d3a5092402c26c9823072ad69b25298ac44b87c1
[linux-2.6.git] / drivers / char / pty.c
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/sysctl.h>
28
29 #include <asm/uaccess.h>
30 #include <asm/system.h>
31 #include <linux/bitops.h>
32 #include <linux/devpts_fs.h>
33
34 /* These are global because they are accessed in tty_io.c */
35 #ifdef CONFIG_UNIX98_PTYS
36 struct tty_driver *ptm_driver;
37 static struct tty_driver *pts_driver;
38 #endif
39
40 static void pty_close(struct tty_struct * tty, struct file * filp)
41 {
42         if (!tty)
43                 return;
44         if (tty->driver->subtype == PTY_TYPE_MASTER) {
45                 if (tty->count > 1)
46                         printk("master pty_close: count = %d!!\n", tty->count);
47         } else {
48                 if (tty->count > 2)
49                         return;
50         }
51         wake_up_interruptible(&tty->read_wait);
52         wake_up_interruptible(&tty->write_wait);
53         tty->packet = 0;
54         if (!tty->link)
55                 return;
56         tty->link->packet = 0;
57         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
58         wake_up_interruptible(&tty->link->read_wait);
59         wake_up_interruptible(&tty->link->write_wait);
60         if (tty->driver->subtype == PTY_TYPE_MASTER) {
61                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
62 #ifdef CONFIG_UNIX98_PTYS
63                 if (tty->driver == ptm_driver)
64                         devpts_pty_kill(tty->index);
65 #endif
66                 tty_vhangup(tty->link);
67         }
68 }
69
70 /*
71  * The unthrottle routine is called by the line discipline to signal
72  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
73  * flag is always set, to force the line discipline to always call the
74  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE 
75  * characters in the queue.  This is necessary since each time this
76  * happens, we need to wake up any sleeping processes that could be
77  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
78  * for the pty buffer to be drained.
79  */
80 static void pty_unthrottle(struct tty_struct * tty)
81 {
82         struct tty_struct *o_tty = tty->link;
83
84         if (!o_tty)
85                 return;
86
87         tty_wakeup(o_tty);
88         set_bit(TTY_THROTTLED, &tty->flags);
89 }
90
91 /*
92  * WSH 05/24/97: modified to 
93  *   (1) use space in tty->flip instead of a shared temp buffer
94  *       The flip buffers aren't being used for a pty, so there's lots
95  *       of space available.  The buffer is protected by a per-pty
96  *       semaphore that should almost never come under contention.
97  *   (2) avoid redundant copying for cases where count >> receive_room
98  * N.B. Calls from user space may now return an error code instead of
99  * a count.
100  *
101  * FIXME: Our pty_write method is called with our ldisc lock held but
102  * not our partners. We can't just take the other one blindly without
103  * risking deadlocks.  There is also the small matter of TTY_DONT_FLIP
104  */
105 static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
106 {
107         struct tty_struct *to = tty->link;
108         int     c;
109
110         if (!to || tty->stopped)
111                 return 0;
112
113         c = to->receive_room;
114         if (c > count)
115                 c = count;
116         to->ldisc.receive_buf(to, buf, NULL, c);
117         
118         return c;
119 }
120
121 static int pty_write_room(struct tty_struct *tty)
122 {
123         struct tty_struct *to = tty->link;
124
125         if (!to || tty->stopped)
126                 return 0;
127
128         return to->receive_room;
129 }
130
131 /*
132  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
133  *      The chars_in_buffer() value is used by the ldisc select() function 
134  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
135  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
136  *
137  *      The Master side needs to allow typed-ahead commands to accumulate
138  *      while being canonicalized, so we report "our buffer" as empty until
139  *      some threshold is reached, and then report the count. (Any count >
140  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock 
141  *      the count returned must be 0 if no canonical data is available to be 
142  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
143  *  
144  *      The Slave side passes all characters in raw mode to the Master side's
145  *      buffer where they can be read immediately, so in this case we can
146  *      return the true count in the buffer.
