Line data Source code
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 :
91 : struct 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 :
135 : static inline size_t read_cnt(struct n_tty_data *ldata)
136 : {
137 0 : return ldata->read_head - ldata->read_tail;
138 : }
139 :
140 : static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
141 : {
142 0 : return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
143 : }
144 :
145 : static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
146 : {
147 0 : return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
148 : }
149 :
150 : static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
151 : {
152 0 : smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
153 0 : return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
154 : }
155 :
156 : static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
157 : {
158 0 : 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 */
162 : static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
163 : {
164 0 : bool icanon = !!L_ICANON(tty);
165 0 : bool no_echo = !L_ECHO(tty);
166 :
167 0 : if (icanon && no_echo)
168 0 : memset(buffer, 0x00, size);
169 : }
170 :
171 0 : static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
172 : {
173 0 : struct n_tty_data *ldata = tty->disc_data;
174 0 : size_t size = N_TTY_BUF_SIZE - tail;
175 0 : void *from = read_buf_addr(ldata, tail);
176 :
177 0 : if (n > size) {
178 0 : tty_audit_add_data(tty, from, size);
179 0 : memcpy(to, from, size);
180 0 : zero_buffer(tty, from, size);
181 0 : to += size;
182 0 : n -= size;
183 0 : from = ldata->read_buf;
184 : }
185 :
186 0 : tty_audit_add_data(tty, from, n);
187 0 : memcpy(to, from, n);
188 0 : zero_buffer(tty, from, n);
189 0 : }
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 : */
202 0 : static void n_tty_kick_worker(struct tty_struct *tty)
203 : {
204 0 : struct n_tty_data *ldata = tty->disc_data;
205 :
206 : /* Did the input worker stop? Restart it */
207 0 : if (unlikely(ldata->no_room)) {
208 0 : ldata->no_room = 0;
209 :
210 0 : 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 0 : WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
217 : "scheduling buffer work for halted ldisc\n");
218 0 : tty_buffer_restart_work(tty->port);
219 : }
220 0 : }
221 :
222 : static ssize_t chars_in_buffer(struct tty_struct *tty)
223 : {
224 0 : struct n_tty_data *ldata = tty->disc_data;
225 0 : ssize_t n = 0;
226 :
227 0 : if (!ldata->icanon)
228 0 : n = ldata->commit_head - ldata->read_tail;
229 : else
230 0 : 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 : */
241 0 : static void n_tty_write_wakeup(struct tty_struct *tty)
242 : {
243 0 : clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
244 0 : kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
245 0 : }
246 :
247 0 : static void n_tty_check_throttle(struct tty_struct *tty)
248 : {
249 0 : 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 0 : if (ldata->icanon && ldata->canon_head == ldata->read_tail)
257 : return;
258 :
259 : while (1) {
260 : int throttled;
261 0 : tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
262 0 : if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
263 : break;
264 0 : throttled = tty_throttle_safe(tty);
265 0 : if (!throttled)
266 : break;
267 : }
268 0 : __tty_set_flow_change(tty, 0);
269 : }
270 :
271 0 : static void n_tty_check_unthrottle(struct tty_struct *tty)
272 : {
273 0 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
274 0 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
275 : return;
276 0 : n_tty_kick_worker(tty);
277 0 : tty_wakeup(tty->link);
278 0 : 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 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
292 0 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
293 : break;
294 0 : n_tty_kick_worker(tty);
295 0 : unthrottled = tty_unthrottle_safe(tty);
296 0 : if (!unthrottled)
297 : break;
298 : }
299 0 : __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 : */
313 : static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
314 : {
315 0 : *read_buf_addr(ldata, ldata->read_head) = c;
316 0 : 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 : */
330 : static void reset_buffer_flags(struct n_tty_data *ldata)
331 : {
332 0 : ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
333 0 : ldata->commit_head = 0;
334 0 : ldata->line_start = 0;
335 :
336 0 : ldata->erasing = 0;
337 0 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
338 0 : ldata->push = 0;
339 :
340 0 : ldata->lookahead_count = 0;
341 : }
342 :
343 0 : static void n_tty_packet_mode_flush(struct tty_struct *tty)
344 : {
345 : unsigned long flags;
346 :
347 0 : if (tty->link->ctrl.packet) {
348 0 : spin_lock_irqsave(&tty->ctrl.lock, flags);
349 0 : tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
350 0 : spin_unlock_irqrestore(&tty->ctrl.lock, flags);
351 0 : wake_up_interruptible(&tty->link->read_wait);
352 : }
353 0 : }
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 : */
368 0 : static void n_tty_flush_buffer(struct tty_struct *tty)
369 : {
370 0 : down_write(&tty->termios_rwsem);
371 0 : reset_buffer_flags(tty->disc_data);
372 0 : n_tty_kick_worker(tty);
373 :
374 0 : if (tty->link)
375 0 : n_tty_packet_mode_flush(tty);
376 0 : up_write(&tty->termios_rwsem);
377 0 : }
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 : */
387 : static 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 : */
400 : static inline int is_continuation(unsigned char c, struct tty_struct *tty)
401 : {
402 0 : 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 : */
424 0 : static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
425 : {
426 0 : struct n_tty_data *ldata = tty->disc_data;
427 : int spaces;
428 :
429 0 : if (!space)
430 : return -1;
431 :
432 0 : switch (c) {
433 : case '\n':
434 0 : if (O_ONLRET(tty))
435 0 : ldata->column = 0;
436 0 : if (O_ONLCR(tty)) {
437 0 : if (space < 2)
438 : return -1;
439 0 : ldata->canon_column = ldata->column = 0;
440 0 : tty->ops->write(tty, "\r\n", 2);
441 0 : return 2;
442 : }
443 0 : ldata->canon_column = ldata->column;
444 0 : break;
445 : case '\r':
