1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  Copyright (C) 1991, 1992  Linus Torvalds
  4 *
  5 *  Added support for a Unix98-style ptmx device.
  6 *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
  7 *
  8 */
  9
 10#include <linux/module.h>
 11#include <linux/errno.h>
 12#include <linux/interrupt.h>
 13#include <linux/tty.h>
 14#include <linux/tty_flip.h>
 15#include <linux/fcntl.h>
 16#include <linux/sched/signal.h>
 17#include <linux/string.h>
 18#include <linux/major.h>
 19#include <linux/mm.h>
 20#include <linux/init.h>
 21#include <linux/device.h>
 22#include <linux/uaccess.h>
 23#include <linux/bitops.h>
 24#include <linux/devpts_fs.h>
 25#include <linux/slab.h>
 26#include <linux/mutex.h>
 27#include <linux/poll.h>
 28#include <linux/mount.h>
 29#include <linux/file.h>
 30#include <linux/ioctl.h>
 31#include <linux/compat.h>
 32
 33#undef TTY_DEBUG_HANGUP
 34#ifdef TTY_DEBUG_HANGUP
 35# define tty_debug_hangup(tty, f, args...)	tty_debug(tty, f, ##args)
 36#else
 37# define tty_debug_hangup(tty, f, args...)	do {} while (0)
 38#endif
 39
 40#ifdef CONFIG_UNIX98_PTYS
 41static struct tty_driver *ptm_driver;
 42static struct tty_driver *pts_driver;
 43static DEFINE_MUTEX(devpts_mutex);
 44#endif
 45
 46static void pty_close(struct tty_struct *tty, struct file *filp)
 47{
 48	BUG_ON(!tty);
 49	if (tty->driver->subtype == PTY_TYPE_MASTER)
 50		WARN_ON(tty->count > 1);
 51	else {
 52		if (tty_io_error(tty))
 53			return;
 54		if (tty->count > 2)
 55			return;
 56	}
 57	set_bit(TTY_IO_ERROR, &tty->flags);
 58	wake_up_interruptible(&tty->read_wait);
 59	wake_up_interruptible(&tty->write_wait);
 60	spin_lock_irq(&tty->ctrl_lock);
 61	tty->packet = 0;
 62	spin_unlock_irq(&tty->ctrl_lock);
 63	/* Review - krefs on tty_link ?? */
 64	if (!tty->link)
 65		return;
 66	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
 67	wake_up_interruptible(&tty->link->read_wait);
 68	wake_up_interruptible(&tty->link->write_wait);
 69	if (tty->driver->subtype == PTY_TYPE_MASTER) {
 70		set_bit(TTY_OTHER_CLOSED, &tty->flags);
 71#ifdef CONFIG_UNIX98_PTYS
 72		if (tty->driver == ptm_driver) {
 73			mutex_lock(&devpts_mutex);
 74			if (tty->link->driver_data)
 75				devpts_pty_kill(tty->link->driver_data);
 76			mutex_unlock(&devpts_mutex);
 77		}
 78#endif
 79		tty_vhangup(tty->link);
 80	}
 81}
 82
 83/*
 84 * The unthrottle routine is called by the line discipline to signal
 85 * that it can receive more characters.  For PTY's, the TTY_THROTTLED
 86 * flag is always set, to force the line discipline to always call the
 87 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
 88 * characters in the queue.  This is necessary since each time this
 89 * happens, we need to wake up any sleeping processes that could be
 90 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
 91 * for the pty buffer to be drained.
 92 */
 93static void pty_unthrottle(struct tty_struct *tty)
 94{
 95	tty_wakeup(tty->link);
 96	set_bit(TTY_THROTTLED, &tty->flags);
 97}
 98
 99/**
100 *	pty_write		-	write to a pty
101 *	@tty: the tty we write from
102 *	@buf: kernel buffer of data
103 *	@count: bytes to write
104 *
105 *	Our "hardware" write method. Data is coming from the ldisc which
106 *	may be in a non sleeping state. We simply throw this at the other
107 *	end of the link as if we were an IRQ handler receiving stuff for
108 *	the other side of the pty/tty pair.
