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
8 * Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to
9 * waiting writers -- Sapan Bhatia <sapan@corewars.org>
11 * When reading this code see also fs/devpts. In particular note that the
12 * driver_data field is used by the devpts side as a binding to the devpts
16 #include <linux/module.h>
18 #include <linux/errno.h>
19 #include <linux/interrupt.h>
20 #include <linux/tty.h>
21 #include <linux/tty_flip.h>
22 #include <linux/fcntl.h>
23 #include <linux/string.h>
24 #include <linux/major.h>
26 #include <linux/init.h>
27 #include <linux/sysctl.h>
28 #include <linux/device.h>
29 #include <linux/uaccess.h>
30 #include <linux/bitops.h>
31 #include <linux/devpts_fs.h>
33 #include <asm/system.h>
35 /* These are global because they are accessed in tty_io.c */
36 #ifdef CONFIG_UNIX98_PTYS
37 struct tty_driver
*ptm_driver
;
38 static struct tty_driver
*pts_driver
;
41 static void pty_close(struct tty_struct
*tty
, struct file
*filp
)
44 if (tty
->driver
->subtype
== PTY_TYPE_MASTER
)
45 WARN_ON(tty
->count
> 1);
50 wake_up_interruptible(&tty
->read_wait
);
51 wake_up_interruptible(&tty
->write_wait
);
55 tty
->link
->packet
= 0;
56 set_bit(TTY_OTHER_CLOSED
, &tty
->link
->flags
);
57 wake_up_interruptible(&tty
->link
->read_wait
);
58 wake_up_interruptible(&tty
->link
->write_wait
);
59 if (tty
->driver
->subtype
== PTY_TYPE_MASTER
) {
60 set_bit(TTY_OTHER_CLOSED
, &tty
->flags
);
61 #ifdef CONFIG_UNIX98_PTYS
62 if (tty
->driver
== ptm_driver
)
63 devpts_pty_kill(tty
->link
);
65 tty_vhangup(tty
->link
);
70 * The unthrottle routine is called by the line discipline to signal
71 * that it can receive more characters. For PTY's, the TTY_THROTTLED
72 * flag is always set, to force the line discipline to always call the
73 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
74 * characters in the queue. This is necessary since each time this
75 * happens, we need to wake up any sleeping processes that could be
76 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
77 * for the pty buffer to be drained.
79 static void pty_unthrottle(struct tty_struct
*tty
)
81 struct tty_struct
*o_tty
= tty
->link
;
87 set_bit(TTY_THROTTLED
, &tty
->flags
);
91 * WSH 05/24/97: modified to
92 * (1) use space in tty->flip instead of a shared temp buffer
93 * The flip buffers aren't being used for a pty, so there's lots
94 * of space available. The buffer is protected by a per-pty
95 * semaphore that should almost never come under contention.
96 * (2) avoid redundant copying for cases where count >> receive_room
97 * N.B. Calls from user space may now return an error code instead of
100 * FIXME: Our pty_write method is called with our ldisc lock held but
101 * not our partners. We can't just take the other one blindly without
104 static int pty_write(struct tty_struct
*tty
, const unsigned char *buf
,
107 struct tty_struct
*to
= tty
->link
;
110 if (!to
|| tty
->stopped
)
113 c
= to
->receive_room
;
116 to
->ldisc
.ops
->receive_buf(to
, buf
, NULL
, c
);
121 static int pty_write_room(struct tty_struct
*tty
)
123 struct tty_struct
*to
= tty
->link
;
125 if (!to
|| tty
->stopped
)
128 return to
->receive_room
;
132 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
133 * The chars_in_buffer() value is used by the ldisc select() function
134 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
135 * The pty driver chars_in_buffer() Master/Slave must behave differently:
137 * The Master side needs to allow typed-ahead commands to accumulate
138 * while being canonicalized, so we report "our buffer" as empty until
139 * some threshold is reached, and then report the count. (Any count >
140 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
141 * the count returned must be 0 if no canonical data is available to be
142 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
144 * The Slave side passes all characters in raw mode to the Master side's
145 * buffer where they can be read immediately, so in this case we can
146 * return the true count in the buffer.
