ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 224 insertions, 0 deletions

diff --git a/lib/kunit/platform-test.c b/lib/kunit/platform-test.c
new file mode 100644
index 000000000..e3debb8fb
--- /dev/null
+++ b/lib/kunit/platform-test.c
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for KUnit platform driver infrastructure.
+ */
+
+#include <linux/platform_device.h>
+
+#include <kunit/platform_device.h>
+#include <kunit/test.h>
+
+/*
+ * Test that kunit_platform_device_alloc() creates a platform device.
+ */
+static void kunit_platform_device_alloc_test(struct kunit *test)
+{
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test,
+			kunit_platform_device_alloc(test, "kunit-platform", 1));
+}
+
+/*
+ * Test that kunit_platform_device_add() registers a platform device on the
+ * platform bus with the proper name and id.
+ */
+static void kunit_platform_device_add_test(struct kunit *test)
+{
+	struct platform_device *pdev;
+	const char *name = "kunit-platform-add";
+	const int id = -1;
+
+	pdev = kunit_platform_device_alloc(test, name, id);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	KUNIT_EXPECT_EQ(test, 0, kunit_platform_device_add(test, pdev));
+	KUNIT_EXPECT_TRUE(test, dev_is_platform(&pdev->dev));
+	KUNIT_EXPECT_STREQ(test, pdev->name, name);
+	KUNIT_EXPECT_EQ(test, pdev->id, id);
+}
+
+/*
+ * Test that kunit_platform_device_add() called twice with the same device name
+ * and id fails the second time and properly cleans up.
+ */
+static void kunit_platform_device_add_twice_fails_test(struct kunit *test)
+{
+	struct platform_device *pdev;
+	const char *name = "kunit-platform-add-2";
+	const int id = -1;
+
+	pdev = kunit_platform_device_alloc(test, name, id);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_add(test, pdev));
+
+	pdev = kunit_platform_device_alloc(test, name, id);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+
+	KUNIT_EXPECT_NE(test, 0, kunit_platform_device_add(test, pdev));
+}
+
+static int kunit_platform_device_find_by_name(struct device *dev, const void *data)
+{
+	return strcmp(dev_name(dev), data) == 0;
+}
+
+/*
+ * Test that kunit_platform_device_add() cleans up by removing the platform
+ * device when the test finishes. */
+static void kunit_platform_device_add_cleans_up(struct kunit *test)
+{
+	struct platform_device *pdev;
+	const char *name = "kunit-platform-clean";
+	const int id = -1;
+	struct kunit fake;
+	struct device *dev;
+
+	kunit_init_test(&fake, "kunit_platform_device_add_fake_test", NULL);
+	KUNIT_ASSERT_EQ(test, fake.status, KUNIT_SUCCESS);
+
+	pdev = kunit_platform_device_alloc(&fake, name, id);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_add(&fake, pdev));
+	dev = bus_find_device(&platform_bus_type, NULL, name,
+			      kunit_platform_device_find_by_name);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+	put_device(dev);
+
+	/* Remove pdev */
+	kunit_cleanup(&fake);
+
+	/*
+	 * Failing to migrate the kunit_resource would lead to an extra
+	 * put_device() call on the platform device. The best we can do here is
+	 * make sure the device no longer exists on the bus, but if something
+	 * is wrong we'll see a refcount underflow here. We can't test for a
+	 * refcount underflow because the kref matches the lifetime of the
+	 * device which should already be freed and could be used by something
+	 * else.
