n_tty: clean up coding style
[linux-2.6.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 unsigned char *alloc_buf(void)
77 {
78         gfp_t prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
79
80         if (PAGE_SIZE != N_TTY_BUF_SIZE)
81                 return kmalloc(N_TTY_BUF_SIZE, prio);
82         else
83                 return (unsigned char *)__get_free_page(prio);
84 }
85
86 static inline void free_buf(unsigned char *buf)
87 {
88         if (PAGE_SIZE != N_TTY_BUF_SIZE)
89                 kfree(buf);
90         else
91                 free_page((unsigned long) buf);
92 }
93
94 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
95                                unsigned char __user *ptr)
96 {
97         tty_audit_add_data(tty, &x, 1);
98         return put_user(x, ptr);
99 }
100
101 /**
102  *      n_tty_set__room -       receive space
103  *      @tty: terminal
104  *
105  *      Called by the driver to find out how much data it is
106  *      permitted to feed to the line discipline without any being lost
107  *      and thus to manage flow control. Not serialized. Answers for the
108  *      "instant".
109  */
110
111 static void n_tty_set_room(struct tty_struct *tty)
112 {
113         /* tty->read_cnt is not read locked ? */
114         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
115
116         /*
117          * If we are doing input canonicalization, and there are no
118          * pending newlines, let characters through without limit, so
119          * that erase characters will be handled.  Other excess
120          * characters will be beeped.
121          */
122         if (left <= 0)
123                 left = tty->icanon && !tty->canon_data;
124         tty->receive_room = left;
125 }
126
127 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
128 {
129         if (tty->read_cnt < N_TTY_BUF_SIZE) {
130                 tty->read_buf[tty->read_head] = c;
131                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
132                 tty->read_cnt++;
133         }
134 }
135
136 /**
137  *      put_tty_queue           -       add character to tty
138  *      @c: character
139  *      @tty: tty device
140  *
141  *      Add a character to the tty read_buf queue. This is done under the
142  *      read_lock to serialize character addition and also to protect us
143  *      against parallel reads or flushes
144  */
145
146 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
147 {
148         unsigned long flags;
149         /*
150          *      The problem of stomping on the buffers ends here.
151          *      Why didn't anyone see this one coming? --AJK
152         */
153         spin_lock_irqsave(&tty->read_lock, flags);
154         put_tty_queue_nolock(c, tty);
155         spin_unlock_irqrestore(&tty->read_lock, flags);
156 }
157
158 /**
159  *      check_unthrottle        -       allow new receive data
160  *      @tty; tty device
161  *
162  *      Check whether to call the driver unthrottle functions
163  *
164  *      Can sleep, may be called under the atomic_read_lock mutex but
165  *      this is not guaranteed.
166  */
167 static void check_unthrottle(struct tty_struct *tty)
168 {
169         if (tty->count)
170                 tty_unthrottle(tty);
171 }
172
173 /**
174  *      reset_buffer_flags      -       reset buffer state
175  *      @tty: terminal to reset
176  *
177  *      Reset the read buffer counters, clear the flags,
178  *      and make sure the driver is unthrottled. Called
179  *      from n_tty_open() and n_tty_flush_buffer().
180  *
181  *      Locking: tty_read_lock for read fields.
182  */
183
184 static void reset_buffer_flags(struct tty_struct *tty)
185 {
186         unsigned long flags;
187
188         spin_lock_irqsave(&tty->read_lock, flags);
189         tty->read_head = tty->read_tail = tty->read_cnt = 0;
190         spin_unlock_irqrestore(&tty->read_lock, flags);
191
192         mutex_lock(&tty->echo_lock);
193         tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
194         mutex_unlock(&tty->echo_lock);
195
196         tty->canon_head = tty->canon_data = tty->erasing = 0;
197         memset(&tty->read_flags, 0, sizeof tty->read_flags);
198         n_tty_set_room(tty);
199         check_unthrottle(tty);
200 }
201
202 /**
203  *      n_tty_flush_buffer      -       clean input queue
204  *      @tty:   terminal device
205  *
206  *      Flush the input buffer. Called when the line discipline is
207  *      being closed, when the tty layer wants the buffer flushed (eg
208  *      at hangup) or when the N_TTY line discipline internally has to
209  *      clean the pending queue (for example some signals).
210  *
211  *      Locking: ctrl_lock, read_lock.
212  */
213
214 static void n_tty_flush_buffer(struct tty_struct *tty)
215 {
216         unsigned long flags;
217         /* clear everything and unthrottle the driver */
218         reset_buffer_flags(tty);
219
220         if (!tty->link)
221                 return;
222
223         spin_lock_irqsave(&tty->ctrl_lock, flags);
224         if (tty->link->packet) {
225                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
226                 wake_up_interruptible(&tty->link->read_wait);
227         }
228         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
229 }
230
231 /**
232  *      n_tty_chars_in_buffer   -       report available bytes
233  *      @tty: tty device
234  *
235  *      Report the number of characters buffered to be delivered to user
236  *      at this instant in time.
237  *
238  *      Locking: read_lock
239  */
240
241 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
242 {
243         unsigned long flags;
244         ssize_t n = 0;
245
246         spin_lock_irqsave(&tty->read_lock, flags);
247         if (!tty->icanon) {
248                 n = tty->read_cnt;
249         } else if (tty->canon_data) {
250                 n = (tty->canon_head > tty->read_tail) ?
251                         tty->canon_head - tty->read_tail :
252                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
253         }
254         spin_unlock_irqrestore(&tty->read_lock, flags);
255         return n;
256 }
257
258 /**
259  *      is_utf8_continuation    -       utf8 multibyte check
260  *      @c: byte to check
261  *
262  *      Returns true if the utf8 character 'c' is a multibyte continuation
263  *      character. We use this to correctly compute the on screen size
264  *      of the character when printing
265  */
266
267 static inline int is_utf8_continuation(unsigned char c)
268 {
269         return (c & 0xc0) == 0x80;
270 }
271
272 /**
273  *      is_continuation         -       multibyte check
274  *      @c: byte to check
275  *
276  *      Returns true if the utf8 character 'c' is a multibyte continuation
277  *      character and the terminal is in unicode mode.
278  */
279
280 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
281 {
282         return I_IUTF8(tty) && is_utf8_continuation(c);
283 }
284
285 /**
286  *      do_output_char                  -       output one character
287  *      @c: character (or partial unicode symbol)
288  *      @tty: terminal device
289  *      @space: space available in tty driver write buffer
290  *
291  *      This is a helper function that handles one output character
292  *      (including special characters like TAB, CR, LF, etc.),
293  *      putting the results in the tty driver's write buffer.
294  *
295  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
296  *      and NLDLY.  They simply aren't relevant in the world today.
297  *      If you ever need them, add them here.
298  *
299  *      Returns the number of bytes of buffer space used or -1 if
300  *      no space left.
301  *
302  *      Locking: should be called under the output_lock to protect
303  *               the column state and space left in the buffer
304  */
305
306 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
307 {
308         int     spaces;
309
310         if (!space)
311                 return -1;
312
313         switch (c) {
314         case '\n':
315                 if (O_ONLRET(tty))
316                         tty->column = 0;
317                 if (O_ONLCR(tty)) {
318                         if (space < 2)
319                                 return -1;
320                         tty->canon_column = tty->column = 0;
321                         tty_put_char(tty, '\r');
322                         tty_put_char(tty, c);
323                         return 2;
324                 }
325                 tty->canon_column = tty->column;
326                 break;
327         case '\r':
328                 if (O_ONOCR(tty) && tty->column == 0)
329                         return 0;
330                 if (O_OCRNL(tty)) {
331                         c = '\n';
332                         if (O_ONLRET(tty))
333                                 tty->canon_column = tty->column = 0;
334                         break;
335                 }
336                 tty->canon_column = tty->column = 0;
337                 break;
338         case '\t':
339                 spaces = 8 - (tty->column & 7);
340                 if (O_TABDLY(tty) == XTABS) {
341                         if (space < spaces)
342                                 return -1;
343                         tty->column += spaces;
344                         tty->ops->write(tty, "        ", spaces);
345                         return spaces;
346                 }
347                 tty->column += spaces;
348                 break;
349         case '\b':
350                 if (tty->column > 0)
351                         tty->column--;
352                 break;
353         default:
354                 if (O_OLCUC(tty))
355                         c = toupper(c);
356                 if (!iscntrl(c) && !is_continuation(c, tty))
357                         tty->column++;
358                 break;
359         }
360
361         tty_put_char(tty, c);
362         return 1;
363 }
364
365 /**
366  *      process_output                  -       output post processor
367  *      @c: character (or partial unicode symbol)
368  *      @tty: terminal device
369  *
370  *      Perform OPOST processing.  Returns -1 when the output device is
371  *      full and the character must be retried.
