[net-next-2.6.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/slab.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_mount()
 *
 *     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 mount_single().
 *
 *     Mounts with 'newinstance' option create a new, private namespace.
 *
 *     NOTE:
 *
 *     For single-mount semantics, devpts cannot use mount_single(),
 *     because mount_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 mount_single() would pick the newinstance
 *     super-block instead of the initial super-block.
 */
static struct dentry *devpts_mount(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data)
{
	int error;
	struct pts_mount_opts opts;
	struct super_block *s;

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

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

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

	return dget(s->s_root);

out_undo_sget:
	deactivate_locked_super(s);
	return ERR_PTR(error);
}

#else
/*
 * This supports only the legacy single-instance semantics (no
 * multiple-instance semantics)
 */
static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags,
		const char *dev_name, void *data)
{
	return mount_single(fs_type, flags, data, devpts_fill_super);
}
#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",
	.mount		= devpts_mount,
	.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)
{
	struct dentry *dentry;
	struct tty_struct *tty;

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

	/* Ensure dentry has not been deleted by devpts_pty_kill() */
	dentry = d_find_alias(pts_inode);
	if (!dentry)
		return NULL;

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

	dput(dentry);

	return tty;
}

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>
5a0e3ad6	18	#include <linux/slab.h>
1da177e4 LT	19	#include <linux/mount.h>
1da177e4 LT	20	#include <linux/tty.h>
718a9163	21	#include <linux/mutex.h>
1fd7317d	22	#include <linux/magic.h>
718a9163	23	#include <linux/idr.h>
1da177e4	24	#include <linux/devpts_fs.h>
7a673c6b	25	#include <linux/parser.h>
3972b7f6	26	#include <linux/fsnotify.h>
b87a267e	27	#include <linux/seq_file.h>
1da177e4	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
1f71ebed SB	93	/*
	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).
	99	*
	100	* Note: @data may be NULL (in which case all options are set to default).
	101	*/
2a1b2dc0	102	static int parse_mount_options(char data, int op, struct pts_mount_opts opts)
1da177e4	103	{
7a673c6b DP	104	char *p;
7a673c6b DP	105
31af0abb SB	106	opts->setuid = 0;
	107	opts->setgid = 0;
	108	opts->uid = 0;
	109	opts->gid = 0;
	110	opts->mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	111	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
7a673c6b	112
2a1b2dc0 SB	113	/* newinstance makes sense only on initial mount */
	114	if (op == PARSE_MOUNT)
	115	opts->newinstance = 0;
	116
7a673c6b DP	117	while ((p = strsep(&data, ",")) != NULL) {
	118	substring_t args[MAX_OPT_ARGS];
	119	int token;
	120	int option;
	121
	122	if (!*p)
1da177e4	123	continue;
7a673c6b DP	124
	125	token = match_token(p, tokens, args);
	126	switch (token) {
	127	case Opt_uid:
	128	if (match_int(&args[0], &option))
	129	return -EINVAL;
31af0abb SB	130	opts->uid = option;
31af0abb SB	131	opts->setuid = 1;
7a673c6b DP	132	break;
	133	case Opt_gid:
	134	if (match_int(&args[0], &option))
	135	return -EINVAL;
31af0abb SB	136	opts->gid = option;
31af0abb SB	137	opts->setgid = 1;
7a673c6b DP	138	break;
	139	case Opt_mode:
