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 <[email protected]>
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 <[email protected]>.
27 : * Also fixed a bug in BLOCKING mode where n_tty_write returns
28 : * EAGAIN
29 : */
30 :
31 : #include <linux/bitmap.h>
32 : #include <linux/bitops.h>
33 : #include <linux/ctype.h>
34 : #include <linux/errno.h>
35 : #include <linux/export.h>
36 : #include <linux/fcntl.h>
37 : #include <linux/file.h>
38 : #include <linux/jiffies.h>
39 : #include <linux/math.h>
40 : #include <linux/poll.h>
41 : #include <linux/ratelimit.h>
42 : #include <linux/sched.h>
43 : #include <linux/signal.h>
44 : #include <linux/slab.h>
45 : #include <linux/string.h>
46 : #include <linux/tty.h>
47 : #include <linux/types.h>
48 : #include <linux/uaccess.h>
49 : #include <linux/vmalloc.h>
50 :
51 : #include "tty.h"
52 :
53 : /*
54 : * Until this number of characters is queued in the xmit buffer, select will
55 : * return "we have room for writes".
56 : */
57 : #define WAKEUP_CHARS 256
58 :
59 : #define N_TTY_BUF_SIZE 4096
60 :
61 : /*
62 : * This defines the low- and high-watermarks for throttling and
63 : * unthrottling the TTY driver. These watermarks are used for
64 : * controlling the space in the read buffer.
65 : */
66 : #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
67 : #define TTY_THRESHOLD_UNTHROTTLE 128
68 :
69 : /*
70 : * Special byte codes used in the echo buffer to represent operations
71 : * or special handling of characters. Bytes in the echo buffer that
72 : * are not part of such special blocks are treated as normal character
73 : * codes.
74 : */
75 : #define ECHO_OP_START 0xff
76 : #define ECHO_OP_MOVE_BACK_COL 0x80
77 : #define ECHO_OP_SET_CANON_COL 0x81
78 : #define ECHO_OP_ERASE_TAB 0x82
79 :
80 : #define ECHO_COMMIT_WATERMARK 256
81 : #define ECHO_BLOCK 256
82 : #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
83 :
84 : struct n_tty_data {
85 : /* producer-published */
86 : size_t read_head;
87 : size_t commit_head;
88 : size_t canon_head;
89 : size_t echo_head;
90 : size_t echo_commit;
91 : size_t echo_mark;
92 : DECLARE_BITMAP(char_map, 256);
93 :
94 : /* private to n_tty_receive_overrun (single-threaded) */
95 : unsigned long overrun_time;
96 : unsigned int num_overrun;
97 :
98 : /* non-atomic */
99 : bool no_room;
100 :
101 : /* must hold exclusive termios_rwsem to reset these */
102 : unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
103 : unsigned char push:1;
104 :
105 : /* shared by producer and consumer */
106 : u8 read_buf[N_TTY_BUF_SIZE];
107 : DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
108 : u8 echo_buf[N_TTY_BUF_SIZE];
109 :
110 : /* consumer-published */
111 : size_t read_tail;
112 : size_t line_start;
113 :
114 : /* # of chars looked ahead (to find software flow control chars) */
115 : size_t lookahead_count;
116 :
117 : /* protected by output lock */
118 : unsigned int column;
119 : unsigned int canon_column;
120 : size_t echo_tail;
121 :
122 : struct mutex atomic_read_lock;
123 : struct mutex output_lock;
124 : };
125 :
126 : #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
127 :
128 33 : static inline size_t read_cnt(struct n_tty_data *ldata)
129 : {
130 33 : return ldata->read_head - ldata->read_tail;
131 : }
132 :
133 0 : static inline u8 read_buf(struct n_tty_data *ldata, size_t i)
134 : {
135 0 : return ldata->read_buf[MASK(i)];
136 : }
137 :
138 74 : static inline u8 *read_buf_addr(struct n_tty_data *ldata, size_t i)
139 : {
140 74 : return &ldata->read_buf[MASK(i)];
141 : }
142 :
143 14 : static inline u8 echo_buf(struct n_tty_data *ldata, size_t i)
144 : {
145 14 : smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
146 14 : return ldata->echo_buf[MASK(i)];
147 : }
148 :
149 14 : static inline u8 *echo_buf_addr(struct n_tty_data *ldata, size_t i)
150 : {
151 14 : return &ldata->echo_buf[MASK(i)];
152 : }
153 :
154 : /* If we are not echoing the data, perhaps this is a secret so erase it */
155 25 : static void zero_buffer(const struct tty_struct *tty, u8 *buffer, size_t size)
156 : {
157 25 : if (L_ICANON(tty) && !L_ECHO(tty))
158 0 : memset(buffer, 0, size);
159 25 : }
160 :
161 0 : static void tty_copy(const struct tty_struct *tty, void *to, size_t tail,
162 : size_t n)
163 : {
164 0 : struct n_tty_data *ldata = tty->disc_data;
165 0 : size_t size = N_TTY_BUF_SIZE - tail;
166 0 : void *from = read_buf_addr(ldata, tail);
167 :
168 0 : if (n > size) {
169 0 : tty_audit_add_data(tty, from, size);
170 0 : memcpy(to, from, size);
171 0 : zero_buffer(tty, from, size);
172 0 : to += size;
173 0 : n -= size;
174 0 : from = ldata->read_buf;
175 0 : }
176 :
177 0 : tty_audit_add_data(tty, from, n);
178 0 : memcpy(to, from, n);
179 0 : zero_buffer(tty, from, n);
180 0 : }
181 :
182 : /**
183 : * n_tty_kick_worker - start input worker (if required)
184 : * @tty: terminal
185 : *
186 : * Re-schedules the flip buffer work if it may have stopped.
187 : *
188 : * Locking:
189 : * * Caller holds exclusive %termios_rwsem, or
190 : * * n_tty_read()/consumer path:
191 : * holds non-exclusive %termios_rwsem
192 : */
193 36 : static void n_tty_kick_worker(const struct tty_struct *tty)
194 : {
195 36 : struct n_tty_data *ldata = tty->disc_data;
196 :
197 : /* Did the input worker stop? Restart it */
198 36 : if (unlikely(READ_ONCE(ldata->no_room))) {
199 0 : WRITE_ONCE(ldata->no_room, 0);
200 :
201 0 : WARN_RATELIMIT(tty->port->itty == NULL,
202 : "scheduling with invalid itty\n");
203 : /* see if ldisc has been killed - if so, this means that
204 : * even though the ldisc has been halted and ->buf.work
205 : * cancelled, ->buf.work is about to be rescheduled
206 : */
207 0 : WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
208 : "scheduling buffer work for halted ldisc\n");
209 0 : tty_buffer_restart_work(tty->port);
210 0 : }
211 36 : }
212 :
213 12 : static ssize_t chars_in_buffer(const struct tty_struct *tty)
214 : {
215 12 : const struct n_tty_data *ldata = tty->disc_data;
216 12 : size_t head = ldata->icanon ? ldata->canon_head : ldata->commit_head;
217 :
218 24 : return head - ldata->read_tail;
219 12 : }
220 :
221 : /**
222 : * n_tty_write_wakeup - asynchronous I/O notifier
223 : * @tty: tty device
224 : *
225 : * Required for the ptys, serial driver etc. since processes that attach
226 : * themselves to the master and rely on ASYNC IO must be woken up.
227 : */
228 0 : static void n_tty_write_wakeup(struct tty_struct *tty)
229 : {
230 0 : clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
231 0 : kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
232 0 : }
233 :
234 1 : static void n_tty_check_throttle(struct tty_struct *tty)
235 : {
236 1 : struct n_tty_data *ldata = tty->disc_data;
237 :
238 : /*
239 : * Check the remaining room for the input canonicalization
240 : * mode. We don't want to throttle the driver if we're in
241 : * canonical mode and don't have a newline yet!
242 : */
243 1 : if (ldata->icanon && ldata->canon_head == ldata->read_tail)
244 0 : return;
245 :
246 1 : do {
247 1 : tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
248 1 : if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
249 1 : break;
250 0 : } while (!tty_throttle_safe(tty));
251 :
252 1 : __tty_set_flow_change(tty, 0);
253 1 : }
254 :
255 12 : static void n_tty_check_unthrottle(struct tty_struct *tty)
256 : {
257 12 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
258 12 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
259 0 : return;
260 12 : n_tty_kick_worker(tty);
261 12 : tty_wakeup(tty->link);
262 12 : return;
263 : }
264 :
265 : /* If there is enough space in the read buffer now, let the
266 : * low-level driver know. We use chars_in_buffer() to
267 : * check the buffer, as it now knows about canonical mode.
268 : * Otherwise, if the driver is throttled and the line is
269 : * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
270 : * we won't get any more characters.
271 : */
272 :
273 0 : do {
274 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
275 0 : if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
276 0 : break;
277 :
278 0 : n_tty_kick_worker(tty);
279 0 : } while (!tty_unthrottle_safe(tty));
280 :
281 0 : __tty_set_flow_change(tty, 0);
282 12 : }
283 :
284 : /**
285 : * put_tty_queue - add character to tty
286 : * @c: character
287 : * @ldata: n_tty data
288 : *
289 : * Add a character to the tty read_buf queue.
290 : *
291 : * Locking:
292 : * * n_tty_receive_buf()/producer path:
293 : * caller holds non-exclusive %termios_rwsem
294 : */
295 9 : static inline void put_tty_queue(u8 c, struct n_tty_data *ldata)
296 : {
297 9 : *read_buf_addr(ldata, ldata->read_head) = c;
298 9 : ldata->read_head++;
299 9 : }
300 :
301 : /**
302 : * reset_buffer_flags - reset buffer state
303 : * @ldata: line disc data to reset
304 : *
305 : * Reset the read buffer counters and clear the flags. Called from
306 : * n_tty_open() and n_tty_flush_buffer().
307 : *
308 : * Locking:
309 : * * caller holds exclusive %termios_rwsem, or
310 : * * (locking is not required)
311 : */
312 12 : static void reset_buffer_flags(struct n_tty_data *ldata)
313 : {
314 12 : ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
315 12 : ldata->commit_head = 0;
316 12 : ldata->line_start = 0;
317 :
318 12 : ldata->erasing = 0;
319 12 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
320 12 : ldata->push = 0;
321 :
322 12 : ldata->lookahead_count = 0;
323 12 : }
324 :
325 0 : static void n_tty_packet_mode_flush(struct tty_struct *tty)
326 : {
327 0 : unsigned long flags;
328 :
329 0 : if (tty->link->ctrl.packet) {
330 0 : spin_lock_irqsave(&tty->ctrl.lock, flags);
331 0 : tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
332 0 : spin_unlock_irqrestore(&tty->ctrl.lock, flags);
333 0 : wake_up_interruptible(&tty->link->read_wait);
334 0 : }
335 0 : }
336 :
337 : /**
338 : * n_tty_flush_buffer - clean input queue
339 : * @tty: terminal device
340 : *
341 : * Flush the input buffer. Called when the tty layer wants the buffer flushed
342 : * (eg at hangup) or when the %N_TTY line discipline internally has to clean
343 : * the pending queue (for example some signals).
344 : *
345 : * Holds %termios_rwsem to exclude producer/consumer while buffer indices are
346 : * reset.
347 : *
348 : * Locking: %ctrl.lock, exclusive %termios_rwsem
349 : */
350 12 : static void n_tty_flush_buffer(struct tty_struct *tty)
351 : {
352 12 : down_write(&tty->termios_rwsem);
353 12 : reset_buffer_flags(tty->disc_data);
354 12 : n_tty_kick_worker(tty);
355 :
356 12 : if (tty->link)
357 0 : n_tty_packet_mode_flush(tty);
358 12 : up_write(&tty->termios_rwsem);
359 12 : }
360 :
361 : /**
362 : * is_utf8_continuation - utf8 multibyte check
363 : * @c: byte to check
364 : *
365 : * Returns: true if the utf8 character @c is a multibyte continuation
366 : * character. We use this to correctly compute the on-screen size of the
367 : * character when printing.
