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>
55 /* number of characters left in xmit buffer before select has we have room */
56 #define WAKEUP_CHARS 256
59 * This defines the low- and high-watermarks for throttling and
60 * unthrottling the TTY driver. These watermarks are used for
61 * controlling the space in the read buffer.
63 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
64 #define TTY_THRESHOLD_UNTHROTTLE 128
67 * Special byte codes used in the echo buffer to represent operations
68 * or special handling of characters. Bytes in the echo buffer that
69 * are not part of such special blocks are treated as normal character
72 #define ECHO_OP_START 0xff
73 #define ECHO_OP_MOVE_BACK_COL 0x80
74 #define ECHO_OP_SET_CANON_COL 0x81
75 #define ECHO_OP_ERASE_TAB 0x82
77 #define ECHO_COMMIT_WATERMARK 256
78 #define ECHO_BLOCK 256
79 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
84 # define n_tty_trace(f, args...) trace_printk(f, ##args)
86 # define n_tty_trace(f, args...)
90 /* producer-published */
95 DECLARE_BITMAP(process_char_map, 256);
97 /* private to n_tty_receive_overrun (single-threaded) */
98 unsigned long overrun_time;
104 /* must hold exclusive termios_rwsem to reset these */
105 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
107 /* shared by producer and consumer */
109 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
110 unsigned char *echo_buf;
114 /* consumer-published */
117 /* protected by output lock */
119 unsigned int canon_column;
122 struct mutex atomic_read_lock;
123 struct mutex output_lock;
126 static inline size_t read_cnt(struct n_tty_data *ldata)
128 return ldata->read_head - ldata->read_tail;
131 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
133 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
136 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
138 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
141 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
143 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
146 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
148 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
151 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
152 unsigned char __user *ptr)
154 struct n_tty_data *ldata = tty->disc_data;
156 tty_audit_add_data(tty, &x, 1, ldata->icanon);
157 return put_user(x, ptr);
160 static int receive_room(struct tty_struct *tty)
162 struct n_tty_data *ldata = tty->disc_data;
166 /* Multiply read_cnt by 3, since each byte might take up to
167 * three times as many spaces when PARMRK is set (depending on
168 * its flags, e.g. parity error). */
169 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
171 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
174 * If we are doing input canonicalization, and there are no
175 * pending newlines, let characters through without limit, so
176 * that erase characters will be handled. Other excess
177 * characters will be beeped.
180 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
186 * n_tty_set_room - receive space
189 * Re-schedules the flip buffer work if space just became available.
191 * Caller holds exclusive termios_rwsem
193 * n_tty_read()/consumer path:
194 * holds non-exclusive termios_rwsem
197 static void n_tty_set_room(struct tty_struct *tty)
199 struct n_tty_data *ldata = tty->disc_data;
201 /* Did this open up the receive buffer? We may need to flip */
202 if (unlikely(ldata->no_room) && receive_room(tty)) {
205 WARN_RATELIMIT(tty->port->itty == NULL,
206 "scheduling with invalid itty\n");
207 /* see if ldisc has been killed - if so, this means that
208 * even though the ldisc has been halted and ->buf.work
209 * cancelled, ->buf.work is about to be rescheduled
211 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
212 "scheduling buffer work for halted ldisc\n");
213 queue_work(system_unbound_wq, &tty->port->buf.work);
217 static ssize_t chars_in_buffer(struct tty_struct *tty)
219 struct n_tty_data *ldata = tty->disc_data;
225 n = ldata->canon_head - ldata->read_tail;
230 * n_tty_write_wakeup - asynchronous I/O notifier
233 * Required for the ptys, serial driver etc. since processes
234 * that attach themselves to the master and rely on ASYNC
235 * IO must be woken up
238 static void n_tty_write_wakeup(struct tty_struct *tty)
240 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
241 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
244 static inline void n_tty_check_throttle(struct tty_struct *tty)
246 if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
249 * Check the remaining room for the input canonicalization
250 * mode. We don't want to throttle the driver if we're in
251 * canonical mode and don't have a newline yet!
255 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
256 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
258 throttled = tty_throttle_safe(tty);
262 __tty_set_flow_change(tty, 0);
265 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
267 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
268 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
269 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
274 n_tty_write_wakeup(tty->link);
275 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
279 /* If there is enough space in the read buffer now, let the
280 * low-level driver know. We use chars_in_buffer() to
281 * check the buffer, as it now knows about canonical mode.
282 * Otherwise, if the driver is throttled and the line is
283 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
284 * we won't get any more characters.
289 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
290 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
295 unthrottled = tty_unthrottle_safe(tty);
299 __tty_set_flow_change(tty, 0);
303 * put_tty_queue - add character to tty
307 * Add a character to the tty read_buf queue.
309 * n_tty_receive_buf()/producer path:
310 * caller holds non-exclusive termios_rwsem
313 * read_head is only considered 'published' if canonical mode is
317 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
319 if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
320 *read_buf_addr(ldata, ldata->read_head) = c;
326 * reset_buffer_flags - reset buffer state
327 * @tty: terminal to reset
329 * Reset the read buffer counters and clear the flags.
330 * Called from n_tty_open() and n_tty_flush_buffer().
332 * Locking: caller holds exclusive termios_rwsem
333 * (or locking is not required)
336 static void reset_buffer_flags(struct n_tty_data *ldata)
338 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
339 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
342 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
345 static void n_tty_packet_mode_flush(struct tty_struct *tty)
349 spin_lock_irqsave(&tty->ctrl_lock, flags);
350 if (tty->link->packet) {
351 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
352 wake_up_interruptible(&tty->link->read_wait);
354 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
358 * n_tty_flush_buffer - clean input queue
359 * @tty: terminal device
361 * Flush the input buffer. Called when the tty layer wants the
362 * buffer flushed (eg at hangup) or when the N_TTY line discipline
363 * internally has to clean the pending queue (for example some signals).
