[linux-block.git] / drivers / char / hw_random / core.c

/*
        Added support for the AMD Geode LX RNG
	(c) Copyright 2004-2005 Advanced Micro Devices, Inc.

	derived from

 	Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
	(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>

 	derived from

        Hardware driver for the AMD 768 Random Number Generator (RNG)
        (c) Copyright 2001 Red Hat Inc <alan@redhat.com>

 	derived from

	Hardware driver for Intel i810 Random Number Generator (RNG)
	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>

	Added generic RNG API
	Copyright 2006 Michael Buesch <m@bues.ch>
	Copyright 2005 (c) MontaVista Software, Inc.

	Please read Documentation/hw_random.txt for details on use.

	----------------------------------------------------------
	This software may be used and distributed according to the terms
        of the GNU General Public License, incorporated herein by reference.

 */


#include <linux/device.h>
#include <linux/hw_random.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/miscdevice.h>
#include <linux/kthread.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/err.h>
#include <asm/uaccess.h>


#define RNG_MODULE_NAME		"hw_random"
#define PFX			RNG_MODULE_NAME ": "
#define RNG_MISCDEV_MINOR	183 /* official */


static struct hwrng *current_rng;
static struct task_struct *hwrng_fill;
static LIST_HEAD(rng_list);
/* Protects rng_list and current_rng */
static DEFINE_MUTEX(rng_mutex);
/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
static DEFINE_MUTEX(reading_mutex);
static int data_avail;
static u8 *rng_buffer, *rng_fillbuf;
static unsigned short current_quality;
static unsigned short default_quality; /* = 0; default to "off" */

module_param(current_quality, ushort, 0644);
MODULE_PARM_DESC(current_quality,
		 "current hwrng entropy estimation per mill");
module_param(default_quality, ushort, 0644);
MODULE_PARM_DESC(default_quality,
		 "default entropy content of hwrng per mill");

static void start_khwrngd(void);

static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
			       int wait);

static size_t rng_buffer_size(void)
{
	return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
}

static void add_early_randomness(struct hwrng *rng)
{
	unsigned char bytes[16];
	int bytes_read;

	mutex_lock(&reading_mutex);
	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
	mutex_unlock(&reading_mutex);
	if (bytes_read > 0)
		add_device_randomness(bytes, bytes_read);
}

static inline void cleanup_rng(struct kref *kref)
{
	struct hwrng *rng = container_of(kref, struct hwrng, ref);

	if (rng->cleanup)
		rng->cleanup(rng);

	complete(&rng->cleanup_done);
}

static void set_current_rng(struct hwrng *rng)
{
	BUG_ON(!mutex_is_locked(&rng_mutex));
	kref_get(&rng->ref);
	current_rng = rng;
}

static void drop_current_rng(void)
{
	BUG_ON(!mutex_is_locked(&rng_mutex));
	if (!current_rng)
		return;

	/* decrease last reference for triggering the cleanup */
	kref_put(&current_rng->ref, cleanup_rng);
	current_rng = NULL;
}

/* Returns ERR_PTR(), NULL or refcounted hwrng */
static struct hwrng *get_current_rng(void)
{
	struct hwrng *rng;

	if (mutex_lock_interruptible(&rng_mutex))
		return ERR_PTR(-ERESTARTSYS);

	rng = current_rng;
	if (rng)
		kref_get(&rng->ref);

	mutex_unlock(&rng_mutex);
	return rng;
}

static void put_rng(struct hwrng *rng)
{
	/*
	 * Hold rng_mutex here so we serialize in case they set_current_rng
	 * on rng again immediately.
	 */
	mutex_lock(&rng_mutex);
	if (rng)
		kref_put(&rng->ref, cleanup_rng);
	mutex_unlock(&rng_mutex);
}

static inline int hwrng_init(struct hwrng *rng)
{
	if (rng->init) {
		int ret;

		ret =  rng->init(rng);
		if (ret)
			return ret;
	}
	add_early_randomness(rng);

	current_quality = rng->quality ? : default_quality;
	current_quality &= 1023;

	if (current_quality == 0 && hwrng_fill)
		kthread_stop(hwrng_fill);
	if (current_quality > 0 && !hwrng_fill)
		start_khwrngd();

	return 0;
}

static int rng_dev_open(struct inode *inode, struct file *filp)
{
	/* enforce read-only access to this chrdev */
	if ((filp->f_mode & FMODE_READ) == 0)
		return -EINVAL;
	if (filp->f_mode & FMODE_WRITE)
		return -EINVAL;
	return 0;
}

static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
			int wait) {
	int present;