	140	if (match_octal(&args[0], &option))
	141	return -EINVAL;
31af0abb	142	opts->mode = option & S_IALLUGO;
7a673c6b	143	break;
1f8f1e29 SB	144	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	145	case Opt_ptmxmode:
	146	if (match_octal(&args[0], &option))
	147	return -EINVAL;
	148	opts->ptmxmode = option & S_IALLUGO;
	149	break;
2a1b2dc0 SB	150	case Opt_newinstance:
	151	/* newinstance makes sense only on initial mount */
	152	if (op == PARSE_MOUNT)
	153	opts->newinstance = 1;
	154	break;
1f8f1e29	155	#endif
7a673c6b DP	156	default:
7a673c6b DP	157	printk(KERN_ERR "devpts: called with bogus options\n");
1da177e4 LT	158	return -EINVAL;
	159	}
	160	}
1da177e4 LT	161
	162	return 0;
	163	}
	164
1f8f1e29 SB	165	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	166	static int mknod_ptmx(struct super_block *sb)
	167	{
	168	int mode;
	169	int rc = -ENOMEM;
	170	struct dentry *dentry;
	171	struct inode *inode;
	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;
	175
	176	mutex_lock(&root->d_inode->i_mutex);
	177
	178	/* If we have already created ptmx node, return */
	179	if (fsi->ptmx_dentry) {
	180	rc = 0;
	181	goto out;
	182	}
	183
	184	dentry = d_alloc_name(root, "ptmx");
	185	if (!dentry) {
	186	printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
	187	goto out;
	188	}
	189
	190	/*
	191	* Create a new 'ptmx' node in this mount of devpts.
	192	*/
	193	inode = new_inode(sb);
	194	if (!inode) {
	195	printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
	196	dput(dentry);
	197	goto out;
	198	}
	199
	200	inode->i_ino = 2;
1f8f1e29 SB	201	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	202
	203	mode = S_IFCHR\|opts->ptmxmode;
	204	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
	205
	206	d_add(dentry, inode);
	207
	208	fsi->ptmx_dentry = dentry;
	209	rc = 0;
1f8f1e29 SB	210	out:
	211	mutex_unlock(&root->d_inode->i_mutex);
	212	return rc;
	213	}
	214
	215	static void update_ptmx_mode(struct pts_fs_info *fsi)
	216	{
	217	struct inode *inode;
	218	if (fsi->ptmx_dentry) {
	219	inode = fsi->ptmx_dentry->d_inode;
	220	inode->i_mode = S_IFCHR\|fsi->mount_opts.ptmxmode;
	221	}
	222	}
	223	#else
	224	static inline void update_ptmx_mode(struct pts_fs_info *fsi)
	225	{
	226	return;
	227	}
	228	#endif
	229
53af8ee4 SB	230	static int devpts_remount(struct super_block sb, int flags, char *data)
53af8ee4 SB	231	{
1f8f1e29	232	int err;
53af8ee4 SB	233	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	234	struct pts_mount_opts *opts = &fsi->mount_opts;
	235
2a1b2dc0	236	err = parse_mount_options(data, PARSE_REMOUNT, opts);
1f8f1e29 SB	237
	238	/*
	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.
	243	*/
	244	update_ptmx_mode(fsi);
	245
	246	return err;
53af8ee4 SB	247	}
53af8ee4 SB	248
b87a267e MS	249	static int devpts_show_options(struct seq_file seq, struct vfsmount vfs)
b87a267e MS	250	{
31af0abb SB	251	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	252	struct pts_mount_opts *opts = &fsi->mount_opts;
	253
	254	if (opts->setuid)
	255	seq_printf(seq, ",uid=%u", opts->uid);
	256	if (opts->setgid)
	257	seq_printf(seq, ",gid=%u", opts->gid);
	258	seq_printf(seq, ",mode=%03o", opts->mode);
1f8f1e29 SB	259	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
	260	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
	261	#endif
b87a267e MS	262
	263	return 0;
	264	}
	265
ee9b6d61	266	static const struct super_operations devpts_sops = {
1da177e4 LT	267	.statfs = simple_statfs,
1da177e4 LT	268	.remount_fs = devpts_remount,
b87a267e	269	.show_options = devpts_show_options,
