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, 94 insertions, 0 deletions

diff --git a/drivers/input/misc/rave-sp-pwrbutton.c b/drivers/input/misc/rave-sp-pwrbutton.c
new file mode 100644
index 000000000..bcab3cdb7
--- /dev/null
+++ b/drivers/input/misc/rave-sp-pwrbutton.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Power Button driver for RAVE SP
+//
+// Copyright (C) 2017 Zodiac Inflight Innovations
+//
+//
+
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/rave-sp.h>
+#include <linux/platform_device.h>
+
+#define RAVE_SP_EVNT_BUTTON_PRESS	(RAVE_SP_EVNT_BASE + 0x00)
+
+struct rave_sp_power_button {
+	struct input_dev *idev;
+	struct notifier_block nb;
+};
+
+static int rave_sp_power_button_event(struct notifier_block *nb,
+				      unsigned long action, void *data)
+{
+	struct rave_sp_power_button *pb =
+		container_of(nb, struct rave_sp_power_button, nb);
+	const u8 event = rave_sp_action_unpack_event(action);
+	const u8 value = rave_sp_action_unpack_value(action);
+	struct input_dev *idev = pb->idev;
+
+	if (event == RAVE_SP_EVNT_BUTTON_PRESS) {
+		input_report_key(idev, KEY_POWER, value);
+		input_sync(idev);
+
+		return NOTIFY_STOP;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int rave_sp_pwrbutton_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rave_sp_power_button *pb;
+	struct input_dev *idev;
+	int error;
+
+	pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
+	if (!pb)
+		return -ENOMEM;
+
+	idev = devm_input_allocate_device(dev);
+	if (!idev)
+		return -ENOMEM;
+
+	idev->name = pdev->name;
+
+	input_set_capability(idev, EV_KEY, KEY_POWER);
+
+	error = input_register_device(idev);
+	if (error)
+		return error;
+
+	pb->idev = idev;
+	pb->nb.notifier_call = rave_sp_power_button_event;
+	pb->nb.priority = 128;
+
+	error = devm_rave_sp_register_event_notifier(dev, &pb->nb);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static const struct of_device_id rave_sp_pwrbutton_of_match[] = {
+	{ .compatible = "zii,rave-sp-pwrbutton" },
+	{}
+};
+
+static struct platform_driver rave_sp_pwrbutton_driver = {
+	.probe = rave_sp_pwrbutton_probe,
+	.driver	= {
+		.name = KBUILD_MODNAME,
+		.of_match_table = rave_sp_pwrbutton_of_match,
+	},
+};
+module_platform_driver(rave_sp_pwrbutton_driver);
+
+MODULE_DEVICE_TABLE(of, rave_sp_pwrbutton_of_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Andrey Vostrikov <andrey.vostrikov@cogentembedded.com>");
+MODULE_AUTHOR("Nikita Yushchenko <nikita.yoush@cogentembedded.com>");
+MODULE_AUTHOR("Andrey Smirnov <andrew.smirnov@gmail.com>");
+MODULE_DESCRIPTION("RAVE SP Power Button driver");