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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/miscdevice.h>
21#include <linux/module.h>
22#include <linux/random.h>
23#include <linux/sched.h>
24#include <linux/sched/signal.h>
25#include <linux/slab.h>
26#include <linux/string.h>
27#include <linux/uaccess.h>
28
29#define RNG_MODULE_NAME "hw_random"
30
31#define RNG_BUFFER_SIZE (SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES)
32
33static struct hwrng *current_rng;
34/* the current rng has been explicitly chosen by user via sysfs */
35static int cur_rng_set_by_user;
36static struct task_struct *hwrng_fill;
37/* list of registered rngs */
38static LIST_HEAD(rng_list);
39/* Protects rng_list and current_rng */
40static DEFINE_MUTEX(rng_mutex);
41/* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
42static DEFINE_MUTEX(reading_mutex);
43static int data_avail;
44static u8 *rng_buffer, *rng_fillbuf;
45static unsigned short current_quality;
46static unsigned short default_quality = 1024; /* default to maximum */
47
48module_param(current_quality, ushort, 0644);
49MODULE_PARM_DESC(current_quality,
50 "current hwrng entropy estimation per 1024 bits of input -- obsolete, use rng_quality instead");
51module_param(default_quality, ushort, 0644);
52MODULE_PARM_DESC(default_quality,
53 "default maximum entropy content of hwrng per 1024 bits of input");
54
55static void drop_current_rng(void);
56static int hwrng_init(struct hwrng *rng);
57static int hwrng_fillfn(void *unused);
58
59static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
60 int wait);
61
62static size_t rng_buffer_size(void)
63{
64 return RNG_BUFFER_SIZE;
65}
66
67static void add_early_randomness(struct hwrng *rng)
68{
69 int bytes_read;
70
71 mutex_lock(&reading_mutex);
72 bytes_read = rng_get_data(rng, rng_fillbuf, 32, 0);
73 mutex_unlock(&reading_mutex);
74 if (bytes_read > 0) {
75 size_t entropy = bytes_read * 8 * rng->quality / 1024;
76 add_hwgenerator_randomness(rng_fillbuf, bytes_read, entropy, false);
77 }
78}
79
80static inline void cleanup_rng(struct kref *kref)
81{
82 struct hwrng *rng = container_of(kref, struct hwrng, ref);
83
84 if (rng->cleanup)
85 rng->cleanup(rng);
86
87 complete(&rng->cleanup_done);
88}
89
90static int set_current_rng(struct hwrng *rng)
91{
92 int err;
93
94 BUG_ON(!mutex_is_locked(&rng_mutex));
95
96 err = hwrng_init(rng);
97 if (err)
98 return err;
99
100 drop_current_rng();
101 current_rng = rng;
102
103 /* if necessary, start hwrng thread */
104 if (!hwrng_fill) {
105 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
106 if (IS_ERR(hwrng_fill)) {
107 pr_err("hwrng_fill thread creation failed\n");
108 hwrng_fill = NULL;
109 }
110 }
111
112 return 0;
113}
114
115static void drop_current_rng(void)
116{
117 BUG_ON(!mutex_is_locked(&rng_mutex));
118 if (!current_rng)
119 return;
120
121 /* decrease last reference for triggering the cleanup */
122 kref_put(¤t_rng->ref, cleanup_rng);
123 current_rng = NULL;
124}
125
126/* Returns ERR_PTR(), NULL or refcounted hwrng */
127static struct hwrng *get_current_rng_nolock(void)
128{
129 if (current_rng)
130 kref_get(¤t_rng->ref);
131
132 return current_rng;
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 = get_current_rng_nolock();
143
144 mutex_unlock(&rng_mutex);
145 return rng;
146}
147
148static void put_rng(struct hwrng *rng)
149{
150 /*
151 * Hold rng_mutex here so we serialize in case they set_current_rng
152 * on rng again immediately.