372  *
373  *      Locking: output_lock to protect column state and space left
374  *               (also, this is called from n_tty_write under the
375  *                tty layer write lock)
376  */
377
378 static int process_output(unsigned char c, struct tty_struct *tty)
379 {
380         int     space, retval;
381
382         mutex_lock(&tty->output_lock);
383
384         space = tty_write_room(tty);
385         retval = do_output_char(c, tty, space);
386
387         mutex_unlock(&tty->output_lock);
388         if (retval < 0)
389                 return -1;
390         else
391                 return 0;
392 }
393
394 /**
395  *      process_output_block            -       block post processor
396  *      @tty: terminal device
397  *      @inbuf: user buffer
398  *      @nr: number of bytes
399  *
400  *      This path is used to speed up block console writes, among other
401  *      things when processing blocks of output data. It handles only
402  *      the simple cases normally found and helps to generate blocks of
403  *      symbols for the console driver and thus improve performance.
404  *
405  *      Locking: output_lock to protect column state and space left
406  *               (also, this is called from n_tty_write under the
407  *                tty layer write lock)
408  */
409
410 static ssize_t process_output_block(struct tty_struct *tty,
411                                     const unsigned char *buf, unsigned int nr)
412 {
413         int     space;
414         int     i;
415         const unsigned char *cp;
416
417         mutex_lock(&tty->output_lock);
418
419         space = tty_write_room(tty);
420         if (!space) {
421                 mutex_unlock(&tty->output_lock);
422                 return 0;
423         }
424         if (nr > space)
425                 nr = space;
426
427         for (i = 0, cp = buf; i < nr; i++, cp++) {
428                 switch (*cp) {
429                 case '\n':
430                         if (O_ONLRET(tty))
431                                 tty->column = 0;
432                         if (O_ONLCR(tty))
433                                 goto break_out;
434                         tty->canon_column = tty->column;
435                         break;
436                 case '\r':
437                         if (O_ONOCR(tty) && tty->column == 0)
438                                 goto break_out;
439                         if (O_OCRNL(tty))
440                                 goto break_out;
441                         tty->canon_column = tty->column = 0;
442                         break;
443                 case '\t':
444                         goto break_out;
445                 case '\b':
446                         if (tty->column > 0)
447                                 tty->column--;
448                         break;
449                 default:
450                         if (O_OLCUC(tty))
451                                 goto break_out;
452                         if (!iscntrl(*cp))
453                                 tty->column++;
454                         break;
455                 }
456         }
457 break_out:
458         i = tty->ops->write(tty, buf, i);
459
460         mutex_unlock(&tty->output_lock);
461         return i;
462 }
463
464 /**
465  *      process_echoes  -       write pending echo characters
466  *      @tty: terminal device
467  *
468  *      Write previously buffered echo (and other ldisc-generated)
469  *      characters to the tty.
470  *
471  *      Characters generated by the ldisc (including echoes) need to
472  *      be buffered because the driver's write buffer can fill during
473  *      heavy program output.  Echoing straight to the driver will
474  *      often fail under these conditions, causing lost characters and
475  *      resulting mismatches of ldisc state information.
476  *
477  *      Since the ldisc state must represent the characters actually sent
478  *      to the driver at the time of the write, operations like certain
479  *      changes in column state are also saved in the buffer and executed
480  *      here.
481  *
482  *      A circular fifo buffer is used so that the most recent characters
483  *      are prioritized.  Also, when control characters are echoed with a
484  *      prefixed "^", the pair is treated atomically and thus not separated.
485  *
486  *      Locking: output_lock to protect column state and space left,
487  *               echo_lock to protect the echo buffer
488  */
489
490 static void process_echoes(struct tty_struct *tty)
491 {
492         int     space, nr;
493         unsigned char c;
494         unsigned char *cp, *buf_end;
495
496         if (!tty->echo_cnt)
497                 return;
498
499         mutex_lock(&tty->output_lock);
500         mutex_lock(&tty->echo_lock);
501
502         space = tty_write_room(tty);
503
504         buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
505         cp = tty->echo_buf + tty->echo_pos;
506         nr = tty->echo_cnt;
507         while (nr > 0) {
508                 c = *cp;
509                 if (c == ECHO_OP_START) {
510                         unsigned char op;
511                         unsigned char *opp;
512                         int no_space_left = 0;
513
514                         /*
515                          * If the buffer byte is the start of a multi-byte
516                          * operation, get the next byte, which is either the
517                          * op code or a control character value.
518                          */
519                         opp = cp + 1;
520                         if (opp == buf_end)
521                                 opp -= N_TTY_BUF_SIZE;
522                         op = *opp;
523
524                         switch (op) {
525                                 unsigned int num_chars, num_bs;
526
527                         case ECHO_OP_ERASE_TAB:
528                                 if (++opp == buf_end)
529                                         opp -= N_TTY_BUF_SIZE;
530                                 num_chars = *opp;
531
532                                 /*
533                                  * Determine how many columns to go back
534                                  * in order to erase the tab.
535                                  * This depends on the number of columns
536                                  * used by other characters within the tab
537                                  * area.  If this (modulo 8) count is from
538                                  * the start of input rather than from a
539                                  * previous tab, we offset by canon column.
540                                  * Otherwise, tab spacing is normal.
541                                  */
542                                 if (!(num_chars & 0x80))
543                                         num_chars += tty->canon_column;
544                                 num_bs = 8 - (num_chars & 7);
545
546                                 if (num_bs > space) {
547                                         no_space_left = 1;
548                                         break;
549                                 }
550                                 space -= num_bs;
551                                 while (num_bs--) {
552                                         tty_put_char(tty, '\b');
553                                         if (tty->column > 0)
554                                                 tty->column--;
555                                 }
556                                 cp += 3;
557                                 nr -= 3;
558                                 break;
559
560                         case ECHO_OP_SET_CANON_COL:
561                                 tty->canon_column = tty->column;
562                                 cp += 2;
563                                 nr -= 2;
564                                 break;
565
566                         case ECHO_OP_MOVE_BACK_COL:
567                                 if (tty->column > 0)
568                                         tty->column--;
569                                 cp += 2;
570                                 nr -= 2;
571                                 break;
572
573                         case ECHO_OP_START:
574                                 /* This is an escaped echo op start code */
575                                 if (!space) {
576                                         no_space_left = 1;
577                                         break;
578                                 }
579                                 tty_put_char(tty, ECHO_OP_START);
580                                 tty->column++;
581                                 space--;
582                                 cp += 2;
583                                 nr -= 2;
584                                 break;
585
586                         default:
587                                 if (iscntrl(op)) {
588                                         if (L_ECHOCTL(tty)) {
589                                                 /*
590                                                  * Ensure there is enough space
591                                                  * for the whole ctrl pair.
