[mirror_ubuntu-artful-kernel.git] / drivers / xen / xenbus / xenbus_dev_frontend.c

/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/sched.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 <linux/slab.h>
#include <linux/miscdevice.h>
#include <linux/init.h>

#include <xen/xenbus.h>
#include <xen/xen.h>
#include <asm/xen/hypervisor.h>

#include "xenbus.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[XENSTORE_PAYLOAD_MAX];
	} u;

	/* Response queue. */
	struct mutex reply_mutex;
	struct list_head read_buffers;
	wait_queue_head_t read_waitq;

	struct kref kref;
};

/* 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);
again:
	while (list_empty(&u->read_buffers)) {
		mutex_unlock(&u->reply_mutex);
		if (filp->f_flags & O_NONBLOCK)
			return -EAGAIN;

		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 != 0) {
			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);
		}
	}
	if (i == 0)
		goto again;

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;
	if (len > XENSTORE_PAYLOAD_MAX)
		return -EINVAL;

	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 *path,
			const char *token)
{
	struct watch_adapter *adap;
	struct xsd_sockmsg hdr;
	const char *token_caller;
	int path_len, tok_len, body_len;
	int ret;
	LIST_HEAD(staging_q);

	adap = container_of(watch, struct watch_adapter, watch);

	token_caller = adap->token;

	path_len = strlen(path) + 1;
	tok_len = strlen(token_caller) + 1;
	body_len = path_len + tok_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_caller, tok_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 void xenbus_file_free(struct kref *kref)
{
	struct xenbus_file_priv *u;
	struct xenbus_transaction_holder *trans, *tmp;
	struct watch_adapter *watch, *tmp_watch;
	struct read_buffer *rb, *tmp_rb;

	u = container_of(kref, struct xenbus_file_priv, kref);

	/*
	 * 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);
	}

	list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
		list_del(&rb->list);
		kfree(rb);
	}
	kfree(u);
}

static struct xenbus_transaction_holder *xenbus_get_transaction(
	struct xenbus_file_priv *u, uint32_t tx_id)
{
	struct xenbus_transaction_holder *trans;

	list_for_each_entry(trans, &u->transactions, list)
		if (trans->handle.id == tx_id)
			return trans;

	return NULL;
}

void xenbus_dev_queue_reply(struct xb_req_data *req)
{
	struct xenbus_file_priv *u = req->par;
	struct xenbus_transaction_holder *trans = NULL;
	int rc;
	LIST_HEAD(staging_q);

	xs_request_exit(req);

	mutex_lock(&u->msgbuffer_mutex);

	if (req->type == XS_TRANSACTION_START) {
		trans = xenbus_get_transaction(u, 0);
		if (WARN_ON(!trans))
			goto out;
		if (req->msg.type == XS_ERROR) {
			list_del(&trans->list);
			kfree(trans);
		} else {
			rc = kstrtou32(req->body, 10, &trans->handle.id);
			if (WARN_ON(rc))
				goto out;
		}
	} else if (req->msg.type == XS_TRANSACTION_END) {
		trans = xenbus_get_transaction(u, req->msg.tx_id);
		if (WARN_ON(!trans))
			goto out;
		list_del(&trans->list);
		kfree(trans);
	}

	mutex_unlock(&u->msgbuffer_mutex);

	mutex_lock(&u->reply_mutex);
	rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
	if (!rc)
		rc = queue_reply(&staging_q, req->body, req->msg.len);
	if (!rc) {
		list_splice_tail(&staging_q, &u->read_buffers);
		wake_up(&u->read_waitq);
	} else {
		queue_cleanup(&staging_q);
	}
	mutex_unlock(&u->reply_mutex);

	kfree(req->body);
	kfree(req);

	kref_put(&u->kref, xenbus_file_free);

	return;

 out:
	mutex_unlock(&u->msgbuffer_mutex);
}

static int xenbus_command_reply(struct xenbus_file_priv *u,
				unsigned int msg_type, const char *reply)
{
	struct {
		struct xsd_sockmsg hdr;
		const char body[16];
	} msg;
	int rc;

