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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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
39
40#include <linux/kernel.h>
41#include <linux/errno.h>
42#include <linux/uio.h>
43#include <linux/notifier.h>
44#include <linux/wait.h>
45#include <linux/fs.h>
46#include <linux/poll.h>
47#include <linux/mutex.h>
48#include <linux/sched.h>
49#include <linux/spinlock.h>
50#include <linux/mount.h>
51#include <linux/pagemap.h>
52#include <linux/uaccess.h>
53#include <linux/init.h>
54#include <linux/namei.h>
55#include <linux/string.h>
56#include <linux/slab.h>
57#include <linux/miscdevice.h>
58#include <linux/workqueue.h>
59
60#include <xen/xenbus.h>
61#include <xen/xen.h>
62#include <asm/xen/hypervisor.h>
63
64#include "xenbus.h"
65
66unsigned int xb_dev_generation_id;
67
68/*
69 * An element of a list of outstanding transactions, for which we're
70 * still waiting a reply.
71 */
72struct xenbus_transaction_holder {
73 struct list_head list;
74 struct xenbus_transaction handle;
75 unsigned int generation_id;
76};
77
78/*
79 * A buffer of data on the queue.
80 */
81struct read_buffer {
82 struct list_head list;
83 unsigned int cons;
84 unsigned int len;
85 char msg[] __counted_by(len);
86};
87
88struct xenbus_file_priv {
89 /*
90 * msgbuffer_mutex is held while partial requests are built up
91 * and complete requests are acted on. It therefore protects
92 * the "transactions" and "watches" lists, and the partial
93 * request length and buffer.
94 *
95 * reply_mutex protects the reply being built up to return to
96 * usermode. It nests inside msgbuffer_mutex but may be held
97 * alone during a watch callback.
98 */
99 struct mutex msgbuffer_mutex;
100
101 /* In-progress transactions */
102 struct list_head transactions;
103
104 /* Active watches. */
105 struct list_head watches;
106
107 /* Partial request. */
108 unsigned int len;
109 union {
110 struct xsd_sockmsg msg;
111 char buffer[XENSTORE_PAYLOAD_MAX];
112 } u;
113
114 /* Response queue. */
115 struct mutex reply_mutex;
116 struct list_head read_buffers;
117 wait_queue_head_t read_waitq;
118
119 struct kref kref;
120
121 struct work_struct wq;
122};
123
124/* Read out any raw xenbus messages queued up. */
125static ssize_t xenbus_file_read(struct file *filp,
126 char __user *ubuf,
127 size_t len, loff_t *ppos)
128{
129 struct xenbus_file_priv *u = filp->private_data;
130 struct read_buffer *rb;
131 ssize_t i;
132 int ret;
133
134 mutex_lock(&u->reply_mutex);
135again:
136 while (list_empty(&u->read_buffers)) {
137 mutex_unlock(&u->reply_mutex);
138 if (filp->f_flags & O_NONBLOCK)
139 return -EAGAIN;
140
141 ret = wait_event_interruptible(u->read_waitq,
142 !list_empty(&u->read_buffers));
143 if (ret)
144 return ret;
145 mutex_lock(&u->reply_mutex);
146 }
147
148 rb = list_entry(u->read_buffers.next, struct read_buffer, list);
149 i = 0;
150 while (i < len) {
151 size_t sz = min_t(size_t, len - i, rb->len - rb->cons);
152
153 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
154
155 i += sz - ret;
156 rb->cons += sz - ret;
157
158 if (ret != 0) {
159 if (i == 0)
160 i = -EFAULT;
161 goto out;
162 }
163
164 /* Clear out buffer if it has been consumed */
165 if (rb->cons == rb->len) {
166 list_del(&rb->list);
167 kfree(rb);
168 if (list_empty(&u->read_buffers))
169 break;
170 rb = list_entry(u->read_buffers.next,
171 struct read_buffer, list);
172 }
173 }
174 if (i == 0)
175 goto again;
176
177out:
178 mutex_unlock(&u->reply_mutex);
179 return i;
180}
181
182/*
183 * Add a buffer to the queue. Caller must hold the appropriate lock
184 * if the queue is not local. (Commonly the caller will build up
185 * multiple queued buffers on a temporary local list, and then add it
186 * to the appropriate list under lock once all the buffers have een
187 * successfully allocated.)
