[mirror_ubuntu-bionic-kernel.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 <mbuesch@freenet.de>
	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/init.h>
#include <linux/miscdevice.h>
#include <linux/delay.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 LIST_HEAD(rng_list);
static DEFINE_MUTEX(rng_mutex);


static inline int hwrng_init(struct hwrng *rng)
{
	if (!rng->init)
		return 0;
	return rng->init(rng);
}

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

static inline int hwrng_data_present(struct hwrng *rng, int wait)
{
	if (!rng->data_present)
		return 1;
	return rng->data_present(rng, wait);
}

static inline int hwrng_data_read(struct hwrng *rng, u32 *data)
{
	return rng->data_read(rng, data);
}


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 ssize_t rng_dev_read(struct file *filp, char __user *buf,
			    size_t size, loff_t *offp)
{
	u32 data;
	ssize_t ret = 0;
	int err = 0;
	int bytes_read;

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

		bytes_read = 0;
		if (hwrng_data_present(current_rng,
				       !(filp->f_flags & O_NONBLOCK)))
			bytes_read = hwrng_data_read(current_rng, &data);
		mutex_unlock(&rng_mutex);

		err = -EAGAIN;
		if (!bytes_read && (filp->f_flags & O_NONBLOCK))
			goto out;

		err = -EFAULT;
		while (bytes_read && size) {
			if (put_user((u8)data, buf++))
				goto out;
			size--;
			ret++;
			bytes_read--;
			data >>= 8;
		}

		if (need_resched())
			schedule_timeout_interruptible(1);
		err = -ERESTARTSYS;
		if (signal_pending(current))
			goto out;
	}
out:
	return ret ? : err;
}


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

static struct miscdevice rng_miscdev = {
	.minor		= RNG_MISCDEV_MINOR,
	.name		= RNG_MODULE_NAME,
	.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;
	ssize_t ret = 0;
	struct hwrng *rng;

	err = mutex_lock_interruptible(&rng_mutex);
	if (err)
		return -ERESTARTSYS;
	buf[0] = '\0';
	list_for_each_entry(rng, &rng_list, list) {
		strncat(buf, rng->name, PAGE_SIZE - ret - 1);
		ret += strlen(rng->name);
		strncat(buf, " ", PAGE_SIZE - ret - 1);
		ret++;
	}
	strncat(buf, "\n", PAGE_SIZE - ret - 1);
	ret++;
	mutex_unlock(&rng_mutex);

	return ret;
}

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;
}

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

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

	mutex_lock(&rng_mutex);

	/* 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;
	}

	must_register_misc = (current_rng == NULL);
	old_rng = current_rng;
	if (!old_rng) {
		err = hwrng_init(rng);
		if (err)
			goto out_unlock;
		current_rng = rng;
	}
	err = 0;
	if (must_register_misc) {
		err = register_miscdev();
		if (err) {
			if (!old_rng) {
				hwrng_cleanup(rng);
				current_rng = NULL;
			}
			goto out_unlock;
		}
	}
	INIT_LIST_HEAD(&rng->list);
	list_add_tail(&rng->list, &rng_list);
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();

	mutex_unlock(&rng_mutex);
}
EXPORT_SYMBOL_GPL(hwrng_unregister);


