284749fb0f6b96d3d6d667332e569ba0d745e048
[karo-tx-linux.git] / drivers / tty / pty.c
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 #include <linux/errno.h>
11 #include <linux/interrupt.h>
12 #include <linux/tty.h>
13 #include <linux/tty_flip.h>
14 #include <linux/fcntl.h>
15 #include <linux/sched/signal.h>
16 #include <linux/string.h>
17 #include <linux/major.h>
18 #include <linux/mm.h>
19 #include <linux/init.h>
20 #include <linux/device.h>
21 #include <linux/uaccess.h>
22 #include <linux/bitops.h>
23 #include <linux/devpts_fs.h>
24 #include <linux/slab.h>
25 #include <linux/mutex.h>
26 #include <linux/poll.h>
27 #include <linux/mount.h>
28 #include <linux/file.h>
29 #include <linux/ioctl.h>
30
31 #undef TTY_DEBUG_HANGUP
32 #ifdef TTY_DEBUG_HANGUP
33 # define tty_debug_hangup(tty, f, args...)      tty_debug(tty, f, ##args)
34 #else
35 # define tty_debug_hangup(tty, f, args...)      do {} while (0)
36 #endif
37
38 #ifdef CONFIG_UNIX98_PTYS
39 static struct tty_driver *ptm_driver;
40 static struct tty_driver *pts_driver;
41 static DEFINE_MUTEX(devpts_mutex);
42 #endif
43
44 static void pty_close(struct tty_struct *tty, struct file *filp)
45 {
46         BUG_ON(!tty);
47         if (tty->driver->subtype == PTY_TYPE_MASTER)
48                 WARN_ON(tty->count > 1);
49         else {
50                 if (tty_io_error(tty))
51                         return;
52                 if (tty->count > 2)
53                         return;
54         }
55         set_bit(TTY_IO_ERROR, &tty->flags);
56         wake_up_interruptible(&tty->read_wait);
57         wake_up_interruptible(&tty->write_wait);
58         spin_lock_irq(&tty->ctrl_lock);
59         tty->packet = 0;
60         spin_unlock_irq(&tty->ctrl_lock);
61         /* Review - krefs on tty_link ?? */
62         if (!tty->link)
63                 return;
64         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
65         wake_up_interruptible(&tty->link->read_wait);
66         wake_up_interruptible(&tty->link->write_wait);
67         if (tty->driver->subtype == PTY_TYPE_MASTER) {
68                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
69 #ifdef CONFIG_UNIX98_PTYS
70                 if (tty->driver == ptm_driver) {
71                         mutex_lock(&devpts_mutex);
72                         if (tty->link->driver_data) {
73                                 struct path *path = tty->link->driver_data;
74
75                                 devpts_pty_kill(path->dentry);
76                                 path_put(path);
77                                 kfree(path);
78                         }
79                         mutex_unlock(&devpts_mutex);
80                 }
81 #endif
82                 tty_vhangup(tty->link);
83         }
84 }
85
86 /*
87  * The unthrottle routine is called by the line discipline to signal
88  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
89  * flag is always set, to force the line discipline to always call the
90  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
91  * characters in the queue.  This is necessary since each time this
92  * happens, we need to wake up any sleeping processes that could be
93  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
94  * for the pty buffer to be drained.
95  */
96 static void pty_unthrottle(struct tty_struct *tty)
97 {
98         tty_wakeup(tty->link);
99         set_bit(TTY_THROTTLED, &tty->flags);
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 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
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         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 */
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         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
224 static 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
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         /* 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
303 static 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 */
327 done:
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  */
342 static 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, POLLIN);
352         }
353 }
354
355 static 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, POLLIN);
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  */
379 static 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
443 err_put_module:
444         module_put(driver->other->owner);
445 err:
446         kfree(ports[0]);
447         kfree(ports[1]);
448         return retval;
449 }
450
451 static 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
459 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
460 {
461         return pty_common_install(driver, tty, true);
462 }
463
464 static 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
472 static 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 static long pty_bsd_compat_ioctl(struct tty_struct *tty,
493                                  unsigned int cmd, unsigned long arg)
494 {
495         /*
496          * PTY ioctls don't require any special translation between 32-bit and
497          * 64-bit userspace, they are already compatible.
