1 // SPDX-License-Identifier: GPL-1.0+
3 * n_tty.c --- implements the N_TTY line discipline.
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,
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.
14 * Written by Theodore Ts'o, Copyright 1994.
16 * This file also contains code originally written by Linus Torvalds,
17 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
19 * Reduced memory usage for older ARM systems - Russell King.
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.
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
31 #include <linux/types.h>
32 #include <linux/major.h>
33 #include <linux/errno.h>
34 #include <linux/signal.h>
35 #include <linux/fcntl.h>
36 #include <linux/sched.h>
37 #include <linux/interrupt.h>
38 #include <linux/tty.h>
39 #include <linux/timer.h>
40 #include <linux/ctype.h>
42 #include <linux/string.h>
43 #include <linux/slab.h>
44 #include <linux/poll.h>
45 #include <linux/bitops.h>
46 #include <linux/audit.h>
47 #include <linux/file.h>
48 #include <linux/uaccess.h>
49 #include <linux/module.h>
50 #include <linux/ratelimit.h>
51 #include <linux/vmalloc.h>
55 * Until this number of characters is queued in the xmit buffer, select will
56 * return "we have room for writes".
58 #define WAKEUP_CHARS 256
61 * This defines the low- and high-watermarks for throttling and
62 * unthrottling the TTY driver. These watermarks are used for
63 * controlling the space in the read buffer.
65 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
66 #define TTY_THRESHOLD_UNTHROTTLE 128
69 * Special byte codes used in the echo buffer to represent operations
70 * or special handling of characters. Bytes in the echo buffer that
71 * are not part of such special blocks are treated as normal character
74 #define ECHO_OP_START 0xff
75 #define ECHO_OP_MOVE_BACK_COL 0x80
76 #define ECHO_OP_SET_CANON_COL 0x81
77 #define ECHO_OP_ERASE_TAB 0x82
79 #define ECHO_COMMIT_WATERMARK 256
80 #define ECHO_BLOCK 256
81 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
86 # define n_tty_trace(f, args...) trace_printk(f, ##args)
88 # define n_tty_trace(f, args...) no_printk(f, ##args)
92 /* producer-published */
99 DECLARE_BITMAP(char_map, 256);
101 /* private to n_tty_receive_overrun (single-threaded) */
102 unsigned long overrun_time;
108 /* must hold exclusive termios_rwsem to reset these */
109 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
110 unsigned char push:1;
112 /* shared by producer and consumer */
113 char read_buf[N_TTY_BUF_SIZE];
114 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
115 unsigned char echo_buf[N_TTY_BUF_SIZE];
117 /* consumer-published */
121 /* protected by output lock */
123 unsigned int canon_column;
126 struct mutex atomic_read_lock;
127 struct mutex output_lock;
130 #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
132 static inline size_t read_cnt(struct n_tty_data *ldata)
134 return ldata->read_head - ldata->read_tail;
137 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
139 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
142 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
144 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
147 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
149 smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
150 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
153 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
155 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
158 /* If we are not echoing the data, perhaps this is a secret so erase it */
159 static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
161 bool icanon = !!L_ICANON(tty);
162 bool no_echo = !L_ECHO(tty);
164 if (icanon && no_echo)
165 memset(buffer, 0x00, size);
168 static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
170 struct n_tty_data *ldata = tty->disc_data;
171 size_t size = N_TTY_BUF_SIZE - tail;
172 void *from = read_buf_addr(ldata, tail);
175 tty_audit_add_data(tty, from, size);
176 memcpy(to, from, size);
177 zero_buffer(tty, from, size);
180 from = ldata->read_buf;
183 tty_audit_add_data(tty, from, n);
185 zero_buffer(tty, from, n);
189 * n_tty_kick_worker - start input worker (if required)
192 * Re-schedules the flip buffer work if it may have stopped
194 * Caller holds exclusive termios_rwsem
196 * n_tty_read()/consumer path:
197 * holds non-exclusive termios_rwsem
200 static void n_tty_kick_worker(struct tty_struct *tty)
202 struct n_tty_data *ldata = tty->disc_data;
204 /* Did the input worker stop? Restart it */
205 if (unlikely(ldata->no_room)) {
208 WARN_RATELIMIT(tty->port->itty == NULL,
209 "scheduling with invalid itty\n");
210 /* see if ldisc has been killed - if so, this means that
211 * even though the ldisc has been halted and ->buf.work
212 * cancelled, ->buf.work is about to be rescheduled
214 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
215 "scheduling buffer work for halted ldisc\n");
216 tty_buffer_restart_work(tty->port);
220 static ssize_t chars_in_buffer(struct tty_struct *tty)
222 struct n_tty_data *ldata = tty->disc_data;
226 n = ldata->commit_head - ldata->read_tail;
228 n = ldata->canon_head - ldata->read_tail;
233 * n_tty_write_wakeup - asynchronous I/O notifier
236 * Required for the ptys, serial driver etc. since processes
237 * that attach themselves to the master and rely on ASYNC
238 * IO must be woken up
241 static void n_tty_write_wakeup(struct tty_struct *tty)
243 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
244 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
247 static void n_tty_check_throttle(struct tty_struct *tty)
249 struct n_tty_data *ldata = tty->disc_data;
252 * Check the remaining room for the input canonicalization
253 * mode. We don't want to throttle the driver if we're in
254 * canonical mode and don't have a newline yet!
256 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
261 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
262 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
264 throttled = tty_throttle_safe(tty);
268 __tty_set_flow_change(tty, 0);
271 static void n_tty_check_unthrottle(struct tty_struct *tty)
273 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
274 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
276 n_tty_kick_worker(tty);
277 tty_wakeup(tty->link);
281 /* If there is enough space in the read buffer now, let the
282 * low-level driver know. We use chars_in_buffer() to
283 * check the buffer, as it now knows about canonical mode.
284 * Otherwise, if the driver is throttled and the line is
285 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
286 * we won't get any more characters.
291 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
292 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
294 n_tty_kick_worker(tty);
295 unthrottled = tty_unthrottle_safe(tty);
299 __tty_set_flow_change(tty, 0);
303 * put_tty_queue - add character to tty
307 * Add a character to the tty read_buf queue.
309 * n_tty_receive_buf()/producer path:
310 * caller holds non-exclusive termios_rwsem
313 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
315 *read_buf_addr(ldata, ldata->read_head) = c;
320 * reset_buffer_flags - reset buffer state
321 * @ldata: line disc data to reset
323 * Reset the read buffer counters and clear the flags.
324 * Called from n_tty_open() and n_tty_flush_buffer().
