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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#include "tty.h"
53
54/*
55 * Until this number of characters is queued in the xmit buffer, select will
56 * return "we have room for writes".
57 */
58#define WAKEUP_CHARS 256
59
60/*
61 * This defines the low- and high-watermarks for throttling and
62 * unthrottling the TTY driver. These watermarks are used for
63 * controlling the space in the read buffer.
64 */
65#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
66#define TTY_THRESHOLD_UNTHROTTLE 128
67
68/*
69 * Special byte codes used in the echo buffer to represent operations
70 * or special handling of characters. Bytes in the echo buffer that
71 * are not part of such special blocks are treated as normal character
72 * codes.
73 */
74#define ECHO_OP_START 0xff
75#define ECHO_OP_MOVE_BACK_COL 0x80
76#define ECHO_OP_SET_CANON_COL 0x81
77#define ECHO_OP_ERASE_TAB 0x82
78
79#define ECHO_COMMIT_WATERMARK 256
80#define ECHO_BLOCK 256
81#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
82
83
84#undef N_TTY_TRACE
85#ifdef N_TTY_TRACE
86# define n_tty_trace(f, args...) trace_printk(f, ##args)
87#else
88# define n_tty_trace(f, args...) no_printk(f, ##args)
89#endif
90
91struct n_tty_data {
92 /* producer-published */
93 size_t read_head;
94 size_t commit_head;
95 size_t canon_head;
96 size_t echo_head;
97 size_t echo_commit;
98 size_t echo_mark;
99 DECLARE_BITMAP(char_map, 256);
100
101 /* private to n_tty_receive_overrun (single-threaded) */
102 unsigned long overrun_time;
103 int num_overrun;
104
105 /* non-atomic */
106 bool no_room;
107
108 /* must hold exclusive termios_rwsem to reset these */
109 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
110 unsigned char push:1;
111
112 /* shared by producer and consumer */
113 char read_buf[N_TTY_BUF_SIZE];
114 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
115 unsigned char echo_buf[N_TTY_BUF_SIZE];
116
117 /* consumer-published */
118 size_t read_tail;
119 size_t line_start;
120
121 /* protected by output lock */
122 unsigned int column;
123 unsigned int canon_column;
124 size_t echo_tail;
125
126 struct mutex atomic_read_lock;
127 struct mutex output_lock;
128};
129
130#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
131
132static inline size_t read_cnt(struct n_tty_data *ldata)
133{
134 return ldata->read_head - ldata->read_tail;
135}
136
137static inline unsigned char read_buf(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 *read_buf_addr(struct n_tty_data *ldata, size_t i)
143{
144 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
145}
146
147static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
148{
149 smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
150 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
151}
152
153static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
154{
155 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
156}
157
158/* If we are not echoing the data, perhaps this is a secret so erase it */
159static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
160{
161 bool icanon = !!L_ICANON(tty);
162 bool no_echo = !L_ECHO(tty);
163
164 if (icanon && no_echo)
165 memset(buffer, 0x00, size);
166}
167
168static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
169{
170 struct n_tty_data *ldata = tty->disc_data;
171 size_t size = N_TTY_BUF_SIZE - tail;
172 void *from = read_buf_addr(ldata, tail);
173
174 if (n > size) {
175 tty_audit_add_data(tty, from, size);
176 memcpy(to, from, size);
177 zero_buffer(tty, from, size);
178 to += size;
179 n -= size;
180 from = ldata->read_buf;
181 }
182
183 tty_audit_add_data(tty, from, n);
184 memcpy(to, from, n);
185 zero_buffer(tty, from, n);
186}
187
188/**
189 * n_tty_kick_worker - start input worker (if required)
190 * @tty: terminal
191 *
192 * Re-schedules the flip buffer work if it may have stopped
193 *
194 * Caller holds exclusive termios_rwsem
195 * or
196 * n_tty_read()/consumer path:
197 * holds non-exclusive termios_rwsem
198 */
199
200static void n_tty_kick_worker(struct tty_struct *tty)
201{
202 struct n_tty_data *ldata = tty->disc_data;
203
204 /* Did the input worker stop? Restart it */
205 if (unlikely(ldata->no_room)) {
206 ldata->no_room = 0;
207
208 WARN_RATELIMIT(tty->port->itty == NULL,
209 "scheduling with invalid itty\n");
210 /* see if ldisc has been killed - if so, this means that
211 * even though the ldisc has been halted and ->buf.work
212 * cancelled, ->buf.work is about to be rescheduled
213 */
214 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
215 "scheduling buffer work for halted ldisc\n");
216 tty_buffer_restart_work(tty->port);
217 }
218}
219
220static ssize_t chars_in_buffer(struct tty_struct *tty)
221{
222 struct n_tty_data *ldata = tty->disc_data;
223 ssize_t n = 0;
224
225 if (!ldata->icanon)
226 n = ldata->commit_head - ldata->read_tail;
227 else
228 n = ldata->canon_head - ldata->read_tail;
229 return n;
230}
231
232/**
233 * n_tty_write_wakeup - asynchronous I/O notifier
234 * @tty: tty device
235 *
236 * Required for the ptys, serial driver etc. since processes
237 * that attach themselves to the master and rely on ASYNC
238 * IO must be woken up
239 */
240
241static void n_tty_write_wakeup(struct tty_struct *tty)
242{
243 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
244 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
245}
246
247static void n_tty_check_throttle(struct tty_struct *tty)
248{
249 struct n_tty_data *ldata = tty->disc_data;
250
251 /*
252 * Check the remaining room for the input canonicalization
253 * mode. We don't want to throttle the driver if we're in
254 * canonical mode and don't have a newline yet!
255 */
256 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
257 return;
258
259 while (1) {
260 int throttled;
261 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
262 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
263 break;
264 throttled = tty_throttle_safe(tty);
265 if (!throttled)
266 break;
267 }
268 __tty_set_flow_change(tty, 0);
269}
270
271static void n_tty_check_unthrottle(struct tty_struct *tty)
272{
273 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
274 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
275 return;
276 n_tty_kick_worker(tty);
277 tty_wakeup(tty->link);
278 return;
279 }
280
281 /* If there is enough space in the read buffer now, let the
282 * low-level driver know. We use chars_in_buffer() to
283 * check the buffer, as it now knows about canonical mode.
284 * Otherwise, if the driver is throttled and the line is
285 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
286 * we won't get any more characters.
287 */
288
289 while (1) {
290 int unthrottled;
291 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
292 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
293 break;
294 n_tty_kick_worker(tty);
295 unthrottled = tty_unthrottle_safe(tty);
296 if (!unthrottled)
297 break;
298 }
299 __tty_set_flow_change(tty, 0);
300}
301
302/**
303 * put_tty_queue - add character to tty
304 * @c: character
305 * @ldata: n_tty data
306 *
307 * Add a character to the tty read_buf queue.
308 *
309 * n_tty_receive_buf()/producer path:
310 * caller holds non-exclusive termios_rwsem
311 */
312
313static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
314{
315 *read_buf_addr(ldata, ldata->read_head) = c;
316 ldata->read_head++;
317}
318
319/**
320 * reset_buffer_flags - reset buffer state
321 * @ldata: line disc data to reset
322 *
323 * Reset the read buffer counters and clear the flags.
324 * Called from n_tty_open() and n_tty_flush_buffer().
325 *
326 * Locking: caller holds exclusive termios_rwsem
327 * (or locking is not required)
328 */
329
330static void reset_buffer_flags(struct n_tty_data *ldata)
331{
332 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
333 ldata->commit_head = 0;
334 ldata->line_start = 0;
335
336 ldata->erasing = 0;
337 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
338 ldata->push = 0;
339}
340
341static void n_tty_packet_mode_flush(struct tty_struct *tty)
342{
343 unsigned long flags;
344
345 if (tty->link->ctrl.packet) {
346 spin_lock_irqsave(&tty->ctrl.lock, flags);
347 tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
348 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
349 wake_up_interruptible(&tty->link->read_wait);
350 }
351}
352
353/**
354 * n_tty_flush_buffer - clean input queue
355 * @tty: terminal device
356 *
357 * Flush the input buffer. Called when the tty layer wants the
358 * buffer flushed (eg at hangup) or when the N_TTY line discipline
359 * internally has to clean the pending queue (for example some signals).
360 *
361 * Holds termios_rwsem to exclude producer/consumer while
362 * buffer indices are reset.
363 *
364 * Locking: ctrl.lock, exclusive termios_rwsem
365 */
366
367static void n_tty_flush_buffer(struct tty_struct *tty)
368{
369 down_write(&tty->termios_rwsem);
370 reset_buffer_flags(tty->disc_data);
371 n_tty_kick_worker(tty);
372
373 if (tty->link)
374 n_tty_packet_mode_flush(tty);
375 up_write(&tty->termios_rwsem);
376}
377
378/**
379 * is_utf8_continuation - utf8 multibyte check
380 * @c: byte to check
381 *
382 * Returns true if the utf8 character 'c' is a multibyte continuation
383 * character. We use this to correctly compute the on screen size
384 * of the character when printing
385 */
386
387static inline int is_utf8_continuation(unsigned char c)
388{
389 return (c & 0xc0) == 0x80;
390}
391
392/**
393 * is_continuation - multibyte check
394 * @c: byte to check
395 * @tty: terminal device
396 *
397 * Returns true if the utf8 character 'c' is a multibyte continuation
398 * character and the terminal is in unicode mode.
