[linux-block.git] / drivers / base / devcoredump.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright(c) 2014 Intel Mobile Communications GmbH
 * Copyright(c) 2015 Intel Deutschland GmbH
 *
 * Author: Johannes Berg <johannes@sipsolutions.net>
 */
#include <linux/module.h>
#include <linux/device.h>
#include <linux/devcoredump.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/workqueue.h>

static struct class devcd_class;

/* global disable flag, for security purposes */
static bool devcd_disabled;

/* if data isn't read by userspace after 5 minutes then delete it */
#define DEVCD_TIMEOUT	(HZ * 60 * 5)

struct devcd_entry {
	struct device devcd_dev;
	void *data;
	size_t datalen;
	/*
	 * Here, mutex is required to serialize the calls to del_wk work between
	 * user/kernel space which happens when devcd is added with device_add()
	 * and that sends uevent to user space. User space reads the uevents,
	 * and calls to devcd_data_write() which try to modify the work which is
	 * not even initialized/queued from devcoredump.
	 *
	 *
	 *
	 *        cpu0(X)                                 cpu1(Y)
	 *
	 *        dev_coredump() uevent sent to user space
	 *        device_add()  ======================> user space process Y reads the
	 *                                              uevents writes to devcd fd
	 *                                              which results into writes to
	 *
	 *                                             devcd_data_write()
	 *                                               mod_delayed_work()
	 *                                                 try_to_grab_pending()
	 *                                                   del_timer()
	 *                                                     debug_assert_init()
	 *       INIT_DELAYED_WORK()
	 *       schedule_delayed_work()
	 *
	 *
	 * Also, mutex alone would not be enough to avoid scheduling of
	 * del_wk work after it get flush from a call to devcd_free()
	 * mentioned as below.
	 *
	 *	disabled_store()
	 *        devcd_free()
	 *          mutex_lock()             devcd_data_write()
	 *          flush_delayed_work()
	 *          mutex_unlock()
	 *                                   mutex_lock()
	 *                                   mod_delayed_work()
	 *                                   mutex_unlock()
	 * So, delete_work flag is required.
	 */
	struct mutex mutex;
	bool delete_work;
	struct module *owner;
	ssize_t (*read)(char *buffer, loff_t offset, size_t count,
			void *data, size_t datalen);
	void (*free)(void *data);
	struct delayed_work del_wk;
	struct device *failing_dev;
};

static struct devcd_entry *dev_to_devcd(struct device *dev)
{
	return container_of(dev, struct devcd_entry, devcd_dev);
}

static void devcd_dev_release(struct device *dev)
{
	struct devcd_entry *devcd = dev_to_devcd(dev);

	devcd->free(devcd->data);
	module_put(devcd->owner);

	/*
	 * this seems racy, but I don't see a notifier or such on
	 * a struct device to know when it goes away?
	 */
	if (devcd->failing_dev->kobj.sd)
		sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
				  "devcoredump");

	put_device(devcd->failing_dev);
	kfree(devcd);
}

static void devcd_del(struct work_struct *wk)
{
	struct devcd_entry *devcd;

	devcd = container_of(wk, struct devcd_entry, del_wk.work);

	device_del(&devcd->devcd_dev);
	put_device(&devcd->devcd_dev);
}

static ssize_t devcd_data_read(struct file *filp, struct kobject *kobj,
			       struct bin_attribute *bin_attr,
			       char *buffer, loff_t offset, size_t count)
{
	struct device *dev = kobj_to_dev(kobj);
	struct devcd_entry *devcd = dev_to_devcd(dev);

	return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
}

static ssize_t devcd_data_write(struct file *filp, struct kobject *kobj,
				struct bin_attribute *bin_attr,
				char *buffer, loff_t offset, size_t count)
{
	struct device *dev = kobj_to_dev(kobj);
	struct devcd_entry *devcd = dev_to_devcd(dev);

	mutex_lock(&devcd->mutex);
	if (!devcd->delete_work) {
		devcd->delete_work = true;
		mod_delayed_work(system_wq, &devcd->del_wk, 0);
	}
	mutex_unlock(&devcd->mutex);

