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 * This file may be redistributed under the terms of the GNU General Public
22 * Reduced memory usage for older ARM systems - Russell King.
24 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
25 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
26 * who actually finally proved there really was a race.
28 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
29 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
30 * Also fixed a bug in BLOCKING mode where n_tty_write returns
34 #include <linux/types.h>
35 #include <linux/major.h>
36 #include <linux/errno.h>
37 #include <linux/signal.h>
38 #include <linux/fcntl.h>
39 #include <linux/sched.h>
40 #include <linux/interrupt.h>
41 #include <linux/tty.h>
42 #include <linux/timer.h>
43 #include <linux/ctype.h>
45 #include <linux/string.h>
46 #include <linux/slab.h>
47 #include <linux/poll.h>
48 #include <linux/bitops.h>
49 #include <linux/audit.h>
50 #include <linux/file.h>
51 #include <linux/uaccess.h>
52 #include <linux/module.h>
53 #include <linux/ratelimit.h>
54 #include <linux/vmalloc.h>
57 /* number of characters left in xmit buffer before select has we have room */
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...)
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 static inline size_t read_cnt(struct n_tty_data *ldata)
132 return ldata->read_head - ldata->read_tail;
135 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
137 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
140 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
142 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
145 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
147 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
150 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
152 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
155 static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
156 size_t tail, size_t n)
158 struct n_tty_data *ldata = tty->disc_data;
159 size_t size = N_TTY_BUF_SIZE - tail;
160 const void *from = read_buf_addr(ldata, tail);
164 tty_audit_add_data(tty, from, size);
165 uncopied = copy_to_user(to, from, size);
170 from = ldata->read_buf;
173 tty_audit_add_data(tty, from, n);
174 return copy_to_user(to, from, n);
178 * n_tty_kick_worker - start input worker (if required)
181 * Re-schedules the flip buffer work if it may have stopped
183 * Caller holds exclusive termios_rwsem
185 * n_tty_read()/consumer path:
186 * holds non-exclusive termios_rwsem
189 static void n_tty_kick_worker(struct tty_struct *tty)
191 struct n_tty_data *ldata = tty->disc_data;
193 /* Did the input worker stop? Restart it */
194 if (unlikely(ldata->no_room)) {
197 WARN_RATELIMIT(tty->port->itty == NULL,
198 "scheduling with invalid itty\n");
199 /* see if ldisc has been killed - if so, this means that
200 * even though the ldisc has been halted and ->buf.work
201 * cancelled, ->buf.work is about to be rescheduled
203 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
204 "scheduling buffer work for halted ldisc\n");
205 tty_buffer_restart_work(tty->port);
209 static ssize_t chars_in_buffer(struct tty_struct *tty)
211 struct n_tty_data *ldata = tty->disc_data;
215 n = ldata->commit_head - ldata->read_tail;
217 n = ldata->canon_head - ldata->read_tail;
222 * n_tty_write_wakeup - asynchronous I/O notifier
225 * Required for the ptys, serial driver etc. since processes
226 * that attach themselves to the master and rely on ASYNC
227 * IO must be woken up
230 static void n_tty_write_wakeup(struct tty_struct *tty)
232 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
233 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
236 static void n_tty_check_throttle(struct tty_struct *tty)
238 struct n_tty_data *ldata = tty->disc_data;
241 * Check the remaining room for the input canonicalization
242 * mode. We don't want to throttle the driver if we're in
243 * canonical mode and don't have a newline yet!
245 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
250 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
251 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
253 throttled = tty_throttle_safe(tty);
257 __tty_set_flow_change(tty, 0);
260 static void n_tty_check_unthrottle(struct tty_struct *tty)
262 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
263 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
265 n_tty_kick_worker(tty);
266 tty_wakeup(tty->link);
270 /* If there is enough space in the read buffer now, let the
271 * low-level driver know. We use chars_in_buffer() to
272 * check the buffer, as it now knows about canonical mode.
273 * Otherwise, if the driver is throttled and the line is
274 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
275 * we won't get any more characters.
280 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
281 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
283 n_tty_kick_worker(tty);
284 unthrottled = tty_unthrottle_safe(tty);
288 __tty_set_flow_change(tty, 0);
292 * put_tty_queue - add character to tty
296 * Add a character to the tty read_buf queue.
298 * n_tty_receive_buf()/producer path:
299 * caller holds non-exclusive termios_rwsem
302 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
304 *read_buf_addr(ldata, ldata->read_head) = c;
309 * reset_buffer_flags - reset buffer state
310 * @tty: terminal to reset
312 * Reset the read buffer counters and clear the flags.
313 * Called from n_tty_open() and n_tty_flush_buffer().
315 * Locking: caller holds exclusive termios_rwsem
316 * (or locking is not required)
319 static void reset_buffer_flags(struct n_tty_data *ldata)
321 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
322 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
323 ldata->commit_head = 0;
324 ldata->echo_mark = 0;
325 ldata->line_start = 0;
328 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
332 static void n_tty_packet_mode_flush(struct tty_struct *tty)
336 if (tty->link->packet) {
337 spin_lock_irqsave(&tty->ctrl_lock, flags);
338 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
339 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
340 wake_up_interruptible(&tty->link->read_wait);
345 * n_tty_flush_buffer - clean input queue
346 * @tty: terminal device
348 * Flush the input buffer. Called when the tty layer wants the
349 * buffer flushed (eg at hangup) or when the N_TTY line discipline
350 * internally has to clean the pending queue (for example some signals).
352 * Holds termios_rwsem to exclude producer/consumer while
353 * buffer indices are reset.
355 * Locking: ctrl_lock, exclusive termios_rwsem
358 static void n_tty_flush_buffer(struct tty_struct *tty)
360 down_write(&tty->termios_rwsem);
361 reset_buffer_flags(tty->disc_data);
362 n_tty_kick_worker(tty);
365 n_tty_packet_mode_flush(tty);
366 up_write(&tty->termios_rwsem);
370 * is_utf8_continuation - utf8 multibyte check
373 * Returns true if the utf8 character 'c' is a multibyte continuation
374 * character. We use this to correctly compute the on screen size
375 * of the character when printing
378 static inline int is_utf8_continuation(unsigned char c)
380 return (c & 0xc0) == 0x80;
384 * is_continuation - multibyte check
387 * Returns true if the utf8 character 'c' is a multibyte continuation
388 * character and the terminal is in unicode mode.
