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725 lines
17 KiB
725 lines
17 KiB
/* |
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* Driver giving user-space access to the kernel's xenbus connection |
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* to xenstore. |
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* |
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* Copyright (c) 2005, Christian Limpach |
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* Copyright (c) 2005, Rusty Russell, IBM Corporation |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU General Public License version 2 |
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* as published by the Free Software Foundation; or, when distributed |
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* separately from the Linux kernel or incorporated into other |
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* software packages, subject to the following license: |
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* |
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* Permission is hereby granted, free of charge, to any person obtaining a copy |
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* of this source file (the "Software"), to deal in the Software without |
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* restriction, including without limitation the rights to use, copy, modify, |
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* merge, publish, distribute, sublicense, and/or sell copies of the Software, |
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* and to permit persons to whom the Software is furnished to do so, subject to |
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* the following conditions: |
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* |
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* The above copyright notice and this permission notice shall be included in |
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* all copies or substantial portions of the Software. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS |
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* IN THE SOFTWARE. |
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* |
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* Changes: |
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* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem |
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* and /proc/xen compatibility mount point. |
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* Turned xenfs into a loadable module. |
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*/ |
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|
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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|
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#include <linux/kernel.h> |
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#include <linux/errno.h> |
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#include <linux/uio.h> |
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#include <linux/notifier.h> |
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#include <linux/wait.h> |
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#include <linux/fs.h> |
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#include <linux/poll.h> |
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#include <linux/mutex.h> |
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#include <linux/sched.h> |
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#include <linux/spinlock.h> |
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#include <linux/mount.h> |
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#include <linux/pagemap.h> |
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#include <linux/uaccess.h> |
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#include <linux/init.h> |
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#include <linux/namei.h> |
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#include <linux/string.h> |
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#include <linux/slab.h> |
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#include <linux/miscdevice.h> |
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#include <linux/workqueue.h> |
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|
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#include <xen/xenbus.h> |
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#include <xen/xen.h> |
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#include <asm/xen/hypervisor.h> |
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#include "xenbus.h" |
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|
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unsigned int xb_dev_generation_id; |
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|
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/* |
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* An element of a list of outstanding transactions, for which we're |
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* still waiting a reply. |
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*/ |
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struct xenbus_transaction_holder { |
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struct list_head list; |
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struct xenbus_transaction handle; |
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unsigned int generation_id; |
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}; |
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|
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/* |
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* A buffer of data on the queue. |
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*/ |
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struct read_buffer { |
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struct list_head list; |
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unsigned int cons; |
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unsigned int len; |
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char msg[]; |
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}; |
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struct xenbus_file_priv { |
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/* |
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* msgbuffer_mutex is held while partial requests are built up |
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* and complete requests are acted on. It therefore protects |
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* the "transactions" and "watches" lists, and the partial |
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* request length and buffer. |
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* |
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* reply_mutex protects the reply being built up to return to |
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* usermode. It nests inside msgbuffer_mutex but may be held |
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* alone during a watch callback. |
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*/ |
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struct mutex msgbuffer_mutex; |
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|
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/* In-progress transactions */ |
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struct list_head transactions; |
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/* Active watches. */ |
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struct list_head watches; |
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/* Partial request. */ |
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unsigned int len; |
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union { |
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struct xsd_sockmsg msg; |
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char buffer[XENSTORE_PAYLOAD_MAX]; |
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} u; |
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/* Response queue. */ |
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struct mutex reply_mutex; |
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struct list_head read_buffers; |
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wait_queue_head_t read_waitq; |
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struct kref kref; |
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struct work_struct wq; |
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}; |
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|
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/* Read out any raw xenbus messages queued up. */ |
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static ssize_t xenbus_file_read(struct file *filp, |
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char __user *ubuf, |
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size_t len, loff_t *ppos) |
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{ |
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struct xenbus_file_priv *u = filp->private_data; |
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struct read_buffer *rb; |
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unsigned i; |
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int ret; |
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mutex_lock(&u->reply_mutex); |
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again: |
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while (list_empty(&u->read_buffers)) { |
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mutex_unlock(&u->reply_mutex); |
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if (filp->f_flags & O_NONBLOCK) |
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return -EAGAIN; |
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ret = wait_event_interruptible(u->read_waitq, |
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!list_empty(&u->read_buffers)); |
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if (ret) |
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return ret; |
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mutex_lock(&u->reply_mutex); |
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} |
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rb = list_entry(u->read_buffers.next, struct read_buffer, list); |
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i = 0; |
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while (i < len) { |
