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 kfree(dev); 102 } 103 } 104 105 static int chaoskey_probe(struct usb_interface *interface, 106 const struct usb_device_id *id) 107 { 108 struct usb_device *udev = interface_to_usbdev(interface); 109 struct usb_host_interface *altsetting = interface->cur_altsetting; 110 struct usb_endpoint_descriptor *epd; 111 int in_ep; 112 struct chaoskey *dev; 113 int result = -ENOMEM; 114 int size; 115 int res; 116 117 usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); 118 119 /* Find the first bulk IN endpoint and its packet size */ 120 res = usb_find_bulk_in_endpoint(altsetting, &epd); 121 if (res) { 122 usb_dbg(interface, "no IN endpoint found"); 123 return res; 124 } 125 126 in_ep = usb_endpoint_num(epd); 127 size = usb_endpoint_maxp(epd); 128 129 /* Validate endpoint and size */ 130 if (size <= 0) { 131 usb_dbg(interface, "invalid size (%d)", size); 132 return -ENODEV; 133 } 134 135 if (size > CHAOSKEY_BUF_LEN) { 136 usb_dbg(interface, "size reduced from %d to %d\n", 137 size, CHAOSKEY_BUF_LEN); 138 size = CHAOSKEY_BUF_LEN; 139 } 140 141 /* Looks good, allocate and initialize */ 142 143 dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); 144 145 if (dev == NULL) 146 goto out; 147 148 dev->buf = kmalloc(size, GFP_KERNEL); 149 150 if (dev->buf == NULL) 151 goto out; 152 153 dev->urb = usb_alloc_urb(0, GFP_KERNEL); 154 155 if (!dev->urb) 156 goto out; 157 158 usb_fill_bulk_urb(dev->urb, 159 udev, 160 usb_rcvbulkpipe(udev, in_ep), 161 dev->buf, 162 size, 163 chaos_read_callback, 164 dev); 165 166 /* Construct a name using the product and serial values. Each 167 * device needs a unique name for the hwrng code 168 */ 169 170 if (udev->product && udev->serial) { 171 dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product, 172 udev->serial); 173 if (dev->name == NULL) 174 goto out; 175 } 176 177 dev->interface = interface; 178 179 dev->in_ep = in_ep; 180 181 if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID) 182 dev->reads_started = true; 183 184 dev->size = size; 185 dev->present = true; 186 187 init_waitqueue_head(&dev->wait_q); 188 189 mutex_init(&dev->lock); 190 mutex_init(&dev->rng_lock); 191 192 usb_set_intfdata(interface, dev); 193 194 result = usb_register_dev(interface, &chaoskey_class); 195 if (result) { 196 usb_err(interface, "Unable to allocate minor number."); 197 goto out; 198 } 199 200 dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; 201 dev->hwrng.read = chaoskey_rng_read; 202 dev->hwrng.quality = 1024; 203 204 dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); 205 if (!dev->hwrng_registered) 206 usb_err(interface, "Unable to register with hwrng"); 207 208 usb_enable_autosuspend(udev); 209 210 usb_dbg(interface, "chaoskey probe success, size %d", dev->size); 211 return 0; 212 213 out: 214 usb_set_intfdata(interface, NULL); 215 chaoskey_free(dev); 216 return result; 217 } 218 219 static void chaoskey_disconnect(struct usb_interface *interface) 220 { 221 struct chaoskey *dev; 222 223 usb_dbg(interface, "disconnect"); 224 dev = usb_get_intfdata(interface); 225 if (!dev) { 226 usb_dbg(interface, "disconnect failed - no dev"); 227 return; 228 } 229 230 if (dev->hwrng_registered) 231 hwrng_unregister(&dev->hwrng); 232 233 usb_deregister_dev(interface, &chaoskey_class); 234 235 usb_set_intfdata(interface, NULL); 236 mutex_lock(&dev->lock); 237 238 dev->present = false; 239 usb_poison_urb(dev->urb); 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 static void chaos_read_callback(struct urb *urb) 315 { 316 struct chaoskey *dev = urb->context; 317 int status = urb->status; 318 319 usb_dbg(dev->interface, "callback status (%d)", status); 320 321 if (status == 0) 322 dev->valid = urb->actual_length; 323 else 324 dev->valid = 0; 325 326 dev->used = 0; 327 328 /* must be seen first before validity is announced */ 329 smp_wmb(); 330 331 dev->reading = false; 332 wake_up(&dev->wait_q); 333 } 334 335 /* Fill the buffer. Called with dev->lock held 336 */ 337 static int _chaoskey_fill(struct chaoskey *dev) 338 { 339 DEFINE_WAIT(wait); 340 int result; 341 bool started; 342 343 usb_dbg(dev->interface, "fill"); 344 345 /* Return immediately if someone called before the buffer was 346 * empty */ 347 if (dev->valid != dev->used) { 348 usb_dbg(dev->interface, "not empty yet (valid %d used %d)", 349 dev->valid, dev->used); 350 return 0; 351 } 352 353 /* Bail if the device has been removed */ 354 if (!dev->present) { 355 usb_dbg(dev->interface, "device not present"); 356 return -ENODEV; 357 } 358 359 /* Make sure the device is awake */ 360 result = usb_autopm_get_interface(dev->interface); 361 if (result) { 362 usb_dbg(dev->interface, "wakeup failed (result %d)", result); 363 return result; 364 } 365 366 dev->reading = true; 367 result = usb_submit_urb(dev->urb, GFP_KERNEL); 368 if (result < 0) { 369 result = usb_translate_errors(result); 370 dev->reading = false; 371 goto out; 372 } 373 374 /* The first read on the Alea takes a little under 2 seconds. 