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
396 * Returns true if the utf8 character 'c' is a multibyte continuation
397 * character and the terminal is in unicode mode.
400 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
402 return I_IUTF8(tty) && is_utf8_continuation(c);
406 * do_output_char - output one character
407 * @c: character (or partial unicode symbol)
408 * @tty: terminal device
409 * @space: space available in tty driver write buffer
411 * This is a helper function that handles one output character
412 * (including special characters like TAB, CR, LF, etc.),
413 * doing OPOST processing and putting the results in the
414 * tty driver's write buffer.
416 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
417 * and NLDLY. They simply aren't relevant in the world today.
418 * If you ever need them, add them here.
420 * Returns the number of bytes of buffer space used or -1 if
423 * Locking: should be called under the output_lock to protect
424 * the column state and space left in the buffer
427 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
429 struct n_tty_data *ldata = tty->disc_data;
442 ldata->canon_column = ldata->column = 0;
443 tty->ops->write(tty, "\r\n", 2);
446 ldata->canon_column = ldata->column;
449 if (O_ONOCR(tty) && ldata->column == 0)
454 ldata->canon_column = ldata->column = 0;
457 ldata->canon_column = ldata->column = 0;
460 spaces = 8 - (ldata->column & 7);
461 if (O_TABDLY(tty) == XTABS) {
464 ldata->column += spaces;
465 tty->ops->write(tty, " ", spaces);
468 ldata->column += spaces;
471 if (ldata->column > 0)
478 if (!is_continuation(c, tty))
484 tty_put_char(tty, c);
489 * process_output - output post processor
490 * @c: character (or partial unicode symbol)
491 * @tty: terminal device
493 * Output one character with OPOST processing.
494 * Returns -1 when the output device is full and the character
497 * Locking: output_lock to protect column state and space left
498 * (also, this is called from n_tty_write under the
499 * tty layer write lock)
502 static int process_output(unsigned char c, struct tty_struct *tty)
504 struct n_tty_data *ldata = tty->disc_data;
507 mutex_lock(&ldata->output_lock);
509 space = tty_write_room(tty);
510 retval = do_output_char(c, tty, space);
512 mutex_unlock(&ldata->output_lock);
520 * process_output_block - block post processor
521 * @tty: terminal device
522 * @buf: character buffer
523 * @nr: number of bytes to output
525 * Output a block of characters with OPOST processing.
526 * Returns the number of characters output.
528 * This path is used to speed up block console writes, among other
529 * things when processing blocks of output data. It handles only
530 * the simple cases normally found and helps to generate blocks of
531 * symbols for the console driver and thus improve performance.
533 * Locking: output_lock to protect column state and space left
534 * (also, this is called from n_tty_write under the
535 * tty layer write lock)
538 static ssize_t process_output_block(struct tty_struct *tty,
539 const unsigned char *buf, unsigned int nr)
541 struct n_tty_data *ldata = tty->disc_data;
544 const unsigned char *cp;
546 mutex_lock(&ldata->output_lock);
548 space = tty_write_room(tty);
550 mutex_unlock(&ldata->output_lock);
556 for (i = 0, cp = buf; i < nr; i++, cp++) {
557 unsigned char c = *cp;
565 ldata->canon_column = ldata->column;
568 if (O_ONOCR(tty) && ldata->column == 0)
572 ldata->canon_column = ldata->column = 0;
577 if (ldata->column > 0)
584 if (!is_continuation(c, tty))
591 i = tty->ops->write(tty, buf, i);
593 mutex_unlock(&ldata->output_lock);
598 * process_echoes - write pending echo characters
599 * @tty: terminal device
601 * Write previously buffered echo (and other ldisc-generated)
602 * characters to the tty.
604 * Characters generated by the ldisc (including echoes) need to
605 * be buffered because the driver's write buffer can fill during
606 * heavy program output. Echoing straight to the driver will
607 * often fail under these conditions, causing lost characters and
608 * resulting mismatches of ldisc state information.
610 * Since the ldisc state must represent the characters actually sent
611 * to the driver at the time of the write, operations like certain
612 * changes in column state are also saved in the buffer and executed
615 * A circular fifo buffer is used so that the most recent characters
616 * are prioritized. Also, when control characters are echoed with a
617 * prefixed "^", the pair is treated atomically and thus not separated.
619 * Locking: callers must hold output_lock
622 static size_t __process_echoes(struct tty_struct *tty)
624 struct n_tty_data *ldata = tty->disc_data;
625 int space, old_space;
629 old_space = space = tty_write_room(tty);
631 tail = ldata->echo_tail;
632 while (MASK(ldata->echo_commit) != MASK(tail)) {
633 c = echo_buf(ldata, tail);
634 if (c == ECHO_OP_START) {
636 int no_space_left = 0;
639 * Since add_echo_byte() is called without holding
640 * output_lock, we might see only portion of multi-byte
643 if (MASK(ldata->echo_commit) == MASK(tail + 1))
646 * If the buffer byte is the start of a multi-byte
647 * operation, get the next byte, which is either the
648 * op code or a control character value.
650 op = echo_buf(ldata, tail + 1);
653 case ECHO_OP_ERASE_TAB: {
654 unsigned int num_chars, num_bs;
656 if (MASK(ldata->echo_commit) == MASK(tail + 2))
658 num_chars = echo_buf(ldata, tail + 2);
661 * Determine how many columns to go back
662 * in order to erase the tab.
663 * This depends on the number of columns
664 * used by other characters within the tab
665 * area. If this (modulo 8) count is from
666 * the start of input rather than from a
667 * previous tab, we offset by canon column.
668 * Otherwise, tab spacing is normal.