	msg.hdr = u->u.msg;
	msg.hdr.type = msg_type;
	msg.hdr.len = strlen(reply) + 1;
	if (msg.hdr.len > sizeof(msg.body))
		return -E2BIG;

	mutex_lock(&u->reply_mutex);
	rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
	wake_up(&u->read_waitq);
	mutex_unlock(&u->reply_mutex);

	if (!rc)
		kref_put(&u->kref, xenbus_file_free);

	return rc;
}

static int xenbus_write_transaction(unsigned msg_type,
				    struct xenbus_file_priv *u)
{
	int rc;
	struct xenbus_transaction_holder *trans = NULL;

	if (msg_type == XS_TRANSACTION_START) {
		trans = kzalloc(sizeof(*trans), GFP_KERNEL);
		if (!trans) {
			rc = -ENOMEM;
			goto out;
		}
		list_add(&trans->list, &u->transactions);
	} else if (u->u.msg.tx_id != 0 &&
		   !xenbus_get_transaction(u, u->u.msg.tx_id))
		return xenbus_command_reply(u, XS_ERROR, "ENOENT");

	rc = xenbus_dev_request_and_reply(&u->u.msg, u);
	if (rc)
		kfree(trans);

out:
	return rc;
}

static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
{
	struct watch_adapter *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 = xenbus_command_reply(u, XS_ERROR, "EINVAL");
		goto out;
	}
	token++;
	if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
		rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
		goto out;
	}

	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(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. */
	rc = xenbus_command_reply(u, msg_type, "OK");

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 > sizeof(u->u.buffer) - u->len) {
		/* 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 != 0) {
		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.
	 */

	kref_get(&u->kref);

	msg_type = u->u.msg.type;

	switch (msg_type) {
	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:
		/* Send out a transaction */
		ret = xenbus_write_transaction(msg_type, u);
		break;
	}
	if (ret != 0) {
		rc = ret;
		kref_put(&u->kref, xenbus_file_free);
	}

	/* 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);

	filp->f_mode &= ~FMODE_ATOMIC_POS; /* cdev-style semantics */

	u = kzalloc(sizeof(*u), GFP_KERNEL);
	if (u == NULL)
		return -ENOMEM;

	kref_init(&u->kref);

	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;

	kref_put(&u->kref, xenbus_file_free);

	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 xen_xenbus_fops = {
	.read = xenbus_file_read,
	.write = xenbus_file_write,
	.open = xenbus_file_open,
	.release = xenbus_file_release,
	.poll = xenbus_file_poll,
	.llseek = no_llseek,
};
EXPORT_SYMBOL_GPL(xen_xenbus_fops);

static struct miscdevice xenbus_dev = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "xen/xenbus",
	.fops = &xen_xenbus_fops,
};

static int __init xenbus_init(void)
{
	int err;

	if (!xen_domain())
		return -ENODEV;

