2 * n_tty.c --- implements the N_TTY line discipline.
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where n_tty_write returns
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52 #include <linux/ratelimit.h>
53 #include <linux/vmalloc.h>
56 /* number of characters left in xmit buffer before select has we have room */
57 #define WAKEUP_CHARS 256
60 * This defines the low- and high-watermarks for throttling and
61 * unthrottling the TTY driver. These watermarks are used for
62 * controlling the space in the read buffer.
64 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
65 #define TTY_THRESHOLD_UNTHROTTLE 128
68 * Special byte codes used in the echo buffer to represent operations
69 * or special handling of characters. Bytes in the echo buffer that
70 * are not part of such special blocks are treated as normal character
73 #define ECHO_OP_START 0xff
74 #define ECHO_OP_MOVE_BACK_COL 0x80
75 #define ECHO_OP_SET_CANON_COL 0x81
76 #define ECHO_OP_ERASE_TAB 0x82
78 #define ECHO_COMMIT_WATERMARK 256
79 #define ECHO_BLOCK 256
80 #define ECHO_DISCARD_WATERMARK N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
85 # define n_tty_trace(f, args...) trace_printk(f, ##args)
87 # define n_tty_trace(f, args...)
91 /* producer-published */
98 DECLARE_BITMAP(char_map, 256);
100 /* private to n_tty_receive_overrun (single-threaded) */
101 unsigned long overrun_time;
107 /* must hold exclusive termios_rwsem to reset these */
108 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
109 unsigned char push:1;
111 /* shared by producer and consumer */
112 char read_buf[N_TTY_BUF_SIZE];
113 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
114 unsigned char echo_buf[N_TTY_BUF_SIZE];
118 /* consumer-published */
122 /* protected by output lock */
124 unsigned int canon_column;
127 struct mutex atomic_read_lock;
128 struct mutex output_lock;
131 static inline size_t read_cnt(struct n_tty_data *ldata)
133 return ldata->read_head - ldata->read_tail;
136 static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
138 return ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
141 static inline unsigned char *read_buf_addr(struct n_tty_data *ldata, size_t i)
143 return &ldata->read_buf[i & (N_TTY_BUF_SIZE - 1)];
146 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
148 return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
151 static inline unsigned char *echo_buf_addr(struct n_tty_data *ldata, size_t i)
153 return &ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
156 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
157 unsigned char __user *ptr)
159 struct n_tty_data *ldata = tty->disc_data;
161 tty_audit_add_data(tty, &x, 1, ldata->icanon);
162 return put_user(x, ptr);
165 static int tty_copy_to_user(struct tty_struct *tty, void __user *to,
166 size_t tail, size_t n)
168 struct n_tty_data *ldata = tty->disc_data;
169 size_t size = N_TTY_BUF_SIZE - tail;
170 const void *from = read_buf_addr(ldata, tail);
174 tty_audit_add_data(tty, from, size, ldata->icanon);
175 uncopied = copy_to_user(to, from, size);
180 from = ldata->read_buf;
183 tty_audit_add_data(tty, from, n, ldata->icanon);
184 return copy_to_user(to, from, n);
188 * n_tty_kick_worker - start input worker (if required)
191 * Re-schedules the flip buffer work if it may have stopped
193 * Caller holds exclusive termios_rwsem
195 * n_tty_read()/consumer path:
196 * holds non-exclusive termios_rwsem
199 static void n_tty_kick_worker(struct tty_struct *tty)
201 struct n_tty_data *ldata = tty->disc_data;
203 /* Did the input worker stop? Restart it */
204 if (unlikely(ldata->no_room)) {
207 WARN_RATELIMIT(tty->port->itty == NULL,
208 "scheduling with invalid itty\n");
209 /* see if ldisc has been killed - if so, this means that
210 * even though the ldisc has been halted and ->buf.work
211 * cancelled, ->buf.work is about to be rescheduled
213 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
214 "scheduling buffer work for halted ldisc\n");
215 tty_buffer_restart_work(tty->port);
219 static ssize_t chars_in_buffer(struct tty_struct *tty)
221 struct n_tty_data *ldata = tty->disc_data;
225 n = ldata->commit_head - ldata->read_tail;
227 n = ldata->canon_head - ldata->read_tail;
232 * n_tty_write_wakeup - asynchronous I/O notifier
235 * Required for the ptys, serial driver etc. since processes
236 * that attach themselves to the master and rely on ASYNC
237 * IO must be woken up
240 static void n_tty_write_wakeup(struct tty_struct *tty)
242 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
243 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
246 static void n_tty_check_throttle(struct tty_struct *tty)
248 struct n_tty_data *ldata = tty->disc_data;
251 * Check the remaining room for the input canonicalization
252 * mode. We don't want to throttle the driver if we're in
253 * canonical mode and don't have a newline yet!
255 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
260 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
261 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
263 throttled = tty_throttle_safe(tty);
267 __tty_set_flow_change(tty, 0);
270 static void n_tty_check_unthrottle(struct tty_struct *tty)
272 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
273 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
277 n_tty_kick_worker(tty);
278 tty_wakeup(tty->link);
282 /* If there is enough space in the read buffer now, let the
283 * low-level driver know. We use chars_in_buffer() to
284 * check the buffer, as it now knows about canonical mode.
285 * Otherwise, if the driver is throttled and the line is
286 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
287 * we won't get any more characters.
292 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
293 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
297 n_tty_kick_worker(tty);
298 unthrottled = tty_unthrottle_safe(tty);
302 __tty_set_flow_change(tty, 0);
306 * put_tty_queue - add character to tty
310 * Add a character to the tty read_buf queue.
312 * n_tty_receive_buf()/producer path:
313 * caller holds non-exclusive termios_rwsem
316 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
318 *read_buf_addr(ldata, ldata->read_head) = c;
323 * reset_buffer_flags - reset buffer state
324 * @tty: terminal to reset
326 * Reset the read buffer counters and clear the flags.
327 * Called from n_tty_open() and n_tty_flush_buffer().
