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 #include "../privcmd.h"
  20
  21 #include <asm/xen/hypervisor.h>
  22
  23 MODULE_DESCRIPTION("Xen filesystem");
  24 MODULE_LICENSE("GPL");
  25
  26 static struct inode *xenfs_make_inode(struct super_block *sb, int mode)
  27 {
  28         struct inode *ret = new_inode(sb);
  29
  30         if (ret) {
  31                 ret->i_mode = mode;
  32                 ret->i_uid = ret->i_gid = 0;
  33                 ret->i_blocks = 0;
  34                 ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
  35         }
  36         return ret;
  37 }
  38
  39 static struct dentry *xenfs_create_file(struct super_block *sb,
  40                                         struct dentry *parent,
  41                                         const char *name,
  42                                         const struct file_operations *fops,
  43                                         void *data,
  44                                         int mode)
  45 {
  46         struct dentry *dentry;
  47         struct inode *inode;
  48
  49         dentry = d_alloc_name(parent, name);
  50         if (!dentry)
  51                 return NULL;
  52
  53         inode = xenfs_make_inode(sb, S_IFREG | mode);
  54         if (!inode) {
  55                 dput(dentry);
  56                 return NULL;
  57         }
  58
  59         inode->i_fop = fops;
  60         inode->i_private = data;
  61
  62         d_add(dentry, inode);
  63         return dentry;
  64 }
  65
  66 static ssize_t capabilities_read(struct file *file, char __user *buf,
  67                                  size_t size, loff_t *off)
  68 {
  69         char *tmp = "";
  70
  71         if (xen_initial_domain())
  72                 tmp = "control_d\n";
  73
  74         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  75 }
  76
  77 static const struct file_operations capabilities_file_ops = {
  78         .read = capabilities_read,
  79         .llseek = default_llseek,
  80 };
  81
  82 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  83 {
  84         static struct tree_descr xenfs_files[] = {
  85                 [1] = {},
  86                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
  87                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  88                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  89                 {""},
  90         };
  91         int rc;
  92
  93         rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  94         if (rc < 0)
  95                 return rc;
  96
  97         if (xen_initial_domain()) {
  98                 xenfs_create_file(sb, sb->s_root, "xsd_kva",
  99                                   &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
 100                 xenfs_create_file(sb, sb->s_root, "xsd_port",
 101                                   &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
 102         }
 103
 104         return rc;
 105 }
 106
 107 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
 108                                   int flags, const char *dev_name,
 109                                   void *data)
 110 {
 111         return mount_single(fs_type, flags, data, xenfs_fill_super);
 112 }
 113
 114 static struct file_system_type xenfs_type = {
 115         .owner =        THIS_MODULE,
 116         .name =         "xenfs",
 117         .mount =        xenfs_mount,
 118         .kill_sb =      kill_litter_super,
 119 };
 120
 121 static int __init xenfs_init(void)
 122 {
 123         if (xen_domain())
 124                 return register_filesystem(&xenfs_type);
 125
 126         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
 127         return 0;
 128 }
 129
 130 static void __exit xenfs_exit(void)
 131 {
 132         if (xen_domain())
 133                 unregister_filesystem(&xenfs_type);
 134 }
 135
 136 module_init(xenfs_init);
 137 module_exit(xenfs_exit);
 138