Loading...
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 /* # of chars looked ahead (to find software flow control chars) */
122 size_t lookahead_count;
123
124 /* protected by output lock */
125 unsigned int column;
126 unsigned int canon_column;
127 size_t echo_tail;
128
129 struct mutex atomic_read_lock;
130 struct mutex output_lock;
131};
132
133#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
134
135static inline size_t read_cnt(struct n_tty_data *ldata)
136{
137 return ldata->read_head - ldata->read_tail;
138}
139
140static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
141{
142 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
143}
144
145static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
146{
147 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
148}
149
150static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
151{
152 smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
153 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
154}
155
156static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
157{
158 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
159}
160
161/* If we are not echoing the data, perhaps this is a secret so erase it */
162static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
163{
164 bool icanon = !!L_ICANON(tty);
165 bool no_echo = !L_ECHO(tty);
166
167 if (icanon && no_echo)
168 memset(buffer, 0x00, size);
169}
170
171static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
172{
173 struct n_tty_data *ldata = tty->disc_data;
174 size_t size = N_TTY_BUF_SIZE - tail;
175 void *from = read_buf_addr(ldata, tail);
176
177 if (n > size) {
178 tty_audit_add_data(tty, from, size);
179 memcpy(to, from, size);
180 zero_buffer(tty, from, size);
181 to += size;
182 n -= size;
183 from = ldata->read_buf;
184 }
185
186 tty_audit_add_data(tty, from, n);
187 memcpy(to, from, n);
188 zero_buffer(tty, from, n);
189}
190
191/**
192 * n_tty_kick_worker - start input worker (if required)
193 * @tty: terminal
194 *
195 * Re-schedules the flip buffer work if it may have stopped.
196 *
197 * Locking:
198 * * Caller holds exclusive %termios_rwsem, or
199 * * n_tty_read()/consumer path:
200 * holds non-exclusive %termios_rwsem
201 */
202static void n_tty_kick_worker(struct tty_struct *tty)
203{
204 struct n_tty_data *ldata = tty->disc_data;
205
206 /* Did the input worker stop? Restart it */
207 if (unlikely(ldata->no_room)) {
208 ldata->no_room = 0;
209
210 WARN_RATELIMIT(tty->port->itty == NULL,
211 "scheduling with invalid itty\n");
212 /* see if ldisc has been killed - if so, this means that
213 * even though the ldisc has been halted and ->buf.work
214 * cancelled, ->buf.work is about to be rescheduled
215 */
216 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
217 "scheduling buffer work for halted ldisc\n");
218 tty_buffer_restart_work(tty->port);
219 }
220}
221
222static ssize_t chars_in_buffer(struct tty_struct *tty)
223{
224 struct n_tty_data *ldata = tty->disc_data;
225 ssize_t n = 0;
226
227 if (!ldata->icanon)
228 n = ldata->commit_head - ldata->read_tail;
229 else
230 n = ldata->canon_head - ldata->read_tail;
231 return n;
232}
233
234/**
235 * n_tty_write_wakeup - asynchronous I/O notifier
236 * @tty: tty device
237 *
238 * Required for the ptys, serial driver etc. since processes that attach
239 * themselves to the master and rely on ASYNC IO must be woken up.
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 * Locking:
310 * * n_tty_receive_buf()/producer path:
311 * caller holds non-exclusive %termios_rwsem
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. Called from
324 * n_tty_open() and n_tty_flush_buffer().
325 *
326 * Locking:
327 * * caller holds exclusive %termios_rwsem, or
328 * * (locking is not required)
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 ldata->lookahead_count = 0;
341}
342
343static void n_tty_packet_mode_flush(struct tty_struct *tty)
344{
345 unsigned long flags;
346
347 if (tty->link->ctrl.packet) {
348 spin_lock_irqsave(&tty->ctrl.lock, flags);
349 tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
350 spin_unlock_irqrestore(&tty->ctrl.lock, flags);
351 wake_up_interruptible(&tty->link->read_wait);
352 }
353}
354
355/**
356 * n_tty_flush_buffer - clean input queue
357 * @tty: terminal device
358 *
359 * Flush the input buffer. Called when the tty layer wants the buffer flushed
360 * (eg at hangup) or when the %N_TTY line discipline internally has to clean
361 * the pending queue (for example some signals).
362 *
363 * Holds %termios_rwsem to exclude producer/consumer while buffer indices are
364 * reset.
365 *
366 * Locking: %ctrl.lock, exclusive %termios_rwsem
367 */
368static void n_tty_flush_buffer(struct tty_struct *tty)
369{
370 down_write(&tty->termios_rwsem);
371 reset_buffer_flags(tty->disc_data);
372 n_tty_kick_worker(tty);
373
374 if (tty->link)
375 n_tty_packet_mode_flush(tty);
376 up_write(&tty->termios_rwsem);
377}
378
379/**
380 * is_utf8_continuation - utf8 multibyte check
381 * @c: byte to check
382 *
383 * Returns: true if the utf8 character @c is a multibyte continuation
384 * character. We use this to correctly compute the on-screen size of the
385 * character when printing.
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 character
398 * and the terminal is in unicode mode.
399 */
400static inline int is_continuation(unsigned char c, struct tty_struct *tty)
401{
402 return I_IUTF8(tty) && is_utf8_continuation(c);
403}
404
405/**
406 * do_output_char - output one character
407 * @c: character (or partial unicode symbol)
408 * @tty: terminal device
409 * @space: space available in tty driver write buffer
410 *
411 * This is a helper function that handles one output character (including
412 * special characters like TAB, CR, LF, etc.), doing OPOST processing and
413 * putting the results in the tty driver's write buffer.
414 *
415 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY.
416 * They simply aren't relevant in the world today. If you ever need them, add
417 * them here.
418 *
419 * Returns: the number of bytes of buffer space used or -1 if no space left.
420 *
421 * Locking: should be called under the %output_lock to protect the column state
422 * and space left in the buffer.
423 */
424static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
425{
426 struct n_tty_data *ldata = tty->disc_data;
427 int spaces;
428
429 if (!space)
430 return -1;
431
432 switch (c) {
433 case '\n':
434 if (O_ONLRET(tty))
435 ldata->column = 0;
436 if (O_ONLCR(tty)) {
437 if (space < 2)
438 return -1;
439 ldata->canon_column = ldata->column = 0;
440 tty->ops->write(tty, "\r\n", 2);
441 return 2;
442 }
443 ldata->canon_column = ldata->column;
444 break;
445 case '\r':
446 if (O_ONOCR(tty) && ldata->column == 0)
447 return 0;
448 if (O_OCRNL(tty)) {
449 c = '\n';
450 if (O_ONLRET(tty))
451 ldata->canon_column = ldata->column = 0;
452 break;
453 }
454 ldata->canon_column = ldata->column = 0;
455 break;
456 case '\t':
457 spaces = 8 - (ldata->column & 7);
458 if (O_TABDLY(tty) == XTABS) {
459 if (space < spaces)
460 return -1;
461 ldata->column += spaces;
462 tty->ops->write(tty, " ", spaces);
463 return spaces;
464 }
465 ldata->column += spaces;
466 break;
467 case '\b':
468 if (ldata->column > 0)
469 ldata->column--;
470 break;
471 default:
472 if (!iscntrl(c)) {
473 if (O_OLCUC(tty))
474 c = toupper(c);
475 if (!is_continuation(c, tty))
476 ldata->column++;
477 }
478 break;
479 }
480
481 tty_put_char(tty, c);
482 return 1;
483}
484
485/**
486 * process_output - output post processor
487 * @c: character (or partial unicode symbol)
488 * @tty: terminal device
489 *
490 * Output one character with OPOST processing.
491 *
492 * Returns: -1 when the output device is full and the character must be
493 * retried.
494 *
495 * Locking: %output_lock to protect column state and space left (also, this is
496 *called from n_tty_write() under the tty layer write lock).
497 */
498static int process_output(unsigned char c, struct tty_struct *tty)
499{
500 struct n_tty_data *ldata = tty->disc_data;
501 int space, retval;
502
503 mutex_lock(&ldata->output_lock);
504
505 space = tty_write_room(tty);
506 retval = do_output_char(c, tty, space);
507
508 mutex_unlock(&ldata->output_lock);
509 if (retval < 0)
510 return -1;
511 else
512 return 0;
513}
514
515/**
516 * process_output_block - block post processor
517 * @tty: terminal device
518 * @buf: character buffer
519 * @nr: number of bytes to output
520 *
521 * Output a block of characters with OPOST processing.
522 *
523 * This path is used to speed up block console writes, among other things when
524 * processing blocks of output data. It handles only the simple cases normally
525 * found and helps to generate blocks of symbols for the console driver and
526 * thus improve performance.
527 *
528 * Returns: the number of characters output.
529 *
530 * Locking: %output_lock to protect column state and space left (also, this is
531 * called from n_tty_write() under the tty layer write lock).
