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#include "tty.h"
33
34#undef TTY_DEBUG_HANGUP
35#ifdef TTY_DEBUG_HANGUP
36# define tty_debug_hangup(tty, f, args...) tty_debug(tty, f, ##args)
37#else
38# define tty_debug_hangup(tty, f, args...) do {} while (0)
39#endif
40
41#ifdef CONFIG_UNIX98_PTYS
42static struct tty_driver *ptm_driver;
43static struct tty_driver *pts_driver;
44static DEFINE_MUTEX(devpts_mutex);
45#endif
46
47static void pty_close(struct tty_struct *tty, struct file *filp)
48{
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(nr: TTY_IO_ERROR, addr: &tty->flags);
58 wake_up_interruptible(&tty->read_wait);
59 wake_up_interruptible(&tty->write_wait);
60 spin_lock_irq(lock: &tty->ctrl.lock);
61 tty->ctrl.packet = false;
62 spin_unlock_irq(lock: &tty->ctrl.lock);
63 /* Review - krefs on tty_link ?? */
64 if (!tty->link)
65 return;
66 set_bit(nr: TTY_OTHER_CLOSED, addr: &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(nr: TTY_OTHER_CLOSED, addr: &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(lock: &devpts_mutex);
77 }
78#endif
79 tty_vhangup(tty: 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: tty->link);
96 set_bit(nr: TTY_THROTTLED, addr: &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 * @c: 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 ssize_t pty_write(struct tty_struct *tty, const u8 *buf, size_t c)
112{
113 struct tty_struct *to = tty->link;
114
115 if (tty->flow.stopped || !c)
116 return 0;
117
118 return tty_insert_flip_string_and_push_buffer(port: to->port, chars: buf, cnt: c);
119}
120
121/**
122 * pty_write_room - write space
123 * @tty: tty we are writing from
124 *
125 * Report how many bytes the ldisc can send into the queue for
126 * the other device.
127 */
128
129static unsigned int pty_write_room(struct tty_struct *tty)
130{
131 if (tty->flow.stopped)
132 return 0;
133 return tty_buffer_space_avail(port: tty->link->port);
134}
135
136/* Set the lock flag on a pty */
137static int pty_set_lock(struct tty_struct *tty, int __user *arg)
138{
139 int val;
140
141 if (get_user(val, arg))
142 return -EFAULT;
143 if (val)
144 set_bit(nr: TTY_PTY_LOCK, addr: &tty->flags);
145 else
146 clear_bit(nr: TTY_PTY_LOCK, addr: &tty->flags);
147 return 0;
148}
149
150static int pty_get_lock(struct tty_struct *tty, int __user *arg)
151{
152 int locked = test_bit(TTY_PTY_LOCK, &tty->flags);
153
154 return put_user(locked, arg);
155}
156
157/* Set the packet mode on a pty */
158static int pty_set_pktmode(struct tty_struct *tty, int __user *arg)
159{
160 int pktmode;
161
162 if (get_user(pktmode, arg))
163 return -EFAULT;
164
165 spin_lock_irq(lock: &tty->ctrl.lock);
166 if (pktmode) {
167 if (!tty->ctrl.packet) {
168 tty->link->ctrl.pktstatus = 0;
169 smp_mb();
170 tty->ctrl.packet = true;
171 }
172 } else
173 tty->ctrl.packet = false;
174 spin_unlock_irq(lock: &tty->ctrl.lock);
175
176 return 0;
177}
178
179/* Get the packet mode of a pty */
180static int pty_get_pktmode(struct tty_struct *tty, int __user *arg)
181{
182 int pktmode = tty->ctrl.packet;
183
184 return put_user(pktmode, arg);
185}
186
187/* Send a signal to the slave */
188static int pty_signal(struct tty_struct *tty, int sig)
189{
190 struct pid *pgrp;
191
192 if (sig != SIGINT && sig != SIGQUIT && sig != SIGTSTP)
193 return -EINVAL;
194
195 if (tty->link) {
196 pgrp = tty_get_pgrp(tty: tty->link);
197 if (pgrp)
