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/bitmap.h>
32#include <linux/bitops.h>
33#include <linux/ctype.h>
34#include <linux/errno.h>
35#include <linux/export.h>
36#include <linux/fcntl.h>
37#include <linux/file.h>
38#include <linux/jiffies.h>
39#include <linux/math.h>
40#include <linux/poll.h>
41#include <linux/ratelimit.h>
42#include <linux/sched.h>
43#include <linux/signal.h>
44#include <linux/slab.h>
45#include <linux/string.h>
46#include <linux/tty.h>
47#include <linux/types.h>
48#include <linux/uaccess.h>
49#include <linux/vmalloc.h>
50
51#include "tty.h"
52
53/*
54 * Until this number of characters is queued in the xmit buffer, select will
55 * return "we have room for writes".
56 */
57#define WAKEUP_CHARS 256
58
59#define N_TTY_BUF_SIZE 4096
60
61/*
62 * This defines the low- and high-watermarks for throttling and
63 * unthrottling the TTY driver. These watermarks are used for
64 * controlling the space in the read buffer.
65 */
66#define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
67#define TTY_THRESHOLD_UNTHROTTLE 128
68
69/*
70 * Special byte codes used in the echo buffer to represent operations
71 * or special handling of characters. Bytes in the echo buffer that
72 * are not part of such special blocks are treated as normal character
73 * codes.
74 */
75#define ECHO_OP_START 0xff
76#define ECHO_OP_MOVE_BACK_COL 0x80
77#define ECHO_OP_SET_CANON_COL 0x81
78#define ECHO_OP_ERASE_TAB 0x82
79
80#define ECHO_COMMIT_WATERMARK 256
81#define ECHO_BLOCK 256
82#define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
83
84struct n_tty_data {
85 /* producer-published */
86 size_t read_head;
87 size_t commit_head;
88 size_t canon_head;
89 size_t echo_head;
90 size_t echo_commit;
91 size_t echo_mark;
92 DECLARE_BITMAP(char_map, 256);
93
94 /* private to n_tty_receive_overrun (single-threaded) */
95 unsigned long overrun_time;
96 unsigned int num_overrun;
97
98 /* non-atomic */
99 bool no_room;
100
101 /* must hold exclusive termios_rwsem to reset these */
102 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
103 unsigned char push:1;
104
105 /* shared by producer and consumer */
106 u8 read_buf[N_TTY_BUF_SIZE];
107 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
108 u8 echo_buf[N_TTY_BUF_SIZE];
109
110 /* consumer-published */
111 size_t read_tail;
112 size_t line_start;
113
114 /* # of chars looked ahead (to find software flow control chars) */
115 size_t lookahead_count;
116
117 /* protected by output lock */
118 unsigned int column;
119 unsigned int canon_column;
120 size_t echo_tail;
121
122 struct mutex atomic_read_lock;
123 struct mutex output_lock;
124};
125
126#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
127
128static inline size_t read_cnt(struct n_tty_data *ldata)
129{
130 return ldata->read_head - ldata->read_tail;
131}
132
133static inline u8 read_buf(struct n_tty_data *ldata, size_t i)
134{
135 return ldata->read_buf[MASK(i)];
136}
137
138static inline u8 *read_buf_addr(struct n_tty_data *ldata, size_t i)
139{
140 return &ldata->read_buf[MASK(i)];
141}
142
143static inline u8 echo_buf(struct n_tty_data *ldata, size_t i)
144{
145 smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
146 return ldata->echo_buf[MASK(i)];
147}
148
149static inline u8 *echo_buf_addr(struct n_tty_data *ldata, size_t i)
150{
151 return &ldata->echo_buf[MASK(i)];
152}
153
154/* If we are not echoing the data, perhaps this is a secret so erase it */
155static void zero_buffer(const struct tty_struct *tty, u8 *buffer, size_t size)
156{
157 if (L_ICANON(tty) && !L_ECHO(tty))
158 memset(s: buffer, c: 0, n: size);
159}
160
161static void tty_copy(const struct tty_struct *tty, void *to, size_t tail,
162 size_t n)
163{
164 struct n_tty_data *ldata = tty->disc_data;
165 size_t size = N_TTY_BUF_SIZE - tail;
166 void *from = read_buf_addr(ldata, i: tail);
167
168 if (n > size) {
169 tty_audit_add_data(tty, data: from, size);
170 memcpy(to, from, len: size);
171 zero_buffer(tty, buffer: from, size);
172 to += size;
173 n -= size;
174 from = ldata->read_buf;
175 }
176
177 tty_audit_add_data(tty, data: from, size: n);
178 memcpy(to, from, len: n);
179 zero_buffer(tty, buffer: from, size: n);
180}
181
182/**
183 * n_tty_kick_worker - start input worker (if required)
184 * @tty: terminal
185 *
186 * Re-schedules the flip buffer work if it may have stopped.
187 *
188 * Locking:
189 * * Caller holds exclusive %termios_rwsem, or
190 * * n_tty_read()/consumer path:
191 * holds non-exclusive %termios_rwsem
192 */
193static void n_tty_kick_worker(const struct tty_struct *tty)
194{
195 struct n_tty_data *ldata = tty->disc_data;
196
197 /* Did the input worker stop? Restart it */
198 if (unlikely(READ_ONCE(ldata->no_room))) {
199 WRITE_ONCE(ldata->no_room, 0);
200
201 WARN_RATELIMIT(tty->port->itty == NULL,
202 "scheduling with invalid itty\n");
203 /* see if ldisc has been killed - if so, this means that
204 * even though the ldisc has been halted and ->buf.work
205 * cancelled, ->buf.work is about to be rescheduled
206 */
207 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
208 "scheduling buffer work for halted ldisc\n");
209 tty_buffer_restart_work(port: tty->port);
210 }
211}
212
213static ssize_t chars_in_buffer(const struct tty_struct *tty)
214{
215 const struct n_tty_data *ldata = tty->disc_data;
216 size_t head = ldata->icanon ? ldata->canon_head : ldata->commit_head;
217
218 return head - ldata->read_tail;
219}
220
221/**
222 * n_tty_write_wakeup - asynchronous I/O notifier
223 * @tty: tty device
224 *
225 * Required for the ptys, serial driver etc. since processes that attach
226 * themselves to the master and rely on ASYNC IO must be woken up.
227 */
228static void n_tty_write_wakeup(struct tty_struct *tty)
229{
230 clear_bit(nr: TTY_DO_WRITE_WAKEUP, addr: &tty->flags);
231 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
232}
233
234static void n_tty_check_throttle(struct tty_struct *tty)
235{
236 struct n_tty_data *ldata = tty->disc_data;
237
238 /*
239 * Check the remaining room for the input canonicalization
240 * mode. We don't want to throttle the driver if we're in
241 * canonical mode and don't have a newline yet!
242 */
243 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
244 return;
245
246 do {
247 tty_set_flow_change(tty, val: TTY_THROTTLE_SAFE);
248 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
249 break;
250 } while (!tty_throttle_safe(tty));
251
252 __tty_set_flow_change(tty, val: 0);
253}
254
255static void n_tty_check_unthrottle(struct tty_struct *tty)
256{
257 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
258 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
259 return;
260 n_tty_kick_worker(tty);
261 tty_wakeup(tty: tty->link);
262 return;
263 }
264
265 /* If there is enough space in the read buffer now, let the
266 * low-level driver know. We use chars_in_buffer() to
267 * check the buffer, as it now knows about canonical mode.
268 * Otherwise, if the driver is throttled and the line is
269 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
270 * we won't get any more characters.
271 */
272
273 do {
274 tty_set_flow_change(tty, val: TTY_UNTHROTTLE_SAFE);
275 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
276 break;
277
278 n_tty_kick_worker(tty);
279 } while (!tty_unthrottle_safe(tty));
280
281 __tty_set_flow_change(tty, val: 0);
282}
283
284/**
285 * put_tty_queue - add character to tty
286 * @c: character
287 * @ldata: n_tty data
288 *
289 * Add a character to the tty read_buf queue.
290 *
291 * Locking:
292 * * n_tty_receive_buf()/producer path:
293 * caller holds non-exclusive %termios_rwsem
294 */
295static inline void put_tty_queue(u8 c, struct n_tty_data *ldata)
296{
297 *read_buf_addr(ldata, i: ldata->read_head) = c;
298 ldata->read_head++;
299}
300
301/**
302 * reset_buffer_flags - reset buffer state
303 * @ldata: line disc data to reset
304 *
305 * Reset the read buffer counters and clear the flags. Called from
306 * n_tty_open() and n_tty_flush_buffer().
307 *
308 * Locking:
309 * * caller holds exclusive %termios_rwsem, or
310 * * (locking is not required)
311 */
312static void reset_buffer_flags(struct n_tty_data *ldata)
313{
314 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
315 ldata->commit_head = 0;
316 ldata->line_start = 0;
317
318 ldata->erasing = 0;
319 bitmap_zero(dst: ldata->read_flags, N_TTY_BUF_SIZE);
320 ldata->push = 0;
321
322 ldata->lookahead_count = 0;
323}
324
325static void n_tty_packet_mode_flush(struct tty_struct *tty)
326{
327 unsigned long flags;
328
329 if (tty->link->ctrl.packet) {
330 spin_lock_irqsave(&tty->ctrl.lock, flags);
331 tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
332 spin_unlock_irqrestore(lock: &tty->ctrl.lock, flags);
333 wake_up_interruptible(&tty->link->read_wait);
334 }
335}
336
337/**
338 * n_tty_flush_buffer - clean input queue
339 * @tty: terminal device
340 *
341 * Flush the input buffer. Called when the tty layer wants the buffer flushed
342 * (eg at hangup) or when the %N_TTY line discipline internally has to clean
343 * the pending queue (for example some signals).
344 *
345 * Holds %termios_rwsem to exclude producer/consumer while buffer indices are
346 * reset.
347 *
348 * Locking: %ctrl.lock, exclusive %termios_rwsem
349 */
350static void n_tty_flush_buffer(struct tty_struct *tty)
351{
352 down_write(sem: &tty->termios_rwsem);
353 reset_buffer_flags(ldata: tty->disc_data);
354 n_tty_kick_worker(tty);
355
356 if (tty->link)
357 n_tty_packet_mode_flush(tty);
358 up_write(sem: &tty->termios_rwsem);
359}
360
361/**
362 * is_utf8_continuation - utf8 multibyte check
363 * @c: byte to check
364 *
365 * Returns: true if the utf8 character @c is a multibyte continuation
366 * character. We use this to correctly compute the on-screen size of the
367 * character when printing.