147  */
148 static int pty_chars_in_buffer(struct tty_struct *tty)
149 {
150         struct tty_struct *to = tty->link;
151         int count;
152
153         /* We should get the line discipline lock for "tty->link" */
154         if (!to || !to->ldisc.chars_in_buffer)
155                 return 0;
156
157         /* The ldisc must report 0 if no characters available to be read */
158         count = to->ldisc.chars_in_buffer(to);
159
160         if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
161
162         /* Master side driver ... if the other side's read buffer is less than 
163          * half full, return 0 to allow writers to proceed; otherwise return
164          * the count.  This leaves a comfortable margin to avoid overflow, 
165          * and still allows half a buffer's worth of typed-ahead commands.
166          */
167         return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
168 }
169
170 /* Set the lock flag on a pty */
171 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
172 {
173         int val;
174         if (get_user(val,arg))
175                 return -EFAULT;
176         if (val)
177                 set_bit(TTY_PTY_LOCK, &tty->flags);
178         else
179                 clear_bit(TTY_PTY_LOCK, &tty->flags);
180         return 0;
181 }
182
183 static void pty_flush_buffer(struct tty_struct *tty)
184 {
185         struct tty_struct *to = tty->link;
186         
187         if (!to)
188                 return;
189         
190         if (to->ldisc.flush_buffer)
191                 to->ldisc.flush_buffer(to);
192         
193         if (to->packet) {
194                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
195                 wake_up_interruptible(&to->read_wait);
196         }
197 }
198
199 static int pty_open(struct tty_struct *tty, struct file * filp)
200 {
201         int     retval = -ENODEV;
202
203         if (!tty || !tty->link)
204                 goto out;
205
206         retval = -EIO;
207         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
208                 goto out;
209         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
210                 goto out;
211         if (tty->link->count != 1)
212                 goto out;
213
214         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
215         set_bit(TTY_THROTTLED, &tty->flags);
216         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
217         retval = 0;
218 out:
219         return retval;
220 }
221
222 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
223 {
224         tty->termios->c_cflag &= ~(CSIZE | PARENB);
225         tty->termios->c_cflag |= (CS8 | CREAD);
226 }
227
228 static struct tty_operations pty_ops = {
229         .open = pty_open,
230         .close = pty_close,
231         .write = pty_write,
232         .write_room = pty_write_room,
233         .flush_buffer = pty_flush_buffer,
234         .chars_in_buffer = pty_chars_in_buffer,
235         .unthrottle = pty_unthrottle,
236         .set_termios = pty_set_termios,
237 };
238
239 /* Traditional BSD devices */
240 #ifdef CONFIG_LEGACY_PTYS
241 static struct tty_driver *pty_driver, *pty_slave_driver;
242
243 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
244                          unsigned int cmd, unsigned long arg)
245 {
246         switch (cmd) {
247         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
248                 return pty_set_lock(tty, (int __user *) arg);
249         }
250         return -ENOIOCTLCMD;
251 }
252
253 static void __init legacy_pty_init(void)
254 {
255
256         pty_driver = alloc_tty_driver(NR_PTYS);
257         if (!pty_driver)
258                 panic("Couldn't allocate pty driver");
259
260         pty_slave_driver = alloc_tty_driver(NR_PTYS);
261         if (!pty_slave_driver)
262                 panic("Couldn't allocate pty slave driver");
263
264         pty_driver->owner = THIS_MODULE;
265         pty_driver->driver_name = "pty_master";
266         pty_driver->name = "pty";
267         pty_driver->major = PTY_MASTER_MAJOR;
268         pty_driver->minor_start = 0;
269         pty_driver->type = TTY_DRIVER_TYPE_PTY;
270         pty_driver->subtype = PTY_TYPE_MASTER;
271         pty_driver->init_termios = tty_std_termios;
272         pty_driver->init_termios.c_iflag = 0;
273         pty_driver->init_termios.c_oflag = 0;
274         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
275         pty_driver->init_termios.c_lflag = 0;
276         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";
284         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;
290         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
291                                         TTY_DRIVER_REAL_RAW;
292         pty_slave_driver->other = pty_driver;
293         tty_set_operations(pty_slave_driver, &pty_ops);
294
295         if (tty_register_driver(pty_driver))
296                 panic("Couldn't register pty driver");
297         if (tty_register_driver(pty_slave_driver))
298                 panic("Couldn't register pty slave driver");
299 }
300 #else
301 static inline void legacy_pty_init(void) { }
302 #endif
303
304 /* Unix98 devices */
305 #ifdef CONFIG_UNIX98_PTYS
306 /*
307  * sysctl support for setting limits on the number of Unix98 ptys allocated.
