2 * linux/drivers/char/pty.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Added support for a Unix98-style ptmx device.
7 * -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
9 * When reading this code see also fs/devpts. In particular note that the
10 * driver_data field is used by the devpts side as a binding to the devpts
14 #include <linux/module.h>
16 #include <linux/errno.h>
17 #include <linux/interrupt.h>
18 #include <linux/tty.h>
19 #include <linux/tty_flip.h>
20 #include <linux/fcntl.h>
21 #include <linux/string.h>
22 #include <linux/major.h>
24 #include <linux/init.h>
25 #include <linux/sysctl.h>
26 #include <linux/device.h>
27 #include <linux/uaccess.h>
28 #include <linux/bitops.h>
29 #include <linux/devpts_fs.h>
31 #include <asm/system.h>
33 /* These are global because they are accessed in tty_io.c */
34 #ifdef CONFIG_UNIX98_PTYS
35 static struct tty_driver
*ptm_driver
;
36 static struct tty_driver
*pts_driver
;
39 static void pty_close(struct tty_struct
*tty
, struct file
*filp
)
42 if (tty
->driver
->subtype
== PTY_TYPE_MASTER
)
43 WARN_ON(tty
->count
> 1);
48 wake_up_interruptible(&tty
->read_wait
);
49 wake_up_interruptible(&tty
->write_wait
);
53 tty
->link
->packet
= 0;
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 devpts_pty_kill(tty
->link
);
63 tty_vhangup(tty
->link
);
68 * The unthrottle routine is called by the line discipline to signal
69 * that it can receive more characters. For PTY's, the TTY_THROTTLED
70 * flag is always set, to force the line discipline to always call the
71 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
72 * characters in the queue. This is necessary since each time this
73 * happens, we need to wake up any sleeping processes that could be
74 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
75 * for the pty buffer to be drained.
77 static void pty_unthrottle(struct tty_struct
*tty
)
79 struct tty_struct
*o_tty
= tty
->link
;
85 set_bit(TTY_THROTTLED
, &tty
->flags
);
89 * WSH 05/24/97: modified to
90 * (1) use space in tty->flip instead of a shared temp buffer
91 * The flip buffers aren't being used for a pty, so there's lots
92 * of space available. The buffer is protected by a per-pty
93 * semaphore that should almost never come under contention.
94 * (2) avoid redundant copying for cases where count >> receive_room
95 * N.B. Calls from user space may now return an error code instead of
98 * FIXME: Our pty_write method is called with our ldisc lock held but
99 * not our partners. We can't just take the other one blindly without
102 static int pty_write(struct tty_struct
*tty
, const unsigned char *buf
,
105 struct tty_struct
*to
= tty
->link
;
108 if (!to
|| tty
->stopped
)
111 c
= to
->receive_room
;
114 to
->ldisc
.ops
->receive_buf(to
, buf
, NULL
, c
);
119 static int pty_write_room(struct tty_struct
*tty
)
121 struct tty_struct
*to
= tty
->link
;
123 if (!to
|| tty
->stopped
)
126 return to
->receive_room
;
130 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
131 * The chars_in_buffer() value is used by the ldisc select() function
132 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
133 * The pty driver chars_in_buffer() Master/Slave must behave differently:
135 * The Master side needs to allow typed-ahead commands to accumulate
136 * while being canonicalized, so we report "our buffer" as empty until
137 * some threshold is reached, and then report the count. (Any count >
138 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
139 * the count returned must be 0 if no canonical data is available to be
140 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
142 * The Slave side passes all characters in raw mode to the Master side's
143 * buffer where they can be read immediately, so in this case we can
144 * return the true count in the buffer.
146 static int pty_chars_in_buffer(struct tty_struct
*tty
)
148 struct tty_struct
*to
= tty
->link
;
151 /* We should get the line discipline lock for "tty->link" */
152 if (!to
|| !to
->ldisc
.ops
->chars_in_buffer
)
155 /* The ldisc must report 0 if no characters available to be read */
156 count
= to
->ldisc
.ops
->chars_in_buffer(to
);
158 if (tty
->driver
->subtype
== PTY_TYPE_SLAVE
)
161 /* Master side driver ... if the other side's read buffer is less than
162 * half full, return 0 to allow writers to proceed; otherwise return
163 * the count. This leaves a comfortable margin to avoid overflow,
164 * and still allows half a buffer's worth of typed-ahead commands.
