aboutsummaryrefslogtreecommitdiff
path: root/gold/dwarf_reader.h
blob: 80b2231327cfe6d5c26eba5c01d54edea36de2e4 (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
// dwarf_reader.h -- parse dwarf2/3 debug information for gold  -*- C++ -*-

// Copyright (C) 2007-2021 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// 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, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.

#ifndef GOLD_DWARF_READER_H
#define GOLD_DWARF_READER_H

#include <vector>
#include <map>
#include <limits.h>
#include <sys/types.h>

#include "elfcpp.h"
#include "elfcpp_swap.h"
#include "dwarf.h"
#include "reloc.h"

namespace gold
{

class Dwarf_info_reader;
struct LineStateMachine;

// This class is used to extract the section index and offset of
// the target of a relocation for a given offset within the section.

class Elf_reloc_mapper
{
 public:
  Elf_reloc_mapper()
  { }

  virtual
  ~Elf_reloc_mapper()
  { }

  // Initialize the relocation tracker for section RELOC_SHNDX.
  bool
  initialize(unsigned int reloc_shndx, unsigned int reloc_type)
  { return this->do_initialize(reloc_shndx, reloc_type); }

  // Return the next reloc_offset.
  off_t
  next_offset()
  { return this->do_next_offset(); }

  // Advance to the next relocation past OFFSET.
  void
  advance(off_t offset)
  { this->do_advance(offset); }

  // Return the section index and offset within the section of the target
  // of the relocation for RELOC_OFFSET in the referring section.
  unsigned int
  get_reloc_target(off_t reloc_offset, off_t* target_offset)
  { return this->do_get_reloc_target(reloc_offset, target_offset); }

  // Checkpoint the current position in the reloc section.
  uint64_t
  checkpoint() const
  { return this->do_checkpoint(); }

  // Reset the current position to the CHECKPOINT.
  void
  reset(uint64_t checkpoint)
  { this->do_reset(checkpoint); }

 protected:
  virtual bool
  do_initialize(unsigned int, unsigned int) = 0;

  // Return the next reloc_offset.
  virtual off_t
  do_next_offset() = 0;

  // Advance to the next relocation past OFFSET.
  virtual void
  do_advance(off_t offset) = 0;

  virtual unsigned int
  do_get_reloc_target(off_t reloc_offset, off_t* target_offset) = 0;

  // Checkpoint the current position in the reloc section.
  virtual uint64_t
  do_checkpoint() const = 0;

  // Reset the current position to the CHECKPOINT.
  virtual void
  do_reset(uint64_t checkpoint) = 0;
};

template<int size, bool big_endian>
class Sized_elf_reloc_mapper : public Elf_reloc_mapper
{
 public:
  Sized_elf_reloc_mapper(Object* object, const unsigned char* symtab,
			 off_t symtab_size)
    : object_(object), symtab_(symtab), symtab_size_(symtab_size),
      reloc_type_(0), track_relocs_()
  { }

 protected:
  bool
  do_initialize(unsigned int reloc_shndx, unsigned int reloc_type);

  // Return the next reloc_offset.
  virtual off_t
  do_next_offset()
  { return this->track_relocs_.next_offset(); }

  // Advance to the next relocation past OFFSET.
  virtual void
  do_advance(off_t offset)
  { this->track_relocs_.advance(offset); }

  unsigned int
  do_get_reloc_target(off_t reloc_offset, off_t* target_offset);

  // Checkpoint the current position in the reloc section.
  uint64_t
  do_checkpoint() const
  { return this->track_relocs_.checkpoint(); }

  // Reset the current position to the CHECKPOINT.
  void
  do_reset(uint64_t checkpoint)
  { this->track_relocs_.reset(checkpoint); }

 private:
  typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;

  // Return the section index of symbol SYMNDX, and copy its value to *VALUE.
  // Set *IS_ORDINARY true if the section index is an ordinary section index.
  unsigned int
  symbol_section(unsigned int symndx, Address* value, bool* is_ordinary);

  // The object file.
  Object* object_;
  // The ELF symbol table.
  const unsigned char* symtab_;
  // The size of the ELF symbol table.
  off_t symtab_size_;
  // Type of the relocation section (SHT_REL or SHT_RELA).
  unsigned int reloc_type_;
  // Relocations for the referring section.
  Track_relocs<size, big_endian> track_relocs_;
};

