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xen: add xenfs to allow usermode <-> Xen interaction

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The xenfs filesystem exports various interfaces to usermode.  Initially
this exports a file to allow usermode to interact with xenbus/xenstore.

Traditionally this appeared in /proc/xen.  Rather than extending procfs,
this patch adds a backward-compat mountpoint on /proc/xen, and provides
a xenfs filesystem which can be mounted there.

Signed-off-by: Alex Zeffertt <alex.zeffertt@eu.citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alex Zeffertt 2009-01-07 18:07:11 -08:00 committed by Linus Torvalds
parent d8220347da
commit 1107ba885e
10 changed files with 716 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
drivers/xen/Kconfig
View File

@ -17,3 +17,27 @@ config XEN_SCRUB_PAGES
is not accidentally visible to other domains. Is it more
secure, but slightly less efficient.
If in doubt, say yes.
config XENFS
tristate "Xen filesystem"
depends on XEN
default y
help
The xen filesystem provides a way for domains to share
information with each other and with the hypervisor.
For example, by reading and writing the "xenbus" file, guests
may pass arbitrary information to the initial domain.
If in doubt, say yes.
config XEN_COMPAT_XENFS
bool "Create compatibility mount point /proc/xen"
depends on XENFS
default y
help
The old xenstore userspace tools expect to find "xenbus"
under /proc/xen, but "xenbus" is now found at the root of the
xenfs filesystem. Selecting this causes the kernel to create
the compatibilty mount point /proc/xen if it is running on
a xen platform.
If in doubt, say yes.

2
drivers/xen/Makefile
View File

@ -1,5 +1,7 @@
obj-y += grant-table.o features.o events.o manage.o
obj-y += xenbus/
obj-$(CONFIG_HOTPLUG_CPU) += cpu_hotplug.o
obj-$(CONFIG_XEN_XENCOMM) += xencomm.o
obj-$(CONFIG_XEN_BALLOON) += balloon.o
obj-$(CONFIG_XENFS) += xenfs/

28
drivers/xen/xenbus/xenbus_probe.c
View File

@ -40,6 +40,7 @@
#include <linux/ctype.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/notifier.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
@ -55,7 +56,10 @@
#include "xenbus_comms.h"
#include "xenbus_probe.h"
int xen_store_evtchn;
EXPORT_SYMBOL(xen_store_evtchn);
struct xenstore_domain_interface *xen_store_interface;
static unsigned long xen_store_mfn;
@ -166,6 +170,9 @@ static int read_backend_details(struct xenbus_device *xendev)
return read_otherend_details(xendev, "backend-id", "backend");
}
static struct device_attribute xenbus_dev_attrs[] = {
__ATTR_NULL
};
/* Bus type for frontend drivers. */
static struct xen_bus_type xenbus_frontend = {
@ -174,12 +181,13 @@ static struct xen_bus_type xenbus_frontend = {
.get_bus_id = frontend_bus_id,
.probe = xenbus_probe_frontend,
.bus = {
.name = "xen",
.match = xenbus_match,
.uevent = xenbus_uevent,
.probe = xenbus_dev_probe,
.remove = xenbus_dev_remove,
.shutdown = xenbus_dev_shutdown,
.name = "xen",
.match = xenbus_match,
.uevent = xenbus_uevent,
.probe = xenbus_dev_probe,
.remove = xenbus_dev_remove,
.shutdown = xenbus_dev_shutdown,
.dev_attrs = xenbus_dev_attrs,
},
};
@ -852,6 +860,14 @@ static int __init xenbus_probe_init(void)
if (!xen_initial_domain())
xenbus_probe(NULL);
#ifdef CONFIG_XEN_COMPAT_XENFS
/*
* Create xenfs mountpoint in /proc for compatibility with
* utilities that expect to find "xenbus" under "/proc/xen".
*/
proc_mkdir("xen", NULL);
#endif
return 0;
out_unreg_back:

1
drivers/xen/xenbus/xenbus_xs.c
View File

@ -184,6 +184,7 @@ void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg)
return ret;
}
EXPORT_SYMBOL(xenbus_dev_request_and_reply);
/* Send message to xs, get kmalloc'ed reply. ERR_PTR() on error. */
static void *xs_talkv(struct xenbus_transaction t,

3
drivers/xen/xenfs/Makefile Normal file
View File

@ -0,0 +1,3 @@
obj-$(CONFIG_XENFS) += xenfs.o
xenfs-objs = super.o xenbus.o

64
drivers/xen/xenfs/super.c Normal file
View File

@ -0,0 +1,64 @@
/*
* xenfs.c - a filesystem for passing info between the a domain and
* the hypervisor.
*
* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
* and /proc/xen compatibility mount point.
* Turned xenfs into a loadable module.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/magic.h>
#include "xenfs.h"
#include <asm/xen/hypervisor.h>
MODULE_DESCRIPTION("Xen filesystem");
MODULE_LICENSE("GPL");
static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
{
static struct tree_descr xenfs_files[] = {
[2] = {"xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR},
{""},
};
return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
}
static int xenfs_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name,
void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
}
static struct file_system_type xenfs_type = {
.owner = THIS_MODULE,
.name = "xenfs",
.get_sb = xenfs_get_sb,
.kill_sb = kill_litter_super,
};
static int __init xenfs_init(void)
{
if (xen_pv_domain())
return register_filesystem(&xenfs_type);
printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
return 0;
}
static void __exit xenfs_exit(void)
{
if (xen_pv_domain())
unregister_filesystem(&xenfs_type);
}
module_init(xenfs_init);
module_exit(xenfs_exit);

