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>
54 * Until this number of characters is queued in the xmit buffer, select will
55 * return "we have room for writes".
57 #define WAKEUP_CHARS 256
60 * This defines the low- and high-watermarks for throttling and
61 * unthrottling the TTY driver. These watermarks are used for
62 * controlling the space in the read buffer.
64 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
65 #define TTY_THRESHOLD_UNTHROTTLE 128
68 * Special byte codes used in the echo buffer to represent operations
69 * or special handling of characters. Bytes in the echo buffer that
70 * are not part of such special blocks are treated as normal character
73 #define ECHO_OP_START 0xff
74 #define ECHO_OP_MOVE_BACK_COL 0x80
75 #define ECHO_OP_SET_CANON_COL 0x81
76 #define ECHO_OP_ERASE_TAB 0x82
78 #define ECHO_COMMIT_WATERMARK 256
79 #define ECHO_BLOCK 256
80 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
85 # define n_tty_trace(f, args...) trace_printk(f, ##args)
87 # define n_tty_trace(f, args...) no_printk(f, ##args)
91 /* producer-published */
98 DECLARE_BITMAP(char_map, 256);
100 /* private to n_tty_receive_overrun (single-threaded) */
101 unsigned long overrun_time;
107 /* must hold exclusive termios_rwsem to reset these */
108 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
109 unsigned char push:1;
111 /* shared by producer and consumer */
112 char read_buf[N_TTY_BUF_SIZE];
113 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
114 unsigned char echo_buf[N_TTY_BUF_SIZE];
116 /* consumer-published */
120 /* protected by output lock */
122 unsigned int canon_column;
125 struct mutex atomic_read_lock;
126 struct mutex output_lock;
129 #define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
131 static inline size_t read_cnt(struct n_tty_data *ldata)
133 return ldata->read_head - ldata->read_tail;
136 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
138 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
141 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
143 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
146 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
148 smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
149 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
152 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
154 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
157 /* If we are not echoing the data, perhaps this is a secret so erase it */
158 static void zero_buffer(struct tty_struct *tty, u8 *buffer, int size)
160 bool icanon = !!L_ICANON(tty);
161 bool no_echo = !L_ECHO(tty);
163 if (icanon && no_echo)
164 memset(buffer, 0x00, size);
167 static void tty_copy(struct tty_struct *tty, void *to, size_t tail, size_t n)
169 struct n_tty_data *ldata = tty->disc_data;
170 size_t size = N_TTY_BUF_SIZE - tail;
171 void *from = read_buf_addr(ldata, tail);
174 tty_audit_add_data(tty, from, size);
175 memcpy(to, from, size);
176 zero_buffer(tty, from, size);
179 from = ldata->read_buf;
182 tty_audit_add_data(tty, from, n);
184 zero_buffer(tty, from, n);
188 * n_tty_kick_worker - start input worker (if required)
191 * Re-schedules the flip buffer work if it may have stopped
193 * Caller holds exclusive termios_rwsem
195 * n_tty_read()/consumer path:
196 * holds non-exclusive termios_rwsem
199 static void n_tty_kick_worker(struct tty_struct *tty)
201 struct n_tty_data *ldata = tty->disc_data;
203 /* Did the input worker stop? Restart it */
204 if (unlikely(ldata->no_room)) {
207 WARN_RATELIMIT(tty->port->itty == NULL,
208 "scheduling with invalid itty\n");
209 /* see if ldisc has been killed - if so, this means that
210 * even though the ldisc has been halted and ->buf.work
211 * cancelled, ->buf.work is about to be rescheduled
213 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
214 "scheduling buffer work for halted ldisc\n");
215 tty_buffer_restart_work(tty->port);
219 static ssize_t chars_in_buffer(struct tty_struct *tty)
221 struct n_tty_data *ldata = tty->disc_data;
225 n = ldata->commit_head - ldata->read_tail;
227 n = ldata->canon_head - ldata->read_tail;
232 * n_tty_write_wakeup - asynchronous I/O notifier
235 * Required for the ptys, serial driver etc. since processes
236 * that attach themselves to the master and rely on ASYNC
237 * IO must be woken up
240 static void n_tty_write_wakeup(struct tty_struct *tty)
242 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
243 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
246 static void n_tty_check_throttle(struct tty_struct *tty)
248 struct n_tty_data *ldata = tty->disc_data;
251 * Check the remaining room for the input canonicalization
252 * mode. We don't want to throttle the driver if we're in
253 * canonical mode and don't have a newline yet!
255 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
260 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
261 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
263 throttled = tty_throttle_safe(tty);
267 __tty_set_flow_change(tty, 0);
270 static void n_tty_check_unthrottle(struct tty_struct *tty)
272 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
273 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
275 n_tty_kick_worker(tty);
276 tty_wakeup(tty->link);
280 /* If there is enough space in the read buffer now, let the
281 * low-level driver know. We use chars_in_buffer() to
282 * check the buffer, as it now knows about canonical mode.
283 * Otherwise, if the driver is throttled and the line is
284 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
285 * we won't get any more characters.
290 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
291 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
293 n_tty_kick_worker(tty);
294 unthrottled = tty_unthrottle_safe(tty);
298 __tty_set_flow_change(tty, 0);
302 * put_tty_queue - add character to tty
306 * Add a character to the tty read_buf queue.
308 * n_tty_receive_buf()/producer path:
309 * caller holds non-exclusive termios_rwsem
312 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
314 *read_buf_addr(ldata, ldata->read_head) = c;
319 * reset_buffer_flags - reset buffer state
320 * @ldata: line disc data to reset
322 * Reset the read buffer counters and clear the flags.
323 * Called from n_tty_open() and n_tty_flush_buffer().
325 * Locking: caller holds exclusive termios_rwsem
326 * (or locking is not required)
329 static void reset_buffer_flags(struct n_tty_data *ldata)
331 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
332 ldata->commit_head = 0;
333 ldata->line_start = 0;
336 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
340 static void n_tty_packet_mode_flush(struct tty_struct *tty)
344 if (tty->link->packet) {
345 spin_lock_irqsave(&tty->ctrl_lock, flags);
346 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
347 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
348 wake_up_interruptible(&tty->link->read_wait);
353 * n_tty_flush_buffer - clean input queue
354 * @tty: terminal device
356 * Flush the input buffer. Called when the tty layer wants the
357 * buffer flushed (eg at hangup) or when the N_TTY line discipline
358 * internally has to clean the pending queue (for example some signals).
360 * Holds termios_rwsem to exclude producer/consumer while
361 * buffer indices are reset.
