2 * n_tty.c --- implements the N_TTY line discipline.
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where n_tty_write returns
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52 #include <linux/ratelimit.h>
53 #include <linux/vmalloc.h>
56 /* number of characters left in xmit buffer before select has we have room */
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...)
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];
118 /* consumer-published */
122 /* protected by output lock */
124 unsigned int canon_column;
127 struct mutex atomic_read_lock;
128 struct mutex output_lock;
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 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
151 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
153 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
156 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
157 unsigned char __user *ptr)
159 struct n_tty_data *ldata = tty->disc_data;
161 tty_audit_add_data(tty, &x, 1, ldata->icanon);
162 return put_user(x, ptr);
165 static inline int tty_copy_to_user(struct tty_struct *tty,
170 struct n_tty_data *ldata = tty->disc_data;
172 tty_audit_add_data(tty, from, n, ldata->icanon);
173 return copy_to_user(to, from, n);
177 * n_tty_kick_worker - start input worker (if required)
180 * Re-schedules the flip buffer work if it may have stopped
182 * Caller holds exclusive termios_rwsem
184 * n_tty_read()/consumer path:
185 * holds non-exclusive termios_rwsem
188 static void n_tty_kick_worker(struct tty_struct *tty)
190 struct n_tty_data *ldata = tty->disc_data;
192 /* Did the input worker stop? Restart it */
193 if (unlikely(ldata->no_room)) {
196 WARN_RATELIMIT(tty->port->itty == NULL,
197 "scheduling with invalid itty\n");
198 /* see if ldisc has been killed - if so, this means that
199 * even though the ldisc has been halted and ->buf.work
200 * cancelled, ->buf.work is about to be rescheduled
202 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
203 "scheduling buffer work for halted ldisc\n");
204 tty_buffer_restart_work(tty->port);
208 static ssize_t chars_in_buffer(struct tty_struct *tty)
210 struct n_tty_data *ldata = tty->disc_data;
214 n = ldata->commit_head - ldata->read_tail;
216 n = ldata->canon_head - ldata->read_tail;
221 * n_tty_write_wakeup - asynchronous I/O notifier
224 * Required for the ptys, serial driver etc. since processes
225 * that attach themselves to the master and rely on ASYNC
226 * IO must be woken up
229 static void n_tty_write_wakeup(struct tty_struct *tty)
231 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
232 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
235 static void n_tty_check_throttle(struct tty_struct *tty)
237 struct n_tty_data *ldata = tty->disc_data;
240 * Check the remaining room for the input canonicalization
241 * mode. We don't want to throttle the driver if we're in
242 * canonical mode and don't have a newline yet!
244 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
249 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
250 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
252 throttled = tty_throttle_safe(tty);
256 __tty_set_flow_change(tty, 0);
259 static void n_tty_check_unthrottle(struct tty_struct *tty)
261 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
262 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
266 n_tty_kick_worker(tty);
267 tty_wakeup(tty->link);
271 /* If there is enough space in the read buffer now, let the
272 * low-level driver know. We use chars_in_buffer() to
273 * check the buffer, as it now knows about canonical mode.
274 * Otherwise, if the driver is throttled and the line is
275 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
276 * we won't get any more characters.
281 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
282 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
286 n_tty_kick_worker(tty);
287 unthrottled = tty_unthrottle_safe(tty);
291 __tty_set_flow_change(tty, 0);
295 * put_tty_queue - add character to tty
299 * Add a character to the tty read_buf queue.
301 * n_tty_receive_buf()/producer path:
302 * caller holds non-exclusive termios_rwsem
305 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
307 *read_buf_addr(ldata, ldata->read_head) = c;
312 * reset_buffer_flags - reset buffer state
313 * @tty: terminal to reset
315 * Reset the read buffer counters and clear the flags.
316 * Called from n_tty_open() and n_tty_flush_buffer().
318 * Locking: caller holds exclusive termios_rwsem
319 * (or locking is not required)
322 static void reset_buffer_flags(struct n_tty_data *ldata)
324 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
325 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
326 ldata->commit_head = 0;
327 ldata->echo_mark = 0;
328 ldata->line_start = 0;
331 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
335 static void n_tty_packet_mode_flush(struct tty_struct *tty)
339 if (tty->link->packet) {
340 spin_lock_irqsave(&tty->ctrl_lock, flags);
341 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
342 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
343 wake_up_interruptible(&tty->link->read_wait);
348 * n_tty_flush_buffer - clean input queue
349 * @tty: terminal device
351 * Flush the input buffer. Called when the tty layer wants the
352 * buffer flushed (eg at hangup) or when the N_TTY line discipline
353 * internally has to clean the pending queue (for example some signals).
355 * Holds termios_rwsem to exclude producer/consumer while
356 * buffer indices are reset.
358 * Locking: ctrl_lock, exclusive termios_rwsem
361 static void n_tty_flush_buffer(struct tty_struct *tty)
363 down_write(&tty->termios_rwsem);
364 reset_buffer_flags(tty->disc_data);
365 n_tty_kick_worker(tty);
368 n_tty_packet_mode_flush(tty);
369 up_write(&tty->termios_rwsem);
373 * n_tty_chars_in_buffer - report available bytes
376 * Report the number of characters buffered to be delivered to user
377 * at this instant in time.
379 * Locking: exclusive termios_rwsem
382 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
386 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
388 down_write(&tty->termios_rwsem);
389 n = chars_in_buffer(tty);
390 up_write(&tty->termios_rwsem);
395 * is_utf8_continuation - utf8 multibyte check
398 * Returns true if the utf8 character 'c' is a multibyte continuation
399 * character. We use this to correctly compute the on screen size
400 * of the character when printing
403 static inline int is_utf8_continuation(unsigned char c)
405 return (c & 0xc0) == 0x80;
409 * is_continuation - multibyte check
412 * Returns true if the utf8 character 'c' is a multibyte continuation
413 * character and the terminal is in unicode mode.
