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>
14 #include <linux/module.h> /* For EXPORT_SYMBOL */
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>
28 #include <asm/uaccess.h>
29 #include <asm/system.h>
30 #include <linux/bitops.h>
31 #include <linux/devpts_fs.h>
33 /* These are global because they are accessed in tty_io.c */
34 #ifdef CONFIG_UNIX98_PTYS
35 struct tty_driver *ptm_driver;
36 static struct tty_driver *pts_driver;
39 static void pty_close(struct tty_struct * tty, struct file * filp)
43 if (tty->driver->subtype == PTY_TYPE_MASTER) {
45 printk("master pty_close: count = %d!!\n", tty->count);
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->index);
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, int count)
106 struct tty_struct *to = tty->link;
109 if (!to || tty->stopped)
112 c = to->receive_room;
115 to->ldisc.ops->receive_buf(to, buf, NULL, c);
120 static int pty_write_room(struct tty_struct *tty)
122 struct tty_struct *to = tty->link;
124 if (!to || tty->stopped)
127 return to->receive_room;
131 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
132 * The chars_in_buffer() value is used by the ldisc select() function
133 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
134 * The pty driver chars_in_buffer() Master/Slave must behave differently:
136 * The Master side needs to allow typed-ahead commands to accumulate
137 * while being canonicalized, so we report "our buffer" as empty until
138 * some threshold is reached, and then report the count. (Any count >
139 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
140 * the count returned must be 0 if no canonical data is available to be
141 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
143 * The Slave side passes all characters in raw mode to the Master side's
144 * buffer where they can be read immediately, so in this case we can
145 * return the true count in the buffer.
147 static int pty_chars_in_buffer(struct tty_struct *tty)
149 struct tty_struct *to = tty->link;
152 /* We should get the line discipline lock for "tty->link" */
153 if (!to || !to->ldisc.ops->chars_in_buffer)
156 /* The ldisc must report 0 if no characters available to be read */
157 count = to->ldisc.ops->chars_in_buffer(to);
159 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
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);
218 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
224 static void pty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
226 tty->termios->c_cflag &= ~(CSIZE | PARENB);
227 tty->termios->c_cflag |= (CS8 | CREAD);
230 static const struct tty_operations pty_ops = {
234 .write_room = pty_write_room,
235 .flush_buffer = pty_flush_buffer,
236 .chars_in_buffer = pty_chars_in_buffer,
237 .unthrottle = pty_unthrottle,
238 .set_termios = pty_set_termios,
241 /* Traditional BSD devices */
242 #ifdef CONFIG_LEGACY_PTYS
243 static struct tty_driver *pty_driver, *pty_slave_driver;
245 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
246 unsigned int cmd, unsigned long arg)
249 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
250 return pty_set_lock(tty, (int __user *) arg);
255 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
256 module_param(legacy_count, int, 0);
258 static const struct tty_operations pty_ops_bsd = {
262 .write_room = pty_write_room,
263 .flush_buffer = pty_flush_buffer,
264 .chars_in_buffer = pty_chars_in_buffer,
265 .unthrottle = pty_unthrottle,
266 .set_termios = pty_set_termios,
267 .ioctl = pty_bsd_ioctl,
270 static void __init legacy_pty_init(void)
272 if (legacy_count <= 0)
275 pty_driver = alloc_tty_driver(legacy_count);
277 panic("Couldn't allocate pty driver");
279 pty_slave_driver = alloc_tty_driver(legacy_count);
280 if (!pty_slave_driver)
281 panic("Couldn't allocate pty slave driver");
283 pty_driver->owner = THIS_MODULE;
284 pty_driver->driver_name = "pty_master";
285 pty_driver->name = "pty";
286 pty_driver->major = PTY_MASTER_MAJOR;
287 pty_driver->minor_start = 0;
288 pty_driver->type = TTY_DRIVER_TYPE_PTY;
289 pty_driver->subtype = PTY_TYPE_MASTER;
290 pty_driver->init_termios = tty_std_termios;
291 pty_driver->init_termios.c_iflag = 0;
292 pty_driver->init_termios.c_oflag = 0;
293 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
