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);
234 * pty_do_resize - resize event
235 * @tty: tty being resized
236 * @real_tty: real tty (not the same as tty if using a pty/tty pair)
237 * @rows: rows (character)
238 * @cols: cols (character)
240 * Update the termios variables and send the neccessary signals to
241 * peform a terminal resize correctly
244 int pty_resize(struct tty_struct *tty, struct winsize *ws)
246 struct pid *pgrp, *rpgrp;
248 struct tty_struct *pty = tty->link;
250 /* For a PTY we need to lock the tty side */
251 mutex_lock(&tty->termios_mutex);
252 if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
255 /* Get the PID values and reference them so we can
256 avoid holding the tty ctrl lock while sending signals.
257 We need to lock these individually however. */
259 spin_lock_irqsave(&tty->ctrl_lock, flags);
260 pgrp = get_pid(tty->pgrp);
261 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
263 spin_lock_irqsave(&pty->ctrl_lock, flags);
264 rpgrp = get_pid(pty->pgrp);
265 spin_unlock_irqrestore(&pty->ctrl_lock, flags);
268 kill_pgrp(pgrp, SIGWINCH, 1);
269 if (rpgrp != pgrp && rpgrp)
270 kill_pgrp(rpgrp, SIGWINCH, 1);
276 pty->winsize = *ws; /* Never used so will go away soon */
278 mutex_unlock(&tty->termios_mutex);
282 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
284 struct tty_struct *o_tty;
285 int idx = tty->index;
288 o_tty = alloc_tty_struct();
291 if (!try_module_get(driver->other->owner)) {
292 /* This cannot in fact currently happen */
293 free_tty_struct(o_tty);
296 initialize_tty_struct(o_tty, driver->other, idx);
298 /* We always use new tty termios data so we can do this
300 retval = tty_init_termios(tty);
304 retval = tty_init_termios(o_tty);
306 tty_free_termios(tty);
311 * Everything allocated ... set up the o_tty structure.
313 driver->other->ttys[idx] = o_tty;
314 tty_driver_kref_get(driver->other);
315 if (driver->subtype == PTY_TYPE_MASTER)
317 /* Establish the links in both directions */
321 tty_driver_kref_get(driver);
323 driver->ttys[idx] = tty;
326 module_put(o_tty->driver->owner);
327 free_tty_struct(o_tty);
332 static const struct tty_operations pty_ops = {
333 .install = pty_install,
337 .write_room = pty_write_room,
338 .flush_buffer = pty_flush_buffer,
339 .chars_in_buffer = pty_chars_in_buffer,
340 .unthrottle = pty_unthrottle,
341 .set_termios = pty_set_termios,
345 /* Traditional BSD devices */
346 #ifdef CONFIG_LEGACY_PTYS
347 static struct tty_driver *pty_driver, *pty_slave_driver;
349 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
350 unsigned int cmd, unsigned long arg)
353 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
354 return pty_set_lock(tty, (int __user *) arg);
359 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
360 module_param(legacy_count, int, 0);
362 static const struct tty_operations pty_ops_bsd = {
366 .write_room = pty_write_room,
367 .flush_buffer = pty_flush_buffer,
368 .chars_in_buffer = pty_chars_in_buffer,
369 .unthrottle = pty_unthrottle,
370 .set_termios = pty_set_termios,
371 .ioctl = pty_bsd_ioctl,
375 static void __init legacy_pty_init(void)
377 if (legacy_count <= 0)
380 pty_driver = alloc_tty_driver(legacy_count);
382 panic("Couldn't allocate pty driver");
384 pty_slave_driver = alloc_tty_driver(legacy_count);
385 if (!pty_slave_driver)
386 panic("Couldn't allocate pty slave driver");
388 pty_driver->owner = THIS_MODULE;
389 pty_driver->driver_name = "pty_master";
390 pty_driver->name = "pty";
391 pty_driver->major = PTY_MASTER_MAJOR;
392 pty_driver->minor_start = 0;
393 pty_driver->type = TTY_DRIVER_TYPE_PTY;
394 pty_driver->subtype = PTY_TYPE_MASTER;
395 pty_driver->init_termios = tty_std_termios;
396 pty_driver->init_termios.c_iflag = 0;
397 pty_driver->init_termios.c_oflag = 0;
398 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
399 pty_driver->init_termios.c_lflag = 0;
400 pty_driver->init_termios.c_ispeed = 38400;
401 pty_driver->init_termios.c_ospeed = 38400;
402 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
403 pty_driver->other = pty_slave_driver;
404 tty_set_operations(pty_driver, &pty_ops);
406 pty_slave_driver->owner = THIS_MODULE;
407 pty_slave_driver->driver_name = "pty_slave";
408 pty_slave_driver->name = "ttyp";
409 pty_slave_driver->major = PTY_SLAVE_MAJOR;
410 pty_slave_driver->minor_start = 0;
411 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
412 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
413 pty_slave_driver->init_termios = tty_std_termios;
414 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
415 pty_slave_driver->init_termios.c_ispeed = 38400;
416 pty_slave_driver->init_termios.c_ospeed = 38400;
417 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
419 pty_slave_driver->other = pty_driver;
420 tty_set_operations(pty_slave_driver, &pty_ops);
422 if (tty_register_driver(pty_driver))
423 panic("Couldn't register pty driver");
424 if (tty_register_driver(pty_slave_driver))
425 panic("Couldn't register pty slave driver");
428 static inline void legacy_pty_init(void) { }
432 #ifdef CONFIG_UNIX98_PTYS
434 * sysctl support for setting limits on the number of Unix98 ptys allocated.
