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