aboutsummaryrefslogtreecommitdiff
path: root/sim/common/callback.c
blob: 570438253cfec9973b461d31c94e2042422b0bb2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
/* Remote target callback routines.
   Copyright 1995, 1996, 1997, 2000, 2002, 2003, 2004, 2007, 2008, 2009
   Free Software Foundation, Inc.
   Contributed by Cygnus Solutions.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* This file provides a standard way for targets to talk to the host OS
   level.  */

#ifdef HAVE_CONFIG_H
#include "cconfig.h"
#endif
#include "ansidecl.h"
#include <stdarg.h>
#include <stdio.h>
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#else
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#endif
#ifdef HAVE_LIMITS_H
/* For PIPE_BUF.  */
#include <limits.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "gdb/callback.h"
#include "targ-vals.h"
/* For xmalloc.  */
#include "libiberty.h"

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifndef PIPE_BUF
#define PIPE_BUF 512
#endif

/* ??? sim_cb_printf should be cb_printf, but until the callback support is
   broken out of the simulator directory, these are here to not require
   sim-utils.h.  */
void sim_cb_printf PARAMS ((host_callback *, const char *, ...));
void sim_cb_eprintf PARAMS ((host_callback *, const char *, ...));

extern CB_TARGET_DEFS_MAP cb_init_syscall_map[];
extern CB_TARGET_DEFS_MAP cb_init_errno_map[];
extern CB_TARGET_DEFS_MAP cb_init_open_map[];

extern int system PARAMS ((const char *));

static int os_init PARAMS ((host_callback *));
static int os_shutdown PARAMS ((host_callback *));
static int os_unlink PARAMS ((host_callback *, const char *));
static long os_time PARAMS ((host_callback *, long *));
static int os_system PARAMS ((host_callback *, const char *));
static int os_rename PARAMS ((host_callback *, const char *, const char *));
static int os_write_stdout PARAMS ((host_callback *, const char *, int));
static void os_flush_stdout PARAMS ((host_callback *));
static int os_write_stderr PARAMS ((host_callback *, const char *, int));
static void os_flush_stderr PARAMS ((host_callback *));
static int os_write PARAMS ((host_callback *, int, const char *, int));
static int os_read_stdin PARAMS ((host_callback *, char *, int));
static int os_read PARAMS ((host_callback *, int, char *, int));
static int os_open PARAMS ((host_callback *, const char *, int));
static int os_lseek PARAMS ((host_callback *, int, long, int));
static int os_isatty PARAMS ((host_callback *, int));
static int os_get_errno PARAMS ((host_callback *));
static int os_close PARAMS ((host_callback *, int));
static void os_vprintf_filtered PARAMS ((host_callback *, const char *, va_list));
static void os_evprintf_filtered PARAMS ((host_callback *, const char *, va_list));
static void os_error PARAMS ((host_callback *, const char *, ...))
#ifdef __GNUC__
  __attribute__ ((__noreturn__))
#endif
  ;
static int fdmap PARAMS ((host_callback *, int));
static int fdbad PARAMS ((host_callback *, int));
static int wrap PARAMS ((host_callback *, int));

/* Set the callback copy of errno from what we see now.  */

static int 
wrap (p, val)
     host_callback *p;
     int val;
{
  p->last_errno = errno;
  return val;
}

/* Make sure the FD provided is ok.  If not, return non-zero
   and set errno. */

static int 
fdbad (p, fd)
     host_callback *p;
     int fd;
{
  if (fd < 0 || fd > MAX_CALLBACK_FDS || p->fd_buddy[fd] < 0)
    {
      p->last_errno = EINVAL;
      return -1;
    }
  return 0;
}

static int 
fdmap (p, fd)
     host_callback *p;
     int fd;
{
  return p->fdmap[fd];
}

static int 
os_close (p, fd)
     host_callback *p;
     int fd;
{
  int result;
  int i, next;

  result = fdbad (p, fd);
  if (result)
    return result;
  /* If this file descripter has one or more buddies (originals /
     duplicates from a dup), just remove it from the circular list.  */
  for (i = fd; (next = p->fd_buddy[i]) != fd; )
    i = next;
  if (fd != i)
    p->fd_buddy[i] = p->fd_buddy[fd];
  else
    {
      if (p->ispipe[fd])
	{
	  int other = p->ispipe[fd];
	  int reader, writer;

	  if (other > 0)
	    {
	      /* Closing the read side.  */
	      reader = fd;
	      writer = other;
	    }
	  else
	    {
	      /* Closing the write side.  */
	      writer = fd;
	      reader = -other;
	    }

