2 * n_tty.c --- implements the N_TTY line discipline.
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where n_tty_write returns
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52 #include <linux/ratelimit.h>
53 #include <linux/vmalloc.h>
56 /* number of characters left in xmit buffer before select has we have room */
57 #define WAKEUP_CHARS 256
60 * This defines the low- and high-watermarks for throttling and
61 * unthrottling the TTY driver. These watermarks are used for
62 * controlling the space in the read buffer.
64 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
65 #define TTY_THRESHOLD_UNTHROTTLE 128
68 * Special byte codes used in the echo buffer to represent operations
69 * or special handling of characters. Bytes in the echo buffer that
70 * are not part of such special blocks are treated as normal character
73 #define ECHO_OP_START 0xff
74 #define ECHO_OP_MOVE_BACK_COL 0x80
75 #define ECHO_OP_SET_CANON_COL 0x81
76 #define ECHO_OP_ERASE_TAB 0x82
78 #define ECHO_COMMIT_WATERMARK 256
79 #define ECHO_BLOCK 256
80 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
85 # define n_tty_trace(f, args...) trace_printk(f, ##args)
87 # define n_tty_trace(f, args...)
91 /* producer-published */
98 DECLARE_BITMAP(char_map, 256);
100 /* private to n_tty_receive_overrun (single-threaded) */
101 unsigned long overrun_time;
107 /* must hold exclusive termios_rwsem to reset these */
108 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
109 unsigned char push:1;
111 /* shared by producer and consumer */
112 char read_buf[N_TTY_BUF_SIZE];
113 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
114 unsigned char echo_buf[N_TTY_BUF_SIZE];
118 /* consumer-published */
122 /* protected by output lock */
124 unsigned int canon_column;
127 struct mutex atomic_read_lock;
128 struct mutex output_lock;
131 static inline size_t read_cnt(struct n_tty_data *ldata)
133 return ldata->read_head - ldata->read_tail;
136 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
138 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
141 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
143 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
146 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
148 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
151 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
153 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
156 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
157 unsigned char __user *ptr)
159 struct n_tty_data *ldata = tty->disc_data;
161 tty_audit_add_data(tty, &x, 1, ldata->icanon);
162 return put_user(x, ptr);
165 static inline int tty_copy_to_user(struct tty_struct *tty,
170 struct n_tty_data *ldata = tty->disc_data;
172 tty_audit_add_data(tty, to, n, ldata->icanon);
173 return copy_to_user(to, from, n);
177 * n_tty_kick_worker - start input worker (if required)
180 * Re-schedules the flip buffer work if it may have stopped
182 * Caller holds exclusive termios_rwsem
184 * n_tty_read()/consumer path:
185 * holds non-exclusive termios_rwsem
188 static void n_tty_kick_worker(struct tty_struct *tty)
190 struct n_tty_data *ldata = tty->disc_data;
192 /* Did the input worker stop? Restart it */
193 if (unlikely(ldata->no_room)) {
196 WARN_RATELIMIT(tty->port->itty == NULL,
197 "scheduling with invalid itty\n");
198 /* see if ldisc has been killed - if so, this means that
199 * even though the ldisc has been halted and ->buf.work
200 * cancelled, ->buf.work is about to be rescheduled
202 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
203 "scheduling buffer work for halted ldisc\n");
204 queue_work(system_unbound_wq, &tty->port->buf.work);
208 static ssize_t chars_in_buffer(struct tty_struct *tty)
210 struct n_tty_data *ldata = tty->disc_data;
214 n = ldata->commit_head - ldata->read_tail;
216 n = ldata->canon_head - ldata->read_tail;
221 * n_tty_write_wakeup - asynchronous I/O notifier
224 * Required for the ptys, serial driver etc. since processes
225 * that attach themselves to the master and rely on ASYNC
226 * IO must be woken up
229 static void n_tty_write_wakeup(struct tty_struct *tty)
231 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
232 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
235 static void n_tty_check_throttle(struct tty_struct *tty)
237 struct n_tty_data *ldata = tty->disc_data;
240 * Check the remaining room for the input canonicalization
241 * mode. We don't want to throttle the driver if we're in
242 * canonical mode and don't have a newline yet!
244 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
249 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
250 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
252 throttled = tty_throttle_safe(tty);
256 __tty_set_flow_change(tty, 0);
259 static void n_tty_check_unthrottle(struct tty_struct *tty)
261 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
262 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
263 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
267 n_tty_kick_worker(tty);
268 n_tty_write_wakeup(tty->link);
269 if (waitqueue_active(&tty->link->write_wait))
270 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
274 /* If there is enough space in the read buffer now, let the
275 * low-level driver know. We use chars_in_buffer() to
276 * check the buffer, as it now knows about canonical mode.
277 * Otherwise, if the driver is throttled and the line is
278 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
279 * we won't get any more characters.
284 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
285 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
289 n_tty_kick_worker(tty);
290 unthrottled = tty_unthrottle_safe(tty);
294 __tty_set_flow_change(tty, 0);
298 * put_tty_queue - add character to tty
302 * Add a character to the tty read_buf queue.
304 * n_tty_receive_buf()/producer path:
305 * caller holds non-exclusive termios_rwsem
308 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
310 *read_buf_addr(ldata, ldata->read_head) = c;
315 * reset_buffer_flags - reset buffer state
316 * @tty: terminal to reset
318 * Reset the read buffer counters and clear the flags.
319 * Called from n_tty_open() and n_tty_flush_buffer().
321 * Locking: caller holds exclusive termios_rwsem
322 * (or locking is not required)
325 static void reset_buffer_flags(struct n_tty_data *ldata)
327 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
328 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
329 ldata->commit_head = 0;
330 ldata->echo_mark = 0;
331 ldata->line_start = 0;
334 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
338 static void n_tty_packet_mode_flush(struct tty_struct *tty)
342 if (tty->link->packet) {
343 spin_lock_irqsave(&tty->ctrl_lock, flags);
344 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
345 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
346 if (waitqueue_active(&tty->link->read_wait))
347 wake_up_interruptible(&tty->link->read_wait);
352 * n_tty_flush_buffer - clean input queue
353 * @tty: terminal device
355 * Flush the input buffer. Called when the tty layer wants the
356 * buffer flushed (eg at hangup) or when the N_TTY line discipline
357 * internally has to clean the pending queue (for example some signals).
359 * Holds termios_rwsem to exclude producer/consumer while
360 * buffer indices are reset.
362 * Locking: ctrl_lock, exclusive termios_rwsem
365 static void n_tty_flush_buffer(struct tty_struct *tty)
367 down_write(&tty->termios_rwsem);
368 reset_buffer_flags(tty->disc_data);
369 n_tty_kick_worker(tty);
372 n_tty_packet_mode_flush(tty);
373 up_write(&tty->termios_rwsem);
377 * n_tty_chars_in_buffer - report available bytes
380 * Report the number of characters buffered to be delivered to user
381 * at this instant in time.
