| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <aDjBtuxyumBrn70B@x1>
Date: Thu, 29 May 2025 17:21:10 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>,
Kan Liang <kan.liang@...ux.intel.com>,
James Clark <james.clark@...aro.org>,
Howard Chu <howardchu95@...il.com>,
Yicong Yang <yangyicong@...ilicon.com>,
Michael Petlan <mpetlan@...hat.com>,
Andi Kleen <ak@...ux.intel.com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
"Dr. David Alan Gilbert" <linux@...blig.org>,
Krzysztof Łopatowski <krzysztof.m.lopatowski@...il.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] perf debug: Add function symbols to dump_stack
On Wed, May 28, 2025 at 10:23:22PM -0700, Ian Rogers wrote:
> Symbolize stack traces by creating a live machine. Add this
> functionality to dump_stack and switch dump_stack users to use
> it. Switch TUI to use it. Add stack traces to the child test function
> which can be useful to diagnose blocked code.
>
> Example output:
> ```
> 8: PERF_RECORD_* events & perf_sample fields : Running (1 active)
> ^C
> Signal (2) while running tests.
> Terminating tests with the same signal
> Internal test harness failure. Completing any started tests:
> : 8: PERF_RECORD_* events & perf_sample fields:
So you are testing it with:
root@...ber:~# perf test PERF_RECORD
8: PERF_RECORD_* events & perf_sample fields : Running (1 active)
^C
Signal (2) while running tests.
Terminating tests with the same signal
Internal test harness failure. Completing any started tests:
8: PERF_RECORD_* events & perf_sample fields : Skip (permissions)
root@...ber:~#
?
I built it with DEBUG=1 and without, and with your patch, following your
example output, I'm not being able to reproduce.
Tried it as well with:
⬢ [acme@...lbx perf-tools-next]$ cat segv.patch
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 8b30c6f16a9eeac1..e55d86f1097d6d79 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -402,6 +402,8 @@ static struct symbol *symbols__find(struct rb_root_cached *symbols, u64 ip)
{
struct rb_node *n;
+ *(int *)NULL = 0;
+
if (symbols == NULL)
return NULL;
⬢ [acme@...lbx perf-tools-next]$ patch -p1 < segv.patch
patching file tools/perf/util/symbol.c
⬢ [acme@...lbx perf-tools-next]$ m
rm: cannot remove '/home/acme/libexec/perf-core/scripts/python/Perf-Trace-Util/lib/Perf/Trace/__pycache__/Core.cpython-313.pyc': Permission denied
make: Entering directory '/home/acme/git/perf-tools-next/tools/perf'
BUILD: Doing 'make -j32' parallel build
Warning: Kernel ABI header differences:
diff -u tools/arch/arm64/include/asm/cputype.h arch/arm64/include/asm/cputype.h
Auto-detecting system features:
... libdw: [ on ]
... glibc: [ on ]
... libelf: [ on ]
... libnuma: [ on ]
... numa_num_possible_cpus: [ on ]
... libperl: [ on ]
... libpython: [ on ]
... libcrypto: [ on ]
... libcapstone: [ on ]
... llvm-perf: [ on ]
... zlib: [ on ]
... lzma: [ on ]
... get_cpuid: [ on ]
... bpf: [ on ]
... libaio: [ on ]
... libzstd: [ on ]
INSTALL libsubcmd_headers
INSTALL libperf_headers
INSTALL libapi_headers
INSTALL libsymbol_headers
INSTALL libbpf_headers
CC /tmp/build/perf-tools-next/util/symbol.o
LD /tmp/build/perf-tools-next/util/perf-util-in.o
LD /tmp/build/perf-tools-next/perf-util-in.o
AR /tmp/build/perf-tools-next/libperf-util.a
LINK /tmp/build/perf-tools-next/perf
GEN /tmp/build/perf-tools-next/python/perf.cpython-313-x86_64-linux-gnu.so
INSTALL binaries
INSTALL tests
INSTALL libperf-jvmti.so
INSTALL libexec
INSTALL perf-archive
INSTALL perf-iostat
INSTALL perl-scripts
INSTALL python-scripts
INSTALL dlfilters
INSTALL perf_completion-script
INSTALL perf-tip
make: Leaving directory '/home/acme/git/perf-tools-next/tools/perf'
18: 'import perf' in python : Ok
⬢ [acme@...lbx perf-tools-next]$
root@...ber:~# perf top
perf: Segmentation fault
-------- backtrace --------
Segmentation fault (core dumped)
root@...ber:~#
Tried also with this, but probably something else is at play:
root@...ber:~# perf probe -x ~/bin/perf dump_stack
Added new event:
probe_perf:dump_stack (on dump_stack in /home/acme/bin/perf)
You can now use it in all perf tools, such as:
perf record -e probe_perf:dump_stack -aR sleep 1
root@...ber:~#
root@...ber:~# perf trace -e probe_perf:dump_stack/max-stack=16/ perf top
perf: Segmentation fault
-------- backtrace --------
root@...ber:~#
Running perf trace on a separate terminal it also doesn't catch
dump_stack being called (that probe point).
