1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * xenfs.c - a filesystem for passing info between the a domain and 4 * the hypervisor. 5 * 6 * 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem 7 * and /proc/xen compatibility mount point. 8 * Turned xenfs into a loadable module. 9 */ 10 11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 12 13 #include <linux/kernel.h> 14 #include <linux/errno.h> 15 #include <linux/module.h> 16 #include <linux/fs.h> 17 #include <linux/fs_context.h> 18 #include <linux/magic.h> 19 20 #include <xen/xen.h> 21 #include <xen/xenbus.h> 22 23 #include "xenfs.h" 24 #include "../privcmd.h" 25 26 #include <asm/xen/hypervisor.h> 27 28 MODULE_DESCRIPTION("Xen filesystem"); 29 MODULE_LICENSE("GPL"); 30 31 static ssize_t capabilities_read(struct file *file, char __user *buf, 32 size_t size, loff_t *off) 33 { 34 char *tmp = ""; 35 36 if (xen_initial_domain()) 37 tmp = "control_d\n"; 38 39 return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp)); 40 } 41 42 static const struct file_operations capabilities_file_ops = { 43 .read = capabilities_read, 44 .llseek = default_llseek, 45 }; 46 47 static int xenfs_fill_super(struct super_block *sb, struct fs_context *fc) 48 { 49 static const struct tree_descr xenfs_files[] = { 50 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR }, 51 { "capabilities", &capabilities_file_ops, S_IRUGO }, 52 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR }, 53 {""}, 54 }; 55 56 static const struct tree_descr xenfs_init_files[] = { 57 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR }, 58 { "capabilities", &capabilities_file_ops, S_IRUGO }, 59 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR }, 60 { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR}, 61 { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR}, 62 #ifdef CONFIG_XEN_SYMS 63 { "xensyms", &xensyms_ops, S_IRUSR}, 64 #endif 65 {""}, 66 }; 67 68 return simple_fill_super(sb, XENFS_SUPER_MAGIC, 69 xen_initial_domain() ? xenfs_init_files : xenfs_files); 70 } 71 72 static int xenfs_get_tree(struct fs_context *fc) 73 { 74 return get_tree_single(fc, xenfs_fill_super); 75 } 76 77 static const struct fs_context_operations xenfs_context_ops = { 78 .get_tree = xenfs_get_tree, 79 }; 80 81 static int xenfs_init_fs_context(struct fs_context *fc) 82 { 83 fc->ops = &xenfs_context_ops; 84 return 0; 85 } 86 87 static struct file_system_type xenfs_type = { 88 .owner = THIS_MODULE, 89 .name = "xenfs", 90 .init_fs_context = xenfs_init_fs_context, 91 .kill_sb = kill_litter_super, 92 }; 93 MODULE_ALIAS_FS("xenfs"); 94 95 static int __init xenfs_init(void) 96 { 97 if (xen_domain()) 98 return register_filesystem(&xenfs_type); 99 100 return 0; 101 } 102 103 static void __exit xenfs_exit(void) 104 { 105 if (xen_domain()) 106 unregister_filesystem(&xenfs_type); 107 } 108 109 module_init(xenfs_init); 110 module_exit(xenfs_exit); 111 112