363 * Locking: ctrl_lock, exclusive termios_rwsem
366 static void n_tty_flush_buffer(struct tty_struct *tty)
368 down_write(&tty->termios_rwsem);
369 reset_buffer_flags(tty->disc_data);
370 n_tty_kick_worker(tty);
373 n_tty_packet_mode_flush(tty);
374 up_write(&tty->termios_rwsem);
378 * is_utf8_continuation - utf8 multibyte check
381 * Returns true if the utf8 character 'c' is a multibyte continuation
382 * character. We use this to correctly compute the on screen size
383 * of the character when printing
386 static inline int is_utf8_continuation(unsigned char c)
388 return (c & 0xc0) == 0x80;
392 * is_continuation - multibyte check
395 * Returns true if the utf8 character 'c' is a multibyte continuation
396 * character and the terminal is in unicode mode.
399 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
401 return I_IUTF8(tty) && is_utf8_continuation(c);
405 * do_output_char - output one character
406 * @c: character (or partial unicode symbol)
407 * @tty: terminal device
408 * @space: space available in tty driver write buffer
410 * This is a helper function that handles one output character
411 * (including special characters like TAB, CR, LF, etc.),
412 * doing OPOST processing and putting the results in the
413 * tty driver's write buffer.
415 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
416 * and NLDLY. They simply aren't relevant in the world today.
417 * If you ever need them, add them here.
419 * Returns the number of bytes of buffer space used or -1 if
422 * Locking: should be called under the output_lock to protect
423 * the column state and space left in the buffer
426 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
428 struct n_tty_data *ldata = tty->disc_data;
441 ldata->canon_column = ldata->column = 0;
442 tty->ops->write(tty, "\r\n", 2);
445 ldata->canon_column = ldata->column;
448 if (O_ONOCR(tty) && ldata->column == 0)
453 ldata->canon_column = ldata->column = 0;
456 ldata->canon_column = ldata->column = 0;
459 spaces = 8 - (ldata->column & 7);
460 if (O_TABDLY(tty) == XTABS) {
463 ldata->column += spaces;
464 tty->ops->write(tty, " ", spaces);
467 ldata->column += spaces;
470 if (ldata->column > 0)
477 if (!is_continuation(c, tty))
483 tty_put_char(tty, c);
488 * process_output - output post processor
489 * @c: character (or partial unicode symbol)
490 * @tty: terminal device
492 * Output one character with OPOST processing.
493 * Returns -1 when the output device is full and the character
496 * Locking: output_lock to protect column state and space left
497 * (also, this is called from n_tty_write under the
498 * tty layer write lock)
501 static int process_output(unsigned char c, struct tty_struct *tty)
503 struct n_tty_data *ldata = tty->disc_data;
506 mutex_lock(&ldata->output_lock);
508 space = tty_write_room(tty);
509 retval = do_output_char(c, tty, space);
511 mutex_unlock(&ldata->output_lock);
519 * process_output_block - block post processor
520 * @tty: terminal device
521 * @buf: character buffer
522 * @nr: number of bytes to output
524 * Output a block of characters with OPOST processing.
525 * Returns the number of characters output.
527 * This path is used to speed up block console writes, among other
528 * things when processing blocks of output data. It handles only
529 * the simple cases normally found and helps to generate blocks of
530 * symbols for the console driver and thus improve performance.
532 * Locking: output_lock to protect column state and space left
533 * (also, this is called from n_tty_write under the
534 * tty layer write lock)
537 static ssize_t process_output_block(struct tty_struct *tty,
538 const unsigned char *buf, unsigned int nr)
540 struct n_tty_data *ldata = tty->disc_data;
543 const unsigned char *cp;
545 mutex_lock(&ldata->output_lock);
547 space = tty_write_room(tty);
549 mutex_unlock(&ldata->output_lock);
555 for (i = 0, cp = buf; i < nr; i++, cp++) {
556 unsigned char c = *cp;
564 ldata->canon_column = ldata->column;
567 if (O_ONOCR(tty) && ldata->column == 0)
571 ldata->canon_column = ldata->column = 0;
576 if (ldata->column > 0)
583 if (!is_continuation(c, tty))
590 i = tty->ops->write(tty, buf, i);
592 mutex_unlock(&ldata->output_lock);
597 * process_echoes - write pending echo characters
598 * @tty: terminal device
600 * Write previously buffered echo (and other ldisc-generated)
601 * characters to the tty.
603 * Characters generated by the ldisc (including echoes) need to
604 * be buffered because the driver's write buffer can fill during
605 * heavy program output. Echoing straight to the driver will
606 * often fail under these conditions, causing lost characters and
607 * resulting mismatches of ldisc state information.
609 * Since the ldisc state must represent the characters actually sent
610 * to the driver at the time of the write, operations like certain
611 * changes in column state are also saved in the buffer and executed
614 * A circular fifo buffer is used so that the most recent characters
615 * are prioritized. Also, when control characters are echoed with a
616 * prefixed "^", the pair is treated atomically and thus not separated.
618 * Locking: callers must hold output_lock
621 static size_t __process_echoes(struct tty_struct *tty)
623 struct n_tty_data *ldata = tty->disc_data;
624 int space, old_space;
628 old_space = space = tty_write_room(tty);
630 tail = ldata->echo_tail;
631 while (MASK(ldata->echo_commit) != MASK(tail)) {
632 c = echo_buf(ldata, tail);
633 if (c == ECHO_OP_START) {
635 int no_space_left = 0;
638 * Since add_echo_byte() is called without holding
639 * output_lock, we might see only portion of multi-byte
642 if (MASK(ldata->echo_commit) == MASK(tail + 1))
645 * If the buffer byte is the start of a multi-byte
646 * operation, get the next byte, which is either the
647 * op code or a control character value.
649 op = echo_buf(ldata, tail + 1);
652 case ECHO_OP_ERASE_TAB: {
653 unsigned int num_chars, num_bs;
655 if (MASK(ldata->echo_commit) == MASK(tail + 2))
657 num_chars = echo_buf(ldata, tail + 2);
660 * Determine how many columns to go back
661 * in order to erase the tab.
662 * This depends on the number of columns
663 * used by other characters within the tab
664 * area. If this (modulo 8) count is from
665 * the start of input rather than from a
666 * previous tab, we offset by canon column.
667 * Otherwise, tab spacing is normal.
669 if (!(num_chars & 0x80))
670 num_chars += ldata->canon_column;
671 num_bs = 8 - (num_chars & 7);
673 if (num_bs > space) {
679 tty_put_char(tty, '\b');
680 if (ldata->column > 0)
686 case ECHO_OP_SET_CANON_COL:
687 ldata->canon_column = ldata->column;
691 case ECHO_OP_MOVE_BACK_COL:
692 if (ldata->column > 0)
698 /* This is an escaped echo op start code */
703 tty_put_char(tty, ECHO_OP_START);
711 * If the op is not a special byte code,
712 * it is a ctrl char tagged to be echoed
713 * as "^X" (where X is the letter
714 * representing the control char).
715 * Note that we must ensure there is
716 * enough space for the whole ctrl pair.
