[mirror_ubuntu-artful-kernel.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/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>

#define DEVPTS_SUPER_MAGIC 0x1cd1

#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

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;

	memset(&opts, 0, sizeof(opts));
	if (data) {
		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 = {
	.owner		= THIS_MODULE,
	.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);
	}
	return err;
}

static void __exit exit_devpts_fs(void)
{
	unregister_filesystem(&devpts_fs_type);
	mntput(devpts_mnt);
}

module_init(init_devpts_fs)
module_exit(exit_devpts_fs)
MODULE_LICENSE("GPL");
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 SB	20	#include <linux/mutex.h>
718a9163 SB	21	#include <linux/idr.h>
1da177e4	22	#include <linux/devpts_fs.h>
7a673c6b	23	#include <linux/parser.h>
3972b7f6	24	#include <linux/fsnotify.h>
b87a267e	25	#include <linux/seq_file.h>
1da177e4 LT	26
	27	#define DEVPTS_SUPER_MAGIC 0x1cd1
	28
b87a267e	29	#define DEVPTS_DEFAULT_MODE 0600
1f8f1e29 SB	30	/*
	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
	34	* permissions.
	35	*/
	36	#define DEVPTS_DEFAULT_PTMX_MODE 0000
527b3e47	37	#define PTMX_MINOR 2
b87a267e	38
718a9163	39	extern int pty_limit; /* Config limit on Unix98 ptys */
718a9163 SB	40	static DEFINE_MUTEX(allocated_ptys_lock);
718a9163 SB	41
1da177e4	42	static struct vfsmount *devpts_mnt;
1da177e4	43
31af0abb	44	struct pts_mount_opts {
1da177e4 LT	45	int setuid;
	46	int setgid;
	47	uid_t uid;
	48	gid_t gid;
	49	umode_t mode;
1f8f1e29	50	umode_t ptmxmode;
2a1b2dc0	51	int newinstance;
31af0abb	52	};
1da177e4	53
7a673c6b	54	enum {
2a1b2dc0	55	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance,
7a673c6b DP	56	Opt_err
	57	};
	58
a447c093	59	static const match_table_t tokens = {
7a673c6b DP	60	{Opt_uid, "uid=%u"},
	61	{Opt_gid, "gid=%u"},
	62	{Opt_mode, "mode=%o"},
1f8f1e29 SB	63	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
1f8f1e29 SB	64	{Opt_ptmxmode, "ptmxmode=%o"},
2a1b2dc0	65	{Opt_newinstance, "newinstance"},
1f8f1e29	66	#endif
7a673c6b DP	67	{Opt_err, NULL}
	68	};
	69
e76b7c01 SB	70	struct pts_fs_info {
e76b7c01 SB	71	struct ida allocated_ptys;
31af0abb	72	struct pts_mount_opts mount_opts;
1f8f1e29	73	struct dentry *ptmx_dentry;
e76b7c01 SB	74	};
	75
	76	static inline struct pts_fs_info DEVPTS_SB(struct super_block sb)
	77	{
	78	return sb->s_fs_info;
	79	}
	80
59e55e6c SB	81	static inline struct super_block pts_sb_from_inode(struct inode inode)
59e55e6c SB	82	{
2a1b2dc0	83	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
59e55e6c SB	84	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
59e55e6c SB	85	return inode->i_sb;
2a1b2dc0	86	#endif
59e55e6c SB	87	return devpts_mnt->mnt_sb;
	88	}
	89
2a1b2dc0 SB	90	#define PARSE_MOUNT 0
	91	#define PARSE_REMOUNT 1
	92
	93	static int parse_mount_options(char data, int op, struct pts_mount_opts opts)
1da177e4	94	{
7a673c6b DP	95	char *p;
7a673c6b DP	96
31af0abb SB	97	opts->setuid = 0;
	98	opts->setgid = 0;
	99	opts->uid = 0;
	100	opts->gid = 0;
	101	opts->mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	102	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
7a673c6b	103
2a1b2dc0 SB	104	/* newinstance makes sense only on initial mount */
	105	if (op == PARSE_MOUNT)
	106	opts->newinstance = 0;
	107
7a673c6b DP	108	while ((p = strsep(&data, ",")) != NULL) {