198 kill_pgrp(pid: pgrp, sig, priv: 1);
199 put_pid(pid: pgrp);
200 }
201 return 0;
202}
203
204static void pty_flush_buffer(struct tty_struct *tty)
205{
206 struct tty_struct *to = tty->link;
207
208 if (!to)
209 return;
210
211 tty_buffer_flush(tty: to, NULL);
212 if (to->ctrl.packet) {
213 spin_lock_irq(lock: &tty->ctrl.lock);
214 tty->ctrl.pktstatus |= TIOCPKT_FLUSHWRITE;
215 wake_up_interruptible(&to->read_wait);
216 spin_unlock_irq(lock: &tty->ctrl.lock);
217 }
218}
219
220static int pty_open(struct tty_struct *tty, struct file *filp)
221{
222 if (!tty || !tty->link)
223 return -ENODEV;
224
225 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
226 goto out;
227 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
228 goto out;
229 if (tty->driver->subtype == PTY_TYPE_SLAVE && tty->link->count != 1)
230 goto out;
231
232 clear_bit(nr: TTY_IO_ERROR, addr: &tty->flags);
233 clear_bit(nr: TTY_OTHER_CLOSED, addr: &tty->link->flags);
234 set_bit(nr: TTY_THROTTLED, addr: &tty->flags);
235 return 0;
236
237out:
238 set_bit(nr: TTY_IO_ERROR, addr: &tty->flags);
239 return -EIO;
240}
241
242static void pty_set_termios(struct tty_struct *tty,
243 const struct ktermios *old_termios)
244{
245 /* See if packet mode change of state. */
246 if (tty->link && tty->link->ctrl.packet) {
247 int extproc = (old_termios->c_lflag & EXTPROC) | L_EXTPROC(tty);
248 int old_flow = ((old_termios->c_iflag & IXON) &&
249 (old_termios->c_cc[VSTOP] == '\023') &&
250 (old_termios->c_cc[VSTART] == '\021'));
251 int new_flow = (I_IXON(tty) &&
252 STOP_CHAR(tty) == '\023' &&
253 START_CHAR(tty) == '\021');
254 if ((old_flow != new_flow) || extproc) {
255 spin_lock_irq(lock: &tty->ctrl.lock);
256 if (old_flow != new_flow) {
257 tty->ctrl.pktstatus &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
258 if (new_flow)
259 tty->ctrl.pktstatus |= TIOCPKT_DOSTOP;
260 else
261 tty->ctrl.pktstatus |= TIOCPKT_NOSTOP;
262 }
263 if (extproc)
264 tty->ctrl.pktstatus |= TIOCPKT_IOCTL;
265 spin_unlock_irq(lock: &tty->ctrl.lock);
266 wake_up_interruptible(&tty->link->read_wait);
267 }
268 }
269
270 tty->termios.c_cflag &= ~(CSIZE | PARENB);
271 tty->termios.c_cflag |= (CS8 | CREAD);
272}
273
274/**
275 * pty_resize - resize event
276 * @tty: tty being resized
277 * @ws: window size being set.
278 *
279 * Update the termios variables and send the necessary signals to
280 * peform a terminal resize correctly
281 */
282
283static int pty_resize(struct tty_struct *tty, struct winsize *ws)
284{
285 struct pid *pgrp, *rpgrp;
286 struct tty_struct *pty = tty->link;
287
288 /* For a PTY we need to lock the tty side */
289 mutex_lock(&tty->winsize_mutex);
290 if (!memcmp(p: ws, q: &tty->winsize, size: sizeof(*ws)))
291 goto done;
292
293 /* Signal the foreground process group of both ptys */
294 pgrp = tty_get_pgrp(tty);
295 rpgrp = tty_get_pgrp(tty: pty);
296
297 if (pgrp)
298 kill_pgrp(pid: pgrp, SIGWINCH, priv: 1);
299 if (rpgrp != pgrp && rpgrp)
300 kill_pgrp(pid: rpgrp, SIGWINCH, priv: 1);
301
302 put_pid(pid: pgrp);
303 put_pid(pid: rpgrp);
304
305 tty->winsize = *ws;
306 pty->winsize = *ws; /* Never used so will go away soon */
307done:
308 mutex_unlock(lock: &tty->winsize_mutex);
309 return 0;
310}
311
312/**
313 * pty_start - start() handler
314 * pty_stop - stop() handler
315 * @tty: tty being flow-controlled
316 *
317 * Propagates the TIOCPKT status to the master pty.
