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/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 : /*
60 : * This defines the low- and high-watermarks for throttling and
61 : * unthrottling the TTY driver. These watermarks are used for
62 : * controlling the space in the read buffer.
63 : */
64 : #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
65 : #define TTY_THRESHOLD_UNTHROTTLE 128
66 :
67 : /*
68 : * Special byte codes used in the echo buffer to represent operations
69 : * or special handling of characters. Bytes in the echo buffer that
70 : * are not part of such special blocks are treated as normal character
71 : * codes.
72 : */
73 : #define ECHO_OP_START 0xff
74 : #define ECHO_OP_MOVE_BACK_COL 0x80
75 : #define ECHO_OP_SET_CANON_COL 0x81
76 : #define ECHO_OP_ERASE_TAB 0x82
77 :
78 : #define ECHO_COMMIT_WATERMARK 256
79 : #define ECHO_BLOCK 256
80 : #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
81 :
82 :
83 : #undef N_TTY_TRACE
84 : #ifdef N_TTY_TRACE
85 : # define n_tty_trace(f, args...) trace_printk(f, ##args)
86 : #else
87 : # define n_tty_trace(f, args...) no_printk(f, ##args)
88 : #endif
89 :
90 : struct n_tty_data {
91 : /* producer-published */
92 : size_t read_head;
93 : size_t commit_head;
94 : size_t canon_head;
95 : size_t echo_head;
96 : size_t echo_commit;
97 : size_t echo_mark;
98 : DECLARE_BITMAP(char_map, 256);
99 :
100 : /* private to n_tty_receive_overrun (single-threaded) */
101 : unsigned long overrun_time;
102 : int num_overrun;
103 :
104 : /* non-atomic */
105 : bool no_room;
106 :
107 : /* must hold exclusive termios_rwsem to reset these */
108 : unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
109 : unsigned char push:1;
110 :
111 : /* shared by producer and consumer */
112 : char read_buf[N_TTY_BUF_SIZE];
113 : DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
114 : unsigned char echo_buf[N_TTY_BUF_SIZE];
115 :
116 : /* consumer-published */
117 : size_t read_tail;
118 : size_t line_start;
119 :
120 : /* # of chars looked ahead (to find software flow control chars) */
121 : size_t lookahead_count;
122 :
123 : /* protected by output lock */
124 : unsigned int column;
125 : unsigned int canon_column;
126 : size_t echo_tail;
127 :
128 : struct mutex atomic_read_lock;
129 : struct mutex output_lock;
130 : };
131 :
132 : #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
133 :
134 : static inline size_t read_cnt(struct n_tty_data *ldata)
135 : {
136 0 : return ldata->read_head - ldata->read_tail;
137 : }
138 :
139 : static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
140 : {
141 0 : return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
142 : }
143 :
144 : static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
145 : {
146 0 : return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
147 : }
148 :
149 : static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
150 : {
151 0 : smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
152 0 : return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
153 : }
154 :
155 : static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
156 : {
157 0 : return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
158 : }
159 :
160 : /* If we are not echoing the data, perhaps this is a secret so erase it */
161 : static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
162 : {
163 0 : bool icanon = !!L_ICANON(tty);
164 0 : bool no_echo = !L_ECHO(tty);
165 :
166 0 : if (icanon && no_echo)
167 0 : memset(buffer, 0x00, size);
168 : }
169 :
170 0 : static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
171 : {
172 0 : struct n_tty_data *ldata = tty->disc_data;
173 0 : size_t size = N_TTY_BUF_SIZE - tail;
174 0 : void *from = read_buf_addr(ldata, tail);
175 :
176 0 : if (n > size) {
177 0 : tty_audit_add_data(tty, from, size);
178 0 : memcpy(to, from, size);
179 0 : zero_buffer(tty, from, size);
180 0 : to += size;
181 0 : n -= size;
182 0 : from = ldata->read_buf;
183 : }
184 :
185 0 : tty_audit_add_data(tty, from, n);
186 0 : memcpy(to, from, n);
187 0 : zero_buffer(tty, from, n);
188 0 : }
189 :
190 : /**
191 : * n_tty_kick_worker - start input worker (if required)
192 : * @tty: terminal
193 : *
194 : * Re-schedules the flip buffer work if it may have stopped.
195 : *
196 : * Locking:
197 : * * Caller holds exclusive %termios_rwsem, or
198 : * * n_tty_read()/consumer path:
199 : * holds non-exclusive %termios_rwsem
200 : */
201 0 : static void n_tty_kick_worker(struct tty_struct *tty)
202 : {
203 0 : struct n_tty_data *ldata = tty->disc_data;
204 :
205 : /* Did the input worker stop? Restart it */
206 0 : if (unlikely(ldata->no_room)) {
207 0 : ldata->no_room = 0;
208 :
209 0 : WARN_RATELIMIT(tty->port->itty == NULL,
210 : "scheduling with invalid itty\n");
211 : /* see if ldisc has been killed - if so, this means that
212 : * even though the ldisc has been halted and ->buf.work
213 : * cancelled, ->buf.work is about to be rescheduled
214 : */
215 0 : WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
216 : "scheduling buffer work for halted ldisc\n");
217 0 : tty_buffer_restart_work(tty->port);
218 : }
219 0 : }
220 :
221 : static ssize_t chars_in_buffer(struct tty_struct *tty)
222 : {
223 0 : struct n_tty_data *ldata = tty->disc_data;
224 0 : ssize_t n = 0;
225 :
226 0 : if (!ldata->icanon)
227 0 : n = ldata->commit_head - ldata->read_tail;
228 : else
229 0 : n = ldata->canon_head - ldata->read_tail;
230 : return n;
231 : }
232 :
233 : /**
234 : * n_tty_write_wakeup - asynchronous I/O notifier
235 : * @tty: tty device
236 : *
237 : * Required for the ptys, serial driver etc. since processes that attach
238 : * themselves to the master and rely on ASYNC IO must be woken up.
239 : */
240 0 : static void n_tty_write_wakeup(struct tty_struct *tty)
241 : {
242 0 : clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
243 0 : kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
244 0 : }
245 :
246 0 : static void n_tty_check_throttle(struct tty_struct *tty)
247 : {
248 0 : struct n_tty_data *ldata = tty->disc_data;
249 :
250 : /*
251 : * Check the remaining room for the input canonicalization
252 : * mode. We don't want to throttle the driver if we're in
253 : * canonical mode and don't have a newline yet!
254 : */
255 0 : if (ldata->icanon && ldata->canon_head == ldata->read_tail)
256 : return;
257 :
258 : while (1) {
259 : int throttled;
260 0 : tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
261 0 : if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
262 : break;
263 0 : throttled = tty_throttle_safe(tty);
264 0 : if (!throttled)
265 : break;
266 : }
267 0 : __tty_set_flow_change(tty, 0);
268 : }
269 :
270 0 : static void n_tty_check_unthrottle(struct tty_struct *tty)
271 : {
272 0 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
273 0 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
274 : return;
275 0 : n_tty_kick_worker(tty);
276 0 : tty_wakeup(tty->link);
277 0 : return;
278 : }
279 :
280 : /* If there is enough space in the read buffer now, let the
281 : * low-level driver know. We use chars_in_buffer() to
282 : * check the buffer, as it now knows about canonical mode.
283 : * Otherwise, if the driver is throttled and the line is
284 : * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
285 : * we won't get any more characters.
286 : */
287 :
288 : while (1) {
289 : int unthrottled;
290 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
291 0 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
292 : break;
293 0 : n_tty_kick_worker(tty);
294 0 : unthrottled = tty_unthrottle_safe(tty);
295 0 : if (!unthrottled)
296 : break;
297 : }
298 0 : __tty_set_flow_change(tty, 0);
299 : }
300 :
301 : /**
302 : * put_tty_queue - add character to tty
303 : * @c: character
304 : * @ldata: n_tty data
305 : *
306 : * Add a character to the tty read_buf queue.
307 : *
308 : * Locking:
309 : * * n_tty_receive_buf()/producer path:
310 : * caller holds non-exclusive %termios_rwsem
311 : */
312 : static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
313 : {
314 0 : *read_buf_addr(ldata, ldata->read_head) = c;
315 0 : ldata->read_head++;
316 : }
317 :
318 : /**
319 : * reset_buffer_flags - reset buffer state
320 : * @ldata: line disc data to reset
321 : *
322 : * Reset the read buffer counters and clear the flags. Called from
323 : * n_tty_open() and n_tty_flush_buffer().
324 : *
325 : * Locking:
326 : * * caller holds exclusive %termios_rwsem, or
327 : * * (locking is not required)
328 : */
329 : static void reset_buffer_flags(struct n_tty_data *ldata)
330 : {
331 0 : ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
332 0 : ldata->commit_head = 0;
333 0 : ldata->line_start = 0;
334 :
335 0 : ldata->erasing = 0;
336 0 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
337 0 : ldata->push = 0;
338 :
339 0 : ldata->lookahead_count = 0;
340 : }
341 :
342 0 : static void n_tty_packet_mode_flush(struct tty_struct *tty)
343 : {
344 : unsigned long flags;
345 :
346 0 : if (tty->link->ctrl.packet) {
347 0 : spin_lock_irqsave(&tty->ctrl.lock, flags);
348 0 : tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
349 0 : spin_unlock_irqrestore(&tty->ctrl.lock, flags);
350 0 : wake_up_interruptible(&tty->link->read_wait);
351 : }
352 0 : }
353 :
354 : /**
355 : * n_tty_flush_buffer - clean input queue
356 : * @tty: terminal device
357 : *
358 : * Flush the input buffer. Called when the tty layer wants the buffer flushed
359 : * (eg at hangup) or when the %N_TTY line discipline internally has to clean
360 : * the pending queue (for example some signals).
361 : *
362 : * Holds %termios_rwsem to exclude producer/consumer while buffer indices are
363 : * reset.
364 : *
365 : * Locking: %ctrl.lock, exclusive %termios_rwsem
366 : */
367 0 : static void n_tty_flush_buffer(struct tty_struct *tty)
368 : {
369 0 : down_write(&tty->termios_rwsem);
370 0 : reset_buffer_flags(tty->disc_data);
371 0 : n_tty_kick_worker(tty);
372 :
373 0 : if (tty->link)
374 0 : n_tty_packet_mode_flush(tty);
375 0 : up_write(&tty->termios_rwsem);
376 0 : }
377 :
378 : /**
379 : * is_utf8_continuation - utf8 multibyte check
380 : * @c: byte to check
381 : *
382 : * Returns: true if the utf8 character @c is a multibyte continuation
383 : * character. We use this to correctly compute the on-screen size of the
384 : * character when printing.
385 : */
386 : static inline int is_utf8_continuation(unsigned char c)
387 : {
388 : return (c & 0xc0) == 0x80;
389 : }
390 :
391 : /**
392 : * is_continuation - multibyte check
393 : * @c: byte to check
394 : * @tty: terminal device
395 : *
396 : * Returns: true if the utf8 character @c is a multibyte continuation character
397 : * and the terminal is in unicode mode.
