2 * n_tty.c --- implements the N_TTY line discipline.
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where n_tty_write returns
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52 #include <linux/ratelimit.h>
55 /* number of characters left in xmit buffer before select has we have room */
56 #define WAKEUP_CHARS 256
59 * This defines the low- and high-watermarks for throttling and
60 * unthrottling the TTY driver. These watermarks are used for
61 * controlling the space in the read buffer.
63 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
64 #define TTY_THRESHOLD_UNTHROTTLE 128
67 * Special byte codes used in the echo buffer to represent operations
68 * or special handling of characters. Bytes in the echo buffer that
69 * are not part of such special blocks are treated as normal character
72 #define ECHO_OP_START 0xff
73 #define ECHO_OP_MOVE_BACK_COL 0x80
74 #define ECHO_OP_SET_CANON_COL 0x81
75 #define ECHO_OP_ERASE_TAB 0x82
79 # define n_tty_trace(f, args...) trace_printk(f, ##args)
81 # define n_tty_trace(f, args...)
85 /* producer-published */
88 DECLARE_BITMAP(process_char_map, 256);
90 /* private to n_tty_receive_overrun (single-threaded) */
91 unsigned long overrun_time;
97 /* must hold exclusive termios_rwsem to reset these */
98 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
100 /* shared by producer and consumer */
102 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
106 /* consumer-published */
109 /* protected by echo_lock */
110 unsigned char *echo_buf;
113 unsigned int echo_cnt;
115 /* protected by output lock */
117 unsigned int canon_column;
119 struct mutex atomic_read_lock;
120 struct mutex output_lock;
121 struct mutex echo_lock;
124 static inline size_t read_cnt(struct n_tty_data *ldata)
126 return ldata->read_head - ldata->read_tail;
129 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
131 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
134 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
136 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
139 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
141 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
144 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
146 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
149 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
150 unsigned char __user *ptr)
152 struct n_tty_data *ldata = tty->disc_data;
154 tty_audit_add_data(tty, &x, 1, ldata->icanon);
155 return put_user(x, ptr);
158 static int receive_room(struct tty_struct *tty)
160 struct n_tty_data *ldata = tty->disc_data;
164 /* Multiply read_cnt by 3, since each byte might take up to
165 * three times as many spaces when PARMRK is set (depending on
166 * its flags, e.g. parity error). */
167 left = N_TTY_BUF_SIZE - read_cnt(ldata) * 3 - 1;
169 left = N_TTY_BUF_SIZE - read_cnt(ldata) - 1;
172 * If we are doing input canonicalization, and there are no
173 * pending newlines, let characters through without limit, so
174 * that erase characters will be handled. Other excess
175 * characters will be beeped.
178 left = ldata->icanon && ldata->canon_head == ldata->read_tail;
184 * n_tty_set_room - receive space
187 * Re-schedules the flip buffer work if space just became available.
189 * Caller holds exclusive termios_rwsem
191 * n_tty_read()/consumer path:
192 * holds non-exclusive termios_rwsem
195 static void n_tty_set_room(struct tty_struct *tty)
197 struct n_tty_data *ldata = tty->disc_data;
199 /* Did this open up the receive buffer? We may need to flip */
200 if (unlikely(ldata->no_room) && receive_room(tty)) {
203 WARN_RATELIMIT(tty->port->itty == NULL,
204 "scheduling with invalid itty\n");
205 /* see if ldisc has been killed - if so, this means that
206 * even though the ldisc has been halted and ->buf.work
207 * cancelled, ->buf.work is about to be rescheduled
209 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
210 "scheduling buffer work for halted ldisc\n");
211 queue_work(system_unbound_wq, &tty->port->buf.work);
215 static ssize_t chars_in_buffer(struct tty_struct *tty)
217 struct n_tty_data *ldata = tty->disc_data;
223 n = ldata->canon_head - ldata->read_tail;
228 * n_tty_write_wakeup - asynchronous I/O notifier
231 * Required for the ptys, serial driver etc. since processes
232 * that attach themselves to the master and rely on ASYNC
233 * IO must be woken up
236 static void n_tty_write_wakeup(struct tty_struct *tty)
238 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
239 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
242 static inline void n_tty_check_throttle(struct tty_struct *tty)
244 if (tty->driver->type == TTY_DRIVER_TYPE_PTY)
247 * Check the remaining room for the input canonicalization
248 * mode. We don't want to throttle the driver if we're in
249 * canonical mode and don't have a newline yet!
253 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
254 if (receive_room(tty) >= TTY_THRESHOLD_THROTTLE)
256 throttled = tty_throttle_safe(tty);
260 __tty_set_flow_change(tty, 0);
263 static inline void n_tty_check_unthrottle(struct tty_struct *tty)
265 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
266 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
267 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
272 n_tty_write_wakeup(tty->link);
273 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
277 /* If there is enough space in the read buffer now, let the
278 * low-level driver know. We use chars_in_buffer() to
279 * check the buffer, as it now knows about canonical mode.
280 * Otherwise, if the driver is throttled and the line is
281 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
282 * we won't get any more characters.
287 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
288 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
293 unthrottled = tty_unthrottle_safe(tty);
297 __tty_set_flow_change(tty, 0);
301 * put_tty_queue - add character to tty
305 * Add a character to the tty read_buf queue.
307 * n_tty_receive_buf()/producer path:
308 * caller holds non-exclusive termios_rwsem
311 * read_head is only considered 'published' if canonical mode is
315 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
317 if (read_cnt(ldata) < N_TTY_BUF_SIZE) {
318 *read_buf_addr(ldata, ldata->read_head) = c;
324 * reset_buffer_flags - reset buffer state
325 * @tty: terminal to reset
327 * Reset the read buffer counters and clear the flags.
328 * Called from n_tty_open() and n_tty_flush_buffer().