416 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
418 return I_IUTF8(tty) && is_utf8_continuation(c);
422 * do_output_char - output one character
423 * @c: character (or partial unicode symbol)
424 * @tty: terminal device
425 * @space: space available in tty driver write buffer
427 * This is a helper function that handles one output character
428 * (including special characters like TAB, CR, LF, etc.),
429 * doing OPOST processing and putting the results in the
430 * tty driver's write buffer.
432 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
433 * and NLDLY. They simply aren't relevant in the world today.
434 * If you ever need them, add them here.
436 * Returns the number of bytes of buffer space used or -1 if
439 * Locking: should be called under the output_lock to protect
440 * the column state and space left in the buffer
443 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
445 struct n_tty_data *ldata = tty->disc_data;
458 ldata->canon_column = ldata->column = 0;
459 tty->ops->write(tty, "\r\n", 2);
462 ldata->canon_column = ldata->column;
465 if (O_ONOCR(tty) && ldata->column == 0)
470 ldata->canon_column = ldata->column = 0;
473 ldata->canon_column = ldata->column = 0;
476 spaces = 8 - (ldata->column & 7);
477 if (O_TABDLY(tty) == XTABS) {
480 ldata->column += spaces;
481 tty->ops->write(tty, " ", spaces);
484 ldata->column += spaces;
487 if (ldata->column > 0)
494 if (!is_continuation(c, tty))
500 tty_put_char(tty, c);
505 * process_output - output post processor
506 * @c: character (or partial unicode symbol)
507 * @tty: terminal device
509 * Output one character with OPOST processing.
510 * Returns -1 when the output device is full and the character
513 * Locking: output_lock to protect column state and space left
514 * (also, this is called from n_tty_write under the
515 * tty layer write lock)
518 static int process_output(unsigned char c, struct tty_struct *tty)
520 struct n_tty_data *ldata = tty->disc_data;
523 mutex_lock(&ldata->output_lock);
525 space = tty_write_room(tty);
526 retval = do_output_char(c, tty, space);
528 mutex_unlock(&ldata->output_lock);
536 * process_output_block - block post processor
537 * @tty: terminal device
538 * @buf: character buffer
539 * @nr: number of bytes to output
541 * Output a block of characters with OPOST processing.
542 * Returns the number of characters output.
544 * This path is used to speed up block console writes, among other
545 * things when processing blocks of output data. It handles only
546 * the simple cases normally found and helps to generate blocks of
547 * symbols for the console driver and thus improve performance.
549 * Locking: output_lock to protect column state and space left
550 * (also, this is called from n_tty_write under the
551 * tty layer write lock)
554 static ssize_t process_output_block(struct tty_struct *tty,
555 const unsigned char *buf, unsigned int nr)
557 struct n_tty_data *ldata = tty->disc_data;
560 const unsigned char *cp;
562 mutex_lock(&ldata->output_lock);
564 space = tty_write_room(tty);
566 mutex_unlock(&ldata->output_lock);
572 for (i = 0, cp = buf; i < nr; i++, cp++) {
573 unsigned char c = *cp;
581 ldata->canon_column = ldata->column;
584 if (O_ONOCR(tty) && ldata->column == 0)
588 ldata->canon_column = ldata->column = 0;
593 if (ldata->column > 0)
600 if (!is_continuation(c, tty))
607 i = tty->ops->write(tty, buf, i);
609 mutex_unlock(&ldata->output_lock);
614 * process_echoes - write pending echo characters
615 * @tty: terminal device
617 * Write previously buffered echo (and other ldisc-generated)
618 * characters to the tty.
620 * Characters generated by the ldisc (including echoes) need to
621 * be buffered because the driver's write buffer can fill during
622 * heavy program output. Echoing straight to the driver will
623 * often fail under these conditions, causing lost characters and
624 * resulting mismatches of ldisc state information.
626 * Since the ldisc state must represent the characters actually sent
627 * to the driver at the time of the write, operations like certain
628 * changes in column state are also saved in the buffer and executed
631 * A circular fifo buffer is used so that the most recent characters
632 * are prioritized. Also, when control characters are echoed with a
633 * prefixed "^", the pair is treated atomically and thus not separated.
635 * Locking: callers must hold output_lock
638 static size_t __process_echoes(struct tty_struct *tty)
640 struct n_tty_data *ldata = tty->disc_data;
641 int space, old_space;
645 old_space = space = tty_write_room(tty);
647 tail = ldata->echo_tail;
648 while (ldata->echo_commit != tail) {
649 c = echo_buf(ldata, tail);
650 if (c == ECHO_OP_START) {
652 int no_space_left = 0;
655 * If the buffer byte is the start of a multi-byte
656 * operation, get the next byte, which is either the
657 * op code or a control character value.
659 op = echo_buf(ldata, tail + 1);
662 unsigned int num_chars, num_bs;
664 case ECHO_OP_ERASE_TAB:
665 num_chars = echo_buf(ldata, tail + 2);
668 * Determine how many columns to go back
669 * in order to erase the tab.
670 * This depends on the number of columns
671 * used by other characters within the tab
672 * area. If this (modulo 8) count is from
673 * the start of input rather than from a
674 * previous tab, we offset by canon column.
675 * Otherwise, tab spacing is normal.
677 if (!(num_chars & 0x80))
678 num_chars += ldata->canon_column;
679 num_bs = 8 - (num_chars & 7);
681 if (num_bs > space) {
687 tty_put_char(tty, '\b');
688 if (ldata->column > 0)
694 case ECHO_OP_SET_CANON_COL:
695 ldata->canon_column = ldata->column;
699 case ECHO_OP_MOVE_BACK_COL:
700 if (ldata->column > 0)
706 /* This is an escaped echo op start code */
711 tty_put_char(tty, ECHO_OP_START);
719 * If the op is not a special byte code,
720 * it is a ctrl char tagged to be echoed
721 * as "^X" (where X is the letter
722 * representing the control char).