// This class is used to read the abbreviations table from the
// .debug_abbrev section of the object file.

class Dwarf_abbrev_table
{
 public:
  // An attribute list entry.
  struct Attribute
  {
    Attribute(unsigned int a, unsigned int f)
      : attr(a), form(f)
    { }
    unsigned int attr;
    unsigned int form;
  };

  // An abbrev code entry.
  struct Abbrev_code
  {
    Abbrev_code(unsigned int t, bool hc)
      : tag(t), has_children(hc), has_sibling_attribute(false), attributes()
    {
      this->attributes.reserve(10);
    }

    void
    add_attribute(unsigned int attr, unsigned int form)
    {
      this->attributes.push_back(Attribute(attr, form));
    }

    // The DWARF tag.
    unsigned int tag;
    // True if the DIE has children.
    bool has_children : 1;
    // True if the DIE has a sibling attribute.
    bool has_sibling_attribute : 1;
    // The list of attributes and forms.
    std::vector<Attribute> attributes;
  };

  Dwarf_abbrev_table()
    : abbrev_shndx_(0), abbrev_offset_(0), buffer_(NULL), buffer_end_(NULL),
      owns_buffer_(false), buffer_pos_(NULL), high_abbrev_codes_()
  {
    memset(this->low_abbrev_codes_, 0, sizeof(this->low_abbrev_codes_));
  }

  ~Dwarf_abbrev_table()
  {
    if (this->owns_buffer_ && this->buffer_ != NULL)
      delete[] this->buffer_;
    this->clear_abbrev_codes();
  }

  // Read the abbrev table from an object file.
  bool
  read_abbrevs(Relobj* object,
	       unsigned int abbrev_shndx,
	       off_t abbrev_offset)
  {
    // If we've already read this abbrev table, return immediately.
    if (this->abbrev_shndx_ > 0
	&& this->abbrev_shndx_ == abbrev_shndx
	&& this->abbrev_offset_ == abbrev_offset)
      return true;
    return this->do_read_abbrevs(object, abbrev_shndx, abbrev_offset);
  }

  // Return the abbrev code entry for CODE.  This is a fast path for
  // abbrev codes that are in the direct lookup table.  If not found
  // there, we call do_get_abbrev() to do the hard work.
  const Abbrev_code*
  get_abbrev(unsigned int code)
  {
    if (code < this->low_abbrev_code_max_
	&& this->low_abbrev_codes_[code] != NULL)
      return this->low_abbrev_codes_[code];
    return this->do_get_abbrev(code);
  }

 private:
  // Read the abbrev table from an object file.
  bool
  do_read_abbrevs(Relobj* object,
		  unsigned int abbrev_shndx,
		  off_t abbrev_offset);

  // Lookup the abbrev code entry for CODE.
  const Abbrev_code*
  do_get_abbrev(unsigned int code);

  // Store an abbrev code entry for CODE.
  void
  store_abbrev(unsigned int code, const Abbrev_code* entry)
  {
    if (code < this->low_abbrev_code_max_)
      this->low_abbrev_codes_[code] = entry;
    else
      this->high_abbrev_codes_[code] = entry;
  }

  // Clear the abbrev code table and release the memory it uses.
  void
  clear_abbrev_codes();

  typedef Unordered_map<unsigned int, const Abbrev_code*> Abbrev_code_table;

  // The section index of the current abbrev table.
  unsigned int abbrev_shndx_;
  // The offset within the section of the current abbrev table.
  off_t abbrev_offset_;
  // The buffer containing the .debug_abbrev section.
  const unsigned char* buffer_;
  const unsigned char* buffer_end_;
  // True if this object owns the buffer and needs to delete it.
  bool owns_buffer_;
  // Pointer to the current position in the buffer.
  const unsigned char* buffer_pos_;
  // The table of abbrev codes.
  // We use a direct-lookup array for low abbrev codes,
  // and store the rest in a hash table.
  static const unsigned int low_abbrev_code_max_ = 256;
  const Abbrev_code* low_abbrev_codes_[low_abbrev_code_max_];
  Abbrev_code_table high_abbrev_codes_;
};

// A DWARF range list.  The start and end offsets are relative
// to the input section SHNDX.  Each range must lie entirely
// within a single section.

class Dwarf_range_list
{
 public:
  struct Range
  {
    Range(unsigned int a_shndx, off_t a_start, off_t a_end)
      : shndx(a_shndx), start(a_start), end(a_end)
    { }

    unsigned int shndx;
    off_t start;
    off_t end;
  };

