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.

Signed-off-by: Guenter Roeck <li...@roeck-us.net>
---
 lib/kunit/Makefile                     |   3 +-
 lib/kunit/backtrace-suppression-test.c | 104 +++++++++++++++++++++++++
 2 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 lib/kunit/backtrace-suppression-test.c

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 545b57c3be48..6a44d2b54ea9 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -19,7 +19,8 @@ endif
 obj-y +=                               hooks.o \
                                        bug.o
 
-obj-$(CONFIG_KUNIT_TEST) +=            kunit-test.o
+obj-$(CONFIG_KUNIT_TEST) +=            kunit-test.o \
+                                       backtrace-suppression-test.o
 
 # 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..47c619283802
--- /dev/null
+++ b/lib/kunit/backtrace-suppression-test.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for suppressing warning tracebacks
+ *
+ * Copyright (C) 2024, Guenter Roeck
+ * Author: Guenter Roeck <li...@roeck-us.net>
+ */
+
+#include <kunit/test.h>
+#include <linux/bug.h>
+
+static void backtrace_suppression_test_warn_direct(struct kunit *test)
+{
+       DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+       WARN(1, "This backtrace should be suppressed");
+       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_direct);
+
+       KUNIT_EXPECT_EQ(test, 
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)
+{
+       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+       START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+       trigger_backtrace_warn();
+       END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+
+       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 
1);
+}
+
+static void backtrace_suppression_test_warn_multi(struct kunit *test)
+{
+       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn);
+       DEFINE_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+       START_SUPPRESSED_WARNING(trigger_backtrace_warn);
+       WARN(1, "This backtrace should be suppressed");
+       trigger_backtrace_warn();
+       END_SUPPRESSED_WARNING(trigger_backtrace_warn);
+       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_multi);
+
+       KUNIT_EXPECT_EQ(test, 
SUPPRESSED_WARNING_COUNT(backtrace_suppression_test_warn_multi), 1);
+       KUNIT_EXPECT_EQ(test, SUPPRESSED_WARNING_COUNT(trigger_backtrace_warn), 
1);
+}
+
+static void backtrace_suppression_test_warn_on_direct(struct kunit *test)
+{
+       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");
+
+       START_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+       WARN_ON(1);
+       END_SUPPRESSED_WARNING(backtrace_suppression_test_warn_on_direct);
+
+       KUNIT_EXPECT_EQ(test,
+                       
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)
+{
+       DEFINE_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+       if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE))
+               kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE");
+
+       START_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+       trigger_backtrace_warn_on();
+       END_SUPPRESSED_WARNING(trigger_backtrace_warn_on);
+
+       KUNIT_EXPECT_EQ(test, 
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");
-- 
2.39.2

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