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 struct inode *xenfs_make_inode(struct super_block *sb, int mode)
  26 {
  27         struct inode *ret = new_inode(sb);
  28
  29         if (ret) {
  30                 ret->i_mode = mode;
  31                 ret->i_uid = ret->i_gid = 0;
  32                 ret->i_blocks = 0;
  33                 ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
  34         }
  35         return ret;
  36 }
  37
  38 static struct dentry *xenfs_create_file(struct super_block *sb,
  39                                         struct dentry *parent,
  40                                         const char *name,
  41                                         const struct file_operations *fops,
  42                                         void *data,
  43                                         int mode)
  44 {
  45         struct dentry *dentry;
  46         struct inode *inode;
  47
  48         dentry = d_alloc_name(parent, name);
  49         if (!dentry)
  50                 return NULL;
  51
  52         inode = xenfs_make_inode(sb, S_IFREG | mode);
  53         if (!inode) {
  54                 dput(dentry);
  55                 return NULL;
  56         }
  57
  58         inode->i_fop = fops;
  59         inode->i_private = data;
  60
  61         d_add(dentry, inode);
  62         return dentry;
  63 }
  64
  65 static ssize_t capabilities_read(struct file *file, char __user *buf,
  66                                  size_t size, loff_t *off)
  67 {
  68         char *tmp = "";
  69
  70         if (xen_initial_domain())
  71                 tmp = "control_d\n";
  72
  73         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  74 }
  75
  76 static const struct file_operations capabilities_file_ops = {
  77         .read = capabilities_read,
  78 };
  79
  80 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  81 {
  82         static struct tree_descr xenfs_files[] = {
  83                 [1] = {},
  84                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
  85                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  86                 {""},
  87         };
  88         int rc;
  89
  90         rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  91         if (rc < 0)
  92                 return rc;
  93
  94         if (xen_initial_domain()) {
  95                 xenfs_create_file(sb, sb->s_root, "xsd_kva",
  96                                   &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
  97                 xenfs_create_file(sb, sb->s_root, "xsd_port",
  98                                   &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
  99         }
 100
 101         return rc;
 102 }
 103
 104 static int xenfs_get_sb(struct file_system_type *fs_type,
 105                         int flags, const char *dev_name,
 106                         void *data, struct vfsmount *mnt)
 107 {
 108         return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt);
 109 }
 110
 111 static struct file_system_type xenfs_type = {
 112         .owner =        THIS_MODULE,
 113         .name =         "xenfs",
 114         .get_sb =       xenfs_get_sb,
 115         .kill_sb =      kill_litter_super,
 116 };
 117
 118 static int __init xenfs_init(void)
 119 {
 120         if (xen_domain())
 121                 return register_filesystem(&xenfs_type);
 122
 123         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
 124         return 0;
 125 }
 126
 127 static void __exit xenfs_exit(void)
 128 {
 129         if (xen_domain())
 130                 unregister_filesystem(&xenfs_type);
 131 }
 132
 133 module_init(xenfs_init);
 134 module_exit(xenfs_exit);
 135