[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 <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 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 inline void hwrng_cleanup(struct hwrng *rng)
{
	if (rng && rng->cleanup)
		rng->cleanup(rng);
}

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;

	while (size) {
		if (mutex_lock_interruptible(&rng_mutex)) {
			err = -ERESTARTSYS;
			goto out;
		}

		if (!current_rng) {
			err = -ENODEV;
			goto out_unlock;
		}

		mutex_lock(&reading_mutex);
		if (!data_avail) {
			bytes_read = rng_get_data(current_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(&rng_mutex);
		mutex_unlock(&reading_mutex);

		if (need_resched())
			schedule_timeout_interruptible(1);

		if (signal_pending(current)) {
			err = -ERESTARTSYS;
			goto out;
		}
	}
out:
	return ret ? : err;
out_unlock:
	mutex_unlock(&rng_mutex);
	goto out;
out_unlock_reading:
	mutex_unlock(&reading_mutex);
	goto out_unlock;
}


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;
			hwrng_cleanup(current_rng);
			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)
{
	int err;
	ssize_t ret;
	const char *name = "none";

	err = mutex_lock_interruptible(&rng_mutex);
	if (err)
		return -ERESTARTSYS;
	if (current_rng)
		name = current_rng->name;
	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
	mutex_unlock(&rng_mutex);

	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()) {
		if (!current_rng)
			break;
		mutex_lock(&reading_mutex);
		rc = rng_get_data(current_rng, rng_fillbuf,
				  rng_buffer_size(), 1);
		mutex_unlock(&reading_mutex);
		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;
	if (!old_rng) {
		err = hwrng_init(rng);
		if (err)
			goto out_unlock;
		current_rng = rng;
	}
	err = 0;
	if (!old_rng) {
		err = register_miscdev();
		if (err) {
			hwrng_cleanup(rng);
			current_rng = NULL;
			goto out_unlock;
		}
	}
	INIT_LIST_HEAD(&rng->list);
	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);
	}

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

void hwrng_unregister(struct hwrng *rng)
{
	int err;

	mutex_lock(&rng_mutex);

	list_del(&rng->list);
	if (current_rng == rng) {
		hwrng_cleanup(rng);
		if (list_empty(&rng_list)) {
			current_rng = NULL;
		} else {
			current_rng = list_entry(rng_list.prev, struct hwrng, list);
			err = hwrng_init(current_rng);
			if (err)
				current_rng = NULL;
		}
	}
	if (list_empty(&rng_list)) {
		unregister_miscdev();
		if (hwrng_fill)
			kthread_stop(hwrng_fill);
	}