329 * Locking: caller holds exclusive termios_rwsem
330 * (or locking is not required)
333 static void reset_buffer_flags(struct n_tty_data *ldata)
335 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
336 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
337 ldata->commit_head = 0;
338 ldata->echo_mark = 0;
339 ldata->line_start = 0;
342 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
346 static void n_tty_packet_mode_flush(struct tty_struct *tty)
350 if (tty->link->packet) {
351 spin_lock_irqsave(&tty->ctrl_lock, flags);
352 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
353 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
354 wake_up_interruptible(&tty->link->read_wait);
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);
376 n_tty_kick_worker(tty);
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 size_t __process_echoes(struct tty_struct *tty)
651 struct n_tty_data *ldata = tty->disc_data;
652 int space, old_space;
656 old_space = space = tty_write_room(tty);
658 tail = ldata->echo_tail;
659 while (ldata->echo_commit != tail) {
660 c = echo_buf(ldata, tail);
661 if (c == ECHO_OP_START) {
663 int no_space_left = 0;
666 * If the buffer byte is the start of a multi-byte
667 * operation, get the next byte, which is either the
668 * op code or a control character value.
670 op = echo_buf(ldata, tail + 1);
673 unsigned int num_chars, num_bs;
675 case ECHO_OP_ERASE_TAB:
676 num_chars = echo_buf(ldata, tail + 2);
679 * Determine how many columns to go back
680 * in order to erase the tab.
681 * This depends on the number of columns
682 * used by other characters within the tab
683 * area. If this (modulo 8) count is from
684 * the start of input rather than from a
685 * previous tab, we offset by canon column.
686 * Otherwise, tab spacing is normal.
688 if (!(num_chars & 0x80))
689 num_chars += ldata->canon_column;
690 num_bs = 8 - (num_chars & 7);
692 if (num_bs > space) {
698 tty_put_char(tty, '\b');
699 if (ldata->column > 0)
705 case ECHO_OP_SET_CANON_COL:
706 ldata->canon_column = ldata->column;
710 case ECHO_OP_MOVE_BACK_COL:
711 if (ldata->column > 0)
717 /* This is an escaped echo op start code */
722 tty_put_char(tty, ECHO_OP_START);
730 * If the op is not a special byte code,
731 * it is a ctrl char tagged to be echoed
732 * as "^X" (where X is the letter
733 * representing the control char).
734 * Note that we must ensure there is
735 * enough space for the whole ctrl pair.
742 tty_put_char(tty, '^');
743 tty_put_char(tty, op ^ 0100);
753 int retval = do_output_char(c, tty, space);
760 tty_put_char(tty, c);
767 /* If the echo buffer is nearly full (so that the possibility exists
768 * of echo overrun before the next commit), then discard enough
769 * data at the tail to prevent a subsequent overrun */
770 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
771 if (echo_buf(ldata, tail) == ECHO_OP_START) {
772 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
780 ldata->echo_tail = tail;
781 return old_space - space;
784 static void commit_echoes(struct tty_struct *tty)
786 struct n_tty_data *ldata = tty->disc_data;
787 size_t nr, old, echoed;
790 head = ldata->echo_head;
791 ldata->echo_mark = head;
792 old = ldata->echo_commit - ldata->echo_tail;
794 /* Process committed echoes if the accumulated # of bytes
795 * is over the threshold (and try again each time another
796 * block is accumulated) */
797 nr = head - ldata->echo_tail;
798 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
801 mutex_lock(&ldata->output_lock);
802 ldata->echo_commit = head;
803 echoed = __process_echoes(tty);
804 mutex_unlock(&ldata->output_lock);
806 if (echoed && tty->ops->flush_chars)
807 tty->ops->flush_chars(tty);
810 static void process_echoes(struct tty_struct *tty)
812 struct n_tty_data *ldata = tty->disc_data;
815 if (ldata->echo_mark == ldata->echo_tail)
818 mutex_lock(&ldata->output_lock);
819 ldata->echo_commit = ldata->echo_mark;
820 echoed = __process_echoes(tty);
821 mutex_unlock(&ldata->output_lock);
823 if (echoed && tty->ops->flush_chars)
824 tty->ops->flush_chars(tty);
827 /* NB: echo_mark and echo_head should be equivalent here */
828 static void flush_echoes(struct tty_struct *tty)
830 struct n_tty_data *ldata = tty->disc_data;
832 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
833 ldata->echo_commit == ldata->echo_head)
836 mutex_lock(&ldata->output_lock);
837 ldata->echo_commit = ldata->echo_head;
838 __process_echoes(tty);
839 mutex_unlock(&ldata->output_lock);
843 * add_echo_byte - add a byte to the echo buffer
844 * @c: unicode byte to echo
847 * Add a character or operation byte to the echo buffer.
850 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
852 *echo_buf_addr(ldata, ldata->echo_head++) = c;
856 * echo_move_back_col - add operation to move back a column
859 * Add an operation to the echo buffer to move back one column.
862 static void echo_move_back_col(struct n_tty_data *ldata)
864 add_echo_byte(ECHO_OP_START, ldata);
865 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
869 * echo_set_canon_col - add operation to set the canon column
872 * Add an operation to the echo buffer to set the canon column
873 * to the current column.
876 static void echo_set_canon_col(struct n_tty_data *ldata)
878 add_echo_byte(ECHO_OP_START, ldata);
879 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
883 * echo_erase_tab - add operation to erase a tab
884 * @num_chars: number of character columns already used
885 * @after_tab: true if num_chars starts after a previous tab
888 * Add an operation to the echo buffer to erase a tab.