723 tty_put_char(tty, '^');
724 tty_put_char(tty, op ^ 0100);
734 int retval = do_output_char(c, tty, space);
741 tty_put_char(tty, c);
748 /* If the echo buffer is nearly full (so that the possibility exists
749 * of echo overrun before the next commit), then discard enough
750 * data at the tail to prevent a subsequent overrun */
751 while (ldata->echo_commit > tail &&
752 ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
753 if (echo_buf(ldata, tail) == ECHO_OP_START) {
754 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
763 ldata->echo_tail = tail;
764 return old_space - space;
767 static void commit_echoes(struct tty_struct *tty)
769 struct n_tty_data *ldata = tty->disc_data;
770 size_t nr, old, echoed;
773 mutex_lock(&ldata->output_lock);
774 head = ldata->echo_head;
775 ldata->echo_mark = head;
776 old = ldata->echo_commit - ldata->echo_tail;
778 /* Process committed echoes if the accumulated # of bytes
779 * is over the threshold (and try again each time another
780 * block is accumulated) */
781 nr = head - ldata->echo_tail;
782 if (nr < ECHO_COMMIT_WATERMARK ||
783 (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
784 mutex_unlock(&ldata->output_lock);
788 ldata->echo_commit = head;
789 echoed = __process_echoes(tty);
790 mutex_unlock(&ldata->output_lock);
792 if (echoed && tty->ops->flush_chars)
793 tty->ops->flush_chars(tty);
796 static void process_echoes(struct tty_struct *tty)
798 struct n_tty_data *ldata = tty->disc_data;
801 if (ldata->echo_mark == ldata->echo_tail)
804 mutex_lock(&ldata->output_lock);
805 ldata->echo_commit = ldata->echo_mark;
806 echoed = __process_echoes(tty);
807 mutex_unlock(&ldata->output_lock);
809 if (echoed && tty->ops->flush_chars)
810 tty->ops->flush_chars(tty);
813 /* NB: echo_mark and echo_head should be equivalent here */
814 static void flush_echoes(struct tty_struct *tty)
816 struct n_tty_data *ldata = tty->disc_data;
818 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
819 ldata->echo_commit == ldata->echo_head)
822 mutex_lock(&ldata->output_lock);
823 ldata->echo_commit = ldata->echo_head;
824 __process_echoes(tty);
825 mutex_unlock(&ldata->output_lock);
829 * add_echo_byte - add a byte to the echo buffer
830 * @c: unicode byte to echo
833 * Add a character or operation byte to the echo buffer.
836 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
838 *echo_buf_addr(ldata, ldata->echo_head) = c;
839 smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
844 * echo_move_back_col - add operation to move back a column
847 * Add an operation to the echo buffer to move back one column.
850 static void echo_move_back_col(struct n_tty_data *ldata)
852 add_echo_byte(ECHO_OP_START, ldata);
853 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
857 * echo_set_canon_col - add operation to set the canon column
860 * Add an operation to the echo buffer to set the canon column
861 * to the current column.
864 static void echo_set_canon_col(struct n_tty_data *ldata)
866 add_echo_byte(ECHO_OP_START, ldata);
867 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
871 * echo_erase_tab - add operation to erase a tab
872 * @num_chars: number of character columns already used
873 * @after_tab: true if num_chars starts after a previous tab
876 * Add an operation to the echo buffer to erase a tab.
878 * Called by the eraser function, which knows how many character
879 * columns have been used since either a previous tab or the start
880 * of input. This information will be used later, along with
881 * canon column (if applicable), to go back the correct number
885 static void echo_erase_tab(unsigned int num_chars, int after_tab,
886 struct n_tty_data *ldata)
888 add_echo_byte(ECHO_OP_START, ldata);
889 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
891 /* We only need to know this modulo 8 (tab spacing) */
894 /* Set the high bit as a flag if num_chars is after a previous tab */
898 add_echo_byte(num_chars, ldata);
902 * echo_char_raw - echo a character raw
903 * @c: unicode byte to echo
904 * @ldata: line disc data
906 * Echo user input back onto the screen. This must be called only when
907 * L_ECHO(tty) is true. Called from the driver receive_buf path.
909 * This variant does not treat control characters specially.
912 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
914 if (c == ECHO_OP_START) {
915 add_echo_byte(ECHO_OP_START, ldata);
916 add_echo_byte(ECHO_OP_START, ldata);
918 add_echo_byte(c, ldata);
923 * echo_char - echo a character
924 * @c: unicode byte to echo
925 * @tty: terminal device
927 * Echo user input back onto the screen. This must be called only when
928 * L_ECHO(tty) is true. Called from the driver receive_buf path.
930 * This variant tags control characters to be echoed as "^X"
931 * (where X is the letter representing the control char).
934 static void echo_char(unsigned char c, struct tty_struct *tty)
936 struct n_tty_data *ldata = tty->disc_data;
938 if (c == ECHO_OP_START) {
939 add_echo_byte(ECHO_OP_START, ldata);
940 add_echo_byte(ECHO_OP_START, ldata);
942 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
943 add_echo_byte(ECHO_OP_START, ldata);
944 add_echo_byte(c, ldata);
949 * finish_erasing - complete erase
953 static inline void finish_erasing(struct n_tty_data *ldata)
955 if (ldata->erasing) {
956 echo_char_raw('/', ldata);
962 * eraser - handle erase function
963 * @c: character input
964 * @tty: terminal device
966 * Perform erase and necessary output when an erase character is
967 * present in the stream from the driver layer. Handles the complexities
968 * of UTF-8 multibyte symbols.
970 * n_tty_receive_buf()/producer path:
971 * caller holds non-exclusive termios_rwsem
974 static void eraser(unsigned char c, struct tty_struct *tty)
976 struct n_tty_data *ldata = tty->disc_data;
977 enum { ERASE, WERASE, KILL } kill_type;
982 if (ldata->read_head == ldata->canon_head) {
983 /* process_output('\a', tty); */ /* what do you think? */
986 if (c == ERASE_CHAR(tty))
988 else if (c == WERASE_CHAR(tty))
992 ldata->read_head = ldata->canon_head;
995 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
996 ldata->read_head = ldata->canon_head;
997 finish_erasing(ldata);
998 echo_char(KILL_CHAR(tty), tty);
999 /* Add a newline if ECHOK is on and ECHOKE is off. */
1001 echo_char_raw('\n', ldata);
1008 while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
1009 head = ldata->read_head;
1011 /* erase a single possibly multibyte character */
1014 c = read_buf(ldata, head);
1015 } while (is_continuation(c, tty) &&
1016 MASK(head) != MASK(ldata->canon_head));
1018 /* do not partially erase */
1019 if (is_continuation(c, tty))
1022 if (kill_type == WERASE) {
1023 /* Equivalent to BSD's ALTWERASE. */
1024 if (isalnum(c) || c == '_')
1026 else if (seen_alnums)
1029 cnt = ldata->read_head - head;
1030 ldata->read_head = head;
1032 if (L_ECHOPRT(tty)) {
1033 if (!ldata->erasing) {
1034 echo_char_raw('\\', ldata);
1037 /* if cnt > 1, output a multi-byte character */
1041 echo_char_raw(read_buf(ldata, head), ldata);
1042 echo_move_back_col(ldata);
1044 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1045 echo_char(ERASE_CHAR(tty), tty);
1046 } else if (c == '\t') {
1047 unsigned int num_chars = 0;
1049 size_t tail = ldata->read_head;
1052 * Count the columns used for characters
1053 * since the start of input or after a
1055 * This info is used to go back the correct
1056 * number of columns.
