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 ssize_t capabilities_read(struct file *file, char __user *buf, 26 size_t size, loff_t *off) 27 { 28 char *tmp = ""; 29 30 if (xen_initial_domain()) 31 tmp = "control_d\n"; 32 33 return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp)); 34 } 35 36 static const struct file_operations capabilities_file_ops = { 37 .read = capabilities_read, 38 }; 39 40 static int xenfs_fill_super(struct super_block *sb, void *data, int silent) 41 { 42 static struct tree_descr xenfs_files[] = { 43 [1] = {}, 44 { "xenbus", &xenbus_file_ops, S_IRUSR|S_IWUSR }, 45 { "capabilities", &capabilities_file_ops, S_IRUGO }, 46 {""}, 47 }; 48 49 return simple_fill_super(sb, XENFS_SUPER_MAGIC, xenfs_files); 50 } 51 52 static int xenfs_get_sb(struct file_system_type *fs_type, 53 int flags, const char *dev_name, 54 void *data, struct vfsmount *mnt) 55 { 56 return get_sb_single(fs_type, flags, data, xenfs_fill_super, mnt); 57 } 58 59 static struct file_system_type xenfs_type = { 60 .owner = THIS_MODULE, 61 .name = "xenfs", 62 .get_sb = xenfs_get_sb, 63 .kill_sb = kill_litter_super, 64 }; 65 66 static int __init xenfs_init(void) 67 { 68 if (xen_pv_domain()) 69 return register_filesystem(&xenfs_type); 70 71 printk(KERN_INFO "XENFS: not registering filesystem on non-xen platform\n"); 72 return 0; 73 } 74 75 static void __exit xenfs_exit(void) 76 { 77 if (xen_pv_domain()) 78 unregister_filesystem(&xenfs_type); 79 } 80 81 module_init(xenfs_init); 82 module_exit(xenfs_exit); 83 84