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 <xen/xen.h>
  17
  18 #include "xenfs.h"
  19
  20 #include <asm/xen/hypervisor.h>
  21
  22 MODULE_DESCRIPTION("Xen filesystem");
  23 MODULE_LICENSE("GPL");
  24
  25 static ssize_t capabilities_read(struct file *file, char __user *buf,
  26                                  size_t size, loff_t *off)
  27 {
  28         char *tmp = "";
  29
  30         if (xen_initial_domain())
  31                 tmp = "control_d\n";
  32
  33         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  34 }
  35
  36 static const struct file_operations capabilities_file_ops = {
  37         .read = capabilities_read,
  38 };
  39
  40 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  41 {
  42         static struct tree_descr xenfs_files[] = {
  43                 [1] = {},
  44                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
  45                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  46                 {""},
  47         };
  48
  49         return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  50 }
  51
  52 static int xenfs_get_sb(struct file_system_type *fs_type,
  53                         int flags, const char *dev_name,
  54                         void *data, struct vfsmount *mnt)
  55 {
  56         return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
  57 }
  58
  59 static struct file_system_type xenfs_type = {
  60         .owner =        THIS_MODULE,
  61         .name =         "xenfs",
  62         .get_sb =       xenfs_get_sb,
  63         .kill_sb =      kill_litter_super,
  64 };
  65
  66 static int __init xenfs_init(void)
  67 {
  68         if (xen_pv_domain())
  69                 return register_filesystem(&xenfs_type);
  70
  71         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
  72         return 0;
  73 }
  74
  75 static void __exit xenfs_exit(void)
  76 {
  77         if (xen_pv_domain())
  78                 unregister_filesystem(&xenfs_type);
  79 }
  80
  81 module_init(xenfs_init);
  82 module_exit(xenfs_exit);
  83