109 */
110
111static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
112{
113	struct tty_struct *to = tty->link;
114	unsigned long flags;
115
116	if (tty->stopped)
117		return 0;
118
119	if (c > 0) {
120		spin_lock_irqsave(&to->port->lock, flags);
121		/* Stuff the data into the input queue of the other end */
122		c = tty_insert_flip_string(to->port, buf, c);
123		/* And shovel */
124		if (c)
125			tty_flip_buffer_push(to->port);
126		spin_unlock_irqrestore(&to->port->lock, flags);
127	}
128	return c;
129}
130
131/**
132 *	pty_write_room	-	write space
133 *	@tty: tty we are writing from
134 *
135 *	Report how many bytes the ldisc can send into the queue for
136 *	the other device.
137 */
138
139static int pty_write_room(struct tty_struct *tty)
140{
141	if (tty->stopped)
142		return 0;
143	return tty_buffer_space_avail(tty->link->port);
144}
145
146/**
147 *	pty_chars_in_buffer	-	characters currently in our tx queue
148 *	@tty: our tty
149 *
150 *	Report how much we have in the transmit queue. As everything is
151 *	instantly at the other end this is easy to implement.
152 */
153
154static int pty_chars_in_buffer(struct tty_struct *tty)
155{
156	return 0;
157}
158
159/* Set the lock flag on a pty */
160static int pty_set_lock(struct tty_struct *tty, int __user *arg)
161{
162	int val;
163	if (get_user(val, arg))
164		return -EFAULT;
165	if (val)
166		set_bit(TTY_PTY_LOCK, &tty->flags);
167	else
168		clear_bit(TTY_PTY_LOCK, &tty->flags);
169	return 0;
170}
171
172static int pty_get_lock(struct tty_struct *tty, int __user *arg)
173{
174	int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
175	return put_user(locked, arg);
176}
177
178/* Set the packet mode on a pty */
179static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
180{
181	int pktmode;
182
183	if (get_user(pktmode, arg))
184		return -EFAULT;
185
186	spin_lock_irq(&tty->ctrl_lock);
187	if (pktmode) {
188		if (!tty->packet) {
189			tty->link->ctrl_status = 0;
190			smp_mb();
191			tty->packet = 1;
192		}
193	} else
194		tty->packet = 0;
195	spin_unlock_irq(&tty->ctrl_lock);
196
197	return 0;
198}
199
200/* Get the packet mode of a pty */
201static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
202{
203	int pktmode = tty->packet;
204	return put_user(pktmode, arg);
205}
206
207/* Send a signal to the slave */
208static int pty_signal(struct tty_struct *tty, int sig)
209{
210	struct pid *pgrp;
211
212	if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
213		return -EINVAL;
214
215	if (tty->link) {
216		pgrp = tty_get_pgrp(tty->link);
217		if (pgrp)
218			kill_pgrp(pgrp, sig, 1);
219		put_pid(pgrp);
220	}
221	return 0;
222}
223
224static void pty_flush_buffer(struct tty_struct *tty)
225{
226	struct tty_struct *to = tty->link;
227
228	if (!to)
229		return;
230
231	tty_buffer_flush(to, NULL);
232	if (to->packet) {
233		spin_lock_irq(&tty->ctrl_lock);
234		tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
235		wake_up_interruptible(&to->read_wait);
236		spin_unlock_irq(&tty->ctrl_lock);
237	}
238}
239
240static int pty_open(struct tty_struct *tty, struct file *filp)
241{
242	if (!tty || !tty->link)
243		return -ENODEV;
244
245	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
246		goto out;
247	if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
248		goto out;
249	if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
250		goto out;
251
252	clear_bit(TTY_IO_ERROR, &tty->flags);
253	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
254	set_bit(TTY_THROTTLED, &tty->flags);
