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Merge pull request #21580 from bluca/core_fork

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Switch coredump ELF parsing to fork+dlopen
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2021-11-30 21:49:53 +01:00 committed by GitHub
commit 4248b9f6a5
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GPG Key ID: 4AEE18F83AFDEB23
11 changed files with 702 additions and 438 deletions
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1
TODO
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@ -394,7 +394,6 @@ Features:
* make us use dynamically fewer deps for containers in general purpose distros:
o turn into dlopen() deps:
- elfutils (always)
- p11-kit-trust (always)
- kmod-libs (only when called from PID 1)
- libblkid (only in RootImage= handling in PID 1, but not elsewhere)

2
meson.build
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@ -2822,7 +2822,6 @@ if conf.get('ENABLE_COREDUMP') == 1
link_with : [libshared],
dependencies : [threads,
libacl,
libdw,
libxz,
liblz4,
libzstd],
@ -2851,7 +2850,6 @@ if conf.get('ENABLE_PSTORE') == 1
link_with : [libshared],
dependencies : [threads,
libacl,
libdw,
libxz,
liblz4,
libzstd],

15
src/coredump/coredump.c
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@ -7,11 +7,6 @@
#include <sys/xattr.h>
#include <unistd.h>
#if HAVE_ELFUTILS
#include <dwarf.h>
#include <elfutils/libdwfl.h>
#endif
#include "sd-daemon.h"
#include "sd-journal.h"
#include "sd-login.h"
@ -27,6 +22,7 @@
#include "copy.h"
#include "coredump-vacuum.h"
#include "dirent-util.h"
#include "elf-util.h"
#include "escape.h"
#include "fd-util.h"
#include "fileio.h"
@ -43,7 +39,6 @@
#include "signal-util.h"
#include "socket-util.h"
#include "special.h"
#include "stacktrace.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
@ -818,15 +813,17 @@ static int submit_coredump(
if (r < 0)
return log_error_errno(r, "Failed to drop privileges: %m");
#if HAVE_ELFUTILS
/* Try to get a stack trace if we can */
if (coredump_size > arg_process_size_max) {
log_debug("Not generating stack trace: core size %"PRIu64" is greater "
"than %"PRIu64" (the configured maximum)",
coredump_size, arg_process_size_max);
} else if (coredump_fd >= 0)
coredump_parse_core(coredump_fd, context->meta[META_EXE], &stacktrace, &json_metadata);
#endif
(void) parse_elf_object(coredump_fd,
context->meta[META_EXE],
/* fork_disable_dump= */endswith(context->meta[META_EXE], "systemd-coredump"), /* avoid loops */
&stacktrace,
&json_metadata);
log:
core_message = strjoina("Process ", context->meta[META_ARGV_PID],

6
src/coredump/meson.build
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@ -6,12 +6,6 @@ systemd_coredump_sources = files('''
coredump-vacuum.h
'''.split())
if conf.get('HAVE_ELFUTILS') == 1
systemd_coredump_sources += files(
'stacktrace.c',
'stacktrace.h')
endif
coredumpctl_sources = files('coredumpctl.c')
if conf.get('ENABLE_COREDUMP') == 1 and install_sysconfdir_samples

