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 #include <linux/parser.h>
22 #include <linux/fsnotify.h>
23 #include <linux/seq_file.h>
24
25 #define DEVPTS_SUPER_MAGIC 0x1cd1
26
27 #define DEVPTS_DEFAULT_MODE 0600
28
29 static struct vfsmount *devpts_mnt;
30 static struct dentry *devpts_root;
31
32 static struct {
33 int setuid;
34 int setgid;
35 uid_t uid;
36 gid_t gid;
37 umode_t mode;
38 } config = {.mode = DEVPTS_DEFAULT_MODE};
39
40 enum {
41 Opt_uid, Opt_gid, Opt_mode,
42 Opt_err
43 };
44
45 static match_table_t tokens = {
46 {Opt_uid, "uid=%u"},
47 {Opt_gid, "gid=%u"},
48 {Opt_mode, "mode=%o"},
49 {Opt_err, NULL}
50 };
51
52 static int devpts_remount(struct super_block *sb, int *flags, char *data)
53 {
54 char *p;
55
56 config.setuid = 0;
57 config.setgid = 0;
58 config.uid = 0;
59 config.gid = 0;
60 config.mode = DEVPTS_DEFAULT_MODE;
61
62 while ((p = strsep(&data, ",")) != NULL) {
63 substring_t args[MAX_OPT_ARGS];
64 int token;
65 int option;
66
67 if (!*p)
68 continue;
69
70 token = match_token(p, tokens, args);
71 switch (token) {
72 case Opt_uid:
73 if (match_int(&args[0], &option))
74 return -EINVAL;
75 config.uid = option;
76 config.setuid = 1;
77 break;
78 case Opt_gid:
79 if (match_int(&args[0], &option))
80 return -EINVAL;
81 config.gid = option;
82 config.setgid = 1;
83 break;
84 case Opt_mode:
85 if (match_octal(&args[0], &option))
86 return -EINVAL;
87 config.mode = option & S_IALLUGO;
88 break;
89 default:
90 printk(KERN_ERR "devpts: called with bogus options\n");
91 return -EINVAL;
92 }
93 }
94
95 return 0;
96 }
97
98 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
99 {
100 if (config.setuid)
101 seq_printf(seq, ",uid=%u", config.uid);
102 if (config.setgid)
103 seq_printf(seq, ",gid=%u", config.gid);
104 seq_printf(seq, ",mode=%03o", config.mode);
105
106 return 0;
107 }
108
109 static const struct super_operations devpts_sops = {
110 .statfs = simple_statfs,
111 .remount_fs = devpts_remount,
112 .show_options = devpts_show_options,
113 };
114
115 static int
116 devpts_fill_super(struct super_block *s, void *data, int silent)
117 {
118 struct inode * inode;
119
120 s->s_blocksize = 1024;
121 s->s_blocksize_bits = 10;
122 s->s_magic = DEVPTS_SUPER_MAGIC;
123 s->s_op = &devpts_sops;
124 s->s_time_gran = 1;
125
126 inode = new_inode(s);
127 if (!inode)
128 goto fail;
129 inode->i_ino = 1;
130 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
131 inode->i_blocks = 0;
132 inode->i_uid = inode->i_gid = 0;
133 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
134 inode->i_op = &simple_dir_inode_operations;
135 inode->i_fop = &simple_dir_operations;
136 inode->i_nlink = 2;
137
138 devpts_root = s->s_root = d_alloc_root(inode);
139 if (s->s_root)
140 return 0;
141
142 printk("devpts: get root dentry failed\n");
143 iput(inode);
144 fail:
145 return -ENOMEM;
146 }
147
148 static int devpts_get_sb(struct file_system_type *fs_type,
149 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
150 {
151 return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
152 }
153
154 static struct file_system_type devpts_fs_type = {
155 .owner = THIS_MODULE,
156 .name = "devpts",
157 .get_sb = devpts_get_sb,
158 .kill_sb = kill_anon_super,
159 };
160
161 /*
162 * The normal naming convention is simply /dev/pts/<number>; this conforms
163 * to the System V naming convention
164 */
165
166 static struct dentry *get_node(int num)
167 {
168 char s[12];
169 struct dentry *root = devpts_root;
170 mutex_lock(&root->d_inode->i_mutex);
171 return lookup_one_len(s, root, sprintf(s, "%d", num));
172 }
173
174 int devpts_pty_new(struct tty_struct *tty)
175 {
176 int number = tty->index;
177 struct tty_driver *driver = tty->driver;
178 dev_t device = MKDEV(driver->major, driver->minor_start+number);
179 struct dentry *dentry;
180 struct inode *inode = new_inode(devpts_mnt->mnt_sb);
181
182 /* We're supposed to be given the slave end of a pty */
183 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
184 BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
185
186 if (!inode)
187 return -ENOMEM;
188
189 inode->i_ino = number+2;
190 inode->i_uid = config.setuid ? config.uid : current->fsuid;
191 inode->i_gid = config.setgid ? config.gid : current->fsgid;
192 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
193 init_special_inode(inode, S_IFCHR|config.mode, device);
194 inode->i_private = tty;
195
196 dentry = get_node(number);
197 if (!IS_ERR(dentry) && !dentry->d_inode) {
198 d_instantiate(dentry, inode);
199 fsnotify_create(devpts_root->d_inode, dentry);
200 }
201
202 mutex_unlock(&devpts_root->d_inode->i_mutex);
203
204 return 0;
205 }
206
207 struct tty_struct *devpts_get_tty(int number)
208 {
209 struct dentry *dentry = get_node(number);
210 struct tty_struct *tty;
211
212 tty = NULL;
213 if (!IS_ERR(dentry)) {
214 if (dentry->d_inode)
215 tty = dentry->d_inode->i_private;
216 dput(dentry);
217 }
218
219 mutex_unlock(&devpts_root->d_inode->i_mutex);
220
221 return tty;
222 }
223
224 void devpts_pty_kill(int number)
225 {
226 struct dentry *dentry = get_node(number);
227
228 if (!IS_ERR(dentry)) {
229 struct inode *inode = dentry->d_inode;
230 if (inode) {
231 inode->i_nlink--;
232 d_delete(dentry);
233 dput(dentry);
234 }
235 dput(dentry);
236 }
237 mutex_unlock(&devpts_root->d_inode->i_mutex);
238 }
239
240 static int __init init_devpts_fs(void)
241 {
242 int err = register_filesystem(&devpts_fs_type);
243 if (!err) {
244 devpts_mnt = kern_mount(&devpts_fs_type);
245 if (IS_ERR(devpts_mnt))
246 err = PTR_ERR(devpts_mnt);
247 }
248 return err;
249 }
250
251 static void __exit exit_devpts_fs(void)
252 {
253 unregister_filesystem(&devpts_fs_type);
254 mntput(devpts_mnt);
255 }
256
257 module_init(init_devpts_fs)
258 module_exit(exit_devpts_fs)
259 MODULE_LICENSE("GPL");
260
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