383 * Locking: exclusive termios_rwsem
386 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
390 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
392 down_write(&tty->termios_rwsem);
393 n = chars_in_buffer(tty);
394 up_write(&tty->termios_rwsem);
399 * is_utf8_continuation - utf8 multibyte check
402 * Returns true if the utf8 character 'c' is a multibyte continuation
403 * character. We use this to correctly compute the on screen size
404 * of the character when printing
407 static inline int is_utf8_continuation(unsigned char c)
409 return (c & 0xc0) == 0x80;
413 * is_continuation - multibyte check
416 * Returns true if the utf8 character 'c' is a multibyte continuation
417 * character and the terminal is in unicode mode.
420 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
422 return I_IUTF8(tty) && is_utf8_continuation(c);
426 * do_output_char - output one character
427 * @c: character (or partial unicode symbol)
428 * @tty: terminal device
429 * @space: space available in tty driver write buffer
431 * This is a helper function that handles one output character
432 * (including special characters like TAB, CR, LF, etc.),
433 * doing OPOST processing and putting the results in the
434 * tty driver's write buffer.
436 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
437 * and NLDLY. They simply aren't relevant in the world today.
438 * If you ever need them, add them here.
440 * Returns the number of bytes of buffer space used or -1 if
443 * Locking: should be called under the output_lock to protect
444 * the column state and space left in the buffer
447 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
449 struct n_tty_data *ldata = tty->disc_data;
462 ldata->canon_column = ldata->column = 0;
463 tty->ops->write(tty, "\r\n", 2);
466 ldata->canon_column = ldata->column;
469 if (O_ONOCR(tty) && ldata->column == 0)
474 ldata->canon_column = ldata->column = 0;
477 ldata->canon_column = ldata->column = 0;
480 spaces = 8 - (ldata->column & 7);
481 if (O_TABDLY(tty) == XTABS) {
484 ldata->column += spaces;
485 tty->ops->write(tty, " ", spaces);
488 ldata->column += spaces;
491 if (ldata->column > 0)
498 if (!is_continuation(c, tty))
504 tty_put_char(tty, c);
509 * process_output - output post processor
510 * @c: character (or partial unicode symbol)
511 * @tty: terminal device
513 * Output one character with OPOST processing.
514 * Returns -1 when the output device is full and the character
517 * Locking: output_lock to protect column state and space left
518 * (also, this is called from n_tty_write under the
519 * tty layer write lock)
522 static int process_output(unsigned char c, struct tty_struct *tty)
524 struct n_tty_data *ldata = tty->disc_data;
527 mutex_lock(&ldata->output_lock);
529 space = tty_write_room(tty);
530 retval = do_output_char(c, tty, space);
532 mutex_unlock(&ldata->output_lock);
540 * process_output_block - block post processor
541 * @tty: terminal device
542 * @buf: character buffer
543 * @nr: number of bytes to output
545 * Output a block of characters with OPOST processing.
546 * Returns the number of characters output.
548 * This path is used to speed up block console writes, among other
549 * things when processing blocks of output data. It handles only
550 * the simple cases normally found and helps to generate blocks of
551 * symbols for the console driver and thus improve performance.
553 * Locking: output_lock to protect column state and space left
554 * (also, this is called from n_tty_write under the
555 * tty layer write lock)
558 static ssize_t process_output_block(struct tty_struct *tty,
559 const unsigned char *buf, unsigned int nr)
561 struct n_tty_data *ldata = tty->disc_data;
564 const unsigned char *cp;
566 mutex_lock(&ldata->output_lock);
568 space = tty_write_room(tty);
570 mutex_unlock(&ldata->output_lock);
576 for (i = 0, cp = buf; i < nr; i++, cp++) {
577 unsigned char c = *cp;
585 ldata->canon_column = ldata->column;
588 if (O_ONOCR(tty) && ldata->column == 0)
592 ldata->canon_column = ldata->column = 0;
597 if (ldata->column > 0)
604 if (!is_continuation(c, tty))
611 i = tty->ops->write(tty, buf, i);
613 mutex_unlock(&ldata->output_lock);
618 * process_echoes - write pending echo characters
619 * @tty: terminal device
621 * Write previously buffered echo (and other ldisc-generated)
622 * characters to the tty.
624 * Characters generated by the ldisc (including echoes) need to
625 * be buffered because the driver's write buffer can fill during
626 * heavy program output. Echoing straight to the driver will
627 * often fail under these conditions, causing lost characters and
628 * resulting mismatches of ldisc state information.
630 * Since the ldisc state must represent the characters actually sent
631 * to the driver at the time of the write, operations like certain
632 * changes in column state are also saved in the buffer and executed
635 * A circular fifo buffer is used so that the most recent characters
636 * are prioritized. Also, when control characters are echoed with a
637 * prefixed "^", the pair is treated atomically and thus not separated.
639 * Locking: callers must hold output_lock
642 static size_t __process_echoes(struct tty_struct *tty)
644 struct n_tty_data *ldata = tty->disc_data;
645 int space, old_space;
649 old_space = space = tty_write_room(tty);
651 tail = ldata->echo_tail;
652 while (ldata->echo_commit != tail) {
653 c = echo_buf(ldata, tail);
654 if (c == ECHO_OP_START) {
656 int no_space_left = 0;
659 * If the buffer byte is the start of a multi-byte
660 * operation, get the next byte, which is either the
661 * op code or a control character value.
663 op = echo_buf(ldata, tail + 1);
666 unsigned int num_chars, num_bs;
668 case ECHO_OP_ERASE_TAB:
669 num_chars = echo_buf(ldata, tail + 2);
672 * Determine how many columns to go back
673 * in order to erase the tab.
674 * This depends on the number of columns
675 * used by other characters within the tab
676 * area. If this (modulo 8) count is from
677 * the start of input rather than from a
678 * previous tab, we offset by canon column.
679 * Otherwise, tab spacing is normal.
681 if (!(num_chars & 0x80))
682 num_chars += ldata->canon_column;
683 num_bs = 8 - (num_chars & 7);
685 if (num_bs > space) {
691 tty_put_char(tty, '\b');
692 if (ldata->column > 0)
698 case ECHO_OP_SET_CANON_COL:
699 ldata->canon_column = ldata->column;
703 case ECHO_OP_MOVE_BACK_COL:
704 if (ldata->column > 0)
710 /* This is an escaped echo op start code */
715 tty_put_char(tty, ECHO_OP_START);
723 * If the op is not a special byte code,
724 * it is a ctrl char tagged to be echoed
725 * as "^X" (where X is the letter
726 * representing the control char).