532 */
533static ssize_t process_output_block(struct tty_struct *tty,
534 const unsigned char *buf, unsigned int nr)
535{
536 struct n_tty_data *ldata = tty->disc_data;
537 int space;
538 int i;
539 const unsigned char *cp;
540
541 mutex_lock(&ldata->output_lock);
542
543 space = tty_write_room(tty);
544 if (space <= 0) {
545 mutex_unlock(&ldata->output_lock);
546 return space;
547 }
548 if (nr > space)
549 nr = space;
550
551 for (i = 0, cp = buf; i < nr; i++, cp++) {
552 unsigned char c = *cp;
553
554 switch (c) {
555 case '\n':
556 if (O_ONLRET(tty))
557 ldata->column = 0;
558 if (O_ONLCR(tty))
559 goto break_out;
560 ldata->canon_column = ldata->column;
561 break;
562 case '\r':
563 if (O_ONOCR(tty) && ldata->column == 0)
564 goto break_out;
565 if (O_OCRNL(tty))
566 goto break_out;
567 ldata->canon_column = ldata->column = 0;
568 break;
569 case '\t':
570 goto break_out;
571 case '\b':
572 if (ldata->column > 0)
573 ldata->column--;
574 break;
575 default:
576 if (!iscntrl(c)) {
577 if (O_OLCUC(tty))
578 goto break_out;
579 if (!is_continuation(c, tty))
580 ldata->column++;
581 }
582 break;
583 }
584 }
585break_out:
586 i = tty->ops->write(tty, buf, i);
587
588 mutex_unlock(&ldata->output_lock);
589 return i;
590}
591
592/**
593 * __process_echoes - write pending echo characters
594 * @tty: terminal device
595 *
596 * Write previously buffered echo (and other ldisc-generated) characters to the
597 * tty.
598 *
599 * Characters generated by the ldisc (including echoes) need to be buffered
600 * because the driver's write buffer can fill during heavy program output.
601 * Echoing straight to the driver will often fail under these conditions,
602 * causing lost characters and resulting mismatches of ldisc state information.
603 *
604 * Since the ldisc state must represent the characters actually sent to the
605 * driver at the time of the write, operations like certain changes in column
606 * state are also saved in the buffer and executed here.
607 *
608 * A circular fifo buffer is used so that the most recent characters are
609 * prioritized. Also, when control characters are echoed with a prefixed "^",
610 * the pair is treated atomically and thus not separated.
611 *
612 * Locking: callers must hold %output_lock.
613 */
614static size_t __process_echoes(struct tty_struct *tty)
615{
616 struct n_tty_data *ldata = tty->disc_data;
617 int space, old_space;
618 size_t tail;
619 unsigned char c;
620
621 old_space = space = tty_write_room(tty);
622
623 tail = ldata->echo_tail;
624 while (MASK(ldata->echo_commit) != MASK(tail)) {
625 c = echo_buf(ldata, tail);
626 if (c == ECHO_OP_START) {
627 unsigned char op;
628 int no_space_left = 0;
629
630 /*
631 * Since add_echo_byte() is called without holding
632 * output_lock, we might see only portion of multi-byte
633 * operation.
634 */
635 if (MASK(ldata->echo_commit) == MASK(tail + 1))
636 goto not_yet_stored;
637 /*
638 * If the buffer byte is the start of a multi-byte
639 * operation, get the next byte, which is either the
640 * op code or a control character value.
641 */
642 op = echo_buf(ldata, tail + 1);
643
644 switch (op) {
645 case ECHO_OP_ERASE_TAB: {
646 unsigned int num_chars, num_bs;
647
648 if (MASK(ldata->echo_commit) == MASK(tail + 2))
649 goto not_yet_stored;
650 num_chars = echo_buf(ldata, tail + 2);
651
652 /*
653 * Determine how many columns to go back
654 * in order to erase the tab.
655 * This depends on the number of columns
656 * used by other characters within the tab
657 * area. If this (modulo 8) count is from
658 * the start of input rather than from a
659 * previous tab, we offset by canon column.
660 * Otherwise, tab spacing is normal.
661 */
662 if (!(num_chars & 0x80))
663 num_chars += ldata->canon_column;
664 num_bs = 8 - (num_chars & 7);
665
666 if (num_bs > space) {
667 no_space_left = 1;
668 break;
669 }
670 space -= num_bs;
671 while (num_bs--) {
672 tty_put_char(tty, '\b');
673 if (ldata->column > 0)
674 ldata->column--;
675 }
676 tail += 3;
677 break;
678 }
679 case ECHO_OP_SET_CANON_COL:
680 ldata->canon_column = ldata->column;
681 tail += 2;
682 break;
683
684 case ECHO_OP_MOVE_BACK_COL:
685 if (ldata->column > 0)
686 ldata->column--;
687 tail += 2;
688 break;
689
690 case ECHO_OP_START:
691 /* This is an escaped echo op start code */
692 if (!space) {
693 no_space_left = 1;
694 break;
695 }
696 tty_put_char(tty, ECHO_OP_START);
697 ldata->column++;
698 space--;
699 tail += 2;
700 break;
701
702 default:
703 /*
704 * If the op is not a special byte code,
705 * it is a ctrl char tagged to be echoed
706 * as "^X" (where X is the letter
707 * representing the control char).
708 * Note that we must ensure there is
709 * enough space for the whole ctrl pair.
710 *
711 */
712 if (space < 2) {
713 no_space_left = 1;
714 break;
715 }
716 tty_put_char(tty, '^');
717 tty_put_char(tty, op ^ 0100);
718 ldata->column += 2;
719 space -= 2;
720 tail += 2;
721 }
722
723 if (no_space_left)
724 break;
725 } else {
726 if (O_OPOST(tty)) {
727 int retval = do_output_char(c, tty, space);
728 if (retval < 0)
729 break;
730 space -= retval;
731 } else {
732 if (!space)
733 break;
734 tty_put_char(tty, c);
735 space -= 1;
736 }
737 tail += 1;
738 }
739 }
740
741 /* If the echo buffer is nearly full (so that the possibility exists
742 * of echo overrun before the next commit), then discard enough
743 * data at the tail to prevent a subsequent overrun */
744 while (ldata->echo_commit > tail &&
745 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
746 if (echo_buf(ldata, tail) == ECHO_OP_START) {
747 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
748 tail += 3;
749 else
750 tail += 2;
751 } else
752 tail++;
753 }
754
755 not_yet_stored:
756 ldata->echo_tail = tail;
757 return old_space - space;
758}
759
760static void commit_echoes(struct tty_struct *tty)
761{
762 struct n_tty_data *ldata = tty->disc_data;
763 size_t nr, old, echoed;
764 size_t head;
765
766 mutex_lock(&ldata->output_lock);
767 head = ldata->echo_head;
768 ldata->echo_mark = head;
769 old = ldata->echo_commit - ldata->echo_tail;
770
771 /* Process committed echoes if the accumulated # of bytes
772 * is over the threshold (and try again each time another
773 * block is accumulated) */
774 nr = head - ldata->echo_tail;
775 if (nr < ECHO_COMMIT_WATERMARK ||
776 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
777 mutex_unlock(&ldata->output_lock);
778 return;
779 }
780
781 ldata->echo_commit = head;
782 echoed = __process_echoes(tty);
783 mutex_unlock(&ldata->output_lock);
784
785 if (echoed && tty->ops->flush_chars)
786 tty->ops->flush_chars(tty);
787}
788
789static void process_echoes(struct tty_struct *tty)
790{
791 struct n_tty_data *ldata = tty->disc_data;
792 size_t echoed;
793
794 if (ldata->echo_mark == ldata->echo_tail)
795 return;
796
797 mutex_lock(&ldata->output_lock);
798 ldata->echo_commit = ldata->echo_mark;
799 echoed = __process_echoes(tty);
800 mutex_unlock(&ldata->output_lock);
801
802 if (echoed && tty->ops->flush_chars)
803 tty->ops->flush_chars(tty);
804}
805
806/* NB: echo_mark and echo_head should be equivalent here */
807static void flush_echoes(struct tty_struct *tty)
808{
809 struct n_tty_data *ldata = tty->disc_data;
810
811 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
812 ldata->echo_commit == ldata->echo_head)
813 return;
814
815 mutex_lock(&ldata->output_lock);
816 ldata->echo_commit = ldata->echo_head;
817 __process_echoes(tty);
818 mutex_unlock(&ldata->output_lock);
819}
820
821/**
822 * add_echo_byte - add a byte to the echo buffer
823 * @c: unicode byte to echo
824 * @ldata: n_tty data
825 *
826 * Add a character or operation byte to the echo buffer.
827 */
828static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
829{
830 *echo_buf_addr(ldata, ldata->echo_head) = c;
831 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
832 ldata->echo_head++;
833}
834
835/**
836 * echo_move_back_col - add operation to move back a column
837 * @ldata: n_tty data
838 *
839 * Add an operation to the echo buffer to move back one column.