446 0 : if (O_ONOCR(tty) && ldata->column == 0)
447 : return 0;
448 0 : if (O_OCRNL(tty)) {
449 0 : c = '\n';
450 0 : if (O_ONLRET(tty))
451 0 : ldata->canon_column = ldata->column = 0;
452 : break;
453 : }
454 0 : ldata->canon_column = ldata->column = 0;
455 0 : break;
456 : case '\t':
457 0 : spaces = 8 - (ldata->column & 7);
458 0 : if (O_TABDLY(tty) == XTABS) {
459 0 : if (space < spaces)
460 : return -1;
461 0 : ldata->column += spaces;
462 0 : tty->ops->write(tty, " ", spaces);
463 0 : return spaces;
464 : }
465 0 : ldata->column += spaces;
466 0 : break;
467 : case '\b':
468 0 : if (ldata->column > 0)
469 0 : ldata->column--;
470 : break;
471 : default:
472 0 : if (!iscntrl(c)) {
473 0 : if (O_OLCUC(tty))
474 : c = toupper(c);
475 0 : if (!is_continuation(c, tty))
476 0 : ldata->column++;
477 : }
478 : break;
479 : }
480 :
481 0 : tty_put_char(tty, c);
482 0 : 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 : */
498 0 : static int process_output(unsigned char c, struct tty_struct *tty)
499 : {
500 0 : struct n_tty_data *ldata = tty->disc_data;
501 : int space, retval;
502 :
503 0 : mutex_lock(&ldata->output_lock);
504 :
505 0 : space = tty_write_room(tty);
506 0 : retval = do_output_char(c, tty, space);
507 :
508 0 : mutex_unlock(&ldata->output_lock);
509 0 : if (retval < 0)
510 : return -1;
511 : else
512 0 : 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 : */
533 0 : static ssize_t process_output_block(struct tty_struct *tty,
534 : const unsigned char *buf, unsigned int nr)
535 : {
536 0 : struct n_tty_data *ldata = tty->disc_data;
537 : int space;
538 : int i;
539 : const unsigned char *cp;
540 :
541 0 : mutex_lock(&ldata->output_lock);
542 :
543 0 : space = tty_write_room(tty);
544 0 : if (space <= 0) {
545 0 : mutex_unlock(&ldata->output_lock);
546 0 : return space;
547 : }
548 0 : if (nr > space)
549 0 : nr = space;
550 :
551 0 : for (i = 0, cp = buf; i < nr; i++, cp++) {
552 0 : unsigned char c = *cp;
553 :
554 0 : switch (c) {
555 : case '\n':
556 0 : if (O_ONLRET(tty))
557 0 : ldata->column = 0;
558 0 : if (O_ONLCR(tty))
559 : goto break_out;
560 0 : ldata->canon_column = ldata->column;
561 0 : break;
562 : case '\r':
563 0 : if (O_ONOCR(tty) && ldata->column == 0)
564 : goto break_out;
565 0 : if (O_OCRNL(tty))
566 : goto break_out;
567 0 : ldata->canon_column = ldata->column = 0;
568 0 : break;
569 : case '\t':
570 : goto break_out;
571 : case '\b':
572 0 : if (ldata->column > 0)
573 0 : ldata->column--;
574 : break;
575 : default:
576 0 : if (!iscntrl(c)) {
577 0 : if (O_OLCUC(tty))
578 : goto break_out;
579 0 : if (!is_continuation(c, tty))
580 0 : ldata->column++;
581 : }
582 : break;
583 : }
584 : }
585 : break_out:
586 0 : i = tty->ops->write(tty, buf, i);
587 :
588 0 : mutex_unlock(&ldata->output_lock);
589 0 : 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 : */
614 0 : static size_t __process_echoes(struct tty_struct *tty)
615 : {
616 0 : struct n_tty_data *ldata = tty->disc_data;
617 : int space, old_space;
618 : size_t tail;
619 : unsigned char c;
620 :
621 0 : old_space = space = tty_write_room(tty);
622 :
623 0 : tail = ldata->echo_tail;
624 0 : while (MASK(ldata->echo_commit) != MASK(tail)) {
625 0 : c = echo_buf(ldata, tail);
626 0 : if (c == ECHO_OP_START) {
627 : unsigned char op;
628 0 : 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 0 : 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 0 : op = echo_buf(ldata, tail + 1);
643 :
644 0 : switch (op) {
645 : case ECHO_OP_ERASE_TAB: {
646 : unsigned int num_chars, num_bs;
647 :
648 0 : if (MASK(ldata->echo_commit) == MASK(tail + 2))
649 : goto not_yet_stored;
650 0 : 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 0 : if (!(num_chars & 0x80))
663 0 : num_chars += ldata->canon_column;
664 0 : num_bs = 8 - (num_chars & 7);
665 :
666 0 : if (num_bs > space) {
667 : no_space_left = 1;
668 : break;
669 : }
670 0 : space -= num_bs;
671 0 : while (num_bs--) {
672 0 : tty_put_char(tty, '\b');
673 0 : if (ldata->column > 0)
674 0 : ldata->column--;
675 : }
676 0 : tail += 3;
677 0 : break;
678 : }
679 : case ECHO_OP_SET_CANON_COL:
680 0 : ldata->canon_column = ldata->column;
681 0 : tail += 2;
682 0 : break;
683 :
684 : case ECHO_OP_MOVE_BACK_COL:
685 0 : if (ldata->column > 0)
686 0 : ldata->column--;
687 0 : tail += 2;
688 0 : break;
689 :
690 : case ECHO_OP_START:
691 : /* This is an escaped echo op start code */
692 0 : if (!space) {
693 : no_space_left = 1;
694 : break;
695 : }
696 0 : tty_put_char(tty, ECHO_OP_START);
697 0 : ldata->column++;
698 0 : space--;
699 0 : tail += 2;
700 0 : 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 0 : if (space < 2) {
713 : no_space_left = 1;
714 : break;
715 : }
716 0 : tty_put_char(tty, '^');
717 0 : tty_put_char(tty, op ^ 0100);
718 0 : ldata->column += 2;
719 0 : space -= 2;
720 0 : tail += 2;
721 : }
722 :
723 0 : if (no_space_left)
724 : break;
725 : } else {
726 0 : if (O_OPOST(tty)) {
727 0 : int retval = do_output_char(c, tty, space);
728 0 : if (retval < 0)
729 : break;
730 0 : space -= retval;
731 : } else {
732 0 : if (!space)
733 : break;
734 0 : tty_put_char(tty, c);
735 0 : space -= 1;
736 : }
737 0 : 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 0 : while (ldata->echo_commit > tail &&
745 0 : ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
746 0 : if (echo_buf(ldata, tail) == ECHO_OP_START) {
747 0 : if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
748 0 : tail += 3;
749 : else
750 0 : tail += 2;
751 : } else
752 0 : tail++;
753 : }
754 :
755 : not_yet_stored:
756 0 : ldata->echo_tail = tail;
757 0 : return old_space - space;
758 : }
759 :
760 0 : static void commit_echoes(struct tty_struct *tty)
761 : {
762 0 : struct n_tty_data *ldata = tty->disc_data;
763 : size_t nr, old, echoed;
764 : size_t head;
765 :
766 0 : mutex_lock(&ldata->output_lock);
767 0 : head = ldata->echo_head;
768 0 : ldata->echo_mark = head;
769 0 : 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 0 : nr = head - ldata->echo_tail;
775 0 : if (nr < ECHO_COMMIT_WATERMARK ||
776 0 : (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
777 0 : mutex_unlock(&ldata->output_lock);
778 0 : return;
779 : }
