Remove obsolete #include <linux/config.h>
[linux-3.10.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/module.h>       /* For EXPORT_SYMBOL */
15
16 #include <linux/errno.h>
17 #include <linux/sched.h>
18 #include <linux/interrupt.h>
19 #include <linux/tty.h>
20 #include <linux/tty_flip.h>
21 #include <linux/fcntl.h>
22 #include <linux/string.h>
23 #include <linux/major.h>
24 #include <linux/mm.h>
25 #include <linux/init.h>
26 #include <linux/sysctl.h>
27
28 #include <asm/uaccess.h>
29 #include <asm/system.h>
30 #include <linux/bitops.h>
31 #include <linux/devpts_fs.h>
32
33 /* These are global because they are accessed in tty_io.c */
34 #ifdef CONFIG_UNIX98_PTYS
35 struct tty_driver *ptm_driver;
36 static struct tty_driver *pts_driver;
37 #endif
38
39 static void pty_close(struct tty_struct * tty, struct file * filp)
40 {
41         if (!tty)
42                 return;
43         if (tty->driver->subtype == PTY_TYPE_MASTER) {
44                 if (tty->count > 1)
45                         printk("master pty_close: count = %d!!\n", tty->count);
46         } else {
47                 if (tty->count > 2)
48                         return;
49         }
50         wake_up_interruptible(&tty->read_wait);
51         wake_up_interruptible(&tty->write_wait);
52         tty->packet = 0;
53         if (!tty->link)
54                 return;
55         tty->link->packet = 0;
56         set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
57         wake_up_interruptible(&tty->link->read_wait);
58         wake_up_interruptible(&tty->link->write_wait);
59         if (tty->driver->subtype == PTY_TYPE_MASTER) {
60                 set_bit(TTY_OTHER_CLOSED, &tty->flags);
61 #ifdef CONFIG_UNIX98_PTYS
62                 if (tty->driver == ptm_driver)
63                         devpts_pty_kill(tty->index);
64 #endif
65                 tty_vhangup(tty->link);
66         }
67 }
68
69 /*
70  * The unthrottle routine is called by the line discipline to signal
71  * that it can receive more characters.  For PTY's, the TTY_THROTTLED
72  * flag is always set, to force the line discipline to always call the
73  * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE 
74  * characters in the queue.  This is necessary since each time this
75  * happens, we need to wake up any sleeping processes that could be
76  * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
77  * for the pty buffer to be drained.
78  */
79 static void pty_unthrottle(struct tty_struct * tty)
80 {
81         struct tty_struct *o_tty = tty->link;
82
83         if (!o_tty)
84                 return;
85
86         tty_wakeup(o_tty);
87         set_bit(TTY_THROTTLED, &tty->flags);
88 }
89
90 /*
91  * WSH 05/24/97: modified to 
92  *   (1) use space in tty->flip instead of a shared temp buffer
93  *       The flip buffers aren't being used for a pty, so there's lots
94  *       of space available.  The buffer is protected by a per-pty
95  *       semaphore that should almost never come under contention.
96  *   (2) avoid redundant copying for cases where count >> receive_room
97  * N.B. Calls from user space may now return an error code instead of
98  * a count.
99  *
100  * FIXME: Our pty_write method is called with our ldisc lock held but
101  * not our partners. We can't just take the other one blindly without
102  * risking deadlocks.
103  */
104 static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count)
105 {
106         struct tty_struct *to = tty->link;
107         int     c;
108
109         if (!to || tty->stopped)
110                 return 0;
111
112         c = to->receive_room;
113         if (c > count)
114                 c = count;
115         to->ldisc.receive_buf(to, buf, NULL, c);
116         
117         return c;
118 }
119
120 static int pty_write_room(struct tty_struct *tty)
121 {
122         struct tty_struct *to = tty->link;
123
124         if (!to || tty->stopped)
125                 return 0;
126
127         return to->receive_room;
128 }
129
130 /*
131  *      WSH 05/24/97:  Modified for asymmetric MASTER/SLAVE behavior
132  *      The chars_in_buffer() value is used by the ldisc select() function 
133  *      to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).
134  *      The pty driver chars_in_buffer() Master/Slave must behave differently:
135  *
136  *      The Master side needs to allow typed-ahead commands to accumulate
137  *      while being canonicalized, so we report "our buffer" as empty until
138  *      some threshold is reached, and then report the count. (Any count >
139  *      WAKEUP_CHARS is regarded by select() as "full".)  To avoid deadlock 
140  *      the count returned must be 0 if no canonical data is available to be 
141  *      read. (The N_TTY ldisc.chars_in_buffer now knows this.)