368 */
369static inline int is_utf8_continuation(u8 c)
370{
371 return (c & 0xc0) == 0x80;
372}
373
374/**
375 * is_continuation - multibyte check
376 * @c: byte to check
377 * @tty: terminal device
378 *
379 * Returns: true if the utf8 character @c is a multibyte continuation character
380 * and the terminal is in unicode mode.
381 */
382static inline int is_continuation(u8 c, const struct tty_struct *tty)
383{
384 return I_IUTF8(tty) && is_utf8_continuation(c);
385}
386
387/**
388 * do_output_char - output one character
389 * @c: character (or partial unicode symbol)
390 * @tty: terminal device
391 * @space: space available in tty driver write buffer
392 *
393 * This is a helper function that handles one output character (including
394 * special characters like TAB, CR, LF, etc.), doing OPOST processing and
395 * putting the results in the tty driver's write buffer.
396 *
397 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY.
398 * They simply aren't relevant in the world today. If you ever need them, add
399 * them here.
400 *
401 * Returns: the number of bytes of buffer space used or -1 if no space left.
402 *
403 * Locking: should be called under the %output_lock to protect the column state
404 * and space left in the buffer.
405 */
406static int do_output_char(u8 c, struct tty_struct *tty, int space)
407{
408 struct n_tty_data *ldata = tty->disc_data;
409 int spaces;
410
411 if (!space)
412 return -1;
413
414 switch (c) {
415 case '\n':
416 if (O_ONLRET(tty))
417 ldata->column = 0;
418 if (O_ONLCR(tty)) {
419 if (space < 2)
420 return -1;
421 ldata->canon_column = ldata->column = 0;
422 tty->ops->write(tty, "\r\n", 2);
423 return 2;
424 }
425 ldata->canon_column = ldata->column;
426 break;
427 case '\r':
428 if (O_ONOCR(tty) && ldata->column == 0)
429 return 0;
430 if (O_OCRNL(tty)) {
431 c = '\n';
432 if (O_ONLRET(tty))
433 ldata->canon_column = ldata->column = 0;
434 break;
435 }
436 ldata->canon_column = ldata->column = 0;
437 break;
438 case '\t':
439 spaces = 8 - (ldata->column & 7);
440 if (O_TABDLY(tty) == XTABS) {
441 if (space < spaces)
442 return -1;
443 ldata->column += spaces;
444 tty->ops->write(tty, " ", spaces);
445 return spaces;
446 }
447 ldata->column += spaces;
448 break;
449 case '\b':
450 if (ldata->column > 0)
451 ldata->column--;
452 break;
453 default:
454 if (!iscntrl(c)) {
455 if (O_OLCUC(tty))
456 c = toupper(c);
457 if (!is_continuation(c, tty))
458 ldata->column++;
459 }
460 break;
461 }
462
463 tty_put_char(tty, c);
464 return 1;
465}
466
467/**
468 * process_output - output post processor
469 * @c: character (or partial unicode symbol)
470 * @tty: terminal device
471 *
472 * Output one character with OPOST processing.
473 *
474 * Returns: -1 when the output device is full and the character must be
475 * retried.
476 *
477 * Locking: %output_lock to protect column state and space left (also, this is
478 *called from n_tty_write() under the tty layer write lock).
479 */
480static int process_output(u8 c, struct tty_struct *tty)
481{
482 struct n_tty_data *ldata = tty->disc_data;
483
484 guard(mutex)(T: &ldata->output_lock);
485
486 if (do_output_char(c, tty, space: tty_write_room(tty)) < 0)
487 return -1;
488
489 return 0;
490}
491
492/**
493 * process_output_block - block post processor
494 * @tty: terminal device
495 * @buf: character buffer
496 * @nr: number of bytes to output
497 *
498 * Output a block of characters with OPOST processing.
499 *
500 * This path is used to speed up block console writes, among other things when
501 * processing blocks of output data. It handles only the simple cases normally
502 * found and helps to generate blocks of symbols for the console driver and
503 * thus improve performance.
504 *
505 * Returns: the number of characters output.
506 *
507 * Locking: %output_lock to protect column state and space left (also, this is
508 * called from n_tty_write() under the tty layer write lock).
509 */
510static ssize_t process_output_block(struct tty_struct *tty,
511 const u8 *buf, unsigned int nr)
512{
513 struct n_tty_data *ldata = tty->disc_data;
514 unsigned int space, i;
515 const u8 *cp;
516
517 guard(mutex)(T: &ldata->output_lock);
518
519 space = tty_write_room(tty);
520 if (space == 0)
521 return 0;
522
523 if (nr > space)
524 nr = space;
525
526 for (i = 0, cp = buf; i < nr; i++, cp++) {
527 u8 c = *cp;
528
529 switch (c) {
530 case '\n':
531 if (O_ONLRET(tty))
532 ldata->column = 0;
533 if (O_ONLCR(tty))
534 goto do_write;
535 ldata->canon_column = ldata->column;
536 break;
537 case '\r':
538 if (O_ONOCR(tty) && ldata->column == 0)
539 goto do_write;
540 if (O_OCRNL(tty))
541 goto do_write;
542 ldata->canon_column = ldata->column = 0;
543 break;
544 case '\t':
545 goto do_write;
546 case '\b':
547 if (ldata->column > 0)
548 ldata->column--;
549 break;
550 default:
551 if (!iscntrl(c)) {
552 if (O_OLCUC(tty))
553 goto do_write;
554 if (!is_continuation(c, tty))
555 ldata->column++;
556 }
557 break;
558 }
559 }
560do_write:
561 return tty->ops->write(tty, buf, i);
562}
563
564static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
565 int space)
566{
567 struct n_tty_data *ldata = tty->disc_data;
568 u8 op;
569
570 /*
571 * Since add_echo_byte() is called without holding output_lock, we
572 * might see only portion of multi-byte operation.
573 */
574 if (MASK(ldata->echo_commit) == MASK(*tail + 1))
575 return -ENODATA;
576
577 /*
578 * If the buffer byte is the start of a multi-byte operation, get the
579 * next byte, which is either the op code or a control character value.
580 */
581 op = echo_buf(ldata, i: *tail + 1);
582
583 switch (op) {
584 case ECHO_OP_ERASE_TAB: {
585 unsigned int num_chars, num_bs;
586
587 if (MASK(ldata->echo_commit) == MASK(*tail + 2))
588 return -ENODATA;
589
590 num_chars = echo_buf(ldata, i: *tail + 2);
591
592 /*
593 * Determine how many columns to go back in order to erase the
594 * tab. This depends on the number of columns used by other
595 * characters within the tab area. If this (modulo 8) count is
596 * from the start of input rather than from a previous tab, we
597 * offset by canon column. Otherwise, tab spacing is normal.
598 */
599 if (!(num_chars & 0x80))
600 num_chars += ldata->canon_column;
601 num_bs = 8 - (num_chars & 7);
602
603 if (num_bs > space)
604 return -ENOSPC;
605
606 space -= num_bs;
607 while (num_bs--) {
608 tty_put_char(tty, c: '\b');
609 if (ldata->column > 0)
610 ldata->column--;
611 }
612 *tail += 3;
613 break;
614 }
615 case ECHO_OP_SET_CANON_COL:
616 ldata->canon_column = ldata->column;
617 *tail += 2;
618 break;
619
620 case ECHO_OP_MOVE_BACK_COL:
621 if (ldata->column > 0)
622 ldata->column--;
623 *tail += 2;
624 break;
625
626 case ECHO_OP_START:
627 /* This is an escaped echo op start code */
628 if (!space)
629 return -ENOSPC;
630
631 tty_put_char(tty, ECHO_OP_START);
632 ldata->column++;
633 space--;
634 *tail += 2;
635 break;
636
637 default:
638 /*
639 * If the op is not a special byte code, it is a ctrl char
640 * tagged to be echoed as "^X" (where X is the letter
641 * representing the control char). Note that we must ensure
642 * there is enough space for the whole ctrl pair.
643 */
644 if (space < 2)
645 return -ENOSPC;
646
647 tty_put_char(tty, c: '^');
648 tty_put_char(tty, c: op ^ 0100);
649 ldata->column += 2;
650 space -= 2;
651 *tail += 2;
652 break;
653 }
654
655 return space;
656}
657
658/**
659 * __process_echoes - write pending echo characters
660 * @tty: terminal device
661 *
662 * Write previously buffered echo (and other ldisc-generated) characters to the
663 * tty.
664 *
665 * Characters generated by the ldisc (including echoes) need to be buffered
666 * because the driver's write buffer can fill during heavy program output.
667 * Echoing straight to the driver will often fail under these conditions,
668 * causing lost characters and resulting mismatches of ldisc state information.
669 *
670 * Since the ldisc state must represent the characters actually sent to the
671 * driver at the time of the write, operations like certain changes in column
672 * state are also saved in the buffer and executed here.
673 *
674 * A circular fifo buffer is used so that the most recent characters are
675 * prioritized. Also, when control characters are echoed with a prefixed "^",
676 * the pair is treated atomically and thus not separated.
677 *
678 * Locking: callers must hold %output_lock.