723 * Note that we must ensure there is
724 * enough space for the whole ctrl pair.
731 tty_put_char(tty, '^');
732 tty_put_char(tty, op ^ 0100);
742 int retval = do_output_char(c, tty, space);
749 tty_put_char(tty, c);
756 /* If the echo buffer is nearly full (so that the possibility exists
757 * of echo overrun before the next commit), then discard enough
758 * data at the tail to prevent a subsequent overrun */
759 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
760 if (echo_buf(ldata, tail) == ECHO_OP_START) {
761 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
769 ldata->echo_tail = tail;
770 return old_space - space;
773 static void commit_echoes(struct tty_struct *tty)
775 struct n_tty_data *ldata = tty->disc_data;
776 size_t nr, old, echoed;
779 head = ldata->echo_head;
780 ldata->echo_mark = head;
781 old = ldata->echo_commit - ldata->echo_tail;
783 /* Process committed echoes if the accumulated # of bytes
784 * is over the threshold (and try again each time another
785 * block is accumulated) */
786 nr = head - ldata->echo_tail;
787 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
790 mutex_lock(&ldata->output_lock);
791 ldata->echo_commit = head;
792 echoed = __process_echoes(tty);
793 mutex_unlock(&ldata->output_lock);
795 if (echoed && tty->ops->flush_chars)
796 tty->ops->flush_chars(tty);
799 static void process_echoes(struct tty_struct *tty)
801 struct n_tty_data *ldata = tty->disc_data;
804 if (ldata->echo_mark == ldata->echo_tail)
807 mutex_lock(&ldata->output_lock);
808 ldata->echo_commit = ldata->echo_mark;
809 echoed = __process_echoes(tty);
810 mutex_unlock(&ldata->output_lock);
812 if (echoed && tty->ops->flush_chars)
813 tty->ops->flush_chars(tty);
816 /* NB: echo_mark and echo_head should be equivalent here */
817 static void flush_echoes(struct tty_struct *tty)
819 struct n_tty_data *ldata = tty->disc_data;
821 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
822 ldata->echo_commit == ldata->echo_head)
825 mutex_lock(&ldata->output_lock);
826 ldata->echo_commit = ldata->echo_head;
827 __process_echoes(tty);
828 mutex_unlock(&ldata->output_lock);
832 * add_echo_byte - add a byte to the echo buffer
833 * @c: unicode byte to echo
836 * Add a character or operation byte to the echo buffer.
839 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
841 *echo_buf_addr(ldata, ldata->echo_head++) = c;
845 * echo_move_back_col - add operation to move back a column
848 * Add an operation to the echo buffer to move back one column.
851 static void echo_move_back_col(struct n_tty_data *ldata)
853 add_echo_byte(ECHO_OP_START, ldata);
854 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
858 * echo_set_canon_col - add operation to set the canon column
861 * Add an operation to the echo buffer to set the canon column
862 * to the current column.
865 static void echo_set_canon_col(struct n_tty_data *ldata)
867 add_echo_byte(ECHO_OP_START, ldata);
868 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
872 * echo_erase_tab - add operation to erase a tab
873 * @num_chars: number of character columns already used
874 * @after_tab: true if num_chars starts after a previous tab
877 * Add an operation to the echo buffer to erase a tab.
879 * Called by the eraser function, which knows how many character
880 * columns have been used since either a previous tab or the start
881 * of input. This information will be used later, along with
882 * canon column (if applicable), to go back the correct number
886 static void echo_erase_tab(unsigned int num_chars, int after_tab,
887 struct n_tty_data *ldata)
889 add_echo_byte(ECHO_OP_START, ldata);
890 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
892 /* We only need to know this modulo 8 (tab spacing) */
895 /* Set the high bit as a flag if num_chars is after a previous tab */
899 add_echo_byte(num_chars, ldata);
903 * echo_char_raw - echo a character raw
904 * @c: unicode byte to echo
905 * @tty: terminal device
907 * Echo user input back onto the screen. This must be called only when
908 * L_ECHO(tty) is true. Called from the driver receive_buf path.
910 * This variant does not treat control characters specially.
913 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
915 if (c == ECHO_OP_START) {
916 add_echo_byte(ECHO_OP_START, ldata);
917 add_echo_byte(ECHO_OP_START, ldata);
919 add_echo_byte(c, ldata);
924 * echo_char - echo a character
925 * @c: unicode byte to echo
926 * @tty: terminal device
928 * Echo user input back onto the screen. This must be called only when
929 * L_ECHO(tty) is true. Called from the driver receive_buf path.
931 * This variant tags control characters to be echoed as "^X"
932 * (where X is the letter representing the control char).
935 static void echo_char(unsigned char c, struct tty_struct *tty)
937 struct n_tty_data *ldata = tty->disc_data;
939 if (c == ECHO_OP_START) {
940 add_echo_byte(ECHO_OP_START, ldata);
941 add_echo_byte(ECHO_OP_START, ldata);
943 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
944 add_echo_byte(ECHO_OP_START, ldata);
945 add_echo_byte(c, ldata);
950 * finish_erasing - complete erase
954 static inline void finish_erasing(struct n_tty_data *ldata)
956 if (ldata->erasing) {
957 echo_char_raw('/', ldata);
963 * eraser - handle erase function
964 * @c: character input
965 * @tty: terminal device
967 * Perform erase and necessary output when an erase character is
968 * present in the stream from the driver layer. Handles the complexities
969 * of UTF-8 multibyte symbols.
