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, 253 insertions, 0 deletions

diff --git a/drivers/input/misc/pwm-beeper.c b/drivers/input/misc/pwm-beeper.c
new file mode 100644
index 000000000..0e19e97d9
--- /dev/null
+++ b/drivers/input/misc/pwm-beeper.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (C) 2010, Lars-Peter Clausen <lars@metafoo.de>
+ *  PWM beeper driver
+ */
+
+#include <linux/input.h>
+#include <linux/regulator/consumer.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+struct pwm_beeper {
+	struct input_dev *input;
+	struct pwm_device *pwm;
+	struct regulator *amplifier;
+	struct work_struct work;
+	unsigned long period;
+	unsigned int bell_frequency;
+	bool suspended;
+	bool amplifier_on;
+};
+
+#define HZ_TO_NANOSECONDS(x) (1000000000UL/(x))
+
+static int pwm_beeper_on(struct pwm_beeper *beeper, unsigned long period)
+{
+	struct pwm_state state;
+	int error;
+
+	pwm_get_state(beeper->pwm, &state);
+
+	state.enabled = true;
+	state.period = period;
+	pwm_set_relative_duty_cycle(&state, 50, 100);
+
+	error = pwm_apply_might_sleep(beeper->pwm, &state);
+	if (error)
+		return error;
+
+	if (!beeper->amplifier_on) {
+		error = regulator_enable(beeper->amplifier);
+		if (error) {
+			pwm_disable(beeper->pwm);
+			return error;
+		}
+
+		beeper->amplifier_on = true;
+	}
+
+	return 0;
+}
+
+static void pwm_beeper_off(struct pwm_beeper *beeper)
+{
+	if (beeper->amplifier_on) {
+		regulator_disable(beeper->amplifier);
+		beeper->amplifier_on = false;
+	}
+
+	pwm_disable(beeper->pwm);
+}
+
+static void pwm_beeper_work(struct work_struct *work)
+{
+	struct pwm_beeper *beeper = container_of(work, struct pwm_beeper, work);
+	unsigned long period = READ_ONCE(beeper->period);
+
+	if (period)
+		pwm_beeper_on(beeper, period);
+	else
+		pwm_beeper_off(beeper);
+}
+
+static int pwm_beeper_event(struct input_dev *input,
+			    unsigned int type, unsigned int code, int value)
+{
+	struct pwm_beeper *beeper = input_get_drvdata(input);
+
+	if (type != EV_SND || value < 0)
+		return -EINVAL;
+
+	switch (code) {
+	case SND_BELL:
+		value = value ? beeper->bell_frequency : 0;
+		break;
+	case SND_TONE:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (value == 0)
+		beeper->period = 0;
+	else
+		beeper->period = HZ_TO_NANOSECONDS(value);
+
+	if (!beeper->suspended)
+		schedule_work(&beeper->work);
+
+	return 0;
+}
+
+static void pwm_beeper_stop(struct pwm_beeper *beeper)
+{
+	cancel_work_sync(&beeper->work);
+	pwm_beeper_off(beeper);
+}
+
+static void pwm_beeper_close(struct input_dev *input)
+{
+	struct pwm_beeper *beeper = input_get_drvdata(input);
+
+	pwm_beeper_stop(beeper);
+}
+
+static int pwm_beeper_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct pwm_beeper *beeper;
+	struct pwm_state state;
+	u32 bell_frequency;
+	int error;
+
+	beeper = devm_kzalloc(dev, sizeof(*beeper), GFP_KERNEL);
+	if (!beeper)
+		return -ENOMEM;
+
+	beeper->pwm = devm_pwm_get(dev, NULL);
+	if (IS_ERR(beeper->pwm))
+		return dev_err_probe(dev, PTR_ERR(beeper->pwm), "Failed to request PWM device\n");
+
+	/* Sync up PWM state and ensure it is off. */
+	pwm_init_state(beeper->pwm, &state);
+	state.enabled = false;
+	error = pwm_apply_might_sleep(beeper->pwm, &state);
+	if (error) {
+		dev_err(dev, "failed to apply initial PWM state: %d\n",
+			error);
+		return error;
+	}
+
+	beeper->amplifier = devm_regulator_get(dev, "amp");
+	if (IS_ERR(beeper->amplifier))
+		return dev_err_probe(dev, PTR_ERR(beeper->amplifier),
+				     "Failed to get 'amp' regulator\n");
+
+	INIT_WORK(&beeper->work, pwm_beeper_work);
+
+	error = device_property_read_u32(dev, "beeper-hz", &bell_frequency);
+	if (error) {
+		bell_frequency = 1000;
+		dev_dbg(dev,
+			"failed to parse 'beeper-hz' property, using default: %uHz\n",
+			bell_frequency);
+	}
+
+	beeper->bell_frequency = bell_frequency;
+
+	beeper->input = devm_input_allocate_device(dev);
+	if (!beeper->input) {
+		dev_err(dev, "Failed to allocate input device\n");
+		return -ENOMEM;
+	}
+
+	beeper->input->name = "pwm-beeper";
+	beeper->input->phys = "pwm/input0";
+	beeper->input->id.bustype = BUS_HOST;
+	beeper->input->id.vendor = 0x001f;
+	beeper->input->id.product = 0x0001;
+	beeper->input->id.version = 0x0100;
+
+	input_set_capability(beeper->input, EV_SND, SND_TONE);
+	input_set_capability(beeper->input, EV_SND, SND_BELL);
+
+	beeper->input->event = pwm_beeper_event;
+	beeper->input->close = pwm_beeper_close;
+
+	input_set_drvdata(beeper->input, beeper);
+
+	error = input_register_device(beeper->input);
+	if (error) {
+		dev_err(dev, "Failed to register input device: %d\n", error);
+		return error;
+	}
+
+	platform_set_drvdata(pdev, beeper);
+
+	return 0;
+}
+
+static int pwm_beeper_suspend(struct device *dev)
+{
+	struct pwm_beeper *beeper = dev_get_drvdata(dev);
+
+	/*
+	 * Spinlock is taken here is not to protect write to
+	 * beeper->suspended, but to ensure that pwm_beeper_event
+	 * does not re-submit work once flag is set.
+	 */
+	scoped_guard(spinlock_irq, &beeper->input->event_lock) {
+		beeper->suspended = true;
+	}
+
+	pwm_beeper_stop(beeper);
+
+	return 0;
+}
+
+static int pwm_beeper_resume(struct device *dev)
+{
+	struct pwm_beeper *beeper = dev_get_drvdata(dev);
+
+	scoped_guard(spinlock_irq, &beeper->input->event_lock) {
+		beeper->suspended = false;
+	}
+
+	/* Let worker figure out if we should resume beeping */
+	schedule_work(&beeper->work);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(pwm_beeper_pm_ops,
+				pwm_beeper_suspend, pwm_beeper_resume);
+
+#ifdef CONFIG_OF
+static const struct of_device_id pwm_beeper_match[] = {
+	{ .compatible = "pwm-beeper", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, pwm_beeper_match);
+#endif
+
+static struct platform_driver pwm_beeper_driver = {
+	.probe	= pwm_beeper_probe,
+	.driver = {
+		.name	= "pwm-beeper",
+		.pm	= pm_sleep_ptr(&pwm_beeper_pm_ops),
+		.of_match_table = of_match_ptr(pwm_beeper_match),
+	},
+};
+module_platform_driver(pwm_beeper_driver);
+
+MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
+MODULE_DESCRIPTION("PWM beeper driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pwm-beeper");