593
drivers/xen/xenfs/xenbus.c Normal file
View File

@ -0,0 +1,593 @@
/*
* Driver giving user-space access to the kernel's xenbus connection
* to xenstore.
*
* Copyright (c) 2005, Christian Limpach
* Copyright (c) 2005, Rusty Russell, IBM Corporation
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Changes:
* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
* and /proc/xen compatibility mount point.
* Turned xenfs into a loadable module.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/uio.h>
#include <linux/notifier.h>
#include <linux/wait.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/namei.h>
#include <linux/string.h>
#include "xenfs.h"
#include "../xenbus/xenbus_comms.h"
#include <xen/xenbus.h>
#include <asm/xen/hypervisor.h>
/*
* An element of a list of outstanding transactions, for which we're
* still waiting a reply.
*/
struct xenbus_transaction_holder {
struct list_head list;
struct xenbus_transaction handle;
};
/*
* A buffer of data on the queue.
*/
struct read_buffer {
struct list_head list;
unsigned int cons;
unsigned int len;
char msg[];
};
struct xenbus_file_priv {
/*
* msgbuffer_mutex is held while partial requests are built up
* and complete requests are acted on. It therefore protects
* the "transactions" and "watches" lists, and the partial
* request length and buffer.
*
* reply_mutex protects the reply being built up to return to
* usermode. It nests inside msgbuffer_mutex but may be held
* alone during a watch callback.
*/
struct mutex msgbuffer_mutex;
/* In-progress transactions */
struct list_head transactions;
/* Active watches. */
struct list_head watches;
/* Partial request. */
unsigned int len;
union {
struct xsd_sockmsg msg;
char buffer[PAGE_SIZE];
} u;
/* Response queue. */
struct mutex reply_mutex;
struct list_head read_buffers;
wait_queue_head_t read_waitq;
};
/* Read out any raw xenbus messages queued up. */
static ssize_t xenbus_file_read(struct file *filp,
char __user *ubuf,
size_t len, loff_t *ppos)
{
struct xenbus_file_priv *u = filp->private_data;
struct read_buffer *rb;
unsigned i;
int ret;
mutex_lock(&u->reply_mutex);
while (list_empty(&u->read_buffers)) {
mutex_unlock(&u->reply_mutex);
ret = wait_event_interruptible(u->read_waitq,
!list_empty(&u->read_buffers));
if (ret)
return ret;
mutex_lock(&u->reply_mutex);
}
rb = list_entry(u->read_buffers.next, struct read_buffer, list);
i = 0;
while (i < len) {
unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
i += sz - ret;
rb->cons += sz - ret;
if (ret != sz) {
if (i == 0)
i = -EFAULT;
goto out;
}
/* Clear out buffer if it has been consumed */
if (rb->cons == rb->len) {
list_del(&rb->list);
kfree(rb);
if (list_empty(&u->read_buffers))
break;
rb = list_entry(u->read_buffers.next,
struct read_buffer, list);
}
}
out:
mutex_unlock(&u->reply_mutex);
return i;
}
/*
* Add a buffer to the queue. Caller must hold the appropriate lock
* if the queue is not local. (Commonly the caller will build up
* multiple queued buffers on a temporary local list, and then add it
* to the appropriate list under lock once all the buffers have een
* successfully allocated.)
*/
static int queue_reply(struct list_head *queue, const void *data, size_t len)
{
struct read_buffer *rb;
if (len == 0)
return 0;
rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
if (rb == NULL)
return -ENOMEM;
rb->cons = 0;
rb->len = len;
memcpy(rb->msg, data, len);
list_add_tail(&rb->list, queue);
return 0;
}
/*
* Free all the read_buffer s on a list.
* Caller must have sole reference to list.
*/
static void queue_cleanup(struct list_head *list)
{
struct read_buffer *rb;
while (!list_empty(list)) {
rb = list_entry(list->next, struct read_buffer, list);
list_del(list->next);
kfree(rb);
}
}
struct watch_adapter {
struct list_head list;
struct xenbus_watch watch;
struct xenbus_file_priv *dev_data;
char *token;
};
static void free_watch_adapter(struct watch_adapter *watch)
{
kfree(watch->watch.node);
kfree(watch->token);
kfree(watch);
}
static struct watch_adapter *alloc_watch_adapter(const char *path,
const char *token)
{
struct watch_adapter *watch;
watch = kzalloc(sizeof(*watch), GFP_KERNEL);
if (watch == NULL)
