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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>
30#include <linux/mutex.h>
31#include <linux/uaccess.h>
32
33static struct usb_driver chaoskey_driver;
34static struct usb_class_driver chaoskey_class;
35static 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
50MODULE_VERSION(DRIVER_VERSION);
51MODULE_AUTHOR(DRIVER_AUTHOR);
52MODULE_DESCRIPTION(DRIVER_DESC);
53MODULE_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
70static const struct usb_device_id chaoskey_table[] = {
71 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) },
72 { },
73};
74MODULE_DEVICE_TABLE(usb, chaoskey_table);
75
76static void chaos_read_callback(struct urb *urb);
77
78/* Driver-local specific stuff */
79struct chaoskey {
80 struct usb_interface *interface;
81 char in_ep;
82 struct mutex lock;
83 struct mutex rng_lock;
84 int open; /* open count */
85 bool present; /* device not disconnected */
86 bool reading; /* ongoing IO */
87 int size; /* size of buf */
88 int valid; /* bytes of buf read */
89 int used; /* bytes of buf consumed */
90 char *name; /* product + serial */
91 struct hwrng hwrng; /* Embedded struct for hwrng */
92 int hwrng_registered; /* registered with hwrng API */
93 wait_queue_head_t wait_q; /* for timeouts */
94 struct urb *urb; /* for performing IO */
95 char *buf;
96};
97
98static void chaoskey_free(struct chaoskey *dev)
99{
100 if (dev) {
101 usb_dbg(dev->interface, "free");
102 usb_free_urb(dev->urb);
103 kfree(dev->name);
104 kfree(dev->buf);
105 kfree(dev);
106 }
107}
108
109static int chaoskey_probe(struct usb_interface *interface,
110 const struct usb_device_id *id)
111{
112 struct usb_device *udev = interface_to_usbdev(interface);
113 struct usb_host_interface *altsetting = interface->cur_altsetting;
114 int i;
115 int in_ep = -1;
116 struct chaoskey *dev;
117 int result = -ENOMEM;
118 int size;
119
120 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial);
121
122 /* Find the first bulk IN endpoint and its packet size */
123 for (i = 0; i < altsetting->desc.bNumEndpoints; i++) {
124 if (usb_endpoint_is_bulk_in(&altsetting->endpoint[i].desc)) {
125 in_ep = usb_endpoint_num(&altsetting->endpoint[i].desc);
126 size = usb_endpoint_maxp(&altsetting->endpoint[i].desc);
127 break;
128 }
129 }
130
131 /* Validate endpoint and size */
132 if (in_ep == -1) {
133 usb_dbg(interface, "no IN endpoint found");
134 return -ENODEV;
135 }
136 if (size <= 0) {
137 usb_dbg(interface, "invalid size (%d)", size);
138 return -ENODEV;
139 }
140
141 if (size > CHAOSKEY_BUF_LEN) {
142 usb_dbg(interface, "size reduced from %d to %d\n",
143 size, CHAOSKEY_BUF_LEN);
144 size = CHAOSKEY_BUF_LEN;
145 }
146
147 /* Looks good, allocate and initialize */
148
149 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL);
150
151 if (dev == NULL)
152 goto out;
153
154 dev->buf = kmalloc(size, GFP_KERNEL);
155
156 if (dev->buf == NULL)
157 goto out;
158
159 dev->urb = usb_alloc_urb(0, GFP_KERNEL);
160
161 if (!dev->urb)
162 goto out;
163
164 usb_fill_bulk_urb(dev->urb,
165 udev,
166 usb_rcvbulkpipe(udev, in_ep),
167 dev->buf,
168 size,
169 chaos_read_callback,
170 dev);
171
172 /* Construct a name using the product and serial values. Each
173 * device needs a unique name for the hwrng code
174 */
175
176 if (udev->product && udev->serial) {
177 dev->name = kmalloc(strlen(udev->product) + 1 +
178 strlen(udev->serial) + 1, GFP_KERNEL);
179 if (dev->name == NULL)
180 goto out;
181
182 strcpy(dev->name, udev->product);
183 strcat(dev->name, "-");
184 strcat(dev->name, udev->serial);
185 }
186
187 dev->interface = interface;
188
189 dev->in_ep = in_ep;
190
191 dev->size = size;
192 dev->present = 1;
193
194 init_waitqueue_head(&dev->wait_q);
195
196 mutex_init(&dev->lock);
197 mutex_init(&dev->rng_lock);
198
199 usb_set_intfdata(interface, dev);
200
201 result = usb_register_dev(interface, &chaoskey_class);
202 if (result) {
203 usb_err(interface, "Unable to allocate minor number.");
204 goto out;
205 }
206
207 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name;
208 dev->hwrng.read = chaoskey_rng_read;
209
210 /* Set the 'quality' metric. Quality is measured in units of
211 * 1/1024's of a bit ("mills"). This should be set to 1024,
212 * but there is a bug in the hwrng core which masks it with
213 * 1023.