330 * Locking: caller holds exclusive termios_rwsem
331 * (or locking is not required)
334 static void reset_buffer_flags(struct n_tty_data *ldata)
336 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
338 mutex_lock(&ldata->echo_lock);
339 ldata->echo_head = ldata->echo_tail = ldata->echo_cnt = 0;
340 mutex_unlock(&ldata->echo_lock);
343 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
346 static void n_tty_packet_mode_flush(struct tty_struct *tty)
350 spin_lock_irqsave(&tty->ctrl_lock, flags);
351 if (tty->link->packet) {
352 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
353 wake_up_interruptible(&tty->link->read_wait);
355 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
359 * n_tty_flush_buffer - clean input queue
360 * @tty: terminal device
362 * Flush the input buffer. Called when the tty layer wants the
363 * buffer flushed (eg at hangup) or when the N_TTY line discipline
364 * internally has to clean the pending queue (for example some signals).
366 * Holds termios_rwsem to exclude producer/consumer while
367 * buffer indices are reset.
369 * Locking: ctrl_lock, exclusive termios_rwsem
372 static void n_tty_flush_buffer(struct tty_struct *tty)
374 down_write(&tty->termios_rwsem);
375 reset_buffer_flags(tty->disc_data);
379 n_tty_packet_mode_flush(tty);
380 up_write(&tty->termios_rwsem);
384 * n_tty_chars_in_buffer - report available bytes
387 * Report the number of characters buffered to be delivered to user
388 * at this instant in time.
390 * Locking: exclusive termios_rwsem
393 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
397 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
399 down_write(&tty->termios_rwsem);
400 n = chars_in_buffer(tty);
401 up_write(&tty->termios_rwsem);
406 * is_utf8_continuation - utf8 multibyte check
409 * Returns true if the utf8 character 'c' is a multibyte continuation
410 * character. We use this to correctly compute the on screen size
411 * of the character when printing
414 static inline int is_utf8_continuation(unsigned char c)
416 return (c & 0xc0) == 0x80;
420 * is_continuation - multibyte check
423 * Returns true if the utf8 character 'c' is a multibyte continuation
424 * character and the terminal is in unicode mode.
427 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
429 return I_IUTF8(tty) && is_utf8_continuation(c);
433 * do_output_char - output one character
434 * @c: character (or partial unicode symbol)
435 * @tty: terminal device
436 * @space: space available in tty driver write buffer
438 * This is a helper function that handles one output character
439 * (including special characters like TAB, CR, LF, etc.),
440 * doing OPOST processing and putting the results in the
441 * tty driver's write buffer.
443 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
444 * and NLDLY. They simply aren't relevant in the world today.
445 * If you ever need them, add them here.
447 * Returns the number of bytes of buffer space used or -1 if
450 * Locking: should be called under the output_lock to protect
451 * the column state and space left in the buffer
454 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
456 struct n_tty_data *ldata = tty->disc_data;
469 ldata->canon_column = ldata->column = 0;
470 tty->ops->write(tty, "\r\n", 2);
473 ldata->canon_column = ldata->column;
476 if (O_ONOCR(tty) && ldata->column == 0)
481 ldata->canon_column = ldata->column = 0;
484 ldata->canon_column = ldata->column = 0;
487 spaces = 8 - (ldata->column & 7);
488 if (O_TABDLY(tty) == XTABS) {
491 ldata->column += spaces;
492 tty->ops->write(tty, " ", spaces);
495 ldata->column += spaces;
498 if (ldata->column > 0)
505 if (!is_continuation(c, tty))
511 tty_put_char(tty, c);
516 * process_output - output post processor
517 * @c: character (or partial unicode symbol)
518 * @tty: terminal device
520 * Output one character with OPOST processing.
521 * Returns -1 when the output device is full and the character
524 * Locking: output_lock to protect column state and space left
525 * (also, this is called from n_tty_write under the
526 * tty layer write lock)
529 static int process_output(unsigned char c, struct tty_struct *tty)
531 struct n_tty_data *ldata = tty->disc_data;
534 mutex_lock(&ldata->output_lock);
536 space = tty_write_room(tty);
537 retval = do_output_char(c, tty, space);
539 mutex_unlock(&ldata->output_lock);
547 * process_output_block - block post processor
548 * @tty: terminal device
549 * @buf: character buffer
550 * @nr: number of bytes to output
552 * Output a block of characters with OPOST processing.
553 * Returns the number of characters output.
555 * This path is used to speed up block console writes, among other
556 * things when processing blocks of output data. It handles only
557 * the simple cases normally found and helps to generate blocks of
558 * symbols for the console driver and thus improve performance.
560 * Locking: output_lock to protect column state and space left
561 * (also, this is called from n_tty_write under the
562 * tty layer write lock)
565 static ssize_t process_output_block(struct tty_struct *tty,
566 const unsigned char *buf, unsigned int nr)
568 struct n_tty_data *ldata = tty->disc_data;
571 const unsigned char *cp;
573 mutex_lock(&ldata->output_lock);
575 space = tty_write_room(tty);
577 mutex_unlock(&ldata->output_lock);
583 for (i = 0, cp = buf; i < nr; i++, cp++) {
584 unsigned char c = *cp;
592 ldata->canon_column = ldata->column;
595 if (O_ONOCR(tty) && ldata->column == 0)
599 ldata->canon_column = ldata->column = 0;
604 if (ldata->column > 0)
611 if (!is_continuation(c, tty))
618 i = tty->ops->write(tty, buf, i);
620 mutex_unlock(&ldata->output_lock);
625 * process_echoes - write pending echo characters
626 * @tty: terminal device
628 * Write previously buffered echo (and other ldisc-generated)
629 * characters to the tty.
631 * Characters generated by the ldisc (including echoes) need to
632 * be buffered because the driver's write buffer can fill during
633 * heavy program output. Echoing straight to the driver will
634 * often fail under these conditions, causing lost characters and
635 * resulting mismatches of ldisc state information.
637 * Since the ldisc state must represent the characters actually sent
638 * to the driver at the time of the write, operations like certain
639 * changes in column state are also saved in the buffer and executed
642 * A circular fifo buffer is used so that the most recent characters
643 * are prioritized. Also, when control characters are echoed with a
644 * prefixed "^", the pair is treated atomically and thus not separated.
