[PATCH v5 3/5] Add unit tests to verify that warning backtrace suppression works.

[Alessandro Carminati <acarmina@redhat.com>]

From: Guenter Roeck <linux@roeck-us.net>

Add unit tests to verify that warning backtrace suppression works.

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.

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>
---
 lib/kunit/Makefile                     |   3 +
 lib/kunit/backtrace-suppression-test.c | 105 +++++++++++++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 lib/kunit/backtrace-suppression-test.c

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 3195e861d63c..05fb19d69709 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -23,6 +23,9 @@ obj-y +=				hooks.o \
 
 obj-$(CONFIG_KUNIT_TEST) +=		kunit-test.o
 obj-$(CONFIG_KUNIT_TEST) +=		platform-test.o
+ifeq ($(CONFIG_KUNIT_SUPPRESS_BACKTRACE),y)
+obj-$(CONFIG_KUNIT_TEST) +=		backtrace-suppression-test.o
+endif
 
 # string-stream-test compiles built-in only.
 ifeq ($(CONFIG_KUNIT_TEST),y)
diff --git a/lib/kunit/backtrace-suppression-test.c b/lib/kunit/backtrace-suppression-test.c
new file mode 100644
index 000000000000..a3d5991b9b15
--- /dev/null
+++ b/lib/kunit/backtrace-suppression-test.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for suppressing warning tracebacks
+ *
+ * Copyright (C) 2024, Guenter Roeck
+ * Author: Guenter Roeck <linux@roeck-us.net>
+ */
+
+#include <kunit/test.h>
+#include <linux/bug.h>
+
+static void backtrace_suppression_test_warn_direct(struct kunit *test)
+{
+	KUNIT_DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+	KUNIT_START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+	WARN(1, "This backtrace should be suppressed");
+	KUNIT_END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+	KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_direct), 1);
+}
+
+static void trigger_backtrace_warn(void)
+{
+	WARN(1, "This backtrace should be suppressed");
+}
+
+static void backtrace_suppression_test_warn_indirect(struct kunit *test)
+{
+	KUNIT_DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+	KUNIT_START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	trigger_backtrace_warn();
+	KUNIT_END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+	KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
+}
+
+static void backtrace_suppression_test_warn_multi(struct kunit *test)
+{
+	KUNIT_DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	KUNIT_DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+	KUNIT_START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+	KUNIT_START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	WARN(1, "This backtrace should be suppressed");
+	trigger_backtrace_warn();
+	KUNIT_END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+	KUNIT_END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+	KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_multi), 1);
+	KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 1);
+}
+
+static void backtrace_suppression_test_warn_on_direct(struct kunit *test)
+{
+	KUNIT_DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+
+	if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE) && !IS_ENABLED(CONFIG_KALLSYMS))
+		kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE or CONFIG_KALLSYMS");
+
+	KUNIT_START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+	WARN_ON(1);
+	KUNIT_END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+
+	KUNIT_EXPECT_EQ(test,
+			KUNIT_SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_on_direct), 1);
+}
+
+static void trigger_backtrace_warn_on(void)
+{
+	WARN_ON(1);
+}
+
+static void backtrace_suppression_test_warn_on_indirect(struct kunit *test)
+{
+	KUNIT_DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+	if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE))
+		kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE");
+
+	KUNIT_START_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+	trigger_backtrace_warn_on();
+	KUNIT_END_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+	KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn_on), 1);
+}
+
+static struct kunit_case backtrace_suppression_test_cases[] = {
+	KUNIT_CASE(backtrace_suppression_test_warn_direct),
+	KUNIT_CASE(backtrace_suppression_test_warn_indirect),
+	KUNIT_CASE(backtrace_suppression_test_warn_multi),
+	KUNIT_CASE(backtrace_suppression_test_warn_on_direct),
+	KUNIT_CASE(backtrace_suppression_test_warn_on_indirect),
+	{}
+};
+
+static struct kunit_suite backtrace_suppression_test_suite = {
+	.name = "backtrace-suppression-test",
+	.test_cases = backtrace_suppression_test_cases,
+};
+kunit_test_suites(&backtrace_suppression_test_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit test to verify warning backtrace suppression");
-- 
2.34.1