1 /*
2 * n_tty.c --- implements the N_TTY line discipline.
3 *
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
7 * anyway...)
8 *
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
12 *
13 * Written by Theodore Ts'o, Copyright 1994.
14 *
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
17 *
18 * This file may be redistributed under the terms of the GNU General Public
19 * License.
20 *
21 * Reduced memory usage for older ARM systems - Russell King.
22 *
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
26 *
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where write_chan returns
30 * EAGAIN
31 */
32
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
43 #include <linux/kd.h>
44 #include <linux/mm.h>
45 #include <linux/string.h>
46 #include <linux/slab.h>
47 #include <linux/poll.h>
48
49 #include <asm/uaccess.h>
50 #include <asm/system.h>
51 #include <asm/bitops.h>
52
53 #define CONSOLE_DEV MKDEV(TTY_MAJOR,0)
54 #define SYSCONS_DEV MKDEV(TTYAUX_MAJOR,1)
55
56 #ifndef MIN
57 #define MIN(a,b) ((a) < (b) ? (a) : (b))
58 #endif
59
60 /* number of characters left in xmit buffer before select has we have room */
61 #define WAKEUP_CHARS 256
62
63 /*
64 * This defines the low- and high-watermarks for throttling and
65 * unthrottling the TTY driver. These watermarks are used for
66 * controlling the space in the read buffer.
67 */
68 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
69 #define TTY_THRESHOLD_UNTHROTTLE 128
70
alloc_buf(void)71 static inline unsigned char *alloc_buf(void)
72 {
73 unsigned char *p;
74 int prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
75
76 if (PAGE_SIZE != N_TTY_BUF_SIZE) {
77 p = kmalloc(N_TTY_BUF_SIZE, prio);
78 if (p)
79 memset(p, 0, N_TTY_BUF_SIZE);
80 } else
81 p = (unsigned char *)get_zeroed_page(prio);
82
83 return p;
84 }
85
free_buf(unsigned char * buf)86 static inline void free_buf(unsigned char *buf)
87 {
88 if (PAGE_SIZE != N_TTY_BUF_SIZE)
89 kfree(buf);
90 else
91 free_page((unsigned long) buf);
92 }
93
put_tty_queue_nolock(unsigned char c,struct tty_struct * tty)94 static inline void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
95 {
96 if (tty->read_cnt < N_TTY_BUF_SIZE) {
97 tty->read_buf[tty->read_head] = c;
98 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
99 tty->read_cnt++;
100 }
101 }
102
put_tty_queue(unsigned char c,struct tty_struct * tty)103 static inline void put_tty_queue(unsigned char c, struct tty_struct *tty)
104 {
105 unsigned long flags;
106 /*
107 * The problem of stomping on the buffers ends here.
108 * Why didn't anyone see this one coming? --AJK
109 */
110 spin_lock_irqsave(&tty->read_lock, flags);
111 put_tty_queue_nolock(c, tty);
112 spin_unlock_irqrestore(&tty->read_lock, flags);
113 }
114
115 /**
116 * check_unthrottle - allow new receive data
117 * @tty; tty device
118 *
119 * Check whether to call the driver.unthrottle function.
120 * We test the TTY_THROTTLED bit first so that it always
121 * indicates the current state. The decision about whether
122 * it is worth allowing more input has been taken by the caller.
123 * Can sleep, may be called under the atomic_read semaphore but
124 * this is not guaranteed.
125 */
126
check_unthrottle(struct tty_struct * tty)127 static void check_unthrottle(struct tty_struct * tty)
128 {
129 if (tty->count &&
130 test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
131 tty->driver.unthrottle)
132 tty->driver.unthrottle(tty);
133 }
134
135 /**
136 * reset_buffer_flags - reset buffer state
137 * @tty: terminal to reset
138 *
139 * Reset the read buffer counters, clear the flags,
140 * and make sure the driver is unthrottled. Called
141 * from n_tty_open() and n_tty_flush_buffer().
142 */
reset_buffer_flags(struct tty_struct * tty)143 static void reset_buffer_flags(struct tty_struct *tty)
144 {
145 unsigned long flags;
146
147 spin_lock_irqsave(&tty->read_lock, flags);
148 tty->read_head = tty->read_tail = tty->read_cnt = 0;
149 spin_unlock_irqrestore(&tty->read_lock, flags);
150 tty->canon_head = tty->canon_data = tty->erasing = 0;
151 memset(&tty->read_flags, 0, sizeof tty->read_flags);
152 check_unthrottle(tty);
153 }
154
155 /**
156 * n_tty_flush_buffer - clean input queue
157 * @tty: terminal device
158 *
159 * Flush the input buffer. Called when the line discipline is
160 * being closed, when the tty layer wants the buffer flushed (eg
161 * at hangup) or when the N_TTY line discipline internally has to
162 * clean the pending queue (for example some signals).
163 *
164 * FIXME: tty->ctrl_status is not spinlocked and relies on
165 * lock_kernel() still.
166 */
167
n_tty_flush_buffer(struct tty_struct * tty)168 void n_tty_flush_buffer(struct tty_struct * tty)
169 {
170 /* clear everything and unthrottle the driver */
171 reset_buffer_flags(tty);
172
173 if (!tty->link)
174 return;
175
176 if (tty->link->packet) {
177 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
178 wake_up_interruptible(&tty->link->read_wait);
179 }
180 }
181
182 /**
183 * n_tty_chars_in_buffer - report available bytes
184 * @tty: tty device
185 *
186 * Report the number of characters buffered to be delivered to user
187 * at this instant in time.
188 */
189
n_tty_chars_in_buffer(struct tty_struct * tty)190 ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
191 {
192 unsigned long flags;
193 ssize_t n = 0;
194
195 spin_lock_irqsave(&tty->read_lock, flags);
196 if (!tty->icanon) {
197 n = tty->read_cnt;
198 } else if (tty->canon_data) {
199 n = (tty->canon_head > tty->read_tail) ?