646 * Locking: output_lock to protect column state and space left,
647 * echo_lock to protect the echo buffer
650 static void process_echoes(struct tty_struct *tty)
652 struct n_tty_data *ldata = tty->disc_data;
657 if (!ldata->echo_cnt)
660 mutex_lock(&ldata->output_lock);
661 mutex_lock(&ldata->echo_lock);
663 space = tty_write_room(tty);
665 tail = ldata->echo_tail;
666 nr = ldata->echo_cnt;
668 c = echo_buf(ldata, tail);
669 if (c == ECHO_OP_START) {
671 int no_space_left = 0;
674 * If the buffer byte is the start of a multi-byte
675 * operation, get the next byte, which is either the
676 * op code or a control character value.
678 op = echo_buf(ldata, tail + 1);
681 unsigned int num_chars, num_bs;
683 case ECHO_OP_ERASE_TAB:
684 num_chars = echo_buf(ldata, tail + 2);
687 * Determine how many columns to go back
688 * in order to erase the tab.
689 * This depends on the number of columns
690 * used by other characters within the tab
691 * area. If this (modulo 8) count is from
692 * the start of input rather than from a
693 * previous tab, we offset by canon column.
694 * Otherwise, tab spacing is normal.
696 if (!(num_chars & 0x80))
697 num_chars += ldata->canon_column;
698 num_bs = 8 - (num_chars & 7);
700 if (num_bs > space) {
706 tty_put_char(tty, '\b');
707 if (ldata->column > 0)
714 case ECHO_OP_SET_CANON_COL:
715 ldata->canon_column = ldata->column;
720 case ECHO_OP_MOVE_BACK_COL:
721 if (ldata->column > 0)
728 /* This is an escaped echo op start code */
733 tty_put_char(tty, ECHO_OP_START);
742 * If the op is not a special byte code,
743 * it is a ctrl char tagged to be echoed
744 * as "^X" (where X is the letter
745 * representing the control char).
746 * Note that we must ensure there is
747 * enough space for the whole ctrl pair.
754 tty_put_char(tty, '^');
755 tty_put_char(tty, op ^ 0100);
766 int retval = do_output_char(c, tty, space);
773 tty_put_char(tty, c);
781 ldata->echo_tail = tail;
782 ldata->echo_cnt = nr;
784 mutex_unlock(&ldata->echo_lock);
785 mutex_unlock(&ldata->output_lock);
787 if (tty->ops->flush_chars)
788 tty->ops->flush_chars(tty);
792 * add_echo_byte - add a byte to the echo buffer
793 * @c: unicode byte to echo
796 * Add a character or operation byte to the echo buffer.
798 * Should be called under the echo lock to protect the echo buffer.
801 static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
803 if (ldata->echo_cnt == N_TTY_BUF_SIZE) {
804 size_t head = ldata->echo_head;
806 * Since the buffer start position needs to be advanced,
807 * be sure to step by a whole operation byte group.
809 if (echo_buf(ldata, head) == ECHO_OP_START) {
810 if (echo_buf(ldata, head + 1) == ECHO_OP_ERASE_TAB) {
811 ldata->echo_tail += 3;
812 ldata->echo_cnt -= 2;
814 ldata->echo_tail += 2;
815 ldata->echo_cnt -= 1;
822 *echo_buf_addr(ldata, ldata->echo_head++) = c;
826 * echo_move_back_col - add operation to move back a column
829 * Add an operation to the echo buffer to move back one column.
831 * Locking: echo_lock to protect the echo buffer
834 static void echo_move_back_col(struct n_tty_data *ldata)
836 mutex_lock(&ldata->echo_lock);
837 add_echo_byte(ECHO_OP_START, ldata);
838 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
839 mutex_unlock(&ldata->echo_lock);
843 * echo_set_canon_col - add operation to set the canon column
846 * Add an operation to the echo buffer to set the canon column
847 * to the current column.
849 * Locking: echo_lock to protect the echo buffer
852 static void echo_set_canon_col(struct n_tty_data *ldata)
854 mutex_lock(&ldata->echo_lock);
855 add_echo_byte(ECHO_OP_START, ldata);
856 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
857 mutex_unlock(&ldata->echo_lock);
861 * echo_erase_tab - add operation to erase a tab
862 * @num_chars: number of character columns already used
863 * @after_tab: true if num_chars starts after a previous tab
866 * Add an operation to the echo buffer to erase a tab.
868 * Called by the eraser function, which knows how many character
869 * columns have been used since either a previous tab or the start
870 * of input. This information will be used later, along with
871 * canon column (if applicable), to go back the correct number
874 * Locking: echo_lock to protect the echo buffer
877 static void echo_erase_tab(unsigned int num_chars, int after_tab,
878 struct n_tty_data *ldata)
880 mutex_lock(&ldata->echo_lock);
882 add_echo_byte(ECHO_OP_START, ldata);
883 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
885 /* We only need to know this modulo 8 (tab spacing) */
888 /* Set the high bit as a flag if num_chars is after a previous tab */
892 add_echo_byte(num_chars, ldata);
894 mutex_unlock(&ldata->echo_lock);
898 * echo_char_raw - echo a character raw
899 * @c: unicode byte to echo
900 * @tty: terminal device
902 * Echo user input back onto the screen. This must be called only when
903 * L_ECHO(tty) is true. Called from the driver receive_buf path.
905 * This variant does not treat control characters specially.
907 * Locking: echo_lock to protect the echo buffer
910 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
912 mutex_lock(&ldata->echo_lock);
913 if (c == ECHO_OP_START) {
914 add_echo_byte(ECHO_OP_START, ldata);
915 add_echo_byte(ECHO_OP_START, ldata);
917 add_echo_byte(c, ldata);
919 mutex_unlock(&ldata->echo_lock);
923 * echo_char - echo a character
924 * @c: unicode byte to echo
925 * @tty: terminal device
927 * Echo user input back onto the screen. This must be called only when
928 * L_ECHO(tty) is true. Called from the driver receive_buf path.