398 : */
399 : static inline int is_continuation(unsigned char c, struct tty_struct *tty)
400 : {
401 0 : return I_IUTF8(tty) && is_utf8_continuation(c);
402 : }
403 :
404 : /**
405 : * do_output_char - output one character
406 : * @c: character (or partial unicode symbol)
407 : * @tty: terminal device
408 : * @space: space available in tty driver write buffer
409 : *
410 : * This is a helper function that handles one output character (including
411 : * special characters like TAB, CR, LF, etc.), doing OPOST processing and
412 : * putting the results in the tty driver's write buffer.
413 : *
414 : * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY.
415 : * They simply aren't relevant in the world today. If you ever need them, add
416 : * them here.
417 : *
418 : * Returns: the number of bytes of buffer space used or -1 if no space left.
419 : *
420 : * Locking: should be called under the %output_lock to protect the column state
421 : * and space left in the buffer.
422 : */
423 0 : static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
424 : {
425 0 : struct n_tty_data *ldata = tty->disc_data;
426 : int spaces;
427 :
428 0 : if (!space)
429 : return -1;
430 :
431 0 : switch (c) {
432 : case '\n':
433 0 : if (O_ONLRET(tty))
434 0 : ldata->column = 0;
435 0 : if (O_ONLCR(tty)) {
436 0 : if (space < 2)
437 : return -1;
438 0 : ldata->canon_column = ldata->column = 0;
439 0 : tty->ops->write(tty, "\r\n", 2);
440 0 : return 2;
441 : }
442 0 : ldata->canon_column = ldata->column;
443 0 : break;
444 : case '\r':
445 0 : if (O_ONOCR(tty) && ldata->column == 0)
446 : return 0;
447 0 : if (O_OCRNL(tty)) {
448 0 : c = '\n';
449 0 : if (O_ONLRET(tty))
450 0 : ldata->canon_column = ldata->column = 0;
451 : break;
452 : }
453 0 : ldata->canon_column = ldata->column = 0;
454 0 : break;
455 : case '\t':
456 0 : spaces = 8 - (ldata->column & 7);
457 0 : if (O_TABDLY(tty) == XTABS) {
458 0 : if (space < spaces)
459 : return -1;
460 0 : ldata->column += spaces;
461 0 : tty->ops->write(tty, " ", spaces);
462 0 : return spaces;
463 : }
464 0 : ldata->column += spaces;
465 0 : break;
466 : case '\b':
467 0 : if (ldata->column > 0)
468 0 : ldata->column--;
469 : break;
470 : default:
471 0 : if (!iscntrl(c)) {
472 0 : if (O_OLCUC(tty))
473 : c = toupper(c);
474 0 : if (!is_continuation(c, tty))
475 0 : ldata->column++;
476 : }
477 : break;
478 : }
479 :
480 0 : tty_put_char(tty, c);
481 0 : return 1;
482 : }
483 :
484 : /**
485 : * process_output - output post processor
486 : * @c: character (or partial unicode symbol)
487 : * @tty: terminal device
488 : *
489 : * Output one character with OPOST processing.
490 : *
491 : * Returns: -1 when the output device is full and the character must be
492 : * retried.
493 : *
494 : * Locking: %output_lock to protect column state and space left (also, this is
495 : *called from n_tty_write() under the tty layer write lock).
496 : */
497 0 : static int process_output(unsigned char c, struct tty_struct *tty)
498 : {
499 0 : struct n_tty_data *ldata = tty->disc_data;
500 : int space, retval;
501 :
502 0 : mutex_lock(&ldata->output_lock);
503 :
504 0 : space = tty_write_room(tty);
505 0 : retval = do_output_char(c, tty, space);
506 :
507 0 : mutex_unlock(&ldata->output_lock);
508 0 : if (retval < 0)
509 : return -1;
510 : else
511 0 : return 0;
512 : }
513 :
514 : /**
515 : * process_output_block - block post processor
516 : * @tty: terminal device
517 : * @buf: character buffer
518 : * @nr: number of bytes to output
519 : *
520 : * Output a block of characters with OPOST processing.
521 : *
522 : * This path is used to speed up block console writes, among other things when
523 : * processing blocks of output data. It handles only the simple cases normally
524 : * found and helps to generate blocks of symbols for the console driver and
525 : * thus improve performance.
526 : *
527 : * Returns: the number of characters output.
528 : *
529 : * Locking: %output_lock to protect column state and space left (also, this is
530 : * called from n_tty_write() under the tty layer write lock).
531 : */
532 0 : static ssize_t process_output_block(struct tty_struct *tty,
533 : const unsigned char *buf, unsigned int nr)
534 : {
535 0 : struct n_tty_data *ldata = tty->disc_data;
536 : int space;
537 : int i;
538 : const unsigned char *cp;
539 :
540 0 : mutex_lock(&ldata->output_lock);
541 :
542 0 : space = tty_write_room(tty);
543 0 : if (space <= 0) {
544 0 : mutex_unlock(&ldata->output_lock);
545 0 : return space;
546 : }
547 0 : if (nr > space)
548 0 : nr = space;
549 :
550 0 : for (i = 0, cp = buf; i < nr; i++, cp++) {
551 0 : unsigned char c = *cp;
552 :
553 0 : switch (c) {
554 : case '\n':
555 0 : if (O_ONLRET(tty))
556 0 : ldata->column = 0;
557 0 : if (O_ONLCR(tty))
558 : goto break_out;
559 0 : ldata->canon_column = ldata->column;
560 0 : break;
561 : case '\r':
562 0 : if (O_ONOCR(tty) && ldata->column == 0)
563 : goto break_out;
564 0 : if (O_OCRNL(tty))
565 : goto break_out;
566 0 : ldata->canon_column = ldata->column = 0;
567 0 : break;
568 : case '\t':
569 : goto break_out;
570 : case '\b':
571 0 : if (ldata->column > 0)
572 0 : ldata->column--;
573 : break;
574 : default:
575 0 : if (!iscntrl(c)) {
576 0 : if (O_OLCUC(tty))
577 : goto break_out;
578 0 : if (!is_continuation(c, tty))
579 0 : ldata->column++;
580 : }
581 : break;
582 : }
583 : }
584 : break_out:
585 0 : i = tty->ops->write(tty, buf, i);
586 :
587 0 : mutex_unlock(&ldata->output_lock);
588 0 : return i;
589 : }
590 :
591 : /**
592 : * __process_echoes - write pending echo characters
593 : * @tty: terminal device
594 : *
595 : * Write previously buffered echo (and other ldisc-generated) characters to the
596 : * tty.
597 : *
598 : * Characters generated by the ldisc (including echoes) need to be buffered
599 : * because the driver's write buffer can fill during heavy program output.
600 : * Echoing straight to the driver will often fail under these conditions,
601 : * causing lost characters and resulting mismatches of ldisc state information.
602 : *
603 : * Since the ldisc state must represent the characters actually sent to the
604 : * driver at the time of the write, operations like certain changes in column
605 : * state are also saved in the buffer and executed here.
606 : *
607 : * A circular fifo buffer is used so that the most recent characters are
608 : * prioritized. Also, when control characters are echoed with a prefixed "^",
609 : * the pair is treated atomically and thus not separated.
610 : *
611 : * Locking: callers must hold %output_lock.
612 : */
613 0 : static size_t __process_echoes(struct tty_struct *tty)
614 : {
615 0 : struct n_tty_data *ldata = tty->disc_data;
616 : int space, old_space;
617 : size_t tail;
618 : unsigned char c;
619 :
620 0 : old_space = space = tty_write_room(tty);
621 :
622 0 : tail = ldata->echo_tail;
623 0 : while (MASK(ldata->echo_commit) != MASK(tail)) {
624 0 : c = echo_buf(ldata, tail);
625 0 : if (c == ECHO_OP_START) {
626 : unsigned char op;
627 0 : bool space_left = true;
628 :
629 : /*
630 : * Since add_echo_byte() is called without holding
631 : * output_lock, we might see only portion of multi-byte
632 : * operation.
633 : */
634 0 : if (MASK(ldata->echo_commit) == MASK(tail + 1))
635 : goto not_yet_stored;
636 : /*
637 : * If the buffer byte is the start of a multi-byte
638 : * operation, get the next byte, which is either the
639 : * op code or a control character value.
640 : */
641 0 : op = echo_buf(ldata, tail + 1);
642 :
643 0 : switch (op) {
644 : case ECHO_OP_ERASE_TAB: {
645 : unsigned int num_chars, num_bs;
646 :
647 0 : if (MASK(ldata->echo_commit) == MASK(tail + 2))
648 : goto not_yet_stored;
649 0 : num_chars = echo_buf(ldata, tail + 2);
650 :
651 : /*
652 : * Determine how many columns to go back
653 : * in order to erase the tab.
654 : * This depends on the number of columns
655 : * used by other characters within the tab
656 : * area. If this (modulo 8) count is from
657 : * the start of input rather than from a
658 : * previous tab, we offset by canon column.
659 : * Otherwise, tab spacing is normal.
660 : */
661 0 : if (!(num_chars & 0x80))
662 0 : num_chars += ldata->canon_column;
663 0 : num_bs = 8 - (num_chars & 7);
664 :
665 0 : if (num_bs > space) {
666 : space_left = false;
667 : break;
668 : }
669 0 : space -= num_bs;
670 0 : while (num_bs--) {
671 0 : tty_put_char(tty, '\b');
672 0 : if (ldata->column > 0)
673 0 : ldata->column--;
674 : }
675 0 : tail += 3;
676 0 : break;
677 : }
678 : case ECHO_OP_SET_CANON_COL:
679 0 : ldata->canon_column = ldata->column;
680 0 : tail += 2;
681 0 : break;
682 :
683 : case ECHO_OP_MOVE_BACK_COL:
684 0 : if (ldata->column > 0)
685 0 : ldata->column--;
686 0 : tail += 2;
687 0 : break;
688 :
689 : case ECHO_OP_START:
690 : /* This is an escaped echo op start code */
691 0 : if (!space) {
692 : space_left = false;
693 : break;
694 : }
695 0 : tty_put_char(tty, ECHO_OP_START);
696 0 : ldata->column++;
697 0 : space--;
698 0 : tail += 2;
699 0 : break;
700 :
701 : default:
702 : /*
703 : * If the op is not a special byte code,
704 : * it is a ctrl char tagged to be echoed
705 : * as "^X" (where X is the letter
706 : * representing the control char).
707 : * Note that we must ensure there is
708 : * enough space for the whole ctrl pair.