840 */
841static void echo_move_back_col(struct n_tty_data *ldata)
842{
843 add_echo_byte(ECHO_OP_START, ldata);
844 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
845}
846
847/**
848 * echo_set_canon_col - add operation to set the canon column
849 * @ldata: n_tty data
850 *
851 * Add an operation to the echo buffer to set the canon column to the current
852 * column.
853 */
854static void echo_set_canon_col(struct n_tty_data *ldata)
855{
856 add_echo_byte(ECHO_OP_START, ldata);
857 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
858}
859
860/**
861 * echo_erase_tab - add operation to erase a tab
862 * @num_chars: number of character columns already used
863 * @after_tab: true if num_chars starts after a previous tab
864 * @ldata: n_tty data
865 *
866 * Add an operation to the echo buffer to erase a tab.
867 *
868 * Called by the eraser function, which knows how many character columns have
869 * been used since either a previous tab or the start of input. This
870 * information will be used later, along with canon column (if applicable), to
871 * go back the correct number of columns.
872 */
873static void echo_erase_tab(unsigned int num_chars, int after_tab,
874 struct n_tty_data *ldata)
875{
876 add_echo_byte(ECHO_OP_START, ldata);
877 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
878
879 /* We only need to know this modulo 8 (tab spacing) */
880 num_chars &= 7;
881
882 /* Set the high bit as a flag if num_chars is after a previous tab */
883 if (after_tab)
884 num_chars |= 0x80;
885
886 add_echo_byte(num_chars, ldata);
887}
888
889/**
890 * echo_char_raw - echo a character raw
891 * @c: unicode byte to echo
892 * @ldata: line disc data
893 *
894 * Echo user input back onto the screen. This must be called only when
895 * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
896 *
897 * This variant does not treat control characters specially.
898 */
899static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
900{
901 if (c == ECHO_OP_START) {
902 add_echo_byte(ECHO_OP_START, ldata);
903 add_echo_byte(ECHO_OP_START, ldata);
904 } else {
905 add_echo_byte(c, ldata);
906 }
907}
908
909/**
910 * echo_char - echo a character
911 * @c: unicode byte to echo
912 * @tty: terminal device
913 *
914 * Echo user input back onto the screen. This must be called only when
915 * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
916 *
917 * This variant tags control characters to be echoed as "^X" (where X is the
918 * letter representing the control char).
919 */
920static void echo_char(unsigned char c, struct tty_struct *tty)
921{
922 struct n_tty_data *ldata = tty->disc_data;
923
924 if (c == ECHO_OP_START) {
925 add_echo_byte(ECHO_OP_START, ldata);
926 add_echo_byte(ECHO_OP_START, ldata);
927 } else {
928 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
929 add_echo_byte(ECHO_OP_START, ldata);
930 add_echo_byte(c, ldata);
931 }
932}
933
934/**
935 * finish_erasing - complete erase
936 * @ldata: n_tty data
937 */
938static inline void finish_erasing(struct n_tty_data *ldata)
939{
940 if (ldata->erasing) {
941 echo_char_raw('/', ldata);
942 ldata->erasing = 0;
943 }
944}
945
946/**
947 * eraser - handle erase function
948 * @c: character input
949 * @tty: terminal device
950 *
951 * Perform erase and necessary output when an erase character is present in the
952 * stream from the driver layer. Handles the complexities of UTF-8 multibyte
953 * symbols.
954 *
955 * Locking: n_tty_receive_buf()/producer path:
956 * caller holds non-exclusive %termios_rwsem
957 */
958static void eraser(unsigned char c, struct tty_struct *tty)
959{
960 struct n_tty_data *ldata = tty->disc_data;
961 enum { ERASE, WERASE, KILL } kill_type;
962 size_t head;
963 size_t cnt;
964 int seen_alnums;
965
966 if (ldata->read_head == ldata->canon_head) {
967 /* process_output('\a', tty); */ /* what do you think? */
968 return;
969 }
970 if (c == ERASE_CHAR(tty))
971 kill_type = ERASE;
972 else if (c == WERASE_CHAR(tty))
973 kill_type = WERASE;
974 else {
975 if (!L_ECHO(tty)) {
976 ldata->read_head = ldata->canon_head;
977 return;
978 }
979 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
980 ldata->read_head = ldata->canon_head;
981 finish_erasing(ldata);
982 echo_char(KILL_CHAR(tty), tty);
983 /* Add a newline if ECHOK is on and ECHOKE is off. */
984 if (L_ECHOK(tty))
985 echo_char_raw('\n', ldata);
986 return;
987 }
988 kill_type = KILL;
989 }
990
991 seen_alnums = 0;
992 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
993 head = ldata->read_head;
994
995 /* erase a single possibly multibyte character */
996 do {
997 head--;
998 c = read_buf(ldata, head);
999 } while (is_continuation(c, tty) &&
1000 MASK(head) != MASK(ldata->canon_head));
1001
1002 /* do not partially erase */
1003 if (is_continuation(c, tty))
1004 break;
1005
1006 if (kill_type == WERASE) {
1007 /* Equivalent to BSD's ALTWERASE. */
1008 if (isalnum(c) || c == '_')
1009 seen_alnums++;
1010 else if (seen_alnums)
1011 break;
1012 }
1013 cnt = ldata->read_head - head;
1014 ldata->read_head = head;
1015 if (L_ECHO(tty)) {
1016 if (L_ECHOPRT(tty)) {
1017 if (!ldata->erasing) {
1018 echo_char_raw('\\', ldata);
1019 ldata->erasing = 1;
1020 }
1021 /* if cnt > 1, output a multi-byte character */
1022 echo_char(c, tty);
1023 while (--cnt > 0) {
1024 head++;
1025 echo_char_raw(read_buf(ldata, head), ldata);
1026 echo_move_back_col(ldata);
1027 }
1028 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1029 echo_char(ERASE_CHAR(tty), tty);
1030 } else if (c == '\t') {
1031 unsigned int num_chars = 0;
1032 int after_tab = 0;
1033 size_t tail = ldata->read_head;
1034
1035 /*
1036 * Count the columns used for characters
1037 * since the start of input or after a
1038 * previous tab.
1039 * This info is used to go back the correct
1040 * number of columns.
1041 */
1042 while (MASK(tail) != MASK(ldata->canon_head)) {
1043 tail--;
1044 c = read_buf(ldata, tail);
1045 if (c == '\t') {
1046 after_tab = 1;
1047 break;
1048 } else if (iscntrl(c)) {
1049 if (L_ECHOCTL(tty))
1050 num_chars += 2;
1051 } else if (!is_continuation(c, tty)) {
1052 num_chars++;
1053 }
1054 }
1055 echo_erase_tab(num_chars, after_tab, ldata);
1056 } else {
1057 if (iscntrl(c) && L_ECHOCTL(tty)) {
1058 echo_char_raw('\b', ldata);
1059 echo_char_raw(' ', ldata);
1060 echo_char_raw('\b', ldata);
1061 }
1062 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1063 echo_char_raw('\b', ldata);
1064 echo_char_raw(' ', ldata);
1065 echo_char_raw('\b', ldata);
1066 }
1067 }
1068 }
1069 if (kill_type == ERASE)
1070 break;
1071 }
1072 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1073 finish_erasing(ldata);
1074}
1075
1076
1077static void __isig(int sig, struct tty_struct *tty)
1078{
1079 struct pid *tty_pgrp = tty_get_pgrp(tty);
1080 if (tty_pgrp) {
1081 kill_pgrp(tty_pgrp, sig, 1);
1082 put_pid(tty_pgrp);
1083 }
1084}
1085
1086/**
1087 * isig - handle the ISIG optio
1088 * @sig: signal
1089 * @tty: terminal
1090 *
1091 * Called when a signal is being sent due to terminal input. Called from the
1092 * &tty_driver.receive_buf() path, so serialized.
1093 *
1094 * Performs input and output flush if !NOFLSH. In this context, the echo
1095 * buffer is 'output'. The signal is processed first to alert any current
1096 * readers or writers to discontinue and exit their i/o loops.
