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66e3e591 KP |
1 | /* |
2 | * chaoskey - driver for ChaosKey device from Altus Metrum. | |
3 | * | |
4 | * This device provides true random numbers using a noise source based | |
5 | * on a reverse-biased p-n junction in avalanche breakdown. More | |
6 | * details can be found at http://chaoskey.org | |
7 | * | |
8 | * The driver connects to the kernel hardware RNG interface to provide | |
9 | * entropy for /dev/random and other kernel activities. It also offers | |
10 | * a separate /dev/ entry to allow for direct access to the random | |
11 | * bit stream. | |
12 | * | |
13 | * Copyright © 2015 Keith Packard <keithp@keithp.com> | |
14 | * | |
15 | * This program is free software; you can redistribute it and/or modify | |
16 | * it under the terms of the GNU General Public License as published by | |
17 | * the Free Software Foundation; version 2 of the License. | |
18 | * | |
19 | * This program is distributed in the hope that it will be useful, but | |
20 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
22 | * General Public License for more details. | |
23 | */ | |
24 | ||
25 | #include <linux/module.h> | |
26 | #include <linux/slab.h> | |
27 | #include <linux/usb.h> | |
28 | #include <linux/wait.h> | |
29 | #include <linux/hw_random.h> | |
8b86ed07 KP |
30 | #include <linux/mutex.h> |
31 | #include <linux/uaccess.h> | |
66e3e591 KP |
32 | |
33 | static struct usb_driver chaoskey_driver; | |
34 | static struct usb_class_driver chaoskey_class; | |
35 | static int chaoskey_rng_read(struct hwrng *rng, void *data, | |
36 | size_t max, bool wait); | |
37 | ||
38 | #define usb_dbg(usb_if, format, arg...) \ | |
39 | dev_dbg(&(usb_if)->dev, format, ## arg) | |
40 | ||
41 | #define usb_err(usb_if, format, arg...) \ | |
42 | dev_err(&(usb_if)->dev, format, ## arg) | |
43 | ||
44 | /* Version Information */ | |
45 | #define DRIVER_VERSION "v0.1" | |
46 | #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com" | |
47 | #define DRIVER_DESC "Altus Metrum ChaosKey driver" | |
48 | #define DRIVER_SHORT "chaoskey" | |
49 | ||
50 | MODULE_VERSION(DRIVER_VERSION); | |
51 | MODULE_AUTHOR(DRIVER_AUTHOR); | |
52 | MODULE_DESCRIPTION(DRIVER_DESC); | |
53 | MODULE_LICENSE("GPL"); | |
54 | ||
55 | #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ | |
56 | #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ | |
57 | ||
58 | #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ | |
59 | ||
60 | #define NAK_TIMEOUT (HZ) /* stall/wait timeout for device */ | |
61 | ||
62 | #ifdef CONFIG_USB_DYNAMIC_MINORS | |
63 | #define USB_CHAOSKEY_MINOR_BASE 0 | |
64 | #else | |
65 | ||
66 | /* IOWARRIOR_MINOR_BASE + 16, not official yet */ | |
67 | #define USB_CHAOSKEY_MINOR_BASE 224 | |
68 | #endif | |
69 | ||
70 | static const struct usb_device_id chaoskey_table[] = { | |
71 | { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, | |
72 | { }, | |
73 | }; | |
74 | MODULE_DEVICE_TABLE(usb, chaoskey_table); | |
75 | ||
76 | /* Driver-local specific stuff */ | |
77 | struct chaoskey { | |
78 | struct usb_interface *interface; | |
79 | char in_ep; | |
80 | struct mutex lock; | |
81 | struct mutex rng_lock; | |
82 | int open; /* open count */ | |
83 | int present; /* device not disconnected */ | |
84 | int size; /* size of buf */ | |
85 | int valid; /* bytes of buf read */ | |
86 | int used; /* bytes of buf consumed */ | |
87 | char *name; /* product + serial */ | |