780 :
781 0 : ldata->echo_commit = head;
782 0 : echoed = __process_echoes(tty);
783 0 : mutex_unlock(&ldata->output_lock);
784 :
785 0 : if (echoed && tty->ops->flush_chars)
786 0 : tty->ops->flush_chars(tty);
787 : }
788 :
789 0 : static void process_echoes(struct tty_struct *tty)
790 : {
791 0 : struct n_tty_data *ldata = tty->disc_data;
792 : size_t echoed;
793 :
794 0 : if (ldata->echo_mark == ldata->echo_tail)
795 : return;
796 :
797 0 : mutex_lock(&ldata->output_lock);
798 0 : ldata->echo_commit = ldata->echo_mark;
799 0 : echoed = __process_echoes(tty);
800 0 : mutex_unlock(&ldata->output_lock);
801 :
802 0 : if (echoed && tty->ops->flush_chars)
803 0 : tty->ops->flush_chars(tty);
804 : }
805 :
806 : /* NB: echo_mark and echo_head should be equivalent here */
807 0 : static void flush_echoes(struct tty_struct *tty)
808 : {
809 0 : struct n_tty_data *ldata = tty->disc_data;
810 :
811 0 : if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
812 0 : ldata->echo_commit == ldata->echo_head)
813 : return;
814 :
815 0 : mutex_lock(&ldata->output_lock);
816 0 : ldata->echo_commit = ldata->echo_head;
817 0 : __process_echoes(tty);
818 0 : 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 : */
828 : static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
829 : {
830 0 : *echo_buf_addr(ldata, ldata->echo_head) = c;
831 0 : smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
832 0 : 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 : */
841 : static void echo_move_back_col(struct n_tty_data *ldata)
842 : {
843 0 : add_echo_byte(ECHO_OP_START, ldata);
844 0 : 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 : */
854 : static void echo_set_canon_col(struct n_tty_data *ldata)
855 : {
856 0 : add_echo_byte(ECHO_OP_START, ldata);
857 0 : 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 : */
873 : static void echo_erase_tab(unsigned int num_chars, int after_tab,
874 : struct n_tty_data *ldata)
875 : {
876 0 : add_echo_byte(ECHO_OP_START, ldata);
877 0 : add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
878 :
879 : /* We only need to know this modulo 8 (tab spacing) */
880 0 : num_chars &= 7;
881 :
882 : /* Set the high bit as a flag if num_chars is after a previous tab */
883 0 : if (after_tab)
884 0 : num_chars |= 0x80;
885 :
886 0 : 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 : */
899 : static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
900 : {
901 0 : if (c == ECHO_OP_START) {
902 0 : 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 : */
920 0 : static void echo_char(unsigned char c, struct tty_struct *tty)
921 : {
922 0 : struct n_tty_data *ldata = tty->disc_data;
923 :
924 0 : if (c == ECHO_OP_START) {
925 0 : add_echo_byte(ECHO_OP_START, ldata);
926 : add_echo_byte(ECHO_OP_START, ldata);
927 : } else {
928 0 : if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
929 : add_echo_byte(ECHO_OP_START, ldata);
930 : add_echo_byte(c, ldata);
931 : }
932 0 : }
933 :
934 : /**
935 : * finish_erasing - complete erase
936 : * @ldata: n_tty data
937 : */
938 : static inline void finish_erasing(struct n_tty_data *ldata)
939 : {
940 0 : if (ldata->erasing) {
941 0 : echo_char_raw('/', ldata);
942 0 : 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 : */
958 0 : static void eraser(unsigned char c, struct tty_struct *tty)
959 : {
960 0 : 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 0 : if (ldata->read_head == ldata->canon_head) {
967 : /* process_output('\a', tty); */ /* what do you think? */
968 : return;
969 : }
970 0 : if (c == ERASE_CHAR(tty))
971 : kill_type = ERASE;
972 0 : else if (c == WERASE_CHAR(tty))
973 : kill_type = WERASE;
974 : else {
975 0 : if (!L_ECHO(tty)) {
976 0 : ldata->read_head = ldata->canon_head;
977 0 : return;
978 : }
979 0 : if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
980 0 : ldata->read_head = ldata->canon_head;
981 0 : finish_erasing(ldata);
982 0 : echo_char(KILL_CHAR(tty), tty);
983 : /* Add a newline if ECHOK is on and ECHOKE is off. */
984 0 : if (L_ECHOK(tty))
985 : echo_char_raw('\n', ldata);
986 : return;
987 : }
988 : kill_type = KILL;
989 : }
990 :
991 0 : seen_alnums = 0;
992 0 : 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 0 : head--;
998 0 : c = read_buf(ldata, head);
999 0 : } while (is_continuation(c, tty) &&
1000 0 : MASK(head) != MASK(ldata->canon_head));
1001 :
1002 : /* do not partially erase */
1003 0 : if (is_continuation(c, tty))
1004 : break;
1005 :
1006 0 : if (kill_type == WERASE) {
1007 : /* Equivalent to BSD's ALTWERASE. */
1008 0 : if (isalnum(c) || c == '_')
1009 0 : seen_alnums++;
1010 0 : else if (seen_alnums)
1011 : break;
1012 : }
1013 0 : cnt = ldata->read_head - head;
1014 0 : ldata->read_head = head;
1015 0 : if (L_ECHO(tty)) {
1016 0 : if (L_ECHOPRT(tty)) {
1017 0 : if (!ldata->erasing) {
1018 0 : echo_char_raw('\\', ldata);
1019 0 : ldata->erasing = 1;
1020 : }
1021 : /* if cnt > 1, output a multi-byte character */
1022 0 : echo_char(c, tty);
1023 0 : while (--cnt > 0) {
1024 0 : head++;
1025 0 : echo_char_raw(read_buf(ldata, head), ldata);
1026 : echo_move_back_col(ldata);
1027 : }
1028 0 : } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1029 0 : echo_char(ERASE_CHAR(tty), tty);
1030 0 : } 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 0 : while (MASK(tail) != MASK(ldata->canon_head)) {
1043 0 : tail--;
1044 0 : c = read_buf(ldata, tail);
1045 0 : if (c == '\t') {
1046 : after_tab = 1;
1047 : break;
1048 0 : } else if (iscntrl(c)) {
1049 0 : if (L_ECHOCTL(tty))
1050 0 : num_chars += 2;
1051 0 : } else if (!is_continuation(c, tty)) {
1052 0 : num_chars++;
1053 : }
1054 : }
1055 : echo_erase_tab(num_chars, after_tab, ldata);
1056 : } else {
1057 0 : if (iscntrl(c) && L_ECHOCTL(tty)) {
1058 0 : echo_char_raw('\b', ldata);
1059 0 : echo_char_raw(' ', ldata);
1060 : echo_char_raw('\b', ldata);
1061 : }
1062 0 : if (!iscntrl(c) || L_ECHOCTL(tty)) {
1063 0 : echo_char_raw('\b', ldata);
1064 0 : echo_char_raw(' ', ldata);
1065 : echo_char_raw('\b', ldata);
1066 : }
1067 : }
1068 : }
1069 0 : if (kill_type == ERASE)
1070 : break;
1071 : }
1072 0 : if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1073 : finish_erasing(ldata);
