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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 n_tty_write 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/mm.h>
44#include <linux/string.h>
45#include <linux/slab.h>
46#include <linux/poll.h>
47#include <linux/bitops.h>
48#include <linux/audit.h>
49#include <linux/file.h>
50#include <linux/uaccess.h>
51#include <linux/module.h>
52
53#include <asm/system.h>
54
55/* number of characters left in xmit buffer before select has we have room */
56#define WAKEUP_CHARS 256
57
58/*
59 * This defines the low- and high-watermarks for throttling and
60 * unthrottling the TTY driver. These watermarks are used for
61 * controlling the space in the read buffer.
62 */
63#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
64#define TTY_THRESHOLD_UNTHROTTLE 128
65
66/*
67 * Special byte codes used in the echo buffer to represent operations
68 * or special handling of characters. Bytes in the echo buffer that
69 * are not part of such special blocks are treated as normal character
70 * codes.
71 */
72#define ECHO_OP_START 0xff
73#define ECHO_OP_MOVE_BACK_COL 0x80
74#define ECHO_OP_SET_CANON_COL 0x81
75#define ECHO_OP_ERASE_TAB 0x82
76
77static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
78 unsigned char __user *ptr)
79{
80 tty_audit_add_data(tty, &x, 1);
81 return put_user(x, ptr);
82}
83
84/**
85 * n_tty_set__room - receive space
86 * @tty: terminal
87 *
88 * Called by the driver to find out how much data it is
89 * permitted to feed to the line discipline without any being lost
90 * and thus to manage flow control. Not serialized. Answers for the
91 * "instant".
92 */
93
94static void n_tty_set_room(struct tty_struct *tty)
95{
96 /* tty->read_cnt is not read locked ? */
97 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
98 int old_left;
99
100 /*
101 * If we are doing input canonicalization, and there are no
102 * pending newlines, let characters through without limit, so
103 * that erase characters will be handled. Other excess
104 * characters will be beeped.
105 */
106 if (left <= 0)
107 left = tty->icanon && !tty->canon_data;
108 old_left = tty->receive_room;
109 tty->receive_room = left;
110
111 /* Did this open up the receive buffer? We may need to flip */
112 if (left && !old_left)
113 schedule_work(&tty->buf.work);
114}
115
116static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
117{
118 if (tty->read_cnt < N_TTY_BUF_SIZE) {
119 tty->read_buf[tty->read_head] = c;
120 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
121 tty->read_cnt++;
122 }
123}
124
125/**
126 * put_tty_queue - add character to tty
127 * @c: character
128 * @tty: tty device
129 *
130 * Add a character to the tty read_buf queue. This is done under the
131 * read_lock to serialize character addition and also to protect us
132 * against parallel reads or flushes
133 */
134
135static void put_tty_queue(unsigned char c, struct tty_struct *tty)
136{
137 unsigned long flags;
138 /*
139 * The problem of stomping on the buffers ends here.
140 * Why didn't anyone see this one coming? --AJK
141 */
142 spin_lock_irqsave(&tty->read_lock, flags);
143 put_tty_queue_nolock(c, tty);
144 spin_unlock_irqrestore(&tty->read_lock, flags);
145}
146
147/**
148 * check_unthrottle - allow new receive data
149 * @tty; tty device
150 *
151 * Check whether to call the driver unthrottle functions
152 *
153 * Can sleep, may be called under the atomic_read_lock mutex but
154 * this is not guaranteed.
155 */
156static void check_unthrottle(struct tty_struct *tty)
157{
158 if (tty->count)
159 tty_unthrottle(tty);
160}
161
162/**
163 * reset_buffer_flags - reset buffer state
164 * @tty: terminal to reset
165 *
166 * Reset the read buffer counters, clear the flags,
167 * and make sure the driver is unthrottled. Called
168 * from n_tty_open() and n_tty_flush_buffer().
169 *
170 * Locking: tty_read_lock for read fields.
171 */
172
173static void reset_buffer_flags(struct tty_struct *tty)
174{
175 unsigned long flags;
176
177 spin_lock_irqsave(&tty->read_lock, flags);
178 tty->read_head = tty->read_tail = tty->read_cnt = 0;
179 spin_unlock_irqrestore(&tty->read_lock, flags);
180
181 mutex_lock(&tty->echo_lock);
182 tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
183 mutex_unlock(&tty->echo_lock);
184
185 tty->canon_head = tty->canon_data = tty->erasing = 0;
186 memset(&tty->read_flags, 0, sizeof tty->read_flags);
187 n_tty_set_room(tty);
188}
189
190/**
191 * n_tty_flush_buffer - clean input queue
192 * @tty: terminal device
193 *
194 * Flush the input buffer. Called when the line discipline is
195 * being closed, when the tty layer wants the buffer flushed (eg
196 * at hangup) or when the N_TTY line discipline internally has to
197 * clean the pending queue (for example some signals).
198 *
199 * Locking: ctrl_lock, read_lock.
200 */
201
202static void n_tty_flush_buffer(struct tty_struct *tty)
203{
204 unsigned long flags;
205 /* clear everything and unthrottle the driver */
206 reset_buffer_flags(tty);
207
208 if (!tty->link)
209 return;
210
211 spin_lock_irqsave(&tty->ctrl_lock, flags);
212 if (tty->link->packet) {
213 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
214 wake_up_interruptible(&tty->link->read_wait);
215 }
216 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
217}
218
219/**
220 * n_tty_chars_in_buffer - report available bytes
221 * @tty: tty device
222 *
223 * Report the number of characters buffered to be delivered to user
224 * at this instant in time.
225 *
226 * Locking: read_lock
227 */
228
229static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
230{
231 unsigned long flags;
232 ssize_t n = 0;
233
234 spin_lock_irqsave(&tty->read_lock, flags);
235 if (!tty->icanon) {
236 n = tty->read_cnt;
237 } else if (tty->canon_data) {
238 n = (tty->canon_head > tty->read_tail) ?
239 tty->canon_head - tty->read_tail :
240 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
241 }
242 spin_unlock_irqrestore(&tty->read_lock, flags);
243 return n;
244}
245
246/**
247 * is_utf8_continuation - utf8 multibyte check
248 * @c: byte to check
249 *
250 * Returns true if the utf8 character 'c' is a multibyte continuation
251 * character. We use this to correctly compute the on screen size
252 * of the character when printing
253 */
254
255static inline int is_utf8_continuation(unsigned char c)
256{
257 return (c & 0xc0) == 0x80;
258}
259
260/**
261 * is_continuation - multibyte check
262 * @c: byte to check
263 *
264 * Returns true if the utf8 character 'c' is a multibyte continuation
265 * character and the terminal is in unicode mode.
266 */
267
268static inline int is_continuation(unsigned char c, struct tty_struct *tty)
269{
270 return I_IUTF8(tty) && is_utf8_continuation(c);
271}
272
273/**
274 * do_output_char - output one character
275 * @c: character (or partial unicode symbol)
276 * @tty: terminal device
277 * @space: space available in tty driver write buffer
278 *
279 * This is a helper function that handles one output character
280 * (including special characters like TAB, CR, LF, etc.),
281 * doing OPOST processing and putting the results in the
282 * tty driver's write buffer.
283 *
284 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
285 * and NLDLY. They simply aren't relevant in the world today.
286 * If you ever need them, add them here.
287 *
288 * Returns the number of bytes of buffer space used or -1 if
289 * no space left.
290 *
291 * Locking: should be called under the output_lock to protect
292 * the column state and space left in the buffer
293 */
294
295static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
296{
297 int spaces;
298
299 if (!space)
300 return -1;
301
302 switch (c) {
303 case '\n':
304 if (O_ONLRET(tty))
305 tty->column = 0;
306 if (O_ONLCR(tty)) {
307 if (space < 2)
308 return -1;
309 tty->canon_column = tty->column = 0;
310 tty->ops->write(tty, "\r\n", 2);
311 return 2;
312 }
313 tty->canon_column = tty->column;
314 break;
315 case '\r':
316 if (O_ONOCR(tty) && tty->column == 0)
317 return 0;
318 if (O_OCRNL(tty)) {
319 c = '\n';
320 if (O_ONLRET(tty))
321 tty->canon_column = tty->column = 0;
322 break;
323 }
324 tty->canon_column = tty->column = 0;
325 break;
326 case '\t':
327 spaces = 8 - (tty->column & 7);
328 if (O_TABDLY(tty) == XTABS) {
329 if (space < spaces)
330 return -1;
331 tty->column += spaces;
332 tty->ops->write(tty, " ", spaces);
333 return spaces;
334 }
335 tty->column += spaces;
336 break;
337 case '\b':
338 if (tty->column > 0)
339 tty->column--;
340 break;
341 default:
342 if (!iscntrl(c)) {
343 if (O_OLCUC(tty))
344 c = toupper(c);
345 if (!is_continuation(c, tty))
346 tty->column++;
347 }
348 break;
349 }
350
351 tty_put_char(tty, c);
352 return 1;
353}
354
355/**
356 * process_output - output post processor
357 * @c: character (or partial unicode symbol)
358 * @tty: terminal device
359 *
360 * Output one character with OPOST processing.
361 * Returns -1 when the output device is full and the character
362 * must be retried.
363 *
364 * Locking: output_lock to protect column state and space left
365 * (also, this is called from n_tty_write under the
366 * tty layer write lock)
367 */
368
369static int process_output(unsigned char c, struct tty_struct *tty)
370{
371 int space, retval;
372
373 mutex_lock(&tty->output_lock);
374
375 space = tty_write_room(tty);
376 retval = do_output_char(c, tty, space);
377
378 mutex_unlock(&tty->output_lock);
379 if (retval < 0)
380 return -1;
381 else
382 return 0;
383}
384
385/**
386 * process_output_block - block post processor
387 * @tty: terminal device
388 * @buf: character buffer
389 * @nr: number of bytes to output
390 *
391 * Output a block of characters with OPOST processing.
392 * Returns the number of characters output.
393 *
394 * This path is used to speed up block console writes, among other
395 * things when processing blocks of output data. It handles only
396 * the simple cases normally found and helps to generate blocks of
397 * symbols for the console driver and thus improve performance.
398 *
399 * Locking: output_lock to protect column state and space left
400 * (also, this is called from n_tty_write under the
401 * tty layer write lock)
402 */
403
404static ssize_t process_output_block(struct tty_struct *tty,
405 const unsigned char *buf, unsigned int nr)
406{
407 int space;
408 int i;
409 const unsigned char *cp;
410
411 mutex_lock(&tty->output_lock);
412
413 space = tty_write_room(tty);
414 if (!space) {
415 mutex_unlock(&tty->output_lock);
416 return 0;
417 }
418 if (nr > space)
419 nr = space;
420
421 for (i = 0, cp = buf; i < nr; i++, cp++) {
422 unsigned char c = *cp;
423
424 switch (c) {
425 case '\n':
426 if (O_ONLRET(tty))
427 tty->column = 0;
428 if (O_ONLCR(tty))
429 goto break_out;
430 tty->canon_column = tty->column;
431 break;
432 case '\r':
433 if (O_ONOCR(tty) && tty->column == 0)
434 goto break_out;
435 if (O_OCRNL(tty))
436 goto break_out;
437 tty->canon_column = tty->column = 0;
438 break;
439 case '\t':
440 goto break_out;
441 case '\b':
442 if (tty->column > 0)
443 tty->column--;
444 break;
445 default:
446 if (!iscntrl(c)) {
447 if (O_OLCUC(tty))
448 goto break_out;
449 if (!is_continuation(c, tty))
450 tty->column++;
451 }
452 break;
453 }
454 }
455break_out:
456 i = tty->ops->write(tty, buf, i);
457
458 mutex_unlock(&tty->output_lock);
459 return i;
460}
461
462/**
463 * process_echoes - write pending echo characters
464 * @tty: terminal device
465 *
466 * Write previously buffered echo (and other ldisc-generated)
467 * characters to the tty.
468 *
469 * Characters generated by the ldisc (including echoes) need to
470 * be buffered because the driver's write buffer can fill during
471 * heavy program output. Echoing straight to the driver will
472 * often fail under these conditions, causing lost characters and
473 * resulting mismatches of ldisc state information.
474 *
475 * Since the ldisc state must represent the characters actually sent
476 * to the driver at the time of the write, operations like certain
477 * changes in column state are also saved in the buffer and executed
478 * here.
479 *
480 * A circular fifo buffer is used so that the most recent characters
481 * are prioritized. Also, when control characters are echoed with a
482 * prefixed "^", the pair is treated atomically and thus not separated.
483 *
484 * Locking: output_lock to protect column state and space left,
485 * echo_lock to protect the echo buffer
486 */
487
488static void process_echoes(struct tty_struct *tty)
489{
490 int space, nr;
491 unsigned char c;
492 unsigned char *cp, *buf_end;
493
494 if (!tty->echo_cnt)
495 return;
496
497 mutex_lock(&tty->output_lock);
498 mutex_lock(&tty->echo_lock);
499
500 space = tty_write_room(tty);
501
502 buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
503 cp = tty->echo_buf + tty->echo_pos;
504 nr = tty->echo_cnt;
505 while (nr > 0) {
506 c = *cp;
507 if (c == ECHO_OP_START) {
508 unsigned char op;
509 unsigned char *opp;
510 int no_space_left = 0;
511
512 /*
513 * If the buffer byte is the start of a multi-byte
514 * operation, get the next byte, which is either the
515 * op code or a control character value.
516 */
517 opp = cp + 1;
518 if (opp == buf_end)
519 opp -= N_TTY_BUF_SIZE;
520 op = *opp;
521
522 switch (op) {
523 unsigned int num_chars, num_bs;
524
525 case ECHO_OP_ERASE_TAB:
526 if (++opp == buf_end)
527 opp -= N_TTY_BUF_SIZE;
528 num_chars = *opp;
529
530 /*
531 * Determine how many columns to go back
532 * in order to erase the tab.
533 * This depends on the number of columns
534 * used by other characters within the tab
535 * area. If this (modulo 8) count is from
536 * the start of input rather than from a
537 * previous tab, we offset by canon column.
538 * Otherwise, tab spacing is normal.
539 */
540 if (!(num_chars & 0x80))
541 num_chars += tty->canon_column;
542 num_bs = 8 - (num_chars & 7);
543
544 if (num_bs > space) {
545 no_space_left = 1;
546 break;
547 }
548 space -= num_bs;
549 while (num_bs--) {
550 tty_put_char(tty, '\b');
551 if (tty->column > 0)
552 tty->column--;
553 }
554 cp += 3;
555 nr -= 3;
556 break;
557
558 case ECHO_OP_SET_CANON_COL:
559 tty->canon_column = tty->column;
560 cp += 2;
561 nr -= 2;
562 break;
563
564 case ECHO_OP_MOVE_BACK_COL:
565 if (tty->column > 0)
566 tty->column--;
567 cp += 2;
568 nr -= 2;
569 break;
570
571 case ECHO_OP_START:
572 /* This is an escaped echo op start code */
573 if (!space) {
574 no_space_left = 1;
575 break;
576 }
577 tty_put_char(tty, ECHO_OP_START);
578 tty->column++;
579 space--;
580 cp += 2;
581 nr -= 2;
582 break;
583
584 default:
585 /*
586 * If the op is not a special byte code,
587 * it is a ctrl char tagged to be echoed
588 * as "^X" (where X is the letter
589 * representing the control char).
590 * Note that we must ensure there is
591 * enough space for the whole ctrl pair.
592 *
593 */
594 if (space < 2) {
595 no_space_left = 1;
596 break;
597 }
598 tty_put_char(tty, '^');
599 tty_put_char(tty, op ^ 0100);
600 tty->column += 2;
601 space -= 2;
602 cp += 2;
603 nr -= 2;
604 }
605
606 if (no_space_left)
607 break;
608 } else {
609 if (O_OPOST(tty) &&
610 !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
611 int retval = do_output_char(c, tty, space);
612 if (retval < 0)
613 break;
614 space -= retval;
615 } else {
616 if (!space)
617 break;
618 tty_put_char(tty, c);
619 space -= 1;
620 }
621 cp += 1;
622 nr -= 1;
623 }
624
625 /* When end of circular buffer reached, wrap around */
626 if (cp >= buf_end)
627 cp -= N_TTY_BUF_SIZE;
628 }
629
630 if (nr == 0) {
631 tty->echo_pos = 0;
632 tty->echo_cnt = 0;
633 tty->echo_overrun = 0;
634 } else {
635 int num_processed = tty->echo_cnt - nr;
636 tty->echo_pos += num_processed;
637 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
638 tty->echo_cnt = nr;
639 if (num_processed > 0)
640 tty->echo_overrun = 0;
641 }
642
643 mutex_unlock(&tty->echo_lock);
644 mutex_unlock(&tty->output_lock);
645
646 if (tty->ops->flush_chars)
647 tty->ops->flush_chars(tty);
648}
649
650/**
651 * add_echo_byte - add a byte to the echo buffer
652 * @c: unicode byte to echo
653 * @tty: terminal device
654 *
655 * Add a character or operation byte to the echo buffer.
