LXR linux/drivers/xen/xenbus/xenbus_dev

   1#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   2
   3#include <linux/slab.h>
   4#include <linux/types.h>
   5#include <linux/mm.h>
   6#include <linux/fs.h>
   7#include <linux/miscdevice.h>
   8#include <linux/init.h>
   9#include <linux/capability.h>
  10
  11#include <xen/xen.h>
  12#include <xen/page.h>
  13#include <xen/xenbus.h>
  14#include <xen/xenbus_dev.h>
  15#include <xen/grant_table.h>
  16#include <xen/events.h>
  17#include <asm/xen/hypervisor.h>
  18
  19#include "xenbus_comms.h"
  20
  21static int xenbus_backend_open(struct inode *inode, struct file *filp)
  22{
  23        if (!capable(CAP_SYS_ADMIN))
  24                return -EPERM;
  25
  26        return nonseekable_open(inode, filp);
  27}
  28
  29static long xenbus_alloc(domid_t domid)
  30{
  31        struct evtchn_alloc_unbound arg;
  32        int err = -EEXIST;
  33
  34        xs_suspend();
  35
  36        /* If xenstored_ready is nonzero, that means we have already talked to
  37         * xenstore and set up watches. These watches will be restored by
  38         * xs_resume, but that requires communication over the port established
  39         * below that is not visible to anyone until the ioctl returns.
  40         *
  41         * This can be resolved by splitting the ioctl into two parts
  42         * (postponing the resume until xenstored is active) but this is
  43         * unnecessarily complex for the intended use where xenstored is only
  44         * started once - so return -EEXIST if it's already running.
  45         */
  46        if (xenstored_ready)
  47                goto out_err;
  48
  49        gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,
  50                        virt_to_gfn(xen_store_interface), 0 /* writable */);
  51
  52        arg.dom = DOMID_SELF;
  53        arg.remote_dom = domid;
  54
  55        err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);
  56        if (err)
  57                goto out_err;
  58
  59        if (xen_store_evtchn > 0)
  60                xb_deinit_comms();
  61
  62        xen_store_evtchn = arg.port;
  63
  64        xs_resume();
  65
  66        return arg.port;
  67
  68 out_err:
  69        xs_suspend_cancel();
  70        return err;
  71}
  72
  73static long xenbus_backend_ioctl(struct file *file, unsigned int cmd,
  74                                 unsigned long data)
  75{
  76        if (!capable(CAP_SYS_ADMIN))
  77                return -EPERM;
  78
  79        switch (cmd) {
  80        case IOCTL_XENBUS_BACKEND_EVTCHN:
  81                if (xen_store_evtchn > 0)
  82                        return xen_store_evtchn;
  83                return -ENODEV;
  84        case IOCTL_XENBUS_BACKEND_SETUP:
  85                return xenbus_alloc(data);
  86        default:
  87                return -ENOTTY;
  88        }
  89}
  90
  91static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
  92{
  93        size_t size = vma->vm_end - vma->vm_start;
  94
  95        if (!capable(CAP_SYS_ADMIN))
  96                return -EPERM;
  97
  98        if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
  99                return -EINVAL;
 100
 101        if (remap_pfn_range(vma, vma->vm_start,
 102                            virt_to_pfn(xen_store_interface),
 103                            size, vma->vm_page_prot))
 104                return -EAGAIN;
 105
 106        return 0;
 107}
 108
 109static const struct file_operations xenbus_backend_fops = {
 110        .open = xenbus_backend_open,
 111        .mmap = xenbus_backend_mmap,
 112        .unlocked_ioctl = xenbus_backend_ioctl,
 113};
 114
 115static struct miscdevice xenbus_backend_dev = {
 116        .minor = MISC_DYNAMIC_MINOR,
 117        .name = "xen/xenbus_backend",
 118        .fops = &xenbus_backend_fops,
 119};
 120
 121static int __init xenbus_backend_init(void)
 122{
 123        int err;
 124
 125        if (!xen_initial_domain())
 126                return -ENODEV;
 127
 128        err = misc_register(&xenbus_backend_dev);
 129        if (err)
 130                pr_err("Could not register xenbus backend device\n");
 131        return err;
 132}
 133device_initcall(xenbus_backend_init);
 134