llvm.org GIT mirror llvm / 46e35ed lib / ExecutionEngine / RuntimeDyld / RuntimeDyld.cpp
46e35ed

Tree @46e35ed (Download .tar.gz)

RuntimeDyld.cpp @46e35edraw · history · blame

  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
//===-- RuntimeDyld.cpp - Run-time dynamic linker for MC-JIT ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of the MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//

#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "RuntimeDyldCheckerImpl.h"
#include "RuntimeDyldCOFF.h"
#include "RuntimeDyldELF.h"
#include "RuntimeDyldImpl.h"
#include "RuntimeDyldMachO.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MutexGuard.h"

using namespace llvm;
using namespace llvm::object;

#define DEBUG_TYPE "dyld"

// Empty out-of-line virtual destructor as the key function.
RuntimeDyldImpl::~RuntimeDyldImpl() {}

// Pin LoadedObjectInfo's vtables to this file.
void RuntimeDyld::LoadedObjectInfo::anchor() {}

namespace llvm {

void RuntimeDyldImpl::registerEHFrames() {}

void RuntimeDyldImpl::deregisterEHFrames() {}

#ifndef NDEBUG
static void dumpSectionMemory(const SectionEntry &S, StringRef State) {
  dbgs() << "----- Contents of section " << S.getName() << " " << State
         << " -----";

  if (S.getAddress() == nullptr) {
    dbgs() << "\n          <section not emitted>\n";
    return;
  }

  const unsigned ColsPerRow = 16;

  uint8_t *DataAddr = S.getAddress();
  uint64_t LoadAddr = S.getLoadAddress();

  unsigned StartPadding = LoadAddr & (ColsPerRow - 1);
  unsigned BytesRemaining = S.getSize();

  if (StartPadding) {
    dbgs() << "\n" << format("0x%016" PRIx64,
                             LoadAddr & ~(uint64_t)(ColsPerRow - 1)) << ":";
    while (StartPadding--)
      dbgs() << "   ";
  }

  while (BytesRemaining > 0) {
    if ((LoadAddr & (ColsPerRow - 1)) == 0)
      dbgs() << "\n" << format("0x%016" PRIx64, LoadAddr) << ":";

    dbgs() << " " << format("%02x", *DataAddr);

    ++DataAddr;
    ++LoadAddr;
    --BytesRemaining;
  }

  dbgs() << "\n";
}
#endif

// Resolve the relocations for all symbols we currently know about.
void RuntimeDyldImpl::resolveRelocations() {
  MutexGuard locked(lock);

  // Print out the sections prior to relocation.
  DEBUG(
    for (int i = 0, e = Sections.size(); i != e; ++i)
      dumpSectionMemory(Sections[i], "before relocations");
  );

  // First, resolve relocations associated with external symbols.
  resolveExternalSymbols();

  // Iterate over all outstanding relocations
  for (auto it = Relocations.begin(), e = Relocations.end(); it != e; ++it) {
    // The Section here (Sections[i]) refers to the section in which the
    // symbol for the relocation is located.  The SectionID in the relocation
    // entry provides the section to which the relocation will be applied.
    int Idx = it->first;
    uint64_t Addr = Sections[Idx].getLoadAddress();
    DEBUG(dbgs() << "Resolving relocations Section #" << Idx << "\t"
                 << format("%p", (uintptr_t)Addr) << "\n");
    resolveRelocationList(it->second, Addr);
  }
  Relocations.clear();

  // Print out sections after relocation.
  DEBUG(
    for (int i = 0, e = Sections.size(); i != e; ++i)
      dumpSectionMemory(Sections[i], "after relocations");
  );

}

void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
                                        uint64_t TargetAddress) {
  MutexGuard locked(lock);
  for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
    if (Sections[i].getAddress() == LocalAddress) {
      reassignSectionAddress(i, TargetAddress);
      return;
    }
  }
  llvm_unreachable("Attempting to remap address of unknown section!");
}

static std::error_code getOffset(const SymbolRef &Sym, SectionRef Sec,
                                 uint64_t &Result) {
  ErrorOr<uint64_t> AddressOrErr = Sym.getAddress();
  if (std::error_code EC = AddressOrErr.getError())
    return EC;
  Result = *AddressOrErr - Sec.getAddress();
  return std::error_code();
}

RuntimeDyldImpl::ObjSectionToIDMap
RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
  MutexGuard locked(lock);

  // Save information about our target
  Arch = (Triple::ArchType)Obj.getArch();
  IsTargetLittleEndian = Obj.isLittleEndian();
  setMipsABI(Obj);

  // Compute the memory size required to load all sections to be loaded
  // and pass this information to the memory manager
  if (MemMgr.needsToReserveAllocationSpace()) {
    uint64_t CodeSize = 0, RODataSize = 0, RWDataSize = 0;
    uint32_t CodeAlign = 1, RODataAlign = 1, RWDataAlign = 1;
    computeTotalAllocSize(Obj, CodeSize, CodeAlign, RODataSize, RODataAlign,
                          RWDataSize, RWDataAlign);
    MemMgr.reserveAllocationSpace(CodeSize, CodeAlign, RODataSize, RODataAlign,
                                  RWDataSize, RWDataAlign);
  }

