOSE_ELF();
}
}
if (elf) {
err = drgn_debug_info_report_elf(load, path, fd, elf,
identity.start,
identity.end, NULL,
NULL);
if (err)
return err;
} else {
if (!identity.have_address_range)
identity.start = identity.end = 0;
Dwfl_Module *dwfl_module =
dwfl_report_module(load->dbinfo->dwfl, path,
identity.start,
identity.end);
if (!dwfl_module)
return drgn_error_libdwfl();
if (identity.build_id_len > 0 &&
dwfl_module_report_build_id(dwfl_module,
identity.build_id,
identity.build_id_len,
0))
return drgn_error_libdwfl();
}
#undef CLOSE_ELF
#undef CLEAR_ELF
}
return NULL;
}
static struct drgn_error *
userspace_core_report_mapped_files(struct drgn_debug_info_load_state *load,
struct userspace_core_report_state *core)
{
struct drgn_error *err;
for (struct drgn_mapped_files_iterator it =
drgn_mapped_files_first(&core->files);
it.entry; it = drgn_mapped_files_next(it)) {
err = userspace_core_maybe_report_file(load, core,
it.entry->key,
drgn_mapped_file_segment_vector_begin(&it.entry->value),
drgn_mapped_file_segment_vector_size(&it.entry->value));
if (err)
return err;
}
return NULL;
}
static struct drgn_error *
userspace_core_report_debug_info(struct drgn_debug_info_load_state *load,
const char *nt_file, size_t nt_file_len)
{
struct drgn_error *err;
struct userspace_core_report_state core = {
.files = HASH_TABLE_INIT,
};
err = userspace_core_get_mapped_files(load, &core, nt_file,
nt_file_len);
if (err)
goto out;
err = userspace_core_report_mapped_files(load, &core);
out:
free(core.segment_buf);
free(core.phdr_buf);
for (struct drgn_mapped_files_iterator it =
drgn_mapped_files_first(&core.files);
it.entry; it = drgn_mapped_files_next(it))
drgn_mapped_file_segment_vector_deinit(&it.entry->value);
drgn_mapped_files_deinit(&core.files);
return err;
}
static struct drgn_error *
userspace_report_elf_file(struct drgn_debug_info_load_state *load,
const char *path)
{
struct drgn_error *err;
int fd;
Elf *elf;
err = open_elf_file(path, &fd, &elf);
if (err)
goto err;
GElf_Ehdr ehdr_mem, *ehdr;
ehdr = gelf_getehdr(elf, &ehdr_mem);
if (!ehdr) {
err = drgn_error_libelf();
goto err_close;
}
/*
* We haven't implemented a way to get the load address for dynamically
* loaded or relocatable files, so for now we report those as unloaded.
*/
uint64_t start = 0, end = 0;
if (ehdr->e_type == ET_EXEC || ehdr->e_type == ET_CORE) {
err = elf_address_range(elf, 0, &start, &end);
if (err)
goto err_close;
}
return drgn_debug_info_report_elf(load, path, fd, elf, start, end, NULL,
NULL);
err_close:
elf_end(elf);
close(fd);
err:
return drgn_debug_info_report_error(load, path, NULL, err);
}
static struct drgn_error *
userspace_report_debug_info(struct drgn_debug_info_load_state *load)
{
struct drgn_error *err;
for (size_t i = 0; i < load->num_paths; i++) {
err = userspace_report_elf_file(load, load->paths[i]);
if (err)
return err;
}
if (load->load_default) {
Dwfl *dwfl = load->dbinfo->dwfl;
struct drgn_program *prog = load->dbinfo->prog;
if (prog->flags & DRGN_PROGRAM_IS_LIVE) {
int ret = dwfl_linux_proc_report(dwfl, prog->pid);
if (ret == -1) {
return drgn_error_libdwfl();
} else if (ret) {
return drgn_error_create_os("dwfl_linux_proc_report",
ret, NULL);
}
} else {
const char *nt_file;
size_t nt_file_len;
char *env = getenv("DRGN_USE_LIBDWFL_REPORT");
if (env && atoi(env)) {
nt_file = NULL;
nt_file_len = 0;
} else {
err = drgn_get_nt_file(prog->core, &nt_file,
&nt_file_len);
if (err)
return err;
}
if (nt_file) {
err = userspace_core_report_debug_info(load,
nt_file,
nt_file_len);
if (err)
return err;
} else if (dwfl_core_file_report(dwfl, prog->core,
NULL) == -1) {
return drgn_error_libdwfl();
}
}
}
return NULL;
}
static int should_apply_relocation_section(Elf *elf, size_t shstrndx,
const GElf_Shdr *shdr)
{
if (shdr->sh_type != SHT_RELA && shdr->sh_type != SHT_REL)
return 0;
const char *scnname = elf_strptr(elf, shstrndx, shdr->sh_name);
if (!scnname)
return -1;
if (shdr->sh_type == SHT_RELA) {
if (!strstartswith(scnname, ".rela."))