1097 *
1098 * Locking: %ctrl.lock
1099 */
1100static void isig(int sig, struct tty_struct *tty)
1101{
1102 struct n_tty_data *ldata = tty->disc_data;
1103
1104 if (L_NOFLSH(tty)) {
1105 /* signal only */
1106 __isig(sig, tty);
1107
1108 } else { /* signal and flush */
1109 up_read(&tty->termios_rwsem);
1110 down_write(&tty->termios_rwsem);
1111
1112 __isig(sig, tty);
1113
1114 /* clear echo buffer */
1115 mutex_lock(&ldata->output_lock);
1116 ldata->echo_head = ldata->echo_tail = 0;
1117 ldata->echo_mark = ldata->echo_commit = 0;
1118 mutex_unlock(&ldata->output_lock);
1119
1120 /* clear output buffer */
1121 tty_driver_flush_buffer(tty);
1122
1123 /* clear input buffer */
1124 reset_buffer_flags(tty->disc_data);
1125
1126 /* notify pty master of flush */
1127 if (tty->link)
1128 n_tty_packet_mode_flush(tty);
1129
1130 up_write(&tty->termios_rwsem);
1131 down_read(&tty->termios_rwsem);
1132 }
1133}
1134
1135/**
1136 * n_tty_receive_break - handle break
1137 * @tty: terminal
1138 *
1139 * An RS232 break event has been hit in the incoming bitstream. This can cause
1140 * a variety of events depending upon the termios settings.
1141 *
1142 * Locking: n_tty_receive_buf()/producer path:
1143 * caller holds non-exclusive termios_rwsem
1144 *
1145 * Note: may get exclusive %termios_rwsem if flushing input buffer
1146 */
1147static void n_tty_receive_break(struct tty_struct *tty)
1148{
1149 struct n_tty_data *ldata = tty->disc_data;
1150
1151 if (I_IGNBRK(tty))
1152 return;
1153 if (I_BRKINT(tty)) {
1154 isig(SIGINT, tty);
1155 return;
1156 }
1157 if (I_PARMRK(tty)) {
1158 put_tty_queue('\377', ldata);
1159 put_tty_queue('\0', ldata);
1160 }
1161 put_tty_queue('\0', ldata);
1162}
1163
1164/**
1165 * n_tty_receive_overrun - handle overrun reporting
1166 * @tty: terminal
1167 *
1168 * Data arrived faster than we could process it. While the tty driver has
1169 * flagged this the bits that were missed are gone forever.
1170 *
1171 * Called from the receive_buf path so single threaded. Does not need locking
1172 * as num_overrun and overrun_time are function private.
1173 */
1174static void n_tty_receive_overrun(struct tty_struct *tty)
1175{
1176 struct n_tty_data *ldata = tty->disc_data;
1177
1178 ldata->num_overrun++;
1179 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1180 time_after(ldata->overrun_time, jiffies)) {
1181 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1182 ldata->overrun_time = jiffies;
1183 ldata->num_overrun = 0;
1184 }
1185}
1186
1187/**
1188 * n_tty_receive_parity_error - error notifier
1189 * @tty: terminal device
1190 * @c: character
1191 *
1192 * Process a parity error and queue the right data to indicate the error case
1193 * if necessary.
1194 *
1195 * Locking: n_tty_receive_buf()/producer path:
1196 * caller holds non-exclusive %termios_rwsem
1197 */
1198static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1199{
1200 struct n_tty_data *ldata = tty->disc_data;
1201
1202 if (I_INPCK(tty)) {
1203 if (I_IGNPAR(tty))
1204 return;
1205 if (I_PARMRK(tty)) {
1206 put_tty_queue('\377', ldata);
1207 put_tty_queue('\0', ldata);
1208 put_tty_queue(c, ldata);
1209 } else
1210 put_tty_queue('\0', ldata);
1211 } else
1212 put_tty_queue(c, ldata);
1213}
1214
1215static void
1216n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1217{
1218 isig(signal, tty);
1219 if (I_IXON(tty))
1220 start_tty(tty);
1221 if (L_ECHO(tty)) {
1222 echo_char(c, tty);
1223 commit_echoes(tty);
1224 } else
1225 process_echoes(tty);
1226}
1227
1228static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
1229{
1230 return c == START_CHAR(tty) || c == STOP_CHAR(tty);
1231}
1232
1233/**
1234 * n_tty_receive_char_flow_ctrl - receive flow control chars
1235 * @tty: terminal device
1236 * @c: character
1237 * @lookahead_done: lookahead has processed this character already
1238 *
1239 * Receive and process flow control character actions.
1240 *
1241 * In case lookahead for flow control chars already handled the character in
1242 * advance to the normal receive, the actions are skipped during normal
1243 * receive.
1244 *
1245 * Returns true if @c is consumed as flow-control character, the character
1246 * must not be treated as normal character.
1247 */
1248static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c,
1249 bool lookahead_done)
1250{
1251 if (!n_tty_is_char_flow_ctrl(tty, c))
1252 return false;
1253
1254 if (lookahead_done)
1255 return true;
1256
1257 if (c == START_CHAR(tty)) {
1258 start_tty(tty);
1259 process_echoes(tty);
1260 return true;
1261 }
1262
1263 /* STOP_CHAR */
1264 stop_tty(tty);
1265 return true;
1266}
1267
1268static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c,
1269 bool lookahead_done)
1270{
1271 struct n_tty_data *ldata = tty->disc_data;
1272
1273 if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
1274 return;
1275
1276 if (L_ISIG(tty)) {
1277 if (c == INTR_CHAR(tty)) {
1278 n_tty_receive_signal_char(tty, SIGINT, c);
1279 return;
1280 } else if (c == QUIT_CHAR(tty)) {
1281 n_tty_receive_signal_char(tty, SIGQUIT, c);
1282 return;
1283 } else if (c == SUSP_CHAR(tty)) {
1284 n_tty_receive_signal_char(tty, SIGTSTP, c);
1285 return;
1286 }
1287 }
1288
1289 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1290 start_tty(tty);
1291 process_echoes(tty);
1292 }
1293
1294 if (c == '\r') {
1295 if (I_IGNCR(tty))
1296 return;
1297 if (I_ICRNL(tty))
1298 c = '\n';
1299 } else if (c == '\n' && I_INLCR(tty))
1300 c = '\r';
1301
1302 if (ldata->icanon) {
1303 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1304 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1305 eraser(c, tty);
1306 commit_echoes(tty);
1307 return;
1308 }
1309 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1310 ldata->lnext = 1;
1311 if (L_ECHO(tty)) {
1312 finish_erasing(ldata);
1313 if (L_ECHOCTL(tty)) {
1314 echo_char_raw('^', ldata);
1315 echo_char_raw('\b', ldata);
1316 commit_echoes(tty);
1317 }
1318 }
1319 return;
1320 }
1321 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1322 size_t tail = ldata->canon_head;
1323
1324 finish_erasing(ldata);
1325 echo_char(c, tty);
1326 echo_char_raw('\n', ldata);
1327 while (MASK(tail) != MASK(ldata->read_head)) {
1328 echo_char(read_buf(ldata, tail), tty);
1329 tail++;
1330 }
1331 commit_echoes(tty);
1332 return;
1333 }
1334 if (c == '\n') {
1335 if (L_ECHO(tty) || L_ECHONL(tty)) {
1336 echo_char_raw('\n', ldata);
1337 commit_echoes(tty);
1338 }
1339 goto handle_newline;
1340 }
1341 if (c == EOF_CHAR(tty)) {
1342 c = __DISABLED_CHAR;
1343 goto handle_newline;
1344 }
1345 if ((c == EOL_CHAR(tty)) ||
1346 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1347 /*
1348 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1349 */
1350 if (L_ECHO(tty)) {
1351 /* Record the column of first canon char. */
1352 if (ldata->canon_head == ldata->read_head)
1353 echo_set_canon_col(ldata);
1354 echo_char(c, tty);
1355 commit_echoes(tty);
1356 }
1357 /*
1358 * XXX does PARMRK doubling happen for
1359 * EOL_CHAR and EOL2_CHAR?
1360 */
1361 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1362 put_tty_queue(c, ldata);
1363
1364handle_newline:
1365 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1366 put_tty_queue(c, ldata);
1367 smp_store_release(&ldata->canon_head, ldata->read_head);
1368 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1369 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1370 return;
1371 }
1372 }
1373
1374 if (L_ECHO(tty)) {
1375 finish_erasing(ldata);
1376 if (c == '\n')
1377 echo_char_raw('\n', ldata);
1378 else {
1379 /* Record the column of first canon char. */
1380 if (ldata->canon_head == ldata->read_head)
1381 echo_set_canon_col(ldata);
1382 echo_char(c, tty);
1383 }
1384 commit_echoes(tty);
1385 }
1386
1387 /* PARMRK doubling check */
1388 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1389 put_tty_queue(c, ldata);
1390
1391 put_tty_queue(c, ldata);
1392}
1393
1394/**
1395 * n_tty_receive_char - perform processing
1396 * @tty: terminal device
1397 * @c: character
1398 *
1399 * Process an individual character of input received from the driver. This is
1400 * serialized with respect to itself by the rules for the driver above.
