[PATCH v4 4/4] selftest: Taint kernel when test module loaded

[David Gow <davidgow@google.com>]

Make any kselftest test module (using the kselftest_module framework)
taint the kernel with TAINT_TEST on module load.

Note that several selftests use kernel modules which are not based on
the kselftest_module framework, and so will not automatically taint the
kernel.

This can be done in two ways:
- Moving the module to the tools/testing directory. All modules under
  this directory will taint the kernel.
- Adding the 'test' module property with:
  MODULE_INFO(test, "Y")

Similarly, selftests which do not load modules into the kernel generally
should not taint the kernel (or possibly should only do so on failure),
as it's assumed that testing from user-space should be safe. Regardless,
they can write to /proc/sys/kernel/tainted if required.

Signed-off-by: David Gow <davidgow@google.com>
---

This still only covers a subset of selftest modules, but combined with
the modpost check for the tools/testing path, it should catch many
future tests. Others can be moved, adapted to use this framework, or
have MODULE_INFO(test, "Y") added. (Alas, I don't have the time to hunt
down all of the tests which don't do this at the moment.

No changes since v3:
https://lore.kernel.org/lkml/20220513083212.3537869-3-davidgow@google.com/

---
 tools/testing/selftests/kselftest_module.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/kselftest_module.h b/tools/testing/selftests/kselftest_module.h
index e2ea41de3f35..226e616b82e0 100644
--- a/tools/testing/selftests/kselftest_module.h
+++ b/tools/testing/selftests/kselftest_module.h
@@ -3,6 +3,7 @@
 #define __KSELFTEST_MODULE_H
 
 #include <linux/module.h>
+#include <linux/panic.h>
 
 /*
  * Test framework for writing test modules to be loaded by kselftest.
@@ -41,6 +42,7 @@ static inline int kstm_report(unsigned int total_tests, unsigned int failed_test
 static int __init __module##_init(void)			\
 {							\
 	pr_info("loaded.\n");				\
+	add_taint(TAINT_KUNIT, LOCKDEP_STILL_OK);	\
 	selftest();					\
 	return kstm_report(total_tests, failed_tests, skipped_tests);	\
 }							\
-- 
2.37.0.rc0.161.g10f37bed90-goog