2 * n_tty.c --- implements the N_TTY line discipline.
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where n_tty_write returns
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52 #include <linux/ratelimit.h>
55 /* number of characters left in xmit buffer before select has we have room */
56 #define WAKEUP_CHARS 256
59 * This defines the low- and high-watermarks for throttling and
60 * unthrottling the TTY driver. These watermarks are used for
61 * controlling the space in the read buffer.
63 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
64 #define TTY_THRESHOLD_UNTHROTTLE 128
67 * Special byte codes used in the echo buffer to represent operations
68 * or special handling of characters. Bytes in the echo buffer that
69 * are not part of such special blocks are treated as normal character
72 #define ECHO_OP_START 0xff
73 #define ECHO_OP_MOVE_BACK_COL 0x80
74 #define ECHO_OP_SET_CANON_COL 0x81
75 #define ECHO_OP_ERASE_TAB 0x82
79 # define n_tty_trace(f, args...) trace_printk(f, ##args)
81 # define n_tty_trace(f, args...)
85 /* producer-published */
88 DECLARE_BITMAP(process_char_map, 256);
90 /* private to n_tty_receive_overrun (single-threaded) */
91 unsigned long overrun_time;
97 /* must hold exclusive termios_rwsem to reset these */
98 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
99 unsigned char echo_overrun:1;
101 /* shared by producer and consumer */
103 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
107 /* consumer-published */
110 /* protected by echo_lock */
111 unsigned char *echo_buf;
112 unsigned int echo_pos;
113 unsigned int echo_cnt;
115 /* protected by output lock */
117 unsigned int canon_column;
119 struct mutex atomic_read_lock;
120 struct mutex output_lock;
121 struct mutex echo_lock;
124 static inline size_t read_cnt(struct n_tty_data *ldata)
126 return ldata->read_head - ldata->read_tail;
129 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
131 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
134 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
136 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
139 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
140 unsigned char __user *ptr)
142 struct n_tty_data *ldata = tty->disc_data;
144 tty_audit_add_data(tty, &x, 1, ldata->icanon);
145 return put_user(x, ptr);
148 static int receive_room(struct tty_struct *tty)
150 struct n_tty_data *ldata = tty->disc_data;
154 /* Multiply read_cnt by 3, since each byte might take up to
155 * three times as many spaces when PARMRK is set (depending on
156 * its flags, e.g. parity error). */
157 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
159 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
162 * If we are doing input canonicalization, and there are no
163 * pending newlines, let characters through without limit, so
164 * that erase characters will be handled. Other excess
165 * characters will be beeped.
168 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
174 * n_tty_set_room - receive space
177 * Re-schedules the flip buffer work if space just became available.
179 * Caller holds exclusive termios_rwsem
181 * n_tty_read()/consumer path:
182 * holds non-exclusive termios_rwsem
185 static void n_tty_set_room(struct tty_struct *tty)
187 struct n_tty_data *ldata = tty->disc_data;
189 /* Did this open up the receive buffer? We may need to flip */
190 if (unlikely(ldata->no_room) && receive_room(tty)) {
193 WARN_RATELIMIT(tty->port->itty == NULL,
194 "scheduling with invalid itty\n");
195 /* see if ldisc has been killed - if so, this means that
196 * even though the ldisc has been halted and ->buf.work
197 * cancelled, ->buf.work is about to be rescheduled
199 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
200 "scheduling buffer work for halted ldisc\n");
201 schedule_work(&tty->port->buf.work);
205 static ssize_t chars_in_buffer(struct tty_struct *tty)
207 struct n_tty_data *ldata = tty->disc_data;
213 n = ldata->canon_head - ldata->read_tail;
217 static inline void n_tty_check_throttle(struct tty_struct *tty)
220 * Check the remaining room for the input canonicalization
221 * mode. We don't want to throttle the driver if we're in
222 * canonical mode and don't have a newline yet!
226 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
227 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
229 throttled = tty_throttle_safe(tty);
233 __tty_set_flow_change(tty, 0);
236 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
238 /* If there is enough space in the read buffer now, let the
239 * low-level driver know. We use chars_in_buffer() to
240 * check the buffer, as it now knows about canonical mode.
241 * Otherwise, if the driver is throttled and the line is
242 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
243 * we won't get any more characters.
248 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
249 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
254 unthrottled = tty_unthrottle_safe(tty);
258 __tty_set_flow_change(tty, 0);
262 * put_tty_queue - add character to tty
266 * Add a character to the tty read_buf queue.
268 * n_tty_receive_buf()/producer path:
269 * caller holds non-exclusive termios_rwsem
272 * read_head is only considered 'published' if canonical mode is
276 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
278 if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
279 *read_buf_addr(ldata, ldata->read_head) = c;
285 * reset_buffer_flags - reset buffer state
286 * @tty: terminal to reset
288 * Reset the read buffer counters and clear the flags.
289 * Called from n_tty_open() and n_tty_flush_buffer().
291 * Locking: caller holds exclusive termios_rwsem
292 * (or locking is not required)
295 static void reset_buffer_flags(struct n_tty_data *ldata)
297 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
299 mutex_lock(&ldata->echo_lock);
300 ldata->echo_pos = ldata->echo_cnt = ldata->echo_overrun = 0;
301 mutex_unlock(&ldata->echo_lock);
304 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
307 static void n_tty_packet_mode_flush(struct tty_struct *tty)
311 spin_lock_irqsave(&tty->ctrl_lock, flags);
312 if (tty->link->packet) {
313 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
314 wake_up_interruptible(&tty->link->read_wait);
316 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
320 * n_tty_flush_buffer - clean input queue
321 * @tty: terminal device
323 * Flush the input buffer. Called when the tty layer wants the
324 * buffer flushed (eg at hangup) or when the N_TTY line discipline
325 * internally has to clean the pending queue (for example some signals).