200 tty->canon_head - tty->read_tail :
201 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
202 }
203 spin_unlock_irqrestore(&tty->read_lock, flags);
204 return n;
205 }
206
207 /*
208 * Perform OPOST processing. Returns -1 when the output device is
209 * full and the character must be retried.
210 */
opost(unsigned char c,struct tty_struct * tty)211 static int opost(unsigned char c, struct tty_struct *tty)
212 {
213 int space, spaces;
214
215 space = tty->driver.write_room(tty);
216 if (!space)
217 return -1;
218
219 if (O_OPOST(tty)) {
220 switch (c) {
221 case '\n':
222 if (O_ONLRET(tty))
223 tty->column = 0;
224 if (O_ONLCR(tty)) {
225 if (space < 2)
226 return -1;
227 tty->driver.put_char(tty, '\r');
228 tty->column = 0;
229 }
230 tty->canon_column = tty->column;
231 break;
232 case '\r':
233 if (O_ONOCR(tty) && tty->column == 0)
234 return 0;
235 if (O_OCRNL(tty)) {
236 c = '\n';
237 if (O_ONLRET(tty))
238 tty->canon_column = tty->column = 0;
239 break;
240 }
241 tty->canon_column = tty->column = 0;
242 break;
243 case '\t':
244 spaces = 8 - (tty->column & 7);
245 if (O_TABDLY(tty) == XTABS) {
246 if (space < spaces)
247 return -1;
248 tty->column += spaces;
249 tty->driver.write(tty, 0, " ", spaces);
250 return 0;
251 }
252 tty->column += spaces;
253 break;
254 case '\b':
255 if (tty->column > 0)
256 tty->column--;
257 break;
258 default:
259 if (O_OLCUC(tty))
260 c = toupper(c);
261 if (!iscntrl(c))
262 tty->column++;
263 break;
264 }
265 }
266 tty->driver.put_char(tty, c);
267 return 0;
268 }
269
270 /**
271 * opost_block - block postprocess
272 * @tty: terminal device
273 * @inbuf: user buffer
274 * @nr: number of bytes
275 *
276 * This path is used to speed up block console writes, among other
277 * things when processing blocks of output data. It handles only
278 * the simple cases normally found and helps to generate blocks of
279 * symbols for the console driver and thus improve performance.
280 *
281 * Called from write_chan under the tty layer write lock.
282 */
283
opost_block(struct tty_struct * tty,const unsigned char * inbuf,unsigned int nr)284 static ssize_t opost_block(struct tty_struct * tty,
285 const unsigned char * inbuf, unsigned int nr)
286 {
287 char buf[80];
288 int space;
289 int i;
290 char *cp;
291
292 space = tty->driver.write_room(tty);
293 if (!space)
294 return 0;
295 if (nr > space)
296 nr = space;
297 if (nr > sizeof(buf))
298 nr = sizeof(buf);
299
300 if (copy_from_user(buf, inbuf, nr))
301 return -EFAULT;
302
303 for (i = 0, cp = buf; i < nr; i++, cp++) {
304 switch (*cp) {
305 case '\n':
306 if (O_ONLRET(tty))
307 tty->column = 0;
308 if (O_ONLCR(tty))
309 goto break_out;
310 tty->canon_column = tty->column;
311 break;
312 case '\r':
313 if (O_ONOCR(tty) && tty->column == 0)
314 goto break_out;
315 if (O_OCRNL(tty)) {
316 *cp = '\n';
317 if (O_ONLRET(tty))
318 tty->canon_column = tty->column = 0;
319 break;
320 }
321 tty->canon_column = tty->column = 0;
322 break;
323 case '\t':
324 goto break_out;
325 case '\b':
326 if (tty->column > 0)
327 tty->column--;
328 break;
329 default:
330 if (O_OLCUC(tty))
331 *cp = toupper(*cp);
332 if (!iscntrl(*cp))
333 tty->column++;
334 break;
335 }
336 }
337 break_out:
338 if (tty->driver.flush_chars)
339 tty->driver.flush_chars(tty);
340 i = tty->driver.write(tty, 0, buf, i);
341 return i;
342 }
343
344
345
put_char(unsigned char c,struct tty_struct * tty)346 static inline void put_char(unsigned char c, struct tty_struct *tty)
347 {
348 tty->driver.put_char(tty, c);
349 }
350
351 /* Must be called only when L_ECHO(tty) is true. */
352
echo_char(unsigned char c,struct tty_struct * tty)353 static void echo_char(unsigned char c, struct tty_struct *tty)
354 {
355 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
356 put_char('^', tty);
357 put_char(c ^ 0100, tty);
358 tty->column += 2;
359 } else
360 opost(c, tty);
361 }
362
finish_erasing(struct tty_struct * tty)363 static inline void finish_erasing(struct tty_struct *tty)
364 {
365 if (tty->erasing) {
366 put_char('/', tty);
367 tty->column += 2;
368 tty->erasing = 0;
369 }
370 }
371
372 /**
373 * eraser - handle erase function
374 * @c: character input
375 * @tty: terminal device
376 *
377 * Perform erase and neccessary output when an erase character is
378 * present in the stream from the driver layer. Handles the complexities
379 * of UTF-8 multibyte symbols.