255	return 0;
256
257out:
258	set_bit(TTY_IO_ERROR, &tty->flags);
259	return -EIO;
260}
261
262static void pty_set_termios(struct tty_struct *tty,
263					struct ktermios *old_termios)
264{
265	/* See if packet mode change of state. */
266	if (tty->link && tty->link->packet) {
267		int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
268		int old_flow = ((old_termios->c_iflag & IXON) &&
269				(old_termios->c_cc[VSTOP] == '\023') &&
270				(old_termios->c_cc[VSTART] == '\021'));
271		int new_flow = (I_IXON(tty) &&
272				STOP_CHAR(tty) == '\023' &&
273				START_CHAR(tty) == '\021');
274		if ((old_flow != new_flow) || extproc) {
275			spin_lock_irq(&tty->ctrl_lock);
276			if (old_flow != new_flow) {
277				tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
278				if (new_flow)
279					tty->ctrl_status |= TIOCPKT_DOSTOP;
280				else
281					tty->ctrl_status |= TIOCPKT_NOSTOP;
282			}
283			if (extproc)
284				tty->ctrl_status |= TIOCPKT_IOCTL;
285			spin_unlock_irq(&tty->ctrl_lock);
286			wake_up_interruptible(&tty->link->read_wait);
287		}
288	}
289
290	tty->termios.c_cflag &= ~(CSIZE | PARENB);
291	tty->termios.c_cflag |= (CS8 | CREAD);
292}
293
294/**
295 *	pty_do_resize		-	resize event
296 *	@tty: tty being resized
297 *	@ws: window size being set.
298 *
299 *	Update the termios variables and send the necessary signals to
300 *	peform a terminal resize correctly
301 */
302
303static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
304{
305	struct pid *pgrp, *rpgrp;
306	struct tty_struct *pty = tty->link;
307
308	/* For a PTY we need to lock the tty side */
309	mutex_lock(&tty->winsize_mutex);
310	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
311		goto done;
312
313	/* Signal the foreground process group of both ptys */
314	pgrp = tty_get_pgrp(tty);
315	rpgrp = tty_get_pgrp(pty);
316
317	if (pgrp)
318		kill_pgrp(pgrp, SIGWINCH, 1);
319	if (rpgrp != pgrp && rpgrp)
320		kill_pgrp(rpgrp, SIGWINCH, 1);
321
322	put_pid(pgrp);
323	put_pid(rpgrp);
324
325	tty->winsize = *ws;
326	pty->winsize = *ws;	/* Never used so will go away soon */
327done:
328	mutex_unlock(&tty->winsize_mutex);
329	return 0;
330}
331
332/**
333 *	pty_start - start() handler
334 *	pty_stop  - stop() handler
335 *	@tty: tty being flow-controlled
336 *
337 *	Propagates the TIOCPKT status to the master pty.
338 *
339 *	NB: only the master pty can be in packet mode so only the slave
340 *	    needs start()/stop() handlers
341 */
342static void pty_start(struct tty_struct *tty)
343{
344	unsigned long flags;
345
346	if (tty->link && tty->link->packet) {
347		spin_lock_irqsave(&tty->ctrl_lock, flags);
348		tty->ctrl_status &= ~TIOCPKT_STOP;
349		tty->ctrl_status |= TIOCPKT_START;
350		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
351		wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
352	}
353}
354
355static void pty_stop(struct tty_struct *tty)
356{
357	unsigned long flags;
358
359	if (tty->link && tty->link->packet) {
360		spin_lock_irqsave(&tty->ctrl_lock, flags);
361		tty->ctrl_status &= ~TIOCPKT_START;
362		tty->ctrl_status |= TIOCPKT_STOP;
363		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
364		wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
365	}
366}
367
368/**
369 *	pty_common_install		-	set up the pty pair
370 *	@driver: the pty driver
371 *	@tty: the tty being instantiated
372 *	@legacy: true if this is BSD style
373 *
374 *	Perform the initial set up for the tty/pty pair. Called from the
375 *	tty layer when the port is first opened.