1401 *
1402 * Locking: n_tty_receive_buf()/producer path:
1403 * caller holds non-exclusive %termios_rwsem
1404 * publishes canon_head if canonical mode is active
1405 */
1406static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1407{
1408 struct n_tty_data *ldata = tty->disc_data;
1409
1410 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1411 start_tty(tty);
1412 process_echoes(tty);
1413 }
1414 if (L_ECHO(tty)) {
1415 finish_erasing(ldata);
1416 /* Record the column of first canon char. */
1417 if (ldata->canon_head == ldata->read_head)
1418 echo_set_canon_col(ldata);
1419 echo_char(c, tty);
1420 commit_echoes(tty);
1421 }
1422 /* PARMRK doubling check */
1423 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1424 put_tty_queue(c, ldata);
1425 put_tty_queue(c, ldata);
1426}
1427
1428static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c,
1429 bool lookahead_done)
1430{
1431 if (I_ISTRIP(tty))
1432 c &= 0x7f;
1433 if (I_IUCLC(tty) && L_IEXTEN(tty))
1434 c = tolower(c);
1435
1436 if (I_IXON(tty)) {
1437 if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
1438 tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1439 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1440 c != SUSP_CHAR(tty)) {
1441 start_tty(tty);
1442 process_echoes(tty);
1443 }
1444 }
1445}
1446
1447static void
1448n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1449{
1450 switch (flag) {
1451 case TTY_BREAK:
1452 n_tty_receive_break(tty);
1453 break;
1454 case TTY_PARITY:
1455 case TTY_FRAME:
1456 n_tty_receive_parity_error(tty, c);
1457 break;
1458 case TTY_OVERRUN:
1459 n_tty_receive_overrun(tty);
1460 break;
1461 default:
1462 tty_err(tty, "unknown flag %d\n", flag);
1463 break;
1464 }
1465}
1466
1467static void
1468n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1469{
1470 struct n_tty_data *ldata = tty->disc_data;
1471
1472 ldata->lnext = 0;
1473 if (likely(flag == TTY_NORMAL)) {
1474 if (I_ISTRIP(tty))
1475 c &= 0x7f;
1476 if (I_IUCLC(tty) && L_IEXTEN(tty))
1477 c = tolower(c);
1478 n_tty_receive_char(tty, c);
1479 } else
1480 n_tty_receive_char_flagged(tty, c, flag);
1481}
1482
1483/* Caller must ensure count > 0 */
1484static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const unsigned char *cp,
1485 const unsigned char *fp, unsigned int count)
1486{
1487 struct n_tty_data *ldata = tty->disc_data;
1488 unsigned char flag = TTY_NORMAL;
1489
1490 ldata->lookahead_count += count;
1491
1492 if (!I_IXON(tty))
1493 return;
1494
1495 while (count--) {
1496 if (fp)
1497 flag = *fp++;
1498 if (likely(flag == TTY_NORMAL))
1499 n_tty_receive_char_flow_ctrl(tty, *cp, false);
1500 cp++;
1501 }
1502}
1503
1504static void
1505n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1506 const char *fp, int count)
1507{
1508 struct n_tty_data *ldata = tty->disc_data;
1509 size_t n, head;
1510
1511 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1512 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1513 memcpy(read_buf_addr(ldata, head), cp, n);
1514 ldata->read_head += n;
1515 cp += n;
1516 count -= n;
1517
1518 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1519 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1520 memcpy(read_buf_addr(ldata, head), cp, n);
1521 ldata->read_head += n;
1522}
1523
1524static void
1525n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1526 const char *fp, int count)
1527{
1528 struct n_tty_data *ldata = tty->disc_data;
1529 char flag = TTY_NORMAL;
1530
1531 while (count--) {
1532 if (fp)
1533 flag = *fp++;
1534 if (likely(flag == TTY_NORMAL))
1535 put_tty_queue(*cp++, ldata);
1536 else
1537 n_tty_receive_char_flagged(tty, *cp++, flag);
1538 }
1539}
1540
1541static void
1542n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1543 const char *fp, int count, bool lookahead_done)
1544{
1545 char flag = TTY_NORMAL;
1546
1547 while (count--) {
1548 if (fp)
1549 flag = *fp++;
1550 if (likely(flag == TTY_NORMAL))
1551 n_tty_receive_char_closing(tty, *cp++, lookahead_done);
1552 }
1553}
1554
1555static void n_tty_receive_buf_standard(struct tty_struct *tty,
1556 const unsigned char *cp, const char *fp, int count, bool lookahead_done)
1557{
1558 struct n_tty_data *ldata = tty->disc_data;
1559 char flag = TTY_NORMAL;
1560
1561 while (count--) {
1562 unsigned char c = *cp++;
1563
1564 if (fp)
1565 flag = *fp++;
1566
1567 if (ldata->lnext) {
1568 n_tty_receive_char_lnext(tty, c, flag);
1569 continue;
1570 }
1571
1572 if (unlikely(flag != TTY_NORMAL)) {
1573 n_tty_receive_char_flagged(tty, c, flag);
1574 continue;
1575 }
1576
1577 if (I_ISTRIP(tty))
1578 c &= 0x7f;
1579 if (I_IUCLC(tty) && L_IEXTEN(tty))
1580 c = tolower(c);
1581 if (L_EXTPROC(tty)) {
1582 put_tty_queue(c, ldata);
1583 continue;
1584 }
1585
1586 if (test_bit(c, ldata->char_map))
1587 n_tty_receive_char_special(tty, c, lookahead_done);
1588 else
1589 n_tty_receive_char(tty, c);
1590 }
1591}
1592
1593static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1594 const char *fp, int count)
1595{
1596 struct n_tty_data *ldata = tty->disc_data;
1597 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1598 size_t la_count = min_t(size_t, ldata->lookahead_count, count);
1599
1600 if (ldata->real_raw)
1601 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1602 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1603 n_tty_receive_buf_raw(tty, cp, fp, count);
1604 else if (tty->closing && !L_EXTPROC(tty)) {
1605 if (la_count > 0)
1606 n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
1607 if (count > la_count)
1608 n_tty_receive_buf_closing(tty, cp, fp, count - la_count, false);
1609 } else {
1610 if (la_count > 0)
1611 n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
1612 if (count > la_count)
1613 n_tty_receive_buf_standard(tty, cp, fp, count - la_count, false);
1614
1615 flush_echoes(tty);
1616 if (tty->ops->flush_chars)
1617 tty->ops->flush_chars(tty);
1618 }
1619
1620 ldata->lookahead_count -= la_count;
1621
1622 if (ldata->icanon && !L_EXTPROC(tty))
1623 return;
1624
1625 /* publish read_head to consumer */
1626 smp_store_release(&ldata->commit_head, ldata->read_head);
1627
1628 if (read_cnt(ldata)) {
1629 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1630 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1631 }
1632}
1633
1634/**
1635 * n_tty_receive_buf_common - process input
1636 * @tty: device to receive input
1637 * @cp: input chars
1638 * @fp: flags for each char (if %NULL, all chars are %TTY_NORMAL)
1639 * @count: number of input chars in @cp
1640 * @flow: enable flow control
1641 *
1642 * Called by the terminal driver when a block of characters has been received.
1643 * This function must be called from soft contexts not from interrupt context.
1644 * The driver is responsible for making calls one at a time and in order (or
1645 * using flush_to_ldisc()).
1646 *
1647 * Returns: the # of input chars from @cp which were processed.
1648 *
1649 * In canonical mode, the maximum line length is 4096 chars (including the line
1650 * termination char); lines longer than 4096 chars are truncated. After 4095
1651 * chars, input data is still processed but not stored. Overflow processing
1652 * ensures the tty can always receive more input until at least one line can be
1653 * read.
1654 *
1655 * In non-canonical mode, the read buffer will only accept 4095 chars; this
1656 * provides the necessary space for a newline char if the input mode is
1657 * switched to canonical.
1658 *
1659 * Note it is possible for the read buffer to _contain_ 4096 chars in
1660 * non-canonical mode: the read buffer could already contain the maximum canon
1661 * line of 4096 chars when the mode is switched to non-canonical.
1662 *
1663 * Locking: n_tty_receive_buf()/producer path:
1664 * claims non-exclusive %termios_rwsem
1665 * publishes commit_head or canon_head
1666 */
1667static int
1668n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1669 const char *fp, int count, int flow)
1670{
1671 struct n_tty_data *ldata = tty->disc_data;
1672 int room, n, rcvd = 0, overflow;
1673
1674 down_read(&tty->termios_rwsem);
1675
1676 do {
1677 /*
1678 * When PARMRK is set, each input char may take up to 3 chars
1679 * in the read buf; reduce the buffer space avail by 3x
1680 *
1681 * If we are doing input canonicalization, and there are no
1682 * pending newlines, let characters through without limit, so
1683 * that erase characters will be handled. Other excess
1684 * characters will be beeped.
