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, 153 insertions, 0 deletions

diff --git a/drivers/input/misc/qnap-mcu-input.c b/drivers/input/misc/qnap-mcu-input.c
new file mode 100644
index 000000000..3be899bfc
--- /dev/null
+++ b/drivers/input/misc/qnap-mcu-input.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Driver for input events on QNAP-MCUs
+ *
+ * Copyright (C) 2024 Heiko Stuebner <heiko@sntech.de>
+ */
+
+#include <linux/input.h>
+#include <linux/mfd/qnap-mcu.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <uapi/linux/input-event-codes.h>
+
+/*
+ * The power-key needs to be pressed for a while to create an event,
+ * so there is no use for overly frequent polling.
+ */
+#define POLL_INTERVAL		500
+
+struct qnap_mcu_input_dev {
+	struct input_dev *input;
+	struct qnap_mcu *mcu;
+	struct device *dev;
+
+	struct work_struct beep_work;
+	int beep_type;
+};
+
+static void qnap_mcu_input_poll(struct input_dev *input)
+{
+	struct qnap_mcu_input_dev *idev = input_get_drvdata(input);
+	static const u8 cmd[] = { '@', 'C', 'V' };
+	u8 reply[4];
+	int state, ret;
+
+	/* poll the power button */
+	ret = qnap_mcu_exec(idev->mcu, cmd, sizeof(cmd), reply, sizeof(reply));
+	if (ret)
+		return;
+
+	/* First bytes must mirror the sent command */
+	if (memcmp(cmd, reply, sizeof(cmd))) {
+		dev_err(idev->dev, "malformed data received\n");
+		return;
+	}
+
+	state = reply[3] - 0x30;
+	input_event(input, EV_KEY, KEY_POWER, state);
+	input_sync(input);
+}
+
+static void qnap_mcu_input_beeper_work(struct work_struct *work)
+{
+	struct qnap_mcu_input_dev *idev =
+		container_of(work, struct qnap_mcu_input_dev, beep_work);
+	const u8 cmd[] = { '@', 'C', (idev->beep_type == SND_TONE) ? '3' : '2' };
+
+	qnap_mcu_exec_with_ack(idev->mcu, cmd, sizeof(cmd));
+}
+
+static int qnap_mcu_input_event(struct input_dev *input, unsigned int type,
+				unsigned int code, int value)
+{
+	struct qnap_mcu_input_dev *idev = input_get_drvdata(input);
+
+	if (type != EV_SND || (code != SND_BELL && code != SND_TONE))
+		return -EOPNOTSUPP;
+
+	if (value < 0)
+		return -EINVAL;
+
+	/* beep runtime is determined by the MCU */
+	if (value == 0)
+		return 0;
+
+	/* Schedule work to actually turn the beeper on */
+	idev->beep_type = code;
+	schedule_work(&idev->beep_work);
+
+	return 0;
+}
+
+static void qnap_mcu_input_close(struct input_dev *input)
+{
+	struct qnap_mcu_input_dev *idev = input_get_drvdata(input);
+
+	cancel_work_sync(&idev->beep_work);
+}
+
+static int qnap_mcu_input_probe(struct platform_device *pdev)
+{
+	struct qnap_mcu *mcu = dev_get_drvdata(pdev->dev.parent);
+	struct qnap_mcu_input_dev *idev;
+	struct device *dev = &pdev->dev;
+	struct input_dev *input;
+	int ret;
+
+	idev = devm_kzalloc(dev, sizeof(*idev), GFP_KERNEL);
+	if (!idev)
+		return -ENOMEM;
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	idev->input = input;
+	idev->dev = dev;
+	idev->mcu = mcu;
+
+	input_set_drvdata(input, idev);
+
+	input->name		= "qnap-mcu";
+	input->phys		= "qnap-mcu-input/input0";
+	input->id.bustype	= BUS_HOST;
+	input->id.vendor	= 0x0001;
+	input->id.product	= 0x0001;
+	input->id.version	= 0x0100;
+	input->event		= qnap_mcu_input_event;
+	input->close		= qnap_mcu_input_close;
+
+	input_set_capability(input, EV_KEY, KEY_POWER);
+	input_set_capability(input, EV_SND, SND_BELL);
+	input_set_capability(input, EV_SND, SND_TONE);
+
+	INIT_WORK(&idev->beep_work, qnap_mcu_input_beeper_work);
+
+	ret = input_setup_polling(input, qnap_mcu_input_poll);
+	if (ret)
+		return dev_err_probe(dev, ret, "unable to set up polling\n");
+
+	input_set_poll_interval(input, POLL_INTERVAL);
+
+	ret = input_register_device(input);
+	if (ret)
+		return dev_err_probe(dev, ret, "unable to register input device\n");
+
+	return 0;
+}
+
+static struct platform_driver qnap_mcu_input_driver = {
+	.probe = qnap_mcu_input_probe,
+	.driver = {
+		.name = "qnap-mcu-input",
+	},
+};
+module_platform_driver(qnap_mcu_input_driver);
+
+MODULE_ALIAS("platform:qnap-mcu-input");
+MODULE_AUTHOR("Heiko Stuebner <heiko@sntech.de>");
+MODULE_DESCRIPTION("QNAP MCU input driver");
+MODULE_LICENSE("GPL");