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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");
1/*
2 * hw_random/core.c: HWRNG core API
3 *
4 * Copyright 2006 Michael Buesch <m@bues.ch>
5 * Copyright 2005 (c) MontaVista Software, Inc.
6 *
7 * Please read Documentation/hw_random.txt for details on use.
8 *
9 * This software may be used and distributed according to the terms
10 * of the GNU General Public License, incorporated herein by reference.
11 */
12
13#include <linux/delay.h>
14#include <linux/device.h>
15#include <linux/err.h>
16#include <linux/fs.h>
17#include <linux/hw_random.h>
18#include <linux/kernel.h>
19#include <linux/kthread.h>
20#include <linux/sched/signal.h>
21#include <linux/miscdevice.h>
22#include <linux/module.h>
23#include <linux/random.h>
24#include <linux/sched.h>
25#include <linux/slab.h>
26#include <linux/uaccess.h>
27
28#define RNG_MODULE_NAME "hw_random"
29
30static struct hwrng *current_rng;
31/* the current rng has been explicitly chosen by user via sysfs */
32static int cur_rng_set_by_user;
33static struct task_struct *hwrng_fill;
34/* list of registered rngs, sorted decending by quality */
35static LIST_HEAD(rng_list);
36/* Protects rng_list and current_rng */
37static DEFINE_MUTEX(rng_mutex);
38/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
39static DEFINE_MUTEX(reading_mutex);
40static int data_avail;
41static u8 *rng_buffer, *rng_fillbuf;
42static unsigned short current_quality;
43static unsigned short default_quality; /* = 0; default to "off" */
44
45module_param(current_quality, ushort, 0644);
46MODULE_PARM_DESC(current_quality,
47 "current hwrng entropy estimation per mill");
48module_param(default_quality, ushort, 0644);
49MODULE_PARM_DESC(default_quality,
50 "default entropy content of hwrng per mill");
51
52static void drop_current_rng(void);
53static int hwrng_init(struct hwrng *rng);
54static void start_khwrngd(void);
55
56static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
57 int wait);
58
59static size_t rng_buffer_size(void)
60{
61 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
62}
63
64static void add_early_randomness(struct hwrng *rng)
65{
66 int bytes_read;
67 size_t size = min_t(size_t, 16, rng_buffer_size());
68
69 mutex_lock(&reading_mutex);
70 bytes_read = rng_get_data(rng, rng_buffer, size, 1);
71 mutex_unlock(&reading_mutex);
72 if (bytes_read > 0)
73 add_device_randomness(rng_buffer, bytes_read);
74}
75
76static inline void cleanup_rng(struct kref *kref)
77{
78 struct hwrng *rng = container_of(kref, struct hwrng, ref);
79
80 if (rng->cleanup)
81 rng->cleanup(rng);
82
83 complete(&rng->cleanup_done);
84}
85
86static int set_current_rng(struct hwrng *rng)
87{
88 int err;
89
90 BUG_ON(!mutex_is_locked(&rng_mutex));
91
92 err = hwrng_init(rng);
93 if (err)
94 return err;
95
96 drop_current_rng();
97 current_rng = rng;
98
99 return 0;
100}
101
102static void drop_current_rng(void)
103{
104 BUG_ON(!mutex_is_locked(&rng_mutex));
105 if (!current_rng)
106 return;
107
108 /* decrease last reference for triggering the cleanup */
109 kref_put(¤t_rng->ref, cleanup_rng);
110 current_rng = NULL;
111}
112
113/* Returns ERR_PTR(), NULL or refcounted hwrng */
114static struct hwrng *get_current_rng(void)
115{
116 struct hwrng *rng;
117
118 if (mutex_lock_interruptible(&rng_mutex))
119 return ERR_PTR(-ERESTARTSYS);
120
121 rng = current_rng;
122 if (rng)
123 kref_get(&rng->ref);
124
125 mutex_unlock(&rng_mutex);
126 return rng;
127}
128
129static void put_rng(struct hwrng *rng)
130{
131 /*
132 * Hold rng_mutex here so we serialize in case they set_current_rng
133 * on rng again immediately.
