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 */
96 DECLARE_BITMAP(char_map, 256);
98 /* private to n_tty_receive_overrun (single-threaded) */
99 unsigned long overrun_time;
105 /* must hold exclusive termios_rwsem to reset these */
106 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
108 /* shared by producer and consumer */
109 char read_buf[N_TTY_BUF_SIZE];
110 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
111 unsigned char echo_buf[N_TTY_BUF_SIZE];
115 /* consumer-published */
119 /* protected by output lock */
121 unsigned int canon_column;
124 struct mutex atomic_read_lock;
125 struct mutex output_lock;
128 static inline size_t read_cnt(struct n_tty_data *ldata)
130 return ldata->read_head - ldata->read_tail;
133 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
135 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
138 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
140 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
143 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
145 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
148 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
150 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
153 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
154 unsigned char __user *ptr)
156 struct n_tty_data *ldata = tty->disc_data;
158 tty_audit_add_data(tty, &x, 1, ldata->icanon);
159 return put_user(x, ptr);
162 static int receive_room(struct tty_struct *tty)
164 struct n_tty_data *ldata = tty->disc_data;
168 /* Multiply read_cnt by 3, since each byte might take up to
169 * three times as many spaces when PARMRK is set (depending on
170 * its flags, e.g. parity error). */
171 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
173 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
176 * If we are doing input canonicalization, and there are no
177 * pending newlines, let characters through without limit, so
178 * that erase characters will be handled. Other excess
179 * characters will be beeped.
182 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
188 * n_tty_set_room - receive space
191 * Re-schedules the flip buffer work if space just became available.
193 * Caller holds exclusive termios_rwsem
195 * n_tty_read()/consumer path:
196 * holds non-exclusive termios_rwsem
199 static void n_tty_set_room(struct tty_struct *tty)
201 struct n_tty_data *ldata = tty->disc_data;
203 /* Did this open up the receive buffer? We may need to flip */
204 if (unlikely(ldata->no_room) && receive_room(tty)) {
207 WARN_RATELIMIT(tty->port->itty == NULL,
208 "scheduling with invalid itty\n");
209 /* see if ldisc has been killed - if so, this means that
210 * even though the ldisc has been halted and ->buf.work
211 * cancelled, ->buf.work is about to be rescheduled
213 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
214 "scheduling buffer work for halted ldisc\n");
215 queue_work(system_unbound_wq, &tty->port->buf.work);
219 static ssize_t chars_in_buffer(struct tty_struct *tty)
221 struct n_tty_data *ldata = tty->disc_data;
227 n = ldata->canon_head - ldata->read_tail;
232 * n_tty_write_wakeup - asynchronous I/O notifier
235 * Required for the ptys, serial driver etc. since processes
236 * that attach themselves to the master and rely on ASYNC
237 * IO must be woken up
240 static void n_tty_write_wakeup(struct tty_struct *tty)
242 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
243 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
246 static void n_tty_check_throttle(struct tty_struct *tty)
248 if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
251 * Check the remaining room for the input canonicalization
252 * mode. We don't want to throttle the driver if we're in
253 * canonical mode and don't have a newline yet!
257 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
258 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
260 throttled = tty_throttle_safe(tty);
264 __tty_set_flow_change(tty, 0);
267 static void n_tty_check_unthrottle(struct tty_struct *tty)
269 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
270 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
271 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
276 n_tty_write_wakeup(tty->link);
277 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
281 /* If there is enough space in the read buffer now, let the
282 * low-level driver know. We use chars_in_buffer() to
283 * check the buffer, as it now knows about canonical mode.
284 * Otherwise, if the driver is throttled and the line is
285 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
286 * we won't get any more characters.
291 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
292 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
297 unthrottled = tty_unthrottle_safe(tty);
301 __tty_set_flow_change(tty, 0);
305 * put_tty_queue - add character to tty
309 * Add a character to the tty read_buf queue.
311 * n_tty_receive_buf()/producer path:
312 * caller holds non-exclusive termios_rwsem
315 * read_head is only considered 'published' if canonical mode is
319 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
321 *read_buf_addr(ldata, ldata->read_head++) = c;
325 * reset_buffer_flags - reset buffer state
326 * @tty: terminal to reset
328 * Reset the read buffer counters and clear the flags.
329 * Called from n_tty_open() and n_tty_flush_buffer().
331 * Locking: caller holds exclusive termios_rwsem
332 * (or locking is not required)
335 static void reset_buffer_flags(struct n_tty_data *ldata)
337 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
338 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
339 ldata->line_start = 0;
342 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
345 static void n_tty_packet_mode_flush(struct tty_struct *tty)
349 spin_lock_irqsave(&tty->ctrl_lock, flags);
350 if (tty->link->packet) {
351 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
352 wake_up_interruptible(&tty->link->read_wait);
354 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
358 * n_tty_flush_buffer - clean input queue
359 * @tty: terminal device
361 * Flush the input buffer. Called when the tty layer wants the
362 * buffer flushed (eg at hangup) or when the N_TTY line discipline
363 * internally has to clean the pending queue (for example some signals).
365 * Holds termios_rwsem to exclude producer/consumer while
366 * buffer indices are reset.
368 * Locking: ctrl_lock, exclusive termios_rwsem
371 static void n_tty_flush_buffer(struct tty_struct *tty)
373 down_write(&tty->termios_rwsem);
374 reset_buffer_flags(tty->disc_data);
378 n_tty_packet_mode_flush(tty);
379 up_write(&tty->termios_rwsem);
383 * n_tty_chars_in_buffer - report available bytes
386 * Report the number of characters buffered to be delivered to user
387 * at this instant in time.
389 * Locking: exclusive termios_rwsem
392 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
396 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
398 down_write(&tty->termios_rwsem);
399 n = chars_in_buffer(tty);
400 up_write(&tty->termios_rwsem);
405 * is_utf8_continuation - utf8 multibyte check
408 * Returns true if the utf8 character 'c' is a multibyte continuation
409 * character. We use this to correctly compute the on screen size
410 * of the character when printing
413 static inline int is_utf8_continuation(unsigned char c)
415 return (c & 0xc0) == 0x80;
419 * is_continuation - multibyte check
422 * Returns true if the utf8 character 'c' is a multibyte continuation
423 * character and the terminal is in unicode mode.