411
src/coredump/stacktrace.c
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@ -1,411 +0,0 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <dwarf.h>
#include <elfutils/libdwelf.h>
#include <elfutils/libdwfl.h>
#include <libelf.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "fileio.h"
#include "fd-util.h"
#include "format-util.h"
#include "hexdecoct.h"
#include "macro.h"
#include "stacktrace.h"
#include "string-util.h"
#include "util.h"
#define FRAMES_MAX 64
#define THREADS_MAX 64
#define ELF_PACKAGE_METADATA_ID 0xcafe1a7e
struct stack_context {
FILE *f;
Dwfl *dwfl;
Elf *elf;
unsigned n_thread;
unsigned n_frame;
JsonVariant **package_metadata;
Set **modules;
};
static int frame_callback(Dwfl_Frame *frame, void *userdata) {
struct stack_context *c = userdata;
Dwarf_Addr pc, pc_adjusted, bias = 0;
_cleanup_free_ Dwarf_Die *scopes = NULL;
const char *fname = NULL, *symbol = NULL;
Dwfl_Module *module;
bool is_activation;
uint64_t module_offset = 0;
assert(frame);
assert(c);
if (c->n_frame >= FRAMES_MAX)
return DWARF_CB_ABORT;
if (!dwfl_frame_pc(frame, &pc, &is_activation))
return DWARF_CB_ABORT;
pc_adjusted = pc - (is_activation ? 0 : 1);
module = dwfl_addrmodule(c->dwfl, pc_adjusted);
if (module) {
Dwarf_Die *s, *cudie;
int n;
Dwarf_Addr start;
cudie = dwfl_module_addrdie(module, pc_adjusted, &bias);
if (cudie) {
n = dwarf_getscopes(cudie, pc_adjusted - bias, &scopes);
for (s = scopes; s < scopes + n; s++) {
if (IN_SET(dwarf_tag(s), DW_TAG_subprogram, DW_TAG_inlined_subroutine, DW_TAG_entry_point)) {
Dwarf_Attribute *a, space;
a = dwarf_attr_integrate(s, DW_AT_MIPS_linkage_name, &space);
if (!a)
a = dwarf_attr_integrate(s, DW_AT_linkage_name, &space);
if (a)
symbol = dwarf_formstring(a);
if (!symbol)
symbol = dwarf_diename(s);
if (symbol)
break;
}
}
}
if (!symbol)
symbol = dwfl_module_addrname(module, pc_adjusted);
fname = dwfl_module_info(module, NULL, &start, NULL, NULL, NULL, NULL, NULL);
module_offset = pc - start;
}
fprintf(c->f, "#%-2u 0x%016" PRIx64 " %s (%s + 0x%" PRIx64 ")\n", c->n_frame, (uint64_t) pc, strna(symbol), strna(fname), module_offset);
c->n_frame++;
return DWARF_CB_OK;
}
static int thread_callback(Dwfl_Thread *thread, void *userdata) {
struct stack_context *c = userdata;
pid_t tid;
assert(thread);
assert(c);
if (c->n_thread >= THREADS_MAX)
return DWARF_CB_ABORT;
if (c->n_thread != 0)
fputc('\n', c->f);
c->n_frame = 0;
tid = dwfl_thread_tid(thread);
fprintf(c->f, "Stack trace of thread " PID_FMT ":\n", tid);
if (dwfl_thread_getframes(thread, frame_callback, c) < 0)
return DWARF_CB_ABORT;
c->n_thread++;
return DWARF_CB_OK;
}
static int parse_package_metadata(const char *name, JsonVariant *id_json, Elf *elf, struct stack_context *c) {
size_t n_program_headers;
int r;
assert(name);
assert(elf);
assert(c);
/* When iterating over PT_LOAD we will visit modules more than once */
if (set_contains(*c->modules, name))
return 0;
r = elf_getphdrnum(elf, &n_program_headers);
if (r < 0) /* Not the handle we are looking for - that's ok, skip it */
return 0;
/* Iterate over all program headers in that ELF object. These will have been copied by
* the kernel verbatim when the core file is generated. */
for (size_t i = 0; i < n_program_headers; ++i) {
size_t note_offset = 0, name_offset, desc_offset;
GElf_Phdr mem, *program_header;
GElf_Nhdr note_header;
Elf_Data *data;
/* Package metadata is in PT_NOTE headers. */
program_header = gelf_getphdr(elf, i, &mem);
if (!program_header || program_header->p_type != PT_NOTE)
continue;
/* Fortunately there is an iterator we can use to walk over the
* elements of a PT_NOTE program header. We are interested in the
* note with type. */
data = elf_getdata_rawchunk(elf,
program_header->p_offset,
program_header->p_filesz,
ELF_T_NHDR);
if (!data)
continue;
while (note_offset < data->d_size &&
(note_offset = gelf_getnote(data, note_offset, &note_header, &name_offset, &desc_offset)) > 0) {
const char *note_name = (const char *)data->d_buf + name_offset;
const char *payload = (const char *)data->d_buf + desc_offset;
if (note_header.n_namesz == 0 || note_header.n_descsz == 0)
continue;
/* Package metadata might have different owners, but the
* magic ID is always the same. */
if (note_header.n_type == ELF_PACKAGE_METADATA_ID) {
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *w = NULL;
r = json_parse(payload, 0, &v, NULL, NULL);
if (r < 0)
return log_error_errno(r, "json_parse on %s failed: %m", payload);
/* First pretty-print to the buffer, so that the metadata goes as
* plaintext in the journal. */
fprintf(c->f, "Metadata for module %s owned by %s found: ",
name, note_name);
json_variant_dump(v, JSON_FORMAT_NEWLINE|JSON_FORMAT_PRETTY, c->f, NULL);
fputc('\n', c->f);
/* Secondly, if we have a build-id, merge it in the same JSON object
* so that it appears all nicely together in the logs/metadata. */
if (id_json) {
r = json_variant_merge(&v, id_json);
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
}
/* Then we build a new object using the module name as the key, and merge it
* with the previous parses, so that in the end it all fits together in a single
* JSON blob. */
r = json_build(&w, JSON_BUILD_OBJECT(JSON_BUILD_PAIR(name, JSON_BUILD_VARIANT(v))));
if (r < 0)
return log_error_errno(r, "Failed to build JSON object: %m");
r = json_variant_merge(c->package_metadata, w);
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
/* Finally stash the name, so we avoid double visits. */
r = set_put_strdup(c->modules, name);
if (r < 0)