1074 : }
1075 :
1076 :
1077 0 : static void __isig(int sig, struct tty_struct *tty)
1078 : {
1079 0 : struct pid *tty_pgrp = tty_get_pgrp(tty);
1080 0 : if (tty_pgrp) {
1081 0 : kill_pgrp(tty_pgrp, sig, 1);
1082 0 : put_pid(tty_pgrp);
1083 : }
1084 0 : }
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 : */
1100 0 : static void isig(int sig, struct tty_struct *tty)
1101 : {
1102 0 : struct n_tty_data *ldata = tty->disc_data;
1103 :
1104 0 : if (L_NOFLSH(tty)) {
1105 : /* signal only */
1106 0 : __isig(sig, tty);
1107 :
1108 : } else { /* signal and flush */
1109 0 : up_read(&tty->termios_rwsem);
1110 0 : down_write(&tty->termios_rwsem);
1111 :
1112 0 : __isig(sig, tty);
1113 :
1114 : /* clear echo buffer */
1115 0 : mutex_lock(&ldata->output_lock);
1116 0 : ldata->echo_head = ldata->echo_tail = 0;
1117 0 : ldata->echo_mark = ldata->echo_commit = 0;
1118 0 : mutex_unlock(&ldata->output_lock);
1119 :
1120 : /* clear output buffer */
1121 0 : tty_driver_flush_buffer(tty);
1122 :
1123 : /* clear input buffer */
1124 0 : reset_buffer_flags(tty->disc_data);
1125 :
1126 : /* notify pty master of flush */
1127 0 : if (tty->link)
1128 0 : n_tty_packet_mode_flush(tty);
1129 :
1130 0 : up_write(&tty->termios_rwsem);
1131 0 : down_read(&tty->termios_rwsem);
1132 : }
1133 0 : }
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 : */
1147 0 : static void n_tty_receive_break(struct tty_struct *tty)
1148 : {
1149 0 : struct n_tty_data *ldata = tty->disc_data;
1150 :
1151 0 : if (I_IGNBRK(tty))
1152 : return;
1153 0 : if (I_BRKINT(tty)) {
1154 0 : isig(SIGINT, tty);
1155 0 : return;
1156 : }
1157 0 : if (I_PARMRK(tty)) {
1158 0 : 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 : */
1174 0 : static void n_tty_receive_overrun(struct tty_struct *tty)
1175 : {
1176 0 : struct n_tty_data *ldata = tty->disc_data;
1177 :
1178 0 : ldata->num_overrun++;
1179 0 : if (time_after(jiffies, ldata->overrun_time + HZ) ||
1180 0 : time_after(ldata->overrun_time, jiffies)) {
1181 0 : tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1182 0 : ldata->overrun_time = jiffies;
1183 0 : ldata->num_overrun = 0;
1184 : }
1185 0 : }
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 : */
1198 0 : static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1199 : {
1200 0 : struct n_tty_data *ldata = tty->disc_data;
1201 :
1202 0 : if (I_INPCK(tty)) {
1203 0 : if (I_IGNPAR(tty))
1204 : return;
1205 0 : if (I_PARMRK(tty)) {
1206 0 : put_tty_queue('\377', ldata);
1207 0 : 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 :
1215 : static void
1216 0 : n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1217 : {
1218 0 : isig(signal, tty);
1219 0 : if (I_IXON(tty))
1220 0 : start_tty(tty);
1221 0 : if (L_ECHO(tty)) {
1222 0 : echo_char(c, tty);
1223 0 : commit_echoes(tty);
1224 : } else
1225 0 : process_echoes(tty);
1226 0 : }
1227 :
1228 : static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
1229 : {
1230 0 : 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 : */
1248 0 : static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c,
1249 : bool lookahead_done)
1250 : {
1251 0 : if (!n_tty_is_char_flow_ctrl(tty, c))
1252 : return false;
1253 :
1254 0 : if (lookahead_done)
1255 : return true;
1256 :
1257 0 : if (c == START_CHAR(tty)) {
1258 0 : start_tty(tty);
1259 0 : process_echoes(tty);
1260 0 : return true;
1261 : }
1262 :
1263 : /* STOP_CHAR */
1264 0 : stop_tty(tty);
1265 0 : return true;
1266 : }
1267 :
1268 0 : static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c,
1269 : bool lookahead_done)
1270 : {
1271 0 : struct n_tty_data *ldata = tty->disc_data;
1272 :
1273 0 : if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
1274 : return;
1275 :
1276 0 : if (L_ISIG(tty)) {
1277 0 : if (c == INTR_CHAR(tty)) {
1278 0 : n_tty_receive_signal_char(tty, SIGINT, c);
1279 0 : return;
1280 0 : } else if (c == QUIT_CHAR(tty)) {
1281 0 : n_tty_receive_signal_char(tty, SIGQUIT, c);
1282 0 : return;
1283 0 : } else if (c == SUSP_CHAR(tty)) {
1284 0 : n_tty_receive_signal_char(tty, SIGTSTP, c);
1285 0 : return;
1286 : }
1287 : }
1288 :
1289 0 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1290 0 : start_tty(tty);
1291 0 : process_echoes(tty);
1292 : }
1293 :
1294 0 : if (c == '\r') {
1295 0 : if (I_IGNCR(tty))
1296 : return;
1297 0 : if (I_ICRNL(tty))
1298 0 : c = '\n';
1299 0 : } else if (c == '\n' && I_INLCR(tty))
1300 0 : c = '\r';
1301 :
1302 0 : if (ldata->icanon) {
1303 0 : if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1304 0 : (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1305 0 : eraser(c, tty);
1306 0 : commit_echoes(tty);
1307 0 : return;
1308 : }
1309 0 : if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1310 0 : ldata->lnext = 1;
1311 0 : if (L_ECHO(tty)) {
1312 0 : finish_erasing(ldata);
1313 0 : if (L_ECHOCTL(tty)) {
1314 0 : echo_char_raw('^', ldata);
1315 0 : echo_char_raw('\b', ldata);
1316 0 : commit_echoes(tty);
1317 : }
1318 : }
1319 : return;
1320 : }
1321 0 : if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1322 0 : size_t tail = ldata->canon_head;
1323 :
1324 0 : finish_erasing(ldata);
1325 0 : echo_char(c, tty);
1326 : echo_char_raw('\n', ldata);
1327 0 : while (MASK(tail) != MASK(ldata->read_head)) {
1328 0 : echo_char(read_buf(ldata, tail), tty);
1329 0 : tail++;
1330 : }
1331 0 : commit_echoes(tty);
1332 0 : return;
1333 : }
1334 0 : if (c == '\n') {
1335 0 : if (L_ECHO(tty) || L_ECHONL(tty)) {
1336 0 : echo_char_raw('\n', ldata);
1337 0 : commit_echoes(tty);
1338 : }
1339 : goto handle_newline;
1340 : }
1341 0 : if (c == EOF_CHAR(tty)) {
1342 : c = __DISABLED_CHAR;
1343 : goto handle_newline;
1344 : }
1345 0 : if ((c == EOL_CHAR(tty)) ||
1346 0 : (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1347 : /*
1348 : * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1349 : */
1350 0 : if (L_ECHO(tty)) {
1351 : /* Record the column of first canon char. */
1352 0 : if (ldata->canon_head == ldata->read_head)
1353 : echo_set_canon_col(ldata);
1354 0 : echo_char(c, tty);
1355 0 : commit_echoes(tty);
1356 : }
1357 : /*
1358 : * XXX does PARMRK doubling happen for
1359 : * EOL_CHAR and EOL2_CHAR?
