Commit | Line | Data |
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1107ba88 AZ |
1 | /* |
2 | * Driver giving user-space access to the kernel's xenbus connection | |
3 | * to xenstore. | |
4 | * | |
5 | * Copyright (c) 2005, Christian Limpach | |
6 | * Copyright (c) 2005, Rusty Russell, IBM Corporation | |
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 | * Changes: | |
33 | * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem | |
34 | * and /proc/xen compatibility mount point. | |
35 | * Turned xenfs into a loadable module. | |
36 | */ | |
37 | ||
38 | #include <linux/kernel.h> | |
39 | #include <linux/errno.h> | |
40 | #include <linux/uio.h> | |
41 | #include <linux/notifier.h> | |
42 | #include <linux/wait.h> | |
43 | #include <linux/fs.h> | |
44 | #include <linux/poll.h> | |
45 | #include <linux/mutex.h> | |
a99bbaf5 | 46 | #include <linux/sched.h> |
1107ba88 AZ |
47 | #include <linux/spinlock.h> |
48 | #include <linux/mount.h> | |
49 | #include <linux/pagemap.h> | |
50 | #include <linux/uaccess.h> | |
51 | #include <linux/init.h> | |
52 | #include <linux/namei.h> | |
53 | #include <linux/string.h> | |
5a0e3ad6 | 54 | #include <linux/slab.h> |
2fb3683e BB |
55 | #include <linux/miscdevice.h> |
56 | #include <linux/module.h> | |
1107ba88 | 57 | |
2fb3683e | 58 | #include "xenbus_comms.h" |
1107ba88 AZ |
59 | |
60 | #include <xen/xenbus.h> | |
b79d2ff9 | 61 | #include <xen/xen.h> |
1107ba88 AZ |
62 | #include <asm/xen/hypervisor.h> |
63 | ||
2fb3683e BB |
64 | MODULE_LICENSE("GPL"); |
65 | ||
1107ba88 AZ |
66 | /* |
67 | * An element of a list of outstanding transactions, for which we're | |
68 | * still waiting a reply. | |
69 | */ | |
70 | struct xenbus_transaction_holder { | |
71 | struct list_head list; | |
72 | struct xenbus_transaction handle; | |
73 | }; | |
74 | ||
75 | /* | |
76 | * A buffer of data on the queue. | |
77 | */ | |
78 | struct read_buffer { | |
79 | struct list_head list; | |
80 | unsigned int cons; | |
81 | unsigned int len; | |
82 | char msg[]; | |
83 | }; | |
84 | ||
85 | struct xenbus_file_priv { | |
86 | /* | |
87 | * msgbuffer_mutex is held while partial requests are built up | |
88 | * and complete requests are acted on. It therefore protects | |
89 | * the "transactions" and "watches" lists, and the partial | |
90 | * request length and buffer. | |
91 | * | |
92 | * reply_mutex protects the reply being built up to return to | |
93 | * usermode. It nests inside msgbuffer_mutex but may be held | |
94 | * alone during a watch callback. | |
95 | */ | |
96 | struct mutex msgbuffer_mutex; | |
97 | ||
98 | /* In-progress transactions */ | |
99 | struct list_head transactions; | |
100 | ||
101 | /* Active watches. */ | |
102 | struct list_head watches; | |
103 | ||
104 | /* Partial request. */ | |
105 | unsigned int len; | |
106 | union { | |
107 | struct xsd_sockmsg msg; | |
50bf7379 | 108 | char buffer[XENSTORE_PAYLOAD_MAX]; |
1107ba88 AZ |
109 | } u; |
110 | ||
111 | /* Response queue. */ | |
112 | struct mutex reply_mutex; | |
113 | struct list_head read_buffers; | |
114 | wait_queue_head_t read_waitq; | |
115 | ||
116 | }; | |
117 | ||
