[PATCH v7 3/5] kunit: Add backtrace suppression self-tests

Albert Esteve
2026-04-20T12:29:15Z

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

Add unit tests to verify that warning backtrace suppression works,
covering WARN() and WARN_ON() with direct calls, indirect calls
through helper functions, and multiple warnings in a single window.

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>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
---
lib/kunit/Makefile | 3 ++
lib/kunit/backtrace-suppression-test.c | 90 ++++++++++++++++++++++++++++++++++
2 files changed, 93 insertions(+)

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index fe177ff3ebdef..b2f2b8ada7b71 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -23,6 +23,9 @@ obj-$(if $(CONFIG_KUNIT),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 0000000000000..2ba5dcb5fef35
--- /dev/null
+++ b/lib/kunit/backtrace-suppression-test.c
@@ -0,0 +1,90 @@
+// 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_START_SUPPRESSED_WARNING(test);
+ WARN(1, "This backtrace should be suppressed");
+ KUNIT_END_SUPPRESSED_WARNING(test);
+
+ KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(), 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_START_SUPPRESSED_WARNING(test);
+ trigger_backtrace_warn();
+ KUNIT_END_SUPPRESSED_WARNING(test);
+
+ KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(), 1);
+}
+
+static void backtrace_suppression_test_warn_multi(struct kunit *test)
+{
+ KUNIT_START_SUPPRESSED_WARNING(test);
+ WARN(1, "This backtrace should be suppressed");
+ trigger_backtrace_warn();
+ KUNIT_END_SUPPRESSED_WARNING(test);
+
+ KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(), 2);
+}
+
+static void backtrace_suppression_test_warn_on_direct(struct kunit *test)
+{
+ if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE) && !IS_ENABLED(CONFIG_KALLSYMS))
+ kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE or CONFIG_KALLSYMS");
+
+ KUNIT_START_SUPPRESSED_WARNING(test);
+ WARN_ON(1);
+ KUNIT_END_SUPPRESSED_WARNING(test);
+
+ KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(), 1);
+}
+
+static void trigger_backtrace_warn_on(void)
+{
+ WARN_ON(1);
+}
+
+static void backtrace_suppression_test_warn_on_indirect(struct kunit *test)
+{
+ if (!IS_ENABLED(CONFIG_DEBUG_BUGVERBOSE))
+ kunit_skip(test, "requires CONFIG_DEBUG_BUGVERBOSE");
+
+ KUNIT_START_SUPPRESSED_WARNING(test);
+ trigger_backtrace_warn_on();
+ KUNIT_END_SUPPRESSED_WARNING(test);
+
+ KUNIT_EXPECT_EQ(test, KUNIT_SUPPRESSED_WARNING_COUNT(), 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");

--
2.52.0