1360 : */
1361 0 : if (c == (unsigned char) '\377' && I_PARMRK(tty))
1362 : put_tty_queue(c, ldata);
1363 :
1364 : handle_newline:
1365 0 : set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1366 0 : put_tty_queue(c, ldata);
1367 0 : smp_store_release(&ldata->canon_head, ldata->read_head);
1368 0 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1369 0 : wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1370 0 : return;
1371 : }
1372 : }
1373 :
1374 0 : if (L_ECHO(tty)) {
1375 0 : finish_erasing(ldata);
1376 0 : if (c == '\n')
1377 : echo_char_raw('\n', ldata);
1378 : else {
1379 : /* Record the column of first canon char. */
1380 0 : if (ldata->canon_head == ldata->read_head)
1381 : echo_set_canon_col(ldata);
1382 0 : echo_char(c, tty);
1383 : }
1384 0 : commit_echoes(tty);
1385 : }
1386 :
1387 : /* PARMRK doubling check */
1388 0 : 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 : */
1406 0 : static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1407 : {
1408 0 : struct n_tty_data *ldata = tty->disc_data;
1409 :
1410 0 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1411 0 : start_tty(tty);
1412 0 : process_echoes(tty);
1413 : }
1414 0 : if (L_ECHO(tty)) {
1415 0 : finish_erasing(ldata);
1416 : /* Record the column of first canon char. */
1417 0 : if (ldata->canon_head == ldata->read_head)
1418 : echo_set_canon_col(ldata);
1419 0 : echo_char(c, tty);
1420 0 : commit_echoes(tty);
1421 : }
1422 : /* PARMRK doubling check */
1423 0 : if (c == (unsigned char) '\377' && I_PARMRK(tty))
1424 : put_tty_queue(c, ldata);
1425 0 : put_tty_queue(c, ldata);
1426 0 : }
1427 :
1428 0 : static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c,
1429 : bool lookahead_done)
1430 : {
1431 0 : if (I_ISTRIP(tty))
1432 0 : c &= 0x7f;
1433 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1434 0 : c = tolower(c);
1435 :
1436 0 : if (I_IXON(tty)) {
1437 0 : if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
1438 0 : tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1439 0 : c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1440 0 : c != SUSP_CHAR(tty)) {
1441 0 : start_tty(tty);
1442 0 : process_echoes(tty);
1443 : }
1444 : }
1445 0 : }
1446 :
1447 : static void
1448 0 : n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1449 : {
1450 0 : switch (flag) {
1451 : case TTY_BREAK:
1452 0 : n_tty_receive_break(tty);
1453 0 : break;
1454 : case TTY_PARITY:
1455 : case TTY_FRAME:
1456 0 : n_tty_receive_parity_error(tty, c);
1457 0 : break;
1458 : case TTY_OVERRUN:
1459 0 : n_tty_receive_overrun(tty);
1460 0 : break;
1461 : default:
1462 0 : tty_err(tty, "unknown flag %d\n", flag);
1463 0 : break;
1464 : }
1465 0 : }
1466 :
1467 : static void
1468 0 : n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1469 : {
1470 0 : struct n_tty_data *ldata = tty->disc_data;
1471 :
1472 0 : ldata->lnext = 0;
1473 0 : if (likely(flag == TTY_NORMAL)) {
1474 0 : if (I_ISTRIP(tty))
1475 0 : c &= 0x7f;
1476 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1477 0 : c = tolower(c);
1478 0 : n_tty_receive_char(tty, c);
1479 : } else
1480 0 : n_tty_receive_char_flagged(tty, c, flag);
1481 0 : }
1482 :
1483 : /* Caller must ensure count > 0 */
1484 0 : static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const unsigned char *cp,
1485 : const unsigned char *fp, unsigned int count)
1486 : {
1487 0 : struct n_tty_data *ldata = tty->disc_data;
1488 0 : unsigned char flag = TTY_NORMAL;
1489 :
1490 0 : ldata->lookahead_count += count;
1491 :
1492 0 : if (!I_IXON(tty))
1493 : return;
1494 :
1495 0 : while (count--) {
1496 0 : if (fp)
1497 0 : flag = *fp++;
1498 0 : if (likely(flag == TTY_NORMAL))
1499 0 : n_tty_receive_char_flow_ctrl(tty, *cp, false);
1500 0 : cp++;
1501 : }
1502 : }
1503 :
1504 : static void
1505 0 : n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1506 : const char *fp, int count)
1507 : {
1508 0 : struct n_tty_data *ldata = tty->disc_data;
1509 : size_t n, head;
1510 :
1511 0 : head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1512 0 : n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1513 0 : memcpy(read_buf_addr(ldata, head), cp, n);
1514 0 : ldata->read_head += n;
1515 0 : cp += n;
1516 0 : count -= n;
1517 :
1518 0 : head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1519 0 : n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1520 0 : memcpy(read_buf_addr(ldata, head), cp, n);
1521 0 : ldata->read_head += n;
1522 0 : }
1523 :
1524 : static void
1525 0 : n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1526 : const char *fp, int count)
1527 : {
1528 0 : struct n_tty_data *ldata = tty->disc_data;
1529 0 : char flag = TTY_NORMAL;
1530 :
1531 0 : while (count--) {
1532 0 : if (fp)
1533 0 : flag = *fp++;
1534 0 : if (likely(flag == TTY_NORMAL))
1535 0 : put_tty_queue(*cp++, ldata);
1536 : else
1537 0 : n_tty_receive_char_flagged(tty, *cp++, flag);
1538 : }
1539 0 : }
1540 :
1541 : static void
1542 0 : n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1543 : const char *fp, int count, bool lookahead_done)
1544 : {
1545 0 : char flag = TTY_NORMAL;
1546 :
1547 0 : while (count--) {
1548 0 : if (fp)
1549 0 : flag = *fp++;
1550 0 : if (likely(flag == TTY_NORMAL))
1551 0 : n_tty_receive_char_closing(tty, *cp++, lookahead_done);
1552 : }
1553 0 : }
1554 :
1555 0 : static 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 0 : struct n_tty_data *ldata = tty->disc_data;
1559 0 : char flag = TTY_NORMAL;
1560 :
1561 0 : while (count--) {
1562 0 : unsigned char c = *cp++;
1563 :
1564 0 : if (fp)
1565 0 : flag = *fp++;
1566 :
1567 0 : if (ldata->lnext) {
1568 0 : n_tty_receive_char_lnext(tty, c, flag);
1569 0 : continue;
1570 : }
1571 :
1572 0 : if (unlikely(flag != TTY_NORMAL)) {
1573 0 : n_tty_receive_char_flagged(tty, c, flag);
1574 0 : continue;
1575 : }
1576 :
1577 0 : if (I_ISTRIP(tty))
1578 0 : c &= 0x7f;
1579 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1580 0 : c = tolower(c);
1581 0 : if (L_EXTPROC(tty)) {
1582 0 : put_tty_queue(c, ldata);
1583 0 : continue;
1584 : }
1585 :
1586 0 : if (test_bit(c, ldata->char_map))
1587 0 : n_tty_receive_char_special(tty, c, lookahead_done);
1588 : else
1589 0 : n_tty_receive_char(tty, c);
1590 : }
1591 0 : }
1592 :
1593 0 : static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1594 : const char *fp, int count)
1595 : {
1596 0 : struct n_tty_data *ldata = tty->disc_data;
1597 0 : bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1598 0 : size_t la_count = min_t(size_t, ldata->lookahead_count, count);
1599 :
1600 0 : if (ldata->real_raw)
1601 0 : n_tty_receive_buf_real_raw(tty, cp, fp, count);