326 * Locking: caller holds exclusive termios_rwsem
327 * (or locking is not required)
330 static void reset_buffer_flags(struct n_tty_data *ldata)
332 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
333 ldata->commit_head = 0;
334 ldata->line_start = 0;
337 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
341 static void n_tty_packet_mode_flush(struct tty_struct *tty)
345 if (tty->link->packet) {
346 spin_lock_irqsave(&tty->ctrl_lock, flags);
347 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
348 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
349 wake_up_interruptible(&tty->link->read_wait);
354 * n_tty_flush_buffer - clean input queue
355 * @tty: terminal device
357 * Flush the input buffer. Called when the tty layer wants the
358 * buffer flushed (eg at hangup) or when the N_TTY line discipline
359 * internally has to clean the pending queue (for example some signals).
361 * Holds termios_rwsem to exclude producer/consumer while
362 * buffer indices are reset.
364 * Locking: ctrl_lock, exclusive termios_rwsem
367 static void n_tty_flush_buffer(struct tty_struct *tty)
369 down_write(&tty->termios_rwsem);
370 reset_buffer_flags(tty->disc_data);
371 n_tty_kick_worker(tty);
374 n_tty_packet_mode_flush(tty);
375 up_write(&tty->termios_rwsem);
379 * is_utf8_continuation - utf8 multibyte check
382 * Returns true if the utf8 character 'c' is a multibyte continuation
383 * character. We use this to correctly compute the on screen size
384 * of the character when printing
387 static inline int is_utf8_continuation(unsigned char c)
389 return (c & 0xc0) == 0x80;
393 * is_continuation - multibyte check
395 * @tty: terminal device
397 * Returns true if the utf8 character 'c' is a multibyte continuation
398 * character and the terminal is in unicode mode.
401 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
403 return I_IUTF8(tty) && is_utf8_continuation(c);
407 * do_output_char - output one character
408 * @c: character (or partial unicode symbol)
409 * @tty: terminal device
410 * @space: space available in tty driver write buffer
412 * This is a helper function that handles one output character
413 * (including special characters like TAB, CR, LF, etc.),
414 * doing OPOST processing and putting the results in the
415 * tty driver's write buffer.
417 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
418 * and NLDLY. They simply aren't relevant in the world today.
419 * If you ever need them, add them here.
421 * Returns the number of bytes of buffer space used or -1 if
424 * Locking: should be called under the output_lock to protect
425 * the column state and space left in the buffer
428 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
430 struct n_tty_data *ldata = tty->disc_data;
443 ldata->canon_column = ldata->column = 0;
444 tty->ops->write(tty, "\r\n", 2);
447 ldata->canon_column = ldata->column;
450 if (O_ONOCR(tty) && ldata->column == 0)
455 ldata->canon_column = ldata->column = 0;
458 ldata->canon_column = ldata->column = 0;
461 spaces = 8 - (ldata->column & 7);
462 if (O_TABDLY(tty) == XTABS) {
465 ldata->column += spaces;
466 tty->ops->write(tty, " ", spaces);
469 ldata->column += spaces;
472 if (ldata->column > 0)
479 if (!is_continuation(c, tty))
485 tty_put_char(tty, c);
490 * process_output - output post processor
491 * @c: character (or partial unicode symbol)
492 * @tty: terminal device
494 * Output one character with OPOST processing.
495 * Returns -1 when the output device is full and the character
498 * Locking: output_lock to protect column state and space left
499 * (also, this is called from n_tty_write under the
500 * tty layer write lock)
503 static int process_output(unsigned char c, struct tty_struct *tty)
505 struct n_tty_data *ldata = tty->disc_data;
508 mutex_lock(&ldata->output_lock);
510 space = tty_write_room(tty);
511 retval = do_output_char(c, tty, space);
513 mutex_unlock(&ldata->output_lock);
521 * process_output_block - block post processor
522 * @tty: terminal device
523 * @buf: character buffer
524 * @nr: number of bytes to output
526 * Output a block of characters with OPOST processing.
527 * Returns the number of characters output.
529 * This path is used to speed up block console writes, among other
530 * things when processing blocks of output data. It handles only
531 * the simple cases normally found and helps to generate blocks of
532 * symbols for the console driver and thus improve performance.
534 * Locking: output_lock to protect column state and space left
535 * (also, this is called from n_tty_write under the
536 * tty layer write lock)
539 static ssize_t process_output_block(struct tty_struct *tty,
540 const unsigned char *buf, unsigned int nr)
542 struct n_tty_data *ldata = tty->disc_data;
545 const unsigned char *cp;
547 mutex_lock(&ldata->output_lock);
549 space = tty_write_room(tty);
551 mutex_unlock(&ldata->output_lock);
557 for (i = 0, cp = buf; i < nr; i++, cp++) {
558 unsigned char c = *cp;
566 ldata->canon_column = ldata->column;
569 if (O_ONOCR(tty) && ldata->column == 0)
573 ldata->canon_column = ldata->column = 0;
578 if (ldata->column > 0)
585 if (!is_continuation(c, tty))
592 i = tty->ops->write(tty, buf, i);
594 mutex_unlock(&ldata->output_lock);
599 * process_echoes - write pending echo characters
600 * @tty: terminal device
602 * Write previously buffered echo (and other ldisc-generated)
603 * characters to the tty.
605 * Characters generated by the ldisc (including echoes) need to
606 * be buffered because the driver's write buffer can fill during
607 * heavy program output. Echoing straight to the driver will
608 * often fail under these conditions, causing lost characters and
609 * resulting mismatches of ldisc state information.
611 * Since the ldisc state must represent the characters actually sent
612 * to the driver at the time of the write, operations like certain
613 * changes in column state are also saved in the buffer and executed
616 * A circular fifo buffer is used so that the most recent characters
617 * are prioritized. Also, when control characters are echoed with a
618 * prefixed "^", the pair is treated atomically and thus not separated.
620 * Locking: callers must hold output_lock
623 static size_t __process_echoes(struct tty_struct *tty)
625 struct n_tty_data *ldata = tty->disc_data;
626 int space, old_space;
630 old_space = space = tty_write_room(tty);
632 tail = ldata->echo_tail;
633 while (MASK(ldata->echo_commit) != MASK(tail)) {
634 c = echo_buf(ldata, tail);
635 if (c == ECHO_OP_START) {
637 int no_space_left = 0;
640 * Since add_echo_byte() is called without holding
641 * output_lock, we might see only portion of multi-byte
644 if (MASK(ldata->echo_commit) == MASK(tail + 1))
647 * If the buffer byte is the start of a multi-byte
648 * operation, get the next byte, which is either the
649 * op code or a control character value.
651 op = echo_buf(ldata, tail + 1);
654 case ECHO_OP_ERASE_TAB: {
655 unsigned int num_chars, num_bs;
657 if (MASK(ldata->echo_commit) == MASK(tail + 2))
659 num_chars = echo_buf(ldata, tail + 2);
662 * Determine how many columns to go back
663 * in order to erase the tab.