592                                                  */
593                                                 if (space < 2) {
594                                                         no_space_left = 1;
595                                                         break;
596                                                 }
597                                                 tty_put_char(tty, '^');
598                                                 tty_put_char(tty, op ^ 0100);
599                                                 tty->column += 2;
600                                                 space -= 2;
601                                         } else {
602                                                 if (!space) {
603                                                         no_space_left = 1;
604                                                         break;
605                                                 }
606                                                 tty_put_char(tty, op);
607                                                 space--;
608                                         }
609                                 }
610                                 /*
611                                  * If above falls through, this was an
612                                  * undefined op.
613                                  */
614                                 cp += 2;
615                                 nr -= 2;
616                         }
617
618                         if (no_space_left)
619                                 break;
620                 } else {
621                         int retval;
622
623                         retval = do_output_char(c, tty, space);
624                         if (retval < 0)
625                                 break;
626                         space -= retval;
627                         cp += 1;
628                         nr -= 1;
629                 }
630
631                 /* When end of circular buffer reached, wrap around */
632                 if (cp >= buf_end)
633                         cp -= N_TTY_BUF_SIZE;
634         }
635
636         if (nr == 0) {
637                 tty->echo_pos = 0;
638                 tty->echo_cnt = 0;
639                 tty->echo_overrun = 0;
640         } else {
641                 int num_processed = tty->echo_cnt - nr;
642                 tty->echo_pos += num_processed;
643                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
644                 tty->echo_cnt = nr;
645                 if (num_processed > 0)
646                         tty->echo_overrun = 0;
647         }
648
649         mutex_unlock(&tty->echo_lock);
650         mutex_unlock(&tty->output_lock);
651
652         if (tty->ops->flush_chars)
653                 tty->ops->flush_chars(tty);
654 }
655
656 /**
657  *      add_echo_byte   -       add a byte to the echo buffer
658  *      @c: unicode byte to echo
659  *      @tty: terminal device
660  *
661  *      Add a character or operation byte to the echo buffer.
662  *
663  *      Should be called under the echo lock to protect the echo buffer.
664  */
665
666 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
667 {
668         int     new_byte_pos;
669
670         if (tty->echo_cnt == N_TTY_BUF_SIZE) {
671                 /* Circular buffer is already at capacity */
672                 new_byte_pos = tty->echo_pos;
673
674                 /*
675                  * Since the buffer start position needs to be advanced,
676                  * be sure to step by a whole operation byte group.
677                  */
678                 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
679                         if (tty->echo_buf[(tty->echo_pos + 1) &
680                                           (N_TTY_BUF_SIZE - 1)] ==
681                                                 ECHO_OP_ERASE_TAB) {
682                                 tty->echo_pos += 3;
683                                 tty->echo_cnt -= 2;
684                         } else {
685                                 tty->echo_pos += 2;
686                                 tty->echo_cnt -= 1;
687                         }
688                 } else {
689                         tty->echo_pos++;
690                 }
691                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
692
693                 tty->echo_overrun = 1;
694         } else {
695                 new_byte_pos = tty->echo_pos + tty->echo_cnt;
696                 new_byte_pos &= N_TTY_BUF_SIZE - 1;
697                 tty->echo_cnt++;
698         }
699
700         tty->echo_buf[new_byte_pos] = c;
701 }
702
703 /**
704  *      echo_move_back_col      -       add operation to move back a column
705  *      @tty: terminal device
706  *
707  *      Add an operation to the echo buffer to move back one column.
708  *
709  *      Locking: echo_lock to protect the echo buffer
710  */
711
712 static void echo_move_back_col(struct tty_struct *tty)
713 {
714         mutex_lock(&tty->echo_lock);
715
716         add_echo_byte(ECHO_OP_START, tty);
717         add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
718
719         mutex_unlock(&tty->echo_lock);
720 }
721
722 /**
723  *      echo_set_canon_col      -       add operation to set the canon column
724  *      @tty: terminal device
725  *
726  *      Add an operation to the echo buffer to set the canon column
727  *      to the current column.
728  *
729  *      Locking: echo_lock to protect the echo buffer
730  */
731
732 static void echo_set_canon_col(struct tty_struct *tty)
733 {
734         mutex_lock(&tty->echo_lock);
735
736         add_echo_byte(ECHO_OP_START, tty);
737         add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
738
739         mutex_unlock(&tty->echo_lock);
740 }
741
742 /**
743  *      echo_erase_tab  -       add operation to erase a tab
744  *      @num_chars: number of character columns already used
745  *      @after_tab: true if num_chars starts after a previous tab
746  *      @tty: terminal device
747  *
748  *      Add an operation to the echo buffer to erase a tab.
749  *
750  *      Called by the eraser function, which knows how many character
751  *      columns have been used since either a previous tab or the start
752  *      of input.  This information will be used later, along with
753  *      canon column (if applicable), to go back the correct number
754  *      of columns.
755  *
756  *      Locking: echo_lock to protect the echo buffer
757  */
758
759 static void echo_erase_tab(unsigned int num_chars, int after_tab,
760                            struct tty_struct *tty)
761 {
762         mutex_lock(&tty->echo_lock);
763
764         add_echo_byte(ECHO_OP_START, tty);
765         add_echo_byte(ECHO_OP_ERASE_TAB, tty);
766
767         /* We only need to know this modulo 8 (tab spacing) */
768         num_chars &= 7;
769
770         /* Set the high bit as a flag if num_chars is after a previous tab */
771         if (after_tab)
772                 num_chars |= 0x80;
773
774         add_echo_byte(num_chars, tty);
775
776         mutex_unlock(&tty->echo_lock);
777 }
778
779 /**
780  *      echo_char_raw   -       echo a character raw
781  *      @c: unicode byte to echo
782  *      @tty: terminal device
783  *
784  *      Echo user input back onto the screen. This must be called only when
785  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
786  *
787  *      This variant does not treat control characters specially.
788  *
789  *      Locking: echo_lock to protect the echo buffer
790  */
791
792 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
793 {
794         mutex_lock(&tty->echo_lock);
795
796         if (c == ECHO_OP_START) {
797                 add_echo_byte(ECHO_OP_START, tty);
798                 add_echo_byte(ECHO_OP_START, tty);
799         } else {
800                 add_echo_byte(c, tty);
801         }
802
803         mutex_unlock(&tty->echo_lock);
804 }
805
806 /**
807  *      echo_char       -       echo a character
808  *      @c: unicode byte to echo
809  *      @tty: terminal device
810  *
811  *      Echo user input back onto the screen. This must be called only when
812  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
813  *
814  *      This variant tags control characters to be possibly echoed as
815  *      as "^X" (where X is the letter representing the control char).
816  *
817  *      Locking: echo_lock to protect the echo buffer
818  */
819
820 static void echo_char(unsigned char c, struct tty_struct *tty)
821 {
822         mutex_lock(&tty->echo_lock);
823
824         if (c == ECHO_OP_START) {
825                 add_echo_byte(ECHO_OP_START, tty);
826                 add_echo_byte(ECHO_OP_START, tty);
827         } else {
828                 if (iscntrl(c) && c != '\t')
829                         add_echo_byte(ECHO_OP_START, tty);
830                 add_echo_byte(c, tty);
831         }
832
833         mutex_unlock(&tty->echo_lock);
834 }
835
836 /**
837  *      finish_erasing          -       complete erase
838  *      @tty: tty doing the erase
839  */
840
841 static inline void finish_erasing(struct tty_struct *tty)
842 {
843         if (tty->erasing) {
844                 echo_char_raw('/', tty);
845                 tty->erasing = 0;
846         }
847 }
848
849 /**
850  *      eraser          -       handle erase function
851  *      @c: character input
852  *      @tty: terminal device
853  *
854  *      Perform erase and necessary output when an erase character is
855  *      present in the stream from the driver layer. Handles the complexities
856  *      of UTF-8 multibyte symbols.
