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
79 # define n_tty_trace(f, args...) trace_printk(f, ##args)
81 # define n_tty_trace(f, args...)
85 /* producer-published */
88 DECLARE_BITMAP(process_char_map, 256);
90 /* private to n_tty_receive_overrun (single-threaded) */
91 unsigned long overrun_time;
97 /* must hold exclusive termios_rwsem to reset these */
98 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
100 /* shared by producer and consumer */
102 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
106 /* consumer-published */
109 /* protected by echo_lock */
110 unsigned char *echo_buf;
114 /* protected by output lock */
116 unsigned int canon_column;
118 struct mutex atomic_read_lock;
119 struct mutex output_lock;
120 struct mutex echo_lock;
123 static inline size_t read_cnt(struct n_tty_data *ldata)
125 return ldata->read_head - ldata->read_tail;
128 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
130 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
133 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
135 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
138 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
140 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
143 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
145 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
148 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
149 unsigned char __user *ptr)
151 struct n_tty_data *ldata = tty->disc_data;
153 tty_audit_add_data(tty, &x, 1, ldata->icanon);
154 return put_user(x, ptr);
157 static int receive_room(struct tty_struct *tty)
159 struct n_tty_data *ldata = tty->disc_data;
163 /* Multiply read_cnt by 3, since each byte might take up to
164 * three times as many spaces when PARMRK is set (depending on
165 * its flags, e.g. parity error). */
166 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
168 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
171 * If we are doing input canonicalization, and there are no
172 * pending newlines, let characters through without limit, so
173 * that erase characters will be handled. Other excess
174 * characters will be beeped.
177 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
183 * n_tty_set_room - receive space
186 * Re-schedules the flip buffer work if space just became available.
188 * Caller holds exclusive termios_rwsem
190 * n_tty_read()/consumer path:
191 * holds non-exclusive termios_rwsem
194 static void n_tty_set_room(struct tty_struct *tty)
196 struct n_tty_data *ldata = tty->disc_data;
198 /* Did this open up the receive buffer? We may need to flip */
199 if (unlikely(ldata->no_room) && receive_room(tty)) {
202 WARN_RATELIMIT(tty->port->itty == NULL,
203 "scheduling with invalid itty\n");
204 /* see if ldisc has been killed - if so, this means that
205 * even though the ldisc has been halted and ->buf.work
206 * cancelled, ->buf.work is about to be rescheduled
208 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
209 "scheduling buffer work for halted ldisc\n");
210 queue_work(system_unbound_wq, &tty->port->buf.work);
214 static ssize_t chars_in_buffer(struct tty_struct *tty)
216 struct n_tty_data *ldata = tty->disc_data;
222 n = ldata->canon_head - ldata->read_tail;
227 * n_tty_write_wakeup - asynchronous I/O notifier
230 * Required for the ptys, serial driver etc. since processes
231 * that attach themselves to the master and rely on ASYNC
232 * IO must be woken up
235 static void n_tty_write_wakeup(struct tty_struct *tty)
237 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
238 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
241 static inline void n_tty_check_throttle(struct tty_struct *tty)
243 if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
246 * Check the remaining room for the input canonicalization
247 * mode. We don't want to throttle the driver if we're in
248 * canonical mode and don't have a newline yet!
252 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
253 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
255 throttled = tty_throttle_safe(tty);
259 __tty_set_flow_change(tty, 0);
262 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
264 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
265 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
266 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
271 n_tty_write_wakeup(tty->link);
272 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
276 /* If there is enough space in the read buffer now, let the
277 * low-level driver know. We use chars_in_buffer() to
278 * check the buffer, as it now knows about canonical mode.
279 * Otherwise, if the driver is throttled and the line is
280 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
281 * we won't get any more characters.
286 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
287 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
292 unthrottled = tty_unthrottle_safe(tty);
296 __tty_set_flow_change(tty, 0);
300 * put_tty_queue - add character to tty
304 * Add a character to the tty read_buf queue.
306 * n_tty_receive_buf()/producer path:
307 * caller holds non-exclusive termios_rwsem
310 * read_head is only considered 'published' if canonical mode is
314 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
316 if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
317 *read_buf_addr(ldata, ldata->read_head) = c;
323 * reset_buffer_flags - reset buffer state
324 * @tty: terminal to reset
326 * Reset the read buffer counters and clear the flags.
327 * Called from n_tty_open() and n_tty_flush_buffer().
329 * Locking: caller holds exclusive termios_rwsem
330 * (or locking is not required)
333 static void reset_buffer_flags(struct n_tty_data *ldata)
335 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
337 mutex_lock(&ldata->echo_lock);
338 ldata->echo_head = ldata->echo_tail = 0;
339 mutex_unlock(&ldata->echo_lock);
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: output_lock to protect column state and space left,
646 * echo_lock to protect the echo buffer
649 static void process_echoes(struct tty_struct *tty)
651 struct n_tty_data *ldata = tty->disc_data;
656 if (ldata->echo_head == ldata->echo_tail)
659 mutex_lock(&ldata->output_lock);
660 mutex_lock(&ldata->echo_lock);
662 space = tty_write_room(tty);
664 tail = ldata->echo_tail;
665 nr = ldata->echo_head - ldata->echo_tail;
667 c = echo_buf(ldata, tail);
668 if (c == ECHO_OP_START) {
670 int no_space_left = 0;
673 * If the buffer byte is the start of a multi-byte
674 * operation, get the next byte, which is either the
675 * op code or a control character value.