327 * Holds termios_rwsem to exclude producer/consumer while
328 * buffer indices are reset.
330 * Locking: ctrl_lock, exclusive termios_rwsem
333 static void n_tty_flush_buffer(struct tty_struct *tty)
335 down_write(&tty->termios_rwsem);
336 reset_buffer_flags(tty->disc_data);
340 n_tty_packet_mode_flush(tty);
341 up_write(&tty->termios_rwsem);
345 * n_tty_chars_in_buffer - report available bytes
348 * Report the number of characters buffered to be delivered to user
349 * at this instant in time.
351 * Locking: exclusive termios_rwsem
354 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
358 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
360 down_write(&tty->termios_rwsem);
361 n = chars_in_buffer(tty);
362 up_write(&tty->termios_rwsem);
367 * is_utf8_continuation - utf8 multibyte check
370 * Returns true if the utf8 character 'c' is a multibyte continuation
371 * character. We use this to correctly compute the on screen size
372 * of the character when printing
375 static inline int is_utf8_continuation(unsigned char c)
377 return (c & 0xc0) == 0x80;
381 * is_continuation - multibyte check
384 * Returns true if the utf8 character 'c' is a multibyte continuation
385 * character and the terminal is in unicode mode.
388 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
390 return I_IUTF8(tty) && is_utf8_continuation(c);
394 * do_output_char - output one character
395 * @c: character (or partial unicode symbol)
396 * @tty: terminal device
397 * @space: space available in tty driver write buffer
399 * This is a helper function that handles one output character
400 * (including special characters like TAB, CR, LF, etc.),
401 * doing OPOST processing and putting the results in the
402 * tty driver's write buffer.
404 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
405 * and NLDLY. They simply aren't relevant in the world today.
406 * If you ever need them, add them here.
408 * Returns the number of bytes of buffer space used or -1 if
411 * Locking: should be called under the output_lock to protect
412 * the column state and space left in the buffer
415 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
417 struct n_tty_data *ldata = tty->disc_data;
430 ldata->canon_column = ldata->column = 0;
431 tty->ops->write(tty, "\r\n", 2);
434 ldata->canon_column = ldata->column;
437 if (O_ONOCR(tty) && ldata->column == 0)
442 ldata->canon_column = ldata->column = 0;
445 ldata->canon_column = ldata->column = 0;
448 spaces = 8 - (ldata->column & 7);
449 if (O_TABDLY(tty) == XTABS) {
452 ldata->column += spaces;
453 tty->ops->write(tty, " ", spaces);
456 ldata->column += spaces;
459 if (ldata->column > 0)
466 if (!is_continuation(c, tty))
472 tty_put_char(tty, c);
477 * process_output - output post processor
478 * @c: character (or partial unicode symbol)
479 * @tty: terminal device
481 * Output one character with OPOST processing.
482 * Returns -1 when the output device is full and the character
485 * Locking: output_lock to protect column state and space left
486 * (also, this is called from n_tty_write under the
487 * tty layer write lock)
490 static int process_output(unsigned char c, struct tty_struct *tty)
492 struct n_tty_data *ldata = tty->disc_data;
495 mutex_lock(&ldata->output_lock);
497 space = tty_write_room(tty);
498 retval = do_output_char(c, tty, space);
500 mutex_unlock(&ldata->output_lock);
508 * process_output_block - block post processor
509 * @tty: terminal device
510 * @buf: character buffer
511 * @nr: number of bytes to output
513 * Output a block of characters with OPOST processing.
514 * Returns the number of characters output.
516 * This path is used to speed up block console writes, among other
517 * things when processing blocks of output data. It handles only
518 * the simple cases normally found and helps to generate blocks of
519 * symbols for the console driver and thus improve performance.
521 * Locking: output_lock to protect column state and space left
522 * (also, this is called from n_tty_write under the
523 * tty layer write lock)
526 static ssize_t process_output_block(struct tty_struct *tty,
527 const unsigned char *buf, unsigned int nr)
529 struct n_tty_data *ldata = tty->disc_data;
532 const unsigned char *cp;
534 mutex_lock(&ldata->output_lock);
536 space = tty_write_room(tty);
538 mutex_unlock(&ldata->output_lock);
544 for (i = 0, cp = buf; i < nr; i++, cp++) {
545 unsigned char c = *cp;
553 ldata->canon_column = ldata->column;
556 if (O_ONOCR(tty) && ldata->column == 0)
560 ldata->canon_column = ldata->column = 0;
565 if (ldata->column > 0)
572 if (!is_continuation(c, tty))
579 i = tty->ops->write(tty, buf, i);
581 mutex_unlock(&ldata->output_lock);
586 * process_echoes - write pending echo characters
587 * @tty: terminal device
589 * Write previously buffered echo (and other ldisc-generated)
590 * characters to the tty.
592 * Characters generated by the ldisc (including echoes) need to
593 * be buffered because the driver's write buffer can fill during
594 * heavy program output. Echoing straight to the driver will
595 * often fail under these conditions, causing lost characters and
596 * resulting mismatches of ldisc state information.
598 * Since the ldisc state must represent the characters actually sent
599 * to the driver at the time of the write, operations like certain
600 * changes in column state are also saved in the buffer and executed
603 * A circular fifo buffer is used so that the most recent characters
604 * are prioritized. Also, when control characters are echoed with a
605 * prefixed "^", the pair is treated atomically and thus not separated.
