aboutsummaryrefslogtreecommitdiff
path: root/gdb/dwarf2-frame.c
blob: 7dbd0dbf753faac7cda5c41bc9c102bea6e24061 (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
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
/* Frame unwinder for frames with DWARF Call Frame Information.

   Copyright 2003 Free Software Foundation, Inc.

   Contributed by Mark Kettenis.

   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 2 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, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "dwarf2expr.h"
#include "elf/dwarf2.h"
#include "frame.h"
#include "frame-base.h"
#include "frame-unwind.h"
#include "gdbcore.h"
#include "gdbtypes.h"
#include "symtab.h"
#include "objfiles.h"
#include "regcache.h"

#include "gdb_assert.h"
#include "gdb_string.h"

#include "dwarf2-frame.h"

/* Call Frame Information (CFI).  */

/* Common Information Entry (CIE).  */

struct dwarf2_cie
{
  /* Offset into the .debug_frame section where this CIE was found.
     Used to identify this CIE.  */
  ULONGEST cie_pointer;

  /* Constant that is factored out of all advance location
     instructions.  */
  ULONGEST code_alignment_factor;

  /* Constants that is factored out of all offset instructions.  */
  LONGEST data_alignment_factor;

  /* Return address column.  */
  ULONGEST return_address_register;

  /* Instruction sequence to initialize a register set.  */
  unsigned char *initial_instructions;
  unsigned char *end;

  /* Encoding of addresses.  */
  unsigned char encoding;

  /* True if a 'z' augmentation existed.  */
  unsigned char saw_z_augmentation;

  struct dwarf2_cie *next;
};

/* Frame Description Entry (FDE).  */

struct dwarf2_fde
{
  /* CIE for this FDE.  */
  struct dwarf2_cie *cie;

  /* First location associated with this FDE.  */
  CORE_ADDR initial_location;

  /* Number of bytes of program instructions described by this FDE.  */
  CORE_ADDR address_range;

  /* Instruction sequence.  */
  unsigned char *instructions;
  unsigned char *end;

  struct dwarf2_fde *next;
};

static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc);


/* Structure describing a frame state.  */

struct dwarf2_frame_state
{
  /* Each register save state can be described in terms of a CFA slot,
     another register, or a location expression.  */
  struct dwarf2_frame_state_reg_info
  {
    struct dwarf2_frame_state_reg
    {
      union {
	LONGEST offset;
	ULONGEST reg;
	unsigned char *exp;
      } loc;
      ULONGEST exp_len;
      enum {
	REG_UNSAVED,
	REG_SAVED_OFFSET,
	REG_SAVED_REG,
	REG_SAVED_EXP,
	REG_UNMODIFIED
      } how;
    } *reg;
    int num_regs;

    /* Used to implement DW_CFA_remember_state.  */
    struct dwarf2_frame_state_reg_info *prev;
  } regs;

  LONGEST cfa_offset;
  ULONGEST cfa_reg;
  unsigned char *cfa_exp;
  enum {
    CFA_UNSET,
    CFA_REG_OFFSET,
    CFA_EXP
  } cfa_how;

  /* The PC described by the current frame state.  */
  CORE_ADDR pc;

  /* Initial register set from the CIE.
     Used to implement DW_CFA_restore.  */
  struct dwarf2_frame_state_reg_info initial;

  /* The information we care about from the CIE.  */
  LONGEST data_align;
  ULONGEST code_align;
  ULONGEST retaddr_column;
};

/* Store the length the expression for the CFA in the `cfa_reg' field,
   which is unused in that case.  */
#define cfa_exp_len cfa_reg

/* Assert that the register set RS is large enough to store NUM_REGS
   columns.  If necessary, enlarge the register set.  */

static void
dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info *rs,
			       int num_regs)
{
  size_t size = sizeof (struct dwarf2_frame_state_reg);

  if (num_regs <= rs->num_regs)
    return;

  rs->reg = (struct dwarf2_frame_state_reg *)
    xrealloc (rs->reg, num_regs * size);

  /* Initialize newly allocated registers.  */
  memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size);
  rs->num_regs = num_regs;
}