	BUG_ON(!mutex_is_locked(&reading_mutex));
	if (rng->read)
		return rng->read(rng, (void *)buffer, size, wait);

	if (rng->data_present)
		present = rng->data_present(rng, wait);
	else
		present = 1;

	if (present)
		return rng->data_read(rng, (u32 *)buffer);

	return 0;
}

static ssize_t rng_dev_read(struct file *filp, char __user *buf,
			    size_t size, loff_t *offp)
{
	ssize_t ret = 0;
	int err = 0;
	int bytes_read, len;
	struct hwrng *rng;

	while (size) {
		rng = get_current_rng();
		if (IS_ERR(rng)) {
			err = PTR_ERR(rng);
			goto out;
		}
		if (!rng) {
			err = -ENODEV;
			goto out;
		}

		mutex_lock(&reading_mutex);
		if (!data_avail) {
			bytes_read = rng_get_data(rng, rng_buffer,
				rng_buffer_size(),
				!(filp->f_flags & O_NONBLOCK));
			if (bytes_read < 0) {
				err = bytes_read;
				goto out_unlock_reading;
			}
			data_avail = bytes_read;
		}

		if (!data_avail) {
			if (filp->f_flags & O_NONBLOCK) {
				err = -EAGAIN;
				goto out_unlock_reading;
			}
		} else {
			len = data_avail;
			if (len > size)
				len = size;

			data_avail -= len;

			if (copy_to_user(buf + ret, rng_buffer + data_avail,
								len)) {
				err = -EFAULT;
				goto out_unlock_reading;
			}

			size -= len;
			ret += len;
		}

		mutex_unlock(&reading_mutex);
		put_rng(rng);

		if (need_resched())
			schedule_timeout_interruptible(1);

		if (signal_pending(current)) {
			err = -ERESTARTSYS;
			goto out;
		}
	}
out:
	return ret ? : err;

out_unlock_reading:
	mutex_unlock(&reading_mutex);
	put_rng(rng);
	goto out;
}


static const struct file_operations rng_chrdev_ops = {
	.owner		= THIS_MODULE,
	.open		= rng_dev_open,
	.read		= rng_dev_read,
	.llseek		= noop_llseek,
};

static struct miscdevice rng_miscdev = {
	.minor		= RNG_MISCDEV_MINOR,
	.name		= RNG_MODULE_NAME,
	.nodename	= "hwrng",
	.fops		= &rng_chrdev_ops,
};


static ssize_t hwrng_attr_current_store(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t len)
{
	int err;
	struct hwrng *rng;

	err = mutex_lock_interruptible(&rng_mutex);
	if (err)
		return -ERESTARTSYS;
	err = -ENODEV;
	list_for_each_entry(rng, &rng_list, list) {
		if (strcmp(rng->name, buf) == 0) {
			if (rng == current_rng) {
				err = 0;
				break;
			}
			err = hwrng_init(rng);
			if (err)
				break;
			drop_current_rng();
			set_current_rng(rng);
			err = 0;
			break;
		}
	}
	mutex_unlock(&rng_mutex);

	return err ? : len;
}

static ssize_t hwrng_attr_current_show(struct device *dev,
				       struct device_attribute *attr,
				       char *buf)
{
	ssize_t ret;
	struct hwrng *rng;

	rng = get_current_rng();
	if (IS_ERR(rng))
		return PTR_ERR(rng);

	ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
	put_rng(rng);

	return ret;
}

static ssize_t hwrng_attr_available_show(struct device *dev,
					 struct device_attribute *attr,
					 char *buf)
{
	int err;
	struct hwrng *rng;

	err = mutex_lock_interruptible(&rng_mutex);
	if (err)
		return -ERESTARTSYS;
	buf[0] = '\0';
	list_for_each_entry(rng, &rng_list, list) {
		strlcat(buf, rng->name, PAGE_SIZE);
		strlcat(buf, " ", PAGE_SIZE);
	}
	strlcat(buf, "\n", PAGE_SIZE);
	mutex_unlock(&rng_mutex);

	return strlen(buf);
}

static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
		   hwrng_attr_current_show,
		   hwrng_attr_current_store);
static DEVICE_ATTR(rng_available, S_IRUGO,
		   hwrng_attr_available_show,
		   NULL);


static void unregister_miscdev(void)
{
	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
	misc_deregister(&rng_miscdev);
}

static int register_miscdev(void)
{
	int err;

	err = misc_register(&rng_miscdev);
	if (err)
		goto out;
	err = device_create_file(rng_miscdev.this_device,
				 &dev_attr_rng_current);
	if (err)
		goto err_misc_dereg;
	err = device_create_file(rng_miscdev.this_device,
				 &dev_attr_rng_available);
	if (err)
		goto err_remove_current;
out:
	return err;

err_remove_current:
	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
err_misc_dereg:
	misc_deregister(&rng_miscdev);
	goto out;
}

static int hwrng_fillfn(void *unused)
{
	long rc;

	while (!kthread_should_stop()) {
		struct hwrng *rng;

		rng = get_current_rng();
		if (IS_ERR(rng) || !rng)
			break;
		mutex_lock(&reading_mutex);
		rc = rng_get_data(rng, rng_fillbuf,
				  rng_buffer_size(), 1);
		mutex_unlock(&reading_mutex);
		put_rng(rng);
		if (rc <= 0) {
			pr_warn("hwrng: no data available\n");
			msleep_interruptible(10000);
			continue;
		}
		/* Outside lock, sure, but y'know: randomness. */
		add_hwgenerator_randomness((void *)rng_fillbuf, rc,
					   rc * current_quality * 8 >> 10);
	}
	hwrng_fill = NULL;
	return 0;
}

static void start_khwrngd(void)
{
	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
	if (hwrng_fill == ERR_PTR(-ENOMEM)) {
		pr_err("hwrng_fill thread creation failed");
		hwrng_fill = NULL;
	}
}

int hwrng_register(struct hwrng *rng)
{
	int err = -EINVAL;
	struct hwrng *old_rng, *tmp;

	if (rng->name == NULL ||
	    (rng->data_read == NULL && rng->read == NULL))
		goto out;

	mutex_lock(&rng_mutex);

	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
	err = -ENOMEM;
	if (!rng_buffer) {
		rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
		if (!rng_buffer)
			goto out_unlock;
	}
	if (!rng_fillbuf) {
		rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
		if (!rng_fillbuf) {
			kfree(rng_buffer);
			goto out_unlock;
		}
	}

	/* Must not register two RNGs with the same name. */
	err = -EEXIST;
	list_for_each_entry(tmp, &rng_list, list) {
		if (strcmp(tmp->name, rng->name) == 0)
			goto out_unlock;
	}

	old_rng = current_rng;
	err = 0;
	if (!old_rng) {
		err = hwrng_init(rng);
		if (err)
			goto out_unlock;
		set_current_rng(rng);

		err = register_miscdev();
		if (err) {
			drop_current_rng();
			goto out_unlock;
		}
	}
	list_add_tail(&rng->list, &rng_list);

	if (old_rng && !rng->init) {
		/*
		 * Use a new device's input to add some randomness to
		 * the system.  If this rng device isn't going to be
		 * used right away, its init function hasn't been
		 * called yet; so only use the randomness from devices
		 * that don't need an init callback.
		 */
		add_early_randomness(rng);
	}

	init_completion(&rng->cleanup_done);

out_unlock:
	mutex_unlock(&rng_mutex);
out:
	return err;
}
EXPORT_SYMBOL_GPL(hwrng_register);

void hwrng_unregister(struct hwrng *rng)
{
	mutex_lock(&rng_mutex);

	list_del(&rng->list);
	if (current_rng == rng) {
		drop_current_rng();
		if (!list_empty(&rng_list)) {
			struct hwrng *tail;

			tail = list_entry(rng_list.prev, struct hwrng, list);