1da177e4 LT	270	};
1da177e4 LT	271
e76b7c01 SB	272	static void *new_pts_fs_info(void)
	273	{
	274	struct pts_fs_info *fsi;
	275
	276	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	277	if (!fsi)
	278	return NULL;
	279
	280	ida_init(&fsi->allocated_ptys);
31af0abb	281	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
1f8f1e29	282	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
e76b7c01 SB	283
	284	return fsi;
	285	}
	286
1da177e4 LT	287	static int
	288	devpts_fill_super(struct super_block s, void data, int silent)
	289	{
1f8f1e29	290	struct inode *inode;
1da177e4 LT	291
	292	s->s_blocksize = 1024;
	293	s->s_blocksize_bits = 10;
	294	s->s_magic = DEVPTS_SUPER_MAGIC;
	295	s->s_op = &devpts_sops;
1da177e4 LT	296	s->s_time_gran = 1;
1da177e4 LT	297
e76b7c01 SB	298	s->s_fs_info = new_pts_fs_info();
	299	if (!s->s_fs_info)
	300	goto fail;
	301
1da177e4 LT	302	inode = new_inode(s);
1da177e4 LT	303	if (!inode)
e76b7c01	304	goto free_fsi;
1da177e4 LT	305	inode->i_ino = 1;
1da177e4 LT	306	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
1da177e4 LT	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;
	310	inode->i_nlink = 2;
	311
59e55e6c	312	s->s_root = d_alloc_root(inode);
1da177e4 LT	313	if (s->s_root)
1da177e4 LT	314	return 0;
1f8f1e29	315
835aa440	316	printk(KERN_ERR "devpts: get root dentry failed\n");
1da177e4	317	iput(inode);
e76b7c01 SB	318
	319	free_fsi:
	320	kfree(s->s_fs_info);
1da177e4 LT	321	fail:
	322	return -ENOMEM;
	323	}
	324
8c056e5b	325	#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
d4076ac5 SB	326	static int compare_init_pts_sb(struct super_block s, void p)
	327	{
	328	if (devpts_mnt)
	329	return devpts_mnt->mnt_sb == s;
2a1b2dc0 SB	330	return 0;
	331	}
	332
2a1b2dc0	333	/*
fc14f2fe	334	* devpts_mount()
1bd79035 SB	335	*
	336	* If the '-o newinstance' mount option was specified, mount a new
	337	* (private) instance of devpts. PTYs created in this instance are
	338	* independent of the PTYs in other devpts instances.
	339	*
	340	* If the '-o newinstance' option was not specified, mount/remount the
	341	* initial kernel mount of devpts. This type of mount gives the
	342	* legacy, single-instance semantics.
289f00e2	343	*
1bd79035 SB	344	* The 'newinstance' option is needed to support multiple namespace
	345	* semantics in devpts while preserving backward compatibility of the
	346	* current 'single-namespace' semantics. i.e all mounts of devpts
	347	* without the 'newinstance' mount option should bind to the initial
fc14f2fe	348	* kernel mount, like mount_single().
d4076ac5	349	*
1bd79035	350	* Mounts with 'newinstance' option create a new, private namespace.
d4076ac5	351	*
1bd79035	352	* NOTE:
d4076ac5	353	*
fc14f2fe AV	354	* For single-mount semantics, devpts cannot use mount_single(),
fc14f2fe AV	355	* because mount_single()/sget() find and use the super-block from
d4076ac5	356	* the most recent mount of devpts. But that recent mount may be a
fc14f2fe	357	* 'newinstance' mount and mount_single() would pick the newinstance
d4076ac5	358	* super-block instead of the initial super-block.
d4076ac5	359	*/
fc14f2fe AV	360	static struct dentry devpts_mount(struct file_system_type fs_type,
fc14f2fe AV	361	int flags, const char dev_name, void data)
1da177e4	362	{
482984f0 SB	363	int error;
482984f0 SB	364	struct pts_mount_opts opts;
1bd79035	365	struct super_block *s;
2a1b2dc0	366
1f71ebed SB	367	error = parse_mount_options(data, PARSE_MOUNT, &opts);
1f71ebed SB	368	if (error)
fc14f2fe	369	return ERR_PTR(error);
