x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 731 insertions, 0 deletions

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
new file mode 100644
index 000000000..a51b0ed53
--- /dev/null
+++ b/drivers/leds/led-class.c
@@ -0,0 +1,731 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * LED Class Core
+ *
+ * Copyright (C) 2005 John Lenz <lenz@cs.wisc.edu>
+ * Copyright (C) 2005-2007 Richard Purdie <rpurdie@openedhand.com>
+ */
+
+#include <linux/ctype.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timer.h>
+#include <uapi/linux/uleds.h>
+#include <linux/of.h>
+#include "leds.h"
+
+static DEFINE_MUTEX(leds_lookup_lock);
+static LIST_HEAD(leds_lookup_list);
+
+static struct workqueue_struct *leds_wq;
+
+static bool led_trigger_is_hw_controlled(struct led_classdev *led_cdev)
+{
+#ifdef CONFIG_LEDS_TRIGGERS
+	guard(rwsem_read)(&led_cdev->trigger_lock);
+	return led_cdev->trigger && led_cdev->trigger->trigger_type;
+#else
+	return false;
+#endif
+}
+
+static ssize_t brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned int brightness;
+
+	if (led_trigger_is_hw_controlled(led_cdev))
+		return -ENODATA;
+
+	mutex_lock(&led_cdev->led_access);
+	led_update_brightness(led_cdev);
+	brightness = led_cdev->brightness;
+	mutex_unlock(&led_cdev->led_access);
+
+	return sysfs_emit(buf, "%u\n", brightness);
+}
+
+static ssize_t brightness_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		goto unlock;
+
+	if (state == LED_OFF)
+		led_trigger_remove(led_cdev);
+	led_set_brightness(led_cdev, state);
+
+	ret = size;
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+static DEVICE_ATTR_RW(brightness);
+
+static ssize_t max_brightness_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned int max_brightness;
+
+	mutex_lock(&led_cdev->led_access);
+	max_brightness = led_cdev->max_brightness;
+	mutex_unlock(&led_cdev->led_access);
+
+	return sysfs_emit(buf, "%u\n", max_brightness);
+}
+static DEVICE_ATTR_RO(max_brightness);
+
+#ifdef CONFIG_LEDS_TRIGGERS
+static const BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);
+static const struct bin_attribute *const led_trigger_bin_attrs[] = {
+	&bin_attr_trigger,
+	NULL,
+};
+static const struct attribute_group led_trigger_group = {
+	.bin_attrs = led_trigger_bin_attrs,
+};
+#endif
+
+static struct attribute *led_class_attrs[] = {
+	&dev_attr_brightness.attr,
+	&dev_attr_max_brightness.attr,
+	NULL,
+};
+
+static const struct attribute_group led_group = {
+	.attrs = led_class_attrs,
+};
+
+static const struct attribute_group *led_groups[] = {
+	&led_group,
+#ifdef CONFIG_LEDS_TRIGGERS
+	&led_trigger_group,
+#endif
+	NULL,
+};
+
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+static ssize_t brightness_hw_changed_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->brightness_hw_changed == -1)
+		return -ENODATA;
+
+	return sysfs_emit(buf, "%u\n", led_cdev->brightness_hw_changed);
+}
+
+static DEVICE_ATTR_RO(brightness_hw_changed);
+
+static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	struct device *dev = led_cdev->dev;
+	int ret;
+
+	ret = device_create_file(dev, &dev_attr_brightness_hw_changed);
+	if (ret) {
+		dev_err(dev, "Error creating brightness_hw_changed\n");
+		return ret;
+	}
+
+	led_cdev->brightness_hw_changed_kn =
+		sysfs_get_dirent(dev->kobj.sd, "brightness_hw_changed");
+	if (!led_cdev->brightness_hw_changed_kn) {
+		dev_err(dev, "Error getting brightness_hw_changed kn\n");
+		device_remove_file(dev, &dev_attr_brightness_hw_changed);
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	sysfs_put(led_cdev->brightness_hw_changed_kn);
+	device_remove_file(led_cdev->dev, &dev_attr_brightness_hw_changed);
+}
+
+void led_classdev_notify_brightness_hw_changed(struct led_classdev *led_cdev, unsigned int brightness)
+{
+	if (WARN_ON(!led_cdev->brightness_hw_changed_kn))
+		return;
+
+	led_cdev->brightness_hw_changed = brightness;
+	sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn);
+}
+EXPORT_SYMBOL_GPL(led_classdev_notify_brightness_hw_changed);
+#else
+static int led_add_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+	return 0;
+}
+static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev)
+{
+}
+#endif
+
+/**
+ * led_classdev_suspend - suspend an led_classdev.
