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/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
37 struct tty_driver *ptm_driver;
38 static struct tty_driver *pts_driver;
39 #endif
40
41 static 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 */
81 static 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 */
106 static 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
114 c = to->ldisc.receive_room(to);
115 if (c > count)
116 c = count;
117 to->ldisc.receive_buf(to, buf, NULL, c);
118
119 return c;
120 }
121
122 static 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
129 return to->ldisc.receive_room(to);
130 }
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 */
149 static int pty_chars_in_buffer(struct tty_struct *tty)
150 {
151 struct tty_struct *to = tty->link;
152 ssize_t (*chars_in_buffer)(struct tty_struct *);
153 int count;
154
155 /* We should get the line discipline lock for "tty->link" */
156 if (!to || !(chars_in_buffer = to->ldisc.chars_in_buffer))
157 return 0;
158
159 /* The ldisc must report 0 if no characters available to be read */
160 count = chars_in_buffer(to);
161
162 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
163
164 /* Master side driver ... if the other side's read buffer is less than
165 * half full, return 0 to allow writers to proceed; otherwise return
166 * the count. This leaves a comfortable margin to avoid overflow,
167 * and still allows half a buffer's worth of typed-ahead commands.
168 */
169 return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
170 }
171
172 /* Set the lock flag on a pty */
173 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
174 {
175 int val;
176 if (get_user(val,arg))
177 return -EFAULT;
178 if (val)
179 set_bit(TTY_PTY_LOCK, &tty->flags);
180 else
181 clear_bit(TTY_PTY_LOCK, &tty->flags);
182 return 0;
183 }
184
185 static void pty_flush_buffer(struct tty_struct *tty)
186 {
187 struct tty_struct *to = tty->link;
188
189 if (!to)
190 return;
191
192 if (to->ldisc.flush_buffer)
193 to->ldisc.flush_buffer(to);
194
195 if (to->packet) {
196 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
197 wake_up_interruptible(&to->read_wait);
198 }
199 }
200
201 static int pty_open(struct tty_struct *tty, struct file * filp)
202 {
203 int retval = -ENODEV;
204
205 if (!tty || !tty->link)
206 goto out;
207
208 retval = -EIO;
209 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
210 goto out;
211 if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
212 goto out;
213 if (tty->link->count != 1)
214 goto out;
215
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);
219 retval = 0;
220 out:
221 return retval;
222 }
223
224 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
225 {
226 tty->termios->c_cflag &= ~(CSIZE | PARENB);
227 tty->termios->c_cflag |= (CS8 | CREAD);
228 }
229
230 static struct tty_operations pty_ops = {
231 .open = pty_open,
232 .close = pty_close,
233 .write = pty_write,
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,
239 };
240
241 /* Traditional BSD devices */
242 #ifdef CONFIG_LEGACY_PTYS
243 static struct tty_driver *pty_driver, *pty_slave_driver;
244
245 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
246 unsigned int cmd, unsigned long arg)
247 {
248 switch (cmd) {
249 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
250 return pty_set_lock(tty, (int __user *) arg);
251 }
252 return -ENOIOCTLCMD;
253 }
254
255 static void __init legacy_pty_init(void)
256 {
257
258 pty_driver = alloc_tty_driver(NR_PTYS);
259 if (!pty_driver)
260 panic("Couldn't allocate pty driver");
261
262 pty_slave_driver = alloc_tty_driver(NR_PTYS);
263 if (!pty_slave_driver)
264 panic("Couldn't allocate pty slave driver");
265
266 pty_driver->owner = THIS_MODULE;
267 pty_driver->driver_name = "pty_master";
268 pty_driver->name = "pty";
269 pty_driver->devfs_name = "pty/m";
270 pty_driver->major = PTY_MASTER_MAJOR;
271 pty_driver->minor_start = 0;
272 pty_driver->type = TTY_DRIVER_TYPE_PTY;
273 pty_driver->subtype = PTY_TYPE_MASTER;
274 pty_driver->init_termios = tty_std_termios;
275 pty_driver->init_termios.c_iflag = 0;
276 pty_driver->init_termios.c_oflag = 0;
277 pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
278 pty_driver->init_termios.c_lflag = 0;
279 pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
280 pty_driver->other = pty_slave_driver;
281 tty_set_operations(pty_driver, &pty_ops);
282 pty_driver->ioctl = pty_bsd_ioctl;
283
284 pty_slave_driver->owner = THIS_MODULE;
285 pty_slave_driver->driver_name = "pty_slave";
286 pty_slave_driver->name = "ttyp";
287 pty_slave_driver->devfs_name = "pty/s";
288 pty_slave_driver->major = PTY_SLAVE_MAJOR;
289 pty_slave_driver->minor_start = 0;
290 pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
291 pty_slave_driver->subtype = PTY_TYPE_SLAVE;
292 pty_slave_driver->init_termios = tty_std_termios;
293 pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
294 pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
295 TTY_DRIVER_REAL_RAW;
296 pty_slave_driver->other = pty_driver;
297 tty_set_operations(pty_slave_driver, &pty_ops);
298
299 if (tty_register_driver(pty_driver))
300 panic("Couldn't register pty driver");
301 if (tty_register_driver(pty_slave_driver))
302 panic("Couldn't register pty slave driver");
303 }
304 #else
305 static inline void legacy_pty_init(void) { }
306 #endif
307
308 /* Unix98 devices */
309 #ifdef CONFIG_UNIX98_PTYS
310 /*
311 * sysctl support for setting limits on the number of Unix98 ptys allocated.