118 | /* Read out any raw xenbus messages queued up. */ | |
119 | static ssize_t xenbus_file_read(struct file *filp, | |
120 | char __user *ubuf, | |
121 | size_t len, loff_t *ppos) | |
122 | { | |
123 | struct xenbus_file_priv *u = filp->private_data; | |
124 | struct read_buffer *rb; | |
125 | unsigned i; | |
126 | int ret; | |
127 | ||
128 | mutex_lock(&u->reply_mutex); | |
7808121b | 129 | again: |
1107ba88 AZ |
130 | while (list_empty(&u->read_buffers)) { |
131 | mutex_unlock(&u->reply_mutex); | |
6280f190 PB |
132 | if (filp->f_flags & O_NONBLOCK) |
133 | return -EAGAIN; | |
134 | ||
1107ba88 AZ |
135 | ret = wait_event_interruptible(u->read_waitq, |
136 | !list_empty(&u->read_buffers)); | |
137 | if (ret) | |
138 | return ret; | |
139 | mutex_lock(&u->reply_mutex); | |
140 | } | |
141 | ||
142 | rb = list_entry(u->read_buffers.next, struct read_buffer, list); | |
143 | i = 0; | |
144 | while (i < len) { | |
145 | unsigned sz = min((unsigned)len - i, rb->len - rb->cons); | |
146 | ||
147 | ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz); | |
148 | ||
149 | i += sz - ret; | |
150 | rb->cons += sz - ret; | |
151 | ||
fb27cfbc | 152 | if (ret != 0) { |
1107ba88 AZ |
153 | if (i == 0) |
154 | i = -EFAULT; | |
155 | goto out; | |
156 | } | |
157 | ||
158 | /* Clear out buffer if it has been consumed */ | |
159 | if (rb->cons == rb->len) { | |
160 | list_del(&rb->list); | |
161 | kfree(rb); | |
162 | if (list_empty(&u->read_buffers)) | |
163 | break; | |
164 | rb = list_entry(u->read_buffers.next, | |
165 | struct read_buffer, list); | |
166 | } | |
167 | } | |
7808121b DDG |
168 | if (i == 0) |
169 | goto again; | |
1107ba88 AZ |
170 | |
171 | out: | |
172 | mutex_unlock(&u->reply_mutex); | |
173 | return i; | |
174 | } | |
175 | ||
176 | /* | |
177 | * Add a buffer to the queue. Caller must hold the appropriate lock | |
178 | * if the queue is not local. (Commonly the caller will build up | |
179 | * multiple queued buffers on a temporary local list, and then add it | |
180 | * to the appropriate list under lock once all the buffers have een | |
181 | * successfully allocated.) | |
182 | */ | |
183 | static int queue_reply(struct list_head *queue, const void *data, size_t len) | |
184 | { | |
185 | struct read_buffer *rb; | |
186 | ||
187 | if (len == 0) | |
188 | return 0; | |
189 | ||
190 | rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL); | |
191 | if (rb == NULL) | |
192 | return -ENOMEM; | |
193 | ||
194 | rb->cons = 0; | |
195 | rb->len = len; | |
196 | ||
197 | memcpy(rb->msg, data, len); | |
198 | ||
199 | list_add_tail(&rb->list, queue); | |
200 | return 0; | |
201 | } | |
202 | ||
203 | /* | |
204 | * Free all the read_buffer s on a list. | |
205 | * Caller must have sole reference to list. | |
206 | */ | |
207 | static void queue_cleanup(struct list_head *list) | |
208 | { | |
209 | struct read_buffer *rb; | |
210 | ||
211 | while (!list_empty(list)) { | |
212 | rb = list_entry(list->next, struct read_buffer, list); | |
213 | list_del(list->next); | |
214 | kfree(rb); | |
215 | } | |
216 | } | |
217 | ||
218 | struct watch_adapter { | |
219 | struct list_head list; | |
220 | struct xenbus_watch watch; | |
