n_tty: Fix echo race
[linux-3.10.git] / drivers / char / n_tty.c
1 /*
2  * n_tty.c --- implements the N_TTY line discipline.
3  *
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,
7  * anyway...)
8  *
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.
12  *
13  * Written by Theodore Ts'o, Copyright 1994.
14  *
15  * This file also contains code originally written by Linus Torvalds,
16  * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
17  *
18  * This file may be redistributed under the terms of the GNU General Public
19  * License.
20  *
21  * Reduced memory usage for older ARM systems  - Russell King.
22  *
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.
26  *
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
30  *              EAGAIN
31  */
32
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>
43 #include <linux/mm.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
52 #include <asm/system.h>
53
54 /* number of characters left in xmit buffer before select has we have room */
55 #define WAKEUP_CHARS 256
56
57 /*
58  * This defines the low- and high-watermarks for throttling and
59  * unthrottling the TTY driver.  These watermarks are used for
60  * controlling the space in the read buffer.
61  */
62 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
63 #define TTY_THRESHOLD_UNTHROTTLE        128
64
65 /*
66  * Special byte codes used in the echo buffer to represent operations
67  * or special handling of characters.  Bytes in the echo buffer that
68  * are not part of such special blocks are treated as normal character
69  * codes.
70  */
71 #define ECHO_OP_START 0xff
72 #define ECHO_OP_MOVE_BACK_COL 0x80
73 #define ECHO_OP_SET_CANON_COL 0x81
74 #define ECHO_OP_ERASE_TAB 0x82
75
76 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
77                                unsigned char __user *ptr)
78 {
79         tty_audit_add_data(tty, &x, 1);
80         return put_user(x, ptr);
81 }
82
83 /**
84  *      n_tty_set__room -       receive space
85  *      @tty: terminal
86  *
87  *      Called by the driver to find out how much data it is
88  *      permitted to feed to the line discipline without any being lost
89  *      and thus to manage flow control. Not serialized. Answers for the
90  *      "instant".
91  */
92
93 static void n_tty_set_room(struct tty_struct *tty)
94 {
95         /* tty->read_cnt is not read locked ? */
96         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
97
98         /*
99          * If we are doing input canonicalization, and there are no
100          * pending newlines, let characters through without limit, so
101          * that erase characters will be handled.  Other excess
102          * characters will be beeped.
103          */
104         if (left <= 0)
105                 left = tty->icanon && !tty->canon_data;
106         tty->receive_room = left;
107 }
108
109 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
110 {
111         if (tty->read_cnt < N_TTY_BUF_SIZE) {
112                 tty->read_buf[tty->read_head] = c;
113                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
114                 tty->read_cnt++;
115         }
116 }
117
118 /**
119  *      put_tty_queue           -       add character to tty
120  *      @c: character
121  *      @tty: tty device
122  *
123  *      Add a character to the tty read_buf queue. This is done under the
124  *      read_lock to serialize character addition and also to protect us
125  *      against parallel reads or flushes
126  */
127
128 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
129 {
130         unsigned long flags;
131         /*
132          *      The problem of stomping on the buffers ends here.
133          *      Why didn't anyone see this one coming? --AJK
134         */
135         spin_lock_irqsave(&tty->read_lock, flags);
136         put_tty_queue_nolock(c, tty);
137         spin_unlock_irqrestore(&tty->read_lock, flags);
138 }
139
140 /**
141  *      check_unthrottle        -       allow new receive data
142  *      @tty; tty device
143  *
144  *      Check whether to call the driver unthrottle functions
145  *
146  *      Can sleep, may be called under the atomic_read_lock mutex but
147  *      this is not guaranteed.
148  */
149 static void check_unthrottle(struct tty_struct *tty)
150 {
151         if (tty->count)
152                 tty_unthrottle(tty);
153 }
154
155 /**
156  *      reset_buffer_flags      -       reset buffer state
157  *      @tty: terminal to reset
158  *
159  *      Reset the read buffer counters, clear the flags,
160  *      and make sure the driver is unthrottled. Called
161  *      from n_tty_open() and n_tty_flush_buffer().
162  *
163  *      Locking: tty_read_lock for read fields.
164  */
165
166 static void reset_buffer_flags(struct tty_struct *tty)
167 {
168         unsigned long flags;
169
170         spin_lock_irqsave(&tty->read_lock, flags);
171         tty->read_head = tty->read_tail = tty->read_cnt = 0;
172         spin_unlock_irqrestore(&tty->read_lock, flags);
173
174         mutex_lock(&tty->echo_lock);
175         tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
176         mutex_unlock(&tty->echo_lock);
177
178         tty->canon_head = tty->canon_data = tty->erasing = 0;
179         memset(&tty->read_flags, 0, sizeof tty->read_flags);
180         n_tty_set_room(tty);
181         check_unthrottle(tty);
182 }
183
184 /**
185  *      n_tty_flush_buffer      -       clean input queue
186  *      @tty:   terminal device
187  *
188  *      Flush the input buffer. Called when the line discipline is
189  *      being closed, when the tty layer wants the buffer flushed (eg
190  *      at hangup) or when the N_TTY line discipline internally has to
191  *      clean the pending queue (for example some signals).
192  *
193  *      Locking: ctrl_lock, read_lock.
194  */
195
196 static void n_tty_flush_buffer(struct tty_struct *tty)
197 {
198         unsigned long flags;
199         /* clear everything and unthrottle the driver */
200         reset_buffer_flags(tty);
201
202         if (!tty->link)
203                 return;
204
205         spin_lock_irqsave(&tty->ctrl_lock, flags);
206         if (tty->link->packet) {
207                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
208                 wake_up_interruptible(&tty->link->read_wait);
209         }
210         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
211 }
212
213 /**
214  *      n_tty_chars_in_buffer   -       report available bytes
215  *      @tty: tty device
216  *
217  *      Report the number of characters buffered to be delivered to user
218  *      at this instant in time.
219  *
220  *      Locking: read_lock
221  */
222
223 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
224 {
225         unsigned long flags;
226         ssize_t n = 0;
227
228         spin_lock_irqsave(&tty->read_lock, flags);
229         if (!tty->icanon) {
230                 n = tty->read_cnt;
231         } else if (tty->canon_data) {
232                 n = (tty->canon_head > tty->read_tail) ?
233                         tty->canon_head - tty->read_tail :
234                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
235         }
236         spin_unlock_irqrestore(&tty->read_lock, flags);
237         return n;
238 }
239
240 /**
241  *      is_utf8_continuation    -       utf8 multibyte check
242  *      @c: byte to check
243  *
244  *      Returns true if the utf8 character 'c' is a multibyte continuation
245  *      character. We use this to correctly compute the on screen size
246  *      of the character when printing
247  */
248
249 static inline int is_utf8_continuation(unsigned char c)
250 {
251         return (c & 0xc0) == 0x80;
252 }
253
254 /**
255  *      is_continuation         -       multibyte check
256  *      @c: byte to check
257  *
258  *      Returns true if the utf8 character 'c' is a multibyte continuation
259  *      character and the terminal is in unicode mode.
260  */
261
262 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
263 {
264         return I_IUTF8(tty) && is_utf8_continuation(c);
265 }
266
267 /**
268  *      do_output_char                  -       output one character
269  *      @c: character (or partial unicode symbol)
270  *      @tty: terminal device
271  *      @space: space available in tty driver write buffer
272  *
273  *      This is a helper function that handles one output character
274  *      (including special characters like TAB, CR, LF, etc.),
275  *      putting the results in the tty driver's write buffer.
276  *
277  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
278  *      and NLDLY.  They simply aren't relevant in the world today.
279  *      If you ever need them, add them here.
280  *
281  *      Returns the number of bytes of buffer space used or -1 if
282  *      no space left.