656 *
657 * Should be called under the echo lock to protect the echo buffer.
658 */
659
660static void add_echo_byte(unsigned char c, struct tty_struct *tty)
661{
662 int new_byte_pos;
663
664 if (tty->echo_cnt == N_TTY_BUF_SIZE) {
665 /* Circular buffer is already at capacity */
666 new_byte_pos = tty->echo_pos;
667
668 /*
669 * Since the buffer start position needs to be advanced,
670 * be sure to step by a whole operation byte group.
671 */
672 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
673 if (tty->echo_buf[(tty->echo_pos + 1) &
674 (N_TTY_BUF_SIZE - 1)] ==
675 ECHO_OP_ERASE_TAB) {
676 tty->echo_pos += 3;
677 tty->echo_cnt -= 2;
678 } else {
679 tty->echo_pos += 2;
680 tty->echo_cnt -= 1;
681 }
682 } else {
683 tty->echo_pos++;
684 }
685 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
686
687 tty->echo_overrun = 1;
688 } else {
689 new_byte_pos = tty->echo_pos + tty->echo_cnt;
690 new_byte_pos &= N_TTY_BUF_SIZE - 1;
691 tty->echo_cnt++;
692 }
693
694 tty->echo_buf[new_byte_pos] = c;
695}
696
697/**
698 * echo_move_back_col - add operation to move back a column
699 * @tty: terminal device
700 *
701 * Add an operation to the echo buffer to move back one column.
702 *
703 * Locking: echo_lock to protect the echo buffer
704 */
705
706static void echo_move_back_col(struct tty_struct *tty)
707{
708 mutex_lock(&tty->echo_lock);
709
710 add_echo_byte(ECHO_OP_START, tty);
711 add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
712
713 mutex_unlock(&tty->echo_lock);
714}
715
716/**
717 * echo_set_canon_col - add operation to set the canon column
718 * @tty: terminal device
719 *
720 * Add an operation to the echo buffer to set the canon column
721 * to the current column.
722 *
723 * Locking: echo_lock to protect the echo buffer
724 */
725
726static void echo_set_canon_col(struct tty_struct *tty)
727{
728 mutex_lock(&tty->echo_lock);
729
730 add_echo_byte(ECHO_OP_START, tty);
731 add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
732
733 mutex_unlock(&tty->echo_lock);
734}
735
736/**
737 * echo_erase_tab - add operation to erase a tab
738 * @num_chars: number of character columns already used
739 * @after_tab: true if num_chars starts after a previous tab
740 * @tty: terminal device
741 *
742 * Add an operation to the echo buffer to erase a tab.
743 *
744 * Called by the eraser function, which knows how many character
745 * columns have been used since either a previous tab or the start
746 * of input. This information will be used later, along with
747 * canon column (if applicable), to go back the correct number
748 * of columns.
749 *
750 * Locking: echo_lock to protect the echo buffer
751 */
752
753static void echo_erase_tab(unsigned int num_chars, int after_tab,
754 struct tty_struct *tty)
755{
756 mutex_lock(&tty->echo_lock);
757
758 add_echo_byte(ECHO_OP_START, tty);
759 add_echo_byte(ECHO_OP_ERASE_TAB, tty);
760
761 /* We only need to know this modulo 8 (tab spacing) */
762 num_chars &= 7;
763
764 /* Set the high bit as a flag if num_chars is after a previous tab */
765 if (after_tab)
766 num_chars |= 0x80;
767
768 add_echo_byte(num_chars, tty);
769
770 mutex_unlock(&tty->echo_lock);
771}
772
773/**
774 * echo_char_raw - echo a character raw
775 * @c: unicode byte to echo
776 * @tty: terminal device
777 *
778 * Echo user input back onto the screen. This must be called only when
779 * L_ECHO(tty) is true. Called from the driver receive_buf path.
780 *
781 * This variant does not treat control characters specially.
782 *
783 * Locking: echo_lock to protect the echo buffer
784 */
785
786static void echo_char_raw(unsigned char c, struct tty_struct *tty)
787{
788 mutex_lock(&tty->echo_lock);
789
790 if (c == ECHO_OP_START) {
791 add_echo_byte(ECHO_OP_START, tty);
792 add_echo_byte(ECHO_OP_START, tty);
793 } else {
794 add_echo_byte(c, tty);
795 }
796
797 mutex_unlock(&tty->echo_lock);
798}
799
800/**
801 * echo_char - echo a character
802 * @c: unicode byte to echo
803 * @tty: terminal device
804 *
805 * Echo user input back onto the screen. This must be called only when
806 * L_ECHO(tty) is true. Called from the driver receive_buf path.
807 *
808 * This variant tags control characters to be echoed as "^X"
809 * (where X is the letter representing the control char).
810 *
811 * Locking: echo_lock to protect the echo buffer
812 */
813
814static void echo_char(unsigned char c, struct tty_struct *tty)
815{
816 mutex_lock(&tty->echo_lock);
817
818 if (c == ECHO_OP_START) {
819 add_echo_byte(ECHO_OP_START, tty);
820 add_echo_byte(ECHO_OP_START, tty);
821 } else {
822 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
823 add_echo_byte(ECHO_OP_START, tty);
824 add_echo_byte(c, tty);
825 }
826
827 mutex_unlock(&tty->echo_lock);
828}
829
830/**
831 * finish_erasing - complete erase
832 * @tty: tty doing the erase
833 */
834
835static inline void finish_erasing(struct tty_struct *tty)
836{
837 if (tty->erasing) {
838 echo_char_raw('/', tty);
839 tty->erasing = 0;
840 }
841}
842
843/**
844 * eraser - handle erase function
845 * @c: character input
846 * @tty: terminal device
847 *
848 * Perform erase and necessary output when an erase character is
849 * present in the stream from the driver layer. Handles the complexities
850 * of UTF-8 multibyte symbols.
851 *
852 * Locking: read_lock for tty buffers
853 */
854
855static void eraser(unsigned char c, struct tty_struct *tty)
856{
857 enum { ERASE, WERASE, KILL } kill_type;
858 int head, seen_alnums, cnt;
859 unsigned long flags;
860
861 /* FIXME: locking needed ? */
862 if (tty->read_head == tty->canon_head) {
863 /* process_output('\a', tty); */ /* what do you think? */
864 return;
865 }
866 if (c == ERASE_CHAR(tty))
867 kill_type = ERASE;
868 else if (c == WERASE_CHAR(tty))
869 kill_type = WERASE;
870 else {
871 if (!L_ECHO(tty)) {
872 spin_lock_irqsave(&tty->read_lock, flags);
873 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
874 (N_TTY_BUF_SIZE - 1));
875 tty->read_head = tty->canon_head;
876 spin_unlock_irqrestore(&tty->read_lock, flags);
877 return;
878 }
879 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
880 spin_lock_irqsave(&tty->read_lock, flags);
881 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
882 (N_TTY_BUF_SIZE - 1));
883 tty->read_head = tty->canon_head;
884 spin_unlock_irqrestore(&tty->read_lock, flags);
885 finish_erasing(tty);
886 echo_char(KILL_CHAR(tty), tty);
887 /* Add a newline if ECHOK is on and ECHOKE is off. */
888 if (L_ECHOK(tty))
889 echo_char_raw('\n', tty);
890 return;
891 }
892 kill_type = KILL;
893 }
894
895 seen_alnums = 0;
896 /* FIXME: Locking ?? */
897 while (tty->read_head != tty->canon_head) {
898 head = tty->read_head;
899
900 /* erase a single possibly multibyte character */
901 do {
902 head = (head - 1) & (N_TTY_BUF_SIZE-1);
903 c = tty->read_buf[head];
904 } while (is_continuation(c, tty) && head != tty->canon_head);
905
906 /* do not partially erase */
907 if (is_continuation(c, tty))
908 break;
909
910 if (kill_type == WERASE) {
911 /* Equivalent to BSD's ALTWERASE. */
912 if (isalnum(c) || c == '_')
913 seen_alnums++;
914 else if (seen_alnums)
915 break;
916 }
917 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
918 spin_lock_irqsave(&tty->read_lock, flags);
919 tty->read_head = head;
920 tty->read_cnt -= cnt;
921 spin_unlock_irqrestore(&tty->read_lock, flags);
922 if (L_ECHO(tty)) {
923 if (L_ECHOPRT(tty)) {
924 if (!tty->erasing) {
925 echo_char_raw('\\', tty);
926 tty->erasing = 1;
927 }
928 /* if cnt > 1, output a multi-byte character */
929 echo_char(c, tty);
930 while (--cnt > 0) {
931 head = (head+1) & (N_TTY_BUF_SIZE-1);
932 echo_char_raw(tty->read_buf[head], tty);
933 echo_move_back_col(tty);
934 }
935 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
936 echo_char(ERASE_CHAR(tty), tty);
937 } else if (c == '\t') {
938 unsigned int num_chars = 0;
939 int after_tab = 0;
940 unsigned long tail = tty->read_head;
941
942 /*
943 * Count the columns used for characters
944 * since the start of input or after a
945 * previous tab.
946 * This info is used to go back the correct
947 * number of columns.
948 */
949 while (tail != tty->canon_head) {
950 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
951 c = tty->read_buf[tail];
952 if (c == '\t') {
953 after_tab = 1;
954 break;
955 } else if (iscntrl(c)) {
956 if (L_ECHOCTL(tty))
957 num_chars += 2;
958 } else if (!is_continuation(c, tty)) {
959 num_chars++;
960 }
961 }
962 echo_erase_tab(num_chars, after_tab, tty);
963 } else {
964 if (iscntrl(c) && L_ECHOCTL(tty)) {
965 echo_char_raw('\b', tty);
966 echo_char_raw(' ', tty);
967 echo_char_raw('\b', tty);
968 }
969 if (!iscntrl(c) || L_ECHOCTL(tty)) {
970 echo_char_raw('\b', tty);
971 echo_char_raw(' ', tty);
972 echo_char_raw('\b', tty);
973 }
974 }
975 }
976 if (kill_type == ERASE)
977 break;
978 }
979 if (tty->read_head == tty->canon_head && L_ECHO(tty))
980 finish_erasing(tty);
981}
982
983/**
984 * isig - handle the ISIG optio
985 * @sig: signal
986 * @tty: terminal
987 * @flush: force flush
988 *
989 * Called when a signal is being sent due to terminal input. This
990 * may caus terminal flushing to take place according to the termios
991 * settings and character used. Called from the driver receive_buf
992 * path so serialized.
993 *
994 * Locking: ctrl_lock, read_lock (both via flush buffer)
995 */
996
997static inline void isig(int sig, struct tty_struct *tty, int flush)
998{
999 if (tty->pgrp)
1000 kill_pgrp(tty->pgrp, sig, 1);
1001 if (flush || !L_NOFLSH(tty)) {
1002 n_tty_flush_buffer(tty);
1003 tty_driver_flush_buffer(tty);
1004 }
1005}
1006
1007/**
1008 * n_tty_receive_break - handle break
1009 * @tty: terminal
1010 *
1011 * An RS232 break event has been hit in the incoming bitstream. This
1012 * can cause a variety of events depending upon the termios settings.
1013 *
1014 * Called from the receive_buf path so single threaded.
1015 */
1016
1017static inline void n_tty_receive_break(struct tty_struct *tty)
1018{
1019 if (I_IGNBRK(tty))
1020 return;
1021 if (I_BRKINT(tty)) {
1022 isig(SIGINT, tty, 1);
1023 return;
1024 }
1025 if (I_PARMRK(tty)) {
1026 put_tty_queue('\377', tty);
1027 put_tty_queue('\0', tty);
1028 }
1029 put_tty_queue('\0', tty);
1030 wake_up_interruptible(&tty->read_wait);
1031}
1032
1033/**
1034 * n_tty_receive_overrun - handle overrun reporting
1035 * @tty: terminal
1036 *
1037 * Data arrived faster than we could process it. While the tty
1038 * driver has flagged this the bits that were missed are gone
1039 * forever.
1040 *
1041 * Called from the receive_buf path so single threaded. Does not
1042 * need locking as num_overrun and overrun_time are function
1043 * private.
1044 */
1045
1046static inline void n_tty_receive_overrun(struct tty_struct *tty)
1047{
1048 char buf[64];
1049
1050 tty->num_overrun++;
1051 if (time_before(tty->overrun_time, jiffies - HZ) ||
1052 time_after(tty->overrun_time, jiffies)) {
1053 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1054 tty_name(tty, buf),
1055 tty->num_overrun);
1056 tty->overrun_time = jiffies;
1057 tty->num_overrun = 0;
1058 }
1059}
1060
1061/**
1062 * n_tty_receive_parity_error - error notifier
1063 * @tty: terminal device
1064 * @c: character
1065 *
1066 * Process a parity error and queue the right data to indicate
1067 * the error case if necessary. Locking as per n_tty_receive_buf.
1068 */
1069static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1070 unsigned char c)
1071{
1072 if (I_IGNPAR(tty))
1073 return;
1074 if (I_PARMRK(tty)) {
1075 put_tty_queue('\377', tty);
1076 put_tty_queue('\0', tty);
1077 put_tty_queue(c, tty);
1078 } else if (I_INPCK(tty))
1079 put_tty_queue('\0', tty);
1080 else
1081 put_tty_queue(c, tty);
1082 wake_up_interruptible(&tty->read_wait);
1083}
1084
1085/**
1086 * n_tty_receive_char - perform processing
1087 * @tty: terminal device
1088 * @c: character
1089 *
1090 * Process an individual character of input received from the driver.
1091 * This is serialized with respect to itself by the rules for the
1092 * driver above.
1093 */
1094
1095static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1096{
1097 unsigned long flags;
1098 int parmrk;
1099
1100 if (tty->raw) {
1101 put_tty_queue(c, tty);
1102 return;
1103 }
1104
1105 if (I_ISTRIP(tty))
1106 c &= 0x7f;
1107 if (I_IUCLC(tty) && L_IEXTEN(tty))
1108 c = tolower(c);
1109
1110 if (L_EXTPROC(tty)) {
1111 put_tty_queue(c, tty);
1112 return;
1113 }
1114
1115 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1116 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1117 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1118 start_tty(tty);
1119 process_echoes(tty);
1120 }
1121
1122 if (tty->closing) {
1123 if (I_IXON(tty)) {
1124 if (c == START_CHAR(tty)) {
1125 start_tty(tty);
1126 process_echoes(tty);
1127 } else if (c == STOP_CHAR(tty))
1128 stop_tty(tty);
1129 }
1130 return;
1131 }
1132
1133 /*
1134 * If the previous character was LNEXT, or we know that this
1135 * character is not one of the characters that we'll have to
1136 * handle specially, do shortcut processing to speed things
1137 * up.
