blob: de14aea34e11f215765c8b718efe65ff595e795a [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/drivers/char/pty.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
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>
10 *
11 *
12 */
13
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include <linux/module.h> /* For EXPORT_SYMBOL */
15
16#include <linux/errno.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070017#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>
23#include <linux/mm.h>
24#include <linux/init.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070025#include <linux/sysctl.h>
26
27#include <asm/uaccess.h>
28#include <asm/system.h>
29#include <linux/bitops.h>
30#include <linux/devpts_fs.h>
31
32/* These are global because they are accessed in tty_io.c */
33#ifdef CONFIG_UNIX98_PTYS
34struct tty_driver *ptm_driver;
35static struct tty_driver *pts_driver;
36#endif
37
38static void pty_close(struct tty_struct * tty, struct file * filp)
39{
40 if (!tty)
41 return;
42 if (tty->driver->subtype == PTY_TYPE_MASTER) {
43 if (tty->count > 1)
44 printk("master pty_close: count = %d!!\n", tty->count);
45 } else {
46 if (tty->count > 2)
47 return;
48 }
49 wake_up_interruptible(&tty->read_wait);
50 wake_up_interruptible(&tty->write_wait);
51 tty->packet = 0;
52 if (!tty->link)
53 return;
54 tty->link->packet = 0;
55 set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
56 wake_up_interruptible(&tty->link->read_wait);
57 wake_up_interruptible(&tty->link->write_wait);
58 if (tty->driver->subtype == PTY_TYPE_MASTER) {
59 set_bit(TTY_OTHER_CLOSED, &tty->flags);
60#ifdef CONFIG_UNIX98_PTYS
61 if (tty->driver == ptm_driver)
62 devpts_pty_kill(tty->index);
63#endif
64 tty_vhangup(tty->link);
65 }
66}
67
68/*
69 * The unthrottle routine is called by the line discipline to signal
70 * that it can receive more characters. For PTY's, the TTY_THROTTLED
71 * flag is always set, to force the line discipline to always call the
72 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE
73 * characters in the queue. This is necessary since each time this
74 * happens, we need to wake up any sleeping processes that could be
75 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
76 * for the pty buffer to be drained.
77 */
78static void pty_unthrottle(struct tty_struct * tty)
79{
80 struct tty_struct *o_tty = tty->link;
81
82 if (!o_tty)
83 return;
84
85 tty_wakeup(o_tty);
86 set_bit(TTY_THROTTLED, &tty->flags);
87}
88
89/*
90 * WSH 05/24/97: modified to
91 * (1) use space in tty->flip instead of a shared temp buffer
92 * The flip buffers aren't being used for a pty, so there's lots
93 * of space available. The buffer is protected by a per-pty
94 * semaphore that should almost never come under contention.
95 * (2) avoid redundant copying for cases where count >> receive_room
96 * N.B. Calls from user space may now return an error code instead of
97 * a count.
98 *
99 * FIXME: Our pty_write method is called with our ldisc lock held but
100 * not our partners. We can't just take the other one blindly without
Paul Fulghum817d6d32006-06-28 04:26:47 -0700101 * risking deadlocks.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 */
103static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
104{
105 struct tty_struct *to = tty->link;
106 int c;
107
108 if (!to || tty->stopped)
109 return 0;
110
Alan Cox33f0f882006-01-09 20:54:13 -0800111 c = to->receive_room;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 if (c > count)
113 c = count;
114 to->ldisc.receive_buf(to, buf, NULL, c);
115
116 return c;
117}
118
119static int pty_write_room(struct tty_struct *tty)
120{
121 struct tty_struct *to = tty->link;
122
123 if (!to || tty->stopped)
124 return 0;
125
Alan Cox33f0f882006-01-09 20:54:13 -0800126 return to->receive_room;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127}
128
129/*
130 * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior
131 * The chars_in_buffer() value is used by the ldisc select() function
132 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
133 * The pty driver chars_in_buffer() Master/Slave must behave differently:
134 *
135 * The Master side needs to allow typed-ahead commands to accumulate
136 * while being canonicalized, so we report "our buffer" as empty until
137 * some threshold is reached, and then report the count. (Any count >
138 * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock
139 * the count returned must be 0 if no canonical data is available to be
140 * read. (The N_TTY ldisc.chars_in_buffer now knows this.)
141 *
142 * The Slave side passes all characters in raw mode to the Master side's
143 * buffer where they can be read immediately, so in this case we can
144 * return the true count in the buffer.