677 op = echo_buf(ldata, tail + 1);
680 unsigned int num_chars, num_bs;
682 case ECHO_OP_ERASE_TAB:
683 num_chars = echo_buf(ldata, tail + 2);
686 * Determine how many columns to go back
687 * in order to erase the tab.
688 * This depends on the number of columns
689 * used by other characters within the tab
690 * area. If this (modulo 8) count is from
691 * the start of input rather than from a
692 * previous tab, we offset by canon column.
693 * Otherwise, tab spacing is normal.
695 if (!(num_chars & 0x80))
696 num_chars += ldata->canon_column;
697 num_bs = 8 - (num_chars & 7);
699 if (num_bs > space) {
705 tty_put_char(tty, '\b');
706 if (ldata->column > 0)
713 case ECHO_OP_SET_CANON_COL:
714 ldata->canon_column = ldata->column;
719 case ECHO_OP_MOVE_BACK_COL:
720 if (ldata->column > 0)
727 /* This is an escaped echo op start code */
732 tty_put_char(tty, ECHO_OP_START);
741 * If the op is not a special byte code,
742 * it is a ctrl char tagged to be echoed
743 * as "^X" (where X is the letter
744 * representing the control char).
745 * Note that we must ensure there is
746 * enough space for the whole ctrl pair.
753 tty_put_char(tty, '^');
754 tty_put_char(tty, op ^ 0100);
765 int retval = do_output_char(c, tty, space);
772 tty_put_char(tty, c);
780 ldata->echo_tail = tail;
782 mutex_unlock(&ldata->echo_lock);
783 mutex_unlock(&ldata->output_lock);
785 if (tty->ops->flush_chars)
786 tty->ops->flush_chars(tty);
790 * add_echo_byte - add a byte to the echo buffer
791 * @c: unicode byte to echo
794 * Add a character or operation byte to the echo buffer.
796 * Should be called under the echo lock to protect the echo buffer.
799 static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
801 if (ldata->echo_head - ldata->echo_tail == N_TTY_BUF_SIZE) {
802 size_t head = ldata->echo_head;
804 * Since the buffer start position needs to be advanced,
805 * be sure to step by a whole operation byte group.
807 if (echo_buf(ldata, head) == ECHO_OP_START) {
808 if (echo_buf(ldata, head + 1) == ECHO_OP_ERASE_TAB)
809 ldata->echo_tail += 3;
811 ldata->echo_tail += 2;
816 *echo_buf_addr(ldata, ldata->echo_head++) = c;
820 * echo_move_back_col - add operation to move back a column
823 * Add an operation to the echo buffer to move back one column.
825 * Locking: echo_lock to protect the echo buffer
828 static void echo_move_back_col(struct n_tty_data *ldata)
830 mutex_lock(&ldata->echo_lock);
831 add_echo_byte(ECHO_OP_START, ldata);
832 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
833 mutex_unlock(&ldata->echo_lock);
837 * echo_set_canon_col - add operation to set the canon column
840 * Add an operation to the echo buffer to set the canon column
841 * to the current column.
843 * Locking: echo_lock to protect the echo buffer
846 static void echo_set_canon_col(struct n_tty_data *ldata)
848 mutex_lock(&ldata->echo_lock);
849 add_echo_byte(ECHO_OP_START, ldata);
850 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
851 mutex_unlock(&ldata->echo_lock);
855 * echo_erase_tab - add operation to erase a tab
856 * @num_chars: number of character columns already used
857 * @after_tab: true if num_chars starts after a previous tab
860 * Add an operation to the echo buffer to erase a tab.
862 * Called by the eraser function, which knows how many character
863 * columns have been used since either a previous tab or the start
864 * of input. This information will be used later, along with
865 * canon column (if applicable), to go back the correct number
868 * Locking: echo_lock to protect the echo buffer
871 static void echo_erase_tab(unsigned int num_chars, int after_tab,
872 struct n_tty_data *ldata)
874 mutex_lock(&ldata->echo_lock);
876 add_echo_byte(ECHO_OP_START, ldata);
877 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
879 /* We only need to know this modulo 8 (tab spacing) */
882 /* Set the high bit as a flag if num_chars is after a previous tab */
886 add_echo_byte(num_chars, ldata);
888 mutex_unlock(&ldata->echo_lock);
892 * echo_char_raw - echo a character raw
893 * @c: unicode byte to echo
894 * @tty: terminal device
896 * Echo user input back onto the screen. This must be called only when
897 * L_ECHO(tty) is true. Called from the driver receive_buf path.
899 * This variant does not treat control characters specially.