365 * Holds termios_rwsem to exclude producer/consumer while
366 * buffer indices are reset.
368 * Locking: ctrl_lock, exclusive termios_rwsem
371 static void n_tty_flush_buffer(struct tty_struct *tty)
373 down_write(&tty->termios_rwsem);
374 reset_buffer_flags(tty->disc_data);
378 n_tty_packet_mode_flush(tty);
379 up_write(&tty->termios_rwsem);
383 * n_tty_chars_in_buffer - report available bytes
386 * Report the number of characters buffered to be delivered to user
387 * at this instant in time.
389 * Locking: exclusive termios_rwsem
392 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
396 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
398 down_write(&tty->termios_rwsem);
399 n = chars_in_buffer(tty);
400 up_write(&tty->termios_rwsem);
405 * is_utf8_continuation - utf8 multibyte check
408 * Returns true if the utf8 character 'c' is a multibyte continuation
409 * character. We use this to correctly compute the on screen size
410 * of the character when printing
413 static inline int is_utf8_continuation(unsigned char c)
415 return (c & 0xc0) == 0x80;
419 * is_continuation - multibyte check
422 * Returns true if the utf8 character 'c' is a multibyte continuation
423 * character and the terminal is in unicode mode.
426 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
428 return I_IUTF8(tty) && is_utf8_continuation(c);
432 * do_output_char - output one character
433 * @c: character (or partial unicode symbol)
434 * @tty: terminal device
435 * @space: space available in tty driver write buffer
437 * This is a helper function that handles one output character
438 * (including special characters like TAB, CR, LF, etc.),
439 * doing OPOST processing and putting the results in the
440 * tty driver's write buffer.
442 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
443 * and NLDLY. They simply aren't relevant in the world today.
444 * If you ever need them, add them here.
446 * Returns the number of bytes of buffer space used or -1 if
449 * Locking: should be called under the output_lock to protect
450 * the column state and space left in the buffer
453 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
455 struct n_tty_data *ldata = tty->disc_data;
468 ldata->canon_column = ldata->column = 0;
469 tty->ops->write(tty, "\r\n", 2);
472 ldata->canon_column = ldata->column;
475 if (O_ONOCR(tty) && ldata->column == 0)
480 ldata->canon_column = ldata->column = 0;
483 ldata->canon_column = ldata->column = 0;
486 spaces = 8 - (ldata->column & 7);
487 if (O_TABDLY(tty) == XTABS) {
490 ldata->column += spaces;
491 tty->ops->write(tty, " ", spaces);
494 ldata->column += spaces;
497 if (ldata->column > 0)
504 if (!is_continuation(c, tty))
510 tty_put_char(tty, c);
515 * process_output - output post processor
516 * @c: character (or partial unicode symbol)
517 * @tty: terminal device
519 * Output one character with OPOST processing.
520 * Returns -1 when the output device is full and the character
523 * Locking: output_lock to protect column state and space left
524 * (also, this is called from n_tty_write under the
525 * tty layer write lock)
528 static int process_output(unsigned char c, struct tty_struct *tty)
530 struct n_tty_data *ldata = tty->disc_data;
533 mutex_lock(&ldata->output_lock);
535 space = tty_write_room(tty);
536 retval = do_output_char(c, tty, space);
538 mutex_unlock(&ldata->output_lock);
546 * process_output_block - block post processor
547 * @tty: terminal device
548 * @buf: character buffer
549 * @nr: number of bytes to output
551 * Output a block of characters with OPOST processing.
552 * Returns the number of characters output.
554 * This path is used to speed up block console writes, among other
555 * things when processing blocks of output data. It handles only
556 * the simple cases normally found and helps to generate blocks of
557 * symbols for the console driver and thus improve performance.
559 * Locking: output_lock to protect column state and space left
560 * (also, this is called from n_tty_write under the
561 * tty layer write lock)
564 static ssize_t process_output_block(struct tty_struct *tty,
565 const unsigned char *buf, unsigned int nr)
567 struct n_tty_data *ldata = tty->disc_data;
570 const unsigned char *cp;
572 mutex_lock(&ldata->output_lock);
574 space = tty_write_room(tty);
576 mutex_unlock(&ldata->output_lock);
582 for (i = 0, cp = buf; i < nr; i++, cp++) {
583 unsigned char c = *cp;
591 ldata->canon_column = ldata->column;
594 if (O_ONOCR(tty) && ldata->column == 0)
598 ldata->canon_column = ldata->column = 0;
603 if (ldata->column > 0)
610 if (!is_continuation(c, tty))
617 i = tty->ops->write(tty, buf, i);
619 mutex_unlock(&ldata->output_lock);
624 * process_echoes - write pending echo characters
625 * @tty: terminal device
627 * Write previously buffered echo (and other ldisc-generated)
628 * characters to the tty.
630 * Characters generated by the ldisc (including echoes) need to
631 * be buffered because the driver's write buffer can fill during
632 * heavy program output. Echoing straight to the driver will
633 * often fail under these conditions, causing lost characters and
634 * resulting mismatches of ldisc state information.
636 * Since the ldisc state must represent the characters actually sent
637 * to the driver at the time of the write, operations like certain
638 * changes in column state are also saved in the buffer and executed
641 * A circular fifo buffer is used so that the most recent characters
642 * are prioritized. Also, when control characters are echoed with a
643 * prefixed "^", the pair is treated atomically and thus not separated.
645 * Locking: callers must hold output_lock
648 static size_t __process_echoes(struct tty_struct *tty)
650 struct n_tty_data *ldata = tty->disc_data;
651 int space, old_space;
655 old_space = space = tty_write_room(tty);
657 tail = ldata->echo_tail;
658 while (ldata->echo_commit != tail) {
659 c = echo_buf(ldata, tail);
660 if (c == ECHO_OP_START) {
662 int no_space_left = 0;
665 * If the buffer byte is the start of a multi-byte
666 * operation, get the next byte, which is either the
667 * op code or a control character value.