399 */
400
401static inline int is_continuation(unsigned char c, struct tty_struct *tty)
402{
403 return I_IUTF8(tty) && is_utf8_continuation(c);
404}
405
406/**
407 * do_output_char - output one character
408 * @c: character (or partial unicode symbol)
409 * @tty: terminal device
410 * @space: space available in tty driver write buffer
411 *
412 * This is a helper function that handles one output character
413 * (including special characters like TAB, CR, LF, etc.),
414 * doing OPOST processing and putting the results in the
415 * tty driver's write buffer.
416 *
417 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
418 * and NLDLY. They simply aren't relevant in the world today.
419 * If you ever need them, add them here.
420 *
421 * Returns the number of bytes of buffer space used or -1 if
422 * no space left.
423 *
424 * Locking: should be called under the output_lock to protect
425 * the column state and space left in the buffer
426 */
427
428static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
429{
430 struct n_tty_data *ldata = tty->disc_data;
431 int spaces;
432
433 if (!space)
434 return -1;
435
436 switch (c) {
437 case '\n':
438 if (O_ONLRET(tty))
439 ldata->column = 0;
440 if (O_ONLCR(tty)) {
441 if (space < 2)
442 return -1;
443 ldata->canon_column = ldata->column = 0;
444 tty->ops->write(tty, "\r\n", 2);
445 return 2;
446 }
447 ldata->canon_column = ldata->column;
448 break;
449 case '\r':
450 if (O_ONOCR(tty) && ldata->column == 0)
451 return 0;
452 if (O_OCRNL(tty)) {
453 c = '\n';
454 if (O_ONLRET(tty))
455 ldata->canon_column = ldata->column = 0;
456 break;
457 }
458 ldata->canon_column = ldata->column = 0;
459 break;
460 case '\t':
461 spaces = 8 - (ldata->column & 7);
462 if (O_TABDLY(tty) == XTABS) {
463 if (space < spaces)
464 return -1;
465 ldata->column += spaces;
466 tty->ops->write(tty, " ", spaces);
467 return spaces;
468 }
469 ldata->column += spaces;
470 break;
471 case '\b':
472 if (ldata->column > 0)
473 ldata->column--;
474 break;
475 default:
476 if (!iscntrl(c)) {
477 if (O_OLCUC(tty))
478 c = toupper(c);
479 if (!is_continuation(c, tty))
480 ldata->column++;
481 }
482 break;
483 }
484
485 tty_put_char(tty, c);
486 return 1;
487}
488
489/**
490 * process_output - output post processor
491 * @c: character (or partial unicode symbol)
492 * @tty: terminal device
493 *
494 * Output one character with OPOST processing.
495 * Returns -1 when the output device is full and the character
496 * must be retried.
497 *
498 * Locking: output_lock to protect column state and space left
499 * (also, this is called from n_tty_write under the
500 * tty layer write lock)
501 */
502
503static int process_output(unsigned char c, struct tty_struct *tty)
504{
505 struct n_tty_data *ldata = tty->disc_data;
506 int space, retval;
507
508 mutex_lock(&ldata->output_lock);
509
510 space = tty_write_room(tty);
511 retval = do_output_char(c, tty, space);
512
513 mutex_unlock(&ldata->output_lock);
514 if (retval < 0)
515 return -1;
516 else
517 return 0;
518}
519
520/**
521 * process_output_block - block post processor
522 * @tty: terminal device
523 * @buf: character buffer
524 * @nr: number of bytes to output
525 *
526 * Output a block of characters with OPOST processing.
527 * Returns the number of characters output.
528 *
529 * This path is used to speed up block console writes, among other
530 * things when processing blocks of output data. It handles only
531 * the simple cases normally found and helps to generate blocks of
532 * symbols for the console driver and thus improve performance.
533 *
534 * Locking: output_lock to protect column state and space left
535 * (also, this is called from n_tty_write under the
536 * tty layer write lock)
537 */
538
539static ssize_t process_output_block(struct tty_struct *tty,
540 const unsigned char *buf, unsigned int nr)
541{
542 struct n_tty_data *ldata = tty->disc_data;
543 int space;
544 int i;
545 const unsigned char *cp;
546
547 mutex_lock(&ldata->output_lock);
548
549 space = tty_write_room(tty);
550 if (space <= 0) {
551 mutex_unlock(&ldata->output_lock);
552 return space;
553 }
554 if (nr > space)
555 nr = space;
556
557 for (i = 0, cp = buf; i < nr; i++, cp++) {
558 unsigned char c = *cp;
559
560 switch (c) {
561 case '\n':
562 if (O_ONLRET(tty))
563 ldata->column = 0;
564 if (O_ONLCR(tty))
565 goto break_out;
566 ldata->canon_column = ldata->column;
567 break;
568 case '\r':
569 if (O_ONOCR(tty) && ldata->column == 0)
570 goto break_out;
571 if (O_OCRNL(tty))
572 goto break_out;
573 ldata->canon_column = ldata->column = 0;
574 break;
575 case '\t':
576 goto break_out;
577 case '\b':
578 if (ldata->column > 0)
579 ldata->column--;
580 break;
581 default:
582 if (!iscntrl(c)) {
583 if (O_OLCUC(tty))
584 goto break_out;
585 if (!is_continuation(c, tty))
586 ldata->column++;
587 }
588 break;
589 }
590 }
591break_out:
592 i = tty->ops->write(tty, buf, i);
593
594 mutex_unlock(&ldata->output_lock);
595 return i;
596}
597
598/**
599 * process_echoes - write pending echo characters
600 * @tty: terminal device
601 *
602 * Write previously buffered echo (and other ldisc-generated)
603 * characters to the tty.
604 *
605 * Characters generated by the ldisc (including echoes) need to
606 * be buffered because the driver's write buffer can fill during
607 * heavy program output. Echoing straight to the driver will
608 * often fail under these conditions, causing lost characters and
609 * resulting mismatches of ldisc state information.
610 *
611 * Since the ldisc state must represent the characters actually sent
612 * to the driver at the time of the write, operations like certain
613 * changes in column state are also saved in the buffer and executed
614 * here.
615 *
616 * A circular fifo buffer is used so that the most recent characters
617 * are prioritized. Also, when control characters are echoed with a
618 * prefixed "^", the pair is treated atomically and thus not separated.
619 *
620 * Locking: callers must hold output_lock
621 */
622
623static size_t __process_echoes(struct tty_struct *tty)
624{
625 struct n_tty_data *ldata = tty->disc_data;
626 int space, old_space;
627 size_t tail;
628 unsigned char c;
629
630 old_space = space = tty_write_room(tty);
631
632 tail = ldata->echo_tail;
633 while (MASK(ldata->echo_commit) != MASK(tail)) {
634 c = echo_buf(ldata, tail);
635 if (c == ECHO_OP_START) {
636 unsigned char op;
637 int no_space_left = 0;
638
639 /*
640 * Since add_echo_byte() is called without holding
641 * output_lock, we might see only portion of multi-byte
642 * operation.
643 */
644 if (MASK(ldata->echo_commit) == MASK(tail + 1))
645 goto not_yet_stored;
646 /*
647 * If the buffer byte is the start of a multi-byte
648 * operation, get the next byte, which is either the
649 * op code or a control character value.
650 */
651 op = echo_buf(ldata, tail + 1);
652
653 switch (op) {
654 case ECHO_OP_ERASE_TAB: {
655 unsigned int num_chars, num_bs;
656
657 if (MASK(ldata->echo_commit) == MASK(tail + 2))
658 goto not_yet_stored;
659 num_chars = echo_buf(ldata, tail + 2);
660
661 /*
662 * Determine how many columns to go back
663 * in order to erase the tab.
664 * This depends on the number of columns
665 * used by other characters within the tab
666 * area. If this (modulo 8) count is from
667 * the start of input rather than from a
668 * previous tab, we offset by canon column.
669 * Otherwise, tab spacing is normal.
670 */
671 if (!(num_chars & 0x80))
672 num_chars += ldata->canon_column;
673 num_bs = 8 - (num_chars & 7);
674
675 if (num_bs > space) {
676 no_space_left = 1;
677 break;
678 }
679 space -= num_bs;
680 while (num_bs--) {
681 tty_put_char(tty, '\b');
682 if (ldata->column > 0)
683 ldata->column--;
684 }
685 tail += 3;
686 break;
687 }
688 case ECHO_OP_SET_CANON_COL:
689 ldata->canon_column = ldata->column;
690 tail += 2;
691 break;
692
693 case ECHO_OP_MOVE_BACK_COL:
694 if (ldata->column > 0)
695 ldata->column--;
696 tail += 2;
697 break;
698
699 case ECHO_OP_START:
700 /* This is an escaped echo op start code */
701 if (!space) {
702 no_space_left = 1;
703 break;
704 }
705 tty_put_char(tty, ECHO_OP_START);
706 ldata->column++;
707 space--;
708 tail += 2;
709 break;
710
711 default:
712 /*
713 * If the op is not a special byte code,
714 * it is a ctrl char tagged to be echoed
715 * as "^X" (where X is the letter
716 * representing the control char).