391 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
393 return I_IUTF8(tty) && is_utf8_continuation(c);
397 * do_output_char - output one character
398 * @c: character (or partial unicode symbol)
399 * @tty: terminal device
400 * @space: space available in tty driver write buffer
402 * This is a helper function that handles one output character
403 * (including special characters like TAB, CR, LF, etc.),
404 * doing OPOST processing and putting the results in the
405 * tty driver's write buffer.
407 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
408 * and NLDLY. They simply aren't relevant in the world today.
409 * If you ever need them, add them here.
411 * Returns the number of bytes of buffer space used or -1 if
414 * Locking: should be called under the output_lock to protect
415 * the column state and space left in the buffer
418 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
420 struct n_tty_data *ldata = tty->disc_data;
433 ldata->canon_column = ldata->column = 0;
434 tty->ops->write(tty, "\r\n", 2);
437 ldata->canon_column = ldata->column;
440 if (O_ONOCR(tty) && ldata->column == 0)
445 ldata->canon_column = ldata->column = 0;
448 ldata->canon_column = ldata->column = 0;
451 spaces = 8 - (ldata->column & 7);
452 if (O_TABDLY(tty) == XTABS) {
455 ldata->column += spaces;
456 tty->ops->write(tty, " ", spaces);
459 ldata->column += spaces;
462 if (ldata->column > 0)
469 if (!is_continuation(c, tty))
475 tty_put_char(tty, c);
480 * process_output - output post processor
481 * @c: character (or partial unicode symbol)
482 * @tty: terminal device
484 * Output one character with OPOST processing.
485 * Returns -1 when the output device is full and the character
488 * Locking: output_lock to protect column state and space left
489 * (also, this is called from n_tty_write under the
490 * tty layer write lock)
493 static int process_output(unsigned char c, struct tty_struct *tty)
495 struct n_tty_data *ldata = tty->disc_data;
498 mutex_lock(&ldata->output_lock);
500 space = tty_write_room(tty);
501 retval = do_output_char(c, tty, space);
503 mutex_unlock(&ldata->output_lock);
511 * process_output_block - block post processor
512 * @tty: terminal device
513 * @buf: character buffer
514 * @nr: number of bytes to output
516 * Output a block of characters with OPOST processing.
517 * Returns the number of characters output.
519 * This path is used to speed up block console writes, among other
520 * things when processing blocks of output data. It handles only
521 * the simple cases normally found and helps to generate blocks of
522 * symbols for the console driver and thus improve performance.
524 * Locking: output_lock to protect column state and space left
525 * (also, this is called from n_tty_write under the
526 * tty layer write lock)
529 static ssize_t process_output_block(struct tty_struct *tty,
530 const unsigned char *buf, unsigned int nr)
532 struct n_tty_data *ldata = tty->disc_data;
535 const unsigned char *cp;
537 mutex_lock(&ldata->output_lock);
539 space = tty_write_room(tty);
541 mutex_unlock(&ldata->output_lock);
547 for (i = 0, cp = buf; i < nr; i++, cp++) {
548 unsigned char c = *cp;
556 ldata->canon_column = ldata->column;
559 if (O_ONOCR(tty) && ldata->column == 0)
563 ldata->canon_column = ldata->column = 0;
568 if (ldata->column > 0)
575 if (!is_continuation(c, tty))
582 i = tty->ops->write(tty, buf, i);
584 mutex_unlock(&ldata->output_lock);
589 * process_echoes - write pending echo characters
590 * @tty: terminal device
592 * Write previously buffered echo (and other ldisc-generated)
593 * characters to the tty.
595 * Characters generated by the ldisc (including echoes) need to
596 * be buffered because the driver's write buffer can fill during
597 * heavy program output. Echoing straight to the driver will
598 * often fail under these conditions, causing lost characters and
599 * resulting mismatches of ldisc state information.
601 * Since the ldisc state must represent the characters actually sent
602 * to the driver at the time of the write, operations like certain
603 * changes in column state are also saved in the buffer and executed
606 * A circular fifo buffer is used so that the most recent characters
607 * are prioritized. Also, when control characters are echoed with a
608 * prefixed "^", the pair is treated atomically and thus not separated.
610 * Locking: callers must hold output_lock
613 static size_t __process_echoes(struct tty_struct *tty)
615 struct n_tty_data *ldata = tty->disc_data;
616 int space, old_space;
620 old_space = space = tty_write_room(tty);
622 tail = ldata->echo_tail;
623 while (ldata->echo_commit != tail) {
624 c = echo_buf(ldata, tail);
625 if (c == ECHO_OP_START) {
627 int no_space_left = 0;
630 * If the buffer byte is the start of a multi-byte
631 * operation, get the next byte, which is either the
632 * op code or a control character value.
634 op = echo_buf(ldata, tail + 1);
637 unsigned int num_chars, num_bs;
639 case ECHO_OP_ERASE_TAB:
640 num_chars = echo_buf(ldata, tail + 2);
643 * Determine how many columns to go back
644 * in order to erase the tab.
645 * This depends on the number of columns
646 * used by other characters within the tab
647 * area. If this (modulo 8) count is from
648 * the start of input rather than from a
649 * previous tab, we offset by canon column.
650 * Otherwise, tab spacing is normal.
652 if (!(num_chars & 0x80))
653 num_chars += ldata->canon_column;
654 num_bs = 8 - (num_chars & 7);
656 if (num_bs > space) {
662 tty_put_char(tty, '\b');
663 if (ldata->column > 0)
669 case ECHO_OP_SET_CANON_COL:
670 ldata->canon_column = ldata->column;
674 case ECHO_OP_MOVE_BACK_COL:
675 if (ldata->column > 0)
681 /* This is an escaped echo op start code */
686 tty_put_char(tty, ECHO_OP_START);
694 * If the op is not a special byte code,
695 * it is a ctrl char tagged to be echoed
696 * as "^X" (where X is the letter
697 * representing the control char).
698 * Note that we must ensure there is
699 * enough space for the whole ctrl pair.
