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); 140 141