679 */
680static size_t __process_echoes(struct tty_struct *tty)
681{
682 struct n_tty_data *ldata = tty->disc_data;
683 unsigned int space, old_space;
684 size_t tail;
685 u8 c;
686
687 old_space = space = tty_write_room(tty);
688
689 tail = ldata->echo_tail;
690 while (MASK(ldata->echo_commit) != MASK(tail)) {
691 c = echo_buf(ldata, i: tail);
692 if (c == ECHO_OP_START) {
693 int ret = n_tty_process_echo_ops(tty, tail: &tail, space);
694 if (ret == -ENODATA)
695 goto not_yet_stored;
696 if (ret < 0)
697 break;
698 space = ret;
699 } else {
700 if (O_OPOST(tty)) {
701 int retval = do_output_char(c, tty, space);
702 if (retval < 0)
703 break;
704 space -= retval;
705 } else {
706 if (!space)
707 break;
708 tty_put_char(tty, c);
709 space -= 1;
710 }
711 tail += 1;
712 }
713 }
714
715 /* If the echo buffer is nearly full (so that the possibility exists
716 * of echo overrun before the next commit), then discard enough
717 * data at the tail to prevent a subsequent overrun */
718 while (ldata->echo_commit > tail &&
719 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
720 if (echo_buf(ldata, i: tail) == ECHO_OP_START) {
721 if (echo_buf(ldata, i: tail + 1) == ECHO_OP_ERASE_TAB)
722 tail += 3;
723 else
724 tail += 2;
725 } else
726 tail++;
727 }
728
729 not_yet_stored:
730 ldata->echo_tail = tail;
731 return old_space - space;
732}
733
734static void commit_echoes(struct tty_struct *tty)
735{
736 struct n_tty_data *ldata = tty->disc_data;
737 size_t nr, old, echoed;
738 size_t head;
739
740 mutex_lock(lock: &ldata->output_lock);
741 head = ldata->echo_head;
742 ldata->echo_mark = head;
743 old = ldata->echo_commit - ldata->echo_tail;
744
745 /* Process committed echoes if the accumulated # of bytes
746 * is over the threshold (and try again each time another
747 * block is accumulated) */
748 nr = head - ldata->echo_tail;
749 if (nr < ECHO_COMMIT_WATERMARK ||
750 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
751 mutex_unlock(lock: &ldata->output_lock);
752 return;
753 }
754
755 ldata->echo_commit = head;
756 echoed = __process_echoes(tty);
757 mutex_unlock(lock: &ldata->output_lock);
758
759 if (echoed && tty->ops->flush_chars)
760 tty->ops->flush_chars(tty);
761}
762
763static void process_echoes(struct tty_struct *tty)
764{
765 struct n_tty_data *ldata = tty->disc_data;
766 size_t echoed;
767
768 if (ldata->echo_mark == ldata->echo_tail)
769 return;
770
771 mutex_lock(lock: &ldata->output_lock);
772 ldata->echo_commit = ldata->echo_mark;
773 echoed = __process_echoes(tty);
774 mutex_unlock(lock: &ldata->output_lock);
775
776 if (echoed && tty->ops->flush_chars)
777 tty->ops->flush_chars(tty);
778}
779
780/* NB: echo_mark and echo_head should be equivalent here */
781static void flush_echoes(struct tty_struct *tty)
782{
783 struct n_tty_data *ldata = tty->disc_data;
784
785 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
786 ldata->echo_commit == ldata->echo_head)
787 return;
788
789 mutex_lock(lock: &ldata->output_lock);
790 ldata->echo_commit = ldata->echo_head;
791 __process_echoes(tty);
792 mutex_unlock(lock: &ldata->output_lock);
793}
794
795/**
796 * add_echo_byte - add a byte to the echo buffer
797 * @c: unicode byte to echo
798 * @ldata: n_tty data
799 *
800 * Add a character or operation byte to the echo buffer.
801 */
802static inline void add_echo_byte(u8 c, struct n_tty_data *ldata)
803{
804 *echo_buf_addr(ldata, i: ldata->echo_head) = c;
805 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
806 ldata->echo_head++;
807}
808
809/**
810 * echo_move_back_col - add operation to move back a column
811 * @ldata: n_tty data
812 *
813 * Add an operation to the echo buffer to move back one column.
814 */
815static void echo_move_back_col(struct n_tty_data *ldata)
816{
817 add_echo_byte(ECHO_OP_START, ldata);
818 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
819}
820
821/**
822 * echo_set_canon_col - add operation to set the canon column
823 * @ldata: n_tty data
824 *
825 * Add an operation to the echo buffer to set the canon column to the current
826 * column.
827 */
828static void echo_set_canon_col(struct n_tty_data *ldata)
829{
830 add_echo_byte(ECHO_OP_START, ldata);
831 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
832}
833
834/**
835 * echo_erase_tab - add operation to erase a tab
836 * @num_chars: number of character columns already used
837 * @after_tab: true if num_chars starts after a previous tab
838 * @ldata: n_tty data
839 *
840 * Add an operation to the echo buffer to erase a tab.
841 *
842 * Called by the eraser function, which knows how many character columns have
843 * been used since either a previous tab or the start of input. This
844 * information will be used later, along with canon column (if applicable), to
845 * go back the correct number of columns.
846 */
847static void echo_erase_tab(unsigned int num_chars, int after_tab,
848 struct n_tty_data *ldata)
849{
850 add_echo_byte(ECHO_OP_START, ldata);
851 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
852
853 /* We only need to know this modulo 8 (tab spacing) */
854 num_chars &= 7;
855
856 /* Set the high bit as a flag if num_chars is after a previous tab */
857 if (after_tab)
858 num_chars |= 0x80;
859
860 add_echo_byte(c: num_chars, ldata);
861}
862
863/**
864 * echo_char_raw - echo a character raw
865 * @c: unicode byte to echo
866 * @ldata: line disc data
867 *
868 * Echo user input back onto the screen. This must be called only when
869 * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
870 *
871 * This variant does not treat control characters specially.
872 */
873static void echo_char_raw(u8 c, struct n_tty_data *ldata)
874{
875 if (c == ECHO_OP_START) {
876 add_echo_byte(ECHO_OP_START, ldata);
877 add_echo_byte(ECHO_OP_START, ldata);
878 } else {
879 add_echo_byte(c, ldata);
880 }
881}
882
883/**
884 * echo_char - echo a character
885 * @c: unicode byte to echo
886 * @tty: terminal device
887 *
888 * Echo user input back onto the screen. This must be called only when
889 * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
890 *
891 * This variant tags control characters to be echoed as "^X" (where X is the
892 * letter representing the control char).
893 */
894static void echo_char(u8 c, const struct tty_struct *tty)
895{
896 struct n_tty_data *ldata = tty->disc_data;
897
898 if (c == ECHO_OP_START) {
899 add_echo_byte(ECHO_OP_START, ldata);
900 add_echo_byte(ECHO_OP_START, ldata);
901 } else {
902 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
903 add_echo_byte(ECHO_OP_START, ldata);
904 add_echo_byte(c, ldata);
905 }
906}
907
908/**
909 * finish_erasing - complete erase
910 * @ldata: n_tty data
911 */
912static inline void finish_erasing(struct n_tty_data *ldata)
913{
914 if (ldata->erasing) {
915 echo_char_raw(c: '/', ldata);
916 ldata->erasing = 0;
917 }
918}
919
920/**
921 * eraser - handle erase function
922 * @c: character input
923 * @tty: terminal device
924 *
925 * Perform erase and necessary output when an erase character is present in the
926 * stream from the driver layer. Handles the complexities of UTF-8 multibyte
927 * symbols.
928 *
929 * Locking: n_tty_receive_buf()/producer path:
930 * caller holds non-exclusive %termios_rwsem
931 */
932static void eraser(u8 c, const struct tty_struct *tty)
933{
934 struct n_tty_data *ldata = tty->disc_data;
935 enum { ERASE, WERASE, KILL } kill_type;
936 size_t head;
937 size_t cnt;
938 int seen_alnums;
939
940 if (ldata->read_head == ldata->canon_head) {
941 /* process_output('\a', tty); */ /* what do you think? */
942 return;
943 }
944 if (c == ERASE_CHAR(tty))
945 kill_type = ERASE;
946 else if (c == WERASE_CHAR(tty))
947 kill_type = WERASE;
948 else {
949 if (!L_ECHO(tty)) {
950 ldata->read_head = ldata->canon_head;
951 return;
952 }
953 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
954 ldata->read_head = ldata->canon_head;
955 finish_erasing(ldata);
956 echo_char(KILL_CHAR(tty), tty);
957 /* Add a newline if ECHOK is on and ECHOKE is off. */
958 if (L_ECHOK(tty))
959 echo_char_raw(c: '\n', ldata);
960 return;
961 }
962 kill_type = KILL;
963 }
964
965 seen_alnums = 0;
966 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
967 head = ldata->read_head;
968
969 /* erase a single possibly multibyte character */
970 do {
971 head--;
972 c = read_buf(ldata, i: head);
973 } while (is_continuation(c, tty) &&
974 MASK(head) != MASK(ldata->canon_head));
975
976 /* do not partially erase */
977 if (is_continuation(c, tty))
978 break;
979
980 if (kill_type == WERASE) {
981 /* Equivalent to BSD's ALTWERASE. */
982 if (isalnum(c) || c == '_')
983 seen_alnums++;
984 else if (seen_alnums)
985 break;
986 }
987 cnt = ldata->read_head - head;
988 ldata->read_head = head;
989 if (L_ECHO(tty)) {
990 if (L_ECHOPRT(tty)) {
991 if (!ldata->erasing) {
992 echo_char_raw(c: '\\', ldata);
993 ldata->erasing = 1;
994 }
995 /* if cnt > 1, output a multi-byte character */
996 echo_char(c, tty);
997 while (--cnt > 0) {
998 head++;
999 echo_char_raw(c: read_buf(ldata, i: head), ldata);
1000 echo_move_back_col(ldata);
1001 }
1002 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1003 echo_char(ERASE_CHAR(tty), tty);
1004 } else if (c == '\t') {
1005 unsigned int num_chars = 0;
1006 int after_tab = 0;
1007 size_t tail = ldata->read_head;
1008
1009 /*
1010 * Count the columns used for characters
1011 * since the start of input or after a
1012 * previous tab.
1013 * This info is used to go back the correct
1014 * number of columns.
