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 #ifdef CONFIG_UNIX98_PTYS
34 static struct tty_driver *ptm_driver;
35 static struct tty_driver *pts_driver;
38 static void pty_close(struct tty_struct *tty, struct file *filp)
41 if (tty->driver->subtype == PTY_TYPE_MASTER)
42 WARN_ON(tty->count > 1);
47 wake_up_interruptible(&tty->read_wait);
48 wake_up_interruptible(&tty->write_wait);
52 tty->link->packet = 0;
53 set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
54 wake_up_interruptible(&tty->link->read_wait);
55 wake_up_interruptible(&tty->link->write_wait);
56 if (tty->driver->subtype == PTY_TYPE_MASTER) {
57 set_bit(TTY_OTHER_CLOSED, &tty->flags);
58 #ifdef CONFIG_UNIX98_PTYS
59 if (tty->driver == ptm_driver)
60 devpts_pty_kill(tty->link);
62 tty_vhangup(tty->link);
67 * The unthrottle routine is called by the line discipline to signal
68 * that it can receive more characters. For PTY's, the TTY_THROTTLED
69 * flag is always set, to force the line discipline to always call the
70 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
71 * characters in the queue. This is necessary since each time this
72 * happens, we need to wake up any sleeping processes that could be
73 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
74 * for the pty buffer to be drained.
76 static void pty_unthrottle(struct tty_struct *tty)
78 tty_wakeup(tty->link);
79 set_bit(TTY_THROTTLED, &tty->flags);
83 * pty_space - report space left for writing
84 * @to: tty we are writing into
86 * The tty buffers allow 64K but we sneak a peak and clip at 8K this
87 * allows a lot of overspill room for echo and other fun messes to
91 static int pty_space(struct tty_struct *to)
93 int n = 8192 - to->buf.memory_used;
100 * pty_write - write to a pty
101 * @tty: the tty we write from
102 * @buf: kernel buffer of data
103 * @count: bytes to write
105 * Our "hardware" write method. Data is coming from the ldisc which
106 * may be in a non sleeping state. We simply throw this at the other
107 * end of the link as if we were an IRQ handler receiving stuff for
108 * the other side of the pty/tty pair.
111 static int pty_write(struct tty_struct *tty, const unsigned char *buf,
114 struct tty_struct *to = tty->link;
120 /* This isn't locked but our 8K is quite sloppy so no
127 /* Stuff the data into the input queue of the other end */
128 c = tty_insert_flip_string(to, buf, c);
130 tty_flip_buffer_push(to);
137 * pty_write_room - write space
138 * @tty: tty we are writing from
140 * Report how many bytes the ldisc can send into the queue for
144 static int pty_write_room(struct tty_struct *tty)
146 return pty_space(tty->link);
150 * pty_chars_in_buffer - characters currently in our tx queue
153 * Report how much we have in the transmit queue. As everything is
154 * instantly at the other end this is easy to implement.
157 static int pty_chars_in_buffer(struct tty_struct *tty)
162 /* Set the lock flag on a pty */
163 static int pty_set_lock(struct tty_struct *tty, int __user *arg)
166 if (get_user(val, arg))
169 set_bit(TTY_PTY_LOCK, &tty->flags);
171 clear_bit(TTY_PTY_LOCK, &tty->flags);
175 static void pty_flush_buffer(struct tty_struct *tty)
177 struct tty_struct *to = tty->link;
182 /* tty_buffer_flush(to); FIXME */
184 spin_lock_irqsave(&tty->ctrl_lock, flags);
185 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
186 wake_up_interruptible(&to->read_wait);
187 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
191 static int pty_open(struct tty_struct *tty, struct file *filp)
193 int retval = -ENODEV;
195 if (!tty || !tty->link)
199 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
201 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
203 if (tty->link->count != 1)
206 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
207 set_bit(TTY_THROTTLED, &tty->flags);
213 static void pty_set_termios(struct tty_struct *tty,
214 struct ktermios *old_termios)
216 tty->termios->c_cflag &= ~(CSIZE | PARENB);
217 tty->termios->c_cflag |= (CS8 | CREAD);
221 * pty_do_resize - resize event
222 * @tty: tty being resized
223 * @ws: window size being set.