607 * Locking: output_lock to protect column state and space left,
608 * echo_lock to protect the echo buffer
611 static void process_echoes(struct tty_struct *tty)
613 struct n_tty_data *ldata = tty->disc_data;
616 unsigned char *cp, *buf_end;
618 if (!ldata->echo_cnt)
621 mutex_lock(&ldata->output_lock);
622 mutex_lock(&ldata->echo_lock);
624 space = tty_write_room(tty);
626 buf_end = ldata->echo_buf + N_TTY_BUF_SIZE;
627 cp = ldata->echo_buf + ldata->echo_pos;
628 nr = ldata->echo_cnt;
631 if (c == ECHO_OP_START) {
634 int no_space_left = 0;
637 * If the buffer byte is the start of a multi-byte
638 * operation, get the next byte, which is either the
639 * op code or a control character value.
643 opp -= N_TTY_BUF_SIZE;
647 unsigned int num_chars, num_bs;
649 case ECHO_OP_ERASE_TAB:
650 if (++opp == buf_end)
651 opp -= N_TTY_BUF_SIZE;
655 * Determine how many columns to go back
656 * in order to erase the tab.
657 * This depends on the number of columns
658 * used by other characters within the tab
659 * area. If this (modulo 8) count is from
660 * the start of input rather than from a
661 * previous tab, we offset by canon column.
662 * Otherwise, tab spacing is normal.
664 if (!(num_chars & 0x80))
665 num_chars += ldata->canon_column;
666 num_bs = 8 - (num_chars & 7);
668 if (num_bs > space) {
674 tty_put_char(tty, '\b');
675 if (ldata->column > 0)
682 case ECHO_OP_SET_CANON_COL:
683 ldata->canon_column = ldata->column;
688 case ECHO_OP_MOVE_BACK_COL:
689 if (ldata->column > 0)
696 /* This is an escaped echo op start code */
701 tty_put_char(tty, ECHO_OP_START);
710 * If the op is not a special byte code,
711 * it is a ctrl char tagged to be echoed
712 * as "^X" (where X is the letter
713 * representing the control char).
714 * Note that we must ensure there is
715 * enough space for the whole ctrl pair.
722 tty_put_char(tty, '^');
723 tty_put_char(tty, op ^ 0100);
734 int retval = do_output_char(c, tty, space);
741 tty_put_char(tty, c);
748 /* When end of circular buffer reached, wrap around */
750 cp -= N_TTY_BUF_SIZE;
756 ldata->echo_overrun = 0;
758 int num_processed = ldata->echo_cnt - nr;
759 ldata->echo_pos += num_processed;
760 ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
761 ldata->echo_cnt = nr;
762 if (num_processed > 0)
763 ldata->echo_overrun = 0;
766 mutex_unlock(&ldata->echo_lock);
767 mutex_unlock(&ldata->output_lock);
769 if (tty->ops->flush_chars)
770 tty->ops->flush_chars(tty);
774 * add_echo_byte - add a byte to the echo buffer
775 * @c: unicode byte to echo
778 * Add a character or operation byte to the echo buffer.
780 * Should be called under the echo lock to protect the echo buffer.
783 static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
787 if (ldata->echo_cnt == N_TTY_BUF_SIZE) {
788 /* Circular buffer is already at capacity */
789 new_byte_pos = ldata->echo_pos;
792 * Since the buffer start position needs to be advanced,
793 * be sure to step by a whole operation byte group.
795 if (ldata->echo_buf[ldata->echo_pos] == ECHO_OP_START) {
796 if (ldata->echo_buf[(ldata->echo_pos + 1) &
797 (N_TTY_BUF_SIZE - 1)] ==
799 ldata->echo_pos += 3;
800 ldata->echo_cnt -= 2;
802 ldata->echo_pos += 2;
803 ldata->echo_cnt -= 1;
808 ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
810 ldata->echo_overrun = 1;
812 new_byte_pos = ldata->echo_pos + ldata->echo_cnt;
813 new_byte_pos &= N_TTY_BUF_SIZE - 1;
817 ldata->echo_buf[new_byte_pos] = c;
821 * echo_move_back_col - add operation to move back a column
824 * Add an operation to the echo buffer to move back one column.
826 * Locking: echo_lock to protect the echo buffer
829 static void echo_move_back_col(struct n_tty_data *ldata)
831 mutex_lock(&ldata->echo_lock);
832 add_echo_byte(ECHO_OP_START, ldata);
833 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
834 mutex_unlock(&ldata->echo_lock);
838 * echo_set_canon_col - add operation to set the canon column
841 * Add an operation to the echo buffer to set the canon column
842 * to the current column.
844 * Locking: echo_lock to protect the echo buffer
847 static void echo_set_canon_col(struct n_tty_data *ldata)
849 mutex_lock(&ldata->echo_lock);
850 add_echo_byte(ECHO_OP_START, ldata);
851 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
852 mutex_unlock(&ldata->echo_lock);
856 * echo_erase_tab - add operation to erase a tab
857 * @num_chars: number of character columns already used
858 * @after_tab: true if num_chars starts after a previous tab
861 * Add an operation to the echo buffer to erase a tab.
863 * Called by the eraser function, which knows how many character
864 * columns have been used since either a previous tab or the start
865 * of input. This information will be used later, along with
866 * canon column (if applicable), to go back the correct number
869 * Locking: echo_lock to protect the echo buffer
872 static void echo_erase_tab(unsigned int num_chars, int after_tab,
873 struct n_tty_data *ldata)
875 mutex_lock(&ldata->echo_lock);
877 add_echo_byte(ECHO_OP_START, ldata);
878 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
880 /* We only need to know this modulo 8 (tab spacing) */
883 /* Set the high bit as a flag if num_chars is after a previous tab */
887 add_echo_byte(num_chars, ldata);
889 mutex_unlock(&ldata->echo_lock);
893 * echo_char_raw - echo a character raw
894 * @c: unicode byte to echo
895 * @tty: terminal device
897 * Echo user input back onto the screen. This must be called only when
898 * L_ECHO(tty) is true. Called from the driver receive_buf path.