/* Copy the register columns in register set RS into newly allocated
   memory and return a pointer to this newly created copy.  */

static struct dwarf2_frame_state_reg *
dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info *rs)
{
  size_t size = rs->num_regs * sizeof (struct dwarf2_frame_state_reg_info);
  struct dwarf2_frame_state_reg *reg;

  reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
  memcpy (reg, rs->reg, size);

  return reg;
}

/* Release the memory allocated to register set RS.  */

static void
dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info *rs)
{
  if (rs)
    {
      dwarf2_frame_state_free_regs (rs->prev);

      xfree (rs->reg);
      xfree (rs);
    }
}

/* Release the memory allocated to the frame state FS.  */

static void
dwarf2_frame_state_free (void *p)
{
  struct dwarf2_frame_state *fs = p;

  dwarf2_frame_state_free_regs (fs->initial.prev);
  dwarf2_frame_state_free_regs (fs->regs.prev);
  xfree (fs->initial.reg);
  xfree (fs->regs.reg);
  xfree (fs);
}


/* Helper functions for execute_stack_op.  */

static CORE_ADDR
read_reg (void *baton, int reg)
{
  struct frame_info *next_frame = (struct frame_info *) baton;
  int regnum;
  char *buf;

  regnum = DWARF2_REG_TO_REGNUM (reg);

  buf = (char *) alloca (register_size (current_gdbarch, regnum));
  frame_unwind_register (next_frame, regnum, buf);
  return extract_typed_address (buf, builtin_type_void_data_ptr);
}

static void
read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len)
{
  read_memory (addr, buf, len);
}

static void
no_get_frame_base (void *baton, unsigned char **start, size_t *length)
{
  internal_error (__FILE__, __LINE__,
		  "Support for DW_OP_fbreg is unimplemented");
}

static CORE_ADDR
no_get_tls_address (void *baton, CORE_ADDR offset)
{
  internal_error (__FILE__, __LINE__,
		  "Support for DW_OP_GNU_push_tls_address is unimplemented");
}

static CORE_ADDR
execute_stack_op (unsigned char *exp, ULONGEST len,
		  struct frame_info *next_frame, CORE_ADDR initial)
{
  struct dwarf_expr_context *ctx;
  CORE_ADDR result;

  ctx = new_dwarf_expr_context ();
  ctx->baton = next_frame;
  ctx->read_reg = read_reg;
  ctx->read_mem = read_mem;
  ctx->get_frame_base = no_get_frame_base;
  ctx->get_tls_address = no_get_tls_address;

  dwarf_expr_push (ctx, initial);
  dwarf_expr_eval (ctx, exp, len);
  result = dwarf_expr_fetch (ctx, 0);

  if (ctx->in_reg)
    result = read_reg (next_frame, result);

  free_dwarf_expr_context (ctx);

  return result;
}


static void
execute_cfa_program (unsigned char *insn_ptr, unsigned char *insn_end,
		     struct frame_info *next_frame,
		     struct dwarf2_frame_state *fs)
{
  CORE_ADDR pc = frame_pc_unwind (next_frame);
  int bytes_read;

  while (insn_ptr < insn_end && fs->pc <= pc)
    {
      unsigned char insn = *insn_ptr++;
      ULONGEST utmp, reg;
      LONGEST offset;

      if ((insn & 0xc0) == DW_CFA_advance_loc)
	fs->pc += (insn & 0x3f) * fs->code_align;
      else if ((insn & 0xc0) == DW_CFA_offset)
	{
	  reg = insn & 0x3f;
	  insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	  offset = utmp * fs->data_align;
	  dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	  fs->regs.reg[reg].how = REG_SAVED_OFFSET;
	  fs->regs.reg[reg].loc.offset = offset;
	}
      else if ((insn & 0xc0) == DW_CFA_restore)
	{
	  gdb_assert (fs->initial.reg);
	  reg = insn & 0x3f;
	  dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	  fs->regs.reg[reg] = fs->initial.reg[reg];
	}
      else
	{
	  switch (insn)
	    {
	    case DW_CFA_set_loc:
	      fs->pc = dwarf2_read_address (insn_ptr, insn_end, &bytes_read);
	      insn_ptr += bytes_read;
	      break;

	    case DW_CFA_advance_loc1:
	      utmp = extract_unsigned_integer (insn_ptr, 1);
	      fs->pc += utmp * fs->code_align;
	      insn_ptr++;
	      break;
	    case DW_CFA_advance_loc2:
	      utmp = extract_unsigned_integer (insn_ptr, 2);
	      fs->pc += utmp * fs->code_align;
	      insn_ptr += 2;
	      break;
	    case DW_CFA_advance_loc4:
	      utmp = extract_unsigned_integer (insn_ptr, 4);
	      fs->pc += utmp * fs->code_align;
	      insn_ptr += 4;
	      break;

