drivers/xen/xenfs/super.c

   1 /*
   2  *  xenfs.c - a filesystem for passing info between the a domain and
   3  *  the hypervisor.
   4  *
   5  * 2008-10-07  Alex Zeffertt    Replaced /proc/xen/xenbus with xenfs filesystem
   6  *                              and /proc/xen compatibility mount point.
   7  *                              Turned xenfs into a loadable module.
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/magic.h>
  15
  16 #include "xenfs.h"
  17
  18 #include <asm/xen/hypervisor.h>
  19
  20 MODULE_DESCRIPTION("Xen filesystem");
  21 MODULE_LICENSE("GPL");
  22
  23 static ssize_t capabilities_read(struct file *file, char __user *buf,
  24                                  size_t size, loff_t *off)
  25 {
  26         char *tmp = "";
  27
  28         if (xen_initial_domain())
  29                 tmp = "control_d\n";
  30
  31         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  32 }
  33
  34 static const struct file_operations capabilities_file_ops = {
  35         .read = capabilities_read,
  36 };
  37
  38 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  39 {
  40         static struct tree_descr xenfs_files[] = {
  41                 [1] = {},
  42                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
  43                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  44                 {""},
  45         };
  46
  47         return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  48 }
  49
  50 static int xenfs_get_sb(struct file_system_type *fs_type,
  51                         int flags, const char *dev_name,
  52                         void *data, struct vfsmount *mnt)
  53 {
  54         return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
  55 }
  56
  57 static struct file_system_type xenfs_type = {
  58         .owner =        THIS_MODULE,
  59         .name =         "xenfs",
  60         .get_sb =       xenfs_get_sb,
  61         .kill_sb =      kill_litter_super,
  62 };
  63
  64 static int __init xenfs_init(void)
  65 {
  66         if (xen_pv_domain())
  67                 return register_filesystem(&xenfs_type);
  68
  69         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
  70         return 0;
  71 }
  72
  73 static void __exit xenfs_exit(void)
  74 {
  75         if (xen_pv_domain())
  76                 unregister_filesystem(&xenfs_type);
  77 }
  78
  79 module_init(xenfs_init);
  80 module_exit(xenfs_exit);
  81