706 tty_put_char(tty, '^');
707 tty_put_char(tty, op ^ 0100);
717 int retval = do_output_char(c, tty, space);
724 tty_put_char(tty, c);
731 /* If the echo buffer is nearly full (so that the possibility exists
732 * of echo overrun before the next commit), then discard enough
733 * data at the tail to prevent a subsequent overrun */
734 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
735 if (echo_buf(ldata, tail) == ECHO_OP_START) {
736 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
744 ldata->echo_tail = tail;
745 return old_space - space;
748 static void commit_echoes(struct tty_struct *tty)
750 struct n_tty_data *ldata = tty->disc_data;
751 size_t nr, old, echoed;
754 head = ldata->echo_head;
755 ldata->echo_mark = head;
756 old = ldata->echo_commit - ldata->echo_tail;
758 /* Process committed echoes if the accumulated # of bytes
759 * is over the threshold (and try again each time another
760 * block is accumulated) */
761 nr = head - ldata->echo_tail;
762 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
765 mutex_lock(&ldata->output_lock);
766 ldata->echo_commit = head;
767 echoed = __process_echoes(tty);
768 mutex_unlock(&ldata->output_lock);
770 if (echoed && tty->ops->flush_chars)
771 tty->ops->flush_chars(tty);
774 static void process_echoes(struct tty_struct *tty)
776 struct n_tty_data *ldata = tty->disc_data;
779 if (ldata->echo_mark == ldata->echo_tail)
782 mutex_lock(&ldata->output_lock);
783 ldata->echo_commit = ldata->echo_mark;
784 echoed = __process_echoes(tty);
785 mutex_unlock(&ldata->output_lock);
787 if (echoed && tty->ops->flush_chars)
788 tty->ops->flush_chars(tty);
791 /* NB: echo_mark and echo_head should be equivalent here */
792 static void flush_echoes(struct tty_struct *tty)
794 struct n_tty_data *ldata = tty->disc_data;
796 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
797 ldata->echo_commit == ldata->echo_head)
800 mutex_lock(&ldata->output_lock);
801 ldata->echo_commit = ldata->echo_head;
802 __process_echoes(tty);
803 mutex_unlock(&ldata->output_lock);
807 * add_echo_byte - add a byte to the echo buffer
808 * @c: unicode byte to echo
811 * Add a character or operation byte to the echo buffer.
814 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
816 *echo_buf_addr(ldata, ldata->echo_head++) = c;
820 * echo_move_back_col - add operation to move back a column
823 * Add an operation to the echo buffer to move back one column.
826 static void echo_move_back_col(struct n_tty_data *ldata)
828 add_echo_byte(ECHO_OP_START, ldata);
829 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
833 * echo_set_canon_col - add operation to set the canon column
836 * Add an operation to the echo buffer to set the canon column
837 * to the current column.
840 static void echo_set_canon_col(struct n_tty_data *ldata)
842 add_echo_byte(ECHO_OP_START, ldata);
843 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
847 * echo_erase_tab - add operation to erase a tab
848 * @num_chars: number of character columns already used
849 * @after_tab: true if num_chars starts after a previous tab
852 * Add an operation to the echo buffer to erase a tab.
854 * Called by the eraser function, which knows how many character
855 * columns have been used since either a previous tab or the start
856 * of input. This information will be used later, along with
857 * canon column (if applicable), to go back the correct number
861 static void echo_erase_tab(unsigned int num_chars, int after_tab,
862 struct n_tty_data *ldata)
864 add_echo_byte(ECHO_OP_START, ldata);
865 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
867 /* We only need to know this modulo 8 (tab spacing) */
870 /* Set the high bit as a flag if num_chars is after a previous tab */
874 add_echo_byte(num_chars, ldata);
878 * echo_char_raw - echo a character raw
879 * @c: unicode byte to echo
880 * @tty: terminal device
882 * Echo user input back onto the screen. This must be called only when
883 * L_ECHO(tty) is true. Called from the driver receive_buf path.
885 * This variant does not treat control characters specially.
888 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
890 if (c == ECHO_OP_START) {
891 add_echo_byte(ECHO_OP_START, ldata);
892 add_echo_byte(ECHO_OP_START, ldata);
894 add_echo_byte(c, ldata);
899 * echo_char - echo a character
900 * @c: unicode byte to echo
901 * @tty: terminal device
903 * Echo user input back onto the screen. This must be called only when
904 * L_ECHO(tty) is true. Called from the driver receive_buf path.
906 * This variant tags control characters to be echoed as "^X"
907 * (where X is the letter representing the control char).
910 static void echo_char(unsigned char c, struct tty_struct *tty)
912 struct n_tty_data *ldata = tty->disc_data;
914 if (c == ECHO_OP_START) {
915 add_echo_byte(ECHO_OP_START, ldata);
916 add_echo_byte(ECHO_OP_START, ldata);
918 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
919 add_echo_byte(ECHO_OP_START, ldata);
920 add_echo_byte(c, ldata);
925 * finish_erasing - complete erase
929 static inline void finish_erasing(struct n_tty_data *ldata)
931 if (ldata->erasing) {
932 echo_char_raw('/', ldata);
938 * eraser - handle erase function
939 * @c: character input
940 * @tty: terminal device
942 * Perform erase and necessary output when an erase character is
943 * present in the stream from the driver layer. Handles the complexities
944 * of UTF-8 multibyte symbols.
946 * n_tty_receive_buf()/producer path:
947 * caller holds non-exclusive termios_rwsem
950 static void eraser(unsigned char c, struct tty_struct *tty)
952 struct n_tty_data *ldata = tty->disc_data;
953 enum { ERASE, WERASE, KILL } kill_type;
958 if (ldata->read_head == ldata->canon_head) {
959 /* process_output('\a', tty); */ /* what do you think? */
962 if (c == ERASE_CHAR(tty))
964 else if (c == WERASE_CHAR(tty))
968 ldata->read_head = ldata->canon_head;
971 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
972 ldata->read_head = ldata->canon_head;
973 finish_erasing(ldata);
974 echo_char(KILL_CHAR(tty), tty);
975 /* Add a newline if ECHOK is on and ECHOKE is off. */
977 echo_char_raw('\n', ldata);
984 while (ldata->read_head != ldata->canon_head) {
985 head = ldata->read_head;
987 /* erase a single possibly multibyte character */
990 c = read_buf(ldata, head);
991 } while (is_continuation(c, tty) && head != ldata->canon_head);
993 /* do not partially erase */
994 if (is_continuation(c, tty))
997 if (kill_type == WERASE) {
998 /* Equivalent to BSD's ALTWERASE. */
999 if (isalnum(c) || c == '_')
1001 else if (seen_alnums)
1004 cnt = ldata->read_head - head;
1005 ldata->read_head = head;
1007 if (L_ECHOPRT(tty)) {
1008 if (!ldata->erasing) {
1009 echo_char_raw('\\', ldata);
1012 /* if cnt > 1, output a multi-byte character */
1016 echo_char_raw(read_buf(ldata, head), ldata);
1017 echo_move_back_col(ldata);
1019 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1020 echo_char(ERASE_CHAR(tty), tty);
1021 } else if (c == '\t') {
1022 unsigned int num_chars = 0;
1024 size_t tail = ldata->read_head;
1027 * Count the columns used for characters
1028 * since the start of input or after a
1030 * This info is used to go back the correct
1031 * number of columns.
