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 inline int tty_copy_to_user(struct tty_struct *tty,
170 struct n_tty_data *ldata = tty->disc_data;
172 tty_audit_add_data(tty, to, n, ldata->icanon);
173 return copy_to_user(to, from, n);
177 * n_tty_kick_worker - start input worker (if required)
180 * Re-schedules the flip buffer work if it may have stopped
182 * Caller holds exclusive termios_rwsem
184 * n_tty_read()/consumer path:
185 * holds non-exclusive termios_rwsem
188 static void n_tty_kick_worker(struct tty_struct *tty)
190 struct n_tty_data *ldata = tty->disc_data;
192 /* Did the input worker stop? Restart it */
193 if (unlikely(ldata->no_room)) {
196 WARN_RATELIMIT(tty->port->itty == NULL,
197 "scheduling with invalid itty\n");
198 /* see if ldisc has been killed - if so, this means that
199 * even though the ldisc has been halted and ->buf.work
200 * cancelled, ->buf.work is about to be rescheduled
202 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
203 "scheduling buffer work for halted ldisc\n");
204 queue_work(system_unbound_wq, &tty->port->buf.work);
208 static ssize_t chars_in_buffer(struct tty_struct *tty)
210 struct n_tty_data *ldata = tty->disc_data;
214 n = ldata->commit_head - ldata->read_tail;
216 n = ldata->canon_head - ldata->read_tail;
221 * n_tty_write_wakeup - asynchronous I/O notifier
224 * Required for the ptys, serial driver etc. since processes
225 * that attach themselves to the master and rely on ASYNC
226 * IO must be woken up
229 static void n_tty_write_wakeup(struct tty_struct *tty)
231 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
232 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
235 static void n_tty_check_throttle(struct tty_struct *tty)
237 struct n_tty_data *ldata = tty->disc_data;
240 * Check the remaining room for the input canonicalization
241 * mode. We don't want to throttle the driver if we're in
242 * canonical mode and don't have a newline yet!
244 if (ldata->icanon && ldata->canon_head == ldata->read_tail)
249 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
250 if (N_TTY_BUF_SIZE - read_cnt(ldata) >= TTY_THRESHOLD_THROTTLE)
252 throttled = tty_throttle_safe(tty);
256 __tty_set_flow_change(tty, 0);
259 static void n_tty_check_unthrottle(struct tty_struct *tty)
261 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
262 tty->link->ldisc->ops->write_wakeup == n_tty_write_wakeup) {
263 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
267 n_tty_kick_worker(tty);
268 n_tty_write_wakeup(tty->link);
269 if (waitqueue_active(&tty->link->write_wait))
270 wake_up_interruptible_poll(&tty->link->write_wait, POLLOUT);
274 /* If there is enough space in the read buffer now, let the
275 * low-level driver know. We use chars_in_buffer() to
276 * check the buffer, as it now knows about canonical mode.
277 * Otherwise, if the driver is throttled and the line is
278 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
279 * we won't get any more characters.
284 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
285 if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
289 n_tty_kick_worker(tty);
290 unthrottled = tty_unthrottle_safe(tty);
294 __tty_set_flow_change(tty, 0);
298 * put_tty_queue - add character to tty
302 * Add a character to the tty read_buf queue.
304 * n_tty_receive_buf()/producer path:
305 * caller holds non-exclusive termios_rwsem
308 static inline void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
310 *read_buf_addr(ldata, ldata->read_head) = c;
315 * reset_buffer_flags - reset buffer state
316 * @tty: terminal to reset
318 * Reset the read buffer counters and clear the flags.
319 * Called from n_tty_open() and n_tty_flush_buffer().
321 * Locking: caller holds exclusive termios_rwsem
322 * (or locking is not required)
325 static void reset_buffer_flags(struct n_tty_data *ldata)
327 ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
328 ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
329 ldata->commit_head = 0;
330 ldata->echo_mark = 0;
331 ldata->line_start = 0;
334 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
338 static void n_tty_packet_mode_flush(struct tty_struct *tty)
342 if (tty->link->packet) {
343 spin_lock_irqsave(&tty->ctrl_lock, flags);
344 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
345 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
346 wake_up_interruptible(&tty->link->read_wait);
351 * n_tty_flush_buffer - clean input queue
352 * @tty: terminal device
354 * Flush the input buffer. Called when the tty layer wants the
355 * buffer flushed (eg at hangup) or when the N_TTY line discipline
356 * internally has to clean the pending queue (for example some signals).
358 * Holds termios_rwsem to exclude producer/consumer while
359 * buffer indices are reset.
361 * Locking: ctrl_lock, exclusive termios_rwsem
364 static void n_tty_flush_buffer(struct tty_struct *tty)
366 down_write(&tty->termios_rwsem);
367 reset_buffer_flags(tty->disc_data);
368 n_tty_kick_worker(tty);
371 n_tty_packet_mode_flush(tty);
372 up_write(&tty->termios_rwsem);
376 * n_tty_chars_in_buffer - report available bytes
379 * Report the number of characters buffered to be delivered to user
380 * at this instant in time.
382 * Locking: exclusive termios_rwsem
385 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
389 WARN_ONCE(1, "%s is deprecated and scheduled for removal.", __func__);
391 down_write(&tty->termios_rwsem);
392 n = chars_in_buffer(tty);
393 up_write(&tty->termios_rwsem);
398 * is_utf8_continuation - utf8 multibyte check
401 * Returns true if the utf8 character 'c' is a multibyte continuation
402 * character. We use this to correctly compute the on screen size
403 * of the character when printing
406 static inline int is_utf8_continuation(unsigned char c)
408 return (c & 0xc0) == 0x80;
412 * is_continuation - multibyte check
415 * Returns true if the utf8 character 'c' is a multibyte continuation
416 * character and the terminal is in unicode mode.
419 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
421 return I_IUTF8(tty) && is_utf8_continuation(c);
425 * do_output_char - output one character
426 * @c: character (or partial unicode symbol)
427 * @tty: terminal device
428 * @space: space available in tty driver write buffer
430 * This is a helper function that handles one output character
431 * (including special characters like TAB, CR, LF, etc.),
432 * doing OPOST processing and putting the results in the
433 * tty driver's write buffer.
435 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
436 * and NLDLY. They simply aren't relevant in the world today.
437 * If you ever need them, add them here.
439 * Returns the number of bytes of buffer space used or -1 if
442 * Locking: should be called under the output_lock to protect
443 * the column state and space left in the buffer
446 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
448 struct n_tty_data *ldata = tty->disc_data;
461 ldata->canon_column = ldata->column = 0;
462 tty->ops->write(tty, "\r\n", 2);
465 ldata->canon_column = ldata->column;
468 if (O_ONOCR(tty) && ldata->column == 0)
473 ldata->canon_column = ldata->column = 0;
476 ldata->canon_column = ldata->column = 0;
479 spaces = 8 - (ldata->column & 7);
480 if (O_TABDLY(tty) == XTABS) {
483 ldata->column += spaces;
484 tty->ops->write(tty, " ", spaces);
487 ldata->column += spaces;
490 if (ldata->column > 0)
497 if (!is_continuation(c, tty))
503 tty_put_char(tty, c);
508 * process_output - output post processor
509 * @c: character (or partial unicode symbol)
510 * @tty: terminal device
512 * Output one character with OPOST processing.