318 *
319 * NB: only the master pty can be in packet mode so only the slave
320 * needs start()/stop() handlers
321 */
322static void pty_start(struct tty_struct *tty)
323{
324 unsigned long flags;
325
326 if (tty->link && tty->link->ctrl.packet) {
327 spin_lock_irqsave(&tty->ctrl.lock, flags);
328 tty->ctrl.pktstatus &= ~TIOCPKT_STOP;
329 tty->ctrl.pktstatus |= TIOCPKT_START;
330 spin_unlock_irqrestore(lock: &tty->ctrl.lock, flags);
331 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
332 }
333}
334
335static void pty_stop(struct tty_struct *tty)
336{
337 unsigned long flags;
338
339 if (tty->link && tty->link->ctrl.packet) {
340 spin_lock_irqsave(&tty->ctrl.lock, flags);
341 tty->ctrl.pktstatus &= ~TIOCPKT_START;
342 tty->ctrl.pktstatus |= TIOCPKT_STOP;
343 spin_unlock_irqrestore(lock: &tty->ctrl.lock, flags);
344 wake_up_interruptible_poll(&tty->link->read_wait, EPOLLIN);
345 }
346}
347
348/**
349 * pty_common_install - set up the pty pair
350 * @driver: the pty driver
351 * @tty: the tty being instantiated
352 * @legacy: true if this is BSD style
353 *
354 * Perform the initial set up for the tty/pty pair. Called from the
355 * tty layer when the port is first opened.
356 *
357 * Locking: the caller must hold the tty_mutex
358 */
359static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
360 bool legacy)
361{
362 struct tty_struct *o_tty;
363 struct tty_port *ports[2];
364 int idx = tty->index;
365 int retval = -ENOMEM;
366
367 /* Opening the slave first has always returned -EIO */
368 if (driver->subtype != PTY_TYPE_MASTER)
369 return -EIO;
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(module: driver->other->owner)) {
376 /* This cannot in fact currently happen */
377 goto err;
378 }
379 o_tty = alloc_tty_struct(driver: driver->other, idx);
380 if (!o_tty)
381 goto err_put_module;
382
383 tty_set_lock_subclass(tty: o_tty);
384 lockdep_set_subclass(&o_tty->termios_rwsem, TTY_LOCK_SLAVE);
385
386 if (legacy) {
387 /* We always use new tty termios data so we can do this
388 the easy way .. */
389 tty_init_termios(tty);
390 tty_init_termios(tty: o_tty);
391
392 driver->other->ttys[idx] = o_tty;
393 driver->ttys[idx] = tty;
394 } else {
395 memset(&tty->termios_locked, 0, sizeof(tty->termios_locked));
396 tty->termios = driver->init_termios;
397 memset(&o_tty->termios_locked, 0, sizeof(tty->termios_locked));
398 o_tty->termios = driver->other->init_termios;
399 }
400
401 /*
402 * Everything allocated ... set up the o_tty structure.
403 */
404 tty_driver_kref_get(d: driver->other);
405 /* Establish the links in both directions */
406 tty->link = o_tty;
407 o_tty->link = tty;
408 tty_port_init(port: ports[0]);
409 tty_port_init(port: ports[1]);
410 tty_buffer_set_limit(port: ports[0], limit: 8192);
411 tty_buffer_set_limit(port: ports[1], limit: 8192);
412 o_tty->port = ports[0];
413 tty->port = ports[1];
414 o_tty->port->itty = o_tty;
415
416 tty_buffer_set_lock_subclass(port: o_tty->port);
417
418 tty_driver_kref_get(d: driver);
419 tty->count++;
420 o_tty->count++;
421 return 0;
422
423err_put_module:
424 module_put(module: driver->other->owner);
425err:
426 kfree(objp: ports[0]);
427 kfree(objp: ports[1]);
428 return retval;
429}
430
431static void pty_cleanup(struct tty_struct *tty)
432{
433 tty_port_put(port: tty->port);
434}
435
436/* Traditional BSD devices */
437#ifdef CONFIG_LEGACY_PTYS
438
439static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
440{
441 return pty_common_install(driver, tty, legacy: true);
442}
443
444static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
445{
446 struct tty_struct *pair = tty->link;
447
448 driver->ttys[tty->index] = NULL;
449 if (pair)
450 pair->driver->ttys[pair->index] = NULL;
451}
452
453static int pty_bsd_ioctl(struct tty_struct *tty,
454 unsigned int cmd, unsigned long arg)
455{
456 switch (cmd) {
457 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
458 return pty_set_lock(tty, arg: (int __user *) arg);
459 case TIOCGPTLCK: /* Get PT Lock status */
460 return pty_get_lock(tty, arg: (int __user *)arg);
461 case TIOCPKT: /* Set PT packet mode */
462 return pty_set_pktmode(tty, arg: (int __user *)arg);
463 case TIOCGPKT: /* Get PT packet mode */
464 return pty_get_pktmode(tty, arg: (int __user *)arg);
465 case TIOCSIG: /* Send signal to other side of pty */
466 return pty_signal(tty, sig: (int) arg);
467 case TIOCGPTN: /* TTY returns ENOTTY, but glibc expects EINVAL here */
468 return -EINVAL;
469 }
470 return -ENOIOCTLCMD;
471}
472
473#ifdef CONFIG_COMPAT
474static long pty_bsd_compat_ioctl(struct tty_struct *tty,
475 unsigned int cmd, unsigned long arg)
476{
477 /*
478 * PTY ioctls don't require any special translation between 32-bit and
479 * 64-bit userspace, they are already compatible.
