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 */
93 DECLARE_BITMAP(process_char_map, 256);
95 /* private to n_tty_receive_overrun (single-threaded) */
96 unsigned long overrun_time;
102 /* must hold exclusive termios_rwsem to reset these */
103 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
105 /* shared by producer and consumer */
107 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
111 /* consumer-published */
114 unsigned char *echo_buf;
119 /* protected by output lock */
121 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;
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: callers must hold output_lock
649 static void __process_echoes(struct tty_struct *tty)
651 struct n_tty_data *ldata = tty->disc_data;
656 space = tty_write_room(tty);
658 tail = ldata->echo_tail;
659 nr = ldata->echo_commit - ldata->echo_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)
707 case ECHO_OP_SET_CANON_COL:
708 ldata->canon_column = ldata->column;
713 case ECHO_OP_MOVE_BACK_COL:
714 if (ldata->column > 0)
721 /* This is an escaped echo op start code */
726 tty_put_char(tty, ECHO_OP_START);
735 * If the op is not a special byte code,
736 * it is a ctrl char tagged to be echoed
737 * as "^X" (where X is the letter
738 * representing the control char).
739 * Note that we must ensure there is
740 * enough space for the whole ctrl pair.
747 tty_put_char(tty, '^');
748 tty_put_char(tty, op ^ 0100);
759 int retval = do_output_char(c, tty, space);
766 tty_put_char(tty, c);
774 /* If the echo buffer is nearly full (so that the possibility exists
775 * of echo overrun before the next commit), then discard enough
776 * data at the tail to prevent a subsequent overrun */
777 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
778 if (echo_buf(ldata, tail == ECHO_OP_START)) {
779 if (echo_buf(ldata, tail) == ECHO_OP_ERASE_TAB)
787 ldata->echo_tail = tail;
790 static void commit_echoes(struct tty_struct *tty)
792 struct n_tty_data *ldata = tty->disc_data;
796 head = ldata->echo_head;
797 old = ldata->echo_commit - ldata->echo_tail;
799 /* Process committed echoes if the accumulated # of bytes
800 * is over the threshold (and try again each time another
801 * block is accumulated) */
802 nr = head - ldata->echo_tail;
803 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
806 mutex_lock(&ldata->output_lock);
807 ldata->echo_commit = head;
808 __process_echoes(tty);
809 mutex_unlock(&ldata->output_lock);
811 if (tty->ops->flush_chars)
812 tty->ops->flush_chars(tty);
815 static void process_echoes(struct tty_struct *tty)
817 struct n_tty_data *ldata = tty->disc_data;
819 if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
822 mutex_lock(&ldata->output_lock);
823 __process_echoes(tty);
824 mutex_unlock(&ldata->output_lock);
826 if (tty->ops->flush_chars)
827 tty->ops->flush_chars(tty);
830 static void flush_echoes(struct tty_struct *tty)
832 struct n_tty_data *ldata = tty->disc_data;
834 if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_head)
837 mutex_lock(&ldata->output_lock);
838 ldata->echo_commit = ldata->echo_head;
839 __process_echoes(tty);
840 mutex_unlock(&ldata->output_lock);
844 * add_echo_byte - add a byte to the echo buffer
845 * @c: unicode byte to echo
848 * Add a character or operation byte to the echo buffer.
851 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
853 *echo_buf_addr(ldata, ldata->echo_head++) = c;
857 * echo_move_back_col - add operation to move back a column
860 * Add an operation to the echo buffer to move back one column.
863 static void echo_move_back_col(struct n_tty_data *ldata)
865 add_echo_byte(ECHO_OP_START, ldata);
866 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
870 * echo_set_canon_col - add operation to set the canon column
873 * Add an operation to the echo buffer to set the canon column
874 * to the current column.
877 static void echo_set_canon_col(struct n_tty_data *ldata)
879 add_echo_byte(ECHO_OP_START, ldata);
880 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
884 * echo_erase_tab - add operation to erase a tab
885 * @num_chars: number of character columns already used
886 * @after_tab: true if num_chars starts after a previous tab
889 * Add an operation to the echo buffer to erase a tab.