930 * This variant tags control characters to be echoed as "^X"
931 * (where X is the letter representing the control char).
933 * Locking: echo_lock to protect the echo buffer
936 static void echo_char(unsigned char c, struct tty_struct *tty)
938 struct n_tty_data *ldata = tty->disc_data;
940 mutex_lock(&ldata->echo_lock);
942 if (c == ECHO_OP_START) {
943 add_echo_byte(ECHO_OP_START, ldata);
944 add_echo_byte(ECHO_OP_START, ldata);
946 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
947 add_echo_byte(ECHO_OP_START, ldata);
948 add_echo_byte(c, ldata);
951 mutex_unlock(&ldata->echo_lock);
955 * finish_erasing - complete erase
959 static inline void finish_erasing(struct n_tty_data *ldata)
961 if (ldata->erasing) {
962 echo_char_raw('/', ldata);
968 * eraser - handle erase function
969 * @c: character input
970 * @tty: terminal device
972 * Perform erase and necessary output when an erase character is
973 * present in the stream from the driver layer. Handles the complexities
974 * of UTF-8 multibyte symbols.
976 * n_tty_receive_buf()/producer path:
977 * caller holds non-exclusive termios_rwsem
980 * Modifying the read_head is not considered a publish in this context
981 * because canonical mode is active -- only canon_head publishes
984 static void eraser(unsigned char c, struct tty_struct *tty)
986 struct n_tty_data *ldata = tty->disc_data;
987 enum { ERASE, WERASE, KILL } kill_type;
992 if (ldata->read_head == ldata->canon_head) {
993 /* process_output('\a', tty); */ /* what do you think? */
996 if (c == ERASE_CHAR(tty))
998 else if (c == WERASE_CHAR(tty))
1002 ldata->read_head = ldata->canon_head;
1005 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1006 ldata->read_head = ldata->canon_head;
1007 finish_erasing(ldata);
1008 echo_char(KILL_CHAR(tty), tty);
1009 /* Add a newline if ECHOK is on and ECHOKE is off. */
1011 echo_char_raw('\n', ldata);
1018 while (ldata->read_head != ldata->canon_head) {
1019 head = ldata->read_head;
1021 /* erase a single possibly multibyte character */
1024 c = read_buf(ldata, head);
1025 } while (is_continuation(c, tty) && head != ldata->canon_head);
1027 /* do not partially erase */
1028 if (is_continuation(c, tty))
1031 if (kill_type == WERASE) {
1032 /* Equivalent to BSD's ALTWERASE. */
1033 if (isalnum(c) || c == '_')
1035 else if (seen_alnums)
1038 cnt = ldata->read_head - head;
1039 ldata->read_head = head;
1041 if (L_ECHOPRT(tty)) {
1042 if (!ldata->erasing) {
1043 echo_char_raw('\\', ldata);
1046 /* if cnt > 1, output a multi-byte character */
1050 echo_char_raw(read_buf(ldata, head), ldata);
1051 echo_move_back_col(ldata);
1053 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1054 echo_char(ERASE_CHAR(tty), tty);
1055 } else if (c == '\t') {
1056 unsigned int num_chars = 0;
1058 size_t tail = ldata->read_head;
1061 * Count the columns used for characters
1062 * since the start of input or after a
1064 * This info is used to go back the correct
1065 * number of columns.
1067 while (tail != ldata->canon_head) {
1069 c = read_buf(ldata, tail);
1073 } else if (iscntrl(c)) {
1076 } else if (!is_continuation(c, tty)) {
1080 echo_erase_tab(num_chars, after_tab, ldata);
1082 if (iscntrl(c) && L_ECHOCTL(tty)) {
1083 echo_char_raw('\b', ldata);
1084 echo_char_raw(' ', ldata);
1085 echo_char_raw('\b', ldata);
1087 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1088 echo_char_raw('\b', ldata);
1089 echo_char_raw(' ', ldata);
1090 echo_char_raw('\b', ldata);
1094 if (kill_type == ERASE)
1097 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1098 finish_erasing(ldata);
1102 * isig - handle the ISIG optio
1106 * Called when a signal is being sent due to terminal input.
1107 * Called from the driver receive_buf path so serialized.
1109 * Locking: ctrl_lock
1112 static inline void isig(int sig, struct tty_struct *tty)
1114 struct pid *tty_pgrp = tty_get_pgrp(tty);
1116 kill_pgrp(tty_pgrp, sig, 1);
1122 * n_tty_receive_break - handle break
1125 * An RS232 break event has been hit in the incoming bitstream. This
1126 * can cause a variety of events depending upon the termios settings.
1128 * n_tty_receive_buf()/producer path:
1129 * caller holds non-exclusive termios_rwsem
1130 * publishes read_head via put_tty_queue()
1132 * Note: may get exclusive termios_rwsem if flushing input buffer
1135 static inline void n_tty_receive_break(struct tty_struct *tty)
1137 struct n_tty_data *ldata = tty->disc_data;
1141 if (I_BRKINT(tty)) {
1143 if (!L_NOFLSH(tty)) {
1144 /* flushing needs exclusive termios_rwsem */
1145 up_read(&tty->termios_rwsem);
1146 n_tty_flush_buffer(tty);
1147 tty_driver_flush_buffer(tty);
1148 down_read(&tty->termios_rwsem);
1152 if (I_PARMRK(tty)) {
1153 put_tty_queue('\377', ldata);
1154 put_tty_queue('\0', ldata);
1156 put_tty_queue('\0', ldata);
1157 wake_up_interruptible(&tty->read_wait);
1161 * n_tty_receive_overrun - handle overrun reporting
1164 * Data arrived faster than we could process it. While the tty
1165 * driver has flagged this the bits that were missed are gone
1168 * Called from the receive_buf path so single threaded. Does not
1169 * need locking as num_overrun and overrun_time are function
1173 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1175 struct n_tty_data *ldata = tty->disc_data;
1178 ldata->num_overrun++;
1179 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1180 time_after(ldata->overrun_time, jiffies)) {
1181 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1183 ldata->num_overrun);
1184 ldata->overrun_time = jiffies;
1185 ldata->num_overrun = 0;
1190 * n_tty_receive_parity_error - error notifier
1191 * @tty: terminal device
1194 * Process a parity error and queue the right data to indicate
1195 * the error case if necessary.