480 */
481 return pty_bsd_ioctl(tty, cmd, arg: (unsigned long)compat_ptr(uptr: arg));
482}
483#else
484#define pty_bsd_compat_ioctl NULL
485#endif
486
487static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
488/*
489 * not really modular, but the easiest way to keep compat with existing
490 * bootargs behaviour is to continue using module_param here.
491 */
492module_param(legacy_count, int, 0);
493
494/*
495 * The master side of a pty can do TIOCSPTLCK and thus
496 * has pty_bsd_ioctl.
497 */
498static const struct tty_operations master_pty_ops_bsd = {
499 .install = pty_install,
500 .open = pty_open,
501 .close = pty_close,
502 .write = pty_write,
503 .write_room = pty_write_room,
504 .flush_buffer = pty_flush_buffer,
505 .unthrottle = pty_unthrottle,
506 .ioctl = pty_bsd_ioctl,
507 .compat_ioctl = pty_bsd_compat_ioctl,
508 .cleanup = pty_cleanup,
509 .resize = pty_resize,
510 .remove = pty_remove
511};
512
513static const struct tty_operations slave_pty_ops_bsd = {
514 .install = pty_install,
515 .open = pty_open,
516 .close = pty_close,
517 .write = pty_write,
518 .write_room = pty_write_room,
519 .flush_buffer = pty_flush_buffer,
520 .unthrottle = pty_unthrottle,
521 .set_termios = pty_set_termios,
522 .cleanup = pty_cleanup,
523 .resize = pty_resize,
524 .start = pty_start,
525 .stop = pty_stop,
526 .remove = pty_remove
527};
528
529static void __init legacy_pty_init(void)
530{
531 struct tty_driver *pty_driver, *pty_slave_driver;
532
533 if (legacy_count <= 0)
534 return;
535
536 pty_driver = tty_alloc_driver(legacy_count,
537 TTY_DRIVER_RESET_TERMIOS |
538 TTY_DRIVER_REAL_RAW |
539 TTY_DRIVER_DYNAMIC_ALLOC);
540 if (IS_ERR(ptr: pty_driver))
541 panic(fmt: "Couldn't allocate pty driver");
542
543 pty_slave_driver = tty_alloc_driver(legacy_count,
544 TTY_DRIVER_RESET_TERMIOS |
545 TTY_DRIVER_REAL_RAW |
546 TTY_DRIVER_DYNAMIC_ALLOC);
547 if (IS_ERR(ptr: pty_slave_driver))
548 panic(fmt: "Couldn't allocate pty slave driver");
549
550 pty_driver->driver_name = "pty_master";
551 pty_driver->name = "pty";
552 pty_driver->major = PTY_MASTER_MAJOR;
553 pty_driver->minor_start = 0;
554 pty_driver->type = TTY_DRIVER_TYPE_PTY;
555 pty_driver->subtype = PTY_TYPE_MASTER;
556 pty_driver->init_termios = tty_std_termios;
557 pty_driver->init_termios.c_iflag = 0;
558 pty_driver->init_termios.c_oflag = 0;
559 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
560 pty_driver->init_termios.c_lflag = 0;
561 pty_driver->init_termios.c_ispeed = 38400;
562 pty_driver->init_termios.c_ospeed = 38400;
563 pty_driver->other = pty_slave_driver;
564 tty_set_operations(driver: pty_driver, op: &master_pty_ops_bsd);
565
566 pty_slave_driver->driver_name = "pty_slave";
567 pty_slave_driver->name = "ttyp";
568 pty_slave_driver->major = PTY_SLAVE_MAJOR;
569 pty_slave_driver->minor_start = 0;
570 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
571 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
572 pty_slave_driver->init_termios = tty_std_termios;
573 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
574 pty_slave_driver->init_termios.c_ispeed = 38400;
575 pty_slave_driver->init_termios.c_ospeed = 38400;
576 pty_slave_driver->other = pty_driver;