435 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
437 int pty_limit = NR_UNIX98_PTY_DEFAULT;
438 static int pty_limit_min;
439 static int pty_limit_max = NR_UNIX98_PTY_MAX;
440 static int pty_count;
442 static struct cdev ptmx_cdev;
444 static struct ctl_table pty_table[] = {
448 .maxlen = sizeof(int),
451 .proc_handler = &proc_dointvec_minmax,
452 .strategy = &sysctl_intvec,
453 .extra1 = &pty_limit_min,
454 .extra2 = &pty_limit_max,
458 .maxlen = sizeof(int),
461 .proc_handler = &proc_dointvec,
467 static struct ctl_table pty_kern_table[] = {
469 .ctl_name = KERN_PTY,
477 static struct ctl_table pty_root_table[] = {
479 .ctl_name = CTL_KERN,
480 .procname = "kernel",
482 .child = pty_kern_table,
488 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
489 unsigned int cmd, unsigned long arg)
492 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
493 return pty_set_lock(tty, (int __user *)arg);
494 case TIOCGPTN: /* Get PT Number */
495 return put_user(tty->index, (unsigned int __user *)arg);
502 * ptm_unix98_lookup - find a pty master
503 * @driver: ptm driver
506 * Look up a pty master device. Called under the tty_mutex for now.
507 * This provides our locking.
510 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
511 struct inode *ptm_inode, int idx)
513 struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
520 * pts_unix98_lookup - find a pty slave
521 * @driver: pts driver
524 * Look up a pty master device. Called under the tty_mutex for now.
525 * This provides our locking.
528 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
529 struct inode *pts_inode, int idx)
531 struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
532 /* Master must be open before slave */
534 return ERR_PTR(-EIO);
538 static void pty_unix98_shutdown(struct tty_struct *tty)
540 /* We have our own method as we don't use the tty index */
544 /* We have no need to install and remove our tty objects as devpts does all
547 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
549 struct tty_struct *o_tty;
550 int idx = tty->index;
552 o_tty = alloc_tty_struct();
555 if (!try_module_get(driver->other->owner)) {
556 /* This cannot in fact currently happen */
557 free_tty_struct(o_tty);
560 initialize_tty_struct(o_tty, driver->other, idx);
562 tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
563 if (tty->termios == NULL)
565 *tty->termios = driver->init_termios;
566 tty->termios_locked = tty->termios + 1;
568 o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
569 if (o_tty->termios == NULL)
571 *o_tty->termios = driver->other->init_termios;
572 o_tty->termios_locked = o_tty->termios + 1;
574 tty_driver_kref_get(driver->other);
575 if (driver->subtype == PTY_TYPE_MASTER)
577 /* Establish the links in both directions */
581 * All structures have been allocated, so now we install them.
582 * Failures after this point use release_tty to clean up, so
583 * there's no need to null out the local pointers.