	return count;
}

static struct bin_attribute devcd_attr_data = {
	.attr = { .name = "data", .mode = S_IRUSR | S_IWUSR, },
	.size = 0,
	.read = devcd_data_read,
	.write = devcd_data_write,
};

static struct bin_attribute *devcd_dev_bin_attrs[] = {
	&devcd_attr_data, NULL,
};

static const struct attribute_group devcd_dev_group = {
	.bin_attrs = devcd_dev_bin_attrs,
};

static const struct attribute_group *devcd_dev_groups[] = {
	&devcd_dev_group, NULL,
};

static int devcd_free(struct device *dev, void *data)
{
	struct devcd_entry *devcd = dev_to_devcd(dev);

	mutex_lock(&devcd->mutex);
	if (!devcd->delete_work)
		devcd->delete_work = true;

	flush_delayed_work(&devcd->del_wk);
	mutex_unlock(&devcd->mutex);
	return 0;
}

static ssize_t disabled_show(struct class *class, struct class_attribute *attr,
			     char *buf)
{
	return sysfs_emit(buf, "%d\n", devcd_disabled);
}

/*
 *
 *	disabled_store()                                	worker()
 *	 class_for_each_device(&devcd_class,
 *		NULL, NULL, devcd_free)
 *         ...
 *         ...
 *	   while ((dev = class_dev_iter_next(&iter))
 *                                                             devcd_del()
 *                                                               device_del()
 *                                                                 put_device() <- last reference
 *             error = fn(dev, data)                           devcd_dev_release()
 *             devcd_free(dev, data)                           kfree(devcd)
 *             mutex_lock(&devcd->mutex);
 *
 *
 * In the above diagram, It looks like disabled_store() would be racing with parallely
 * running devcd_del() and result in memory abort while acquiring devcd->mutex which
 * is called after kfree of devcd memory  after dropping its last reference with
 * put_device(). However, this will not happens as fn(dev, data) runs
 * with its own reference to device via klist_node so it is not its last reference.
 * so, above situation would not occur.
 */

static ssize_t disabled_store(struct class *class, struct class_attribute *attr,
			      const char *buf, size_t count)
{
	long tmp = simple_strtol(buf, NULL, 10);

	/*
	 * This essentially makes the attribute write-once, since you can't
	 * go back to not having it disabled. This is intentional, it serves
	 * as a system lockdown feature.
	 */
	if (tmp != 1)
		return -EINVAL;

	devcd_disabled = true;

	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);

	return count;
}
static CLASS_ATTR_RW(disabled);

static struct attribute *devcd_class_attrs[] = {
	&class_attr_disabled.attr,
	NULL,
};
ATTRIBUTE_GROUPS(devcd_class);

static struct class devcd_class = {
	.name		= "devcoredump",
	.owner		= THIS_MODULE,
	.dev_release	= devcd_dev_release,
	.dev_groups	= devcd_dev_groups,
	.class_groups	= devcd_class_groups,
};

static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
			   void *data, size_t datalen)
{
	return memory_read_from_buffer(buffer, count, &offset, data, datalen);
}

static void devcd_freev(void *data)
{
	vfree(data);
}

/**
 * dev_coredumpv - create device coredump with vmalloc data
 * @dev: the struct device for the crashed device
 * @data: vmalloc data containing the device coredump
 * @datalen: length of the data
 * @gfp: allocation flags
 *
 * This function takes ownership of the vmalloc'ed data and will free
 * it when it is no longer used. See dev_coredumpm() for more information.
 */
void dev_coredumpv(struct device *dev, void *data, size_t datalen,
		   gfp_t gfp)
{
	dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
}
EXPORT_SYMBOL_GPL(dev_coredumpv);

static int devcd_match_failing(struct device *dev, const void *failing)
{
	struct devcd_entry *devcd = dev_to_devcd(dev);

	return devcd->failing_dev == failing;
}

/**
 * devcd_free_sgtable - free all the memory of the given scatterlist table
 * (i.e. both pages and scatterlist instances)
 * NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
 * using the sg_chain function then that function should be called only once
 * on the chained table
 * @data: pointer to sg_table to free
 */
static void devcd_free_sgtable(void *data)
{
	_devcd_free_sgtable(data);
}

