[PATCH] kasan: Enable KUnit integration whenever CONFIG_KUNIT is enabled

[David Gow <davidgow@google.com>]

Enable the KASAN/KUnit integration even when the KASAN tests are
disabled, as it's useful for testing other things under KASAN.
Essentially, this reverts commit 49d9977ac909 ("kasan: check CONFIG_KASAN_KUNIT_TEST instead of CONFIG_KUNIT").

To mitigate the performance impact slightly, add a likely() to the check
for a currently running test.

There's more we can do for performance if/when it becomes more of a
problem, such as only enabling the "expect a KASAN failure" support wif
the KASAN tests are enabled, or putting the whole thing behind a "kunit
tests are running" static branch (which I do plan to do eventually).

Fixes: 49d9977ac909 ("kasan: check CONFIG_KASAN_KUNIT_TEST instead of CONFIG_KUNIT")
Signed-off-by: David Gow <davidgow@google.com>
---

Basically, hiding the KASAN/KUnit integration broke being able to just
pass --kconfig_add CONFIG_KASAN=y to kunit_tool to enable KASAN
integration. We didn't notice this, because usually
CONFIG_KUNIT_ALL_TESTS is enabled, which in turn enables
CONFIG_KASAN_KUNIT_TEST. However, using a separate .kunitconfig might
result in failures being missed.

Take, for example:
./tools/testing/kunit/kunit.py run --kconfig_add CONFIG_KASAN=y \
	--kunitconfig drivers/gpu/drm/tests

This should run the drm tests with KASAN enabled, but even if there's a
KASAN failure (such as the one fixed by [1]), kunit_tool will report
success.

[1]: https://lore.kernel.org/dri-devel/20221019073239.3779180-1-davidgow@google.com/

---
 mm/kasan/kasan.h  | 2 +-
 mm/kasan/report.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index abbcc1b0eec5..afacef14c7f4 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -261,7 +261,7 @@ struct kasan_stack_ring {
 
 #endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
 
-#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
+#if IS_ENABLED(CONFIG_KUNIT)
 /* Used in KUnit-compatible KASAN tests. */
 struct kunit_kasan_status {
 	bool report_found;
diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index df3602062bfd..efa063b9d093 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -114,7 +114,7 @@ EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
 
 #endif
 
-#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
+#if IS_ENABLED(CONFIG_KUNIT)
 static void update_kunit_status(bool sync)
 {
 	struct kunit *test;
@@ -122,7 +122,7 @@ static void update_kunit_status(bool sync)
 	struct kunit_kasan_status *status;
 
 	test = current->kunit_test;
-	if (!test)
+	if (likely(!test))
 		return;
 
 	resource = kunit_find_named_resource(test, "kasan_status");
-- 
2.38.0.413.g74048e4d9e-goog