513 * Returns -1 when the output device is full and the character
516 * Locking: output_lock to protect column state and space left
517 * (also, this is called from n_tty_write under the
518 * tty layer write lock)
521 static int process_output(unsigned char c, struct tty_struct *tty)
523 struct n_tty_data *ldata = tty->disc_data;
526 mutex_lock(&ldata->output_lock);
528 space = tty_write_room(tty);
529 retval = do_output_char(c, tty, space);
531 mutex_unlock(&ldata->output_lock);
539 * process_output_block - block post processor
540 * @tty: terminal device
541 * @buf: character buffer
542 * @nr: number of bytes to output
544 * Output a block of characters with OPOST processing.
545 * Returns the number of characters output.
547 * This path is used to speed up block console writes, among other
548 * things when processing blocks of output data. It handles only
549 * the simple cases normally found and helps to generate blocks of
550 * symbols for the console driver and thus improve performance.
552 * Locking: output_lock to protect column state and space left
553 * (also, this is called from n_tty_write under the
554 * tty layer write lock)
557 static ssize_t process_output_block(struct tty_struct *tty,
558 const unsigned char *buf, unsigned int nr)
560 struct n_tty_data *ldata = tty->disc_data;
563 const unsigned char *cp;
565 mutex_lock(&ldata->output_lock);
567 space = tty_write_room(tty);
569 mutex_unlock(&ldata->output_lock);
575 for (i = 0, cp = buf; i < nr; i++, cp++) {
576 unsigned char c = *cp;
584 ldata->canon_column = ldata->column;
587 if (O_ONOCR(tty) && ldata->column == 0)
591 ldata->canon_column = ldata->column = 0;
596 if (ldata->column > 0)
603 if (!is_continuation(c, tty))
610 i = tty->ops->write(tty, buf, i);
612 mutex_unlock(&ldata->output_lock);
617 * process_echoes - write pending echo characters
618 * @tty: terminal device
620 * Write previously buffered echo (and other ldisc-generated)
621 * characters to the tty.
623 * Characters generated by the ldisc (including echoes) need to
624 * be buffered because the driver's write buffer can fill during
625 * heavy program output. Echoing straight to the driver will
626 * often fail under these conditions, causing lost characters and
627 * resulting mismatches of ldisc state information.
629 * Since the ldisc state must represent the characters actually sent
630 * to the driver at the time of the write, operations like certain
631 * changes in column state are also saved in the buffer and executed
634 * A circular fifo buffer is used so that the most recent characters
635 * are prioritized. Also, when control characters are echoed with a
636 * prefixed "^", the pair is treated atomically and thus not separated.
638 * Locking: callers must hold output_lock
641 static size_t __process_echoes(struct tty_struct *tty)
643 struct n_tty_data *ldata = tty->disc_data;
644 int space, old_space;
648 old_space = space = tty_write_room(tty);
650 tail = ldata->echo_tail;
651 while (ldata->echo_commit != tail) {
652 c = echo_buf(ldata, tail);
653 if (c == ECHO_OP_START) {
655 int no_space_left = 0;
658 * If the buffer byte is the start of a multi-byte
659 * operation, get the next byte, which is either the
660 * op code or a control character value.
662 op = echo_buf(ldata, tail + 1);
665 unsigned int num_chars, num_bs;
667 case ECHO_OP_ERASE_TAB:
668 num_chars = echo_buf(ldata, tail + 2);
671 * Determine how many columns to go back
672 * in order to erase the tab.
673 * This depends on the number of columns
674 * used by other characters within the tab
675 * area. If this (modulo 8) count is from
676 * the start of input rather than from a
677 * previous tab, we offset by canon column.
678 * Otherwise, tab spacing is normal.
680 if (!(num_chars & 0x80))
681 num_chars += ldata->canon_column;
682 num_bs = 8 - (num_chars & 7);
684 if (num_bs > space) {
690 tty_put_char(tty, '\b');
691 if (ldata->column > 0)
697 case ECHO_OP_SET_CANON_COL:
698 ldata->canon_column = ldata->column;
702 case ECHO_OP_MOVE_BACK_COL:
703 if (ldata->column > 0)
709 /* This is an escaped echo op start code */
714 tty_put_char(tty, ECHO_OP_START);
722 * If the op is not a special byte code,
723 * it is a ctrl char tagged to be echoed
724 * as "^X" (where X is the letter
725 * representing the control char).
726 * Note that we must ensure there is
727 * enough space for the whole ctrl pair.
734 tty_put_char(tty, '^');
735 tty_put_char(tty, op ^ 0100);
745 int retval = do_output_char(c, tty, space);
752 tty_put_char(tty, c);
759 /* If the echo buffer is nearly full (so that the possibility exists
760 * of echo overrun before the next commit), then discard enough
761 * data at the tail to prevent a subsequent overrun */
762 while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
763 if (echo_buf(ldata, tail) == ECHO_OP_START) {
764 if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
772 ldata->echo_tail = tail;
773 return old_space - space;
776 static void commit_echoes(struct tty_struct *tty)
778 struct n_tty_data *ldata = tty->disc_data;
779 size_t nr, old, echoed;
782 head = ldata->echo_head;
783 ldata->echo_mark = head;
784 old = ldata->echo_commit - ldata->echo_tail;
786 /* Process committed echoes if the accumulated # of bytes
787 * is over the threshold (and try again each time another
788 * block is accumulated) */
789 nr = head - ldata->echo_tail;
790 if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
793 mutex_lock(&ldata->output_lock);
794 ldata->echo_commit = head;
795 echoed = __process_echoes(tty);
796 mutex_unlock(&ldata->output_lock);
798 if (echoed && tty->ops->flush_chars)
799 tty->ops->flush_chars(tty);
802 static void process_echoes(struct tty_struct *tty)
804 struct n_tty_data *ldata = tty->disc_data;
807 if (ldata->echo_mark == ldata->echo_tail)
810 mutex_lock(&ldata->output_lock);
811 ldata->echo_commit = ldata->echo_mark;
812 echoed = __process_echoes(tty);
813 mutex_unlock(&ldata->output_lock);
815 if (echoed && tty->ops->flush_chars)
816 tty->ops->flush_chars(tty);
819 /* NB: echo_mark and echo_head should be equivalent here */
820 static void flush_echoes(struct tty_struct *tty)
822 struct n_tty_data *ldata = tty->disc_data;
824 if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
825 ldata->echo_commit == ldata->echo_head)
828 mutex_lock(&ldata->output_lock);
829 ldata->echo_commit = ldata->echo_head;
830 __process_echoes(tty);
831 mutex_unlock(&ldata->output_lock);
835 * add_echo_byte - add a byte to the echo buffer
836 * @c: unicode byte to echo
839 * Add a character or operation byte to the echo buffer.