368 : */
369 1058 : static inline int is_utf8_continuation(u8 c)
370 : {
371 1058 : return (c & 0xc0) == 0x80;
372 : }
373 :
374 : /**
375 : * is_continuation - multibyte check
376 : * @c: byte to check
377 : * @tty: terminal device
378 : *
379 : * Returns: true if the utf8 character @c is a multibyte continuation character
380 : * and the terminal is in unicode mode.
381 : */
382 1203 : static inline int is_continuation(u8 c, const struct tty_struct *tty)
383 : {
384 1203 : return I_IUTF8(tty) && is_utf8_continuation(c);
385 : }
386 :
387 : /**
388 : * do_output_char - output one character
389 : * @c: character (or partial unicode symbol)
390 : * @tty: terminal device
391 : * @space: space available in tty driver write buffer
392 : *
393 : * This is a helper function that handles one output character (including
394 : * special characters like TAB, CR, LF, etc.), doing OPOST processing and
395 : * putting the results in the tty driver's write buffer.
396 : *
397 : * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY.
398 : * They simply aren't relevant in the world today. If you ever need them, add
399 : * them here.
400 : *
401 : * Returns: the number of bytes of buffer space used or -1 if no space left.
402 : *
403 : * Locking: should be called under the %output_lock to protect the column state
404 : * and space left in the buffer.
405 : */
406 35 : static int do_output_char(u8 c, struct tty_struct *tty, int space)
407 : {
408 35 : struct n_tty_data *ldata = tty->disc_data;
409 35 : int spaces;
410 :
411 35 : if (!space)
412 0 : return -1;
413 :
414 35 : switch (c) {
415 : case '\n':
416 28 : if (O_ONLRET(tty))
417 0 : ldata->column = 0;
418 28 : if (O_ONLCR(tty)) {
419 28 : if (space < 2)
420 0 : return -1;
421 28 : ldata->canon_column = ldata->column = 0;
422 28 : tty->ops->write(tty, "\r\n", 2);
423 28 : return 2;
424 : }
425 0 : ldata->canon_column = ldata->column;
426 0 : break;
427 : case '\r':
428 0 : if (O_ONOCR(tty) && ldata->column == 0)
429 0 : return 0;
430 0 : if (O_OCRNL(tty)) {
431 0 : c = '\n';
432 0 : if (O_ONLRET(tty))
433 0 : ldata->canon_column = ldata->column = 0;
434 0 : break;
435 : }
436 0 : ldata->canon_column = ldata->column = 0;
437 0 : break;
438 : case '\t':
439 0 : spaces = 8 - (ldata->column & 7);
440 0 : if (O_TABDLY(tty) == XTABS) {
441 0 : if (space < spaces)
442 0 : return -1;
443 0 : ldata->column += spaces;
444 0 : tty->ops->write(tty, " ", spaces);
445 0 : return spaces;
446 : }
447 0 : ldata->column += spaces;
448 0 : break;
449 : case '\b':
450 0 : if (ldata->column > 0)
451 0 : ldata->column--;
452 0 : break;
453 : default:
454 7 : if (!iscntrl(c)) {
455 7 : if (O_OLCUC(tty))
456 0 : c = toupper(c);
457 7 : if (!is_continuation(c, tty))
458 7 : ldata->column++;
459 7 : }
460 7 : break;
461 : }
462 :
463 7 : tty_put_char(tty, c);
464 7 : return 1;
465 35 : }
466 :
467 : /**
468 : * process_output - output post processor
469 : * @c: character (or partial unicode symbol)
470 : * @tty: terminal device
471 : *
472 : * Output one character with OPOST processing.
473 : *
474 : * Returns: -1 when the output device is full and the character must be
475 : * retried.
476 : *
477 : * Locking: %output_lock to protect column state and space left (also, this is
478 : *called from n_tty_write() under the tty layer write lock).
479 : */
480 27 : static int process_output(u8 c, struct tty_struct *tty)
481 : {
482 27 : struct n_tty_data *ldata = tty->disc_data;
483 :
484 27 : guard(mutex)(&ldata->output_lock);
485 :
486 27 : if (do_output_char(c, tty, tty_write_room(tty)) < 0)
487 0 : return -1;
488 :
489 27 : return 0;
490 27 : }
491 :
492 : /**
493 : * process_output_block - block post processor
494 : * @tty: terminal device
495 : * @buf: character buffer
496 : * @nr: number of bytes to output
497 : *
498 : * Output a block of characters with OPOST processing.
499 : *
500 : * This path is used to speed up block console writes, among other things when
501 : * processing blocks of output data. It handles only the simple cases normally
502 : * found and helps to generate blocks of symbols for the console driver and
503 : * thus improve performance.
504 : *
505 : * Returns: the number of characters output.
506 : *
507 : * Locking: %output_lock to protect column state and space left (also, this is
508 : * called from n_tty_write() under the tty layer write lock).
509 : */
510 31 : static ssize_t process_output_block(struct tty_struct *tty,
511 : const u8 *buf, unsigned int nr)
512 : {
513 31 : struct n_tty_data *ldata = tty->disc_data;
514 31 : unsigned int space, i;
515 31 : const u8 *cp;
516 :
517 31 : guard(mutex)(&ldata->output_lock);
518 :
519 31 : space = tty_write_room(tty);
520 31 : if (space == 0)
521 0 : return 0;
522 :
523 31 : if (nr > space)
524 0 : nr = space;
525 :
526 1227 : for (i = 0, cp = buf; i < nr; i++, cp++) {
527 1223 : u8 c = *cp;
528 :
529 1223 : switch (c) {
530 : case '\n':
531 27 : if (O_ONLRET(tty))
532 0 : ldata->column = 0;
533 27 : if (O_ONLCR(tty))
534 27 : goto do_write;
535 0 : ldata->canon_column = ldata->column;
536 0 : break;
537 : case '\r':
538 0 : if (O_ONOCR(tty) && ldata->column == 0)
539 0 : goto do_write;
540 0 : if (O_OCRNL(tty))
541 0 : goto do_write;
542 0 : ldata->canon_column = ldata->column = 0;
543 0 : break;
544 : case '\t':
545 0 : goto do_write;
546 : case '\b':
547 0 : if (ldata->column > 0)
548 0 : ldata->column--;
549 0 : break;
550 : default:
551 1196 : if (!iscntrl(c)) {
552 1196 : if (O_OLCUC(tty))
553 0 : goto do_write;
554 1196 : if (!is_continuation(c, tty))
555 1196 : ldata->column++;
556 1196 : }
557 1196 : break;
558 : }
559 1227 : }
560 : do_write:
561 31 : return tty->ops->write(tty, buf, i);
562 31 : }
563 :
564 3 : static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
565 : int space)
566 : {
567 3 : struct n_tty_data *ldata = tty->disc_data;
568 3 : u8 op;
569 :
570 : /*
571 : * Since add_echo_byte() is called without holding output_lock, we
572 : * might see only portion of multi-byte operation.
573 : */
574 3 : if (MASK(ldata->echo_commit) == MASK(*tail + 1))
575 0 : return -ENODATA;
576 :
577 : /*
578 : * If the buffer byte is the start of a multi-byte operation, get the
579 : * next byte, which is either the op code or a control character value.
580 : */
581 3 : op = echo_buf(ldata, *tail + 1);
582 :
583 3 : switch (op) {
584 : case ECHO_OP_ERASE_TAB: {
585 0 : unsigned int num_chars, num_bs;
586 :
587 0 : if (MASK(ldata->echo_commit) == MASK(*tail + 2))
588 0 : return -ENODATA;
589 :
590 0 : num_chars = echo_buf(ldata, *tail + 2);
591 :
592 : /*
593 : * Determine how many columns to go back in order to erase the
594 : * tab. This depends on the number of columns used by other
595 : * characters within the tab area. If this (modulo 8) count is
596 : * from the start of input rather than from a previous tab, we
597 : * offset by canon column. Otherwise, tab spacing is normal.
598 : */
599 0 : if (!(num_chars & 0x80))
600 0 : num_chars += ldata->canon_column;
601 0 : num_bs = 8 - (num_chars & 7);
602 :
603 0 : if (num_bs > space)
604 0 : return -ENOSPC;
605 :
606 0 : space -= num_bs;
607 0 : while (num_bs--) {
608 0 : tty_put_char(tty, '\b');
609 0 : if (ldata->column > 0)
610 0 : ldata->column--;
611 : }
612 0 : *tail += 3;
613 0 : break;
614 0 : }
615 : case ECHO_OP_SET_CANON_COL:
616 2 : ldata->canon_column = ldata->column;
617 2 : *tail += 2;
618 2 : break;
619 :
620 : case ECHO_OP_MOVE_BACK_COL:
621 0 : if (ldata->column > 0)
622 0 : ldata->column--;
623 0 : *tail += 2;
624 0 : break;
625 :
626 : case ECHO_OP_START:
627 : /* This is an escaped echo op start code */
628 0 : if (!space)
629 0 : return -ENOSPC;
630 :
631 0 : tty_put_char(tty, ECHO_OP_START);
632 0 : ldata->column++;
633 0 : space--;
634 0 : *tail += 2;
635 0 : break;
636 :
637 : default:
638 : /*
639 : * If the op is not a special byte code, it is a ctrl char
640 : * tagged to be echoed as "^X" (where X is the letter
641 : * representing the control char). Note that we must ensure
642 : * there is enough space for the whole ctrl pair.
643 : */
644 1 : if (space < 2)
645 0 : return -ENOSPC;
646 :
647 1 : tty_put_char(tty, '^');
648 1 : tty_put_char(tty, op ^ 0100);
649 1 : ldata->column += 2;
650 1 : space -= 2;
651 1 : *tail += 2;
652 1 : break;
653 : }
654 :
655 3 : return space;
656 3 : }
657 :
658 : /**
659 : * __process_echoes - write pending echo characters
660 : * @tty: terminal device
661 : *
662 : * Write previously buffered echo (and other ldisc-generated) characters to the
663 : * tty.
664 : *
665 : * Characters generated by the ldisc (including echoes) need to be buffered
666 : * because the driver's write buffer can fill during heavy program output.
667 : * Echoing straight to the driver will often fail under these conditions,
668 : * causing lost characters and resulting mismatches of ldisc state information.
669 : *
670 : * Since the ldisc state must represent the characters actually sent to the
671 : * driver at the time of the write, operations like certain changes in column
672 : * state are also saved in the buffer and executed here.
673 : *
674 : * A circular fifo buffer is used so that the most recent characters are
675 : * prioritized. Also, when control characters are echoed with a prefixed "^",
676 : * the pair is treated atomically and thus not separated.
677 : *
678 : * Locking: callers must hold %output_lock.