727 * Note that we must ensure there is
728 * enough space for the whole ctrl pair.
735 tty_put_char(tty, '^');
736 tty_put_char(tty, op ^ 0100);
746 int retval = do_output_char(c, tty, space);
753 tty_put_char(tty, c);
760 /* If the echo buffer is nearly full (so that the possibility exists
761 * of echo overrun before the next commit), then discard enough
762 * data at the tail to prevent a subsequent overrun */
763 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
764 if (echo_buf(ldata, tail) == ECHO_OP_START) {
765 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
773 ldata->echo_tail = tail;
774 return old_space - space;
777 static void commit_echoes(struct tty_struct *tty)
779 struct n_tty_data *ldata = tty->disc_data;
780 size_t nr, old, echoed;
783 head = ldata->echo_head;
784 ldata->echo_mark = head;
785 old = ldata->echo_commit - ldata->echo_tail;
787 /* Process committed echoes if the accumulated # of bytes
788 * is over the threshold (and try again each time another
789 * block is accumulated) */
790 nr = head - ldata->echo_tail;
791 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
794 mutex_lock(&ldata->output_lock);
795 ldata->echo_commit = head;
796 echoed = __process_echoes(tty);
797 mutex_unlock(&ldata->output_lock);
799 if (echoed && tty->ops->flush_chars)
800 tty->ops->flush_chars(tty);
803 static void process_echoes(struct tty_struct *tty)
805 struct n_tty_data *ldata = tty->disc_data;
808 if (ldata->echo_mark == ldata->echo_tail)
811 mutex_lock(&ldata->output_lock);
812 ldata->echo_commit = ldata->echo_mark;
813 echoed = __process_echoes(tty);
814 mutex_unlock(&ldata->output_lock);
816 if (echoed && tty->ops->flush_chars)
817 tty->ops->flush_chars(tty);
820 /* NB: echo_mark and echo_head should be equivalent here */
821 static void flush_echoes(struct tty_struct *tty)
823 struct n_tty_data *ldata = tty->disc_data;
825 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
826 ldata->echo_commit == ldata->echo_head)
829 mutex_lock(&ldata->output_lock);
830 ldata->echo_commit = ldata->echo_head;
831 __process_echoes(tty);
832 mutex_unlock(&ldata->output_lock);
836 * add_echo_byte - add a byte to the echo buffer
837 * @c: unicode byte to echo
840 * Add a character or operation byte to the echo buffer.
843 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
845 *echo_buf_addr(ldata, ldata->echo_head++) = c;
849 * echo_move_back_col - add operation to move back a column
852 * Add an operation to the echo buffer to move back one column.
855 static void echo_move_back_col(struct n_tty_data *ldata)
857 add_echo_byte(ECHO_OP_START, ldata);
858 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
862 * echo_set_canon_col - add operation to set the canon column
865 * Add an operation to the echo buffer to set the canon column
866 * to the current column.
869 static void echo_set_canon_col(struct n_tty_data *ldata)
871 add_echo_byte(ECHO_OP_START, ldata);
872 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
876 * echo_erase_tab - add operation to erase a tab
877 * @num_chars: number of character columns already used
878 * @after_tab: true if num_chars starts after a previous tab
881 * Add an operation to the echo buffer to erase a tab.
883 * Called by the eraser function, which knows how many character
884 * columns have been used since either a previous tab or the start
885 * of input. This information will be used later, along with
886 * canon column (if applicable), to go back the correct number
890 static void echo_erase_tab(unsigned int num_chars, int after_tab,
891 struct n_tty_data *ldata)
893 add_echo_byte(ECHO_OP_START, ldata);
894 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
896 /* We only need to know this modulo 8 (tab spacing) */
899 /* Set the high bit as a flag if num_chars is after a previous tab */
903 add_echo_byte(num_chars, ldata);
907 * echo_char_raw - echo a character raw
908 * @c: unicode byte to echo
909 * @tty: terminal device
911 * Echo user input back onto the screen. This must be called only when
912 * L_ECHO(tty) is true. Called from the driver receive_buf path.
914 * This variant does not treat control characters specially.
917 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
919 if (c == ECHO_OP_START) {
920 add_echo_byte(ECHO_OP_START, ldata);
921 add_echo_byte(ECHO_OP_START, ldata);
923 add_echo_byte(c, ldata);
928 * echo_char - echo a character
929 * @c: unicode byte to echo
930 * @tty: terminal device
932 * Echo user input back onto the screen. This must be called only when
933 * L_ECHO(tty) is true. Called from the driver receive_buf path.
935 * This variant tags control characters to be echoed as "^X"
936 * (where X is the letter representing the control char).
939 static void echo_char(unsigned char c, struct tty_struct *tty)
941 struct n_tty_data *ldata = tty->disc_data;
943 if (c == ECHO_OP_START) {
944 add_echo_byte(ECHO_OP_START, ldata);
945 add_echo_byte(ECHO_OP_START, ldata);
947 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
948 add_echo_byte(ECHO_OP_START, ldata);
949 add_echo_byte(c, ldata);
954 * finish_erasing - complete erase
958 static inline void finish_erasing(struct n_tty_data *ldata)
960 if (ldata->erasing) {
961 echo_char_raw('/', ldata);
967 * eraser - handle erase function
968 * @c: character input
969 * @tty: terminal device
971 * Perform erase and necessary output when an erase character is
972 * present in the stream from the driver layer. Handles the complexities
973 * of UTF-8 multibyte symbols.
975 * n_tty_receive_buf()/producer path:
976 * caller holds non-exclusive termios_rwsem
979 static void eraser(unsigned char c, struct tty_struct *tty)
981 struct n_tty_data *ldata = tty->disc_data;
982 enum { ERASE, WERASE, KILL } kill_type;
987 if (ldata->read_head == ldata->canon_head) {
988 /* process_output('\a', tty); */ /* what do you think? */
991 if (c == ERASE_CHAR(tty))
993 else if (c == WERASE_CHAR(tty))
997 ldata->read_head = ldata->canon_head;
1000 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1001 ldata->read_head = ldata->canon_head;
1002 finish_erasing(ldata);
1003 echo_char(KILL_CHAR(tty), tty);
1004 /* Add a newline if ECHOK is on and ECHOKE is off. */
1006 echo_char_raw('\n', ldata);
1013 while (ldata->read_head != ldata->canon_head) {
1014 head = ldata->read_head;
1016 /* erase a single possibly multibyte character */
1019 c = read_buf(ldata, head);
1020 } while (is_continuation(c, tty) && head != ldata->canon_head);
1022 /* do not partially erase */
1023 if (is_continuation(c, tty))
1026 if (kill_type == WERASE) {
1027 /* Equivalent to BSD's ALTWERASE. */
1028 if (isalnum(c) || c == '_')
1030 else if (seen_alnums)
1033 cnt = ldata->read_head - head;
1034 ldata->read_head = head;
1036 if (L_ECHOPRT(tty)) {
1037 if (!ldata->erasing) {
1038 echo_char_raw('\\', ldata);
1041 /* if cnt > 1, output a multi-byte character */
1045 echo_char_raw(read_buf(ldata, head), ldata);
1046 echo_move_back_col(ldata);
1048 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1049 echo_char(ERASE_CHAR(tty), tty);
1050 } else if (c == '\t') {
1051 unsigned int num_chars = 0;
1053 size_t tail = ldata->read_head;
1056 * Count the columns used for characters
1057 * since the start of input or after a
1059 * This info is used to go back the correct
1060 * number of columns.
