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 n_tty_data *ldata = tty->disc_data;
1114 struct pid *tty_pgrp = tty_get_pgrp(tty);
1116 kill_pgrp(tty_pgrp, sig, 1);
1120 if (!L_NOFLSH(tty)) {
1121 up_read(&tty->termios_rwsem);
1122 down_write(&tty->termios_rwsem);
1124 /* clear echo buffer */
1125 mutex_lock(&ldata->output_lock);
1126 ldata->echo_head = ldata->echo_tail = 0;
1127 ldata->echo_mark = ldata->echo_commit = 0;
1128 mutex_unlock(&ldata->output_lock);
1130 /* clear output buffer */
1131 tty_driver_flush_buffer(tty);
1133 /* clear input buffer */
1134 reset_buffer_flags(tty->disc_data);
1136 /* notify pty master of flush */
1138 n_tty_packet_mode_flush(tty);
1140 up_write(&tty->termios_rwsem);
1141 down_read(&tty->termios_rwsem);
1146 * n_tty_receive_break - handle break
1149 * An RS232 break event has been hit in the incoming bitstream. This
1150 * can cause a variety of events depending upon the termios settings.
1152 * n_tty_receive_buf()/producer path:
1153 * caller holds non-exclusive termios_rwsem
1155 * Note: may get exclusive termios_rwsem if flushing input buffer
1158 static void n_tty_receive_break(struct tty_struct *tty)
1160 struct n_tty_data *ldata = tty->disc_data;
1164 if (I_BRKINT(tty)) {
1168 if (I_PARMRK(tty)) {
1169 put_tty_queue('\377', ldata);
1170 put_tty_queue('\0', ldata);
1172 put_tty_queue('\0', ldata);
1173 if (waitqueue_active(&tty->read_wait))
1174 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1178 * n_tty_receive_overrun - handle overrun reporting
1181 * Data arrived faster than we could process it. While the tty
1182 * driver has flagged this the bits that were missed are gone
1185 * Called from the receive_buf path so single threaded. Does not
1186 * need locking as num_overrun and overrun_time are function
1190 static void n_tty_receive_overrun(struct tty_struct *tty)
1192 struct n_tty_data *ldata = tty->disc_data;
1195 ldata->num_overrun++;
1196 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1197 time_after(ldata->overrun_time, jiffies)) {
1198 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1200 ldata->num_overrun);
1201 ldata->overrun_time = jiffies;
1202 ldata->num_overrun = 0;
1207 * n_tty_receive_parity_error - error notifier
1208 * @tty: terminal device
1211 * Process a parity error and queue the right data to indicate
1212 * the error case if necessary.
1214 * n_tty_receive_buf()/producer path:
1215 * caller holds non-exclusive termios_rwsem
1217 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1219 struct n_tty_data *ldata = tty->disc_data;
1224 if (I_PARMRK(tty)) {
1225 put_tty_queue('\377', ldata);
1226 put_tty_queue('\0', ldata);
1227 put_tty_queue(c, ldata);
1229 put_tty_queue('\0', ldata);
1231 put_tty_queue(c, ldata);
1232 if (waitqueue_active(&tty->read_wait))
1233 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1237 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1246 process_echoes(tty);
1251 * n_tty_receive_char - perform processing
1252 * @tty: terminal device
1255 * Process an individual character of input received from the driver.