901 * Locking: echo_lock to protect the echo buffer
904 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
906 mutex_lock(&ldata->echo_lock);
907 if (c == ECHO_OP_START) {
908 add_echo_byte(ECHO_OP_START, ldata);
909 add_echo_byte(ECHO_OP_START, ldata);
911 add_echo_byte(c, ldata);
913 mutex_unlock(&ldata->echo_lock);
917 * echo_char - echo a character
918 * @c: unicode byte to echo
919 * @tty: terminal device
921 * Echo user input back onto the screen. This must be called only when
922 * L_ECHO(tty) is true. Called from the driver receive_buf path.
924 * This variant tags control characters to be echoed as "^X"
925 * (where X is the letter representing the control char).
927 * Locking: echo_lock to protect the echo buffer
930 static void echo_char(unsigned char c, struct tty_struct *tty)
932 struct n_tty_data *ldata = tty->disc_data;
934 mutex_lock(&ldata->echo_lock);
936 if (c == ECHO_OP_START) {
937 add_echo_byte(ECHO_OP_START, ldata);
938 add_echo_byte(ECHO_OP_START, ldata);
940 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
941 add_echo_byte(ECHO_OP_START, ldata);
942 add_echo_byte(c, ldata);
945 mutex_unlock(&ldata->echo_lock);
949 * finish_erasing - complete erase
953 static inline void finish_erasing(struct n_tty_data *ldata)
955 if (ldata->erasing) {
956 echo_char_raw('/', ldata);
962 * eraser - handle erase function
963 * @c: character input
964 * @tty: terminal device
966 * Perform erase and necessary output when an erase character is
967 * present in the stream from the driver layer. Handles the complexities
968 * of UTF-8 multibyte symbols.
970 * n_tty_receive_buf()/producer path:
971 * caller holds non-exclusive termios_rwsem
974 * Modifying the read_head is not considered a publish in this context
975 * because canonical mode is active -- only canon_head publishes
978 static void eraser(unsigned char c, struct tty_struct *tty)
980 struct n_tty_data *ldata = tty->disc_data;
981 enum { ERASE, WERASE, KILL } kill_type;
986 if (ldata->read_head == ldata->canon_head) {
987 /* process_output('\a', tty); */ /* what do you think? */
990 if (c == ERASE_CHAR(tty))
992 else if (c == WERASE_CHAR(tty))
996 ldata->read_head = ldata->canon_head;
999 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1000 ldata->read_head = ldata->canon_head;
1001 finish_erasing(ldata);
1002 echo_char(KILL_CHAR(tty), tty);
1003 /* Add a newline if ECHOK is on and ECHOKE is off. */
1005 echo_char_raw('\n', ldata);
1012 while (ldata->read_head != ldata->canon_head) {
1013 head = ldata->read_head;
1015 /* erase a single possibly multibyte character */
1018 c = read_buf(ldata, head);
1019 } while (is_continuation(c, tty) && head != ldata->canon_head);
1021 /* do not partially erase */
1022 if (is_continuation(c, tty))
1025 if (kill_type == WERASE) {
1026 /* Equivalent to BSD's ALTWERASE. */
1027 if (isalnum(c) || c == '_')
1029 else if (seen_alnums)
1032 cnt = ldata->read_head - head;
1033 ldata->read_head = head;
1035 if (L_ECHOPRT(tty)) {
1036 if (!ldata->erasing) {
1037 echo_char_raw('\\', ldata);
1040 /* if cnt > 1, output a multi-byte character */
1044 echo_char_raw(read_buf(ldata, head), ldata);
1045 echo_move_back_col(ldata);
1047 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1048 echo_char(ERASE_CHAR(tty), tty);
1049 } else if (c == '\t') {
1050 unsigned int num_chars = 0;
1052 size_t tail = ldata->read_head;
1055 * Count the columns used for characters
1056 * since the start of input or after a
1058 * This info is used to go back the correct
1059 * number of columns.
1061 while (tail != ldata->canon_head) {
1063 c = read_buf(ldata, tail);
1067 } else if (iscntrl(c)) {
1070 } else if (!is_continuation(c, tty)) {
1074 echo_erase_tab(num_chars, after_tab, ldata);
1076 if (iscntrl(c) && L_ECHOCTL(tty)) {
1077 echo_char_raw('\b', ldata);
1078 echo_char_raw(' ', ldata);
1079 echo_char_raw('\b', ldata);
1081 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1082 echo_char_raw('\b', ldata);
1083 echo_char_raw(' ', ldata);
1084 echo_char_raw('\b', ldata);
1088 if (kill_type == ERASE)
1091 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1092 finish_erasing(ldata);
1096 * isig - handle the ISIG optio
1100 * Called when a signal is being sent due to terminal input.
1101 * Called from the driver receive_buf path so serialized.
1103 * Locking: ctrl_lock
1106 static inline void isig(int sig, struct tty_struct *tty)
1108 struct pid *tty_pgrp = tty_get_pgrp(tty);
1110 kill_pgrp(tty_pgrp, sig, 1);
1116 * n_tty_receive_break - handle break
1119 * An RS232 break event has been hit in the incoming bitstream. This
1120 * can cause a variety of events depending upon the termios settings.