1197 * n_tty_receive_buf()/producer path:
1198 * caller holds non-exclusive termios_rwsem
1199 * publishes read_head via put_tty_queue()
1201 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1204 struct n_tty_data *ldata = tty->disc_data;
1208 if (I_PARMRK(tty)) {
1209 put_tty_queue('\377', ldata);
1210 put_tty_queue('\0', ldata);
1211 put_tty_queue(c, ldata);
1212 } else if (I_INPCK(tty))
1213 put_tty_queue('\0', ldata);
1215 put_tty_queue(c, ldata);
1216 wake_up_interruptible(&tty->read_wait);
1220 * n_tty_receive_char - perform processing
1221 * @tty: terminal device
1224 * Process an individual character of input received from the driver.
1225 * This is serialized with respect to itself by the rules for the
1228 * n_tty_receive_buf()/producer path:
1229 * caller holds non-exclusive termios_rwsem
1230 * publishes canon_head if canonical mode is active
1231 * otherwise, publishes read_head via put_tty_queue()
1234 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1236 struct n_tty_data *ldata = tty->disc_data;
1240 put_tty_queue(c, ldata);
1246 if (I_IUCLC(tty) && L_IEXTEN(tty))
1249 if (L_EXTPROC(tty)) {
1250 put_tty_queue(c, ldata);
1254 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1255 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1256 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1258 process_echoes(tty);
1263 if (c == START_CHAR(tty)) {
1265 process_echoes(tty);
1266 } else if (c == STOP_CHAR(tty))
1273 * If the previous character was LNEXT, or we know that this
1274 * character is not one of the characters that we'll have to
1275 * handle specially, do shortcut processing to speed things
1278 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1280 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1281 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1282 /* beep if no space */
1284 process_output('\a', tty);
1288 finish_erasing(ldata);
1289 /* Record the column of first canon char. */
1290 if (ldata->canon_head == ldata->read_head)
1291 echo_set_canon_col(ldata);
1293 process_echoes(tty);
1296 put_tty_queue(c, ldata);
1297 put_tty_queue(c, ldata);
1302 if (c == START_CHAR(tty)) {
1304 process_echoes(tty);
1307 if (c == STOP_CHAR(tty)) {
1316 if (c == INTR_CHAR(tty))
1319 if (c == QUIT_CHAR(tty))
1322 if (c == SUSP_CHAR(tty)) {
1324 if (!L_NOFLSH(tty)) {
1325 /* flushing needs exclusive termios_rwsem */
1326 up_read(&tty->termios_rwsem);
1327 n_tty_flush_buffer(tty);
1328 tty_driver_flush_buffer(tty);
1329 down_read(&tty->termios_rwsem);
1335 process_echoes(tty);
1347 } else if (c == '\n' && I_INLCR(tty))
1350 if (ldata->icanon) {
1351 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1352 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1354 process_echoes(tty);
1357 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1360 finish_erasing(ldata);
1361 if (L_ECHOCTL(tty)) {
1362 echo_char_raw('^', ldata);
1363 echo_char_raw('\b', ldata);
1364 process_echoes(tty);
1369 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1371 size_t tail = ldata->canon_head;
1373 finish_erasing(ldata);
1375 echo_char_raw('\n', ldata);
1376 while (tail != ldata->read_head) {
1377 echo_char(read_buf(ldata, tail), tty);
1380 process_echoes(tty);
1384 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1386 process_output('\a', tty);
1389 if (L_ECHO(tty) || L_ECHONL(tty)) {
1390 echo_char_raw('\n', ldata);
1391 process_echoes(tty);
1393 goto handle_newline;
1395 if (c == EOF_CHAR(tty)) {
1396 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1398 if (ldata->canon_head != ldata->read_head)
1399 set_bit(TTY_PUSH, &tty->flags);
1400 c = __DISABLED_CHAR;
1401 goto handle_newline;
1403 if ((c == EOL_CHAR(tty)) ||
1404 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1405 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1407 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1409 process_output('\a', tty);
1413 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1416 /* Record the column of first canon char. */
1417 if (ldata->canon_head == ldata->read_head)
1418 echo_set_canon_col(ldata);
1420 process_echoes(tty);
1423 * XXX does PARMRK doubling happen for
1424 * EOL_CHAR and EOL2_CHAR?
