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, 135 insertions, 0 deletions

diff --git a/drivers/leds/leds-spi-byte.c b/drivers/leds/leds-spi-byte.c
new file mode 100644
index 000000000..0217557aa
--- /dev/null
+++ b/drivers/leds/leds-spi-byte.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de>
+
+/*
+ * The driver supports controllers with a very simple SPI protocol:
+ * - one LED is controlled by a single byte on MOSI
+ * - the value of the byte gives the brightness between two values (lowest to
+ *   highest)
+ * - no return value is necessary (no MISO signal)
+ *
+ * The value for minimum and maximum brightness depends on the device
+ * (compatible string).
+ *
+ * Supported devices:
+ * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
+ *   for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
+ *   controller:
+ *   * Higher two bits set a mode. Lower six bits are a parameter.
+ *   * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)
+ *   * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From
+ *     some tests, the period is about (50ms + 102ms * parameter). There is a
+ *     slightly different pattern starting from 0x10 (longer gap between the
+ *     pulses) but the time still follows that calculation.
+ *   * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
+ *     slight jump in the pattern at 0x10.
+ *   * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
+ *     (105ms * parameter)
+ *   NOTE: This driver currently only supports mode 00.
+ */
+
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/property.h>
+#include <linux/spi/spi.h>
+#include <uapi/linux/uleds.h>
+
+struct spi_byte_chipdef {
+	/* SPI byte that will be send to switch the LED off */
+	u8	off_value;
+	/* SPI byte that will be send to switch the LED to maximum brightness */
+	u8	max_value;
+};
+
+struct spi_byte_led {
+	struct led_classdev		ldev;
+	struct spi_device		*spi;
+	char				name[LED_MAX_NAME_SIZE];
+	struct mutex			mutex;
+	const struct spi_byte_chipdef	*cdef;
+};
+
+static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
+	.off_value = 0x0,
+	.max_value = 0x3F,
+};
+
+static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
+					    enum led_brightness brightness)
+{
+	struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);
+	u8 value;
+	int ret;
+
+	value = (u8) brightness + led->cdef->off_value;
+
+	mutex_lock(&led->mutex);
+	ret = spi_write(led->spi, &value, sizeof(value));
+	mutex_unlock(&led->mutex);
+
+	return ret;
+}
+
+static int spi_byte_probe(struct spi_device *spi)
+{
+	struct fwnode_handle *child __free(fwnode_handle) = NULL;
+	struct device *dev = &spi->dev;
+	struct spi_byte_led *led;
+	struct led_init_data init_data = {};
+	enum led_default_state state;
+	int ret;
+
+	if (device_get_child_node_count(dev) != 1) {
+		dev_err(dev, "Device must have exactly one LED sub-node.");
+		return -EINVAL;
+	}
+
+	led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
+	if (!led)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &led->mutex);
+	if (ret)
+		return ret;
+
+	led->spi = spi;
+	led->cdef = device_get_match_data(dev);
+	led->ldev.brightness = LED_OFF;
+	led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
+	led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
+
+	child = device_get_next_child_node(dev, NULL);
+
+	state = led_init_default_state_get(child);
+	if (state == LEDS_DEFSTATE_ON)
+		led->ldev.brightness = led->ldev.max_brightness;
+	spi_byte_brightness_set_blocking(&led->ldev,
+					 led->ldev.brightness);
+
+	init_data.fwnode = child;
+	init_data.devicename = "leds-spi-byte";
+	init_data.default_label = ":";
+
+	return devm_led_classdev_register_ext(dev, &led->ldev, &init_data);
+}
+
+static const struct of_device_id spi_byte_dt_ids[] = {
+	{ .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
+	{}
+};
+MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);
+
+static struct spi_driver spi_byte_driver = {
+	.probe		= spi_byte_probe,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= spi_byte_dt_ids,
+	},
+};
+module_spi_driver(spi_byte_driver);
+
+MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
+MODULE_DESCRIPTION("single byte SPI LED driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:leds-spi-byte");