88 | struct hwrng hwrng; /* Embedded struct for hwrng */ | |
89 | int hwrng_registered; /* registered with hwrng API */ | |
90 | wait_queue_head_t wait_q; /* for timeouts */ | |
91 | char *buf; | |
92 | }; | |
93 | ||
94 | static void chaoskey_free(struct chaoskey *dev) | |
95 | { | |
96 | usb_dbg(dev->interface, "free"); | |
97 | kfree(dev->name); | |
98 | kfree(dev->buf); | |
99 | kfree(dev); | |
100 | } | |
101 | ||
102 | static int chaoskey_probe(struct usb_interface *interface, | |
103 | const struct usb_device_id *id) | |
104 | { | |
105 | struct usb_device *udev = interface_to_usbdev(interface); | |
106 | struct usb_host_interface *altsetting = interface->cur_altsetting; | |
107 | int i; | |
108 | int in_ep = -1; | |
109 | struct chaoskey *dev; | |
110 | int result; | |
111 | int size; | |
112 | ||
113 | usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); | |
114 | ||
115 | /* Find the first bulk IN endpoint and its packet size */ | |
116 | for (i = 0; i < altsetting->desc.bNumEndpoints; i++) { | |
117 | if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) { | |
8b86ed07 KP |
118 | in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc); |
119 | size = usb_endpoint_maxp(&altsetting->endpoint[i].desc); | |
66e3e591 KP |
120 | break; |
121 | } | |
122 | } | |
123 | ||
124 | /* Validate endpoint and size */ | |
125 | if (in_ep == -1) { | |
126 | usb_dbg(interface, "no IN endpoint found"); | |
127 | return -ENODEV; | |
128 | } | |
129 | if (size <= 0) { | |
130 | usb_dbg(interface, "invalid size (%d)", size); | |
131 | return -ENODEV; | |
132 | } | |
133 | ||
134 | if (size > CHAOSKEY_BUF_LEN) { | |
135 | usb_dbg(interface, "size reduced from %d to %d\n", | |
136 | size, CHAOSKEY_BUF_LEN); | |
137 | size = CHAOSKEY_BUF_LEN; | |
138 | } | |
139 | ||
140 | /* Looks good, allocate and initialize */ | |
141 | ||
142 | dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); | |
143 | ||
144 | if (dev == NULL) | |
145 | return -ENOMEM; | |
146 | ||
147 | dev->buf = kmalloc(size, GFP_KERNEL); | |
148 | ||
149 | if (dev->buf == NULL) { | |
150 | kfree(dev); | |
151 | return -ENOMEM; | |
152 | } | |
153 | ||
154 | /* Construct a name using the product and serial values. Each | |
155 | * device needs a unique name for the hwrng code | |
156 | */ | |
157 | ||
158 | if (udev->product && udev->serial) { | |
159 | dev->name = kmalloc(strlen(udev->product) + 1 + | |
160 | strlen(udev->serial) + 1, GFP_KERNEL); | |
161 | if (dev->name == NULL) { | |
162 | kfree(dev->buf); | |
163 | kfree(dev); | |
164 | return -ENOMEM; | |
165 | } | |
166 | ||
167 | strcpy(dev->name, udev->product); | |
168 | strcat(dev->name, "-"); | |
169 | strcat(dev->name, udev->serial); | |
170 | } | |
171 | ||
172 | dev->interface = interface; | |
173 | ||
174 | dev->in_ep = in_ep; | |
175 | ||
176 | dev->size = size; | |
177 | dev->present = 1; | |
178 | ||
179 | init_waitqueue_head(&dev->wait_q); | |
180 | ||
181 | mutex_init(&dev->lock); | |
182 | mutex_init(&dev->rng_lock); | |
183 | ||
184 | usb_set_intfdata(interface, dev); | |
185 | ||
186 | result = usb_register_dev(interface, &chaoskey_class); | |
187 | if (result) { | |
188 | usb_err(interface, "Unable to allocate minor number."); | |
189 | usb_set_intfdata(interface, NULL); | |
190 | chaoskey_free(dev); | |
191 | return result; | |
192 | } | |
193 | ||
194 | dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; | |
195 | dev->hwrng.read = chaoskey_rng_read; | |
196 | ||
