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, 113 insertions, 0 deletions

diff --git a/drivers/input/mouse/rpcmouse.c b/drivers/input/mouse/rpcmouse.c
new file mode 100644
index 000000000..6774029e0
--- /dev/null
+++ b/drivers/input/mouse/rpcmouse.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Acorn RiscPC mouse driver for Linux/ARM
+ *
+ *  Copyright (c) 2000-2002 Vojtech Pavlik
+ *  Copyright (C) 1996-2002 Russell King
+ */
+
+/*
+ *
+ * This handles the Acorn RiscPCs mouse.  We basically have a couple of
+ * hardware registers that track the sensor count for the X-Y movement and
+ * another register holding the button state.  On every VSYNC interrupt we read
+ * the complete state and then work out if something has changed.
+ */
+
+#include <linux/module.h>
+#include <linux/ptrace.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/io.h>
+
+#include <mach/hardware.h>
+#include <asm/irq.h>
+#include <asm/hardware/iomd.h>
+
+MODULE_AUTHOR("Vojtech Pavlik, Russell King");
+MODULE_DESCRIPTION("Acorn RiscPC mouse driver");
+MODULE_LICENSE("GPL");
+
+static short rpcmouse_lastx, rpcmouse_lasty;
+static struct input_dev *rpcmouse_dev;
+
+static irqreturn_t rpcmouse_irq(int irq, void *dev_id)
+{
+	struct input_dev *dev = dev_id;
+	short x, y, dx, dy, b;
+
+	x = (short) iomd_readl(IOMD_MOUSEX);
+	y = (short) iomd_readl(IOMD_MOUSEY);
+	b = (short) (__raw_readl(IOMEM(0xe0310000)) ^ 0x70);
+
+	dx = x - rpcmouse_lastx;
+	dy = y - rpcmouse_lasty;
+
+	rpcmouse_lastx = x;
+	rpcmouse_lasty = y;
+
+	input_report_rel(dev, REL_X, dx);
+	input_report_rel(dev, REL_Y, -dy);
+
+	input_report_key(dev, BTN_LEFT,   b & 0x40);
+	input_report_key(dev, BTN_MIDDLE, b & 0x20);
+	input_report_key(dev, BTN_RIGHT,  b & 0x10);
+
+	input_sync(dev);
+
+	return IRQ_HANDLED;
+}
+
+
+static int __init rpcmouse_init(void)
+{
+	int err;
+
+	rpcmouse_dev = input_allocate_device();
+	if (!rpcmouse_dev)
+		return -ENOMEM;
+
+	rpcmouse_dev->name = "Acorn RiscPC Mouse";
+	rpcmouse_dev->phys = "rpcmouse/input0";
+	rpcmouse_dev->id.bustype = BUS_HOST;
+	rpcmouse_dev->id.vendor  = 0x0005;
+	rpcmouse_dev->id.product = 0x0001;
+	rpcmouse_dev->id.version = 0x0100;
+
+	rpcmouse_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	rpcmouse_dev->keybit[BIT_WORD(BTN_LEFT)] = BIT_MASK(BTN_LEFT) |
+		BIT_MASK(BTN_MIDDLE) | BIT_MASK(BTN_RIGHT);
+	rpcmouse_dev->relbit[0]	= BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+
+	rpcmouse_lastx = (short) iomd_readl(IOMD_MOUSEX);
+	rpcmouse_lasty = (short) iomd_readl(IOMD_MOUSEY);
+
+	if (request_irq(IRQ_VSYNCPULSE, rpcmouse_irq, IRQF_SHARED, "rpcmouse", rpcmouse_dev)) {
+		printk(KERN_ERR "rpcmouse: unable to allocate VSYNC interrupt\n");
+		err = -EBUSY;
+		goto err_free_dev;
+	}
+
+	err = input_register_device(rpcmouse_dev);
+	if (err)
+		goto err_free_irq;
+
+	return 0;
+
+ err_free_irq:
+	free_irq(IRQ_VSYNCPULSE, rpcmouse_dev);
+ err_free_dev:
+	input_free_device(rpcmouse_dev);
+
+	return err;
+}
+
+static void __exit rpcmouse_exit(void)
+{
+	free_irq(IRQ_VSYNCPULSE, rpcmouse_dev);
+	input_unregister_device(rpcmouse_dev);
+}
+
+module_init(rpcmouse_init);
+module_exit(rpcmouse_exit);