1 /******************************************************************************
4 * This is the kernel equivalent of the "xs" library. We don't need everything
5 * and we use xenbus_comms for communication.
7 * Copyright (C) 2005 Rusty Russell, IBM Corporation
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License version 2
11 * as published by the Free Software Foundation; or, when distributed
12 * separately from the Linux kernel or incorporated into other
13 * software packages, subject to the following license:
15 * Permission is hereby granted, free of charge, to any person obtaining a copy
16 * of this source file (the "Software"), to deal in the Software without
17 * restriction, including without limitation the rights to use, copy, modify,
18 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
19 * and to permit persons to whom the Software is furnished to do so, subject to
20 * the following conditions:
22 * The above copyright notice and this permission notice shall be included in
23 * all copies or substantial portions of the Software.
25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
34 #include <linux/unistd.h>
35 #include <linux/errno.h>
36 #include <linux/types.h>
37 #include <linux/uio.h>
38 #include <linux/kernel.h>
39 #include <linux/string.h>
40 #include <linux/err.h>
41 #include <linux/slab.h>
42 #include <linux/fcntl.h>
43 #include <linux/kthread.h>
44 #include <linux/rwsem.h>
45 #include <linux/module.h>
46 #include <linux/mutex.h>
47 #include <xen/xenbus.h>
48 #include "xenbus_comms.h"
50 struct xs_stored_msg
{
51 struct list_head list
;
53 struct xsd_sockmsg hdr
;
61 /* Queued watch events. */
63 struct xenbus_watch
*handle
;
65 unsigned int vec_size
;
71 /* A list of replies. Currently only one will ever be outstanding. */
72 struct list_head reply_list
;
73 spinlock_t reply_lock
;
74 wait_queue_head_t reply_waitq
;
77 * Mutex ordering: transaction_mutex -> watch_mutex -> request_mutex.
78 * response_mutex is never taken simultaneously with the other three.
80 * transaction_mutex must be held before incrementing
81 * transaction_count. The mutex is held when a suspend is in
82 * progress to prevent new transactions starting.
84 * When decrementing transaction_count to zero the wait queue
85 * should be woken up, the suspend code waits for count to
89 /* One request at a time. */
90 struct mutex request_mutex
;
92 /* Protect xenbus reader thread against save/restore. */
93 struct mutex response_mutex
;
95 /* Protect transactions against save/restore. */
96 struct mutex transaction_mutex
;
97 atomic_t transaction_count
;
98 wait_queue_head_t transaction_wq
;
100 /* Protect watch (de)register against save/restore. */
101 struct rw_semaphore watch_mutex
;
104 static struct xs_handle xs_state
;
106 /* List of registered watches, and a lock to protect it. */
107 static LIST_HEAD(watches
);
108 static DEFINE_SPINLOCK(watches_lock
);
110 /* List of pending watch callback events, and a lock to protect it. */
111 static LIST_HEAD(watch_events
);
112 static DEFINE_SPINLOCK(watch_events_lock
);
115 * Details of the xenwatch callback kernel thread. The thread waits on the
116 * watch_events_waitq for work to do (queued on watch_events list). When it
117 * wakes up it acquires the xenwatch_mutex before reading the list and
