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 
capabilities_read(struct file * file,char __user * buf,size_t size,loff_t * off)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 
xenfs_fill_super(struct super_block * sb,struct fs_context * fc)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 
xenfs_get_tree(struct fs_context * fc)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 
xenfs_init_fs_context(struct fs_context * fc)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 
xenfs_init(void)95 static int __init xenfs_init(void)
96 {
97 	if (xen_domain())
98 		return register_filesystem(&xenfs_type);
99 
100 	return 0;
101 }
102 
xenfs_exit(void)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