221 | struct xenbus_file_priv *dev_data; | |
222 | char *token; | |
223 | }; | |
224 | ||
225 | static void free_watch_adapter(struct watch_adapter *watch) | |
226 | { | |
227 | kfree(watch->watch.node); | |
228 | kfree(watch->token); | |
229 | kfree(watch); | |
230 | } | |
231 | ||
232 | static struct watch_adapter *alloc_watch_adapter(const char *path, | |
233 | const char *token) | |
234 | { | |
235 | struct watch_adapter *watch; | |
236 | ||
237 | watch = kzalloc(sizeof(*watch), GFP_KERNEL); | |
238 | if (watch == NULL) | |
239 | goto out_fail; | |
240 | ||
241 | watch->watch.node = kstrdup(path, GFP_KERNEL); | |
242 | if (watch->watch.node == NULL) | |
243 | goto out_free; | |
244 | ||
245 | watch->token = kstrdup(token, GFP_KERNEL); | |
246 | if (watch->token == NULL) | |
247 | goto out_free; | |
248 | ||
249 | return watch; | |
250 | ||
251 | out_free: | |
252 | free_watch_adapter(watch); | |
253 | ||
254 | out_fail: | |
255 | return NULL; | |
256 | } | |
257 | ||
258 | static void watch_fired(struct xenbus_watch *watch, | |
259 | const char **vec, | |
260 | unsigned int len) | |
261 | { | |
262 | struct watch_adapter *adap; | |
263 | struct xsd_sockmsg hdr; | |
264 | const char *path, *token; | |
265 | int path_len, tok_len, body_len, data_len = 0; | |
266 | int ret; | |
267 | LIST_HEAD(staging_q); | |
268 | ||
269 | adap = container_of(watch, struct watch_adapter, watch); | |
270 | ||
271 | path = vec[XS_WATCH_PATH]; | |
272 | token = adap->token; | |
273 | ||
274 | path_len = strlen(path) + 1; | |
275 | tok_len = strlen(token) + 1; | |
276 | if (len > 2) | |
277 | data_len = vec[len] - vec[2] + 1; | |
278 | body_len = path_len + tok_len + data_len; | |
279 | ||
280 | hdr.type = XS_WATCH_EVENT; | |
281 | hdr.len = body_len; | |
282 | ||
283 | mutex_lock(&adap->dev_data->reply_mutex); | |
284 | ||
285 | ret = queue_reply(&staging_q, &hdr, sizeof(hdr)); | |
286 | if (!ret) | |
287 | ret = queue_reply(&staging_q, path, path_len); | |
288 | if (!ret) | |
289 | ret = queue_reply(&staging_q, token, tok_len); | |
290 | if (!ret && len > 2) | |
291 | ret = queue_reply(&staging_q, vec[2], data_len); | |
292 | ||
293 | if (!ret) { | |
294 | /* success: pass reply list onto watcher */ | |
295 | list_splice_tail(&staging_q, &adap->dev_data->read_buffers); | |
296 | wake_up(&adap->dev_data->read_waitq); | |
297 | } else | |
298 | queue_cleanup(&staging_q); | |
299 | ||
300 | mutex_unlock(&adap->dev_data->reply_mutex); | |
301 | } | |
302 | ||
303 | static int xenbus_write_transaction(unsigned msg_type, | |
304 | struct xenbus_file_priv *u) | |
305 | { | |
e88a0faa | 306 | int rc; |
1107ba88 AZ |
307 | void *reply; |
308 | struct xenbus_transaction_holder *trans = NULL; | |
309 | LIST_HEAD(staging_q); | |
310 | ||
311 | if (msg_type == XS_TRANSACTION_START) { | |
312 | trans = kmalloc(sizeof(*trans), GFP_KERNEL); | |
313 | if (!trans) { | |
314 | rc = -ENOMEM; | |
315 | goto out; | |
316 | } | |
317 | } | |
318 | ||
319 | reply = xenbus_dev_request_and_reply(&u->u.msg); | |
320 | if (IS_ERR(reply)) { | |
321 | kfree(trans); | |
322 | rc = PTR_ERR(reply); | |
323 | goto out; | |
324 | } | |
