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, 222 insertions, 0 deletions

diff --git a/drivers/input/serio/parkbd.c b/drivers/input/serio/parkbd.c
new file mode 100644
index 000000000..09a24413d
--- /dev/null
+++ b/drivers/input/serio/parkbd.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Parallel port to Keyboard port adapter driver for Linux
+ *
+ *  Copyright (c) 1999-2004 Vojtech Pavlik
+ */
+
+
+/*
+ * To connect an AT or XT keyboard to the parallel port, a fairly simple adapter
+ * can be made:
+ * 
+ *  Parallel port            Keyboard port
+ *
+ *     +5V --------------------- +5V (4)
+ *  
+ *                 ______
+ *     +5V -------|______|--.
+ *                          |
+ *     ACK (10) ------------|
+ *                          |--- KBD CLOCK (5)
+ *     STROBE (1) ---|<|----'
+ *     
+ *                 ______
+ *     +5V -------|______|--.
+ *                          |
+ *     BUSY (11) -----------|
+ *                          |--- KBD DATA (1)
+ *     AUTOFD (14) --|<|----'
+ *
+ *     GND (18-25) ------------- GND (3)
+ *     
+ * The diodes can be fairly any type, and the resistors should be somewhere
+ * around 5 kOhm, but the adapter will likely work without the resistors,
+ * too.
+ *
+ * The +5V source can be taken either from USB, from mouse or keyboard ports,
+ * or from a joystick port. Unfortunately, the parallel port of a PC doesn't
+ * have a +5V pin, and feeding the keyboard from signal pins is out of question
+ * with 300 mA power reqirement of a typical AT keyboard.
+ */
+
+#include <linux/module.h>
+#include <linux/parport.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/serio.h>
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION("Parallel port to Keyboard port adapter driver");
+MODULE_LICENSE("GPL");
+
+static unsigned int parkbd_pp_no;
+module_param_named(port, parkbd_pp_no, int, 0);
+MODULE_PARM_DESC(port, "Parallel port the adapter is connected to (default is 0)");
+
+static unsigned int parkbd_mode = SERIO_8042;
+module_param_named(mode, parkbd_mode, uint, 0);
+MODULE_PARM_DESC(mode, "Mode of operation: XT = 0/AT = 1 (default)");
+
+#define PARKBD_CLOCK	0x01	/* Strobe & Ack */
+#define PARKBD_DATA	0x02	/* AutoFd & Busy */
+
+static int parkbd_buffer;
+static int parkbd_counter;
+static unsigned long parkbd_last;
+static int parkbd_writing;
+static unsigned long parkbd_start;
+
+static struct pardevice *parkbd_dev;
+static struct serio *parkbd_port;
+
+static int parkbd_readlines(void)
+{
+	return (parport_read_status(parkbd_dev->port) >> 6) ^ 2;
+}
+
+static void parkbd_writelines(int data)
+{
+	parport_write_control(parkbd_dev->port, (~data & 3) | 0x10);
+}
+
+static int parkbd_write(struct serio *port, unsigned char c)
+{
+	unsigned char p;
+
+	if (!parkbd_mode) return -1;
+
+        p = c ^ (c >> 4);
+	p = p ^ (p >> 2);
+	p = p ^ (p >> 1);
+
+	parkbd_counter = 0;
+	parkbd_writing = 1;
+	parkbd_buffer = c | (((int) (~p & 1)) << 8) | 0x600;
+
+	parkbd_writelines(2);
+
+	return 0;
+}
+
+static void parkbd_interrupt(void *dev_id)
+{
+
+	if (parkbd_writing) {
+
+		if (parkbd_counter && ((parkbd_counter == 11) || time_after(jiffies, parkbd_last + HZ/100))) {
+			parkbd_counter = 0;
+			parkbd_buffer = 0;
+			parkbd_writing = 0;
+			parkbd_writelines(3);
+			return;
+		}
+
+		parkbd_writelines(((parkbd_buffer >> parkbd_counter++) & 1) | 2);
+
+		if (parkbd_counter == 11) {
+			parkbd_counter = 0;
+			parkbd_buffer = 0;
+			parkbd_writing = 0;
+			parkbd_writelines(3);
+		}
+
+	} else {
+
+		if ((parkbd_counter == parkbd_mode + 10) || time_after(jiffies, parkbd_last + HZ/100)) {
+			parkbd_counter = 0;
+			parkbd_buffer = 0;
+		}
+
+		parkbd_buffer |= (parkbd_readlines() >> 1) << parkbd_counter++;
+
+		if (parkbd_counter == parkbd_mode + 10)
+			serio_interrupt(parkbd_port, (parkbd_buffer >> (2 - parkbd_mode)) & 0xff, 0);
+	}
+
+	parkbd_last = jiffies;
+}
+
+static int parkbd_getport(struct parport *pp)
+{
+	struct pardev_cb parkbd_parport_cb;
+
+	memset(&parkbd_parport_cb, 0, sizeof(parkbd_parport_cb));
+	parkbd_parport_cb.irq_func = parkbd_interrupt;
+	parkbd_parport_cb.flags = PARPORT_FLAG_EXCL;
+
+	parkbd_dev = parport_register_dev_model(pp, "parkbd",
+						&parkbd_parport_cb, 0);
+
+	if (!parkbd_dev)
+		return -ENODEV;
+
+	if (parport_claim(parkbd_dev)) {
+		parport_unregister_device(parkbd_dev);
+		return -EBUSY;
+	}
+
+	parkbd_start = jiffies;
+
+	return 0;
+}
+
+static struct serio *parkbd_allocate_serio(void)
+{
+	struct serio *serio;
+
+	serio = kzalloc_obj(*serio);
+	if (serio) {
+		serio->id.type = parkbd_mode;
+		serio->write = parkbd_write;
+		strscpy(serio->name, "PARKBD AT/XT keyboard adapter", sizeof(serio->name));
+		snprintf(serio->phys, sizeof(serio->phys), "%s/serio0", parkbd_dev->port->name);
+	}
+
+	return serio;
+}
+
+static void parkbd_attach(struct parport *pp)
+{
+	if (pp->number != parkbd_pp_no) {
+		pr_debug("Not using parport%d.\n", pp->number);
+		return;
+	}
+
+	if (parkbd_getport(pp))
+		return;
+
+	parkbd_port = parkbd_allocate_serio();
+	if (!parkbd_port) {
+		parport_release(parkbd_dev);
+		parport_unregister_device(parkbd_dev);
+		return;
+	}
+
+	parkbd_writelines(3);
+
+	serio_register_port(parkbd_port);
+
+	printk(KERN_INFO "serio: PARKBD %s adapter on %s\n",
+                        parkbd_mode ? "AT" : "XT", parkbd_dev->port->name);
+
+	return;
+}
+
+static void parkbd_detach(struct parport *port)
+{
+	if (!parkbd_port || port->number != parkbd_pp_no)
+		return;
+
+	parport_release(parkbd_dev);
+	serio_unregister_port(parkbd_port);
+	parport_unregister_device(parkbd_dev);
+	parkbd_port = NULL;
+}
+
+static struct parport_driver parkbd_parport_driver = {
+	.name = "parkbd",
+	.match_port = parkbd_attach,
+	.detach = parkbd_detach,
+};
+module_parport_driver(parkbd_parport_driver);