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 static void pty_flush_buffer(struct tty_struct *tty)
176 struct tty_struct *to = tty->link;
181 /* tty_buffer_flush(to); FIXME */
183 spin_lock_irqsave(&tty->ctrl_lock, flags);
184 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
185 wake_up_interruptible(&to->read_wait);
186 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
190 static int pty_open(struct tty_struct *tty, struct file *filp)
192 int retval = -ENODEV;
194 if (!tty || !tty->link)
198 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
200 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
202 if (tty->link->count != 1)
205 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
206 set_bit(TTY_THROTTLED, &tty->flags);
212 static void pty_set_termios(struct tty_struct *tty,
213 struct ktermios *old_termios)
215 tty->termios->c_cflag &= ~(CSIZE | PARENB);
216 tty->termios->c_cflag |= (CS8 | CREAD);
220 * pty_do_resize - resize event
221 * @tty: tty being resized
222 * @ws: window size being set.
224 * Update the termios variables and send the necessary signals to
225 * peform a terminal resize correctly
228 int pty_resize(struct tty_struct *tty, struct winsize *ws)
230 struct pid *pgrp, *rpgrp;
232 struct tty_struct *pty = tty->link;
234 /* For a PTY we need to lock the tty side */
235 mutex_lock(&tty->termios_mutex);
236 if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
239 /* Get the PID values and reference them so we can
240 avoid holding the tty ctrl lock while sending signals.
241 We need to lock these individually however. */
243 spin_lock_irqsave(&tty->ctrl_lock, flags);
244 pgrp = get_pid(tty->pgrp);
245 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
247 spin_lock_irqsave(&pty->ctrl_lock, flags);
248 rpgrp = get_pid(pty->pgrp);
249 spin_unlock_irqrestore(&pty->ctrl_lock, flags);
252 kill_pgrp(pgrp, SIGWINCH, 1);
253 if (rpgrp != pgrp && rpgrp)
254 kill_pgrp(rpgrp, SIGWINCH, 1);
260 pty->winsize = *ws; /* Never used so will go away soon */
262 mutex_unlock(&tty->termios_mutex);
266 /* Traditional BSD devices */
267 #ifdef CONFIG_LEGACY_PTYS
269 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
271 struct tty_struct *o_tty;
272 int idx = tty->index;
275 o_tty = alloc_tty_struct();
278 if (!try_module_get(driver->other->owner)) {
279 /* This cannot in fact currently happen */
280 free_tty_struct(o_tty);
283 initialize_tty_struct(o_tty, driver->other, idx);
285 /* We always use new tty termios data so we can do this
287 retval = tty_init_termios(tty);
291 retval = tty_init_termios(o_tty);
293 tty_free_termios(tty);
298 * Everything allocated ... set up the o_tty structure.
300 driver->other->ttys[idx] = o_tty;
301 tty_driver_kref_get(driver->other);
302 if (driver->subtype == PTY_TYPE_MASTER)
304 /* Establish the links in both directions */
308 tty_driver_kref_get(driver);
310 driver->ttys[idx] = tty;
313 module_put(o_tty->driver->owner);
314 free_tty_struct(o_tty);
318 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
319 unsigned int cmd, unsigned long arg)
322 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
323 return pty_set_lock(tty, (int __user *) arg);
328 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
329 module_param(legacy_count, int, 0);
332 * The master side of a pty can do TIOCSPTLCK and thus
335 static const struct tty_operations master_pty_ops_bsd = {
336 .install = pty_install,
340 .write_room = pty_write_room,
341 .flush_buffer = pty_flush_buffer,
342 .chars_in_buffer = pty_chars_in_buffer,
343 .unthrottle = pty_unthrottle,
344 .set_termios = pty_set_termios,
345 .ioctl = pty_bsd_ioctl,
349 static const struct tty_operations slave_pty_ops_bsd = {
350 .install = pty_install,
354 .write_room = pty_write_room,
355 .flush_buffer = pty_flush_buffer,
356 .chars_in_buffer = pty_chars_in_buffer,
357 .unthrottle = pty_unthrottle,
358 .set_termios = pty_set_termios,
362 static void __init legacy_pty_init(void)
364 struct tty_driver *pty_driver, *pty_slave_driver;
366 if (legacy_count <= 0)
369 pty_driver = alloc_tty_driver(legacy_count);
371 panic("Couldn't allocate pty driver");
373 pty_slave_driver = alloc_tty_driver(legacy_count);
374 if (!pty_slave_driver)
375 panic("Couldn't allocate pty slave driver");
377 pty_driver->owner = THIS_MODULE;
378 pty_driver->driver_name = "pty_master";
379 pty_driver->name = "pty";
380 pty_driver->major = PTY_MASTER_MAJOR;