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unsigned sz = min((unsigned)len - i, rb->len - rb->cons); |
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ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz); |
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i += sz - ret; |
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rb->cons += sz - ret; |
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if (ret != 0) { |
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if (i == 0) |
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i = -EFAULT; |
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goto out; |
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} |
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/* Clear out buffer if it has been consumed */ |
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if (rb->cons == rb->len) { |
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list_del(&rb->list); |
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kfree(rb); |
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if (list_empty(&u->read_buffers)) |
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break; |
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rb = list_entry(u->read_buffers.next, |
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struct read_buffer, list); |
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} |
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} |
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if (i == 0) |
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goto again; |
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out: |
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mutex_unlock(&u->reply_mutex); |
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return i; |
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} |
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/* |
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* Add a buffer to the queue. Caller must hold the appropriate lock |
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* if the queue is not local. (Commonly the caller will build up |
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* multiple queued buffers on a temporary local list, and then add it |
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* to the appropriate list under lock once all the buffers have een |
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* successfully allocated.) |
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*/ |
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static int queue_reply(struct list_head *queue, const void *data, size_t len) |
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{ |
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struct read_buffer *rb; |
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|
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if (len == 0) |
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return 0; |
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if (len > XENSTORE_PAYLOAD_MAX) |
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return -EINVAL; |
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rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL); |
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if (rb == NULL) |
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return -ENOMEM; |
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rb->cons = 0; |
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rb->len = len; |
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memcpy(rb->msg, data, len); |
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list_add_tail(&rb->list, queue); |
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return 0; |
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} |
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/* |
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* Free all the read_buffer s on a list. |
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* Caller must have sole reference to list. |
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*/ |
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static void queue_cleanup(struct list_head *list) |
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{ |
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struct read_buffer *rb; |
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while (!list_empty(list)) { |
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rb = list_entry(list->next, struct read_buffer, list); |
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list_del(list->next); |
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kfree(rb); |
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} |
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} |
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struct watch_adapter { |
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struct list_head list; |
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struct xenbus_watch watch; |
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struct xenbus_file_priv *dev_data; |
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char *token; |
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}; |
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static void free_watch_adapter(struct watch_adapter *watch) |
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{ |
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kfree(watch->watch.node); |
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kfree(watch->token); |
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kfree(watch); |
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} |
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static struct watch_adapter *alloc_watch_adapter(const char *path, |
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const char *token) |
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{ |
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struct watch_adapter *watch; |
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watch = kzalloc(sizeof(*watch), GFP_KERNEL); |
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if (watch == NULL) |
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goto out_fail; |
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watch->watch.node = kstrdup(path, GFP_KERNEL); |
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if (watch->watch.node == NULL) |
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goto out_free; |
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watch->token = kstrdup(token, GFP_KERNEL); |
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if (watch->token == NULL) |
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goto out_free; |
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return watch; |
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out_free: |
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free_watch_adapter(watch); |
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out_fail: |
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return NULL; |
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} |
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static void watch_fired(struct xenbus_watch *watch, |
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const char *path, |
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const char *token) |
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{ |
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struct watch_adapter *adap; |
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struct xsd_sockmsg hdr; |
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const char *token_caller; |
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int path_len, tok_len, body_len; |
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int ret; |
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LIST_HEAD(staging_q); |
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adap = container_of(watch, struct watch_adapter, watch); |
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token_caller = adap->token; |
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path_len = strlen(path) + 1; |
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tok_len = strlen(token_caller) + 1; |
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body_len = path_len + tok_len; |
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hdr.type = XS_WATCH_EVENT; |
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hdr.len = body_len; |
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mutex_lock(&adap->dev_data->reply_mutex); |
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ret = queue_reply(&staging_q, &hdr, sizeof(hdr)); |
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if (!ret) |
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ret = queue_reply(&staging_q, path, path_len); |
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if (!ret) |
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ret = queue_reply(&staging_q, token_caller, tok_len); |
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if (!ret) { |
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/* success: pass reply list onto watcher */ |
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list_splice_tail(&staging_q, &adap->dev_data->read_buffers); |
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wake_up(&adap->dev_data->read_waitq); |
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} else |
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queue_cleanup(&staging_q); |
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mutex_unlock(&adap->dev_data->reply_mutex); |
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} |
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static void xenbus_worker(struct work_struct *wq) |
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{ |
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struct xenbus_file_priv *u; |
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struct xenbus_transaction_holder *trans, *tmp; |
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struct watch_adapter *watch, *tmp_watch; |
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struct read_buffer *rb, *tmp_rb; |
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u = container_of(wq, struct xenbus_file_priv, wq); |
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/* |
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* No need for locking here because there are no other users, |
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* by definition. |
