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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/kernel.h>
  13 #include <linux/errno.h>
  14 #include <linux/module.h>
  15 #include <linux/fs.h>
  16 #include <linux/magic.h>
  17
  18 #include <xen/xen.h>
  19 #include <xen/xenbus.h>
  20
  21 #include "xenfs.h"
  22 #include "../privcmd.h"
  23
  24 #include <asm/xen/hypervisor.h>
  25
  26 MODULE_DESCRIPTION("Xen filesystem");
  27 MODULE_LICENSE("GPL");
  28
  29 static ssize_t capabilities_read(struct file *file, char __user *buf,
  30                                  size_t size, loff_t *off)
  31 {
  32         char *tmp = "";
  33
  34         if (xen_initial_domain())
  35                 tmp = "control_d\n";
  36
  37         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  38 }
  39
  40 static const struct file_operations capabilities_file_ops = {
  41         .read = capabilities_read,
  42         .llseek = default_llseek,
  43 };
  44
  45 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  46 {
  47         static const struct tree_descr xenfs_files[] = {
  48                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  49                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  50                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  51                 {""},
  52         };
  53
  54         static const struct tree_descr xenfs_init_files[] = {
  55                 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  56                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  57                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  58                 { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR},
  59                 { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR},
  60 #ifdef CONFIG_XEN_SYMS
  61                 { "xensyms", &xensyms_ops, S_IRUSR},
  62 #endif
  63                 {""},
  64         };
  65
  66         return simple_fill_super(sb, XENFS_SUPER_MAGIC,
  67                         xen_initial_domain() ? xenfs_init_files : xenfs_files);
  68 }
  69
  70 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
  71                                   int flags, const char *dev_name,
  72                                   void *data)
  73 {
  74         return mount_single(fs_type, flags, data, xenfs_fill_super);
  75 }
  76
  77 static struct file_system_type xenfs_type = {
  78         .owner =        THIS_MODULE,
  79         .name =         "xenfs",
  80         .mount =        xenfs_mount,
  81         .kill_sb =      kill_litter_super,
  82 };
  83 MODULE_ALIAS_FS("xenfs");
  84
  85 static int __init xenfs_init(void)
  86 {
  87         if (xen_domain())
  88                 return register_filesystem(&xenfs_type);
  89
  90         pr_info("not registering filesystem on non-xen platform\n");
  91         return 0;
  92 }
  93
  94 static void __exit xenfs_exit(void)
  95 {
  96         if (xen_domain())
  97                 unregister_filesystem(&xenfs_type);
  98 }
  99
 100 module_init(xenfs_init);
 101 module_exit(xenfs_exit);
 102