	mutex_unlock(&rng_mutex);
}
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>
844dd05f MB	45	#include <asm/uaccess.h>
	46
	47
	48	#define RNG_MODULE_NAME "hw_random"
	49	#define PFX RNG_MODULE_NAME ": "
	50	#define RNG_MISCDEV_MINOR 183 /* official */
	51
	52
	53	static struct hwrng *current_rng;
be4000bc	54	static struct task_struct *hwrng_fill;
844dd05f	55	static LIST_HEAD(rng_list);
9372b35e	56	/* Protects rng_list and current_rng */
844dd05f	57	static DEFINE_MUTEX(rng_mutex);
9372b35e RR	58	/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
9372b35e RR	59	static DEFINE_MUTEX(reading_mutex);
9996508b	60	static int data_avail;
be4000bc	61	static u8 rng_buffer, rng_fillbuf;
0f734e6e TD	62	static unsigned short current_quality;
0f734e6e TD	63	static unsigned short default_quality; /* = 0; default to "off" */
be4000bc TD	64
	65	module_param(current_quality, ushort, 0644);
	66	MODULE_PARM_DESC(current_quality,
	67	"current hwrng entropy estimation per mill");
0f734e6e TD	68	module_param(default_quality, ushort, 0644);
	69	MODULE_PARM_DESC(default_quality,
	70	"default entropy content of hwrng per mill");
be4000bc TD	71
be4000bc TD	72	static void start_khwrngd(void);
f7f154f1	73
d3cc7996 AS	74	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	75	int wait);
	76
f7f154f1 RR	77	static size_t rng_buffer_size(void)
	78	{
	79	return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
	80	}
844dd05f	81
d3cc7996 AS	82	static void add_early_randomness(struct hwrng *rng)
	83	{
	84	unsigned char bytes[16];
	85	int bytes_read;
	86
9372b35e	87	mutex_lock(&reading_mutex);
d3cc7996	88	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
9372b35e	89	mutex_unlock(&reading_mutex);
d3cc7996 AS	90	if (bytes_read > 0)
	91	add_device_randomness(bytes, bytes_read);
	92	}
	93
844dd05f MB	94	static inline int hwrng_init(struct hwrng *rng)
844dd05f MB	95	{
d3cc7996 AS	96	if (rng->init) {
	97	int ret;
	98
	99	ret = rng->init(rng);
	100	if (ret)
	101	return ret;
	102	}
	103	add_early_randomness(rng);
be4000bc	104
0f734e6e TD	105	current_quality = rng->quality ? : default_quality;
	106	current_quality &= 1023;
	107
	108	if (current_quality == 0 && hwrng_fill)
	109	kthread_stop(hwrng_fill);
be4000bc TD	110	if (current_quality > 0 && !hwrng_fill)
	111	start_khwrngd();
	112
d3cc7996	113	return 0;
844dd05f MB	114	}
	115
	116	static inline void hwrng_cleanup(struct hwrng *rng)
	117	{
	118	if (rng && rng->cleanup)
	119	rng->cleanup(rng);
	120	}
	121
844dd05f MB	122	static int rng_dev_open(struct inode inode, struct file filp)
	123	{
	124	/* enforce read-only access to this chrdev */
	125	if ((filp->f_mode & FMODE_READ) == 0)
	126	return -EINVAL;
	127	if (filp->f_mode & FMODE_WRITE)
	128	return -EINVAL;
	129	return 0;
	130	}
	131
9996508b IM	132	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	133	int wait) {
	134	int present;
	135
9372b35e	136	BUG_ON(!mutex_is_locked(&reading_mutex));
9996508b IM	137	if (rng->read)
	138	return rng->read(rng, (void *)buffer, size, wait);
	139
	140	if (rng->data_present)
	141	present = rng->data_present(rng, wait);
	142	else
	143	present = 1;
	144
	145	if (present)
	146	return rng->data_read(rng, (u32 *)buffer);
	147
	148	return 0;
	149	}
	150
844dd05f MB	151	static ssize_t rng_dev_read(struct file filp, char __user buf,
	152	size_t size, loff_t *offp)
	153	{
844dd05f	154	ssize_t ret = 0;
984e976f	155	int err = 0;
9996508b	156	int bytes_read, len;
844dd05f MB	157
844dd05f MB	158	while (size) {
9996508b IM	159	if (mutex_lock_interruptible(&rng_mutex)) {
9996508b IM	160	err = -ERESTARTSYS;
844dd05f	161	goto out;
9996508b IM	162	}
9996508b IM	163
844dd05f	164	if (!current_rng) {
844dd05f	165	err = -ENODEV;
9996508b	166	goto out_unlock;
844dd05f	167	}
984e976f	168
9372b35e	169	mutex_lock(&reading_mutex);
9996508b IM	170	if (!data_avail) {
9996508b IM	171	bytes_read = rng_get_data(current_rng, rng_buffer,
f7f154f1	172	rng_buffer_size(),
9996508b IM	173	!(filp->f_flags & O_NONBLOCK));
	174	if (bytes_read < 0) {
	175	err = bytes_read;
9372b35e	176	goto out_unlock_reading;
9996508b IM	177	}
9996508b IM	178	data_avail = bytes_read;
893f1128	179	}
844dd05f	180
9996508b IM	181	if (!data_avail) {