670 if (!(num_chars & 0x80))
671 num_chars += ldata->canon_column;
672 num_bs = 8 - (num_chars & 7);
674 if (num_bs > space) {
680 tty_put_char(tty, '\b');
681 if (ldata->column > 0)
687 case ECHO_OP_SET_CANON_COL:
688 ldata->canon_column = ldata->column;
692 case ECHO_OP_MOVE_BACK_COL:
693 if (ldata->column > 0)
699 /* This is an escaped echo op start code */
704 tty_put_char(tty, ECHO_OP_START);
712 * If the op is not a special byte code,
713 * it is a ctrl char tagged to be echoed
714 * as "^X" (where X is the letter
715 * representing the control char).
716 * Note that we must ensure there is
717 * enough space for the whole ctrl pair.
724 tty_put_char(tty, '^');
725 tty_put_char(tty, op ^ 0100);
735 int retval = do_output_char(c, tty, space);
742 tty_put_char(tty, c);
749 /* If the echo buffer is nearly full (so that the possibility exists
750 * of echo overrun before the next commit), then discard enough
751 * data at the tail to prevent a subsequent overrun */
752 while (ldata->echo_commit > tail &&
753 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
754 if (echo_buf(ldata, tail) == ECHO_OP_START) {
755 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
764 ldata->echo_tail = tail;
765 return old_space - space;
768 static void commit_echoes(struct tty_struct *tty)
770 struct n_tty_data *ldata = tty->disc_data;
771 size_t nr, old, echoed;
774 mutex_lock(&ldata->output_lock);
775 head = ldata->echo_head;
776 ldata->echo_mark = head;
777 old = ldata->echo_commit - ldata->echo_tail;
779 /* Process committed echoes if the accumulated # of bytes
780 * is over the threshold (and try again each time another
781 * block is accumulated) */
782 nr = head - ldata->echo_tail;
783 if (nr < ECHO_COMMIT_WATERMARK ||
784 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
785 mutex_unlock(&ldata->output_lock);
789 ldata->echo_commit = head;
790 echoed = __process_echoes(tty);
791 mutex_unlock(&ldata->output_lock);
793 if (echoed && tty->ops->flush_chars)
794 tty->ops->flush_chars(tty);
797 static void process_echoes(struct tty_struct *tty)
799 struct n_tty_data *ldata = tty->disc_data;
802 if (ldata->echo_mark == ldata->echo_tail)
805 mutex_lock(&ldata->output_lock);
806 ldata->echo_commit = ldata->echo_mark;
807 echoed = __process_echoes(tty);
808 mutex_unlock(&ldata->output_lock);
810 if (echoed && tty->ops->flush_chars)
811 tty->ops->flush_chars(tty);
814 /* NB: echo_mark and echo_head should be equivalent here */
815 static void flush_echoes(struct tty_struct *tty)
817 struct n_tty_data *ldata = tty->disc_data;
819 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
820 ldata->echo_commit == ldata->echo_head)
823 mutex_lock(&ldata->output_lock);
824 ldata->echo_commit = ldata->echo_head;
825 __process_echoes(tty);
826 mutex_unlock(&ldata->output_lock);
830 * add_echo_byte - add a byte to the echo buffer
831 * @c: unicode byte to echo
834 * Add a character or operation byte to the echo buffer.
837 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
839 *echo_buf_addr(ldata, ldata->echo_head) = c;
840 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
845 * echo_move_back_col - add operation to move back a column
848 * Add an operation to the echo buffer to move back one column.
851 static void echo_move_back_col(struct n_tty_data *ldata)
853 add_echo_byte(ECHO_OP_START, ldata);
854 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
858 * echo_set_canon_col - add operation to set the canon column
861 * Add an operation to the echo buffer to set the canon column
862 * to the current column.
865 static void echo_set_canon_col(struct n_tty_data *ldata)
867 add_echo_byte(ECHO_OP_START, ldata);
868 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
872 * echo_erase_tab - add operation to erase a tab
873 * @num_chars: number of character columns already used
874 * @after_tab: true if num_chars starts after a previous tab
877 * Add an operation to the echo buffer to erase a tab.
879 * Called by the eraser function, which knows how many character
880 * columns have been used since either a previous tab or the start
881 * of input. This information will be used later, along with
882 * canon column (if applicable), to go back the correct number
886 static void echo_erase_tab(unsigned int num_chars, int after_tab,
887 struct n_tty_data *ldata)
889 add_echo_byte(ECHO_OP_START, ldata);
890 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
892 /* We only need to know this modulo 8 (tab spacing) */
895 /* Set the high bit as a flag if num_chars is after a previous tab */
899 add_echo_byte(num_chars, ldata);
903 * echo_char_raw - echo a character raw
904 * @c: unicode byte to echo
905 * @ldata: line disc data
907 * Echo user input back onto the screen. This must be called only when
908 * L_ECHO(tty) is true. Called from the driver receive_buf path.
910 * This variant does not treat control characters specially.
913 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
915 if (c == ECHO_OP_START) {
916 add_echo_byte(ECHO_OP_START, ldata);
917 add_echo_byte(ECHO_OP_START, ldata);
919 add_echo_byte(c, ldata);
924 * echo_char - echo a character
925 * @c: unicode byte to echo
926 * @tty: terminal device
928 * Echo user input back onto the screen. This must be called only when
929 * L_ECHO(tty) is true. Called from the driver receive_buf path.
931 * This variant tags control characters to be echoed as "^X"
932 * (where X is the letter representing the control char).
935 static void echo_char(unsigned char c, struct tty_struct *tty)
937 struct n_tty_data *ldata = tty->disc_data;
939 if (c == ECHO_OP_START) {
940 add_echo_byte(ECHO_OP_START, ldata);
941 add_echo_byte(ECHO_OP_START, ldata);
943 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
944 add_echo_byte(ECHO_OP_START, ldata);
945 add_echo_byte(c, ldata);
950 * finish_erasing - complete erase
954 static inline void finish_erasing(struct n_tty_data *ldata)
956 if (ldata->erasing) {
957 echo_char_raw('/', ldata);
963 * eraser - handle erase function
964 * @c: character input
965 * @tty: terminal device
967 * Perform erase and necessary output when an erase character is
968 * present in the stream from the driver layer. Handles the complexities
969 * of UTF-8 multibyte symbols.
