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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
30static struct hwrng *current_rng;
31static struct task_struct *hwrng_fill;
32static LIST_HEAD(rng_list);
33
34static DEFINE_MUTEX(rng_mutex);
35
36static DEFINE_MUTEX(reading_mutex);
37static int data_avail;
38static u8 *rng_buffer, *rng_fillbuf;
39static unsigned short current_quality;
40static unsigned short default_quality;
41
42module_param(current_quality, ushort, 0644);
43MODULE_PARM_DESC(current_quality,
44 "current hwrng entropy estimation per mill");
45module_param(default_quality, ushort, 0644);
46MODULE_PARM_DESC(default_quality,
47 "default entropy content of hwrng per mill");
48
49static void drop_current_rng(void);
50static int hwrng_init(struct hwrng *rng);
51static void start_khwrngd(void);
52
53static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
54 int wait);
55
56static size_t rng_buffer_size(void)
57{
58 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
59}
60
61static void add_early_randomness(struct hwrng *rng)
62{
63 int bytes_read;
64 size_t size = min_t(size_t, 16, rng_buffer_size());
65
66 mutex_lock(&reading_mutex);
67 bytes_read = rng_get_data(rng, rng_buffer, size, 1);
68 mutex_unlock(&reading_mutex);
69 if (bytes_read > 0)
70 add_device_randomness(rng_buffer, bytes_read);
71}
72
73static inline void cleanup_rng(struct kref *kref)
74{
75 struct hwrng *rng = container_of(kref, struct hwrng, ref);
76
77 if (rng->cleanup)
78 rng->cleanup(rng);
79
80 complete(&rng->cleanup_done);
81}
82
83static int set_current_rng(struct hwrng *rng)
84{
85 int err;
86
87 BUG_ON(!mutex_is_locked(&rng_mutex));
88
89 err = hwrng_init(rng);
90 if (err)
91 return err;
92
93 drop_current_rng();
94 current_rng = rng;
95
96 return 0;
97}
98
99static void drop_current_rng(void)
100{
101 BUG_ON(!mutex_is_locked(&rng_mutex));
102 if (!current_rng)
103 return;
104
105
106 kref_put(¤t_rng->ref, cleanup_rng);
107 current_rng = NULL;
108}
109
110
111static struct hwrng *get_current_rng(void)
112{
113 struct hwrng *rng;
114
115 if (mutex_lock_interruptible(&rng_mutex))
116 return ERR_PTR(-ERESTARTSYS);
117
118 rng = current_rng;
119 if (rng)
120 kref_get(&rng->ref);
121
122 mutex_unlock(&rng_mutex);
123 return rng;
124}
125
126static void put_rng(struct hwrng *rng)
127{
128
129
130
131
132 mutex_lock(&rng_mutex);
133 if (rng)
134 kref_put(&rng->ref, cleanup_rng);
135 mutex_unlock(&rng_mutex);
136}
137
138static int hwrng_init(struct hwrng *rng)
139{
140 if (kref_get_unless_zero(&rng->ref))
141 goto skip_init;
142
143 if (rng->init) {
144 int ret;
145
146 ret = rng->init(rng);
147 if (ret)
148 return ret;
149 }
150
151 kref_init(&rng->ref);
152 reinit_completion(&rng->cleanup_done);
153
154skip_init:
155 add_early_randomness(rng);
156
157 current_quality = rng->quality ? : default_quality;
158 if (current_quality > 1024)
159 current_quality = 1024;
160
161 if (current_quality == 0 && hwrng_fill)
162 kthread_stop(hwrng_fill);
163 if (current_quality > 0 && !hwrng_fill)
164 start_khwrngd();
165
166 return 0;
167}
168
169static int rng_dev_open(struct inode *inode, struct file *filp)
170{
171
172 if ((filp->f_mode & FMODE_READ) == 0)
173 return -EINVAL;
174 if (filp->f_mode & FMODE_WRITE)
175 return -EINVAL;
176 return 0;
177}
178
179static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
180 int wait) {
181 int present;
182
183 BUG_ON(!mutex_is_locked(&reading_mutex));
184 if (rng->read)
185 return rng->read(rng, (void *)buffer, size, wait);
186
187 if (rng->data_present)
188 present = rng->data_present(rng, wait);
189 else
190 present = 1;
191
192 if (present)
193 return rng->data_read(rng, (u32 *)buffer);
194
195 return 0;
196}
197
198static ssize_t rng_dev_read(struct file *filp, char __user *buf,
199 size_t size, loff_t *offp)
200{
201 ssize_t ret = 0;