283  *
284  *      Locking: should be called under the output_lock to protect
285  *               the column state and space left in the buffer
286  */
287
288 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
289 {
290         int     spaces;
291
292         if (!space)
293                 return -1;
294
295         switch (c) {
296         case '\n':
297                 if (O_ONLRET(tty))
298                         tty->column = 0;
299                 if (O_ONLCR(tty)) {
300                         if (space < 2)
301                                 return -1;
302                         tty->canon_column = tty->column = 0;
303                         tty_put_char(tty, '\r');
304                         tty_put_char(tty, c);
305                         return 2;
306                 }
307                 tty->canon_column = tty->column;
308                 break;
309         case '\r':
310                 if (O_ONOCR(tty) && tty->column == 0)
311                         return 0;
312                 if (O_OCRNL(tty)) {
313                         c = '\n';
314                         if (O_ONLRET(tty))
315                                 tty->canon_column = tty->column = 0;
316                         break;
317                 }
318                 tty->canon_column = tty->column = 0;
319                 break;
320         case '\t':
321                 spaces = 8 - (tty->column & 7);
322                 if (O_TABDLY(tty) == XTABS) {
323                         if (space < spaces)
324                                 return -1;
325                         tty->column += spaces;
326                         tty->ops->write(tty, "        ", spaces);
327                         return spaces;
328                 }
329                 tty->column += spaces;
330                 break;
331         case '\b':
332                 if (tty->column > 0)
333                         tty->column--;
334                 break;
335         default:
336                 if (!iscntrl(c)) {
337                         if (O_OLCUC(tty))
338                                 c = toupper(c);
339                         if (!is_continuation(c, tty))
340                                 tty->column++;
341                 }
342                 break;
343         }
344
345         tty_put_char(tty, c);
346         return 1;
347 }
348
349 /**
350  *      process_output                  -       output post processor
351  *      @c: character (or partial unicode symbol)
352  *      @tty: terminal device
353  *
354  *      Perform OPOST processing.  Returns -1 when the output device is
355  *      full and the character must be retried.
356  *
357  *      Locking: output_lock to protect column state and space left
358  *               (also, this is called from n_tty_write under the
359  *                tty layer write lock)
360  */
361
362 static int process_output(unsigned char c, struct tty_struct *tty)
363 {
364         int     space, retval;
365
366         mutex_lock(&tty->output_lock);
367
368         space = tty_write_room(tty);
369         retval = do_output_char(c, tty, space);
370
371         mutex_unlock(&tty->output_lock);
372         if (retval < 0)
373                 return -1;
374         else
375                 return 0;
376 }
377
378 /**
379  *      process_output_block            -       block post processor
380  *      @tty: terminal device
381  *      @inbuf: user buffer
382  *      @nr: number of bytes
383  *
384  *      This path is used to speed up block console writes, among other
385  *      things when processing blocks of output data. It handles only
386  *      the simple cases normally found and helps to generate blocks of
387  *      symbols for the console driver and thus improve performance.
388  *
389  *      Locking: output_lock to protect column state and space left
390  *               (also, this is called from n_tty_write under the
391  *                tty layer write lock)
392  */
393
394 static ssize_t process_output_block(struct tty_struct *tty,
395                                     const unsigned char *buf, unsigned int nr)
396 {
397         int     space;
398         int     i;
399         const unsigned char *cp;
400
401         mutex_lock(&tty->output_lock);
402
403         space = tty_write_room(tty);
404         if (!space) {
405                 mutex_unlock(&tty->output_lock);
406                 return 0;
407         }
408         if (nr > space)
409                 nr = space;
410
411         for (i = 0, cp = buf; i < nr; i++, cp++) {
412                 unsigned char c = *cp;
413
414                 switch (c) {
415                 case '\n':
416                         if (O_ONLRET(tty))
417                                 tty->column = 0;
418                         if (O_ONLCR(tty))
419                                 goto break_out;
420                         tty->canon_column = tty->column;
421                         break;
422                 case '\r':
423                         if (O_ONOCR(tty) && tty->column == 0)
424                                 goto break_out;
425                         if (O_OCRNL(tty))
426                                 goto break_out;
427                         tty->canon_column = tty->column = 0;
428                         break;
429                 case '\t':
430                         goto break_out;
431                 case '\b':
432                         if (tty->column > 0)
433                                 tty->column--;
434                         break;
435                 default:
436                         if (!iscntrl(c)) {
437                                 if (O_OLCUC(tty))
438                                         goto break_out;
439                                 if (!is_continuation(c, tty))
440                                         tty->column++;
441                         }
442                         break;
443                 }
444         }
445 break_out:
446         i = tty->ops->write(tty, buf, i);
447
448         mutex_unlock(&tty->output_lock);
449         return i;
450 }
451
452 /**
453  *      process_echoes  -       write pending echo characters
454  *      @tty: terminal device
455  *
456  *      Write previously buffered echo (and other ldisc-generated)
457  *      characters to the tty.
458  *
459  *      Characters generated by the ldisc (including echoes) need to
460  *      be buffered because the driver's write buffer can fill during
461  *      heavy program output.  Echoing straight to the driver will
462  *      often fail under these conditions, causing lost characters and
463  *      resulting mismatches of ldisc state information.
464  *
465  *      Since the ldisc state must represent the characters actually sent
466  *      to the driver at the time of the write, operations like certain
467  *      changes in column state are also saved in the buffer and executed
468  *      here.
469  *
470  *      A circular fifo buffer is used so that the most recent characters
471  *      are prioritized.  Also, when control characters are echoed with a
472  *      prefixed "^", the pair is treated atomically and thus not separated.
473  *
474  *      Locking: output_lock to protect column state and space left,
475  *               echo_lock to protect the echo buffer
476  */
477
478 static void process_echoes(struct tty_struct *tty)
479 {
480         int     space, nr;
481         unsigned char c;
482         unsigned char *cp, *buf_end;
483
484         if (!tty->echo_cnt)
485                 return;
486
487         mutex_lock(&tty->output_lock);
488         mutex_lock(&tty->echo_lock);
489
490         space = tty_write_room(tty);
491
492         buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
493         cp = tty->echo_buf + tty->echo_pos;
494         nr = tty->echo_cnt;
495         while (nr > 0) {
496                 c = *cp;
497                 if (c == ECHO_OP_START) {
498                         unsigned char op;
499                         unsigned char *opp;
500                         int no_space_left = 0;
501
502                         /*
503                          * If the buffer byte is the start of a multi-byte
504                          * operation, get the next byte, which is either the
505                          * op code or a control character value.
506                          */
507                         opp = cp + 1;
508                         if (opp == buf_end)
509                                 opp -= N_TTY_BUF_SIZE;
510                         op = *opp;
511
512                         switch (op) {
513                                 unsigned int num_chars, num_bs;
514
515                         case ECHO_OP_ERASE_TAB:
516                                 if (++opp == buf_end)
517                                         opp -= N_TTY_BUF_SIZE;
518                                 num_chars = *opp;
519
520                                 /*
521                                  * Determine how many columns to go back
522                                  * in order to erase the tab.
523                                  * This depends on the number of columns
524                                  * used by other characters within the tab
525                                  * area.  If this (modulo 8) count is from
526                                  * the start of input rather than from a
527                                  * previous tab, we offset by canon column.
528                                  * Otherwise, tab spacing is normal.
529                                  */
530                                 if (!(num_chars & 0x80))
531                                         num_chars += tty->canon_column;
532                                 num_bs = 8 - (num_chars & 7);
533
534                                 if (num_bs > space) {
535                                         no_space_left = 1;
536                                         break;
537                                 }
538                                 space -= num_bs;
539                                 while (num_bs--) {
540                                         tty_put_char(tty, '\b');
541                                         if (tty->column > 0)
542                                                 tty->column--;
543                                 }
544                                 cp += 3;
545                                 nr -= 3;
546                                 break;
547
548                         case ECHO_OP_SET_CANON_COL:
549                                 tty->canon_column = tty->column;
550                                 cp += 2;
551                                 nr -= 2;
552                                 break;
553
554                         case ECHO_OP_MOVE_BACK_COL:
555                                 if (tty->column > 0)
556                                         tty->column--;
557                                 cp += 2;
558                                 nr -= 2;
559                                 break;
560
561                         case ECHO_OP_START:
562                                 /* This is an escaped echo op start code */
563                                 if (!space) {
564                                         no_space_left = 1;
565                                         break;
566                                 }
567                                 tty_put_char(tty, ECHO_OP_START);
568                                 tty->column++;
569                                 space--;
570                                 cp += 2;
571                                 nr -= 2;
572                                 break;
573
574                         default:
575                                 if (iscntrl(op)) {
576                                         if (L_ECHOCTL(tty)) {
577                                                 /*
578                                                  * Ensure there is enough space
579                                                  * for the whole ctrl pair.
