1 /* -*- linux-c -*- --------------------------------------------------------- *
3 * linux/fs/devpts/inode.c
5 * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
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.
11 * ------------------------------------------------------------------------- */
13 #include <linux/module.h>
14 #include <linux/init.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>
27 #define DEVPTS_SUPER_MAGIC 0x1cd1
29 #define DEVPTS_DEFAULT_MODE 0600
31 * ptmx is a new node in /dev/pts and will be unused in legacy (single-
32 * instance) mode. To prevent surprises in user space, set permissions of
33 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
36 #define DEVPTS_DEFAULT_PTMX_MODE 0000
39 extern int pty_limit; /* Config limit on Unix98 ptys */
40 static DEFINE_MUTEX(allocated_ptys_lock);
42 static struct vfsmount *devpts_mnt;
44 struct pts_mount_opts {
55 Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
59 static const match_table_t tokens = {
62 {Opt_mode, "mode=%o"},
63 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
64 {Opt_ptmxmode, "ptmxmode=%o"},
65 {Opt_newinstance, "newinstance"},
71 struct ida allocated_ptys;
72 struct pts_mount_opts mount_opts;
73 struct dentry *ptmx_dentry;
76 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
81 static inline struct super_block *pts_sb_from_inode(struct inode *inode)
83 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
84 if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
87 return devpts_mnt->mnt_sb;
91 #define PARSE_REMOUNT 1
93 static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
101 opts->mode = DEVPTS_DEFAULT_MODE;
102 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
104 /* newinstance makes sense only on initial mount */
105 if (op == PARSE_MOUNT)
106 opts->newinstance = 0;
108 while ((p = strsep(&data, ",")) != NULL) {
109 substring_t args[MAX_OPT_ARGS];
116 token = match_token(p, tokens, args);
119 if (match_int(&args[0], &option))
125 if (match_int(&args[0], &option))
131 if (match_octal(&args[0], &option))
133 opts->mode = option & S_IALLUGO;
135 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
137 if (match_octal(&args[0], &option))
139 opts->ptmxmode = option & S_IALLUGO;
141 case Opt_newinstance:
142 /* newinstance makes sense only on initial mount */
143 if (op == PARSE_MOUNT)
144 opts->newinstance = 1;
148 printk(KERN_ERR "devpts: called with bogus options\n");
156 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
157 static int mknod_ptmx(struct super_block *sb)
161 struct dentry *dentry;
163 struct dentry *root = sb->s_root;
164 struct pts_fs_info *fsi = DEVPTS_SB(sb);
165 struct pts_mount_opts *opts = &fsi->mount_opts;
167 mutex_lock(&root->d_inode->i_mutex);
169 /* If we have already created ptmx node, return */
170 if (fsi->ptmx_dentry) {
175 dentry = d_alloc_name(root, "ptmx");
177 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
182 * Create a new 'ptmx' node in this mount of devpts.
184 inode = new_inode(sb);
186 printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
192 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
194 mode = S_IFCHR|opts->ptmxmode;
195 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
197 d_add(dentry, inode);
199 fsi->ptmx_dentry = dentry;
202 printk(KERN_DEBUG "Created ptmx node in devpts ino %lu\n",
205 mutex_unlock(&root->d_inode->i_mutex);
209 static void update_ptmx_mode(struct pts_fs_info *fsi)
212 if (fsi->ptmx_dentry) {
213 inode = fsi->ptmx_dentry->d_inode;
214 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
218 static inline void update_ptmx_mode(struct pts_fs_info *fsi)
224 static int devpts_remount(struct super_block *sb, int *flags, char *data)
227 struct pts_fs_info *fsi = DEVPTS_SB(sb);
228 struct pts_mount_opts *opts = &fsi->mount_opts;
230 err = parse_mount_options(data, PARSE_REMOUNT, opts);
233 * parse_mount_options() restores options to default values
234 * before parsing and may have changed ptmxmode. So, update the
235 * mode in the inode too. Bogus options don't fail the remount,
236 * so do this even on error return.