1122 * n_tty_receive_buf()/producer path:
1123 * caller holds non-exclusive termios_rwsem
1124 * publishes read_head via put_tty_queue()
1126 * Note: may get exclusive termios_rwsem if flushing input buffer
1129 static inline void n_tty_receive_break(struct tty_struct *tty)
1131 struct n_tty_data *ldata = tty->disc_data;
1135 if (I_BRKINT(tty)) {
1137 if (!L_NOFLSH(tty)) {
1138 /* flushing needs exclusive termios_rwsem */
1139 up_read(&tty->termios_rwsem);
1140 n_tty_flush_buffer(tty);
1141 tty_driver_flush_buffer(tty);
1142 down_read(&tty->termios_rwsem);
1146 if (I_PARMRK(tty)) {
1147 put_tty_queue('\377', ldata);
1148 put_tty_queue('\0', ldata);
1150 put_tty_queue('\0', ldata);
1151 wake_up_interruptible(&tty->read_wait);
1155 * n_tty_receive_overrun - handle overrun reporting
1158 * Data arrived faster than we could process it. While the tty
1159 * driver has flagged this the bits that were missed are gone
1162 * Called from the receive_buf path so single threaded. Does not
1163 * need locking as num_overrun and overrun_time are function
1167 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1169 struct n_tty_data *ldata = tty->disc_data;
1172 ldata->num_overrun++;
1173 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1174 time_after(ldata->overrun_time, jiffies)) {
1175 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1177 ldata->num_overrun);
1178 ldata->overrun_time = jiffies;
1179 ldata->num_overrun = 0;
1184 * n_tty_receive_parity_error - error notifier
1185 * @tty: terminal device
1188 * Process a parity error and queue the right data to indicate
1189 * the error case if necessary.
1191 * n_tty_receive_buf()/producer path:
1192 * caller holds non-exclusive termios_rwsem
1193 * publishes read_head via put_tty_queue()
1195 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1198 struct n_tty_data *ldata = tty->disc_data;
1202 if (I_PARMRK(tty)) {
1203 put_tty_queue('\377', ldata);
1204 put_tty_queue('\0', ldata);
1205 put_tty_queue(c, ldata);
1206 } else if (I_INPCK(tty))
1207 put_tty_queue('\0', ldata);
1209 put_tty_queue(c, ldata);
1210 wake_up_interruptible(&tty->read_wait);
1214 * n_tty_receive_char - perform processing
1215 * @tty: terminal device
1218 * Process an individual character of input received from the driver.
1219 * This is serialized with respect to itself by the rules for the
1222 * n_tty_receive_buf()/producer path:
1223 * caller holds non-exclusive termios_rwsem
1224 * publishes canon_head if canonical mode is active
1225 * otherwise, publishes read_head via put_tty_queue()
1228 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1230 struct n_tty_data *ldata = tty->disc_data;
1234 put_tty_queue(c, ldata);
1240 if (I_IUCLC(tty) && L_IEXTEN(tty))
1243 if (L_EXTPROC(tty)) {
1244 put_tty_queue(c, ldata);
1248 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1249 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1250 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1252 process_echoes(tty);
1257 if (c == START_CHAR(tty)) {
1259 process_echoes(tty);
1260 } else if (c == STOP_CHAR(tty))
1267 * If the previous character was LNEXT, or we know that this
1268 * character is not one of the characters that we'll have to
1269 * handle specially, do shortcut processing to speed things
1272 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1274 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1275 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1276 /* beep if no space */
1278 process_output('\a', tty);
1282 finish_erasing(ldata);
1283 /* Record the column of first canon char. */
1284 if (ldata->canon_head == ldata->read_head)
1285 echo_set_canon_col(ldata);
1287 process_echoes(tty);
1290 put_tty_queue(c, ldata);
1291 put_tty_queue(c, ldata);
1296 if (c == START_CHAR(tty)) {
1298 process_echoes(tty);
1301 if (c == STOP_CHAR(tty)) {
1310 if (c == INTR_CHAR(tty))
1313 if (c == QUIT_CHAR(tty))
1316 if (c == SUSP_CHAR(tty)) {
1318 if (!L_NOFLSH(tty)) {
1319 /* flushing needs exclusive termios_rwsem */
1320 up_read(&tty->termios_rwsem);
1321 n_tty_flush_buffer(tty);
1322 tty_driver_flush_buffer(tty);
1323 down_read(&tty->termios_rwsem);
1329 process_echoes(tty);
1341 } else if (c == '\n' && I_INLCR(tty))
1344 if (ldata->icanon) {
1345 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1346 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1348 process_echoes(tty);
1351 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1354 finish_erasing(ldata);
1355 if (L_ECHOCTL(tty)) {
1356 echo_char_raw('^', ldata);
1357 echo_char_raw('\b', ldata);
1358 process_echoes(tty);
1363 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1365 size_t tail = ldata->canon_head;
1367 finish_erasing(ldata);
1369 echo_char_raw('\n', ldata);
1370 while (tail != ldata->read_head) {
1371 echo_char(read_buf(ldata, tail), tty);
1374 process_echoes(tty);
1378 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1380 process_output('\a', tty);
1383 if (L_ECHO(tty) || L_ECHONL(tty)) {
1384 echo_char_raw('\n', ldata);
1385 process_echoes(tty);
1387 goto handle_newline;
1389 if (c == EOF_CHAR(tty)) {
1390 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1392 if (ldata->canon_head != ldata->read_head)
1393 set_bit(TTY_PUSH, &tty->flags);
1394 c = __DISABLED_CHAR;
1395 goto handle_newline;
1397 if ((c == EOL_CHAR(tty)) ||
1398 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1399 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1401 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1403 process_output('\a', tty);
1407 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1410 /* Record the column of first canon char. */
1411 if (ldata->canon_head == ldata->read_head)
1412 echo_set_canon_col(ldata);
1414 process_echoes(tty);
1417 * XXX does PARMRK doubling happen for
1418 * EOL_CHAR and EOL2_CHAR?