971 * n_tty_receive_buf()/producer path:
972 * caller holds non-exclusive termios_rwsem
975 static void eraser(unsigned char c, struct tty_struct *tty)
977 struct n_tty_data *ldata = tty->disc_data;
978 enum { ERASE, WERASE, KILL } kill_type;
983 if (ldata->read_head == ldata->canon_head) {
984 /* process_output('\a', tty); */ /* what do you think? */
987 if (c == ERASE_CHAR(tty))
989 else if (c == WERASE_CHAR(tty))
993 ldata->read_head = ldata->canon_head;
996 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
997 ldata->read_head = ldata->canon_head;
998 finish_erasing(ldata);
999 echo_char(KILL_CHAR(tty), tty);
1000 /* Add a newline if ECHOK is on and ECHOKE is off. */
1002 echo_char_raw('\n', ldata);
1009 while (ldata->read_head != ldata->canon_head) {
1010 head = ldata->read_head;
1012 /* erase a single possibly multibyte character */
1015 c = read_buf(ldata, head);
1016 } while (is_continuation(c, tty) && head != 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 (tail != 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 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1203 ldata->num_overrun);
1204 ldata->overrun_time = jiffies;
1205 ldata->num_overrun = 0;
1210 * n_tty_receive_parity_error - error notifier
1211 * @tty: terminal device
1214 * Process a parity error and queue the right data to indicate
1215 * the error case if necessary.
1217 * n_tty_receive_buf()/producer path:
1218 * caller holds non-exclusive termios_rwsem
1220 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1222 struct n_tty_data *ldata = tty->disc_data;
1227 if (I_PARMRK(tty)) {
1228 put_tty_queue('\377', ldata);
1229 put_tty_queue('\0', ldata);
1230 put_tty_queue(c, ldata);
1232 put_tty_queue('\0', ldata);
1234 put_tty_queue(c, ldata);
1238 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1247 process_echoes(tty);
1252 * n_tty_receive_char - perform processing
1253 * @tty: terminal device
1256 * Process an individual character of input received from the driver.
1257 * This is serialized with respect to itself by the rules for the
1260 * n_tty_receive_buf()/producer path:
1261 * caller holds non-exclusive termios_rwsem
1262 * publishes canon_head if canonical mode is active
1264 * Returns 1 if LNEXT was received, else returns 0
1268 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1270 struct n_tty_data *ldata = tty->disc_data;
1273 if (c == START_CHAR(tty)) {
1275 process_echoes(tty);
1278 if (c == STOP_CHAR(tty)) {
1285 if (c == INTR_CHAR(tty)) {
1286 n_tty_receive_signal_char(tty, SIGINT, c);
1288 } else if (c == QUIT_CHAR(tty)) {
1289 n_tty_receive_signal_char(tty, SIGQUIT, c);
1291 } else if (c == SUSP_CHAR(tty)) {
1292 n_tty_receive_signal_char(tty, SIGTSTP, c);
1297 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1299 process_echoes(tty);
1307 } else if (c == '\n' && I_INLCR(tty))
1310 if (ldata->icanon) {
1311 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1312 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1317 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1320 finish_erasing(ldata);
1321 if (L_ECHOCTL(tty)) {
1322 echo_char_raw('^', ldata);
1323 echo_char_raw('\b', ldata);
1329 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1330 size_t tail = ldata->canon_head;
1332 finish_erasing(ldata);
1334 echo_char_raw('\n', ldata);
1335 while (tail != ldata->read_head) {
1336 echo_char(read_buf(ldata, tail), tty);
1343 if (L_ECHO(tty) || L_ECHONL(tty)) {
1344 echo_char_raw('\n', ldata);
1347 goto handle_newline;
1349 if (c == EOF_CHAR(tty)) {
1350 c = __DISABLED_CHAR;
1351 goto handle_newline;
1353 if ((c == EOL_CHAR(tty)) ||
1354 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1356 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1359 /* Record the column of first canon char. */
1360 if (ldata->canon_head == ldata->read_head)
1361 echo_set_canon_col(ldata);
1366 * XXX does PARMRK doubling happen for
1367 * EOL_CHAR and EOL2_CHAR?
1369 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1370 put_tty_queue(c, ldata);
1373 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1374 put_tty_queue(c, ldata);
1375 smp_store_release(&ldata->canon_head, ldata->read_head);
1376 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1377 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1383 finish_erasing(ldata);
1385 echo_char_raw('\n', ldata);
1387 /* Record the column of first canon char. */
1388 if (ldata->canon_head == ldata->read_head)
1389 echo_set_canon_col(ldata);
1395 /* PARMRK doubling check */
1396 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1397 put_tty_queue(c, ldata);
1399 put_tty_queue(c, ldata);
1404 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1406 struct n_tty_data *ldata = tty->disc_data;
1408 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1410 process_echoes(tty);
1413 finish_erasing(ldata);
1414 /* Record the column of first canon char. */
1415 if (ldata->canon_head == ldata->read_head)
1416 echo_set_canon_col(ldata);
1420 /* PARMRK doubling check */
1421 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1422 put_tty_queue(c, ldata);
1423 put_tty_queue(c, ldata);
1426 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1428 n_tty_receive_char_inline(tty, c);
1432 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1434 struct n_tty_data *ldata = tty->disc_data;
1436 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1438 process_echoes(tty);
1441 finish_erasing(ldata);
1442 /* Record the column of first canon char. */
1443 if (ldata->canon_head == ldata->read_head)
1444 echo_set_canon_col(ldata);
1448 put_tty_queue(c, ldata);
1451 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1455 if (I_IUCLC(tty) && L_IEXTEN(tty))
1459 if (c == STOP_CHAR(tty))
1461 else if (c == START_CHAR(tty) ||
