drivers/char/tpm/xen-tpmfront.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Implementation of the Xen vTPM device frontend
   4  *
   5  * Author:  Daniel De Graaf <dgdegra@tycho.nsa.gov>
   6  */
   7 #include <linux/errno.h>
   8 #include <linux/err.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/freezer.h>
  11 #include <xen/xen.h>
  12 #include <xen/events.h>
  13 #include <xen/interface/io/tpmif.h>
  14 #include <xen/grant_table.h>
  15 #include <xen/xenbus.h>
  16 #include <xen/page.h>
  17 #include "tpm.h"
  18 #include <xen/platform_pci.h>
  19
  20 struct tpm_private {
  21         struct tpm_chip *chip;
  22         struct xenbus_device *dev;
  23
  24         struct vtpm_shared_page *shr;
  25
  26         unsigned int evtchn;
  27         int ring_ref;
  28         domid_t backend_id;
  29         int irq;
  30         wait_queue_head_t read_queue;
  31 };
  32
  33 enum status_bits {
  34         VTPM_STATUS_RUNNING  = 0x1,
  35         VTPM_STATUS_IDLE     = 0x2,
  36         VTPM_STATUS_RESULT   = 0x4,
  37         VTPM_STATUS_CANCELED = 0x8,
  38 };
  39
  40 static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
  41                                         bool check_cancel, bool *canceled)
  42 {
  43         u8 status = chip->ops->status(chip);
  44
  45         *canceled = false;
  46         if ((status & mask) == mask)
  47                 return true;
  48         if (check_cancel && chip->ops->req_canceled(chip, status)) {
  49                 *canceled = true;
  50                 return true;
  51         }
  52         return false;
  53 }
  54
  55 static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
  56                 unsigned long timeout, wait_queue_head_t *queue,
  57                 bool check_cancel)
  58 {
  59         unsigned long stop;
  60         long rc;
  61         u8 status;
  62         bool canceled = false;
  63
  64         /* check current status */
  65         status = chip->ops->status(chip);
  66         if ((status & mask) == mask)
  67                 return 0;
  68
  69         stop = jiffies + timeout;
  70
  71         if (chip->flags & TPM_CHIP_FLAG_IRQ) {
  72 again:
  73                 timeout = stop - jiffies;
  74                 if ((long)timeout <= 0)
  75                         return -ETIME;
  76                 rc = wait_event_interruptible_timeout(*queue,
  77                         wait_for_tpm_stat_cond(chip, mask, check_cancel,
  78                                                &canceled),
  79                         timeout);
  80                 if (rc > 0) {
  81                         if (canceled)
  82                                 return -ECANCELED;
  83                         return 0;
  84                 }
  85                 if (rc == -ERESTARTSYS && freezing(current)) {
  86                         clear_thread_flag(TIF_SIGPENDING);
  87                         goto again;
  88                 }
  89         } else {
  90                 do {
  91                         tpm_msleep(TPM_TIMEOUT);
  92                         status = chip->ops->status(chip);
  93                         if ((status & mask) == mask)
  94                                 return 0;
  95                 } while (time_before(jiffies, stop));
  96         }
  97         return -ETIME;
  98 }
  99
 100 static u8 vtpm_status(struct tpm_chip *chip)
 101 {
 102         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 103         switch (priv->shr->state) {
 104         case VTPM_STATE_IDLE:
 105                 return VTPM_STATUS_IDLE | VTPM_STATUS_CANCELED;
 106         case VTPM_STATE_FINISH:
 107                 return VTPM_STATUS_IDLE | VTPM_STATUS_RESULT;
 108         case VTPM_STATE_SUBMIT:
 109         case VTPM_STATE_CANCEL: /* cancel requested, not yet canceled */
 110                 return VTPM_STATUS_RUNNING;
 111         default:
 112                 return 0;
 113         }
 114 }
 115
 116 static bool vtpm_req_canceled(struct tpm_chip *chip, u8 status)
 117 {
 118         return status & VTPM_STATUS_CANCELED;
 119 }
 120
 121 static void vtpm_cancel(struct tpm_chip *chip)
 122 {
 123         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 124         priv->shr->state = VTPM_STATE_CANCEL;
 125         wmb();
 126         notify_remote_via_evtchn(priv->evtchn);
 127 }
 128
 129 static size_t shr_data_offset(struct vtpm_shared_page *shr)
 130 {
 131         return struct_size(shr, extra_pages, shr->nr_extra_pages);
 132 }
 133
 134 static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 135 {
 136         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 137         struct vtpm_shared_page *shr = priv->shr;
 138         size_t offset = shr_data_offset(shr);
 139
 140         u32 ordinal;
 141         unsigned long duration;
 142
 143         if (offset > PAGE_SIZE)