166 return (count
< N_TTY_BUF_SIZE
/2) ? 0 : count
;
169 /* Set the lock flag on a pty */
170 static int pty_set_lock(struct tty_struct
*tty
, int __user
*arg
)
173 if (get_user(val
, arg
))
176 set_bit(TTY_PTY_LOCK
, &tty
->flags
);
178 clear_bit(TTY_PTY_LOCK
, &tty
->flags
);
182 static void pty_flush_buffer(struct tty_struct
*tty
)
184 struct tty_struct
*to
= tty
->link
;
190 if (to
->ldisc
.ops
->flush_buffer
)
191 to
->ldisc
.ops
->flush_buffer(to
);
194 spin_lock_irqsave(&tty
->ctrl_lock
, flags
);
195 tty
->ctrl_status
|= TIOCPKT_FLUSHWRITE
;
196 wake_up_interruptible(&to
->read_wait
);
197 spin_unlock_irqrestore(&tty
->ctrl_lock
, flags
);
201 static int pty_open(struct tty_struct
*tty
, struct file
*filp
)
203 int retval
= -ENODEV
;
205 if (!tty
|| !tty
->link
)
209 if (test_bit(TTY_OTHER_CLOSED
, &tty
->flags
))
211 if (test_bit(TTY_PTY_LOCK
, &tty
->link
->flags
))
213 if (tty
->link
->count
!= 1)
216 clear_bit(TTY_OTHER_CLOSED
, &tty
->link
->flags
);
217 set_bit(TTY_THROTTLED
, &tty
->flags
);
223 static void pty_set_termios(struct tty_struct
*tty
,
224 struct ktermios
*old_termios
)
226 tty
->termios
->c_cflag
&= ~(CSIZE
| PARENB
);
227 tty
->termios
->c_cflag
|= (CS8
| CREAD
);
231 * pty_do_resize - resize event
232 * @tty: tty being resized
233 * @real_tty: real tty (not the same as tty if using a pty/tty pair)
234 * @rows: rows (character)
235 * @cols: cols (character)
237 * Update the termios variables and send the neccessary signals to
238 * peform a terminal resize correctly
241 int pty_resize(struct tty_struct
*tty
, struct winsize
*ws
)
243 struct pid
*pgrp
, *rpgrp
;
245 struct tty_struct
*pty
= tty
->link
;
247 /* For a PTY we need to lock the tty side */
248 mutex_lock(&tty
->termios_mutex
);
249 if (!memcmp(ws
, &tty
->winsize
, sizeof(*ws
)))
252 /* Get the PID values and reference them so we can
253 avoid holding the tty ctrl lock while sending signals.
254 We need to lock these individually however. */
256 spin_lock_irqsave(&tty
->ctrl_lock
, flags
);
257 pgrp
= get_pid(tty
->pgrp
);
258 spin_unlock_irqrestore(&tty
->ctrl_lock
, flags
);
260 spin_lock_irqsave(&pty
->ctrl_lock
, flags
);
261 rpgrp
= get_pid(pty
->pgrp
);
262 spin_unlock_irqrestore(&pty
->ctrl_lock
, flags
);
265 kill_pgrp(pgrp
, SIGWINCH
, 1);
266 if (rpgrp
!= pgrp
&& rpgrp
)
267 kill_pgrp(rpgrp
, SIGWINCH
, 1);
273 pty
->winsize
= *ws
; /* Never used so will go away soon */
275 mutex_unlock(&tty
->termios_mutex
);
279 static int pty_install(struct tty_driver
*driver
, struct tty_struct
*tty
)
281 struct tty_struct
*o_tty
;
282 int idx
= tty
->index
;
285 o_tty
= alloc_tty_struct();
288 if (!try_module_get(driver
->other
->owner
)) {
289 /* This cannot in fact currently happen */
290 free_tty_struct(o_tty
);
293 initialize_tty_struct(o_tty
, driver
->other
, idx
);
295 /* We always use new tty termios data so we can do this
297 retval
= tty_init_termios(tty
);
301 retval
= tty_init_termios(o_tty
);
303 tty_free_termios(tty
);
308 * Everything allocated ... set up the o_tty structure.