1421 put_tty_queue(c, ldata);
1424 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1425 put_tty_queue(c, ldata);
1426 ldata->canon_head = ldata->read_head;
1427 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1428 if (waitqueue_active(&tty->read_wait))
1429 wake_up_interruptible(&tty->read_wait);
1434 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1435 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1436 /* beep if no space */
1438 process_output('\a', tty);
1442 finish_erasing(ldata);
1444 echo_char_raw('\n', ldata);
1446 /* Record the column of first canon char. */
1447 if (ldata->canon_head == ldata->read_head)
1448 echo_set_canon_col(ldata);
1451 process_echoes(tty);
1455 put_tty_queue(c, ldata);
1457 put_tty_queue(c, ldata);
1461 * n_tty_receive_buf - data receive
1462 * @tty: terminal device
1465 * @count: characters
1467 * Called by the terminal driver when a block of characters has
1468 * been received. This function must be called from soft contexts
1469 * not from interrupt context. The driver is responsible for making
1470 * calls one at a time and in order (or using flush_to_ldisc)
1472 * n_tty_receive_buf()/producer path:
1473 * claims non-exclusive termios_rwsem
1474 * publishes read_head and canon_head
1477 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1478 char *fp, int count)
1480 struct n_tty_data *ldata = tty->disc_data;
1481 const unsigned char *p;
1482 char *f, flags = TTY_NORMAL;
1485 if (ldata->real_raw) {
1488 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1489 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1490 n = min_t(size_t, count, n);
1491 memcpy(read_buf_addr(ldata, head), cp, n);
1492 ldata->read_head += n;
1496 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1497 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1498 n = min_t(size_t, count, n);
1499 memcpy(read_buf_addr(ldata, head), cp, n);
1500 ldata->read_head += n;
1504 for (i = count, p = cp, f = fp; i; i--, p++) {
1509 n_tty_receive_char(tty, *p);
1512 n_tty_receive_break(tty);
1516 n_tty_receive_parity_error(tty, *p);
1519 n_tty_receive_overrun(tty);
1522 printk(KERN_ERR "%s: unknown flag %d\n",
1523 tty_name(tty, buf), flags);
1527 if (tty->ops->flush_chars)
1528 tty->ops->flush_chars(tty);
1531 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1533 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1534 if (waitqueue_active(&tty->read_wait))
1535 wake_up_interruptible(&tty->read_wait);
1538 n_tty_check_throttle(tty);
1541 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1542 char *fp, int count)
1544 down_read(&tty->termios_rwsem);
1545 __receive_buf(tty, cp, fp, count);
1546 up_read(&tty->termios_rwsem);
1549 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1550 char *fp, int count)
1552 struct n_tty_data *ldata = tty->disc_data;
1555 down_read(&tty->termios_rwsem);
1557 tty->receive_room = room = receive_room(tty);
1560 count = min(count, room);
1562 __receive_buf(tty, cp, fp, count);
1564 up_read(&tty->termios_rwsem);
1569 int is_ignored(int sig)
1571 return (sigismember(¤t->blocked, sig) ||
1572 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1576 * n_tty_set_termios - termios data changed
1578 * @old: previous data
1580 * Called by the tty layer when the user changes termios flags so
1581 * that the line discipline can plan ahead. This function cannot sleep
1582 * and is protected from re-entry by the tty layer. The user is
1583 * guaranteed that this function will not be re-entered or in progress
1584 * when the ldisc is closed.
1586 * Locking: Caller holds tty->termios_rwsem
1589 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1591 struct n_tty_data *ldata = tty->disc_data;
1592 int canon_change = 1;
1595 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1597 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1598 ldata->canon_head = ldata->read_tail;
1603 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1604 wake_up_interruptible(&tty->read_wait);
1606 ldata->icanon = (L_ICANON(tty) != 0);
1608 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1609 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1610 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1612 bitmap_zero(ldata->process_char_map, 256);
1614 if (I_IGNCR(tty) || I_ICRNL(tty))
1615 set_bit('\r', ldata->process_char_map);
1617 set_bit('\n', ldata->process_char_map);
1619 if (L_ICANON(tty)) {
1620 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1621 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1622 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1623 set_bit('\n', ldata->process_char_map);
1624 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1625 if (L_IEXTEN(tty)) {
1626 set_bit(WERASE_CHAR(tty),
1627 ldata->process_char_map);
1628 set_bit(LNEXT_CHAR(tty),
1629 ldata->process_char_map);
1630 set_bit(EOL2_CHAR(tty),
1631 ldata->process_char_map);
1633 set_bit(REPRINT_CHAR(tty),
1634 ldata->process_char_map);
1638 set_bit(START_CHAR(tty), ldata->process_char_map);
1639 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1642 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1643 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1644 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1646 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1648 ldata->real_raw = 0;
1651 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1652 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1653 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1654 ldata->real_raw = 1;
1656 ldata->real_raw = 0;
1658 n_tty_set_room(tty);
1660 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1661 * been stopped by STOP_CHAR(tty) before it.
