2 * Driver giving user-space access to the kernel's xenbus connection
5 * Copyright (c) 2005, Christian Limpach
6 * Copyright (c) 2005, Rusty Russell, IBM Corporation
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:
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:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
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
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.
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>
44 #include <linux/poll.h>
45 #include <linux/mutex.h>
46 #include <linux/sched.h>
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>
54 #include <linux/slab.h>
55 #include <linux/miscdevice.h>
56 #include <linux/module.h>
58 #include "xenbus_comms.h"
60 #include <xen/xenbus.h>
62 #include <asm/xen/hypervisor.h>
64 MODULE_LICENSE("GPL");
67 * An element of a list of outstanding transactions, for which we're
68 * still waiting a reply.
70 struct xenbus_transaction_holder {
71 struct list_head list;
72 struct xenbus_transaction handle;
76 * A buffer of data on the queue.
79 struct list_head list;
85 struct xenbus_file_priv {
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.
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.
96 struct mutex msgbuffer_mutex;
98 /* In-progress transactions */
99 struct list_head transactions;
101 /* Active watches. */
102 struct list_head watches;
104 /* Partial request. */
107 struct xsd_sockmsg msg;
108 char buffer[XENSTORE_PAYLOAD_MAX];
111 /* Response queue. */
112 struct mutex reply_mutex;
113 struct list_head read_buffers;
114 wait_queue_head_t read_waitq;
118 /* Read out any raw xenbus messages queued up. */
119 static ssize_t xenbus_file_read(struct file *filp,
121 size_t len, loff_t *ppos)
123 struct xenbus_file_priv *u = filp->private_data;
124 struct read_buffer *rb;
128 mutex_lock(&u->reply_mutex);
130 while (list_empty(&u->read_buffers)) {
131 mutex_unlock(&u->reply_mutex);
132 if (filp->f_flags & O_NONBLOCK)
135 ret = wait_event_interruptible(u->read_waitq,
136 !list_empty(&u->read_buffers));
139 mutex_lock(&u->reply_mutex);
142 rb = list_entry(u->read_buffers.next, struct read_buffer, list);
145 unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
147 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
150 rb->cons += sz - ret;
158 /* Clear out buffer if it has been consumed */
159 if (rb->cons == rb->len) {
162 if (list_empty(&u->read_buffers))
164 rb = list_entry(u->read_buffers.next,
165 struct read_buffer, list);
172 mutex_unlock(&u->reply_mutex);
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.)
183 static int queue_reply(struct list_head *queue, const void *data, size_t len)
185 struct read_buffer *rb;
190 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
197 memcpy(rb->msg, data, len);
199 list_add_tail(&rb->list, queue);
204 * Free all the read_buffer s on a list.
205 * Caller must have sole reference to list.
207 static void queue_cleanup(struct list_head *list)
209 struct read_buffer *rb;
211 while (!list_empty(list)) {
212 rb = list_entry(list->next, struct read_buffer, list);
213 list_del(list->next);
218 struct watch_adapter {
219 struct list_head list;
220 struct xenbus_watch watch;
221 struct xenbus_file_priv *dev_data;
225 static void free_watch_adapter(struct watch_adapter *watch)
227 kfree(watch->watch.node);
232 static struct watch_adapter *alloc_watch_adapter(const char *path,
235 struct watch_adapter *watch;
237 watch = kzalloc(sizeof(*watch), GFP_KERNEL);
241 watch->watch.node = kstrdup(path, GFP_KERNEL);
242 if (watch->watch.node == NULL)
245 watch->token = kstrdup(token, GFP_KERNEL);
246 if (watch->token == NULL)
252 free_watch_adapter(watch);
258 static void watch_fired(struct xenbus_watch *watch,
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;
267 LIST_HEAD(staging_q);
269 adap = container_of(watch, struct watch_adapter, watch);
271 path = vec[XS_WATCH_PATH];
274 path_len = strlen(path) + 1;
275 tok_len = strlen(token) + 1;
277 data_len = vec[len] - vec[2] + 1;
278 body_len = path_len + tok_len + data_len;
280 hdr.type = XS_WATCH_EVENT;
283 mutex_lock(&adap->dev_data->reply_mutex);
285 ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
287 ret = queue_reply(&staging_q, path, path_len);
289 ret = queue_reply(&staging_q, token, tok_len);
291 ret = queue_reply(&staging_q, vec[2], data_len);
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);
298 queue_cleanup(&staging_q);
300 mutex_unlock(&adap->dev_data->reply_mutex);
303 static int xenbus_write_transaction(unsigned msg_type,