890 * Called by the eraser function, which knows how many character
891 * columns have been used since either a previous tab or the start
892 * of input. This information will be used later, along with
893 * canon column (if applicable), to go back the correct number
897 static void echo_erase_tab(unsigned int num_chars, int after_tab,
898 struct n_tty_data *ldata)
900 add_echo_byte(ECHO_OP_START, ldata);
901 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
903 /* We only need to know this modulo 8 (tab spacing) */
906 /* Set the high bit as a flag if num_chars is after a previous tab */
910 add_echo_byte(num_chars, ldata);
914 * echo_char_raw - echo a character raw
915 * @c: unicode byte to echo
916 * @tty: terminal device
918 * Echo user input back onto the screen. This must be called only when
919 * L_ECHO(tty) is true. Called from the driver receive_buf path.
921 * This variant does not treat control characters specially.
924 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
926 if (c == ECHO_OP_START) {
927 add_echo_byte(ECHO_OP_START, ldata);
928 add_echo_byte(ECHO_OP_START, ldata);
930 add_echo_byte(c, ldata);
935 * echo_char - echo a character
936 * @c: unicode byte to echo
937 * @tty: terminal device
939 * Echo user input back onto the screen. This must be called only when
940 * L_ECHO(tty) is true. Called from the driver receive_buf path.
942 * This variant tags control characters to be echoed as "^X"
943 * (where X is the letter representing the control char).
946 static void echo_char(unsigned char c, struct tty_struct *tty)
948 struct n_tty_data *ldata = tty->disc_data;
950 if (c == ECHO_OP_START) {
951 add_echo_byte(ECHO_OP_START, ldata);
952 add_echo_byte(ECHO_OP_START, ldata);
954 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
955 add_echo_byte(ECHO_OP_START, ldata);
956 add_echo_byte(c, ldata);
961 * finish_erasing - complete erase
965 static inline void finish_erasing(struct n_tty_data *ldata)
967 if (ldata->erasing) {
968 echo_char_raw('/', ldata);
974 * eraser - handle erase function
975 * @c: character input
976 * @tty: terminal device
978 * Perform erase and necessary output when an erase character is
979 * present in the stream from the driver layer. Handles the complexities
980 * of UTF-8 multibyte symbols.
982 * n_tty_receive_buf()/producer path:
983 * caller holds non-exclusive termios_rwsem
986 static void eraser(unsigned char c, struct tty_struct *tty)
988 struct n_tty_data *ldata = tty->disc_data;
989 enum { ERASE, WERASE, KILL } kill_type;
994 if (ldata->read_head == ldata->canon_head) {
995 /* process_output('\a', tty); */ /* what do you think? */
998 if (c == ERASE_CHAR(tty))
1000 else if (c == WERASE_CHAR(tty))
1004 ldata->read_head = ldata->canon_head;
1007 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1008 ldata->read_head = ldata->canon_head;
1009 finish_erasing(ldata);
1010 echo_char(KILL_CHAR(tty), tty);
1011 /* Add a newline if ECHOK is on and ECHOKE is off. */
1013 echo_char_raw('\n', ldata);
1020 while (ldata->read_head != ldata->canon_head) {
1021 head = ldata->read_head;
1023 /* erase a single possibly multibyte character */
1026 c = read_buf(ldata, head);
1027 } while (is_continuation(c, tty) && head != ldata->canon_head);
1029 /* do not partially erase */
1030 if (is_continuation(c, tty))
1033 if (kill_type == WERASE) {
1034 /* Equivalent to BSD's ALTWERASE. */
1035 if (isalnum(c) || c == '_')
1037 else if (seen_alnums)
1040 cnt = ldata->read_head - head;
1041 ldata->read_head = head;
1043 if (L_ECHOPRT(tty)) {
1044 if (!ldata->erasing) {
1045 echo_char_raw('\\', ldata);
1048 /* if cnt > 1, output a multi-byte character */
1052 echo_char_raw(read_buf(ldata, head), ldata);
1053 echo_move_back_col(ldata);
1055 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1056 echo_char(ERASE_CHAR(tty), tty);
1057 } else if (c == '\t') {
1058 unsigned int num_chars = 0;
1060 size_t tail = ldata->read_head;
1063 * Count the columns used for characters
1064 * since the start of input or after a
1066 * This info is used to go back the correct
1067 * number of columns.
1069 while (tail != ldata->canon_head) {
1071 c = read_buf(ldata, tail);
1075 } else if (iscntrl(c)) {
1078 } else if (!is_continuation(c, tty)) {
1082 echo_erase_tab(num_chars, after_tab, ldata);
1084 if (iscntrl(c) && L_ECHOCTL(tty)) {
1085 echo_char_raw('\b', ldata);
1086 echo_char_raw(' ', ldata);
1087 echo_char_raw('\b', 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);
1096 if (kill_type == ERASE)
1099 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1100 finish_erasing(ldata);
1104 * isig - handle the ISIG optio
1108 * Called when a signal is being sent due to terminal input.
1109 * Called from the driver receive_buf path so serialized.
1111 * Performs input and output flush if !NOFLSH. In this context, the echo
1112 * buffer is 'output'. The signal is processed first to alert any current
1113 * readers or writers to discontinue and exit their i/o loops.
1115 * Locking: ctrl_lock
1118 static void __isig(int sig, struct tty_struct *tty)
1120 struct pid *tty_pgrp = tty_get_pgrp(tty);
1122 kill_pgrp(tty_pgrp, sig, 1);
1127 static void isig(int sig, struct tty_struct *tty)
1129 struct n_tty_data *ldata = tty->disc_data;
1131 if (L_NOFLSH(tty)) {
1135 } else { /* signal and flush */
1136 up_read(&tty->termios_rwsem);
1137 down_write(&tty->termios_rwsem);
1141 /* clear echo buffer */
1142 mutex_lock(&ldata->output_lock);
1143 ldata->echo_head = ldata->echo_tail = 0;
1144 ldata->echo_mark = ldata->echo_commit = 0;
1145 mutex_unlock(&ldata->output_lock);
1147 /* clear output buffer */
1148 tty_driver_flush_buffer(tty);
1150 /* clear input buffer */
1151 reset_buffer_flags(tty->disc_data);
1153 /* notify pty master of flush */
1155 n_tty_packet_mode_flush(tty);
1157 up_write(&tty->termios_rwsem);
1158 down_read(&tty->termios_rwsem);
1163 * n_tty_receive_break - handle break
1166 * An RS232 break event has been hit in the incoming bitstream. This
1167 * can cause a variety of events depending upon the termios settings.