153 */
154 mutex_lock(&rng_mutex);
155 if (rng)
156 kref_put(&rng->ref, cleanup_rng);
157 mutex_unlock(&rng_mutex);
158}
159
160static int hwrng_init(struct hwrng *rng)
161{
162 if (kref_get_unless_zero(&rng->ref))
163 goto skip_init;
164
165 if (rng->init) {
166 int ret;
167
168 ret = rng->init(rng);
169 if (ret)
170 return ret;
171 }
172
173 kref_init(&rng->ref);
174 reinit_completion(&rng->cleanup_done);
175
176skip_init:
177 rng->quality = min_t(u16, min_t(u16, default_quality, 1024), rng->quality ?: 1024);
178 current_quality = rng->quality; /* obsolete */
179
180 return 0;
181}
182
183static int rng_dev_open(struct inode *inode, struct file *filp)
184{
185 /* enforce read-only access to this chrdev */
186 if ((filp->f_mode & FMODE_READ) == 0)
187 return -EINVAL;
188 if (filp->f_mode & FMODE_WRITE)
189 return -EINVAL;
190 return 0;
191}
192
193static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
194 int wait) {
195 int present;
196
197 BUG_ON(!mutex_is_locked(&reading_mutex));
198 if (rng->read)
199 return rng->read(rng, (void *)buffer, size, wait);
200
201 if (rng->data_present)
202 present = rng->data_present(rng, wait);
203 else
204 present = 1;
205
206 if (present)
207 return rng->data_read(rng, (u32 *)buffer);
208
209 return 0;
210}
211
212static ssize_t rng_dev_read(struct file *filp, char __user *buf,
213 size_t size, loff_t *offp)
214{
215 u8 buffer[RNG_BUFFER_SIZE];
216 ssize_t ret = 0;
217 int err = 0;
218 int bytes_read, len;
219 struct hwrng *rng;
220
221 while (size) {
222 rng = get_current_rng();
223 if (IS_ERR(rng)) {
224 err = PTR_ERR(rng);
225 goto out;
226 }
227 if (!rng) {
228 err = -ENODEV;
229 goto out;
230 }
231
232 if (mutex_lock_interruptible(&reading_mutex)) {
233 err = -ERESTARTSYS;
234 goto out_put;
235 }
236 if (!data_avail) {
237 bytes_read = rng_get_data(rng, rng_buffer,
238 rng_buffer_size(),
239 !(filp->f_flags & O_NONBLOCK));
240 if (bytes_read < 0) {
241 err = bytes_read;
242 goto out_unlock_reading;
243 } else if (bytes_read == 0 &&
244 (filp->f_flags & O_NONBLOCK)) {
245 err = -EAGAIN;
246 goto out_unlock_reading;
247 }
248
249 data_avail = bytes_read;
250 }
251
252 len = data_avail;
253 if (len) {
254 if (len > size)
255 len = size;
256
257 data_avail -= len;
258
259 memcpy(buffer, rng_buffer + data_avail, len);
260 }
261 mutex_unlock(&reading_mutex);
262 put_rng(rng);
263
264 if (len) {
265 if (copy_to_user(buf + ret, buffer, len)) {
266 err = -EFAULT;
267 goto out;
268 }
269
270 size -= len;
271 ret += len;
272 }
273
274
275 if (need_resched())
276 schedule_timeout_interruptible(1);
277
278 if (signal_pending(current)) {
279 err = -ERESTARTSYS;
280 goto out;
281 }
282 }
283out:
284 memzero_explicit(buffer, sizeof(buffer));
285 return ret ? : err;
286
287out_unlock_reading:
288 mutex_unlock(&reading_mutex);
289out_put:
290 put_rng(rng);
291 goto out;
292}
293
294static const struct file_operations rng_chrdev_ops = {
295 .owner = THIS_MODULE,
296 .open = rng_dev_open,
297 .read = rng_dev_read,
298 .llseek = noop_llseek,
299};
300
301static const struct attribute_group *rng_dev_groups[];
302
303static struct miscdevice rng_miscdev = {
304 .minor = HWRNG_MINOR,
305 .name = RNG_MODULE_NAME,
306 .nodename = "hwrng",
307 .fops = &rng_chrdev_ops,
308 .groups = rng_dev_groups,
309};
310
311static int enable_best_rng(void)
312{
313 struct hwrng *rng, *new_rng = NULL;
314 int ret = -ENODEV;
315
316 BUG_ON(!mutex_is_locked(&rng_mutex));
317
318 /* no rng to use? */
319 if (list_empty(&rng_list)) {
320 drop_current_rng();
321 cur_rng_set_by_user = 0;
322 return 0;
323 }
324
325 /* use the rng which offers the best quality */
326 list_for_each_entry(rng, &rng_list, list) {
327 if (!new_rng || rng->quality > new_rng->quality)
328 new_rng = rng;
329 }
330
331 ret = ((new_rng == current_rng) ? 0 : set_current_rng(new_rng));
332 if (!ret)
333 cur_rng_set_by_user = 0;
334
335 return ret;
336}
337
338static ssize_t rng_current_store(struct device *dev,
339 struct device_attribute *attr,
