1 files changed, 486 insertions, 183 deletions

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index a0f7724852eb..96d7fe41b373 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -1,76 +1,169 @@
 /*
-        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.
-
+ * 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/module.h>
 #include <linux/kernel.h>
-#include <linux/fs.h>
-#include <linux/sched.h>
-#include <linux/init.h>
+#include <linux/kthread.h>
 #include <linux/miscdevice.h>
-#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
 #include <linux/slab.h>
-#include <asm/uaccess.h>
-
+#include <linux/string.h>
+#include <linux/uaccess.h>
 
 #define RNG_MODULE_NAME		"hw_random"
-#define PFX			RNG_MODULE_NAME ": "
-#define RNG_MISCDEV_MINOR	183 /* official */
 
+#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;
+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 SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
+	return RNG_BUFFER_SIZE;
 }
 
-static inline int hwrng_init(struct hwrng *rng)
+static inline void cleanup_rng(struct kref *kref)
 {
-	if (!rng->init)
-		return 0;
-	return rng->init(rng);
+	struct hwrng *rng = container_of(kref, struct hwrng, ref);
+
+	if (rng->cleanup)
+		rng->cleanup(rng);
+
+	complete(&rng->cleanup_done);
 }
 
-static inline void hwrng_cleanup(struct hwrng *rng)
+static int set_current_rng(struct hwrng *rng)
 {
-	if (rng && rng->cleanup)
-		rng->cleanup(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)
@@ -87,8 +180,16 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
 			int wait) {
 	int present;
 
-	if (rng->read)
-		return rng->read(rng, (void *)buffer, size, wait);
+	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);
@@ -104,55 +205,65 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
 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) {
-		if (mutex_lock_interruptible(&rng_mutex)) {
-			err = -ERESTARTSYS;
+		rng = get_current_rng();
+		if (IS_ERR(rng)) {
+			err = PTR_ERR(rng);
 			goto out;
 		}
-
-		if (!current_rng) {
+		if (!rng) {
 			err = -ENODEV;
-			goto out_unlock;
+			goto out;
 		}
 
+		if (mutex_lock_interruptible(&reading_mutex)) {
+			err = -ERESTARTSYS;
+			goto out_put;
+		}
 		if (!data_avail) {
-			bytes_read = rng_get_data(current_rng, rng_buffer,
+			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;
+				goto out_unlock_reading;
+			} else if (bytes_read == 0 &&
+				   (filp->f_flags & O_NONBLOCK)) {
+				err = -EAGAIN;
+				goto out_unlock_reading;
 			}
+
 			data_avail = bytes_read;
 		}
 
-		if (!data_avail) {
-			if (filp->f_flags & O_NONBLOCK) {
-				err = -EAGAIN;
-				goto out_unlock;
-			}
-		} else {
-			len = data_avail;
+		len = data_avail;
+		if (len) {
 			if (len > size)
 				len = size;
 
 			data_avail -= len;
 
-			if (copy_to_user(buf + ret, rng_buffer + 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_unlock;
+				goto out;
 			}
 
 			size -= len;
 			ret += len;
 		}
 
-		mutex_unlock(&rng_mutex);
 
 		if (need_resched())
 			schedule_timeout_interruptible(1);
@@ -163,13 +274,16 @@ static ssize_t rng_dev_read(struct file *filp, char __user *buf,
 		}
 	}
 out:
+	memzero_explicit(buffer, sizeof(buffer));
 	return ret ? : err;
-out_unlock:
-	mutex_unlock(&rng_mutex);
+
+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,
@@ -177,70 +291,100 @@ static const struct file_operations rng_chrdev_ops = {
 	.llseek		= noop_llseek,
 };
 
+static const struct attribute_group *rng_dev_groups[];
+
 static struct miscdevice rng_miscdev = {
-	.minor		= RNG_MISCDEV_MINOR,
+	.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));
 