1256 * This is serialized with respect to itself by the rules for the
1259 * n_tty_receive_buf()/producer path:
1260 * caller holds non-exclusive termios_rwsem
1261 * publishes canon_head if canonical mode is active
1263 * Returns 1 if LNEXT was received, else returns 0
1267 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1269 struct n_tty_data *ldata = tty->disc_data;
1272 if (c == START_CHAR(tty)) {
1274 process_echoes(tty);
1277 if (c == STOP_CHAR(tty)) {
1284 if (c == INTR_CHAR(tty)) {
1285 n_tty_receive_signal_char(tty, SIGINT, c);
1287 } else if (c == QUIT_CHAR(tty)) {
1288 n_tty_receive_signal_char(tty, SIGQUIT, c);
1290 } else if (c == SUSP_CHAR(tty)) {
1291 n_tty_receive_signal_char(tty, SIGTSTP, c);
1296 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1298 process_echoes(tty);
1306 } else if (c == '\n' && I_INLCR(tty))
1309 if (ldata->icanon) {
1310 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1311 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1316 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1319 finish_erasing(ldata);
1320 if (L_ECHOCTL(tty)) {
1321 echo_char_raw('^', ldata);
1322 echo_char_raw('\b', ldata);
1328 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1329 size_t tail = ldata->canon_head;
1331 finish_erasing(ldata);
1333 echo_char_raw('\n', ldata);
1334 while (tail != ldata->read_head) {
1335 echo_char(read_buf(ldata, tail), tty);
1342 if (L_ECHO(tty) || L_ECHONL(tty)) {
1343 echo_char_raw('\n', ldata);
1346 goto handle_newline;
1348 if (c == EOF_CHAR(tty)) {
1349 c = __DISABLED_CHAR;
1350 goto handle_newline;
1352 if ((c == EOL_CHAR(tty)) ||
1353 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1355 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1358 /* Record the column of first canon char. */
1359 if (ldata->canon_head == ldata->read_head)
1360 echo_set_canon_col(ldata);
1365 * XXX does PARMRK doubling happen for
1366 * EOL_CHAR and EOL2_CHAR?
1368 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1369 put_tty_queue(c, ldata);
1372 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1373 put_tty_queue(c, ldata);
1374 smp_store_release(&ldata->canon_head, ldata->read_head);
1375 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1376 if (waitqueue_active(&tty->read_wait))
1377 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1383 finish_erasing(ldata);
1385 echo_char_raw('\n', ldata);
1387 /* Record the column of first canon char. */
1388 if (ldata->canon_head == ldata->read_head)
1389 echo_set_canon_col(ldata);
1395 /* PARMRK doubling check */
1396 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1397 put_tty_queue(c, ldata);
1399 put_tty_queue(c, ldata);
1404 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1406 struct n_tty_data *ldata = tty->disc_data;
1408 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1410 process_echoes(tty);
1413 finish_erasing(ldata);
1414 /* Record the column of first canon char. */
1415 if (ldata->canon_head == ldata->read_head)
1416 echo_set_canon_col(ldata);
1420 /* PARMRK doubling check */
1421 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1422 put_tty_queue(c, ldata);
1423 put_tty_queue(c, ldata);
1426 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1428 n_tty_receive_char_inline(tty, c);
1432 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1434 struct n_tty_data *ldata = tty->disc_data;
1436 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1438 process_echoes(tty);
1441 finish_erasing(ldata);
1442 /* Record the column of first canon char. */
1443 if (ldata->canon_head == ldata->read_head)
1444 echo_set_canon_col(ldata);
1448 put_tty_queue(c, ldata);
1451 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1455 if (I_IUCLC(tty) && L_IEXTEN(tty))
1459 if (c == STOP_CHAR(tty))
1461 else if (c == START_CHAR(tty) ||
1462 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1463 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1464 c != SUSP_CHAR(tty))) {
1466 process_echoes(tty);
1472 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1478 n_tty_receive_break(tty);
1482 n_tty_receive_parity_error(tty, c);
1485 n_tty_receive_overrun(tty);
1488 printk(KERN_ERR "%s: unknown flag %d\n",
1489 tty_name(tty, buf), flag);
1495 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1497 struct n_tty_data *ldata = tty->disc_data;
