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/magic.h> 18 19 #include <xen/xen.h> 20 #include <xen/xenbus.h> 21 22 #include "xenfs.h" 23 #include "../privcmd.h" 24 25 #include <asm/xen/hypervisor.h> 26 27 MODULE_DESCRIPTION("Xen filesystem"); 28 MODULE_LICENSE("GPL"); 29 30 static ssize_t capabilities_read(struct file *file, char __user *buf, 31 size_t size, loff_t *off) 32 { 33 char *tmp = ""; 34 35 if (xen_initial_domain()) 36 tmp = "control_d\n"; 37 38 return simple_read_from_buffer(buf, size, off, tmp, strlen(tmp)); 39 } 40 41 static const struct file_operations capabilities_file_ops = { 42 .read = capabilities_read, 43 .llseek = default_llseek, 44 }; 45 46 static int xenfs_fill_super(struct super_block *sb, void *data, int silent) 47 { 48 static const struct tree_descr xenfs_files[] = { 49 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR }, 50 { "capabilities", &capabilities_file_ops, S_IRUGO }, 51 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR }, 52 {""}, 53 }; 54 55 static const struct tree_descr xenfs_init_files[] = { 56 [2] = { "xenbus", &xen_xenbus_fops, S_IRUSR|S_IWUSR }, 57 { "capabilities", &capabilities_file_ops, S_IRUGO }, 58 { "privcmd", &xen_privcmd_fops, S_IRUSR|S_IWUSR }, 59 { "xsd_kva", &xsd_kva_file_ops, S_IRUSR|S_IWUSR}, 60 { "xsd_port", &xsd_port_file_ops, S_IRUSR|S_IWUSR}, 61 #ifdef CONFIG_XEN_SYMS 62 { "xensyms", &xensyms_ops, S_IRUSR}, 63 #endif 64 {""}, 65 }; 66 67 return simple_fill_super(sb, XENFS_SUPER_MAGIC, 68 xen_initial_domain() ? xenfs_init_files : xenfs_files); 69 } 70 71 static struct dentry *xenfs_mount(struct file_system_type *fs_type, 72 int flags, const char *dev_name, 73 void *data) 74 { 75 return mount_single(fs_type, flags, data, xenfs_fill_super); 76 } 77 78 static struct file_system_type xenfs_type = { 79 .owner = THIS_MODULE, 80 .name = "xenfs", 81 .mount = xenfs_mount, 82 .kill_sb = kill_litter_super, 83 }; 84 MODULE_ALIAS_FS("xenfs"); 85 86 static int __init xenfs_init(void) 87 { 88 if (xen_domain()) 89 return register_filesystem(&xenfs_type); 90 91 return 0; 92 } 93 94 static void __exit xenfs_exit(void) 95 { 96 if (xen_domain()) 97 unregister_filesystem(&xenfs_type); 98 } 99 100 module_init(xenfs_init); 101 module_exit(xenfs_exit); 102 103