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 * @ws: window size being set.
235 * Update the termios variables and send the neccessary signals to
236 * peform a terminal resize correctly
239 int pty_resize(struct tty_struct *tty, struct winsize *ws)
241 struct pid *pgrp, *rpgrp;
243 struct tty_struct *pty = tty->link;
245 /* For a PTY we need to lock the tty side */
246 mutex_lock(&tty->termios_mutex);
247 if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
250 /* Get the PID values and reference them so we can
251 avoid holding the tty ctrl lock while sending signals.
252 We need to lock these individually however. */
254 spin_lock_irqsave(&tty->ctrl_lock, flags);
255 pgrp = get_pid(tty->pgrp);
256 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
258 spin_lock_irqsave(&pty->ctrl_lock, flags);
259 rpgrp = get_pid(pty->pgrp);
260 spin_unlock_irqrestore(&pty->ctrl_lock, flags);
263 kill_pgrp(pgrp, SIGWINCH, 1);
264 if (rpgrp != pgrp && rpgrp)
265 kill_pgrp(rpgrp, SIGWINCH, 1);
271 pty->winsize = *ws; /* Never used so will go away soon */
273 mutex_unlock(&tty->termios_mutex);
277 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
279 struct tty_struct *o_tty;
280 int idx = tty->index;
283 o_tty = alloc_tty_struct();
286 if (!try_module_get(driver->other->owner)) {
287 /* This cannot in fact currently happen */
288 free_tty_struct(o_tty);
291 initialize_tty_struct(o_tty, driver->other, idx);
293 /* We always use new tty termios data so we can do this
295 retval = tty_init_termios(tty);
299 retval = tty_init_termios(o_tty);
301 tty_free_termios(tty);
306 * Everything allocated ... set up the o_tty structure.
308 driver->other->ttys[idx] = o_tty;
309 tty_driver_kref_get(driver->other);
310 if (driver->subtype == PTY_TYPE_MASTER)
312 /* Establish the links in both directions */
316 tty_driver_kref_get(driver);
318 driver->ttys[idx] = tty;
321 module_put(o_tty->driver->owner);
322 free_tty_struct(o_tty);
327 static const struct tty_operations pty_ops = {
328 .install = pty_install,
332 .write_room = pty_write_room,
333 .flush_buffer = pty_flush_buffer,
334 .chars_in_buffer = pty_chars_in_buffer,
335 .unthrottle = pty_unthrottle,
336 .set_termios = pty_set_termios,
340 /* Traditional BSD devices */
341 #ifdef CONFIG_LEGACY_PTYS
342 static struct tty_driver *pty_driver, *pty_slave_driver;
344 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
345 unsigned int cmd, unsigned long arg)
348 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
349 return pty_set_lock(tty, (int __user *) arg);
354 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
355 module_param(legacy_count, int, 0);
357 static const struct tty_operations pty_ops_bsd = {
361 .write_room = pty_write_room,
362 .flush_buffer = pty_flush_buffer,
363 .chars_in_buffer = pty_chars_in_buffer,
364 .unthrottle = pty_unthrottle,
365 .set_termios = pty_set_termios,
366 .ioctl = pty_bsd_ioctl,
370 static void __init legacy_pty_init(void)
372 if (legacy_count <= 0)
375 pty_driver = alloc_tty_driver(legacy_count);
377 panic("Couldn't allocate pty driver");
379 pty_slave_driver = alloc_tty_driver(legacy_count);
380 if (!pty_slave_driver)
381 panic("Couldn't allocate pty slave driver");
383 pty_driver->owner = THIS_MODULE;
384 pty_driver->driver_name = "pty_master";
385 pty_driver->name = "pty";
386 pty_driver->major = PTY_MASTER_MAJOR;
387 pty_driver->minor_start = 0;
388 pty_driver->type = TTY_DRIVER_TYPE_PTY;
389 pty_driver->subtype = PTY_TYPE_MASTER;
390 pty_driver->init_termios = tty_std_termios;
391 pty_driver->init_termios.c_iflag = 0;
392 pty_driver->init_termios.c_oflag = 0;
393 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
394 pty_driver->init_termios.c_lflag = 0;
395 pty_driver->init_termios.c_ispeed = 38400;
396 pty_driver->init_termios.c_ospeed = 38400;
397 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
398 pty_driver->other = pty_slave_driver;
399 tty_set_operations(pty_driver, &pty_ops);
401 pty_slave_driver->owner = THIS_MODULE;
402 pty_slave_driver->driver_name = "pty_slave";
403 pty_slave_driver->name = "ttyp";
404 pty_slave_driver->major = PTY_SLAVE_MAJOR;
405 pty_slave_driver->minor_start = 0;
406 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
407 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
408 pty_slave_driver->init_termios = tty_std_termios;
409 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
410 pty_slave_driver->init_termios.c_ispeed = 38400;
411 pty_slave_driver->init_termios.c_ospeed = 38400;
412 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
414 pty_slave_driver->other = pty_driver;
415 tty_set_operations(pty_slave_driver, &pty_ops);
417 if (tty_register_driver(pty_driver))
418 panic("Couldn't register pty driver");
419 if (tty_register_driver(pty_slave_driver))
420 panic("Couldn't register pty slave driver");
423 static inline void legacy_pty_init(void) { }
427 #ifdef CONFIG_UNIX98_PTYS
429 * sysctl support for setting limits on the number of Unix98 ptys allocated.