+ * @led_cdev: the led_classdev to suspend.
+ */
+void led_classdev_suspend(struct led_classdev *led_cdev)
+{
+	led_cdev->flags |= LED_SUSPENDED;
+	led_set_brightness_nopm(led_cdev, 0);
+	flush_work(&led_cdev->set_brightness_work);
+}
+EXPORT_SYMBOL_GPL(led_classdev_suspend);
+
+/**
+ * led_classdev_resume - resume an led_classdev.
+ * @led_cdev: the led_classdev to resume.
+ */
+void led_classdev_resume(struct led_classdev *led_cdev)
+{
+	led_set_brightness_nopm(led_cdev, led_cdev->brightness);
+
+	if (led_cdev->flash_resume)
+		led_cdev->flash_resume(led_cdev);
+
+	led_cdev->flags &= ~LED_SUSPENDED;
+}
+EXPORT_SYMBOL_GPL(led_classdev_resume);
+
+#ifdef CONFIG_PM_SLEEP
+static int led_suspend(struct device *dev)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->flags & LED_CORE_SUSPENDRESUME)
+		led_classdev_suspend(led_cdev);
+
+	return 0;
+}
+
+static int led_resume(struct device *dev)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->flags & LED_CORE_SUSPENDRESUME)
+		led_classdev_resume(led_cdev);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(leds_class_dev_pm_ops, led_suspend, led_resume);
+
+static struct led_classdev *led_module_get(struct device *led_dev)
+{
+	struct led_classdev *led_cdev;
+
+	if (!led_dev)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	led_cdev = dev_get_drvdata(led_dev);
+
+	if (!try_module_get(led_cdev->dev->parent->driver->owner)) {
+		put_device(led_cdev->dev);
+		return ERR_PTR(-ENODEV);
+	}
+
+	return led_cdev;
+}
+
+static const struct class leds_class = {
+	.name = "leds",
+	.dev_groups = led_groups,
+	.pm = &leds_class_dev_pm_ops,
+};
+
+/**
+ * fwnode_led_get() - request a LED device via the LED framework
+ * @fwnode: firmware node to get the LED device from
+ * @index: the index of the LED
+ * @name: the name of the LED used to map it to its function, if present
+ *
+ * Returns the LED device parsed from the phandle specified in the "leds"
+ * property of a device tree node or a negative error-code on failure.
+ */
+static struct led_classdev *fwnode_led_get(struct fwnode_handle *fwnode,
+					   int index, const char *name)
+{
+	struct fwnode_handle *led_node;
+	struct device *led_dev;
+
+	/*
+	 * For named LEDs, first look up the name in the "led-names" property.
+	 * If it cannot be found, then fwnode_find_reference() will propagate
+	 * the error.
+	 */
+	if (name)
+		index = fwnode_property_match_string(fwnode, "led-names",
+						     name);
+	led_node = fwnode_find_reference(fwnode, "leds", index);
+	if (IS_ERR(led_node))
+		return ERR_CAST(led_node);
+
+	led_dev = class_find_device_by_fwnode(&leds_class, led_node);
+	fwnode_handle_put(led_node);
+
+	return led_module_get(led_dev);
+}
+
+/**
+ * led_put() - release a LED device
+ * @led_cdev: LED device
+ */
+void led_put(struct led_classdev *led_cdev)
+{
+	module_put(led_cdev->dev->parent->driver->owner);
+	put_device(led_cdev->dev);
+}
+EXPORT_SYMBOL_GPL(led_put);
+
+static void devm_led_release(struct device *dev, void *res)
+{
+	struct led_classdev **p = res;
+
+	led_put(*p);
+}
+
+static struct led_classdev *__devm_led_get(struct device *dev, struct led_classdev *led)
+{
+	struct led_classdev **dr;
+
+	dr = devres_alloc(devm_led_release, sizeof(struct led_classdev *), GFP_KERNEL);
+	if (!dr) {
+		led_put(led);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	*dr = led;
+	devres_add(dev, dr);
+
+	return led;
+}
+
+/**
+ * devm_of_led_get - Resource-managed request of a LED device
+ * @dev:	LED consumer
+ * @index:	index of the LED to obtain in the consumer
+ *
+ * The device node of the device is parse to find the request LED device.