709 : *
710 : */
711 0 : if (space < 2) {
712 : space_left = false;
713 : break;
714 : }
715 0 : tty_put_char(tty, '^');
716 0 : tty_put_char(tty, op ^ 0100);
717 0 : ldata->column += 2;
718 0 : space -= 2;
719 0 : tail += 2;
720 : }
721 :
722 0 : if (!space_left)
723 : break;
724 : } else {
725 0 : if (O_OPOST(tty)) {
726 0 : int retval = do_output_char(c, tty, space);
727 0 : if (retval < 0)
728 : break;
729 0 : space -= retval;
730 : } else {
731 0 : if (!space)
732 : break;
733 0 : tty_put_char(tty, c);
734 0 : space -= 1;
735 : }
736 0 : tail += 1;
737 : }
738 : }
739 :
740 : /* If the echo buffer is nearly full (so that the possibility exists
741 : * of echo overrun before the next commit), then discard enough
742 : * data at the tail to prevent a subsequent overrun */
743 0 : while (ldata->echo_commit > tail &&
744 0 : ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
745 0 : if (echo_buf(ldata, tail) == ECHO_OP_START) {
746 0 : if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
747 0 : tail += 3;
748 : else
749 0 : tail += 2;
750 : } else
751 0 : tail++;
752 : }
753 :
754 : not_yet_stored:
755 0 : ldata->echo_tail = tail;
756 0 : return old_space - space;
757 : }
758 :
759 0 : static void commit_echoes(struct tty_struct *tty)
760 : {
761 0 : struct n_tty_data *ldata = tty->disc_data;
762 : size_t nr, old, echoed;
763 : size_t head;
764 :
765 0 : mutex_lock(&ldata->output_lock);
766 0 : head = ldata->echo_head;
767 0 : ldata->echo_mark = head;
768 0 : old = ldata->echo_commit - ldata->echo_tail;
769 :
770 : /* Process committed echoes if the accumulated # of bytes
771 : * is over the threshold (and try again each time another
772 : * block is accumulated) */
773 0 : nr = head - ldata->echo_tail;
774 0 : if (nr < ECHO_COMMIT_WATERMARK ||
775 0 : (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
776 0 : mutex_unlock(&ldata->output_lock);
777 0 : return;
778 : }
779 :
780 0 : ldata->echo_commit = head;
781 0 : echoed = __process_echoes(tty);
782 0 : mutex_unlock(&ldata->output_lock);
783 :
784 0 : if (echoed && tty->ops->flush_chars)
785 0 : tty->ops->flush_chars(tty);
786 : }
787 :
788 0 : static void process_echoes(struct tty_struct *tty)
789 : {
790 0 : struct n_tty_data *ldata = tty->disc_data;
791 : size_t echoed;
792 :
793 0 : if (ldata->echo_mark == ldata->echo_tail)
794 : return;
795 :
796 0 : mutex_lock(&ldata->output_lock);
797 0 : ldata->echo_commit = ldata->echo_mark;
798 0 : echoed = __process_echoes(tty);
799 0 : mutex_unlock(&ldata->output_lock);
800 :
801 0 : if (echoed && tty->ops->flush_chars)
802 0 : tty->ops->flush_chars(tty);
803 : }
804 :
805 : /* NB: echo_mark and echo_head should be equivalent here */
806 0 : static void flush_echoes(struct tty_struct *tty)
807 : {
808 0 : struct n_tty_data *ldata = tty->disc_data;
809 :
810 0 : if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
811 0 : ldata->echo_commit == ldata->echo_head)
812 : return;
813 :
814 0 : mutex_lock(&ldata->output_lock);
815 0 : ldata->echo_commit = ldata->echo_head;
816 0 : __process_echoes(tty);
817 0 : mutex_unlock(&ldata->output_lock);
818 : }
819 :
820 : /**
821 : * add_echo_byte - add a byte to the echo buffer
822 : * @c: unicode byte to echo
823 : * @ldata: n_tty data
824 : *
825 : * Add a character or operation byte to the echo buffer.
826 : */
827 : static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
828 : {
829 0 : *echo_buf_addr(ldata, ldata->echo_head) = c;
830 0 : smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
831 0 : ldata->echo_head++;
832 : }
833 :
834 : /**
835 : * echo_move_back_col - add operation to move back a column
836 : * @ldata: n_tty data
837 : *
838 : * Add an operation to the echo buffer to move back one column.
839 : */
840 : static void echo_move_back_col(struct n_tty_data *ldata)
841 : {
842 0 : add_echo_byte(ECHO_OP_START, ldata);
843 0 : add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
844 : }
845 :
846 : /**
847 : * echo_set_canon_col - add operation to set the canon column
848 : * @ldata: n_tty data
849 : *
850 : * Add an operation to the echo buffer to set the canon column to the current
851 : * column.
852 : */
853 : static void echo_set_canon_col(struct n_tty_data *ldata)
854 : {
855 0 : add_echo_byte(ECHO_OP_START, ldata);
856 0 : add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
857 : }
858 :
859 : /**
860 : * echo_erase_tab - add operation to erase a tab
861 : * @num_chars: number of character columns already used
862 : * @after_tab: true if num_chars starts after a previous tab
863 : * @ldata: n_tty data
864 : *
865 : * Add an operation to the echo buffer to erase a tab.
866 : *
867 : * Called by the eraser function, which knows how many character columns have
868 : * been used since either a previous tab or the start of input. This
869 : * information will be used later, along with canon column (if applicable), to
870 : * go back the correct number of columns.
871 : */
872 : static void echo_erase_tab(unsigned int num_chars, int after_tab,
873 : struct n_tty_data *ldata)
874 : {
875 0 : add_echo_byte(ECHO_OP_START, ldata);
876 0 : add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
877 :
878 : /* We only need to know this modulo 8 (tab spacing) */
879 0 : num_chars &= 7;
880 :
881 : /* Set the high bit as a flag if num_chars is after a previous tab */
882 0 : if (after_tab)
883 0 : num_chars |= 0x80;
884 :
885 0 : add_echo_byte(num_chars, ldata);
886 : }
887 :
888 : /**
889 : * echo_char_raw - echo a character raw
890 : * @c: unicode byte to echo
891 : * @ldata: line disc data
892 : *
893 : * Echo user input back onto the screen. This must be called only when
894 : * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
895 : *
896 : * This variant does not treat control characters specially.
897 : */
898 : static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
899 : {
900 0 : if (c == ECHO_OP_START) {
901 0 : add_echo_byte(ECHO_OP_START, ldata);
902 : add_echo_byte(ECHO_OP_START, ldata);
903 : } else {
904 : add_echo_byte(c, ldata);
905 : }
906 : }
907 :
908 : /**
909 : * echo_char - echo a character
910 : * @c: unicode byte to echo
911 : * @tty: terminal device
912 : *
913 : * Echo user input back onto the screen. This must be called only when
914 : * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
915 : *
916 : * This variant tags control characters to be echoed as "^X" (where X is the
917 : * letter representing the control char).
918 : */
919 0 : static void echo_char(unsigned char c, struct tty_struct *tty)
920 : {
921 0 : struct n_tty_data *ldata = tty->disc_data;
922 :
923 0 : if (c == ECHO_OP_START) {
924 0 : add_echo_byte(ECHO_OP_START, ldata);
925 : add_echo_byte(ECHO_OP_START, ldata);
926 : } else {
927 0 : if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
928 : add_echo_byte(ECHO_OP_START, ldata);
929 : add_echo_byte(c, ldata);
930 : }
931 0 : }
932 :
933 : /**
934 : * finish_erasing - complete erase
935 : * @ldata: n_tty data
936 : */
937 : static inline void finish_erasing(struct n_tty_data *ldata)
938 : {
939 0 : if (ldata->erasing) {
940 0 : echo_char_raw('/', ldata);
941 0 : ldata->erasing = 0;
942 : }
943 : }
944 :
945 : /**
946 : * eraser - handle erase function
947 : * @c: character input
948 : * @tty: terminal device
949 : *
950 : * Perform erase and necessary output when an erase character is present in the
951 : * stream from the driver layer. Handles the complexities of UTF-8 multibyte
952 : * symbols.
953 : *
954 : * Locking: n_tty_receive_buf()/producer path:
955 : * caller holds non-exclusive %termios_rwsem
956 : */
957 0 : static void eraser(unsigned char c, struct tty_struct *tty)
958 : {
959 0 : struct n_tty_data *ldata = tty->disc_data;
960 : enum { ERASE, WERASE, KILL } kill_type;
961 : size_t head;
962 : size_t cnt;
963 : int seen_alnums;
964 :
965 0 : if (ldata->read_head == ldata->canon_head) {
966 : /* process_output('\a', tty); */ /* what do you think? */
967 : return;
968 : }
969 0 : if (c == ERASE_CHAR(tty))
970 : kill_type = ERASE;
971 0 : else if (c == WERASE_CHAR(tty))
972 : kill_type = WERASE;
973 : else {
974 0 : if (!L_ECHO(tty)) {
975 0 : ldata->read_head = ldata->canon_head;
976 0 : return;
977 : }
978 0 : if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
979 0 : ldata->read_head = ldata->canon_head;
980 0 : finish_erasing(ldata);
981 0 : echo_char(KILL_CHAR(tty), tty);
982 : /* Add a newline if ECHOK is on and ECHOKE is off. */
983 0 : if (L_ECHOK(tty))
984 : echo_char_raw('\n', ldata);
985 : return;
986 : }
987 : kill_type = KILL;
988 : }
989 :
990 0 : seen_alnums = 0;
991 0 : while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
992 : head = ldata->read_head;
993 :
994 : /* erase a single possibly multibyte character */
995 : do {
996 0 : head--;
997 0 : c = read_buf(ldata, head);
998 0 : } while (is_continuation(c, tty) &&
999 0 : MASK(head) != MASK(ldata->canon_head));
1000 :
1001 : /* do not partially erase */
1002 0 : if (is_continuation(c, tty))
1003 : break;
1004 :
1005 0 : if (kill_type == WERASE) {
1006 : /* Equivalent to BSD's ALTWERASE. */
1007 0 : if (isalnum(c) || c == '_')
1008 0 : seen_alnums++;
1009 0 : else if (seen_alnums)
1010 : break;
1011 : }
1012 0 : cnt = ldata->read_head - head;
1013 0 : ldata->read_head = head;
1014 0 : if (L_ECHO(tty)) {
1015 0 : if (L_ECHOPRT(tty)) {
1016 0 : if (!ldata->erasing) {
1017 0 : echo_char_raw('\\', ldata);
1018 0 : ldata->erasing = 1;
1019 : }
1020 : /* if cnt > 1, output a multi-byte character */
1021 0 : echo_char(c, tty);
1022 0 : while (--cnt > 0) {
1023 0 : head++;
1024 0 : echo_char_raw(read_buf(ldata, head), ldata);
1025 : echo_move_back_col(ldata);
1026 : }
1027 0 : } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1028 0 : echo_char(ERASE_CHAR(tty), tty);
1029 0 : } else if (c == '\t') {
1030 : unsigned int num_chars = 0;
1031 : int after_tab = 0;
1032 : size_t tail = ldata->read_head;
1033 :
1034 : /*
1035 : * Count the columns used for characters
1036 : * since the start of input or after a
1037 : * previous tab.
1038 : * This info is used to go back the correct
1039 : * number of columns.