	err = misc_register(&xenbus_dev);
	if (err)
		pr_err("Could not register xenbus frontend device\n");
	return err;
}
device_initcall(xenbus_init);
Commit	Line	Data
1107ba88 AZ	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
283c0972 JP	38	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
283c0972 JP	39
1107ba88 AZ	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>
a99bbaf5	48	#include <linux/sched.h>
1107ba88 AZ	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>
5a0e3ad6	56	#include <linux/slab.h>
2fb3683e	57	#include <linux/miscdevice.h>
ab1241a1	58	#include <linux/init.h>
1107ba88	59
1107ba88	60	#include <xen/xenbus.h>
b79d2ff9	61	#include <xen/xen.h>
1107ba88 AZ	62	#include <asm/xen/hypervisor.h>
1107ba88 AZ	63
332f791d JG	64	#include "xenbus.h"
332f791d JG	65
1107ba88 AZ	66	/*
	67	* An element of a list of outstanding transactions, for which we're
	68	* still waiting a reply.
	69	*/
	70	struct xenbus_transaction_holder {
	71	struct list_head list;
	72	struct xenbus_transaction handle;
	73	};
	74
	75	/*
	76	* A buffer of data on the queue.
	77	*/
	78	struct read_buffer {
	79	struct list_head list;
	80	unsigned int cons;
	81	unsigned int len;
	82	char msg[];
	83	};
	84
	85	struct xenbus_file_priv {
	86	/*
	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.
	91	*
	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.
	95	*/
	96	struct mutex msgbuffer_mutex;
	97
	98	/* In-progress transactions */
	99	struct list_head transactions;
	100
	101	/* Active watches. */
	102	struct list_head watches;
	103
	104	/* Partial request. */
	105	unsigned int len;
	106	union {
	107	struct xsd_sockmsg msg;
50bf7379	108	char buffer[XENSTORE_PAYLOAD_MAX];
1107ba88 AZ	109	} u;
	110
	111	/* Response queue. */
	112	struct mutex reply_mutex;
	113	struct list_head read_buffers;
	114	wait_queue_head_t read_waitq;
	115
fd8aa909	116	struct kref kref;
1107ba88 AZ	117	};
	118
	119	/* Read out any raw xenbus messages queued up. */
	120	static ssize_t xenbus_file_read(struct file *filp,
	121	char __user *ubuf,
	122	size_t len, loff_t *ppos)
	123	{
	124	struct xenbus_file_priv *u = filp->private_data;
	125	struct read_buffer *rb;
	126	unsigned i;
	127	int ret;
	128
	129	mutex_lock(&u->reply_mutex);
7808121b	130	again:
1107ba88 AZ	131	while (list_empty(&u->read_buffers)) {
1107ba88 AZ	132	mutex_unlock(&u->reply_mutex);
6280f190 PB	133	if (filp->f_flags & O_NONBLOCK)
	134	return -EAGAIN;
	135
1107ba88 AZ	136	ret = wait_event_interruptible(u->read_waitq,
	137	!list_empty(&u->read_buffers));
	138	if (ret)
	139	return ret;
	140	mutex_lock(&u->reply_mutex);
	141	}
	142
	143	rb = list_entry(u->read_buffers.next, struct read_buffer, list);
	144	i = 0;
	145	while (i < len) {
	146	unsigned sz = min((unsigned)len - i, rb->len - rb->cons);
	147
	148	ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
	149
	150	i += sz - ret;
	151	rb->cons += sz - ret;
	152
fb27cfbc	153	if (ret != 0) {
1107ba88 AZ	154	if (i == 0)
	155	i = -EFAULT;
	156	goto out;
	157	}
	158
	159	/* Clear out buffer if it has been consumed */
	160	if (rb->cons == rb->len) {
	161	list_del(&rb->list);
	162	kfree(rb);
	163	if (list_empty(&u->read_buffers))
	164	break;
	165	rb = list_entry(u->read_buffers.next,
	166	struct read_buffer, list);
	167	}
	168	}
7808121b DDG	169	if (i == 0)
7808121b DDG	170	goto again;
1107ba88 AZ	171
	172	out:
	173	mutex_unlock(&u->reply_mutex);
	174	return i;
	175	}
	176
	177	/*
