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, 202 insertions, 0 deletions

diff --git a/drivers/input/joystick/zhenhua.c b/drivers/input/joystick/zhenhua.c
new file mode 100644
index 000000000..8ca189663
--- /dev/null
+++ b/drivers/input/joystick/zhenhua.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  derived from "twidjoy.c"
+ *
+ *  Copyright (c) 2008 Martin Kebert
+ *  Copyright (c) 2001 Arndt Schoenewald
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *  Copyright (c) 2000 Mark Fletcher
+ */
+
+/*
+ * Driver to use 4CH RC transmitter using Zhen Hua 5-byte protocol (Walkera Lama,
+ * EasyCopter etc.) as a joystick under Linux.
+ *
+ * RC transmitters using Zhen Hua 5-byte protocol are cheap four channels
+ * transmitters for control a RC planes or RC helicopters with possibility to
+ * connect on a serial port.
+ * Data coming from transmitter is in this order:
+ * 1. byte = synchronisation byte
+ * 2. byte = X axis
+ * 3. byte = Y axis
+ * 4. byte = RZ axis
+ * 5. byte = Z axis
+ * (and this is repeated)
+ *
+ * For questions or feedback regarding this driver module please contact:
+ * Martin Kebert <gkmarty@gmail.com> - but I am not a C-programmer nor kernel
+ * coder :-(
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/bitrev.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"RC transmitter with 5-byte Zhen Hua protocol joystick driver"
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Constants.
+ */
+
+#define ZHENHUA_MAX_LENGTH 5
+
+/*
+ * Zhen Hua data.
+ */
+
+struct zhenhua {
+	struct input_dev *dev;
+	int idx;
+	unsigned char data[ZHENHUA_MAX_LENGTH];
+	char phys[32];
+};
+
+/*
+ * zhenhua_process_packet() decodes packets the driver receives from the
+ * RC transmitter. It updates the data accordingly.
+ */
+
+static void zhenhua_process_packet(struct zhenhua *zhenhua)
+{
+	struct input_dev *dev = zhenhua->dev;
+	unsigned char *data = zhenhua->data;
+
+	input_report_abs(dev, ABS_Y, data[1]);
+	input_report_abs(dev, ABS_X, data[2]);
+	input_report_abs(dev, ABS_RZ, data[3]);
+	input_report_abs(dev, ABS_Z, data[4]);
+
+	input_sync(dev);
+}
+
+/*
+ * zhenhua_interrupt() is called by the low level driver when characters
+ * are ready for us. We then buffer them for further processing, or call the
+ * packet processing routine.
+ */
+
+static irqreturn_t zhenhua_interrupt(struct serio *serio, unsigned char data, unsigned int flags)
+{
+	struct zhenhua *zhenhua = serio_get_drvdata(serio);
+
+	/* All Zhen Hua packets are 5 bytes. The fact that the first byte
+	 * is allways 0xf7 and all others are in range 0x32 - 0xc8 (50-200)
+	 * can be used to check and regain sync. */
+
+	if (data == 0xef)
+		zhenhua->idx = 0;	/* this byte starts a new packet */
+	else if (zhenhua->idx == 0)
+		return IRQ_HANDLED;	/* wrong MSB -- ignore this byte */
+
+	if (zhenhua->idx < ZHENHUA_MAX_LENGTH)
+		zhenhua->data[zhenhua->idx++] = bitrev8(data);
+
+	if (zhenhua->idx == ZHENHUA_MAX_LENGTH) {
+		zhenhua_process_packet(zhenhua);
+		zhenhua->idx = 0;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * zhenhua_disconnect() is the opposite of zhenhua_connect()
+ */
+
+static void zhenhua_disconnect(struct serio *serio)
+{
+	struct zhenhua *zhenhua = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(zhenhua->dev);
+	kfree(zhenhua);
+}
+
+/*
+ * zhenhua_connect() is the routine that is called when someone adds a
+ * new serio device. It looks for the Twiddler, and if found, registers
+ * it as an input device.
+ */
+
+static int zhenhua_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct zhenhua *zhenhua;
+	struct input_dev *input_dev;
+	int err = -ENOMEM;
+
+	zhenhua = kzalloc_obj(*zhenhua);
+	input_dev = input_allocate_device();
+	if (!zhenhua || !input_dev)
+		goto fail1;
+
+	zhenhua->dev = input_dev;
+	snprintf(zhenhua->phys, sizeof(zhenhua->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "Zhen Hua 5-byte device";
+	input_dev->phys = zhenhua->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_ZHENHUA;
+	input_dev->id.product = 0x0001;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT(EV_ABS);
+	input_set_abs_params(input_dev, ABS_X, 50, 200, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y, 50, 200, 0, 0);
+	input_set_abs_params(input_dev, ABS_Z, 50, 200, 0, 0);
+	input_set_abs_params(input_dev, ABS_RZ, 50, 200, 0, 0);
+
+	serio_set_drvdata(serio, zhenhua);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(zhenhua->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(zhenhua);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id zhenhua_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_ZHENHUA,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, zhenhua_serio_ids);
+
+static struct serio_driver zhenhua_drv = {
+	.driver		= {
+		.name	= "zhenhua",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= zhenhua_serio_ids,
+	.interrupt	= zhenhua_interrupt,
+	.connect	= zhenhua_connect,
+	.disconnect	= zhenhua_disconnect,
+};
+
+module_serio_driver(zhenhua_drv);