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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(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 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}
541EXPORT_SYMBOL_GPL(hwrng_unregister);
542
543static void devm_hwrng_release(struct device *dev, void *res)
544{
545 hwrng_unregister(*(struct hwrng **)res);
546}
547
548static 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
558int 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}
577EXPORT_SYMBOL_GPL(devm_hwrng_register);
578
579void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
580{
581 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
582}
583EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
584
585static int __init hwrng_modinit(void)
586{
587 int ret = -ENOMEM;
588
589 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
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
609static 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
620module_init(hwrng_modinit);
621module_exit(hwrng_modexit);
622
623MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
624MODULE_LICENSE("GPL");