	109	substring_t args[MAX_OPT_ARGS];
	110	int token;
	111	int option;
	112
	113	if (!*p)
1da177e4	114	continue;
7a673c6b DP	115
	116	token = match_token(p, tokens, args);
	117	switch (token) {
	118	case Opt_uid:
	119	if (match_int(&args[0], &option))
	120	return -EINVAL;
31af0abb SB	121	opts->uid = option;
31af0abb SB	122	opts->setuid = 1;
7a673c6b DP	123	break;
	124	case Opt_gid:
	125	if (match_int(&args[0], &option))
	126	return -EINVAL;
31af0abb SB	127	opts->gid = option;
31af0abb SB	128	opts->setgid = 1;
7a673c6b DP	129	break;
	130	case Opt_mode:
	131	if (match_octal(&args[0], &option))
	132	return -EINVAL;
31af0abb	133	opts->mode = option & S_IALLUGO;
7a673c6b	134	break;
1f8f1e29 SB	135	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	136	case Opt_ptmxmode:
	137	if (match_octal(&args[0], &option))
	138	return -EINVAL;
	139	opts->ptmxmode = option & S_IALLUGO;
	140	break;
2a1b2dc0 SB	141	case Opt_newinstance:
	142	/* newinstance makes sense only on initial mount */
	143	if (op == PARSE_MOUNT)
	144	opts->newinstance = 1;
	145	break;
1f8f1e29	146	#endif
7a673c6b DP	147	default:
7a673c6b DP	148	printk(KERN_ERR "devpts: called with bogus options\n");
1da177e4 LT	149	return -EINVAL;
	150	}
	151	}
1da177e4 LT	152
	153	return 0;
	154	}
	155
1f8f1e29 SB	156	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	157	static int mknod_ptmx(struct super_block *sb)
	158	{
	159	int mode;
	160	int rc = -ENOMEM;
	161	struct dentry *dentry;
	162	struct inode *inode;
	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;
	166
	167	mutex_lock(&root->d_inode->i_mutex);
	168
	169	/* If we have already created ptmx node, return */
	170	if (fsi->ptmx_dentry) {
	171	rc = 0;
	172	goto out;
	173	}
	174
	175	dentry = d_alloc_name(root, "ptmx");
	176	if (!dentry) {
	177	printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
	178	goto out;
	179	}
	180
	181	/*
	182	* Create a new 'ptmx' node in this mount of devpts.
	183	*/
	184	inode = new_inode(sb);
	185	if (!inode) {
	186	printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
	187	dput(dentry);
	188	goto out;
	189	}
	190
	191	inode->i_ino = 2;
1f8f1e29 SB	192	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	193
	194	mode = S_IFCHR\|opts->ptmxmode;
	195	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
	196
	197	d_add(dentry, inode);
	198
	199	fsi->ptmx_dentry = dentry;
	200	rc = 0;
1f8f1e29 SB	201	out:
	202	mutex_unlock(&root->d_inode->i_mutex);
	203	return rc;
	204	}
	205
	206	static void update_ptmx_mode(struct pts_fs_info *fsi)
	207	{
	208	struct inode *inode;
	209	if (fsi->ptmx_dentry) {
	210	inode = fsi->ptmx_dentry->d_inode;
	211	inode->i_mode = S_IFCHR\|fsi->mount_opts.ptmxmode;
	212	}
	213	}
	214	#else
	215	static inline void update_ptmx_mode(struct pts_fs_info *fsi)
	216	{
	217	return;
	218	}
	219	#endif
	220
53af8ee4 SB	221	static int devpts_remount(struct super_block sb, int flags, char *data)
53af8ee4 SB	222	{
1f8f1e29	223	int err;
53af8ee4 SB	224	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	225	struct pts_mount_opts *opts = &fsi->mount_opts;
	226
2a1b2dc0	227	err = parse_mount_options(data, PARSE_REMOUNT, opts);
1f8f1e29 SB	228
	229	/*
	230	* parse_mount_options() restores options to default values
	231	* before parsing and may have changed ptmxmode. So, update the
	232	* mode in the inode too. Bogus options don't fail the remount,
	233	* so do this even on error return.
