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

/*
 * hw_random/core.c: HWRNG core API
 *
 * Copyright 2006 Michael Buesch <m@bues.ch>
 * Copyright 2005 (c) MontaVista Software, Inc.
 *
 * Please read Documentation/admin-guide/hw_random.rst 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/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/hw_random.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/uaccess.h>

#define RNG_MODULE_NAME		"hw_random"

#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES)

static struct hwrng *current_rng;
/* the current rng has been explicitly chosen by user via sysfs */
static int cur_rng_set_by_user;
static struct task_struct *hwrng_fill;
/* list of registered rngs */
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 = 1024; /* default to maximum */

module_param(current_quality, ushort, 0644);
MODULE_PARM_DESC(current_quality,
		 "current hwrng entropy estimation per 1024 bits of input -- obsolete, use rng_quality instead");
module_param(default_quality, ushort, 0644);
MODULE_PARM_DESC(default_quality,
		 "default maximum entropy content of hwrng per 1024 bits of input");

static void drop_current_rng(void);
static int hwrng_init(struct hwrng *rng);
static int hwrng_fillfn(void *unused);

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

static size_t rng_buffer_size(void)
{
	return RNG_BUFFER_SIZE;
}

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 int set_current_rng(struct hwrng *rng)
{
	int err;

	BUG_ON(!mutex_is_locked(&rng_mutex));

	err = hwrng_init(rng);
	if (err)
		return err;

	drop_current_rng();
	current_rng = rng;

	/* if necessary, start hwrng thread */
	if (!hwrng_fill) {
		hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
		if (IS_ERR(hwrng_fill)) {
			pr_err("hwrng_fill thread creation failed\n");
			hwrng_fill = NULL;
		}
	}

	return 0;
}

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_nolock(void)
{
	if (current_rng)
		kref_get(&current_rng->ref);

	return current_rng;
}

static struct hwrng *get_current_rng(void)
{
	struct hwrng *rng;

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

	rng = get_current_rng_nolock();

	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 int hwrng_init(struct hwrng *rng)
{
	if (kref_get_unless_zero(&rng->ref))
		goto skip_init;

	if (rng->init) {
		int ret;

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

	kref_init(&rng->ref);
	reinit_completion(&rng->cleanup_done);

skip_init:
	current_quality = rng->quality; /* obsolete */

	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) {
		int err;

		err = rng->read(rng, buffer, size, wait);
		if (WARN_ON_ONCE(err > 0 && err > size))
			err = size;

		return err;
	}

	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)
{
	u8 buffer[RNG_BUFFER_SIZE];
	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;
		}

		if (mutex_lock_interruptible(&reading_mutex)) {
			err = -ERESTARTSYS;
			goto out_put;
		}
		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;
			} else if (bytes_read == 0 &&
				   (filp->f_flags & O_NONBLOCK)) {
				err = -EAGAIN;
				goto out_unlock_reading;
			}

			data_avail = bytes_read;
		}

		len = data_avail;
		if (len) {
			if (len > size)
				len = size;

			data_avail -= len;

			memcpy(buffer, rng_buffer + data_avail, len);
		}
		mutex_unlock(&reading_mutex);
		put_rng(rng);

		if (len) {
			if (copy_to_user(buf + ret, buffer, len)) {
				err = -EFAULT;
				goto out;
			}

			size -= len;
			ret += len;
		}


		if (need_resched())
			schedule_timeout_interruptible(1);

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

out_unlock_reading:
	mutex_unlock(&reading_mutex);
out_put:
	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 const struct attribute_group *rng_dev_groups[];

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

static int enable_best_rng(void)
{
	struct hwrng *rng, *new_rng = NULL;
	int ret = -ENODEV;

	BUG_ON(!mutex_is_locked(&rng_mutex));

	/* no rng to use? */
	if (list_empty(&rng_list)) {
		drop_current_rng();
		cur_rng_set_by_user = 0;
		return 0;
	}

	/* use the rng which offers the best quality */
	list_for_each_entry(rng, &rng_list, list) {
		if (!new_rng || rng->quality > new_rng->quality)
			new_rng = rng;
	}

	ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
	if (!ret)
		cur_rng_set_by_user = 0;

	return ret;
}

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

	err = mutex_lock_interruptible(&rng_mutex);
	if (err)
		return -ERESTARTSYS;

	if (sysfs_streq(buf, "")) {
		err = enable_best_rng();
	} else {
		list_for_each_entry(rng, &rng_list, list) {
			if (sysfs_streq(rng->name, buf)) {
				err = set_current_rng(rng);
				if (!err)
					cur_rng_set_by_user = 1;
				break;
			}
		}
	}
	new_rng = get_current_rng_nolock();
	mutex_unlock(&rng_mutex);

	if (new_rng)
		put_rng(new_rng);

	return err ? : len;
}

static ssize_t rng_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 = sysfs_emit(buf, "%s\n", rng ? rng->name : "none");
	put_rng(rng);

	return ret;
}

static ssize_t rng_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 ssize_t rng_selected_show(struct device *dev,
				 struct device_attribute *attr,
				 char *buf)
{
	return sysfs_emit(buf, "%d\n", cur_rng_set_by_user);
}

static ssize_t rng_quality_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);

	if (!rng) /* no need to put_rng */
		return -ENODEV;

	ret = sysfs_emit(buf, "%hu\n", rng->quality);
	put_rng(rng);

	return ret;
}

static ssize_t rng_quality_store(struct device *dev,
				 struct device_attribute *attr,
				 const char *buf, size_t len)
{
	u16 quality;
	int ret = -EINVAL;

	if (len < 2)
		return -EINVAL;

	ret = mutex_lock_interruptible(&rng_mutex);
	if (ret)
		return -ERESTARTSYS;

	ret = kstrtou16(buf, 0, &quality);
	if (ret || quality > 1024) {
		ret = -EINVAL;
		goto out;
	}

	if (!current_rng) {
		ret = -ENODEV;
		goto out;
	}

	current_rng->quality = quality;
	current_quality = quality; /* obsolete */

	/* the best available RNG may have changed */
	ret = enable_best_rng();

out:
	mutex_unlock(&rng_mutex);
	return ret ? ret : len;
}

static DEVICE_ATTR_RW(rng_current);
static DEVICE_ATTR_RO(rng_available);
static DEVICE_ATTR_RO(rng_selected);
static DEVICE_ATTR_RW(rng_quality);

static struct attribute *rng_dev_attrs[] = {
	&dev_attr_rng_current.attr,
	&dev_attr_rng_available.attr,
	&dev_attr_rng_selected.attr,
	&dev_attr_rng_quality.attr,
	NULL
};

ATTRIBUTE_GROUPS(rng_dev);

static int hwrng_fillfn(void *unused)
{
	size_t entropy, entropy_credit = 0; /* in 1/1024 of a bit */
	long rc;

	while (!kthread_should_stop()) {
		unsigned short quality;
		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);
		if (current_quality != rng->quality)
			rng->quality = current_quality; /* obsolete */
		quality = rng->quality;
		mutex_unlock(&reading_mutex);

		if (rc <= 0)
			hwrng_msleep(rng, 10000);

		put_rng(rng);

		if (rc <= 0)
			continue;

		/* If we cannot credit at least one bit of entropy,
		 * keep track of the remainder for the next iteration
		 */
		entropy = rc * quality * 8 + entropy_credit;
		if ((entropy >> 10) == 0)
			entropy_credit = entropy;

		/* Outside lock, sure, but y'know: randomness. */
		add_hwgenerator_randomness((void *)rng_fillbuf, rc,
					   entropy >> 10, true);
	}
	hwrng_fill = NULL;
	return 0;
}

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

	if (!rng->name || (!rng->data_read && !rng->read))
		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;
	}
	list_add_tail(&rng->list, &rng_list);

	init_completion(&rng->cleanup_done);
	complete(&rng->cleanup_done);
	init_completion(&rng->dying);