			if (hwrng_init(tail) == 0)
				set_current_rng(tail);
		}
	}

	if (list_empty(&rng_list)) {
		mutex_unlock(&rng_mutex);
		unregister_miscdev();
		if (hwrng_fill)
			kthread_stop(hwrng_fill);
	} else
		mutex_unlock(&rng_mutex);

	wait_for_completion(&rng->cleanup_done);
}
EXPORT_SYMBOL_GPL(hwrng_unregister);

static void __exit hwrng_exit(void)
{
	mutex_lock(&rng_mutex);
	BUG_ON(current_rng);
	kfree(rng_buffer);
	kfree(rng_fillbuf);
	mutex_unlock(&rng_mutex);
}

module_exit(hwrng_exit);

MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
844dd05f MB	1	/*
	2	Added support for the AMD Geode LX RNG
	3	(c) Copyright 2004-2005 Advanced Micro Devices, Inc.
	4
	5	derived from
	6
	7	Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
	8	(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
	9
	10	derived from
	11
	12	Hardware driver for the AMD 768 Random Number Generator (RNG)
	13	(c) Copyright 2001 Red Hat Inc <alan@redhat.com>
	14
	15	derived from
	16
	17	Hardware driver for Intel i810 Random Number Generator (RNG)
	18	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
	19	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
	20
	21	Added generic RNG API
eb032b98	22	Copyright 2006 Michael Buesch <m@bues.ch>
844dd05f MB	23	Copyright 2005 (c) MontaVista Software, Inc.
	24
	25	Please read Documentation/hw_random.txt for details on use.
	26
	27	----------------------------------------------------------
	28	This software may be used and distributed according to the terms
	29	of the GNU General Public License, incorporated herein by reference.
	30
	31	*/
	32
	33
	34	#include <linux/device.h>
	35	#include <linux/hw_random.h>
	36	#include <linux/module.h>
	37	#include <linux/kernel.h>
	38	#include <linux/fs.h>
914e2637	39	#include <linux/sched.h>
844dd05f	40	#include <linux/miscdevice.h>
be4000bc	41	#include <linux/kthread.h>
844dd05f	42	#include <linux/delay.h>
f7f154f1	43	#include <linux/slab.h>
d9e79726	44	#include <linux/random.h>
3a2c0ba5	45	#include <linux/err.h>
844dd05f MB	46	#include <asm/uaccess.h>
	47
	48
	49	#define RNG_MODULE_NAME "hw_random"
	50	#define PFX RNG_MODULE_NAME ": "
	51	#define RNG_MISCDEV_MINOR 183 /* official */
	52
	53
	54	static struct hwrng *current_rng;
be4000bc	55	static struct task_struct *hwrng_fill;
844dd05f	56	static LIST_HEAD(rng_list);
9372b35e	57	/* Protects rng_list and current_rng */
844dd05f	58	static DEFINE_MUTEX(rng_mutex);
9372b35e RR	59	/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
9372b35e RR	60	static DEFINE_MUTEX(reading_mutex);
9996508b	61	static int data_avail;
be4000bc	62	static u8 rng_buffer, rng_fillbuf;
0f734e6e TD	63	static unsigned short current_quality;
0f734e6e TD	64	static unsigned short default_quality; /* = 0; default to "off" */
be4000bc TD	65
	66	module_param(current_quality, ushort, 0644);
	67	MODULE_PARM_DESC(current_quality,
	68	"current hwrng entropy estimation per mill");
0f734e6e TD	69	module_param(default_quality, ushort, 0644);
	70	MODULE_PARM_DESC(default_quality,
	71	"default entropy content of hwrng per mill");
be4000bc TD	72
be4000bc TD	73	static void start_khwrngd(void);
f7f154f1	74
d3cc7996 AS	75	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	76	int wait);
