drivers/char/tpm/xen-tpmfront.c

   1 /*
   2  * Implementation of the Xen vTPM device frontend
   3  *
   4  * Author:  Daniel De Graaf <dgdegra@tycho.nsa.gov>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2,
   8  * as published by the Free Software Foundation.
   9  */
  10 #include <linux/errno.h>
  11 #include <linux/err.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/freezer.h>
  14 #include <xen/xen.h>
  15 #include <xen/events.h>
  16 #include <xen/interface/io/tpmif.h>
  17 #include <xen/grant_table.h>
  18 #include <xen/xenbus.h>
  19 #include <xen/page.h>
  20 #include "tpm.h"
  21 #include <xen/platform_pci.h>
  22
  23 struct tpm_private {
  24         struct tpm_chip *chip;
  25         struct xenbus_device *dev;
  26
  27         struct vtpm_shared_page *shr;
  28
  29         unsigned int evtchn;
  30         int ring_ref;
  31         domid_t backend_id;
  32         int irq;
  33         wait_queue_head_t read_queue;
  34 };
  35
  36 enum status_bits {
  37         VTPM_STATUS_RUNNING  = 0x1,
  38         VTPM_STATUS_IDLE     = 0x2,
  39         VTPM_STATUS_RESULT   = 0x4,
  40         VTPM_STATUS_CANCELED = 0x8,
  41 };
  42
  43 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
  44                                         bool check_cancel, bool *canceled)
  45 {
  46         u8 status = chip->ops->status(chip);
  47
  48         *canceled = false;
  49         if ((status & mask) == mask)
  50                 return true;
  51         if (check_cancel && chip->ops->req_canceled(chip, status)) {
  52                 *canceled = true;
  53                 return true;
  54         }
  55         return false;
  56 }
  57
  58 static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
  59                 unsigned long timeout, wait_queue_head_t *queue,
  60                 bool check_cancel)
  61 {
  62         unsigned long stop;
  63         long rc;
  64         u8 status;
  65         bool canceled = false;
  66
  67         /* check current status */
  68         status = chip->ops->status(chip);
  69         if ((status & mask) == mask)
  70                 return 0;
  71
  72         stop = jiffies + timeout;
  73
  74         if (chip->flags & TPM_CHIP_FLAG_IRQ) {
  75 again:
  76                 timeout = stop - jiffies;
  77                 if ((long)timeout <= 0)
  78                         return -ETIME;
  79                 rc = wait_event_interruptible_timeout(*queue,
  80                         wait_for_tpm_stat_cond(chip, mask, check_cancel,
  81                                                &canceled),
  82                         timeout);
  83                 if (rc > 0) {
  84                         if (canceled)
  85                                 return -ECANCELED;
  86                         return 0;
  87                 }
  88                 if (rc == -ERESTARTSYS && freezing(current)) {
  89                         clear_thread_flag(TIF_SIGPENDING);
  90                         goto again;
  91                 }
  92         } else {
  93                 do {
  94                         tpm_msleep(TPM_TIMEOUT);
  95                         status = chip->ops->status(chip);
  96                         if ((status & mask) == mask)
  97                                 return 0;
  98                 } while (time_before(jiffies, stop));
  99         }
 100         return -ETIME;
 101 }
 102
 103 static u8 vtpm_status(struct tpm_chip *chip)
 104 {
 105         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 106         switch (priv->shr->state) {
 107         case VTPM_STATE_IDLE:
 108                 return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED;
 109         case VTPM_STATE_FINISH:
 110                 return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT;
 111         case VTPM_STATE_SUBMIT:
 112         case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */
 113                 return VTPM_STATUS_RUNNING;
 114         default:
 115                 return 0;
 116         }
 117 }
 118
 119 static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
 120 {
 121         return status & VTPM_STATUS_CANCELED;
 122 }
 123
 124 static void vtpm_cancel(struct tpm_chip *chip)
 125 {
 126         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 127         priv->shr->state = VTPM_STATE_CANCEL;
 128         wmb();
 129         notify_remote_via_evtchn(priv->evtchn);
 130 }
 131
 132 static unsigned int shr_data_offset(struct vtpm_shared_page *shr)
 133 {
 134         return sizeof(*shr) + sizeof(u32) * shr->nr_extra_pages;
 135 }
 136
 137 static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 138 {
 139         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 140         struct vtpm_shared_page *shr = priv->shr;
 141         unsigned int offset = shr_data_offset(shr);
 142
 143         u32 ordinal;
 144         unsigned long duration;
 145
 146         if (offset > PAGE_SIZE)
 147                 return -EINVAL;
 148
 149         if (offset + count > PAGE_SIZE)