goto out_fail;
watch->watch.node = kstrdup(path, GFP_KERNEL);
if (watch->watch.node == NULL)
goto out_free;
watch->token = kstrdup(token, GFP_KERNEL);
if (watch->token == NULL)
goto out_free;
return watch;
out_free:
free_watch_adapter(watch);
out_fail:
return NULL;
}
static void watch_fired(struct xenbus_watch *watch,
const char **vec,
unsigned int len)
{
struct watch_adapter *adap;
struct xsd_sockmsg hdr;
const char *path, *token;
int path_len, tok_len, body_len, data_len = 0;
int ret;
LIST_HEAD(staging_q);
adap = container_of(watch, struct watch_adapter, watch);
path = vec[XS_WATCH_PATH];
token = adap->token;
path_len = strlen(path) + 1;
tok_len = strlen(token) + 1;
if (len > 2)
data_len = vec[len] - vec[2] + 1;
body_len = path_len + tok_len + data_len;
hdr.type = XS_WATCH_EVENT;
hdr.len = body_len;
mutex_lock(&adap->dev_data->reply_mutex);
ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
if (!ret)
ret = queue_reply(&staging_q, path, path_len);
if (!ret)
ret = queue_reply(&staging_q, token, tok_len);
if (!ret && len > 2)
ret = queue_reply(&staging_q, vec[2], data_len);
if (!ret) {
/* success: pass reply list onto watcher */
list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
wake_up(&adap->dev_data->read_waitq);
} else
queue_cleanup(&staging_q);
mutex_unlock(&adap->dev_data->reply_mutex);
}
static int xenbus_write_transaction(unsigned msg_type,
struct xenbus_file_priv *u)
{
int rc, ret;
void *reply;
struct xenbus_transaction_holder *trans = NULL;
LIST_HEAD(staging_q);
if (msg_type == XS_TRANSACTION_START) {
trans = kmalloc(sizeof(*trans), GFP_KERNEL);
if (!trans) {
rc = -ENOMEM;
goto out;
}
}
reply = xenbus_dev_request_and_reply(&u->u.msg);
if (IS_ERR(reply)) {
kfree(trans);
rc = PTR_ERR(reply);
goto out;
}
if (msg_type == XS_TRANSACTION_START) {
trans->handle.id = simple_strtoul(reply, NULL, 0);
list_add(&trans->list, &u->transactions);
} else if (msg_type == XS_TRANSACTION_END) {
list_for_each_entry(trans, &u->transactions, list)
if (trans->handle.id == u->u.msg.tx_id)
break;
BUG_ON(&trans->list == &u->transactions);
list_del(&trans->list);
kfree(trans);
}
mutex_lock(&u->reply_mutex);
ret = queue_reply(&staging_q, &u->u.msg, sizeof(u->u.msg));
if (!ret)
ret = queue_reply(&staging_q, reply, u->u.msg.len);
if (!ret) {
list_splice_tail(&staging_q, &u->read_buffers);
wake_up(&u->read_waitq);
} else {
queue_cleanup(&staging_q);
rc = ret;
}
mutex_unlock(&u->reply_mutex);
kfree(reply);
out:
return rc;
}
static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
{
struct watch_adapter *watch, *tmp_watch;
char *path, *token;
int err, rc;
LIST_HEAD(staging_q);
path = u->u.buffer + sizeof(u->u.msg);
token = memchr(path, 0, u->u.msg.len);
if (token == NULL) {
rc = -EILSEQ;
goto out;
}
token++;
if (msg_type == XS_WATCH) {
watch = alloc_watch_adapter(path, token);
if (watch == NULL) {
rc = -ENOMEM;
goto out;
}
watch->watch.callback = watch_fired;
watch->dev_data = u;
err = register_xenbus_watch(&watch->watch);
if (err) {
free_watch_adapter(watch);
rc = err;
goto out;
}
list_add(&watch->list, &u->watches);
} else {
list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
if (!strcmp(watch->token, token) &&
!strcmp(watch->watch.node, path)) {
unregister_xenbus_watch(&watch->watch);
list_del(&watch->list);
free_watch_adapter(watch);
break;
}
}
}
/* Success. Synthesize a reply to say all is OK. */
{
struct {
struct xsd_sockmsg hdr;
char body[3];
} __packed reply = {
{
.type = msg_type,
.len = sizeof(reply.body)
},
"OK"
};
mutex_lock(&u->reply_mutex);
rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));
mutex_unlock(&u->reply_mutex);
}
out:
return rc;
}
static ssize_t xenbus_file_write(struct file *filp,
const char __user *ubuf,
size_t len, loff_t *ppos)
{
struct xenbus_file_priv *u = filp->private_data;
uint32_t msg_type;
int rc = len;
int ret;
LIST_HEAD(staging_q);
/*
* We're expecting usermode to be writing properly formed
* xenbus messages. If they write an incomplete message we
* buffer it up. Once it is complete, we act on it.
*/
/*
* Make sure concurrent writers can't stomp all over each
* other's messages and make a mess of our partial message
