xref: /linux/drivers/xen/xenfs/super.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
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