	  /* If there was data in the buffer, make a last "now empty"
	     call, then deallocate data.  */
	  if (p->pipe_buffer[writer].buffer != NULL)
	    {
	      (*p->pipe_empty) (p, reader, writer);
	      free (p->pipe_buffer[writer].buffer);
	      p->pipe_buffer[writer].buffer = NULL;
	    }

	  /* Clear pipe data for this side.  */
	  p->pipe_buffer[fd].size = 0;
	  p->ispipe[fd] = 0;

	  /* If this was the first close, mark the other side as the
	     only remaining side.  */
	  if (fd != abs (other))
	    p->ispipe[abs (other)] = -other;
	  p->fd_buddy[fd] = -1;
	  return 0;
	}

      result = wrap (p, close (fdmap (p, fd)));
    }
  p->fd_buddy[fd] = -1;

  return result;
}


/* taken from gdb/util.c:notice_quit() - should be in a library */


#if defined(__GO32__) || defined (_MSC_VER)
static int
os_poll_quit (p)
     host_callback *p;
{
#if defined(__GO32__)
  int kbhit ();
  int getkey ();
  if (kbhit ())
    {
      int k = getkey ();
      if (k == 1)
	{
	  return 1;
	}
      else if (k == 2)
	{
	  return 1;
	}
      else 
	{
	  sim_cb_eprintf (p, "CTRL-A to quit, CTRL-B to quit harder\n");
	}
    }
#endif
#if defined (_MSC_VER)
  /* NB - this will not compile! */
  int k = win32pollquit();
  if (k == 1)
    return 1;
  else if (k == 2)
    return 1;
#endif
  return 0;
}
#else
#define os_poll_quit 0
#endif /* defined(__GO32__) || defined(_MSC_VER) */

static int 
os_get_errno (p)
     host_callback *p;
{
  return cb_host_to_target_errno (p, p->last_errno);
}


static int 
os_isatty (p, fd)
     host_callback *p;
     int fd;
{
  int result;

  result = fdbad (p, fd);
  if (result)
    return result;
  result = wrap (p, isatty (fdmap (p, fd)));

  return result;
}

static int 
os_lseek (p, fd, off, way)
     host_callback *p;
     int fd;
     long off;
     int way;
{
  int result;

  result = fdbad (p, fd);
  if (result)
    return result;
  result = lseek (fdmap (p, fd), off, way);
  return result;
}

static int 
os_open (p, name, flags)
     host_callback *p;
     const char *name;
     int flags;
{
  int i;
  for (i = 0; i < MAX_CALLBACK_FDS; i++)
    {
      if (p->fd_buddy[i] < 0)
	{
	  int f = open (name, cb_target_to_host_open (p, flags), 0644);
	  if (f < 0)
	    {
	      p->last_errno = errno;
	      return f;
	    }
	  p->fd_buddy[i] = i;
	  p->fdmap[i] = f;
	  return i;
	}
    }
  p->last_errno = EMFILE;
  return -1;
}

static int 
os_read (p, fd, buf, len)
     host_callback *p;
     int fd;
     char *buf;
     int len;
{
  int result;

  result = fdbad (p, fd);
  if (result)
    return result;
  if (p->ispipe[fd])
    {
      int writer = p->ispipe[fd];

      /* Can't read from the write-end.  */
      if (writer < 0)
	{
	  p->last_errno = EBADF;
	  return -1;
	}

      /* Nothing to read if nothing is written.  */
      if (p->pipe_buffer[writer].size == 0)
	return 0;

      /* Truncate read request size to buffer size minus what's already
         read.  */
      if (len > p->pipe_buffer[writer].size - p->pipe_buffer[fd].size)
	len = p->pipe_buffer[writer].size - p->pipe_buffer[fd].size;

      memcpy (buf, p->pipe_buffer[writer].buffer + p->pipe_buffer[fd].size,
	      len);