1602 0 : else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1603 0 : n_tty_receive_buf_raw(tty, cp, fp, count);
1604 0 : else if (tty->closing && !L_EXTPROC(tty)) {
1605 0 : if (la_count > 0)
1606 0 : n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
1607 0 : if (count > la_count)
1608 0 : n_tty_receive_buf_closing(tty, cp, fp, count - la_count, false);
1609 : } else {
1610 0 : if (la_count > 0)
1611 0 : n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
1612 0 : if (count > la_count)
1613 0 : n_tty_receive_buf_standard(tty, cp, fp, count - la_count, false);
1614 :
1615 0 : flush_echoes(tty);
1616 0 : if (tty->ops->flush_chars)
1617 0 : tty->ops->flush_chars(tty);
1618 : }
1619 :
1620 0 : ldata->lookahead_count -= la_count;
1621 :
1622 0 : if (ldata->icanon && !L_EXTPROC(tty))
1623 : return;
1624 :
1625 : /* publish read_head to consumer */
1626 0 : smp_store_release(&ldata->commit_head, ldata->read_head);
1627 :
1628 0 : if (read_cnt(ldata)) {
1629 0 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1630 0 : 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 : */
1667 : static int
1668 0 : n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1669 : const char *fp, int count, int flow)
1670 : {
1671 0 : struct n_tty_data *ldata = tty->disc_data;
1672 0 : int room, n, rcvd = 0, overflow;
1673 :
1674 0 : 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 0 : size_t tail = smp_load_acquire(&ldata->read_tail);
1691 :
1692 0 : room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1693 0 : if (I_PARMRK(tty))
1694 0 : room = (room + 2) / 3;
1695 0 : room--;
1696 0 : if (room <= 0) {
1697 0 : overflow = ldata->icanon && ldata->canon_head == tail;
1698 0 : if (overflow && room < 0)
1699 0 : ldata->read_head--;
1700 0 : room = overflow;
1701 0 : ldata->no_room = flow && !room;
1702 : } else
1703 : overflow = 0;
1704 :
1705 0 : n = min(count, room);
1706 0 : if (!n)
1707 : break;
1708 :
1709 : /* ignore parity errors if handling overflow */
1710 0 : if (!overflow || !fp || *fp != TTY_PARITY)
1711 0 : __receive_buf(tty, cp, fp, n);
1712 :
1713 0 : cp += n;
1714 0 : if (fp)
1715 0 : fp += n;
1716 0 : count -= n;
1717 0 : rcvd += n;
1718 0 : } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1719 :
1720 0 : tty->receive_room = room;
1721 :
1722 : /* Unthrottle if handling overflow on pty */
1723 0 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1724 0 : if (overflow) {
1725 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1726 0 : tty_unthrottle_safe(tty);
1727 0 : __tty_set_flow_change(tty, 0);
1728 : }
1729 : } else
1730 0 : n_tty_check_throttle(tty);
1731 :
1732 0 : up_read(&tty->termios_rwsem);
1733 :
1734 0 : return rcvd;
1735 : }
1736 :
1737 0 : static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1738 : const char *fp, int count)
1739 : {
1740 0 : n_tty_receive_buf_common(tty, cp, fp, count, 0);
1741 0 : }
1742 :
1743 0 : static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1744 : const char *fp, int count)
1745 : {
1746 0 : 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 : */
1761 0 : static void n_tty_set_termios(struct tty_struct *tty, const struct ktermios *old)
1762 : {
1763 0 : struct n_tty_data *ldata = tty->disc_data;
1764 :
1765 0 : if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1766 0 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1767 0 : ldata->line_start = ldata->read_tail;
1768 0 : if (!L_ICANON(tty) || !read_cnt(ldata)) {
1769 0 : ldata->canon_head = ldata->read_tail;
1770 0 : ldata->push = 0;
1771 : } else {
1772 0 : set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1773 : ldata->read_flags);
1774 0 : ldata->canon_head = ldata->read_head;
1775 0 : ldata->push = 1;
1776 : }
1777 0 : ldata->commit_head = ldata->read_head;
1778 0 : ldata->erasing = 0;
1779 0 : ldata->lnext = 0;
1780 : }
1781 :
1782 0 : ldata->icanon = (L_ICANON(tty) != 0);
1783 :
1784 0 : if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1785 0 : I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1786 0 : I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1787 0 : I_PARMRK(tty)) {
1788 0 : bitmap_zero(ldata->char_map, 256);
1789 :
1790 0 : if (I_IGNCR(tty) || I_ICRNL(tty))
1791 0 : set_bit('\r', ldata->char_map);
1792 0 : if (I_INLCR(tty))
1793 0 : set_bit('\n', ldata->char_map);
1794 :
1795 0 : if (L_ICANON(tty)) {
1796 0 : set_bit(ERASE_CHAR(tty), ldata->char_map);
1797 0 : set_bit(KILL_CHAR(tty), ldata->char_map);
1798 0 : set_bit(EOF_CHAR(tty), ldata->char_map);
1799 0 : set_bit('\n', ldata->char_map);
1800 0 : set_bit(EOL_CHAR(tty), ldata->char_map);
1801 0 : if (L_IEXTEN(tty)) {
1802 0 : set_bit(WERASE_CHAR(tty), ldata->char_map);
1803 0 : set_bit(LNEXT_CHAR(tty), ldata->char_map);
1804 0 : set_bit(EOL2_CHAR(tty), ldata->char_map);
1805 0 : if (L_ECHO(tty))
1806 0 : set_bit(REPRINT_CHAR(tty),
1807 : ldata->char_map);
1808 : }
1809 : }
1810 0 : if (I_IXON(tty)) {
1811 0 : set_bit(START_CHAR(tty), ldata->char_map);
1812 0 : set_bit(STOP_CHAR(tty), ldata->char_map);
1813 : }
1814 0 : if (L_ISIG(tty)) {
1815 0 : set_bit(INTR_CHAR(tty), ldata->char_map);
1816 0 : set_bit(QUIT_CHAR(tty), ldata->char_map);
1817 0 : set_bit(SUSP_CHAR(tty), ldata->char_map);
1818 : }
1819 0 : clear_bit(__DISABLED_CHAR, ldata->char_map);
1820 0 : ldata->raw = 0;
1821 0 : ldata->real_raw = 0;
1822 : } else {
1823 0 : ldata->raw = 1;
1824 0 : if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1825 0 : (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1826 0 : (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1827 0 : ldata->real_raw = 1;
1828 : else
1829 0 : 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 0 : if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1836 0 : start_tty(tty);
1837 0 : process_echoes(tty);
1838 : }
1839 :
1840 : /* The termios change make the tty ready for I/O */
1841 0 : wake_up_interruptible(&tty->write_wait);
1842 0 : wake_up_interruptible(&tty->read_wait);
1843 0 : }
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 : */
1853 0 : static void n_tty_close(struct tty_struct *tty)
1854 : {
1855 0 : struct n_tty_data *ldata = tty->disc_data;
1856 :
1857 0 : if (tty->link)
1858 0 : n_tty_packet_mode_flush(tty);
1859 :
1860 0 : down_write(&tty->termios_rwsem);
1861 0 : vfree(ldata);
1862 0 : tty->disc_data = NULL;
1863 0 : up_write(&tty->termios_rwsem);
1864 0 : }
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 : */
1874 0 : static 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 0 : ldata = vzalloc(sizeof(*ldata));
1880 0 : if (!ldata)
1881 : return -ENOMEM;
1882 :
1883 0 : ldata->overrun_time = jiffies;
1884 0 : mutex_init(&ldata->atomic_read_lock);