340 const char *buf, size_t len)
341{
342 int err;
343 struct hwrng *rng, *old_rng, *new_rng;
344
345 err = mutex_lock_interruptible(&rng_mutex);
346 if (err)
347 return -ERESTARTSYS;
348
349 old_rng = current_rng;
350 if (sysfs_streq(buf, "")) {
351 err = enable_best_rng();
352 } else {
353 list_for_each_entry(rng, &rng_list, list) {
354 if (sysfs_streq(rng->name, buf)) {
355 err = set_current_rng(rng);
356 if (!err)
357 cur_rng_set_by_user = 1;
358 break;
359 }
360 }
361 }
362 new_rng = get_current_rng_nolock();
363 mutex_unlock(&rng_mutex);
364
365 if (new_rng) {
366 if (new_rng != old_rng)
367 add_early_randomness(new_rng);
368 put_rng(new_rng);
369 }
370
371 return err ? : len;
372}
373
374static ssize_t rng_current_show(struct device *dev,
375 struct device_attribute *attr,
376 char *buf)
377{
378 ssize_t ret;
379 struct hwrng *rng;
380
381 rng = get_current_rng();
382 if (IS_ERR(rng))
383 return PTR_ERR(rng);
384
385 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
386 put_rng(rng);
387
388 return ret;
389}
390
391static ssize_t rng_available_show(struct device *dev,
392 struct device_attribute *attr,
393 char *buf)
394{
395 int err;
396 struct hwrng *rng;
397
398 err = mutex_lock_interruptible(&rng_mutex);
399 if (err)
400 return -ERESTARTSYS;
401 buf[0] = '\0';
402 list_for_each_entry(rng, &rng_list, list) {
403 strlcat(buf, rng->name, PAGE_SIZE);
404 strlcat(buf, " ", PAGE_SIZE);
405 }
406 strlcat(buf, "\n", PAGE_SIZE);
407 mutex_unlock(&rng_mutex);
408
409 return strlen(buf);
410}
411
412static ssize_t rng_selected_show(struct device *dev,
413 struct device_attribute *attr,
414 char *buf)
415{
416 return sysfs_emit(buf, "%d\n", cur_rng_set_by_user);
417}
418
419static ssize_t rng_quality_show(struct device *dev,
420 struct device_attribute *attr,
421 char *buf)
422{
423 ssize_t ret;
424 struct hwrng *rng;
425
426 rng = get_current_rng();
427 if (IS_ERR(rng))
428 return PTR_ERR(rng);
429
430 if (!rng) /* no need to put_rng */
431 return -ENODEV;
432
433 ret = sysfs_emit(buf, "%hu\n", rng->quality);
434 put_rng(rng);
435
436 return ret;
437}
438
439static ssize_t rng_quality_store(struct device *dev,
440 struct device_attribute *attr,
441 const char *buf, size_t len)
442{
443 u16 quality;
444 int ret = -EINVAL;
445
446 if (len < 2)
447 return -EINVAL;
448
449 ret = mutex_lock_interruptible(&rng_mutex);
450 if (ret)
451 return -ERESTARTSYS;
452
453 ret = kstrtou16(buf, 0, &quality);
454 if (ret || quality > 1024) {
455 ret = -EINVAL;
456 goto out;
457 }
458
459 if (!current_rng) {
460 ret = -ENODEV;
461 goto out;
462 }
463
464 current_rng->quality = quality;
465 current_quality = quality; /* obsolete */
466
467 /* the best available RNG may have changed */
468 ret = enable_best_rng();
469
470out:
471 mutex_unlock(&rng_mutex);
472 return ret ? ret : len;
473}
474
475static DEVICE_ATTR_RW(rng_current);
476static DEVICE_ATTR_RO(rng_available);
477static DEVICE_ATTR_RO(rng_selected);
478static DEVICE_ATTR_RW(rng_quality);
479
480static struct attribute *rng_dev_attrs[] = {
481 &dev_attr_rng_current.attr,
482 &dev_attr_rng_available.attr,
483 &dev_attr_rng_selected.attr,
484 &dev_attr_rng_quality.attr,
485 NULL
486};
487
488ATTRIBUTE_GROUPS(rng_dev);
489
490static void __exit unregister_miscdev(void)
491{
492 misc_deregister(&rng_miscdev);
493}
494
495static int __init register_miscdev(void)
496{
497 return misc_register(&rng_miscdev);
498}
499
500static int hwrng_fillfn(void *unused)
501{
502 size_t entropy, entropy_credit = 0; /* in 1/1024 of a bit */
503 long rc;
504
505 while (!kthread_should_stop()) {
506 unsigned short quality;
507 struct hwrng *rng;
508
509 rng = get_current_rng();
510 if (IS_ERR(rng) || !rng)
511 break;
512 mutex_lock(&reading_mutex);
513 rc = rng_get_data(rng, rng_fillbuf,
514 rng_buffer_size(), 1);
515 if (current_quality != rng->quality)
516 rng->quality = current_quality; /* obsolete */
517 quality = rng->quality;
518 mutex_unlock(&reading_mutex);
519
520 if (rc <= 0)
521 hwrng_msleep(rng, 10000);