      /* Account for what we just read.  */
      p->pipe_buffer[fd].size += len;

      /* If we've read everything, empty and deallocate the buffer and
	 signal buffer-empty to client.  (This isn't expected to be a
	 hot path in the simulator, so we don't hold on to the buffer.)  */
      if (p->pipe_buffer[fd].size == p->pipe_buffer[writer].size)
	{
	  free (p->pipe_buffer[writer].buffer);
	  p->pipe_buffer[writer].buffer = NULL;
	  p->pipe_buffer[fd].size = 0;
	  p->pipe_buffer[writer].size = 0;
	  (*p->pipe_empty) (p, fd, writer);
	}

      return len;
    }

  result = wrap (p, read (fdmap (p, fd), buf, len));
  return result;
}

static int 
os_read_stdin (p, buf, len)
     host_callback *p;
     char *buf;
     int len;
{
  return wrap (p, read (0, buf, len));
}

static int 
os_write (p, fd, buf, len)
     host_callback *p;
     int fd;
     const char *buf;
     int len;
{
  int result;
  int real_fd;

  result = fdbad (p, fd);
  if (result)
    return result;

  if (p->ispipe[fd])
    {
      int reader = -p->ispipe[fd];

      /* Can't write to the read-end.  */
      if (reader < 0)
	{
	  p->last_errno = EBADF;
	  return -1;
	}

      /* Can't write to pipe with closed read end.
	 FIXME: We should send a SIGPIPE.  */
      if (reader == fd)
	{
	  p->last_errno = EPIPE;
	  return -1;
	}

      /* As a sanity-check, we bail out it the buffered contents is much
	 larger than the size of the buffer on the host.  We don't want
	 to run out of memory in the simulator due to a target program
	 bug if we can help it.  Unfortunately, regarding the value that
	 reaches the simulated program, it's no use returning *less*
	 than the requested amount, because cb_syscall loops calling
	 this function until the whole amount is done.  */
      if (p->pipe_buffer[fd].size + len > 10 * PIPE_BUF)
	{
	  p->last_errno = EFBIG;
	  return -1;
	}

      p->pipe_buffer[fd].buffer
	= xrealloc (p->pipe_buffer[fd].buffer, p->pipe_buffer[fd].size + len);
      memcpy (p->pipe_buffer[fd].buffer + p->pipe_buffer[fd].size,
	      buf, len);
      p->pipe_buffer[fd].size += len;

      (*p->pipe_nonempty) (p, reader, fd);
      return len;
    }

  real_fd = fdmap (p, fd);
  switch (real_fd)
    {
    default:
      result = wrap (p, write (real_fd, buf, len));
      break;
    case 1:
      result = p->write_stdout (p, buf, len);
      break;
    case 2:
      result = p->write_stderr (p, buf, len);
      break;
    }
  return result;
}

static int 
os_write_stdout (p, buf, len)
     host_callback *p ATTRIBUTE_UNUSED;
     const char *buf;
     int len;
{
  return fwrite (buf, 1, len, stdout);
}

static void
os_flush_stdout (p)
     host_callback *p ATTRIBUTE_UNUSED;
{
  fflush (stdout);
}

static int 
os_write_stderr (p, buf, len)
     host_callback *p ATTRIBUTE_UNUSED;
     const char *buf;
     int len;
{
  return fwrite (buf, 1, len, stderr);
}

static void
os_flush_stderr (p)
     host_callback *p ATTRIBUTE_UNUSED;
{
  fflush (stderr);
}

static int 
os_rename (p, f1, f2)
     host_callback *p;
     const char *f1;
     const char *f2;
{
  return wrap (p, rename (f1, f2));
}


static int
os_system (p, s)
     host_callback *p;
     const char *s;
{
  return wrap (p, system (s));
}

static long 
os_time (p, t)
     host_callback *p;
     long *t;
{
  return wrap (p, time (t));
}


static int 
os_unlink (p, f1)
     host_callback *p;
     const char *f1;
{
  return wrap (p, unlink (f1));
}

