kunit: Add backtrace suppression self-tests

Add unit tests to verify that warning backtrace suppression works.

Tests cover both API forms:
- Scoped: kunit_warning_suppress() with in-block count verification
  and post-block inactivity check.
- Direct functions: kunit_start/end_suppress_warning() with
  sequential independent suppression blocks and per-block counts.

Furthermore, tests verify incremental warning counting, that
kunit_has_active_suppress_warning() transitions correctly around
suppression boundaries, and that suppression active in the test
kthread does not leak to a separate kthread.

If backtrace suppression does _not_ work, the unit tests will likely
trigger unsuppressed backtraces, which should actually help to get
the affected architectures / platforms fixed.

Link: https://lore.kernel.org/r/20260514-kunit_add_support-v11-2-b36a530a6d8f@redhat.com
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Acked-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Alessandro Carminati <acarmina@redhat.com>
Reviewed-by: David Gow <david@davidgow.net>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 4592f9d0aa8d..2e8a6b71a2ab 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -22,6 +22,7 @@ obj-$(if $(CONFIG_KUNIT),y) +=		hooks.o
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
 obj-$(CONFIG_KUNIT_TEST) +=		platform-test.o
+obj-$(CONFIG_KUNIT_TEST) +=		backtrace-suppression-test.o
 
 # string-stream-test compiles built-in only.
 ifeq ($(CONFIG_KUNIT_TEST),y)