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/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 /* official */
52
53
54 static struct hwrng *current_rng;
55 static struct task_struct *hwrng_fill;
56 static LIST_HEAD(rng_list);
57 /* Protects rng_list and current_rng */
58 static DEFINE_MUTEX(rng_mutex);
59 /* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
60 static DEFINE_MUTEX(reading_mutex);
61 static int data_avail;
62 static u8 *rng_buffer, *rng_fillbuf;
63 static unsigned short current_quality;
64 static unsigned short default_quality; /* = 0; default to "off" */
65
66 module_param(current_quality, ushort, 0644);
67 MODULE_PARM_DESC(current_quality,
68 "current hwrng entropy estimation per mill");
69 module_param(default_quality, ushort, 0644);
70 MODULE_PARM_DESC(default_quality,
71 "default entropy content of hwrng per mill");
72
73 static void drop_current_rng(void);
74 static int hwrng_init(struct hwrng *rng);
75 static void start_khwrngd(void);
76
77 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
78 int wait);
79
rng_buffer_size(void)80 static size_t rng_buffer_size(void)
81 {
82 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
83 }
84
add_early_randomness(struct hwrng * rng)85 static void add_early_randomness(struct hwrng *rng)
86 {
87 int bytes_read;
88 size_t size = min_t(size_t, 16, rng_buffer_size());
89
90 mutex_lock(&reading_mutex);
91 bytes_read = rng_get_data(rng, rng_buffer, size, 1);
92 mutex_unlock(&reading_mutex);
93 if (bytes_read > 0)
94 add_device_randomness(rng_buffer, bytes_read);
95 }
96
cleanup_rng(struct kref * kref)97 static 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
set_current_rng(struct hwrng * rng)107 static 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
drop_current_rng(void)123 static void drop_current_rng(void)
124 {
125 BUG_ON(!mutex_is_locked(&rng_mutex));
126 if (!current_rng)
127 return;
128
129 /* decrease last reference for triggering the cleanup */
130 kref_put(¤t_rng->ref, cleanup_rng);
131 current_rng = NULL;
132 }
133
134 /* Returns ERR_PTR(), NULL or refcounted hwrng */
get_current_rng(void)135 static 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
put_rng(struct hwrng * rng)150 static void put_rng(struct hwrng *rng)
151 {
152 /*
153 * Hold rng_mutex here so we serialize in case they set_current_rng
154 * on rng again immediately.
155 */
156 mutex_lock(&rng_mutex);
157 if (rng)
158 kref_put(&rng->ref, cleanup_rng);
159 mutex_unlock(&rng_mutex);
160 }
161
hwrng_init(struct hwrng * rng)162 static 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
178 skip_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
rng_dev_open(struct inode * inode,struct file * filp)193 static int rng_dev_open(struct inode *inode, struct file *filp)
194 {
195 /* enforce read-only access to this chrdev */
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
rng_get_data(struct hwrng * rng,u8 * buffer,size_t size,int wait)203 static 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
rng_dev_read(struct file * filp,char __user * buf,size_t size,loff_t * offp)222 static 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 if (mutex_lock_interruptible(&reading_mutex)) {
242 err = -ERESTARTSYS;
243 goto out_put;
244 }
245 if (!data_avail) {
246 bytes_read = rng_get_data(rng, rng_buffer,
247 rng_buffer_size(),
248 !(filp->f_flags & O_NONBLOCK));
249 if (bytes_read < 0) {
250 err = bytes_read;
251 goto out_unlock_reading;
252 }
253 data_avail = bytes_read;
254 }
255
256 if (!data_avail) {
257 if (filp->f_flags & O_NONBLOCK) {
258 err = -EAGAIN;
259 goto out_unlock_reading;
260 }
261 } else {
262 len = data_avail;
263 if (len > size)
264 len = size;
265
266 data_avail -= len;
267
268 if (copy_to_user(buf + ret, rng_buffer + data_avail,
269 len)) {
270 err = -EFAULT;
271 goto out_unlock_reading;
272 }
273
274 size -= len;
275 ret += len;
276 }
277
278 mutex_unlock(&reading_mutex);
279 put_rng(rng);
280
281 if (need_resched())
282 schedule_timeout_interruptible(1);
283
284 if (signal_pending(current)) {
285 err = -ERESTARTSYS;
286 goto out;
287 }
288 }
289 out:
290 return ret ? : err;
291
292 out_unlock_reading:
293 mutex_unlock(&reading_mutex);
294 out_put:
295 put_rng(rng);
296 goto out;
297 }
298
299
300 static const struct file_operations rng_chrdev_ops = {
301 .owner = THIS_MODULE,
302 .open = rng_dev_open,
303 .read = rng_dev_read,
304 .llseek = noop_llseek,
