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/sched.h>
22 #include <linux/string.h>
23 #include <linux/major.h>
25 #include <linux/init.h>
26 #include <linux/smp_lock.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>
32 #include <linux/slab.h>
34 #include <asm/system.h>
36 #ifdef CONFIG_UNIX98_PTYS
37 static 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 tty_wakeup(tty->link);
82 set_bit(TTY_THROTTLED, &tty->flags);
86 * pty_space - report space left for writing
87 * @to: tty we are writing into
89 * The tty buffers allow 64K but we sneak a peak and clip at 8K this
90 * allows a lot of overspill room for echo and other fun messes to
94 static int pty_space(struct tty_struct *to)
96 int n = 8192 - to->buf.memory_used;
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
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.
114 static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)
116 struct tty_struct *to = tty->link;
122 /* Stuff the data into the input queue of the other end */
123 c = tty_insert_flip_string(to, buf, c);
126 tty_flip_buffer_push(to);
134 * pty_write_room - write space
135 * @tty: tty we are writing from
137 * Report how many bytes the ldisc can send into the queue for
141 static int pty_write_room(struct tty_struct *tty)
145 return pty_space(tty->link);
149 * pty_chars_in_buffer - characters currently in our tx queue
152 * Report how much we have in the transmit queue. As everything is
153 * instantly at the other end this is easy to implement.
156 static int pty_chars_in_buffer(struct tty_struct *tty)
161 /* Set the lock flag on a pty */
162 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
165 if (get_user(val, arg))
168 set_bit(TTY_PTY_LOCK, &tty->flags);
170 clear_bit(TTY_PTY_LOCK, &tty->flags);
174 /* Send a signal to the slave */
175 static int pty_signal(struct tty_struct *tty, int sig)
181 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
182 pgrp = get_pid(tty->link->pgrp);
183 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
185 kill_pgrp(pgrp, sig, 1);
191 static void pty_flush_buffer(struct tty_struct *tty)
193 struct tty_struct *to = tty->link;
198 /* tty_buffer_flush(to); FIXME */
200 spin_lock_irqsave(&tty->ctrl_lock, flags);
201 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
202 wake_up_interruptible(&to->read_wait);
203 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
207 static int pty_open(struct tty_struct *tty, struct file *filp)
209 int retval = -ENODEV;
211 if (!tty || !tty->link)
215 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
217 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
219 if (tty->link->count != 1)
222 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
223 set_bit(TTY_THROTTLED, &tty->flags);
229 static void pty_set_termios(struct tty_struct *tty,
230 struct ktermios *old_termios)
232 tty->termios->c_cflag &= ~(CSIZE | PARENB);
233 tty->termios->c_cflag |= (CS8 | CREAD);
237 * pty_do_resize - resize event
238 * @tty: tty being resized
239 * @ws: window size being set.
241 * Update the termios variables and send the necessary signals to
242 * peform a terminal resize correctly
245 int pty_resize(struct tty_struct *tty, struct winsize *ws)
247 struct pid *pgrp, *rpgrp;
249 struct tty_struct *pty = tty->link;
251 /* For a PTY we need to lock the tty side */
252 mutex_lock(&tty->termios_mutex);
253 if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
256 /* Get the PID values and reference them so we can
257 avoid holding the tty ctrl lock while sending signals.
258 We need to lock these individually however. */
260 spin_lock_irqsave(&tty->ctrl_lock, flags);
261 pgrp = get_pid(tty->pgrp);
262 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
264 spin_lock_irqsave(&pty->ctrl_lock, flags);
265 rpgrp = get_pid(pty->pgrp);
266 spin_unlock_irqrestore(&pty->ctrl_lock, flags);
269 kill_pgrp(pgrp, SIGWINCH, 1);
270 if (rpgrp != pgrp && rpgrp)
271 kill_pgrp(rpgrp, SIGWINCH, 1);
277 pty->winsize = *ws; /* Never used so will go away soon */
279 mutex_unlock(&tty->termios_mutex);
283 /* Traditional BSD devices */
284 #ifdef CONFIG_LEGACY_PTYS
286 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
288 struct tty_struct *o_tty;
289 int idx = tty->index;
292 o_tty = alloc_tty_struct();
295 if (!try_module_get(driver->other->owner)) {
296 /* This cannot in fact currently happen */
297 free_tty_struct(o_tty);
300 initialize_tty_struct(o_tty, driver->other, idx);
302 /* We always use new tty termios data so we can do this
304 retval = tty_init_termios(tty);
308 retval = tty_init_termios(o_tty);
310 tty_free_termios(tty);
315 * Everything allocated ... set up the o_tty structure.
