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