188 */
189static int queue_reply(struct list_head *queue, const void *data, size_t len)
190{
191 struct read_buffer *rb;
192
193 if (len == 0)
194 return 0;
195 if (len > XENSTORE_PAYLOAD_MAX)
196 return -EINVAL;
197
198 rb = kmalloc(struct_size(rb, msg, len), GFP_KERNEL);
199 if (rb == NULL)
200 return -ENOMEM;
201
202 rb->cons = 0;
203 rb->len = len;
204
205 memcpy(rb->msg, data, len);
206
207 list_add_tail(&rb->list, queue);
208 return 0;
209}
210
211/*
212 * Free all the read_buffer s on a list.
213 * Caller must have sole reference to list.
214 */
215static void queue_cleanup(struct list_head *list)
216{
217 struct read_buffer *rb;
218
219 while (!list_empty(list)) {
220 rb = list_entry(list->next, struct read_buffer, list);
221 list_del(list->next);
222 kfree(rb);
223 }
224}
225
226struct watch_adapter {
227 struct list_head list;
228 struct xenbus_watch watch;
229 struct xenbus_file_priv *dev_data;
230 char *token;
231};
232
233static void free_watch_adapter(struct watch_adapter *watch)
234{
235 kfree(watch->watch.node);
236 kfree(watch->token);
237 kfree(watch);
238}
239
240static struct watch_adapter *alloc_watch_adapter(const char *path,
241 const char *token)
242{
243 struct watch_adapter *watch;
244
245 watch = kzalloc(sizeof(*watch), GFP_KERNEL);
246 if (watch == NULL)
247 goto out_fail;
248
249 watch->watch.node = kstrdup(path, GFP_KERNEL);
250 if (watch->watch.node == NULL)
251 goto out_free;
252
253 watch->token = kstrdup(token, GFP_KERNEL);
254 if (watch->token == NULL)
255 goto out_free;
256
257 return watch;
258
259out_free:
260 free_watch_adapter(watch);
261
262out_fail:
263 return NULL;
264}
265
266static void watch_fired(struct xenbus_watch *watch,
267 const char *path,
268 const char *token)
269{
270 struct watch_adapter *adap;
271 struct xsd_sockmsg hdr;
272 const char *token_caller;
273 int path_len, tok_len, body_len;
274 int ret;
275 LIST_HEAD(staging_q);
276
277 adap = container_of(watch, struct watch_adapter, watch);
278
279 token_caller = adap->token;
280
281 path_len = strlen(path) + 1;
282 tok_len = strlen(token_caller) + 1;
283 body_len = path_len + tok_len;
284
285 hdr.type = XS_WATCH_EVENT;
286 hdr.len = body_len;
287
288 mutex_lock(&adap->dev_data->reply_mutex);
289
290 ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
291 if (!ret)
292 ret = queue_reply(&staging_q, path, path_len);
293 if (!ret)
294 ret = queue_reply(&staging_q, token_caller, tok_len);
295
296 if (!ret) {
297 /* success: pass reply list onto watcher */
298 list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
299 wake_up(&adap->dev_data->read_waitq);
300 } else
301 queue_cleanup(&staging_q);
302
303 mutex_unlock(&adap->dev_data->reply_mutex);
304}
305
306static void xenbus_worker(struct work_struct *wq)
307{
308 struct xenbus_file_priv *u;
309 struct xenbus_transaction_holder *trans, *tmp;
310 struct watch_adapter *watch, *tmp_watch;
311 struct read_buffer *rb, *tmp_rb;
312
313 u = container_of(wq, struct xenbus_file_priv, wq);
314
315 /*
316 * No need for locking here because there are no other users,
317 * by definition.
318 */
319
320 list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
321 xenbus_transaction_end(trans->handle, 1);
322 list_del(&trans->list);
323 kfree(trans);
324 }
325
326 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
327 unregister_xenbus_watch(&watch->watch);
328 list_del(&watch->list);
329 free_watch_adapter(watch);
330 }
331
332 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
333 list_del(&rb->list);
334 kfree(rb);
335 }
336 kfree(u);
337}
338
339static void xenbus_file_free(struct kref *kref)
340{
341 struct xenbus_file_priv *u;
342
343 /*
344 * We might be called in xenbus_thread().
345 * Use workqueue to avoid deadlock.
