/drivers/char/hw_random/core.c

  1/*
  2        Added support for the AMD Geode LX RNG
  3	(c) Copyright 2004-2005 Advanced Micro Devices, Inc.
  4
  5	derived from
  6
  7 	Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
  8	(c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
  9
 10 	derived from
 11
 12        Hardware driver for the AMD 768 Random Number Generator (RNG)
 13        (c) Copyright 2001 Red Hat Inc <alan@redhat.com>
 14
 15 	derived from
 16
 17	Hardware driver for Intel i810 Random Number Generator (RNG)
 18	Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
 19	Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
 20
 21	Added generic RNG API
 22	Copyright 2006 Michael Buesch <mbuesch@freenet.de>
 23	Copyright 2005 (c) MontaVista Software, Inc.
 24
 25	Please read Documentation/hw_random.txt for details on use.
 26
 27	----------------------------------------------------------
 28	This software may be used and distributed according to the terms
 29        of the GNU General Public License, incorporated herein by reference.
 30
 31 */
 32
 33
 34#include <linux/device.h>
 35#include <linux/hw_random.h>
 36#include <linux/module.h>
 37#include <linux/kernel.h>
 38#include <linux/fs.h>
 39#include <linux/sched.h>
 40#include <linux/init.h>
 41#include <linux/miscdevice.h>
 42#include <linux/delay.h>
 43#include <asm/uaccess.h>
 44
 45
 46#define RNG_MODULE_NAME		"hw_random"
 47#define PFX			RNG_MODULE_NAME ": "
 48#define RNG_MISCDEV_MINOR	183 /* official */
 49
 50
 51static struct hwrng *current_rng;
 52static LIST_HEAD(rng_list);
 53static DEFINE_MUTEX(rng_mutex);
 54static int data_avail;
 55static u8 rng_buffer[SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES]
 56	__cacheline_aligned;
 57
 58static inline int hwrng_init(struct hwrng *rng)
 59{
 60	if (!rng->init)
 61		return 0;
 62	return rng->init(rng);
 63}
 64
 65static inline void hwrng_cleanup(struct hwrng *rng)
 66{
 67	if (rng && rng->cleanup)
 68		rng->cleanup(rng);
 69}
 70
 71static int rng_dev_open(struct inode *inode, struct file *filp)
 72{
 73	/* enforce read-only access to this chrdev */
 74	if ((filp->f_mode & FMODE_READ) == 0)
 75		return -EINVAL;
 76	if (filp->f_mode & FMODE_WRITE)
 77		return -EINVAL;
 78	return 0;
 79}
 80
 81static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
 82			int wait) {
 83	int present;
 84
 85	if (rng->read)
 86		return rng->read(rng, (void *)buffer, size, wait);
 87
 88	if (rng->data_present)
 89		present = rng->data_present(rng, wait);
 90	else
 91		present = 1;
 92
 93	if (present)
 94		return rng->data_read(rng, (u32 *)buffer);
 95
 96	return 0;
 97}
 98
 99static ssize_t rng_dev_read(struct file *filp, char __user *buf,
100			    size_t size, loff_t *offp)
101{
102	ssize_t ret = 0;
103	int err = 0;
104	int bytes_read, len;
105
106	while (size) {
107		if (mutex_lock_interruptible(&rng_mutex)) {
108			err = -ERESTARTSYS;
109			goto out;
110		}
111
112		if (!current_rng) {
113			err = -ENODEV;
114			goto out_unlock;
115		}
116
117		if (!data_avail) {
118			bytes_read = rng_get_data(current_rng, rng_buffer,
119				sizeof(rng_buffer),
120				!(filp->f_flags & O_NONBLOCK));
121			if (bytes_read < 0) {
122				err = bytes_read;
123				goto out_unlock;
124			}
125			data_avail = bytes_read;
126		}
127
128		if (!data_avail) {
129			if (filp->f_flags & O_NONBLOCK) {
130				err = -EAGAIN;
131				goto out_unlock;
132			}
133		} else {
134			len = data_avail;
135			if (len > size)
136				len = size;
137
138			data_avail -= len;
139
140			if (copy_to_user(buf + ret, rng_buffer + data_avail,
141								len)) {
142				err = -EFAULT;
143				goto out_unlock;
144			}
145
146			size -= len;
147			ret += len;
148		}
149
150		mutex_unlock(&rng_mutex);
151
152		if (need_resched())
153			schedule_timeout_interruptible(1);
154
155		if (signal_pending(current)) {
156			err = -ERESTARTSYS;
157			goto out;
158		}
159	}
160out:
161	return ret ? : err;
162out_unlock:
163	mutex_unlock(&rng_mutex);
164	goto out;
165}
166
167
168static const struct file_operations rng_chrdev_ops = {
169	.owner		= THIS_MODULE,
170	.open		= rng_dev_open,
171	.read		= rng_dev_read,
172	.llseek		= noop_llseek,
173};
174
175static struct miscdevice rng_miscdev = {
176	.minor		= RNG_MISCDEV_MINOR,
177	.name		= RNG_MODULE_NAME,
178	.nodename	= "hwrng",
179	.fops		= &rng_chrdev_ops,
180};
181
182
183static ssize_t hwrng_attr_current_store(struct device *dev,
