blob: 9b5a2c0e7008c82183649e6006784088ceabd220 [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
14#include <linux/config.h>
15#include <linux/module.h> /* For EXPORT_SYMBOL */
16
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>
25#include <linux/mm.h>
26#include <linux/init.h>
27#include <linux/devfs_fs_kernel.h>
28#include <linux/sysctl.h>
29
30#include <asm/uaccess.h>
31#include <asm/system.h>
32#include <linux/bitops.h>
33#include <linux/devpts_fs.h>
34
35/* These are global because they are accessed in tty_io.c */
36#ifdef CONFIG_UNIX98_PTYS
37struct tty_driver *ptm_driver;
38static struct tty_driver *pts_driver;
39#endif
40
41static void pty_close(struct tty_struct * tty, struct file * filp)
42{
43 if (!tty)
44 return;
45 if (tty->driver->subtype == PTY_TYPE_MASTER) {
46 if (tty->count > 1)
47 printk("master pty_close: count = %d!!\n", tty->count);
48 } else {
49 if (tty->count > 2)
50 return;
51 }
52 wake_up_interruptible(&tty->read_wait);
53 wake_up_interruptible(&tty->write_wait);
54 tty->packet = 0;
55 if (!tty->link)
56 return;
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);
66#endif
67 tty_vhangup(tty->link);
68 }
69}
70
71/*
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.
80 */
81static void pty_unthrottle(struct tty_struct * tty)
82{
83 struct tty_struct *o_tty = tty->link;
84
85 if (!o_tty)
86 return;
87
88 tty_wakeup(o_tty);
89 set_bit(TTY_THROTTLED, &tty->flags);
90}
91
92/*
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
100 * a count.
101 *
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
105 */
106static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
107{
108 struct tty_struct *to = tty->link;
109 int c;
110
111 if (!to || tty->stopped)
112 return 0;
113
Alan Cox33f0f882006-01-09 20:54:13 -0800114 c = to->receive_room;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 if (c > count)
116 c = count;
117 to->ldisc.receive_buf(to, buf, NULL, c);
118
119 return c;
120}
121
122static int pty_write_room(struct tty_struct *tty)
123{
124 struct tty_struct *to = tty->link;
125
126 if (!to || tty->stopped)
127 return 0;
128
Alan Cox33f0f882006-01-09 20:54:13 -0800129 return to->receive_room;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130}
131
132/*
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:
137 *
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.)
144 *
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.
148 */
149static int pty_chars_in_buffer(struct tty_struct *tty)
150{
151 struct tty_struct *to = tty->link;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 int count;
153
154 /* We should get the line discipline lock for "tty->link" */
Jason Baronff55fe22005-09-09 13:01:57 -0700155 if (!to || !to->ldisc.chars_in_buffer)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 return 0;
157
158 /* The ldisc must report 0 if no characters available to be read */
Jason Baronff55fe22005-09-09 13:01:57 -0700159 count = to->ldisc.chars_in_buffer(to);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
161 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
162
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.
167 */
168 return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
169}
170
171/* Set the lock flag on a pty */
172static int pty_set_lock(struct tty_struct *tty, int __user * arg)
173{
174 int val;
175 if (get_user(val,arg))
176 return -EFAULT;
177 if (val)
178 set_bit(TTY_PTY_LOCK, &tty->flags);
179 else
180 clear_bit(TTY_PTY_LOCK, &tty->flags);
181 return 0;
182}
183
184static void pty_flush_buffer(struct tty_struct *tty)
185{
186 struct tty_struct *to = tty->link;
187
188 if (!to)
189 return;
190
191 if (to->ldisc.flush_buffer)
192 to->ldisc.flush_buffer(to);
193
194 if (to->packet) {
195 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
196 wake_up_interruptible(&to->read_wait);
197 }
198}
199
200static int pty_open(struct tty_struct *tty, struct file * filp)
201{
202 int retval = -ENODEV;
203
204 if (!tty || !tty->link)
205 goto out;
206
207 retval = -EIO;
208 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
209 goto out;
210 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
211 goto out;
212 if (tty->link->count != 1)
213 goto out;
214
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);
218 retval = 0;
219out:
220 return retval;
221}
222
223static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
224{
225 tty->termios->c_cflag &= ~(CSIZE | PARENB);
226 tty->termios->c_cflag |= (CS8 | CREAD);
227}
228
229static struct tty_operations pty_ops = {
230 .open = pty_open,
231 .close = pty_close,
232 .write = pty_write,
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,
238};
239
240/* Traditional BSD devices */
241#ifdef CONFIG_LEGACY_PTYS
242static struct tty_driver *pty_driver, *pty_slave_driver;
243
244static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
245 unsigned int cmd, unsigned long arg)
246{
247 switch (cmd) {
248 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
249 return pty_set_lock(tty, (int __user *) arg);
250 }
251 return -ENOIOCTLCMD;
252}
253
254static void __init legacy_pty_init(void)
255{
256
257 pty_driver = alloc_tty_driver(NR_PTYS);
258 if (!pty_driver)
259 panic("Couldn't allocate pty driver");
260
261 pty_slave_driver = alloc_tty_driver(NR_PTYS);
262 if (!pty_slave_driver)
263 panic("Couldn't allocate pty slave driver");
264
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;
282
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 |
294 TTY_DRIVER_REAL_RAW;
295 pty_slave_driver->other = pty_driver;
296 tty_set_operations(pty_slave_driver, &pty_ops);
297
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");
302}
303#else
304static inline void legacy_pty_init(void) { }
305#endif
306
307/* Unix98 devices */
308#ifdef CONFIG_UNIX98_PTYS
309/*
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.
312 */
313int pty_limit = NR_UNIX98_PTY_DEFAULT;
314static int pty_limit_min = 0;
315static int pty_limit_max = NR_UNIX98_PTY_MAX;
316
317ctl_table pty_table[] = {
318 {
319 .ctl_name = PTY_MAX,
320 .procname = "max",
321 .maxlen = sizeof(int),
322 .mode = 0644,
323 .data = &pty_limit,
324 .proc_handler = &proc_dointvec_minmax,
325 .strategy = &sysctl_intvec,
326 .extra1 = &pty_limit_min,
327 .extra2 = &pty_limit_max,
328 }, {
329 .ctl_name = PTY_NR,
330 .procname = "nr",
331 .maxlen = sizeof(int),
332 .mode = 0444,
333 .proc_handler = &proc_dointvec,
334 }, {
335 .ctl_name = 0
336 }
337};
338
339static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
340 unsigned int cmd, unsigned long arg)
341{
342 switch (cmd) {
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);
347 }
348
349 return -ENOIOCTLCMD;
350}
351
352static void __init unix98_pty_init(void)
353{
354 devfs_mk_dir("pts");
355 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
356 if (!ptm_driver)
357 panic("Couldn't allocate Unix98 ptm driver");
358 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
359 if (!pts_driver)
360 panic("Couldn't allocate Unix98 pts driver");
361
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;
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;
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);
393
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");
398
399 pty_table[1].data = &ptm_driver->refcount;
400}
401#else
402static inline void unix98_pty_init(void) { }
403#endif
404
405static int __init pty_init(void)
406{
407 legacy_pty_init();
408 unix98_pty_init();
409 return 0;
410}
411module_init(pty_init);