	/* Adjust quality field to always have a proper value */
	rng->quality = min_t(u16, min_t(u16, default_quality, 1024), rng->quality ?: 1024);

	if (!current_rng ||
	    (!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
		/*
		 * Set new rng as current as the new rng source
		 * provides better entropy quality and was not
		 * chosen by userspace.
		 */
		err = set_current_rng(rng);
		if (err)
			goto out_unlock;
	}
	mutex_unlock(&rng_mutex);
	return 0;
out_unlock:
	mutex_unlock(&rng_mutex);
out:
	return err;
}
EXPORT_SYMBOL_GPL(hwrng_register);

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

	mutex_lock(&rng_mutex);

	list_del(&rng->list);
	complete_all(&rng->dying);
	if (current_rng == rng) {
		err = enable_best_rng();
		if (err) {
			drop_current_rng();
			cur_rng_set_by_user = 0;
		}
	}

	new_rng = get_current_rng_nolock();
	if (list_empty(&rng_list)) {
		mutex_unlock(&rng_mutex);
		if (hwrng_fill)
			kthread_stop(hwrng_fill);
	} else
		mutex_unlock(&rng_mutex);

	if (new_rng)
		put_rng(new_rng);

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

static void devm_hwrng_release(struct device *dev, void *res)
{
	hwrng_unregister(*(struct hwrng **)res);
}

static int devm_hwrng_match(struct device *dev, void *res, void *data)
{
	struct hwrng **r = res;

	if (WARN_ON(!r || !*r))
		return 0;

	return *r == data;
}

int devm_hwrng_register(struct device *dev, struct hwrng *rng)
{
	struct hwrng **ptr;
	int error;

	ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return -ENOMEM;

	error = hwrng_register(rng);
	if (error) {
		devres_free(ptr);
		return error;
	}

	*ptr = rng;
	devres_add(dev, ptr);
	return 0;
}
EXPORT_SYMBOL_GPL(devm_hwrng_register);

void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
{
	devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
}
EXPORT_SYMBOL_GPL(devm_hwrng_unregister);

long hwrng_msleep(struct hwrng *rng, unsigned int msecs)
{
	unsigned long timeout = msecs_to_jiffies(msecs) + 1;

	return wait_for_completion_interruptible_timeout(&rng->dying, timeout);
}
EXPORT_SYMBOL_GPL(hwrng_msleep);

long hwrng_yield(struct hwrng *rng)
{
	return wait_for_completion_interruptible_timeout(&rng->dying, 1);
}
EXPORT_SYMBOL_GPL(hwrng_yield);

static int __init hwrng_modinit(void)
{
	int ret;

	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
	if (!rng_buffer)
		return -ENOMEM;

	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
	if (!rng_fillbuf) {
		kfree(rng_buffer);
		return -ENOMEM;
	}

	ret = misc_register(&rng_miscdev);
	if (ret) {
		kfree(rng_fillbuf);
		kfree(rng_buffer);
	}

	return ret;
}

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

	misc_deregister(&rng_miscdev);
}

fs_initcall(hwrng_modinit); /* depends on misc_register() */
module_exit(hwrng_modexit);

MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
	1	/*
	2	* hw_random/core.c: HWRNG core API
	3	*
	4	* Copyright 2006 Michael Buesch <m@bues.ch>
	5	* Copyright 2005 (c) MontaVista Software, Inc.
	6	*
	7	* Please read Documentation/admin-guide/hw_random.rst for details on use.
	8	*
	9	* This software may be used and distributed according to the terms
	10	* of the GNU General Public License, incorporated herein by reference.
	11	*/
	12
	13	#include <linux/delay.h>
	14	#include <linux/device.h>
	15	#include <linux/err.h>
	16	#include <linux/fs.h>
	17	#include <linux/hw_random.h>
	18	#include <linux/kernel.h>
	19	#include <linux/kthread.h>
	20	#include <linux/miscdevice.h>
	21	#include <linux/module.h>
	22	#include <linux/random.h>
	23	#include <linux/sched.h>
	24	#include <linux/sched/signal.h>
	25	#include <linux/slab.h>
	26	#include <linux/string.h>
	27	#include <linux/uaccess.h>
	28
	29	#define RNG_MODULE_NAME "hw_random"
	30
	31	#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES)
	32
	33	static struct hwrng *current_rng;
	34	/* the current rng has been explicitly chosen by user via sysfs */
	35	static int cur_rng_set_by_user;
	36	static struct task_struct *hwrng_fill;
	37	/* list of registered rngs */
	38	static LIST_HEAD(rng_list);
	39	/* Protects rng_list and current_rng */
	40	static DEFINE_MUTEX(rng_mutex);
	41	/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
	42	static DEFINE_MUTEX(reading_mutex);
	43	static int data_avail;
	44	static u8 rng_buffer, rng_fillbuf;
	45	static unsigned short current_quality;
	46	static unsigned short default_quality = 1024; /* default to maximum */
	47
	48	module_param(current_quality, ushort, 0644);
	49	MODULE_PARM_DESC(current_quality,
	50	"current hwrng entropy estimation per 1024 bits of input -- obsolete, use rng_quality instead");
	51	module_param(default_quality, ushort, 0644);
	52	MODULE_PARM_DESC(default_quality,
	53	"default maximum entropy content of hwrng per 1024 bits of input");
	54
	55	static void drop_current_rng(void);
	56	static int hwrng_init(struct hwrng *rng);
	57	static int hwrng_fillfn(void *unused);
	58
	59	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	60	int wait);
	61
	62	static size_t rng_buffer_size(void)
	63	{
	64	return RNG_BUFFER_SIZE;
	65	}
	66
	67	static inline void cleanup_rng(struct kref *kref)
	68	{
	69	struct hwrng *rng = container_of(kref, struct hwrng, ref);
	70
	71	if (rng->cleanup)
	72	rng->cleanup(rng);
	73
	74	complete(&rng->cleanup_done);
	75	}
	76
	77	static int set_current_rng(struct hwrng *rng)
	78	{
	79	int err;
	80
	81	BUG_ON(!mutex_is_locked(&rng_mutex));
	82
	83	err = hwrng_init(rng);
	84	if (err)
	85	return err;
	86
	87	drop_current_rng();
	88	current_rng = rng;
	89
	90	/* if necessary, start hwrng thread */
	91	if (!hwrng_fill) {
	92	hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
	93	if (IS_ERR(hwrng_fill)) {
	94	pr_err("hwrng_fill thread creation failed\n");
	95	hwrng_fill = NULL;
	96	}
	97	}
	98
	99	return 0;
	100	}
	101
	102	static void drop_current_rng(void)
	103	{
	104	BUG_ON(!mutex_is_locked(&rng_mutex));
	105	if (!current_rng)
	106	return;
	107
	108	/* decrease last reference for triggering the cleanup */
	109	kref_put(&current_rng->ref, cleanup_rng);
	110	current_rng = NULL;
	111	}
	112
	113	/* Returns ERR_PTR(), NULL or refcounted hwrng */
	114	static struct hwrng *get_current_rng_nolock(void)