380 */
381
eraser(unsigned char c,struct tty_struct * tty)382 static void eraser(unsigned char c, struct tty_struct *tty)
383 {
384 enum { ERASE, WERASE, KILL } kill_type;
385 int head, seen_alnums;
386 unsigned long flags;
387
388 if (tty->read_head == tty->canon_head) {
389 /* opost('\a', tty); */ /* what do you think? */
390 return;
391 }
392 if (c == ERASE_CHAR(tty))
393 kill_type = ERASE;
394 else if (c == WERASE_CHAR(tty))
395 kill_type = WERASE;
396 else {
397 if (!L_ECHO(tty)) {
398 spin_lock_irqsave(&tty->read_lock, flags);
399 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
400 (N_TTY_BUF_SIZE - 1));
401 tty->read_head = tty->canon_head;
402 spin_unlock_irqrestore(&tty->read_lock, flags);
403 return;
404 }
405 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
406 spin_lock_irqsave(&tty->read_lock, flags);
407 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
408 (N_TTY_BUF_SIZE - 1));
409 tty->read_head = tty->canon_head;
410 spin_unlock_irqrestore(&tty->read_lock, flags);
411 finish_erasing(tty);
412 echo_char(KILL_CHAR(tty), tty);
413 /* Add a newline if ECHOK is on and ECHOKE is off. */
414 if (L_ECHOK(tty))
415 opost('\n', tty);
416 return;
417 }
418 kill_type = KILL;
419 }
420
421 seen_alnums = 0;
422 while (tty->read_head != tty->canon_head) {
423 head = (tty->read_head - 1) & (N_TTY_BUF_SIZE-1);
424 c = tty->read_buf[head];
425 if (kill_type == WERASE) {
426 /* Equivalent to BSD's ALTWERASE. */
427 if (isalnum(c) || c == '_')
428 seen_alnums++;
429 else if (seen_alnums)
430 break;
431 }
432 spin_lock_irqsave(&tty->read_lock, flags);
433 tty->read_head = head;
434 tty->read_cnt--;
435 spin_unlock_irqrestore(&tty->read_lock, flags);
436 if (L_ECHO(tty)) {
437 if (L_ECHOPRT(tty)) {
438 if (!tty->erasing) {
439 put_char('\\', tty);
440 tty->column++;
441 tty->erasing = 1;
442 }
443 echo_char(c, tty);
444 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
445 echo_char(ERASE_CHAR(tty), tty);
446 } else if (c == '\t') {
447 unsigned int col = tty->canon_column;
448 unsigned long tail = tty->canon_head;
449
450 /* Find the column of the last char. */
451 while (tail != tty->read_head) {
452 c = tty->read_buf[tail];
453 if (c == '\t')
454 col = (col | 7) + 1;
455 else if (iscntrl(c)) {
456 if (L_ECHOCTL(tty))
457 col += 2;
458 } else
459 col++;
460 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
461 }
462
463 /* should never happen */
464 if (tty->column > 0x80000000)
465 tty->column = 0;
466
467 /* Now backup to that column. */
468 while (tty->column > col) {
469 /* Can't use opost here. */
470 put_char('\b', tty);
471 if (tty->column > 0)
472 tty->column--;
473 }
474 } else {
475 if (iscntrl(c) && L_ECHOCTL(tty)) {
476 put_char('\b', tty);
477 put_char(' ', tty);
478 put_char('\b', tty);
479 if (tty->column > 0)
480 tty->column--;
481 }
482 if (!iscntrl(c) || L_ECHOCTL(tty)) {
483 put_char('\b', tty);
484 put_char(' ', tty);
485 put_char('\b', tty);
486 if (tty->column > 0)
487 tty->column--;
488 }
489 }
490 }
491 if (kill_type == ERASE)
492 break;
493 }
494 if (tty->read_head == tty->canon_head)
495 finish_erasing(tty);
496 }
497
498 /**
499 * isig - handle the ISIG optio
500 * @sig: signal
501 * @tty: terminal
502 * @flush: force flush
503 *
504 * Called when a signal is being sent due to terminal input. This
505 * may caus terminal flushing to take place according to the termios
506 * settings and character used. Called from the driver receive_buf
507 * path so serialized.
508 */
509
isig(int sig,struct tty_struct * tty,int flush)510 static inline void isig(int sig, struct tty_struct *tty, int flush)
511 {
512 if (tty->pgrp > 0)
513 kill_pg(tty->pgrp, sig, 1);
514 if (flush || !L_NOFLSH(tty)) {
515 n_tty_flush_buffer(tty);
516 if (tty->driver.flush_buffer)
517 tty->driver.flush_buffer(tty);
518 }
519 }
520
521 /**
522 * n_tty_receive_break - handle break
523 * @tty: terminal
524 *
525 * An RS232 break event has been hit in the incoming bitstream. This
526 * can cause a variety of events depending upon the termios settings.
527 *
528 * Called from the receive_buf path so single threaded.
529 */
530
n_tty_receive_break(struct tty_struct * tty)531 static inline void n_tty_receive_break(struct tty_struct *tty)
532 {
533 if (I_IGNBRK(tty))
534 return;
535 if (I_BRKINT(tty)) {
536 isig(SIGINT, tty, 1);
537 return;
538 }
539 if (I_PARMRK(tty)) {
540 put_tty_queue('\377', tty);
541 put_tty_queue('\0', tty);
542 }
543 put_tty_queue('\0', tty);
544 wake_up_interruptible(&tty->read_wait);
545 }
546
547 /**
548 * n_tty_receive_overrun - handle overrun reporting
549 * @tty: terminal
550 *
551 * Data arrived faster than we could process it. While the tty
552 * driver has flagged this the bits that were missed are gone
553 * forever.
554 *
555 * Called from the receive_buf path so single threaded. Does not
556 * need locking as num_overrun and overrun_time are function
557 * private.
558 */
559
n_tty_receive_overrun(struct tty_struct * tty)560 static inline void n_tty_receive_overrun(struct tty_struct *tty)
561 {
562 char buf[64];
563
564 tty->num_overrun++;
565 if (time_before(tty->overrun_time, jiffies - HZ)) {
566 printk(KERN_WARNING "%s: %d input overrun(s)\n", tty_name(tty, buf),
567 tty->num_overrun);
568 tty->overrun_time = jiffies;
569 tty->num_overrun = 0;
570 }
571 }
572
573 /**
574 * n_tty_receive_parity_error - error notifier
575 * @tty: terminal device
576 * @c: character
577 *
578 * Process a parity error and queue the right data to indicate
579 * the error case if neccessary. Locking as per n_tty_receive_buf.