	77
f7f154f1 RR	78	static size_t rng_buffer_size(void)
	79	{
	80	return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
	81	}
844dd05f	82
d3cc7996 AS	83	static void add_early_randomness(struct hwrng *rng)
	84	{
	85	unsigned char bytes[16];
	86	int bytes_read;
	87
9372b35e	88	mutex_lock(&reading_mutex);
d3cc7996	89	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
9372b35e	90	mutex_unlock(&reading_mutex);
d3cc7996 AS	91	if (bytes_read > 0)
	92	add_device_randomness(bytes, bytes_read);
	93	}
	94
3a2c0ba5 RR	95	static inline void cleanup_rng(struct kref *kref)
	96	{
	97	struct hwrng *rng = container_of(kref, struct hwrng, ref);
	98
	99	if (rng->cleanup)
	100	rng->cleanup(rng);
a027f30d	101
77584ee5	102	complete(&rng->cleanup_done);
3a2c0ba5 RR	103	}
	104
	105	static void set_current_rng(struct hwrng *rng)
	106	{
	107	BUG_ON(!mutex_is_locked(&rng_mutex));
	108	kref_get(&rng->ref);
	109	current_rng = rng;
	110	}
	111
	112	static void drop_current_rng(void)
	113	{
	114	BUG_ON(!mutex_is_locked(&rng_mutex));
	115	if (!current_rng)
	116	return;
	117
	118	/* decrease last reference for triggering the cleanup */
	119	kref_put(&current_rng->ref, cleanup_rng);
	120	current_rng = NULL;
	121	}
	122
	123	/* Returns ERR_PTR(), NULL or refcounted hwrng */
	124	static struct hwrng *get_current_rng(void)
	125	{
	126	struct hwrng *rng;
	127
	128	if (mutex_lock_interruptible(&rng_mutex))
	129	return ERR_PTR(-ERESTARTSYS);
	130
	131	rng = current_rng;
	132	if (rng)
	133	kref_get(&rng->ref);
	134
	135	mutex_unlock(&rng_mutex);
	136	return rng;
	137	}
	138
	139	static void put_rng(struct hwrng *rng)
	140	{
	141	/*
	142	* Hold rng_mutex here so we serialize in case they set_current_rng
	143	* on rng again immediately.
	144	*/
	145	mutex_lock(&rng_mutex);
	146	if (rng)
	147	kref_put(&rng->ref, cleanup_rng);
	148	mutex_unlock(&rng_mutex);
	149	}
	150
844dd05f MB	151	static inline int hwrng_init(struct hwrng *rng)
844dd05f MB	152	{
d3cc7996 AS	153	if (rng->init) {
	154	int ret;
	155
	156	ret = rng->init(rng);
	157	if (ret)
	158	return ret;
	159	}
	160	add_early_randomness(rng);
be4000bc	161
0f734e6e TD	162	current_quality = rng->quality ? : default_quality;
	163	current_quality &= 1023;
	164
	165	if (current_quality == 0 && hwrng_fill)
	166	kthread_stop(hwrng_fill);
be4000bc TD	167	if (current_quality > 0 && !hwrng_fill)
	168	start_khwrngd();
	169
d3cc7996	170	return 0;
844dd05f MB	171	}
844dd05f MB	172
844dd05f MB	173	static int rng_dev_open(struct inode inode, struct file filp)
	174	{
	175	/* enforce read-only access to this chrdev */
	176	if ((filp->f_mode & FMODE_READ) == 0)
	177	return -EINVAL;
	178	if (filp->f_mode & FMODE_WRITE)
	179	return -EINVAL;
	180	return 0;
	181	}
	182
9996508b IM	183	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	184	int wait) {
	185	int present;
	186
9372b35e	187	BUG_ON(!mutex_is_locked(&reading_mutex));
9996508b IM	188	if (rng->read)
	189	return rng->read(rng, (void *)buffer, size, wait);
	190
	191	if (rng->data_present)
	192	present = rng->data_present(rng, wait);
	193	else
	194	present = 1;
	195
	196	if (present)
	197	return rng->data_read(rng, (u32 *)buffer);
	198
	199	return 0;
	200	}
