kernel/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
  20 #include "xenfs.h"
  21 #include "../privcmd.h"
  22 #include "../xenbus/xenbus_comms.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 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 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                 {""},
  61         };
  62
  63         return simple_fill_super(sb, XENFS_SUPER_MAGIC,
  64                         xen_initial_domain() ? xenfs_init_files : xenfs_files);
  65 }
  66
  67 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
  68                                   int flags, const char *dev_name,
  69                                   void *data)
  70 {
  71         return mount_single(fs_type, flags, data, xenfs_fill_super);
  72 }
  73
  74 static struct file_system_type xenfs_type = {
  75         .owner =        THIS_MODULE,
  76         .name =         "xenfs",
  77         .mount =        xenfs_mount,
  78         .kill_sb =      kill_litter_super,
  79 };
  80 MODULE_ALIAS_FS("xenfs");
  81
  82 static int __init xenfs_init(void)
  83 {
  84         if (xen_domain())
  85                 return register_filesystem(&xenfs_type);
  86
  87         pr_info("not registering filesystem on non-xen platform\n");
  88         return 0;
  89 }
  90
  91 static void __exit xenfs_exit(void)
  92 {
  93         if (xen_domain())
  94                 unregister_filesystem(&xenfs_type);
  95 }
  96
  97 module_init(xenfs_init);
  98 module_exit(xenfs_exit);
  99