842 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
844 *echo_buf_addr(ldata, ldata->echo_head++) = c;
848 * echo_move_back_col - add operation to move back a column
851 * Add an operation to the echo buffer to move back one column.
854 static void echo_move_back_col(struct n_tty_data *ldata)
856 add_echo_byte(ECHO_OP_START, ldata);
857 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
861 * echo_set_canon_col - add operation to set the canon column
864 * Add an operation to the echo buffer to set the canon column
865 * to the current column.
868 static void echo_set_canon_col(struct n_tty_data *ldata)
870 add_echo_byte(ECHO_OP_START, ldata);
871 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
875 * echo_erase_tab - add operation to erase a tab
876 * @num_chars: number of character columns already used
877 * @after_tab: true if num_chars starts after a previous tab
880 * Add an operation to the echo buffer to erase a tab.
882 * Called by the eraser function, which knows how many character
883 * columns have been used since either a previous tab or the start
884 * of input. This information will be used later, along with
885 * canon column (if applicable), to go back the correct number
889 static void echo_erase_tab(unsigned int num_chars, int after_tab,
890 struct n_tty_data *ldata)
892 add_echo_byte(ECHO_OP_START, ldata);
893 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
895 /* We only need to know this modulo 8 (tab spacing) */
898 /* Set the high bit as a flag if num_chars is after a previous tab */
902 add_echo_byte(num_chars, ldata);
906 * echo_char_raw - echo a character raw
907 * @c: unicode byte to echo
908 * @tty: terminal device
910 * Echo user input back onto the screen. This must be called only when
911 * L_ECHO(tty) is true. Called from the driver receive_buf path.
913 * This variant does not treat control characters specially.
916 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
918 if (c == ECHO_OP_START) {
919 add_echo_byte(ECHO_OP_START, ldata);
920 add_echo_byte(ECHO_OP_START, ldata);
922 add_echo_byte(c, ldata);
927 * echo_char - echo a character
928 * @c: unicode byte to echo
929 * @tty: terminal device
931 * Echo user input back onto the screen. This must be called only when
932 * L_ECHO(tty) is true. Called from the driver receive_buf path.
934 * This variant tags control characters to be echoed as "^X"
935 * (where X is the letter representing the control char).
938 static void echo_char(unsigned char c, struct tty_struct *tty)
940 struct n_tty_data *ldata = tty->disc_data;
942 if (c == ECHO_OP_START) {
943 add_echo_byte(ECHO_OP_START, ldata);
944 add_echo_byte(ECHO_OP_START, ldata);
946 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
947 add_echo_byte(ECHO_OP_START, ldata);
948 add_echo_byte(c, ldata);
953 * finish_erasing - complete erase
957 static inline void finish_erasing(struct n_tty_data *ldata)
959 if (ldata->erasing) {
960 echo_char_raw('/', ldata);
966 * eraser - handle erase function
967 * @c: character input
968 * @tty: terminal device
970 * Perform erase and necessary output when an erase character is
971 * present in the stream from the driver layer. Handles the complexities
972 * of UTF-8 multibyte symbols.
974 * n_tty_receive_buf()/producer path:
975 * caller holds non-exclusive termios_rwsem
978 static void eraser(unsigned char c, struct tty_struct *tty)
980 struct n_tty_data *ldata = tty->disc_data;
981 enum { ERASE, WERASE, KILL } kill_type;
986 if (ldata->read_head == ldata->canon_head) {
987 /* process_output('\a', tty); */ /* what do you think? */
990 if (c == ERASE_CHAR(tty))
992 else if (c == WERASE_CHAR(tty))
996 ldata->read_head = ldata->canon_head;
999 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
1000 ldata->read_head = ldata->canon_head;
1001 finish_erasing(ldata);
1002 echo_char(KILL_CHAR(tty), tty);
1003 /* Add a newline if ECHOK is on and ECHOKE is off. */
1005 echo_char_raw('\n', ldata);
1012 while (ldata->read_head != ldata->canon_head) {
1013 head = ldata->read_head;
1015 /* erase a single possibly multibyte character */
1018 c = read_buf(ldata, head);
1019 } while (is_continuation(c, tty) && head != ldata->canon_head);
1021 /* do not partially erase */
1022 if (is_continuation(c, tty))
1025 if (kill_type == WERASE) {
1026 /* Equivalent to BSD's ALTWERASE. */
1027 if (isalnum(c) || c == '_')
1029 else if (seen_alnums)
1032 cnt = ldata->read_head - head;
1033 ldata->read_head = head;
1035 if (L_ECHOPRT(tty)) {
1036 if (!ldata->erasing) {
1037 echo_char_raw('\\', ldata);
1040 /* if cnt > 1, output a multi-byte character */
1044 echo_char_raw(read_buf(ldata, head), ldata);
1045 echo_move_back_col(ldata);
1047 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
1048 echo_char(ERASE_CHAR(tty), tty);
1049 } else if (c == '\t') {
1050 unsigned int num_chars = 0;
1052 size_t tail = ldata->read_head;
1055 * Count the columns used for characters
1056 * since the start of input or after a
1058 * This info is used to go back the correct
1059 * number of columns.
1061 while (tail != ldata->canon_head) {
1063 c = read_buf(ldata, tail);
1067 } else if (iscntrl(c)) {
1070 } else if (!is_continuation(c, tty)) {
1074 echo_erase_tab(num_chars, after_tab, ldata);
1076 if (iscntrl(c) && L_ECHOCTL(tty)) {
1077 echo_char_raw('\b', ldata);
1078 echo_char_raw(' ', ldata);
1079 echo_char_raw('\b', ldata);
1081 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1082 echo_char_raw('\b', ldata);
1083 echo_char_raw(' ', ldata);
1084 echo_char_raw('\b', ldata);
1088 if (kill_type == ERASE)
1091 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1092 finish_erasing(ldata);
1096 * isig - handle the ISIG optio
1100 * Called when a signal is being sent due to terminal input.
1101 * Called from the driver receive_buf path so serialized.
1103 * Performs input and output flush if !NOFLSH. In this context, the echo
1104 * buffer is 'output'. The signal is processed first to alert any current
1105 * readers or writers to discontinue and exit their i/o loops.
1107 * Locking: ctrl_lock
1110 static void __isig(int sig, struct tty_struct *tty)
1112 struct pid *tty_pgrp = tty_get_pgrp(tty);
1114 kill_pgrp(tty_pgrp, sig, 1);
1119 static void isig(int sig, struct tty_struct *tty)
1121 struct n_tty_data *ldata = tty->disc_data;
1123 if (L_NOFLSH(tty)) {
1127 } else { /* signal and flush */
1128 up_read(&tty->termios_rwsem);
1129 down_write(&tty->termios_rwsem);
1133 /* clear echo buffer */
1134 mutex_lock(&ldata->output_lock);
1135 ldata->echo_head = ldata->echo_tail = 0;
1136 ldata->echo_mark = ldata->echo_commit = 0;
1137 mutex_unlock(&ldata->output_lock);
1139 /* clear output buffer */
1140 tty_driver_flush_buffer(tty);
1142 /* clear input buffer */
1143 reset_buffer_flags(tty->disc_data);
1145 /* notify pty master of flush */
1147 n_tty_packet_mode_flush(tty);
1149 up_write(&tty->termios_rwsem);
1150 down_read(&tty->termios_rwsem);
1155 * n_tty_receive_break - handle break
1158 * An RS232 break event has been hit in the incoming bitstream. This
1159 * can cause a variety of events depending upon the termios settings.
