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core.c
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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 <[email protected]>
9 
10  derived from
11 
12  Hardware driver for the AMD 768 Random Number Generator (RNG)
13  (c) Copyright 2001 Red Hat Inc <[email protected]>
14 
15  derived from
16 
17  Hardware driver for Intel i810 Random Number Generator (RNG)
18  Copyright 2000,2001 Jeff Garzik <[email protected]>
19  Copyright 2000,2001 Philipp Rumpf <[email protected]>
20 
21  Added generic RNG API
22  Copyright 2006 Michael Buesch <[email protected]>
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/init.h>
41 #include <linux/miscdevice.h>
42 #include <linux/delay.h>
43 #include <asm/uaccess.h>
44 
45 
46 #define RNG_MODULE_NAME "hw_random"
47 #define PFX RNG_MODULE_NAME ": "
48 #define RNG_MISCDEV_MINOR 183 /* official */
49 
50 
51 static struct hwrng *current_rng;
52 static LIST_HEAD(rng_list);
53 static DEFINE_MUTEX(rng_mutex);
54 static int data_avail;
55 static u8 rng_buffer[SMP_CACHE_BYTES < 32 ? 32 : SMP_CACHE_BYTES]
56  __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  return 0;
79 }
80 
81 static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
82  int wait) {
83  int present;
84 
85  if (rng->read)
86  return rng->read(rng, (void *)buffer, size, wait);
87 
88  if (rng->data_present)
89  present = rng->data_present(rng, wait);
90  else
91  present = 1;
92 
93  if (present)
94  return rng->data_read(rng, (u32 *)buffer);
95 
96  return 0;
97 }
98 
99 static ssize_t rng_dev_read(struct file *filp, char __user *buf,
100  size_t size, loff_t *offp)
101 {
102  ssize_t ret = 0;
103  int err = 0;
104  int bytes_read, len;
105 
106  while (size) {
107  if (mutex_lock_interruptible(&rng_mutex)) {
108  err = -ERESTARTSYS;
109  goto out;
110  }
111 
112  if (!current_rng) {
113  err = -ENODEV;
114  goto out_unlock;
115  }
116 
117  if (!data_avail) {
118  bytes_read = rng_get_data(current_rng, rng_buffer,
119  sizeof(rng_buffer),
120  !(filp->f_flags & O_NONBLOCK));
121  if (bytes_read < 0) {
122  err = bytes_read;
123  goto out_unlock;
124  }
125  data_avail = bytes_read;
126  }
127 
128  if (!data_avail) {
129  if (filp->f_flags & O_NONBLOCK) {
130  err = -EAGAIN;
131  goto out_unlock;
132  }
133  } else {
134  len = data_avail;
135  if (len > size)
136  len = size;
137 
138  data_avail -= len;
139 
140  if (copy_to_user(buf + ret, rng_buffer + data_avail,
141  len)) {
142  err = -EFAULT;
143  goto out_unlock;
144  }
145 
146  size -= len;
147  ret += len;
148  }
149 
150  mutex_unlock(&rng_mutex);
151 
152  if (need_resched())
153  schedule_timeout_interruptible(1);
154 
155  if (signal_pending(current)) {
156  err = -ERESTARTSYS;
157  goto out;
158  }
159  }
160 out:
161  return ret ? : err;
162 out_unlock:
163  mutex_unlock(&rng_mutex);
164  goto out;
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  .llseek = noop_llseek,
173 };
174 
175 static struct miscdevice rng_miscdev = {
176  .minor = RNG_MISCDEV_MINOR,
177  .name = RNG_MODULE_NAME,
178  .nodename = "hwrng",
179  .fops = &rng_chrdev_ops,
180 };
181 
182 
183 static ssize_t hwrng_attr_current_store(struct device *dev,
184  struct device_attribute *attr,
185  const char *buf, size_t len)
186 {
187  int err;
188  struct hwrng *rng;
189 
190  err = mutex_lock_interruptible(&rng_mutex);
191  if (err)
192  return -ERESTARTSYS;
193  err = -ENODEV;
194  list_for_each_entry(rng, &rng_list, list) {
195  if (strcmp(rng->name, buf) == 0) {
196  if (rng == current_rng) {
197  err = 0;
198  break;
199  }
200  err = hwrng_init(rng);
201  if (err)
202  break;
203  hwrng_cleanup(current_rng);
204  current_rng = rng;
205  err = 0;
206  break;
207  }
208  }
209  mutex_unlock(&rng_mutex);
210 
211  return err ? : len;
212 }
213 
214 static ssize_t hwrng_attr_current_show(struct device *dev,