	178	* Add a buffer to the queue. Caller must hold the appropriate lock
	179	* if the queue is not local. (Commonly the caller will build up
	180	* multiple queued buffers on a temporary local list, and then add it
	181	* to the appropriate list under lock once all the buffers have een
	182	* successfully allocated.)
	183	*/
	184	static int queue_reply(struct list_head queue, const void data, size_t len)
	185	{
	186	struct read_buffer *rb;
	187
	188	if (len == 0)
	189	return 0;
85c0a87c IY	190	if (len > XENSTORE_PAYLOAD_MAX)
85c0a87c IY	191	return -EINVAL;
1107ba88 AZ	192
	193	rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
	194	if (rb == NULL)
	195	return -ENOMEM;
	196
	197	rb->cons = 0;
	198	rb->len = len;
	199
	200	memcpy(rb->msg, data, len);
	201
	202	list_add_tail(&rb->list, queue);
	203	return 0;
	204	}
	205
	206	/*
	207	* Free all the read_buffer s on a list.
	208	* Caller must have sole reference to list.
	209	*/
	210	static void queue_cleanup(struct list_head *list)
	211	{
	212	struct read_buffer *rb;
	213
	214	while (!list_empty(list)) {
	215	rb = list_entry(list->next, struct read_buffer, list);
	216	list_del(list->next);
	217	kfree(rb);
	218	}
	219	}
	220
	221	struct watch_adapter {
	222	struct list_head list;
	223	struct xenbus_watch watch;
	224	struct xenbus_file_priv *dev_data;
	225	char *token;
	226	};
	227
	228	static void free_watch_adapter(struct watch_adapter *watch)
	229	{
	230	kfree(watch->watch.node);
	231	kfree(watch->token);
	232	kfree(watch);
	233	}
	234
	235	static struct watch_adapter alloc_watch_adapter(const char path,
	236	const char *token)
	237	{
	238	struct watch_adapter *watch;
	239
	240	watch = kzalloc(sizeof(*watch), GFP_KERNEL);
	241	if (watch == NULL)
	242	goto out_fail;
	243
	244	watch->watch.node = kstrdup(path, GFP_KERNEL);
	245	if (watch->watch.node == NULL)
	246	goto out_free;
	247
	248	watch->token = kstrdup(token, GFP_KERNEL);
	249	if (watch->token == NULL)
	250	goto out_free;
	251
	252	return watch;
	253
	254	out_free:
	255	free_watch_adapter(watch);
256
257	out_fail:
258	return NULL;
259	}
260
261	static void watch_fired(struct xenbus_watch *watch,
5584ea25 JG	262	const char *path,
5584ea25 JG	263	const char *token)
1107ba88 AZ	264	{
	265	struct watch_adapter *adap;
	266	struct xsd_sockmsg hdr;
5584ea25 JG	267	const char *token_caller;
5584ea25 JG	268	int path_len, tok_len, body_len;
1107ba88 AZ	269	int ret;
	270	LIST_HEAD(staging_q);
	271
	272	adap = container_of(watch, struct watch_adapter, watch);
	273
5584ea25	274	token_caller = adap->token;
1107ba88 AZ	275
1107ba88 AZ	276	path_len = strlen(path) + 1;
5584ea25 JG	277	tok_len = strlen(token_caller) + 1;
5584ea25 JG	278	body_len = path_len + tok_len;
1107ba88 AZ	279
	280	hdr.type = XS_WATCH_EVENT;
	281	hdr.len = body_len;
	282
	283	mutex_lock(&adap->dev_data->reply_mutex);
	284
	285	ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
	286	if (!ret)
	287	ret = queue_reply(&staging_q, path, path_len);
	288	if (!ret)
5584ea25	289	ret = queue_reply(&staging_q, token_caller, tok_len);
1107ba88 AZ	290
	291	if (!ret) {
	292	/* success: pass reply list onto watcher */
	293	list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
	294	wake_up(&adap->dev_data->read_waitq);
	295	} else
	296	queue_cleanup(&staging_q);
	297
	298	mutex_unlock(&adap->dev_data->reply_mutex);
	299	}
	300
fd8aa909 JG	301	static void xenbus_file_free(struct kref *kref)
	302	{
	303	struct xenbus_file_priv *u;
	304	struct xenbus_transaction_holder trans, tmp;
