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
77 #define ECHO_COMMIT_WATERMARK 256
78 #define ECHO_BLOCK 256
79 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
84 # define n_tty_trace(f, args...) trace_printk(f, ##args)
86 # define n_tty_trace(f, args...)
90 /* producer-published */
95 DECLARE_BITMAP(process_char_map, 256);
97 /* private to n_tty_receive_overrun (single-threaded) */
98 unsigned long overrun_time;
104 /* must hold exclusive termios_rwsem to reset these */
105 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
107 /* shared by producer and consumer */
109 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
110 unsigned char *echo_buf;
114 /* consumer-published */
118 /* protected by output lock */
120 unsigned int canon_column;
123 struct mutex atomic_read_lock;
124 struct mutex output_lock;
127 static inline size_t read_cnt(struct n_tty_data *ldata)
129 return ldata->read_head - ldata->read_tail;
132 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
134 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
137 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
139 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
142 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
144 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
147 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
149 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
152 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
153 unsigned char __user *ptr)
155 struct n_tty_data *ldata = tty->disc_data;
157 tty_audit_add_data(tty, &x, 1, ldata->icanon);
158 return put_user(x, ptr);
161 static int receive_room(struct tty_struct *tty)
163 struct n_tty_data *ldata = tty->disc_data;
167 /* Multiply read_cnt by 3, since each byte might take up to
168 * three times as many spaces when PARMRK is set (depending on
169 * its flags, e.g. parity error). */
170 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
172 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
175 * If we are doing input canonicalization, and there are no
176 * pending newlines, let characters through without limit, so
177 * that erase characters will be handled. Other excess
178 * characters will be beeped.
181 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
187 * n_tty_set_room - receive space
190 * Re-schedules the flip buffer work if space just became available.
192 * Caller holds exclusive termios_rwsem
194 * n_tty_read()/consumer path:
195 * holds non-exclusive termios_rwsem
198 static void n_tty_set_room(struct tty_struct *tty)
200 struct n_tty_data *ldata = tty->disc_data;
202 /* Did this open up the receive buffer? We may need to flip */
203 if (unlikely(ldata->no_room) && receive_room(tty)) {
206 WARN_RATELIMIT(tty->port->itty == NULL,
207 "scheduling with invalid itty\n");
208 /* see if ldisc has been killed - if so, this means that
209 * even though the ldisc has been halted and ->buf.work
210 * cancelled, ->buf.work is about to be rescheduled
212 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
213 "scheduling buffer work for halted ldisc\n");
214 queue_work(system_unbound_wq, &tty->port->buf.work);
218 static ssize_t chars_in_buffer(struct tty_struct *tty)
220 struct n_tty_data *ldata = tty->disc_data;
226 n = ldata->canon_head - ldata->read_tail;
231 * n_tty_write_wakeup - asynchronous I/O notifier
234 * Required for the ptys, serial driver etc. since processes
235 * that attach themselves to the master and rely on ASYNC
236 * IO must be woken up
239 static void n_tty_write_wakeup(struct tty_struct *tty)
241 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
242 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
245 static inline void n_tty_check_throttle(struct tty_struct *tty)
247 if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
250 * Check the remaining room for the input canonicalization
251 * mode. We don't want to throttle the driver if we're in
252 * canonical mode and don't have a newline yet!
256 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
257 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
259 throttled = tty_throttle_safe(tty);
263 __tty_set_flow_change(tty, 0);
266 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
268 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
269 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
270 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
275 n_tty_write_wakeup(tty->link);
276 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
280 /* If there is enough space in the read buffer now, let the
281 * low-level driver know. We use chars_in_buffer() to
282 * check the buffer, as it now knows about canonical mode.
283 * Otherwise, if the driver is throttled and the line is
284 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
285 * we won't get any more characters.
290 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
291 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
296 unthrottled = tty_unthrottle_safe(tty);
300 __tty_set_flow_change(tty, 0);
304 * put_tty_queue - add character to tty
308 * Add a character to the tty read_buf queue.
310 * n_tty_receive_buf()/producer path:
311 * caller holds non-exclusive termios_rwsem
314 * read_head is only considered 'published' if canonical mode is
318 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
320 if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
321 *read_buf_addr(ldata, ldata->read_head) = c;
327 * reset_buffer_flags - reset buffer state
328 * @tty: terminal to reset
330 * Reset the read buffer counters and clear the flags.
331 * Called from n_tty_open() and n_tty_flush_buffer().