142  *  
143  *      The Slave side passes all characters in raw mode to the Master side's
144  *      buffer where they can be read immediately, so in this case we can
145  *      return the true count in the buffer.
146  */
147 static int pty_chars_in_buffer(struct tty_struct *tty)
148 {
149         struct tty_struct *to = tty->link;
150         int count;
151
152         /* We should get the line discipline lock for "tty->link" */
153         if (!to || !to->ldisc.chars_in_buffer)
154                 return 0;
155
156         /* The ldisc must report 0 if no characters available to be read */
157         count = to->ldisc.chars_in_buffer(to);
158
159         if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
160
161         /* Master side driver ... if the other side's read buffer is less than 
162          * half full, return 0 to allow writers to proceed; otherwise return
163          * the count.  This leaves a comfortable margin to avoid overflow, 
164          * and still allows half a buffer's worth of typed-ahead commands.
165          */
166         return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);
167 }
168
169 /* Set the lock flag on a pty */
170 static int pty_set_lock(struct tty_struct *tty, int __user * arg)
171 {
172         int val;
173         if (get_user(val,arg))
174                 return -EFAULT;
175         if (val)
176                 set_bit(TTY_PTY_LOCK, &tty->flags);
177         else
178                 clear_bit(TTY_PTY_LOCK, &tty->flags);
179         return 0;
180 }
181
182 static void pty_flush_buffer(struct tty_struct *tty)
183 {
184         struct tty_struct *to = tty->link;
185         
186         if (!to)
187                 return;
188         
189         if (to->ldisc.flush_buffer)
190                 to->ldisc.flush_buffer(to);
191         
192         if (to->packet) {
193                 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
194                 wake_up_interruptible(&to->read_wait);
195         }
196 }
197
198 static int pty_open(struct tty_struct *tty, struct file * filp)
199 {
200         int     retval = -ENODEV;
201
202         if (!tty || !tty->link)
203                 goto out;
204
205         retval = -EIO;
206         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
207                 goto out;
208         if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
209                 goto out;
210         if (tty->link->count != 1)
211                 goto out;
212
213         clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
214         set_bit(TTY_THROTTLED, &tty->flags);
215         set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
216         retval = 0;
217 out:
218         return retval;
219 }
220
221 static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)
222 {
223         tty->termios->c_cflag &= ~(CSIZE | PARENB);
224         tty->termios->c_cflag |= (CS8 | CREAD);
225 }
226
227 static struct tty_operations pty_ops = {
228         .open = pty_open,
229         .close = pty_close,
230         .write = pty_write,
231         .write_room = pty_write_room,
232         .flush_buffer = pty_flush_buffer,
233         .chars_in_buffer = pty_chars_in_buffer,
234         .unthrottle = pty_unthrottle,
235         .set_termios = pty_set_termios,
236 };
237
238 /* Traditional BSD devices */
239 #ifdef CONFIG_LEGACY_PTYS
240 static struct tty_driver *pty_driver, *pty_slave_driver;
241
242 static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
243                          unsigned int cmd, unsigned long arg)
244 {
245         switch (cmd) {
246         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
247                 return pty_set_lock(tty, (int __user *) arg);
248         }
249         return -ENOIOCTLCMD;
250 }
251
252 static void __init legacy_pty_init(void)
253 {
254
255         pty_driver = alloc_tty_driver(NR_PTYS);
256         if (!pty_driver)
257                 panic("Couldn't allocate pty driver");
258
259         pty_slave_driver = alloc_tty_driver(NR_PTYS);
260         if (!pty_slave_driver)
261                 panic("Couldn't allocate pty slave driver");
262
263         pty_driver->owner = THIS_MODULE;
264         pty_driver->driver_name = "pty_master";
265         pty_driver->name = "pty";
266         pty_driver->major = PTY_MASTER_MAJOR;
267         pty_driver->minor_start = 0;
268         pty_driver->type = TTY_DRIVER_TYPE_PTY;
269         pty_driver->subtype = PTY_TYPE_MASTER;
270         pty_driver->init_termios = tty_std_termios;
271         pty_driver->init_termios.c_iflag = 0;
272         pty_driver->init_termios.c_oflag = 0;
273         pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
274         pty_driver->init_termios.c_lflag = 0;
275         pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
276         pty_driver->other = pty_slave_driver;
277         tty_set_operations(pty_driver, &pty_ops);
278         pty_driver->ioctl = pty_bsd_ioctl;
279
280         pty_slave_driver->owner = THIS_MODULE;
281         pty_slave_driver->driver_name = "pty_slave";
282         pty_slave_driver->name = "ttyp";
283         pty_slave_driver->major = PTY_SLAVE_MAJOR;
284         pty_slave_driver->minor_start = 0;
285         pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
286         pty_slave_driver->subtype = PTY_TYPE_SLAVE;
287         pty_slave_driver->init_termios = tty_std_termios;
288         pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
289         pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
290                                         TTY_DRIVER_REAL_RAW;
291         pty_slave_driver->other = pty_driver;
292         tty_set_operations(pty_slave_driver, &pty_ops);
293
294         if (tty_register_driver(pty_driver))
295                 panic("Couldn't register pty driver");
296         if (tty_register_driver(pty_slave_driver))
297                 panic("Couldn't register pty slave driver");
298 }
299 #else
300 static inline void legacy_pty_init(void) { }
301 #endif
302
303 /* Unix98 devices */
304 #ifdef CONFIG_UNIX98_PTYS
305 /*
306  * sysctl support for setting limits on the number of Unix98 ptys allocated.