  Dwarf_range_list()
    : range_list_()
  { }

  void
  add(unsigned int shndx, off_t start, off_t end)
  { this->range_list_.push_back(Range(shndx, start, end)); }

  size_t
  size() const
  { return this->range_list_.size(); }

  const Range&
  operator[](off_t i) const
  { return this->range_list_[i]; }

 private:
  std::vector<Range> range_list_;
};

// This class is used to read the ranges table from the
// .debug_ranges section of the object file.

class Dwarf_ranges_table
{
 public:
  Dwarf_ranges_table(Dwarf_info_reader* dwinfo)
    : dwinfo_(dwinfo), ranges_shndx_(0), ranges_buffer_(NULL),
      ranges_buffer_end_(NULL), owns_ranges_buffer_(false),
      ranges_reloc_mapper_(NULL), reloc_type_(0), output_section_offset_(0)
  { }

  ~Dwarf_ranges_table()
  {
    if (this->owns_ranges_buffer_ && this->ranges_buffer_ != NULL)
      delete[] this->ranges_buffer_;
    if (this->ranges_reloc_mapper_ != NULL)
      delete this->ranges_reloc_mapper_;
  }

  // Read the ranges table from an object file.
  bool
  read_ranges_table(Relobj* object,
		    const unsigned char* symtab,
		    off_t symtab_size,
		    unsigned int ranges_shndx);

  // Read the range table from an object file.
  Dwarf_range_list*
  read_range_list(Relobj* object,
		  const unsigned char* symtab,
		  off_t symtab_size,
		  unsigned int address_size,
		  unsigned int ranges_shndx,
		  off_t ranges_offset);

  // Look for a relocation at offset OFF in the range table,
  // and return the section index and offset of the target.
  unsigned int
  lookup_reloc(off_t off, off_t* target_off);

 private:
  // The Dwarf_info_reader, for reading data.
  Dwarf_info_reader* dwinfo_;
  // The section index of the ranges table.
  unsigned int ranges_shndx_;
  // The buffer containing the .debug_ranges section.
  const unsigned char* ranges_buffer_;
  const unsigned char* ranges_buffer_end_;
  // True if this object owns the buffer and needs to delete it.
  bool owns_ranges_buffer_;
  // Relocation mapper for the .debug_ranges section.
  Elf_reloc_mapper* ranges_reloc_mapper_;
  // Type of the relocation section (SHT_REL or SHT_RELA).
  unsigned int reloc_type_;
  // For incremental update links, this will hold the offset of the
  // input section within the output section.  Offsets read from
  // relocated data will be relative to the output section, and need
  // to be corrected before reading data from the input section.
  uint64_t output_section_offset_;
};

// This class is used to read the pubnames and pubtypes tables from the
// .debug_pubnames and .debug_pubtypes sections of the object file.

class Dwarf_pubnames_table
{
 public:
  Dwarf_pubnames_table(Dwarf_info_reader* dwinfo, bool is_pubtypes)
    : dwinfo_(dwinfo), buffer_(NULL), buffer_end_(NULL), owns_buffer_(false),
      offset_size_(0), pinfo_(NULL), end_of_table_(NULL),
      is_pubtypes_(is_pubtypes), is_gnu_style_(false),
      unit_length_(0), cu_offset_(0)
  { }

  ~Dwarf_pubnames_table()
  {
    if (this->owns_buffer_ && this->buffer_ != NULL)
      delete[] this->buffer_;
  }

  // Read the pubnames section from the object file, using the symbol
  // table for relocating it.
  bool
  read_section(Relobj* object, const unsigned char* symbol_table,
               off_t symtab_size);

  // Read the header for the set at OFFSET.
  bool
  read_header(off_t offset);

  // Return the offset to the cu within the info or types section.
  off_t
  cu_offset()
  { return this->cu_offset_; }

  // Return the size of this subsection of the table.  The unit length
  // doesn't include the size of its own field.
  off_t
  subsection_size()
  { return this->unit_length_; }