/**
 * devcd_read_from_sgtable - copy data from sg_table to a given buffer
 * and return the number of bytes read
 * @buffer: the buffer to copy the data to it
 * @buf_len: the length of the buffer
 * @data: the scatterlist table to copy from
 * @offset: start copy from @offset@ bytes from the head of the data
 *	in the given scatterlist
 * @data_len: the length of the data in the sg_table
 */
static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
				       size_t buf_len, void *data,
				       size_t data_len)
{
	struct scatterlist *table = data;

	if (offset > data_len)
		return -EINVAL;

	if (offset + buf_len > data_len)
		buf_len = data_len - offset;
	return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
				  offset);
}

/**
 * dev_coredumpm - create device coredump with read/free methods
 * @dev: the struct device for the crashed device
 * @owner: the module that contains the read/free functions, use %THIS_MODULE
 * @data: data cookie for the @read/@free functions
 * @datalen: length of the data
 * @gfp: allocation flags
 * @read: function to read from the given buffer
 * @free: function to free the given buffer
 *
 * Creates a new device coredump for the given device. If a previous one hasn't
 * been read yet, the new coredump is discarded. The data lifetime is determined
 * by the device coredump framework and when it is no longer needed the @free
 * function will be called to free the data.
 */
void dev_coredumpm(struct device *dev, struct module *owner,
		   void *data, size_t datalen, gfp_t gfp,
		   ssize_t (*read)(char *buffer, loff_t offset, size_t count,
				   void *data, size_t datalen),
		   void (*free)(void *data))
{
	static atomic_t devcd_count = ATOMIC_INIT(0);
	struct devcd_entry *devcd;
	struct device *existing;

	if (devcd_disabled)
		goto free;

	existing = class_find_device(&devcd_class, NULL, dev,
				     devcd_match_failing);
	if (existing) {
		put_device(existing);
		goto free;
	}

	if (!try_module_get(owner))
		goto free;

	devcd = kzalloc(sizeof(*devcd), gfp);
	if (!devcd)
		goto put_module;

	devcd->owner = owner;
	devcd->data = data;
	devcd->datalen = datalen;
	devcd->read = read;
	devcd->free = free;
	devcd->failing_dev = get_device(dev);
	devcd->delete_work = false;

	mutex_init(&devcd->mutex);
	device_initialize(&devcd->devcd_dev);

	dev_set_name(&devcd->devcd_dev, "devcd%d",
		     atomic_inc_return(&devcd_count));
	devcd->devcd_dev.class = &devcd_class;

	mutex_lock(&devcd->mutex);
	if (device_add(&devcd->devcd_dev))
		goto put_device;

	/*
	 * These should normally not fail, but there is no problem
	 * continuing without the links, so just warn instead of
	 * failing.
	 */
	if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
			      "failing_device") ||
	    sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
		              "devcoredump"))
		dev_warn(dev, "devcoredump create_link failed\n");

	INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
	schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
	mutex_unlock(&devcd->mutex);
	return;
 put_device:
	put_device(&devcd->devcd_dev);
	mutex_unlock(&devcd->mutex);
 put_module:
	module_put(owner);
 free:
	free(data);
}
EXPORT_SYMBOL_GPL(dev_coredumpm);

/**
 * dev_coredumpsg - create device coredump that uses scatterlist as data
 * parameter
 * @dev: the struct device for the crashed device
 * @table: the dump data
 * @datalen: length of the data
 * @gfp: allocation flags
 *
 * Creates a new device coredump for the given device. If a previous one hasn't
 * been read yet, the new coredump is discarded. The data lifetime is determined
 * by the device coredump framework and when it is no longer needed
 * it will free the data.
 */
void dev_coredumpsg(struct device *dev, struct scatterlist *table,
		    size_t datalen, gfp_t gfp)
{
	dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
		      devcd_free_sgtable);
}
EXPORT_SYMBOL_GPL(dev_coredumpsg);

static int __init devcoredump_init(void)
{
	return class_register(&devcd_class);
}
__initcall(devcoredump_init);