214 *
215 * The patch that has been merged to the crypto development
216 * tree for that bug limits the value to 1024 at most, so by
217 * setting this to 1024 + 1023, we get 1023 before the fix is
218 * merged and 1024 afterwards. We'll patch this driver once
219 * both bits of code are in the same tree.
220 */
221 dev->hwrng.quality = 1024 + 1023;
222
223 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0);
224 if (!dev->hwrng_registered)
225 usb_err(interface, "Unable to register with hwrng");
226
227 usb_enable_autosuspend(udev);
228
229 usb_dbg(interface, "chaoskey probe success, size %d", dev->size);
230 return 0;
231
232out:
233 usb_set_intfdata(interface, NULL);
234 chaoskey_free(dev);
235 return result;
236}
237
238static void chaoskey_disconnect(struct usb_interface *interface)
239{
240 struct chaoskey *dev;
241
242 usb_dbg(interface, "disconnect");
243 dev = usb_get_intfdata(interface);
244 if (!dev) {
245 usb_dbg(interface, "disconnect failed - no dev");
246 return;
247 }
248
249 if (dev->hwrng_registered)
250 hwrng_unregister(&dev->hwrng);
251
252 usb_deregister_dev(interface, &chaoskey_class);
253
254 usb_set_intfdata(interface, NULL);
255 mutex_lock(&dev->lock);
256
257 dev->present = 0;
258 usb_poison_urb(dev->urb);
259
260 if (!dev->open) {
261 mutex_unlock(&dev->lock);
262 chaoskey_free(dev);
263 } else
264 mutex_unlock(&dev->lock);
265
266 usb_dbg(interface, "disconnect done");
267}
268
269static int chaoskey_open(struct inode *inode, struct file *file)
270{
271 struct chaoskey *dev;
272 struct usb_interface *interface;
273
274 /* get the interface from minor number and driver information */
275 interface = usb_find_interface(&chaoskey_driver, iminor(inode));
276 if (!interface)
277 return -ENODEV;
278
279 usb_dbg(interface, "open");
280
281 dev = usb_get_intfdata(interface);
282 if (!dev) {
283 usb_dbg(interface, "open (dev)");
284 return -ENODEV;
285 }
286
287 file->private_data = dev;
288 mutex_lock(&dev->lock);
289 ++dev->open;
290 mutex_unlock(&dev->lock);
291
292 usb_dbg(interface, "open success");
293 return 0;
294}
295
296static int chaoskey_release(struct inode *inode, struct file *file)
297{
298 struct chaoskey *dev = file->private_data;
299 struct usb_interface *interface;
300
301 if (dev == NULL)
302 return -ENODEV;
303
304 interface = dev->interface;
305
306 usb_dbg(interface, "release");
307
308 mutex_lock(&dev->lock);
309
310 usb_dbg(interface, "open count at release is %d", dev->open);
311
312 if (dev->open <= 0) {
313 usb_dbg(interface, "invalid open count (%d)", dev->open);
314 mutex_unlock(&dev->lock);
315 return -ENODEV;
316 }
317
318 --dev->open;
319
320 if (!dev->present) {
321 if (dev->open == 0) {
322 mutex_unlock(&dev->lock);
323 chaoskey_free(dev);
324 } else
325 mutex_unlock(&dev->lock);
326 } else
327 mutex_unlock(&dev->lock);
328
329 usb_dbg(interface, "release success");
330 return 0;
331}
332
333static void chaos_read_callback(struct urb *urb)
334{
335 struct chaoskey *dev = urb->context;
336 int status = urb->status;
337
338 usb_dbg(dev->interface, "callback status (%d)", status);
339
340 if (status == 0)
341 dev->valid = urb->actual_length;
342 else
343 dev->valid = 0;
344
345 dev->used = 0;
346
347 /* must be seen first before validity is announced */
348 smp_wmb();
349
350 dev->reading = false;
351 wake_up(&dev->wait_q);
352}
353
354/* Fill the buffer. Called with dev->lock held
355 */
356static int _chaoskey_fill(struct chaoskey *dev)
357{
358 DEFINE_WAIT(wait);
359 int result;
360
361 usb_dbg(dev->interface, "fill");
362
363 /* Return immediately if someone called before the buffer was
364 * empty */
365 if (dev->valid != dev->used) {
366 usb_dbg(dev->interface, "not empty yet (valid %d used %d)",
367 dev->valid, dev->used);
368 return 0;
369 }
370
371 /* Bail if the device has been removed */
372 if (!dev->present) {
373 usb_dbg(dev->interface, "device not present");
374 return -ENODEV;
375 }
376
377 /* Make sure the device is awake */
378 result = usb_autopm_get_interface(dev->interface);
379 if (result) {
380 usb_dbg(dev->interface, "wakeup failed (result %d)", result);
381 return result;
382 }
383
384 dev->reading = true;
385 result = usb_submit_urb(dev->urb, GFP_KERNEL);
386 if (result < 0) {
387 result = usb_translate_errors(result);
388 dev->reading = false;
389 goto out;
390 }
391
392 result = wait_event_interruptible_timeout(
393 dev->wait_q,
394 !dev->reading,
395 NAK_TIMEOUT);
