aboutsummaryrefslogtreecommitdiff
path: root/gold/ehframe.cc
blob: 57eb031fafc5eb114e066cd0ee5dcdd6b0daee77 (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
1288
1289
1290
1291
1292
// ehframe.cc -- handle exception frame sections for gold

// Copyright (C) 2006-2016 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.

#include "gold.h"

#include <cstring>
#include <algorithm>

#include "elfcpp.h"
#include "dwarf.h"
#include "symtab.h"
#include "reloc.h"
#include "ehframe.h"

namespace gold
{

// This file handles generation of the exception frame header that
// gcc's runtime support libraries use to find unwind information at
// runtime.  This file also handles discarding duplicate exception
// frame information.

// The exception frame header starts with four bytes:

// 0: The version number, currently 1.

// 1: The encoding of the pointer to the exception frames.  This can
//    be any DWARF unwind encoding (DW_EH_PE_*).  It is normally a 4
//    byte PC relative offset (DW_EH_PE_pcrel | DW_EH_PE_sdata4).

// 2: The encoding of the count of the number of FDE pointers in the
//    lookup table.  This can be any DWARF unwind encoding, and in
//    particular can be DW_EH_PE_omit if the count is omitted.  It is
//    normally a 4 byte unsigned count (DW_EH_PE_udata4).

// 3: The encoding of the lookup table entries.  Currently gcc's
//    libraries will only support DW_EH_PE_datarel | DW_EH_PE_sdata4,
//    which means that the values are 4 byte offsets from the start of
//    the table.

// The exception frame header is followed by a pointer to the contents
// of the exception frame section (.eh_frame).  This pointer is
// encoded as specified in the byte at offset 1 of the header (i.e.,
// it is normally a 4 byte PC relative offset).

// If there is a lookup table, this is followed by the count of the
// number of FDE pointers, encoded as specified in the byte at offset
// 2 of the header (i.e., normally a 4 byte unsigned integer).

// This is followed by the table, which should start at an 4-byte
// aligned address in memory.  Each entry in the table is 8 bytes.
// Each entry represents an FDE.  The first four bytes of each entry
// are an offset to the starting PC for the FDE.  The last four bytes
// of each entry are an offset to the FDE data.  The offsets are from
// the start of the exception frame header information.  The entries
// are in sorted order by starting PC.

const int eh_frame_hdr_size = 4;

// Construct the exception frame header.

Eh_frame_hdr::Eh_frame_hdr(Output_section* eh_frame_section,
			   const Eh_frame* eh_frame_data)
  : Output_section_data(4),
    eh_frame_section_(eh_frame_section),
    eh_frame_data_(eh_frame_data),
    fde_offsets_(),
    any_unrecognized_eh_frame_sections_(false)
{
}

// Set the size of the exception frame header.

void
Eh_frame_hdr::set_final_data_size()
{
  unsigned int data_size = eh_frame_hdr_size + 4;
  if (!this->any_unrecognized_eh_frame_sections_)
    {
      unsigned int fde_count = this->eh_frame_data_->fde_count();
      if (fde_count != 0)
	data_size += 4 + 8 * fde_count;
      this->fde_offsets_.reserve(fde_count);
    }
  this->set_data_size(data_size);
}

// Write the data to the file.

void
Eh_frame_hdr::do_write(Output_file* of)
{
  switch (parameters->size_and_endianness())
    {
#ifdef HAVE_TARGET_32_LITTLE
    case Parameters::TARGET_32_LITTLE:
      this->do_sized_write<32, false>(of);
      break;
#endif
#ifdef HAVE_TARGET_32_BIG
    case Parameters::TARGET_32_BIG:
      this->do_sized_write<32, true>(of);
      break;
#endif
#ifdef HAVE_TARGET_64_LITTLE
    case Parameters::TARGET_64_LITTLE:
      this->do_sized_write<64, false>(of);
      break;
#endif
#ifdef HAVE_TARGET_64_BIG
    case Parameters::TARGET_64_BIG:
      this->do_sized_write<64, true>(of);
      break;
#endif
    default:
      gold_unreachable();
    }
}

// Write the data to the file with the right endianness.

template<int size, bool big_endian>
void
Eh_frame_hdr::do_sized_write(Output_file* of)
{
  const off_t off = this->offset();
  const off_t oview_size = this->data_size();
  unsigned char* const oview = of->get_output_view(off, oview_size);

  // Version number.
  oview[0] = 1;

  // Write out a 4 byte PC relative offset to the address of the
  // .eh_frame section.
  oview[1] = elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4;
  uint64_t eh_frame_address = this->eh_frame_section_->address();
  uint64_t eh_frame_hdr_address = this->address();
  uint64_t eh_frame_offset = (eh_frame_address -
			      (eh_frame_hdr_address + 4));
  elfcpp::Swap<32, big_endian>::writeval(oview + 4, eh_frame_offset);

  if (this->any_unrecognized_eh_frame_sections_
      || this->fde_offsets_.empty())
    {
      // There are no FDEs, or we didn't recognize the format of the
      // some of the .eh_frame sections, so we can't write out the
      // sorted table.
      oview[2] = elfcpp::DW_EH_PE_omit;
      oview[3] = elfcpp::DW_EH_PE_omit;

      gold_assert(oview_size == 8);
    }
  else
    {
      oview[2] = elfcpp::DW_EH_PE_udata4;
      oview[3] = elfcpp::DW_EH_PE_datarel | elfcpp::DW_EH_PE_sdata4;

      elfcpp::Swap<32, big_endian>::writeval(oview + 8,
					     this->fde_offsets_.size());