1462 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1463 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1464 c != SUSP_CHAR(tty))) {
1466 process_echoes(tty);
1472 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1476 n_tty_receive_break(tty);
1480 n_tty_receive_parity_error(tty, c);
1483 n_tty_receive_overrun(tty);
1486 printk(KERN_ERR "%s: unknown flag %d\n",
1487 tty_name(tty), flag);
1493 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1495 struct n_tty_data *ldata = tty->disc_data;
1498 if (likely(flag == TTY_NORMAL)) {
1501 if (I_IUCLC(tty) && L_IEXTEN(tty))
1503 n_tty_receive_char(tty, c);
1505 n_tty_receive_char_flagged(tty, c, flag);
1509 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1510 char *fp, int count)
1512 struct n_tty_data *ldata = tty->disc_data;
1515 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1516 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1517 memcpy(read_buf_addr(ldata, head), cp, n);
1518 ldata->read_head += n;
1522 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1523 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1524 memcpy(read_buf_addr(ldata, head), cp, n);
1525 ldata->read_head += n;
1529 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1530 char *fp, int count)
1532 struct n_tty_data *ldata = tty->disc_data;
1533 char flag = TTY_NORMAL;
1538 if (likely(flag == TTY_NORMAL))
1539 put_tty_queue(*cp++, ldata);
1541 n_tty_receive_char_flagged(tty, *cp++, flag);
1546 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1547 char *fp, int count)
1549 char flag = TTY_NORMAL;
1554 if (likely(flag == TTY_NORMAL))
1555 n_tty_receive_char_closing(tty, *cp++);
1557 n_tty_receive_char_flagged(tty, *cp++, flag);
1562 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1563 char *fp, int count)
1565 struct n_tty_data *ldata = tty->disc_data;
1566 char flag = TTY_NORMAL;
1571 if (likely(flag == TTY_NORMAL)) {
1572 unsigned char c = *cp++;
1576 if (I_IUCLC(tty) && L_IEXTEN(tty))
1578 if (L_EXTPROC(tty)) {
1579 put_tty_queue(c, ldata);
1582 if (!test_bit(c, ldata->char_map))
1583 n_tty_receive_char_inline(tty, c);
1584 else if (n_tty_receive_char_special(tty, c) && count) {
1587 n_tty_receive_char_lnext(tty, *cp++, flag);
1591 n_tty_receive_char_flagged(tty, *cp++, flag);
1596 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1597 char *fp, int count)
1599 struct n_tty_data *ldata = tty->disc_data;
1600 char flag = TTY_NORMAL;
1605 if (likely(flag == TTY_NORMAL)) {
1606 unsigned char c = *cp++;
1608 if (!test_bit(c, ldata->char_map))
1609 n_tty_receive_char_fast(tty, c);
1610 else if (n_tty_receive_char_special(tty, c) && count) {
1613 n_tty_receive_char_lnext(tty, *cp++, flag);
1617 n_tty_receive_char_flagged(tty, *cp++, flag);
1621 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1622 char *fp, int count)
1624 struct n_tty_data *ldata = tty->disc_data;
1625 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1627 if (ldata->real_raw)
1628 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1629 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1630 n_tty_receive_buf_raw(tty, cp, fp, count);
1631 else if (tty->closing && !L_EXTPROC(tty))
1632 n_tty_receive_buf_closing(tty, cp, fp, count);
1635 char flag = TTY_NORMAL;
1639 n_tty_receive_char_lnext(tty, *cp++, flag);
1643 if (!preops && !I_PARMRK(tty))
1644 n_tty_receive_buf_fast(tty, cp, fp, count);
1646 n_tty_receive_buf_standard(tty, cp, fp, count);
1649 if (tty->ops->flush_chars)
1650 tty->ops->flush_chars(tty);
1653 if (ldata->icanon && !L_EXTPROC(tty))
1656 /* publish read_head to consumer */
1657 smp_store_release(&ldata->commit_head, ldata->read_head);
1659 if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
1660 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1661 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1666 * n_tty_receive_buf_common - process input
1667 * @tty: device to receive input
1669 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1670 * @count: number of input chars in @cp
1672 * Called by the terminal driver when a block of characters has
1673 * been received. This function must be called from soft contexts
1674 * not from interrupt context. The driver is responsible for making
1675 * calls one at a time and in order (or using flush_to_ldisc)
1677 * Returns the # of input chars from @cp which were processed.
1679 * In canonical mode, the maximum line length is 4096 chars (including
1680 * the line termination char); lines longer than 4096 chars are
1681 * truncated. After 4095 chars, input data is still processed but
1682 * not stored. Overflow processing ensures the tty can always
1683 * receive more input until at least one line can be read.
1685 * In non-canonical mode, the read buffer will only accept 4095 chars;
1686 * this provides the necessary space for a newline char if the input
1687 * mode is switched to canonical.
1689 * Note it is possible for the read buffer to _contain_ 4096 chars
1690 * in non-canonical mode: the read buffer could already contain the
1691 * maximum canon line of 4096 chars when the mode is switched to
1694 * n_tty_receive_buf()/producer path:
1695 * claims non-exclusive termios_rwsem
1696 * publishes commit_head or canon_head
1699 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1700 char *fp, int count, int flow)
1702 struct n_tty_data *ldata = tty->disc_data;
1703 int room, n, rcvd = 0, overflow;
1705 down_read(&tty->termios_rwsem);
1709 * When PARMRK is set, each input char may take up to 3 chars
1710 * in the read buf; reduce the buffer space avail by 3x
1712 * If we are doing input canonicalization, and there are no
1713 * pending newlines, let characters through without limit, so
1714 * that erase characters will be handled. Other excess
1715 * characters will be beeped.