	    case DW_CFA_offset_extended:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	      offset = utmp * fs->data_align;
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      fs->regs.reg[reg].how = REG_SAVED_OFFSET;
	      fs->regs.reg[reg].loc.offset = offset;
	      break;

	    case DW_CFA_restore_extended:
	      gdb_assert (fs->initial.reg);
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      fs->regs.reg[reg] = fs->initial.reg[reg];
	      break;

	    case DW_CFA_undefined:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      fs->regs.reg[reg].how = REG_UNSAVED;
	      break;

	    case DW_CFA_same_value:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      fs->regs.reg[reg].how = REG_UNMODIFIED;
	      break;

	    case DW_CFA_register:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      fs->regs.reg[reg].loc.reg = utmp;
	      break;

	    case DW_CFA_remember_state:
	      {
		struct dwarf2_frame_state_reg_info *new_rs;

		new_rs = XMALLOC (struct dwarf2_frame_state_reg_info);
		*new_rs = fs->regs;
		fs->regs.reg = dwarf2_frame_state_copy_regs (&fs->regs);
		fs->regs.prev = new_rs;
	      }
	      break;

	    case DW_CFA_restore_state:
	      {
		struct dwarf2_frame_state_reg_info *old_rs = fs->regs.prev;

		gdb_assert (old_rs);

		xfree (fs->regs.reg);
		fs->regs = *old_rs;
		xfree (old_rs);
	      }
	      break;

	    case DW_CFA_def_cfa:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	      fs->cfa_offset = utmp;
	      fs->cfa_how = CFA_REG_OFFSET;
	      break;

	    case DW_CFA_def_cfa_register:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
	      fs->cfa_how = CFA_REG_OFFSET;
	      break;

	    case DW_CFA_def_cfa_offset:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_offset);
	      /* cfa_how deliberately not set.  */
	      break;

	    case DW_CFA_def_cfa_expression:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_exp_len);
	      fs->cfa_exp = insn_ptr;
	      fs->cfa_how = CFA_EXP;
	      insn_ptr += fs->cfa_exp_len;
	      break;

	    case DW_CFA_expression:
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &reg);
	      dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	      fs->regs.reg[reg].loc.exp = insn_ptr;
	      fs->regs.reg[reg].exp_len = utmp;
	      fs->regs.reg[reg].how = REG_SAVED_EXP;
	      insn_ptr += utmp;
	      break;

	    case DW_CFA_nop:
	      break;

	    case DW_CFA_GNU_args_size:
	      /* Ignored.  */
	      insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
	      break;

	    default:
	      internal_error (__FILE__, __LINE__, "Unknown CFI encountered.");
	    }
	}
    }

  /* Don't allow remember/restore between CIE and FDE programs.  */
  dwarf2_frame_state_free_regs (fs->regs.prev);
  fs->regs.prev = NULL;
}

struct dwarf2_frame_cache
{
  /* DWARF Call Frame Address.  */
  CORE_ADDR cfa;

  /* Saved registers, indexed by GDB register number, not by DWARF
     register number.  */
  struct dwarf2_frame_state_reg *reg;
};

struct dwarf2_frame_cache *
dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
{
  struct cleanup *old_chain;
  int num_regs = NUM_REGS + NUM_PSEUDO_REGS;
  struct dwarf2_frame_cache *cache;
  struct dwarf2_frame_state *fs;
  struct dwarf2_fde *fde;
  int reg;

  if (*this_cache)
    return *this_cache;

  /* Allocate a new cache.  */
  cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
  cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);

  /* Allocate and initialize the frame state.  */
  fs = XMALLOC (struct dwarf2_frame_state);
  memset (fs, 0, sizeof (struct dwarf2_frame_state));
  old_chain = make_cleanup (dwarf2_frame_state_free, fs);

  /* Unwind the PC.

     Note that if NEXT_FRAME is never supposed to return (i.e. a call
     to abort), the compiler might optimize away the instruction at
     NEXT_FRAME's return address.  As a result the return address will
     point at some random instruction, and the CFI for that
     instruction is probably wortless to us.  GCC's unwinder solves
     this problem by substracting 1 from the return address to get an
     address in the middle of a presumed call instruction (or the
     instruction in the associated delay slot).  This should only be
     done for "normal" frames and not for resume-type frames (signal
     handlers, sentinel frames, dummy frames).