498          */
499         return pty_bsd_ioctl(tty, cmd, arg);
500 }
501
502 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
503 /*
504  * not really modular, but the easiest way to keep compat with existing
505  * bootargs behaviour is to continue using module_param here.
506  */
507 module_param(legacy_count, int, 0);
508
509 /*
510  * The master side of a pty can do TIOCSPTLCK and thus
511  * has pty_bsd_ioctl.
512  */
513 static const struct tty_operations master_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         .chars_in_buffer = pty_chars_in_buffer,
521         .unthrottle = pty_unthrottle,
522         .ioctl = pty_bsd_ioctl,
523         .compat_ioctl = pty_bsd_compat_ioctl,
524         .cleanup = pty_cleanup,
525         .resize = pty_resize,
526         .remove = pty_remove
527 };
528
529 static const struct tty_operations slave_pty_ops_bsd = {
530         .install = pty_install,
531         .open = pty_open,
532         .close = pty_close,
533         .write = pty_write,
534         .write_room = pty_write_room,
535         .flush_buffer = pty_flush_buffer,
536         .chars_in_buffer = pty_chars_in_buffer,
537         .unthrottle = pty_unthrottle,
538         .set_termios = pty_set_termios,
539         .cleanup = pty_cleanup,
540         .resize = pty_resize,
541         .start = pty_start,
542         .stop = pty_stop,
543         .remove = pty_remove
544 };
545
546 static void __init legacy_pty_init(void)
547 {
548         struct tty_driver *pty_driver, *pty_slave_driver;
549
550         if (legacy_count <= 0)
551                 return;
552
553         pty_driver = tty_alloc_driver(legacy_count,
554                         TTY_DRIVER_RESET_TERMIOS |
555                         TTY_DRIVER_REAL_RAW |
556                         TTY_DRIVER_DYNAMIC_ALLOC);
557         if (IS_ERR(pty_driver))
558                 panic("Couldn't allocate pty driver");
559
560         pty_slave_driver = tty_alloc_driver(legacy_count,
561                         TTY_DRIVER_RESET_TERMIOS |
562                         TTY_DRIVER_REAL_RAW |
563                         TTY_DRIVER_DYNAMIC_ALLOC);
564         if (IS_ERR(pty_slave_driver))
565                 panic("Couldn't allocate pty slave driver");
566
567         pty_driver->driver_name = "pty_master";
568         pty_driver->name = "pty";
569         pty_driver->major = PTY_MASTER_MAJOR;
570         pty_driver->minor_start = 0;
571         pty_driver->type = TTY_DRIVER_TYPE_PTY;
572         pty_driver->subtype = PTY_TYPE_MASTER;
573         pty_driver->init_termios = tty_std_termios;
574         pty_driver->init_termios.c_iflag = 0;
575         pty_driver->init_termios.c_oflag = 0;
576         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
577         pty_driver->init_termios.c_lflag = 0;
578         pty_driver->init_termios.c_ispeed = 38400;
579         pty_driver->init_termios.c_ospeed = 38400;
580         pty_driver->other = pty_slave_driver;
581         tty_set_operations(pty_driver, &master_pty_ops_bsd);
582
583         pty_slave_driver->driver_name = "pty_slave";
584         pty_slave_driver->name = "ttyp";
585         pty_slave_driver->major = PTY_SLAVE_MAJOR;
586         pty_slave_driver->minor_start = 0;
587         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
588         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
589         pty_slave_driver->init_termios = tty_std_termios;
590         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
591         pty_slave_driver->init_termios.c_ispeed = 38400;
592         pty_slave_driver->init_termios.c_ospeed = 38400;
593         pty_slave_driver->other = pty_driver;
594         tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
595
596         if (tty_register_driver(pty_driver))
597                 panic("Couldn't register pty driver");
598         if (tty_register_driver(pty_slave_driver))
599                 panic("Couldn't register pty slave driver");
600 }
601 #else
602 static inline void legacy_pty_init(void) { }
603 #endif
604
605 /* Unix98 devices */
606 #ifdef CONFIG_UNIX98_PTYS
607 static struct cdev ptmx_cdev;
608
609 /**
610  *      pty_open_peer - open the peer of a pty
611  *      @tty: the peer of the pty being opened
612  *
613  *      Open the cached dentry in tty->link, providing a safe way for userspace
614  *      to get the slave end of a pty (where they have the master fd and cannot
615  *      access or trust the mount namespace /dev/pts was mounted inside).
