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 #define usb_dbg(usb_if, format, arg...) \ 31 dev_dbg(&(usb_if)->dev, format, ## arg) 32 33 #define usb_err(usb_if, format, arg...) \ 34 dev_err(&(usb_if)->dev, format, ## arg) 35 36 /* Version Information */ 37 #define DRIVER_AUTHOR "Keith Packard, keithp@keithp.com" 38 #define DRIVER_DESC "Altus Metrum ChaosKey driver" 39 #define DRIVER_SHORT "chaoskey" 40 41 MODULE_AUTHOR(DRIVER_AUTHOR); 42 MODULE_DESCRIPTION(DRIVER_DESC); 43 MODULE_LICENSE("GPL"); 44 45 #define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ 46 #define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ 47 48 #define ALEA_VENDOR_ID 0x12d8 /* Araneus */ 49 #define ALEA_PRODUCT_ID 0x0001 /* Alea I */ 50 51 #define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ 52 53 #define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */ 54 #define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */ 55 56 #ifdef CONFIG_USB_DYNAMIC_MINORS 57 #define USB_CHAOSKEY_MINOR_BASE 0 58 #else 59 60 /* IOWARRIOR_MINOR_BASE + 16, not official yet */ 61 #define USB_CHAOSKEY_MINOR_BASE 224 62 #endif 63 64 static const struct usb_device_id chaoskey_table[] = { 65 { USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, 66 { USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) }, 67 { }, 68 }; 69 MODULE_DEVICE_TABLE(usb, chaoskey_table); 70 71 static void chaos_read_callback(struct urb *urb); 72 73 /* Driver-local specific stuff */ 74 struct chaoskey { 75 struct usb_interface *interface; 76 char in_ep; 77 struct mutex lock; 78 struct mutex rng_lock; 79 int open; /* open count */ 80 bool present; /* device not disconnected */ 81 bool reading; /* ongoing IO */ 82 bool reads_started; /* track first read for Alea */ 83 int size; /* size of buf */ 84 int valid; /* bytes of buf read */ 85 int used; /* bytes of buf consumed */ 86 char *name; /* product + serial */ 87 struct hwrng hwrng; /* Embedded struct for hwrng */ 88 int hwrng_registered; /* registered with hwrng API */ 89 wait_queue_head_t wait_q; /* for timeouts */ 90 struct urb *urb; /* for performing IO */ 91 char *buf; 92 }; 93 94 static void chaoskey_free(struct chaoskey *dev) 95 { 96 if (dev) { 97 usb_dbg(dev->interface, "free"); 98 usb_free_urb(dev->urb); 99 kfree(dev->name); 100 kfree(dev->buf); 101 usb_put_intf(dev->interface); 102 kfree(dev); 103 } 104 } 105 106 static int chaoskey_probe(struct usb_interface *interface, 107 const struct usb_device_id *id) 108 { 109 struct usb_device *udev = interface_to_usbdev(interface); 110 struct usb_host_interface *altsetting = interface->cur_altsetting; 111 struct usb_endpoint_descriptor *epd; 112 int in_ep; 113 struct chaoskey *dev; 114 int result = -ENOMEM; 115 int size; 116 int res; 117 118 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); 119 120 /* Find the first bulk IN endpoint and its packet size */ 121 res = usb_find_bulk_in_endpoint(altsetting, &epd); 122 if (res) { 123 usb_dbg(interface, "no IN endpoint found"); 124 return res; 125 } 126 127 in_ep = usb_endpoint_num(epd); 128 size = usb_endpoint_maxp(epd); 129 130 /* Validate endpoint and size */ 131 if (size <= 0) { 132 usb_dbg(interface, "invalid size (%d)", size); 133 return -ENODEV; 134 } 135 136 if (size > CHAOSKEY_BUF_LEN) { 137 usb_dbg(interface, "size reduced from %d to %d\n", 138 size, CHAOSKEY_BUF_LEN); 139 size = CHAOSKEY_BUF_LEN; 140 } 141 142 /* Looks good, allocate and initialize */ 143 