	182	if (filp->f_flags & O_NONBLOCK) {
	183	err = -EAGAIN;
9372b35e	184	goto out_unlock_reading;
9996508b IM	185	}
	186	} else {
	187	len = data_avail;
	188	if (len > size)
	189	len = size;
	190
	191	data_avail -= len;
	192
	193	if (copy_to_user(buf + ret, rng_buffer + data_avail,
	194	len)) {
	195	err = -EFAULT;
9372b35e	196	goto out_unlock_reading;
9996508b IM	197	}
	198
	199	size -= len;
	200	ret += len;
844dd05f MB	201	}
844dd05f MB	202
9996508b	203	mutex_unlock(&rng_mutex);
9372b35e	204	mutex_unlock(&reading_mutex);
9996508b	205
844dd05f MB	206	if (need_resched())
844dd05f MB	207	schedule_timeout_interruptible(1);
9996508b IM	208
	209	if (signal_pending(current)) {
	210	err = -ERESTARTSYS;
844dd05f	211	goto out;
9996508b	212	}
844dd05f MB	213	}
	214	out:
	215	return ret ? : err;
f5908267 HX	216	out_unlock:
	217	mutex_unlock(&rng_mutex);
	218	goto out;
9372b35e RR	219	out_unlock_reading:
	220	mutex_unlock(&reading_mutex);
	221	goto out_unlock;
844dd05f MB	222	}
	223
	224
62322d25	225	static const struct file_operations rng_chrdev_ops = {
844dd05f MB	226	.owner = THIS_MODULE,
	227	.open = rng_dev_open,
	228	.read = rng_dev_read,
6038f373	229	.llseek = noop_llseek,
844dd05f MB	230	};
	231
	232	static struct miscdevice rng_miscdev = {
	233	.minor = RNG_MISCDEV_MINOR,
	234	.name = RNG_MODULE_NAME,
e454cea2	235	.nodename = "hwrng",
844dd05f MB	236	.fops = &rng_chrdev_ops,
	237	};
	238
	239
94fbcded GKH	240	static ssize_t hwrng_attr_current_store(struct device *dev,
94fbcded GKH	241	struct device_attribute *attr,
844dd05f MB	242	const char *buf, size_t len)
	243	{
	244	int err;
	245	struct hwrng *rng;
	246
	247	err = mutex_lock_interruptible(&rng_mutex);
	248	if (err)
	249	return -ERESTARTSYS;
	250	err = -ENODEV;
	251	list_for_each_entry(rng, &rng_list, list) {
	252	if (strcmp(rng->name, buf) == 0) {
	253	if (rng == current_rng) {
	254	err = 0;
	255	break;
	256	}
	257	err = hwrng_init(rng);
	258	if (err)
	259	break;
	260	hwrng_cleanup(current_rng);
	261	current_rng = rng;
	262	err = 0;
	263	break;
	264	}
	265	}
	266	mutex_unlock(&rng_mutex);
	267
	268	return err ? : len;
	269	}
	270
94fbcded GKH	271	static ssize_t hwrng_attr_current_show(struct device *dev,
94fbcded GKH	272	struct device_attribute *attr,
844dd05f MB	273	char *buf)
	274	{
	275	int err;
	276	ssize_t ret;
	277	const char *name = "none";
	278
	279	err = mutex_lock_interruptible(&rng_mutex);
	280	if (err)
	281	return -ERESTARTSYS;
	282	if (current_rng)
	283	name = current_rng->name;
	284	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
	285	mutex_unlock(&rng_mutex);
	286
	287	return ret;
	288	}
	289
94fbcded GKH	290	static ssize_t hwrng_attr_available_show(struct device *dev,
94fbcded GKH	291	struct device_attribute *attr,
844dd05f MB	292	char *buf)
	293	{
	294	int err;
844dd05f MB	295	struct hwrng *rng;
	296
	297	err = mutex_lock_interruptible(&rng_mutex);
	298	if (err)
	299	return -ERESTARTSYS;
	300	buf[0] = '\0';
	301	list_for_each_entry(rng, &rng_list, list) {
61daf055 RS	302	strlcat(buf, rng->name, PAGE_SIZE);
61daf055 RS	303	strlcat(buf, " ", PAGE_SIZE);
844dd05f	304	}
61daf055	305	strlcat(buf, "\n", PAGE_SIZE);
844dd05f MB	306	mutex_unlock(&rng_mutex);
844dd05f MB	307
61daf055	308	return strlen(buf);
844dd05f MB	309	}
844dd05f MB	310
94fbcded GKH	311	static DEVICE_ATTR(rng_current, S_IRUGO \| S_IWUSR,
	312	hwrng_attr_current_show,
	313	hwrng_attr_current_store);
	314	static DEVICE_ATTR(rng_available, S_IRUGO,
	315	hwrng_attr_available_show,
	316	NULL);
844dd05f MB	317
844dd05f MB	318
b844eba2	319	static void unregister_miscdev(void)
844dd05f	320	{
94fbcded GKH	321	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
94fbcded GKH	322	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
b844eba2	323	misc_deregister(&rng_miscdev);
844dd05f MB	324	}
	325
	326	static int register_miscdev(void)
	327	{
	328	int err;
	329
	330	err = misc_register(&rng_miscdev);
	331	if (err)
	332	goto out;
94fbcded GKH	333	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	334	&dev_attr_rng_current);
844dd05f MB	335	if (err)
844dd05f MB	336	goto err_misc_dereg;
94fbcded GKH	337	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	338	&dev_attr_rng_available);
844dd05f MB	339	if (err)
