drivers/char/hw_random/core.c - maze/linux - Git at Google

 /*
         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/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 LIST_HEAD(rng_list);
 static DEFINE_MUTEX(rng_mutex);
 static int data_avail;
 static u8 *rng_buffer;

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

 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 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;

 	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;
 		}

 		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;
 			}
 			data_avail = bytes_read;
 		}

 		if (!data_avail) {
 			if (filp->f_flags & O_NONBLOCK) {
 				err = -EAGAIN;
 				goto out_unlock;
 			}
 		} 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;
 			}

 			size -= len;
 			ret += len;
 		}

 		mutex_unlock(&rng_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;
 }


 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;
 	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 err = -EINVAL;
 	struct hwrng *old_rng, *tmp;
 	unsigned char bytes[16];
 	int bytes_read;

 	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;
 	}

 	/* 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);

 	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
 	if (bytes_read > 0)
 		add_device_randomness(bytes, bytes_read);
 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);

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

 module_exit(hwrng_exit);

 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
 MODULE_LICENSE("GPL");
	/*
	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/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 LIST_HEAD(rng_list);
	static DEFINE_MUTEX(rng_mutex);
	static int data_avail;
	static u8 *rng_buffer;

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

	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 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;

	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;
	}

	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;
	}
	data_avail = bytes_read;
	}

	if (!data_avail) {
	if (filp->f_flags & O_NONBLOCK) {
	err = -EAGAIN;
	goto out_unlock;
	}
	} 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;
	}

	size -= len;
	ret += len;
	}

	mutex_unlock(&rng_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;
	}


	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;
	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 err = -EINVAL;
	struct hwrng old_rng, tmp;
	unsigned char bytes[16];
	int bytes_read;

	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;
	}

	/* 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);

	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
	if (bytes_read > 0)
	add_device_randomness(bytes, bytes_read);
	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);

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

	module_exit(hwrng_exit);

	MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
	MODULE_LICENSE("GPL");