1015 */
1016 while (MASK(tail) != MASK(ldata->canon_head)) {
1017 tail--;
1018 c = read_buf(ldata, i: tail);
1019 if (c == '\t') {
1020 after_tab = 1;
1021 break;
1022 } else if (iscntrl(c)) {
1023 if (L_ECHOCTL(tty))
1024 num_chars += 2;
1025 } else if (!is_continuation(c, tty)) {
1026 num_chars++;
1027 }
1028 }
1029 echo_erase_tab(num_chars, after_tab, ldata);
1030 } else {
1031 if (iscntrl(c) && L_ECHOCTL(tty)) {
1032 echo_char_raw(c: '\b', ldata);
1033 echo_char_raw(c: ' ', ldata);
1034 echo_char_raw(c: '\b', ldata);
1035 }
1036 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1037 echo_char_raw(c: '\b', ldata);
1038 echo_char_raw(c: ' ', ldata);
1039 echo_char_raw(c: '\b', ldata);
1040 }
1041 }
1042 }
1043 if (kill_type == ERASE)
1044 break;
1045 }
1046 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1047 finish_erasing(ldata);
1048}
1049
1050
1051static void __isig(int sig, struct tty_struct *tty)
1052{
1053 struct pid *tty_pgrp = tty_get_pgrp(tty);
1054 if (tty_pgrp) {
1055 kill_pgrp(pid: tty_pgrp, sig, priv: 1);
1056 put_pid(pid: tty_pgrp);
1057 }
1058}
1059
1060/**
1061 * isig - handle the ISIG optio
1062 * @sig: signal
1063 * @tty: terminal
1064 *
1065 * Called when a signal is being sent due to terminal input. Called from the
1066 * &tty_driver.receive_buf() path, so serialized.
1067 *
1068 * Performs input and output flush if !NOFLSH. In this context, the echo
1069 * buffer is 'output'. The signal is processed first to alert any current
1070 * readers or writers to discontinue and exit their i/o loops.
1071 *
1072 * Locking: %ctrl.lock
1073 */
1074static void isig(int sig, struct tty_struct *tty)
1075{
1076 struct n_tty_data *ldata = tty->disc_data;
1077
1078 if (L_NOFLSH(tty)) {
1079 /* signal only */
1080 __isig(sig, tty);
1081
1082 } else { /* signal and flush */
1083 up_read(sem: &tty->termios_rwsem);
1084 down_write(sem: &tty->termios_rwsem);
1085
1086 __isig(sig, tty);
1087
1088 /* clear echo buffer */
1089 mutex_lock(lock: &ldata->output_lock);
1090 ldata->echo_head = ldata->echo_tail = 0;
1091 ldata->echo_mark = ldata->echo_commit = 0;
1092 mutex_unlock(lock: &ldata->output_lock);
1093
1094 /* clear output buffer */
1095 tty_driver_flush_buffer(tty);
1096
1097 /* clear input buffer */
1098 reset_buffer_flags(ldata: tty->disc_data);
1099
1100 /* notify pty master of flush */
1101 if (tty->link)
1102 n_tty_packet_mode_flush(tty);
1103
1104 up_write(sem: &tty->termios_rwsem);
1105 down_read(sem: &tty->termios_rwsem);
1106 }
1107}
1108
1109/**
1110 * n_tty_receive_break - handle break
1111 * @tty: terminal
1112 *
1113 * An RS232 break event has been hit in the incoming bitstream. This can cause
1114 * a variety of events depending upon the termios settings.
1115 *
1116 * Locking: n_tty_receive_buf()/producer path:
1117 * caller holds non-exclusive termios_rwsem
1118 *
1119 * Note: may get exclusive %termios_rwsem if flushing input buffer
1120 */
1121static void n_tty_receive_break(struct tty_struct *tty)
1122{
1123 struct n_tty_data *ldata = tty->disc_data;
1124
1125 if (I_IGNBRK(tty))
1126 return;
1127 if (I_BRKINT(tty)) {
1128 isig(SIGINT, tty);
1129 return;
1130 }
1131 if (I_PARMRK(tty)) {
1132 put_tty_queue(c: '\377', ldata);
1133 put_tty_queue(c: '\0', ldata);
1134 }
1135 put_tty_queue(c: '\0', ldata);
1136}
1137
1138/**
1139 * n_tty_receive_overrun - handle overrun reporting
1140 * @tty: terminal
1141 *
1142 * Data arrived faster than we could process it. While the tty driver has
1143 * flagged this the bits that were missed are gone forever.
1144 *
1145 * Called from the receive_buf path so single threaded. Does not need locking
1146 * as num_overrun and overrun_time are function private.
1147 */
1148static void n_tty_receive_overrun(const struct tty_struct *tty)
1149{
1150 struct n_tty_data *ldata = tty->disc_data;
1151
1152 ldata->num_overrun++;
1153 if (time_is_before_jiffies(ldata->overrun_time + HZ)) {
1154 tty_warn(tty, "%u input overrun(s)\n", ldata->num_overrun);
1155 ldata->overrun_time = jiffies;
1156 ldata->num_overrun = 0;
1157 }
1158}
1159
1160/**
1161 * n_tty_receive_parity_error - error notifier
1162 * @tty: terminal device
1163 * @c: character
1164 *
1165 * Process a parity error and queue the right data to indicate the error case
1166 * if necessary.
1167 *
1168 * Locking: n_tty_receive_buf()/producer path:
1169 * caller holds non-exclusive %termios_rwsem
1170 */
1171static void n_tty_receive_parity_error(const struct tty_struct *tty,
1172 u8 c)
1173{
1174 struct n_tty_data *ldata = tty->disc_data;
1175
1176 if (I_INPCK(tty)) {
1177 if (I_IGNPAR(tty))
1178 return;
1179 if (I_PARMRK(tty)) {
1180 put_tty_queue(c: '\377', ldata);
1181 put_tty_queue(c: '\0', ldata);
1182 put_tty_queue(c, ldata);
1183 } else
1184 put_tty_queue(c: '\0', ldata);
1185 } else
1186 put_tty_queue(c, ldata);
1187}
1188
1189static void
1190n_tty_receive_signal_char(struct tty_struct *tty, int signal, u8 c)
1191{
1192 isig(sig: signal, tty);
1193 if (I_IXON(tty))
1194 start_tty(tty);
1195 if (L_ECHO(tty)) {
1196 echo_char(c, tty);
1197 commit_echoes(tty);
1198 } else
1199 process_echoes(tty);
1200}
1201
1202static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, u8 c)
1203{
1204 return c == START_CHAR(tty) || c == STOP_CHAR(tty);
1205}
1206
1207/**
1208 * n_tty_receive_char_flow_ctrl - receive flow control chars
1209 * @tty: terminal device
1210 * @c: character
1211 * @lookahead_done: lookahead has processed this character already
1212 *
1213 * Receive and process flow control character actions.
1214 *
1215 * In case lookahead for flow control chars already handled the character in
1216 * advance to the normal receive, the actions are skipped during normal
1217 * receive.
1218 *
1219 * Returns true if @c is consumed as flow-control character, the character
1220 * must not be treated as normal character.
1221 */
1222static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, u8 c,
1223 bool lookahead_done)
1224{
1225 if (!n_tty_is_char_flow_ctrl(tty, c))
1226 return false;
1227
1228 if (lookahead_done)
1229 return true;
1230
1231 if (c == START_CHAR(tty)) {
1232 start_tty(tty);
1233 process_echoes(tty);
1234 return true;
1235 }
1236
1237 /* STOP_CHAR */
1238 stop_tty(tty);
1239 return true;
1240}
1241
1242static void n_tty_receive_handle_newline(struct tty_struct *tty, u8 c)
1243{
1244 struct n_tty_data *ldata = tty->disc_data;
1245
1246 set_bit(MASK(ldata->read_head), addr: ldata->read_flags);
1247 put_tty_queue(c, ldata);
1248 smp_store_release(&ldata->canon_head, ldata->read_head);
1249 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1250 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1251}
1252
1253static bool n_tty_receive_char_canon(struct tty_struct *tty, u8 c)
1254{
1255 struct n_tty_data *ldata = tty->disc_data;
1256
1257 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1258 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1259 eraser(c, tty);
1260 commit_echoes(tty);
1261
1262 return true;
1263 }
1264
1265 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1266 ldata->lnext = 1;
1267 if (L_ECHO(tty)) {
1268 finish_erasing(ldata);
1269 if (L_ECHOCTL(tty)) {
1270 echo_char_raw(c: '^', ldata);
1271 echo_char_raw(c: '\b', ldata);
1272 commit_echoes(tty);
1273 }
1274 }
1275
1276 return true;
1277 }
1278
1279 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1280 size_t tail = ldata->canon_head;
1281
1282 finish_erasing(ldata);
1283 echo_char(c, tty);
1284 echo_char_raw(c: '\n', ldata);
1285 while (MASK(tail) != MASK(ldata->read_head)) {
1286 echo_char(c: read_buf(ldata, i: tail), tty);
1287 tail++;
1288 }
1289 commit_echoes(tty);
1290
1291 return true;
1292 }
1293
1294 if (c == '\n') {
1295 if (L_ECHO(tty) || L_ECHONL(tty)) {
1296 echo_char_raw(c: '\n', ldata);
1297 commit_echoes(tty);
1298 }
1299 n_tty_receive_handle_newline(tty, c);
1300
1301 return true;
1302 }
1303
1304 if (c == EOF_CHAR(tty)) {
1305 c = __DISABLED_CHAR;
1306 n_tty_receive_handle_newline(tty, c);
1307
1308 return true;
1309 }
1310
1311 if ((c == EOL_CHAR(tty)) ||
1312 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1313 /*
1314 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1315 */
1316 if (L_ECHO(tty)) {
1317 /* Record the column of first canon char. */
1318 if (ldata->canon_head == ldata->read_head)
1319 echo_set_canon_col(ldata);
1320 echo_char(c, tty);
1321 commit_echoes(tty);
1322 }
1323 /*
1324 * XXX does PARMRK doubling happen for
1325 * EOL_CHAR and EOL2_CHAR?