376 *
377 *	Locking: the caller must hold the tty_mutex
378 */
379static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
380		bool legacy)
381{
382	struct tty_struct *o_tty;
383	struct tty_port *ports[2];
384	int idx = tty->index;
385	int retval = -ENOMEM;
386
387	/* Opening the slave first has always returned -EIO */
388	if (driver->subtype != PTY_TYPE_MASTER)
389		return -EIO;
390
391	ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
392	ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
393	if (!ports[0] || !ports[1])
394		goto err;
395	if (!try_module_get(driver->other->owner)) {
396		/* This cannot in fact currently happen */
397		goto err;
398	}
399	o_tty = alloc_tty_struct(driver->other, idx);
400	if (!o_tty)
401		goto err_put_module;
402
403	tty_set_lock_subclass(o_tty);
404	lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
405
406	if (legacy) {
407		/* We always use new tty termios data so we can do this
408		   the easy way .. */
409		tty_init_termios(tty);
410		tty_init_termios(o_tty);
411
412		driver->other->ttys[idx] = o_tty;
413		driver->ttys[idx] = tty;
414	} else {
415		memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
416		tty->termios = driver->init_termios;
417		memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
418		o_tty->termios = driver->other->init_termios;
419	}
420
421	/*
422	 * Everything allocated ... set up the o_tty structure.
423	 */
424	tty_driver_kref_get(driver->other);
425	/* Establish the links in both directions */
426	tty->link   = o_tty;
427	o_tty->link = tty;
428	tty_port_init(ports[0]);
429	tty_port_init(ports[1]);
430	tty_buffer_set_limit(ports[0], 8192);
431	tty_buffer_set_limit(ports[1], 8192);
432	o_tty->port = ports[0];
433	tty->port = ports[1];
434	o_tty->port->itty = o_tty;
435
436	tty_buffer_set_lock_subclass(o_tty->port);
437
438	tty_driver_kref_get(driver);
439	tty->count++;
440	o_tty->count++;
441	return 0;
442
443err_put_module:
444	module_put(driver->other->owner);
445err:
446	kfree(ports[0]);
447	kfree(ports[1]);
448	return retval;
449}
450
451static void pty_cleanup(struct tty_struct *tty)
452{
453	tty_port_put(tty->port);
454}
455
456/* Traditional BSD devices */
457#ifdef CONFIG_LEGACY_PTYS
458
459static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
460{
461	return pty_common_install(driver, tty, true);
462}
463
464static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
465{
466	struct tty_struct *pair = tty->link;
467	driver->ttys[tty->index] = NULL;
468	if (pair)
469		pair->driver->ttys[pair->index] = NULL;
470}
471
472static int pty_bsd_ioctl(struct tty_struct *tty,
473			 unsigned int cmd, unsigned long arg)
474{
475	switch (cmd) {
476	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
477		return pty_set_lock(tty, (int __user *) arg);
478	case TIOCGPTLCK: /* Get PT Lock status */
479		return pty_get_lock(tty, (int __user *)arg);
480	case TIOCPKT: /* Set PT packet mode */
481		return pty_set_pktmode(tty, (int __user *)arg);
482	case TIOCGPKT: /* Get PT packet mode */
483		return pty_get_pktmode(tty, (int __user *)arg);
484	case TIOCSIG:    /* Send signal to other side of pty */
485		return pty_signal(tty, (int) arg);
486	case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
487		return -EINVAL;
488	}
489	return -ENOIOCTLCMD;
490}
491
492#ifdef CONFIG_COMPAT
493static long pty_bsd_compat_ioctl(struct tty_struct *tty,
494				 unsigned int cmd, unsigned long arg)
495{
496	/*
497	 * PTY ioctls don't require any special translation between 32-bit and
498	 * 64-bit userspace, they are already compatible.
