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/slab.h>
19 #include <linux/mount.h>
20 #include <linux/tty.h>
21 #include <linux/mutex.h>
22 #include <linux/magic.h>
23 #include <linux/idr.h>
24 #include <linux/devpts_fs.h>
25 #include <linux/parser.h>
26 #include <linux/fsnotify.h>
27 #include <linux/seq_file.h>
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
94 * parse_mount_options():
95 * Set @opts to mount options specified in @data. If an option is not
96 * specified in @data, set it to its default value. The exception is
97 * 'newinstance' option which can only be set/cleared on a mount (i.e.
98 * cannot be changed during remount).
100 * Note: @data may be NULL (in which case all options are set to default).
102 static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
110 opts->mode = DEVPTS_DEFAULT_MODE;
111 opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
113 /* newinstance makes sense only on initial mount */
114 if (op == PARSE_MOUNT)
115 opts->newinstance = 0;
117 while ((p = strsep(&data, ",")) != NULL) {
118 substring_t args[MAX_OPT_ARGS];
125 token = match_token(p, tokens, args);
128 if (match_int(&args[0], &option))
134 if (match_int(&args[0], &option))
140 if (match_octal(&args[0], &option))
142 opts->mode = option & S_IALLUGO;
144 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
146 if (match_octal(&args[0], &option))
148 opts->ptmxmode = option & S_IALLUGO;
150 case Opt_newinstance:
151 /* newinstance makes sense only on initial mount */
152 if (op == PARSE_MOUNT)
153 opts->newinstance = 1;
157 printk(KERN_ERR "devpts: called with bogus options\n");
165 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
166 static int mknod_ptmx(struct super_block *sb)
170 struct dentry *dentry;
172 struct dentry *root = sb->s_root;
173 struct pts_fs_info *fsi = DEVPTS_SB(sb);
174 struct pts_mount_opts *opts = &fsi->mount_opts;
176 mutex_lock(&root->d_inode->i_mutex);
178 /* If we have already created ptmx node, return */
179 if (fsi->ptmx_dentry) {
184 dentry = d_alloc_name(root, "ptmx");
186 printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
191 * Create a new 'ptmx' node in this mount of devpts.
193 inode = new_inode(sb);
195 printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
201 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
203 mode = S_IFCHR|opts->ptmxmode;
204 init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
206 d_add(dentry, inode);
208 fsi->ptmx_dentry = dentry;
211 mutex_unlock(&root->d_inode->i_mutex);
215 static void update_ptmx_mode(struct pts_fs_info *fsi)
218 if (fsi->ptmx_dentry) {
219 inode = fsi->ptmx_dentry->d_inode;
220 inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
224 static inline void update_ptmx_mode(struct pts_fs_info *fsi)
230 static int devpts_remount(struct super_block *sb, int *flags, char *data)
233 struct pts_fs_info *fsi = DEVPTS_SB(sb);
234 struct pts_mount_opts *opts = &fsi->mount_opts;
236 err = parse_mount_options(data, PARSE_REMOUNT, opts);
239 * parse_mount_options() restores options to default values
240 * before parsing and may have changed ptmxmode. So, update the
241 * mode in the inode too. Bogus options don't fail the remount,
242 * so do this even on error return.
244 update_ptmx_mode(fsi);
249 static int devpts_show_options(struct seq_file *seq, struct dentry *root)
251 struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb);
252 struct pts_mount_opts *opts = &fsi->mount_opts;
255 seq_printf(seq, ",uid=%u", opts->uid);
257 seq_printf(seq, ",gid=%u", opts->gid);
258 seq_printf(seq, ",mode=%03o", opts->mode);
259 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
260 seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
266 static const struct super_operations devpts_sops = {
267 .statfs = simple_statfs,
268 .remount_fs = devpts_remount,
269 .show_options = devpts_show_options,
272 static void *new_pts_fs_info(void)
274 struct pts_fs_info *fsi;
276 fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
280 ida_init(&fsi->allocated_ptys);
281 fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
282 fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
288 devpts_fill_super(struct super_block *s, void *data, int silent)
292 s->s_blocksize = 1024;
293 s->s_blocksize_bits = 10;
294 s->s_magic = DEVPTS_SUPER_MAGIC;
295 s->s_op = &devpts_sops;
298 s->s_fs_info = new_pts_fs_info();
302 inode = new_inode(s);
306 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
307 inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
308 inode->i_op = &simple_dir_inode_operations;
309 inode->i_fop = &simple_dir_operations;
312 s->s_root = d_alloc_root(inode);
316 printk(KERN_ERR "devpts: get root dentry failed\n");
323 #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
324 static int compare_init_pts_sb(struct super_block *s, void *p)
327 return devpts_mnt->mnt_sb == s;
334 * If the '-o newinstance' mount option was specified, mount a new
335 * (private) instance of devpts. PTYs created in this instance are
336 * independent of the PTYs in other devpts instances.
338 * If the '-o newinstance' option was not specified, mount/remount the
339 * initial kernel mount of devpts. This type of mount gives the
340 * legacy, single-instance semantics.