580 */
n_tty_receive_parity_error(struct tty_struct * tty,unsigned char c)581 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
582 unsigned char c)
583 {
584 if (I_IGNPAR(tty)) {
585 return;
586 }
587 if (I_PARMRK(tty)) {
588 put_tty_queue('\377', tty);
589 put_tty_queue('\0', tty);
590 put_tty_queue(c, tty);
591 } else if (I_INPCK(tty))
592 put_tty_queue('\0', tty);
593 else
594 put_tty_queue(c, tty);
595 wake_up_interruptible(&tty->read_wait);
596 }
597
598 /**
599 * n_tty_receive_char - perform processing
600 * @tty: terminal device
601 * @c: character
602 *
603 * Process an individual character of input received from the driver.
604 * This is serialized with respect to itself by the rules for the
605 * driver above.
606 */
607
n_tty_receive_char(struct tty_struct * tty,unsigned char c)608 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
609 {
610 unsigned long flags;
611
612 if (tty->raw) {
613 put_tty_queue(c, tty);
614 return;
615 }
616
617 if (tty->stopped && !tty->flow_stopped &&
618 I_IXON(tty) && I_IXANY(tty)) {
619 start_tty(tty);
620 return;
621 }
622
623 if (I_ISTRIP(tty))
624 c &= 0x7f;
625 if (I_IUCLC(tty) && L_IEXTEN(tty))
626 c=tolower(c);
627
628 if (tty->closing) {
629 if (I_IXON(tty)) {
630 if (c == START_CHAR(tty))
631 start_tty(tty);
632 else if (c == STOP_CHAR(tty))
633 stop_tty(tty);
634 }
635 return;
636 }
637
638 /*
639 * If the previous character was LNEXT, or we know that this
640 * character is not one of the characters that we'll have to
641 * handle specially, do shortcut processing to speed things
642 * up.
643 */
644 if (!test_bit(c, &tty->process_char_map) || tty->lnext) {
645 finish_erasing(tty);
646 tty->lnext = 0;
647 if (L_ECHO(tty)) {
648 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
649 put_char('\a', tty); /* beep if no space */
650 return;
651 }
652 /* Record the column of first canon char. */
653 if (tty->canon_head == tty->read_head)
654 tty->canon_column = tty->column;
655 echo_char(c, tty);
656 }
657 if (I_PARMRK(tty) && c == (unsigned char) '\377')
658 put_tty_queue(c, tty);
659 put_tty_queue(c, tty);
660 return;
661 }
662
663 if (c == '\r') {
664 if (I_IGNCR(tty))
665 return;
666 if (I_ICRNL(tty))
667 c = '\n';
668 } else if (c == '\n' && I_INLCR(tty))
669 c = '\r';
670 if (I_IXON(tty)) {
671 if (c == START_CHAR(tty)) {
672 start_tty(tty);
673 return;
674 }
675 if (c == STOP_CHAR(tty)) {
676 stop_tty(tty);
677 return;
678 }
679 }
680 if (L_ISIG(tty)) {
681 int signal;
682 signal = SIGINT;
683 if (c == INTR_CHAR(tty))
684 goto send_signal;
685 signal = SIGQUIT;
686 if (c == QUIT_CHAR(tty))
687 goto send_signal;
688 signal = SIGTSTP;
689 if (c == SUSP_CHAR(tty)) {
690 send_signal:
691 isig(signal, tty, 0);
692 return;
693 }
694 }
695 if (tty->icanon) {
696 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
697 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
698 eraser(c, tty);
699 return;
700 }
701 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
702 tty->lnext = 1;
703 if (L_ECHO(tty)) {
704 finish_erasing(tty);
705 if (L_ECHOCTL(tty)) {
706 put_char('^', tty);
707 put_char('\b', tty);
708 }
709 }
710 return;
711 }
712 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
713 L_IEXTEN(tty)) {
714 unsigned long tail = tty->canon_head;
715
716 finish_erasing(tty);
717 echo_char(c, tty);
718 opost('\n', tty);
719 while (tail != tty->read_head) {
720 echo_char(tty->read_buf[tail], tty);
721 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
722 }
723 return;
724 }
725 if (c == '\n') {
726 if (L_ECHO(tty) || L_ECHONL(tty)) {
727 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
728 put_char('\a', tty);
729 return;
730 }
731 opost('\n', tty);
732 }
733 goto handle_newline;
734 }
735 if (c == EOF_CHAR(tty)) {
736 if (tty->canon_head != tty->read_head)
737 set_bit(TTY_PUSH, &tty->flags);
738 c = __DISABLED_CHAR;
739 goto handle_newline;
740 }
741 if ((c == EOL_CHAR(tty)) ||
742 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
743 /*
744 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
745 */
746 if (L_ECHO(tty)) {
747 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
748 put_char('\a', tty);
749 return;
750 }
751 /* Record the column of first canon char. */
752 if (tty->canon_head == tty->read_head)
753 tty->canon_column = tty->column;
754 echo_char(c, tty);
755 }
756 /*
757 * XXX does PARMRK doubling happen for
758 * EOL_CHAR and EOL2_CHAR?
759 */
760 if (I_PARMRK(tty) && c == (unsigned char) '\377')
761 put_tty_queue(c, tty);
762
763 handle_newline:
764 spin_lock_irqsave(&tty->read_lock, flags);
765 set_bit(tty->read_head, &tty->read_flags);
766 put_tty_queue_nolock(c, tty);
767 tty->canon_head = tty->read_head;
768 tty->canon_data++;
769 spin_unlock_irqrestore(&tty->read_lock, flags);
770 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
771 if (waitqueue_active(&tty->read_wait))
772 wake_up_interruptible(&tty->read_wait);
773 return;
774 }
775 }
776
777 finish_erasing(tty);
778 if (L_ECHO(tty)) {
779 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
780 put_char('\a', tty); /* beep if no space */
781 return;
782 }
783 if (c == '\n')
784 opost('\n', tty);
785 else {
786 /* Record the column of first canon char. */
787 if (tty->canon_head == tty->read_head)
788 tty->canon_column = tty->column;
789 echo_char(c, tty);
790 }
791 }
792
793 if (I_PARMRK(tty) && c == (unsigned char) '\377')
794 put_tty_queue(c, tty);
795
796 put_tty_queue(c, tty);
797 }
798
799 /**
800 * n_tty_receive_room - receive space
801 * @tty: terminal
802 *
803 * Called by the driver to find out how much data it is
804 * permitted to feed to the line discipline without any being lost
805 * and thus to manage flow control. Not serialized. Answers for the
806 * "instant".
