> On Feb 22, 2020, at 9:43 PM, Andrii Nakryiko <andriin@xxxxxx> wrote:
>
> Due to various bugs in test 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@xxxxxx>
> ---
> tools/testing/selftests/bpf/Makefile | 2 +-
> tools/testing/selftests/bpf/test_progs.c | 26 ++++++++++++++++++++++++
> 2 files changed, 27 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..531ab3e7e5e5 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 +619,22 @@ 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);
> + 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 +642,16 @@ 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;
>
> + env.stdout = stdout;
> + env.stderr = stderr;
We have the same code in stdio_hijack(). Maybe remove those in
stdio_hijack()?
> + sigaction(SIGSEGV, &sigact, NULL);
> +
> err = argp_parse(&argp, argc, argv, 0, NULL, &env);
> if (err)
> return err;
> --
> 2.17.1
>
