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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/init.h> | |
40 | #include <linux/miscdevice.h> | |
41 | #include <linux/delay.h> | |
42 | #include <asm/uaccess.h> | |
43 | ||
44 | ||
45 | #define RNG_MODULE_NAME "hw_random" | |
46 | #define PFX RNG_MODULE_NAME ": " | |
47 | #define RNG_MISCDEV_MINOR 183 /* official */ | |
48 | ||
49 | ||
50 | static struct hwrng *current_rng; | |
51 | static LIST_HEAD(rng_list); | |
52 | static DEFINE_MUTEX(rng_mutex); | |
53 | ||
54 | ||
55 | static inline int hwrng_init(struct hwrng *rng) | |
56 | { | |
57 | if (!rng->init) | |
58 | return 0; | |
59 | return rng->init(rng); | |
60 | } | |
61 | ||
62 | static inline void hwrng_cleanup(struct hwrng *rng) | |
63 | { | |
64 | if (rng && rng->cleanup) | |
65 | rng->cleanup(rng); | |
66 | } | |
67 | ||
68 | static inline int hwrng_data_present(struct hwrng *rng) | |
69 | { | |
70 | if (!rng->data_present) | |
71 | return 1; | |
72 | return rng->data_present(rng); | |
73 | } | |
74 | ||
75 | static inline int hwrng_data_read(struct hwrng *rng, u32 *data) | |
76 | { | |
77 | return rng->data_read(rng, data); | |
78 | } | |
79 | ||
80 | ||
81 | static int rng_dev_open(struct inode *inode, struct file *filp) | |
82 | { | |
83 | /* enforce read-only access to this chrdev */ | |
84 | if ((filp->f_mode & FMODE_READ) == 0) | |
85 | return -EINVAL; | |
86 | if (filp->f_mode & FMODE_WRITE) | |
87 | return -EINVAL; | |
88 | return 0; | |
89 | } | |
90 | ||
91 | static ssize_t rng_dev_read(struct file *filp, char __user *buf, | |
92 | size_t size, loff_t *offp) | |
93 | { | |
94 | u32 data; | |
95 | ssize_t ret = 0; | |
96 | int i, err = 0; | |
97 | int data_present; | |
98 | int bytes_read; | |
99 | ||
100 | while (size) { | |
101 | err = -ERESTARTSYS; | |
102 | if (mutex_lock_interruptible(&rng_mutex)) | |
103 | goto out; | |
104 | if (!current_rng) { | |
105 | mutex_unlock(&rng_mutex); | |
106 | err = -ENODEV; | |
107 | goto out; | |
108 | } | |
109 | if (filp->f_flags & O_NONBLOCK) { | |
110 | data_present = hwrng_data_present(current_rng); | |
111 | } else { | |
112 | /* Some RNG require some time between data_reads to gather | |
113 | * new entropy. Poll it. | |
114 | */ | |
115 | for (i = 0; i < 20; i++) { | |
116 | data_present = hwrng_data_present(current_rng); | |
117 | if (data_present) | |
118 | break; | |
119 | udelay(10); | |
120 | } | |
121 | } | |
122 | bytes_read = 0; | |
123 | if (data_present) | |
124 | bytes_read = hwrng_data_read(current_rng, &data); | |
125 | mutex_unlock(&rng_mutex); | |
126 | ||
127 | err = -EAGAIN; | |
128 | if (!bytes_read && (filp->f_flags & O_NONBLOCK)) | |
129 | goto out; | |
130 | ||
131 | err = -EFAULT; | |
132 | while (bytes_read && size) { | |
133 | if (put_user((u8)data, buf++)) | |
134 | goto out; | |
135 | size--; | |
136 | ret++; | |
137 | bytes_read--; | |
138 | data >>= 8; | |
139 | } | |
140 | ||
141 | if (need_resched()) | |
142 | schedule_timeout_interruptible(1); | |
