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/miscdevice.h>
21 #include <linux/module.h>
22 #include <linux/random.h>
23 #include <linux/sched.h>
24 #include <linux/slab.h>
25 #include <linux/uaccess.h>
27 #define RNG_MODULE_NAME "hw_random"
29 static struct hwrng
*current_rng
;
30 static struct task_struct
*hwrng_fill
;
31 static LIST_HEAD(rng_list
);
32 /* Protects rng_list and current_rng */
33 static DEFINE_MUTEX(rng_mutex
);
34 /* Protects rng read functions, data_avail, rng_buffer and rng_fillbuf */
35 static DEFINE_MUTEX(reading_mutex
);
36 static int data_avail
;
37 static u8
*rng_buffer
, *rng_fillbuf
;
38 static unsigned short current_quality
;
39 static unsigned short default_quality
; /* = 0; default to "off" */
41 module_param(current_quality
, ushort
, 0644);
42 MODULE_PARM_DESC(current_quality
,
43 "current hwrng entropy estimation per mill");
44 module_param(default_quality
, ushort
, 0644);
45 MODULE_PARM_DESC(default_quality
,
46 "default entropy content of hwrng per mill");
48 static void drop_current_rng(void);
49 static int hwrng_init(struct hwrng
*rng
);
50 static void start_khwrngd(void);
52 static inline int rng_get_data(struct hwrng
*rng
, u8
*buffer
, size_t size
,
55 static size_t rng_buffer_size(void)
57 return SMP_CACHE_BYTES
< 32 ? 32 : SMP_CACHE_BYTES
;
60 static void add_early_randomness(struct hwrng
*rng
)
63 size_t size
= min_t(size_t, 16, rng_buffer_size());
65 mutex_lock(&reading_mutex
);
66 bytes_read
= rng_get_data(rng
, rng_buffer
, size
, 1);
67 mutex_unlock(&reading_mutex
);
69 add_device_randomness(rng_buffer
, bytes_read
);
72 static inline void cleanup_rng(struct kref
*kref
)
74 struct hwrng
*rng
= container_of(kref
, struct hwrng
, ref
);
79 complete(&rng
->cleanup_done
);
82 static int set_current_rng(struct hwrng
*rng
)
86 BUG_ON(!mutex_is_locked(&rng_mutex
));
88 err
= hwrng_init(rng
);
98 static void drop_current_rng(void)
100 BUG_ON(!mutex_is_locked(&rng_mutex
));
104 /* decrease last reference for triggering the cleanup */
105 kref_put(¤t_rng
->ref
, cleanup_rng
);
109 /* Returns ERR_PTR(), NULL or refcounted hwrng */
110 static struct hwrng
*get_current_rng(void)
114 if (mutex_lock_interruptible(&rng_mutex
))
115 return ERR_PTR(-ERESTARTSYS
);
121 mutex_unlock(&rng_mutex
);
125 static void put_rng(struct hwrng
*rng
)
128 * Hold rng_mutex here so we serialize in case they set_current_rng
129 * on rng again immediately.
