This source file includes following definitions.
- rng_buffer_size
- add_early_randomness
- cleanup_rng
- set_current_rng
- drop_current_rng
- get_current_rng
- put_rng
- hwrng_init
- rng_dev_open
- rng_get_data
- rng_dev_read
- enable_best_rng
- hwrng_attr_current_store
- hwrng_attr_current_show
- hwrng_attr_available_show
- hwrng_attr_selected_show
- unregister_miscdev
- register_miscdev
- hwrng_fillfn
- start_khwrngd
- hwrng_register
- hwrng_unregister
- devm_hwrng_release
- devm_hwrng_match
- devm_hwrng_register
- devm_hwrng_unregister
- hwrng_modinit
- hwrng_modexit
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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
30 static struct hwrng *current_rng;
31
32 static int cur_rng_set_by_user;
33 static struct task_struct *hwrng_fill;
34
35 static LIST_HEAD(rng_list);
36
37 static DEFINE_MUTEX(rng_mutex);
38
39 static DEFINE_MUTEX(reading_mutex);
40 static int data_avail;
41 static u8 *rng_buffer, *rng_fillbuf;
42 static unsigned short current_quality;
43 static unsigned short default_quality;
44
45 module_param(current_quality, ushort, 0644);
46 MODULE_PARM_DESC(current_quality,
47 "current hwrng entropy estimation per 1024 bits of input");
48 module_param(default_quality, ushort, 0644);
49 MODULE_PARM_DESC(default_quality,
50 "default entropy content of hwrng per 1024 bits of input");
51
52 static void drop_current_rng(void);
53 static int hwrng_init(struct hwrng *rng);
54 static void start_khwrngd(void);
55
56 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
57 int wait);
58
59 static size_t rng_buffer_size(void)
60 {
61 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
62 }
63
64 static 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
76 static 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
86 static 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
102 static void drop_current_rng(void)
103 {
104 BUG_ON(!mutex_is_locked(&rng_mutex));
105 if (!current_rng)
106 return;
107
108
109 kref_put(¤t_rng->ref, cleanup_rng);
110 current_rng = NULL;
111 }
112
113
114 static 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
129 static void put_rng(struct hwrng *rng)
130 {
131
132
133
134
135 mutex_lock(&rng_mutex);
136 if (rng)
137 kref_put(&rng->ref, cleanup_rng);
138 mutex_unlock(&rng_mutex);
139 }
140
141 static 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
157 skip_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
172 static int rng_dev_open(struct inode *inode, struct file *filp)
173 {
174
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
182 static 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
201 static 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 }
268 out:
269 return ret ? : err;
270
271 out_unlock_reading:
272 mutex_unlock(&reading_mutex);
273 out_put:
274 put_rng(rng);
275 goto out;
276 }
277
278 static 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
285 static const struct attribute_group *rng_dev_groups[];
286
287 static 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
295 static int enable_best_rng(void)
296 {
297 int ret = -ENODEV;
298
299 BUG_ON(!mutex_is_locked(&rng_mutex));
300
301
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
318 static 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
346 static 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
363 static 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
384 static 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
391 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
392 hwrng_attr_current_show,
393 hwrng_attr_current_store);
394 static DEVICE_ATTR(rng_available, S_IRUGO,
395 hwrng_attr_available_show,
396 NULL);
397 static DEVICE_ATTR(rng_selected, S_IRUGO,
398 hwrng_attr_selected_show,
399 NULL);
400
401 static 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
408 ATTRIBUTE_GROUPS(rng_dev);
409
410 static void __exit unregister_miscdev(void)
411 {
412 misc_deregister(&rng_miscdev);
413 }
414
415 static int __init register_miscdev(void)
416 {
417 return misc_register(&rng_miscdev);
418 }
419
420 static 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
441 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
442 rc * current_quality * 8 >> 10);
443 }
444 hwrng_fill = NULL;
445 return 0;
446 }
447
448 static 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
457 int 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
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
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
491
492
493
494 err = set_current_rng(rng);
495 if (err)
496 goto out_unlock;
497 }
498
499 if (old_rng && !rng->init) {
500
501
502
503
504
505
506
507 add_early_randomness(rng);
508 }
509
510 out_unlock:
511 mutex_unlock(&rng_mutex);
512 out:
513 return err;
514 }
515 EXPORT_SYMBOL_GPL(hwrng_register);
516
517 void hwrng_unregister(struct hwrng *rng)
518 {
519 int err;
520
521 mutex_lock(&rng_mutex);
522
523 list_del(&rng->list);
524 if (current_rng == rng) {
525 err = enable_best_rng();
526 if (err) {
527 drop_current_rng();
528 cur_rng_set_by_user = 0;
529 }
530 }
531
532 if (list_empty(&rng_list)) {
533 mutex_unlock(&rng_mutex);
534 if (hwrng_fill)
535 kthread_stop(hwrng_fill);
536 } else
537 mutex_unlock(&rng_mutex);
538
539 wait_for_completion(&rng->cleanup_done);
540 }
541 EXPORT_SYMBOL_GPL(hwrng_unregister);
542
543 static void devm_hwrng_release(struct device *dev, void *res)
544 {
545 hwrng_unregister(*(struct hwrng **)res);
546 }
547
548 static int devm_hwrng_match(struct device *dev, void *res, void *data)
549 {
550 struct hwrng **r = res;
551
552 if (WARN_ON(!r || !*r))
553 return 0;
554
555 return *r == data;
556 }
557
558 int devm_hwrng_register(struct device *dev, struct hwrng *rng)
559 {
560 struct hwrng **ptr;
561 int error;
562
563 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
564 if (!ptr)
565 return -ENOMEM;
566
567 error = hwrng_register(rng);
568 if (error) {
569 devres_free(ptr);
570 return error;
571 }
572
573 *ptr = rng;
574 devres_add(dev, ptr);
575 return 0;
576 }
577 EXPORT_SYMBOL_GPL(devm_hwrng_register);
578
579 void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
580 {
581 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
582 }
583 EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
584
585 static int __init hwrng_modinit(void)
586 {
587 int ret = -ENOMEM;
588
589
590 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
591 if (!rng_buffer)
592 return -ENOMEM;
593
594 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
595 if (!rng_fillbuf) {
596 kfree(rng_buffer);
597 return -ENOMEM;
598 }
599
600 ret = register_miscdev();
601 if (ret) {
602 kfree(rng_fillbuf);
603 kfree(rng_buffer);
604 }
605
606 return ret;
607 }
608
609 static void __exit hwrng_modexit(void)
610 {
611 mutex_lock(&rng_mutex);
612 BUG_ON(current_rng);
613 kfree(rng_buffer);
614 kfree(rng_fillbuf);
615 mutex_unlock(&rng_mutex);
616
617 unregister_miscdev();
618 }
619
620 module_init(hwrng_modinit);
621 module_exit(hwrng_modexit);
622
623 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
624 MODULE_LICENSE("GPL");