	201
844dd05f MB	202	static ssize_t rng_dev_read(struct file filp, char __user buf,
	203	size_t size, loff_t *offp)
	204	{
844dd05f	205	ssize_t ret = 0;
984e976f	206	int err = 0;
9996508b	207	int bytes_read, len;
3a2c0ba5	208	struct hwrng *rng;
844dd05f MB	209
844dd05f MB	210	while (size) {
3a2c0ba5 RR	211	rng = get_current_rng();
	212	if (IS_ERR(rng)) {
	213	err = PTR_ERR(rng);
844dd05f	214	goto out;
9996508b	215	}
3a2c0ba5	216	if (!rng) {
844dd05f	217	err = -ENODEV;
3a2c0ba5	218	goto out;
844dd05f	219	}
984e976f	220
9372b35e	221	mutex_lock(&reading_mutex);
9996508b	222	if (!data_avail) {
3a2c0ba5	223	bytes_read = rng_get_data(rng, rng_buffer,
f7f154f1	224	rng_buffer_size(),
9996508b IM	225	!(filp->f_flags & O_NONBLOCK));
	226	if (bytes_read < 0) {
	227	err = bytes_read;
9372b35e	228	goto out_unlock_reading;
9996508b IM	229	}
9996508b IM	230	data_avail = bytes_read;
893f1128	231	}
844dd05f	232
9996508b IM	233	if (!data_avail) {
	234	if (filp->f_flags & O_NONBLOCK) {
	235	err = -EAGAIN;
9372b35e	236	goto out_unlock_reading;
9996508b IM	237	}
	238	} else {
	239	len = data_avail;
	240	if (len > size)
	241	len = size;
	242
	243	data_avail -= len;
	244
	245	if (copy_to_user(buf + ret, rng_buffer + data_avail,
	246	len)) {
	247	err = -EFAULT;
9372b35e	248	goto out_unlock_reading;
9996508b IM	249	}
	250
	251	size -= len;
	252	ret += len;
844dd05f MB	253	}
844dd05f MB	254
9372b35e	255	mutex_unlock(&reading_mutex);
3a2c0ba5	256	put_rng(rng);
9996508b	257
844dd05f MB	258	if (need_resched())
844dd05f MB	259	schedule_timeout_interruptible(1);
9996508b IM	260
	261	if (signal_pending(current)) {
	262	err = -ERESTARTSYS;
844dd05f	263	goto out;
9996508b	264	}
844dd05f MB	265	}
	266	out:
	267	return ret ? : err;
3a2c0ba5	268
9372b35e RR	269	out_unlock_reading:
9372b35e RR	270	mutex_unlock(&reading_mutex);
3a2c0ba5 RR	271	put_rng(rng);
3a2c0ba5 RR	272	goto out;
844dd05f MB	273	}
	274
	275
62322d25	276	static const struct file_operations rng_chrdev_ops = {
844dd05f MB	277	.owner = THIS_MODULE,
	278	.open = rng_dev_open,
	279	.read = rng_dev_read,
6038f373	280	.llseek = noop_llseek,
844dd05f MB	281	};
	282
	283	static struct miscdevice rng_miscdev = {
	284	.minor = RNG_MISCDEV_MINOR,
	285	.name = RNG_MODULE_NAME,
e454cea2	286	.nodename = "hwrng",
844dd05f MB	287	.fops = &rng_chrdev_ops,
	288	};
	289
	290
94fbcded GKH	291	static ssize_t hwrng_attr_current_store(struct device *dev,
94fbcded GKH	292	struct device_attribute *attr,
844dd05f MB	293	const char *buf, size_t len)
	294	{
	295	int err;
	296	struct hwrng *rng;
	297
	298	err = mutex_lock_interruptible(&rng_mutex);
	299	if (err)
	300	return -ERESTARTSYS;
	301	err = -ENODEV;
	302	list_for_each_entry(rng, &rng_list, list) {
	303	if (strcmp(rng->name, buf) == 0) {
	304	if (rng == current_rng) {
	305	err = 0;
	306	break;
	307	}
	308	err = hwrng_init(rng);
	309	if (err)
	310	break;
3a2c0ba5 RR	311	drop_current_rng();
3a2c0ba5 RR	312	set_current_rng(rng);
844dd05f MB	313	err = 0;
	314	break;
	315	}
	316	}
	317	mutex_unlock(&rng_mutex);
	318
	319	return err ? : len;
	320	}
	321
94fbcded GKH	322	static ssize_t hwrng_attr_current_show(struct device *dev,
94fbcded GKH	323	struct device_attribute *attr,