580                                                  */
581                                                 if (space < 2) {
582                                                         no_space_left = 1;
583                                                         break;
584                                                 }
585                                                 tty_put_char(tty, '^');
586                                                 tty_put_char(tty, op ^ 0100);
587                                                 tty->column += 2;
588                                                 space -= 2;
589                                         } else {
590                                                 if (!space) {
591                                                         no_space_left = 1;
592                                                         break;
593                                                 }
594                                                 tty_put_char(tty, op);
595                                                 space--;
596                                         }
597                                 }
598                                 /*
599                                  * If above falls through, this was an
600                                  * undefined op.
601                                  */
602                                 cp += 2;
603                                 nr -= 2;
604                         }
605
606                         if (no_space_left)
607                                 break;
608                 } else {
609                         int retval;
610
611                         retval = do_output_char(c, tty, space);
612                         if (retval < 0)
613                                 break;
614                         space -= retval;
615                         cp += 1;
616                         nr -= 1;
617                 }
618
619                 /* When end of circular buffer reached, wrap around */
620                 if (cp >= buf_end)
621                         cp -= N_TTY_BUF_SIZE;
622         }
623
624         if (nr == 0) {
625                 tty->echo_pos = 0;
626                 tty->echo_cnt = 0;
627                 tty->echo_overrun = 0;
628         } else {
629                 int num_processed = tty->echo_cnt - nr;
630                 tty->echo_pos += num_processed;
631                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
632                 tty->echo_cnt = nr;
633                 if (num_processed > 0)
634                         tty->echo_overrun = 0;
635         }
636
637         mutex_unlock(&tty->echo_lock);
638         mutex_unlock(&tty->output_lock);
639
640         if (tty->ops->flush_chars)
641                 tty->ops->flush_chars(tty);
642 }
643
644 /**
645  *      add_echo_byte   -       add a byte to the echo buffer
646  *      @c: unicode byte to echo
647  *      @tty: terminal device
648  *
649  *      Add a character or operation byte to the echo buffer.
650  *
651  *      Should be called under the echo lock to protect the echo buffer.
652  */
653
654 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
655 {
656         int     new_byte_pos;
657
658         if (tty->echo_cnt == N_TTY_BUF_SIZE) {
659                 /* Circular buffer is already at capacity */
660                 new_byte_pos = tty->echo_pos;
661
662                 /*
663                  * Since the buffer start position needs to be advanced,
664                  * be sure to step by a whole operation byte group.
665                  */
666                 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
667                         if (tty->echo_buf[(tty->echo_pos + 1) &
668                                           (N_TTY_BUF_SIZE - 1)] ==
669                                                 ECHO_OP_ERASE_TAB) {
670                                 tty->echo_pos += 3;
671                                 tty->echo_cnt -= 2;
672                         } else {
673                                 tty->echo_pos += 2;
674                                 tty->echo_cnt -= 1;
675                         }
676                 } else {
677                         tty->echo_pos++;
678                 }
679                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
680
681                 tty->echo_overrun = 1;
682         } else {
683                 new_byte_pos = tty->echo_pos + tty->echo_cnt;
684                 new_byte_pos &= N_TTY_BUF_SIZE - 1;
685                 tty->echo_cnt++;
686         }
687
688         tty->echo_buf[new_byte_pos] = c;
689 }
690
691 /**
692  *      echo_move_back_col      -       add operation to move back a column
693  *      @tty: terminal device
694  *
695  *      Add an operation to the echo buffer to move back one column.
696  *
697  *      Locking: echo_lock to protect the echo buffer
698  */
699
700 static void echo_move_back_col(struct tty_struct *tty)
701 {
702         mutex_lock(&tty->echo_lock);
703
704         add_echo_byte(ECHO_OP_START, tty);
705         add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
706
707         mutex_unlock(&tty->echo_lock);
708 }
709
710 /**
711  *      echo_set_canon_col      -       add operation to set the canon column
712  *      @tty: terminal device
713  *
714  *      Add an operation to the echo buffer to set the canon column
715  *      to the current column.
716  *
717  *      Locking: echo_lock to protect the echo buffer
718  */
719
720 static void echo_set_canon_col(struct tty_struct *tty)
721 {
722         mutex_lock(&tty->echo_lock);
723
724         add_echo_byte(ECHO_OP_START, tty);
725         add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
726
727         mutex_unlock(&tty->echo_lock);
728 }
729
730 /**
731  *      echo_erase_tab  -       add operation to erase a tab
732  *      @num_chars: number of character columns already used
733  *      @after_tab: true if num_chars starts after a previous tab
734  *      @tty: terminal device
735  *
736  *      Add an operation to the echo buffer to erase a tab.
737  *
738  *      Called by the eraser function, which knows how many character
739  *      columns have been used since either a previous tab or the start
740  *      of input.  This information will be used later, along with
741  *      canon column (if applicable), to go back the correct number
742  *      of columns.
743  *
744  *      Locking: echo_lock to protect the echo buffer
745  */
746
747 static void echo_erase_tab(unsigned int num_chars, int after_tab,
748                            struct tty_struct *tty)
749 {
750         mutex_lock(&tty->echo_lock);
751
752         add_echo_byte(ECHO_OP_START, tty);
753         add_echo_byte(ECHO_OP_ERASE_TAB, tty);
754
755         /* We only need to know this modulo 8 (tab spacing) */
756         num_chars &= 7;
757
758         /* Set the high bit as a flag if num_chars is after a previous tab */
759         if (after_tab)
760                 num_chars |= 0x80;
761
762         add_echo_byte(num_chars, tty);
763
764         mutex_unlock(&tty->echo_lock);
765 }
766
767 /**
768  *      echo_char_raw   -       echo a character raw
769  *      @c: unicode byte to echo
770  *      @tty: terminal device
771  *
772  *      Echo user input back onto the screen. This must be called only when
773  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
774  *
775  *      This variant does not treat control characters specially.
776  *
777  *      Locking: echo_lock to protect the echo buffer
778  */
779
780 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
781 {
782         mutex_lock(&tty->echo_lock);
783
784         if (c == ECHO_OP_START) {
785                 add_echo_byte(ECHO_OP_START, tty);
786                 add_echo_byte(ECHO_OP_START, tty);
787         } else {
788                 add_echo_byte(c, tty);
789         }
790
791         mutex_unlock(&tty->echo_lock);
792 }
793
794 /**
795  *      echo_char       -       echo a character
796  *      @c: unicode byte to echo
797  *      @tty: terminal device
798  *
799  *      Echo user input back onto the screen. This must be called only when
800  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
801  *
802  *      This variant tags control characters to be possibly echoed as
803  *      as "^X" (where X is the letter representing the control char).
804  *
805  *      Locking: echo_lock to protect the echo buffer
806  */
807
808 static void echo_char(unsigned char c, struct tty_struct *tty)
809 {
810         mutex_lock(&tty->echo_lock);
811
812         if (c == ECHO_OP_START) {
813                 add_echo_byte(ECHO_OP_START, tty);
814                 add_echo_byte(ECHO_OP_START, tty);
815         } else {
816                 if (iscntrl(c) && c != '\t')
817                         add_echo_byte(ECHO_OP_START, tty);
818                 add_echo_byte(c, tty);
819         }
820
821         mutex_unlock(&tty->echo_lock);
822 }
823
824 /**
825  *      finish_erasing          -       complete erase
826  *      @tty: tty doing the erase
827  */
828
829 static inline void finish_erasing(struct tty_struct *tty)
830 {
831         if (tty->erasing) {
832                 echo_char_raw('/', tty);
833                 tty->erasing = 0;
834         }
835 }
836
837 /**
838  *      eraser          -       handle erase function
839  *      @c: character input
840  *      @tty: terminal device
841  *
842  *      Perform erase and necessary output when an erase character is
843  *      present in the stream from the driver layer. Handles the complexities
844  *      of UTF-8 multibyte symbols.