669 op = echo_buf(ldata, tail + 1);
672 unsigned int num_chars, num_bs;
674 case ECHO_OP_ERASE_TAB:
675 num_chars = echo_buf(ldata, tail + 2);
678 * Determine how many columns to go back
679 * in order to erase the tab.
680 * This depends on the number of columns
681 * used by other characters within the tab
682 * area. If this (modulo 8) count is from
683 * the start of input rather than from a
684 * previous tab, we offset by canon column.
685 * Otherwise, tab spacing is normal.
687 if (!(num_chars & 0x80))
688 num_chars += ldata->canon_column;
689 num_bs = 8 - (num_chars & 7);
691 if (num_bs > space) {
697 tty_put_char(tty, '\b');
698 if (ldata->column > 0)
704 case ECHO_OP_SET_CANON_COL:
705 ldata->canon_column = ldata->column;
709 case ECHO_OP_MOVE_BACK_COL:
710 if (ldata->column > 0)
716 /* This is an escaped echo op start code */
721 tty_put_char(tty, ECHO_OP_START);
729 * If the op is not a special byte code,
730 * it is a ctrl char tagged to be echoed
731 * as "^X" (where X is the letter
732 * representing the control char).
733 * Note that we must ensure there is
734 * enough space for the whole ctrl pair.
741 tty_put_char(tty, '^');
742 tty_put_char(tty, op ^ 0100);
752 int retval = do_output_char(c, tty, space);
759 tty_put_char(tty, c);
766 /* If the echo buffer is nearly full (so that the possibility exists
767 * of echo overrun before the next commit), then discard enough
768 * data at the tail to prevent a subsequent overrun */
769 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
770 if (echo_buf(ldata, tail == ECHO_OP_START)) {
771 if (echo_buf(ldata, tail) == ECHO_OP_ERASE_TAB)
779 ldata->echo_tail = tail;
780 return old_space - space;
783 static void commit_echoes(struct tty_struct *tty)
785 struct n_tty_data *ldata = tty->disc_data;
786 size_t nr, old, echoed;
789 head = ldata->echo_head;
790 old = ldata->echo_commit - ldata->echo_tail;
792 /* Process committed echoes if the accumulated # of bytes
793 * is over the threshold (and try again each time another
794 * block is accumulated) */
795 nr = head - ldata->echo_tail;
796 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
799 mutex_lock(&ldata->output_lock);
800 ldata->echo_commit = head;
801 echoed = __process_echoes(tty);
802 mutex_unlock(&ldata->output_lock);
804 if (echoed && tty->ops->flush_chars)
805 tty->ops->flush_chars(tty);
808 static void process_echoes(struct tty_struct *tty)
810 struct n_tty_data *ldata = tty->disc_data;
813 if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
816 mutex_lock(&ldata->output_lock);
817 echoed = __process_echoes(tty);
818 mutex_unlock(&ldata->output_lock);
820 if (echoed && tty->ops->flush_chars)
821 tty->ops->flush_chars(tty);
824 static void flush_echoes(struct tty_struct *tty)
826 struct n_tty_data *ldata = tty->disc_data;
828 if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_head)
831 mutex_lock(&ldata->output_lock);
832 ldata->echo_commit = ldata->echo_head;
833 __process_echoes(tty);
834 mutex_unlock(&ldata->output_lock);
838 * add_echo_byte - add a byte to the echo buffer
839 * @c: unicode byte to echo
842 * Add a character or operation byte to the echo buffer.
845 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
847 *echo_buf_addr(ldata, ldata->echo_head++) = c;
851 * echo_move_back_col - add operation to move back a column
854 * Add an operation to the echo buffer to move back one column.
857 static void echo_move_back_col(struct n_tty_data *ldata)
859 add_echo_byte(ECHO_OP_START, ldata);
860 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
864 * echo_set_canon_col - add operation to set the canon column
867 * Add an operation to the echo buffer to set the canon column
868 * to the current column.
871 static void echo_set_canon_col(struct n_tty_data *ldata)
873 add_echo_byte(ECHO_OP_START, ldata);
874 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
878 * echo_erase_tab - add operation to erase a tab
879 * @num_chars: number of character columns already used
880 * @after_tab: true if num_chars starts after a previous tab
883 * Add an operation to the echo buffer to erase a tab.
885 * Called by the eraser function, which knows how many character
886 * columns have been used since either a previous tab or the start
887 * of input. This information will be used later, along with
888 * canon column (if applicable), to go back the correct number
892 static void echo_erase_tab(unsigned int num_chars, int after_tab,
893 struct n_tty_data *ldata)
895 add_echo_byte(ECHO_OP_START, ldata);
896 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
898 /* We only need to know this modulo 8 (tab spacing) */
901 /* Set the high bit as a flag if num_chars is after a previous tab */
905 add_echo_byte(num_chars, ldata);
909 * echo_char_raw - echo a character raw
910 * @c: unicode byte to echo
911 * @tty: terminal device
913 * Echo user input back onto the screen. This must be called only when
914 * L_ECHO(tty) is true. Called from the driver receive_buf path.
916 * This variant does not treat control characters specially.
919 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
921 if (c == ECHO_OP_START) {
922 add_echo_byte(ECHO_OP_START, ldata);
923 add_echo_byte(ECHO_OP_START, ldata);
925 add_echo_byte(c, ldata);
930 * echo_char - echo a character
931 * @c: unicode byte to echo
932 * @tty: terminal device
934 * Echo user input back onto the screen. This must be called only when
935 * L_ECHO(tty) is true. Called from the driver receive_buf path.
937 * This variant tags control characters to be echoed as "^X"
938 * (where X is the letter representing the control char).
