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>
57 #include "../xenbus/xenbus_comms.h"
59 #include <xen/xenbus.h>
60 #include <asm/xen/hypervisor.h>
63 * An element of a list of outstanding transactions, for which we're
64 * still waiting a reply.
66 struct xenbus_transaction_holder {
67 struct list_head list;
68 struct xenbus_transaction handle;
72 * A buffer of data on the queue.
75 struct list_head list;
81 struct xenbus_file_priv {
83 * msgbuffer_mutex is held while partial requests are built up
84 * and complete requests are acted on. It therefore protects
85 * the "transactions" and "watches" lists, and the partial
86 * request length and buffer.
88 * reply_mutex protects the reply being built up to return to
89 * usermode. It nests inside msgbuffer_mutex but may be held
90 * alone during a watch callback.
92 struct mutex msgbuffer_mutex;
94 /* In-progress transactions */
95 struct list_head transactions;
98 struct list_head watches;
100 /* Partial request. */
103 struct xsd_sockmsg msg;
104 char buffer[PAGE_SIZE];
107 /* Response queue. */
108 struct mutex reply_mutex;
109 struct list_head read_buffers;
110 wait_queue_head_t read_waitq;
114 /* Read out any raw xenbus messages queued up. */
115 static ssize_t xenbus_file_read(struct file *filp,
117 size_t len, loff_t *ppos)
119 struct xenbus_file_priv *u = filp->private_data;
120 struct read_buffer *rb;
124 mutex_lock(&u->reply_mutex);
125 while (list_empty(&u->read_buffers)) {
126 mutex_unlock(&u->reply_mutex);
127 if (filp->f_flags & O_NONBLOCK)
130 ret = wait_event_interruptible(u->read_waitq,
131 !list_empty(&u->read_buffers));
134 mutex_lock(&u->reply_mutex);
137 rb = list_entry(u->read_buffers.next, struct read_buffer, list);
140 unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
142 ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
145 rb->cons += sz - ret;
153 /* Clear out buffer if it has been consumed */
154 if (rb->cons == rb->len) {
157 if (list_empty(&u->read_buffers))
159 rb = list_entry(u->read_buffers.next,
160 struct read_buffer, list);
165 mutex_unlock(&u->reply_mutex);
170 * Add a buffer to the queue. Caller must hold the appropriate lock
171 * if the queue is not local. (Commonly the caller will build up
172 * multiple queued buffers on a temporary local list, and then add it
173 * to the appropriate list under lock once all the buffers have een
174 * successfully allocated.)
176 static int queue_reply(struct list_head *queue, const void *data, size_t len)
178 struct read_buffer *rb;
183 rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
190 memcpy(rb->msg, data, len);
192 list_add_tail(&rb->list, queue);
197 * Free all the read_buffer s on a list.
198 * Caller must have sole reference to list.
200 static void queue_cleanup(struct list_head *list)
202 struct read_buffer *rb;
204 while (!list_empty(list)) {
205 rb = list_entry(list->next, struct read_buffer, list);
206 list_del(list->next);
211 struct watch_adapter {
212 struct list_head list;
213 struct xenbus_watch watch;
214 struct xenbus_file_priv *dev_data;
218 static void free_watch_adapter(struct watch_adapter *watch)
220 kfree(watch->watch.node);
225 static struct watch_adapter *alloc_watch_adapter(const char *path,
228 struct watch_adapter *watch;
230 watch = kzalloc(sizeof(*watch), GFP_KERNEL);
234 watch->watch.node = kstrdup(path, GFP_KERNEL);
235 if (watch->watch.node == NULL)
238 watch->token = kstrdup(token, GFP_KERNEL);
239 if (watch->token == NULL)
245 free_watch_adapter(watch);
251 static void watch_fired(struct xenbus_watch *watch,
255 struct watch_adapter *adap;
256 struct xsd_sockmsg hdr;
257 const char *path, *token;
258 int path_len, tok_len, body_len, data_len = 0;
260 LIST_HEAD(staging_q);
262 adap = container_of(watch, struct watch_adapter, watch);
264 path = vec[XS_WATCH_PATH];
267 path_len = strlen(path) + 1;
268 tok_len = strlen(token) + 1;
270 data_len = vec[len] - vec[2] + 1;
271 body_len = path_len + tok_len + data_len;
273 hdr.type = XS_WATCH_EVENT;
276 mutex_lock(&adap->dev_data->reply_mutex);
278 ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
280 ret = queue_reply(&staging_q, path, path_len);
282 ret = queue_reply(&staging_q, token, tok_len);
284 ret = queue_reply(&staging_q, vec[2], data_len);
287 /* success: pass reply list onto watcher */
288 list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
289 wake_up(&adap->dev_data->read_waitq);
291 queue_cleanup(&staging_q);
293 mutex_unlock(&adap->dev_data->reply_mutex);
296 static int xenbus_write_transaction(unsigned msg_type,
297 struct xenbus_file_priv *u)
301 struct xenbus_transaction_holder *trans = NULL;
302 LIST_HEAD(staging_q);
304 if (msg_type == XS_TRANSACTION_START) {
305 trans = kmalloc(sizeof(*trans), GFP_KERNEL);
312 reply = xenbus_dev_request_and_reply(&u->u.msg);
319 if (msg_type == XS_TRANSACTION_START) {