1062 while (tail != ldata->canon_head) {
1064 c = read_buf(ldata, tail);
1068 } else if (iscntrl(c)) {
1071 } else if (!is_continuation(c, tty)) {
1075 echo_erase_tab(num_chars, after_tab, ldata);
1077 if (iscntrl(c) && L_ECHOCTL(tty)) {
1078 echo_char_raw('\b', ldata);
1079 echo_char_raw(' ', ldata);
1080 echo_char_raw('\b', ldata);
1082 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1083 echo_char_raw('\b', ldata);
1084 echo_char_raw(' ', ldata);
1085 echo_char_raw('\b', ldata);
1089 if (kill_type == ERASE)
1092 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1093 finish_erasing(ldata);
1097 * isig - handle the ISIG optio
1101 * Called when a signal is being sent due to terminal input.
1102 * Called from the driver receive_buf path so serialized.
1104 * Performs input and output flush if !NOFLSH. In this context, the echo
1105 * buffer is 'output'. The signal is processed first to alert any current
1106 * readers or writers to discontinue and exit their i/o loops.
1108 * Locking: ctrl_lock
1111 static void __isig(int sig, struct tty_struct *tty)
1113 struct pid *tty_pgrp = tty_get_pgrp(tty);
1115 kill_pgrp(tty_pgrp, sig, 1);
1120 static void isig(int sig, struct tty_struct *tty)
1122 struct n_tty_data *ldata = tty->disc_data;
1124 if (L_NOFLSH(tty)) {
1128 } else { /* signal and flush */
1129 up_read(&tty->termios_rwsem);
1130 down_write(&tty->termios_rwsem);
1134 /* clear echo buffer */
1135 mutex_lock(&ldata->output_lock);
1136 ldata->echo_head = ldata->echo_tail = 0;
1137 ldata->echo_mark = ldata->echo_commit = 0;
1138 mutex_unlock(&ldata->output_lock);
1140 /* clear output buffer */
1141 tty_driver_flush_buffer(tty);
1143 /* clear input buffer */
1144 reset_buffer_flags(tty->disc_data);
1146 /* notify pty master of flush */
1148 n_tty_packet_mode_flush(tty);
1150 up_write(&tty->termios_rwsem);
1151 down_read(&tty->termios_rwsem);
1156 * n_tty_receive_break - handle break
1159 * An RS232 break event has been hit in the incoming bitstream. This
1160 * can cause a variety of events depending upon the termios settings.
1162 * n_tty_receive_buf()/producer path:
1163 * caller holds non-exclusive termios_rwsem
1165 * Note: may get exclusive termios_rwsem if flushing input buffer
1168 static void n_tty_receive_break(struct tty_struct *tty)
1170 struct n_tty_data *ldata = tty->disc_data;
1174 if (I_BRKINT(tty)) {
1178 if (I_PARMRK(tty)) {
1179 put_tty_queue('\377', ldata);
1180 put_tty_queue('\0', ldata);
1182 put_tty_queue('\0', ldata);
1183 if (waitqueue_active(&tty->read_wait))
1184 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1188 * n_tty_receive_overrun - handle overrun reporting
1191 * Data arrived faster than we could process it. While the tty
1192 * driver has flagged this the bits that were missed are gone
1195 * Called from the receive_buf path so single threaded. Does not
1196 * need locking as num_overrun and overrun_time are function
1200 static void n_tty_receive_overrun(struct tty_struct *tty)
1202 struct n_tty_data *ldata = tty->disc_data;
1204 ldata->num_overrun++;
1205 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1206 time_after(ldata->overrun_time, jiffies)) {
1207 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1209 ldata->num_overrun);
1210 ldata->overrun_time = jiffies;
1211 ldata->num_overrun = 0;
1216 * n_tty_receive_parity_error - error notifier
1217 * @tty: terminal device
1220 * Process a parity error and queue the right data to indicate
1221 * the error case if necessary.
1223 * n_tty_receive_buf()/producer path:
1224 * caller holds non-exclusive termios_rwsem
1226 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1228 struct n_tty_data *ldata = tty->disc_data;
1233 if (I_PARMRK(tty)) {
1234 put_tty_queue('\377', ldata);
1235 put_tty_queue('\0', ldata);
1236 put_tty_queue(c, ldata);
1238 put_tty_queue('\0', ldata);
1240 put_tty_queue(c, ldata);
1241 if (waitqueue_active(&tty->read_wait))
1242 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1246 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1255 process_echoes(tty);
1260 * n_tty_receive_char - perform processing
1261 * @tty: terminal device
1264 * Process an individual character of input received from the driver.
1265 * This is serialized with respect to itself by the rules for the
1268 * n_tty_receive_buf()/producer path:
1269 * caller holds non-exclusive termios_rwsem
1270 * publishes canon_head if canonical mode is active
1272 * Returns 1 if LNEXT was received, else returns 0
1276 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1278 struct n_tty_data *ldata = tty->disc_data;
1281 if (c == START_CHAR(tty)) {
1283 process_echoes(tty);
1286 if (c == STOP_CHAR(tty)) {
1293 if (c == INTR_CHAR(tty)) {
1294 n_tty_receive_signal_char(tty, SIGINT, c);
1296 } else if (c == QUIT_CHAR(tty)) {
1297 n_tty_receive_signal_char(tty, SIGQUIT, c);
1299 } else if (c == SUSP_CHAR(tty)) {
1300 n_tty_receive_signal_char(tty, SIGTSTP, c);
1305 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1307 process_echoes(tty);
1315 } else if (c == '\n' && I_INLCR(tty))
1318 if (ldata->icanon) {
1319 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1320 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1325 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1328 finish_erasing(ldata);
1329 if (L_ECHOCTL(tty)) {
1330 echo_char_raw('^', ldata);
1331 echo_char_raw('\b', ldata);
1337 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1338 size_t tail = ldata->canon_head;
1340 finish_erasing(ldata);
1342 echo_char_raw('\n', ldata);
1343 while (tail != ldata->read_head) {
1344 echo_char(read_buf(ldata, tail), tty);
1351 if (L_ECHO(tty) || L_ECHONL(tty)) {
1352 echo_char_raw('\n', ldata);
1355 goto handle_newline;
1357 if (c == EOF_CHAR(tty)) {
1358 c = __DISABLED_CHAR;
1359 goto handle_newline;
1361 if ((c == EOL_CHAR(tty)) ||
1362 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1364 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1367 /* Record the column of first canon char. */
1368 if (ldata->canon_head == ldata->read_head)
1369 echo_set_canon_col(ldata);
1374 * XXX does PARMRK doubling happen for
1375 * EOL_CHAR and EOL2_CHAR?