197 | /* Set the 'quality' metric. Quality is measured in units of | |
198 | * 1/1024's of a bit ("mills"). This should be set to 1024, | |
199 | * but there is a bug in the hwrng core which masks it with | |
200 | * 1023. | |
201 | * | |
202 | * The patch that has been merged to the crypto development | |
203 | * tree for that bug limits the value to 1024 at most, so by | |
204 | * setting this to 1024 + 1023, we get 1023 before the fix is | |
205 | * merged and 1024 afterwards. We'll patch this driver once | |
206 | * both bits of code are in the same tree. | |
207 | */ | |
208 | dev->hwrng.quality = 1024 + 1023; | |
209 | ||
210 | dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); | |
211 | if (!dev->hwrng_registered) | |
212 | usb_err(interface, "Unable to register with hwrng"); | |
213 | ||
214 | usb_enable_autosuspend(udev); | |
215 | ||
216 | usb_dbg(interface, "chaoskey probe success, size %d", dev->size); | |
217 | return 0; | |
218 | } | |
219 | ||
220 | static void chaoskey_disconnect(struct usb_interface *interface) | |
221 | { | |
222 | struct chaoskey *dev; | |
223 | ||
224 | usb_dbg(interface, "disconnect"); | |
225 | dev = usb_get_intfdata(interface); | |
226 | if (!dev) { | |
227 | usb_dbg(interface, "disconnect failed - no dev"); | |
228 | return; | |
229 | } | |
230 | ||
231 | if (dev->hwrng_registered) | |
232 | hwrng_unregister(&dev->hwrng); | |
233 | ||
234 | usb_deregister_dev(interface, &chaoskey_class); | |
235 | ||
236 | usb_set_intfdata(interface, NULL); | |
237 | mutex_lock(&dev->lock); | |
238 | ||
239 | dev->present = 0; | |
240 | ||
241 | if (!dev->open) { | |
242 | mutex_unlock(&dev->lock); | |
243 | chaoskey_free(dev); | |
244 | } else | |
245 | mutex_unlock(&dev->lock); | |
246 | ||
247 | usb_dbg(interface, "disconnect done"); | |
248 | } | |
249 | ||
250 | static int chaoskey_open(struct inode *inode, struct file *file) | |
251 | { | |
252 | struct chaoskey *dev; | |
253 | struct usb_interface *interface; | |
254 | ||
255 | /* get the interface from minor number and driver information */ | |
256 | interface = usb_find_interface(&chaoskey_driver, iminor(inode)); | |
257 | if (!interface) | |
258 | return -ENODEV; | |
259 | ||
260 | usb_dbg(interface, "open"); | |
261 | ||
262 | dev = usb_get_intfdata(interface); | |
263 | if (!dev) { | |
264 | usb_dbg(interface, "open (dev)"); | |
265 | return -ENODEV; | |
266 | } | |
267 | ||
268 | file->private_data = dev; | |
269 | mutex_lock(&dev->lock); | |
270 | ++dev->open; | |
271 | mutex_unlock(&dev->lock); | |
272 | ||
273 | usb_dbg(interface, "open success"); | |
274 | return 0; | |
275 | } | |
276 | ||
277 | static int chaoskey_release(struct inode *inode, struct file *file) | |
278 | { | |
279 | struct chaoskey *dev = file->private_data; | |
280 | struct usb_interface *interface; | |
281 | ||
282 | if (dev == NULL) | |
283 | return -ENODEV; | |
284 | ||
285 | interface = dev->interface; | |
286 | ||
287 | usb_dbg(interface, "release"); | |
288 | ||
289 | mutex_lock(&dev->lock); | |
290 | ||
291 | usb_dbg(interface, "open count at release is %d", dev->open); | |
292 | ||
293 | if (dev->open <= 0) { | |
294 | usb_dbg(interface, "invalid open count (%d)", dev->open); | |
295 | mutex_unlock(&dev->lock); | |
296 | return -ENODEV; | |
297 | } | |
298 | ||
299 | --dev->open; | |
300 | ||
301 | if (!dev->present) { | |
302 | if (dev->open == 0) { | |
303 | mutex_unlock(&dev->lock); | |
304 | chaoskey_free(dev); | |
305 | } else | |