891 * Called by the eraser function, which knows how many character
892 * columns have been used since either a previous tab or the start
893 * of input. This information will be used later, along with
894 * canon column (if applicable), to go back the correct number
898 static void echo_erase_tab(unsigned int num_chars, int after_tab,
899 struct n_tty_data *ldata)
901 add_echo_byte(ECHO_OP_START, ldata);
902 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
904 /* We only need to know this modulo 8 (tab spacing) */
907 /* Set the high bit as a flag if num_chars is after a previous tab */
911 add_echo_byte(num_chars, ldata);
915 * echo_char_raw - echo a character raw
916 * @c: unicode byte to echo
917 * @tty: terminal device
919 * Echo user input back onto the screen. This must be called only when
920 * L_ECHO(tty) is true. Called from the driver receive_buf path.
922 * This variant does not treat control characters specially.
925 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
927 if (c == ECHO_OP_START) {
928 add_echo_byte(ECHO_OP_START, ldata);
929 add_echo_byte(ECHO_OP_START, ldata);
931 add_echo_byte(c, ldata);
936 * echo_char - echo a character
937 * @c: unicode byte to echo
938 * @tty: terminal device
940 * Echo user input back onto the screen. This must be called only when
941 * L_ECHO(tty) is true. Called from the driver receive_buf path.
943 * This variant tags control characters to be echoed as "^X"
944 * (where X is the letter representing the control char).
947 static void echo_char(unsigned char c, struct tty_struct *tty)
949 struct n_tty_data *ldata = tty->disc_data;
951 if (c == ECHO_OP_START) {
952 add_echo_byte(ECHO_OP_START, ldata);
953 add_echo_byte(ECHO_OP_START, ldata);
955 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
956 add_echo_byte(ECHO_OP_START, ldata);
957 add_echo_byte(c, ldata);
962 * finish_erasing - complete erase
966 static inline void finish_erasing(struct n_tty_data *ldata)
968 if (ldata->erasing) {
969 echo_char_raw('/', ldata);
975 * eraser - handle erase function
976 * @c: character input
977 * @tty: terminal device
979 * Perform erase and necessary output when an erase character is
980 * present in the stream from the driver layer. Handles the complexities
981 * of UTF-8 multibyte symbols.
983 * n_tty_receive_buf()/producer path:
984 * caller holds non-exclusive termios_rwsem
987 * Modifying the read_head is not considered a publish in this context
988 * because canonical mode is active -- only canon_head publishes
991 static void eraser(unsigned char c, struct tty_struct *tty)
993 struct n_tty_data *ldata = tty->disc_data;
994 enum { ERASE, WERASE, KILL } kill_type;
999 if (ldata->read_head == ldata->canon_head) {
1000 /* process_output('\a', tty); */ /* what do you think? */
1003 if (c == ERASE_CHAR(tty))
1005 else if (c == WERASE_CHAR(tty))
1009 ldata->read_head = ldata->canon_head;
1012 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1013 ldata->read_head = ldata->canon_head;
1014 finish_erasing(ldata);
1015 echo_char(KILL_CHAR(tty), tty);
1016 /* Add a newline if ECHOK is on and ECHOKE is off. */
1018 echo_char_raw('\n', ldata);
1025 while (ldata->read_head != ldata->canon_head) {
1026 head = ldata->read_head;
1028 /* erase a single possibly multibyte character */
1031 c = read_buf(ldata, head);
1032 } while (is_continuation(c, tty) && head != ldata->canon_head);
1034 /* do not partially erase */
1035 if (is_continuation(c, tty))
1038 if (kill_type == WERASE) {
1039 /* Equivalent to BSD's ALTWERASE. */
1040 if (isalnum(c) || c == '_')
1042 else if (seen_alnums)
1045 cnt = ldata->read_head - head;
1046 ldata->read_head = head;
1048 if (L_ECHOPRT(tty)) {
1049 if (!ldata->erasing) {
1050 echo_char_raw('\\', ldata);
1053 /* if cnt > 1, output a multi-byte character */
1057 echo_char_raw(read_buf(ldata, head), ldata);
1058 echo_move_back_col(ldata);
1060 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1061 echo_char(ERASE_CHAR(tty), tty);
1062 } else if (c == '\t') {
1063 unsigned int num_chars = 0;
1065 size_t tail = ldata->read_head;
1068 * Count the columns used for characters
1069 * since the start of input or after a
1071 * This info is used to go back the correct
1072 * number of columns.