333 * Locking: caller holds exclusive termios_rwsem
334 * (or locking is not required)
337 static void reset_buffer_flags(struct n_tty_data *ldata)
339 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
340 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
341 ldata->line_start = 0;
344 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
347 static void n_tty_packet_mode_flush(struct tty_struct *tty)
351 spin_lock_irqsave(&tty->ctrl_lock, flags);
352 if (tty->link->packet) {
353 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
354 wake_up_interruptible(&tty->link->read_wait);
356 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
360 * n_tty_flush_buffer - clean input queue
361 * @tty: terminal device
363 * Flush the input buffer. Called when the tty layer wants the
364 * buffer flushed (eg at hangup) or when the N_TTY line discipline
365 * internally has to clean the pending queue (for example some signals).
367 * Holds termios_rwsem to exclude producer/consumer while
368 * buffer indices are reset.
370 * Locking: ctrl_lock, exclusive termios_rwsem
373 static void n_tty_flush_buffer(struct tty_struct *tty)
375 down_write(&tty->termios_rwsem);
376 reset_buffer_flags(tty->disc_data);
380 n_tty_packet_mode_flush(tty);
381 up_write(&tty->termios_rwsem);
385 * n_tty_chars_in_buffer - report available bytes
388 * Report the number of characters buffered to be delivered to user
389 * at this instant in time.
391 * Locking: exclusive termios_rwsem
394 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
398 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
400 down_write(&tty->termios_rwsem);
401 n = chars_in_buffer(tty);
402 up_write(&tty->termios_rwsem);
407 * is_utf8_continuation - utf8 multibyte check
410 * Returns true if the utf8 character 'c' is a multibyte continuation
411 * character. We use this to correctly compute the on screen size
412 * of the character when printing
415 static inline int is_utf8_continuation(unsigned char c)
417 return (c & 0xc0) == 0x80;
421 * is_continuation - multibyte check
424 * Returns true if the utf8 character 'c' is a multibyte continuation
425 * character and the terminal is in unicode mode.
428 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
430 return I_IUTF8(tty) && is_utf8_continuation(c);
434 * do_output_char - output one character
435 * @c: character (or partial unicode symbol)
436 * @tty: terminal device
437 * @space: space available in tty driver write buffer
439 * This is a helper function that handles one output character
440 * (including special characters like TAB, CR, LF, etc.),
441 * doing OPOST processing and putting the results in the
442 * tty driver's write buffer.
444 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
445 * and NLDLY. They simply aren't relevant in the world today.
446 * If you ever need them, add them here.
448 * Returns the number of bytes of buffer space used or -1 if
451 * Locking: should be called under the output_lock to protect
452 * the column state and space left in the buffer
455 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
457 struct n_tty_data *ldata = tty->disc_data;
470 ldata->canon_column = ldata->column = 0;
471 tty->ops->write(tty, "\r\n", 2);
474 ldata->canon_column = ldata->column;
477 if (O_ONOCR(tty) && ldata->column == 0)
482 ldata->canon_column = ldata->column = 0;
485 ldata->canon_column = ldata->column = 0;
488 spaces = 8 - (ldata->column & 7);
489 if (O_TABDLY(tty) == XTABS) {
492 ldata->column += spaces;
493 tty->ops->write(tty, " ", spaces);
496 ldata->column += spaces;
499 if (ldata->column > 0)
506 if (!is_continuation(c, tty))
512 tty_put_char(tty, c);
517 * process_output - output post processor
518 * @c: character (or partial unicode symbol)
519 * @tty: terminal device
521 * Output one character with OPOST processing.
522 * Returns -1 when the output device is full and the character
525 * Locking: output_lock to protect column state and space left
526 * (also, this is called from n_tty_write under the
527 * tty layer write lock)
530 static int process_output(unsigned char c, struct tty_struct *tty)
532 struct n_tty_data *ldata = tty->disc_data;
535 mutex_lock(&ldata->output_lock);
537 space = tty_write_room(tty);
538 retval = do_output_char(c, tty, space);
540 mutex_unlock(&ldata->output_lock);
548 * process_output_block - block post processor
549 * @tty: terminal device
550 * @buf: character buffer
551 * @nr: number of bytes to output
553 * Output a block of characters with OPOST processing.
554 * Returns the number of characters output.
556 * This path is used to speed up block console writes, among other
557 * things when processing blocks of output data. It handles only
558 * the simple cases normally found and helps to generate blocks of
559 * symbols for the console driver and thus improve performance.
561 * Locking: output_lock to protect column state and space left
562 * (also, this is called from n_tty_write under the
563 * tty layer write lock)
566 static ssize_t process_output_block(struct tty_struct *tty,
567 const unsigned char *buf, unsigned int nr)
569 struct n_tty_data *ldata = tty->disc_data;
572 const unsigned char *cp;
574 mutex_lock(&ldata->output_lock);
576 space = tty_write_room(tty);
578 mutex_unlock(&ldata->output_lock);
584 for (i = 0, cp = buf; i < nr; i++, cp++) {
585 unsigned char c = *cp;
593 ldata->canon_column = ldata->column;
596 if (O_ONOCR(tty) && ldata->column == 0)
600 ldata->canon_column = ldata->column = 0;
605 if (ldata->column > 0)
612 if (!is_continuation(c, tty))
619 i = tty->ops->write(tty, buf, i);
621 mutex_unlock(&ldata->output_lock);
626 * process_echoes - write pending echo characters
627 * @tty: terminal device
629 * Write previously buffered echo (and other ldisc-generated)
630 * characters to the tty.
