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