499	 */
500	return pty_bsd_ioctl(tty, cmd, (unsigned long)compat_ptr(arg));
501}
502#else
503#define pty_bsd_compat_ioctl NULL
504#endif
505
506static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
507/*
508 * not really modular, but the easiest way to keep compat with existing
509 * bootargs behaviour is to continue using module_param here.
510 */
511module_param(legacy_count, int, 0);
512
513/*
514 * The master side of a pty can do TIOCSPTLCK and thus
515 * has pty_bsd_ioctl.
516 */
517static const struct tty_operations master_pty_ops_bsd = {
518	.install = pty_install,
519	.open = pty_open,
520	.close = pty_close,
521	.write = pty_write,
522	.write_room = pty_write_room,
523	.flush_buffer = pty_flush_buffer,
524	.chars_in_buffer = pty_chars_in_buffer,
525	.unthrottle = pty_unthrottle,
526	.ioctl = pty_bsd_ioctl,
527	.compat_ioctl = pty_bsd_compat_ioctl,
528	.cleanup = pty_cleanup,
529	.resize = pty_resize,
530	.remove = pty_remove
531};
532
533static const struct tty_operations slave_pty_ops_bsd = {
534	.install = pty_install,
535	.open = pty_open,
536	.close = pty_close,
537	.write = pty_write,
538	.write_room = pty_write_room,
539	.flush_buffer = pty_flush_buffer,
540	.chars_in_buffer = pty_chars_in_buffer,
541	.unthrottle = pty_unthrottle,
542	.set_termios = pty_set_termios,
543	.cleanup = pty_cleanup,
544	.resize = pty_resize,
545	.start = pty_start,
546	.stop = pty_stop,
547	.remove = pty_remove
548};
549
550static void __init legacy_pty_init(void)
551{
552	struct tty_driver *pty_driver, *pty_slave_driver;
553
554	if (legacy_count <= 0)
555		return;
556
557	pty_driver = tty_alloc_driver(legacy_count,
558			TTY_DRIVER_RESET_TERMIOS |
559			TTY_DRIVER_REAL_RAW |
560			TTY_DRIVER_DYNAMIC_ALLOC);
561	if (IS_ERR(pty_driver))
562		panic("Couldn't allocate pty driver");
563
564	pty_slave_driver = tty_alloc_driver(legacy_count,
565			TTY_DRIVER_RESET_TERMIOS |
566			TTY_DRIVER_REAL_RAW |
567			TTY_DRIVER_DYNAMIC_ALLOC);
568	if (IS_ERR(pty_slave_driver))
569		panic("Couldn't allocate pty slave driver");
570
571	pty_driver->driver_name = "pty_master";
572	pty_driver->name = "pty";
573	pty_driver->major = PTY_MASTER_MAJOR;
574	pty_driver->minor_start = 0;
575	pty_driver->type = TTY_DRIVER_TYPE_PTY;
576	pty_driver->subtype = PTY_TYPE_MASTER;
577	pty_driver->init_termios = tty_std_termios;
578	pty_driver->init_termios.c_iflag = 0;
579	pty_driver->init_termios.c_oflag = 0;
580	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
581	pty_driver->init_termios.c_lflag = 0;
582	pty_driver->init_termios.c_ispeed = 38400;
583	pty_driver->init_termios.c_ospeed = 38400;
584	pty_driver->other = pty_slave_driver;
585	tty_set_operations(pty_driver, &master_pty_ops_bsd);
586
587	pty_slave_driver->driver_name = "pty_slave";
588	pty_slave_driver->name = "ttyp";
589	pty_slave_driver->major = PTY_SLAVE_MAJOR;
590	pty_slave_driver->minor_start = 0;
591	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
592	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
593	pty_slave_driver->init_termios = tty_std_termios;
594	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
595	pty_slave_driver->init_termios.c_ispeed = 38400;
596	pty_slave_driver->init_termios.c_ospeed = 38400;
597	pty_slave_driver->other = pty_driver;
598	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
599
600	if (tty_register_driver(pty_driver))
601		panic("Couldn't register pty driver");
602	if (tty_register_driver(pty_slave_driver))
603		panic("Couldn't register pty slave driver");
604}
605#else
606static inline void legacy_pty_init(void) { }
607#endif
608
609/* Unix98 devices */
610#ifdef CONFIG_UNIX98_PTYS
611static struct cdev ptmx_cdev;
612
613/**
614 *	ptm_open_peer - open the peer of a pty
615 *	@master: the open struct file of the ptmx device node
616 *	@tty: the master of the pty being opened
617 *	@flags: the flags for open
618 *
619 *	Provide a race free way for userspace to open the slave end of a pty
620 *	(where they have the master fd and cannot access or trust the mount
621 *	namespace /dev/pts was mounted inside).
