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2d2ec0642a
Another interesting anti-pattern. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
554 lines
12 KiB
C
554 lines
12 KiB
C
/*
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Added support for the AMD Geode LX RNG
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(c) Copyright 2004-2005 Advanced Micro Devices, Inc.
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derived from
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Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
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(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
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derived from
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Hardware driver for the AMD 768 Random Number Generator (RNG)
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(c) Copyright 2001 Red Hat Inc <alan@redhat.com>
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derived from
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Hardware driver for Intel i810 Random Number Generator (RNG)
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Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
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Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
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Added generic RNG API
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Copyright 2006 Michael Buesch <m@bues.ch>
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Copyright 2005 (c) MontaVista Software, Inc.
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Please read Documentation/hw_random.txt for details on use.
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----------------------------------------------------------
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This software may be used and distributed according to the terms
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of the GNU General Public License, incorporated herein by reference.
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*/
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#include <linux/device.h>
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#include <linux/hw_random.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/miscdevice.h>
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#include <linux/kthread.h>
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#include <linux/delay.h>
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#include <linux/slab.h>
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#include <linux/random.h>
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#include <linux/err.h>
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#include <asm/uaccess.h>
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#define RNG_MODULE_NAME "hw_random"
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#define PFX RNG_MODULE_NAME ": "
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#define RNG_MISCDEV_MINOR 183 /* official */
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static struct hwrng *current_rng;
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static struct task_struct *hwrng_fill;
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static LIST_HEAD(rng_list);
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/* Protects rng_list and current_rng */
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static DEFINE_MUTEX(rng_mutex);
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/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
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static DEFINE_MUTEX(reading_mutex);
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static int data_avail;
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static u8 *rng_buffer, *rng_fillbuf;
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static DECLARE_WAIT_QUEUE_HEAD(rng_done);
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static unsigned short current_quality;
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static unsigned short default_quality; /* = 0; default to "off" */
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module_param(current_quality, ushort, 0644);
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MODULE_PARM_DESC(current_quality,
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"current hwrng entropy estimation per mill");
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module_param(default_quality, ushort, 0644);
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MODULE_PARM_DESC(default_quality,
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"default entropy content of hwrng per mill");
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static void start_khwrngd(void);
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static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
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int wait);
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static size_t rng_buffer_size(void)
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{
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return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
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}
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static void add_early_randomness(struct hwrng *rng)
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{
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unsigned char bytes[16];
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int bytes_read;
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mutex_lock(&reading_mutex);
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bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
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mutex_unlock(&reading_mutex);
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if (bytes_read > 0)
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add_device_randomness(bytes, bytes_read);
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}
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static inline void cleanup_rng(struct kref *kref)
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{
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struct hwrng *rng = container_of(kref, struct hwrng, ref);
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if (rng->cleanup)
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rng->cleanup(rng);
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/* cleanup_done should be updated after cleanup finishes */
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smp_wmb();
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rng->cleanup_done = true;
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wake_up_all(&rng_done);
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}
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static void set_current_rng(struct hwrng *rng)
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{
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BUG_ON(!mutex_is_locked(&rng_mutex));
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kref_get(&rng->ref);
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current_rng = rng;
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}
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static void drop_current_rng(void)
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{
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BUG_ON(!mutex_is_locked(&rng_mutex));
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if (!current_rng)
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return;
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/* decrease last reference for triggering the cleanup */
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kref_put(¤t_rng->ref, cleanup_rng);
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current_rng = NULL;
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}
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/* Returns ERR_PTR(), NULL or refcounted hwrng */
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static struct hwrng *get_current_rng(void)
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{
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struct hwrng *rng;
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if (mutex_lock_interruptible(&rng_mutex))
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return ERR_PTR(-ERESTARTSYS);
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rng = current_rng;
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if (rng)
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kref_get(&rng->ref);
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mutex_unlock(&rng_mutex);
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return rng;
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}
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static void put_rng(struct hwrng *rng)
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{
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/*
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* Hold rng_mutex here so we serialize in case they set_current_rng
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* on rng again immediately.