148 static int pty_chars_in_buffer(struct tty_struct
*tty
)
150 struct tty_struct
*to
= tty
->link
;
153 /* We should get the line discipline lock for "tty->link" */
154 if (!to
|| !to
->ldisc
.ops
->chars_in_buffer
)
157 /* The ldisc must report 0 if no characters available to be read */
158 count
= to
->ldisc
.ops
->chars_in_buffer(to
);
160 if (tty
->driver
->subtype
== PTY_TYPE_SLAVE
)
163 /* Master side driver ... if the other side's read buffer is less than
164 * half full, return 0 to allow writers to proceed; otherwise return
165 * the count. This leaves a comfortable margin to avoid overflow,
166 * and still allows half a buffer's worth of typed-ahead commands.
168 return (count
< N_TTY_BUF_SIZE
/2) ? 0 : count
;
171 /* Set the lock flag on a pty */
172 static int pty_set_lock(struct tty_struct
*tty
, int __user
*arg
)
175 if (get_user(val
, arg
))
178 set_bit(TTY_PTY_LOCK
, &tty
->flags
);
180 clear_bit(TTY_PTY_LOCK
, &tty
->flags
);
184 static void pty_flush_buffer(struct tty_struct
*tty
)
186 struct tty_struct
*to
= tty
->link
;
192 if (to
->ldisc
.ops
->flush_buffer
)
193 to
->ldisc
.ops
->flush_buffer(to
);
196 spin_lock_irqsave(&tty
->ctrl_lock
, flags
);
197 tty
->ctrl_status
|= TIOCPKT_FLUSHWRITE
;
198 wake_up_interruptible(&to
->read_wait
);
199 spin_unlock_irqrestore(&tty
->ctrl_lock
, flags
);
203 static int pty_open(struct tty_struct
*tty
, struct file
*filp
)
205 int retval
= -ENODEV
;
207 if (!tty
|| !tty
->link
)
211 if (test_bit(TTY_OTHER_CLOSED
, &tty
->flags
))
213 if (test_bit(TTY_PTY_LOCK
, &tty
->link
->flags
))
215 if (tty
->link
->count
!= 1)
218 clear_bit(TTY_OTHER_CLOSED
, &tty
->link
->flags
);
219 set_bit(TTY_THROTTLED
, &tty
->flags
);
220 set_bit(TTY_DO_WRITE_WAKEUP
, &tty
->flags
);
226 static void pty_set_termios(struct tty_struct
*tty
,
227 struct ktermios
*old_termios
)
229 tty
->termios
->c_cflag
&= ~(CSIZE
| PARENB
);
230 tty
->termios
->c_cflag
|= (CS8
| CREAD
);
233 static int pty_install(struct tty_driver
*driver
, struct tty_struct
*tty
)
235 struct tty_struct
*o_tty
;
236 int idx
= tty
->index
;
239 o_tty
= alloc_tty_struct();
242 if (!try_module_get(driver
->other
->owner
)) {
243 /* This cannot in fact currently happen */
244 free_tty_struct(o_tty
);
247 initialize_tty_struct(o_tty
, driver
->other
, idx
);
249 /* We always use new tty termios data so we can do this
251 retval
= tty_init_termios(tty
);
255 retval
= tty_init_termios(o_tty
);
257 tty_free_termios(tty
);
262 * Everything allocated ... set up the o_tty structure.