145 */
146static int pty_chars_in_buffer(struct tty_struct *tty)
147{
148 struct tty_struct *to = tty->link;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 int count;
150
151 /* We should get the line discipline lock for "tty->link" */
Jason Baronff55fe22005-09-09 13:01:57 -0700152 if (!to || !to->ldisc.chars_in_buffer)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 return 0;
154
155 /* The ldisc must report 0 if no characters available to be read */
Jason Baronff55fe22005-09-09 13:01:57 -0700156 count = to->ldisc.chars_in_buffer(to);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157
158 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
159
160 /* Master side driver ... if the other side's read buffer is less than
161 * half full, return 0 to allow writers to proceed; otherwise return
162 * the count. This leaves a comfortable margin to avoid overflow,
163 * and still allows half a buffer's worth of typed-ahead commands.
164 */
165 return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
166}
167
168/* Set the lock flag on a pty */
169static int pty_set_lock(struct tty_struct *tty, int __user * arg)
170{
171 int val;
172 if (get_user(val,arg))
173 return -EFAULT;
174 if (val)
175 set_bit(TTY_PTY_LOCK, &tty->flags);
176 else
177 clear_bit(TTY_PTY_LOCK, &tty->flags);
178 return 0;
179}
180
181static void pty_flush_buffer(struct tty_struct *tty)
182{
183 struct tty_struct *to = tty->link;
184
185 if (!to)
186 return;
187
188 if (to->ldisc.flush_buffer)
189 to->ldisc.flush_buffer(to);
190
191 if (to->packet) {
192 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
193 wake_up_interruptible(&to->read_wait);
194 }
195}
196
197static int pty_open(struct tty_struct *tty, struct file * filp)
198{
199 int retval = -ENODEV;
200
201 if (!tty || !tty->link)
202 goto out;
203
204 retval = -EIO;
205 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
206 goto out;
207 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
208 goto out;
209 if (tty->link->count != 1)
210 goto out;
211
212 clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
213 set_bit(TTY_THROTTLED, &tty->flags);
214 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
215 retval = 0;
216out:
217 return retval;
218}
219
Alan Cox606d0992006-12-08 02:38:45 -0800220static void pty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221{
222 tty->termios->c_cflag &= ~(CSIZE | PARENB);
223 tty->termios->c_cflag |= (CS8 | CREAD);
224}
225
Jeff Dikeb68e31d2006-10-02 02:17:18 -0700226static const struct tty_operations pty_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 .open = pty_open,
228 .close = pty_close,
229 .write = pty_write,
230 .write_room = pty_write_room,
231 .flush_buffer = pty_flush_buffer,
232 .chars_in_buffer = pty_chars_in_buffer,
233 .unthrottle = pty_unthrottle,
234 .set_termios = pty_set_termios,
235};
236
237/* Traditional BSD devices */
238#ifdef CONFIG_LEGACY_PTYS
239static struct tty_driver *pty_driver, *pty_slave_driver;
240
241static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
242 unsigned int cmd, unsigned long arg)
243{
244 switch (cmd) {
245 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
246 return pty_set_lock(tty, (int __user *) arg);
247 }
248 return -ENOIOCTLCMD;
249}
250
251static void __init legacy_pty_init(void)
252{
253
254 pty_driver = alloc_tty_driver(NR_PTYS);
255 if (!pty_driver)
256 panic("Couldn't allocate pty driver");
257
258 pty_slave_driver = alloc_tty_driver(NR_PTYS);
259 if (!pty_slave_driver)
260 panic("Couldn't allocate pty slave driver");
261
262 pty_driver->owner = THIS_MODULE;
263 pty_driver->driver_name = "pty_master";
264 pty_driver->name = "pty";
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 pty_driver->major = PTY_MASTER_MAJOR;
266 pty_driver->minor_start = 0;
267 pty_driver->type = TTY_DRIVER_TYPE_PTY;
268 pty_driver->subtype = PTY_TYPE_MASTER;
269 pty_driver->init_termios = tty_std_termios;
270 pty_driver->init_termios.c_iflag = 0;
271 pty_driver->init_termios.c_oflag = 0;
272 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
273 pty_driver->init_termios.c_lflag = 0;
Alan Cox606d0992006-12-08 02:38:45 -0800274 pty_driver->init_termios.c_ispeed = 38400;
275 pty_driver->init_termios.c_ospeed = 38400;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
277 pty_driver->other = pty_slave_driver;
278 tty_set_operations(pty_driver, &pty_ops);
279 pty_driver->ioctl = pty_bsd_ioctl;
280
281 pty_slave_driver->owner = THIS_MODULE;
282 pty_slave_driver->driver_name = "pty_slave";
283 pty_slave_driver->name = "ttyp";
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284 pty_slave_driver->major = PTY_SLAVE_MAJOR;
285 pty_slave_driver->minor_start = 0;
286 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
287 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
288 pty_slave_driver->init_termios = tty_std_termios;
289 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
Alan Cox606d0992006-12-08 02:38:45 -0800290 pty_slave_driver->init_termios.c_ispeed = 38400;
291 pty_slave_driver->init_termios.c_ospeed = 38400;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
293 TTY_DRIVER_REAL_RAW;
294 pty_slave_driver->other = pty_driver;
295 tty_set_operations(pty_slave_driver, &pty_ops);
296
297 if (tty_register_driver(pty_driver))
298 panic("Couldn't register pty driver");
299 if (tty_register_driver(pty_slave_driver))
300 panic("Couldn't register pty slave driver");
301}
302#else
303static inline void legacy_pty_init(void) { }
304#endif
305
306/* Unix98 devices */
307#ifdef CONFIG_UNIX98_PTYS
308/*
309 * sysctl support for setting limits on the number of Unix98 ptys allocated.