1074 while (tail != ldata->canon_head) {
1076 c = read_buf(ldata, tail);
1080 } else if (iscntrl(c)) {
1083 } else if (!is_continuation(c, tty)) {
1087 echo_erase_tab(num_chars, after_tab, ldata);
1089 if (iscntrl(c) && L_ECHOCTL(tty)) {
1090 echo_char_raw('\b', ldata);
1091 echo_char_raw(' ', ldata);
1092 echo_char_raw('\b', ldata);
1094 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1095 echo_char_raw('\b', ldata);
1096 echo_char_raw(' ', ldata);
1097 echo_char_raw('\b', ldata);
1101 if (kill_type == ERASE)
1104 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1105 finish_erasing(ldata);
1109 * isig - handle the ISIG optio
1113 * Called when a signal is being sent due to terminal input.
1114 * Called from the driver receive_buf path so serialized.
1116 * Locking: ctrl_lock
1119 static inline void isig(int sig, struct tty_struct *tty)
1121 struct pid *tty_pgrp = tty_get_pgrp(tty);
1123 kill_pgrp(tty_pgrp, sig, 1);
1129 * n_tty_receive_break - handle break
1132 * An RS232 break event has been hit in the incoming bitstream. This
1133 * can cause a variety of events depending upon the termios settings.
1135 * n_tty_receive_buf()/producer path:
1136 * caller holds non-exclusive termios_rwsem
1137 * publishes read_head via put_tty_queue()
1139 * Note: may get exclusive termios_rwsem if flushing input buffer
1142 static inline void n_tty_receive_break(struct tty_struct *tty)
1144 struct n_tty_data *ldata = tty->disc_data;
1148 if (I_BRKINT(tty)) {
1150 if (!L_NOFLSH(tty)) {
1151 /* flushing needs exclusive termios_rwsem */
1152 up_read(&tty->termios_rwsem);
1153 n_tty_flush_buffer(tty);
1154 tty_driver_flush_buffer(tty);
1155 down_read(&tty->termios_rwsem);
1159 if (I_PARMRK(tty)) {
1160 put_tty_queue('\377', ldata);
1161 put_tty_queue('\0', ldata);
1163 put_tty_queue('\0', ldata);
1164 wake_up_interruptible(&tty->read_wait);
1168 * n_tty_receive_overrun - handle overrun reporting
1171 * Data arrived faster than we could process it. While the tty
1172 * driver has flagged this the bits that were missed are gone
1175 * Called from the receive_buf path so single threaded. Does not
1176 * need locking as num_overrun and overrun_time are function
1180 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1182 struct n_tty_data *ldata = tty->disc_data;
1185 ldata->num_overrun++;
1186 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1187 time_after(ldata->overrun_time, jiffies)) {
1188 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1190 ldata->num_overrun);
1191 ldata->overrun_time = jiffies;
1192 ldata->num_overrun = 0;
1197 * n_tty_receive_parity_error - error notifier
1198 * @tty: terminal device
1201 * Process a parity error and queue the right data to indicate
1202 * the error case if necessary.
1204 * n_tty_receive_buf()/producer path:
1205 * caller holds non-exclusive termios_rwsem
1206 * publishes read_head via put_tty_queue()
1208 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1211 struct n_tty_data *ldata = tty->disc_data;
1215 if (I_PARMRK(tty)) {
1216 put_tty_queue('\377', ldata);
1217 put_tty_queue('\0', ldata);
1218 put_tty_queue(c, ldata);
1219 } else if (I_INPCK(tty))
1220 put_tty_queue('\0', ldata);
1222 put_tty_queue(c, ldata);
1223 wake_up_interruptible(&tty->read_wait);
1227 * n_tty_receive_char - perform processing
1228 * @tty: terminal device
1231 * Process an individual character of input received from the driver.
