[linux-2.6-block.git] / fs / devpts / inode.c

/* -*- linux-c -*- --------------------------------------------------------- *
 *
 * linux/fs/devpts/inode.c
 *
 *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.h>
#include <linux/magic.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>

#define DEVPTS_DEFAULT_MODE 0600
/*
 * ptmx is a new node in /dev/pts and will be unused in legacy (single-
 * instance) mode. To prevent surprises in user space, set permissions of
 * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
 * permissions.
 */
#define DEVPTS_DEFAULT_PTMX_MODE 0000
#define PTMX_MINOR	2

extern int pty_limit;			/* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);

static struct vfsmount *devpts_mnt;

struct pts_mount_opts {
	int setuid;
	int setgid;
	uid_t   uid;
	gid_t   gid;
	umode_t mode;
	umode_t ptmxmode;
	int newinstance;
};

enum {
	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
	Opt_err
};

static const match_table_t tokens = {
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_mode, "mode=%o"},
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	{Opt_ptmxmode, "ptmxmode=%o"},
	{Opt_newinstance, "newinstance"},
#endif
	{Opt_err, NULL}
};

struct pts_fs_info {
	struct ida allocated_ptys;
	struct pts_mount_opts mount_opts;
	struct dentry *ptmx_dentry;
};

static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return inode->i_sb;
#endif
	return devpts_mnt->mnt_sb;
}

#define PARSE_MOUNT	0
#define PARSE_REMOUNT	1

/*
 * parse_mount_options():
 * 	Set @opts to mount options specified in @data. If an option is not
 * 	specified in @data, set it to its default value. The exception is
 * 	'newinstance' option which can only be set/cleared on a mount (i.e.
 * 	cannot be changed during remount).
 *
 * Note: @data may be NULL (in which case all options are set to default).
 */
static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts)
{
	char *p;

	opts->setuid  = 0;
	opts->setgid  = 0;
	opts->uid     = 0;
	opts->gid     = 0;
	opts->mode    = DEVPTS_DEFAULT_MODE;
	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;

	/* newinstance makes sense only on initial mount */
	if (op == PARSE_MOUNT)
		opts->newinstance = 0;

	while ((p = strsep(&data, ",")) != NULL) {
		substring_t args[MAX_OPT_ARGS];
		int token;
		int option;

		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_uid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->uid = option;
			opts->setuid = 1;
			break;
		case Opt_gid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->gid = option;
			opts->setgid = 1;
			break;
		case Opt_mode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
		case Opt_ptmxmode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->ptmxmode = option & S_IALLUGO;
			break;
		case Opt_newinstance:
			/* newinstance makes sense only on initial mount */
			if (op == PARSE_MOUNT)
				opts->newinstance = 1;
			break;
#endif
		default:
			printk(KERN_ERR "devpts: called with bogus options\n");
			return -EINVAL;
		}
	}

	return 0;
}

#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
static int mknod_ptmx(struct super_block *sb)
{
	int mode;
	int rc = -ENOMEM;
	struct dentry *dentry;
	struct inode *inode;
	struct dentry *root = sb->s_root;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	mutex_lock(&root->d_inode->i_mutex);

	/* If we have already created ptmx node, return */
	if (fsi->ptmx_dentry) {
		rc = 0;
		goto out;
	}

	dentry = d_alloc_name(root, "ptmx");
	if (!dentry) {
		printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
		goto out;
	}

	/*
	 * Create a new 'ptmx' node in this mount of devpts.
	 */
	inode = new_inode(sb);
	if (!inode) {
		printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
		dput(dentry);
		goto out;
	}

	inode->i_ino = 2;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

	mode = S_IFCHR|opts->ptmxmode;
	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));

	d_add(dentry, inode);

	fsi->ptmx_dentry = dentry;
	rc = 0;
out:
	mutex_unlock(&root->d_inode->i_mutex);
	return rc;
}

static void update_ptmx_mode(struct pts_fs_info *fsi)
{
	struct inode *inode;
	if (fsi->ptmx_dentry) {
		inode = fsi->ptmx_dentry->d_inode;
		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
	}
}
#else
static inline void update_ptmx_mode(struct pts_fs_info *fsi)
{
       return;
}
#endif

static int devpts_remount(struct super_block *sb, int *flags, char *data)
{
	int err;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	err = parse_mount_options(data, PARSE_REMOUNT, opts);