941 static void echo_char(unsigned char c, struct tty_struct *tty)
943 struct n_tty_data *ldata = tty->disc_data;
945 if (c == ECHO_OP_START) {
946 add_echo_byte(ECHO_OP_START, ldata);
947 add_echo_byte(ECHO_OP_START, ldata);
949 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
950 add_echo_byte(ECHO_OP_START, ldata);
951 add_echo_byte(c, ldata);
956 * finish_erasing - complete erase
960 static inline void finish_erasing(struct n_tty_data *ldata)
962 if (ldata->erasing) {
963 echo_char_raw('/', ldata);
969 * eraser - handle erase function
970 * @c: character input
971 * @tty: terminal device
973 * Perform erase and necessary output when an erase character is
974 * present in the stream from the driver layer. Handles the complexities
975 * of UTF-8 multibyte symbols.
977 * n_tty_receive_buf()/producer path:
978 * caller holds non-exclusive termios_rwsem
981 * Modifying the read_head is not considered a publish in this context
982 * because canonical mode is active -- only canon_head publishes
985 static void eraser(unsigned char c, struct tty_struct *tty)
987 struct n_tty_data *ldata = tty->disc_data;
988 enum { ERASE, WERASE, KILL } kill_type;
993 if (ldata->read_head == ldata->canon_head) {
994 /* process_output('\a', tty); */ /* what do you think? */
997 if (c == ERASE_CHAR(tty))
999 else if (c == WERASE_CHAR(tty))
1003 ldata->read_head = ldata->canon_head;
1006 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1007 ldata->read_head = ldata->canon_head;
1008 finish_erasing(ldata);
1009 echo_char(KILL_CHAR(tty), tty);
1010 /* Add a newline if ECHOK is on and ECHOKE is off. */
1012 echo_char_raw('\n', ldata);
1019 while (ldata->read_head != ldata->canon_head) {
1020 head = ldata->read_head;
1022 /* erase a single possibly multibyte character */
1025 c = read_buf(ldata, head);
1026 } while (is_continuation(c, tty) && head != ldata->canon_head);
1028 /* do not partially erase */
1029 if (is_continuation(c, tty))
1032 if (kill_type == WERASE) {
1033 /* Equivalent to BSD's ALTWERASE. */
1034 if (isalnum(c) || c == '_')
1036 else if (seen_alnums)
1039 cnt = ldata->read_head - head;
1040 ldata->read_head = head;
1042 if (L_ECHOPRT(tty)) {
1043 if (!ldata->erasing) {
1044 echo_char_raw('\\', ldata);
1047 /* if cnt > 1, output a multi-byte character */
1051 echo_char_raw(read_buf(ldata, head), ldata);
1052 echo_move_back_col(ldata);
1054 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1055 echo_char(ERASE_CHAR(tty), tty);
1056 } else if (c == '\t') {
1057 unsigned int num_chars = 0;
1059 size_t tail = ldata->read_head;
1062 * Count the columns used for characters
1063 * since the start of input or after a
1065 * This info is used to go back the correct
1066 * number of columns.
1068 while (tail != ldata->canon_head) {
1070 c = read_buf(ldata, tail);
1074 } else if (iscntrl(c)) {
1077 } else if (!is_continuation(c, tty)) {
1081 echo_erase_tab(num_chars, after_tab, ldata);
1083 if (iscntrl(c) && L_ECHOCTL(tty)) {
1084 echo_char_raw('\b', ldata);
1085 echo_char_raw(' ', ldata);
1086 echo_char_raw('\b', ldata);
1088 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1089 echo_char_raw('\b', ldata);
1090 echo_char_raw(' ', ldata);
1091 echo_char_raw('\b', ldata);
1095 if (kill_type == ERASE)
1098 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1099 finish_erasing(ldata);
1103 * isig - handle the ISIG optio
1107 * Called when a signal is being sent due to terminal input.
1108 * Called from the driver receive_buf path so serialized.
1110 * Locking: ctrl_lock
1113 static inline void isig(int sig, struct tty_struct *tty)
1115 struct pid *tty_pgrp = tty_get_pgrp(tty);
1117 kill_pgrp(tty_pgrp, sig, 1);
1123 * n_tty_receive_break - handle break
1126 * An RS232 break event has been hit in the incoming bitstream. This
1127 * can cause a variety of events depending upon the termios settings.
1129 * n_tty_receive_buf()/producer path:
1130 * caller holds non-exclusive termios_rwsem
1131 * publishes read_head via put_tty_queue()
1133 * Note: may get exclusive termios_rwsem if flushing input buffer
1136 static inline void n_tty_receive_break(struct tty_struct *tty)
1138 struct n_tty_data *ldata = tty->disc_data;
1142 if (I_BRKINT(tty)) {
1144 if (!L_NOFLSH(tty)) {
1145 /* flushing needs exclusive termios_rwsem */
1146 up_read(&tty->termios_rwsem);
1147 n_tty_flush_buffer(tty);
1148 tty_driver_flush_buffer(tty);
1149 down_read(&tty->termios_rwsem);
1153 if (I_PARMRK(tty)) {
1154 put_tty_queue('\377', ldata);
1155 put_tty_queue('\0', ldata);
1157 put_tty_queue('\0', ldata);
1158 wake_up_interruptible(&tty->read_wait);
1162 * n_tty_receive_overrun - handle overrun reporting
1165 * Data arrived faster than we could process it. While the tty
1166 * driver has flagged this the bits that were missed are gone
1169 * Called from the receive_buf path so single threaded. Does not
1170 * need locking as num_overrun and overrun_time are function
1174 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1176 struct n_tty_data *ldata = tty->disc_data;
1179 ldata->num_overrun++;
1180 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1181 time_after(ldata->overrun_time, jiffies)) {
1182 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1184 ldata->num_overrun);
1185 ldata->overrun_time = jiffies;
1186 ldata->num_overrun = 0;
1191 * n_tty_receive_parity_error - error notifier
1192 * @tty: terminal device
1195 * Process a parity error and queue the right data to indicate
1196 * the error case if necessary.