346 */
347 u = container_of(kref, struct xenbus_file_priv, kref);
348 schedule_work(&u->wq);
349}
350
351static struct xenbus_transaction_holder *xenbus_get_transaction(
352 struct xenbus_file_priv *u, uint32_t tx_id)
353{
354 struct xenbus_transaction_holder *trans;
355
356 list_for_each_entry(trans, &u->transactions, list)
357 if (trans->handle.id == tx_id)
358 return trans;
359
360 return NULL;
361}
362
363void xenbus_dev_queue_reply(struct xb_req_data *req)
364{
365 struct xenbus_file_priv *u = req->par;
366 struct xenbus_transaction_holder *trans = NULL;
367 int rc;
368 LIST_HEAD(staging_q);
369
370 xs_request_exit(req);
371
372 mutex_lock(&u->msgbuffer_mutex);
373
374 if (req->type == XS_TRANSACTION_START) {
375 trans = xenbus_get_transaction(u, 0);
376 if (WARN_ON(!trans))
377 goto out;
378 if (req->msg.type == XS_ERROR) {
379 list_del(&trans->list);
380 kfree(trans);
381 } else {
382 rc = kstrtou32(req->body, 10, &trans->handle.id);
383 if (WARN_ON(rc))
384 goto out;
385 }
386 } else if (req->type == XS_TRANSACTION_END) {
387 trans = xenbus_get_transaction(u, req->msg.tx_id);
388 if (WARN_ON(!trans))
389 goto out;
390 list_del(&trans->list);
391 kfree(trans);
392 }
393
394 mutex_unlock(&u->msgbuffer_mutex);
395
396 mutex_lock(&u->reply_mutex);
397 rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
398 if (!rc)
399 rc = queue_reply(&staging_q, req->body, req->msg.len);
400 if (!rc) {
401 list_splice_tail(&staging_q, &u->read_buffers);
402 wake_up(&u->read_waitq);
403 } else {
404 queue_cleanup(&staging_q);
405 }
406 mutex_unlock(&u->reply_mutex);
407
408 kfree(req->body);
409 kfree(req);
410
411 kref_put(&u->kref, xenbus_file_free);
412
413 return;
414
415 out:
416 mutex_unlock(&u->msgbuffer_mutex);
417}
418
419static int xenbus_command_reply(struct xenbus_file_priv *u,
420 unsigned int msg_type, const char *reply)
421{
422 struct {
423 struct xsd_sockmsg hdr;
424 char body[16];
425 } msg;
426 int rc;
427
428 msg.hdr = u->u.msg;
429 msg.hdr.type = msg_type;
430 msg.hdr.len = strlen(reply) + 1;
431 if (msg.hdr.len > sizeof(msg.body))
432 return -E2BIG;
433 memcpy(&msg.body, reply, msg.hdr.len);
434
435 mutex_lock(&u->reply_mutex);
436 rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
437 wake_up(&u->read_waitq);
438 mutex_unlock(&u->reply_mutex);
439
440 if (!rc)
441 kref_put(&u->kref, xenbus_file_free);
442
443 return rc;
444}
445
446static int xenbus_write_transaction(unsigned msg_type,
447 struct xenbus_file_priv *u)
448{
449 int rc;
450 struct xenbus_transaction_holder *trans = NULL;
451 struct {
452 struct xsd_sockmsg hdr;
453 char body[];
454 } *msg = (void *)u->u.buffer;
455
456 if (msg_type == XS_TRANSACTION_START) {
457 trans = kzalloc(sizeof(*trans), GFP_KERNEL);
458 if (!trans) {
459 rc = -ENOMEM;
460 goto out;
461 }
462 trans->generation_id = xb_dev_generation_id;
463 list_add(&trans->list, &u->transactions);
464 } else if (msg->hdr.tx_id != 0 &&
465 !xenbus_get_transaction(u, msg->hdr.tx_id))
466 return xenbus_command_reply(u, XS_ERROR, "ENOENT");
467 else if (msg_type == XS_TRANSACTION_END &&
468 !(msg->hdr.len == 2 &&
469 (!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
470 return xenbus_command_reply(u, XS_ERROR, "EINVAL");
471 else if (msg_type == XS_TRANSACTION_END) {
472 trans = xenbus_get_transaction(u, msg->hdr.tx_id);
473 if (trans && trans->generation_id != xb_dev_generation_id) {
474 list_del(&trans->list);
475 kfree(trans);
476 if (!strcmp(msg->body, "T"))
477 return xenbus_command_reply(u, XS_ERROR,
478 "EAGAIN");
479 else
480 return xenbus_command_reply(u,
481 XS_TRANSACTION_END,
482 "OK");
483 }
484 }
485