1033 while (tail != ldata->canon_head) {
1035 c = read_buf(ldata, tail);
1039 } else if (iscntrl(c)) {
1042 } else if (!is_continuation(c, tty)) {
1046 echo_erase_tab(num_chars, after_tab, ldata);
1048 if (iscntrl(c) && L_ECHOCTL(tty)) {
1049 echo_char_raw('\b', ldata);
1050 echo_char_raw(' ', ldata);
1051 echo_char_raw('\b', ldata);
1053 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1054 echo_char_raw('\b', ldata);
1055 echo_char_raw(' ', ldata);
1056 echo_char_raw('\b', ldata);
1060 if (kill_type == ERASE)
1063 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1064 finish_erasing(ldata);
1068 * isig - handle the ISIG optio
1072 * Called when a signal is being sent due to terminal input.
1073 * Called from the driver receive_buf path so serialized.
1075 * Performs input and output flush if !NOFLSH. In this context, the echo
1076 * buffer is 'output'. The signal is processed first to alert any current
1077 * readers or writers to discontinue and exit their i/o loops.
1079 * Locking: ctrl_lock
1082 static void __isig(int sig, struct tty_struct *tty)
1084 struct pid *tty_pgrp = tty_get_pgrp(tty);
1086 kill_pgrp(tty_pgrp, sig, 1);
1091 static void isig(int sig, struct tty_struct *tty)
1093 struct n_tty_data *ldata = tty->disc_data;
1095 if (L_NOFLSH(tty)) {
1099 } else { /* signal and flush */
1100 up_read(&tty->termios_rwsem);
1101 down_write(&tty->termios_rwsem);
1105 /* clear echo buffer */
1106 mutex_lock(&ldata->output_lock);
1107 ldata->echo_head = ldata->echo_tail = 0;
1108 ldata->echo_mark = ldata->echo_commit = 0;
1109 mutex_unlock(&ldata->output_lock);
1111 /* clear output buffer */
1112 tty_driver_flush_buffer(tty);
1114 /* clear input buffer */
1115 reset_buffer_flags(tty->disc_data);
1117 /* notify pty master of flush */
1119 n_tty_packet_mode_flush(tty);
1121 up_write(&tty->termios_rwsem);
1122 down_read(&tty->termios_rwsem);
1127 * n_tty_receive_break - handle break
1130 * An RS232 break event has been hit in the incoming bitstream. This
1131 * can cause a variety of events depending upon the termios settings.
1133 * n_tty_receive_buf()/producer path:
1134 * caller holds non-exclusive termios_rwsem
1136 * Note: may get exclusive termios_rwsem if flushing input buffer
1139 static void n_tty_receive_break(struct tty_struct *tty)
1141 struct n_tty_data *ldata = tty->disc_data;
1145 if (I_BRKINT(tty)) {
1149 if (I_PARMRK(tty)) {
1150 put_tty_queue('\377', ldata);
1151 put_tty_queue('\0', ldata);
1153 put_tty_queue('\0', ldata);
1157 * n_tty_receive_overrun - handle overrun reporting
1160 * Data arrived faster than we could process it. While the tty
1161 * driver has flagged this the bits that were missed are gone
1164 * Called from the receive_buf path so single threaded. Does not
1165 * need locking as num_overrun and overrun_time are function
1169 static void n_tty_receive_overrun(struct tty_struct *tty)
1171 struct n_tty_data *ldata = tty->disc_data;
1173 ldata->num_overrun++;
1174 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1175 time_after(ldata->overrun_time, jiffies)) {
1176 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1177 ldata->overrun_time = jiffies;
1178 ldata->num_overrun = 0;
1183 * n_tty_receive_parity_error - error notifier
1184 * @tty: terminal device
1187 * Process a parity error and queue the right data to indicate
1188 * the error case if necessary.
1190 * n_tty_receive_buf()/producer path:
1191 * caller holds non-exclusive termios_rwsem
1193 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1195 struct n_tty_data *ldata = tty->disc_data;
1200 if (I_PARMRK(tty)) {
1201 put_tty_queue('\377', ldata);
1202 put_tty_queue('\0', ldata);
1203 put_tty_queue(c, ldata);
1205 put_tty_queue('\0', ldata);
1207 put_tty_queue(c, ldata);
1211 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1220 process_echoes(tty);
1225 * n_tty_receive_char - perform processing
1226 * @tty: terminal device
1229 * Process an individual character of input received from the driver.
