2 Added support for the AMD Geode LX RNG
3 (c) Copyright 2004-2005 Advanced Micro Devices, Inc.
7 Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
8 (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
12 Hardware driver for the AMD 768 Random Number Generator (RNG)
13 (c) Copyright 2001 Red Hat Inc <alan@redhat.com>
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>
22 Copyright 2006 Michael Buesch <m@bues.ch>
23 Copyright 2005 (c) MontaVista Software, Inc.
25 Please read Documentation/hw_random.txt for details on use.
27 ----------------------------------------------------------
28 This software may be used and distributed according to the terms
29 of the GNU General Public License, incorporated herein by reference.
34 #include <linux/device.h>
35 #include <linux/hw_random.h>
36 #include <linux/module.h>
37 #include <linux/kernel.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>
49 #define RNG_MODULE_NAME "hw_random"
50 #define PFX RNG_MODULE_NAME ": "
51 #define RNG_MISCDEV_MINOR 183 /* official */
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" */
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");
73 static void drop_current_rng(void);
74 static int hwrng_init(struct hwrng *rng);
75 static void start_khwrngd(void);
77 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
80 static size_t rng_buffer_size(void)
82 return SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES;
85 static void add_early_randomness(struct hwrng *rng)
87 unsigned char bytes[16];
90 mutex_lock(&reading_mutex);
91 bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
92 mutex_unlock(&reading_mutex);
94 add_device_randomness(bytes, bytes_read);
97 static inline void cleanup_rng(struct kref *kref)
99 struct hwrng *rng = container_of(kref, struct hwrng, ref);
104 complete(&rng->cleanup_done);
107 static int set_current_rng(struct hwrng *rng)
111 BUG_ON(!mutex_is_locked(&rng_mutex));
113 err = hwrng_init(rng);
123 static void drop_current_rng(void)
125 BUG_ON(!mutex_is_locked(&rng_mutex));
129 /* decrease last reference for triggering the cleanup */
130 kref_put(¤t_rng->ref, cleanup_rng);
134 /* Returns ERR_PTR(), NULL or refcounted hwrng */
135 static struct hwrng *get_current_rng(void)
139 if (mutex_lock_interruptible(&rng_mutex))
140 return ERR_PTR(-ERESTARTSYS);
146 mutex_unlock(&rng_mutex);
150 static void put_rng(struct hwrng *rng)
153 * Hold rng_mutex here so we serialize in case they set_current_rng
154 * on rng again immediately.
156 mutex_lock(&rng_mutex);
158 kref_put(&rng->ref, cleanup_rng);
159 mutex_unlock(&rng_mutex);
162 static int hwrng_init(struct hwrng *rng)
164 if (kref_get_unless_zero(&rng->ref))
170 ret = rng->init(rng);
175 kref_init(&rng->ref);
176 reinit_completion(&rng->cleanup_done);
179 add_early_randomness(rng);
181 current_quality = rng->quality ? : default_quality;
182 current_quality &= 1023;
184 if (current_quality == 0 && hwrng_fill)
185 kthread_stop(hwrng_fill);
186 if (current_quality > 0 && !hwrng_fill)
192 static int rng_dev_open(struct inode *inode, struct file *filp)
194 /* enforce read-only access to this chrdev */
195 if ((filp->f_mode & FMODE_READ) == 0)
197 if (filp->f_mode & FMODE_WRITE)
202 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
206 BUG_ON(!mutex_is_locked(&reading_mutex));
208 return rng->read(rng, (void *)buffer, size, wait);
210 if (rng->data_present)
211 present = rng->data_present(rng, wait);
216 return rng->data_read(rng, (u32 *)buffer);
221 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
222 size_t size, loff_t *offp)
230 rng = get_current_rng();
240 mutex_lock(&reading_mutex);
242 bytes_read = rng_get_data(rng, rng_buffer,
244 !(filp->f_flags & O_NONBLOCK));
245 if (bytes_read < 0) {
247 goto out_unlock_reading;
249 data_avail = bytes_read;
253 if (filp->f_flags & O_NONBLOCK) {
255 goto out_unlock_reading;
264 if (copy_to_user(buf + ret, rng_buffer + data_avail,
267 goto out_unlock_reading;
274 mutex_unlock(&reading_mutex);
278 schedule_timeout_interruptible(1);
280 if (signal_pending(current)) {
289 mutex_unlock(&reading_mutex);
295 static const struct file_operations rng_chrdev_ops = {
296 .owner = THIS_MODULE,
297 .open = rng_dev_open,
298 .read = rng_dev_read,
299 .llseek = noop_llseek,
302 static struct miscdevice rng_miscdev = {