306 | mutex_unlock(&dev->lock); | |
307 | } else | |
308 | mutex_unlock(&dev->lock); | |
309 | ||
310 | usb_dbg(interface, "release success"); | |
311 | return 0; | |
312 | } | |
313 | ||
314 | /* Fill the buffer. Called with dev->lock held | |
315 | */ | |
316 | static int _chaoskey_fill(struct chaoskey *dev) | |
317 | { | |
318 | DEFINE_WAIT(wait); | |
319 | int result; | |
320 | int this_read; | |
321 | struct usb_device *udev = interface_to_usbdev(dev->interface); | |
322 | ||
323 | usb_dbg(dev->interface, "fill"); | |
324 | ||
325 | /* Return immediately if someone called before the buffer was | |
326 | * empty */ | |
327 | if (dev->valid != dev->used) { | |
328 | usb_dbg(dev->interface, "not empty yet (valid %d used %d)", | |
329 | dev->valid, dev->used); | |
330 | return 0; | |
331 | } | |
332 | ||
333 | /* Bail if the device has been removed */ | |
334 | if (!dev->present) { | |
335 | usb_dbg(dev->interface, "device not present"); | |
336 | return -ENODEV; | |
337 | } | |
338 | ||
339 | /* Make sure the device is awake */ | |
340 | result = usb_autopm_get_interface(dev->interface); | |
341 | if (result) { | |
342 | usb_dbg(dev->interface, "wakeup failed (result %d)", result); | |
343 | return result; | |
344 | } | |
345 | ||
346 | result = usb_bulk_msg(udev, | |
347 | usb_rcvbulkpipe(udev, dev->in_ep), | |
348 | dev->buf, dev->size, &this_read, | |
349 | NAK_TIMEOUT); | |
350 | ||
351 | /* Let the device go back to sleep eventually */ | |
352 | usb_autopm_put_interface(dev->interface); | |
353 | ||
354 | if (result == 0) { | |
355 | dev->valid = this_read; | |
356 | dev->used = 0; | |
357 | } | |
358 | ||
359 | usb_dbg(dev->interface, "bulk_msg result %d this_read %d", | |
360 | result, this_read); | |
361 | ||
362 | return result; | |
363 | } | |
364 | ||
365 | static ssize_t chaoskey_read(struct file *file, | |
366 | char __user *buffer, | |
367 | size_t count, | |
368 | loff_t *ppos) | |
369 | { | |
370 | struct chaoskey *dev; | |
371 | ssize_t read_count = 0; | |
372 | int this_time; | |
373 | int result = 0; | |
374 | unsigned long remain; | |
375 | ||
376 | dev = file->private_data; | |
377 | ||
378 | if (dev == NULL || !dev->present) | |
379 | return -ENODEV; | |
380 | ||
381 | usb_dbg(dev->interface, "read %zu", count); | |
382 | ||
383 | while (count > 0) { | |
384 | ||
385 | /* Grab the rng_lock briefly to ensure that the hwrng interface | |
386 | * gets priority over other user access | |
387 | */ | |
388 | result = mutex_lock_interruptible(&dev->rng_lock); | |
389 | if (result) | |
390 | goto bail; | |
391 | mutex_unlock(&dev->rng_lock); | |
392 | ||
393 | result = mutex_lock_interruptible(&dev->lock); | |
394 | if (result) | |
395 | goto bail; | |
396 | if (dev->valid == dev->used) { | |
397 | result = _chaoskey_fill(dev); | |
398 | if (result) { | |
399 | mutex_unlock(&dev->lock); | |
400 | goto bail; | |
401 | } | |
402 | ||
403 | /* Read returned zero bytes */ | |
404 | if (dev->used == dev->valid) { | |
405 | mutex_unlock(&dev->lock); | |
406 | goto bail; | |
407 | } | |
408 | } | |
409 | ||
410 | this_time = dev->valid - dev->used; | |
411 | if (this_time > count) | |
412 | this_time = count; | |
413 | ||
414 | remain = copy_to_user(buffer, dev->buf + dev->used, this_time); | |
415 | if (remain) { | |
416 | result = -EFAULT; | |
417 | ||
418 | /* Consume the bytes that were copied so we don't leak | |
419 | * data to user space | |
420 | */ | |
421 | dev->used += this_time - remain; | |