return log_error_errno(r, "set_put_strdup failed: %m");
return 1;
}
}
}
/* Didn't find package metadata for this module - that's ok, just go to the next. */
return 0;
}
static int module_callback(Dwfl_Module *mod, void **userdata, const char *name, Dwarf_Addr start, void *arg) {
_cleanup_(json_variant_unrefp) JsonVariant *id_json = NULL;
struct stack_context *c = arg;
size_t n_program_headers;
GElf_Addr id_vaddr, bias;
const unsigned char *id;
int id_len, r;
Elf *elf;
assert(mod);
assert(c);
if (!name)
name = "(unnamed)"; /* For logging purposes */
/* We are iterating on each "module", which is what dwfl calls ELF objects contained in the
* core file, and extracting the build-id first and then the package metadata.
* We proceed in a best-effort fashion - not all ELF objects might contain both or either.
* The build-id is easy, as libdwfl parses it during the dwfl_core_file_report() call and
* stores it separately in an internal library struct. */
id_len = dwfl_module_build_id(mod, &id, &id_vaddr);
if (id_len <= 0)
/* If we don't find a build-id, note it in the journal message, and try
* anyway to find the package metadata. It's unlikely to have the latter
* without the former, but there's no hard rule. */
fprintf(c->f, "Found module %s without build-id.\n", name);
else {
JsonVariant *build_id;
/* We will later parse package metadata json and pass it to our caller. Prepare the
* build-id in json format too, so that it can be appended and parsed cleanly. It
* will then be added as metadata to the journal message with the stack trace. */
r = json_build(&id_json, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("buildId", JSON_BUILD_HEX(id, id_len))));
if (r < 0) {
log_error_errno(r, "json_build on build-id failed: %m");
return DWARF_CB_ABORT;
}
build_id = json_variant_by_key(id_json, "buildId");
assert_se(build_id);
fprintf(c->f, "Found module %s with build-id: %s\n", name, json_variant_string(build_id));
}
/* The .note.package metadata is more difficult. From the module, we need to get a reference
* to the ELF object first. We might be lucky and just get it from elfutils. */
elf = dwfl_module_getelf(mod, &bias);
if (elf) {
r = parse_package_metadata(name, id_json, elf, c);
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
return DWARF_CB_OK;
} else
elf = c->elf;
/* We did not get the ELF object, or it's just a reference to the core. That is likely
* because we didn't get direct access to the executable, and the version of elfutils does
* not yet support parsing it out of the core file directly.
* So fallback to manual extraction - get the PT_LOAD section from the core,
* and if it's the right one we can interpret it as an Elf object, and parse
* its notes manually. */
r = elf_getphdrnum(elf, &n_program_headers);
if (r < 0) {
log_warning("Could not parse number of program headers from core file: %s",
elf_errmsg(-1)); /* -1 retrieves the most recent error */
return DWARF_CB_OK;
}
for (size_t i = 0; i < n_program_headers; ++i) {
GElf_Phdr mem, *program_header;
Elf_Data *data;
/* The core file stores the ELF files in the PT_LOAD segment. */
program_header = gelf_getphdr(elf, i, &mem);
if (!program_header || program_header->p_type != PT_LOAD)
continue;
/* Now get a usable Elf reference, and parse the notes from it. */
data = elf_getdata_rawchunk(elf,
program_header->p_offset,
program_header->p_filesz,
ELF_T_NHDR);
if (!data)
continue;
Elf *memelf = elf_memory(data->d_buf, data->d_size);
if (!memelf)
continue;
r = parse_package_metadata(name, id_json, memelf, c);
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
break;
}
return DWARF_CB_OK;
}
static int parse_core(int fd, const char *executable, char **ret, JsonVariant **ret_package_metadata) {
static const Dwfl_Callbacks callbacks = {
.find_elf = dwfl_build_id_find_elf,
.section_address = dwfl_offline_section_address,
.find_debuginfo = dwfl_standard_find_debuginfo,
};
_cleanup_(json_variant_unrefp) JsonVariant *package_metadata = NULL;
_cleanup_(set_freep) Set *modules = NULL;
struct stack_context c = {
.package_metadata = &package_metadata,
.modules = &modules,
};
char *buf = NULL;
size_t sz = 0;
int r;
assert(fd >= 0);
assert(ret);
if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
return -errno;
c.f = open_memstream_unlocked(&buf, &sz);
if (!c.f)
return -ENOMEM;
elf_version(EV_CURRENT);
c.elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
if (!c.elf) {
r = -EINVAL;
goto finish;
}
c.dwfl = dwfl_begin(&callbacks);
if (!c.dwfl) {
r = -EINVAL;
goto finish;
}
if (dwfl_core_file_report(c.dwfl, c.elf, executable) < 0) {
r = -EINVAL;
goto finish;
}
if (dwfl_report_end(c.dwfl, NULL, NULL) != 0) {
r = -EINVAL;
goto finish;
}
if (dwfl_getmodules(c.dwfl, &module_callback, &c, 0) < 0) {
r = -EINVAL;
goto finish;
}
if (dwfl_core_file_attach(c.dwfl, c.elf) < 0) {
r = -EINVAL;
goto finish;
}
if (dwfl_getthreads(c.dwfl, thread_callback, &c) < 0) {
r = -EINVAL;
goto finish;
}
c.f = safe_fclose(c.f);
*ret = TAKE_PTR(buf);
if (ret_package_metadata)
*ret_package_metadata = TAKE_PTR(package_metadata);
r = 0;
finish:
if (c.dwfl)
dwfl_end(c.dwfl);
if (c.elf)
elf_end(c.elf);
safe_fclose(c.f);
free(buf);
return r;
}
void coredump_parse_core(int fd, const char *executable, char **ret, JsonVariant **ret_package_metadata) {
int r;
r = parse_core(fd, executable, ret, ret_package_metadata);
if (r == -EINVAL)
log_warning("Failed to generate stack trace: %s", dwfl_errmsg(dwfl_errno()));
else if (r < 0)
log_warning_errno(r, "Failed to generate stack trace: %m");
}

