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 <linux/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 static 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 set_bit(TTY_OTHER_CLOSED
, &tty
->link
->flags
);
59 wake_up_interruptible(&tty
->link
->read_wait
);
60 wake_up_interruptible(&tty
->link
->write_wait
);
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
, const unsigned char *buf
, int count
)
108 struct tty_struct
*to
= tty
->link
;
111 if (!to
|| tty
->stopped
)
114 c
= to
->ldisc
.receive_room(to
);
117 to
->ldisc
.receive_buf(to
, buf
, NULL
, c
);
122 static int pty_write_room(struct tty_struct
*tty
)
124 struct tty_struct
*to
= tty
->link
;
126 if (!to
|| tty
->stopped
)
129 return to
->ldisc
.receive_room(to
);
133 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
134 * The chars_in_buffer() value is used by the ldisc select() function
135 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
136 * The pty driver chars_in_buffer() Master/Slave must behave differently:
138 * The Master side needs to allow typed-ahead commands to accumulate
139 * while being canonicalized, so we report "our buffer" as empty until
140 * some threshold is reached, and then report the count. (Any count >
141 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
142 * the count returned must be 0 if no canonical data is available to be
143 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
145 * The Slave side passes all characters in raw mode to the Master side's
146 * buffer where they can be read immediately, so in this case we can
147 * return the true count in the buffer.
149 static int pty_chars_in_buffer(struct tty_struct
*tty
)
151 struct tty_struct
*to
= tty
->link
;
154 /* We should get the line discipline lock for "tty->link" */
155 if (!to
|| !to
->ldisc
.chars_in_buffer
)
158 /* The ldisc must report 0 if no characters available to be read */
159 count
= to
->ldisc
.chars_in_buffer(to
);
161 if (tty
->driver
->subtype
== PTY_TYPE_SLAVE
) return count
;
163 /* Master side driver ... if the other side's read buffer is less than
164 * half full, return 0 to allow writers to proceed; otherwise return
165 * the count. This leaves a comfortable margin to avoid overflow,
166 * and still allows half a buffer's worth of typed-ahead commands.
168 return ((count
< N_TTY_BUF_SIZE
/2) ? 0 : count
);
171 /* Set the lock flag on a pty */
172 static int pty_set_lock(struct tty_struct
*tty
, int __user
* arg
)
175 if (get_user(val
,arg
))
178 set_bit(TTY_PTY_LOCK
, &tty
->flags
);
180 clear_bit(TTY_PTY_LOCK
, &tty
->flags
);
184 static void pty_flush_buffer(struct tty_struct
*tty
)
186 struct tty_struct
*to
= tty
->link
;
191 if (to
->ldisc
.flush_buffer
)
192 to
->ldisc
.flush_buffer(to
);
195 tty
->ctrl_status
|= TIOCPKT_FLUSHWRITE
;
196 wake_up_interruptible(&to
->read_wait
);
200 static int pty_open(struct tty_struct
*tty
, struct file
* filp
)
202 int retval
= -ENODEV
;
204 if (!tty
|| !tty
->link
)
208 if (test_bit(TTY_OTHER_CLOSED
, &tty
->flags
))
210 if (test_bit(TTY_PTY_LOCK
, &tty
->link
->flags
))
212 if (tty
->link
->count
!= 1)
215 clear_bit(TTY_OTHER_CLOSED
, &tty
->link
->flags
);
216 set_bit(TTY_THROTTLED
, &tty
->flags
);
217 set_bit(TTY_DO_WRITE_WAKEUP
, &tty
->flags
);
223 static void pty_set_termios(struct tty_struct
*tty
, struct termios
*old_termios
)
225 tty
->termios
->c_cflag
&= ~(CSIZE
| PARENB
);
226 tty
->termios
->c_cflag
|= (CS8
| CREAD
);
229 static struct tty_operations pty_ops
= {
233 .write_room
= pty_write_room
,
234 .flush_buffer
= pty_flush_buffer
,
235 .chars_in_buffer
= pty_chars_in_buffer
,
236 .unthrottle
= pty_unthrottle
,
237 .set_termios
= pty_set_termios
,
240 /* Traditional BSD devices */
241 #ifdef CONFIG_LEGACY_PTYS
242 static struct tty_driver
*pty_driver
, *pty_slave_driver
;
244 static int pty_bsd_ioctl(struct tty_struct
*tty
, struct file
*file
,
245 unsigned int cmd
, unsigned long arg
)
248 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
249 return pty_set_lock(tty
, (int __user
*) arg
);
254 static void __init
legacy_pty_init(void)
257 pty_driver
= alloc_tty_driver(NR_PTYS
);
259 panic("Couldn't allocate pty driver");
261 pty_slave_driver
= alloc_tty_driver(NR_PTYS
);
262 if (!pty_slave_driver
)
263 panic("Couldn't allocate pty slave driver");
265 pty_driver
->owner
= THIS_MODULE
;
266 pty_driver
->driver_name
= "pty_master";
267 pty_driver
->name
= "pty";
268 pty_driver
->devfs_name
= "pty/m";
269 pty_driver
->major
= PTY_MASTER_MAJOR
;
270 pty_driver
->minor_start
= 0;
271 pty_driver
->type
= TTY_DRIVER_TYPE_PTY
;
272 pty_driver
->subtype
= PTY_TYPE_MASTER
;
273 pty_driver
->init_termios
= tty_std_termios
;
274 pty_driver
->init_termios
.c_iflag
= 0;
275 pty_driver
->init_termios
.c_oflag
= 0;
276 pty_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
277 pty_driver
->init_termios
.c_lflag
= 0;
278 pty_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
;
279 pty_driver
->other
= pty_slave_driver
;
280 tty_set_operations(pty_driver
, &pty_ops
);
281 pty_driver
->ioctl
= pty_bsd_ioctl
;
283 pty_slave_driver
->owner
= THIS_MODULE
;
284 pty_slave_driver
->driver_name
= "pty_slave";
285 pty_slave_driver
->name
= "ttyp";
286 pty_slave_driver
->devfs_name
= "pty/s";
287 pty_slave_driver
->major
= PTY_SLAVE_MAJOR
;
288 pty_slave_driver
->minor_start
= 0;
289 pty_slave_driver
->type
= TTY_DRIVER_TYPE_PTY
;
290 pty_slave_driver
->subtype
= PTY_TYPE_SLAVE
;
291 pty_slave_driver
->init_termios
= tty_std_termios
;
292 pty_slave_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
293 pty_slave_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
|
295 pty_slave_driver
->other
= pty_driver
;
296 tty_set_operations(pty_slave_driver
, &pty_ops
);
298 if (tty_register_driver(pty_driver
))
299 panic("Couldn't register pty driver");
300 if (tty_register_driver(pty_slave_driver
))
301 panic("Couldn't register pty slave driver");
304 static inline void legacy_pty_init(void) { }
308 #ifdef CONFIG_UNIX98_PTYS
310 * sysctl support for setting limits on the number of Unix98 ptys allocated.