  // Read the next name from the set.  If the pubname table is gnu-style,
  // FLAG_BYTE is set to the high-byte of a gdb_index version 7 cu_index.
  const char*
  next_name(uint8_t* flag_byte);

 private:
  // The Dwarf_info_reader, for reading data.
  Dwarf_info_reader* dwinfo_;
  // The buffer containing the .debug_ranges section.
  const unsigned char* buffer_;
  const unsigned char* buffer_end_;
  // True if this object owns the buffer and needs to delete it.
  bool owns_buffer_;
  // The size of a DWARF offset for the current set.
  unsigned int offset_size_;
  // The current position within the buffer.
  const unsigned char* pinfo_;
  // The end of the current pubnames table.
  const unsigned char* end_of_table_;
  // TRUE if this is a .debug_pubtypes section.
  bool is_pubtypes_;
  // Gnu-style pubnames table. This style has an extra flag byte between the
  // offset and the name, and is used for generating version 7 of gdb-index.
  bool is_gnu_style_;
  // Fields read from the header.
  uint64_t unit_length_;
  off_t cu_offset_;

  // Track relocations for this table so we can find the CUs that
  // correspond to the subsections.
  Elf_reloc_mapper* reloc_mapper_;
  // Type of the relocation section (SHT_REL or SHT_RELA).
  unsigned int reloc_type_;
};

// This class represents a DWARF Debug Info Entry (DIE).

class Dwarf_die
{
 public:
  // An attribute value.
  struct Attribute_value
  {
    unsigned int attr;
    unsigned int form;
    union
    {
      int64_t intval;
      uint64_t uintval;
      const char* stringval;
      const unsigned char* blockval;
      off_t refval;
    } val;
    union
    {
      // Section index for reference forms.
      unsigned int shndx;
      // Block length for block forms.
      unsigned int blocklen;
      // Attribute offset for DW_FORM_strp.
      unsigned int attr_off;
    } aux;
  };

  // A list of attribute values.
  typedef std::vector<Attribute_value> Attributes;

  Dwarf_die(Dwarf_info_reader* dwinfo,
	    off_t die_offset,
	    Dwarf_die* parent);

  // Return the DWARF tag for this DIE.
  unsigned int
  tag() const
  {
    if (this->abbrev_code_ == NULL)
      return 0;
    return this->abbrev_code_->tag;
  }

  // Return true if this DIE has children.
  bool
  has_children() const
  {
    gold_assert(this->abbrev_code_ != NULL);
    return this->abbrev_code_->has_children;
  }

  // Return true if this DIE has a sibling attribute.
  bool
  has_sibling_attribute() const
  {
    gold_assert(this->abbrev_code_ != NULL);
    return this->abbrev_code_->has_sibling_attribute;
  }

  // Return the value of attribute ATTR.
  const Attribute_value*
  attribute(unsigned int attr);

  // Return the value of the DW_AT_name attribute.
  const char*
  name()
  {
    if (this->name_ == NULL)
      this->set_name();
    return this->name_;
  }

  // Return the value of the DW_AT_linkage_name
  // or DW_AT_MIPS_linkage_name attribute.
  const char*
  linkage_name()
  {
    if (this->linkage_name_ == NULL)
      this->set_linkage_name();
    return this->linkage_name_;
  }

  // Return the value of the DW_AT_specification attribute.
  off_t
  specification()
  {
    if (!this->attributes_read_)
      this->read_attributes();
    return this->specification_;
  }

  // Return the value of the DW_AT_abstract_origin attribute.
  off_t
  abstract_origin()
  {
    if (!this->attributes_read_)
      this->read_attributes();
    return this->abstract_origin_;
  }

  // Return the value of attribute ATTR as a string.
  const char*
  string_attribute(unsigned int attr);

  // Return the value of attribute ATTR as an integer.
  int64_t
  int_attribute(unsigned int attr);

  // Return the value of attribute ATTR as an unsigned integer.
  uint64_t
  uint_attribute(unsigned int attr);

  // Return the value of attribute ATTR as a reference.
  off_t
  ref_attribute(unsigned int attr, unsigned int* shndx);

  // Return the value of attribute ATTR as a address.
  off_t
  address_attribute(unsigned int attr, unsigned int* shndx);

  // Return the value of attribute ATTR as a flag.
  bool
  flag_attribute(unsigned int attr)
  { return this->int_attribute(attr) != 0; }

  // Return true if this DIE is a declaration.
  bool
  is_declaration()
  { return this->flag_attribute(elfcpp::DW_AT_declaration); }

  // Return the parent of this DIE.
  Dwarf_die*
  parent() const
  { return this->parent_; }