664 * This depends on the number of columns
665 * used by other characters within the tab
666 * area. If this (modulo 8) count is from
667 * the start of input rather than from a
668 * previous tab, we offset by canon column.
669 * Otherwise, tab spacing is normal.
671 if (!(num_chars & 0x80))
672 num_chars += ldata->canon_column;
673 num_bs = 8 - (num_chars & 7);
675 if (num_bs > space) {
681 tty_put_char(tty, '\b');
682 if (ldata->column > 0)
688 case ECHO_OP_SET_CANON_COL:
689 ldata->canon_column = ldata->column;
693 case ECHO_OP_MOVE_BACK_COL:
694 if (ldata->column > 0)
700 /* This is an escaped echo op start code */
705 tty_put_char(tty, ECHO_OP_START);
713 * If the op is not a special byte code,
714 * it is a ctrl char tagged to be echoed
715 * as "^X" (where X is the letter
716 * representing the control char).
717 * Note that we must ensure there is
718 * enough space for the whole ctrl pair.
725 tty_put_char(tty, '^');
726 tty_put_char(tty, op ^ 0100);
736 int retval = do_output_char(c, tty, space);
743 tty_put_char(tty, c);
750 /* If the echo buffer is nearly full (so that the possibility exists
751 * of echo overrun before the next commit), then discard enough
752 * data at the tail to prevent a subsequent overrun */
753 while (ldata->echo_commit > tail &&
754 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
755 if (echo_buf(ldata, tail) == ECHO_OP_START) {
756 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
765 ldata->echo_tail = tail;
766 return old_space - space;
769 static void commit_echoes(struct tty_struct *tty)
771 struct n_tty_data *ldata = tty->disc_data;
772 size_t nr, old, echoed;
775 mutex_lock(&ldata->output_lock);
776 head = ldata->echo_head;
777 ldata->echo_mark = head;
778 old = ldata->echo_commit - ldata->echo_tail;
780 /* Process committed echoes if the accumulated # of bytes
781 * is over the threshold (and try again each time another
782 * block is accumulated) */
783 nr = head - ldata->echo_tail;
784 if (nr < ECHO_COMMIT_WATERMARK ||
785 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
786 mutex_unlock(&ldata->output_lock);
790 ldata->echo_commit = head;
791 echoed = __process_echoes(tty);
792 mutex_unlock(&ldata->output_lock);
794 if (echoed && tty->ops->flush_chars)
795 tty->ops->flush_chars(tty);
798 static void process_echoes(struct tty_struct *tty)
800 struct n_tty_data *ldata = tty->disc_data;
803 if (ldata->echo_mark == ldata->echo_tail)
806 mutex_lock(&ldata->output_lock);
807 ldata->echo_commit = ldata->echo_mark;
808 echoed = __process_echoes(tty);
809 mutex_unlock(&ldata->output_lock);
811 if (echoed && tty->ops->flush_chars)
812 tty->ops->flush_chars(tty);
815 /* NB: echo_mark and echo_head should be equivalent here */
816 static void flush_echoes(struct tty_struct *tty)
818 struct n_tty_data *ldata = tty->disc_data;
820 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
821 ldata->echo_commit == ldata->echo_head)
824 mutex_lock(&ldata->output_lock);
825 ldata->echo_commit = ldata->echo_head;
826 __process_echoes(tty);
827 mutex_unlock(&ldata->output_lock);
831 * add_echo_byte - add a byte to the echo buffer
832 * @c: unicode byte to echo
835 * Add a character or operation byte to the echo buffer.
838 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
840 *echo_buf_addr(ldata, ldata->echo_head) = c;
841 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
846 * echo_move_back_col - add operation to move back a column
849 * Add an operation to the echo buffer to move back one column.
852 static void echo_move_back_col(struct n_tty_data *ldata)
854 add_echo_byte(ECHO_OP_START, ldata);
855 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
859 * echo_set_canon_col - add operation to set the canon column
862 * Add an operation to the echo buffer to set the canon column
863 * to the current column.
866 static void echo_set_canon_col(struct n_tty_data *ldata)
868 add_echo_byte(ECHO_OP_START, ldata);
869 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
873 * echo_erase_tab - add operation to erase a tab
874 * @num_chars: number of character columns already used
875 * @after_tab: true if num_chars starts after a previous tab
878 * Add an operation to the echo buffer to erase a tab.
880 * Called by the eraser function, which knows how many character
881 * columns have been used since either a previous tab or the start
882 * of input. This information will be used later, along with
883 * canon column (if applicable), to go back the correct number
887 static void echo_erase_tab(unsigned int num_chars, int after_tab,
888 struct n_tty_data *ldata)
890 add_echo_byte(ECHO_OP_START, ldata);
891 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
893 /* We only need to know this modulo 8 (tab spacing) */
896 /* Set the high bit as a flag if num_chars is after a previous tab */
900 add_echo_byte(num_chars, ldata);
904 * echo_char_raw - echo a character raw
905 * @c: unicode byte to echo
906 * @ldata: line disc data
908 * Echo user input back onto the screen. This must be called only when
909 * L_ECHO(tty) is true. Called from the driver receive_buf path.
911 * This variant does not treat control characters specially.
914 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
916 if (c == ECHO_OP_START) {
917 add_echo_byte(ECHO_OP_START, ldata);
918 add_echo_byte(ECHO_OP_START, ldata);
920 add_echo_byte(c, ldata);
925 * echo_char - echo a character
926 * @c: unicode byte to echo
927 * @tty: terminal device
929 * Echo user input back onto the screen. This must be called only when
930 * L_ECHO(tty) is true. Called from the driver receive_buf path.
932 * This variant tags control characters to be echoed as "^X"
933 * (where X is the letter representing the control char).
936 static void echo_char(unsigned char c, struct tty_struct *tty)
938 struct n_tty_data *ldata = tty->disc_data;
940 if (c == ECHO_OP_START) {
941 add_echo_byte(ECHO_OP_START, ldata);
942 add_echo_byte(ECHO_OP_START, ldata);
944 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
945 add_echo_byte(ECHO_OP_START, ldata);
946 add_echo_byte(c, ldata);
951 * finish_erasing - complete erase
955 static inline void finish_erasing(struct n_tty_data *ldata)
957 if (ldata->erasing) {
958 echo_char_raw('/', ldata);
964 * eraser - handle erase function
965 * @c: character input
966 * @tty: terminal device
968 * Perform erase and necessary output when an erase character is
969 * present in the stream from the driver layer. Handles the complexities
970 * of UTF-8 multibyte symbols.