134 */
135 mutex_lock(&rng_mutex);
136 if (rng)
137 kref_put(&rng->ref, cleanup_rng);
138 mutex_unlock(&rng_mutex);
139}
140
141static int hwrng_init(struct hwrng *rng)
142{
143 if (kref_get_unless_zero(&rng->ref))
144 goto skip_init;
145
146 if (rng->init) {
147 int ret;
148
149 ret = rng->init(rng);
150 if (ret)
151 return ret;
152 }
153
154 kref_init(&rng->ref);
155 reinit_completion(&rng->cleanup_done);
156
157skip_init:
158 add_early_randomness(rng);
159
160 current_quality = rng->quality ? : default_quality;
161 if (current_quality > 1024)
162 current_quality = 1024;
163
164 if (current_quality == 0 && hwrng_fill)
165 kthread_stop(hwrng_fill);
166 if (current_quality > 0 && !hwrng_fill)
167 start_khwrngd();
168
169 return 0;
170}
171
172static int rng_dev_open(struct inode *inode, struct file *filp)
173{
174 /* enforce read-only access to this chrdev */
175 if ((filp->f_mode & FMODE_READ) == 0)
176 return -EINVAL;
177 if (filp->f_mode & FMODE_WRITE)
178 return -EINVAL;
179 return 0;
180}
181
182static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
183 int wait) {
184 int present;
185
186 BUG_ON(!mutex_is_locked(&reading_mutex));
187 if (rng->read)
188 return rng->read(rng, (void *)buffer, size, wait);
189
190 if (rng->data_present)
191 present = rng->data_present(rng, wait);
192 else
193 present = 1;
194
195 if (present)
196 return rng->data_read(rng, (u32 *)buffer);
197
198 return 0;
199}
200
201static ssize_t rng_dev_read(struct file *filp, char __user *buf,
202 size_t size, loff_t *offp)
203{
204 ssize_t ret = 0;
205 int err = 0;
206 int bytes_read, len;
207 struct hwrng *rng;
208
209 while (size) {
210 rng = get_current_rng();
211 if (IS_ERR(rng)) {
212 err = PTR_ERR(rng);
213 goto out;
214 }
215 if (!rng) {
216 err = -ENODEV;
217 goto out;
218 }
219
220 if (mutex_lock_interruptible(&reading_mutex)) {
221 err = -ERESTARTSYS;
222 goto out_put;
223 }
224 if (!data_avail) {
225 bytes_read = rng_get_data(rng, rng_buffer,
226 rng_buffer_size(),
227 !(filp->f_flags & O_NONBLOCK));
228 if (bytes_read < 0) {
229 err = bytes_read;
230 goto out_unlock_reading;
231 }
232 data_avail = bytes_read;
233 }
234
235 if (!data_avail) {
236 if (filp->f_flags & O_NONBLOCK) {
237 err = -EAGAIN;
238 goto out_unlock_reading;
239 }
240 } else {
241 len = data_avail;
242 if (len > size)
243 len = size;
244
245 data_avail -= len;
246
247 if (copy_to_user(buf + ret, rng_buffer + data_avail,
248 len)) {
249 err = -EFAULT;
250 goto out_unlock_reading;
251 }
252
253 size -= len;
254 ret += len;
255 }
256
257 mutex_unlock(&reading_mutex);
258 put_rng(rng);
259
260 if (need_resched())
261 schedule_timeout_interruptible(1);
262
263 if (signal_pending(current)) {
264 err = -ERESTARTSYS;
265 goto out;
266 }
267 }
268out:
269 return ret ? : err;
270
271out_unlock_reading:
272 mutex_unlock(&reading_mutex);
273out_put:
274 put_rng(rng);
275 goto out;
276}
277
278static const struct file_operations rng_chrdev_ops = {
279 .owner = THIS_MODULE,
280 .open = rng_dev_open,
281 .read = rng_dev_read,
282 .llseek = noop_llseek,
283};
284
285static const struct attribute_group *rng_dev_groups[];
286
287static struct miscdevice rng_miscdev = {
288 .minor = HWRNG_MINOR,
289 .name = RNG_MODULE_NAME,
290 .nodename = "hwrng",
291 .fops = &rng_chrdev_ops,
292 .groups = rng_dev_groups,
293};
294
295static int enable_best_rng(void)
296{
297 int ret = -ENODEV;
298
299 BUG_ON(!mutex_is_locked(&rng_mutex));
300
301 /* rng_list is sorted by quality, use the best (=first) one */
302 if (!list_empty(&rng_list)) {
303 struct hwrng *new_rng;
304
305 new_rng = list_entry(rng_list.next, struct hwrng, list);
306 ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
307 if (!ret)
308 cur_rng_set_by_user = 0;
309 } else {
310 drop_current_rng();
311 cur_rng_set_by_user = 0;
312 ret = 0;
313 }
314
315 return ret;
316}
317
318static ssize_t hwrng_attr_current_store(struct device *dev,
319 struct device_attribute *attr,
320 const char *buf, size_t len)
321{
322 int err = -ENODEV;
323 struct hwrng *rng;
324