+ * The LED device returned from this function is automatically released
+ * on driver detach.
+ *
+ * @return a pointer to a LED device or ERR_PTR(errno) on failure.
+ */
+struct led_classdev *__must_check devm_of_led_get(struct device *dev,
+						  int index)
+{
+	struct led_classdev *led;
+
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	led = fwnode_led_get(dev_fwnode(dev), index, NULL);
+	if (IS_ERR(led))
+		return led;
+
+	return __devm_led_get(dev, led);
+}
+EXPORT_SYMBOL_GPL(devm_of_led_get);
+
+/**
+ * led_get() - request a LED device via the LED framework
+ * @dev: device for which to get the LED device
+ * @con_id: name of the LED from the device's point of view
+ *
+ * @return a pointer to a LED device or ERR_PTR(errno) on failure.
+ */
+struct led_classdev *led_get(struct device *dev, char *con_id)
+{
+	struct led_lookup_data *lookup;
+	struct led_classdev *led_cdev;
+	const char *provider = NULL;
+	struct device *led_dev;
+
+	led_cdev = fwnode_led_get(dev_fwnode(dev), -1, con_id);
+	if (!IS_ERR(led_cdev) || PTR_ERR(led_cdev) != -ENOENT)
+		return led_cdev;
+
+	mutex_lock(&leds_lookup_lock);
+	list_for_each_entry(lookup, &leds_lookup_list, list) {
+		if (!strcmp(lookup->dev_id, dev_name(dev)) &&
+		    !strcmp(lookup->con_id, con_id)) {
+			provider = kstrdup_const(lookup->provider, GFP_KERNEL);
+			break;
+		}
+	}
+	mutex_unlock(&leds_lookup_lock);
+
+	if (!provider)
+		return ERR_PTR(-ENOENT);
+
+	led_dev = class_find_device_by_name(&leds_class, provider);
+	kfree_const(provider);
+
+	return led_module_get(led_dev);
+}
+EXPORT_SYMBOL_GPL(led_get);
+
+/**
+ * devm_led_get() - request a LED device via the LED framework
+ * @dev: device for which to get the LED device
+ * @con_id: name of the LED from the device's point of view
+ *
+ * The LED device returned from this function is automatically released
+ * on driver detach.
+ *
+ * @return a pointer to a LED device or ERR_PTR(errno) on failure.
+ */
+struct led_classdev *devm_led_get(struct device *dev, char *con_id)
+{
+	struct led_classdev *led;
+
+	led = led_get(dev, con_id);
+	if (IS_ERR(led))
+		return led;
+
+	return __devm_led_get(dev, led);
+}
+EXPORT_SYMBOL_GPL(devm_led_get);
+
+/**
+ * led_add_lookup() - Add a LED lookup table entry
+ * @led_lookup: the lookup table entry to add
+ *
+ * Add a LED lookup table entry. On systems without devicetree the lookup table
+ * is used by led_get() to find LEDs.
+ */
+void led_add_lookup(struct led_lookup_data *led_lookup)
+{
+	mutex_lock(&leds_lookup_lock);
+	list_add_tail(&led_lookup->list, &leds_lookup_list);
+	mutex_unlock(&leds_lookup_lock);
+}
+EXPORT_SYMBOL_GPL(led_add_lookup);
+
+/**
+ * led_remove_lookup() - Remove a LED lookup table entry
+ * @led_lookup: the lookup table entry to remove
+ */
+void led_remove_lookup(struct led_lookup_data *led_lookup)
+{
+	if (!led_lookup)
+		return;
+
+	mutex_lock(&leds_lookup_lock);
+	list_del(&led_lookup->list);
+	mutex_unlock(&leds_lookup_lock);
+}
+EXPORT_SYMBOL_GPL(led_remove_lookup);
+
+/**
+ * devm_of_led_get_optional - Resource-managed request of an optional LED device
+ * @dev:	LED consumer
+ * @index:	index of the LED to obtain in the consumer
+ *
+ * The device node of the device is parsed to find the requested LED device.
+ * The LED device returned from this function is automatically released
+ * on driver detach.
+ *
+ * @return a pointer to a LED device, ERR_PTR(errno) on failure and NULL if the
+ * led was not found.
