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)
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, 0);
92 mutex_unlock(&reading_mutex);
94 add_device_randomness(rng_buffer, 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 if (current_quality > 1024)
183 current_quality = 1024;
185 if (current_quality == 0 && hwrng_fill)
186 kthread_stop(hwrng_fill);
187 if (current_quality > 0 && !hwrng_fill)
193 static int rng_dev_open(struct inode *inode, struct file *filp)
195 /* enforce read-only access to this chrdev */
196 if ((filp->f_mode & FMODE_READ) == 0)
198 if (filp->f_mode & FMODE_WRITE)
203 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
207 BUG_ON(!mutex_is_locked(&reading_mutex));
209 return rng->read(rng, (void *)buffer, size, wait);
211 if (rng->data_present)
212 present = rng->data_present(rng, wait);
217 return rng->data_read(rng, (u32 *)buffer);
222 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
223 size_t size, loff_t *offp)
231 rng = get_current_rng();
241 if (mutex_lock_interruptible(&reading_mutex)) {
246 bytes_read = rng_get_data(rng, rng_buffer,
248 !(filp->f_flags & O_NONBLOCK));
249 if (bytes_read < 0) {
251 goto out_unlock_reading;
253 data_avail = bytes_read;
257 if (filp->f_flags & O_NONBLOCK) {
259 goto out_unlock_reading;
268 if (copy_to_user(buf + ret, rng_buffer + data_avail,
271 goto out_unlock_reading;
278 mutex_unlock(&reading_mutex);
282 schedule_timeout_interruptible(1);
284 if (signal_pending(current)) {
293 mutex_unlock(&reading_mutex);
300 static const struct file_operations rng_chrdev_ops = {
301 .owner = THIS_MODULE,
302 .open = rng_dev_open,
303 .read = rng_dev_read,
304 .llseek = noop_llseek,
307 static const struct attribute_group *rng_dev_groups[];
309 static struct miscdevice rng_miscdev = {
310 .minor = RNG_MISCDEV_MINOR,
311 .name = RNG_MODULE_NAME,
313 .fops = &rng_chrdev_ops,
314 .groups = rng_dev_groups,
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 list_for_each_entry(rng, &rng_list, list) {
330 if (sysfs_streq(rng->name, buf)) {
332 if (rng != current_rng)
333 err = set_current_rng(rng);
337 mutex_unlock(&rng_mutex);
342 static ssize_t hwrng_attr_current_show(struct device *dev,
343 struct device_attribute *attr,
349 rng = get_current_rng();
353 ret = snprintf(buf, PAGE_SIZE, "%s\n", rng ? rng->name : "none");
359 static ssize_t hwrng_attr_available_show(struct device *dev,
360 struct device_attribute *attr,
366 err = mutex_lock_interruptible(&rng_mutex);
370 list_for_each_entry(rng, &rng_list, list) {
371 strlcat(buf, rng->name, PAGE_SIZE);
372 strlcat(buf, " ", PAGE_SIZE);
374 strlcat(buf, "\n", PAGE_SIZE);
375 mutex_unlock(&rng_mutex);
380 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
381 hwrng_attr_current_show,
382 hwrng_attr_current_store);
383 static DEVICE_ATTR(rng_available, S_IRUGO,
384 hwrng_attr_available_show,
387 static struct attribute *rng_dev_attrs[] = {
388 &dev_attr_rng_current.attr,
389 &dev_attr_rng_available.attr,
393 ATTRIBUTE_GROUPS(rng_dev);
395 static void __exit unregister_miscdev(void)
397 misc_deregister(&rng_miscdev);
400 static int __init register_miscdev(void)
402 return misc_register(&rng_miscdev);
405 static int hwrng_fillfn(void *unused)
409 while (!kthread_should_stop()) {
412 rng = get_current_rng();
413 if (IS_ERR(rng) || !rng)
415 mutex_lock(&reading_mutex);
416 rc = rng_get_data(rng, rng_fillbuf,
417 rng_buffer_size(), 1);
418 mutex_unlock(&reading_mutex);
421 pr_warn("hwrng: no data available\n");
422 msleep_interruptible(10000);
425 /* Outside lock, sure, but y'know: randomness. */
426 add_hwgenerator_randomness((void *)rng_fillbuf, rc,
427 rc * current_quality * 8 >> 10);
433 static void start_khwrngd(void)
435 hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng");
436 if (IS_ERR(hwrng_fill)) {
437 pr_err("hwrng_fill thread creation failed");
442 int hwrng_register(struct hwrng *rng)
445 struct hwrng *old_rng, *tmp;
447 if (rng->name == NULL ||
448 (rng->data_read == NULL && rng->read == NULL))
451 mutex_lock(&rng_mutex);
453 /* kmalloc makes this safe for virt_to_page() in virtio_rng.c */
456 rng_buffer = kmalloc(rng_buffer_size(), GFP_KERNEL);
461 rng_fillbuf = kmalloc(rng_buffer_size(), GFP_KERNEL);
468 /* Must not register two RNGs with the same name. */
470 list_for_each_entry(tmp, &rng_list, list) {
471 if (strcmp(tmp->name, rng->name) == 0)
475 init_completion(&rng->cleanup_done);
476 complete(&rng->cleanup_done);
478 old_rng = current_rng;
481 err = set_current_rng(rng);
485 list_add_tail(&rng->list, &rng_list);
487 if (old_rng && !rng->init) {
489 * Use a new device's input to add some randomness to
490 * the system. If this rng device isn't going to be
491 * used right away, its init function hasn't been
492 * called yet; so only use the randomness from devices
493 * that don't need an init callback.
495 add_early_randomness(rng);
499 mutex_unlock(&rng_mutex);
503 EXPORT_SYMBOL_GPL(hwrng_register);
505 void hwrng_unregister(struct hwrng *rng)
507 mutex_lock(&rng_mutex);
509 list_del(&rng->list);
510 if (current_rng == rng) {
512 if (!list_empty(&rng_list)) {
515 tail = list_entry(rng_list.prev, struct hwrng, list);
517 set_current_rng(tail);
521 if (list_empty(&rng_list)) {
522 mutex_unlock(&rng_mutex);
524 kthread_stop(hwrng_fill);
526 mutex_unlock(&rng_mutex);
528 wait_for_completion(&rng->cleanup_done);
530 EXPORT_SYMBOL_GPL(hwrng_unregister);
532 static void devm_hwrng_release(struct device *dev, void *res)
534 hwrng_unregister(*(struct hwrng **)res);
537 static int devm_hwrng_match(struct device *dev, void *res, void *data)
539 struct hwrng **r = res;
541 if (WARN_ON(!r || !*r))
547 int devm_hwrng_register(struct device *dev, struct hwrng *rng)
552 ptr = devres_alloc(devm_hwrng_release, sizeof(*ptr), GFP_KERNEL);
556 error = hwrng_register(rng);
563 devres_add(dev, ptr);
566 EXPORT_SYMBOL_GPL(devm_hwrng_register);
568 void devm_hwrng_unregister(struct device *dev, struct hwrng *rng)
570 devres_release(dev, devm_hwrng_release, devm_hwrng_match, rng);
572 EXPORT_SYMBOL_GPL(devm_hwrng_unregister);
574 static int __init hwrng_modinit(void)
576 return register_miscdev();
579 static void __exit hwrng_modexit(void)
581 mutex_lock(&rng_mutex);
585 mutex_unlock(&rng_mutex);
587 unregister_miscdev();
590 module_init(hwrng_modinit);
591 module_exit(hwrng_modexit);
593 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
594 MODULE_LICENSE("GPL");