static int
os_stat (p, file, buf)
     host_callback *p;
     const char *file;
     struct stat *buf;
{
  /* ??? There is an issue of when to translate to the target layout.
     One could do that inside this function, or one could have the
     caller do it.  It's more flexible to let the caller do it, though
     I'm not sure the flexibility will ever be useful.  */
  return wrap (p, stat (file, buf));
}

static int
os_fstat (p, fd, buf)
     host_callback *p;
     int fd;
     struct stat *buf;
{
  if (fdbad (p, fd))
    return -1;

  if (p->ispipe[fd])
    {
#if defined (HAVE_STRUCT_STAT_ST_ATIME) || defined (HAVE_STRUCT_STAT_ST_CTIME) || defined (HAVE_STRUCT_STAT_ST_MTIME)
      time_t t = (*p->time) (p, NULL);
#endif

      /* We have to fake the struct stat contents, since the pipe is
	 made up in the simulator.  */
      memset (buf, 0, sizeof (*buf));

#ifdef HAVE_STRUCT_STAT_ST_MODE
      buf->st_mode = S_IFIFO;
#endif

      /* If more accurate tracking than current-time is needed (for
	 example, on GNU/Linux we get accurate numbers), the p->time
	 callback (which may be something other than os_time) should
	 happen for each read and write, and we'd need to keep track of
	 atime, ctime and mtime.  */
#ifdef HAVE_STRUCT_STAT_ST_ATIME
      buf->st_atime = t;
#endif
#ifdef HAVE_STRUCT_STAT_ST_CTIME
      buf->st_ctime = t;
#endif
#ifdef HAVE_STRUCT_STAT_ST_MTIME
      buf->st_mtime = t;
#endif
      return 0;
    }

  /* ??? There is an issue of when to translate to the target layout.
     One could do that inside this function, or one could have the
     caller do it.  It's more flexible to let the caller do it, though
     I'm not sure the flexibility will ever be useful.  */
  return wrap (p, fstat (fdmap (p, fd), buf));
}

static int
os_lstat (p, file, buf)
     host_callback *p;
     const char *file;
     struct stat *buf;
{
  /* NOTE: hpn/2004-12-12: Same issue here as with os_fstat.  */
#ifdef HAVE_LSTAT
  return wrap (p, lstat (file, buf));
#else
  return wrap (p, stat (file, buf));
#endif
}

static int 
os_ftruncate (p, fd, len)
     host_callback *p;
     int fd;
     long len;
{
  int result;

  result = fdbad (p, fd);
  if (p->ispipe[fd])
    {
      p->last_errno = EINVAL;
      return -1;
    }
  if (result)
    return result;
#ifdef HAVE_FTRUNCATE
  result = wrap (p, ftruncate (fdmap (p, fd), len));
#else
  p->last_errno = EINVAL;
  result = -1;
#endif
  return result;
}

static int
os_truncate (p, file, len)
     host_callback *p;
     const char *file;
     long len;
{
#ifdef HAVE_TRUNCATE
  return wrap (p, truncate (file, len));
#else
  p->last_errno = EINVAL;
  return -1;
#endif
}

static int
os_pipe (p, filedes)
     host_callback *p;
     int *filedes;
{
  int i;

  /* We deliberately don't use fd 0.  It's probably stdin anyway.  */
  for (i = 1; i < MAX_CALLBACK_FDS; i++)
    {
      int j;

      if (p->fd_buddy[i] < 0)
	for (j = i + 1; j < MAX_CALLBACK_FDS; j++)
	  if (p->fd_buddy[j] < 0)
	    {
	      /* Found two free fd:s.  Set stat to allocated and mark
		 pipeness.  */
	      p->fd_buddy[i] = i;
	      p->fd_buddy[j] = j;
	      p->ispipe[i] = j;
	      p->ispipe[j] = -i;
	      filedes[0] = i;
	      filedes[1] = j;

	      /* Poison the FD map to make bugs apparent.  */
	      p->fdmap[i] = -1;
	      p->fdmap[j] = -1;
	      return 0;
	    }
    }

  p->last_errno = EMFILE;
  return -1;
}

/* Stub functions for pipe support.  They should always be overridden in
   targets using the pipe support, but that's up to the target.  */