	/*
	 * parse_mount_options() restores options to default values
	 * before parsing and may have changed ptmxmode. So, update the
	 * mode in the inode too. Bogus options don't fail the remount,
	 * so do this even on error return.
	 */
	update_ptmx_mode(fsi);

	return err;
}

static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	if (opts->setuid)
		seq_printf(seq, ",uid=%u", opts->uid);
	if (opts->setgid)
		seq_printf(seq, ",gid=%u", opts->gid);
	seq_printf(seq, ",mode=%03o", opts->mode);
#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
#endif

	return 0;
}

static const struct super_operations devpts_sops = {
	.statfs		= simple_statfs,
	.remount_fs	= devpts_remount,
	.show_options	= devpts_show_options,
};

static void *new_pts_fs_info(void)
{
	struct pts_fs_info *fsi;

	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	if (!fsi)
		return NULL;

	ida_init(&fsi->allocated_ptys);
	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;

	return fsi;
}

static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
	struct inode *inode;

	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = DEVPTS_SUPER_MAGIC;
	s->s_op = &devpts_sops;
	s->s_time_gran = 1;

	s->s_fs_info = new_pts_fs_info();
	if (!s->s_fs_info)
		goto fail;

	inode = new_inode(s);
	if (!inode)
		goto free_fsi;
	inode->i_ino = 1;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;
	inode->i_nlink = 2;

	s->s_root = d_alloc_root(inode);
	if (s->s_root)
		return 0;

	printk(KERN_ERR "devpts: get root dentry failed\n");
	iput(inode);

free_fsi:
	kfree(s->s_fs_info);
fail:
	return -ENOMEM;
}

#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
static int compare_init_pts_sb(struct super_block *s, void *p)
{
	if (devpts_mnt)
		return devpts_mnt->mnt_sb == s;
	return 0;
}

/*
 * devpts_get_sb()
 *
 *     If the '-o newinstance' mount option was specified, mount a new
 *     (private) instance of devpts.  PTYs created in this instance are
 *     independent of the PTYs in other devpts instances.
 *
 *     If the '-o newinstance' option was not specified, mount/remount the
 *     initial kernel mount of devpts.  This type of mount gives the
 *     legacy, single-instance semantics.
 *
 *     The 'newinstance' option is needed to support multiple namespace
 *     semantics in devpts while preserving backward compatibility of the
 *     current 'single-namespace' semantics. i.e all mounts of devpts
 *     without the 'newinstance' mount option should bind to the initial
 *     kernel mount, like get_sb_single().
 *
 *     Mounts with 'newinstance' option create a new, private namespace.
 *
 *     NOTE:
 *
 *     For single-mount semantics, devpts cannot use get_sb_single(),
 *     because get_sb_single()/sget() find and use the super-block from
 *     the most recent mount of devpts. But that recent mount may be a
 *     'newinstance' mount and get_sb_single() would pick the newinstance
 *     super-block instead of the initial super-block.
 */
static int devpts_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	int error;
	struct pts_mount_opts opts;
	struct super_block *s;

	error = parse_mount_options(data, PARSE_MOUNT, &opts);
	if (error)
		return error;

	if (opts.newinstance)
		s = sget(fs_type, NULL, set_anon_super, NULL);
	else
		s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);

	if (IS_ERR(s))
		return PTR_ERR(s);

	if (!s->s_root) {
		s->s_flags = flags;
		error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
		if (error)
			goto out_undo_sget;
		s->s_flags |= MS_ACTIVE;
	}

	simple_set_mnt(mnt, s);

	memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));

	error = mknod_ptmx(s);
	if (error)
		goto out_dput;

	return 0;

out_dput:
	dput(s->s_root); /* undo dget() in simple_set_mnt() */

out_undo_sget:
	deactivate_locked_super(s);
	return error;
}

#else
/*
 * This supports only the legacy single-instance semantics (no
 * multiple-instance semantics)
 */
static int devpts_get_sb(struct file_system_type *fs_type, int flags,
		const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}
#endif

static void devpts_kill_sb(struct super_block *sb)
{
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	kfree(fsi);
	kill_litter_super(sb);
}

static struct file_system_type devpts_fs_type = {
	.name		= "devpts",
	.get_sb		= devpts_get_sb,
	.kill_sb	= devpts_kill_sb,
};