120 static pid_t xenwatch_pid
;
121 static DEFINE_MUTEX(xenwatch_mutex
);
122 static DECLARE_WAIT_QUEUE_HEAD(watch_events_waitq
);
124 static int get_error(const char *errorstring
)
128 for (i
= 0; strcmp(errorstring
, xsd_errors
[i
].errstring
) != 0; i
++) {
129 if (i
== ARRAY_SIZE(xsd_errors
) - 1) {
131 "XENBUS xen store gave: unknown error %s",
136 return xsd_errors
[i
].errnum
;
139 static void *read_reply(enum xsd_sockmsg_type
*type
, unsigned int *len
)
141 struct xs_stored_msg
*msg
;
144 spin_lock(&xs_state
.reply_lock
);
146 while (list_empty(&xs_state
.reply_list
)) {
147 spin_unlock(&xs_state
.reply_lock
);
148 wait_event(xs_state
.reply_waitq
,
149 !list_empty(&xs_state
.reply_list
));
150 spin_lock(&xs_state
.reply_lock
);
153 msg
= list_entry(xs_state
.reply_list
.next
,
154 struct xs_stored_msg
, list
);
155 list_del(&msg
->list
);
157 spin_unlock(&xs_state
.reply_lock
);
159 *type
= msg
->hdr
.type
;
162 body
= msg
->u
.reply
.body
;
169 static void transaction_start(void)
171 mutex_lock(&xs_state
.transaction_mutex
);
172 atomic_inc(&xs_state
.transaction_count
);
173 mutex_unlock(&xs_state
.transaction_mutex
);
176 static void transaction_end(void)
178 if (atomic_dec_and_test(&xs_state
.transaction_count
))
179 wake_up(&xs_state
.transaction_wq
);
182 static void transaction_suspend(void)
184 mutex_lock(&xs_state
.transaction_mutex
);
185 wait_event(xs_state
.transaction_wq
,
186 atomic_read(&xs_state
.transaction_count
) == 0);
189 static void transaction_resume(void)
191 mutex_unlock(&xs_state
.transaction_mutex
);
194 void *xenbus_dev_request_and_reply(struct xsd_sockmsg
*msg
)
197 struct xsd_sockmsg req_msg
= *msg
;
200 if (req_msg
.type
== XS_TRANSACTION_START
)
203 mutex_lock(&xs_state
.request_mutex
);
205 err
= xb_write(msg
, sizeof(*msg
) + msg
->len
);
207 msg
->type
= XS_ERROR
;
210 ret
= read_reply(&msg
->type
, &msg
->len
);
212 mutex_unlock(&xs_state
.request_mutex
);
214 if ((msg
->type
== XS_TRANSACTION_END
) ||
215 ((req_msg
.type
== XS_TRANSACTION_START
) &&
216 (msg
->type
== XS_ERROR
)))
221 EXPORT_SYMBOL(xenbus_dev_request_and_reply
);
223 /* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */
224 static void *xs_talkv(struct xenbus_transaction t
,
225 enum xsd_sockmsg_type type
,
226 const struct kvec
*iovec
,
227 unsigned int num_vecs
,
230 struct xsd_sockmsg msg
;
239 for (i
= 0; i
< num_vecs
; i
++)
240 msg
.len
+= iovec
[i
].iov_len
;
242 mutex_lock(&xs_state
.request_mutex
);
244 err
= xb_write(&msg
, sizeof(msg
));
246 mutex_unlock(&xs_state
.request_mutex
);
250 for (i
= 0; i
< num_vecs
; i
++) {
251 err
= xb_write(iovec
[i
].iov_base
, iovec
[i
].iov_len
);
253 mutex_unlock(&xs_state
.request_mutex
);
258 ret
= read_reply(&msg
.type
, len
);
260 mutex_unlock(&xs_state
.request_mutex
);
265 if (msg
.type
== XS_ERROR
) {
266 err
= get_error(ret
);
268 return ERR_PTR(-err
);
271 if (msg
.type
!= type
) {
272 if (printk_ratelimit())
274 "XENBUS unexpected type [%d], expected [%d]\n",
277 return ERR_PTR(-EINVAL
);
282 /* Simplified version of xs_talkv: single message. */
283 static void *xs_single(struct xenbus_transaction t
,
284 enum xsd_sockmsg_type type
,
290 iovec
.iov_base
= (void *)string
;
291 iovec
.iov_len
= strlen(string
) + 1;
292 return xs_talkv(t
, type
, &iovec
, 1, len
);
295 /* Many commands only need an ack, don't care what it says. */