1058 while (MASK(tail) != MASK(ldata->canon_head)) {
1060 c = read_buf(ldata, tail);
1064 } else if (iscntrl(c)) {
1067 } else if (!is_continuation(c, tty)) {
1071 echo_erase_tab(num_chars, after_tab, ldata);
1073 if (iscntrl(c) && L_ECHOCTL(tty)) {
1074 echo_char_raw('\b', ldata);
1075 echo_char_raw(' ', ldata);
1076 echo_char_raw('\b', ldata);
1078 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1079 echo_char_raw('\b', ldata);
1080 echo_char_raw(' ', ldata);
1081 echo_char_raw('\b', ldata);
1085 if (kill_type == ERASE)
1088 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1089 finish_erasing(ldata);
1093 * isig - handle the ISIG optio
1097 * Called when a signal is being sent due to terminal input.
1098 * Called from the driver receive_buf path so serialized.
1100 * Performs input and output flush if !NOFLSH. In this context, the echo
1101 * buffer is 'output'. The signal is processed first to alert any current
1102 * readers or writers to discontinue and exit their i/o loops.
1104 * Locking: ctrl_lock
1107 static void __isig(int sig, struct tty_struct *tty)
1109 struct pid *tty_pgrp = tty_get_pgrp(tty);
1111 kill_pgrp(tty_pgrp, sig, 1);
1116 static void isig(int sig, struct tty_struct *tty)
1118 struct n_tty_data *ldata = tty->disc_data;
1120 if (L_NOFLSH(tty)) {
1124 } else { /* signal and flush */
1125 up_read(&tty->termios_rwsem);
1126 down_write(&tty->termios_rwsem);
1130 /* clear echo buffer */
1131 mutex_lock(&ldata->output_lock);
1132 ldata->echo_head = ldata->echo_tail = 0;
1133 ldata->echo_mark = ldata->echo_commit = 0;
1134 mutex_unlock(&ldata->output_lock);
1136 /* clear output buffer */
1137 tty_driver_flush_buffer(tty);
1139 /* clear input buffer */
1140 reset_buffer_flags(tty->disc_data);
1142 /* notify pty master of flush */
1144 n_tty_packet_mode_flush(tty);
1146 up_write(&tty->termios_rwsem);
1147 down_read(&tty->termios_rwsem);
1152 * n_tty_receive_break - handle break
1155 * An RS232 break event has been hit in the incoming bitstream. This
1156 * can cause a variety of events depending upon the termios settings.
1158 * n_tty_receive_buf()/producer path:
1159 * caller holds non-exclusive termios_rwsem
1161 * Note: may get exclusive termios_rwsem if flushing input buffer
1164 static void n_tty_receive_break(struct tty_struct *tty)
1166 struct n_tty_data *ldata = tty->disc_data;
1170 if (I_BRKINT(tty)) {
1174 if (I_PARMRK(tty)) {
1175 put_tty_queue('\377', ldata);
1176 put_tty_queue('\0', ldata);
1178 put_tty_queue('\0', ldata);
1182 * n_tty_receive_overrun - handle overrun reporting
1185 * Data arrived faster than we could process it. While the tty
1186 * driver has flagged this the bits that were missed are gone
1189 * Called from the receive_buf path so single threaded. Does not
1190 * need locking as num_overrun and overrun_time are function
1194 static void n_tty_receive_overrun(struct tty_struct *tty)
1196 struct n_tty_data *ldata = tty->disc_data;
1198 ldata->num_overrun++;
1199 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1200 time_after(ldata->overrun_time, jiffies)) {
1201 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1202 ldata->overrun_time = jiffies;
1203 ldata->num_overrun = 0;
1208 * n_tty_receive_parity_error - error notifier
1209 * @tty: terminal device
1212 * Process a parity error and queue the right data to indicate
1213 * the error case if necessary.
1215 * n_tty_receive_buf()/producer path:
1216 * caller holds non-exclusive termios_rwsem
1218 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1220 struct n_tty_data *ldata = tty->disc_data;
1225 if (I_PARMRK(tty)) {
1226 put_tty_queue('\377', ldata);
1227 put_tty_queue('\0', ldata);
1228 put_tty_queue(c, ldata);
1230 put_tty_queue('\0', ldata);
1232 put_tty_queue(c, ldata);
1236 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1245 process_echoes(tty);
1250 * n_tty_receive_char - perform processing
1251 * @tty: terminal device
1254 * Process an individual character of input received from the driver.
1255 * This is serialized with respect to itself by the rules for the
1258 * n_tty_receive_buf()/producer path:
1259 * caller holds non-exclusive termios_rwsem
1260 * publishes canon_head if canonical mode is active
1262 * Returns 1 if LNEXT was received, else returns 0
1266 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1268 struct n_tty_data *ldata = tty->disc_data;
1271 if (c == START_CHAR(tty)) {
1273 process_echoes(tty);
1276 if (c == STOP_CHAR(tty)) {
1283 if (c == INTR_CHAR(tty)) {
1284 n_tty_receive_signal_char(tty, SIGINT, c);
1286 } else if (c == QUIT_CHAR(tty)) {
1287 n_tty_receive_signal_char(tty, SIGQUIT, c);
1289 } else if (c == SUSP_CHAR(tty)) {
1290 n_tty_receive_signal_char(tty, SIGTSTP, c);
1295 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1297 process_echoes(tty);
1305 } else if (c == '\n' && I_INLCR(tty))
1308 if (ldata->icanon) {
1309 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1310 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1315 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1318 finish_erasing(ldata);
1319 if (L_ECHOCTL(tty)) {
1320 echo_char_raw('^', ldata);
1321 echo_char_raw('\b', ldata);
1327 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1328 size_t tail = ldata->canon_head;
1330 finish_erasing(ldata);
1332 echo_char_raw('\n', ldata);
1333 while (MASK(tail) != MASK(ldata->read_head)) {
1334 echo_char(read_buf(ldata, tail), tty);
1341 if (L_ECHO(tty) || L_ECHONL(tty)) {
1342 echo_char_raw('\n', ldata);
1345 goto handle_newline;
1347 if (c == EOF_CHAR(tty)) {
1348 c = __DISABLED_CHAR;
1349 goto handle_newline;
1351 if ((c == EOL_CHAR(tty)) ||
1352 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1354 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1357 /* Record the column of first canon char. */
1358 if (ldata->canon_head == ldata->read_head)
1359 echo_set_canon_col(ldata);
1364 * XXX does PARMRK doubling happen for
1365 * EOL_CHAR and EOL2_CHAR?
