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, 134 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-versatile.c b/drivers/i2c/busses/i2c-versatile.c
new file mode 100644
index 000000000..a1ab6ef6f
--- /dev/null
+++ b/drivers/i2c/busses/i2c-versatile.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  i2c-versatile.c
+ *
+ *  Copyright (C) 2006 ARM Ltd.
+ *  written by Russell King, Deep Blue Solutions Ltd.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/i2c-algo-bit.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+
+#define I2C_CONTROL	0x00
+#define I2C_CONTROLS	0x00
+#define I2C_CONTROLC	0x04
+#define SCL		(1 << 0)
+#define SDA		(1 << 1)
+
+struct i2c_versatile {
+	struct i2c_adapter	 adap;
+	struct i2c_algo_bit_data algo;
+	void __iomem		 *base;
+};
+
+static void i2c_versatile_setsda(void *data, int state)
+{
+	struct i2c_versatile *i2c = data;
+
+	writel(SDA, i2c->base + (state ? I2C_CONTROLS : I2C_CONTROLC));
+}
+
+static void i2c_versatile_setscl(void *data, int state)
+{
+	struct i2c_versatile *i2c = data;
+
+	writel(SCL, i2c->base + (state ? I2C_CONTROLS : I2C_CONTROLC));
+}
+
+static int i2c_versatile_getsda(void *data)
+{
+	struct i2c_versatile *i2c = data;
+	return !!(readl(i2c->base + I2C_CONTROL) & SDA);
+}
+
+static int i2c_versatile_getscl(void *data)
+{
+	struct i2c_versatile *i2c = data;
+	return !!(readl(i2c->base + I2C_CONTROL) & SCL);
+}
+
+static const struct i2c_algo_bit_data i2c_versatile_algo = {
+	.setsda	= i2c_versatile_setsda,
+	.setscl = i2c_versatile_setscl,
+	.getsda	= i2c_versatile_getsda,
+	.getscl = i2c_versatile_getscl,
+	.udelay	= 30,
+	.timeout = HZ,
+};
+
+static int i2c_versatile_probe(struct platform_device *dev)
+{
+	struct i2c_versatile *i2c;
+	int ret;
+
+	i2c = devm_kzalloc(&dev->dev, sizeof(struct i2c_versatile), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	i2c->base = devm_platform_get_and_ioremap_resource(dev, 0, NULL);
+	if (IS_ERR(i2c->base))
+		return PTR_ERR(i2c->base);
+
+	writel(SCL | SDA, i2c->base + I2C_CONTROLS);
+
+	i2c->adap.owner = THIS_MODULE;
+	strscpy(i2c->adap.name, "Versatile I2C adapter", sizeof(i2c->adap.name));
+	i2c->adap.algo_data = &i2c->algo;
+	i2c->adap.dev.parent = &dev->dev;
+	i2c->adap.dev.of_node = dev->dev.of_node;
+	i2c->algo = i2c_versatile_algo;
+	i2c->algo.data = i2c;
+
+	i2c->adap.nr = dev->id;
+	ret = i2c_bit_add_numbered_bus(&i2c->adap);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(dev, i2c);
+
+	return 0;
+}
+
+static void i2c_versatile_remove(struct platform_device *dev)
+{
+	struct i2c_versatile *i2c = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&i2c->adap);
+}
+
+static const struct of_device_id i2c_versatile_match[] = {
+	{ .compatible = "arm,versatile-i2c", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, i2c_versatile_match);
+
+static struct platform_driver i2c_versatile_driver = {
+	.probe		= i2c_versatile_probe,
+	.remove		= i2c_versatile_remove,
+	.driver		= {
+		.name	= "versatile-i2c",
+		.of_match_table = i2c_versatile_match,
+	},
+};
+
+static int __init i2c_versatile_init(void)
+{
+	return platform_driver_register(&i2c_versatile_driver);
+}
+
+static void __exit i2c_versatile_exit(void)
+{
+	platform_driver_unregister(&i2c_versatile_driver);
+}
+
+subsys_initcall(i2c_versatile_init);
+module_exit(i2c_versatile_exit);
+
+MODULE_DESCRIPTION("ARM Versatile I2C bus driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:versatile-i2c");