1232 * This is serialized with respect to itself by the rules for the
1235 * n_tty_receive_buf()/producer path:
1236 * caller holds non-exclusive termios_rwsem
1237 * publishes canon_head if canonical mode is active
1238 * otherwise, publishes read_head via put_tty_queue()
1241 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1243 struct n_tty_data *ldata = tty->disc_data;
1247 put_tty_queue(c, ldata);
1253 if (I_IUCLC(tty) && L_IEXTEN(tty))
1256 if (L_EXTPROC(tty)) {
1257 put_tty_queue(c, ldata);
1261 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1262 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1263 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1265 process_echoes(tty);
1270 if (c == START_CHAR(tty)) {
1272 process_echoes(tty);
1273 } else if (c == STOP_CHAR(tty))
1280 * If the previous character was LNEXT, or we know that this
1281 * character is not one of the characters that we'll have to
1282 * handle specially, do shortcut processing to speed things
1285 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1287 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1288 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1289 /* beep if no space */
1291 process_output('\a', tty);
1295 finish_erasing(ldata);
1296 /* Record the column of first canon char. */
1297 if (ldata->canon_head == ldata->read_head)
1298 echo_set_canon_col(ldata);
1303 put_tty_queue(c, ldata);
1304 put_tty_queue(c, ldata);
1309 if (c == START_CHAR(tty)) {
1314 if (c == STOP_CHAR(tty)) {
1323 if (c == INTR_CHAR(tty))
1326 if (c == QUIT_CHAR(tty))
1329 if (c == SUSP_CHAR(tty)) {
1331 if (!L_NOFLSH(tty)) {
1332 /* flushing needs exclusive termios_rwsem */
1333 up_read(&tty->termios_rwsem);
1334 n_tty_flush_buffer(tty);
1335 tty_driver_flush_buffer(tty);
1336 down_read(&tty->termios_rwsem);
1354 } else if (c == '\n' && I_INLCR(tty))
1357 if (ldata->icanon) {
1358 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1359 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1364 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1367 finish_erasing(ldata);
1368 if (L_ECHOCTL(tty)) {
1369 echo_char_raw('^', ldata);
1370 echo_char_raw('\b', ldata);
1376 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1378 size_t tail = ldata->canon_head;
1380 finish_erasing(ldata);
1382 echo_char_raw('\n', ldata);
1383 while (tail != ldata->read_head) {
1384 echo_char(read_buf(ldata, tail), tty);
1391 if (read_cnt(ldata) >= N_TTY_BUF_SIZE) {
1393 process_output('\a', tty);
1396 if (L_ECHO(tty) || L_ECHONL(tty)) {
1397 echo_char_raw('\n', ldata);
1400 goto handle_newline;
1402 if (c == EOF_CHAR(tty)) {
1403 if (read_cnt(ldata) >= N_TTY_BUF_SIZE)
1405 if (ldata->canon_head != ldata->read_head)
1406 set_bit(TTY_PUSH, &tty->flags);
1407 c = __DISABLED_CHAR;
1408 goto handle_newline;
1410 if ((c == EOL_CHAR(tty)) ||
1411 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1412 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1414 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk)) {
1416 process_output('\a', tty);
1420 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1423 /* Record the column of first canon char. */
1424 if (ldata->canon_head == ldata->read_head)
1425 echo_set_canon_col(ldata);
1430 * XXX does PARMRK doubling happen for
1431 * EOL_CHAR and EOL2_CHAR?
1434 put_tty_queue(c, ldata);
1437 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1438 put_tty_queue(c, ldata);
1439 ldata->canon_head = ldata->read_head;
1440 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1441 if (waitqueue_active(&tty->read_wait))
1442 wake_up_interruptible(&tty->read_wait);
1447 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1448 if (read_cnt(ldata) >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1449 /* beep if no space */
1451 process_output('\a', tty);
1455 finish_erasing(ldata);
1457 echo_char_raw('\n', ldata);
1459 /* Record the column of first canon char. */
1460 if (ldata->canon_head == ldata->read_head)
1461 echo_set_canon_col(ldata);
1468 put_tty_queue(c, ldata);
1470 put_tty_queue(c, ldata);
1474 * n_tty_receive_buf - data receive
1475 * @tty: terminal device
1478 * @count: characters
1480 * Called by the terminal driver when a block of characters has
1481 * been received. This function must be called from soft contexts
1482 * not from interrupt context. The driver is responsible for making
1483 * calls one at a time and in order (or using flush_to_ldisc)
1485 * n_tty_receive_buf()/producer path:
1486 * claims non-exclusive termios_rwsem
1487 * publishes read_head and canon_head
1490 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1491 char *fp, int count)
1493 struct n_tty_data *ldata = tty->disc_data;
1494 const unsigned char *p;
1495 char *f, flags = TTY_NORMAL;