1367 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1368 put_tty_queue(c, ldata);
1371 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1372 put_tty_queue(c, ldata);
1373 smp_store_release(&ldata->canon_head, ldata->read_head);
1374 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1375 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1381 finish_erasing(ldata);
1383 echo_char_raw('\n', ldata);
1385 /* Record the column of first canon char. */
1386 if (ldata->canon_head == ldata->read_head)
1387 echo_set_canon_col(ldata);
1393 /* PARMRK doubling check */
1394 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1395 put_tty_queue(c, ldata);
1397 put_tty_queue(c, ldata);
1402 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1404 struct n_tty_data *ldata = tty->disc_data;
1406 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1408 process_echoes(tty);
1411 finish_erasing(ldata);
1412 /* Record the column of first canon char. */
1413 if (ldata->canon_head == ldata->read_head)
1414 echo_set_canon_col(ldata);
1418 /* PARMRK doubling check */
1419 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1420 put_tty_queue(c, ldata);
1421 put_tty_queue(c, ldata);
1424 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1426 n_tty_receive_char_inline(tty, c);
1430 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1432 struct n_tty_data *ldata = tty->disc_data;
1434 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1436 process_echoes(tty);
1439 finish_erasing(ldata);
1440 /* Record the column of first canon char. */
1441 if (ldata->canon_head == ldata->read_head)
1442 echo_set_canon_col(ldata);
1446 put_tty_queue(c, ldata);
1449 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1453 if (I_IUCLC(tty) && L_IEXTEN(tty))
1457 if (c == STOP_CHAR(tty))
1459 else if (c == START_CHAR(tty) ||
1460 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1461 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1462 c != SUSP_CHAR(tty))) {
1464 process_echoes(tty);
1470 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1474 n_tty_receive_break(tty);
1478 n_tty_receive_parity_error(tty, c);
1481 n_tty_receive_overrun(tty);
1484 tty_err(tty, "unknown flag %d\n", flag);
1490 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1492 struct n_tty_data *ldata = tty->disc_data;
1495 if (likely(flag == TTY_NORMAL)) {
1498 if (I_IUCLC(tty) && L_IEXTEN(tty))
1500 n_tty_receive_char(tty, c);
1502 n_tty_receive_char_flagged(tty, c, flag);
1506 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1507 char *fp, int count)
1509 struct n_tty_data *ldata = tty->disc_data;
1512 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1513 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1514 memcpy(read_buf_addr(ldata, head), cp, n);
1515 ldata->read_head += n;
1519 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1520 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1521 memcpy(read_buf_addr(ldata, head), cp, n);
1522 ldata->read_head += n;
1526 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1527 char *fp, int count)
1529 struct n_tty_data *ldata = tty->disc_data;
1530 char flag = TTY_NORMAL;
1535 if (likely(flag == TTY_NORMAL))
1536 put_tty_queue(*cp++, ldata);
1538 n_tty_receive_char_flagged(tty, *cp++, flag);
1543 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1544 char *fp, int count)
1546 char flag = TTY_NORMAL;
1551 if (likely(flag == TTY_NORMAL))
1552 n_tty_receive_char_closing(tty, *cp++);
1557 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1558 char *fp, int count)
1560 struct n_tty_data *ldata = tty->disc_data;
1561 char flag = TTY_NORMAL;
1566 if (likely(flag == TTY_NORMAL)) {
1567 unsigned char c = *cp++;
1571 if (I_IUCLC(tty) && L_IEXTEN(tty))
1573 if (L_EXTPROC(tty)) {
1574 put_tty_queue(c, ldata);
1577 if (!test_bit(c, ldata->char_map))
1578 n_tty_receive_char_inline(tty, c);
1579 else if (n_tty_receive_char_special(tty, c) && count) {
1582 n_tty_receive_char_lnext(tty, *cp++, flag);
1586 n_tty_receive_char_flagged(tty, *cp++, flag);
1591 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1592 char *fp, int count)
1594 struct n_tty_data *ldata = tty->disc_data;
1595 char flag = TTY_NORMAL;
1600 if (likely(flag == TTY_NORMAL)) {
1601 unsigned char c = *cp++;
1603 if (!test_bit(c, ldata->char_map))
1604 n_tty_receive_char_fast(tty, c);
1605 else if (n_tty_receive_char_special(tty, c) && count) {
1608 n_tty_receive_char_lnext(tty, *cp++, flag);
1612 n_tty_receive_char_flagged(tty, *cp++, flag);
1616 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1617 char *fp, int count)
1619 struct n_tty_data *ldata = tty->disc_data;
1620 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1622 if (ldata->real_raw)
1623 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1624 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1625 n_tty_receive_buf_raw(tty, cp, fp, count);
1626 else if (tty->closing && !L_EXTPROC(tty))
1627 n_tty_receive_buf_closing(tty, cp, fp, count);
1630 char flag = TTY_NORMAL;
1634 n_tty_receive_char_lnext(tty, *cp++, flag);
1638 if (!preops && !I_PARMRK(tty))
1639 n_tty_receive_buf_fast(tty, cp, fp, count);
1641 n_tty_receive_buf_standard(tty, cp, fp, count);
1644 if (tty->ops->flush_chars)
1645 tty->ops->flush_chars(tty);
1648 if (ldata->icanon && !L_EXTPROC(tty))
1651 /* publish read_head to consumer */
1652 smp_store_release(&ldata->commit_head, ldata->read_head);
1654 if (read_cnt(ldata)) {
1655 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1656 wake_up_interruptible_poll(&tty->read_wait, EPOLLIN | EPOLLRDNORM);
1661 * n_tty_receive_buf_common - process input
1662 * @tty: device to receive input
1664 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1665 * @count: number of input chars in @cp
1667 * Called by the terminal driver when a block of characters has
1668 * been received. This function must be called from soft contexts
1669 * not from interrupt context. The driver is responsible for making
1670 * calls one at a time and in order (or using flush_to_ldisc)
1672 * Returns the # of input chars from @cp which were processed.
1674 * In canonical mode, the maximum line length is 4096 chars (including
1675 * the line termination char); lines longer than 4096 chars are
1676 * truncated. After 4095 chars, input data is still processed but
1677 * not stored. Overflow processing ensures the tty can always
1678 * receive more input until at least one line can be read.
1680 * In non-canonical mode, the read buffer will only accept 4095 chars;
1681 * this provides the necessary space for a newline char if the input
1682 * mode is switched to canonical.