342 * The 'newinstance' option is needed to support multiple namespace
343 * semantics in devpts while preserving backward compatibility of the
344 * current 'single-namespace' semantics. i.e all mounts of devpts
345 * without the 'newinstance' mount option should bind to the initial
346 * kernel mount, like mount_single().
348 * Mounts with 'newinstance' option create a new, private namespace.
352 * For single-mount semantics, devpts cannot use mount_single(),
353 * because mount_single()/sget() find and use the super-block from
354 * the most recent mount of devpts. But that recent mount may be a
355 * 'newinstance' mount and mount_single() would pick the newinstance
356 * super-block instead of the initial super-block.
358 static struct dentry *devpts_mount(struct file_system_type *fs_type,
359 int flags, const char *dev_name, void *data)
362 struct pts_mount_opts opts;
363 struct super_block *s;
365 error = parse_mount_options(data, PARSE_MOUNT, &opts);
367 return ERR_PTR(error);
369 if (opts.newinstance)
370 s = sget(fs_type, NULL, set_anon_super, NULL);
372 s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
379 error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
382 s->s_flags |= MS_ACTIVE;
385 memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
387 error = mknod_ptmx(s);
391 return dget(s->s_root);
394 deactivate_locked_super(s);
395 return ERR_PTR(error);
400 * This supports only the legacy single-instance semantics (no
401 * multiple-instance semantics)
403 static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
404 const char *dev_name, void *data)
406 return mount_single(fs_type, flags, data, devpts_fill_super);
410 static void devpts_kill_sb(struct super_block *sb)
412 struct pts_fs_info *fsi = DEVPTS_SB(sb);
415 kill_litter_super(sb);
418 static struct file_system_type devpts_fs_type = {
420 .mount = devpts_mount,
421 .kill_sb = devpts_kill_sb,
425 * The normal naming convention is simply /dev/pts/<number>; this conforms
426 * to the System V naming convention
429 int devpts_new_index(struct inode *ptmx_inode)
431 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
432 struct pts_fs_info *fsi = DEVPTS_SB(sb);
437 if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
440 mutex_lock(&allocated_ptys_lock);
441 ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
443 mutex_unlock(&allocated_ptys_lock);
444 if (ida_ret == -EAGAIN)
449 if (index >= pty_limit) {
450 ida_remove(&fsi->allocated_ptys, index);
451 mutex_unlock(&allocated_ptys_lock);
454 mutex_unlock(&allocated_ptys_lock);
458 void devpts_kill_index(struct inode *ptmx_inode, int idx)
460 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
461 struct pts_fs_info *fsi = DEVPTS_SB(sb);
463 mutex_lock(&allocated_ptys_lock);
464 ida_remove(&fsi->allocated_ptys, idx);
465 mutex_unlock(&allocated_ptys_lock);
468 int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
470 /* tty layer puts index from devpts_new_index() in here */
471 int number = tty->index;
472 struct tty_driver *driver = tty->driver;
473 dev_t device = MKDEV(driver->major, driver->minor_start+number);
474 struct dentry *dentry;
475 struct super_block *sb = pts_sb_from_inode(ptmx_inode);
476 struct inode *inode = new_inode(sb);
477 struct dentry *root = sb->s_root;
478 struct pts_fs_info *fsi = DEVPTS_SB(sb);
479 struct pts_mount_opts *opts = &fsi->mount_opts;
483 /* We're supposed to be given the slave end of a pty */
484 BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
485 BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
490 inode->i_ino = number + 3;
491 inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
492 inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
493 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
494 init_special_inode(inode, S_IFCHR|opts->mode, device);
495 inode->i_private = tty;
496 tty->driver_data = inode;
498 sprintf(s, "%d", number);
500 mutex_lock(&root->d_inode->i_mutex);
502 dentry = d_alloc_name(root, s);
504 d_add(dentry, inode);
505 fsnotify_create(root->d_inode, dentry);
511 mutex_unlock(&root->d_inode->i_mutex);
516 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
518 struct dentry *dentry;
519 struct tty_struct *tty;
521 BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
523 /* Ensure dentry has not been deleted by devpts_pty_kill() */
524 dentry = d_find_alias(pts_inode);
529 if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
530 tty = (struct tty_struct *)pts_inode->i_private;
537 void devpts_pty_kill(struct tty_struct *tty)
539 struct inode *inode = tty->driver_data;
540 struct super_block *sb = pts_sb_from_inode(inode);
541 struct dentry *root = sb->s_root;
542 struct dentry *dentry;
544 BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
546 mutex_lock(&root->d_inode->i_mutex);
548 dentry = d_find_alias(inode);
552 dput(dentry); /* d_alloc_name() in devpts_pty_new() */
553 dput(dentry); /* d_find_alias above */
555 mutex_unlock(&root->d_inode->i_mutex);
558 static int __init init_devpts_fs(void)
560 int err = register_filesystem(&devpts_fs_type);
562 devpts_mnt = kern_mount(&devpts_fs_type);
563 if (IS_ERR(devpts_mnt)) {
564 err = PTR_ERR(devpts_mnt);
565 unregister_filesystem(&devpts_fs_type);
570 module_init(init_devpts_fs)