310 driver
->other
->ttys
[idx
] = o_tty
;
311 tty_driver_kref_get(driver
->other
);
312 if (driver
->subtype
== PTY_TYPE_MASTER
)
314 /* Establish the links in both directions */
318 tty_driver_kref_get(driver
);
320 driver
->ttys
[idx
] = tty
;
323 module_put(o_tty
->driver
->owner
);
324 free_tty_struct(o_tty
);
329 static const struct tty_operations pty_ops
= {
330 .install
= pty_install
,
334 .write_room
= pty_write_room
,
335 .flush_buffer
= pty_flush_buffer
,
336 .chars_in_buffer
= pty_chars_in_buffer
,
337 .unthrottle
= pty_unthrottle
,
338 .set_termios
= pty_set_termios
,
342 /* Traditional BSD devices */
343 #ifdef CONFIG_LEGACY_PTYS
344 static struct tty_driver
*pty_driver
, *pty_slave_driver
;
346 static int pty_bsd_ioctl(struct tty_struct
*tty
, struct file
*file
,
347 unsigned int cmd
, unsigned long arg
)
350 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
351 return pty_set_lock(tty
, (int __user
*) arg
);
356 static int legacy_count
= CONFIG_LEGACY_PTY_COUNT
;
357 module_param(legacy_count
, int, 0);
359 static const struct tty_operations pty_ops_bsd
= {
363 .write_room
= pty_write_room
,
364 .flush_buffer
= pty_flush_buffer
,
365 .chars_in_buffer
= pty_chars_in_buffer
,
366 .unthrottle
= pty_unthrottle
,
367 .set_termios
= pty_set_termios
,
368 .ioctl
= pty_bsd_ioctl
,
372 static void __init
legacy_pty_init(void)
374 if (legacy_count
<= 0)
377 pty_driver
= alloc_tty_driver(legacy_count
);
379 panic("Couldn't allocate pty driver");
381 pty_slave_driver
= alloc_tty_driver(legacy_count
);
382 if (!pty_slave_driver
)
383 panic("Couldn't allocate pty slave driver");
385 pty_driver
->owner
= THIS_MODULE
;
386 pty_driver
->driver_name
= "pty_master";
387 pty_driver
->name
= "pty";
388 pty_driver
->major
= PTY_MASTER_MAJOR
;
389 pty_driver
->minor_start
= 0;
390 pty_driver
->type
= TTY_DRIVER_TYPE_PTY
;
391 pty_driver
->subtype
= PTY_TYPE_MASTER
;
392 pty_driver
->init_termios
= tty_std_termios
;
393 pty_driver
->init_termios
.c_iflag
= 0;
394 pty_driver
->init_termios
.c_oflag
= 0;
395 pty_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
396 pty_driver
->init_termios
.c_lflag
= 0;
397 pty_driver
->init_termios
.c_ispeed
= 38400;
398 pty_driver
->init_termios
.c_ospeed
= 38400;
399 pty_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
;
400 pty_driver
->other
= pty_slave_driver
;
401 tty_set_operations(pty_driver
, &pty_ops
);
403 pty_slave_driver
->owner
= THIS_MODULE
;
404 pty_slave_driver
->driver_name
= "pty_slave";
405 pty_slave_driver
->name
= "ttyp";
406 pty_slave_driver
->major
= PTY_SLAVE_MAJOR
;
407 pty_slave_driver
->minor_start
= 0;
408 pty_slave_driver
->type
= TTY_DRIVER_TYPE_PTY
;
409 pty_slave_driver
->subtype
= PTY_TYPE_SLAVE
;
410 pty_slave_driver
->init_termios
= tty_std_termios
;
411 pty_slave_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
412 pty_slave_driver
->init_termios
.c_ispeed
= 38400;
413 pty_slave_driver
->init_termios
.c_ospeed
= 38400;
414 pty_slave_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
|
416 pty_slave_driver
->other
= pty_driver
;
417 tty_set_operations(pty_slave_driver
, &pty_ops
);
419 if (tty_register_driver(pty_driver
))
420 panic("Couldn't register pty driver");
421 if (tty_register_driver(pty_slave_driver
))
422 panic("Couldn't register pty slave driver");
425 static inline void legacy_pty_init(void) { }
429 #ifdef CONFIG_UNIX98_PTYS
431 * sysctl support for setting limits on the number of Unix98 ptys allocated.
