![Rafael J. Wysocki](/assets/img/avatar_default.png)
Make it possible to unregister a Hardware Random Number Generator device object in a safe way during a suspend/resume cycle. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Michael Buesch <mb@bu3sch.de> Cc: Michael Buesch <mb@bu3sch.de> Cc: Pavel Machek <pavel@ucw.cz> Cc: "John W. Linville" <linville@tuxdriver.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Len Brown <lenb@kernel.org> Cc: Greg KH <greg@kroah.com> Cc: Kay Sievers <kay.sievers@vrfy.org> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
344 lines
7.1 KiB
C
344 lines
7.1 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 <mbuesch@freenet.de>
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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/init.h>
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#include <linux/miscdevice.h>
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#include <linux/delay.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 LIST_HEAD(rng_list);
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static DEFINE_MUTEX(rng_mutex);
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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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return 0;
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return rng->init(rng);
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}
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static inline void hwrng_cleanup(struct hwrng *rng)
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{
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if (rng && rng->cleanup)
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rng->cleanup(rng);
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}
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static inline int hwrng_data_present(struct hwrng *rng, int wait)
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{
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if (!rng->data_present)
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return 1;
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return rng->data_present(rng, wait);
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}
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static inline int hwrng_data_read(struct hwrng *rng, u32 *data)
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{
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return rng->data_read(rng, data);
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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 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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u32 data;
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ssize_t ret = 0;
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int err = 0;
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int bytes_read;
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while (size) {
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err = -ERESTARTSYS;
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if (mutex_lock_interruptible(&rng_mutex))
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goto out;
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if (!current_rng) {
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mutex_unlock(&rng_mutex);
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err = -ENODEV;
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goto out;
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}
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bytes_read = 0;
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if (hwrng_data_present(current_rng,
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!(filp->f_flags & O_NONBLOCK)))
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bytes_read = hwrng_data_read(current_rng, &data);
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mutex_unlock(&rng_mutex);
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err = -EAGAIN;
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if (!bytes_read && (filp->f_flags & O_NONBLOCK))
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goto out;
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err = -EFAULT;
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while (bytes_read && size) {
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if (put_user((u8)data, buf++))
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goto out;
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size--;
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ret++;
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bytes_read--;
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data >>= 8;
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}
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if (need_resched())
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schedule_timeout_interruptible(1);
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err = -ERESTARTSYS;
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if (signal_pending(current))
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goto out;
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}
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out:
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return ret ? : err;
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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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};
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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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.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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hwrng_cleanup(current_rng);
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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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int err;
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ssize_t ret;
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const char *name = "none";
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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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if (current_rng)
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name = current_rng->name;
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ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
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mutex_unlock(&rng_mutex);
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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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ssize_t ret = 0;
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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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strncat(buf, rng->name, PAGE_SIZE - ret - 1);
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ret += strlen(rng->name);
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strncat(buf, " ", PAGE_SIZE - ret - 1);
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ret++;
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}
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strncat(buf, "\n", PAGE_SIZE - ret - 1);
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ret++;
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mutex_unlock(&rng_mutex);
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return ret;
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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(bool suspended)
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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, suspended);
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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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int hwrng_register(struct hwrng *rng)
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{
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int must_register_misc;
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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)
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goto out;
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mutex_lock(&rng_mutex);
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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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must_register_misc = (current_rng == NULL);
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old_rng = current_rng;
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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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current_rng = rng;
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}
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err = 0;
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if (must_register_misc) {
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err = register_miscdev();
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if (err) {
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if (!old_rng) {
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hwrng_cleanup(rng);
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current_rng = NULL;
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}
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goto out_unlock;
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}
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}
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INIT_LIST_HEAD(&rng->list);
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list_add_tail(&rng->list, &rng_list);
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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, bool suspended)
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{
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int err;
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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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hwrng_cleanup(rng);
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if (list_empty(&rng_list)) {
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current_rng = NULL;
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} else {
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current_rng = list_entry(rng_list.prev, struct hwrng, list);
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err = hwrng_init(current_rng);
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if (err)
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current_rng = NULL;
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}
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}
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if (list_empty(&rng_list))
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unregister_miscdev(suspended);
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mutex_unlock(&rng_mutex);
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}
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EXPORT_SYMBOL_GPL(__hwrng_unregister);
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MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
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MODULE_LICENSE("GPL");
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