1138 */
1139 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1140 tty->lnext = 0;
1141 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1142 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1143 /* beep if no space */
1144 if (L_ECHO(tty))
1145 process_output('\a', tty);
1146 return;
1147 }
1148 if (L_ECHO(tty)) {
1149 finish_erasing(tty);
1150 /* Record the column of first canon char. */
1151 if (tty->canon_head == tty->read_head)
1152 echo_set_canon_col(tty);
1153 echo_char(c, tty);
1154 process_echoes(tty);
1155 }
1156 if (parmrk)
1157 put_tty_queue(c, tty);
1158 put_tty_queue(c, tty);
1159 return;
1160 }
1161
1162 if (I_IXON(tty)) {
1163 if (c == START_CHAR(tty)) {
1164 start_tty(tty);
1165 process_echoes(tty);
1166 return;
1167 }
1168 if (c == STOP_CHAR(tty)) {
1169 stop_tty(tty);
1170 return;
1171 }
1172 }
1173
1174 if (L_ISIG(tty)) {
1175 int signal;
1176 signal = SIGINT;
1177 if (c == INTR_CHAR(tty))
1178 goto send_signal;
1179 signal = SIGQUIT;
1180 if (c == QUIT_CHAR(tty))
1181 goto send_signal;
1182 signal = SIGTSTP;
1183 if (c == SUSP_CHAR(tty)) {
1184send_signal:
1185 /*
1186 * Note that we do not use isig() here because we want
1187 * the order to be:
1188 * 1) flush, 2) echo, 3) signal
1189 */
1190 if (!L_NOFLSH(tty)) {
1191 n_tty_flush_buffer(tty);
1192 tty_driver_flush_buffer(tty);
1193 }
1194 if (I_IXON(tty))
1195 start_tty(tty);
1196 if (L_ECHO(tty)) {
1197 echo_char(c, tty);
1198 process_echoes(tty);
1199 }
1200 if (tty->pgrp)
1201 kill_pgrp(tty->pgrp, signal, 1);
1202 return;
1203 }
1204 }
1205
1206 if (c == '\r') {
1207 if (I_IGNCR(tty))
1208 return;
1209 if (I_ICRNL(tty))
1210 c = '\n';
1211 } else if (c == '\n' && I_INLCR(tty))
1212 c = '\r';
1213
1214 if (tty->icanon) {
1215 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1216 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1217 eraser(c, tty);
1218 process_echoes(tty);
1219 return;
1220 }
1221 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1222 tty->lnext = 1;
1223 if (L_ECHO(tty)) {
1224 finish_erasing(tty);
1225 if (L_ECHOCTL(tty)) {
1226 echo_char_raw('^', tty);
1227 echo_char_raw('\b', tty);
1228 process_echoes(tty);
1229 }
1230 }
1231 return;
1232 }
1233 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1234 L_IEXTEN(tty)) {
1235 unsigned long tail = tty->canon_head;
1236
1237 finish_erasing(tty);
1238 echo_char(c, tty);
1239 echo_char_raw('\n', tty);
1240 while (tail != tty->read_head) {
1241 echo_char(tty->read_buf[tail], tty);
1242 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1243 }
1244 process_echoes(tty);
1245 return;
1246 }
1247 if (c == '\n') {
1248 if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1249 if (L_ECHO(tty))
1250 process_output('\a', tty);
1251 return;
1252 }
1253 if (L_ECHO(tty) || L_ECHONL(tty)) {
1254 echo_char_raw('\n', tty);
1255 process_echoes(tty);
1256 }
1257 goto handle_newline;
1258 }
1259 if (c == EOF_CHAR(tty)) {
1260 if (tty->read_cnt >= N_TTY_BUF_SIZE)
1261 return;
1262 if (tty->canon_head != tty->read_head)
1263 set_bit(TTY_PUSH, &tty->flags);
1264 c = __DISABLED_CHAR;
1265 goto handle_newline;
1266 }
1267 if ((c == EOL_CHAR(tty)) ||
1268 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1269 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1270 ? 1 : 0;
1271 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1272 if (L_ECHO(tty))
1273 process_output('\a', tty);
1274 return;
1275 }
1276 /*
1277 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1278 */
1279 if (L_ECHO(tty)) {
1280 /* Record the column of first canon char. */
1281 if (tty->canon_head == tty->read_head)
1282 echo_set_canon_col(tty);
1283 echo_char(c, tty);
1284 process_echoes(tty);
1285 }
1286 /*
1287 * XXX does PARMRK doubling happen for
1288 * EOL_CHAR and EOL2_CHAR?
1289 */
1290 if (parmrk)
1291 put_tty_queue(c, tty);
1292
1293handle_newline:
1294 spin_lock_irqsave(&tty->read_lock, flags);
1295 set_bit(tty->read_head, tty->read_flags);
1296 put_tty_queue_nolock(c, tty);
1297 tty->canon_head = tty->read_head;
1298 tty->canon_data++;
1299 spin_unlock_irqrestore(&tty->read_lock, flags);
1300 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1301 if (waitqueue_active(&tty->read_wait))
1302 wake_up_interruptible(&tty->read_wait);
1303 return;
1304 }
1305 }
1306
1307 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1308 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1309 /* beep if no space */
1310 if (L_ECHO(tty))
1311 process_output('\a', tty);
1312 return;
1313 }
1314 if (L_ECHO(tty)) {
1315 finish_erasing(tty);
1316 if (c == '\n')
1317 echo_char_raw('\n', tty);
1318 else {
1319 /* Record the column of first canon char. */
1320 if (tty->canon_head == tty->read_head)
1321 echo_set_canon_col(tty);
1322 echo_char(c, tty);
1323 }
1324 process_echoes(tty);
1325 }
1326
1327 if (parmrk)
1328 put_tty_queue(c, tty);
1329
1330 put_tty_queue(c, tty);
1331}
1332
1333
1334/**
1335 * n_tty_write_wakeup - asynchronous I/O notifier
1336 * @tty: tty device
1337 *
1338 * Required for the ptys, serial driver etc. since processes
1339 * that attach themselves to the master and rely on ASYNC
1340 * IO must be woken up
1341 */
1342
1343static void n_tty_write_wakeup(struct tty_struct *tty)
1344{
1345 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1346 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1347}
1348
1349/**
1350 * n_tty_receive_buf - data receive
1351 * @tty: terminal device
1352 * @cp: buffer
1353 * @fp: flag buffer
1354 * @count: characters
1355 *
1356 * Called by the terminal driver when a block of characters has
1357 * been received. This function must be called from soft contexts
1358 * not from interrupt context. The driver is responsible for making
1359 * calls one at a time and in order (or using flush_to_ldisc)
1360 */
1361
1362static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1363 char *fp, int count)
1364{
1365 const unsigned char *p;
1366 char *f, flags = TTY_NORMAL;
1367 int i;
1368 char buf[64];
1369 unsigned long cpuflags;
1370
1371 if (!tty->read_buf)
1372 return;
1373
1374 if (tty->real_raw) {
1375 spin_lock_irqsave(&tty->read_lock, cpuflags);
1376 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1377 N_TTY_BUF_SIZE - tty->read_head);
1378 i = min(count, i);
1379 memcpy(tty->read_buf + tty->read_head, cp, i);
1380 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1381 tty->read_cnt += i;
1382 cp += i;
1383 count -= i;
1384
1385 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1386 N_TTY_BUF_SIZE - tty->read_head);
1387 i = min(count, i);
1388 memcpy(tty->read_buf + tty->read_head, cp, i);
1389 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1390 tty->read_cnt += i;
1391 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1392 } else {
1393 for (i = count, p = cp, f = fp; i; i--, p++) {
1394 if (f)
1395 flags = *f++;
1396 switch (flags) {
1397 case TTY_NORMAL:
1398 n_tty_receive_char(tty, *p);
1399 break;
1400 case TTY_BREAK:
1401 n_tty_receive_break(tty);
1402 break;
1403 case TTY_PARITY:
1404 case TTY_FRAME:
1405 n_tty_receive_parity_error(tty, *p);
1406 break;
1407 case TTY_OVERRUN:
1408 n_tty_receive_overrun(tty);
1409 break;
1410 default:
1411 printk(KERN_ERR "%s: unknown flag %d\n",
1412 tty_name(tty, buf), flags);
1413 break;
1414 }
1415 }
1416 if (tty->ops->flush_chars)
1417 tty->ops->flush_chars(tty);
1418 }
1419
1420 n_tty_set_room(tty);
1421
1422 if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
1423 L_EXTPROC(tty)) {
1424 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1425 if (waitqueue_active(&tty->read_wait))
1426 wake_up_interruptible(&tty->read_wait);
1427 }
1428
1429 /*
1430 * Check the remaining room for the input canonicalization
1431 * mode. We don't want to throttle the driver if we're in
1432 * canonical mode and don't have a newline yet!
1433 */
1434 if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1435 tty_throttle(tty);
1436}
1437
1438int is_ignored(int sig)
1439{
1440 return (sigismember(¤t->blocked, sig) ||
1441 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1442}
1443
1444/**
1445 * n_tty_set_termios - termios data changed
1446 * @tty: terminal
1447 * @old: previous data
1448 *
1449 * Called by the tty layer when the user changes termios flags so
1450 * that the line discipline can plan ahead. This function cannot sleep
1451 * and is protected from re-entry by the tty layer. The user is
1452 * guaranteed that this function will not be re-entered or in progress
1453 * when the ldisc is closed.
1454 *
1455 * Locking: Caller holds tty->termios_mutex
1456 */
1457
1458static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1459{
1460 int canon_change = 1;
1461 BUG_ON(!tty);
1462
1463 if (old)
1464 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1465 if (canon_change) {
1466 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1467 tty->canon_head = tty->read_tail;
1468 tty->canon_data = 0;
1469 tty->erasing = 0;
1470 }
1471
1472 if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1473 wake_up_interruptible(&tty->read_wait);
1474
1475 tty->icanon = (L_ICANON(tty) != 0);
1476 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1477 tty->raw = 1;
1478 tty->real_raw = 1;
1479 n_tty_set_room(tty);
1480 return;
1481 }
1482 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1483 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1484 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1485 I_PARMRK(tty)) {
1486 memset(tty->process_char_map, 0, 256/8);
1487
1488 if (I_IGNCR(tty) || I_ICRNL(tty))
1489 set_bit('\r', tty->process_char_map);
1490 if (I_INLCR(tty))
1491 set_bit('\n', tty->process_char_map);
1492
1493 if (L_ICANON(tty)) {
1494 set_bit(ERASE_CHAR(tty), tty->process_char_map);
1495 set_bit(KILL_CHAR(tty), tty->process_char_map);
1496 set_bit(EOF_CHAR(tty), tty->process_char_map);
1497 set_bit('\n', tty->process_char_map);
1498 set_bit(EOL_CHAR(tty), tty->process_char_map);
1499 if (L_IEXTEN(tty)) {
1500 set_bit(WERASE_CHAR(tty),
1501 tty->process_char_map);
1502 set_bit(LNEXT_CHAR(tty),
1503 tty->process_char_map);
1504 set_bit(EOL2_CHAR(tty),
1505 tty->process_char_map);
1506 if (L_ECHO(tty))
1507 set_bit(REPRINT_CHAR(tty),
1508 tty->process_char_map);
1509 }
1510 }
1511 if (I_IXON(tty)) {
1512 set_bit(START_CHAR(tty), tty->process_char_map);
1513 set_bit(STOP_CHAR(tty), tty->process_char_map);
1514 }
1515 if (L_ISIG(tty)) {
1516 set_bit(INTR_CHAR(tty), tty->process_char_map);
1517 set_bit(QUIT_CHAR(tty), tty->process_char_map);
1518 set_bit(SUSP_CHAR(tty), tty->process_char_map);
1519 }
1520 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1521 tty->raw = 0;
1522 tty->real_raw = 0;
1523 } else {
1524 tty->raw = 1;
1525 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1526 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1527 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1528 tty->real_raw = 1;
1529 else
1530 tty->real_raw = 0;
1531 }
1532 n_tty_set_room(tty);
1533 /* The termios change make the tty ready for I/O */
1534 wake_up_interruptible(&tty->write_wait);
1535 wake_up_interruptible(&tty->read_wait);
1536}
1537
1538/**
1539 * n_tty_close - close the ldisc for this tty
1540 * @tty: device
1541 *
1542 * Called from the terminal layer when this line discipline is
1543 * being shut down, either because of a close or becsuse of a
1544 * discipline change. The function will not be called while other
1545 * ldisc methods are in progress.
1546 */
1547
1548static void n_tty_close(struct tty_struct *tty)
1549{
1550 n_tty_flush_buffer(tty);
1551 if (tty->read_buf) {
1552 kfree(tty->read_buf);
1553 tty->read_buf = NULL;
1554 }
1555 if (tty->echo_buf) {
1556 kfree(tty->echo_buf);
1557 tty->echo_buf = NULL;
1558 }
1559}
1560
1561/**
1562 * n_tty_open - open an ldisc
1563 * @tty: terminal to open
1564 *
1565 * Called when this line discipline is being attached to the
1566 * terminal device. Can sleep. Called serialized so that no
1567 * other events will occur in parallel. No further open will occur
1568 * until a close.
1569 */
1570
1571static int n_tty_open(struct tty_struct *tty)
1572{
1573 if (!tty)
1574 return -EINVAL;
1575
1576 /* These are ugly. Currently a malloc failure here can panic */
1577 if (!tty->read_buf) {
1578 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1579 if (!tty->read_buf)
1580 return -ENOMEM;
1581 }
1582 if (!tty->echo_buf) {
1583 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1584
1585 if (!tty->echo_buf)
1586 return -ENOMEM;
1587 }
1588 reset_buffer_flags(tty);
1589 tty_unthrottle(tty);
1590 tty->column = 0;
1591 n_tty_set_termios(tty, NULL);
1592 tty->minimum_to_wake = 1;
1593 tty->closing = 0;
1594 return 0;
1595}
1596
1597static inline int input_available_p(struct tty_struct *tty, int amt)
1598{
1599 tty_flush_to_ldisc(tty);
1600 if (tty->icanon && !L_EXTPROC(tty)) {
1601 if (tty->canon_data)
1602 return 1;
1603 } else if (tty->read_cnt >= (amt ? amt : 1))
1604 return 1;
1605
1606 return 0;
1607}
1608
1609/**
1610 * copy_from_read_buf - copy read data directly
1611 * @tty: terminal device
1612 * @b: user data
1613 * @nr: size of data
1614 *
1615 * Helper function to speed up n_tty_read. It is only called when
1616 * ICANON is off; it copies characters straight from the tty queue to
1617 * user space directly. It can be profitably called twice; once to
1618 * drain the space from the tail pointer to the (physical) end of the
1619 * buffer, and once to drain the space from the (physical) beginning of
1620 * the buffer to head pointer.
1621 *
1622 * Called under the tty->atomic_read_lock sem
1623 *
1624 */
1625
1626static int copy_from_read_buf(struct tty_struct *tty,
1627 unsigned char __user **b,
1628 size_t *nr)
1629
1630{
1631 int retval;
1632 size_t n;
1633 unsigned long flags;
1634
1635 retval = 0;
1636 spin_lock_irqsave(&tty->read_lock, flags);
1637 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1638 n = min(*nr, n);
1639 spin_unlock_irqrestore(&tty->read_lock, flags);
1640 if (n) {
1641 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1642 n -= retval;
1643 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1644 spin_lock_irqsave(&tty->read_lock, flags);
1645 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1646 tty->read_cnt -= n;
1647 /* Turn single EOF into zero-length read */
1648 if (L_EXTPROC(tty) && tty->icanon && n == 1) {
1649 if (!tty->read_cnt && (*b)[n-1] == EOF_CHAR(tty))
1650 n--;
1651 }
1652 spin_unlock_irqrestore(&tty->read_lock, flags);
1653 *b += n;
1654 *nr -= n;
1655 }
1656 return retval;
1657}
1658
1659extern ssize_t redirected_tty_write(struct file *, const char __user *,
1660 size_t, loff_t *);
1661
1662/**
1663 * job_control - check job control
1664 * @tty: tty
1665 * @file: file handle
1666 *
1667 * Perform job control management checks on this file/tty descriptor
1668 * and if appropriate send any needed signals and return a negative
1669 * error code if action should be taken.
1670 *
1671 * FIXME:
1672 * Locking: None - redirected write test is safe, testing
1673 * current->signal should possibly lock current->sighand
1674 * pgrp locking ?
1675 */
1676
1677static int job_control(struct tty_struct *tty, struct file *file)
1678{
1679 /* Job control check -- must be done at start and after
1680 every sleep (POSIX.1 7.1.1.4). */
1681 /* NOTE: not yet done after every sleep pending a thorough
1682 check of the logic of this change. -- jlc */
1683 /* don't stop on /dev/console */
1684 if (file->f_op->write != redirected_tty_write &&
1685 current->signal->tty == tty) {
1686 if (!tty->pgrp)
1687 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1688 else if (task_pgrp(current) != tty->pgrp) {
1689 if (is_ignored(SIGTTIN) ||
1690 is_current_pgrp_orphaned())
1691 return -EIO;
1692 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1693 set_thread_flag(TIF_SIGPENDING);
1694 return -ERESTARTSYS;
1695 }
1696 }
1697 return 0;
1698}
1699
1700
1701/**
1702 * n_tty_read - read function for tty
1703 * @tty: tty device
1704 * @file: file object
1705 * @buf: userspace buffer pointer
1706 * @nr: size of I/O
1707 *
1708 * Perform reads for the line discipline. We are guaranteed that the
1709 * line discipline will not be closed under us but we may get multiple
1710 * parallel readers and must handle this ourselves. We may also get
1711 * a hangup. Always called in user context, may sleep.
1712 *
1713 * This code must be sure never to sleep through a hangup.
1714 */
1715
1716static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1717 unsigned char __user *buf, size_t nr)
1718{
1719 unsigned char __user *b = buf;
1720 DECLARE_WAITQUEUE(wait, current);
1721 int c;
1722 int minimum, time;
1723 ssize_t retval = 0;
1724 ssize_t size;
1725 long timeout;
1726 unsigned long flags;
1727 int packet;
1728
1729do_it_again:
1730
1731 BUG_ON(!tty->read_buf);
1732
1733 c = job_control(tty, file);
1734 if (c < 0)
1735 return c;
1736
1737 minimum = time = 0;
1738 timeout = MAX_SCHEDULE_TIMEOUT;
1739 if (!tty->icanon) {
1740 time = (HZ / 10) * TIME_CHAR(tty);
1741 minimum = MIN_CHAR(tty);
1742 if (minimum) {
1743 if (time)
1744 tty->minimum_to_wake = 1;
1745 else if (!waitqueue_active(&tty->read_wait) ||
1746 (tty->minimum_to_wake > minimum))
1747 tty->minimum_to_wake = minimum;
1748 } else {
1749 timeout = 0;
1750 if (time) {
1751 timeout = time;
1752 time = 0;
1753 }
1754 tty->minimum_to_wake = minimum = 1;
1755 }
1756 }
1757
1758 /*
1759 * Internal serialization of reads.