426 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
428 return I_IUTF8(tty) && is_utf8_continuation(c);
432 * do_output_char - output one character
433 * @c: character (or partial unicode symbol)
434 * @tty: terminal device
435 * @space: space available in tty driver write buffer
437 * This is a helper function that handles one output character
438 * (including special characters like TAB, CR, LF, etc.),
439 * doing OPOST processing and putting the results in the
440 * tty driver's write buffer.
442 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
443 * and NLDLY. They simply aren't relevant in the world today.
444 * If you ever need them, add them here.
446 * Returns the number of bytes of buffer space used or -1 if
449 * Locking: should be called under the output_lock to protect
450 * the column state and space left in the buffer
453 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
455 struct n_tty_data *ldata = tty->disc_data;
468 ldata->canon_column = ldata->column = 0;
469 tty->ops->write(tty, "\r\n", 2);
472 ldata->canon_column = ldata->column;
475 if (O_ONOCR(tty) && ldata->column == 0)
480 ldata->canon_column = ldata->column = 0;
483 ldata->canon_column = ldata->column = 0;
486 spaces = 8 - (ldata->column & 7);
487 if (O_TABDLY(tty) == XTABS) {
490 ldata->column += spaces;
491 tty->ops->write(tty, " ", spaces);
494 ldata->column += spaces;
497 if (ldata->column > 0)
504 if (!is_continuation(c, tty))
510 tty_put_char(tty, c);
515 * process_output - output post processor
516 * @c: character (or partial unicode symbol)
517 * @tty: terminal device
519 * Output one character with OPOST processing.
520 * Returns -1 when the output device is full and the character
523 * Locking: output_lock to protect column state and space left
524 * (also, this is called from n_tty_write under the
525 * tty layer write lock)
528 static int process_output(unsigned char c, struct tty_struct *tty)
530 struct n_tty_data *ldata = tty->disc_data;
533 mutex_lock(&ldata->output_lock);
535 space = tty_write_room(tty);
536 retval = do_output_char(c, tty, space);
538 mutex_unlock(&ldata->output_lock);
546 * process_output_block - block post processor
547 * @tty: terminal device
548 * @buf: character buffer
549 * @nr: number of bytes to output
551 * Output a block of characters with OPOST processing.
552 * Returns the number of characters output.
554 * This path is used to speed up block console writes, among other
555 * things when processing blocks of output data. It handles only
556 * the simple cases normally found and helps to generate blocks of
557 * symbols for the console driver and thus improve performance.
559 * Locking: output_lock to protect column state and space left
560 * (also, this is called from n_tty_write under the
561 * tty layer write lock)
564 static ssize_t process_output_block(struct tty_struct *tty,
565 const unsigned char *buf, unsigned int nr)
567 struct n_tty_data *ldata = tty->disc_data;
570 const unsigned char *cp;
572 mutex_lock(&ldata->output_lock);
574 space = tty_write_room(tty);
576 mutex_unlock(&ldata->output_lock);
582 for (i = 0, cp = buf; i < nr; i++, cp++) {
583 unsigned char c = *cp;
591 ldata->canon_column = ldata->column;
594 if (O_ONOCR(tty) && ldata->column == 0)
598 ldata->canon_column = ldata->column = 0;
603 if (ldata->column > 0)
610 if (!is_continuation(c, tty))
617 i = tty->ops->write(tty, buf, i);
619 mutex_unlock(&ldata->output_lock);
624 * process_echoes - write pending echo characters
625 * @tty: terminal device
627 * Write previously buffered echo (and other ldisc-generated)
628 * characters to the tty.
630 * Characters generated by the ldisc (including echoes) need to
631 * be buffered because the driver's write buffer can fill during
632 * heavy program output. Echoing straight to the driver will
633 * often fail under these conditions, causing lost characters and
634 * resulting mismatches of ldisc state information.
636 * Since the ldisc state must represent the characters actually sent
637 * to the driver at the time of the write, operations like certain
638 * changes in column state are also saved in the buffer and executed
641 * A circular fifo buffer is used so that the most recent characters
642 * are prioritized. Also, when control characters are echoed with a
643 * prefixed "^", the pair is treated atomically and thus not separated.
645 * Locking: callers must hold output_lock
648 static size_t __process_echoes(struct tty_struct *tty)
650 struct n_tty_data *ldata = tty->disc_data;
651 int space, old_space;
655 old_space = space = tty_write_room(tty);
657 tail = ldata->echo_tail;
658 while (ldata->echo_commit != tail) {
659 c = echo_buf(ldata, tail);
660 if (c == ECHO_OP_START) {
662 int no_space_left = 0;
665 * If the buffer byte is the start of a multi-byte
666 * operation, get the next byte, which is either the
667 * op code or a control character value.
669 op = echo_buf(ldata, tail + 1);
672 unsigned int num_chars, num_bs;
674 case ECHO_OP_ERASE_TAB:
675 num_chars = echo_buf(ldata, tail + 2);
678 * Determine how many columns to go back
679 * in order to erase the tab.
680 * This depends on the number of columns
681 * used by other characters within the tab
682 * area. If this (modulo 8) count is from
683 * the start of input rather than from a
684 * previous tab, we offset by canon column.
685 * Otherwise, tab spacing is normal.
687 if (!(num_chars & 0x80))
688 num_chars += ldata->canon_column;
689 num_bs = 8 - (num_chars & 7);
691 if (num_bs > space) {
697 tty_put_char(tty, '\b');
698 if (ldata->column > 0)
704 case ECHO_OP_SET_CANON_COL:
705 ldata->canon_column = ldata->column;
709 case ECHO_OP_MOVE_BACK_COL:
710 if (ldata->column > 0)
716 /* This is an escaped echo op start code */
721 tty_put_char(tty, ECHO_OP_START);
729 * If the op is not a special byte code,
730 * it is a ctrl char tagged to be echoed
731 * as "^X" (where X is the letter
732 * representing the control char).
733 * Note that we must ensure there is
734 * enough space for the whole ctrl pair.