  // Return the offset of this DIE.
  off_t
  offset() const
  { return this->die_offset_; }

  // Return the offset of this DIE's first child.
  off_t
  child_offset();

  // Set the offset of this DIE's next sibling.
  void
  set_sibling_offset(off_t sibling_offset)
  { this->sibling_offset_ = sibling_offset; }

  // Return the offset of this DIE's next sibling.
  off_t
  sibling_offset();

 private:
  typedef Dwarf_abbrev_table::Abbrev_code Abbrev_code;

  // Read all the attributes of the DIE.
  bool
  read_attributes();

  // Set the name of the DIE if present.
  void
  set_name();

  // Set the linkage name if present.
  void
  set_linkage_name();

  // Skip all the attributes of the DIE and return the offset
  // of the next DIE.
  off_t
  skip_attributes();

  // The Dwarf_info_reader, for reading attributes.
  Dwarf_info_reader* dwinfo_;
  // The parent of this DIE.
  Dwarf_die* parent_;
  // Offset of this DIE within its compilation unit.
  off_t die_offset_;
  // Offset of the first attribute, relative to the beginning of the DIE.
  off_t attr_offset_;
  // Offset of the first child, relative to the compilation unit.
  off_t child_offset_;
  // Offset of the next sibling, relative to the compilation unit.
  off_t sibling_offset_;
  // The abbreviation table entry.
  const Abbrev_code* abbrev_code_;
  // The list of attributes.
  Attributes attributes_;
  // True if the attributes have been read.
  bool attributes_read_;
  // The following fields hold common attributes to avoid a linear
  // search through the attribute list.
  // The DIE name (DW_AT_name).
  const char* name_;
  // Offset of the name in the string table (for DW_FORM_strp).
  off_t name_off_;
  // The linkage name (DW_AT_linkage_name or DW_AT_MIPS_linkage_name).
  const char* linkage_name_;
  // Offset of the linkage name in the string table (for DW_FORM_strp).
  off_t linkage_name_off_;
  // Section index of the string table (for DW_FORM_strp).
  unsigned int string_shndx_;
  // The value of a DW_AT_specification attribute.
  off_t specification_;
  // The value of a DW_AT_abstract_origin attribute.
  off_t abstract_origin_;
};

// This class is used to read the debug info from the .debug_info
// or .debug_types sections.  This is a base class that implements
// the generic parsing of the compilation unit header and DIE
// structure.  The parse() method parses the entire section, and
// calls the various visit_xxx() methods for each header.  Clients
// should derive a new class from this one and implement the
// visit_compilation_unit() and visit_type_unit() functions.

class Dwarf_info_reader
{
 public:
  Dwarf_info_reader(bool is_type_unit,
		    Relobj* object,
		    const unsigned char* symtab,
		    off_t symtab_size,
		    unsigned int shndx,
		    unsigned int reloc_shndx,
		    unsigned int reloc_type)
    : is_type_unit_(is_type_unit), object_(object), symtab_(symtab),
      symtab_size_(symtab_size), shndx_(shndx), reloc_shndx_(reloc_shndx),
      reloc_type_(reloc_type), abbrev_shndx_(0), string_shndx_(0),
      buffer_(NULL), buffer_end_(NULL), cu_offset_(0), cu_length_(0),
      offset_size_(0), address_size_(0), cu_version_(0),
      abbrev_table_(), ranges_table_(this),
      reloc_mapper_(NULL), string_buffer_(NULL), string_buffer_end_(NULL),
      owns_string_buffer_(false), string_output_section_offset_(0)
  { }

  virtual
  ~Dwarf_info_reader()
  {
    if (this->reloc_mapper_ != NULL)
      delete this->reloc_mapper_;
    if (this->owns_string_buffer_ && this->string_buffer_ != NULL)
      delete[] this->string_buffer_;
  }

  // Begin parsing the debug info.  This calls visit_compilation_unit()
  // or visit_type_unit() for each compilation or type unit found in the
  // section, and visit_die() for each top-level DIE.
  void
  parse();

  // Return the abbrev code entry for a CODE.
  const Dwarf_abbrev_table::Abbrev_code*
  get_abbrev(unsigned int code)
  { return this->abbrev_table_.get_abbrev(code); }

  // Return a pointer to the DWARF info buffer at OFFSET.
  const unsigned char*
  buffer_at_offset(off_t offset) const
  {
    const unsigned char* p = this->buffer_ + this->cu_offset_ + offset;
    if (this->check_buffer(p + 1))
      return p;
    return NULL;
  }