432 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
434 int pty_limit
= NR_UNIX98_PTY_DEFAULT
;
435 static int pty_limit_min
;
436 static int pty_limit_max
= NR_UNIX98_PTY_MAX
;
437 static int pty_count
;
439 static struct cdev ptmx_cdev
;
441 static struct ctl_table pty_table
[] = {
445 .maxlen
= sizeof(int),
448 .proc_handler
= &proc_dointvec_minmax
,
449 .strategy
= &sysctl_intvec
,
450 .extra1
= &pty_limit_min
,
451 .extra2
= &pty_limit_max
,
455 .maxlen
= sizeof(int),
458 .proc_handler
= &proc_dointvec
,
464 static struct ctl_table pty_kern_table
[] = {
466 .ctl_name
= KERN_PTY
,
474 static struct ctl_table pty_root_table
[] = {
476 .ctl_name
= CTL_KERN
,
477 .procname
= "kernel",
479 .child
= pty_kern_table
,
485 static int pty_unix98_ioctl(struct tty_struct
*tty
, struct file
*file
,
486 unsigned int cmd
, unsigned long arg
)
489 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
490 return pty_set_lock(tty
, (int __user
*)arg
);
491 case TIOCGPTN
: /* Get PT Number */
492 return put_user(tty
->index
, (unsigned int __user
*)arg
);
499 * ptm_unix98_lookup - find a pty master
500 * @driver: ptm driver
503 * Look up a pty master device. Called under the tty_mutex for now.
504 * This provides our locking.
507 static struct tty_struct
*ptm_unix98_lookup(struct tty_driver
*driver
,
508 struct inode
*ptm_inode
, int idx
)
510 struct tty_struct
*tty
= devpts_get_tty(ptm_inode
, idx
);
517 * pts_unix98_lookup - find a pty slave
518 * @driver: pts driver
521 * Look up a pty master device. Called under the tty_mutex for now.
522 * This provides our locking.
525 static struct tty_struct
*pts_unix98_lookup(struct tty_driver
*driver
,
526 struct inode
*pts_inode
, int idx
)
528 struct tty_struct
*tty
= devpts_get_tty(pts_inode
, idx
);
529 /* Master must be open before slave */
531 return ERR_PTR(-EIO
);
535 static void pty_unix98_shutdown(struct tty_struct
*tty
)
537 /* We have our own method as we don't use the tty index */
541 /* We have no need to install and remove our tty objects as devpts does all
544 static int pty_unix98_install(struct tty_driver
*driver
, struct tty_struct
*tty
)
546 struct tty_struct
*o_tty
;
547 int idx
= tty
->index
;
549 o_tty
= alloc_tty_struct();
552 if (!try_module_get(driver
->other
->owner
)) {
553 /* This cannot in fact currently happen */
554 free_tty_struct(o_tty
);
557 initialize_tty_struct(o_tty
, driver
->other
, idx
);
559 tty
->termios
= kzalloc(sizeof(struct ktermios
[2]), GFP_KERNEL
);
560 if (tty
->termios
== NULL
)
562 *tty
->termios
= driver
->init_termios
;
563 tty
->termios_locked
= tty
->termios
+ 1;
565 o_tty
->termios
= kzalloc(sizeof(struct ktermios
[2]), GFP_KERNEL
);
566 if (o_tty
->termios
== NULL
)
568 *o_tty
->termios
= driver
->other
->init_termios
;
569 o_tty
->termios_locked
= o_tty
->termios
+ 1;
571 tty_driver_kref_get(driver
->other
);
572 if (driver
->subtype
== PTY_TYPE_MASTER
)
574 /* Establish the links in both directions */
578 * All structures have been allocated, so now we install them.
579 * Failures after this point use release_tty to clean up, so
580 * there's no need to null out the local pointers.
582 tty_driver_kref_get(driver
);
587 kfree(o_tty
->termios
);
588 module_put(o_tty
->driver
->owner
);
589 free_tty_struct(o_tty
);
594 static void pty_unix98_remove(struct tty_driver
*driver
, struct tty_struct
*tty
)
599 static const struct tty_operations ptm_unix98_ops
= {
600 .lookup
= ptm_unix98_lookup
,
601 .install
= pty_unix98_install
,
602 .remove
= pty_unix98_remove
,
606 .write_room
= pty_write_room
,
607 .flush_buffer
= pty_flush_buffer
,
608 .chars_in_buffer
= pty_chars_in_buffer
,
609 .unthrottle
= pty_unthrottle
,
610 .set_termios
= pty_set_termios
,
611 .ioctl
= pty_unix98_ioctl
,
612 .shutdown
= pty_unix98_shutdown
,
616 static const struct tty_operations pty_unix98_ops
= {
617 .lookup
= pts_unix98_lookup
,
618 .install
= pty_unix98_install
,
619 .remove
= pty_unix98_remove
,
623 .write_room
= pty_write_room
,
624 .flush_buffer
= pty_flush_buffer
,
625 .chars_in_buffer
= pty_chars_in_buffer
,
626 .unthrottle
= pty_unthrottle
,
627 .set_termios
= pty_set_termios
,
628 .shutdown
= pty_unix98_shutdown
632 * ptmx_open - open a unix 98 pty master
633 * @inode: inode of device file
634 * @filp: file pointer to tty
636 * Allocate a unix98 pty master device from the ptmx driver.