381 pty_driver->minor_start = 0;
382 pty_driver->type = TTY_DRIVER_TYPE_PTY;
383 pty_driver->subtype = PTY_TYPE_MASTER;
384 pty_driver->init_termios = tty_std_termios;
385 pty_driver->init_termios.c_iflag = 0;
386 pty_driver->init_termios.c_oflag = 0;
387 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
388 pty_driver->init_termios.c_lflag = 0;
389 pty_driver->init_termios.c_ispeed = 38400;
390 pty_driver->init_termios.c_ospeed = 38400;
391 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
392 pty_driver->other = pty_slave_driver;
393 tty_set_operations(pty_driver, &master_pty_ops_bsd);
395 pty_slave_driver->owner = THIS_MODULE;
396 pty_slave_driver->driver_name = "pty_slave";
397 pty_slave_driver->name = "ttyp";
398 pty_slave_driver->major = PTY_SLAVE_MAJOR;
399 pty_slave_driver->minor_start = 0;
400 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
401 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
402 pty_slave_driver->init_termios = tty_std_termios;
403 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
404 pty_slave_driver->init_termios.c_ispeed = 38400;
405 pty_slave_driver->init_termios.c_ospeed = 38400;
406 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
408 pty_slave_driver->other = pty_driver;
409 tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);
411 if (tty_register_driver(pty_driver))
412 panic("Couldn't register pty driver");
413 if (tty_register_driver(pty_slave_driver))
414 panic("Couldn't register pty slave driver");
417 static inline void legacy_pty_init(void) { }
421 #ifdef CONFIG_UNIX98_PTYS
423 * sysctl support for setting limits on the number of Unix98 ptys allocated.
424 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
426 int pty_limit = NR_UNIX98_PTY_DEFAULT;
427 static int pty_limit_min;
428 static int pty_limit_max = NR_UNIX98_PTY_MAX;
429 static int pty_count;
431 static struct cdev ptmx_cdev;
433 static struct ctl_table pty_table[] = {
436 .maxlen = sizeof(int),
439 .proc_handler = proc_dointvec_minmax,
440 .extra1 = &pty_limit_min,
441 .extra2 = &pty_limit_max,
444 .maxlen = sizeof(int),
447 .proc_handler = proc_dointvec,
452 static struct ctl_table pty_kern_table[] = {
461 static struct ctl_table pty_root_table[] = {
463 .procname = "kernel",
465 .child = pty_kern_table,
471 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
472 unsigned int cmd, unsigned long arg)
475 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
476 return pty_set_lock(tty, (int __user *)arg);
477 case TIOCGPTN: /* Get PT Number */
478 return put_user(tty->index, (unsigned int __user *)arg);
485 * ptm_unix98_lookup - find a pty master
486 * @driver: ptm driver
489 * Look up a pty master device. Called under the tty_mutex for now.
490 * This provides our locking.
493 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
494 struct inode *ptm_inode, int idx)
496 struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
503 * pts_unix98_lookup - find a pty slave
504 * @driver: pts driver
507 * Look up a pty master device. Called under the tty_mutex for now.
508 * This provides our locking.
511 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
512 struct inode *pts_inode, int idx)
514 struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
515 /* Master must be open before slave */
517 return ERR_PTR(-EIO);
521 static void pty_unix98_shutdown(struct tty_struct *tty)
523 /* We have our own method as we don't use the tty index */
527 /* We have no need to install and remove our tty objects as devpts does all
530 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
532 struct tty_struct *o_tty;
533 int idx = tty->index;
535 o_tty = alloc_tty_struct();
538 if (!try_module_get(driver->other->owner)) {
539 /* This cannot in fact currently happen */
540 free_tty_struct(o_tty);
543 initialize_tty_struct(o_tty, driver->other, idx);
545 tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
546 if (tty->termios == NULL)
548 *tty->termios = driver->init_termios;
549 tty->termios_locked = tty->termios + 1;
551 o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
552 if (o_tty->termios == NULL)
554 *o_tty->termios = driver->other->init_termios;
555 o_tty->termios_locked = o_tty->termios + 1;
557 tty_driver_kref_get(driver->other);
558 if (driver->subtype == PTY_TYPE_MASTER)
560 /* Establish the links in both directions */
564 * All structures have been allocated, so now we install them.
