agp: Remove the BKL from agp_open
[sfrench/cifs-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
56
57 static inline int hwrng_init(struct hwrng *rng)
58 {
59         if (!rng->init)
60                 return 0;
61         return rng->init(rng);
62 }
63
64 static inline void hwrng_cleanup(struct hwrng *rng)
65 {
66         if (rng && rng->cleanup)
67                 rng->cleanup(rng);
68 }
69
70 static inline int hwrng_data_present(struct hwrng *rng, int wait)
71 {
72         if (!rng->data_present)
73                 return 1;
74         return rng->data_present(rng, wait);
75 }
76
77 static inline int hwrng_data_read(struct hwrng *rng, u32 *data)
78 {
79         return rng->data_read(rng, data);
80 }
81
82
83 static int rng_dev_open(struct inode *inode, struct file *filp)
84 {
85         /* enforce read-only access to this chrdev */
86         if ((filp->f_mode & FMODE_READ) == 0)
87                 return -EINVAL;
88         if (filp->f_mode & FMODE_WRITE)
89                 return -EINVAL;
90         return 0;
91 }
92
93 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
94                             size_t size, loff_t *offp)
95 {
96         u32 data;
97         ssize_t ret = 0;
98         int err = 0;
99         int bytes_read;
100
101         while (size) {
102                 err = -ERESTARTSYS;
103                 if (mutex_lock_interruptible(&rng_mutex))
104                         goto out;
105                 if (!current_rng) {
106                         mutex_unlock(&rng_mutex);
107                         err = -ENODEV;
108                         goto out;
109                 }
110
111                 bytes_read = 0;
112                 if (hwrng_data_present(current_rng,
113                                        !(filp->f_flags & O_NONBLOCK)))
114                         bytes_read = hwrng_data_read(current_rng, &data);
115                 mutex_unlock(&rng_mutex);
116
117                 err = -EAGAIN;
118                 if (!bytes_read && (filp->f_flags & O_NONBLOCK))
119                         goto out;
120                 if (bytes_read < 0) {
121                         err = bytes_read;
122                         goto out;
123                 }
124
125                 err = -EFAULT;
126                 while (bytes_read && size) {
127                         if (put_user((u8)data, buf++))
128                                 goto out;
129                         size--;
130                         ret++;
131                         bytes_read--;
132                         data >>= 8;
133                 }
134
135                 if (need_resched())
136                         schedule_timeout_interruptible(1);
137                 err = -ERESTARTSYS;
138                 if (signal_pending(current))
139                         goto out;
140         }
141 out:
142         return ret ? : err;
143 }
144
145
146 static const struct file_operations rng_chrdev_ops = {
147         .owner          = THIS_MODULE,
148         .open           = rng_dev_open,
149         .read           = rng_dev_read,
150 };
151
152 static struct miscdevice rng_miscdev = {
153         .minor          = RNG_MISCDEV_MINOR,
154         .name           = RNG_MODULE_NAME,
155         .nodename       = "hwrng",
156         .fops           = &rng_chrdev_ops,
157 };
158
159
160 static ssize_t hwrng_attr_current_store(struct device *dev,
161                                         struct device_attribute *attr,
162                                         const char *buf, size_t len)
163 {
164         int err;
165         struct hwrng *rng;
166
167         err = mutex_lock_interruptible(&rng_mutex);
168         if (err)
169                 return -ERESTARTSYS;
170         err = -ENODEV;
171         list_for_each_entry(rng, &rng_list, list) {
172                 if (strcmp(rng->name, buf) == 0) {
173                         if (rng == current_rng) {
174                                 err = 0;
175                                 break;
176                         }
177                         err = hwrng_init(rng);
178                         if (err)
179                                 break;
180                         hwrng_cleanup(current_rng);
181                         current_rng = rng;
182                         err = 0;
183                         break;
184                 }
185         }
186         mutex_unlock(&rng_mutex);
187
188         return err ? : len;
189 }
190
191 static ssize_t hwrng_attr_current_show(struct device *dev,
192                                        struct device_attribute *attr,
193                                        char *buf)
194 {
195         int err;
196         ssize_t ret;
197         const char *name = "none";
198
199         err = mutex_lock_interruptible(&rng_mutex);