return 0;
scnname += sizeof(".rela.") - 1;
} else {
if (!strstartswith(scnname, ".rel."))
return 0;
scnname += sizeof(".rel.") - 1;
}
return (strstartswith(scnname, "debug_") ||
strstartswith(scnname, "orc_"));
}
static inline struct drgn_error *get_reloc_sym_value(const void *syms,
size_t num_syms,
const uint64_t *sh_addrs,
size_t shdrnum,
bool is_64_bit,
bool bswap,
uint32_t r_sym,
uint64_t *ret)
{
if (r_sym >= num_syms) {
return drgn_error_create(DRGN_ERROR_OTHER,
"invalid ELF relocation symbol");
}
uint16_t st_shndx;
uint64_t st_value;
if (is_64_bit) {
const Elf64_Sym *sym = (Elf64_Sym *)syms + r_sym;
memcpy(&st_shndx, &sym->st_shndx, sizeof(st_shndx));
memcpy(&st_value, &sym->st_value, sizeof(st_value));
if (bswap) {
st_shndx = bswap_16(st_shndx);
st_value = bswap_64(st_value);
}
} else {
const Elf32_Sym *sym = (Elf32_Sym *)syms + r_sym;
memcpy(&st_shndx, &sym->st_shndx, sizeof(st_shndx));
uint32_t st_value32;
memcpy(&st_value32, &sym->st_value, sizeof(st_value32));
if (bswap) {
st_shndx = bswap_16(st_shndx);
st_value32 = bswap_32(st_value32);
}
st_value = st_value32;
}
if (st_shndx >= shdrnum) {
return drgn_error_create(DRGN_ERROR_OTHER,
"invalid ELF symbol section index");
}
*ret = sh_addrs[st_shndx] + st_value;
return NULL;
}
static struct drgn_error *
apply_elf_relas(const struct drgn_relocating_section *relocating,
Elf_Data *reloc_data, Elf_Data *symtab_data,
const uint64_t *sh_addrs, size_t shdrnum,
const struct drgn_platform *platform)
{
struct drgn_error *err;
bool is_64_bit = drgn_platform_is_64_bit(platform);
bool bswap = drgn_platform_bswap(platform);
apply_elf_reloc_fn *apply_elf_reloc = platform->arch->apply_elf_reloc;
const void *relocs = reloc_data->d_buf;
size_t reloc_size = is_64_bit ? sizeof(Elf64_Rela) : sizeof(Elf32_Rela);
size_t num_relocs = reloc_data->d_size / reloc_size;
const void *syms = symtab_data->d_buf;
size_t sym_size = is_64_bit ? sizeof(Elf64_Sym) : sizeof(Elf32_Sym);
size_t num_syms = symtab_data->d_size / sym_size;
for (size_t i = 0; i < num_relocs; i++) {
uint64_t r_offset;
uint32_t r_sym;
uint32_t r_type;
int64_t r_addend;
if (is_64_bit) {
const Elf64_Rela *rela = (Elf64_Rela *)relocs + i;
uint64_t r_info;
memcpy(&r_offset, &rela->r_offset, sizeof(r_offset));
memcpy(&r_info, &rela->r_info, sizeof(r_info));
memcpy(&r_addend, &rela->r_addend, sizeof(r_addend));
if (bswap) {
r_offset = bswap_64(r_offset);
r_info = bswap_64(r_info);
r_addend = bswap_64(r_addend);
}
r_sym = ELF64_R_SYM(r_info);
r_type = ELF64_R_TYPE(r_info);
} else {
const Elf32_Rela *rela32 = (Elf32_Rela *)relocs + i;
uint32_t r_offset32;
uint32_t r_info32;
int32_t r_addend32;
memcpy(&r_offset32, &rela32->r_offset, sizeof(r_offset32));
memcpy(&r_info32, &rela32->r_info, sizeof(r_info32));
memcpy(&r_addend32, &rela32->r_addend, sizeof(r_addend32));
if (bswap) {
r_offset32 = bswap_32(r_offset32);
r_info32 = bswap_32(r_info32);
r_addend32 = bswap_32(r_addend32);
}
r_offset = r_offset32;
r_sym = ELF32_R_SYM(r_info32);
r_type = ELF32_R_TYPE(r_info32);
r_addend = r_addend32;
}
uint64_t sym_value;
err = get_reloc_sym_value(syms, num_syms, sh_addrs, shdrnum,
is_64_bit, bswap, r_sym, &sym_value);
if (err)
return err;
err = apply_elf_reloc(relocating, r_offset, r_type, &r_addend,
sym_value);
if (err)
return err;
}
return NULL;
}
static struct drgn_error *
apply_elf_rels(const struct drgn_relocating_section *relocating,
Elf_Data *reloc_data, Elf_Data *symtab_data,
const uint64_t *sh_addrs, size_t shdrnum,
const struct drgn_platform *platform)
{
struct drgn_error *err;
bool is_64_bit = drgn_platform_is_64_bit(platform);
bool bswap = drgn_platform_bswap(platform);
apply_elf_reloc_fn *apply_elf_reloc = platform->arch->apply_elf_reloc;
const void *relocs = reloc_data->d_buf;
size_t reloc_size = is_64_bit ? sizeof(Elf64_Rel) : sizeof(Elf32_Rel);
size_t num_relocs = reloc_data->d_size / reloc_size;
const void *syms = symtab_data->d_buf;