2a1b2dc0	370
482984f0	371	if (opts.newinstance)
1bd79035	372	s = sget(fs_type, NULL, set_anon_super, NULL);
482984f0	373	else
1bd79035	374	s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
945cf2c7	375
1bd79035	376	if (IS_ERR(s))
fc14f2fe	377	return ERR_CAST(s);
1bd79035 SB	378
	379	if (!s->s_root) {
	380	s->s_flags = flags;
	381	error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
	382	if (error)
	383	goto out_undo_sget;
	384	s->s_flags \|= MS_ACTIVE;
	385	}
	386
1bd79035	387	memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
945cf2c7	388
1bd79035	389	error = mknod_ptmx(s);
945cf2c7	390	if (error)
89468071	391	goto out_undo_sget;
945cf2c7	392
fc14f2fe	393	return dget(s->s_root);
1bd79035 SB	394
1bd79035 SB	395	out_undo_sget:
6f5bbff9	396	deactivate_locked_super(s);
fc14f2fe	397	return ERR_PTR(error);
1da177e4	398	}
482984f0	399
2a1b2dc0 SB	400	#else
	401	/*
	402	* This supports only the legacy single-instance semantics (no
	403	* multiple-instance semantics)
	404	*/
fc14f2fe AV	405	static struct dentry devpts_mount(struct file_system_type fs_type, int flags,
fc14f2fe AV	406	const char dev_name, void data)
2a1b2dc0	407	{
fc14f2fe	408	return mount_single(fs_type, flags, data, devpts_fill_super);
2a1b2dc0 SB	409	}
2a1b2dc0 SB	410	#endif
1da177e4	411
e76b7c01 SB	412	static void devpts_kill_sb(struct super_block *sb)
	413	{
	414	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	415
	416	kfree(fsi);
1f8f1e29	417	kill_litter_super(sb);
e76b7c01 SB	418	}
e76b7c01 SB	419
1da177e4	420	static struct file_system_type devpts_fs_type = {
1da177e4	421	.name = "devpts",
fc14f2fe	422	.mount = devpts_mount,
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	{
edfacdd6 SB	516	struct dentry *dentry;
	517	struct tty_struct *tty;
	518
527b3e47	519	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
1da177e4	520
edfacdd6 SB	521	/* Ensure dentry has not been deleted by devpts_pty_kill() */
	522	dentry = d_find_alias(pts_inode);
	523	if (!dentry)
	524	return NULL;
	525
	526	tty = NULL;
527b3e47	527	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
edfacdd6 SB	528	tty = (struct tty_struct *)pts_inode->i_private;
	529
	530	dput(dentry);
	531
	532	return tty;
1da177e4 LT	533	}
1da177e4 LT	534
15f1a633	535	void devpts_pty_kill(struct tty_struct *tty)
1da177e4	536	{
a6f37daa	537	struct inode *inode = tty->driver_data;
59e55e6c SB	538	struct super_block *sb = pts_sb_from_inode(inode);
59e55e6c SB	539	struct dentry *root = sb->s_root;
a6f37daa	540	struct dentry *dentry;
1da177e4	541
a6f37daa SB	542	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
a6f37daa SB	543
59e55e6c	544	mutex_lock(&root->d_inode->i_mutex);
a6f37daa SB	545
a6f37daa SB	546	dentry = d_find_alias(inode);
2a1b2dc0 SB	547	if (IS_ERR(dentry))
	548	goto out;
	549
	550	if (dentry) {
a6f37daa SB	551	inode->i_nlink--;
a6f37daa SB	552	d_delete(dentry);
835aa440	553	dput(dentry); /* d_alloc_name() in devpts_pty_new() */
1da177e4	554	}
a6f37daa	555
835aa440	556	dput(dentry); /* d_find_alias above */
2a1b2dc0	557	out:
59e55e6c	558	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	559	}
	560
	561	static int __init init_devpts_fs(void)
	562	{
	563	int err = register_filesystem(&devpts_fs_type);
	564	if (!err) {
	565	devpts_mnt = kern_mount(&devpts_fs_type);
93d5581e	566	if (IS_ERR(devpts_mnt)) {
1da177e4	567	err = PTR_ERR(devpts_mnt);
93d5581e AC	568	unregister_filesystem(&devpts_fs_type);
93d5581e AC	569	}
1da177e4 LT	570	}
	571	return err;
	572	}
1da177e4	573	module_init(init_devpts_fs)