971 * n_tty_receive_buf()/producer path:
972 * caller holds non-exclusive termios_rwsem
975 static void eraser(unsigned char c, struct tty_struct *tty)
977 struct n_tty_data *ldata = tty->disc_data;
978 enum { ERASE, WERASE, KILL } kill_type;
983 if (ldata->read_head == ldata->canon_head) {
984 /* process_output('\a', tty); */ /* what do you think? */
987 if (c == ERASE_CHAR(tty))
989 else if (c == WERASE_CHAR(tty))
993 ldata->read_head = ldata->canon_head;
996 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
997 ldata->read_head = ldata->canon_head;
998 finish_erasing(ldata);
999 echo_char(KILL_CHAR(tty), tty);
1000 /* Add a newline if ECHOK is on and ECHOKE is off. */
1002 echo_char_raw('\n', ldata);
1009 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
1010 head = ldata->read_head;
1012 /* erase a single possibly multibyte character */
1015 c = read_buf(ldata, head);
1016 } while (is_continuation(c, tty) &&
1017 MASK(head) != MASK(ldata->canon_head));
1019 /* do not partially erase */
1020 if (is_continuation(c, tty))
1023 if (kill_type == WERASE) {
1024 /* Equivalent to BSD's ALTWERASE. */
1025 if (isalnum(c) || c == '_')
1027 else if (seen_alnums)
1030 cnt = ldata->read_head - head;
1031 ldata->read_head = head;
1033 if (L_ECHOPRT(tty)) {
1034 if (!ldata->erasing) {
1035 echo_char_raw('\\', ldata);
1038 /* if cnt > 1, output a multi-byte character */
1042 echo_char_raw(read_buf(ldata, head), ldata);
1043 echo_move_back_col(ldata);
1045 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1046 echo_char(ERASE_CHAR(tty), tty);
1047 } else if (c == '\t') {
1048 unsigned int num_chars = 0;
1050 size_t tail = ldata->read_head;
1053 * Count the columns used for characters
1054 * since the start of input or after a
1056 * This info is used to go back the correct
1057 * number of columns.
1059 while (MASK(tail) != MASK(ldata->canon_head)) {
1061 c = read_buf(ldata, tail);
1065 } else if (iscntrl(c)) {
1068 } else if (!is_continuation(c, tty)) {
1072 echo_erase_tab(num_chars, after_tab, ldata);
1074 if (iscntrl(c) && L_ECHOCTL(tty)) {
1075 echo_char_raw('\b', ldata);
1076 echo_char_raw(' ', ldata);
1077 echo_char_raw('\b', ldata);
1079 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1080 echo_char_raw('\b', ldata);
1081 echo_char_raw(' ', ldata);
1082 echo_char_raw('\b', ldata);
1086 if (kill_type == ERASE)
1089 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1090 finish_erasing(ldata);
1094 * isig - handle the ISIG optio
1098 * Called when a signal is being sent due to terminal input.
1099 * Called from the driver receive_buf path so serialized.
1101 * Performs input and output flush if !NOFLSH. In this context, the echo
1102 * buffer is 'output'. The signal is processed first to alert any current
1103 * readers or writers to discontinue and exit their i/o loops.
1105 * Locking: ctrl_lock
1108 static void __isig(int sig, struct tty_struct *tty)
1110 struct pid *tty_pgrp = tty_get_pgrp(tty);
1112 kill_pgrp(tty_pgrp, sig, 1);
1117 static void isig(int sig, struct tty_struct *tty)
1119 struct n_tty_data *ldata = tty->disc_data;
1121 if (L_NOFLSH(tty)) {
1125 } else { /* signal and flush */
1126 up_read(&tty->termios_rwsem);
1127 down_write(&tty->termios_rwsem);
1131 /* clear echo buffer */
1132 mutex_lock(&ldata->output_lock);
1133 ldata->echo_head = ldata->echo_tail = 0;
1134 ldata->echo_mark = ldata->echo_commit = 0;
1135 mutex_unlock(&ldata->output_lock);
1137 /* clear output buffer */
1138 tty_driver_flush_buffer(tty);
1140 /* clear input buffer */
1141 reset_buffer_flags(tty->disc_data);
1143 /* notify pty master of flush */
1145 n_tty_packet_mode_flush(tty);
1147 up_write(&tty->termios_rwsem);
1148 down_read(&tty->termios_rwsem);
1153 * n_tty_receive_break - handle break
1156 * An RS232 break event has been hit in the incoming bitstream. This
1157 * can cause a variety of events depending upon the termios settings.
1159 * n_tty_receive_buf()/producer path:
1160 * caller holds non-exclusive termios_rwsem
1162 * Note: may get exclusive termios_rwsem if flushing input buffer
1165 static void n_tty_receive_break(struct tty_struct *tty)
1167 struct n_tty_data *ldata = tty->disc_data;
1171 if (I_BRKINT(tty)) {
1175 if (I_PARMRK(tty)) {
1176 put_tty_queue('\377', ldata);
1177 put_tty_queue('\0', ldata);
1179 put_tty_queue('\0', ldata);
1183 * n_tty_receive_overrun - handle overrun reporting
1186 * Data arrived faster than we could process it. While the tty
1187 * driver has flagged this the bits that were missed are gone
1190 * Called from the receive_buf path so single threaded. Does not
1191 * need locking as num_overrun and overrun_time are function
1195 static void n_tty_receive_overrun(struct tty_struct *tty)
1197 struct n_tty_data *ldata = tty->disc_data;
1199 ldata->num_overrun++;
1200 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1201 time_after(ldata->overrun_time, jiffies)) {
1202 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1203 ldata->overrun_time = jiffies;
1204 ldata->num_overrun = 0;
1209 * n_tty_receive_parity_error - error notifier
1210 * @tty: terminal device
1213 * Process a parity error and queue the right data to indicate
1214 * the error case if necessary.
