From: Andrii Nakryiko <andriin@fb.com>
Date: Mon, 24 Feb 2020 16:08:47 -0800
Subject: selftests/bpf: Print backtrace on SIGSEGV in test_progs
Patch-mainline: v5.7-rc1
Git-commit: 9fb156bb82a33f01708fbbb8828836a4219efc3d
References: bsc#1177028
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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200225000847.3965188-1-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
tools/testing/selftests/bpf/Makefile | 2 +-
tools/testing/selftests/bpf/test_progs.c | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
--- 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
--- 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_na
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;