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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/admin-guide/hw_random.rst 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 1024 bits of input");
48module_param(default_quality, ushort, 0644);
49MODULE_PARM_DESC(default_quality,
50 "default entropy content of hwrng per 1024 bits of input");
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, 0);
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_nolock(void)
115{
116 if (current_rng)
117 kref_get(¤t_rng->ref);
118
119 return current_rng;
120}
121
122static struct hwrng *get_current_rng(void)
123{
124 struct hwrng *rng;
125
126 if (mutex_lock_interruptible(&rng_mutex))
127 return ERR_PTR(-ERESTARTSYS);
128
129 rng = get_current_rng_nolock();
130
131 mutex_unlock(&rng_mutex);
132 return rng;
133}
134
135static void put_rng(struct hwrng *rng)
136{
137 /*
138 * Hold rng_mutex here so we serialize in case they set_current_rng
139 * on rng again immediately.
140 */
141 mutex_lock(&rng_mutex);
142 if (rng)
143 kref_put(&rng->ref, cleanup_rng);
144 mutex_unlock(&rng_mutex);
145}
146
147static int hwrng_init(struct hwrng *rng)
148{
149 if (kref_get_unless_zero(&rng->ref))
150 goto skip_init;
151
152 if (rng->init) {
153 int ret;
154
155 ret = rng->init(rng);
156 if (ret)
157 return ret;
158 }
159
160 kref_init(&rng->ref);
161 reinit_completion(&rng->cleanup_done);
162
163skip_init:
164 current_quality = rng->quality ? : default_quality;
165 if (current_quality > 1024)
166 current_quality = 1024;
167
168 if (current_quality == 0 && hwrng_fill)
169 kthread_stop(hwrng_fill);
170 if (current_quality > 0 && !hwrng_fill)
171 start_khwrngd();
172
173 return 0;
174}
175
176static int rng_dev_open(struct inode *inode, struct file *filp)
177{
178 /* enforce read-only access to this chrdev */
179 if ((filp->f_mode & FMODE_READ) == 0)
180 return -EINVAL;
181 if (filp->f_mode & FMODE_WRITE)
182 return -EINVAL;
183 return 0;
184}
185
186static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
187 int wait) {
188 int present;
189
190 BUG_ON(!mutex_is_locked(&reading_mutex));
191 if (rng->read)
192 return rng->read(rng, (void *)buffer, size, wait);
193
194 if (rng->data_present)
195 present = rng->data_present(rng, wait);
196 else
197 present = 1;
198
199 if (present)
200 return rng->data_read(rng, (u32 *)buffer);
201
202 return 0;
203}
204
205static ssize_t rng_dev_read(struct file *filp, char __user *buf,
206 size_t size, loff_t *offp)
207{
208 ssize_t ret = 0;
209 int err = 0;
210 int bytes_read, len;
211 struct hwrng *rng;
212
213 while (size) {
214 rng = get_current_rng();
215 if (IS_ERR(rng)) {
216 err = PTR_ERR(rng);
217 goto out;
218 }
219 if (!rng) {
220 err = -ENODEV;
221 goto out;
222 }
223
224 if (mutex_lock_interruptible(&reading_mutex)) {
225 err = -ERESTARTSYS;
226 goto out_put;
227 }
228 if (!data_avail) {
229 bytes_read = rng_get_data(rng, rng_buffer,
230 rng_buffer_size(),
231 !(filp->f_flags & O_NONBLOCK));
232 if (bytes_read < 0) {
233 err = bytes_read;
234 goto out_unlock_reading;
235 }
236 data_avail = bytes_read;
237 }
238
239 if (!data_avail) {
240 if (filp->f_flags & O_NONBLOCK) {
241 err = -EAGAIN;
242 goto out_unlock_reading;
243 }
244 } else {
245 len = data_avail;
246 if (len > size)
247 len = size;
248
249 data_avail -= len;
250
251 if (copy_to_user(buf + ret, rng_buffer + data_avail,
252 len)) {
253 err = -EFAULT;
254 goto out_unlock_reading;
255 }
256
257 size -= len;
258 ret += len;
259 }
260
261 mutex_unlock(&reading_mutex);
262 put_rng(rng);
263
264 if (need_resched())
265 schedule_timeout_interruptible(1);
266
267 if (signal_pending(current)) {
268 err = -ERESTARTSYS;
269 goto out;
270 }
271 }
272out:
273 return ret ? : err;
274
275out_unlock_reading:
276 mutex_unlock(&reading_mutex);
277out_put:
278 put_rng(rng);
279 goto out;
280}
281
282static const struct file_operations rng_chrdev_ops = {
283 .owner = THIS_MODULE,
284 .open = rng_dev_open,
285 .read = rng_dev_read,
286 .llseek = noop_llseek,
287};
288
289static const struct attribute_group *rng_dev_groups[];
290
291static struct miscdevice rng_miscdev = {
292 .minor = HWRNG_MINOR,
293 .name = RNG_MODULE_NAME,
294 .nodename = "hwrng",
295 .fops = &rng_chrdev_ops,
296 .groups = rng_dev_groups,
297};
298
299static int enable_best_rng(void)
300{
301 int ret = -ENODEV;
302
303 BUG_ON(!mutex_is_locked(&rng_mutex));
304
305 /* rng_list is sorted by quality, use the best (=first) one */
306 if (!list_empty(&rng_list)) {
307 struct hwrng *new_rng;
308
309 new_rng = list_entry(rng_list.next, struct hwrng, list);
310 ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