622 */
623int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
624{
625	int fd = -1;
626	struct file *filp;
627	int retval = -EINVAL;
628	struct path path;
629
630	if (tty->driver != ptm_driver)
631		return -EIO;
632
633	fd = get_unused_fd_flags(flags);
634	if (fd < 0) {
635		retval = fd;
636		goto err;
637	}
638
639	/* Compute the slave's path */
640	path.mnt = devpts_mntget(master, tty->driver_data);
641	if (IS_ERR(path.mnt)) {
642		retval = PTR_ERR(path.mnt);
643		goto err_put;
644	}
645	path.dentry = tty->link->driver_data;
646
647	filp = dentry_open(&path, flags, current_cred());
648	mntput(path.mnt);
649	if (IS_ERR(filp)) {
650		retval = PTR_ERR(filp);
651		goto err_put;
652	}
653
654	fd_install(fd, filp);
655	return fd;
656
657err_put:
658	put_unused_fd(fd);
659err:
660	return retval;
661}
662
663static int pty_unix98_ioctl(struct tty_struct *tty,
664			    unsigned int cmd, unsigned long arg)
665{
666	switch (cmd) {
667	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
668		return pty_set_lock(tty, (int __user *)arg);
669	case TIOCGPTLCK: /* Get PT Lock status */
670		return pty_get_lock(tty, (int __user *)arg);
671	case TIOCPKT: /* Set PT packet mode */
672		return pty_set_pktmode(tty, (int __user *)arg);
673	case TIOCGPKT: /* Get PT packet mode */
674		return pty_get_pktmode(tty, (int __user *)arg);
675	case TIOCGPTN: /* Get PT Number */
676		return put_user(tty->index, (unsigned int __user *)arg);
677	case TIOCSIG:    /* Send signal to other side of pty */
678		return pty_signal(tty, (int) arg);
679	}
680
681	return -ENOIOCTLCMD;
682}
683
684#ifdef CONFIG_COMPAT
685static long pty_unix98_compat_ioctl(struct tty_struct *tty,
686				 unsigned int cmd, unsigned long arg)
687{
688	/*
689	 * PTY ioctls don't require any special translation between 32-bit and
690	 * 64-bit userspace, they are already compatible.
691	 */
692	return pty_unix98_ioctl(tty, cmd,
693		cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(arg));
694}
695#else
696#define pty_unix98_compat_ioctl NULL
697#endif
698
699/**
700 *	ptm_unix98_lookup	-	find a pty master
701 *	@driver: ptm driver
702 *	@idx: tty index
703 *
704 *	Look up a pty master device. Called under the tty_mutex for now.
705 *	This provides our locking.
706 */
707
708static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
709		struct file *file, int idx)
710{
711	/* Master must be open via /dev/ptmx */
712	return ERR_PTR(-EIO);
713}
714
715/**
716 *	pts_unix98_lookup	-	find a pty slave
717 *	@driver: pts driver
718 *	@idx: tty index
719 *
720 *	Look up a pty master device. Called under the tty_mutex for now.
721 *	This provides our locking for the tty pointer.