1377 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1378 put_tty_queue(c, ldata);
1381 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1382 put_tty_queue(c, ldata);
1383 smp_store_release(&ldata->canon_head, ldata->read_head);
1384 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1385 if (waitqueue_active(&tty->read_wait))
1386 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1392 finish_erasing(ldata);
1394 echo_char_raw('\n', ldata);
1396 /* Record the column of first canon char. */
1397 if (ldata->canon_head == ldata->read_head)
1398 echo_set_canon_col(ldata);
1404 /* PARMRK doubling check */
1405 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1406 put_tty_queue(c, ldata);
1408 put_tty_queue(c, ldata);
1413 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1415 struct n_tty_data *ldata = tty->disc_data;
1417 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1419 process_echoes(tty);
1422 finish_erasing(ldata);
1423 /* Record the column of first canon char. */
1424 if (ldata->canon_head == ldata->read_head)
1425 echo_set_canon_col(ldata);
1429 /* PARMRK doubling check */
1430 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1431 put_tty_queue(c, ldata);
1432 put_tty_queue(c, ldata);
1435 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1437 n_tty_receive_char_inline(tty, c);
1441 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1443 struct n_tty_data *ldata = tty->disc_data;
1445 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1447 process_echoes(tty);
1450 finish_erasing(ldata);
1451 /* Record the column of first canon char. */
1452 if (ldata->canon_head == ldata->read_head)
1453 echo_set_canon_col(ldata);
1457 put_tty_queue(c, ldata);
1460 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1464 if (I_IUCLC(tty) && L_IEXTEN(tty))
1468 if (c == STOP_CHAR(tty))
1470 else if (c == START_CHAR(tty) ||
1471 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1472 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1473 c != SUSP_CHAR(tty))) {
1475 process_echoes(tty);
1481 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1485 n_tty_receive_break(tty);
1489 n_tty_receive_parity_error(tty, c);
1492 n_tty_receive_overrun(tty);
1495 printk(KERN_ERR "%s: unknown flag %d\n",
1496 tty_name(tty), flag);
1502 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1504 struct n_tty_data *ldata = tty->disc_data;
1507 if (likely(flag == TTY_NORMAL)) {
1510 if (I_IUCLC(tty) && L_IEXTEN(tty))
1512 n_tty_receive_char(tty, c);
1514 n_tty_receive_char_flagged(tty, c, flag);
1518 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1519 char *fp, int count)
1521 struct n_tty_data *ldata = tty->disc_data;
1524 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1525 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1526 memcpy(read_buf_addr(ldata, head), cp, n);
1527 ldata->read_head += n;
1531 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1532 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1533 memcpy(read_buf_addr(ldata, head), cp, n);
1534 ldata->read_head += n;
1538 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1539 char *fp, int count)
1541 struct n_tty_data *ldata = tty->disc_data;
1542 char flag = TTY_NORMAL;
1547 if (likely(flag == TTY_NORMAL))
1548 put_tty_queue(*cp++, ldata);
1550 n_tty_receive_char_flagged(tty, *cp++, flag);
1555 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1556 char *fp, int count)
1558 char flag = TTY_NORMAL;
1563 if (likely(flag == TTY_NORMAL))
1564 n_tty_receive_char_closing(tty, *cp++);
1566 n_tty_receive_char_flagged(tty, *cp++, flag);
1571 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1572 char *fp, int count)
1574 struct n_tty_data *ldata = tty->disc_data;
1575 char flag = TTY_NORMAL;
1580 if (likely(flag == TTY_NORMAL)) {
1581 unsigned char c = *cp++;
1585 if (I_IUCLC(tty) && L_IEXTEN(tty))
1587 if (L_EXTPROC(tty)) {
1588 put_tty_queue(c, ldata);
1591 if (!test_bit(c, ldata->char_map))
1592 n_tty_receive_char_inline(tty, c);
1593 else if (n_tty_receive_char_special(tty, c) && count) {
1596 n_tty_receive_char_lnext(tty, *cp++, flag);
1600 n_tty_receive_char_flagged(tty, *cp++, flag);
1605 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1606 char *fp, int count)
1608 struct n_tty_data *ldata = tty->disc_data;
1609 char flag = TTY_NORMAL;
1614 if (likely(flag == TTY_NORMAL)) {
1615 unsigned char c = *cp++;
1617 if (!test_bit(c, ldata->char_map))
1618 n_tty_receive_char_fast(tty, c);
1619 else if (n_tty_receive_char_special(tty, c) && count) {
1622 n_tty_receive_char_lnext(tty, *cp++, flag);
1626 n_tty_receive_char_flagged(tty, *cp++, flag);
1630 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1631 char *fp, int count)
1633 struct n_tty_data *ldata = tty->disc_data;
1634 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1636 if (ldata->real_raw)
1637 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1638 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1639 n_tty_receive_buf_raw(tty, cp, fp, count);
1640 else if (tty->closing && !L_EXTPROC(tty))
1641 n_tty_receive_buf_closing(tty, cp, fp, count);
1644 char flag = TTY_NORMAL;
1648 n_tty_receive_char_lnext(tty, *cp++, flag);
1652 if (!preops && !I_PARMRK(tty))
1653 n_tty_receive_buf_fast(tty, cp, fp, count);
1655 n_tty_receive_buf_standard(tty, cp, fp, count);
1658 if (tty->ops->flush_chars)
1659 tty->ops->flush_chars(tty);
1662 if (ldata->icanon && !L_EXTPROC(tty))
1665 /* publish read_head to consumer */
1666 smp_store_release(&ldata->commit_head, ldata->read_head);
1668 if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
1669 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1670 if (waitqueue_active(&tty->read_wait))
1671 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1676 * n_tty_receive_buf_common - process input
1677 * @tty: device to receive input
1679 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1680 * @count: number of input chars in @cp
1682 * Called by the terminal driver when a block of characters has
1683 * been received. This function must be called from soft contexts
1684 * not from interrupt context. The driver is responsible for making
1685 * calls one at a time and in order (or using flush_to_ldisc)
1687 * Returns the # of input chars from @cp which were processed.
