xref: /openbmc/linux/fs/devpts/inode.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /* -*- linux-c -*- --------------------------------------------------------- *
2  *
3  * linux/fs/devpts/inode.c
4  *
5  *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
6  *
7  * This file is part of the Linux kernel and is made available under
8  * the terms of the GNU General Public License, version 2, or at your
9  * option, any later version, incorporated herein by reference.
10  *
11  * ------------------------------------------------------------------------- */
12 
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/fs.h>
16 #include <linux/sched.h>
17 #include <linux/namei.h>
18 #include <linux/mount.h>
19 #include <linux/tty.h>
20 #include <linux/devpts_fs.h>
21 
22 #define DEVPTS_SUPER_MAGIC 0x1cd1
23 
24 static struct vfsmount *devpts_mnt;
25 static struct dentry *devpts_root;
26 
27 static struct {
28 	int setuid;
29 	int setgid;
30 	uid_t   uid;
31 	gid_t   gid;
32 	umode_t mode;
33 } config = {.mode = 0600};
34 
35 static int devpts_remount(struct super_block *sb, int *flags, char *data)
36 {
37 	int setuid = 0;
38 	int setgid = 0;
39 	uid_t uid = 0;
40 	gid_t gid = 0;
41 	umode_t mode = 0600;
42 	char *this_char;
43 
44 	this_char = NULL;
45 	while ((this_char = strsep(&data, ",")) != NULL) {
46 		int n;
47 		char dummy;
48 		if (!*this_char)
49 			continue;
50 		if (sscanf(this_char, "uid=%i%c", &n, &dummy) == 1) {
51 			setuid = 1;
52 			uid = n;
53 		} else if (sscanf(this_char, "gid=%i%c", &n, &dummy) == 1) {
54 			setgid = 1;
55 			gid = n;
56 		} else if (sscanf(this_char, "mode=%o%c", &n, &dummy) == 1)
57 			mode = n & ~S_IFMT;
58 		else {
59 			printk("devpts: called with bogus options\n");
60 			return -EINVAL;
61 		}
62 	}
63 	config.setuid  = setuid;
64 	config.setgid  = setgid;
65 	config.uid     = uid;
66 	config.gid     = gid;
67 	config.mode    = mode;
68 
69 	return 0;
70 }
71 
72 static struct super_operations devpts_sops = {
73 	.statfs		= simple_statfs,
74 	.remount_fs	= devpts_remount,
75 };
76 
77 static int
78 devpts_fill_super(struct super_block *s, void *data, int silent)
79 {
80 	struct inode * inode;
81 
82 	s->s_blocksize = 1024;
83 	s->s_blocksize_bits = 10;
84 	s->s_magic = DEVPTS_SUPER_MAGIC;
85 	s->s_op = &devpts_sops;
86 	s->s_time_gran = 1;
87 
88 	inode = new_inode(s);
89 	if (!inode)
90 		goto fail;
91 	inode->i_ino = 1;
92 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
93 	inode->i_blocks = 0;
94 	inode->i_blksize = 1024;
95 	inode->i_uid = inode->i_gid = 0;
96 	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
97 	inode->i_op = &simple_dir_inode_operations;
98 	inode->i_fop = &simple_dir_operations;
99 	inode->i_nlink = 2;
100 
101 	devpts_root = s->s_root = d_alloc_root(inode);
102 	if (s->s_root)
103 		return 0;
104 
105 	printk("devpts: get root dentry failed\n");
106 	iput(inode);
107 fail:
108 	return -ENOMEM;
109 }
110 
111 static struct super_block *devpts_get_sb(struct file_system_type *fs_type,
112 	int flags, const char *dev_name, void *data)
113 {
114 	return get_sb_single(fs_type, flags, data, devpts_fill_super);
115 }
116 
117 static struct file_system_type devpts_fs_type = {
118 	.owner		= THIS_MODULE,
119 	.name		= "devpts",
120 	.get_sb		= devpts_get_sb,
121 	.kill_sb	= kill_anon_super,
122 };
123 
124 /*
125  * The normal naming convention is simply /dev/pts/<number>; this conforms
126  * to the System V naming convention
127  */
128 
129 static struct dentry *get_node(int num)
130 {
131 	char s[12];
132 	struct dentry *root = devpts_root;
133 	down(&root->d_inode->i_sem);
134 	return lookup_one_len(s, root, sprintf(s, "%d", num));
135 }
136 
137 int devpts_pty_new(struct tty_struct *tty)
138 {
139 	int number = tty->index;
140 	struct tty_driver *driver = tty->driver;
141 	dev_t device = MKDEV(driver->major, driver->minor_start+number);
142 	struct dentry *dentry;
143 	struct inode *inode = new_inode(devpts_mnt->mnt_sb);
144 
145 	/* We're supposed to be given the slave end of a pty */
146 	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
147 	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
148 
149 	if (!inode)
150 		return -ENOMEM;
151 
152 	inode->i_ino = number+2;
153 	inode->i_blksize = 1024;
154 	inode->i_uid = config.setuid ? config.uid : current->fsuid;
155 	inode->i_gid = config.setgid ? config.gid : current->fsgid;
156 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
157 	init_special_inode(inode, S_IFCHR|config.mode, device);
158 	inode->u.generic_ip = tty;
159 
160 	dentry = get_node(number);
161 	if (!IS_ERR(dentry) && !dentry->d_inode)
162 		d_instantiate(dentry, inode);
163 
164 	up(&devpts_root->d_inode->i_sem);
165 
166 	return 0;
167 }
168 
169 struct tty_struct *devpts_get_tty(int number)
170 {
171 	struct dentry *dentry = get_node(number);
172 	struct tty_struct *tty;
173 
174 	tty = NULL;
175 	if (!IS_ERR(dentry)) {
176 		if (dentry->d_inode)
177 			tty = dentry->d_inode->u.generic_ip;
178 		dput(dentry);
179 	}
180 
181 	up(&devpts_root->d_inode->i_sem);
182 
183 	return tty;
184 }
185 
186 void devpts_pty_kill(int number)
187 {
188 	struct dentry *dentry = get_node(number);
189 
190 	if (!IS_ERR(dentry)) {
191 		struct inode *inode = dentry->d_inode;
192 		if (inode) {
193 			inode->i_nlink--;
194 			d_delete(dentry);
195 			dput(dentry);
196 		}
197 		dput(dentry);
198 	}
199 	up(&devpts_root->d_inode->i_sem);
200 }
201 
202 static int __init init_devpts_fs(void)
203 {
204 	int err = register_filesystem(&devpts_fs_type);
205 	if (!err) {
206 		devpts_mnt = kern_mount(&devpts_fs_type);
207 		if (IS_ERR(devpts_mnt))
208 			err = PTR_ERR(devpts_mnt);
209 	}
210 	return err;
211 }
212 
213 static void __exit exit_devpts_fs(void)
214 {
215 	unregister_filesystem(&devpts_fs_type);
216 	mntput(devpts_mnt);
217 }
218 
219 module_init(init_devpts_fs)
220 module_exit(exit_devpts_fs)
221 MODULE_LICENSE("GPL");
222