857  *
858  *      Locking: read_lock for tty buffers
859  */
860
861 static void eraser(unsigned char c, struct tty_struct *tty)
862 {
863         enum { ERASE, WERASE, KILL } kill_type;
864         int head, seen_alnums, cnt;
865         unsigned long flags;
866
867         /* FIXME: locking needed ? */
868         if (tty->read_head == tty->canon_head) {
869                 /* echo_char_raw('\a', tty); */ /* what do you think? */
870                 return;
871         }
872         if (c == ERASE_CHAR(tty))
873                 kill_type = ERASE;
874         else if (c == WERASE_CHAR(tty))
875                 kill_type = WERASE;
876         else {
877                 if (!L_ECHO(tty)) {
878                         spin_lock_irqsave(&tty->read_lock, flags);
879                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
880                                           (N_TTY_BUF_SIZE - 1));
881                         tty->read_head = tty->canon_head;
882                         spin_unlock_irqrestore(&tty->read_lock, flags);
883                         return;
884                 }
885                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
886                         spin_lock_irqsave(&tty->read_lock, flags);
887                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
888                                           (N_TTY_BUF_SIZE - 1));
889                         tty->read_head = tty->canon_head;
890                         spin_unlock_irqrestore(&tty->read_lock, flags);
891                         finish_erasing(tty);
892                         echo_char(KILL_CHAR(tty), tty);
893                         /* Add a newline if ECHOK is on and ECHOKE is off. */
894                         if (L_ECHOK(tty))
895                                 echo_char_raw('\n', tty);
896                         return;
897                 }
898                 kill_type = KILL;
899         }
900
901         seen_alnums = 0;
902         /* FIXME: Locking ?? */
903         while (tty->read_head != tty->canon_head) {
904                 head = tty->read_head;
905
906                 /* erase a single possibly multibyte character */
907                 do {
908                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
909                         c = tty->read_buf[head];
910                 } while (is_continuation(c, tty) && head != tty->canon_head);
911
912                 /* do not partially erase */
913                 if (is_continuation(c, tty))
914                         break;
915
916                 if (kill_type == WERASE) {
917                         /* Equivalent to BSD's ALTWERASE. */
918                         if (isalnum(c) || c == '_')
919                                 seen_alnums++;
920                         else if (seen_alnums)
921                                 break;
922                 }
923                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
924                 spin_lock_irqsave(&tty->read_lock, flags);
925                 tty->read_head = head;
926                 tty->read_cnt -= cnt;
927                 spin_unlock_irqrestore(&tty->read_lock, flags);
928                 if (L_ECHO(tty)) {
929                         if (L_ECHOPRT(tty)) {
930                                 if (!tty->erasing) {
931                                         echo_char_raw('\\', tty);
932                                         tty->erasing = 1;
933                                 }
934                                 /* if cnt > 1, output a multi-byte character */
935                                 echo_char(c, tty);
936                                 while (--cnt > 0) {
937                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
938                                         echo_char_raw(tty->read_buf[head], tty);
939                                         echo_move_back_col(tty);
940                                 }
941                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
942                                 echo_char(ERASE_CHAR(tty), tty);
943                         } else if (c == '\t') {
944                                 unsigned int num_chars = 0;
945                                 int after_tab = 0;
946                                 unsigned long tail = tty->read_head;
947
948                                 /*
949                                  * Count the columns used for characters
950                                  * since the start of input or after a
951                                  * previous tab.
952                                  * This info is used to go back the correct
953                                  * number of columns.
954                                  */
955                                 while (tail != tty->canon_head) {
956                                         tail = (tail-1) & (N_TTY_BUF_SIZE-1);
957                                         c = tty->read_buf[tail];
958                                         if (c == '\t') {
959                                                 after_tab = 1;
960                                                 break;
961                                         } else if (iscntrl(c)) {
962                                                 if (L_ECHOCTL(tty))
963                                                         num_chars += 2;
964                                         } else if (!is_continuation(c, tty)) {
965                                                 num_chars++;
966                                         }
967                                 }
968                                 echo_erase_tab(num_chars, after_tab, tty);
969                         } else {
970                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
971                                         echo_char_raw('\b', tty);
972                                         echo_char_raw(' ', tty);
973                                         echo_char_raw('\b', tty);
974                                 }
975                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
976                                         echo_char_raw('\b', tty);
977                                         echo_char_raw(' ', tty);
978                                         echo_char_raw('\b', tty);
979                                 }
980                         }
981                 }
982                 if (kill_type == ERASE)
983                         break;
984         }
985         if (tty->read_head == tty->canon_head && L_ECHO(tty))
986                 finish_erasing(tty);
987 }
988
989 /**
990  *      isig            -       handle the ISIG optio
991  *      @sig: signal
992  *      @tty: terminal
993  *      @flush: force flush
994  *
995  *      Called when a signal is being sent due to terminal input. This
996  *      may caus terminal flushing to take place according to the termios
997  *      settings and character used. Called from the driver receive_buf
998  *      path so serialized.
999  *
1000  *      Locking: ctrl_lock, read_lock (both via flush buffer)
1001  */
1002
1003 static inline void isig(int sig, struct tty_struct *tty, int flush)
1004 {
1005         if (tty->pgrp)
1006                 kill_pgrp(tty->pgrp, sig, 1);
1007         if (flush || !L_NOFLSH(tty)) {
1008                 n_tty_flush_buffer(tty);
1009                 tty_driver_flush_buffer(tty);
1010         }
1011 }
1012
1013 /**
1014  *      n_tty_receive_break     -       handle break
1015  *      @tty: terminal
1016  *
1017  *      An RS232 break event has been hit in the incoming bitstream. This
1018  *      can cause a variety of events depending upon the termios settings.
1019  *
1020  *      Called from the receive_buf path so single threaded.
1021  */
1022
1023 static inline void n_tty_receive_break(struct tty_struct *tty)
1024 {
1025         if (I_IGNBRK(tty))
1026                 return;
1027         if (I_BRKINT(tty)) {
1028                 isig(SIGINT, tty, 1);
1029                 return;
1030         }
1031         if (I_PARMRK(tty)) {
1032                 put_tty_queue('\377', tty);
1033                 put_tty_queue('\0', tty);
1034         }
1035         put_tty_queue('\0', tty);
1036         wake_up_interruptible(&tty->read_wait);
1037 }
1038
1039 /**
1040  *      n_tty_receive_overrun   -       handle overrun reporting
1041  *      @tty: terminal
1042  *
1043  *      Data arrived faster than we could process it. While the tty
1044  *      driver has flagged this the bits that were missed are gone
1045  *      forever.
1046  *
1047  *      Called from the receive_buf path so single threaded. Does not
1048  *      need locking as num_overrun and overrun_time are function
1049  *      private.
1050  */
1051
1052 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1053 {
1054         char buf[64];
1055
1056         tty->num_overrun++;
1057         if (time_before(tty->overrun_time, jiffies - HZ) ||
1058                         time_after(tty->overrun_time, jiffies)) {
1059                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1060                         tty_name(tty, buf),
1061                         tty->num_overrun);
1062                 tty->overrun_time = jiffies;
1063                 tty->num_overrun = 0;
1064         }
1065 }
1066
1067 /**
1068  *      n_tty_receive_parity_error      -       error notifier
1069  *      @tty: terminal device
1070  *      @c: character
1071  *
1072  *      Process a parity error and queue the right data to indicate
1073  *      the error case if necessary. Locking as per n_tty_receive_buf.
1074  */
1075 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1076                                               unsigned char c)
1077 {
1078         if (I_IGNPAR(tty))
1079                 return;
1080         if (I_PARMRK(tty)) {
1081                 put_tty_queue('\377', tty);
1082                 put_tty_queue('\0', tty);
1083                 put_tty_queue(c, tty);
1084         } else  if (I_INPCK(tty))
1085                 put_tty_queue('\0', tty);
1086         else
1087                 put_tty_queue(c, tty);
1088         wake_up_interruptible(&tty->read_wait);
1089 }
1090
1091 /**
1092  *      n_tty_receive_char      -       perform processing
1093  *      @tty: terminal device
1094  *      @c: character
1095  *
1096  *      Process an individual character of input received from the driver.