1427 put_tty_queue(c, ldata);
1430 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1431 put_tty_queue(c, ldata);
1432 ldata->canon_head = ldata->read_head;
1433 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1434 if (waitqueue_active(&tty->read_wait))
1435 wake_up_interruptible(&tty->read_wait);
1440 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1441 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1442 /* beep if no space */
1444 process_output('\a', tty);
1448 finish_erasing(ldata);
1450 echo_char_raw('\n', ldata);
1452 /* Record the column of first canon char. */
1453 if (ldata->canon_head == ldata->read_head)
1454 echo_set_canon_col(ldata);
1457 process_echoes(tty);
1461 put_tty_queue(c, ldata);
1463 put_tty_queue(c, ldata);
1467 * n_tty_receive_buf - data receive
1468 * @tty: terminal device
1471 * @count: characters
1473 * Called by the terminal driver when a block of characters has
1474 * been received. This function must be called from soft contexts
1475 * not from interrupt context. The driver is responsible for making
1476 * calls one at a time and in order (or using flush_to_ldisc)
1478 * n_tty_receive_buf()/producer path:
1479 * claims non-exclusive termios_rwsem
1480 * publishes read_head and canon_head
1483 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1484 char *fp, int count)
1486 struct n_tty_data *ldata = tty->disc_data;
1487 const unsigned char *p;
1488 char *f, 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, p = cp, f = fp; i; i--, p++) {
1515 n_tty_receive_char(tty, *p);
1518 n_tty_receive_break(tty);
1522 n_tty_receive_parity_error(tty, *p);
1525 n_tty_receive_overrun(tty);
1528 printk(KERN_ERR "%s: unknown flag %d\n",
1529 tty_name(tty, buf), flags);
1533 if (tty->ops->flush_chars)
1534 tty->ops->flush_chars(tty);
1537 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1539 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1540 if (waitqueue_active(&tty->read_wait))
1541 wake_up_interruptible(&tty->read_wait);
1544 n_tty_check_throttle(tty);
1547 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1548 char *fp, int count)
1550 down_read(&tty->termios_rwsem);
1551 __receive_buf(tty, cp, fp, count);
1552 up_read(&tty->termios_rwsem);
1555 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1556 char *fp, int count)
1558 struct n_tty_data *ldata = tty->disc_data;
1561 down_read(&tty->termios_rwsem);
1563 tty->receive_room = room = receive_room(tty);
1566 count = min(count, room);
1568 __receive_buf(tty, cp, fp, count);
1570 up_read(&tty->termios_rwsem);
1575 int is_ignored(int sig)
1577 return (sigismember(¤t->blocked, sig) ||
1578 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1582 * n_tty_set_termios - termios data changed
1584 * @old: previous data
1586 * Called by the tty layer when the user changes termios flags so
1587 * that the line discipline can plan ahead. This function cannot sleep
1588 * and is protected from re-entry by the tty layer. The user is
1589 * guaranteed that this function will not be re-entered or in progress
1590 * when the ldisc is closed.
1592 * Locking: Caller holds tty->termios_rwsem
1595 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1597 struct n_tty_data *ldata = tty->disc_data;
1598 int canon_change = 1;
1601 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1603 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1604 ldata->canon_head = ldata->read_tail;
1609 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1610 wake_up_interruptible(&tty->read_wait);
1612 ldata->icanon = (L_ICANON(tty) != 0);
1614 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1615 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1616 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1618 bitmap_zero(ldata->process_char_map, 256);
1620 if (I_IGNCR(tty) || I_ICRNL(tty))
1621 set_bit('\r', ldata->process_char_map);
1623 set_bit('\n', ldata->process_char_map);
1625 if (L_ICANON(tty)) {
1626 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1627 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1628 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1629 set_bit('\n', ldata->process_char_map);
1630 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1631 if (L_IEXTEN(tty)) {
1632 set_bit(WERASE_CHAR(tty),
1633 ldata->process_char_map);
1634 set_bit(LNEXT_CHAR(tty),
1635 ldata->process_char_map);
1636 set_bit(EOL2_CHAR(tty),
1637 ldata->process_char_map);
1639 set_bit(REPRINT_CHAR(tty),
1640 ldata->process_char_map);
1644 set_bit(START_CHAR(tty), ldata->process_char_map);
1645 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1648 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1649 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1650 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1652 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1654 ldata->real_raw = 0;
1657 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1658 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1659 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1660 ldata->real_raw = 1;
1662 ldata->real_raw = 0;
1664 n_tty_set_room(tty);
1666 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1667 * been stopped by STOP_CHAR(tty) before it.
1669 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1673 /* The termios change make the tty ready for I/O */
1674 wake_up_interruptible(&tty->write_wait);
1675 wake_up_interruptible(&tty->read_wait);
1679 * n_tty_close - close the ldisc for this tty
1682 * Called from the terminal layer when this line discipline is
1683 * being shut down, either because of a close or becsuse of a
1684 * discipline change. The function will not be called while other
1685 * ldisc methods are in progress.
1688 static void n_tty_close(struct tty_struct *tty)
1690 struct n_tty_data *ldata = tty->disc_data;
1693 n_tty_packet_mode_flush(tty);
1695 kfree(ldata->read_buf);
1696 kfree(ldata->echo_buf);
1698 tty->disc_data = NULL;
1702 * n_tty_open - open an ldisc
1703 * @tty: terminal to open
1705 * Called when this line discipline is being attached to the
1706 * terminal device. Can sleep. Called serialized so that no
1707 * other events will occur in parallel. No further open will occur
1711 static int n_tty_open(struct tty_struct *tty)
1713 struct n_tty_data *ldata;
1715 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1719 ldata->overrun_time = jiffies;
1720 mutex_init(&ldata->atomic_read_lock);
1721 mutex_init(&ldata->output_lock);
1722 mutex_init(&ldata->echo_lock);
1724 /* These are ugly. Currently a malloc failure here can panic */
1725 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1726 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1727 if (!ldata->read_buf || !ldata->echo_buf)
1730 tty->disc_data = ldata;
1731 reset_buffer_flags(tty->disc_data);
1733 ldata->minimum_to_wake = 1;
1735 /* indicate buffer work may resume */
1736 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1737 n_tty_set_termios(tty, NULL);
1738 tty_unthrottle(tty);
1742 kfree(ldata->read_buf);
1743 kfree(ldata->echo_buf);
1749 static inline int input_available_p(struct tty_struct *tty, int amt)
1751 struct n_tty_data *ldata = tty->disc_data;
1753 if (ldata->icanon && !L_EXTPROC(tty)) {
1754 if (ldata->canon_head != ldata->read_tail)
1756 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1763 * copy_from_read_buf - copy read data directly
1764 * @tty: terminal device
1768 * Helper function to speed up n_tty_read. It is only called when
1769 * ICANON is off; it copies characters straight from the tty queue to
1770 * user space directly. It can be profitably called twice; once to
1771 * drain the space from the tail pointer to the (physical) end of the
1772 * buffer, and once to drain the space from the (physical) beginning of
1773 * the buffer to head pointer.
