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 unsigned int shr_data_offset(struct vtpm_shared_page *shr)
 130 {
 131         return sizeof(*shr) + sizeof(u32) * 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         unsigned int 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         unsigned int 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         grant_ref_t gref;
 257
 258         priv->shr = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
 259         if (!priv->shr) {
 260                 xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 261                 return -ENOMEM;
 262         }
 263
 264         rv = xenbus_grant_ring(dev, priv->shr, 1, &gref);
 265         if (rv < 0)
 266                 return rv;
 267
 268         priv->ring_ref = gref;
 269
 270         rv = xenbus_alloc_evtchn(dev, &priv->evtchn);
 271         if (rv)
 272                 return rv;
 273
 274         rv = bind_evtchn_to_irqhandler(priv->evtchn, tpmif_interrupt, 0,
 275                                        "tpmif", priv);
 276         if (rv <= 0) {
 277                 xenbus_dev_fatal(dev, rv, "allocating TPM irq");
 278                 return rv;
 279         }
 280         priv->irq = rv;
 281
 282  again:
 283         rv = xenbus_transaction_start(&xbt);
 284         if (rv) {
 285                 xenbus_dev_fatal(dev, rv, "starting transaction");
 286                 return rv;
 287         }
 288
 289         rv = xenbus_printf(xbt, dev->nodename,
 290                         "ring-ref", "%u", priv->ring_ref);
 291         if (rv) {
 292                 message = "writing ring-ref";
 293                 goto abort_transaction;
 294         }
 295
 296         rv = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
 297                         priv->evtchn);
 298         if (rv) {
 299                 message = "writing event-channel";
 300                 goto abort_transaction;
 301         }
 302
 303         rv = xenbus_printf(xbt, dev->nodename, "feature-protocol-v2", "1");
 304         if (rv) {
 305                 message = "writing feature-protocol-v2";
 306                 goto abort_transaction;
 307         }
 308
 309         rv = xenbus_transaction_end(xbt, 0);
 310         if (rv == -EAGAIN)
 311                 goto again;
 312         if (rv) {
 313                 xenbus_dev_fatal(dev, rv, "completing transaction");
 314                 return rv;
 315         }
 316
 317         xenbus_switch_state(dev, XenbusStateInitialised);
 318
 319         return 0;
 320
 321  abort_transaction:
 322         xenbus_transaction_end(xbt, 1);
 323         if (message)
 324                 xenbus_dev_error(dev, rv, "%s", message);
 325
 326         return rv;
 327 }
 328
 329 static void ring_free(struct tpm_private *priv)
 330 {
 331         if (!priv)
 332                 return;
 333
 334         if (priv->ring_ref)
 335                 gnttab_end_foreign_access(priv->ring_ref, 0,
 336                                 (unsigned long)priv->shr);
 337         else
 338                 free_page((unsigned long)priv->shr);
 339
 340         if (priv->irq)
 341                 unbind_from_irqhandler(priv->irq, priv);
 342
 343         kfree(priv);
 344 }
 345
 346 static int tpmfront_probe(struct xenbus_device *dev,
 347                 const struct xenbus_device_id *id)
 348 {
 349         struct tpm_private *priv;
 350         int rv;
 351
 352         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 353         if (!priv) {
 354                 xenbus_dev_fatal(dev, -ENOMEM, "allocating priv structure");
 355                 return -ENOMEM;
 356         }
 357
 358         rv = setup_chip(&dev->dev, priv);
 359         if (rv) {
 360                 kfree(priv);
 361                 return rv;
 362         }
 363
 364         rv = setup_ring(dev, priv);
 365         if (rv) {
 366                 ring_free(priv);
 367                 return rv;
 368         }
 369
 370         tpm_get_timeouts(priv->chip);
 371
 372         return tpm_chip_register(priv->chip);
 373 }
 374
 375 static int tpmfront_remove(struct xenbus_device *dev)
 376 {
 377         struct tpm_chip *chip = dev_get_drvdata(&dev->dev);
 378         struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 379         tpm_chip_unregister(chip);
 380         ring_free(priv);
 381         dev_set_drvdata(&chip->dev, NULL);
 382         return 0;
 383 }
 384
 385 static int tpmfront_resume(struct xenbus_device *dev)
 386 {
 387         /* A suspend/resume/migrate will interrupt a vTPM anyway */
 388         tpmfront_remove(dev);
 389         return tpmfront_probe(dev, NULL);
 390 }
 391
 392 static void backend_changed(struct xenbus_device *dev,
 393                 enum xenbus_state backend_state)
 394 {
 395         switch (backend_state) {
 396         case XenbusStateInitialised:
 397         case XenbusStateConnected:
 398                 if (dev->state == XenbusStateConnected)
 399                         break;
 400
 401                 if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
 402                                           0)) {
 403                         xenbus_dev_fatal(dev, -EINVAL,
 404                                         "vTPM protocol 2 required");
 405                         return;
 406                 }
 407                 xenbus_switch_state(dev, XenbusStateConnected);
 408                 break;
 409
 410         case XenbusStateClosing:
 411         case XenbusStateClosed:
 412                 device_unregister(&dev->dev);
 413                 xenbus_frontend_closed(dev);
 414                 break;
 415         default:
 416                 break;
 417         }
 418 }
 419
 420 static const struct xenbus_device_id tpmfront_ids[] = {
 421         { "vtpm" },
 422         { "" }
 423 };
 424 MODULE_ALIAS("xen:vtpm");
 425
 426 static struct xenbus_driver tpmfront_driver = {
 427         .ids = tpmfront_ids,
 428         .probe = tpmfront_probe,
 429         .remove = tpmfront_remove,
 430         .resume = tpmfront_resume,
 431         .otherend_changed = backend_changed,
 432 };
 433
 434 static int __init xen_tpmfront_init(void)
 435 {
 436         if (!xen_domain())
 437                 return -ENODEV;
 438
 439         if (!xen_has_pv_devices())
 440                 return -ENODEV;
 441
 442         return xenbus_register_frontend(&tpmfront_driver);
 443 }
 444 module_init(xen_tpmfront_init);
 445
 446 static void __exit xen_tpmfront_exit(void)
 447 {
 448         xenbus_unregister_driver(&tpmfront_driver);
 449 }
 450 module_exit(xen_tpmfront_exit);
 451
 452 MODULE_AUTHOR("Daniel De Graaf <dgdegra@tycho.nsa.gov>");
 453 MODULE_DESCRIPTION("Xen vTPM Driver");
 454 MODULE_LICENSE("GPL");