294 pty_driver->init_termios.c_lflag = 0;
295 pty_driver->init_termios.c_ispeed = 38400;
296 pty_driver->init_termios.c_ospeed = 38400;
297 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
298 pty_driver->other = pty_slave_driver;
299 tty_set_operations(pty_driver, &pty_ops);
301 pty_slave_driver->owner = THIS_MODULE;
302 pty_slave_driver->driver_name = "pty_slave";
303 pty_slave_driver->name = "ttyp";
304 pty_slave_driver->major = PTY_SLAVE_MAJOR;
305 pty_slave_driver->minor_start = 0;
306 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
307 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
308 pty_slave_driver->init_termios = tty_std_termios;
309 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
310 pty_slave_driver->init_termios.c_ispeed = 38400;
311 pty_slave_driver->init_termios.c_ospeed = 38400;
312 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
314 pty_slave_driver->other = pty_driver;
315 tty_set_operations(pty_slave_driver, &pty_ops);
317 if (tty_register_driver(pty_driver))
318 panic("Couldn't register pty driver");
319 if (tty_register_driver(pty_slave_driver))
320 panic("Couldn't register pty slave driver");
323 static inline void legacy_pty_init(void) { }
327 #ifdef CONFIG_UNIX98_PTYS
329 * sysctl support for setting limits on the number of Unix98 ptys allocated.
330 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
332 int pty_limit = NR_UNIX98_PTY_DEFAULT;
333 static int pty_limit_min = 0;
334 static int pty_limit_max = NR_UNIX98_PTY_MAX;
336 static struct cdev ptmx_cdev;
338 static struct ctl_table pty_table[] = {
342 .maxlen = sizeof(int),
345 .proc_handler = &proc_dointvec_minmax,
346 .strategy = &sysctl_intvec,
347 .extra1 = &pty_limit_min,
348 .extra2 = &pty_limit_max,
352 .maxlen = sizeof(int),
354 .proc_handler = &proc_dointvec,
360 static struct ctl_table pty_kern_table[] = {
362 .ctl_name = KERN_PTY,
370 static struct ctl_table pty_root_table[] = {
372 .ctl_name = CTL_KERN,
373 .procname = "kernel",
375 .child = pty_kern_table,
381 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
382 unsigned int cmd, unsigned long arg)
385 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
386 return pty_set_lock(tty, (int __user *)arg);
387 case TIOCGPTN: /* Get PT Number */
388 return put_user(tty->index, (unsigned int __user *)arg);
395 * ptm_unix98_lookup - find a pty master
396 * @driver: ptm driver
399 * Look up a pty master device. Called under the tty_mutex for now.
400 * This provides our locking.
403 static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver, int idx)
405 struct tty_struct *tty = devpts_get_tty(idx);
412 * pts_unix98_lookup - find a pty slave
413 * @driver: pts driver
416 * Look up a pty master device. Called under the tty_mutex for now.
417 * This provides our locking.
420 static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver, int idx)
422 struct tty_struct *tty = devpts_get_tty(idx);
423 /* Master must be open before slave */
425 return ERR_PTR(-EIO);
429 static void pty_shutdown(struct tty_struct *tty)
431 /* We have our own method as we don't use the tty index */
433 kfree(tty->termios_locked);
436 /* We have no need to install and remove our tty objects as devpts does all
439 static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
444 static void pty_remove(struct tty_driver *driver, struct tty_struct *tty)
448 static const struct tty_operations ptm_unix98_ops = {
449 .lookup = ptm_unix98_lookup,
450 .install = pty_install,
451 .remove = pty_remove,
455 .write_room = pty_write_room,
456 .flush_buffer = pty_flush_buffer,
457 .chars_in_buffer = pty_chars_in_buffer,
458 .unthrottle = pty_unthrottle,
459 .set_termios = pty_set_termios,
460 .ioctl = pty_unix98_ioctl,
461 .shutdown = pty_shutdown
464 static const struct tty_operations pty_unix98_ops = {
465 .lookup = pts_unix98_lookup,
466 .install = pty_install,
467 .remove = pty_remove,
471 .write_room = pty_write_room,
472 .flush_buffer = pty_flush_buffer,
473 .chars_in_buffer = pty_chars_in_buffer,
474 .unthrottle = pty_unthrottle,
475 .set_termios = pty_set_termios,
479 * ptmx_open - open a unix 98 pty master
480 * @inode: inode of device file
481 * @filp: file pointer to tty
483 * Allocate a unix98 pty master device from the ptmx driver.
