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, 188 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/inexio.c b/drivers/input/touchscreen/inexio.c
new file mode 100644
index 000000000..2fa04eaec
--- /dev/null
+++ b/drivers/input/touchscreen/inexio.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * iNexio serial touchscreen driver
+ *
+ * Copyright (c) 2008 Richard Lemon
+ * Based on the mtouch driver (c) Vojtech Pavlik and Dan Streetman
+ */
+
+
+/*
+ * 2008/06/19 Richard Lemon <richard@codelemon.com>
+ *   Copied mtouch.c and edited for iNexio protocol
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"iNexio serial touchscreen driver"
+
+MODULE_AUTHOR("Richard Lemon <richard@codelemon.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define INEXIO_FORMAT_TOUCH_BIT 0x01
+#define INEXIO_FORMAT_LENGTH 5
+#define INEXIO_RESPONSE_BEGIN_BYTE 0x80
+
+/* todo: check specs for max length of all responses */
+#define INEXIO_MAX_LENGTH 16
+
+#define INEXIO_MIN_XC 0
+#define INEXIO_MAX_XC 0x3fff
+#define INEXIO_MIN_YC 0
+#define INEXIO_MAX_YC 0x3fff
+
+#define INEXIO_GET_XC(data) (((data[1])<<7) | data[2])
+#define INEXIO_GET_YC(data) (((data[3])<<7) | data[4])
+#define INEXIO_GET_TOUCHED(data) (INEXIO_FORMAT_TOUCH_BIT & data[0])
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct inexio {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[INEXIO_MAX_LENGTH];
+	char phys[32];
+};
+
+static void inexio_process_data(struct inexio *pinexio)
+{
+	struct input_dev *dev = pinexio->dev;
+
+	if (INEXIO_FORMAT_LENGTH == ++pinexio->idx) {
+		input_report_abs(dev, ABS_X, INEXIO_GET_XC(pinexio->data));
+		input_report_abs(dev, ABS_Y, INEXIO_GET_YC(pinexio->data));
+		input_report_key(dev, BTN_TOUCH, INEXIO_GET_TOUCHED(pinexio->data));
+		input_sync(dev);
+
+		pinexio->idx = 0;
+	}
+}
+
+static irqreturn_t inexio_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct inexio *pinexio = serio_get_drvdata(serio);
+
+	pinexio->data[pinexio->idx] = data;
+
+	if (INEXIO_RESPONSE_BEGIN_BYTE&pinexio->data[0])
+		inexio_process_data(pinexio);
+	else
+		dev_dbg(&serio->dev,
+			"unknown/unsynchronized data from device, byte %x\n",
+			pinexio->data[0]);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * inexio_disconnect() is the opposite of inexio_connect()
+ */
+
+static void inexio_disconnect(struct serio *serio)
+{
+	struct inexio *pinexio = serio_get_drvdata(serio);
+
+	input_get_device(pinexio->dev);
+	input_unregister_device(pinexio->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(pinexio->dev);
+	kfree(pinexio);
+}
+
+/*
+ * inexio_connect() is the routine that is called when someone adds a
+ * new serio device that supports iNexio protocol and registers it as
+ * an input device. This is usually accomplished using inputattach.
+ */
+
+static int inexio_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct inexio *pinexio;
+	struct input_dev *input_dev;
+	int err;
+
+	pinexio = kzalloc_obj(*pinexio);
+	input_dev = input_allocate_device();
+	if (!pinexio || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	pinexio->serio = serio;
+	pinexio->dev = input_dev;
+	scnprintf(pinexio->phys, sizeof(pinexio->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "iNexio Serial TouchScreen";
+	input_dev->phys = pinexio->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_INEXIO;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0001;
+	input_dev->dev.parent = &serio->dev;
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+	input_set_abs_params(pinexio->dev, ABS_X, INEXIO_MIN_XC, INEXIO_MAX_XC, 0, 0);
+	input_set_abs_params(pinexio->dev, ABS_Y, INEXIO_MIN_YC, INEXIO_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, pinexio);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(pinexio->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(pinexio);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id inexio_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_INEXIO,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, inexio_serio_ids);
+
+static struct serio_driver inexio_drv = {
+	.driver		= {
+		.name	= "inexio",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= inexio_serio_ids,
+	.interrupt	= inexio_interrupt,
+	.connect	= inexio_connect,
+	.disconnect	= inexio_disconnect,
+};
+
+module_serio_driver(inexio_drv);