486 rc = xenbus_dev_request_and_reply(&msg->hdr, u);
487 if (rc && trans) {
488 list_del(&trans->list);
489 kfree(trans);
490 }
491
492out:
493 return rc;
494}
495
496static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
497{
498 struct watch_adapter *watch;
499 char *path, *token;
500 int err, rc;
501
502 path = u->u.buffer + sizeof(u->u.msg);
503 token = memchr(path, 0, u->u.msg.len);
504 if (token == NULL) {
505 rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
506 goto out;
507 }
508 token++;
509 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
510 rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
511 goto out;
512 }
513
514 if (msg_type == XS_WATCH) {
515 watch = alloc_watch_adapter(path, token);
516 if (watch == NULL) {
517 rc = -ENOMEM;
518 goto out;
519 }
520
521 watch->watch.callback = watch_fired;
522 watch->dev_data = u;
523
524 err = register_xenbus_watch(&watch->watch);
525 if (err) {
526 free_watch_adapter(watch);
527 rc = err;
528 goto out;
529 }
530 list_add(&watch->list, &u->watches);
531 } else {
532 list_for_each_entry(watch, &u->watches, list) {
533 if (!strcmp(watch->token, token) &&
534 !strcmp(watch->watch.node, path)) {
535 unregister_xenbus_watch(&watch->watch);
536 list_del(&watch->list);
537 free_watch_adapter(watch);
538 break;
539 }
540 }
541 }
542
543 /* Success. Synthesize a reply to say all is OK. */
544 rc = xenbus_command_reply(u, msg_type, "OK");
545
546out:
547 return rc;
548}
549
550static ssize_t xenbus_file_write(struct file *filp,
551 const char __user *ubuf,
552 size_t len, loff_t *ppos)
553{
554 struct xenbus_file_priv *u = filp->private_data;
555 uint32_t msg_type;
556 int rc = len;
557 int ret;
558
559 /*
560 * We're expecting usermode to be writing properly formed
561 * xenbus messages. If they write an incomplete message we
562 * buffer it up. Once it is complete, we act on it.
563 */
564
565 /*
566 * Make sure concurrent writers can't stomp all over each
567 * other's messages and make a mess of our partial message
568 * buffer. We don't make any attemppt to stop multiple
569 * writers from making a mess of each other's incomplete
570 * messages; we're just trying to guarantee our own internal
571 * consistency and make sure that single writes are handled
572 * atomically.
573 */
574 mutex_lock(&u->msgbuffer_mutex);
575
576 /* Get this out of the way early to avoid confusion */
577 if (len == 0)
578 goto out;
579
580 /* Can't write a xenbus message larger we can buffer */
581 if (len > sizeof(u->u.buffer) - u->len) {
582 /* On error, dump existing buffer */
583 u->len = 0;
584 rc = -EINVAL;
585 goto out;
586 }
587
588 ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
589
590 if (ret != 0) {
591 rc = -EFAULT;
592 goto out;
593 }
594
595 /* Deal with a partial copy. */
596 len -= ret;
597 rc = len;
598
599 u->len += len;
600
601 /* Return if we haven't got a full message yet */
602 if (u->len < sizeof(u->u.msg))
603 goto out; /* not even the header yet */
604
605 /* If we're expecting a message that's larger than we can
606 possibly send, dump what we have and return an error. */
607 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
608 rc = -E2BIG;
609 u->len = 0;
610 goto out;
611 }
612
613 if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
614 goto out; /* incomplete data portion */
615
616 /*
617 * OK, now we have a complete message. Do something with it.
618 */
619
620 kref_get(&u->kref);
621
622 msg_type = u->u.msg.type;
623
624 switch (msg_type) {
625 case XS_WATCH:
626 case XS_UNWATCH:
627 /* (Un)Ask for some path to be watched for changes */
628 ret = xenbus_write_watch(msg_type, u);
629 break;
630
631 default:
