1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * chaoskey - driver for ChaosKey device from Altus Metrum. 4 * 5 * This device provides true random numbers using a noise source based 6 * on a reverse-biased p-n junction in avalanche breakdown. More 7 * details can be found at http://chaoskey.org 8 * 9 * The driver connects to the kernel hardware RNG interface to provide 10 * entropy for /dev/random and other kernel activities. It also offers 11 * a separate /dev/ entry to allow for direct access to the random 12 * bit stream. 13 * 14 * Copyright © 2015 Keith Packard <keithp@keithp.com> 15 */ 16 17 #include <linux/module.h> 18 #include <linux/slab.h> 19 #include <linux/usb.h> 20 #include <linux/wait.h> 21 #include <linux/hw_random.h> 22 #include <linux/mutex.h> 23 #include <linux/uaccess.h> 24 25 static struct usb_driver chaoskey_driver; 26 static struct usb_class_driver chaoskey_class; 27 static int chaoskey_rng_read(struct hwrng *rng, void *data, 28 size_t max, bool wait); 29 30 static DEFINE_MUTEX(chaoskey_list_lock); 31 32 #define usb_dbg(usb_if, format, arg...) \ 33 dev_dbg(&(usb_if)->dev, format, ## arg) 34 35 #define usb_err(usb_if, format, arg...) \ 36 dev_err(&(usb_if)->dev, format, ## arg) 37 38 /* Version Information */ 39 #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com" 40 #define DRIVER_DESC "Altus Metrum ChaosKey driver" 41 #define DRIVER_SHORT "chaoskey" 42 43 MODULE_AUTHOR(DRIVER_AUTHOR); 44 MODULE_DESCRIPTION(DRIVER_DESC); 45 MODULE_LICENSE("GPL"); 46 47 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ 48 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ 49 50 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */ 51 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */ 52 53 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ 54 55 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */ 56 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */ 57 58 #ifdef CONFIG_USB_DYNAMIC_MINORS 59 #define USB_CHAOSKEY_MINOR_BASE 0 60 #else 61 62 /* IOWARRIOR_MINOR_BASE + 16, not official yet */ 63 #define USB_CHAOSKEY_MINOR_BASE 224 64 #endif 65 66 static const struct usb_device_id chaoskey_table[] = { 67 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, 68 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) }, 69 { }, 70 }; 71 MODULE_DEVICE_TABLE(usb, chaoskey_table); 72 73 static void chaos_read_callback(struct urb *urb); 74 75 /* Driver-local specific stuff */ 76 struct chaoskey { 77 struct usb_interface *interface; 78 char in_ep; 79 struct mutex lock; 80 struct mutex rng_lock; 81 int open; /* open count */ 82 bool present; /* device not disconnected */ 83 bool reading; /* ongoing IO */ 84 bool reads_started; /* track first read for Alea */ 85 int size; /* size of buf */ 86 int valid; /* bytes of buf read */ 87 int used; /* bytes of buf consumed */ 88 char *name; /* product + serial */ 89 struct hwrng hwrng; /* Embedded struct for hwrng */ 90 int hwrng_registered; /* registered with hwrng API */ 91 wait_queue_head_t wait_q; /* for timeouts */ 92 struct urb *urb; /* for performing IO */ 93 char *buf; 94 }; 95 96 static void chaoskey_free(struct chaoskey *dev) 97 { 98 if (dev) { 99 usb_dbg(dev->interface, "free"); 100 usb_free_urb(dev->urb); 101 kfree(dev->name); 102 kfree(dev->buf); 103 usb_put_intf(dev->interface); 104 kfree(dev); 105 } 106 } 107 108 static int chaoskey_probe(struct usb_interface *interface, 109 const struct usb_device_id *id) 110 { 111 struct usb_device *udev = interface_to_usbdev(interface); 112 struct usb_host_interface *altsetting = interface->cur_altsetting; 113 struct usb_endpoint_descriptor *epd; 114 int in_ep; 115 struct chaoskey *dev; 116 int result = -ENOMEM; 117 int size; 118 int res; 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 res = usb_find_bulk_in_endpoint(altsetting, &epd); 124 