  // Read a possibly unaligned integer of SIZE.
  template <int valsize>
  inline typename elfcpp::Valtype_base<valsize>::Valtype
  read_from_pointer(const unsigned char* source);

  // Read a possibly unaligned integer of SIZE.  Update SOURCE after read.
  template <int valsize>
  inline typename elfcpp::Valtype_base<valsize>::Valtype
  read_from_pointer(const unsigned char** source);

  // Look for a relocation at offset ATTR_OFF in the dwarf info,
  // and return the section index and offset of the target.
  unsigned int
  lookup_reloc(off_t attr_off, off_t* target_off);

  // Return a string from the DWARF string table.
  const char*
  get_string(off_t str_off, unsigned int string_shndx);

  // Return the size of a DWARF offset.
  unsigned int
  offset_size() const
  { return this->offset_size_; }

  // Return the size of an address.
  unsigned int
  address_size() const
  { return this->address_size_; }

  // Return the size of a DW_FORM_ref_addr.
  // In DWARF v2, this was the size of an address; in DWARF v3 and later,
  // it is the size of an DWARF offset.
  unsigned int
  ref_addr_size() const
  { return this->cu_version_ > 2 ? this->offset_size_ : this->address_size_; }

  // Set the section index of the .debug_abbrev section.
  // We use this if there are no relocations for the .debug_info section.
  // If not set, the code parse() routine will search for the section by name.
  void
  set_abbrev_shndx(unsigned int abbrev_shndx)
  { this->abbrev_shndx_ = abbrev_shndx; }

  // Return a pointer to the object file's ELF symbol table.
  const unsigned char*
  symtab() const
  { return this->symtab_; }

  // Return the size of the object file's ELF symbol table.
  off_t
  symtab_size() const
  { return this->symtab_size_; }

  // Return the offset of the current compilation unit.
  off_t
  cu_offset() const
  { return this->cu_offset_; }

 protected:
  // Begin parsing the debug info.  This calls visit_compilation_unit()
  // or visit_type_unit() for each compilation or type unit found in the
  // section, and visit_die() for each top-level DIE.
  template<bool big_endian>
  void
  do_parse();

  // The following methods are hooks that are meant to be implemented
  // by a derived class.  A default, do-nothing, implementation of
  // each is provided for this base class.

  // Visit a compilation unit.
  virtual void
  visit_compilation_unit(off_t cu_offset, off_t cu_length, Dwarf_die* root_die);

  // Visit a type unit.
  virtual void
  visit_type_unit(off_t tu_offset, off_t tu_length, off_t type_offset,
		  uint64_t signature, Dwarf_die* root_die);

  // Read the range table.
  Dwarf_range_list*
  read_range_list(unsigned int ranges_shndx, off_t ranges_offset)
  {
    return this->ranges_table_.read_range_list(this->object_,
					       this->symtab_,
					       this->symtab_size_,
					       this->address_size_,
					       ranges_shndx,
					       ranges_offset);
  }

  // Return the object.
  Relobj*
  object() const
  { return this->object_; }

  // Checkpoint the relocation tracker.
  uint64_t
  get_reloc_checkpoint() const
  { return this->reloc_mapper_->checkpoint(); }

  // Reset the relocation tracker to the CHECKPOINT.
  void
  reset_relocs(uint64_t checkpoint)
  { this->reloc_mapper_->reset(checkpoint); }

 private:
  // Print a warning about a corrupt debug section.
  void
  warn_corrupt_debug_section() const;

  // Check that P is within the bounds of the current section.
  bool
  check_buffer(const unsigned char* p) const
  {
    if (p > this->buffer_ + this->cu_offset_ + this->cu_length_)
      {
	this->warn_corrupt_debug_section();
	return false;
      }
    return true;
  }

  // Read the DWARF string table.
  bool
  read_string_table(unsigned int string_shndx)
  {
    // If we've already read this string table, return immediately.
    if (this->string_shndx_ > 0 && this->string_shndx_ == string_shndx)
      return true;
    if (string_shndx == 0 && this->string_shndx_ > 0)
      return true;
    return this->do_read_string_table(string_shndx);
  }

  bool
  do_read_string_table(unsigned int string_shndx);

