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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/miscdevice.h>
41#include <linux/kthread.h>
42#include <linux/delay.h>
43#include <linux/slab.h>
44#include <linux/random.h>
45#include <linux/err.h>
46#include <asm/uaccess.h>
47
48
49#define RNG_MODULE_NAME "hw_random"
50#define PFX RNG_MODULE_NAME ": "
51#define RNG_MISCDEV_MINOR 183
52
53
54static struct hwrng *current_rng;
55static struct task_struct *hwrng_fill;
56static LIST_HEAD(rng_list);
57
58static DEFINE_MUTEX(rng_mutex);
59
60static DEFINE_MUTEX(reading_mutex);
61static int data_avail;
62static u8 *rng_buffer, *rng_fillbuf;
63static unsigned short current_quality;
64static unsigned short default_quality;
65
66module_param(current_quality, ushort, 0644);
67MODULE_PARM_DESC(current_quality,
68 "current hwrng entropy estimation per mill");
69module_param(default_quality, ushort, 0644);
70MODULE_PARM_DESC(default_quality,
71 "default entropy content of hwrng per mill");
72
73static void drop_current_rng(void);
74static int hwrng_init(struct hwrng *rng);
75static void start_khwrngd(void);
76
77static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
78 int wait);
79
80static size_t rng_buffer_size(void)
81{
82 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
83}
84
85static void add_early_randomness(struct hwrng *rng)
86{
87 unsigned char bytes[16];
88 int bytes_read;
89
90 mutex_lock(&reading_mutex);
91 bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
92 mutex_unlock(&reading_mutex);
93 if (bytes_read > 0)
94 add_device_randomness(bytes, bytes_read);
95}
96
97static inline void cleanup_rng(struct kref *kref)
98{
99 struct hwrng *rng = container_of(kref, struct hwrng, ref);
100
101 if (rng->cleanup)
102 rng->cleanup(rng);
103
104 complete(&rng->cleanup_done);
105}
106
107static int set_current_rng(struct hwrng *rng)
108{
109 int err;
110
111 BUG_ON(!mutex_is_locked(&rng_mutex));
112
113 err = hwrng_init(rng);
114 if (err)
115 return err;
116
117 drop_current_rng();
118 current_rng = rng;
119
120 return 0;
121}
122
123static void drop_current_rng(void)
124{
125 BUG_ON(!mutex_is_locked(&rng_mutex));
126 if (!current_rng)
127 return;
128
129
130 kref_put(¤t_rng->ref, cleanup_rng);
131 current_rng = NULL;
132}
133
134
135static struct hwrng *get_current_rng(void)
136{
137 struct hwrng *rng;
138
139 if (mutex_lock_interruptible(&rng_mutex))
140 return ERR_PTR(-ERESTARTSYS);
141
142 rng = current_rng;
143 if (rng)
144 kref_get(&rng->ref);
145
146 mutex_unlock(&rng_mutex);
147 return rng;
148}
149
150static void put_rng(struct hwrng *rng)
151{
152
153
154
155
156 mutex_lock(&rng_mutex);
157 if (rng)
158 kref_put(&rng->ref, cleanup_rng);
159 mutex_unlock(&rng_mutex);
160}
161
162static int hwrng_init(struct hwrng *rng)
163{
164 if (kref_get_unless_zero(&rng->ref))
165 goto skip_init;
166
167 if (rng->init) {
168 int ret;
169
170 ret = rng->init(rng);
171 if (ret)
172 return ret;
173 }
174
175 kref_init(&rng->ref);
176 reinit_completion(&rng->cleanup_done);
177
178skip_init:
179 add_early_randomness(rng);
180
181 current_quality = rng->quality ? : default_quality;
182 if (current_quality > 1024)
183 current_quality = 1024;
184
185 if (current_quality == 0 && hwrng_fill)
186 kthread_stop(hwrng_fill);
187 if (current_quality > 0 && !hwrng_fill)
188 start_khwrngd();
189
190 return 0;
191}
192
193static int rng_dev_open(struct inode *inode, struct file *filp)
194{
195
196 if ((filp->f_mode & FMODE_READ) == 0)
197 return -EINVAL;
198 if (filp->f_mode & FMODE_WRITE)
199 return -EINVAL;
200 return 0;
201}
202
203static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
204 int wait) {
205 int present;
206
207 BUG_ON(!mutex_is_locked(&reading_mutex));
208 if (rng->read)
209 return rng->read(rng, (void *)buffer, size, wait);
210
211 if (rng->data_present)
212 present = rng->data_present(rng, wait);
213 else
214 present = 1;
215