717 * Note that we must ensure there is
718 * enough space for the whole ctrl pair.
719 *
720 */
721 if (space < 2) {
722 no_space_left = 1;
723 break;
724 }
725 tty_put_char(tty, '^');
726 tty_put_char(tty, op ^ 0100);
727 ldata->column += 2;
728 space -= 2;
729 tail += 2;
730 }
731
732 if (no_space_left)
733 break;
734 } else {
735 if (O_OPOST(tty)) {
736 int retval = do_output_char(c, tty, space);
737 if (retval < 0)
738 break;
739 space -= retval;
740 } else {
741 if (!space)
742 break;
743 tty_put_char(tty, c);
744 space -= 1;
745 }
746 tail += 1;
747 }
748 }
749
750 /* If the echo buffer is nearly full (so that the possibility exists
751 * of echo overrun before the next commit), then discard enough
752 * data at the tail to prevent a subsequent overrun */
753 while (ldata->echo_commit > tail &&
754 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
755 if (echo_buf(ldata, tail) == ECHO_OP_START) {
756 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
757 tail += 3;
758 else
759 tail += 2;
760 } else
761 tail++;
762 }
763
764 not_yet_stored:
765 ldata->echo_tail = tail;
766 return old_space - space;
767}
768
769static void commit_echoes(struct tty_struct *tty)
770{
771 struct n_tty_data *ldata = tty->disc_data;
772 size_t nr, old, echoed;
773 size_t head;
774
775 mutex_lock(&ldata->output_lock);
776 head = ldata->echo_head;
777 ldata->echo_mark = head;
778 old = ldata->echo_commit - ldata->echo_tail;
779
780 /* Process committed echoes if the accumulated # of bytes
781 * is over the threshold (and try again each time another
782 * block is accumulated) */
783 nr = head - ldata->echo_tail;
784 if (nr < ECHO_COMMIT_WATERMARK ||
785 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
786 mutex_unlock(&ldata->output_lock);
787 return;
788 }
789
790 ldata->echo_commit = head;
791 echoed = __process_echoes(tty);
792 mutex_unlock(&ldata->output_lock);
793
794 if (echoed && tty->ops->flush_chars)
795 tty->ops->flush_chars(tty);
796}
797
798static void process_echoes(struct tty_struct *tty)
799{
800 struct n_tty_data *ldata = tty->disc_data;
801 size_t echoed;
802
803 if (ldata->echo_mark == ldata->echo_tail)
804 return;
805
806 mutex_lock(&ldata->output_lock);
807 ldata->echo_commit = ldata->echo_mark;
808 echoed = __process_echoes(tty);
809 mutex_unlock(&ldata->output_lock);
810
811 if (echoed && tty->ops->flush_chars)
812 tty->ops->flush_chars(tty);
813}
814
815/* NB: echo_mark and echo_head should be equivalent here */
816static void flush_echoes(struct tty_struct *tty)
817{
818 struct n_tty_data *ldata = tty->disc_data;
819
820 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
821 ldata->echo_commit == ldata->echo_head)
822 return;
823
824 mutex_lock(&ldata->output_lock);
825 ldata->echo_commit = ldata->echo_head;
826 __process_echoes(tty);
827 mutex_unlock(&ldata->output_lock);
828}
829
830/**
831 * add_echo_byte - add a byte to the echo buffer
832 * @c: unicode byte to echo
833 * @ldata: n_tty data
834 *
835 * Add a character or operation byte to the echo buffer.
836 */
837
838static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
839{
840 *echo_buf_addr(ldata, ldata->echo_head) = c;
841 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
842 ldata->echo_head++;
843}
844
845/**
846 * echo_move_back_col - add operation to move back a column
847 * @ldata: n_tty data
848 *
849 * Add an operation to the echo buffer to move back one column.
850 */
851
852static void echo_move_back_col(struct n_tty_data *ldata)
853{
854 add_echo_byte(ECHO_OP_START, ldata);
855 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
856}
857
858/**
859 * echo_set_canon_col - add operation to set the canon column
860 * @ldata: n_tty data
861 *
862 * Add an operation to the echo buffer to set the canon column
863 * to the current column.
864 */
865
866static void echo_set_canon_col(struct n_tty_data *ldata)
867{
868 add_echo_byte(ECHO_OP_START, ldata);
869 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
870}
871
872/**
873 * echo_erase_tab - add operation to erase a tab
874 * @num_chars: number of character columns already used
875 * @after_tab: true if num_chars starts after a previous tab
876 * @ldata: n_tty data
877 *
878 * Add an operation to the echo buffer to erase a tab.
879 *
880 * Called by the eraser function, which knows how many character
881 * columns have been used since either a previous tab or the start
882 * of input. This information will be used later, along with
883 * canon column (if applicable), to go back the correct number
884 * of columns.
885 */
886
887static void echo_erase_tab(unsigned int num_chars, int after_tab,
888 struct n_tty_data *ldata)
889{
890 add_echo_byte(ECHO_OP_START, ldata);
891 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
892
893 /* We only need to know this modulo 8 (tab spacing) */
894 num_chars &= 7;
895
896 /* Set the high bit as a flag if num_chars is after a previous tab */
897 if (after_tab)
898 num_chars |= 0x80;
899
900 add_echo_byte(num_chars, ldata);
901}
902
903/**
904 * echo_char_raw - echo a character raw
905 * @c: unicode byte to echo
906 * @ldata: line disc data
907 *
908 * Echo user input back onto the screen. This must be called only when
909 * L_ECHO(tty) is true. Called from the driver receive_buf path.
910 *
911 * This variant does not treat control characters specially.
912 */
913
914static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
915{
916 if (c == ECHO_OP_START) {
917 add_echo_byte(ECHO_OP_START, ldata);
918 add_echo_byte(ECHO_OP_START, ldata);
919 } else {
920 add_echo_byte(c, ldata);
921 }
922}
923
924/**
925 * echo_char - echo a character
926 * @c: unicode byte to echo
927 * @tty: terminal device
928 *
929 * Echo user input back onto the screen. This must be called only when
930 * L_ECHO(tty) is true. Called from the driver receive_buf path.
931 *
932 * This variant tags control characters to be echoed as "^X"
933 * (where X is the letter representing the control char).
934 */
935
936static void echo_char(unsigned char c, struct tty_struct *tty)
937{
938 struct n_tty_data *ldata = tty->disc_data;
939
940 if (c == ECHO_OP_START) {
941 add_echo_byte(ECHO_OP_START, ldata);
942 add_echo_byte(ECHO_OP_START, ldata);
943 } else {
944 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
945 add_echo_byte(ECHO_OP_START, ldata);
946 add_echo_byte(c, ldata);
947 }
948}
949
950/**
951 * finish_erasing - complete erase
952 * @ldata: n_tty data
953 */
954
955static inline void finish_erasing(struct n_tty_data *ldata)
956{
957 if (ldata->erasing) {
958 echo_char_raw('/', ldata);
959 ldata->erasing = 0;
960 }
961}
962
963/**
964 * eraser - handle erase function
965 * @c: character input
966 * @tty: terminal device
967 *
968 * Perform erase and necessary output when an erase character is
969 * present in the stream from the driver layer. Handles the complexities
970 * of UTF-8 multibyte symbols.