size_t sym_size = is_64_bit ? sizeof(Elf64_Sym) : sizeof(Elf32_Sym);
size_t num_syms = symtab_data->d_size / sym_size;
for (size_t i = 0; i < num_relocs; i++) {
uint64_t r_offset;
uint32_t r_sym;
uint32_t r_type;
if (is_64_bit) {
const Elf64_Rel *rel = (Elf64_Rel *)relocs + i;
uint64_t r_info;
memcpy(&r_offset, &rel->r_offset, sizeof(r_offset));
memcpy(&r_info, &rel->r_info, sizeof(r_info));
if (bswap) {
r_offset = bswap_64(r_offset);
r_info = bswap_64(r_info);
}
r_sym = ELF64_R_SYM(r_info);
r_type = ELF64_R_TYPE(r_info);
} else {
const Elf32_Rel *rel32 = (Elf32_Rel *)relocs + i;
uint32_t r_offset32;
uint32_t r_info32;
memcpy(&r_offset32, &rel32->r_offset, sizeof(r_offset32));
memcpy(&r_info32, &rel32->r_info, sizeof(r_info32));
if (bswap) {
r_offset32 = bswap_32(r_offset32);
r_info32 = bswap_32(r_info32);
}
r_offset = r_offset32;
r_sym = ELF32_R_SYM(r_info32);
r_type = ELF32_R_TYPE(r_info32);
}
uint64_t sym_value;
err = get_reloc_sym_value(syms, num_syms, sh_addrs, shdrnum,
is_64_bit, bswap, r_sym, &sym_value);
if (err)
return err;
err = apply_elf_reloc(relocating, r_offset, r_type, NULL,
sym_value);
if (err)
return err;
}
return NULL;
}
/*
* Before the debugging information in a relocatable ELF file (e.g., Linux
* kernel module) can be used, it must have ELF relocations applied. This is
* usually done by libdwfl. However, libdwfl is relatively slow at it. This is a
* much faster implementation.
*/
static struct drgn_error *relocate_elf_file(Elf *elf)
{
struct drgn_error *err;
GElf_Ehdr ehdr_mem, *ehdr;
ehdr = gelf_getehdr(elf, &ehdr_mem);
if (!ehdr)
return drgn_error_libelf();
if (ehdr->e_type != ET_REL) {
/* Not a relocatable file. */
return NULL;
}
struct drgn_platform platform;
drgn_platform_from_elf(ehdr, &platform);
if (!platform.arch->apply_elf_reloc) {
/* Unsupported; fall back to libdwfl. */
return NULL;
}
size_t shdrnum;
if (elf_getshdrnum(elf, &shdrnum))
return drgn_error_libelf();
_cleanup_free_ uint64_t *sh_addrs =
calloc(shdrnum, sizeof(sh_addrs[0]));
if (!sh_addrs && shdrnum > 0)
return &drgn_enomem;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn(elf, scn))) {
GElf_Shdr *shdr, shdr_mem;
shdr = gelf_getshdr(scn, &shdr_mem);
if (!shdr)
return drgn_error_libelf();
sh_addrs[elf_ndxscn(scn)] = shdr->sh_addr;
}
size_t shstrndx;
if (elf_getshdrstrndx(elf, &shstrndx))
return drgn_error_libelf();
Elf_Scn *reloc_scn = NULL;
while ((reloc_scn = elf_nextscn(elf, reloc_scn))) {
GElf_Shdr *reloc_shdr, reloc_shdr_mem;
reloc_shdr = gelf_getshdr(reloc_scn, &reloc_shdr_mem);
if (!reloc_shdr)
return drgn_error_libelf();
int r = should_apply_relocation_section(elf, shstrndx,
reloc_shdr);
if (r < 0)
return drgn_error_libelf();
if (r) {
Elf_Scn *scn = elf_getscn(elf, reloc_shdr->sh_info);
if (!scn)
return drgn_error_libelf();
GElf_Shdr *shdr, shdr_mem;
shdr = gelf_getshdr(scn, &shdr_mem);
if (!shdr)
return drgn_error_libelf();
if (shdr->sh_type == SHT_NOBITS)
continue;
Elf_Scn *symtab_scn = elf_getscn(elf,
reloc_shdr->sh_link);
if (!symtab_scn)
return drgn_error_libelf();
shdr = gelf_getshdr(symtab_scn, &shdr_mem);
if (!shdr)
return drgn_error_libelf();
if (shdr->sh_type == SHT_NOBITS) {
return drgn_error_create(DRGN_ERROR_OTHER,
"relocation symbol table has no data");
}
Elf_Data *data, *reloc_data, *symtab_data;
if ((err = read_elf_section(scn, &data)) ||
(err = read_elf_section(reloc_scn, &reloc_data)) ||
(err = read_elf_section(symtab_scn, &symtab_data)))
return err;
struct drgn_relocating_section relocating = {
.buf = data->d_buf,
.buf_size = data->d_size,
.addr = sh_addrs[elf_ndxscn(scn)],
.bswap = drgn_platform_bswap(&platform),
};
if (reloc_shdr->sh_type == SHT_RELA) {
err = apply_elf_relas(&relocating, reloc_data,
symtab_data, sh_addrs,
shdrnum, &platform);
} else {
err = apply_elf_rels(&relocating, reloc_data,
symtab_data, sh_addrs,
shdrnum, &platform);
}
if (err)
return err;
/*
* Mark the relocation section as empty so that libdwfl
* doesn't try to apply it again.