585 tty_driver_kref_get(driver);
590 kfree(o_tty->termios);
591 module_put(o_tty->driver->owner);
592 free_tty_struct(o_tty);
597 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
602 static const struct tty_operations ptm_unix98_ops = {
603 .lookup = ptm_unix98_lookup,
604 .install = pty_unix98_install,
605 .remove = pty_unix98_remove,
609 .write_room = pty_write_room,
610 .flush_buffer = pty_flush_buffer,
611 .chars_in_buffer = pty_chars_in_buffer,
612 .unthrottle = pty_unthrottle,
613 .set_termios = pty_set_termios,
614 .ioctl = pty_unix98_ioctl,
615 .shutdown = pty_unix98_shutdown,
619 static const struct tty_operations pty_unix98_ops = {
620 .lookup = pts_unix98_lookup,
621 .install = pty_unix98_install,
622 .remove = pty_unix98_remove,
626 .write_room = pty_write_room,
627 .flush_buffer = pty_flush_buffer,
628 .chars_in_buffer = pty_chars_in_buffer,
629 .unthrottle = pty_unthrottle,
630 .set_termios = pty_set_termios,
631 .shutdown = pty_unix98_shutdown
635 * ptmx_open - open a unix 98 pty master
636 * @inode: inode of device file
637 * @filp: file pointer to tty
639 * Allocate a unix98 pty master device from the ptmx driver.
641 * Locking: tty_mutex protects the init_dev work. tty->count should
643 * allocated_ptys_lock handles the list of free pty numbers
646 static int __ptmx_open(struct inode *inode, struct file *filp)
648 struct tty_struct *tty;
652 nonseekable_open(inode, filp);
654 /* find a device that is not in use. */
655 index = devpts_new_index(inode);
659 mutex_lock(&tty_mutex);
660 tty = tty_init_dev(ptm_driver, index, 1);
661 mutex_unlock(&tty_mutex);
664 retval = PTR_ERR(tty);
668 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
669 filp->private_data = tty;
670 file_move(filp, &tty->tty_files);
672 retval = devpts_pty_new(inode, tty->link);
676 retval = ptm_driver->ops->open(tty, filp);
680 tty_release_dev(filp);
683 devpts_kill_index(inode, index);
687 static int ptmx_open(struct inode *inode, struct file *filp)
692 ret = __ptmx_open(inode, filp);
697 static struct file_operations ptmx_fops;
699 static void __init unix98_pty_init(void)
701 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
703 panic("Couldn't allocate Unix98 ptm driver");
704 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
706 panic("Couldn't allocate Unix98 pts driver");
708 ptm_driver->owner = THIS_MODULE;
709 ptm_driver->driver_name = "pty_master";
710 ptm_driver->name = "ptm";
711 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
712 ptm_driver->minor_start = 0;
713 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
714 ptm_driver->subtype = PTY_TYPE_MASTER;
715 ptm_driver->init_termios = tty_std_termios;
716 ptm_driver->init_termios.c_iflag = 0;
717 ptm_driver->init_termios.c_oflag = 0;
718 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
719 ptm_driver->init_termios.c_lflag = 0;
720 ptm_driver->init_termios.c_ispeed = 38400;
721 ptm_driver->init_termios.c_ospeed = 38400;
722 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
723 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
724 ptm_driver->other = pts_driver;
725 tty_set_operations(ptm_driver, &ptm_unix98_ops);
727 pts_driver->owner = THIS_MODULE;
728 pts_driver->driver_name = "pty_slave";
729 pts_driver->name = "pts";
730 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
731 pts_driver->minor_start = 0;
732 pts_driver->type = TTY_DRIVER_TYPE_PTY;
733 pts_driver->subtype = PTY_TYPE_SLAVE;
734 pts_driver->init_termios = tty_std_termios;
735 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
736 pts_driver->init_termios.c_ispeed = 38400;
737 pts_driver->init_termios.c_ospeed = 38400;
738 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
739 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
740 pts_driver->other = ptm_driver;
741 tty_set_operations(pts_driver, &pty_unix98_ops);
743 if (tty_register_driver(ptm_driver))
744 panic("Couldn't register Unix98 ptm driver");
745 if (tty_register_driver(pts_driver))
746 panic("Couldn't register Unix98 pts driver");
748 register_sysctl_table(pty_root_table);
750 /* Now create the /dev/ptmx special device */
751 tty_default_fops(&ptmx_fops);
752 ptmx_fops.open = ptmx_open;
754 cdev_init(&ptmx_cdev, &ptmx_fops);
755 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
756 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
757 panic("Couldn't register /dev/ptmx driver\n");
758 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
762 static inline void unix98_pty_init(void) { }
765 static int __init pty_init(void)
771 module_init(pty_init);