143 | err = -ERESTARTSYS; | |
144 | if (signal_pending(current)) | |
145 | goto out; | |
146 | } | |
147 | out: | |
148 | return ret ? : err; | |
149 | } | |
150 | ||
151 | ||
152 | static struct file_operations rng_chrdev_ops = { | |
153 | .owner = THIS_MODULE, | |
154 | .open = rng_dev_open, | |
155 | .read = rng_dev_read, | |
156 | }; | |
157 | ||
158 | static struct miscdevice rng_miscdev = { | |
159 | .minor = RNG_MISCDEV_MINOR, | |
160 | .name = RNG_MODULE_NAME, | |
161 | .fops = &rng_chrdev_ops, | |
162 | }; | |
163 | ||
164 | ||
165 | static ssize_t hwrng_attr_current_store(struct class_device *class, | |
166 | const char *buf, size_t len) | |
167 | { | |
168 | int err; | |
169 | struct hwrng *rng; | |
170 | ||
171 | err = mutex_lock_interruptible(&rng_mutex); | |
172 | if (err) | |
173 | return -ERESTARTSYS; | |
174 | err = -ENODEV; | |
175 | list_for_each_entry(rng, &rng_list, list) { | |
176 | if (strcmp(rng->name, buf) == 0) { | |
177 | if (rng == current_rng) { | |
178 | err = 0; | |
179 | break; | |
180 | } | |
181 | err = hwrng_init(rng); | |
182 | if (err) | |
183 | break; | |
184 | hwrng_cleanup(current_rng); | |
185 | current_rng = rng; | |
186 | err = 0; | |
187 | break; | |
188 | } | |
189 | } | |
190 | mutex_unlock(&rng_mutex); | |
191 | ||
192 | return err ? : len; | |
193 | } | |
194 | ||
195 | static ssize_t hwrng_attr_current_show(struct class_device *class, | |
196 | char *buf) | |
197 | { | |
198 | int err; | |
199 | ssize_t ret; | |
200 | const char *name = "none"; | |
201 | ||
202 | err = mutex_lock_interruptible(&rng_mutex); | |
203 | if (err) | |
204 | return -ERESTARTSYS; | |
205 | if (current_rng) | |
206 | name = current_rng->name; | |
207 | ret = snprintf(buf, PAGE_SIZE, "%s\n", name); | |
208 | mutex_unlock(&rng_mutex); | |
209 | ||
210 | return ret; | |
211 | } | |
212 | ||
213 | static ssize_t hwrng_attr_available_show(struct class_device *class, | |
214 | char *buf) | |
215 | { | |
216 | int err; | |
217 | ssize_t ret = 0; | |
218 | struct hwrng *rng; | |
219 | ||
220 | err = mutex_lock_interruptible(&rng_mutex); | |
221 | if (err) | |
222 | return -ERESTARTSYS; | |
223 | buf[0] = '\0'; | |
224 | list_for_each_entry(rng, &rng_list, list) { | |
225 | strncat(buf, rng->name, PAGE_SIZE - ret - 1); | |
226 | ret += strlen(rng->name); | |
227 | strncat(buf, " ", PAGE_SIZE - ret - 1); | |
228 | ret++; | |
229 | } | |
230 | strncat(buf, "\n", PAGE_SIZE - ret - 1); | |
231 | ret++; | |
232 | mutex_unlock(&rng_mutex); | |
233 | ||
234 | return ret; | |
235 | } | |
236 | ||
237 | static CLASS_DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR, | |
238 | hwrng_attr_current_show, | |
239 | hwrng_attr_current_store); | |
240 | static CLASS_DEVICE_ATTR(rng_available, S_IRUGO, | |
241 | hwrng_attr_available_show, | |
242 | NULL); | |
243 | ||
244 | ||
245 | static void unregister_miscdev(void) | |
246 | { | |
247 | class_device_remove_file(rng_miscdev.class, | |
248 | &class_device_attr_rng_available); | |