6
src/coredump/stacktrace.h
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@ -1,6 +0,0 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "json.h"
void coredump_parse_core(int fd, const char *executable, char **ret, JsonVariant **ret_package_metadata);

677
src/shared/elf-util.c Normal file
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@ -0,0 +1,677 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#if HAVE_ELFUTILS
#include <dwarf.h>
#include <elfutils/libdwelf.h>
#include <elfutils/libdwfl.h>
#include <libelf.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <unistd.h>
#include "alloc-util.h"
#include "dlfcn-util.h"
#include "elf-util.h"
#include "errno-util.h"
#include "fileio.h"
#include "fd-util.h"
#include "format-util.h"
#include "hexdecoct.h"
#include "io-util.h"
#include "macro.h"
#include "process-util.h"
#include "rlimit-util.h"
#include "string-util.h"
#include "util.h"
#define FRAMES_MAX 64
#define THREADS_MAX 64
#define ELF_PACKAGE_METADATA_ID 0xcafe1a7e
static void *dw_dl = NULL;
static void *elf_dl = NULL;
/* libdw symbols */
Dwarf_Attribute *(*sym_dwarf_attr_integrate)(Dwarf_Die *, unsigned int, Dwarf_Attribute *);
const char *(*sym_dwarf_diename)(Dwarf_Die *);
const char *(*sym_dwarf_formstring)(Dwarf_Attribute *);
int (*sym_dwarf_getscopes)(Dwarf_Die *, Dwarf_Addr, Dwarf_Die **);
int (*sym_dwarf_getscopes_die)(Dwarf_Die *, Dwarf_Die **);
Elf *(*sym_dwelf_elf_begin)(int);
ssize_t (*sym_dwelf_elf_gnu_build_id)(Elf *, const void **);
int (*sym_dwarf_tag)(Dwarf_Die *);
Dwfl_Module *(*sym_dwfl_addrmodule)(Dwfl *, Dwarf_Addr);
Dwfl *(*sym_dwfl_begin)(const Dwfl_Callbacks *);
int (*sym_dwfl_build_id_find_elf)(Dwfl_Module *, void **, const char *, Dwarf_Addr, char **, Elf **);
int (*sym_dwfl_core_file_attach)(Dwfl *, Elf *);
int (*sym_dwfl_core_file_report)(Dwfl *, Elf *, const char *);
void (*sym_dwfl_end)(Dwfl *);
const char *(*sym_dwfl_errmsg)(int);
int (*sym_dwfl_errno)(void);
bool (*sym_dwfl_frame_pc)(Dwfl_Frame *, Dwarf_Addr *, bool *);
ptrdiff_t (*sym_dwfl_getmodules)(Dwfl *, int (*)(Dwfl_Module *, void **, const char *, Dwarf_Addr, void *), void *, ptrdiff_t);
int (*sym_dwfl_getthreads)(Dwfl *, int (*)(Dwfl_Thread *, void *), void *);
Dwarf_Die *(*sym_dwfl_module_addrdie)(Dwfl_Module *, Dwarf_Addr, Dwarf_Addr *);
const char *(*sym_dwfl_module_addrname)(Dwfl_Module *, GElf_Addr);
int (*sym_dwfl_module_build_id)(Dwfl_Module *, const unsigned char **, GElf_Addr *);
Elf *(*sym_dwfl_module_getelf)(Dwfl_Module *, GElf_Addr *);
const char *(*sym_dwfl_module_info)(Dwfl_Module *, void ***, Dwarf_Addr *, Dwarf_Addr *, Dwarf_Addr *, Dwarf_Addr *, const char **, const char **);
int (*sym_dwfl_offline_section_address)(Dwfl_Module *, void **, const char *, Dwarf_Addr, const char *, GElf_Word, const GElf_Shdr *, Dwarf_Addr *);
int (*sym_dwfl_report_end)(Dwfl *, int (*)(Dwfl_Module *, void *, const char *, Dwarf_Addr, void *), void *);
int (*sym_dwfl_standard_find_debuginfo)(Dwfl_Module *, void **, const char *, Dwarf_Addr, const char *, const char *, GElf_Word, char **);
int (*sym_dwfl_thread_getframes)(Dwfl_Thread *, int (*)(Dwfl_Frame *, void *), void *);
pid_t (*sym_dwfl_thread_tid)(Dwfl_Thread *);
/* libelf symbols */
Elf *(*sym_elf_begin)(int, Elf_Cmd, Elf *);
int (*sym_elf_end)(Elf *);
Elf_Data *(*sym_elf_getdata_rawchunk)(Elf *, int64_t, size_t, Elf_Type);
GElf_Ehdr *(*sym_gelf_getehdr)(Elf *, GElf_Ehdr *);
int (*sym_elf_getphdrnum)(Elf *, size_t *);
const char *(*sym_elf_errmsg)(int);
int (*sym_elf_errno)(void);
Elf *(*sym_elf_memory)(char *, size_t);
unsigned int (*sym_elf_version)(unsigned int);
GElf_Phdr *(*sym_gelf_getphdr)(Elf *, int, GElf_Phdr *);
size_t (*sym_gelf_getnote)(Elf_Data *, size_t, GElf_Nhdr *, size_t *, size_t *);
static int dlopen_dw(void) {
int r;
r = dlopen_many_sym_or_warn(
&dw_dl, "libdw.so.1", LOG_DEBUG,
DLSYM_ARG(dwarf_getscopes),
DLSYM_ARG(dwarf_getscopes_die),
DLSYM_ARG(dwarf_tag),
DLSYM_ARG(dwarf_attr_integrate),
DLSYM_ARG(dwarf_formstring),
DLSYM_ARG(dwarf_diename),
DLSYM_ARG(dwelf_elf_gnu_build_id),
DLSYM_ARG(dwelf_elf_begin),
DLSYM_ARG(dwfl_addrmodule),
DLSYM_ARG(dwfl_frame_pc),
DLSYM_ARG(dwfl_module_addrdie),
DLSYM_ARG(dwfl_module_addrname),
DLSYM_ARG(dwfl_module_info),
DLSYM_ARG(dwfl_module_build_id),
DLSYM_ARG(dwfl_module_getelf),
DLSYM_ARG(dwfl_begin),
DLSYM_ARG(dwfl_core_file_report),
DLSYM_ARG(dwfl_report_end),
DLSYM_ARG(dwfl_getmodules),
DLSYM_ARG(dwfl_core_file_attach),
DLSYM_ARG(dwfl_end),
DLSYM_ARG(dwfl_errmsg),
DLSYM_ARG(dwfl_errno),
DLSYM_ARG(dwfl_build_id_find_elf),
DLSYM_ARG(dwfl_standard_find_debuginfo),
DLSYM_ARG(dwfl_thread_tid),
DLSYM_ARG(dwfl_thread_getframes),
DLSYM_ARG(dwfl_getthreads),
DLSYM_ARG(dwfl_offline_section_address));
if (r <= 0)
return r;
return 1;
}
static int dlopen_elf(void) {
int r;
r = dlopen_many_sym_or_warn(
&elf_dl, "libelf.so.1", LOG_DEBUG,
DLSYM_ARG(elf_begin),
DLSYM_ARG(elf_end),
DLSYM_ARG(elf_getphdrnum),
DLSYM_ARG(elf_getdata_rawchunk),
DLSYM_ARG(elf_errmsg),
DLSYM_ARG(elf_errno),
DLSYM_ARG(elf_memory),
DLSYM_ARG(elf_version),
DLSYM_ARG(gelf_getehdr),
DLSYM_ARG(gelf_getphdr),