      // We have the offsets of the FDEs in the .eh_frame section.  We
      // couldn't easily get the PC values before, as they depend on
      // relocations which are, of course, target specific.  This code
      // is run after all those relocations have been applied to the
      // output file.  Here we read the output file again to find the
      // PC values.  Then we sort the list and write it out.

      Fde_addresses<size> fde_addresses(this->fde_offsets_.size());
      this->get_fde_addresses<size, big_endian>(of, &this->fde_offsets_,
						&fde_addresses);

      std::sort(fde_addresses.begin(), fde_addresses.end(),
		Fde_address_compare<size>());

      typename elfcpp::Elf_types<size>::Elf_Addr output_address;
      output_address = this->address();

      unsigned char* pfde = oview + 12;
      for (typename Fde_addresses<size>::iterator p = fde_addresses.begin();
	   p != fde_addresses.end();
	   ++p)
	{
	  elfcpp::Swap<32, big_endian>::writeval(pfde,
						 p->first - output_address);
	  elfcpp::Swap<32, big_endian>::writeval(pfde + 4,
						 p->second - output_address);
	  pfde += 8;
	}

      gold_assert(pfde - oview == oview_size);
    }

  of->write_output_view(off, oview_size, oview);
}

// Given the offset FDE_OFFSET of an FDE in the .eh_frame section, and
// the contents of the .eh_frame section EH_FRAME_CONTENTS, where the
// FDE's encoding is FDE_ENCODING, return the output address of the
// FDE's PC.

template<int size, bool big_endian>
typename elfcpp::Elf_types<size>::Elf_Addr
Eh_frame_hdr::get_fde_pc(
    typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address,
    const unsigned char* eh_frame_contents,
    section_offset_type fde_offset,
    unsigned char fde_encoding)
{
  // The FDE starts with a 4 byte length and a 4 byte offset to the
  // CIE.  The PC follows.
  const unsigned char* p = eh_frame_contents + fde_offset + 8;

  typename elfcpp::Elf_types<size>::Elf_Addr pc;
  bool is_signed = (fde_encoding & elfcpp::DW_EH_PE_signed) != 0;
  int pc_size = fde_encoding & 7;
  if (pc_size == elfcpp::DW_EH_PE_absptr)
    {
      if (size == 32)
	pc_size = elfcpp::DW_EH_PE_udata4;
      else if (size == 64)
	pc_size = elfcpp::DW_EH_PE_udata8;
      else
	gold_unreachable();
    }

  switch (pc_size)
    {
    case elfcpp::DW_EH_PE_udata2:
      pc = elfcpp::Swap<16, big_endian>::readval(p);
      if (is_signed)
	pc = (pc ^ 0x8000) - 0x8000;
      break;

    case elfcpp::DW_EH_PE_udata4:
      pc = elfcpp::Swap<32, big_endian>::readval(p);
      if (size > 32 && is_signed)
	pc = (pc ^ 0x80000000) - 0x80000000;
      break;

    case elfcpp::DW_EH_PE_udata8:
      gold_assert(size == 64);
      pc = elfcpp::Swap_unaligned<64, big_endian>::readval(p);
      break;

    default:
      // All other cases were rejected in Eh_frame::read_cie.
      gold_unreachable();
    }

  switch (fde_encoding & 0x70)
    {
    case 0:
      break;

    case elfcpp::DW_EH_PE_pcrel:
      pc += eh_frame_address + fde_offset + 8;
      break;

    case elfcpp::DW_EH_PE_datarel:
      pc += parameters->target().ehframe_datarel_base();
      break;

    default:
      // If other cases arise, then we have to handle them, or we have
      // to reject them by returning false in Eh_frame::read_cie.
      gold_unreachable();
    }

  gold_assert((fde_encoding & elfcpp::DW_EH_PE_indirect) == 0);

  return pc;
}

// Given an array of FDE offsets in the .eh_frame section, return an
// array of offsets from the exception frame header to the FDE's
// output PC and to the output address of the FDE itself.  We get the
// FDE's PC by actually looking in the .eh_frame section we just wrote
// to the output file.

