[PATCH v2 2/2] debugobject: add unit test for static debug object

[Schspa Shi]

Add test case to enusre that static debug object correctness.

Tested on little-endian arm64 qemu, result:

[    2.385735] KTAP version 1
[    2.385860] 1..1
[    2.386406]     KTAP version 1
[    2.386658]     # Subtest: static debugobject init
[    2.386726]     1..1
[    2.401777]     ok 1 static_debugobject_test
[    2.402455] ok 1 static debugobject init

Signed-off-by: Schspa Shi <schspa@xxxxxxxxx>
---
 MAINTAINERS                    |   5 ++
 lib/Kconfig.debug              |  14 ++++
 lib/Makefile                   |   2 +
 lib/test_static_debug_object.c | 125 +++++++++++++++++++++++++++++++++
 4 files changed, 146 insertions(+)
 create mode 100644 lib/test_static_debug_object.c

diff --git a/MAINTAINERS b/MAINTAINERS
index b0db911207ba4..38187e2921691 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -23202,6 +23202,11 @@ L:	linux-mm@xxxxxxxxx
 S:	Maintained
 F:	mm/zswap.c
 
+STATIC DEBUGOBJECT TEST
+M:	Schspa Shi <schspa@xxxxxxxxx>
+S:	Maintained
+F:	lib/test_static_debug_object.c
+
 THE REST
 M:	Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
 L:	linux-kernel@xxxxxxxxxxxxxxx
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c8b379e2e9adc..9d5ee631d4380 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2801,6 +2801,20 @@ config TEST_CLOCKSOURCE_WATCHDOG
 
 	  If unsure, say N.
 
+config TEST_STATIC_DEBUGOBJECT
+	tristate "KUnit test for static debugobject"
+	depends on KUNIT
+	select KPROBES
+	select DEBUG_OBJECTS
+	select DEBUG_OBJECTS_TIMERS
+	help
+	  This builds the static debugobject unit test, which runs on boot.
+	  Tests the static debug object correctness.
+	  For more information on KUnit and unit tests in general please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.
+
 endif # RUNTIME_TESTING_MENU
 
 config ARCH_USE_MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index baf2821f7a00f..f663686beabd9 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -427,3 +427,5 @@ $(obj)/$(TEST_FORTIFY_LOG): $(addprefix $(obj)/, $(TEST_FORTIFY_LOGS)) FORCE
 ifeq ($(CONFIG_FORTIFY_SOURCE),y)
 $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)
 endif
+
+obj-$(CONFIG_TEST_STATIC_DEBUGOBJECT) += test_static_debug_object.o
diff --git a/lib/test_static_debug_object.c b/lib/test_static_debug_object.c
new file mode 100644
index 0000000000000..8a0d6ab5c24b5
--- /dev/null
+++ b/lib/test_static_debug_object.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * THis module tests the static debugobject via a static timer instance. This
+ * test use kretprobe to inject some delay to make the problem easier to
+ * reproduce.
+ *
+ * Copyright (c) 2023, Schspa Shi <schspa@xxxxxxxxx>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/timer.h>
+#include <linux/delay.h>
+#include <linux/kprobes.h>
+#include <linux/workqueue.h>
+#include <linux/cpu.h>
+#include <kunit/test.h>
+
+static void ktest_timer_func(struct timer_list *);
+
+static DEFINE_TIMER(ktest_timer, ktest_timer_func);
+static int timer_stop;
+DEFINE_SPINLOCK(tlock);
+
+static DEFINE_PER_CPU(struct work_struct, timer_debugobject_test_work);
+
+static void timer_debugobject_workfn(struct work_struct *work)
+{
+	mod_timer(&ktest_timer, jiffies + (5 * HZ));
+}
+
+/*
+ * Reaper for links from keyrings to dead keys.
+ */
+static void ktest_timer_func(struct timer_list *t)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&tlock, flags);
+	if (!timer_stop)
+		mod_timer(&ktest_timer, jiffies + (1 * HZ));
+	spin_unlock_irqrestore(&tlock, flags);
+}
+
+
+static int static_object_check_handler(
+	struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+	void *address;
+
+	address = (void *)regs_get_register(regs, 0);
+
+	if (address == &ktest_timer) {
+		int this_cpu = raw_smp_processor_id();
+		/*
+		 * This hook point adds an extra delay to make the problem
+		 * easier to reproduce. We need different delay for
+		 * differenct processor.
+		 */
+		mdelay(this_cpu * 100);
+	}
+
+	return 0;
+}
+
+
+static struct kretprobe is_static_kretprobes = {
+	.entry_handler = static_object_check_handler,
+	.data_size = 0,
+	/* Probe up to 512 instances concurrently. */
+	.maxactive = 512,
+	.kp = {
+		.symbol_name = "timer_is_static_object",
+	}
+};
+
+
+static void static_debugobject_test(struct kunit *test)
+{
+	unsigned long flags;
+	int cpu;
+	int ret;
+
+	ret = register_kretprobe(&is_static_kretprobes);
+	KUNIT_ASSERT_EQ(test, ret, 0);
+
+	/* Do test */
+	cpus_read_lock();
+	for_each_online_cpu(cpu) {
+		struct work_struct *work =
+			&per_cpu(timer_debugobject_test_work, cpu);
+		INIT_WORK(work, timer_debugobject_workfn);
+		schedule_work_on(cpu, work);
+	}
+
+	for_each_online_cpu(cpu) {
+		struct work_struct *work =
+			&per_cpu(timer_debugobject_test_work, cpu);
+		flush_work(work);
+	}
+	cpus_read_unlock();
+
+	spin_lock_irqsave(&tlock, flags);
+	timer_stop = 0;
+	spin_unlock_irqrestore(&tlock, flags);
+
+	del_timer_sync(&ktest_timer);
+
+	unregister_kretprobe(&is_static_kretprobes);
+}
+
+static struct kunit_case static_debugobject_init_cases[] = {
+	KUNIT_CASE(static_debugobject_test),
+	{}
+};
+
+static struct kunit_suite static_debugobject_suite = {
+	.name = "static debugobject init",
+	.test_cases = static_debugobject_init_cases,
+};
+
+kunit_test_suite(static_debugobject_suite);
+MODULE_AUTHOR("Schspa <schspa@xxxxxxxxx>");
+MODULE_LICENSE("GPL");
-- 
2.39.2