[PATCH v2 bpf-next] selftests/bpf: print backtrace on SIGSEGV in test_progs
From: Andrii Nakryiko <hidden>
Date: 2020-02-25 00:08:58
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
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 <redacted> --- 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