971 *
972 * n_tty_receive_buf()/producer path:
973 * caller holds non-exclusive termios_rwsem
974 */
975
976static void eraser(unsigned char c, struct tty_struct *tty)
977{
978 struct n_tty_data *ldata = tty->disc_data;
979 enum { ERASE, WERASE, KILL } kill_type;
980 size_t head;
981 size_t cnt;
982 int seen_alnums;
983
984 if (ldata->read_head == ldata->canon_head) {
985 /* process_output('\a', tty); */ /* what do you think? */
986 return;
987 }
988 if (c == ERASE_CHAR(tty))
989 kill_type = ERASE;
990 else if (c == WERASE_CHAR(tty))
991 kill_type = WERASE;
992 else {
993 if (!L_ECHO(tty)) {
994 ldata->read_head = ldata->canon_head;
995 return;
996 }
997 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
998 ldata->read_head = ldata->canon_head;
999 finish_erasing(ldata);
1000 echo_char(KILL_CHAR(tty), tty);
1001 /* Add a newline if ECHOK is on and ECHOKE is off. */
1002 if (L_ECHOK(tty))
1003 echo_char_raw('\n', ldata);
1004 return;
1005 }
1006 kill_type = KILL;
1007 }
1008
1009 seen_alnums = 0;
1010 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
1011 head = ldata->read_head;
1012
1013 /* erase a single possibly multibyte character */
1014 do {
1015 head--;
1016 c = read_buf(ldata, head);
1017 } while (is_continuation(c, tty) &&
1018 MASK(head) != MASK(ldata->canon_head));
1019
1020 /* do not partially erase */
1021 if (is_continuation(c, tty))
1022 break;
1023
1024 if (kill_type == WERASE) {
1025 /* Equivalent to BSD's ALTWERASE. */
1026 if (isalnum(c) || c == '_')
1027 seen_alnums++;
1028 else if (seen_alnums)
1029 break;
1030 }
1031 cnt = ldata->read_head - head;
1032 ldata->read_head = head;
1033 if (L_ECHO(tty)) {
1034 if (L_ECHOPRT(tty)) {
1035 if (!ldata->erasing) {
1036 echo_char_raw('\\', ldata);
1037 ldata->erasing = 1;
1038 }
1039 /* if cnt > 1, output a multi-byte character */
1040 echo_char(c, tty);
1041 while (--cnt > 0) {
1042 head++;
1043 echo_char_raw(read_buf(ldata, head), ldata);
1044 echo_move_back_col(ldata);
1045 }
1046 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1047 echo_char(ERASE_CHAR(tty), tty);
1048 } else if (c == '\t') {
1049 unsigned int num_chars = 0;
1050 int after_tab = 0;
1051 size_t tail = ldata->read_head;
1052
1053 /*
1054 * Count the columns used for characters
1055 * since the start of input or after a
1056 * previous tab.
1057 * This info is used to go back the correct
1058 * number of columns.
1059 */
1060 while (MASK(tail) != MASK(ldata->canon_head)) {
1061 tail--;
1062 c = read_buf(ldata, tail);
1063 if (c == '\t') {
1064 after_tab = 1;
1065 break;
1066 } else if (iscntrl(c)) {
1067 if (L_ECHOCTL(tty))
1068 num_chars += 2;
1069 } else if (!is_continuation(c, tty)) {
1070 num_chars++;
1071 }
1072 }
1073 echo_erase_tab(num_chars, after_tab, ldata);
1074 } else {
1075 if (iscntrl(c) && L_ECHOCTL(tty)) {
1076 echo_char_raw('\b', ldata);
1077 echo_char_raw(' ', ldata);
1078 echo_char_raw('\b', ldata);
1079 }
1080 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1081 echo_char_raw('\b', ldata);
1082 echo_char_raw(' ', ldata);
1083 echo_char_raw('\b', ldata);
1084 }
1085 }
1086 }
1087 if (kill_type == ERASE)
1088 break;
1089 }
1090 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1091 finish_erasing(ldata);
1092}
1093
1094/**
1095 * isig - handle the ISIG optio
1096 * @sig: signal
1097 * @tty: terminal
1098 *
1099 * Called when a signal is being sent due to terminal input.
1100 * Called from the driver receive_buf path so serialized.
1101 *
1102 * Performs input and output flush if !NOFLSH. In this context, the echo
1103 * buffer is 'output'. The signal is processed first to alert any current
1104 * readers or writers to discontinue and exit their i/o loops.
1105 *
1106 * Locking: ctrl.lock
1107 */
1108
1109static void __isig(int sig, struct tty_struct *tty)
1110{
1111 struct pid *tty_pgrp = tty_get_pgrp(tty);
1112 if (tty_pgrp) {
1113 kill_pgrp(tty_pgrp, sig, 1);
1114 put_pid(tty_pgrp);
1115 }
1116}
1117
1118static void isig(int sig, struct tty_struct *tty)
1119{
1120 struct n_tty_data *ldata = tty->disc_data;
1121
1122 if (L_NOFLSH(tty)) {
1123 /* signal only */
1124 __isig(sig, tty);
1125
1126 } else { /* signal and flush */
1127 up_read(&tty->termios_rwsem);
1128 down_write(&tty->termios_rwsem);
1129
1130 __isig(sig, tty);
1131
1132 /* clear echo buffer */
1133 mutex_lock(&ldata->output_lock);
1134 ldata->echo_head = ldata->echo_tail = 0;
1135 ldata->echo_mark = ldata->echo_commit = 0;
1136 mutex_unlock(&ldata->output_lock);
1137
1138 /* clear output buffer */
1139 tty_driver_flush_buffer(tty);
1140
1141 /* clear input buffer */
1142 reset_buffer_flags(tty->disc_data);
1143
1144 /* notify pty master of flush */
1145 if (tty->link)
1146 n_tty_packet_mode_flush(tty);
1147
1148 up_write(&tty->termios_rwsem);
1149 down_read(&tty->termios_rwsem);
1150 }
1151}
1152
1153/**
1154 * n_tty_receive_break - handle break
1155 * @tty: terminal
1156 *
1157 * An RS232 break event has been hit in the incoming bitstream. This
1158 * can cause a variety of events depending upon the termios settings.
1159 *
1160 * n_tty_receive_buf()/producer path:
1161 * caller holds non-exclusive termios_rwsem
1162 *
1163 * Note: may get exclusive termios_rwsem if flushing input buffer
1164 */
1165
1166static void n_tty_receive_break(struct tty_struct *tty)
1167{
1168 struct n_tty_data *ldata = tty->disc_data;
1169
1170 if (I_IGNBRK(tty))
1171 return;
1172 if (I_BRKINT(tty)) {
1173 isig(SIGINT, tty);
1174 return;
1175 }
1176 if (I_PARMRK(tty)) {
1177 put_tty_queue('\377', ldata);
1178 put_tty_queue('\0', ldata);
1179 }
1180 put_tty_queue('\0', ldata);
1181}
1182
1183/**
1184 * n_tty_receive_overrun - handle overrun reporting
1185 * @tty: terminal
1186 *
1187 * Data arrived faster than we could process it. While the tty
1188 * driver has flagged this the bits that were missed are gone
1189 * forever.
1190 *
1191 * Called from the receive_buf path so single threaded. Does not
1192 * need locking as num_overrun and overrun_time are function
1193 * private.
1194 */
1195
1196static void n_tty_receive_overrun(struct tty_struct *tty)
1197{
1198 struct n_tty_data *ldata = tty->disc_data;
1199
1200 ldata->num_overrun++;
1201 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1202 time_after(ldata->overrun_time, jiffies)) {
1203 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1204 ldata->overrun_time = jiffies;
1205 ldata->num_overrun = 0;
1206 }
1207}
1208
1209/**
1210 * n_tty_receive_parity_error - error notifier
1211 * @tty: terminal device
1212 * @c: character
1213 *
1214 * Process a parity error and queue the right data to indicate
1215 * the error case if necessary.
1216 *
1217 * n_tty_receive_buf()/producer path:
1218 * caller holds non-exclusive termios_rwsem
1219 */
1220static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1221{
1222 struct n_tty_data *ldata = tty->disc_data;
1223
1224 if (I_INPCK(tty)) {
1225 if (I_IGNPAR(tty))
1226 return;
1227 if (I_PARMRK(tty)) {
1228 put_tty_queue('\377', ldata);
1229 put_tty_queue('\0', ldata);
1230 put_tty_queue(c, ldata);
1231 } else
1232 put_tty_queue('\0', ldata);
1233 } else
1234 put_tty_queue(c, ldata);
1235}
1236
1237static void
1238n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1239{
1240 isig(signal, tty);
1241 if (I_IXON(tty))
1242 start_tty(tty);
1243 if (L_ECHO(tty)) {
1244 echo_char(c, tty);
1245 commit_echoes(tty);
1246 } else
1247 process_echoes(tty);
1248}
1249
1250/**
1251 * n_tty_receive_char - perform processing
1252 * @tty: terminal device
1253 * @c: character
1254 *
1255 * Process an individual character of input received from the driver.
1256 * This is serialized with respect to itself by the rules for the
1257 * driver above.