1161 * n_tty_receive_buf()/producer path:
1162 * caller holds non-exclusive termios_rwsem
1164 * Note: may get exclusive termios_rwsem if flushing input buffer
1167 static void n_tty_receive_break(struct tty_struct *tty)
1169 struct n_tty_data *ldata = tty->disc_data;
1173 if (I_BRKINT(tty)) {
1177 if (I_PARMRK(tty)) {
1178 put_tty_queue('\377', ldata);
1179 put_tty_queue('\0', ldata);
1181 put_tty_queue('\0', ldata);
1182 if (waitqueue_active(&tty->read_wait))
1183 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1187 * n_tty_receive_overrun - handle overrun reporting
1190 * Data arrived faster than we could process it. While the tty
1191 * driver has flagged this the bits that were missed are gone
1194 * Called from the receive_buf path so single threaded. Does not
1195 * need locking as num_overrun and overrun_time are function
1199 static void n_tty_receive_overrun(struct tty_struct *tty)
1201 struct n_tty_data *ldata = tty->disc_data;
1203 ldata->num_overrun++;
1204 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1205 time_after(ldata->overrun_time, jiffies)) {
1206 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1208 ldata->num_overrun);
1209 ldata->overrun_time = jiffies;
1210 ldata->num_overrun = 0;
1215 * n_tty_receive_parity_error - error notifier
1216 * @tty: terminal device
1219 * Process a parity error and queue the right data to indicate
1220 * the error case if necessary.
1222 * n_tty_receive_buf()/producer path:
1223 * caller holds non-exclusive termios_rwsem
1225 static void n_tty_receive_parity_error(struct tty_struct *tty, unsigned char c)
1227 struct n_tty_data *ldata = tty->disc_data;
1232 if (I_PARMRK(tty)) {
1233 put_tty_queue('\377', ldata);
1234 put_tty_queue('\0', ldata);
1235 put_tty_queue(c, ldata);
1237 put_tty_queue('\0', ldata);
1239 put_tty_queue(c, ldata);
1240 if (waitqueue_active(&tty->read_wait))
1241 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1245 n_tty_receive_signal_char(struct tty_struct *tty, int signal, unsigned char c)
1254 process_echoes(tty);
1259 * n_tty_receive_char - perform processing
1260 * @tty: terminal device
1263 * Process an individual character of input received from the driver.
1264 * This is serialized with respect to itself by the rules for the
1267 * n_tty_receive_buf()/producer path:
1268 * caller holds non-exclusive termios_rwsem
1269 * publishes canon_head if canonical mode is active
1271 * Returns 1 if LNEXT was received, else returns 0
1275 n_tty_receive_char_special(struct tty_struct *tty, unsigned char c)
1277 struct n_tty_data *ldata = tty->disc_data;
1280 if (c == START_CHAR(tty)) {
1282 process_echoes(tty);
1285 if (c == STOP_CHAR(tty)) {
1292 if (c == INTR_CHAR(tty)) {
1293 n_tty_receive_signal_char(tty, SIGINT, c);
1295 } else if (c == QUIT_CHAR(tty)) {
1296 n_tty_receive_signal_char(tty, SIGQUIT, c);
1298 } else if (c == SUSP_CHAR(tty)) {
1299 n_tty_receive_signal_char(tty, SIGTSTP, c);
1304 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1306 process_echoes(tty);
1314 } else if (c == '\n' && I_INLCR(tty))
1317 if (ldata->icanon) {
1318 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1319 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1324 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1327 finish_erasing(ldata);
1328 if (L_ECHOCTL(tty)) {
1329 echo_char_raw('^', ldata);
1330 echo_char_raw('\b', ldata);
1336 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) && L_IEXTEN(tty)) {
1337 size_t tail = ldata->canon_head;
1339 finish_erasing(ldata);
1341 echo_char_raw('\n', ldata);
1342 while (tail != ldata->read_head) {
1343 echo_char(read_buf(ldata, tail), tty);
1350 if (L_ECHO(tty) || L_ECHONL(tty)) {
1351 echo_char_raw('\n', ldata);
1354 goto handle_newline;
1356 if (c == EOF_CHAR(tty)) {
1357 c = __DISABLED_CHAR;
1358 goto handle_newline;
1360 if ((c == EOL_CHAR(tty)) ||
1361 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1363 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1366 /* Record the column of first canon char. */
1367 if (ldata->canon_head == ldata->read_head)
1368 echo_set_canon_col(ldata);
1373 * XXX does PARMRK doubling happen for
1374 * EOL_CHAR and EOL2_CHAR?