317 driver->other->ttys[idx] = o_tty;
318 tty_driver_kref_get(driver->other);
319 if (driver->subtype == PTY_TYPE_MASTER)
321 /* Establish the links in both directions */
325 tty_driver_kref_get(driver);
327 driver->ttys[idx] = tty;
330 module_put(o_tty->driver->owner);
331 free_tty_struct(o_tty);
335 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
336 unsigned int cmd, unsigned long arg)
339 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
340 return pty_set_lock(tty, (int __user *) arg);
341 case TIOCSIG: /* Send signal to other side of pty */
342 return pty_signal(tty, (int) arg);
347 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
348 module_param(legacy_count, int, 0);
351 * The master side of a pty can do TIOCSPTLCK and thus
354 static const struct tty_operations master_pty_ops_bsd = {
355 .install = pty_install,
359 .write_room = pty_write_room,
360 .flush_buffer = pty_flush_buffer,
361 .chars_in_buffer = pty_chars_in_buffer,
362 .unthrottle = pty_unthrottle,
363 .set_termios = pty_set_termios,
364 .ioctl = pty_bsd_ioctl,
368 static const struct tty_operations slave_pty_ops_bsd = {
369 .install = pty_install,
373 .write_room = pty_write_room,
374 .flush_buffer = pty_flush_buffer,
375 .chars_in_buffer = pty_chars_in_buffer,
376 .unthrottle = pty_unthrottle,
377 .set_termios = pty_set_termios,
381 static void __init legacy_pty_init(void)
383 struct tty_driver *pty_driver, *pty_slave_driver;
385 if (legacy_count <= 0)
388 pty_driver = alloc_tty_driver(legacy_count);
390 panic("Couldn't allocate pty driver");
392 pty_slave_driver = alloc_tty_driver(legacy_count);
393 if (!pty_slave_driver)
394 panic("Couldn't allocate pty slave driver");
396 pty_driver->owner = THIS_MODULE;
397 pty_driver->driver_name = "pty_master";
398 pty_driver->name = "pty";
399 pty_driver->major = PTY_MASTER_MAJOR;
400 pty_driver->minor_start = 0;
401 pty_driver->type = TTY_DRIVER_TYPE_PTY;
402 pty_driver->subtype = PTY_TYPE_MASTER;
403 pty_driver->init_termios = tty_std_termios;
404 pty_driver->init_termios.c_iflag = 0;
405 pty_driver->init_termios.c_oflag = 0;
406 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
407 pty_driver->init_termios.c_lflag = 0;
408 pty_driver->init_termios.c_ispeed = 38400;
409 pty_driver->init_termios.c_ospeed = 38400;
410 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
411 pty_driver->other = pty_slave_driver;
412 tty_set_operations(pty_driver, &master_pty_ops_bsd);
414 pty_slave_driver->owner = THIS_MODULE;
415 pty_slave_driver->driver_name = "pty_slave";
416 pty_slave_driver->name = "ttyp";
417 pty_slave_driver->major = PTY_SLAVE_MAJOR;
418 pty_slave_driver->minor_start = 0;
419 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
420 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
421 pty_slave_driver->init_termios = tty_std_termios;
422 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
423 pty_slave_driver->init_termios.c_ispeed = 38400;
424 pty_slave_driver->init_termios.c_ospeed = 38400;
425 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
427 pty_slave_driver->other = pty_driver;
428 tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
430 if (tty_register_driver(pty_driver))
431 panic("Couldn't register pty driver");
432 if (tty_register_driver(pty_slave_driver))
433 panic("Couldn't register pty slave driver");
436 static inline void legacy_pty_init(void) { }
440 #ifdef CONFIG_UNIX98_PTYS
442 * sysctl support for setting limits on the number of Unix98 ptys allocated.
