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