296 static int xs_error(char *reply
)
299 return PTR_ERR(reply
);
304 static unsigned int count_strings(const char *strings
, unsigned int len
)
309 for (p
= strings
, num
= 0; p
< strings
+ len
; p
+= strlen(p
) + 1)
315 /* Return the path to dir with /name appended. Buffer must be kfree()'ed. */
316 static char *join(const char *dir
, const char *name
)
320 if (strlen(name
) == 0)
321 buffer
= kasprintf(GFP_NOIO
| __GFP_HIGH
, "%s", dir
);
323 buffer
= kasprintf(GFP_NOIO
| __GFP_HIGH
, "%s/%s", dir
, name
);
324 return (!buffer
) ? ERR_PTR(-ENOMEM
) : buffer
;
327 static char **split(char *strings
, unsigned int len
, unsigned int *num
)
331 /* Count the strings. */
332 *num
= count_strings(strings
, len
);
334 /* Transfer to one big alloc for easy freeing. */
335 ret
= kmalloc(*num
* sizeof(char *) + len
, GFP_NOIO
| __GFP_HIGH
);
338 return ERR_PTR(-ENOMEM
);
340 memcpy(&ret
[*num
], strings
, len
);
343 strings
= (char *)&ret
[*num
];
344 for (p
= strings
, *num
= 0; p
< strings
+ len
; p
+= strlen(p
) + 1)
350 char **xenbus_directory(struct xenbus_transaction t
,
351 const char *dir
, const char *node
, unsigned int *num
)
353 char *strings
, *path
;
356 path
= join(dir
, node
);
358 return (char **)path
;
360 strings
= xs_single(t
, XS_DIRECTORY
, path
, &len
);
363 return (char **)strings
;
365 return split(strings
, len
, num
);
367 EXPORT_SYMBOL_GPL(xenbus_directory
);
369 /* Check if a path exists. Return 1 if it does. */
370 int xenbus_exists(struct xenbus_transaction t
,
371 const char *dir
, const char *node
)
376 d
= xenbus_directory(t
, dir
, node
, &dir_n
);
382 EXPORT_SYMBOL_GPL(xenbus_exists
);
384 /* Get the value of a single file.
385 * Returns a kmalloced value: call free() on it after use.
386 * len indicates length in bytes.
388 void *xenbus_read(struct xenbus_transaction t
,
389 const char *dir
, const char *node
, unsigned int *len
)
394 path
= join(dir
, node
);
398 ret
= xs_single(t
, XS_READ
, path
, len
);
402 EXPORT_SYMBOL_GPL(xenbus_read
);
404 /* Write the value of a single file.
405 * Returns -err on failure.
407 int xenbus_write(struct xenbus_transaction t
,
408 const char *dir
, const char *node
, const char *string
)
411 struct kvec iovec
[2];
414 path
= join(dir
, node
);
416 return PTR_ERR(path
);
418 iovec
[0].iov_base
= (void *)path
;
419 iovec
[0].iov_len
= strlen(path
) + 1;
420 iovec
[1].iov_base
= (void *)string
;
421 iovec
[1].iov_len
= strlen(string
);
423 ret
= xs_error(xs_talkv(t
, XS_WRITE
, iovec
, ARRAY_SIZE(iovec
), NULL
));
427 EXPORT_SYMBOL_GPL(xenbus_write
);
429 /* Create a new directory. */
430 int xenbus_mkdir(struct xenbus_transaction t
,
431 const char *dir
, const char *node
)
436 path
= join(dir
, node
);
438 return PTR_ERR(path
);
440 ret
= xs_error(xs_single(t
, XS_MKDIR
, path
, NULL
));
444 EXPORT_SYMBOL_GPL(xenbus_mkdir
);
446 /* Destroy a file or directory (directories must be empty). */
447 int xenbus_rm(struct xenbus_transaction t
, const char *dir
, const char *node
)
452 path
= join(dir
, node
);
454 return PTR_ERR(path
);
456 ret
= xs_error(xs_single(t
, XS_RM
, path
, NULL
));
460 EXPORT_SYMBOL_GPL(xenbus_rm
);
462 /* Start a transaction: changes by others will not be seen during this
463 * transaction, and changes will not be visible to others until end.
