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