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*/
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mutex_lock(&rng_mutex);
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if (rng)
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kref_put(&rng->ref, cleanup_rng);
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mutex_unlock(&rng_mutex);
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}
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static inline int hwrng_init(struct hwrng *rng)
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{
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if (rng->init) {
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int ret;
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ret = rng->init(rng);
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if (ret)
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return ret;
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}
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add_early_randomness(rng);
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current_quality = rng->quality ? : default_quality;
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current_quality &= 1023;
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if (current_quality == 0 && hwrng_fill)
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kthread_stop(hwrng_fill);
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if (current_quality > 0 && !hwrng_fill)
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start_khwrngd();
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return 0;
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}
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static int rng_dev_open(struct inode *inode, struct file *filp)
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{
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/* enforce read-only access to this chrdev */
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if ((filp->f_mode & FMODE_READ) == 0)
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return -EINVAL;
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if (filp->f_mode & FMODE_WRITE)
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return -EINVAL;
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return 0;
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}
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static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
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int wait) {
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int present;
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BUG_ON(!mutex_is_locked(&reading_mutex));
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if (rng->read)
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return rng->read(rng, (void *)buffer, size, wait);
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if (rng->data_present)
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present = rng->data_present(rng, wait);
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else
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present = 1;
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if (present)
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return rng->data_read(rng, (u32 *)buffer);
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return 0;
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}
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static ssize_t rng_dev_read(struct file *filp, char __user *buf,
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size_t size, loff_t *offp)
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{
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ssize_t ret = 0;
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int err = 0;
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int bytes_read, len;
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struct hwrng *rng;
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while (size) {
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rng = get_current_rng();
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if (IS_ERR(rng)) {
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err = PTR_ERR(rng);
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goto out;
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}
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if (!rng) {
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err = -ENODEV;
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goto out;
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}
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mutex_lock(&reading_mutex);
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if (!data_avail) {
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bytes_read = rng_get_data(rng, rng_buffer,
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rng_buffer_size(),
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!(filp->f_flags & O_NONBLOCK));
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if (bytes_read < 0) {
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err = bytes_read;
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goto out_unlock_reading;
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}
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data_avail = bytes_read;
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}
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if (!data_avail) {
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if (filp->f_flags & O_NONBLOCK) {
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err = -EAGAIN;
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goto out_unlock_reading;
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}
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} else {
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len = data_avail;
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if (len > size)
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len = size;
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data_avail -= len;
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if (copy_to_user(buf + ret, rng_buffer + data_avail,
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len)) {
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err = -EFAULT;
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goto out_unlock_reading;
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}
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size -= len;
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ret += len;
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}
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mutex_unlock(&reading_mutex);
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put_rng(rng);
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if (need_resched())
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schedule_timeout_interruptible(1);
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if (signal_pending(current)) {
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err = -ERESTARTSYS;
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goto out;
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}
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}
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out:
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return ret ? : err;
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out_unlock_reading:
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mutex_unlock(&reading_mutex);
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put_rng(rng);
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goto out;
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}
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static const struct file_operations rng_chrdev_ops = {
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.owner = THIS_MODULE,
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.open = rng_dev_open,
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.read = rng_dev_read,
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.llseek = noop_llseek,
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};
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static struct miscdevice rng_miscdev = {
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.minor = RNG_MISCDEV_MINOR,
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.name = RNG_MODULE_NAME,
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.nodename = "hwrng",
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.fops = &rng_chrdev_ops,
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};
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static ssize_t hwrng_attr_current_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t len)
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{
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int err;
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struct hwrng *rng;
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err = mutex_lock_interruptible(&rng_mutex);
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if (err)
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return -ERESTARTSYS;
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err = -ENODEV;
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list_for_each_entry(rng, &rng_list, list) {
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if (strcmp(rng->name, buf) == 0) {
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if (rng == current_rng) {
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err = 0;
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break;
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}
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err = hwrng_init(rng);
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if (err)
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break;
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drop_current_rng();
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set_current_rng(rng);
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err = 0;
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break;
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}
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}
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mutex_unlock(&rng_mutex);
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return err ? : len;
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}
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static ssize_t hwrng_attr_current_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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ssize_t ret;
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struct hwrng *rng;
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rng = get_current_rng();
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if (IS_ERR(rng))
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return PTR_ERR(rng);
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ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
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put_rng(rng);
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return ret;
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}
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static ssize_t hwrng_attr_available_show(struct device *dev,
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struct device_attribute *attr,
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char *buf)
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{
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int err;
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struct hwrng *rng;
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err = mutex_lock_interruptible(&rng_mutex);
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if (err)
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return -ERESTARTSYS;
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buf[0] = '\0';
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list_for_each_entry(rng, &rng_list, list) {
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strlcat(buf, rng->name, PAGE_SIZE);
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strlcat(buf, " ", PAGE_SIZE);
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}
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strlcat(buf, "\n", PAGE_SIZE);
