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