972 * n_tty_receive_buf()/producer path:
973 * caller holds non-exclusive termios_rwsem
976 static void eraser(unsigned char c, struct tty_struct *tty)
978 struct n_tty_data *ldata = tty->disc_data;
979 enum { ERASE, WERASE, KILL } kill_type;
984 if (ldata->read_head == ldata->canon_head) {
985 /* process_output('\a', tty); */ /* what do you think? */
988 if (c == ERASE_CHAR(tty))
990 else if (c == WERASE_CHAR(tty))
994 ldata->read_head = ldata->canon_head;
997 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
998 ldata->read_head = ldata->canon_head;
999 finish_erasing(ldata);
1000 echo_char(KILL_CHAR(tty), tty);
1001 /* Add a newline if ECHOK is on and ECHOKE is off. */
1003 echo_char_raw('\n', ldata);
1010 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
1011 head = ldata->read_head;
1013 /* erase a single possibly multibyte character */
1016 c = read_buf(ldata, head);
1017 } while (is_continuation(c, tty) &&
1018 MASK(head) != MASK(ldata->canon_head));
1020 /* do not partially erase */
1021 if (is_continuation(c, tty))
1024 if (kill_type == WERASE) {
1025 /* Equivalent to BSD's ALTWERASE. */
1026 if (isalnum(c) || c == '_')
1028 else if (seen_alnums)
1031 cnt = ldata->read_head - head;
1032 ldata->read_head = head;
1034 if (L_ECHOPRT(tty)) {
1035 if (!ldata->erasing) {
1036 echo_char_raw('\\', ldata);
1039 /* if cnt > 1, output a multi-byte character */
1043 echo_char_raw(read_buf(ldata, head), ldata);
1044 echo_move_back_col(ldata);
1046 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1047 echo_char(ERASE_CHAR(tty), tty);
1048 } else if (c == '\t') {
1049 unsigned int num_chars = 0;
1051 size_t tail = ldata->read_head;
1054 * Count the columns used for characters
1055 * since the start of input or after a
1057 * This info is used to go back the correct
1058 * number of columns.
1060 while (MASK(tail) != MASK(ldata->canon_head)) {
1062 c = read_buf(ldata, tail);
1066 } else if (iscntrl(c)) {
1069 } else if (!is_continuation(c, tty)) {
1073 echo_erase_tab(num_chars, after_tab, ldata);
1075 if (iscntrl(c) && L_ECHOCTL(tty)) {
1076 echo_char_raw('\b', ldata);
1077 echo_char_raw(' ', ldata);
1078 echo_char_raw('\b', ldata);
1080 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1081 echo_char_raw('\b', ldata);
1082 echo_char_raw(' ', ldata);
1083 echo_char_raw('\b', ldata);
1087 if (kill_type == ERASE)
1090 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1091 finish_erasing(ldata);
1095 * isig - handle the ISIG optio
1099 * Called when a signal is being sent due to terminal input.
1100 * Called from the driver receive_buf path so serialized.
1102 * Performs input and output flush if !NOFLSH. In this context, the echo
1103 * buffer is 'output'. The signal is processed first to alert any current
1104 * readers or writers to discontinue and exit their i/o loops.
1106 * Locking: ctrl_lock
1109 static void __isig(int sig, struct tty_struct *tty)
1111 struct pid *tty_pgrp = tty_get_pgrp(tty);
1113 kill_pgrp(tty_pgrp, sig, 1);
1118 static void isig(int sig, struct tty_struct *tty)
1120 struct n_tty_data *ldata = tty->disc_data;
1122 if (L_NOFLSH(tty)) {
1126 } else { /* signal and flush */
1127 up_read(&tty->termios_rwsem);
1128 down_write(&tty->termios_rwsem);
1132 /* clear echo buffer */
1133 mutex_lock(&ldata->output_lock);
1134 ldata->echo_head = ldata->echo_tail = 0;
1135 ldata->echo_mark = ldata->echo_commit = 0;
1136 mutex_unlock(&ldata->output_lock);
1138 /* clear output buffer */
1139 tty_driver_flush_buffer(tty);
1141 /* clear input buffer */
1142 reset_buffer_flags(tty->disc_data);
1144 /* notify pty master of flush */
1146 n_tty_packet_mode_flush(tty);
1148 up_write(&tty->termios_rwsem);
1149 down_read(&tty->termios_rwsem);
1154 * n_tty_receive_break - handle break
1157 * An RS232 break event has been hit in the incoming bitstream. This
1158 * can cause a variety of events depending upon the termios settings.
1160 * n_tty_receive_buf()/producer path:
1161 * caller holds non-exclusive termios_rwsem
1163 * Note: may get exclusive termios_rwsem if flushing input buffer
1166 static void n_tty_receive_break(struct tty_struct *tty)
1168 struct n_tty_data *ldata = tty->disc_data;
1172 if (I_BRKINT(tty)) {
1176 if (I_PARMRK(tty)) {
1177 put_tty_queue('\377', ldata);
1178 put_tty_queue('\0', ldata);
1180 put_tty_queue('\0', ldata);
1184 * n_tty_receive_overrun - handle overrun reporting
1187 * Data arrived faster than we could process it. While the tty
1188 * driver has flagged this the bits that were missed are gone
1191 * Called from the receive_buf path so single threaded. Does not
1192 * need locking as num_overrun and overrun_time are function
1196 static void n_tty_receive_overrun(struct tty_struct *tty)
1198 struct n_tty_data *ldata = tty->disc_data;
1200 ldata->num_overrun++;
1201 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1202 time_after(ldata->overrun_time, jiffies)) {
1203 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1204 ldata->overrun_time = jiffies;
1205 ldata->num_overrun = 0;
1210 * n_tty_receive_parity_error - error notifier
1211 * @tty: terminal device
1214 * Process a parity error and queue the right data to indicate
1215 * the error case if necessary.
1217 * n_tty_receive_buf()/producer path:
1218 * caller holds non-exclusive termios_rwsem
1220 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1222 struct n_tty_data *ldata = tty->disc_data;
1227 if (I_PARMRK(tty)) {
1228 put_tty_queue('\377', ldata);
1229 put_tty_queue('\0', ldata);
1230 put_tty_queue(c, ldata);
1232 put_tty_queue('\0', ldata);
1234 put_tty_queue(c, ldata);
1238 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1247 process_echoes(tty);
1252 * n_tty_receive_char - perform processing
1253 * @tty: terminal device
1256 * Process an individual character of input received from the driver.