325 | ||
326 | if (msg_type == XS_TRANSACTION_START) { | |
327 | trans->handle.id = simple_strtoul(reply, NULL, 0); | |
328 | ||
329 | list_add(&trans->list, &u->transactions); | |
330 | } else if (msg_type == XS_TRANSACTION_END) { | |
331 | list_for_each_entry(trans, &u->transactions, list) | |
332 | if (trans->handle.id == u->u.msg.tx_id) | |
333 | break; | |
334 | BUG_ON(&trans->list == &u->transactions); | |
335 | list_del(&trans->list); | |
336 | ||
337 | kfree(trans); | |
338 | } | |
339 | ||
340 | mutex_lock(&u->reply_mutex); | |
e88a0faa IC |
341 | rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg)); |
342 | if (!rc) | |
343 | rc = queue_reply(&staging_q, reply, u->u.msg.len); | |
344 | if (!rc) { | |
1107ba88 AZ |
345 | list_splice_tail(&staging_q, &u->read_buffers); |
346 | wake_up(&u->read_waitq); | |
347 | } else { | |
348 | queue_cleanup(&staging_q); | |
1107ba88 AZ |
349 | } |
350 | mutex_unlock(&u->reply_mutex); | |
351 | ||
352 | kfree(reply); | |
353 | ||
354 | out: | |
355 | return rc; | |
356 | } | |
357 | ||
358 | static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u) | |
359 | { | |
360 | struct watch_adapter *watch, *tmp_watch; | |
361 | char *path, *token; | |
362 | int err, rc; | |
363 | LIST_HEAD(staging_q); | |
364 | ||
365 | path = u->u.buffer + sizeof(u->u.msg); | |
366 | token = memchr(path, 0, u->u.msg.len); | |
367 | if (token == NULL) { | |
368 | rc = -EILSEQ; | |
369 | goto out; | |
370 | } | |
371 | token++; | |
a43a5ccd JB |
372 | if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) { |
373 | rc = -EILSEQ; | |
374 | goto out; | |
375 | } | |
1107ba88 AZ |
376 | |
377 | if (msg_type == XS_WATCH) { | |
378 | watch = alloc_watch_adapter(path, token); | |
379 | if (watch == NULL) { | |
380 | rc = -ENOMEM; | |
381 | goto out; | |
382 | } | |
383 | ||
384 | watch->watch.callback = watch_fired; | |
385 | watch->dev_data = u; | |
386 | ||
387 | err = register_xenbus_watch(&watch->watch); | |
388 | if (err) { | |
389 | free_watch_adapter(watch); | |
390 | rc = err; | |
391 | goto out; | |
392 | } | |
393 | list_add(&watch->list, &u->watches); | |
394 | } else { | |
395 | list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { | |
396 | if (!strcmp(watch->token, token) && | |
397 | !strcmp(watch->watch.node, path)) { | |
398 | unregister_xenbus_watch(&watch->watch); | |
399 | list_del(&watch->list); | |
400 | free_watch_adapter(watch); | |
401 | break; | |
402 | } | |
403 | } | |
404 | } | |
405 | ||
406 | /* Success. Synthesize a reply to say all is OK. */ | |
407 | { | |
408 | struct { | |
409 | struct xsd_sockmsg hdr; | |
410 | char body[3]; | |
411 | } __packed reply = { | |
412 | { | |
413 | .type = msg_type, | |
414 | .len = sizeof(reply.body) | |
415 | }, | |
416 | "OK" | |
417 | }; | |
418 | ||
419 | mutex_lock(&u->reply_mutex); | |
420 | rc = queue_reply(&u->read_buffers, &reply, sizeof(reply)); | |
76ce7618 | 421 | wake_up(&u->read_waitq); |
1107ba88 AZ |
422 | mutex_unlock(&u->reply_mutex); |
423 | } | |
424 | ||
425 | out: | |
426 | return rc; | |
427 | } | |
428 | ||
429 | static ssize_t xenbus_file_write(struct file *filp, | |
