1/*
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/module.h>	/* For EXPORT_SYMBOL */
15
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>
23#include <linux/mm.h>
24#include <linux/init.h>
25#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
89static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
90{
91	struct tty_struct *to = tty->link;
92	int	c;
93
94	if (!to || tty->stopped)
95		return 0;
96
97	c = to->receive_room;
98	if (c > count)
99		c = count;
100	to->ldisc.receive_buf(to, buf, NULL, c);
101
102	return c;
103}
104
105static int pty_write_room(struct tty_struct *tty)
106{
107	struct tty_struct *to = tty->link;
108
109	if (!to || tty->stopped)
110		return 0;
111
112	return to->receive_room;
113}
114
115/*
116 *	WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
117 *	The chars_in_buffer() value is used by the ldisc select() function
118 *	to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
119 *	The pty driver chars_in_buffer() Master/Slave must behave differently:
120 *
121 *      The Master side needs to allow typed-ahead commands to accumulate
122 *      while being canonicalized, so we report "our buffer" as empty until
123 *	some threshold is reached, and then report the count. (Any count >
124 *	WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock
125 *	the count returned must be 0 if no canonical data is available to be
126 *	read. (The N_TTY ldisc.chars_in_buffer now knows this.)
127 *
128 *	The Slave side passes all characters in raw mode to the Master side's
129 *	buffer where they can be read immediately, so in this case we can
130 *	return the true count in the buffer.
131 */
132static int pty_chars_in_buffer(struct tty_struct *tty)
133{
134	struct tty_struct *to = tty->link;
135	int count;
136
137	/* We should get the line discipline lock for "tty->link" */
138	if (!to || !to->ldisc.chars_in_buffer)
139		return 0;
140
141	/* The ldisc must report 0 if no characters available to be read */
142	count = to->ldisc.chars_in_buffer(to);
143
144	if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
145
146	/* Master side driver ... if the other side's read buffer is less than
147	 * half full, return 0 to allow writers to proceed; otherwise return
148	 * the count.  This leaves a comfortable margin to avoid overflow,
149	 * and still allows half a buffer's worth of typed-ahead commands.
150	 */
151	return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
152}
153
154/* Set the lock flag on a pty */
155static int pty_set_lock(struct tty_struct *tty, int __user * arg)
156{
157	int val;
158	if (get_user(val,arg))
159		return -EFAULT;
160	if (val)
161		set_bit(TTY_PTY_LOCK, &tty->flags);
162	else
163		clear_bit(TTY_PTY_LOCK, &tty->flags);
164	return 0;
165}
166
167static void pty_flush_buffer(struct tty_struct *tty)
168{
169	struct tty_struct *to = tty->link;
170
171	if (!to)
172		return;
173
174	if (to->ldisc.flush_buffer)
175		to->ldisc.flush_buffer(to);
176
177	if (to->packet) {
178		tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
179		wake_up_interruptible(&to->read_wait);
180	}
181}
182
183static int pty_open(struct tty_struct *tty, struct file * filp)
184{
185	int	retval = -ENODEV;
186
187	if (!tty || !tty->link)
188		goto out;
189
190	retval = -EIO;
191	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
192		goto out;
193	if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
194		goto out;
195	if (tty->link->count != 1)
196		goto out;
197
198	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
199	set_bit(TTY_THROTTLED, &tty->flags);
200	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
201	retval = 0;
202out:
203	return retval;
204}
205
206static void pty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
207{
208        tty->termios->c_cflag &= ~(CSIZE | PARENB);
209        tty->termios->c_cflag |= (CS8 | CREAD);
210}
211
212static const struct tty_operations pty_ops = {
213	.open = pty_open,
214	.close = pty_close,
215	.write = pty_write,
216	.write_room = pty_write_room,
217	.flush_buffer = pty_flush_buffer,
218	.chars_in_buffer = pty_chars_in_buffer,
219	.unthrottle = pty_unthrottle,
220	.set_termios = pty_set_termios,
221};
222
223/* Traditional BSD devices */
224#ifdef CONFIG_LEGACY_PTYS
225static struct tty_driver *pty_driver, *pty_slave_driver;
226
227static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
228			 unsigned int cmd, unsigned long arg)
229{
230	switch (cmd) {
231	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
232		return pty_set_lock(tty, (int __user *) arg);
233	}
234	return -ENOIOCTLCMD;
235}
236
237static void __init legacy_pty_init(void)
238{
239
240	pty_driver = alloc_tty_driver(NR_PTYS);
241	if (!pty_driver)
242		panic("Couldn't allocate pty driver");
243
244	pty_slave_driver = alloc_tty_driver(NR_PTYS);
245	if (!pty_slave_driver)
246		panic("Couldn't allocate pty slave driver");
247
248	pty_driver->owner = THIS_MODULE;
249	pty_driver->driver_name = "pty_master";
250	pty_driver->name = "pty";
251	pty_driver->major = PTY_MASTER_MAJOR;
252	pty_driver->minor_start = 0;
253	pty_driver->type = TTY_DRIVER_TYPE_PTY;