465 int xenbus_transaction_start(struct xenbus_transaction
*t
)
471 id_str
= xs_single(XBT_NIL
, XS_TRANSACTION_START
, "", NULL
);
472 if (IS_ERR(id_str
)) {
474 return PTR_ERR(id_str
);
477 t
->id
= simple_strtoul(id_str
, NULL
, 0);
481 EXPORT_SYMBOL_GPL(xenbus_transaction_start
);
483 /* End a transaction.
484 * If abandon is true, transaction is discarded instead of committed.
486 int xenbus_transaction_end(struct xenbus_transaction t
, int abort
)
492 strcpy(abortstr
, "F");
494 strcpy(abortstr
, "T");
496 err
= xs_error(xs_single(t
, XS_TRANSACTION_END
, abortstr
, NULL
));
502 EXPORT_SYMBOL_GPL(xenbus_transaction_end
);
504 /* Single read and scanf: returns -errno or num scanned. */
505 int xenbus_scanf(struct xenbus_transaction t
,
506 const char *dir
, const char *node
, const char *fmt
, ...)
512 val
= xenbus_read(t
, dir
, node
, NULL
);
517 ret
= vsscanf(val
, fmt
, ap
);
520 /* Distinctive errno. */
525 EXPORT_SYMBOL_GPL(xenbus_scanf
);
527 /* Single printf and write: returns -errno or 0. */
528 int xenbus_printf(struct xenbus_transaction t
,
529 const char *dir
, const char *node
, const char *fmt
, ...)
533 #define PRINTF_BUFFER_SIZE 4096
536 printf_buffer
= kmalloc(PRINTF_BUFFER_SIZE
, GFP_NOIO
| __GFP_HIGH
);
537 if (printf_buffer
== NULL
)
541 ret
= vsnprintf(printf_buffer
, PRINTF_BUFFER_SIZE
, fmt
, ap
);
544 BUG_ON(ret
> PRINTF_BUFFER_SIZE
-1);
545 ret
= xenbus_write(t
, dir
, node
, printf_buffer
);
547 kfree(printf_buffer
);
551 EXPORT_SYMBOL_GPL(xenbus_printf
);
553 /* Takes tuples of names, scanf-style args, and void **, NULL terminated. */
554 int xenbus_gather(struct xenbus_transaction t
, const char *dir
, ...)
561 while (ret
== 0 && (name
= va_arg(ap
, char *)) != NULL
) {
562 const char *fmt
= va_arg(ap
, char *);
563 void *result
= va_arg(ap
, void *);
566 p
= xenbus_read(t
, dir
, name
, NULL
);
572 if (sscanf(p
, fmt
, result
) == 0)
576 *(char **)result
= p
;
581 EXPORT_SYMBOL_GPL(xenbus_gather
);
583 static int xs_watch(const char *path
, const char *token
)
587 iov
[0].iov_base
= (void *)path
;
588 iov
[0].iov_len
= strlen(path
) + 1;
589 iov
[1].iov_base
= (void *)token
;
590 iov
[1].iov_len
= strlen(token
) + 1;
592 return xs_error(xs_talkv(XBT_NIL
, XS_WATCH
, iov
,
593 ARRAY_SIZE(iov
), NULL
));
596 static int xs_unwatch(const char *path
, const char *token
)
600 iov
[0].iov_base
= (char *)path
;
601 iov
[0].iov_len
= strlen(path
) + 1;
602 iov
[1].iov_base
= (char *)token
;
603 iov
[1].iov_len
= strlen(token
) + 1;
605 return xs_error(xs_talkv(XBT_NIL
, XS_UNWATCH
, iov
,
606 ARRAY_SIZE(iov
), NULL
));
609 static struct xenbus_watch
*find_watch(const char *token
)
611 struct xenbus_watch
*i
, *cmp
;
613 cmp
= (void *)simple_strtoul(token
, NULL
, 16);
615 list_for_each_entry(i
, &watches
, list
)
622 /* Register callback to watch this node. */
623 int register_xenbus_watch(struct xenbus_watch
*watch
)
625 /* Pointer in ascii is the token. */
626 char token
[sizeof(watch
) * 2 + 1];
629 sprintf(token
, "%lX", (long)watch
);
631 down_read(&xs_state
.watch_mutex
);
633 spin_lock(&watches_lock