741 tty_put_char(tty, '^');
742 tty_put_char(tty, op ^ 0100);
752 int retval = do_output_char(c, tty, space);
759 tty_put_char(tty, c);
766 /* If the echo buffer is nearly full (so that the possibility exists
767 * of echo overrun before the next commit), then discard enough
768 * data at the tail to prevent a subsequent overrun */
769 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
770 if (echo_buf(ldata, tail) == ECHO_OP_START) {
771 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
779 ldata->echo_tail = tail;
780 return old_space - space;
783 static void commit_echoes(struct tty_struct *tty)
785 struct n_tty_data *ldata = tty->disc_data;
786 size_t nr, old, echoed;
789 head = ldata->echo_head;
790 old = ldata->echo_commit - ldata->echo_tail;
792 /* Process committed echoes if the accumulated # of bytes
793 * is over the threshold (and try again each time another
794 * block is accumulated) */
795 nr = head - ldata->echo_tail;
796 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
799 mutex_lock(&ldata->output_lock);
800 ldata->echo_commit = head;
801 echoed = __process_echoes(tty);
802 mutex_unlock(&ldata->output_lock);
804 if (echoed && tty->ops->flush_chars)
805 tty->ops->flush_chars(tty);
808 static void process_echoes(struct tty_struct *tty)
810 struct n_tty_data *ldata = tty->disc_data;
813 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
814 ldata->echo_commit == ldata->echo_tail)
817 mutex_lock(&ldata->output_lock);
818 echoed = __process_echoes(tty);
819 mutex_unlock(&ldata->output_lock);
821 if (echoed && tty->ops->flush_chars)
822 tty->ops->flush_chars(tty);
825 static void flush_echoes(struct tty_struct *tty)
827 struct n_tty_data *ldata = tty->disc_data;
829 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
830 ldata->echo_commit == ldata->echo_head)
833 mutex_lock(&ldata->output_lock);
834 ldata->echo_commit = ldata->echo_head;
835 __process_echoes(tty);
836 mutex_unlock(&ldata->output_lock);
840 * add_echo_byte - add a byte to the echo buffer
841 * @c: unicode byte to echo
844 * Add a character or operation byte to the echo buffer.
847 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
849 *echo_buf_addr(ldata, ldata->echo_head++) = c;
853 * echo_move_back_col - add operation to move back a column
856 * Add an operation to the echo buffer to move back one column.
859 static void echo_move_back_col(struct n_tty_data *ldata)
861 add_echo_byte(ECHO_OP_START, ldata);
862 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
866 * echo_set_canon_col - add operation to set the canon column
869 * Add an operation to the echo buffer to set the canon column
870 * to the current column.
873 static void echo_set_canon_col(struct n_tty_data *ldata)
875 add_echo_byte(ECHO_OP_START, ldata);
876 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
880 * echo_erase_tab - add operation to erase a tab
881 * @num_chars: number of character columns already used
882 * @after_tab: true if num_chars starts after a previous tab
885 * Add an operation to the echo buffer to erase a tab.
887 * Called by the eraser function, which knows how many character
888 * columns have been used since either a previous tab or the start
889 * of input. This information will be used later, along with
890 * canon column (if applicable), to go back the correct number
894 static void echo_erase_tab(unsigned int num_chars, int after_tab,
895 struct n_tty_data *ldata)
897 add_echo_byte(ECHO_OP_START, ldata);
898 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
900 /* We only need to know this modulo 8 (tab spacing) */
903 /* Set the high bit as a flag if num_chars is after a previous tab */
907 add_echo_byte(num_chars, ldata);
911 * echo_char_raw - echo a character raw
912 * @c: unicode byte to echo
913 * @tty: terminal device
915 * Echo user input back onto the screen. This must be called only when
916 * L_ECHO(tty) is true. Called from the driver receive_buf path.
918 * This variant does not treat control characters specially.
921 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
923 if (c == ECHO_OP_START) {
924 add_echo_byte(ECHO_OP_START, ldata);
925 add_echo_byte(ECHO_OP_START, ldata);
927 add_echo_byte(c, ldata);
932 * echo_char - echo a character
933 * @c: unicode byte to echo
934 * @tty: terminal device
936 * Echo user input back onto the screen. This must be called only when
937 * L_ECHO(tty) is true. Called from the driver receive_buf path.
939 * This variant tags control characters to be echoed as "^X"
940 * (where X is the letter representing the control char).
943 static void echo_char(unsigned char c, struct tty_struct *tty)
945 struct n_tty_data *ldata = tty->disc_data;
947 if (c == ECHO_OP_START) {
948 add_echo_byte(ECHO_OP_START, ldata);
949 add_echo_byte(ECHO_OP_START, ldata);
951 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
952 add_echo_byte(ECHO_OP_START, ldata);
953 add_echo_byte(c, ldata);
958 * finish_erasing - complete erase
962 static inline void finish_erasing(struct n_tty_data *ldata)
964 if (ldata->erasing) {
965 echo_char_raw('/', ldata);
971 * eraser - handle erase function
972 * @c: character input
973 * @tty: terminal device
975 * Perform erase and necessary output when an erase character is
976 * present in the stream from the driver layer. Handles the complexities
977 * of UTF-8 multibyte symbols.
979 * n_tty_receive_buf()/producer path:
980 * caller holds non-exclusive termios_rwsem
983 * Modifying the read_head is not considered a publish in this context
984 * because canonical mode is active -- only canon_head publishes
987 static void eraser(unsigned char c, struct tty_struct *tty)
989 struct n_tty_data *ldata = tty->disc_data;
990 enum { ERASE, WERASE, KILL } kill_type;
995 if (ldata->read_head == ldata->canon_head) {
996 /* process_output('\a', tty); */ /* what do you think? */
999 if (c == ERASE_CHAR(tty))
1001 else if (c == WERASE_CHAR(tty))
1005 ldata->read_head = ldata->canon_head;
1008 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1009 ldata->read_head = ldata->canon_head;
1010 finish_erasing(ldata);
1011 echo_char(KILL_CHAR(tty), tty);
1012 /* Add a newline if ECHOK is on and ECHOKE is off. */
1014 echo_char_raw('\n', ldata);
1021 while (ldata->read_head != ldata->canon_head) {
1022 head = ldata->read_head;
1024 /* erase a single possibly multibyte character */
1027 c = read_buf(ldata, head);
1028 } while (is_continuation(c, tty) && head != ldata->canon_head);
1030 /* do not partially erase */
1031 if (is_continuation(c, tty))
1034 if (kill_type == WERASE) {
1035 /* Equivalent to BSD's ALTWERASE. */
1036 if (isalnum(c) || c == '_')
1038 else if (seen_alnums)
1041 cnt = ldata->read_head - head;
1042 ldata->read_head = head;
1044 if (L_ECHOPRT(tty)) {
1045 if (!ldata->erasing) {
1046 echo_char_raw('\\', ldata);
1049 /* if cnt > 1, output a multi-byte character */
1053 echo_char_raw(read_buf(ldata, head), ldata);
1054 echo_move_back_col(ldata);
1056 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1057 echo_char(ERASE_CHAR(tty), tty);
1058 } else if (c == '\t') {
1059 unsigned int num_chars = 0;
1061 size_t tail = ldata->read_head;
1064 * Count the columns used for characters
1065 * since the start of input or after a
1067 * This info is used to go back the correct
1068 * number of columns.