1230 * This is serialized with respect to itself by the rules for the
1233 * n_tty_receive_buf()/producer path:
1234 * caller holds non-exclusive termios_rwsem
1235 * publishes canon_head if canonical mode is active
1237 * Returns 1 if LNEXT was received, else returns 0
1241 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1243 struct n_tty_data *ldata = tty->disc_data;
1246 if (c == START_CHAR(tty)) {
1248 process_echoes(tty);
1251 if (c == STOP_CHAR(tty)) {
1258 if (c == INTR_CHAR(tty)) {
1259 n_tty_receive_signal_char(tty, SIGINT, c);
1261 } else if (c == QUIT_CHAR(tty)) {
1262 n_tty_receive_signal_char(tty, SIGQUIT, c);
1264 } else if (c == SUSP_CHAR(tty)) {
1265 n_tty_receive_signal_char(tty, SIGTSTP, c);
1270 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1272 process_echoes(tty);
1280 } else if (c == '\n' && I_INLCR(tty))
1283 if (ldata->icanon) {
1284 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1285 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1290 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1293 finish_erasing(ldata);
1294 if (L_ECHOCTL(tty)) {
1295 echo_char_raw('^', ldata);
1296 echo_char_raw('\b', ldata);
1302 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1303 size_t tail = ldata->canon_head;
1305 finish_erasing(ldata);
1307 echo_char_raw('\n', ldata);
1308 while (tail != ldata->read_head) {
1309 echo_char(read_buf(ldata, tail), tty);
1316 if (L_ECHO(tty) || L_ECHONL(tty)) {
1317 echo_char_raw('\n', ldata);
1320 goto handle_newline;
1322 if (c == EOF_CHAR(tty)) {
1323 c = __DISABLED_CHAR;
1324 goto handle_newline;
1326 if ((c == EOL_CHAR(tty)) ||
1327 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1329 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1332 /* Record the column of first canon char. */
1333 if (ldata->canon_head == ldata->read_head)
1334 echo_set_canon_col(ldata);
1339 * XXX does PARMRK doubling happen for
1340 * EOL_CHAR and EOL2_CHAR?
1342 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1343 put_tty_queue(c, ldata);
1346 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1347 put_tty_queue(c, ldata);
1348 smp_store_release(&ldata->canon_head, ldata->read_head);
1349 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1350 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1356 finish_erasing(ldata);
1358 echo_char_raw('\n', ldata);
1360 /* Record the column of first canon char. */
1361 if (ldata->canon_head == ldata->read_head)
1362 echo_set_canon_col(ldata);
1368 /* PARMRK doubling check */
1369 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1370 put_tty_queue(c, ldata);
1372 put_tty_queue(c, ldata);
1377 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1379 struct n_tty_data *ldata = tty->disc_data;
1381 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1383 process_echoes(tty);
1386 finish_erasing(ldata);
1387 /* Record the column of first canon char. */
1388 if (ldata->canon_head == ldata->read_head)
1389 echo_set_canon_col(ldata);
1393 /* PARMRK doubling check */
1394 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1395 put_tty_queue(c, ldata);
1396 put_tty_queue(c, ldata);
1399 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1401 n_tty_receive_char_inline(tty, c);
1405 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1407 struct n_tty_data *ldata = tty->disc_data;
1409 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1411 process_echoes(tty);
1414 finish_erasing(ldata);
1415 /* Record the column of first canon char. */
1416 if (ldata->canon_head == ldata->read_head)
1417 echo_set_canon_col(ldata);
1421 put_tty_queue(c, ldata);
1424 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1428 if (I_IUCLC(tty) && L_IEXTEN(tty))
1432 if (c == STOP_CHAR(tty))
1434 else if (c == START_CHAR(tty) ||
1435 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1436 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1437 c != SUSP_CHAR(tty))) {
1439 process_echoes(tty);
1445 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1449 n_tty_receive_break(tty);
1453 n_tty_receive_parity_error(tty, c);
1456 n_tty_receive_overrun(tty);
1459 tty_err(tty, "unknown flag %d\n", flag);
1465 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1467 struct n_tty_data *ldata = tty->disc_data;
1470 if (likely(flag == TTY_NORMAL)) {
1473 if (I_IUCLC(tty) && L_IEXTEN(tty))
1475 n_tty_receive_char(tty, c);
1477 n_tty_receive_char_flagged(tty, c, flag);
1481 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1482 char *fp, int count)
1484 struct n_tty_data *ldata = tty->disc_data;
1487 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1488 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1489 memcpy(read_buf_addr(ldata, head), cp, n);
1490 ldata->read_head += n;
1494 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1495 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1496 memcpy(read_buf_addr(ldata, head), cp, n);
1497 ldata->read_head += n;
1501 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1502 char *fp, int count)
1504 struct n_tty_data *ldata = tty->disc_data;
1505 char flag = TTY_NORMAL;
1510 if (likely(flag == TTY_NORMAL))
1511 put_tty_queue(*cp++, ldata);
1513 n_tty_receive_char_flagged(tty, *cp++, flag);
1518 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1519 char *fp, int count)
1521 char flag = TTY_NORMAL;
1526 if (likely(flag == TTY_NORMAL))
1527 n_tty_receive_char_closing(tty, *cp++);
1532 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1533 char *fp, int count)
1535 struct n_tty_data *ldata = tty->disc_data;
1536 char flag = TTY_NORMAL;
1541 if (likely(flag == TTY_NORMAL)) {
1542 unsigned char c = *cp++;
1546 if (I_IUCLC(tty) && L_IEXTEN(tty))
1548 if (L_EXTPROC(tty)) {
1549 put_tty_queue(c, ldata);
1552 if (!test_bit(c, ldata->char_map))
1553 n_tty_receive_char_inline(tty, c);
1554 else if (n_tty_receive_char_special(tty, c) && count) {
1557 n_tty_receive_char_lnext(tty, *cp++, flag);
1561 n_tty_receive_char_flagged(tty, *cp++, flag);
1566 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1567 char *fp, int count)
1569 struct n_tty_data *ldata = tty->disc_data;
1570 char flag = TTY_NORMAL;
1575 if (likely(flag == TTY_NORMAL)) {
1576 unsigned char c = *cp++;
1578 if (!test_bit(c, ldata->char_map))
1579 n_tty_receive_char_fast(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);
1591 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1592 char *fp, int count)
1594 struct n_tty_data *ldata = tty->disc_data;
1595 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1597 if (ldata->real_raw)
1598 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1599 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1600 n_tty_receive_buf_raw(tty, cp, fp, count);
1601 else if (tty->closing && !L_EXTPROC(tty))
1602 n_tty_receive_buf_closing(tty, cp, fp, count);
1605 char flag = TTY_NORMAL;
1609 n_tty_receive_char_lnext(tty, *cp++, flag);
1613 if (!preops && !I_PARMRK(tty))
1614 n_tty_receive_buf_fast(tty, cp, fp, count);
1616 n_tty_receive_buf_standard(tty, cp, fp, count);
1619 if (tty->ops->flush_chars)
1620 tty->ops->flush_chars(tty);
1623 if (ldata->icanon && !L_EXTPROC(tty))
1626 /* publish read_head to consumer */
1627 smp_store_release(&ldata->commit_head, ldata->read_head);
1629 if (read_cnt(ldata)) {
1630 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1631 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1636 * n_tty_receive_buf_common - process input
1637 * @tty: device to receive input
1639 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1640 * @count: number of input chars in @cp
1642 * Called by the terminal driver when a block of characters has
1643 * been received. This function must be called from soft contexts
1644 * not from interrupt context. The driver is responsible for making
1645 * calls one at a time and in order (or using flush_to_ldisc)
1647 * Returns the # of input chars from @cp which were processed.
