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/config.h>
15 #include <linux/module.h> /* For EXPORT_SYMBOL */
17 #include <linux/errno.h>
18 #include <linux/sched.h>
19 #include <linux/interrupt.h>
20 #include <linux/tty.h>
21 #include <linux/tty_flip.h>
22 #include <linux/fcntl.h>
23 #include <linux/string.h>
24 #include <linux/major.h>
26 #include <linux/init.h>
27 #include <linux/devfs_fs_kernel.h>
28 #include <linux/sysctl.h>
30 #include <asm/uaccess.h>
31 #include <asm/system.h>
32 #include <asm/bitops.h>
33 #include <linux/devpts_fs.h>
35 /* These are global because they are accessed in tty_io.c */
36 #ifdef CONFIG_UNIX98_PTYS
37 struct tty_driver *ptm_driver;
38 struct tty_driver *pts_driver;
41 static void pty_close(struct tty_struct * tty, struct file * filp)
45 if (tty->driver->subtype == PTY_TYPE_MASTER) {
47 printk("master pty_close: count = %d!!\n", tty->count);
52 wake_up_interruptible(&tty->read_wait);
53 wake_up_interruptible(&tty->write_wait);
57 tty->link->packet = 0;
58 wake_up_interruptible(&tty->link->read_wait);
59 wake_up_interruptible(&tty->link->write_wait);
60 set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
61 if (tty->driver->subtype == PTY_TYPE_MASTER) {
62 set_bit(TTY_OTHER_CLOSED, &tty->flags);
63 #ifdef CONFIG_UNIX98_PTYS
64 if (tty->driver == ptm_driver)
65 devpts_pty_kill(tty->index);
67 tty_vhangup(tty->link);
72 * The unthrottle routine is called by the line discipline to signal
73 * that it can receive more characters. For PTY's, the TTY_THROTTLED
74 * flag is always set, to force the line discipline to always call the
75 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
76 * characters in the queue. This is necessary since each time this
77 * happens, we need to wake up any sleeping processes that could be
78 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
79 * for the pty buffer to be drained.
81 static void pty_unthrottle(struct tty_struct * tty)
83 struct tty_struct *o_tty = tty->link;
89 set_bit(TTY_THROTTLED, &tty->flags);
93 * WSH 05/24/97: modified to
94 * (1) use space in tty->flip instead of a shared temp buffer
95 * The flip buffers aren't being used for a pty, so there's lots
96 * of space available. The buffer is protected by a per-pty
97 * semaphore that should almost never come under contention.
98 * (2) avoid redundant copying for cases where count >> receive_room
99 * N.B. Calls from user space may now return an error code instead of
102 * FIXME: Our pty_write method is called with our ldisc lock held but
103 * not our partners. We can't just take the other one blindly without
104 * risking deadlocks. There is also the small matter of TTY_DONT_FLIP
106 static int pty_write(struct tty_struct * tty, int from_user,
107 const unsigned char *buf, int count)
109 struct tty_struct *to = tty->link;
113 if (!to || tty->stopped)
117 down(&tty->flip.pty_sem);
118 temp_buffer = &tty->flip.char_buf[0];
120 /* check space so we don't copy needlessly */
121 n = to->ldisc.receive_room(to);
126 n = min(n, PTY_BUF_SIZE);
127 n -= copy_from_user(temp_buffer, buf, n);
134 /* check again in case the buffer filled up */
135 room = to->ldisc.receive_room(to);
142 to->ldisc.receive_buf(to, temp_buffer, NULL, n);
144 up(&tty->flip.pty_sem);
146 c = to->ldisc.receive_room(to);
149 to->ldisc.receive_buf(to, buf, NULL, c);
155 static int pty_write_room(struct tty_struct *tty)
157 struct tty_struct *to = tty->link;
159 if (!to || tty->stopped)
162 return to->ldisc.receive_room(to);
166 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
167 * The chars_in_buffer() value is used by the ldisc select() function
168 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
169 * The pty driver chars_in_buffer() Master/Slave must behave differently:
171 * The Master side needs to allow typed-ahead commands to accumulate
172 * while being canonicalized, so we report "our buffer" as empty until
173 * some threshold is reached, and then report the count. (Any count >
174 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
175 * the count returned must be 0 if no canonical data is available to be
176 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
178 * The Slave side passes all characters in raw mode to the Master side's
179 * buffer where they can be read immediately, so in this case we can
180 * return the true count in the buffer.
182 static int pty_chars_in_buffer(struct tty_struct *tty)
184 struct tty_struct *to = tty->link;
187 if (!to || !to->ldisc.chars_in_buffer)
190 /* The ldisc must report 0 if no characters available to be read */
191 count = to->ldisc.chars_in_buffer(to);
193 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
195 /* Master side driver ... if the other side's read buffer is less than
196 * half full, return 0 to allow writers to proceed; otherwise return
197 * the count. This leaves a comfortable margin to avoid overflow,
198 * and still allows half a buffer's worth of typed-ahead commands.