144 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 145 146 if (dev == NULL) 147 goto out; 148 149 dev->interface = usb_get_intf(interface); 150 151 dev->buf = kmalloc(size, GFP_KERNEL); 152 153 if (dev->buf == NULL) 154 goto out; 155 156 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 157 158 if (!dev->urb) 159 goto out; 160 161 usb_fill_bulk_urb(dev->urb, 162 udev, 163 usb_rcvbulkpipe(udev, in_ep), 164 dev->buf, 165 size, 166 chaos_read_callback, 167 dev); 168 169 /* Construct a name using the product and serial values. Each 170 * device needs a unique name for the hwrng code 171 */ 172 173 if (udev->product && udev->serial) { 174 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product, 175 udev->serial); 176 if (dev->name == NULL) 177 goto out; 178 } 179 180 dev->in_ep = in_ep; 181 182 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID) 183 dev->reads_started = true; 184 185 dev->size = size; 186 dev->present = true; 187 188 init_waitqueue_head(&dev->wait_q); 189 190 mutex_init(&dev->lock); 191 mutex_init(&dev->rng_lock); 192 193 usb_set_intfdata(interface, dev); 194 195 result = usb_register_dev(interface, &chaoskey_class); 196 if (result) { 197 usb_err(interface, "Unable to allocate minor number."); 198 goto out; 199 } 200 201 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 202 dev->hwrng.read = chaoskey_rng_read; 203 dev->hwrng.quality = 1024; 204 205 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 206 if (!dev->hwrng_registered) 207 usb_err(interface, "Unable to register with hwrng"); 208 209 usb_enable_autosuspend(udev); 210 211 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 212 return 0; 213 214 out: 215 usb_set_intfdata(interface, NULL); 216 chaoskey_free(dev); 217 return result; 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 = false; 240 usb_poison_urb(dev->urb); 241 242 if (!dev->open) { 243 mutex_unlock(&dev->lock); 244 chaoskey_free(dev); 245 } else 246 mutex_unlock(&dev->lock); 247 248 usb_dbg(interface, "disconnect done"); 249 } 250 251 static int chaoskey_open(struct inode *inode, struct file *file) 252 { 253 struct chaoskey *dev; 254 struct usb_interface *interface; 255 256 /* get the interface from minor number and driver information */ 257 interface = usb_find_interface(&chaoskey_driver, iminor(inode)); 258 if (!interface) 259 return -ENODEV; 260 261 usb_dbg(interface, "open"); 262 263 dev = usb_get_intfdata(interface); 264 if (!dev) { 265 usb_dbg(interface, "open (dev)"); 266 return -ENODEV; 267 } 268 269 file->private_data = dev; 270 mutex_lock(&dev->lock); 271 ++dev->open; 272 mutex_unlock(&dev->lock); 273 274 usb_dbg(interface, "open success"); 275 return 0; 276 } 277 278 static int chaoskey_release(struct inode *inode, struct file *file) 279 { 280 struct chaoskey *dev = file->private_data; 281 struct usb_interface *interface; 282 283 if (dev == NULL) 284 return -ENODEV; 285 286 interface = dev->interface; 287 288 usb_dbg(interface, "release"); 289 290 mutex_lock(&dev->lock); 291 292 usb_dbg(interface, "open count at release is %d", dev->open); 293 294 if (dev->open <= 0) { 295 usb_dbg(interface, "invalid open count (%d)", dev->open); 296 mutex_unlock(&dev->lock); 297 return -ENODEV; 298 } 299 300 --dev->open; 301 302 if (!dev->present) { 303 if (dev->open == 0) { 304 mutex_unlock(&dev->lock); 305 chaoskey_free(dev); 306 } else 307 mutex_unlock(&dev->lock); 308 } else 309 mutex_unlock(&dev->lock); 310 311 