xref: /openbmc/linux/drivers/tty/pty.c (revision 6774def6)
1 /*
2  *  Copyright (C) 1991, 1992  Linus Torvalds
3  *
4  *  Added support for a Unix98-style ptmx device.
5  *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
6  *
7  */
8 
9 #include <linux/module.h>
10 
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.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 
29 
30 #ifdef CONFIG_UNIX98_PTYS
31 static struct tty_driver *ptm_driver;
32 static struct tty_driver *pts_driver;
33 static DEFINE_MUTEX(devpts_mutex);
34 #endif
35 
36 static void pty_close(struct tty_struct *tty, struct file *filp)
37 {
38 	BUG_ON(!tty);
39 	if (tty->driver->subtype == PTY_TYPE_MASTER)
40 		WARN_ON(tty->count > 1);
41 	else {
42 		if (test_bit(TTY_IO_ERROR, &tty->flags))
43 			return;
44 		if (tty->count > 2)
45 			return;
46 	}
47 	set_bit(TTY_IO_ERROR, &tty->flags);
48 	wake_up_interruptible(&tty->read_wait);
49 	wake_up_interruptible(&tty->write_wait);
50 	tty->packet = 0;
51 	/* Review - krefs on tty_link ?? */
52 	if (!tty->link)
53 		return;
54 	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
55 	wake_up_interruptible(&tty->link->read_wait);
56 	wake_up_interruptible(&tty->link->write_wait);
57 	if (tty->driver->subtype == PTY_TYPE_MASTER) {
58 		set_bit(TTY_OTHER_CLOSED, &tty->flags);
59 #ifdef CONFIG_UNIX98_PTYS
60 		if (tty->driver == ptm_driver) {
61 			mutex_lock(&devpts_mutex);
62 			if (tty->link->driver_data)
63 				devpts_pty_kill(tty->link->driver_data);
64 			mutex_unlock(&devpts_mutex);
65 		}
66 #endif
67 		tty_unlock(tty);
68 		tty_vhangup(tty->link);
69 		tty_lock(tty);
70 	}
71 }
72 
73 /*
74  * The unthrottle routine is called by the line discipline to signal
75  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
76  * flag is always set, to force the line discipline to always call the
77  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
78  * characters in the queue.  This is necessary since each time this
79  * happens, we need to wake up any sleeping processes that could be
80  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
81  * for the pty buffer to be drained.
82  */
83 static void pty_unthrottle(struct tty_struct *tty)
84 {
85 	tty_wakeup(tty->link);
86 	set_bit(TTY_THROTTLED, &tty->flags);
87 }
88 
89 /**
90  *	pty_space	-	report space left for writing
91  *	@to: tty we are writing into
92  *
93  *	Limit the buffer space used by ptys to 8k.
94  */
95 
96 static int pty_space(struct tty_struct *to)
97 {
98 	int n = tty_buffer_space_avail(to->port);
99 	return min(n, 8192);
100 }
101 
102 /**
103  *	pty_write		-	write to a pty
104  *	@tty: the tty we write from
105  *	@buf: kernel buffer of data
106  *	@count: bytes to write
107  *
108  *	Our "hardware" write method. Data is coming from the ldisc which
109  *	may be in a non sleeping state. We simply throw this at the other
110  *	end of the link as if we were an IRQ handler receiving stuff for
111  *	the other side of the pty/tty pair.