807 */
808
n_tty_receive_room(struct tty_struct * tty)809 static int n_tty_receive_room(struct tty_struct *tty)
810 {
811 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
812
813 /*
814 * If we are doing input canonicalization, and there are no
815 * pending newlines, let characters through without limit, so
816 * that erase characters will be handled. Other excess
817 * characters will be beeped.
818 */
819 if (tty->icanon && !tty->canon_data)
820 return N_TTY_BUF_SIZE;
821
822 if (left > 0)
823 return left;
824 return 0;
825 }
826
827 /**
828 * n_tty_write_wakeup - asynchronous I/O notifier
829 * @tty: tty device
830 *
831 * Required for the ptys, serial driver etc. since processes
832 * that attach themselves to the master and rely on ASYNC
833 * IO must be woken up
834 */
835
n_tty_write_wakeup(struct tty_struct * tty)836 static void n_tty_write_wakeup(struct tty_struct *tty)
837 {
838 if (tty->fasync)
839 {
840 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
841 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
842 }
843 return;
844 }
845
846 /**
847 * n_tty_receive_buf - data receive
848 * @tty: terminal device
849 * @cp: buffer
850 * @fp: flag buffer
851 * @count: characters
852 *
853 * Called by the terminal driver when a block of characters has
854 * been received. This function must be called from soft contexts
855 * not from interrupt context. The driver is responsible for making
856 * calls one at a time and in order (or using queue_ldisc)
857 */
858
n_tty_receive_buf(struct tty_struct * tty,const unsigned char * cp,char * fp,int count)859 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
860 char *fp, int count)
861 {
862 const unsigned char *p;
863 char *f, flags = TTY_NORMAL;
864 int i;
865 char buf[64];
866 unsigned long cpuflags;
867
868 if (!tty->read_buf)
869 return;
870
871 if (tty->real_raw) {
872 spin_lock_irqsave(&tty->read_lock, cpuflags);
873 i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
874 N_TTY_BUF_SIZE - tty->read_head));
875 memcpy(tty->read_buf + tty->read_head, cp, i);
876 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
877 tty->read_cnt += i;
878 cp += i;
879 count -= i;
880
881 i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
882 N_TTY_BUF_SIZE - tty->read_head));
883 memcpy(tty->read_buf + tty->read_head, cp, i);
884 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
885 tty->read_cnt += i;
886 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
887 } else {
888 for (i=count, p = cp, f = fp; i; i--, p++) {
889 if (f)
890 flags = *f++;
891 switch (flags) {
892 case TTY_NORMAL:
893 n_tty_receive_char(tty, *p);
894 break;
895 case TTY_BREAK:
896 n_tty_receive_break(tty);
897 break;
898 case TTY_PARITY:
899 case TTY_FRAME:
900 n_tty_receive_parity_error(tty, *p);
901 break;
902 case TTY_OVERRUN:
903 n_tty_receive_overrun(tty);
904 break;
905 default:
906 printk("%s: unknown flag %d\n",
907 tty_name(tty, buf), flags);
908 break;
909 }
910 }
911 if (tty->driver.flush_chars)
912 tty->driver.flush_chars(tty);
913 }
914
915 if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
916 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
917 if (waitqueue_active(&tty->read_wait))
918 wake_up_interruptible(&tty->read_wait);
919 }
920
921 /*
922 * Check the remaining room for the input canonicalization
923 * mode. We don't want to throttle the driver if we're in
924 * canonical mode and don't have a newline yet!
925 */
926 if (n_tty_receive_room(tty) < TTY_THRESHOLD_THROTTLE) {
927 /* check TTY_THROTTLED first so it indicates our state */
928 if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
929 tty->driver.throttle)
930 tty->driver.throttle(tty);
931 }
932 }
933
is_ignored(int sig)934 int is_ignored(int sig)
935 {
936 return (sigismember(¤t->blocked, sig) ||
937 current->sig->action[sig-1].sa.sa_handler == SIG_IGN);
938 }
939
940 /**
941 * n_tty_set_termios - termios data changed
942 * @tty: terminal
943 * @old: previous data
944 *
945 * Called by the tty layer when the user changes termios flags so
946 * that the line discipline can plan ahead. This function cannot sleep
947 * and is protected from re-entry by the tty layer. The user is
948 * guaranteed that this function will not be re-entered or in progress
949 * when the ldisc is closed.
