drivers/xen/xenbus/xenbus_client.c

   1 /******************************************************************************
   2  * Client-facing interface for the Xenbus driver.  In other words, the
   3  * interface between the Xenbus and the device-specific code, be it the
   4  * frontend or the backend of that driver.
   5  *
   6  * Copyright (C) 2005 XenSource Ltd
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  */
  32
  33 #include <linux/slab.h>
  34 #include <linux/types.h>
  35 #include <linux/vmalloc.h>
  36 #include <asm/xen/hypervisor.h>
  37 #include <xen/interface/xen.h>
  38 #include <xen/interface/event_channel.h>
  39 #include <xen/events.h>
  40 #include <xen/grant_table.h>
  41 #include <xen/xenbus.h>
  42
  43 const char *xenbus_strstate(enum xenbus_state state)
  44 {
  45         static const char *const name[] = {
  46                 [ XenbusStateUnknown      ] = "Unknown",
  47                 [ XenbusStateInitialising ] = "Initialising",
  48                 [ XenbusStateInitWait     ] = "InitWait",
  49                 [ XenbusStateInitialised  ] = "Initialised",
  50                 [ XenbusStateConnected    ] = "Connected",
  51                 [ XenbusStateClosing      ] = "Closing",
  52                 [ XenbusStateClosed       ] = "Closed",
  53                 [XenbusStateReconfiguring] = "Reconfiguring",
  54                 [XenbusStateReconfigured] = "Reconfigured",
  55         };
  56         return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
  57 }
  58 EXPORT_SYMBOL_GPL(xenbus_strstate);
  59
  60 /**
  61  * xenbus_watch_path - register a watch
  62  * @dev: xenbus device
  63  * @path: path to watch
  64  * @watch: watch to register
  65  * @callback: callback to register
  66  *
  67  * Register a @watch on the given path, using the given xenbus_watch structure
  68  * for storage, and the given @callback function as the callback.  Return 0 on
  69  * success, or -errno on error.  On success, the given @path will be saved as
  70  * @watch->node, and remains the caller's to free.  On error, @watch->node will
  71  * be NULL, the device will switch to %XenbusStateClosing, and the error will
  72  * be saved in the store.
  73  */
  74 int xenbus_watch_path(struct xenbus_device *dev, const char *path,
  75                       struct xenbus_watch *watch,
  76                       void (*callback)(struct xenbus_watch *,
  77                                        const char **, unsigned int))
  78 {
  79         int err;
  80
  81         watch->node = path;
  82         watch->callback = callback;
  83
  84         err = register_xenbus_watch(watch);
  85
  86         if (err) {
  87                 watch->node = NULL;
  88                 watch->callback = NULL;
  89                 xenbus_dev_fatal(dev, err, "adding watch on %s", path);
  90         }
  91
  92         return err;
  93 }
  94 EXPORT_SYMBOL_GPL(xenbus_watch_path);
  95
  96
  97 /**
  98  * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path
  99  * @dev: xenbus device
 100  * @watch: watch to register
 101  * @callback: callback to register
 102  * @pathfmt: format of path to watch
 103  *
 104  * Register a watch on the given @path, using the given xenbus_watch
 105  * structure for storage, and the given @callback function as the callback.
 106  * Return 0 on success, or -errno on error.  On success, the watched path
 107  * (@path/@path2) will be saved as @watch->node, and becomes the caller's to
 108  * kfree().  On error, watch->node will be NULL, so the caller has nothing to
 109  * free, the device will switch to %XenbusStateClosing, and the error will be
 110  * saved in the store.
 111  */
 112 int xenbus_watch_pathfmt(struct xenbus_device *dev,
 113                          struct xenbus_watch *watch,
 114                          void (*callback)(struct xenbus_watch *,
 115                                         const char **, unsigned int),
 116                          const char *pathfmt, ...)
