[PATCH] kselftest/coredump: reintroduce null pointer dereference

[Emanuele Rocca <emanuele.rocca@arm.com>]

Commit 673a55cc49da replaced the null pointer dereference used in
crashing_child() with __builtin_trap to address the following LLVM warnings:

 coredump_test_helpers.c:59:6: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference]
 coredump_test_helpers.c:59:6: note: consider using __builtin_trap() or qualifying pointer with 'volatile'

All coredump tests expect crashing_child() to result in a SIGSEGV. However, the
behavior of __builtin_trap is architecture-dependent. On x86 it yields SIGILL,
on aarch64 SIGTRAP. Given that neither of those signals are SIGSEGV, both
coredump_socket_test and coredump_socket_protocol_test are currently failing:

 get_pidfd_info: mask=0xd7, coredump_mask=0x5, coredump_signal=5
 socket_coredump_signal_sigsegv: coredump_signal=5, expected SIGSEGV=11

Qualify the pointer with volatile instead of calling __builtin_trap to fix the
tests.

Signed-off-by: Emanuele Rocca <emanuele.rocca@arm.com>
---
 tools/testing/selftests/coredump/coredump_test_helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c
index 5c8adee63641..2c850e0b1b57 100644
--- a/tools/testing/selftests/coredump/coredump_test_helpers.c
+++ b/tools/testing/selftests/coredump/coredump_test_helpers.c
@@ -56,7 +56,7 @@ void crashing_child(void)
 		pthread_create(&thread, NULL, do_nothing, NULL);
 
 	/* crash on purpose */
-	__builtin_trap();
+	i = *(volatile int *)NULL;
 }
 
 int create_detached_tmpfs(void)
-- 
2.43.0