304 struct xenbus_file_priv *u)
308 struct xenbus_transaction_holder *trans = NULL;
309 LIST_HEAD(staging_q);
311 if (msg_type == XS_TRANSACTION_START) {
312 trans = kmalloc(sizeof(*trans), GFP_KERNEL);
319 reply = xenbus_dev_request_and_reply(&u->u.msg);
326 if (msg_type == XS_TRANSACTION_START) {
327 trans->handle.id = simple_strtoul(reply, NULL, 0);
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)
334 BUG_ON(&trans->list == &u->transactions);
335 list_del(&trans->list);
340 mutex_lock(&u->reply_mutex);
341 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
343 rc = queue_reply(&staging_q, reply, u->u.msg.len);
345 list_splice_tail(&staging_q, &u->read_buffers);
346 wake_up(&u->read_waitq);
348 queue_cleanup(&staging_q);
350 mutex_unlock(&u->reply_mutex);
358 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
360 struct watch_adapter *watch, *tmp_watch;
363 LIST_HEAD(staging_q);
365 path = u->u.buffer + sizeof(u->u.msg);
366 token = memchr(path, 0, u->u.msg.len);
372 if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
377 if (msg_type == XS_WATCH) {
378 watch = alloc_watch_adapter(path, token);
384 watch->watch.callback = watch_fired;
387 err = register_xenbus_watch(&watch->watch);
389 free_watch_adapter(watch);
393 list_add(&watch->list, &u->watches);
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);
406 /* Success. Synthesize a reply to say all is OK. */
409 struct xsd_sockmsg hdr;
414 .len = sizeof(reply.body)
419 mutex_lock(&u->reply_mutex);
420 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
421 wake_up(&u->read_waitq);
422 mutex_unlock(&u->reply_mutex);
429 static ssize_t xenbus_file_write(struct file *filp,
430 const char __user *ubuf,
431 size_t len, loff_t *ppos)
433 struct xenbus_file_priv *u = filp->private_data;
437 LIST_HEAD(staging_q);
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.
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
454 mutex_lock(&u->msgbuffer_mutex);
456 /* Get this out of the way early to avoid confusion */
460 /* Can't write a xenbus message larger we can buffer */
461 if (len > sizeof(u->u.buffer) - u->len) {
462 /* On error, dump existing buffer */
468 ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
475 /* Deal with a partial copy. */
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 */
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)) {
493 if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
494 goto out; /* incomplete data portion */
497 * OK, now we have a complete message. Do something with it.
500 msg_type = u->u.msg.type;
505 /* (Un)Ask for some path to be watched for changes */
506 ret = xenbus_write_watch(msg_type, u);
510 /* Send out a transaction */
511 ret = xenbus_write_transaction(msg_type, u);
517 /* Buffered message consumed */
521 mutex_unlock(&u->msgbuffer_mutex);
525 static int xenbus_file_open(struct inode *inode, struct file *filp)
527 struct xenbus_file_priv *u;
529 if (xen_store_evtchn == 0)
532 nonseekable_open(inode, filp);
534 u = kzalloc(sizeof(*u), GFP_KERNEL);
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);
543 mutex_init(&u->reply_mutex);
544 mutex_init(&u->msgbuffer_mutex);
546 filp->private_data = u;
551 static int xenbus_file_release(struct inode *inode, struct file *filp)
553 struct xenbus_file_priv *u = filp->private_data;
554 struct xenbus_transaction_holder *trans, *tmp;
555 struct watch_adapter *watch, *tmp_watch;
556 struct read_buffer *rb, *tmp_rb;
559 * No need for locking here because there are no other users,
563 list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
564 xenbus_transaction_end(trans->handle, 1);
565 list_del(&trans->list);
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);
575 list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
584 static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
586 struct xenbus_file_priv *u = file->private_data;
588 poll_wait(file, &u->read_waitq, wait);
589 if (!list_empty(&u->read_buffers))
590 return POLLIN | POLLRDNORM;
594 const struct file_operations xen_xenbus_fops = {
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,
602 EXPORT_SYMBOL_GPL(xen_xenbus_fops);
604 static struct miscdevice xenbus_dev = {
605 .minor = MISC_DYNAMIC_MINOR,
606 .name = "xen/xenbus",
607 .fops = &xen_xenbus_fops,
610 static int __init xenbus_init(void)
617 err = misc_register(&xenbus_dev);
619 printk(KERN_ERR "Could not register xenbus frontend device\n");
623 static void __exit xenbus_exit(void)
625 misc_deregister(&xenbus_dev);
628 module_init(xenbus_init);
629 module_exit(xenbus_exit);