root@...ber:~# perf top --stdio
PerfTop: 0 irqs/sec kernel: 0.0% exact: 0.0% lost: 0/0 drop: 0/0 [4000Hz cycles:P], (all, 32 CPUs)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------
perf: Segmentation fault
Segmentation fault (core dumped)
root@...ber:~#
root@...ber:~# nm ~/bin/perf | grep dump_stack
0000000000637eaa T __dump_stack
00000000006380fa T dump_stack
000000000063816b T sighandler_dump_stack
root@...ber:~#
⬢ [acme@...lbx perf-tools-next]$ rpm -q glibc
glibc-2.41-5.fc42.x86_64
root@...ber:~# uname -a
Linux number 6.14.8-300.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Thu May 22 19:26:02 UTC 2025 x86_64 GNU/Linux
root@...ber:~#
What am I missing?
- Arnaldo
> ____ unexpected signal (2) ____
> #0 0x5590fb6209b6 in child_test_sig_handler builtin-test.c:243
> #1 0x7f4a91e49e20 in __restore_rt libc_sigaction.c:0
> #2 0x7f4a91ee4f33 in clock_nanosleep@...BC_2.2.5 clock_nanosleep.c:71
> #3 0x7f4a91ef0333 in __nanosleep nanosleep.c:26
> #4 0x7f4a91f01f68 in __sleep sleep.c:55
> #5 0x5590fb638c63 in test__PERF_RECORD perf-record.c:295
> #6 0x5590fb620b43 in run_test_child builtin-test.c:269
> #7 0x5590fb5b83ab in start_command run-command.c:127
> #8 0x5590fb621572 in start_test builtin-test.c:467
> #9 0x5590fb621a47 in __cmd_test builtin-test.c:573
> #10 0x5590fb6225ea in cmd_test builtin-test.c:775
> #11 0x5590fb5a9099 in run_builtin perf.c:351
> #12 0x5590fb5a9340 in handle_internal_command perf.c:404
> #13 0x5590fb5a9499 in run_argv perf.c:451
> #14 0x5590fb5a97e2 in main perf.c:558
> #15 0x7f4a91e33d68 in __libc_start_call_main libc_start_call_main.h:74
> #16 0x7f4a91e33e25 in __libc_start_main@@GLIBC_2.34 libc-start.c:128
> #17 0x5590fb4fd6d1 in _start perf[436d1]
> ```
>
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
> v2: Fix NO_BACKTRACE=1 build (Arnaldo)
> ---
> tools/perf/tests/builtin-test.c | 15 +++++++-
> tools/perf/ui/tui/setup.c | 2 +-
> tools/perf/util/debug.c | 68 +++++++++++++++++++++++++++------
> tools/perf/util/debug.h | 1 +
> 4 files changed, 73 insertions(+), 13 deletions(-)
>
> diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> index 45d3d8b3317a..80375ca39a37 100644
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -6,6 +6,9 @@
> */
> #include <fcntl.h>
> #include <errno.h>
> +#ifdef HAVE_BACKTRACE_SUPPORT
> +#include <execinfo.h>
> +#endif
> #include <poll.h>
> #include <unistd.h>
> #include <setjmp.h>
> @@ -231,6 +234,16 @@ static jmp_buf run_test_jmp_buf;
>
> static void child_test_sig_handler(int sig)
> {
> +#ifdef HAVE_BACKTRACE_SUPPORT
> + void *stackdump[32];
> + size_t stackdump_size;
> +#endif
> +
> + fprintf(stderr, "\n---- unexpected signal (%d) ----\n", sig);
> +#ifdef HAVE_BACKTRACE_SUPPORT
> + stackdump_size = backtrace(stackdump, ARRAY_SIZE(stackdump));
> + __dump_stack(stderr, stackdump, stackdump_size);
> +#endif
> siglongjmp(run_test_jmp_buf, sig);
> }
>
> @@ -244,7 +257,7 @@ static int run_test_child(struct child_process *process)
>
> err = sigsetjmp(run_test_jmp_buf, 1);
> if (err) {
> - fprintf(stderr, "\n---- unexpected signal (%d) ----\n", err);
> + /* Received signal. */
> err = err > 0 ? -err : -1;
> goto err_out;
> }
> diff --git a/tools/perf/ui/tui/setup.c b/tools/perf/ui/tui/setup.c
> index 16c6eff4d241..022534eed68c 100644
> --- a/tools/perf/ui/tui/setup.c
> +++ b/tools/perf/ui/tui/setup.c
> @@ -108,7 +108,7 @@ static void ui__signal_backtrace(int sig)
>