216 if (present)
217 return rng->data_read(rng, (u32 *)buffer);
218
219 return 0;
220}
221
222static ssize_t rng_dev_read(struct file *filp, char __user *buf,
223 size_t size, loff_t *offp)
224{
225 ssize_t ret = 0;
226 int err = 0;
227 int bytes_read, len;
228 struct hwrng *rng;
229
230 while (size) {
231 rng = get_current_rng();
232 if (IS_ERR(rng)) {
233 err = PTR_ERR(rng);
234 goto out;
235 }
236 if (!rng) {
237 err = -ENODEV;
238 goto out;
239 }
240
241 mutex_lock(&reading_mutex);
242 if (!data_avail) {
243 bytes_read = rng_get_data(rng, rng_buffer,
244 rng_buffer_size(),
245 !(filp->f_flags & O_NONBLOCK));
246 if (bytes_read < 0) {
247 err = bytes_read;
248 goto out_unlock_reading;
249 }
250 data_avail = bytes_read;
251 }
252
253 if (!data_avail) {
254 if (filp->f_flags & O_NONBLOCK) {
255 err = -EAGAIN;
256 goto out_unlock_reading;
257 }
258 } else {
259 len = data_avail;
260 if (len > size)
261 len = size;
262
263 data_avail -= len;
264
265 if (copy_to_user(buf + ret, rng_buffer + data_avail,
266 len)) {
267 err = -EFAULT;
268 goto out_unlock_reading;
269 }
270
271 size -= len;
272 ret += len;
273 }
274
275 mutex_unlock(&reading_mutex);
276 put_rng(rng);
277
278 if (need_resched())
279 schedule_timeout_interruptible(1);
280
281 if (signal_pending(current)) {
282 err = -ERESTARTSYS;
283 goto out;
284 }
285 }
286out:
287 return ret ? : err;
288
289out_unlock_reading:
290 mutex_unlock(&reading_mutex);
291 put_rng(rng);
292 goto out;
293}
294
295
296static const struct file_operations rng_chrdev_ops = {
297 .owner = THIS_MODULE,
298 .open = rng_dev_open,
299 .read = rng_dev_read,
300 .llseek = noop_llseek,
301};
302
303static const struct attribute_group *rng_dev_groups[];
304
305static struct miscdevice rng_miscdev = {
306 .minor = RNG_MISCDEV_MINOR,
307 .name = RNG_MODULE_NAME,
308 .nodename = "hwrng",
309 .fops = &rng_chrdev_ops,
310 .groups = rng_dev_groups,
311};
312
313
314static ssize_t hwrng_attr_current_store(struct device *dev,
315 struct device_attribute *attr,
316 const char *buf, size_t len)
317{
318 int err;
319 struct hwrng *rng;
320
321 err = mutex_lock_interruptible(&rng_mutex);
322 if (err)
323 return -ERESTARTSYS;
324 err = -ENODEV;
325 list_for_each_entry(rng, &rng_list, list) {
326 if (strcmp(rng->name, buf) == 0) {
327 err = 0;
328 if (rng != current_rng)
329 err = set_current_rng(rng);
330 break;
331 }
332 }
333 mutex_unlock(&rng_mutex);
334
335 return err ? : len;
336}
337
338static ssize_t hwrng_attr_current_show(struct device *dev,
339 struct device_attribute *attr,
340 char *buf)
341{
342 ssize_t ret;
343 struct hwrng *rng;
344
345 rng = get_current_rng();
346 if (IS_ERR(rng))
347 return PTR_ERR(rng);
348
349 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
350 put_rng(rng);
351
352 return ret;
353}
354
355static ssize_t hwrng_attr_available_show(struct device *dev,
356 struct device_attribute *attr,
357 char *buf)
358{
359 int err;
360 struct hwrng *rng;
361
362 err = mutex_lock_interruptible(&rng_mutex);
363 if (err)
364 return -ERESTARTSYS;
365 buf[0] = '\0';
366 list_for_each_entry(rng, &rng_list, list) {
367 strlcat(buf, rng->name, PAGE_SIZE);
368 strlcat(buf, " ", PAGE_SIZE);
369 }
370 strlcat(buf, "\n", PAGE_SIZE);
371 mutex_unlock(&rng_mutex);
372
373 return strlen(buf);
374}
375
376static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
377 hwrng_attr_current_show,
378 hwrng_attr_current_store);
379static DEVICE_ATTR(rng_available, S_IRUGO,
380 hwrng_attr_available_show,
381 NULL);
382
383static struct attribute *rng_dev_attrs[] = {
384 &dev_attr_rng_current.attr,
385 &dev_attr_rng_available.attr,
386 NULL
387};
388
389ATTRIBUTE_GROUPS(rng_dev);
390
391static void __exit unregister_miscdev(void)
392{
393 misc_deregister(&rng_miscdev);
394}
395
396static int __init register_miscdev(void)
397{
398 return misc_register(&rng_miscdev);
399}
400
401static int hwrng_fillfn(void *unused)
402{
403 long rc;