static void __exit devcoredump_exit(void)
{
	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
	class_unregister(&devcd_class);
}
__exitcall(devcoredump_exit);
Commit	Line	Data
989d42e8	1	// SPDX-License-Identifier: GPL-2.0
833c9545	2	/*
833c9545	3	* Copyright(c) 2014 Intel Mobile Communications GmbH
52256637	4	* Copyright(c) 2015 Intel Deutschland GmbH
833c9545	5	*
833c9545 JB	6	* Author: Johannes Berg <johannes@sipsolutions.net>
	7	*/
	8	#include <linux/module.h>
	9	#include <linux/device.h>
	10	#include <linux/devcoredump.h>
	11	#include <linux/list.h>
	12	#include <linux/slab.h>
	13	#include <linux/fs.h>
	14	#include <linux/workqueue.h>
	15
d4533329 JB	16	static struct class devcd_class;
	17
	18	/* global disable flag, for security purposes */
	19	static bool devcd_disabled;
	20
833c9545 JB	21	/* if data isn't read by userspace after 5 minutes then delete it */
	22	#define DEVCD_TIMEOUT (HZ * 60 * 5)
	23
	24	struct devcd_entry {
	25	struct device devcd_dev;
52256637	26	void *data;
833c9545	27	size_t datalen;
01daccf7 MO	28	/*
	29	* Here, mutex is required to serialize the calls to del_wk work between
	30	* user/kernel space which happens when devcd is added with device_add()
	31	* and that sends uevent to user space. User space reads the uevents,
	32	* and calls to devcd_data_write() which try to modify the work which is
	33	* not even initialized/queued from devcoredump.
	34	*
	35	*
	36	*
	37	* cpu0(X) cpu1(Y)
	38	*
	39	* dev_coredump() uevent sent to user space
	40	* device_add() ======================> user space process Y reads the
	41	* uevents writes to devcd fd
	42	* which results into writes to
	43	*
	44	* devcd_data_write()
	45	* mod_delayed_work()
	46	* try_to_grab_pending()
	47	* del_timer()
	48	* debug_assert_init()
	49	* INIT_DELAYED_WORK()
	50	* schedule_delayed_work()
	51	*
	52	*
	53	* Also, mutex alone would not be enough to avoid scheduling of
	54	* del_wk work after it get flush from a call to devcd_free()
	55	* mentioned as below.
	56	*
	57	* disabled_store()
	58	* devcd_free()
	59	* mutex_lock() devcd_data_write()
	60	* flush_delayed_work()
	61	* mutex_unlock()
	62	* mutex_lock()
	63	* mod_delayed_work()
	64	* mutex_unlock()
	65	* So, delete_work flag is required.
	66	*/
	67	struct mutex mutex;
	68	bool delete_work;
833c9545 JB	69	struct module *owner;
833c9545 JB	70	ssize_t (read)(char buffer, loff_t offset, size_t count,
52256637 AE	71	void *data, size_t datalen);
52256637 AE	72	void (free)(void data);
833c9545 JB	73	struct delayed_work del_wk;
	74	struct device *failing_dev;
	75	};
	76
	77	static struct devcd_entry dev_to_devcd(struct device dev)
	78	{
	79	return container_of(dev, struct devcd_entry, devcd_dev);
	80	}
	81
	82	static void devcd_dev_release(struct device *dev)
	83	{
	84	struct devcd_entry *devcd = dev_to_devcd(dev);
	85
	86	devcd->free(devcd->data);
	87	module_put(devcd->owner);
	88
	89	/*
	90	* this seems racy, but I don't see a notifier or such on
	91	* a struct device to know when it goes away?
	92	*/
	93	if (devcd->failing_dev->kobj.sd)
	94	sysfs_delete_link(&devcd->failing_dev->kobj, &dev->kobj,
	95	"devcoredump");
	96
	97	put_device(devcd->failing_dev);
	98	kfree(devcd);
	99	}
	100
	101	static void devcd_del(struct work_struct *wk)
	102	{
	103	struct devcd_entry *devcd;
	104
	105	devcd = container_of(wk, struct devcd_entry, del_wk.work);
	106
	107	device_del(&devcd->devcd_dev);
	108	put_device(&devcd->devcd_dev);
	109	}
	110
	111	static ssize_t devcd_data_read(struct file filp, struct kobject kobj,