112  */
113 
114 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
115 {
116 	struct tty_struct *to = tty->link;
117 
118 	if (tty->stopped)
119 		return 0;
120 
121 	if (c > 0) {
122 		/* Stuff the data into the input queue of the other end */
123 		c = tty_insert_flip_string(to->port, buf, c);
124 		/* And shovel */
125 		if (c)
126 			tty_flip_buffer_push(to->port);
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 
139 static int pty_write_room(struct tty_struct *tty)
140 {
141 	if (tty->stopped)
142 		return 0;
143 	return pty_space(tty->link);
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 
154 static int pty_chars_in_buffer(struct tty_struct *tty)
155 {
156 	return 0;
157 }
158 
159 /* Set the lock flag on a pty */
160 static 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 
172 static 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 */
179 static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
180 {
181 	unsigned long flags;
182 	int pktmode;
183 
184 	if (get_user(pktmode, arg))
185 		return -EFAULT;
186 
187 	spin_lock_irqsave(&tty->ctrl_lock, flags);
188 	if (pktmode) {
189 		if (!tty->packet) {
190 			tty->packet = 1;
191 			tty->link->ctrl_status = 0;
192 		}
193 	} else
194 		tty->packet = 0;
195 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
196 
197 	return 0;
198 }
199 
200 /* Get the packet mode of a pty */
201 static 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 */
208 static int pty_signal(struct tty_struct *tty, int sig)
209 {
210 	unsigned long flags;
211 	struct pid *pgrp;
212 
213 	if (tty->link) {
214 		spin_lock_irqsave(&tty->link->ctrl_lock, flags);
215 		pgrp = get_pid(tty->link->pgrp);
216 		spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
217 
218 		kill_pgrp(pgrp, sig, 1);
219 		put_pid(pgrp);
220 	}
221 	return 0;
222 }
223 
224 static void pty_flush_buffer(struct tty_struct *tty)
225 {
226 	struct tty_struct *to = tty->link;
227 	unsigned long flags;
228 
229 	if (!to)
230 		return;
231 	/* tty_buffer_flush(to); FIXME */
232 	if (to->packet) {
233 		spin_lock_irqsave(&tty->ctrl_lock, flags);
234 		tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
235 		wake_up_interruptible(&to->read_wait);
236 		spin_unlock_irqrestore(&tty->ctrl_lock, flags);
237 	}
238 }
239 
240 static 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 
257 out:
258 	set_bit(TTY_IO_ERROR, &tty->flags);
259 	return -EIO;
260 }
261 
262 static void pty_set_termios(struct tty_struct *tty,
263 					struct ktermios *old_termios)
264 {
265 	tty->termios.c_cflag &= ~(CSIZE | PARENB);
266 	tty->termios.c_cflag |= (CS8 | CREAD);
267 }
268 
269 /**
270  *	pty_do_resize		-	resize event
271  *	@tty: tty being resized
272  *	@ws: window size being set.
273  *
274  *	Update the termios variables and send the necessary signals to
275  *	peform a terminal resize correctly
276  */
277 
278 static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
279 {
280 	struct pid *pgrp, *rpgrp;
281 	unsigned long flags;
282 	struct tty_struct *pty = tty->link;
283 
284 	/* For a PTY we need to lock the tty side */
285 	mutex_lock(&tty->winsize_mutex);
286 	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
287 		goto done;
288 
289 	/* Get the PID values and reference them so we can
290 	   avoid holding the tty ctrl lock while sending signals.
291 	   We need to lock these individually however. */
292 
293 	spin_lock_irqsave(&tty->ctrl_lock, flags);
294 	pgrp = get_pid(tty->pgrp);
295 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
296 
297 	spin_lock_irqsave(&pty->ctrl_lock, flags);
298 	rpgrp = get_pid(pty->pgrp);
299 	spin_unlock_irqrestore(&pty->ctrl_lock, flags);
300 
301 	if (pgrp)
302 		kill_pgrp(pgrp, SIGWINCH, 1);
303 	if (rpgrp != pgrp && rpgrp)
304 		kill_pgrp(rpgrp, SIGWINCH, 1);
305 
306 	put_pid(pgrp);
307 	put_pid(rpgrp);
308 
309 	tty->winsize = *ws;
310 	pty->winsize = *ws;	/* Never used so will go away soon */
311 done:
312 	mutex_unlock(&tty->winsize_mutex);
313 	return 0;
314 }
315 
316 /**
317  *	pty_start - start() handler
318  *	pty_stop  - stop() handler
319  *	@tty: tty being flow-controlled
320  *
321  *	Propagates the TIOCPKT status to the master pty.