1500 if (likely(flag == TTY_NORMAL)) {
1503 if (I_IUCLC(tty) && L_IEXTEN(tty))
1505 n_tty_receive_char(tty, c);
1507 n_tty_receive_char_flagged(tty, c, flag);
1511 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1512 char *fp, int count)
1514 struct n_tty_data *ldata = tty->disc_data;
1517 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1518 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1519 memcpy(read_buf_addr(ldata, head), cp, n);
1520 ldata->read_head += n;
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 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1532 char *fp, int count)
1534 struct n_tty_data *ldata = tty->disc_data;
1535 char flag = TTY_NORMAL;
1540 if (likely(flag == TTY_NORMAL))
1541 put_tty_queue(*cp++, ldata);
1543 n_tty_receive_char_flagged(tty, *cp++, flag);
1548 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1549 char *fp, int count)
1551 char flag = TTY_NORMAL;
1556 if (likely(flag == TTY_NORMAL))
1557 n_tty_receive_char_closing(tty, *cp++);
1559 n_tty_receive_char_flagged(tty, *cp++, flag);
1564 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1565 char *fp, int count)
1567 struct n_tty_data *ldata = tty->disc_data;
1568 char flag = TTY_NORMAL;
1573 if (likely(flag == TTY_NORMAL)) {
1574 unsigned char c = *cp++;
1578 if (I_IUCLC(tty) && L_IEXTEN(tty))
1580 if (L_EXTPROC(tty)) {
1581 put_tty_queue(c, ldata);
1584 if (!test_bit(c, ldata->char_map))
1585 n_tty_receive_char_inline(tty, c);
1586 else if (n_tty_receive_char_special(tty, c) && count) {
1589 n_tty_receive_char_lnext(tty, *cp++, flag);
1593 n_tty_receive_char_flagged(tty, *cp++, flag);
1598 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1599 char *fp, int count)
1601 struct n_tty_data *ldata = tty->disc_data;
1602 char flag = TTY_NORMAL;
1607 if (likely(flag == TTY_NORMAL)) {
1608 unsigned char c = *cp++;
1610 if (!test_bit(c, ldata->char_map))
1611 n_tty_receive_char_fast(tty, c);
1612 else if (n_tty_receive_char_special(tty, c) && count) {
1615 n_tty_receive_char_lnext(tty, *cp++, flag);
1619 n_tty_receive_char_flagged(tty, *cp++, flag);
1623 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1624 char *fp, int count)
1626 struct n_tty_data *ldata = tty->disc_data;
1627 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1629 if (ldata->real_raw)
1630 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1631 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1632 n_tty_receive_buf_raw(tty, cp, fp, count);
1633 else if (tty->closing && !L_EXTPROC(tty))
1634 n_tty_receive_buf_closing(tty, cp, fp, count);
1637 char flag = TTY_NORMAL;
1641 n_tty_receive_char_lnext(tty, *cp++, flag);
1645 if (!preops && !I_PARMRK(tty))
1646 n_tty_receive_buf_fast(tty, cp, fp, count);
1648 n_tty_receive_buf_standard(tty, cp, fp, count);
1651 if (tty->ops->flush_chars)
1652 tty->ops->flush_chars(tty);
1655 if (ldata->icanon && !L_EXTPROC(tty))
1658 /* publish read_head to consumer */
1659 smp_store_release(&ldata->commit_head, ldata->read_head);
1661 if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
1662 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1663 if (waitqueue_active(&tty->read_wait))
1664 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1669 * n_tty_receive_buf_common - process input
1670 * @tty: device to receive input
1672 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1673 * @count: number of input chars in @cp
1675 * Called by the terminal driver when a block of characters has
1676 * been received. This function must be called from soft contexts
1677 * not from interrupt context. The driver is responsible for making
1678 * calls one at a time and in order (or using flush_to_ldisc)
1680 * Returns the # of input chars from @cp which were processed.
1682 * In canonical mode, the maximum line length is 4096 chars (including
1683 * the line termination char); lines longer than 4096 chars are
1684 * truncated. After 4095 chars, input data is still processed but
1685 * not stored. Overflow processing ensures the tty can always
1686 * receive more input until at least one line can be read.
1688 * In non-canonical mode, the read buffer will only accept 4095 chars;
1689 * this provides the necessary space for a newline char if the input
1690 * mode is switched to canonical.