900 * This variant does not treat control characters specially.
902 * Locking: echo_lock to protect the echo buffer
905 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
907 mutex_lock(&ldata->echo_lock);
908 if (c == ECHO_OP_START) {
909 add_echo_byte(ECHO_OP_START, ldata);
910 add_echo_byte(ECHO_OP_START, ldata);
912 add_echo_byte(c, ldata);
914 mutex_unlock(&ldata->echo_lock);
918 * echo_char - echo a character
919 * @c: unicode byte to echo
920 * @tty: terminal device
922 * Echo user input back onto the screen. This must be called only when
923 * L_ECHO(tty) is true. Called from the driver receive_buf path.
925 * This variant tags control characters to be echoed as "^X"
926 * (where X is the letter representing the control char).
928 * Locking: echo_lock to protect the echo buffer
931 static void echo_char(unsigned char c, struct tty_struct *tty)
933 struct n_tty_data *ldata = tty->disc_data;
935 mutex_lock(&ldata->echo_lock);
937 if (c == ECHO_OP_START) {
938 add_echo_byte(ECHO_OP_START, ldata);
939 add_echo_byte(ECHO_OP_START, ldata);
941 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
942 add_echo_byte(ECHO_OP_START, ldata);
943 add_echo_byte(c, ldata);
946 mutex_unlock(&ldata->echo_lock);
950 * finish_erasing - complete erase
954 static inline void finish_erasing(struct n_tty_data *ldata)
956 if (ldata->erasing) {
957 echo_char_raw('/', ldata);
963 * eraser - handle erase function
964 * @c: character input
965 * @tty: terminal device
967 * Perform erase and necessary output when an erase character is
968 * present in the stream from the driver layer. Handles the complexities
969 * of UTF-8 multibyte symbols.
971 * n_tty_receive_buf()/producer path:
972 * caller holds non-exclusive termios_rwsem
975 * Modifying the read_head is not considered a publish in this context
976 * because canonical mode is active -- only canon_head publishes
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 * Locking: ctrl_lock
1107 static inline void isig(int sig, struct tty_struct *tty)
1109 struct pid *tty_pgrp = tty_get_pgrp(tty);
1111 kill_pgrp(tty_pgrp, sig, 1);
1117 * n_tty_receive_break - handle break
1120 * An RS232 break event has been hit in the incoming bitstream. This
1121 * can cause a variety of events depending upon the termios settings.
1123 * n_tty_receive_buf()/producer path:
1124 * caller holds non-exclusive termios_rwsem
1125 * publishes read_head via put_tty_queue()
1127 * Note: may get exclusive termios_rwsem if flushing input buffer
1130 static inline void n_tty_receive_break(struct tty_struct *tty)
1132 struct n_tty_data *ldata = tty->disc_data;
1136 if (I_BRKINT(tty)) {
1138 if (!L_NOFLSH(tty)) {
1139 /* flushing needs exclusive termios_rwsem */
1140 up_read(&tty->termios_rwsem);
1141 n_tty_flush_buffer(tty);
1142 tty_driver_flush_buffer(tty);
1143 down_read(&tty->termios_rwsem);
1147 if (I_PARMRK(tty)) {
1148 put_tty_queue('\377', ldata);
1149 put_tty_queue('\0', ldata);
1151 put_tty_queue('\0', ldata);
1152 wake_up_interruptible(&tty->read_wait);
1156 * n_tty_receive_overrun - handle overrun reporting
1159 * Data arrived faster than we could process it. While the tty
1160 * driver has flagged this the bits that were missed are gone
1163 * Called from the receive_buf path so single threaded. Does not
1164 * need locking as num_overrun and overrun_time are function
1168 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1170 struct n_tty_data *ldata = tty->disc_data;
1173 ldata->num_overrun++;
1174 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1175 time_after(ldata->overrun_time, jiffies)) {
1176 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1178 ldata->num_overrun);
1179 ldata->overrun_time = jiffies;
1180 ldata->num_overrun = 0;
1185 * n_tty_receive_parity_error - error notifier
1186 * @tty: terminal device
1189 * Process a parity error and queue the right data to indicate
1190 * the error case if necessary.
1192 * n_tty_receive_buf()/producer path:
1193 * caller holds non-exclusive termios_rwsem
1194 * publishes read_head via put_tty_queue()
1196 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1199 struct n_tty_data *ldata = tty->disc_data;
1203 if (I_PARMRK(tty)) {
1204 put_tty_queue('\377', ldata);
1205 put_tty_queue('\0', ldata);
1206 put_tty_queue(c, ldata);
1207 } else if (I_INPCK(tty))
1208 put_tty_queue('\0', ldata);
1210 put_tty_queue(c, ldata);
1211 wake_up_interruptible(&tty->read_wait);
1215 * n_tty_receive_char - perform processing
1216 * @tty: terminal device
1219 * Process an individual character of input received from the driver.