430 | const char __user *ubuf, | |
431 | size_t len, loff_t *ppos) | |
432 | { | |
433 | struct xenbus_file_priv *u = filp->private_data; | |
434 | uint32_t msg_type; | |
435 | int rc = len; | |
436 | int ret; | |
437 | LIST_HEAD(staging_q); | |
438 | ||
439 | /* | |
440 | * We're expecting usermode to be writing properly formed | |
441 | * xenbus messages. If they write an incomplete message we | |
442 | * buffer it up. Once it is complete, we act on it. | |
443 | */ | |
444 | ||
445 | /* | |
446 | * Make sure concurrent writers can't stomp all over each | |
447 | * other's messages and make a mess of our partial message | |
448 | * buffer. We don't make any attemppt to stop multiple | |
449 | * writers from making a mess of each other's incomplete | |
450 | * messages; we're just trying to guarantee our own internal | |
451 | * consistency and make sure that single writes are handled | |
452 | * atomically. | |
453 | */ | |
454 | mutex_lock(&u->msgbuffer_mutex); | |
455 | ||
456 | /* Get this out of the way early to avoid confusion */ | |
457 | if (len == 0) | |
458 | goto out; | |
459 | ||
460 | /* Can't write a xenbus message larger we can buffer */ | |
1bcaba51 | 461 | if (len > sizeof(u->u.buffer) - u->len) { |
1107ba88 AZ |
462 | /* On error, dump existing buffer */ |
463 | u->len = 0; | |
464 | rc = -EINVAL; | |
465 | goto out; | |
466 | } | |
467 | ||
468 | ret = copy_from_user(u->u.buffer + u->len, ubuf, len); | |
469 | ||
fb27cfbc | 470 | if (ret != 0) { |
1107ba88 AZ |
471 | rc = -EFAULT; |
472 | goto out; | |
473 | } | |
474 | ||
475 | /* Deal with a partial copy. */ | |
476 | len -= ret; | |
477 | rc = len; | |
478 | ||
479 | u->len += len; | |
480 | ||
481 | /* Return if we haven't got a full message yet */ | |
482 | if (u->len < sizeof(u->u.msg)) | |
483 | goto out; /* not even the header yet */ | |
484 | ||
485 | /* If we're expecting a message that's larger than we can | |
486 | possibly send, dump what we have and return an error. */ | |
487 | if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) { | |
488 | rc = -E2BIG; | |
489 | u->len = 0; | |
490 | goto out; | |
491 | } | |
492 | ||
493 | if (u->len < (sizeof(u->u.msg) + u->u.msg.len)) | |
494 | goto out; /* incomplete data portion */ | |
495 | ||
496 | /* | |
497 | * OK, now we have a complete message. Do something with it. | |
498 | */ | |
499 | ||
500 | msg_type = u->u.msg.type; | |
501 | ||
502 | switch (msg_type) { | |
1107ba88 AZ |
503 | case XS_WATCH: |
504 | case XS_UNWATCH: | |
505 | /* (Un)Ask for some path to be watched for changes */ | |
506 | ret = xenbus_write_watch(msg_type, u); | |
507 | break; | |
508 | ||
509 | default: | |
6d6df2e4 DO |
510 | /* Send out a transaction */ |
511 | ret = xenbus_write_transaction(msg_type, u); | |
1107ba88 AZ |
512 | break; |
513 | } | |
514 | if (ret != 0) | |
515 | rc = ret; | |
516 | ||
517 | /* Buffered message consumed */ | |
518 | u->len = 0; | |
519 | ||
520 | out: | |
521 | mutex_unlock(&u->msgbuffer_mutex); | |
522 | return rc; | |
523 | } | |
524 | ||
525 | static int xenbus_file_open(struct inode *inode, struct file *filp) | |
526 | { | |
527 | struct xenbus_file_priv *u; | |