202 int err = 0;
203 int bytes_read, len;
204 struct hwrng *rng;
205
206 while (size) {
207 rng = get_current_rng();
208 if (IS_ERR(rng)) {
209 err = PTR_ERR(rng);
210 goto out;
211 }
212 if (!rng) {
213 err = -ENODEV;
214 goto out;
215 }
216
217 if (mutex_lock_interruptible(&reading_mutex)) {
218 err = -ERESTARTSYS;
219 goto out_put;
220 }
221 if (!data_avail) {
222 bytes_read = rng_get_data(rng, rng_buffer,
223 rng_buffer_size(),
224 !(filp->f_flags & O_NONBLOCK));
225 if (bytes_read < 0) {
226 err = bytes_read;
227 goto out_unlock_reading;
228 }
229 data_avail = bytes_read;
230 }
231
232 if (!data_avail) {
233 if (filp->f_flags & O_NONBLOCK) {
234 err = -EAGAIN;
235 goto out_unlock_reading;
236 }
237 } else {
238 len = data_avail;
239 if (len > size)
240 len = size;
241
242 data_avail -= len;
243
244 if (copy_to_user(buf + ret, rng_buffer + data_avail,
245 len)) {
246 err = -EFAULT;
247 goto out_unlock_reading;
248 }
249
250 size -= len;
251 ret += len;
252 }
253
254 mutex_unlock(&reading_mutex);
255 put_rng(rng);
256
257 if (need_resched())
258 schedule_timeout_interruptible(1);
259
260 if (signal_pending(current)) {
261 err = -ERESTARTSYS;
262 goto out;
263 }
264 }
265out:
266 return ret ? : err;
267
268out_unlock_reading:
269 mutex_unlock(&reading_mutex);
270out_put:
271 put_rng(rng);
272 goto out;
273}
274
275static const struct file_operations rng_chrdev_ops = {
276 .owner = THIS_MODULE,
277 .open = rng_dev_open,
278 .read = rng_dev_read,
279 .llseek = noop_llseek,
280};
281
282static const struct attribute_group *rng_dev_groups[];
283
284static struct miscdevice rng_miscdev = {
285 .minor = HWRNG_MINOR,
286 .name = RNG_MODULE_NAME,
287 .nodename = "hwrng",
288 .fops = &rng_chrdev_ops,
289 .groups = rng_dev_groups,
290};
291
292static ssize_t hwrng_attr_current_store(struct device *dev,
293 struct device_attribute *attr,
294 const char *buf, size_t len)
295{
296 int err;
297 struct hwrng *rng;
298
299 err = mutex_lock_interruptible(&rng_mutex);
300 if (err)
301 return -ERESTARTSYS;
302 err = -ENODEV;
303 list_for_each_entry(rng, &rng_list, list) {
304 if (sysfs_streq(rng->name, buf)) {
305 err = 0;
306 if (rng != current_rng)
307 err = set_current_rng(rng);
308 break;
309 }
310 }
311 mutex_unlock(&rng_mutex);
312
313 return err ? : len;
314}
315
316static ssize_t hwrng_attr_current_show(struct device *dev,
317 struct device_attribute *attr,
318 char *buf)
319{
320 ssize_t ret;
321 struct hwrng *rng;
322
323 rng = get_current_rng();
324 if (IS_ERR(rng))
325 return PTR_ERR(rng);
326
327 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
328 put_rng(rng);
329
330 return ret;
331}
332
333static ssize_t hwrng_attr_available_show(struct device *dev,
334 struct device_attribute *attr,
335 char *buf)
336{
337 int err;
338 struct hwrng *rng;
339
340 err = mutex_lock_interruptible(&rng_mutex);
341 if (err)
342 return -ERESTARTSYS;
343 buf[0] = '\0';
344 list_for_each_entry(rng, &rng_list, list) {
345 strlcat(buf, rng->name, PAGE_SIZE);
346 strlcat(buf, " ", PAGE_SIZE);
347 }
348 strlcat(buf, "\n", PAGE_SIZE);
349 mutex_unlock(&rng_mutex);
350
351 return strlen(buf);
352}
353
354static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
355 hwrng_attr_current_show,
356 hwrng_attr_current_store);
357static DEVICE_ATTR(rng_available, S_IRUGO,
358 hwrng_attr_available_show,
359 NULL);
360
361static struct attribute *rng_dev_attrs[] = {
362 &dev_attr_rng_current.attr,
363 &dev_attr_rng_available.attr,
364 NULL
365};
366
367ATTRIBUTE_GROUPS(rng_dev);
368
369static void __exit unregister_miscdev(void)
370{
371 misc_deregister(&rng_miscdev);
372}
373
374static int __init register_miscdev(void)
375{
376 return misc_register(&rng_miscdev);
377}
378
379static int hwrng_fillfn(void *unused)
380{
381 long rc;
382
383 while (!kthread_should_stop()) {
384 struct hwrng *rng;
385
