ia64/linux-2.6.18-xen.hg

view drivers/char/pty.c @ 893:f994bfe9b93b

linux/blktap2: reduce TLB flush scope

c/s 885 added very coarse TLB flushing. Since these flushes always
follow single page updates, single page flushes (when available) are
sufficient.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Jun 04 10:32:57 2009 +0100 (2009-06-04)
parents 831230e53067
children
line source
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 */
14 #include <linux/module.h> /* For EXPORT_SYMBOL */
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>
28 #include <asm/uaccess.h>
29 #include <asm/system.h>
30 #include <linux/bitops.h>
31 #include <linux/devpts_fs.h>
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
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 }
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;
83 if (!o_tty)
84 return;
86 tty_wakeup(o_tty);
87 set_bit(TTY_THROTTLED, &tty->flags);
88 }
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;
109 if (!to || tty->stopped)
110 return 0;
112 c = to->receive_room;
113 if (c > count)
114 c = count;
115 to->ldisc.receive_buf(to, buf, NULL, c);
117 return c;
118 }
120 static int pty_write_room(struct tty_struct *tty)
121 {
122 struct tty_struct *to = tty->link;
124 if (!to || tty->stopped)
125 return 0;
127 return to->receive_room;
128 }
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;
152 /* We should get the line discipline lock for "tty->link" */
153 if (!to || !to->ldisc.chars_in_buffer)
154 return 0;
156 /* The ldisc must report 0 if no characters available to be read */
157 count = to->ldisc.chars_in_buffer(to);
159 if (tty->driver->subtype == PTY_TYPE_SLAVE) return count;
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 }
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 }
182 static void pty_flush_buffer(struct tty_struct *tty)
183 {
184 struct tty_struct *to = tty->link;
186 if (!to)
187 return;
189 if (to->ldisc.flush_buffer)
190 to->ldisc.flush_buffer(to);
192 if (to->packet) {
193 tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
194 wake_up_interruptible(&to->read_wait);
195 }
196 }
198 static int pty_open(struct tty_struct *tty, struct file * filp)
199 {
200 int retval = -ENODEV;
202 if (!tty || !tty->link)
203 goto out;
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;
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 }
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 }
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 };
238 /* Traditional BSD devices */
239 #ifdef CONFIG_LEGACY_PTYS
240 static struct tty_driver *pty_driver, *pty_slave_driver;
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 }
252 static void __init legacy_pty_init(void)
253 {
255 pty_driver = alloc_tty_driver(NR_PTYS);
256 if (!pty_driver)
257 panic("Couldn't allocate pty driver");
259 pty_slave_driver = alloc_tty_driver(NR_PTYS);
260 if (!pty_slave_driver)
261 panic("Couldn't allocate pty slave driver");
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;
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);
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
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;
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 };
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 }
345 return -ENOIOCTLCMD;
346 }
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");
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;
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);
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");
394 pty_table[1].data = &ptm_driver->refcount;
395 }
396 #else
397 static inline void unix98_pty_init(void) { }
398 #endif
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);