1326 */
1327 if (c == '\377' && I_PARMRK(tty))
1328 put_tty_queue(c, ldata);
1329
1330 n_tty_receive_handle_newline(tty, c);
1331
1332 return true;
1333 }
1334
1335 return false;
1336}
1337
1338static void n_tty_receive_char_special(struct tty_struct *tty, u8 c,
1339 bool lookahead_done)
1340{
1341 struct n_tty_data *ldata = tty->disc_data;
1342
1343 if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
1344 return;
1345
1346 if (L_ISIG(tty)) {
1347 if (c == INTR_CHAR(tty)) {
1348 n_tty_receive_signal_char(tty, SIGINT, c);
1349 return;
1350 } else if (c == QUIT_CHAR(tty)) {
1351 n_tty_receive_signal_char(tty, SIGQUIT, c);
1352 return;
1353 } else if (c == SUSP_CHAR(tty)) {
1354 n_tty_receive_signal_char(tty, SIGTSTP, c);
1355 return;
1356 }
1357 }
1358
1359 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1360 start_tty(tty);
1361 process_echoes(tty);
1362 }
1363
1364 if (c == '\r') {
1365 if (I_IGNCR(tty))
1366 return;
1367 if (I_ICRNL(tty))
1368 c = '\n';
1369 } else if (c == '\n' && I_INLCR(tty))
1370 c = '\r';
1371
1372 if (ldata->icanon && n_tty_receive_char_canon(tty, c))
1373 return;
1374
1375 if (L_ECHO(tty)) {
1376 finish_erasing(ldata);
1377 if (c == '\n')
1378 echo_char_raw(c: '\n', ldata);
1379 else {
1380 /* Record the column of first canon char. */
1381 if (ldata->canon_head == ldata->read_head)
1382 echo_set_canon_col(ldata);
1383 echo_char(c, tty);
1384 }
1385 commit_echoes(tty);
1386 }
1387
1388 /* PARMRK doubling check */
1389 if (c == '\377' && I_PARMRK(tty))
1390 put_tty_queue(c, ldata);
1391
1392 put_tty_queue(c, ldata);
1393}
1394
1395/**
1396 * n_tty_receive_char - perform processing
1397 * @tty: terminal device
1398 * @c: character
1399 *
1400 * Process an individual character of input received from the driver. This is
1401 * serialized with respect to itself by the rules for the driver above.
1402 *
1403 * Locking: n_tty_receive_buf()/producer path:
1404 * caller holds non-exclusive %termios_rwsem
1405 * publishes canon_head if canonical mode is active
1406 */
1407static void n_tty_receive_char(struct tty_struct *tty, u8 c)
1408{
1409 struct n_tty_data *ldata = tty->disc_data;
1410
1411 if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1412 start_tty(tty);
1413 process_echoes(tty);
1414 }
1415 if (L_ECHO(tty)) {
1416 finish_erasing(ldata);
1417 /* Record the column of first canon char. */
1418 if (ldata->canon_head == ldata->read_head)
1419 echo_set_canon_col(ldata);
1420 echo_char(c, tty);
1421 commit_echoes(tty);
1422 }
1423 /* PARMRK doubling check */
1424 if (c == '\377' && I_PARMRK(tty))
1425 put_tty_queue(c, ldata);
1426 put_tty_queue(c, ldata);
1427}
1428
1429static void n_tty_receive_char_closing(struct tty_struct *tty, u8 c,
1430 bool lookahead_done)
1431{
1432 if (I_ISTRIP(tty))
1433 c &= 0x7f;
1434 if (I_IUCLC(tty) && L_IEXTEN(tty))
1435 c = tolower(c);
1436
1437 if (I_IXON(tty)) {
1438 if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
1439 tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1440 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1441 c != SUSP_CHAR(tty)) {
1442 start_tty(tty);
1443 process_echoes(tty);
1444 }
1445 }
1446}
1447
1448static void
1449n_tty_receive_char_flagged(struct tty_struct *tty, u8 c, u8 flag)
1450{
1451 switch (flag) {
1452 case TTY_BREAK:
1453 n_tty_receive_break(tty);
1454 break;
1455 case TTY_PARITY:
1456 case TTY_FRAME:
1457 n_tty_receive_parity_error(tty, c);
1458 break;
1459 case TTY_OVERRUN:
1460 n_tty_receive_overrun(tty);
1461 break;
1462 default:
1463 tty_err(tty, "unknown flag %u\n", flag);
1464 break;
1465 }
1466}
1467
1468static void
1469n_tty_receive_char_lnext(struct tty_struct *tty, u8 c, u8 flag)
1470{
1471 struct n_tty_data *ldata = tty->disc_data;
1472
1473 ldata->lnext = 0;
1474 if (likely(flag == TTY_NORMAL)) {
1475 if (I_ISTRIP(tty))
1476 c &= 0x7f;
1477 if (I_IUCLC(tty) && L_IEXTEN(tty))
1478 c = tolower(c);
1479 n_tty_receive_char(tty, c);
1480 } else
1481 n_tty_receive_char_flagged(tty, c, flag);
1482}
1483
1484/* Caller must ensure count > 0 */
1485static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const u8 *cp,
1486 const u8 *fp, size_t count)
1487{
1488 struct n_tty_data *ldata = tty->disc_data;
1489 u8 flag = TTY_NORMAL;
1490
1491 ldata->lookahead_count += count;
1492
1493 if (!I_IXON(tty))
1494 return;
1495
1496 while (count--) {
1497 if (fp)
1498 flag = *fp++;
1499 if (likely(flag == TTY_NORMAL))
1500 n_tty_receive_char_flow_ctrl(tty, c: *cp, lookahead_done: false);
1501 cp++;
1502 }
1503}
1504
1505static void
1506n_tty_receive_buf_real_raw(const struct tty_struct *tty, const u8 *cp,
1507 size_t count)
1508{
1509 struct n_tty_data *ldata = tty->disc_data;
1510
1511 /* handle buffer wrap-around by a loop */
1512 for (unsigned int i = 0; i < 2; i++) {
1513 size_t head = MASK(ldata->read_head);
1514 size_t n = min(count, N_TTY_BUF_SIZE - head);
1515
1516 memcpy(to: read_buf_addr(ldata, i: head), from: cp, len: n);
1517
1518 ldata->read_head += n;
1519 cp += n;
1520 count -= n;
1521 }
1522}
1523
1524static void
1525n_tty_receive_buf_raw(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1526 size_t count)
1527{
1528 struct n_tty_data *ldata = tty->disc_data;
1529 u8 flag = TTY_NORMAL;
1530
1531 while (count--) {
1532 if (fp)
1533 flag = *fp++;
1534 if (likely(flag == TTY_NORMAL))
1535 put_tty_queue(c: *cp++, ldata);
1536 else
1537 n_tty_receive_char_flagged(tty, c: *cp++, flag);
1538 }
1539}
1540
1541static void
1542n_tty_receive_buf_closing(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1543 size_t count, bool lookahead_done)
1544{
1545 u8 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, c: *cp++, lookahead_done);
1552 }
1553}
1554
1555static void n_tty_receive_buf_standard(struct tty_struct *tty, const u8 *cp,
1556 const u8 *fp, size_t count,
1557 bool lookahead_done)
1558{
1559 struct n_tty_data *ldata = tty->disc_data;
1560 u8 flag = TTY_NORMAL;
1561
1562 while (count--) {
1563 u8 c = *cp++;
1564
1565 if (fp)
1566 flag = *fp++;
1567
1568 if (ldata->lnext) {
1569 n_tty_receive_char_lnext(tty, c, flag);
1570 continue;
1571 }
1572
1573 if (unlikely(flag != TTY_NORMAL)) {
1574 n_tty_receive_char_flagged(tty, c, flag);
1575 continue;
1576 }
1577
1578 if (I_ISTRIP(tty))
1579 c &= 0x7f;
1580 if (I_IUCLC(tty) && L_IEXTEN(tty))
1581 c = tolower(c);
1582 if (L_EXTPROC(tty)) {
1583 put_tty_queue(c, ldata);
1584 continue;
1585 }
1586
1587 if (test_bit(c, ldata->char_map))
1588 n_tty_receive_char_special(tty, c, lookahead_done);
1589 else
1590 n_tty_receive_char(tty, c);
1591 }
1592}
1593
1594static void __receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1595 size_t count)
1596{
1597 struct n_tty_data *ldata = tty->disc_data;
1598 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1599 size_t la_count = min(ldata->lookahead_count, count);
1600
1601 if (ldata->real_raw)
1602 n_tty_receive_buf_real_raw(tty, cp, count);
1603 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1604 n_tty_receive_buf_raw(tty, cp, fp, count);
1605 else if (tty->closing && !L_EXTPROC(tty)) {
1606 if (la_count > 0) {
1607 n_tty_receive_buf_closing(tty, cp, fp, count: la_count, lookahead_done: true);
1608 cp += la_count;
1609 if (fp)
1610 fp += la_count;
1611 count -= la_count;
1612 }
1613 if (count > 0)
1614 n_tty_receive_buf_closing(tty, cp, fp, count, lookahead_done: false);
1615 } else {
1616 if (la_count > 0) {
1617 n_tty_receive_buf_standard(tty, cp, fp, count: la_count, lookahead_done: true);
1618 cp += la_count;
1619 if (fp)
1620 fp += la_count;
1621 count -= la_count;
1622 }
1623 if (count > 0)
1624 n_tty_receive_buf_standard(tty, cp, fp, count, lookahead_done: false);
1625
1626 flush_echoes(tty);
1627 if (tty->ops->flush_chars)
1628 tty->ops->flush_chars(tty);
1629 }
1630
1631 ldata->lookahead_count -= la_count;
1632
1633 if (ldata->icanon && !L_EXTPROC(tty))
1634 return;
1635
1636 /* publish read_head to consumer */
1637 smp_store_release(&ldata->commit_head, ldata->read_head);
1638
1639 if (read_cnt(ldata)) {
1640 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1641 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1642 }
1643}
1644
1645/**
1646 * n_tty_receive_buf_common - process input
1647 * @tty: device to receive input
1648 * @cp: input chars
1649 * @fp: flags for each char (if %NULL, all chars are %TTY_NORMAL)
1650 * @count: number of input chars in @cp
1651 * @flow: enable flow control
1652 *
1653 * Called by the terminal driver when a block of characters has been received.
1654 * This function must be called from soft contexts not from interrupt context.
1655 * The driver is responsible for making calls one at a time and in order (or
1656 * using flush_to_ldisc()).
1657 *
1658 * Returns: the # of input chars from @cp which were processed.
1659 *
1660 * In canonical mode, the maximum line length is 4096 chars (including the line
1661 * termination char); lines longer than 4096 chars are truncated. After 4095
1662 * chars, input data is still processed but not stored. Overflow processing
1663 * ensures the tty can always receive more input until at least one line can be
1664 * read.
1665 *
1666 * In non-canonical mode, the read buffer will only accept 4095 chars; this
1667 * provides the necessary space for a newline char if the input mode is
1668 * switched to canonical.