1498 if (ldata->real_raw) {
1501 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1502 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1503 n = min_t(size_t, count, n);
1504 memcpy(read_buf_addr(ldata, head), cp, n);
1505 ldata->read_head += n;
1509 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1510 n = N_TTY_BUF_SIZE - max(read_cnt(ldata), head);
1511 n = min_t(size_t, count, n);
1512 memcpy(read_buf_addr(ldata, head), cp, n);
1513 ldata->read_head += n;
1517 for (i = count, p = cp, f = fp; i; i--, p++) {
1522 n_tty_receive_char(tty, *p);
1525 n_tty_receive_break(tty);
1529 n_tty_receive_parity_error(tty, *p);
1532 n_tty_receive_overrun(tty);
1535 printk(KERN_ERR "%s: unknown flag %d\n",
1536 tty_name(tty, buf), flags);
1542 if (tty->ops->flush_chars)
1543 tty->ops->flush_chars(tty);
1546 if ((!ldata->icanon && (read_cnt(ldata) >= ldata->minimum_to_wake)) ||
1548 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1549 if (waitqueue_active(&tty->read_wait))
1550 wake_up_interruptible(&tty->read_wait);
1553 n_tty_check_throttle(tty);
1556 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1557 char *fp, int count)
1559 down_read(&tty->termios_rwsem);
1560 __receive_buf(tty, cp, fp, count);
1561 up_read(&tty->termios_rwsem);
1564 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1565 char *fp, int count)
1567 struct n_tty_data *ldata = tty->disc_data;
1570 down_read(&tty->termios_rwsem);
1572 tty->receive_room = room = receive_room(tty);
1575 count = min(count, room);
1577 __receive_buf(tty, cp, fp, count);
1579 up_read(&tty->termios_rwsem);
1584 int is_ignored(int sig)
1586 return (sigismember(¤t->blocked, sig) ||
1587 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1591 * n_tty_set_termios - termios data changed
1593 * @old: previous data
1595 * Called by the tty layer when the user changes termios flags so
1596 * that the line discipline can plan ahead. This function cannot sleep
1597 * and is protected from re-entry by the tty layer. The user is
1598 * guaranteed that this function will not be re-entered or in progress
1599 * when the ldisc is closed.
1601 * Locking: Caller holds tty->termios_rwsem
1604 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1606 struct n_tty_data *ldata = tty->disc_data;
1607 int canon_change = 1;
1610 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1612 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1613 ldata->canon_head = ldata->read_tail;
1618 if (canon_change && !L_ICANON(tty) && read_cnt(ldata))
1619 wake_up_interruptible(&tty->read_wait);
1621 ldata->icanon = (L_ICANON(tty) != 0);
1623 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1624 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1625 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1627 bitmap_zero(ldata->process_char_map, 256);
1629 if (I_IGNCR(tty) || I_ICRNL(tty))
1630 set_bit('\r', ldata->process_char_map);
1632 set_bit('\n', ldata->process_char_map);
1634 if (L_ICANON(tty)) {
1635 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1636 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1637 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1638 set_bit('\n', ldata->process_char_map);
1639 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1640 if (L_IEXTEN(tty)) {
1641 set_bit(WERASE_CHAR(tty),
1642 ldata->process_char_map);
1643 set_bit(LNEXT_CHAR(tty),
1644 ldata->process_char_map);
1645 set_bit(EOL2_CHAR(tty),
1646 ldata->process_char_map);
1648 set_bit(REPRINT_CHAR(tty),
1649 ldata->process_char_map);
1653 set_bit(START_CHAR(tty), ldata->process_char_map);
1654 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1657 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1658 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1659 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1661 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1663 ldata->real_raw = 0;
1666 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1667 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1668 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1669 ldata->real_raw = 1;
1671 ldata->real_raw = 0;
1673 n_tty_set_room(tty);
1675 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1676 * been stopped by STOP_CHAR(tty) before it.
1678 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1682 /* The termios change make the tty ready for I/O */
1683 wake_up_interruptible(&tty->write_wait);
1684 wake_up_interruptible(&tty->read_wait);
1688 * n_tty_close - close the ldisc for this tty
1691 * Called from the terminal layer when this line discipline is
1692 * being shut down, either because of a close or becsuse of a
1693 * discipline change. The function will not be called while other
1694 * ldisc methods are in progress.