485 * Locking: tty_mutex protects the init_dev work. tty->count should
487 * allocated_ptys_lock handles the list of free pty numbers
490 static int __ptmx_open(struct inode *inode, struct file *filp)
492 struct tty_struct *tty;
496 nonseekable_open(inode, filp);
498 /* find a device that is not in use. */
499 index = devpts_new_index();
503 mutex_lock(&tty_mutex);
504 tty = tty_init_dev(ptm_driver, index, 1);
505 mutex_unlock(&tty_mutex);
508 retval = PTR_ERR(tty);
512 set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
513 filp->private_data = tty;
514 file_move(filp, &tty->tty_files);
516 retval = devpts_pty_new(tty->link);
520 retval = ptm_driver->ops->open(tty, filp);
524 tty_release_dev(filp);
527 devpts_kill_index(index);
531 static int ptmx_open(struct inode *inode, struct file *filp)
536 ret = __ptmx_open(inode, filp);
541 static struct file_operations ptmx_fops;
543 static void __init unix98_pty_init(void)
545 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
547 panic("Couldn't allocate Unix98 ptm driver");
548 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
550 panic("Couldn't allocate Unix98 pts driver");
552 ptm_driver->owner = THIS_MODULE;
553 ptm_driver->driver_name = "pty_master";
554 ptm_driver->name = "ptm";
555 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
556 ptm_driver->minor_start = 0;
557 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
558 ptm_driver->subtype = PTY_TYPE_MASTER;
559 ptm_driver->init_termios = tty_std_termios;
560 ptm_driver->init_termios.c_iflag = 0;
561 ptm_driver->init_termios.c_oflag = 0;
562 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
563 ptm_driver->init_termios.c_lflag = 0;
564 ptm_driver->init_termios.c_ispeed = 38400;
565 ptm_driver->init_termios.c_ospeed = 38400;
566 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
567 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
568 ptm_driver->other = pts_driver;
569 tty_set_operations(ptm_driver, &ptm_unix98_ops);
571 pts_driver->owner = THIS_MODULE;
572 pts_driver->driver_name = "pty_slave";
573 pts_driver->name = "pts";
574 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
575 pts_driver->minor_start = 0;
576 pts_driver->type = TTY_DRIVER_TYPE_PTY;
577 pts_driver->subtype = PTY_TYPE_SLAVE;
578 pts_driver->init_termios = tty_std_termios;
579 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
580 pts_driver->init_termios.c_ispeed = 38400;
581 pts_driver->init_termios.c_ospeed = 38400;
582 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
583 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
584 pts_driver->other = ptm_driver;
585 tty_set_operations(pts_driver, &pty_unix98_ops);
587 if (tty_register_driver(ptm_driver))
588 panic("Couldn't register Unix98 ptm driver");
589 if (tty_register_driver(pts_driver))
590 panic("Couldn't register Unix98 pts driver");
594 pty_table[1].data = &ptm_driver->refcount;
596 register_sysctl_table(pty_root_table);
598 /* Now create the /dev/ptmx special device */
599 tty_default_fops(&ptmx_fops);
600 ptmx_fops.open = ptmx_open;
602 cdev_init(&ptmx_cdev, &ptmx_fops);
603 if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
604 register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
605 panic("Couldn't register /dev/ptmx driver\n");
606 device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
610 static inline void unix98_pty_init(void) { }
613 static int __init pty_init(void)
619 module_init(pty_init);