264 driver
->other
->ttys
[idx
] = o_tty
;
265 tty_driver_kref_get(driver
->other
);
266 if (driver
->subtype
== PTY_TYPE_MASTER
)
268 /* Establish the links in both directions */
272 tty_driver_kref_get(driver
);
274 driver
->ttys
[idx
] = tty
;
277 module_put(o_tty
->driver
->owner
);
278 free_tty_struct(o_tty
);
283 static const struct tty_operations pty_ops
= {
284 .install
= pty_install
,
288 .write_room
= pty_write_room
,
289 .flush_buffer
= pty_flush_buffer
,
290 .chars_in_buffer
= pty_chars_in_buffer
,
291 .unthrottle
= pty_unthrottle
,
292 .set_termios
= pty_set_termios
,
295 /* Traditional BSD devices */
296 #ifdef CONFIG_LEGACY_PTYS
297 static struct tty_driver
*pty_driver
, *pty_slave_driver
;
299 static int pty_bsd_ioctl(struct tty_struct
*tty
, struct file
*file
,
300 unsigned int cmd
, unsigned long arg
)
303 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
304 return pty_set_lock(tty
, (int __user
*) arg
);
309 static int legacy_count
= CONFIG_LEGACY_PTY_COUNT
;
310 module_param(legacy_count
, int, 0);
312 static const struct tty_operations pty_ops_bsd
= {
316 .write_room
= pty_write_room
,
317 .flush_buffer
= pty_flush_buffer
,
318 .chars_in_buffer
= pty_chars_in_buffer
,
319 .unthrottle
= pty_unthrottle
,
320 .set_termios
= pty_set_termios
,
321 .ioctl
= pty_bsd_ioctl
,
324 static void __init
legacy_pty_init(void)
326 if (legacy_count
<= 0)
329 pty_driver
= alloc_tty_driver(legacy_count
);
331 panic("Couldn't allocate pty driver");
333 pty_slave_driver
= alloc_tty_driver(legacy_count
);
334 if (!pty_slave_driver
)
335 panic("Couldn't allocate pty slave driver");
337 pty_driver
->owner
= THIS_MODULE
;
338 pty_driver
->driver_name
= "pty_master";
339 pty_driver
->name
= "pty";
340 pty_driver
->major
= PTY_MASTER_MAJOR
;
341 pty_driver
->minor_start
= 0;
342 pty_driver
->type
= TTY_DRIVER_TYPE_PTY
;
343 pty_driver
->subtype
= PTY_TYPE_MASTER
;
344 pty_driver
->init_termios
= tty_std_termios
;
345 pty_driver
->init_termios
.c_iflag
= 0;
346 pty_driver
->init_termios
.c_oflag
= 0;
347 pty_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
348 pty_driver
->init_termios
.c_lflag
= 0;
349 pty_driver
->init_termios
.c_ispeed
= 38400;
350 pty_driver
->init_termios
.c_ospeed
= 38400;
351 pty_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
;
352 pty_driver
->other
= pty_slave_driver
;
353 tty_set_operations(pty_driver
, &pty_ops
);
355 pty_slave_driver
->owner
= THIS_MODULE
;
356 pty_slave_driver
->driver_name
= "pty_slave";
357 pty_slave_driver
->name
= "ttyp";
358 pty_slave_driver
->major
= PTY_SLAVE_MAJOR
;
359 pty_slave_driver
->minor_start
= 0;
360 pty_slave_driver
->type
= TTY_DRIVER_TYPE_PTY
;
361 pty_slave_driver
->subtype
= PTY_TYPE_SLAVE
;
362 pty_slave_driver
->init_termios
= tty_std_termios
;
363 pty_slave_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
364 pty_slave_driver
->init_termios
.c_ispeed
= 38400;
365 pty_slave_driver
->init_termios
.c_ospeed
= 38400;
366 pty_slave_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
|
368 pty_slave_driver
->other
= pty_driver
;
369 tty_set_operations(pty_slave_driver
, &pty_ops
);
371 if (tty_register_driver(pty_driver
))
372 panic("Couldn't register pty driver");
373 if (tty_register_driver(pty_slave_driver
))
374 panic("Couldn't register pty slave driver");
377 static inline void legacy_pty_init(void) { }
381 #ifdef CONFIG_UNIX98_PTYS
383 * sysctl support for setting limits on the number of Unix98 ptys allocated.
384 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
386 int pty_limit
= NR_UNIX98_PTY_DEFAULT
;
387 static int pty_limit_min
;
388 static int pty_limit_max
= NR_UNIX98_PTY_MAX
;
389 static int pty_count
;
391 static struct cdev ptmx_cdev
;
393 static struct ctl_table pty_table
[] = {
397 .maxlen
= sizeof(int),
400 .proc_handler
= &proc_dointvec_minmax
,
401 .strategy
= &sysctl_intvec
,
402 .extra1
= &pty_limit_min
,
403 .extra2
= &pty_limit_max
,
407 .maxlen
= sizeof(int),
410 .proc_handler
= &proc_dointvec
,
416 static struct ctl_table pty_kern_table
[] = {
418 .ctl_name
= KERN_PTY
,
426 static struct ctl_table pty_root_table
[] = {
428 .ctl_name
= CTL_KERN
,
429 .procname
= "kernel",
431 .child
= pty_kern_table
,
437 static int pty_unix98_ioctl(struct tty_struct
*tty
, struct file
*file
,
438 unsigned int cmd
, unsigned long arg
)
441 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
442 return pty_set_lock(tty
, (int __user
*)arg
);
443 case TIOCGPTN
: /* Get PT Number */
444 return put_user(tty
->index
, (unsigned int __user
*)arg
);
451 * ptm_unix98_lookup - find a pty master
452 * @driver: ptm driver
455 * Look up a pty master device. Called under the tty_mutex for now.