1775 * Called under the ldata->atomic_read_lock sem
1777 * n_tty_read()/consumer path:
1778 * caller holds non-exclusive termios_rwsem
1779 * read_tail published
1782 static int copy_from_read_buf(struct tty_struct *tty,
1783 unsigned char __user **b,
1787 struct n_tty_data *ldata = tty->disc_data;
1791 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1794 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1797 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1799 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1800 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1802 ldata->read_tail += n;
1803 /* Turn single EOF into zero-length read */
1804 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1813 * canon_copy_from_read_buf - copy read data in canonical mode
1814 * @tty: terminal device
1818 * Helper function for n_tty_read. It is only called when ICANON is on;
1819 * it copies one line of input up to and including the line-delimiting
1820 * character into the user-space buffer.
1822 * Called under the atomic_read_lock mutex
1824 * n_tty_read()/consumer path:
1825 * caller holds non-exclusive termios_rwsem
1826 * read_tail published
1829 static int canon_copy_from_read_buf(struct tty_struct *tty,
1830 unsigned char __user **b,
1833 struct n_tty_data *ldata = tty->disc_data;
1834 size_t n, size, more, c;
1839 /* N.B. avoid overrun if nr == 0 */
1840 n = min(*nr, read_cnt(ldata));
1844 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1845 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1847 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1848 __func__, *nr, tail, n, size);
1850 eol = find_next_bit(ldata->read_flags, size, tail);
1851 more = n - (size - tail);
1852 if (eol == N_TTY_BUF_SIZE && more) {
1853 /* scan wrapped without finding set bit */
1854 eol = find_next_bit(ldata->read_flags, more, 0);
1857 } else if (eol != size)
1860 size = N_TTY_BUF_SIZE - tail;
1861 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1864 if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
1867 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1868 __func__, eol, found, n, c, size, more);
1871 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1874 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1876 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1884 clear_bit(eol, ldata->read_flags);
1885 smp_mb__after_clear_bit();
1886 ldata->read_tail += c;
1889 tty_audit_push(tty);
1893 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1897 * job_control - check job control
1899 * @file: file handle
1901 * Perform job control management checks on this file/tty descriptor
1902 * and if appropriate send any needed signals and return a negative
1903 * error code if action should be taken.
1905 * Locking: redirected write test is safe
1906 * current->signal->tty check is safe
1907 * ctrl_lock to safely reference tty->pgrp
1910 static int job_control(struct tty_struct *tty, struct file *file)
1912 /* Job control check -- must be done at start and after
1913 every sleep (POSIX.1 7.1.1.4). */
1914 /* NOTE: not yet done after every sleep pending a thorough
1915 check of the logic of this change. -- jlc */
1916 /* don't stop on /dev/console */
1917 if (file->f_op->write == redirected_tty_write ||
1918 current->signal->tty != tty)
1921 spin_lock_irq(&tty->ctrl_lock);
1923 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1924 else if (task_pgrp(current) != tty->pgrp) {
1925 spin_unlock_irq(&tty->ctrl_lock);
1926 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1928 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1929 set_thread_flag(TIF_SIGPENDING);
1930 return -ERESTARTSYS;
1932 spin_unlock_irq(&tty->ctrl_lock);
1938 * n_tty_read - read function for tty
1940 * @file: file object
1941 * @buf: userspace buffer pointer
1944 * Perform reads for the line discipline. We are guaranteed that the
1945 * line discipline will not be closed under us but we may get multiple
1946 * parallel readers and must handle this ourselves. We may also get
1947 * a hangup. Always called in user context, may sleep.
1949 * This code must be sure never to sleep through a hangup.
1951 * n_tty_read()/consumer path:
1952 * claims non-exclusive termios_rwsem
1953 * publishes read_tail
1956 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1957 unsigned char __user *buf, size_t nr)
1959 struct n_tty_data *ldata = tty->disc_data;
1960 unsigned char __user *b = buf;
1961 DECLARE_WAITQUEUE(wait, current);
1967 unsigned long flags;
1971 c = job_control(tty, file);
1975 down_read(&tty->termios_rwsem);
1978 timeout = MAX_SCHEDULE_TIMEOUT;
1979 if (!ldata->icanon) {
1980 minimum = MIN_CHAR(tty);
1982 time = (HZ / 10) * TIME_CHAR(tty);
1984 ldata->minimum_to_wake = 1;
1985 else if (!waitqueue_active(&tty->read_wait) ||
1986 (ldata->minimum_to_wake > minimum))
1987 ldata->minimum_to_wake = minimum;
1989 timeout = (HZ / 10) * TIME_CHAR(tty);
1990 ldata->minimum_to_wake = minimum = 1;
1995 * Internal serialization of reads.
1997 if (file->f_flags & O_NONBLOCK) {
1998 if (!mutex_trylock(&ldata->atomic_read_lock)) {
1999 up_read(&tty->termios_rwsem);
2003 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2004 up_read(&tty->termios_rwsem);
2005 return -ERESTARTSYS;
2008 packet = tty->packet;
2010 add_wait_queue(&tty->read_wait, &wait);
2012 /* First test for status change. */
2013 if (packet && tty->link->ctrl_status) {
2017 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2018 cs = tty->link->ctrl_status;
2019 tty->link->ctrl_status = 0;
2020 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2021 if (tty_put_user(tty, cs, b++)) {
2029 /* This statement must be first before checking for input
2030 so that any interrupt will set the state back to
2032 set_current_state(TASK_INTERRUPTIBLE);
2034 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2035 ((minimum - (b - buf)) >= 1))
2036 ldata->minimum_to_wake = (minimum - (b - buf));
2038 if (!input_available_p(tty, 0)) {
2039 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2043 if (tty_hung_up_p(file))
2047 if (file->f_flags & O_NONBLOCK) {
2051 if (signal_pending(current)) {
2052 retval = -ERESTARTSYS;
2055 n_tty_set_room(tty);
2056 up_read(&tty->termios_rwsem);
2058 timeout = schedule_timeout(timeout);
2060 down_read(&tty->termios_rwsem);
2063 __set_current_state(TASK_RUNNING);
2065 /* Deal with packet mode. */
2066 if (packet && b == buf) {
2067 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2075 if (ldata->icanon && !L_EXTPROC(tty)) {
2076 retval = canon_copy_from_read_buf(tty, &b, &nr);
2081 /* The copy function takes the read lock and handles
2082 locking internally for this case */
2083 uncopied = copy_from_read_buf(tty, &b, &nr);
2084 uncopied += copy_from_read_buf(tty, &b, &nr);
2091 n_tty_check_unthrottle(tty);
2093 if (b - buf >= minimum)
2098 mutex_unlock(&ldata->atomic_read_lock);
2099 remove_wait_queue(&tty->read_wait, &wait);
2101 if (!waitqueue_active(&tty->read_wait))
2102 ldata->minimum_to_wake = minimum;
2104 __set_current_state(TASK_RUNNING);
2109 clear_bit(TTY_PUSH, &tty->flags);
2110 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
2111 up_read(&tty->termios_rwsem);
2115 n_tty_set_room(tty);
2116 up_read(&tty->termios_rwsem);
2121 * n_tty_write - write function for tty
2123 * @file: file object
2124 * @buf: userspace buffer pointer
2127 * Write function of the terminal device. This is serialized with
2128 * respect to other write callers but not to termios changes, reads
2129 * and other such events. Since the receive code will echo characters,
2130 * thus calling driver write methods, the output_lock is used in
2131 * the output processing functions called here as well as in the
2132 * echo processing function to protect the column state and space
2133 * left in the buffer.
