Per-mount 'config' object
[linux-2.6.git] / fs / devpts / inode.c
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/mutex.h>
21 #include <linux/idr.h>
22 #include <linux/devpts_fs.h>
23 #include <linux/parser.h>
24 #include <linux/fsnotify.h>
25 #include <linux/seq_file.h>
26
27 #define DEVPTS_SUPER_MAGIC 0x1cd1
28
29 #define DEVPTS_DEFAULT_MODE 0600
30 #define PTMX_MINOR      2
31
32 extern int pty_limit;                   /* Config limit on Unix98 ptys */
33 static DEFINE_MUTEX(allocated_ptys_lock);
34
35 static struct vfsmount *devpts_mnt;
36
37 struct pts_mount_opts {
38         int setuid;
39         int setgid;
40         uid_t   uid;
41         gid_t   gid;
42         umode_t mode;
43 };
44
45 enum {
46         Opt_uid, Opt_gid, Opt_mode,
47         Opt_err
48 };
49
50 static const match_table_t tokens = {
51         {Opt_uid, "uid=%u"},
52         {Opt_gid, "gid=%u"},
53         {Opt_mode, "mode=%o"},
54         {Opt_err, NULL}
55 };
56
57 struct pts_fs_info {
58         struct ida allocated_ptys;
59         struct pts_mount_opts mount_opts;
60 };
61
62 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
63 {
64         return sb->s_fs_info;
65 }
66
67 static inline struct super_block *pts_sb_from_inode(struct inode *inode)
68 {
69         if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
70                 return inode->i_sb;
71
72         return devpts_mnt->mnt_sb;
73 }
74
75 static int devpts_remount(struct super_block *sb, int *flags, char *data)
76 {
77         char *p;
78         struct pts_fs_info *fsi = DEVPTS_SB(sb);
79         struct pts_mount_opts *opts = &fsi->mount_opts;
80
81         opts->setuid  = 0;
82         opts->setgid  = 0;
83         opts->uid     = 0;
84         opts->gid     = 0;
85         opts->mode    = DEVPTS_DEFAULT_MODE;
86
87         while ((p = strsep(&data, ",")) != NULL) {
88                 substring_t args[MAX_OPT_ARGS];
89                 int token;
90                 int option;
91
92                 if (!*p)
93                         continue;
94
95                 token = match_token(p, tokens, args);
96                 switch (token) {
97                 case Opt_uid:
98                         if (match_int(&args[0], &option))
99                                 return -EINVAL;
100                         opts->uid = option;
101                         opts->setuid = 1;
102                         break;
103                 case Opt_gid:
104                         if (match_int(&args[0], &option))
105                                 return -EINVAL;
106                         opts->gid = option;
107                         opts->setgid = 1;
108                         break;
109                 case Opt_mode:
110                         if (match_octal(&args[0], &option))
111                                 return -EINVAL;
112                         opts->mode = option & S_IALLUGO;
113                         break;
114                 default:
115                         printk(KERN_ERR "devpts: called with bogus options\n");
116                         return -EINVAL;
117                 }
118         }
119
120         return 0;
121 }
122
123 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
124 {
125         struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
126         struct pts_mount_opts *opts = &fsi->mount_opts;
127
128         if (opts->setuid)
129                 seq_printf(seq, ",uid=%u", opts->uid);
130         if (opts->setgid)
131                 seq_printf(seq, ",gid=%u", opts->gid);
132         seq_printf(seq, ",mode=%03o", opts->mode);
133
134         return 0;
135 }
136
137 static const struct super_operations devpts_sops = {
138         .statfs         = simple_statfs,
139         .remount_fs     = devpts_remount,
140         .show_options   = devpts_show_options,
141 };
142
143 static void *new_pts_fs_info(void)
144 {
145         struct pts_fs_info *fsi;
146
147         fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
148         if (!fsi)
149                 return NULL;
150
151         ida_init(&fsi->allocated_ptys);
152         fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
153
154         return fsi;
155 }
156
157 static int
158 devpts_fill_super(struct super_block *s, void *data, int silent)
159 {
160         struct inode * inode;
161
162         s->s_blocksize = 1024;
163         s->s_blocksize_bits = 10;
164         s->s_magic = DEVPTS_SUPER_MAGIC;
165         s->s_op = &devpts_sops;
166         s->s_time_gran = 1;
167
168         s->s_fs_info = new_pts_fs_info();
169         if (!s->s_fs_info)
170                 goto fail;
171
172         inode = new_inode(s);
173         if (!inode)
174                 goto free_fsi;
175         inode->i_ino = 1;
176         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
177         inode->i_blocks = 0;
178         inode->i_uid = inode->i_gid = 0;
179         inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
180         inode->i_op = &simple_dir_inode_operations;
181         inode->i_fop = &simple_dir_operations;
182         inode->i_nlink = 2;
183
184         s->s_root = d_alloc_root(inode);
185         if (s->s_root)
186                 return 0;
187         
188         printk("devpts: get root dentry failed\n");
189         iput(inode);
190
191 free_fsi:
192         kfree(s->s_fs_info);