1169 * n_tty_receive_buf()/producer path:
1170 * caller holds non-exclusive termios_rwsem
1172 * Note: may get exclusive termios_rwsem if flushing input buffer
1175 static void n_tty_receive_break(struct tty_struct *tty)
1177 struct n_tty_data *ldata = tty->disc_data;
1181 if (I_BRKINT(tty)) {
1185 if (I_PARMRK(tty)) {
1186 put_tty_queue('\377', ldata);
1187 put_tty_queue('\0', ldata);
1189 put_tty_queue('\0', ldata);
1193 * n_tty_receive_overrun - handle overrun reporting
1196 * Data arrived faster than we could process it. While the tty
1197 * driver has flagged this the bits that were missed are gone
1200 * Called from the receive_buf path so single threaded. Does not
1201 * need locking as num_overrun and overrun_time are function
1205 static void n_tty_receive_overrun(struct tty_struct *tty)
1207 struct n_tty_data *ldata = tty->disc_data;
1209 ldata->num_overrun++;
1210 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1211 time_after(ldata->overrun_time, jiffies)) {
1212 tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
1213 ldata->overrun_time = jiffies;
1214 ldata->num_overrun = 0;
1219 * n_tty_receive_parity_error - error notifier
1220 * @tty: terminal device
1223 * Process a parity error and queue the right data to indicate
1224 * the error case if necessary.
1226 * n_tty_receive_buf()/producer path:
1227 * caller holds non-exclusive termios_rwsem
1229 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1231 struct n_tty_data *ldata = tty->disc_data;
1236 if (I_PARMRK(tty)) {
1237 put_tty_queue('\377', ldata);
1238 put_tty_queue('\0', ldata);
1239 put_tty_queue(c, ldata);
1241 put_tty_queue('\0', ldata);
1243 put_tty_queue(c, ldata);
1247 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1256 process_echoes(tty);
1261 * n_tty_receive_char - perform processing
1262 * @tty: terminal device
1265 * Process an individual character of input received from the driver.
1266 * This is serialized with respect to itself by the rules for the
1269 * n_tty_receive_buf()/producer path:
1270 * caller holds non-exclusive termios_rwsem
1271 * publishes canon_head if canonical mode is active
1273 * Returns 1 if LNEXT was received, else returns 0
1277 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1279 struct n_tty_data *ldata = tty->disc_data;
1282 if (c == START_CHAR(tty)) {
1284 process_echoes(tty);
1287 if (c == STOP_CHAR(tty)) {
1294 if (c == INTR_CHAR(tty)) {
1295 n_tty_receive_signal_char(tty, SIGINT, c);
1297 } else if (c == QUIT_CHAR(tty)) {
1298 n_tty_receive_signal_char(tty, SIGQUIT, c);
1300 } else if (c == SUSP_CHAR(tty)) {
1301 n_tty_receive_signal_char(tty, SIGTSTP, c);
1306 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1308 process_echoes(tty);
1316 } else if (c == '\n' && I_INLCR(tty))
1319 if (ldata->icanon) {
1320 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1321 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1326 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1329 finish_erasing(ldata);
1330 if (L_ECHOCTL(tty)) {
1331 echo_char_raw('^', ldata);
1332 echo_char_raw('\b', ldata);
1338 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1339 size_t tail = ldata->canon_head;
1341 finish_erasing(ldata);
1343 echo_char_raw('\n', ldata);
1344 while (tail != ldata->read_head) {
1345 echo_char(read_buf(ldata, tail), tty);
1352 if (L_ECHO(tty) || L_ECHONL(tty)) {
1353 echo_char_raw('\n', ldata);
1356 goto handle_newline;
1358 if (c == EOF_CHAR(tty)) {
1359 c = __DISABLED_CHAR;
1360 goto handle_newline;
1362 if ((c == EOL_CHAR(tty)) ||
1363 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1365 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1368 /* Record the column of first canon char. */
1369 if (ldata->canon_head == ldata->read_head)
1370 echo_set_canon_col(ldata);
1375 * XXX does PARMRK doubling happen for
1376 * EOL_CHAR and EOL2_CHAR?
