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 <linux/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)
88 size_t size = min_t(size_t, 16, rng_buffer_size());
90 mutex_lock(&reading_mutex);
91 bytes_read = rng_get_data(rng, rng_buffer, size, 1);
92 mutex_unlock(&reading_mutex);
94 add_device_randomness(rng_buffer, bytes_read);
95 memset(rng_buffer, 0, size);
98 static inline void cleanup_rng(struct kref *kref)
100 struct hwrng *rng = container_of(kref, struct hwrng, ref);
105 complete(&rng->cleanup_done);
108 static int set_current_rng(struct hwrng *rng)
112 BUG_ON(!mutex_is_locked(&rng_mutex));
114 err = hwrng_init(rng);
124 static void drop_current_rng(void)
126 BUG_ON(!mutex_is_locked(&rng_mutex));
130 /* decrease last reference for triggering the cleanup */
131 kref_put(¤t_rng->ref, cleanup_rng);
135 /* Returns ERR_PTR(), NULL or refcounted hwrng */
136 static struct hwrng *get_current_rng(void)
140 if (mutex_lock_interruptible(&rng_mutex))
141 return ERR_PTR(-ERESTARTSYS);
147 mutex_unlock(&rng_mutex);
151 static void put_rng(struct hwrng *rng)
154 * Hold rng_mutex here so we serialize in case they set_current_rng
155 * on rng again immediately.
157 mutex_lock(&rng_mutex);
159 kref_put(&rng->ref, cleanup_rng);
160 mutex_unlock(&rng_mutex);
163 static int hwrng_init(struct hwrng *rng)
165 if (kref_get_unless_zero(&rng->ref))
171 ret = rng->init(rng);
176 kref_init(&rng->ref);
177 reinit_completion(&rng->cleanup_done);
180 add_early_randomness(rng);
182 current_quality = rng->quality ? : default_quality;
183 if (current_quality > 1024)
184 current_quality = 1024;
186 if (current_quality == 0 && hwrng_fill)
187 kthread_stop(hwrng_fill);
188 if (current_quality > 0 && !hwrng_fill)
194 static int rng_dev_open(struct inode *inode, struct file *filp)
196 /* enforce read-only access to this chrdev */
197 if ((filp->f_mode & FMODE_READ) == 0)
199 if (filp->f_mode & FMODE_WRITE)
204 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
208 BUG_ON(!mutex_is_locked(&reading_mutex));
210 return rng->read(rng, (void *)buffer, size, wait);
212 if (rng->data_present)
213 present = rng->data_present(rng, wait);
218 return rng->data_read(rng, (u32 *)buffer);
223 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
224 size_t size, loff_t *offp)
232 rng = get_current_rng();
242 if (mutex_lock_interruptible(&reading_mutex)) {
247 bytes_read = rng_get_data(rng, rng_buffer,
249 !(filp->f_flags & O_NONBLOCK));
250 if (bytes_read < 0) {
252 goto out_unlock_reading;
254 data_avail = bytes_read;
258 if (filp->f_flags & O_NONBLOCK) {
260 goto out_unlock_reading;
269 if (copy_to_user(buf + ret, rng_buffer + data_avail,
272 goto out_unlock_reading;
279 mutex_unlock(&reading_mutex);
283 schedule_timeout_interruptible(1);
285 if (signal_pending(current)) {
291 memset(rng_buffer, 0, rng_buffer_size());
295 mutex_unlock(&reading_mutex);
302 static const struct file_operations rng_chrdev_ops = {
303 .owner = THIS_MODULE,
304 .open = rng_dev_open,
305 .read = rng_dev_read,
306 .llseek = noop_llseek,
309 static const struct attribute_group *rng_dev_groups[];
311 static struct miscdevice rng_miscdev = {
312 .minor = RNG_MISCDEV_MINOR,
313 .name = RNG_MODULE_NAME,
315 .fops = &rng_chrdev_ops,
316 .groups = rng_dev_groups,
320 static ssize_t hwrng_attr_current_store(struct device *dev,
321 struct device_attribute *attr,
322 const char *buf, size_t len)
327 err = mutex_lock_interruptible(&rng_mutex);
331 list_for_each_entry(rng, &rng_list, list) {
332 if (sysfs_streq(rng->name, buf)) {
334 if (rng != current_rng)
335 err = set_current_rng(rng);
339 mutex_unlock(&rng_mutex);
344 static ssize_t hwrng_attr_current_show(struct device *dev,
345 struct device_attribute *attr,
351 rng = get_current_rng();
355 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
361 static ssize_t hwrng_attr_available_show(struct device *dev,
362 struct device_attribute *attr,
368 err = mutex_lock_interruptible(&rng_mutex);