1685 *
1686 * paired with store in *_copy_from_read_buf() -- guarantees
1687 * the consumer has loaded the data in read_buf up to the new
1688 * read_tail (so this producer will not overwrite unread data)
1689 */
1690 size_t tail = smp_load_acquire(&ldata->read_tail);
1691
1692 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1693 if (I_PARMRK(tty))
1694 room = (room + 2) / 3;
1695 room--;
1696 if (room <= 0) {
1697 overflow = ldata->icanon && ldata->canon_head == tail;
1698 if (overflow && room < 0)
1699 ldata->read_head--;
1700 room = overflow;
1701 ldata->no_room = flow && !room;
1702 } else
1703 overflow = 0;
1704
1705 n = min(count, room);
1706 if (!n)
1707 break;
1708
1709 /* ignore parity errors if handling overflow */
1710 if (!overflow || !fp || *fp != TTY_PARITY)
1711 __receive_buf(tty, cp, fp, n);
1712
1713 cp += n;
1714 if (fp)
1715 fp += n;
1716 count -= n;
1717 rcvd += n;
1718 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1719
1720 tty->receive_room = room;
1721
1722 /* Unthrottle if handling overflow on pty */
1723 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1724 if (overflow) {
1725 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1726 tty_unthrottle_safe(tty);
1727 __tty_set_flow_change(tty, 0);
1728 }
1729 } else
1730 n_tty_check_throttle(tty);
1731
1732 up_read(&tty->termios_rwsem);
1733
1734 return rcvd;
1735}
1736
1737static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1738 const char *fp, int count)
1739{
1740 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1741}
1742
1743static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1744 const char *fp, int count)
1745{
1746 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1747}
1748
1749/**
1750 * n_tty_set_termios - termios data changed
1751 * @tty: terminal
1752 * @old: previous data
1753 *
1754 * Called by the tty layer when the user changes termios flags so that the line
1755 * discipline can plan ahead. This function cannot sleep and is protected from
1756 * re-entry by the tty layer. The user is guaranteed that this function will
1757 * not be re-entered or in progress when the ldisc is closed.
1758 *
1759 * Locking: Caller holds @tty->termios_rwsem
1760 */
1761static void n_tty_set_termios(struct tty_struct *tty, const struct ktermios *old)
1762{
1763 struct n_tty_data *ldata = tty->disc_data;
1764
1765 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1766 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1767 ldata->line_start = ldata->read_tail;
1768 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1769 ldata->canon_head = ldata->read_tail;
1770 ldata->push = 0;
1771 } else {
1772 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1773 ldata->read_flags);
1774 ldata->canon_head = ldata->read_head;
1775 ldata->push = 1;
1776 }
1777 ldata->commit_head = ldata->read_head;
1778 ldata->erasing = 0;
1779 ldata->lnext = 0;
1780 }
1781
1782 ldata->icanon = (L_ICANON(tty) != 0);
1783
1784 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1785 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1786 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1787 I_PARMRK(tty)) {
1788 bitmap_zero(ldata->char_map, 256);
1789
1790 if (I_IGNCR(tty) || I_ICRNL(tty))
1791 set_bit('\r', ldata->char_map);
1792 if (I_INLCR(tty))
1793 set_bit('\n', ldata->char_map);
1794
1795 if (L_ICANON(tty)) {
1796 set_bit(ERASE_CHAR(tty), ldata->char_map);
1797 set_bit(KILL_CHAR(tty), ldata->char_map);
1798 set_bit(EOF_CHAR(tty), ldata->char_map);
1799 set_bit('\n', ldata->char_map);
1800 set_bit(EOL_CHAR(tty), ldata->char_map);
1801 if (L_IEXTEN(tty)) {
1802 set_bit(WERASE_CHAR(tty), ldata->char_map);
1803 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1804 set_bit(EOL2_CHAR(tty), ldata->char_map);
1805 if (L_ECHO(tty))
1806 set_bit(REPRINT_CHAR(tty),
1807 ldata->char_map);
1808 }
1809 }
1810 if (I_IXON(tty)) {
1811 set_bit(START_CHAR(tty), ldata->char_map);
1812 set_bit(STOP_CHAR(tty), ldata->char_map);
1813 }
1814 if (L_ISIG(tty)) {
1815 set_bit(INTR_CHAR(tty), ldata->char_map);
1816 set_bit(QUIT_CHAR(tty), ldata->char_map);
1817 set_bit(SUSP_CHAR(tty), ldata->char_map);
1818 }
1819 clear_bit(__DISABLED_CHAR, ldata->char_map);
1820 ldata->raw = 0;
1821 ldata->real_raw = 0;
1822 } else {
1823 ldata->raw = 1;
1824 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1825 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1826 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1827 ldata->real_raw = 1;
1828 else
1829 ldata->real_raw = 0;
1830 }
1831 /*
1832 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1833 * been stopped by STOP_CHAR(tty) before it.
1834 */
1835 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1836 start_tty(tty);
1837 process_echoes(tty);
1838 }
1839
1840 /* The termios change make the tty ready for I/O */
1841 wake_up_interruptible(&tty->write_wait);
1842 wake_up_interruptible(&tty->read_wait);
1843}
1844
1845/**
1846 * n_tty_close - close the ldisc for this tty
1847 * @tty: device
1848 *
1849 * Called from the terminal layer when this line discipline is being shut down,
1850 * either because of a close or becsuse of a discipline change. The function
1851 * will not be called while other ldisc methods are in progress.
1852 */
1853static void n_tty_close(struct tty_struct *tty)
1854{
1855 struct n_tty_data *ldata = tty->disc_data;
1856
1857 if (tty->link)
1858 n_tty_packet_mode_flush(tty);
1859
1860 down_write(&tty->termios_rwsem);
1861 vfree(ldata);
1862 tty->disc_data = NULL;
1863 up_write(&tty->termios_rwsem);
1864}
1865
1866/**
1867 * n_tty_open - open an ldisc
1868 * @tty: terminal to open
1869 *
1870 * Called when this line discipline is being attached to the terminal device.
1871 * Can sleep. Called serialized so that no other events will occur in parallel.
1872 * No further open will occur until a close.
1873 */
1874static int n_tty_open(struct tty_struct *tty)
1875{
1876 struct n_tty_data *ldata;
1877
1878 /* Currently a malloc failure here can panic */
1879 ldata = vzalloc(sizeof(*ldata));
1880 if (!ldata)
1881 return -ENOMEM;
1882
1883 ldata->overrun_time = jiffies;
1884 mutex_init(&ldata->atomic_read_lock);
1885 mutex_init(&ldata->output_lock);
1886
1887 tty->disc_data = ldata;
1888 tty->closing = 0;
1889 /* indicate buffer work may resume */
1890 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1891 n_tty_set_termios(tty, NULL);
1892 tty_unthrottle(tty);
1893 return 0;
1894}
1895
1896static inline int input_available_p(struct tty_struct *tty, int poll)
1897{
1898 struct n_tty_data *ldata = tty->disc_data;
1899 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1900
1901 if (ldata->icanon && !L_EXTPROC(tty))
1902 return ldata->canon_head != ldata->read_tail;
1903 else
1904 return ldata->commit_head - ldata->read_tail >= amt;
1905}
1906
1907/**
1908 * copy_from_read_buf - copy read data directly
1909 * @tty: terminal device
1910 * @kbp: data
1911 * @nr: size of data
1912 *
1913 * Helper function to speed up n_tty_read(). It is only called when %ICANON is
1914 * off; it copies characters straight from the tty queue.
1915 *
1916 * Returns: true if it successfully copied data, but there is still more data
1917 * to be had.
1918 *
1919 * Locking:
1920 * * called under the @ldata->atomic_read_lock sem
1921 * * n_tty_read()/consumer path:
1922 * caller holds non-exclusive %termios_rwsem;
1923 * read_tail published
1924 */
1925static bool copy_from_read_buf(struct tty_struct *tty,
1926 unsigned char **kbp,
1927 size_t *nr)
1928
1929{
1930 struct n_tty_data *ldata = tty->disc_data;
1931 size_t n;
1932 bool is_eof;
1933 size_t head = smp_load_acquire(&ldata->commit_head);
1934 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1935
1936 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1937 n = min(*nr, n);
1938 if (n) {
1939 unsigned char *from = read_buf_addr(ldata, tail);
1940 memcpy(*kbp, from, n);
1941 is_eof = n == 1 && *from == EOF_CHAR(tty);
1942 tty_audit_add_data(tty, from, n);
1943 zero_buffer(tty, from, n);
1944 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1945 /* Turn single EOF into zero-length read */
1946 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1947 (head == ldata->read_tail))
1948 return false;
1949 *kbp += n;
1950 *nr -= n;
1951
1952 /* If we have more to copy, let the caller know */
1953 return head != ldata->read_tail;
1954 }
1955 return false;
1956}
1957
1958/**
1959 * canon_copy_from_read_buf - copy read data in canonical mode
1960 * @tty: terminal device
1961 * @kbp: data
1962 * @nr: size of data
1963 *
1964 * Helper function for n_tty_read(). It is only called when %ICANON is on; it
1965 * copies one line of input up to and including the line-delimiting character
1966 * into the result buffer.