1257 * This is serialized with respect to itself by the rules for the
1260 * n_tty_receive_buf()/producer path:
1261 * caller holds non-exclusive termios_rwsem
1262 * publishes canon_head if canonical mode is active
1264 * Returns 1 if LNEXT was received, else returns 0
1268 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1270 struct n_tty_data *ldata = tty->disc_data;
1273 if (c == START_CHAR(tty)) {
1275 process_echoes(tty);
1278 if (c == STOP_CHAR(tty)) {
1285 if (c == INTR_CHAR(tty)) {
1286 n_tty_receive_signal_char(tty, SIGINT, c);
1288 } else if (c == QUIT_CHAR(tty)) {
1289 n_tty_receive_signal_char(tty, SIGQUIT, c);
1291 } else if (c == SUSP_CHAR(tty)) {
1292 n_tty_receive_signal_char(tty, SIGTSTP, c);
1297 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1299 process_echoes(tty);
1307 } else if (c == '\n' && I_INLCR(tty))
1310 if (ldata->icanon) {
1311 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1312 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1317 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1320 finish_erasing(ldata);
1321 if (L_ECHOCTL(tty)) {
1322 echo_char_raw('^', ldata);
1323 echo_char_raw('\b', ldata);
1329 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1330 size_t tail = ldata->canon_head;
1332 finish_erasing(ldata);
1334 echo_char_raw('\n', ldata);
1335 while (MASK(tail) != MASK(ldata->read_head)) {
1336 echo_char(read_buf(ldata, tail), tty);
1343 if (L_ECHO(tty) || L_ECHONL(tty)) {
1344 echo_char_raw('\n', ldata);
1347 goto handle_newline;
1349 if (c == EOF_CHAR(tty)) {
1350 c = __DISABLED_CHAR;
1351 goto handle_newline;
1353 if ((c == EOL_CHAR(tty)) ||
1354 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1356 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1359 /* Record the column of first canon char. */
1360 if (ldata->canon_head == ldata->read_head)
1361 echo_set_canon_col(ldata);
1366 * XXX does PARMRK doubling happen for
1367 * EOL_CHAR and EOL2_CHAR?
1369 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1370 put_tty_queue(c, ldata);
1373 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1374 put_tty_queue(c, ldata);
1375 smp_store_release(&ldata->canon_head, ldata->read_head);
1376 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1377 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1383 finish_erasing(ldata);
1385 echo_char_raw('\n', ldata);
1387 /* Record the column of first canon char. */
1388 if (ldata->canon_head == ldata->read_head)
1389 echo_set_canon_col(ldata);
1395 /* PARMRK doubling check */
1396 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1397 put_tty_queue(c, ldata);
1399 put_tty_queue(c, ldata);
1404 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1406 struct n_tty_data *ldata = tty->disc_data;
1408 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1410 process_echoes(tty);
1413 finish_erasing(ldata);
1414 /* Record the column of first canon char. */
1415 if (ldata->canon_head == ldata->read_head)
1416 echo_set_canon_col(ldata);
1420 /* PARMRK doubling check */
1421 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1422 put_tty_queue(c, ldata);
1423 put_tty_queue(c, ldata);
1426 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1428 n_tty_receive_char_inline(tty, c);
1432 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1434 struct n_tty_data *ldata = tty->disc_data;
1436 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1438 process_echoes(tty);
1441 finish_erasing(ldata);
1442 /* Record the column of first canon char. */
1443 if (ldata->canon_head == ldata->read_head)
1444 echo_set_canon_col(ldata);
1448 put_tty_queue(c, ldata);
1451 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1455 if (I_IUCLC(tty) && L_IEXTEN(tty))
1459 if (c == STOP_CHAR(tty))
1461 else if (c == START_CHAR(tty) ||
1462 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1463 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1464 c != SUSP_CHAR(tty))) {
1466 process_echoes(tty);
1472 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1476 n_tty_receive_break(tty);
1480 n_tty_receive_parity_error(tty, c);
1483 n_tty_receive_overrun(tty);
1486 tty_err(tty, "unknown flag %d\n", flag);
1492 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1494 struct n_tty_data *ldata = tty->disc_data;
1497 if (likely(flag == TTY_NORMAL)) {
1500 if (I_IUCLC(tty) && L_IEXTEN(tty))
1502 n_tty_receive_char(tty, c);
1504 n_tty_receive_char_flagged(tty, c, flag);
1508 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1509 char *fp, int count)
1511 struct n_tty_data *ldata = tty->disc_data;
1514 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1515 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1516 memcpy(read_buf_addr(ldata, head), cp, n);
1517 ldata->read_head += n;
1521 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1522 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1523 memcpy(read_buf_addr(ldata, head), cp, n);
1524 ldata->read_head += n;
1528 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1529 char *fp, int count)
1531 struct n_tty_data *ldata = tty->disc_data;
1532 char flag = TTY_NORMAL;
1537 if (likely(flag == TTY_NORMAL))
1538 put_tty_queue(*cp++, ldata);
1540 n_tty_receive_char_flagged(tty, *cp++, flag);
1545 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1546 char *fp, int count)
1548 char flag = TTY_NORMAL;
1553 if (likely(flag == TTY_NORMAL))
1554 n_tty_receive_char_closing(tty, *cp++);
1559 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1560 char *fp, int count)
1562 struct n_tty_data *ldata = tty->disc_data;
1563 char flag = TTY_NORMAL;
1568 if (likely(flag == TTY_NORMAL)) {
1569 unsigned char c = *cp++;
1573 if (I_IUCLC(tty) && L_IEXTEN(tty))
1575 if (L_EXTPROC(tty)) {
1576 put_tty_queue(c, ldata);
1579 if (!test_bit(c, ldata->char_map))
1580 n_tty_receive_char_inline(tty, c);
1581 else if (n_tty_receive_char_special(tty, c) && count) {
1584 n_tty_receive_char_lnext(tty, *cp++, flag);
1588 n_tty_receive_char_flagged(tty, *cp++, flag);
1593 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1594 char *fp, int count)
1596 struct n_tty_data *ldata = tty->disc_data;
1597 char flag = TTY_NORMAL;
1602 if (likely(flag == TTY_NORMAL)) {
1603 unsigned char c = *cp++;
1605 if (!test_bit(c, ldata->char_map))
1606 n_tty_receive_char_fast(tty, c);
1607 else if (n_tty_receive_char_special(tty, c) && count) {
1610 n_tty_receive_char_lnext(tty, *cp++, flag);
1614 n_tty_receive_char_flagged(tty, *cp++, flag);
1618 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1619 char *fp, int count)
1621 struct n_tty_data *ldata = tty->disc_data;
1622 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1624 if (ldata->real_raw)
1625 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1626 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1627 n_tty_receive_buf_raw(tty, cp, fp, count);
1628 else if (tty->closing && !L_EXTPROC(tty))
1629 n_tty_receive_buf_closing(tty, cp, fp, count);
1632 char flag = TTY_NORMAL;
1636 n_tty_receive_char_lnext(tty, *cp++, flag);
1640 if (!preops && !I_PARMRK(tty))
1641 n_tty_receive_buf_fast(tty, cp, fp, count);
1643 n_tty_receive_buf_standard(tty, cp, fp, count);
1646 if (tty->ops->flush_chars)
1647 tty->ops->flush_chars(tty);
1650 if (ldata->icanon && !L_EXTPROC(tty))
1653 /* publish read_head to consumer */
1654 smp_store_release(&ldata->commit_head, ldata->read_head);
1656 if (read_cnt(ldata)) {
1657 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1658 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN);
1663 * n_tty_receive_buf_common - process input
1664 * @tty: device to receive input
1666 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1667 * @count: number of input chars in @cp
1668 * @flow: enable flow control
1670 * Called by the terminal driver when a block of characters has
1671 * been received. This function must be called from soft contexts
1672 * not from interrupt context. The driver is responsible for making
1673 * calls one at a time and in order (or using flush_to_ldisc)
1675 * Returns the # of input chars from @cp which were processed.