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mutex_unlock(&rng_mutex);
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return strlen(buf);
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}
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static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
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hwrng_attr_current_show,
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hwrng_attr_current_store);
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static DEVICE_ATTR(rng_available, S_IRUGO,
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hwrng_attr_available_show,
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NULL);
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static void unregister_miscdev(void)
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{
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device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
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device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
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misc_deregister(&rng_miscdev);
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}
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static int register_miscdev(void)
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{
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int err;
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err = misc_register(&rng_miscdev);
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if (err)
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goto out;
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err = device_create_file(rng_miscdev.this_device,
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&dev_attr_rng_current);
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if (err)
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goto err_misc_dereg;
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err = device_create_file(rng_miscdev.this_device,
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&dev_attr_rng_available);
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if (err)
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goto err_remove_current;
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out:
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return err;
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err_remove_current:
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device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
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err_misc_dereg:
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misc_deregister(&rng_miscdev);
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goto out;
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}
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static int hwrng_fillfn(void *unused)
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{
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long rc;
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while (!kthread_should_stop()) {
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struct hwrng *rng;
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rng = get_current_rng();
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if (IS_ERR(rng) || !rng)
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break;
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mutex_lock(&reading_mutex);
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rc = rng_get_data(rng, rng_fillbuf,
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rng_buffer_size(), 1);
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mutex_unlock(&reading_mutex);
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put_rng(rng);
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if (rc <= 0) {
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pr_warn("hwrng: no data available\n");
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msleep_interruptible(10000);
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continue;
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}
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/* Outside lock, sure, but y'know: randomness. */
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add_hwgenerator_randomness((void *)rng_fillbuf, rc,
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rc * current_quality * 8 >> 10);
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}
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hwrng_fill = NULL;
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return 0;
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}
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static void start_khwrngd(void)
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{
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hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
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if (hwrng_fill == ERR_PTR(-ENOMEM)) {
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pr_err("hwrng_fill thread creation failed");
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hwrng_fill = NULL;
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}
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}
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int hwrng_register(struct hwrng *rng)
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{
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int err = -EINVAL;
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struct hwrng *old_rng, *tmp;
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if (rng->name == NULL ||
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(rng->data_read == NULL && rng->read == NULL))
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goto out;
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mutex_lock(&rng_mutex);
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/* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
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err = -ENOMEM;
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if (!rng_buffer) {
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rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
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if (!rng_buffer)
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goto out_unlock;
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}
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if (!rng_fillbuf) {
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rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
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if (!rng_fillbuf) {
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kfree(rng_buffer);
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goto out_unlock;
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}
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}
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/* Must not register two RNGs with the same name. */
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err = -EEXIST;
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list_for_each_entry(tmp, &rng_list, list) {
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if (strcmp(tmp->name, rng->name) == 0)
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goto out_unlock;
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}
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old_rng = current_rng;
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err = 0;
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if (!old_rng) {
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err = hwrng_init(rng);
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if (err)
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goto out_unlock;
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set_current_rng(rng);
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err = register_miscdev();
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if (err) {
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drop_current_rng();
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goto out_unlock;
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}
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}
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list_add_tail(&rng->list, &rng_list);
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if (old_rng && !rng->init) {
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/*
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* Use a new device's input to add some randomness to
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* the system. If this rng device isn't going to be
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* used right away, its init function hasn't been
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* called yet; so only use the randomness from devices
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* that don't need an init callback.
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*/
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add_early_randomness(rng);
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}
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rng->cleanup_done = false;
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out_unlock:
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mutex_unlock(&rng_mutex);
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out:
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return err;
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}
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EXPORT_SYMBOL_GPL(hwrng_register);
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void hwrng_unregister(struct hwrng *rng)
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{
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mutex_lock(&rng_mutex);
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list_del(&rng->list);
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if (current_rng == rng) {
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drop_current_rng();
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if (!list_empty(&rng_list)) {
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struct hwrng *tail;
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tail = list_entry(rng_list.prev, struct hwrng, list);
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if (hwrng_init(tail) == 0)
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set_current_rng(tail);
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}
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}
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if (list_empty(&rng_list)) {
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mutex_unlock(&rng_mutex);
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unregister_miscdev();
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if (hwrng_fill)
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kthread_stop(hwrng_fill);
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} else
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mutex_unlock(&rng_mutex);
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/* Just in case rng is reading right now, wait. */
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wait_event(rng_done, rng->cleanup_done &&
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atomic_read(&rng->ref.refcount) == 0);
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}
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EXPORT_SYMBOL_GPL(hwrng_unregister);
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static void __exit hwrng_exit(void)
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{
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mutex_lock(&rng_mutex);
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BUG_ON(current_rng);
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kfree(rng_buffer);
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kfree(rng_fillbuf);
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mutex_unlock(&rng_mutex);
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}
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module_exit(hwrng_exit);
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MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
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MODULE_LICENSE("GPL");
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