     We don't do what GCC's does here (yet).  It's not clear how
     reliable the method is.  There's also a problem with finding the
     right FDE; see the comment in dwarf_frame_p.  If dwarf_frame_p
     selected this frame unwinder because it found the FDE for the
     next function, using the adjusted return address might not yield
     a FDE at all.  The problem isn't specific to DWARF CFI; other
     unwinders loose in similar ways.  Therefore it's probably
     acceptable to leave things slightly broken for now.  */
  fs->pc = frame_pc_unwind (next_frame);

  /* Find the correct FDE.  */
  fde = dwarf2_frame_find_fde (&fs->pc);
  gdb_assert (fde != NULL);

  /* Extract any interesting information from the CIE.  */
  fs->data_align = fde->cie->data_alignment_factor;
  fs->code_align = fde->cie->code_alignment_factor;
  fs->retaddr_column = fde->cie->return_address_register;

  /* First decode all the insns in the CIE.  */
  execute_cfa_program (fde->cie->initial_instructions,
		       fde->cie->end, next_frame, fs);

  /* Save the initialized register set.  */
  fs->initial = fs->regs;
  fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);

  /* Then decode the insns in the FDE up to our target PC.  */
  execute_cfa_program (fde->instructions, fde->end, next_frame, fs);

  /* Caclulate the CFA.  */
  switch (fs->cfa_how)
    {
    case CFA_REG_OFFSET:
      cache->cfa = read_reg (next_frame, fs->cfa_reg);
      cache->cfa += fs->cfa_offset;
      break;

    case CFA_EXP:
      cache->cfa =
	execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0);
      break;

    default:
      internal_error (__FILE__, __LINE__, "Unknown CFA rule.");
    }

  /* Save the register info in the cache.  */
  for (reg = 0; reg < fs->regs.num_regs; reg++)
    {
      int regnum;

      /* Skip the return address column.  */
      if (reg == fs->retaddr_column)
	continue;

      /* Use the GDB register number as index.  */
      regnum = DWARF2_REG_TO_REGNUM (reg);

      if (regnum >= 0 && regnum < num_regs)
	cache->reg[regnum] = fs->regs.reg[reg];
    }

  /* Store the location of the return addess.  If the return address
     column (adjusted) is not the same as gdb's PC_REGNUM, then this
     implies a copy from the ra column register.  */
  if (fs->retaddr_column < fs->regs.num_regs
      && fs->regs.reg[fs->retaddr_column].how != REG_UNSAVED)
    cache->reg[PC_REGNUM] = fs->regs.reg[fs->retaddr_column];
  else
    {
      reg = DWARF2_REG_TO_REGNUM (fs->retaddr_column);
      if (reg != PC_REGNUM)
	{
	  cache->reg[PC_REGNUM].loc.reg = reg;
	  cache->reg[PC_REGNUM].how = REG_SAVED_REG;
	}
    }

  do_cleanups (old_chain);

  *this_cache = cache;
  return cache;
}

static void
dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
		      struct frame_id *this_id)
{
  struct dwarf2_frame_cache *cache =
    dwarf2_frame_cache (next_frame, this_cache);

  (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
}

static void
dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
			    int regnum, int *optimizedp,
			    enum lval_type *lvalp, CORE_ADDR *addrp,
			    int *realnump, void *valuep)
{
  struct dwarf2_frame_cache *cache =
    dwarf2_frame_cache (next_frame, this_cache);

  switch (cache->reg[regnum].how)
    {
    case REG_UNSAVED:
      *optimizedp = 1;
      *lvalp = not_lval;
      *addrp = 0;
      *realnump = -1;
      if (regnum == SP_REGNUM)
	{
	  /* GCC defines the CFA as the value of the stack pointer
	     just before the call instruction is executed.  Do other
	     compilers use the same definition?  */
	  *optimizedp = 0;
	  if (valuep)
	    {
	      /* Store the value.  */
	      store_typed_address (valuep, builtin_type_void_data_ptr,
				   cache->cfa);
	    }
	}
      else if (valuep)
	{
	  /* In some cases, for example %eflags on the i386, we have
	     to provide a sane value, even though this register wasn't
	     saved.  Assume we can get it from NEXT_FRAME.  */
	  frame_unwind_register (next_frame, regnum, valuep);
	}
      break;