1677 * In canonical mode, the maximum line length is 4096 chars (including
1678 * the line termination char); lines longer than 4096 chars are
1679 * truncated. After 4095 chars, input data is still processed but
1680 * not stored. Overflow processing ensures the tty can always
1681 * receive more input until at least one line can be read.
1683 * In non-canonical mode, the read buffer will only accept 4095 chars;
1684 * this provides the necessary space for a newline char if the input
1685 * mode is switched to canonical.
1687 * Note it is possible for the read buffer to _contain_ 4096 chars
1688 * in non-canonical mode: the read buffer could already contain the
1689 * maximum canon line of 4096 chars when the mode is switched to
1692 * n_tty_receive_buf()/producer path:
1693 * claims non-exclusive termios_rwsem
1694 * publishes commit_head or canon_head
1697 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1698 char *fp, int count, int flow)
1700 struct n_tty_data *ldata = tty->disc_data;
1701 int room, n, rcvd = 0, overflow;
1703 down_read(&tty->termios_rwsem);
1707 * When PARMRK is set, each input char may take up to 3 chars
1708 * in the read buf; reduce the buffer space avail by 3x
1710 * If we are doing input canonicalization, and there are no
1711 * pending newlines, let characters through without limit, so
1712 * that erase characters will be handled. Other excess
1713 * characters will be beeped.
1715 * paired with store in *_copy_from_read_buf() -- guarantees
1716 * the consumer has loaded the data in read_buf up to the new
1717 * read_tail (so this producer will not overwrite unread data)
1719 size_t tail = smp_load_acquire(&ldata->read_tail);
1721 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1723 room = (room + 2) / 3;
1726 overflow = ldata->icanon && ldata->canon_head == tail;
1727 if (overflow && room < 0)
1730 ldata->no_room = flow && !room;
1734 n = min(count, room);
1738 /* ignore parity errors if handling overflow */
1739 if (!overflow || !fp || *fp != TTY_PARITY)
1740 __receive_buf(tty, cp, fp, n);
1747 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1749 tty->receive_room = room;
1751 /* Unthrottle if handling overflow on pty */
1752 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1754 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1755 tty_unthrottle_safe(tty);
1756 __tty_set_flow_change(tty, 0);
1759 n_tty_check_throttle(tty);
1761 up_read(&tty->termios_rwsem);
1766 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1767 char *fp, int count)
1769 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1772 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1773 char *fp, int count)
1775 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1779 * n_tty_set_termios - termios data changed
1781 * @old: previous data
1783 * Called by the tty layer when the user changes termios flags so
1784 * that the line discipline can plan ahead. This function cannot sleep
1785 * and is protected from re-entry by the tty layer. The user is
1786 * guaranteed that this function will not be re-entered or in progress
1787 * when the ldisc is closed.
1789 * Locking: Caller holds tty->termios_rwsem
1792 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1794 struct n_tty_data *ldata = tty->disc_data;
1796 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1797 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1798 ldata->line_start = ldata->read_tail;
1799 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1800 ldata->canon_head = ldata->read_tail;
1803 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1805 ldata->canon_head = ldata->read_head;
1808 ldata->commit_head = ldata->read_head;
1813 ldata->icanon = (L_ICANON(tty) != 0);
1815 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1816 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1817 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1819 bitmap_zero(ldata->char_map, 256);
1821 if (I_IGNCR(tty) || I_ICRNL(tty))
1822 set_bit('\r', ldata->char_map);
1824 set_bit('\n', ldata->char_map);
1826 if (L_ICANON(tty)) {
1827 set_bit(ERASE_CHAR(tty), ldata->char_map);
1828 set_bit(KILL_CHAR(tty), ldata->char_map);
1829 set_bit(EOF_CHAR(tty), ldata->char_map);
1830 set_bit('\n', ldata->char_map);
1831 set_bit(EOL_CHAR(tty), ldata->char_map);
1832 if (L_IEXTEN(tty)) {
1833 set_bit(WERASE_CHAR(tty), ldata->char_map);
1834 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1835 set_bit(EOL2_CHAR(tty), ldata->char_map);
1837 set_bit(REPRINT_CHAR(tty),
1842 set_bit(START_CHAR(tty), ldata->char_map);
1843 set_bit(STOP_CHAR(tty), ldata->char_map);
1846 set_bit(INTR_CHAR(tty), ldata->char_map);
1847 set_bit(QUIT_CHAR(tty), ldata->char_map);
1848 set_bit(SUSP_CHAR(tty), ldata->char_map);
1850 clear_bit(__DISABLED_CHAR, ldata->char_map);
1852 ldata->real_raw = 0;
1855 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1856 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1857 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1858 ldata->real_raw = 1;
1860 ldata->real_raw = 0;
1863 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1864 * been stopped by STOP_CHAR(tty) before it.
1866 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1868 process_echoes(tty);
1871 /* The termios change make the tty ready for I/O */
1872 wake_up_interruptible(&tty->write_wait);
1873 wake_up_interruptible(&tty->read_wait);
1877 * n_tty_close - close the ldisc for this tty
1880 * Called from the terminal layer when this line discipline is
1881 * being shut down, either because of a close or becsuse of a
1882 * discipline change. The function will not be called while other
1883 * ldisc methods are in progress.