1697 static void n_tty_close(struct tty_struct *tty)
1699 struct n_tty_data *ldata = tty->disc_data;
1702 n_tty_packet_mode_flush(tty);
1704 kfree(ldata->read_buf);
1705 kfree(ldata->echo_buf);
1707 tty->disc_data = NULL;
1711 * n_tty_open - open an ldisc
1712 * @tty: terminal to open
1714 * Called when this line discipline is being attached to the
1715 * terminal device. Can sleep. Called serialized so that no
1716 * other events will occur in parallel. No further open will occur
1720 static int n_tty_open(struct tty_struct *tty)
1722 struct n_tty_data *ldata;
1724 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1728 ldata->overrun_time = jiffies;
1729 mutex_init(&ldata->atomic_read_lock);
1730 mutex_init(&ldata->output_lock);
1732 /* These are ugly. Currently a malloc failure here can panic */
1733 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1734 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1735 if (!ldata->read_buf || !ldata->echo_buf)
1738 tty->disc_data = ldata;
1739 reset_buffer_flags(tty->disc_data);
1741 ldata->minimum_to_wake = 1;
1743 /* indicate buffer work may resume */
1744 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1745 n_tty_set_termios(tty, NULL);
1746 tty_unthrottle(tty);
1750 kfree(ldata->read_buf);
1751 kfree(ldata->echo_buf);
1757 static inline int input_available_p(struct tty_struct *tty, int amt)
1759 struct n_tty_data *ldata = tty->disc_data;
1761 if (ldata->icanon && !L_EXTPROC(tty)) {
1762 if (ldata->canon_head != ldata->read_tail)
1764 } else if (read_cnt(ldata) >= (amt ? amt : 1))
1771 * copy_from_read_buf - copy read data directly
1772 * @tty: terminal device
1776 * Helper function to speed up n_tty_read. It is only called when
1777 * ICANON is off; it copies characters straight from the tty queue to
1778 * user space directly. It can be profitably called twice; once to
1779 * drain the space from the tail pointer to the (physical) end of the
1780 * buffer, and once to drain the space from the (physical) beginning of
1781 * the buffer to head pointer.
1783 * Called under the ldata->atomic_read_lock sem
1785 * n_tty_read()/consumer path:
1786 * caller holds non-exclusive termios_rwsem
1787 * read_tail published
1790 static int copy_from_read_buf(struct tty_struct *tty,
1791 unsigned char __user **b,
1795 struct n_tty_data *ldata = tty->disc_data;
1799 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1802 n = min(read_cnt(ldata), N_TTY_BUF_SIZE - tail);
1805 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1807 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
1808 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
1810 ldata->read_tail += n;
1811 /* Turn single EOF into zero-length read */
1812 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))
1821 * canon_copy_from_read_buf - copy read data in canonical mode
1822 * @tty: terminal device
1826 * Helper function for n_tty_read. It is only called when ICANON is on;
1827 * it copies one line of input up to and including the line-delimiting
1828 * character into the user-space buffer.
1830 * Called under the atomic_read_lock mutex
1832 * n_tty_read()/consumer path:
1833 * caller holds non-exclusive termios_rwsem
1834 * read_tail published
1837 static int canon_copy_from_read_buf(struct tty_struct *tty,
1838 unsigned char __user **b,
1841 struct n_tty_data *ldata = tty->disc_data;
1842 size_t n, size, more, c;
1847 /* N.B. avoid overrun if nr == 0 */
1848 n = min(*nr, read_cnt(ldata));
1852 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
1853 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
1855 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
1856 __func__, *nr, tail, n, size);
1858 eol = find_next_bit(ldata->read_flags, size, tail);
1859 more = n - (size - tail);
1860 if (eol == N_TTY_BUF_SIZE && more) {
1861 /* scan wrapped without finding set bit */
1862 eol = find_next_bit(ldata->read_flags, more, 0);
1865 } else if (eol != size)
1868 size = N_TTY_BUF_SIZE - tail;
1869 n = (found + eol + size) & (N_TTY_BUF_SIZE - 1);
1872 if (found && read_buf(ldata, eol) == __DISABLED_CHAR)
1875 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
1876 __func__, eol, found, n, c, size, more);
1879 ret = copy_to_user(*b, read_buf_addr(ldata, tail), size);
1882 ret = copy_to_user(*b + size, ldata->read_buf, n - size);
1884 ret = copy_to_user(*b, read_buf_addr(ldata, tail), n);
1892 clear_bit(eol, ldata->read_flags);
1893 smp_mb__after_clear_bit();
1894 ldata->read_tail += c;
1897 tty_audit_push(tty);
1901 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1905 * job_control - check job control
1907 * @file: file handle
1909 * Perform job control management checks on this file/tty descriptor
1910 * and if appropriate send any needed signals and return a negative
1911 * error code if action should be taken.