+	 */
+	dev = bus_find_device(&platform_bus_type, NULL, name,
+			      kunit_platform_device_find_by_name);
+	KUNIT_EXPECT_PTR_EQ(test, NULL, dev);
+	put_device(dev);
+}
+
+/*
+ * Test suite for struct platform_device kunit APIs
+ */
+static struct kunit_case kunit_platform_device_test_cases[] = {
+	KUNIT_CASE(kunit_platform_device_alloc_test),
+	KUNIT_CASE(kunit_platform_device_add_test),
+	KUNIT_CASE(kunit_platform_device_add_twice_fails_test),
+	KUNIT_CASE(kunit_platform_device_add_cleans_up),
+	{}
+};
+
+static struct kunit_suite kunit_platform_device_suite = {
+	.name = "kunit_platform_device",
+	.test_cases = kunit_platform_device_test_cases,
+};
+
+struct kunit_platform_driver_test_context {
+	struct platform_driver pdrv;
+	const char *data;
+};
+
+static const char * const test_data = "test data";
+
+static inline struct kunit_platform_driver_test_context *
+to_test_context(struct platform_device *pdev)
+{
+	return container_of(to_platform_driver(pdev->dev.driver),
+			    struct kunit_platform_driver_test_context,
+			    pdrv);
+}
+
+static int kunit_platform_driver_probe(struct platform_device *pdev)
+{
+	struct kunit_platform_driver_test_context *ctx;
+
+	ctx = to_test_context(pdev);
+	ctx->data = test_data;
+
+	return 0;
+}
+
+/* Test that kunit_platform_driver_register() registers a driver that probes. */
+static void kunit_platform_driver_register_test(struct kunit *test)
+{
+	struct platform_device *pdev;
+	struct kunit_platform_driver_test_context *ctx;
+	DECLARE_COMPLETION_ONSTACK(comp);
+	const char *name = "kunit-platform-register";
+
+	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
+
+	pdev = kunit_platform_device_alloc(test, name, -1);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_add(test, pdev));
+
+	ctx->pdrv.probe = kunit_platform_driver_probe;
+	ctx->pdrv.driver.name = name;
+	ctx->pdrv.driver.owner = THIS_MODULE;
+
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_prepare_wait_for_probe(test, pdev, &comp));
+
+	KUNIT_EXPECT_EQ(test, 0, kunit_platform_driver_register(test, &ctx->pdrv));
+	KUNIT_EXPECT_NE(test, 0, wait_for_completion_timeout(&comp, 3 * HZ));
+	KUNIT_EXPECT_STREQ(test, ctx->data, test_data);
+}
+
+/*
+ * Test that kunit_platform_device_prepare_wait_for_probe() completes the completion
+ * when the device is already probed.
+ */
+static void kunit_platform_device_prepare_wait_for_probe_completes_when_already_probed(struct kunit *test)
+{
+	struct platform_device *pdev;
+	struct kunit_platform_driver_test_context *ctx;
+	DECLARE_COMPLETION_ONSTACK(comp);
+	const char *name = "kunit-platform-wait";
+
+	ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
+
+	pdev = kunit_platform_device_alloc(test, name, -1);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_add(test, pdev));
+
+	ctx->pdrv.probe = kunit_platform_driver_probe;
+	ctx->pdrv.driver.name = name;
+	ctx->pdrv.driver.owner = THIS_MODULE;
+
+	/* Make sure driver has actually probed */
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_prepare_wait_for_probe(test, pdev, &comp));
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_driver_register(test, &ctx->pdrv));
+	KUNIT_ASSERT_NE(test, 0, wait_for_completion_timeout(&comp, 3 * HZ));
+
+	reinit_completion(&comp);
+	KUNIT_ASSERT_EQ(test, 0, kunit_platform_device_prepare_wait_for_probe(test, pdev, &comp));
+
+	KUNIT_EXPECT_NE(test, 0, wait_for_completion_timeout(&comp, HZ));
+}
+
+static struct kunit_case kunit_platform_driver_test_cases[] = {
+	KUNIT_CASE(kunit_platform_driver_register_test),
+	KUNIT_CASE(kunit_platform_device_prepare_wait_for_probe_completes_when_already_probed),
+	{}
+};
+
+/*
+ * Test suite for struct platform_driver kunit APIs
+ */
+static struct kunit_suite kunit_platform_driver_suite = {
+	.name = "kunit_platform_driver",
+	.test_cases = kunit_platform_driver_test_cases,
+};
+
+kunit_test_suites(
+	&kunit_platform_device_suite,
+	&kunit_platform_driver_suite,
+);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit test for KUnit platform driver infrastructure");