1220 * This is serialized with respect to itself by the rules for the
1223 * n_tty_receive_buf()/producer path:
1224 * caller holds non-exclusive termios_rwsem
1225 * publishes canon_head if canonical mode is active
1226 * otherwise, publishes read_head via put_tty_queue()
1229 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1231 struct n_tty_data *ldata = tty->disc_data;
1235 put_tty_queue(c, ldata);
1241 if (I_IUCLC(tty) && L_IEXTEN(tty))
1244 if (L_EXTPROC(tty)) {
1245 put_tty_queue(c, ldata);
1249 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1250 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1251 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1253 process_echoes(tty);
1258 if (c == START_CHAR(tty)) {
1260 process_echoes(tty);
1261 } else if (c == STOP_CHAR(tty))
1268 * If the previous character was LNEXT, or we know that this
1269 * character is not one of the characters that we'll have to
1270 * handle specially, do shortcut processing to speed things
1273 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1275 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1276 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1277 /* beep if no space */
1279 process_output('\a', tty);
1283 finish_erasing(ldata);
1284 /* Record the column of first canon char. */
1285 if (ldata->canon_head == ldata->read_head)
1286 echo_set_canon_col(ldata);
1288 process_echoes(tty);
1291 put_tty_queue(c, ldata);
1292 put_tty_queue(c, ldata);
1297 if (c == START_CHAR(tty)) {
1299 process_echoes(tty);
1302 if (c == STOP_CHAR(tty)) {
1311 if (c == INTR_CHAR(tty))
1314 if (c == QUIT_CHAR(tty))
1317 if (c == SUSP_CHAR(tty)) {
1319 if (!L_NOFLSH(tty)) {
1320 /* flushing needs exclusive termios_rwsem */
1321 up_read(&tty->termios_rwsem);
1322 n_tty_flush_buffer(tty);
1323 tty_driver_flush_buffer(tty);
1324 down_read(&tty->termios_rwsem);
1330 process_echoes(tty);
1342 } else if (c == '\n' && I_INLCR(tty))
1345 if (ldata->icanon) {
1346 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1347 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1349 process_echoes(tty);
1352 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1355 finish_erasing(ldata);
1356 if (L_ECHOCTL(tty)) {
1357 echo_char_raw('^', ldata);
1358 echo_char_raw('\b', ldata);
1359 process_echoes(tty);
1364 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1366 size_t tail = ldata->canon_head;
1368 finish_erasing(ldata);
1370 echo_char_raw('\n', ldata);
1371 while (tail != ldata->read_head) {
1372 echo_char(read_buf(ldata, tail), tty);
1375 process_echoes(tty);
1379 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1381 process_output('\a', tty);
1384 if (L_ECHO(tty) || L_ECHONL(tty)) {
1385 echo_char_raw('\n', ldata);
1386 process_echoes(tty);
1388 goto handle_newline;
1390 if (c == EOF_CHAR(tty)) {
1391 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1393 if (ldata->canon_head != ldata->read_head)
1394 set_bit(TTY_PUSH, &tty->flags);
1395 c = __DISABLED_CHAR;
1396 goto handle_newline;
1398 if ((c == EOL_CHAR(tty)) ||
1399 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1400 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1402 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1404 process_output('\a', tty);
1408 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1411 /* Record the column of first canon char. */
1412 if (ldata->canon_head == ldata->read_head)
1413 echo_set_canon_col(ldata);
1415 process_echoes(tty);
1418 * XXX does PARMRK doubling happen for
1419 * EOL_CHAR and EOL2_CHAR?
1422 put_tty_queue(c, ldata);
1425 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1426 put_tty_queue(c, ldata);
1427 ldata->canon_head = ldata->read_head;
1428 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1429 if (waitqueue_active(&tty->read_wait))
1430 wake_up_interruptible(&tty->read_wait);
1435 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1436 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1437 /* beep if no space */
1439 process_output('\a', tty);
1443 finish_erasing(ldata);
1445 echo_char_raw('\n', ldata);
1447 /* Record the column of first canon char. */
1448 if (ldata->canon_head == ldata->read_head)
1449 echo_set_canon_col(ldata);
1452 process_echoes(tty);
1456 put_tty_queue(c, ldata);
1458 put_tty_queue(c, ldata);
1463 * n_tty_write_wakeup - asynchronous I/O notifier
1466 * Required for the ptys, serial driver etc. since processes
1467 * that attach themselves to the master and rely on ASYNC
1468 * IO must be woken up
1471 static void n_tty_write_wakeup(struct tty_struct *tty)
1473 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1474 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1478 * n_tty_receive_buf - data receive
1479 * @tty: terminal device
1482 * @count: characters
1484 * Called by the terminal driver when a block of characters has
1485 * been received. This function must be called from soft contexts
1486 * not from interrupt context. The driver is responsible for making
1487 * calls one at a time and in order (or using flush_to_ldisc)
1489 * n_tty_receive_buf()/producer path:
1490 * claims non-exclusive termios_rwsem
1491 * publishes read_head and canon_head
1494 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1495 char *fp, int count)
1497 struct n_tty_data *ldata = tty->disc_data;
1498 const unsigned char *p;
1499 char *f, flags = TTY_NORMAL;
1502 if (ldata->real_raw) {
1505 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1506 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1507 n = min_t(size_t, count, n);
1508 memcpy(read_buf_addr(ldata, head), cp, n);
1509 ldata->read_head += n;
1513 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1514 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1515 n = min_t(size_t, count, n);
1516 memcpy(read_buf_addr(ldata, head), cp, n);
1517 ldata->read_head += n;
1521 for (i = count, p = cp, f = fp; i; i--, p++) {
1526 n_tty_receive_char(tty, *p);
1529 n_tty_receive_break(tty);
1533 n_tty_receive_parity_error(tty, *p);
1536 n_tty_receive_overrun(tty);
1539 printk(KERN_ERR "%s: unknown flag %d\n",
1540 tty_name(tty, buf), flags);
1544 if (tty->ops->flush_chars)
1545 tty->ops->flush_chars(tty);
1548 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1550 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1551 if (waitqueue_active(&tty->read_wait))
1552 wake_up_interruptible(&tty->read_wait);
1555 n_tty_check_throttle(tty);
1558 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1559 char *fp, int count)
1561 down_read(&tty->termios_rwsem);
1562 __receive_buf(tty, cp, fp, count);
1563 up_read(&tty->termios_rwsem);
1566 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1567 char *fp, int count)
1569 struct n_tty_data *ldata = tty->disc_data;
1572 down_read(&tty->termios_rwsem);
1574 tty->receive_room = room = receive_room(tty);
1577 count = min(count, room);
1579 __receive_buf(tty, cp, fp, count);
1581 up_read(&tty->termios_rwsem);
1586 int is_ignored(int sig)
1588 return (sigismember(¤t->blocked, sig) ||
1589 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1593 * n_tty_set_termios - termios data changed
1595 * @old: previous data
1597 * Called by the tty layer when the user changes termios flags so
1598 * that the line discipline can plan ahead. This function cannot sleep
1599 * and is protected from re-entry by the tty layer. The user is
1600 * guaranteed that this function will not be re-entered or in progress
1601 * when the ldisc is closed.