1378 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1379 put_tty_queue(c, ldata);
1382 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1383 put_tty_queue(c, ldata);
1384 smp_store_release(&ldata->canon_head, ldata->read_head);
1385 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1386 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1392 finish_erasing(ldata);
1394 echo_char_raw('\n', ldata);
1396 /* Record the column of first canon char. */
1397 if (ldata->canon_head == ldata->read_head)
1398 echo_set_canon_col(ldata);
1404 /* PARMRK doubling check */
1405 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1406 put_tty_queue(c, ldata);
1408 put_tty_queue(c, ldata);
1413 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1415 struct n_tty_data *ldata = tty->disc_data;
1417 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1419 process_echoes(tty);
1422 finish_erasing(ldata);
1423 /* Record the column of first canon char. */
1424 if (ldata->canon_head == ldata->read_head)
1425 echo_set_canon_col(ldata);
1429 /* PARMRK doubling check */
1430 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1431 put_tty_queue(c, ldata);
1432 put_tty_queue(c, ldata);
1435 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1437 n_tty_receive_char_inline(tty, c);
1441 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1443 struct n_tty_data *ldata = tty->disc_data;
1445 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1447 process_echoes(tty);
1450 finish_erasing(ldata);
1451 /* Record the column of first canon char. */
1452 if (ldata->canon_head == ldata->read_head)
1453 echo_set_canon_col(ldata);
1457 put_tty_queue(c, ldata);
1460 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1464 if (I_IUCLC(tty) && L_IEXTEN(tty))
1468 if (c == STOP_CHAR(tty))
1470 else if (c == START_CHAR(tty) ||
1471 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1472 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1473 c != SUSP_CHAR(tty))) {
1475 process_echoes(tty);
1481 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1485 n_tty_receive_break(tty);
1489 n_tty_receive_parity_error(tty, c);
1492 n_tty_receive_overrun(tty);
1495 tty_err(tty, "unknown flag %d\n", flag);
1501 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1503 struct n_tty_data *ldata = tty->disc_data;
1506 if (likely(flag == TTY_NORMAL)) {
1509 if (I_IUCLC(tty) && L_IEXTEN(tty))
1511 n_tty_receive_char(tty, c);
1513 n_tty_receive_char_flagged(tty, c, flag);
1517 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1518 char *fp, int count)
1520 struct n_tty_data *ldata = tty->disc_data;
1523 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1524 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1525 memcpy(read_buf_addr(ldata, head), cp, n);
1526 ldata->read_head += n;
1530 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1531 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1532 memcpy(read_buf_addr(ldata, head), cp, n);
1533 ldata->read_head += n;
1537 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1538 char *fp, int count)
1540 struct n_tty_data *ldata = tty->disc_data;
1541 char flag = TTY_NORMAL;
1546 if (likely(flag == TTY_NORMAL))
1547 put_tty_queue(*cp++, ldata);
1549 n_tty_receive_char_flagged(tty, *cp++, flag);
1554 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1555 char *fp, int count)
1557 char flag = TTY_NORMAL;
1562 if (likely(flag == TTY_NORMAL))
1563 n_tty_receive_char_closing(tty, *cp++);
1565 n_tty_receive_char_flagged(tty, *cp++, flag);
1570 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1571 char *fp, int count)
1573 struct n_tty_data *ldata = tty->disc_data;
1574 char flag = TTY_NORMAL;
1579 if (likely(flag == TTY_NORMAL)) {
1580 unsigned char c = *cp++;
1584 if (I_IUCLC(tty) && L_IEXTEN(tty))
1586 if (L_EXTPROC(tty)) {
1587 put_tty_queue(c, ldata);
1590 if (!test_bit(c, ldata->char_map))
1591 n_tty_receive_char_inline(tty, c);
1592 else if (n_tty_receive_char_special(tty, c) && count) {
1595 n_tty_receive_char_lnext(tty, *cp++, flag);
1599 n_tty_receive_char_flagged(tty, *cp++, flag);
1604 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1605 char *fp, int count)
1607 struct n_tty_data *ldata = tty->disc_data;
1608 char flag = TTY_NORMAL;
1613 if (likely(flag == TTY_NORMAL)) {
1614 unsigned char c = *cp++;
1616 if (!test_bit(c, ldata->char_map))
1617 n_tty_receive_char_fast(tty, c);
1618 else if (n_tty_receive_char_special(tty, c) && count) {
1621 n_tty_receive_char_lnext(tty, *cp++, flag);
1625 n_tty_receive_char_flagged(tty, *cp++, flag);
1629 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1630 char *fp, int count)
1632 struct n_tty_data *ldata = tty->disc_data;
1633 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1635 if (ldata->real_raw)
1636 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1637 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1638 n_tty_receive_buf_raw(tty, cp, fp, count);
1639 else if (tty->closing && !L_EXTPROC(tty))
1640 n_tty_receive_buf_closing(tty, cp, fp, count);
1643 char flag = TTY_NORMAL;
1647 n_tty_receive_char_lnext(tty, *cp++, flag);
1651 if (!preops && !I_PARMRK(tty))
1652 n_tty_receive_buf_fast(tty, cp, fp, count);
1654 n_tty_receive_buf_standard(tty, cp, fp, count);
1657 if (tty->ops->flush_chars)
1658 tty->ops->flush_chars(tty);
1661 if (ldata->icanon && !L_EXTPROC(tty))
1664 /* publish read_head to consumer */
1665 smp_store_release(&ldata->commit_head, ldata->read_head);
1667 if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
1668 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1669 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1674 * n_tty_receive_buf_common - process input
1675 * @tty: device to receive input
1677 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1678 * @count: number of input chars in @cp
1680 * Called by the terminal driver when a block of characters has
1681 * been received. This function must be called from soft contexts
1682 * not from interrupt context. The driver is responsible for making
1683 * calls one at a time and in order (or using flush_to_ldisc)
1685 * Returns the # of input chars from @cp which were processed.
1687 * In canonical mode, the maximum line length is 4096 chars (including
1688 * the line termination char); lines longer than 4096 chars are
1689 * truncated. After 4095 chars, input data is still processed but
1690 * not stored. Overflow processing ensures the tty can always
1691 * receive more input until at least one line can be read.
1693 * In non-canonical mode, the read buffer will only accept 4095 chars;
1694 * this provides the necessary space for a newline char if the input
1695 * mode is switched to canonical.
1697 * Note it is possible for the read buffer to _contain_ 4096 chars
1698 * in non-canonical mode: the read buffer could already contain the
1699 * maximum canon line of 4096 chars when the mode is switched to
1702 * n_tty_receive_buf()/producer path:
1703 * claims non-exclusive termios_rwsem
1704 * publishes commit_head or canon_head
1707 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1708 char *fp, int count, int flow)
1710 struct n_tty_data *ldata = tty->disc_data;
1711 int room, n, rcvd = 0, overflow;
1713 down_read(&tty->termios_rwsem);
1717 * When PARMRK is set, each input char may take up to 3 chars
1718 * in the read buf; reduce the buffer space avail by 3x
1720 * If we are doing input canonicalization, and there are no
1721 * pending newlines, let characters through without limit, so
1722 * that erase characters will be handled. Other excess
1723 * characters will be beeped.