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
	22	Copyright 2006 Michael Buesch <mbuesch@freenet.de>
	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 MB	40	#include <linux/init.h>
	41	#include <linux/miscdevice.h>
	42	#include <linux/delay.h>
	43	#include <asm/uaccess.h>
	44
	45
	46	#define RNG_MODULE_NAME "hw_random"
	47	#define PFX RNG_MODULE_NAME ": "
	48	#define RNG_MISCDEV_MINOR 183 /* official */
	49
	50
	51	static struct hwrng *current_rng;
	52	static LIST_HEAD(rng_list);
	53	static DEFINE_MUTEX(rng_mutex);
	54
	55
	56	static inline int hwrng_init(struct hwrng *rng)
	57	{
	58	if (!rng->init)
	59	return 0;
	60	return rng->init(rng);
	61	}
	62
	63	static inline void hwrng_cleanup(struct hwrng *rng)
	64	{
	65	if (rng && rng->cleanup)
	66	rng->cleanup(rng);
	67	}
	68
984e976f	69	static inline int hwrng_data_present(struct hwrng *rng, int wait)
844dd05f MB	70	{
	71	if (!rng->data_present)
	72	return 1;
984e976f	73	return rng->data_present(rng, wait);
844dd05f MB	74	}
	75
	76	static inline int hwrng_data_read(struct hwrng rng, u32 data)
	77	{
	78	return rng->data_read(rng, data);
	79	}
	80
	81
	82	static int rng_dev_open(struct inode inode, struct file filp)
	83	{
	84	/* enforce read-only access to this chrdev */
	85	if ((filp->f_mode & FMODE_READ) == 0)
	86	return -EINVAL;
	87	if (filp->f_mode & FMODE_WRITE)
	88	return -EINVAL;
	89	return 0;
	90	}
	91
	92	static ssize_t rng_dev_read(struct file filp, char __user buf,
	93	size_t size, loff_t *offp)
	94	{
	95	u32 data;
	96	ssize_t ret = 0;
984e976f	97	int err = 0;
844dd05f MB	98	int bytes_read;
	99
	100	while (size) {
	101	err = -ERESTARTSYS;
	102	if (mutex_lock_interruptible(&rng_mutex))
	103	goto out;
	104	if (!current_rng) {
	105	mutex_unlock(&rng_mutex);
	106	err = -ENODEV;
	107	goto out;
	108	}
984e976f	109
844dd05f	110	bytes_read = 0;
984e976f PM	111	if (hwrng_data_present(current_rng,
984e976f PM	112	!(filp->f_flags & O_NONBLOCK)))
844dd05f MB	113	bytes_read = hwrng_data_read(current_rng, &data);
	114	mutex_unlock(&rng_mutex);
	115
	116	err = -EAGAIN;
	117	if (!bytes_read && (filp->f_flags & O_NONBLOCK))
	118	goto out;
	119
	120	err = -EFAULT;
	121	while (bytes_read && size) {
	122	if (put_user((u8)data, buf++))
	123	goto out;
	124	size--;
	125	ret++;
	126	bytes_read--;
	127	data >>= 8;
	128	}
	129
	130	if (need_resched())
	131	schedule_timeout_interruptible(1);
	132	err = -ERESTARTSYS;
	133	if (signal_pending(current))
	134	goto out;
	135	}
	136	out:
	137	return ret ? : err;
	138	}
	139
	140
62322d25	141	static const struct file_operations rng_chrdev_ops = {
844dd05f MB	142	.owner = THIS_MODULE,
	143	.open = rng_dev_open,
	144	.read = rng_dev_read,
	145	};
	146
	147	static struct miscdevice rng_miscdev = {
	148	.minor = RNG_MISCDEV_MINOR,
	149	.name = RNG_MODULE_NAME,
	150	.fops = &rng_chrdev_ops,
	151	};
	152
	153
94fbcded GKH	154	static ssize_t hwrng_attr_current_store(struct device *dev,
94fbcded GKH	155	struct device_attribute *attr,
844dd05f MB	156	const char *buf, size_t len)
	157	{
	158	int err;
	159	struct hwrng *rng;
	160
	161	err = mutex_lock_interruptible(&rng_mutex);
	162	if (err)
	163	return -ERESTARTSYS;
	164	err = -ENODEV;
	165	list_for_each_entry(rng, &rng_list, list) {
	166	if (strcmp(rng->name, buf) == 0) {
	167	if (rng == current_rng) {
	168	err = 0;
	169	break;
	170	}
	171	err = hwrng_init(rng);
	172	if (err)
	173	break;
	174	hwrng_cleanup(current_rng);
	175	current_rng = rng;
	176	err = 0;
	177	break;
	178	}
	179	}
	180	mutex_unlock(&rng_mutex);
	181
	182	return err ? : len;
	183	}
	184
94fbcded GKH	185	static ssize_t hwrng_attr_current_show(struct device *dev,
94fbcded GKH	186	struct device_attribute *attr,
844dd05f MB	187	char *buf)
	188	{
	189	int err;
	190	ssize_t ret;
	191	const char *name = "none";
	192