1040 : */
1041 0 : while (MASK(tail) != MASK(ldata->canon_head)) {
1042 0 : tail--;
1043 0 : c = read_buf(ldata, tail);
1044 0 : if (c == '\t') {
1045 : after_tab = 1;
1046 : break;
1047 0 : } else if (iscntrl(c)) {
1048 0 : if (L_ECHOCTL(tty))
1049 0 : num_chars += 2;
1050 0 : } else if (!is_continuation(c, tty)) {
1051 0 : num_chars++;
1052 : }
1053 : }
1054 : echo_erase_tab(num_chars, after_tab, ldata);
1055 : } else {
1056 0 : if (iscntrl(c) && L_ECHOCTL(tty)) {
1057 0 : echo_char_raw('\b', ldata);
1058 0 : echo_char_raw(' ', ldata);
1059 : echo_char_raw('\b', ldata);
1060 : }
1061 0 : if (!iscntrl(c) || L_ECHOCTL(tty)) {
1062 0 : echo_char_raw('\b', ldata);
1063 0 : echo_char_raw(' ', ldata);
1064 : echo_char_raw('\b', ldata);
1065 : }
1066 : }
1067 : }
1068 0 : if (kill_type == ERASE)
1069 : break;
1070 : }
1071 0 : if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1072 : finish_erasing(ldata);
1073 : }
1074 :
1075 :
1076 0 : static void __isig(int sig, struct tty_struct *tty)
1077 : {
1078 0 : struct pid *tty_pgrp = tty_get_pgrp(tty);
1079 0 : if (tty_pgrp) {
1080 0 : kill_pgrp(tty_pgrp, sig, 1);
1081 0 : put_pid(tty_pgrp);
1082 : }
1083 0 : }
1084 :
1085 : /**
1086 : * isig - handle the ISIG optio
1087 : * @sig: signal
1088 : * @tty: terminal
1089 : *
1090 : * Called when a signal is being sent due to terminal input. Called from the
1091 : * &tty_driver.receive_buf() path, so serialized.
1092 : *
1093 : * Performs input and output flush if !NOFLSH. In this context, the echo
1094 : * buffer is 'output'. The signal is processed first to alert any current
1095 : * readers or writers to discontinue and exit their i/o loops.
1096 : *
1097 : * Locking: %ctrl.lock
1098 : */
1099 0 : static void isig(int sig, struct tty_struct *tty)
1100 : {
1101 0 : struct n_tty_data *ldata = tty->disc_data;
1102 :
1103 0 : if (L_NOFLSH(tty)) {
1104 : /* signal only */
1105 0 : __isig(sig, tty);
1106 :
1107 : } else { /* signal and flush */
1108 0 : up_read(&tty->termios_rwsem);
1109 0 : down_write(&tty->termios_rwsem);
1110 :
1111 0 : __isig(sig, tty);
1112 :
1113 : /* clear echo buffer */
1114 0 : mutex_lock(&ldata->output_lock);
1115 0 : ldata->echo_head = ldata->echo_tail = 0;
1116 0 : ldata->echo_mark = ldata->echo_commit = 0;
1117 0 : mutex_unlock(&ldata->output_lock);
1118 :
1119 : /* clear output buffer */
1120 0 : tty_driver_flush_buffer(tty);
1121 :
1122 : /* clear input buffer */
1123 0 : reset_buffer_flags(tty->disc_data);
1124 :
1125 : /* notify pty master of flush */
1126 0 : if (tty->link)
1127 0 : n_tty_packet_mode_flush(tty);
1128 :
1129 0 : up_write(&tty->termios_rwsem);
1130 0 : down_read(&tty->termios_rwsem);
1131 : }
1132 0 : }
1133 :
1134 : /**
1135 : * n_tty_receive_break - handle break
1136 : * @tty: terminal
1137 : *
1138 : * An RS232 break event has been hit in the incoming bitstream. This can cause
1139 : * a variety of events depending upon the termios settings.
1140 : *
1141 : * Locking: n_tty_receive_buf()/producer path:
1142 : * caller holds non-exclusive termios_rwsem
1143 : *
1144 : * Note: may get exclusive %termios_rwsem if flushing input buffer
1145 : */
1146 0 : static void n_tty_receive_break(struct tty_struct *tty)
1147 : {
1148 0 : struct n_tty_data *ldata = tty->disc_data;
1149 :
1150 0 : if (I_IGNBRK(tty))
1151 : return;
1152 0 : if (I_BRKINT(tty)) {
1153 0 : isig(SIGINT, tty);
1154 0 : return;
1155 : }
1156 0 : if (I_PARMRK(tty)) {
1157 0 : put_tty_queue('\377', ldata);
1158 : put_tty_queue('\0', ldata);
1159 : }
1160 : put_tty_queue('\0', ldata);
1161 : }
1162 :
1163 : /**
1164 : * n_tty_receive_overrun - handle overrun reporting
1165 : * @tty: terminal
1166 : *
1167 : * Data arrived faster than we could process it. While the tty driver has
1168 : * flagged this the bits that were missed are gone forever.
1169 : *
1170 : * Called from the receive_buf path so single threaded. Does not need locking
1171 : * as num_overrun and overrun_time are function private.
1172 : */
1173 0 : static void n_tty_receive_overrun(struct tty_struct *tty)
1174 : {
1175 0 : struct n_tty_data *ldata = tty->disc_data;
1176 :
1177 0 : ldata->num_overrun++;
1178 0 : if (time_after(jiffies, ldata->overrun_time + HZ) ||
1179 0 : time_after(ldata->overrun_time, jiffies)) {
1180 0 : tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1181 0 : ldata->overrun_time = jiffies;
1182 0 : ldata->num_overrun = 0;
1183 : }
1184 0 : }
1185 :
1186 : /**
1187 : * n_tty_receive_parity_error - error notifier
1188 : * @tty: terminal device
1189 : * @c: character
1190 : *
1191 : * Process a parity error and queue the right data to indicate the error case
1192 : * if necessary.
1193 : *
1194 : * Locking: n_tty_receive_buf()/producer path:
1195 : * caller holds non-exclusive %termios_rwsem
1196 : */
1197 0 : static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1198 : {
1199 0 : struct n_tty_data *ldata = tty->disc_data;
1200 :
1201 0 : if (I_INPCK(tty)) {
1202 0 : if (I_IGNPAR(tty))
1203 : return;
1204 0 : if (I_PARMRK(tty)) {
1205 0 : put_tty_queue('\377', ldata);
1206 0 : put_tty_queue('\0', ldata);
1207 : put_tty_queue(c, ldata);
1208 : } else
1209 : put_tty_queue('\0', ldata);
1210 : } else
1211 : put_tty_queue(c, ldata);
1212 : }
1213 :
1214 : static void
1215 0 : n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1216 : {
1217 0 : isig(signal, tty);
1218 0 : if (I_IXON(tty))
1219 0 : start_tty(tty);
1220 0 : if (L_ECHO(tty)) {
1221 0 : echo_char(c, tty);
1222 0 : commit_echoes(tty);
1223 : } else
1224 0 : process_echoes(tty);
1225 0 : }
1226 :
1227 : static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, unsigned char c)
1228 : {
1229 0 : return c == START_CHAR(tty) || c == STOP_CHAR(tty);
1230 : }
1231 :
1232 : /**
1233 : * n_tty_receive_char_flow_ctrl - receive flow control chars
1234 : * @tty: terminal device
1235 : * @c: character
1236 : * @lookahead_done: lookahead has processed this character already
1237 : *
1238 : * Receive and process flow control character actions.
1239 : *
1240 : * In case lookahead for flow control chars already handled the character in
1241 : * advance to the normal receive, the actions are skipped during normal
1242 : * receive.
1243 : *
1244 : * Returns true if @c is consumed as flow-control character, the character
1245 : * must not be treated as normal character.
1246 : */
1247 0 : static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, unsigned char c,
1248 : bool lookahead_done)
1249 : {
1250 0 : if (!n_tty_is_char_flow_ctrl(tty, c))
1251 : return false;
1252 :
1253 0 : if (lookahead_done)
1254 : return true;
1255 :
1256 0 : if (c == START_CHAR(tty)) {
1257 0 : start_tty(tty);
1258 0 : process_echoes(tty);
1259 0 : return true;
1260 : }
1261 :
1262 : /* STOP_CHAR */
1263 0 : stop_tty(tty);
1264 0 : return true;
1265 : }
1266 :
1267 0 : static void n_tty_receive_char_special(struct tty_struct *tty, unsigned char c,
1268 : bool lookahead_done)
1269 : {
1270 0 : struct n_tty_data *ldata = tty->disc_data;
1271 :
1272 0 : if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
1273 : return;
1274 :
1275 0 : if (L_ISIG(tty)) {
1276 0 : if (c == INTR_CHAR(tty)) {
1277 0 : n_tty_receive_signal_char(tty, SIGINT, c);
1278 0 : return;
1279 0 : } else if (c == QUIT_CHAR(tty)) {
1280 0 : n_tty_receive_signal_char(tty, SIGQUIT, c);
1281 0 : return;
1282 0 : } else if (c == SUSP_CHAR(tty)) {
1283 0 : n_tty_receive_signal_char(tty, SIGTSTP, c);
1284 0 : return;
1285 : }
1286 : }
1287 :
1288 0 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1289 0 : start_tty(tty);
1290 0 : process_echoes(tty);
1291 : }
1292 :
1293 0 : if (c == '\r') {
1294 0 : if (I_IGNCR(tty))
1295 : return;
1296 0 : if (I_ICRNL(tty))
1297 0 : c = '\n';
1298 0 : } else if (c == '\n' && I_INLCR(tty))
1299 0 : c = '\r';
1300 :
1301 0 : if (ldata->icanon) {
1302 0 : if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1303 0 : (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1304 0 : eraser(c, tty);
1305 0 : commit_echoes(tty);
1306 0 : return;
1307 : }
1308 0 : if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1309 0 : ldata->lnext = 1;
1310 0 : if (L_ECHO(tty)) {
1311 0 : finish_erasing(ldata);
1312 0 : if (L_ECHOCTL(tty)) {
1313 0 : echo_char_raw('^', ldata);
1314 0 : echo_char_raw('\b', ldata);
1315 0 : commit_echoes(tty);
1316 : }
1317 : }
1318 : return;
1319 : }
1320 0 : if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1321 0 : size_t tail = ldata->canon_head;
1322 :
1323 0 : finish_erasing(ldata);
1324 0 : echo_char(c, tty);
1325 : echo_char_raw('\n', ldata);
1326 0 : while (MASK(tail) != MASK(ldata->read_head)) {
1327 0 : echo_char(read_buf(ldata, tail), tty);
1328 0 : tail++;
1329 : }
1330 0 : commit_echoes(tty);
1331 0 : return;
1332 : }
1333 0 : if (c == '\n') {
1334 0 : if (L_ECHO(tty) || L_ECHONL(tty)) {
1335 0 : echo_char_raw('\n', ldata);
1336 0 : commit_echoes(tty);
1337 : }
1338 : goto handle_newline;
1339 : }
1340 0 : if (c == EOF_CHAR(tty)) {
1341 : c = __DISABLED_CHAR;
1342 : goto handle_newline;
1343 : }
1344 0 : if ((c == EOL_CHAR(tty)) ||
1345 0 : (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1346 : /*
1347 : * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1348 : */
1349 0 : if (L_ECHO(tty)) {
1350 : /* Record the column of first canon char. */
1351 0 : if (ldata->canon_head == ldata->read_head)
1352 : echo_set_canon_col(ldata);
1353 0 : echo_char(c, tty);
1354 0 : commit_echoes(tty);
1355 : }
1356 : /*
1357 : * XXX does PARMRK doubling happen for
1358 : * EOL_CHAR and EOL2_CHAR?