1692 * Note it is possible for the read buffer to _contain_ 4096 chars
1693 * in non-canonical mode: the read buffer could already contain the
1694 * maximum canon line of 4096 chars when the mode is switched to
1697 * n_tty_receive_buf()/producer path:
1698 * claims non-exclusive termios_rwsem
1699 * publishes commit_head or canon_head
1702 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1703 char *fp, int count, int flow)
1705 struct n_tty_data *ldata = tty->disc_data;
1706 int room, n, rcvd = 0, overflow;
1708 down_read(&tty->termios_rwsem);
1712 * When PARMRK is set, each input char may take up to 3 chars
1713 * in the read buf; reduce the buffer space avail by 3x
1715 * If we are doing input canonicalization, and there are no
1716 * pending newlines, let characters through without limit, so
1717 * that erase characters will be handled. Other excess
1718 * characters will be beeped.
1720 * paired with store in *_copy_from_read_buf() -- guarantees
1721 * the consumer has loaded the data in read_buf up to the new
1722 * read_tail (so this producer will not overwrite unread data)
1724 size_t tail = smp_load_acquire(&ldata->read_tail);
1726 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1728 room = (room + 2) / 3;
1731 overflow = ldata->icanon && ldata->canon_head == tail;
1732 if (overflow && room < 0)
1735 ldata->no_room = flow && !room;
1739 n = min(count, room);
1743 /* ignore parity errors if handling overflow */
1744 if (!overflow || !fp || *fp != TTY_PARITY)
1745 __receive_buf(tty, cp, fp, n);
1754 tty->receive_room = room;
1756 /* Unthrottle if handling overflow on pty */
1757 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1759 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1760 tty_unthrottle_safe(tty);
1761 __tty_set_flow_change(tty, 0);
1764 n_tty_check_throttle(tty);
1766 up_read(&tty->termios_rwsem);
1771 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1772 char *fp, int count)
1774 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1777 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1778 char *fp, int count)
1780 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1783 int is_ignored(int sig)
1785 return (sigismember(¤t->blocked, sig) ||
1786 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1790 * n_tty_set_termios - termios data changed
1792 * @old: previous data
1794 * Called by the tty layer when the user changes termios flags so
1795 * that the line discipline can plan ahead. This function cannot sleep
1796 * and is protected from re-entry by the tty layer. The user is
1797 * guaranteed that this function will not be re-entered or in progress
1798 * when the ldisc is closed.
1800 * Locking: Caller holds tty->termios_rwsem
1803 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1805 struct n_tty_data *ldata = tty->disc_data;
1807 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1808 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1809 ldata->line_start = ldata->read_tail;
1810 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1811 ldata->canon_head = ldata->read_tail;
1814 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1816 ldata->canon_head = ldata->read_head;
1819 ldata->commit_head = ldata->read_head;
1824 ldata->icanon = (L_ICANON(tty) != 0);
1826 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1827 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1828 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1830 bitmap_zero(ldata->char_map, 256);
1832 if (I_IGNCR(tty) || I_ICRNL(tty))
1833 set_bit('\r', ldata->char_map);
1835 set_bit('\n', ldata->char_map);
1837 if (L_ICANON(tty)) {
1838 set_bit(ERASE_CHAR(tty), ldata->char_map);
1839 set_bit(KILL_CHAR(tty), ldata->char_map);
1840 set_bit(EOF_CHAR(tty), ldata->char_map);
1841 set_bit('\n', ldata->char_map);
1842 set_bit(EOL_CHAR(tty), ldata->char_map);
1843 if (L_IEXTEN(tty)) {
1844 set_bit(WERASE_CHAR(tty), ldata->char_map);
1845 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1846 set_bit(EOL2_CHAR(tty), ldata->char_map);
1848 set_bit(REPRINT_CHAR(tty),
1853 set_bit(START_CHAR(tty), ldata->char_map);
1854 set_bit(STOP_CHAR(tty), ldata->char_map);
1857 set_bit(INTR_CHAR(tty), ldata->char_map);
1858 set_bit(QUIT_CHAR(tty), ldata->char_map);
1859 set_bit(SUSP_CHAR(tty), ldata->char_map);
1861 clear_bit(__DISABLED_CHAR, ldata->char_map);
1863 ldata->real_raw = 0;
1866 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1867 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1868 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1869 ldata->real_raw = 1;
1871 ldata->real_raw = 0;
1874 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1875 * been stopped by STOP_CHAR(tty) before it.
