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, 114 insertions, 0 deletions

diff --git a/drivers/input/misc/gpio-beeper.c b/drivers/input/misc/gpio-beeper.c
new file mode 100644
index 000000000..3d65cb4f4
--- /dev/null
+++ b/drivers/input/misc/gpio-beeper.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic GPIO beeper driver
+ *
+ * Copyright (C) 2013-2014 Alexander Shiyan <shc_work@mail.ru>
+ */
+
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of.h>
+#include <linux/workqueue.h>
+#include <linux/platform_device.h>
+
+#define BEEPER_MODNAME		"gpio-beeper"
+
+struct gpio_beeper {
+	struct work_struct	work;
+	struct gpio_desc	*desc;
+	bool			beeping;
+};
+
+static void gpio_beeper_toggle(struct gpio_beeper *beep, bool on)
+{
+	gpiod_set_value_cansleep(beep->desc, on);
+}
+
+static void gpio_beeper_work(struct work_struct *work)
+{
+	struct gpio_beeper *beep = container_of(work, struct gpio_beeper, work);
+
+	gpio_beeper_toggle(beep, beep->beeping);
+}
+
+static int gpio_beeper_event(struct input_dev *dev, unsigned int type,
+			     unsigned int code, int value)
+{
+	struct gpio_beeper *beep = input_get_drvdata(dev);
+
+	if (type != EV_SND || code != SND_BELL)
+		return -ENOTSUPP;
+
+	if (value < 0)
+		return -EINVAL;
+
+	beep->beeping = value;
+	/* Schedule work to actually turn the beeper on or off */
+	schedule_work(&beep->work);
+
+	return 0;
+}
+
+static void gpio_beeper_close(struct input_dev *input)
+{
+	struct gpio_beeper *beep = input_get_drvdata(input);
+
+	cancel_work_sync(&beep->work);
+	gpio_beeper_toggle(beep, false);
+}
+
+static int gpio_beeper_probe(struct platform_device *pdev)
+{
+	struct gpio_beeper *beep;
+	struct input_dev *input;
+
+	beep = devm_kzalloc(&pdev->dev, sizeof(*beep), GFP_KERNEL);
+	if (!beep)
+		return -ENOMEM;
+
+	beep->desc = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_LOW);
+	if (IS_ERR(beep->desc))
+		return PTR_ERR(beep->desc);
+
+	input = devm_input_allocate_device(&pdev->dev);
+	if (!input)
+		return -ENOMEM;
+
+	INIT_WORK(&beep->work, gpio_beeper_work);
+
+	input->name		= pdev->name;
+	input->id.bustype	= BUS_HOST;
+	input->id.vendor	= 0x0001;
+	input->id.product	= 0x0001;
+	input->id.version	= 0x0100;
+	input->close		= gpio_beeper_close;
+	input->event		= gpio_beeper_event;
+
+	input_set_capability(input, EV_SND, SND_BELL);
+
+	input_set_drvdata(input, beep);
+
+	return input_register_device(input);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id gpio_beeper_of_match[] = {
+	{ .compatible = "gpio-beeper", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, gpio_beeper_of_match);
+#endif
+
+static struct platform_driver gpio_beeper_platform_driver = {
+	.driver	= {
+		.name		= BEEPER_MODNAME,
+		.of_match_table	= of_match_ptr(gpio_beeper_of_match),
+	},
+	.probe	= gpio_beeper_probe,
+};
+module_platform_driver(gpio_beeper_platform_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
+MODULE_DESCRIPTION("Generic GPIO beeper driver");