1885 0 : mutex_init(&ldata->output_lock);
1886 :
1887 0 : tty->disc_data = ldata;
1888 0 : tty->closing = 0;
1889 : /* indicate buffer work may resume */
1890 0 : clear_bit(TTY_LDISC_HALTED, &tty->flags);
1891 0 : n_tty_set_termios(tty, NULL);
1892 0 : tty_unthrottle(tty);
1893 0 : return 0;
1894 : }
1895 :
1896 : static inline int input_available_p(struct tty_struct *tty, int poll)
1897 : {
1898 0 : struct n_tty_data *ldata = tty->disc_data;
1899 0 : int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1900 :
1901 0 : if (ldata->icanon && !L_EXTPROC(tty))
1902 0 : return ldata->canon_head != ldata->read_tail;
1903 : else
1904 0 : 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 : */
1925 0 : static bool copy_from_read_buf(struct tty_struct *tty,
1926 : unsigned char **kbp,
1927 : size_t *nr)
1928 :
1929 : {
1930 0 : struct n_tty_data *ldata = tty->disc_data;
1931 : size_t n;
1932 : bool is_eof;
1933 0 : size_t head = smp_load_acquire(&ldata->commit_head);
1934 0 : size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1935 :
1936 0 : n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1937 0 : n = min(*nr, n);
1938 0 : if (n) {
1939 0 : unsigned char *from = read_buf_addr(ldata, tail);
1940 0 : memcpy(*kbp, from, n);
1941 0 : is_eof = n == 1 && *from == EOF_CHAR(tty);
1942 0 : tty_audit_add_data(tty, from, n);
1943 0 : zero_buffer(tty, from, n);
1944 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1945 : /* Turn single EOF into zero-length read */
1946 0 : if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1947 0 : (head == ldata->read_tail))
1948 : return false;
1949 0 : *kbp += n;
1950 0 : *nr -= n;
1951 :
1952 : /* If we have more to copy, let the caller know */
1953 0 : 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 : */
1980 0 : static bool canon_copy_from_read_buf(struct tty_struct *tty,
1981 : unsigned char **kbp,
1982 : size_t *nr)
1983 : {
1984 0 : 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 0 : int found = 0;
1989 :
1990 : /* N.B. avoid overrun if nr == 0 */
1991 0 : if (!*nr)
1992 : return false;
1993 :
1994 0 : canon_head = smp_load_acquire(&ldata->canon_head);
1995 0 : n = min(*nr, canon_head - ldata->read_tail);
1996 :
1997 0 : tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1998 0 : 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 0 : eol = find_next_bit(ldata->read_flags, size, tail);
2004 0 : more = n - (size - tail);
2005 0 : if (eol == N_TTY_BUF_SIZE && more) {
2006 : /* scan wrapped without finding set bit */
2007 0 : eol = find_first_bit(ldata->read_flags, more);
2008 0 : found = eol != more;
2009 : } else
2010 0 : found = eol != size;
2011 :
2012 0 : n = eol - tail;
2013 0 : if (n > N_TTY_BUF_SIZE)
2014 0 : n += N_TTY_BUF_SIZE;
2015 0 : c = n + found;
2016 :
2017 0 : 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 0 : tty_copy(tty, *kbp, tail, n);
2024 0 : *kbp += n;
2025 0 : *nr -= n;
2026 :
2027 0 : if (found)
2028 0 : clear_bit(eol, ldata->read_flags);
2029 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2030 :
2031 0 : if (found) {
2032 0 : if (!ldata->push)
2033 0 : ldata->line_start = ldata->read_tail;
2034 : else
2035 0 : 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 0 : 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 : */
2049 0 : static void canon_skip_eof(struct tty_struct *tty)
2050 : {
2051 0 : struct n_tty_data *ldata = tty->disc_data;
2052 : size_t tail, canon_head;
2053 :
2054 0 : canon_head = smp_load_acquire(&ldata->canon_head);
2055 0 : tail = ldata->read_tail;
2056 :
2057 : // No data?
2058 0 : if (tail == canon_head)
2059 : return;
2060 :
2061 : // See if the tail position is EOF in the circular buffer
2062 0 : tail &= (N_TTY_BUF_SIZE - 1);
2063 0 : if (!test_bit(tail, ldata->read_flags))
2064 : return;
2065 0 : if (read_buf(ldata, tail) != __DISABLED_CHAR)
2066 : return;
2067 :
2068 : // Clear the EOL bit, skip the EOF char.
2069 0 : clear_bit(tail, ldata->read_flags);
2070 0 : 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 : */
2087 : static 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 0 : if (file->f_op->write_iter == redirected_tty_write)
2095 : return 0;
2096 :
2097 0 : 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 : */
2121 0 : static 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 0 : struct n_tty_data *ldata = tty->disc_data;
2126 0 : unsigned char *kb = kbuf;
2127 0 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2128 : int c;
2129 : int minimum, time;
2130 0 : 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 0 : if (*cookie) {
2142 0 : 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 0 : if (!nr)
2149 0 : canon_skip_eof(tty);
2150 0 : else if (canon_copy_from_read_buf(tty, &kb, &nr))
2151 0 : return kb - kbuf;
2152 : } else {
2153 0 : if (copy_from_read_buf(tty, &kb, &nr))
2154 0 : return kb - kbuf;
2155 : }
2156 :
2157 : /* No more data - release locks and stop retries */
2158 0 : n_tty_kick_worker(tty);
2159 0 : n_tty_check_unthrottle(tty);
2160 0 : up_read(&tty->termios_rwsem);
2161 0 : mutex_unlock(&ldata->atomic_read_lock);
2162 0 : *cookie = NULL;
2163 0 : return kb - kbuf;
2164 : }
2165 :
2166 0 : c = job_control(tty, file);
2167 0 : if (c < 0)
2168 0 : return c;
2169 :
2170 : /*
2171 : * Internal serialization of reads.
2172 : */
2173 0 : if (file->f_flags & O_NONBLOCK) {
2174 0 : if (!mutex_trylock(&ldata->atomic_read_lock))
2175 : return -EAGAIN;
2176 : } else {
2177 0 : if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2178 : return -ERESTARTSYS;
2179 : }
2180 :
2181 0 : down_read(&tty->termios_rwsem);
2182 :
2183 0 : minimum = time = 0;
2184 0 : timeout = MAX_SCHEDULE_TIMEOUT;
2185 0 : if (!ldata->icanon) {
2186 0 : minimum = MIN_CHAR(tty);
2187 0 : if (minimum) {
2188 0 : time = (HZ / 10) * TIME_CHAR(tty);
2189 : } else {
2190 0 : timeout = (HZ / 10) * TIME_CHAR(tty);
2191 0 : minimum = 1;
2192 : }
2193 : }
2194 :
2195 0 : packet = tty->ctrl.packet;
2196 0 : old_tail = ldata->read_tail;
2197 :
2198 0 : add_wait_queue(&tty->read_wait, &wait);
2199 0 : while (nr) {
2200 : /* First test for status change. */
2201 0 : if (packet && tty->link->ctrl.pktstatus) {
2202 : unsigned char cs;
2203 0 : if (kb != kbuf)
2204 : break;
2205 0 : spin_lock_irq(&tty->link->ctrl.lock);
2206 0 : cs = tty->link->ctrl.pktstatus;
2207 0 : tty->link->ctrl.pktstatus = 0;
2208 0 : spin_unlock_irq(&tty->link->ctrl.lock);
2209 0 : *kb++ = cs;
2210 0 : nr--;
2211 0 : break;
2212 : }
2213 :
2214 0 : if (!input_available_p(tty, 0)) {
2215 0 : up_read(&tty->termios_rwsem);
2216 0 : tty_buffer_flush_work(tty->port);
2217 0 : down_read(&tty->termios_rwsem);
2218 0 : if (!input_available_p(tty, 0)) {