1877 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1879 process_echoes(tty);
1882 /* The termios change make the tty ready for I/O */
1883 if (waitqueue_active(&tty->write_wait))
1884 wake_up_interruptible(&tty->write_wait);
1885 if (waitqueue_active(&tty->read_wait))
1886 wake_up_interruptible(&tty->read_wait);
1890 * n_tty_close - close the ldisc for this tty
1893 * Called from the terminal layer when this line discipline is
1894 * being shut down, either because of a close or becsuse of a
1895 * discipline change. The function will not be called while other
1896 * ldisc methods are in progress.
1899 static void n_tty_close(struct tty_struct *tty)
1901 struct n_tty_data *ldata = tty->disc_data;
1904 n_tty_packet_mode_flush(tty);
1907 tty->disc_data = NULL;
1911 * n_tty_open - open an ldisc
1912 * @tty: terminal to open
1914 * Called when this line discipline is being attached to the
1915 * terminal device. Can sleep. Called serialized so that no
1916 * other events will occur in parallel. No further open will occur
1920 static int n_tty_open(struct tty_struct *tty)
1922 struct n_tty_data *ldata;
1924 /* Currently a malloc failure here can panic */
1925 ldata = vmalloc(sizeof(*ldata));
1929 ldata->overrun_time = jiffies;
1930 mutex_init(&ldata->atomic_read_lock);
1931 mutex_init(&ldata->output_lock);
1933 tty->disc_data = ldata;
1934 reset_buffer_flags(tty->disc_data);
1936 ldata->canon_column = 0;
1937 ldata->minimum_to_wake = 1;
1938 ldata->num_overrun = 0;
1942 /* indicate buffer work may resume */
1943 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1944 n_tty_set_termios(tty, NULL);
1945 tty_unthrottle(tty);
1952 static inline int input_available_p(struct tty_struct *tty, int poll)
1954 struct n_tty_data *ldata = tty->disc_data;
1955 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1957 if (ldata->icanon && !L_EXTPROC(tty))
1958 return ldata->canon_head != ldata->read_tail;
1960 return ldata->commit_head - ldata->read_tail >= amt;
1963 static inline int check_other_done(struct tty_struct *tty)
1965 int done = test_bit(TTY_OTHER_DONE, &tty->flags);
1967 /* paired with cmpxchg() in check_other_closed(); ensures
1968 * read buffer head index is not stale
1970 smp_mb__after_atomic();
1976 * copy_from_read_buf - copy read data directly
1977 * @tty: terminal device
1981 * Helper function to speed up n_tty_read. It is only called when
1982 * ICANON is off; it copies characters straight from the tty queue to
1983 * user space directly. It can be profitably called twice; once to
1984 * drain the space from the tail pointer to the (physical) end of the
1985 * buffer, and once to drain the space from the (physical) beginning of
1986 * the buffer to head pointer.
1988 * Called under the ldata->atomic_read_lock sem
1990 * n_tty_read()/consumer path:
1991 * caller holds non-exclusive termios_rwsem
1992 * read_tail published
1995 static int copy_from_read_buf(struct tty_struct *tty,
1996 unsigned char __user **b,
2000 struct n_tty_data *ldata = tty->disc_data;
2004 size_t head = smp_load_acquire(&ldata->commit_head);
2005 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2008 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
2011 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
2013 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
2014 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
2016 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
2017 /* Turn single EOF into zero-length read */
2018 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
2019 (head == ldata->read_tail))
2028 * canon_copy_from_read_buf - copy read data in canonical mode
2029 * @tty: terminal device
2033 * Helper function for n_tty_read. It is only called when ICANON is on;
2034 * it copies one line of input up to and including the line-delimiting
2035 * character into the user-space buffer.