1725 * paired with store in *_copy_from_read_buf() -- guarantees
1726 * the consumer has loaded the data in read_buf up to the new
1727 * read_tail (so this producer will not overwrite unread data)
1729 size_t tail = smp_load_acquire(&ldata->read_tail);
1731 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1733 room = (room + 2) / 3;
1736 overflow = ldata->icanon && ldata->canon_head == tail;
1737 if (overflow && room < 0)
1740 ldata->no_room = flow && !room;
1744 n = min(count, room);
1748 /* ignore parity errors if handling overflow */
1749 if (!overflow || !fp || *fp != TTY_PARITY)
1750 __receive_buf(tty, cp, fp, n);
1759 tty->receive_room = room;
1761 /* Unthrottle if handling overflow on pty */
1762 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1764 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1765 tty_unthrottle_safe(tty);
1766 __tty_set_flow_change(tty, 0);
1769 n_tty_check_throttle(tty);
1771 up_read(&tty->termios_rwsem);
1776 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1777 char *fp, int count)
1779 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1782 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1783 char *fp, int count)
1785 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1788 int is_ignored(int sig)
1790 return (sigismember(¤t->blocked, sig) ||
1791 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1795 * n_tty_set_termios - termios data changed
1797 * @old: previous data
1799 * Called by the tty layer when the user changes termios flags so
1800 * that the line discipline can plan ahead. This function cannot sleep
1801 * and is protected from re-entry by the tty layer. The user is
1802 * guaranteed that this function will not be re-entered or in progress
1803 * when the ldisc is closed.
1805 * Locking: Caller holds tty->termios_rwsem
1808 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1810 struct n_tty_data *ldata = tty->disc_data;
1812 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1813 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1814 ldata->line_start = ldata->read_tail;
1815 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1816 ldata->canon_head = ldata->read_tail;
1819 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1821 ldata->canon_head = ldata->read_head;
1824 ldata->commit_head = ldata->read_head;
1829 ldata->icanon = (L_ICANON(tty) != 0);
1831 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1832 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1833 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1835 bitmap_zero(ldata->char_map, 256);
1837 if (I_IGNCR(tty) || I_ICRNL(tty))
1838 set_bit('\r', ldata->char_map);
1840 set_bit('\n', ldata->char_map);
1842 if (L_ICANON(tty)) {
1843 set_bit(ERASE_CHAR(tty), ldata->char_map);
1844 set_bit(KILL_CHAR(tty), ldata->char_map);
1845 set_bit(EOF_CHAR(tty), ldata->char_map);
1846 set_bit('\n', ldata->char_map);
1847 set_bit(EOL_CHAR(tty), ldata->char_map);
1848 if (L_IEXTEN(tty)) {
1849 set_bit(WERASE_CHAR(tty), ldata->char_map);
1850 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1851 set_bit(EOL2_CHAR(tty), ldata->char_map);
1853 set_bit(REPRINT_CHAR(tty),
1858 set_bit(START_CHAR(tty), ldata->char_map);
1859 set_bit(STOP_CHAR(tty), ldata->char_map);
1862 set_bit(INTR_CHAR(tty), ldata->char_map);
1863 set_bit(QUIT_CHAR(tty), ldata->char_map);
1864 set_bit(SUSP_CHAR(tty), ldata->char_map);
1866 clear_bit(__DISABLED_CHAR, ldata->char_map);
1868 ldata->real_raw = 0;
1871 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1872 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1873 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1874 ldata->real_raw = 1;
1876 ldata->real_raw = 0;
1879 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1880 * been stopped by STOP_CHAR(tty) before it.
1882 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1884 process_echoes(tty);
1887 /* The termios change make the tty ready for I/O */
1888 wake_up_interruptible(&tty->write_wait);
1889 wake_up_interruptible(&tty->read_wait);
1893 * n_tty_close - close the ldisc for this tty
1896 * Called from the terminal layer when this line discipline is
1897 * being shut down, either because of a close or becsuse of a
1898 * discipline change. The function will not be called while other
1899 * ldisc methods are in progress.
1902 static void n_tty_close(struct tty_struct *tty)
1904 struct n_tty_data *ldata = tty->disc_data;
1907 n_tty_packet_mode_flush(tty);
1910 tty->disc_data = NULL;
1914 * n_tty_open - open an ldisc
1915 * @tty: terminal to open
1917 * Called when this line discipline is being attached to the
1918 * terminal device. Can sleep. Called serialized so that no
1919 * other events will occur in parallel. No further open will occur
1923 static int n_tty_open(struct tty_struct *tty)
1925 struct n_tty_data *ldata;
1927 /* Currently a malloc failure here can panic */
1928 ldata = vmalloc(sizeof(*ldata));
1932 ldata->overrun_time = jiffies;
1933 mutex_init(&ldata->atomic_read_lock);
1934 mutex_init(&ldata->output_lock);
1936 tty->disc_data = ldata;
1937 reset_buffer_flags(tty->disc_data);
1939 ldata->canon_column = 0;
1940 ldata->minimum_to_wake = 1;
1941 ldata->num_overrun = 0;
1945 /* indicate buffer work may resume */
1946 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1947 n_tty_set_termios(tty, NULL);
1948 tty_unthrottle(tty);
1955 static inline int input_available_p(struct tty_struct *tty, int poll)
1957 struct n_tty_data *ldata = tty->disc_data;
1958 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1960 if (ldata->icanon && !L_EXTPROC(tty))
1961 return ldata->canon_head != ldata->read_tail;
1963 return ldata->commit_head - ldata->read_tail >= amt;
1966 static inline int check_other_done(struct tty_struct *tty)
1968 int done = test_bit(TTY_OTHER_DONE, &tty->flags);
1970 /* paired with cmpxchg() in check_other_closed(); ensures
1971 * read buffer head index is not stale
1973 smp_mb__after_atomic();
1979 * copy_from_read_buf - copy read data directly
1980 * @tty: terminal device
1984 * Helper function to speed up n_tty_read. It is only called when
1985 * ICANON is off; it copies characters straight from the tty queue to
1986 * user space directly. It can be profitably called twice; once to
1987 * drain the space from the tail pointer to the (physical) end of the
1988 * buffer, and once to drain the space from the (physical) beginning of
1989 * the buffer to head pointer.