	193	err = mutex_lock_interruptible(&rng_mutex);
	194	if (err)
	195	return -ERESTARTSYS;
	196	if (current_rng)
	197	name = current_rng->name;
	198	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
	199	mutex_unlock(&rng_mutex);
	200
	201	return ret;
	202	}
	203
94fbcded GKH	204	static ssize_t hwrng_attr_available_show(struct device *dev,
94fbcded GKH	205	struct device_attribute *attr,
844dd05f MB	206	char *buf)
	207	{
	208	int err;
	209	ssize_t ret = 0;
	210	struct hwrng *rng;
	211
	212	err = mutex_lock_interruptible(&rng_mutex);
	213	if (err)
	214	return -ERESTARTSYS;
	215	buf[0] = '\0';
	216	list_for_each_entry(rng, &rng_list, list) {
	217	strncat(buf, rng->name, PAGE_SIZE - ret - 1);
	218	ret += strlen(rng->name);
	219	strncat(buf, " ", PAGE_SIZE - ret - 1);
	220	ret++;
	221	}
	222	strncat(buf, "\n", PAGE_SIZE - ret - 1);
	223	ret++;
	224	mutex_unlock(&rng_mutex);
	225
	226	return ret;
	227	}
	228
94fbcded GKH	229	static DEVICE_ATTR(rng_current, S_IRUGO \| S_IWUSR,
	230	hwrng_attr_current_show,
	231	hwrng_attr_current_store);
	232	static DEVICE_ATTR(rng_available, S_IRUGO,
	233	hwrng_attr_available_show,
	234	NULL);
844dd05f MB	235
	236
	237	static void unregister_miscdev(void)
	238	{
94fbcded GKH	239	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
94fbcded GKH	240	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
844dd05f MB	241	misc_deregister(&rng_miscdev);
	242	}
	243
	244	static int register_miscdev(void)
	245	{
	246	int err;
	247
	248	err = misc_register(&rng_miscdev);
	249	if (err)
	250	goto out;
94fbcded GKH	251	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	252	&dev_attr_rng_current);
844dd05f MB	253	if (err)
844dd05f MB	254	goto err_misc_dereg;
94fbcded GKH	255	err = device_create_file(rng_miscdev.this_device,
94fbcded GKH	256	&dev_attr_rng_available);
844dd05f MB	257	if (err)
	258	goto err_remove_current;
	259	out:
	260	return err;
	261
	262	err_remove_current:
94fbcded	263	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
844dd05f MB	264	err_misc_dereg:
	265	misc_deregister(&rng_miscdev);
	266	goto out;
	267	}
	268
	269	int hwrng_register(struct hwrng *rng)
	270	{
	271	int must_register_misc;
	272	int err = -EINVAL;
	273	struct hwrng old_rng, tmp;
	274
	275	if (rng->name == NULL \|\|
	276	rng->data_read == NULL)
	277	goto out;
	278
	279	mutex_lock(&rng_mutex);
	280
	281	/* Must not register two RNGs with the same name. */
	282	err = -EEXIST;
	283	list_for_each_entry(tmp, &rng_list, list) {
	284	if (strcmp(tmp->name, rng->name) == 0)
	285	goto out_unlock;
	286	}
	287
	288	must_register_misc = (current_rng == NULL);
	289	old_rng = current_rng;
	290	if (!old_rng) {
	291	err = hwrng_init(rng);
	292	if (err)
	293	goto out_unlock;
	294	current_rng = rng;
	295	}
	296	err = 0;
	297	if (must_register_misc) {
	298	err = register_miscdev();
	299	if (err) {
	300	if (!old_rng) {
	301	hwrng_cleanup(rng);
	302	current_rng = NULL;
	303	}
	304	goto out_unlock;
	305	}
	306	}
	307	INIT_LIST_HEAD(&rng->list);
	308	list_add_tail(&rng->list, &rng_list);
	309	out_unlock:
	310	mutex_unlock(&rng_mutex);
	311	out:
	312	return err;
	313	}
	314	EXPORT_SYMBOL_GPL(hwrng_register);
	315
	316	void hwrng_unregister(struct hwrng *rng)
	317	{
	318	int err;
	319
	320	mutex_lock(&rng_mutex);
	321
	322	list_del(&rng->list);
	323	if (current_rng == rng) {
	324	hwrng_cleanup(rng);
	325	if (list_empty(&rng_list)) {
	326	current_rng = NULL;
	327	} else {
328	current_rng = list_entry(rng_list.prev, struct hwrng, list);
329	err = hwrng_init(current_rng);
330	if (err)
331	current_rng = NULL;
332	}
333	}
334	if (list_empty(&rng_list))
335	unregister_miscdev();
336
337	mutex_unlock(&rng_mutex);
338	}
339	EXPORT_SYMBOL_GPL(hwrng_unregister);
340
341
342	MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
343	MODULE_LICENSE("GPL");