tty: simplify calling of put_pid.
[linux-2.6] / 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/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
34 struct tty_driver *ptm_driver;
35 static struct tty_driver *pts_driver;
36 #endif
37
38 static 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  */
78 static 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
101  * risking deadlocks.
102  */
103 static 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
111         c = to->receive_room;
112         if (c > count)
113                 c = count;
114         to->ldisc.receive_buf(to, buf, NULL, c);
115         
116         return c;
117 }
118
119 static 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
126         return to->receive_room;
127 }
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  */
146 static int pty_chars_in_buffer(struct tty_struct *tty)
147 {
148         struct tty_struct *to = tty->link;
149         int count;
150
151         /* We should get the line discipline lock for "tty->link" */
152         if (!to || !to->ldisc.chars_in_buffer)
153                 return 0;
154
155         /* The ldisc must report 0 if no characters available to be read */
156         count = to->ldisc.chars_in_buffer(to);
157
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 */
169 static 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
181 static 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
197 static 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;
216 out:
217         return retval;
218 }
219
220 static void pty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
221 {
222         tty->termios->c_cflag &= ~(CSIZE | PARENB);
223         tty->termios->c_cflag |= (CS8 | CREAD);
224 }
225
226 static const struct tty_operations pty_ops = {
227         .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
239 static struct tty_driver *pty_driver, *pty_slave_driver;
240
241 static 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
251 static 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";
265         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;
274         pty_driver->init_termios.c_ispeed = 38400;
275         pty_driver->init_termios.c_ospeed = 38400;
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->init_termios.c_ispeed = 38400;
291         pty_slave_driver->init_termios.c_ospeed = 38400;
292         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
303 static 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  */
312 int pty_limit = NR_UNIX98_PTY_DEFAULT;
313 static int pty_limit_min = 0;
314 static int pty_limit_max = NR_UNIX98_PTY_MAX;
315
316 ctl_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
338 static 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
351 static void __init unix98_pty_init(void)
352 {
353         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;
372         ptm_driver->init_termios.c_ispeed = 38400;
373         ptm_driver->init_termios.c_ospeed = 38400;
374         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
375                 TTY_DRIVER_DYNAMIC_DEV | 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->init_termios.c_ispeed = 38400;
390         pts_driver->init_termios.c_ospeed = 38400;
391         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
392                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
393         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
404 static inline void unix98_pty_init(void) { }
405 #endif
406
407 static int __init pty_init(void)
408 {
409         legacy_pty_init();
410         unix98_pty_init();
411         return 0;
412 }
413 module_init(pty_init);