template<int size, bool big_endian>
void
Eh_frame_hdr::get_fde_addresses(Output_file* of,
				const Fde_offsets* fde_offsets,
				Fde_addresses<size>* fde_addresses)
{
  typename elfcpp::Elf_types<size>::Elf_Addr eh_frame_address;
  eh_frame_address = this->eh_frame_section_->address();
  off_t eh_frame_offset = this->eh_frame_section_->offset();
  off_t eh_frame_size = this->eh_frame_section_->data_size();
  const unsigned char* eh_frame_contents = of->get_input_view(eh_frame_offset,
							      eh_frame_size);

  for (Fde_offsets::const_iterator p = fde_offsets->begin();
       p != fde_offsets->end();
       ++p)
    {
      typename elfcpp::Elf_types<size>::Elf_Addr fde_pc;
      fde_pc = this->get_fde_pc<size, big_endian>(eh_frame_address,
						  eh_frame_contents,
						  p->first, p->second);
      fde_addresses->push_back(fde_pc, eh_frame_address + p->first);
    }

  of->free_input_view(eh_frame_offset, eh_frame_size, eh_frame_contents);
}

// Class Fde.

// Write the FDE to OVIEW starting at OFFSET.  CIE_OFFSET is the
// offset of the CIE in OVIEW.  OUTPUT_OFFSET is the offset of the
// Eh_frame section within the output section.  FDE_ENCODING is the
// encoding, from the CIE.  ADDRALIGN is the required alignment.
// ADDRESS is the virtual address of OVIEW.  Record the FDE pc for
// EH_FRAME_HDR.  Return the new offset.

template<int size, bool big_endian>
section_offset_type
Fde::write(unsigned char* oview, section_offset_type output_offset,
	   section_offset_type offset, uint64_t address, unsigned int addralign,
	   section_offset_type cie_offset, unsigned char fde_encoding,
	   Eh_frame_hdr* eh_frame_hdr)
{
  gold_assert((offset & (addralign - 1)) == 0);

  size_t length = this->contents_.length();

  // We add 8 when getting the aligned length to account for the
  // length word and the CIE offset.
  size_t aligned_full_length = align_address(length + 8, addralign);

  // Write the length of the FDE as a 32-bit word.  The length word
  // does not include the four bytes of the length word itself, but it
  // does include the offset to the CIE.
  elfcpp::Swap<32, big_endian>::writeval(oview + offset,
                                         aligned_full_length - 4);

  // Write the offset to the CIE as a 32-bit word.  This is the
  // difference between the address of the offset word itself and the
  // CIE address.
  elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4,
					 offset + 4 - cie_offset);

  // Copy the rest of the FDE.  Note that this is run before
  // relocation processing is done on this section, so the relocations
  // will later be applied to the FDE data.
  memcpy(oview + offset + 8, this->contents_.data(), length);

  // If this FDE is associated with a PLT, fill in the PLT's address
  // and size.
  if (this->object_ == NULL)
    {
      gold_assert(memcmp(oview + offset + 8, "\0\0\0\0\0\0\0\0", 8) == 0);
      uint64_t paddress;
      off_t psize;
      parameters->target().plt_fde_location(this->u_.from_linker.plt,
					    oview + offset + 8,
					    &paddress, &psize);
      uint64_t poffset = paddress - (address + offset + 8);
      int32_t spoffset = static_cast<int32_t>(poffset);
      uint32_t upsize = static_cast<uint32_t>(psize);
      if (static_cast<uint64_t>(static_cast<int64_t>(spoffset)) != poffset
	  || static_cast<off_t>(upsize) != psize)
	gold_warning(_("overflow in PLT unwind data; "
		       "unwinding through PLT may fail"));
      elfcpp::Swap<32, big_endian>::writeval(oview + offset + 8, spoffset);
      elfcpp::Swap<32, big_endian>::writeval(oview + offset + 12, upsize);
    }

  if (aligned_full_length > length + 8)
    memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8));

  // Tell the exception frame header about this FDE.
  if (eh_frame_hdr != NULL)
    eh_frame_hdr->record_fde(output_offset + offset, fde_encoding);

  return offset + aligned_full_length;
}

// Class Cie.

// Destructor.

Cie::~Cie()
{
  for (std::vector<Fde*>::iterator p = this->fdes_.begin();
       p != this->fdes_.end();
       ++p)
    delete *p;
}

// Set the output offset of a CIE.  Return the new output offset.

section_offset_type
Cie::set_output_offset(section_offset_type output_offset,
		       unsigned int addralign,
		       Output_section_data *output_data)
{
  size_t length = this->contents_.length();

  // Add 4 for length and 4 for zero CIE identifier tag.
  length += 8;

  if (this->object_ != NULL)
    {
      // Add a mapping so that relocations are applied correctly.
      this->object_->add_merge_mapping(output_data, this->shndx_,
                                       this->input_offset_, length,
                                       output_offset);
    }

  length = align_address(length, addralign);

  for (std::vector<Fde*>::const_iterator p = this->fdes_.begin();
       p != this->fdes_.end();
       ++p)
    {
      (*p)->add_mapping(output_offset + length, output_data);

      size_t fde_length = (*p)->length();
      fde_length = align_address(fde_length, addralign);
      length += fde_length;
    }

  return output_offset + length;
}

// Write the CIE to OVIEW starting at OFFSET.  OUTPUT_OFFSET is the
// offset of the Eh_frame section within the output section.  Round up
// the bytes to ADDRALIGN.  ADDRESS is the virtual address of OVIEW.
// EH_FRAME_HDR is the exception frame header for FDE recording.
// POST_FDES stashes FDEs created after mappings were done, for later
// writing.  Return the new offset.