320 trans->handle.id = simple_strtoul(reply, NULL, 0);
322 list_add(&trans->list, &u->transactions);
323 } else if (msg_type == XS_TRANSACTION_END) {
324 list_for_each_entry(trans, &u->transactions, list)
325 if (trans->handle.id == u->u.msg.tx_id)
327 BUG_ON(&trans->list == &u->transactions);
328 list_del(&trans->list);
333 mutex_lock(&u->reply_mutex);
334 rc = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
336 rc = queue_reply(&staging_q, reply, u->u.msg.len);
338 list_splice_tail(&staging_q, &u->read_buffers);
339 wake_up(&u->read_waitq);
341 queue_cleanup(&staging_q);
343 mutex_unlock(&u->reply_mutex);
351 static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
353 struct watch_adapter *watch, *tmp_watch;
356 LIST_HEAD(staging_q);
358 path = u->u.buffer + sizeof(u->u.msg);
359 token = memchr(path, 0, u->u.msg.len);
366 if (msg_type == XS_WATCH) {
367 watch = alloc_watch_adapter(path, token);
373 watch->watch.callback = watch_fired;
376 err = register_xenbus_watch(&watch->watch);
378 free_watch_adapter(watch);
382 list_add(&watch->list, &u->watches);
384 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
385 if (!strcmp(watch->token, token) &&
386 !strcmp(watch->watch.node, path)) {
387 unregister_xenbus_watch(&watch->watch);
388 list_del(&watch->list);
389 free_watch_adapter(watch);
395 /* Success. Synthesize a reply to say all is OK. */
398 struct xsd_sockmsg hdr;
403 .len = sizeof(reply.body)
408 mutex_lock(&u->reply_mutex);
409 rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
410 mutex_unlock(&u->reply_mutex);
417 static ssize_t xenbus_file_write(struct file *filp,
418 const char __user *ubuf,
419 size_t len, loff_t *ppos)
421 struct xenbus_file_priv *u = filp->private_data;
425 LIST_HEAD(staging_q);
428 * We're expecting usermode to be writing properly formed
429 * xenbus messages. If they write an incomplete message we
430 * buffer it up. Once it is complete, we act on it.
434 * Make sure concurrent writers can't stomp all over each
435 * other's messages and make a mess of our partial message
436 * buffer. We don't make any attemppt to stop multiple
437 * writers from making a mess of each other's incomplete
438 * messages; we're just trying to guarantee our own internal
439 * consistency and make sure that single writes are handled
442 mutex_lock(&u->msgbuffer_mutex);
444 /* Get this out of the way early to avoid confusion */
448 /* Can't write a xenbus message larger we can buffer */
449 if ((len + u->len) > sizeof(u->u.buffer)) {
450 /* On error, dump existing buffer */
456 ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
463 /* Deal with a partial copy. */
469 /* Return if we haven't got a full message yet */
470 if (u->len < sizeof(u->u.msg))
471 goto out; /* not even the header yet */
473 /* If we're expecting a message that's larger than we can
474 possibly send, dump what we have and return an error. */
475 if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
481 if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
482 goto out; /* incomplete data portion */
485 * OK, now we have a complete message. Do something with it.
488 msg_type = u->u.msg.type;
491 case XS_TRANSACTION_START:
492 case XS_TRANSACTION_END:
497 case XS_GET_DOMAIN_PATH:
502 /* Send out a transaction */
503 ret = xenbus_write_transaction(msg_type, u);
508 /* (Un)Ask for some path to be watched for changes */
509 ret = xenbus_write_watch(msg_type, u);
519 /* Buffered message consumed */
523 mutex_unlock(&u->msgbuffer_mutex);
527 static int xenbus_file_open(struct inode *inode, struct file *filp)
529 struct xenbus_file_priv *u;
531 if (xen_store_evtchn == 0)
534 nonseekable_open(inode, filp);
536 u = kzalloc(sizeof(*u), GFP_KERNEL);
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);
545 mutex_init(&u->reply_mutex);
546 mutex_init(&u->msgbuffer_mutex);
548 filp->private_data = u;
553 static int xenbus_file_release(struct inode *inode, struct file *filp)
555 struct xenbus_file_priv *u = filp->private_data;
556 struct xenbus_transaction_holder *trans, *tmp;
557 struct watch_adapter *watch, *tmp_watch;
560 * No need for locking here because there are no other users,
564 list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
565 xenbus_transaction_end(trans->handle, 1);
566 list_del(&trans->list);
570 list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
571 unregister_xenbus_watch(&watch->watch);
572 list_del(&watch->list);
573 free_watch_adapter(watch);
581 static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
583 struct xenbus_file_priv *u = file->private_data;
585 poll_wait(file, &u->read_waitq, wait);
586 if (!list_empty(&u->read_buffers))
587 return POLLIN | POLLRDNORM;
591 const struct file_operations xenbus_file_ops = {
592 .read = xenbus_file_read,
593 .write = xenbus_file_write,
594 .open = xenbus_file_open,
595 .release = xenbus_file_release,
596 .poll = xenbus_file_poll,