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 "xenfs.h" 17 18 #include <asm/xen/hypervisor.h> 19 20 MODULE_DESCRIPTION("Xen filesystem"); 21 MODULE_LICENSE("GPL"); 22 23 static ssize_t capabilities_read(struct file *file, char __user *buf, 24 size_t size, loff_t *off) 25 { 26 char *tmp = ""; 27 28 if (xen_initial_domain()) 29 tmp = "control_d\n"; 30 31 return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp)); 32 } 33 34 static const struct file_operations capabilities_file_ops = { 35 .read = capabilities_read, 36 }; 37 38 static int xenfs_fill_super(struct super_block *sb, void *data, int silent) 39 { 40 static struct tree_descr xenfs_files[] = { 41 [1] = {}, 42 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR }, 43 { "capabilities", &capabilities_file_ops, S_IRUGO }, 44 {""}, 45 }; 46 47 return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files); 48 } 49 50 static int xenfs_get_sb(struct file_system_type *fs_type, 51 int flags, const char *dev_name, 52 void *data, struct vfsmount *mnt) 53 { 54 return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt); 55 } 56 57 static struct file_system_type xenfs_type = { 58 .owner = THIS_MODULE, 59 .name = "xenfs", 60 .get_sb = xenfs_get_sb, 61 .kill_sb = kill_litter_super, 62 }; 63 64 static int __init xenfs_init(void) 65 { 66 if (xen_pv_domain()) 67 return register_filesystem(&xenfs_type); 68 69 printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n"); 70 return 0; 71 } 72 73 static void __exit xenfs_exit(void) 74 { 75 if (xen_pv_domain()) 76 unregister_filesystem(&xenfs_type); 77 } 78 79 module_init(xenfs_init); 80 module_exit(xenfs_exit); 81 82