616  */
617 static struct file *pty_open_peer(struct tty_struct *tty, int flags)
618 {
619         if (tty->driver->subtype != PTY_TYPE_MASTER)
620                 return ERR_PTR(-EIO);
621         return dentry_open(tty->link->driver_data, flags, current_cred());
622 }
623
624 static int pty_get_peer(struct tty_struct *tty, int flags)
625 {
626         int fd = -1;
627         struct file *filp = NULL;
628         int retval = -EINVAL;
629
630         fd = get_unused_fd_flags(0);
631         if (fd < 0) {
632                 retval = fd;
633                 goto err;
634         }
635
636         filp = pty_open_peer(tty, flags);
637         if (IS_ERR(filp)) {
638                 retval = PTR_ERR(filp);
639                 goto err_put;
640         }
641
642         fd_install(fd, filp);
643         return fd;
644
645 err_put:
646         put_unused_fd(fd);
647 err:
648         return retval;
649 }
650
651 static int pty_unix98_ioctl(struct tty_struct *tty,
652                             unsigned int cmd, unsigned long arg)
653 {
654         switch (cmd) {
655         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
656                 return pty_set_lock(tty, (int __user *)arg);
657         case TIOCGPTLCK: /* Get PT Lock status */
658                 return pty_get_lock(tty, (int __user *)arg);
659         case TIOCPKT: /* Set PT packet mode */
660                 return pty_set_pktmode(tty, (int __user *)arg);
661         case TIOCGPKT: /* Get PT packet mode */
662                 return pty_get_pktmode(tty, (int __user *)arg);
663         case TIOCGPTN: /* Get PT Number */
664                 return put_user(tty->index, (unsigned int __user *)arg);
665         case TIOCGPTPEER: /* Open the other end */
666                 return pty_get_peer(tty, (int) arg);
667         case TIOCSIG:    /* Send signal to other side of pty */
668                 return pty_signal(tty, (int) arg);
669         }
670
671         return -ENOIOCTLCMD;
672 }
673
674 static long pty_unix98_compat_ioctl(struct tty_struct *tty,
675                                  unsigned int cmd, unsigned long arg)
676 {
677         /*
678          * PTY ioctls don't require any special translation between 32-bit and
679          * 64-bit userspace, they are already compatible.
680          */
681         return pty_unix98_ioctl(tty, cmd, arg);
682 }
683
684 /**
685  *      ptm_unix98_lookup       -       find a pty master
686  *      @driver: ptm driver
687  *      @idx: tty index
688  *
689  *      Look up a pty master device. Called under the tty_mutex for now.
690  *      This provides our locking.
691  */
692
693 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
694                 struct file *file, int idx)
695 {
696         /* Master must be open via /dev/ptmx */
697         return ERR_PTR(-EIO);
698 }
699
700 /**
701  *      pts_unix98_lookup       -       find a pty slave
702  *      @driver: pts driver
703  *      @idx: tty index
704  *
705  *      Look up a pty master device. Called under the tty_mutex for now.
706  *      This provides our locking for the tty pointer.