1760 */
1761 if (file->f_flags & O_NONBLOCK) {
1762 if (!mutex_trylock(&tty->atomic_read_lock))
1763 return -EAGAIN;
1764 } else {
1765 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1766 return -ERESTARTSYS;
1767 }
1768 packet = tty->packet;
1769
1770 add_wait_queue(&tty->read_wait, &wait);
1771 while (nr) {
1772 /* First test for status change. */
1773 if (packet && tty->link->ctrl_status) {
1774 unsigned char cs;
1775 if (b != buf)
1776 break;
1777 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1778 cs = tty->link->ctrl_status;
1779 tty->link->ctrl_status = 0;
1780 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1781 if (tty_put_user(tty, cs, b++)) {
1782 retval = -EFAULT;
1783 b--;
1784 break;
1785 }
1786 nr--;
1787 break;
1788 }
1789 /* This statement must be first before checking for input
1790 so that any interrupt will set the state back to
1791 TASK_RUNNING. */
1792 set_current_state(TASK_INTERRUPTIBLE);
1793
1794 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1795 ((minimum - (b - buf)) >= 1))
1796 tty->minimum_to_wake = (minimum - (b - buf));
1797
1798 if (!input_available_p(tty, 0)) {
1799 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1800 retval = -EIO;
1801 break;
1802 }
1803 if (tty_hung_up_p(file))
1804 break;
1805 if (!timeout)
1806 break;
1807 if (file->f_flags & O_NONBLOCK) {
1808 retval = -EAGAIN;
1809 break;
1810 }
1811 if (signal_pending(current)) {
1812 retval = -ERESTARTSYS;
1813 break;
1814 }
1815 /* FIXME: does n_tty_set_room need locking ? */
1816 n_tty_set_room(tty);
1817 timeout = schedule_timeout(timeout);
1818 BUG_ON(!tty->read_buf);
1819 continue;
1820 }
1821 __set_current_state(TASK_RUNNING);
1822
1823 /* Deal with packet mode. */
1824 if (packet && b == buf) {
1825 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1826 retval = -EFAULT;
1827 b--;
1828 break;
1829 }
1830 nr--;
1831 }
1832
1833 if (tty->icanon && !L_EXTPROC(tty)) {
1834 /* N.B. avoid overrun if nr == 0 */
1835 while (nr && tty->read_cnt) {
1836 int eol;
1837
1838 eol = test_and_clear_bit(tty->read_tail,
1839 tty->read_flags);
1840 c = tty->read_buf[tty->read_tail];
1841 spin_lock_irqsave(&tty->read_lock, flags);
1842 tty->read_tail = ((tty->read_tail+1) &
1843 (N_TTY_BUF_SIZE-1));
1844 tty->read_cnt--;
1845 if (eol) {
1846 /* this test should be redundant:
1847 * we shouldn't be reading data if
1848 * canon_data is 0
1849 */
1850 if (--tty->canon_data < 0)
1851 tty->canon_data = 0;
1852 }
1853 spin_unlock_irqrestore(&tty->read_lock, flags);
1854
1855 if (!eol || (c != __DISABLED_CHAR)) {
1856 if (tty_put_user(tty, c, b++)) {
1857 retval = -EFAULT;
1858 b--;
1859 break;
1860 }
1861 nr--;
1862 }
1863 if (eol) {
1864 tty_audit_push(tty);
1865 break;
1866 }
1867 }
1868 if (retval)
1869 break;
1870 } else {
1871 int uncopied;
1872 /* The copy function takes the read lock and handles
1873 locking internally for this case */
1874 uncopied = copy_from_read_buf(tty, &b, &nr);
1875 uncopied += copy_from_read_buf(tty, &b, &nr);
1876 if (uncopied) {
1877 retval = -EFAULT;
1878 break;
1879 }
1880 }
1881
1882 /* If there is enough space in the read buffer now, let the
1883 * low-level driver know. We use n_tty_chars_in_buffer() to
1884 * check the buffer, as it now knows about canonical mode.
1885 * Otherwise, if the driver is throttled and the line is
1886 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1887 * we won't get any more characters.
1888 */
1889 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1890 n_tty_set_room(tty);
1891 check_unthrottle(tty);
1892 }
1893
1894 if (b - buf >= minimum)
1895 break;
1896 if (time)
1897 timeout = time;
1898 }
1899 mutex_unlock(&tty->atomic_read_lock);
1900 remove_wait_queue(&tty->read_wait, &wait);
1901
1902 if (!waitqueue_active(&tty->read_wait))
1903 tty->minimum_to_wake = minimum;
1904
1905 __set_current_state(TASK_RUNNING);
1906 size = b - buf;
1907 if (size) {
1908 retval = size;
1909 if (nr)
1910 clear_bit(TTY_PUSH, &tty->flags);
1911 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1912 goto do_it_again;
1913
1914 n_tty_set_room(tty);
1915 return retval;
1916}
1917
1918/**
1919 * n_tty_write - write function for tty
1920 * @tty: tty device
1921 * @file: file object
1922 * @buf: userspace buffer pointer
1923 * @nr: size of I/O
1924 *
1925 * Write function of the terminal device. This is serialized with
1926 * respect to other write callers but not to termios changes, reads
1927 * and other such events. Since the receive code will echo characters,
1928 * thus calling driver write methods, the output_lock is used in
1929 * the output processing functions called here as well as in the
1930 * echo processing function to protect the column state and space
1931 * left in the buffer.
1932 *
1933 * This code must be sure never to sleep through a hangup.
1934 *
1935 * Locking: output_lock to protect column state and space left
1936 * (note that the process_output*() functions take this
1937 * lock themselves)
1938 */
1939
1940static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1941 const unsigned char *buf, size_t nr)
1942{
1943 const unsigned char *b = buf;
1944 DECLARE_WAITQUEUE(wait, current);
1945 int c;
1946 ssize_t retval = 0;
1947
1948 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1949 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1950 retval = tty_check_change(tty);
1951 if (retval)
1952 return retval;
1953 }
1954
1955 /* Write out any echoed characters that are still pending */
1956 process_echoes(tty);
1957
1958 add_wait_queue(&tty->write_wait, &wait);
1959 while (1) {
1960 set_current_state(TASK_INTERRUPTIBLE);
1961 if (signal_pending(current)) {
1962 retval = -ERESTARTSYS;
1963 break;
1964 }
1965 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1966 retval = -EIO;
1967 break;
1968 }
1969 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1970 while (nr > 0) {
1971 ssize_t num = process_output_block(tty, b, nr);
1972 if (num < 0) {
1973 if (num == -EAGAIN)
1974 break;
1975 retval = num;
1976 goto break_out;
1977 }
1978 b += num;
1979 nr -= num;
1980 if (nr == 0)
1981 break;
1982 c = *b;
1983 if (process_output(c, tty) < 0)
1984 break;
1985 b++; nr--;
1986 }
1987 if (tty->ops->flush_chars)
1988 tty->ops->flush_chars(tty);
1989 } else {
1990 while (nr > 0) {
1991 c = tty->ops->write(tty, b, nr);
1992 if (c < 0) {
1993 retval = c;
1994 goto break_out;
1995 }
1996 if (!c)
1997 break;
1998 b += c;
1999 nr -= c;
2000 }
2001 }
2002 if (!nr)
2003 break;
2004 if (file->f_flags & O_NONBLOCK) {
2005 retval = -EAGAIN;
2006 break;
2007 }
2008 schedule();
2009 }
2010break_out:
2011 __set_current_state(TASK_RUNNING);
2012 remove_wait_queue(&tty->write_wait, &wait);
2013 if (b - buf != nr && tty->fasync)
2014 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2015 return (b - buf) ? b - buf : retval;
2016}
2017
2018/**
2019 * n_tty_poll - poll method for N_TTY
2020 * @tty: terminal device
2021 * @file: file accessing it
2022 * @wait: poll table
2023 *
2024 * Called when the line discipline is asked to poll() for data or
2025 * for special events. This code is not serialized with respect to
2026 * other events save open/close.
2027 *
2028 * This code must be sure never to sleep through a hangup.
2029 * Called without the kernel lock held - fine
2030 */
2031
2032static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2033 poll_table *wait)
2034{
2035 unsigned int mask = 0;
2036
2037 poll_wait(file, &tty->read_wait, wait);
2038 poll_wait(file, &tty->write_wait, wait);
2039 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2040 mask |= POLLIN | POLLRDNORM;
2041 if (tty->packet && tty->link->ctrl_status)
2042 mask |= POLLPRI | POLLIN | POLLRDNORM;
2043 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2044 mask |= POLLHUP;
2045 if (tty_hung_up_p(file))
2046 mask |= POLLHUP;
2047 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2048 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2049 tty->minimum_to_wake = MIN_CHAR(tty);
2050 else
2051 tty->minimum_to_wake = 1;
2052 }
2053 if (tty->ops->write && !tty_is_writelocked(tty) &&
2054 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2055 tty_write_room(tty) > 0)
2056 mask |= POLLOUT | POLLWRNORM;
2057 return mask;
2058}
2059
2060static unsigned long inq_canon(struct tty_struct *tty)
2061{
2062 int nr, head, tail;
2063
2064 if (!tty->canon_data)
2065 return 0;
2066 head = tty->canon_head;
2067 tail = tty->read_tail;
2068 nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2069 /* Skip EOF-chars.. */
2070 while (head != tail) {
2071 if (test_bit(tail, tty->read_flags) &&
2072 tty->read_buf[tail] == __DISABLED_CHAR)
2073 nr--;
2074 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2075 }
2076 return nr;
2077}
2078
2079static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2080 unsigned int cmd, unsigned long arg)
2081{
2082 int retval;
2083
2084 switch (cmd) {
2085 case TIOCOUTQ:
2086 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2087 case TIOCINQ:
2088 /* FIXME: Locking */
2089 retval = tty->read_cnt;
2090 if (L_ICANON(tty))
2091 retval = inq_canon(tty);
2092 return put_user(retval, (unsigned int __user *) arg);
2093 default:
2094 return n_tty_ioctl_helper(tty, file, cmd, arg);
2095 }
2096}
2097
2098struct tty_ldisc_ops tty_ldisc_N_TTY = {
2099 .magic = TTY_LDISC_MAGIC,
2100 .name = "n_tty",
2101 .open = n_tty_open,
2102 .close = n_tty_close,
2103 .flush_buffer = n_tty_flush_buffer,
2104 .chars_in_buffer = n_tty_chars_in_buffer,
2105 .read = n_tty_read,
2106 .write = n_tty_write,
2107 .ioctl = n_tty_ioctl,
2108 .set_termios = n_tty_set_termios,
2109 .poll = n_tty_poll,
2110 .receive_buf = n_tty_receive_buf,
2111 .write_wakeup = n_tty_write_wakeup
2112};
2113
2114/**
2115 * n_tty_inherit_ops - inherit N_TTY methods
2116 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2117 *
2118 * Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2119 * methods.
2120 */
2121
2122void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2123{
2124 *ops = tty_ldisc_N_TTY;
2125 ops->owner = NULL;
2126 ops->refcount = ops->flags = 0;
2127}
2128EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
1// SPDX-License-Identifier: GPL-1.0+
2/*
3 * n_tty.c --- implements the N_TTY line discipline.
4 *
5 * This code used to be in tty_io.c, but things are getting hairy
6 * enough that it made sense to split things off. (The N_TTY
7 * processing has changed so much that it's hardly recognizable,
8 * anyway...)
9 *
10 * Note that the open routine for N_TTY is guaranteed never to return
11 * an error. This is because Linux will fall back to setting a line
12 * to N_TTY if it can not switch to any other line discipline.
13 *
14 * Written by Theodore Ts'o, Copyright 1994.
15 *
16 * This file also contains code originally written by Linus Torvalds,
17 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 *
19 * Reduced memory usage for older ARM systems - Russell King.
20 *
21 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
22 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
23 * who actually finally proved there really was a race.
24 *
25 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
26 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
27 * Also fixed a bug in BLOCKING mode where n_tty_write returns
28 * EAGAIN
29 */
30
31#include <linux/types.h>
32#include <linux/major.h>
33#include <linux/errno.h>
34#include <linux/signal.h>
35#include <linux/fcntl.h>
36#include <linux/sched.h>
37#include <linux/interrupt.h>
38#include <linux/tty.h>
39#include <linux/timer.h>
40#include <linux/ctype.h>
41#include <linux/mm.h>
42#include <linux/string.h>
43#include <linux/slab.h>
44#include <linux/poll.h>
45#include <linux/bitops.h>
46#include <linux/audit.h>
47#include <linux/file.h>
48#include <linux/uaccess.h>
49#include <linux/module.h>
50#include <linux/ratelimit.h>
51#include <linux/vmalloc.h>
52
53
54/* number of characters left in xmit buffer before select has we have room */
55#define WAKEUP_CHARS 256
56
57/*
58 * This defines the low- and high-watermarks for throttling and
59 * unthrottling the TTY driver. These watermarks are used for
60 * controlling the space in the read buffer.
61 */
62#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
63#define TTY_THRESHOLD_UNTHROTTLE 128
64
65/*
66 * Special byte codes used in the echo buffer to represent operations
67 * or special handling of characters. Bytes in the echo buffer that
68 * are not part of such special blocks are treated as normal character
69 * codes.
70 */
71#define ECHO_OP_START 0xff
72#define ECHO_OP_MOVE_BACK_COL 0x80
73#define ECHO_OP_SET_CANON_COL 0x81
74#define ECHO_OP_ERASE_TAB 0x82
75
76#define ECHO_COMMIT_WATERMARK 256
77#define ECHO_BLOCK 256
78#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
79
80
81#undef N_TTY_TRACE
82#ifdef N_TTY_TRACE
83# define n_tty_trace(f, args...) trace_printk(f, ##args)
84#else
85# define n_tty_trace(f, args...)
86#endif
87
88struct n_tty_data {
89 /* producer-published */
90 size_t read_head;
91 size_t commit_head;
92 size_t canon_head;
93 size_t echo_head;
94 size_t echo_commit;
95 size_t echo_mark;
96 DECLARE_BITMAP(char_map, 256);
97
98 /* private to n_tty_receive_overrun (single-threaded) */
99 unsigned long overrun_time;
100 int num_overrun;
101
102 /* non-atomic */
103 bool no_room;
104
105 /* must hold exclusive termios_rwsem to reset these */
106 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
107 unsigned char push:1;
108
109 /* shared by producer and consumer */
110 char read_buf[N_TTY_BUF_SIZE];
111 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
112 unsigned char echo_buf[N_TTY_BUF_SIZE];
113
114 /* consumer-published */
115 size_t read_tail;
116 size_t line_start;
117
118 /* protected by output lock */
119 unsigned int column;
120 unsigned int canon_column;
121 size_t echo_tail;
122
123 struct mutex atomic_read_lock;
124 struct mutex output_lock;
125};
126
127static inline size_t read_cnt(struct n_tty_data *ldata)
128{
129 return ldata->read_head - ldata->read_tail;
130}
131
132static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
133{
134 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
135}
136
137static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
138{
139 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
140}
141
142static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
143{
144 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
145}
146
147static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
148{
149 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
150}
151
152static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
153 size_t tail, size_t n)
154{
155 struct n_tty_data *ldata = tty->disc_data;
156 size_t size = N_TTY_BUF_SIZE - tail;
157 const void *from = read_buf_addr(ldata, tail);
158 int uncopied;
159
160 if (n > size) {
161 tty_audit_add_data(tty, from, size);
162 uncopied = copy_to_user(to, from, size);
163 if (uncopied)
164 return uncopied;
165 to += size;
166 n -= size;
167 from = ldata->read_buf;
168 }
169
170 tty_audit_add_data(tty, from, n);
171 return copy_to_user(to, from, n);
172}
173
174/**
175 * n_tty_kick_worker - start input worker (if required)
176 * @tty: terminal
177 *
178 * Re-schedules the flip buffer work if it may have stopped
179 *
180 * Caller holds exclusive termios_rwsem
181 * or
182 * n_tty_read()/consumer path:
183 * holds non-exclusive termios_rwsem
184 */
185
186static void n_tty_kick_worker(struct tty_struct *tty)
187{
188 struct n_tty_data *ldata = tty->disc_data;
189
190 /* Did the input worker stop? Restart it */
191 if (unlikely(ldata->no_room)) {
192 ldata->no_room = 0;
193
194 WARN_RATELIMIT(tty->port->itty == NULL,
195 "scheduling with invalid itty\n");
196 /* see if ldisc has been killed - if so, this means that
197 * even though the ldisc has been halted and ->buf.work
198 * cancelled, ->buf.work is about to be rescheduled
199 */
200 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
201 "scheduling buffer work for halted ldisc\n");
202 tty_buffer_restart_work(tty->port);
203 }
204}
205
206static ssize_t chars_in_buffer(struct tty_struct *tty)
207{
208 struct n_tty_data *ldata = tty->disc_data;
209 ssize_t n = 0;
210
211 if (!ldata->icanon)
212 n = ldata->commit_head - ldata->read_tail;
213 else
214 n = ldata->canon_head - ldata->read_tail;
215 return n;
216}
217
218/**
219 * n_tty_write_wakeup - asynchronous I/O notifier
220 * @tty: tty device
221 *
222 * Required for the ptys, serial driver etc. since processes
223 * that attach themselves to the master and rely on ASYNC
224 * IO must be woken up
225 */
226
227static void n_tty_write_wakeup(struct tty_struct *tty)
228{
229 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
230 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
231}
232
233static void n_tty_check_throttle(struct tty_struct *tty)
234{
235 struct n_tty_data *ldata = tty->disc_data;
236
237 /*
238 * Check the remaining room for the input canonicalization
239 * mode. We don't want to throttle the driver if we're in
240 * canonical mode and don't have a newline yet!