DLSYM_ARG(gelf_getnote));
if (r <= 0)
return r;
return 1;
}
typedef struct StackContext {
FILE *f;
Dwfl *dwfl;
Elf *elf;
unsigned n_thread;
unsigned n_frame;
JsonVariant **package_metadata;
Set **modules;
} StackContext;
static StackContext* stack_context_destroy(StackContext *c) {
if (!c)
return NULL;
c->f = safe_fclose(c->f);
if (c->dwfl) {
sym_dwfl_end(c->dwfl);
c->dwfl = NULL;
}
if (c->elf) {
sym_elf_end(c->elf);
c->elf = NULL;
}
return NULL;
}
DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(Elf *, sym_elf_end, NULL);
static int frame_callback(Dwfl_Frame *frame, void *userdata) {
StackContext *c = userdata;
Dwarf_Addr pc, pc_adjusted, bias = 0;
_cleanup_free_ Dwarf_Die *scopes = NULL;
const char *fname = NULL, *symbol = NULL;
Dwfl_Module *module;
bool is_activation;
uint64_t module_offset = 0;
assert(frame);
assert(c);
if (c->n_frame >= FRAMES_MAX)
return DWARF_CB_ABORT;
if (!sym_dwfl_frame_pc(frame, &pc, &is_activation))
return DWARF_CB_ABORT;
pc_adjusted = pc - (is_activation ? 0 : 1);
module = sym_dwfl_addrmodule(c->dwfl, pc_adjusted);
if (module) {
Dwarf_Die *s, *cudie;
int n;
Dwarf_Addr start;
cudie = sym_dwfl_module_addrdie(module, pc_adjusted, &bias);
if (cudie) {
n = sym_dwarf_getscopes(cudie, pc_adjusted - bias, &scopes);
if (n > 0)
for (s = scopes; s && s < scopes + n; s++) {
if (IN_SET(sym_dwarf_tag(s), DW_TAG_subprogram, DW_TAG_inlined_subroutine, DW_TAG_entry_point)) {
Dwarf_Attribute *a, space;
a = sym_dwarf_attr_integrate(s, DW_AT_MIPS_linkage_name, &space);
if (!a)
a = sym_dwarf_attr_integrate(s, DW_AT_linkage_name, &space);
if (a)
symbol = sym_dwarf_formstring(a);
if (!symbol)
symbol = sym_dwarf_diename(s);
if (symbol)
break;
}
}
}
if (!symbol)
symbol = sym_dwfl_module_addrname(module, pc_adjusted);
fname = sym_dwfl_module_info(module, NULL, &start, NULL, NULL, NULL, NULL, NULL);
module_offset = pc - start;
}
if (c->f)
fprintf(c->f, "#%-2u 0x%016" PRIx64 " %s (%s + 0x%" PRIx64 ")\n", c->n_frame, (uint64_t) pc, strna(symbol), strna(fname), module_offset);
c->n_frame++;
return DWARF_CB_OK;
}
static int thread_callback(Dwfl_Thread *thread, void *userdata) {
StackContext *c = userdata;
pid_t tid;
assert(thread);
assert(c);
if (c->n_thread >= THREADS_MAX)
return DWARF_CB_ABORT;
if (c->n_thread != 0 && c->f)
fputc('\n', c->f);
c->n_frame = 0;
if (c->f) {
tid = sym_dwfl_thread_tid(thread);
fprintf(c->f, "Stack trace of thread " PID_FMT ":\n", tid);
}
if (sym_dwfl_thread_getframes(thread, frame_callback, c) < 0)
return DWARF_CB_ABORT;
c->n_thread++;
return DWARF_CB_OK;
}
static int parse_package_metadata(const char *name, JsonVariant *id_json, Elf *elf, StackContext *c) {
size_t n_program_headers;
int r;
assert(name);
assert(elf);
assert(c);
/* When iterating over PT_LOAD we will visit modules more than once */
if (set_contains(*c->modules, name))
return 0;
r = sym_elf_getphdrnum(elf, &n_program_headers);
if (r < 0) /* Not the handle we are looking for - that's ok, skip it */
return 0;
/* Iterate over all program headers in that ELF object. These will have been copied by
* the kernel verbatim when the core file is generated. */
for (size_t i = 0; i < n_program_headers; ++i) {
size_t note_offset = 0, name_offset, desc_offset;
GElf_Phdr mem, *program_header;
GElf_Nhdr note_header;
Elf_Data *data;
/* Package metadata is in PT_NOTE headers. */
program_header = sym_gelf_getphdr(elf, i, &mem);
if (!program_header || program_header->p_type != PT_NOTE)
continue;
/* Fortunately there is an iterator we can use to walk over the
* elements of a PT_NOTE program header. We are interested in the
* note with type. */
data = sym_elf_getdata_rawchunk(elf,
program_header->p_offset,
program_header->p_filesz,
ELF_T_NHDR);
if (!data)
continue;
while (note_offset < data->d_size &&
(note_offset = sym_gelf_getnote(data, note_offset, &note_header, &name_offset, &desc_offset)) > 0) {
const char *note_name = (const char *)data->d_buf + name_offset;
const char *payload = (const char *)data->d_buf + desc_offset;
if (note_header.n_namesz == 0 || note_header.n_descsz == 0)
continue;
/* Package metadata might have different owners, but the
* magic ID is always the same. */
if (note_header.n_type == ELF_PACKAGE_METADATA_ID) {
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *w = NULL;
r = json_parse(payload, 0, &v, NULL, NULL);
if (r < 0)
return log_error_errno(r, "json_parse on %s failed: %m", payload);
/* First pretty-print to the buffer, so that the metadata goes as
* plaintext in the journal. */
if (c->f) {
fprintf(c->f, "Metadata for module %s owned by %s found: ",
name, note_name);
json_variant_dump(v, JSON_FORMAT_NEWLINE|JSON_FORMAT_PRETTY, c->f, NULL);
fputc('\n', c->f);
}
/* Secondly, if we have a build-id, merge it in the same JSON object
* so that it appears all nicely together in the logs/metadata. */
if (id_json) {
r = json_variant_merge(&v, id_json);
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
}
/* Then we build a new object using the module name as the key, and merge it
* with the previous parses, so that in the end it all fits together in a single