396
397 if (result < 0)
398 goto out;
399
400 if (result == 0)
401 result = -ETIMEDOUT;
402 else
403 result = dev->valid;
404out:
405 /* Let the device go back to sleep eventually */
406 usb_autopm_put_interface(dev->interface);
407
408 usb_dbg(dev->interface, "read %d bytes", dev->valid);
409
410 return result;
411}
412
413static ssize_t chaoskey_read(struct file *file,
414 char __user *buffer,
415 size_t count,
416 loff_t *ppos)
417{
418 struct chaoskey *dev;
419 ssize_t read_count = 0;
420 int this_time;
421 int result = 0;
422 unsigned long remain;
423
424 dev = file->private_data;
425
426 if (dev == NULL || !dev->present)
427 return -ENODEV;
428
429 usb_dbg(dev->interface, "read %zu", count);
430
431 while (count > 0) {
432
433 /* Grab the rng_lock briefly to ensure that the hwrng interface
434 * gets priority over other user access
435 */
436 result = mutex_lock_interruptible(&dev->rng_lock);
437 if (result)
438 goto bail;
439 mutex_unlock(&dev->rng_lock);
440
441 result = mutex_lock_interruptible(&dev->lock);
442 if (result)
443 goto bail;
444 if (dev->valid == dev->used) {
445 result = _chaoskey_fill(dev);
446 if (result < 0) {
447 mutex_unlock(&dev->lock);
448 goto bail;
449 }
450 }
451
452 this_time = dev->valid - dev->used;
453 if (this_time > count)
454 this_time = count;
455
456 remain = copy_to_user(buffer, dev->buf + dev->used, this_time);
457 if (remain) {
458 result = -EFAULT;
459
460 /* Consume the bytes that were copied so we don't leak
461 * data to user space
462 */
463 dev->used += this_time - remain;
464 mutex_unlock(&dev->lock);
465 goto bail;
466 }
467
468 count -= this_time;
469 read_count += this_time;
470 buffer += this_time;
471 dev->used += this_time;
472 mutex_unlock(&dev->lock);
473 }
474bail:
475 if (read_count) {
476 usb_dbg(dev->interface, "read %zu bytes", read_count);
477 return read_count;
478 }
479 usb_dbg(dev->interface, "empty read, result %d", result);
480 if (result == -ETIMEDOUT)
481 result = -EAGAIN;
482 return result;
483}
484
485static int chaoskey_rng_read(struct hwrng *rng, void *data,
486 size_t max, bool wait)
487{
488 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng);
489 int this_time;
490
491 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait);
492
493 if (!dev->present) {
494 usb_dbg(dev->interface, "device not present");
495 return 0;
496 }
497
498 /* Hold the rng_lock until we acquire the device lock so that
499 * this operation gets priority over other user access to the
500 * device
501 */
502 mutex_lock(&dev->rng_lock);
503
504 mutex_lock(&dev->lock);
505
506 mutex_unlock(&dev->rng_lock);
507
508 /* Try to fill the buffer if empty. It doesn't actually matter
509 * if _chaoskey_fill works; we'll just return zero bytes as
510 * the buffer will still be empty
511 */
512 if (dev->valid == dev->used)
513 (void) _chaoskey_fill(dev);
514
515 this_time = dev->valid - dev->used;
516 if (this_time > max)
517 this_time = max;
518
519 memcpy(data, dev->buf + dev->used, this_time);
520
521 dev->used += this_time;
522
523 mutex_unlock(&dev->lock);
524
525 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time);
526 return this_time;
527}
528
529#ifdef CONFIG_PM
530static int chaoskey_suspend(struct usb_interface *interface,
531 pm_message_t message)
532{
533 usb_dbg(interface, "suspend");
534 return 0;
535}
536
537static int chaoskey_resume(struct usb_interface *interface)
538{
539 usb_dbg(interface, "resume");
540 return 0;
541}
542#else
543#define chaoskey_suspend NULL
544#define chaoskey_resume NULL
545#endif
546
547/* file operation pointers */
548static const struct file_operations chaoskey_fops = {
549 .owner = THIS_MODULE,
550 .read = chaoskey_read,
551 .open = chaoskey_open,
552 .release = chaoskey_release,
553 .llseek = default_llseek,
554};
555
556/* class driver information */
557static struct usb_class_driver chaoskey_class = {
558 .name = "chaoskey%d",
559 .fops = &chaoskey_fops,
560 .minor_base = USB_CHAOSKEY_MINOR_BASE,
561};
562
563/* usb specific object needed to register this driver with the usb subsystem */
564static struct usb_driver chaoskey_driver = {
565 .name = DRIVER_SHORT,
566 .probe = chaoskey_probe,
567 .disconnect = chaoskey_disconnect,
568 .suspend = chaoskey_suspend,
569 .resume = chaoskey_resume,
570 .reset_resume = chaoskey_resume,
571 .id_table = chaoskey_table,
572 .supports_autosuspend = 1,
573};
574
575module_usb_driver(chaoskey_driver);
576