308  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
309  */
310 int pty_limit = NR_UNIX98_PTY_DEFAULT;
311 static int pty_limit_min = 0;
312 static int pty_limit_max = NR_UNIX98_PTY_MAX;
313
314 ctl_table pty_table[] = {
315         {
316                 .ctl_name       = PTY_MAX,
317                 .procname       = "max",
318                 .maxlen         = sizeof(int),
319                 .mode           = 0644,
320                 .data           = &pty_limit,
321                 .proc_handler   = &proc_dointvec_minmax,
322                 .strategy       = &sysctl_intvec,
323                 .extra1         = &pty_limit_min,
324                 .extra2         = &pty_limit_max,
325         }, {
326                 .ctl_name       = PTY_NR,
327                 .procname       = "nr",
328                 .maxlen         = sizeof(int),
329                 .mode           = 0444,
330                 .proc_handler   = &proc_dointvec,
331         }, {
332                 .ctl_name       = 0
333         }
334 };
335
336 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
337                             unsigned int cmd, unsigned long arg)
338 {
339         switch (cmd) {
340         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
341                 return pty_set_lock(tty, (int __user *)arg);
342         case TIOCGPTN: /* Get PT Number */
343                 return put_user(tty->index, (unsigned int __user *)arg);
344         }
345
346         return -ENOIOCTLCMD;
347 }
348
349 static void __init unix98_pty_init(void)
350 {
351         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
352         if (!ptm_driver)
353                 panic("Couldn't allocate Unix98 ptm driver");
354         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
355         if (!pts_driver)
356                 panic("Couldn't allocate Unix98 pts driver");
357
358         ptm_driver->owner = THIS_MODULE;
359         ptm_driver->driver_name = "pty_master";
360         ptm_driver->name = "ptm";
361         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
362         ptm_driver->minor_start = 0;
363         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
364         ptm_driver->subtype = PTY_TYPE_MASTER;
365         ptm_driver->init_termios = tty_std_termios;
366         ptm_driver->init_termios.c_iflag = 0;
367         ptm_driver->init_termios.c_oflag = 0;
368         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
369         ptm_driver->init_termios.c_lflag = 0;
370         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
371                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
372         ptm_driver->other = pts_driver;
373         tty_set_operations(ptm_driver, &pty_ops);
374         ptm_driver->ioctl = pty_unix98_ioctl;
375
376         pts_driver->owner = THIS_MODULE;
377         pts_driver->driver_name = "pty_slave";
378         pts_driver->name = "pts";
379         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
380         pts_driver->minor_start = 0;
381         pts_driver->type = TTY_DRIVER_TYPE_PTY;
382         pts_driver->subtype = PTY_TYPE_SLAVE;
383         pts_driver->init_termios = tty_std_termios;
384         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
385         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
386                 TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM;
387         pts_driver->other = ptm_driver;
388         tty_set_operations(pts_driver, &pty_ops);
389         
390         if (tty_register_driver(ptm_driver))
391                 panic("Couldn't register Unix98 ptm driver");
392         if (tty_register_driver(pts_driver))
393                 panic("Couldn't register Unix98 pts driver");
394
395         pty_table[1].data = &ptm_driver->refcount;
396 }
397 #else
398 static inline void unix98_pty_init(void) { }
399 #endif
400
401 static int __init pty_init(void)
402 {
403         legacy_pty_init();
404         unix98_pty_init();
405         return 0;
406 }
407 module_init(pty_init);