 144                 return -EINVAL;
 145
 146         if (offset + count > PAGE_SIZE)
 147                 return -EINVAL;
 148
 149         /* Wait for completion of any existing command or cancellation */
 150         if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, chip->timeout_c,
 151                         &priv->read_queue, true) < 0) {
 152                 vtpm_cancel(chip);
 153                 return -ETIME;
 154         }
 155
 156         memcpy(offset + (u8 *)shr, buf, count);
 157         shr->length = count;
 158         barrier();
 159         shr->state = VTPM_STATE_SUBMIT;
 160         wmb();
 161         notify_remote_via_evtchn(priv->evtchn);
 162
 163         ordinal = be32_to_cpu(((struct tpm_header *)buf)->ordinal);
 164         duration = tpm_calc_ordinal_duration(chip, ordinal);
 165
 166         if (wait_for_tpm_stat(chip, VTPM_STATUS_IDLE, duration,
 167                         &priv->read_queue, true) < 0) {
 168                 /* got a signal or timeout, try to cancel */
 169                 vtpm_cancel(chip);
 170                 return -ETIME;
 171         }
 172
 173         return 0;
 174 }
 175
 176 static int vtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 177 {
 178         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 179         struct vtpm_shared_page *shr = priv->shr;
 180         size_t offset = shr_data_offset(shr);
 181         size_t length = shr->length;
 182
 183         if (shr->state == VTPM_STATE_IDLE)
 184                 return -ECANCELED;
 185
 186         /* In theory the wait at the end of _send makes this one unnecessary */
 187         if (wait_for_tpm_stat(chip, VTPM_STATUS_RESULT, chip->timeout_c,
 188                         &priv->read_queue, true) < 0) {
 189                 vtpm_cancel(chip);
 190                 return -ETIME;
 191         }
 192
 193         if (offset > PAGE_SIZE)
 194                 return -EIO;
 195
 196         if (offset + length > PAGE_SIZE)
 197                 length = PAGE_SIZE - offset;
 198
 199         if (length > count)
 200                 length = count;
 201
 202         memcpy(buf, offset + (u8 *)shr, length);
 203
 204         return length;
 205 }
 206
 207 static const struct tpm_class_ops tpm_vtpm = {
 208         .status = vtpm_status,
 209         .recv = vtpm_recv,
 210         .send = vtpm_send,
 211         .cancel = vtpm_cancel,
 212         .req_complete_mask = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
 213         .req_complete_val  = VTPM_STATUS_IDLE | VTPM_STATUS_RESULT,
 214         .req_canceled      = vtpm_req_canceled,
 215 };
 216
 217 static irqreturn_t tpmif_interrupt(int dummy, void *dev_id)
 218 {
 219         struct tpm_private *priv = dev_id;
 220
 221         switch (priv->shr->state) {
 222         case VTPM_STATE_IDLE:
 223         case VTPM_STATE_FINISH:
 224                 wake_up_interruptible(&priv->read_queue);
 225                 break;
 226         case VTPM_STATE_SUBMIT:
 227         case VTPM_STATE_CANCEL:
 228         default:
 229                 break;
 230         }
 231         return IRQ_HANDLED;
 232 }
 233
 234 static int setup_chip(struct device *dev, struct tpm_private *priv)
 235 {
 236         struct tpm_chip *chip;
 237
 238         chip = tpmm_chip_alloc(dev, &tpm_vtpm);
 239         if (IS_ERR(chip))
 240                 return PTR_ERR(chip);
 241
 242         init_waitqueue_head(&priv->read_queue);
 243
 244         priv->chip = chip;
 245         dev_set_drvdata(&chip->dev, priv);
 246
 247         return 0;
 248 }
 249
 250 /* caller must clean up in case of errors */
 251 static int setup_ring(struct xenbus_device *dev, struct tpm_private *priv)
 252 {
 253         struct xenbus_transaction xbt;
 254         const char *message = NULL;
 255         int rv;
 256
 257         rv = xenbus_setup_ring(dev, GFP_KERNEL, (void **)&priv->shr, 1,
 258                                &priv->ring_ref);
 259         if (rv < 0)
 260                 return rv;
 261
 262         rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
 263         if (rv)
 264                 return rv;
 265
 266         rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
 267                                        "tpmif", priv);
 268         if (rv <= 0) {
 269                 xenbus_dev_fatal(dev, rv, "allocating TPM irq");
 270                 return rv;
 271         }
 272         priv->irq = rv;
 273
 274  again:
 275         rv = xenbus_transaction_start(&xbt);
 276         if (rv) {
 277                 xenbus_dev_fatal(dev, rv, "starting transaction");
 278                 return rv;
 279         }
 280
 281         rv = xenbus_printf(xbt, dev->nodename,
 282                         "ring-ref", "%u", priv->ring_ref);
 283         if (rv) {
 284                 message = "writing ring-ref";
 285                 goto abort_transaction;