	115	{
	116	if (current_rng)
	117	kref_get(&current_rng->ref);
	118
	119	return current_rng;
	120	}
	121
	122	static struct hwrng *get_current_rng(void)
	123	{
	124	struct hwrng *rng;
	125
	126	if (mutex_lock_interruptible(&rng_mutex))
	127	return ERR_PTR(-ERESTARTSYS);
	128
	129	rng = get_current_rng_nolock();
	130
	131	mutex_unlock(&rng_mutex);
	132	return rng;
	133	}
	134
	135	static void put_rng(struct hwrng *rng)
	136	{
	137	/*
	138	* Hold rng_mutex here so we serialize in case they set_current_rng
	139	* on rng again immediately.
	140	*/
	141	mutex_lock(&rng_mutex);
	142	if (rng)
	143	kref_put(&rng->ref, cleanup_rng);
	144	mutex_unlock(&rng_mutex);
	145	}
	146
	147	static int hwrng_init(struct hwrng *rng)
	148	{
	149	if (kref_get_unless_zero(&rng->ref))
	150	goto skip_init;
	151
	152	if (rng->init) {
	153	int ret;
	154
	155	ret = rng->init(rng);
	156	if (ret)
	157	return ret;
	158	}
	159
	160	kref_init(&rng->ref);
	161	reinit_completion(&rng->cleanup_done);
	162
	163	skip_init:
	164	current_quality = rng->quality; /* obsolete */
	165
	166	return 0;
	167	}
	168
	169	static int rng_dev_open(struct inode inode, struct file filp)
	170	{
	171	/* enforce read-only access to this chrdev */
	172	if ((filp->f_mode & FMODE_READ) == 0)
	173	return -EINVAL;
	174	if (filp->f_mode & FMODE_WRITE)
	175	return -EINVAL;
	176	return 0;
	177	}
	178
	179	static inline int rng_get_data(struct hwrng rng, u8 buffer, size_t size,
	180	int wait) {
	181	int present;
	182
	183	BUG_ON(!mutex_is_locked(&reading_mutex));
	184	if (rng->read) {
	185	int err;
	186
	187	err = rng->read(rng, buffer, size, wait);
	188	if (WARN_ON_ONCE(err > 0 && err > size))
	189	err = size;
	190
	191	return err;
	192	}
	193
	194	if (rng->data_present)
	195	present = rng->data_present(rng, wait);
	196	else
	197	present = 1;
	198
	199	if (present)
	200	return rng->data_read(rng, (u32 *)buffer);
	201
	202	return 0;
	203	}
	204
	205	static ssize_t rng_dev_read(struct file filp, char __user buf,
	206	size_t size, loff_t *offp)
	207	{
	208	u8 buffer[RNG_BUFFER_SIZE];
	209	ssize_t ret = 0;
	210	int err = 0;
	211	int bytes_read, len;
	212	struct hwrng *rng;
	213
	214	while (size) {
	215	rng = get_current_rng();
	216	if (IS_ERR(rng)) {
	217	err = PTR_ERR(rng);
	218	goto out;
	219	}
	220	if (!rng) {
	221	err = -ENODEV;
	222	goto out;
	223	}
	224
	225	if (mutex_lock_interruptible(&reading_mutex)) {
	226	err = -ERESTARTSYS;
	227	goto out_put;
	228	}
	229	if (!data_avail) {
	230	bytes_read = rng_get_data(rng, rng_buffer,
	231	rng_buffer_size(),
	232	!(filp->f_flags & O_NONBLOCK));
	233	if (bytes_read < 0) {
	234	err = bytes_read;
	235	goto out_unlock_reading;
	236	} else if (bytes_read == 0 &&
	237	(filp->f_flags & O_NONBLOCK)) {
	238	err = -EAGAIN;
	239	goto out_unlock_reading;
	240	}
	241
	242	data_avail = bytes_read;
	243	}
	244
	245	len = data_avail;
	246	if (len) {
	247	if (len > size)
	248	len = size;
	249
	250	data_avail -= len;
	251
	252	memcpy(buffer, rng_buffer + data_avail, len);
	253	}
	254	mutex_unlock(&reading_mutex);
	255	put_rng(rng);
	256
	257	if (len) {
	258	if (copy_to_user(buf + ret, buffer, len)) {
	259	err = -EFAULT;
	260	goto out;
	261	}
	262
	263	size -= len;
	264	ret += len;
	265	}
	266
	267
	268	if (need_resched())
	269	schedule_timeout_interruptible(1);
	270
	271	if (signal_pending(current)) {
	272	err = -ERESTARTSYS;