679 : */
680 1 : static size_t __process_echoes(struct tty_struct *tty)
681 : {
682 1 : struct n_tty_data *ldata = tty->disc_data;
683 1 : unsigned int space, old_space;
684 1 : size_t tail;
685 1 : u8 c;
686 :
687 1 : old_space = space = tty_write_room(tty);
688 :
689 1 : tail = ldata->echo_tail;
690 12 : while (MASK(ldata->echo_commit) != MASK(tail)) {
691 11 : c = echo_buf(ldata, tail);
692 11 : if (c == ECHO_OP_START) {
693 3 : int ret = n_tty_process_echo_ops(tty, &tail, space);
694 3 : if (ret == -ENODATA)
695 0 : goto not_yet_stored;
696 3 : if (ret < 0)
697 0 : break;
698 3 : space = ret;
699 3 : } else {
700 8 : if (O_OPOST(tty)) {
701 8 : int retval = do_output_char(c, tty, space);
702 8 : if (retval < 0)
703 0 : break;
704 8 : space -= retval;
705 8 : } else {
706 0 : if (!space)
707 0 : break;
708 0 : tty_put_char(tty, c);
709 0 : space -= 1;
710 : }
711 8 : tail += 1;
712 : }
713 : }
714 :
715 : /* If the echo buffer is nearly full (so that the possibility exists
716 : * of echo overrun before the next commit), then discard enough
717 : * data at the tail to prevent a subsequent overrun */
718 1 : while (ldata->echo_commit > tail &&
719 0 : ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
720 0 : if (echo_buf(ldata, tail) == ECHO_OP_START) {
721 0 : if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
722 0 : tail += 3;
723 : else
724 0 : tail += 2;
725 0 : } else
726 0 : tail++;
727 : }
728 :
729 : not_yet_stored:
730 1 : ldata->echo_tail = tail;
731 1 : return old_space - space;
732 1 : }
733 :
734 9 : static void commit_echoes(struct tty_struct *tty)
735 : {
736 9 : struct n_tty_data *ldata = tty->disc_data;
737 9 : size_t nr, old, echoed;
738 9 : size_t head;
739 :
740 9 : mutex_lock(&ldata->output_lock);
741 9 : head = ldata->echo_head;
742 9 : ldata->echo_mark = head;
743 9 : old = ldata->echo_commit - ldata->echo_tail;
744 :
745 : /* Process committed echoes if the accumulated # of bytes
746 : * is over the threshold (and try again each time another
747 : * block is accumulated) */
748 9 : nr = head - ldata->echo_tail;
749 9 : if (nr < ECHO_COMMIT_WATERMARK ||
750 0 : (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
751 9 : mutex_unlock(&ldata->output_lock);
752 9 : return;
753 : }
754 :
755 0 : ldata->echo_commit = head;
756 0 : echoed = __process_echoes(tty);
757 0 : mutex_unlock(&ldata->output_lock);
758 :
759 0 : if (echoed && tty->ops->flush_chars)
760 0 : tty->ops->flush_chars(tty);
761 9 : }
762 :
763 44 : static void process_echoes(struct tty_struct *tty)
764 : {
765 44 : struct n_tty_data *ldata = tty->disc_data;
766 44 : size_t echoed;
767 :
768 44 : if (ldata->echo_mark == ldata->echo_tail)
769 44 : return;
770 :
771 0 : mutex_lock(&ldata->output_lock);
772 0 : ldata->echo_commit = ldata->echo_mark;
773 0 : echoed = __process_echoes(tty);
774 0 : mutex_unlock(&ldata->output_lock);
775 :
776 0 : if (echoed && tty->ops->flush_chars)
777 0 : tty->ops->flush_chars(tty);
778 44 : }
779 :
780 : /* NB: echo_mark and echo_head should be equivalent here */
781 1 : static void flush_echoes(struct tty_struct *tty)
782 : {
783 1 : struct n_tty_data *ldata = tty->disc_data;
784 :
785 1 : if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
786 1 : ldata->echo_commit == ldata->echo_head)
787 0 : return;
788 :
789 1 : mutex_lock(&ldata->output_lock);
790 1 : ldata->echo_commit = ldata->echo_head;
791 1 : __process_echoes(tty);
792 1 : mutex_unlock(&ldata->output_lock);
793 1 : }
794 :
795 : /**
796 : * add_echo_byte - add a byte to the echo buffer
797 : * @c: unicode byte to echo
798 : * @ldata: n_tty data
799 : *
800 : * Add a character or operation byte to the echo buffer.
801 : */
802 14 : static inline void add_echo_byte(u8 c, struct n_tty_data *ldata)
803 : {
804 14 : *echo_buf_addr(ldata, ldata->echo_head) = c;
805 14 : smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
806 14 : ldata->echo_head++;
807 14 : }
808 :
809 : /**
810 : * echo_move_back_col - add operation to move back a column
811 : * @ldata: n_tty data
812 : *
813 : * Add an operation to the echo buffer to move back one column.
814 : */
815 0 : static void echo_move_back_col(struct n_tty_data *ldata)
816 : {
817 0 : add_echo_byte(ECHO_OP_START, ldata);
818 0 : add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
819 0 : }
820 :
821 : /**
822 : * echo_set_canon_col - add operation to set the canon column
823 : * @ldata: n_tty data
824 : *
825 : * Add an operation to the echo buffer to set the canon column to the current
826 : * column.
827 : */
828 2 : static void echo_set_canon_col(struct n_tty_data *ldata)
829 : {
830 2 : add_echo_byte(ECHO_OP_START, ldata);
831 2 : add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
832 2 : }
833 :
834 : /**
835 : * echo_erase_tab - add operation to erase a tab
836 : * @num_chars: number of character columns already used
837 : * @after_tab: true if num_chars starts after a previous tab
838 : * @ldata: n_tty data
839 : *
840 : * Add an operation to the echo buffer to erase a tab.
841 : *
842 : * Called by the eraser function, which knows how many character columns have
843 : * been used since either a previous tab or the start of input. This
844 : * information will be used later, along with canon column (if applicable), to
845 : * go back the correct number of columns.
846 : */
847 0 : static void echo_erase_tab(unsigned int num_chars, int after_tab,
848 : struct n_tty_data *ldata)
849 : {
850 0 : add_echo_byte(ECHO_OP_START, ldata);
851 0 : add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
852 :
853 : /* We only need to know this modulo 8 (tab spacing) */
854 0 : num_chars &= 7;
855 :
856 : /* Set the high bit as a flag if num_chars is after a previous tab */
857 0 : if (after_tab)
858 0 : num_chars |= 0x80;
859 :
860 0 : add_echo_byte(num_chars, ldata);
861 0 : }
862 :
863 : /**
864 : * echo_char_raw - echo a character raw
865 : * @c: unicode byte to echo
866 : * @ldata: line disc data
867 : *
868 : * Echo user input back onto the screen. This must be called only when
869 : * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
870 : *
871 : * This variant does not treat control characters specially.
872 : */
873 1 : static void echo_char_raw(u8 c, struct n_tty_data *ldata)
874 : {
875 1 : if (c == ECHO_OP_START) {
876 0 : add_echo_byte(ECHO_OP_START, ldata);
877 0 : add_echo_byte(ECHO_OP_START, ldata);
878 0 : } else {
879 1 : add_echo_byte(c, ldata);
880 : }
881 1 : }
882 :
883 : /**
884 : * echo_char - echo a character
885 : * @c: unicode byte to echo
886 : * @tty: terminal device
887 : *
888 : * Echo user input back onto the screen. This must be called only when
889 : * L_ECHO(tty) is true. Called from the &tty_driver.receive_buf() path.
890 : *
891 : * This variant tags control characters to be echoed as "^X" (where X is the
892 : * letter representing the control char).
893 : */
894 8 : static void echo_char(u8 c, const struct tty_struct *tty)
895 : {
896 8 : struct n_tty_data *ldata = tty->disc_data;
897 :
898 8 : if (c == ECHO_OP_START) {
899 0 : add_echo_byte(ECHO_OP_START, ldata);
900 0 : add_echo_byte(ECHO_OP_START, ldata);
901 0 : } else {
902 8 : if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
903 1 : add_echo_byte(ECHO_OP_START, ldata);
904 8 : add_echo_byte(c, ldata);
905 : }
906 8 : }
907 :
908 : /**
909 : * finish_erasing - complete erase
910 : * @ldata: n_tty data
911 : */
912 8 : static inline void finish_erasing(struct n_tty_data *ldata)
913 : {
914 8 : if (ldata->erasing) {
915 0 : echo_char_raw('/', ldata);
916 0 : ldata->erasing = 0;
917 0 : }
918 8 : }
919 :
920 : /**
921 : * eraser - handle erase function
922 : * @c: character input
923 : * @tty: terminal device
924 : *
925 : * Perform erase and necessary output when an erase character is present in the
926 : * stream from the driver layer. Handles the complexities of UTF-8 multibyte
927 : * symbols.
928 : *
929 : * Locking: n_tty_receive_buf()/producer path:
930 : * caller holds non-exclusive %termios_rwsem
931 : */
932 0 : static void eraser(u8 c, const struct tty_struct *tty)
933 : {
934 0 : struct n_tty_data *ldata = tty->disc_data;
935 0 : enum { ERASE, WERASE, KILL } kill_type;
936 0 : size_t head;
937 0 : size_t cnt;
938 0 : int seen_alnums;
939 :
940 0 : if (ldata->read_head == ldata->canon_head) {
941 : /* process_output('\a', tty); */ /* what do you think? */
942 0 : return;
943 : }
944 0 : if (c == ERASE_CHAR(tty))
945 0 : kill_type = ERASE;
946 0 : else if (c == WERASE_CHAR(tty))
947 0 : kill_type = WERASE;
948 : else {
949 0 : if (!L_ECHO(tty)) {
950 0 : ldata->read_head = ldata->canon_head;
951 0 : return;
952 : }
953 0 : if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
954 0 : ldata->read_head = ldata->canon_head;
955 0 : finish_erasing(ldata);
956 0 : echo_char(KILL_CHAR(tty), tty);
957 : /* Add a newline if ECHOK is on and ECHOKE is off. */
958 0 : if (L_ECHOK(tty))
959 0 : echo_char_raw('\n', ldata);
960 0 : return;
961 : }
962 0 : kill_type = KILL;
963 : }
964 :
965 0 : seen_alnums = 0;
966 0 : while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
967 0 : head = ldata->read_head;
968 :
969 : /* erase a single possibly multibyte character */
970 0 : do {
971 0 : head--;
972 0 : c = read_buf(ldata, head);
973 0 : } while (is_continuation(c, tty) &&
974 0 : MASK(head) != MASK(ldata->canon_head));
975 :
976 : /* do not partially erase */
977 0 : if (is_continuation(c, tty))
978 0 : break;
979 :
980 0 : if (kill_type == WERASE) {
981 : /* Equivalent to BSD's ALTWERASE. */
982 0 : if (isalnum(c) || c == '_')
983 0 : seen_alnums++;
984 0 : else if (seen_alnums)
985 0 : break;
986 0 : }
987 0 : cnt = ldata->read_head - head;
988 0 : ldata->read_head = head;
989 0 : if (L_ECHO(tty)) {
990 0 : if (L_ECHOPRT(tty)) {
991 0 : if (!ldata->erasing) {
992 0 : echo_char_raw('\\', ldata);
993 0 : ldata->erasing = 1;
994 0 : }
995 : /* if cnt > 1, output a multi-byte character */
996 0 : echo_char(c, tty);
997 0 : while (--cnt > 0) {
998 0 : head++;
999 0 : echo_char_raw(read_buf(ldata, head), ldata);
1000 0 : echo_move_back_col(ldata);
1001 : }
1002 0 : } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1003 0 : echo_char(ERASE_CHAR(tty), tty);
1004 0 : } else if (c == '\t') {
1005 0 : unsigned int num_chars = 0;
1006 0 : int after_tab = 0;
1007 0 : size_t tail = ldata->read_head;
1008 :
1009 : /*
1010 : * Count the columns used for characters
1011 : * since the start of input or after a
1012 : * previous tab.
1013 : * This info is used to go back the correct
1014 : * number of columns.