1886 static void n_tty_close(struct tty_struct *tty)
1888 struct n_tty_data *ldata = tty->disc_data;
1891 n_tty_packet_mode_flush(tty);
1893 down_write(&tty->termios_rwsem);
1895 tty->disc_data = NULL;
1896 up_write(&tty->termios_rwsem);
1900 * n_tty_open - open an ldisc
1901 * @tty: terminal to open
1903 * Called when this line discipline is being attached to the
1904 * terminal device. Can sleep. Called serialized so that no
1905 * other events will occur in parallel. No further open will occur
1909 static int n_tty_open(struct tty_struct *tty)
1911 struct n_tty_data *ldata;
1913 /* Currently a malloc failure here can panic */
1914 ldata = vzalloc(sizeof(*ldata));
1918 ldata->overrun_time = jiffies;
1919 mutex_init(&ldata->atomic_read_lock);
1920 mutex_init(&ldata->output_lock);
1922 tty->disc_data = ldata;
1924 /* indicate buffer work may resume */
1925 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1926 n_tty_set_termios(tty, NULL);
1927 tty_unthrottle(tty);
1931 static inline int input_available_p(struct tty_struct *tty, int poll)
1933 struct n_tty_data *ldata = tty->disc_data;
1934 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1936 if (ldata->icanon && !L_EXTPROC(tty))
1937 return ldata->canon_head != ldata->read_tail;
1939 return ldata->commit_head - ldata->read_tail >= amt;
1943 * copy_from_read_buf - copy read data directly
1944 * @tty: terminal device
1948 * Helper function to speed up n_tty_read. It is only called when
1949 * ICANON is off; it copies characters straight from the tty queue.
1951 * Called under the ldata->atomic_read_lock sem
1953 * Returns true if it successfully copied data, but there is still
1954 * more data to be had.
1956 * n_tty_read()/consumer path:
1957 * caller holds non-exclusive termios_rwsem
1958 * read_tail published
1961 static bool copy_from_read_buf(struct tty_struct *tty,
1962 unsigned char **kbp,
1966 struct n_tty_data *ldata = tty->disc_data;
1969 size_t head = smp_load_acquire(&ldata->commit_head);
1970 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1972 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1975 unsigned char *from = read_buf_addr(ldata, tail);
1976 memcpy(*kbp, from, n);
1977 is_eof = n == 1 && *from == EOF_CHAR(tty);
1978 tty_audit_add_data(tty, from, n);
1979 zero_buffer(tty, from, n);
1980 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1981 /* Turn single EOF into zero-length read */
1982 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1983 (head == ldata->read_tail))
1988 /* If we have more to copy, let the caller know */
1989 return head != ldata->read_tail;
1995 * canon_copy_from_read_buf - copy read data in canonical mode
1996 * @tty: terminal device
2000 * Helper function for n_tty_read. It is only called when ICANON is on;
2001 * it copies one line of input up to and including the line-delimiting
2002 * character into the result buffer.
2004 * NB: When termios is changed from non-canonical to canonical mode and
2005 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2006 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2007 * This causes data already processed as input to be immediately available
2008 * as input although a newline has not been received.
2010 * Called under the atomic_read_lock mutex
2012 * n_tty_read()/consumer path:
2013 * caller holds non-exclusive termios_rwsem
2014 * read_tail published
2017 static bool canon_copy_from_read_buf(struct tty_struct *tty,
2018 unsigned char **kbp,
2021 struct n_tty_data *ldata = tty->disc_data;
2022 size_t n, size, more, c;
2024 size_t tail, canon_head;
2027 /* N.B. avoid overrun if nr == 0 */
2031 canon_head = smp_load_acquire(&ldata->canon_head);
2032 n = min(*nr + 1, canon_head - ldata->read_tail);
2034 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2035 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2037 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2038 __func__, *nr, tail, n, size);
2040 eol = find_next_bit(ldata->read_flags, size, tail);
2041 more = n - (size - tail);
2042 if (eol == N_TTY_BUF_SIZE && more) {
2043 /* scan wrapped without finding set bit */
2044 eol = find_next_bit(ldata->read_flags, more, 0);
2045 found = eol != more;
2047 found = eol != size;
2050 if (n > N_TTY_BUF_SIZE)
2051 n += N_TTY_BUF_SIZE;
2054 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2059 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2060 __func__, eol, found, n, c, tail, more);
2062 tty_copy(tty, *kbp, tail, n);
2067 clear_bit(eol, ldata->read_flags);
2068 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2072 ldata->line_start = ldata->read_tail;
2079 /* No EOL found - do a continuation retry if there is more data */
2080 return ldata->read_tail != canon_head;
2084 * job_control - check job control
2086 * @file: file handle
2088 * Perform job control management checks on this file/tty descriptor
2089 * and if appropriate send any needed signals and return a negative
2090 * error code if action should be taken.
2092 * Locking: redirected write test is safe
2093 * current->signal->tty check is safe
2094 * ctrl_lock to safely reference tty->pgrp
2097 static int job_control(struct tty_struct *tty, struct file *file)
2099 /* Job control check -- must be done at start and after
2100 every sleep (POSIX.1 7.1.1.4). */
2101 /* NOTE: not yet done after every sleep pending a thorough
2102 check of the logic of this change. -- jlc */
2103 /* don't stop on /dev/console */
2104 if (file->f_op->write_iter == redirected_tty_write)
2107 return __tty_check_change(tty, SIGTTIN);
2112 * n_tty_read - read function for tty
2114 * @file: file object
2115 * @buf: userspace buffer pointer
2118 * Perform reads for the line discipline. We are guaranteed that the
2119 * line discipline will not be closed under us but we may get multiple
2120 * parallel readers and must handle this ourselves. We may also get
2121 * a hangup. Always called in user context, may sleep.
2123 * This code must be sure never to sleep through a hangup.
2125 * n_tty_read()/consumer path:
2126 * claims non-exclusive termios_rwsem
2127 * publishes read_tail
2130 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2131 unsigned char *kbuf, size_t nr,
2132 void **cookie, unsigned long offset)
2134 struct n_tty_data *ldata = tty->disc_data;
2135 unsigned char *kb = kbuf;
2136 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2145 * Is this a continuation of a read started earler?
2147 * If so, we still hold the atomic_read_lock and the
2148 * termios_rwsem, and can just continue to copy data.
2151 if (ldata->icanon && !L_EXTPROC(tty)) {
2152 if (canon_copy_from_read_buf(tty, &kb, &nr))
2155 if (copy_from_read_buf(tty, &kb, &nr))
2159 /* No more data - release locks and stop retries */
2160 n_tty_kick_worker(tty);
2161 n_tty_check_unthrottle(tty);
2162 up_read(&tty->termios_rwsem);
2163 mutex_unlock(&ldata->atomic_read_lock);
2168 c = job_control(tty, file);
2173 * Internal serialization of reads.
