[PATCH] selftests: Fix asan linkage to work with clang

[Ryan Roberts <ryan.roberts@arm.com>]

Both fchmodat2 and openat2 statically link against libasan (for
explanation of why, look at the fixes commit). This is done using
`-static-libasan`. However, it turns out that clang uses a different
option, `-static-libsan`. This caused clang to fail to compile the
tests.

Fix this by using cc-option to figure out which variant to use.

While we are at it, stop passing helpers.h as a compilation unit. This
was causing another clang error due to name conflict with helpers.c's
object file. This header shouldn't be directly compiled anyway.

Fixes: c652df8a4a9d ("selftests: link libasan statically for tests with -fsanitize=address")
Reported-by: kernel test robot <yujie.liu@intel.com>
Closes: https://lore.kernel.org/r/202404141807.LgsqXPY5-lkp@intel.com/
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---

Applies on v6.9-rc4.

Thanks,
Ryan

 tools/testing/selftests/fchmodat2/Makefile | 5 ++++-
 tools/testing/selftests/openat2/Makefile   | 7 +++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/fchmodat2/Makefile b/tools/testing/selftests/fchmodat2/Makefile
index 71ec34bf1501..a68bb5a00797 100644
--- a/tools/testing/selftests/fchmodat2/Makefile
+++ b/tools/testing/selftests/fchmodat2/Makefile
@@ -1,6 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
+# We need this for the "cc-option" macro.
+include ../../../build/Build.include

-CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan $(KHDR_INCLUDES)
+CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined $(KHDR_INCLUDES)
+CFLAGS += $(call cc-option, -static-libasan) $(call cc-option, -static-libsan)
 TEST_GEN_PROGS := fchmodat2_test

 include ../lib.mk
diff --git a/tools/testing/selftests/openat2/Makefile b/tools/testing/selftests/openat2/Makefile
index 254d676a2689..02af9b6ca5eb 100644
--- a/tools/testing/selftests/openat2/Makefile
+++ b/tools/testing/selftests/openat2/Makefile
@@ -1,8 +1,11 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
+# We need this for the "cc-option" macro.
+include ../../../build/Build.include

-CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined -static-libasan
+CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
+CFLAGS += $(call cc-option, -static-libasan) $(call cc-option, -static-libsan)
 TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test

 include ../lib.mk

-$(TEST_GEN_PROGS): helpers.c helpers.h
+$(TEST_GEN_PROGS): helpers.c
--
2.25.1