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); 139 140