1649 * In canonical mode, the maximum line length is 4096 chars (including
1650 * the line termination char); lines longer than 4096 chars are
1651 * truncated. After 4095 chars, input data is still processed but
1652 * not stored. Overflow processing ensures the tty can always
1653 * receive more input until at least one line can be read.
1655 * In non-canonical mode, the read buffer will only accept 4095 chars;
1656 * this provides the necessary space for a newline char if the input
1657 * mode is switched to canonical.
1659 * Note it is possible for the read buffer to _contain_ 4096 chars
1660 * in non-canonical mode: the read buffer could already contain the
1661 * maximum canon line of 4096 chars when the mode is switched to
1664 * n_tty_receive_buf()/producer path:
1665 * claims non-exclusive termios_rwsem
1666 * publishes commit_head or canon_head
1669 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1670 char *fp, int count, int flow)
1672 struct n_tty_data *ldata = tty->disc_data;
1673 int room, n, rcvd = 0, overflow;
1675 down_read(&tty->termios_rwsem);
1679 * When PARMRK is set, each input char may take up to 3 chars
1680 * in the read buf; reduce the buffer space avail by 3x
1682 * If we are doing input canonicalization, and there are no
1683 * pending newlines, let characters through without limit, so
1684 * that erase characters will be handled. Other excess
1685 * characters will be beeped.
1687 * paired with store in *_copy_from_read_buf() -- guarantees
1688 * the consumer has loaded the data in read_buf up to the new
1689 * read_tail (so this producer will not overwrite unread data)
1691 size_t tail = smp_load_acquire(&ldata->read_tail);
1693 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1695 room = (room + 2) / 3;
1698 overflow = ldata->icanon && ldata->canon_head == tail;
1699 if (overflow && room < 0)
1702 ldata->no_room = flow && !room;
1706 n = min(count, room);
1710 /* ignore parity errors if handling overflow */
1711 if (!overflow || !fp || *fp != TTY_PARITY)
1712 __receive_buf(tty, cp, fp, n);
1721 tty->receive_room = room;
1723 /* Unthrottle if handling overflow on pty */
1724 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1726 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1727 tty_unthrottle_safe(tty);
1728 __tty_set_flow_change(tty, 0);
1731 n_tty_check_throttle(tty);
1733 up_read(&tty->termios_rwsem);
1738 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1739 char *fp, int count)
1741 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1744 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1745 char *fp, int count)
1747 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1751 * n_tty_set_termios - termios data changed
1753 * @old: previous data
1755 * Called by the tty layer when the user changes termios flags so
1756 * that the line discipline can plan ahead. This function cannot sleep
1757 * and is protected from re-entry by the tty layer. The user is
1758 * guaranteed that this function will not be re-entered or in progress
1759 * when the ldisc is closed.
1761 * Locking: Caller holds tty->termios_rwsem
1764 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1766 struct n_tty_data *ldata = tty->disc_data;
1768 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1769 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1770 ldata->line_start = ldata->read_tail;
1771 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1772 ldata->canon_head = ldata->read_tail;
1775 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1777 ldata->canon_head = ldata->read_head;
1780 ldata->commit_head = ldata->read_head;
1785 ldata->icanon = (L_ICANON(tty) != 0);
1787 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1788 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1789 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1791 bitmap_zero(ldata->char_map, 256);
1793 if (I_IGNCR(tty) || I_ICRNL(tty))
1794 set_bit('\r', ldata->char_map);
1796 set_bit('\n', ldata->char_map);
1798 if (L_ICANON(tty)) {
1799 set_bit(ERASE_CHAR(tty), ldata->char_map);
1800 set_bit(KILL_CHAR(tty), ldata->char_map);
1801 set_bit(EOF_CHAR(tty), ldata->char_map);
1802 set_bit('\n', ldata->char_map);
1803 set_bit(EOL_CHAR(tty), ldata->char_map);
1804 if (L_IEXTEN(tty)) {
1805 set_bit(WERASE_CHAR(tty), ldata->char_map);
1806 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1807 set_bit(EOL2_CHAR(tty), ldata->char_map);
1809 set_bit(REPRINT_CHAR(tty),
1814 set_bit(START_CHAR(tty), ldata->char_map);
1815 set_bit(STOP_CHAR(tty), ldata->char_map);
1818 set_bit(INTR_CHAR(tty), ldata->char_map);
1819 set_bit(QUIT_CHAR(tty), ldata->char_map);
1820 set_bit(SUSP_CHAR(tty), ldata->char_map);
1822 clear_bit(__DISABLED_CHAR, ldata->char_map);
1824 ldata->real_raw = 0;
1827 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1828 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1829 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1830 ldata->real_raw = 1;
1832 ldata->real_raw = 0;
1835 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1836 * been stopped by STOP_CHAR(tty) before it.
1838 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1840 process_echoes(tty);
1843 /* The termios change make the tty ready for I/O */
1844 wake_up_interruptible(&tty->write_wait);
1845 wake_up_interruptible(&tty->read_wait);
1849 * n_tty_close - close the ldisc for this tty
1852 * Called from the terminal layer when this line discipline is
1853 * being shut down, either because of a close or becsuse of a
1854 * discipline change. The function will not be called while other
1855 * ldisc methods are in progress.