1359 : */
1360 0 : if (c == (unsigned char) '\377' && I_PARMRK(tty))
1361 : put_tty_queue(c, ldata);
1362 :
1363 : handle_newline:
1364 0 : set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1365 0 : put_tty_queue(c, ldata);
1366 0 : smp_store_release(&ldata->canon_head, ldata->read_head);
1367 0 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1368 0 : wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1369 0 : return;
1370 : }
1371 : }
1372 :
1373 0 : if (L_ECHO(tty)) {
1374 0 : finish_erasing(ldata);
1375 0 : if (c == '\n')
1376 : echo_char_raw('\n', ldata);
1377 : else {
1378 : /* Record the column of first canon char. */
1379 0 : if (ldata->canon_head == ldata->read_head)
1380 : echo_set_canon_col(ldata);
1381 0 : echo_char(c, tty);
1382 : }
1383 0 : commit_echoes(tty);
1384 : }
1385 :
1386 : /* PARMRK doubling check */
1387 0 : if (c == (unsigned char) '\377' && I_PARMRK(tty))
1388 : put_tty_queue(c, ldata);
1389 :
1390 : put_tty_queue(c, ldata);
1391 : }
1392 :
1393 : /**
1394 : * n_tty_receive_char - perform processing
1395 : * @tty: terminal device
1396 : * @c: character
1397 : *
1398 : * Process an individual character of input received from the driver. This is
1399 : * serialized with respect to itself by the rules for the driver above.
1400 : *
1401 : * Locking: n_tty_receive_buf()/producer path:
1402 : * caller holds non-exclusive %termios_rwsem
1403 : * publishes canon_head if canonical mode is active
1404 : */
1405 0 : static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1406 : {
1407 0 : struct n_tty_data *ldata = tty->disc_data;
1408 :
1409 0 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1410 0 : start_tty(tty);
1411 0 : process_echoes(tty);
1412 : }
1413 0 : if (L_ECHO(tty)) {
1414 0 : finish_erasing(ldata);
1415 : /* Record the column of first canon char. */
1416 0 : if (ldata->canon_head == ldata->read_head)
1417 : echo_set_canon_col(ldata);
1418 0 : echo_char(c, tty);
1419 0 : commit_echoes(tty);
1420 : }
1421 : /* PARMRK doubling check */
1422 0 : if (c == (unsigned char) '\377' && I_PARMRK(tty))
1423 : put_tty_queue(c, ldata);
1424 0 : put_tty_queue(c, ldata);
1425 0 : }
1426 :
1427 0 : static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c,
1428 : bool lookahead_done)
1429 : {
1430 0 : if (I_ISTRIP(tty))
1431 0 : c &= 0x7f;
1432 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1433 0 : c = tolower(c);
1434 :
1435 0 : if (I_IXON(tty)) {
1436 0 : if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
1437 0 : tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1438 0 : c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1439 0 : c != SUSP_CHAR(tty)) {
1440 0 : start_tty(tty);
1441 0 : process_echoes(tty);
1442 : }
1443 : }
1444 0 : }
1445 :
1446 : static void
1447 0 : n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1448 : {
1449 0 : switch (flag) {
1450 : case TTY_BREAK:
1451 0 : n_tty_receive_break(tty);
1452 0 : break;
1453 : case TTY_PARITY:
1454 : case TTY_FRAME:
1455 0 : n_tty_receive_parity_error(tty, c);
1456 0 : break;
1457 : case TTY_OVERRUN:
1458 0 : n_tty_receive_overrun(tty);
1459 0 : break;
1460 : default:
1461 0 : tty_err(tty, "unknown flag %d\n", flag);
1462 0 : break;
1463 : }
1464 0 : }
1465 :
1466 : static void
1467 0 : n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1468 : {
1469 0 : struct n_tty_data *ldata = tty->disc_data;
1470 :
1471 0 : ldata->lnext = 0;
1472 0 : if (likely(flag == TTY_NORMAL)) {
1473 0 : if (I_ISTRIP(tty))
1474 0 : c &= 0x7f;
1475 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1476 0 : c = tolower(c);
1477 0 : n_tty_receive_char(tty, c);
1478 : } else
1479 0 : n_tty_receive_char_flagged(tty, c, flag);
1480 0 : }
1481 :
1482 : /* Caller must ensure count > 0 */
1483 0 : static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const unsigned char *cp,
1484 : const unsigned char *fp, unsigned int count)
1485 : {
1486 0 : struct n_tty_data *ldata = tty->disc_data;
1487 0 : unsigned char flag = TTY_NORMAL;
1488 :
1489 0 : ldata->lookahead_count += count;
1490 :
1491 0 : if (!I_IXON(tty))
1492 : return;
1493 :
1494 0 : while (count--) {
1495 0 : if (fp)
1496 0 : flag = *fp++;
1497 0 : if (likely(flag == TTY_NORMAL))
1498 0 : n_tty_receive_char_flow_ctrl(tty, *cp, false);
1499 0 : cp++;
1500 : }
1501 : }
1502 :
1503 : static void
1504 0 : n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1505 : const char *fp, int count)
1506 : {
1507 0 : struct n_tty_data *ldata = tty->disc_data;
1508 : size_t n, head;
1509 :
1510 0 : head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1511 0 : n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1512 0 : memcpy(read_buf_addr(ldata, head), cp, n);
1513 0 : ldata->read_head += n;
1514 0 : cp += n;
1515 0 : count -= n;
1516 :
1517 0 : head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1518 0 : n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1519 0 : memcpy(read_buf_addr(ldata, head), cp, n);
1520 0 : ldata->read_head += n;
1521 0 : }
1522 :
1523 : static void
1524 0 : n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1525 : const char *fp, int count)
1526 : {
1527 0 : struct n_tty_data *ldata = tty->disc_data;
1528 0 : char flag = TTY_NORMAL;
1529 :
1530 0 : while (count--) {
1531 0 : if (fp)
1532 0 : flag = *fp++;
1533 0 : if (likely(flag == TTY_NORMAL))
1534 0 : put_tty_queue(*cp++, ldata);
1535 : else
1536 0 : n_tty_receive_char_flagged(tty, *cp++, flag);
1537 : }
1538 0 : }
1539 :
1540 : static void
1541 0 : n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1542 : const char *fp, int count, bool lookahead_done)
1543 : {
1544 0 : char flag = TTY_NORMAL;
1545 :
1546 0 : while (count--) {
1547 0 : if (fp)
1548 0 : flag = *fp++;
1549 0 : if (likely(flag == TTY_NORMAL))
1550 0 : n_tty_receive_char_closing(tty, *cp++, lookahead_done);
1551 : }
1552 0 : }
1553 :
1554 0 : static void n_tty_receive_buf_standard(struct tty_struct *tty,
1555 : const unsigned char *cp, const char *fp, int count, bool lookahead_done)
1556 : {
1557 0 : struct n_tty_data *ldata = tty->disc_data;
1558 0 : char flag = TTY_NORMAL;
1559 :
1560 0 : while (count--) {
1561 0 : unsigned char c = *cp++;
1562 :
1563 0 : if (fp)
1564 0 : flag = *fp++;
1565 :
1566 0 : if (ldata->lnext) {
1567 0 : n_tty_receive_char_lnext(tty, c, flag);
1568 0 : continue;
1569 : }
1570 :
1571 0 : if (unlikely(flag != TTY_NORMAL)) {
1572 0 : n_tty_receive_char_flagged(tty, c, flag);
1573 0 : continue;
1574 : }
1575 :
1576 0 : if (I_ISTRIP(tty))
1577 0 : c &= 0x7f;
1578 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1579 0 : c = tolower(c);
1580 0 : if (L_EXTPROC(tty)) {
1581 0 : put_tty_queue(c, ldata);
1582 0 : continue;
1583 : }
1584 :
1585 0 : if (test_bit(c, ldata->char_map))
1586 0 : n_tty_receive_char_special(tty, c, lookahead_done);
1587 : else
1588 0 : n_tty_receive_char(tty, c);
1589 : }
1590 0 : }
1591 :
1592 0 : static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1593 : const char *fp, int count)
1594 : {
1595 0 : struct n_tty_data *ldata = tty->disc_data;
1596 0 : bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1597 0 : size_t la_count = min_t(size_t, ldata->lookahead_count, count);
1598 :
1599 0 : if (ldata->real_raw)
1600 0 : n_tty_receive_buf_real_raw(tty, cp, fp, count);
1601 0 : else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1602 0 : n_tty_receive_buf_raw(tty, cp, fp, count);
1603 0 : else if (tty->closing && !L_EXTPROC(tty)) {
1604 0 : if (la_count > 0)
1605 0 : n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
1606 0 : if (count > la_count)
1607 0 : n_tty_receive_buf_closing(tty, cp, fp, count - la_count, false);
1608 : } else {
1609 0 : if (la_count > 0)
1610 0 : n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
1611 0 : if (count > la_count)
1612 0 : n_tty_receive_buf_standard(tty, cp, fp, count - la_count, false);
1613 :
1614 0 : flush_echoes(tty);
1615 0 : if (tty->ops->flush_chars)
1616 0 : tty->ops->flush_chars(tty);
1617 : }
1618 :
1619 0 : ldata->lookahead_count -= la_count;
1620 :
1621 0 : if (ldata->icanon && !L_EXTPROC(tty))
1622 : return;
1623 :
1624 : /* publish read_head to consumer */
1625 0 : smp_store_release(&ldata->commit_head, ldata->read_head);
1626 :
1627 0 : if (read_cnt(ldata)) {
1628 0 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1629 0 : wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1630 : }
1631 : }
1632 :
1633 : /**
1634 : * n_tty_receive_buf_common - process input
1635 : * @tty: device to receive input
1636 : * @cp: input chars
1637 : * @fp: flags for each char (if %NULL, all chars are %TTY_NORMAL)
1638 : * @count: number of input chars in @cp
1639 : * @flow: enable flow control
1640 : *
1641 : * Called by the terminal driver when a block of characters has been received.
1642 : * This function must be called from soft contexts not from interrupt context.
1643 : * The driver is responsible for making calls one at a time and in order (or
1644 : * using flush_to_ldisc()).
1645 : *
1646 : * Returns: the # of input chars from @cp which were processed.