1669 *
1670 * Note it is possible for the read buffer to _contain_ 4096 chars in
1671 * non-canonical mode: the read buffer could already contain the maximum canon
1672 * line of 4096 chars when the mode is switched to non-canonical.
1673 *
1674 * Locking: n_tty_receive_buf()/producer path:
1675 * claims non-exclusive %termios_rwsem
1676 * publishes commit_head or canon_head
1677 */
1678static size_t
1679n_tty_receive_buf_common(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1680 size_t count, bool flow)
1681{
1682 struct n_tty_data *ldata = tty->disc_data;
1683 size_t n, rcvd = 0;
1684 int room, overflow;
1685
1686 down_read(sem: &tty->termios_rwsem);
1687
1688 do {
1689 /*
1690 * When PARMRK is set, each input char may take up to 3 chars
1691 * in the read buf; reduce the buffer space avail by 3x
1692 *
1693 * If we are doing input canonicalization, and there are no
1694 * pending newlines, let characters through without limit, so
1695 * that erase characters will be handled. Other excess
1696 * characters will be beeped.
1697 *
1698 * paired with store in *_copy_from_read_buf() -- guarantees
1699 * the consumer has loaded the data in read_buf up to the new
1700 * read_tail (so this producer will not overwrite unread data)
1701 */
1702 size_t tail = smp_load_acquire(&ldata->read_tail);
1703
1704 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1705 if (I_PARMRK(tty))
1706 room = DIV_ROUND_UP(room, 3);
1707 room--;
1708 if (room <= 0) {
1709 overflow = ldata->icanon && ldata->canon_head == tail;
1710 if (overflow && room < 0)
1711 ldata->read_head--;
1712 room = overflow;
1713 WRITE_ONCE(ldata->no_room, flow && !room);
1714 } else
1715 overflow = 0;
1716
1717 n = min_t(size_t, count, room);
1718 if (!n)
1719 break;
1720
1721 /* ignore parity errors if handling overflow */
1722 if (!overflow || !fp || *fp != TTY_PARITY)
1723 __receive_buf(tty, cp, fp, count: n);
1724
1725 cp += n;
1726 if (fp)
1727 fp += n;
1728 count -= n;
1729 rcvd += n;
1730 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1731
1732 tty->receive_room = room;
1733
1734 /* Unthrottle if handling overflow on pty */
1735 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1736 if (overflow) {
1737 tty_set_flow_change(tty, val: TTY_UNTHROTTLE_SAFE);
1738 tty_unthrottle_safe(tty);
1739 __tty_set_flow_change(tty, val: 0);
1740 }
1741 } else
1742 n_tty_check_throttle(tty);
1743
1744 if (unlikely(ldata->no_room)) {
1745 /*
1746 * Barrier here is to ensure to read the latest read_tail in
1747 * chars_in_buffer() and to make sure that read_tail is not loaded
1748 * before ldata->no_room is set.
1749 */
1750 smp_mb();
1751 if (!chars_in_buffer(tty))
1752 n_tty_kick_worker(tty);
1753 }
1754
1755 up_read(sem: &tty->termios_rwsem);
1756
1757 return rcvd;
1758}
1759
1760static void n_tty_receive_buf(struct tty_struct *tty, const u8 *cp,
1761 const u8 *fp, size_t count)
1762{
1763 n_tty_receive_buf_common(tty, cp, fp, count, flow: false);
1764}
1765
1766static size_t n_tty_receive_buf2(struct tty_struct *tty, const u8 *cp,
1767 const u8 *fp, size_t count)
1768{
1769 return n_tty_receive_buf_common(tty, cp, fp, count, flow: true);
1770}
1771
1772/**
1773 * n_tty_set_termios - termios data changed
1774 * @tty: terminal
1775 * @old: previous data
1776 *
1777 * Called by the tty layer when the user changes termios flags so that the line
1778 * discipline can plan ahead. This function cannot sleep and is protected from
1779 * re-entry by the tty layer. The user is guaranteed that this function will
1780 * not be re-entered or in progress when the ldisc is closed.
1781 *
1782 * Locking: Caller holds @tty->termios_rwsem
1783 */
1784static void n_tty_set_termios(struct tty_struct *tty, const struct ktermios *old)
1785{
1786 struct n_tty_data *ldata = tty->disc_data;
1787
1788 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1789 bitmap_zero(dst: ldata->read_flags, N_TTY_BUF_SIZE);
1790 ldata->line_start = ldata->read_tail;
1791 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1792 ldata->canon_head = ldata->read_tail;
1793 ldata->push = 0;
1794 } else {
1795 set_bit(MASK(ldata->read_head - 1), addr: ldata->read_flags);
1796 ldata->canon_head = ldata->read_head;
1797 ldata->push = 1;
1798 }
1799 ldata->commit_head = ldata->read_head;
1800 ldata->erasing = 0;
1801 ldata->lnext = 0;
1802 }
1803
1804 ldata->icanon = (L_ICANON(tty) != 0);
1805
1806 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1807 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1808 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1809 I_PARMRK(tty)) {
1810 bitmap_zero(dst: ldata->char_map, nbits: 256);
1811
1812 if (I_IGNCR(tty) || I_ICRNL(tty))
1813 set_bit(nr: '\r', addr: ldata->char_map);
1814 if (I_INLCR(tty))
1815 set_bit(nr: '\n', addr: ldata->char_map);
1816
1817 if (L_ICANON(tty)) {
1818 set_bit(ERASE_CHAR(tty), addr: ldata->char_map);
1819 set_bit(KILL_CHAR(tty), addr: ldata->char_map);
1820 set_bit(EOF_CHAR(tty), addr: ldata->char_map);
1821 set_bit(nr: '\n', addr: ldata->char_map);
1822 set_bit(EOL_CHAR(tty), addr: ldata->char_map);
1823 if (L_IEXTEN(tty)) {
1824 set_bit(WERASE_CHAR(tty), addr: ldata->char_map);
1825 set_bit(LNEXT_CHAR(tty), addr: ldata->char_map);
1826 set_bit(EOL2_CHAR(tty), addr: ldata->char_map);
1827 if (L_ECHO(tty))
1828 set_bit(REPRINT_CHAR(tty),
1829 addr: ldata->char_map);
1830 }
1831 }
1832 if (I_IXON(tty)) {
1833 set_bit(START_CHAR(tty), addr: ldata->char_map);
1834 set_bit(STOP_CHAR(tty), addr: ldata->char_map);
1835 }
1836 if (L_ISIG(tty)) {
1837 set_bit(INTR_CHAR(tty), addr: ldata->char_map);
1838 set_bit(QUIT_CHAR(tty), addr: ldata->char_map);
1839 set_bit(SUSP_CHAR(tty), addr: ldata->char_map);
1840 }
1841 clear_bit(__DISABLED_CHAR, addr: ldata->char_map);
1842 ldata->raw = 0;
1843 ldata->real_raw = 0;
1844 } else {
1845 ldata->raw = 1;
1846 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1847 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1848 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1849 ldata->real_raw = 1;
1850 else
1851 ldata->real_raw = 0;
1852 }
1853 /*
1854 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1855 * been stopped by STOP_CHAR(tty) before it.
1856 */
1857 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1858 start_tty(tty);
1859 process_echoes(tty);
1860 }
1861
1862 /* The termios change make the tty ready for I/O */
1863 wake_up_interruptible(&tty->write_wait);
1864 wake_up_interruptible(&tty->read_wait);
1865}
1866
1867/**
1868 * n_tty_close - close the ldisc for this tty
1869 * @tty: device
1870 *
1871 * Called from the terminal layer when this line discipline is being shut down,
1872 * either because of a close or becsuse of a discipline change. The function
1873 * will not be called while other ldisc methods are in progress.
1874 */
1875static void n_tty_close(struct tty_struct *tty)
1876{
1877 struct n_tty_data *ldata = tty->disc_data;
1878
1879 if (tty->link)
1880 n_tty_packet_mode_flush(tty);
1881
1882 down_write(sem: &tty->termios_rwsem);
1883 vfree(addr: ldata);
1884 tty->disc_data = NULL;
1885 up_write(sem: &tty->termios_rwsem);
1886}
1887
1888/**
1889 * n_tty_open - open an ldisc
1890 * @tty: terminal to open
1891 *
1892 * Called when this line discipline is being attached to the terminal device.
1893 * Can sleep. Called serialized so that no other events will occur in parallel.
1894 * No further open will occur until a close.
1895 */
1896static int n_tty_open(struct tty_struct *tty)
1897{
1898 struct n_tty_data *ldata;
1899
1900 /* Currently a malloc failure here can panic */
1901 ldata = vzalloc(sizeof(*ldata));
1902 if (!ldata)
1903 return -ENOMEM;
1904
1905 ldata->overrun_time = jiffies;
1906 mutex_init(&ldata->atomic_read_lock);
1907 mutex_init(&ldata->output_lock);
1908
1909 tty->disc_data = ldata;
1910 tty->closing = 0;
1911 /* indicate buffer work may resume */
1912 clear_bit(nr: TTY_LDISC_HALTED, addr: &tty->flags);
1913 n_tty_set_termios(tty, NULL);
1914 tty_unthrottle(tty);
1915 return 0;
1916}
1917
1918static inline int input_available_p(const struct tty_struct *tty, int poll)
1919{
1920 const struct n_tty_data *ldata = tty->disc_data;
1921 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1922
1923 if (ldata->icanon && !L_EXTPROC(tty))
1924 return ldata->canon_head != ldata->read_tail;
1925 else
1926 return ldata->commit_head - ldata->read_tail >= amt;
1927}
1928
1929/**
1930 * copy_from_read_buf - copy read data directly
1931 * @tty: terminal device
1932 * @kbp: data
1933 * @nr: size of data
1934 *
1935 * Helper function to speed up n_tty_read(). It is only called when %ICANON is
1936 * off; it copies characters straight from the tty queue.
1937 *
1938 * Returns: true if it successfully copied data, but there is still more data
1939 * to be had.