844dd05f MB	324	char *buf)
844dd05f MB	325	{
844dd05f	326	ssize_t ret;
3a2c0ba5	327	struct hwrng *rng;
844dd05f	328
3a2c0ba5 RR	329	rng = get_current_rng();
	330	if (IS_ERR(rng))
	331	return PTR_ERR(rng);
	332
	333	ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
	334	put_rng(rng);
844dd05f MB	335
	336	return ret;
	337	}
	338
94fbcded GKH	339	static ssize_t hwrng_attr_available_show(struct device *dev,
94fbcded GKH	340	struct device_attribute *attr,
844dd05f MB	341	char *buf)
	342	{
	343	int err;
844dd05f MB	344	struct hwrng *rng;
	345
	346	err = mutex_lock_interruptible(&rng_mutex);
	347	if (err)
	348	return -ERESTARTSYS;
	349	buf[0] = '\0';
	350	list_for_each_entry(rng, &rng_list, list) {
61daf055 RS	351	strlcat(buf, rng->name, PAGE_SIZE);
61daf055 RS	352	strlcat(buf, " ", PAGE_SIZE);
844dd05f	353	}
61daf055	354	strlcat(buf, "\n", PAGE_SIZE);
844dd05f MB	355	mutex_unlock(&rng_mutex);
844dd05f MB	356
61daf055	357	return strlen(buf);
844dd05f MB	358	}
844dd05f MB	359
94fbcded GKH	360	static DEVICE_ATTR(rng_current, S_IRUGO \| S_IWUSR,
	361	hwrng_attr_current_show,
	362	hwrng_attr_current_store);
	363	static DEVICE_ATTR(rng_available, S_IRUGO,
	364	hwrng_attr_available_show,
	365	NULL);
844dd05f MB	366
844dd05f MB	367
b844eba2	368	static void unregister_miscdev(void)
844dd05f	369	{
94fbcded GKH	370	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
94fbcded GKH	371	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
b844eba2	372	misc_deregister(&rng_miscdev);
844dd05f MB	373	}
	374
	375	static int register_miscdev(void)
	376	{
	377	int err;
	378
	379	err = misc_register(&rng_miscdev);
	380	if (err)
	381	goto out;
94fbcded GKH	382	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	383	&dev_attr_rng_current);
844dd05f MB	384	if (err)
844dd05f MB	385	goto err_misc_dereg;
94fbcded GKH	386	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	387	&dev_attr_rng_available);
844dd05f MB	388	if (err)
	389	goto err_remove_current;
	390	out:
	391	return err;
	392
	393	err_remove_current:
94fbcded	394	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
844dd05f MB	395	err_misc_dereg:
	396	misc_deregister(&rng_miscdev);
	397	goto out;
	398	}
	399
be4000bc TD	400	static int hwrng_fillfn(void *unused)
	401	{
	402	long rc;
	403
	404	while (!kthread_should_stop()) {
3a2c0ba5 RR	405	struct hwrng *rng;
	406
	407	rng = get_current_rng();
	408	if (IS_ERR(rng) \|\| !rng)
be4000bc	409	break;
9372b35e	410	mutex_lock(&reading_mutex);
3a2c0ba5	411	rc = rng_get_data(rng, rng_fillbuf,
be4000bc	412	rng_buffer_size(), 1);
9372b35e	413	mutex_unlock(&reading_mutex);
3a2c0ba5	414	put_rng(rng);
be4000bc TD	415	if (rc <= 0) {
	416	pr_warn("hwrng: no data available\n");
	417	msleep_interruptible(10000);
	418	continue;
	419	}
9372b35e	420	/* Outside lock, sure, but y'know: randomness. */
be4000bc	421	add_hwgenerator_randomness((void *)rng_fillbuf, rc,
e02b8765	422	rc * current_quality * 8 >> 10);
be4000bc	423	}
9dda727d	424	hwrng_fill = NULL;
be4000bc TD	425	return 0;
	426	}
	427
	428	static void start_khwrngd(void)
	429	{
	430	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
	431	if (hwrng_fill == ERR_PTR(-ENOMEM)) {
	432	pr_err("hwrng_fill thread creation failed");