632 /* Send out a transaction */
633 ret = xenbus_write_transaction(msg_type, u);
634 break;
635 }
636 if (ret != 0) {
637 rc = ret;
638 kref_put(&u->kref, xenbus_file_free);
639 }
640
641 /* Buffered message consumed */
642 u->len = 0;
643
644 out:
645 mutex_unlock(&u->msgbuffer_mutex);
646 return rc;
647}
648
649static int xenbus_file_open(struct inode *inode, struct file *filp)
650{
651 struct xenbus_file_priv *u;
652
653 if (xen_store_evtchn == 0)
654 return -ENOENT;
655
656 stream_open(inode, filp);
657
658 u = kzalloc(sizeof(*u), GFP_KERNEL);
659 if (u == NULL)
660 return -ENOMEM;
661
662 kref_init(&u->kref);
663
664 INIT_LIST_HEAD(&u->transactions);
665 INIT_LIST_HEAD(&u->watches);
666 INIT_LIST_HEAD(&u->read_buffers);
667 init_waitqueue_head(&u->read_waitq);
668 INIT_WORK(&u->wq, xenbus_worker);
669
670 mutex_init(&u->reply_mutex);
671 mutex_init(&u->msgbuffer_mutex);
672
673 filp->private_data = u;
674
675 return 0;
676}
677
678static int xenbus_file_release(struct inode *inode, struct file *filp)
679{
680 struct xenbus_file_priv *u = filp->private_data;
681
682 kref_put(&u->kref, xenbus_file_free);
683
684 return 0;
685}
686
687static __poll_t xenbus_file_poll(struct file *file, poll_table *wait)
688{
689 struct xenbus_file_priv *u = file->private_data;
690
691 poll_wait(file, &u->read_waitq, wait);
692 if (!list_empty(&u->read_buffers))
693 return EPOLLIN | EPOLLRDNORM;
694 return 0;
695}
696
697const struct file_operations xen_xenbus_fops = {
698 .read = xenbus_file_read,
699 .write = xenbus_file_write,
700 .open = xenbus_file_open,
701 .release = xenbus_file_release,
702 .poll = xenbus_file_poll,
703 .llseek = no_llseek,
704};
705EXPORT_SYMBOL_GPL(xen_xenbus_fops);
706
707static struct miscdevice xenbus_dev = {
708 .minor = MISC_DYNAMIC_MINOR,
709 .name = "xen/xenbus",
710 .fops = &xen_xenbus_fops,
711};
712
713static int __init xenbus_init(void)
714{
715 int err;
716
717 if (!xen_domain())
718 return -ENODEV;
719
720 err = misc_register(&xenbus_dev);
721 if (err)
722 pr_err("Could not register xenbus frontend device\n");
723 return err;
724}
725device_initcall(xenbus_init);
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
39
40#include <linux/kernel.h>
41#include <linux/errno.h>
42#include <linux/uio.h>
43#include <linux/notifier.h>
44#include <linux/wait.h>
45#include <linux/fs.h>
46#include <linux/poll.h>
47#include <linux/mutex.h>
48#include <linux/sched.h>
49#include <linux/spinlock.h>
50#include <linux/mount.h>
51#include <linux/pagemap.h>
52#include <linux/uaccess.h>
53#include <linux/init.h>
54#include <linux/namei.h>
55#include <linux/string.h>
56#include <linux/slab.h>
57#include <linux/miscdevice.h>
58#include <linux/module.h>
59
60#include "xenbus_comms.h"
61
62#include <xen/xenbus.h>
63#include <xen/xen.h>
64#include <asm/xen/hypervisor.h>
65
66MODULE_LICENSE("GPL");
67
68/*
69 * An element of a list of outstanding transactions, for which we're
70 * still waiting a reply.
71 */
72struct xenbus_transaction_holder {
73 struct list_head list;
74 struct xenbus_transaction handle;
75};
76
77/*
78 * A buffer of data on the queue.
79 */
80struct read_buffer {
81 struct list_head list;
82 unsigned int cons;
83 unsigned int len;
84 char msg[];
85};
86
87struct xenbus_file_priv {
88 /*
89 * msgbuffer_mutex is held while partial requests are built up
90 * and complete requests are acted on. It therefore protects
91 * the "transactions" and "watches" lists, and the partial
92 * request length and buffer.
93 *
94 * reply_mutex protects the reply being built up to return to
95 * usermode. It nests inside msgbuffer_mutex but may be held
96 * alone during a watch callback.