311 if (!ret)
312 cur_rng_set_by_user = 0;
313 } else {
314 drop_current_rng();
315 cur_rng_set_by_user = 0;
316 ret = 0;
317 }
318
319 return ret;
320}
321
322static ssize_t hwrng_attr_current_store(struct device *dev,
323 struct device_attribute *attr,
324 const char *buf, size_t len)
325{
326 int err = -ENODEV;
327 struct hwrng *rng, *old_rng, *new_rng;
328
329 err = mutex_lock_interruptible(&rng_mutex);
330 if (err)
331 return -ERESTARTSYS;
332
333 old_rng = current_rng;
334 if (sysfs_streq(buf, "")) {
335 err = enable_best_rng();
336 } else {
337 list_for_each_entry(rng, &rng_list, list) {
338 if (sysfs_streq(rng->name, buf)) {
339 cur_rng_set_by_user = 1;
340 err = set_current_rng(rng);
341 break;
342 }
343 }
344 }
345 new_rng = get_current_rng_nolock();
346 mutex_unlock(&rng_mutex);
347
348 if (new_rng) {
349 if (new_rng != old_rng)
350 add_early_randomness(new_rng);
351 put_rng(new_rng);
352 }
353
354 return err ? : len;
355}
356
357static ssize_t hwrng_attr_current_show(struct device *dev,
358 struct device_attribute *attr,
359 char *buf)
360{
361 ssize_t ret;
362 struct hwrng *rng;
363
364 rng = get_current_rng();
365 if (IS_ERR(rng))
366 return PTR_ERR(rng);
367
368 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
369 put_rng(rng);
370
371 return ret;
372}
373
374static ssize_t hwrng_attr_available_show(struct device *dev,
375 struct device_attribute *attr,
376 char *buf)
377{
378 int err;
379 struct hwrng *rng;
380
381 err = mutex_lock_interruptible(&rng_mutex);
382 if (err)
383 return -ERESTARTSYS;
384 buf[0] = '\0';
385 list_for_each_entry(rng, &rng_list, list) {
386 strlcat(buf, rng->name, PAGE_SIZE);
387 strlcat(buf, " ", PAGE_SIZE);
388 }
389 strlcat(buf, "\n", PAGE_SIZE);
390 mutex_unlock(&rng_mutex);
391
392 return strlen(buf);
393}
394
395static ssize_t hwrng_attr_selected_show(struct device *dev,
396 struct device_attribute *attr,
397 char *buf)
398{
399 return snprintf(buf, PAGE_SIZE, "%d\n", cur_rng_set_by_user);
400}
401
402static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
403 hwrng_attr_current_show,
404 hwrng_attr_current_store);
405static DEVICE_ATTR(rng_available, S_IRUGO,
406 hwrng_attr_available_show,
407 NULL);
408static DEVICE_ATTR(rng_selected, S_IRUGO,
409 hwrng_attr_selected_show,
410 NULL);
411
412static struct attribute *rng_dev_attrs[] = {
413 &dev_attr_rng_current.attr,
414 &dev_attr_rng_available.attr,
415 &dev_attr_rng_selected.attr,
416 NULL
417};
418
419ATTRIBUTE_GROUPS(rng_dev);
420
421static void __exit unregister_miscdev(void)
422{
423 misc_deregister(&rng_miscdev);
424}
425
426static int __init register_miscdev(void)
427{
428 return misc_register(&rng_miscdev);
429}
430
431static int hwrng_fillfn(void *unused)
432{
433 long rc;
434
435 while (!kthread_should_stop()) {
436 struct hwrng *rng;
437
438 rng = get_current_rng();
439 if (IS_ERR(rng) || !rng)
440 break;
441 mutex_lock(&reading_mutex);
442 rc = rng_get_data(rng, rng_fillbuf,
443 rng_buffer_size(), 1);
444 mutex_unlock(&reading_mutex);
445 put_rng(rng);
446 if (rc <= 0) {
447 pr_warn("hwrng: no data available\n");
448 msleep_interruptible(10000);
449 continue;
450 }
451 /* Outside lock, sure, but y'know: randomness. */
452 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
453 rc * current_quality * 8 >> 10);
454 }
455 hwrng_fill = NULL;
456 return 0;
457}
458
459static void start_khwrngd(void)
460{
461 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
462 if (IS_ERR(hwrng_fill)) {
463 pr_err("hwrng_fill thread creation failed\n");
464 hwrng_fill = NULL;
465 }
466}
467
468int hwrng_register(struct hwrng *rng)
469{
470 int err = -EINVAL;
471 struct hwrng *tmp;
472 struct list_head *rng_list_ptr;
473 bool is_new_current = false;
474
475 if (!rng->name || (!rng->data_read && !rng->read))
476 goto out;
477
478 mutex_lock(&rng_mutex);
479
480 /* Must not register two RNGs with the same name. */
481 err = -EEXIST;
482 list_for_each_entry(tmp, &rng_list, list) {
483 if (strcmp(tmp->name, rng->name) == 0)
484 goto out_unlock;
485 }
486
487 init_completion(&rng->cleanup_done);
488 complete(&rng->cleanup_done);
489
490 /* rng_list is sorted by decreasing quality */
491 list_for_each(rng_list_ptr, &rng_list) {
492 tmp = list_entry(rng_list_ptr, struct hwrng, list);
493 if (tmp->quality < rng->quality)
494 break;
495 }
496 list_add_tail(&rng->list, rng_list_ptr);
497
498 if (!current_rng ||
499 (!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
500 /*
501 * Set new rng as current as the new rng source
502 * provides better entropy quality and was not
503 * chosen by userspace.
