2 * hw_random/core.c: HWRNG core API
4 * Copyright 2006 Michael Buesch <m@bues.ch>
5 * Copyright 2005 (c) MontaVista Software, Inc.
7 * Please read Documentation/hw_random.txt for details on use.
9 * This software may be used and distributed according to the terms
10 * of the GNU General Public License, incorporated herein by reference.
13 #include <linux/delay.h>
14 #include <linux/device.h>
15 #include <linux/err.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>
28 #define RNG_MODULE_NAME "hw_random"
30 static struct hwrng
*current_rng
;
31 /* the current rng has been explicitly chosen by user via sysfs */
32 static int cur_rng_set_by_user
;
33 static struct task_struct
*hwrng_fill
;
34 /* list of registered rngs, sorted decending by quality */
35 static LIST_HEAD(rng_list
);
36 /* Protects rng_list and current_rng */
37 static DEFINE_MUTEX(rng_mutex
);
38 /* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
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
; /* = 0; default to "off" */
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");
52 static void drop_current_rng(void);
53 static int hwrng_init(struct hwrng
*rng
);
54 static void start_khwrngd(void);
56 static inline int rng_get_data(struct hwrng
*rng
, u8
*buffer
, size_t size
,
59 static size_t rng_buffer_size(void)
61 return SMP_CACHE_BYTES
< 32 ? 32 : SMP_CACHE_BYTES
;
64 static void add_early_randomness(struct hwrng
*rng
)
67 size_t size
= min_t(size_t, 16, rng_buffer_size());
69 mutex_lock(&reading_mutex
);
70 bytes_read
= rng_get_data(rng
, rng_buffer
, size
, 1);
71 mutex_unlock(&reading_mutex
);
73 add_device_randomness(rng_buffer
, bytes_read
);
76 static inline void cleanup_rng(struct kref
*kref
)
78 struct hwrng
*rng
= container_of(kref
, struct hwrng
, ref
);
83 complete(&rng
->cleanup_done
);
86 static int set_current_rng(struct hwrng
*rng
)
90 BUG_ON(!mutex_is_locked(&rng_mutex
));
92 err
= hwrng_init(rng
);
102 static void drop_current_rng(void)
104 BUG_ON(!mutex_is_locked(&rng_mutex
));
108 /* decrease last reference for triggering the cleanup */
109 kref_put(¤t_rng
->ref
, cleanup_rng
);
113 /* Returns ERR_PTR(), NULL or refcounted hwrng */
114 static struct hwrng
*get_current_rng(void)
118 if (mutex_lock_interruptible(&rng_mutex
))
119 return ERR_PTR(-ERESTARTSYS
);
125 mutex_unlock(&rng_mutex
);
129 static void put_rng(struct hwrng
*rng
)
132 * Hold rng_mutex here so we serialize in case they set_current_rng
133 * on rng again immediately.