1913 * Locking: redirected write test is safe
1914 * current->signal->tty check is safe
1915 * ctrl_lock to safely reference tty->pgrp
1918 static int job_control(struct tty_struct *tty, struct file *file)
1920 /* Job control check -- must be done at start and after
1921 every sleep (POSIX.1 7.1.1.4). */
1922 /* NOTE: not yet done after every sleep pending a thorough
1923 check of the logic of this change. -- jlc */
1924 /* don't stop on /dev/console */
1925 if (file->f_op->write == redirected_tty_write ||
1926 current->signal->tty != tty)
1929 spin_lock_irq(&tty->ctrl_lock);
1931 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1932 else if (task_pgrp(current) != tty->pgrp) {
1933 spin_unlock_irq(&tty->ctrl_lock);
1934 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1936 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1937 set_thread_flag(TIF_SIGPENDING);
1938 return -ERESTARTSYS;
1940 spin_unlock_irq(&tty->ctrl_lock);
1946 * n_tty_read - read function for tty
1948 * @file: file object
1949 * @buf: userspace buffer pointer
1952 * Perform reads for the line discipline. We are guaranteed that the
1953 * line discipline will not be closed under us but we may get multiple
1954 * parallel readers and must handle this ourselves. We may also get
1955 * a hangup. Always called in user context, may sleep.
1957 * This code must be sure never to sleep through a hangup.
1959 * n_tty_read()/consumer path:
1960 * claims non-exclusive termios_rwsem
1961 * publishes read_tail
1964 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1965 unsigned char __user *buf, size_t nr)
1967 struct n_tty_data *ldata = tty->disc_data;
1968 unsigned char __user *b = buf;
1969 DECLARE_WAITQUEUE(wait, current);
1975 unsigned long flags;
1979 c = job_control(tty, file);
1983 down_read(&tty->termios_rwsem);
1986 timeout = MAX_SCHEDULE_TIMEOUT;
1987 if (!ldata->icanon) {
1988 minimum = MIN_CHAR(tty);
1990 time = (HZ / 10) * TIME_CHAR(tty);
1992 ldata->minimum_to_wake = 1;
1993 else if (!waitqueue_active(&tty->read_wait) ||
1994 (ldata->minimum_to_wake > minimum))
1995 ldata->minimum_to_wake = minimum;
1997 timeout = (HZ / 10) * TIME_CHAR(tty);
1998 ldata->minimum_to_wake = minimum = 1;
2003 * Internal serialization of reads.
2005 if (file->f_flags & O_NONBLOCK) {
2006 if (!mutex_trylock(&ldata->atomic_read_lock)) {
2007 up_read(&tty->termios_rwsem);
2011 if (mutex_lock_interruptible(&ldata->atomic_read_lock)) {
2012 up_read(&tty->termios_rwsem);
2013 return -ERESTARTSYS;
2016 packet = tty->packet;
2018 add_wait_queue(&tty->read_wait, &wait);
2020 /* First test for status change. */
2021 if (packet && tty->link->ctrl_status) {
2025 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
2026 cs = tty->link->ctrl_status;
2027 tty->link->ctrl_status = 0;
2028 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
2029 if (tty_put_user(tty, cs, b++)) {
2037 /* This statement must be first before checking for input
2038 so that any interrupt will set the state back to
2040 set_current_state(TASK_INTERRUPTIBLE);
2042 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2043 ((minimum - (b - buf)) >= 1))
2044 ldata->minimum_to_wake = (minimum - (b - buf));
2046 if (!input_available_p(tty, 0)) {
2047 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
2051 if (tty_hung_up_p(file))
2055 if (file->f_flags & O_NONBLOCK) {
2059 if (signal_pending(current)) {
2060 retval = -ERESTARTSYS;
2063 n_tty_set_room(tty);
2064 up_read(&tty->termios_rwsem);
2066 timeout = schedule_timeout(timeout);
2068 down_read(&tty->termios_rwsem);
2071 __set_current_state(TASK_RUNNING);
2073 /* Deal with packet mode. */
2074 if (packet && b == buf) {
2075 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2083 if (ldata->icanon && !L_EXTPROC(tty)) {
2084 retval = canon_copy_from_read_buf(tty, &b, &nr);
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);
2117 clear_bit(TTY_PUSH, &tty->flags);
2118 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags)) {
2119 up_read(&tty->termios_rwsem);
2123 n_tty_set_room(tty);
2124 up_read(&tty->termios_rwsem);
2129 * n_tty_write - write function for tty
2131 * @file: file object
2132 * @buf: userspace buffer pointer
2135 * Write function of the terminal device. This is serialized with
2136 * respect to other write callers but not to termios changes, reads
2137 * and other such events. Since the receive code will echo characters,
2138 * thus calling driver write methods, the output_lock is used in
2139 * the output processing functions called here as well as in the
2140 * echo processing function to protect the column state and space
2141 * left in the buffer.
2143 * This code must be sure never to sleep through a hangup.