template<int size, bool big_endian>
section_offset_type
Cie::write(unsigned char* oview, section_offset_type output_offset,
	   section_offset_type offset, uint64_t address,
	   unsigned int addralign, Eh_frame_hdr* eh_frame_hdr,
	   Post_fdes* post_fdes)
{
  gold_assert((offset & (addralign - 1)) == 0);

  section_offset_type cie_offset = offset;

  size_t length = this->contents_.length();

  // We add 8 when getting the aligned length to account for the
  // length word and the CIE tag.
  size_t aligned_full_length = align_address(length + 8, addralign);

  // Write the length of the CIE as a 32-bit word.  The length word
  // does not include the four bytes of the length word itself.
  elfcpp::Swap<32, big_endian>::writeval(oview + offset,
                                         aligned_full_length - 4);

  // Write the tag which marks this as a CIE: a 32-bit zero.
  elfcpp::Swap<32, big_endian>::writeval(oview + offset + 4, 0);

  // Write out the CIE data.
  memcpy(oview + offset + 8, this->contents_.data(), length);

  if (aligned_full_length > length + 8)
    memset(oview + offset + length + 8, 0, aligned_full_length - (length + 8));

  offset += aligned_full_length;

  // Write out the associated FDEs.
  unsigned char fde_encoding = this->fde_encoding_;
  for (std::vector<Fde*>::const_iterator p = this->fdes_.begin();
       p != this->fdes_.end();
       ++p)
    {
      if ((*p)->post_map())
	post_fdes->push_back(Post_fde(*p, cie_offset, fde_encoding));
      else
	offset = (*p)->write<size, big_endian>(oview, output_offset, offset,
					       address, addralign, cie_offset,
					       fde_encoding, eh_frame_hdr);
    }

  return offset;
}

// We track all the CIEs we see, and merge them when possible.  This
// works because each FDE holds an offset to the relevant CIE: we
// rewrite the FDEs to point to the merged CIE.  This is worthwhile
// because in a typical C++ program many FDEs in many different object
// files will use the same CIE.

// An equality operator for Cie.

bool
operator==(const Cie& cie1, const Cie& cie2)
{
  return (cie1.personality_name_ == cie2.personality_name_
	  && cie1.contents_ == cie2.contents_);
}

// A less-than operator for Cie.

bool
operator<(const Cie& cie1, const Cie& cie2)
{
  if (cie1.personality_name_ != cie2.personality_name_)
    return cie1.personality_name_ < cie2.personality_name_;
  return cie1.contents_ < cie2.contents_;
}

// Class Eh_frame.

Eh_frame::Eh_frame()
  : Output_section_data(Output_data::default_alignment()),
    eh_frame_hdr_(NULL),
    cie_offsets_(),
    unmergeable_cie_offsets_(),
    mappings_are_done_(false),
    final_data_size_(0)
{
}

// Skip an LEB128, updating *PP to point to the next character.
// Return false if we ran off the end of the string.

bool
Eh_frame::skip_leb128(const unsigned char** pp, const unsigned char* pend)
{
  const unsigned char* p;
  for (p = *pp; p < pend; ++p)
    {
      if ((*p & 0x80) == 0)
	{
	  *pp = p + 1;
	  return true;
	}
    }
  return false;
}

// Add input section SHNDX in OBJECT to an exception frame section.
// SYMBOLS is the contents of the symbol table section (size
// SYMBOLS_SIZE), SYMBOL_NAMES is the symbol names section (size
// SYMBOL_NAMES_SIZE).  RELOC_SHNDX is the index of a relocation
// section applying to SHNDX, or 0 if none, or -1U if more than one.
// RELOC_TYPE is the type of the reloc section if there is one, either
// SHT_REL or SHT_RELA.  We try to parse the input exception frame
// data into our data structures.  If we can't do it, we return false
// to mean that the section should be handled as a normal input
// section.

template<int size, bool big_endian>
Eh_frame::Eh_frame_section_disposition
Eh_frame::add_ehframe_input_section(
    Sized_relobj_file<size, big_endian>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type)
{
  // Get the section contents.
  section_size_type contents_len;
  const unsigned char* pcontents = object->section_contents(shndx,
							    &contents_len,
							    false);
  if (contents_len == 0)
    return EH_EMPTY_SECTION;

  // If this is the marker section for the end of the data, then
  // return false to force it to be handled as an ordinary input
  // section.  If we don't do this, we won't correctly handle the case
  // of unrecognized .eh_frame sections.
  if (contents_len == 4
      && elfcpp::Swap<32, big_endian>::readval(pcontents) == 0)
    return EH_END_MARKER_SECTION;