1015 : */
1016 0 : while (MASK(tail) != MASK(ldata->canon_head)) {
1017 0 : tail--;
1018 0 : c = read_buf(ldata, tail);
1019 0 : if (c == '\t') {
1020 0 : after_tab = 1;
1021 0 : break;
1022 0 : } else if (iscntrl(c)) {
1023 0 : if (L_ECHOCTL(tty))
1024 0 : num_chars += 2;
1025 0 : } else if (!is_continuation(c, tty)) {
1026 0 : num_chars++;
1027 0 : }
1028 : }
1029 0 : echo_erase_tab(num_chars, after_tab, ldata);
1030 0 : } else {
1031 0 : if (iscntrl(c) && L_ECHOCTL(tty)) {
1032 0 : echo_char_raw('\b', ldata);
1033 0 : echo_char_raw(' ', ldata);
1034 0 : echo_char_raw('\b', ldata);
1035 0 : }
1036 0 : if (!iscntrl(c) || L_ECHOCTL(tty)) {
1037 0 : echo_char_raw('\b', ldata);
1038 0 : echo_char_raw(' ', ldata);
1039 0 : echo_char_raw('\b', ldata);
1040 0 : }
1041 : }
1042 0 : }
1043 0 : if (kill_type == ERASE)
1044 0 : break;
1045 : }
1046 0 : if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1047 0 : finish_erasing(ldata);
1048 0 : }
1049 :
1050 :
1051 0 : static void __isig(int sig, struct tty_struct *tty)
1052 : {
1053 0 : struct pid *tty_pgrp = tty_get_pgrp(tty);
1054 0 : if (tty_pgrp) {
1055 0 : kill_pgrp(tty_pgrp, sig, 1);
1056 0 : put_pid(tty_pgrp);
1057 0 : }
1058 0 : }
1059 :
1060 : /**
1061 : * isig - handle the ISIG optio
1062 : * @sig: signal
1063 : * @tty: terminal
1064 : *
1065 : * Called when a signal is being sent due to terminal input. Called from the
1066 : * &tty_driver.receive_buf() path, so serialized.
1067 : *
1068 : * Performs input and output flush if !NOFLSH. In this context, the echo
1069 : * buffer is 'output'. The signal is processed first to alert any current
1070 : * readers or writers to discontinue and exit their i/o loops.
1071 : *
1072 : * Locking: %ctrl.lock
1073 : */
1074 0 : static void isig(int sig, struct tty_struct *tty)
1075 : {
1076 0 : struct n_tty_data *ldata = tty->disc_data;
1077 :
1078 0 : if (L_NOFLSH(tty)) {
1079 : /* signal only */
1080 0 : __isig(sig, tty);
1081 :
1082 0 : } else { /* signal and flush */
1083 0 : up_read(&tty->termios_rwsem);
1084 0 : down_write(&tty->termios_rwsem);
1085 :
1086 0 : __isig(sig, tty);
1087 :
1088 : /* clear echo buffer */
1089 0 : mutex_lock(&ldata->output_lock);
1090 0 : ldata->echo_head = ldata->echo_tail = 0;
1091 0 : ldata->echo_mark = ldata->echo_commit = 0;
1092 0 : mutex_unlock(&ldata->output_lock);
1093 :
1094 : /* clear output buffer */
1095 0 : tty_driver_flush_buffer(tty);
1096 :
1097 : /* clear input buffer */
1098 0 : reset_buffer_flags(tty->disc_data);
1099 :
1100 : /* notify pty master of flush */
1101 0 : if (tty->link)
1102 0 : n_tty_packet_mode_flush(tty);
1103 :
1104 0 : up_write(&tty->termios_rwsem);
1105 0 : down_read(&tty->termios_rwsem);
1106 : }
1107 0 : }
1108 :
1109 : /**
1110 : * n_tty_receive_break - handle break
1111 : * @tty: terminal
1112 : *
1113 : * An RS232 break event has been hit in the incoming bitstream. This can cause
1114 : * a variety of events depending upon the termios settings.
1115 : *
1116 : * Locking: n_tty_receive_buf()/producer path:
1117 : * caller holds non-exclusive termios_rwsem
1118 : *
1119 : * Note: may get exclusive %termios_rwsem if flushing input buffer
1120 : */
1121 0 : static void n_tty_receive_break(struct tty_struct *tty)
1122 : {
1123 0 : struct n_tty_data *ldata = tty->disc_data;
1124 :
1125 0 : if (I_IGNBRK(tty))
1126 0 : return;
1127 0 : if (I_BRKINT(tty)) {
1128 0 : isig(SIGINT, tty);
1129 0 : return;
1130 : }
1131 0 : if (I_PARMRK(tty)) {
1132 0 : put_tty_queue('\377', ldata);
1133 0 : put_tty_queue('\0', ldata);
1134 0 : }
1135 0 : put_tty_queue('\0', ldata);
1136 0 : }
1137 :
1138 : /**
1139 : * n_tty_receive_overrun - handle overrun reporting
1140 : * @tty: terminal
1141 : *
1142 : * Data arrived faster than we could process it. While the tty driver has
1143 : * flagged this the bits that were missed are gone forever.
1144 : *
1145 : * Called from the receive_buf path so single threaded. Does not need locking
1146 : * as num_overrun and overrun_time are function private.
1147 : */
1148 0 : static void n_tty_receive_overrun(const struct tty_struct *tty)
1149 : {
1150 0 : struct n_tty_data *ldata = tty->disc_data;
1151 :
1152 0 : ldata->num_overrun++;
1153 0 : if (time_is_before_jiffies(ldata->overrun_time + HZ)) {
1154 0 : tty_warn(tty, "%u input overrun(s)\n", ldata->num_overrun);
1155 0 : ldata->overrun_time = jiffies;
1156 0 : ldata->num_overrun = 0;
1157 0 : }
1158 0 : }
1159 :
1160 : /**
1161 : * n_tty_receive_parity_error - error notifier
1162 : * @tty: terminal device
1163 : * @c: character
1164 : *
1165 : * Process a parity error and queue the right data to indicate the error case
1166 : * if necessary.
1167 : *
1168 : * Locking: n_tty_receive_buf()/producer path:
1169 : * caller holds non-exclusive %termios_rwsem
1170 : */
1171 0 : static void n_tty_receive_parity_error(const struct tty_struct *tty,
1172 : u8 c)
1173 : {
1174 0 : struct n_tty_data *ldata = tty->disc_data;
1175 :
1176 0 : if (I_INPCK(tty)) {
1177 0 : if (I_IGNPAR(tty))
1178 0 : return;
1179 0 : if (I_PARMRK(tty)) {
1180 0 : put_tty_queue('\377', ldata);
1181 0 : put_tty_queue('\0', ldata);
1182 0 : put_tty_queue(c, ldata);
1183 0 : } else
1184 0 : put_tty_queue('\0', ldata);
1185 0 : } else
1186 0 : put_tty_queue(c, ldata);
1187 0 : }
1188 :
1189 : static void
1190 0 : n_tty_receive_signal_char(struct tty_struct *tty, int signal, u8 c)
1191 : {
1192 0 : isig(signal, tty);
1193 0 : if (I_IXON(tty))
1194 0 : start_tty(tty);
1195 0 : if (L_ECHO(tty)) {
1196 0 : echo_char(c, tty);
1197 0 : commit_echoes(tty);
1198 0 : } else
1199 0 : process_echoes(tty);
1200 0 : }
1201 :
1202 1 : static bool n_tty_is_char_flow_ctrl(struct tty_struct *tty, u8 c)
1203 : {
1204 1 : return c == START_CHAR(tty) || c == STOP_CHAR(tty);
1205 : }
1206 :
1207 : /**
1208 : * n_tty_receive_char_flow_ctrl - receive flow control chars
1209 : * @tty: terminal device
1210 : * @c: character
1211 : * @lookahead_done: lookahead has processed this character already
1212 : *
1213 : * Receive and process flow control character actions.
1214 : *
1215 : * In case lookahead for flow control chars already handled the character in
1216 : * advance to the normal receive, the actions are skipped during normal
1217 : * receive.
1218 : *
1219 : * Returns true if @c is consumed as flow-control character, the character
1220 : * must not be treated as normal character.
1221 : */
1222 1 : static bool n_tty_receive_char_flow_ctrl(struct tty_struct *tty, u8 c,
1223 : bool lookahead_done)
1224 : {
1225 1 : if (!n_tty_is_char_flow_ctrl(tty, c))
1226 1 : return false;
1227 :
1228 0 : if (lookahead_done)
1229 0 : return true;
1230 :
1231 0 : if (c == START_CHAR(tty)) {
1232 0 : start_tty(tty);
1233 0 : process_echoes(tty);
1234 0 : return true;
1235 : }
1236 :
1237 : /* STOP_CHAR */
1238 0 : stop_tty(tty);
1239 0 : return true;
1240 1 : }
1241 :
1242 1 : static void n_tty_receive_handle_newline(struct tty_struct *tty, u8 c)
1243 : {
1244 1 : struct n_tty_data *ldata = tty->disc_data;
1245 :
1246 1 : set_bit(MASK(ldata->read_head), ldata->read_flags);
1247 1 : put_tty_queue(c, ldata);
1248 1 : smp_store_release(&ldata->canon_head, ldata->read_head);
1249 1 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1250 1 : wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1251 1 : }
1252 :
1253 1 : static bool n_tty_receive_char_canon(struct tty_struct *tty, u8 c)
1254 : {
1255 1 : struct n_tty_data *ldata = tty->disc_data;
1256 :
1257 1 : if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1258 1 : (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1259 0 : eraser(c, tty);
1260 0 : commit_echoes(tty);
1261 :
1262 0 : return true;
1263 : }
1264 :
1265 1 : if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1266 0 : ldata->lnext = 1;
1267 0 : if (L_ECHO(tty)) {
1268 0 : finish_erasing(ldata);
1269 0 : if (L_ECHOCTL(tty)) {
1270 0 : echo_char_raw('^', ldata);
1271 0 : echo_char_raw('\b', ldata);
1272 0 : commit_echoes(tty);
1273 0 : }
1274 0 : }
1275 :
1276 0 : return true;
1277 : }
1278 :
1279 1 : if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1280 0 : size_t tail = ldata->canon_head;
1281 :
1282 0 : finish_erasing(ldata);
1283 0 : echo_char(c, tty);
1284 0 : echo_char_raw('\n', ldata);
1285 0 : while (MASK(tail) != MASK(ldata->read_head)) {
1286 0 : echo_char(read_buf(ldata, tail), tty);
1287 0 : tail++;
1288 : }
1289 0 : commit_echoes(tty);
1290 :
1291 0 : return true;
1292 0 : }
1293 :
1294 1 : if (c == '\n') {
1295 1 : if (L_ECHO(tty) || L_ECHONL(tty)) {
1296 1 : echo_char_raw('\n', ldata);
1297 1 : commit_echoes(tty);
1298 1 : }
1299 1 : n_tty_receive_handle_newline(tty, c);
1300 :
1301 1 : return true;
1302 : }
1303 :
1304 0 : if (c == EOF_CHAR(tty)) {
1305 0 : c = __DISABLED_CHAR;
1306 0 : n_tty_receive_handle_newline(tty, c);
1307 :
1308 0 : return true;
1309 : }
1310 :
1311 0 : if ((c == EOL_CHAR(tty)) ||
1312 0 : (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1313 : /*
1314 : * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1315 : */
1316 0 : if (L_ECHO(tty)) {
1317 : /* Record the column of first canon char. */
1318 0 : if (ldata->canon_head == ldata->read_head)
1319 0 : echo_set_canon_col(ldata);
1320 0 : echo_char(c, tty);
1321 0 : commit_echoes(tty);
1322 0 : }
1323 : /*
1324 : * XXX does PARMRK doubling happen for
1325 : * EOL_CHAR and EOL2_CHAR?