1070 while (tail != ldata->canon_head) {
1072 c = read_buf(ldata, tail);
1076 } else if (iscntrl(c)) {
1079 } else if (!is_continuation(c, tty)) {
1083 echo_erase_tab(num_chars, after_tab, ldata);
1085 if (iscntrl(c) && L_ECHOCTL(tty)) {
1086 echo_char_raw('\b', ldata);
1087 echo_char_raw(' ', ldata);
1088 echo_char_raw('\b', ldata);
1090 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1091 echo_char_raw('\b', ldata);
1092 echo_char_raw(' ', ldata);
1093 echo_char_raw('\b', ldata);
1097 if (kill_type == ERASE)
1100 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1101 finish_erasing(ldata);
1105 * isig - handle the ISIG optio
1109 * Called when a signal is being sent due to terminal input.
1110 * Called from the driver receive_buf path so serialized.
1112 * Locking: ctrl_lock
1115 static void isig(int sig, struct tty_struct *tty)
1117 struct pid *tty_pgrp = tty_get_pgrp(tty);
1119 kill_pgrp(tty_pgrp, sig, 1);
1125 * n_tty_receive_break - handle break
1128 * An RS232 break event has been hit in the incoming bitstream. This
1129 * can cause a variety of events depending upon the termios settings.
1131 * n_tty_receive_buf()/producer path:
1132 * caller holds non-exclusive termios_rwsem
1133 * publishes read_head via put_tty_queue()
1135 * Note: may get exclusive termios_rwsem if flushing input buffer
1138 static void n_tty_receive_break(struct tty_struct *tty)
1140 struct n_tty_data *ldata = tty->disc_data;
1144 if (I_BRKINT(tty)) {
1146 if (!L_NOFLSH(tty)) {
1147 /* flushing needs exclusive termios_rwsem */
1148 up_read(&tty->termios_rwsem);
1149 n_tty_flush_buffer(tty);
1150 tty_driver_flush_buffer(tty);
1151 down_read(&tty->termios_rwsem);
1155 if (I_PARMRK(tty)) {
1156 put_tty_queue('\377', ldata);
1157 put_tty_queue('\0', ldata);
1159 put_tty_queue('\0', ldata);
1160 wake_up_interruptible(&tty->read_wait);
1164 * n_tty_receive_overrun - handle overrun reporting
1167 * Data arrived faster than we could process it. While the tty
1168 * driver has flagged this the bits that were missed are gone
1171 * Called from the receive_buf path so single threaded. Does not
1172 * need locking as num_overrun and overrun_time are function
1176 static void n_tty_receive_overrun(struct tty_struct *tty)
1178 struct n_tty_data *ldata = tty->disc_data;
1181 ldata->num_overrun++;
1182 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1183 time_after(ldata->overrun_time, jiffies)) {
1184 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1186 ldata->num_overrun);
1187 ldata->overrun_time = jiffies;
1188 ldata->num_overrun = 0;
1193 * n_tty_receive_parity_error - error notifier
1194 * @tty: terminal device
1197 * Process a parity error and queue the right data to indicate
1198 * the error case if necessary.
1200 * n_tty_receive_buf()/producer path:
1201 * caller holds non-exclusive termios_rwsem
1202 * publishes read_head via put_tty_queue()
1204 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1206 struct n_tty_data *ldata = tty->disc_data;
1210 if (I_PARMRK(tty)) {
1211 put_tty_queue('\377', ldata);
1212 put_tty_queue('\0', ldata);
1213 put_tty_queue(c, ldata);
1214 } else if (I_INPCK(tty))
1215 put_tty_queue('\0', ldata);
1217 put_tty_queue(c, ldata);
1218 wake_up_interruptible(&tty->read_wait);
1222 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1224 if (!L_NOFLSH(tty)) {
1225 /* flushing needs exclusive termios_rwsem */
1226 up_read(&tty->termios_rwsem);
1227 n_tty_flush_buffer(tty);
1228 tty_driver_flush_buffer(tty);
1229 down_read(&tty->termios_rwsem);
1242 * n_tty_receive_char - perform processing
1243 * @tty: terminal device
1246 * Process an individual character of input received from the driver.
1247 * This is serialized with respect to itself by the rules for the
1250 * n_tty_receive_buf()/producer path:
1251 * caller holds non-exclusive termios_rwsem
1252 * publishes canon_head if canonical mode is active
1253 * otherwise, publishes read_head via put_tty_queue()
1255 * Returns 1 if LNEXT was received, else returns 0
1259 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1261 struct n_tty_data *ldata = tty->disc_data;
1265 if (c == START_CHAR(tty)) {
1270 if (c == STOP_CHAR(tty)) {
1277 if (c == INTR_CHAR(tty)) {
1278 n_tty_receive_signal_char(tty, SIGINT, c);
1280 } else if (c == QUIT_CHAR(tty)) {
1281 n_tty_receive_signal_char(tty, SIGQUIT, c);
1283 } else if (c == SUSP_CHAR(tty)) {
1284 n_tty_receive_signal_char(tty, SIGTSTP, c);
1289 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1291 process_echoes(tty);
1299 } else if (c == '\n' && I_INLCR(tty))
1302 if (ldata->icanon) {
1303 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1304 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1309 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1312 finish_erasing(ldata);
1313 if (L_ECHOCTL(tty)) {
1314 echo_char_raw('^', ldata);
1315 echo_char_raw('\b', ldata);
1321 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1322 size_t tail = ldata->canon_head;
1324 finish_erasing(ldata);
1326 echo_char_raw('\n', ldata);
1327 while (tail != ldata->read_head) {
1328 echo_char(read_buf(ldata, tail), tty);
1335 if (L_ECHO(tty) || L_ECHONL(tty)) {
1336 echo_char_raw('\n', ldata);
1339 goto handle_newline;
1341 if (c == EOF_CHAR(tty)) {
1342 c = __DISABLED_CHAR;
1343 goto handle_newline;
1345 if ((c == EOL_CHAR(tty)) ||
1346 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1347 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1350 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1353 /* Record the column of first canon char. */
1354 if (ldata->canon_head == ldata->read_head)
1355 echo_set_canon_col(ldata);
1360 * XXX does PARMRK doubling happen for
1361 * EOL_CHAR and EOL2_CHAR?
