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         .llseek = default_llseek,
  79 };
  80
  81 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  82 {
  83         static struct tree_descr xenfs_files[] = {
  84                 [1] = {},
  85                 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR },
  86                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  87                 { "privcmd", &privcmd_file_ops, S_IRUSR|S_IWUSR },
  88                 {""},
  89         };
  90         int rc;
  91
  92         rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  93         if (rc < 0)
  94                 return rc;
  95
  96         if (xen_initial_domain()) {
  97                 xenfs_create_file(sb, sb->s_root, "xsd_kva",
  98                                   &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
  99                 xenfs_create_file(sb, sb->s_root, "xsd_port",
 100                                   &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
 101         }
 102
 103         return rc;
 104 }
 105
 106 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
 107                                   int flags, const char *dev_name,
 108                                   void *data)
 109 {
 110         return mount_single(fs_type, flags, data, xenfs_fill_super);
 111 }
 112
 113 static struct file_system_type xenfs_type = {
 114         .owner =        THIS_MODULE,
 115         .name =         "xenfs",
 116         .mount =        xenfs_mount,
 117         .kill_sb =      kill_litter_super,
 118 };
 119
 120 static int __init xenfs_init(void)
 121 {
 122         if (xen_domain())
 123                 return register_filesystem(&xenfs_type);
 124
 125         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
 126         return 0;
 127 }
 128
 129 static void __exit xenfs_exit(void)
 130 {
 131         if (xen_domain())
 132                 unregister_filesystem(&xenfs_type);
 133 }
 134
 135 module_init(xenfs_init);
 136 module_exit(xenfs_exit);
 137