/*
 * The normal naming convention is simply /dev/pts/<number>; this conforms
 * to the System V naming convention
 */

int devpts_new_index(struct inode *ptmx_inode)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	int index;
	int ida_ret;

retry:
	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
		return -ENOMEM;

	mutex_lock(&allocated_ptys_lock);
	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
	if (ida_ret < 0) {
		mutex_unlock(&allocated_ptys_lock);
		if (ida_ret == -EAGAIN)
			goto retry;
		return -EIO;
	}

	if (index >= pty_limit) {
		ida_remove(&fsi->allocated_ptys, index);
		mutex_unlock(&allocated_ptys_lock);
		return -EIO;
	}
	mutex_unlock(&allocated_ptys_lock);
	return index;
}

void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	mutex_lock(&allocated_ptys_lock);
	ida_remove(&fsi->allocated_ptys, idx);
	mutex_unlock(&allocated_ptys_lock);
}

int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
	/* tty layer puts index from devpts_new_index() in here */
	int number = tty->index;
	struct tty_driver *driver = tty->driver;
	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	struct dentry *dentry;
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct inode *inode = new_inode(sb);
	struct dentry *root = sb->s_root;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;
	char s[12];

	/* We're supposed to be given the slave end of a pty */
	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);

	if (!inode)
		return -ENOMEM;

	inode->i_ino = number + 3;
	inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
	inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	init_special_inode(inode, S_IFCHR|opts->mode, device);
	inode->i_private = tty;
	tty->driver_data = inode;

	sprintf(s, "%d", number);

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_alloc_name(root, s);
	if (!IS_ERR(dentry)) {
		d_add(dentry, inode);
		fsnotify_create(root->d_inode, dentry);
	}

	mutex_unlock(&root->d_inode->i_mutex);

	return 0;
}

struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return (struct tty_struct *)pts_inode->i_private;
	return NULL;
}

void devpts_pty_kill(struct tty_struct *tty)
{
	struct inode *inode = tty->driver_data;
	struct super_block *sb = pts_sb_from_inode(inode);
	struct dentry *root = sb->s_root;
	struct dentry *dentry;

	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_find_alias(inode);
	if (IS_ERR(dentry))
		goto out;

	if (dentry) {
		inode->i_nlink--;
		d_delete(dentry);
		dput(dentry);	/* d_alloc_name() in devpts_pty_new() */
	}

	dput(dentry);		/* d_find_alias above */
out:
	mutex_unlock(&root->d_inode->i_mutex);
}