	234	*/
	235	update_ptmx_mode(fsi);
	236
	237	return err;
53af8ee4 SB	238	}
53af8ee4 SB	239
b87a267e MS	240	static int devpts_show_options(struct seq_file seq, struct vfsmount vfs)
b87a267e MS	241	{
31af0abb SB	242	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	243	struct pts_mount_opts *opts = &fsi->mount_opts;
	244
	245	if (opts->setuid)
	246	seq_printf(seq, ",uid=%u", opts->uid);
	247	if (opts->setgid)
	248	seq_printf(seq, ",gid=%u", opts->gid);
	249	seq_printf(seq, ",mode=%03o", opts->mode);
1f8f1e29 SB	250	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	251	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
	252	#endif
b87a267e MS	253
	254	return 0;
	255	}
	256
ee9b6d61	257	static const struct super_operations devpts_sops = {
1da177e4 LT	258	.statfs = simple_statfs,
1da177e4 LT	259	.remount_fs = devpts_remount,
b87a267e	260	.show_options = devpts_show_options,
1da177e4 LT	261	};
1da177e4 LT	262
e76b7c01 SB	263	static void *new_pts_fs_info(void)
	264	{
	265	struct pts_fs_info *fsi;
	266
	267	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	268	if (!fsi)
	269	return NULL;
	270
	271	ida_init(&fsi->allocated_ptys);
31af0abb	272	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	273	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
e76b7c01 SB	274
	275	return fsi;
	276	}
	277
1da177e4 LT	278	static int
	279	devpts_fill_super(struct super_block s, void data, int silent)
	280	{
1f8f1e29	281	struct inode *inode;
1da177e4 LT	282
	283	s->s_blocksize = 1024;
	284	s->s_blocksize_bits = 10;
	285	s->s_magic = DEVPTS_SUPER_MAGIC;
	286	s->s_op = &devpts_sops;
1da177e4 LT	287	s->s_time_gran = 1;
1da177e4 LT	288
e76b7c01 SB	289	s->s_fs_info = new_pts_fs_info();
	290	if (!s->s_fs_info)
	291	goto fail;
	292
1da177e4 LT	293	inode = new_inode(s);
1da177e4 LT	294	if (!inode)
e76b7c01	295	goto free_fsi;
1da177e4 LT	296	inode->i_ino = 1;
1da177e4 LT	297	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
1da177e4 LT	298	inode->i_mode = S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR;
	299	inode->i_op = &simple_dir_inode_operations;
	300	inode->i_fop = &simple_dir_operations;
	301	inode->i_nlink = 2;
	302
59e55e6c	303	s->s_root = d_alloc_root(inode);
1da177e4 LT	304	if (s->s_root)
1da177e4 LT	305	return 0;
1f8f1e29	306
835aa440	307	printk(KERN_ERR "devpts: get root dentry failed\n");
1da177e4	308	iput(inode);
e76b7c01 SB	309
	310	free_fsi:
	311	kfree(s->s_fs_info);
1da177e4 LT	312	fail:
	313	return -ENOMEM;
	314	}
	315
8c056e5b	316	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
d4076ac5 SB	317	static int compare_init_pts_sb(struct super_block s, void p)
	318	{
	319	if (devpts_mnt)
	320	return devpts_mnt->mnt_sb == s;
2a1b2dc0 SB	321	return 0;
	322	}
	323
2a1b2dc0	324	/*
1bd79035 SB	325	* devpts_get_sb()
	326	*
	327	* If the '-o newinstance' mount option was specified, mount a new
	328	* (private) instance of devpts. PTYs created in this instance are
	329	* independent of the PTYs in other devpts instances.
	330	*
	331	* If the '-o newinstance' option was not specified, mount/remount the
	332	* initial kernel mount of devpts. This type of mount gives the
	333	* legacy, single-instance semantics.
289f00e2	334	*
1bd79035 SB	335	* The 'newinstance' option is needed to support multiple namespace
	336	* semantics in devpts while preserving backward compatibility of the
	337	* current 'single-namespace' semantics. i.e all mounts of devpts
	338	* without the 'newinstance' mount option should bind to the initial
	339	* kernel mount, like get_sb_single().
d4076ac5	340	*
1bd79035	341	* Mounts with 'newinstance' option create a new, private namespace.
d4076ac5	342	*
1bd79035	343	* NOTE:
d4076ac5	344	*
1bd79035	345	* For single-mount semantics, devpts cannot use get_sb_single(),
d4076ac5 SB	346	* because get_sb_single()/sget() find and use the super-block from
	347	* the most recent mount of devpts. But that recent mount may be a
	348	* 'newinstance' mount and get_sb_single() would pick the newinstance
	349	* super-block instead of the initial super-block.