430 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
432 int pty_limit = NR_UNIX98_PTY_DEFAULT;
433 static int pty_limit_min;
434 static int pty_limit_max = NR_UNIX98_PTY_MAX;
435 static int pty_count;
437 static struct cdev ptmx_cdev;
439 static struct ctl_table pty_table[] = {
443 .maxlen = sizeof(int),
446 .proc_handler = &proc_dointvec_minmax,
447 .strategy = &sysctl_intvec,
448 .extra1 = &pty_limit_min,
449 .extra2 = &pty_limit_max,
453 .maxlen = sizeof(int),
456 .proc_handler = &proc_dointvec,
462 static struct ctl_table pty_kern_table[] = {
464 .ctl_name = KERN_PTY,
472 static struct ctl_table pty_root_table[] = {
474 .ctl_name = CTL_KERN,
475 .procname = "kernel",
477 .child = pty_kern_table,
483 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
484 unsigned int cmd, unsigned long arg)
487 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
488 return pty_set_lock(tty, (int __user *)arg);
489 case TIOCGPTN: /* Get PT Number */
490 return put_user(tty->index, (unsigned int __user *)arg);
497 * ptm_unix98_lookup - find a pty master
498 * @driver: ptm driver
501 * Look up a pty master device. Called under the tty_mutex for now.
502 * This provides our locking.
505 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
506 struct inode *ptm_inode, int idx)
508 struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
515 * pts_unix98_lookup - find a pty slave
516 * @driver: pts driver
519 * Look up a pty master device. Called under the tty_mutex for now.
520 * This provides our locking.
523 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
524 struct inode *pts_inode, int idx)
526 struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
527 /* Master must be open before slave */
529 return ERR_PTR(-EIO);
533 static void pty_unix98_shutdown(struct tty_struct *tty)
535 /* We have our own method as we don't use the tty index */
539 /* We have no need to install and remove our tty objects as devpts does all
542 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
544 struct tty_struct *o_tty;
545 int idx = tty->index;
547 o_tty = alloc_tty_struct();
550 if (!try_module_get(driver->other->owner)) {
551 /* This cannot in fact currently happen */
552 free_tty_struct(o_tty);
555 initialize_tty_struct(o_tty, driver->other, idx);
557 tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
558 if (tty->termios == NULL)
560 *tty->termios = driver->init_termios;
561 tty->termios_locked = tty->termios + 1;
563 o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
564 if (o_tty->termios == NULL)
566 *o_tty->termios = driver->other->init_termios;
567 o_tty->termios_locked = o_tty->termios + 1;
569 tty_driver_kref_get(driver->other);
570 if (driver->subtype == PTY_TYPE_MASTER)
572 /* Establish the links in both directions */
576 * All structures have been allocated, so now we install them.
577 * Failures after this point use release_tty to clean up, so
578 * there's no need to null out the local pointers.