static int __init init_devpts_fs(void)
{
	int err = register_filesystem(&devpts_fs_type);
	if (!err) {
		devpts_mnt = kern_mount(&devpts_fs_type);
		if (IS_ERR(devpts_mnt)) {
			err = PTR_ERR(devpts_mnt);
			unregister_filesystem(&devpts_fs_type);
		}
	}
	return err;
}
module_init(init_devpts_fs)
Commit	Line	Data
1da177e4 LT	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>
718a9163	20	#include <linux/mutex.h>
1fd7317d	21	#include <linux/magic.h>
718a9163	22	#include <linux/idr.h>
1da177e4	23	#include <linux/devpts_fs.h>
7a673c6b	24	#include <linux/parser.h>
3972b7f6	25	#include <linux/fsnotify.h>
b87a267e	26	#include <linux/seq_file.h>
1da177e4	27
b87a267e	28	#define DEVPTS_DEFAULT_MODE 0600
1f8f1e29 SB	29	/*
	30	* ptmx is a new node in /dev/pts and will be unused in legacy (single-
	31	* instance) mode. To prevent surprises in user space, set permissions of
	32	* ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
	33	* permissions.
	34	*/
	35	#define DEVPTS_DEFAULT_PTMX_MODE 0000
527b3e47	36	#define PTMX_MINOR 2
b87a267e	37
718a9163	38	extern int pty_limit; /* Config limit on Unix98 ptys */
718a9163 SB	39	static DEFINE_MUTEX(allocated_ptys_lock);
718a9163 SB	40
1da177e4	41	static struct vfsmount *devpts_mnt;
1da177e4	42
31af0abb	43	struct pts_mount_opts {
1da177e4 LT	44	int setuid;
	45	int setgid;
	46	uid_t uid;
	47	gid_t gid;
	48	umode_t mode;
1f8f1e29	49	umode_t ptmxmode;
2a1b2dc0	50	int newinstance;
31af0abb	51	};
1da177e4	52
7a673c6b	53	enum {
2a1b2dc0	54	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
7a673c6b DP	55	Opt_err
	56	};
	57
a447c093	58	static const match_table_t tokens = {
7a673c6b DP	59	{Opt_uid, "uid=%u"},
	60	{Opt_gid, "gid=%u"},
	61	{Opt_mode, "mode=%o"},
1f8f1e29 SB	62	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
1f8f1e29 SB	63	{Opt_ptmxmode, "ptmxmode=%o"},
2a1b2dc0	64	{Opt_newinstance, "newinstance"},
1f8f1e29	65	#endif
7a673c6b DP	66	{Opt_err, NULL}
	67	};
	68
e76b7c01 SB	69	struct pts_fs_info {
e76b7c01 SB	70	struct ida allocated_ptys;
31af0abb	71	struct pts_mount_opts mount_opts;
1f8f1e29	72	struct dentry *ptmx_dentry;
e76b7c01 SB	73	};
	74
	75	static inline struct pts_fs_info DEVPTS_SB(struct super_block sb)
	76	{
	77	return sb->s_fs_info;
	78	}
	79
59e55e6c SB	80	static inline struct super_block pts_sb_from_inode(struct inode inode)
59e55e6c SB	81	{
2a1b2dc0	82	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
59e55e6c SB	83	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
59e55e6c SB	84	return inode->i_sb;
2a1b2dc0	85	#endif
59e55e6c SB	86	return devpts_mnt->mnt_sb;
	87	}
	88
2a1b2dc0 SB	89	#define PARSE_MOUNT 0
	90	#define PARSE_REMOUNT 1
	91
1f71ebed SB	92	/*
	93	* parse_mount_options():
	94	* Set @opts to mount options specified in @data. If an option is not
	95	* specified in @data, set it to its default value. The exception is
	96	* 'newinstance' option which can only be set/cleared on a mount (i.e.
	97	* cannot be changed during remount).
	98	*
	99	* Note: @data may be NULL (in which case all options are set to default).
	100	*/
2a1b2dc0	101	static int parse_mount_options(char data, int op, struct pts_mount_opts opts)
1da177e4	102	{
7a673c6b DP	103	char *p;
7a673c6b DP	104
31af0abb SB	105	opts->setuid = 0;
	106	opts->setgid = 0;
	107	opts->uid = 0;
	108	opts->gid = 0;
	109	opts->mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	110	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
7a673c6b	111
2a1b2dc0 SB	112	/* newinstance makes sense only on initial mount */
	113	if (op == PARSE_MOUNT)
	114	opts->newinstance = 0;
	115
7a673c6b DP	116	while ((p = strsep(&data, ",")) != NULL) {