);
634 BUG_ON(find_watch(token
));
635 list_add(&watch
->list
, &watches
);
636 spin_unlock(&watches_lock
);
638 err
= xs_watch(watch
->node
, token
);
640 /* Ignore errors due to multiple registration. */
641 if ((err
!= 0) && (err
!= -EEXIST
)) {
642 spin_lock(&watches_lock
);
643 list_del(&watch
->list
);
644 spin_unlock(&watches_lock
);
647 up_read(&xs_state
.watch_mutex
);
651 EXPORT_SYMBOL_GPL(register_xenbus_watch
);
653 void unregister_xenbus_watch(struct xenbus_watch
*watch
)
655 struct xs_stored_msg
*msg
, *tmp
;
656 char token
[sizeof(watch
) * 2 + 1];
659 sprintf(token
, "%lX", (long)watch
);
661 down_read(&xs_state
.watch_mutex
);
663 spin_lock(&watches_lock
);
664 BUG_ON(!find_watch(token
));
665 list_del(&watch
->list
);
666 spin_unlock(&watches_lock
);
668 err
= xs_unwatch(watch
->node
, token
);
671 "XENBUS Failed to release watch %s: %i\n",
674 up_read(&xs_state
.watch_mutex
);
676 /* Make sure there are no callbacks running currently (unless
678 if (current
->pid
!= xenwatch_pid
)
679 mutex_lock(&xenwatch_mutex
);
681 /* Cancel pending watch events. */
682 spin_lock(&watch_events_lock
);
683 list_for_each_entry_safe(msg
, tmp
, &watch_events
, list
) {
684 if (msg
->u
.watch
.handle
!= watch
)
686 list_del(&msg
->list
);
687 kfree(msg
->u
.watch
.vec
);
690 spin_unlock(&watch_events_lock
);
692 if (current
->pid
!= xenwatch_pid
)
693 mutex_unlock(&xenwatch_mutex
);
695 EXPORT_SYMBOL_GPL(unregister_xenbus_watch
);
697 void xs_suspend(void)
699 transaction_suspend();
700 down_write(&xs_state
.watch_mutex
);
701 mutex_lock(&xs_state
.request_mutex
);
702 mutex_lock(&xs_state
.response_mutex
);
707 struct xenbus_watch
*watch
;
708 char token
[sizeof(watch
) * 2 + 1];
712 mutex_unlock(&xs_state
.response_mutex
);
713 mutex_unlock(&xs_state
.request_mutex
);
714 transaction_resume();
716 /* No need for watches_lock: the watch_mutex is sufficient. */
717 list_for_each_entry(watch
, &watches
, list
) {
718 sprintf(token
, "%lX", (long)watch
);
719 xs_watch(watch
->node
, token
);
722 up_write(&xs_state
.watch_mutex
);
725 void xs_suspend_cancel(void)
727 mutex_unlock(&xs_state
.response_mutex
);
728 mutex_unlock(&xs_state
.request_mutex
);
729 up_write(&xs_state
.watch_mutex
);
730 mutex_unlock(&xs_state
.transaction_mutex
);
733 static int xenwatch_thread(void *unused
)
735 struct list_head
*ent
;
736 struct xs_stored_msg
*msg
;
739 wait_event_interruptible(watch_events_waitq
,
740 !list_empty(&watch_events
));
742 if (kthread_should_stop())
745 mutex_lock(&xenwatch_mutex
);
747 spin_lock(&watch_events_lock
);
748 ent
= watch_events
.next
;
749 if (ent
!= &watch_events
)
751 spin_unlock(&watch_events_lock
);
753 if (ent
!= &watch_events
) {
754 msg
= list_entry(ent
, struct xs_stored_msg
, list
);
755 msg
->u
.watch
.handle
->callback(
757 (const char **)msg
->u
.watch
.vec
,
758 msg
->u
.watch
.vec_size
);
759 kfree(msg
->u
.watch
.vec
);
763 mutex_unlock(&xenwatch_mutex
);
769 static int process_msg(void)
771 struct xs_stored_msg
*msg
;
776 * We must disallow save/restore while reading a xenstore message.
