Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
[linux-2.6.git] / drivers / char / hw_random / core.c
1 /*
2         Added support for the AMD Geode LX RNG
3         (c) Copyright 2004-2005 Advanced Micro Devices, Inc.
4
5         derived from
6
7         Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
8         (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
9
10         derived from
11
12         Hardware driver for the AMD 768 Random Number Generator (RNG)
13         (c) Copyright 2001 Red Hat Inc <alan@redhat.com>
14
15         derived from
16
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>
20
21         Added generic RNG API
22         Copyright 2006 Michael Buesch <mbuesch@freenet.de>
23         Copyright 2005 (c) MontaVista Software, Inc.
24
25         Please read Documentation/hw_random.txt for details on use.
26
27         ----------------------------------------------------------
28         This software may be used and distributed according to the terms
29         of the GNU General Public License, incorporated herein by reference.
30
31  */
32
33
34 #include <linux/device.h>
35 #include <linux/hw_random.h>
36 #include <linux/module.h>
37 #include <linux/kernel.h>
38 #include <linux/fs.h>
39 #include <linux/sched.h>
40 #include <linux/smp_lock.h>
41 #include <linux/init.h>
42 #include <linux/miscdevice.h>
43 #include <linux/delay.h>
44 #include <asm/uaccess.h>
45
46
47 #define RNG_MODULE_NAME         "hw_random"
48 #define PFX                     RNG_MODULE_NAME ": "
49 #define RNG_MISCDEV_MINOR       183 /* official */
50
51
52 static struct hwrng *current_rng;
53 static LIST_HEAD(rng_list);
54 static DEFINE_MUTEX(rng_mutex);
55 static int data_avail;
56 static u8 rng_buffer[SMP_CACHE_BYTES] __cacheline_aligned;
57
58 static inline int hwrng_init(struct hwrng *rng)
59 {
60         if (!rng->init)
61                 return 0;
62         return rng->init(rng);
63 }
64
65 static inline void hwrng_cleanup(struct hwrng *rng)
66 {
67         if (rng && rng->cleanup)
68                 rng->cleanup(rng);
69 }
70
71 static int rng_dev_open(struct inode *inode, struct file *filp)
72 {
73         /* enforce read-only access to this chrdev */
74         if ((filp->f_mode & FMODE_READ) == 0)
75                 return -EINVAL;
76         if (filp->f_mode & FMODE_WRITE)
77                 return -EINVAL;
78         cycle_kernel_lock();
79         return 0;
80 }
81
82 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
83                         int wait) {
84         int present;
85
86         if (rng->read)
87                 return rng->read(rng, (void *)buffer, size, wait);
88
89         if (rng->data_present)
90                 present = rng->data_present(rng, wait);
91         else
92                 present = 1;
93
94         if (present)
95                 return rng->data_read(rng, (u32 *)buffer);
96
97         return 0;
98 }
99
100 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
101                             size_t size, loff_t *offp)
102 {
103         ssize_t ret = 0;
104         int err = 0;
105         int bytes_read, len;
106
107         while (size) {
108                 if (mutex_lock_interruptible(&rng_mutex)) {
109                         err = -ERESTARTSYS;
110                         goto out;
111                 }
112
113                 if (!current_rng) {
114                         err = -ENODEV;
115                         goto out_unlock;
116                 }
117
118                 if (!data_avail) {
119                         bytes_read = rng_get_data(current_rng, rng_buffer,
120                                 sizeof(rng_buffer),
121                                 !(filp->f_flags & O_NONBLOCK));
122                         if (bytes_read < 0) {
123                                 err = bytes_read;
124                                 goto out_unlock;
125                         }
126                         data_avail = bytes_read;
127                 }
128
129                 if (!data_avail) {
130                         if (filp->f_flags & O_NONBLOCK) {
131                                 err = -EAGAIN;
132                                 goto out_unlock;
133                         }
134                 } else {
135                         len = data_avail;
136                         if (len > size)
137                                 len = size;
138
139                         data_avail -= len;
140
141                         if (copy_to_user(buf + ret, rng_buffer + data_avail,
142                                                                 len)) {
143                                 err = -EFAULT;
144                                 goto out_unlock;
145                         }
146
147                         size -= len;
148                         ret += len;
149                 }
150
151                 mutex_unlock(&rng_mutex);
152
153                 if (need_resched())
154                         schedule_timeout_interruptible(1);
155
156                 if (signal_pending(current)) {
157                         err = -ERESTARTSYS;
158                         goto out;
159                 }
160         }
161 out_unlock:
162         mutex_unlock(&rng_mutex);
163 out:
164         return ret ? : err;
165 }
166
167
168 static const struct file_operations rng_chrdev_ops = {
169         .owner          = THIS_MODULE,
170         .open           = rng_dev_open,
171         .read           = rng_dev_read,
172 };
173
174 static struct miscdevice rng_miscdev = {
175         .minor          = RNG_MISCDEV_MINOR,
176         .name           = RNG_MODULE_NAME,
177         .nodename       = "hwrng",
178         .fops           = &rng_chrdev_ops,
179 };
180
181
182 static ssize_t hwrng_attr_current_store(struct device *dev,
183                                         struct device_attribute *attr,
184                                         const char *buf, size_t len)
185 {
186         int err;
187         struct hwrng *rng;
188