	117	substring_t args[MAX_OPT_ARGS];
	118	int token;
	119	int option;
	120
	121	if (!*p)
1da177e4	122	continue;
7a673c6b DP	123
	124	token = match_token(p, tokens, args);
	125	switch (token) {
	126	case Opt_uid:
	127	if (match_int(&args[0], &option))
	128	return -EINVAL;
31af0abb SB	129	opts->uid = option;
31af0abb SB	130	opts->setuid = 1;
7a673c6b DP	131	break;
	132	case Opt_gid:
	133	if (match_int(&args[0], &option))
	134	return -EINVAL;
31af0abb SB	135	opts->gid = option;
31af0abb SB	136	opts->setgid = 1;
7a673c6b DP	137	break;
	138	case Opt_mode:
	139	if (match_octal(&args[0], &option))
	140	return -EINVAL;
31af0abb	141	opts->mode = option & S_IALLUGO;
7a673c6b	142	break;
1f8f1e29 SB	143	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	144	case Opt_ptmxmode:
	145	if (match_octal(&args[0], &option))
	146	return -EINVAL;
	147	opts->ptmxmode = option & S_IALLUGO;
	148	break;
2a1b2dc0 SB	149	case Opt_newinstance:
	150	/* newinstance makes sense only on initial mount */
	151	if (op == PARSE_MOUNT)
	152	opts->newinstance = 1;
	153	break;
1f8f1e29	154	#endif
7a673c6b DP	155	default:
7a673c6b DP	156	printk(KERN_ERR "devpts: called with bogus options\n");
1da177e4 LT	157	return -EINVAL;
	158	}
	159	}
1da177e4 LT	160
	161	return 0;
	162	}
	163
1f8f1e29 SB	164	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	165	static int mknod_ptmx(struct super_block *sb)
	166	{
	167	int mode;
	168	int rc = -ENOMEM;
	169	struct dentry *dentry;
	170	struct inode *inode;
	171	struct dentry *root = sb->s_root;
	172	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	173	struct pts_mount_opts *opts = &fsi->mount_opts;
	174
	175	mutex_lock(&root->d_inode->i_mutex);
	176
	177	/* If we have already created ptmx node, return */
	178	if (fsi->ptmx_dentry) {
	179	rc = 0;
	180	goto out;
	181	}
	182
	183	dentry = d_alloc_name(root, "ptmx");
	184	if (!dentry) {
	185	printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
	186	goto out;
	187	}
	188
	189	/*
	190	* Create a new 'ptmx' node in this mount of devpts.
	191	*/
	192	inode = new_inode(sb);
	193	if (!inode) {
	194	printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
	195	dput(dentry);
	196	goto out;
	197	}
	198
	199	inode->i_ino = 2;
1f8f1e29 SB	200	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	201
	202	mode = S_IFCHR\|opts->ptmxmode;
	203	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
	204
	205	d_add(dentry, inode);
	206
	207	fsi->ptmx_dentry = dentry;
	208	rc = 0;
1f8f1e29 SB	209	out:
	210	mutex_unlock(&root->d_inode->i_mutex);
	211	return rc;
	212	}
	213
	214	static void update_ptmx_mode(struct pts_fs_info *fsi)
	215	{
	216	struct inode *inode;
	217	if (fsi->ptmx_dentry) {
	218	inode = fsi->ptmx_dentry->d_inode;
	219	inode->i_mode = S_IFCHR\|fsi->mount_opts.ptmxmode;
	220	}
	221	}
	222	#else
	223	static inline void update_ptmx_mode(struct pts_fs_info *fsi)
	224	{
	225	return;
	226	}
	227	#endif
	228
53af8ee4 SB	229	static int devpts_remount(struct super_block sb, int flags, char *data)
53af8ee4 SB	230	{
1f8f1e29	231	int err;
53af8ee4 SB	232	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	233	struct pts_mount_opts *opts = &fsi->mount_opts;
	234
2a1b2dc0	235	err = parse_mount_options(data, PARSE_REMOUNT, opts);
1f8f1e29 SB	236
	237	/*
	238	* parse_mount_options() restores options to default values
	239	* before parsing and may have changed ptmxmode. So, update the
	240	* mode in the inode too. Bogus options don't fail the remount,
	241	* so do this even on error return.
	242	*/
	243	update_ptmx_mode(fsi);
	244
	245	return err;
53af8ee4 SB	246	}
53af8ee4 SB	247
