linux/tools/testing/selftests/pidfd
Axel Rasmussen 4cbd93c3c1 pidfd: fix test failure due to stack overflow on some arches
When running the pidfd_fdinfo_test on arm64, it fails for me. After some
digging, the reason is that the child exits due to SIGBUS, because it
overflows the 1024 byte stack we've reserved for it.

To fix the issue, increase the stack size to 8192 bytes (this number is
somewhat arbitrary, and was arrived at through experimentation -- I kept
doubling until the failure no longer occurred).

Also, let's make the issue easier to debug. wait_for_pid() returns an
ambiguous value: it may return -1 in all of these cases:

1. waitpid() itself returned -1
2. waitpid() returned success, but we found !WIFEXITED(status).
3. The child process exited, but it did so with a -1 exit code.

There's no way for the caller to tell the difference. So, at least log
which occurred, so the test runner can debug things.

While debugging this, I found that we had !WIFEXITED(), because the
child exited due to a signal. This seems like a reasonably common case,
so also print out whether or not we have WIFSIGNALED(), and the
associated WTERMSIG() (if any). This lets us see the SIGBUS I'm fixing
clearly when it occurs.

Finally, I'm suspicious of allocating the child's stack on our stack.
man clone(2) suggests that the correct way to do this is with mmap(),
and in particular by setting MAP_STACK. So, switch to doing it that way
instead.

Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
2022-02-04 13:06:39 -07:00
..
.gitignore selftests/pidfd: add pidfd setns tests 2020-05-13 11:41:22 +02:00
config selftests: pidfd: add CONFIG_CHECKPOINT_RESTORE=y to config 2020-10-27 17:02:03 -06:00
Makefile selftests/pidfd: add pidfd setns tests 2020-05-13 11:41:22 +02:00
pidfd_fdinfo_test.c pidfd: fix test failure due to stack overflow on some arches 2022-02-04 13:06:39 -07:00
pidfd_getfd_test.c selftests: pidfd: skip test on kcmp() ENOSYS 2020-10-27 17:01:45 -06:00
pidfd_open_test.c selftests: pidfd: fix compilation errors due to wait.h 2020-10-27 16:51:36 -06:00
pidfd_poll_test.c selftests: pidfd: fix compilation errors due to wait.h 2020-10-27 16:51:36 -06:00
pidfd_setns_test.c selftests: pidfd: drop needless linux/kcmp.h inclusion in pidfd_setns_test.c 2020-10-27 17:04:01 -06:00
pidfd_test.c selftests: pidfd: use ksft_test_result_skip() when skipping test 2020-10-27 17:01:24 -06:00
pidfd_wait.c tests: remove O_NONBLOCK before waiting for WSTOPPED 2020-10-09 11:56:51 +02:00
pidfd.h pidfd: fix test failure due to stack overflow on some arches 2022-02-04 13:06:39 -07:00