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, 200 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-cgbc.c b/drivers/gpio/gpio-cgbc.c
new file mode 100644
index 000000000..84b5ed3c6
--- /dev/null
+++ b/drivers/gpio/gpio-cgbc.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Congatec Board Controller GPIO driver
+ *
+ * Copyright (C) 2024 Bootlin
+ * Author: Thomas Richard <thomas.richard@bootlin.com>
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/mfd/cgbc.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+
+#define CGBC_GPIO_NGPIO	14
+
+#define CGBC_GPIO_CMD_GET	0x64
+#define CGBC_GPIO_CMD_SET	0x65
+#define CGBC_GPIO_CMD_DIR_GET	0x66
+#define CGBC_GPIO_CMD_DIR_SET	0x67
+
+struct cgbc_gpio_data {
+	struct gpio_chip	chip;
+	struct cgbc_device_data	*cgbc;
+	struct mutex lock;
+};
+
+static int cgbc_gpio_cmd(struct cgbc_device_data *cgbc,
+			 u8 cmd0, u8 cmd1, u8 cmd2, u8 *value)
+{
+	u8 cmd[3] = {cmd0, cmd1, cmd2};
+
+	return cgbc_command(cgbc, cmd, sizeof(cmd), value, 1, NULL);
+}
+
+static int cgbc_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+	struct cgbc_device_data *cgbc = gpio->cgbc;
+	int ret;
+	u8 val;
+
+	scoped_guard(mutex, &gpio->lock)
+		ret = cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_GET, (offset > 7) ? 1 : 0, 0, &val);
+
+	offset %= 8;
+
+	if (ret)
+		return ret;
+
+	return !!(val & BIT(offset));
+}
+
+static int __cgbc_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			   int value)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+	struct cgbc_device_data *cgbc = gpio->cgbc;
+	u8 val;
+	int ret;
+
+	ret = cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_GET, (offset > 7) ? 1 : 0, 0, &val);
+	if (ret)
+		return ret;
+
+	if (value)
+		val |= BIT(offset % 8);
+	else
+		val &= ~(BIT(offset % 8));
+
+	return cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_SET, (offset > 7) ? 1 : 0, val, &val);
+}
+
+static int cgbc_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+
+	guard(mutex)(&gpio->lock);
+
+	return __cgbc_gpio_set(chip, offset, value);
+}
+
+static int cgbc_gpio_direction_set(struct gpio_chip *chip,
+				   unsigned int offset, int direction)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+	struct cgbc_device_data *cgbc = gpio->cgbc;
+	int ret;
+	u8 val;
+
+	ret = cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_DIR_GET, (offset > 7) ? 1 : 0, 0, &val);
+	if (ret)
+		goto end;
+
+	if (direction == GPIO_LINE_DIRECTION_IN)
+		val &= ~(BIT(offset % 8));
+	else
+		val |= BIT(offset % 8);
+
+	ret = cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_DIR_SET, (offset > 7) ? 1 : 0, val, &val);
+
+end:
+	return ret;
+}
+
+static int cgbc_gpio_direction_input(struct gpio_chip *chip,
+				     unsigned int offset)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+
+	guard(mutex)(&gpio->lock);
+	return cgbc_gpio_direction_set(chip, offset, GPIO_LINE_DIRECTION_IN);
+}
+
+static int cgbc_gpio_direction_output(struct gpio_chip *chip,
+				      unsigned int offset, int value)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+	int ret;
+
+	guard(mutex)(&gpio->lock);
+
+	ret = __cgbc_gpio_set(chip, offset, value);
+	if (ret)
+		return ret;
+
+	return cgbc_gpio_direction_set(chip, offset, GPIO_LINE_DIRECTION_OUT);
+}
+
+static int cgbc_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+	struct cgbc_gpio_data *gpio = gpiochip_get_data(chip);
+	struct cgbc_device_data *cgbc = gpio->cgbc;
+	int ret;
+	u8 val;
+
+	scoped_guard(mutex, &gpio->lock)
+		ret = cgbc_gpio_cmd(cgbc, CGBC_GPIO_CMD_DIR_GET, (offset > 7) ? 1 : 0, 0, &val);
+
+	if (ret)
+		return ret;
+
+	if (val & BIT(offset % 8))
+		return GPIO_LINE_DIRECTION_OUT;
+	else
+		return GPIO_LINE_DIRECTION_IN;
+}
+
+static int cgbc_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cgbc_device_data *cgbc = dev_get_drvdata(dev->parent);
+	struct cgbc_gpio_data *gpio;
+	struct gpio_chip *chip;
+	int ret;
+
+	gpio = devm_kzalloc(dev, sizeof(*gpio), GFP_KERNEL);
+	if (!gpio)
+		return -ENOMEM;
+
+	gpio->cgbc = cgbc;
+
+	platform_set_drvdata(pdev, gpio);
+
+	chip = &gpio->chip;
+	chip->label = dev_name(&pdev->dev);
+	chip->owner = THIS_MODULE;
+	chip->parent = dev;
+	chip->base = -1;
+	chip->direction_input = cgbc_gpio_direction_input;
+	chip->direction_output = cgbc_gpio_direction_output;
+	chip->get_direction = cgbc_gpio_get_direction;
+	chip->get = cgbc_gpio_get;
+	chip->set = cgbc_gpio_set;
+	chip->ngpio = CGBC_GPIO_NGPIO;
+
+	ret = devm_mutex_init(dev, &gpio->lock);
+	if (ret)
+		return ret;
+
+	ret = devm_gpiochip_add_data(dev, chip, gpio);
+	if (ret)
+		return dev_err_probe(dev, ret, "Could not register GPIO chip\n");
+
+	return 0;
+}
+
+static struct platform_driver cgbc_gpio_driver = {
+	.driver = {
+		.name = "cgbc-gpio",
+	},
+	.probe	= cgbc_gpio_probe,
+};
+
+module_platform_driver(cgbc_gpio_driver);
+
+MODULE_DESCRIPTION("Congatec Board Controller GPIO Driver");
+MODULE_AUTHOR("Thomas Richard <thomas.richard@bootlin.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:cgbc-gpio");