b87a267e MS	248	static int devpts_show_options(struct seq_file seq, struct vfsmount vfs)
b87a267e MS	249	{
31af0abb SB	250	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	251	struct pts_mount_opts *opts = &fsi->mount_opts;
	252
	253	if (opts->setuid)
	254	seq_printf(seq, ",uid=%u", opts->uid);
	255	if (opts->setgid)
	256	seq_printf(seq, ",gid=%u", opts->gid);
	257	seq_printf(seq, ",mode=%03o", opts->mode);
1f8f1e29 SB	258	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	259	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
	260	#endif
b87a267e MS	261
	262	return 0;
	263	}
	264
ee9b6d61	265	static const struct super_operations devpts_sops = {
1da177e4 LT	266	.statfs = simple_statfs,
1da177e4 LT	267	.remount_fs = devpts_remount,
b87a267e	268	.show_options = devpts_show_options,
1da177e4 LT	269	};
1da177e4 LT	270
e76b7c01 SB	271	static void *new_pts_fs_info(void)
	272	{
	273	struct pts_fs_info *fsi;
	274
	275	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	276	if (!fsi)
	277	return NULL;
	278
	279	ida_init(&fsi->allocated_ptys);
31af0abb	280	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	281	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
e76b7c01 SB	282
	283	return fsi;
	284	}
	285
1da177e4 LT	286	static int
	287	devpts_fill_super(struct super_block s, void data, int silent)
	288	{
1f8f1e29	289	struct inode *inode;
1da177e4 LT	290
	291	s->s_blocksize = 1024;
	292	s->s_blocksize_bits = 10;
	293	s->s_magic = DEVPTS_SUPER_MAGIC;
	294	s->s_op = &devpts_sops;
1da177e4 LT	295	s->s_time_gran = 1;
1da177e4 LT	296
e76b7c01 SB	297	s->s_fs_info = new_pts_fs_info();
	298	if (!s->s_fs_info)
	299	goto fail;
	300
1da177e4 LT	301	inode = new_inode(s);
1da177e4 LT	302	if (!inode)
e76b7c01	303	goto free_fsi;
1da177e4 LT	304	inode->i_ino = 1;
1da177e4 LT	305	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
1da177e4 LT	306	inode->i_mode = S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR;
	307	inode->i_op = &simple_dir_inode_operations;
	308	inode->i_fop = &simple_dir_operations;
	309	inode->i_nlink = 2;
	310
59e55e6c	311	s->s_root = d_alloc_root(inode);
1da177e4 LT	312	if (s->s_root)
1da177e4 LT	313	return 0;
1f8f1e29	314
835aa440	315	printk(KERN_ERR "devpts: get root dentry failed\n");
1da177e4	316	iput(inode);
e76b7c01 SB	317
	318	free_fsi:
	319	kfree(s->s_fs_info);
1da177e4 LT	320	fail:
	321	return -ENOMEM;
	322	}
	323
8c056e5b	324	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
d4076ac5 SB	325	static int compare_init_pts_sb(struct super_block s, void p)
	326	{
	327	if (devpts_mnt)
	328	return devpts_mnt->mnt_sb == s;
2a1b2dc0 SB	329	return 0;
	330	}
	331
2a1b2dc0	332	/*
1bd79035 SB	333	* devpts_get_sb()
	334	*
	335	* If the '-o newinstance' mount option was specified, mount a new
	336	* (private) instance of devpts. PTYs created in this instance are
	337	* independent of the PTYs in other devpts instances.
	338	*
	339	* If the '-o newinstance' option was not specified, mount/remount the
	340	* initial kernel mount of devpts. This type of mount gives the
	341	* legacy, single-instance semantics.
289f00e2	342	*
1bd79035 SB	343	* The 'newinstance' option is needed to support multiple namespace
	344	* semantics in devpts while preserving backward compatibility of the
	345	* current 'single-namespace' semantics. i.e all mounts of devpts
	346	* without the 'newinstance' mount option should bind to the initial
	347	* kernel mount, like get_sb_single().
d4076ac5	348	*
1bd79035	349	* Mounts with 'newinstance' option create a new, private namespace.
d4076ac5	350	*
1bd79035	351	* NOTE:
d4076ac5	352	*
1bd79035	353	* For single-mount semantics, devpts cannot use get_sb_single(),