	305	struct watch_adapter watch, tmp_watch;
	306	struct read_buffer rb, tmp_rb;
	307
	308	u = container_of(kref, struct xenbus_file_priv, kref);
	309
	310	/*
	311	* No need for locking here because there are no other users,
	312	* by definition.
	313	*/
	314
	315	list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
	316	xenbus_transaction_end(trans->handle, 1);
	317	list_del(&trans->list);
	318	kfree(trans);
	319	}
	320
	321	list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
	322	unregister_xenbus_watch(&watch->watch);
	323	list_del(&watch->list);
	324	free_watch_adapter(watch);
	325	}
	326
	327	list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
	328	list_del(&rb->list);
	329	kfree(rb);
	330	}
	331	kfree(u);
	332	}
	333
	334	static struct xenbus_transaction_holder *xenbus_get_transaction(
	335	struct xenbus_file_priv *u, uint32_t tx_id)
	336	{
	337	struct xenbus_transaction_holder *trans;
	338
	339	list_for_each_entry(trans, &u->transactions, list)
	340	if (trans->handle.id == tx_id)
	341	return trans;
	342
	343	return NULL;
	344	}
	345
	346	void xenbus_dev_queue_reply(struct xb_req_data *req)
	347	{
	348	struct xenbus_file_priv *u = req->par;
	349	struct xenbus_transaction_holder *trans = NULL;
	350	int rc;
	351	LIST_HEAD(staging_q);
	352
	353	xs_request_exit(req);
	354
	355	mutex_lock(&u->msgbuffer_mutex);
	356
	357	if (req->type == XS_TRANSACTION_START) {
	358	trans = xenbus_get_transaction(u, 0);
	359	if (WARN_ON(!trans))
	360	goto out;
	361	if (req->msg.type == XS_ERROR) {
	362	list_del(&trans->list);
	363	kfree(trans);
	364	} else {
365	rc = kstrtou32(req->body, 10, &trans->handle.id);
366	if (WARN_ON(rc))
367	goto out;
368	}
369	} else if (req->msg.type == XS_TRANSACTION_END) {
370	trans = xenbus_get_transaction(u, req->msg.tx_id);
371	if (WARN_ON(!trans))
372	goto out;
373	list_del(&trans->list);
374	kfree(trans);
375	}
376
377	mutex_unlock(&u->msgbuffer_mutex);
378
379	mutex_lock(&u->reply_mutex);
380	rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
381	if (!rc)
382	rc = queue_reply(&staging_q, req->body, req->msg.len);
383	if (!rc) {
384	list_splice_tail(&staging_q, &u->read_buffers);
385	wake_up(&u->read_waitq);
386	} else {
387	queue_cleanup(&staging_q);
388	}
389	mutex_unlock(&u->reply_mutex);
390
391	kfree(req->body);
392	kfree(req);
393
394	kref_put(&u->kref, xenbus_file_free);
395
396	return;
397
398	out:
399	mutex_unlock(&u->msgbuffer_mutex);
400	}
401
9a6161fe JG	402	static int xenbus_command_reply(struct xenbus_file_priv *u,
	403	unsigned int msg_type, const char *reply)
	404	{
	405	struct {
	406	struct xsd_sockmsg hdr;
	407	const char body[16];
	408	} msg;
	409	int rc;
	410
	411	msg.hdr = u->u.msg;
	412	msg.hdr.type = msg_type;
	413	msg.hdr.len = strlen(reply) + 1;
	414	if (msg.hdr.len > sizeof(msg.body))
	415	return -E2BIG;
	416
	417	mutex_lock(&u->reply_mutex);
	418	rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
	419	wake_up(&u->read_waitq);
	420	mutex_unlock(&u->reply_mutex);
	421
fd8aa909 JG	422	if (!rc)
	423	kref_put(&u->kref, xenbus_file_free);
	424
9a6161fe JG	425	return rc;
	426	}
	427
1107ba88 AZ	428	static int xenbus_write_transaction(unsigned msg_type,
	429	struct xenbus_file_priv *u)
	430	{
e88a0faa	431	int rc;
1107ba88	432	struct xenbus_transaction_holder *trans = NULL;
1107ba88 AZ	433
1107ba88 AZ	434	if (msg_type == XS_TRANSACTION_START) {
fd8aa909	435	trans = kzalloc(sizeof(*trans), GFP_KERNEL);