1198 * n_tty_receive_buf()/producer path:
1199 * caller holds non-exclusive termios_rwsem
1200 * publishes read_head via put_tty_queue()
1202 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1205 struct n_tty_data *ldata = tty->disc_data;
1209 if (I_PARMRK(tty)) {
1210 put_tty_queue('\377', ldata);
1211 put_tty_queue('\0', ldata);
1212 put_tty_queue(c, ldata);
1213 } else if (I_INPCK(tty))
1214 put_tty_queue('\0', ldata);
1216 put_tty_queue(c, ldata);
1217 wake_up_interruptible(&tty->read_wait);
1221 * n_tty_receive_char - perform processing
1222 * @tty: terminal device
1225 * Process an individual character of input received from the driver.
1226 * This is serialized with respect to itself by the rules for the
1229 * n_tty_receive_buf()/producer path:
1230 * caller holds non-exclusive termios_rwsem
1231 * publishes canon_head if canonical mode is active
1232 * otherwise, publishes read_head via put_tty_queue()
1235 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1237 struct n_tty_data *ldata = tty->disc_data;
1241 put_tty_queue(c, ldata);
1247 if (I_IUCLC(tty) && L_IEXTEN(tty))
1250 if (L_EXTPROC(tty)) {
1251 put_tty_queue(c, ldata);
1255 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1256 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1257 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1259 process_echoes(tty);
1264 if (c == START_CHAR(tty)) {
1266 process_echoes(tty);
1267 } else if (c == STOP_CHAR(tty))
1274 * If the previous character was LNEXT, or we know that this
1275 * character is not one of the characters that we'll have to
1276 * handle specially, do shortcut processing to speed things
1279 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1281 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1282 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1283 /* beep if no space */
1285 process_output('\a', tty);
1289 finish_erasing(ldata);
1290 /* Record the column of first canon char. */
1291 if (ldata->canon_head == ldata->read_head)
1292 echo_set_canon_col(ldata);
1297 put_tty_queue(c, ldata);
1298 put_tty_queue(c, ldata);
1303 if (c == START_CHAR(tty)) {
1308 if (c == STOP_CHAR(tty)) {
1317 if (c == INTR_CHAR(tty))
1320 if (c == QUIT_CHAR(tty))
1323 if (c == SUSP_CHAR(tty)) {
1325 if (!L_NOFLSH(tty)) {
1326 /* flushing needs exclusive termios_rwsem */
1327 up_read(&tty->termios_rwsem);
1328 n_tty_flush_buffer(tty);
1329 tty_driver_flush_buffer(tty);
1330 down_read(&tty->termios_rwsem);
1348 } else if (c == '\n' && I_INLCR(tty))
1351 if (ldata->icanon) {
1352 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1353 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1358 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1361 finish_erasing(ldata);
1362 if (L_ECHOCTL(tty)) {
1363 echo_char_raw('^', ldata);
1364 echo_char_raw('\b', ldata);
1370 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1372 size_t tail = ldata->canon_head;
1374 finish_erasing(ldata);
1376 echo_char_raw('\n', ldata);
1377 while (tail != ldata->read_head) {
1378 echo_char(read_buf(ldata, tail), tty);
1385 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1387 process_output('\a', tty);
1390 if (L_ECHO(tty) || L_ECHONL(tty)) {
1391 echo_char_raw('\n', ldata);
1394 goto handle_newline;
1396 if (c == EOF_CHAR(tty)) {
1397 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1399 if (ldata->canon_head != ldata->read_head)
1400 set_bit(TTY_PUSH, &tty->flags);
1401 c = __DISABLED_CHAR;
1402 goto handle_newline;
1404 if ((c == EOL_CHAR(tty)) ||
1405 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1406 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1408 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1410 process_output('\a', tty);
1414 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1417 /* Record the column of first canon char. */
1418 if (ldata->canon_head == ldata->read_head)
1419 echo_set_canon_col(ldata);
1424 * XXX does PARMRK doubling happen for
1425 * EOL_CHAR and EOL2_CHAR?
1428 put_tty_queue(c, ldata);
1431 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1432 put_tty_queue(c, ldata);
1433 ldata->canon_head = ldata->read_head;
1434 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1435 if (waitqueue_active(&tty->read_wait))
1436 wake_up_interruptible(&tty->read_wait);
1441 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1442 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1443 /* beep if no space */
1445 process_output('\a', tty);
1449 finish_erasing(ldata);
1451 echo_char_raw('\n', ldata);
1453 /* Record the column of first canon char. */
1454 if (ldata->canon_head == ldata->read_head)
1455 echo_set_canon_col(ldata);
1462 put_tty_queue(c, ldata);
1464 put_tty_queue(c, ldata);
1468 * n_tty_receive_buf - data receive
1469 * @tty: terminal device
1472 * @count: characters
1474 * Called by the terminal driver when a block of characters has
1475 * been received. This function must be called from soft contexts
1476 * not from interrupt context. The driver is responsible for making
1477 * calls one at a time and in order (or using flush_to_ldisc)
1479 * n_tty_receive_buf()/producer path:
1480 * claims non-exclusive termios_rwsem
1481 * publishes read_head and canon_head
1484 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1485 char *fp, int count)
1487 struct n_tty_data *ldata = tty->disc_data;
1488 const unsigned char *p;
1489 char *f, flags = TTY_NORMAL;
1492 if (ldata->real_raw) {
1495 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1496 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1497 n = min_t(size_t, count, n);
1498 memcpy(read_buf_addr(ldata, head), cp, n);
1499 ldata->read_head += n;
1503 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1504 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1505 n = min_t(size_t, count, n);
1506 memcpy(read_buf_addr(ldata, head), cp, n);
1507 ldata->read_head += n;
1511 for (i = count, p = cp, f = fp; i; i--, p++) {
1516 n_tty_receive_char(tty, *p);
1519 n_tty_receive_break(tty);
1523 n_tty_receive_parity_error(tty, *p);
1526 n_tty_receive_overrun(tty);
1529 printk(KERN_ERR "%s: unknown flag %d\n",
1530 tty_name(tty, buf), flags);
1536 if (tty->ops->flush_chars)
1537 tty->ops->flush_chars(tty);
1540 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1542 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1543 if (waitqueue_active(&tty->read_wait))
1544 wake_up_interruptible(&tty->read_wait);
1547 n_tty_check_throttle(tty);
1550 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1551 char *fp, int count)
1553 down_read(&tty->termios_rwsem);
1554 __receive_buf(tty, cp, fp, count);
1555 up_read(&tty->termios_rwsem);
1558 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1559 char *fp, int count)
1561 struct n_tty_data *ldata = tty->disc_data;
1564 down_read(&tty->termios_rwsem);
1566 tty->receive_room = room = receive_room(tty);
1569 count = min(count, room);
1571 __receive_buf(tty, cp, fp, count);
1573 up_read(&tty->termios_rwsem);
1578 int is_ignored(int sig)
1580 return (sigismember(¤t->blocked, sig) ||
1581 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1585 * n_tty_set_termios - termios data changed
1587 * @old: previous data
1589 * Called by the tty layer when the user changes termios flags so
1590 * that the line discipline can plan ahead. This function cannot sleep
1591 * and is protected from re-entry by the tty layer. The user is
1592 * guaranteed that this function will not be re-entered or in progress
1593 * when the ldisc is closed.