1647 : *
1648 : * In canonical mode, the maximum line length is 4096 chars (including the line
1649 : * termination char); lines longer than 4096 chars are truncated. After 4095
1650 : * chars, input data is still processed but not stored. Overflow processing
1651 : * ensures the tty can always receive more input until at least one line can be
1652 : * read.
1653 : *
1654 : * In non-canonical mode, the read buffer will only accept 4095 chars; this
1655 : * provides the necessary space for a newline char if the input mode is
1656 : * switched to canonical.
1657 : *
1658 : * Note it is possible for the read buffer to _contain_ 4096 chars in
1659 : * non-canonical mode: the read buffer could already contain the maximum canon
1660 : * line of 4096 chars when the mode is switched to non-canonical.
1661 : *
1662 : * Locking: n_tty_receive_buf()/producer path:
1663 : * claims non-exclusive %termios_rwsem
1664 : * publishes commit_head or canon_head
1665 : */
1666 : static int
1667 0 : n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1668 : const char *fp, int count, int flow)
1669 : {
1670 0 : struct n_tty_data *ldata = tty->disc_data;
1671 0 : int room, n, rcvd = 0, overflow;
1672 :
1673 0 : down_read(&tty->termios_rwsem);
1674 :
1675 : do {
1676 : /*
1677 : * When PARMRK is set, each input char may take up to 3 chars
1678 : * in the read buf; reduce the buffer space avail by 3x
1679 : *
1680 : * If we are doing input canonicalization, and there are no
1681 : * pending newlines, let characters through without limit, so
1682 : * that erase characters will be handled. Other excess
1683 : * characters will be beeped.
1684 : *
1685 : * paired with store in *_copy_from_read_buf() -- guarantees
1686 : * the consumer has loaded the data in read_buf up to the new
1687 : * read_tail (so this producer will not overwrite unread data)
1688 : */
1689 0 : size_t tail = smp_load_acquire(&ldata->read_tail);
1690 :
1691 0 : room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1692 0 : if (I_PARMRK(tty))
1693 0 : room = DIV_ROUND_UP(room, 3);
1694 0 : room--;
1695 0 : if (room <= 0) {
1696 0 : overflow = ldata->icanon && ldata->canon_head == tail;
1697 0 : if (overflow && room < 0)
1698 0 : ldata->read_head--;
1699 0 : room = overflow;
1700 0 : ldata->no_room = flow && !room;
1701 : } else
1702 : overflow = 0;
1703 :
1704 0 : n = min(count, room);
1705 0 : if (!n)
1706 : break;
1707 :
1708 : /* ignore parity errors if handling overflow */
1709 0 : if (!overflow || !fp || *fp != TTY_PARITY)
1710 0 : __receive_buf(tty, cp, fp, n);
1711 :
1712 0 : cp += n;
1713 0 : if (fp)
1714 0 : fp += n;
1715 0 : count -= n;
1716 0 : rcvd += n;
1717 0 : } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1718 :
1719 0 : tty->receive_room = room;
1720 :
1721 : /* Unthrottle if handling overflow on pty */
1722 0 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1723 0 : if (overflow) {
1724 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1725 0 : tty_unthrottle_safe(tty);
1726 0 : __tty_set_flow_change(tty, 0);
1727 : }
1728 : } else
1729 0 : n_tty_check_throttle(tty);
1730 :
1731 0 : up_read(&tty->termios_rwsem);
1732 :
1733 0 : return rcvd;
1734 : }
1735 :
1736 0 : static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1737 : const char *fp, int count)
1738 : {
1739 0 : n_tty_receive_buf_common(tty, cp, fp, count, 0);
1740 0 : }
1741 :
1742 0 : static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1743 : const char *fp, int count)
1744 : {
1745 0 : return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1746 : }
1747 :
1748 : /**
1749 : * n_tty_set_termios - termios data changed
1750 : * @tty: terminal
1751 : * @old: previous data
1752 : *
1753 : * Called by the tty layer when the user changes termios flags so that the line
1754 : * discipline can plan ahead. This function cannot sleep and is protected from
1755 : * re-entry by the tty layer. The user is guaranteed that this function will
1756 : * not be re-entered or in progress when the ldisc is closed.
1757 : *
1758 : * Locking: Caller holds @tty->termios_rwsem
1759 : */
1760 0 : static void n_tty_set_termios(struct tty_struct *tty, const struct ktermios *old)
1761 : {
1762 0 : struct n_tty_data *ldata = tty->disc_data;
1763 :
1764 0 : if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1765 0 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1766 0 : ldata->line_start = ldata->read_tail;
1767 0 : if (!L_ICANON(tty) || !read_cnt(ldata)) {
1768 0 : ldata->canon_head = ldata->read_tail;
1769 0 : ldata->push = 0;
1770 : } else {
1771 0 : set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1772 : ldata->read_flags);
1773 0 : ldata->canon_head = ldata->read_head;
1774 0 : ldata->push = 1;
1775 : }
1776 0 : ldata->commit_head = ldata->read_head;
1777 0 : ldata->erasing = 0;
1778 0 : ldata->lnext = 0;
1779 : }
1780 :
1781 0 : ldata->icanon = (L_ICANON(tty) != 0);
1782 :
1783 0 : if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1784 0 : I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1785 0 : I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1786 0 : I_PARMRK(tty)) {
1787 0 : bitmap_zero(ldata->char_map, 256);
1788 :
1789 0 : if (I_IGNCR(tty) || I_ICRNL(tty))
1790 0 : set_bit('\r', ldata->char_map);
1791 0 : if (I_INLCR(tty))
1792 0 : set_bit('\n', ldata->char_map);
1793 :
1794 0 : if (L_ICANON(tty)) {
1795 0 : set_bit(ERASE_CHAR(tty), ldata->char_map);
1796 0 : set_bit(KILL_CHAR(tty), ldata->char_map);
1797 0 : set_bit(EOF_CHAR(tty), ldata->char_map);
1798 0 : set_bit('\n', ldata->char_map);
1799 0 : set_bit(EOL_CHAR(tty), ldata->char_map);
1800 0 : if (L_IEXTEN(tty)) {
1801 0 : set_bit(WERASE_CHAR(tty), ldata->char_map);
1802 0 : set_bit(LNEXT_CHAR(tty), ldata->char_map);
1803 0 : set_bit(EOL2_CHAR(tty), ldata->char_map);
1804 0 : if (L_ECHO(tty))
1805 0 : set_bit(REPRINT_CHAR(tty),
1806 : ldata->char_map);
1807 : }
1808 : }
1809 0 : if (I_IXON(tty)) {
1810 0 : set_bit(START_CHAR(tty), ldata->char_map);
1811 0 : set_bit(STOP_CHAR(tty), ldata->char_map);
1812 : }
1813 0 : if (L_ISIG(tty)) {
1814 0 : set_bit(INTR_CHAR(tty), ldata->char_map);
1815 0 : set_bit(QUIT_CHAR(tty), ldata->char_map);
1816 0 : set_bit(SUSP_CHAR(tty), ldata->char_map);
1817 : }
1818 0 : clear_bit(__DISABLED_CHAR, ldata->char_map);
1819 0 : ldata->raw = 0;
1820 0 : ldata->real_raw = 0;
1821 : } else {
1822 0 : ldata->raw = 1;
1823 0 : if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1824 0 : (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1825 0 : (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1826 0 : ldata->real_raw = 1;
1827 : else
1828 0 : ldata->real_raw = 0;
1829 : }
1830 : /*
1831 : * Fix tty hang when I_IXON(tty) is cleared, but the tty
1832 : * been stopped by STOP_CHAR(tty) before it.
1833 : */
1834 0 : if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1835 0 : start_tty(tty);
1836 0 : process_echoes(tty);
1837 : }
1838 :
1839 : /* The termios change make the tty ready for I/O */
1840 0 : wake_up_interruptible(&tty->write_wait);
1841 0 : wake_up_interruptible(&tty->read_wait);
1842 0 : }
1843 :
1844 : /**
1845 : * n_tty_close - close the ldisc for this tty
1846 : * @tty: device
1847 : *
1848 : * Called from the terminal layer when this line discipline is being shut down,
1849 : * either because of a close or becsuse of a discipline change. The function
1850 : * will not be called while other ldisc methods are in progress.
1851 : */
1852 0 : static void n_tty_close(struct tty_struct *tty)
1853 : {
1854 0 : struct n_tty_data *ldata = tty->disc_data;
1855 :
1856 0 : if (tty->link)
1857 0 : n_tty_packet_mode_flush(tty);
1858 :
1859 0 : down_write(&tty->termios_rwsem);
1860 0 : vfree(ldata);
1861 0 : tty->disc_data = NULL;
1862 0 : up_write(&tty->termios_rwsem);
1863 0 : }
1864 :
1865 : /**
1866 : * n_tty_open - open an ldisc
1867 : * @tty: terminal to open
1868 : *
1869 : * Called when this line discipline is being attached to the terminal device.
1870 : * Can sleep. Called serialized so that no other events will occur in parallel.
1871 : * No further open will occur until a close.
1872 : */
1873 0 : static int n_tty_open(struct tty_struct *tty)
1874 : {
1875 : struct n_tty_data *ldata;
1876 :
1877 : /* Currently a malloc failure here can panic */
1878 0 : ldata = vzalloc(sizeof(*ldata));
1879 0 : if (!ldata)
1880 : return -ENOMEM;
1881 :
1882 0 : ldata->overrun_time = jiffies;
1883 0 : mutex_init(&ldata->atomic_read_lock);
1884 0 : mutex_init(&ldata->output_lock);
1885 :
1886 0 : tty->disc_data = ldata;
1887 0 : tty->closing = 0;
1888 : /* indicate buffer work may resume */
1889 0 : clear_bit(TTY_LDISC_HALTED, &tty->flags);
1890 0 : n_tty_set_termios(tty, NULL);
1891 0 : tty_unthrottle(tty);
1892 0 : return 0;
1893 : }
1894 :
1895 : static inline int input_available_p(struct tty_struct *tty, int poll)
1896 : {
1897 0 : struct n_tty_data *ldata = tty->disc_data;
1898 0 : int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1899 :
1900 0 : if (ldata->icanon && !L_EXTPROC(tty))
1901 0 : return ldata->canon_head != ldata->read_tail;
1902 : else
1903 0 : return ldata->commit_head - ldata->read_tail >= amt;
1904 : }
1905 :
1906 : /**
1907 : * copy_from_read_buf - copy read data directly
1908 : * @tty: terminal device
1909 : * @kbp: data
1910 : * @nr: size of data
1911 : *
1912 : * Helper function to speed up n_tty_read(). It is only called when %ICANON is
1913 : * off; it copies characters straight from the tty queue.
1914 : *
1915 : * Returns: true if it successfully copied data, but there is still more data
1916 : * to be had.