225 * Update the termios variables and send the neccessary signals to
226 * peform a terminal resize correctly
229 int pty_resize(struct tty_struct *tty, struct winsize *ws)
231 struct pid *pgrp, *rpgrp;
233 struct tty_struct *pty = tty->link;
235 /* For a PTY we need to lock the tty side */
236 mutex_lock(&tty->termios_mutex);
237 if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
240 /* Get the PID values and reference them so we can
241 avoid holding the tty ctrl lock while sending signals.
242 We need to lock these individually however. */
244 spin_lock_irqsave(&tty->ctrl_lock, flags);
245 pgrp = get_pid(tty->pgrp);
246 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
248 spin_lock_irqsave(&pty->ctrl_lock, flags);
249 rpgrp = get_pid(pty->pgrp);
250 spin_unlock_irqrestore(&pty->ctrl_lock, flags);
253 kill_pgrp(pgrp, SIGWINCH, 1);
254 if (rpgrp != pgrp && rpgrp)
255 kill_pgrp(rpgrp, SIGWINCH, 1);
261 pty->winsize = *ws; /* Never used so will go away soon */
263 mutex_unlock(&tty->termios_mutex);
267 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
269 struct tty_struct *o_tty;
270 int idx = tty->index;
273 o_tty = alloc_tty_struct();
276 if (!try_module_get(driver->other->owner)) {
277 /* This cannot in fact currently happen */
278 free_tty_struct(o_tty);
281 initialize_tty_struct(o_tty, driver->other, idx);
283 /* We always use new tty termios data so we can do this
285 retval = tty_init_termios(tty);
289 retval = tty_init_termios(o_tty);
291 tty_free_termios(tty);
296 * Everything allocated ... set up the o_tty structure.
298 driver->other->ttys[idx] = o_tty;
299 tty_driver_kref_get(driver->other);
300 if (driver->subtype == PTY_TYPE_MASTER)
302 /* Establish the links in both directions */
306 tty_driver_kref_get(driver);
308 driver->ttys[idx] = tty;
311 module_put(o_tty->driver->owner);
312 free_tty_struct(o_tty);
317 static const struct tty_operations pty_ops = {
318 .install = pty_install,
322 .write_room = pty_write_room,
323 .flush_buffer = pty_flush_buffer,
324 .chars_in_buffer = pty_chars_in_buffer,
325 .unthrottle = pty_unthrottle,
326 .set_termios = pty_set_termios,
330 /* Traditional BSD devices */
331 #ifdef CONFIG_LEGACY_PTYS
332 static struct tty_driver *pty_driver, *pty_slave_driver;
334 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
335 unsigned int cmd, unsigned long arg)
338 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
339 return pty_set_lock(tty, (int __user *) arg);
344 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
345 module_param(legacy_count, int, 0);
347 static const struct tty_operations pty_ops_bsd = {
351 .write_room = pty_write_room,
352 .flush_buffer = pty_flush_buffer,
353 .chars_in_buffer = pty_chars_in_buffer,
354 .unthrottle = pty_unthrottle,
355 .set_termios = pty_set_termios,
356 .ioctl = pty_bsd_ioctl,
360 static void __init legacy_pty_init(void)
362 if (legacy_count <= 0)
365 pty_driver = alloc_tty_driver(legacy_count);
367 panic("Couldn't allocate pty driver");
369 pty_slave_driver = alloc_tty_driver(legacy_count);
370 if (!pty_slave_driver)
371 panic("Couldn't allocate pty slave driver");
373 pty_driver->owner = THIS_MODULE;
374 pty_driver->driver_name = "pty_master";
375 pty_driver->name = "pty";
376 pty_driver->major = PTY_MASTER_MAJOR;
377 pty_driver->minor_start = 0;
378 pty_driver->type = TTY_DRIVER_TYPE_PTY;
379 pty_driver->subtype = PTY_TYPE_MASTER;
380 pty_driver->init_termios = tty_std_termios;
381 pty_driver->init_termios.c_iflag = 0;
382 pty_driver->init_termios.c_oflag = 0;
383 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
384 pty_driver->init_termios.c_lflag = 0;
385 pty_driver->init_termios.c_ispeed = 38400;
386 pty_driver->init_termios.c_ospeed = 38400;
387 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
388 pty_driver->other = pty_slave_driver;
389 tty_set_operations(pty_driver, &pty_ops);
391 pty_slave_driver->owner = THIS_MODULE;
392 pty_slave_driver->driver_name = "pty_slave";
393 pty_slave_driver->name = "ttyp";
394 pty_slave_driver->major = PTY_SLAVE_MAJOR;
395 pty_slave_driver->minor_start = 0;
396 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
397 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
398 pty_slave_driver->init_termios = tty_std_termios;
399 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
400 pty_slave_driver->init_termios.c_ispeed = 38400;
401 pty_slave_driver->init_termios.c_ospeed = 38400;
402 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
404 pty_slave_driver->other = pty_driver;
405 tty_set_operations(pty_slave_driver, &pty_ops);
407 if (tty_register_driver(pty_driver))
408 panic("Couldn't register pty driver");
409 if (tty_register_driver(pty_slave_driver))
410 panic("Couldn't register pty slave driver");
413 static inline void legacy_pty_init(void) { }
417 #ifdef CONFIG_UNIX98_PTYS
419 * sysctl support for setting limits on the number of Unix98 ptys allocated.