	273	goto out;
	274	}
	275	}
	276	out:
	277	memzero_explicit(buffer, sizeof(buffer));
	278	return ret ? : err;
	279
	280	out_unlock_reading:
	281	mutex_unlock(&reading_mutex);
	282	out_put:
	283	put_rng(rng);
	284	goto out;
	285	}
	286
	287	static const struct file_operations rng_chrdev_ops = {
	288	.owner = THIS_MODULE,
	289	.open = rng_dev_open,
	290	.read = rng_dev_read,
	291	.llseek = noop_llseek,
	292	};
	293
	294	static const struct attribute_group *rng_dev_groups[];
	295
	296	static struct miscdevice rng_miscdev = {
	297	.minor = HWRNG_MINOR,
	298	.name = RNG_MODULE_NAME,
	299	.nodename = "hwrng",
	300	.fops = &rng_chrdev_ops,
	301	.groups = rng_dev_groups,
	302	};
	303
	304	static int enable_best_rng(void)
	305	{
	306	struct hwrng rng, new_rng = NULL;
	307	int ret = -ENODEV;
	308
	309	BUG_ON(!mutex_is_locked(&rng_mutex));
	310
	311	/* no rng to use? */
	312	if (list_empty(&rng_list)) {
	313	drop_current_rng();
	314	cur_rng_set_by_user = 0;
	315	return 0;
	316	}
	317
	318	/* use the rng which offers the best quality */
	319	list_for_each_entry(rng, &rng_list, list) {
	320	if (!new_rng \|\| rng->quality > new_rng->quality)
	321	new_rng = rng;
	322	}
	323
	324	ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
	325	if (!ret)
	326	cur_rng_set_by_user = 0;
	327
	328	return ret;
	329	}
	330
	331	static ssize_t rng_current_store(struct device *dev,
	332	struct device_attribute *attr,
	333	const char *buf, size_t len)
	334	{
	335	int err;
	336	struct hwrng rng, new_rng;
	337
	338	err = mutex_lock_interruptible(&rng_mutex);
	339	if (err)
	340	return -ERESTARTSYS;
	341
	342	if (sysfs_streq(buf, "")) {
	343	err = enable_best_rng();
	344	} else {
	345	list_for_each_entry(rng, &rng_list, list) {
	346	if (sysfs_streq(rng->name, buf)) {
	347	err = set_current_rng(rng);
	348	if (!err)
	349	cur_rng_set_by_user = 1;
	350	break;
	351	}
	352	}
	353	}
	354	new_rng = get_current_rng_nolock();
	355	mutex_unlock(&rng_mutex);
	356
	357	if (new_rng)
	358	put_rng(new_rng);
	359
	360	return err ? : len;
	361	}
	362
	363	static ssize_t rng_current_show(struct device *dev,
	364	struct device_attribute *attr,
	365	char *buf)
	366	{
	367	ssize_t ret;
	368	struct hwrng *rng;
	369
	370	rng = get_current_rng();
	371	if (IS_ERR(rng))
	372	return PTR_ERR(rng);
	373
	374	ret = sysfs_emit(buf, "%s\n", rng ? rng->name : "none");
	375	put_rng(rng);
	376
	377	return ret;
	378	}
	379
	380	static ssize_t rng_available_show(struct device *dev,
	381	struct device_attribute *attr,
	382	char *buf)
	383	{
	384	int err;
	385	struct hwrng *rng;
	386
	387	err = mutex_lock_interruptible(&rng_mutex);
	388	if (err)
	389	return -ERESTARTSYS;
	390	buf[0] = '\0';
	391	list_for_each_entry(rng, &rng_list, list) {
	392	strlcat(buf, rng->name, PAGE_SIZE);
	393	strlcat(buf, " ", PAGE_SIZE);
	394	}
	395	strlcat(buf, "\n", PAGE_SIZE);
	396	mutex_unlock(&rng_mutex);
	397
	398	return strlen(buf);
	399	}
	400
	401	static ssize_t rng_selected_show(struct device *dev,
	402	struct device_attribute *attr,
	403	char *buf)
	404	{
	405	return sysfs_emit(buf, "%d\n", cur_rng_set_by_user);
	406	}
	407
	408	static ssize_t rng_quality_show(struct device *dev,
	409	struct device_attribute *attr,
	410	char *buf)
	411	{
	412	ssize_t ret;
	413	struct hwrng *rng;
	414
	415	rng = get_current_rng();
	416	if (IS_ERR(rng))
	417	return PTR_ERR(rng);
	418
	419	if (!rng) /* no need to put_rng */