1364 put_tty_queue(c, ldata);
1367 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1368 put_tty_queue(c, ldata);
1369 ldata->canon_head = ldata->read_head;
1370 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1371 if (waitqueue_active(&tty->read_wait))
1372 wake_up_interruptible(&tty->read_wait);
1377 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1379 finish_erasing(ldata);
1381 echo_char_raw('\n', ldata);
1383 /* Record the column of first canon char. */
1384 if (ldata->canon_head == ldata->read_head)
1385 echo_set_canon_col(ldata);
1392 put_tty_queue(c, ldata);
1394 put_tty_queue(c, ldata);
1399 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1401 struct n_tty_data *ldata = tty->disc_data;
1404 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1406 process_echoes(tty);
1409 finish_erasing(ldata);
1410 /* Record the column of first canon char. */
1411 if (ldata->canon_head == ldata->read_head)
1412 echo_set_canon_col(ldata);
1416 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1418 put_tty_queue(c, ldata);
1419 put_tty_queue(c, ldata);
1422 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1424 n_tty_receive_char_inline(tty, c);
1428 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1430 struct n_tty_data *ldata = tty->disc_data;
1432 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1434 process_echoes(tty);
1437 finish_erasing(ldata);
1438 /* Record the column of first canon char. */
1439 if (ldata->canon_head == ldata->read_head)
1440 echo_set_canon_col(ldata);
1444 put_tty_queue(c, ldata);
1448 n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1452 if (I_IUCLC(tty) && L_IEXTEN(tty))
1456 if (c == STOP_CHAR(tty))
1458 else if (c == START_CHAR(tty) ||
1459 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1460 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1461 c != SUSP_CHAR(tty))) {
1463 process_echoes(tty);
1469 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1475 n_tty_receive_break(tty);
1479 n_tty_receive_parity_error(tty, c);
1482 n_tty_receive_overrun(tty);
1485 printk(KERN_ERR "%s: unknown flag %d\n",
1486 tty_name(tty, buf), flag);
1492 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1494 struct n_tty_data *ldata = tty->disc_data;
1497 if (likely(flag == TTY_NORMAL)) {
1500 if (I_IUCLC(tty) && L_IEXTEN(tty))
1502 n_tty_receive_char(tty, c);
1504 n_tty_receive_char_flagged(tty, c, flag);
1508 * n_tty_receive_buf - data receive
1509 * @tty: terminal device
1512 * @count: characters
1514 * Called by the terminal driver when a block of characters has
1515 * been received. This function must be called from soft contexts
1516 * not from interrupt context. The driver is responsible for making
1517 * calls one at a time and in order (or using flush_to_ldisc)
1519 * n_tty_receive_buf()/producer path:
1520 * claims non-exclusive termios_rwsem
1521 * publishes read_head and canon_head
1525 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1526 char *fp, int count)
1528 struct n_tty_data *ldata = tty->disc_data;
1531 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1532 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1533 n = min_t(size_t, count, n);
1534 memcpy(read_buf_addr(ldata, head), cp, n);
1535 ldata->read_head += n;
1539 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1540 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1541 n = min_t(size_t, count, n);
1542 memcpy(read_buf_addr(ldata, head), cp, n);
1543 ldata->read_head += n;
1547 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1548 char *fp, int count)
1550 struct n_tty_data *ldata = tty->disc_data;
1551 char flag = TTY_NORMAL;
1556 if (likely(flag == TTY_NORMAL))
1557 put_tty_queue(*cp++, ldata);
1559 n_tty_receive_char_flagged(tty, *cp++, flag);
1564 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1565 char *fp, int count)
1567 char flag = TTY_NORMAL;
1572 if (likely(flag == TTY_NORMAL))
1573 n_tty_receive_char_closing(tty, *cp++);
1575 n_tty_receive_char_flagged(tty, *cp++, flag);
1580 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1581 char *fp, int count)
1583 struct n_tty_data *ldata = tty->disc_data;
1584 char flag = TTY_NORMAL;
1589 if (likely(flag == TTY_NORMAL)) {
1590 unsigned char c = *cp++;
1594 if (I_IUCLC(tty) && L_IEXTEN(tty))
1596 if (L_EXTPROC(tty)) {
1597 put_tty_queue(c, ldata);
1600 if (!test_bit(c, ldata->char_map))
1601 n_tty_receive_char_inline(tty, c);
1602 else if (n_tty_receive_char_special(tty, c) && count) {
1605 n_tty_receive_char_lnext(tty, *cp++, flag);
1609 n_tty_receive_char_flagged(tty, *cp++, flag);
1614 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1615 char *fp, int count)
1617 struct n_tty_data *ldata = tty->disc_data;
1618 char flag = TTY_NORMAL;
1623 if (likely(flag == TTY_NORMAL)) {
1624 unsigned char c = *cp++;
1626 if (!test_bit(c, ldata->char_map))
1627 n_tty_receive_char_fast(tty, c);
1628 else if (n_tty_receive_char_special(tty, c) && count) {
1631 n_tty_receive_char_lnext(tty, *cp++, flag);
1635 n_tty_receive_char_flagged(tty, *cp++, flag);
1639 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1640 char *fp, int count)
1642 struct n_tty_data *ldata = tty->disc_data;
1643 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1645 if (ldata->real_raw)
1646 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1647 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1648 n_tty_receive_buf_raw(tty, cp, fp, count);
1649 else if (tty->closing && !L_EXTPROC(tty))
1650 n_tty_receive_buf_closing(tty, cp, fp, count);
1653 char flag = TTY_NORMAL;
1657 n_tty_receive_char_lnext(tty, *cp++, flag);
1661 if (!preops && !I_PARMRK(tty))
1662 n_tty_receive_buf_fast(tty, cp, fp, count);