443 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
445 int pty_limit = NR_UNIX98_PTY_DEFAULT;
446 static int pty_limit_min;
447 static int pty_limit_max = NR_UNIX98_PTY_MAX;
448 static int pty_count;
450 static struct cdev ptmx_cdev;
452 static struct ctl_table pty_table[] = {
455 .maxlen = sizeof(int),
458 .proc_handler = proc_dointvec_minmax,
459 .extra1 = &pty_limit_min,
460 .extra2 = &pty_limit_max,
463 .maxlen = sizeof(int),
466 .proc_handler = proc_dointvec,
471 static struct ctl_table pty_kern_table[] = {
480 static struct ctl_table pty_root_table[] = {
482 .procname = "kernel",
484 .child = pty_kern_table,
490 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
491 unsigned int cmd, unsigned long arg)
494 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
495 return pty_set_lock(tty, (int __user *)arg);
496 case TIOCGPTN: /* Get PT Number */
497 return put_user(tty->index, (unsigned int __user *)arg);
498 case TIOCSIG: /* Send signal to other side of pty */
499 return pty_signal(tty, (int) arg);
506 * ptm_unix98_lookup - find a pty master
507 * @driver: ptm driver
510 * Look up a pty master device. Called under the tty_mutex for now.
511 * This provides our locking.
514 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
515 struct inode *ptm_inode, int idx)
517 struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
524 * pts_unix98_lookup - find a pty slave
525 * @driver: pts driver
528 * Look up a pty master device. Called under the tty_mutex for now.
529 * This provides our locking.
532 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
533 struct inode *pts_inode, int idx)
535 struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
536 /* Master must be open before slave */
538 return ERR_PTR(-EIO);
542 static void pty_unix98_shutdown(struct tty_struct *tty)
544 /* We have our own method as we don't use the tty index */
548 /* We have no need to install and remove our tty objects as devpts does all
551 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
553 struct tty_struct *o_tty;
554 int idx = tty->index;
556 o_tty = alloc_tty_struct();
559 if (!try_module_get(driver->other->owner)) {
560 /* This cannot in fact currently happen */
561 free_tty_struct(o_tty);
564 initialize_tty_struct(o_tty, driver->other, idx);
566 tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
567 if (tty->termios == NULL)
569 *tty->termios = driver->init_termios;
570 tty->termios_locked = tty->termios + 1;
572 o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
573 if (o_tty->termios == NULL)
575 *o_tty->termios = driver->other->init_termios;
576 o_tty->termios_locked = o_tty->termios + 1;
578 tty_driver_kref_get(driver->other);
579 if (driver->subtype == PTY_TYPE_MASTER)
581 /* Establish the links in both directions */
585 * All structures have been allocated, so now we install them.
586 * Failures after this point use release_tty to clean up, so
587 * there's no need to null out the local pointers.
589 tty_driver_kref_get(driver);
594 kfree(o_tty->termios);
595 module_put(o_tty->driver->owner);
596 free_tty_struct(o_tty);
601 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
606 static const struct tty_operations ptm_unix98_ops = {
607 .lookup = ptm_unix98_lookup,
608 .install = pty_unix98_install,
609 .remove = pty_unix98_remove,
613 .write_room = pty_write_room,
614 .flush_buffer = pty_flush_buffer,
615 .chars_in_buffer = pty_chars_in_buffer,
616 .unthrottle = pty_unthrottle,
617 .set_termios = pty_set_termios,
618 .ioctl = pty_unix98_ioctl,
619 .shutdown = pty_unix98_shutdown,
623 static const struct tty_operations pty_unix98_ops = {
624 .lookup = pts_unix98_lookup,
625 .install = pty_unix98_install,
626 .remove = pty_unix98_remove,
630 .write_room = pty_write_room,
631 .flush_buffer = pty_flush_buffer,
632 .chars_in_buffer = pty_chars_in_buffer,
633 .unthrottle = pty_unthrottle,
634 .set_termios = pty_set_termios,
635 .shutdown = pty_unix98_shutdown
639 * ptmx_open - open a unix 98 pty master
640 * @inode: inode of device file
641 * @filp: file pointer to tty
643 * Allocate a unix98 pty master device from the ptmx driver.