528 | ||
529 | if (xen_store_evtchn == 0) | |
530 | return -ENOENT; | |
531 | ||
532 | nonseekable_open(inode, filp); | |
533 | ||
534 | u = kzalloc(sizeof(*u), GFP_KERNEL); | |
535 | if (u == NULL) | |
536 | return -ENOMEM; | |
537 | ||
538 | INIT_LIST_HEAD(&u->transactions); | |
539 | INIT_LIST_HEAD(&u->watches); | |
540 | INIT_LIST_HEAD(&u->read_buffers); | |
541 | init_waitqueue_head(&u->read_waitq); | |
542 | ||
543 | mutex_init(&u->reply_mutex); | |
544 | mutex_init(&u->msgbuffer_mutex); | |
545 | ||
546 | filp->private_data = u; | |
547 | ||
548 | return 0; | |
549 | } | |
550 | ||
551 | static int xenbus_file_release(struct inode *inode, struct file *filp) | |
552 | { | |
553 | struct xenbus_file_priv *u = filp->private_data; | |
554 | struct xenbus_transaction_holder *trans, *tmp; | |
555 | struct watch_adapter *watch, *tmp_watch; | |
6a5b3bef | 556 | struct read_buffer *rb, *tmp_rb; |
1107ba88 AZ |
557 | |
558 | /* | |
559 | * No need for locking here because there are no other users, | |
560 | * by definition. | |
561 | */ | |
562 | ||
563 | list_for_each_entry_safe(trans, tmp, &u->transactions, list) { | |
564 | xenbus_transaction_end(trans->handle, 1); | |
565 | list_del(&trans->list); | |
566 | kfree(trans); | |
567 | } | |
568 | ||
569 | list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { | |
570 | unregister_xenbus_watch(&watch->watch); | |
571 | list_del(&watch->list); | |
572 | free_watch_adapter(watch); | |
573 | } | |
574 | ||
6a5b3bef DDG |
575 | list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) { |
576 | list_del(&rb->list); | |
577 | kfree(rb); | |
578 | } | |
1107ba88 AZ |
579 | kfree(u); |
580 | ||
581 | return 0; | |
582 | } | |
583 | ||
584 | static unsigned int xenbus_file_poll(struct file *file, poll_table *wait) | |
585 | { | |
586 | struct xenbus_file_priv *u = file->private_data; | |
587 | ||
588 | poll_wait(file, &u->read_waitq, wait); | |
589 | if (!list_empty(&u->read_buffers)) | |
590 | return POLLIN | POLLRDNORM; | |
591 | return 0; | |
592 | } | |
593 | ||
2fb3683e | 594 | const struct file_operations xen_xenbus_fops = { |
1107ba88 AZ |
595 | .read = xenbus_file_read, |
596 | .write = xenbus_file_write, | |
597 | .open = xenbus_file_open, | |
598 | .release = xenbus_file_release, | |
599 | .poll = xenbus_file_poll, | |
6038f373 | 600 | .llseek = no_llseek, |
1107ba88 | 601 | }; |
2fb3683e BB |
602 | EXPORT_SYMBOL_GPL(xen_xenbus_fops); |
603 | ||
604 | static struct miscdevice xenbus_dev = { | |
605 | .minor = MISC_DYNAMIC_MINOR, | |
606 | .name = "xen/xenbus", | |
607 | .fops = &xen_xenbus_fops, | |
608 | }; | |
609 | ||
610 | static int __init xenbus_init(void) | |
611 | { | |
612 | int err; | |
613 | ||
614 | if (!xen_domain()) | |
615 | return -ENODEV; | |
616 | ||
617 | err = misc_register(&xenbus_dev); | |
618 | if (err) | |
fe7acdbe | 619 | printk(KERN_ERR "Could not register xenbus frontend device\n"); |
2fb3683e BB |
620 | return err; |
621 | } | |
622 | ||
623 | static void __exit xenbus_exit(void) | |
624 | { | |
625 | misc_deregister(&xenbus_dev); | |
626 | } | |
627 | ||
628 | module_init(xenbus_init); | |
629 | module_exit(xenbus_exit); |