1097  *      This is serialized with respect to itself by the rules for the
1098  *      driver above.
1099  */
1100
1101 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1102 {
1103         unsigned long flags;
1104
1105         if (tty->raw) {
1106                 put_tty_queue(c, tty);
1107                 return;
1108         }
1109
1110         if (I_ISTRIP(tty))
1111                 c &= 0x7f;
1112         if (I_IUCLC(tty) && L_IEXTEN(tty))
1113                 c = tolower(c);
1114
1115         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1116             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1117             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1118                 start_tty(tty);
1119                 process_echoes(tty);
1120         }
1121
1122         if (tty->closing) {
1123                 if (I_IXON(tty)) {
1124                         if (c == START_CHAR(tty)) {
1125                                 start_tty(tty);
1126                                 process_echoes(tty);
1127                         } else if (c == STOP_CHAR(tty))
1128                                 stop_tty(tty);
1129                 }
1130                 return;
1131         }
1132
1133         /*
1134          * If the previous character was LNEXT, or we know that this
1135          * character is not one of the characters that we'll have to
1136          * handle specially, do shortcut processing to speed things
1137          * up.
1138          */
1139         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1140                 tty->lnext = 0;
1141                 if (L_ECHO(tty)) {
1142                         finish_erasing(tty);
1143                         if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
1144                                 /* beep if no space */
1145                                 echo_char_raw('\a', tty);
1146                                 process_echoes(tty);
1147                                 return;
1148                         }
1149                         /* Record the column of first canon char. */
1150                         if (tty->canon_head == tty->read_head)
1151                                 echo_set_canon_col(tty);
1152                         echo_char(c, tty);
1153                         process_echoes(tty);
1154                 }
1155                 if (I_PARMRK(tty) && c == (unsigned char) '\377')
1156                         put_tty_queue(c, tty);
1157                 put_tty_queue(c, tty);
1158                 return;
1159         }
1160
1161         if (I_IXON(tty)) {
1162                 if (c == START_CHAR(tty)) {
1163                         start_tty(tty);
1164                         process_echoes(tty);
1165                         return;
1166                 }
1167                 if (c == STOP_CHAR(tty)) {
1168                         stop_tty(tty);
1169                         return;
1170                 }
1171         }
1172
1173         if (L_ISIG(tty)) {
1174                 int signal;
1175                 signal = SIGINT;
1176                 if (c == INTR_CHAR(tty))
1177                         goto send_signal;
1178                 signal = SIGQUIT;
1179                 if (c == QUIT_CHAR(tty))
1180                         goto send_signal;
1181                 signal = SIGTSTP;
1182                 if (c == SUSP_CHAR(tty)) {
1183 send_signal:
1184                         /*
1185                          * Note that we do not use isig() here because we want
1186                          * the order to be:
1187                          * 1) flush, 2) echo, 3) signal
1188                          */
1189                         if (!L_NOFLSH(tty)) {
1190                                 n_tty_flush_buffer(tty);
1191                                 tty_driver_flush_buffer(tty);
1192                         }
1193                         if (I_IXON(tty))
1194                                 start_tty(tty);
1195                         if (L_ECHO(tty)) {
1196                                 echo_char(c, tty);
1197                                 process_echoes(tty);
1198                         }
1199                         if (tty->pgrp)
1200                                 kill_pgrp(tty->pgrp, signal, 1);
1201                         return;
1202                 }
1203         }
1204
1205         if (c == '\r') {
1206                 if (I_IGNCR(tty))
1207                         return;
1208                 if (I_ICRNL(tty))
1209                         c = '\n';
1210         } else if (c == '\n' && I_INLCR(tty))
1211                 c = '\r';
1212
1213         if (tty->icanon) {
1214                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1215                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1216                         eraser(c, tty);
1217                         process_echoes(tty);
1218                         return;
1219                 }
1220                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1221                         tty->lnext = 1;
1222                         if (L_ECHO(tty)) {
1223                                 finish_erasing(tty);
1224                                 if (L_ECHOCTL(tty)) {
1225                                         echo_char_raw('^', tty);
1226                                         echo_char_raw('\b', tty);
1227                                         process_echoes(tty);
1228                                 }
1229                         }
1230                         return;
1231                 }
1232                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1233                     L_IEXTEN(tty)) {
1234                         unsigned long tail = tty->canon_head;
1235
1236                         finish_erasing(tty);
1237                         echo_char(c, tty);
1238                         echo_char_raw('\n', tty);
1239                         while (tail != tty->read_head) {
1240                                 echo_char(tty->read_buf[tail], tty);
1241                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1242                         }
1243                         process_echoes(tty);
1244                         return;
1245                 }
1246                 if (c == '\n') {
1247                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1248                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
1249                                         echo_char_raw('\a', tty);
1250                                 echo_char_raw('\n', tty);
1251                                 process_echoes(tty);
1252                         }
1253                         goto handle_newline;
1254                 }
1255                 if (c == EOF_CHAR(tty)) {
1256                         if (tty->canon_head != tty->read_head)
1257                                 set_bit(TTY_PUSH, &tty->flags);
1258                         c = __DISABLED_CHAR;
1259                         goto handle_newline;
1260                 }
1261                 if ((c == EOL_CHAR(tty)) ||
1262                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1263                         /*
1264                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1265                          */
1266                         if (L_ECHO(tty)) {
1267                                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
1268                                         echo_char_raw('\a', 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 (I_PARMRK(tty) && c == (unsigned char) '\377')
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         if (L_ECHO(tty)) {
1297                 finish_erasing(tty);
1298                 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
1299                         /* beep if no space */
1300                         echo_char_raw('\a', tty);
1301                         process_echoes(tty);
1302                         return;
1303                 }
1304                 if (c == '\n')
1305                         echo_char_raw('\n', tty);
1306                 else {
1307                         /* Record the column of first canon char. */
1308                         if (tty->canon_head == tty->read_head)
1309                                 echo_set_canon_col(tty);
1310                         echo_char(c, tty);
1311                 }
1312                 process_echoes(tty);
1313         }
1314
1315         if (I_PARMRK(tty) && c == (unsigned char) '\377')
1316                 put_tty_queue(c, tty);
1317
1318         put_tty_queue(c, tty);
1319 }
1320
1321
1322 /**
1323  *      n_tty_write_wakeup      -       asynchronous I/O notifier
1324  *      @tty: tty device
1325  *
1326  *      Required for the ptys, serial driver etc. since processes
1327  *      that attach themselves to the master and rely on ASYNC
1328  *      IO must be woken up
1329  */
1330
1331 static void n_tty_write_wakeup(struct tty_struct *tty)
1332 {
1333         /* Write out any echoed characters that are still pending */
1334         process_echoes(tty);
1335
1336         if (tty->fasync) {
1337                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1338                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1339         }
1340 }
1341
1342 /**
1343  *      n_tty_receive_buf       -       data receive
1344  *      @tty: terminal device
1345  *      @cp: buffer
1346  *      @fp: flag buffer
1347  *      @count: characters
1348  *
1349  *      Called by the terminal driver when a block of characters has
1350  *      been received. This function must be called from soft contexts
1351  *      not from interrupt context. The driver is responsible for making
1352  *      calls one at a time and in order (or using flush_to_ldisc)
1353  */
1354
1355 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1356                               char *fp, int count)
1357 {
1358         const unsigned char *p;
1359         char *f, flags = TTY_NORMAL;
1360         int     i;
1361         char    buf[64];
1362         unsigned long cpuflags;
1363
1364         if (!tty->read_buf)
1365                 return;
1366
1367         if (tty->real_raw) {
1368                 spin_lock_irqsave(&tty->read_lock, cpuflags);
1369                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1370                         N_TTY_BUF_SIZE - tty->read_head);
1371                 i = min(count, i);
1372                 memcpy(tty->read_buf + tty->read_head, cp, i);
1373                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1374                 tty->read_cnt += i;
1375                 cp += i;
1376                 count -= i;
1377
1378                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1379                         N_TTY_BUF_SIZE - tty->read_head);
1380                 i = min(count, i);
1381                 memcpy(tty->read_buf + tty->read_head, cp, i);
1382                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1383                 tty->read_cnt += i;
1384                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1385         } else {
1386                 for (i = count, p = cp, f = fp; i; i--, p++) {
1387                         if (f)
1388                                 flags = *f++;
1389                         switch (flags) {
1390                         case TTY_NORMAL:
1391                                 n_tty_receive_char(tty, *p);
1392                                 break;
1393                         case TTY_BREAK:
1394                                 n_tty_receive_break(tty);
1395                                 break;
1396                         case TTY_PARITY:
1397                         case TTY_FRAME:
1398                                 n_tty_receive_parity_error(tty, *p);
1399                                 break;
1400                         case TTY_OVERRUN:
1401                                 n_tty_receive_overrun(tty);
1402                                 break;
1403                         default:
1404                                 printk(KERN_ERR "%s: unknown flag %d\n",
1405                                        tty_name(tty, buf), flags);
1406                                 break;
1407                         }
1408                 }
1409                 if (tty->ops->flush_chars)
1410                         tty->ops->flush_chars(tty);
1411         }
1412
1413         n_tty_set_room(tty);
1414
1415         if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1416                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1417                 if (waitqueue_active(&tty->read_wait))
1418                         wake_up_interruptible(&tty->read_wait);
1419         }
1420
1421         /*
1422          * Check the remaining room for the input canonicalization
1423          * mode.  We don't want to throttle the driver if we're in
1424          * canonical mode and don't have a newline yet!