	433	hwrng_fill = NULL;
	434	}
	435	}
	436
844dd05f MB	437	int hwrng_register(struct hwrng *rng)
844dd05f MB	438	{
844dd05f MB	439	int err = -EINVAL;
	440	struct hwrng old_rng, tmp;
	441
	442	if (rng->name == NULL \|\|
9996508b	443	(rng->data_read == NULL && rng->read == NULL))
844dd05f MB	444	goto out;
	445
	446	mutex_lock(&rng_mutex);
	447
f7f154f1 RR	448	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
	449	err = -ENOMEM;
	450	if (!rng_buffer) {
	451	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
	452	if (!rng_buffer)
	453	goto out_unlock;
	454	}
be4000bc TD	455	if (!rng_fillbuf) {
	456	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
	457	if (!rng_fillbuf) {
	458	kfree(rng_buffer);
	459	goto out_unlock;
	460	}
	461	}
f7f154f1	462
844dd05f MB	463	/* Must not register two RNGs with the same name. */
	464	err = -EEXIST;
	465	list_for_each_entry(tmp, &rng_list, list) {
	466	if (strcmp(tmp->name, rng->name) == 0)
	467	goto out_unlock;
	468	}
	469
844dd05f	470	old_rng = current_rng;
ebbbfa24	471	err = 0;
844dd05f MB	472	if (!old_rng) {
	473	err = hwrng_init(rng);
	474	if (err)
	475	goto out_unlock;
3a2c0ba5	476	set_current_rng(rng);
ebbbfa24	477
844dd05f MB	478	err = register_miscdev();
844dd05f MB	479	if (err) {
3a2c0ba5	480	drop_current_rng();
844dd05f MB	481	goto out_unlock;
	482	}
	483	}
844dd05f	484	list_add_tail(&rng->list, &rng_list);
d9e79726	485
d3cc7996 AS	486	if (old_rng && !rng->init) {
	487	/*
	488	* Use a new device's input to add some randomness to
	489	* the system. If this rng device isn't going to be
	490	* used right away, its init function hasn't been
	491	* called yet; so only use the randomness from devices
	492	* that don't need an init callback.
	493	*/
	494	add_early_randomness(rng);
	495	}
	496
77584ee5	497	init_completion(&rng->cleanup_done);
a027f30d	498
844dd05f MB	499	out_unlock:
	500	mutex_unlock(&rng_mutex);
	501	out:
	502	return err;
	503	}
	504	EXPORT_SYMBOL_GPL(hwrng_register);
	505
b844eba2	506	void hwrng_unregister(struct hwrng *rng)
844dd05f	507	{
844dd05f MB	508	mutex_lock(&rng_mutex);
	509
	510	list_del(&rng->list);
	511	if (current_rng == rng) {
3a2c0ba5 RR	512	drop_current_rng();
	513	if (!list_empty(&rng_list)) {
	514	struct hwrng *tail;
	515
	516	tail = list_entry(rng_list.prev, struct hwrng, list);
	517
	518	if (hwrng_init(tail) == 0)
	519	set_current_rng(tail);
844dd05f MB	520	}
844dd05f MB	521	}
3a2c0ba5	522
be4000bc	523	if (list_empty(&rng_list)) {
1dacb395	524	mutex_unlock(&rng_mutex);
b844eba2	525	unregister_miscdev();
be4000bc TD	526	if (hwrng_fill)
be4000bc TD	527	kthread_stop(hwrng_fill);
1dacb395 AK	528	} else
1dacb395 AK	529	mutex_unlock(&rng_mutex);
a027f30d	530
77584ee5	531	wait_for_completion(&rng->cleanup_done);
844dd05f	532	}
b844eba2	533	EXPORT_SYMBOL_GPL(hwrng_unregister);
844dd05f	534
b7d44d94 ST	535	static void __exit hwrng_exit(void)
	536	{
	537	mutex_lock(&rng_mutex);
	538	BUG_ON(current_rng);
	539	kfree(rng_buffer);
be4000bc	540	kfree(rng_fillbuf);
b7d44d94 ST	541	mutex_unlock(&rng_mutex);
	542	}
	543
	544	module_exit(hwrng_exit);
844dd05f MB	545
	546	MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
	547	MODULE_LICENSE("GPL");