if (res) { 125 usb_dbg(interface, "no IN endpoint found"); 126 return res; 127 } 128 129 in_ep = usb_endpoint_num(epd); 130 size = usb_endpoint_maxp(epd); 131 132 /* Validate endpoint and size */ 133 if (size <= 0) { 134 usb_dbg(interface, "invalid size (%d)", size); 135 return -ENODEV; 136 } 137 138 if (size > CHAOSKEY_BUF_LEN) { 139 usb_dbg(interface, "size reduced from %d to %d\n", 140 size, CHAOSKEY_BUF_LEN); 141 size = CHAOSKEY_BUF_LEN; 142 } 143 144 /* Looks good, allocate and initialize */ 145 146 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 147 148 if (dev == NULL) 149 goto out; 150 151 dev->interface = usb_get_intf(interface); 152 153 dev->buf = kmalloc(size, GFP_KERNEL); 154 155 if (dev->buf == NULL) 156 goto out; 157 158 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 159 160 if (!dev->urb) 161 goto out; 162 163 usb_fill_bulk_urb(dev->urb, 164 udev, 165 usb_rcvbulkpipe(udev, in_ep), 166 dev->buf, 167 size, 168 chaos_read_callback, 169 dev); 170 171 /* Construct a name using the product and serial values. Each 172 * device needs a unique name for the hwrng code 173 */ 174 175 if (udev->product && udev->serial) { 176 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product, 177 udev->serial); 178 if (dev->name == NULL) 179 goto out; 180 } 181 182 dev->in_ep = in_ep; 183 184 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID) 185 dev->reads_started = true; 186 187 dev->size = size; 188 dev->present = true; 189 190 init_waitqueue_head(&dev->wait_q); 191 192 mutex_init(&dev->lock); 193 mutex_init(&dev->rng_lock); 194 195 usb_set_intfdata(interface, dev); 196 197 result = usb_register_dev(interface, &chaoskey_class); 198 if (result) { 199 usb_err(interface, "Unable to allocate minor number."); 200 goto out; 201 } 202 203 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 204 dev->hwrng.read = chaoskey_rng_read; 205 206 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 207 if (!dev->hwrng_registered) 208 usb_err(interface, "Unable to register with hwrng"); 209 210 usb_enable_autosuspend(udev); 211 212 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 213 return 0; 214 215 out: 216 usb_set_intfdata(interface, NULL); 217 chaoskey_free(dev); 218 return result; 219 } 220 221 static void chaoskey_disconnect(struct usb_interface *interface) 222 { 223 struct chaoskey *dev; 224 225 usb_dbg(interface, "disconnect"); 226 dev = usb_get_intfdata(interface); 227 if (!dev) { 228 usb_dbg(interface, "disconnect failed - no dev"); 229 return; 230 } 231 232 if (dev->hwrng_registered) 233 hwrng_unregister(&dev->hwrng); 234 235 usb_deregister_dev(interface, &chaoskey_class); 236 237 usb_set_intfdata(interface, NULL); 238 mutex_lock(&chaoskey_list_lock); 239 mutex_lock(&dev->lock); 240 241 dev->present = false; 242 usb_poison_urb(dev->urb); 243 244 if (!dev->open) { 245 mutex_unlock(&dev->lock); 246 chaoskey_free(dev); 247 } else 248 mutex_unlock(&dev->lock); 249 250 mutex_unlock(&chaoskey_list_lock); 251 usb_dbg(interface, "disconnect done"); 252 } 253 254 static int chaoskey_open(struct inode *inode, struct file *file) 255 { 256 struct chaoskey *dev; 257 struct usb_interface *interface; 258 int rv = 0; 259 260 /* get the interface from minor number and driver information */ 261 interface = usb_find_interface(&chaoskey_driver, iminor(inode)); 262 if (!interface) 263 return -ENODEV; 264 265 usb_dbg(interface, "open"); 266 267 dev = usb_get_intfdata(interface); 268 if (!dev) { 269 usb_dbg(interface, "open (dev)"); 270 return -ENODEV; 271 } 272 273 file->private_data = dev; 274 mutex_lock(&chaoskey_list_lock); 275 mutex_lock(&dev->lock); 276 if (dev->present) 277 ++dev->open; 278 else 279 rv = -ENODEV; 280 mutex_unlock(&dev->lock); 281 mutex_unlock(&chaoskey_list_lock); 282 283 return rv; 284 } 285 286 static int chaoskey_release(struct inode *inode, struct file *file) 287 { 288 struct chaoskey *dev = file->private_data; 289 struct usb_interface *interface; 290 int rv = 0; 291 292 if (dev == NULL) 293 return -ENODEV; 294 295 interface = dev->interface; 296 297 usb_dbg(interface, "release"); 298 299 mutex_lock(&chaoskey_list_lock); 300 mutex_lock(&dev->lock); 301 302 usb_dbg(interface, "open count at release is %d", dev->open); 303 304 if (dev->open <= 0) { 305 usb_dbg(interface, "invalid open count (%d)", dev->open); 306 rv = -ENODEV; 307 goto bail; 308 } 309 310 --dev->open; 311 312 if (!dev->present) { 313 if (dev->open == 0) { 314 mutex_unlock(&dev->lock); 315 chaoskey_free(dev); 316 goto destruction; 317 } 318 } 319 bail: 320 mutex_unlock(&dev->lock); 321 destruction: 322 mutex_unlock(&chaoskey_list_lock); 323 usb_dbg(interface, "release success"); 324 return rv; 325 } 326 327 static void chaos_read_callback(struct urb *urb) 328 { 329 struct chaoskey *dev = urb->context; 330 int status = urb->status; 331 332 usb_dbg(dev->interface, "callback status (%d)", status); 333 334 if (status == 0) 335 dev->valid = urb->actual_length; 336 else 337 dev->valid = 0; 338 339 dev->used = 0; 340 341 /* must be seen first before validity is announced */ 342 smp_wmb(); 343 344 dev->reading = false; 345 wake_up(&dev->wait_q); 346 } 347 348 /* Fill the buffer. Called with dev->lock held 349 */ 350 static int _chaoskey_fill(struct chaoskey *dev) 351 { 352 DEFINE_WAIT(wait); 353 int result; 354 bool started; 355 356 usb_dbg(dev->interface, "fill"); 357 358 /* Return immediately if someone called before the buffer was 359 * empty */ 360 if (dev->valid != dev->used) { 361 usb_dbg(dev->interface, "not empty yet (valid %d used %d)", 362 dev->valid, dev->used); 363 return 0; 364 } 365 366 /* Bail if the device has been removed */ 367 if (!dev->present) { 368 usb_dbg(dev->interface, "device not present"); 369 return -ENODEV; 370 } 371 372 /* Make sure the device is awake */ 373 result = usb_autopm_get_interface(dev->interface); 374 if (result) { 375 usb_dbg(dev->interface, "wakeup failed (result %d)", result); 376 return result; 377 } 378 379 dev->reading = true; 380 result = usb_submit_urb(dev->urb, GFP_KERNEL); 381 if (result < 0) { 382 result = usb_translate_errors(result); 383 dev->reading = false; 384 goto out; 385 } 386 387 /* The first read on the Alea takes a little under 2 seconds. 388 * Reads after the first read take only a few microseconds 389 * though. Presumably the entropy-generating circuit needs 390 * time to ramp up. So, we wait longer on the first read. 391 */ 392 started = dev->reads_started; 393 dev->reads_started = true; 394 result = wait_event_interruptible_timeout( 395 dev->wait_q, 396 !dev->reading, 397 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) ); 398 399 if (result < 0) { 400 usb_kill_urb(dev->urb); 401 goto out; 402 } 403 404 if (result == 0) { 405 result = -ETIMEDOUT; 406 usb_kill_urb(dev->urb); 407 } else { 408 result = dev->valid; 409 } 410 out: 411 /* Let the device go back to sleep eventually */ 412 usb_autopm_put_interface(dev->interface); 413 414 usb_dbg(dev->interface, "read %d bytes", dev->valid); 415 416 return result; 417 } 418 419 static ssize_t chaoskey_read(struct file *file, 420 char __user *buffer, 421 size_t count, 422 loff_t *ppos) 423 { 424 struct chaoskey *dev; 425 ssize_t read_count = 0; 426 int this_time; 427 int result = 0; 428 unsigned long remain; 429 430 dev = file->private_data; 431 432 if (dev == NULL || !dev->present) 433 return -ENODEV; 434 435 usb_dbg(dev->interface, "read %zu", count); 436 437 while (count > 0) { 438 439 /* Grab the rng_lock briefly to ensure that the hwrng interface 440 * gets priority over other user access 441 */ 442 result = mutex_lock_interruptible(&dev->rng_lock); 443 if (result) 444 goto bail; 445 mutex_unlock(&dev->rng_lock); 446 447 