/* Called when the simulator says that the pipe at (reader, writer) is
   now empty (so the writer should leave its waiting state).  */

static void
os_pipe_empty (p, reader, writer)
     host_callback *p;
     int reader;
     int writer;
{
}

/* Called when the simulator says the pipe at (reader, writer) is now
   non-empty (so the writer should wait).  */

static void
os_pipe_nonempty (p, reader, writer)
     host_callback *p;
     int reader;
     int writer;
{
}

static int
os_shutdown (p)
     host_callback *p;
{
  int i, next, j;
  for (i = 0; i < MAX_CALLBACK_FDS; i++)
    {
      int do_close = 1;

      /* Zero out all pipe state.  Don't call callbacks for non-empty
	 pipes; the target program has likely terminated at this point
	 or we're called at initialization time.  */
      p->ispipe[i] = 0;
      p->pipe_buffer[i].size = 0;
      p->pipe_buffer[i].buffer = NULL;

      next = p->fd_buddy[i];
      if (next < 0)
	continue;
      do
	{
	  j = next;
	  if (j == MAX_CALLBACK_FDS)
	    do_close = 0;
	  next = p->fd_buddy[j];
	  p->fd_buddy[j] = -1;
	  /* At the initial call of os_init, we got -1, 0, 0, 0, ...  */
	  if (next < 0)
	    {
	      p->fd_buddy[i] = -1;
	      do_close = 0;
	      break;
	    }
	}
      while (j != i);
      if (do_close)
	close (p->fdmap[i]);
    }
  return 1;
}

static int
os_init (p)
     host_callback *p;
{
  int i;

  os_shutdown (p);
  for (i = 0; i < 3; i++)
    {
      p->fdmap[i] = i;
      p->fd_buddy[i] = i - 1;
    }
  p->fd_buddy[0] = MAX_CALLBACK_FDS;
  p->fd_buddy[MAX_CALLBACK_FDS] = 2;

  p->syscall_map = cb_init_syscall_map;
  p->errno_map = cb_init_errno_map;
  p->open_map = cb_init_open_map;

  return 1;
}

/* DEPRECATED */

/* VARARGS */
static void
os_printf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, ...)
{
  va_list args;
  va_start (args, format);

  vfprintf (stdout, format, args);
  va_end (args);
}

/* VARARGS */
static void
os_vprintf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, va_list args)
{
  vprintf (format, args);
}

/* VARARGS */
static void
os_evprintf_filtered (host_callback *p ATTRIBUTE_UNUSED, const char *format, va_list args)
{
  vfprintf (stderr, format, args);
}

/* VARARGS */
static void
os_error (host_callback *p ATTRIBUTE_UNUSED, const char *format, ...)
{
  va_list args;
  va_start (args, format);

  vfprintf (stderr, format, args);
  fprintf (stderr, "\n");

  va_end (args);
  exit (1);
}

host_callback default_callback =
{
  os_close,
  os_get_errno,
  os_isatty,
  os_lseek,
  os_open,
  os_read,
  os_read_stdin,
  os_rename,
  os_system,
  os_time,
  os_unlink,
  os_write,
  os_write_stdout,
  os_flush_stdout,
  os_write_stderr,
  os_flush_stderr,

  os_stat,
  os_fstat,
  os_lstat,

  os_ftruncate,
  os_truncate,

  os_pipe,
  os_pipe_empty,
  os_pipe_nonempty,

  os_poll_quit,

  os_shutdown,
  os_init,

  os_printf_filtered,  /* deprecated */

  os_vprintf_filtered,
  os_evprintf_filtered,
  os_error,

  0, 		/* last errno */

  { 0, },	/* fdmap */
  { -1, },	/* fd_buddy */
  { 0, },	/* ispipe */
  { { 0, 0 }, }, /* pipe_buffer */

  0, /* syscall_map */
  0, /* errno_map */
  0, /* open_map */
  0, /* signal_map */
  0, /* stat_map */
	
  /* Defaults expected to be overridden at initialization, where needed.  */
  BFD_ENDIAN_UNKNOWN, /* target_endian */
  4, /* target_sizeof_int */

  HOST_CALLBACK_MAGIC,
};

/* Read in a file describing the target's system call values.
   E.g. maybe someone will want to use something other than newlib.
   This assumes that the basic system call recognition and value passing/
   returning is supported.  So maybe some coding/recompilation will be
   necessary, but not as much.