1107ba88 AZ	436	if (!trans) {
	437	rc = -ENOMEM;
	438	goto out;
	439	}
fd8aa909 JG	440	list_add(&trans->list, &u->transactions);
	441	} else if (u->u.msg.tx_id != 0 &&
	442	!xenbus_get_transaction(u, u->u.msg.tx_id))
	443	return xenbus_command_reply(u, XS_ERROR, "ENOENT");
1107ba88	444
fd8aa909 JG	445	rc = xenbus_dev_request_and_reply(&u->u.msg, u);
fd8aa909 JG	446	if (rc)
1107ba88	447	kfree(trans);
1107ba88 AZ	448
	449	out:
	450	return rc;
	451	}
	452
	453	static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
	454	{
e1e5b3ff	455	struct watch_adapter *watch;
1107ba88 AZ	456	char path, token;
	457	int err, rc;
	458	LIST_HEAD(staging_q);
	459
	460	path = u->u.buffer + sizeof(u->u.msg);
	461	token = memchr(path, 0, u->u.msg.len);
	462	if (token == NULL) {
9a6161fe	463	rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
1107ba88 AZ	464	goto out;
	465	}
	466	token++;
a43a5ccd	467	if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
9a6161fe	468	rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
a43a5ccd JB	469	goto out;
a43a5ccd JB	470	}
1107ba88 AZ	471
	472	if (msg_type == XS_WATCH) {
	473	watch = alloc_watch_adapter(path, token);
	474	if (watch == NULL) {
	475	rc = -ENOMEM;
	476	goto out;
	477	}
	478
	479	watch->watch.callback = watch_fired;
	480	watch->dev_data = u;
	481
	482	err = register_xenbus_watch(&watch->watch);
	483	if (err) {
	484	free_watch_adapter(watch);
	485	rc = err;
	486	goto out;
	487	}
	488	list_add(&watch->list, &u->watches);
	489	} else {
e1e5b3ff	490	list_for_each_entry(watch, &u->watches, list) {
1107ba88 AZ	491	if (!strcmp(watch->token, token) &&
	492	!strcmp(watch->watch.node, path)) {
	493	unregister_xenbus_watch(&watch->watch);
	494	list_del(&watch->list);
	495	free_watch_adapter(watch);
	496	break;
	497	}
	498	}
	499	}
	500
	501	/* Success. Synthesize a reply to say all is OK. */
9a6161fe	502	rc = xenbus_command_reply(u, msg_type, "OK");
1107ba88 AZ	503
	504	out:
	505	return rc;
	506	}
	507
	508	static ssize_t xenbus_file_write(struct file *filp,
	509	const char __user *ubuf,
	510	size_t len, loff_t *ppos)
	511	{
	512	struct xenbus_file_priv *u = filp->private_data;
	513	uint32_t msg_type;
	514	int rc = len;
	515	int ret;
	516	LIST_HEAD(staging_q);
	517
	518	/*
	519	* We're expecting usermode to be writing properly formed
	520	* xenbus messages. If they write an incomplete message we
	521	* buffer it up. Once it is complete, we act on it.
	522	*/
	523
	524	/*
	525	* Make sure concurrent writers can't stomp all over each
	526	* other's messages and make a mess of our partial message
	527	* buffer. We don't make any attemppt to stop multiple
	528	* writers from making a mess of each other's incomplete
	529	* messages; we're just trying to guarantee our own internal
	530	* consistency and make sure that single writes are handled
	531	* atomically.
	532	*/
	533	mutex_lock(&u->msgbuffer_mutex);
	534
	535	/* Get this out of the way early to avoid confusion */
	536	if (len == 0)
	537	goto out;
	538
	539	/* Can't write a xenbus message larger we can buffer */
1bcaba51	540	if (len > sizeof(u->u.buffer) - u->len) {
1107ba88 AZ	541	/* On error, dump existing buffer */
	542	u->len = 0;
	543	rc = -EINVAL;
	544	goto out;
	545	}
	546
	547	ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
	548
fb27cfbc	549	if (ret != 0) {
1107ba88 AZ	550	rc = -EFAULT;
	551	goto out;
	552	}
	553
	554	/* Deal with a partial copy. */
	555	len -= ret;
	556	rc = len;
	557
	558	u->len += len;