  New_cies new_cies;
  if (!this->do_add_ehframe_input_section(object, symbols, symbols_size,
					  symbol_names, symbol_names_size,
					  shndx, reloc_shndx,
					  reloc_type, pcontents,
					  contents_len, &new_cies))
    {
      if (this->eh_frame_hdr_ != NULL)
	this->eh_frame_hdr_->found_unrecognized_eh_frame_section();

      for (New_cies::iterator p = new_cies.begin();
	   p != new_cies.end();
	   ++p)
	delete p->first;

      return EH_UNRECOGNIZED_SECTION;
    }

  // Now that we know we are using this section, record any new CIEs
  // that we found.
  for (New_cies::const_iterator p = new_cies.begin();
       p != new_cies.end();
       ++p)
    {
      if (p->second)
	this->cie_offsets_.insert(p->first);
      else
	this->unmergeable_cie_offsets_.push_back(p->first);
    }

  return EH_OPTIMIZABLE_SECTION;
}

// The bulk of the implementation of add_ehframe_input_section.

template<int size, bool big_endian>
bool
Eh_frame::do_add_ehframe_input_section(
    Sized_relobj_file<size, big_endian>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type,
    const unsigned char* pcontents,
    section_size_type contents_len,
    New_cies* new_cies)
{
  Track_relocs<size, big_endian> relocs;

  const unsigned char* p = pcontents;
  const unsigned char* pend = p + contents_len;

  // Get the contents of the reloc section if any.
  if (!relocs.initialize(object, reloc_shndx, reloc_type))
    return false;

  // Keep track of which CIEs are at which offsets.
  Offsets_to_cie cies;

  while (p < pend)
    {
      if (pend - p < 4)
	return false;

      // There shouldn't be any relocations here.
      if (relocs.advance(p + 4 - pcontents) > 0)
	return false;

      unsigned int len = elfcpp::Swap<32, big_endian>::readval(p);
      p += 4;
      if (len == 0)
	{
	  // We should only find a zero-length entry at the end of the
	  // section.
	  if (p < pend)
	    return false;
	  break;
	}
      // We don't support a 64-bit .eh_frame.
      if (len == 0xffffffff)
	return false;
      if (static_cast<unsigned int>(pend - p) < len)
	return false;

      const unsigned char* const pentend = p + len;

      if (pend - p < 4)
	return false;
      if (relocs.advance(p + 4 - pcontents) > 0)
	return false;

      unsigned int id = elfcpp::Swap<32, big_endian>::readval(p);
      p += 4;

      if (id == 0)
	{
	  // CIE.
	  if (!this->read_cie(object, shndx, symbols, symbols_size,
			      symbol_names, symbol_names_size,
			      pcontents, p, pentend, &relocs, &cies,
			      new_cies))
	    return false;
	}
      else
	{
	  // FDE.
	  if (!this->read_fde(object, shndx, symbols, symbols_size,
			      pcontents, id, p, pentend, &relocs, &cies))
	    return false;
	}

      p = pentend;
    }

  return true;
}

// Read a CIE.  Return false if we can't parse the information.

template<int size, bool big_endian>
bool
Eh_frame::read_cie(Sized_relobj_file<size, big_endian>* object,
		   unsigned int shndx,
		   const unsigned char* symbols,
		   section_size_type symbols_size,
		   const unsigned char* symbol_names,
		   section_size_type symbol_names_size,
		   const unsigned char* pcontents,
		   const unsigned char* pcie,
		   const unsigned char* pcieend,
		   Track_relocs<size, big_endian>* relocs,
		   Offsets_to_cie* cies,
		   New_cies* new_cies)
{
  bool mergeable = true;

  // We need to find the personality routine if there is one, since we
  // can only merge CIEs which use the same routine.  We also need to
  // find the FDE encoding if there is one, so that we can read the PC
  // from the FDE.

  const unsigned char* p = pcie;

  if (pcieend - p < 1)
    return false;
  unsigned char version = *p++;
  if (version != 1 && version != 3)
    return false;

  const unsigned char* paug = p;
  const void* paugendv = memchr(p, '\0', pcieend - p);
  const unsigned char* paugend = static_cast<const unsigned char*>(paugendv);
  if (paugend == NULL)
    return false;
  p = paugend + 1;

  if (paug[0] == 'e' && paug[1] == 'h')
    {
      // This is a CIE from gcc before version 3.0.  We can't merge
      // these.  We can still read the FDEs.
      mergeable = false;
      paug += 2;
      if (*paug != '\0')
	return false;
      if (pcieend - p < size / 8)
	return false;
      p += size / 8;
    }

  // Skip the code alignment.
  if (!skip_leb128(&p, pcieend))
    return false;

  // Skip the data alignment.
  if (!skip_leb128(&p, pcieend))
    return false;