322  *
323  *	NB: only the master pty can be in packet mode so only the slave
324  *	    needs start()/stop() handlers
325  */
326 static void pty_start(struct tty_struct *tty)
327 {
328 	unsigned long flags;
329 
330 	spin_lock_irqsave(&tty->ctrl_lock, flags);
331 	if (tty->link && tty->link->packet) {
332 		tty->ctrl_status &= ~TIOCPKT_STOP;
333 		tty->ctrl_status |= TIOCPKT_START;
334 		wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
335 	}
336 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
337 }
338 
339 static void pty_stop(struct tty_struct *tty)
340 {
341 	unsigned long flags;
342 
343 	spin_lock_irqsave(&tty->ctrl_lock, flags);
344 	if (tty->link && tty->link->packet) {
345 		tty->ctrl_status &= ~TIOCPKT_START;
346 		tty->ctrl_status |= TIOCPKT_STOP;
347 		wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
348 	}
349 	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
350 }
351 
352 /**
353  *	pty_common_install		-	set up the pty pair
354  *	@driver: the pty driver
355  *	@tty: the tty being instantiated
356  *	@legacy: true if this is BSD style
357  *
358  *	Perform the initial set up for the tty/pty pair. Called from the
359  *	tty layer when the port is first opened.
360  *
361  *	Locking: the caller must hold the tty_mutex
362  */
363 static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
364 		bool legacy)
365 {
366 	struct tty_struct *o_tty;
367 	struct tty_port *ports[2];
368 	int idx = tty->index;
369 	int retval = -ENOMEM;
370 
371 	ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
372 	ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
373 	if (!ports[0] || !ports[1])
374 		goto err;
375 	if (!try_module_get(driver->other->owner)) {
376 		/* This cannot in fact currently happen */
377 		goto err;
378 	}
379 	o_tty = alloc_tty_struct(driver->other, idx);
380 	if (!o_tty)
381 		goto err_put_module;
382 
383 	if (legacy) {
384 		/* We always use new tty termios data so we can do this
385 		   the easy way .. */
386 		retval = tty_init_termios(tty);
387 		if (retval)
388 			goto err_deinit_tty;
389 
390 		retval = tty_init_termios(o_tty);
391 		if (retval)
392 			goto err_free_termios;
393 
394 		driver->other->ttys[idx] = o_tty;
395 		driver->ttys[idx] = tty;
396 	} else {
397 		memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
398 		tty->termios = driver->init_termios;
399 		memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
400 		o_tty->termios = driver->other->init_termios;
401 	}
402 
403 	/*
404 	 * Everything allocated ... set up the o_tty structure.