1425          */
1426         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1427                 tty_throttle(tty);
1428 }
1429
1430 int is_ignored(int sig)
1431 {
1432         return (sigismember(&current->blocked, sig) ||
1433                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1434 }
1435
1436 /**
1437  *      n_tty_set_termios       -       termios data changed
1438  *      @tty: terminal
1439  *      @old: previous data
1440  *
1441  *      Called by the tty layer when the user changes termios flags so
1442  *      that the line discipline can plan ahead. This function cannot sleep
1443  *      and is protected from re-entry by the tty layer. The user is
1444  *      guaranteed that this function will not be re-entered or in progress
1445  *      when the ldisc is closed.
1446  *
1447  *      Locking: Caller holds tty->termios_mutex
1448  */
1449
1450 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1451 {
1452         int canon_change = 1;
1453         BUG_ON(!tty);
1454
1455         if (old)
1456                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1457         if (canon_change) {
1458                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1459                 tty->canon_head = tty->read_tail;
1460                 tty->canon_data = 0;
1461                 tty->erasing = 0;
1462         }
1463
1464         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1465                 wake_up_interruptible(&tty->read_wait);
1466
1467         tty->icanon = (L_ICANON(tty) != 0);
1468         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1469                 tty->raw = 1;
1470                 tty->real_raw = 1;
1471                 n_tty_set_room(tty);
1472                 return;
1473         }
1474         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1475             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1476             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1477             I_PARMRK(tty)) {
1478                 memset(tty->process_char_map, 0, 256/8);
1479
1480                 if (I_IGNCR(tty) || I_ICRNL(tty))
1481                         set_bit('\r', tty->process_char_map);
1482                 if (I_INLCR(tty))
1483                         set_bit('\n', tty->process_char_map);
1484
1485                 if (L_ICANON(tty)) {
1486                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1487                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1488                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1489                         set_bit('\n', tty->process_char_map);
1490                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1491                         if (L_IEXTEN(tty)) {
1492                                 set_bit(WERASE_CHAR(tty),
1493                                         tty->process_char_map);
1494                                 set_bit(LNEXT_CHAR(tty),
1495                                         tty->process_char_map);
1496                                 set_bit(EOL2_CHAR(tty),
1497                                         tty->process_char_map);
1498                                 if (L_ECHO(tty))
1499                                         set_bit(REPRINT_CHAR(tty),
1500                                                 tty->process_char_map);
1501                         }
1502                 }
1503                 if (I_IXON(tty)) {
1504                         set_bit(START_CHAR(tty), tty->process_char_map);
1505                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1506                 }
1507                 if (L_ISIG(tty)) {
1508                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1509                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1510                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1511                 }
1512                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1513                 tty->raw = 0;
1514                 tty->real_raw = 0;
1515         } else {
1516                 tty->raw = 1;
1517                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1518                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1519                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1520                         tty->real_raw = 1;
1521                 else
1522                         tty->real_raw = 0;
1523         }
1524         n_tty_set_room(tty);
1525         /* The termios change make the tty ready for I/O */
1526         wake_up_interruptible(&tty->write_wait);
1527         wake_up_interruptible(&tty->read_wait);
1528 }
1529
1530 /**
1531  *      n_tty_close             -       close the ldisc for this tty
1532  *      @tty: device
1533  *
1534  *      Called from the terminal layer when this line discipline is
1535  *      being shut down, either because of a close or becsuse of a
1536  *      discipline change. The function will not be called while other
1537  *      ldisc methods are in progress.
1538  */
1539
1540 static void n_tty_close(struct tty_struct *tty)
1541 {
1542         n_tty_flush_buffer(tty);
1543         if (tty->read_buf) {
1544                 free_buf(tty->read_buf);
1545                 tty->read_buf = NULL;
1546         }
1547         if (tty->echo_buf) {
1548                 free_buf(tty->echo_buf);
1549                 tty->echo_buf = NULL;
1550         }
1551 }
1552
1553 /**
1554  *      n_tty_open              -       open an ldisc
1555  *      @tty: terminal to open
1556  *
1557  *      Called when this line discipline is being attached to the
1558  *      terminal device. Can sleep. Called serialized so that no
1559  *      other events will occur in parallel. No further open will occur
1560  *      until a close.
1561  */
1562
1563 static int n_tty_open(struct tty_struct *tty)
1564 {
1565         if (!tty)
1566                 return -EINVAL;
1567
1568         /* These are ugly. Currently a malloc failure here can panic */
1569         if (!tty->read_buf) {
1570                 tty->read_buf = alloc_buf();
1571                 if (!tty->read_buf)
1572                         return -ENOMEM;
1573         }
1574         if (!tty->echo_buf) {
1575                 tty->echo_buf = alloc_buf();
1576                 if (!tty->echo_buf)
1577                         return -ENOMEM;
1578         }
1579         memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
1580         memset(tty->echo_buf, 0, N_TTY_BUF_SIZE);
1581         reset_buffer_flags(tty);
1582         tty->column = 0;
1583         n_tty_set_termios(tty, NULL);
1584         tty->minimum_to_wake = 1;
1585         tty->closing = 0;
1586         return 0;
1587 }
1588
1589 static inline int input_available_p(struct tty_struct *tty, int amt)
1590 {
1591         if (tty->icanon) {
1592                 if (tty->canon_data)
1593                         return 1;
1594         } else if (tty->read_cnt >= (amt ? amt : 1))
1595                 return 1;
1596
1597         return 0;
1598 }
1599
1600 /**
1601  *      copy_from_read_buf      -       copy read data directly
1602  *      @tty: terminal device
1603  *      @b: user data
1604  *      @nr: size of data
1605  *
1606  *      Helper function to speed up n_tty_read.  It is only called when
1607  *      ICANON is off; it copies characters straight from the tty queue to
1608  *      user space directly.  It can be profitably called twice; once to
1609  *      drain the space from the tail pointer to the (physical) end of the
1610  *      buffer, and once to drain the space from the (physical) beginning of
1611  *      the buffer to head pointer.