1917 : *
1918 : * Locking:
1919 : * * called under the @ldata->atomic_read_lock sem
1920 : * * n_tty_read()/consumer path:
1921 : * caller holds non-exclusive %termios_rwsem;
1922 : * read_tail published
1923 : */
1924 0 : static bool copy_from_read_buf(struct tty_struct *tty,
1925 : unsigned char **kbp,
1926 : size_t *nr)
1927 :
1928 : {
1929 0 : struct n_tty_data *ldata = tty->disc_data;
1930 : size_t n;
1931 : bool is_eof;
1932 0 : size_t head = smp_load_acquire(&ldata->commit_head);
1933 0 : size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1934 :
1935 0 : n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1936 0 : n = min(*nr, n);
1937 0 : if (n) {
1938 0 : unsigned char *from = read_buf_addr(ldata, tail);
1939 0 : memcpy(*kbp, from, n);
1940 0 : is_eof = n == 1 && *from == EOF_CHAR(tty);
1941 0 : tty_audit_add_data(tty, from, n);
1942 0 : zero_buffer(tty, from, n);
1943 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1944 : /* Turn single EOF into zero-length read */
1945 0 : if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1946 0 : (head == ldata->read_tail))
1947 : return false;
1948 0 : *kbp += n;
1949 0 : *nr -= n;
1950 :
1951 : /* If we have more to copy, let the caller know */
1952 0 : return head != ldata->read_tail;
1953 : }
1954 : return false;
1955 : }
1956 :
1957 : /**
1958 : * canon_copy_from_read_buf - copy read data in canonical mode
1959 : * @tty: terminal device
1960 : * @kbp: data
1961 : * @nr: size of data
1962 : *
1963 : * Helper function for n_tty_read(). It is only called when %ICANON is on; it
1964 : * copies one line of input up to and including the line-delimiting character
1965 : * into the result buffer.
1966 : *
1967 : * Note: When termios is changed from non-canonical to canonical mode and the
1968 : * read buffer contains data, n_tty_set_termios() simulates an EOF push (as if
1969 : * C-d were input) _without_ the %DISABLED_CHAR in the buffer. This causes data
1970 : * already processed as input to be immediately available as input although a
1971 : * newline has not been received.
1972 : *
1973 : * Locking:
1974 : * * called under the %atomic_read_lock mutex
1975 : * * n_tty_read()/consumer path:
1976 : * caller holds non-exclusive %termios_rwsem;
1977 : * read_tail published
1978 : */
1979 0 : static bool canon_copy_from_read_buf(struct tty_struct *tty,
1980 : unsigned char **kbp,
1981 : size_t *nr)
1982 : {
1983 0 : struct n_tty_data *ldata = tty->disc_data;
1984 : size_t n, size, more, c;
1985 : size_t eol;
1986 : size_t tail, canon_head;
1987 0 : int found = 0;
1988 :
1989 : /* N.B. avoid overrun if nr == 0 */
1990 0 : if (!*nr)
1991 : return false;
1992 :
1993 0 : canon_head = smp_load_acquire(&ldata->canon_head);
1994 0 : n = min(*nr, canon_head - ldata->read_tail);
1995 :
1996 0 : tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1997 0 : size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1998 :
1999 : n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2000 : __func__, *nr, tail, n, size);
2001 :
2002 0 : eol = find_next_bit(ldata->read_flags, size, tail);
2003 0 : more = n - (size - tail);
2004 0 : if (eol == N_TTY_BUF_SIZE && more) {
2005 : /* scan wrapped without finding set bit */
2006 0 : eol = find_first_bit(ldata->read_flags, more);
2007 0 : found = eol != more;
2008 : } else
2009 0 : found = eol != size;
2010 :
2011 0 : n = eol - tail;
2012 0 : if (n > N_TTY_BUF_SIZE)
2013 0 : n += N_TTY_BUF_SIZE;
2014 0 : c = n + found;
2015 :
2016 0 : if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
2017 : n = c;
2018 :
2019 : n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2020 : __func__, eol, found, n, c, tail, more);
2021 :
2022 0 : tty_copy(tty, *kbp, tail, n);
2023 0 : *kbp += n;
2024 0 : *nr -= n;
2025 :
2026 0 : if (found)
2027 0 : clear_bit(eol, ldata->read_flags);
2028 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2029 :
2030 0 : if (found) {
2031 0 : if (!ldata->push)
2032 0 : ldata->line_start = ldata->read_tail;
2033 : else
2034 0 : ldata->push = 0;
2035 : tty_audit_push();
2036 : return false;
2037 : }
2038 :
2039 : /* No EOL found - do a continuation retry if there is more data */
2040 0 : return ldata->read_tail != canon_head;
2041 : }
2042 :
2043 : /*
2044 : * If we finished a read at the exact location of an
2045 : * EOF (special EOL character that's a __DISABLED_CHAR)
2046 : * in the stream, silently eat the EOF.
2047 : */
2048 0 : static void canon_skip_eof(struct tty_struct *tty)
2049 : {
2050 0 : struct n_tty_data *ldata = tty->disc_data;
2051 : size_t tail, canon_head;
2052 :
2053 0 : canon_head = smp_load_acquire(&ldata->canon_head);
2054 0 : tail = ldata->read_tail;
2055 :
2056 : // No data?
2057 0 : if (tail == canon_head)
2058 : return;
2059 :
2060 : // See if the tail position is EOF in the circular buffer
2061 0 : tail &= (N_TTY_BUF_SIZE - 1);
2062 0 : if (!test_bit(tail, ldata->read_flags))
2063 : return;
2064 0 : if (read_buf(ldata, tail) != __DISABLED_CHAR)
2065 : return;
2066 :
2067 : // Clear the EOL bit, skip the EOF char.
2068 0 : clear_bit(tail, ldata->read_flags);
2069 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2070 : }
2071 :
2072 : /**
2073 : * job_control - check job control
2074 : * @tty: tty
2075 : * @file: file handle
2076 : *
2077 : * Perform job control management checks on this @file/@tty descriptor and if
2078 : * appropriate send any needed signals and return a negative error code if
2079 : * action should be taken.
2080 : *
2081 : * Locking:
2082 : * * redirected write test is safe
2083 : * * current->signal->tty check is safe
2084 : * * ctrl.lock to safely reference @tty->ctrl.pgrp
2085 : */
2086 : static int job_control(struct tty_struct *tty, struct file *file)
2087 : {
2088 : /* Job control check -- must be done at start and after
2089 : every sleep (POSIX.1 7.1.1.4). */
2090 : /* NOTE: not yet done after every sleep pending a thorough
2091 : check of the logic of this change. -- jlc */
2092 : /* don't stop on /dev/console */
2093 0 : if (file->f_op->write_iter == redirected_tty_write)
2094 : return 0;
2095 :
2096 0 : return __tty_check_change(tty, SIGTTIN);
2097 : }
2098 :
2099 :
2100 : /**
2101 : * n_tty_read - read function for tty
2102 : * @tty: tty device
2103 : * @file: file object
2104 : * @kbuf: kernelspace buffer pointer
2105 : * @nr: size of I/O
2106 : * @cookie: if non-%NULL, this is a continuation read
2107 : * @offset: where to continue reading from (unused in n_tty)
2108 : *
2109 : * Perform reads for the line discipline. We are guaranteed that the line
2110 : * discipline will not be closed under us but we may get multiple parallel
2111 : * readers and must handle this ourselves. We may also get a hangup. Always
2112 : * called in user context, may sleep.
2113 : *
2114 : * This code must be sure never to sleep through a hangup.
2115 : *
2116 : * Locking: n_tty_read()/consumer path:
2117 : * claims non-exclusive termios_rwsem;
2118 : * publishes read_tail
2119 : */
2120 0 : static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2121 : unsigned char *kbuf, size_t nr,
2122 : void **cookie, unsigned long offset)
2123 : {
2124 0 : struct n_tty_data *ldata = tty->disc_data;
2125 0 : unsigned char *kb = kbuf;
2126 0 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2127 : int c;
2128 : int minimum, time;
2129 0 : ssize_t retval = 0;
2130 : long timeout;
2131 : bool packet;
2132 : size_t old_tail;
2133 :
2134 : /*
2135 : * Is this a continuation of a read started earler?
2136 : *
2137 : * If so, we still hold the atomic_read_lock and the
2138 : * termios_rwsem, and can just continue to copy data.
2139 : */
2140 0 : if (*cookie) {
2141 0 : if (ldata->icanon && !L_EXTPROC(tty)) {
2142 : /*
2143 : * If we have filled the user buffer, see
2144 : * if we should skip an EOF character before
2145 : * releasing the lock and returning done.
2146 : */
2147 0 : if (!nr)
2148 0 : canon_skip_eof(tty);
2149 0 : else if (canon_copy_from_read_buf(tty, &kb, &nr))
2150 0 : return kb - kbuf;
2151 : } else {
2152 0 : if (copy_from_read_buf(tty, &kb, &nr))
2153 0 : return kb - kbuf;
2154 : }
2155 :
2156 : /* No more data - release locks and stop retries */
2157 0 : n_tty_kick_worker(tty);
2158 0 : n_tty_check_unthrottle(tty);
2159 0 : up_read(&tty->termios_rwsem);
2160 0 : mutex_unlock(&ldata->atomic_read_lock);
2161 0 : *cookie = NULL;
2162 0 : return kb - kbuf;
2163 : }
2164 :
2165 0 : c = job_control(tty, file);
2166 0 : if (c < 0)
2167 0 : return c;
2168 :
2169 : /*
2170 : * Internal serialization of reads.
2171 : */
2172 0 : if (file->f_flags & O_NONBLOCK) {
2173 0 : if (!mutex_trylock(&ldata->atomic_read_lock))
2174 : return -EAGAIN;
2175 : } else {
2176 0 : if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2177 : return -ERESTARTSYS;
2178 : }
2179 :
2180 0 : down_read(&tty->termios_rwsem);
2181 :
2182 0 : minimum = time = 0;
2183 0 : timeout = MAX_SCHEDULE_TIMEOUT;
2184 0 : if (!ldata->icanon) {
2185 0 : minimum = MIN_CHAR(tty);
2186 0 : if (minimum) {
2187 0 : time = (HZ / 10) * TIME_CHAR(tty);
2188 : } else {
2189 0 : timeout = (HZ / 10) * TIME_CHAR(tty);
2190 0 : minimum = 1;
2191 : }
2192 : }
2193 :
2194 0 : packet = tty->ctrl.packet;
2195 0 : old_tail = ldata->read_tail;
2196 :
2197 0 : add_wait_queue(&tty->read_wait, &wait);
2198 0 : while (nr) {
2199 : /* First test for status change. */
2200 0 : if (packet && tty->link->ctrl.pktstatus) {
2201 : unsigned char cs;
2202 0 : if (kb != kbuf)
2203 : break;
2204 0 : spin_lock_irq(&tty->link->ctrl.lock);
2205 0 : cs = tty->link->ctrl.pktstatus;
2206 0 : tty->link->ctrl.pktstatus = 0;
2207 0 : spin_unlock_irq(&tty->link->ctrl.lock);
2208 0 : *kb++ = cs;
2209 0 : nr--;
2210 0 : break;
2211 : }
2212 :
2213 0 : if (!input_available_p(tty, 0)) {
2214 0 : up_read(&tty->termios_rwsem);
2215 0 : tty_buffer_flush_work(tty->port);
2216 0 : down_read(&tty->termios_rwsem);
2217 0 : if (!input_available_p(tty, 0)) {
2218 0 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2219 : retval = -EIO;
2220 : break;
2221 : }
2222 0 : if (tty_hung_up_p(file))
2223 : break;
2224 : /*
2225 : * Abort readers for ttys which never actually
2226 : * get hung up. See __tty_hangup().