305 };
306
307 static const struct attribute_group *rng_dev_groups[];
308
309 static struct miscdevice rng_miscdev = {
310 .minor = RNG_MISCDEV_MINOR,
311 .name = RNG_MODULE_NAME,
312 .nodename = "hwrng",
313 .fops = &rng_chrdev_ops,
314 .groups = rng_dev_groups,
315 };
316
317
hwrng_attr_current_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t len)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;
323 struct hwrng *rng;
324
325 err = mutex_lock_interruptible(&rng_mutex);
326 if (err)
327 return -ERESTARTSYS;
328 err = -ENODEV;
329 list_for_each_entry(rng, &rng_list, list) {
330 if (sysfs_streq(rng->name, buf)) {
331 err = 0;
332 if (rng != current_rng)
333 err = set_current_rng(rng);
334 break;
335 }
336 }
337 mutex_unlock(&rng_mutex);
338
339 return err ? : len;
340 }
341
hwrng_attr_current_show(struct device * dev,struct device_attribute * attr,char * buf)342 static ssize_t hwrng_attr_current_show(struct device *dev,
343 struct device_attribute *attr,
344 char *buf)
345 {
346 ssize_t ret;
347 struct hwrng *rng;
348
349 rng = get_current_rng();
350 if (IS_ERR(rng))
351 return PTR_ERR(rng);
352
353 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
354 put_rng(rng);
355
356 return ret;
357 }
358
hwrng_attr_available_show(struct device * dev,struct device_attribute * attr,char * buf)359 static ssize_t hwrng_attr_available_show(struct device *dev,
360 struct device_attribute *attr,
361 char *buf)
362 {
363 int err;
364 struct hwrng *rng;
365
366 err = mutex_lock_interruptible(&rng_mutex);
367 if (err)
368 return -ERESTARTSYS;
369 buf[0] = '\0';
370 list_for_each_entry(rng, &rng_list, list) {
371 strlcat(buf, rng->name, PAGE_SIZE);
372 strlcat(buf, " ", PAGE_SIZE);
373 }
374 strlcat(buf, "\n", PAGE_SIZE);
375 mutex_unlock(&rng_mutex);
376
377 return strlen(buf);
378 }
379
380 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
381 hwrng_attr_current_show,
382 hwrng_attr_current_store);
383 static DEVICE_ATTR(rng_available, S_IRUGO,
384 hwrng_attr_available_show,
385 NULL);
386
387 static struct attribute *rng_dev_attrs[] = {
388 &dev_attr_rng_current.attr,
389 &dev_attr_rng_available.attr,
390 NULL
391 };
392
393 ATTRIBUTE_GROUPS(rng_dev);
394
unregister_miscdev(void)395 static void __exit unregister_miscdev(void)
396 {
397 misc_deregister(&rng_miscdev);
398 }
399
register_miscdev(void)400 static int __init register_miscdev(void)
401 {
402 return misc_register(&rng_miscdev);
403 }
404
hwrng_fillfn(void * unused)405 static int hwrng_fillfn(void *unused)
406 {
407 long rc;
408
409 while (!kthread_should_stop()) {
410 struct hwrng *rng;
411
412 rng = get_current_rng();
413 if (IS_ERR(rng) || !rng)
414 break;
415 mutex_lock(&reading_mutex);
416 rc = rng_get_data(rng, rng_fillbuf,
417 rng_buffer_size(), 1);
418 mutex_unlock(&reading_mutex);
419 put_rng(rng);
420 if (rc <= 0) {
421 pr_warn("hwrng: no data available\n");
422 msleep_interruptible(10000);
423 continue;
424 }
425 /* Outside lock, sure, but y'know: randomness. */
426 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
427 rc * current_quality * 8 >> 10);
428 }
429 hwrng_fill = NULL;
430 return 0;
431 }
432
start_khwrngd(void)433 static void start_khwrngd(void)
434 {
435 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
436 if (IS_ERR(hwrng_fill)) {
437 pr_err("hwrng_fill thread creation failed");
438 hwrng_fill = NULL;
439 }
440 }
441
hwrng_register(struct hwrng * rng)442 int hwrng_register(struct hwrng *rng)
443 {
444 int err = -EINVAL;
445 struct hwrng *old_rng, *tmp;
446
447 if (rng->name == NULL ||
448 (rng->data_read == NULL && rng->read == NULL))
449 goto out;
450
451 mutex_lock(&rng_mutex);
452 /* Must not register two RNGs with the same name. */
453 err = -EEXIST;
454 list_for_each_entry(tmp, &rng_list, list) {
455 if (strcmp(tmp->name, rng->name) == 0)
456 goto out_unlock;
457 }
458
459 init_completion(&rng->cleanup_done);
460 complete(&rng->cleanup_done);
461
462 old_rng = current_rng;
463 err = 0;
464 if (!old_rng) {
465 err = set_current_rng(rng);
466 if (err)
467 goto out_unlock;
468 }
469 list_add_tail(&rng->list, &rng_list);
470
471 if (old_rng && !rng->init) {
472 /*
473 * Use a new device's input to add some randomness to
474 * the system. If this rng device isn't going to be
475 * used right away, its init function hasn't been
476 * called yet; so only use the randomness from devices
477 * that don't need an init callback.