1612  *
1613  *      Called under the tty->atomic_read_lock sem
1614  *
1615  */
1616
1617 static int copy_from_read_buf(struct tty_struct *tty,
1618                                       unsigned char __user **b,
1619                                       size_t *nr)
1620
1621 {
1622         int retval;
1623         size_t n;
1624         unsigned long flags;
1625
1626         retval = 0;
1627         spin_lock_irqsave(&tty->read_lock, flags);
1628         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1629         n = min(*nr, n);
1630         spin_unlock_irqrestore(&tty->read_lock, flags);
1631         if (n) {
1632                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1633                 n -= retval;
1634                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1635                 spin_lock_irqsave(&tty->read_lock, flags);
1636                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1637                 tty->read_cnt -= n;
1638                 spin_unlock_irqrestore(&tty->read_lock, flags);
1639                 *b += n;
1640                 *nr -= n;
1641         }
1642         return retval;
1643 }
1644
1645 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1646                                                         size_t, loff_t *);
1647
1648 /**
1649  *      job_control             -       check job control
1650  *      @tty: tty
1651  *      @file: file handle
1652  *
1653  *      Perform job control management checks on this file/tty descriptor
1654  *      and if appropriate send any needed signals and return a negative
1655  *      error code if action should be taken.
1656  *
1657  *      FIXME:
1658  *      Locking: None - redirected write test is safe, testing
1659  *      current->signal should possibly lock current->sighand
1660  *      pgrp locking ?
1661  */
1662
1663 static int job_control(struct tty_struct *tty, struct file *file)
1664 {
1665         /* Job control check -- must be done at start and after
1666            every sleep (POSIX.1 7.1.1.4). */
1667         /* NOTE: not yet done after every sleep pending a thorough
1668            check of the logic of this change. -- jlc */
1669         /* don't stop on /dev/console */
1670         if (file->f_op->write != redirected_tty_write &&
1671             current->signal->tty == tty) {
1672                 if (!tty->pgrp)
1673                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1674                 else if (task_pgrp(current) != tty->pgrp) {
1675                         if (is_ignored(SIGTTIN) ||
1676                             is_current_pgrp_orphaned())
1677                                 return -EIO;
1678                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1679                         set_thread_flag(TIF_SIGPENDING);
1680                         return -ERESTARTSYS;
1681                 }
1682         }
1683         return 0;
1684 }
1685
1686
1687 /**
1688  *      n_tty_read              -       read function for tty
1689  *      @tty: tty device
1690  *      @file: file object
1691  *      @buf: userspace buffer pointer
1692  *      @nr: size of I/O
1693  *
1694  *      Perform reads for the line discipline. We are guaranteed that the
1695  *      line discipline will not be closed under us but we may get multiple
1696  *      parallel readers and must handle this ourselves. We may also get
1697  *      a hangup. Always called in user context, may sleep.
1698  *
1699  *      This code must be sure never to sleep through a hangup.
1700  */
1701
1702 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1703                          unsigned char __user *buf, size_t nr)
1704 {
1705         unsigned char __user *b = buf;
1706         DECLARE_WAITQUEUE(wait, current);
1707         int c;
1708         int minimum, time;
1709         ssize_t retval = 0;
1710         ssize_t size;
1711         long timeout;
1712         unsigned long flags;
1713         int packet;
1714
1715 do_it_again:
1716
1717         BUG_ON(!tty->read_buf);
1718
1719         c = job_control(tty, file);
1720         if (c < 0)
1721                 return c;
1722
1723         minimum = time = 0;
1724         timeout = MAX_SCHEDULE_TIMEOUT;
1725         if (!tty->icanon) {
1726                 time = (HZ / 10) * TIME_CHAR(tty);
1727                 minimum = MIN_CHAR(tty);
1728                 if (minimum) {
1729                         if (time)
1730                                 tty->minimum_to_wake = 1;
1731                         else if (!waitqueue_active(&tty->read_wait) ||
1732                                  (tty->minimum_to_wake > minimum))
1733                                 tty->minimum_to_wake = minimum;
1734                 } else {
1735                         timeout = 0;
1736                         if (time) {
1737                                 timeout = time;
1738                                 time = 0;
1739                         }
1740                         tty->minimum_to_wake = minimum = 1;
1741                 }
1742         }
1743
1744         /*
1745          *      Internal serialization of reads.
1746          */
1747         if (file->f_flags & O_NONBLOCK) {
1748                 if (!mutex_trylock(&tty->atomic_read_lock))
1749                         return -EAGAIN;
1750         } else {
1751                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1752                         return -ERESTARTSYS;
1753         }
1754         packet = tty->packet;
1755
1756         add_wait_queue(&tty->read_wait, &wait);
1757         while (nr) {
1758                 /* First test for status change. */
1759                 if (packet && tty->link->ctrl_status) {
1760                         unsigned char cs;
1761                         if (b != buf)
1762                                 break;
1763                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1764                         cs = tty->link->ctrl_status;
1765                         tty->link->ctrl_status = 0;
1766                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1767                         if (tty_put_user(tty, cs, b++)) {
1768                                 retval = -EFAULT;
1769                                 b--;
1770                                 break;
1771                         }
1772                         nr--;
1773                         break;
1774                 }
1775                 /* This statement must be first before checking for input
1776                    so that any interrupt will set the state back to
1777                    TASK_RUNNING. */
1778                 set_current_state(TASK_INTERRUPTIBLE);
1779
1780                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1781                     ((minimum - (b - buf)) >= 1))
1782                         tty->minimum_to_wake = (minimum - (b - buf));
1783
1784                 if (!input_available_p(tty, 0)) {
1785                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1786                                 retval = -EIO;
1787                                 break;
1788                         }
1789                         if (tty_hung_up_p(file))
1790                                 break;
1791                         if (!timeout)
1792                                 break;
1793                         if (file->f_flags & O_NONBLOCK) {
1794                                 retval = -EAGAIN;
1795                                 break;
1796                         }
1797                         if (signal_pending(current)) {
1798                                 retval = -ERESTARTSYS;
1799                                 break;
1800                         }
1801                         /* FIXME: does n_tty_set_room need locking ? */
1802                         n_tty_set_room(tty);
1803                         timeout = schedule_timeout(timeout);
1804                         continue;
1805                 }
1806                 __set_current_state(TASK_RUNNING);
1807
1808                 /* Deal with packet mode. */
1809                 if (packet && b == buf) {
1810                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1811                                 retval = -EFAULT;
1812                                 b--;
1813                                 break;
1814                         }
1815                         nr--;
1816                 }
1817
1818                 if (tty->icanon) {
1819                         /* N.B. avoid overrun if nr == 0 */
1820                         while (nr && tty->read_cnt) {
1821                                 int eol;
1822
1823                                 eol = test_and_clear_bit(tty->read_tail,
1824                                                 tty->read_flags);
1825                                 c = tty->read_buf[tty->read_tail];
1826                                 spin_lock_irqsave(&tty->read_lock, flags);
1827                                 tty->read_tail = ((tty->read_tail+1) &
1828                                                   (N_TTY_BUF_SIZE-1));
1829                                 tty->read_cnt--;
1830                                 if (eol) {
1831                                         /* this test should be redundant:
1832                                          * we shouldn't be reading data if
1833                                          * canon_data is 0
1834                                          */
1835                                         if (--tty->canon_data < 0)
1836                                                 tty->canon_data = 0;
1837                                 }
1838                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1839
1840                                 if (!eol || (c != __DISABLED_CHAR)) {
1841                                         if (tty_put_user(tty, c, b++)) {
1842                                                 retval = -EFAULT;
1843                                                 b--;
1844                                                 break;
1845                                         }
1846                                         nr--;
1847                                 }
1848                                 if (eol) {
1849                                         tty_audit_push(tty);
1850                                         break;
1851                                 }
1852                         }
1853                         if (retval)
1854                                 break;
1855                 } else {
1856                         int uncopied;
1857                         /* The copy function takes the read lock and handles
1858                            locking internally for this case */
1859                         uncopied = copy_from_read_buf(tty, &b, &nr);
1860                         uncopied += copy_from_read_buf(tty, &b, &nr);
1861                         if (uncopied) {
1862                                 retval = -EFAULT;
1863                                 break;
1864                         }
1865                 }
1866
1867                 /* If there is enough space in the read buffer now, let the
1868                  * low-level driver know. We use n_tty_chars_in_buffer() to
1869                  * check the buffer, as it now knows about canonical mode.