241 */
242 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
243 return;
244
245 while (1) {
246 int throttled;
247 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
248 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
249 break;
250 throttled = tty_throttle_safe(tty);
251 if (!throttled)
252 break;
253 }
254 __tty_set_flow_change(tty, 0);
255}
256
257static void n_tty_check_unthrottle(struct tty_struct *tty)
258{
259 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
260 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
261 return;
262 n_tty_kick_worker(tty);
263 tty_wakeup(tty->link);
264 return;
265 }
266
267 /* If there is enough space in the read buffer now, let the
268 * low-level driver know. We use chars_in_buffer() to
269 * check the buffer, as it now knows about canonical mode.
270 * Otherwise, if the driver is throttled and the line is
271 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
272 * we won't get any more characters.
273 */
274
275 while (1) {
276 int unthrottled;
277 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
278 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
279 break;
280 n_tty_kick_worker(tty);
281 unthrottled = tty_unthrottle_safe(tty);
282 if (!unthrottled)
283 break;
284 }
285 __tty_set_flow_change(tty, 0);
286}
287
288/**
289 * put_tty_queue - add character to tty
290 * @c: character
291 * @ldata: n_tty data
292 *
293 * Add a character to the tty read_buf queue.
294 *
295 * n_tty_receive_buf()/producer path:
296 * caller holds non-exclusive termios_rwsem
297 */
298
299static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
300{
301 *read_buf_addr(ldata, ldata->read_head) = c;
302 ldata->read_head++;
303}
304
305/**
306 * reset_buffer_flags - reset buffer state
307 * @tty: terminal to reset
308 *
309 * Reset the read buffer counters and clear the flags.
310 * Called from n_tty_open() and n_tty_flush_buffer().
311 *
312 * Locking: caller holds exclusive termios_rwsem
313 * (or locking is not required)
314 */
315
316static void reset_buffer_flags(struct n_tty_data *ldata)
317{
318 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
319 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
320 ldata->commit_head = 0;
321 ldata->echo_mark = 0;
322 ldata->line_start = 0;
323
324 ldata->erasing = 0;
325 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
326 ldata->push = 0;
327}
328
329static void n_tty_packet_mode_flush(struct tty_struct *tty)
330{
331 unsigned long flags;
332
333 if (tty->link->packet) {
334 spin_lock_irqsave(&tty->ctrl_lock, flags);
335 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
336 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
337 wake_up_interruptible(&tty->link->read_wait);
338 }
339}
340
341/**
342 * n_tty_flush_buffer - clean input queue
343 * @tty: terminal device
344 *
345 * Flush the input buffer. Called when the tty layer wants the
346 * buffer flushed (eg at hangup) or when the N_TTY line discipline
347 * internally has to clean the pending queue (for example some signals).
348 *
349 * Holds termios_rwsem to exclude producer/consumer while
350 * buffer indices are reset.
351 *
352 * Locking: ctrl_lock, exclusive termios_rwsem
353 */
354
355static void n_tty_flush_buffer(struct tty_struct *tty)
356{
357 down_write(&tty->termios_rwsem);
358 reset_buffer_flags(tty->disc_data);
359 n_tty_kick_worker(tty);
360
361 if (tty->link)
362 n_tty_packet_mode_flush(tty);
363 up_write(&tty->termios_rwsem);
364}
365
366/**
367 * is_utf8_continuation - utf8 multibyte check
368 * @c: byte to check
369 *
370 * Returns true if the utf8 character 'c' is a multibyte continuation
371 * character. We use this to correctly compute the on screen size
372 * of the character when printing
373 */
374
375static inline int is_utf8_continuation(unsigned char c)
376{
377 return (c & 0xc0) == 0x80;
378}
379
380/**
381 * is_continuation - multibyte check
382 * @c: byte to check
383 *
384 * Returns true if the utf8 character 'c' is a multibyte continuation
385 * character and the terminal is in unicode mode.
386 */
387
388static inline int is_continuation(unsigned char c, struct tty_struct *tty)
389{
390 return I_IUTF8(tty) && is_utf8_continuation(c);
391}
392
393/**
394 * do_output_char - output one character
395 * @c: character (or partial unicode symbol)
396 * @tty: terminal device
397 * @space: space available in tty driver write buffer
398 *
399 * This is a helper function that handles one output character
400 * (including special characters like TAB, CR, LF, etc.),
401 * doing OPOST processing and putting the results in the
402 * tty driver's write buffer.
403 *
404 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
405 * and NLDLY. They simply aren't relevant in the world today.
406 * If you ever need them, add them here.
407 *
408 * Returns the number of bytes of buffer space used or -1 if
409 * no space left.
410 *
411 * Locking: should be called under the output_lock to protect
412 * the column state and space left in the buffer
413 */
414
415static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
416{
417 struct n_tty_data *ldata = tty->disc_data;
418 int spaces;
419
420 if (!space)
421 return -1;
422
423 switch (c) {
424 case '\n':
425 if (O_ONLRET(tty))
426 ldata->column = 0;
427 if (O_ONLCR(tty)) {
428 if (space < 2)
429 return -1;
430 ldata->canon_column = ldata->column = 0;
431 tty->ops->write(tty, "\r\n", 2);
432 return 2;
433 }
434 ldata->canon_column = ldata->column;
435 break;
436 case '\r':
437 if (O_ONOCR(tty) && ldata->column == 0)
438 return 0;
439 if (O_OCRNL(tty)) {
440 c = '\n';
441 if (O_ONLRET(tty))
442 ldata->canon_column = ldata->column = 0;
443 break;
444 }
445 ldata->canon_column = ldata->column = 0;
446 break;
447 case '\t':
448 spaces = 8 - (ldata->column & 7);
449 if (O_TABDLY(tty) == XTABS) {
450 if (space < spaces)
451 return -1;
452 ldata->column += spaces;
453 tty->ops->write(tty, " ", spaces);
454 return spaces;
455 }
456 ldata->column += spaces;
457 break;
458 case '\b':
459 if (ldata->column > 0)
460 ldata->column--;
461 break;
462 default:
463 if (!iscntrl(c)) {
464 if (O_OLCUC(tty))
465 c = toupper(c);
466 if (!is_continuation(c, tty))
467 ldata->column++;
468 }
469 break;
470 }
471
472 tty_put_char(tty, c);
473 return 1;
474}
475
476/**
477 * process_output - output post processor
478 * @c: character (or partial unicode symbol)
479 * @tty: terminal device
480 *
481 * Output one character with OPOST processing.
482 * Returns -1 when the output device is full and the character
483 * must be retried.
484 *
485 * Locking: output_lock to protect column state and space left
486 * (also, this is called from n_tty_write under the
487 * tty layer write lock)
488 */
489
490static int process_output(unsigned char c, struct tty_struct *tty)
491{
492 struct n_tty_data *ldata = tty->disc_data;
493 int space, retval;
494
495 mutex_lock(&ldata->output_lock);
496
497 space = tty_write_room(tty);
498 retval = do_output_char(c, tty, space);
499
500 mutex_unlock(&ldata->output_lock);
501 if (retval < 0)
502 return -1;
503 else
504 return 0;
505}
506
507/**
508 * process_output_block - block post processor
509 * @tty: terminal device
510 * @buf: character buffer
511 * @nr: number of bytes to output
512 *
513 * Output a block of characters with OPOST processing.
514 * Returns the number of characters output.
515 *
516 * This path is used to speed up block console writes, among other
517 * things when processing blocks of output data. It handles only
518 * the simple cases normally found and helps to generate blocks of
519 * symbols for the console driver and thus improve performance.
520 *
521 * Locking: output_lock to protect column state and space left
522 * (also, this is called from n_tty_write under the
523 * tty layer write lock)
524 */
525
526static ssize_t process_output_block(struct tty_struct *tty,
527 const unsigned char *buf, unsigned int nr)
528{
529 struct n_tty_data *ldata = tty->disc_data;
530 int space;
531 int i;
532 const unsigned char *cp;
533
534 mutex_lock(&ldata->output_lock);
535
536 space = tty_write_room(tty);
537 if (!space) {
538 mutex_unlock(&ldata->output_lock);
539 return 0;
540 }
541 if (nr > space)
542 nr = space;
543
544 for (i = 0, cp = buf; i < nr; i++, cp++) {
545 unsigned char c = *cp;
546
547 switch (c) {
548 case '\n':
549 if (O_ONLRET(tty))
550 ldata->column = 0;
551 if (O_ONLCR(tty))
552 goto break_out;
553 ldata->canon_column = ldata->column;
554 break;
555 case '\r':
556 if (O_ONOCR(tty) && ldata->column == 0)
557 goto break_out;
558 if (O_OCRNL(tty))
559 goto break_out;
560 ldata->canon_column = ldata->column = 0;
561 break;
562 case '\t':
563 goto break_out;
564 case '\b':
565 if (ldata->column > 0)
566 ldata->column--;
567 break;
568 default:
569 if (!iscntrl(c)) {
570 if (O_OLCUC(tty))
571 goto break_out;
572 if (!is_continuation(c, tty))
573 ldata->column++;
574 }
575 break;
576 }
577 }
578break_out:
579 i = tty->ops->write(tty, buf, i);
580
581 mutex_unlock(&ldata->output_lock);
582 return i;
583}
584
585/**
586 * process_echoes - write pending echo characters
587 * @tty: terminal device
588 *
589 * Write previously buffered echo (and other ldisc-generated)
590 * characters to the tty.
591 *
592 * Characters generated by the ldisc (including echoes) need to
593 * be buffered because the driver's write buffer can fill during
594 * heavy program output. Echoing straight to the driver will
595 * often fail under these conditions, causing lost characters and
596 * resulting mismatches of ldisc state information.
597 *
598 * Since the ldisc state must represent the characters actually sent
599 * to the driver at the time of the write, operations like certain
600 * changes in column state are also saved in the buffer and executed
601 * here.
602 *
603 * A circular fifo buffer is used so that the most recent characters
604 * are prioritized. Also, when control characters are echoed with a
605 * prefixed "^", the pair is treated atomically and thus not separated.
606 *
607 * Locking: callers must hold output_lock
608 */
609
610static size_t __process_echoes(struct tty_struct *tty)
611{
612 struct n_tty_data *ldata = tty->disc_data;
613 int space, old_space;
614 size_t tail;
615 unsigned char c;
616
617 old_space = space = tty_write_room(tty);
618
619 tail = ldata->echo_tail;
620 while (ldata->echo_commit != tail) {
621 c = echo_buf(ldata, tail);
622 if (c == ECHO_OP_START) {
623 unsigned char op;
624 int no_space_left = 0;
625
626 /*
627 * If the buffer byte is the start of a multi-byte
628 * operation, get the next byte, which is either the
629 * op code or a control character value.
630 */
631 op = echo_buf(ldata, tail + 1);
632
633 switch (op) {
634 unsigned int num_chars, num_bs;
635
636 case ECHO_OP_ERASE_TAB:
637 num_chars = echo_buf(ldata, tail + 2);
638
639 /*
640 * Determine how many columns to go back
641 * in order to erase the tab.
642 * This depends on the number of columns
643 * used by other characters within the tab
644 * area. If this (modulo 8) count is from
645 * the start of input rather than from a
646 * previous tab, we offset by canon column.
647 * Otherwise, tab spacing is normal.
648 */
649 if (!(num_chars & 0x80))
650 num_chars += ldata->canon_column;
651 num_bs = 8 - (num_chars & 7);
652
653 if (num_bs > space) {
654 no_space_left = 1;
655 break;
656 }
657 space -= num_bs;
658 while (num_bs--) {
659 tty_put_char(tty, '\b');
660 if (ldata->column > 0)
661 ldata->column--;
662 }
663 tail += 3;
664 break;
665
666 case ECHO_OP_SET_CANON_COL:
667 ldata->canon_column = ldata->column;
668 tail += 2;
669 break;
670
671 case ECHO_OP_MOVE_BACK_COL:
672 if (ldata->column > 0)
673 ldata->column--;
674 tail += 2;
675 break;
676
677 case ECHO_OP_START:
678 /* This is an escaped echo op start code */
679 if (!space) {
680 no_space_left = 1;
681 break;
682 }
683 tty_put_char(tty, ECHO_OP_START);
684 ldata->column++;
685 space--;
686 tail += 2;
687 break;
688
689 default:
690 /*
691 * If the op is not a special byte code,
692 * it is a ctrl char tagged to be echoed
693 * as "^X" (where X is the letter
694 * representing the control char).
695 * Note that we must ensure there is
696 * enough space for the whole ctrl pair.
697 *
698 */
699 if (space < 2) {
700 no_space_left = 1;
701 break;
702 }
703 tty_put_char(tty, '^');
704 tty_put_char(tty, op ^ 0100);
705 ldata->column += 2;
706 space -= 2;
707 tail += 2;
708 }
709
710 if (no_space_left)
711 break;
712 } else {
713 if (O_OPOST(tty)) {
714 int retval = do_output_char(c, tty, space);
715 if (retval < 0)
716 break;
717 space -= retval;
718 } else {
719 if (!space)
720 break;
721 tty_put_char(tty, c);
722 space -= 1;
723 }
724 tail += 1;
725 }
726 }
727
728 /* If the echo buffer is nearly full (so that the possibility exists
729 * of echo overrun before the next commit), then discard enough
730 * data at the tail to prevent a subsequent overrun */
731 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
732 if (echo_buf(ldata, tail) == ECHO_OP_START) {
733 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
734 tail += 3;
735 else
736 tail += 2;
737 } else
738 tail++;
739 }
740
741 ldata->echo_tail = tail;
742 return old_space - space;
743}
744
745static void commit_echoes(struct tty_struct *tty)
746{
747 struct n_tty_data *ldata = tty->disc_data;
748 size_t nr, old, echoed;
749 size_t head;
750
751 head = ldata->echo_head;
752 ldata->echo_mark = head;
753 old = ldata->echo_commit - ldata->echo_tail;
754
755 /* Process committed echoes if the accumulated # of bytes
756 * is over the threshold (and try again each time another
757 * block is accumulated) */
758 nr = head - ldata->echo_tail;
759 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
760 return;
761
762 mutex_lock(&ldata->output_lock);
763 ldata->echo_commit = head;
764 echoed = __process_echoes(tty);
765 mutex_unlock(&ldata->output_lock);
766
767 if (echoed && tty->ops->flush_chars)
768 tty->ops->flush_chars(tty);
769}
770
771static void process_echoes(struct tty_struct *tty)
772{
773 struct n_tty_data *ldata = tty->disc_data;
774 size_t echoed;
775
776 if (ldata->echo_mark == ldata->echo_tail)
777 return;
778
779 mutex_lock(&ldata->output_lock);
780 ldata->echo_commit = ldata->echo_mark;
781 echoed = __process_echoes(tty);
782 mutex_unlock(&ldata->output_lock);
783
784 if (echoed && tty->ops->flush_chars)
785 tty->ops->flush_chars(tty);
786}
787
788/* NB: echo_mark and echo_head should be equivalent here */
789static void flush_echoes(struct tty_struct *tty)
790{
791 struct n_tty_data *ldata = tty->disc_data;
792
793 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
794 ldata->echo_commit == ldata->echo_head)
795 return;
796
797 mutex_lock(&ldata->output_lock);
798 ldata->echo_commit = ldata->echo_head;
799 __process_echoes(tty);
800 mutex_unlock(&ldata->output_lock);
801}
802
803/**
804 * add_echo_byte - add a byte to the echo buffer
805 * @c: unicode byte to echo
806 * @ldata: n_tty data
807 *
808 * Add a character or operation byte to the echo buffer.