565 * Failures after this point use release_tty to clean up, so
566 * there's no need to null out the local pointers.
568 tty_driver_kref_get(driver);
573 kfree(o_tty->termios);
574 module_put(o_tty->driver->owner);
575 free_tty_struct(o_tty);
580 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
585 static const struct tty_operations ptm_unix98_ops = {
586 .lookup = ptm_unix98_lookup,
587 .install = pty_unix98_install,
588 .remove = pty_unix98_remove,
592 .write_room = pty_write_room,
593 .flush_buffer = pty_flush_buffer,
594 .chars_in_buffer = pty_chars_in_buffer,
595 .unthrottle = pty_unthrottle,
596 .set_termios = pty_set_termios,
597 .ioctl = pty_unix98_ioctl,
598 .shutdown = pty_unix98_shutdown,
602 static const struct tty_operations pty_unix98_ops = {
603 .lookup = pts_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 .shutdown = pty_unix98_shutdown
618 * ptmx_open - open a unix 98 pty master
619 * @inode: inode of device file
620 * @filp: file pointer to tty
622 * Allocate a unix98 pty master device from the ptmx driver.
624 * Locking: tty_mutex protects the init_dev work. tty->count should
626 * allocated_ptys_lock handles the list of free pty numbers
629 static int __ptmx_open(struct inode *inode, struct file *filp)
631 struct tty_struct *tty;
635 nonseekable_open(inode, filp);
637 /* find a device that is not in use. */
638 index = devpts_new_index(inode);
642 mutex_lock(&tty_mutex);
643 tty = tty_init_dev(ptm_driver, index, 1);
644 mutex_unlock(&tty_mutex);
647 retval = PTR_ERR(tty);
651 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
652 filp->private_data = tty;
653 file_move(filp, &tty->tty_files);
655 retval = devpts_pty_new(inode, tty->link);
659 retval = ptm_driver->ops->open(tty, filp);
663 tty_release(inode, filp);
666 devpts_kill_index(inode, index);
670 static int ptmx_open(struct inode *inode, struct file *filp)
675 ret = __ptmx_open(inode, filp);
680 static struct file_operations ptmx_fops;
682 static void __init unix98_pty_init(void)
684 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
686 panic("Couldn't allocate Unix98 ptm driver");
687 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
689 panic("Couldn't allocate Unix98 pts driver");
691 ptm_driver->owner = THIS_MODULE;
692 ptm_driver->driver_name = "pty_master";
693 ptm_driver->name = "ptm";
694 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
695 ptm_driver->minor_start = 0;
696 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
697 ptm_driver->subtype = PTY_TYPE_MASTER;
698 ptm_driver->init_termios = tty_std_termios;
699 ptm_driver->init_termios.c_iflag = 0;
700 ptm_driver->init_termios.c_oflag = 0;
701 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
702 ptm_driver->init_termios.c_lflag = 0;
703 ptm_driver->init_termios.c_ispeed = 38400;
704 ptm_driver->init_termios.c_ospeed = 38400;
705 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
706 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
707 ptm_driver->other = pts_driver;
708 tty_set_operations(ptm_driver, &ptm_unix98_ops);
710 pts_driver->owner = THIS_MODULE;
711 pts_driver->driver_name = "pty_slave";
712 pts_driver->name = "pts";
713 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
714 pts_driver->minor_start = 0;
715 pts_driver->type = TTY_DRIVER_TYPE_PTY;
716 pts_driver->subtype = PTY_TYPE_SLAVE;
717 pts_driver->init_termios = tty_std_termios;
718 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
719 pts_driver->init_termios.c_ispeed = 38400;
720 pts_driver->init_termios.c_ospeed = 38400;
721 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
722 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
723 pts_driver->other = ptm_driver;
724 tty_set_operations(pts_driver, &pty_unix98_ops);
726 if (tty_register_driver(ptm_driver))
727 panic("Couldn't register Unix98 ptm driver");
728 if (tty_register_driver(pts_driver))
729 panic("Couldn't register Unix98 pts driver");
731 register_sysctl_table(pty_root_table);
733 /* Now create the /dev/ptmx special device */
734 tty_default_fops(&ptmx_fops);
735 ptmx_fops.open = ptmx_open;
737 cdev_init(&ptmx_cdev, &ptmx_fops);
738 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
739 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
740 panic("Couldn't register /dev/ptmx driver\n");
741 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
745 static inline void unix98_pty_init(void) { }
748 static int __init pty_init(void)
754 module_init(pty_init);