950 */
951
n_tty_set_termios(struct tty_struct * tty,struct termios * old)952 static void n_tty_set_termios(struct tty_struct *tty, struct termios * old)
953 {
954 if (!tty)
955 return;
956
957 tty->icanon = (L_ICANON(tty) != 0);
958 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
959 tty->raw = 1;
960 tty->real_raw = 1;
961 return;
962 }
963 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
964 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
965 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
966 I_PARMRK(tty)) {
967 memset(tty->process_char_map, 0, 256/8);
968
969 if (I_IGNCR(tty) || I_ICRNL(tty))
970 set_bit('\r', &tty->process_char_map);
971 if (I_INLCR(tty))
972 set_bit('\n', &tty->process_char_map);
973
974 if (L_ICANON(tty)) {
975 set_bit(ERASE_CHAR(tty), &tty->process_char_map);
976 set_bit(KILL_CHAR(tty), &tty->process_char_map);
977 set_bit(EOF_CHAR(tty), &tty->process_char_map);
978 set_bit('\n', &tty->process_char_map);
979 set_bit(EOL_CHAR(tty), &tty->process_char_map);
980 if (L_IEXTEN(tty)) {
981 set_bit(WERASE_CHAR(tty),
982 &tty->process_char_map);
983 set_bit(LNEXT_CHAR(tty),
984 &tty->process_char_map);
985 set_bit(EOL2_CHAR(tty),
986 &tty->process_char_map);
987 if (L_ECHO(tty))
988 set_bit(REPRINT_CHAR(tty),
989 &tty->process_char_map);
990 }
991 }
992 if (I_IXON(tty)) {
993 set_bit(START_CHAR(tty), &tty->process_char_map);
994 set_bit(STOP_CHAR(tty), &tty->process_char_map);
995 }
996 if (L_ISIG(tty)) {
997 set_bit(INTR_CHAR(tty), &tty->process_char_map);
998 set_bit(QUIT_CHAR(tty), &tty->process_char_map);
999 set_bit(SUSP_CHAR(tty), &tty->process_char_map);
1000 }
1001 clear_bit(__DISABLED_CHAR, &tty->process_char_map);
1002 tty->raw = 0;
1003 tty->real_raw = 0;
1004 } else {
1005 tty->raw = 1;
1006 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1007 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1008 (tty->driver.flags & TTY_DRIVER_REAL_RAW))
1009 tty->real_raw = 1;
1010 else
1011 tty->real_raw = 0;
1012 }
1013 }
1014
1015 /**
1016 * n_tty_close - close the ldisc for this tty
1017 * @tty: device
1018 *
1019 * Called from the terminal layer when this line discipline is
1020 * being shut down, either because of a close or becsuse of a
1021 * discipline change. The function will not be called while other
1022 * ldisc methods are in progress.
1023 */
1024
n_tty_close(struct tty_struct * tty)1025 static void n_tty_close(struct tty_struct *tty)
1026 {
1027 n_tty_flush_buffer(tty);
1028 if (tty->read_buf) {
1029 free_buf(tty->read_buf);
1030 tty->read_buf = 0;
1031 }
1032 }
1033
1034 /**
1035 * n_tty_open - open an ldisc
1036 * @tty: terminal to open
1037 *
1038 * Called when this line discipline is being attached to the
1039 * terminal device. Can sleep. Called serialized so that no
1040 * other events will occur in parallel. No further open will occur
1041 * until a close.
1042 */
1043
n_tty_open(struct tty_struct * tty)1044 static int n_tty_open(struct tty_struct *tty)
1045 {
1046 if (!tty)
1047 return -EINVAL;
1048
1049 /* This one is ugly. Currently a malloc failure here can panic */
1050 if (!tty->read_buf) {
1051 tty->read_buf = alloc_buf();
1052 if (!tty->read_buf)
1053 return -ENOMEM;
1054 }
1055 memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
1056 reset_buffer_flags(tty);
1057 tty->column = 0;
1058 n_tty_set_termios(tty, 0);
1059 tty->minimum_to_wake = 1;
1060 tty->closing = 0;
1061 return 0;
1062 }
1063
input_available_p(struct tty_struct * tty,int amt)1064 static inline int input_available_p(struct tty_struct *tty, int amt)
1065 {
1066 if (tty->icanon) {
1067 if (tty->canon_data)
1068 return 1;
1069 } else if (tty->read_cnt >= (amt ? amt : 1))
1070 return 1;
1071
1072 return 0;
1073 }
1074
1075 /**
1076 * copy_from_read_buf - copy read data directly
1077 * @tty: terminal device
1078 * @b: user data
1079 * @nr: size of data
1080 *
1081 * Helper function to speed up read_chan. It is only called when
1082 * ICANON is off; it copies characters straight from the tty queue to
1083 * user space directly. It can be profitably called twice; once to
1084 * drain the space from the tail pointer to the (physical) end of the
1085 * buffer, and once to drain the space from the (physical) beginning of
1086 * the buffer to head pointer.
1087 *
1088 * Called under the tty->atomic_read sem and with TTY_DONT_FLIP set
1089 *
1090 */
1091
copy_from_read_buf(struct tty_struct * tty,unsigned char ** b,size_t * nr)1092 static inline int copy_from_read_buf(struct tty_struct *tty,
1093 unsigned char **b,
1094 size_t *nr)
1095
1096 {
1097 int retval;
1098 ssize_t n;
1099 unsigned long flags;
1100
1101 retval = 0;
1102 spin_lock_irqsave(&tty->read_lock, flags);
1103 n = MIN(*nr, MIN(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail));
1104 spin_unlock_irqrestore(&tty->read_lock, flags);
1105 if (n) {
1106 mb();
1107 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1108 n -= retval;
1109 spin_lock_irqsave(&tty->read_lock, flags);
1110 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1111 tty->read_cnt -= n;
1112 spin_unlock_irqrestore(&tty->read_lock, flags);
1113 *b += n;
1114 *nr -= n;
1115 }
1116 return retval;
1117 }
1118
1119 /**
1120 * job_control - check job control
1121 * @tty: tty
1122 * @file: file handle
1123 *
1124 * Perform job control management checks on this file/tty descriptor
1125 * and if appropriate send any needed signals and return a negative
1126 * error code if action should be taken.
1127 */
1128
job_control(struct tty_struct * tty,struct file * file)1129 static int job_control(struct tty_struct *tty, struct file *file)
1130 {
1131 /* Job control check -- must be done at start and after
1132 every sleep (POSIX.1 7.1.1.4). */
1133 /* NOTE: not yet done after every sleep pending a thorough
1134 check of the logic of this change. -- jlc */
1135 /* don't stop on /dev/console */
1136 if (file->f_dentry->d_inode->i_rdev != CONSOLE_DEV &&
1137 file->f_dentry->d_inode->i_rdev != SYSCONS_DEV &&
1138 current->tty == tty) {
1139 if (tty->pgrp <= 0)
1140 printk("read_chan: tty->pgrp <= 0!\n");
1141 else if (current->pgrp != tty->pgrp) {
1142 if (is_ignored(SIGTTIN) ||
1143 is_orphaned_pgrp(current->pgrp))
1144 return -EIO;
1145 kill_pg(current->pgrp, SIGTTIN, 1);
1146 return -ERESTARTSYS;
1147 }
1148 }
1149 return 0;
1150 }
1151
1152
1153 /**
1154 * read_chan - read function for tty
1155 * @tty: tty device
1156 * @file: file object
1157 * @buf: userspace buffer pointer
1158 * @nr: size of I/O
1159 *
1160 * Perform reads for the line discipline. We are guaranteed that the
1161 * line discipline will not be closed under us but we may get multiple
1162 * parallel readers and must handle this ourselves. We may also get
1163 * a hangup. Always called in user context, may sleep.