1991 * Called under the ldata->atomic_read_lock sem
1993 * n_tty_read()/consumer path:
1994 * caller holds non-exclusive termios_rwsem
1995 * read_tail published
1998 static int copy_from_read_buf(struct tty_struct *tty,
1999 unsigned char __user **b,
2003 struct n_tty_data *ldata = tty->disc_data;
2007 size_t head = smp_load_acquire(&ldata->commit_head);
2008 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2011 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
2014 const unsigned char *from = read_buf_addr(ldata, tail);
2015 retval = copy_to_user(*b, from, n);
2017 is_eof = n == 1 && *from == EOF_CHAR(tty);
2018 tty_audit_add_data(tty, from, n, ldata->icanon);
2019 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
2020 /* Turn single EOF into zero-length read */
2021 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
2022 (head == ldata->read_tail))
2031 * canon_copy_from_read_buf - copy read data in canonical mode
2032 * @tty: terminal device
2036 * Helper function for n_tty_read. It is only called when ICANON is on;
2037 * it copies one line of input up to and including the line-delimiting
2038 * character into the user-space buffer.
2040 * NB: When termios is changed from non-canonical to canonical mode and
2041 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2042 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2043 * This causes data already processed as input to be immediately available
2044 * as input although a newline has not been received.
2046 * Called under the atomic_read_lock mutex
2048 * n_tty_read()/consumer path:
2049 * caller holds non-exclusive termios_rwsem
2050 * read_tail published
2053 static int canon_copy_from_read_buf(struct tty_struct *tty,
2054 unsigned char __user **b,
2057 struct n_tty_data *ldata = tty->disc_data;
2058 size_t n, size, more, c;
2063 /* N.B. avoid overrun if nr == 0 */
2067 n = min(*nr + 1, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2069 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2070 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2072 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2073 __func__, *nr, tail, n, size);
2075 eol = find_next_bit(ldata->read_flags, size, tail);
2076 more = n - (size - tail);
2077 if (eol == N_TTY_BUF_SIZE && more) {
2078 /* scan wrapped without finding set bit */
2079 eol = find_next_bit(ldata->read_flags, more, 0);
2080 found = eol != more;
2082 found = eol != size;
2085 if (n > N_TTY_BUF_SIZE)
2086 n += N_TTY_BUF_SIZE;
2089 if (!found || read_buf(ldata, eol) != __DISABLED_CHAR) {
2094 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
2095 __func__, eol, found, n, c, tail, more);
2097 ret = tty_copy_to_user(tty, *b, tail, n);
2104 clear_bit(eol, ldata->read_flags);
2105 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2109 ldata->line_start = ldata->read_tail;
2112 tty_audit_push(tty);
2117 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2121 * job_control - check job control
2123 * @file: file handle
2125 * Perform job control management checks on this file/tty descriptor
2126 * and if appropriate send any needed signals and return a negative
2127 * error code if action should be taken.
2129 * Locking: redirected write test is safe
2130 * current->signal->tty check is safe
2131 * ctrl_lock to safely reference tty->pgrp
2134 static int job_control(struct tty_struct *tty, struct file *file)
2136 /* Job control check -- must be done at start and after
2137 every sleep (POSIX.1 7.1.1.4). */
2138 /* NOTE: not yet done after every sleep pending a thorough
2139 check of the logic of this change. -- jlc */
2140 /* don't stop on /dev/console */
2141 if (file->f_op->write == redirected_tty_write)
2144 return __tty_check_change(tty, SIGTTIN);
2149 * n_tty_read - read function for tty
2151 * @file: file object
2152 * @buf: userspace buffer pointer
2155 * Perform reads for the line discipline. We are guaranteed that the
2156 * line discipline will not be closed under us but we may get multiple
2157 * parallel readers and must handle this ourselves. We may also get
2158 * a hangup. Always called in user context, may sleep.
2160 * This code must be sure never to sleep through a hangup.
2162 * n_tty_read()/consumer path:
2163 * claims non-exclusive termios_rwsem
2164 * publishes read_tail
2167 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2168 unsigned char __user *buf, size_t nr)
2170 struct n_tty_data *ldata = tty->disc_data;
2171 unsigned char __user *b = buf;
2172 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2180 c = job_control(tty, file);
2185 * Internal serialization of reads.
2187 if (file->f_flags & O_NONBLOCK) {
2188 if (!mutex_trylock(&ldata->atomic_read_lock))
2191 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2192 return -ERESTARTSYS;
2195 down_read(&tty->termios_rwsem);
2198 timeout = MAX_SCHEDULE_TIMEOUT;
2199 if (!ldata->icanon) {
2200 minimum = MIN_CHAR(tty);
2202 time = (HZ / 10) * TIME_CHAR(tty);
2204 ldata->minimum_to_wake = 1;
2205 else if (!waitqueue_active(&tty->read_wait) ||
2206 (ldata->minimum_to_wake > minimum))
2207 ldata->minimum_to_wake = minimum;
2209 timeout = (HZ / 10) * TIME_CHAR(tty);
2210 ldata->minimum_to_wake = minimum = 1;
2214 packet = tty->packet;
2215 tail = ldata->read_tail;
2217 add_wait_queue(&tty->read_wait, &wait);
2219 /* First test for status change. */
2220 if (packet && tty->link->ctrl_status) {
2224 spin_lock_irq(&tty->link->ctrl_lock);
2225 cs = tty->link->ctrl_status;
2226 tty->link->ctrl_status = 0;
2227 spin_unlock_irq(&tty->link->ctrl_lock);
2228 if (tty_put_user(tty, cs, b++)) {
2237 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2238 ((minimum - (b - buf)) >= 1))
2239 ldata->minimum_to_wake = (minimum - (b - buf));
2241 done = check_other_done(tty);
2243 if (!input_available_p(tty, 0)) {
2248 if (tty_hung_up_p(file))
2252 if (file->f_flags & O_NONBLOCK) {
2256 if (signal_pending(current)) {
2257 retval = -ERESTARTSYS;
2260 up_read(&tty->termios_rwsem);
2262 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2265 down_read(&tty->termios_rwsem);
2269 if (ldata->icanon && !L_EXTPROC(tty)) {
2270 retval = canon_copy_from_read_buf(tty, &b, &nr);
2276 /* Deal with packet mode. */
2277 if (packet && b == buf) {
2278 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2286 uncopied = copy_from_read_buf(tty, &b, &nr);
2287 uncopied += copy_from_read_buf(tty, &b, &nr);
2294 n_tty_check_unthrottle(tty);
2296 if (b - buf >= minimum)
2301 if (tail != ldata->read_tail)
2302 n_tty_kick_worker(tty);
2303 up_read(&tty->termios_rwsem);
2305 remove_wait_queue(&tty->read_wait, &wait);
2306 if (!waitqueue_active(&tty->read_wait))
2307 ldata->minimum_to_wake = minimum;
2309 mutex_unlock(&ldata->atomic_read_lock);
2318 * n_tty_write - write function for tty
2320 * @file: file object
2321 * @buf: userspace buffer pointer
2324 * Write function of the terminal device. This is serialized with
2325 * respect to other write callers but not to termios changes, reads
2326 * and other such events. Since the receive code will echo characters,
2327 * thus calling driver write methods, the output_lock is used in
2328 * the output processing functions called here as well as in the
2329 * echo processing function to protect the column state and space
2330 * left in the buffer.