usb_dbg(interface, "release success"); 312 return 0; 313 } 314 315 static void chaos_read_callback(struct urb *urb) 316 { 317 struct chaoskey *dev = urb->context; 318 int status = urb->status; 319 320 usb_dbg(dev->interface, "callback status (%d)", status); 321 322 if (status == 0) 323 dev->valid = urb->actual_length; 324 else 325 dev->valid = 0; 326 327 dev->used = 0; 328 329 /* must be seen first before validity is announced */ 330 smp_wmb(); 331 332 dev->reading = false; 333 wake_up(&dev->wait_q); 334 } 335 336 /* Fill the buffer. Called with dev->lock held 337 */ 338 static int _chaoskey_fill(struct chaoskey *dev) 339 { 340 DEFINE_WAIT(wait); 341 int result; 342 bool started; 343 344 usb_dbg(dev->interface, "fill"); 345 346 /* Return immediately if someone called before the buffer was 347 * empty */ 348 if (dev->valid != dev->used) { 349 usb_dbg(dev->interface, "not empty yet (valid %d used %d)", 350 dev->valid, dev->used); 351 return 0; 352 } 353 354 /* Bail if the device has been removed */ 355 if (!dev->present) { 356 usb_dbg(dev->interface, "device not present"); 357 return -ENODEV; 358 } 359 360 /* Make sure the device is awake */ 361 result = usb_autopm_get_interface(dev->interface); 362 if (result) { 363 usb_dbg(dev->interface, "wakeup failed (result %d)", result); 364 return result; 365 } 366 367 dev->reading = true; 368 result = usb_submit_urb(dev->urb, GFP_KERNEL); 369 if (result < 0) { 370 result = usb_translate_errors(result); 371 dev->reading = false; 372 goto out; 373 } 374 375 /* The first read on the Alea takes a little under 2 seconds. 376 * Reads after the first read take only a few microseconds 377 * though. Presumably the entropy-generating circuit needs 378 * time to ramp up. So, we wait longer on the first read. 379 */ 380 started = dev->reads_started; 381 dev->reads_started = true; 382 result = wait_event_interruptible_timeout( 383 dev->wait_q, 384 !dev->reading, 385 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) ); 386 387 if (result < 0) { 388 usb_kill_urb(dev->urb); 389 goto out; 390 } 391 392 if (result == 0) { 393 result = -ETIMEDOUT; 394 usb_kill_urb(dev->urb); 395 } else { 396 result = dev->valid; 397 } 398 out: 399 /* Let the device go back to sleep eventually */ 400 usb_autopm_put_interface(dev->interface); 401 402 usb_dbg(dev->interface, "read %d bytes", dev->valid); 403 404 return result; 405 } 406 407 static ssize_t chaoskey_read(struct file *file, 408 char __user *buffer, 409 size_t count, 410 loff_t *ppos) 411 { 412 struct chaoskey *dev; 413 ssize_t read_count = 0; 414 int this_time; 415 int result = 0; 416 unsigned long remain; 417 418 dev = file->private_data; 419 420 if (dev == NULL || !dev->present) 421 return -ENODEV; 422 423 usb_dbg(dev->interface, "read %zu", count); 424 425 while (count > 0) { 426 427 /* Grab the rng_lock briefly to ensure that the hwrng interface 428 * gets priority over other user access 429 */ 430 result = mutex_lock_interruptible(&dev->rng_lock); 431 if (result) 432 goto bail; 433 mutex_unlock(&dev->rng_lock); 434 435 result = mutex_lock_interruptible(&dev->lock); 436 if (result) 437 goto bail; 438 if (dev->valid == dev->used) { 439 result = _chaoskey_fill(dev); 440 if (result < 0) { 441 mutex_unlock(&dev->lock); 442 goto bail; 443 } 444 } 445 446 this_time = dev->valid - dev->used; 447 if (this_time > count) 448 this_time = count; 449 450 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 451 if (remain) { 