632 * Characters generated by the ldisc (including echoes) need to
633 * be buffered because the driver's write buffer can fill during
634 * heavy program output. Echoing straight to the driver will
635 * often fail under these conditions, causing lost characters and
636 * resulting mismatches of ldisc state information.
638 * Since the ldisc state must represent the characters actually sent
639 * to the driver at the time of the write, operations like certain
640 * changes in column state are also saved in the buffer and executed
643 * A circular fifo buffer is used so that the most recent characters
644 * are prioritized. Also, when control characters are echoed with a
645 * prefixed "^", the pair is treated atomically and thus not separated.
647 * Locking: callers must hold output_lock
650 static size_t __process_echoes(struct tty_struct *tty)
652 struct n_tty_data *ldata = tty->disc_data;
653 int space, old_space;
657 old_space = space = tty_write_room(tty);
659 tail = ldata->echo_tail;
660 while (ldata->echo_commit != tail) {
661 c = echo_buf(ldata, tail);
662 if (c == ECHO_OP_START) {
664 int no_space_left = 0;
667 * If the buffer byte is the start of a multi-byte
668 * operation, get the next byte, which is either the
669 * op code or a control character value.
671 op = echo_buf(ldata, tail + 1);
674 unsigned int num_chars, num_bs;
676 case ECHO_OP_ERASE_TAB:
677 num_chars = echo_buf(ldata, tail + 2);
680 * Determine how many columns to go back
681 * in order to erase the tab.
682 * This depends on the number of columns
683 * used by other characters within the tab
684 * area. If this (modulo 8) count is from
685 * the start of input rather than from a
686 * previous tab, we offset by canon column.
687 * Otherwise, tab spacing is normal.
689 if (!(num_chars & 0x80))
690 num_chars += ldata->canon_column;
691 num_bs = 8 - (num_chars & 7);
693 if (num_bs > space) {
699 tty_put_char(tty, '\b');
700 if (ldata->column > 0)
706 case ECHO_OP_SET_CANON_COL:
707 ldata->canon_column = ldata->column;
711 case ECHO_OP_MOVE_BACK_COL:
712 if (ldata->column > 0)
718 /* This is an escaped echo op start code */
723 tty_put_char(tty, ECHO_OP_START);
731 * If the op is not a special byte code,
732 * it is a ctrl char tagged to be echoed
733 * as "^X" (where X is the letter
734 * representing the control char).
735 * Note that we must ensure there is
736 * enough space for the whole ctrl pair.
743 tty_put_char(tty, '^');
744 tty_put_char(tty, op ^ 0100);
754 int retval = do_output_char(c, tty, space);
761 tty_put_char(tty, c);
768 /* If the echo buffer is nearly full (so that the possibility exists
769 * of echo overrun before the next commit), then discard enough
770 * data at the tail to prevent a subsequent overrun */
771 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
772 if (echo_buf(ldata, tail == ECHO_OP_START)) {
773 if (echo_buf(ldata, tail) == ECHO_OP_ERASE_TAB)
781 ldata->echo_tail = tail;
782 return old_space - space;
785 static void commit_echoes(struct tty_struct *tty)
787 struct n_tty_data *ldata = tty->disc_data;
788 size_t nr, old, echoed;
791 head = ldata->echo_head;
792 old = ldata->echo_commit - ldata->echo_tail;
794 /* Process committed echoes if the accumulated # of bytes
795 * is over the threshold (and try again each time another
796 * block is accumulated) */
797 nr = head - ldata->echo_tail;
798 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
801 mutex_lock(&ldata->output_lock);
802 ldata->echo_commit = head;
803 echoed = __process_echoes(tty);
804 mutex_unlock(&ldata->output_lock);
806 if (echoed && tty->ops->flush_chars)
807 tty->ops->flush_chars(tty);
810 static void process_echoes(struct tty_struct *tty)
812 struct n_tty_data *ldata = tty->disc_data;
815 if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
818 mutex_lock(&ldata->output_lock);
819 echoed = __process_echoes(tty);
820 mutex_unlock(&ldata->output_lock);
822 if (echoed && tty->ops->flush_chars)
823 tty->ops->flush_chars(tty);
826 static void flush_echoes(struct tty_struct *tty)
828 struct n_tty_data *ldata = tty->disc_data;
830 if (!L_ECHO(tty) || 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 inline 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 inline 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 inline 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 inline void n_tty_receive_parity_error(struct tty_struct *tty,
1207 struct n_tty_data *ldata = tty->disc_data;
1211 if (I_PARMRK(tty)) {
1212 put_tty_queue('\377', ldata);
1213 put_tty_queue('\0', ldata);
1214 put_tty_queue(c, ldata);
1215 } else if (I_INPCK(tty))
1216 put_tty_queue('\0', ldata);
1218 put_tty_queue(c, ldata);
1219 wake_up_interruptible(&tty->read_wait);
1223 * n_tty_receive_char - perform processing
1224 * @tty: terminal device
1227 * Process an individual character of input received from the driver.