254	pty_driver->subtype = PTY_TYPE_MASTER;
255	pty_driver->init_termios = tty_std_termios;
256	pty_driver->init_termios.c_iflag = 0;
257	pty_driver->init_termios.c_oflag = 0;
258	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
259	pty_driver->init_termios.c_lflag = 0;
260	pty_driver->init_termios.c_ispeed = 38400;
261	pty_driver->init_termios.c_ospeed = 38400;
262	pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
263	pty_driver->other = pty_slave_driver;
264	tty_set_operations(pty_driver, &pty_ops);
265	pty_driver->ioctl = pty_bsd_ioctl;
266
267	pty_slave_driver->owner = THIS_MODULE;
268	pty_slave_driver->driver_name = "pty_slave";
269	pty_slave_driver->name = "ttyp";
270	pty_slave_driver->major = PTY_SLAVE_MAJOR;
271	pty_slave_driver->minor_start = 0;
272	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
273	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
274	pty_slave_driver->init_termios = tty_std_termios;
275	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
276	pty_slave_driver->init_termios.c_ispeed = 38400;
277	pty_slave_driver->init_termios.c_ospeed = 38400;
278	pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
279					TTY_DRIVER_REAL_RAW;
280	pty_slave_driver->other = pty_driver;
281	tty_set_operations(pty_slave_driver, &pty_ops);
282
283	if (tty_register_driver(pty_driver))
284		panic("Couldn't register pty driver");
285	if (tty_register_driver(pty_slave_driver))
286		panic("Couldn't register pty slave driver");
287}
288#else
289static inline void legacy_pty_init(void) { }
290#endif
291
292/* Unix98 devices */
293#ifdef CONFIG_UNIX98_PTYS
294/*
295 * sysctl support for setting limits on the number of Unix98 ptys allocated.
296 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
297 */
298int pty_limit = NR_UNIX98_PTY_DEFAULT;
299static int pty_limit_min = 0;
300static int pty_limit_max = NR_UNIX98_PTY_MAX;
301
302ctl_table pty_table[] = {
303	{
304		.ctl_name	= PTY_MAX,
305		.procname	= "max",
306		.maxlen		= sizeof(int),
307		.mode		= 0644,
308		.data		= &pty_limit,
309		.proc_handler	= &proc_dointvec_minmax,
310		.strategy	= &sysctl_intvec,
311		.extra1		= &pty_limit_min,
312		.extra2		= &pty_limit_max,
313	}, {
314		.ctl_name	= PTY_NR,
315		.procname	= "nr",
316		.maxlen		= sizeof(int),
317		.mode		= 0444,
318		.proc_handler	= &proc_dointvec,
319	}, {
320		.ctl_name	= 0
321	}
322};
323
324static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
325			    unsigned int cmd, unsigned long arg)
326{
327	switch (cmd) {
328	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
329		return pty_set_lock(tty, (int __user *)arg);
330	case TIOCGPTN: /* Get PT Number */
331		return put_user(tty->index, (unsigned int __user *)arg);
332	}
333
334	return -ENOIOCTLCMD;
335}
336
337static void __init unix98_pty_init(void)
338{
339	ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
340	if (!ptm_driver)
341		panic("Couldn't allocate Unix98 ptm driver");
342	pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
343	if (!pts_driver)
344		panic("Couldn't allocate Unix98 pts driver");
345
346	ptm_driver->owner = THIS_MODULE;
347	ptm_driver->driver_name = "pty_master";
348	ptm_driver->name = "ptm";
349	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
350	ptm_driver->minor_start = 0;
351	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
352	ptm_driver->subtype = PTY_TYPE_MASTER;
353	ptm_driver->init_termios = tty_std_termios;
354	ptm_driver->init_termios.c_iflag = 0;
355	ptm_driver->init_termios.c_oflag = 0;
356	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
357	ptm_driver->init_termios.c_lflag = 0;
358	ptm_driver->init_termios.c_ispeed = 38400;
359	ptm_driver->init_termios.c_ospeed = 38400;
360	ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
361		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
362	ptm_driver->other = pts_driver;
363	tty_set_operations(ptm_driver, &pty_ops);
364	ptm_driver->ioctl = pty_unix98_ioctl;
365
366	pts_driver->owner = THIS_MODULE;
367	pts_driver->driver_name = "pty_slave";
368	pts_driver->name = "pts";
369	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
370	pts_driver->minor_start = 0;
371	pts_driver->type = TTY_DRIVER_TYPE_PTY;
372	pts_driver->subtype = PTY_TYPE_SLAVE;
373	pts_driver->init_termios = tty_std_termios;
374	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
375	pts_driver->init_termios.c_ispeed = 38400;
376	pts_driver->init_termios.c_ospeed = 38400;
377	pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
378		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
379	pts_driver->other = ptm_driver;
380	tty_set_operations(pts_driver, &pty_ops);
381
382	if (tty_register_driver(ptm_driver))
383		panic("Couldn't register Unix98 ptm driver");
384	if (tty_register_driver(pts_driver))
385		panic("Couldn't register Unix98 pts driver");
386
387	pty_table[1].data = &ptm_driver->refcount;
388}
389#else
390static inline void unix98_pty_init(void) { }
391#endif
392
393static int __init pty_init(void)
394{
395	legacy_pty_init();
396	unix98_pty_init();
397	return 0;
398}
399module_init(pty_init);
400