1216 * n_tty_receive_buf()/producer path:
1217 * caller holds non-exclusive termios_rwsem
1219 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1221 struct n_tty_data *ldata = tty->disc_data;
1226 if (I_PARMRK(tty)) {
1227 put_tty_queue('\377', ldata);
1228 put_tty_queue('\0', ldata);
1229 put_tty_queue(c, ldata);
1231 put_tty_queue('\0', ldata);
1233 put_tty_queue(c, ldata);
1237 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1246 process_echoes(tty);
1251 * n_tty_receive_char - perform processing
1252 * @tty: terminal device
1255 * Process an individual character of input received from the driver.
1256 * This is serialized with respect to itself by the rules for the
1259 * n_tty_receive_buf()/producer path:
1260 * caller holds non-exclusive termios_rwsem
1261 * publishes canon_head if canonical mode is active
1263 * Returns 1 if LNEXT was received, else returns 0
1267 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1269 struct n_tty_data *ldata = tty->disc_data;
1272 if (c == START_CHAR(tty)) {
1274 process_echoes(tty);
1277 if (c == STOP_CHAR(tty)) {
1284 if (c == INTR_CHAR(tty)) {
1285 n_tty_receive_signal_char(tty, SIGINT, c);
1287 } else if (c == QUIT_CHAR(tty)) {
1288 n_tty_receive_signal_char(tty, SIGQUIT, c);
1290 } else if (c == SUSP_CHAR(tty)) {
1291 n_tty_receive_signal_char(tty, SIGTSTP, c);
1296 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1298 process_echoes(tty);
1306 } else if (c == '\n' && I_INLCR(tty))
1309 if (ldata->icanon) {
1310 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1311 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1316 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1319 finish_erasing(ldata);
1320 if (L_ECHOCTL(tty)) {
1321 echo_char_raw('^', ldata);
1322 echo_char_raw('\b', ldata);
1328 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1329 size_t tail = ldata->canon_head;
1331 finish_erasing(ldata);
1333 echo_char_raw('\n', ldata);
1334 while (MASK(tail) != MASK(ldata->read_head)) {
1335 echo_char(read_buf(ldata, tail), tty);
1342 if (L_ECHO(tty) || L_ECHONL(tty)) {
1343 echo_char_raw('\n', ldata);
1346 goto handle_newline;
1348 if (c == EOF_CHAR(tty)) {
1349 c = __DISABLED_CHAR;
1350 goto handle_newline;
1352 if ((c == EOL_CHAR(tty)) ||
1353 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1355 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1358 /* Record the column of first canon char. */
1359 if (ldata->canon_head == ldata->read_head)
1360 echo_set_canon_col(ldata);
1365 * XXX does PARMRK doubling happen for
1366 * EOL_CHAR and EOL2_CHAR?
1368 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1369 put_tty_queue(c, ldata);
1372 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1373 put_tty_queue(c, ldata);
1374 smp_store_release(&ldata->canon_head, ldata->read_head);
1375 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1376 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1382 finish_erasing(ldata);
1384 echo_char_raw('\n', ldata);
1386 /* Record the column of first canon char. */
1387 if (ldata->canon_head == ldata->read_head)
1388 echo_set_canon_col(ldata);
1394 /* PARMRK doubling check */
1395 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1396 put_tty_queue(c, ldata);
1398 put_tty_queue(c, ldata);
1403 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1405 struct n_tty_data *ldata = tty->disc_data;
1407 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1409 process_echoes(tty);
1412 finish_erasing(ldata);
1413 /* Record the column of first canon char. */
1414 if (ldata->canon_head == ldata->read_head)
1415 echo_set_canon_col(ldata);
1419 /* PARMRK doubling check */
1420 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1421 put_tty_queue(c, ldata);
1422 put_tty_queue(c, ldata);
1425 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1427 n_tty_receive_char_inline(tty, c);
1431 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1433 struct n_tty_data *ldata = tty->disc_data;
1435 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1437 process_echoes(tty);
1440 finish_erasing(ldata);
1441 /* Record the column of first canon char. */
1442 if (ldata->canon_head == ldata->read_head)
1443 echo_set_canon_col(ldata);
1447 put_tty_queue(c, ldata);
1450 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1454 if (I_IUCLC(tty) && L_IEXTEN(tty))
1458 if (c == STOP_CHAR(tty))
1460 else if (c == START_CHAR(tty) ||
1461 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1462 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1463 c != SUSP_CHAR(tty))) {
1465 process_echoes(tty);
1471 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1475 n_tty_receive_break(tty);
1479 n_tty_receive_parity_error(tty, c);
1482 n_tty_receive_overrun(tty);
1485 tty_err(tty, "unknown flag %d\n", flag);
1491 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1493 struct n_tty_data *ldata = tty->disc_data;
1496 if (likely(flag == TTY_NORMAL)) {
1499 if (I_IUCLC(tty) && L_IEXTEN(tty))
1501 n_tty_receive_char(tty, c);
1503 n_tty_receive_char_flagged(tty, c, flag);
1507 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1508 char *fp, int count)
1510 struct n_tty_data *ldata = tty->disc_data;
1513 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1514 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1515 memcpy(read_buf_addr(ldata, head), cp, n);
1516 ldata->read_head += n;
1520 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1521 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1522 memcpy(read_buf_addr(ldata, head), cp, n);
1523 ldata->read_head += n;
1527 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1528 char *fp, int count)
1530 struct n_tty_data *ldata = tty->disc_data;
1531 char flag = TTY_NORMAL;
1536 if (likely(flag == TTY_NORMAL))
1537 put_tty_queue(*cp++, ldata);
1539 n_tty_receive_char_flagged(tty, *cp++, flag);
1544 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1545 char *fp, int count)