1858 static void n_tty_close(struct tty_struct *tty)
1860 struct n_tty_data *ldata = tty->disc_data;
1863 n_tty_packet_mode_flush(tty);
1866 tty->disc_data = NULL;
1870 * n_tty_open - open an ldisc
1871 * @tty: terminal to open
1873 * Called when this line discipline is being attached to the
1874 * terminal device. Can sleep. Called serialized so that no
1875 * other events will occur in parallel. No further open will occur
1879 static int n_tty_open(struct tty_struct *tty)
1881 struct n_tty_data *ldata;
1883 /* Currently a malloc failure here can panic */
1884 ldata = vmalloc(sizeof(*ldata));
1888 ldata->overrun_time = jiffies;
1889 mutex_init(&ldata->atomic_read_lock);
1890 mutex_init(&ldata->output_lock);
1892 tty->disc_data = ldata;
1893 reset_buffer_flags(tty->disc_data);
1895 ldata->canon_column = 0;
1896 ldata->num_overrun = 0;
1900 /* indicate buffer work may resume */
1901 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1902 n_tty_set_termios(tty, NULL);
1903 tty_unthrottle(tty);
1910 static inline int input_available_p(struct tty_struct *tty, int poll)
1912 struct n_tty_data *ldata = tty->disc_data;
1913 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1915 if (ldata->icanon && !L_EXTPROC(tty))
1916 return ldata->canon_head != ldata->read_tail;
1918 return ldata->commit_head - ldata->read_tail >= amt;
1922 * copy_from_read_buf - copy read data directly
1923 * @tty: terminal device
1927 * Helper function to speed up n_tty_read. It is only called when
1928 * ICANON is off; it copies characters straight from the tty queue to
1929 * user space directly. It can be profitably called twice; once to
1930 * drain the space from the tail pointer to the (physical) end of the
1931 * buffer, and once to drain the space from the (physical) beginning of
1932 * the buffer to head pointer.
1934 * Called under the ldata->atomic_read_lock sem
1936 * n_tty_read()/consumer path:
1937 * caller holds non-exclusive termios_rwsem
1938 * read_tail published
1941 static int copy_from_read_buf(struct tty_struct *tty,
1942 unsigned char __user **b,
1946 struct n_tty_data *ldata = tty->disc_data;
1950 size_t head = smp_load_acquire(&ldata->commit_head);
1951 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1954 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
1957 const unsigned char *from = read_buf_addr(ldata, tail);
1958 retval = copy_to_user(*b, from, n);
1960 is_eof = n == 1 && *from == EOF_CHAR(tty);
1961 tty_audit_add_data(tty, from, n);
1962 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
1963 /* Turn single EOF into zero-length read */
1964 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
1965 (head == ldata->read_tail))
1974 * canon_copy_from_read_buf - copy read data in canonical mode
1975 * @tty: terminal device
1979 * Helper function for n_tty_read. It is only called when ICANON is on;
1980 * it copies one line of input up to and including the line-delimiting
1981 * character into the user-space buffer.
1983 * NB: When termios is changed from non-canonical to canonical mode and
1984 * the read buffer contains data, n_tty_set_termios() simulates an EOF
1985 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
1986 * This causes data already processed as input to be immediately available
1987 * as input although a newline has not been received.
1989 * Called under the atomic_read_lock mutex
1991 * n_tty_read()/consumer path:
1992 * caller holds non-exclusive termios_rwsem
1993 * read_tail published
1996 static int canon_copy_from_read_buf(struct tty_struct *tty,
1997 unsigned char __user **b,
2000 struct n_tty_data *ldata = tty->disc_data;
2001 size_t n, size, more, c;
2006 /* N.B. avoid overrun if nr == 0 */
2010 n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2012 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2013 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2015 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2016 __func__, *nr, tail, n, size);
2018 eol = find_next_bit(ldata->read_flags, size, tail);
2019 more = n - (size - tail);
2020 if (eol == N_TTY_BUF_SIZE && more) {
2021 /* scan wrapped without finding set bit */
2022 eol = find_next_bit(ldata->read_flags, more, 0);
2023 found = eol != more;
2025 found = eol != size;
2028 if (n > N_TTY_BUF_SIZE)
2029 n += N_TTY_BUF_SIZE;
2032 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2037 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2038 __func__, eol, found, n, c, tail, more);
2040 ret = tty_copy_to_user(tty, *b, tail, n);
2047 clear_bit(eol, ldata->read_flags);
2048 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2052 ldata->line_start = ldata->read_tail;
2060 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2064 * job_control - check job control
2066 * @file: file handle
2068 * Perform job control management checks on this file/tty descriptor
2069 * and if appropriate send any needed signals and return a negative
2070 * error code if action should be taken.
2072 * Locking: redirected write test is safe
2073 * current->signal->tty check is safe
2074 * ctrl_lock to safely reference tty->pgrp
2077 static int job_control(struct tty_struct *tty, struct file *file)
2079 /* Job control check -- must be done at start and after
2080 every sleep (POSIX.1 7.1.1.4). */
2081 /* NOTE: not yet done after every sleep pending a thorough
2082 check of the logic of this change. -- jlc */
2083 /* don't stop on /dev/console */
2084 if (file->f_op->write == redirected_tty_write)
2087 return __tty_check_change(tty, SIGTTIN);
2092 * n_tty_read - read function for tty
2094 * @file: file object
2095 * @buf: userspace buffer pointer
2098 * Perform reads for the line discipline. We are guaranteed that the
2099 * line discipline will not be closed under us but we may get multiple
2100 * parallel readers and must handle this ourselves. We may also get
2101 * a hangup. Always called in user context, may sleep.
2103 * This code must be sure never to sleep through a hangup.
2105 * n_tty_read()/consumer path:
2106 * claims non-exclusive termios_rwsem
2107 * publishes read_tail
2110 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2111 unsigned char __user *buf, size_t nr)
2113 struct n_tty_data *ldata = tty->disc_data;
2114 unsigned char __user *b = buf;
2115 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2123 c = job_control(tty, file);
2128 * Internal serialization of reads.
