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