372 list_for_each_entry(rng, &rng_list, list) {
373 strlcat(buf, rng->name, PAGE_SIZE);
374 strlcat(buf, " ", PAGE_SIZE);
376 strlcat(buf, "\n", PAGE_SIZE);
377 mutex_unlock(&rng_mutex);
382 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
383 hwrng_attr_current_show,
384 hwrng_attr_current_store);
385 static DEVICE_ATTR(rng_available, S_IRUGO,
386 hwrng_attr_available_show,
389 static struct attribute *rng_dev_attrs[] = {
390 &dev_attr_rng_current.attr,
391 &dev_attr_rng_available.attr,
395 ATTRIBUTE_GROUPS(rng_dev);
397 static void __exit unregister_miscdev(void)
399 misc_deregister(&rng_miscdev);
402 static int __init register_miscdev(void)
404 return misc_register(&rng_miscdev);
407 static int hwrng_fillfn(void *unused)
411 while (!kthread_should_stop()) {
414 rng = get_current_rng();
415 if (IS_ERR(rng) || !rng)
417 mutex_lock(&reading_mutex);
418 rc = rng_get_data(rng, rng_fillbuf,
419 rng_buffer_size(), 1);
420 mutex_unlock(&reading_mutex);
423 pr_warn("hwrng: no data available\n");
424 msleep_interruptible(10000);
427 /* Outside lock, sure, but y'know: randomness. */
428 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
429 rc * current_quality * 8 >> 10);
430 memset(rng_fillbuf, 0, rng_buffer_size());
436 static void start_khwrngd(void)
438 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
439 if (IS_ERR(hwrng_fill)) {
440 pr_err("hwrng_fill thread creation failed");
445 int hwrng_register(struct hwrng *rng)
448 struct hwrng *old_rng, *tmp;
450 if (rng->name == NULL ||
451 (rng->data_read == NULL && rng->read == NULL))
454 mutex_lock(&rng_mutex);
455 /* Must not register two RNGs with the same name. */
457 list_for_each_entry(tmp, &rng_list, list) {
458 if (strcmp(tmp->name, rng->name) == 0)
462 init_completion(&rng->cleanup_done);
463 complete(&rng->cleanup_done);
465 old_rng = current_rng;
468 err = set_current_rng(rng);
472 list_add_tail(&rng->list, &rng_list);
474 if (old_rng && !rng->init) {
476 * Use a new device's input to add some randomness to
477 * the system. If this rng device isn't going to be
478 * used right away, its init function hasn't been
479 * called yet; so only use the randomness from devices
480 * that don't need an init callback.
482 add_early_randomness(rng);
486 mutex_unlock(&rng_mutex);
490 EXPORT_SYMBOL_GPL(hwrng_register);
492 void hwrng_unregister(struct hwrng *rng)
494 mutex_lock(&rng_mutex);
496 list_del(&rng->list);
497 if (current_rng == rng) {
499 if (!list_empty(&rng_list)) {
502 tail = list_entry(rng_list.prev, struct hwrng, list);
504 set_current_rng(tail);
508 if (list_empty(&rng_list)) {
509 mutex_unlock(&rng_mutex);
511 kthread_stop(hwrng_fill);
513 mutex_unlock(&rng_mutex);
515 wait_for_completion(&rng->cleanup_done);
517 EXPORT_SYMBOL_GPL(hwrng_unregister);
519 static void devm_hwrng_release(struct device *dev, void *res)
521 hwrng_unregister(*(struct hwrng **)res);
524 static int devm_hwrng_match(struct device *dev, void *res, void *data)
526 struct hwrng **r = res;
528 if (WARN_ON(!r || !*r))
534 int devm_hwrng_register(struct device *dev, struct hwrng *rng)
539 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
543 error = hwrng_register(rng);
550 devres_add(dev, ptr);
553 EXPORT_SYMBOL_GPL(devm_hwrng_register);
555 void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
557 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
559 EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
561 static int __init hwrng_modinit(void)
565 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
566 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
570 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
576 ret = register_miscdev();
585 static void __exit hwrng_modexit(void)
587 mutex_lock(&rng_mutex);
591 mutex_unlock(&rng_mutex);
593 unregister_miscdev();
596 module_init(hwrng_modinit);
597 module_exit(hwrng_modexit);
599 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
600 MODULE_LICENSE("GPL");