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