707  */
708
709 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
710                 struct file *file, int idx)
711 {
712         struct tty_struct *tty;
713
714         mutex_lock(&devpts_mutex);
715         tty = devpts_get_priv(file->f_path.dentry);
716         mutex_unlock(&devpts_mutex);
717         /* Master must be open before slave */
718         if (!tty)
719                 return ERR_PTR(-EIO);
720         return tty;
721 }
722
723 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
724 {
725         return pty_common_install(driver, tty, false);
726 }
727
728 /* this is called once with whichever end is closed last */
729 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
730 {
731         struct pts_fs_info *fsi;
732
733         if (tty->driver->subtype == PTY_TYPE_MASTER)
734                 fsi = tty->driver_data;
735         else
736                 fsi = tty->link->driver_data;
737
738         if (fsi) {
739                 devpts_kill_index(fsi, tty->index);
740                 devpts_release(fsi);
741         }
742 }
743
744 static const struct tty_operations ptm_unix98_ops = {
745         .lookup = ptm_unix98_lookup,
746         .install = pty_unix98_install,
747         .remove = pty_unix98_remove,
748         .open = pty_open,
749         .close = pty_close,
750         .write = pty_write,
751         .write_room = pty_write_room,
752         .flush_buffer = pty_flush_buffer,
753         .chars_in_buffer = pty_chars_in_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 };
760
761 static const struct tty_operations pty_unix98_ops = {
762         .lookup = pts_unix98_lookup,
763         .install = pty_unix98_install,
764         .remove = pty_unix98_remove,
765         .open = pty_open,
766         .close = pty_close,
767         .write = pty_write,
768         .write_room = pty_write_room,
769         .flush_buffer = pty_flush_buffer,
770         .chars_in_buffer = pty_chars_in_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
790 static int ptmx_open(struct inode *inode, struct file *filp)
791 {
792         struct pts_fs_info *fsi;
793         struct tty_struct *tty;
794         struct path *pts_path;
795         struct dentry *dentry;
796         int retval;
797         int index;
798
799         nonseekable_open(inode, filp);
800
801         /* We refuse fsnotify events on ptmx, since it's a shared resource */
802         filp->f_mode |= FMODE_NONOTIFY;
803
804         retval = tty_alloc_file(filp);
805         if (retval)
806                 return retval;
807
808         fsi = devpts_acquire(filp);
809         if (IS_ERR(fsi)) {
810                 retval = PTR_ERR(fsi);
811                 goto out_free_file;
812         }
813
814         /* find a device that is not in use. */
815         mutex_lock(&devpts_mutex);
816         index = devpts_new_index(fsi);
817         mutex_unlock(&devpts_mutex);
818
819         retval = index;
820         if (index < 0)
821                 goto out_put_fsi;
822
823
824         mutex_lock(&tty_mutex);
825         tty = tty_init_dev(ptm_driver, index);
826         /* The tty returned here is locked so we can safely
827            drop the mutex */
828         mutex_unlock(&tty_mutex);
829
830         retval = PTR_ERR(tty);
831         if (IS_ERR(tty))
832                 goto out;
833
834         /*
835          * From here on out, the tty is "live", and the index and
836          * fsi will be killed/put by the tty_release()
837          */
838         set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
839         tty->driver_data = fsi;
840
841         tty_add_file(tty, filp);
842
843         dentry = devpts_pty_new(fsi, index, tty->link);
844         if (IS_ERR(dentry)) {
845                 retval = PTR_ERR(dentry);
846                 goto err_release;
847         }
848         /* We need to cache a fake path for TIOCGPTPEER. */
849         pts_path = kmalloc(sizeof(struct path), GFP_KERNEL);
850         if (!pts_path)
851                 goto err_release;
852         pts_path->mnt = filp->f_path.mnt;
853         pts_path->dentry = dentry;
854         path_get(pts_path);