  // True if this is a type unit; false for a compilation unit.
  bool is_type_unit_;
  // The object containing the .debug_info or .debug_types input section.
  Relobj* object_;
  // The ELF symbol table.
  const unsigned char* symtab_;
  // The size of the ELF symbol table.
  off_t symtab_size_;
  // Index of the .debug_info or .debug_types section.
  unsigned int shndx_;
  // Index of the relocation section.
  unsigned int reloc_shndx_;
  // Type of the relocation section (SHT_REL or SHT_RELA).
  unsigned int reloc_type_;
  // Index of the .debug_abbrev section (0 if not known).
  unsigned int abbrev_shndx_;
  // Index of the .debug_str section.
  unsigned int string_shndx_;
  // The buffer for the debug info.
  const unsigned char* buffer_;
  const unsigned char* buffer_end_;
  // Offset of the current compilation unit.
  off_t cu_offset_;
  // Length of the current compilation unit.
  off_t cu_length_;
  // Size of a DWARF offset for the current compilation unit.
  unsigned int offset_size_;
  // Size of an address for the target architecture.
  unsigned int address_size_;
  // Compilation unit version number.
  unsigned int cu_version_;
  // Abbreviations table for current compilation unit.
  Dwarf_abbrev_table abbrev_table_;
  // Ranges table for the current compilation unit.
  Dwarf_ranges_table ranges_table_;
  // Relocation mapper for the section.
  Elf_reloc_mapper* reloc_mapper_;
  // The buffer for the debug string table.
  const char* string_buffer_;
  const char* string_buffer_end_;
  // True if this object owns the buffer and needs to delete it.
  bool owns_string_buffer_;
  // For incremental update links, this will hold the offset of the
  // input .debug_str section within the output section.  Offsets read
  // from relocated data will be relative to the output section, and need
  // to be corrected before reading data from the input section.
  uint64_t string_output_section_offset_;
};

// We can't do better than to keep the offsets in a sorted vector.
// Here, offset is the key, and file_num/line_num is the value.
struct Offset_to_lineno_entry
{
  off_t offset;
  int header_num;  // which file-list to use (i.e. which .o file are we in)
  // A pointer into files_.
  unsigned int file_num : sizeof(int) * CHAR_BIT - 1;
  // True if this was the last entry for the current offset, meaning
  // it's the line that actually applies.
  unsigned int last_line_for_offset : 1;
  // The line number in the source file.  -1 to indicate end-of-function.
  int line_num;

  // This sorts by offsets first, and then puts the correct line to
  // report for a given offset at the beginning of the run of equal
  // offsets (so that asking for 1 line gives the best answer).  This
  // is not a total ordering.
  bool operator<(const Offset_to_lineno_entry& that) const
  {
    if (this->offset != that.offset)
      return this->offset < that.offset;
    // Note the '>' which makes this sort 'true' first.
    return this->last_line_for_offset > that.last_line_for_offset;
  }
};

// This class is used to read the line information from the debugging
// section of an object file.

class Dwarf_line_info
{
 public:
  Dwarf_line_info()
  { }

  virtual
  ~Dwarf_line_info()
  { }

  // Given a section number and an offset, returns the associated
  // file and line-number, as a string: "file:lineno".  If unable
  // to do the mapping, returns the empty string.  You must call
  // read_line_mappings() before calling this function.  If
  // 'other_lines' is non-NULL, fills that in with other line
  // numbers assigned to the same offset.
  std::string
  addr2line(unsigned int shndx, off_t offset,
            std::vector<std::string>* other_lines)
  { return this->do_addr2line(shndx, offset, other_lines); }

  // A helper function for a single addr2line lookup.  It also keeps a
  // cache of the last CACHE_SIZE Dwarf_line_info objects it created;
  // set to 0 not to cache at all.  The larger CACHE_SIZE is, the more
  // chance this routine won't have to re-create a Dwarf_line_info
  // object for its addr2line computation; such creations are slow.
  // NOTE: Not thread-safe, so only call from one thread at a time.
  static std::string
  one_addr2line(Object* object, unsigned int shndx, off_t offset,
                size_t cache_size, std::vector<std::string>* other_lines);