504 */
505 err = set_current_rng(rng);
506 if (err)
507 goto out_unlock;
508 /* to use current_rng in add_early_randomness() we need
509 * to take a ref
510 */
511 is_new_current = true;
512 kref_get(&rng->ref);
513 }
514 mutex_unlock(&rng_mutex);
515 if (is_new_current || !rng->init) {
516 /*
517 * Use a new device's input to add some randomness to
518 * the system. If this rng device isn't going to be
519 * used right away, its init function hasn't been
520 * called yet by set_current_rng(); so only use the
521 * randomness from devices that don't need an init callback
522 */
523 add_early_randomness(rng);
524 }
525 if (is_new_current)
526 put_rng(rng);
527 return 0;
528out_unlock:
529 mutex_unlock(&rng_mutex);
530out:
531 return err;
532}
533EXPORT_SYMBOL_GPL(hwrng_register);
534
535void hwrng_unregister(struct hwrng *rng)
536{
537 struct hwrng *old_rng, *new_rng;
538 int err;
539
540 mutex_lock(&rng_mutex);
541
542 old_rng = current_rng;
543 list_del(&rng->list);
544 if (current_rng == rng) {
545 err = enable_best_rng();
546 if (err) {
547 drop_current_rng();
548 cur_rng_set_by_user = 0;
549 }
550 }
551
552 new_rng = get_current_rng_nolock();
553 if (list_empty(&rng_list)) {
554 mutex_unlock(&rng_mutex);
555 if (hwrng_fill)
556 kthread_stop(hwrng_fill);
557 } else
558 mutex_unlock(&rng_mutex);
559
560 if (new_rng) {
561 if (old_rng != new_rng)
562 add_early_randomness(new_rng);
563 put_rng(new_rng);
564 }
565
566 wait_for_completion(&rng->cleanup_done);
567}
568EXPORT_SYMBOL_GPL(hwrng_unregister);
569
570static void devm_hwrng_release(struct device *dev, void *res)
571{
572 hwrng_unregister(*(struct hwrng **)res);
573}
574
575static int devm_hwrng_match(struct device *dev, void *res, void *data)
576{
577 struct hwrng **r = res;
578
579 if (WARN_ON(!r || !*r))
580 return 0;
581
582 return *r == data;
583}
584
585int devm_hwrng_register(struct device *dev, struct hwrng *rng)
586{
587 struct hwrng **ptr;
588 int error;
589
590 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
591 if (!ptr)
592 return -ENOMEM;
593
594 error = hwrng_register(rng);
595 if (error) {
596 devres_free(ptr);
597 return error;
598 }
599
600 *ptr = rng;
601 devres_add(dev, ptr);
602 return 0;
603}
604EXPORT_SYMBOL_GPL(devm_hwrng_register);
605
606void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
607{
608 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
609}
610EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
611
612static int __init hwrng_modinit(void)
613{
614 int ret;
615
616 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
617 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
618 if (!rng_buffer)
619 return -ENOMEM;
620
621 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
622 if (!rng_fillbuf) {
623 kfree(rng_buffer);
624 return -ENOMEM;
625 }
626
627 ret = register_miscdev();
628 if (ret) {
629 kfree(rng_fillbuf);
630 kfree(rng_buffer);
631 }
632
633 return ret;
634}
635
636static void __exit hwrng_modexit(void)
637{
638 mutex_lock(&rng_mutex);
639 BUG_ON(current_rng);
640 kfree(rng_buffer);
641 kfree(rng_fillbuf);
642 mutex_unlock(&rng_mutex);
643
644 unregister_miscdev();
645}
646
647module_init(hwrng_modinit);
648module_exit(hwrng_modexit);
649
650MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
651MODULE_LICENSE("GPL");