809 */
810
811static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
812{
813 *echo_buf_addr(ldata, ldata->echo_head++) = c;
814}
815
816/**
817 * echo_move_back_col - add operation to move back a column
818 * @ldata: n_tty data
819 *
820 * Add an operation to the echo buffer to move back one column.
821 */
822
823static void echo_move_back_col(struct n_tty_data *ldata)
824{
825 add_echo_byte(ECHO_OP_START, ldata);
826 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
827}
828
829/**
830 * echo_set_canon_col - add operation to set the canon column
831 * @ldata: n_tty data
832 *
833 * Add an operation to the echo buffer to set the canon column
834 * to the current column.
835 */
836
837static void echo_set_canon_col(struct n_tty_data *ldata)
838{
839 add_echo_byte(ECHO_OP_START, ldata);
840 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
841}
842
843/**
844 * echo_erase_tab - add operation to erase a tab
845 * @num_chars: number of character columns already used
846 * @after_tab: true if num_chars starts after a previous tab
847 * @ldata: n_tty data
848 *
849 * Add an operation to the echo buffer to erase a tab.
850 *
851 * Called by the eraser function, which knows how many character
852 * columns have been used since either a previous tab or the start
853 * of input. This information will be used later, along with
854 * canon column (if applicable), to go back the correct number
855 * of columns.
856 */
857
858static void echo_erase_tab(unsigned int num_chars, int after_tab,
859 struct n_tty_data *ldata)
860{
861 add_echo_byte(ECHO_OP_START, ldata);
862 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
863
864 /* We only need to know this modulo 8 (tab spacing) */
865 num_chars &= 7;
866
867 /* Set the high bit as a flag if num_chars is after a previous tab */
868 if (after_tab)
869 num_chars |= 0x80;
870
871 add_echo_byte(num_chars, ldata);
872}
873
874/**
875 * echo_char_raw - echo a character raw
876 * @c: unicode byte to echo
877 * @tty: terminal device
878 *
879 * Echo user input back onto the screen. This must be called only when
880 * L_ECHO(tty) is true. Called from the driver receive_buf path.
881 *
882 * This variant does not treat control characters specially.
883 */
884
885static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
886{
887 if (c == ECHO_OP_START) {
888 add_echo_byte(ECHO_OP_START, ldata);
889 add_echo_byte(ECHO_OP_START, ldata);
890 } else {
891 add_echo_byte(c, ldata);
892 }
893}
894
895/**
896 * echo_char - echo a character
897 * @c: unicode byte to echo
898 * @tty: terminal device
899 *
900 * Echo user input back onto the screen. This must be called only when
901 * L_ECHO(tty) is true. Called from the driver receive_buf path.
902 *
903 * This variant tags control characters to be echoed as "^X"
904 * (where X is the letter representing the control char).
905 */
906
907static void echo_char(unsigned char c, struct tty_struct *tty)
908{
909 struct n_tty_data *ldata = tty->disc_data;
910
911 if (c == ECHO_OP_START) {
912 add_echo_byte(ECHO_OP_START, ldata);
913 add_echo_byte(ECHO_OP_START, ldata);
914 } else {
915 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
916 add_echo_byte(ECHO_OP_START, ldata);
917 add_echo_byte(c, ldata);
918 }
919}
920
921/**
922 * finish_erasing - complete erase
923 * @ldata: n_tty data
924 */
925
926static inline void finish_erasing(struct n_tty_data *ldata)
927{
928 if (ldata->erasing) {
929 echo_char_raw('/', ldata);
930 ldata->erasing = 0;
931 }
932}
933
934/**
935 * eraser - handle erase function
936 * @c: character input
937 * @tty: terminal device
938 *
939 * Perform erase and necessary output when an erase character is
940 * present in the stream from the driver layer. Handles the complexities
941 * of UTF-8 multibyte symbols.
942 *
943 * n_tty_receive_buf()/producer path:
944 * caller holds non-exclusive termios_rwsem
945 */
946
947static void eraser(unsigned char c, struct tty_struct *tty)
948{
949 struct n_tty_data *ldata = tty->disc_data;
950 enum { ERASE, WERASE, KILL } kill_type;
951 size_t head;
952 size_t cnt;
953 int seen_alnums;
954
955 if (ldata->read_head == ldata->canon_head) {
956 /* process_output('\a', tty); */ /* what do you think? */
957 return;
958 }
959 if (c == ERASE_CHAR(tty))
960 kill_type = ERASE;
961 else if (c == WERASE_CHAR(tty))
962 kill_type = WERASE;
963 else {
964 if (!L_ECHO(tty)) {
965 ldata->read_head = ldata->canon_head;
966 return;
967 }
968 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
969 ldata->read_head = ldata->canon_head;
970 finish_erasing(ldata);
971 echo_char(KILL_CHAR(tty), tty);
972 /* Add a newline if ECHOK is on and ECHOKE is off. */
973 if (L_ECHOK(tty))
974 echo_char_raw('\n', ldata);
975 return;
976 }
977 kill_type = KILL;
978 }
979
980 seen_alnums = 0;
981 while (ldata->read_head != ldata->canon_head) {
982 head = ldata->read_head;
983
984 /* erase a single possibly multibyte character */
985 do {
986 head--;
987 c = read_buf(ldata, head);
988 } while (is_continuation(c, tty) && head != ldata->canon_head);
989
990 /* do not partially erase */
991 if (is_continuation(c, tty))
992 break;
993
994 if (kill_type == WERASE) {
995 /* Equivalent to BSD's ALTWERASE. */
996 if (isalnum(c) || c == '_')
997 seen_alnums++;
998 else if (seen_alnums)
999 break;
1000 }
1001 cnt = ldata->read_head - head;
1002 ldata->read_head = head;
1003 if (L_ECHO(tty)) {
1004 if (L_ECHOPRT(tty)) {
1005 if (!ldata->erasing) {
1006 echo_char_raw('\\', ldata);
1007 ldata->erasing = 1;
1008 }
1009 /* if cnt > 1, output a multi-byte character */
1010 echo_char(c, tty);
1011 while (--cnt > 0) {
1012 head++;
1013 echo_char_raw(read_buf(ldata, head), ldata);
1014 echo_move_back_col(ldata);
1015 }
1016 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1017 echo_char(ERASE_CHAR(tty), tty);
1018 } else if (c == '\t') {
1019 unsigned int num_chars = 0;
1020 int after_tab = 0;
1021 size_t tail = ldata->read_head;
1022
1023 /*
1024 * Count the columns used for characters
1025 * since the start of input or after a
1026 * previous tab.
1027 * This info is used to go back the correct
1028 * number of columns.
1029 */
1030 while (tail != ldata->canon_head) {
1031 tail--;
1032 c = read_buf(ldata, tail);
1033 if (c == '\t') {
1034 after_tab = 1;
1035 break;
1036 } else if (iscntrl(c)) {
1037 if (L_ECHOCTL(tty))
1038 num_chars += 2;
1039 } else if (!is_continuation(c, tty)) {
1040 num_chars++;
1041 }
1042 }
1043 echo_erase_tab(num_chars, after_tab, ldata);
1044 } else {
1045 if (iscntrl(c) && L_ECHOCTL(tty)) {
1046 echo_char_raw('\b', ldata);
1047 echo_char_raw(' ', ldata);
1048 echo_char_raw('\b', ldata);
1049 }
1050 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1051 echo_char_raw('\b', ldata);
1052 echo_char_raw(' ', ldata);
1053 echo_char_raw('\b', ldata);
1054 }
1055 }
1056 }
1057 if (kill_type == ERASE)
1058 break;
1059 }
1060 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1061 finish_erasing(ldata);
1062}
1063
1064/**
1065 * isig - handle the ISIG optio
1066 * @sig: signal
1067 * @tty: terminal
1068 *
1069 * Called when a signal is being sent due to terminal input.
1070 * Called from the driver receive_buf path so serialized.
1071 *
1072 * Performs input and output flush if !NOFLSH. In this context, the echo
1073 * buffer is 'output'. The signal is processed first to alert any current
1074 * readers or writers to discontinue and exit their i/o loops.
1075 *
1076 * Locking: ctrl_lock
1077 */
1078
1079static void __isig(int sig, struct tty_struct *tty)
1080{
1081 struct pid *tty_pgrp = tty_get_pgrp(tty);
1082 if (tty_pgrp) {
1083 kill_pgrp(tty_pgrp, sig, 1);
1084 put_pid(tty_pgrp);
1085 }
1086}
1087
1088static void isig(int sig, struct tty_struct *tty)
1089{
1090 struct n_tty_data *ldata = tty->disc_data;
1091
1092 if (L_NOFLSH(tty)) {
1093 /* signal only */
1094 __isig(sig, tty);
1095
1096 } else { /* signal and flush */
1097 up_read(&tty->termios_rwsem);
1098 down_write(&tty->termios_rwsem);
1099
1100 __isig(sig, tty);
1101
1102 /* clear echo buffer */
1103 mutex_lock(&ldata->output_lock);
1104 ldata->echo_head = ldata->echo_tail = 0;
1105 ldata->echo_mark = ldata->echo_commit = 0;
1106 mutex_unlock(&ldata->output_lock);
1107
1108 /* clear output buffer */
1109 tty_driver_flush_buffer(tty);
1110
1111 /* clear input buffer */
1112 reset_buffer_flags(tty->disc_data);
1113
1114 /* notify pty master of flush */
1115 if (tty->link)
1116 n_tty_packet_mode_flush(tty);
1117
1118 up_write(&tty->termios_rwsem);
1119 down_read(&tty->termios_rwsem);
1120 }
1121}
1122
1123/**
1124 * n_tty_receive_break - handle break
1125 * @tty: terminal
1126 *
1127 * An RS232 break event has been hit in the incoming bitstream. This
1128 * can cause a variety of events depending upon the termios settings.
1129 *
1130 * n_tty_receive_buf()/producer path:
1131 * caller holds non-exclusive termios_rwsem
1132 *
1133 * Note: may get exclusive termios_rwsem if flushing input buffer
1134 */
1135
1136static void n_tty_receive_break(struct tty_struct *tty)
1137{
1138 struct n_tty_data *ldata = tty->disc_data;
1139
1140 if (I_IGNBRK(tty))
1141 return;
1142 if (I_BRKINT(tty)) {
1143 isig(SIGINT, tty);
1144 return;
1145 }
1146 if (I_PARMRK(tty)) {
1147 put_tty_queue('\377', ldata);
1148 put_tty_queue('\0', ldata);
1149 }
1150 put_tty_queue('\0', ldata);
1151}
1152
1153/**
1154 * n_tty_receive_overrun - handle overrun reporting
1155 * @tty: terminal
1156 *
1157 * Data arrived faster than we could process it. While the tty
1158 * driver has flagged this the bits that were missed are gone
1159 * forever.
1160 *
1161 * Called from the receive_buf path so single threaded. Does not
1162 * need locking as num_overrun and overrun_time are function
1163 * private.
1164 */
1165
1166static void n_tty_receive_overrun(struct tty_struct *tty)
1167{
1168 struct n_tty_data *ldata = tty->disc_data;
1169
1170 ldata->num_overrun++;
1171 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1172 time_after(ldata->overrun_time, jiffies)) {
1173 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1174 ldata->overrun_time = jiffies;
1175 ldata->num_overrun = 0;
1176 }
1177}
1178
1179/**
1180 * n_tty_receive_parity_error - error notifier
1181 * @tty: terminal device
1182 * @c: character
1183 *
1184 * Process a parity error and queue the right data to indicate
1185 * the error case if necessary.
1186 *
1187 * n_tty_receive_buf()/producer path:
1188 * caller holds non-exclusive termios_rwsem
1189 */
1190static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1191{
1192 struct n_tty_data *ldata = tty->disc_data;
1193
1194 if (I_INPCK(tty)) {
1195 if (I_IGNPAR(tty))
1196 return;
1197 if (I_PARMRK(tty)) {
1198 put_tty_queue('\377', ldata);
1199 put_tty_queue('\0', ldata);
1200 put_tty_queue(c, ldata);
1201 } else
1202 put_tty_queue('\0', ldata);
1203 } else
1204 put_tty_queue(c, ldata);
1205}
1206
1207static void
1208n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1209{
1210 isig(signal, tty);
1211 if (I_IXON(tty))
1212 start_tty(tty);
1213 if (L_ECHO(tty)) {
1214 echo_char(c, tty);
1215 commit_echoes(tty);
1216 } else
1217 process_echoes(tty);
1218 return;
1219}
1220
1221/**
1222 * n_tty_receive_char - perform processing
1223 * @tty: terminal device
1224 * @c: character
1225 *
1226 * Process an individual character of input received from the driver.
1227 * This is serialized with respect to itself by the rules for the
1228 * driver above.
1229 *
1230 * n_tty_receive_buf()/producer path:
1231 * caller holds non-exclusive termios_rwsem
1232 * publishes canon_head if canonical mode is active
1233 *
1234 * Returns 1 if LNEXT was received, else returns 0
1235 */
1236
1237static int
1238n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1239{
1240 struct n_tty_data *ldata = tty->disc_data;
1241
1242 if (I_IXON(tty)) {
1243 if (c == START_CHAR(tty)) {
1244 start_tty(tty);
1245 process_echoes(tty);
1246 return 0;
1247 }
1248 if (c == STOP_CHAR(tty)) {
1249 stop_tty(tty);
1250 return 0;
1251 }
1252 }
1253
1254 if (L_ISIG(tty)) {
1255 if (c == INTR_CHAR(tty)) {
1256 n_tty_receive_signal_char(tty, SIGINT, c);
1257 return 0;
1258 } else if (c == QUIT_CHAR(tty)) {
1259 n_tty_receive_signal_char(tty, SIGQUIT, c);
1260 return 0;
1261 } else if (c == SUSP_CHAR(tty)) {
1262 n_tty_receive_signal_char(tty, SIGTSTP, c);
1263 return 0;
1264 }
1265 }
1266
1267 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1268 start_tty(tty);
1269 process_echoes(tty);
1270 }
1271
1272 if (c == '\r') {
1273 if (I_IGNCR(tty))
1274 return 0;
1275 if (I_ICRNL(tty))
1276 c = '\n';
1277 } else if (c == '\n' && I_INLCR(tty))
1278 c = '\r';
1279
1280 if (ldata->icanon) {
1281 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1282 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1283 eraser(c, tty);
1284 commit_echoes(tty);
1285 return 0;
1286 }
1287 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1288 ldata->lnext = 1;
1289 if (L_ECHO(tty)) {
1290 finish_erasing(ldata);
1291 if (L_ECHOCTL(tty)) {
1292 echo_char_raw('^', ldata);
1293 echo_char_raw('\b', ldata);
1294 commit_echoes(tty);
1295 }
1296 }
1297 return 1;
1298 }
1299 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1300 size_t tail = ldata->canon_head;
1301
1302 finish_erasing(ldata);
1303 echo_char(c, tty);
1304 echo_char_raw('\n', ldata);
1305 while (tail != ldata->read_head) {
1306 echo_char(read_buf(ldata, tail), tty);
1307 tail++;
1308 }
1309 commit_echoes(tty);
1310 return 0;
1311 }
1312 if (c == '\n') {
1313 if (L_ECHO(tty) || L_ECHONL(tty)) {
1314 echo_char_raw('\n', ldata);
1315 commit_echoes(tty);
1316 }
1317 goto handle_newline;
1318 }
1319 if (c == EOF_CHAR(tty)) {
1320 c = __DISABLED_CHAR;
1321 goto handle_newline;
1322 }
1323 if ((c == EOL_CHAR(tty)) ||
1324 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1325 /*
1326 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1327 */
1328 if (L_ECHO(tty)) {
1329 /* Record the column of first canon char. */
1330 if (ldata->canon_head == ldata->read_head)
1331 echo_set_canon_col(ldata);
1332 echo_char(c, tty);
1333 commit_echoes(tty);
1334 }
1335 /*
1336 * XXX does PARMRK doubling happen for
1337 * EOL_CHAR and EOL2_CHAR?