845  *
846  *      Locking: read_lock for tty buffers
847  */
848
849 static void eraser(unsigned char c, struct tty_struct *tty)
850 {
851         enum { ERASE, WERASE, KILL } kill_type;
852         int head, seen_alnums, cnt;
853         unsigned long flags;
854
855         /* FIXME: locking needed ? */
856         if (tty->read_head == tty->canon_head) {
857                 /* process_output('\a', tty); */ /* what do you think? */
858                 return;
859         }
860         if (c == ERASE_CHAR(tty))
861                 kill_type = ERASE;
862         else if (c == WERASE_CHAR(tty))
863                 kill_type = WERASE;
864         else {
865                 if (!L_ECHO(tty)) {
866                         spin_lock_irqsave(&tty->read_lock, flags);
867                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
868                                           (N_TTY_BUF_SIZE - 1));
869                         tty->read_head = tty->canon_head;
870                         spin_unlock_irqrestore(&tty->read_lock, flags);
871                         return;
872                 }
873                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
874                         spin_lock_irqsave(&tty->read_lock, flags);
875                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
876                                           (N_TTY_BUF_SIZE - 1));
877                         tty->read_head = tty->canon_head;
878                         spin_unlock_irqrestore(&tty->read_lock, flags);
879                         finish_erasing(tty);
880                         echo_char(KILL_CHAR(tty), tty);
881                         /* Add a newline if ECHOK is on and ECHOKE is off. */
882                         if (L_ECHOK(tty))
883                                 echo_char_raw('\n', tty);
884                         return;
885                 }
886                 kill_type = KILL;
887         }
888
889         seen_alnums = 0;
890         /* FIXME: Locking ?? */
891         while (tty->read_head != tty->canon_head) {
892                 head = tty->read_head;
893
894                 /* erase a single possibly multibyte character */
895                 do {
896                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
897                         c = tty->read_buf[head];
898                 } while (is_continuation(c, tty) && head != tty->canon_head);
899
900                 /* do not partially erase */
901                 if (is_continuation(c, tty))
902                         break;
903
904                 if (kill_type == WERASE) {
905                         /* Equivalent to BSD's ALTWERASE. */
906                         if (isalnum(c) || c == '_')
907                                 seen_alnums++;
908                         else if (seen_alnums)
909                                 break;
910                 }
911                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
912                 spin_lock_irqsave(&tty->read_lock, flags);
913                 tty->read_head = head;
914                 tty->read_cnt -= cnt;
915                 spin_unlock_irqrestore(&tty->read_lock, flags);
916                 if (L_ECHO(tty)) {
917                         if (L_ECHOPRT(tty)) {
918                                 if (!tty->erasing) {
919                                         echo_char_raw('\\', tty);
920                                         tty->erasing = 1;
921                                 }
922                                 /* if cnt > 1, output a multi-byte character */
923                                 echo_char(c, tty);
924                                 while (--cnt > 0) {
925                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
926                                         echo_char_raw(tty->read_buf[head], tty);
927                                         echo_move_back_col(tty);
928                                 }
929                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
930                                 echo_char(ERASE_CHAR(tty), tty);
931                         } else if (c == '\t') {
932                                 unsigned int num_chars = 0;
933                                 int after_tab = 0;
934                                 unsigned long tail = tty->read_head;
935
936                                 /*
937                                  * Count the columns used for characters
938                                  * since the start of input or after a
939                                  * previous tab.
940                                  * This info is used to go back the correct
941                                  * number of columns.
942                                  */
943                                 while (tail != tty->canon_head) {
944                                         tail = (tail-1) & (N_TTY_BUF_SIZE-1);
945                                         c = tty->read_buf[tail];
946                                         if (c == '\t') {
947                                                 after_tab = 1;
948                                                 break;
949                                         } else if (iscntrl(c)) {
950                                                 if (L_ECHOCTL(tty))
951                                                         num_chars += 2;
952                                         } else if (!is_continuation(c, tty)) {
953                                                 num_chars++;
954                                         }
955                                 }
956                                 echo_erase_tab(num_chars, after_tab, tty);
957                         } else {
958                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
959                                         echo_char_raw('\b', tty);
960                                         echo_char_raw(' ', tty);
961                                         echo_char_raw('\b', tty);
962                                 }
963                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
964                                         echo_char_raw('\b', tty);
965                                         echo_char_raw(' ', tty);
966                                         echo_char_raw('\b', tty);
967                                 }
968                         }
969                 }
970                 if (kill_type == ERASE)
971                         break;
972         }
973         if (tty->read_head == tty->canon_head && L_ECHO(tty))
974                 finish_erasing(tty);
975 }
976
977 /**
978  *      isig            -       handle the ISIG optio
979  *      @sig: signal
980  *      @tty: terminal
981  *      @flush: force flush
982  *
983  *      Called when a signal is being sent due to terminal input. This
984  *      may caus terminal flushing to take place according to the termios
985  *      settings and character used. Called from the driver receive_buf
986  *      path so serialized.
987  *
988  *      Locking: ctrl_lock, read_lock (both via flush buffer)
989  */
990
991 static inline void isig(int sig, struct tty_struct *tty, int flush)
992 {
993         if (tty->pgrp)
994                 kill_pgrp(tty->pgrp, sig, 1);
995         if (flush || !L_NOFLSH(tty)) {
996                 n_tty_flush_buffer(tty);
997                 tty_driver_flush_buffer(tty);
998         }
999 }
1000
1001 /**
1002  *      n_tty_receive_break     -       handle break
1003  *      @tty: terminal
1004  *
1005  *      An RS232 break event has been hit in the incoming bitstream. This
1006  *      can cause a variety of events depending upon the termios settings.
1007  *
1008  *      Called from the receive_buf path so single threaded.
1009  */
1010
1011 static inline void n_tty_receive_break(struct tty_struct *tty)
1012 {
1013         if (I_IGNBRK(tty))
1014                 return;
1015         if (I_BRKINT(tty)) {
1016                 isig(SIGINT, tty, 1);
1017                 return;
1018         }
1019         if (I_PARMRK(tty)) {
1020                 put_tty_queue('\377', tty);
1021                 put_tty_queue('\0', tty);
1022         }
1023         put_tty_queue('\0', tty);
1024         wake_up_interruptible(&tty->read_wait);
1025 }
1026
1027 /**
1028  *      n_tty_receive_overrun   -       handle overrun reporting
1029  *      @tty: terminal
1030  *
1031  *      Data arrived faster than we could process it. While the tty
1032  *      driver has flagged this the bits that were missed are gone
1033  *      forever.
1034  *
1035  *      Called from the receive_buf path so single threaded. Does not
1036  *      need locking as num_overrun and overrun_time are function
1037  *      private.
1038  */
1039
1040 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1041 {
1042         char buf[64];
1043
1044         tty->num_overrun++;
1045         if (time_before(tty->overrun_time, jiffies - HZ) ||
1046                         time_after(tty->overrun_time, jiffies)) {
1047                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1048                         tty_name(tty, buf),
1049                         tty->num_overrun);
1050                 tty->overrun_time = jiffies;
1051                 tty->num_overrun = 0;
1052         }
1053 }
1054
1055 /**
1056  *      n_tty_receive_parity_error      -       error notifier
1057  *      @tty: terminal device
1058  *      @c: character
1059  *
1060  *      Process a parity error and queue the right data to indicate
1061  *      the error case if necessary. Locking as per n_tty_receive_buf.
1062  */
1063 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1064                                               unsigned char c)
1065 {
1066         if (I_IGNPAR(tty))
1067                 return;
1068         if (I_PARMRK(tty)) {
1069                 put_tty_queue('\377', tty);
1070                 put_tty_queue('\0', tty);
1071                 put_tty_queue(c, tty);
1072         } else  if (I_INPCK(tty))
1073                 put_tty_queue('\0', tty);
1074         else
1075                 put_tty_queue(c, tty);
1076         wake_up_interruptible(&tty->read_wait);
1077 }
1078
1079 /**
1080  *      n_tty_receive_char      -       perform processing
1081  *      @tty: terminal device
1082  *      @c: character
1083  *
1084  *      Process an individual character of input received from the driver.