1258 *
1259 * n_tty_receive_buf()/producer path:
1260 * caller holds non-exclusive termios_rwsem
1261 * publishes canon_head if canonical mode is active
1262 */
1263static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1264{
1265 struct n_tty_data *ldata = tty->disc_data;
1266
1267 if (I_IXON(tty)) {
1268 if (c == START_CHAR(tty)) {
1269 start_tty(tty);
1270 process_echoes(tty);
1271 return;
1272 }
1273 if (c == STOP_CHAR(tty)) {
1274 stop_tty(tty);
1275 return;
1276 }
1277 }
1278
1279 if (L_ISIG(tty)) {
1280 if (c == INTR_CHAR(tty)) {
1281 n_tty_receive_signal_char(tty, SIGINT, c);
1282 return;
1283 } else if (c == QUIT_CHAR(tty)) {
1284 n_tty_receive_signal_char(tty, SIGQUIT, c);
1285 return;
1286 } else if (c == SUSP_CHAR(tty)) {
1287 n_tty_receive_signal_char(tty, SIGTSTP, c);
1288 return;
1289 }
1290 }
1291
1292 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1293 start_tty(tty);
1294 process_echoes(tty);
1295 }
1296
1297 if (c == '\r') {
1298 if (I_IGNCR(tty))
1299 return;
1300 if (I_ICRNL(tty))
1301 c = '\n';
1302 } else if (c == '\n' && I_INLCR(tty))
1303 c = '\r';
1304
1305 if (ldata->icanon) {
1306 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1307 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1308 eraser(c, tty);
1309 commit_echoes(tty);
1310 return;
1311 }
1312 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1313 ldata->lnext = 1;
1314 if (L_ECHO(tty)) {
1315 finish_erasing(ldata);
1316 if (L_ECHOCTL(tty)) {
1317 echo_char_raw('^', ldata);
1318 echo_char_raw('\b', ldata);
1319 commit_echoes(tty);
1320 }
1321 }
1322 return;
1323 }
1324 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1325 size_t tail = ldata->canon_head;
1326
1327 finish_erasing(ldata);
1328 echo_char(c, tty);
1329 echo_char_raw('\n', ldata);
1330 while (MASK(tail) != MASK(ldata->read_head)) {
1331 echo_char(read_buf(ldata, tail), tty);
1332 tail++;
1333 }
1334 commit_echoes(tty);
1335 return;
1336 }
1337 if (c == '\n') {
1338 if (L_ECHO(tty) || L_ECHONL(tty)) {
1339 echo_char_raw('\n', ldata);
1340 commit_echoes(tty);
1341 }
1342 goto handle_newline;
1343 }
1344 if (c == EOF_CHAR(tty)) {
1345 c = __DISABLED_CHAR;
1346 goto handle_newline;
1347 }
1348 if ((c == EOL_CHAR(tty)) ||
1349 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1350 /*
1351 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1352 */
1353 if (L_ECHO(tty)) {
1354 /* Record the column of first canon char. */
1355 if (ldata->canon_head == ldata->read_head)
1356 echo_set_canon_col(ldata);
1357 echo_char(c, tty);
1358 commit_echoes(tty);
1359 }
1360 /*
1361 * XXX does PARMRK doubling happen for
1362 * EOL_CHAR and EOL2_CHAR?
1363 */
1364 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1365 put_tty_queue(c, ldata);
1366
1367handle_newline:
1368 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1369 put_tty_queue(c, ldata);
1370 smp_store_release(&ldata->canon_head, ldata->read_head);
1371 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1372 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1373 return;
1374 }
1375 }
1376
1377 if (L_ECHO(tty)) {
1378 finish_erasing(ldata);
1379 if (c == '\n')
1380 echo_char_raw('\n', ldata);
1381 else {
1382 /* Record the column of first canon char. */
1383 if (ldata->canon_head == ldata->read_head)
1384 echo_set_canon_col(ldata);
1385 echo_char(c, tty);
1386 }
1387 commit_echoes(tty);
1388 }
1389
1390 /* PARMRK doubling check */
1391 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1392 put_tty_queue(c, ldata);
1393
1394 put_tty_queue(c, ldata);
1395}
1396
1397static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1398{
1399 struct n_tty_data *ldata = tty->disc_data;
1400
1401 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1402 start_tty(tty);
1403 process_echoes(tty);
1404 }
1405 if (L_ECHO(tty)) {
1406 finish_erasing(ldata);
1407 /* Record the column of first canon char. */
1408 if (ldata->canon_head == ldata->read_head)
1409 echo_set_canon_col(ldata);
1410 echo_char(c, tty);
1411 commit_echoes(tty);
1412 }
1413 /* PARMRK doubling check */
1414 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1415 put_tty_queue(c, ldata);
1416 put_tty_queue(c, ldata);
1417}
1418
1419static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1420{
1421 if (I_ISTRIP(tty))
1422 c &= 0x7f;
1423 if (I_IUCLC(tty) && L_IEXTEN(tty))
1424 c = tolower(c);
1425
1426 if (I_IXON(tty)) {
1427 if (c == STOP_CHAR(tty))
1428 stop_tty(tty);
1429 else if (c == START_CHAR(tty) ||
1430 (tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1431 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1432 c != SUSP_CHAR(tty))) {
1433 start_tty(tty);
1434 process_echoes(tty);
1435 }
1436 }
1437}
1438
1439static void
1440n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1441{
1442 switch (flag) {
1443 case TTY_BREAK:
1444 n_tty_receive_break(tty);
1445 break;
1446 case TTY_PARITY:
1447 case TTY_FRAME:
1448 n_tty_receive_parity_error(tty, c);
1449 break;
1450 case TTY_OVERRUN:
1451 n_tty_receive_overrun(tty);
1452 break;
1453 default:
1454 tty_err(tty, "unknown flag %d\n", flag);
1455 break;
1456 }
1457}
1458
1459static void
1460n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1461{
1462 struct n_tty_data *ldata = tty->disc_data;
1463
1464 ldata->lnext = 0;
1465 if (likely(flag == TTY_NORMAL)) {
1466 if (I_ISTRIP(tty))
1467 c &= 0x7f;
1468 if (I_IUCLC(tty) && L_IEXTEN(tty))
1469 c = tolower(c);
1470 n_tty_receive_char(tty, c);
1471 } else
1472 n_tty_receive_char_flagged(tty, c, flag);
1473}
1474
1475static void
1476n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1477 const char *fp, int count)
1478{
1479 struct n_tty_data *ldata = tty->disc_data;
1480 size_t n, head;
1481
1482 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1483 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1484 memcpy(read_buf_addr(ldata, head), cp, n);
1485 ldata->read_head += n;
1486 cp += n;
1487 count -= n;
1488
1489 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1490 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1491 memcpy(read_buf_addr(ldata, head), cp, n);
1492 ldata->read_head += n;
1493}
1494
1495static void
1496n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1497 const char *fp, int count)
1498{
1499 struct n_tty_data *ldata = tty->disc_data;
1500 char flag = TTY_NORMAL;
1501
1502 while (count--) {
1503 if (fp)
1504 flag = *fp++;
1505 if (likely(flag == TTY_NORMAL))
1506 put_tty_queue(*cp++, ldata);
1507 else
1508 n_tty_receive_char_flagged(tty, *cp++, flag);
1509 }
1510}
1511
1512static void
1513n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1514 const char *fp, int count)
1515{
1516 char flag = TTY_NORMAL;
1517
1518 while (count--) {
1519 if (fp)
1520 flag = *fp++;
1521 if (likely(flag == TTY_NORMAL))
1522 n_tty_receive_char_closing(tty, *cp++);
1523 }
1524}
1525
1526static void n_tty_receive_buf_standard(struct tty_struct *tty,
1527 const unsigned char *cp, const char *fp, int count)
1528{
1529 struct n_tty_data *ldata = tty->disc_data;
1530 char flag = TTY_NORMAL;
1531
1532 while (count--) {
1533 unsigned char c = *cp++;
1534
1535 if (fp)
1536 flag = *fp++;
1537
1538 if (ldata->lnext) {
1539 n_tty_receive_char_lnext(tty, c, flag);
1540 continue;
1541 }
1542
1543 if (unlikely(flag != TTY_NORMAL)) {
1544 n_tty_receive_char_flagged(tty, c, flag);
1545 continue;
1546 }
1547
1548 if (I_ISTRIP(tty))
1549 c &= 0x7f;
1550 if (I_IUCLC(tty) && L_IEXTEN(tty))
1551 c = tolower(c);
1552 if (L_EXTPROC(tty)) {
1553 put_tty_queue(c, ldata);
1554 continue;
1555 }
1556
1557 if (test_bit(c, ldata->char_map))
1558 n_tty_receive_char_special(tty, c);
1559 else
1560 n_tty_receive_char(tty, c);
1561 }
1562}
1563
1564static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1565 const char *fp, int count)
1566{
1567 struct n_tty_data *ldata = tty->disc_data;
1568 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1569
1570 if (ldata->real_raw)
1571 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1572 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1573 n_tty_receive_buf_raw(tty, cp, fp, count);
1574 else if (tty->closing && !L_EXTPROC(tty))
1575 n_tty_receive_buf_closing(tty, cp, fp, count);
1576 else {
1577 n_tty_receive_buf_standard(tty, cp, fp, count);
1578
1579 flush_echoes(tty);
1580 if (tty->ops->flush_chars)
1581 tty->ops->flush_chars(tty);
1582 }
1583
1584 if (ldata->icanon && !L_EXTPROC(tty))
1585 return;
1586
1587 /* publish read_head to consumer */
1588 smp_store_release(&ldata->commit_head, ldata->read_head);
1589
1590 if (read_cnt(ldata)) {
1591 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1592 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1593 }
1594}
1595
1596/**
1597 * n_tty_receive_buf_common - process input
1598 * @tty: device to receive input
1599 * @cp: input chars
1600 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1601 * @count: number of input chars in @cp
1602 * @flow: enable flow control
1603 *
1604 * Called by the terminal driver when a block of characters has
1605 * been received. This function must be called from soft contexts
1606 * not from interrupt context. The driver is responsible for making
1607 * calls one at a time and in order (or using flush_to_ldisc)
1608 *
1609 * Returns the # of input chars from @cp which were processed.