> printf("-------- backtrace --------\n");
> size = backtrace(stackdump, ARRAY_SIZE(stackdump));
> - backtrace_symbols_fd(stackdump, size, STDOUT_FILENO);
> + __dump_stack(stdout, stackdump, size);
>
> exit(0);
> }
> diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c
> index f9ef7d045c92..0c7c6a9e158b 100644
> --- a/tools/perf/util/debug.c
> +++ b/tools/perf/util/debug.c
> @@ -14,11 +14,18 @@
> #ifdef HAVE_BACKTRACE_SUPPORT
> #include <execinfo.h>
> #endif
> +#include "addr_location.h"
> #include "color.h"
> -#include "event.h"
> #include "debug.h"
> +#include "event.h"
> +#include "machine.h"
> +#include "map.h"
> #include "print_binary.h"
> +#include "srcline.h"
> +#include "symbol.h"
> +#include "synthetic-events.h"
> #include "target.h"
> +#include "thread.h"
> #include "trace-event.h"
> #include "ui/helpline.h"
> #include "ui/ui.h"
> @@ -298,21 +305,60 @@ void perf_debug_setup(void)
> libapi_set_print(pr_warning_wrapper, pr_warning_wrapper, pr_debug_wrapper);
> }
>
> +void __dump_stack(FILE *file, void **stackdump, size_t stackdump_size)
> +{
> + /* TODO: async safety. printf, malloc, etc. aren't safe inside a signal handler. */
> + pid_t pid = getpid();
> + struct machine *machine = machine__new_live(/*kernel_maps=*/false, pid);
> + struct thread *thread = NULL;
> +
> + if (machine)
> + thread = machine__find_thread(machine, pid, pid);
> +
> +#ifdef HAVE_BACKTRACE_SUPPORT
> + if (!machine || !thread) {
> + /*
> + * Backtrace functions are async signal safe. Fall back on them
> + * if machine/thread creation fails.
> + */
> + backtrace_symbols_fd(stackdump, stackdump_size, fileno(file));
> + machine__delete(machine);
> + return;
> + }
> +#endif
> +
> + for (size_t i = 0; i < stackdump_size; i++) {
> + struct addr_location al;
> + u64 addr = (u64)stackdump[i];
> + bool printed = false;
> +
> + addr_location__init(&al);
> + if (thread && thread__find_map(thread, PERF_RECORD_MISC_USER, addr, &al)) {
> + al.sym = map__find_symbol(al.map, al.addr);
> + if (al.sym) {
> + fprintf(file, " #%zd %p in %s ", i, stackdump[i], al.sym->name);
> + printed = true;
> + }
> + }
> + if (!printed)
> + fprintf(file, " #%zd %p ", i, stackdump[i]);
> +
> + map__fprintf_srcline(al.map, al.addr, "", file);
> + fprintf(file, "\n");
> + addr_location__exit(&al);
> + }
> + thread__put(thread);
> + machine__delete(machine);
> +}
> +
> /* Obtain a backtrace and print it to stdout. */
> #ifdef HAVE_BACKTRACE_SUPPORT
> void dump_stack(void)
> {
> - void *array[16];
> - size_t size = backtrace(array, ARRAY_SIZE(array));
> - char **strings = backtrace_symbols(array, size);
> - size_t i;
> -
> - printf("Obtained %zd stack frames.\n", size);
> -
> - for (i = 0; i < size; i++)
> - printf("%s\n", strings[i]);
> + void *stackdump[32];
> + size_t size = backtrace(stackdump, ARRAY_SIZE(stackdump));
>
> - free(strings);
> + __dump_stack(stdout, stackdump, size);
> }
> #else
> void dump_stack(void) {}
> diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h
> index a4026d1fd6a3..6b737e195ce1 100644
> --- a/tools/perf/util/debug.h
> +++ b/tools/perf/util/debug.h
> @@ -85,6 +85,7 @@ void debug_set_display_time(bool set);
> void perf_debug_setup(void);
> int perf_quiet_option(void);
>
> +void __dump_stack(FILE *file, void **stackdump, size_t stackdump_size);
> void dump_stack(void);
> void sighandler_dump_stack(int sig);
>
> --
> 2.49.0.1204.g71687c7c1d-goog
>
Powered by blists - more mailing lists