238 update_ptmx_mode(fsi);
243 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
245 struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
246 struct pts_mount_opts *opts = &fsi->mount_opts;
249 seq_printf(seq, ",uid=%u", opts->uid);
251 seq_printf(seq, ",gid=%u", opts->gid);
252 seq_printf(seq, ",mode=%03o", opts->mode);
253 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
254 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
260 static const struct super_operations devpts_sops = {
261 .statfs = simple_statfs,
262 .remount_fs = devpts_remount,
263 .show_options = devpts_show_options,
266 static void *new_pts_fs_info(void)
268 struct pts_fs_info *fsi;
270 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
274 ida_init(&fsi->allocated_ptys);
275 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
276 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
282 devpts_fill_super(struct super_block *s, void *data, int silent)
286 s->s_blocksize = 1024;
287 s->s_blocksize_bits = 10;
288 s->s_magic = DEVPTS_SUPER_MAGIC;
289 s->s_op = &devpts_sops;
292 s->s_fs_info = new_pts_fs_info();
296 inode = new_inode(s);
300 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
301 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
302 inode->i_op = &simple_dir_inode_operations;
303 inode->i_fop = &simple_dir_operations;
306 s->s_root = d_alloc_root(inode);
310 printk(KERN_ERR "devpts: get root dentry failed\n");
319 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
320 static int compare_init_pts_sb(struct super_block *s, void *p)
323 return devpts_mnt->mnt_sb == s;
328 * Safely parse the mount options in @data and update @opts.
330 * devpts ends up parsing options two times during mount, due to the
331 * two modes of operation it supports. The first parse occurs in
332 * devpts_get_sb() when determining the mode (single-instance or
333 * multi-instance mode). The second parse happens in devpts_remount()
334 * or new_pts_mount() depending on the mode.
336 * Parsing of options modifies the @data making subsequent parsing
337 * incorrect. So make a local copy of @data and parse it.
339 * Return: 0 On success, -errno on error
341 static int safe_parse_mount_options(void *data, struct pts_mount_opts *opts)
349 /* Use kstrdup() ? */
350 datacp = kmalloc(PAGE_SIZE, GFP_KERNEL);
354 memcpy(datacp, data, PAGE_SIZE);
355 rc = parse_mount_options((char *)datacp, PARSE_MOUNT, opts);
362 * Mount a new (private) instance of devpts. PTYs created in this
363 * instance are independent of the PTYs in other devpts instances.
365 static int new_pts_mount(struct file_system_type *fs_type, int flags,
366 void *data, struct vfsmount *mnt)
369 struct pts_fs_info *fsi;
370 struct pts_mount_opts *opts;
372 printk(KERN_NOTICE "devpts: newinstance mount\n");
374 err = get_sb_nodev(fs_type, flags, data, devpts_fill_super, mnt);
378 fsi = DEVPTS_SB(mnt->mnt_sb);
379 opts = &fsi->mount_opts;
381 err = parse_mount_options(data, PARSE_MOUNT, opts);
385 err = mknod_ptmx(mnt->mnt_sb);
392 dput(mnt->mnt_sb->s_root);
393 deactivate_super(mnt->mnt_sb);
398 * Check if 'newinstance' mount option was specified in @data.
400 * Return: -errno on error (eg: invalid mount options specified)
401 * : 1 if 'newinstance' mount option was specified
402 * : 0 if 'newinstance' mount option was NOT specified
404 static int is_new_instance_mount(void *data)
407 struct pts_mount_opts opts;
412 rc = safe_parse_mount_options(data, &opts);
414 rc = opts.newinstance;
422 * This interface is needed to support multiple namespace semantics in
423 * devpts while preserving backward compatibility of the current 'single-
424 * namespace' semantics. i.e all mounts of devpts without the 'newinstance'
425 * mount option should bind to the initial kernel mount, like
428 * Mounts with 'newinstance' option create a new private namespace.
430 * But for single-mount semantics, devpts cannot use get_sb_single(),
431 * because get_sb_single()/sget() find and use the super-block from
432 * the most recent mount of devpts. But that recent mount may be a
433 * 'newinstance' mount and get_sb_single() would pick the newinstance
434 * super-block instead of the initial super-block.
436 * This interface is identical to get_sb_single() except that it
437 * consistently selects the 'single-namespace' superblock even in the
438 * presence of the private namespace (i.e 'newinstance') super-blocks.
440 static int get_init_pts_sb(struct file_system_type *fs_type, int flags,
441 void *data, struct vfsmount *mnt)
443 struct super_block *s;
446 s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
452 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
454 up_write(&s->s_umount);
458 s->s_flags |= MS_ACTIVE;
460 do_remount_sb(s, flags, data, 0);
461 return simple_set_mnt(mnt, s);
465 * Mount or remount the initial kernel mount of devpts. This type of
466 * mount maintains the legacy, single-instance semantics, while the
467 * kernel still allows multiple-instances.