1717 * paired with store in *_copy_from_read_buf() -- guarantees
1718 * the consumer has loaded the data in read_buf up to the new
1719 * read_tail (so this producer will not overwrite unread data)
1721 size_t tail = smp_load_acquire(&ldata->read_tail);
1723 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1725 room = (room + 2) / 3;
1728 overflow = ldata->icanon && ldata->canon_head == tail;
1729 if (overflow && room < 0)
1732 ldata->no_room = flow && !room;
1736 n = min(count, room);
1740 /* ignore parity errors if handling overflow */
1741 if (!overflow || !fp || *fp != TTY_PARITY)
1742 __receive_buf(tty, cp, fp, n);
1751 tty->receive_room = room;
1753 /* Unthrottle if handling overflow on pty */
1754 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1756 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1757 tty_unthrottle_safe(tty);
1758 __tty_set_flow_change(tty, 0);
1761 n_tty_check_throttle(tty);
1763 up_read(&tty->termios_rwsem);
1768 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1769 char *fp, int count)
1771 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1774 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1775 char *fp, int count)
1777 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1780 int is_ignored(int sig)
1782 return (sigismember(¤t->blocked, sig) ||
1783 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1787 * n_tty_set_termios - termios data changed
1789 * @old: previous data
1791 * Called by the tty layer when the user changes termios flags so
1792 * that the line discipline can plan ahead. This function cannot sleep
1793 * and is protected from re-entry by the tty layer. The user is
1794 * guaranteed that this function will not be re-entered or in progress
1795 * when the ldisc is closed.
1797 * Locking: Caller holds tty->termios_rwsem
1800 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1802 struct n_tty_data *ldata = tty->disc_data;
1804 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1805 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1806 ldata->line_start = ldata->read_tail;
1807 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1808 ldata->canon_head = ldata->read_tail;
1811 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1813 ldata->canon_head = ldata->read_head;
1816 ldata->commit_head = ldata->read_head;
1821 ldata->icanon = (L_ICANON(tty) != 0);
1823 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1824 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1825 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1827 bitmap_zero(ldata->char_map, 256);
1829 if (I_IGNCR(tty) || I_ICRNL(tty))
1830 set_bit('\r', ldata->char_map);
1832 set_bit('\n', ldata->char_map);
1834 if (L_ICANON(tty)) {
1835 set_bit(ERASE_CHAR(tty), ldata->char_map);
1836 set_bit(KILL_CHAR(tty), ldata->char_map);
1837 set_bit(EOF_CHAR(tty), ldata->char_map);
1838 set_bit('\n', ldata->char_map);
1839 set_bit(EOL_CHAR(tty), ldata->char_map);
1840 if (L_IEXTEN(tty)) {
1841 set_bit(WERASE_CHAR(tty), ldata->char_map);
1842 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1843 set_bit(EOL2_CHAR(tty), ldata->char_map);
1845 set_bit(REPRINT_CHAR(tty),
1850 set_bit(START_CHAR(tty), ldata->char_map);
1851 set_bit(STOP_CHAR(tty), ldata->char_map);
1854 set_bit(INTR_CHAR(tty), ldata->char_map);
1855 set_bit(QUIT_CHAR(tty), ldata->char_map);
1856 set_bit(SUSP_CHAR(tty), ldata->char_map);
1858 clear_bit(__DISABLED_CHAR, ldata->char_map);
1860 ldata->real_raw = 0;
1863 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1864 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1865 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1866 ldata->real_raw = 1;
1868 ldata->real_raw = 0;
1871 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1872 * been stopped by STOP_CHAR(tty) before it.
1874 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1876 process_echoes(tty);
1879 /* The termios change make the tty ready for I/O */
1880 wake_up_interruptible(&tty->write_wait);
1881 wake_up_interruptible(&tty->read_wait);
1885 * n_tty_close - close the ldisc for this tty
1888 * Called from the terminal layer when this line discipline is
1889 * being shut down, either because of a close or becsuse of a
1890 * discipline change. The function will not be called while other
1891 * ldisc methods are in progress.
1894 static void n_tty_close(struct tty_struct *tty)
1896 struct n_tty_data *ldata = tty->disc_data;
1899 n_tty_packet_mode_flush(tty);
1902 tty->disc_data = NULL;
1906 * n_tty_open - open an ldisc
1907 * @tty: terminal to open
1909 * Called when this line discipline is being attached to the
1910 * terminal device. Can sleep. Called serialized so that no
1911 * other events will occur in parallel. No further open will occur
1915 static int n_tty_open(struct tty_struct *tty)
1917 struct n_tty_data *ldata;
1919 /* Currently a malloc failure here can panic */
1920 ldata = vmalloc(sizeof(*ldata));
1924 ldata->overrun_time = jiffies;
1925 mutex_init(&ldata->atomic_read_lock);
1926 mutex_init(&ldata->output_lock);
1928 tty->disc_data = ldata;
1929 reset_buffer_flags(tty->disc_data);
1931 ldata->canon_column = 0;
1932 ldata->minimum_to_wake = 1;
1933 ldata->num_overrun = 0;
1937 /* indicate buffer work may resume */
1938 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1939 n_tty_set_termios(tty, NULL);
1940 tty_unthrottle(tty);
1947 static inline int input_available_p(struct tty_struct *tty, int poll)
1949 struct n_tty_data *ldata = tty->disc_data;
1950 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1952 if (ldata->icanon && !L_EXTPROC(tty))
1953 return ldata->canon_head != ldata->read_tail;
1955 return ldata->commit_head - ldata->read_tail >= amt;
1958 static inline int check_other_done(struct tty_struct *tty)
1960 int done = test_bit(TTY_OTHER_DONE, &tty->flags);
1962 /* paired with cmpxchg() in check_other_closed(); ensures
1963 * read buffer head index is not stale
1965 smp_mb__after_atomic();
1971 * copy_from_read_buf - copy read data directly
1972 * @tty: terminal device
1976 * Helper function to speed up n_tty_read. It is only called when
1977 * ICANON is off; it copies characters straight from the tty queue to
1978 * user space directly. It can be profitably called twice; once to
1979 * drain the space from the tail pointer to the (physical) end of the
1980 * buffer, and once to drain the space from the (physical) beginning of
1981 * the buffer to head pointer.