2037 * NB: When termios is changed from non-canonical to canonical mode and
2038 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2039 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2040 * This causes data already processed as input to be immediately available
2041 * as input although a newline has not been received.
2043 * Called under the atomic_read_lock mutex
2045 * n_tty_read()/consumer path:
2046 * caller holds non-exclusive termios_rwsem
2047 * read_tail published
2050 static int canon_copy_from_read_buf(struct tty_struct *tty,
2051 unsigned char __user **b,
2054 struct n_tty_data *ldata = tty->disc_data;
2055 size_t n, size, more, c;
2061 /* N.B. avoid overrun if nr == 0 */
2062 n = min(*nr, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2066 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2067 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2069 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2070 __func__, *nr, tail, n, size);
2072 eol = find_next_bit(ldata->read_flags, size, tail);
2073 more = n - (size - tail);
2074 if (eol == N_TTY_BUF_SIZE && more) {
2075 /* scan wrapped without finding set bit */
2076 eol = find_next_bit(ldata->read_flags, more, 0);
2079 } else if (eol != size)
2082 size = N_TTY_BUF_SIZE - tail;
2084 if (n > N_TTY_BUF_SIZE)
2085 n += N_TTY_BUF_SIZE;
2089 if (found && !ldata->push && read_buf(ldata, eol) == __DISABLED_CHAR) {
2091 eof_push = !n && ldata->read_tail != ldata->line_start;
2094 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
2095 __func__, eol, found, n, c, size, more);
2098 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), size);
2101 ret = tty_copy_to_user(tty, *b + size, ldata->read_buf, n - size);
2103 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), n);
2111 clear_bit(eol, ldata->read_flags);
2112 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2116 ldata->line_start = ldata->read_tail;
2119 tty_audit_push(tty);
2121 return eof_push ? -EAGAIN : 0;
2124 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2128 * job_control - check job control
2130 * @file: file handle
2132 * Perform job control management checks on this file/tty descriptor
2133 * and if appropriate send any needed signals and return a negative
2134 * error code if action should be taken.
2136 * Locking: redirected write test is safe
2137 * current->signal->tty check is safe
2138 * ctrl_lock to safely reference tty->pgrp
2141 static int job_control(struct tty_struct *tty, struct file *file)
2143 /* Job control check -- must be done at start and after
2144 every sleep (POSIX.1 7.1.1.4). */
2145 /* NOTE: not yet done after every sleep pending a thorough
2146 check of the logic of this change. -- jlc */
2147 /* don't stop on /dev/console */
2148 if (file->f_op->write == redirected_tty_write ||
2149 current->signal->tty != tty)
2152 spin_lock_irq(&tty->ctrl_lock);
2154 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
2155 else if (task_pgrp(current) != tty->pgrp) {
2156 spin_unlock_irq(&tty->ctrl_lock);
2157 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
2159 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
2160 set_thread_flag(TIF_SIGPENDING);
2161 return -ERESTARTSYS;
2163 spin_unlock_irq(&tty->ctrl_lock);
2169 * n_tty_read - read function for tty
2171 * @file: file object
2172 * @buf: userspace buffer pointer
2175 * Perform reads for the line discipline. We are guaranteed that the
2176 * line discipline will not be closed under us but we may get multiple
2177 * parallel readers and must handle this ourselves. We may also get
2178 * a hangup. Always called in user context, may sleep.
2180 * This code must be sure never to sleep through a hangup.
2182 * n_tty_read()/consumer path:
2183 * claims non-exclusive termios_rwsem
2184 * publishes read_tail
2187 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2188 unsigned char __user *buf, size_t nr)
2190 struct n_tty_data *ldata = tty->disc_data;
2191 unsigned char __user *b = buf;
2192 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2200 c = job_control(tty, file);
2205 * Internal serialization of reads.