1547 char flag = TTY_NORMAL;
1552 if (likely(flag == TTY_NORMAL))
1553 n_tty_receive_char_closing(tty, *cp++);
1558 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1559 char *fp, int count)
1561 struct n_tty_data *ldata = tty->disc_data;
1562 char flag = TTY_NORMAL;
1567 if (likely(flag == TTY_NORMAL)) {
1568 unsigned char c = *cp++;
1572 if (I_IUCLC(tty) && L_IEXTEN(tty))
1574 if (L_EXTPROC(tty)) {
1575 put_tty_queue(c, ldata);
1578 if (!test_bit(c, ldata->char_map))
1579 n_tty_receive_char_inline(tty, c);
1580 else if (n_tty_receive_char_special(tty, c) && count) {
1583 n_tty_receive_char_lnext(tty, *cp++, flag);
1587 n_tty_receive_char_flagged(tty, *cp++, flag);
1592 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1593 char *fp, int count)
1595 struct n_tty_data *ldata = tty->disc_data;
1596 char flag = TTY_NORMAL;
1601 if (likely(flag == TTY_NORMAL)) {
1602 unsigned char c = *cp++;
1604 if (!test_bit(c, ldata->char_map))
1605 n_tty_receive_char_fast(tty, c);
1606 else if (n_tty_receive_char_special(tty, c) && count) {
1609 n_tty_receive_char_lnext(tty, *cp++, flag);
1613 n_tty_receive_char_flagged(tty, *cp++, flag);
1617 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1618 char *fp, int count)
1620 struct n_tty_data *ldata = tty->disc_data;
1621 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1623 if (ldata->real_raw)
1624 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1625 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1626 n_tty_receive_buf_raw(tty, cp, fp, count);
1627 else if (tty->closing && !L_EXTPROC(tty))
1628 n_tty_receive_buf_closing(tty, cp, fp, count);
1631 char flag = TTY_NORMAL;
1635 n_tty_receive_char_lnext(tty, *cp++, flag);
1639 if (!preops && !I_PARMRK(tty))
1640 n_tty_receive_buf_fast(tty, cp, fp, count);
1642 n_tty_receive_buf_standard(tty, cp, fp, count);
1645 if (tty->ops->flush_chars)
1646 tty->ops->flush_chars(tty);
1649 if (ldata->icanon && !L_EXTPROC(tty))
1652 /* publish read_head to consumer */
1653 smp_store_release(&ldata->commit_head, ldata->read_head);
1655 if (read_cnt(ldata)) {
1656 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1657 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1662 * n_tty_receive_buf_common - process input
1663 * @tty: device to receive input
1665 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1666 * @count: number of input chars in @cp
1668 * Called by the terminal driver when a block of characters has
1669 * been received. This function must be called from soft contexts
1670 * not from interrupt context. The driver is responsible for making
1671 * calls one at a time and in order (or using flush_to_ldisc)
1673 * Returns the # of input chars from @cp which were processed.
1675 * In canonical mode, the maximum line length is 4096 chars (including
1676 * the line termination char); lines longer than 4096 chars are
1677 * truncated. After 4095 chars, input data is still processed but
1678 * not stored. Overflow processing ensures the tty can always
1679 * receive more input until at least one line can be read.
1681 * In non-canonical mode, the read buffer will only accept 4095 chars;
1682 * this provides the necessary space for a newline char if the input
1683 * mode is switched to canonical.
1685 * Note it is possible for the read buffer to _contain_ 4096 chars
1686 * in non-canonical mode: the read buffer could already contain the
1687 * maximum canon line of 4096 chars when the mode is switched to
1690 * n_tty_receive_buf()/producer path:
1691 * claims non-exclusive termios_rwsem
1692 * publishes commit_head or canon_head
1695 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1696 char *fp, int count, int flow)
1698 struct n_tty_data *ldata = tty->disc_data;
1699 int room, n, rcvd = 0, overflow;
1701 down_read(&tty->termios_rwsem);
1705 * When PARMRK is set, each input char may take up to 3 chars
1706 * in the read buf; reduce the buffer space avail by 3x
1708 * If we are doing input canonicalization, and there are no
1709 * pending newlines, let characters through without limit, so
1710 * that erase characters will be handled. Other excess
1711 * characters will be beeped.
1713 * paired with store in *_copy_from_read_buf() -- guarantees
1714 * the consumer has loaded the data in read_buf up to the new
1715 * read_tail (so this producer will not overwrite unread data)
1717 size_t tail = smp_load_acquire(&ldata->read_tail);
1719 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1721 room = (room + 2) / 3;
1724 overflow = ldata->icanon && ldata->canon_head == tail;
1725 if (overflow && room < 0)
1728 ldata->no_room = flow && !room;
1732 n = min(count, room);
1736 /* ignore parity errors if handling overflow */
1737 if (!overflow || !fp || *fp != TTY_PARITY)
1738 __receive_buf(tty, cp, fp, n);
1745 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1747 tty->receive_room = room;
1749 /* Unthrottle if handling overflow on pty */
1750 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1752 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1753 tty_unthrottle_safe(tty);
1754 __tty_set_flow_change(tty, 0);
1757 n_tty_check_throttle(tty);
1759 up_read(&tty->termios_rwsem);
1764 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1765 char *fp, int count)
1767 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1770 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1771 char *fp, int count)
1773 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1777 * n_tty_set_termios - termios data changed
1779 * @old: previous data
1781 * Called by the tty layer when the user changes termios flags so
1782 * that the line discipline can plan ahead. This function cannot sleep
1783 * and is protected from re-entry by the tty layer. The user is
1784 * guaranteed that this function will not be re-entered or in progress
1785 * when the ldisc is closed.