97 */
98 struct mutex msgbuffer_mutex;
99
100 /* In-progress transactions */
101 struct list_head transactions;
102
103 /* Active watches. */
104 struct list_head watches;
105
106 /* Partial request. */
107 unsigned int len;
108 union {
109 struct xsd_sockmsg msg;
110 char buffer[XENSTORE_PAYLOAD_MAX];
111 } u;
112
113 /* Response queue. */
114 struct mutex reply_mutex;
115 struct list_head read_buffers;
116 wait_queue_head_t read_waitq;
117
118};
119
120/* Read out any raw xenbus messages queued up. */
121static ssize_t xenbus_file_read(struct file *filp,
122 char __user *ubuf,
123 size_t len, loff_t *ppos)
124{
125 struct xenbus_file_priv *u = filp->private_data;
126 struct read_buffer *rb;
127 unsigned i;
128 int ret;
129
130 mutex_lock(&u->reply_mutex);
131again:
132 while (list_empty(&u->read_buffers)) {
133 mutex_unlock(&u->reply_mutex);
134 if (filp->f_flags & O_NONBLOCK)
135 return -EAGAIN;
136
137 ret = wait_event_interruptible(u->read_waitq,
138 !list_empty(&u->read_buffers));
139 if (ret)
140 return ret;
141 mutex_lock(&u->reply_mutex);
142 }
143
144 rb = list_entry(u->read_buffers.next, struct read_buffer, list);
145 i = 0;
146 while (i < len) {
147 unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
148
149 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
150
151 i += sz - ret;
152 rb->cons += sz - ret;
153
154 if (ret != 0) {
155 if (i == 0)
156 i = -EFAULT;
157 goto out;
158 }
159
160 /* Clear out buffer if it has been consumed */
161 if (rb->cons == rb->len) {
162 list_del(&rb->list);
163 kfree(rb);
164 if (list_empty(&u->read_buffers))
165 break;
166 rb = list_entry(u->read_buffers.next,
167 struct read_buffer, list);
168 }
169 }
170 if (i == 0)
171 goto again;
172
173out:
174 mutex_unlock(&u->reply_mutex);
175 return i;
176}
177
178/*
179 * Add a buffer to the queue. Caller must hold the appropriate lock
180 * if the queue is not local. (Commonly the caller will build up
181 * multiple queued buffers on a temporary local list, and then add it
182 * to the appropriate list under lock once all the buffers have een
183 * successfully allocated.)
184 */
185static int queue_reply(struct list_head *queue, const void *data, size_t len)
186{
187 struct read_buffer *rb;
188
189 if (len == 0)
190 return 0;
191
192 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
193 if (rb == NULL)
194 return -ENOMEM;
195
196 rb->cons = 0;
197 rb->len = len;
198
199 memcpy(rb->msg, data, len);
200
201 list_add_tail(&rb->list, queue);
202 return 0;
203}
204
205/*
206 * Free all the read_buffer s on a list.
207 * Caller must have sole reference to list.
208 */
209static void queue_cleanup(struct list_head *list)
210{
211 struct read_buffer *rb;
212
213 while (!list_empty(list)) {
214 rb = list_entry(list->next, struct read_buffer, list);
215 list_del(list->next);
216 kfree(rb);
217 }
218}
219
220struct watch_adapter {
221 struct list_head list;
222 struct xenbus_watch watch;
223 struct xenbus_file_priv *dev_data;
224 char *token;
225};
226
227static void free_watch_adapter(struct watch_adapter *watch)
228{
229 kfree(watch->watch.node);
230 kfree(watch->token);
231 kfree(watch);
232}
233
234static struct watch_adapter *alloc_watch_adapter(const char *path,
235 const char *token)
236{
237 struct watch_adapter *watch;
238
239 watch = kzalloc(sizeof(*watch), GFP_KERNEL);
240 if (watch == NULL)
241 goto out_fail;
242
243 watch->watch.node = kstrdup(path, GFP_KERNEL);
244 if (watch->watch.node == NULL)
245 goto out_free;
246
247 watch->token = kstrdup(token, GFP_KERNEL);
248 if (watch->token == NULL)
249 goto out_free;
250
251 return watch;
252
253out_free:
254 free_watch_adapter(watch);
255
256out_fail:
257 return NULL;
258}
259
260static void watch_fired(struct xenbus_watch *watch,
261 const char **vec,
262 unsigned int len)
263{
264 struct watch_adapter *adap;
265 struct xsd_sockmsg hdr;
266 const char *path, *token;
267 int path_len, tok_len, body_len, data_len = 0;
268 int ret;
269 LIST_HEAD(staging_q);
270
271 adap = container_of(watch, struct watch_adapter, watch);
272
273 path = vec[XS_WATCH_PATH];
274 token = adap->token;
275
276 path_len = strlen(path) + 1;
277 tok_len = strlen(token) + 1;
278 if (len > 2)
279 data_len = vec[len] - vec[2] + 1;
280 body_len = path_len + tok_len + data_len;
281
282 hdr.type = XS_WATCH_EVENT;