478 */
479 add_early_randomness(rng);
480 }
481
482 out_unlock:
483 mutex_unlock(&rng_mutex);
484 out:
485 return err;
486 }
487 EXPORT_SYMBOL_GPL(hwrng_register);
488
hwrng_unregister(struct hwrng * rng)489 void hwrng_unregister(struct hwrng *rng)
490 {
491 mutex_lock(&rng_mutex);
492
493 list_del(&rng->list);
494 if (current_rng == rng) {
495 drop_current_rng();
496 if (!list_empty(&rng_list)) {
497 struct hwrng *tail;
498
499 tail = list_entry(rng_list.prev, struct hwrng, list);
500
501 set_current_rng(tail);
502 }
503 }
504
505 if (list_empty(&rng_list)) {
506 mutex_unlock(&rng_mutex);
507 if (hwrng_fill)
508 kthread_stop(hwrng_fill);
509 } else
510 mutex_unlock(&rng_mutex);
511
512 wait_for_completion(&rng->cleanup_done);
513 }
514 EXPORT_SYMBOL_GPL(hwrng_unregister);
515
devm_hwrng_release(struct device * dev,void * res)516 static void devm_hwrng_release(struct device *dev, void *res)
517 {
518 hwrng_unregister(*(struct hwrng **)res);
519 }
520
devm_hwrng_match(struct device * dev,void * res,void * data)521 static int devm_hwrng_match(struct device *dev, void *res, void *data)
522 {
523 struct hwrng **r = res;
524
525 if (WARN_ON(!r || !*r))
526 return 0;
527
528 return *r == data;
529 }
530
devm_hwrng_register(struct device * dev,struct hwrng * rng)531 int devm_hwrng_register(struct device *dev, struct hwrng *rng)
532 {
533 struct hwrng **ptr;
534 int error;
535
536 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
537 if (!ptr)
538 return -ENOMEM;
539
540 error = hwrng_register(rng);
541 if (error) {
542 devres_free(ptr);
543 return error;
544 }
545
546 *ptr = rng;
547 devres_add(dev, ptr);
548 return 0;
549 }
550 EXPORT_SYMBOL_GPL(devm_hwrng_register);
551
devm_hwrng_unregister(struct device * dev,struct hwrng * rng)552 void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
553 {
554 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
555 }
556 EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
557
hwrng_modinit(void)558 static int __init hwrng_modinit(void)
559 {
560 int ret = -ENOMEM;
561
562 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
563 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
564 if (!rng_buffer)
565 return -ENOMEM;
566
567 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
568 if (!rng_fillbuf) {
569 kfree(rng_buffer);
570 return -ENOMEM;
571 }
572
573 ret = register_miscdev();
574 if (ret) {
575 kfree(rng_fillbuf);
576 kfree(rng_buffer);
577 }
578
579 return ret;
580 }
581
hwrng_modexit(void)582 static void __exit hwrng_modexit(void)
583 {
584 mutex_lock(&rng_mutex);
585 BUG_ON(current_rng);
586 kfree(rng_buffer);
587 kfree(rng_fillbuf);
588 mutex_unlock(&rng_mutex);
589
590 unregister_miscdev();
591 }
592
593 module_init(hwrng_modinit);
594 module_exit(hwrng_modexit);
595
596 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
597 MODULE_LICENSE("GPL");
598