1228 * This is serialized with respect to itself by the rules for the
1231 * n_tty_receive_buf()/producer path:
1232 * caller holds non-exclusive termios_rwsem
1233 * publishes canon_head if canonical mode is active
1234 * otherwise, publishes read_head via put_tty_queue()
1237 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1239 struct n_tty_data *ldata = tty->disc_data;
1243 put_tty_queue(c, ldata);
1249 if (I_IUCLC(tty) && L_IEXTEN(tty))
1252 if (L_EXTPROC(tty)) {
1253 put_tty_queue(c, ldata);
1257 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1258 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1259 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1261 process_echoes(tty);
1266 if (c == START_CHAR(tty)) {
1268 process_echoes(tty);
1269 } else if (c == STOP_CHAR(tty))
1276 * If the previous character was LNEXT, or we know that this
1277 * character is not one of the characters that we'll have to
1278 * handle specially, do shortcut processing to speed things
1281 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1283 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1284 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1285 /* beep if no space */
1287 process_output('\a', tty);
1291 finish_erasing(ldata);
1292 /* Record the column of first canon char. */
1293 if (ldata->canon_head == ldata->read_head)
1294 echo_set_canon_col(ldata);
1299 put_tty_queue(c, ldata);
1300 put_tty_queue(c, ldata);
1305 if (c == START_CHAR(tty)) {
1310 if (c == STOP_CHAR(tty)) {
1319 if (c == INTR_CHAR(tty))
1322 if (c == QUIT_CHAR(tty))
1325 if (c == SUSP_CHAR(tty)) {
1327 if (!L_NOFLSH(tty)) {
1328 /* flushing needs exclusive termios_rwsem */
1329 up_read(&tty->termios_rwsem);
1330 n_tty_flush_buffer(tty);
1331 tty_driver_flush_buffer(tty);
1332 down_read(&tty->termios_rwsem);
1350 } else if (c == '\n' && I_INLCR(tty))
1353 if (ldata->icanon) {
1354 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1355 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1360 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1363 finish_erasing(ldata);
1364 if (L_ECHOCTL(tty)) {
1365 echo_char_raw('^', ldata);
1366 echo_char_raw('\b', ldata);
1372 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1374 size_t tail = ldata->canon_head;
1376 finish_erasing(ldata);
1378 echo_char_raw('\n', ldata);
1379 while (tail != ldata->read_head) {
1380 echo_char(read_buf(ldata, tail), tty);
1387 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1389 process_output('\a', tty);
1392 if (L_ECHO(tty) || L_ECHONL(tty)) {
1393 echo_char_raw('\n', ldata);
1396 goto handle_newline;
1398 if (c == EOF_CHAR(tty)) {
1399 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1401 c = __DISABLED_CHAR;
1402 goto handle_newline;
1404 if ((c == EOL_CHAR(tty)) ||
1405 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1406 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1408 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1410 process_output('\a', tty);
1414 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1417 /* Record the column of first canon char. */
1418 if (ldata->canon_head == ldata->read_head)
1419 echo_set_canon_col(ldata);
1424 * XXX does PARMRK doubling happen for
1425 * EOL_CHAR and EOL2_CHAR?