1787 * Locking: Caller holds tty->termios_rwsem
1790 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1792 struct n_tty_data *ldata = tty->disc_data;
1794 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1795 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1796 ldata->line_start = ldata->read_tail;
1797 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1798 ldata->canon_head = ldata->read_tail;
1801 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1803 ldata->canon_head = ldata->read_head;
1806 ldata->commit_head = ldata->read_head;
1811 ldata->icanon = (L_ICANON(tty) != 0);
1813 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1814 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1815 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1817 bitmap_zero(ldata->char_map, 256);
1819 if (I_IGNCR(tty) || I_ICRNL(tty))
1820 set_bit('\r', ldata->char_map);
1822 set_bit('\n', ldata->char_map);
1824 if (L_ICANON(tty)) {
1825 set_bit(ERASE_CHAR(tty), ldata->char_map);
1826 set_bit(KILL_CHAR(tty), ldata->char_map);
1827 set_bit(EOF_CHAR(tty), ldata->char_map);
1828 set_bit('\n', ldata->char_map);
1829 set_bit(EOL_CHAR(tty), ldata->char_map);
1830 if (L_IEXTEN(tty)) {
1831 set_bit(WERASE_CHAR(tty), ldata->char_map);
1832 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1833 set_bit(EOL2_CHAR(tty), ldata->char_map);
1835 set_bit(REPRINT_CHAR(tty),
1840 set_bit(START_CHAR(tty), ldata->char_map);
1841 set_bit(STOP_CHAR(tty), ldata->char_map);
1844 set_bit(INTR_CHAR(tty), ldata->char_map);
1845 set_bit(QUIT_CHAR(tty), ldata->char_map);
1846 set_bit(SUSP_CHAR(tty), ldata->char_map);
1848 clear_bit(__DISABLED_CHAR, ldata->char_map);
1850 ldata->real_raw = 0;
1853 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1854 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1855 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1856 ldata->real_raw = 1;
1858 ldata->real_raw = 0;
1861 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1862 * been stopped by STOP_CHAR(tty) before it.
1864 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1866 process_echoes(tty);
1869 /* The termios change make the tty ready for I/O */
1870 wake_up_interruptible(&tty->write_wait);
1871 wake_up_interruptible(&tty->read_wait);
1875 * n_tty_close - close the ldisc for this tty
1878 * Called from the terminal layer when this line discipline is
1879 * being shut down, either because of a close or becsuse of a
1880 * discipline change. The function will not be called while other
1881 * ldisc methods are in progress.
1884 static void n_tty_close(struct tty_struct *tty)
1886 struct n_tty_data *ldata = tty->disc_data;
1889 n_tty_packet_mode_flush(tty);
1892 tty->disc_data = NULL;
1896 * n_tty_open - open an ldisc
1897 * @tty: terminal to open
1899 * Called when this line discipline is being attached to the
1900 * terminal device. Can sleep. Called serialized so that no
1901 * other events will occur in parallel. No further open will occur
1905 static int n_tty_open(struct tty_struct *tty)
1907 struct n_tty_data *ldata;
1909 /* Currently a malloc failure here can panic */
1910 ldata = vzalloc(sizeof(*ldata));
1914 ldata->overrun_time = jiffies;
1915 mutex_init(&ldata->atomic_read_lock);
1916 mutex_init(&ldata->output_lock);
1918 tty->disc_data = ldata;
1920 /* indicate buffer work may resume */
1921 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1922 n_tty_set_termios(tty, NULL);
1923 tty_unthrottle(tty);
1927 static inline int input_available_p(struct tty_struct *tty, int poll)
1929 struct n_tty_data *ldata = tty->disc_data;
1930 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1932 if (ldata->icanon && !L_EXTPROC(tty))
1933 return ldata->canon_head != ldata->read_tail;
1935 return ldata->commit_head - ldata->read_tail >= amt;
1939 * copy_from_read_buf - copy read data directly
1940 * @tty: terminal device
1944 * Helper function to speed up n_tty_read. It is only called when
1945 * ICANON is off; it copies characters straight from the tty queue.
1947 * Called under the ldata->atomic_read_lock sem
1949 * Returns true if it successfully copied data, but there is still
1950 * more data to be had.
1952 * n_tty_read()/consumer path:
1953 * caller holds non-exclusive termios_rwsem
1954 * read_tail published
1957 static bool copy_from_read_buf(struct tty_struct *tty,
1958 unsigned char **kbp,
1962 struct n_tty_data *ldata = tty->disc_data;
1965 size_t head = smp_load_acquire(&ldata->commit_head);
1966 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1968 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1971 unsigned char *from = read_buf_addr(ldata, tail);
1972 memcpy(*kbp, from, n);
1973 is_eof = n == 1 && *from == EOF_CHAR(tty);
1974 tty_audit_add_data(tty, from, n);
1975 zero_buffer(tty, from, n);
1976 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1977 /* Turn single EOF into zero-length read */
1978 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1979 (head == ldata->read_tail))
1984 /* If we have more to copy, let the caller know */
1985 return head != ldata->read_tail;
1991 * canon_copy_from_read_buf - copy read data in canonical mode
1992 * @tty: terminal device
1996 * Helper function for n_tty_read. It is only called when ICANON is on;
1997 * it copies one line of input up to and including the line-delimiting
1998 * character into the result buffer.
2000 * NB: When termios is changed from non-canonical to canonical mode and
2001 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2002 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2003 * This causes data already processed as input to be immediately available
2004 * as input although a newline has not been received.