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*/ |
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list_for_each_entry_safe(trans, tmp, &u->transactions, list) { |
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xenbus_transaction_end(trans->handle, 1); |
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list_del(&trans->list); |
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kfree(trans); |
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} |
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list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) { |
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unregister_xenbus_watch(&watch->watch); |
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list_del(&watch->list); |
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free_watch_adapter(watch); |
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} |
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list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) { |
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list_del(&rb->list); |
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kfree(rb); |
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} |
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kfree(u); |
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} |
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static void xenbus_file_free(struct kref *kref) |
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{ |
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struct xenbus_file_priv *u; |
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/* |
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* We might be called in xenbus_thread(). |
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* Use workqueue to avoid deadlock. |
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*/ |
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u = container_of(kref, struct xenbus_file_priv, kref); |
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schedule_work(&u->wq); |
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} |
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static struct xenbus_transaction_holder *xenbus_get_transaction( |
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struct xenbus_file_priv *u, uint32_t tx_id) |
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{ |
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struct xenbus_transaction_holder *trans; |
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list_for_each_entry(trans, &u->transactions, list) |
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if (trans->handle.id == tx_id) |
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return trans; |
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return NULL; |
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} |
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void xenbus_dev_queue_reply(struct xb_req_data *req) |
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{ |
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struct xenbus_file_priv *u = req->par; |
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struct xenbus_transaction_holder *trans = NULL; |
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int rc; |
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LIST_HEAD(staging_q); |
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xs_request_exit(req); |
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mutex_lock(&u->msgbuffer_mutex); |
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if (req->type == XS_TRANSACTION_START) { |
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trans = xenbus_get_transaction(u, 0); |
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if (WARN_ON(!trans)) |
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goto out; |
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if (req->msg.type == XS_ERROR) { |
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list_del(&trans->list); |
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kfree(trans); |
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} else { |
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rc = kstrtou32(req->body, 10, &trans->handle.id); |
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if (WARN_ON(rc)) |
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goto out; |
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} |
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} else if (req->type == XS_TRANSACTION_END) { |
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trans = xenbus_get_transaction(u, req->msg.tx_id); |
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if (WARN_ON(!trans)) |
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goto out; |
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list_del(&trans->list); |
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kfree(trans); |
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} |
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mutex_unlock(&u->msgbuffer_mutex); |
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mutex_lock(&u->reply_mutex); |
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rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg)); |
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if (!rc) |
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rc = queue_reply(&staging_q, req->body, req->msg.len); |
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if (!rc) { |
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list_splice_tail(&staging_q, &u->read_buffers); |
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wake_up(&u->read_waitq); |
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} else { |
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queue_cleanup(&staging_q); |
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} |
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mutex_unlock(&u->reply_mutex); |
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kfree(req->body); |
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kfree(req); |
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kref_put(&u->kref, xenbus_file_free); |
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return; |
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out: |
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mutex_unlock(&u->msgbuffer_mutex); |
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} |
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static int xenbus_command_reply(struct xenbus_file_priv *u, |
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unsigned int msg_type, const char *reply) |
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{ |
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struct { |
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struct xsd_sockmsg hdr; |
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char body[16]; |
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} msg; |
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int rc; |
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|
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msg.hdr = u->u.msg; |
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msg.hdr.type = msg_type; |
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msg.hdr.len = strlen(reply) + 1; |
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if (msg.hdr.len > sizeof(msg.body)) |
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return -E2BIG; |
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memcpy(&msg.body, reply, msg.hdr.len); |
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mutex_lock(&u->reply_mutex); |
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rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len); |
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wake_up(&u->read_waitq); |
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mutex_unlock(&u->reply_mutex); |
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|
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if (!rc) |
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kref_put(&u->kref, xenbus_file_free); |
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return rc; |
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} |
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static int xenbus_write_transaction(unsigned msg_type, |
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struct xenbus_file_priv *u) |
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{ |
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int rc; |
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struct xenbus_transaction_holder *trans = NULL; |
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struct { |
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struct xsd_sockmsg hdr; |
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char body[]; |
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} *msg = (void *)u->u.buffer; |
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|
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if (msg_type == XS_TRANSACTION_START) { |
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trans = kzalloc(sizeof(*trans), GFP_KERNEL); |
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if (!trans) { |
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rc = -ENOMEM; |
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goto out; |
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} |
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trans->generation_id = xb_dev_generation_id; |
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list_add(&trans->list, &u->transactions); |
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} else if (msg->hdr.tx_id != 0 && |
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!xenbus_get_transaction(u, msg->hdr.tx_id)) |
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return xenbus_command_reply(u, XS_ERROR, "ENOENT"); |
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else if (msg_type == XS_TRANSACTION_END && |
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!(msg->hdr.len == 2 && |
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(!strcmp(msg->body, "T") || !strcmp(msg->body, "F")))) |
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return xenbus_command_reply(u, XS_ERROR, "EINVAL"); |
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else if (msg_type == XS_TRANSACTION_END) { |
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trans = xenbus_get_transaction(u, msg->hdr.tx_id); |
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if (trans && trans->generation_id != xb_dev_generation_id) { |