1689 * In canonical mode, the maximum line length is 4096 chars (including
1690 * the line termination char); lines longer than 4096 chars are
1691 * truncated. After 4095 chars, input data is still processed but
1692 * not stored. Overflow processing ensures the tty can always
1693 * receive more input until at least one line can be read.
1695 * In non-canonical mode, the read buffer will only accept 4095 chars;
1696 * this provides the necessary space for a newline char if the input
1697 * mode is switched to canonical.
1699 * Note it is possible for the read buffer to _contain_ 4096 chars
1700 * in non-canonical mode: the read buffer could already contain the
1701 * maximum canon line of 4096 chars when the mode is switched to
1704 * n_tty_receive_buf()/producer path:
1705 * claims non-exclusive termios_rwsem
1706 * publishes commit_head or canon_head
1709 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1710 char *fp, int count, int flow)
1712 struct n_tty_data *ldata = tty->disc_data;
1713 int room, n, rcvd = 0, overflow;
1715 down_read(&tty->termios_rwsem);
1719 * When PARMRK is set, each input char may take up to 3 chars
1720 * in the read buf; reduce the buffer space avail by 3x
1722 * If we are doing input canonicalization, and there are no
1723 * pending newlines, let characters through without limit, so
1724 * that erase characters will be handled. Other excess
1725 * characters will be beeped.
1727 * paired with store in *_copy_from_read_buf() -- guarantees
1728 * the consumer has loaded the data in read_buf up to the new
1729 * read_tail (so this producer will not overwrite unread data)
1731 size_t tail = smp_load_acquire(&ldata->read_tail);
1733 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1735 room = (room + 2) / 3;
1738 overflow = ldata->icanon && ldata->canon_head == tail;
1739 if (overflow && room < 0)
1742 ldata->no_room = flow && !room;
1746 n = min(count, room);
1750 /* ignore parity errors if handling overflow */
1751 if (!overflow || !fp || *fp != TTY_PARITY)
1752 __receive_buf(tty, cp, fp, n);
1761 tty->receive_room = room;
1763 /* Unthrottle if handling overflow on pty */
1764 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1766 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1767 tty_unthrottle_safe(tty);
1768 __tty_set_flow_change(tty, 0);
1771 n_tty_check_throttle(tty);
1773 up_read(&tty->termios_rwsem);
1778 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1779 char *fp, int count)
1781 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1784 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1785 char *fp, int count)
1787 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1790 int is_ignored(int sig)
1792 return (sigismember(¤t->blocked, sig) ||
1793 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1797 * n_tty_set_termios - termios data changed
1799 * @old: previous data
1801 * Called by the tty layer when the user changes termios flags so
1802 * that the line discipline can plan ahead. This function cannot sleep
1803 * and is protected from re-entry by the tty layer. The user is
1804 * guaranteed that this function will not be re-entered or in progress
1805 * when the ldisc is closed.
1807 * Locking: Caller holds tty->termios_rwsem
1810 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1812 struct n_tty_data *ldata = tty->disc_data;
1814 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1815 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1816 ldata->line_start = ldata->read_tail;
1817 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1818 ldata->canon_head = ldata->read_tail;
1821 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1823 ldata->canon_head = ldata->read_head;
1826 ldata->commit_head = ldata->read_head;
1831 ldata->icanon = (L_ICANON(tty) != 0);
1833 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1834 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1835 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1837 bitmap_zero(ldata->char_map, 256);
1839 if (I_IGNCR(tty) || I_ICRNL(tty))
1840 set_bit('\r', ldata->char_map);
1842 set_bit('\n', ldata->char_map);
1844 if (L_ICANON(tty)) {
1845 set_bit(ERASE_CHAR(tty), ldata->char_map);
1846 set_bit(KILL_CHAR(tty), ldata->char_map);
1847 set_bit(EOF_CHAR(tty), ldata->char_map);
1848 set_bit('\n', ldata->char_map);
1849 set_bit(EOL_CHAR(tty), ldata->char_map);
1850 if (L_IEXTEN(tty)) {
1851 set_bit(WERASE_CHAR(tty), ldata->char_map);
1852 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1853 set_bit(EOL2_CHAR(tty), ldata->char_map);
1855 set_bit(REPRINT_CHAR(tty),
1860 set_bit(START_CHAR(tty), ldata->char_map);
1861 set_bit(STOP_CHAR(tty), ldata->char_map);
1864 set_bit(INTR_CHAR(tty), ldata->char_map);
1865 set_bit(QUIT_CHAR(tty), ldata->char_map);
1866 set_bit(SUSP_CHAR(tty), ldata->char_map);
1868 clear_bit(__DISABLED_CHAR, ldata->char_map);
1870 ldata->real_raw = 0;
1873 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1874 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1875 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1876 ldata->real_raw = 1;
1878 ldata->real_raw = 0;
1881 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1882 * been stopped by STOP_CHAR(tty) before it.
1884 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1886 process_echoes(tty);
1889 /* The termios change make the tty ready for I/O */
1890 if (waitqueue_active(&tty->write_wait))
1891 wake_up_interruptible(&tty->write_wait);
1892 if (waitqueue_active(&tty->read_wait))
1893 wake_up_interruptible(&tty->read_wait);
1897 * n_tty_close - close the ldisc for this tty
1900 * Called from the terminal layer when this line discipline is
1901 * being shut down, either because of a close or becsuse of a
1902 * discipline change. The function will not be called while other
1903 * ldisc methods are in progress.
1906 static void n_tty_close(struct tty_struct *tty)
1908 struct n_tty_data *ldata = tty->disc_data;
1911 n_tty_packet_mode_flush(tty);
1914 tty->disc_data = NULL;
1918 * n_tty_open - open an ldisc
1919 * @tty: terminal to open
1921 * Called when this line discipline is being attached to the
1922 * terminal device. Can sleep. Called serialized so that no
1923 * other events will occur in parallel. No further open will occur
1927 static int n_tty_open(struct tty_struct *tty)
1929 struct n_tty_data *ldata;
1931 /* Currently a malloc failure here can panic */
1932 ldata = vmalloc(sizeof(*ldata));
1936 ldata->overrun_time = jiffies;
1937 mutex_init(&ldata->atomic_read_lock);
1938 mutex_init(&ldata->output_lock);
1940 tty->disc_data = ldata;
1941 reset_buffer_flags(tty->disc_data);
1943 ldata->canon_column = 0;
1944 ldata->minimum_to_wake = 1;
1945 ldata->num_overrun = 0;
1949 /* indicate buffer work may resume */
1950 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1951 n_tty_set_termios(tty, NULL);
1952 tty_unthrottle(tty);
1959 static inline int input_available_p(struct tty_struct *tty, int poll)
1961 struct n_tty_data *ldata = tty->disc_data;
1962 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1964 if (ldata->icanon && !L_EXTPROC(tty))
1965 return ldata->canon_head != ldata->read_tail;
1967 return ldata->commit_head - ldata->read_tail >= amt;
1970 static inline int check_other_done(struct tty_struct *tty)
1972 int done = test_bit(TTY_OTHER_DONE, &tty->flags);
1974 /* paired with cmpxchg() in check_other_closed(); ensures
1975 * read buffer head index is not stale
1977 smp_mb__after_atomic();
1983 * copy_from_read_buf - copy read data directly
1984 * @tty: terminal device
1988 * Helper function to speed up n_tty_read. It is only called when
1989 * ICANON is off; it copies characters straight from the tty queue to
1990 * user space directly. It can be profitably called twice; once to
1991 * drain the space from the tail pointer to the (physical) end of the
1992 * buffer, and once to drain the space from the (physical) beginning of
1993 * the buffer to head pointer.