777 * A partial read across s/r leaves us out of sync with xenstored.
780 err
= xb_wait_for_data_to_read();
783 mutex_lock(&xs_state
.response_mutex
);
784 if (xb_data_to_read())
786 /* We raced with save/restore: pending data 'disappeared'. */
787 mutex_unlock(&xs_state
.response_mutex
);
791 msg
= kmalloc(sizeof(*msg
), GFP_NOIO
| __GFP_HIGH
);
797 err
= xb_read(&msg
->hdr
, sizeof(msg
->hdr
));
803 body
= kmalloc(msg
->hdr
.len
+ 1, GFP_NOIO
| __GFP_HIGH
);
810 err
= xb_read(body
, msg
->hdr
.len
);
816 body
[msg
->hdr
.len
] = '\0';
818 if (msg
->hdr
.type
== XS_WATCH_EVENT
) {
819 msg
->u
.watch
.vec
= split(body
, msg
->hdr
.len
,
820 &msg
->u
.watch
.vec_size
);
821 if (IS_ERR(msg
->u
.watch
.vec
)) {
822 err
= PTR_ERR(msg
->u
.watch
.vec
);
827 spin_lock(&watches_lock
);
828 msg
->u
.watch
.handle
= find_watch(
829 msg
->u
.watch
.vec
[XS_WATCH_TOKEN
]);
830 if (msg
->u
.watch
.handle
!= NULL
) {
831 spin_lock(&watch_events_lock
);
832 list_add_tail(&msg
->list
, &watch_events
);
833 wake_up(&watch_events_waitq
);
834 spin_unlock(&watch_events_lock
);
836 kfree(msg
->u
.watch
.vec
);
839 spin_unlock(&watches_lock
);
841 msg
->u
.reply
.body
= body
;
842 spin_lock(&xs_state
.reply_lock
);
843 list_add_tail(&msg
->list
, &xs_state
.reply_list
);
844 spin_unlock(&xs_state
.reply_lock
);
845 wake_up(&xs_state
.reply_waitq
);
849 mutex_unlock(&xs_state
.response_mutex
);
853 static int xenbus_thread(void *unused
)
860 printk(KERN_WARNING
"XENBUS error %d while reading "
862 if (kthread_should_stop())
872 struct task_struct
*task
;
874 INIT_LIST_HEAD(&xs_state
.reply_list
);
875 spin_lock_init(&xs_state
.reply_lock
);
876 init_waitqueue_head(&xs_state
.reply_waitq
);
878 mutex_init(&xs_state
.request_mutex
);
879 mutex_init(&xs_state
.response_mutex
);
880 mutex_init(&xs_state
.transaction_mutex
);
881 init_rwsem(&xs_state
.watch_mutex
);
882 atomic_set(&xs_state
.transaction_count
, 0);
883 init_waitqueue_head(&xs_state
.transaction_wq
);
885 /* Initialize the shared memory rings to talk to xenstored */
886 err
= xb_init_comms();
890 task
= kthread_run(xenwatch_thread
, NULL
, "xenwatch");
892 return PTR_ERR(task
);
893 xenwatch_pid
= task
->pid
;
895 task
= kthread_run(xenbus_thread
, NULL
, "xenbus");
897 return PTR_ERR(task
);