1610 *
1611 * In canonical mode, the maximum line length is 4096 chars (including
1612 * the line termination char); lines longer than 4096 chars are
1613 * truncated. After 4095 chars, input data is still processed but
1614 * not stored. Overflow processing ensures the tty can always
1615 * receive more input until at least one line can be read.
1616 *
1617 * In non-canonical mode, the read buffer will only accept 4095 chars;
1618 * this provides the necessary space for a newline char if the input
1619 * mode is switched to canonical.
1620 *
1621 * Note it is possible for the read buffer to _contain_ 4096 chars
1622 * in non-canonical mode: the read buffer could already contain the
1623 * maximum canon line of 4096 chars when the mode is switched to
1624 * non-canonical.
1625 *
1626 * n_tty_receive_buf()/producer path:
1627 * claims non-exclusive termios_rwsem
1628 * publishes commit_head or canon_head
1629 */
1630static int
1631n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1632 const char *fp, int count, int flow)
1633{
1634 struct n_tty_data *ldata = tty->disc_data;
1635 int room, n, rcvd = 0, overflow;
1636
1637 down_read(&tty->termios_rwsem);
1638
1639 do {
1640 /*
1641 * When PARMRK is set, each input char may take up to 3 chars
1642 * in the read buf; reduce the buffer space avail by 3x
1643 *
1644 * If we are doing input canonicalization, and there are no
1645 * pending newlines, let characters through without limit, so
1646 * that erase characters will be handled. Other excess
1647 * characters will be beeped.
1648 *
1649 * paired with store in *_copy_from_read_buf() -- guarantees
1650 * the consumer has loaded the data in read_buf up to the new
1651 * read_tail (so this producer will not overwrite unread data)
1652 */
1653 size_t tail = smp_load_acquire(&ldata->read_tail);
1654
1655 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1656 if (I_PARMRK(tty))
1657 room = (room + 2) / 3;
1658 room--;
1659 if (room <= 0) {
1660 overflow = ldata->icanon && ldata->canon_head == tail;
1661 if (overflow && room < 0)
1662 ldata->read_head--;
1663 room = overflow;
1664 ldata->no_room = flow && !room;
1665 } else
1666 overflow = 0;
1667
1668 n = min(count, room);
1669 if (!n)
1670 break;
1671
1672 /* ignore parity errors if handling overflow */
1673 if (!overflow || !fp || *fp != TTY_PARITY)
1674 __receive_buf(tty, cp, fp, n);
1675
1676 cp += n;
1677 if (fp)
1678 fp += n;
1679 count -= n;
1680 rcvd += n;
1681 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1682
1683 tty->receive_room = room;
1684
1685 /* Unthrottle if handling overflow on pty */
1686 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1687 if (overflow) {
1688 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1689 tty_unthrottle_safe(tty);
1690 __tty_set_flow_change(tty, 0);
1691 }
1692 } else
1693 n_tty_check_throttle(tty);
1694
1695 up_read(&tty->termios_rwsem);
1696
1697 return rcvd;
1698}
1699
1700static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1701 const char *fp, int count)
1702{
1703 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1704}
1705
1706static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1707 const char *fp, int count)
1708{
1709 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1710}
1711
1712/**
1713 * n_tty_set_termios - termios data changed
1714 * @tty: terminal
1715 * @old: previous data
1716 *
1717 * Called by the tty layer when the user changes termios flags so
1718 * that the line discipline can plan ahead. This function cannot sleep
1719 * and is protected from re-entry by the tty layer. The user is
1720 * guaranteed that this function will not be re-entered or in progress
1721 * when the ldisc is closed.
1722 *
1723 * Locking: Caller holds tty->termios_rwsem
1724 */
1725
1726static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1727{
1728 struct n_tty_data *ldata = tty->disc_data;
1729
1730 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1731 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1732 ldata->line_start = ldata->read_tail;
1733 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1734 ldata->canon_head = ldata->read_tail;
1735 ldata->push = 0;
1736 } else {
1737 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1738 ldata->read_flags);
1739 ldata->canon_head = ldata->read_head;
1740 ldata->push = 1;
1741 }
1742 ldata->commit_head = ldata->read_head;
1743 ldata->erasing = 0;
1744 ldata->lnext = 0;
1745 }
1746
1747 ldata->icanon = (L_ICANON(tty) != 0);
1748
1749 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1750 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1751 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1752 I_PARMRK(tty)) {
1753 bitmap_zero(ldata->char_map, 256);
1754
1755 if (I_IGNCR(tty) || I_ICRNL(tty))
1756 set_bit('\r', ldata->char_map);
1757 if (I_INLCR(tty))
1758 set_bit('\n', ldata->char_map);
1759
1760 if (L_ICANON(tty)) {
1761 set_bit(ERASE_CHAR(tty), ldata->char_map);
1762 set_bit(KILL_CHAR(tty), ldata->char_map);
1763 set_bit(EOF_CHAR(tty), ldata->char_map);
1764 set_bit('\n', ldata->char_map);
1765 set_bit(EOL_CHAR(tty), ldata->char_map);
1766 if (L_IEXTEN(tty)) {
1767 set_bit(WERASE_CHAR(tty), ldata->char_map);
1768 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1769 set_bit(EOL2_CHAR(tty), ldata->char_map);
1770 if (L_ECHO(tty))
1771 set_bit(REPRINT_CHAR(tty),
1772 ldata->char_map);
1773 }
1774 }
1775 if (I_IXON(tty)) {
1776 set_bit(START_CHAR(tty), ldata->char_map);
1777 set_bit(STOP_CHAR(tty), ldata->char_map);
1778 }
1779 if (L_ISIG(tty)) {
1780 set_bit(INTR_CHAR(tty), ldata->char_map);
1781 set_bit(QUIT_CHAR(tty), ldata->char_map);
1782 set_bit(SUSP_CHAR(tty), ldata->char_map);
1783 }
1784 clear_bit(__DISABLED_CHAR, ldata->char_map);
1785 ldata->raw = 0;
1786 ldata->real_raw = 0;
1787 } else {
1788 ldata->raw = 1;
1789 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1790 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1791 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1792 ldata->real_raw = 1;
1793 else
1794 ldata->real_raw = 0;
1795 }
1796 /*
1797 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1798 * been stopped by STOP_CHAR(tty) before it.
1799 */
1800 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1801 start_tty(tty);
1802 process_echoes(tty);
1803 }
1804
1805 /* The termios change make the tty ready for I/O */
1806 wake_up_interruptible(&tty->write_wait);
1807 wake_up_interruptible(&tty->read_wait);
1808}
1809
1810/**
1811 * n_tty_close - close the ldisc for this tty
1812 * @tty: device
1813 *
1814 * Called from the terminal layer when this line discipline is
1815 * being shut down, either because of a close or becsuse of a
1816 * discipline change. The function will not be called while other
1817 * ldisc methods are in progress.
1818 */
1819
1820static void n_tty_close(struct tty_struct *tty)
1821{
1822 struct n_tty_data *ldata = tty->disc_data;
1823
1824 if (tty->link)
1825 n_tty_packet_mode_flush(tty);
1826
1827 down_write(&tty->termios_rwsem);
1828 vfree(ldata);
1829 tty->disc_data = NULL;
1830 up_write(&tty->termios_rwsem);
1831}
1832
1833/**
1834 * n_tty_open - open an ldisc
1835 * @tty: terminal to open
1836 *
1837 * Called when this line discipline is being attached to the
1838 * terminal device. Can sleep. Called serialized so that no
1839 * other events will occur in parallel. No further open will occur
1840 * until a close.
1841 */
1842
1843static int n_tty_open(struct tty_struct *tty)
1844{
1845 struct n_tty_data *ldata;
1846
1847 /* Currently a malloc failure here can panic */
1848 ldata = vzalloc(sizeof(*ldata));
1849 if (!ldata)
1850 return -ENOMEM;
1851
1852 ldata->overrun_time = jiffies;
1853 mutex_init(&ldata->atomic_read_lock);
1854 mutex_init(&ldata->output_lock);
1855
1856 tty->disc_data = ldata;
1857 tty->closing = 0;
1858 /* indicate buffer work may resume */
1859 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1860 n_tty_set_termios(tty, NULL);
1861 tty_unthrottle(tty);
1862 return 0;
1863}
1864
1865static inline int input_available_p(struct tty_struct *tty, int poll)
1866{
1867 struct n_tty_data *ldata = tty->disc_data;
1868 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1869
1870 if (ldata->icanon && !L_EXTPROC(tty))
1871 return ldata->canon_head != ldata->read_tail;
1872 else
1873 return ldata->commit_head - ldata->read_tail >= amt;
1874}
1875
1876/**
1877 * copy_from_read_buf - copy read data directly
1878 * @tty: terminal device
1879 * @kbp: data
1880 * @nr: size of data
1881 *
1882 * Helper function to speed up n_tty_read. It is only called when
1883 * ICANON is off; it copies characters straight from the tty queue.