452 result = -EFAULT; 453 454 /* Consume the bytes that were copied so we don't leak 455 * data to user space 456 */ 457 dev->used += this_time - remain; 458 mutex_unlock(&dev->lock); 459 goto bail; 460 } 461 462 count -= this_time; 463 read_count += this_time; 464 buffer += this_time; 465 dev->used += this_time; 466 mutex_unlock(&dev->lock); 467 } 468 bail: 469 if (read_count) { 470 usb_dbg(dev->interface, "read %zu bytes", read_count); 471 return read_count; 472 } 473 usb_dbg(dev->interface, "empty read, result %d", result); 474 if (result == -ETIMEDOUT) 475 result = -EAGAIN; 476 return result; 477 } 478 479 static int chaoskey_rng_read(struct hwrng *rng, void *data, 480 size_t max, bool wait) 481 { 482 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 483 int this_time; 484 485 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 486 487 if (!dev->present) { 488 usb_dbg(dev->interface, "device not present"); 489 return 0; 490 } 491 492 /* Hold the rng_lock until we acquire the device lock so that 493 * this operation gets priority over other user access to the 494 * device 495 */ 496 mutex_lock(&dev->rng_lock); 497 498 mutex_lock(&dev->lock); 499 500 mutex_unlock(&dev->rng_lock); 501 502 /* Try to fill the buffer if empty. It doesn't actually matter 503 * if _chaoskey_fill works; we'll just return zero bytes as 504 * the buffer will still be empty 505 */ 506 if (dev->valid == dev->used) 507 (void) _chaoskey_fill(dev); 508 509 this_time = dev->valid - dev->used; 510 if (this_time > max) 511 this_time = max; 512 513 memcpy(data, dev->buf + dev->used, this_time); 514 515 dev->used += this_time; 516 517 mutex_unlock(&dev->lock); 518 519 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 520 return this_time; 521 } 522 523 #ifdef CONFIG_PM 524 static int chaoskey_suspend(struct usb_interface *interface, 525 pm_message_t message) 526 { 527 usb_dbg(interface, "suspend"); 528 return 0; 529 } 530 531 static int chaoskey_resume(struct usb_interface *interface) 532 { 533 struct chaoskey *dev; 534 struct usb_device *udev = interface_to_usbdev(interface); 535 536 usb_dbg(interface, "resume"); 537 dev = usb_get_intfdata(interface); 538 539 /* 540 * We may have lost power. 541 * In that case the device that needs a long time 542 * for the first requests needs an extended timeout 543 * again 544 */ 545 if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID) 546 dev->reads_started = false; 547 548 return 0; 549 } 550 #else 551 #define chaoskey_suspend NULL 552 #define chaoskey_resume NULL 553 #endif 554 555 /* file operation pointers */ 556 static const struct file_operations chaoskey_fops = { 557 .owner = THIS_MODULE, 558 .read = chaoskey_read, 559 .open = chaoskey_open, 560 .release = chaoskey_release, 561 .llseek = default_llseek, 562 }; 563 564 /* class driver information */ 565 static struct usb_class_driver chaoskey_class = { 566 .name = "chaoskey%d", 567 .fops = &chaoskey_fops, 568 .minor_base = USB_CHAOSKEY_MINOR_BASE, 569 }; 570 571 /* usb specific object needed to register this driver with the usb subsystem */ 572 static struct usb_driver chaoskey_driver = { 573 .name = DRIVER_SHORT, 574 .probe = chaoskey_probe, 575 .disconnect = chaoskey_disconnect, 576 .suspend = chaoskey_suspend, 577 .resume = chaoskey_resume, 578 .reset_resume = chaoskey_resume, 579 .id_table = chaoskey_table, 580 .supports_autosuspend = 1, 581 }; 582 583 module_usb_driver(chaoskey_driver); 584 585