1967 *
1968 * Note: When termios is changed from non-canonical to canonical mode and the
1969 * read buffer contains data, n_tty_set_termios() simulates an EOF push (as if
1970 * C-d were input) _without_ the %DISABLED_CHAR in the buffer. This causes data
1971 * already processed as input to be immediately available as input although a
1972 * newline has not been received.
1973 *
1974 * Locking:
1975 * * called under the %atomic_read_lock mutex
1976 * * n_tty_read()/consumer path:
1977 * caller holds non-exclusive %termios_rwsem;
1978 * read_tail published
1979 */
1980static bool canon_copy_from_read_buf(struct tty_struct *tty,
1981 unsigned char **kbp,
1982 size_t *nr)
1983{
1984 struct n_tty_data *ldata = tty->disc_data;
1985 size_t n, size, more, c;
1986 size_t eol;
1987 size_t tail, canon_head;
1988 int found = 0;
1989
1990 /* N.B. avoid overrun if nr == 0 */
1991 if (!*nr)
1992 return false;
1993
1994 canon_head = smp_load_acquire(&ldata->canon_head);
1995 n = min(*nr, canon_head - ldata->read_tail);
1996
1997 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1998 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1999
2000 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2001 __func__, *nr, tail, n, size);
2002
2003 eol = find_next_bit(ldata->read_flags, size, tail);
2004 more = n - (size - tail);
2005 if (eol == N_TTY_BUF_SIZE && more) {
2006 /* scan wrapped without finding set bit */
2007 eol = find_first_bit(ldata->read_flags, more);
2008 found = eol != more;
2009 } else
2010 found = eol != size;
2011
2012 n = eol - tail;
2013 if (n > N_TTY_BUF_SIZE)
2014 n += N_TTY_BUF_SIZE;
2015 c = n + found;
2016
2017 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
2018 n = c;
2019
2020 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2021 __func__, eol, found, n, c, tail, more);
2022
2023 tty_copy(tty, *kbp, tail, n);
2024 *kbp += n;
2025 *nr -= n;
2026
2027 if (found)
2028 clear_bit(eol, ldata->read_flags);
2029 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2030
2031 if (found) {
2032 if (!ldata->push)
2033 ldata->line_start = ldata->read_tail;
2034 else
2035 ldata->push = 0;
2036 tty_audit_push();
2037 return false;
2038 }
2039
2040 /* No EOL found - do a continuation retry if there is more data */
2041 return ldata->read_tail != canon_head;
2042}
2043
2044/*
2045 * If we finished a read at the exact location of an
2046 * EOF (special EOL character that's a __DISABLED_CHAR)
2047 * in the stream, silently eat the EOF.
2048 */
2049static void canon_skip_eof(struct tty_struct *tty)
2050{
2051 struct n_tty_data *ldata = tty->disc_data;
2052 size_t tail, canon_head;
2053
2054 canon_head = smp_load_acquire(&ldata->canon_head);
2055 tail = ldata->read_tail;
2056
2057 // No data?
2058 if (tail == canon_head)
2059 return;
2060
2061 // See if the tail position is EOF in the circular buffer
2062 tail &= (N_TTY_BUF_SIZE - 1);
2063 if (!test_bit(tail, ldata->read_flags))
2064 return;
2065 if (read_buf(ldata, tail) != __DISABLED_CHAR)
2066 return;
2067
2068 // Clear the EOL bit, skip the EOF char.
2069 clear_bit(tail, ldata->read_flags);
2070 smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2071}
2072
2073/**
2074 * job_control - check job control
2075 * @tty: tty
2076 * @file: file handle
2077 *
2078 * Perform job control management checks on this @file/@tty descriptor and if
2079 * appropriate send any needed signals and return a negative error code if
2080 * action should be taken.
2081 *
2082 * Locking:
2083 * * redirected write test is safe
2084 * * current->signal->tty check is safe
2085 * * ctrl.lock to safely reference @tty->ctrl.pgrp
2086 */
2087static int job_control(struct tty_struct *tty, struct file *file)
2088{
2089 /* Job control check -- must be done at start and after
2090 every sleep (POSIX.1 7.1.1.4). */
2091 /* NOTE: not yet done after every sleep pending a thorough
2092 check of the logic of this change. -- jlc */
2093 /* don't stop on /dev/console */
2094 if (file->f_op->write_iter == redirected_tty_write)
2095 return 0;
2096
2097 return __tty_check_change(tty, SIGTTIN);
2098}
2099
2100
2101/**
2102 * n_tty_read - read function for tty
2103 * @tty: tty device
2104 * @file: file object
2105 * @kbuf: kernelspace buffer pointer
2106 * @nr: size of I/O
2107 * @cookie: if non-%NULL, this is a continuation read
2108 * @offset: where to continue reading from (unused in n_tty)
2109 *
2110 * Perform reads for the line discipline. We are guaranteed that the line
2111 * discipline will not be closed under us but we may get multiple parallel
2112 * readers and must handle this ourselves. We may also get a hangup. Always
2113 * called in user context, may sleep.
2114 *
2115 * This code must be sure never to sleep through a hangup.
2116 *
2117 * Locking: n_tty_read()/consumer path:
2118 * claims non-exclusive termios_rwsem;
2119 * publishes read_tail
2120 */
2121static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2122 unsigned char *kbuf, size_t nr,
2123 void **cookie, unsigned long offset)
2124{
2125 struct n_tty_data *ldata = tty->disc_data;
2126 unsigned char *kb = kbuf;
2127 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2128 int c;
2129 int minimum, time;
2130 ssize_t retval = 0;
2131 long timeout;
2132 bool packet;
2133 size_t old_tail;
2134
2135 /*
2136 * Is this a continuation of a read started earler?
2137 *
2138 * If so, we still hold the atomic_read_lock and the
2139 * termios_rwsem, and can just continue to copy data.
2140 */
2141 if (*cookie) {
2142 if (ldata->icanon && !L_EXTPROC(tty)) {
2143 /*
2144 * If we have filled the user buffer, see
2145 * if we should skip an EOF character before
2146 * releasing the lock and returning done.
2147 */
2148 if (!nr)
2149 canon_skip_eof(tty);
2150 else if (canon_copy_from_read_buf(tty, &kb, &nr))
2151 return kb - kbuf;
2152 } else {
2153 if (copy_from_read_buf(tty, &kb, &nr))
2154 return kb - kbuf;
2155 }
2156
2157 /* No more data - release locks and stop retries */
2158 n_tty_kick_worker(tty);
2159 n_tty_check_unthrottle(tty);
2160 up_read(&tty->termios_rwsem);
2161 mutex_unlock(&ldata->atomic_read_lock);
2162 *cookie = NULL;
2163 return kb - kbuf;
2164 }
2165
2166 c = job_control(tty, file);
2167 if (c < 0)
2168 return c;
2169
2170 /*
2171 * Internal serialization of reads.
2172 */
2173 if (file->f_flags & O_NONBLOCK) {
2174 if (!mutex_trylock(&ldata->atomic_read_lock))
2175 return -EAGAIN;
2176 } else {
2177 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2178 return -ERESTARTSYS;
2179 }
2180
2181 down_read(&tty->termios_rwsem);
2182
2183 minimum = time = 0;
2184 timeout = MAX_SCHEDULE_TIMEOUT;
2185 if (!ldata->icanon) {
2186 minimum = MIN_CHAR(tty);
2187 if (minimum) {
2188 time = (HZ / 10) * TIME_CHAR(tty);
2189 } else {
2190 timeout = (HZ / 10) * TIME_CHAR(tty);
2191 minimum = 1;
2192 }
2193 }
2194
2195 packet = tty->ctrl.packet;
2196 old_tail = ldata->read_tail;
2197
2198 add_wait_queue(&tty->read_wait, &wait);
2199 while (nr) {
2200 /* First test for status change. */
2201 if (packet && tty->link->ctrl.pktstatus) {
2202 unsigned char cs;
2203 if (kb != kbuf)
2204 break;
2205 spin_lock_irq(&tty->link->ctrl.lock);
2206 cs = tty->link->ctrl.pktstatus;
2207 tty->link->ctrl.pktstatus = 0;
2208 spin_unlock_irq(&tty->link->ctrl.lock);
2209 *kb++ = cs;
2210 nr--;
2211 break;
2212 }
2213
2214 if (!input_available_p(tty, 0)) {
2215 up_read(&tty->termios_rwsem);
2216 tty_buffer_flush_work(tty->port);
2217 down_read(&tty->termios_rwsem);
2218 if (!input_available_p(tty, 0)) {
2219 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2220 retval = -EIO;
2221 break;
2222 }
2223 if (tty_hung_up_p(file))
2224 break;
2225 /*
2226 * Abort readers for ttys which never actually
2227 * get hung up. See __tty_hangup().