1884 *
1885 * Called under the ldata->atomic_read_lock sem
1886 *
1887 * Returns true if it successfully copied data, but there is still
1888 * more data to be had.
1889 *
1890 * n_tty_read()/consumer path:
1891 * caller holds non-exclusive termios_rwsem
1892 * read_tail published
1893 */
1894
1895static bool copy_from_read_buf(struct tty_struct *tty,
1896 unsigned char **kbp,
1897 size_t *nr)
1898
1899{
1900 struct n_tty_data *ldata = tty->disc_data;
1901 size_t n;
1902 bool is_eof;
1903 size_t head = smp_load_acquire(&ldata->commit_head);
1904 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1905
1906 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1907 n = min(*nr, n);
1908 if (n) {
1909 unsigned char *from = read_buf_addr(ldata, tail);
1910 memcpy(*kbp, from, n);
1911 is_eof = n == 1 && *from == EOF_CHAR(tty);
1912 tty_audit_add_data(tty, from, n);
1913 zero_buffer(tty, from, n);
1914 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1915 /* Turn single EOF into zero-length read */
1916 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1917 (head == ldata->read_tail))
1918 return false;
1919 *kbp += n;
1920 *nr -= n;
1921
1922 /* If we have more to copy, let the caller know */
1923 return head != ldata->read_tail;
1924 }
1925 return false;
1926}
1927
1928/**
1929 * canon_copy_from_read_buf - copy read data in canonical mode
1930 * @tty: terminal device
1931 * @kbp: data
1932 * @nr: size of data
1933 *
1934 * Helper function for n_tty_read. It is only called when ICANON is on;
1935 * it copies one line of input up to and including the line-delimiting
1936 * character into the result buffer.
1937 *
1938 * NB: When termios is changed from non-canonical to canonical mode and
1939 * the read buffer contains data, n_tty_set_termios() simulates an EOF
1940 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
1941 * This causes data already processed as input to be immediately available
1942 * as input although a newline has not been received.
1943 *
1944 * Called under the atomic_read_lock mutex
1945 *
1946 * n_tty_read()/consumer path:
1947 * caller holds non-exclusive termios_rwsem
1948 * read_tail published
1949 */
1950
1951static bool canon_copy_from_read_buf(struct tty_struct *tty,
1952 unsigned char **kbp,
1953 size_t *nr)
1954{
1955 struct n_tty_data *ldata = tty->disc_data;
1956 size_t n, size, more, c;
1957 size_t eol;
1958 size_t tail, canon_head;
1959 int found = 0;
1960
1961 /* N.B. avoid overrun if nr == 0 */
1962 if (!*nr)
1963 return false;
1964
1965 canon_head = smp_load_acquire(&ldata->canon_head);
1966 n = min(*nr + 1, canon_head - ldata->read_tail);
1967
1968 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1969 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1970
1971 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1972 __func__, *nr, tail, n, size);
1973
1974 eol = find_next_bit(ldata->read_flags, size, tail);
1975 more = n - (size - tail);
1976 if (eol == N_TTY_BUF_SIZE && more) {
1977 /* scan wrapped without finding set bit */
1978 eol = find_next_bit(ldata->read_flags, more, 0);
1979 found = eol != more;
1980 } else
1981 found = eol != size;
1982
1983 n = eol - tail;
1984 if (n > N_TTY_BUF_SIZE)
1985 n += N_TTY_BUF_SIZE;
1986 c = n + found;
1987
1988 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
1989 c = min(*nr, c);
1990 n = c;
1991 }
1992
1993 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
1994 __func__, eol, found, n, c, tail, more);
1995
1996 tty_copy(tty, *kbp, tail, n);
1997 *kbp += n;
1998 *nr -= n;
1999
2000 if (found)
2001 clear_bit(eol, ldata->read_flags);
2002 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2003
2004 if (found) {
2005 if (!ldata->push)
2006 ldata->line_start = ldata->read_tail;
2007 else
2008 ldata->push = 0;
2009 tty_audit_push();
2010 return false;
2011 }
2012
2013 /* No EOL found - do a continuation retry if there is more data */
2014 return ldata->read_tail != canon_head;
2015}
2016
2017/**
2018 * job_control - check job control
2019 * @tty: tty
2020 * @file: file handle
2021 *
2022 * Perform job control management checks on this file/tty descriptor
2023 * and if appropriate send any needed signals and return a negative
2024 * error code if action should be taken.
2025 *
2026 * Locking: redirected write test is safe
2027 * current->signal->tty check is safe
2028 * ctrl.lock to safely reference tty->ctrl.pgrp
2029 */
2030
2031static int job_control(struct tty_struct *tty, struct file *file)
2032{
2033 /* Job control check -- must be done at start and after
2034 every sleep (POSIX.1 7.1.1.4). */
2035 /* NOTE: not yet done after every sleep pending a thorough
2036 check of the logic of this change. -- jlc */
2037 /* don't stop on /dev/console */
2038 if (file->f_op->write_iter == redirected_tty_write)
2039 return 0;
2040
2041 return __tty_check_change(tty, SIGTTIN);
2042}
2043
2044
2045/**
2046 * n_tty_read - read function for tty
2047 * @tty: tty device
2048 * @file: file object
2049 * @buf: userspace buffer pointer
2050 * @nr: size of I/O
2051 *
2052 * Perform reads for the line discipline. We are guaranteed that the
2053 * line discipline will not be closed under us but we may get multiple
2054 * parallel readers and must handle this ourselves. We may also get
2055 * a hangup. Always called in user context, may sleep.
2056 *
2057 * This code must be sure never to sleep through a hangup.
2058 *
2059 * n_tty_read()/consumer path:
2060 * claims non-exclusive termios_rwsem
2061 * publishes read_tail
2062 */
2063
2064static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2065 unsigned char *kbuf, size_t nr,
2066 void **cookie, unsigned long offset)
2067{
2068 struct n_tty_data *ldata = tty->disc_data;
2069 unsigned char *kb = kbuf;
2070 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2071 int c;
2072 int minimum, time;
2073 ssize_t retval = 0;
2074 long timeout;
2075 bool packet;
2076 size_t tail;
2077
2078 /*
2079 * Is this a continuation of a read started earler?
2080 *
2081 * If so, we still hold the atomic_read_lock and the
2082 * termios_rwsem, and can just continue to copy data.
2083 */
2084 if (*cookie) {
2085 if (ldata->icanon && !L_EXTPROC(tty)) {
2086 if (canon_copy_from_read_buf(tty, &kb, &nr))
2087 return kb - kbuf;
2088 } else {
2089 if (copy_from_read_buf(tty, &kb, &nr))
2090 return kb - kbuf;
2091 }
2092
2093 /* No more data - release locks and stop retries */
2094 n_tty_kick_worker(tty);
2095 n_tty_check_unthrottle(tty);
2096 up_read(&tty->termios_rwsem);
2097 mutex_unlock(&ldata->atomic_read_lock);
2098 *cookie = NULL;
2099 return kb - kbuf;
2100 }
2101
2102 c = job_control(tty, file);
2103 if (c < 0)
2104 return c;
2105
2106 /*
2107 * Internal serialization of reads.
2108 */
2109 if (file->f_flags & O_NONBLOCK) {
2110 if (!mutex_trylock(&ldata->atomic_read_lock))
2111 return -EAGAIN;
2112 } else {
2113 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2114 return -ERESTARTSYS;
2115 }
2116
2117 down_read(&tty->termios_rwsem);
2118
2119 minimum = time = 0;
2120 timeout = MAX_SCHEDULE_TIMEOUT;
2121 if (!ldata->icanon) {
2122 minimum = MIN_CHAR(tty);
2123 if (minimum) {
2124 time = (HZ / 10) * TIME_CHAR(tty);
2125 } else {
2126 timeout = (HZ / 10) * TIME_CHAR(tty);
2127 minimum = 1;
2128 }
2129 }
2130
2131 packet = tty->ctrl.packet;
2132 tail = ldata->read_tail;
2133
2134 add_wait_queue(&tty->read_wait, &wait);
2135 while (nr) {
2136 /* First test for status change. */
2137 if (packet && tty->link->ctrl.pktstatus) {
2138 unsigned char cs;
2139 if (kb != kbuf)
2140 break;
2141 spin_lock_irq(&tty->link->ctrl.lock);
2142 cs = tty->link->ctrl.pktstatus;
2143 tty->link->ctrl.pktstatus = 0;
2144 spin_unlock_irq(&tty->link->ctrl.lock);
2145 *kb++ = cs;
2146 nr--;
2147 break;
2148 }
2149
2150 if (!input_available_p(tty, 0)) {
2151 up_read(&tty->termios_rwsem);
2152 tty_buffer_flush_work(tty->port);
2153 down_read(&tty->termios_rwsem);
2154 if (!input_available_p(tty, 0)) {
2155 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2156 retval = -EIO;
2157 break;
2158 }
2159 if (tty_hung_up_p(file))
2160 break;
2161 /*
2162 * Abort readers for ttys which never actually
2163 * get hung up. See __tty_hangup().