580 tty_driver_kref_get(driver);
585 kfree(o_tty->termios);
586 module_put(o_tty->driver->owner);
587 free_tty_struct(o_tty);
592 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
597 static const struct tty_operations ptm_unix98_ops = {
598 .lookup = ptm_unix98_lookup,
599 .install = pty_unix98_install,
600 .remove = pty_unix98_remove,
604 .write_room = pty_write_room,
605 .flush_buffer = pty_flush_buffer,
606 .chars_in_buffer = pty_chars_in_buffer,
607 .unthrottle = pty_unthrottle,
608 .set_termios = pty_set_termios,
609 .ioctl = pty_unix98_ioctl,
610 .shutdown = pty_unix98_shutdown,
614 static const struct tty_operations pty_unix98_ops = {
615 .lookup = pts_unix98_lookup,
616 .install = pty_unix98_install,
617 .remove = pty_unix98_remove,
621 .write_room = pty_write_room,
622 .flush_buffer = pty_flush_buffer,
623 .chars_in_buffer = pty_chars_in_buffer,
624 .unthrottle = pty_unthrottle,
625 .set_termios = pty_set_termios,
626 .shutdown = pty_unix98_shutdown
630 * ptmx_open - open a unix 98 pty master
631 * @inode: inode of device file
632 * @filp: file pointer to tty
634 * Allocate a unix98 pty master device from the ptmx driver.
636 * Locking: tty_mutex protects the init_dev work. tty->count should
638 * allocated_ptys_lock handles the list of free pty numbers
641 static int __ptmx_open(struct inode *inode, struct file *filp)
643 struct tty_struct *tty;
647 nonseekable_open(inode, filp);
649 /* find a device that is not in use. */
650 index = devpts_new_index(inode);
654 mutex_lock(&tty_mutex);
655 tty = tty_init_dev(ptm_driver, index, 1);
656 mutex_unlock(&tty_mutex);
659 retval = PTR_ERR(tty);
663 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
664 filp->private_data = tty;
665 file_move(filp, &tty->tty_files);
667 retval = devpts_pty_new(inode, tty->link);
671 retval = ptm_driver->ops->open(tty, filp);
675 tty_release_dev(filp);
678 devpts_kill_index(inode, index);
682 static int ptmx_open(struct inode *inode, struct file *filp)
687 ret = __ptmx_open(inode, filp);
692 static struct file_operations ptmx_fops;
694 static void __init unix98_pty_init(void)
696 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
698 panic("Couldn't allocate Unix98 ptm driver");
699 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
701 panic("Couldn't allocate Unix98 pts driver");
703 ptm_driver->owner = THIS_MODULE;
704 ptm_driver->driver_name = "pty_master";
705 ptm_driver->name = "ptm";
706 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
707 ptm_driver->minor_start = 0;
708 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
709 ptm_driver->subtype = PTY_TYPE_MASTER;
710 ptm_driver->init_termios = tty_std_termios;
711 ptm_driver->init_termios.c_iflag = 0;
712 ptm_driver->init_termios.c_oflag = 0;
713 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
714 ptm_driver->init_termios.c_lflag = 0;
715 ptm_driver->init_termios.c_ispeed = 38400;
716 ptm_driver->init_termios.c_ospeed = 38400;
717 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
718 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
719 ptm_driver->other = pts_driver;
720 tty_set_operations(ptm_driver, &ptm_unix98_ops);
722 pts_driver->owner = THIS_MODULE;
723 pts_driver->driver_name = "pty_slave";
724 pts_driver->name = "pts";
725 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
726 pts_driver->minor_start = 0;
727 pts_driver->type = TTY_DRIVER_TYPE_PTY;
728 pts_driver->subtype = PTY_TYPE_SLAVE;
729 pts_driver->init_termios = tty_std_termios;
730 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
731 pts_driver->init_termios.c_ispeed = 38400;
732 pts_driver->init_termios.c_ospeed = 38400;
733 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
734 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
735 pts_driver->other = ptm_driver;
736 tty_set_operations(pts_driver, &pty_unix98_ops);
738 if (tty_register_driver(ptm_driver))
739 panic("Couldn't register Unix98 ptm driver");
740 if (tty_register_driver(pts_driver))
741 panic("Couldn't register Unix98 pts driver");
743 register_sysctl_table(pty_root_table);
745 /* Now create the /dev/ptmx special device */
746 tty_default_fops(&ptmx_fops);
747 ptmx_fops.open = ptmx_open;
749 cdev_init(&ptmx_cdev, &ptmx_fops);
750 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
751 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
752 panic("Couldn't register /dev/ptmx driver\n");
753 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
757 static inline void unix98_pty_init(void) { }
760 static int __init pty_init(void)
766 module_init(pty_init);