1664 n_tty_receive_buf_standard(tty, cp, fp, count);
1667 if (tty->ops->flush_chars)
1668 tty->ops->flush_chars(tty);
1671 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1673 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1674 if (waitqueue_active(&tty->read_wait))
1675 wake_up_interruptible(&tty->read_wait);
1679 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1680 char *fp, int count)
1684 down_read(&tty->termios_rwsem);
1687 room = receive_room(tty);
1688 n = min(count, room);
1691 __receive_buf(tty, cp, fp, n);
1698 tty->receive_room = room;
1699 n_tty_check_throttle(tty);
1700 up_read(&tty->termios_rwsem);
1703 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1704 char *fp, int count)
1706 struct n_tty_data *ldata = tty->disc_data;
1707 int room, n, rcvd = 0;
1709 down_read(&tty->termios_rwsem);
1712 room = receive_room(tty);
1713 n = min(count, room);
1719 __receive_buf(tty, cp, fp, n);
1727 tty->receive_room = room;
1728 n_tty_check_throttle(tty);
1729 up_read(&tty->termios_rwsem);
1734 int is_ignored(int sig)
1736 return (sigismember(¤t->blocked, sig) ||
1737 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1741 * n_tty_set_termios - termios data changed
1743 * @old: previous data
1745 * Called by the tty layer when the user changes termios flags so
1746 * that the line discipline can plan ahead. This function cannot sleep
1747 * and is protected from re-entry by the tty layer. The user is
1748 * guaranteed that this function will not be re-entered or in progress
1749 * when the ldisc is closed.
1751 * Locking: Caller holds tty->termios_rwsem
1754 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1756 struct n_tty_data *ldata = tty->disc_data;
1758 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1759 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1760 ldata->line_start = ldata->canon_head = ldata->read_tail;
1765 ldata->icanon = (L_ICANON(tty) != 0);
1767 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1768 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1769 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1771 bitmap_zero(ldata->char_map, 256);
1773 if (I_IGNCR(tty) || I_ICRNL(tty))
1774 set_bit('\r', ldata->char_map);
1776 set_bit('\n', ldata->char_map);
1778 if (L_ICANON(tty)) {
1779 set_bit(ERASE_CHAR(tty), ldata->char_map);
1780 set_bit(KILL_CHAR(tty), ldata->char_map);
1781 set_bit(EOF_CHAR(tty), ldata->char_map);
1782 set_bit('\n', ldata->char_map);
1783 set_bit(EOL_CHAR(tty), ldata->char_map);
1784 if (L_IEXTEN(tty)) {
1785 set_bit(WERASE_CHAR(tty), ldata->char_map);
1786 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1787 set_bit(EOL2_CHAR(tty), ldata->char_map);
1789 set_bit(REPRINT_CHAR(tty),
1794 set_bit(START_CHAR(tty), ldata->char_map);
1795 set_bit(STOP_CHAR(tty), ldata->char_map);
1798 set_bit(INTR_CHAR(tty), ldata->char_map);
1799 set_bit(QUIT_CHAR(tty), ldata->char_map);
1800 set_bit(SUSP_CHAR(tty), ldata->char_map);
1802 clear_bit(__DISABLED_CHAR, ldata->char_map);
1804 ldata->real_raw = 0;
1807 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1808 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1809 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1810 ldata->real_raw = 1;
1812 ldata->real_raw = 0;
1814 n_tty_set_room(tty);
1816 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1817 * been stopped by STOP_CHAR(tty) before it.
1819 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped)
1822 /* The termios change make the tty ready for I/O */
1823 wake_up_interruptible(&tty->write_wait);
1824 wake_up_interruptible(&tty->read_wait);
1828 * n_tty_close - close the ldisc for this tty
1831 * Called from the terminal layer when this line discipline is
1832 * being shut down, either because of a close or becsuse of a
1833 * discipline change. The function will not be called while other
1834 * ldisc methods are in progress.
1837 static void n_tty_close(struct tty_struct *tty)
1839 struct n_tty_data *ldata = tty->disc_data;
1842 n_tty_packet_mode_flush(tty);
1845 tty->disc_data = NULL;
1849 * n_tty_open - open an ldisc
1850 * @tty: terminal to open
1852 * Called when this line discipline is being attached to the
1853 * terminal device. Can sleep. Called serialized so that no
1854 * other events will occur in parallel. No further open will occur
1858 static int n_tty_open(struct tty_struct *tty)
1860 struct n_tty_data *ldata;
1862 /* Currently a malloc failure here can panic */
1863 ldata = vmalloc(sizeof(*ldata));
1867 ldata->overrun_time = jiffies;
1868 mutex_init(&ldata->atomic_read_lock);
1869 mutex_init(&ldata->output_lock);
1871 tty->disc_data = ldata;
1872 reset_buffer_flags(tty->disc_data);
1874 ldata->canon_column = 0;
1875 ldata->minimum_to_wake = 1;
1876 ldata->num_overrun = 0;
1880 /* indicate buffer work may resume */
1881 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1882 n_tty_set_termios(tty, NULL);
1883 tty_unthrottle(tty);
1890 static inline int input_available_p(struct tty_struct *tty, int amt)
1892 struct n_tty_data *ldata = tty->disc_data;
1894 if (ldata->icanon && !L_EXTPROC(tty)) {
1895 if (ldata->canon_head != ldata->read_tail)
1897 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1904 * copy_from_read_buf - copy read data directly
1905 * @tty: terminal device
1909 * Helper function to speed up n_tty_read. It is only called when
1910 * ICANON is off; it copies characters straight from the tty queue to
1911 * user space directly. It can be profitably called twice; once to
1912 * drain the space from the tail pointer to the (physical) end of the
1913 * buffer, and once to drain the space from the (physical) beginning of
1914 * the buffer to head pointer.