+ */
+struct led_classdev *__must_check devm_of_led_get_optional(struct device *dev,
+							int index)
+{
+	struct led_classdev *led;
+
+	led = devm_of_led_get(dev, index);
+	if (IS_ERR(led) && PTR_ERR(led) == -ENOENT)
+		return NULL;
+
+	return led;
+}
+EXPORT_SYMBOL_GPL(devm_of_led_get_optional);
+
+static int led_classdev_next_name(const char *init_name, char *name,
+				  size_t len)
+{
+	unsigned int i = 0;
+	int ret = 0;
+	struct device *dev;
+
+	strscpy(name, init_name, len);
+
+	while ((ret < len) &&
+	       (dev = class_find_device_by_name(&leds_class, name))) {
+		put_device(dev);
+		ret = snprintf(name, len, "%s_%u", init_name, ++i);
+	}
+
+	if (ret >= len)
+		return -ENOMEM;
+
+	return i;
+}
+
+/**
+ * led_classdev_register_ext - register a new object of led_classdev class
+ *			       with init data.
+ *
+ * @parent: parent of LED device
+ * @led_cdev: the led_classdev structure for this device.
+ * @init_data: LED class device initialization data
+ */
+int led_classdev_register_ext(struct device *parent,
+			      struct led_classdev *led_cdev,
+			      struct led_init_data *init_data)
+{
+	char composed_name[LED_MAX_NAME_SIZE];
+	char final_name[LED_MAX_NAME_SIZE];
+	const char *proposed_name = composed_name;
+	int ret;
+
+	if (init_data) {
+		if (init_data->devname_mandatory && !init_data->devicename) {
+			dev_err(parent, "Mandatory device name is missing");
+			return -EINVAL;
+		}
+		ret = led_compose_name(parent, init_data, composed_name);
+		if (ret < 0)
+			return ret;
+
+		if (init_data->fwnode) {
+			fwnode_property_read_string(init_data->fwnode,
+				"linux,default-trigger",
+				&led_cdev->default_trigger);
+
+			if (fwnode_property_present(init_data->fwnode,
+						    "retain-state-shutdown"))
+				led_cdev->flags |= LED_RETAIN_AT_SHUTDOWN;
+
+			fwnode_property_read_u32(init_data->fwnode,
+				"max-brightness",
+				&led_cdev->max_brightness);
+
+			if (fwnode_property_present(init_data->fwnode, "color"))
+				fwnode_property_read_u32(init_data->fwnode, "color",
+							 &led_cdev->color);
+		}
+	} else {
+		proposed_name = led_cdev->name;
+	}
+
+	ret = led_classdev_next_name(proposed_name, final_name, sizeof(final_name));
+	if (ret < 0)
+		return ret;
+	else if (ret && led_cdev->flags & LED_REJECT_NAME_CONFLICT)
+		return -EEXIST;
+	else if (ret)
+		dev_warn(parent, "Led %s renamed to %s due to name collision\n",
+			 proposed_name, final_name);
+
+	if (led_cdev->color >= LED_COLOR_ID_MAX)
+		dev_warn(parent, "LED %s color identifier out of range\n", final_name);
+
+	mutex_init(&led_cdev->led_access);
+	mutex_lock(&led_cdev->led_access);
+	led_cdev->dev = device_create_with_groups(&leds_class, parent, 0,
+						  led_cdev, led_cdev->groups, "%s", final_name);
+	if (IS_ERR(led_cdev->dev)) {
+		mutex_unlock(&led_cdev->led_access);
+		return PTR_ERR(led_cdev->dev);
+	}
+	if (init_data && init_data->fwnode)
+		device_set_node(led_cdev->dev, init_data->fwnode);
+
+	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) {
+		ret = led_add_brightness_hw_changed(led_cdev);
+		if (ret) {
+			device_unregister(led_cdev->dev);
+			led_cdev->dev = NULL;
+			mutex_unlock(&led_cdev->led_access);
+			return ret;
+		}
+	}
+
+	led_cdev->work_flags = 0;
+#ifdef CONFIG_LEDS_TRIGGERS
+	init_rwsem(&led_cdev->trigger_lock);
+#endif
+#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED
+	led_cdev->brightness_hw_changed = -1;
+#endif
+	if (!led_cdev->max_brightness)
+		led_cdev->max_brightness = LED_FULL;
+
+	led_update_brightness(led_cdev);
+
+	led_cdev->wq = leds_wq;
+
+	led_init_core(led_cdev);
+
+	/* add to the list of leds */
+	down_write(&leds_list_lock);
+	list_add_tail(&led_cdev->node, &leds_list);
+	up_write(&leds_list_lock);
+
+#ifdef CONFIG_LEDS_TRIGGERS
+	led_trigger_set_default(led_cdev);
+#endif
+
+	mutex_unlock(&led_cdev->led_access);
+
+	dev_dbg(parent, "Registered led device: %s\n",
+			led_cdev->name);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(led_classdev_register_ext);
+
+/**
+ * led_classdev_unregister - unregisters a object of led_properties class.