722 */
723
724static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
725		struct file *file, int idx)
726{
727	struct tty_struct *tty;
728
729	mutex_lock(&devpts_mutex);
730	tty = devpts_get_priv(file->f_path.dentry);
731	mutex_unlock(&devpts_mutex);
732	/* Master must be open before slave */
733	if (!tty)
734		return ERR_PTR(-EIO);
735	return tty;
736}
737
738static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
739{
740	return pty_common_install(driver, tty, false);
741}
742
743/* this is called once with whichever end is closed last */
744static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
745{
746	struct pts_fs_info *fsi;
747
748	if (tty->driver->subtype == PTY_TYPE_MASTER)
749		fsi = tty->driver_data;
750	else
751		fsi = tty->link->driver_data;
752
753	if (fsi) {
754		devpts_kill_index(fsi, tty->index);
755		devpts_release(fsi);
756	}
757}
758
759static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
760{
761	seq_printf(m, "tty-index:\t%d\n", tty->index);
762}
763
764static const struct tty_operations ptm_unix98_ops = {
765	.lookup = ptm_unix98_lookup,
766	.install = pty_unix98_install,
767	.remove = pty_unix98_remove,
768	.open = pty_open,
769	.close = pty_close,
770	.write = pty_write,
771	.write_room = pty_write_room,
772	.flush_buffer = pty_flush_buffer,
773	.chars_in_buffer = pty_chars_in_buffer,
774	.unthrottle = pty_unthrottle,
775	.ioctl = pty_unix98_ioctl,
776	.compat_ioctl = pty_unix98_compat_ioctl,
777	.resize = pty_resize,
778	.cleanup = pty_cleanup,
779	.show_fdinfo = pty_show_fdinfo,
780};
781
782static const struct tty_operations pty_unix98_ops = {
783	.lookup = pts_unix98_lookup,
784	.install = pty_unix98_install,
785	.remove = pty_unix98_remove,
786	.open = pty_open,
787	.close = pty_close,
788	.write = pty_write,
789	.write_room = pty_write_room,
790	.flush_buffer = pty_flush_buffer,
791	.chars_in_buffer = pty_chars_in_buffer,
792	.unthrottle = pty_unthrottle,
793	.set_termios = pty_set_termios,
794	.start = pty_start,
795	.stop = pty_stop,
796	.cleanup = pty_cleanup,
797};
798
799/**
800 *	ptmx_open		-	open a unix 98 pty master
801 *	@inode: inode of device file
802 *	@filp: file pointer to tty
803 *
804 *	Allocate a unix98 pty master device from the ptmx driver.
805 *
806 *	Locking: tty_mutex protects the init_dev work. tty->count should
807 *		protect the rest.
808 *		allocated_ptys_lock handles the list of free pty numbers
809 */
810
811static int ptmx_open(struct inode *inode, struct file *filp)
812{
813	struct pts_fs_info *fsi;
814	struct tty_struct *tty;
815	struct dentry *dentry;
816	int retval;
817	int index;
818
819	nonseekable_open(inode, filp);
820
821	/* We refuse fsnotify events on ptmx, since it's a shared resource */
822	filp->f_mode |= FMODE_NONOTIFY;
823
824	retval = tty_alloc_file(filp);
825	if (retval)
826		return retval;
827
828	fsi = devpts_acquire(filp);
829	if (IS_ERR(fsi)) {
830		retval = PTR_ERR(fsi);
831		goto out_free_file;
832	}
833
834	/* find a device that is not in use. */
835	mutex_lock(&devpts_mutex);
836	index = devpts_new_index(fsi);
837	mutex_unlock(&devpts_mutex);
838
839	retval = index;
840	if (index < 0)
841		goto out_put_fsi;
842
843
844	mutex_lock(&tty_mutex);
845	tty = tty_init_dev(ptm_driver, index);
846	/* The tty returned here is locked so we can safely
847	   drop the mutex */
848	mutex_unlock(&tty_mutex);
849
850	retval = PTR_ERR(tty);
851	if (IS_ERR(tty))
852		goto out;
853
854	/*
855	 * From here on out, the tty is "live", and the index and
