drivers/xen/xenbus/xenbus_dev_backend.c

   1 #include <linux/slab.h>
   2 #include <linux/types.h>
   3 #include <linux/mm.h>
   4 #include <linux/fs.h>
   5 #include <linux/miscdevice.h>
   6 #include <linux/module.h>
   7 #include <linux/capability.h>
   8
   9 #include <xen/xen.h>
  10 #ifdef CONFIG_PARAVIRT_XEN
  11 #include <xen/page.h>
  12 #endif
  13 #include <xen/xenbus_dev.h>
  14
  15 #include "xenbus_comms.h"
  16
  17 MODULE_LICENSE("GPL");
  18
  19 static int xenbus_backend_open(struct inode *inode, struct file *filp)
  20 {
  21         if (!capable(CAP_SYS_ADMIN))
  22                 return -EPERM;
  23
  24         return nonseekable_open(inode, filp);
  25 }
  26
  27 static long xenbus_backend_ioctl(struct file *file, unsigned int cmd, unsigned long data)
  28 {
  29         if (!capable(CAP_SYS_ADMIN))
  30                 return -EPERM;
  31
  32         switch (cmd) {
  33                 case IOCTL_XENBUS_BACKEND_EVTCHN:
  34                         if (xen_store_evtchn > 0)
  35                                 return xen_store_evtchn;
  36                         return -ENODEV;
  37
  38                 default:
  39                         return -ENOTTY;
  40         }
  41 }
  42
  43 static int xenbus_backend_mmap(struct file *file, struct vm_area_struct *vma)
  44 {
  45         size_t size = vma->vm_end - vma->vm_start;
  46
  47         if (!capable(CAP_SYS_ADMIN))
  48                 return -EPERM;
  49
  50         if ((size > PAGE_SIZE) || (vma->vm_pgoff != 0))
  51                 return -EINVAL;
  52
  53         if (remap_pfn_range(vma, vma->vm_start,
  54                             PFN_DOWN(__pa(xen_store_interface)),
  55                             size, vma->vm_page_prot))
  56                 return -EAGAIN;
  57
  58         return 0;
  59 }
  60
  61 const struct file_operations xenbus_backend_fops = {
  62         .open = xenbus_backend_open,
  63         .mmap = xenbus_backend_mmap,
  64         .unlocked_ioctl = xenbus_backend_ioctl,
  65 };
  66
  67 static struct miscdevice xenbus_backend_dev = {
  68         .minor = MISC_DYNAMIC_MINOR,
  69         .name = "xen/xenbus_backend",
  70         .fops = &xenbus_backend_fops,
  71 };
  72
  73 static int __init xenbus_backend_init(void)
  74 {
  75         int err;
  76
  77         if (!xen_initial_domain())
  78                 return -ENODEV;
  79
  80         err = misc_register(&xenbus_backend_dev);
  81         if (err)
  82                 printk(KERN_ERR "Could not register xenbus backend device\n");
  83         return err;
  84 }
  85
  86 static void __exit xenbus_backend_exit(void)
  87 {
  88         misc_deregister(&xenbus_backend_dev);
  89 }
  90
  91 module_init(xenbus_backend_init);
  92 module_exit(xenbus_backend_exit);