  // This reclaims all the memory that one_addr2line may have cached.
  // Use this when you know you will not be calling one_addr2line again.
  static void
  clear_addr2line_cache();

 private:
  virtual std::string
  do_addr2line(unsigned int shndx, off_t offset,
               std::vector<std::string>* other_lines) = 0;
};

template<int size, bool big_endian>
class Sized_dwarf_line_info : public Dwarf_line_info
{
 public:
  // Initializes a .debug_line reader for a given object file.
  // If SHNDX is specified and non-negative, only read the debug
  // information that pertains to the specified section.
  Sized_dwarf_line_info(Object* object, unsigned int read_shndx = -1U);

  virtual
  ~Sized_dwarf_line_info()
  {
    if (this->buffer_start_ != NULL)
      delete[] this->buffer_start_;
  }

 private:
  std::string
  do_addr2line(unsigned int shndx, off_t offset,
               std::vector<std::string>* other_lines);

  // Formats a file and line number to a string like "dirname/filename:lineno".
  std::string
  format_file_lineno(const Offset_to_lineno_entry& lineno) const;

  // Start processing line info, and populates the offset_map_.
  // If SHNDX is non-negative, only store debug information that
  // pertains to the specified section.
  void
  read_line_mappings(unsigned int shndx);

  // Reads the relocation section associated with .debug_line and
  // stores relocation information in reloc_map_.
  void
  read_relocs();

  // Reads the DWARF2/3 header for this line info.  Each takes as input
  // a starting buffer position, and returns the ending position.
  const unsigned char*
  read_header_prolog(const unsigned char* lineptr);

  const unsigned char*
  read_header_tables(const unsigned char* lineptr);

  // Reads the DWARF2/3 line information.  If shndx is non-negative,
  // discard all line information that doesn't pertain to the given
  // section.
  const unsigned char*
  read_lines(const unsigned char* lineptr, unsigned int shndx);

  // Process a single line info opcode at START using the state
  // machine at LSM.  Return true if we should define a line using the
  // current state of the line state machine.  Place the length of the
  // opcode in LEN.
  bool
  process_one_opcode(const unsigned char* start,
                     struct LineStateMachine* lsm, size_t* len);

  // Some parts of processing differ depending on whether the input
  // was a .o file or not.
  bool input_is_relobj();

  // If we saw anything amiss while parsing, we set this to false.
  // Then addr2line will always fail (rather than return possibly-
  // corrupt data).
  bool data_valid_;

  // A DWARF2/3 line info header.  This is not the same size as in the
  // actual file, as the one in the file may have a 32 bit or 64 bit
  // lengths.

  struct Dwarf_line_infoHeader
  {
    off_t total_length;
    int version;
    off_t prologue_length;
    int min_insn_length; // insn stands for instruction
    int max_ops_per_insn; // Added in DWARF-4.
    bool default_is_stmt; // stmt stands for statement
    signed char line_base;
    int line_range;
    unsigned char opcode_base;
    std::vector<unsigned char> std_opcode_lengths;
    int offset_size;
  } header_;

  // buffer is the buffer for our line info, starting at exactly where
  // the line info to read is.
  const unsigned char* buffer_;
  const unsigned char* buffer_end_;
  // If the buffer was allocated temporarily, and therefore must be
  // deallocated in the dtor, this contains a pointer to the start
  // of the buffer.
  const unsigned char* buffer_start_;

  // This has relocations that point into buffer.
  Sized_elf_reloc_mapper<size, big_endian>* reloc_mapper_;
  // The type of the reloc section in track_relocs_--SHT_REL or SHT_RELA.
  unsigned int track_relocs_type_;

  // This is used to figure out what section to apply a relocation to.
  const unsigned char* symtab_buffer_;
  section_size_type symtab_buffer_size_;

  // Holds the directories and files as we see them.  We have an array
  // of directory-lists, one for each .o file we're reading (usually
  // there will just be one, but there may be more if input is a .so).
  std::vector<std::vector<std::string> > directories_;
  // The first part is an index into directories_, the second the filename.
  std::vector<std::vector< std::pair<int, std::string> > > files_;

  // An index into the current directories_ and files_ vectors.
  int current_header_index_;

  // A sorted map from offset of the relocation target to the shndx
  // and addend for the relocation.
  typedef std::map<off_t, std::pair<unsigned int, off_t> >
  Reloc_map;
  Reloc_map reloc_map_;

  // We have a vector of offset->lineno entries for every input section.
  typedef Unordered_map<unsigned int, std::vector<Offset_to_lineno_entry> >
  Lineno_map;

  Lineno_map line_number_map_;
};

} // End namespace gold.

#endif // !defined(GOLD_DWARF_READER_H)