    case REG_SAVED_OFFSET:
      *optimizedp = 0;
      *lvalp = lval_memory;
      *addrp = cache->cfa + cache->reg[regnum].loc.offset;
      *realnump = -1;
      if (valuep)
	{
	  /* Read the value in from memory.  */
	  read_memory (*addrp, valuep,
		       register_size (current_gdbarch, regnum));
	}
      break;

    case REG_SAVED_REG:
      regnum = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
      frame_register_unwind (next_frame, regnum,
			     optimizedp, lvalp, addrp, realnump, valuep);
      break;

    case REG_SAVED_EXP:
      *optimizedp = 0;
      *lvalp = lval_memory;
      *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
				 cache->reg[regnum].exp_len,
				 next_frame, cache->cfa);
      *realnump = -1;
      if (valuep)
	{
	  /* Read the value in from memory.  */
	  read_memory (*addrp, valuep,
		       register_size (current_gdbarch, regnum));
	}
      break;

    case REG_UNMODIFIED:
      frame_register_unwind (next_frame, regnum,
			     optimizedp, lvalp, addrp, realnump, valuep);
      break;

    default:
      internal_error (__FILE__, __LINE__, "Unknown register rule.");
    }
}

static const struct frame_unwind dwarf2_frame_unwind =
{
  NORMAL_FRAME,
  dwarf2_frame_this_id,
  dwarf2_frame_prev_register
};

const struct frame_unwind *
dwarf2_frame_p (CORE_ADDR pc)
{
  /* The way GDB works, this function can be called with PC just after
     the last instruction of the function we're supposed to return the
     unwind methods for.  In that case we won't find the correct FDE;
     instead we find the FDE for the next function, or we won't find
     an FDE at all.  There is a possible solution (see the comment in
     dwarf2_frame_cache), GDB doesn't pass us enough information to
     implement it.  */
  if (dwarf2_frame_find_fde (&pc))
    return &dwarf2_frame_unwind;

  return NULL;
}


/* There is no explicitly defined relationship between the CFA and the
   location of frame's local variables and arguments/parameters.
   Therefore, frame base methods on this page should probably only be
   used as a last resort, just to avoid printing total garbage as a
   response to the "info frame" command.  */

static CORE_ADDR
dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
{
  struct dwarf2_frame_cache *cache =
    dwarf2_frame_cache (next_frame, this_cache);

  return cache->cfa;
}

static const struct frame_base dwarf2_frame_base =
{
  &dwarf2_frame_unwind,
  dwarf2_frame_base_address,
  dwarf2_frame_base_address,
  dwarf2_frame_base_address
};

const struct frame_base *
dwarf2_frame_base_p (CORE_ADDR pc)
{
  if (dwarf2_frame_find_fde (&pc))
    return &dwarf2_frame_base;

  return NULL;
}

/* A minimal decoding of DWARF2 compilation units.  We only decode
   what's needed to get to the call frame information.  */

struct comp_unit
{
  /* Keep the bfd convenient.  */
  bfd *abfd;

  struct objfile *objfile;

  /* Linked list of CIEs for this object.  */
  struct dwarf2_cie *cie;

  /* Address size for this unit - from unit header.  */
  unsigned char addr_size;

  /* Pointer to the .debug_frame section loaded into memory.  */
  char *dwarf_frame_buffer;

  /* Length of the loaded .debug_frame section.  */
  unsigned long dwarf_frame_size;

  /* Pointer to the .debug_frame section.  */
  asection *dwarf_frame_section;
};

static unsigned int
read_1_byte (bfd *bfd, char *buf)
{
  return bfd_get_8 (abfd, (bfd_byte *) buf);
}

static unsigned int
read_4_bytes (bfd *abfd, char *buf)
{
  return bfd_get_32 (abfd, (bfd_byte *) buf);
}

static ULONGEST
read_8_bytes (bfd *abfd, char *buf)
{
  return bfd_get_64 (abfd, (bfd_byte *) buf);
}

static ULONGEST
read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
{
  ULONGEST result;
  unsigned int num_read;
  int shift;
  unsigned char byte;

  result = 0;
  shift = 0;
  num_read = 0;

  do
    {
      byte = bfd_get_8 (abfd, (bfd_byte *) buf);
      buf++;
      num_read++;
      result |= ((byte & 0x7f) << shift);
      shift += 7;
    }
  while (byte & 0x80);