+ * @led_cdev: the led device to unregister
+ *
+ * Unregisters a previously registered via led_classdev_register object.
+ */
+void led_classdev_unregister(struct led_classdev *led_cdev)
+{
+	if (IS_ERR_OR_NULL(led_cdev->dev))
+		return;
+
+#ifdef CONFIG_LEDS_TRIGGERS
+	down_write(&led_cdev->trigger_lock);
+	if (led_cdev->trigger)
+		led_trigger_set(led_cdev, NULL);
+	up_write(&led_cdev->trigger_lock);
+#endif
+
+	led_cdev->flags |= LED_UNREGISTERING;
+
+	/* Stop blinking */
+	led_stop_software_blink(led_cdev);
+
+	if (!(led_cdev->flags & LED_RETAIN_AT_SHUTDOWN))
+		led_set_brightness(led_cdev, LED_OFF);
+
+	flush_work(&led_cdev->set_brightness_work);
+
+	if (led_cdev->flags & LED_BRIGHT_HW_CHANGED)
+		led_remove_brightness_hw_changed(led_cdev);
+
+	device_unregister(led_cdev->dev);
+
+	down_write(&leds_list_lock);
+	list_del(&led_cdev->node);
+	up_write(&leds_list_lock);
+
+	mutex_destroy(&led_cdev->led_access);
+}
+EXPORT_SYMBOL_GPL(led_classdev_unregister);
+
+static void devm_led_classdev_release(struct device *dev, void *res)
+{
+	led_classdev_unregister(*(struct led_classdev **)res);
+}
+
+/**
+ * devm_led_classdev_register_ext - resource managed led_classdev_register_ext()
+ *
+ * @parent: parent of LED device
+ * @led_cdev: the led_classdev structure for this device.
+ * @init_data: LED class device initialization data
+ */
+int devm_led_classdev_register_ext(struct device *parent,
+				   struct led_classdev *led_cdev,
+				   struct led_init_data *init_data)
+{
+	struct led_classdev **dr;
+	int rc;
+
+	dr = devres_alloc(devm_led_classdev_release, sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	rc = led_classdev_register_ext(parent, led_cdev, init_data);
+	if (rc) {
+		devres_free(dr);
+		return rc;
+	}
+
+	*dr = led_cdev;
+	devres_add(parent, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_led_classdev_register_ext);
+
+static int devm_led_classdev_match(struct device *dev, void *res, void *data)
+{
+	struct led_classdev **p = res;
+
+	if (WARN_ON(!p || !*p))
+		return 0;
+
+	return *p == data;
+}
+
+/**
+ * devm_led_classdev_unregister() - resource managed led_classdev_unregister()
+ * @dev: The device to unregister.
+ * @led_cdev: the led_classdev structure for this device.
+ */
+void devm_led_classdev_unregister(struct device *dev,
+				  struct led_classdev *led_cdev)
+{
+	WARN_ON(devres_release(dev,
+			       devm_led_classdev_release,
+			       devm_led_classdev_match, led_cdev));
+}
+EXPORT_SYMBOL_GPL(devm_led_classdev_unregister);
+
+static int __init leds_init(void)
+{
+	leds_wq = alloc_ordered_workqueue("leds", 0);
+	if (!leds_wq) {
+		pr_err("Failed to create LEDs ordered workqueue\n");
+		return -ENOMEM;
+	}
+
+	return class_register(&leds_class);
+}
+
+static void __exit leds_exit(void)
+{
+	class_unregister(&leds_class);
+	destroy_workqueue(leds_wq);
+}
+
+subsys_initcall(leds_init);
+module_exit(leds_exit);
+
+MODULE_AUTHOR("John Lenz, Richard Purdie");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("LED Class Interface");