1916 * Called under the ldata->atomic_read_lock sem
1918 * n_tty_read()/consumer path:
1919 * caller holds non-exclusive termios_rwsem
1920 * read_tail published
1923 static int copy_from_read_buf(struct tty_struct *tty,
1924 unsigned char __user **b,
1928 struct n_tty_data *ldata = tty->disc_data;
1932 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1935 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1938 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1940 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1941 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1943 ldata->read_tail += n;
1944 /* Turn single EOF into zero-length read */
1945 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1954 * canon_copy_from_read_buf - copy read data in canonical mode
1955 * @tty: terminal device
1959 * Helper function for n_tty_read. It is only called when ICANON is on;
1960 * it copies one line of input up to and including the line-delimiting
1961 * character into the user-space buffer.
1963 * Called under the atomic_read_lock mutex
1965 * n_tty_read()/consumer path:
1966 * caller holds non-exclusive termios_rwsem
1967 * read_tail published
1970 static int canon_copy_from_read_buf(struct tty_struct *tty,
1971 unsigned char __user **b,
1974 struct n_tty_data *ldata = tty->disc_data;
1975 size_t n, size, more, c;
1981 /* N.B. avoid overrun if nr == 0 */
1982 n = min(*nr, read_cnt(ldata));
1986 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1987 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1989 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1990 __func__, *nr, tail, n, size);
1992 eol = find_next_bit(ldata->read_flags, size, tail);
1993 more = n - (size - tail);
1994 if (eol == N_TTY_BUF_SIZE && more) {
1995 /* scan wrapped without finding set bit */
1996 eol = find_next_bit(ldata->read_flags, more, 0);
1999 } else if (eol != size)
2002 size = N_TTY_BUF_SIZE - tail;
2009 if (found && read_buf(ldata, eol) == __DISABLED_CHAR) {
2011 eof_push = !n && ldata->read_tail != ldata->line_start;
2014 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
2015 __func__, eol, found, n, c, size, more);
2018 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
2021 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
2023 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
2031 clear_bit(eol, ldata->read_flags);
2032 smp_mb__after_clear_bit();
2033 ldata->read_tail += c;
2036 ldata->line_start = ldata->read_tail;
2037 tty_audit_push(tty);
2039 return eof_push ? -EAGAIN : 0;
2042 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2046 * job_control - check job control
2048 * @file: file handle
2050 * Perform job control management checks on this file/tty descriptor
2051 * and if appropriate send any needed signals and return a negative
2052 * error code if action should be taken.
2054 * Locking: redirected write test is safe
2055 * current->signal->tty check is safe
2056 * ctrl_lock to safely reference tty->pgrp
2059 static int job_control(struct tty_struct *tty, struct file *file)
2061 /* Job control check -- must be done at start and after
2062 every sleep (POSIX.1 7.1.1.4). */
2063 /* NOTE: not yet done after every sleep pending a thorough
2064 check of the logic of this change. -- jlc */
2065 /* don't stop on /dev/console */
2066 if (file->f_op->write == redirected_tty_write ||
2067 current->signal->tty != tty)
2070 spin_lock_irq(&tty->ctrl_lock);
2072 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
2073 else if (task_pgrp(current) != tty->pgrp) {
2074 spin_unlock_irq(&tty->ctrl_lock);
2075 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
2077 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
2078 set_thread_flag(TIF_SIGPENDING);
2079 return -ERESTARTSYS;
2081 spin_unlock_irq(&tty->ctrl_lock);
2087 * n_tty_read - read function for tty
2089 * @file: file object
2090 * @buf: userspace buffer pointer
2093 * Perform reads for the line discipline. We are guaranteed that the
2094 * line discipline will not be closed under us but we may get multiple
2095 * parallel readers and must handle this ourselves. We may also get
2096 * a hangup. Always called in user context, may sleep.
2098 * This code must be sure never to sleep through a hangup.
2100 * n_tty_read()/consumer path:
2101 * claims non-exclusive termios_rwsem
2102 * publishes read_tail
2105 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2106 unsigned char __user *buf, size_t nr)
2108 struct n_tty_data *ldata = tty->disc_data;
2109 unsigned char __user *b = buf;
2110 DECLARE_WAITQUEUE(wait, current);
2115 unsigned long flags;
2118 c = job_control(tty, file);
2123 * Internal serialization of reads.
2125 if (file->f_flags & O_NONBLOCK) {
2126 if (!mutex_trylock(&ldata->atomic_read_lock))
2129 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2130 return -ERESTARTSYS;
2133 down_read(&tty->termios_rwsem);
2136 timeout = MAX_SCHEDULE_TIMEOUT;
2137 if (!ldata->icanon) {
2138 minimum = MIN_CHAR(tty);
2140 time = (HZ / 10) * TIME_CHAR(tty);
2142 ldata->minimum_to_wake = 1;
2143 else if (!waitqueue_active(&tty->read_wait) ||
2144 (ldata->minimum_to_wake > minimum))
2145 ldata->minimum_to_wake = minimum;
2147 timeout = (HZ / 10) * TIME_CHAR(tty);
2148 ldata->minimum_to_wake = minimum = 1;
2152 packet = tty->packet;
2154 add_wait_queue(&tty->read_wait, &wait);
2156 /* First test for status change. */
2157 if (packet && tty->link->ctrl_status) {
2161 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2162 cs = tty->link->ctrl_status;
2163 tty->link->ctrl_status = 0;
2164 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2165 if (tty_put_user(tty, cs, b++)) {
2173 /* This statement must be first before checking for input
2174 so that any interrupt will set the state back to
2176 set_current_state(TASK_INTERRUPTIBLE);
2178 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2179 ((minimum - (b - buf)) >= 1))
2180 ldata->minimum_to_wake = (minimum - (b - buf));
2182 if (!input_available_p(tty, 0)) {
2183 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2184 up_read(&tty->termios_rwsem);
2185 tty_flush_to_ldisc(tty);
2186 down_read(&tty->termios_rwsem);
2187 if (!input_available_p(tty, 0)) {
2192 if (tty_hung_up_p(file))
2196 if (file->f_flags & O_NONBLOCK) {
2200 if (signal_pending(current)) {
2201 retval = -ERESTARTSYS;
2204 n_tty_set_room(tty);
2205 up_read(&tty->termios_rwsem);
2207 timeout = schedule_timeout(timeout);
2209 down_read(&tty->termios_rwsem);
2213 __set_current_state(TASK_RUNNING);
2215 /* Deal with packet mode. */
2216 if (packet && b == buf) {
2217 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2225 if (ldata->icanon && !L_EXTPROC(tty)) {
2226 retval = canon_copy_from_read_buf(tty, &b, &nr);
2227 if (retval == -EAGAIN) {
2234 /* The copy function takes the read lock and handles
2235 locking internally for this case */
2236 uncopied = copy_from_read_buf(tty, &b, &nr);
2237 uncopied += copy_from_read_buf(tty, &b, &nr);
2244 n_tty_check_unthrottle(tty);
2246 if (b - buf >= minimum)
2251 n_tty_set_room(tty);
2252 up_read(&tty->termios_rwsem);
2254 remove_wait_queue(&tty->read_wait, &wait);
2255 if (!waitqueue_active(&tty->read_wait))
2256 ldata->minimum_to_wake = minimum;
2258 mutex_unlock(&ldata->atomic_read_lock);
2260 __set_current_state(TASK_RUNNING);
2268 * n_tty_write - write function for tty
2270 * @file: file object
2271 * @buf: userspace buffer pointer
2274 * Write function of the terminal device. This is serialized with
2275 * respect to other write callers but not to termios changes, reads
2276 * and other such events. Since the receive code will echo characters,
2277 * thus calling driver write methods, the output_lock is used in
2278 * the output processing functions called here as well as in the
2279 * echo processing function to protect the column state and space
2280 * left in the buffer.