249 | class_device_remove_file(rng_miscdev.class, | |
250 | &class_device_attr_rng_current); | |
251 | misc_deregister(&rng_miscdev); | |
252 | } | |
253 | ||
254 | static int register_miscdev(void) | |
255 | { | |
256 | int err; | |
257 | ||
258 | err = misc_register(&rng_miscdev); | |
259 | if (err) | |
260 | goto out; | |
261 | err = class_device_create_file(rng_miscdev.class, | |
262 | &class_device_attr_rng_current); | |
263 | if (err) | |
264 | goto err_misc_dereg; | |
265 | err = class_device_create_file(rng_miscdev.class, | |
266 | &class_device_attr_rng_available); | |
267 | if (err) | |
268 | goto err_remove_current; | |
269 | out: | |
270 | return err; | |
271 | ||
272 | err_remove_current: | |
273 | class_device_remove_file(rng_miscdev.class, | |
274 | &class_device_attr_rng_current); | |
275 | err_misc_dereg: | |
276 | misc_deregister(&rng_miscdev); | |
277 | goto out; | |
278 | } | |
279 | ||
280 | int hwrng_register(struct hwrng *rng) | |
281 | { | |
282 | int must_register_misc; | |
283 | int err = -EINVAL; | |
284 | struct hwrng *old_rng, *tmp; | |
285 | ||
286 | if (rng->name == NULL || | |
287 | rng->data_read == NULL) | |
288 | goto out; | |
289 | ||
290 | mutex_lock(&rng_mutex); | |
291 | ||
292 | /* Must not register two RNGs with the same name. */ | |
293 | err = -EEXIST; | |
294 | list_for_each_entry(tmp, &rng_list, list) { | |
295 | if (strcmp(tmp->name, rng->name) == 0) | |
296 | goto out_unlock; | |
297 | } | |
298 | ||
299 | must_register_misc = (current_rng == NULL); | |
300 | old_rng = current_rng; | |
301 | if (!old_rng) { | |
302 | err = hwrng_init(rng); | |
303 | if (err) | |
304 | goto out_unlock; | |
305 | current_rng = rng; | |
306 | } | |
307 | err = 0; | |
308 | if (must_register_misc) { | |
309 | err = register_miscdev(); | |
310 | if (err) { | |
311 | if (!old_rng) { | |
312 | hwrng_cleanup(rng); | |
313 | current_rng = NULL; | |
314 | } | |
315 | goto out_unlock; | |
316 | } | |
317 | } | |
318 | INIT_LIST_HEAD(&rng->list); | |
319 | list_add_tail(&rng->list, &rng_list); | |
320 | out_unlock: | |
321 | mutex_unlock(&rng_mutex); | |
322 | out: | |
323 | return err; | |
324 | } | |
325 | EXPORT_SYMBOL_GPL(hwrng_register); | |
326 | ||
327 | void hwrng_unregister(struct hwrng *rng) | |
328 | { | |
329 | int err; | |
330 | ||
331 | mutex_lock(&rng_mutex); | |
332 | ||
333 | list_del(&rng->list); | |
334 | if (current_rng == rng) { | |
335 | hwrng_cleanup(rng); | |
336 | if (list_empty(&rng_list)) { | |
337 | current_rng = NULL; | |
338 | } else { | |
339 | current_rng = list_entry(rng_list.prev, struct hwrng, list); | |
340 | err = hwrng_init(current_rng); | |
341 | if (err) | |
342 | current_rng = NULL; | |
343 | } | |
344 | } | |
345 | if (list_empty(&rng_list)) | |
346 | unregister_miscdev(); | |
347 | ||
348 | mutex_unlock(&rng_mutex); | |
349 | } | |
350 | EXPORT_SYMBOL_GPL(hwrng_unregister); | |
351 | ||
352 | ||
353 | MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver"); | |
354 | MODULE_LICENSE("GPL"); |