1338 */
1339 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1340 put_tty_queue(c, ldata);
1341
1342handle_newline:
1343 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1344 put_tty_queue(c, ldata);
1345 smp_store_release(&ldata->canon_head, ldata->read_head);
1346 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1347 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1348 return 0;
1349 }
1350 }
1351
1352 if (L_ECHO(tty)) {
1353 finish_erasing(ldata);
1354 if (c == '\n')
1355 echo_char_raw('\n', ldata);
1356 else {
1357 /* Record the column of first canon char. */
1358 if (ldata->canon_head == ldata->read_head)
1359 echo_set_canon_col(ldata);
1360 echo_char(c, tty);
1361 }
1362 commit_echoes(tty);
1363 }
1364
1365 /* PARMRK doubling check */
1366 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1367 put_tty_queue(c, ldata);
1368
1369 put_tty_queue(c, ldata);
1370 return 0;
1371}
1372
1373static inline void
1374n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1375{
1376 struct n_tty_data *ldata = tty->disc_data;
1377
1378 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1379 start_tty(tty);
1380 process_echoes(tty);
1381 }
1382 if (L_ECHO(tty)) {
1383 finish_erasing(ldata);
1384 /* Record the column of first canon char. */
1385 if (ldata->canon_head == ldata->read_head)
1386 echo_set_canon_col(ldata);
1387 echo_char(c, tty);
1388 commit_echoes(tty);
1389 }
1390 /* PARMRK doubling check */
1391 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1392 put_tty_queue(c, ldata);
1393 put_tty_queue(c, ldata);
1394}
1395
1396static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1397{
1398 n_tty_receive_char_inline(tty, c);
1399}
1400
1401static inline void
1402n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1403{
1404 struct n_tty_data *ldata = tty->disc_data;
1405
1406 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1407 start_tty(tty);
1408 process_echoes(tty);
1409 }
1410 if (L_ECHO(tty)) {
1411 finish_erasing(ldata);
1412 /* Record the column of first canon char. */
1413 if (ldata->canon_head == ldata->read_head)
1414 echo_set_canon_col(ldata);
1415 echo_char(c, tty);
1416 commit_echoes(tty);
1417 }
1418 put_tty_queue(c, ldata);
1419}
1420
1421static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1422{
1423 if (I_ISTRIP(tty))
1424 c &= 0x7f;
1425 if (I_IUCLC(tty) && L_IEXTEN(tty))
1426 c = tolower(c);
1427
1428 if (I_IXON(tty)) {
1429 if (c == STOP_CHAR(tty))
1430 stop_tty(tty);
1431 else if (c == START_CHAR(tty) ||
1432 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1433 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1434 c != SUSP_CHAR(tty))) {
1435 start_tty(tty);
1436 process_echoes(tty);
1437 }
1438 }
1439}
1440
1441static void
1442n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1443{
1444 switch (flag) {
1445 case TTY_BREAK:
1446 n_tty_receive_break(tty);
1447 break;
1448 case TTY_PARITY:
1449 case TTY_FRAME:
1450 n_tty_receive_parity_error(tty, c);
1451 break;
1452 case TTY_OVERRUN:
1453 n_tty_receive_overrun(tty);
1454 break;
1455 default:
1456 tty_err(tty, "unknown flag %d\n", flag);
1457 break;
1458 }
1459}
1460
1461static void
1462n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1463{
1464 struct n_tty_data *ldata = tty->disc_data;
1465
1466 ldata->lnext = 0;
1467 if (likely(flag == TTY_NORMAL)) {
1468 if (I_ISTRIP(tty))
1469 c &= 0x7f;
1470 if (I_IUCLC(tty) && L_IEXTEN(tty))
1471 c = tolower(c);
1472 n_tty_receive_char(tty, c);
1473 } else
1474 n_tty_receive_char_flagged(tty, c, flag);
1475}
1476
1477static void
1478n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1479 char *fp, int count)
1480{
1481 struct n_tty_data *ldata = tty->disc_data;
1482 size_t n, head;
1483
1484 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1485 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1486 memcpy(read_buf_addr(ldata, head), cp, n);
1487 ldata->read_head += n;
1488 cp += n;
1489 count -= n;
1490
1491 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1492 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1493 memcpy(read_buf_addr(ldata, head), cp, n);
1494 ldata->read_head += n;
1495}
1496
1497static void
1498n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1499 char *fp, int count)
1500{
1501 struct n_tty_data *ldata = tty->disc_data;
1502 char flag = TTY_NORMAL;
1503
1504 while (count--) {
1505 if (fp)
1506 flag = *fp++;
1507 if (likely(flag == TTY_NORMAL))
1508 put_tty_queue(*cp++, ldata);
1509 else
1510 n_tty_receive_char_flagged(tty, *cp++, flag);
1511 }
1512}
1513
1514static void
1515n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1516 char *fp, int count)
1517{
1518 char flag = TTY_NORMAL;
1519
1520 while (count--) {
1521 if (fp)
1522 flag = *fp++;
1523 if (likely(flag == TTY_NORMAL))
1524 n_tty_receive_char_closing(tty, *cp++);
1525 }
1526}
1527
1528static void
1529n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1530 char *fp, int count)
1531{
1532 struct n_tty_data *ldata = tty->disc_data;
1533 char flag = TTY_NORMAL;
1534
1535 while (count--) {
1536 if (fp)
1537 flag = *fp++;
1538 if (likely(flag == TTY_NORMAL)) {
1539 unsigned char c = *cp++;
1540
1541 if (I_ISTRIP(tty))
1542 c &= 0x7f;
1543 if (I_IUCLC(tty) && L_IEXTEN(tty))
1544 c = tolower(c);
1545 if (L_EXTPROC(tty)) {
1546 put_tty_queue(c, ldata);
1547 continue;
1548 }
1549 if (!test_bit(c, ldata->char_map))
1550 n_tty_receive_char_inline(tty, c);
1551 else if (n_tty_receive_char_special(tty, c) && count) {
1552 if (fp)
1553 flag = *fp++;
1554 n_tty_receive_char_lnext(tty, *cp++, flag);
1555 count--;
1556 }
1557 } else
1558 n_tty_receive_char_flagged(tty, *cp++, flag);
1559 }
1560}
1561
1562static void
1563n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1564 char *fp, int count)
1565{
1566 struct n_tty_data *ldata = tty->disc_data;
1567 char flag = TTY_NORMAL;
1568
1569 while (count--) {
1570 if (fp)
1571 flag = *fp++;
1572 if (likely(flag == TTY_NORMAL)) {
1573 unsigned char c = *cp++;
1574
1575 if (!test_bit(c, ldata->char_map))
1576 n_tty_receive_char_fast(tty, c);
1577 else if (n_tty_receive_char_special(tty, c) && count) {
1578 if (fp)
1579 flag = *fp++;
1580 n_tty_receive_char_lnext(tty, *cp++, flag);
1581 count--;
1582 }
1583 } else
1584 n_tty_receive_char_flagged(tty, *cp++, flag);
1585 }
1586}
1587
1588static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1589 char *fp, int count)
1590{
1591 struct n_tty_data *ldata = tty->disc_data;
1592 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1593
1594 if (ldata->real_raw)
1595 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1596 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1597 n_tty_receive_buf_raw(tty, cp, fp, count);
1598 else if (tty->closing && !L_EXTPROC(tty))
1599 n_tty_receive_buf_closing(tty, cp, fp, count);
1600 else {
1601 if (ldata->lnext) {
1602 char flag = TTY_NORMAL;
1603
1604 if (fp)
1605 flag = *fp++;
1606 n_tty_receive_char_lnext(tty, *cp++, flag);
1607 count--;
1608 }
1609
1610 if (!preops && !I_PARMRK(tty))
1611 n_tty_receive_buf_fast(tty, cp, fp, count);
1612 else
1613 n_tty_receive_buf_standard(tty, cp, fp, count);
1614
1615 flush_echoes(tty);
1616 if (tty->ops->flush_chars)
1617 tty->ops->flush_chars(tty);
1618 }
1619
1620 if (ldata->icanon && !L_EXTPROC(tty))
1621 return;
1622
1623 /* publish read_head to consumer */
1624 smp_store_release(&ldata->commit_head, ldata->read_head);
1625
1626 if (read_cnt(ldata)) {
1627 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1628 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1629 }
1630}
1631
1632/**
1633 * n_tty_receive_buf_common - process input
1634 * @tty: device to receive input
1635 * @cp: input chars
1636 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1637 * @count: number of input chars in @cp
1638 *
1639 * Called by the terminal driver when a block of characters has
1640 * been received. This function must be called from soft contexts
1641 * not from interrupt context. The driver is responsible for making
1642 * calls one at a time and in order (or using flush_to_ldisc)
1643 *
1644 * Returns the # of input chars from @cp which were processed.
1645 *
1646 * In canonical mode, the maximum line length is 4096 chars (including
1647 * the line termination char); lines longer than 4096 chars are
1648 * truncated. After 4095 chars, input data is still processed but
1649 * not stored. Overflow processing ensures the tty can always
1650 * receive more input until at least one line can be read.
1651 *
1652 * In non-canonical mode, the read buffer will only accept 4095 chars;
1653 * this provides the necessary space for a newline char if the input
1654 * mode is switched to canonical.
1655 *
1656 * Note it is possible for the read buffer to _contain_ 4096 chars
1657 * in non-canonical mode: the read buffer could already contain the
1658 * maximum canon line of 4096 chars when the mode is switched to
1659 * non-canonical.
1660 *
1661 * n_tty_receive_buf()/producer path:
1662 * claims non-exclusive termios_rwsem
1663 * publishes commit_head or canon_head
1664 */
1665static int
1666n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1667 char *fp, int count, int flow)
1668{
1669 struct n_tty_data *ldata = tty->disc_data;
1670 int room, n, rcvd = 0, overflow;
1671
1672 down_read(&tty->termios_rwsem);
1673
1674 while (1) {
1675 /*
1676 * When PARMRK is set, each input char may take up to 3 chars
1677 * in the read buf; reduce the buffer space avail by 3x
1678 *
1679 * If we are doing input canonicalization, and there are no
1680 * pending newlines, let characters through without limit, so
1681 * that erase characters will be handled. Other excess
1682 * characters will be beeped.
1683 *
1684 * paired with store in *_copy_from_read_buf() -- guarantees
1685 * the consumer has loaded the data in read_buf up to the new
1686 * read_tail (so this producer will not overwrite unread data)
1687 */
1688 size_t tail = smp_load_acquire(&ldata->read_tail);
1689
1690 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1691 if (I_PARMRK(tty))
1692 room = (room + 2) / 3;
1693 room--;
1694 if (room <= 0) {
1695 overflow = ldata->icanon && ldata->canon_head == tail;
1696 if (overflow && room < 0)
1697 ldata->read_head--;
1698 room = overflow;
1699 ldata->no_room = flow && !room;
1700 } else
1701 overflow = 0;
1702
1703 n = min(count, room);
1704 if (!n)
1705 break;
1706
1707 /* ignore parity errors if handling overflow */
1708 if (!overflow || !fp || *fp != TTY_PARITY)
1709 __receive_buf(tty, cp, fp, n);
1710
1711 cp += n;
1712 if (fp)
1713 fp += n;
1714 count -= n;
1715 rcvd += n;
1716 }
1717
1718 tty->receive_room = room;
1719
1720 /* Unthrottle if handling overflow on pty */
1721 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1722 if (overflow) {
1723 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1724 tty_unthrottle_safe(tty);
1725 __tty_set_flow_change(tty, 0);
1726 }
1727 } else
1728 n_tty_check_throttle(tty);
1729
1730 up_read(&tty->termios_rwsem);
1731
1732 return rcvd;
1733}
1734
1735static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1736 char *fp, int count)
1737{
1738 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1739}
1740
1741static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1742 char *fp, int count)
1743{
1744 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1745}
1746
1747/**
1748 * n_tty_set_termios - termios data changed
1749 * @tty: terminal
1750 * @old: previous data
1751 *
1752 * Called by the tty layer when the user changes termios flags so
1753 * that the line discipline can plan ahead. This function cannot sleep
1754 * and is protected from re-entry by the tty layer. The user is
1755 * guaranteed that this function will not be re-entered or in progress
1756 * when the ldisc is closed.
1757 *
1758 * Locking: Caller holds tty->termios_rwsem
1759 */
1760
1761static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1762{
1763 struct n_tty_data *ldata = tty->disc_data;
1764
1765 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1766 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1767 ldata->line_start = ldata->read_tail;
1768 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1769 ldata->canon_head = ldata->read_tail;
1770 ldata->push = 0;
1771 } else {
1772 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1773 ldata->read_flags);
1774 ldata->canon_head = ldata->read_head;
1775 ldata->push = 1;
1776 }
1777 ldata->commit_head = ldata->read_head;
1778 ldata->erasing = 0;
1779 ldata->lnext = 0;
1780 }
1781
1782 ldata->icanon = (L_ICANON(tty) != 0);
1783
1784 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1785 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1786 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1787 I_PARMRK(tty)) {
1788 bitmap_zero(ldata->char_map, 256);
1789
1790 if (I_IGNCR(tty) || I_ICRNL(tty))
1791 set_bit('\r', ldata->char_map);
1792 if (I_INLCR(tty))
1793 set_bit('\n', ldata->char_map);
1794
1795 if (L_ICANON(tty)) {
1796 set_bit(ERASE_CHAR(tty), ldata->char_map);
1797 set_bit(KILL_CHAR(tty), ldata->char_map);
1798 set_bit(EOF_CHAR(tty), ldata->char_map);
1799 set_bit('\n', ldata->char_map);
1800 set_bit(EOL_CHAR(tty), ldata->char_map);
1801 if (L_IEXTEN(tty)) {
1802 set_bit(WERASE_CHAR(tty), ldata->char_map);
1803 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1804 set_bit(EOL2_CHAR(tty), ldata->char_map);
1805 if (L_ECHO(tty))
1806 set_bit(REPRINT_CHAR(tty),
1807 ldata->char_map);
1808 }
1809 }
1810 if (I_IXON(tty)) {
1811 set_bit(START_CHAR(tty), ldata->char_map);
1812 set_bit(STOP_CHAR(tty), ldata->char_map);
1813 }
1814 if (L_ISIG(tty)) {
1815 set_bit(INTR_CHAR(tty), ldata->char_map);
1816 set_bit(QUIT_CHAR(tty), ldata->char_map);
1817 set_bit(SUSP_CHAR(tty), ldata->char_map);
1818 }
1819 clear_bit(__DISABLED_CHAR, ldata->char_map);
1820 ldata->raw = 0;
1821 ldata->real_raw = 0;
1822 } else {
1823 ldata->raw = 1;
1824 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1825 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1826 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1827 ldata->real_raw = 1;
1828 else
1829 ldata->real_raw = 0;
1830 }
1831 /*
1832 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1833 * been stopped by STOP_CHAR(tty) before it.
1834 */
1835 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1836 start_tty(tty);
1837 process_echoes(tty);
1838 }
1839
1840 /* The termios change make the tty ready for I/O */
1841 wake_up_interruptible(&tty->write_wait);
1842 wake_up_interruptible(&tty->read_wait);
1843}
1844
1845/**
1846 * n_tty_close - close the ldisc for this tty
1847 * @tty: device
1848 *
1849 * Called from the terminal layer when this line discipline is
1850 * being shut down, either because of a close or becsuse of a
1851 * discipline change. The function will not be called while other
1852 * ldisc methods are in progress.
1853 */
1854
1855static void n_tty_close(struct tty_struct *tty)
1856{
1857 struct n_tty_data *ldata = tty->disc_data;
1858
1859 if (tty->link)
1860 n_tty_packet_mode_flush(tty);
1861
1862 vfree(ldata);
1863 tty->disc_data = NULL;
1864}
1865
1866/**
1867 * n_tty_open - open an ldisc
1868 * @tty: terminal to open
1869 *
1870 * Called when this line discipline is being attached to the
1871 * terminal device. Can sleep. Called serialized so that no
1872 * other events will occur in parallel. No further open will occur
1873 * until a close.
1874 */
1875
1876static int n_tty_open(struct tty_struct *tty)
1877{
1878 struct n_tty_data *ldata;
1879
1880 /* Currently a malloc failure here can panic */
1881 ldata = vmalloc(sizeof(*ldata));
1882 if (!ldata)
1883 goto err;
1884
1885 ldata->overrun_time = jiffies;
1886 mutex_init(&ldata->atomic_read_lock);
1887 mutex_init(&ldata->output_lock);
1888
1889 tty->disc_data = ldata;
1890 reset_buffer_flags(tty->disc_data);
1891 ldata->column = 0;
1892 ldata->canon_column = 0;
1893 ldata->num_overrun = 0;
1894 ldata->no_room = 0;
1895 ldata->lnext = 0;
1896 tty->closing = 0;
1897 /* indicate buffer work may resume */
1898 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1899 n_tty_set_termios(tty, NULL);
1900 tty_unthrottle(tty);
1901
1902 return 0;
1903err:
1904 return -ENOMEM;
1905}
1906
1907static inline int input_available_p(struct tty_struct *tty, int poll)
1908{
1909 struct n_tty_data *ldata = tty->disc_data;
1910 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1911
1912 if (ldata->icanon && !L_EXTPROC(tty))
1913 return ldata->canon_head != ldata->read_tail;
1914 else
1915 return ldata->commit_head - ldata->read_tail >= amt;
1916}
1917
1918/**
1919 * copy_from_read_buf - copy read data directly
1920 * @tty: terminal device
1921 * @b: user data
1922 * @nr: size of data
1923 *
1924 * Helper function to speed up n_tty_read. It is only called when
1925 * ICANON is off; it copies characters straight from the tty queue to
1926 * user space directly. It can be profitably called twice; once to
1927 * drain the space from the tail pointer to the (physical) end of the
1928 * buffer, and once to drain the space from the (physical) beginning of
1929 * the buffer to head pointer.