	112	struct bin_attribute *bin_attr,
	113	char *buffer, loff_t offset, size_t count)
	114	{
	115	struct device *dev = kobj_to_dev(kobj);
	116	struct devcd_entry *devcd = dev_to_devcd(dev);
	117
	118	return devcd->read(buffer, offset, count, devcd->data, devcd->datalen);
	119	}
	120
	121	static ssize_t devcd_data_write(struct file filp, struct kobject kobj,
	122	struct bin_attribute *bin_attr,
	123	char *buffer, loff_t offset, size_t count)
	124	{
	125	struct device *dev = kobj_to_dev(kobj);
	126	struct devcd_entry *devcd = dev_to_devcd(dev);
	127
01daccf7 MO	128	mutex_lock(&devcd->mutex);
	129	if (!devcd->delete_work) {
	130	devcd->delete_work = true;
	131	mod_delayed_work(system_wq, &devcd->del_wk, 0);
	132	}
	133	mutex_unlock(&devcd->mutex);
833c9545 JB	134
	135	return count;
	136	}
	137
	138	static struct bin_attribute devcd_attr_data = {
	139	.attr = { .name = "data", .mode = S_IRUSR \| S_IWUSR, },
	140	.size = 0,
	141	.read = devcd_data_read,
	142	.write = devcd_data_write,
	143	};
	144
	145	static struct bin_attribute *devcd_dev_bin_attrs[] = {
	146	&devcd_attr_data, NULL,
	147	};
	148
	149	static const struct attribute_group devcd_dev_group = {
	150	.bin_attrs = devcd_dev_bin_attrs,
	151	};
	152
	153	static const struct attribute_group *devcd_dev_groups[] = {
	154	&devcd_dev_group, NULL,
	155	};
	156
d4533329 JB	157	static int devcd_free(struct device dev, void data)
	158	{
	159	struct devcd_entry *devcd = dev_to_devcd(dev);
	160
01daccf7 MO	161	mutex_lock(&devcd->mutex);
	162	if (!devcd->delete_work)
	163	devcd->delete_work = true;
	164
d4533329	165	flush_delayed_work(&devcd->del_wk);
01daccf7	166	mutex_unlock(&devcd->mutex);
d4533329 JB	167	return 0;
	168	}
	169
	170	static ssize_t disabled_show(struct class class, struct class_attribute attr,
	171	char *buf)
	172	{
948b3edb	173	return sysfs_emit(buf, "%d\n", devcd_disabled);
d4533329 JB	174	}
d4533329 JB	175
01daccf7 MO	176	/*
	177	*
	178	* disabled_store() worker()
	179	* class_for_each_device(&devcd_class,
	180	* NULL, NULL, devcd_free)
	181	* ...
	182	* ...
	183	* while ((dev = class_dev_iter_next(&iter))
	184	* devcd_del()
	185	* device_del()
	186	* put_device() <- last reference
	187	* error = fn(dev, data) devcd_dev_release()
	188	* devcd_free(dev, data) kfree(devcd)
	189	* mutex_lock(&devcd->mutex);
	190	*
	191	*
	192	* In the above diagram, It looks like disabled_store() would be racing with parallely
	193	* running devcd_del() and result in memory abort while acquiring devcd->mutex which
	194	* is called after kfree of devcd memory after dropping its last reference with
	195	* put_device(). However, this will not happens as fn(dev, data) runs
	196	* with its own reference to device via klist_node so it is not its last reference.
	197	* so, above situation would not occur.
	198	*/
	199
d4533329 JB	200	static ssize_t disabled_store(struct class class, struct class_attribute attr,
	201	const char *buf, size_t count)
	202	{
	203	long tmp = simple_strtol(buf, NULL, 10);
	204
	205	/*
	206	* This essentially makes the attribute write-once, since you can't
	207	* go back to not having it disabled. This is intentional, it serves
	208	* as a system lockdown feature.
	209	*/
	210	if (tmp != 1)
	211	return -EINVAL;
	212
	213	devcd_disabled = true;
	214
	215	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
	216
	217	return count;
	218	}
f76d2527	219	static CLASS_ATTR_RW(disabled);
d4533329	220
f76d2527 GKH	221	static struct attribute *devcd_class_attrs[] = {
	222	&class_attr_disabled.attr,
	223	NULL,
d4533329	224	};