* JSON blob. */
r = json_build(&w, JSON_BUILD_OBJECT(JSON_BUILD_PAIR(name, JSON_BUILD_VARIANT(v))));
if (r < 0)
return log_error_errno(r, "Failed to build JSON object: %m");
r = json_variant_merge(c->package_metadata, w);
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
/* Finally stash the name, so we avoid double visits. */
r = set_put_strdup(c->modules, name);
if (r < 0)
return log_error_errno(r, "set_put_strdup failed: %m");
return 1;
}
}
}
/* Didn't find package metadata for this module - that's ok, just go to the next. */
return 0;
}
/* Get the build-id out of an ELF object or a dwarf core module. */
static int parse_buildid(Dwfl_Module *mod, Elf *elf, const char *name, StackContext *c, JsonVariant **ret_id_json) {
_cleanup_(json_variant_unrefp) JsonVariant *id_json = NULL;
const unsigned char *id;
GElf_Addr id_vaddr;
ssize_t id_len;
int r;
assert(mod || elf);
assert(c);
if (mod)
id_len = sym_dwfl_module_build_id(mod, &id, &id_vaddr);
else
id_len = sym_dwelf_elf_gnu_build_id(elf, (const void **)&id);
if (id_len <= 0) {
/* If we don't find a build-id, note it in the journal message, and try
* anyway to find the package metadata. It's unlikely to have the latter
* without the former, but there's no hard rule. */
if (c->f)
fprintf(c->f, "Module %s without build-id.\n", name);
} else {
/* We will later parse package metadata json and pass it to our caller. Prepare the
* build-id in json format too, so that it can be appended and parsed cleanly. It
* will then be added as metadata to the journal message with the stack trace. */
r = json_build(&id_json, JSON_BUILD_OBJECT(JSON_BUILD_PAIR("buildId", JSON_BUILD_HEX(id, id_len))));
if (r < 0)
return log_error_errno(r, "json_build on build-id failed: %m");
if (c->f) {
JsonVariant *build_id = json_variant_by_key(id_json, "buildId");
assert(build_id);
fprintf(c->f, "Module %s with build-id %s\n", name, json_variant_string(build_id));
}
}
if (ret_id_json)
*ret_id_json = TAKE_PTR(id_json);
return 0;
}
static int module_callback(Dwfl_Module *mod, void **userdata, const char *name, Dwarf_Addr start, void *arg) {
_cleanup_(json_variant_unrefp) JsonVariant *id_json = NULL;
StackContext *c = arg;
size_t n_program_headers;
GElf_Addr bias;
int r;
Elf *elf;
assert(mod);
assert(c);
if (!name)
name = "(unnamed)"; /* For logging purposes */
/* We are iterating on each "module", which is what dwfl calls ELF objects contained in the
* core file, and extracting the build-id first and then the package metadata.
* We proceed in a best-effort fashion - not all ELF objects might contain both or either.
* The build-id is easy, as libdwfl parses it during the sym_dwfl_core_file_report() call and
* stores it separately in an internal library struct. */
r = parse_buildid(mod, NULL, name, c, &id_json);
if (r < 0)
return DWARF_CB_ABORT;
/* The .note.package metadata is more difficult. From the module, we need to get a reference
* to the ELF object first. We might be lucky and just get it from elfutils. */
elf = sym_dwfl_module_getelf(mod, &bias);
if (elf) {
r = parse_package_metadata(name, id_json, elf, c);
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
return DWARF_CB_OK;
} else
elf = c->elf;
/* We did not get the ELF object, or it's just a reference to the core. That is likely
* because we didn't get direct access to the executable, and the version of elfutils does
* not yet support parsing it out of the core file directly.
* So fallback to manual extraction - get the PT_LOAD section from the core,
* and if it's the right one we can interpret it as an Elf object, and parse
* its notes manually. */
r = sym_elf_getphdrnum(elf, &n_program_headers);
if (r < 0) {
log_warning("Could not parse number of program headers from core file: %s",
sym_elf_errmsg(-1)); /* -1 retrieves the most recent error */
return DWARF_CB_OK;
}
for (size_t i = 0; i < n_program_headers; ++i) {
GElf_Phdr mem, *program_header;
Elf_Data *data;
/* The core file stores the ELF files in the PT_LOAD segment. */
program_header = sym_gelf_getphdr(elf, i, &mem);
if (!program_header || program_header->p_type != PT_LOAD)
continue;
/* Now get a usable Elf reference, and parse the notes from it. */
data = sym_elf_getdata_rawchunk(elf,
program_header->p_offset,
program_header->p_filesz,
ELF_T_NHDR);
if (!data)
continue;
_cleanup_(sym_elf_endp) Elf *memelf = sym_elf_memory(data->d_buf, data->d_size);
if (!memelf)
continue;
r = parse_package_metadata(name, id_json, memelf, c);
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
break;
}
return DWARF_CB_OK;
}
static int parse_core(int fd, const char *executable, char **ret, JsonVariant **ret_package_metadata) {
const Dwfl_Callbacks callbacks = {
.find_elf = sym_dwfl_build_id_find_elf,
.section_address = sym_dwfl_offline_section_address,
.find_debuginfo = sym_dwfl_standard_find_debuginfo,
};
_cleanup_(json_variant_unrefp) JsonVariant *package_metadata = NULL;
_cleanup_(set_freep) Set *modules = NULL;
_cleanup_free_ char *buf = NULL; /* buf should be freed last, c.f closed first (via stack_context_destroy) */
_cleanup_(stack_context_destroy) StackContext c = {