 286         }
 287
 288         rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 289                         priv->evtchn);
 290         if (rv) {
 291                 message = "writing event-channel";
 292                 goto abort_transaction;
 293         }
 294
 295         rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
 296         if (rv) {
 297                 message = "writing feature-protocol-v2";
 298                 goto abort_transaction;
 299         }
 300
 301         rv = xenbus_transaction_end(xbt, 0);
 302         if (rv == -EAGAIN)
 303                 goto again;
 304         if (rv) {
 305                 xenbus_dev_fatal(dev, rv, "completing transaction");
 306                 return rv;
 307         }
 308
 309         xenbus_switch_state(dev, XenbusStateInitialised);
 310
 311         return 0;
 312
 313  abort_transaction:
 314         xenbus_transaction_end(xbt, 1);
 315         if (message)
 316                 xenbus_dev_error(dev, rv, "%s", message);
 317
 318         return rv;
 319 }
 320
 321 static void ring_free(struct tpm_private *priv)
 322 {
 323         if (!priv)
 324                 return;
 325
 326         xenbus_teardown_ring((void **)&priv->shr, 1, &priv->ring_ref);
 327
 328         if (priv->irq)
 329                 unbind_from_irqhandler(priv->irq, priv);
 330
 331         kfree(priv);
 332 }
 333
 334 static int tpmfront_probe(struct xenbus_device *dev,
 335                 const struct xenbus_device_id *id)
 336 {
 337         struct tpm_private *priv;
 338         int rv;
 339
 340         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 341         if (!priv) {
 342                 xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
 343                 return -ENOMEM;
 344         }
 345
 346         rv = setup_chip(&dev->dev, priv);
 347         if (rv) {
 348                 kfree(priv);
 349                 return rv;
 350         }
 351
 352         rv = setup_ring(dev, priv);
 353         if (rv) {
 354                 ring_free(priv);
 355                 return rv;
 356         }
 357
 358         tpm_get_timeouts(priv->chip);
 359
 360         return tpm_chip_register(priv->chip);
 361 }
 362
 363 static void tpmfront_remove(struct xenbus_device *dev)
 364 {
 365         struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
 366         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 367         tpm_chip_unregister(chip);
 368         ring_free(priv);
 369         dev_set_drvdata(&chip->dev, NULL);
 370 }
 371
 372 static int tpmfront_resume(struct xenbus_device *dev)
 373 {
 374         /* A suspend/resume/migrate will interrupt a vTPM anyway */
 375         tpmfront_remove(dev);
 376         return tpmfront_probe(dev, NULL);
 377 }
 378
 379 static void backend_changed(struct xenbus_device *dev,
 380                 enum xenbus_state backend_state)
 381 {
 382         switch (backend_state) {
 383         case XenbusStateInitialised:
 384         case XenbusStateConnected:
 385                 if (dev->state == XenbusStateConnected)
 386                         break;
 387
 388                 if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
 389                                           0)) {
 390                         xenbus_dev_fatal(dev, -EINVAL,
 391                                         "vTPM protocol 2 required");
 392                         return;
 393                 }
 394                 xenbus_switch_state(dev, XenbusStateConnected);
 395                 break;
 396
 397         case XenbusStateClosing:
 398         case XenbusStateClosed:
 399                 device_unregister(&dev->dev);
 400                 xenbus_frontend_closed(dev);
 401                 break;
 402         default:
 403                 break;
 404         }
 405 }
 406
 407 static const struct xenbus_device_id tpmfront_ids[] = {
 408         { "vtpm" },
 409         { "" }
 410 };
 411 MODULE_ALIAS("xen:vtpm");
 412
 413 static struct xenbus_driver tpmfront_driver = {
 414         .ids = tpmfront_ids,
 415         .probe = tpmfront_probe,
 416         .remove = tpmfront_remove,
 417         .resume = tpmfront_resume,
 418         .otherend_changed = backend_changed,
 419 };
 420
 421 static int __init xen_tpmfront_init(void)
 422 {
 423         if (!xen_domain())
 424                 return -ENODEV;
 425
 426         if (!xen_has_pv_devices())
 427                 return -ENODEV;
 428
 429         return xenbus_register_frontend(&tpmfront_driver);
 430 }
 431 module_init(xen_tpmfront_init);
 432
 433 static void __exit xen_tpmfront_exit(void)
 434 {
 435         xenbus_unregister_driver(&tpmfront_driver);
 436 }
 437 module_exit(xen_tpmfront_exit);
 438
 439 MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
 440 MODULE_DESCRIPTION("Xen vTPM Driver");
 441 MODULE_LICENSE("GPL");