405 	 */
406 	tty_driver_kref_get(driver->other);
407 	if (driver->subtype == PTY_TYPE_MASTER)
408 		o_tty->count++;
409 	/* Establish the links in both directions */
410 	tty->link   = o_tty;
411 	o_tty->link = tty;
412 	tty_port_init(ports[0]);
413 	tty_port_init(ports[1]);
414 	o_tty->port = ports[0];
415 	tty->port = ports[1];
416 	o_tty->port->itty = o_tty;
417 
418 	tty_driver_kref_get(driver);
419 	tty->count++;
420 	return 0;
421 err_free_termios:
422 	if (legacy)
423 		tty_free_termios(tty);
424 err_deinit_tty:
425 	deinitialize_tty_struct(o_tty);
426 	free_tty_struct(o_tty);
427 err_put_module:
428 	module_put(driver->other->owner);
429 err:
430 	kfree(ports[0]);
431 	kfree(ports[1]);
432 	return retval;
433 }
434 
435 static void pty_cleanup(struct tty_struct *tty)
436 {
437 	tty_port_put(tty->port);
438 }
439 
440 /* Traditional BSD devices */
441 #ifdef CONFIG_LEGACY_PTYS
442 
443 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
444 {
445 	return pty_common_install(driver, tty, true);
446 }
447 
448 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
449 {
450 	struct tty_struct *pair = tty->link;
451 	driver->ttys[tty->index] = NULL;
452 	if (pair)
453 		pair->driver->ttys[pair->index] = NULL;
454 }
455 
456 static int pty_bsd_ioctl(struct tty_struct *tty,
457 			 unsigned int cmd, unsigned long arg)
458 {
459 	switch (cmd) {
460 	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
461 		return pty_set_lock(tty, (int __user *) arg);
462 	case TIOCGPTLCK: /* Get PT Lock status */
463 		return pty_get_lock(tty, (int __user *)arg);
464 	case TIOCPKT: /* Set PT packet mode */
465 		return pty_set_pktmode(tty, (int __user *)arg);
466 	case TIOCGPKT: /* Get PT packet mode */
467 		return pty_get_pktmode(tty, (int __user *)arg);
468 	case TIOCSIG:    /* Send signal to other side of pty */
469 		return pty_signal(tty, (int) arg);
470 	case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
471 		return -EINVAL;
472 	}
473 	return -ENOIOCTLCMD;
474 }
475 
476 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
477 module_param(legacy_count, int, 0);
478 
479 /*
480  * The master side of a pty can do TIOCSPTLCK and thus
481  * has pty_bsd_ioctl.
482  */
483 static const struct tty_operations master_pty_ops_bsd = {
484 	.install = pty_install,
485 	.open = pty_open,
486 	.close = pty_close,
487 	.write = pty_write,
488 	.write_room = pty_write_room,
489 	.flush_buffer = pty_flush_buffer,
490 	.chars_in_buffer = pty_chars_in_buffer,
491 	.unthrottle = pty_unthrottle,
492 	.set_termios = pty_set_termios,
493 	.ioctl = pty_bsd_ioctl,
494 	.cleanup = pty_cleanup,
495 	.resize = pty_resize,
496 	.remove = pty_remove
497 };
498 
499 static const struct tty_operations slave_pty_ops_bsd = {
500 	.install = pty_install,
501 	.open = pty_open,
502 	.close = pty_close,
503 	.write = pty_write,
504 	.write_room = pty_write_room,
505 	.flush_buffer = pty_flush_buffer,
506 	.chars_in_buffer = pty_chars_in_buffer,
507 	.unthrottle = pty_unthrottle,
508 	.set_termios = pty_set_termios,
509 	.cleanup = pty_cleanup,
510 	.resize = pty_resize,
511 	.start = pty_start,
512 	.stop = pty_stop,
513 	.remove = pty_remove
514 };
515 
516 static void __init legacy_pty_init(void)
517 {
518 	struct tty_driver *pty_driver, *pty_slave_driver;
519 
520 	if (legacy_count <= 0)
521 		return;
522 
523 	pty_driver = tty_alloc_driver(legacy_count,
524 			TTY_DRIVER_RESET_TERMIOS |
525 			TTY_DRIVER_REAL_RAW |