  // Skip the return column.
  if (version == 1)
    {
      if (pcieend - p < 1)
	return false;
      ++p;
    }
  else
    {
      if (!skip_leb128(&p, pcieend))
	return false;
    }

  if (*paug == 'z')
    {
      ++paug;
      // Skip the augmentation size.
      if (!skip_leb128(&p, pcieend))
	return false;
    }

  unsigned char fde_encoding = elfcpp::DW_EH_PE_absptr;
  int per_offset = -1;
  while (*paug != '\0')
    {
      switch (*paug)
	{
	case 'L': // LSDA encoding.
	  if (pcieend - p < 1)
	    return false;
	  ++p;
	  break;

	case 'R': // FDE encoding.
	  if (pcieend - p < 1)
	    return false;
	  fde_encoding = *p;
	  switch (fde_encoding & 7)
	    {
	    case elfcpp::DW_EH_PE_absptr:
	    case elfcpp::DW_EH_PE_udata2:
	    case elfcpp::DW_EH_PE_udata4:
	    case elfcpp::DW_EH_PE_udata8:
	      break;
	    default:
	      // We don't expect to see any other cases here, and
	      // we're not prepared to handle them.
	      return false;
	    }
	  ++p;
	  break;

	case 'S':
	  break;

	case 'P':
	  // Personality encoding.
	  {
	    if (pcieend - p < 1)
	      return false;
	    unsigned char per_encoding = *p;
	    ++p;

	    if ((per_encoding & 0x60) == 0x60)
	      return false;
	    unsigned int per_width;
	    switch (per_encoding & 7)
	      {
	      case elfcpp::DW_EH_PE_udata2:
		per_width = 2;
		break;
	      case elfcpp::DW_EH_PE_udata4:
		per_width = 4;
		break;
	      case elfcpp::DW_EH_PE_udata8:
		per_width = 8;
		break;
	      case elfcpp::DW_EH_PE_absptr:
		per_width = size / 8;
		break;
	      default:
		return false;
	      }

	    if ((per_encoding & 0xf0) == elfcpp::DW_EH_PE_aligned)
	      {
		unsigned int len = p - pcie;
		len += per_width - 1;
		len &= ~ (per_width - 1);
		if (static_cast<unsigned int>(pcieend - p) < len)
		  return false;
		p += len;
	      }

	    per_offset = p - pcontents;

	    if (static_cast<unsigned int>(pcieend - p) < per_width)
	      return false;
	    p += per_width;
	  }
	  break;

	default:
	  return false;
	}

      ++paug;
    }

  const char* personality_name = "";
  if (per_offset != -1)
    {
      if (relocs->advance(per_offset) > 0)
	return false;
      if (relocs->next_offset() != per_offset)
	return false;

      unsigned int personality_symndx = relocs->next_symndx();
      if (personality_symndx == -1U)
	return false;

      if (personality_symndx < object->local_symbol_count())
	{
	  // We can only merge this CIE if the personality routine is
	  // a global symbol.  We can still read the FDEs.
	  mergeable = false;
	}
      else
	{
	  const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
	  if (personality_symndx >= symbols_size / sym_size)
	    return false;
	  elfcpp::Sym<size, big_endian> sym(symbols
					    + (personality_symndx * sym_size));
	  unsigned int name_offset = sym.get_st_name();
	  if (name_offset >= symbol_names_size)
	    return false;
	  personality_name = (reinterpret_cast<const char*>(symbol_names)
			      + name_offset);
	}

      int r = relocs->advance(per_offset + 1);
      gold_assert(r == 1);
    }

  if (relocs->advance(pcieend - pcontents) > 0)
    return false;

  Cie cie(object, shndx, (pcie - 8) - pcontents, fde_encoding, 
	  personality_name, pcie, pcieend - pcie);
  Cie* cie_pointer = NULL;
  if (mergeable)
    {
      Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie);
      if (find_cie != this->cie_offsets_.end())
	cie_pointer = *find_cie;
      else
	{
	  // See if we already saw this CIE in this object file.
	  for (New_cies::const_iterator pc = new_cies->begin();
	       pc != new_cies->end();
	       ++pc)
	    {
	      if (*(pc->first) == cie)
		{
		  cie_pointer = pc->first;
		  break;
		}
	    }
	}
    }

  if (cie_pointer == NULL)
    {
      cie_pointer = new Cie(cie);
      new_cies->push_back(std::make_pair(cie_pointer, mergeable));
    }
  else
    {
      // We are deleting this CIE.  Record that in our mapping from
      // input sections to the output section.  At this point we don't
      // know for sure that we are doing a special mapping for this
      // input section, but that's OK--if we don't do a special
      // mapping, nobody will ever ask for the mapping we add here.
      object->add_merge_mapping(this, shndx, (pcie - 8) - pcontents,
                                pcieend - (pcie - 8), -1);
    }

  // Record this CIE plus the offset in the input section.
  cies->insert(std::make_pair(pcie - pcontents, cie_pointer));

  return true;
}

// Read an FDE.  Return false if we can't parse the information.