f76d2527	225	ATTRIBUTE_GROUPS(devcd_class);
d4533329	226
833c9545 JB	227	static struct class devcd_class = {
	228	.name = "devcoredump",
	229	.owner = THIS_MODULE,
	230	.dev_release = devcd_dev_release,
	231	.dev_groups = devcd_dev_groups,
f76d2527	232	.class_groups = devcd_class_groups,
833c9545 JB	233	};
	234
	235	static ssize_t devcd_readv(char *buffer, loff_t offset, size_t count,
52256637	236	void *data, size_t datalen)
833c9545	237	{
ce684d95	238	return memory_read_from_buffer(buffer, count, &offset, data, datalen);
833c9545 JB	239	}
833c9545 JB	240
52256637 AE	241	static void devcd_freev(void *data)
	242	{
	243	vfree(data);
	244	}
	245
833c9545 JB	246	/**
	247	* dev_coredumpv - create device coredump with vmalloc data
	248	* @dev: the struct device for the crashed device
	249	* @data: vmalloc data containing the device coredump
	250	* @datalen: length of the data
	251	* @gfp: allocation flags
	252	*
	253	* This function takes ownership of the vmalloc'ed data and will free
	254	* it when it is no longer used. See dev_coredumpm() for more information.
	255	*/
52256637	256	void dev_coredumpv(struct device dev, void data, size_t datalen,
833c9545 JB	257	gfp_t gfp)
833c9545 JB	258	{
52256637	259	dev_coredumpm(dev, NULL, data, datalen, gfp, devcd_readv, devcd_freev);
833c9545 JB	260	}
	261	EXPORT_SYMBOL_GPL(dev_coredumpv);
	262
	263	static int devcd_match_failing(struct device dev, const void failing)
	264	{
	265	struct devcd_entry *devcd = dev_to_devcd(dev);
	266
	267	return devcd->failing_dev == failing;
	268	}
	269
52256637 AE	270	/**
	271	* devcd_free_sgtable - free all the memory of the given scatterlist table
	272	* (i.e. both pages and scatterlist instances)
	273	* NOTE: if two tables allocated with devcd_alloc_sgtable and then chained
	274	* using the sg_chain function then that function should be called only once
	275	* on the chained table
cc710790	276	* @data: pointer to sg_table to free
52256637 AE	277	*/
	278	static void devcd_free_sgtable(void *data)
	279	{
	280	_devcd_free_sgtable(data);
	281	}
	282
	283	/**
cc710790	284	* devcd_read_from_sgtable - copy data from sg_table to a given buffer
52256637 AE	285	* and return the number of bytes read
	286	* @buffer: the buffer to copy the data to it
	287	* @buf_len: the length of the buffer
	288	* @data: the scatterlist table to copy from
	289	* @offset: start copy from @offset@ bytes from the head of the data
	290	* in the given scatterlist
	291	* @data_len: the length of the data in the sg_table
	292	*/
	293	static ssize_t devcd_read_from_sgtable(char *buffer, loff_t offset,
	294	size_t buf_len, void *data,
	295	size_t data_len)
	296	{
	297	struct scatterlist *table = data;
	298
	299	if (offset > data_len)
	300	return -EINVAL;
	301
	302	if (offset + buf_len > data_len)
	303	buf_len = data_len - offset;
	304	return sg_pcopy_to_buffer(table, sg_nents(table), buffer, buf_len,
	305	offset);
	306	}
	307
833c9545 JB	308	/**
	309	* dev_coredumpm - create device coredump with read/free methods
	310	* @dev: the struct device for the crashed device
	311	* @owner: the module that contains the read/free functions, use %THIS_MODULE
	312	* @data: data cookie for the @read/@free functions
	313	* @datalen: length of the data
	314	* @gfp: allocation flags
	315	* @read: function to read from the given buffer
	316	* @free: function to free the given buffer
	317	*
	318	* Creates a new device coredump for the given device. If a previous one hasn't
	319	* been read yet, the new coredump is discarded. The data lifetime is determined