386 rng = get_current_rng();
387 if (IS_ERR(rng) || !rng)
388 break;
389 mutex_lock(&reading_mutex);
390 rc = rng_get_data(rng, rng_fillbuf,
391 rng_buffer_size(), 1);
392 mutex_unlock(&reading_mutex);
393 put_rng(rng);
394 if (rc <= 0) {
395 pr_warn("hwrng: no data available\n");
396 msleep_interruptible(10000);
397 continue;
398 }
399
400 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
401 rc * current_quality * 8 >> 10);
402 }
403 hwrng_fill = NULL;
404 return 0;
405}
406
407static void start_khwrngd(void)
408{
409 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
410 if (IS_ERR(hwrng_fill)) {
411 pr_err("hwrng_fill thread creation failed");
412 hwrng_fill = NULL;
413 }
414}
415
416int hwrng_register(struct hwrng *rng)
417{
418 int err = -EINVAL;
419 struct hwrng *old_rng, *tmp;
420
421 if (!rng->name || (!rng->data_read && !rng->read))
422 goto out;
423
424 mutex_lock(&rng_mutex);
425
426 err = -EEXIST;
427 list_for_each_entry(tmp, &rng_list, list) {
428 if (strcmp(tmp->name, rng->name) == 0)
429 goto out_unlock;
430 }
431
432 init_completion(&rng->cleanup_done);
433 complete(&rng->cleanup_done);
434
435 old_rng = current_rng;
436 err = 0;
437 if (!old_rng) {
438 err = set_current_rng(rng);
439 if (err)
440 goto out_unlock;
441 }
442 list_add_tail(&rng->list, &rng_list);
443
444 if (old_rng && !rng->init) {
445
446
447
448
449
450
451
452 add_early_randomness(rng);
453 }
454
455out_unlock:
456 mutex_unlock(&rng_mutex);
457out:
458 return err;
459}
460EXPORT_SYMBOL_GPL(hwrng_register);
461
462void hwrng_unregister(struct hwrng *rng)
463{
464 mutex_lock(&rng_mutex);
465
466 list_del(&rng->list);
467 if (current_rng == rng) {
468 drop_current_rng();
469 if (!list_empty(&rng_list)) {
470 struct hwrng *tail;
471
472 tail = list_entry(rng_list.prev, struct hwrng, list);
473
474 set_current_rng(tail);
475 }
476 }
477
478 if (list_empty(&rng_list)) {
479 mutex_unlock(&rng_mutex);
480 if (hwrng_fill)
481 kthread_stop(hwrng_fill);
482 } else
483 mutex_unlock(&rng_mutex);
484
485 wait_for_completion(&rng->cleanup_done);
486}
487EXPORT_SYMBOL_GPL(hwrng_unregister);
488
489static void devm_hwrng_release(struct device *dev, void *res)
490{
491 hwrng_unregister(*(struct hwrng **)res);
492}
493
494static int devm_hwrng_match(struct device *dev, void *res, void *data)
495{
496 struct hwrng **r = res;
497
498 if (WARN_ON(!r || !*r))
499 return 0;
500
501 return *r == data;
502}
503
504int devm_hwrng_register(struct device *dev, struct hwrng *rng)
505{
506 struct hwrng **ptr;
507 int error;
508
509 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
510 if (!ptr)
511 return -ENOMEM;
512
513 error = hwrng_register(rng);
514 if (error) {
515 devres_free(ptr);
516 return error;
517 }
518
519 *ptr = rng;
520 devres_add(dev, ptr);
521 return 0;
522}
523EXPORT_SYMBOL_GPL(devm_hwrng_register);
524
525void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
526{
527 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
528}
529EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
530
531static int __init hwrng_modinit(void)
532{
533 int ret = -ENOMEM;
534
535
536 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
537 if (!rng_buffer)
538 return -ENOMEM;
539
540 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
541 if (!rng_fillbuf) {
542 kfree(rng_buffer);
543 return -ENOMEM;
544 }
545
546 ret = register_miscdev();
547 if (ret) {
548 kfree(rng_fillbuf);
549 kfree(rng_buffer);
550 }
551
552 return ret;
553}
554
555static void __exit hwrng_modexit(void)
556{
557 mutex_lock(&rng_mutex);
558 BUG_ON(current_rng);
559 kfree(rng_buffer);
560 kfree(rng_fillbuf);
561 mutex_unlock(&rng_mutex);
562
563 unregister_miscdev();
564}
565
566module_init(hwrng_modinit);
567module_exit(hwrng_modexit);
568
569MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
570MODULE_LICENSE("GPL");
571