	559
	560	/* Return if we haven't got a full message yet */
	561	if (u->len < sizeof(u->u.msg))
	562	goto out; /* not even the header yet */
	563
	564	/* If we're expecting a message that's larger than we can
	565	possibly send, dump what we have and return an error. */
	566	if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
	567	rc = -E2BIG;
	568	u->len = 0;
	569	goto out;
	570	}
	571
	572	if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
	573	goto out; /* incomplete data portion */
	574
	575	/*
	576	* OK, now we have a complete message. Do something with it.
	577	*/
	578
fd8aa909 JG	579	kref_get(&u->kref);
fd8aa909 JG	580
1107ba88 AZ	581	msg_type = u->u.msg.type;
	582
	583	switch (msg_type) {
1107ba88 AZ	584	case XS_WATCH:
	585	case XS_UNWATCH:
	586	/* (Un)Ask for some path to be watched for changes */
	587	ret = xenbus_write_watch(msg_type, u);
	588	break;
	589
	590	default:
6d6df2e4 DO	591	/* Send out a transaction */
6d6df2e4 DO	592	ret = xenbus_write_transaction(msg_type, u);
1107ba88 AZ	593	break;
1107ba88 AZ	594	}
fd8aa909	595	if (ret != 0) {
1107ba88	596	rc = ret;
fd8aa909 JG	597	kref_put(&u->kref, xenbus_file_free);
fd8aa909 JG	598	}
1107ba88 AZ	599
	600	/* Buffered message consumed */
	601	u->len = 0;
	602
	603	out:
	604	mutex_unlock(&u->msgbuffer_mutex);
	605	return rc;
	606	}
	607
	608	static int xenbus_file_open(struct inode inode, struct file filp)
	609	{
	610	struct xenbus_file_priv *u;
	611
	612	if (xen_store_evtchn == 0)
	613	return -ENOENT;
	614
	615	nonseekable_open(inode, filp);
	616
581d21a2 DV	617	filp->f_mode &= ~FMODE_ATOMIC_POS; /* cdev-style semantics */
581d21a2 DV	618
1107ba88 AZ	619	u = kzalloc(sizeof(*u), GFP_KERNEL);
	620	if (u == NULL)
	621	return -ENOMEM;
	622
fd8aa909 JG	623	kref_init(&u->kref);
fd8aa909 JG	624
1107ba88 AZ	625	INIT_LIST_HEAD(&u->transactions);
	626	INIT_LIST_HEAD(&u->watches);
	627	INIT_LIST_HEAD(&u->read_buffers);
	628	init_waitqueue_head(&u->read_waitq);
	629
	630	mutex_init(&u->reply_mutex);
	631	mutex_init(&u->msgbuffer_mutex);
	632
	633	filp->private_data = u;
	634
	635	return 0;
	636	}
	637
	638	static int xenbus_file_release(struct inode inode, struct file filp)
	639	{
	640	struct xenbus_file_priv *u = filp->private_data;
1107ba88	641
fd8aa909	642	kref_put(&u->kref, xenbus_file_free);
1107ba88 AZ	643
	644	return 0;
	645	}
	646
	647	static unsigned int xenbus_file_poll(struct file file, poll_table wait)
	648	{
	649	struct xenbus_file_priv *u = file->private_data;
	650
	651	poll_wait(file, &u->read_waitq, wait);
	652	if (!list_empty(&u->read_buffers))
	653	return POLLIN \| POLLRDNORM;
	654	return 0;
	655	}
	656
2fb3683e	657	const struct file_operations xen_xenbus_fops = {
1107ba88 AZ	658	.read = xenbus_file_read,
	659	.write = xenbus_file_write,
	660	.open = xenbus_file_open,
	661	.release = xenbus_file_release,
	662	.poll = xenbus_file_poll,
6038f373	663	.llseek = no_llseek,
1107ba88	664	};
2fb3683e BB	665	EXPORT_SYMBOL_GPL(xen_xenbus_fops);
	666
	667	static struct miscdevice xenbus_dev = {
	668	.minor = MISC_DYNAMIC_MINOR,
	669	.name = "xen/xenbus",
	670	.fops = &xen_xenbus_fops,
	671	};
	672
	673	static int __init xenbus_init(void)
	674	{
	675	int err;
	676
	677	if (!xen_domain())
	678	return -ENODEV;
	679
	680	err = misc_register(&xenbus_dev);
	681	if (err)
283c0972	682	pr_err("Could not register xenbus frontend device\n");
2fb3683e BB	683	return err;
2fb3683e BB	684	}
ab1241a1	685	device_initcall(xenbus_init);