1940 *
1941 * Locking:
1942 * * called under the @ldata->atomic_read_lock sem
1943 * * n_tty_read()/consumer path:
1944 * caller holds non-exclusive %termios_rwsem;
1945 * read_tail published
1946 */
1947static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
1948 size_t *nr)
1949
1950{
1951 struct n_tty_data *ldata = tty->disc_data;
1952 size_t n;
1953 bool is_eof;
1954 size_t head = smp_load_acquire(&ldata->commit_head);
1955 size_t tail = MASK(ldata->read_tail);
1956
1957 n = min3(head - ldata->read_tail, N_TTY_BUF_SIZE - tail, *nr);
1958 if (!n)
1959 return false;
1960
1961 u8 *from = read_buf_addr(ldata, i: tail);
1962 memcpy(to: *kbp, from, len: n);
1963 is_eof = n == 1 && *from == EOF_CHAR(tty);
1964 tty_audit_add_data(tty, data: from, size: n);
1965 zero_buffer(tty, buffer: from, size: n);
1966 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1967
1968 /* Turn single EOF into zero-length read */
1969 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1970 head == ldata->read_tail)
1971 return false;
1972
1973 *kbp += n;
1974 *nr -= n;
1975
1976 /* If we have more to copy, let the caller know */
1977 return head != ldata->read_tail;
1978}
1979
1980/**
1981 * canon_copy_from_read_buf - copy read data in canonical mode
1982 * @tty: terminal device
1983 * @kbp: data
1984 * @nr: size of data
1985 *
1986 * Helper function for n_tty_read(). It is only called when %ICANON is on; it
1987 * copies one line of input up to and including the line-delimiting character
1988 * into the result buffer.
1989 *
1990 * Note: When termios is changed from non-canonical to canonical mode and the
1991 * read buffer contains data, n_tty_set_termios() simulates an EOF push (as if
1992 * C-d were input) _without_ the %DISABLED_CHAR in the buffer. This causes data
1993 * already processed as input to be immediately available as input although a
1994 * newline has not been received.
1995 *
1996 * Locking:
1997 * * called under the %atomic_read_lock mutex
1998 * * n_tty_read()/consumer path:
1999 * caller holds non-exclusive %termios_rwsem;
2000 * read_tail published
2001 */
2002static bool canon_copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
2003 size_t *nr)
2004{
2005 struct n_tty_data *ldata = tty->disc_data;
2006 size_t n, size, more, c;
2007 size_t eol;
2008 size_t tail, canon_head;
2009 int found = 0;
2010
2011 /* N.B. avoid overrun if nr == 0 */
2012 if (!*nr)
2013 return false;
2014
2015 canon_head = smp_load_acquire(&ldata->canon_head);
2016 n = min(*nr, canon_head - ldata->read_tail);
2017
2018 tail = MASK(ldata->read_tail);
2019 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2020
2021 eol = find_next_bit(addr: ldata->read_flags, size, offset: tail);
2022 more = n - (size - tail);
2023 if (eol == N_TTY_BUF_SIZE && more) {
2024 /* scan wrapped without finding set bit */
2025 eol = find_first_bit(addr: ldata->read_flags, size: more);
2026 found = eol != more;
2027 } else
2028 found = eol != size;
2029
2030 n = eol - tail;
2031 if (n > N_TTY_BUF_SIZE)
2032 n += N_TTY_BUF_SIZE;
2033 c = n + found;
2034
2035 if (!found || read_buf(ldata, i: eol) != __DISABLED_CHAR)
2036 n = c;
2037
2038 tty_copy(tty, to: *kbp, tail, n);
2039 *kbp += n;
2040 *nr -= n;
2041
2042 if (found)
2043 clear_bit(nr: eol, addr: ldata->read_flags);
2044 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2045
2046 if (found) {
2047 if (!ldata->push)
2048 ldata->line_start = ldata->read_tail;
2049 else
2050 ldata->push = 0;
2051 tty_audit_push();
2052 return false;
2053 }
2054
2055 /* No EOL found - do a continuation retry if there is more data */
2056 return ldata->read_tail != canon_head;
2057}
2058
2059/*
2060 * If we finished a read at the exact location of an
2061 * EOF (special EOL character that's a __DISABLED_CHAR)
2062 * in the stream, silently eat the EOF.
2063 */
2064static void canon_skip_eof(struct n_tty_data *ldata)
2065{
2066 size_t tail, canon_head;
2067
2068 canon_head = smp_load_acquire(&ldata->canon_head);
2069 tail = ldata->read_tail;
2070
2071 // No data?
2072 if (tail == canon_head)
2073 return;
2074
2075 // See if the tail position is EOF in the circular buffer
2076 tail &= (N_TTY_BUF_SIZE - 1);
2077 if (!test_bit(tail, ldata->read_flags))
2078 return;
2079 if (read_buf(ldata, i: tail) != __DISABLED_CHAR)
2080 return;
2081
2082 // Clear the EOL bit, skip the EOF char.
2083 clear_bit(nr: tail, addr: ldata->read_flags);
2084 smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2085}
2086
2087/**
2088 * job_control - check job control
2089 * @tty: tty
2090 * @file: file handle
2091 *
2092 * Perform job control management checks on this @file/@tty descriptor and if
2093 * appropriate send any needed signals and return a negative error code if
2094 * action should be taken.
2095 *
2096 * Locking:
2097 * * redirected write test is safe
2098 * * current->signal->tty check is safe
2099 * * ctrl.lock to safely reference @tty->ctrl.pgrp
2100 */
2101static int job_control(struct tty_struct *tty, struct file *file)
2102{
2103 /* Job control check -- must be done at start and after
2104 every sleep (POSIX.1 7.1.1.4). */
2105 /* NOTE: not yet done after every sleep pending a thorough
2106 check of the logic of this change. -- jlc */
2107 /* don't stop on /dev/console */
2108 if (file->f_op->write_iter == redirected_tty_write)
2109 return 0;
2110
2111 return __tty_check_change(tty, SIGTTIN);
2112}
2113
2114/*
2115 * We still hold the atomic_read_lock and the termios_rwsem, and can just
2116 * continue to copy data.
2117 */
2118static ssize_t n_tty_continue_cookie(struct tty_struct *tty, u8 *kbuf,
2119 size_t nr, void **cookie)
2120{
2121 struct n_tty_data *ldata = tty->disc_data;
2122 u8 *kb = kbuf;
2123
2124 if (ldata->icanon && !L_EXTPROC(tty)) {
2125 /*
2126 * If we have filled the user buffer, see if we should skip an
2127 * EOF character before releasing the lock and returning done.
2128 */
2129 if (!nr)
2130 canon_skip_eof(ldata);
2131 else if (canon_copy_from_read_buf(tty, kbp: &kb, nr: &nr))
2132 return kb - kbuf;
2133 } else {
2134 if (copy_from_read_buf(tty, kbp: &kb, nr: &nr))
2135 return kb - kbuf;
2136 }
2137
2138 /* No more data - release locks and stop retries */
2139 n_tty_kick_worker(tty);
2140 n_tty_check_unthrottle(tty);
2141 up_read(sem: &tty->termios_rwsem);
2142 mutex_unlock(lock: &ldata->atomic_read_lock);
2143 *cookie = NULL;
2144
2145 return kb - kbuf;
2146}
2147
2148static int n_tty_wait_for_input(struct tty_struct *tty, struct file *file,
2149 struct wait_queue_entry *wait, long *timeout)
2150{
2151 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2152 return -EIO;
2153 if (tty_hung_up_p(filp: file))
2154 return 0;
2155 /*
2156 * Abort readers for ttys which never actually get hung up.
2157 * See __tty_hangup().
2158 */
2159 if (test_bit(TTY_HUPPING, &tty->flags))
2160 return 0;
2161 if (!*timeout)
2162 return 0;
2163 if (tty_io_nonblock(tty, file))
2164 return -EAGAIN;
2165 if (signal_pending(current))
2166 return -ERESTARTSYS;
2167
2168 up_read(sem: &tty->termios_rwsem);
2169 *timeout = wait_woken(wq_entry: wait, TASK_INTERRUPTIBLE, timeout: *timeout);
2170 down_read(sem: &tty->termios_rwsem);
2171
2172 return 1;
2173}
2174
2175/**
2176 * n_tty_read - read function for tty
2177 * @tty: tty device
2178 * @file: file object
2179 * @kbuf: kernelspace buffer pointer
2180 * @nr: size of I/O
2181 * @cookie: if non-%NULL, this is a continuation read
2182 * @offset: where to continue reading from (unused in n_tty)
2183 *
2184 * Perform reads for the line discipline. We are guaranteed that the line
2185 * discipline will not be closed under us but we may get multiple parallel
2186 * readers and must handle this ourselves. We may also get a hangup. Always
2187 * called in user context, may sleep.
2188 *
2189 * This code must be sure never to sleep through a hangup.
2190 *
2191 * Locking: n_tty_read()/consumer path:
2192 * claims non-exclusive termios_rwsem;
2193 * publishes read_tail
2194 */
2195static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
2196 size_t nr, void **cookie, unsigned long offset)
2197{
2198 struct n_tty_data *ldata = tty->disc_data;
2199 u8 *kb = kbuf;
2200 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2201 int minimum, time;
2202 ssize_t retval;
2203 long timeout;
2204 bool packet;
2205 size_t old_tail;
2206
2207 /* Is this a continuation of a read started earlier? */
2208 if (*cookie)
2209 return n_tty_continue_cookie(tty, kbuf, nr, cookie);
2210
2211 retval = job_control(tty, file);
2212 if (retval < 0)
2213 return retval;
2214
2215 /*
2216 * Internal serialization of reads.