193 fail:
194         return -ENOMEM;
195 }
196
197 static int devpts_get_sb(struct file_system_type *fs_type,
198         int flags, const char *dev_name, void *data, struct vfsmount *mnt)
199 {
200         return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
201 }
202
203 static void devpts_kill_sb(struct super_block *sb)
204 {
205         struct pts_fs_info *fsi = DEVPTS_SB(sb);
206
207         kfree(fsi);
208         kill_anon_super(sb);
209 }
210
211 static struct file_system_type devpts_fs_type = {
212         .owner          = THIS_MODULE,
213         .name           = "devpts",
214         .get_sb         = devpts_get_sb,
215         .kill_sb        = devpts_kill_sb,
216 };
217
218 /*
219  * The normal naming convention is simply /dev/pts/<number>; this conforms
220  * to the System V naming convention
221  */
222
223 int devpts_new_index(struct inode *ptmx_inode)
224 {
225         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
226         struct pts_fs_info *fsi = DEVPTS_SB(sb);
227         int index;
228         int ida_ret;
229
230 retry:
231         if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
232                 return -ENOMEM;
233         }
234
235         mutex_lock(&allocated_ptys_lock);
236         ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
237         if (ida_ret < 0) {
238                 mutex_unlock(&allocated_ptys_lock);
239                 if (ida_ret == -EAGAIN)
240                         goto retry;
241                 return -EIO;
242         }
243
244         if (index >= pty_limit) {
245                 ida_remove(&fsi->allocated_ptys, index);
246                 mutex_unlock(&allocated_ptys_lock);
247                 return -EIO;
248         }
249         mutex_unlock(&allocated_ptys_lock);
250         return index;
251 }
252
253 void devpts_kill_index(struct inode *ptmx_inode, int idx)
254 {
255         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
256         struct pts_fs_info *fsi = DEVPTS_SB(sb);
257
258         mutex_lock(&allocated_ptys_lock);
259         ida_remove(&fsi->allocated_ptys, idx);
260         mutex_unlock(&allocated_ptys_lock);
261 }
262
263 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
264 {
265         int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
266         struct tty_driver *driver = tty->driver;
267         dev_t device = MKDEV(driver->major, driver->minor_start+number);
268         struct dentry *dentry;
269         struct super_block *sb = pts_sb_from_inode(ptmx_inode);
270         struct inode *inode = new_inode(sb);
271         struct dentry *root = sb->s_root;
272         struct pts_fs_info *fsi = DEVPTS_SB(sb);
273         struct pts_mount_opts *opts = &fsi->mount_opts;
274         char s[12];
275
276         /* We're supposed to be given the slave end of a pty */
277         BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
278         BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
279
280         if (!inode)
281                 return -ENOMEM;
282
283         inode->i_ino = number+2;
284         inode->i_uid = config.setuid ? config.uid : current_fsuid();
285         inode->i_gid = config.setgid ? config.gid : current_fsgid();
286         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
287         init_special_inode(inode, S_IFCHR|opts->mode, device);
288         inode->i_private = tty;
289         tty->driver_data = inode;
290
291         sprintf(s, "%d", number);
292
293         mutex_lock(&root->d_inode->i_mutex);
294
295         dentry = d_alloc_name(root, s);
296         if (!IS_ERR(dentry)) {
297                 d_add(dentry, inode);
298                 fsnotify_create(root->d_inode, dentry);
299         }
300
301         mutex_unlock(&root->d_inode->i_mutex);
302
303         return 0;
304 }
305
306 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
307 {
308         BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
309
310         if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
311                 return (struct tty_struct *)pts_inode->i_private;
312         return NULL;
313 }
314
315 void devpts_pty_kill(struct tty_struct *tty)
316 {
317         struct inode *inode = tty->driver_data;
318         struct super_block *sb = pts_sb_from_inode(inode);
319         struct dentry *root = sb->s_root;
320         struct dentry *dentry;
321
322         BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
323
324         mutex_lock(&root->d_inode->i_mutex);
325
326         dentry = d_find_alias(inode);
327         if (dentry && !IS_ERR(dentry)) {
328                 inode->i_nlink--;
329                 d_delete(dentry);
330                 dput(dentry);
331         }
332
333         mutex_unlock(&root->d_inode->i_mutex);
334 }
335
336 static int __init init_devpts_fs(void)
337 {
338         int err = register_filesystem(&devpts_fs_type);
339         if (!err) {
340                 devpts_mnt = kern_mount(&devpts_fs_type);
341                 if (IS_ERR(devpts_mnt))
342                         err = PTR_ERR(devpts_mnt);
343         }
344         return err;
345 }
346
347 static void __exit exit_devpts_fs(void)
348 {
349         unregister_filesystem(&devpts_fs_type);
350         mntput(devpts_mnt);
351 }
352
353 module_init(init_devpts_fs)
354 module_exit(exit_devpts_fs)
355 MODULE_LICENSE("GPL");