2175 if (file->f_flags & O_NONBLOCK) {
2176 if (!mutex_trylock(&ldata->atomic_read_lock))
2179 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2180 return -ERESTARTSYS;
2183 down_read(&tty->termios_rwsem);
2186 timeout = MAX_SCHEDULE_TIMEOUT;
2187 if (!ldata->icanon) {
2188 minimum = MIN_CHAR(tty);
2190 time = (HZ / 10) * TIME_CHAR(tty);
2192 timeout = (HZ / 10) * TIME_CHAR(tty);
2197 packet = tty->packet;
2198 tail = ldata->read_tail;
2200 add_wait_queue(&tty->read_wait, &wait);
2202 /* First test for status change. */
2203 if (packet && tty->link->ctrl_status) {
2207 spin_lock_irq(&tty->link->ctrl_lock);
2208 cs = tty->link->ctrl_status;
2209 tty->link->ctrl_status = 0;
2210 spin_unlock_irq(&tty->link->ctrl_lock);
2216 if (!input_available_p(tty, 0)) {
2217 up_read(&tty->termios_rwsem);
2218 tty_buffer_flush_work(tty->port);
2219 down_read(&tty->termios_rwsem);
2220 if (!input_available_p(tty, 0)) {
2221 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2225 if (tty_hung_up_p(file))
2228 * Abort readers for ttys which never actually
2229 * get hung up. See __tty_hangup().
2231 if (test_bit(TTY_HUPPING, &tty->flags))
2235 if (tty_io_nonblock(tty, file)) {
2239 if (signal_pending(current)) {
2240 retval = -ERESTARTSYS;
2243 up_read(&tty->termios_rwsem);
2245 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2248 down_read(&tty->termios_rwsem);
2253 if (ldata->icanon && !L_EXTPROC(tty)) {
2254 if (canon_copy_from_read_buf(tty, &kb, &nr))
2255 goto more_to_be_read;
2257 /* Deal with packet mode. */
2258 if (packet && kb == kbuf) {
2259 *kb++ = TIOCPKT_DATA;
2264 * Copy data, and if there is more to be had
2265 * and we have nothing more to wait for, then
2266 * let's mark us for retries.
2268 * NOTE! We return here with both the termios_sem
2269 * and atomic_read_lock still held, the retries
2270 * will release them when done.
2272 if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2274 remove_wait_queue(&tty->read_wait, &wait);
2280 n_tty_check_unthrottle(tty);
2282 if (kb - kbuf >= minimum)
2287 if (tail != ldata->read_tail)
2288 n_tty_kick_worker(tty);
2289 up_read(&tty->termios_rwsem);
2291 remove_wait_queue(&tty->read_wait, &wait);
2292 mutex_unlock(&ldata->atomic_read_lock);
2301 * n_tty_write - write function for tty
2303 * @file: file object
2304 * @buf: userspace buffer pointer
2307 * Write function of the terminal device. This is serialized with
2308 * respect to other write callers but not to termios changes, reads
2309 * and other such events. Since the receive code will echo characters,
2310 * thus calling driver write methods, the output_lock is used in
2311 * the output processing functions called here as well as in the
2312 * echo processing function to protect the column state and space
2313 * left in the buffer.
2315 * This code must be sure never to sleep through a hangup.
2317 * Locking: output_lock to protect column state and space left
2318 * (note that the process_output*() functions take this
2322 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2323 const unsigned char *buf, size_t nr)
2325 const unsigned char *b = buf;
2326 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2330 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2331 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2332 retval = tty_check_change(tty);
2337 down_read(&tty->termios_rwsem);
2339 /* Write out any echoed characters that are still pending */
2340 process_echoes(tty);
2342 add_wait_queue(&tty->write_wait, &wait);
2344 if (signal_pending(current)) {
2345 retval = -ERESTARTSYS;
2348 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2354 ssize_t num = process_output_block(tty, b, nr);
2366 if (process_output(c, tty) < 0)
2370 if (tty->ops->flush_chars)
2371 tty->ops->flush_chars(tty);
2373 struct n_tty_data *ldata = tty->disc_data;
2376 mutex_lock(&ldata->output_lock);
2377 c = tty->ops->write(tty, b, nr);
2378 mutex_unlock(&ldata->output_lock);
2391 if (tty_io_nonblock(tty, file)) {
2395 up_read(&tty->termios_rwsem);
2397 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2399 down_read(&tty->termios_rwsem);
2402 remove_wait_queue(&tty->write_wait, &wait);
2403 if (nr && tty->fasync)
2404 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2405 up_read(&tty->termios_rwsem);
2406 return (b - buf) ? b - buf : retval;
2410 * n_tty_poll - poll method for N_TTY
2411 * @tty: terminal device
2412 * @file: file accessing it
2415 * Called when the line discipline is asked to poll() for data or
2416 * for special events. This code is not serialized with respect to
2417 * other events save open/close.
2419 * This code must be sure never to sleep through a hangup.
2420 * Called without the kernel lock held - fine
2423 static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2428 poll_wait(file, &tty->read_wait, wait);
2429 poll_wait(file, &tty->write_wait, wait);
2430 if (input_available_p(tty, 1))
2431 mask |= EPOLLIN | EPOLLRDNORM;
2433 tty_buffer_flush_work(tty->port);
2434 if (input_available_p(tty, 1))
2435 mask |= EPOLLIN | EPOLLRDNORM;
2437 if (tty->packet && tty->link->ctrl_status)
2438 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2439 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2441 if (tty_hung_up_p(file))
2443 if (tty->ops->write && !tty_is_writelocked(tty) &&
2444 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2445 tty_write_room(tty) > 0)
2446 mask |= EPOLLOUT | EPOLLWRNORM;
2450 static unsigned long inq_canon(struct n_tty_data *ldata)
2452 size_t nr, head, tail;
2454 if (ldata->canon_head == ldata->read_tail)
2456 head = ldata->canon_head;
2457 tail = ldata->read_tail;
2459 /* Skip EOF-chars.. */
2460 while (MASK(head) != MASK(tail)) {
2461 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2462 read_buf(ldata, tail) == __DISABLED_CHAR)
2469 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2470 unsigned int cmd, unsigned long arg)
2472 struct n_tty_data *ldata = tty->disc_data;
2477 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2479 down_write(&tty->termios_rwsem);
2480 if (L_ICANON(tty) && !L_EXTPROC(tty))
2481 retval = inq_canon(ldata);
2483 retval = read_cnt(ldata);
2484 up_write(&tty->termios_rwsem);
2485 return put_user(retval, (unsigned int __user *) arg);
2487 return n_tty_ioctl_helper(tty, file, cmd, arg);
2491 static struct tty_ldisc_ops n_tty_ops = {
2492 .owner = THIS_MODULE,
2495 .close = n_tty_close,
2496 .flush_buffer = n_tty_flush_buffer,
2498 .write = n_tty_write,
2499 .ioctl = n_tty_ioctl,
2500 .set_termios = n_tty_set_termios,
2502 .receive_buf = n_tty_receive_buf,
2503 .write_wakeup = n_tty_write_wakeup,
2504 .receive_buf2 = n_tty_receive_buf2,
2508 * n_tty_inherit_ops - inherit N_TTY methods
2509 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2511 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2514 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2518 ops->refcount = ops->flags = 0;
2520 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2522 void __init n_tty_init(void)
2524 tty_register_ldisc(N_TTY, &n_tty_ops);