2164 */
2165 if (test_bit(TTY_HUPPING, &tty->flags))
2166 break;
2167 if (!timeout)
2168 break;
2169 if (tty_io_nonblock(tty, file)) {
2170 retval = -EAGAIN;
2171 break;
2172 }
2173 if (signal_pending(current)) {
2174 retval = -ERESTARTSYS;
2175 break;
2176 }
2177 up_read(&tty->termios_rwsem);
2178
2179 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2180 timeout);
2181
2182 down_read(&tty->termios_rwsem);
2183 continue;
2184 }
2185 }
2186
2187 if (ldata->icanon && !L_EXTPROC(tty)) {
2188 if (canon_copy_from_read_buf(tty, &kb, &nr))
2189 goto more_to_be_read;
2190 } else {
2191 /* Deal with packet mode. */
2192 if (packet && kb == kbuf) {
2193 *kb++ = TIOCPKT_DATA;
2194 nr--;
2195 }
2196
2197 /*
2198 * Copy data, and if there is more to be had
2199 * and we have nothing more to wait for, then
2200 * let's mark us for retries.
2201 *
2202 * NOTE! We return here with both the termios_sem
2203 * and atomic_read_lock still held, the retries
2204 * will release them when done.
2205 */
2206 if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2207more_to_be_read:
2208 remove_wait_queue(&tty->read_wait, &wait);
2209 *cookie = cookie;
2210 return kb - kbuf;
2211 }
2212 }
2213
2214 n_tty_check_unthrottle(tty);
2215
2216 if (kb - kbuf >= minimum)
2217 break;
2218 if (time)
2219 timeout = time;
2220 }
2221 if (tail != ldata->read_tail)
2222 n_tty_kick_worker(tty);
2223 up_read(&tty->termios_rwsem);
2224
2225 remove_wait_queue(&tty->read_wait, &wait);
2226 mutex_unlock(&ldata->atomic_read_lock);
2227
2228 if (kb - kbuf)
2229 retval = kb - kbuf;
2230
2231 return retval;
2232}
2233
2234/**
2235 * n_tty_write - write function for tty
2236 * @tty: tty device
2237 * @file: file object
2238 * @buf: userspace buffer pointer
2239 * @nr: size of I/O
2240 *
2241 * Write function of the terminal device. This is serialized with
2242 * respect to other write callers but not to termios changes, reads
2243 * and other such events. Since the receive code will echo characters,
2244 * thus calling driver write methods, the output_lock is used in
2245 * the output processing functions called here as well as in the
2246 * echo processing function to protect the column state and space
2247 * left in the buffer.
2248 *
2249 * This code must be sure never to sleep through a hangup.
2250 *
2251 * Locking: output_lock to protect column state and space left
2252 * (note that the process_output*() functions take this
2253 * lock themselves)
2254 */
2255
2256static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2257 const unsigned char *buf, size_t nr)
2258{
2259 const unsigned char *b = buf;
2260 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2261 int c;
2262 ssize_t retval = 0;
2263
2264 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2265 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2266 retval = tty_check_change(tty);
2267 if (retval)
2268 return retval;
2269 }
2270
2271 down_read(&tty->termios_rwsem);
2272
2273 /* Write out any echoed characters that are still pending */
2274 process_echoes(tty);
2275
2276 add_wait_queue(&tty->write_wait, &wait);
2277 while (1) {
2278 if (signal_pending(current)) {
2279 retval = -ERESTARTSYS;
2280 break;
2281 }
2282 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2283 retval = -EIO;
2284 break;
2285 }
2286 if (O_OPOST(tty)) {
2287 while (nr > 0) {
2288 ssize_t num = process_output_block(tty, b, nr);
2289 if (num < 0) {
2290 if (num == -EAGAIN)
2291 break;
2292 retval = num;
2293 goto break_out;
2294 }
2295 b += num;
2296 nr -= num;
2297 if (nr == 0)
2298 break;
2299 c = *b;
2300 if (process_output(c, tty) < 0)
2301 break;
2302 b++; nr--;
2303 }
2304 if (tty->ops->flush_chars)
2305 tty->ops->flush_chars(tty);
2306 } else {
2307 struct n_tty_data *ldata = tty->disc_data;
2308
2309 while (nr > 0) {
2310 mutex_lock(&ldata->output_lock);
2311 c = tty->ops->write(tty, b, nr);
2312 mutex_unlock(&ldata->output_lock);
2313 if (c < 0) {
2314 retval = c;
2315 goto break_out;
2316 }
2317 if (!c)
2318 break;
2319 b += c;
2320 nr -= c;
2321 }
2322 }
2323 if (!nr)
2324 break;
2325 if (tty_io_nonblock(tty, file)) {
2326 retval = -EAGAIN;
2327 break;
2328 }
2329 up_read(&tty->termios_rwsem);
2330
2331 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2332
2333 down_read(&tty->termios_rwsem);
2334 }
2335break_out:
2336 remove_wait_queue(&tty->write_wait, &wait);
2337 if (nr && tty->fasync)
2338 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2339 up_read(&tty->termios_rwsem);
2340 return (b - buf) ? b - buf : retval;
2341}
2342
2343/**
2344 * n_tty_poll - poll method for N_TTY
2345 * @tty: terminal device
2346 * @file: file accessing it
2347 * @wait: poll table
2348 *
2349 * Called when the line discipline is asked to poll() for data or
2350 * for special events. This code is not serialized with respect to
2351 * other events save open/close.
2352 *
2353 * This code must be sure never to sleep through a hangup.
2354 * Called without the kernel lock held - fine
2355 */
2356
2357static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2358 poll_table *wait)
2359{
2360 __poll_t mask = 0;
2361
2362 poll_wait(file, &tty->read_wait, wait);
2363 poll_wait(file, &tty->write_wait, wait);
2364 if (input_available_p(tty, 1))
2365 mask |= EPOLLIN | EPOLLRDNORM;
2366 else {
2367 tty_buffer_flush_work(tty->port);
2368 if (input_available_p(tty, 1))
2369 mask |= EPOLLIN | EPOLLRDNORM;
2370 }
2371 if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2372 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2373 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2374 mask |= EPOLLHUP;
2375 if (tty_hung_up_p(file))
2376 mask |= EPOLLHUP;
2377 if (tty->ops->write && !tty_is_writelocked(tty) &&
2378 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2379 tty_write_room(tty) > 0)
2380 mask |= EPOLLOUT | EPOLLWRNORM;
2381 return mask;
2382}
2383
2384static unsigned long inq_canon(struct n_tty_data *ldata)
2385{
2386 size_t nr, head, tail;
2387
2388 if (ldata->canon_head == ldata->read_tail)
2389 return 0;
2390 head = ldata->canon_head;
2391 tail = ldata->read_tail;
2392 nr = head - tail;
2393 /* Skip EOF-chars.. */
2394 while (MASK(head) != MASK(tail)) {
2395 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2396 read_buf(ldata, tail) == __DISABLED_CHAR)
2397 nr--;
2398 tail++;
2399 }
2400 return nr;
2401}
2402
2403static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2404 unsigned int cmd, unsigned long arg)
2405{
2406 struct n_tty_data *ldata = tty->disc_data;
2407 int retval;
2408
2409 switch (cmd) {
2410 case TIOCOUTQ:
2411 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2412 case TIOCINQ:
2413 down_write(&tty->termios_rwsem);
2414 if (L_ICANON(tty) && !L_EXTPROC(tty))
2415 retval = inq_canon(ldata);
2416 else
2417 retval = read_cnt(ldata);
2418 up_write(&tty->termios_rwsem);
2419 return put_user(retval, (unsigned int __user *) arg);
2420 default:
2421 return n_tty_ioctl_helper(tty, file, cmd, arg);
2422 }
2423}
2424
2425static struct tty_ldisc_ops n_tty_ops = {
2426 .owner = THIS_MODULE,
2427 .num = N_TTY,
2428 .name = "n_tty",
2429 .open = n_tty_open,
2430 .close = n_tty_close,
2431 .flush_buffer = n_tty_flush_buffer,
2432 .read = n_tty_read,
2433 .write = n_tty_write,
2434 .ioctl = n_tty_ioctl,
2435 .set_termios = n_tty_set_termios,
2436 .poll = n_tty_poll,
2437 .receive_buf = n_tty_receive_buf,
2438 .write_wakeup = n_tty_write_wakeup,
2439 .receive_buf2 = n_tty_receive_buf2,
2440};
2441
2442/**
2443 * n_tty_inherit_ops - inherit N_TTY methods
2444 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2445 *
2446 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2447 */
2448
2449void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2450{
2451 *ops = n_tty_ops;
2452 ops->owner = NULL;
2453 ops->flags = 0;
2454}
2455EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2456
2457void __init n_tty_init(void)
2458{
2459 tty_register_ldisc(&n_tty_ops);
2460}