1870                  * Otherwise, if the driver is throttled and the line is
1871                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1872                  * we won't get any more characters.
1873                  */
1874                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1875                         n_tty_set_room(tty);
1876                         check_unthrottle(tty);
1877                 }
1878
1879                 if (b - buf >= minimum)
1880                         break;
1881                 if (time)
1882                         timeout = time;
1883         }
1884         mutex_unlock(&tty->atomic_read_lock);
1885         remove_wait_queue(&tty->read_wait, &wait);
1886
1887         if (!waitqueue_active(&tty->read_wait))
1888                 tty->minimum_to_wake = minimum;
1889
1890         __set_current_state(TASK_RUNNING);
1891         size = b - buf;
1892         if (size) {
1893                 retval = size;
1894                 if (nr)
1895                         clear_bit(TTY_PUSH, &tty->flags);
1896         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1897                  goto do_it_again;
1898
1899         n_tty_set_room(tty);
1900         return retval;
1901 }
1902
1903 /**
1904  *      n_tty_write             -       write function for tty
1905  *      @tty: tty device
1906  *      @file: file object
1907  *      @buf: userspace buffer pointer
1908  *      @nr: size of I/O
1909  *
1910  *      Write function of the terminal device.  This is serialized with
1911  *      respect to other write callers but not to termios changes, reads
1912  *      and other such events.  Since the receive code will echo characters,
1913  *      thus calling driver write methods, the output_lock is used in
1914  *      the output processing functions called here as well as in the
1915  *      echo processing function to protect the column state and space
1916  *      left in the buffer.
1917  *
1918  *      This code must be sure never to sleep through a hangup.
1919  *
1920  *      Locking: output_lock to protect column state and space left
1921  *               (note that the process_output*() functions take this
1922  *                lock themselves)
1923  */
1924
1925 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1926                            const unsigned char *buf, size_t nr)
1927 {
1928         const unsigned char *b = buf;
1929         DECLARE_WAITQUEUE(wait, current);
1930         int c;
1931         ssize_t retval = 0;
1932
1933         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1934         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1935                 retval = tty_check_change(tty);
1936                 if (retval)
1937                         return retval;
1938         }
1939
1940         /* Write out any echoed characters that are still pending */
1941         process_echoes(tty);
1942
1943         add_wait_queue(&tty->write_wait, &wait);
1944         while (1) {
1945                 set_current_state(TASK_INTERRUPTIBLE);
1946                 if (signal_pending(current)) {
1947                         retval = -ERESTARTSYS;
1948                         break;
1949                 }
1950                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1951                         retval = -EIO;
1952                         break;
1953                 }
1954                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1955                         while (nr > 0) {
1956                                 ssize_t num = process_output_block(tty, b, nr);
1957                                 if (num < 0) {
1958                                         if (num == -EAGAIN)
1959                                                 break;
1960                                         retval = num;
1961                                         goto break_out;
1962                                 }
1963                                 b += num;
1964                                 nr -= num;
1965                                 if (nr == 0)
1966                                         break;
1967                                 c = *b;
1968                                 if (process_output(c, tty) < 0)
1969                                         break;
1970                                 b++; nr--;
1971                         }
1972                         if (tty->ops->flush_chars)
1973                                 tty->ops->flush_chars(tty);
1974                 } else {
1975                         while (nr > 0) {
1976                                 c = tty->ops->write(tty, b, nr);
1977                                 if (c < 0) {
1978                                         retval = c;
1979                                         goto break_out;
1980                                 }
1981                                 if (!c)
1982                                         break;
1983                                 b += c;
1984                                 nr -= c;
1985                         }
1986                 }
1987                 if (!nr)
1988                         break;
1989                 if (file->f_flags & O_NONBLOCK) {
1990                         retval = -EAGAIN;
1991                         break;
1992                 }
1993                 schedule();
1994         }
1995 break_out:
1996         __set_current_state(TASK_RUNNING);
1997         remove_wait_queue(&tty->write_wait, &wait);
1998         return (b - buf) ? b - buf : retval;
1999 }
2000
2001 /**
2002  *      n_tty_poll              -       poll method for N_TTY
2003  *      @tty: terminal device
2004  *      @file: file accessing it
2005  *      @wait: poll table
2006  *
2007  *      Called when the line discipline is asked to poll() for data or
2008  *      for special events. This code is not serialized with respect to
2009  *      other events save open/close.
2010  *
2011  *      This code must be sure never to sleep through a hangup.
2012  *      Called without the kernel lock held - fine
2013  */
2014
2015 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2016                                                         poll_table *wait)
2017 {
2018         unsigned int mask = 0;
2019
2020         poll_wait(file, &tty->read_wait, wait);
2021         poll_wait(file, &tty->write_wait, wait);
2022         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2023                 mask |= POLLIN | POLLRDNORM;
2024         if (tty->packet && tty->link->ctrl_status)
2025                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2026         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2027                 mask |= POLLHUP;
2028         if (tty_hung_up_p(file))
2029                 mask |= POLLHUP;
2030         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2031                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2032                         tty->minimum_to_wake = MIN_CHAR(tty);
2033                 else
2034                         tty->minimum_to_wake = 1;
2035         }
2036         if (tty->ops->write && !tty_is_writelocked(tty) &&
2037                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2038                         tty_write_room(tty) > 0)
2039                 mask |= POLLOUT | POLLWRNORM;
2040         return mask;
2041 }
2042
2043 static unsigned long inq_canon(struct tty_struct *tty)
2044 {
2045         int nr, head, tail;
2046
2047         if (!tty->canon_data)
2048                 return 0;
2049         head = tty->canon_head;
2050         tail = tty->read_tail;
2051         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2052         /* Skip EOF-chars.. */
2053         while (head != tail) {
2054                 if (test_bit(tail, tty->read_flags) &&
2055                     tty->read_buf[tail] == __DISABLED_CHAR)
2056                         nr--;
2057                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2058         }
2059         return nr;
2060 }
2061
2062 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2063                        unsigned int cmd, unsigned long arg)
2064 {
2065         int retval;
2066
2067         switch (cmd) {
2068         case TIOCOUTQ:
2069                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2070         case TIOCINQ:
2071                 /* FIXME: Locking */
2072                 retval = tty->read_cnt;
2073                 if (L_ICANON(tty))
2074                         retval = inq_canon(tty);
2075                 return put_user(retval, (unsigned int __user *) arg);
2076         default:
2077                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2078         }
2079 }
2080
2081 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2082         .magic           = TTY_LDISC_MAGIC,
2083         .name            = "n_tty",
2084         .open            = n_tty_open,
2085         .close           = n_tty_close,
2086         .flush_buffer    = n_tty_flush_buffer,
2087         .chars_in_buffer = n_tty_chars_in_buffer,
2088         .read            = n_tty_read,
2089         .write           = n_tty_write,
2090         .ioctl           = n_tty_ioctl,
2091         .set_termios     = n_tty_set_termios,
2092         .poll            = n_tty_poll,
2093         .receive_buf     = n_tty_receive_buf,
2094         .write_wakeup    = n_tty_write_wakeup
2095 };