1326 : */
1327 0 : if (c == '\377' && I_PARMRK(tty))
1328 0 : put_tty_queue(c, ldata);
1329 :
1330 0 : n_tty_receive_handle_newline(tty, c);
1331 :
1332 0 : return true;
1333 : }
1334 :
1335 0 : return false;
1336 1 : }
1337 :
1338 1 : static void n_tty_receive_char_special(struct tty_struct *tty, u8 c,
1339 : bool lookahead_done)
1340 : {
1341 1 : struct n_tty_data *ldata = tty->disc_data;
1342 :
1343 1 : if (I_IXON(tty) && n_tty_receive_char_flow_ctrl(tty, c, lookahead_done))
1344 0 : return;
1345 :
1346 1 : if (L_ISIG(tty)) {
1347 1 : if (c == INTR_CHAR(tty)) {
1348 0 : n_tty_receive_signal_char(tty, SIGINT, c);
1349 0 : return;
1350 1 : } else if (c == QUIT_CHAR(tty)) {
1351 0 : n_tty_receive_signal_char(tty, SIGQUIT, c);
1352 0 : return;
1353 1 : } else if (c == SUSP_CHAR(tty)) {
1354 0 : n_tty_receive_signal_char(tty, SIGTSTP, c);
1355 0 : return;
1356 : }
1357 1 : }
1358 :
1359 1 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1360 0 : start_tty(tty);
1361 0 : process_echoes(tty);
1362 0 : }
1363 :
1364 1 : if (c == '\r') {
1365 0 : if (I_IGNCR(tty))
1366 0 : return;
1367 0 : if (I_ICRNL(tty))
1368 0 : c = '\n';
1369 1 : } else if (c == '\n' && I_INLCR(tty))
1370 0 : c = '\r';
1371 :
1372 1 : if (ldata->icanon && n_tty_receive_char_canon(tty, c))
1373 1 : return;
1374 :
1375 0 : if (L_ECHO(tty)) {
1376 0 : finish_erasing(ldata);
1377 0 : if (c == '\n')
1378 0 : echo_char_raw('\n', ldata);
1379 : else {
1380 : /* Record the column of first canon char. */
1381 0 : if (ldata->canon_head == ldata->read_head)
1382 0 : echo_set_canon_col(ldata);
1383 0 : echo_char(c, tty);
1384 : }
1385 0 : commit_echoes(tty);
1386 0 : }
1387 :
1388 : /* PARMRK doubling check */
1389 0 : if (c == '\377' && I_PARMRK(tty))
1390 0 : put_tty_queue(c, ldata);
1391 :
1392 0 : put_tty_queue(c, ldata);
1393 1 : }
1394 :
1395 : /**
1396 : * n_tty_receive_char - perform processing
1397 : * @tty: terminal device
1398 : * @c: character
1399 : *
1400 : * Process an individual character of input received from the driver. This is
1401 : * serialized with respect to itself by the rules for the driver above.
1402 : *
1403 : * Locking: n_tty_receive_buf()/producer path:
1404 : * caller holds non-exclusive %termios_rwsem
1405 : * publishes canon_head if canonical mode is active
1406 : */
1407 8 : static void n_tty_receive_char(struct tty_struct *tty, u8 c)
1408 : {
1409 8 : struct n_tty_data *ldata = tty->disc_data;
1410 :
1411 8 : if (tty->flow.stopped && !tty->flow.tco_stopped && I_IXON(tty) && I_IXANY(tty)) {
1412 0 : start_tty(tty);
1413 0 : process_echoes(tty);
1414 0 : }
1415 8 : if (L_ECHO(tty)) {
1416 8 : finish_erasing(ldata);
1417 : /* Record the column of first canon char. */
1418 8 : if (ldata->canon_head == ldata->read_head)
1419 2 : echo_set_canon_col(ldata);
1420 8 : echo_char(c, tty);
1421 8 : commit_echoes(tty);
1422 8 : }
1423 : /* PARMRK doubling check */
1424 8 : if (c == '\377' && I_PARMRK(tty))
1425 0 : put_tty_queue(c, ldata);
1426 8 : put_tty_queue(c, ldata);
1427 8 : }
1428 :
1429 0 : static void n_tty_receive_char_closing(struct tty_struct *tty, u8 c,
1430 : bool lookahead_done)
1431 : {
1432 0 : if (I_ISTRIP(tty))
1433 0 : c &= 0x7f;
1434 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1435 0 : c = tolower(c);
1436 :
1437 0 : if (I_IXON(tty)) {
1438 0 : if (!n_tty_receive_char_flow_ctrl(tty, c, lookahead_done) &&
1439 0 : tty->flow.stopped && !tty->flow.tco_stopped && I_IXANY(tty) &&
1440 0 : c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1441 0 : c != SUSP_CHAR(tty)) {
1442 0 : start_tty(tty);
1443 0 : process_echoes(tty);
1444 0 : }
1445 0 : }
1446 0 : }
1447 :
1448 : static void
1449 0 : n_tty_receive_char_flagged(struct tty_struct *tty, u8 c, u8 flag)
1450 : {
1451 0 : switch (flag) {
1452 : case TTY_BREAK:
1453 0 : n_tty_receive_break(tty);
1454 0 : break;
1455 : case TTY_PARITY:
1456 : case TTY_FRAME:
1457 0 : n_tty_receive_parity_error(tty, c);
1458 0 : break;
1459 : case TTY_OVERRUN:
1460 0 : n_tty_receive_overrun(tty);
1461 0 : break;
1462 : default:
1463 0 : tty_err(tty, "unknown flag %u\n", flag);
1464 0 : break;
1465 : }
1466 0 : }
1467 :
1468 : static void
1469 0 : n_tty_receive_char_lnext(struct tty_struct *tty, u8 c, u8 flag)
1470 : {
1471 0 : struct n_tty_data *ldata = tty->disc_data;
1472 :
1473 0 : ldata->lnext = 0;
1474 0 : if (likely(flag == TTY_NORMAL)) {
1475 0 : if (I_ISTRIP(tty))
1476 0 : c &= 0x7f;
1477 0 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1478 0 : c = tolower(c);
1479 0 : n_tty_receive_char(tty, c);
1480 0 : } else
1481 0 : n_tty_receive_char_flagged(tty, c, flag);
1482 0 : }
1483 :
1484 : /* Caller must ensure count > 0 */
1485 0 : static void n_tty_lookahead_flow_ctrl(struct tty_struct *tty, const u8 *cp,
1486 : const u8 *fp, size_t count)
1487 : {
1488 0 : struct n_tty_data *ldata = tty->disc_data;
1489 0 : u8 flag = TTY_NORMAL;
1490 :
1491 0 : ldata->lookahead_count += count;
1492 :
1493 0 : if (!I_IXON(tty))
1494 0 : return;
1495 :
1496 0 : while (count--) {
1497 0 : if (fp)
1498 0 : flag = *fp++;
1499 0 : if (likely(flag == TTY_NORMAL))
1500 0 : n_tty_receive_char_flow_ctrl(tty, *cp, false);
1501 0 : cp++;
1502 : }
1503 0 : }
1504 :
1505 : static void
1506 20 : n_tty_receive_buf_real_raw(const struct tty_struct *tty, const u8 *cp,
1507 : size_t count)
1508 : {
1509 20 : struct n_tty_data *ldata = tty->disc_data;
1510 :
1511 : /* handle buffer wrap-around by a loop */
1512 60 : for (unsigned int i = 0; i < 2; i++) {
1513 40 : size_t head = MASK(ldata->read_head);
1514 40 : size_t n = min(count, N_TTY_BUF_SIZE - head);
1515 :
1516 40 : memcpy(read_buf_addr(ldata, head), cp, n);
1517 :
1518 40 : ldata->read_head += n;
1519 40 : cp += n;
1520 40 : count -= n;
1521 40 : }
1522 20 : }
1523 :
1524 : static void
1525 0 : n_tty_receive_buf_raw(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1526 : size_t count)
1527 : {
1528 0 : struct n_tty_data *ldata = tty->disc_data;
1529 0 : u8 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 u8 *cp, const u8 *fp,
1543 : size_t count, bool lookahead_done)
1544 : {
1545 0 : u8 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 1 : static void n_tty_receive_buf_standard(struct tty_struct *tty, const u8 *cp,
1556 : const u8 *fp, size_t count,
1557 : bool lookahead_done)
1558 : {
1559 1 : struct n_tty_data *ldata = tty->disc_data;
1560 1 : u8 flag = TTY_NORMAL;
1561 :
1562 10 : while (count--) {
1563 9 : u8 c = *cp++;
1564 :
1565 9 : if (fp)
1566 0 : flag = *fp++;
1567 :
1568 9 : if (ldata->lnext) {
1569 0 : n_tty_receive_char_lnext(tty, c, flag);
1570 0 : continue;
1571 : }
1572 :
1573 9 : if (unlikely(flag != TTY_NORMAL)) {
1574 0 : n_tty_receive_char_flagged(tty, c, flag);
1575 0 : continue;
1576 : }
1577 :
1578 9 : if (I_ISTRIP(tty))
1579 0 : c &= 0x7f;
1580 9 : if (I_IUCLC(tty) && L_IEXTEN(tty))
1581 0 : c = tolower(c);
1582 9 : if (L_EXTPROC(tty)) {
1583 0 : put_tty_queue(c, ldata);
1584 0 : continue;
1585 : }
1586 :
1587 9 : if (test_bit(c, ldata->char_map))
1588 1 : n_tty_receive_char_special(tty, c, lookahead_done);
1589 : else
1590 8 : n_tty_receive_char(tty, c);
1591 9 : }
1592 1 : }
1593 :
1594 21 : static void __receive_buf(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1595 : size_t count)
1596 : {
1597 21 : struct n_tty_data *ldata = tty->disc_data;
1598 21 : bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1599 21 : size_t la_count = min(ldata->lookahead_count, count);
1600 :
1601 21 : if (ldata->real_raw)
1602 20 : n_tty_receive_buf_real_raw(tty, cp, count);
1603 1 : else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1604 0 : n_tty_receive_buf_raw(tty, cp, fp, count);
1605 1 : else if (tty->closing && !L_EXTPROC(tty)) {
1606 0 : if (la_count > 0) {
1607 0 : n_tty_receive_buf_closing(tty, cp, fp, la_count, true);
1608 0 : cp += la_count;
1609 0 : if (fp)
1610 0 : fp += la_count;
1611 0 : count -= la_count;
1612 0 : }
1613 0 : if (count > 0)
1614 0 : n_tty_receive_buf_closing(tty, cp, fp, count, false);
1615 0 : } else {
1616 1 : if (la_count > 0) {
1617 0 : n_tty_receive_buf_standard(tty, cp, fp, la_count, true);
1618 0 : cp += la_count;
1619 0 : if (fp)
1620 0 : fp += la_count;
1621 0 : count -= la_count;
1622 0 : }
1623 1 : if (count > 0)
1624 1 : n_tty_receive_buf_standard(tty, cp, fp, count, false);
1625 :
1626 1 : flush_echoes(tty);
1627 1 : if (tty->ops->flush_chars)
1628 0 : tty->ops->flush_chars(tty);
1629 : }
1630 :
1631 21 : ldata->lookahead_count -= la_count;
1632 :
1633 21 : if (ldata->icanon && !L_EXTPROC(tty))
1634 1 : return;
1635 :
1636 : /* publish read_head to consumer */
1637 20 : smp_store_release(&ldata->commit_head, ldata->read_head);
1638 :
1639 20 : if (read_cnt(ldata)) {
1640 20 : kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1641 20 : wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1642 20 : }
1643 21 : }
1644 :
1645 : /**
1646 : * n_tty_receive_buf_common - process input
1647 : * @tty: device to receive input
1648 : * @cp: input chars
1649 : * @fp: flags for each char (if %NULL, all chars are %TTY_NORMAL)
1650 : * @count: number of input chars in @cp
1651 : * @flow: enable flow control
1652 : *
1653 : * Called by the terminal driver when a block of characters has been received.
1654 : * This function must be called from soft contexts not from interrupt context.
