[PATCH v2 1/2] kunit: add extra assertions to KUnit test cases

add extra assertions for each individual test case, that checks that
both `debug_locks` and `TAINT_WARN` are intact after the test is run.
The assertions are optional behind CONFIG_KUNIT_EXTRA_ASSERTS.

Signed-off-by: Malte Wechter <[email protected]>
---
 lib/kunit/Kconfig     | 12 ++++++++++++
 lib/kunit/try-catch.c | 23 ++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
index 94ff8e4089bfb..38801f7493669 100644
--- a/lib/kunit/Kconfig
+++ b/lib/kunit/Kconfig
@@ -142,4 +142,16 @@ config KUNIT_UML_PCI
 
 	  If unsure, say N.
 
+config KUNIT_EXTRA_ASSERTS
+	bool "Enable extra assertions in KUnit tests"
+	depends on LOCKDEP
+	default n
+	help
+		Enables all extra assertions for KUnit which includes asserting `TAINT_WARN` and
+		`debug_locks` from lockdep. A KUnit test suite (and test case) is inserted
+		at the start of all KUnit test suites. This makes assertions prior to running any
+		tests, as a pre-test integrity check. Assertions are made after each test case which
+		asserts that each test case did not trigger either `TAINT_WARN` or `debug_locks`.
+
+		If unsure, say N.
 endif # KUNIT
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
index d84a879f0a789..7eea3af4c9671 100644
--- a/lib/kunit/try-catch.c
+++ b/lib/kunit/try-catch.c
@@ -41,6 +41,11 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 	struct completion *task_done;
 	int exit_code, time_remaining;
 
+	#ifdef CONFIG_KUNIT_EXTRA_ASSERTS
+	int debug_locks_snapshot = debug_locks;
+	int tainted_warn_snapshot = test_taint(TAINT_WARN);
+	#endif
+
 	try_catch->context = context;
 	try_catch->try_result = 0;
 	task_struct = kthread_create(kunit_generic_run_threadfn_adapter,
@@ -70,7 +75,23 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 	put_task_struct(task_struct);
 	exit_code = try_catch->try_result;
 
-	if (!exit_code)
+	#ifdef CONFIG_KUNIT_EXTRA_ASSERTS
+	bool extra_assert = false;
+
+	if (debug_locks_snapshot != debug_locks && !exit_code) {
+		extra_assert = true;
+		try_catch->try_result = -EDEADLK;
+		kunit_err(test, "Test triggered lockdep\n");
+	} else if (tainted_warn_snapshot != test_taint(TAINT_WARN) && !exit_code) {
+		extra_assert = true;
+		try_catch->try_result = -EDEADLK;
+		kunit_err(test, "Test tainted kernel with TAINT_WARN\n");
+	}
+	#else
+	bool extra_assert = false;
+	#endif
+
+	if (!exit_code && !extra_assert)
 		return;
 
 	if (exit_code == -EFAULT)

-- 
2.51.2