 117 {
 118         int err;
 119         va_list ap;
 120         char *path;
 121
 122         va_start(ap, pathfmt);
 123         path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap);
 124         va_end(ap);
 125
 126         if (!path) {
 127                 xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch");
 128                 return -ENOMEM;
 129         }
 130         err = xenbus_watch_path(dev, path, watch, callback);
 131
 132         if (err)
 133                 kfree(path);
 134         return err;
 135 }
 136 EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt);
 137
 138 static void xenbus_switch_fatal(struct xenbus_device *, int, int,
 139                                 const char *, ...);
 140
 141 static int
 142 __xenbus_switch_state(struct xenbus_device *dev,
 143                       enum xenbus_state state, int depth)
 144 {
 145         /* We check whether the state is currently set to the given value, and
 146            if not, then the state is set.  We don't want to unconditionally
 147            write the given state, because we don't want to fire watches
 148            unnecessarily.  Furthermore, if the node has gone, we don't write
 149            to it, as the device will be tearing down, and we don't want to
 150            resurrect that directory.
 151
 152            Note that, because of this cached value of our state, this
 153            function will not take a caller's Xenstore transaction
 154            (something it was trying to in the past) because dev->state
 155            would not get reset if the transaction was aborted.
 156          */
 157
 158         struct xenbus_transaction xbt;
 159         int current_state;
 160         int err, abort;
 161
 162         if (state == dev->state)
 163                 return 0;
 164
 165 again:
 166         abort = 1;
 167
 168         err = xenbus_transaction_start(&xbt);
 169         if (err) {
 170                 xenbus_switch_fatal(dev, depth, err, "starting transaction");
 171                 return 0;
 172         }
 173
 174         err = xenbus_scanf(xbt, dev->nodename, "state", "%d", &current_state);
 175         if (err != 1)
 176                 goto abort;
 177
 178         err = xenbus_printf(xbt, dev->nodename, "state", "%d", state);
 179         if (err) {
 180                 xenbus_switch_fatal(dev, depth, err, "writing new state");
 181                 goto abort;
 182         }
 183
 184         abort = 0;
 185 abort:
 186         err = xenbus_transaction_end(xbt, abort);
 187         if (err) {
 188                 if (err == -EAGAIN && !abort)
 189                         goto again;
 190                 xenbus_switch_fatal(dev, depth, err, "ending transaction");
 191         } else
 192                 dev->state = state;
 193
 194         return 0;
 195 }
 196
 197 /**
 198  * xenbus_switch_state
 199  * @dev: xenbus device
 200  * @state: new state
 201  *
 202  * Advertise in the store a change of the given driver to the given new_state.
 203  * Return 0 on success, or -errno on error.  On error, the device will switch
 204  * to XenbusStateClosing, and the error will be saved in the store.
 205  */
 206 int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
 207 {
 208         return __xenbus_switch_state(dev, state, 0);
 209 }
 210
 211 EXPORT_SYMBOL_GPL(xenbus_switch_state);
 212
 213 int xenbus_frontend_closed(struct xenbus_device *dev)
 214 {
 215         xenbus_switch_state(dev, XenbusStateClosed);
 216         complete(&dev->down);
 217         return 0;
 218 }
 219 EXPORT_SYMBOL_GPL(xenbus_frontend_closed);
 220
 221 /**
 222  * Return the path to the error node for the given device, or NULL on failure.
 223  * If the value returned is non-NULL, then it is the caller's to kfree.
 224  */
 225 static char *error_path(struct xenbus_device *dev)
 226 {
 227         return kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
 228 }
 229
 230
 231 static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
 232                                 const char *fmt, va_list ap)
 233 {
 234         int ret;
 235         unsigned int len;
 236         char *printf_buffer = NULL;
 237         char *path_buffer = NULL;
 238
 239 #define PRINTF_BUFFER_SIZE 4096
 240         printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
 241         if (printf_buffer == NULL)
 242                 goto fail;
 243
 244         len = sprintf(printf_buffer, "%i ", -err);
 245         ret = vsnprintf(printf_buffer+len, PRINTF_BUFFER_SIZE-len, fmt, ap);
 246
 247         BUG_ON(len + ret > PRINTF_BUFFER_SIZE-1);
 248
 249         dev_err(&dev->dev, "%s\n", printf_buffer);
 250
 251         path_buffer = error_path(dev);
 252
 253         if (path_buffer == NULL) {
 254                 dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
 255                        dev->nodename, printf_buffer);
 256                 goto fail;
 257         }
 258
 259         if (xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer) != 0) {
 260                 dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
 261                        dev->nodename, printf_buffer);
 262                 goto fail;
 263         }
 264
 265 fail:
 266         kfree(printf_buffer);
 267         kfree(path_buffer);
 268 }
 269
 270
 271 /**
 272  * xenbus_dev_error
 273  * @dev: xenbus device
 274  * @err: error to report
 275  * @fmt: error message format
 276  *
 277  * Report the given negative errno into the store, along with the given
 278  * formatted message.