1655 : * The driver is responsible for making calls one at a time and in order (or
1656 : * using flush_to_ldisc()).
1657 : *
1658 : * Returns: the # of input chars from @cp which were processed.
1659 : *
1660 : * In canonical mode, the maximum line length is 4096 chars (including the line
1661 : * termination char); lines longer than 4096 chars are truncated. After 4095
1662 : * chars, input data is still processed but not stored. Overflow processing
1663 : * ensures the tty can always receive more input until at least one line can be
1664 : * read.
1665 : *
1666 : * In non-canonical mode, the read buffer will only accept 4095 chars; this
1667 : * provides the necessary space for a newline char if the input mode is
1668 : * switched to canonical.
1669 : *
1670 : * Note it is possible for the read buffer to _contain_ 4096 chars in
1671 : * non-canonical mode: the read buffer could already contain the maximum canon
1672 : * line of 4096 chars when the mode is switched to non-canonical.
1673 : *
1674 : * Locking: n_tty_receive_buf()/producer path:
1675 : * claims non-exclusive %termios_rwsem
1676 : * publishes commit_head or canon_head
1677 : */
1678 : static size_t
1679 21 : n_tty_receive_buf_common(struct tty_struct *tty, const u8 *cp, const u8 *fp,
1680 : size_t count, bool flow)
1681 : {
1682 21 : struct n_tty_data *ldata = tty->disc_data;
1683 21 : size_t n, rcvd = 0;
1684 21 : int room, overflow;
1685 :
1686 21 : down_read(&tty->termios_rwsem);
1687 :
1688 21 : do {
1689 : /*
1690 : * When PARMRK is set, each input char may take up to 3 chars
1691 : * in the read buf; reduce the buffer space avail by 3x
1692 : *
1693 : * If we are doing input canonicalization, and there are no
1694 : * pending newlines, let characters through without limit, so
1695 : * that erase characters will be handled. Other excess
1696 : * characters will be beeped.
1697 : *
1698 : * paired with store in *_copy_from_read_buf() -- guarantees
1699 : * the consumer has loaded the data in read_buf up to the new
1700 : * read_tail (so this producer will not overwrite unread data)
1701 : */
1702 42 : size_t tail = smp_load_acquire(&ldata->read_tail);
1703 :
1704 42 : room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1705 42 : if (I_PARMRK(tty))
1706 0 : room = DIV_ROUND_UP(room, 3);
1707 42 : room--;
1708 42 : if (room <= 0) {
1709 0 : overflow = ldata->icanon && ldata->canon_head == tail;
1710 0 : if (overflow && room < 0)
1711 0 : ldata->read_head--;
1712 0 : room = overflow;
1713 0 : WRITE_ONCE(ldata->no_room, flow && !room);
1714 0 : } else
1715 42 : overflow = 0;
1716 :
1717 42 : n = min_t(size_t, count, room);
1718 42 : if (!n)
1719 21 : break;
1720 :
1721 : /* ignore parity errors if handling overflow */
1722 21 : if (!overflow || !fp || *fp != TTY_PARITY)
1723 21 : __receive_buf(tty, cp, fp, n);
1724 :
1725 21 : cp += n;
1726 21 : if (fp)
1727 0 : fp += n;
1728 21 : count -= n;
1729 21 : rcvd += n;
1730 42 : } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1731 :
1732 21 : tty->receive_room = room;
1733 :
1734 : /* Unthrottle if handling overflow on pty */
1735 21 : if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1736 20 : if (overflow) {
1737 0 : tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1738 0 : tty_unthrottle_safe(tty);
1739 0 : __tty_set_flow_change(tty, 0);
1740 0 : }
1741 20 : } else
1742 1 : n_tty_check_throttle(tty);
1743 :
1744 21 : if (unlikely(ldata->no_room)) {
1745 : /*
1746 : * Barrier here is to ensure to read the latest read_tail in
1747 : * chars_in_buffer() and to make sure that read_tail is not loaded
1748 : * before ldata->no_room is set.
1749 : */
1750 0 : smp_mb();
1751 0 : if (!chars_in_buffer(tty))
1752 0 : n_tty_kick_worker(tty);
1753 0 : }
1754 :
1755 21 : up_read(&tty->termios_rwsem);
1756 :
1757 42 : return rcvd;
1758 21 : }
1759 :
1760 0 : static void n_tty_receive_buf(struct tty_struct *tty, const u8 *cp,
1761 : const u8 *fp, size_t count)
1762 : {
1763 0 : n_tty_receive_buf_common(tty, cp, fp, count, false);
1764 0 : }
1765 :
1766 21 : static size_t n_tty_receive_buf2(struct tty_struct *tty, const u8 *cp,
1767 : const u8 *fp, size_t count)
1768 : {
1769 21 : return n_tty_receive_buf_common(tty, cp, fp, count, true);
1770 : }
1771 :
1772 : /**
1773 : * n_tty_set_termios - termios data changed
1774 : * @tty: terminal
1775 : * @old: previous data
1776 : *
1777 : * Called by the tty layer when the user changes termios flags so that the line
1778 : * discipline can plan ahead. This function cannot sleep and is protected from
1779 : * re-entry by the tty layer. The user is guaranteed that this function will
1780 : * not be re-entered or in progress when the ldisc is closed.
1781 : *
1782 : * Locking: Caller holds @tty->termios_rwsem
1783 : */
1784 12 : static void n_tty_set_termios(struct tty_struct *tty, const struct ktermios *old)
1785 : {
1786 12 : struct n_tty_data *ldata = tty->disc_data;
1787 :
1788 12 : if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1789 12 : bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1790 12 : ldata->line_start = ldata->read_tail;
1791 12 : if (!L_ICANON(tty) || !read_cnt(ldata)) {
1792 12 : ldata->canon_head = ldata->read_tail;
1793 12 : ldata->push = 0;
1794 12 : } else {
1795 0 : set_bit(MASK(ldata->read_head - 1), ldata->read_flags);
1796 0 : ldata->canon_head = ldata->read_head;
1797 0 : ldata->push = 1;
1798 : }
1799 12 : ldata->commit_head = ldata->read_head;
1800 12 : ldata->erasing = 0;
1801 12 : ldata->lnext = 0;
1802 12 : }
1803 :
1804 12 : ldata->icanon = (L_ICANON(tty) != 0);
1805 :
1806 12 : if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1807 12 : I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1808 0 : I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1809 0 : I_PARMRK(tty)) {
1810 12 : bitmap_zero(ldata->char_map, 256);
1811 :
1812 12 : if (I_IGNCR(tty) || I_ICRNL(tty))
1813 12 : set_bit('\r', ldata->char_map);
1814 12 : if (I_INLCR(tty))
1815 0 : set_bit('\n', ldata->char_map);
1816 :
1817 12 : if (L_ICANON(tty)) {
1818 12 : set_bit(ERASE_CHAR(tty), ldata->char_map);
1819 12 : set_bit(KILL_CHAR(tty), ldata->char_map);
1820 12 : set_bit(EOF_CHAR(tty), ldata->char_map);
1821 12 : set_bit('\n', ldata->char_map);
1822 12 : set_bit(EOL_CHAR(tty), ldata->char_map);
1823 12 : if (L_IEXTEN(tty)) {
1824 12 : set_bit(WERASE_CHAR(tty), ldata->char_map);
1825 12 : set_bit(LNEXT_CHAR(tty), ldata->char_map);
1826 12 : set_bit(EOL2_CHAR(tty), ldata->char_map);
1827 12 : if (L_ECHO(tty))
1828 12 : set_bit(REPRINT_CHAR(tty),
1829 12 : ldata->char_map);
1830 12 : }
1831 12 : }
1832 12 : if (I_IXON(tty)) {
1833 12 : set_bit(START_CHAR(tty), ldata->char_map);
1834 12 : set_bit(STOP_CHAR(tty), ldata->char_map);
1835 12 : }
1836 12 : if (L_ISIG(tty)) {
1837 12 : set_bit(INTR_CHAR(tty), ldata->char_map);
1838 12 : set_bit(QUIT_CHAR(tty), ldata->char_map);
1839 12 : set_bit(SUSP_CHAR(tty), ldata->char_map);
1840 12 : }
1841 12 : clear_bit(__DISABLED_CHAR, ldata->char_map);
1842 12 : ldata->raw = 0;
1843 12 : ldata->real_raw = 0;
1844 12 : } else {
1845 0 : ldata->raw = 1;
1846 0 : if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1847 0 : (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1848 0 : (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1849 0 : ldata->real_raw = 1;
1850 : else
1851 0 : ldata->real_raw = 0;
1852 : }
1853 : /*
1854 : * Fix tty hang when I_IXON(tty) is cleared, but the tty
1855 : * been stopped by STOP_CHAR(tty) before it.
1856 : */
1857 12 : if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow.tco_stopped) {
1858 0 : start_tty(tty);
1859 0 : process_echoes(tty);
1860 0 : }
1861 :
1862 : /* The termios change make the tty ready for I/O */
1863 12 : wake_up_interruptible(&tty->write_wait);
1864 12 : wake_up_interruptible(&tty->read_wait);
1865 12 : }
1866 :
1867 : /**
1868 : * n_tty_close - close the ldisc for this tty
1869 : * @tty: device
1870 : *
1871 : * Called from the terminal layer when this line discipline is being shut down,
1872 : * either because of a close or becsuse of a discipline change. The function
1873 : * will not be called while other ldisc methods are in progress.
1874 : */
1875 6 : static void n_tty_close(struct tty_struct *tty)
1876 : {
1877 6 : struct n_tty_data *ldata = tty->disc_data;
1878 :
1879 6 : if (tty->link)
1880 0 : n_tty_packet_mode_flush(tty);
1881 :
1882 6 : down_write(&tty->termios_rwsem);
1883 6 : vfree(ldata);
1884 6 : tty->disc_data = NULL;
1885 6 : up_write(&tty->termios_rwsem);
1886 6 : }
1887 :
1888 : /**
1889 : * n_tty_open - open an ldisc
1890 : * @tty: terminal to open
1891 : *
1892 : * Called when this line discipline is being attached to the terminal device.
1893 : * Can sleep. Called serialized so that no other events will occur in parallel.
1894 : * No further open will occur until a close.
1895 : */
1896 12 : static int n_tty_open(struct tty_struct *tty)
1897 : {
1898 12 : struct n_tty_data *ldata;
1899 :
1900 : /* Currently a malloc failure here can panic */
1901 12 : ldata = vzalloc(sizeof(*ldata));
1902 12 : if (!ldata)
1903 0 : return -ENOMEM;
1904 :
1905 12 : ldata->overrun_time = jiffies;
1906 12 : mutex_init(&ldata->atomic_read_lock);
1907 12 : mutex_init(&ldata->output_lock);
1908 :
1909 12 : tty->disc_data = ldata;
1910 12 : tty->closing = 0;
1911 : /* indicate buffer work may resume */
1912 12 : clear_bit(TTY_LDISC_HALTED, &tty->flags);
1913 12 : n_tty_set_termios(tty, NULL);
1914 12 : tty_unthrottle(tty);
1915 12 : return 0;
1916 12 : }
1917 :
1918 172 : static inline int input_available_p(const struct tty_struct *tty, int poll)
1919 : {
1920 172 : const struct n_tty_data *ldata = tty->disc_data;
1921 172 : int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1922 :
1923 172 : if (ldata->icanon && !L_EXTPROC(tty))
1924 0 : return ldata->canon_head != ldata->read_tail;
1925 : else
1926 172 : return ldata->commit_head - ldata->read_tail >= amt;
1927 172 : }
1928 :
1929 : /**
1930 : * copy_from_read_buf - copy read data directly
1931 : * @tty: terminal device
1932 : * @kbp: data
1933 : * @nr: size of data
1934 : *
1935 : * Helper function to speed up n_tty_read(). It is only called when %ICANON is
1936 : * off; it copies characters straight from the tty queue.