312 * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
313 */
314 int pty_limit = NR_UNIX98_PTY_DEFAULT;
315 static int pty_limit_min = 0;
316 static int pty_limit_max = NR_UNIX98_PTY_MAX;
317
318 ctl_table pty_table[] = {
319 {
320 .ctl_name = PTY_MAX,
321 .procname = "max",
322 .maxlen = sizeof(int),
323 .mode = 0644,
324 .data = &pty_limit,
325 .proc_handler = &proc_dointvec_minmax,
326 .strategy = &sysctl_intvec,
327 .extra1 = &pty_limit_min,
328 .extra2 = &pty_limit_max,
329 }, {
330 .ctl_name = PTY_NR,
331 .procname = "nr",
332 .maxlen = sizeof(int),
333 .mode = 0444,
334 .proc_handler = &proc_dointvec,
335 }, {
336 .ctl_name = 0
337 }
338 };
339
340 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
341 unsigned int cmd, unsigned long arg)
342 {
343 switch (cmd) {
344 case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
345 return pty_set_lock(tty, (int __user *)arg);
346 case TIOCGPTN: /* Get PT Number */
347 return put_user(tty->index, (unsigned int __user *)arg);
348 }
349
350 return -ENOIOCTLCMD;
351 }
352
353 static void __init unix98_pty_init(void)
354 {
355 devfs_mk_dir("pts");
356 ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
357 if (!ptm_driver)
358 panic("Couldn't allocate Unix98 ptm driver");
359 pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
360 if (!pts_driver)
361 panic("Couldn't allocate Unix98 pts driver");
362
363 ptm_driver->owner = THIS_MODULE;
364 ptm_driver->driver_name = "pty_master";
365 ptm_driver->name = "ptm";
366 ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
367 ptm_driver->minor_start = 0;
368 ptm_driver->type = TTY_DRIVER_TYPE_PTY;
369 ptm_driver->subtype = PTY_TYPE_MASTER;
370 ptm_driver->init_termios = tty_std_termios;
371 ptm_driver->init_termios.c_iflag = 0;
372 ptm_driver->init_termios.c_oflag = 0;
373 ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
374 ptm_driver->init_termios.c_lflag = 0;
375 ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
376 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
377 ptm_driver->other = pts_driver;
378 tty_set_operations(ptm_driver, &pty_ops);
379 ptm_driver->ioctl = pty_unix98_ioctl;
380
381 pts_driver->owner = THIS_MODULE;
382 pts_driver->driver_name = "pty_slave";
383 pts_driver->name = "pts";
384 pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
385 pts_driver->minor_start = 0;
386 pts_driver->type = TTY_DRIVER_TYPE_PTY;
387 pts_driver->subtype = PTY_TYPE_SLAVE;
388 pts_driver->init_termios = tty_std_termios;
389 pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
390 pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
391 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
392 pts_driver->other = ptm_driver;
393 tty_set_operations(pts_driver, &pty_ops);
394
395 if (tty_register_driver(ptm_driver))
396 panic("Couldn't register Unix98 ptm driver");
397 if (tty_register_driver(pts_driver))
398 panic("Couldn't register Unix98 pts driver");
399
400 pty_table[1].data = &ptm_driver->refcount;
401 }
402 #else
403 static inline void unix98_pty_init(void) { }
404 #endif
405
406 static int __init pty_init(void)
407 {
408 legacy_pty_init();
409 unix98_pty_init();
410 return 0;
411 }
412 module_init(pty_init);
413
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