*/
reloc_shdr->sh_size = 0;
if (!gelf_update_shdr(reloc_scn, reloc_shdr))
return drgn_error_libelf();
reloc_data->d_size = 0;
}
}
return NULL;
}
static struct drgn_error *
drgn_module_find_files(struct drgn_debug_info_load_state *load,
struct drgn_module *module)
{
struct drgn_error *err;
if (module->elf) {
err = relocate_elf_file(module->elf);
if (err)
return err;
}
GElf_Addr loaded_file_bias;
Elf *loaded_elf = NULL;
Dwarf_Addr debug_file_bias;
Dwarf *dwarf;
err = NULL;
#pragma omp critical(drgn_module_find_files)
{
// We don't need the loaded file for the Linux kernel, and we
// always report the debug file as the main file to libdwfl.
if (!(load->dbinfo->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)) {
loaded_elf = dwfl_module_getelf(module->dwfl_module,
&loaded_file_bias);
if (!loaded_elf)
err = drgn_error_libdwfl();
}
if (!err) {
dwarf = dwfl_module_getdwarf(module->dwfl_module,
&debug_file_bias);
if (!dwarf)
err = drgn_error_libdwfl();
}
}
if (err)
return err;
const char *loaded_file_path;
const char *debug_file_path;
dwfl_module_info(module->dwfl_module, NULL, NULL, NULL, NULL, NULL,
&loaded_file_path, &debug_file_path);
// If the loaded file also has debugging information, debug_file_path is
// NULL. (debug_file_path is also NULL if libdwfl got the debug file
// from debuginfod, so this isn't 100% correct, but it'll at least
// identify the module.)
if (!debug_file_path)
debug_file_path = loaded_file_path;
module->debug_file_bias = debug_file_bias;
err = drgn_elf_file_create(module, debug_file_path, dwarf_getelf(dwarf),
&module->debug_file);
if (err) {
module->debug_file = NULL;
return err;
}
module->debug_file->dwarf = dwarf;
if (!module->debug_file->scns[DRGN_SCN_DEBUG_INFO] ||
!module->debug_file->scns[DRGN_SCN_DEBUG_ABBREV]) {
return drgn_error_create(DRGN_ERROR_OTHER,
"missing debugging information sections");
}
Dwarf *altdwarf = dwarf_getalt(dwarf);
if (altdwarf) {
Elf *altelf = dwarf_getelf(altdwarf);
if (!altelf)
return drgn_error_libdw();
size_t shstrndx;
if (elf_getshdrstrndx(altelf, &shstrndx))
return drgn_error_libelf();
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn(altelf, scn))) {
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr(scn, &shdr_mem);
if (!shdr)
return drgn_error_libelf();
if (shdr->sh_type != SHT_PROGBITS)
continue;
const char *scnname = elf_strptr(altelf, shstrndx,
shdr->sh_name);
if (!scnname)
return drgn_error_libelf();
/*
* TODO: save more sections and support imported units.