526 			TTY_DRIVER_DYNAMIC_ALLOC);
527 	if (IS_ERR(pty_driver))
528 		panic("Couldn't allocate pty driver");
529 
530 	pty_slave_driver = tty_alloc_driver(legacy_count,
531 			TTY_DRIVER_RESET_TERMIOS |
532 			TTY_DRIVER_REAL_RAW |
533 			TTY_DRIVER_DYNAMIC_ALLOC);
534 	if (IS_ERR(pty_slave_driver))
535 		panic("Couldn't allocate pty slave driver");
536 
537 	pty_driver->driver_name = "pty_master";
538 	pty_driver->name = "pty";
539 	pty_driver->major = PTY_MASTER_MAJOR;
540 	pty_driver->minor_start = 0;
541 	pty_driver->type = TTY_DRIVER_TYPE_PTY;
542 	pty_driver->subtype = PTY_TYPE_MASTER;
543 	pty_driver->init_termios = tty_std_termios;
544 	pty_driver->init_termios.c_iflag = 0;
545 	pty_driver->init_termios.c_oflag = 0;
546 	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
547 	pty_driver->init_termios.c_lflag = 0;
548 	pty_driver->init_termios.c_ispeed = 38400;
549 	pty_driver->init_termios.c_ospeed = 38400;
550 	pty_driver->other = pty_slave_driver;
551 	tty_set_operations(pty_driver, &master_pty_ops_bsd);
552 
553 	pty_slave_driver->driver_name = "pty_slave";
554 	pty_slave_driver->name = "ttyp";
555 	pty_slave_driver->major = PTY_SLAVE_MAJOR;
556 	pty_slave_driver->minor_start = 0;
557 	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
558 	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
559 	pty_slave_driver->init_termios = tty_std_termios;
560 	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
561 	pty_slave_driver->init_termios.c_ispeed = 38400;
562 	pty_slave_driver->init_termios.c_ospeed = 38400;
563 	pty_slave_driver->other = pty_driver;
564 	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
565 
566 	if (tty_register_driver(pty_driver))
567 		panic("Couldn't register pty driver");
568 	if (tty_register_driver(pty_slave_driver))
569 		panic("Couldn't register pty slave driver");
570 }
571 #else
572 static inline void legacy_pty_init(void) { }
573 #endif
574 
575 /* Unix98 devices */
576 #ifdef CONFIG_UNIX98_PTYS
577 
578 static struct cdev ptmx_cdev;
579 
580 static int pty_unix98_ioctl(struct tty_struct *tty,
581 			    unsigned int cmd, unsigned long arg)
582 {
583 	switch (cmd) {
584 	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
585 		return pty_set_lock(tty, (int __user *)arg);
586 	case TIOCGPTLCK: /* Get PT Lock status */
587 		return pty_get_lock(tty, (int __user *)arg);
588 	case TIOCPKT: /* Set PT packet mode */
589 		return pty_set_pktmode(tty, (int __user *)arg);
590 	case TIOCGPKT: /* Get PT packet mode */
591 		return pty_get_pktmode(tty, (int __user *)arg);
592 	case TIOCGPTN: /* Get PT Number */
593 		return put_user(tty->index, (unsigned int __user *)arg);
594 	case TIOCSIG:    /* Send signal to other side of pty */
595 		return pty_signal(tty, (int) arg);
596 	}
597 
598 	return -ENOIOCTLCMD;
599 }
600 
601 /**
602  *	ptm_unix98_lookup	-	find a pty master
603  *	@driver: ptm driver
604  *	@idx: tty index
605  *
606  *	Look up a pty master device. Called under the tty_mutex for now.
607  *	This provides our locking.
608  */
609 
610 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
611 		struct inode *ptm_inode, int idx)
612 {
613 	/* Master must be open via /dev/ptmx */
614 	return ERR_PTR(-EIO);
615 }
616 
617 /**
618  *	pts_unix98_lookup	-	find a pty slave
619  *	@driver: pts driver
620  *	@idx: tty index
621  *
622  *	Look up a pty master device. Called under the tty_mutex for now.
623  *	This provides our locking for the tty pointer.