184					struct device_attribute *attr,
185					const char *buf, size_t len)
186{
187	int err;
188	struct hwrng *rng;
189
190	err = mutex_lock_interruptible(&rng_mutex);
191	if (err)
192		return -ERESTARTSYS;
193	err = -ENODEV;
194	list_for_each_entry(rng, &rng_list, list) {
195		if (strcmp(rng->name, buf) == 0) {
196			if (rng == current_rng) {
197				err = 0;
198				break;
199			}
200			err = hwrng_init(rng);
201			if (err)
202				break;
203			hwrng_cleanup(current_rng);
204			current_rng = rng;
205			err = 0;
206			break;
207		}
208	}
209	mutex_unlock(&rng_mutex);
210
211	return err ? : len;
212}
213
214static ssize_t hwrng_attr_current_show(struct device *dev,
215				       struct device_attribute *attr,
216				       char *buf)
217{
218	int err;
219	ssize_t ret;
220	const char *name = "none";
221
222	err = mutex_lock_interruptible(&rng_mutex);
223	if (err)
224		return -ERESTARTSYS;
225	if (current_rng)
226		name = current_rng->name;
227	ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
228	mutex_unlock(&rng_mutex);
229
230	return ret;
231}
232
233static ssize_t hwrng_attr_available_show(struct device *dev,
234					 struct device_attribute *attr,
235					 char *buf)
236{
237	int err;
238	ssize_t ret = 0;
239	struct hwrng *rng;
240
241	err = mutex_lock_interruptible(&rng_mutex);
242	if (err)
243		return -ERESTARTSYS;
244	buf[0] = '\0';
245	list_for_each_entry(rng, &rng_list, list) {
246		strncat(buf, rng->name, PAGE_SIZE - ret - 1);
247		ret += strlen(rng->name);
248		strncat(buf, " ", PAGE_SIZE - ret - 1);
249		ret++;
250	}
251	strncat(buf, "\n", PAGE_SIZE - ret - 1);
252	ret++;
253	mutex_unlock(&rng_mutex);
254
255	return ret;
256}
257
258static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
259		   hwrng_attr_current_show,
260		   hwrng_attr_current_store);
261static DEVICE_ATTR(rng_available, S_IRUGO,
262		   hwrng_attr_available_show,
263		   NULL);
264
265
266static void unregister_miscdev(void)
267{
268	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
269	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
270	misc_deregister(&rng_miscdev);
271}
272
273static int register_miscdev(void)
274{
275	int err;
276
277	err = misc_register(&rng_miscdev);
278	if (err)
279		goto out;
280	err = device_create_file(rng_miscdev.this_device,
281				 &dev_attr_rng_current);
282	if (err)
283		goto err_misc_dereg;
284	err = device_create_file(rng_miscdev.this_device,
285				 &dev_attr_rng_available);
286	if (err)
287		goto err_remove_current;
288out:
289	return err;
290
291err_remove_current:
292	device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
293err_misc_dereg:
294	misc_deregister(&rng_miscdev);
295	goto out;
296}
297
298int hwrng_register(struct hwrng *rng)
299{
300	int must_register_misc;
301	int err = -EINVAL;
302	struct hwrng *old_rng, *tmp;
303
304	if (rng->name == NULL ||
305	    (rng->data_read == NULL && rng->read == NULL))
306		goto out;
307
308	mutex_lock(&rng_mutex);
309
310	/* Must not register two RNGs with the same name. */
311	err = -EEXIST;
312	list_for_each_entry(tmp, &rng_list, list) {
313		if (strcmp(tmp->name, rng->name) == 0)
314			goto out_unlock;
315	}
316
317	must_register_misc = (current_rng == NULL);
318	old_rng = current_rng;
319	if (!old_rng) {
320		err = hwrng_init(rng);
321		if (err)
322			goto out_unlock;
323		current_rng = rng;
324	}
325	err = 0;
326	if (must_register_misc) {
327		err = register_miscdev();
328		if (err) {
329			if (!old_rng) {
330				hwrng_cleanup(rng);
331				current_rng = NULL;
332			}
333			goto out_unlock;
334		}
335	}
336	INIT_LIST_HEAD(&rng->list);
337	list_add_tail(&rng->list, &rng_list);
338out_unlock:
339	mutex_unlock(&rng_mutex);
340out:
341	return err;
342}
343EXPORT_SYMBOL_GPL(hwrng_register);
344
345void hwrng_unregister(struct hwrng *rng)
346{
347	int err;
348
349	mutex_lock(&rng_mutex);
350
351	list_del(&rng->list);
352	if (current_rng == rng) {
353		hwrng_cleanup(rng);
354		if (list_empty(&rng_list)) {
355			current_rng = NULL;
356		} else {
357			current_rng = list_entry(rng_list.prev, struct hwrng, list);
358			err = hwrng_init(current_rng);
359			if (err)
360				current_rng = NULL;
361		}
362	}
363	if (list_empty(&rng_list))
364		unregister_miscdev();
365
366	mutex_unlock(&rng_mutex);
367}
368EXPORT_SYMBOL_GPL(hwrng_unregister);
369
370
371MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
372MODULE_LICENSE("GPL");