1663 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1667 /* The termios change make the tty ready for I/O */
1668 wake_up_interruptible(&tty->write_wait);
1669 wake_up_interruptible(&tty->read_wait);
1673 * n_tty_close - close the ldisc for this tty
1676 * Called from the terminal layer when this line discipline is
1677 * being shut down, either because of a close or becsuse of a
1678 * discipline change. The function will not be called while other
1679 * ldisc methods are in progress.
1682 static void n_tty_close(struct tty_struct *tty)
1684 struct n_tty_data *ldata = tty->disc_data;
1687 n_tty_packet_mode_flush(tty);
1689 kfree(ldata->read_buf);
1690 kfree(ldata->echo_buf);
1692 tty->disc_data = NULL;
1696 * n_tty_open - open an ldisc
1697 * @tty: terminal to open
1699 * Called when this line discipline is being attached to the
1700 * terminal device. Can sleep. Called serialized so that no
1701 * other events will occur in parallel. No further open will occur
1705 static int n_tty_open(struct tty_struct *tty)
1707 struct n_tty_data *ldata;
1709 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1713 ldata->overrun_time = jiffies;
1714 mutex_init(&ldata->atomic_read_lock);
1715 mutex_init(&ldata->output_lock);
1716 mutex_init(&ldata->echo_lock);
1718 /* These are ugly. Currently a malloc failure here can panic */
1719 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1720 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1721 if (!ldata->read_buf || !ldata->echo_buf)
1724 tty->disc_data = ldata;
1725 reset_buffer_flags(tty->disc_data);
1727 ldata->minimum_to_wake = 1;
1729 /* indicate buffer work may resume */
1730 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1731 n_tty_set_termios(tty, NULL);
1732 tty_unthrottle(tty);
1736 kfree(ldata->read_buf);
1737 kfree(ldata->echo_buf);
1743 static inline int input_available_p(struct tty_struct *tty, int amt)
1745 struct n_tty_data *ldata = tty->disc_data;
1747 if (ldata->icanon && !L_EXTPROC(tty)) {
1748 if (ldata->canon_head != ldata->read_tail)
1750 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1757 * copy_from_read_buf - copy read data directly
1758 * @tty: terminal device
1762 * Helper function to speed up n_tty_read. It is only called when
1763 * ICANON is off; it copies characters straight from the tty queue to
1764 * user space directly. It can be profitably called twice; once to
1765 * drain the space from the tail pointer to the (physical) end of the
1766 * buffer, and once to drain the space from the (physical) beginning of
1767 * the buffer to head pointer.
1769 * Called under the ldata->atomic_read_lock sem
1771 * n_tty_read()/consumer path:
1772 * caller holds non-exclusive termios_rwsem
1773 * read_tail published
1776 static int copy_from_read_buf(struct tty_struct *tty,
1777 unsigned char __user **b,
1781 struct n_tty_data *ldata = tty->disc_data;
1785 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1788 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1791 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1793 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1794 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1796 ldata->read_tail += n;
1797 /* Turn single EOF into zero-length read */
1798 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1807 * canon_copy_from_read_buf - copy read data in canonical mode
1808 * @tty: terminal device
1812 * Helper function for n_tty_read. It is only called when ICANON is on;
1813 * it copies one line of input up to and including the line-delimiting
1814 * character into the user-space buffer.
1816 * Called under the atomic_read_lock mutex
1818 * n_tty_read()/consumer path:
1819 * caller holds non-exclusive termios_rwsem
1820 * read_tail published
1823 static int canon_copy_from_read_buf(struct tty_struct *tty,
1824 unsigned char __user **b,
1827 struct n_tty_data *ldata = tty->disc_data;
1828 size_t n, size, more, c;
1833 /* N.B. avoid overrun if nr == 0 */
1834 n = min(*nr, read_cnt(ldata));
1838 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1839 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1841 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1842 __func__, *nr, tail, n, size);
1844 eol = find_next_bit(ldata->read_flags, size, tail);
1845 more = n - (size - tail);
1846 if (eol == N_TTY_BUF_SIZE && more) {
1847 /* scan wrapped without finding set bit */
1848 eol = find_next_bit(ldata->read_flags, more, 0);
1851 } else if (eol != size)
1854 size = N_TTY_BUF_SIZE - tail;
1855 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1858 if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
1861 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1862 __func__, eol, found, n, c, size, more);
1865 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1868 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1870 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1878 clear_bit(eol, ldata->read_flags);
1879 smp_mb__after_clear_bit();
1880 ldata->read_tail += c;
1883 tty_audit_push(tty);
1887 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1891 * job_control - check job control
1893 * @file: file handle
1895 * Perform job control management checks on this file/tty descriptor
1896 * and if appropriate send any needed signals and return a negative
1897 * error code if action should be taken.