d4076ac5	350	*/
454e2398 DH	351	static int devpts_get_sb(struct file_system_type *fs_type,
454e2398 DH	352	int flags, const char dev_name, void data, struct vfsmount *mnt)
1da177e4	353	{
482984f0 SB	354	int error;
482984f0 SB	355	struct pts_mount_opts opts;
1bd79035	356	struct super_block *s;
2a1b2dc0	357
482984f0 SB	358	memset(&opts, 0, sizeof(opts));
	359	if (data) {
	360	error = parse_mount_options(data, PARSE_MOUNT, &opts);
	361	if (error)
	362	return error;
	363	}
2a1b2dc0	364
482984f0	365	if (opts.newinstance)
1bd79035	366	s = sget(fs_type, NULL, set_anon_super, NULL);
482984f0	367	else
1bd79035	368	s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
945cf2c7	369
1bd79035 SB	370	if (IS_ERR(s))
	371	return PTR_ERR(s);
	372
	373	if (!s->s_root) {
	374	s->s_flags = flags;
	375	error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
	376	if (error)
	377	goto out_undo_sget;
	378	s->s_flags \|= MS_ACTIVE;
	379	}
	380
	381	simple_set_mnt(mnt, s);
	382
	383	memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
945cf2c7	384
1bd79035	385	error = mknod_ptmx(s);
945cf2c7 SB	386	if (error)
	387	goto out_dput;
	388
	389	return 0;
	390
	391	out_dput:
6f5bbff9	392	dput(s->s_root); /* undo dget() in simple_set_mnt() */
1bd79035 SB	393
1bd79035 SB	394	out_undo_sget:
6f5bbff9	395	deactivate_locked_super(s);
945cf2c7	396	return error;
1da177e4	397	}
482984f0	398
2a1b2dc0 SB	399	#else
	400	/*
	401	* This supports only the legacy single-instance semantics (no
	402	* multiple-instance semantics)
	403	*/
	404	static int devpts_get_sb(struct file_system_type *fs_type, int flags,
	405	const char dev_name, void data, struct vfsmount *mnt)
	406	{
	407	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
	408	}
	409	#endif
1da177e4	410
e76b7c01 SB	411	static void devpts_kill_sb(struct super_block *sb)
	412	{
	413	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	414
	415	kfree(fsi);
1f8f1e29	416	kill_litter_super(sb);
e76b7c01 SB	417	}
e76b7c01 SB	418
1da177e4 LT	419	static struct file_system_type devpts_fs_type = {
	420	.owner = THIS_MODULE,
	421	.name = "devpts",
	422	.get_sb = devpts_get_sb,
e76b7c01	423	.kill_sb = devpts_kill_sb,
1da177e4 LT	424	};
	425
	426	/*
	427	* The normal naming convention is simply /dev/pts/<number>; this conforms
	428	* to the System V naming convention
	429	*/
	430
15f1a633	431	int devpts_new_index(struct inode *ptmx_inode)
718a9163	432	{
e76b7c01 SB	433	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
e76b7c01 SB	434	struct pts_fs_info *fsi = DEVPTS_SB(sb);
718a9163	435	int index;
7ee7c12b	436	int ida_ret;
718a9163 SB	437
718a9163 SB	438	retry:
835aa440	439	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL))
718a9163	440	return -ENOMEM;
718a9163 SB	441
718a9163 SB	442	mutex_lock(&allocated_ptys_lock);
e76b7c01	443	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
7ee7c12b	444	if (ida_ret < 0) {
718a9163	445	mutex_unlock(&allocated_ptys_lock);
7ee7c12b	446	if (ida_ret == -EAGAIN)
718a9163 SB	447	goto retry;
	448	return -EIO;
	449	}
	450
	451	if (index >= pty_limit) {
e76b7c01	452	ida_remove(&fsi->allocated_ptys, index);
718a9163 SB	453	mutex_unlock(&allocated_ptys_lock);
	454	return -EIO;
	455	}
	456	mutex_unlock(&allocated_ptys_lock);
	457	return index;
	458	}
	459
15f1a633	460	void devpts_kill_index(struct inode *ptmx_inode, int idx)
718a9163	461	{
e76b7c01 SB	462	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	463	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	464
718a9163	465	mutex_lock(&allocated_ptys_lock);