1428 put_tty_queue(c, ldata);
1431 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1432 put_tty_queue(c, ldata);
1433 ldata->canon_head = ldata->read_head;
1434 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1435 if (waitqueue_active(&tty->read_wait))
1436 wake_up_interruptible(&tty->read_wait);
1441 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1442 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1443 /* beep if no space */
1445 process_output('\a', tty);
1449 finish_erasing(ldata);
1451 echo_char_raw('\n', ldata);
1453 /* Record the column of first canon char. */
1454 if (ldata->canon_head == ldata->read_head)
1455 echo_set_canon_col(ldata);
1462 put_tty_queue(c, ldata);
1464 put_tty_queue(c, ldata);
1468 * n_tty_receive_buf - data receive
1469 * @tty: terminal device
1472 * @count: characters
1474 * Called by the terminal driver when a block of characters has
1475 * been received. This function must be called from soft contexts
1476 * not from interrupt context. The driver is responsible for making
1477 * calls one at a time and in order (or using flush_to_ldisc)
1479 * n_tty_receive_buf()/producer path:
1480 * claims non-exclusive termios_rwsem
1481 * publishes read_head and canon_head
1484 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1485 char *fp, int count)
1487 struct n_tty_data *ldata = tty->disc_data;
1488 char flags = TTY_NORMAL;
1491 if (ldata->real_raw) {
1494 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1495 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1496 n = min_t(size_t, count, n);
1497 memcpy(read_buf_addr(ldata, head), cp, n);
1498 ldata->read_head += n;
1502 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1503 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1504 n = min_t(size_t, count, n);
1505 memcpy(read_buf_addr(ldata, head), cp, n);
1506 ldata->read_head += n;
1510 for (i = count; i; i--, cp++) {
1515 n_tty_receive_char(tty, *cp);
1518 n_tty_receive_break(tty);
1522 n_tty_receive_parity_error(tty, *cp);
1525 n_tty_receive_overrun(tty);
1528 printk(KERN_ERR "%s: unknown flag %d\n",
1529 tty_name(tty, buf), flags);
1535 if (tty->ops->flush_chars)
1536 tty->ops->flush_chars(tty);
1539 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1541 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1542 if (waitqueue_active(&tty->read_wait))
1543 wake_up_interruptible(&tty->read_wait);
1546 n_tty_check_throttle(tty);
1549 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1550 char *fp, int count)
1552 down_read(&tty->termios_rwsem);
1553 __receive_buf(tty, cp, fp, count);
1554 up_read(&tty->termios_rwsem);
1557 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1558 char *fp, int count)
1560 struct n_tty_data *ldata = tty->disc_data;
1563 down_read(&tty->termios_rwsem);
1565 tty->receive_room = room = receive_room(tty);
1568 count = min(count, room);
1570 __receive_buf(tty, cp, fp, count);
1572 up_read(&tty->termios_rwsem);
1577 int is_ignored(int sig)
1579 return (sigismember(¤t->blocked, sig) ||
1580 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1584 * n_tty_set_termios - termios data changed
1586 * @old: previous data
1588 * Called by the tty layer when the user changes termios flags so
1589 * that the line discipline can plan ahead. This function cannot sleep
1590 * and is protected from re-entry by the tty layer. The user is
1591 * guaranteed that this function will not be re-entered or in progress
1592 * when the ldisc is closed.
1594 * Locking: Caller holds tty->termios_rwsem
1597 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1599 struct n_tty_data *ldata = tty->disc_data;
1600 int canon_change = 1;
1603 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1605 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1606 ldata->line_start = 0;
1607 ldata->canon_head = ldata->read_tail;
1612 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1613 wake_up_interruptible(&tty->read_wait);
1615 ldata->icanon = (L_ICANON(tty) != 0);
1617 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1618 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1619 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1621 bitmap_zero(ldata->process_char_map, 256);
1623 if (I_IGNCR(tty) || I_ICRNL(tty))
1624 set_bit('\r', ldata->process_char_map);
1626 set_bit('\n', ldata->process_char_map);
1628 if (L_ICANON(tty)) {
1629 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1630 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1631 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1632 set_bit('\n', ldata->process_char_map);
1633 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1634 if (L_IEXTEN(tty)) {
1635 set_bit(WERASE_CHAR(tty),
1636 ldata->process_char_map);
1637 set_bit(LNEXT_CHAR(tty),
1638 ldata->process_char_map);
1639 set_bit(EOL2_CHAR(tty),
1640 ldata->process_char_map);
1642 set_bit(REPRINT_CHAR(tty),
1643 ldata->process_char_map);
1647 set_bit(START_CHAR(tty), ldata->process_char_map);
1648 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1651 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1652 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1653 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1655 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1657 ldata->real_raw = 0;
1660 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1661 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1662 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1663 ldata->real_raw = 1;
1665 ldata->real_raw = 0;
1667 n_tty_set_room(tty);
1669 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1670 * been stopped by STOP_CHAR(tty) before it.
1672 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1676 /* The termios change make the tty ready for I/O */
1677 wake_up_interruptible(&tty->write_wait);
1678 wake_up_interruptible(&tty->read_wait);
1682 * n_tty_close - close the ldisc for this tty
1685 * Called from the terminal layer when this line discipline is
1686 * being shut down, either because of a close or becsuse of a
1687 * discipline change. The function will not be called while other
1688 * ldisc methods are in progress.