1085  *      This is serialized with respect to itself by the rules for the
1086  *      driver above.
1087  */
1088
1089 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1090 {
1091         unsigned long flags;
1092         int parmrk;
1093
1094         if (tty->raw) {
1095                 put_tty_queue(c, tty);
1096                 return;
1097         }
1098
1099         if (I_ISTRIP(tty))
1100                 c &= 0x7f;
1101         if (I_IUCLC(tty) && L_IEXTEN(tty))
1102                 c = tolower(c);
1103
1104         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1105             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1106             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1107                 start_tty(tty);
1108                 process_echoes(tty);
1109         }
1110
1111         if (tty->closing) {
1112                 if (I_IXON(tty)) {
1113                         if (c == START_CHAR(tty)) {
1114                                 start_tty(tty);
1115                                 process_echoes(tty);
1116                         } else if (c == STOP_CHAR(tty))
1117                                 stop_tty(tty);
1118                 }
1119                 return;
1120         }
1121
1122         /*
1123          * If the previous character was LNEXT, or we know that this
1124          * character is not one of the characters that we'll have to
1125          * handle specially, do shortcut processing to speed things
1126          * up.
1127          */
1128         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1129                 tty->lnext = 0;
1130                 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1131                 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1132                         /* beep if no space */
1133                         if (L_ECHO(tty))
1134                                 process_output('\a', tty);
1135                         return;
1136                 }
1137                 if (L_ECHO(tty)) {
1138                         finish_erasing(tty);
1139                         /* Record the column of first canon char. */
1140                         if (tty->canon_head == tty->read_head)
1141                                 echo_set_canon_col(tty);
1142                         echo_char(c, tty);
1143                         process_echoes(tty);
1144                 }
1145                 if (parmrk)
1146                         put_tty_queue(c, tty);
1147                 put_tty_queue(c, tty);
1148                 return;
1149         }
1150
1151         if (I_IXON(tty)) {
1152                 if (c == START_CHAR(tty)) {
1153                         start_tty(tty);
1154                         process_echoes(tty);
1155                         return;
1156                 }
1157                 if (c == STOP_CHAR(tty)) {
1158                         stop_tty(tty);
1159                         return;
1160                 }
1161         }
1162
1163         if (L_ISIG(tty)) {
1164                 int signal;
1165                 signal = SIGINT;
1166                 if (c == INTR_CHAR(tty))
1167                         goto send_signal;
1168                 signal = SIGQUIT;
1169                 if (c == QUIT_CHAR(tty))
1170                         goto send_signal;
1171                 signal = SIGTSTP;
1172                 if (c == SUSP_CHAR(tty)) {
1173 send_signal:
1174                         /*
1175                          * Note that we do not use isig() here because we want
1176                          * the order to be:
1177                          * 1) flush, 2) echo, 3) signal
1178                          */
1179                         if (!L_NOFLSH(tty)) {
1180                                 n_tty_flush_buffer(tty);
1181                                 tty_driver_flush_buffer(tty);
1182                         }
1183                         if (I_IXON(tty))
1184                                 start_tty(tty);
1185                         if (L_ECHO(tty)) {
1186                                 echo_char(c, tty);
1187                                 process_echoes(tty);
1188                         }
1189                         if (tty->pgrp)
1190                                 kill_pgrp(tty->pgrp, signal, 1);
1191                         return;
1192                 }
1193         }
1194
1195         if (c == '\r') {
1196                 if (I_IGNCR(tty))
1197                         return;
1198                 if (I_ICRNL(tty))
1199                         c = '\n';
1200         } else if (c == '\n' && I_INLCR(tty))
1201                 c = '\r';
1202
1203         if (tty->icanon) {
1204                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1205                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1206                         eraser(c, tty);
1207                         process_echoes(tty);
1208                         return;
1209                 }
1210                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1211                         tty->lnext = 1;
1212                         if (L_ECHO(tty)) {
1213                                 finish_erasing(tty);
1214                                 if (L_ECHOCTL(tty)) {
1215                                         echo_char_raw('^', tty);
1216                                         echo_char_raw('\b', tty);
1217                                         process_echoes(tty);
1218                                 }
1219                         }
1220                         return;
1221                 }
1222                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1223                     L_IEXTEN(tty)) {
1224                         unsigned long tail = tty->canon_head;
1225
1226                         finish_erasing(tty);
1227                         echo_char(c, tty);
1228                         echo_char_raw('\n', tty);
1229                         while (tail != tty->read_head) {
1230                                 echo_char(tty->read_buf[tail], tty);
1231                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1232                         }
1233                         process_echoes(tty);
1234                         return;
1235                 }
1236                 if (c == '\n') {
1237                         if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1238                                 if (L_ECHO(tty))
1239                                         process_output('\a', tty);
1240                                 return;
1241                         }
1242                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1243                                 echo_char_raw('\n', tty);
1244                                 process_echoes(tty);
1245                         }
1246                         goto handle_newline;
1247                 }
1248                 if (c == EOF_CHAR(tty)) {
1249                         if (tty->read_cnt >= N_TTY_BUF_SIZE)
1250                                 return;
1251                         if (tty->canon_head != tty->read_head)
1252                                 set_bit(TTY_PUSH, &tty->flags);
1253                         c = __DISABLED_CHAR;
1254                         goto handle_newline;
1255                 }
1256                 if ((c == EOL_CHAR(tty)) ||
1257                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1258                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1259                                  ? 1 : 0;
1260                         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1261                                 if (L_ECHO(tty))
1262                                         process_output('\a', tty);
1263                                 return;
1264                         }
1265                         /*
1266                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1267                          */
1268                         if (L_ECHO(tty)) {
1269                                 /* Record the column of first canon char. */
1270                                 if (tty->canon_head == tty->read_head)
1271                                         echo_set_canon_col(tty);
1272                                 echo_char(c, tty);
1273                                 process_echoes(tty);
1274                         }
1275                         /*
1276                          * XXX does PARMRK doubling happen for
1277                          * EOL_CHAR and EOL2_CHAR?
