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selftests/bpf: Print backtrace on SIGSEGV in test_progs

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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
This commit is contained in:
Andrii Nakryiko
2020-02-24 16:08:47 -08:00
committed by Daniel Borkmann
parent e0360423d0
commit 9fb156bb82
2 changed files with 26 additions and 1 deletions
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25
tools/testing/selftests/bpf/test_progs.c
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@@ -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;