1376 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1377 put_tty_queue(c, ldata);
1380 set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
1381 put_tty_queue(c, ldata);
1382 smp_store_release(&ldata->canon_head, ldata->read_head);
1383 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1384 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1390 finish_erasing(ldata);
1392 echo_char_raw('\n', ldata);
1394 /* Record the column of first canon char. */
1395 if (ldata->canon_head == ldata->read_head)
1396 echo_set_canon_col(ldata);
1402 /* PARMRK doubling check */
1403 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1404 put_tty_queue(c, ldata);
1406 put_tty_queue(c, ldata);
1411 n_tty_receive_char_inline(struct tty_struct *tty, unsigned char c)
1413 struct n_tty_data *ldata = tty->disc_data;
1415 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1417 process_echoes(tty);
1420 finish_erasing(ldata);
1421 /* Record the column of first canon char. */
1422 if (ldata->canon_head == ldata->read_head)
1423 echo_set_canon_col(ldata);
1427 /* PARMRK doubling check */
1428 if (c == (unsigned char) '\377' && I_PARMRK(tty))
1429 put_tty_queue(c, ldata);
1430 put_tty_queue(c, ldata);
1433 static void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1435 n_tty_receive_char_inline(tty, c);
1439 n_tty_receive_char_fast(struct tty_struct *tty, unsigned char c)
1441 struct n_tty_data *ldata = tty->disc_data;
1443 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) && I_IXANY(tty)) {
1445 process_echoes(tty);
1448 finish_erasing(ldata);
1449 /* Record the column of first canon char. */
1450 if (ldata->canon_head == ldata->read_head)
1451 echo_set_canon_col(ldata);
1455 put_tty_queue(c, ldata);
1458 static void n_tty_receive_char_closing(struct tty_struct *tty, unsigned char c)
1462 if (I_IUCLC(tty) && L_IEXTEN(tty))
1466 if (c == STOP_CHAR(tty))
1468 else if (c == START_CHAR(tty) ||
1469 (tty->stopped && !tty->flow_stopped && I_IXANY(tty) &&
1470 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) &&
1471 c != SUSP_CHAR(tty))) {
1473 process_echoes(tty);
1479 n_tty_receive_char_flagged(struct tty_struct *tty, unsigned char c, char flag)
1483 n_tty_receive_break(tty);
1487 n_tty_receive_parity_error(tty, c);
1490 n_tty_receive_overrun(tty);
1493 printk(KERN_ERR "%s: unknown flag %d\n",
1494 tty_name(tty), flag);
1500 n_tty_receive_char_lnext(struct tty_struct *tty, unsigned char c, char flag)
1502 struct n_tty_data *ldata = tty->disc_data;
1505 if (likely(flag == TTY_NORMAL)) {
1508 if (I_IUCLC(tty) && L_IEXTEN(tty))
1510 n_tty_receive_char(tty, c);
1512 n_tty_receive_char_flagged(tty, c, flag);
1516 n_tty_receive_buf_real_raw(struct tty_struct *tty, const unsigned char *cp,
1517 char *fp, int count)
1519 struct n_tty_data *ldata = tty->disc_data;
1522 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1523 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1524 memcpy(read_buf_addr(ldata, head), cp, n);
1525 ldata->read_head += n;
1529 head = ldata->read_head & (N_TTY_BUF_SIZE - 1);
1530 n = min_t(size_t, count, N_TTY_BUF_SIZE - head);
1531 memcpy(read_buf_addr(ldata, head), cp, n);
1532 ldata->read_head += n;
1536 n_tty_receive_buf_raw(struct tty_struct *tty, const unsigned char *cp,
1537 char *fp, int count)
1539 struct n_tty_data *ldata = tty->disc_data;
1540 char flag = TTY_NORMAL;
1545 if (likely(flag == TTY_NORMAL))
1546 put_tty_queue(*cp++, ldata);
1548 n_tty_receive_char_flagged(tty, *cp++, flag);
1553 n_tty_receive_buf_closing(struct tty_struct *tty, const unsigned char *cp,
1554 char *fp, int count)
1556 char flag = TTY_NORMAL;
1561 if (likely(flag == TTY_NORMAL))
1562 n_tty_receive_char_closing(tty, *cp++);
1564 n_tty_receive_char_flagged(tty, *cp++, flag);
1569 n_tty_receive_buf_standard(struct tty_struct *tty, const unsigned char *cp,
1570 char *fp, int count)
1572 struct n_tty_data *ldata = tty->disc_data;
1573 char flag = TTY_NORMAL;
1578 if (likely(flag == TTY_NORMAL)) {
1579 unsigned char c = *cp++;
1583 if (I_IUCLC(tty) && L_IEXTEN(tty))
1585 if (L_EXTPROC(tty)) {
1586 put_tty_queue(c, ldata);
1589 if (!test_bit(c, ldata->char_map))
1590 n_tty_receive_char_inline(tty, c);
1591 else if (n_tty_receive_char_special(tty, c) && count) {
1594 n_tty_receive_char_lnext(tty, *cp++, flag);
1598 n_tty_receive_char_flagged(tty, *cp++, flag);
1603 n_tty_receive_buf_fast(struct tty_struct *tty, const unsigned char *cp,
1604 char *fp, int count)
1606 struct n_tty_data *ldata = tty->disc_data;
1607 char flag = TTY_NORMAL;
1612 if (likely(flag == TTY_NORMAL)) {
1613 unsigned char c = *cp++;
1615 if (!test_bit(c, ldata->char_map))
1616 n_tty_receive_char_fast(tty, c);
1617 else if (n_tty_receive_char_special(tty, c) && count) {
1620 n_tty_receive_char_lnext(tty, *cp++, flag);
1624 n_tty_receive_char_flagged(tty, *cp++, flag);
1628 static void __receive_buf(struct tty_struct *tty, const unsigned char *cp,
1629 char *fp, int count)
1631 struct n_tty_data *ldata = tty->disc_data;
1632 bool preops = I_ISTRIP(tty) || (I_IUCLC(tty) && L_IEXTEN(tty));
1634 if (ldata->real_raw)
1635 n_tty_receive_buf_real_raw(tty, cp, fp, count);
1636 else if (ldata->raw || (L_EXTPROC(tty) && !preops))
1637 n_tty_receive_buf_raw(tty, cp, fp, count);
1638 else if (tty->closing && !L_EXTPROC(tty))
1639 n_tty_receive_buf_closing(tty, cp, fp, count);
1642 char flag = TTY_NORMAL;
1646 n_tty_receive_char_lnext(tty, *cp++, flag);
1650 if (!preops && !I_PARMRK(tty))
1651 n_tty_receive_buf_fast(tty, cp, fp, count);
1653 n_tty_receive_buf_standard(tty, cp, fp, count);
1656 if (tty->ops->flush_chars)
1657 tty->ops->flush_chars(tty);
1660 if (ldata->icanon && !L_EXTPROC(tty))
1663 /* publish read_head to consumer */
1664 smp_store_release(&ldata->commit_head, ldata->read_head);
1666 if ((read_cnt(ldata) >= ldata->minimum_to_wake) || L_EXTPROC(tty)) {
1667 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1668 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
1673 * n_tty_receive_buf_common - process input
1674 * @tty: device to receive input
1676 * @fp: flags for each char (if NULL, all chars are TTY_NORMAL)
1677 * @count: number of input chars in @cp
1679 * Called by the terminal driver when a block of characters has
1680 * been received. This function must be called from soft contexts
1681 * not from interrupt context. The driver is responsible for making
1682 * calls one at a time and in order (or using flush_to_ldisc)
1684 * Returns the # of input chars from @cp which were processed.
1686 * In canonical mode, the maximum line length is 4096 chars (including
1687 * the line termination char); lines longer than 4096 chars are
1688 * truncated. After 4095 chars, input data is still processed but
1689 * not stored. Overflow processing ensures the tty can always
1690 * receive more input until at least one line can be read.
1692 * In non-canonical mode, the read buffer will only accept 4095 chars;
1693 * this provides the necessary space for a newline char if the input
1694 * mode is switched to canonical.
1696 * Note it is possible for the read buffer to _contain_ 4096 chars
1697 * in non-canonical mode: the read buffer could already contain the
1698 * maximum canon line of 4096 chars when the mode is switched to
1701 * n_tty_receive_buf()/producer path:
1702 * claims non-exclusive termios_rwsem
1703 * publishes commit_head or canon_head
1706 n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp,
1707 char *fp, int count, int flow)
1709 struct n_tty_data *ldata = tty->disc_data;
1710 int room, n, rcvd = 0, overflow;
1712 down_read(&tty->termios_rwsem);
1716 * When PARMRK is set, each input char may take up to 3 chars
1717 * in the read buf; reduce the buffer space avail by 3x
1719 * If we are doing input canonicalization, and there are no
1720 * pending newlines, let characters through without limit, so
1721 * that erase characters will be handled. Other excess
1722 * characters will be beeped.