	420	return -ENODEV;
	421
	422	ret = sysfs_emit(buf, "%hu\n", rng->quality);
	423	put_rng(rng);
	424
	425	return ret;
	426	}
	427
	428	static ssize_t rng_quality_store(struct device *dev,
	429	struct device_attribute *attr,
	430	const char *buf, size_t len)
	431	{
	432	u16 quality;
	433	int ret = -EINVAL;
	434
	435	if (len < 2)
	436	return -EINVAL;
	437
	438	ret = mutex_lock_interruptible(&rng_mutex);
	439	if (ret)
	440	return -ERESTARTSYS;
	441
	442	ret = kstrtou16(buf, 0, &quality);
	443	if (ret \|\| quality > 1024) {
	444	ret = -EINVAL;
	445	goto out;
	446	}
	447
	448	if (!current_rng) {
	449	ret = -ENODEV;
	450	goto out;
	451	}
	452
	453	current_rng->quality = quality;
	454	current_quality = quality; /* obsolete */
	455
	456	/* the best available RNG may have changed */
	457	ret = enable_best_rng();
	458
	459	out:
	460	mutex_unlock(&rng_mutex);
	461	return ret ? ret : len;
	462	}
	463
	464	static DEVICE_ATTR_RW(rng_current);
	465	static DEVICE_ATTR_RO(rng_available);
	466	static DEVICE_ATTR_RO(rng_selected);
	467	static DEVICE_ATTR_RW(rng_quality);
	468
	469	static struct attribute *rng_dev_attrs[] = {
	470	&dev_attr_rng_current.attr,
	471	&dev_attr_rng_available.attr,
	472	&dev_attr_rng_selected.attr,
	473	&dev_attr_rng_quality.attr,
	474	NULL
	475	};
	476
	477	ATTRIBUTE_GROUPS(rng_dev);
	478
	479	static int hwrng_fillfn(void *unused)
	480	{
	481	size_t entropy, entropy_credit = 0; /* in 1/1024 of a bit */
	482	long rc;
	483
	484	while (!kthread_should_stop()) {
	485	unsigned short quality;
	486	struct hwrng *rng;
	487
	488	rng = get_current_rng();
	489	if (IS_ERR(rng) \|\| !rng)
	490	break;
	491	mutex_lock(&reading_mutex);
	492	rc = rng_get_data(rng, rng_fillbuf,
	493	rng_buffer_size(), 1);
	494	if (current_quality != rng->quality)
	495	rng->quality = current_quality; /* obsolete */
	496	quality = rng->quality;
	497	mutex_unlock(&reading_mutex);
	498
	499	if (rc <= 0)
	500	hwrng_msleep(rng, 10000);
	501
	502	put_rng(rng);
	503
	504	if (rc <= 0)
	505	continue;
	506
	507	/* If we cannot credit at least one bit of entropy,
	508	* keep track of the remainder for the next iteration
	509	*/
	510	entropy = rc * quality * 8 + entropy_credit;
	511	if ((entropy >> 10) == 0)
	512	entropy_credit = entropy;
	513
	514	/* Outside lock, sure, but y'know: randomness. */
	515	add_hwgenerator_randomness((void *)rng_fillbuf, rc,
	516	entropy >> 10, true);
	517	}
	518	hwrng_fill = NULL;
	519	return 0;
	520	}
	521
	522	int hwrng_register(struct hwrng *rng)
	523	{
	524	int err = -EINVAL;
	525	struct hwrng *tmp;
	526
	527	if (!rng->name \|\| (!rng->data_read && !rng->read))
	528	goto out;
	529
	530	mutex_lock(&rng_mutex);
	531
	532	/* Must not register two RNGs with the same name. */
	533	err = -EEXIST;
	534	list_for_each_entry(tmp, &rng_list, list) {
	535	if (strcmp(tmp->name, rng->name) == 0)
	536	goto out_unlock;
	537	}
	538	list_add_tail(&rng->list, &rng_list);
	539
	540	init_completion(&rng->cleanup_done);
	541	complete(&rng->cleanup_done);
	542	init_completion(&rng->dying);
	543
	544	/* Adjust quality field to always have a proper value */
	545	rng->quality = min_t(u16, min_t(u16, default_quality, 1024), rng->quality ?: 1024);
	546
	547	if (!current_rng \|\|
	548	(!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
	549	/*
	550	* Set new rng as current as the new rng source
	551	* provides better entropy quality and was not