1691 static void n_tty_close(struct tty_struct *tty)
1693 struct n_tty_data *ldata = tty->disc_data;
1696 n_tty_packet_mode_flush(tty);
1698 kfree(ldata->read_buf);
1699 kfree(ldata->echo_buf);
1701 tty->disc_data = NULL;
1705 * n_tty_open - open an ldisc
1706 * @tty: terminal to open
1708 * Called when this line discipline is being attached to the
1709 * terminal device. Can sleep. Called serialized so that no
1710 * other events will occur in parallel. No further open will occur
1714 static int n_tty_open(struct tty_struct *tty)
1716 struct n_tty_data *ldata;
1718 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1722 ldata->overrun_time = jiffies;
1723 mutex_init(&ldata->atomic_read_lock);
1724 mutex_init(&ldata->output_lock);
1726 /* These are ugly. Currently a malloc failure here can panic */
1727 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1728 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1729 if (!ldata->read_buf || !ldata->echo_buf)
1732 tty->disc_data = ldata;
1733 reset_buffer_flags(tty->disc_data);
1735 ldata->minimum_to_wake = 1;
1737 /* indicate buffer work may resume */
1738 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1739 n_tty_set_termios(tty, NULL);
1740 tty_unthrottle(tty);
1744 kfree(ldata->read_buf);
1745 kfree(ldata->echo_buf);
1751 static inline int input_available_p(struct tty_struct *tty, int amt)
1753 struct n_tty_data *ldata = tty->disc_data;
1755 if (ldata->icanon && !L_EXTPROC(tty)) {
1756 if (ldata->canon_head != ldata->read_tail)
1758 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1765 * copy_from_read_buf - copy read data directly
1766 * @tty: terminal device
1770 * Helper function to speed up n_tty_read. It is only called when
1771 * ICANON is off; it copies characters straight from the tty queue to
1772 * user space directly. It can be profitably called twice; once to
1773 * drain the space from the tail pointer to the (physical) end of the
1774 * buffer, and once to drain the space from the (physical) beginning of
1775 * the buffer to head pointer.
1777 * Called under the ldata->atomic_read_lock sem
1779 * n_tty_read()/consumer path:
1780 * caller holds non-exclusive termios_rwsem
1781 * read_tail published
1784 static int copy_from_read_buf(struct tty_struct *tty,
1785 unsigned char __user **b,
1789 struct n_tty_data *ldata = tty->disc_data;
1793 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1796 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1799 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1801 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1802 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1804 ldata->read_tail += n;
1805 /* Turn single EOF into zero-length read */
1806 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1815 * canon_copy_from_read_buf - copy read data in canonical mode
1816 * @tty: terminal device
1820 * Helper function for n_tty_read. It is only called when ICANON is on;
1821 * it copies one line of input up to and including the line-delimiting
1822 * character into the user-space buffer.
1824 * Called under the atomic_read_lock mutex
1826 * n_tty_read()/consumer path:
1827 * caller holds non-exclusive termios_rwsem
1828 * read_tail published
1831 static int canon_copy_from_read_buf(struct tty_struct *tty,
1832 unsigned char __user **b,
1835 struct n_tty_data *ldata = tty->disc_data;
1836 size_t n, size, more, c;
1842 /* N.B. avoid overrun if nr == 0 */
1843 n = min(*nr, read_cnt(ldata));
1847 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1848 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1850 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1851 __func__, *nr, tail, n, size);
1853 eol = find_next_bit(ldata->read_flags, size, tail);
1854 more = n - (size - tail);
1855 if (eol == N_TTY_BUF_SIZE && more) {
1856 /* scan wrapped without finding set bit */
1857 eol = find_next_bit(ldata->read_flags, more, 0);
1860 } else if (eol != size)
1863 size = N_TTY_BUF_SIZE - tail;
1864 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1867 if (found && read_buf(ldata, eol) == __DISABLED_CHAR) {
1869 eof_push = !n && ldata->read_tail != ldata->line_start;
1872 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1873 __func__, eol, found, n, c, size, more);
1876 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1879 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1881 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1889 clear_bit(eol, ldata->read_flags);
1890 smp_mb__after_clear_bit();
1891 ldata->read_tail += c;
1894 ldata->line_start = ldata->read_tail;
1895 tty_audit_push(tty);
1897 return eof_push ? -EAGAIN : 0;
1900 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1904 * job_control - check job control
1906 * @file: file handle
1908 * Perform job control management checks on this file/tty descriptor
1909 * and if appropriate send any needed signals and return a negative
1910 * error code if action should be taken.