 150                 return -EINVAL;
 151
 152         /* Wait for completion of any existing command or cancellation */
 153         if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->timeout_c,
 154                         &priv->read_queue, true) < 0) {
 155                 vtpm_cancel(chip);
 156                 return -ETIME;
 157         }
 158
 159         memcpy(offset + (u8 *)shr, buf, count);
 160         shr->length = count;
 161         barrier();
 162         shr->state = VTPM_STATE_SUBMIT;
 163         wmb();
 164         notify_remote_via_evtchn(priv->evtchn);
 165
 166         ordinal = be32_to_cpu(((struct tpm_input_header*)buf)->ordinal);
 167         duration = tpm_calc_ordinal_duration(chip, ordinal);
 168
 169         if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
 170                         &priv->read_queue, true) < 0) {
 171                 /* got a signal or timeout, try to cancel */
 172                 vtpm_cancel(chip);
 173                 return -ETIME;
 174         }
 175
 176         return count;
 177 }
 178
 179 static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 180 {
 181         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 182         struct vtpm_shared_page *shr = priv->shr;
 183         unsigned int offset = shr_data_offset(shr);
 184         size_t length = shr->length;
 185
 186         if (shr->state == VTPM_STATE_IDLE)
 187                 return -ECANCELED;
 188
 189         /* In theory the wait at the end of _send makes this one unnecessary */
 190         if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->timeout_c,
 191                         &priv->read_queue, true) < 0) {
 192                 vtpm_cancel(chip);
 193                 return -ETIME;
 194         }
 195
 196         if (offset > PAGE_SIZE)
 197                 return -EIO;
 198
 199         if (offset + length > PAGE_SIZE)
 200                 length = PAGE_SIZE - offset;
 201
 202         if (length > count)
 203                 length = count;
 204
 205         memcpy(buf, offset + (u8 *)shr, length);
 206
 207         return length;
 208 }
 209
 210 static const struct tpm_class_ops tpm_vtpm = {
 211         .status = vtpm_status,
 212         .recv = vtpm_recv,
 213         .send = vtpm_send,
 214         .cancel = vtpm_cancel,
 215         .req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
 216         .req_complete_val  = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
 217         .req_canceled      = vtpm_req_canceled,
 218 };
 219
 220 static irqreturn_t tpmif_interrupt(int dummy, void *dev_id)
 221 {
 222         struct tpm_private *priv = dev_id;
 223
 224         switch (priv->shr->state) {
 225         case VTPM_STATE_IDLE:
 226         case VTPM_STATE_FINISH:
 227                 wake_up_interruptible(&priv->read_queue);
 228                 break;
 229         case VTPM_STATE_SUBMIT:
 230         case VTPM_STATE_CANCEL:
 231         default:
 232                 break;
 233         }
 234         return IRQ_HANDLED;
 235 }
 236
 237 static int setup_chip(struct device *dev, struct tpm_private *priv)
 238 {
 239         struct tpm_chip *chip;
 240
 241         chip = tpmm_chip_alloc(dev, &tpm_vtpm);
 242         if (IS_ERR(chip))
 243                 return PTR_ERR(chip);
 244
 245         init_waitqueue_head(&priv->read_queue);
 246
 247         priv->chip = chip;
 248         dev_set_drvdata(&chip->dev, priv);
 249
 250         return 0;
 251 }
 252
 253 /* caller must clean up in case of errors */
 254 static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
 255 {
 256         struct xenbus_transaction xbt;
 257         const char *message = NULL;
 258         int rv;
 259         grant_ref_t gref;
 260
 261         priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
 262         if (!priv->shr) {
 263                 xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 264                 return -ENOMEM;
 265         }
 266
 267         rv = xenbus_grant_ring(dev, &priv->shr, 1, &gref);
 268         if (rv < 0)
 269                 return rv;
 270
 271         priv->ring_ref = gref;
 272
 273         rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
 274         if (rv)
 275                 return rv;
 276
 277         rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
 278                                        "tpmif", priv);
 279         if (rv <= 0) {
 280                 xenbus_dev_fatal(dev, rv, "allocating TPM irq");
 281                 return rv;
 282         }
 283         priv->irq = rv;
 284
 285  again:
 286         rv = xenbus_transaction_start(&xbt);
 287         if (rv) {
 288                 xenbus_dev_fatal(dev, rv, "starting transaction");
 289                 return rv;
 290         }
 291
 292         rv = xenbus_printf(xbt, dev->nodename,
 293                         "ring-ref", "%u", priv->ring_ref);
 294         if (rv) {
 295                 message = "writing ring-ref";
 296                 goto abort_transaction;