2145 * Locking: output_lock to protect column state and space left
2146 * (note that the process_output*() functions take this
2150 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2151 const unsigned char *buf, size_t nr)
2153 const unsigned char *b = buf;
2154 DECLARE_WAITQUEUE(wait, current);
2158 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2159 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2160 retval = tty_check_change(tty);
2165 down_read(&tty->termios_rwsem);
2167 /* Write out any echoed characters that are still pending */
2168 process_echoes(tty);
2170 add_wait_queue(&tty->write_wait, &wait);
2172 set_current_state(TASK_INTERRUPTIBLE);
2173 if (signal_pending(current)) {
2174 retval = -ERESTARTSYS;
2177 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2183 ssize_t num = process_output_block(tty, b, nr);
2195 if (process_output(c, tty) < 0)
2199 if (tty->ops->flush_chars)
2200 tty->ops->flush_chars(tty);
2203 c = tty->ops->write(tty, b, nr);
2216 if (file->f_flags & O_NONBLOCK) {
2220 up_read(&tty->termios_rwsem);
2224 down_read(&tty->termios_rwsem);
2227 __set_current_state(TASK_RUNNING);
2228 remove_wait_queue(&tty->write_wait, &wait);
2229 if (b - buf != nr && tty->fasync)
2230 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2231 up_read(&tty->termios_rwsem);
2232 return (b - buf) ? b - buf : retval;
2236 * n_tty_poll - poll method for N_TTY
2237 * @tty: terminal device
2238 * @file: file accessing it
2241 * Called when the line discipline is asked to poll() for data or
2242 * for special events. This code is not serialized with respect to
2243 * other events save open/close.
2245 * This code must be sure never to sleep through a hangup.
2246 * Called without the kernel lock held - fine
2249 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2252 struct n_tty_data *ldata = tty->disc_data;
2253 unsigned int mask = 0;
2255 poll_wait(file, &tty->read_wait, wait);
2256 poll_wait(file, &tty->write_wait, wait);
2257 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2258 mask |= POLLIN | POLLRDNORM;
2259 if (tty->packet && tty->link->ctrl_status)
2260 mask |= POLLPRI | POLLIN | POLLRDNORM;
2261 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2263 if (tty_hung_up_p(file))
2265 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2266 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2267 ldata->minimum_to_wake = MIN_CHAR(tty);
2269 ldata->minimum_to_wake = 1;
2271 if (tty->ops->write && !tty_is_writelocked(tty) &&
2272 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2273 tty_write_room(tty) > 0)
2274 mask |= POLLOUT | POLLWRNORM;
2278 static unsigned long inq_canon(struct n_tty_data *ldata)
2280 size_t nr, head, tail;
2282 if (ldata->canon_head == ldata->read_tail)
2284 head = ldata->canon_head;
2285 tail = ldata->read_tail;
2287 /* Skip EOF-chars.. */
2288 while (head != tail) {
2289 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2290 read_buf(ldata, tail) == __DISABLED_CHAR)
2297 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2298 unsigned int cmd, unsigned long arg)
2300 struct n_tty_data *ldata = tty->disc_data;
2305 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2307 down_write(&tty->termios_rwsem);
2309 retval = inq_canon(ldata);
2311 retval = read_cnt(ldata);
2312 up_write(&tty->termios_rwsem);
2313 return put_user(retval, (unsigned int __user *) arg);
2315 return n_tty_ioctl_helper(tty, file, cmd, arg);
2319 static void n_tty_fasync(struct tty_struct *tty, int on)
2321 struct n_tty_data *ldata = tty->disc_data;
2323 if (!waitqueue_active(&tty->read_wait)) {
2325 ldata->minimum_to_wake = 1;
2326 else if (!tty->fasync)
2327 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2331 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2332 .magic = TTY_LDISC_MAGIC,
2335 .close = n_tty_close,
2336 .flush_buffer = n_tty_flush_buffer,
2337 .chars_in_buffer = n_tty_chars_in_buffer,
2339 .write = n_tty_write,
2340 .ioctl = n_tty_ioctl,
2341 .set_termios = n_tty_set_termios,
2343 .receive_buf = n_tty_receive_buf,
2344 .write_wakeup = n_tty_write_wakeup,
2345 .fasync = n_tty_fasync,
2346 .receive_buf2 = n_tty_receive_buf2,
2350 * n_tty_inherit_ops - inherit N_TTY methods
2351 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2353 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2357 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2359 *ops = tty_ldisc_N_TTY;
2361 ops->refcount = ops->flags = 0;
2363 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);