577 tty_set_operations(driver: pty_slave_driver, op: &slave_pty_ops_bsd);
578
579 if (tty_register_driver(driver: pty_driver))
580 panic(fmt: "Couldn't register pty driver");
581 if (tty_register_driver(driver: pty_slave_driver))
582 panic(fmt: "Couldn't register pty slave driver");
583}
584#else
585static inline void legacy_pty_init(void) { }
586#endif
587
588/* Unix98 devices */
589#ifdef CONFIG_UNIX98_PTYS
590static struct cdev ptmx_cdev;
591
592/**
593 * ptm_open_peer - open the peer of a pty
594 * @master: the open struct file of the ptmx device node
595 * @tty: the master of the pty being opened
596 * @flags: the flags for open
597 *
598 * Provide a race free way for userspace to open the slave end of a pty
599 * (where they have the master fd and cannot access or trust the mount
600 * namespace /dev/pts was mounted inside).
601 */
602int ptm_open_peer(struct file *master, struct tty_struct *tty, int flags)
603{
604 int fd;
605 struct file *filp;
606 int retval = -EINVAL;
607 struct path path;
608
609 if (tty->driver != ptm_driver)
610 return -EIO;
611
612 fd = get_unused_fd_flags(flags);
613 if (fd < 0) {
614 retval = fd;
615 goto err;
616 }
617
618 /* Compute the slave's path */
619 path.mnt = devpts_mntget(master, tty->driver_data);
620 if (IS_ERR(ptr: path.mnt)) {
621 retval = PTR_ERR(ptr: path.mnt);
622 goto err_put;
623 }
624 path.dentry = tty->link->driver_data;
625
626 filp = dentry_open(path: &path, flags, current_cred());
627 mntput(mnt: path.mnt);
628 if (IS_ERR(ptr: filp)) {
629 retval = PTR_ERR(ptr: filp);
630 goto err_put;
631 }
632
633 fd_install(fd, file: filp);
634 return fd;
635
636err_put:
637 put_unused_fd(fd);
638err:
639 return retval;
640}
641
642static int pty_unix98_ioctl(struct tty_struct *tty,
643 unsigned int cmd, unsigned long arg)
644{
645 switch (cmd) {
646 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
647 return pty_set_lock(tty, arg: (int __user *)arg);
648 case TIOCGPTLCK: /* Get PT Lock status */
649 return pty_get_lock(tty, arg: (int __user *)arg);
650 case TIOCPKT: /* Set PT packet mode */
651 return pty_set_pktmode(tty, arg: (int __user *)arg);
652 case TIOCGPKT: /* Get PT packet mode */
653 return pty_get_pktmode(tty, arg: (int __user *)arg);
654 case TIOCGPTN: /* Get PT Number */
655 return put_user(tty->index, (unsigned int __user *)arg);
656 case TIOCSIG: /* Send signal to other side of pty */
657 return pty_signal(tty, sig: (int) arg);
658 }
659
660 return -ENOIOCTLCMD;
661}
662
663#ifdef CONFIG_COMPAT
664static long pty_unix98_compat_ioctl(struct tty_struct *tty,
665 unsigned int cmd, unsigned long arg)
666{
667 /*
668 * PTY ioctls don't require any special translation between 32-bit and
669 * 64-bit userspace, they are already compatible.
670 */
671 return pty_unix98_ioctl(tty, cmd,
672 arg: cmd == TIOCSIG ? arg : (unsigned long)compat_ptr(uptr: arg));
673}
674#else
675#define pty_unix98_compat_ioctl NULL
676#endif
677
678/**
679 * ptm_unix98_lookup - find a pty master
680 * @driver: ptm driver
681 * @file: unused
682 * @idx: tty index
683 *
684 * Look up a pty master device. Called under the tty_mutex for now.
685 * This provides our locking.