 297         }
 298
 299         rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 300                         priv->evtchn);
 301         if (rv) {
 302                 message = "writing event-channel";
 303                 goto abort_transaction;
 304         }
 305
 306         rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
 307         if (rv) {
 308                 message = "writing feature-protocol-v2";
 309                 goto abort_transaction;
 310         }
 311
 312         rv = xenbus_transaction_end(xbt, 0);
 313         if (rv == -EAGAIN)
 314                 goto again;
 315         if (rv) {
 316                 xenbus_dev_fatal(dev, rv, "completing transaction");
 317                 return rv;
 318         }
 319
 320         xenbus_switch_state(dev, XenbusStateInitialised);
 321
 322         return 0;
 323
 324  abort_transaction:
 325         xenbus_transaction_end(xbt, 1);
 326         if (message)
 327                 xenbus_dev_error(dev, rv, "%s", message);
 328
 329         return rv;
 330 }
 331
 332 static void ring_free(struct tpm_private *priv)
 333 {
 334         if (!priv)
 335                 return;
 336
 337         if (priv->ring_ref)
 338                 gnttab_end_foreign_access(priv->ring_ref, 0,
 339                                 (unsigned long)priv->shr);
 340         else
 341                 free_page((unsigned long)priv->shr);
 342
 343         if (priv->irq)
 344                 unbind_from_irqhandler(priv->irq, priv);
 345
 346         kfree(priv);
 347 }
 348
 349 static int tpmfront_probe(struct xenbus_device *dev,
 350                 const struct xenbus_device_id *id)
 351 {
 352         struct tpm_private *priv;
 353         int rv;
 354
 355         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 356         if (!priv) {
 357                 xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
 358                 return -ENOMEM;
 359         }
 360
 361         rv = setup_chip(&dev->dev, priv);
 362         if (rv) {
 363                 kfree(priv);
 364                 return rv;
 365         }
 366
 367         rv = setup_ring(dev, priv);
 368         if (rv) {
 369                 ring_free(priv);
 370                 return rv;
 371         }
 372
 373         tpm_get_timeouts(priv->chip);
 374
 375         return tpm_chip_register(priv->chip);
 376 }
 377
 378 static int tpmfront_remove(struct xenbus_device *dev)
 379 {
 380         struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
 381         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 382         tpm_chip_unregister(chip);
 383         ring_free(priv);
 384         dev_set_drvdata(&chip->dev, NULL);
 385         return 0;
 386 }
 387
 388 static int tpmfront_resume(struct xenbus_device *dev)
 389 {
 390         /* A suspend/resume/migrate will interrupt a vTPM anyway */
 391         tpmfront_remove(dev);
 392         return tpmfront_probe(dev, NULL);
 393 }
 394
 395 static void backend_changed(struct xenbus_device *dev,
 396                 enum xenbus_state backend_state)
 397 {
 398         switch (backend_state) {
 399         case XenbusStateInitialised:
 400         case XenbusStateConnected:
 401                 if (dev->state == XenbusStateConnected)
 402                         break;
 403
 404                 if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
 405                                           0)) {
 406                         xenbus_dev_fatal(dev, -EINVAL,
 407                                         "vTPM protocol 2 required");
 408                         return;
 409                 }
 410                 xenbus_switch_state(dev, XenbusStateConnected);
 411                 break;
 412
 413         case XenbusStateClosing:
 414         case XenbusStateClosed:
 415                 device_unregister(&dev->dev);
 416                 xenbus_frontend_closed(dev);
 417                 break;
 418         default:
 419                 break;
 420         }
 421 }
 422
 423 static const struct xenbus_device_id tpmfront_ids[] = {
 424         { "vtpm" },
 425         { "" }
 426 };
 427 MODULE_ALIAS("xen:vtpm");
 428
 429 static struct xenbus_driver tpmfront_driver = {
 430         .ids = tpmfront_ids,
 431         .probe = tpmfront_probe,
 432         .remove = tpmfront_remove,
 433         .resume = tpmfront_resume,
 434         .otherend_changed = backend_changed,
 435 };
 436
 437 static int __init xen_tpmfront_init(void)
 438 {
 439         if (!xen_domain())
 440                 return -ENODEV;
 441
 442         if (!xen_has_pv_devices())
 443                 return -ENODEV;
 444
 445         return xenbus_register_frontend(&tpmfront_driver);
 446 }
 447 module_init(xen_tpmfront_init);
 448
 449 static void __exit xen_tpmfront_exit(void)
 450 {
 451         xenbus_unregister_driver(&tpmfront_driver);
 452 }
 453 module_exit(xen_tpmfront_exit);
 454
 455 MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
 456 MODULE_DESCRIPTION("Xen vTPM Driver");
 457 MODULE_LICENSE("GPL");