1724 * paired with store in *_copy_from_read_buf() -- guarantees
1725 * the consumer has loaded the data in read_buf up to the new
1726 * read_tail (so this producer will not overwrite unread data)
1728 size_t tail = smp_load_acquire(&ldata->read_tail);
1730 room = N_TTY_BUF_SIZE - (ldata->read_head - tail);
1732 room = (room + 2) / 3;
1735 overflow = ldata->icanon && ldata->canon_head == tail;
1736 if (overflow && room < 0)
1739 ldata->no_room = flow && !room;
1743 n = min(count, room);
1747 /* ignore parity errors if handling overflow */
1748 if (!overflow || !fp || *fp != TTY_PARITY)
1749 __receive_buf(tty, cp, fp, n);
1758 tty->receive_room = room;
1760 /* Unthrottle if handling overflow on pty */
1761 if (tty->driver->type == TTY_DRIVER_TYPE_PTY) {
1763 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1764 tty_unthrottle_safe(tty);
1765 __tty_set_flow_change(tty, 0);
1768 n_tty_check_throttle(tty);
1770 up_read(&tty->termios_rwsem);
1775 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1776 char *fp, int count)
1778 n_tty_receive_buf_common(tty, cp, fp, count, 0);
1781 static int n_tty_receive_buf2(struct tty_struct *tty, const unsigned char *cp,
1782 char *fp, int count)
1784 return n_tty_receive_buf_common(tty, cp, fp, count, 1);
1787 int is_ignored(int sig)
1789 return (sigismember(¤t->blocked, sig) ||
1790 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1794 * n_tty_set_termios - termios data changed
1796 * @old: previous data
1798 * Called by the tty layer when the user changes termios flags so
1799 * that the line discipline can plan ahead. This function cannot sleep
1800 * and is protected from re-entry by the tty layer. The user is
1801 * guaranteed that this function will not be re-entered or in progress
1802 * when the ldisc is closed.
1804 * Locking: Caller holds tty->termios_rwsem
1807 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1809 struct n_tty_data *ldata = tty->disc_data;
1811 if (!old || (old->c_lflag ^ tty->termios.c_lflag) & ICANON) {
1812 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1813 ldata->line_start = ldata->read_tail;
1814 if (!L_ICANON(tty) || !read_cnt(ldata)) {
1815 ldata->canon_head = ldata->read_tail;
1818 set_bit((ldata->read_head - 1) & (N_TTY_BUF_SIZE - 1),
1820 ldata->canon_head = ldata->read_head;
1823 ldata->commit_head = ldata->read_head;
1828 ldata->icanon = (L_ICANON(tty) != 0);
1830 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1831 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1832 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1834 bitmap_zero(ldata->char_map, 256);
1836 if (I_IGNCR(tty) || I_ICRNL(tty))
1837 set_bit('\r', ldata->char_map);
1839 set_bit('\n', ldata->char_map);
1841 if (L_ICANON(tty)) {
1842 set_bit(ERASE_CHAR(tty), ldata->char_map);
1843 set_bit(KILL_CHAR(tty), ldata->char_map);
1844 set_bit(EOF_CHAR(tty), ldata->char_map);
1845 set_bit('\n', ldata->char_map);
1846 set_bit(EOL_CHAR(tty), ldata->char_map);
1847 if (L_IEXTEN(tty)) {
1848 set_bit(WERASE_CHAR(tty), ldata->char_map);
1849 set_bit(LNEXT_CHAR(tty), ldata->char_map);
1850 set_bit(EOL2_CHAR(tty), ldata->char_map);
1852 set_bit(REPRINT_CHAR(tty),
1857 set_bit(START_CHAR(tty), ldata->char_map);
1858 set_bit(STOP_CHAR(tty), ldata->char_map);
1861 set_bit(INTR_CHAR(tty), ldata->char_map);
1862 set_bit(QUIT_CHAR(tty), ldata->char_map);
1863 set_bit(SUSP_CHAR(tty), ldata->char_map);
1865 clear_bit(__DISABLED_CHAR, ldata->char_map);
1867 ldata->real_raw = 0;
1870 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1871 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1872 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1873 ldata->real_raw = 1;
1875 ldata->real_raw = 0;
1878 * Fix tty hang when I_IXON(tty) is cleared, but the tty
1879 * been stopped by STOP_CHAR(tty) before it.
1881 if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1883 process_echoes(tty);
1886 /* The termios change make the tty ready for I/O */
1887 wake_up_interruptible(&tty->write_wait);
1888 wake_up_interruptible(&tty->read_wait);
1892 * n_tty_close - close the ldisc for this tty
1895 * Called from the terminal layer when this line discipline is
1896 * being shut down, either because of a close or becsuse of a
1897 * discipline change. The function will not be called while other
1898 * ldisc methods are in progress.
1901 static void n_tty_close(struct tty_struct *tty)
1903 struct n_tty_data *ldata = tty->disc_data;
1906 n_tty_packet_mode_flush(tty);
1909 tty->disc_data = NULL;
1913 * n_tty_open - open an ldisc
1914 * @tty: terminal to open
1916 * Called when this line discipline is being attached to the
1917 * terminal device. Can sleep. Called serialized so that no
1918 * other events will occur in parallel. No further open will occur
1922 static int n_tty_open(struct tty_struct *tty)
1924 struct n_tty_data *ldata;
1926 /* Currently a malloc failure here can panic */
1927 ldata = vmalloc(sizeof(*ldata));
1931 ldata->overrun_time = jiffies;
1932 mutex_init(&ldata->atomic_read_lock);
1933 mutex_init(&ldata->output_lock);
1935 tty->disc_data = ldata;
1936 reset_buffer_flags(tty->disc_data);
1938 ldata->canon_column = 0;
1939 ldata->minimum_to_wake = 1;
1940 ldata->num_overrun = 0;
1944 /* indicate buffer work may resume */
1945 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1946 n_tty_set_termios(tty, NULL);
1947 tty_unthrottle(tty);
1954 static inline int input_available_p(struct tty_struct *tty, int poll)
1956 struct n_tty_data *ldata = tty->disc_data;
1957 int amt = poll && !TIME_CHAR(tty) && MIN_CHAR(tty) ? MIN_CHAR(tty) : 1;
1959 if (ldata->icanon && !L_EXTPROC(tty))
1960 return ldata->canon_head != ldata->read_tail;
1962 return ldata->commit_head - ldata->read_tail >= amt;
1965 static inline int check_other_done(struct tty_struct *tty)
1967 int done = test_bit(TTY_OTHER_DONE, &tty->flags);
1969 /* paired with cmpxchg() in check_other_closed(); ensures
1970 * read buffer head index is not stale
1972 smp_mb__after_atomic();
1978 * copy_from_read_buf - copy read data directly
1979 * @tty: terminal device
1983 * Helper function to speed up n_tty_read. It is only called when
1984 * ICANON is off; it copies characters straight from the tty queue to
1985 * user space directly. It can be profitably called twice; once to
1986 * drain the space from the tail pointer to the (physical) end of the
1987 * buffer, and once to drain the space from the (physical) beginning of
1988 * the buffer to head pointer.