469 static int init_pts_mount(struct file_system_type *fs_type, int flags,
470 void *data, struct vfsmount *mnt)
474 err = get_init_pts_sb(fs_type, flags, data, mnt);
478 err = mknod_ptmx(mnt->mnt_sb);
480 dput(mnt->mnt_sb->s_root);
481 deactivate_super(mnt->mnt_sb);
487 static int devpts_get_sb(struct file_system_type *fs_type,
488 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
492 new = is_new_instance_mount(data);
497 return new_pts_mount(fs_type, flags, data, mnt);
499 return init_pts_mount(fs_type, flags, data, mnt);
503 * This supports only the legacy single-instance semantics (no
504 * multiple-instance semantics)
506 static int devpts_get_sb(struct file_system_type *fs_type, int flags,
507 const char *dev_name, void *data, struct vfsmount *mnt)
509 return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
513 static void devpts_kill_sb(struct super_block *sb)
515 struct pts_fs_info *fsi = DEVPTS_SB(sb);
518 kill_litter_super(sb);
521 static struct file_system_type devpts_fs_type = {
522 .owner = THIS_MODULE,
524 .get_sb = devpts_get_sb,
525 .kill_sb = devpts_kill_sb,
529 * The normal naming convention is simply /dev/pts/<number>; this conforms
530 * to the System V naming convention
533 int devpts_new_index(struct inode *ptmx_inode)
535 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
536 struct pts_fs_info *fsi = DEVPTS_SB(sb);
541 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
544 mutex_lock(&allocated_ptys_lock);
545 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
547 mutex_unlock(&allocated_ptys_lock);
548 if (ida_ret == -EAGAIN)
553 if (index >= pty_limit) {
554 ida_remove(&fsi->allocated_ptys, index);
555 mutex_unlock(&allocated_ptys_lock);
558 mutex_unlock(&allocated_ptys_lock);
562 void devpts_kill_index(struct inode *ptmx_inode, int idx)
564 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
565 struct pts_fs_info *fsi = DEVPTS_SB(sb);
567 mutex_lock(&allocated_ptys_lock);
568 ida_remove(&fsi->allocated_ptys, idx);
569 mutex_unlock(&allocated_ptys_lock);
572 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
574 /* tty layer puts index from devpts_new_index() in here */
575 int number = tty->index;
576 struct tty_driver *driver = tty->driver;
577 dev_t device = MKDEV(driver->major, driver->minor_start+number);
578 struct dentry *dentry;
579 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
580 struct inode *inode = new_inode(sb);
581 struct dentry *root = sb->s_root;
582 struct pts_fs_info *fsi = DEVPTS_SB(sb);
583 struct pts_mount_opts *opts = &fsi->mount_opts;
586 /* We're supposed to be given the slave end of a pty */
587 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
588 BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
593 inode->i_ino = number + 3;
594 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
595 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
596 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
597 init_special_inode(inode, S_IFCHR|opts->mode, device);
598 inode->i_private = tty;
599 tty->driver_data = inode;
601 sprintf(s, "%d", number);
603 mutex_lock(&root->d_inode->i_mutex);
605 dentry = d_alloc_name(root, s);
606 if (!IS_ERR(dentry)) {
607 d_add(dentry, inode);
608 fsnotify_create(root->d_inode, dentry);
611 mutex_unlock(&root->d_inode->i_mutex);
616 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
618 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
620 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
621 return (struct tty_struct *)pts_inode->i_private;
625 void devpts_pty_kill(struct tty_struct *tty)
627 struct inode *inode = tty->driver_data;
628 struct super_block *sb = pts_sb_from_inode(inode);
629 struct dentry *root = sb->s_root;
630 struct dentry *dentry;
632 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
634 mutex_lock(&root->d_inode->i_mutex);
636 dentry = d_find_alias(inode);
643 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
646 dput(dentry); /* d_find_alias above */
648 mutex_unlock(&root->d_inode->i_mutex);
651 static int __init init_devpts_fs(void)
653 int err = register_filesystem(&devpts_fs_type);
655 devpts_mnt = kern_mount(&devpts_fs_type);
656 if (IS_ERR(devpts_mnt))
657 err = PTR_ERR(devpts_mnt);
662 static void __exit exit_devpts_fs(void)
664 unregister_filesystem(&devpts_fs_type);
668 module_init(init_devpts_fs)
669 module_exit(exit_devpts_fs)
670 MODULE_LICENSE("GPL");