1995 * Called under the ldata->atomic_read_lock sem
1997 * n_tty_read()/consumer path:
1998 * caller holds non-exclusive termios_rwsem
1999 * read_tail published
2002 static int copy_from_read_buf(struct tty_struct *tty,
2003 unsigned char __user **b,
2007 struct n_tty_data *ldata = tty->disc_data;
2011 size_t head = smp_load_acquire(&ldata->commit_head);
2012 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2015 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
2018 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
2020 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
2021 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
2023 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
2024 /* Turn single EOF into zero-length read */
2025 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
2026 (head == ldata->read_tail))
2035 * canon_copy_from_read_buf - copy read data in canonical mode
2036 * @tty: terminal device
2040 * Helper function for n_tty_read. It is only called when ICANON is on;
2041 * it copies one line of input up to and including the line-delimiting
2042 * character into the user-space buffer.
2044 * NB: When termios is changed from non-canonical to canonical mode and
2045 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2046 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2047 * This causes data already processed as input to be immediately available
2048 * as input although a newline has not been received.
2050 * Called under the atomic_read_lock mutex
2052 * n_tty_read()/consumer path:
2053 * caller holds non-exclusive termios_rwsem
2054 * read_tail published
2057 static int canon_copy_from_read_buf(struct tty_struct *tty,
2058 unsigned char __user **b,
2061 struct n_tty_data *ldata = tty->disc_data;
2062 size_t n, size, more, c;
2068 /* N.B. avoid overrun if nr == 0 */
2069 n = min(*nr, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2073 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2074 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2076 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2077 __func__, *nr, tail, n, size);
2079 eol = find_next_bit(ldata->read_flags, size, tail);
2080 more = n - (size - tail);
2081 if (eol == N_TTY_BUF_SIZE && more) {
2082 /* scan wrapped without finding set bit */
2083 eol = find_next_bit(ldata->read_flags, more, 0);
2086 } else if (eol != size)
2089 size = N_TTY_BUF_SIZE - tail;
2091 if (n > N_TTY_BUF_SIZE)
2092 n += N_TTY_BUF_SIZE;
2096 if (found && !ldata->push && read_buf(ldata, eol) == __DISABLED_CHAR) {
2098 eof_push = !n && ldata->read_tail != ldata->line_start;
2101 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
2102 __func__, eol, found, n, c, size, more);
2105 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), size);
2108 ret = tty_copy_to_user(tty, *b + size, ldata->read_buf, n - size);
2110 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), n);
2118 clear_bit(eol, ldata->read_flags);
2119 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2123 ldata->line_start = ldata->read_tail;
2126 tty_audit_push(tty);
2128 return eof_push ? -EAGAIN : 0;
2131 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2135 * job_control - check job control
2137 * @file: file handle
2139 * Perform job control management checks on this file/tty descriptor
2140 * and if appropriate send any needed signals and return a negative
2141 * error code if action should be taken.
2143 * Locking: redirected write test is safe
2144 * current->signal->tty check is safe
2145 * ctrl_lock to safely reference tty->pgrp
2148 static int job_control(struct tty_struct *tty, struct file *file)
2152 /* Job control check -- must be done at start and after
2153 every sleep (POSIX.1 7.1.1.4). */
2154 /* NOTE: not yet done after every sleep pending a thorough
2155 check of the logic of this change. -- jlc */
2156 /* don't stop on /dev/console */
2157 if (file->f_op->write == redirected_tty_write ||
2158 current->signal->tty != tty)
2162 pgrp = task_pgrp(current);
2164 spin_lock_irq(&tty->ctrl_lock);
2166 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
2167 else if (pgrp != tty->pgrp) {
2168 spin_unlock_irq(&tty->ctrl_lock);
2169 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) {
2173 kill_pgrp(pgrp, SIGTTIN, 1);
2175 set_thread_flag(TIF_SIGPENDING);
2176 return -ERESTARTSYS;
2178 spin_unlock_irq(&tty->ctrl_lock);
2185 * n_tty_read - read function for tty
2187 * @file: file object
2188 * @buf: userspace buffer pointer
2191 * Perform reads for the line discipline. We are guaranteed that the
2192 * line discipline will not be closed under us but we may get multiple
2193 * parallel readers and must handle this ourselves. We may also get
2194 * a hangup. Always called in user context, may sleep.
2196 * This code must be sure never to sleep through a hangup.
2198 * n_tty_read()/consumer path:
2199 * claims non-exclusive termios_rwsem
2200 * publishes read_tail
2203 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2204 unsigned char __user *buf, size_t nr)
2206 struct n_tty_data *ldata = tty->disc_data;
2207 unsigned char __user *b = buf;
2208 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2216 c = job_control(tty, file);
2221 * Internal serialization of reads.