result = mutex_lock_interruptible(&dev->lock); 448 if (result) 449 goto bail; 450 if (dev->valid == dev->used) { 451 result = _chaoskey_fill(dev); 452 if (result < 0) { 453 mutex_unlock(&dev->lock); 454 goto bail; 455 } 456 } 457 458 this_time = dev->valid - dev->used; 459 if (this_time > count) 460 this_time = count; 461 462 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 463 if (remain) { 464 result = -EFAULT; 465 466 /* Consume the bytes that were copied so we don't leak 467 * data to user space 468 */ 469 dev->used += this_time - remain; 470 mutex_unlock(&dev->lock); 471 goto bail; 472 } 473 474 count -= this_time; 475 read_count += this_time; 476 buffer += this_time; 477 dev->used += this_time; 478 mutex_unlock(&dev->lock); 479 } 480 bail: 481 if (read_count) { 482 usb_dbg(dev->interface, "read %zu bytes", read_count); 483 return read_count; 484 } 485 usb_dbg(dev->interface, "empty read, result %d", result); 486 if (result == -ETIMEDOUT) 487 result = -EAGAIN; 488 return result; 489 } 490 491 static int chaoskey_rng_read(struct hwrng *rng, void *data, 492 size_t max, bool wait) 493 { 494 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 495 int this_time; 496 497 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 498 499 if (!dev->present) { 500 usb_dbg(dev->interface, "device not present"); 501 return 0; 502 } 503 504 /* Hold the rng_lock until we acquire the device lock so that 505 * this operation gets priority over other user access to the 506 * device 507 */ 508 mutex_lock(&dev->rng_lock); 509 510 mutex_lock(&dev->lock); 511 512 mutex_unlock(&dev->rng_lock); 513 514 /* Try to fill the buffer if empty. It doesn't actually matter 515 * if _chaoskey_fill works; we'll just return zero bytes as 516 * the buffer will still be empty 517 */ 518 if (dev->valid == dev->used) 519 (void) _chaoskey_fill(dev); 520 521 this_time = dev->valid - dev->used; 522 if (this_time > max) 523 this_time = max; 524 525 memcpy(data, dev->buf + dev->used, this_time); 526 527 dev->used += this_time; 528 529 mutex_unlock(&dev->lock); 530 531 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 532 return this_time; 533 } 534 535 #ifdef CONFIG_PM 536 static int chaoskey_suspend(struct usb_interface *interface, 537 pm_message_t message) 538 { 539 usb_dbg(interface, "suspend"); 540 return 0; 541 } 542 543 static int chaoskey_resume(struct usb_interface *interface) 544 { 545 struct chaoskey *dev; 546 struct usb_device *udev = interface_to_usbdev(interface); 547 548 usb_dbg(interface, "resume"); 549 dev = usb_get_intfdata(interface); 550 551 /* 552 * We may have lost power. 553 * In that case the device that needs a long time 554 * for the first requests needs an extended timeout 555 * again 556 */ 557 if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID) 558 dev->reads_started = false; 559 560 return 0; 561 } 562 #else 563 #define chaoskey_suspend NULL 564 #define chaoskey_resume NULL 565 #endif 566 567 /* file operation pointers */ 568 static const struct file_operations chaoskey_fops = { 569 .owner = THIS_MODULE, 570 .read = chaoskey_read, 571 .open = chaoskey_open, 572 .release = chaoskey_release, 573 .llseek = default_llseek, 574 }; 575 576 /* class driver information */ 577 static struct usb_class_driver chaoskey_class = { 578 .name = "chaoskey%d", 579 .fops = &chaoskey_fops, 580 .minor_base = USB_CHAOSKEY_MINOR_BASE, 581 }; 582 583 /* usb specific object needed to register this driver with the usb subsystem */ 584 static struct usb_driver chaoskey_driver = { 585 .name = DRIVER_SHORT, 586 .probe = chaoskey_probe, 587 .disconnect = chaoskey_disconnect, 588 .suspend = chaoskey_suspend, 589 .resume = chaoskey_resume, 590 .reset_resume = chaoskey_resume, 591 .id_table = chaoskey_table, 592 .supports_autosuspend = 1, 593 }; 594 595 module_usb_driver(chaoskey_driver); 596 597