d4076ac5 SB	354	* because get_sb_single()/sget() find and use the super-block from
	355	* the most recent mount of devpts. But that recent mount may be a
	356	* 'newinstance' mount and get_sb_single() would pick the newinstance
	357	* super-block instead of the initial super-block.
d4076ac5	358	*/
454e2398 DH	359	static int devpts_get_sb(struct file_system_type *fs_type,
454e2398 DH	360	int flags, const char dev_name, void data, struct vfsmount *mnt)
1da177e4	361	{
482984f0 SB	362	int error;
482984f0 SB	363	struct pts_mount_opts opts;
1bd79035	364	struct super_block *s;
2a1b2dc0	365
1f71ebed SB	366	error = parse_mount_options(data, PARSE_MOUNT, &opts);
	367	if (error)
	368	return error;
2a1b2dc0	369
482984f0	370	if (opts.newinstance)
1bd79035	371	s = sget(fs_type, NULL, set_anon_super, NULL);
482984f0	372	else
1bd79035	373	s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
945cf2c7	374
1bd79035 SB	375	if (IS_ERR(s))
	376	return PTR_ERR(s);
	377
	378	if (!s->s_root) {
	379	s->s_flags = flags;
	380	error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
	381	if (error)
	382	goto out_undo_sget;
	383	s->s_flags \|= MS_ACTIVE;
	384	}
	385
	386	simple_set_mnt(mnt, s);
	387
	388	memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
945cf2c7	389
1bd79035	390	error = mknod_ptmx(s);
945cf2c7 SB	391	if (error)
	392	goto out_dput;
	393
	394	return 0;
	395
	396	out_dput:
6f5bbff9	397	dput(s->s_root); /* undo dget() in simple_set_mnt() */
1bd79035 SB	398
1bd79035 SB	399	out_undo_sget:
6f5bbff9	400	deactivate_locked_super(s);
945cf2c7	401	return error;
1da177e4	402	}
482984f0	403
2a1b2dc0 SB	404	#else
	405	/*
	406	* This supports only the legacy single-instance semantics (no
	407	* multiple-instance semantics)
	408	*/
	409	static int devpts_get_sb(struct file_system_type *fs_type, int flags,
	410	const char dev_name, void data, struct vfsmount *mnt)
	411	{
	412	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
	413	}
	414	#endif
1da177e4	415
e76b7c01 SB	416	static void devpts_kill_sb(struct super_block *sb)
	417	{
	418	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	419
	420	kfree(fsi);
1f8f1e29	421	kill_litter_super(sb);
e76b7c01 SB	422	}
e76b7c01 SB	423
1da177e4	424	static struct file_system_type devpts_fs_type = {
1da177e4 LT	425	.name = "devpts",
1da177e4 LT	426	.get_sb = devpts_get_sb,
e76b7c01	427	.kill_sb = devpts_kill_sb,
1da177e4 LT	428	};
	429
	430	/*
	431	* The normal naming convention is simply /dev/pts/<number>; this conforms
	432	* to the System V naming convention
	433	*/
	434
15f1a633	435	int devpts_new_index(struct inode *ptmx_inode)
718a9163	436	{
e76b7c01 SB	437	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
e76b7c01 SB	438	struct pts_fs_info *fsi = DEVPTS_SB(sb);
718a9163	439	int index;
7ee7c12b	440	int ida_ret;
718a9163 SB	441
718a9163 SB	442	retry:
835aa440	443	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
718a9163	444	return -ENOMEM;
718a9163 SB	445
718a9163 SB	446	mutex_lock(&allocated_ptys_lock);
e76b7c01	447	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
7ee7c12b	448	if (ida_ret < 0) {
718a9163	449	mutex_unlock(&allocated_ptys_lock);
7ee7c12b	450	if (ida_ret == -EAGAIN)
718a9163 SB	451	goto retry;
	452	return -EIO;
	453	}
	454
	455	if (index >= pty_limit) {
e76b7c01	456	ida_remove(&fsi->allocated_ptys, index);
718a9163 SB	457	mutex_unlock(&allocated_ptys_lock);
	458	return -EIO;
	459	}
	460	mutex_unlock(&allocated_ptys_lock);
	461	return index;
	462	}
	463
15f1a633	464	void devpts_kill_index(struct inode *ptmx_inode, int idx)
718a9163	465	{