1603 * Locking: Caller holds tty->termios_rwsem
1606 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1608 struct n_tty_data *ldata = tty->disc_data;
1609 int canon_change = 1;
1612 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1614 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1615 ldata->canon_head = ldata->read_tail;
1620 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1621 wake_up_interruptible(&tty->read_wait);
1623 ldata->icanon = (L_ICANON(tty) != 0);
1625 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1626 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1627 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1629 bitmap_zero(ldata->process_char_map, 256);
1631 if (I_IGNCR(tty) || I_ICRNL(tty))
1632 set_bit('\r', ldata->process_char_map);
1634 set_bit('\n', ldata->process_char_map);
1636 if (L_ICANON(tty)) {
1637 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1638 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1639 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1640 set_bit('\n', ldata->process_char_map);
1641 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1642 if (L_IEXTEN(tty)) {
1643 set_bit(WERASE_CHAR(tty),
1644 ldata->process_char_map);
1645 set_bit(LNEXT_CHAR(tty),
1646 ldata->process_char_map);
1647 set_bit(EOL2_CHAR(tty),
1648 ldata->process_char_map);
1650 set_bit(REPRINT_CHAR(tty),
1651 ldata->process_char_map);
1655 set_bit(START_CHAR(tty), ldata->process_char_map);
1656 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1659 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1660 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1661 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1663 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1665 ldata->real_raw = 0;
1668 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1669 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1670 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1671 ldata->real_raw = 1;
1673 ldata->real_raw = 0;
1675 n_tty_set_room(tty);
1677 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1678 * been stopped by STOP_CHAR(tty) before it.
1680 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1684 /* The termios change make the tty ready for I/O */
1685 wake_up_interruptible(&tty->write_wait);
1686 wake_up_interruptible(&tty->read_wait);
1690 * n_tty_close - close the ldisc for this tty
1693 * Called from the terminal layer when this line discipline is
1694 * being shut down, either because of a close or becsuse of a
1695 * discipline change. The function will not be called while other
1696 * ldisc methods are in progress.
1699 static void n_tty_close(struct tty_struct *tty)
1701 struct n_tty_data *ldata = tty->disc_data;
1704 n_tty_packet_mode_flush(tty);
1706 kfree(ldata->read_buf);
1707 kfree(ldata->echo_buf);
1709 tty->disc_data = NULL;
1713 * n_tty_open - open an ldisc
1714 * @tty: terminal to open
1716 * Called when this line discipline is being attached to the
1717 * terminal device. Can sleep. Called serialized so that no
1718 * other events will occur in parallel. No further open will occur
1722 static int n_tty_open(struct tty_struct *tty)
1724 struct n_tty_data *ldata;
1726 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1730 ldata->overrun_time = jiffies;
1731 mutex_init(&ldata->atomic_read_lock);
1732 mutex_init(&ldata->output_lock);
1733 mutex_init(&ldata->echo_lock);
1735 /* These are ugly. Currently a malloc failure here can panic */
1736 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1737 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1738 if (!ldata->read_buf || !ldata->echo_buf)
1741 tty->disc_data = ldata;
1742 reset_buffer_flags(tty->disc_data);
1744 ldata->minimum_to_wake = 1;
1746 /* indicate buffer work may resume */
1747 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1748 n_tty_set_termios(tty, NULL);
1749 tty_unthrottle(tty);
1753 kfree(ldata->read_buf);
1754 kfree(ldata->echo_buf);
1760 static inline int input_available_p(struct tty_struct *tty, int amt)
1762 struct n_tty_data *ldata = tty->disc_data;
1764 if (ldata->icanon && !L_EXTPROC(tty)) {
1765 if (ldata->canon_head != ldata->read_tail)
1767 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1774 * copy_from_read_buf - copy read data directly
1775 * @tty: terminal device
1779 * Helper function to speed up n_tty_read. It is only called when
1780 * ICANON is off; it copies characters straight from the tty queue to
1781 * user space directly. It can be profitably called twice; once to
1782 * drain the space from the tail pointer to the (physical) end of the
1783 * buffer, and once to drain the space from the (physical) beginning of
1784 * the buffer to head pointer.
1786 * Called under the ldata->atomic_read_lock sem
1788 * n_tty_read()/consumer path:
1789 * caller holds non-exclusive termios_rwsem
1790 * read_tail published
1793 static int copy_from_read_buf(struct tty_struct *tty,
1794 unsigned char __user **b,
1798 struct n_tty_data *ldata = tty->disc_data;
1802 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1805 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1808 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1810 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1811 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1813 ldata->read_tail += n;
1814 /* Turn single EOF into zero-length read */
1815 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1824 * canon_copy_from_read_buf - copy read data in canonical mode
1825 * @tty: terminal device
1829 * Helper function for n_tty_read. It is only called when ICANON is on;
1830 * it copies one line of input up to and including the line-delimiting
1831 * character into the user-space buffer.
