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    Subject[PATCH 3/6] xen: Add xenbus_backend device
    Date
    Access for xenstored to the event channel and pre-allocated ring is
    managed via xenfs. This adds its own character device featuring mmap
    for the ring and an ioctl for the event channel.

    Signed-off-by: Bastian Blank <waldi@debian.org>
    Acked-by: Ian Campbell <ian.campbell@citrix.com>
    ---
    drivers/xen/xenbus/Makefile | 1 +
    drivers/xen/xenbus/xenbus_dev_backend.c | 89 +++++++++++++++++++++++++++++++
    include/xen/xenbus_dev.h | 41 ++++++++++++++
    3 files changed, 131 insertions(+), 0 deletions(-)
    create mode 100644 drivers/xen/xenbus/xenbus_dev_backend.c
    create mode 100644 include/xen/xenbus_dev.h

    diff --git a/drivers/xen/xenbus/Makefile b/drivers/xen/xenbus/Makefile
    index a2ea363..31e2e90 100644
    --- a/drivers/xen/xenbus/Makefile
    +++ b/drivers/xen/xenbus/Makefile
    @@ -10,4 +10,5 @@ xenbus-objs += xenbus_probe.o
    xenbus-be-objs-$(CONFIG_XEN_BACKEND) += xenbus_probe_backend.o
    xenbus-objs += $(xenbus-be-objs-y)

    +obj-$(CONFIG_XEN_BACKEND) += xenbus_dev_backend.o
    obj-$(CONFIG_XEN_XENBUS_FRONTEND) += xenbus_probe_frontend.o
    diff --git a/drivers/xen/xenbus/xenbus_dev_backend.c b/drivers/xen/xenbus/xenbus_dev_backend.c
    new file mode 100644
    index 0000000..a2092bd
    --- /dev/null
    +++ b/drivers/xen/xenbus/xenbus_dev_backend.c
    @@ -0,0 +1,89 @@
    +#include <linux/slab.h>
    +#include <linux/types.h>
    +#include <linux/mm.h>
    +#include <linux/fs.h>
    +#include <linux/miscdevice.h>
    +#include <linux/module.h>
    +#include <linux/capability.h>
    +
    +#include <xen/page.h>
    +#include <xen/xenbus_dev.h>
    +
    +#include "xenbus_comms.h"
    +
    +MODULE_LICENSE("GPL");
    +
    +static int xenbus_backend_open(struct inode *inode, struct file *filp)
    +{
    + if (!capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    + return nonseekable_open(inode, filp);
    +}
    +
    +static long xenbus_backend_ioctl(struct file *file, unsigned int cmd, unsigned long data)
    +{
    + if (!capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    + switch (cmd) {
    + case IOCTL_XENBUS_BACKEND_EVTCHN:
    + if (xen_store_evtchn > 0)
    + return xen_store_evtchn;
    + return -ENODEV;
    +
    + default:
    + return -ENOTTY;
    + }
    +}
    +
    +static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
    +{
    + size_t size = vma->vm_end - vma->vm_start;
    +
    + if (!capable(CAP_SYS_ADMIN))
    + return -EPERM;
    +
    + if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
    + return -EINVAL;
    +
    + if (remap_pfn_range(vma, vma->vm_start,
    + virt_to_pfn(xen_store_interface),
    + size, vma->vm_page_prot))
    + return -EAGAIN;
    +
    + return 0;
    +}
    +
    +const struct file_operations xenbus_backend_fops = {
    + .open = xenbus_backend_open,
    + .mmap = xenbus_backend_mmap,
    + .unlocked_ioctl = xenbus_backend_ioctl,
    +};
    +
    +static struct miscdevice xenbus_backend_dev = {
    + .minor = MISC_DYNAMIC_MINOR,
    + .name = "xen/xenbus_backend",
    + .fops = &xenbus_backend_fops,
    +};
    +
    +static int __init xenbus_backend_init(void)
    +{
    + int err;
    +
    + if (!xen_initial_domain())
    + return -ENODEV;
    +
    + err = misc_register(&xenbus_backend_dev);
    + if (err)
    + printk(KERN_ERR "Could not register xenbus backend device\n");
    + return err;
    +}
    +
    +static void __exit xenbus_backend_exit(void)
    +{
    + misc_deregister(&xenbus_backend_dev);
    +}
    +
    +module_init(xenbus_backend_init);
    +module_exit(xenbus_backend_exit);
    diff --git a/include/xen/xenbus_dev.h b/include/xen/xenbus_dev.h
    new file mode 100644
    index 0000000..ac5f0fe
    --- /dev/null
    +++ b/include/xen/xenbus_dev.h
    @@ -0,0 +1,41 @@
    +/******************************************************************************
    + * evtchn.h
    + *
    + * Interface to /dev/xen/xenbus_backend.
    + *
    + * Copyright (c) 2011 Bastian Blank <waldi@debian.org>
    + *
    + * 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.
    + */
    +
    +#ifndef __LINUX_XEN_XENBUS_DEV_H__
    +#define __LINUX_XEN_XENBUS_DEV_H__
    +
    +#include <linux/ioctl.h>
    +
    +#define IOCTL_XENBUS_BACKEND_EVTCHN \
    + _IOC(_IOC_NONE, 'B', 0, 0)
    +
    +#endif /* __LINUX_XEN_XENBUS_DEV_H__ */
    --
    1.7.7.3


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