1990 * Called under the ldata->atomic_read_lock sem
1992 * n_tty_read()/consumer path:
1993 * caller holds non-exclusive termios_rwsem
1994 * read_tail published
1997 static int copy_from_read_buf(struct tty_struct *tty,
1998 unsigned char __user **b,
2002 struct n_tty_data *ldata = tty->disc_data;
2006 size_t head = smp_load_acquire(&ldata->commit_head);
2007 size_t tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2010 n = min(head - ldata->read_tail, N_TTY_BUF_SIZE - tail);
2013 retval = copy_to_user(*b, read_buf_addr(ldata, tail), n);
2015 is_eof = n == 1 && read_buf(ldata, tail) == EOF_CHAR(tty);
2016 tty_audit_add_data(tty, read_buf_addr(ldata, tail), n,
2018 smp_store_release(&ldata->read_tail, ldata->read_tail + n);
2019 /* Turn single EOF into zero-length read */
2020 if (L_EXTPROC(tty) && ldata->icanon && is_eof &&
2021 (head == ldata->read_tail))
2030 * canon_copy_from_read_buf - copy read data in canonical mode
2031 * @tty: terminal device
2035 * Helper function for n_tty_read. It is only called when ICANON is on;
2036 * it copies one line of input up to and including the line-delimiting
2037 * character into the user-space buffer.
2039 * NB: When termios is changed from non-canonical to canonical mode and
2040 * the read buffer contains data, n_tty_set_termios() simulates an EOF
2041 * push (as if C-d were input) _without_ the DISABLED_CHAR in the buffer.
2042 * This causes data already processed as input to be immediately available
2043 * as input although a newline has not been received.
2045 * Called under the atomic_read_lock mutex
2047 * n_tty_read()/consumer path:
2048 * caller holds non-exclusive termios_rwsem
2049 * read_tail published
2052 static int canon_copy_from_read_buf(struct tty_struct *tty,
2053 unsigned char __user **b,
2056 struct n_tty_data *ldata = tty->disc_data;
2057 size_t n, size, more, c;
2063 /* N.B. avoid overrun if nr == 0 */
2064 n = min(*nr, smp_load_acquire(&ldata->canon_head) - ldata->read_tail);
2068 tail = ldata->read_tail & (N_TTY_BUF_SIZE - 1);
2069 size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
2071 n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
2072 __func__, *nr, tail, n, size);
2074 eol = find_next_bit(ldata->read_flags, size, tail);
2075 more = n - (size - tail);
2076 if (eol == N_TTY_BUF_SIZE && more) {
2077 /* scan wrapped without finding set bit */
2078 eol = find_next_bit(ldata->read_flags, more, 0);
2081 } else if (eol != size)
2084 size = N_TTY_BUF_SIZE - tail;
2086 if (n > N_TTY_BUF_SIZE)
2087 n += N_TTY_BUF_SIZE;
2091 if (found && !ldata->push && read_buf(ldata, eol) == __DISABLED_CHAR) {
2093 eof_push = !n && ldata->read_tail != ldata->line_start;
2096 n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu size:%zu more:%zu\n",
2097 __func__, eol, found, n, c, size, more);
2100 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), size);
2103 ret = tty_copy_to_user(tty, *b + size, ldata->read_buf, n - size);
2105 ret = tty_copy_to_user(tty, *b, read_buf_addr(ldata, tail), n);
2113 clear_bit(eol, ldata->read_flags);
2114 smp_store_release(&ldata->read_tail, ldata->read_tail + c);
2118 ldata->line_start = ldata->read_tail;
2121 tty_audit_push(tty);
2123 return eof_push ? -EAGAIN : 0;
2126 extern ssize_t redirected_tty_write(struct file *, const char __user *,
2130 * job_control - check job control
2132 * @file: file handle
2134 * Perform job control management checks on this file/tty descriptor
2135 * and if appropriate send any needed signals and return a negative
2136 * error code if action should be taken.
2138 * Locking: redirected write test is safe
2139 * current->signal->tty check is safe
2140 * ctrl_lock to safely reference tty->pgrp
2143 static int job_control(struct tty_struct *tty, struct file *file)
2147 /* Job control check -- must be done at start and after
2148 every sleep (POSIX.1 7.1.1.4). */
2149 /* NOTE: not yet done after every sleep pending a thorough
2150 check of the logic of this change. -- jlc */
2151 /* don't stop on /dev/console */
2152 if (file->f_op->write == redirected_tty_write ||
2153 current->signal->tty != tty)
2157 pgrp = task_pgrp(current);
2159 spin_lock_irq(&tty->ctrl_lock);
2161 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
2162 else if (pgrp != tty->pgrp) {
2163 spin_unlock_irq(&tty->ctrl_lock);
2164 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) {
2168 kill_pgrp(pgrp, SIGTTIN, 1);
2170 set_thread_flag(TIF_SIGPENDING);
2171 return -ERESTARTSYS;
2173 spin_unlock_irq(&tty->ctrl_lock);
2180 * n_tty_read - read function for tty
2182 * @file: file object
2183 * @buf: userspace buffer pointer
2186 * Perform reads for the line discipline. We are guaranteed that the
2187 * line discipline will not be closed under us but we may get multiple
2188 * parallel readers and must handle this ourselves. We may also get
2189 * a hangup. Always called in user context, may sleep.
2191 * This code must be sure never to sleep through a hangup.
2193 * n_tty_read()/consumer path:
2194 * claims non-exclusive termios_rwsem
2195 * publishes read_tail
2198 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
2199 unsigned char __user *buf, size_t nr)
2201 struct n_tty_data *ldata = tty->disc_data;
2202 unsigned char __user *b = buf;
2203 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2211 c = job_control(tty, file);
2216 * Internal serialization of reads.