1164 *
1165 * This code must be sure never to sleep through a hangup.
1166 */
1167
read_chan(struct tty_struct * tty,struct file * file,unsigned char __user * buf,size_t nr)1168 static ssize_t read_chan(struct tty_struct *tty, struct file *file,
1169 unsigned char __user *buf, size_t nr)
1170 {
1171 unsigned char __user *b = buf;
1172 DECLARE_WAITQUEUE(wait, current);
1173 int c;
1174 int minimum, time;
1175 ssize_t retval = 0;
1176 ssize_t size;
1177 long timeout;
1178 unsigned long flags;
1179
1180 do_it_again:
1181
1182 if (!tty->read_buf) {
1183 printk("n_tty_read_chan: called with read_buf == NULL?!?\n");
1184 return -EIO;
1185 }
1186
1187 c = job_control(tty, file);
1188 if(c < 0)
1189 return c;
1190
1191 minimum = time = 0;
1192 timeout = MAX_SCHEDULE_TIMEOUT;
1193 if (!tty->icanon) {
1194 time = (HZ / 10) * TIME_CHAR(tty);
1195 minimum = MIN_CHAR(tty);
1196 if (minimum) {
1197 if (time)
1198 tty->minimum_to_wake = 1;
1199 else if (!waitqueue_active(&tty->read_wait) ||
1200 (tty->minimum_to_wake > minimum))
1201 tty->minimum_to_wake = minimum;
1202 } else {
1203 timeout = 0;
1204 if (time) {
1205 timeout = time;
1206 time = 0;
1207 }
1208 tty->minimum_to_wake = minimum = 1;
1209 }
1210 }
1211
1212 /*
1213 * Internal serialization of reads.
1214 */
1215 if (file->f_flags & O_NONBLOCK) {
1216 if (down_trylock(&tty->atomic_read))
1217 return -EAGAIN;
1218 }
1219 else {
1220 if (down_interruptible(&tty->atomic_read))
1221 return -ERESTARTSYS;
1222 }
1223
1224 add_wait_queue(&tty->read_wait, &wait);
1225 set_bit(TTY_DONT_FLIP, &tty->flags);
1226 while (nr) {
1227 /* First test for status change. */
1228 if (tty->packet && tty->link->ctrl_status) {
1229 unsigned char cs;
1230 if (b != buf)
1231 break;
1232 cs = tty->link->ctrl_status;
1233 tty->link->ctrl_status = 0;
1234 put_user(cs, b++);
1235 nr--;
1236 break;
1237 }
1238 /* This statement must be first before checking for input
1239 so that any interrupt will set the state back to
1240 TASK_RUNNING. */
1241 set_current_state(TASK_INTERRUPTIBLE);
1242
1243 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1244 ((minimum - (b - buf)) >= 1))
1245 tty->minimum_to_wake = (minimum - (b - buf));
1246
1247 if (!input_available_p(tty, 0)) {
1248 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1249 retval = -EIO;
1250 break;
1251 }
1252 if (tty_hung_up_p(file))
1253 break;
1254 if (!timeout)
1255 break;
1256 if (file->f_flags & O_NONBLOCK) {
1257 retval = -EAGAIN;
1258 break;
1259 }
1260 if (signal_pending(current)) {
1261 retval = -ERESTARTSYS;
1262 break;
1263 }
1264 clear_bit(TTY_DONT_FLIP, &tty->flags);
1265 timeout = schedule_timeout(timeout);
1266 set_bit(TTY_DONT_FLIP, &tty->flags);
1267 continue;
1268 }
1269 current->state = TASK_RUNNING;
1270
1271 /* Deal with packet mode. */
1272 if (tty->packet && b == buf) {
1273 put_user(TIOCPKT_DATA, b++);
1274 nr--;
1275 }
1276
1277 if (tty->icanon) {
1278 /* N.B. avoid overrun if nr == 0 */
1279 while (nr && tty->read_cnt) {
1280 int eol;
1281
1282 eol = test_and_clear_bit(tty->read_tail,
1283 &tty->read_flags);
1284 c = tty->read_buf[tty->read_tail];
1285 spin_lock_irqsave(&tty->read_lock, flags);
1286 tty->read_tail = ((tty->read_tail+1) &
1287 (N_TTY_BUF_SIZE-1));
1288 tty->read_cnt--;
1289 if (eol) {
1290 /* this test should be redundant:
1291 * we shouldn't be reading data if
1292 * canon_data is 0
1293 */
1294 if (--tty->canon_data < 0)
1295 tty->canon_data = 0;
1296 }
1297 spin_unlock_irqrestore(&tty->read_lock, flags);
1298
1299 if (!eol || (c != __DISABLED_CHAR)) {
1300 put_user(c, b++);
1301 nr--;
1302 }
1303 if (eol)
1304 break;
1305 }
1306 } else {
1307 int uncopied;
1308 uncopied = copy_from_read_buf(tty, &b, &nr);
1309 uncopied += copy_from_read_buf(tty, &b, &nr);
1310 if (uncopied) {
1311 retval = -EFAULT;
1312 break;
1313 }
1314 }
1315
1316 /* If there is enough space in the read buffer now, let the
1317 * low-level driver know. We use n_tty_chars_in_buffer() to
1318 * check the buffer, as it now knows about canonical mode.
1319 * Otherwise, if the driver is throttled and the line is
1320 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1321 * we won't get any more characters.