	340	goto err_remove_current;
	341	out:
	342	return err;
	343
	344	err_remove_current:
94fbcded	345	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
844dd05f MB	346	err_misc_dereg:
	347	misc_deregister(&rng_miscdev);
	348	goto out;
	349	}
	350
be4000bc TD	351	static int hwrng_fillfn(void *unused)
	352	{
	353	long rc;
	354
	355	while (!kthread_should_stop()) {
	356	if (!current_rng)
	357	break;
9372b35e	358	mutex_lock(&reading_mutex);
be4000bc TD	359	rc = rng_get_data(current_rng, rng_fillbuf,
be4000bc TD	360	rng_buffer_size(), 1);
9372b35e	361	mutex_unlock(&reading_mutex);
be4000bc TD	362	if (rc <= 0) {
	363	pr_warn("hwrng: no data available\n");
	364	msleep_interruptible(10000);
	365	continue;
	366	}
9372b35e	367	/* Outside lock, sure, but y'know: randomness. */
be4000bc	368	add_hwgenerator_randomness((void *)rng_fillbuf, rc,
e02b8765	369	rc * current_quality * 8 >> 10);
be4000bc	370	}
9dda727d	371	hwrng_fill = NULL;
be4000bc TD	372	return 0;
	373	}
	374
	375	static void start_khwrngd(void)
	376	{
	377	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
	378	if (hwrng_fill == ERR_PTR(-ENOMEM)) {
	379	pr_err("hwrng_fill thread creation failed");
	380	hwrng_fill = NULL;
	381	}
	382	}
	383
844dd05f MB	384	int hwrng_register(struct hwrng *rng)
844dd05f MB	385	{
844dd05f MB	386	int err = -EINVAL;
	387	struct hwrng old_rng, tmp;
	388
	389	if (rng->name == NULL \|\|
9996508b	390	(rng->data_read == NULL && rng->read == NULL))
844dd05f MB	391	goto out;
	392
	393	mutex_lock(&rng_mutex);
	394
f7f154f1 RR	395	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
	396	err = -ENOMEM;
	397	if (!rng_buffer) {
	398	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
	399	if (!rng_buffer)
	400	goto out_unlock;
	401	}
be4000bc TD	402	if (!rng_fillbuf) {
	403	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
	404	if (!rng_fillbuf) {
	405	kfree(rng_buffer);
	406	goto out_unlock;
	407	}
	408	}
f7f154f1	409
844dd05f MB	410	/* Must not register two RNGs with the same name. */
	411	err = -EEXIST;
	412	list_for_each_entry(tmp, &rng_list, list) {
	413	if (strcmp(tmp->name, rng->name) == 0)
	414	goto out_unlock;
	415	}
	416
844dd05f MB	417	old_rng = current_rng;
	418	if (!old_rng) {
	419	err = hwrng_init(rng);
	420	if (err)
	421	goto out_unlock;
	422	current_rng = rng;
	423	}
	424	err = 0;
d167b6e1	425	if (!old_rng) {
844dd05f MB	426	err = register_miscdev();
844dd05f MB	427	if (err) {
d167b6e1 DC	428	hwrng_cleanup(rng);
d167b6e1 DC	429	current_rng = NULL;
844dd05f MB	430	goto out_unlock;
	431	}
	432	}
	433	INIT_LIST_HEAD(&rng->list);
	434	list_add_tail(&rng->list, &rng_list);
d9e79726	435
d3cc7996 AS	436	if (old_rng && !rng->init) {
	437	/*
	438	* Use a new device's input to add some randomness to
	439	* the system. If this rng device isn't going to be
	440	* used right away, its init function hasn't been
	441	* called yet; so only use the randomness from devices
	442	* that don't need an init callback.
	443	*/
	444	add_early_randomness(rng);
	445	}
	446
844dd05f MB	447	out_unlock:
	448	mutex_unlock(&rng_mutex);
	449	out:
	450	return err;
	451	}
	452	EXPORT_SYMBOL_GPL(hwrng_register);
	453
b844eba2	454	void hwrng_unregister(struct hwrng *rng)
844dd05f MB	455	{
	456	int err;
	457
	458	mutex_lock(&rng_mutex);
	459
	460	list_del(&rng->list);
	461	if (current_rng == rng) {
	462	hwrng_cleanup(rng);
	463	if (list_empty(&rng_list)) {
	464	current_rng = NULL;
	465	} else {
	466	current_rng = list_entry(rng_list.prev, struct hwrng, list);
	467	err = hwrng_init(current_rng);
	468	if (err)
	469	current_rng = NULL;
	470	}
	471	}
be4000bc	472	if (list_empty(&rng_list)) {
b844eba2	473	unregister_miscdev();
be4000bc TD	474	if (hwrng_fill)
	475	kthread_stop(hwrng_fill);
	476	}
844dd05f MB	477
	478	mutex_unlock(&rng_mutex);
	479	}
b844eba2	480	EXPORT_SYMBOL_GPL(hwrng_unregister);
844dd05f	481
b7d44d94 ST	482	static void __exit hwrng_exit(void)
	483	{
	484	mutex_lock(&rng_mutex);
	485	BUG_ON(current_rng);
	486	kfree(rng_buffer);
be4000bc	487	kfree(rng_fillbuf);
b7d44d94 ST	488	mutex_unlock(&rng_mutex);
	489	}
	490
	491	module_exit(hwrng_exit);
844dd05f MB	492
	493	MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
	494	MODULE_LICENSE("GPL");