624  */
625 
626 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
627 		struct inode *pts_inode, int idx)
628 {
629 	struct tty_struct *tty;
630 
631 	mutex_lock(&devpts_mutex);
632 	tty = devpts_get_priv(pts_inode);
633 	mutex_unlock(&devpts_mutex);
634 	/* Master must be open before slave */
635 	if (!tty)
636 		return ERR_PTR(-EIO);
637 	return tty;
638 }
639 
640 /* We have no need to install and remove our tty objects as devpts does all
641    the work for us */
642 
643 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
644 {
645 	return pty_common_install(driver, tty, false);
646 }
647 
648 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
649 {
650 }
651 
652 /* this is called once with whichever end is closed last */
653 static void pty_unix98_shutdown(struct tty_struct *tty)
654 {
655 	devpts_kill_index(tty->driver_data, tty->index);
656 }
657 
658 static const struct tty_operations ptm_unix98_ops = {
659 	.lookup = ptm_unix98_lookup,
660 	.install = pty_unix98_install,
661 	.remove = pty_unix98_remove,
662 	.open = pty_open,
663 	.close = pty_close,
664 	.write = pty_write,
665 	.write_room = pty_write_room,
666 	.flush_buffer = pty_flush_buffer,
667 	.chars_in_buffer = pty_chars_in_buffer,
668 	.unthrottle = pty_unthrottle,
669 	.set_termios = pty_set_termios,
670 	.ioctl = pty_unix98_ioctl,
671 	.resize = pty_resize,
672 	.shutdown = pty_unix98_shutdown,
673 	.cleanup = pty_cleanup
674 };
675 
676 static const struct tty_operations pty_unix98_ops = {
677 	.lookup = pts_unix98_lookup,
678 	.install = pty_unix98_install,
679 	.remove = pty_unix98_remove,
680 	.open = pty_open,
681 	.close = pty_close,
682 	.write = pty_write,
683 	.write_room = pty_write_room,
684 	.flush_buffer = pty_flush_buffer,
685 	.chars_in_buffer = pty_chars_in_buffer,
686 	.unthrottle = pty_unthrottle,
687 	.set_termios = pty_set_termios,
688 	.start = pty_start,
689 	.stop = pty_stop,
690 	.shutdown = pty_unix98_shutdown,
691 	.cleanup = pty_cleanup,
692 };
693 
694 /**
695  *	ptmx_open		-	open a unix 98 pty master
696  *	@inode: inode of device file
697  *	@filp: file pointer to tty
698  *
699  *	Allocate a unix98 pty master device from the ptmx driver.
700  *
701  *	Locking: tty_mutex protects the init_dev work. tty->count should
702  *		protect the rest.
703  *		allocated_ptys_lock handles the list of free pty numbers
704  */
705 
706 static int ptmx_open(struct inode *inode, struct file *filp)
707 {
708 	struct tty_struct *tty;
709 	struct inode *slave_inode;
710 	int retval;
711 	int index;
712 
713 	nonseekable_open(inode, filp);
714 
715 	/* We refuse fsnotify events on ptmx, since it's a shared resource */
716 	filp->f_mode |= FMODE_NONOTIFY;
717 
718 	retval = tty_alloc_file(filp);
719 	if (retval)
720 		return retval;
721 
722 	/* find a device that is not in use. */
723 	mutex_lock(&devpts_mutex);
724 	index = devpts_new_index(inode);
725 	if (index < 0) {
726 		retval = index;
727 		mutex_unlock(&devpts_mutex);
728 		goto err_file;
729 	}
730 
731 	mutex_unlock(&devpts_mutex);
732 
733 	mutex_lock(&tty_mutex);
734 	tty = tty_init_dev(ptm_driver, index);
735 
736 	if (IS_ERR(tty)) {
737 		retval = PTR_ERR(tty);
738 		goto out;
739 	}
740 
741 	/* The tty returned here is locked so we can safely
742 	   drop the mutex */
743 	mutex_unlock(&tty_mutex);
744 
745 	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
746 	tty->driver_data = inode;
747 