200         if (err)
201                 return -ERESTARTSYS;
202         if (current_rng)
203                 name = current_rng->name;
204         ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
205         mutex_unlock(&rng_mutex);
206
207         return ret;
208 }
209
210 static ssize_t hwrng_attr_available_show(struct device *dev,
211                                          struct device_attribute *attr,
212                                          char *buf)
213 {
214         int err;
215         ssize_t ret = 0;
216         struct hwrng *rng;
217
218         err = mutex_lock_interruptible(&rng_mutex);
219         if (err)
220                 return -ERESTARTSYS;
221         buf[0] = '\0';
222         list_for_each_entry(rng, &rng_list, list) {
223                 strncat(buf, rng->name, PAGE_SIZE - ret - 1);
224                 ret += strlen(rng->name);
225                 strncat(buf, " ", PAGE_SIZE - ret - 1);
226                 ret++;
227         }
228         strncat(buf, "\n", PAGE_SIZE - ret - 1);
229         ret++;
230         mutex_unlock(&rng_mutex);
231
232         return ret;
233 }
234
235 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
236                    hwrng_attr_current_show,
237                    hwrng_attr_current_store);
238 static DEVICE_ATTR(rng_available, S_IRUGO,
239                    hwrng_attr_available_show,
240                    NULL);
241
242
243 static void unregister_miscdev(void)
244 {
245         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
246         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
247         misc_deregister(&rng_miscdev);
248 }
249
250 static int register_miscdev(void)
251 {
252         int err;
253
254         err = misc_register(&rng_miscdev);
255         if (err)
256                 goto out;
257         err = device_create_file(rng_miscdev.this_device,
258                                  &dev_attr_rng_current);
259         if (err)
260                 goto err_misc_dereg;
261         err = device_create_file(rng_miscdev.this_device,
262                                  &dev_attr_rng_available);
263         if (err)
264                 goto err_remove_current;
265 out:
266         return err;
267
268 err_remove_current:
269         device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
270 err_misc_dereg:
271         misc_deregister(&rng_miscdev);
272         goto out;
273 }
274
275 int hwrng_register(struct hwrng *rng)
276 {
277         int must_register_misc;
278         int err = -EINVAL;
279         struct hwrng *old_rng, *tmp;
280
281         if (rng->name == NULL ||
282             rng->data_read == NULL)
283                 goto out;
284
285         mutex_lock(&rng_mutex);
286
287         /* Must not register two RNGs with the same name. */
288         err = -EEXIST;
289         list_for_each_entry(tmp, &rng_list, list) {
290                 if (strcmp(tmp->name, rng->name) == 0)
291                         goto out_unlock;
292         }
293
294         must_register_misc = (current_rng == NULL);
295         old_rng = current_rng;
296         if (!old_rng) {
297                 err = hwrng_init(rng);
298                 if (err)
299                         goto out_unlock;
300                 current_rng = rng;
301         }
302         err = 0;
303         if (must_register_misc) {
304                 err = register_miscdev();
305                 if (err) {
306                         if (!old_rng) {
307                                 hwrng_cleanup(rng);
308                                 current_rng = NULL;
309                         }
310                         goto out_unlock;
311                 }
312         }
313         INIT_LIST_HEAD(&rng->list);
314         list_add_tail(&rng->list, &rng_list);
315 out_unlock:
316         mutex_unlock(&rng_mutex);
317 out:
318         return err;
319 }
320 EXPORT_SYMBOL_GPL(hwrng_register);
321
322 void hwrng_unregister(struct hwrng *rng)
323 {
324         int err;
325
326         mutex_lock(&rng_mutex);
327
328         list_del(&rng->list);
329         if (current_rng == rng) {
330                 hwrng_cleanup(rng);
331                 if (list_empty(&rng_list)) {
332                         current_rng = NULL;
333                 } else {
334                         current_rng = list_entry(rng_list.prev, struct hwrng, list);
335                         err = hwrng_init(current_rng);
336                         if (err)
337                                 current_rng = NULL;
338                 }
339         }
340         if (list_empty(&rng_list))
341                 unregister_miscdev();
342
343         mutex_unlock(&rng_mutex);
344 }
345 EXPORT_SYMBOL_GPL(hwrng_unregister);
346
347
348 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
349 MODULE_LICENSE("GPL");