1278                          */
1279                         if (parmrk)
1280                                 put_tty_queue(c, tty);
1281
1282 handle_newline:
1283                         spin_lock_irqsave(&tty->read_lock, flags);
1284                         set_bit(tty->read_head, tty->read_flags);
1285                         put_tty_queue_nolock(c, tty);
1286                         tty->canon_head = tty->read_head;
1287                         tty->canon_data++;
1288                         spin_unlock_irqrestore(&tty->read_lock, flags);
1289                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1290                         if (waitqueue_active(&tty->read_wait))
1291                                 wake_up_interruptible(&tty->read_wait);
1292                         return;
1293                 }
1294         }
1295
1296         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1297         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1298                 /* beep if no space */
1299                 if (L_ECHO(tty))
1300                         process_output('\a', tty);
1301                 return;
1302         }
1303         if (L_ECHO(tty)) {
1304                 finish_erasing(tty);
1305                 if (c == '\n')
1306                         echo_char_raw('\n', tty);
1307                 else {
1308                         /* Record the column of first canon char. */
1309                         if (tty->canon_head == tty->read_head)
1310                                 echo_set_canon_col(tty);
1311                         echo_char(c, tty);
1312                 }
1313                 process_echoes(tty);
1314         }
1315
1316         if (parmrk)
1317                 put_tty_queue(c, tty);
1318
1319         put_tty_queue(c, tty);
1320 }
1321
1322
1323 /**
1324  *      n_tty_write_wakeup      -       asynchronous I/O notifier
1325  *      @tty: tty device
1326  *
1327  *      Required for the ptys, serial driver etc. since processes
1328  *      that attach themselves to the master and rely on ASYNC
1329  *      IO must be woken up
1330  */
1331
1332 static void n_tty_write_wakeup(struct tty_struct *tty)
1333 {
1334         if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1335                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1336 }
1337
1338 /**
1339  *      n_tty_receive_buf       -       data receive
1340  *      @tty: terminal device
1341  *      @cp: buffer
1342  *      @fp: flag buffer
1343  *      @count: characters
1344  *
1345  *      Called by the terminal driver when a block of characters has
1346  *      been received. This function must be called from soft contexts
1347  *      not from interrupt context. The driver is responsible for making
1348  *      calls one at a time and in order (or using flush_to_ldisc)
1349  */
1350
1351 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1352                               char *fp, int count)
1353 {
1354         const unsigned char *p;
1355         char *f, flags = TTY_NORMAL;
1356         int     i;
1357         char    buf[64];
1358         unsigned long cpuflags;
1359
1360         if (!tty->read_buf)
1361                 return;
1362
1363         if (tty->real_raw) {
1364                 spin_lock_irqsave(&tty->read_lock, cpuflags);
1365                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1366                         N_TTY_BUF_SIZE - tty->read_head);
1367                 i = min(count, i);
1368                 memcpy(tty->read_buf + tty->read_head, cp, i);
1369                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1370                 tty->read_cnt += i;
1371                 cp += i;
1372                 count -= i;
1373
1374                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1375                         N_TTY_BUF_SIZE - tty->read_head);
1376                 i = min(count, i);
1377                 memcpy(tty->read_buf + tty->read_head, cp, i);
1378                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1379                 tty->read_cnt += i;
1380                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1381         } else {
1382                 for (i = count, p = cp, f = fp; i; i--, p++) {
1383                         if (f)
1384                                 flags = *f++;
1385                         switch (flags) {
1386                         case TTY_NORMAL:
1387                                 n_tty_receive_char(tty, *p);
1388                                 break;
1389                         case TTY_BREAK:
1390                                 n_tty_receive_break(tty);
1391                                 break;
1392                         case TTY_PARITY:
1393                         case TTY_FRAME:
1394                                 n_tty_receive_parity_error(tty, *p);
1395                                 break;
1396                         case TTY_OVERRUN:
1397                                 n_tty_receive_overrun(tty);
1398                                 break;
1399                         default:
1400                                 printk(KERN_ERR "%s: unknown flag %d\n",
1401                                        tty_name(tty, buf), flags);
1402                                 break;
1403                         }
1404                 }
1405                 if (tty->ops->flush_chars)
1406                         tty->ops->flush_chars(tty);
1407         }
1408
1409         n_tty_set_room(tty);
1410
1411         if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1412                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1413                 if (waitqueue_active(&tty->read_wait))
1414                         wake_up_interruptible(&tty->read_wait);
1415         }
1416
1417         /*
1418          * Check the remaining room for the input canonicalization
1419          * mode.  We don't want to throttle the driver if we're in
1420          * canonical mode and don't have a newline yet!
1421          */
1422         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1423                 tty_throttle(tty);
1424 }
1425
1426 int is_ignored(int sig)
1427 {
1428         return (sigismember(&current->blocked, sig) ||
1429                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1430 }
1431
1432 /**
1433  *      n_tty_set_termios       -       termios data changed
1434  *      @tty: terminal
1435  *      @old: previous data
1436  *
1437  *      Called by the tty layer when the user changes termios flags so
1438  *      that the line discipline can plan ahead. This function cannot sleep
1439  *      and is protected from re-entry by the tty layer. The user is
1440  *      guaranteed that this function will not be re-entered or in progress
1441  *      when the ldisc is closed.
1442  *
1443  *      Locking: Caller holds tty->termios_mutex
1444  */
1445
1446 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1447 {
1448         int canon_change = 1;
1449         BUG_ON(!tty);
1450
1451         if (old)
1452                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1453         if (canon_change) {
1454                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1455                 tty->canon_head = tty->read_tail;
1456                 tty->canon_data = 0;
1457                 tty->erasing = 0;
1458         }
1459
1460         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1461                 wake_up_interruptible(&tty->read_wait);
1462
1463         tty->icanon = (L_ICANON(tty) != 0);
1464         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1465                 tty->raw = 1;
1466                 tty->real_raw = 1;
1467                 n_tty_set_room(tty);
1468                 return;
1469         }
1470         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1471             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1472             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1473             I_PARMRK(tty)) {
1474                 memset(tty->process_char_map, 0, 256/8);
1475
1476                 if (I_IGNCR(tty) || I_ICRNL(tty))
1477                         set_bit('\r', tty->process_char_map);
1478                 if (I_INLCR(tty))
1479                         set_bit('\n', tty->process_char_map);
1480
1481                 if (L_ICANON(tty)) {
1482                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1483                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1484                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1485                         set_bit('\n', tty->process_char_map);
1486                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1487                         if (L_IEXTEN(tty)) {
1488                                 set_bit(WERASE_CHAR(tty),
1489                                         tty->process_char_map);
1490                                 set_bit(LNEXT_CHAR(tty),
1491                                         tty->process_char_map);
1492                                 set_bit(EOL2_CHAR(tty),
1493                                         tty->process_char_map);
1494                                 if (L_ECHO(tty))
1495                                         set_bit(REPRINT_CHAR(tty),
1496                                                 tty->process_char_map);
1497                         }
1498                 }
1499                 if (I_IXON(tty)) {
1500                         set_bit(START_CHAR(tty), tty->process_char_map);
1501                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1502                 }
1503                 if (L_ISIG(tty)) {
1504                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1505                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1506                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1507                 }
1508                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1509                 tty->raw = 0;
1510                 tty->real_raw = 0;
1511         } else {
1512                 tty->raw = 1;
1513                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1514                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1515                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1516                         tty->real_raw = 1;
1517                 else
1518                         tty->real_raw = 0;
1519         }
1520         n_tty_set_room(tty);
1521         /* The termios change make the tty ready for I/O */
1522         wake_up_interruptible(&tty->write_wait);
1523         wake_up_interruptible(&tty->read_wait);
1524 }
1525
1526 /**
1527  *      n_tty_close             -       close the ldisc for this tty
1528  *      @tty: device
1529  *
1530  *      Called from the terminal layer when this line discipline is
1531  *      being shut down, either because of a close or becsuse of a
1532  *      discipline change. The function will not be called while other
1533  *      ldisc methods are in progress.
1534  */
1535
1536 static void n_tty_close(struct tty_struct *tty)
1537 {
1538         n_tty_flush_buffer(tty);
1539         if (tty->read_buf) {
1540                 kfree(tty->read_buf);
1541                 tty->read_buf = NULL;
1542         }
1543         if (tty->echo_buf) {
1544                 kfree(tty->echo_buf);
1545                 tty->echo_buf = NULL;
1546         }
1547 }
1548
1549 /**
1550  *      n_tty_open              -       open an ldisc
1551  *      @tty: terminal to open
1552  *
1553  *      Called when this line discipline is being attached to the
1554  *      terminal device. Can sleep. Called serialized so that no
1555  *      other events will occur in parallel. No further open will occur
1556  *      until a close.
1557  */
1558
1559 static int n_tty_open(struct tty_struct *tty)
1560 {
1561         if (!tty)
1562                 return -EINVAL;
1563
1564         /* These are ugly. Currently a malloc failure here can panic */
1565         if (!tty->read_buf) {
1566                 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1567                 if (!tty->read_buf)
1568                         return -ENOMEM;
1569         }
1570         if (!tty->echo_buf) {
1571                 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1572
1573                 if (!tty->echo_buf)
1574                         return -ENOMEM;
1575         }
1576         reset_buffer_flags(tty);
1577         tty->column = 0;
1578         n_tty_set_termios(tty, NULL);
1579         tty->minimum_to_wake = 1;
1580         tty->closing = 0;
1581         return 0;
1582 }
1583
1584 static inline int input_available_p(struct tty_struct *tty, int amt)
1585 {
1586         if (tty->icanon) {
1587                 if (tty->canon_data)
1588                         return 1;
1589         } else if (tty->read_cnt >= (amt ? amt : 1))
1590                 return 1;
1591
1592         return 0;
1593 }
1594
1595 /**
1596  *      copy_from_read_buf      -       copy read data directly
1597  *      @tty: terminal device
1598  *      @b: user data
1599  *      @nr: size of data
1600  *
1601  *      Helper function to speed up n_tty_read.  It is only called when
1602  *      ICANON is off; it copies characters straight from the tty queue to
1603  *      user space directly.  It can be profitably called twice; once to
1604  *      drain the space from the tail pointer to the (physical) end of the
1605  *      buffer, and once to drain the space from the (physical) beginning of
1606  *      the buffer to head pointer.