	552	* chosen by userspace.
	553	*/
	554	err = set_current_rng(rng);
	555	if (err)
	556	goto out_unlock;
	557	}
	558	mutex_unlock(&rng_mutex);
	559	return 0;
	560	out_unlock:
	561	mutex_unlock(&rng_mutex);
	562	out:
	563	return err;
	564	}
	565	EXPORT_SYMBOL_GPL(hwrng_register);
	566
	567	void hwrng_unregister(struct hwrng *rng)
	568	{
	569	struct hwrng *new_rng;
	570	int err;
	571
	572	mutex_lock(&rng_mutex);
	573
	574	list_del(&rng->list);
	575	complete_all(&rng->dying);
	576	if (current_rng == rng) {
	577	err = enable_best_rng();
	578	if (err) {
	579	drop_current_rng();
	580	cur_rng_set_by_user = 0;
	581	}
	582	}
	583
	584	new_rng = get_current_rng_nolock();
	585	if (list_empty(&rng_list)) {
	586	mutex_unlock(&rng_mutex);
	587	if (hwrng_fill)
	588	kthread_stop(hwrng_fill);
	589	} else
	590	mutex_unlock(&rng_mutex);
	591
	592	if (new_rng)
	593	put_rng(new_rng);
	594
	595	wait_for_completion(&rng->cleanup_done);
	596	}
	597	EXPORT_SYMBOL_GPL(hwrng_unregister);
	598
	599	static void devm_hwrng_release(struct device dev, void res)
	600	{
	601	hwrng_unregister((struct hwrng *)res);
	602	}
	603
	604	static int devm_hwrng_match(struct device dev, void res, void *data)
	605	{
	606	struct hwrng **r = res;
	607
	608	if (WARN_ON(!r \|\| !*r))
	609	return 0;
	610
	611	return *r == data;
	612	}
	613
	614	int devm_hwrng_register(struct device dev, struct hwrng rng)
	615	{
	616	struct hwrng **ptr;
	617	int error;
	618
	619	ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
	620	if (!ptr)
	621	return -ENOMEM;
	622
	623	error = hwrng_register(rng);
	624	if (error) {
	625	devres_free(ptr);
	626	return error;
	627	}
	628
	629	*ptr = rng;
	630	devres_add(dev, ptr);
	631	return 0;
	632	}
	633	EXPORT_SYMBOL_GPL(devm_hwrng_register);
	634
	635	void devm_hwrng_unregister(struct device dev, struct hwrng rng)
	636	{
	637	devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
	638	}
	639	EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
	640
	641	long hwrng_msleep(struct hwrng *rng, unsigned int msecs)
	642	{
	643	unsigned long timeout = msecs_to_jiffies(msecs) + 1;
	644
	645	return wait_for_completion_interruptible_timeout(&rng->dying, timeout);
	646	}
	647	EXPORT_SYMBOL_GPL(hwrng_msleep);
	648
	649	long hwrng_yield(struct hwrng *rng)
	650	{
	651	return wait_for_completion_interruptible_timeout(&rng->dying, 1);
	652	}
	653	EXPORT_SYMBOL_GPL(hwrng_yield);
	654
	655	static int __init hwrng_modinit(void)
	656	{
	657	int ret;
	658
	659	/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
	660	rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
	661	if (!rng_buffer)
	662	return -ENOMEM;
	663
	664	rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
	665	if (!rng_fillbuf) {
	666	kfree(rng_buffer);
	667	return -ENOMEM;
	668	}
	669
	670	ret = misc_register(&rng_miscdev);
	671	if (ret) {
	672	kfree(rng_fillbuf);
	673	kfree(rng_buffer);
	674	}
	675
	676	return ret;
	677	}
	678
	679	static void __exit hwrng_modexit(void)
	680	{
	681	mutex_lock(&rng_mutex);
	682	BUG_ON(current_rng);
	683	kfree(rng_buffer);
	684	kfree(rng_fillbuf);
	685	mutex_unlock(&rng_mutex);
	686
	687	misc_deregister(&rng_miscdev);
	688	}
	689
	690	fs_initcall(hwrng_modinit); /* depends on misc_register() */
	691	module_exit(hwrng_modexit);
	692
	693	MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
	694	MODULE_LICENSE("GPL");