310 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
311 */
312int pty_limit = NR_UNIX98_PTY_DEFAULT;
313static int pty_limit_min = 0;
314static int pty_limit_max = NR_UNIX98_PTY_MAX;
315
316ctl_table pty_table[] = {
317 {
318 .ctl_name = PTY_MAX,
319 .procname = "max",
320 .maxlen = sizeof(int),
321 .mode = 0644,
322 .data = &pty_limit,
323 .proc_handler = &proc_dointvec_minmax,
324 .strategy = &sysctl_intvec,
325 .extra1 = &pty_limit_min,
326 .extra2 = &pty_limit_max,
327 }, {
328 .ctl_name = PTY_NR,
329 .procname = "nr",
330 .maxlen = sizeof(int),
331 .mode = 0444,
332 .proc_handler = &proc_dointvec,
333 }, {
334 .ctl_name = 0
335 }
336};
337
338static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
339 unsigned int cmd, unsigned long arg)
340{
341 switch (cmd) {
342 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
343 return pty_set_lock(tty, (int __user *)arg);
344 case TIOCGPTN: /* Get PT Number */
345 return put_user(tty->index, (unsigned int __user *)arg);
346 }
347
348 return -ENOIOCTLCMD;
349}
350
351static void __init unix98_pty_init(void)
352{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
354 if (!ptm_driver)
355 panic("Couldn't allocate Unix98 ptm driver");
356 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
357 if (!pts_driver)
358 panic("Couldn't allocate Unix98 pts driver");
359
360 ptm_driver->owner = THIS_MODULE;
361 ptm_driver->driver_name = "pty_master";
362 ptm_driver->name = "ptm";
363 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
364 ptm_driver->minor_start = 0;
365 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
366 ptm_driver->subtype = PTY_TYPE_MASTER;
367 ptm_driver->init_termios = tty_std_termios;
368 ptm_driver->init_termios.c_iflag = 0;
369 ptm_driver->init_termios.c_oflag = 0;
370 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
371 ptm_driver->init_termios.c_lflag = 0;
Alan Cox606d0992006-12-08 02:38:45 -0800372 ptm_driver->init_termios.c_ispeed = 38400;
373 ptm_driver->init_termios.c_ospeed = 38400;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
Greg Kroah-Hartman331b8312005-06-20 21:15:16 -0700375 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 ptm_driver->other = pts_driver;
377 tty_set_operations(ptm_driver, &pty_ops);
378 ptm_driver->ioctl = pty_unix98_ioctl;
379
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;
Alan Cox606d0992006-12-08 02:38:45 -0800389 pts_driver->init_termios.c_ispeed = 38400;
390 pts_driver->init_termios.c_ospeed = 38400;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
Greg Kroah-Hartman331b8312005-06-20 21:15:16 -0700392 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 pts_driver->other = ptm_driver;
394 tty_set_operations(pts_driver, &pty_ops);
395
396 if (tty_register_driver(ptm_driver))
397 panic("Couldn't register Unix98 ptm driver");
398 if (tty_register_driver(pts_driver))
399 panic("Couldn't register Unix98 pts driver");
400
401 pty_table[1].data = &ptm_driver->refcount;
402}
403#else
404static inline void unix98_pty_init(void) { }
405#endif
406
407static int __init pty_init(void)
408{
409 legacy_pty_init();
410 unix98_pty_init();
411 return 0;
412}
413module_init(pty_init);