135 mutex_lock(&rng_mutex
);
137 kref_put(&rng
->ref
, cleanup_rng
);
138 mutex_unlock(&rng_mutex
);
141 static int hwrng_init(struct hwrng
*rng
)
143 if (kref_get_unless_zero(&rng
->ref
))
149 ret
= rng
->init(rng
);
154 kref_init(&rng
->ref
);
155 reinit_completion(&rng
->cleanup_done
);
158 add_early_randomness(rng
);
160 current_quality
= rng
->quality
? : default_quality
;
161 if (current_quality
> 1024)
162 current_quality
= 1024;
164 if (current_quality
== 0 && hwrng_fill
)
165 kthread_stop(hwrng_fill
);
166 if (current_quality
> 0 && !hwrng_fill
)
172 static int rng_dev_open(struct inode
*inode
, struct file
*filp
)
174 /* enforce read-only access to this chrdev */
175 if ((filp
->f_mode
& FMODE_READ
) == 0)
177 if (filp
->f_mode
& FMODE_WRITE
)
182 static inline int rng_get_data(struct hwrng
*rng
, u8
*buffer
, size_t size
,
186 BUG_ON(!mutex_is_locked(&reading_mutex
));
188 return rng
->read(rng
, (void *)buffer
, size
, wait
);
190 if (rng
->data_present
)
191 present
= rng
->data_present(rng
, wait
);
196 return rng
->data_read(rng
, (u32
*)buffer
);
201 static ssize_t
rng_dev_read(struct file
*filp
, char __user
*buf
,
202 size_t size
, loff_t
*offp
)
210 rng
= get_current_rng();
220 if (mutex_lock_interruptible(&reading_mutex
)) {
225 bytes_read
= rng_get_data(rng
, rng_buffer
,
227 !(filp
->f_flags
& O_NONBLOCK
));
228 if (bytes_read
< 0) {
230 goto out_unlock_reading
;
232 data_avail
= bytes_read
;
236 if (filp
->f_flags
& O_NONBLOCK
) {
238 goto out_unlock_reading
;
247 if (copy_to_user(buf
+ ret
, rng_buffer
+ data_avail
,
250 goto out_unlock_reading
;
257 mutex_unlock(&reading_mutex
);
261 schedule_timeout_interruptible(1);
263 if (signal_pending(current
)) {
272 mutex_unlock(&reading_mutex
);
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
,
285 static const struct attribute_group
*rng_dev_groups
[];
287 static struct miscdevice rng_miscdev
= {
288 .minor
= HWRNG_MINOR
,
289 .name
= RNG_MODULE_NAME
,
291 .fops
= &rng_chrdev_ops
,
292 .groups
= rng_dev_groups
,
295 static int enable_best_rng(void)
299 BUG_ON(!mutex_is_locked(&rng_mutex
));
301 /* rng_list is sorted by quality, use the best (=first) one */
302 if (!list_empty(&rng_list
)) {
303 struct hwrng
*new_rng
;
305 new_rng
= list_entry(rng_list
.next
, struct hwrng
, list
);
306 ret
= ((new_rng
== current_rng
) ? 0 : set_current_rng(new_rng
));
308 cur_rng_set_by_user
= 0;
311 cur_rng_set_by_user
= 0;
318 static ssize_t
hwrng_attr_current_store(struct device
*dev
,
319 struct device_attribute
*attr
,
320 const char *buf
, size_t len
)
325 err
= mutex_lock_interruptible(&rng_mutex
);
329 if (sysfs_streq(buf
, "")) {
330 err
= enable_best_rng();
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
);
341 mutex_unlock(&rng_mutex
);
346 static ssize_t
hwrng_attr_current_show(struct device
*dev
,
347 struct device_attribute
*attr
,
353 rng
= get_current_rng();
357 ret
= snprintf(buf
, PAGE_SIZE
, "%s\n", rng
? rng
->name
: "none");
363 static ssize_t
hwrng_attr_available_show(struct device
*dev
,
364 struct device_attribute
*attr
,
370 err
= mutex_lock_interruptible(&rng_mutex
);
374 list_for_each_entry(rng
, &rng_list
, list
) {
375 strlcat(buf
, rng
->name
, PAGE_SIZE
);
376 strlcat(buf
, " ", PAGE_SIZE
);
378 strlcat(buf
, "\n", PAGE_SIZE
);
379 mutex_unlock(&rng_mutex
);
384 static ssize_t
hwrng_attr_selected_show(struct device
*dev
,
385 struct device_attribute
*attr
,
388 return snprintf(buf
, PAGE_SIZE
, "%d\n", cur_rng_set_by_user
);
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
,
397 static DEVICE_ATTR(rng_selected
, S_IRUGO
,