1912 * Locking: redirected write test is safe
1913 * current->signal->tty check is safe
1914 * ctrl_lock to safely reference tty->pgrp
1917 static int job_control(struct tty_struct *tty, struct file *file)
1919 /* Job control check -- must be done at start and after
1920 every sleep (POSIX.1 7.1.1.4). */
1921 /* NOTE: not yet done after every sleep pending a thorough
1922 check of the logic of this change. -- jlc */
1923 /* don't stop on /dev/console */
1924 if (file->f_op->write == redirected_tty_write ||
1925 current->signal->tty != tty)
1928 spin_lock_irq(&tty->ctrl_lock);
1930 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1931 else if (task_pgrp(current) != tty->pgrp) {
1932 spin_unlock_irq(&tty->ctrl_lock);
1933 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1935 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1936 set_thread_flag(TIF_SIGPENDING);
1937 return -ERESTARTSYS;
1939 spin_unlock_irq(&tty->ctrl_lock);
1945 * n_tty_read - read function for tty
1947 * @file: file object
1948 * @buf: userspace buffer pointer
1951 * Perform reads for the line discipline. We are guaranteed that the
1952 * line discipline will not be closed under us but we may get multiple
1953 * parallel readers and must handle this ourselves. We may also get
1954 * a hangup. Always called in user context, may sleep.
1956 * This code must be sure never to sleep through a hangup.
1958 * n_tty_read()/consumer path:
1959 * claims non-exclusive termios_rwsem
1960 * publishes read_tail
1963 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1964 unsigned char __user *buf, size_t nr)
1966 struct n_tty_data *ldata = tty->disc_data;
1967 unsigned char __user *b = buf;
1968 DECLARE_WAITQUEUE(wait, current);
1973 unsigned long flags;
1976 c = job_control(tty, file);
1980 down_read(&tty->termios_rwsem);
1983 timeout = MAX_SCHEDULE_TIMEOUT;
1984 if (!ldata->icanon) {
1985 minimum = MIN_CHAR(tty);
1987 time = (HZ / 10) * TIME_CHAR(tty);
1989 ldata->minimum_to_wake = 1;
1990 else if (!waitqueue_active(&tty->read_wait) ||
1991 (ldata->minimum_to_wake > minimum))
1992 ldata->minimum_to_wake = minimum;
1994 timeout = (HZ / 10) * TIME_CHAR(tty);
1995 ldata->minimum_to_wake = minimum = 1;
2000 * Internal serialization of reads.
2002 if (file->f_flags & O_NONBLOCK) {
2003 if (!mutex_trylock(&ldata->atomic_read_lock)) {
2004 up_read(&tty->termios_rwsem);
2008 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2009 up_read(&tty->termios_rwsem);
2010 return -ERESTARTSYS;
2013 packet = tty->packet;
2015 add_wait_queue(&tty->read_wait, &wait);
2017 /* First test for status change. */
2018 if (packet && tty->link->ctrl_status) {
2022 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2023 cs = tty->link->ctrl_status;
2024 tty->link->ctrl_status = 0;
2025 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2026 if (tty_put_user(tty, cs, b++)) {
2034 /* This statement must be first before checking for input
2035 so that any interrupt will set the state back to
2037 set_current_state(TASK_INTERRUPTIBLE);
2039 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2040 ((minimum - (b - buf)) >= 1))
2041 ldata->minimum_to_wake = (minimum - (b - buf));
2043 if (!input_available_p(tty, 0)) {
2044 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2048 if (tty_hung_up_p(file))
2052 if (file->f_flags & O_NONBLOCK) {
2056 if (signal_pending(current)) {
2057 retval = -ERESTARTSYS;
2060 n_tty_set_room(tty);
2061 up_read(&tty->termios_rwsem);
2063 timeout = schedule_timeout(timeout);
2065 down_read(&tty->termios_rwsem);
2068 __set_current_state(TASK_RUNNING);
2070 /* Deal with packet mode. */
2071 if (packet && b == buf) {
2072 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2080 if (ldata->icanon && !L_EXTPROC(tty)) {
2081 retval = canon_copy_from_read_buf(tty, &b, &nr);
2082 if (retval == -EAGAIN) {
2089 /* The copy function takes the read lock and handles
2090 locking internally for this case */
2091 uncopied = copy_from_read_buf(tty, &b, &nr);
2092 uncopied += copy_from_read_buf(tty, &b, &nr);
2099 n_tty_check_unthrottle(tty);
2101 if (b - buf >= minimum)
2106 mutex_unlock(&ldata->atomic_read_lock);
2107 remove_wait_queue(&tty->read_wait, &wait);
2109 if (!waitqueue_active(&tty->read_wait))
2110 ldata->minimum_to_wake = minimum;
2112 __set_current_state(TASK_RUNNING);
2116 n_tty_set_room(tty);
2117 up_read(&tty->termios_rwsem);
2122 * n_tty_write - write function for tty
2124 * @file: file object
2125 * @buf: userspace buffer pointer
2128 * Write function of the terminal device. This is serialized with
2129 * respect to other write callers but not to termios changes, reads
2130 * and other such events. Since the receive code will echo characters,
2131 * thus calling driver write methods, the output_lock is used in
2132 * the output processing functions called here as well as in the
2133 * echo processing function to protect the column state and space
2134 * left in the buffer.