645 * Locking: tty_mutex protects the init_dev work. tty->count should
647 * allocated_ptys_lock handles the list of free pty numbers
650 static int __ptmx_open(struct inode *inode, struct file *filp)
652 struct tty_struct *tty;
656 nonseekable_open(inode, filp);
658 /* find a device that is not in use. */
659 index = devpts_new_index(inode);
663 mutex_lock(&tty_mutex);
664 tty = tty_init_dev(ptm_driver, index, 1);
665 mutex_unlock(&tty_mutex);
668 retval = PTR_ERR(tty);
672 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
673 filp->private_data = tty;
674 file_move(filp, &tty->tty_files);
676 retval = devpts_pty_new(inode, tty->link);
680 retval = ptm_driver->ops->open(tty, filp);
684 tty_release(inode, filp);
687 devpts_kill_index(inode, index);
691 static int ptmx_open(struct inode *inode, struct file *filp)
696 ret = __ptmx_open(inode, filp);
701 static struct file_operations ptmx_fops;
703 static void __init unix98_pty_init(void)
705 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
707 panic("Couldn't allocate Unix98 ptm driver");
708 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
710 panic("Couldn't allocate Unix98 pts driver");
712 ptm_driver->owner = THIS_MODULE;
713 ptm_driver->driver_name = "pty_master";
714 ptm_driver->name = "ptm";
715 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
716 ptm_driver->minor_start = 0;
717 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
718 ptm_driver->subtype = PTY_TYPE_MASTER;
719 ptm_driver->init_termios = tty_std_termios;
720 ptm_driver->init_termios.c_iflag = 0;
721 ptm_driver->init_termios.c_oflag = 0;
722 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
723 ptm_driver->init_termios.c_lflag = 0;
724 ptm_driver->init_termios.c_ispeed = 38400;
725 ptm_driver->init_termios.c_ospeed = 38400;
726 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
727 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
728 ptm_driver->other = pts_driver;
729 tty_set_operations(ptm_driver, &ptm_unix98_ops);
731 pts_driver->owner = THIS_MODULE;
732 pts_driver->driver_name = "pty_slave";
733 pts_driver->name = "pts";
734 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
735 pts_driver->minor_start = 0;
736 pts_driver->type = TTY_DRIVER_TYPE_PTY;
737 pts_driver->subtype = PTY_TYPE_SLAVE;
738 pts_driver->init_termios = tty_std_termios;
739 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
740 pts_driver->init_termios.c_ispeed = 38400;
741 pts_driver->init_termios.c_ospeed = 38400;
742 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
743 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
744 pts_driver->other = ptm_driver;
745 tty_set_operations(pts_driver, &pty_unix98_ops);
747 if (tty_register_driver(ptm_driver))
748 panic("Couldn't register Unix98 ptm driver");
749 if (tty_register_driver(pts_driver))
750 panic("Couldn't register Unix98 pts driver");
752 register_sysctl_table(pty_root_table);
754 /* Now create the /dev/ptmx special device */
755 tty_default_fops(&ptmx_fops);
756 ptmx_fops.open = ptmx_open;
758 cdev_init(&ptmx_cdev, &ptmx_fops);
759 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
760 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
761 panic("Couldn't register /dev/ptmx driver\n");
762 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
766 static inline void unix98_pty_init(void) { }
769 static int __init pty_init(void)
775 module_init(pty_init);