   If an error occurs, the existing mapping is not changed.  */

CB_RC
cb_read_target_syscall_maps (cb, file)
     host_callback *cb;
     const char *file;
{
  CB_TARGET_DEFS_MAP *syscall_map, *errno_map, *open_map, *signal_map;
  const char *stat_map;
  FILE *f;

  if ((f = fopen (file, "r")) == NULL)
    return CB_RC_ACCESS;

  /* ... read in and parse file ... */

  fclose (f);
  return CB_RC_NO_MEM; /* FIXME:wip */

  /* Free storage allocated for any existing maps.  */
  if (cb->syscall_map)
    free (cb->syscall_map);
  if (cb->errno_map)
    free (cb->errno_map);
  if (cb->open_map)
    free (cb->open_map);
  if (cb->signal_map)
    free (cb->signal_map);
  if (cb->stat_map)
    free ((PTR) cb->stat_map);

  cb->syscall_map = syscall_map;
  cb->errno_map = errno_map;
  cb->open_map = open_map;
  cb->signal_map = signal_map;
  cb->stat_map = stat_map;

  return CB_RC_OK;
}

/* Translate the target's version of a syscall number to the host's.
   This isn't actually the host's version, rather a canonical form.
   ??? Perhaps this should be renamed to ..._canon_syscall.  */

int
cb_target_to_host_syscall (cb, target_val)
     host_callback *cb;
     int target_val;
{
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->syscall_map[0]; m->target_val != -1; ++m)
    if (m->target_val == target_val)
      return m->host_val;

  return -1;
}

/* FIXME: sort tables if large.
   Alternatively, an obvious improvement for errno conversion is
   to machine generate a function with a large switch().  */

/* Translate the host's version of errno to the target's.  */

int
cb_host_to_target_errno (cb, host_val)
     host_callback *cb;
     int host_val;
{
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->errno_map[0]; m->host_val; ++m)
    if (m->host_val == host_val)
      return m->target_val;

  /* ??? Which error to return in this case is up for grabs.
     Note that some missing values may have standard alternatives.
     For now return 0 and require caller to deal with it.  */
  return 0;
}

/* Given a set of target bitmasks for the open system call,
   return the host equivalent.
   Mapping open flag values is best done by looping so there's no need
   to machine generate this function.  */

int
cb_target_to_host_open (cb, target_val)
     host_callback *cb;
     int target_val;
{
  int host_val = 0;
  CB_TARGET_DEFS_MAP *m;

  for (m = &cb->open_map[0]; m->host_val != -1; ++m)
    {
      switch (m->target_val)
	{
	  /* O_RDONLY can be (and usually is) 0 which needs to be treated
	     specially.  */
	case TARGET_O_RDONLY :
	case TARGET_O_WRONLY :
	case TARGET_O_RDWR :
	  if ((target_val & (TARGET_O_RDONLY | TARGET_O_WRONLY | TARGET_O_RDWR))
	      == m->target_val)
	    host_val |= m->host_val;
	  /* Handle the host/target differentiating between binary and
             text mode.  Only one case is of importance */
#if ! defined (TARGET_O_BINARY) && defined (O_BINARY)
	  host_val |= O_BINARY;
#endif
	  break;
	default :
	  if ((m->target_val & target_val) == m->target_val)
	    host_val |= m->host_val;
	  break;
	}
    }

  return host_val;
}

/* Utility for e.g. cb_host_to_target_stat to store values in the target's
   stat struct.  */

void
cb_store_target_endian (cb, p, size, val)
     host_callback *cb;
     char *p;
     int size;
     long val; /* ??? must be as big as target word size */
{
  if (cb->target_endian == BFD_ENDIAN_BIG)
    {
      p += size;
      while (size-- > 0)
	{
	  *--p = val;
	  val >>= 8;
	}
    }
  else
    {
      while (size-- > 0)
	{
	  *p++ = val;
	  val >>= 8;
	}
    }
}

/* Translate a host's stat struct into a target's.
   If HS is NULL, just compute the length of the buffer required,
   TS is ignored.

