selftests/bpf: Print backtrace on SIGSEGV in test_progs (9fb156bb) · Commits · 戴 / test

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

tools/testing/selftests/bpf/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -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

tools/testing/selftests/bpf/test_progs.c

+25 −0

Original line number	Diff line number	Diff line
		@@ -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;

Admin message