283 hdr.len = body_len;
284
285 mutex_lock(&adap->dev_data->reply_mutex);
286
287 ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
288 if (!ret)
289 ret = queue_reply(&staging_q, path, path_len);
290 if (!ret)
291 ret = queue_reply(&staging_q, token, tok_len);
292 if (!ret && len > 2)
293 ret = queue_reply(&staging_q, vec[2], data_len);
294
295 if (!ret) {
296 /* success: pass reply list onto watcher */
297 list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
298 wake_up(&adap->dev_data->read_waitq);
299 } else
300 queue_cleanup(&staging_q);
301
302 mutex_unlock(&adap->dev_data->reply_mutex);
303}
304
305static int xenbus_write_transaction(unsigned msg_type,
306 struct xenbus_file_priv *u)
307{
308 int rc;
309 void *reply;
310 struct xenbus_transaction_holder *trans = NULL;
311 LIST_HEAD(staging_q);
312
313 if (msg_type == XS_TRANSACTION_START) {
314 trans = kmalloc(sizeof(*trans), GFP_KERNEL);
315 if (!trans) {
316 rc = -ENOMEM;
317 goto out;
318 }
319 }
320
321 reply = xenbus_dev_request_and_reply(&u->u.msg);
322 if (IS_ERR(reply)) {
323 kfree(trans);
324 rc = PTR_ERR(reply);
325 goto out;
326 }
327
328 if (msg_type == XS_TRANSACTION_START) {
329 trans->handle.id = simple_strtoul(reply, NULL, 0);
330
331 list_add(&trans->list, &u->transactions);
332 } else if (msg_type == XS_TRANSACTION_END) {
333 list_for_each_entry(trans, &u->transactions, list)
334 if (trans->handle.id == u->u.msg.tx_id)
335 break;
336 BUG_ON(&trans->list == &u->transactions);
337 list_del(&trans->list);
338
339 kfree(trans);
340 }
341
342 mutex_lock(&u->reply_mutex);
343 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
344 if (!rc)
345 rc = queue_reply(&staging_q, reply, u->u.msg.len);
346 if (!rc) {
347 list_splice_tail(&staging_q, &u->read_buffers);
348 wake_up(&u->read_waitq);
349 } else {
350 queue_cleanup(&staging_q);
351 }
352 mutex_unlock(&u->reply_mutex);
353
354 kfree(reply);
355
356out:
357 return rc;
358}
359
360static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
361{
362 struct watch_adapter *watch, *tmp_watch;
363 char *path, *token;
364 int err, rc;
365 LIST_HEAD(staging_q);
366
367 path = u->u.buffer + sizeof(u->u.msg);
368 token = memchr(path, 0, u->u.msg.len);
369 if (token == NULL) {
370 rc = -EILSEQ;
371 goto out;
372 }
373 token++;
374 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
375 rc = -EILSEQ;
376 goto out;
377 }
378
379 if (msg_type == XS_WATCH) {
380 watch = alloc_watch_adapter(path, token);
381 if (watch == NULL) {
382 rc = -ENOMEM;
383 goto out;
384 }
385
386 watch->watch.callback = watch_fired;
387 watch->dev_data = u;
388
389 err = register_xenbus_watch(&watch->watch);
390 if (err) {
391 free_watch_adapter(watch);
392 rc = err;
393 goto out;
394 }
395 list_add(&watch->list, &u->watches);
396 } else {
397 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
398 if (!strcmp(watch->token, token) &&
399 !strcmp(watch->watch.node, path)) {
400 unregister_xenbus_watch(&watch->watch);
401 list_del(&watch->list);
402 free_watch_adapter(watch);
403 break;
404 }
405 }
406 }
407
408 /* Success. Synthesize a reply to say all is OK. */
409 {
410 struct {
411 struct xsd_sockmsg hdr;
412 char body[3];
413 } __packed reply = {
414 {
415 .type = msg_type,
416 .len = sizeof(reply.body)
417 },
418 "OK"
419 };
420
421 mutex_lock(&u->reply_mutex);
422 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
423 wake_up(&u->read_waitq);
424 mutex_unlock(&u->reply_mutex);
425 }
426
427out:
428 return rc;
429}
430
431static ssize_t xenbus_file_write(struct file *filp,
432 const char __user *ubuf,
433 size_t len, loff_t *ppos)
434{
435 struct xenbus_file_priv *u = filp->private_data;
436 uint32_t msg_type;
437 int rc = len;
438 int ret;
439 LIST_HEAD(staging_q);
440
441 /*
442 * We're expecting usermode to be writing properly formed
443 * xenbus messages. If they write an incomplete message we
444 * buffer it up. Once it is complete, we act on it.
445 */
446
447 /*
448 * Make sure concurrent writers can't stomp all over each
449 * other's messages and make a mess of our partial message
450 * buffer. We don't make any attemppt to stop multiple
451 * writers from making a mess of each other's incomplete
452 * messages; we're just trying to guarantee our own internal
453 * consistency and make sure that single writes are handled
454 * atomically.