1937 : *
1938 : * Returns: true if it successfully copied data, but there is still more data
1939 : * to be had.
1940 : *
1941 : * Locking:
1942 : * * called under the @ldata->atomic_read_lock sem
1943 : * * n_tty_read()/consumer path:
1944 : * caller holds non-exclusive %termios_rwsem;
1945 : * read_tail published
1946 : */
1947 25 : static bool copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
1948 : size_t *nr)
1949 :
1950 : {
1951 25 : struct n_tty_data *ldata = tty->disc_data;
1952 25 : size_t n;
1953 25 : bool is_eof;
1954 25 : size_t head = smp_load_acquire(&ldata->commit_head);
1955 25 : size_t tail = MASK(ldata->read_tail);
1956 :
1957 25 : n = min3(head - ldata->read_tail, N_TTY_BUF_SIZE - tail, *nr);
1958 25 : if (!n)
1959 0 : return false;
1960 :
1961 25 : u8 *from = read_buf_addr(ldata, tail);
1962 25 : memcpy(*kbp, from, n);
1963 25 : is_eof = n == 1 && *from == EOF_CHAR(tty);
1964 25 : tty_audit_add_data(tty, from, n);
1965 25 : zero_buffer(tty, from, n);
1966 25 : smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1967 :
1968 : /* Turn single EOF into zero-length read */
1969 25 : if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1970 0 : head == ldata->read_tail)
1971 0 : return false;
1972 :
1973 25 : *kbp += n;
1974 25 : *nr -= n;
1975 :
1976 : /* If we have more to copy, let the caller know */
1977 25 : return head != ldata->read_tail;
1978 25 : }
1979 :
1980 : /**
1981 : * canon_copy_from_read_buf - copy read data in canonical mode
1982 : * @tty: terminal device
1983 : * @kbp: data
1984 : * @nr: size of data
1985 : *
1986 : * Helper function for n_tty_read(). It is only called when %ICANON is on; it
1987 : * copies one line of input up to and including the line-delimiting character
1988 : * into the result buffer.
1989 : *
1990 : * Note: When termios is changed from non-canonical to canonical mode and the
1991 : * read buffer contains data, n_tty_set_termios() simulates an EOF push (as if
1992 : * C-d were input) _without_ the %DISABLED_CHAR in the buffer. This causes data
1993 : * already processed as input to be immediately available as input although a
1994 : * newline has not been received.
1995 : *
1996 : * Locking:
1997 : * * called under the %atomic_read_lock mutex
1998 : * * n_tty_read()/consumer path:
1999 : * caller holds non-exclusive %termios_rwsem;
2000 : * read_tail published
2001 : */
2002 0 : static bool canon_copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
2003 : size_t *nr)
2004 : {
2005 0 : struct n_tty_data *ldata = tty->disc_data;
2006 0 : size_t n, size, more, c;
2007 0 : size_t eol;
2008 0 : size_t tail, canon_head;
2009 0 : int found = 0;
2010 :
2011 : /* N.B. avoid overrun if nr == 0 */
2012 0 : if (!*nr)
2013 0 : return false;
2014 :
2015 0 : canon_head = smp_load_acquire(&ldata->canon_head);
2016 0 : n = min(*nr, canon_head - ldata->read_tail);
2017 :
2018 0 : tail = MASK(ldata->read_tail);
2019 0 : size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2020 :
2021 0 : eol = find_next_bit(ldata->read_flags, size, tail);
2022 0 : more = n - (size - tail);
2023 0 : if (eol == N_TTY_BUF_SIZE && more) {
2024 : /* scan wrapped without finding set bit */
2025 0 : eol = find_first_bit(ldata->read_flags, more);
2026 0 : found = eol != more;
2027 0 : } else
2028 0 : found = eol != size;
2029 :
2030 0 : n = eol - tail;
2031 0 : if (n > N_TTY_BUF_SIZE)
2032 0 : n += N_TTY_BUF_SIZE;
2033 0 : c = n + found;
2034 :
2035 0 : if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
2036 0 : n = c;
2037 :
2038 0 : tty_copy(tty, *kbp, tail, n);
2039 0 : *kbp += n;
2040 0 : *nr -= n;
2041 :
2042 0 : if (found)
2043 0 : clear_bit(eol, ldata->read_flags);
2044 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2045 :
2046 0 : if (found) {
2047 0 : if (!ldata->push)
2048 0 : ldata->line_start = ldata->read_tail;
2049 : else
2050 0 : ldata->push = 0;
2051 0 : tty_audit_push();
2052 0 : return false;
2053 : }
2054 :
2055 : /* No EOL found - do a continuation retry if there is more data */
2056 0 : return ldata->read_tail != canon_head;
2057 0 : }
2058 :
2059 : /*
2060 : * If we finished a read at the exact location of an
2061 : * EOF (special EOL character that's a __DISABLED_CHAR)
2062 : * in the stream, silently eat the EOF.
2063 : */
2064 0 : static void canon_skip_eof(struct n_tty_data *ldata)
2065 : {
2066 0 : size_t tail, canon_head;
2067 :
2068 0 : canon_head = smp_load_acquire(&ldata->canon_head);
2069 0 : tail = ldata->read_tail;
2070 :
2071 : // No data?
2072 0 : if (tail == canon_head)
2073 0 : return;
2074 :
2075 : // See if the tail position is EOF in the circular buffer
2076 0 : tail &= (N_TTY_BUF_SIZE - 1);
2077 0 : if (!test_bit(tail, ldata->read_flags))
2078 0 : return;
2079 0 : if (read_buf(ldata, tail) != __DISABLED_CHAR)
2080 0 : return;
2081 :
2082 : // Clear the EOL bit, skip the EOF char.
2083 0 : clear_bit(tail, ldata->read_flags);
2084 0 : smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2085 0 : }
2086 :
2087 : /**
2088 : * job_control - check job control
2089 : * @tty: tty
2090 : * @file: file handle
2091 : *
2092 : * Perform job control management checks on this @file/@tty descriptor and if
2093 : * appropriate send any needed signals and return a negative error code if
2094 : * action should be taken.
2095 : *
2096 : * Locking:
2097 : * * redirected write test is safe
2098 : * * current->signal->tty check is safe
2099 : * * ctrl.lock to safely reference @tty->ctrl.pgrp
2100 : */
2101 12 : static int job_control(struct tty_struct *tty, struct file *file)
2102 : {
2103 : /* Job control check -- must be done at start and after
2104 : every sleep (POSIX.1 7.1.1.4). */
2105 : /* NOTE: not yet done after every sleep pending a thorough
2106 : check of the logic of this change. -- jlc */
2107 : /* don't stop on /dev/console */
2108 12 : if (file->f_op->write_iter == redirected_tty_write)
2109 0 : return 0;
2110 :
2111 12 : return __tty_check_change(tty, SIGTTIN);
2112 12 : }
2113 :
2114 : /*
2115 : * We still hold the atomic_read_lock and the termios_rwsem, and can just
2116 : * continue to copy data.
2117 : */
2118 13 : static ssize_t n_tty_continue_cookie(struct tty_struct *tty, u8 *kbuf,
2119 : size_t nr, void **cookie)
2120 : {
2121 13 : struct n_tty_data *ldata = tty->disc_data;
2122 13 : u8 *kb = kbuf;
2123 :
2124 13 : if (ldata->icanon && !L_EXTPROC(tty)) {
2125 : /*
2126 : * If we have filled the user buffer, see if we should skip an
2127 : * EOF character before releasing the lock and returning done.
2128 : */
2129 0 : if (!nr)
2130 0 : canon_skip_eof(ldata);
2131 0 : else if (canon_copy_from_read_buf(tty, &kb, &nr))
2132 0 : return kb - kbuf;
2133 0 : } else {
2134 13 : if (copy_from_read_buf(tty, &kb, &nr))
2135 10 : return kb - kbuf;
2136 : }
2137 :
2138 : /* No more data - release locks and stop retries */
2139 3 : n_tty_kick_worker(tty);
2140 3 : n_tty_check_unthrottle(tty);
2141 3 : up_read(&tty->termios_rwsem);
2142 3 : mutex_unlock(&ldata->atomic_read_lock);
2143 3 : *cookie = NULL;
2144 :
2145 3 : return kb - kbuf;
2146 13 : }
2147 :
2148 0 : static int n_tty_wait_for_input(struct tty_struct *tty, struct file *file,
2149 : struct wait_queue_entry *wait, long *timeout)
2150 : {
2151 0 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2152 0 : return -EIO;
2153 0 : if (tty_hung_up_p(file))
2154 0 : return 0;
2155 : /*
2156 : * Abort readers for ttys which never actually get hung up.
2157 : * See __tty_hangup().
2158 : */
2159 0 : if (test_bit(TTY_HUPPING, &tty->flags))
2160 0 : return 0;
2161 0 : if (!*timeout)
2162 0 : return 0;
2163 0 : if (tty_io_nonblock(tty, file))
2164 0 : return -EAGAIN;
2165 0 : if (signal_pending(current))
2166 0 : return -ERESTARTSYS;
2167 :
2168 0 : up_read(&tty->termios_rwsem);
2169 0 : *timeout = wait_woken(wait, TASK_INTERRUPTIBLE, *timeout);
2170 0 : down_read(&tty->termios_rwsem);
2171 :
2172 0 : return 1;
2173 0 : }
2174 :
2175 : /**
2176 : * n_tty_read - read function for tty
2177 : * @tty: tty device
2178 : * @file: file object
2179 : * @kbuf: kernelspace buffer pointer
2180 : * @nr: size of I/O
2181 : * @cookie: if non-%NULL, this is a continuation read
2182 : * @offset: where to continue reading from (unused in n_tty)
2183 : *
2184 : * Perform reads for the line discipline. We are guaranteed that the line
2185 : * discipline will not be closed under us but we may get multiple parallel
2186 : * readers and must handle this ourselves. We may also get a hangup. Always
2187 : * called in user context, may sleep.
2188 : *
2189 : * This code must be sure never to sleep through a hangup.
2190 : *
2191 : * Locking: n_tty_read()/consumer path:
2192 : * claims non-exclusive termios_rwsem;
2193 : * publishes read_tail
2194 : */
2195 25 : static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
2196 : size_t nr, void **cookie, unsigned long offset)
2197 : {
2198 25 : struct n_tty_data *ldata = tty->disc_data;
2199 25 : u8 *kb = kbuf;
2200 25 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2201 25 : int minimum, time;
2202 25 : ssize_t retval;
2203 25 : long timeout;
2204 25 : bool packet;
2205 25 : size_t old_tail;
2206 :
2207 : /* Is this a continuation of a read started earlier? */
2208 25 : if (*cookie)
2209 13 : return n_tty_continue_cookie(tty, kbuf, nr, cookie);
2210 :
2211 12 : retval = job_control(tty, file);
2212 12 : if (retval < 0)
2213 0 : return retval;
2214 :
2215 : /*
2216 : * Internal serialization of reads.