522
523 put_rng(rng);
524
525 if (rc <= 0)
526 continue;
527
528 /* If we cannot credit at least one bit of entropy,
529 * keep track of the remainder for the next iteration
530 */
531 entropy = rc * quality * 8 + entropy_credit;
532 if ((entropy >> 10) == 0)
533 entropy_credit = entropy;
534
535 /* Outside lock, sure, but y'know: randomness. */
536 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
537 entropy >> 10, true);
538 }
539 hwrng_fill = NULL;
540 return 0;
541}
542
543int hwrng_register(struct hwrng *rng)
544{
545 int err = -EINVAL;
546 struct hwrng *tmp;
547 bool is_new_current = false;
548
549 if (!rng->name || (!rng->data_read && !rng->read))
550 goto out;
551
552 mutex_lock(&rng_mutex);
553
554 /* Must not register two RNGs with the same name. */
555 err = -EEXIST;
556 list_for_each_entry(tmp, &rng_list, list) {
557 if (strcmp(tmp->name, rng->name) == 0)
558 goto out_unlock;
559 }
560 list_add_tail(&rng->list, &rng_list);
561
562 init_completion(&rng->cleanup_done);
563 complete(&rng->cleanup_done);
564 init_completion(&rng->dying);
565
566 if (!current_rng ||
567 (!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
568 /*
569 * Set new rng as current as the new rng source
570 * provides better entropy quality and was not
571 * chosen by userspace.
572 */
573 err = set_current_rng(rng);
574 if (err)
575 goto out_unlock;
576 /* to use current_rng in add_early_randomness() we need
577 * to take a ref
578 */
579 is_new_current = true;
580 kref_get(&rng->ref);
581 }
582 mutex_unlock(&rng_mutex);
583 if (is_new_current || !rng->init) {
584 /*
585 * Use a new device's input to add some randomness to
586 * the system. If this rng device isn't going to be
587 * used right away, its init function hasn't been
588 * called yet by set_current_rng(); so only use the
589 * randomness from devices that don't need an init callback
590 */
591 add_early_randomness(rng);
592 }
593 if (is_new_current)
594 put_rng(rng);
595 return 0;
596out_unlock:
597 mutex_unlock(&rng_mutex);
598out:
599 return err;
600}
601EXPORT_SYMBOL_GPL(hwrng_register);
602
603void hwrng_unregister(struct hwrng *rng)
604{
605 struct hwrng *old_rng, *new_rng;
606 int err;
607
608 mutex_lock(&rng_mutex);
609
610 old_rng = current_rng;
611 list_del(&rng->list);
612 complete_all(&rng->dying);
613 if (current_rng == rng) {
614 err = enable_best_rng();
615 if (err) {
616 drop_current_rng();
617 cur_rng_set_by_user = 0;
618 }
619 }
620
621 new_rng = get_current_rng_nolock();
622 if (list_empty(&rng_list)) {
623 mutex_unlock(&rng_mutex);
624 if (hwrng_fill)
625 kthread_stop(hwrng_fill);
626 } else
627 mutex_unlock(&rng_mutex);
628
629 if (new_rng) {
630 if (old_rng != new_rng)
631 add_early_randomness(new_rng);
632 put_rng(new_rng);
633 }
634
635 wait_for_completion(&rng->cleanup_done);
636}
637EXPORT_SYMBOL_GPL(hwrng_unregister);
638
639static void devm_hwrng_release(struct device *dev, void *res)
640{
641 hwrng_unregister(*(struct hwrng **)res);
642}
643
644static int devm_hwrng_match(struct device *dev, void *res, void *data)
645{
646 struct hwrng **r = res;
647
648 if (WARN_ON(!r || !*r))
649 return 0;
650
651 return *r == data;
652}
653
654int devm_hwrng_register(struct device *dev, struct hwrng *rng)
655{
656 struct hwrng **ptr;
657 int error;
658
659 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
660 if (!ptr)
661 return -ENOMEM;
662
663 error = hwrng_register(rng);
664 if (error) {
665 devres_free(ptr);
666 return error;
667 }
668
669 *ptr = rng;
670 devres_add(dev, ptr);
671 return 0;
672}
673EXPORT_SYMBOL_GPL(devm_hwrng_register);
674
675void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
676{
677 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
678}
679EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
680
681long hwrng_msleep(struct hwrng *rng, unsigned int msecs)
682{
683 unsigned long timeout = msecs_to_jiffies(msecs) + 1;
684
685 return wait_for_completion_interruptible_timeout(&rng->dying, timeout);
686}