455 */
456 mutex_lock(&u->msgbuffer_mutex);
457
458 /* Get this out of the way early to avoid confusion */
459 if (len == 0)
460 goto out;
461
462 /* Can't write a xenbus message larger we can buffer */
463 if (len > sizeof(u->u.buffer) - u->len) {
464 /* On error, dump existing buffer */
465 u->len = 0;
466 rc = -EINVAL;
467 goto out;
468 }
469
470 ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
471
472 if (ret != 0) {
473 rc = -EFAULT;
474 goto out;
475 }
476
477 /* Deal with a partial copy. */
478 len -= ret;
479 rc = len;
480
481 u->len += len;
482
483 /* Return if we haven't got a full message yet */
484 if (u->len < sizeof(u->u.msg))
485 goto out; /* not even the header yet */
486
487 /* If we're expecting a message that's larger than we can
488 possibly send, dump what we have and return an error. */
489 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
490 rc = -E2BIG;
491 u->len = 0;
492 goto out;
493 }
494
495 if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
496 goto out; /* incomplete data portion */
497
498 /*
499 * OK, now we have a complete message. Do something with it.
500 */
501
502 msg_type = u->u.msg.type;
503
504 switch (msg_type) {
505 case XS_WATCH:
506 case XS_UNWATCH:
507 /* (Un)Ask for some path to be watched for changes */
508 ret = xenbus_write_watch(msg_type, u);
509 break;
510
511 default:
512 /* Send out a transaction */
513 ret = xenbus_write_transaction(msg_type, u);
514 break;
515 }
516 if (ret != 0)
517 rc = ret;
518
519 /* Buffered message consumed */
520 u->len = 0;
521
522 out:
523 mutex_unlock(&u->msgbuffer_mutex);
524 return rc;
525}
526
527static int xenbus_file_open(struct inode *inode, struct file *filp)
528{
529 struct xenbus_file_priv *u;
530
531 if (xen_store_evtchn == 0)
532 return -ENOENT;
533
534 nonseekable_open(inode, filp);
535
536 u = kzalloc(sizeof(*u), GFP_KERNEL);
537 if (u == NULL)
538 return -ENOMEM;
539
540 INIT_LIST_HEAD(&u->transactions);
541 INIT_LIST_HEAD(&u->watches);
542 INIT_LIST_HEAD(&u->read_buffers);
543 init_waitqueue_head(&u->read_waitq);
544
545 mutex_init(&u->reply_mutex);
546 mutex_init(&u->msgbuffer_mutex);
547
548 filp->private_data = u;
549
550 return 0;
551}
552
553static int xenbus_file_release(struct inode *inode, struct file *filp)
554{
555 struct xenbus_file_priv *u = filp->private_data;
556 struct xenbus_transaction_holder *trans, *tmp;
557 struct watch_adapter *watch, *tmp_watch;
558 struct read_buffer *rb, *tmp_rb;
559
560 /*
561 * No need for locking here because there are no other users,
562 * by definition.
563 */
564
565 list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
566 xenbus_transaction_end(trans->handle, 1);
567 list_del(&trans->list);
568 kfree(trans);
569 }
570
571 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
572 unregister_xenbus_watch(&watch->watch);
573 list_del(&watch->list);
574 free_watch_adapter(watch);
575 }
576
577 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
578 list_del(&rb->list);
579 kfree(rb);
580 }
581 kfree(u);
582
583 return 0;
584}
585
586static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
587{
588 struct xenbus_file_priv *u = file->private_data;
589
590 poll_wait(file, &u->read_waitq, wait);
591 if (!list_empty(&u->read_buffers))
592 return POLLIN | POLLRDNORM;
593 return 0;
594}
595
596const struct file_operations xen_xenbus_fops = {
597 .read = xenbus_file_read,
598 .write = xenbus_file_write,
599 .open = xenbus_file_open,
600 .release = xenbus_file_release,
601 .poll = xenbus_file_poll,
602 .llseek = no_llseek,
603};
604EXPORT_SYMBOL_GPL(xen_xenbus_fops);
605
606static struct miscdevice xenbus_dev = {
607 .minor = MISC_DYNAMIC_MINOR,
608 .name = "xen/xenbus",
609 .fops = &xen_xenbus_fops,
610};
611
612static int __init xenbus_init(void)
613{
614 int err;
615
616 if (!xen_domain())
617 return -ENODEV;
618
619 err = misc_register(&xenbus_dev);
620 if (err)
621 pr_err("Could not register xenbus frontend device\n");
622 return err;
623}
624
625static void __exit xenbus_exit(void)
626{
627 misc_deregister(&xenbus_dev);
628}
629
630module_init(xenbus_init);
631module_exit(xenbus_exit);