*/
if (strcmp(scnname, ".debug_info") == 0 &&
!module->debug_file->alt_debug_info_data) {
err = read_elf_section(scn,
&module->debug_file->alt_debug_info_data);
if (err)
return err;
} else if (strcmp(scnname, ".debug_str") == 0 &&
!module->debug_file->alt_debug_str_data) {
err = read_elf_section(scn,
&module->debug_file->alt_debug_str_data);
if (err)
return err;
}
}
}
err = drgn_elf_file_precache_sections(module->debug_file);
if (err)
return err;
if (loaded_elf) {
module->loaded_file_bias = loaded_file_bias;
if (loaded_elf == module->debug_file->elf) {
module->loaded_file = module->debug_file;
} else {
err = drgn_elf_file_create(module, loaded_file_path,
loaded_elf,
&module->loaded_file);
if (err) {
module->loaded_file = NULL;
return err;
}
}
}
return NULL;
}
static struct drgn_error *
drgn_debug_info_read_module(struct drgn_debug_info_load_state *load,
struct drgn_dwarf_index_state *index,
struct drgn_module *head)
{
struct drgn_error *err;
struct drgn_module *module;
for (module = head; module; module = module->next) {
err = drgn_module_find_files(load, module);
if (err) {
module->err = err;
continue;
}
module->state = DRGN_DEBUG_INFO_MODULE_INDEXING;
return drgn_dwarf_index_read_file(index, module->debug_file);
}
/*
* We checked all of the files and didn't find debugging information.
* Report why for each one.
*
* (If we did find debugging information, we discard errors on the
* unused files.)
*/
err = NULL;
#pragma omp critical(drgn_debug_info_read_module_error)
for (module = head; module; module = module->next) {
const char *name =
dwfl_module_info(module->dwfl_module, NULL, NULL, NULL,
NULL, NULL, NULL, NULL);
if (module->err) {
err = drgn_debug_info_report_error(load, name, NULL,
module->err);
module->err = NULL;
} else {
err = drgn_debug_info_report_error(load, name,
"no debugging information",
NULL);
}
if (err)
break;
}
return err;
}
static struct drgn_error *
drgn_debug_info_update_index(struct drgn_debug_info_load_state *load)
{
if (drgn_module_vector_empty(&load->new_modules))
return NULL;
struct drgn_debug_info *dbinfo = load->dbinfo;
if (!c_string_set_reserve(&dbinfo->module_names,
c_string_set_size(&dbinfo->module_names)
+ drgn_module_vector_size(&load->new_modules)))
return &drgn_enomem;
struct drgn_dwarf_index_state index;
if (!drgn_dwarf_index_state_init(&index, dbinfo))
return &drgn_enomem;
struct drgn_error *err = NULL;
#pragma omp parallel for schedule(dynamic) num_threads(drgn_num_threads)
for (size_t i = 0; i < drgn_module_vector_size(&load->new_modules); i++) {
if (err)
continue;
struct drgn_module *module =
*drgn_module_vector_at(&load->new_modules, i);
struct drgn_error *module_err =
drgn_debug_info_read_module(load, &index, module);
if (module_err) {
#pragma omp critical(drgn_debug_info_update_index_error)
if (err)
drgn_error_destroy(module_err);
else
err = module_err;
}
}
if (!err) {
drgn_debug_info_free_modules(dbinfo, true, false);
err = drgn_dwarf_info_update_index(&index);
}
drgn_dwarf_index_state_deinit(&index);
return err;
}
struct drgn_error *
drgn_debug_info_report_flush(struct drgn_debug_info_load_state *load)
{
struct drgn_debug_info *dbinfo = load->dbinfo;
my_dwfl_report_end(dbinfo, NULL, NULL);
struct drgn_error *err = drgn_debug_info_update_index(load);
dwfl_report_begin_add(dbinfo->dwfl);
if (err)
return err;
drgn_module_vector_clear(&load->new_modules);
return NULL;
}
static struct drgn_error *
drgn_debug_info_report_finalize_errors(struct drgn_debug_info_load_state *load)
{
if (load->num_errors > load->max_errors &&
(!string_builder_line_break(&load->errors) ||
!string_builder_appendf(&load->errors, "... %u more",
load->num_errors - load->max_errors))) {
string_builder_deinit(&load->errors);
return &drgn_enomem;
}
if (load->num_errors) {
return drgn_error_from_string_builder(DRGN_ERROR_MISSING_DEBUG_INFO,
&load->errors);
} else {
return NULL;
}
}
struct drgn_error *drgn_debug_info_load(struct drgn_debug_info *dbinfo,
const char **paths, size_t n,
bool load_default, bool load_main)
{
struct drgn_program *prog = dbinfo->prog;
struct drgn_error *err;
if (load_default)
load_main = true;
const char *max_errors = getenv("DRGN_MAX_DEBUG_INFO_ERRORS");
struct drgn_debug_info_load_state load = {
.dbinfo = dbinfo,
.paths = paths,
.num_paths = n,
.load_default = load_default,
.load_main = load_main,
.new_modules = VECTOR_INIT,
.errors = STRING_BUILDER_INIT,
.max_errors = max_errors ? atoi(max_errors) : 5,
};
dwfl_report_begin_add(dbinfo->dwfl);
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
err = linux_kernel_report_debug_info(&load);
else
err = userspace_report_debug_info(&load);
my_dwfl_report_end(dbinfo, NULL, NULL);
if (err)
goto err;
/*
* userspace_report_debug_info() reports the main debugging information
* directly with libdwfl, so we need to report it to dbinfo.