748 	tty_add_file(tty, filp);
749 
750 	slave_inode = devpts_pty_new(inode,
751 			MKDEV(UNIX98_PTY_SLAVE_MAJOR, index), index,
752 			tty->link);
753 	if (IS_ERR(slave_inode)) {
754 		retval = PTR_ERR(slave_inode);
755 		goto err_release;
756 	}
757 	tty->link->driver_data = slave_inode;
758 
759 	retval = ptm_driver->ops->open(tty, filp);
760 	if (retval)
761 		goto err_release;
762 
763 	tty_unlock(tty);
764 	return 0;
765 err_release:
766 	tty_unlock(tty);
767 	tty_release(inode, filp);
768 	return retval;
769 out:
770 	mutex_unlock(&tty_mutex);
771 	devpts_kill_index(inode, index);
772 err_file:
773 	tty_free_file(filp);
774 	return retval;
775 }
776 
777 static struct file_operations ptmx_fops;
778 
779 static void __init unix98_pty_init(void)
780 {
781 	ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
782 			TTY_DRIVER_RESET_TERMIOS |
783 			TTY_DRIVER_REAL_RAW |
784 			TTY_DRIVER_DYNAMIC_DEV |
785 			TTY_DRIVER_DEVPTS_MEM |
786 			TTY_DRIVER_DYNAMIC_ALLOC);
787 	if (IS_ERR(ptm_driver))
788 		panic("Couldn't allocate Unix98 ptm driver");
789 	pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
790 			TTY_DRIVER_RESET_TERMIOS |
791 			TTY_DRIVER_REAL_RAW |
792 			TTY_DRIVER_DYNAMIC_DEV |
793 			TTY_DRIVER_DEVPTS_MEM |
794 			TTY_DRIVER_DYNAMIC_ALLOC);
795 	if (IS_ERR(pts_driver))
796 		panic("Couldn't allocate Unix98 pts driver");
797 
798 	ptm_driver->driver_name = "pty_master";
799 	ptm_driver->name = "ptm";
800 	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
801 	ptm_driver->minor_start = 0;
802 	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
803 	ptm_driver->subtype = PTY_TYPE_MASTER;
804 	ptm_driver->init_termios = tty_std_termios;
805 	ptm_driver->init_termios.c_iflag = 0;
806 	ptm_driver->init_termios.c_oflag = 0;
807 	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
808 	ptm_driver->init_termios.c_lflag = 0;
809 	ptm_driver->init_termios.c_ispeed = 38400;
810 	ptm_driver->init_termios.c_ospeed = 38400;
811 	ptm_driver->other = pts_driver;
812 	tty_set_operations(ptm_driver, &ptm_unix98_ops);
813 
814 	pts_driver->driver_name = "pty_slave";
815 	pts_driver->name = "pts";
816 	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
817 	pts_driver->minor_start = 0;
818 	pts_driver->type = TTY_DRIVER_TYPE_PTY;
819 	pts_driver->subtype = PTY_TYPE_SLAVE;
820 	pts_driver->init_termios = tty_std_termios;
821 	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
822 	pts_driver->init_termios.c_ispeed = 38400;
823 	pts_driver->init_termios.c_ospeed = 38400;
824 	pts_driver->other = ptm_driver;
825 	tty_set_operations(pts_driver, &pty_unix98_ops);
826 
827 	if (tty_register_driver(ptm_driver))
828 		panic("Couldn't register Unix98 ptm driver");
829 	if (tty_register_driver(pts_driver))
830 		panic("Couldn't register Unix98 pts driver");
831 
832 	/* Now create the /dev/ptmx special device */
833 	tty_default_fops(&ptmx_fops);
834 	ptmx_fops.open = ptmx_open;
835 
836 	cdev_init(&ptmx_cdev, &ptmx_fops);
837 	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
838 	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
839 		panic("Couldn't register /dev/ptmx driver");
840 	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
841 }
842 
843 #else
844 static inline void unix98_pty_init(void) { }
845 #endif
846 
847 static int __init pty_init(void)
848 {
849 	legacy_pty_init();
850 	unix98_pty_init();
851 	return 0;
852 }
853 module_init(pty_init);
854