* buffer. We don't make any attemppt to stop multiple
* writers from making a mess of each other's incomplete
* messages; we're just trying to guarantee our own internal
* consistency and make sure that single writes are handled
* atomically.
*/
mutex_lock(&u->msgbuffer_mutex);
/* Get this out of the way early to avoid confusion */
if (len == 0)
goto out;
/* Can't write a xenbus message larger we can buffer */
if ((len + u->len) > sizeof(u->u.buffer)) {
/* On error, dump existing buffer */
u->len = 0;
rc = -EINVAL;
goto out;
}
ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
if (ret == len) {
rc = -EFAULT;
goto out;
}
/* Deal with a partial copy. */
len -= ret;
rc = len;
u->len += len;
/* Return if we haven't got a full message yet */
if (u->len < sizeof(u->u.msg))
goto out; /* not even the header yet */
/* If we're expecting a message that's larger than we can
possibly send, dump what we have and return an error. */
if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
rc = -E2BIG;
u->len = 0;
goto out;
}
if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
goto out; /* incomplete data portion */
/*
* OK, now we have a complete message. Do something with it.
*/
msg_type = u->u.msg.type;
switch (msg_type) {
case XS_TRANSACTION_START:
case XS_TRANSACTION_END:
case XS_DIRECTORY:
case XS_READ:
case XS_GET_PERMS:
case XS_RELEASE:
case XS_GET_DOMAIN_PATH:
case XS_WRITE:
case XS_MKDIR:
case XS_RM:
case XS_SET_PERMS:
/* Send out a transaction */
ret = xenbus_write_transaction(msg_type, u);
break;
case XS_WATCH:
case XS_UNWATCH:
/* (Un)Ask for some path to be watched for changes */
ret = xenbus_write_watch(msg_type, u);
break;
default:
ret = -EINVAL;
break;
}
if (ret != 0)
rc = ret;
/* Buffered message consumed */
u->len = 0;
out:
mutex_unlock(&u->msgbuffer_mutex);
return rc;
}
static int xenbus_file_open(struct inode *inode, struct file *filp)
{
struct xenbus_file_priv *u;
if (xen_store_evtchn == 0)
return -ENOENT;
nonseekable_open(inode, filp);
u = kzalloc(sizeof(*u), GFP_KERNEL);
if (u == NULL)
return -ENOMEM;
INIT_LIST_HEAD(&u->transactions);
INIT_LIST_HEAD(&u->watches);
INIT_LIST_HEAD(&u->read_buffers);
init_waitqueue_head(&u->read_waitq);
mutex_init(&u->reply_mutex);
mutex_init(&u->msgbuffer_mutex);
filp->private_data = u;
return 0;
}
static int xenbus_file_release(struct inode *inode, struct file *filp)
{
struct xenbus_file_priv *u = filp->private_data;
struct xenbus_transaction_holder *trans, *tmp;
struct watch_adapter *watch, *tmp_watch;
/*
* No need for locking here because there are no other users,
* by definition.
*/
list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
xenbus_transaction_end(trans->handle, 1);
list_del(&trans->list);
kfree(trans);
}
list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
unregister_xenbus_watch(&watch->watch);
list_del(&watch->list);
free_watch_adapter(watch);
}
kfree(u);
return 0;
}
static unsigned int xenbus_file_poll(struct file *file, poll_table *wait)
{
struct xenbus_file_priv *u = file->private_data;
poll_wait(file, &u->read_waitq, wait);
if (!list_empty(&u->read_buffers))
return POLLIN | POLLRDNORM;
return 0;
}
const struct file_operations xenbus_file_ops = {
.read = xenbus_file_read,
.write = xenbus_file_write,
.open = xenbus_file_open,
.release = xenbus_file_release,
.poll = xenbus_file_poll,
};

6
drivers/xen/xenfs/xenfs.h Normal file
View File

@ -0,0 +1,6 @@
#ifndef _XENFS_XENBUS_H
#define _XENFS_XENBUS_H
extern const struct file_operations xenbus_file_ops;
#endif /* _XENFS_XENBUS_H */

1
include/linux/magic.h
View File

@ -13,6 +13,7 @@
#define EFS_SUPER_MAGIC 0x414A53
#define EXT2_SUPER_MAGIC 0xEF53
#define EXT3_SUPER_MAGIC 0xEF53
#define XENFS_SUPER_MAGIC 0xabba1974
#define EXT4_SUPER_MAGIC 0xEF53
#define HPFS_SUPER_MAGIC 0xf995e849
#define ISOFS_SUPER_MAGIC 0x9660

2
include/xen/xenbus.h
View File

@ -136,8 +136,6 @@ struct xenbus_transaction
/* Nil transaction ID. */
#define XBT_NIL ((struct xenbus_transaction) { 0 })
int __init xenbus_dev_init(void);
char **xenbus_directory(struct xenbus_transaction t,
const char *dir, const char *node, unsigned int *num);
void *xenbus_read(struct xenbus_transaction t,