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 retval
= tty_init_dev(ptm_driver
, index
, &tty
, 1);
505 mutex_unlock(&tty_mutex
);
510 set_bit(TTY_PTY_LOCK
, &tty
->flags
); /* LOCK THE SLAVE */
511 filp
->private_data
= tty
;
512 file_move(filp
, &tty
->tty_files
);
514 retval
= devpts_pty_new(tty
->link
);
518 retval
= ptm_driver
->ops
->open(tty
, filp
);
522 tty_release_dev(filp
);
525 devpts_kill_index(index
);
529 static int ptmx_open(struct inode
*inode
, struct file
*filp
)
534 ret
= __ptmx_open(inode
, filp
);
539 static struct file_operations ptmx_fops
;
541 static void __init
unix98_pty_init(void)
543 ptm_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
545 panic("Couldn't allocate Unix98 ptm driver");
546 pts_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
548 panic("Couldn't allocate Unix98 pts driver");
550 ptm_driver
->owner
= THIS_MODULE
;
551 ptm_driver
->driver_name
= "pty_master";
552 ptm_driver
->name
= "ptm";
553 ptm_driver
->major
= UNIX98_PTY_MASTER_MAJOR
;
554 ptm_driver
->minor_start
= 0;
555 ptm_driver
->type
= TTY_DRIVER_TYPE_PTY
;
556 ptm_driver
->subtype
= PTY_TYPE_MASTER
;
557 ptm_driver
->init_termios
= tty_std_termios
;
558 ptm_driver
->init_termios
.c_iflag
= 0;
559 ptm_driver
->init_termios
.c_oflag
= 0;
560 ptm_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
561 ptm_driver
->init_termios
.c_lflag
= 0;
562 ptm_driver
->init_termios
.c_ispeed
= 38400;
563 ptm_driver
->init_termios
.c_ospeed
= 38400;
564 ptm_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
565 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
566 ptm_driver
->other
= pts_driver
;
567 tty_set_operations(ptm_driver
, &ptm_unix98_ops
);
569 pts_driver
->owner
= THIS_MODULE
;
570 pts_driver
->driver_name
= "pty_slave";
571 pts_driver
->name
= "pts";
572 pts_driver
->major
= UNIX98_PTY_SLAVE_MAJOR
;
573 pts_driver
->minor_start
= 0;
574 pts_driver
->type
= TTY_DRIVER_TYPE_PTY
;
575 pts_driver
->subtype
= PTY_TYPE_SLAVE
;
576 pts_driver
->init_termios
= tty_std_termios
;
577 pts_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
578 pts_driver
->init_termios
.c_ispeed
= 38400;
579 pts_driver
->init_termios
.c_ospeed
= 38400;
580 pts_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
581 TTY_DRIVER_DYNAMIC_DEV
| TTY_DRIVER_DEVPTS_MEM
;
582 pts_driver
->other
= ptm_driver
;
583 tty_set_operations(pts_driver
, &pty_unix98_ops
);
585 if (tty_register_driver(ptm_driver
))
586 panic("Couldn't register Unix98 ptm driver");
587 if (tty_register_driver(pts_driver
))
588 panic("Couldn't register Unix98 pts driver");
592 pty_table
[1].data
= &ptm_driver
->refcount
;
594 register_sysctl_table(pty_root_table
);
596 /* Now create the /dev/ptmx special device */
597 tty_default_fops(&ptmx_fops
);
598 ptmx_fops
.open
= ptmx_open
;
600 cdev_init(&ptmx_cdev
, &ptmx_fops
);
601 if (cdev_add(&ptmx_cdev
, MKDEV(TTYAUX_MAJOR
, 2), 1) ||
602 register_chrdev_region(MKDEV(TTYAUX_MAJOR
, 2), 1, "/dev/ptmx") < 0)
603 panic("Couldn't register /dev/ptmx driver\n");
604 device_create(tty_class
, NULL
, MKDEV(TTYAUX_MAJOR
, 2), NULL
, "ptmx");
608 static inline void unix98_pty_init(void) { }
611 static int __init
pty_init(void)
617 module_init(pty_init
);