2218 if (file->f_flags & O_NONBLOCK) {
2219 if (!mutex_trylock(&ldata->atomic_read_lock))
2222 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
2223 return -ERESTARTSYS;
2226 down_read(&tty->termios_rwsem);
2229 timeout = MAX_SCHEDULE_TIMEOUT;
2230 if (!ldata->icanon) {
2231 minimum = MIN_CHAR(tty);
2233 time = (HZ / 10) * TIME_CHAR(tty);
2235 ldata->minimum_to_wake = 1;
2236 else if (!waitqueue_active(&tty->read_wait) ||
2237 (ldata->minimum_to_wake > minimum))
2238 ldata->minimum_to_wake = minimum;
2240 timeout = (HZ / 10) * TIME_CHAR(tty);
2241 ldata->minimum_to_wake = minimum = 1;
2245 packet = tty->packet;
2246 tail = ldata->read_tail;
2248 add_wait_queue(&tty->read_wait, &wait);
2250 /* First test for status change. */
2251 if (packet && tty->link->ctrl_status) {
2255 spin_lock_irq(&tty->link->ctrl_lock);
2256 cs = tty->link->ctrl_status;
2257 tty->link->ctrl_status = 0;
2258 spin_unlock_irq(&tty->link->ctrl_lock);
2259 if (tty_put_user(tty, cs, b++)) {
2268 if (((minimum - (b - buf)) < ldata->minimum_to_wake) &&
2269 ((minimum - (b - buf)) >= 1))
2270 ldata->minimum_to_wake = (minimum - (b - buf));
2272 done = check_other_done(tty);
2274 if (!input_available_p(tty, 0)) {
2279 if (tty_hung_up_p(file))
2283 if (file->f_flags & O_NONBLOCK) {
2287 if (signal_pending(current)) {
2288 retval = -ERESTARTSYS;
2291 up_read(&tty->termios_rwsem);
2293 timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
2296 down_read(&tty->termios_rwsem);
2300 if (ldata->icanon && !L_EXTPROC(tty)) {
2301 retval = canon_copy_from_read_buf(tty, &b, &nr);
2302 if (retval == -EAGAIN) {
2310 /* Deal with packet mode. */
2311 if (packet && b == buf) {
2312 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
2320 uncopied = copy_from_read_buf(tty, &b, &nr);
2321 uncopied += copy_from_read_buf(tty, &b, &nr);
2328 n_tty_check_unthrottle(tty);
2330 if (b - buf >= minimum)
2335 if (tail != ldata->read_tail)
2336 n_tty_kick_worker(tty);
2337 up_read(&tty->termios_rwsem);
2339 remove_wait_queue(&tty->read_wait, &wait);
2340 if (!waitqueue_active(&tty->read_wait))
2341 ldata->minimum_to_wake = minimum;
2343 mutex_unlock(&ldata->atomic_read_lock);
2352 * n_tty_write - write function for tty
2354 * @file: file object
2355 * @buf: userspace buffer pointer
2358 * Write function of the terminal device. This is serialized with
2359 * respect to other write callers but not to termios changes, reads
2360 * and other such events. Since the receive code will echo characters,
2361 * thus calling driver write methods, the output_lock is used in
2362 * the output processing functions called here as well as in the
2363 * echo processing function to protect the column state and space
2364 * left in the buffer.
2366 * This code must be sure never to sleep through a hangup.
2368 * Locking: output_lock to protect column state and space left
2369 * (note that the process_output*() functions take this
2373 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2374 const unsigned char *buf, size_t nr)
2376 const unsigned char *b = buf;
2377 DEFINE_WAIT_FUNC(wait, woken_wake_function);
2381 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2382 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2383 retval = tty_check_change(tty);
2388 down_read(&tty->termios_rwsem);
2390 /* Write out any echoed characters that are still pending */
2391 process_echoes(tty);
2393 add_wait_queue(&tty->write_wait, &wait);
2395 if (signal_pending(current)) {
2396 retval = -ERESTARTSYS;
2399 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2405 ssize_t num = process_output_block(tty, b, nr);
2417 if (process_output(c, tty) < 0)
2421 if (tty->ops->flush_chars)
2422 tty->ops->flush_chars(tty);
2424 struct n_tty_data *ldata = tty->disc_data;
2427 mutex_lock(&ldata->output_lock);
2428 c = tty->ops->write(tty, b, nr);
2429 mutex_unlock(&ldata->output_lock);
2442 if (file->f_flags & O_NONBLOCK) {
2446 up_read(&tty->termios_rwsem);
2448 wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
2450 down_read(&tty->termios_rwsem);
2453 remove_wait_queue(&tty->write_wait, &wait);
2454 if (b - buf != nr && tty->fasync)
2455 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2456 up_read(&tty->termios_rwsem);
2457 return (b - buf) ? b - buf : retval;
2461 * n_tty_poll - poll method for N_TTY
2462 * @tty: terminal device
2463 * @file: file accessing it
2466 * Called when the line discipline is asked to poll() for data or
2467 * for special events. This code is not serialized with respect to
2468 * other events save open/close.
2470 * This code must be sure never to sleep through a hangup.
2471 * Called without the kernel lock held - fine
2474 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2477 struct n_tty_data *ldata = tty->disc_data;
2478 unsigned int mask = 0;
2480 poll_wait(file, &tty->read_wait, wait);
2481 poll_wait(file, &tty->write_wait, wait);
2482 if (check_other_done(tty))
2484 if (input_available_p(tty, 1))
2485 mask |= POLLIN | POLLRDNORM;
2486 if (tty->packet && tty->link->ctrl_status)
2487 mask |= POLLPRI | POLLIN | POLLRDNORM;
2488 if (tty_hung_up_p(file))
2490 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2491 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2492 ldata->minimum_to_wake = MIN_CHAR(tty);
2494 ldata->minimum_to_wake = 1;
2496 if (tty->ops->write && !tty_is_writelocked(tty) &&
2497 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2498 tty_write_room(tty) > 0)
2499 mask |= POLLOUT | POLLWRNORM;
2503 static unsigned long inq_canon(struct n_tty_data *ldata)
2505 size_t nr, head, tail;
2507 if (ldata->canon_head == ldata->read_tail)
2509 head = ldata->canon_head;
2510 tail = ldata->read_tail;
2512 /* Skip EOF-chars.. */
2513 while (head != tail) {
2514 if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
2515 read_buf(ldata, tail) == __DISABLED_CHAR)
2522 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2523 unsigned int cmd, unsigned long arg)
2525 struct n_tty_data *ldata = tty->disc_data;
2530 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2532 down_write(&tty->termios_rwsem);
2534 retval = inq_canon(ldata);
2536 retval = read_cnt(ldata);
2537 up_write(&tty->termios_rwsem);
2538 return put_user(retval, (unsigned int __user *) arg);
2540 return n_tty_ioctl_helper(tty, file, cmd, arg);
2544 static void n_tty_fasync(struct tty_struct *tty, int on)
2546 struct n_tty_data *ldata = tty->disc_data;
2548 if (!waitqueue_active(&tty->read_wait)) {
2550 ldata->minimum_to_wake = 1;
2551 else if (!tty->fasync)
2552 ldata->minimum_to_wake = N_TTY_BUF_SIZE;
2556 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2557 .magic = TTY_LDISC_MAGIC,
2560 .close = n_tty_close,
2561 .flush_buffer = n_tty_flush_buffer,
2562 .chars_in_buffer = n_tty_chars_in_buffer,
2564 .write = n_tty_write,
2565 .ioctl = n_tty_ioctl,
2566 .set_termios = n_tty_set_termios,
2568 .receive_buf = n_tty_receive_buf,
2569 .write_wakeup = n_tty_write_wakeup,
2570 .fasync = n_tty_fasync,
2571 .receive_buf2 = n_tty_receive_buf2,
2575 * n_tty_inherit_ops - inherit N_TTY methods
2576 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2578 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2582 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2584 *ops = tty_ldisc_N_TTY;
2586 ops->refcount = ops->flags = 0;
2588 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);