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list_del(&trans->list); |
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kfree(trans); |
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if (!strcmp(msg->body, "T")) |
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return xenbus_command_reply(u, XS_ERROR, |
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"EAGAIN"); |
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else |
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return xenbus_command_reply(u, |
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XS_TRANSACTION_END, |
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"OK"); |
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} |
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} |
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rc = xenbus_dev_request_and_reply(&msg->hdr, u); |
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if (rc && trans) { |
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list_del(&trans->list); |
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kfree(trans); |
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} |
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|
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out: |
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return rc; |
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} |
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|
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static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u) |
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{ |
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struct watch_adapter *watch; |
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char *path, *token; |
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int err, rc; |
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|
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path = u->u.buffer + sizeof(u->u.msg); |
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token = memchr(path, 0, u->u.msg.len); |
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if (token == NULL) { |
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rc = xenbus_command_reply(u, XS_ERROR, "EINVAL"); |
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goto out; |
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} |
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token++; |
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if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) { |
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rc = xenbus_command_reply(u, XS_ERROR, "EINVAL"); |
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goto out; |
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} |
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|
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if (msg_type == XS_WATCH) { |
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watch = alloc_watch_adapter(path, token); |
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if (watch == NULL) { |
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rc = -ENOMEM; |
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goto out; |
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} |
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|
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watch->watch.callback = watch_fired; |
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watch->dev_data = u; |
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err = register_xenbus_watch(&watch->watch); |
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if (err) { |
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free_watch_adapter(watch); |
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rc = err; |
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goto out; |
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} |
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list_add(&watch->list, &u->watches); |
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} else { |
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list_for_each_entry(watch, &u->watches, list) { |
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if (!strcmp(watch->token, token) && |
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!strcmp(watch->watch.node, path)) { |
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unregister_xenbus_watch(&watch->watch); |
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list_del(&watch->list); |
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free_watch_adapter(watch); |
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break; |
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} |
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} |
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} |
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/* Success. Synthesize a reply to say all is OK. */ |
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rc = xenbus_command_reply(u, msg_type, "OK"); |
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|
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out: |
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return rc; |
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} |
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static ssize_t xenbus_file_write(struct file *filp, |
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const char __user *ubuf, |
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size_t len, loff_t *ppos) |
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{ |
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struct xenbus_file_priv *u = filp->private_data; |
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uint32_t msg_type; |
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int rc = len; |
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int ret; |
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|
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/* |
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* We're expecting usermode to be writing properly formed |
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* xenbus messages. If they write an incomplete message we |
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* buffer it up. Once it is complete, we act on it. |
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*/ |
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|
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/* |
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* Make sure concurrent writers can't stomp all over each |
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* other's messages and make a mess of our partial message |
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* buffer. We don't make any attemppt to stop multiple |
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* writers from making a mess of each other's incomplete |
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* messages; we're just trying to guarantee our own internal |
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* consistency and make sure that single writes are handled |
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* atomically. |
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*/ |
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mutex_lock(&u->msgbuffer_mutex); |
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|
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/* Get this out of the way early to avoid confusion */ |
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if (len == 0) |
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goto out; |
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|
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/* Can't write a xenbus message larger we can buffer */ |
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if (len > sizeof(u->u.buffer) - u->len) { |
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/* On error, dump existing buffer */ |
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u->len = 0; |
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rc = -EINVAL; |
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goto out; |
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} |
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|
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ret = copy_from_user(u->u.buffer + u->len, ubuf, len); |
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|
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if (ret != 0) { |
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rc = -EFAULT; |
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goto out; |
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} |
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|
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/* Deal with a partial copy. */ |
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len -= ret; |
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rc = len; |
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|
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u->len += len; |
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|
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/* Return if we haven't got a full message yet */ |
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if (u->len < sizeof(u->u.msg)) |
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goto out; /* not even the header yet */ |
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|
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/* If we're expecting a message that's larger than we can |
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possibly send, dump what we have and return an error. */ |
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if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) { |
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rc = -E2BIG; |
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u->len = 0; |
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goto out; |
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} |
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|
|
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; |
|
|
|
stream_open(inode, filp); |
|
|
|
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); |
|
INIT_WORK(&u->wq, xenbus_worker); |
|
|
|
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 __poll_t 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 EPOLLIN | EPOLLRDNORM; |
|
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);
|
|
|