  *bytes_read_ptr = num_read;

  return result;
}

static LONGEST
read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
{
  LONGEST result;
  int shift;
  unsigned int num_read;
  unsigned char byte;

  result = 0;
  shift = 0;
  num_read = 0;

  do
    {
      byte = bfd_get_8 (abfd, (bfd_byte *) buf);
      buf++;
      num_read++;
      result |= ((byte & 0x7f) << shift);
      shift += 7;
    }
  while (byte & 0x80);

  if ((shift < 32) && (byte & 0x40))
    result |= -(1 << shift);

  *bytes_read_ptr = num_read;

  return result;
}

static ULONGEST
read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
{
  LONGEST result;

  result = bfd_get_32 (abfd, (bfd_byte *) buf);
  if (result == 0xffffffff)
    {
      result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
      *bytes_read_ptr = 12;
    }
  else
    *bytes_read_ptr = 4;

  return result;
}


/* Pointer encoding helper functions.  */

/* GCC supports exception handling based on DWARF2 CFI.  However, for
   technical reasons, it encodes addresses in its FDE's in a different
   way.  Several "pointer encodings" are supported.  The encoding
   that's used for a particular FDE is determined by the 'R'
   augmentation in the associated CIE.  The argument of this
   augmentation is a single byte.  

   The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
   LEB128.  This is encoded in bits 0, 1 and 2.  Bit 3 encodes whether
   the address is signed or unsigned.  Bits 4, 5 and 6 encode how the
   address should be interpreted (absolute, relative to the current
   position in the FDE, ...).  Bit 7, indicates that the address
   should be dereferenced.  */

static unsigned char
encoding_for_size (unsigned int size)
{
  switch (size)
    {
    case 2:
      return DW_EH_PE_udata2;
    case 4:
      return DW_EH_PE_udata4;
    case 8:
      return DW_EH_PE_udata8;
    default:
      internal_error (__FILE__, __LINE__, "Unsupported address size");
    }
}

static unsigned int
size_of_encoded_value (unsigned char encoding)
{
  if (encoding == DW_EH_PE_omit)
    return 0;

  switch (encoding & 0x07)
    {
    case DW_EH_PE_absptr:
      return TYPE_LENGTH (builtin_type_void_data_ptr);
    case DW_EH_PE_udata2:
      return 2;
    case DW_EH_PE_udata4:
      return 4;
    case DW_EH_PE_udata8:
      return 8;
    default:
      internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
    }
}

static CORE_ADDR
read_encoded_value (struct comp_unit *unit, unsigned char encoding,
		    char *buf, unsigned int *bytes_read_ptr)
{
  CORE_ADDR base;

  /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
     FDE's.  */
  if (encoding & DW_EH_PE_indirect)
    internal_error (__FILE__, __LINE__, 
		    "Unsupported encoding: DW_EH_PE_indirect");

  switch (encoding & 0x70)
    {
    case DW_EH_PE_absptr:
      base = 0;
      break;
    case DW_EH_PE_pcrel:
      base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
      base += (buf - unit->dwarf_frame_buffer);
      break;
    default:
      internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
    }

  if ((encoding & 0x0f) == 0x00)
    encoding |= encoding_for_size (TYPE_LENGTH(builtin_type_void_data_ptr));

  switch (encoding & 0x0f)
    {
    case DW_EH_PE_udata2:
      *bytes_read_ptr = 2;
      return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
    case DW_EH_PE_udata4:
      *bytes_read_ptr = 4;
      return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
    case DW_EH_PE_udata8:
      *bytes_read_ptr = 8;
      return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
    case DW_EH_PE_sdata2:
      *bytes_read_ptr = 2;
      return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
    case DW_EH_PE_sdata4:
      *bytes_read_ptr = 4;
      return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
    case DW_EH_PE_sdata8:
      *bytes_read_ptr = 8;
      return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
    default:
      internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
    }
}