1930 *
1931 * Called under the ldata->atomic_read_lock sem
1932 *
1933 * n_tty_read()/consumer path:
1934 * caller holds non-exclusive termios_rwsem
1935 * read_tail published
1936 */
1937
1938static int copy_from_read_buf(struct tty_struct *tty,
1939 unsigned char __user **b,
1940 size_t *nr)
1941
1942{
1943 struct n_tty_data *ldata = tty->disc_data;
1944 int retval;
1945 size_t n;
1946 bool is_eof;
1947 size_t head = smp_load_acquire(&ldata->commit_head);
1948 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1949
1950 retval = 0;
1951 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1952 n = min(*nr, n);
1953 if (n) {
1954 const unsigned char *from = read_buf_addr(ldata, tail);
1955 retval = copy_to_user(*b, from, n);
1956 n -= retval;
1957 is_eof = n == 1 && *from == EOF_CHAR(tty);
1958 tty_audit_add_data(tty, from, n);
1959 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1960 /* Turn single EOF into zero-length read */
1961 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1962 (head == ldata->read_tail))
1963 n = 0;
1964 *b += n;
1965 *nr -= n;
1966 }
1967 return retval;
1968}
1969
1970/**
1971 * canon_copy_from_read_buf - copy read data in canonical mode
1972 * @tty: terminal device
1973 * @b: user data
1974 * @nr: size of data
1975 *
1976 * Helper function for n_tty_read. It is only called when ICANON is on;
1977 * it copies one line of input up to and including the line-delimiting
1978 * character into the user-space buffer.
1979 *
1980 * NB: When termios is changed from non-canonical to canonical mode and
1981 * the read buffer contains data, n_tty_set_termios() simulates an EOF
1982 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
1983 * This causes data already processed as input to be immediately available
1984 * as input although a newline has not been received.
1985 *
1986 * Called under the atomic_read_lock mutex
1987 *
1988 * n_tty_read()/consumer path:
1989 * caller holds non-exclusive termios_rwsem
1990 * read_tail published
1991 */
1992
1993static int canon_copy_from_read_buf(struct tty_struct *tty,
1994 unsigned char __user **b,
1995 size_t *nr)
1996{
1997 struct n_tty_data *ldata = tty->disc_data;
1998 size_t n, size, more, c;
1999 size_t eol;
2000 size_t tail;
2001 int ret, found = 0;
2002
2003 /* N.B. avoid overrun if nr == 0 */
2004 if (!*nr)
2005 return 0;
2006
2007 n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2008
2009 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2010 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2011
2012 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2013 __func__, *nr, tail, n, size);
2014
2015 eol = find_next_bit(ldata->read_flags, size, tail);
2016 more = n - (size - tail);
2017 if (eol == N_TTY_BUF_SIZE && more) {
2018 /* scan wrapped without finding set bit */
2019 eol = find_next_bit(ldata->read_flags, more, 0);
2020 found = eol != more;
2021 } else
2022 found = eol != size;
2023
2024 n = eol - tail;
2025 if (n > N_TTY_BUF_SIZE)
2026 n += N_TTY_BUF_SIZE;
2027 c = n + found;
2028
2029 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2030 c = min(*nr, c);
2031 n = c;
2032 }
2033
2034 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2035 __func__, eol, found, n, c, tail, more);
2036
2037 ret = tty_copy_to_user(tty, *b, tail, n);
2038 if (ret)
2039 return -EFAULT;
2040 *b += n;
2041 *nr -= n;
2042
2043 if (found)
2044 clear_bit(eol, ldata->read_flags);
2045 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2046
2047 if (found) {
2048 if (!ldata->push)
2049 ldata->line_start = ldata->read_tail;
2050 else
2051 ldata->push = 0;
2052 tty_audit_push();
2053 }
2054 return 0;
2055}
2056
2057extern ssize_t redirected_tty_write(struct file *, const char __user *,
2058 size_t, loff_t *);
2059
2060/**
2061 * job_control - check job control
2062 * @tty: tty
2063 * @file: file handle
2064 *
2065 * Perform job control management checks on this file/tty descriptor
2066 * and if appropriate send any needed signals and return a negative
2067 * error code if action should be taken.
2068 *
2069 * Locking: redirected write test is safe
2070 * current->signal->tty check is safe
2071 * ctrl_lock to safely reference tty->pgrp
2072 */
2073
2074static int job_control(struct tty_struct *tty, struct file *file)
2075{
2076 /* Job control check -- must be done at start and after
2077 every sleep (POSIX.1 7.1.1.4). */
2078 /* NOTE: not yet done after every sleep pending a thorough
2079 check of the logic of this change. -- jlc */
2080 /* don't stop on /dev/console */
2081 if (file->f_op->write == redirected_tty_write)
2082 return 0;
2083
2084 return __tty_check_change(tty, SIGTTIN);
2085}
2086
2087
2088/**
2089 * n_tty_read - read function for tty
2090 * @tty: tty device
2091 * @file: file object
2092 * @buf: userspace buffer pointer
2093 * @nr: size of I/O
2094 *
2095 * Perform reads for the line discipline. We are guaranteed that the
2096 * line discipline will not be closed under us but we may get multiple
2097 * parallel readers and must handle this ourselves. We may also get
2098 * a hangup. Always called in user context, may sleep.
2099 *
2100 * This code must be sure never to sleep through a hangup.
2101 *
2102 * n_tty_read()/consumer path:
2103 * claims non-exclusive termios_rwsem
2104 * publishes read_tail
2105 */
2106
2107static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2108 unsigned char __user *buf, size_t nr)
2109{
2110 struct n_tty_data *ldata = tty->disc_data;
2111 unsigned char __user *b = buf;
2112 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2113 int c;
2114 int minimum, time;
2115 ssize_t retval = 0;
2116 long timeout;
2117 int packet;
2118 size_t tail;
2119
2120 c = job_control(tty, file);
2121 if (c < 0)
2122 return c;
2123
2124 /*
2125 * Internal serialization of reads.
2126 */
2127 if (file->f_flags & O_NONBLOCK) {
2128 if (!mutex_trylock(&ldata->atomic_read_lock))
2129 return -EAGAIN;
2130 } else {
2131 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2132 return -ERESTARTSYS;
2133 }
2134
2135 down_read(&tty->termios_rwsem);
2136
2137 minimum = time = 0;
2138 timeout = MAX_SCHEDULE_TIMEOUT;
2139 if (!ldata->icanon) {
2140 minimum = MIN_CHAR(tty);
2141 if (minimum) {
2142 time = (HZ / 10) * TIME_CHAR(tty);
2143 } else {
2144 timeout = (HZ / 10) * TIME_CHAR(tty);
2145 minimum = 1;
2146 }
2147 }
2148
2149 packet = tty->packet;
2150 tail = ldata->read_tail;
2151
2152 add_wait_queue(&tty->read_wait, &wait);
2153 while (nr) {
2154 /* First test for status change. */
2155 if (packet && tty->link->ctrl_status) {
2156 unsigned char cs;
2157 if (b != buf)
2158 break;
2159 spin_lock_irq(&tty->link->ctrl_lock);
2160 cs = tty->link->ctrl_status;
2161 tty->link->ctrl_status = 0;
2162 spin_unlock_irq(&tty->link->ctrl_lock);
2163 if (put_user(cs, b)) {
2164 retval = -EFAULT;
2165 break;
2166 }
2167 b++;
2168 nr--;
2169 break;
2170 }
2171
2172 if (!input_available_p(tty, 0)) {
2173 up_read(&tty->termios_rwsem);
2174 tty_buffer_flush_work(tty->port);
2175 down_read(&tty->termios_rwsem);
2176 if (!input_available_p(tty, 0)) {
2177 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2178 retval = -EIO;
2179 break;
2180 }
2181 if (tty_hung_up_p(file))
2182 break;
2183 /*
2184 * Abort readers for ttys which never actually
2185 * get hung up. See __tty_hangup().
2186 */
2187 if (test_bit(TTY_HUPPING, &tty->flags))
2188 break;
2189 if (!timeout)
2190 break;
2191 if (file->f_flags & O_NONBLOCK) {
2192 retval = -EAGAIN;
2193 break;
2194 }
2195 if (signal_pending(current)) {
2196 retval = -ERESTARTSYS;
2197 break;
2198 }
2199 up_read(&tty->termios_rwsem);
2200
2201 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2202 timeout);
2203
2204 down_read(&tty->termios_rwsem);
2205 continue;
2206 }
2207 }
2208
2209 if (ldata->icanon && !L_EXTPROC(tty)) {
2210 retval = canon_copy_from_read_buf(tty, &b, &nr);
2211 if (retval)
2212 break;
2213 } else {
2214 int uncopied;
2215
2216 /* Deal with packet mode. */
2217 if (packet && b == buf) {
2218 if (put_user(TIOCPKT_DATA, b)) {
2219 retval = -EFAULT;
2220 break;
2221 }
2222 b++;
2223 nr--;
2224 }
2225
2226 uncopied = copy_from_read_buf(tty, &b, &nr);
2227 uncopied += copy_from_read_buf(tty, &b, &nr);
2228 if (uncopied) {
2229 retval = -EFAULT;
2230 break;
2231 }
2232 }
2233
2234 n_tty_check_unthrottle(tty);
2235
2236 if (b - buf >= minimum)
2237 break;
2238 if (time)
2239 timeout = time;
2240 }
2241 if (tail != ldata->read_tail)
2242 n_tty_kick_worker(tty);
2243 up_read(&tty->termios_rwsem);
2244
2245 remove_wait_queue(&tty->read_wait, &wait);
2246 mutex_unlock(&ldata->atomic_read_lock);
2247
2248 if (b - buf)
2249 retval = b - buf;
2250
2251 return retval;
2252}
2253
2254/**
2255 * n_tty_write - write function for tty
2256 * @tty: tty device
2257 * @file: file object
2258 * @buf: userspace buffer pointer
2259 * @nr: size of I/O
2260 *
2261 * Write function of the terminal device. This is serialized with
2262 * respect to other write callers but not to termios changes, reads
2263 * and other such events. Since the receive code will echo characters,
2264 * thus calling driver write methods, the output_lock is used in
2265 * the output processing functions called here as well as in the
2266 * echo processing function to protect the column state and space
2267 * left in the buffer.
2268 *
2269 * This code must be sure never to sleep through a hangup.
2270 *
2271 * Locking: output_lock to protect column state and space left
2272 * (note that the process_output*() functions take this
2273 * lock themselves)
2274 */
2275
2276static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2277 const unsigned char *buf, size_t nr)
2278{
2279 const unsigned char *b = buf;
2280 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2281 int c;
2282 ssize_t retval = 0;
2283
2284 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2285 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2286 retval = tty_check_change(tty);
2287 if (retval)
2288 return retval;
2289 }
2290
2291 down_read(&tty->termios_rwsem);
2292
2293 /* Write out any echoed characters that are still pending */
2294 process_echoes(tty);
2295
2296 add_wait_queue(&tty->write_wait, &wait);
2297 while (1) {
2298 if (signal_pending(current)) {
2299 retval = -ERESTARTSYS;
2300 break;
2301 }
2302 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2303 retval = -EIO;
2304 break;
2305 }
2306 if (O_OPOST(tty)) {
2307 while (nr > 0) {
2308 ssize_t num = process_output_block(tty, b, nr);
2309 if (num < 0) {
2310 if (num == -EAGAIN)
2311 break;
2312 retval = num;
2313 goto break_out;
2314 }
2315 b += num;
2316 nr -= num;
2317 if (nr == 0)
2318 break;
2319 c = *b;
2320 if (process_output(c, tty) < 0)
2321 break;
2322 b++; nr--;
2323 }
2324 if (tty->ops->flush_chars)
2325 tty->ops->flush_chars(tty);
2326 } else {
2327 struct n_tty_data *ldata = tty->disc_data;
2328
2329 while (nr > 0) {
2330 mutex_lock(&ldata->output_lock);
2331 c = tty->ops->write(tty, b, nr);
2332 mutex_unlock(&ldata->output_lock);
2333 if (c < 0) {
2334 retval = c;
2335 goto break_out;
2336 }
2337 if (!c)
2338 break;
2339 b += c;
2340 nr -= c;
2341 }
2342 }
2343 if (!nr)
2344 break;
2345 if (file->f_flags & O_NONBLOCK) {
2346 retval = -EAGAIN;
2347 break;
2348 }
2349 up_read(&tty->termios_rwsem);
2350
2351 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2352
2353 down_read(&tty->termios_rwsem);
2354 }
2355break_out:
2356 remove_wait_queue(&tty->write_wait, &wait);
2357 if (nr && tty->fasync)
2358 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2359 up_read(&tty->termios_rwsem);
2360 return (b - buf) ? b - buf : retval;
2361}
2362
2363/**
2364 * n_tty_poll - poll method for N_TTY
2365 * @tty: terminal device
2366 * @file: file accessing it
2367 * @wait: poll table
2368 *
2369 * Called when the line discipline is asked to poll() for data or
2370 * for special events. This code is not serialized with respect to
2371 * other events save open/close.
2372 *
2373 * This code must be sure never to sleep through a hangup.
2374 * Called without the kernel lock held - fine
2375 */
2376
2377static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2378 poll_table *wait)
2379{
2380 __poll_t mask = 0;
2381
2382 poll_wait(file, &tty->read_wait, wait);
2383 poll_wait(file, &tty->write_wait, wait);
2384 if (input_available_p(tty, 1))
2385 mask |= EPOLLIN | EPOLLRDNORM;
2386 else {
2387 tty_buffer_flush_work(tty->port);
2388 if (input_available_p(tty, 1))
2389 mask |= EPOLLIN | EPOLLRDNORM;
2390 }
2391 if (tty->packet && tty->link->ctrl_status)
2392 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2393 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2394 mask |= EPOLLHUP;
2395 if (tty_hung_up_p(file))
2396 mask |= EPOLLHUP;
2397 if (tty->ops->write && !tty_is_writelocked(tty) &&
2398 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2399 tty_write_room(tty) > 0)
2400 mask |= EPOLLOUT | EPOLLWRNORM;
2401 return mask;
2402}
2403
2404static unsigned long inq_canon(struct n_tty_data *ldata)
2405{
2406 size_t nr, head, tail;
2407
2408 if (ldata->canon_head == ldata->read_tail)
2409 return 0;
2410 head = ldata->canon_head;
2411 tail = ldata->read_tail;
2412 nr = head - tail;
2413 /* Skip EOF-chars.. */
2414 while (head != tail) {
2415 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2416 read_buf(ldata, tail) == __DISABLED_CHAR)
2417 nr--;
2418 tail++;
2419 }
2420 return nr;
2421}
2422
2423static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2424 unsigned int cmd, unsigned long arg)
2425{
2426 struct n_tty_data *ldata = tty->disc_data;
2427 int retval;
2428
2429 switch (cmd) {
2430 case TIOCOUTQ:
2431 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2432 case TIOCINQ:
2433 down_write(&tty->termios_rwsem);
2434 if (L_ICANON(tty) && !L_EXTPROC(tty))
2435 retval = inq_canon(ldata);
2436 else
2437 retval = read_cnt(ldata);
2438 up_write(&tty->termios_rwsem);
2439 return put_user(retval, (unsigned int __user *) arg);
2440 default:
2441 return n_tty_ioctl_helper(tty, file, cmd, arg);
2442 }
2443}
2444
2445static struct tty_ldisc_ops n_tty_ops = {
2446 .magic = TTY_LDISC_MAGIC,
2447 .name = "n_tty",
2448 .open = n_tty_open,
2449 .close = n_tty_close,
2450 .flush_buffer = n_tty_flush_buffer,
2451 .read = n_tty_read,
2452 .write = n_tty_write,
2453 .ioctl = n_tty_ioctl,
2454 .set_termios = n_tty_set_termios,
2455 .poll = n_tty_poll,
2456 .receive_buf = n_tty_receive_buf,
2457 .write_wakeup = n_tty_write_wakeup,
2458 .receive_buf2 = n_tty_receive_buf2,
2459};
2460
2461/**
2462 * n_tty_inherit_ops - inherit N_TTY methods
2463 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2464 *
2465 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2466 */
2467
2468void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2469{
2470 *ops = n_tty_ops;
2471 ops->owner = NULL;
2472 ops->refcount = ops->flags = 0;
2473}
2474EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2475
2476void __init n_tty_init(void)
2477{
2478 tty_register_ldisc(N_TTY, &n_tty_ops);
2479}