	320	* by the device coredump framework and when it is no longer needed the @free
	321	* function will be called to free the data.
	322	*/
	323	void dev_coredumpm(struct device dev, struct module owner,
52256637	324	void *data, size_t datalen, gfp_t gfp,
833c9545	325	ssize_t (read)(char buffer, loff_t offset, size_t count,
52256637 AE	326	void *data, size_t datalen),
52256637 AE	327	void (free)(void data))
833c9545 JB	328	{
	329	static atomic_t devcd_count = ATOMIC_INIT(0);
	330	struct devcd_entry *devcd;
	331	struct device *existing;
	332
d4533329 JB	333	if (devcd_disabled)
	334	goto free;
	335
833c9545 JB	336	existing = class_find_device(&devcd_class, NULL, dev,
	337	devcd_match_failing);
	338	if (existing) {
	339	put_device(existing);
	340	goto free;
	341	}
	342
	343	if (!try_module_get(owner))
	344	goto free;
	345
	346	devcd = kzalloc(sizeof(*devcd), gfp);
	347	if (!devcd)
	348	goto put_module;
	349
	350	devcd->owner = owner;
	351	devcd->data = data;
	352	devcd->datalen = datalen;
	353	devcd->read = read;
	354	devcd->free = free;
	355	devcd->failing_dev = get_device(dev);
01daccf7	356	devcd->delete_work = false;
833c9545	357
01daccf7	358	mutex_init(&devcd->mutex);
833c9545 JB	359	device_initialize(&devcd->devcd_dev);
	360
	361	dev_set_name(&devcd->devcd_dev, "devcd%d",
	362	atomic_inc_return(&devcd_count));
	363	devcd->devcd_dev.class = &devcd_class;
	364
01daccf7	365	mutex_lock(&devcd->mutex);
833c9545 JB	366	if (device_add(&devcd->devcd_dev))
	367	goto put_device;
	368
53f95c55 AB	369	/*
	370	* These should normally not fail, but there is no problem
	371	* continuing without the links, so just warn instead of
	372	* failing.
	373	*/
833c9545	374	if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
53f95c55 AB	375	"failing_device") \|\|
	376	sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
	377	"devcoredump"))
	378	dev_warn(dev, "devcoredump create_link failed\n");
833c9545 JB	379
	380	INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
	381	schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);
01daccf7	382	mutex_unlock(&devcd->mutex);
833c9545 JB	383	return;
	384	put_device:
	385	put_device(&devcd->devcd_dev);
01daccf7	386	mutex_unlock(&devcd->mutex);
833c9545 JB	387	put_module:
	388	module_put(owner);
	389	free:
	390	free(data);
	391	}
	392	EXPORT_SYMBOL_GPL(dev_coredumpm);
	393
52256637	394	/**
2a77eec0	395	* dev_coredumpsg - create device coredump that uses scatterlist as data
52256637 AE	396	* parameter
	397	* @dev: the struct device for the crashed device
	398	* @table: the dump data
	399	* @datalen: length of the data
	400	* @gfp: allocation flags
	401	*
	402	* Creates a new device coredump for the given device. If a previous one hasn't
	403	* been read yet, the new coredump is discarded. The data lifetime is determined
	404	* by the device coredump framework and when it is no longer needed
	405	* it will free the data.
	406	*/
	407	void dev_coredumpsg(struct device dev, struct scatterlist table,
	408	size_t datalen, gfp_t gfp)
	409	{
	410	dev_coredumpm(dev, NULL, table, datalen, gfp, devcd_read_from_sgtable,
	411	devcd_free_sgtable);
	412	}
	413	EXPORT_SYMBOL_GPL(dev_coredumpsg);
	414
833c9545 JB	415	static int __init devcoredump_init(void)
	416	{
	417	return class_register(&devcd_class);
	418	}
	419	__initcall(devcoredump_init);
	420
833c9545 JB	421	static void __exit devcoredump_exit(void)
	422	{
	423	class_for_each_device(&devcd_class, NULL, NULL, devcd_free);
	424	class_unregister(&devcd_class);
	425	}
	426	__exitcall(devcoredump_exit);