325 err = mutex_lock_interruptible(&rng_mutex);
326 if (err)
327 return -ERESTARTSYS;
328
329 if (sysfs_streq(buf, "")) {
330 err = enable_best_rng();
331 } else {
332 list_for_each_entry(rng, &rng_list, list) {
333 if (sysfs_streq(rng->name, buf)) {
334 cur_rng_set_by_user = 1;
335 err = set_current_rng(rng);
336 break;
337 }
338 }
339 }
340
341 mutex_unlock(&rng_mutex);
342
343 return err ? : len;
344}
345
346static ssize_t hwrng_attr_current_show(struct device *dev,
347 struct device_attribute *attr,
348 char *buf)
349{
350 ssize_t ret;
351 struct hwrng *rng;
352
353 rng = get_current_rng();
354 if (IS_ERR(rng))
355 return PTR_ERR(rng);
356
357 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
358 put_rng(rng);
359
360 return ret;
361}
362
363static ssize_t hwrng_attr_available_show(struct device *dev,
364 struct device_attribute *attr,
365 char *buf)
366{
367 int err;
368 struct hwrng *rng;
369
370 err = mutex_lock_interruptible(&rng_mutex);
371 if (err)
372 return -ERESTARTSYS;
373 buf[0] = '\0';
374 list_for_each_entry(rng, &rng_list, list) {
375 strlcat(buf, rng->name, PAGE_SIZE);
376 strlcat(buf, " ", PAGE_SIZE);
377 }
378 strlcat(buf, "\n", PAGE_SIZE);
379 mutex_unlock(&rng_mutex);
380
381 return strlen(buf);
382}
383
384static ssize_t hwrng_attr_selected_show(struct device *dev,
385 struct device_attribute *attr,
386 char *buf)
387{
388 return snprintf(buf, PAGE_SIZE, "%d\n", cur_rng_set_by_user);
389}
390
391static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
392 hwrng_attr_current_show,
393 hwrng_attr_current_store);
394static DEVICE_ATTR(rng_available, S_IRUGO,
395 hwrng_attr_available_show,
396 NULL);
397static DEVICE_ATTR(rng_selected, S_IRUGO,
398 hwrng_attr_selected_show,
399 NULL);
400
401static struct attribute *rng_dev_attrs[] = {
402 &dev_attr_rng_current.attr,
403 &dev_attr_rng_available.attr,
404 &dev_attr_rng_selected.attr,
405 NULL
406};
407
408ATTRIBUTE_GROUPS(rng_dev);
409
410static void __exit unregister_miscdev(void)
411{
412 misc_deregister(&rng_miscdev);
413}
414
415static int __init register_miscdev(void)
416{
417 return misc_register(&rng_miscdev);
418}
419
420static int hwrng_fillfn(void *unused)
421{
422 long rc;
423
424 while (!kthread_should_stop()) {
425 struct hwrng *rng;
426
427 rng = get_current_rng();
428 if (IS_ERR(rng) || !rng)
429 break;
430 mutex_lock(&reading_mutex);
431 rc = rng_get_data(rng, rng_fillbuf,
432 rng_buffer_size(), 1);
433 mutex_unlock(&reading_mutex);
434 put_rng(rng);
435 if (rc <= 0) {
436 pr_warn("hwrng: no data available\n");
437 msleep_interruptible(10000);
438 continue;
439 }
440 /* Outside lock, sure, but y'know: randomness. */
441 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
442 rc * current_quality * 8 >> 10);
443 }
444 hwrng_fill = NULL;
445 return 0;
446}
447
448static void start_khwrngd(void)
449{
450 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
451 if (IS_ERR(hwrng_fill)) {
452 pr_err("hwrng_fill thread creation failed\n");
453 hwrng_fill = NULL;
454 }
455}
456
457int hwrng_register(struct hwrng *rng)
458{
459 int err = -EINVAL;
460 struct hwrng *old_rng, *tmp;
461 struct list_head *rng_list_ptr;
462
463 if (!rng->name || (!rng->data_read && !rng->read))
464 goto out;
465
466 mutex_lock(&rng_mutex);
467 /* Must not register two RNGs with the same name. */
468 err = -EEXIST;
469 list_for_each_entry(tmp, &rng_list, list) {
470 if (strcmp(tmp->name, rng->name) == 0)
471 goto out_unlock;
472 }
473
474 init_completion(&rng->cleanup_done);
475 complete(&rng->cleanup_done);
476
477 /* rng_list is sorted by decreasing quality */
478 list_for_each(rng_list_ptr, &rng_list) {
479 tmp = list_entry(rng_list_ptr, struct hwrng, list);
480 if (tmp->quality < rng->quality)
481 break;
482 }
483 list_add_tail(&rng->list, rng_list_ptr);
484
485 old_rng = current_rng;
486 err = 0;
487 if (!old_rng ||
488 (!cur_rng_set_by_user && rng->quality > old_rng->quality)) {
489 /*
490 * Set new rng as current as the new rng source
491 * provides better entropy quality and was not
492 * chosen by userspace.