215  struct device_attribute *attr,
216  char *buf)
217 {
218  int err;
219  ssize_t ret;
220  const char *name = "none";
221 
222  err = mutex_lock_interruptible(&rng_mutex);
223  if (err)
224  return -ERESTARTSYS;
225  if (current_rng)
226  name = current_rng->name;
227  ret = snprintf(buf, PAGE_SIZE, "%s\n", name);
228  mutex_unlock(&rng_mutex);
229 
230  return ret;
231 }
232 
233 static ssize_t hwrng_attr_available_show(struct device *dev,
234  struct device_attribute *attr,
235  char *buf)
236 {
237  int err;
238  ssize_t ret = 0;
239  struct hwrng *rng;
240 
241  err = mutex_lock_interruptible(&rng_mutex);
242  if (err)
243  return -ERESTARTSYS;
244  buf[0] = '\0';
245  list_for_each_entry(rng, &rng_list, list) {
246  strncat(buf, rng->name, PAGE_SIZE - ret - 1);
247  ret += strlen(rng->name);
248  strncat(buf, " ", PAGE_SIZE - ret - 1);
249  ret++;
250  }
251  strncat(buf, "\n", PAGE_SIZE - ret - 1);
252  ret++;
253  mutex_unlock(&rng_mutex);
254 
255  return ret;
256 }
257 
258 static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
259  hwrng_attr_current_show,
260  hwrng_attr_current_store);
261 static DEVICE_ATTR(rng_available, S_IRUGO,
262  hwrng_attr_available_show,
263  NULL);
264 
265 
266 static void unregister_miscdev(void)
267 {
268  device_remove_file(rng_miscdev.this_device, &dev_attr_rng_available);
269  device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
270  misc_deregister(&rng_miscdev);
271 }
272 
273 static int register_miscdev(void)
274 {
275  int err;
276 
277  err = misc_register(&rng_miscdev);
278  if (err)
279  goto out;
280  err = device_create_file(rng_miscdev.this_device,
281  &dev_attr_rng_current);
282  if (err)
283  goto err_misc_dereg;
284  err = device_create_file(rng_miscdev.this_device,
285  &dev_attr_rng_available);
286  if (err)
287  goto err_remove_current;
288 out:
289  return err;
290 
291 err_remove_current:
292  device_remove_file(rng_miscdev.this_device, &dev_attr_rng_current);
293 err_misc_dereg:
294  misc_deregister(&rng_miscdev);
295  goto out;
296 }
297 
298 int hwrng_register(struct hwrng *rng)
299 {
300  int must_register_misc;
301  int err = -EINVAL;
302  struct hwrng *old_rng, *tmp;
303 
304  if (rng->name == NULL ||
305  (rng->data_read == NULL && rng->read == NULL))
306  goto out;
307 
308  mutex_lock(&rng_mutex);
309 
310  /* Must not register two RNGs with the same name. */
311  err = -EEXIST;
312  list_for_each_entry(tmp, &rng_list, list) {
313  if (strcmp(tmp->name, rng->name) == 0)
314  goto out_unlock;
315  }
316 
317  must_register_misc = (current_rng == NULL);
318  old_rng = current_rng;
319  if (!old_rng) {
320  err = hwrng_init(rng);
321  if (err)
322  goto out_unlock;
323  current_rng = rng;
324  }
325  err = 0;
326  if (must_register_misc) {
327  err = register_miscdev();
328  if (err) {
329  if (!old_rng) {
330  hwrng_cleanup(rng);
331  current_rng = NULL;
332  }
333  goto out_unlock;
334  }
335  }
336  INIT_LIST_HEAD(&rng->list);
337  list_add_tail(&rng->list, &rng_list);
338 out_unlock:
339  mutex_unlock(&rng_mutex);
340 out:
341  return err;
342 }
343 EXPORT_SYMBOL_GPL(hwrng_register);
344 
345 void hwrng_unregister(struct hwrng *rng)
346 {
347  int err;
348 
349  mutex_lock(&rng_mutex);
350 
351  list_del(&rng->list);
352  if (current_rng == rng) {
353  hwrng_cleanup(rng);
354  if (list_empty(&rng_list)) {
355  current_rng = NULL;
356  } else {
357  current_rng = list_entry(rng_list.prev, struct hwrng, list);
358  err = hwrng_init(current_rng);
359  if (err)
360  current_rng = NULL;
361  }
362  }
363  if (list_empty(&rng_list))
364  unregister_miscdev();
365 
366  mutex_unlock(&rng_mutex);
367 }
368 EXPORT_SYMBOL_GPL(hwrng_unregister);
369 
370 
371 MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver");
372 MODULE_LICENSE("GPL");
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