1595 * Locking: Caller holds tty->termios_rwsem
1598 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1600 struct n_tty_data *ldata = tty->disc_data;
1601 int canon_change = 1;
1604 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1606 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1607 ldata->canon_head = ldata->read_tail;
1612 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1613 wake_up_interruptible(&tty->read_wait);
1615 ldata->icanon = (L_ICANON(tty) != 0);
1617 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1618 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1619 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1621 bitmap_zero(ldata->process_char_map, 256);
1623 if (I_IGNCR(tty) || I_ICRNL(tty))
1624 set_bit('\r', ldata->process_char_map);
1626 set_bit('\n', ldata->process_char_map);
1628 if (L_ICANON(tty)) {
1629 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1630 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1631 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1632 set_bit('\n', ldata->process_char_map);
1633 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1634 if (L_IEXTEN(tty)) {
1635 set_bit(WERASE_CHAR(tty),
1636 ldata->process_char_map);
1637 set_bit(LNEXT_CHAR(tty),
1638 ldata->process_char_map);
1639 set_bit(EOL2_CHAR(tty),
1640 ldata->process_char_map);
1642 set_bit(REPRINT_CHAR(tty),
1643 ldata->process_char_map);
1647 set_bit(START_CHAR(tty), ldata->process_char_map);
1648 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1651 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1652 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1653 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1655 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1657 ldata->real_raw = 0;
1660 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1661 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1662 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1663 ldata->real_raw = 1;
1665 ldata->real_raw = 0;
1667 n_tty_set_room(tty);
1669 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1670 * been stopped by STOP_CHAR(tty) before it.
1672 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1676 /* The termios change make the tty ready for I/O */
1677 wake_up_interruptible(&tty->write_wait);
1678 wake_up_interruptible(&tty->read_wait);
1682 * n_tty_close - close the ldisc for this tty
1685 * Called from the terminal layer when this line discipline is
1686 * being shut down, either because of a close or becsuse of a
1687 * discipline change. The function will not be called while other
1688 * ldisc methods are in progress.
1691 static void n_tty_close(struct tty_struct *tty)
1693 struct n_tty_data *ldata = tty->disc_data;
1696 n_tty_packet_mode_flush(tty);
1698 kfree(ldata->read_buf);
1699 kfree(ldata->echo_buf);
1701 tty->disc_data = NULL;
1705 * n_tty_open - open an ldisc
1706 * @tty: terminal to open
1708 * Called when this line discipline is being attached to the
1709 * terminal device. Can sleep. Called serialized so that no
1710 * other events will occur in parallel. No further open will occur
1714 static int n_tty_open(struct tty_struct *tty)
1716 struct n_tty_data *ldata;
1718 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1722 ldata->overrun_time = jiffies;
1723 mutex_init(&ldata->atomic_read_lock);
1724 mutex_init(&ldata->output_lock);
1726 /* These are ugly. Currently a malloc failure here can panic */
1727 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1728 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1729 if (!ldata->read_buf || !ldata->echo_buf)
1732 tty->disc_data = ldata;
1733 reset_buffer_flags(tty->disc_data);
1735 ldata->minimum_to_wake = 1;
1737 /* indicate buffer work may resume */
1738 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1739 n_tty_set_termios(tty, NULL);
1740 tty_unthrottle(tty);
1744 kfree(ldata->read_buf);
1745 kfree(ldata->echo_buf);
1751 static inline int input_available_p(struct tty_struct *tty, int amt)
1753 struct n_tty_data *ldata = tty->disc_data;
1755 if (ldata->icanon && !L_EXTPROC(tty)) {
1756 if (ldata->canon_head != ldata->read_tail)
1758 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1765 * copy_from_read_buf - copy read data directly
1766 * @tty: terminal device
1770 * Helper function to speed up n_tty_read. It is only called when
1771 * ICANON is off; it copies characters straight from the tty queue to
1772 * user space directly. It can be profitably called twice; once to
1773 * drain the space from the tail pointer to the (physical) end of the
1774 * buffer, and once to drain the space from the (physical) beginning of
1775 * the buffer to head pointer.
1777 * Called under the ldata->atomic_read_lock sem
1779 * n_tty_read()/consumer path:
1780 * caller holds non-exclusive termios_rwsem
1781 * read_tail published
1784 static int copy_from_read_buf(struct tty_struct *tty,
1785 unsigned char __user **b,
1789 struct n_tty_data *ldata = tty->disc_data;
1793 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1796 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1799 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1801 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1802 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1804 ldata->read_tail += n;
1805 /* Turn single EOF into zero-length read */
1806 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1815 * canon_copy_from_read_buf - copy read data in canonical mode
1816 * @tty: terminal device
1820 * Helper function for n_tty_read. It is only called when ICANON is on;
1821 * it copies one line of input up to and including the line-delimiting
1822 * character into the user-space buffer.