1833 * Called under the atomic_read_lock mutex
1835 * n_tty_read()/consumer path:
1836 * caller holds non-exclusive termios_rwsem
1837 * read_tail published
1840 static int canon_copy_from_read_buf(struct tty_struct *tty,
1841 unsigned char __user **b,
1844 struct n_tty_data *ldata = tty->disc_data;
1845 size_t n, size, more, c;
1850 /* N.B. avoid overrun if nr == 0 */
1851 n = min(*nr, read_cnt(ldata));
1855 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1856 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1858 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1859 __func__, *nr, tail, n, size);
1861 eol = find_next_bit(ldata->read_flags, size, tail);
1862 more = n - (size - tail);
1863 if (eol == N_TTY_BUF_SIZE && more) {
1864 /* scan wrapped without finding set bit */
1865 eol = find_next_bit(ldata->read_flags, more, 0);
1868 } else if (eol != size)
1871 size = N_TTY_BUF_SIZE - tail;
1872 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1875 if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
1878 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1879 __func__, eol, found, n, c, size, more);
1882 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1885 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1887 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1895 clear_bit(eol, ldata->read_flags);
1896 smp_mb__after_clear_bit();
1897 ldata->read_tail += c;
1900 tty_audit_push(tty);
1904 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1908 * job_control - check job control
1910 * @file: file handle
1912 * Perform job control management checks on this file/tty descriptor
1913 * and if appropriate send any needed signals and return a negative
1914 * error code if action should be taken.
1916 * Locking: redirected write test is safe
1917 * current->signal->tty check is safe
1918 * ctrl_lock to safely reference tty->pgrp
1921 static int job_control(struct tty_struct *tty, struct file *file)
1923 /* Job control check -- must be done at start and after
1924 every sleep (POSIX.1 7.1.1.4). */
1925 /* NOTE: not yet done after every sleep pending a thorough
1926 check of the logic of this change. -- jlc */
1927 /* don't stop on /dev/console */
1928 if (file->f_op->write == redirected_tty_write ||
1929 current->signal->tty != tty)
1932 spin_lock_irq(&tty->ctrl_lock);
1934 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1935 else if (task_pgrp(current) != tty->pgrp) {
1936 spin_unlock_irq(&tty->ctrl_lock);
1937 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1939 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1940 set_thread_flag(TIF_SIGPENDING);
1941 return -ERESTARTSYS;
1943 spin_unlock_irq(&tty->ctrl_lock);
1949 * n_tty_read - read function for tty
1951 * @file: file object
1952 * @buf: userspace buffer pointer
1955 * Perform reads for the line discipline. We are guaranteed that the
1956 * line discipline will not be closed under us but we may get multiple
1957 * parallel readers and must handle this ourselves. We may also get
1958 * a hangup. Always called in user context, may sleep.
1960 * This code must be sure never to sleep through a hangup.
1962 * n_tty_read()/consumer path:
1963 * claims non-exclusive termios_rwsem
1964 * publishes read_tail
1967 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1968 unsigned char __user *buf, size_t nr)
1970 struct n_tty_data *ldata = tty->disc_data;
1971 unsigned char __user *b = buf;
1972 DECLARE_WAITQUEUE(wait, current);
1978 unsigned long flags;
1982 c = job_control(tty, file);
1986 down_read(&tty->termios_rwsem);
1989 timeout = MAX_SCHEDULE_TIMEOUT;
1990 if (!ldata->icanon) {
1991 minimum = MIN_CHAR(tty);
1993 time = (HZ / 10) * TIME_CHAR(tty);
1995 ldata->minimum_to_wake = 1;
1996 else if (!waitqueue_active(&tty->read_wait) ||
1997 (ldata->minimum_to_wake > minimum))
1998 ldata->minimum_to_wake = minimum;
2000 timeout = (HZ / 10) * TIME_CHAR(tty);
2001 ldata->minimum_to_wake = minimum = 1;
2006 * Internal serialization of reads.
2008 if (file->f_flags & O_NONBLOCK) {
2009 if (!mutex_trylock(&ldata->atomic_read_lock)) {
2010 up_read(&tty->termios_rwsem);
2014 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2015 up_read(&tty->termios_rwsem);
2016 return -ERESTARTSYS;
2019 packet = tty->packet;
2021 add_wait_queue(&tty->read_wait, &wait);
2023 /* First test for status change. */
2024 if (packet && tty->link->ctrl_status) {
2028 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2029 cs = tty->link->ctrl_status;
2030 tty->link->ctrl_status = 0;
2031 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2032 if (tty_put_user(tty, cs, b++)) {
2040 /* This statement must be first before checking for input
2041 so that any interrupt will set the state back to
2043 set_current_state(TASK_INTERRUPTIBLE);
2045 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2046 ((minimum - (b - buf)) >= 1))
2047 ldata->minimum_to_wake = (minimum - (b - buf));
2049 if (!input_available_p(tty, 0)) {
2050 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2054 if (tty_hung_up_p(file))
2058 if (file->f_flags & O_NONBLOCK) {
2062 if (signal_pending(current)) {
2063 retval = -ERESTARTSYS;
2066 n_tty_set_room(tty);
2067 up_read(&tty->termios_rwsem);
2069 timeout = schedule_timeout(timeout);
2071 down_read(&tty->termios_rwsem);
2074 __set_current_state(TASK_RUNNING);
2076 /* Deal with packet mode. */
2077 if (packet && b == buf) {
2078 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2086 if (ldata->icanon && !L_EXTPROC(tty)) {
2087 retval = canon_copy_from_read_buf(tty, &b, &nr);
2092 /* The copy function takes the read lock and handles
2093 locking internally for this case */
2094 uncopied = copy_from_read_buf(tty, &b, &nr);
2095 uncopied += copy_from_read_buf(tty, &b, &nr);
2102 n_tty_check_unthrottle(tty);
2104 if (b - buf >= minimum)
2109 mutex_unlock(&ldata->atomic_read_lock);
2110 remove_wait_queue(&tty->read_wait, &wait);
2112 if (!waitqueue_active(&tty->read_wait))
2113 ldata->minimum_to_wake = minimum;
2115 __set_current_state(TASK_RUNNING);
2120 clear_bit(TTY_PUSH, &tty->flags);
2121 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
2122 up_read(&tty->termios_rwsem);
2126 n_tty_set_room(tty);
2127 up_read(&tty->termios_rwsem);
2132 * n_tty_write - write function for tty
2134 * @file: file object
2135 * @buf: userspace buffer pointer
2138 * Write function of the terminal device. This is serialized with
2139 * respect to other write callers but not to termios changes, reads
2140 * and other such events. Since the receive code will echo characters,
2141 * thus calling driver write methods, the output_lock is used in
2142 * the output processing functions called here as well as in the
2143 * echo processing function to protect the column state and space
2144 * left in the buffer.