2228 */
2229 if (test_bit(TTY_HUPPING, &tty->flags))
2230 break;
2231 if (!timeout)
2232 break;
2233 if (tty_io_nonblock(tty, file)) {
2234 retval = -EAGAIN;
2235 break;
2236 }
2237 if (signal_pending(current)) {
2238 retval = -ERESTARTSYS;
2239 break;
2240 }
2241 up_read(&tty->termios_rwsem);
2242
2243 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2244 timeout);
2245
2246 down_read(&tty->termios_rwsem);
2247 continue;
2248 }
2249 }
2250
2251 if (ldata->icanon && !L_EXTPROC(tty)) {
2252 if (canon_copy_from_read_buf(tty, &kb, &nr))
2253 goto more_to_be_read;
2254 } else {
2255 /* Deal with packet mode. */
2256 if (packet && kb == kbuf) {
2257 *kb++ = TIOCPKT_DATA;
2258 nr--;
2259 }
2260
2261 /*
2262 * Copy data, and if there is more to be had
2263 * and we have nothing more to wait for, then
2264 * let's mark us for retries.
2265 *
2266 * NOTE! We return here with both the termios_sem
2267 * and atomic_read_lock still held, the retries
2268 * will release them when done.
2269 */
2270 if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2271more_to_be_read:
2272 remove_wait_queue(&tty->read_wait, &wait);
2273 *cookie = cookie;
2274 return kb - kbuf;
2275 }
2276 }
2277
2278 n_tty_check_unthrottle(tty);
2279
2280 if (kb - kbuf >= minimum)
2281 break;
2282 if (time)
2283 timeout = time;
2284 }
2285 if (old_tail != ldata->read_tail)
2286 n_tty_kick_worker(tty);
2287 up_read(&tty->termios_rwsem);
2288
2289 remove_wait_queue(&tty->read_wait, &wait);
2290 mutex_unlock(&ldata->atomic_read_lock);
2291
2292 if (kb - kbuf)
2293 retval = kb - kbuf;
2294
2295 return retval;
2296}
2297
2298/**
2299 * n_tty_write - write function for tty
2300 * @tty: tty device
2301 * @file: file object
2302 * @buf: userspace buffer pointer
2303 * @nr: size of I/O
2304 *
2305 * Write function of the terminal device. This is serialized with respect to
2306 * other write callers but not to termios changes, reads and other such events.
2307 * Since the receive code will echo characters, thus calling driver write
2308 * methods, the %output_lock is used in the output processing functions called
2309 * here as well as in the echo processing function to protect the column state
2310 * and space left in the buffer.
2311 *
2312 * This code must be sure never to sleep through a hangup.
2313 *
2314 * Locking: output_lock to protect column state and space left
2315 * (note that the process_output*() functions take this lock themselves)
2316 */
2317
2318static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2319 const unsigned char *buf, size_t nr)
2320{
2321 const unsigned char *b = buf;
2322 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2323 int c;
2324 ssize_t retval = 0;
2325
2326 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2327 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2328 retval = tty_check_change(tty);
2329 if (retval)
2330 return retval;
2331 }
2332
2333 down_read(&tty->termios_rwsem);
2334
2335 /* Write out any echoed characters that are still pending */
2336 process_echoes(tty);
2337
2338 add_wait_queue(&tty->write_wait, &wait);
2339 while (1) {
2340 if (signal_pending(current)) {
2341 retval = -ERESTARTSYS;
2342 break;
2343 }
2344 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2345 retval = -EIO;
2346 break;
2347 }
2348 if (O_OPOST(tty)) {
2349 while (nr > 0) {
2350 ssize_t num = process_output_block(tty, b, nr);
2351 if (num < 0) {
2352 if (num == -EAGAIN)
2353 break;
2354 retval = num;
2355 goto break_out;
2356 }
2357 b += num;
2358 nr -= num;
2359 if (nr == 0)
2360 break;
2361 c = *b;
2362 if (process_output(c, tty) < 0)
2363 break;
2364 b++; nr--;
2365 }
2366 if (tty->ops->flush_chars)
2367 tty->ops->flush_chars(tty);
2368 } else {
2369 struct n_tty_data *ldata = tty->disc_data;
2370
2371 while (nr > 0) {
2372 mutex_lock(&ldata->output_lock);
2373 c = tty->ops->write(tty, b, nr);
2374 mutex_unlock(&ldata->output_lock);
2375 if (c < 0) {
2376 retval = c;
2377 goto break_out;
2378 }
2379 if (!c)
2380 break;
2381 b += c;
2382 nr -= c;
2383 }
2384 }
2385 if (!nr)
2386 break;
2387 if (tty_io_nonblock(tty, file)) {
2388 retval = -EAGAIN;
2389 break;
2390 }
2391 up_read(&tty->termios_rwsem);
2392
2393 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2394
2395 down_read(&tty->termios_rwsem);
2396 }
2397break_out:
2398 remove_wait_queue(&tty->write_wait, &wait);
2399 if (nr && tty->fasync)
2400 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2401 up_read(&tty->termios_rwsem);
2402 return (b - buf) ? b - buf : retval;
2403}
2404
2405/**
2406 * n_tty_poll - poll method for N_TTY
2407 * @tty: terminal device
2408 * @file: file accessing it
2409 * @wait: poll table
2410 *
2411 * Called when the line discipline is asked to poll() for data or for special
2412 * events. This code is not serialized with respect to other events save
2413 * open/close.
2414 *
2415 * This code must be sure never to sleep through a hangup.
2416 *
2417 * Locking: called without the kernel lock held -- fine.
2418 */
2419static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2420 poll_table *wait)
2421{
2422 __poll_t mask = 0;
2423
2424 poll_wait(file, &tty->read_wait, wait);
2425 poll_wait(file, &tty->write_wait, wait);
2426 if (input_available_p(tty, 1))
2427 mask |= EPOLLIN | EPOLLRDNORM;
2428 else {
2429 tty_buffer_flush_work(tty->port);
2430 if (input_available_p(tty, 1))
2431 mask |= EPOLLIN | EPOLLRDNORM;
2432 }
2433 if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2434 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2435 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2436 mask |= EPOLLHUP;
2437 if (tty_hung_up_p(file))
2438 mask |= EPOLLHUP;
2439 if (tty->ops->write && !tty_is_writelocked(tty) &&
2440 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2441 tty_write_room(tty) > 0)
2442 mask |= EPOLLOUT | EPOLLWRNORM;
2443 return mask;
2444}
2445
2446static unsigned long inq_canon(struct n_tty_data *ldata)
2447{
2448 size_t nr, head, tail;
2449
2450 if (ldata->canon_head == ldata->read_tail)
2451 return 0;
2452 head = ldata->canon_head;
2453 tail = ldata->read_tail;
2454 nr = head - tail;
2455 /* Skip EOF-chars.. */
2456 while (MASK(head) != MASK(tail)) {
2457 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2458 read_buf(ldata, tail) == __DISABLED_CHAR)
2459 nr--;
2460 tail++;
2461 }
2462 return nr;
2463}
2464
2465static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
2466 unsigned long arg)
2467{
2468 struct n_tty_data *ldata = tty->disc_data;
2469 int retval;
2470
2471 switch (cmd) {
2472 case TIOCOUTQ:
2473 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2474 case TIOCINQ:
2475 down_write(&tty->termios_rwsem);
2476 if (L_ICANON(tty) && !L_EXTPROC(tty))
2477 retval = inq_canon(ldata);
2478 else
2479 retval = read_cnt(ldata);
2480 up_write(&tty->termios_rwsem);
2481 return put_user(retval, (unsigned int __user *) arg);
2482 default:
2483 return n_tty_ioctl_helper(tty, cmd, arg);
2484 }
2485}
2486
2487static struct tty_ldisc_ops n_tty_ops = {
2488 .owner = THIS_MODULE,
2489 .num = N_TTY,
2490 .name = "n_tty",
2491 .open = n_tty_open,
2492 .close = n_tty_close,
2493 .flush_buffer = n_tty_flush_buffer,
2494 .read = n_tty_read,
2495 .write = n_tty_write,
2496 .ioctl = n_tty_ioctl,
2497 .set_termios = n_tty_set_termios,
2498 .poll = n_tty_poll,
2499 .receive_buf = n_tty_receive_buf,
2500 .write_wakeup = n_tty_write_wakeup,
2501 .receive_buf2 = n_tty_receive_buf2,
2502 .lookahead_buf = n_tty_lookahead_flow_ctrl,
2503};
2504
2505/**
2506 * n_tty_inherit_ops - inherit N_TTY methods
2507 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2508 *
2509 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2510 */
2511
2512void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2513{
2514 *ops = n_tty_ops;
2515 ops->owner = NULL;
2516}
2517EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2518
2519void __init n_tty_init(void)
2520{
2521 tty_register_ldisc(&n_tty_ops);
2522}