686 */
687
688static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
689 struct file *file, int idx)
690{
691 /* Master must be open via /dev/ptmx */
692 return ERR_PTR(error: -EIO);
693}
694
695/**
696 * pts_unix98_lookup - find a pty slave
697 * @driver: pts driver
698 * @file: file pointer to tty
699 * @idx: tty index
700 *
701 * Look up a pty master device. Called under the tty_mutex for now.
702 * This provides our locking for the tty pointer.
703 */
704
705static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
706 struct file *file, int idx)
707{
708 struct tty_struct *tty;
709
710 mutex_lock(&devpts_mutex);
711 tty = devpts_get_priv(file->f_path.dentry);
712 mutex_unlock(lock: &devpts_mutex);
713 /* Master must be open before slave */
714 if (!tty)
715 return ERR_PTR(error: -EIO);
716 return tty;
717}
718
719static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
720{
721 return pty_common_install(driver, tty, legacy: false);
722}
723
724/* this is called once with whichever end is closed last */
725static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
726{
727 struct pts_fs_info *fsi;
728
729 if (tty->driver->subtype == PTY_TYPE_MASTER)
730 fsi = tty->driver_data;
731 else
732 fsi = tty->link->driver_data;
733
734 if (fsi) {
735 devpts_kill_index(fsi, tty->index);
736 devpts_release(fsi);
737 }
738}
739
740static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
741{
742 seq_printf(m, fmt: "tty-index:\t%d\n", tty->index);
743}
744
745static const struct tty_operations ptm_unix98_ops = {
746 .lookup = ptm_unix98_lookup,
747 .install = pty_unix98_install,
748 .remove = pty_unix98_remove,
749 .open = pty_open,
750 .close = pty_close,
751 .write = pty_write,
752 .write_room = pty_write_room,
753 .flush_buffer = pty_flush_buffer,
754 .unthrottle = pty_unthrottle,
755 .ioctl = pty_unix98_ioctl,
756 .compat_ioctl = pty_unix98_compat_ioctl,
757 .resize = pty_resize,
758 .cleanup = pty_cleanup,
759 .show_fdinfo = pty_show_fdinfo,
760};
761
762static const struct tty_operations pty_unix98_ops = {
763 .lookup = pts_unix98_lookup,
764 .install = pty_unix98_install,
765 .remove = pty_unix98_remove,
766 .open = pty_open,
767 .close = pty_close,
768 .write = pty_write,
769 .write_room = pty_write_room,
770 .flush_buffer = pty_flush_buffer,
771 .unthrottle = pty_unthrottle,
772 .set_termios = pty_set_termios,
773 .start = pty_start,
774 .stop = pty_stop,
775 .cleanup = pty_cleanup,
776};
777
778/**
779 * ptmx_open - open a unix 98 pty master
780 * @inode: inode of device file
781 * @filp: file pointer to tty
782 *
783 * Allocate a unix98 pty master device from the ptmx driver.
784 *
785 * Locking: tty_mutex protects the init_dev work. tty->count should
786 * protect the rest.
787 * allocated_ptys_lock handles the list of free pty numbers
788 */
789
790static int ptmx_open(struct inode *inode, struct file *filp)
791{
792 struct pts_fs_info *fsi;
793 struct tty_struct *tty;
794 struct dentry *dentry;
795 int retval;
796 int index;
797
798 nonseekable_open(inode, filp);
799
800 /* We refuse fsnotify events on ptmx, since it's a shared resource */
801 file_set_fsnotify_mode(file: filp, FMODE_NONOTIFY);
802
803 retval = tty_alloc_file(file: filp);
804 if (retval)
805 return retval;
806
807 fsi = devpts_acquire(filp);
808 if (IS_ERR(ptr: fsi)) {
809 retval = PTR_ERR(ptr: fsi);
810 goto out_free_file;
811 }
812
813 /* find a device that is not in use. */
814 mutex_lock(&devpts_mutex);
815 index = devpts_new_index(fsi);
816 mutex_unlock(lock: &devpts_mutex);
817
818 retval = index;
819 if (index < 0)
820 goto out_put_fsi;
821
822
823 mutex_lock(&tty_mutex);
824 tty = tty_init_dev(driver: ptm_driver, idx: index);
825 /* The tty returned here is locked so we can safely
826 drop the mutex */
827 mutex_unlock(lock: &tty_mutex);
828
829 retval = PTR_ERR(ptr: tty);