2135 * This code must be sure never to sleep through a hangup.
2137 * Locking: output_lock to protect column state and space left
2138 * (note that the process_output*() functions take this
2142 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2143 const unsigned char *buf, size_t nr)
2145 const unsigned char *b = buf;
2146 DECLARE_WAITQUEUE(wait, current);
2150 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2151 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2152 retval = tty_check_change(tty);
2157 down_read(&tty->termios_rwsem);
2159 /* Write out any echoed characters that are still pending */
2160 process_echoes(tty);
2162 add_wait_queue(&tty->write_wait, &wait);
2164 set_current_state(TASK_INTERRUPTIBLE);
2165 if (signal_pending(current)) {
2166 retval = -ERESTARTSYS;
2169 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2175 ssize_t num = process_output_block(tty, b, nr);
2187 if (process_output(c, tty) < 0)
2191 if (tty->ops->flush_chars)
2192 tty->ops->flush_chars(tty);
2195 c = tty->ops->write(tty, b, nr);
2208 if (file->f_flags & O_NONBLOCK) {
2212 up_read(&tty->termios_rwsem);
2216 down_read(&tty->termios_rwsem);
2219 __set_current_state(TASK_RUNNING);
2220 remove_wait_queue(&tty->write_wait, &wait);
2221 if (b - buf != nr && tty->fasync)
2222 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2223 up_read(&tty->termios_rwsem);
2224 return (b - buf) ? b - buf : retval;
2228 * n_tty_poll - poll method for N_TTY
2229 * @tty: terminal device
2230 * @file: file accessing it
2233 * Called when the line discipline is asked to poll() for data or
2234 * for special events. This code is not serialized with respect to
2235 * other events save open/close.
2237 * This code must be sure never to sleep through a hangup.
2238 * Called without the kernel lock held - fine
2241 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2244 struct n_tty_data *ldata = tty->disc_data;
2245 unsigned int mask = 0;
2247 poll_wait(file, &tty->read_wait, wait);
2248 poll_wait(file, &tty->write_wait, wait);
2249 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2250 mask |= POLLIN | POLLRDNORM;
2251 if (tty->packet && tty->link->ctrl_status)
2252 mask |= POLLPRI | POLLIN | POLLRDNORM;
2253 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2255 if (tty_hung_up_p(file))
2257 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2258 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2259 ldata->minimum_to_wake = MIN_CHAR(tty);
2261 ldata->minimum_to_wake = 1;
2263 if (tty->ops->write && !tty_is_writelocked(tty) &&
2264 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2265 tty_write_room(tty) > 0)
2266 mask |= POLLOUT | POLLWRNORM;
2270 static unsigned long inq_canon(struct n_tty_data *ldata)
2272 size_t nr, head, tail;
2274 if (ldata->canon_head == ldata->read_tail)
2276 head = ldata->canon_head;
2277 tail = ldata->read_tail;
2279 /* Skip EOF-chars.. */
2280 while (head != tail) {
2281 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2282 read_buf(ldata, tail) == __DISABLED_CHAR)
2289 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2290 unsigned int cmd, unsigned long arg)
2292 struct n_tty_data *ldata = tty->disc_data;
2297 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2299 down_write(&tty->termios_rwsem);
2301 retval = inq_canon(ldata);
2303 retval = read_cnt(ldata);
2304 up_write(&tty->termios_rwsem);
2305 return put_user(retval, (unsigned int __user *) arg);
2307 return n_tty_ioctl_helper(tty, file, cmd, arg);
2311 static void n_tty_fasync(struct tty_struct *tty, int on)
2313 struct n_tty_data *ldata = tty->disc_data;
2315 if (!waitqueue_active(&tty->read_wait)) {
2317 ldata->minimum_to_wake = 1;
2318 else if (!tty->fasync)
2319 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2323 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2324 .magic = TTY_LDISC_MAGIC,
2327 .close = n_tty_close,
2328 .flush_buffer = n_tty_flush_buffer,
2329 .chars_in_buffer = n_tty_chars_in_buffer,
2331 .write = n_tty_write,
2332 .ioctl = n_tty_ioctl,
2333 .set_termios = n_tty_set_termios,
2335 .receive_buf = n_tty_receive_buf,
2336 .write_wakeup = n_tty_write_wakeup,
2337 .fasync = n_tty_fasync,
2338 .receive_buf2 = n_tty_receive_buf2,
2342 * n_tty_inherit_ops - inherit N_TTY methods
2343 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2345 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2349 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2351 *ops = tty_ldisc_N_TTY;
2353 ops->refcount = ops->flags = 0;
2355 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);