*/
if (!(prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) && load_main &&
dwfl_getmodules(dbinfo->dwfl, drgn_debug_info_report_dwfl_module,
&load, 0)) {
err = &drgn_enomem;
goto err;
}
err = drgn_debug_info_update_index(&load);
if (err)
goto err;
/*
* TODO: for core dumps, we need to add memory reader segments for
* read-only segments of the loaded binaries since those aren't saved in
* the core dump.
*/
err = drgn_debug_info_report_finalize_errors(&load);
out:
drgn_module_vector_deinit(&load.new_modules);
return err;
err:
drgn_debug_info_free_modules(dbinfo, false, false);
string_builder_deinit(&load.errors);
goto out;
}
struct elf_symbols_search_arg {
const char *name;
uint64_t address;
enum drgn_find_symbol_flags flags;
struct drgn_error *err;
struct drgn_symbol_result_builder *builder;
};
static bool elf_symbol_match(struct elf_symbols_search_arg *arg, GElf_Addr addr,
const GElf_Sym *sym, const char *name)
{
if ((arg->flags & DRGN_FIND_SYMBOL_NAME) && strcmp(name, arg->name) != 0)
return false;
if ((arg->flags & DRGN_FIND_SYMBOL_ADDR) &&
(arg->address < addr || arg->address >= addr + sym->st_size))
return false;
return true;
}
static bool elf_symbol_store_match(struct elf_symbols_search_arg *arg,
GElf_Sym *elf_sym, GElf_Addr addr,
const char *name)
{
struct drgn_symbol *sym;
if (arg->flags == (DRGN_FIND_SYMBOL_ONE | DRGN_FIND_SYMBOL_NAME)) {
int binding = GELF_ST_BIND(elf_sym->st_info);
/*
* The order of precedence is
* GLOBAL = UNIQUE > WEAK > LOCAL = everything else
*
* If we found a global or unique symbol, return it
* immediately. If we found a weak symbol, then save it,
* which may overwrite a previously found weak or local
* symbol. Otherwise, save the symbol only if we haven't
* found another symbol.
*/
if (binding != STB_GLOBAL
&& binding != STB_GNU_UNIQUE
&& binding != STB_WEAK
&& drgn_symbol_result_builder_count(arg->builder) > 0)
return false;
sym = malloc(sizeof(*sym));
if (!sym) {
arg->err = &drgn_enomem;
return true;
}
drgn_symbol_from_elf(name, addr, elf_sym, sym);
if (!drgn_symbol_result_builder_add(arg->builder, sym)) {
arg->err = &drgn_enomem;
drgn_symbol_destroy(sym);
}
/* Abort on error, or short-circuit if we found a global or
* unique symbol */
return (arg->err || sym->binding == DRGN_SYMBOL_BINDING_GLOBAL
|| sym->binding == DRGN_SYMBOL_BINDING_UNIQUE);
} else {
sym = malloc(sizeof(*sym));
if (!sym) {
arg->err = &drgn_enomem;
return true;
}
drgn_symbol_from_elf(name, addr, elf_sym, sym);
if (!drgn_symbol_result_builder_add(arg->builder, sym)) {
arg->err = &drgn_enomem;
drgn_symbol_destroy(sym);
}
/* Abort on error, or short-circuit for single lookup */
return (arg->err || (arg->flags & DRGN_FIND_SYMBOL_ONE));
}
}
static int elf_symbols_search_cb(Dwfl_Module *dwfl_module, void **userdatap,
const char *module_name, Dwarf_Addr base,
void *cb_arg)
{
struct elf_symbols_search_arg *arg = cb_arg;
int symtab_len = dwfl_module_getsymtab(dwfl_module);
if (symtab_len == -1)
return DWARF_CB_OK;
/* Ignore the zeroth null symbol */
for (int i = 1; i < symtab_len; i++) {
GElf_Sym elf_sym;
GElf_Addr elf_addr;
const char *name = dwfl_module_getsym_info(dwfl_module, i,
&elf_sym, &elf_addr,
NULL, NULL, NULL);
if (!name || !elf_symbol_match(arg, elf_addr, &elf_sym, name))
continue;
if (elf_symbol_store_match(arg, &elf_sym, elf_addr, name))
return DWARF_CB_ABORT;
}
return DWARF_CB_OK;
}
static struct drgn_error *
elf_symbols_search(const char *name, uint64_t addr, enum drgn_find_symbol_flags flags,
void *data, struct drgn_symbol_result_builder *builder)
{
Dwfl_Module *dwfl_module = NULL;
struct drgn_program *prog = data;
struct elf_symbols_search_arg arg = {
.name = name,