 279  */
 280 void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
 281 {
 282         va_list ap;
 283
 284         va_start(ap, fmt);
 285         xenbus_va_dev_error(dev, err, fmt, ap);
 286         va_end(ap);
 287 }
 288 EXPORT_SYMBOL_GPL(xenbus_dev_error);
 289
 290 /**
 291  * xenbus_dev_fatal
 292  * @dev: xenbus device
 293  * @err: error to report
 294  * @fmt: error message format
 295  *
 296  * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by
 297  * xenbus_switch_state(dev, XenbusStateClosing) to schedule an orderly
 298  * closedown of this driver and its peer.
 299  */
 300
 301 void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
 302 {
 303         va_list ap;
 304
 305         va_start(ap, fmt);
 306         xenbus_va_dev_error(dev, err, fmt, ap);
 307         va_end(ap);
 308
 309         xenbus_switch_state(dev, XenbusStateClosing);
 310 }
 311 EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
 312
 313 /**
 314  * Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
 315  * avoiding recursion within xenbus_switch_state.
 316  */
 317 static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
 318                                 const char *fmt, ...)
 319 {
 320         va_list ap;
 321
 322         va_start(ap, fmt);
 323         xenbus_va_dev_error(dev, err, fmt, ap);
 324         va_end(ap);
 325
 326         if (!depth)
 327                 __xenbus_switch_state(dev, XenbusStateClosing, 1);
 328 }
 329
 330 /**
 331  * xenbus_grant_ring
 332  * @dev: xenbus device
 333  * @ring_mfn: mfn of ring to grant
 334
 335  * Grant access to the given @ring_mfn to the peer of the given device.  Return
 336  * 0 on success, or -errno on error.  On error, the device will switch to
 337  * XenbusStateClosing, and the error will be saved in the store.
 338  */
 339 int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn)
 340 {
 341         int err = gnttab_grant_foreign_access(dev->otherend_id, ring_mfn, 0);
 342         if (err < 0)
 343                 xenbus_dev_fatal(dev, err, "granting access to ring page");
 344         return err;
 345 }
 346 EXPORT_SYMBOL_GPL(xenbus_grant_ring);
 347
 348
 349 /**
 350  * Allocate an event channel for the given xenbus_device, assigning the newly
 351  * created local port to *port.  Return 0 on success, or -errno on error.  On
 352  * error, the device will switch to XenbusStateClosing, and the error will be
 353  * saved in the store.
 354  */
 355 int xenbus_alloc_evtchn(struct xenbus_device *dev, int *port)
 356 {
 357         struct evtchn_alloc_unbound alloc_unbound;
 358         int err;
 359
 360         alloc_unbound.dom = DOMID_SELF;
 361         alloc_unbound.remote_dom = dev->otherend_id;
 362
 363         err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
 364                                           &alloc_unbound);
 365         if (err)
 366                 xenbus_dev_fatal(dev, err, "allocating event channel");
 367         else
 368                 *port = alloc_unbound.port;
 369
 370         return err;
 371 }
 372 EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
 373
 374
 375 /**
 376  * Bind to an existing interdomain event channel in another domain. Returns 0
 377  * on success and stores the local port in *port. On error, returns -errno,
 378  * switches the device to XenbusStateClosing, and saves the error in XenStore.
