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/serio/rpckbd.c b/drivers/input/serio/rpckbd.c
new file mode 100644
index 000000000..4d817850b
--- /dev/null
+++ b/drivers/input/serio/rpckbd.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *  Copyright (c) 2002 Russell King
+ */
+
+/*
+ * Acorn RiscPC PS/2 keyboard controller driver for Linux/ARM
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/serio.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+#include <mach/hardware.h>
+#include <asm/hardware/iomd.h>
+
+MODULE_AUTHOR("Vojtech Pavlik, Russell King");
+MODULE_DESCRIPTION("Acorn RiscPC PS/2 keyboard controller driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:kart");
+
+struct rpckbd_data {
+	int tx_irq;
+	int rx_irq;
+};
+
+static int rpckbd_write(struct serio *port, unsigned char val)
+{
+	while (!(iomd_readb(IOMD_KCTRL) & (1 << 7)))
+		cpu_relax();
+
+	iomd_writeb(val, IOMD_KARTTX);
+
+	return 0;
+}
+
+static irqreturn_t rpckbd_rx(int irq, void *dev_id)
+{
+	struct serio *port = dev_id;
+	unsigned int byte;
+	int handled = IRQ_NONE;
+
+	while (iomd_readb(IOMD_KCTRL) & (1 << 5)) {
+		byte = iomd_readb(IOMD_KARTRX);
+
+		serio_interrupt(port, byte, 0);
+		handled = IRQ_HANDLED;
+	}
+	return handled;
+}
+
+static irqreturn_t rpckbd_tx(int irq, void *dev_id)
+{
+	return IRQ_HANDLED;
+}
+
+static int rpckbd_open(struct serio *port)
+{
+	struct rpckbd_data *rpckbd = port->port_data;
+
+	/* Reset the keyboard state machine. */
+	iomd_writeb(0, IOMD_KCTRL);
+	iomd_writeb(8, IOMD_KCTRL);
+	iomd_readb(IOMD_KARTRX);
+
+	if (request_irq(rpckbd->rx_irq, rpckbd_rx, 0, "rpckbd", port) != 0) {
+		printk(KERN_ERR "rpckbd.c: Could not allocate keyboard receive IRQ\n");
+		return -EBUSY;
+	}
+
+	if (request_irq(rpckbd->tx_irq, rpckbd_tx, 0, "rpckbd", port) != 0) {
+		printk(KERN_ERR "rpckbd.c: Could not allocate keyboard transmit IRQ\n");
+		free_irq(rpckbd->rx_irq, port);
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+static void rpckbd_close(struct serio *port)
+{
+	struct rpckbd_data *rpckbd = port->port_data;
+
+	free_irq(rpckbd->rx_irq, port);
+	free_irq(rpckbd->tx_irq, port);
+}
+
+/*
+ * Allocate and initialize serio structure for subsequent registration
+ * with serio core.
+ */
+static int rpckbd_probe(struct platform_device *dev)
+{
+	struct rpckbd_data *rpckbd;
+	struct serio *serio;
+	int tx_irq, rx_irq;
+
+	rx_irq = platform_get_irq(dev, 0);
+	if (rx_irq < 0)
+		return rx_irq;
+
+	tx_irq = platform_get_irq(dev, 1);
+	if (tx_irq < 0)
+		return tx_irq;
+
+	serio = kzalloc_obj(*serio);
+	rpckbd = kzalloc_obj(*rpckbd);
+	if (!serio || !rpckbd) {
+		kfree(rpckbd);
+		kfree(serio);
+		return -ENOMEM;
+	}
+
+	rpckbd->rx_irq = rx_irq;
+	rpckbd->tx_irq = tx_irq;
+
+	serio->id.type		= SERIO_8042;
+	serio->write		= rpckbd_write;
+	serio->open		= rpckbd_open;
+	serio->close		= rpckbd_close;
+	serio->dev.parent	= &dev->dev;
+	serio->port_data	= rpckbd;
+	strscpy(serio->name, "RiscPC PS/2 kbd port", sizeof(serio->name));
+	strscpy(serio->phys, "rpckbd/serio0", sizeof(serio->phys));
+
+	platform_set_drvdata(dev, serio);
+	serio_register_port(serio);
+	return 0;
+}
+
+static void rpckbd_remove(struct platform_device *dev)
+{
+	struct serio *serio = platform_get_drvdata(dev);
+	struct rpckbd_data *rpckbd = serio->port_data;
+
+	serio_unregister_port(serio);
+	kfree(rpckbd);
+}
+
+static struct platform_driver rpckbd_driver = {
+	.probe		= rpckbd_probe,
+	.remove		= rpckbd_remove,
+	.driver		= {
+		.name	= "kart",
+	},
+};
+module_platform_driver(rpckbd_driver);