131 mutex_lock(&rng_mutex
);
133 kref_put(&rng
->ref
, cleanup_rng
);
134 mutex_unlock(&rng_mutex
);
137 static int hwrng_init(struct hwrng
*rng
)
139 if (kref_get_unless_zero(&rng
->ref
))
145 ret
= rng
->init(rng
);
150 kref_init(&rng
->ref
);
151 reinit_completion(&rng
->cleanup_done
);
154 add_early_randomness(rng
);
156 current_quality
= rng
->quality
? : default_quality
;
157 if (current_quality
> 1024)
158 current_quality
= 1024;
160 if (current_quality
== 0 && hwrng_fill
)
161 kthread_stop(hwrng_fill
);
162 if (current_quality
> 0 && !hwrng_fill
)
168 static int rng_dev_open(struct inode
*inode
, struct file
*filp
)
170 /* enforce read-only access to this chrdev */
171 if ((filp
->f_mode
& FMODE_READ
) == 0)
173 if (filp
->f_mode
& FMODE_WRITE
)
178 static inline int rng_get_data(struct hwrng
*rng
, u8
*buffer
, size_t size
,
182 BUG_ON(!mutex_is_locked(&reading_mutex
));
184 return rng
->read(rng
, (void *)buffer
, size
, wait
);
186 if (rng
->data_present
)
187 present
= rng
->data_present(rng
, wait
);
192 return rng
->data_read(rng
, (u32
*)buffer
);
197 static ssize_t
rng_dev_read(struct file
*filp
, char __user
*buf
,
198 size_t size
, loff_t
*offp
)
206 rng
= get_current_rng();
216 if (mutex_lock_interruptible(&reading_mutex
)) {
221 bytes_read
= rng_get_data(rng
, rng_buffer
,
223 !(filp
->f_flags
& O_NONBLOCK
));
224 if (bytes_read
< 0) {
226 goto out_unlock_reading
;
228 data_avail
= bytes_read
;
232 if (filp
->f_flags
& O_NONBLOCK
) {
234 goto out_unlock_reading
;
243 if (copy_to_user(buf
+ ret
, rng_buffer
+ data_avail
,
246 goto out_unlock_reading
;
253 mutex_unlock(&reading_mutex
);
257 schedule_timeout_interruptible(1);
259 if (signal_pending(current
)) {
268 mutex_unlock(&reading_mutex
);
274 static const struct file_operations rng_chrdev_ops
= {
275 .owner
= THIS_MODULE
,
276 .open
= rng_dev_open
,
277 .read
= rng_dev_read
,
278 .llseek
= noop_llseek
,
281 static const struct attribute_group
*rng_dev_groups
[];
283 static struct miscdevice rng_miscdev
= {
284 .minor
= HWRNG_MINOR
,
285 .name
= RNG_MODULE_NAME
,
287 .fops
= &rng_chrdev_ops
,
288 .groups
= rng_dev_groups
,
291 static ssize_t
hwrng_attr_current_store(struct device
*dev
,
292 struct device_attribute
*attr
,
293 const char *buf
, size_t len
)
298 err
= mutex_lock_interruptible(&rng_mutex
);
302 list_for_each_entry(rng
, &rng_list
, list
) {
303 if (sysfs_streq(rng
->name
, buf
)) {
305 if (rng
!= current_rng
)
306 err
= set_current_rng(rng
);
310 mutex_unlock(&rng_mutex
);
315 static ssize_t
hwrng_attr_current_show(struct device
*dev
,
316 struct device_attribute
*attr
,
322 rng
= get_current_rng();
326 ret
= snprintf(buf
, PAGE_SIZE
, "%s\n", rng
? rng
->name
: "none");
332 static ssize_t
hwrng_attr_available_show(struct device
*dev
,
333 struct device_attribute
*attr
,
339 err
= mutex_lock_interruptible(&rng_mutex
);
343 list_for_each_entry(rng
, &rng_list
, list
) {
344 strlcat(buf
, rng
->name
, PAGE_SIZE
);
345 strlcat(buf
, " ", PAGE_SIZE
);
347 strlcat(buf
, "\n", PAGE_SIZE
);
348 mutex_unlock(&rng_mutex
);
353 static DEVICE_ATTR(rng_current
, S_IRUGO
| S_IWUSR
,
354 hwrng_attr_current_show
,
355 hwrng_attr_current_store
);
356 static DEVICE_ATTR(rng_available
, S_IRUGO
,
357 hwrng_attr_available_show
,
360 static struct attribute
*rng_dev_attrs
[] = {
361 &dev_attr_rng_current
.attr
,
362 &dev_attr_rng_available
.attr
,
366 ATTRIBUTE_GROUPS(rng_dev
);
368 static void __exit