2136 * This code must be sure never to sleep through a hangup.
2138 * Locking: output_lock to protect column state and space left
2139 * (note that the process_output*() functions take this
2143 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2144 const unsigned char *buf, size_t nr)
2146 const unsigned char *b = buf;
2147 DECLARE_WAITQUEUE(wait, current);
2151 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2152 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2153 retval = tty_check_change(tty);
2158 down_read(&tty->termios_rwsem);
2160 /* Write out any echoed characters that are still pending */
2161 process_echoes(tty);
2163 add_wait_queue(&tty->write_wait, &wait);
2165 set_current_state(TASK_INTERRUPTIBLE);
2166 if (signal_pending(current)) {
2167 retval = -ERESTARTSYS;
2170 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2176 ssize_t num = process_output_block(tty, b, nr);
2188 if (process_output(c, tty) < 0)
2192 if (tty->ops->flush_chars)
2193 tty->ops->flush_chars(tty);
2196 c = tty->ops->write(tty, b, nr);
2209 if (file->f_flags & O_NONBLOCK) {
2213 up_read(&tty->termios_rwsem);
2217 down_read(&tty->termios_rwsem);
2220 __set_current_state(TASK_RUNNING);
2221 remove_wait_queue(&tty->write_wait, &wait);
2222 if (b - buf != nr && tty->fasync)
2223 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2224 up_read(&tty->termios_rwsem);
2225 return (b - buf) ? b - buf : retval;
2229 * n_tty_poll - poll method for N_TTY
2230 * @tty: terminal device
2231 * @file: file accessing it
2234 * Called when the line discipline is asked to poll() for data or
2235 * for special events. This code is not serialized with respect to
2236 * other events save open/close.
2238 * This code must be sure never to sleep through a hangup.
2239 * Called without the kernel lock held - fine
2242 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2245 struct n_tty_data *ldata = tty->disc_data;
2246 unsigned int mask = 0;
2248 poll_wait(file, &tty->read_wait, wait);
2249 poll_wait(file, &tty->write_wait, wait);
2250 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2251 mask |= POLLIN | POLLRDNORM;
2252 if (tty->packet && tty->link->ctrl_status)
2253 mask |= POLLPRI | POLLIN | POLLRDNORM;
2254 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2256 if (tty_hung_up_p(file))
2258 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2259 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2260 ldata->minimum_to_wake = MIN_CHAR(tty);
2262 ldata->minimum_to_wake = 1;
2264 if (tty->ops->write && !tty_is_writelocked(tty) &&
2265 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2266 tty_write_room(tty) > 0)
2267 mask |= POLLOUT | POLLWRNORM;
2271 static unsigned long inq_canon(struct n_tty_data *ldata)
2273 size_t nr, head, tail;
2275 if (ldata->canon_head == ldata->read_tail)
2277 head = ldata->canon_head;
2278 tail = ldata->read_tail;
2280 /* Skip EOF-chars.. */
2281 while (head != tail) {
2282 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2283 read_buf(ldata, tail) == __DISABLED_CHAR)
2290 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2291 unsigned int cmd, unsigned long arg)
2293 struct n_tty_data *ldata = tty->disc_data;
2298 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2300 down_write(&tty->termios_rwsem);
2302 retval = inq_canon(ldata);
2304 retval = read_cnt(ldata);
2305 up_write(&tty->termios_rwsem);
2306 return put_user(retval, (unsigned int __user *) arg);
2308 return n_tty_ioctl_helper(tty, file, cmd, arg);
2312 static void n_tty_fasync(struct tty_struct *tty, int on)
2314 struct n_tty_data *ldata = tty->disc_data;
2316 if (!waitqueue_active(&tty->read_wait)) {
2318 ldata->minimum_to_wake = 1;
2319 else if (!tty->fasync)
2320 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2324 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2325 .magic = TTY_LDISC_MAGIC,
2328 .close = n_tty_close,
2329 .flush_buffer = n_tty_flush_buffer,
2330 .chars_in_buffer = n_tty_chars_in_buffer,
2332 .write = n_tty_write,
2333 .ioctl = n_tty_ioctl,
2334 .set_termios = n_tty_set_termios,
2336 .receive_buf = n_tty_receive_buf,
2337 .write_wakeup = n_tty_write_wakeup,
2338 .fasync = n_tty_fasync,
2339 .receive_buf2 = n_tty_receive_buf2,
2343 * n_tty_inherit_ops - inherit N_TTY methods
2344 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2346 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2350 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2352 *ops = tty_ldisc_N_TTY;
2354 ops->refcount = ops->flags = 0;
2356 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);