1684 * Note it is possible for the read buffer to _contain_ 4096 chars
1685 * in non-canonical mode: the read buffer could already contain the
1686 * maximum canon line of 4096 chars when the mode is switched to
1689 * n_tty_receive_buf()/producer path:
1690 * claims non-exclusive termios_rwsem
1691 * publishes commit_head or canon_head
1694 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1695 char *fp, int count, int flow)
1697 struct n_tty_data *ldata = tty->disc_data;
1698 int room, n, rcvd = 0, overflow;
1700 down_read(&tty->termios_rwsem);
1704 * When PARMRK is set, each input char may take up to 3 chars
1705 * in the read buf; reduce the buffer space avail by 3x
1707 * If we are doing input canonicalization, and there are no
1708 * pending newlines, let characters through without limit, so
1709 * that erase characters will be handled. Other excess
1710 * characters will be beeped.
1712 * paired with store in *_copy_from_read_buf() -- guarantees
1713 * the consumer has loaded the data in read_buf up to the new
1714 * read_tail (so this producer will not overwrite unread data)
1716 size_t tail = smp_load_acquire(&ldata->read_tail);
1718 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1720 room = (room + 2) / 3;
1723 overflow = ldata->icanon && ldata->canon_head == tail;
1724 if (overflow && room < 0)
1727 ldata->no_room = flow && !room;
1731 n = min(count, room);
1735 /* ignore parity errors if handling overflow */
1736 if (!overflow || !fp || *fp != TTY_PARITY)
1737 __receive_buf(tty, cp, fp, n);
1744 } while (!test_bit(TTY_LDISC_CHANGING, &tty->flags));
1746 tty->receive_room = room;
1748 /* Unthrottle if handling overflow on pty */
1749 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1751 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1752 tty_unthrottle_safe(tty);
1753 __tty_set_flow_change(tty, 0);
1756 n_tty_check_throttle(tty);
1758 up_read(&tty->termios_rwsem);
1763 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1764 char *fp, int count)
1766 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1769 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1770 char *fp, int count)
1772 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1776 * n_tty_set_termios - termios data changed
1778 * @old: previous data
1780 * Called by the tty layer when the user changes termios flags so
1781 * that the line discipline can plan ahead. This function cannot sleep
1782 * and is protected from re-entry by the tty layer. The user is
1783 * guaranteed that this function will not be re-entered or in progress
1784 * when the ldisc is closed.
1786 * Locking: Caller holds tty->termios_rwsem
1789 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1791 struct n_tty_data *ldata = tty->disc_data;
1793 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & (ICANON | EXTPROC)) {
1794 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1795 ldata->line_start = ldata->read_tail;
1796 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1797 ldata->canon_head = ldata->read_tail;
1800 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1802 ldata->canon_head = ldata->read_head;
1805 ldata->commit_head = ldata->read_head;
1810 ldata->icanon = (L_ICANON(tty) != 0);
1812 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1813 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1814 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1816 bitmap_zero(ldata->char_map, 256);
1818 if (I_IGNCR(tty) || I_ICRNL(tty))
1819 set_bit('\r', ldata->char_map);
1821 set_bit('\n', ldata->char_map);
1823 if (L_ICANON(tty)) {
1824 set_bit(ERASE_CHAR(tty), ldata->char_map);
1825 set_bit(KILL_CHAR(tty), ldata->char_map);
1826 set_bit(EOF_CHAR(tty), ldata->char_map);
1827 set_bit('\n', ldata->char_map);
1828 set_bit(EOL_CHAR(tty), ldata->char_map);
1829 if (L_IEXTEN(tty)) {
1830 set_bit(WERASE_CHAR(tty), ldata->char_map);
1831 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1832 set_bit(EOL2_CHAR(tty), ldata->char_map);
1834 set_bit(REPRINT_CHAR(tty),
1839 set_bit(START_CHAR(tty), ldata->char_map);
1840 set_bit(STOP_CHAR(tty), ldata->char_map);
1843 set_bit(INTR_CHAR(tty), ldata->char_map);
1844 set_bit(QUIT_CHAR(tty), ldata->char_map);
1845 set_bit(SUSP_CHAR(tty), ldata->char_map);
1847 clear_bit(__DISABLED_CHAR, ldata->char_map);
1849 ldata->real_raw = 0;
1852 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1853 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1854 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1855 ldata->real_raw = 1;
1857 ldata->real_raw = 0;
1860 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1861 * been stopped by STOP_CHAR(tty) before it.
1863 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1865 process_echoes(tty);
1868 /* The termios change make the tty ready for I/O */
1869 wake_up_interruptible(&tty->write_wait);
1870 wake_up_interruptible(&tty->read_wait);
1874 * n_tty_close - close the ldisc for this tty
1877 * Called from the terminal layer when this line discipline is
1878 * being shut down, either because of a close or becsuse of a
1879 * discipline change. The function will not be called while other
1880 * ldisc methods are in progress.
1883 static void n_tty_close(struct tty_struct *tty)
1885 struct n_tty_data *ldata = tty->disc_data;
1888 n_tty_packet_mode_flush(tty);
1891 tty->disc_data = NULL;
1895 * n_tty_open - open an ldisc
1896 * @tty: terminal to open
1898 * Called when this line discipline is being attached to the
1899 * terminal device. Can sleep. Called serialized so that no
1900 * other events will occur in parallel. No further open will occur
1904 static int n_tty_open(struct tty_struct *tty)
1906 struct n_tty_data *ldata;
1908 /* Currently a malloc failure here can panic */
1909 ldata = vzalloc(sizeof(*ldata));
1913 ldata->overrun_time = jiffies;
1914 mutex_init(&ldata->atomic_read_lock);
1915 mutex_init(&ldata->output_lock);
1917 tty->disc_data = ldata;
1919 /* indicate buffer work may resume */
1920 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1921 n_tty_set_termios(tty, NULL);
1922 tty_unthrottle(tty);
1926 static inline int input_available_p(struct tty_struct *tty, int poll)
1928 struct n_tty_data *ldata = tty->disc_data;
1929 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1931 if (ldata->icanon && !L_EXTPROC(tty))
1932 return ldata->canon_head != ldata->read_tail;
1934 return ldata->commit_head - ldata->read_tail >= amt;
1938 * copy_from_read_buf - copy read data directly
1939 * @tty: terminal device
1943 * Helper function to speed up n_tty_read. It is only called when
1944 * ICANON is off; it copies characters straight from the tty queue.
1946 * Called under the ldata->atomic_read_lock sem
1948 * Returns true if it successfully copied data, but there is still
1949 * more data to be had.
