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, 121 insertions, 0 deletions

diff --git a/include/kunit/of.h b/include/kunit/of.h
new file mode 100644
index 000000000..75a760a4e
--- /dev/null
+++ b/include/kunit/of.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KUNIT_OF_H
+#define _KUNIT_OF_H
+
+#include <kunit/test.h>
+
+struct device_node;
+
+#ifdef CONFIG_OF
+
+void of_node_put_kunit(struct kunit *test, struct device_node *node);
+
+#else
+
+static inline
+void of_node_put_kunit(struct kunit *test, struct device_node *node)
+{
+	kunit_skip(test, "requires CONFIG_OF");
+}
+
+#endif /* !CONFIG_OF */
+
+#if defined(CONFIG_OF) && defined(CONFIG_OF_OVERLAY) && defined(CONFIG_OF_EARLY_FLATTREE)
+
+int of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,
+			       u32 overlay_fdt_size, int *ovcs_id);
+#else
+
+static inline int
+of_overlay_fdt_apply_kunit(struct kunit *test, void *overlay_fdt,
+			   u32 overlay_fdt_size, int *ovcs_id)
+{
+	kunit_skip(test, "requires CONFIG_OF and CONFIG_OF_OVERLAY and CONFIG_OF_EARLY_FLATTREE for root node");
+	return -EINVAL;
+}
+
+#endif
+
+/**
+ * __of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() variant
+ * @test: test context
+ * @overlay_begin: start address of overlay to apply
+ * @overlay_end: end address of overlay to apply
+ *
+ * This is mostly internal API. See of_overlay_apply_kunit() for the wrapper
+ * that makes this easier to use.
+ *
+ * Similar to of_overlay_fdt_apply(), except the overlay is managed by the test
+ * case and is automatically removed with of_overlay_remove() after the test
+ * case concludes.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static inline int __of_overlay_apply_kunit(struct kunit *test,
+					   u8 *overlay_begin,
+					   const u8 *overlay_end)
+{
+	int unused;
+
+	return of_overlay_fdt_apply_kunit(test, overlay_begin,
+					  overlay_end - overlay_begin,
+					  &unused);
+}
+
+#define of_overlay_begin(overlay_name) __dtbo_##overlay_name##_begin
+#define of_overlay_end(overlay_name) __dtbo_##overlay_name##_end
+
+#define OF_OVERLAY_DECLARE(overlay_name)			\
+	extern uint8_t of_overlay_begin(overlay_name)[];	\
+	extern uint8_t of_overlay_end(overlay_name)[]		\
+
+/**
+ * of_overlay_apply_kunit() - Test managed of_overlay_fdt_apply() for built-in overlays
+ * @test: test context
+ * @overlay_name: name of overlay to apply
+ *
+ * This macro is used to apply a device tree overlay built with the
+ * cmd_dt_S_dtbo rule in scripts/Makefile.lib that has been compiled into the
+ * kernel image or KUnit test module. The overlay is automatically removed when
+ * the test is finished.
+ *
+ * Unit tests that need device tree nodes should compile an overlay file with
+ * @overlay_name\.dtbo.o in their Makefile along with their unit test and then
+ * load the overlay during their test. The @overlay_name matches the filename
+ * of the overlay without the dtbo filename extension. If CONFIG_OF_OVERLAY is
+ * not enabled, the @test will be skipped.
+ *
+ * In the Makefile
+ *
+ * .. code-block:: none
+ *
+ *	obj-$(CONFIG_OF_OVERLAY_KUNIT_TEST) += overlay_test.o kunit_overlay_test.dtbo.o
+ *
+ * In the test
+ *
+ * .. code-block:: c
+ *
+ *	static void of_overlay_kunit_of_overlay_apply(struct kunit *test)
+ *	{
+ *		struct device_node *np;
+ *
+ *		KUNIT_ASSERT_EQ(test, 0,
+ *				of_overlay_apply_kunit(test, kunit_overlay_test));
+ *
+ *		np = of_find_node_by_name(NULL, "test-kunit");
+ *		KUNIT_EXPECT_NOT_ERR_OR_NULL(test, np);
+ *		of_node_put(np);
+ *	}
+ *
+ * Return: 0 on success, negative errno on failure.
+ */
+#define of_overlay_apply_kunit(test, overlay_name)		\
+({								\
+	OF_OVERLAY_DECLARE(overlay_name);			\
+								\
+	__of_overlay_apply_kunit((test),			\
+			of_overlay_begin(overlay_name),		\
+			of_overlay_end(overlay_name));		\
+})
+
+#endif