   The result is the size of the target's stat struct,
   or zero if an error occurred during the translation.  */

int
cb_host_to_target_stat (cb, hs, ts)
     host_callback *cb;
     const struct stat *hs;
     PTR ts;
{
  const char *m = cb->stat_map;
  char *p;

  if (hs == NULL)
    ts = NULL;
  p = ts;

  while (m)
    {
      char *q = strchr (m, ',');
      int size;

      /* FIXME: Use sscanf? */
      if (q == NULL)
	{
	  /* FIXME: print error message */
	  return 0;
	}
      size = atoi (q + 1);
      if (size == 0)
	{
	  /* FIXME: print error message */
	  return 0;
	}

      if (hs != NULL)
	{
	  if (0)
	    ;
	  /* Defined here to avoid emacs indigestion on a lone "else".  */
#undef ST_x
#define ST_x(FLD)					\
	  else if (strncmp (m, #FLD, q - m) == 0)	\
	    cb_store_target_endian (cb, p, size, hs->FLD)

#ifdef HAVE_STRUCT_STAT_ST_DEV
	  ST_x (st_dev);
#endif
#ifdef HAVE_STRUCT_STAT_ST_INO
	  ST_x (st_ino);
#endif
#ifdef HAVE_STRUCT_STAT_ST_MODE
	  ST_x (st_mode);
#endif
#ifdef HAVE_STRUCT_STAT_ST_NLINK
	  ST_x (st_nlink);
#endif
#ifdef HAVE_STRUCT_STAT_ST_UID
	  ST_x (st_uid);
#endif
#ifdef HAVE_STRUCT_STAT_ST_GID
	  ST_x (st_gid);
#endif
#ifdef HAVE_STRUCT_STAT_ST_RDEV
	  ST_x (st_rdev);
#endif
#ifdef HAVE_STRUCT_STAT_ST_SIZE
	  ST_x (st_size);
#endif
#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
	  ST_x (st_blksize);
#endif
#ifdef HAVE_STRUCT_STAT_ST_BLOCKS
	  ST_x (st_blocks);
#endif
#ifdef HAVE_STRUCT_STAT_ST_ATIME
	  ST_x (st_atime);
#endif
#ifdef HAVE_STRUCT_STAT_ST_MTIME
	  ST_x (st_mtime);
#endif
#ifdef HAVE_STRUCT_STAT_ST_CTIME
	  ST_x (st_ctime);
#endif
#undef ST_x
	  /* FIXME:wip */
	  else
	    /* Unsupported field, store 0.  */
	    cb_store_target_endian (cb, p, size, 0);
	}

      p += size;
      m = strchr (q, ':');
      if (m)
	++m;
    }

  return p - (char *) ts;
}

/* Cover functions to the vfprintf callbacks.

   ??? If one thinks of the callbacks as a subsystem onto itself [or part of
   a larger "remote target subsystem"] with a well defined interface, then
   one would think that the subsystem would provide these.  However, until
   one is allowed to create such a subsystem (with its own source tree
   independent of any particular user), such a critter can't exist.  Thus
   these functions are here for the time being.  */

void
sim_cb_printf (host_callback *p, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  p->vprintf_filtered (p, fmt, ap);
  va_end (ap);
}

void
sim_cb_eprintf (host_callback *p, const char *fmt, ...)
{
  va_list ap;

  va_start (ap, fmt);
  p->evprintf_filtered (p, fmt, ap);
  va_end (ap);
}

int
cb_is_stdin (host_callback *cb, int fd)
{
  return fdbad (cb, fd) ? 0 : fdmap (cb, fd) == 0;
}

int
cb_is_stdout (host_callback *cb, int fd)
{
  return fdbad (cb, fd) ? 0 : fdmap (cb, fd) == 1;
}

int
cb_is_stderr (host_callback *cb, int fd)
{
  return fdbad (cb, fd) ? 0 : fdmap (cb, fd) == 2;
}