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 #include "../xenbus/xenbus_comms.h"
  21
  22 #include <asm/xen/hypervisor.h>
  23
  24 MODULE_DESCRIPTION("Xen filesystem");
  25 MODULE_LICENSE("GPL");
  26
  27 static struct inode *xenfs_make_inode(struct super_block *sb, int mode)
  28 {
  29         struct inode *ret = new_inode(sb);
  30
  31         if (ret) {
  32                 ret->i_mode = mode;
  33                 ret->i_uid = GLOBAL_ROOT_UID;
  34                 ret->i_gid = GLOBAL_ROOT_GID;
  35                 ret->i_blocks = 0;
  36                 ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
  37         }
  38         return ret;
  39 }
  40
  41 static struct dentry *xenfs_create_file(struct super_block *sb,
  42                                         struct dentry *parent,
  43                                         const char *name,
  44                                         const struct file_operations *fops,
  45                                         void *data,
  46                                         int mode)
  47 {
  48         struct dentry *dentry;
  49         struct inode *inode;
  50
  51         dentry = d_alloc_name(parent, name);
  52         if (!dentry)
  53                 return NULL;
  54
  55         inode = xenfs_make_inode(sb, S_IFREG | mode);
  56         if (!inode) {
  57                 dput(dentry);
  58                 return NULL;
  59         }
  60
  61         inode->i_fop = fops;
  62         inode->i_private = data;
  63
  64         d_add(dentry, inode);
  65         return dentry;
  66 }
  67
  68 static ssize_t capabilities_read(struct file *file, char __user *buf,
  69                                  size_t size, loff_t *off)
  70 {
  71         char *tmp = "";
  72
  73         if (xen_initial_domain())
  74                 tmp = "control_d\n";
  75
  76         return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp));
  77 }
  78
  79 static const struct file_operations capabilities_file_ops = {
  80         .read = capabilities_read,
  81         .llseek = default_llseek,
  82 };
  83
  84 static int xenfs_fill_super(struct super_block *sb, void *data, int silent)
  85 {
  86         static struct tree_descr xenfs_files[] = {
  87                 [1] = {},
  88                 { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR },
  89                 { "capabilities", &capabilities_file_ops, S_IRUGO },
  90                 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR },
  91                 {""},
  92         };
  93         int rc;
  94
  95         rc = simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files);
  96         if (rc < 0)
  97                 return rc;
  98
  99         if (xen_initial_domain()) {
 100                 xenfs_create_file(sb, sb->s_root, "xsd_kva",
 101                                   &xsd_kva_file_ops, NULL, S_IRUSR|S_IWUSR);
 102                 xenfs_create_file(sb, sb->s_root, "xsd_port",
 103                                   &xsd_port_file_ops, NULL, S_IRUSR|S_IWUSR);
 104         }
 105
 106         return rc;
 107 }
 108
 109 static struct dentry *xenfs_mount(struct file_system_type *fs_type,
 110                                   int flags, const char *dev_name,
 111                                   void *data)
 112 {
 113         return mount_single(fs_type, flags, data, xenfs_fill_super);
 114 }
 115
 116 static struct file_system_type xenfs_type = {
 117         .owner =        THIS_MODULE,
 118         .name =         "xenfs",
 119         .mount =        xenfs_mount,
 120         .kill_sb =      kill_litter_super,
 121 };
 122
 123 static int __init xenfs_init(void)
 124 {
 125         if (xen_domain())
 126                 return register_filesystem(&xenfs_type);
 127
 128         printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n");
 129         return 0;
 130 }
 131
 132 static void __exit xenfs_exit(void)
 133 {
 134         if (xen_domain())
 135                 unregister_filesystem(&xenfs_type);
 136 }
 137
 138 module_init(xenfs_init);
 139 module_exit(xenfs_exit);
 140