e76b7c01	466	ida_remove(&fsi->allocated_ptys, idx);
718a9163 SB	467	mutex_unlock(&allocated_ptys_lock);
	468	}
	469
15f1a633	470	int devpts_pty_new(struct inode ptmx_inode, struct tty_struct tty)
1da177e4	471	{
835aa440 AC	472	/* tty layer puts index from devpts_new_index() in here */
835aa440 AC	473	int number = tty->index;
1da177e4 LT	474	struct tty_driver *driver = tty->driver;
	475	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	476	struct dentry *dentry;
59e55e6c SB	477	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	478	struct inode *inode = new_inode(sb);
	479	struct dentry *root = sb->s_root;
31af0abb SB	480	struct pts_fs_info *fsi = DEVPTS_SB(sb);
31af0abb SB	481	struct pts_mount_opts *opts = &fsi->mount_opts;
89a52e10	482	char s[12];
1da177e4 LT	483
	484	/* We're supposed to be given the slave end of a pty */
	485	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	486	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
	487
	488	if (!inode)
	489	return -ENOMEM;
	490
d0eafc7d DH	491	inode->i_ino = number + 3;
	492	inode->i_uid = opts->setuid ? opts->uid : current_fsuid();
	493	inode->i_gid = opts->setgid ? opts->gid : current_fsgid();
1da177e4	494	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
31af0abb	495	init_special_inode(inode, S_IFCHR\|opts->mode, device);
8e18e294	496	inode->i_private = tty;
a6f37daa	497	tty->driver_data = inode;
1da177e4	498
89a52e10 SB	499	sprintf(s, "%d", number);
89a52e10 SB	500
59e55e6c	501	mutex_lock(&root->d_inode->i_mutex);
89a52e10	502
59e55e6c	503	dentry = d_alloc_name(root, s);
89a52e10 SB	504	if (!IS_ERR(dentry)) {
89a52e10 SB	505	d_add(dentry, inode);
59e55e6c	506	fsnotify_create(root->d_inode, dentry);
3972b7f6	507	}
1da177e4	508
59e55e6c	509	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	510
	511	return 0;
	512	}
	513
15f1a633	514	struct tty_struct devpts_get_tty(struct inode pts_inode, int number)
1da177e4	515	{
527b3e47	516	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
1da177e4	517
527b3e47 SB	518	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	519	return (struct tty_struct *)pts_inode->i_private;
	520	return NULL;
1da177e4 LT	521	}
1da177e4 LT	522
15f1a633	523	void devpts_pty_kill(struct tty_struct *tty)
1da177e4	524	{
a6f37daa	525	struct inode *inode = tty->driver_data;
59e55e6c SB	526	struct super_block *sb = pts_sb_from_inode(inode);
59e55e6c SB	527	struct dentry *root = sb->s_root;
a6f37daa	528	struct dentry *dentry;
1da177e4	529
a6f37daa SB	530	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
a6f37daa SB	531
59e55e6c	532	mutex_lock(&root->d_inode->i_mutex);
a6f37daa SB	533
a6f37daa SB	534	dentry = d_find_alias(inode);
2a1b2dc0 SB	535	if (IS_ERR(dentry))
	536	goto out;
	537
	538	if (dentry) {
a6f37daa SB	539	inode->i_nlink--;
a6f37daa SB	540	d_delete(dentry);
835aa440	541	dput(dentry); /* d_alloc_name() in devpts_pty_new() */
1da177e4	542	}
a6f37daa	543
835aa440	544	dput(dentry); /* d_find_alias above */
2a1b2dc0	545	out:
59e55e6c	546	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	547	}
	548
	549	static int __init init_devpts_fs(void)
	550	{
	551	int err = register_filesystem(&devpts_fs_type);
	552	if (!err) {
	553	devpts_mnt = kern_mount(&devpts_fs_type);
	554	if (IS_ERR(devpts_mnt))
	555	err = PTR_ERR(devpts_mnt);
	556	}
	557	return err;
	558	}
	559
	560	static void __exit exit_devpts_fs(void)
	561	{
	562	unregister_filesystem(&devpts_fs_type);
	563	mntput(devpts_mnt);
	564	}
	565
	566	module_init(init_devpts_fs)
	567	module_exit(exit_devpts_fs)
	568	MODULE_LICENSE("GPL");