unregister_miscdev(void)
370 misc_deregister(&rng_miscdev
);
373 static int __init
register_miscdev(void)
375 return misc_register(&rng_miscdev
);
378 static int hwrng_fillfn(void *unused
)
382 while (!kthread_should_stop()) {
385 rng
= get_current_rng();
386 if (IS_ERR(rng
) || !rng
)
388 mutex_lock(&reading_mutex
);
389 rc
= rng_get_data(rng
, rng_fillbuf
,
390 rng_buffer_size(), 1);
391 mutex_unlock(&reading_mutex
);
394 pr_warn("hwrng: no data available\n");
395 msleep_interruptible(10000);
398 /* Outside lock, sure, but y'know: randomness. */
399 add_hwgenerator_randomness((void *)rng_fillbuf
, rc
,
400 rc
* current_quality
* 8 >> 10);
406 static void start_khwrngd(void)
408 hwrng_fill
= kthread_run(hwrng_fillfn
, NULL
, "hwrng");
409 if (IS_ERR(hwrng_fill
)) {
410 pr_err("hwrng_fill thread creation failed");
415 int hwrng_register(struct hwrng
*rng
)
418 struct hwrng
*old_rng
, *tmp
;
420 if (!rng
->name
|| (!rng
->data_read
&& !rng
->read
))
423 mutex_lock(&rng_mutex
);
424 /* Must not register two RNGs with the same name. */
426 list_for_each_entry(tmp
, &rng_list
, list
) {
427 if (strcmp(tmp
->name
, rng
->name
) == 0)
431 init_completion(&rng
->cleanup_done
);
432 complete(&rng
->cleanup_done
);
434 old_rng
= current_rng
;
437 err
= set_current_rng(rng
);
441 list_add_tail(&rng
->list
, &rng_list
);
443 if (old_rng
&& !rng
->init
) {
445 * Use a new device's input to add some randomness to
446 * the system. If this rng device isn't going to be
447 * used right away, its init function hasn't been
448 * called yet; so only use the randomness from devices
449 * that don't need an init callback.
451 add_early_randomness(rng
);
455 mutex_unlock(&rng_mutex
);
459 EXPORT_SYMBOL_GPL(hwrng_register
);
461 void hwrng_unregister(struct hwrng
*rng
)
463 mutex_lock(&rng_mutex
);
465 list_del(&rng
->list
);
466 if (current_rng
== rng
) {
468 if (!list_empty(&rng_list
)) {
471 tail
= list_entry(rng_list
.prev
, struct hwrng
, list
);
473 set_current_rng(tail
);
477 if (list_empty(&rng_list
)) {
478 mutex_unlock(&rng_mutex
);
480 kthread_stop(hwrng_fill
);
482 mutex_unlock(&rng_mutex
);
484 wait_for_completion(&rng
->cleanup_done
);
486 EXPORT_SYMBOL_GPL(hwrng_unregister
);
488 static void devm_hwrng_release(struct device
*dev
, void *res
)
490 hwrng_unregister(*(struct hwrng
**)res
);
493 static int devm_hwrng_match(struct device
*dev
, void *res
, void *data
)
495 struct hwrng
**r
= res
;
497 if (WARN_ON(!r
|| !*r
))
503 int devm_hwrng_register(struct device
*dev
, struct hwrng
*rng
)
508 ptr
= devres_alloc(devm_hwrng_release
, sizeof(*ptr
), GFP_KERNEL
);
512 error
= hwrng_register(rng
);
519 devres_add(dev
, ptr
);
522 EXPORT_SYMBOL_GPL(devm_hwrng_register
);
524 void devm_hwrng_unregister(struct device
*dev
, struct hwrng
*rng
)
526 devres_release(dev
, devm_hwrng_release
, devm_hwrng_match
, rng
);
528 EXPORT_SYMBOL_GPL(devm_hwrng_unregister
);
530 static int __init
hwrng_modinit(void)
534 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
535 rng_buffer
= kmalloc(rng_buffer_size(), GFP_KERNEL
);
539 rng_fillbuf
= kmalloc(rng_buffer_size(), GFP_KERNEL
);
545 ret
= register_miscdev();
554 static void __exit
hwrng_modexit(void)
556 mutex_lock(&rng_mutex
);
560 mutex_unlock(&rng_mutex
);
562 unregister_miscdev();
565 module_init(hwrng_modinit
);
566 module_exit(hwrng_modexit
);
568 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
569 MODULE_LICENSE("GPL");