422 | mutex_unlock(&dev->lock); | |
423 | goto bail; | |
424 | } | |
425 | ||
426 | count -= this_time; | |
427 | read_count += this_time; | |
428 | buffer += this_time; | |
429 | dev->used += this_time; | |
430 | mutex_unlock(&dev->lock); | |
431 | } | |
432 | bail: | |
433 | if (read_count) { | |
434 | usb_dbg(dev->interface, "read %zu bytes", read_count); | |
435 | return read_count; | |
436 | } | |
437 | usb_dbg(dev->interface, "empty read, result %d", result); | |
438 | return result; | |
439 | } | |
440 | ||
441 | static int chaoskey_rng_read(struct hwrng *rng, void *data, | |
442 | size_t max, bool wait) | |
443 | { | |
444 | struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); | |
445 | int this_time; | |
446 | ||
447 | usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); | |
448 | ||
449 | if (!dev->present) { | |
450 | usb_dbg(dev->interface, "device not present"); | |
451 | return 0; | |
452 | } | |
453 | ||
454 | /* Hold the rng_lock until we acquire the device lock so that | |
455 | * this operation gets priority over other user access to the | |
456 | * device | |
457 | */ | |
458 | mutex_lock(&dev->rng_lock); | |
459 | ||
460 | mutex_lock(&dev->lock); | |
461 | ||
462 | mutex_unlock(&dev->rng_lock); | |
463 | ||
464 | /* Try to fill the buffer if empty. It doesn't actually matter | |
465 | * if _chaoskey_fill works; we'll just return zero bytes as | |
466 | * the buffer will still be empty | |
467 | */ | |
468 | if (dev->valid == dev->used) | |
469 | (void) _chaoskey_fill(dev); | |
470 | ||
471 | this_time = dev->valid - dev->used; | |
472 | if (this_time > max) | |
473 | this_time = max; | |
474 | ||
475 | memcpy(data, dev->buf, this_time); | |
476 | ||
477 | dev->used += this_time; | |
478 | ||
479 | mutex_unlock(&dev->lock); | |
480 | ||
481 | usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); | |
482 | return this_time; | |
483 | } | |
484 | ||
485 | #ifdef CONFIG_PM | |
486 | static int chaoskey_suspend(struct usb_interface *interface, | |
487 | pm_message_t message) | |
488 | { | |
489 | usb_dbg(interface, "suspend"); | |
490 | return 0; | |
491 | } | |
492 | ||
493 | static int chaoskey_resume(struct usb_interface *interface) | |
494 | { | |
495 | usb_dbg(interface, "resume"); | |
496 | return 0; | |
497 | } | |
498 | #else | |
499 | #define chaoskey_suspend NULL | |
500 | #define chaoskey_resume NULL | |
501 | #endif | |
502 | ||
503 | /* file operation pointers */ | |
504 | static const struct file_operations chaoskey_fops = { | |
505 | .owner = THIS_MODULE, | |
506 | .read = chaoskey_read, | |
507 | .open = chaoskey_open, | |
508 | .release = chaoskey_release, | |
509 | .llseek = default_llseek, | |
510 | }; | |
511 | ||
512 | /* class driver information */ | |
513 | static struct usb_class_driver chaoskey_class = { | |
514 | .name = "chaoskey%d", | |
515 | .fops = &chaoskey_fops, | |
516 | .minor_base = USB_CHAOSKEY_MINOR_BASE, | |
517 | }; | |
518 | ||
519 | /* usb specific object needed to register this driver with the usb subsystem */ | |
520 | static struct usb_driver chaoskey_driver = { | |
521 | .name = DRIVER_SHORT, | |
522 | .probe = chaoskey_probe, | |
523 | .disconnect = chaoskey_disconnect, | |
524 | .suspend = chaoskey_suspend, | |
525 | .resume = chaoskey_resume, | |
526 | .reset_resume = chaoskey_resume, | |
527 | .id_table = chaoskey_table, | |
528 | .supports_autosuspend = 1, | |
529 | }; | |
530 | ||
531 | module_usb_driver(chaoskey_driver); | |
532 |