1951 * n_tty_read()/consumer path:
1952 * caller holds non-exclusive termios_rwsem
1953 * read_tail published
1956 static bool copy_from_read_buf(struct tty_struct *tty,
1957 unsigned char **kbp,
1961 struct n_tty_data *ldata = tty->disc_data;
1964 size_t head = smp_load_acquire(&ldata->commit_head);
1965 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1967 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1970 unsigned char *from = read_buf_addr(ldata, tail);
1971 memcpy(*kbp, from, n);
1972 is_eof = n == 1 && *from == EOF_CHAR(tty);
1973 tty_audit_add_data(tty, from, n);
1974 zero_buffer(tty, from, n);
1975 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1976 /* Turn single EOF into zero-length read */
1977 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1978 (head == ldata->read_tail))
1983 /* If we have more to copy, let the caller know */
1984 return head != ldata->read_tail;
1990 * canon_copy_from_read_buf - copy read data in canonical mode
1991 * @tty: terminal device
1995 * Helper function for n_tty_read. It is only called when ICANON is on;
1996 * it copies one line of input up to and including the line-delimiting
1997 * character into the result buffer.
1999 * NB: When termios is changed from non-canonical to canonical mode and
2000 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2001 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2002 * This causes data already processed as input to be immediately available
2003 * as input although a newline has not been received.
2005 * Called under the atomic_read_lock mutex
2007 * n_tty_read()/consumer path:
2008 * caller holds non-exclusive termios_rwsem
2009 * read_tail published
2012 static bool canon_copy_from_read_buf(struct tty_struct *tty,
2013 unsigned char **kbp,
2016 struct n_tty_data *ldata = tty->disc_data;
2017 size_t n, size, more, c;
2019 size_t tail, canon_head;
2022 /* N.B. avoid overrun if nr == 0 */
2026 canon_head = smp_load_acquire(&ldata->canon_head);
2027 n = min(*nr, canon_head - ldata->read_tail);
2029 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2030 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2032 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2033 __func__, *nr, tail, n, size);
2035 eol = find_next_bit(ldata->read_flags, size, tail);
2036 more = n - (size - tail);
2037 if (eol == N_TTY_BUF_SIZE && more) {
2038 /* scan wrapped without finding set bit */
2039 eol = find_next_bit(ldata->read_flags, more, 0);
2040 found = eol != more;
2042 found = eol != size;
2045 if (n > N_TTY_BUF_SIZE)
2046 n += N_TTY_BUF_SIZE;
2049 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
2052 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2053 __func__, eol, found, n, c, tail, more);
2055 tty_copy(tty, *kbp, tail, n);
2060 clear_bit(eol, ldata->read_flags);
2061 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2065 ldata->line_start = ldata->read_tail;
2072 /* No EOL found - do a continuation retry if there is more data */
2073 return ldata->read_tail != canon_head;
2077 * If we finished a read at the exact location of an
2078 * EOF (special EOL character that's a __DISABLED_CHAR)
2079 * in the stream, silently eat the EOF.
2081 static void canon_skip_eof(struct tty_struct *tty)
2083 struct n_tty_data *ldata = tty->disc_data;
2084 size_t tail, canon_head;
2086 canon_head = smp_load_acquire(&ldata->canon_head);
2087 tail = ldata->read_tail;
2090 if (tail == canon_head)
2093 // See if the tail position is EOF in the circular buffer
2094 tail &= (N_TTY_BUF_SIZE - 1);
2095 if (!test_bit(tail, ldata->read_flags))
2097 if (read_buf(ldata, tail) != __DISABLED_CHAR)
2100 // Clear the EOL bit, skip the EOF char.
2101 clear_bit(tail, ldata->read_flags);
2102 smp_store_release(&ldata->read_tail, ldata->read_tail + 1);
2106 * job_control - check job control
2108 * @file: file handle
2110 * Perform job control management checks on this file/tty descriptor
2111 * and if appropriate send any needed signals and return a negative
2112 * error code if action should be taken.
2114 * Locking: redirected write test is safe
2115 * current->signal->tty check is safe
2116 * ctrl_lock to safely reference tty->pgrp
2119 static int job_control(struct tty_struct *tty, struct file *file)
2121 /* Job control check -- must be done at start and after
2122 every sleep (POSIX.1 7.1.1.4). */
2123 /* NOTE: not yet done after every sleep pending a thorough
2124 check of the logic of this change. -- jlc */
2125 /* don't stop on /dev/console */
2126 if (file->f_op->write_iter == redirected_tty_write)
2129 return __tty_check_change(tty, SIGTTIN);
2134 * n_tty_read - read function for tty
2136 * @file: file object
2137 * @buf: userspace buffer pointer
2140 * Perform reads for the line discipline. We are guaranteed that the
2141 * line discipline will not be closed under us but we may get multiple
2142 * parallel readers and must handle this ourselves. We may also get
2143 * a hangup. Always called in user context, may sleep.
2145 * This code must be sure never to sleep through a hangup.
2147 * n_tty_read()/consumer path:
2148 * claims non-exclusive termios_rwsem
2149 * publishes read_tail
2152 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2153 unsigned char *kbuf, size_t nr,
2154 void **cookie, unsigned long offset)
2156 struct n_tty_data *ldata = tty->disc_data;
2157 unsigned char *kb = kbuf;
2158 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2167 * Is this a continuation of a read started earler?
2169 * If so, we still hold the atomic_read_lock and the
2170 * termios_rwsem, and can just continue to copy data.
2173 if (ldata->icanon && !L_EXTPROC(tty)) {
2175 * If we have filled the user buffer, see
2176 * if we should skip an EOF character before
2177 * releasing the lock and returning done.
2180 canon_skip_eof(tty);
2181 else if (canon_copy_from_read_buf(tty, &kb, &nr))
2184 if (copy_from_read_buf(tty, &kb, &nr))
2188 /* No more data - release locks and stop retries */
2189 n_tty_kick_worker(tty);
2190 n_tty_check_unthrottle(tty);
2191 up_read(&tty->termios_rwsem);
2192 mutex_unlock(&ldata->atomic_read_lock);
2197 c = job_control(tty, file);
2202 * Internal serialization of reads.
2204 if (file->f_flags & O_NONBLOCK) {
2205 if (!mutex_trylock(&ldata->atomic_read_lock))
2208 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2209 return -ERESTARTSYS;
2212 down_read(&tty->termios_rwsem);
2215 timeout = MAX_SCHEDULE_TIMEOUT;
2216 if (!ldata->icanon) {
2217 minimum = MIN_CHAR(tty);
2219 time = (HZ / 10) * TIME_CHAR(tty);
2221 timeout = (HZ / 10) * TIME_CHAR(tty);
2226 packet = tty->packet;
2227 tail = ldata->read_tail;
2229 add_wait_queue(&tty->read_wait, &wait);
2231 /* First test for status change. */
2232 if (packet && tty->link->ctrl_status) {
2236 spin_lock_irq(&tty->link->ctrl_lock);
2237 cs = tty->link->ctrl_status;
2238 tty->link->ctrl_status = 0;
2239 spin_unlock_irq(&tty->link->ctrl_lock);
2245 if (!input_available_p(tty, 0)) {
2246 up_read(&tty->termios_rwsem);
2247 tty_buffer_flush_work(tty->port);
2248 down_read(&tty->termios_rwsem);
2249 if (!input_available_p(tty, 0)) {
2250 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2254 if (tty_hung_up_p(file))
2257 * Abort readers for ttys which never actually
2258 * get hung up. See __tty_hangup().