200 return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
203 /* Set the lock flag on a pty */
204 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
207 if (get_user(val,arg))
210 set_bit(TTY_PTY_LOCK, &tty->flags);
212 clear_bit(TTY_PTY_LOCK, &tty->flags);
216 static void pty_flush_buffer(struct tty_struct *tty)
218 struct tty_struct *to = tty->link;
223 if (to->ldisc.flush_buffer)
224 to->ldisc.flush_buffer(to);
227 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
228 wake_up_interruptible(&to->read_wait);
232 static int pty_open(struct tty_struct *tty, struct file * filp)
234 int retval = -ENODEV;
236 if (!tty || !tty->link)
240 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
242 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
244 if (tty->link->count != 1)
247 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
248 set_bit(TTY_THROTTLED, &tty->flags);
249 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
255 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
257 tty->termios->c_cflag &= ~(CSIZE | PARENB);
258 tty->termios->c_cflag |= (CS8 | CREAD);
261 static struct tty_operations pty_ops = {
265 .write_room = pty_write_room,
266 .flush_buffer = pty_flush_buffer,
267 .chars_in_buffer = pty_chars_in_buffer,
268 .unthrottle = pty_unthrottle,
269 .set_termios = pty_set_termios,
272 /* Traditional BSD devices */
273 #ifdef CONFIG_LEGACY_PTYS
274 static struct tty_driver *pty_driver, *pty_slave_driver;
276 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
277 unsigned int cmd, unsigned long arg)
280 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
281 return pty_set_lock(tty, (int __user *) arg);
286 static void __init legacy_pty_init(void)
289 pty_driver = alloc_tty_driver(NR_PTYS);
291 panic("Couldn't allocate pty driver");
293 pty_slave_driver = alloc_tty_driver(NR_PTYS);
294 if (!pty_slave_driver)
295 panic("Couldn't allocate pty slave driver");
297 pty_driver->owner = THIS_MODULE;
298 pty_driver->driver_name = "pty_master";
299 pty_driver->name = "pty";
300 pty_driver->devfs_name = "pty/m";
301 pty_driver->major = PTY_MASTER_MAJOR;
302 pty_driver->minor_start = 0;
303 pty_driver->type = TTY_DRIVER_TYPE_PTY;
304 pty_driver->subtype = PTY_TYPE_MASTER;
305 pty_driver->init_termios = tty_std_termios;
306 pty_driver->init_termios.c_iflag = 0;
307 pty_driver->init_termios.c_oflag = 0;
308 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
309 pty_driver->init_termios.c_lflag = 0;
310 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
311 pty_driver->other = pty_slave_driver;
312 tty_set_operations(pty_driver, &pty_ops);
313 pty_driver->ioctl = pty_bsd_ioctl;
315 pty_slave_driver->owner = THIS_MODULE;
316 pty_slave_driver->driver_name = "pty_slave";
317 pty_slave_driver->name = "ttyp";
318 pty_slave_driver->devfs_name = "pty/s";
319 pty_slave_driver->major = PTY_SLAVE_MAJOR;
320 pty_slave_driver->minor_start = 0;
321 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
322 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
323 pty_slave_driver->init_termios = tty_std_termios;
324 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
325 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
327 pty_slave_driver->other = pty_driver;
328 tty_set_operations(pty_slave_driver, &pty_ops);
330 if (tty_register_driver(pty_driver))
331 panic("Couldn't register pty driver");
332 if (tty_register_driver(pty_slave_driver))
333 panic("Couldn't register pty slave driver");
336 static inline void legacy_pty_init(void) { }
340 #ifdef CONFIG_UNIX98_PTYS
342 * sysctl support for setting limits on the number of Unix98 ptys allocated.
343 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
345 int pty_limit = NR_UNIX98_PTY_DEFAULT;
346 static int pty_limit_min = 0;
347 static int pty_limit_max = NR_UNIX98_PTY_MAX;
349 ctl_table pty_table[] = {
353 .maxlen = sizeof(int),
356 .proc_handler = &proc_dointvec_minmax,
357 .strategy = &sysctl_intvec,
358 .extra1 = &pty_limit_min,
359 .extra2 = &pty_limit_max,
363 .maxlen = sizeof(int),
365 .proc_handler = &proc_dointvec,
371 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
372 unsigned int cmd, unsigned long arg)
375 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
376 return pty_set_lock(tty, (int __user *)arg);
377 case TIOCGPTN: /* Get PT Number */
378 return put_user(tty->index, (unsigned int __user *)arg);
384 static void __init unix98_pty_init(void)
387 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
389 panic("Couldn't allocate Unix98 ptm driver");
390 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
392 panic("Couldn't allocate Unix98 pts driver");
394 ptm_driver->owner = THIS_MODULE;
395 ptm_driver->driver_name = "pty_master";
396 ptm_driver->name = "ptm";
397 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
398 ptm_driver->minor_start = 0;
399 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
400 ptm_driver->subtype = PTY_TYPE_MASTER;
401 ptm_driver->init_termios = tty_std_termios;
402 ptm_driver->init_termios.c_iflag = 0;
403 ptm_driver->init_termios.c_oflag = 0;
404 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
405 ptm_driver->init_termios.c_lflag = 0;
406 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
407 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
408 ptm_driver->other = pts_driver;
409 tty_set_operations(ptm_driver, &pty_ops);
410 ptm_driver->ioctl = pty_unix98_ioctl;
412 pts_driver->owner = THIS_MODULE;
413 pts_driver->driver_name = "pty_slave";
414 pts_driver->name = "pts";
415 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
416 pts_driver->minor_start = 0;
417 pts_driver->type = TTY_DRIVER_TYPE_PTY;
418 pts_driver->subtype = PTY_TYPE_SLAVE;
419 pts_driver->init_termios = tty_std_termios;
420 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
421 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
422 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
423 pts_driver->other = ptm_driver;
424 tty_set_operations(pts_driver, &pty_ops);
426 if (tty_register_driver(ptm_driver))
427 panic("Couldn't register Unix98 ptm driver");
428 if (tty_register_driver(pts_driver))
429 panic("Couldn't register Unix98 pts driver");
431 pty_table[1].data = &ptm_driver->refcount;
434 static inline void unix98_pty_init(void) { }
437 static int __init pty_init(void)
443 module_init(pty_init);