1824 * Called under the atomic_read_lock mutex
1826 * n_tty_read()/consumer path:
1827 * caller holds non-exclusive termios_rwsem
1828 * read_tail published
1831 static int canon_copy_from_read_buf(struct tty_struct *tty,
1832 unsigned char __user **b,
1835 struct n_tty_data *ldata = tty->disc_data;
1836 size_t n, size, more, c;
1841 /* N.B. avoid overrun if nr == 0 */
1842 n = min(*nr, read_cnt(ldata));
1846 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1847 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1849 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1850 __func__, *nr, tail, n, size);
1852 eol = find_next_bit(ldata->read_flags, size, tail);
1853 more = n - (size - tail);
1854 if (eol == N_TTY_BUF_SIZE && more) {
1855 /* scan wrapped without finding set bit */
1856 eol = find_next_bit(ldata->read_flags, more, 0);
1859 } else if (eol != size)
1862 size = N_TTY_BUF_SIZE - tail;
1863 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1866 if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
1869 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1870 __func__, eol, found, n, c, size, more);
1873 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1876 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1878 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1886 clear_bit(eol, ldata->read_flags);
1887 smp_mb__after_clear_bit();
1888 ldata->read_tail += c;
1891 tty_audit_push(tty);
1895 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1899 * job_control - check job control
1901 * @file: file handle
1903 * Perform job control management checks on this file/tty descriptor
1904 * and if appropriate send any needed signals and return a negative
1905 * error code if action should be taken.
1907 * Locking: redirected write test is safe
1908 * current->signal->tty check is safe
1909 * ctrl_lock to safely reference tty->pgrp
1912 static int job_control(struct tty_struct *tty, struct file *file)
1914 /* Job control check -- must be done at start and after
1915 every sleep (POSIX.1 7.1.1.4). */
1916 /* NOTE: not yet done after every sleep pending a thorough
1917 check of the logic of this change. -- jlc */
1918 /* don't stop on /dev/console */
1919 if (file->f_op->write == redirected_tty_write ||
1920 current->signal->tty != tty)
1923 spin_lock_irq(&tty->ctrl_lock);
1925 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1926 else if (task_pgrp(current) != tty->pgrp) {
1927 spin_unlock_irq(&tty->ctrl_lock);
1928 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1930 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1931 set_thread_flag(TIF_SIGPENDING);
1932 return -ERESTARTSYS;
1934 spin_unlock_irq(&tty->ctrl_lock);
1940 * n_tty_read - read function for tty
1942 * @file: file object
1943 * @buf: userspace buffer pointer
1946 * Perform reads for the line discipline. We are guaranteed that the
1947 * line discipline will not be closed under us but we may get multiple
1948 * parallel readers and must handle this ourselves. We may also get
1949 * a hangup. Always called in user context, may sleep.
1951 * This code must be sure never to sleep through a hangup.
1953 * n_tty_read()/consumer path:
1954 * claims non-exclusive termios_rwsem
1955 * publishes read_tail
1958 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1959 unsigned char __user *buf, size_t nr)
1961 struct n_tty_data *ldata = tty->disc_data;
1962 unsigned char __user *b = buf;
1963 DECLARE_WAITQUEUE(wait, current);
1969 unsigned long flags;
1973 c = job_control(tty, file);
1977 down_read(&tty->termios_rwsem);
1980 timeout = MAX_SCHEDULE_TIMEOUT;
1981 if (!ldata->icanon) {
1982 minimum = MIN_CHAR(tty);
1984 time = (HZ / 10) * TIME_CHAR(tty);
1986 ldata->minimum_to_wake = 1;
1987 else if (!waitqueue_active(&tty->read_wait) ||
1988 (ldata->minimum_to_wake > minimum))
1989 ldata->minimum_to_wake = minimum;
1991 timeout = (HZ / 10) * TIME_CHAR(tty);
1992 ldata->minimum_to_wake = minimum = 1;
1997 * Internal serialization of reads.
1999 if (file->f_flags & O_NONBLOCK) {
2000 if (!mutex_trylock(&ldata->atomic_read_lock)) {
2001 up_read(&tty->termios_rwsem);
2005 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2006 up_read(&tty->termios_rwsem);
2007 return -ERESTARTSYS;
2010 packet = tty->packet;
2012 add_wait_queue(&tty->read_wait, &wait);
2014 /* First test for status change. */
2015 if (packet && tty->link->ctrl_status) {
2019 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2020 cs = tty->link->ctrl_status;
2021 tty->link->ctrl_status = 0;
2022 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2023 if (tty_put_user(tty, cs, b++)) {
2031 /* This statement must be first before checking for input
2032 so that any interrupt will set the state back to
2034 set_current_state(TASK_INTERRUPTIBLE);
2036 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2037 ((minimum - (b - buf)) >= 1))
2038 ldata->minimum_to_wake = (minimum - (b - buf));
2040 if (!input_available_p(tty, 0)) {
2041 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2045 if (tty_hung_up_p(file))
2049 if (file->f_flags & O_NONBLOCK) {
2053 if (signal_pending(current)) {
2054 retval = -ERESTARTSYS;
2057 n_tty_set_room(tty);
2058 up_read(&tty->termios_rwsem);
2060 timeout = schedule_timeout(timeout);
2062 down_read(&tty->termios_rwsem);
2065 __set_current_state(TASK_RUNNING);
2067 /* Deal with packet mode. */
2068 if (packet && b == buf) {
2069 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2077 if (ldata->icanon && !L_EXTPROC(tty)) {
2078 retval = canon_copy_from_read_buf(tty, &b, &nr);
2083 /* The copy function takes the read lock and handles
2084 locking internally for this case */
2085 uncopied = copy_from_read_buf(tty, &b, &nr);
2086 uncopied += copy_from_read_buf(tty, &b, &nr);
2093 n_tty_check_unthrottle(tty);
2095 if (b - buf >= minimum)
2100 mutex_unlock(&ldata->atomic_read_lock);
2101 remove_wait_queue(&tty->read_wait, &wait);
2103 if (!waitqueue_active(&tty->read_wait))
2104 ldata->minimum_to_wake = minimum;
2106 __set_current_state(TASK_RUNNING);
2111 clear_bit(TTY_PUSH, &tty->flags);
2112 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
2113 up_read(&tty->termios_rwsem);
2117 n_tty_set_room(tty);
2118 up_read(&tty->termios_rwsem);
2123 * n_tty_write - write function for tty
2125 * @file: file object
2126 * @buf: userspace buffer pointer
2129 * Write function of the terminal device. This is serialized with
2130 * respect to other write callers but not to termios changes, reads
2131 * and other such events. Since the receive code will echo characters,
2132 * thus calling driver write methods, the output_lock is used in
2133 * the output processing functions called here as well as in the
2134 * echo processing function to protect the column state and space
2135 * left in the buffer.