1607  *
1608  *      Called under the tty->atomic_read_lock sem
1609  *
1610  */
1611
1612 static int copy_from_read_buf(struct tty_struct *tty,
1613                                       unsigned char __user **b,
1614                                       size_t *nr)
1615
1616 {
1617         int retval;
1618         size_t n;
1619         unsigned long flags;
1620
1621         retval = 0;
1622         spin_lock_irqsave(&tty->read_lock, flags);
1623         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1624         n = min(*nr, n);
1625         spin_unlock_irqrestore(&tty->read_lock, flags);
1626         if (n) {
1627                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1628                 n -= retval;
1629                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1630                 spin_lock_irqsave(&tty->read_lock, flags);
1631                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1632                 tty->read_cnt -= n;
1633                 spin_unlock_irqrestore(&tty->read_lock, flags);
1634                 *b += n;
1635                 *nr -= n;
1636         }
1637         return retval;
1638 }
1639
1640 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1641                                                         size_t, loff_t *);
1642
1643 /**
1644  *      job_control             -       check job control
1645  *      @tty: tty
1646  *      @file: file handle
1647  *
1648  *      Perform job control management checks on this file/tty descriptor
1649  *      and if appropriate send any needed signals and return a negative
1650  *      error code if action should be taken.
1651  *
1652  *      FIXME:
1653  *      Locking: None - redirected write test is safe, testing
1654  *      current->signal should possibly lock current->sighand
1655  *      pgrp locking ?
1656  */
1657
1658 static int job_control(struct tty_struct *tty, struct file *file)
1659 {
1660         /* Job control check -- must be done at start and after
1661            every sleep (POSIX.1 7.1.1.4). */
1662         /* NOTE: not yet done after every sleep pending a thorough
1663            check of the logic of this change. -- jlc */
1664         /* don't stop on /dev/console */
1665         if (file->f_op->write != redirected_tty_write &&
1666             current->signal->tty == tty) {
1667                 if (!tty->pgrp)
1668                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1669                 else if (task_pgrp(current) != tty->pgrp) {
1670                         if (is_ignored(SIGTTIN) ||
1671                             is_current_pgrp_orphaned())
1672                                 return -EIO;
1673                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1674                         set_thread_flag(TIF_SIGPENDING);
1675                         return -ERESTARTSYS;
1676                 }
1677         }
1678         return 0;
1679 }
1680
1681
1682 /**
1683  *      n_tty_read              -       read function for tty
1684  *      @tty: tty device
1685  *      @file: file object
1686  *      @buf: userspace buffer pointer
1687  *      @nr: size of I/O
1688  *
1689  *      Perform reads for the line discipline. We are guaranteed that the
1690  *      line discipline will not be closed under us but we may get multiple
1691  *      parallel readers and must handle this ourselves. We may also get
1692  *      a hangup. Always called in user context, may sleep.
1693  *
1694  *      This code must be sure never to sleep through a hangup.
1695  */
1696
1697 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1698                          unsigned char __user *buf, size_t nr)
1699 {
1700         unsigned char __user *b = buf;
1701         DECLARE_WAITQUEUE(wait, current);
1702         int c;
1703         int minimum, time;
1704         ssize_t retval = 0;
1705         ssize_t size;
1706         long timeout;
1707         unsigned long flags;
1708         int packet;
1709
1710 do_it_again:
1711
1712         BUG_ON(!tty->read_buf);
1713
1714         c = job_control(tty, file);
1715         if (c < 0)
1716                 return c;
1717
1718         minimum = time = 0;
1719         timeout = MAX_SCHEDULE_TIMEOUT;
1720         if (!tty->icanon) {
1721                 time = (HZ / 10) * TIME_CHAR(tty);
1722                 minimum = MIN_CHAR(tty);
1723                 if (minimum) {
1724                         if (time)
1725                                 tty->minimum_to_wake = 1;
1726                         else if (!waitqueue_active(&tty->read_wait) ||
1727                                  (tty->minimum_to_wake > minimum))
1728                                 tty->minimum_to_wake = minimum;
1729                 } else {
1730                         timeout = 0;
1731                         if (time) {
1732                                 timeout = time;
1733                                 time = 0;
1734                         }
1735                         tty->minimum_to_wake = minimum = 1;
1736                 }
1737         }
1738
1739         /*
1740          *      Internal serialization of reads.
1741          */
1742         if (file->f_flags & O_NONBLOCK) {
1743                 if (!mutex_trylock(&tty->atomic_read_lock))
1744                         return -EAGAIN;
1745         } else {
1746                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1747                         return -ERESTARTSYS;
1748         }
1749         packet = tty->packet;
1750
1751         add_wait_queue(&tty->read_wait, &wait);
1752         while (nr) {
1753                 /* First test for status change. */
1754                 if (packet && tty->link->ctrl_status) {
1755                         unsigned char cs;
1756                         if (b != buf)
1757                                 break;
1758                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1759                         cs = tty->link->ctrl_status;
1760                         tty->link->ctrl_status = 0;
1761                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1762                         if (tty_put_user(tty, cs, b++)) {
1763                                 retval = -EFAULT;
1764                                 b--;
1765                                 break;
1766                         }
1767                         nr--;
1768                         break;
1769                 }
1770                 /* This statement must be first before checking for input
1771                    so that any interrupt will set the state back to
1772                    TASK_RUNNING. */
1773                 set_current_state(TASK_INTERRUPTIBLE);
1774
1775                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1776                     ((minimum - (b - buf)) >= 1))
1777                         tty->minimum_to_wake = (minimum - (b - buf));
1778
1779                 if (!input_available_p(tty, 0)) {
1780                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1781                                 retval = -EIO;
1782                                 break;
1783                         }
1784                         if (tty_hung_up_p(file))
1785                                 break;
1786                         if (!timeout)
1787                                 break;
1788                         if (file->f_flags & O_NONBLOCK) {
1789                                 retval = -EAGAIN;
1790                                 break;
1791                         }
1792                         if (signal_pending(current)) {
1793                                 retval = -ERESTARTSYS;
1794                                 break;
1795                         }
1796                         /* FIXME: does n_tty_set_room need locking ? */
1797                         n_tty_set_room(tty);
1798                         timeout = schedule_timeout(timeout);
1799                         continue;
1800                 }
1801                 __set_current_state(TASK_RUNNING);
1802
1803                 /* Deal with packet mode. */
1804                 if (packet && b == buf) {
1805                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1806                                 retval = -EFAULT;
1807                                 b--;
1808                                 break;
1809                         }
1810                         nr--;
1811                 }
1812
1813                 if (tty->icanon) {
1814                         /* N.B. avoid overrun if nr == 0 */
1815                         while (nr && tty->read_cnt) {
1816                                 int eol;
1817
1818                                 eol = test_and_clear_bit(tty->read_tail,
1819                                                 tty->read_flags);
1820                                 c = tty->read_buf[tty->read_tail];
1821                                 spin_lock_irqsave(&tty->read_lock, flags);
1822                                 tty->read_tail = ((tty->read_tail+1) &
1823                                                   (N_TTY_BUF_SIZE-1));
1824                                 tty->read_cnt--;
1825                                 if (eol) {
1826                                         /* this test should be redundant:
1827                                          * we shouldn't be reading data if
1828                                          * canon_data is 0
1829                                          */
1830                                         if (--tty->canon_data < 0)
1831                                                 tty->canon_data = 0;
1832                                 }
1833                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1834
1835                                 if (!eol || (c != __DISABLED_CHAR)) {
1836                                         if (tty_put_user(tty, c, b++)) {
1837                                                 retval = -EFAULT;
1838                                                 b--;
1839                                                 break;
1840                                         }
1841                                         nr--;
1842                                 }
1843                                 if (eol) {
1844                                         tty_audit_push(tty);
1845                                         break;
1846                                 }
1847                         }
1848                         if (retval)
1849                                 break;
1850                 } else {
1851                         int uncopied;
1852                         /* The copy function takes the read lock and handles
1853                            locking internally for this case */
1854                         uncopied = copy_from_read_buf(tty, &b, &nr);
1855                         uncopied += copy_from_read_buf(tty, &b, &nr);
1856                         if (uncopied) {
1857                                 retval = -EFAULT;
1858                                 break;
1859                         }
1860                 }
1861
1862                 /* If there is enough space in the read buffer now, let the
1863                  * low-level driver know. We use n_tty_chars_in_buffer() to
1864                  * check the buffer, as it now knows about canonical mode.