.address = addr,
.flags = flags,
.err = NULL,
.builder = builder,
};
if (arg.flags & DRGN_FIND_SYMBOL_ADDR) {
dwfl_module = dwfl_addrmodule(prog->dbinfo.dwfl, arg.address);
if (!dwfl_module)
return NULL;
}
if ((arg.flags & (DRGN_FIND_SYMBOL_ADDR | DRGN_FIND_SYMBOL_ONE))
== (DRGN_FIND_SYMBOL_ADDR | DRGN_FIND_SYMBOL_ONE)) {
GElf_Off offset;
GElf_Sym elf_sym;
const char *name = dwfl_module_addrinfo(
dwfl_module, addr, &offset,
&elf_sym, NULL, NULL, NULL);
if (!name)
return NULL;
struct drgn_symbol *sym = malloc(sizeof(*sym));
if (!sym)
return &drgn_enomem;
drgn_symbol_from_elf(name, addr - offset, &elf_sym, sym);
if (!drgn_symbol_result_builder_add(builder, sym)) {
arg.err = &drgn_enomem;
drgn_symbol_destroy(sym);
}
} else if (dwfl_module) {
elf_symbols_search_cb(dwfl_module, NULL, NULL, 0, &arg);
} else {
dwfl_getmodules(prog->dbinfo.dwfl, elf_symbols_search_cb, &arg, 0);
}
return arg.err;
}
bool drgn_debug_info_is_indexed(struct drgn_debug_info *dbinfo,
const char *name)
{
return c_string_set_search(&dbinfo->module_names, &name).entry != NULL;
}
void drgn_debug_info_init(struct drgn_debug_info *dbinfo,
struct drgn_program *prog)
{
dbinfo->prog = prog;
dbinfo->dwfl = dwfl_begin(&drgn_dwfl_callbacks);
// This is temporary until we stop using libdwfl, and is extremely
// unlikely to fail anwyays, so don't bother propagating an error up.
if (!dbinfo->dwfl)
abort();
const struct drgn_type_finder_ops type_finder_ops = {
.find = drgn_debug_info_find_type,
};
drgn_program_register_type_finder_impl(prog, &dbinfo->type_finder,
"dwarf", &type_finder_ops,
dbinfo, 0);
const struct drgn_object_finder_ops object_finder_ops = {
.find = drgn_debug_info_find_object,
};
drgn_program_register_object_finder_impl(prog, &dbinfo->object_finder,
"dwarf", &object_finder_ops,
dbinfo, 0);
const struct drgn_symbol_finder_ops symbol_finder_ops = {
.find = elf_symbols_search,
};
drgn_program_register_symbol_finder_impl(prog, &dbinfo->symbol_finder,
"elf", &symbol_finder_ops,
prog, 0);
drgn_module_table_init(&dbinfo->modules);
c_string_set_init(&dbinfo->module_names);
drgn_dwarf_info_init(dbinfo);
}
void drgn_debug_info_deinit(struct drgn_debug_info *dbinfo)
{
drgn_dwarf_info_deinit(dbinfo);
c_string_set_deinit(&dbinfo->module_names);
drgn_debug_info_free_modules(dbinfo, false, true);
assert(drgn_module_table_empty(&dbinfo->modules));
drgn_module_table_deinit(&dbinfo->modules);
dwfl_end(dbinfo->dwfl);
}
struct drgn_elf_file *drgn_module_find_dwarf_file(struct drgn_module *module,
Dwarf *dwarf)
{
if (!module->debug_file)
return NULL;
if (dwarf == module->debug_file->dwarf)
return module->debug_file;
struct drgn_elf_file_dwarf_table_iterator it =
drgn_elf_file_dwarf_table_search(&module->split_dwarf_files,
&dwarf);
return it.entry ? *it.entry : NULL;
}
struct drgn_error *
drgn_module_create_split_dwarf_file(struct drgn_module *module,
const char *name, Dwarf *dwarf,
struct drgn_elf_file **ret)
{
struct drgn_error *err;
err = drgn_elf_file_create(module, name, dwarf_getelf(dwarf), ret);
if (err)
return err;
err = drgn_elf_file_precache_sections(*ret);
if (err) {
drgn_elf_file_destroy(*ret);
return err;
}
(*ret)->dwarf = dwarf;
int r = drgn_elf_file_dwarf_table_insert(&module->split_dwarf_files,
ret, NULL);
if (r < 0) {
drgn_elf_file_destroy(*ret);
return &drgn_enomem;
}
assert(r > 0);
return NULL;
}
struct drgn_error *
drgn_module_find_cfi(struct drgn_program *prog, struct drgn_module *module,
uint64_t pc, struct drgn_elf_file **file_ret,
struct drgn_cfi_row **row_ret, bool *interrupted_ret,
drgn_register_number *ret_addr_regno_ret)
{
struct drgn_error *err;
// If the file's platform doesn't match the program's, we can't use its
// CFI.