.package_metadata = &package_metadata,
.modules = &modules,
};
size_t sz = 0;
int r;
assert(fd >= 0);
if (lseek(fd, 0, SEEK_SET) == (off_t) -1)
return log_warning_errno(errno, "Failed to seek to beginning of the core file: %m");
if (ret) {
c.f = open_memstream_unlocked(&buf, &sz);
if (!c.f)
return log_oom();
}
sym_elf_version(EV_CURRENT);
c.elf = sym_elf_begin(fd, ELF_C_READ_MMAP, NULL);
if (!c.elf)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, elf_begin() failed: %s", sym_elf_errmsg(sym_elf_errno()));
c.dwfl = sym_dwfl_begin(&callbacks);
if (!c.dwfl)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_begin() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (sym_dwfl_core_file_report(c.dwfl, c.elf, executable) < 0)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_core_file_report() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (sym_dwfl_report_end(c.dwfl, NULL, NULL) != 0)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_report_end() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (sym_dwfl_getmodules(c.dwfl, &module_callback, &c, 0) < 0)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_getmodules() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (sym_dwfl_core_file_attach(c.dwfl, c.elf) < 0)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_core_file_attach() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (sym_dwfl_getthreads(c.dwfl, thread_callback, &c) < 0)
return log_warning_errno(SYNTHETIC_ERRNO(EINVAL), "Could not parse core file, dwfl_getthreads() failed: %s", sym_dwfl_errmsg(sym_dwfl_errno()));
if (ret) {
r = fflush_and_check(c.f);
if (r < 0)
return log_warning_errno(r, "Could not parse core file, flushing file buffer failed: %m");
c.f = safe_fclose(c.f);
*ret = TAKE_PTR(buf);
}
if (ret_package_metadata)
*ret_package_metadata = TAKE_PTR(package_metadata);
return 0;
}
int parse_elf_object(int fd, const char *executable, bool fork_disable_dump, char **ret, JsonVariant **ret_package_metadata) {
_cleanup_close_pair_ int error_pipe[2] = { -1, -1 }, return_pipe[2] = { -1, -1 }, json_pipe[2] = { -1, -1 };
_cleanup_(json_variant_unrefp) JsonVariant *package_metadata = NULL;
_cleanup_free_ char *buf = NULL;
int r;
r = dlopen_dw();
if (r < 0)
return r;
r = dlopen_elf();
if (r < 0)
return r;
r = RET_NERRNO(pipe2(error_pipe, O_CLOEXEC|O_NONBLOCK));
if (r < 0)
return r;
if (ret) {
r = RET_NERRNO(pipe2(return_pipe, O_CLOEXEC));
if (r < 0)
return r;
}
if (ret_package_metadata) {
r = RET_NERRNO(pipe2(json_pipe, O_CLOEXEC));
if (r < 0)
return r;
}
/* Parsing possibly malformed data is crash-happy, so fork. In case we crash,
* the core file will not be lost, and the messages will still be attached to
* the journal. Reading the elf object might be slow, but it still has an upper
* bound since the core files have an upper size limit. It's also not doing any
* system call or interacting with the system in any way, besides reading from
* the file descriptor and writing into these four pipes. */
r = safe_fork_full("(sd-parse-elf)",
(int[]){ fd, error_pipe[1], return_pipe[1], json_pipe[1] },
4,
FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE|FORK_NEW_USERNS|FORK_WAIT|FORK_REOPEN_LOG,
NULL);
if (r < 0) {
if (r == -EPROTO) { /* We should have the errno from the child, but don't clobber original error */
int e, k;
k = read(error_pipe[0], &e, sizeof(e));
if (k < 0 && errno != EAGAIN) /* Pipe is non-blocking, EAGAIN means there's nothing */
return -errno;
if (k == sizeof(e))
return e; /* propagate error sent to us from child */
if (k != 0)
return -EIO;
}
return r;
}
if (r == 0) {
/* We want to avoid loops, given this can be called from systemd-coredump */
if (fork_disable_dump)
prctl(PR_SET_DUMPABLE, 0);
r = parse_core(fd, executable, ret ? &buf : NULL, ret_package_metadata ? &package_metadata : NULL);
if (r < 0)
goto child_fail;
if (buf) {
r = loop_write(return_pipe[1], buf, strlen(buf), false);
if (r < 0)
goto child_fail;
return_pipe[1] = safe_close(return_pipe[1]);
}
if (package_metadata) {
_cleanup_fclose_ FILE *json_out = NULL;
json_out = take_fdopen(&json_pipe[1], "w");
if (!json_out) {
r = -errno;
goto child_fail;
}
json_variant_dump(package_metadata, JSON_FORMAT_FLUSH, json_out, NULL);
}
_exit(EXIT_SUCCESS);
child_fail:
(void) write(error_pipe[1], &r, sizeof(r));
_exit(EXIT_FAILURE);
}
error_pipe[1] = safe_close(error_pipe[1]);
return_pipe[1] = safe_close(return_pipe[1]);
json_pipe[1] = safe_close(json_pipe[1]);
if (ret) {
_cleanup_fclose_ FILE *in = NULL;
in = take_fdopen(&return_pipe[0], "r");
if (!in)
return -errno;
r = read_full_stream(in, &buf, NULL);
if (r < 0)
return r;
}
if (ret_package_metadata) {
_cleanup_fclose_ FILE *json_in = NULL;
json_in = take_fdopen(&json_pipe[0], "r");
if (!json_in)
return -errno;
r = json_parse_file(json_in, NULL, 0, &package_metadata, NULL, NULL);
if (r < 0 && r != -EINVAL) /* EINVAL: json was empty, so we got nothing, but that's ok */
return r;
}
if (ret)
*ret = TAKE_PTR(buf);
if (ret_package_metadata)
*ret_package_metadata = TAKE_PTR(package_metadata);
return 0;
}
#endif