/* GCC uses a single CIE for all FDEs in a .debug_frame section.
   That's why we use a simple linked list here.  */

static struct dwarf2_cie *
find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
{
  struct dwarf2_cie *cie = unit->cie;

  while (cie)
    {
      if (cie->cie_pointer == cie_pointer)
	return cie;

      cie = cie->next;
    }

  return NULL;
}

static void
add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
{
  cie->next = unit->cie;
  unit->cie = cie;
}

/* Find the FDE for *PC.  Return a pointer to the FDE, and store the
   inital location associated with it into *PC.  */

static struct dwarf2_fde *
dwarf2_frame_find_fde (CORE_ADDR *pc)
{
  struct objfile *objfile;

  ALL_OBJFILES (objfile)
    {
      struct dwarf2_fde *fde;
      CORE_ADDR offset;

      offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
      
      fde = objfile->sym_private;
      while (fde)
	{
	  if (*pc >= fde->initial_location + offset
	      && *pc < fde->initial_location + offset + fde->address_range)
	    {
	      *pc = fde->initial_location + offset;
	      return fde;
	    }

	  fde = fde->next;
	}
    }

  return NULL;
}

static void
add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
{
  fde->next = unit->objfile->sym_private;
  unit->objfile->sym_private = fde;
}

#ifdef CC_HAS_LONG_LONG
#define DW64_CIE_ID 0xffffffffffffffffULL
#else
#define DW64_CIE_ID ~0
#endif

/* Read a CIE or FDE in BUF and decode it.  */

static char *
decode_frame_entry (struct comp_unit *unit, char *buf, int eh_frame_p)
{
  LONGEST length;
  unsigned int bytes_read;
  int dwarf64_p = 0;
  ULONGEST cie_id = DW_CIE_ID;
  ULONGEST cie_pointer;
  char *start = buf;
  char *end;

  length = read_initial_length (unit->abfd, buf, &bytes_read);
  buf += bytes_read;
  end = buf + length;

  if (length == 0)
    return end;

  if (bytes_read == 12)
    dwarf64_p = 1;

  /* In a .eh_frame section, zero is used to distinguish CIEs from
     FDEs.  */
  if (eh_frame_p)
    cie_id = 0;
  else if (dwarf64_p)
    cie_id = DW64_CIE_ID;

  if (dwarf64_p)
    {
      cie_pointer = read_8_bytes (unit->abfd, buf);
      buf += 8;
    }
  else
    {
      cie_pointer = read_4_bytes (unit->abfd, buf);
      buf += 4;
    }

  if (cie_pointer == cie_id)
    {
      /* This is a CIE.  */
      struct dwarf2_cie *cie;
      char *augmentation;

      /* Record the offset into the .debug_frame section of this CIE.  */
      cie_pointer = start - unit->dwarf_frame_buffer;

      /* Check whether we've already read it.  */
      if (find_cie (unit, cie_pointer))
	return end;

      cie = (struct dwarf2_cie *)
	obstack_alloc (&unit->objfile->psymbol_obstack,
		       sizeof (struct dwarf2_cie));
      cie->initial_instructions = NULL;
      cie->cie_pointer = cie_pointer;

      /* The encoding for FDE's in a normal .debug_frame section
         depends on the target address size as specified in the
         Compilation Unit Header.  */
      cie->encoding = encoding_for_size (unit->addr_size);

      /* Check version number.  */
      gdb_assert (read_1_byte (unit->abfd, buf) == DW_CIE_VERSION);
      buf += 1;

      /* Interpret the interesting bits of the augmentation.  */
      augmentation = buf;
      buf = augmentation + strlen (augmentation) + 1;

      /* The GCC 2.x "eh" augmentation has a pointer immediately
         following the augmentation string, so it must be handled
         first.  */
      if (augmentation[0] == 'e' && augmentation[1] == 'h')
	{
	  /* Skip.  */
	  buf += TYPE_LENGTH (builtin_type_void_data_ptr);
	  augmentation += 2;
	}

      cie->code_alignment_factor =
	read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
      buf += bytes_read;

      cie->data_alignment_factor =
	read_signed_leb128 (unit->abfd, buf, &bytes_read);
      buf += bytes_read;

      cie->return_address_register = read_1_byte (unit->abfd, buf);
      buf += 1;

      cie->saw_z_augmentation = (*augmentation == 'z');
      if (cie->saw_z_augmentation)
	{
	  ULONGEST length;

	  length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
	  buf += bytes_read;
	  cie->initial_instructions = buf + length;
	  augmentation++;
	}

      while (*augmentation)
	{
	  /* "L" indicates a byte showing how the LSDA pointer is encoded.  */
	  if (*augmentation == 'L')
	    {
	      /* Skip.  */
	      buf++;
	      augmentation++;
	    }