2217 : */
2218 12 : if (file->f_flags & O_NONBLOCK) {
2219 12 : if (!mutex_trylock(&ldata->atomic_read_lock))
2220 0 : return -EAGAIN;
2221 12 : } else {
2222 0 : if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2223 0 : return -ERESTARTSYS;
2224 : }
2225 :
2226 12 : down_read(&tty->termios_rwsem);
2227 :
2228 12 : minimum = time = 0;
2229 12 : timeout = MAX_SCHEDULE_TIMEOUT;
2230 12 : if (!ldata->icanon) {
2231 12 : minimum = MIN_CHAR(tty);
2232 12 : if (minimum) {
2233 12 : time = (HZ / 10) * TIME_CHAR(tty);
2234 12 : } else {
2235 0 : timeout = (HZ / 10) * TIME_CHAR(tty);
2236 0 : minimum = 1;
2237 : }
2238 12 : }
2239 :
2240 12 : packet = tty->ctrl.packet;
2241 12 : old_tail = ldata->read_tail;
2242 :
2243 12 : add_wait_queue(&tty->read_wait, &wait);
2244 12 : while (nr) {
2245 : /* First test for status change. */
2246 12 : if (packet && tty->link->ctrl.pktstatus) {
2247 0 : u8 cs;
2248 0 : if (kb != kbuf)
2249 0 : break;
2250 0 : spin_lock_irq(&tty->link->ctrl.lock);
2251 0 : cs = tty->link->ctrl.pktstatus;
2252 0 : tty->link->ctrl.pktstatus = 0;
2253 0 : spin_unlock_irq(&tty->link->ctrl.lock);
2254 0 : *kb++ = cs;
2255 0 : nr--;
2256 0 : break;
2257 0 : }
2258 :
2259 12 : if (!input_available_p(tty, 0)) {
2260 0 : up_read(&tty->termios_rwsem);
2261 0 : tty_buffer_flush_work(tty->port);
2262 0 : down_read(&tty->termios_rwsem);
2263 0 : if (!input_available_p(tty, 0)) {
2264 0 : int ret = n_tty_wait_for_input(tty, file, &wait,
2265 : &timeout);
2266 0 : if (ret <= 0) {
2267 0 : retval = ret;
2268 0 : break;
2269 : }
2270 0 : continue;
2271 0 : }
2272 0 : }
2273 :
2274 12 : if (ldata->icanon && !L_EXTPROC(tty)) {
2275 0 : if (canon_copy_from_read_buf(tty, &kb, &nr))
2276 0 : goto more_to_be_read;
2277 0 : } else {
2278 : /* Deal with packet mode. */
2279 12 : if (packet && kb == kbuf) {
2280 0 : *kb++ = TIOCPKT_DATA;
2281 0 : nr--;
2282 0 : }
2283 :
2284 12 : if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum)
2285 3 : goto more_to_be_read;
2286 : }
2287 :
2288 9 : n_tty_check_unthrottle(tty);
2289 :
2290 9 : if (kb - kbuf >= minimum)
2291 9 : break;
2292 0 : if (time)
2293 0 : timeout = time;
2294 : }
2295 9 : if (old_tail != ldata->read_tail) {
2296 : /*
2297 : * Make sure no_room is not read in n_tty_kick_worker()
2298 : * before setting ldata->read_tail in copy_from_read_buf().
2299 : */
2300 9 : smp_mb();
2301 9 : n_tty_kick_worker(tty);
2302 9 : }
2303 9 : up_read(&tty->termios_rwsem);
2304 :
2305 9 : remove_wait_queue(&tty->read_wait, &wait);
2306 9 : mutex_unlock(&ldata->atomic_read_lock);
2307 :
2308 9 : if (kb - kbuf)
2309 9 : retval = kb - kbuf;
2310 :
2311 9 : return retval;
2312 : more_to_be_read:
2313 : /*
2314 : * There is more to be had and we have nothing more to wait for, so
2315 : * let's mark us for retries.
2316 : *
2317 : * NOTE! We return here with both the termios_sem and atomic_read_lock
2318 : * still held, the retries will release them when done.
2319 : */
2320 3 : remove_wait_queue(&tty->read_wait, &wait);
2321 3 : *cookie = cookie;
2322 :
2323 3 : return kb - kbuf;
2324 25 : }
2325 :
2326 : /**
2327 : * n_tty_write - write function for tty
2328 : * @tty: tty device
2329 : * @file: file object
2330 : * @buf: userspace buffer pointer
2331 : * @nr: size of I/O
2332 : *
2333 : * Write function of the terminal device. This is serialized with respect to
2334 : * other write callers but not to termios changes, reads and other such events.
2335 : * Since the receive code will echo characters, thus calling driver write
2336 : * methods, the %output_lock is used in the output processing functions called
2337 : * here as well as in the echo processing function to protect the column state
2338 : * and space left in the buffer.
2339 : *
2340 : * This code must be sure never to sleep through a hangup.
2341 : *
2342 : * Locking: output_lock to protect column state and space left
2343 : * (note that the process_output*() functions take this lock themselves)
2344 : */
2345 :
2346 44 : static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2347 : const u8 *buf, size_t nr)
2348 : {
2349 44 : const u8 *b = buf;
2350 44 : DEFINE_WAIT_FUNC(wait, woken_wake_function);
2351 44 : ssize_t num, retval = 0;
2352 :
2353 : /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2354 44 : if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2355 0 : retval = tty_check_change(tty);
2356 0 : if (retval)
2357 0 : return retval;
2358 0 : }
2359 :
2360 44 : down_read(&tty->termios_rwsem);
2361 :
2362 : /* Write out any echoed characters that are still pending */
2363 44 : process_echoes(tty);
2364 :
2365 44 : add_wait_queue(&tty->write_wait, &wait);
2366 90 : while (1) {
2367 45 : if (signal_pending(current)) {
2368 0 : retval = -ERESTARTSYS;
2369 0 : break;
2370 : }
2371 45 : if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2372 2 : retval = -EIO;
2373 2 : break;
2374 : }
2375 45 : if (O_OPOST(tty)) {
2376 58 : while (nr > 0) {
2377 31 : num = process_output_block(tty, b, nr);
2378 31 : if (num < 0) {
2379 0 : if (num == -EAGAIN)
2380 0 : break;
2381 0 : retval = num;
2382 0 : goto break_out;
2383 : }
2384 31 : b += num;
2385 31 : nr -= num;
2386 31 : if (nr == 0)
2387 4 : break;
2388 27 : if (process_output(*b, tty) < 0)
2389 0 : break;
2390 27 : b++; nr--;
2391 : }
2392 31 : if (tty->ops->flush_chars)
2393 0 : tty->ops->flush_chars(tty);
2394 31 : } else {
2395 14 : struct n_tty_data *ldata = tty->disc_data;
2396 :
2397 28 : while (nr > 0) {
2398 14 : mutex_lock(&ldata->output_lock);
2399 14 : num = tty->ops->write(tty, b, nr);
2400 14 : mutex_unlock(&ldata->output_lock);
2401 14 : if (num < 0) {
2402 0 : retval = num;
2403 0 : goto break_out;
2404 : }
2405 14 : if (!num)
2406 0 : break;
2407 14 : b += num;
2408 14 : nr -= num;
2409 : }
2410 14 : }
2411 46 : if (!nr)
2412 45 : break;
2413 1 : if (tty_io_nonblock(tty, file)) {
2414 0 : retval = -EAGAIN;
2415 0 : break;
2416 : }
2417 1 : up_read(&tty->termios_rwsem);
2418 :
2419 1 : wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2420 :
2421 1 : down_read(&tty->termios_rwsem);
2422 : }
2423 : break_out:
2424 45 : remove_wait_queue(&tty->write_wait, &wait);
2425 45 : if (nr && tty->fasync)
2426 0 : set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2427 45 : up_read(&tty->termios_rwsem);
2428 45 : return (b - buf) ? b - buf : retval;
2429 46 : }
2430 :
2431 : /**
2432 : * n_tty_poll - poll method for N_TTY
2433 : * @tty: terminal device
2434 : * @file: file accessing it
2435 : * @wait: poll table
2436 : *
2437 : * Called when the line discipline is asked to poll() for data or for special
2438 : * events. This code is not serialized with respect to other events save
2439 : * open/close.
2440 : *
2441 : * This code must be sure never to sleep through a hangup.
2442 : *
2443 : * Locking: called without the kernel lock held -- fine.
2444 : */
2445 86 : static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2446 : poll_table *wait)
2447 : {
2448 86 : __poll_t mask = 0;
2449 :
2450 86 : poll_wait(file, &tty->read_wait, wait);
2451 86 : poll_wait(file, &tty->write_wait, wait);
2452 86 : if (input_available_p(tty, 1))
2453 12 : mask |= EPOLLIN | EPOLLRDNORM;
2454 : else {
2455 74 : tty_buffer_flush_work(tty->port);
2456 74 : if (input_available_p(tty, 1))
2457 0 : mask |= EPOLLIN | EPOLLRDNORM;
2458 : }
2459 86 : if (tty->ctrl.packet && tty->link->ctrl.pktstatus)
2460 0 : mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2461 86 : if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2462 0 : mask |= EPOLLHUP;
2463 86 : if (tty_hung_up_p(file))
2464 0 : mask |= EPOLLHUP;
2465 86 : if (tty->ops->write && !tty_is_writelocked(tty) &&
2466 86 : tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2467 85 : tty_write_room(tty) > 0)
2468 85 : mask |= EPOLLOUT | EPOLLWRNORM;
2469 172 : return mask;
2470 86 : }
2471 :
2472 0 : static unsigned long inq_canon(struct n_tty_data *ldata)
2473 : {
2474 0 : size_t nr, head, tail;
2475 :
2476 0 : if (ldata->canon_head == ldata->read_tail)
2477 0 : return 0;
2478 0 : head = ldata->canon_head;
2479 0 : tail = ldata->read_tail;
2480 0 : nr = head - tail;
2481 : /* Skip EOF-chars.. */
2482 0 : while (MASK(head) != MASK(tail)) {
2483 0 : if (test_bit(MASK(tail), ldata->read_flags) &&
2484 0 : read_buf(ldata, tail) == __DISABLED_CHAR)
2485 0 : nr--;
2486 0 : tail++;
2487 : }
2488 0 : return nr;
2489 0 : }
2490 :
2491 18 : static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
2492 : unsigned long arg)
2493 : {
2494 18 : struct n_tty_data *ldata = tty->disc_data;
2495 18 : unsigned int num;
2496 :
2497 18 : switch (cmd) {
2498 : case TIOCOUTQ:
2499 0 : return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2500 : case TIOCINQ:
2501 0 : down_write(&tty->termios_rwsem);
2502 0 : if (L_ICANON(tty) && !L_EXTPROC(tty))
2503 0 : num = inq_canon(ldata);
2504 : else
2505 0 : num = read_cnt(ldata);
2506 0 : up_write(&tty->termios_rwsem);
2507 0 : return put_user(num, (unsigned int __user *) arg);
2508 : default:
2509 18 : return n_tty_ioctl_helper(tty, cmd, arg);
2510 : }
2511 18 : }
2512 :
2513 : static struct tty_ldisc_ops n_tty_ops = {
2514 : .owner = THIS_MODULE,
2515 : .num = N_TTY,
2516 : .name = "n_tty",
2517 : .open = n_tty_open,
2518 : .close = n_tty_close,
2519 : .flush_buffer = n_tty_flush_buffer,
2520 : .read = n_tty_read,
2521 : .write = n_tty_write,
2522 : .ioctl = n_tty_ioctl,
2523 : .set_termios = n_tty_set_termios,
2524 : .poll = n_tty_poll,
2525 : .receive_buf = n_tty_receive_buf,
2526 : .write_wakeup = n_tty_write_wakeup,
2527 : .receive_buf2 = n_tty_receive_buf2,
2528 : .lookahead_buf = n_tty_lookahead_flow_ctrl,
2529 : };
2530 :
2531 : /**
2532 : * n_tty_inherit_ops - inherit N_TTY methods
2533 : * @ops: struct tty_ldisc_ops where to save N_TTY methods
2534 : *
2535 : * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2536 : */
2537 :
2538 0 : void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2539 : {
2540 0 : *ops = n_tty_ops;
2541 0 : ops->owner = NULL;
2542 0 : }
2543 : EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2544 :
2545 0 : void __init n_tty_init(void)
2546 : {
2547 0 : tty_register_ldisc(&n_tty_ops);
2548 0 : }
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