856	 * fsi will be killed/put by the tty_release()
857	 */
858	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
859	tty->driver_data = fsi;
860
861	tty_add_file(tty, filp);
862
863	dentry = devpts_pty_new(fsi, index, tty->link);
864	if (IS_ERR(dentry)) {
865		retval = PTR_ERR(dentry);
866		goto err_release;
867	}
868	tty->link->driver_data = dentry;
869
870	retval = ptm_driver->ops->open(tty, filp);
871	if (retval)
872		goto err_release;
873
874	tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
875
876	tty_unlock(tty);
877	return 0;
878err_release:
879	tty_unlock(tty);
880	// This will also put-ref the fsi
881	tty_release(inode, filp);
882	return retval;
883out:
884	devpts_kill_index(fsi, index);
885out_put_fsi:
886	devpts_release(fsi);
887out_free_file:
888	tty_free_file(filp);
889	return retval;
890}
891
892static struct file_operations ptmx_fops __ro_after_init;
893
894static void __init unix98_pty_init(void)
895{
896	ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
897			TTY_DRIVER_RESET_TERMIOS |
898			TTY_DRIVER_REAL_RAW |
899			TTY_DRIVER_DYNAMIC_DEV |
900			TTY_DRIVER_DEVPTS_MEM |
901			TTY_DRIVER_DYNAMIC_ALLOC);
902	if (IS_ERR(ptm_driver))
903		panic("Couldn't allocate Unix98 ptm driver");
904	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
905			TTY_DRIVER_RESET_TERMIOS |
906			TTY_DRIVER_REAL_RAW |
907			TTY_DRIVER_DYNAMIC_DEV |
908			TTY_DRIVER_DEVPTS_MEM |
909			TTY_DRIVER_DYNAMIC_ALLOC);
910	if (IS_ERR(pts_driver))
911		panic("Couldn't allocate Unix98 pts driver");
912
913	ptm_driver->driver_name = "pty_master";
914	ptm_driver->name = "ptm";
915	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
916	ptm_driver->minor_start = 0;
917	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
918	ptm_driver->subtype = PTY_TYPE_MASTER;
919	ptm_driver->init_termios = tty_std_termios;
920	ptm_driver->init_termios.c_iflag = 0;
921	ptm_driver->init_termios.c_oflag = 0;
922	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
923	ptm_driver->init_termios.c_lflag = 0;
924	ptm_driver->init_termios.c_ispeed = 38400;
925	ptm_driver->init_termios.c_ospeed = 38400;
926	ptm_driver->other = pts_driver;
927	tty_set_operations(ptm_driver, &ptm_unix98_ops);
928
929	pts_driver->driver_name = "pty_slave";
930	pts_driver->name = "pts";
931	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
932	pts_driver->minor_start = 0;
933	pts_driver->type = TTY_DRIVER_TYPE_PTY;
934	pts_driver->subtype = PTY_TYPE_SLAVE;
935	pts_driver->init_termios = tty_std_termios;
936	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
937	pts_driver->init_termios.c_ispeed = 38400;
938	pts_driver->init_termios.c_ospeed = 38400;
939	pts_driver->other = ptm_driver;
940	tty_set_operations(pts_driver, &pty_unix98_ops);
941
942	if (tty_register_driver(ptm_driver))
943		panic("Couldn't register Unix98 ptm driver");
944	if (tty_register_driver(pts_driver))
945		panic("Couldn't register Unix98 pts driver");
946
947	/* Now create the /dev/ptmx special device */
948	tty_default_fops(&ptmx_fops);
949	ptmx_fops.open = ptmx_open;
950
951	cdev_init(&ptmx_cdev, &ptmx_fops);
952	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
953	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
954		panic("Couldn't register /dev/ptmx driver");
955	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
956}
957
958#else
959static inline void unix98_pty_init(void) { }
960#endif
961
962static int __init pty_init(void)
963{
964	legacy_pty_init();
965	unix98_pty_init();
966	return 0;
967}
968device_initcall(pty_init);