2006 * Called under the atomic_read_lock mutex
2008 * n_tty_read()/consumer path:
2009 * caller holds non-exclusive termios_rwsem
2010 * read_tail published
2013 static bool canon_copy_from_read_buf(struct tty_struct *tty,
2014 unsigned char **kbp,
2017 struct n_tty_data *ldata = tty->disc_data;
2018 size_t n, size, more, c;
2020 size_t tail, canon_head;
2023 /* N.B. avoid overrun if nr == 0 */
2027 canon_head = smp_load_acquire(&ldata->canon_head);
2028 n = min(*nr, canon_head - ldata->read_tail);
2030 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2031 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2033 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2034 __func__, *nr, tail, n, size);
2036 eol = find_next_bit(ldata->read_flags, size, tail);
2037 more = n - (size - tail);
2038 if (eol == N_TTY_BUF_SIZE && more) {
2039 /* scan wrapped without finding set bit */
2040 eol = find_next_bit(ldata->read_flags, more, 0);
2041 found = eol != more;
2043 found = eol != size;
2046 if (n > N_TTY_BUF_SIZE)
2047 n += N_TTY_BUF_SIZE;
2050 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
2053 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2054 __func__, eol, found, n, c, tail, more);
2056 tty_copy(tty, *kbp, tail, n);
2061 clear_bit(eol, ldata->read_flags);
2062 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2066 ldata->line_start = ldata->read_tail;
2073 /* No EOL found - do a continuation retry if there is more data */
2074 return ldata->read_tail != canon_head;
2078 * If we finished a read at the exact location of an
2079 * EOF (special EOL character that's a __DISABLED_CHAR)
2080 * in the stream, silently eat the EOF.
2082 static void canon_skip_eof(struct tty_struct *tty)
2084 struct n_tty_data *ldata = tty->disc_data;
2085 size_t tail, canon_head;
2087 canon_head = smp_load_acquire(&ldata->canon_head);
2088 tail = ldata->read_tail;
2091 if (tail == canon_head)
2094 // See if the tail position is EOF in the circular buffer
2095 tail &= (N_TTY_BUF_SIZE - 1);
2096 if (!test_bit(tail, ldata->read_flags))
2098 if (read_buf(ldata, tail) != __DISABLED_CHAR)
2101 // Clear the EOL bit, skip the EOF char.
2102 clear_bit(tail, ldata->read_flags);
2103 smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2107 * job_control - check job control
2109 * @file: file handle
2111 * Perform job control management checks on this file/tty descriptor
2112 * and if appropriate send any needed signals and return a negative
2113 * error code if action should be taken.
2115 * Locking: redirected write test is safe
2116 * current->signal->tty check is safe
2117 * ctrl_lock to safely reference tty->pgrp
2120 static int job_control(struct tty_struct *tty, struct file *file)
2122 /* Job control check -- must be done at start and after
2123 every sleep (POSIX.1 7.1.1.4). */
2124 /* NOTE: not yet done after every sleep pending a thorough
2125 check of the logic of this change. -- jlc */
2126 /* don't stop on /dev/console */
2127 if (file->f_op->write_iter == redirected_tty_write)
2130 return __tty_check_change(tty, SIGTTIN);
2135 * n_tty_read - read function for tty
2137 * @file: file object
2138 * @buf: userspace buffer pointer
2141 * Perform reads for the line discipline. We are guaranteed that the
2142 * line discipline will not be closed under us but we may get multiple
2143 * parallel readers and must handle this ourselves. We may also get
2144 * a hangup. Always called in user context, may sleep.
2146 * This code must be sure never to sleep through a hangup.
2148 * n_tty_read()/consumer path:
2149 * claims non-exclusive termios_rwsem
2150 * publishes read_tail
2153 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2154 unsigned char *kbuf, size_t nr,
2155 void **cookie, unsigned long offset)
2157 struct n_tty_data *ldata = tty->disc_data;
2158 unsigned char *kb = kbuf;
2159 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2168 * Is this a continuation of a read started earler?
2170 * If so, we still hold the atomic_read_lock and the
2171 * termios_rwsem, and can just continue to copy data.
2174 if (ldata->icanon && !L_EXTPROC(tty)) {
2176 * If we have filled the user buffer, see
2177 * if we should skip an EOF character before
2178 * releasing the lock and returning done.
2181 canon_skip_eof(tty);
2182 else if (canon_copy_from_read_buf(tty, &kb, &nr))
2185 if (copy_from_read_buf(tty, &kb, &nr))
2189 /* No more data - release locks and stop retries */
2190 n_tty_kick_worker(tty);
2191 n_tty_check_unthrottle(tty);
2192 up_read(&tty->termios_rwsem);
2193 mutex_unlock(&ldata->atomic_read_lock);
2198 c = job_control(tty, file);
2203 * Internal serialization of reads.
2205 if (file->f_flags & O_NONBLOCK) {
2206 if (!mutex_trylock(&ldata->atomic_read_lock))
2209 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2210 return -ERESTARTSYS;
2213 down_read(&tty->termios_rwsem);
2216 timeout = MAX_SCHEDULE_TIMEOUT;
2217 if (!ldata->icanon) {
2218 minimum = MIN_CHAR(tty);
2220 time = (HZ / 10) * TIME_CHAR(tty);
2222 timeout = (HZ / 10) * TIME_CHAR(tty);
2227 packet = tty->packet;
2228 tail = ldata->read_tail;
2230 add_wait_queue(&tty->read_wait, &wait);
2232 /* First test for status change. */
2233 if (packet && tty->link->ctrl_status) {
2237 spin_lock_irq(&tty->link->ctrl_lock);
2238 cs = tty->link->ctrl_status;
2239 tty->link->ctrl_status = 0;
2240 spin_unlock_irq(&tty->link->ctrl_lock);
2246 if (!input_available_p(tty, 0)) {
2247 up_read(&tty->termios_rwsem);
2248 tty_buffer_flush_work(tty->port);
2249 down_read(&tty->termios_rwsem);
2250 if (!input_available_p(tty, 0)) {
2251 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2255 if (tty_hung_up_p(file))
2258 * Abort readers for ttys which never actually
2259 * get hung up. See __tty_hangup().