493 */
494 err = set_current_rng(rng);
495 if (err)
496 goto out_unlock;
497 }
498
499 if (old_rng && !rng->init) {
500 /*
501 * Use a new device's input to add some randomness to
502 * the system. If this rng device isn't going to be
503 * used right away, its init function hasn't been
504 * called yet; so only use the randomness from devices
505 * that don't need an init callback.
506 */
507 add_early_randomness(rng);
508 }
509
510out_unlock:
511 mutex_unlock(&rng_mutex);
512out:
513 return err;
514}
515EXPORT_SYMBOL_GPL(hwrng_register);
516
517void hwrng_unregister(struct hwrng *rng)
518{
519 mutex_lock(&rng_mutex);
520
521 list_del(&rng->list);
522 if (current_rng == rng)
523 enable_best_rng();
524
525 if (list_empty(&rng_list)) {
526 mutex_unlock(&rng_mutex);
527 if (hwrng_fill)
528 kthread_stop(hwrng_fill);
529 } else
530 mutex_unlock(&rng_mutex);
531
532 wait_for_completion(&rng->cleanup_done);
533}
534EXPORT_SYMBOL_GPL(hwrng_unregister);
535
536static void devm_hwrng_release(struct device *dev, void *res)
537{
538 hwrng_unregister(*(struct hwrng **)res);
539}
540
541static int devm_hwrng_match(struct device *dev, void *res, void *data)
542{
543 struct hwrng **r = res;
544
545 if (WARN_ON(!r || !*r))
546 return 0;
547
548 return *r == data;
549}
550
551int devm_hwrng_register(struct device *dev, struct hwrng *rng)
552{
553 struct hwrng **ptr;
554 int error;
555
556 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
557 if (!ptr)
558 return -ENOMEM;
559
560 error = hwrng_register(rng);
561 if (error) {
562 devres_free(ptr);
563 return error;
564 }
565
566 *ptr = rng;
567 devres_add(dev, ptr);
568 return 0;
569}
570EXPORT_SYMBOL_GPL(devm_hwrng_register);
571
572void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
573{
574 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
575}
576EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
577
578static int __init hwrng_modinit(void)
579{
580 int ret = -ENOMEM;
581
582 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
583 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
584 if (!rng_buffer)
585 return -ENOMEM;
586
587 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
588 if (!rng_fillbuf) {
589 kfree(rng_buffer);
590 return -ENOMEM;
591 }
592
593 ret = register_miscdev();
594 if (ret) {
595 kfree(rng_fillbuf);
596 kfree(rng_buffer);
597 }
598
599 return ret;
600}
601
602static void __exit hwrng_modexit(void)
603{
604 mutex_lock(&rng_mutex);
605 BUG_ON(current_rng);
606 kfree(rng_buffer);
607 kfree(rng_fillbuf);
608 mutex_unlock(&rng_mutex);
609
610 unregister_miscdev();
611}
612
613module_init(hwrng_modinit);
614module_exit(hwrng_modexit);
615
616MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
617MODULE_LICENSE("GPL");