311 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
313 int pty_limit
= NR_UNIX98_PTY_DEFAULT
;
314 static int pty_limit_min
= 0;
315 static int pty_limit_max
= NR_UNIX98_PTY_MAX
;
317 ctl_table pty_table
[] = {
321 .maxlen
= sizeof(int),
324 .proc_handler
= &proc_dointvec_minmax
,
325 .strategy
= &sysctl_intvec
,
326 .extra1
= &pty_limit_min
,
327 .extra2
= &pty_limit_max
,
331 .maxlen
= sizeof(int),
333 .proc_handler
= &proc_dointvec
,
339 static int pty_unix98_ioctl(struct tty_struct
*tty
, struct file
*file
,
340 unsigned int cmd
, unsigned long arg
)
343 case TIOCSPTLCK
: /* Set PT Lock (disallow slave open) */
344 return pty_set_lock(tty
, (int __user
*)arg
);
345 case TIOCGPTN
: /* Get PT Number */
346 return put_user(tty
->index
, (unsigned int __user
*)arg
);
352 static void __init
unix98_pty_init(void)
355 ptm_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
357 panic("Couldn't allocate Unix98 ptm driver");
358 pts_driver
= alloc_tty_driver(NR_UNIX98_PTY_MAX
);
360 panic("Couldn't allocate Unix98 pts driver");
362 ptm_driver
->owner
= THIS_MODULE
;
363 ptm_driver
->driver_name
= "pty_master";
364 ptm_driver
->name
= "ptm";
365 ptm_driver
->major
= UNIX98_PTY_MASTER_MAJOR
;
366 ptm_driver
->minor_start
= 0;
367 ptm_driver
->type
= TTY_DRIVER_TYPE_PTY
;
368 ptm_driver
->subtype
= PTY_TYPE_MASTER
;
369 ptm_driver
->init_termios
= tty_std_termios
;
370 ptm_driver
->init_termios
.c_iflag
= 0;
371 ptm_driver
->init_termios
.c_oflag
= 0;
372 ptm_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
373 ptm_driver
->init_termios
.c_lflag
= 0;
374 ptm_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
375 TTY_DRIVER_NO_DEVFS
| TTY_DRIVER_DEVPTS_MEM
;
376 ptm_driver
->other
= pts_driver
;
377 tty_set_operations(ptm_driver
, &pty_ops
);
378 ptm_driver
->ioctl
= pty_unix98_ioctl
;
380 pts_driver
->owner
= THIS_MODULE
;
381 pts_driver
->driver_name
= "pty_slave";
382 pts_driver
->name
= "pts";
383 pts_driver
->major
= UNIX98_PTY_SLAVE_MAJOR
;
384 pts_driver
->minor_start
= 0;
385 pts_driver
->type
= TTY_DRIVER_TYPE_PTY
;
386 pts_driver
->subtype
= PTY_TYPE_SLAVE
;
387 pts_driver
->init_termios
= tty_std_termios
;
388 pts_driver
->init_termios
.c_cflag
= B38400
| CS8
| CREAD
;
389 pts_driver
->flags
= TTY_DRIVER_RESET_TERMIOS
| TTY_DRIVER_REAL_RAW
|
390 TTY_DRIVER_NO_DEVFS
| TTY_DRIVER_DEVPTS_MEM
;
391 pts_driver
->other
= ptm_driver
;
392 tty_set_operations(pts_driver
, &pty_ops
);
394 if (tty_register_driver(ptm_driver
))
395 panic("Couldn't register Unix98 ptm driver");
396 if (tty_register_driver(pts_driver
))
397 panic("Couldn't register Unix98 pts driver");
399 pty_table
[1].data
= &ptm_driver
->refcount
;
402 static inline void unix98_pty_init(void) { }
405 static int __init
pty_init(void)
411 module_init(pty_init
);