404
405 while (!kthread_should_stop()) {
406 struct hwrng *rng;
407
408 rng = get_current_rng();
409 if (IS_ERR(rng) || !rng)
410 break;
411 mutex_lock(&reading_mutex);
412 rc = rng_get_data(rng, rng_fillbuf,
413 rng_buffer_size(), 1);
414 mutex_unlock(&reading_mutex);
415 put_rng(rng);
416 if (rc <= 0) {
417 pr_warn("hwrng: no data available\n");
418 msleep_interruptible(10000);
419 continue;
420 }
421
422 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
423 rc * current_quality * 8 >> 10);
424 }
425 hwrng_fill = NULL;
426 return 0;
427}
428
429static void start_khwrngd(void)
430{
431 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
432 if (hwrng_fill == ERR_PTR(-ENOMEM)) {
433 pr_err("hwrng_fill thread creation failed");
434 hwrng_fill = NULL;
435 }
436}
437
438int hwrng_register(struct hwrng *rng)
439{
440 int err = -EINVAL;
441 struct hwrng *old_rng, *tmp;
442
443 if (rng->name == NULL ||
444 (rng->data_read == NULL && rng->read == NULL))
445 goto out;
446
447 mutex_lock(&rng_mutex);
448
449
450 err = -ENOMEM;
451 if (!rng_buffer) {
452 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
453 if (!rng_buffer)
454 goto out_unlock;
455 }
456 if (!rng_fillbuf) {
457 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
458 if (!rng_fillbuf) {
459 kfree(rng_buffer);
460 goto out_unlock;
461 }
462 }
463
464
465 err = -EEXIST;
466 list_for_each_entry(tmp, &rng_list, list) {
467 if (strcmp(tmp->name, rng->name) == 0)
468 goto out_unlock;
469 }
470
471 init_completion(&rng->cleanup_done);
472 complete(&rng->cleanup_done);
473
474 old_rng = current_rng;
475 err = 0;
476 if (!old_rng) {
477 err = set_current_rng(rng);
478 if (err)
479 goto out_unlock;
480 }
481 list_add_tail(&rng->list, &rng_list);
482
483 if (old_rng && !rng->init) {
484
485
486
487
488
489
490
491 add_early_randomness(rng);
492 }
493
494out_unlock:
495 mutex_unlock(&rng_mutex);
496out:
497 return err;
498}
499EXPORT_SYMBOL_GPL(hwrng_register);
500
501void hwrng_unregister(struct hwrng *rng)
502{
503 mutex_lock(&rng_mutex);
504
505 list_del(&rng->list);
506 if (current_rng == rng) {
507 drop_current_rng();
508 if (!list_empty(&rng_list)) {
509 struct hwrng *tail;
510
511 tail = list_entry(rng_list.prev, struct hwrng, list);
512
513 set_current_rng(tail);
514 }
515 }
516
517 if (list_empty(&rng_list)) {
518 mutex_unlock(&rng_mutex);
519 if (hwrng_fill)
520 kthread_stop(hwrng_fill);
521 } else
522 mutex_unlock(&rng_mutex);
523
524 wait_for_completion(&rng->cleanup_done);
525}
526EXPORT_SYMBOL_GPL(hwrng_unregister);
527
528static void devm_hwrng_release(struct device *dev, void *res)
529{
530 hwrng_unregister(*(struct hwrng **)res);
531}
532
533static int devm_hwrng_match(struct device *dev, void *res, void *data)
534{
535 struct hwrng **r = res;
536
537 if (WARN_ON(!r || !*r))
538 return 0;
539
540 return *r == data;
541}
542
543int devm_hwrng_register(struct device *dev, struct hwrng *rng)
544{
545 struct hwrng **ptr;
546 int error;
547
548 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
549 if (!ptr)
550 return -ENOMEM;
551
552 error = hwrng_register(rng);
553 if (error) {
554 devres_free(ptr);
555 return error;
556 }
557
558 *ptr = rng;
559 devres_add(dev, ptr);
560 return 0;
561}
562EXPORT_SYMBOL_GPL(devm_hwrng_register);
563
564void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
565{
566 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
567}
568EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
569
570static int __init hwrng_modinit(void)
571{
572 return register_miscdev();
573}
574
575static void __exit hwrng_modexit(void)
576{
577 mutex_lock(&rng_mutex);
578 BUG_ON(current_rng);
579 kfree(rng_buffer);
580 kfree(rng_fillbuf);
581 mutex_unlock(&rng_mutex);
582
583 unregister_miscdev();
584}
585
586module_init(hwrng_modinit);
587module_exit(hwrng_modexit);
588
589MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
590MODULE_LICENSE("GPL");
591