2137 * This code must be sure never to sleep through a hangup.
2139 * Locking: output_lock to protect column state and space left
2140 * (note that the process_output*() functions take this
2144 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2145 const unsigned char *buf, size_t nr)
2147 const unsigned char *b = buf;
2148 DECLARE_WAITQUEUE(wait, current);
2152 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2153 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2154 retval = tty_check_change(tty);
2159 down_read(&tty->termios_rwsem);
2161 /* Write out any echoed characters that are still pending */
2162 process_echoes(tty);
2164 add_wait_queue(&tty->write_wait, &wait);
2166 set_current_state(TASK_INTERRUPTIBLE);
2167 if (signal_pending(current)) {
2168 retval = -ERESTARTSYS;
2171 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2177 ssize_t num = process_output_block(tty, b, nr);
2189 if (process_output(c, tty) < 0)
2193 if (tty->ops->flush_chars)
2194 tty->ops->flush_chars(tty);
2197 c = tty->ops->write(tty, b, nr);
2210 if (file->f_flags & O_NONBLOCK) {
2214 up_read(&tty->termios_rwsem);
2218 down_read(&tty->termios_rwsem);
2221 __set_current_state(TASK_RUNNING);
2222 remove_wait_queue(&tty->write_wait, &wait);
2223 if (b - buf != nr && tty->fasync)
2224 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2225 up_read(&tty->termios_rwsem);
2226 return (b - buf) ? b - buf : retval;
2230 * n_tty_poll - poll method for N_TTY
2231 * @tty: terminal device
2232 * @file: file accessing it
2235 * Called when the line discipline is asked to poll() for data or
2236 * for special events. This code is not serialized with respect to
2237 * other events save open/close.
2239 * This code must be sure never to sleep through a hangup.
2240 * Called without the kernel lock held - fine
2243 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2246 struct n_tty_data *ldata = tty->disc_data;
2247 unsigned int mask = 0;
2249 poll_wait(file, &tty->read_wait, wait);
2250 poll_wait(file, &tty->write_wait, wait);
2251 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2252 mask |= POLLIN | POLLRDNORM;
2253 if (tty->packet && tty->link->ctrl_status)
2254 mask |= POLLPRI | POLLIN | POLLRDNORM;
2255 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2257 if (tty_hung_up_p(file))
2259 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2260 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2261 ldata->minimum_to_wake = MIN_CHAR(tty);
2263 ldata->minimum_to_wake = 1;
2265 if (tty->ops->write && !tty_is_writelocked(tty) &&
2266 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2267 tty_write_room(tty) > 0)
2268 mask |= POLLOUT | POLLWRNORM;
2272 static unsigned long inq_canon(struct n_tty_data *ldata)
2274 size_t nr, head, tail;
2276 if (ldata->canon_head == ldata->read_tail)
2278 head = ldata->canon_head;
2279 tail = ldata->read_tail;
2281 /* Skip EOF-chars.. */
2282 while (head != tail) {
2283 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2284 read_buf(ldata, tail) == __DISABLED_CHAR)
2291 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2292 unsigned int cmd, unsigned long arg)
2294 struct n_tty_data *ldata = tty->disc_data;
2299 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2301 down_write(&tty->termios_rwsem);
2303 retval = inq_canon(ldata);
2305 retval = read_cnt(ldata);
2306 up_write(&tty->termios_rwsem);
2307 return put_user(retval, (unsigned int __user *) arg);
2309 return n_tty_ioctl_helper(tty, file, cmd, arg);
2313 static void n_tty_fasync(struct tty_struct *tty, int on)
2315 struct n_tty_data *ldata = tty->disc_data;
2317 if (!waitqueue_active(&tty->read_wait)) {
2319 ldata->minimum_to_wake = 1;
2320 else if (!tty->fasync)
2321 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2325 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2326 .magic = TTY_LDISC_MAGIC,
2329 .close = n_tty_close,
2330 .flush_buffer = n_tty_flush_buffer,
2331 .chars_in_buffer = n_tty_chars_in_buffer,
2333 .write = n_tty_write,
2334 .ioctl = n_tty_ioctl,
2335 .set_termios = n_tty_set_termios,
2337 .receive_buf = n_tty_receive_buf,
2338 .write_wakeup = n_tty_write_wakeup,
2339 .fasync = n_tty_fasync,
2340 .receive_buf2 = n_tty_receive_buf2,
2344 * n_tty_inherit_ops - inherit N_TTY methods
2345 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2347 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2351 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2353 *ops = tty_ldisc_N_TTY;
2355 ops->refcount = ops->flags = 0;
2357 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);