kunit: Handle test faults

Previously, when a kernel test thread crashed (e.g. NULL pointer
dereference, general protection fault), the KUnit test hanged for 30
seconds and exited with a timeout error.

Fix this issue by waiting on task_struct->vfork_done instead of the
custom kunit_try_catch.try_completion, and track the execution state by
initially setting try_result with -EINTR and only setting it to 0 if
the test passed.

Fix kunit_generic_run_threadfn_adapter() signature by returning 0
instead of calling kthread_complete_and_exit().  Because thread's exit
code is never checked, always set it to 0 to make it clear.  To make
this explicit, export kthread_exit() for KUnit tests built as module.

Fix the -EINTR error message, which couldn't be reached until now.

This is tested with a following patch.

Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Gow <davidgow@google.com>
Tested-by: Rae Moar <rmoar@google.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240408074625.65017-5-mic@digikod.net
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/kthread.c b/kernel/kthread.c
index c5e40830c1f2..f7be976ff88a 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -315,6 +315,7 @@ void __noreturn kthread_exit(long result)
 	kthread->result = result;
 	do_exit(0);
 }
+EXPORT_SYMBOL(kthread_exit);
 
 /**
  * kthread_complete_and_exit - Exit the current kthread.