2332 * This code must be sure never to sleep through a hangup.
2334 * Locking: output_lock to protect column state and space left
2335 * (note that the process_output*() functions take this
2339 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2340 const unsigned char *buf, size_t nr)
2342 const unsigned char *b = buf;
2343 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2347 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2348 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2349 retval = tty_check_change(tty);
2354 down_read(&tty->termios_rwsem);
2356 /* Write out any echoed characters that are still pending */
2357 process_echoes(tty);
2359 add_wait_queue(&tty->write_wait, &wait);
2361 if (signal_pending(current)) {
2362 retval = -ERESTARTSYS;
2365 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2371 ssize_t num = process_output_block(tty, b, nr);
2383 if (process_output(c, tty) < 0)
2387 if (tty->ops->flush_chars)
2388 tty->ops->flush_chars(tty);
2390 struct n_tty_data *ldata = tty->disc_data;
2393 mutex_lock(&ldata->output_lock);
2394 c = tty->ops->write(tty, b, nr);
2395 mutex_unlock(&ldata->output_lock);
2408 if (file->f_flags & O_NONBLOCK) {
2412 up_read(&tty->termios_rwsem);
2414 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2416 down_read(&tty->termios_rwsem);
2419 remove_wait_queue(&tty->write_wait, &wait);
2420 if (b - buf != nr && tty->fasync)
2421 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2422 up_read(&tty->termios_rwsem);
2423 return (b - buf) ? b - buf : retval;
2427 * n_tty_poll - poll method for N_TTY
2428 * @tty: terminal device
2429 * @file: file accessing it
2432 * Called when the line discipline is asked to poll() for data or
2433 * for special events. This code is not serialized with respect to
2434 * other events save open/close.
2436 * This code must be sure never to sleep through a hangup.
2437 * Called without the kernel lock held - fine
2440 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2443 struct n_tty_data *ldata = tty->disc_data;
2444 unsigned int mask = 0;
2446 poll_wait(file, &tty->read_wait, wait);
2447 poll_wait(file, &tty->write_wait, wait);
2448 if (check_other_done(tty))
2450 if (input_available_p(tty, 1))
2451 mask |= POLLIN | POLLRDNORM;
2452 if (tty->packet && tty->link->ctrl_status)
2453 mask |= POLLPRI | POLLIN | POLLRDNORM;
2454 if (tty_hung_up_p(file))
2456 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2457 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2458 ldata->minimum_to_wake = MIN_CHAR(tty);
2460 ldata->minimum_to_wake = 1;
2462 if (tty->ops->write && !tty_is_writelocked(tty) &&
2463 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2464 tty_write_room(tty) > 0)
2465 mask |= POLLOUT | POLLWRNORM;
2469 static unsigned long inq_canon(struct n_tty_data *ldata)
2471 size_t nr, head, tail;
2473 if (ldata->canon_head == ldata->read_tail)
2475 head = ldata->canon_head;
2476 tail = ldata->read_tail;
2478 /* Skip EOF-chars.. */
2479 while (head != tail) {
2480 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2481 read_buf(ldata, tail) == __DISABLED_CHAR)
2488 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2489 unsigned int cmd, unsigned long arg)
2491 struct n_tty_data *ldata = tty->disc_data;
2496 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2498 down_write(&tty->termios_rwsem);
2500 retval = inq_canon(ldata);
2502 retval = read_cnt(ldata);
2503 up_write(&tty->termios_rwsem);
2504 return put_user(retval, (unsigned int __user *) arg);
2506 return n_tty_ioctl_helper(tty, file, cmd, arg);
2510 static void n_tty_fasync(struct tty_struct *tty, int on)
2512 struct n_tty_data *ldata = tty->disc_data;
2514 if (!waitqueue_active(&tty->read_wait)) {
2516 ldata->minimum_to_wake = 1;
2517 else if (!tty->fasync)
2518 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2522 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2523 .magic = TTY_LDISC_MAGIC,
2526 .close = n_tty_close,
2527 .flush_buffer = n_tty_flush_buffer,
2528 .chars_in_buffer = n_tty_chars_in_buffer,
2530 .write = n_tty_write,
2531 .ioctl = n_tty_ioctl,
2532 .set_termios = n_tty_set_termios,
2534 .receive_buf = n_tty_receive_buf,
2535 .write_wakeup = n_tty_write_wakeup,
2536 .fasync = n_tty_fasync,
2537 .receive_buf2 = n_tty_receive_buf2,
2541 * n_tty_inherit_ops - inherit N_TTY methods
2542 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2544 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2548 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2550 *ops = tty_ldisc_N_TTY;
2552 ops->refcount = ops->flags = 0;
2554 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);