1865                  * Otherwise, if the driver is throttled and the line is
1866                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1867                  * we won't get any more characters.
1868                  */
1869                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1870                         n_tty_set_room(tty);
1871                         check_unthrottle(tty);
1872                 }
1873
1874                 if (b - buf >= minimum)
1875                         break;
1876                 if (time)
1877                         timeout = time;
1878         }
1879         mutex_unlock(&tty->atomic_read_lock);
1880         remove_wait_queue(&tty->read_wait, &wait);
1881
1882         if (!waitqueue_active(&tty->read_wait))
1883                 tty->minimum_to_wake = minimum;
1884
1885         __set_current_state(TASK_RUNNING);
1886         size = b - buf;
1887         if (size) {
1888                 retval = size;
1889                 if (nr)
1890                         clear_bit(TTY_PUSH, &tty->flags);
1891         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1892                  goto do_it_again;
1893
1894         n_tty_set_room(tty);
1895         return retval;
1896 }
1897
1898 /**
1899  *      n_tty_write             -       write function for tty
1900  *      @tty: tty device
1901  *      @file: file object
1902  *      @buf: userspace buffer pointer
1903  *      @nr: size of I/O
1904  *
1905  *      Write function of the terminal device.  This is serialized with
1906  *      respect to other write callers but not to termios changes, reads
1907  *      and other such events.  Since the receive code will echo characters,
1908  *      thus calling driver write methods, the output_lock is used in
1909  *      the output processing functions called here as well as in the
1910  *      echo processing function to protect the column state and space
1911  *      left in the buffer.
1912  *
1913  *      This code must be sure never to sleep through a hangup.
1914  *
1915  *      Locking: output_lock to protect column state and space left
1916  *               (note that the process_output*() functions take this
1917  *                lock themselves)
1918  */
1919
1920 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1921                            const unsigned char *buf, size_t nr)
1922 {
1923         const unsigned char *b = buf;
1924         DECLARE_WAITQUEUE(wait, current);
1925         int c;
1926         ssize_t retval = 0;
1927
1928         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1929         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1930                 retval = tty_check_change(tty);
1931                 if (retval)
1932                         return retval;
1933         }
1934
1935         /* Write out any echoed characters that are still pending */
1936         process_echoes(tty);
1937
1938         add_wait_queue(&tty->write_wait, &wait);
1939         while (1) {
1940                 set_current_state(TASK_INTERRUPTIBLE);
1941                 if (signal_pending(current)) {
1942                         retval = -ERESTARTSYS;
1943                         break;
1944                 }
1945                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1946                         retval = -EIO;
1947                         break;
1948                 }
1949                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1950                         while (nr > 0) {
1951                                 ssize_t num = process_output_block(tty, b, nr);
1952                                 if (num < 0) {
1953                                         if (num == -EAGAIN)
1954                                                 break;
1955                                         retval = num;
1956                                         goto break_out;
1957                                 }
1958                                 b += num;
1959                                 nr -= num;
1960                                 if (nr == 0)
1961                                         break;
1962                                 c = *b;
1963                                 if (process_output(c, tty) < 0)
1964                                         break;
1965                                 b++; nr--;
1966                         }
1967                         if (tty->ops->flush_chars)
1968                                 tty->ops->flush_chars(tty);
1969                 } else {
1970                         while (nr > 0) {
1971                                 c = tty->ops->write(tty, b, nr);
1972                                 if (c < 0) {
1973                                         retval = c;
1974                                         goto break_out;
1975                                 }
1976                                 if (!c)
1977                                         break;
1978                                 b += c;
1979                                 nr -= c;
1980                         }
1981                 }
1982                 if (!nr)
1983                         break;
1984                 if (file->f_flags & O_NONBLOCK) {
1985                         retval = -EAGAIN;
1986                         break;
1987                 }
1988                 schedule();
1989         }
1990 break_out:
1991         __set_current_state(TASK_RUNNING);
1992         remove_wait_queue(&tty->write_wait, &wait);
1993         if (b - buf != nr && tty->fasync)
1994                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1995         return (b - buf) ? b - buf : retval;
1996 }
1997
1998 /**
1999  *      n_tty_poll              -       poll method for N_TTY
2000  *      @tty: terminal device
2001  *      @file: file accessing it
2002  *      @wait: poll table
2003  *
2004  *      Called when the line discipline is asked to poll() for data or
2005  *      for special events. This code is not serialized with respect to
2006  *      other events save open/close.
2007  *
2008  *      This code must be sure never to sleep through a hangup.
2009  *      Called without the kernel lock held - fine
2010  */
2011
2012 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2013                                                         poll_table *wait)
2014 {
2015         unsigned int mask = 0;
2016
2017         poll_wait(file, &tty->read_wait, wait);
2018         poll_wait(file, &tty->write_wait, wait);
2019         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2020                 mask |= POLLIN | POLLRDNORM;
2021         if (tty->packet && tty->link->ctrl_status)
2022                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2023         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2024                 mask |= POLLHUP;
2025         if (tty_hung_up_p(file))
2026                 mask |= POLLHUP;
2027         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2028                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2029                         tty->minimum_to_wake = MIN_CHAR(tty);
2030                 else
2031                         tty->minimum_to_wake = 1;
2032         }
2033         if (tty->ops->write && !tty_is_writelocked(tty) &&
2034                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2035                         tty_write_room(tty) > 0)
2036                 mask |= POLLOUT | POLLWRNORM;
2037         return mask;
2038 }
2039
2040 static unsigned long inq_canon(struct tty_struct *tty)
2041 {
2042         int nr, head, tail;
2043
2044         if (!tty->canon_data)
2045                 return 0;
2046         head = tty->canon_head;
2047         tail = tty->read_tail;
2048         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2049         /* Skip EOF-chars.. */
2050         while (head != tail) {
2051                 if (test_bit(tail, tty->read_flags) &&
2052                     tty->read_buf[tail] == __DISABLED_CHAR)
2053                         nr--;
2054                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2055         }
2056         return nr;
2057 }
2058
2059 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2060                        unsigned int cmd, unsigned long arg)
2061 {
2062         int retval;
2063
2064         switch (cmd) {
2065         case TIOCOUTQ:
2066                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2067         case TIOCINQ:
2068                 /* FIXME: Locking */
2069                 retval = tty->read_cnt;
2070                 if (L_ICANON(tty))
2071                         retval = inq_canon(tty);
2072                 return put_user(retval, (unsigned int __user *) arg);
2073         default:
2074                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2075         }
2076 }
2077
2078 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2079         .magic           = TTY_LDISC_MAGIC,
2080         .name            = "n_tty",
2081         .open            = n_tty_open,
2082         .close           = n_tty_close,
2083         .flush_buffer    = n_tty_flush_buffer,
2084         .chars_in_buffer = n_tty_chars_in_buffer,
2085         .read            = n_tty_read,
2086         .write           = n_tty_write,
2087         .ioctl           = n_tty_ioctl,
2088         .set_termios     = n_tty_set_termios,
2089         .poll            = n_tty_poll,
2090         .receive_buf     = n_tty_receive_buf,
2091         .write_wakeup    = n_tty_write_wakeup
2092 };