687EXPORT_SYMBOL_GPL(hwrng_msleep);
688
689long hwrng_yield(struct hwrng *rng)
690{
691 return wait_for_completion_interruptible_timeout(&rng->dying, 1);
692}
693EXPORT_SYMBOL_GPL(hwrng_yield);
694
695static int __init hwrng_modinit(void)
696{
697 int ret;
698
699 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
700 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
701 if (!rng_buffer)
702 return -ENOMEM;
703
704 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
705 if (!rng_fillbuf) {
706 kfree(rng_buffer);
707 return -ENOMEM;
708 }
709
710 ret = register_miscdev();
711 if (ret) {
712 kfree(rng_fillbuf);
713 kfree(rng_buffer);
714 }
715
716 return ret;
717}
718
719static void __exit hwrng_modexit(void)
720{
721 mutex_lock(&rng_mutex);
722 BUG_ON(current_rng);
723 kfree(rng_buffer);
724 kfree(rng_fillbuf);
725 mutex_unlock(&rng_mutex);
726
727 unregister_miscdev();
728}
729
730fs_initcall(hwrng_modinit); /* depends on misc_register() */
731module_exit(hwrng_modexit);
732
733MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
734MODULE_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 rng_current_store(struct device *dev,
323 struct device_attribute *attr,
324 const char *buf, size_t len)
325{
326 int err;
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 rng_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 rng_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 rng_selected_show(struct device *dev,
396 struct device_attribute *attr,
397 char *buf)
398{
399 return sysfs_emit(buf, "%d\n", cur_rng_set_by_user);
400}
401
402static DEVICE_ATTR_RW(rng_current);
403static DEVICE_ATTR_RO(rng_available);
404static DEVICE_ATTR_RO(rng_selected);
405
406static struct attribute *rng_dev_attrs[] = {
407 &dev_attr_rng_current.attr,
408 &dev_attr_rng_available.attr,
409 &dev_attr_rng_selected.attr,
410 NULL
411};
412
413ATTRIBUTE_GROUPS(rng_dev);
414
415static void __exit unregister_miscdev(void)
416{
417 misc_deregister(&rng_miscdev);
418}
419
420static int __init register_miscdev(void)
421{
422 return misc_register(&rng_miscdev);
423}
424
425static int hwrng_fillfn(void *unused)
426{
427 long rc;
428
429 while (!kthread_should_stop()) {
430 struct hwrng *rng;
431
432 rng = get_current_rng();
433 if (IS_ERR(rng) || !rng)
434 break;
435 mutex_lock(&reading_mutex);
436 rc = rng_get_data(rng, rng_fillbuf,
437 rng_buffer_size(), 1);
438 mutex_unlock(&reading_mutex);
439 put_rng(rng);
440 if (rc <= 0) {
441 pr_warn("hwrng: no data available\n");
442 msleep_interruptible(10000);
443 continue;
444 }
445 /* Outside lock, sure, but y'know: randomness. */
446 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
447 rc * current_quality * 8 >> 10);
448 }
449 hwrng_fill = NULL;
450 return 0;
451}
452
453static void start_khwrngd(void)
454{
455 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
456 if (IS_ERR(hwrng_fill)) {
457 pr_err("hwrng_fill thread creation failed\n");
458 hwrng_fill = NULL;
459 }
460}
461
462int hwrng_register(struct hwrng *rng)
463{
464 int err = -EINVAL;
465 struct hwrng *tmp;
466 struct list_head *rng_list_ptr;
467 bool is_new_current = false;
468
469 if (!rng->name || (!rng->data_read && !rng->read))
470 goto out;
471
472 mutex_lock(&rng_mutex);
473
474 /* Must not register two RNGs with the same name. */
475 err = -EEXIST;
476 list_for_each_entry(tmp, &rng_list, list) {
477 if (strcmp(tmp->name, rng->name) == 0)
478 goto out_unlock;
479 }
480
481 init_completion(&rng->cleanup_done);
482 complete(&rng->cleanup_done);
483
484 /* rng_list is sorted by decreasing quality */
485 list_for_each(rng_list_ptr, &rng_list) {
486 tmp = list_entry(rng_list_ptr, struct hwrng, list);
487 if (tmp->quality < rng->quality)
488 break;
489 }
490 list_add_tail(&rng->list, rng_list_ptr);
491
492 if (!current_rng ||
493 (!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
494 /*
495 * Set new rng as current as the new rng source
496 * provides better entropy quality and was not
497 * chosen by userspace.