const bool can_use_loaded_file =
(module->loaded_file &&
drgn_platforms_equal(&module->loaded_file->platform,
&prog->platform));
const bool can_use_debug_file =
(module->debug_file &&
drgn_platforms_equal(&module->debug_file->platform,
&prog->platform));
if (prog->prefer_orc_unwinder) {
if (can_use_debug_file) {
*file_ret = module->debug_file;
err = drgn_module_find_orc_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
if (err != &drgn_not_found)
return err;
err = drgn_module_find_dwarf_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
if (err != &drgn_not_found)
return err;
}
if (can_use_loaded_file) {
*file_ret = module->loaded_file;
return drgn_module_find_eh_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
}
} else {
if (can_use_debug_file) {
*file_ret = module->debug_file;
err = drgn_module_find_dwarf_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
if (err != &drgn_not_found)
return err;
}
if (can_use_loaded_file) {
*file_ret = module->loaded_file;
err = drgn_module_find_eh_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
if (err != &drgn_not_found)
return err;
}
if (can_use_debug_file) {
*file_ret = module->debug_file;
return drgn_module_find_orc_cfi(module, pc, row_ret,
interrupted_ret,
ret_addr_regno_ret);
}
}
return &drgn_not_found;
}
#if !_ELFUTILS_PREREQ(0, 175)
static Elf *dwelf_elf_begin(int fd)
{
return elf_begin(fd, ELF_C_READ_MMAP_PRIVATE, NULL);
}
#endif
struct drgn_error *open_elf_file(const char *path, int *fd_ret, Elf **elf_ret)
{
struct drgn_error *err;
*fd_ret = open(path, O_RDONLY);
if (*fd_ret == -1)
return drgn_error_create_os("open", errno, path);
*elf_ret = dwelf_elf_begin(*fd_ret);
if (!*elf_ret) {
err = drgn_error_libelf();
goto err_fd;
}
if (elf_kind(*elf_ret) != ELF_K_ELF) {
err = drgn_error_create(DRGN_ERROR_OTHER, "not an ELF file");
goto err_elf;
}
return NULL;
err_elf:
elf_end(*elf_ret);
err_fd:
close(*fd_ret);
return err;
}
struct drgn_error *find_elf_file(char **path_ret, int *fd_ret, Elf **elf_ret,
const char * const *path_formats, ...)
{
struct drgn_error *err;
size_t i;
for (i = 0; path_formats[i]; i++) {
va_list ap;
int ret;
char *path;
int fd;
Elf *elf;
va_start(ap, path_formats);
ret = vasprintf(&path, path_formats[i], ap);
va_end(ap);
if (ret == -1)
return &drgn_enomem;
fd = open(path, O_RDONLY);
if (fd == -1) {
free(path);
continue;
}
elf = dwelf_elf_begin(fd);
if (!elf) {
close(fd);
free(path);
continue;
}
if (elf_kind(elf) != ELF_K_ELF) {
err = drgn_error_format(DRGN_ERROR_OTHER,
"%s: not an ELF file", path);
elf_end(elf);
close(fd);
free(path);
return err;
}
*path_ret = path;
*fd_ret = fd;
*elf_ret = elf;
return NULL;
}
*path_ret = NULL;
*fd_ret = -1;
*elf_ret = NULL;
return NULL;
}
/*
* Get the start address from the first loadable segment and the end address
* from the last loadable segment.
*
* The ELF specification states that loadable segments are sorted on p_vaddr.
* However, vmlinux on x86-64 has an out of order segment for .data..percpu, and
* Arm has a couple for .vector and .stubs. Thankfully, those are placed in the
* middle by the vmlinux linker script, so we can still rely on the first and
* last loadable segments.
*/
struct drgn_error *elf_address_range(Elf *elf, uint64_t bias,
uint64_t *start_ret, uint64_t *end_ret)
{
size_t phnum;
if (elf_getphdrnum(elf, &phnum) != 0)
return drgn_error_libelf();
GElf_Phdr phdr_mem, *phdr;
size_t i;
for (i = 0; i < phnum; i++) {
phdr = gelf_getphdr(elf, i, &phdr_mem);
if (!phdr)
return drgn_error_libelf();
if (phdr->p_type == PT_LOAD) {
uint64_t align = phdr->p_align ? phdr->p_align : 1;
*start_ret = (phdr->p_vaddr & -align) + bias;
break;
}
}
if (i >= phnum) {
/* There were no loadable segments. */
*start_ret = *end_ret = 0;
return NULL;
}
for (i = phnum; i-- > 0;) {
phdr = gelf_getphdr(elf, i, &phdr_mem);
if (!phdr)
return drgn_error_libelf();
if (phdr->p_type == PT_LOAD) {
*end_ret = (phdr->p_vaddr + phdr->p_memsz) + bias;
if (*start_ret >= *end_ret)
*start_ret = *end_ret = 0;
return NULL;
}
}
/* We found a loadable segment earlier, so this shouldn't happen. */
assert(!"PT_LOAD segment disappeared");
*end_ret = 0;
return NULL;
}
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