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, 209 insertions, 0 deletions

diff --git a/drivers/input/serio/ambakmi.c b/drivers/input/serio/ambakmi.c
new file mode 100644
index 000000000..046b8f388
--- /dev/null
+++ b/drivers/input/serio/ambakmi.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  linux/drivers/input/serio/ambakmi.c
+ *
+ *  Copyright (C) 2000-2003 Deep Blue Solutions Ltd.
+ *  Copyright (C) 2002 Russell King.
+ */
+#include <linux/module.h>
+#include <linux/serio.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/amba/bus.h>
+#include <linux/amba/kmi.h>
+#include <linux/clk.h>
+
+#include <asm/io.h>
+#include <asm/irq.h>
+
+#define KMI_BASE	(kmi->base)
+
+struct amba_kmi_port {
+	struct serio		*io;
+	struct clk		*clk;
+	void __iomem		*base;
+	unsigned int		irq;
+	unsigned int		divisor;
+	unsigned int		open;
+};
+
+static irqreturn_t amba_kmi_int(int irq, void *dev_id)
+{
+	struct amba_kmi_port *kmi = dev_id;
+	unsigned int status = readb(KMIIR);
+	int handled = IRQ_NONE;
+
+	while (status & KMIIR_RXINTR) {
+		serio_interrupt(kmi->io, readb(KMIDATA), 0);
+		status = readb(KMIIR);
+		handled = IRQ_HANDLED;
+	}
+
+	return handled;
+}
+
+static int amba_kmi_write(struct serio *io, unsigned char val)
+{
+	struct amba_kmi_port *kmi = io->port_data;
+	unsigned int timeleft = 10000; /* timeout in 100ms */
+
+	while ((readb(KMISTAT) & KMISTAT_TXEMPTY) == 0 && --timeleft)
+		udelay(10);
+
+	if (timeleft)
+		writeb(val, KMIDATA);
+
+	return timeleft ? 0 : SERIO_TIMEOUT;
+}
+
+static int amba_kmi_open(struct serio *io)
+{
+	struct amba_kmi_port *kmi = io->port_data;
+	unsigned int divisor;
+	int ret;
+
+	ret = clk_prepare_enable(kmi->clk);
+	if (ret)
+		goto out;
+
+	divisor = clk_get_rate(kmi->clk) / 8000000 - 1;
+	writeb(divisor, KMICLKDIV);
+	writeb(KMICR_EN, KMICR);
+
+	ret = request_irq(kmi->irq, amba_kmi_int, IRQF_SHARED, "kmi-pl050",
+			  kmi);
+	if (ret) {
+		printk(KERN_ERR "kmi: failed to claim IRQ%d\n", kmi->irq);
+		writeb(0, KMICR);
+		goto clk_disable;
+	}
+
+	writeb(KMICR_EN | KMICR_RXINTREN, KMICR);
+
+	return 0;
+
+ clk_disable:
+	clk_disable_unprepare(kmi->clk);
+ out:
+	return ret;
+}
+
+static void amba_kmi_close(struct serio *io)
+{
+	struct amba_kmi_port *kmi = io->port_data;
+
+	writeb(0, KMICR);
+
+	free_irq(kmi->irq, kmi);
+	clk_disable_unprepare(kmi->clk);
+}
+
+static int amba_kmi_probe(struct amba_device *dev,
+	const struct amba_id *id)
+{
+	struct amba_kmi_port *kmi;
+	struct serio *io;
+	int ret;
+
+	ret = amba_request_regions(dev, NULL);
+	if (ret)
+		return ret;
+
+	kmi = kzalloc_obj(*kmi);
+	io = kzalloc_obj(*io);
+	if (!kmi || !io) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+
+	io->id.type	= SERIO_8042;
+	io->write	= amba_kmi_write;
+	io->open	= amba_kmi_open;
+	io->close	= amba_kmi_close;
+	strscpy(io->name, dev_name(&dev->dev), sizeof(io->name));
+	strscpy(io->phys, dev_name(&dev->dev), sizeof(io->phys));
+	io->port_data	= kmi;
+	io->dev.parent	= &dev->dev;
+
+	kmi->io		= io;
+	kmi->base	= ioremap(dev->res.start, resource_size(&dev->res));
+	if (!kmi->base) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	kmi->clk = clk_get(&dev->dev, "KMIREFCLK");
+	if (IS_ERR(kmi->clk)) {
+		ret = PTR_ERR(kmi->clk);
+		goto unmap;
+	}
+
+	kmi->irq = dev->irq[0];
+	amba_set_drvdata(dev, kmi);
+
+	serio_register_port(kmi->io);
+	return 0;
+
+ unmap:
+	iounmap(kmi->base);
+ out:
+	kfree(kmi);
+	kfree(io);
+	amba_release_regions(dev);
+	return ret;
+}
+
+static void amba_kmi_remove(struct amba_device *dev)
+{
+	struct amba_kmi_port *kmi = amba_get_drvdata(dev);
+
+	serio_unregister_port(kmi->io);
+	clk_put(kmi->clk);
+	iounmap(kmi->base);
+	kfree(kmi);
+	amba_release_regions(dev);
+}
+
+static int amba_kmi_resume(struct device *dev)
+{
+	struct amba_kmi_port *kmi = dev_get_drvdata(dev);
+
+	/* kick the serio layer to rescan this port */
+	serio_reconnect(kmi->io);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(amba_kmi_dev_pm_ops, NULL, amba_kmi_resume);
+
+static const struct amba_id amba_kmi_idtable[] = {
+	{
+		.id	= 0x00041050,
+		.mask	= 0x000fffff,
+	},
+	{ 0, 0 }
+};
+
+MODULE_DEVICE_TABLE(amba, amba_kmi_idtable);
+
+static struct amba_driver ambakmi_driver = {
+	.drv		= {
+		.name	= "kmi-pl050",
+		.pm	= pm_sleep_ptr(&amba_kmi_dev_pm_ops),
+	},
+	.id_table	= amba_kmi_idtable,
+	.probe		= amba_kmi_probe,
+	.remove		= amba_kmi_remove,
+};
+
+module_amba_driver(ambakmi_driver);
+
+MODULE_AUTHOR("Russell King <rmk@arm.linux.org.uk>");
+MODULE_DESCRIPTION("AMBA KMI controller driver");
+MODULE_LICENSE("GPL");