1899 * Locking: redirected write test is safe
1900 * current->signal->tty check is safe
1901 * ctrl_lock to safely reference tty->pgrp
1904 static int job_control(struct tty_struct *tty, struct file *file)
1906 /* Job control check -- must be done at start and after
1907 every sleep (POSIX.1 7.1.1.4). */
1908 /* NOTE: not yet done after every sleep pending a thorough
1909 check of the logic of this change. -- jlc */
1910 /* don't stop on /dev/console */
1911 if (file->f_op->write == redirected_tty_write ||
1912 current->signal->tty != tty)
1915 spin_lock_irq(&tty->ctrl_lock);
1917 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1918 else if (task_pgrp(current) != tty->pgrp) {
1919 spin_unlock_irq(&tty->ctrl_lock);
1920 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1922 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1923 set_thread_flag(TIF_SIGPENDING);
1924 return -ERESTARTSYS;
1926 spin_unlock_irq(&tty->ctrl_lock);
1932 * n_tty_read - read function for tty
1934 * @file: file object
1935 * @buf: userspace buffer pointer
1938 * Perform reads for the line discipline. We are guaranteed that the
1939 * line discipline will not be closed under us but we may get multiple
1940 * parallel readers and must handle this ourselves. We may also get
1941 * a hangup. Always called in user context, may sleep.
1943 * This code must be sure never to sleep through a hangup.
1945 * n_tty_read()/consumer path:
1946 * claims non-exclusive termios_rwsem
1947 * publishes read_tail
1950 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1951 unsigned char __user *buf, size_t nr)
1953 struct n_tty_data *ldata = tty->disc_data;
1954 unsigned char __user *b = buf;
1955 DECLARE_WAITQUEUE(wait, current);
1961 unsigned long flags;
1965 c = job_control(tty, file);
1969 down_read(&tty->termios_rwsem);
1972 timeout = MAX_SCHEDULE_TIMEOUT;
1973 if (!ldata->icanon) {
1974 minimum = MIN_CHAR(tty);
1976 time = (HZ / 10) * TIME_CHAR(tty);
1978 ldata->minimum_to_wake = 1;
1979 else if (!waitqueue_active(&tty->read_wait) ||
1980 (ldata->minimum_to_wake > minimum))
1981 ldata->minimum_to_wake = minimum;
1983 timeout = (HZ / 10) * TIME_CHAR(tty);
1984 ldata->minimum_to_wake = minimum = 1;
1989 * Internal serialization of reads.
1991 if (file->f_flags & O_NONBLOCK) {
1992 if (!mutex_trylock(&ldata->atomic_read_lock)) {
1993 up_read(&tty->termios_rwsem);
1997 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
1998 up_read(&tty->termios_rwsem);
1999 return -ERESTARTSYS;
2002 packet = tty->packet;
2004 add_wait_queue(&tty->read_wait, &wait);
2006 /* First test for status change. */
2007 if (packet && tty->link->ctrl_status) {
2011 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2012 cs = tty->link->ctrl_status;
2013 tty->link->ctrl_status = 0;
2014 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2015 if (tty_put_user(tty, cs, b++)) {
2023 /* This statement must be first before checking for input
2024 so that any interrupt will set the state back to
2026 set_current_state(TASK_INTERRUPTIBLE);
2028 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2029 ((minimum - (b - buf)) >= 1))
2030 ldata->minimum_to_wake = (minimum - (b - buf));
2032 if (!input_available_p(tty, 0)) {
2033 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2037 if (tty_hung_up_p(file))
2041 if (file->f_flags & O_NONBLOCK) {
2045 if (signal_pending(current)) {
2046 retval = -ERESTARTSYS;
2049 n_tty_set_room(tty);
2050 up_read(&tty->termios_rwsem);
2052 timeout = schedule_timeout(timeout);
2054 down_read(&tty->termios_rwsem);
2057 __set_current_state(TASK_RUNNING);
2059 /* Deal with packet mode. */
2060 if (packet && b == buf) {
2061 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2069 if (ldata->icanon && !L_EXTPROC(tty)) {
2070 retval = canon_copy_from_read_buf(tty, &b, &nr);
2075 /* The copy function takes the read lock and handles
2076 locking internally for this case */
2077 uncopied = copy_from_read_buf(tty, &b, &nr);
2078 uncopied += copy_from_read_buf(tty, &b, &nr);
2085 n_tty_check_unthrottle(tty);
2087 if (b - buf >= minimum)
2092 mutex_unlock(&ldata->atomic_read_lock);
2093 remove_wait_queue(&tty->read_wait, &wait);
2095 if (!waitqueue_active(&tty->read_wait))
2096 ldata->minimum_to_wake = minimum;
2098 __set_current_state(TASK_RUNNING);
2103 clear_bit(TTY_PUSH, &tty->flags);
2104 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
2105 up_read(&tty->termios_rwsem);
2109 n_tty_set_room(tty);
2110 up_read(&tty->termios_rwsem);
2115 * n_tty_write - write function for tty
2117 * @file: file object
2118 * @buf: userspace buffer pointer
2121 * Write function of the terminal device. This is serialized with
2122 * respect to other write callers but not to termios changes, reads
2123 * and other such events. Since the receive code will echo characters,
2124 * thus calling driver write methods, the output_lock is used in
2125 * the output processing functions called here as well as in the
2126 * echo processing function to protect the column state and space
2127 * left in the buffer.