2223 if (file->f_flags & O_NONBLOCK) {
2224 if (!mutex_trylock(&ldata->atomic_read_lock))
2227 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2228 return -ERESTARTSYS;
2231 down_read(&tty->termios_rwsem);
2234 timeout = MAX_SCHEDULE_TIMEOUT;
2235 if (!ldata->icanon) {
2236 minimum = MIN_CHAR(tty);
2238 time = (HZ / 10) * TIME_CHAR(tty);
2240 ldata->minimum_to_wake = 1;
2241 else if (!waitqueue_active(&tty->read_wait) ||
2242 (ldata->minimum_to_wake > minimum))
2243 ldata->minimum_to_wake = minimum;
2245 timeout = (HZ / 10) * TIME_CHAR(tty);
2246 ldata->minimum_to_wake = minimum = 1;
2250 packet = tty->packet;
2251 tail = ldata->read_tail;
2253 add_wait_queue(&tty->read_wait, &wait);
2255 /* First test for status change. */
2256 if (packet && tty->link->ctrl_status) {
2260 spin_lock_irq(&tty->link->ctrl_lock);
2261 cs = tty->link->ctrl_status;
2262 tty->link->ctrl_status = 0;
2263 spin_unlock_irq(&tty->link->ctrl_lock);
2264 if (tty_put_user(tty, cs, b++)) {
2273 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2274 ((minimum - (b - buf)) >= 1))
2275 ldata->minimum_to_wake = (minimum - (b - buf));
2277 done = check_other_done(tty);
2279 if (!input_available_p(tty, 0)) {
2284 if (tty_hung_up_p(file))
2288 if (file->f_flags & O_NONBLOCK) {
2292 if (signal_pending(current)) {
2293 retval = -ERESTARTSYS;
2296 up_read(&tty->termios_rwsem);
2298 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2301 down_read(&tty->termios_rwsem);
2305 if (ldata->icanon && !L_EXTPROC(tty)) {
2306 retval = canon_copy_from_read_buf(tty, &b, &nr);
2307 if (retval == -EAGAIN) {
2315 /* Deal with packet mode. */
2316 if (packet && b == buf) {
2317 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2325 uncopied = copy_from_read_buf(tty, &b, &nr);
2326 uncopied += copy_from_read_buf(tty, &b, &nr);
2333 n_tty_check_unthrottle(tty);
2335 if (b - buf >= minimum)
2340 if (tail != ldata->read_tail)
2341 n_tty_kick_worker(tty);
2342 up_read(&tty->termios_rwsem);
2344 remove_wait_queue(&tty->read_wait, &wait);
2345 if (!waitqueue_active(&tty->read_wait))
2346 ldata->minimum_to_wake = minimum;
2348 mutex_unlock(&ldata->atomic_read_lock);
2357 * n_tty_write - write function for tty
2359 * @file: file object
2360 * @buf: userspace buffer pointer
2363 * Write function of the terminal device. This is serialized with
2364 * respect to other write callers but not to termios changes, reads
2365 * and other such events. Since the receive code will echo characters,
2366 * thus calling driver write methods, the output_lock is used in
2367 * the output processing functions called here as well as in the
2368 * echo processing function to protect the column state and space
2369 * left in the buffer.
2371 * This code must be sure never to sleep through a hangup.
2373 * Locking: output_lock to protect column state and space left
2374 * (note that the process_output*() functions take this
2378 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2379 const unsigned char *buf, size_t nr)
2381 const unsigned char *b = buf;
2382 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2386 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2387 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2388 retval = tty_check_change(tty);
2393 down_read(&tty->termios_rwsem);
2395 /* Write out any echoed characters that are still pending */
2396 process_echoes(tty);
2398 add_wait_queue(&tty->write_wait, &wait);
2400 if (signal_pending(current)) {
2401 retval = -ERESTARTSYS;
2404 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2410 ssize_t num = process_output_block(tty, b, nr);
2422 if (process_output(c, tty) < 0)
2426 if (tty->ops->flush_chars)
2427 tty->ops->flush_chars(tty);
2429 struct n_tty_data *ldata = tty->disc_data;
2432 mutex_lock(&ldata->output_lock);
2433 c = tty->ops->write(tty, b, nr);
2434 mutex_unlock(&ldata->output_lock);
2447 if (file->f_flags & O_NONBLOCK) {
2451 up_read(&tty->termios_rwsem);
2453 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2455 down_read(&tty->termios_rwsem);
2458 remove_wait_queue(&tty->write_wait, &wait);
2459 if (b - buf != nr && tty->fasync)
2460 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2461 up_read(&tty->termios_rwsem);
2462 return (b - buf) ? b - buf : retval;
2466 * n_tty_poll - poll method for N_TTY
2467 * @tty: terminal device
2468 * @file: file accessing it
2471 * Called when the line discipline is asked to poll() for data or
2472 * for special events. This code is not serialized with respect to
2473 * other events save open/close.
2475 * This code must be sure never to sleep through a hangup.
2476 * Called without the kernel lock held - fine
2479 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2482 struct n_tty_data *ldata = tty->disc_data;
2483 unsigned int mask = 0;
2485 poll_wait(file, &tty->read_wait, wait);
2486 poll_wait(file, &tty->write_wait, wait);
2487 if (check_other_done(tty))
2489 if (input_available_p(tty, 1))
2490 mask |= POLLIN | POLLRDNORM;
2491 if (tty->packet && tty->link->ctrl_status)
2492 mask |= POLLPRI | POLLIN | POLLRDNORM;
2493 if (tty_hung_up_p(file))
2495 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2496 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2497 ldata->minimum_to_wake = MIN_CHAR(tty);
2499 ldata->minimum_to_wake = 1;
2501 if (tty->ops->write && !tty_is_writelocked(tty) &&
2502 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2503 tty_write_room(tty) > 0)
2504 mask |= POLLOUT | POLLWRNORM;
2508 static unsigned long inq_canon(struct n_tty_data *ldata)
2510 size_t nr, head, tail;
2512 if (ldata->canon_head == ldata->read_tail)
2514 head = ldata->canon_head;
2515 tail = ldata->read_tail;
2517 /* Skip EOF-chars.. */
2518 while (head != tail) {
2519 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2520 read_buf(ldata, tail) == __DISABLED_CHAR)
2527 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2528 unsigned int cmd, unsigned long arg)
2530 struct n_tty_data *ldata = tty->disc_data;
2535 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2537 down_write(&tty->termios_rwsem);
2539 retval = inq_canon(ldata);
2541 retval = read_cnt(ldata);
2542 up_write(&tty->termios_rwsem);
2543 return put_user(retval, (unsigned int __user *) arg);
2545 return n_tty_ioctl_helper(tty, file, cmd, arg);
2549 static void n_tty_fasync(struct tty_struct *tty, int on)
2551 struct n_tty_data *ldata = tty->disc_data;
2553 if (!waitqueue_active(&tty->read_wait)) {
2555 ldata->minimum_to_wake = 1;
2556 else if (!tty->fasync)
2557 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2561 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2562 .magic = TTY_LDISC_MAGIC,
2565 .close = n_tty_close,
2566 .flush_buffer = n_tty_flush_buffer,
2567 .chars_in_buffer = n_tty_chars_in_buffer,
2569 .write = n_tty_write,
2570 .ioctl = n_tty_ioctl,
2571 .set_termios = n_tty_set_termios,
2573 .receive_buf = n_tty_receive_buf,
2574 .write_wakeup = n_tty_write_wakeup,
2575 .fasync = n_tty_fasync,
2576 .receive_buf2 = n_tty_receive_buf2,
2580 * n_tty_inherit_ops - inherit N_TTY methods
2581 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2583 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2587 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2589 *ops = tty_ldisc_N_TTY;
2591 ops->refcount = ops->flags = 0;
2593 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);