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, 152 insertions, 0 deletions

diff --git a/drivers/input/keyboard/xtkbd.c b/drivers/input/keyboard/xtkbd.c
new file mode 100644
index 000000000..c0b4978a8
--- /dev/null
+++ b/drivers/input/keyboard/xtkbd.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 1999-2001 Vojtech Pavlik
+ */
+
+/*
+ * XT keyboard driver for Linux
+ */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"XT keyboard driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+#define XTKBD_EMUL0	0xe0
+#define XTKBD_EMUL1	0xe1
+#define XTKBD_KEY	0x7f
+#define XTKBD_RELEASE	0x80
+
+static unsigned char xtkbd_keycode[256] = {
+	  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15,
+	 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
+	 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
+	 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
+	 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
+	 80, 81, 82, 83,  0,  0,  0, 87, 88,  0,  0,  0,  0,  0,  0,  0,
+	  0,  0,  0,  0,  0, 87, 88,  0,  0,  0,  0,110,111,103,108,105,
+	106
+};
+
+struct xtkbd {
+	unsigned char keycode[256];
+	struct input_dev *dev;
+	struct serio *serio;
+	char phys[32];
+};
+
+static irqreturn_t xtkbd_interrupt(struct serio *serio,
+	unsigned char data, unsigned int flags)
+{
+	struct xtkbd *xtkbd = serio_get_drvdata(serio);
+
+	switch (data) {
+		case XTKBD_EMUL0:
+		case XTKBD_EMUL1:
+			break;
+		default:
+
+			if (xtkbd->keycode[data & XTKBD_KEY]) {
+				input_report_key(xtkbd->dev, xtkbd->keycode[data & XTKBD_KEY], !(data & XTKBD_RELEASE));
+				input_sync(xtkbd->dev);
+			} else {
+				printk(KERN_WARNING "xtkbd.c: Unknown key (scancode %#x) %s.\n",
+					data & XTKBD_KEY, data & XTKBD_RELEASE ? "released" : "pressed");
+			}
+	}
+	return IRQ_HANDLED;
+}
+
+static int xtkbd_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct xtkbd *xtkbd;
+	struct input_dev *input_dev;
+	int err = -ENOMEM;
+	int i;
+
+	xtkbd = kmalloc_obj(*xtkbd);
+	input_dev = input_allocate_device();
+	if (!xtkbd || !input_dev)
+		goto fail1;
+
+	xtkbd->serio = serio;
+	xtkbd->dev = input_dev;
+	snprintf(xtkbd->phys, sizeof(xtkbd->phys), "%s/input0", serio->phys);
+	memcpy(xtkbd->keycode, xtkbd_keycode, sizeof(xtkbd->keycode));
+
+	input_dev->name = "XT Keyboard";
+	input_dev->phys = xtkbd->phys;
+	input_dev->id.bustype = BUS_XTKBD;
+	input_dev->id.vendor  = 0x0001;
+	input_dev->id.product = 0x0001;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+	input_dev->keycode = xtkbd->keycode;
+	input_dev->keycodesize = sizeof(unsigned char);
+	input_dev->keycodemax = ARRAY_SIZE(xtkbd_keycode);
+
+	for (i = 0; i < 255; i++)
+		set_bit(xtkbd->keycode[i], input_dev->keybit);
+	clear_bit(0, input_dev->keybit);
+
+	serio_set_drvdata(serio, xtkbd);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(xtkbd->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(xtkbd);
+	return err;
+}
+
+static void xtkbd_disconnect(struct serio *serio)
+{
+	struct xtkbd *xtkbd = serio_get_drvdata(serio);
+
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_unregister_device(xtkbd->dev);
+	kfree(xtkbd);
+}
+
+static const struct serio_device_id xtkbd_serio_ids[] = {
+	{
+		.type	= SERIO_XT,
+		.proto	= SERIO_ANY,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, xtkbd_serio_ids);
+
+static struct serio_driver xtkbd_drv = {
+	.driver		= {
+		.name	= "xtkbd",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= xtkbd_serio_ids,
+	.interrupt	= xtkbd_interrupt,
+	.connect	= xtkbd_connect,
+	.disconnect	= xtkbd_disconnect,
+};
+
+module_serio_driver(xtkbd_drv);