2219 0 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2220 : retval = -EIO;
2221 : break;
2222 : }
2223 0 : 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 0 : if (test_bit(TTY_HUPPING, &tty->flags))
2230 : break;
2231 0 : if (!timeout)
2232 : break;
2233 0 : if (tty_io_nonblock(tty, file)) {
2234 : retval = -EAGAIN;
2235 : break;
2236 : }
2237 0 : if (signal_pending(current)) {
2238 : retval = -ERESTARTSYS;
2239 : break;
2240 : }
2241 0 : up_read(&tty->termios_rwsem);
2242 :
2243 0 : timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2244 : timeout);
2245 :
2246 0 : down_read(&tty->termios_rwsem);
2247 0 : continue;
2248 : }
2249 : }
2250 :
2251 0 : if (ldata->icanon && !L_EXTPROC(tty)) {
2252 0 : if (canon_copy_from_read_buf(tty, &kb, &nr))
2253 : goto more_to_be_read;
2254 : } else {
2255 : /* Deal with packet mode. */
2256 0 : if (packet && kb == kbuf) {
2257 0 : *kb++ = TIOCPKT_DATA;
2258 0 : 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 0 : if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2271 : more_to_be_read:
2272 0 : remove_wait_queue(&tty->read_wait, &wait);
2273 0 : *cookie = cookie;
2274 0 : return kb - kbuf;
2275 : }
2276 : }
2277 :
2278 0 : n_tty_check_unthrottle(tty);
2279 :
2280 0 : if (kb - kbuf >= minimum)
2281 : break;
2282 0 : if (time)
2283 0 : timeout = time;
2284 : }
2285 0 : if (old_tail != ldata->read_tail)
2286 0 : n_tty_kick_worker(tty);
2287 0 : up_read(&tty->termios_rwsem);
2288 :
2289 0 : remove_wait_queue(&tty->read_wait, &wait);
2290 0 : mutex_unlock(&ldata->atomic_read_lock);
2291 :
2292 0 : if (kb - kbuf)
2293 0 : 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 :
2318 0 : static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2319 : const unsigned char *buf, size_t nr)
2320 : {
2321 0 : const unsigned char *b = buf;
2322 0 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2323 : int c;
2324 0 : ssize_t retval = 0;
2325 :
2326 : /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2327 0 : if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2328 0 : retval = tty_check_change(tty);
2329 0 : if (retval)
2330 : return retval;
2331 : }
2332 :
2333 0 : down_read(&tty->termios_rwsem);
2334 :
2335 : /* Write out any echoed characters that are still pending */
2336 0 : process_echoes(tty);
2337 :
2338 0 : add_wait_queue(&tty->write_wait, &wait);
2339 : while (1) {
2340 0 : if (signal_pending(current)) {
2341 : retval = -ERESTARTSYS;
2342 : break;
2343 : }
2344 0 : if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2345 : retval = -EIO;
2346 : break;
2347 : }
2348 0 : if (O_OPOST(tty)) {
2349 0 : while (nr > 0) {
2350 0 : ssize_t num = process_output_block(tty, b, nr);
2351 0 : if (num < 0) {
2352 0 : if (num == -EAGAIN)
2353 : break;
2354 : retval = num;
2355 : goto break_out;
2356 : }
2357 0 : b += num;
2358 0 : nr -= num;
2359 0 : if (nr == 0)
2360 : break;
2361 0 : c = *b;
2362 0 : if (process_output(c, tty) < 0)
2363 : break;
2364 0 : b++; nr--;
2365 : }
2366 0 : if (tty->ops->flush_chars)
2367 0 : tty->ops->flush_chars(tty);
2368 : } else {
2369 0 : struct n_tty_data *ldata = tty->disc_data;
2370 :
2371 0 : while (nr > 0) {
2372 0 : mutex_lock(&ldata->output_lock);
2373 0 : c = tty->ops->write(tty, b, nr);
2374 0 : mutex_unlock(&ldata->output_lock);
2375 0 : if (c < 0) {
2376 0 : retval = c;
2377 0 : goto break_out;
2378 : }
2379 0 : if (!c)
2380 : break;
2381 0 : b += c;
2382 0 : nr -= c;
2383 : }
2384 : }
2385 0 : if (!nr)
2386 : break;
2387 0 : if (tty_io_nonblock(tty, file)) {
2388 : retval = -EAGAIN;
2389 : break;
2390 : }
2391 0 : up_read(&tty->termios_rwsem);
2392 :
2393 0 : wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2394 :
2395 0 : down_read(&tty->termios_rwsem);
2396 : }
2397 : break_out:
2398 0 : remove_wait_queue(&tty->write_wait, &wait);
2399 0 : if (nr && tty->fasync)
2400 0 : set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2401 0 : up_read(&tty->termios_rwsem);
2402 0 : 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 : */
2419 0 : static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2420 : poll_table *wait)
2421 : {
2422 0 : __poll_t mask = 0;
2423 :
2424 0 : poll_wait(file, &tty->read_wait, wait);
2425 0 : poll_wait(file, &tty->write_wait, wait);
2426 0 : if (input_available_p(tty, 1))
2427 : mask |= EPOLLIN | EPOLLRDNORM;
2428 : else {
2429 0 : tty_buffer_flush_work(tty->port);
2430 0 : if (input_available_p(tty, 1))
2431 0 : mask |= EPOLLIN | EPOLLRDNORM;
2432 : }
2433 0 : if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2434 0 : mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2435 0 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2436 0 : mask |= EPOLLHUP;
2437 0 : if (tty_hung_up_p(file))
2438 0 : mask |= EPOLLHUP;
2439 0 : if (tty->ops->write && !tty_is_writelocked(tty) &&
2440 0 : tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2441 0 : tty_write_room(tty) > 0)
2442 0 : mask |= EPOLLOUT | EPOLLWRNORM;
2443 0 : return mask;
2444 : }
2445 :
2446 0 : static unsigned long inq_canon(struct n_tty_data *ldata)
2447 : {
2448 : size_t nr, head, tail;
2449 :
2450 0 : if (ldata->canon_head == ldata->read_tail)
2451 : return 0;
2452 0 : head = ldata->canon_head;
2453 0 : tail = ldata->read_tail;
2454 0 : nr = head - tail;
2455 : /* Skip EOF-chars.. */
2456 0 : while (MASK(head) != MASK(tail)) {
2457 0 : if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2458 0 : read_buf(ldata, tail) == __DISABLED_CHAR)
2459 0 : nr--;
2460 0 : tail++;
2461 : }
2462 : return nr;
2463 : }
2464 :
2465 0 : static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
2466 : unsigned long arg)
2467 : {
2468 0 : struct n_tty_data *ldata = tty->disc_data;
2469 : int retval;
2470 :
2471 0 : switch (cmd) {
2472 : case TIOCOUTQ:
2473 0 : return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2474 : case TIOCINQ:
2475 0 : down_write(&tty->termios_rwsem);
2476 0 : if (L_ICANON(tty) && !L_EXTPROC(tty))
2477 0 : retval = inq_canon(ldata);
2478 : else
2479 0 : retval = read_cnt(ldata);
2480 0 : up_write(&tty->termios_rwsem);
2481 0 : return put_user(retval, (unsigned int __user *) arg);
2482 : default:
2483 0 : return n_tty_ioctl_helper(tty, cmd, arg);
2484 : }
2485 : }
2486 :
2487 : static 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 :
2512 0 : void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2513 : {
2514 0 : *ops = n_tty_ops;
2515 0 : ops->owner = NULL;
2516 0 : }
2517 : EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2518 :
2519 1 : void __init n_tty_init(void)
2520 : {
2521 1 : tty_register_ldisc(&n_tty_ops);
2522 1 : }
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