855         tty->link->driver_data = pts_path;
856
857         retval = ptm_driver->ops->open(tty, filp);
858         if (retval)
859                 goto err_path_put;
860
861         tty_debug_hangup(tty, "opening (count=%d)\n", tty->count);
862
863         tty_unlock(tty);
864         return 0;
865 err_path_put:
866         path_put(pts_path);
867         kfree(pts_path);
868 err_release:
869         tty_unlock(tty);
870         // This will also put-ref the fsi
871         tty_release(inode, filp);
872         return retval;
873 out:
874         devpts_kill_index(fsi, index);
875 out_put_fsi:
876         devpts_release(fsi);
877 out_free_file:
878         tty_free_file(filp);
879         return retval;
880 }
881
882 static struct file_operations ptmx_fops __ro_after_init;
883
884 static void __init unix98_pty_init(void)
885 {
886         ptm_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
887                         TTY_DRIVER_RESET_TERMIOS |
888                         TTY_DRIVER_REAL_RAW |
889                         TTY_DRIVER_DYNAMIC_DEV |
890                         TTY_DRIVER_DEVPTS_MEM |
891                         TTY_DRIVER_DYNAMIC_ALLOC);
892         if (IS_ERR(ptm_driver))
893                 panic("Couldn't allocate Unix98 ptm driver");
894         pts_driver = tty_alloc_driver(NR_UNIX98_PTY_MAX,
895                         TTY_DRIVER_RESET_TERMIOS |
896                         TTY_DRIVER_REAL_RAW |
897                         TTY_DRIVER_DYNAMIC_DEV |
898                         TTY_DRIVER_DEVPTS_MEM |
899                         TTY_DRIVER_DYNAMIC_ALLOC);
900         if (IS_ERR(pts_driver))
901                 panic("Couldn't allocate Unix98 pts driver");
902
903         ptm_driver->driver_name = "pty_master";
904         ptm_driver->name = "ptm";
905         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
906         ptm_driver->minor_start = 0;
907         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
908         ptm_driver->subtype = PTY_TYPE_MASTER;
909         ptm_driver->init_termios = tty_std_termios;
910         ptm_driver->init_termios.c_iflag = 0;
911         ptm_driver->init_termios.c_oflag = 0;
912         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
913         ptm_driver->init_termios.c_lflag = 0;
914         ptm_driver->init_termios.c_ispeed = 38400;
915         ptm_driver->init_termios.c_ospeed = 38400;
916         ptm_driver->other = pts_driver;
917         tty_set_operations(ptm_driver, &ptm_unix98_ops);
918
919         pts_driver->driver_name = "pty_slave";
920         pts_driver->name = "pts";
921         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
922         pts_driver->minor_start = 0;
923         pts_driver->type = TTY_DRIVER_TYPE_PTY;
924         pts_driver->subtype = PTY_TYPE_SLAVE;
925         pts_driver->init_termios = tty_std_termios;
926         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
927         pts_driver->init_termios.c_ispeed = 38400;
928         pts_driver->init_termios.c_ospeed = 38400;
929         pts_driver->other = ptm_driver;
930         tty_set_operations(pts_driver, &pty_unix98_ops);
931
932         if (tty_register_driver(ptm_driver))
933                 panic("Couldn't register Unix98 ptm driver");
934         if (tty_register_driver(pts_driver))
935                 panic("Couldn't register Unix98 pts driver");
936
937         /* Now create the /dev/ptmx special device */
938         tty_default_fops(&ptmx_fops);
939         ptmx_fops.open = ptmx_open;
940
941         cdev_init(&ptmx_cdev, &ptmx_fops);
942         if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
943             register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
944                 panic("Couldn't register /dev/ptmx driver");
945         device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
946 }
947
948 #else
949 static inline void unix98_pty_init(void) { }
950 #endif
951
952 static int __init pty_init(void)
953 {
954         legacy_pty_init();
955         unix98_pty_init();
956         return 0;
957 }
958 device_initcall(pty_init);