2227 : */
2228 0 : if (test_bit(TTY_HUPPING, &tty->flags))
2229 : break;
2230 0 : if (!timeout)
2231 : break;
2232 0 : if (tty_io_nonblock(tty, file)) {
2233 : retval = -EAGAIN;
2234 : break;
2235 : }
2236 0 : if (signal_pending(current)) {
2237 : retval = -ERESTARTSYS;
2238 : break;
2239 : }
2240 0 : up_read(&tty->termios_rwsem);
2241 :
2242 0 : timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2243 : timeout);
2244 :
2245 0 : down_read(&tty->termios_rwsem);
2246 0 : continue;
2247 : }
2248 : }
2249 :
2250 0 : if (ldata->icanon && !L_EXTPROC(tty)) {
2251 0 : if (canon_copy_from_read_buf(tty, &kb, &nr))
2252 : goto more_to_be_read;
2253 : } else {
2254 : /* Deal with packet mode. */
2255 0 : if (packet && kb == kbuf) {
2256 0 : *kb++ = TIOCPKT_DATA;
2257 0 : nr--;
2258 : }
2259 :
2260 : /*
2261 : * Copy data, and if there is more to be had
2262 : * and we have nothing more to wait for, then
2263 : * let's mark us for retries.
2264 : *
2265 : * NOTE! We return here with both the termios_sem
2266 : * and atomic_read_lock still held, the retries
2267 : * will release them when done.
2268 : */
2269 0 : if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2270 : more_to_be_read:
2271 0 : remove_wait_queue(&tty->read_wait, &wait);
2272 0 : *cookie = cookie;
2273 0 : return kb - kbuf;
2274 : }
2275 : }
2276 :
2277 0 : n_tty_check_unthrottle(tty);
2278 :
2279 0 : if (kb - kbuf >= minimum)
2280 : break;
2281 0 : if (time)
2282 0 : timeout = time;
2283 : }
2284 0 : if (old_tail != ldata->read_tail)
2285 0 : n_tty_kick_worker(tty);
2286 0 : up_read(&tty->termios_rwsem);
2287 :
2288 0 : remove_wait_queue(&tty->read_wait, &wait);
2289 0 : mutex_unlock(&ldata->atomic_read_lock);
2290 :
2291 0 : if (kb - kbuf)
2292 0 : retval = kb - kbuf;
2293 :
2294 : return retval;
2295 : }
2296 :
2297 : /**
2298 : * n_tty_write - write function for tty
2299 : * @tty: tty device
2300 : * @file: file object
2301 : * @buf: userspace buffer pointer
2302 : * @nr: size of I/O
2303 : *
2304 : * Write function of the terminal device. This is serialized with respect to
2305 : * other write callers but not to termios changes, reads and other such events.
2306 : * Since the receive code will echo characters, thus calling driver write
2307 : * methods, the %output_lock is used in the output processing functions called
2308 : * here as well as in the echo processing function to protect the column state
2309 : * and space left in the buffer.
2310 : *
2311 : * This code must be sure never to sleep through a hangup.
2312 : *
2313 : * Locking: output_lock to protect column state and space left
2314 : * (note that the process_output*() functions take this lock themselves)
2315 : */
2316 :
2317 0 : static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2318 : const unsigned char *buf, size_t nr)
2319 : {
2320 0 : const unsigned char *b = buf;
2321 0 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2322 : int c;
2323 0 : ssize_t retval = 0;
2324 :
2325 : /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2326 0 : if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2327 0 : retval = tty_check_change(tty);
2328 0 : if (retval)
2329 : return retval;
2330 : }
2331 :
2332 0 : down_read(&tty->termios_rwsem);
2333 :
2334 : /* Write out any echoed characters that are still pending */
2335 0 : process_echoes(tty);
2336 :
2337 0 : add_wait_queue(&tty->write_wait, &wait);
2338 : while (1) {
2339 0 : if (signal_pending(current)) {
2340 : retval = -ERESTARTSYS;
2341 : break;
2342 : }
2343 0 : if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2344 : retval = -EIO;
2345 : break;
2346 : }
2347 0 : if (O_OPOST(tty)) {
2348 0 : while (nr > 0) {
2349 0 : ssize_t num = process_output_block(tty, b, nr);
2350 0 : if (num < 0) {
2351 0 : if (num == -EAGAIN)
2352 : break;
2353 : retval = num;
2354 : goto break_out;
2355 : }
2356 0 : b += num;
2357 0 : nr -= num;
2358 0 : if (nr == 0)
2359 : break;
2360 0 : c = *b;
2361 0 : if (process_output(c, tty) < 0)
2362 : break;
2363 0 : b++; nr--;
2364 : }
2365 0 : if (tty->ops->flush_chars)
2366 0 : tty->ops->flush_chars(tty);
2367 : } else {
2368 0 : struct n_tty_data *ldata = tty->disc_data;
2369 :
2370 0 : while (nr > 0) {
2371 0 : mutex_lock(&ldata->output_lock);
2372 0 : c = tty->ops->write(tty, b, nr);
2373 0 : mutex_unlock(&ldata->output_lock);
2374 0 : if (c < 0) {
2375 0 : retval = c;
2376 0 : goto break_out;
2377 : }
2378 0 : if (!c)
2379 : break;
2380 0 : b += c;
2381 0 : nr -= c;
2382 : }
2383 : }
2384 0 : if (!nr)
2385 : break;
2386 0 : if (tty_io_nonblock(tty, file)) {
2387 : retval = -EAGAIN;
2388 : break;
2389 : }
2390 0 : up_read(&tty->termios_rwsem);
2391 :
2392 0 : wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2393 :
2394 0 : down_read(&tty->termios_rwsem);
2395 : }
2396 : break_out:
2397 0 : remove_wait_queue(&tty->write_wait, &wait);
2398 0 : if (nr && tty->fasync)
2399 0 : set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2400 0 : up_read(&tty->termios_rwsem);
2401 0 : return (b - buf) ? b - buf : retval;
2402 : }
2403 :
2404 : /**
2405 : * n_tty_poll - poll method for N_TTY
2406 : * @tty: terminal device
2407 : * @file: file accessing it
2408 : * @wait: poll table
2409 : *
2410 : * Called when the line discipline is asked to poll() for data or for special
2411 : * events. This code is not serialized with respect to other events save
2412 : * open/close.
2413 : *
2414 : * This code must be sure never to sleep through a hangup.
2415 : *
2416 : * Locking: called without the kernel lock held -- fine.
2417 : */
2418 0 : static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2419 : poll_table *wait)
2420 : {
2421 0 : __poll_t mask = 0;
2422 :
2423 0 : poll_wait(file, &tty->read_wait, wait);
2424 0 : poll_wait(file, &tty->write_wait, wait);
2425 0 : if (input_available_p(tty, 1))
2426 : mask |= EPOLLIN | EPOLLRDNORM;
2427 : else {
2428 0 : tty_buffer_flush_work(tty->port);
2429 0 : if (input_available_p(tty, 1))
2430 0 : mask |= EPOLLIN | EPOLLRDNORM;
2431 : }
2432 0 : if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2433 0 : mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2434 0 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2435 0 : mask |= EPOLLHUP;
2436 0 : if (tty_hung_up_p(file))
2437 0 : mask |= EPOLLHUP;
2438 0 : if (tty->ops->write && !tty_is_writelocked(tty) &&
2439 0 : tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2440 0 : tty_write_room(tty) > 0)
2441 0 : mask |= EPOLLOUT | EPOLLWRNORM;
2442 0 : return mask;
2443 : }
2444 :
2445 0 : static unsigned long inq_canon(struct n_tty_data *ldata)
2446 : {
2447 : size_t nr, head, tail;
2448 :
2449 0 : if (ldata->canon_head == ldata->read_tail)
2450 : return 0;
2451 0 : head = ldata->canon_head;
2452 0 : tail = ldata->read_tail;
2453 0 : nr = head - tail;
2454 : /* Skip EOF-chars.. */
2455 0 : while (MASK(head) != MASK(tail)) {
2456 0 : if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2457 0 : read_buf(ldata, tail) == __DISABLED_CHAR)
2458 0 : nr--;
2459 0 : tail++;
2460 : }
2461 : return nr;
2462 : }
2463 :
2464 0 : static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
2465 : unsigned long arg)
2466 : {
2467 0 : struct n_tty_data *ldata = tty->disc_data;
2468 : int retval;
2469 :
2470 0 : switch (cmd) {
2471 : case TIOCOUTQ:
2472 0 : return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2473 : case TIOCINQ:
2474 0 : down_write(&tty->termios_rwsem);
2475 0 : if (L_ICANON(tty) && !L_EXTPROC(tty))
2476 0 : retval = inq_canon(ldata);
2477 : else
2478 0 : retval = read_cnt(ldata);
2479 0 : up_write(&tty->termios_rwsem);
2480 0 : return put_user(retval, (unsigned int __user *) arg);
2481 : default:
2482 0 : return n_tty_ioctl_helper(tty, cmd, arg);
2483 : }
2484 : }
2485 :
2486 : static struct tty_ldisc_ops n_tty_ops = {
2487 : .owner = THIS_MODULE,
2488 : .num = N_TTY,
2489 : .name = "n_tty",
2490 : .open = n_tty_open,
2491 : .close = n_tty_close,
2492 : .flush_buffer = n_tty_flush_buffer,
2493 : .read = n_tty_read,
2494 : .write = n_tty_write,
2495 : .ioctl = n_tty_ioctl,
2496 : .set_termios = n_tty_set_termios,
2497 : .poll = n_tty_poll,
2498 : .receive_buf = n_tty_receive_buf,
2499 : .write_wakeup = n_tty_write_wakeup,
2500 : .receive_buf2 = n_tty_receive_buf2,
2501 : .lookahead_buf = n_tty_lookahead_flow_ctrl,
2502 : };
2503 :
2504 : /**
2505 : * n_tty_inherit_ops - inherit N_TTY methods
2506 : * @ops: struct tty_ldisc_ops where to save N_TTY methods
2507 : *
2508 : * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2509 : */
2510 :
2511 0 : void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2512 : {
2513 0 : *ops = n_tty_ops;
2514 0 : ops->owner = NULL;
2515 0 : }
2516 : EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2517 :
2518 1 : void __init n_tty_init(void)
2519 : {
2520 1 : tty_register_ldisc(&n_tty_ops);
2521 1 : }
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