template<int size, bool big_endian>
bool
Eh_frame::read_fde(Sized_relobj_file<size, big_endian>* object,
		   unsigned int shndx,
		   const unsigned char* symbols,
		   section_size_type symbols_size,
		   const unsigned char* pcontents,
		   unsigned int offset,
		   const unsigned char* pfde,
		   const unsigned char* pfdeend,
		   Track_relocs<size, big_endian>* relocs,
		   Offsets_to_cie* cies)
{
  // OFFSET is the distance between the 4 bytes before PFDE to the
  // start of the CIE.  The offset we recorded for the CIE is 8 bytes
  // after the start of the CIE--after the length and the zero tag.
  unsigned int cie_offset = (pfde - 4 - pcontents) - offset + 8;
  Offsets_to_cie::const_iterator pcie = cies->find(cie_offset);
  if (pcie == cies->end())
    return false;
  Cie* cie = pcie->second;

  // The FDE should start with a reloc to the start of the code which
  // it describes.
  if (relocs->advance(pfde - pcontents) > 0)
    return false;

  if (relocs->next_offset() != pfde - pcontents)
    return false;

  unsigned int symndx = relocs->next_symndx();
  if (symndx == -1U)
    return false;

  // There can be another reloc in the FDE, if the CIE specifies an
  // LSDA (language specific data area).  We currently don't care.  We
  // will care later if we want to optimize the LSDA from an absolute
  // pointer to a PC relative offset when generating a shared library.
  relocs->advance(pfdeend - pcontents);

  // Find the section index for code that this FDE describes.
  // If we have discarded the section, we can also discard the FDE.
  unsigned int fde_shndx;
  const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
  if (symndx >= symbols_size / sym_size)
    return false;
  elfcpp::Sym<size, big_endian> sym(symbols + symndx * sym_size);
  bool is_ordinary;
  fde_shndx = object->adjust_sym_shndx(symndx, sym.get_st_shndx(),
				       &is_ordinary);
  bool is_discarded = (is_ordinary
		       && fde_shndx != elfcpp::SHN_UNDEF
		       && fde_shndx < object->shnum()
		       && !object->is_section_included(fde_shndx));

  // Fetch the address range field from the FDE. The offset and size
  // of the field depends on the PC encoding given in the CIE, but
  // it is always an absolute value. If the address range is 0, this
  // FDE corresponds to a function that was discarded during optimization
  // (too late to discard the corresponding FDE).
  uint64_t address_range = 0;
  int pc_size = cie->fde_encoding() & 7;
  if (pc_size == elfcpp::DW_EH_PE_absptr)
    pc_size = size == 32 ? elfcpp::DW_EH_PE_udata4 : elfcpp::DW_EH_PE_udata8;
  switch (pc_size)
    {
    case elfcpp::DW_EH_PE_udata2:
      address_range = elfcpp::Swap<16, big_endian>::readval(pfde + 2);
      break;
    case elfcpp::DW_EH_PE_udata4:
      address_range = elfcpp::Swap<32, big_endian>::readval(pfde + 4);
      break;
    case elfcpp::DW_EH_PE_udata8:
      gold_assert(size == 64);
      address_range = elfcpp::Swap_unaligned<64, big_endian>::readval(pfde + 8);
      break;
    default:
      // All other cases were rejected in Eh_frame::read_cie.
      gold_unreachable();
    }

  if (is_discarded || address_range == 0)
    {
      // This FDE applies to a discarded function.  We
      // can discard this FDE.
      object->add_merge_mapping(this, shndx, (pfde - 8) - pcontents,
                                pfdeend - (pfde - 8), -1);
      return true;
    }

  cie->add_fde(new Fde(object, shndx, (pfde - 8) - pcontents,
		       pfde, pfdeend - pfde));

  return true;
}

// Add unwind information for a PLT.

void
Eh_frame::add_ehframe_for_plt(Output_data* plt, const unsigned char* cie_data,
			      size_t cie_length, const unsigned char* fde_data,
			      size_t fde_length)
{
  Cie cie(NULL, 0, 0, elfcpp::DW_EH_PE_pcrel | elfcpp::DW_EH_PE_sdata4, "",
	  cie_data, cie_length);
  Cie_offsets::iterator find_cie = this->cie_offsets_.find(&cie);
  Cie* pcie;
  if (find_cie != this->cie_offsets_.end())
    pcie = *find_cie;
  else
    {
      gold_assert(!this->mappings_are_done_);
      pcie = new Cie(cie);
      this->cie_offsets_.insert(pcie);
    }

  Fde* fde = new Fde(plt, fde_data, fde_length, this->mappings_are_done_);
  pcie->add_fde(fde);

  if (this->mappings_are_done_)
    this->final_data_size_ += align_address(fde_length + 8, this->addralign());
}

// Return the number of FDEs.

unsigned int
Eh_frame::fde_count() const
{
  unsigned int ret = 0;
  for (Unmergeable_cie_offsets::const_iterator p =
	 this->unmergeable_cie_offsets_.begin();
       p != this->unmergeable_cie_offsets_.end();
       ++p)
    ret += (*p)->fde_count();
  for (Cie_offsets::const_iterator p = this->cie_offsets_.begin();
       p != this->cie_offsets_.end();
       ++p)
    ret += (*p)->fde_count();
  return ret;
}

