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/*
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 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;
bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
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);
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;
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;
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);
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();
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");