2146 * This code must be sure never to sleep through a hangup.
2148 * Locking: output_lock to protect column state and space left
2149 * (note that the process_output*() functions take this
2153 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2154 const unsigned char *buf, size_t nr)
2156 const unsigned char *b = buf;
2157 DECLARE_WAITQUEUE(wait, current);
2161 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2162 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2163 retval = tty_check_change(tty);
2168 down_read(&tty->termios_rwsem);
2170 /* Write out any echoed characters that are still pending */
2171 process_echoes(tty);
2173 add_wait_queue(&tty->write_wait, &wait);
2175 set_current_state(TASK_INTERRUPTIBLE);
2176 if (signal_pending(current)) {
2177 retval = -ERESTARTSYS;
2180 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2186 ssize_t num = process_output_block(tty, b, nr);
2198 if (process_output(c, tty) < 0)
2202 if (tty->ops->flush_chars)
2203 tty->ops->flush_chars(tty);
2206 c = tty->ops->write(tty, b, nr);
2219 if (file->f_flags & O_NONBLOCK) {
2223 up_read(&tty->termios_rwsem);
2227 down_read(&tty->termios_rwsem);
2230 __set_current_state(TASK_RUNNING);
2231 remove_wait_queue(&tty->write_wait, &wait);
2232 if (b - buf != nr && tty->fasync)
2233 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2234 up_read(&tty->termios_rwsem);
2235 return (b - buf) ? b - buf : retval;
2239 * n_tty_poll - poll method for N_TTY
2240 * @tty: terminal device
2241 * @file: file accessing it
2244 * Called when the line discipline is asked to poll() for data or
2245 * for special events. This code is not serialized with respect to
2246 * other events save open/close.
2248 * This code must be sure never to sleep through a hangup.
2249 * Called without the kernel lock held - fine
2252 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2255 struct n_tty_data *ldata = tty->disc_data;
2256 unsigned int mask = 0;
2258 poll_wait(file, &tty->read_wait, wait);
2259 poll_wait(file, &tty->write_wait, wait);
2260 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2261 mask |= POLLIN | POLLRDNORM;
2262 if (tty->packet && tty->link->ctrl_status)
2263 mask |= POLLPRI | POLLIN | POLLRDNORM;
2264 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2266 if (tty_hung_up_p(file))
2268 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2269 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2270 ldata->minimum_to_wake = MIN_CHAR(tty);
2272 ldata->minimum_to_wake = 1;
2274 if (tty->ops->write && !tty_is_writelocked(tty) &&
2275 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2276 tty_write_room(tty) > 0)
2277 mask |= POLLOUT | POLLWRNORM;
2281 static unsigned long inq_canon(struct n_tty_data *ldata)
2283 size_t nr, head, tail;
2285 if (ldata->canon_head == ldata->read_tail)
2287 head = ldata->canon_head;
2288 tail = ldata->read_tail;
2290 /* Skip EOF-chars.. */
2291 while (head != tail) {
2292 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2293 read_buf(ldata, tail) == __DISABLED_CHAR)
2300 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2301 unsigned int cmd, unsigned long arg)
2303 struct n_tty_data *ldata = tty->disc_data;
2308 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2310 down_write(&tty->termios_rwsem);
2312 retval = inq_canon(ldata);
2314 retval = read_cnt(ldata);
2315 up_write(&tty->termios_rwsem);
2316 return put_user(retval, (unsigned int __user *) arg);
2318 return n_tty_ioctl_helper(tty, file, cmd, arg);
2322 static void n_tty_fasync(struct tty_struct *tty, int on)
2324 struct n_tty_data *ldata = tty->disc_data;
2326 if (!waitqueue_active(&tty->read_wait)) {
2328 ldata->minimum_to_wake = 1;
2329 else if (!tty->fasync)
2330 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2334 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2335 .magic = TTY_LDISC_MAGIC,
2338 .close = n_tty_close,
2339 .flush_buffer = n_tty_flush_buffer,
2340 .chars_in_buffer = n_tty_chars_in_buffer,
2342 .write = n_tty_write,
2343 .ioctl = n_tty_ioctl,
2344 .set_termios = n_tty_set_termios,
2346 .receive_buf = n_tty_receive_buf,
2347 .write_wakeup = n_tty_write_wakeup,
2348 .fasync = n_tty_fasync,
2349 .receive_buf2 = n_tty_receive_buf2,
2353 * n_tty_inherit_ops - inherit N_TTY methods
2354 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2356 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2360 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2362 *ops = tty_ldisc_N_TTY;
2364 ops->refcount = ops->flags = 0;
2366 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);