398 hwrng_attr_selected_show
,
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
,
408 ATTRIBUTE_GROUPS(rng_dev
);
410 static void __exit
unregister_miscdev(void)
412 misc_deregister(&rng_miscdev
);
415 static int __init
register_miscdev(void)
417 return misc_register(&rng_miscdev
);
420 static int hwrng_fillfn(void *unused
)
424 while (!kthread_should_stop()) {
427 rng
= get_current_rng();
428 if (IS_ERR(rng
) || !rng
)
430 mutex_lock(&reading_mutex
);
431 rc
= rng_get_data(rng
, rng_fillbuf
,
432 rng_buffer_size(), 1);
433 mutex_unlock(&reading_mutex
);
436 pr_warn("hwrng: no data available\n");
437 msleep_interruptible(10000);
440 /* Outside lock, sure, but y'know: randomness. */
441 add_hwgenerator_randomness((void *)rng_fillbuf
, rc
,
442 rc
* current_quality
* 8 >> 10);
448 static void start_khwrngd(void)
450 hwrng_fill
= kthread_run(hwrng_fillfn
, NULL
, "hwrng");
451 if (IS_ERR(hwrng_fill
)) {
452 pr_err("hwrng_fill thread creation failed\n");
457 int hwrng_register(struct hwrng
*rng
)
460 struct hwrng
*old_rng
, *tmp
;
461 struct list_head
*rng_list_ptr
;
463 if (!rng
->name
|| (!rng
->data_read
&& !rng
->read
))
466 mutex_lock(&rng_mutex
);
467 /* Must not register two RNGs with the same name. */
469 list_for_each_entry(tmp
, &rng_list
, list
) {
470 if (strcmp(tmp
->name
, rng
->name
) == 0)
474 init_completion(&rng
->cleanup_done
);
475 complete(&rng
->cleanup_done
);
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
)
483 list_add_tail(&rng
->list
, rng_list_ptr
);
485 old_rng
= current_rng
;
488 (!cur_rng_set_by_user
&& rng
->quality
> old_rng
->quality
)) {
490 * Set new rng as current as the new rng source
491 * provides better entropy quality and was not
492 * chosen by userspace.
494 err
= set_current_rng(rng
);
499 if (old_rng
&& !rng
->init
) {
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.
507 add_early_randomness(rng
);
511 mutex_unlock(&rng_mutex
);
515 EXPORT_SYMBOL_GPL(hwrng_register
);
517 void hwrng_unregister(struct hwrng
*rng
)
521 mutex_lock(&rng_mutex
);
523 list_del(&rng
->list
);
524 if (current_rng
== rng
) {
525 err
= enable_best_rng();
528 cur_rng_set_by_user
= 0;
532 if (list_empty(&rng_list
)) {
533 mutex_unlock(&rng_mutex
);
535 kthread_stop(hwrng_fill
);
537 mutex_unlock(&rng_mutex
);
539 wait_for_completion(&rng
->cleanup_done
);
541 EXPORT_SYMBOL_GPL(hwrng_unregister
);
543 static void devm_hwrng_release(struct device
*dev
, void *res
)
545 hwrng_unregister(*(struct hwrng
**)res
);
548 static int devm_hwrng_match(struct device
*dev
, void *res
, void *data
)
550 struct hwrng
**r
= res
;
552 if (WARN_ON(!r
|| !*r
))
558 int devm_hwrng_register(struct device
*dev
, struct hwrng
*rng
)
563 ptr
= devres_alloc(devm_hwrng_release
, sizeof(*ptr
), GFP_KERNEL
);
567 error
= hwrng_register(rng
);
574 devres_add(dev
, ptr
);
577 EXPORT_SYMBOL_GPL(devm_hwrng_register
);
579 void devm_hwrng_unregister(struct device
*dev
, struct hwrng
*rng
)
581 devres_release(dev
, devm_hwrng_release
, devm_hwrng_match
, rng
);
583 EXPORT_SYMBOL_GPL(devm_hwrng_unregister
);
585 static int __init
hwrng_modinit(void)
589 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
590 rng_buffer
= kmalloc(rng_buffer_size(), GFP_KERNEL
);
594 rng_fillbuf
= kmalloc(rng_buffer_size(), GFP_KERNEL
);
600 ret
= register_miscdev();
609 static void __exit
hwrng_modexit(void)
611 mutex_lock(&rng_mutex
);
615 mutex_unlock(&rng_mutex
);
617 unregister_miscdev();
620 module_init(hwrng_modinit
);
621 module_exit(hwrng_modexit
);
623 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
624 MODULE_LICENSE("GPL");