189         err = mutex_lock_interruptible(&rng_mutex);
190         if (err)
191                 return -ERESTARTSYS;
192         err = -ENODEV;
193         list_for_each_entry(rng, &rng_list, list) {
194                 if (strcmp(rng->name, buf) == 0) {
195                         if (rng == current_rng) {
196                                 err = 0;
197                                 break;
198                         }
199                         err = hwrng_init(rng);
200                         if (err)
201                                 break;
202                         hwrng_cleanup(current_rng);
203                         current_rng = rng;
204                         err = 0;
205                         break;
206                 }
207         }
208         mutex_unlock(&rng_mutex);
209
210         return err ? : len;
211 }
212
213 static ssize_t hwrng_attr_current_show(struct device *dev,
214                                        struct device_attribute *attr,
215                                        char *buf)
216 {
217         int err;
218         ssize_t ret;
219         const char *name = "none";
220
221         err = mutex_lock_interruptible(&rng_mutex);
222         if (err)
223                 return -ERESTARTSYS;
224         if (current_rng)
225                 name = current_rng->name;
226         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
227         mutex_unlock(&rng_mutex);
228
229         return ret;
230 }
231
232 static ssize_t hwrng_attr_available_show(struct device *dev,
233                                          struct device_attribute *attr,
234                                          char *buf)
235 {
236         int err;
237         ssize_t ret = 0;
238         struct hwrng *rng;
239
240         err = mutex_lock_interruptible(&rng_mutex);
241         if (err)
242                 return -ERESTARTSYS;
243         buf[0] = '\0';
244         list_for_each_entry(rng, &rng_list, list) {
245                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
246                 ret += strlen(rng->name);
247                 strncat(buf, " ", PAGE_SIZE - ret - 1);
248                 ret++;
249         }
250         strncat(buf, "\n", PAGE_SIZE - ret - 1);
251         ret++;
252         mutex_unlock(&rng_mutex);
253
254         return ret;
255 }
256
257 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
258                    hwrng_attr_current_show,
259                    hwrng_attr_current_store);
260 static DEVICE_ATTR(rng_available, S_IRUGO,
261                    hwrng_attr_available_show,
262                    NULL);
263
264
265 static void unregister_miscdev(void)
266 {
267         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
268         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
269         misc_deregister(&rng_miscdev);
270 }
271
272 static int register_miscdev(void)
273 {
274         int err;
275
276         err = misc_register(&rng_miscdev);
277         if (err)
278                 goto out;
279         err = device_create_file(rng_miscdev.this_device,
280                                  &dev_attr_rng_current);
281         if (err)
282                 goto err_misc_dereg;
283         err = device_create_file(rng_miscdev.this_device,
284                                  &dev_attr_rng_available);
285         if (err)
286                 goto err_remove_current;
287 out:
288         return err;
289
290 err_remove_current:
291         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
292 err_misc_dereg:
293         misc_deregister(&rng_miscdev);
294         goto out;
295 }
296
297 int hwrng_register(struct hwrng *rng)
298 {
299         int must_register_misc;
300         int err = -EINVAL;
301         struct hwrng *old_rng, *tmp;
302
303         if (rng->name == NULL ||
304             (rng->data_read == NULL && rng->read == NULL))
305                 goto out;
306
307         mutex_lock(&rng_mutex);
308
309         /* Must not register two RNGs with the same name. */
310         err = -EEXIST;
311         list_for_each_entry(tmp, &rng_list, list) {
312                 if (strcmp(tmp->name, rng->name) == 0)
313                         goto out_unlock;
314         }
315
316         must_register_misc = (current_rng == NULL);
317         old_rng = current_rng;
318         if (!old_rng) {
319                 err = hwrng_init(rng);
320                 if (err)
321                         goto out_unlock;
322                 current_rng = rng;
323         }
324         err = 0;
325         if (must_register_misc) {
326                 err = register_miscdev();
327                 if (err) {
328                         if (!old_rng) {
329                                 hwrng_cleanup(rng);
330                                 current_rng = NULL;
331                         }
332                         goto out_unlock;
333                 }
334         }
335         INIT_LIST_HEAD(&rng->list);
336         list_add_tail(&rng->list, &rng_list);
337 out_unlock:
338         mutex_unlock(&rng_mutex);
339 out:
340         return err;
341 }
342 EXPORT_SYMBOL_GPL(hwrng_register);
343
344 void hwrng_unregister(struct hwrng *rng)
345 {
346         int err;
347
348         mutex_lock(&rng_mutex);
349
350         list_del(&rng->list);
351         if (current_rng == rng) {
352                 hwrng_cleanup(rng);
353                 if (list_empty(&rng_list)) {
354                         current_rng = NULL;
355                 } else {
356                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
357                         err = hwrng_init(current_rng);
358                         if (err)
359                                 current_rng = NULL;
360                 }
361         }
362         if (list_empty(&rng_list))
363                 unregister_miscdev();
364
365         mutex_unlock(&rng_mutex);
366 }
367 EXPORT_SYMBOL_GPL(hwrng_unregister);
368
369
370 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
371 MODULE_LICENSE("GPL");