2261 if (test_bit(TTY_HUPPING, &tty->flags))
2265 if (tty_io_nonblock(tty, file)) {
2269 if (signal_pending(current)) {
2270 retval = -ERESTARTSYS;
2273 up_read(&tty->termios_rwsem);
2275 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2278 down_read(&tty->termios_rwsem);
2283 if (ldata->icanon && !L_EXTPROC(tty)) {
2284 if (canon_copy_from_read_buf(tty, &kb, &nr))
2285 goto more_to_be_read;
2287 /* Deal with packet mode. */
2288 if (packet && kb == kbuf) {
2289 *kb++ = TIOCPKT_DATA;
2294 * Copy data, and if there is more to be had
2295 * and we have nothing more to wait for, then
2296 * let's mark us for retries.
2298 * NOTE! We return here with both the termios_sem
2299 * and atomic_read_lock still held, the retries
2300 * will release them when done.
2302 if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2304 remove_wait_queue(&tty->read_wait, &wait);
2310 n_tty_check_unthrottle(tty);
2312 if (kb - kbuf >= minimum)
2317 if (tail != ldata->read_tail)
2318 n_tty_kick_worker(tty);
2319 up_read(&tty->termios_rwsem);
2321 remove_wait_queue(&tty->read_wait, &wait);
2322 mutex_unlock(&ldata->atomic_read_lock);
2331 * n_tty_write - write function for tty
2333 * @file: file object
2334 * @buf: userspace buffer pointer
2337 * Write function of the terminal device. This is serialized with
2338 * respect to other write callers but not to termios changes, reads
2339 * and other such events. Since the receive code will echo characters,
2340 * thus calling driver write methods, the output_lock is used in
2341 * the output processing functions called here as well as in the
2342 * echo processing function to protect the column state and space
2343 * left in the buffer.
2345 * This code must be sure never to sleep through a hangup.
2347 * Locking: output_lock to protect column state and space left
2348 * (note that the process_output*() functions take this
2352 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2353 const unsigned char *buf, size_t nr)
2355 const unsigned char *b = buf;
2356 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2360 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2361 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2362 retval = tty_check_change(tty);
2367 down_read(&tty->termios_rwsem);
2369 /* Write out any echoed characters that are still pending */
2370 process_echoes(tty);
2372 add_wait_queue(&tty->write_wait, &wait);
2374 if (signal_pending(current)) {
2375 retval = -ERESTARTSYS;
2378 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2384 ssize_t num = process_output_block(tty, b, nr);
2396 if (process_output(c, tty) < 0)
2400 if (tty->ops->flush_chars)
2401 tty->ops->flush_chars(tty);
2403 struct n_tty_data *ldata = tty->disc_data;
2406 mutex_lock(&ldata->output_lock);
2407 c = tty->ops->write(tty, b, nr);
2408 mutex_unlock(&ldata->output_lock);
2421 if (tty_io_nonblock(tty, file)) {
2425 up_read(&tty->termios_rwsem);
2427 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2429 down_read(&tty->termios_rwsem);
2432 remove_wait_queue(&tty->write_wait, &wait);
2433 if (nr && tty->fasync)
2434 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2435 up_read(&tty->termios_rwsem);
2436 return (b - buf) ? b - buf : retval;
2440 * n_tty_poll - poll method for N_TTY
2441 * @tty: terminal device
2442 * @file: file accessing it
2445 * Called when the line discipline is asked to poll() for data or
2446 * for special events. This code is not serialized with respect to
2447 * other events save open/close.
2449 * This code must be sure never to sleep through a hangup.
2450 * Called without the kernel lock held - fine
2453 static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2458 poll_wait(file, &tty->read_wait, wait);
2459 poll_wait(file, &tty->write_wait, wait);
2460 if (input_available_p(tty, 1))
2461 mask |= EPOLLIN | EPOLLRDNORM;
2463 tty_buffer_flush_work(tty->port);
2464 if (input_available_p(tty, 1))
2465 mask |= EPOLLIN | EPOLLRDNORM;
2467 if (tty->packet && tty->link->ctrl_status)
2468 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2469 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2471 if (tty_hung_up_p(file))
2473 if (tty->ops->write && !tty_is_writelocked(tty) &&
2474 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2475 tty_write_room(tty) > 0)
2476 mask |= EPOLLOUT | EPOLLWRNORM;
2480 static unsigned long inq_canon(struct n_tty_data *ldata)
2482 size_t nr, head, tail;
2484 if (ldata->canon_head == ldata->read_tail)
2486 head = ldata->canon_head;
2487 tail = ldata->read_tail;
2489 /* Skip EOF-chars.. */
2490 while (MASK(head) != MASK(tail)) {
2491 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2492 read_buf(ldata, tail) == __DISABLED_CHAR)
2499 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2500 unsigned int cmd, unsigned long arg)
2502 struct n_tty_data *ldata = tty->disc_data;
2507 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2509 down_write(&tty->termios_rwsem);
2510 if (L_ICANON(tty) && !L_EXTPROC(tty))
2511 retval = inq_canon(ldata);
2513 retval = read_cnt(ldata);
2514 up_write(&tty->termios_rwsem);
2515 return put_user(retval, (unsigned int __user *) arg);
2517 return n_tty_ioctl_helper(tty, file, cmd, arg);
2521 static struct tty_ldisc_ops n_tty_ops = {
2522 .magic = TTY_LDISC_MAGIC,
2525 .close = n_tty_close,
2526 .flush_buffer = n_tty_flush_buffer,
2528 .write = n_tty_write,
2529 .ioctl = n_tty_ioctl,
2530 .set_termios = n_tty_set_termios,
2532 .receive_buf = n_tty_receive_buf,
2533 .write_wakeup = n_tty_write_wakeup,
2534 .receive_buf2 = n_tty_receive_buf2,
2538 * n_tty_inherit_ops - inherit N_TTY methods
2539 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2541 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2544 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2548 ops->refcount = ops->flags = 0;
2550 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2552 void __init n_tty_init(void)
2554 tty_register_ldisc(N_TTY, &n_tty_ops);