1983 * Called under the ldata->atomic_read_lock sem
1985 * n_tty_read()/consumer path:
1986 * caller holds non-exclusive termios_rwsem
1987 * read_tail published
1990 static int copy_from_read_buf(struct tty_struct *tty,
1991 unsigned char __user **b,
1995 struct n_tty_data *ldata = tty->disc_data;
1999 size_t head = smp_load_acquire(&ldata->commit_head);
2000 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2003 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
2006 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
2008 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
2009 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
2011 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
2012 /* Turn single EOF into zero-length read */
2013 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
2014 (head == ldata->read_tail))
2023 * canon_copy_from_read_buf - copy read data in canonical mode
2024 * @tty: terminal device
2028 * Helper function for n_tty_read. It is only called when ICANON is on;
2029 * it copies one line of input up to and including the line-delimiting
2030 * character into the user-space buffer.
2032 * NB: When termios is changed from non-canonical to canonical mode and
2033 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2034 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2035 * This causes data already processed as input to be immediately available
2036 * as input although a newline has not been received.
2038 * Called under the atomic_read_lock mutex
2040 * n_tty_read()/consumer path:
2041 * caller holds non-exclusive termios_rwsem
2042 * read_tail published
2045 static int canon_copy_from_read_buf(struct tty_struct *tty,
2046 unsigned char __user **b,
2049 struct n_tty_data *ldata = tty->disc_data;
2050 size_t n, size, more, c;
2055 /* N.B. avoid overrun if nr == 0 */
2059 n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2061 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2062 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2064 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2065 __func__, *nr, tail, n, size);
2067 eol = find_next_bit(ldata->read_flags, size, tail);
2068 more = n - (size - tail);
2069 if (eol == N_TTY_BUF_SIZE && more) {
2070 /* scan wrapped without finding set bit */
2071 eol = find_next_bit(ldata->read_flags, more, 0);
2074 } else if (eol != size)
2077 size = N_TTY_BUF_SIZE - tail;
2079 if (n > N_TTY_BUF_SIZE)
2080 n += N_TTY_BUF_SIZE;
2083 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2088 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
2089 __func__, eol, found, n, c, size, more);
2092 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), size);
2095 ret = tty_copy_to_user(tty, *b + size, ldata->read_buf, n - size);
2097 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), n);
2105 clear_bit(eol, ldata->read_flags);
2106 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2110 ldata->line_start = ldata->read_tail;
2113 tty_audit_push(tty);
2118 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2122 * job_control - check job control
2124 * @file: file handle
2126 * Perform job control management checks on this file/tty descriptor
2127 * and if appropriate send any needed signals and return a negative
2128 * error code if action should be taken.
2130 * Locking: redirected write test is safe
2131 * current->signal->tty check is safe
2132 * ctrl_lock to safely reference tty->pgrp
2135 static int job_control(struct tty_struct *tty, struct file *file)
2137 /* Job control check -- must be done at start and after
2138 every sleep (POSIX.1 7.1.1.4). */
2139 /* NOTE: not yet done after every sleep pending a thorough
2140 check of the logic of this change. -- jlc */
2141 /* don't stop on /dev/console */
2142 if (file->f_op->write == redirected_tty_write)
2145 return __tty_check_change(tty, SIGTTIN);
2150 * n_tty_read - read function for tty
2152 * @file: file object
2153 * @buf: userspace buffer pointer
2156 * Perform reads for the line discipline. We are guaranteed that the
2157 * line discipline will not be closed under us but we may get multiple
2158 * parallel readers and must handle this ourselves. We may also get
2159 * a hangup. Always called in user context, may sleep.
2161 * This code must be sure never to sleep through a hangup.
2163 * n_tty_read()/consumer path:
2164 * claims non-exclusive termios_rwsem
2165 * publishes read_tail
2168 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2169 unsigned char __user *buf, size_t nr)
2171 struct n_tty_data *ldata = tty->disc_data;
2172 unsigned char __user *b = buf;
2173 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2181 c = job_control(tty, file);
2186 * Internal serialization of reads.
2188 if (file->f_flags & O_NONBLOCK) {
2189 if (!mutex_trylock(&ldata->atomic_read_lock))
2192 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2193 return -ERESTARTSYS;
2196 down_read(&tty->termios_rwsem);
2199 timeout = MAX_SCHEDULE_TIMEOUT;
2200 if (!ldata->icanon) {
2201 minimum = MIN_CHAR(tty);
2203 time = (HZ / 10) * TIME_CHAR(tty);
2205 ldata->minimum_to_wake = 1;
2206 else if (!waitqueue_active(&tty->read_wait) ||
2207 (ldata->minimum_to_wake > minimum))
2208 ldata->minimum_to_wake = minimum;
2210 timeout = (HZ / 10) * TIME_CHAR(tty);
2211 ldata->minimum_to_wake = minimum = 1;
2215 packet = tty->packet;
2216 tail = ldata->read_tail;
2218 add_wait_queue(&tty->read_wait, &wait);
2220 /* First test for status change. */
2221 if (packet && tty->link->ctrl_status) {
2225 spin_lock_irq(&tty->link->ctrl_lock);
2226 cs = tty->link->ctrl_status;
2227 tty->link->ctrl_status = 0;
2228 spin_unlock_irq(&tty->link->ctrl_lock);
2229 if (tty_put_user(tty, cs, b++)) {
2238 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2239 ((minimum - (b - buf)) >= 1))
2240 ldata->minimum_to_wake = (minimum - (b - buf));
2242 done = check_other_done(tty);
2244 if (!input_available_p(tty, 0)) {
2249 if (tty_hung_up_p(file))
2253 if (file->f_flags & O_NONBLOCK) {
2257 if (signal_pending(current)) {
2258 retval = -ERESTARTSYS;
2261 up_read(&tty->termios_rwsem);
2263 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2266 down_read(&tty->termios_rwsem);
2270 if (ldata->icanon && !L_EXTPROC(tty)) {
2271 retval = canon_copy_from_read_buf(tty, &b, &nr);
2277 /* Deal with packet mode. */
2278 if (packet && b == buf) {
2279 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2287 uncopied = copy_from_read_buf(tty, &b, &nr);
2288 uncopied += copy_from_read_buf(tty, &b, &nr);
2295 n_tty_check_unthrottle(tty);
2297 if (b - buf >= minimum)
2302 if (tail != ldata->read_tail)
2303 n_tty_kick_worker(tty);
2304 up_read(&tty->termios_rwsem);
2306 remove_wait_queue(&tty->read_wait, &wait);
2307 if (!waitqueue_active(&tty->read_wait))
2308 ldata->minimum_to_wake = minimum;
2310 mutex_unlock(&ldata->atomic_read_lock);
2319 * n_tty_write - write function for tty
2321 * @file: file object
2322 * @buf: userspace buffer pointer
2325 * Write function of the terminal device. This is serialized with
2326 * respect to other write callers but not to termios changes, reads
2327 * and other such events. Since the receive code will echo characters,
2328 * thus calling driver write methods, the output_lock is used in
2329 * the output processing functions called here as well as in the
2330 * echo processing function to protect the column state and space
2331 * left in the buffer.