	  /* "R" indicates a byte indicating how FDE addresses are encoded.  */
	  else if (*augmentation == 'R')
	    {
	      cie->encoding = *buf++;
	      augmentation++;
	    }

	  /* "P" indicates a personality routine in the CIE augmentation.  */
	  else if (*augmentation == 'P')
	    {
	      /* Skip.  */
	      buf += size_of_encoded_value (*buf++);
	      augmentation++;
	    }

	  /* Otherwise we have an unknown augmentation.
	     Bail out unless we saw a 'z' prefix.  */
	  else
	    {
	      if (cie->initial_instructions == NULL)
		return end;

	      /* Skip unknown augmentations.  */
	      buf = cie->initial_instructions;
	      break;
	    }
	}

      cie->initial_instructions = buf;
      cie->end = end;

      add_cie (unit, cie);
    }
  else
    {
      /* This is a FDE.  */
      struct dwarf2_fde *fde;

      if (eh_frame_p)
	{
	  /* In an .eh_frame section, the CIE pointer is the delta
             between the address within the FDE where the CIE pointer
             is stored and the address of the CIE.  Convert it to an
             offset into the .eh_frame section.  */
	  cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
	  cie_pointer -= (dwarf64_p ? 8 : 4);
	}

      fde = (struct dwarf2_fde *)
	obstack_alloc (&unit->objfile->psymbol_obstack,
		       sizeof (struct dwarf2_fde));
      fde->cie = find_cie (unit, cie_pointer);
      if (fde->cie == NULL)
	{
	  decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
			      eh_frame_p);
	  fde->cie = find_cie (unit, cie_pointer);
	}

      gdb_assert (fde->cie != NULL);

      fde->initial_location =
	read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
      buf += bytes_read;

      fde->address_range =
	read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
      buf += bytes_read;

      /* A 'z' augmentation in the CIE implies the presence of an
	 augmentation field in the FDE as well.  The only thing known
	 to be in here at present is the LSDA entry for EH.  So we
	 can skip the whole thing.  */
      if (fde->cie->saw_z_augmentation)
	{
	  ULONGEST length;

	  length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
	  buf += bytes_read + length;
	}

      fde->instructions = buf;
      fde->end = end;

      add_fde (unit, fde);
    }

  return end;
}


/* FIXME: kettenis/20030504: This still needs to be integrated with
   dwarf2read.c in a better way.  */

/* Imported from dwarf2read.c.  */
extern file_ptr dwarf_frame_offset;
extern unsigned int dwarf_frame_size;
extern asection *dwarf_frame_section;
extern file_ptr dwarf_eh_frame_offset;
extern unsigned int dwarf_eh_frame_size;
extern asection *dwarf_eh_frame_section;

/* Imported from dwarf2read.c.  */
extern char *dwarf2_read_section (struct objfile *objfile, file_ptr offset,
				  unsigned int size, asection *sectp);

void
dwarf2_build_frame_info (struct objfile *objfile)
{
  struct comp_unit unit;
  char *frame_ptr;

  /* Build a minimal decoding of the DWARF2 compilation unit.  */
  unit.abfd = objfile->obfd;
  unit.objfile = objfile;
  unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8;

  /* First add the information from the .eh_frame section.  That way,
     the FDEs from that section are searched last.  */
  if (dwarf_eh_frame_offset)
    {
      unit.cie = NULL;
      unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
						     dwarf_eh_frame_offset,
						     dwarf_eh_frame_size,
						     dwarf_eh_frame_section);

      unit.dwarf_frame_size = dwarf_eh_frame_size;
      unit.dwarf_frame_section = dwarf_eh_frame_section;

      frame_ptr = unit.dwarf_frame_buffer;
      while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
	frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
    }

  if (dwarf_frame_offset)
    {
      unit.cie = NULL;
      unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
						     dwarf_frame_offset,
						     dwarf_frame_size,
						     dwarf_frame_section);
      unit.dwarf_frame_size = dwarf_frame_size;
      unit.dwarf_frame_section = dwarf_frame_section;

      frame_ptr = unit.dwarf_frame_buffer;
      while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
	frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
    }
}