2207 if (file->f_flags & O_NONBLOCK) {
2208 if (!mutex_trylock(&ldata->atomic_read_lock))
2211 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2212 return -ERESTARTSYS;
2215 down_read(&tty->termios_rwsem);
2218 timeout = MAX_SCHEDULE_TIMEOUT;
2219 if (!ldata->icanon) {
2220 minimum = MIN_CHAR(tty);
2222 time = (HZ / 10) * TIME_CHAR(tty);
2224 ldata->minimum_to_wake = 1;
2225 else if (!waitqueue_active(&tty->read_wait) ||
2226 (ldata->minimum_to_wake > minimum))
2227 ldata->minimum_to_wake = minimum;
2229 timeout = (HZ / 10) * TIME_CHAR(tty);
2230 ldata->minimum_to_wake = minimum = 1;
2234 packet = tty->packet;
2235 tail = ldata->read_tail;
2237 add_wait_queue(&tty->read_wait, &wait);
2239 /* First test for status change. */
2240 if (packet && tty->link->ctrl_status) {
2244 spin_lock_irq(&tty->link->ctrl_lock);
2245 cs = tty->link->ctrl_status;
2246 tty->link->ctrl_status = 0;
2247 spin_unlock_irq(&tty->link->ctrl_lock);
2248 if (tty_put_user(tty, cs, b++)) {
2257 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2258 ((minimum - (b - buf)) >= 1))
2259 ldata->minimum_to_wake = (minimum - (b - buf));
2261 done = check_other_done(tty);
2263 if (!input_available_p(tty, 0)) {
2268 if (tty_hung_up_p(file))
2272 if (file->f_flags & O_NONBLOCK) {
2276 if (signal_pending(current)) {
2277 retval = -ERESTARTSYS;
2280 up_read(&tty->termios_rwsem);
2282 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2285 down_read(&tty->termios_rwsem);
2289 if (ldata->icanon && !L_EXTPROC(tty)) {
2290 retval = canon_copy_from_read_buf(tty, &b, &nr);
2291 if (retval == -EAGAIN) {
2299 /* Deal with packet mode. */
2300 if (packet && b == buf) {
2301 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2309 uncopied = copy_from_read_buf(tty, &b, &nr);
2310 uncopied += copy_from_read_buf(tty, &b, &nr);
2317 n_tty_check_unthrottle(tty);
2319 if (b - buf >= minimum)
2324 if (tail != ldata->read_tail)
2325 n_tty_kick_worker(tty);
2326 up_read(&tty->termios_rwsem);
2328 remove_wait_queue(&tty->read_wait, &wait);
2329 if (!waitqueue_active(&tty->read_wait))
2330 ldata->minimum_to_wake = minimum;
2332 mutex_unlock(&ldata->atomic_read_lock);
2341 * n_tty_write - write function for tty
2343 * @file: file object
2344 * @buf: userspace buffer pointer
2347 * Write function of the terminal device. This is serialized with
2348 * respect to other write callers but not to termios changes, reads
2349 * and other such events. Since the receive code will echo characters,
2350 * thus calling driver write methods, the output_lock is used in
2351 * the output processing functions called here as well as in the
2352 * echo processing function to protect the column state and space
2353 * left in the buffer.
2355 * This code must be sure never to sleep through a hangup.