456 * This provides our locking.
459 static struct tty_struct
*ptm_unix98_lookup(struct tty_driver
*driver
,
460 struct inode
*ptm_inode
, int idx
)
462 struct tty_struct
*tty
= devpts_get_tty(ptm_inode
, idx
);
469 * pts_unix98_lookup - find a pty slave
470 * @driver: pts driver
473 * Look up a pty master device. Called under the tty_mutex for now.
474 * This provides our locking.
477 static struct tty_struct
*pts_unix98_lookup(struct tty_driver
*driver
,
478 struct inode
*pts_inode
, int idx
)
480 struct tty_struct
*tty
= devpts_get_tty(pts_inode
, idx
);
481 /* Master must be open before slave */
483 return ERR_PTR(-EIO
);
487 static void pty_unix98_shutdown(struct tty_struct
*tty
)
489 /* We have our own method as we don't use the tty index */
493 /* We have no need to install and remove our tty objects as devpts does all
496 static int pty_unix98_install(struct tty_driver
*driver
, struct tty_struct
*tty
)
498 struct tty_struct
*o_tty
;
499 int idx
= tty
->index
;
501 o_tty
= alloc_tty_struct();
504 if (!try_module_get(driver
->other
->owner
)) {
505 /* This cannot in fact currently happen */
506 free_tty_struct(o_tty
);
509 initialize_tty_struct(o_tty
, driver
->other
, idx
);
511 tty
->termios
= kzalloc(sizeof(struct ktermios
[2]), GFP_KERNEL
);
512 if (tty
->termios
== NULL
)
514 *tty
->termios
= driver
->init_termios
;
515 tty
->termios_locked
= tty
->termios
+ 1;
517 o_tty
->termios
= kzalloc(sizeof(struct ktermios
[2]), GFP_KERNEL
);
518 if (o_tty
->termios
== NULL
)
520 *o_tty
->termios
= driver
->other
->init_termios
;
521 o_tty
->termios_locked
= o_tty
->termios
+ 1;
523 tty_driver_kref_get(driver
->other
);
524 if (driver
->subtype
== PTY_TYPE_MASTER
)
526 /* Establish the links in both directions */
530 * All structures have been allocated, so now we install them.
531 * Failures after this point use release_tty to clean up, so
532 * there's no need to null out the local pointers.
534 tty_driver_kref_get(driver
);
539 kfree(o_tty
->termios
);
540 module_put(o_tty
->driver
->owner
);
541 free_tty_struct(o_tty
);
546 static void pty_unix98_remove(struct tty_driver
*driver
, struct tty_struct
*tty
)
551 static const struct tty_operations ptm_unix98_ops
= {
552 .lookup
= ptm_unix98_lookup
,
553 .install
= pty_unix98_install
,
554 .remove
= pty_unix98_remove
,
558 .write_room
= pty_write_room
,
559 .flush_buffer
= pty_flush_buffer
,
560 .chars_in_buffer
= pty_chars_in_buffer
,
561 .unthrottle
= pty_unthrottle
,
562 .set_termios
= pty_set_termios
,
563 .ioctl
= pty_unix98_ioctl
,
564 .shutdown
= pty_unix98_shutdown
567 static const struct tty_operations pty_unix98_ops
= {
568 .lookup
= pts_unix98_lookup
,
569 .install
= pty_unix98_install
,
570 .remove
= pty_unix98_remove
,
574 .write_room
= pty_write_room
,
575 .flush_buffer
= pty_flush_buffer
,
576 .chars_in_buffer
= pty_chars_in_buffer
,
577 .unthrottle
= pty_unthrottle
,
578 .set_termios
= pty_set_termios
,
579 .shutdown
= pty_unix98_shutdown
583 * ptmx_open - open a unix 98 pty master
584 * @inode: inode of device file
585 * @filp: file pointer to tty
587 * Allocate a unix98 pty master device from the ptmx driver.