-static ssize_t hwrng_attr_current_store(struct device *dev,
-					struct device_attribute *attr,
-					const char *buf, size_t len)
+	/* 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;
+	struct hwrng *rng, *new_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;
+
+	if (sysfs_streq(buf, "")) {
+		err = enable_best_rng();
+	} else if (sysfs_streq(buf, "none")) {
+		cur_rng_set_by_user = 1;
+		drop_current_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;
 			}
-			err = hwrng_init(rng);
-			if (err)
-				break;
-			hwrng_cleanup(current_rng);
-			current_rng = rng;
-			err = 0;
-			break;
 		}
 	}
+	new_rng = get_current_rng_nolock();
 	mutex_unlock(&rng_mutex);
 
+	if (new_rng)
+		put_rng(new_rng);
+
 	return err ? : len;
 }
 
-static ssize_t hwrng_attr_current_show(struct device *dev,
-				       struct device_attribute *attr,
-				       char *buf)
+static ssize_t rng_current_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
 {
-	int err;
 	ssize_t ret;
-	const char *name = "none";
+	struct hwrng *rng;
 
-	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);
+	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 hwrng_attr_available_show(struct device *dev,
-					 struct device_attribute *attr,
-					 char *buf)
+static ssize_t rng_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);
@@ -248,106 +392,174 @@ static ssize_t hwrng_attr_available_show(struct device *dev,
 		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++;
+		strlcat(buf, rng->name, PAGE_SIZE);
+		strlcat(buf, " ", PAGE_SIZE);
 	}
-	strncat(buf, "\n", PAGE_SIZE - ret - 1);
-	ret++;
+	strlcat(buf, "none\n", PAGE_SIZE);
 	mutex_unlock(&rng_mutex);
 
-	return ret;
+	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 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 void unregister_miscdev(void)
+static ssize_t rng_quality_show(struct device *dev,
+				struct device_attribute *attr,
+				char *buf)
 {
-	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);
+	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 int register_miscdev(void)
+static ssize_t rng_quality_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t len)
 {
-	int err;
+	u16 quality;
+	int ret = -EINVAL;
 
-	err = misc_register(&rng_miscdev);
-	if (err)
+	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;
-	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;
+	}
+
+	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:
-	return err;
+	mutex_unlock(&rng_mutex);
+	return ret ? ret : len;
+}
 
-err_remove_current:
-	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
-err_misc_dereg:
-	misc_deregister(&rng_miscdev);
-	goto out;
+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 must_register_misc;
 	int err = -EINVAL;
-	struct hwrng *old_rng, *tmp;
+	struct hwrng *tmp;
 
-	if (rng->name == NULL ||
-	    (rng->data_read == NULL && rng->read == NULL))
+	if (!rng->name || (!rng->data_read && !rng->read))
 		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;
-	}
-
 	/* 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);
 
-	must_register_misc = (current_rng == NULL);
-	old_rng = current_rng;
-	if (!old_rng) {
-		err = hwrng_init(rng);
+	init_completion(&rng->cleanup_done);
+	complete(&rng->cleanup_done);
+	init_completion(&rng->dying);
+
+	/* Adjust quality field to always have a proper value */
+	rng->quality = min3(default_quality, 1024, rng->quality ?: 1024);
+
+	if (!cur_rng_set_by_user &&
+	    (!current_rng || 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;
-		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);
+	mutex_unlock(&rng_mutex);
+	return 0;
 out_unlock:
 	mutex_unlock(&rng_mutex);
 out:
@@ -357,38 +569,129 @@ 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) {
-		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;
+		err = enable_best_rng();
+		if (err) {
+			drop_current_rng();
+			cur_rng_set_by_user = 0;
 		}
 	}
-	if (list_empty(&rng_list))
-		unregister_miscdev();
 
-	mutex_unlock(&rng_mutex);
+	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 __exit hwrng_exit(void)
+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);
 }
 
-module_exit(hwrng_exit);
+fs_initcall(hwrng_modinit); /* depends on misc_register() */
+module_exit(hwrng_modexit);
 
 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");