2282 * This code must be sure never to sleep through a hangup.
2284 * Locking: output_lock to protect column state and space left
2285 * (note that the process_output*() functions take this
2289 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2290 const unsigned char *buf, size_t nr)
2292 const unsigned char *b = buf;
2293 DECLARE_WAITQUEUE(wait, current);
2297 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2298 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2299 retval = tty_check_change(tty);
2304 down_read(&tty->termios_rwsem);
2306 /* Write out any echoed characters that are still pending */
2307 process_echoes(tty);
2309 add_wait_queue(&tty->write_wait, &wait);
2311 set_current_state(TASK_INTERRUPTIBLE);
2312 if (signal_pending(current)) {
2313 retval = -ERESTARTSYS;
2316 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2322 ssize_t num = process_output_block(tty, b, nr);
2334 if (process_output(c, tty) < 0)
2338 if (tty->ops->flush_chars)
2339 tty->ops->flush_chars(tty);
2342 c = tty->ops->write(tty, b, nr);
2355 if (file->f_flags & O_NONBLOCK) {
2359 up_read(&tty->termios_rwsem);
2363 down_read(&tty->termios_rwsem);
2366 __set_current_state(TASK_RUNNING);
2367 remove_wait_queue(&tty->write_wait, &wait);
2368 if (b - buf != nr && tty->fasync)
2369 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2370 up_read(&tty->termios_rwsem);
2371 return (b - buf) ? b - buf : retval;
2375 * n_tty_poll - poll method for N_TTY
2376 * @tty: terminal device
2377 * @file: file accessing it
2380 * Called when the line discipline is asked to poll() for data or
2381 * for special events. This code is not serialized with respect to
2382 * other events save open/close.
2384 * This code must be sure never to sleep through a hangup.
2385 * Called without the kernel lock held - fine
2388 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2391 struct n_tty_data *ldata = tty->disc_data;
2392 unsigned int mask = 0;
2394 poll_wait(file, &tty->read_wait, wait);
2395 poll_wait(file, &tty->write_wait, wait);
2396 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2397 mask |= POLLIN | POLLRDNORM;
2398 if (tty->packet && tty->link->ctrl_status)
2399 mask |= POLLPRI | POLLIN | POLLRDNORM;
2400 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2402 if (tty_hung_up_p(file))
2404 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2405 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2406 ldata->minimum_to_wake = MIN_CHAR(tty);
2408 ldata->minimum_to_wake = 1;
2410 if (tty->ops->write && !tty_is_writelocked(tty) &&
2411 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2412 tty_write_room(tty) > 0)
2413 mask |= POLLOUT | POLLWRNORM;
2417 static unsigned long inq_canon(struct n_tty_data *ldata)
2419 size_t nr, head, tail;
2421 if (ldata->canon_head == ldata->read_tail)
2423 head = ldata->canon_head;
2424 tail = ldata->read_tail;
2426 /* Skip EOF-chars.. */
2427 while (head != tail) {
2428 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2429 read_buf(ldata, tail) == __DISABLED_CHAR)
2436 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2437 unsigned int cmd, unsigned long arg)
2439 struct n_tty_data *ldata = tty->disc_data;
2444 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2446 down_write(&tty->termios_rwsem);
2448 retval = inq_canon(ldata);
2450 retval = read_cnt(ldata);
2451 up_write(&tty->termios_rwsem);
2452 return put_user(retval, (unsigned int __user *) arg);
2454 return n_tty_ioctl_helper(tty, file, cmd, arg);
2458 static void n_tty_fasync(struct tty_struct *tty, int on)
2460 struct n_tty_data *ldata = tty->disc_data;
2462 if (!waitqueue_active(&tty->read_wait)) {
2464 ldata->minimum_to_wake = 1;
2465 else if (!tty->fasync)
2466 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2470 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2471 .magic = TTY_LDISC_MAGIC,
2474 .close = n_tty_close,
2475 .flush_buffer = n_tty_flush_buffer,
2476 .chars_in_buffer = n_tty_chars_in_buffer,
2478 .write = n_tty_write,
2479 .ioctl = n_tty_ioctl,
2480 .set_termios = n_tty_set_termios,
2482 .receive_buf = n_tty_receive_buf,
2483 .write_wakeup = n_tty_write_wakeup,
2484 .fasync = n_tty_fasync,
2485 .receive_buf2 = n_tty_receive_buf2,
2489 * n_tty_inherit_ops - inherit N_TTY methods
2490 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2492 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2496 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2498 *ops = tty_ldisc_N_TTY;
2500 ops->refcount = ops->flags = 0;
2502 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);