15
src/shared/elf-util.h Normal file
View File

@ -0,0 +1,15 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include "json.h"
#if HAVE_ELFUTILS
/* Parse an ELF object in a forked process, so that errors while iterating over
* untrusted and potentially malicious data do not propagate to the main caller's process.
* If fork_disable_dump, the child process will not dump core if it crashes. */
int parse_elf_object(int fd, const char *executable, bool fork_disable_dump, char **ret, JsonVariant **ret_package_metadata);
#else
static inline int parse_elf_object(int fd, const char *executable, bool fork_disable_dump, char **ret, JsonVariant **ret_package_metadata) {
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "elfutils disabled, parsing ELF objects not supported");
}
#endif

2
src/shared/meson.build
View File

@ -107,6 +107,8 @@ shared_sources = files('''
dropin.h
efi-loader.c
efi-loader.h
elf-util.c
elf-util.h
enable-mempool.c
env-file-label.c
env-file-label.h

2
test/test-functions
View File

@ -1174,7 +1174,7 @@ install_missing_libraries() {
local lib path
# A number of dependencies is now optional via dlopen, so the install
# script will not pick them up, since it looks at linkage.
for lib in libcryptsetup libidn libidn2 pwquality libqrencode tss2-esys tss2-rc tss2-mu libfido2 libbpf; do
for lib in libcryptsetup libidn libidn2 pwquality libqrencode tss2-esys tss2-rc tss2-mu libfido2 libbpf libelf libdw; do
ddebug "Searching for $lib via pkg-config"
if pkg-config --exists "$lib"; then
path="$(pkg-config --variable=libdir "$lib")"

3
units/systemd-coredump@.service.in
View File

@ -35,11 +35,10 @@ ProtectKernelTunables=yes
ProtectKernelLogs=yes
ProtectSystem=strict
RestrictAddressFamilies=AF_UNIX
RestrictNamespaces=yes
RestrictRealtime=yes
RestrictSUIDSGID=yes
RuntimeMaxSec=5min
StateDirectory=systemd/coredump
SystemCallArchitectures=native
SystemCallErrorNumber=EPERM
SystemCallFilter=@system-service
SystemCallFilter=@system-service @mount