589 * Locking: tty_mutex protects the init_dev work. tty->count should
591 * allocated_ptys_lock handles the list of free pty numbers
594 static int __ptmx_open(struct inode
*inode
, struct file
*filp
)
596 struct tty_struct
*tty
;
600 nonseekable_open(inode
, filp
);
602 /* find a device that is not in use. */
603 index
= devpts_new_index(inode
);
607 mutex_lock(&tty_mutex
);
608 tty
= tty_init_dev(ptm_driver
, index
, 1);
609 mutex_unlock(&tty_mutex
);
612 retval
= PTR_ERR(tty
);
616 set_bit(TTY_PTY_LOCK
, &tty
->flags
); /* LOCK THE SLAVE */
617 filp
->private_data
= tty
;
618 file_move(filp
, &tty
->tty_files
);
620 retval
= devpts_pty_new(inode
, tty
->link
);
624 retval
= ptm_driver
->ops
->open(tty
, filp
);
628 tty_release_dev(filp
);
631 devpts_kill_index(inode
, index
);
635 static int ptmx_open(struct inode
*inode
, struct file
*filp
)
640 ret
= __ptmx_open(inode
, filp
);
645 static struct file_operations ptmx_fops
;
647 static void __init
unix98_pty_init(void)
649 ptm_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
651 panic("Couldn't allocate Unix98 ptm driver");
652 pts_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
654 panic("Couldn't allocate Unix98 pts driver");
656 ptm_driver
->owner
= THIS_MODULE
;
657 ptm_driver
->driver_name
= "pty_master";
658 ptm_driver
->name
= "ptm";
659 ptm_driver
->major
= UNIX98_PTY_MASTER_MAJOR
;
660 ptm_driver
->minor_start
= 0;
661 ptm_driver
->type
= TTY_DRIVER_TYPE_PTY
;
662 ptm_driver
->subtype
= PTY_TYPE_MASTER
;
663 ptm_driver
->init_termios
= tty_std_termios
;
664 ptm_driver
->init_termios
.c_iflag
= 0;
665 ptm_driver
->init_termios
.c_oflag
= 0;
666 ptm_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
667 ptm_driver
->init_termios
.c_lflag
= 0;
668 ptm_driver
->init_termios
.c_ispeed
= 38400;
669 ptm_driver
->init_termios
.c_ospeed
= 38400;
670 ptm_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
671 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
672 ptm_driver
->other
= pts_driver
;
673 tty_set_operations(ptm_driver
, &ptm_unix98_ops
);
675 pts_driver
->owner
= THIS_MODULE
;
676 pts_driver
->driver_name
= "pty_slave";
677 pts_driver
->name
= "pts";
678 pts_driver
->major
= UNIX98_PTY_SLAVE_MAJOR
;
679 pts_driver
->minor_start
= 0;
680 pts_driver
->type
= TTY_DRIVER_TYPE_PTY
;
681 pts_driver
->subtype
= PTY_TYPE_SLAVE
;
682 pts_driver
->init_termios
= tty_std_termios
;
683 pts_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
684 pts_driver
->init_termios
.c_ispeed
= 38400;
685 pts_driver
->init_termios
.c_ospeed
= 38400;
686 pts_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
687 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
688 pts_driver
->other
= ptm_driver
;
689 tty_set_operations(pts_driver
, &pty_unix98_ops
);
691 if (tty_register_driver(ptm_driver
))
692 panic("Couldn't register Unix98 ptm driver");
693 if (tty_register_driver(pts_driver
))
694 panic("Couldn't register Unix98 pts driver");
696 register_sysctl_table(pty_root_table
);
698 /* Now create the /dev/ptmx special device */
699 tty_default_fops(&ptmx_fops
);
700 ptmx_fops
.open
= ptmx_open
;
702 cdev_init(&ptmx_cdev
, &ptmx_fops
);
703 if (cdev_add(&ptmx_cdev
, MKDEV(TTYAUX_MAJOR
, 2), 1) ||
704 register_chrdev_region(MKDEV(TTYAUX_MAJOR
, 2), 1, "/dev/ptmx") < 0)
705 panic("Couldn't register /dev/ptmx driver\n");
706 device_create(tty_class
, NULL
, MKDEV(TTYAUX_MAJOR
, 2), NULL
, "ptmx");
710 static inline void unix98_pty_init(void) { }
713 static int __init
pty_init(void)
719 module_init(pty_init
);