// Set the final data size.

void
Eh_frame::set_final_data_size()
{
  // We can be called more than once if Layout::set_segment_offsets
  // finds a better mapping.  We don't want to add all the mappings
  // again.
  if (this->mappings_are_done_)
    {
      this->set_data_size(this->final_data_size_);
      return;
    }

  section_offset_type output_start = 0;
  if (this->is_offset_valid())
    output_start = this->offset() - this->output_section()->offset();
  section_offset_type output_offset = output_start;

  for (Unmergeable_cie_offsets::iterator p =
	 this->unmergeable_cie_offsets_.begin();
       p != this->unmergeable_cie_offsets_.end();
       ++p)
    output_offset = (*p)->set_output_offset(output_offset,
					    this->addralign(),
					    this);

  for (Cie_offsets::iterator p = this->cie_offsets_.begin();
       p != this->cie_offsets_.end();
       ++p)
    output_offset = (*p)->set_output_offset(output_offset,
					    this->addralign(),
					    this);

  this->mappings_are_done_ = true;
  this->final_data_size_ = output_offset - output_start;

  gold_assert((output_offset & (this->addralign() - 1)) == 0);
  this->set_data_size(this->final_data_size_);
}

// Return an output offset for an input offset.

bool
Eh_frame::do_output_offset(const Relobj* object, unsigned int shndx,
			   section_offset_type offset,
			   section_offset_type* poutput) const
{
  return object->merge_output_offset(shndx, offset, poutput);
}

// Write the data to the output file.

void
Eh_frame::do_write(Output_file* of)
{
  const off_t offset = this->offset();
  const off_t oview_size = this->data_size();
  unsigned char* const oview = of->get_output_view(offset, oview_size);

  switch (parameters->size_and_endianness())
    {
#ifdef HAVE_TARGET_32_LITTLE
    case Parameters::TARGET_32_LITTLE:
      this->do_sized_write<32, false>(oview);
      break;
#endif
#ifdef HAVE_TARGET_32_BIG
    case Parameters::TARGET_32_BIG:
      this->do_sized_write<32, true>(oview);
      break;
#endif
#ifdef HAVE_TARGET_64_LITTLE
    case Parameters::TARGET_64_LITTLE:
      this->do_sized_write<64, false>(oview);
      break;
#endif
#ifdef HAVE_TARGET_64_BIG
    case Parameters::TARGET_64_BIG:
      this->do_sized_write<64, true>(oview);
      break;
#endif
    default:
      gold_unreachable();
    }

  of->write_output_view(offset, oview_size, oview);
}

// Write the data to the output file--template version.

template<int size, bool big_endian>
void
Eh_frame::do_sized_write(unsigned char* oview)
{
  uint64_t address = this->address();
  unsigned int addralign = this->addralign();
  section_offset_type o = 0;
  const off_t output_offset = this->offset() - this->output_section()->offset();
  Post_fdes post_fdes;
  for (Unmergeable_cie_offsets::iterator p =
	 this->unmergeable_cie_offsets_.begin();
       p != this->unmergeable_cie_offsets_.end();
       ++p)
    o = (*p)->write<size, big_endian>(oview, output_offset, o, address,
				      addralign, this->eh_frame_hdr_,
				      &post_fdes);
  for (Cie_offsets::iterator p = this->cie_offsets_.begin();
       p != this->cie_offsets_.end();
       ++p)
    o = (*p)->write<size, big_endian>(oview, output_offset, o, address,
				      addralign, this->eh_frame_hdr_,
				      &post_fdes);
  for (Post_fdes::iterator p = post_fdes.begin();
       p != post_fdes.end();
       ++p)
    o = (*p).fde->write<size, big_endian>(oview, output_offset, o, address,
					  addralign, (*p).cie_offset,
					  (*p).fde_encoding,
					  this->eh_frame_hdr_);
}

#ifdef HAVE_TARGET_32_LITTLE
template
Eh_frame::Eh_frame_section_disposition
Eh_frame::add_ehframe_input_section<32, false>(
    Sized_relobj_file<32, false>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type);
#endif

#ifdef HAVE_TARGET_32_BIG
template
Eh_frame::Eh_frame_section_disposition
Eh_frame::add_ehframe_input_section<32, true>(
    Sized_relobj_file<32, true>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type);
#endif

#ifdef HAVE_TARGET_64_LITTLE
template
Eh_frame::Eh_frame_section_disposition
Eh_frame::add_ehframe_input_section<64, false>(
    Sized_relobj_file<64, false>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type);
#endif

#ifdef HAVE_TARGET_64_BIG
template
Eh_frame::Eh_frame_section_disposition
Eh_frame::add_ehframe_input_section<64, true>(
    Sized_relobj_file<64, true>* object,
    const unsigned char* symbols,
    section_size_type symbols_size,
    const unsigned char* symbol_names,
    section_size_type symbol_names_size,
    unsigned int shndx,
    unsigned int reloc_shndx,
    unsigned int reloc_type);
#endif

} // End namespace gold.