303 .minor = RNG_MISCDEV_MINOR,
304 .name = RNG_MODULE_NAME,
306 .fops = &rng_chrdev_ops,
310 static ssize_t hwrng_attr_current_store(struct device *dev,
311 struct device_attribute *attr,
312 const char *buf, size_t len)
317 err = mutex_lock_interruptible(&rng_mutex);
321 list_for_each_entry(rng, &rng_list, list) {
322 if (strcmp(rng->name, buf) == 0) {
324 if (rng != current_rng)
325 err = set_current_rng(rng);
329 mutex_unlock(&rng_mutex);
334 static ssize_t hwrng_attr_current_show(struct device *dev,
335 struct device_attribute *attr,
341 rng = get_current_rng();
345 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
351 static ssize_t hwrng_attr_available_show(struct device *dev,
352 struct device_attribute *attr,
358 err = mutex_lock_interruptible(&rng_mutex);
362 list_for_each_entry(rng, &rng_list, list) {
363 strlcat(buf, rng->name, PAGE_SIZE);
364 strlcat(buf, " ", PAGE_SIZE);
366 strlcat(buf, "\n", PAGE_SIZE);
367 mutex_unlock(&rng_mutex);
372 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
373 hwrng_attr_current_show,
374 hwrng_attr_current_store);
375 static DEVICE_ATTR(rng_available, S_IRUGO,
376 hwrng_attr_available_show,
380 static void __exit unregister_miscdev(void)
382 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
383 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
384 misc_deregister(&rng_miscdev);
387 static int __init register_miscdev(void)
391 err = misc_register(&rng_miscdev);
394 err = device_create_file(rng_miscdev.this_device,
395 &dev_attr_rng_current);
398 err = device_create_file(rng_miscdev.this_device,
399 &dev_attr_rng_available);
401 goto err_remove_current;
406 device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
408 misc_deregister(&rng_miscdev);
412 static int hwrng_fillfn(void *unused)
416 while (!kthread_should_stop()) {
419 rng = get_current_rng();
420 if (IS_ERR(rng) || !rng)
422 mutex_lock(&reading_mutex);
423 rc = rng_get_data(rng, rng_fillbuf,
424 rng_buffer_size(), 1);
425 mutex_unlock(&reading_mutex);
428 pr_warn("hwrng: no data available\n");
429 msleep_interruptible(10000);
432 /* Outside lock, sure, but y'know: randomness. */
433 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
434 rc * current_quality * 8 >> 10);
440 static void start_khwrngd(void)
442 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
443 if (hwrng_fill == ERR_PTR(-ENOMEM)) {
444 pr_err("hwrng_fill thread creation failed");
449 int hwrng_register(struct hwrng *rng)
452 struct hwrng *old_rng, *tmp;
454 if (rng->name == NULL ||
455 (rng->data_read == NULL && rng->read == NULL))
458 mutex_lock(&rng_mutex);
460 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
463 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
468 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
475 /* Must not register two RNGs with the same name. */
477 list_for_each_entry(tmp, &rng_list, list) {
478 if (strcmp(tmp->name, rng->name) == 0)
482 init_completion(&rng->cleanup_done);
483 complete(&rng->cleanup_done);
485 old_rng = current_rng;
488 err = set_current_rng(rng);
492 list_add_tail(&rng->list, &rng_list);
494 if (old_rng && !rng->init) {
496 * Use a new device's input to add some randomness to
497 * the system. If this rng device isn't going to be
498 * used right away, its init function hasn't been
499 * called yet; so only use the randomness from devices
500 * that don't need an init callback.
502 add_early_randomness(rng);
506 mutex_unlock(&rng_mutex);
510 EXPORT_SYMBOL_GPL(hwrng_register);
512 void hwrng_unregister(struct hwrng *rng)
514 mutex_lock(&rng_mutex);
516 list_del(&rng->list);
517 if (current_rng == rng) {
519 if (!list_empty(&rng_list)) {
522 tail = list_entry(rng_list.prev, struct hwrng, list);
524 set_current_rng(tail);
528 if (list_empty(&rng_list)) {
529 mutex_unlock(&rng_mutex);
531 kthread_stop(hwrng_fill);
533 mutex_unlock(&rng_mutex);
535 wait_for_completion(&rng->cleanup_done);
537 EXPORT_SYMBOL_GPL(hwrng_unregister);
539 static int __init hwrng_modinit(void)
541 return register_miscdev();
544 static void __exit hwrng_modexit(void)
546 mutex_lock(&rng_mutex);
550 mutex_unlock(&rng_mutex);
552 unregister_miscdev();
555 module_init(hwrng_modinit);
556 module_exit(hwrng_modexit);
558 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
559 MODULE_LICENSE("GPL");