830 if (IS_ERR(ptr: tty))
831 goto out;
832
833 /*
834 * From here on out, the tty is "live", and the index and
835 * fsi will be killed/put by the tty_release()
836 */
837 set_bit(nr: TTY_PTY_LOCK, addr: &tty->flags); /* LOCK THE SLAVE */
838 tty->driver_data = fsi;
839
840 tty_add_file(tty, file: filp);
841
842 dentry = devpts_pty_new(fsi, index, tty->link);
843 if (IS_ERR(ptr: dentry)) {
844 retval = PTR_ERR(ptr: dentry);
845 goto err_release;
846 }
847 tty->link->driver_data = dentry;
848
849 retval = ptm_driver->ops->open(tty, filp);
850 if (retval)
851 goto err_release;
852
853 tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
854
855 tty_unlock(tty);
856 return 0;
857err_release:
858 tty_unlock(tty);
859 // This will also put-ref the fsi
860 tty_release(inode, filp);
861 return retval;
862out:
863 devpts_kill_index(fsi, index);
864out_put_fsi:
865 devpts_release(fsi);
866out_free_file:
867 tty_free_file(file: filp);
868 return retval;
869}
870
871static struct file_operations ptmx_fops __ro_after_init;
872
873static void __init unix98_pty_init(void)
874{
875 ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
876 TTY_DRIVER_RESET_TERMIOS |
877 TTY_DRIVER_REAL_RAW |
878 TTY_DRIVER_DYNAMIC_DEV |
879 TTY_DRIVER_DEVPTS_MEM |
880 TTY_DRIVER_DYNAMIC_ALLOC);
881 if (IS_ERR(ptr: ptm_driver))
882 panic(fmt: "Couldn't allocate Unix98 ptm driver");
883 pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
884 TTY_DRIVER_RESET_TERMIOS |
885 TTY_DRIVER_REAL_RAW |
886 TTY_DRIVER_DYNAMIC_DEV |
887 TTY_DRIVER_DEVPTS_MEM |
888 TTY_DRIVER_DYNAMIC_ALLOC);
889 if (IS_ERR(ptr: pts_driver))
890 panic(fmt: "Couldn't allocate Unix98 pts driver");
891
892 ptm_driver->driver_name = "pty_master";
893 ptm_driver->name = "ptm";
894 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
895 ptm_driver->minor_start = 0;
896 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
897 ptm_driver->subtype = PTY_TYPE_MASTER;
898 ptm_driver->init_termios = tty_std_termios;
899 ptm_driver->init_termios.c_iflag = 0;
900 ptm_driver->init_termios.c_oflag = 0;
901 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
902 ptm_driver->init_termios.c_lflag = 0;
903 ptm_driver->init_termios.c_ispeed = 38400;
904 ptm_driver->init_termios.c_ospeed = 38400;
905 ptm_driver->other = pts_driver;
906 tty_set_operations(driver: ptm_driver, op: &ptm_unix98_ops);
907
908 pts_driver->driver_name = "pty_slave";
909 pts_driver->name = "pts";
910 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
911 pts_driver->minor_start = 0;
912 pts_driver->type = TTY_DRIVER_TYPE_PTY;
913 pts_driver->subtype = PTY_TYPE_SLAVE;
914 pts_driver->init_termios = tty_std_termios;
915 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
916 pts_driver->init_termios.c_ispeed = 38400;
917 pts_driver->init_termios.c_ospeed = 38400;
918 pts_driver->other = ptm_driver;
919 tty_set_operations(driver: pts_driver, op: &pty_unix98_ops);
920
921 if (tty_register_driver(driver: ptm_driver))
922 panic(fmt: "Couldn't register Unix98 ptm driver");
923 if (tty_register_driver(driver: pts_driver))
924 panic(fmt: "Couldn't register Unix98 pts driver");
925
926 /* Now create the /dev/ptmx special device */
927 tty_default_fops(fops: &ptmx_fops);
928 ptmx_fops.open = ptmx_open;
929
930 cdev_init(&ptmx_cdev, &ptmx_fops);
931 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
932 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
933 panic(fmt: "Couldn't register /dev/ptmx driver");
934 device_create(cls: &tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, fmt: "ptmx");
935}
936
937#else
938static inline void unix98_pty_init(void) { }
939#endif
940
941static int __init pty_init(void)
942{
943 legacy_pty_init();
944 unix98_pty_init();
945 return 0;
946}
947device_initcall(pty_init);
948

source code of linux/drivers/tty/pty.c