420 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
422 int pty_limit = NR_UNIX98_PTY_DEFAULT;
423 static int pty_limit_min;
424 static int pty_limit_max = NR_UNIX98_PTY_MAX;
425 static int pty_count;
427 static struct cdev ptmx_cdev;
429 static struct ctl_table pty_table[] = {
433 .maxlen = sizeof(int),
436 .proc_handler = &proc_dointvec_minmax,
437 .strategy = &sysctl_intvec,
438 .extra1 = &pty_limit_min,
439 .extra2 = &pty_limit_max,
443 .maxlen = sizeof(int),
446 .proc_handler = &proc_dointvec,
452 static struct ctl_table pty_kern_table[] = {
454 .ctl_name = KERN_PTY,
462 static struct ctl_table pty_root_table[] = {
464 .ctl_name = CTL_KERN,
465 .procname = "kernel",
467 .child = pty_kern_table,
473 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
474 unsigned int cmd, unsigned long arg)
477 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
478 return pty_set_lock(tty, (int __user *)arg);
479 case TIOCGPTN: /* Get PT Number */
480 return put_user(tty->index, (unsigned int __user *)arg);
487 * ptm_unix98_lookup - find a pty master
488 * @driver: ptm driver
491 * Look up a pty master device. Called under the tty_mutex for now.
492 * This provides our locking.
495 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
496 struct inode *ptm_inode, int idx)
498 struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);
505 * pts_unix98_lookup - find a pty slave
506 * @driver: pts driver
509 * Look up a pty master device. Called under the tty_mutex for now.
510 * This provides our locking.
513 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
514 struct inode *pts_inode, int idx)
516 struct tty_struct *tty = devpts_get_tty(pts_inode, idx);
517 /* Master must be open before slave */
519 return ERR_PTR(-EIO);
523 static void pty_unix98_shutdown(struct tty_struct *tty)
525 /* We have our own method as we don't use the tty index */
529 /* We have no need to install and remove our tty objects as devpts does all
532 static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)
534 struct tty_struct *o_tty;
535 int idx = tty->index;
537 o_tty = alloc_tty_struct();
540 if (!try_module_get(driver->other->owner)) {
541 /* This cannot in fact currently happen */
542 free_tty_struct(o_tty);
545 initialize_tty_struct(o_tty, driver->other, idx);
547 tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
548 if (tty->termios == NULL)
550 *tty->termios = driver->init_termios;
551 tty->termios_locked = tty->termios + 1;
553 o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
554 if (o_tty->termios == NULL)
556 *o_tty->termios = driver->other->init_termios;
557 o_tty->termios_locked = o_tty->termios + 1;
559 tty_driver_kref_get(driver->other);
560 if (driver->subtype == PTY_TYPE_MASTER)
562 /* Establish the links in both directions */
566 * All structures have been allocated, so now we install them.
567 * Failures after this point use release_tty to clean up, so
568 * there's no need to null out the local pointers.