498 */
499 err = set_current_rng(rng);
500 if (err)
501 goto out_unlock;
502 /* to use current_rng in add_early_randomness() we need
503 * to take a ref
504 */
505 is_new_current = true;
506 kref_get(&rng->ref);
507 }
508 mutex_unlock(&rng_mutex);
509 if (is_new_current || !rng->init) {
510 /*
511 * Use a new device's input to add some randomness to
512 * the system. If this rng device isn't going to be
513 * used right away, its init function hasn't been
514 * called yet by set_current_rng(); so only use the
515 * randomness from devices that don't need an init callback
516 */
517 add_early_randomness(rng);
518 }
519 if (is_new_current)
520 put_rng(rng);
521 return 0;
522out_unlock:
523 mutex_unlock(&rng_mutex);
524out:
525 return err;
526}
527EXPORT_SYMBOL_GPL(hwrng_register);
528
529void hwrng_unregister(struct hwrng *rng)
530{
531 struct hwrng *old_rng, *new_rng;
532 int err;
533
534 mutex_lock(&rng_mutex);
535
536 old_rng = current_rng;
537 list_del(&rng->list);
538 if (current_rng == rng) {
539 err = enable_best_rng();
540 if (err) {
541 drop_current_rng();
542 cur_rng_set_by_user = 0;
543 }
544 }
545
546 new_rng = get_current_rng_nolock();
547 if (list_empty(&rng_list)) {
548 mutex_unlock(&rng_mutex);
549 if (hwrng_fill)
550 kthread_stop(hwrng_fill);
551 } else
552 mutex_unlock(&rng_mutex);
553
554 if (new_rng) {
555 if (old_rng != new_rng)
556 add_early_randomness(new_rng);
557 put_rng(new_rng);
558 }
559
560 wait_for_completion(&rng->cleanup_done);
561}
562EXPORT_SYMBOL_GPL(hwrng_unregister);
563
564static void devm_hwrng_release(struct device *dev, void *res)
565{
566 hwrng_unregister(*(struct hwrng **)res);
567}
568
569static int devm_hwrng_match(struct device *dev, void *res, void *data)
570{
571 struct hwrng **r = res;
572
573 if (WARN_ON(!r || !*r))
574 return 0;
575
576 return *r == data;
577}
578
579int devm_hwrng_register(struct device *dev, struct hwrng *rng)
580{
581 struct hwrng **ptr;
582 int error;
583
584 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
585 if (!ptr)
586 return -ENOMEM;
587
588 error = hwrng_register(rng);
589 if (error) {
590 devres_free(ptr);
591 return error;
592 }
593
594 *ptr = rng;
595 devres_add(dev, ptr);
596 return 0;
597}
598EXPORT_SYMBOL_GPL(devm_hwrng_register);
599
600void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
601{
602 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
603}
604EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
605
606static int __init hwrng_modinit(void)
607{
608 int ret;
609
610 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
611 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
612 if (!rng_buffer)
613 return -ENOMEM;
614
615 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
616 if (!rng_fillbuf) {
617 kfree(rng_buffer);
618 return -ENOMEM;
619 }
620
621 ret = register_miscdev();
622 if (ret) {
623 kfree(rng_fillbuf);
624 kfree(rng_buffer);
625 }
626
627 return ret;
628}
629
630static void __exit hwrng_modexit(void)
631{
632 mutex_lock(&rng_mutex);
633 BUG_ON(current_rng);
634 kfree(rng_buffer);
635 kfree(rng_fillbuf);
636 mutex_unlock(&rng_mutex);
637
638 unregister_miscdev();
639}
640
641module_init(hwrng_modinit);
642module_exit(hwrng_modexit);
643
644MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
645MODULE_LICENSE("GPL");