307  * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
308  */
309 int pty_limit = NR_UNIX98_PTY_DEFAULT;
310 static int pty_limit_min = 0;
311 static int pty_limit_max = NR_UNIX98_PTY_MAX;
312
313 ctl_table pty_table[] = {
314         {
315                 .ctl_name       = PTY_MAX,
316                 .procname       = "max",
317                 .maxlen         = sizeof(int),
318                 .mode           = 0644,
319                 .data           = &pty_limit,
320                 .proc_handler   = &proc_dointvec_minmax,
321                 .strategy       = &sysctl_intvec,
322                 .extra1         = &pty_limit_min,
323                 .extra2         = &pty_limit_max,
324         }, {
325                 .ctl_name       = PTY_NR,
326                 .procname       = "nr",
327                 .maxlen         = sizeof(int),
328                 .mode           = 0444,
329                 .proc_handler   = &proc_dointvec,
330         }, {
331                 .ctl_name       = 0
332         }
333 };
334
335 static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file,
336                             unsigned int cmd, unsigned long arg)
337 {
338         switch (cmd) {
339         case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
340                 return pty_set_lock(tty, (int __user *)arg);
341         case TIOCGPTN: /* Get PT Number */
342                 return put_user(tty->index, (unsigned int __user *)arg);
343         }
344
345         return -ENOIOCTLCMD;
346 }
347
348 static void __init unix98_pty_init(void)
349 {
350         ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
351         if (!ptm_driver)
352                 panic("Couldn't allocate Unix98 ptm driver");
353         pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
354         if (!pts_driver)
355                 panic("Couldn't allocate Unix98 pts driver");
356
357         ptm_driver->owner = THIS_MODULE;
358         ptm_driver->driver_name = "pty_master";
359         ptm_driver->name = "ptm";
360         ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
361         ptm_driver->minor_start = 0;
362         ptm_driver->type = TTY_DRIVER_TYPE_PTY;
363         ptm_driver->subtype = PTY_TYPE_MASTER;
364         ptm_driver->init_termios = tty_std_termios;
365         ptm_driver->init_termios.c_iflag = 0;
366         ptm_driver->init_termios.c_oflag = 0;
367         ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
368         ptm_driver->init_termios.c_lflag = 0;
369         ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
370                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
371         ptm_driver->other = pts_driver;
372         tty_set_operations(ptm_driver, &pty_ops);
373         ptm_driver->ioctl = pty_unix98_ioctl;
374
375         pts_driver->owner = THIS_MODULE;
376         pts_driver->driver_name = "pty_slave";
377         pts_driver->name = "pts";
378         pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
379         pts_driver->minor_start = 0;
380         pts_driver->type = TTY_DRIVER_TYPE_PTY;
381         pts_driver->subtype = PTY_TYPE_SLAVE;
382         pts_driver->init_termios = tty_std_termios;
383         pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
384         pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |
385                 TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;
386         pts_driver->other = ptm_driver;
387         tty_set_operations(pts_driver, &pty_ops);
388         
389         if (tty_register_driver(ptm_driver))
390                 panic("Couldn't register Unix98 ptm driver");
391         if (tty_register_driver(pts_driver))
392                 panic("Couldn't register Unix98 pts driver");
393
394         pty_table[1].data = &ptm_driver->refcount;
395 }
396 #else
397 static inline void unix98_pty_init(void) { }
398 #endif
399
400 static int __init pty_init(void)
401 {
402         legacy_pty_init();
403         unix98_pty_init();
404         return 0;
405 }
406 module_init(pty_init);