2130 if (file->f_flags & O_NONBLOCK) {
2131 if (!mutex_trylock(&ldata->atomic_read_lock))
2134 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2135 return -ERESTARTSYS;
2138 down_read(&tty->termios_rwsem);
2141 timeout = MAX_SCHEDULE_TIMEOUT;
2142 if (!ldata->icanon) {
2143 minimum = MIN_CHAR(tty);
2145 time = (HZ / 10) * TIME_CHAR(tty);
2147 timeout = (HZ / 10) * TIME_CHAR(tty);
2152 packet = tty->packet;
2153 tail = ldata->read_tail;
2155 add_wait_queue(&tty->read_wait, &wait);
2157 /* First test for status change. */
2158 if (packet && tty->link->ctrl_status) {
2162 spin_lock_irq(&tty->link->ctrl_lock);
2163 cs = tty->link->ctrl_status;
2164 tty->link->ctrl_status = 0;
2165 spin_unlock_irq(&tty->link->ctrl_lock);
2166 if (put_user(cs, b)) {
2175 if (!input_available_p(tty, 0)) {
2176 up_read(&tty->termios_rwsem);
2177 tty_buffer_flush_work(tty->port);
2178 down_read(&tty->termios_rwsem);
2179 if (!input_available_p(tty, 0)) {
2180 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2184 if (tty_hung_up_p(file))
2188 if (file->f_flags & O_NONBLOCK) {
2192 if (signal_pending(current)) {
2193 retval = -ERESTARTSYS;
2196 up_read(&tty->termios_rwsem);
2198 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2201 down_read(&tty->termios_rwsem);
2206 if (ldata->icanon && !L_EXTPROC(tty)) {
2207 retval = canon_copy_from_read_buf(tty, &b, &nr);
2213 /* Deal with packet mode. */
2214 if (packet && b == buf) {
2215 if (put_user(TIOCPKT_DATA, b)) {
2223 uncopied = copy_from_read_buf(tty, &b, &nr);
2224 uncopied += copy_from_read_buf(tty, &b, &nr);
2231 n_tty_check_unthrottle(tty);
2233 if (b - buf >= minimum)
2238 if (tail != ldata->read_tail)
2239 n_tty_kick_worker(tty);
2240 up_read(&tty->termios_rwsem);
2242 remove_wait_queue(&tty->read_wait, &wait);
2243 mutex_unlock(&ldata->atomic_read_lock);
2252 * n_tty_write - write function for tty
2254 * @file: file object
2255 * @buf: userspace buffer pointer
2258 * Write function of the terminal device. This is serialized with
2259 * respect to other write callers but not to termios changes, reads
2260 * and other such events. Since the receive code will echo characters,
2261 * thus calling driver write methods, the output_lock is used in
2262 * the output processing functions called here as well as in the
2263 * echo processing function to protect the column state and space
2264 * left in the buffer.
2266 * This code must be sure never to sleep through a hangup.
2268 * Locking: output_lock to protect column state and space left
2269 * (note that the process_output*() functions take this
2273 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2274 const unsigned char *buf, size_t nr)
2276 const unsigned char *b = buf;
2277 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2281 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2282 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2283 retval = tty_check_change(tty);
2288 down_read(&tty->termios_rwsem);
2290 /* Write out any echoed characters that are still pending */
2291 process_echoes(tty);
2293 add_wait_queue(&tty->write_wait, &wait);
2295 if (signal_pending(current)) {
2296 retval = -ERESTARTSYS;
2299 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2305 ssize_t num = process_output_block(tty, b, nr);
2317 if (process_output(c, tty) < 0)
2321 if (tty->ops->flush_chars)
2322 tty->ops->flush_chars(tty);
2324 struct n_tty_data *ldata = tty->disc_data;
2327 mutex_lock(&ldata->output_lock);
2328 c = tty->ops->write(tty, b, nr);
2329 mutex_unlock(&ldata->output_lock);
2342 if (file->f_flags & O_NONBLOCK) {
2346 up_read(&tty->termios_rwsem);
2348 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2350 down_read(&tty->termios_rwsem);
2353 remove_wait_queue(&tty->write_wait, &wait);
2354 if (nr && tty->fasync)
2355 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2356 up_read(&tty->termios_rwsem);
2357 return (b - buf) ? b - buf : retval;
2361 * n_tty_poll - poll method for N_TTY
2362 * @tty: terminal device
2363 * @file: file accessing it
2366 * Called when the line discipline is asked to poll() for data or
2367 * for special events. This code is not serialized with respect to
2368 * other events save open/close.
2370 * This code must be sure never to sleep through a hangup.
2371 * Called without the kernel lock held - fine
2374 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2377 unsigned int mask = 0;
2379 poll_wait(file, &tty->read_wait, wait);
2380 poll_wait(file, &tty->write_wait, wait);
2381 if (input_available_p(tty, 1))
2382 mask |= POLLIN | POLLRDNORM;
2384 tty_buffer_flush_work(tty->port);
2385 if (input_available_p(tty, 1))
2386 mask |= POLLIN | POLLRDNORM;
2388 if (tty->packet && tty->link->ctrl_status)
2389 mask |= POLLPRI | POLLIN | POLLRDNORM;
2390 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2392 if (tty_hung_up_p(file))
2394 if (tty->ops->write && !tty_is_writelocked(tty) &&
2395 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2396 tty_write_room(tty) > 0)
2397 mask |= POLLOUT | POLLWRNORM;
2401 static unsigned long inq_canon(struct n_tty_data *ldata)
2403 size_t nr, head, tail;
2405 if (ldata->canon_head == ldata->read_tail)
2407 head = ldata->canon_head;
2408 tail = ldata->read_tail;
2410 /* Skip EOF-chars.. */
2411 while (head != tail) {
2412 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2413 read_buf(ldata, tail) == __DISABLED_CHAR)
2420 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2421 unsigned int cmd, unsigned long arg)
2423 struct n_tty_data *ldata = tty->disc_data;
2428 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2430 down_write(&tty->termios_rwsem);
2432 retval = inq_canon(ldata);
2434 retval = read_cnt(ldata);
2435 up_write(&tty->termios_rwsem);
2436 return put_user(retval, (unsigned int __user *) arg);
2438 return n_tty_ioctl_helper(tty, file, cmd, arg);
2442 static struct tty_ldisc_ops n_tty_ops = {
2443 .magic = TTY_LDISC_MAGIC,
2446 .close = n_tty_close,
2447 .flush_buffer = n_tty_flush_buffer,
2449 .write = n_tty_write,
2450 .ioctl = n_tty_ioctl,
2451 .set_termios = n_tty_set_termios,
2453 .receive_buf = n_tty_receive_buf,
2454 .write_wakeup = n_tty_write_wakeup,
2455 .receive_buf2 = n_tty_receive_buf2,
2459 * n_tty_inherit_ops - inherit N_TTY methods
2460 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2462 * Enables a 'subclass' line discipline to 'inherit' N_TTY methods.
2465 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2469 ops->refcount = ops->flags = 0;
2471 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);
2473 void __init n_tty_init(void)
2475 tty_register_ldisc(N_TTY, &n_tty_ops);