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, 137 insertions, 0 deletions

diff --git a/drivers/leds/leds-syscon.c b/drivers/leds/leds-syscon.c
new file mode 100644
index 000000000..d633ad519
--- /dev/null
+++ b/drivers/leds/leds-syscon.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic Syscon LEDs Driver
+ *
+ * Copyright (c) 2014, Linaro Limited
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
+#include <linux/leds.h>
+
+/**
+ * struct syscon_led - state container for syscon based LEDs
+ * @cdev: LED class device for this LED
+ * @map: regmap to access the syscon device backing this LED
+ * @offset: the offset into the syscon regmap for the LED register
+ * @mask: the bit in the register corresponding to the LED
+ * @state: current state of the LED
+ */
+struct syscon_led {
+	struct led_classdev cdev;
+	struct regmap *map;
+	u32 offset;
+	u32 mask;
+	bool state;
+};
+
+static void syscon_led_set(struct led_classdev *led_cdev,
+	enum led_brightness value)
+{
+	struct syscon_led *sled =
+		container_of(led_cdev, struct syscon_led, cdev);
+	u32 val;
+	int ret;
+
+	if (value == LED_OFF) {
+		val = 0;
+		sled->state = false;
+	} else {
+		val = sled->mask;
+		sled->state = true;
+	}
+
+	ret = regmap_update_bits(sled->map, sled->offset, sled->mask, val);
+	if (ret < 0)
+		dev_err(sled->cdev.dev, "error updating LED status\n");
+}
+
+static int syscon_led_probe(struct platform_device *pdev)
+{
+	struct led_init_data init_data = {};
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev_of_node(dev);
+	struct device *parent;
+	struct regmap *map;
+	struct syscon_led *sled;
+	enum led_default_state state;
+	u32 value;
+	int ret;
+
+	parent = dev->parent;
+	if (!parent) {
+		dev_err(dev, "no parent for syscon LED\n");
+		return -ENODEV;
+	}
+	map = syscon_node_to_regmap(dev_of_node(parent));
+	if (IS_ERR(map)) {
+		dev_err(dev, "no regmap for syscon LED parent\n");
+		return PTR_ERR(map);
+	}
+
+	sled = devm_kzalloc(dev, sizeof(*sled), GFP_KERNEL);
+	if (!sled)
+		return -ENOMEM;
+
+	sled->map = map;
+
+	if (of_property_read_u32(np, "reg", &sled->offset) &&
+	    of_property_read_u32(np, "offset", &sled->offset))
+		return -EINVAL;
+	if (of_property_read_u32(np, "mask", &sled->mask))
+		return -EINVAL;
+
+	init_data.fwnode = of_fwnode_handle(np);
+
+	state = led_init_default_state_get(init_data.fwnode);
+	switch (state) {
+	case LEDS_DEFSTATE_ON:
+		ret = regmap_update_bits(map, sled->offset, sled->mask, sled->mask);
+		if (ret < 0)
+			return ret;
+		sled->state = true;
+		break;
+	case LEDS_DEFSTATE_KEEP:
+		ret = regmap_read(map, sled->offset, &value);
+		if (ret < 0)
+			return ret;
+		sled->state = !!(value & sled->mask);
+		break;
+	default:
+		ret = regmap_update_bits(map, sled->offset, sled->mask, 0);
+		if (ret < 0)
+			return ret;
+		sled->state = false;
+	}
+	sled->cdev.brightness_set = syscon_led_set;
+
+	ret = devm_led_classdev_register_ext(dev, &sled->cdev, &init_data);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(pdev, sled);
+	dev_info(dev, "registered LED %s\n", sled->cdev.name);
+
+	return 0;
+}
+
+static const struct of_device_id of_syscon_leds_match[] = {
+	{ .compatible = "register-bit-led", },
+	{},
+};
+
+static struct platform_driver syscon_led_driver = {
+	.probe		= syscon_led_probe,
+	.driver		= {
+		.name	= "leds-syscon",
+		.of_match_table = of_syscon_leds_match,
+		.suppress_bind_attrs = true,
+	},
+};
+builtin_platform_driver(syscon_led_driver);