2217 */
2218 if (file->f_flags & O_NONBLOCK) {
2219 if (!mutex_trylock(lock: &ldata->atomic_read_lock))
2220 return -EAGAIN;
2221 } else {
2222 if (mutex_lock_interruptible(lock: &ldata->atomic_read_lock))
2223 return -ERESTARTSYS;
2224 }
2225
2226 down_read(sem: &tty->termios_rwsem);
2227
2228 minimum = time = 0;
2229 timeout = MAX_SCHEDULE_TIMEOUT;
2230 if (!ldata->icanon) {
2231 minimum = MIN_CHAR(tty);
2232 if (minimum) {
2233 time = (HZ / 10) * TIME_CHAR(tty);
2234 } else {
2235 timeout = (HZ / 10) * TIME_CHAR(tty);
2236 minimum = 1;
2237 }
2238 }
2239
2240 packet = tty->ctrl.packet;
2241 old_tail = ldata->read_tail;
2242
2243 add_wait_queue(wq_head: &tty->read_wait, wq_entry: &wait);
2244 while (nr) {
2245 /* First test for status change. */
2246 if (packet && tty->link->ctrl.pktstatus) {
2247 u8 cs;
2248 if (kb != kbuf)
2249 break;
2250 spin_lock_irq(lock: &tty->link->ctrl.lock);
2251 cs = tty->link->ctrl.pktstatus;
2252 tty->link->ctrl.pktstatus = 0;
2253 spin_unlock_irq(lock: &tty->link->ctrl.lock);
2254 *kb++ = cs;
2255 nr--;
2256 break;
2257 }
2258
2259 if (!input_available_p(tty, poll: 0)) {
2260 up_read(sem: &tty->termios_rwsem);
2261 tty_buffer_flush_work(port: tty->port);
2262 down_read(sem: &tty->termios_rwsem);
2263 if (!input_available_p(tty, poll: 0)) {
2264 int ret = n_tty_wait_for_input(tty, file, wait: &wait,
2265 timeout: &timeout);
2266 if (ret <= 0) {
2267 retval = ret;
2268 break;
2269 }
2270 continue;
2271 }
2272 }
2273
2274 if (ldata->icanon && !L_EXTPROC(tty)) {
2275 if (canon_copy_from_read_buf(tty, kbp: &kb, nr: &nr))
2276 goto more_to_be_read;
2277 } else {
2278 /* Deal with packet mode. */
2279 if (packet && kb == kbuf) {
2280 *kb++ = TIOCPKT_DATA;
2281 nr--;
2282 }
2283
2284 if (copy_from_read_buf(tty, kbp: &kb, nr: &nr) && kb - kbuf >= minimum)
2285 goto more_to_be_read;
2286 }
2287
2288 n_tty_check_unthrottle(tty);
2289
2290 if (kb - kbuf >= minimum)
2291 break;
2292 if (time)
2293 timeout = time;
2294 }
2295 if (old_tail != ldata->read_tail) {
2296 /*
2297 * Make sure no_room is not read in n_tty_kick_worker()
2298 * before setting ldata->read_tail in copy_from_read_buf().
2299 */
2300 smp_mb();
2301 n_tty_kick_worker(tty);
2302 }
2303 up_read(sem: &tty->termios_rwsem);
2304
2305 remove_wait_queue(wq_head: &tty->read_wait, wq_entry: &wait);
2306 mutex_unlock(lock: &ldata->atomic_read_lock);
2307
2308 if (kb - kbuf)
2309 retval = kb - kbuf;
2310
2311 return retval;
2312more_to_be_read:
2313 /*
2314 * There is more to be had and we have nothing more to wait for, so
2315 * let's mark us for retries.
2316 *
2317 * NOTE! We return here with both the termios_sem and atomic_read_lock
2318 * still held, the retries will release them when done.
2319 */
2320 remove_wait_queue(wq_head: &tty->read_wait, wq_entry: &wait);
2321 *cookie = cookie;
2322
2323 return kb - kbuf;
2324}
2325
2326/**
2327 * n_tty_write - write function for tty
2328 * @tty: tty device
2329 * @file: file object
2330 * @buf: userspace buffer pointer
2331 * @nr: size of I/O
2332 *
2333 * Write function of the terminal device. This is serialized with respect to
2334 * other write callers but not to termios changes, reads and other such events.
2335 * Since the receive code will echo characters, thus calling driver write
2336 * methods, the %output_lock is used in the output processing functions called
2337 * here as well as in the echo processing function to protect the column state
2338 * and space left in the buffer.
2339 *
2340 * This code must be sure never to sleep through a hangup.
2341 *
2342 * Locking: output_lock to protect column state and space left
2343 * (note that the process_output*() functions take this lock themselves)
2344 */
2345
2346static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2347 const u8 *buf, size_t nr)
2348{
2349 const u8 *b = buf;
2350 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2351 ssize_t num, retval = 0;
2352
2353 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2354 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2355 retval = tty_check_change(tty);
2356 if (retval)
2357 return retval;
2358 }
2359
2360 down_read(sem: &tty->termios_rwsem);
2361
2362 /* Write out any echoed characters that are still pending */
2363 process_echoes(tty);
2364
2365 add_wait_queue(wq_head: &tty->write_wait, wq_entry: &wait);
2366 while (1) {
2367 if (signal_pending(current)) {
2368 retval = -ERESTARTSYS;
2369 break;
2370 }
2371 if (tty_hung_up_p(filp: file) || (tty->link && !tty->link->count)) {
2372 retval = -EIO;
2373 break;
2374 }
2375 if (O_OPOST(tty)) {
2376 while (nr > 0) {
2377 num = process_output_block(tty, buf: b, nr);
2378 if (num < 0) {
2379 if (num == -EAGAIN)
2380 break;
2381 retval = num;
2382 goto break_out;
2383 }
2384 b += num;
2385 nr -= num;
2386 if (nr == 0)
2387 break;
2388 if (process_output(c: *b, tty) < 0)
2389 break;
2390 b++; nr--;
2391 }
2392 if (tty->ops->flush_chars)
2393 tty->ops->flush_chars(tty);
2394 } else {
2395 struct n_tty_data *ldata = tty->disc_data;
2396
2397 while (nr > 0) {
2398 mutex_lock(lock: &ldata->output_lock);
2399 num = tty->ops->write(tty, b, nr);
2400 mutex_unlock(lock: &ldata->output_lock);
2401 if (num < 0) {
2402 retval = num;
2403 goto break_out;
2404 }
2405 if (!num)
2406 break;
2407 b += num;
2408 nr -= num;
2409 }
2410 }
2411 if (!nr)
2412 break;
2413 if (tty_io_nonblock(tty, file)) {
2414 retval = -EAGAIN;
2415 break;
2416 }
2417 up_read(sem: &tty->termios_rwsem);
2418
2419 wait_woken(wq_entry: &wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2420
2421 down_read(sem: &tty->termios_rwsem);
2422 }
2423break_out:
2424 remove_wait_queue(wq_head: &tty->write_wait, wq_entry: &wait);
2425 if (nr && tty->fasync)
2426 set_bit(nr: TTY_DO_WRITE_WAKEUP, addr: &tty->flags);
2427 up_read(sem: &tty->termios_rwsem);
2428 return (b - buf) ? b - buf : retval;
2429}
2430
2431/**
2432 * n_tty_poll - poll method for N_TTY
2433 * @tty: terminal device
2434 * @file: file accessing it
2435 * @wait: poll table
2436 *
2437 * Called when the line discipline is asked to poll() for data or for special
2438 * events. This code is not serialized with respect to other events save
2439 * open/close.
2440 *
2441 * This code must be sure never to sleep through a hangup.
2442 *
2443 * Locking: called without the kernel lock held -- fine.
2444 */
2445static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2446 poll_table *wait)
2447{
2448 __poll_t mask = 0;
2449
2450 poll_wait(filp: file, wait_address: &tty->read_wait, p: wait);
2451 poll_wait(filp: file, wait_address: &tty->write_wait, p: wait);
2452 if (input_available_p(tty, poll: 1))
2453 mask |= EPOLLIN | EPOLLRDNORM;
2454 else {
2455 tty_buffer_flush_work(port: tty->port);
2456 if (input_available_p(tty, poll: 1))
2457 mask |= EPOLLIN | EPOLLRDNORM;
2458 }
2459 if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2460 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2461 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2462 mask |= EPOLLHUP;
2463 if (tty_hung_up_p(filp: file))
2464 mask |= EPOLLHUP;
2465 if (tty->ops->write && !tty_is_writelocked(tty) &&
2466 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2467 tty_write_room(tty) > 0)
2468 mask |= EPOLLOUT | EPOLLWRNORM;
2469 return mask;
2470}
2471
2472static unsigned long inq_canon(struct n_tty_data *ldata)
2473{
2474 size_t nr, head, tail;
2475
2476 if (ldata->canon_head == ldata->read_tail)
2477 return 0;
2478 head = ldata->canon_head;
2479 tail = ldata->read_tail;
2480 nr = head - tail;
2481 /* Skip EOF-chars.. */
2482 while (MASK(head) != MASK(tail)) {
2483 if (test_bit(MASK(tail), ldata->read_flags) &&
2484 read_buf(ldata, i: tail) == __DISABLED_CHAR)
2485 nr--;
2486 tail++;
2487 }
2488 return nr;
2489}
2490
2491static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
2492 unsigned long arg)
2493{
2494 struct n_tty_data *ldata = tty->disc_data;
2495 unsigned int num;
2496
2497 switch (cmd) {
2498 case TIOCOUTQ:
2499 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2500 case TIOCINQ:
2501 down_write(sem: &tty->termios_rwsem);
2502 if (L_ICANON(tty) && !L_EXTPROC(tty))
2503 num = inq_canon(ldata);
2504 else
2505 num = read_cnt(ldata);
2506 up_write(sem: &tty->termios_rwsem);
2507 return put_user(num, (unsigned int __user *) arg);
2508 default:
2509 return n_tty_ioctl_helper(tty, cmd, arg);
2510 }
2511}
2512
2513static struct tty_ldisc_ops n_tty_ops = {
2514 .owner = THIS_MODULE,
2515 .num = N_TTY,
2516 .name = "n_tty",
2517 .open = n_tty_open,
2518 .close = n_tty_close,
2519 .flush_buffer = n_tty_flush_buffer,
2520 .read = n_tty_read,
2521 .write = n_tty_write,
2522 .ioctl = n_tty_ioctl,
2523 .set_termios = n_tty_set_termios,
2524 .poll = n_tty_poll,
2525 .receive_buf = n_tty_receive_buf,
2526 .write_wakeup = n_tty_write_wakeup,
2527 .receive_buf2 = n_tty_receive_buf2,
2528 .lookahead_buf = n_tty_lookahead_flow_ctrl,
2529};
2530
2531/**
2532 * n_tty_inherit_ops - inherit N_TTY methods
2533 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2534 *
2535 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2536 */
2537
2538void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2539{
2540 *ops = n_tty_ops;
2541 ops->owner = NULL;
2542}
2543EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2544
2545void __init n_tty_init(void)
2546{
2547 tty_register_ldisc(new_ldisc: &n_tty_ops);
2548}
2549