* [PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs
@ 2020-02-25 0:08 Andrii Nakryiko
2020-02-25 5:51 ` Song Liu
2020-02-25 21:58 ` Daniel Borkmann
0 siblings, 2 replies; 3+ messages in thread
From: Andrii Nakryiko @ 2020-02-25 0:08 UTC (permalink / raw)
To: bpf, netdev, ast, daniel; +Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko
Due to various bugs in tests clean up code (usually), if host system is
misconfigured, it happens that test_progs will just crash in the middle of
running a test with little to no indication of where and why the crash
happened. For cases where coredump is not readily available (e.g., inside
a CI), it's very helpful to have a stack trace, which lead to crash, to be
printed out. This change adds a signal handler that will capture and print out
symbolized backtrace:
$ sudo ./test_progs -t mmap
test_mmap:PASS:skel_open_and_load 0 nsec
test_mmap:PASS:bss_mmap 0 nsec
test_mmap:PASS:data_mmap 0 nsec
Caught signal #11!
Stack trace:
./test_progs(crash_handler+0x18)[0x42a888]
/lib64/libpthread.so.0(+0xf5d0)[0x7f2aab5175d0]
./test_progs(test_mmap+0x3c0)[0x41f0a0]
./test_progs(main+0x160)[0x407d10]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7f2aab15d3d5]
./test_progs[0x407ebc]
[1] 1988412 segmentation fault (core dumped) sudo ./test_progs -t mmap
Unfortunately, glibc's symbolization support is unable to symbolize static
functions, only global ones will be present in stack trace. But it's still a
step forward without adding extra libraries to get a better symbolization.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/testing/selftests/bpf/Makefile | 2 +-
tools/testing/selftests/bpf/test_progs.c | 25 ++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 2a583196fa51..50c63c21e6fd 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -20,7 +20,7 @@ CLANG ?= clang
LLC ?= llc
LLVM_OBJCOPY ?= llvm-objcopy
BPF_GCC ?= $(shell command -v bpf-gcc;)
-CFLAGS += -g -Wall -O2 $(GENFLAGS) -I$(CURDIR) -I$(APIDIR) \
+CFLAGS += -g -rdynamic -Wall -O2 $(GENFLAGS) -I$(CURDIR) -I$(APIDIR) \
-I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR) -I$(TOOLSINCDIR) \
-Dbpf_prog_load=bpf_prog_test_load \
-Dbpf_load_program=bpf_test_load_program
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index bab1e6f1d8f1..a969c77e9456 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -6,6 +6,8 @@
#include "bpf_rlimit.h"
#include <argp.h>
#include <string.h>
+#include <signal.h>
+#include <execinfo.h> /* backtrace */
/* defined in test_progs.h */
struct test_env env = {};
@@ -617,6 +619,23 @@ int cd_flavor_subdir(const char *exec_name)
return chdir(flavor);
}
+#define MAX_BACKTRACE_SZ 128
+void crash_handler(int signum)
+{
+ void *bt[MAX_BACKTRACE_SZ];
+ size_t sz;
+
+ sz = backtrace(bt, ARRAY_SIZE(bt));
+
+ if (env.test)
+ dump_test_log(env.test, true);
+ if (env.stdout)
+ stdio_restore();
+
+ fprintf(stderr, "Caught signal #%d!\nStack trace:\n", signum);
+ backtrace_symbols_fd(bt, sz, STDERR_FILENO);
+}
+
int main(int argc, char **argv)
{
static const struct argp argp = {
@@ -624,8 +643,14 @@ int main(int argc, char **argv)
.parser = parse_arg,
.doc = argp_program_doc,
};
+ struct sigaction sigact = {
+ .sa_handler = crash_handler,
+ .sa_flags = SA_RESETHAND,
+ };
int err, i;
+ sigaction(SIGSEGV, &sigact, NULL);
+
err = argp_parse(&argp, argc, argv, 0, NULL, &env);
if (err)
return err;
--
2.17.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs
2020-02-25 0:08 [PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs Andrii Nakryiko
@ 2020-02-25 5:51 ` Song Liu
2020-02-25 21:58 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Song Liu @ 2020-02-25 5:51 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, Networking, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Kernel Team
On Mon, Feb 24, 2020 at 4:09 PM Andrii Nakryiko <andriin@fb.com> wrote:
>
> Due to various bugs in tests clean up code (usually), if host system is
> misconfigured, it happens that test_progs will just crash in the middle of
> running a test with little to no indication of where and why the crash
> happened. For cases where coredump is not readily available (e.g., inside
> a CI), it's very helpful to have a stack trace, which lead to crash, to be
> printed out. This change adds a signal handler that will capture and print out
> symbolized backtrace:
>
> $ sudo ./test_progs -t mmap
> test_mmap:PASS:skel_open_and_load 0 nsec
> test_mmap:PASS:bss_mmap 0 nsec
> test_mmap:PASS:data_mmap 0 nsec
> Caught signal #11!
> Stack trace:
> ./test_progs(crash_handler+0x18)[0x42a888]
> /lib64/libpthread.so.0(+0xf5d0)[0x7f2aab5175d0]
> ./test_progs(test_mmap+0x3c0)[0x41f0a0]
> ./test_progs(main+0x160)[0x407d10]
> /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f2aab15d3d5]
> ./test_progs[0x407ebc]
> [1] 1988412 segmentation fault (core dumped) sudo ./test_progs -t mmap
>
> Unfortunately, glibc's symbolization support is unable to symbolize static
> functions, only global ones will be present in stack trace. But it's still a
> step forward without adding extra libraries to get a better symbolization.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs
2020-02-25 0:08 [PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs Andrii Nakryiko
2020-02-25 5:51 ` Song Liu
@ 2020-02-25 21:58 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2020-02-25 21:58 UTC (permalink / raw)
To: Andrii Nakryiko, bpf, netdev, ast; +Cc: andrii.nakryiko, kernel-team
On 2/25/20 1:08 AM, Andrii Nakryiko wrote:
> Due to various bugs in tests clean up code (usually), if host system is
> misconfigured, it happens that test_progs will just crash in the middle of
> running a test with little to no indication of where and why the crash
> happened. For cases where coredump is not readily available (e.g., inside
> a CI), it's very helpful to have a stack trace, which lead to crash, to be
> printed out. This change adds a signal handler that will capture and print out
> symbolized backtrace:
>
> $ sudo ./test_progs -t mmap
> test_mmap:PASS:skel_open_and_load 0 nsec
> test_mmap:PASS:bss_mmap 0 nsec
> test_mmap:PASS:data_mmap 0 nsec
> Caught signal #11!
> Stack trace:
> ./test_progs(crash_handler+0x18)[0x42a888]
> /lib64/libpthread.so.0(+0xf5d0)[0x7f2aab5175d0]
> ./test_progs(test_mmap+0x3c0)[0x41f0a0]
> ./test_progs(main+0x160)[0x407d10]
> /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f2aab15d3d5]
> ./test_progs[0x407ebc]
> [1] 1988412 segmentation fault (core dumped) sudo ./test_progs -t mmap
>
> Unfortunately, glibc's symbolization support is unable to symbolize static
> functions, only global ones will be present in stack trace. But it's still a
> step forward without adding extra libraries to get a better symbolization.
>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Applied, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-02-25 5:51 ` Song Liu
2020-02-25 21:58 ` Daniel Borkmann
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