e76b7c01 SB	466	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	467	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	468
718a9163	469	mutex_lock(&allocated_ptys_lock);
e76b7c01	470	ida_remove(&fsi->allocated_ptys, idx);
718a9163 SB	471	mutex_unlock(&allocated_ptys_lock);
	472	}
	473
15f1a633	474	int devpts_pty_new(struct inode ptmx_inode, struct tty_struct tty)
1da177e4	475	{
835aa440 AC	476	/* tty layer puts index from devpts_new_index() in here */
835aa440 AC	477	int number = tty->index;
1da177e4 LT	478	struct tty_driver *driver = tty->driver;
	479	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	480	struct dentry *dentry;
59e55e6c SB	481	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	482	struct inode *inode = new_inode(sb);
	483	struct dentry *root = sb->s_root;
31af0abb SB	484	struct pts_fs_info *fsi = DEVPTS_SB(sb);
31af0abb SB	485	struct pts_mount_opts *opts = &fsi->mount_opts;
89a52e10	486	char s[12];
1da177e4 LT	487
	488	/* We're supposed to be given the slave end of a pty */
	489	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	490	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
	491
	492	if (!inode)
	493	return -ENOMEM;
	494
d0eafc7d DH	495	inode->i_ino = number + 3;
	496	inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
	497	inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
1da177e4	498	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
31af0abb	499	init_special_inode(inode, S_IFCHR\|opts->mode, device);
8e18e294	500	inode->i_private = tty;
a6f37daa	501	tty->driver_data = inode;
1da177e4	502
89a52e10 SB	503	sprintf(s, "%d", number);
89a52e10 SB	504
59e55e6c	505	mutex_lock(&root->d_inode->i_mutex);
89a52e10	506
59e55e6c	507	dentry = d_alloc_name(root, s);
89a52e10 SB	508	if (!IS_ERR(dentry)) {
89a52e10 SB	509	d_add(dentry, inode);
59e55e6c	510	fsnotify_create(root->d_inode, dentry);
3972b7f6	511	}
1da177e4	512
59e55e6c	513	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	514
	515	return 0;
	516	}
	517
15f1a633	518	struct tty_struct devpts_get_tty(struct inode pts_inode, int number)
1da177e4	519	{
527b3e47	520	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
1da177e4	521
527b3e47 SB	522	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	523	return (struct tty_struct *)pts_inode->i_private;
	524	return NULL;
1da177e4 LT	525	}
1da177e4 LT	526
15f1a633	527	void devpts_pty_kill(struct tty_struct *tty)
1da177e4	528	{
a6f37daa	529	struct inode *inode = tty->driver_data;
59e55e6c SB	530	struct super_block *sb = pts_sb_from_inode(inode);
59e55e6c SB	531	struct dentry *root = sb->s_root;
a6f37daa	532	struct dentry *dentry;
1da177e4	533
a6f37daa SB	534	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
a6f37daa SB	535
59e55e6c	536	mutex_lock(&root->d_inode->i_mutex);
a6f37daa SB	537
a6f37daa SB	538	dentry = d_find_alias(inode);
2a1b2dc0 SB	539	if (IS_ERR(dentry))
	540	goto out;
	541
	542	if (dentry) {
a6f37daa SB	543	inode->i_nlink--;
a6f37daa SB	544	d_delete(dentry);
835aa440	545	dput(dentry); /* d_alloc_name() in devpts_pty_new() */
1da177e4	546	}
a6f37daa	547
835aa440	548	dput(dentry); /* d_find_alias above */
2a1b2dc0	549	out:
59e55e6c	550	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	551	}
	552
	553	static int __init init_devpts_fs(void)
	554	{
	555	int err = register_filesystem(&devpts_fs_type);
	556	if (!err) {
	557	devpts_mnt = kern_mount(&devpts_fs_type);
93d5581e	558	if (IS_ERR(devpts_mnt)) {
1da177e4	559	err = PTR_ERR(devpts_mnt);
93d5581e AC	560	unregister_filesystem(&devpts_fs_type);
93d5581e AC	561	}
1da177e4 LT	562	}
	563	return err;
	564	}
1da177e4	565	module_init(init_devpts_fs)