570 tty_driver_kref_get(driver);
575 kfree(o_tty->termios);
576 module_put(o_tty->driver->owner);
577 free_tty_struct(o_tty);
582 static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
587 static const struct tty_operations ptm_unix98_ops = {
588 .lookup = ptm_unix98_lookup,
589 .install = pty_unix98_install,
590 .remove = pty_unix98_remove,
594 .write_room = pty_write_room,
595 .flush_buffer = pty_flush_buffer,
596 .chars_in_buffer = pty_chars_in_buffer,
597 .unthrottle = pty_unthrottle,
598 .set_termios = pty_set_termios,
599 .ioctl = pty_unix98_ioctl,
600 .shutdown = pty_unix98_shutdown,
604 static const struct tty_operations pty_unix98_ops = {
605 .lookup = pts_unix98_lookup,
606 .install = pty_unix98_install,
607 .remove = pty_unix98_remove,
611 .write_room = pty_write_room,
612 .flush_buffer = pty_flush_buffer,
613 .chars_in_buffer = pty_chars_in_buffer,
614 .unthrottle = pty_unthrottle,
615 .set_termios = pty_set_termios,
616 .shutdown = pty_unix98_shutdown
620 * ptmx_open - open a unix 98 pty master
621 * @inode: inode of device file
622 * @filp: file pointer to tty
624 * Allocate a unix98 pty master device from the ptmx driver.
626 * Locking: tty_mutex protects the init_dev work. tty->count should
628 * allocated_ptys_lock handles the list of free pty numbers
631 static int __ptmx_open(struct inode *inode, struct file *filp)
633 struct tty_struct *tty;
637 nonseekable_open(inode, filp);
639 /* find a device that is not in use. */
640 index = devpts_new_index(inode);
644 mutex_lock(&tty_mutex);
645 tty = tty_init_dev(ptm_driver, index, 1);
646 mutex_unlock(&tty_mutex);
649 retval = PTR_ERR(tty);
653 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
654 filp->private_data = tty;
655 file_move(filp, &tty->tty_files);
657 retval = devpts_pty_new(inode, tty->link);
661 retval = ptm_driver->ops->open(tty, filp);
665 tty_release_dev(filp);
668 devpts_kill_index(inode, index);
672 static int ptmx_open(struct inode *inode, struct file *filp)
677 ret = __ptmx_open(inode, filp);
682 static struct file_operations ptmx_fops;
684 static void __init unix98_pty_init(void)
686 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
688 panic("Couldn't allocate Unix98 ptm driver");
689 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
691 panic("Couldn't allocate Unix98 pts driver");
693 ptm_driver->owner = THIS_MODULE;
694 ptm_driver->driver_name = "pty_master";
695 ptm_driver->name = "ptm";
696 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
697 ptm_driver->minor_start = 0;
698 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
699 ptm_driver->subtype = PTY_TYPE_MASTER;
700 ptm_driver->init_termios = tty_std_termios;
701 ptm_driver->init_termios.c_iflag = 0;
702 ptm_driver->init_termios.c_oflag = 0;
703 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
704 ptm_driver->init_termios.c_lflag = 0;
705 ptm_driver->init_termios.c_ispeed = 38400;
706 ptm_driver->init_termios.c_ospeed = 38400;
707 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
708 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
709 ptm_driver->other = pts_driver;
710 tty_set_operations(ptm_driver, &ptm_unix98_ops);
712 pts_driver->owner = THIS_MODULE;
713 pts_driver->driver_name = "pty_slave";
714 pts_driver->name = "pts";
715 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
716 pts_driver->minor_start = 0;
717 pts_driver->type = TTY_DRIVER_TYPE_PTY;
718 pts_driver->subtype = PTY_TYPE_SLAVE;
719 pts_driver->init_termios = tty_std_termios;
720 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
721 pts_driver->init_termios.c_ispeed = 38400;
722 pts_driver->init_termios.c_ospeed = 38400;
723 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
724 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
725 pts_driver->other = ptm_driver;
726 tty_set_operations(pts_driver, &pty_unix98_ops);
728 if (tty_register_driver(ptm_driver))
729 panic("Couldn't register Unix98 ptm driver");
730 if (tty_register_driver(pts_driver))
731 panic("Couldn't register Unix98 pts driver");
733 register_sysctl_table(pty_root_table);
735 /* Now create the /dev/ptmx special device */
736 tty_default_fops(&ptmx_fops);
737 ptmx_fops.open = ptmx_open;
739 cdev_init(&ptmx_cdev, &ptmx_fops);
740 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
741 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
742 panic("Couldn't register /dev/ptmx driver\n");
743 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
747 static inline void unix98_pty_init(void) { }
750 static int __init pty_init(void)
756 module_init(pty_init);