375 * Reads after the first read take only a few microseconds 376 * though. Presumably the entropy-generating circuit needs 377 * time to ramp up. So, we wait longer on the first read. 378 */ 379 started = dev->reads_started; 380 dev->reads_started = true; 381 result = wait_event_interruptible_timeout( 382 dev->wait_q, 383 !dev->reading, 384 (started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) ); 385 386 if (result < 0) 387 goto out; 388 389 if (result == 0) 390 result = -ETIMEDOUT; 391 else 392 result = dev->valid; 393 out: 394 /* Let the device go back to sleep eventually */ 395 usb_autopm_put_interface(dev->interface); 396 397 usb_dbg(dev->interface, "read %d bytes", dev->valid); 398 399 return result; 400 } 401 402 static ssize_t chaoskey_read(struct file *file, 403 char __user *buffer, 404 size_t count, 405 loff_t *ppos) 406 { 407 struct chaoskey *dev; 408 ssize_t read_count = 0; 409 int this_time; 410 int result = 0; 411 unsigned long remain; 412 413 dev = file->private_data; 414 415 if (dev == NULL || !dev->present) 416 return -ENODEV; 417 418 usb_dbg(dev->interface, "read %zu", count); 419 420 while (count > 0) { 421 422 /* Grab the rng_lock briefly to ensure that the hwrng interface 423 * gets priority over other user access 424 */ 425 result = mutex_lock_interruptible(&dev->rng_lock); 426 if (result) 427 goto bail; 428 mutex_unlock(&dev->rng_lock); 429 430 result = mutex_lock_interruptible(&dev->lock); 431 if (result) 432 goto bail; 433 if (dev->valid == dev->used) { 434 result = _chaoskey_fill(dev); 435 if (result < 0) { 436 mutex_unlock(&dev->lock); 437 goto bail; 438 } 439 } 440 441 this_time = dev->valid - dev->used; 442 if (this_time > count) 443 this_time = count; 444 445 remain = copy_to_user(buffer, dev->buf + dev->used, this_time); 446 if (remain) { 447 result = -EFAULT; 448 449 /* Consume the bytes that were copied so we don't leak 450 * data to user space 451 */ 452 dev->used += this_time - remain; 453 mutex_unlock(&dev->lock); 454 goto bail; 455 } 456 457 count -= this_time; 458 read_count += this_time; 459 buffer += this_time; 460 dev->used += this_time; 461 mutex_unlock(&dev->lock); 462 } 463 bail: 464 if (read_count) { 465 usb_dbg(dev->interface, "read %zu bytes", read_count); 466 return read_count; 467 } 468 usb_dbg(dev->interface, "empty read, result %d", result); 469 if (result == -ETIMEDOUT) 470 result = -EAGAIN; 471 return result; 472 } 473 474 static int chaoskey_rng_read(struct hwrng *rng, void *data, 475 size_t max, bool wait) 476 { 477 struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); 478 int this_time; 479 480 usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); 481 482 if (!dev->present) { 483 usb_dbg(dev->interface, "device not present"); 484 return 0; 485 } 486 487 /* Hold the rng_lock until we acquire the device lock so that 488 * this operation gets priority over other user access to the 489 * device 490 */ 491 mutex_lock(&dev->rng_lock); 492 493 mutex_lock(&dev->lock); 494 495 mutex_unlock(&dev->rng_lock); 496 497 /* Try to fill the buffer if empty. It doesn't actually matter 498 * if _chaoskey_fill works; we'll just return zero bytes as 499 * the buffer will still be empty 500 */ 501 if (dev->valid == dev->used) 502 (void) _chaoskey_fill(dev); 503 504 this_time = dev->valid - dev->used; 505 if (this_time > max) 506 this_time = max; 507 508 memcpy(data, dev->buf + dev->used, this_time); 509 510 dev->used += this_time; 511 512 mutex_unlock(&dev->lock); 513 514 usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); 515 return this_time; 516 } 517 518 #ifdef CONFIG_PM 519 static int chaoskey_suspend(struct usb_interface *interface, 520 pm_message_t message) 521 { 522 usb_dbg(interface, "suspend"); 523 return 0; 524 } 525 526 static int chaoskey_resume(struct usb_interface *interface) 527 { 528 usb_dbg(interface, "resume"); 529 return 0; 530 } 531 #else 532 #define chaoskey_suspend NULL 533 #define chaoskey_resume NULL 534 #endif 535 536 /* file operation pointers */ 537 static const struct file_operations chaoskey_fops = { 538 .owner = THIS_MODULE, 539 .read = chaoskey_read, 540 .open = chaoskey_open, 541 .release = chaoskey_release, 542 .llseek = default_llseek, 543 }; 544 545 /* class driver information */ 546 static struct usb_class_driver chaoskey_class = { 547 .name = "chaoskey%d", 548 .fops = &chaoskey_fops, 549 .minor_base = USB_CHAOSKEY_MINOR_BASE, 550 }; 551 552 /* usb specific object needed to register this driver with the usb subsystem */ 553 static struct usb_driver chaoskey_driver = { 554 .name = DRIVER_SHORT, 555 .probe = chaoskey_probe, 556 .disconnect = chaoskey_disconnect, 557 .suspend = chaoskey_suspend, 558 .resume = chaoskey_resume, 559 .reset_resume = chaoskey_resume, 560 .id_table = chaoskey_table, 561 .supports_autosuspend = 1, 562 }; 563 564 module_usb_driver(chaoskey_driver); 565 566