2357 * Locking: output_lock to protect column state and space left
2358 * (note that the process_output*() functions take this
2362 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2363 const unsigned char *buf, size_t nr)
2365 const unsigned char *b = buf;
2366 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2370 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2371 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2372 retval = tty_check_change(tty);
2377 down_read(&tty->termios_rwsem);
2379 /* Write out any echoed characters that are still pending */
2380 process_echoes(tty);
2382 add_wait_queue(&tty->write_wait, &wait);
2384 if (signal_pending(current)) {
2385 retval = -ERESTARTSYS;
2388 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2394 ssize_t num = process_output_block(tty, b, nr);
2406 if (process_output(c, tty) < 0)
2410 if (tty->ops->flush_chars)
2411 tty->ops->flush_chars(tty);
2413 struct n_tty_data *ldata = tty->disc_data;
2416 mutex_lock(&ldata->output_lock);
2417 c = tty->ops->write(tty, b, nr);
2418 mutex_unlock(&ldata->output_lock);
2431 if (file->f_flags & O_NONBLOCK) {
2435 up_read(&tty->termios_rwsem);
2437 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2439 down_read(&tty->termios_rwsem);
2442 remove_wait_queue(&tty->write_wait, &wait);
2443 if (b - buf != nr && tty->fasync)
2444 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2445 up_read(&tty->termios_rwsem);
2446 return (b - buf) ? b - buf : retval;
2450 * n_tty_poll - poll method for N_TTY
2451 * @tty: terminal device
2452 * @file: file accessing it
2455 * Called when the line discipline is asked to poll() for data or
2456 * for special events. This code is not serialized with respect to
2457 * other events save open/close.
2459 * This code must be sure never to sleep through a hangup.
2460 * Called without the kernel lock held - fine
2463 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2466 struct n_tty_data *ldata = tty->disc_data;
2467 unsigned int mask = 0;
2469 poll_wait(file, &tty->read_wait, wait);
2470 poll_wait(file, &tty->write_wait, wait);
2471 if (check_other_done(tty))
2473 if (input_available_p(tty, 1))
2474 mask |= POLLIN | POLLRDNORM;
2475 if (tty->packet && tty->link->ctrl_status)
2476 mask |= POLLPRI | POLLIN | POLLRDNORM;
2477 if (tty_hung_up_p(file))
2479 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2480 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2481 ldata->minimum_to_wake = MIN_CHAR(tty);
2483 ldata->minimum_to_wake = 1;
2485 if (tty->ops->write && !tty_is_writelocked(tty) &&
2486 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2487 tty_write_room(tty) > 0)
2488 mask |= POLLOUT | POLLWRNORM;
2492 static unsigned long inq_canon(struct n_tty_data *ldata)
2494 size_t nr, head, tail;
2496 if (ldata->canon_head == ldata->read_tail)
2498 head = ldata->canon_head;
2499 tail = ldata->read_tail;
2501 /* Skip EOF-chars.. */
2502 while (head != tail) {
2503 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2504 read_buf(ldata, tail) == __DISABLED_CHAR)
2511 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2512 unsigned int cmd, unsigned long arg)
2514 struct n_tty_data *ldata = tty->disc_data;
2519 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2521 down_write(&tty->termios_rwsem);
2523 retval = inq_canon(ldata);
2525 retval = read_cnt(ldata);
2526 up_write(&tty->termios_rwsem);
2527 return put_user(retval, (unsigned int __user *) arg);
2529 return n_tty_ioctl_helper(tty, file, cmd, arg);
2533 static void n_tty_fasync(struct tty_struct *tty, int on)
2535 struct n_tty_data *ldata = tty->disc_data;
2537 if (!waitqueue_active(&tty->read_wait)) {
2539 ldata->minimum_to_wake = 1;
2540 else if (!tty->fasync)
2541 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2545 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2546 .magic = TTY_LDISC_MAGIC,
2549 .close = n_tty_close,
2550 .flush_buffer = n_tty_flush_buffer,
2551 .chars_in_buffer = n_tty_chars_in_buffer,
2553 .write = n_tty_write,
2554 .ioctl = n_tty_ioctl,
2555 .set_termios = n_tty_set_termios,
2557 .receive_buf = n_tty_receive_buf,
2558 .write_wakeup = n_tty_write_wakeup,
2559 .fasync = n_tty_fasync,
2560 .receive_buf2 = n_tty_receive_buf2,
2564 * n_tty_inherit_ops - inherit N_TTY methods
2565 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2567 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2571 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2573 *ops = tty_ldisc_N_TTY;
2575 ops->refcount = ops->flags = 0;
2577 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);