 379  */
 380 int xenbus_bind_evtchn(struct xenbus_device *dev, int remote_port, int *port)
 381 {
 382         struct evtchn_bind_interdomain bind_interdomain;
 383         int err;
 384
 385         bind_interdomain.remote_dom = dev->otherend_id;
 386         bind_interdomain.remote_port = remote_port;
 387
 388         err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
 389                                           &bind_interdomain);
 390         if (err)
 391                 xenbus_dev_fatal(dev, err,
 392                                  "binding to event channel %d from domain %d",
 393                                  remote_port, dev->otherend_id);
 394         else
 395                 *port = bind_interdomain.local_port;
 396
 397         return err;
 398 }
 399 EXPORT_SYMBOL_GPL(xenbus_bind_evtchn);
 400
 401
 402 /**
 403  * Free an existing event channel. Returns 0 on success or -errno on error.
 404  */
 405 int xenbus_free_evtchn(struct xenbus_device *dev, int port)
 406 {
 407         struct evtchn_close close;
 408         int err;
 409
 410         close.port = port;
 411
 412         err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
 413         if (err)
 414                 xenbus_dev_error(dev, err, "freeing event channel %d", port);
 415
 416         return err;
 417 }
 418 EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
 419
 420
 421 /**
 422  * xenbus_map_ring_valloc
 423  * @dev: xenbus device
 424  * @gnt_ref: grant reference
 425  * @vaddr: pointer to address to be filled out by mapping
 426  *
 427  * Based on Rusty Russell's skeleton driver's map_page.
 428  * Map a page of memory into this domain from another domain's grant table.
 429  * xenbus_map_ring_valloc allocates a page of virtual address space, maps the
 430  * page to that address, and sets *vaddr to that address.
 431  * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
 432  * or -ENOMEM on error. If an error is returned, device will switch to
 433  * XenbusStateClosing and the error message will be saved in XenStore.
 434  */
 435 int xenbus_map_ring_valloc(struct xenbus_device *dev, int gnt_ref, void **vaddr)
 436 {
 437         struct gnttab_map_grant_ref op = {
 438                 .flags = GNTMAP_host_map,
 439                 .ref   = gnt_ref,
 440                 .dom   = dev->otherend_id,
 441         };
 442         struct vm_struct *area;
 443
 444         *vaddr = NULL;
 445
 446         area = xen_alloc_vm_area(PAGE_SIZE);
 447         if (!area)
 448                 return -ENOMEM;
 449
 450         op.host_addr = (unsigned long)area->addr;
 451
 452         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 453                 BUG();
 454
 455         if (op.status != GNTST_okay) {
 456                 xen_free_vm_area(area);
 457                 xenbus_dev_fatal(dev, op.status,
 458                                  "mapping in shared page %d from domain %d",
 459                                  gnt_ref, dev->otherend_id);
 460                 return op.status;
 461         }
 462
 463         /* Stuff the handle in an unused field */
 464         area->phys_addr = (unsigned long)op.handle;
 465
 466         *vaddr = area->addr;
 467         return 0;
 468 }
 469 EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
 470
 471
 472 /**
 473  * xenbus_map_ring
 474  * @dev: xenbus device
 475  * @gnt_ref: grant reference
 476  * @handle: pointer to grant handle to be filled
 477  * @vaddr: address to be mapped to
 478  *
 479  * Map a page of memory into this domain from another domain's grant table.
 480  * xenbus_map_ring does not allocate the virtual address space (you must do
 481  * this yourself!). It only maps in the page to the specified address.
 482  * Returns 0 on success, and GNTST_* (see xen/include/interface/grant_table.h)
 483  * or -ENOMEM on error. If an error is returned, device will switch to
 484  * XenbusStateClosing and the error message will be saved in XenStore.