1322 */
1323 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
1324 check_unthrottle(tty);
1325
1326 if (b - buf >= minimum)
1327 break;
1328 if (time)
1329 timeout = time;
1330 }
1331 clear_bit(TTY_DONT_FLIP, &tty->flags);
1332 up(&tty->atomic_read);
1333 remove_wait_queue(&tty->read_wait, &wait);
1334
1335 if (!waitqueue_active(&tty->read_wait))
1336 tty->minimum_to_wake = minimum;
1337
1338 current->state = TASK_RUNNING;
1339 size = b - buf;
1340 if (size) {
1341 retval = size;
1342 if (nr)
1343 clear_bit(TTY_PUSH, &tty->flags);
1344 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1345 goto do_it_again;
1346
1347 return retval;
1348 }
1349
1350 /**
1351 * write_chan - write function for tty
1352 * @tty: tty device
1353 * @file: file object
1354 * @buf: userspace buffer pointer
1355 * @nr: size of I/O
1356 *
1357 * Write function of the terminal device. This is serialized with
1358 * respect to other write callers but not to termios changes, reads
1359 * and other such events. We must be careful with N_TTY as the receive
1360 * code will echo characters, thus calling driver write methods.
1361 *
1362 * This code must be sure never to sleep through a hangup.
1363 */
1364
write_chan(struct tty_struct * tty,struct file * file,const unsigned char * buf,size_t nr)1365 static ssize_t write_chan(struct tty_struct * tty, struct file * file,
1366 const unsigned char * buf, size_t nr)
1367 {
1368 const unsigned char *b = buf;
1369 DECLARE_WAITQUEUE(wait, current);
1370 int c;
1371 ssize_t retval = 0;
1372
1373 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1374 if (L_TOSTOP(tty) &&
1375 file->f_dentry->d_inode->i_rdev != CONSOLE_DEV &&
1376 file->f_dentry->d_inode->i_rdev != SYSCONS_DEV) {
1377 retval = tty_check_change(tty);
1378 if (retval)
1379 return retval;
1380 }
1381
1382 add_wait_queue(&tty->write_wait, &wait);
1383 while (1) {
1384 set_current_state(TASK_INTERRUPTIBLE);
1385 if (signal_pending(current)) {
1386 retval = -ERESTARTSYS;
1387 break;
1388 }
1389 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1390 retval = -EIO;
1391 break;
1392 }
1393 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1394 while (nr > 0) {
1395 ssize_t num = opost_block(tty, b, nr);
1396 if (num < 0) {
1397 if (num == -EAGAIN)
1398 break;
1399 retval = num;
1400 goto break_out;
1401 }
1402 b += num;
1403 nr -= num;
1404 if (nr == 0)
1405 break;
1406 get_user(c, b);
1407 if (opost(c, tty) < 0)
1408 break;
1409 b++; nr--;
1410 }
1411 if (tty->driver.flush_chars)
1412 tty->driver.flush_chars(tty);
1413 } else {
1414 c = tty->driver.write(tty, 1, b, nr);
1415 if (c < 0) {
1416 retval = c;
1417 goto break_out;
1418 }
1419 b += c;
1420 nr -= c;
1421 }
1422 if (!nr)
1423 break;
1424 if (file->f_flags & O_NONBLOCK) {
1425 retval = -EAGAIN;
1426 break;
1427 }
1428 schedule();
1429 }
1430 break_out:
1431 current->state = TASK_RUNNING;
1432 remove_wait_queue(&tty->write_wait, &wait);
1433 return (b - buf) ? b - buf : retval;
1434 }
1435
1436 /**
1437 * normal_poll - poll method for N_TTY
1438 * @tty: terminal device
1439 * @file: file accessing it
1440 * @wait: poll table
1441 *
1442 * Called when the line discipline is asked to poll() for data or
1443 * for special events. This code is not serialized with respect to
1444 * other events save open/close.
1445 *
1446 * This code must be sure never to sleep through a hangup.
1447 * Called without the kernel lock held - fine
1448 *
1449 * FIXME: if someone changes the VMIN or discipline settings for the
1450 * terminal while another process is in poll() the poll does not
1451 * recompute the new limits. Possibly set_termios should issue
1452 * a read wakeup to fix this bug.
1453 */
1454
normal_poll(struct tty_struct * tty,struct file * file,poll_table * wait)1455 static unsigned int normal_poll(struct tty_struct * tty, struct file * file, poll_table *wait)
1456 {
1457 unsigned int mask = 0;
1458
1459 poll_wait(file, &tty->read_wait, wait);
1460 poll_wait(file, &tty->write_wait, wait);
1461 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
1462 mask |= POLLIN | POLLRDNORM;
1463 if (tty->packet && tty->link->ctrl_status)
1464 mask |= POLLPRI | POLLIN | POLLRDNORM;
1465 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
1466 mask |= POLLHUP;
1467 if (tty_hung_up_p(file))
1468 mask |= POLLHUP;
1469 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
1470 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
1471 tty->minimum_to_wake = MIN_CHAR(tty);
1472 else
1473 tty->minimum_to_wake = 1;
1474 }
1475 if (tty->driver.chars_in_buffer(tty) < WAKEUP_CHARS &&
1476 tty->driver.write_room(tty) > 0)
1477 mask |= POLLOUT | POLLWRNORM;
1478 return mask;
1479 }
1480
1481 struct tty_ldisc tty_ldisc_N_TTY = {
1482 TTY_LDISC_MAGIC, /* magic */
1483 "n_tty", /* name */
1484 0, /* num */
1485 0, /* flags */
1486 n_tty_open, /* open */
1487 n_tty_close, /* close */
1488 n_tty_flush_buffer, /* flush_buffer */
1489 n_tty_chars_in_buffer, /* chars_in_buffer */
1490 read_chan, /* read */
1491 write_chan, /* write */
1492 n_tty_ioctl, /* ioctl */
1493 n_tty_set_termios, /* set_termios */
1494 normal_poll, /* poll */
1495 NULL, /* hangup */
1496 n_tty_receive_buf, /* receive_buf */
1497 n_tty_receive_room, /* receive_room */
1498 n_tty_write_wakeup /* write_wakeup */
1499 };
1500
1501