2260 if (test_bit(TTY_HUPPING, &tty->flags))
2264 if (tty_io_nonblock(tty, file)) {
2268 if (signal_pending(current)) {
2269 retval = -ERESTARTSYS;
2272 up_read(&tty->termios_rwsem);
2274 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2277 down_read(&tty->termios_rwsem);
2282 if (ldata->icanon && !L_EXTPROC(tty)) {
2283 if (canon_copy_from_read_buf(tty, &kb, &nr))
2284 goto more_to_be_read;
2286 /* Deal with packet mode. */
2287 if (packet && kb == kbuf) {
2288 *kb++ = TIOCPKT_DATA;
2293 * Copy data, and if there is more to be had
2294 * and we have nothing more to wait for, then
2295 * let's mark us for retries.
2297 * NOTE! We return here with both the termios_sem
2298 * and atomic_read_lock still held, the retries
2299 * will release them when done.
2301 if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
2303 remove_wait_queue(&tty->read_wait, &wait);
2309 n_tty_check_unthrottle(tty);
2311 if (kb - kbuf >= minimum)
2316 if (tail != ldata->read_tail)
2317 n_tty_kick_worker(tty);
2318 up_read(&tty->termios_rwsem);
2320 remove_wait_queue(&tty->read_wait, &wait);
2321 mutex_unlock(&ldata->atomic_read_lock);
2330 * n_tty_write - write function for tty
2332 * @file: file object
2333 * @buf: userspace buffer pointer
2336 * Write function of the terminal device. This is serialized with
2337 * respect to other write callers but not to termios changes, reads
2338 * and other such events. Since the receive code will echo characters,
2339 * thus calling driver write methods, the output_lock is used in
2340 * the output processing functions called here as well as in the
2341 * echo processing function to protect the column state and space
2342 * left in the buffer.
2344 * This code must be sure never to sleep through a hangup.
2346 * Locking: output_lock to protect column state and space left
2347 * (note that the process_output*() functions take this
2351 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2352 const unsigned char *buf, size_t nr)
2354 const unsigned char *b = buf;
2355 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2359 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2360 if (L_TOSTOP(tty) && file->f_op->write_iter != redirected_tty_write) {
2361 retval = tty_check_change(tty);
2366 down_read(&tty->termios_rwsem);
2368 /* Write out any echoed characters that are still pending */
2369 process_echoes(tty);
2371 add_wait_queue(&tty->write_wait, &wait);
2373 if (signal_pending(current)) {
2374 retval = -ERESTARTSYS;
2377 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2383 ssize_t num = process_output_block(tty, b, nr);
2395 if (process_output(c, tty) < 0)
2399 if (tty->ops->flush_chars)
2400 tty->ops->flush_chars(tty);
2402 struct n_tty_data *ldata = tty->disc_data;
2405 mutex_lock(&ldata->output_lock);
2406 c = tty->ops->write(tty, b, nr);
2407 mutex_unlock(&ldata->output_lock);
2420 if (tty_io_nonblock(tty, file)) {
2424 up_read(&tty->termios_rwsem);
2426 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2428 down_read(&tty->termios_rwsem);
2431 remove_wait_queue(&tty->write_wait, &wait);
2432 if (nr && tty->fasync)
2433 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2434 up_read(&tty->termios_rwsem);
2435 return (b - buf) ? b - buf : retval;
2439 * n_tty_poll - poll method for N_TTY
2440 * @tty: terminal device
2441 * @file: file accessing it
2444 * Called when the line discipline is asked to poll() for data or
2445 * for special events. This code is not serialized with respect to
2446 * other events save open/close.
2448 * This code must be sure never to sleep through a hangup.
2449 * Called without the kernel lock held - fine
2452 static __poll_t n_tty_poll(struct tty_struct *tty, struct file *file,
2457 poll_wait(file, &tty->read_wait, wait);
2458 poll_wait(file, &tty->write_wait, wait);
2459 if (input_available_p(tty, 1))
2460 mask |= EPOLLIN | EPOLLRDNORM;
2462 tty_buffer_flush_work(tty->port);
2463 if (input_available_p(tty, 1))
2464 mask |= EPOLLIN | EPOLLRDNORM;
2466 if (tty->packet && tty->link->ctrl_status)
2467 mask |= EPOLLPRI | EPOLLIN | EPOLLRDNORM;
2468 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2470 if (tty_hung_up_p(file))
2472 if (tty->ops->write && !tty_is_writelocked(tty) &&
2473 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2474 tty_write_room(tty) > 0)
2475 mask |= EPOLLOUT | EPOLLWRNORM;
2479 static unsigned long inq_canon(struct n_tty_data *ldata)
2481 size_t nr, head, tail;
2483 if (ldata->canon_head == ldata->read_tail)
2485 head = ldata->canon_head;
2486 tail = ldata->read_tail;
2488 /* Skip EOF-chars.. */
2489 while (MASK(head) != MASK(tail)) {
2490 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2491 read_buf(ldata, tail) == __DISABLED_CHAR)
2498 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2499 unsigned int cmd, unsigned long arg)
2501 struct n_tty_data *ldata = tty->disc_data;
2506 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2508 down_write(&tty->termios_rwsem);
2509 if (L_ICANON(tty) && !L_EXTPROC(tty))
2510 retval = inq_canon(ldata);
2512 retval = read_cnt(ldata);
2513 up_write(&tty->termios_rwsem);
2514 return put_user(retval, (unsigned int __user *) arg);
2516 return n_tty_ioctl_helper(tty, file, cmd, arg);
2520 static struct tty_ldisc_ops n_tty_ops = {
2521 .magic = TTY_LDISC_MAGIC,
2524 .close = n_tty_close,
2525 .flush_buffer = n_tty_flush_buffer,
2527 .write = n_tty_write,
2528 .ioctl = n_tty_ioctl,
2529 .set_termios = n_tty_set_termios,
2531 .receive_buf = n_tty_receive_buf,
2532 .write_wakeup = n_tty_write_wakeup,
2533 .receive_buf2 = n_tty_receive_buf2,
2537 * n_tty_inherit_ops - inherit N_TTY methods
2538 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2540 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2543 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2547 ops->refcount = ops->flags = 0;
2549 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2551 void __init n_tty_init(void)
2553 tty_register_ldisc(N_TTY, &n_tty_ops);