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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 <m@bues.ch>
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");