 485  */
 486 int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
 487                     grant_handle_t *handle, void *vaddr)
 488 {
 489         struct gnttab_map_grant_ref op = {
 490                 .host_addr = (unsigned long)vaddr,
 491                 .flags     = GNTMAP_host_map,
 492                 .ref       = gnt_ref,
 493                 .dom       = dev->otherend_id,
 494         };
 495
 496         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1))
 497                 BUG();
 498
 499         if (op.status != GNTST_okay) {
 500                 xenbus_dev_fatal(dev, op.status,
 501                                  "mapping in shared page %d from domain %d",
 502                                  gnt_ref, dev->otherend_id);
 503         } else
 504                 *handle = op.handle;
 505
 506         return op.status;
 507 }
 508 EXPORT_SYMBOL_GPL(xenbus_map_ring);
 509
 510
 511 /**
 512  * xenbus_unmap_ring_vfree
 513  * @dev: xenbus device
 514  * @vaddr: addr to unmap
 515  *
 516  * Based on Rusty Russell's skeleton driver's unmap_page.
 517  * Unmap a page of memory in this domain that was imported from another domain.
 518  * Use xenbus_unmap_ring_vfree if you mapped in your memory with
 519  * xenbus_map_ring_valloc (it will free the virtual address space).
 520  * Returns 0 on success and returns GNTST_* on error
 521  * (see xen/include/interface/grant_table.h).
 522  */
 523 int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
 524 {
 525         struct vm_struct *area;
 526         struct gnttab_unmap_grant_ref op = {
 527                 .host_addr = (unsigned long)vaddr,
 528         };
 529
 530         /* It'd be nice if linux/vmalloc.h provided a find_vm_area(void *addr)
 531          * method so that we don't have to muck with vmalloc internals here.
 532          * We could force the user to hang on to their struct vm_struct from
 533          * xenbus_map_ring_valloc, but these 6 lines considerably simplify
 534          * this API.
 535          */
 536         read_lock(&vmlist_lock);
 537         for (area = vmlist; area != NULL; area = area->next) {
 538                 if (area->addr == vaddr)
 539                         break;
 540         }
 541         read_unlock(&vmlist_lock);
 542
 543         if (!area) {
 544                 xenbus_dev_error(dev, -ENOENT,
 545                                  "can't find mapped virtual address %p", vaddr);
 546                 return GNTST_bad_virt_addr;
 547         }
 548
 549         op.handle = (grant_handle_t)area->phys_addr;
 550
 551         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 552                 BUG();
 553
 554         if (op.status == GNTST_okay)
 555                 xen_free_vm_area(area);
 556         else
 557                 xenbus_dev_error(dev, op.status,
 558                                  "unmapping page at handle %d error %d",
 559                                  (int16_t)area->phys_addr, op.status);
 560
 561         return op.status;
 562 }
 563 EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
 564
 565
 566 /**
 567  * xenbus_unmap_ring
 568  * @dev: xenbus device
 569  * @handle: grant handle
 570  * @vaddr: addr to unmap
 571  *
 572  * Unmap a page of memory in this domain that was imported from another domain.
 573  * Returns 0 on success and returns GNTST_* on error
 574  * (see xen/include/interface/grant_table.h).
 575  */
 576 int xenbus_unmap_ring(struct xenbus_device *dev,
 577                       grant_handle_t handle, void *vaddr)
 578 {
 579         struct gnttab_unmap_grant_ref op = {
 580                 .host_addr = (unsigned long)vaddr,
 581                 .handle    = handle,
 582         };
 583
 584         if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1))
 585                 BUG();
 586
 587         if (op.status != GNTST_okay)
 588                 xenbus_dev_error(dev, op.status,
 589                                  "unmapping page at handle %d error %d",
 590                                  handle, op.status);
 591
 592         return op.status;
 593 }
 594 EXPORT_SYMBOL_GPL(xenbus_unmap_ring);
 595
 596
 597 /**
 598  * xenbus_read_driver_state
 599  * @path: path for driver
 600  *
 601  * Return the state of the driver rooted at the given store path, or
 602  * XenbusStateUnknown if no state can be read.
 603  */
 604 enum xenbus_state xenbus_read_driver_state(const char *path)
 605 {
 606         enum xenbus_state result;
 607         int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
 608         if (err)
 609                 result = XenbusStateUnknown;
 610
 611         return result;
 612 }
 613 EXPORT_SYMBOL_GPL(xenbus_read_driver_state);