638 * Locking: tty_mutex protects the init_dev work. tty->count should
640 * allocated_ptys_lock handles the list of free pty numbers
643 static int __ptmx_open(struct inode
*inode
, struct file
*filp
)
645 struct tty_struct
*tty
;
649 nonseekable_open(inode
, filp
);
651 /* find a device that is not in use. */
652 index
= devpts_new_index(inode
);
656 mutex_lock(&tty_mutex
);
657 tty
= tty_init_dev(ptm_driver
, index
, 1);
658 mutex_unlock(&tty_mutex
);
661 retval
= PTR_ERR(tty
);
665 set_bit(TTY_PTY_LOCK
, &tty
->flags
); /* LOCK THE SLAVE */
666 filp
->private_data
= tty
;
667 file_move(filp
, &tty
->tty_files
);
669 retval
= devpts_pty_new(inode
, tty
->link
);
673 retval
= ptm_driver
->ops
->open(tty
, filp
);
677 tty_release_dev(filp
);
680 devpts_kill_index(inode
, index
);
684 static int ptmx_open(struct inode
*inode
, struct file
*filp
)
689 ret
= __ptmx_open(inode
, filp
);
694 static struct file_operations ptmx_fops
;
696 static void __init
unix98_pty_init(void)
698 ptm_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
700 panic("Couldn't allocate Unix98 ptm driver");
701 pts_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
703 panic("Couldn't allocate Unix98 pts driver");
705 ptm_driver
->owner
= THIS_MODULE
;
706 ptm_driver
->driver_name
= "pty_master";
707 ptm_driver
->name
= "ptm";
708 ptm_driver
->major
= UNIX98_PTY_MASTER_MAJOR
;
709 ptm_driver
->minor_start
= 0;
710 ptm_driver
->type
= TTY_DRIVER_TYPE_PTY
;
711 ptm_driver
->subtype
= PTY_TYPE_MASTER
;
712 ptm_driver
->init_termios
= tty_std_termios
;
713 ptm_driver
->init_termios
.c_iflag
= 0;
714 ptm_driver
->init_termios
.c_oflag
= 0;
715 ptm_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
716 ptm_driver
->init_termios
.c_lflag
= 0;
717 ptm_driver
->init_termios
.c_ispeed
= 38400;
718 ptm_driver
->init_termios
.c_ospeed
= 38400;
719 ptm_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
720 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
721 ptm_driver
->other
= pts_driver
;
722 tty_set_operations(ptm_driver
, &ptm_unix98_ops
);
724 pts_driver
->owner
= THIS_MODULE
;
725 pts_driver
->driver_name
= "pty_slave";
726 pts_driver
->name
= "pts";
727 pts_driver
->major
= UNIX98_PTY_SLAVE_MAJOR
;
728 pts_driver
->minor_start
= 0;
729 pts_driver
->type
= TTY_DRIVER_TYPE_PTY
;
730 pts_driver
->subtype
= PTY_TYPE_SLAVE
;
731 pts_driver
->init_termios
= tty_std_termios
;
732 pts_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
733 pts_driver
->init_termios
.c_ispeed
= 38400;
734 pts_driver
->init_termios
.c_ospeed
= 38400;
735 pts_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
736 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
737 pts_driver
->other
= ptm_driver
;
738 tty_set_operations(pts_driver
, &pty_unix98_ops
);
740 if (tty_register_driver(ptm_driver
))
741 panic("Couldn't register Unix98 ptm driver");
742 if (tty_register_driver(pts_driver
))
743 panic("Couldn't register Unix98 pts driver");
745 register_sysctl_table(pty_root_table
);
747 /* Now create the /dev/ptmx special device */
748 tty_default_fops(&ptmx_fops
);
749 ptmx_fops
.open
= ptmx_open
;
751 cdev_init(&ptmx_cdev
, &ptmx_fops
);
752 if (cdev_add(&ptmx_cdev
, MKDEV(TTYAUX_MAJOR
, 2), 1) ||
753 register_chrdev_region(MKDEV(TTYAUX_MAJOR
, 2), 1, "/dev/ptmx") < 0)
754 panic("Couldn't register /dev/ptmx driver\n");
755 device_create(tty_class
, NULL
, MKDEV(TTYAUX_MAJOR
, 2), NULL
, "ptmx");
759 static inline void unix98_pty_init(void) { }
762 static int __init
pty_init(void)
768 module_init(pty_init
);