2129 * This code must be sure never to sleep through a hangup.
2131 * Locking: output_lock to protect column state and space left
2132 * (note that the process_output*() functions take this
2136 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2137 const unsigned char *buf, size_t nr)
2139 const unsigned char *b = buf;
2140 DECLARE_WAITQUEUE(wait, current);
2144 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2145 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2146 retval = tty_check_change(tty);
2151 down_read(&tty->termios_rwsem);
2153 /* Write out any echoed characters that are still pending */
2154 process_echoes(tty);
2156 add_wait_queue(&tty->write_wait, &wait);
2158 set_current_state(TASK_INTERRUPTIBLE);
2159 if (signal_pending(current)) {
2160 retval = -ERESTARTSYS;
2163 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2169 ssize_t num = process_output_block(tty, b, nr);
2181 if (process_output(c, tty) < 0)
2185 if (tty->ops->flush_chars)
2186 tty->ops->flush_chars(tty);
2189 c = tty->ops->write(tty, b, nr);
2202 if (file->f_flags & O_NONBLOCK) {
2206 up_read(&tty->termios_rwsem);
2210 down_read(&tty->termios_rwsem);
2213 __set_current_state(TASK_RUNNING);
2214 remove_wait_queue(&tty->write_wait, &wait);
2215 if (b - buf != nr && tty->fasync)
2216 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2217 up_read(&tty->termios_rwsem);
2218 return (b - buf) ? b - buf : retval;
2222 * n_tty_poll - poll method for N_TTY
2223 * @tty: terminal device
2224 * @file: file accessing it
2227 * Called when the line discipline is asked to poll() for data or
2228 * for special events. This code is not serialized with respect to
2229 * other events save open/close.
2231 * This code must be sure never to sleep through a hangup.
2232 * Called without the kernel lock held - fine
2235 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2238 struct n_tty_data *ldata = tty->disc_data;
2239 unsigned int mask = 0;
2241 poll_wait(file, &tty->read_wait, wait);
2242 poll_wait(file, &tty->write_wait, wait);
2243 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2244 mask |= POLLIN | POLLRDNORM;
2245 if (tty->packet && tty->link->ctrl_status)
2246 mask |= POLLPRI | POLLIN | POLLRDNORM;
2247 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2249 if (tty_hung_up_p(file))
2251 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2252 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2253 ldata->minimum_to_wake = MIN_CHAR(tty);
2255 ldata->minimum_to_wake = 1;
2257 if (tty->ops->write && !tty_is_writelocked(tty) &&
2258 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2259 tty_write_room(tty) > 0)
2260 mask |= POLLOUT | POLLWRNORM;
2264 static unsigned long inq_canon(struct n_tty_data *ldata)
2266 size_t nr, head, tail;
2268 if (ldata->canon_head == ldata->read_tail)
2270 head = ldata->canon_head;
2271 tail = ldata->read_tail;
2273 /* Skip EOF-chars.. */
2274 while (head != tail) {
2275 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2276 read_buf(ldata, tail) == __DISABLED_CHAR)
2283 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2284 unsigned int cmd, unsigned long arg)
2286 struct n_tty_data *ldata = tty->disc_data;
2291 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2293 down_write(&tty->termios_rwsem);
2295 retval = inq_canon(ldata);
2297 retval = read_cnt(ldata);
2298 up_write(&tty->termios_rwsem);
2299 return put_user(retval, (unsigned int __user *) arg);
2301 return n_tty_ioctl_helper(tty, file, cmd, arg);
2305 static void n_tty_fasync(struct tty_struct *tty, int on)
2307 struct n_tty_data *ldata = tty->disc_data;
2309 if (!waitqueue_active(&tty->read_wait)) {
2311 ldata->minimum_to_wake = 1;
2312 else if (!tty->fasync)
2313 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2317 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2318 .magic = TTY_LDISC_MAGIC,
2321 .close = n_tty_close,
2322 .flush_buffer = n_tty_flush_buffer,
2323 .chars_in_buffer = n_tty_chars_in_buffer,
2325 .write = n_tty_write,
2326 .ioctl = n_tty_ioctl,
2327 .set_termios = n_tty_set_termios,
2329 .receive_buf = n_tty_receive_buf,
2330 .write_wakeup = n_tty_write_wakeup,
2331 .fasync = n_tty_fasync,
2332 .receive_buf2 = n_tty_receive_buf2,
2336 * n_tty_inherit_ops - inherit N_TTY methods
2337 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2339 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2343 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2345 *ops = tty_ldisc_N_TTY;
2347 ops->refcount = ops->flags = 0;
2349 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);