2333 * This code must be sure never to sleep through a hangup.
2335 * Locking: output_lock to protect column state and space left
2336 * (note that the process_output*() functions take this
2340 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2341 const unsigned char *buf, size_t nr)
2343 const unsigned char *b = buf;
2344 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2348 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2349 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2350 retval = tty_check_change(tty);
2355 down_read(&tty->termios_rwsem);
2357 /* Write out any echoed characters that are still pending */
2358 process_echoes(tty);
2360 add_wait_queue(&tty->write_wait, &wait);
2362 if (signal_pending(current)) {
2363 retval = -ERESTARTSYS;
2366 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2372 ssize_t num = process_output_block(tty, b, nr);
2384 if (process_output(c, tty) < 0)
2388 if (tty->ops->flush_chars)
2389 tty->ops->flush_chars(tty);
2391 struct n_tty_data *ldata = tty->disc_data;
2394 mutex_lock(&ldata->output_lock);
2395 c = tty->ops->write(tty, b, nr);
2396 mutex_unlock(&ldata->output_lock);
2409 if (file->f_flags & O_NONBLOCK) {
2413 up_read(&tty->termios_rwsem);
2415 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2417 down_read(&tty->termios_rwsem);
2420 remove_wait_queue(&tty->write_wait, &wait);
2421 if (b - buf != nr && tty->fasync)
2422 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2423 up_read(&tty->termios_rwsem);
2424 return (b - buf) ? b - buf : retval;
2428 * n_tty_poll - poll method for N_TTY
2429 * @tty: terminal device
2430 * @file: file accessing it
2433 * Called when the line discipline is asked to poll() for data or
2434 * for special events. This code is not serialized with respect to
2435 * other events save open/close.
2437 * This code must be sure never to sleep through a hangup.
2438 * Called without the kernel lock held - fine
2441 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2444 struct n_tty_data *ldata = tty->disc_data;
2445 unsigned int mask = 0;
2447 poll_wait(file, &tty->read_wait, wait);
2448 poll_wait(file, &tty->write_wait, wait);
2449 if (check_other_done(tty))
2451 if (input_available_p(tty, 1))
2452 mask |= POLLIN | POLLRDNORM;
2453 if (tty->packet && tty->link->ctrl_status)
2454 mask |= POLLPRI | POLLIN | POLLRDNORM;
2455 if (tty_hung_up_p(file))
2457 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2458 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2459 ldata->minimum_to_wake = MIN_CHAR(tty);
2461 ldata->minimum_to_wake = 1;
2463 if (tty->ops->write && !tty_is_writelocked(tty) &&
2464 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2465 tty_write_room(tty) > 0)
2466 mask |= POLLOUT | POLLWRNORM;
2470 static unsigned long inq_canon(struct n_tty_data *ldata)
2472 size_t nr, head, tail;
2474 if (ldata->canon_head == ldata->read_tail)
2476 head = ldata->canon_head;
2477 tail = ldata->read_tail;
2479 /* Skip EOF-chars.. */
2480 while (head != tail) {
2481 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2482 read_buf(ldata, tail) == __DISABLED_CHAR)
2489 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2490 unsigned int cmd, unsigned long arg)
2492 struct n_tty_data *ldata = tty->disc_data;
2497 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2499 down_write(&tty->termios_rwsem);
2501 retval = inq_canon(ldata);
2503 retval = read_cnt(ldata);
2504 up_write(&tty->termios_rwsem);
2505 return put_user(retval, (unsigned int __user *) arg);
2507 return n_tty_ioctl_helper(tty, file, cmd, arg);
2511 static void n_tty_fasync(struct tty_struct *tty, int on)
2513 struct n_tty_data *ldata = tty->disc_data;
2515 if (!waitqueue_active(&tty->read_wait)) {
2517 ldata->minimum_to_wake = 1;
2518 else if (!tty->fasync)
2519 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2523 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2524 .magic = TTY_LDISC_MAGIC,
2527 .close = n_tty_close,
2528 .flush_buffer = n_tty_flush_buffer,
2529 .chars_in_buffer = n_tty_chars_in_buffer,
2531 .write = n_tty_write,
2532 .ioctl = n_tty_ioctl,
2533 .set_termios = n_tty_set_termios,
2535 .receive_buf = n_tty_receive_buf,
2536 .write_wakeup = n_tty_write_wakeup,
2537 .fasync = n_tty_fasync,
2538 .receive_buf2 = n_tty_receive_buf2,
2542 * n_tty_inherit_ops - inherit N_TTY methods
2543 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2545 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2549 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2551 *ops = tty_ldisc_N_TTY;
2553 ops->refcount = ops->flags = 0;
2555 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);