  // Used sections from the object file
  ObjSectionToIDMap LocalSections;

  // Common symbols requiring allocation, with their sizes and alignments
  CommonSymbolList CommonSymbols;

  // Parse symbols
  DEBUG(dbgs() << "Parse symbols:\n");
  for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
       ++I) {
    uint32_t Flags = I->getFlags();

    if (Flags & SymbolRef::SF_Common)
      CommonSymbols.push_back(*I);
    else {
      ErrorOr<object::SymbolRef::Type> SymTypeOrErr = I->getType();
      Check(SymTypeOrErr.getError());
      object::SymbolRef::Type SymType = *SymTypeOrErr;

      // Get symbol name.
      ErrorOr<StringRef> NameOrErr = I->getName();
      Check(NameOrErr.getError());
      StringRef Name = *NameOrErr;
  
      // Compute JIT symbol flags.
      JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
      if (Flags & SymbolRef::SF_Weak)
        RTDyldSymFlags |= JITSymbolFlags::Weak;
      if (Flags & SymbolRef::SF_Exported)
        RTDyldSymFlags |= JITSymbolFlags::Exported;

      if (Flags & SymbolRef::SF_Absolute &&
          SymType != object::SymbolRef::ST_File) {
        auto Addr = I->getAddress();
        Check(Addr.getError());
        uint64_t SectOffset = *Addr;
        unsigned SectionID = AbsoluteSymbolSection;

        DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
                     << " SID: " << SectionID << " Offset: "
                     << format("%p", (uintptr_t)SectOffset)
                     << " flags: " << Flags << "\n");
        GlobalSymbolTable[Name] =
          SymbolTableEntry(SectionID, SectOffset, RTDyldSymFlags);
      } else if (SymType == object::SymbolRef::ST_Function ||
                 SymType == object::SymbolRef::ST_Data ||
                 SymType == object::SymbolRef::ST_Unknown ||
                 SymType == object::SymbolRef::ST_Other) {

        ErrorOr<section_iterator> SIOrErr = I->getSection();
        Check(SIOrErr.getError());
        section_iterator SI = *SIOrErr;
        if (SI == Obj.section_end())
          continue;
        // Get symbol offset.
        uint64_t SectOffset;
        Check(getOffset(*I, *SI, SectOffset));
        bool IsCode = SI->isText();
        unsigned SectionID = findOrEmitSection(Obj, *SI, IsCode, LocalSections);

        DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
                     << " SID: " << SectionID << " Offset: "
                     << format("%p", (uintptr_t)SectOffset)
                     << " flags: " << Flags << "\n");
        GlobalSymbolTable[Name] =
          SymbolTableEntry(SectionID, SectOffset, RTDyldSymFlags);
      }
    }
  }

  // Allocate common symbols
  emitCommonSymbols(Obj, CommonSymbols);

  // Parse and process relocations
  DEBUG(dbgs() << "Parse relocations:\n");
  for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
       SI != SE; ++SI) {
    unsigned SectionID = 0;
    StubMap Stubs;
    section_iterator RelocatedSection = SI->getRelocatedSection();

    if (RelocatedSection == SE)
      continue;

    relocation_iterator I = SI->relocation_begin();
    relocation_iterator E = SI->relocation_end();

    if (I == E && !ProcessAllSections)
      continue;

    bool IsCode = RelocatedSection->isText();
    SectionID =
        findOrEmitSection(Obj, *RelocatedSection, IsCode, LocalSections);
    DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");

    for (; I != E;)
      I = processRelocationRef(SectionID, I, Obj, LocalSections, Stubs);

    // If there is an attached checker, notify it about the stubs for this
    // section so that they can be verified.
    if (Checker)
      Checker->registerStubMap(Obj.getFileName(), SectionID, Stubs);
  }

  // Give the subclasses a chance to tie-up any loose ends.
  finalizeLoad(Obj, LocalSections);

//   for (auto E : LocalSections)
//     llvm::dbgs() << "Added: " << E.first.getRawDataRefImpl() << " -> " << E.second << "\n";

  return LocalSections;
}

// A helper method for computeTotalAllocSize.
// Computes the memory size required to allocate sections with the given sizes,
// assuming that all sections are allocated with the given alignment
static uint64_t
computeAllocationSizeForSections(std::vector<uint64_t> &SectionSizes,
                                 uint64_t Alignment) {
  uint64_t TotalSize = 0;
  for (size_t Idx = 0, Cnt = SectionSizes.size(); Idx < Cnt; Idx++) {
    uint64_t AlignedSize =
        (SectionSizes[Idx] + Alignment - 1) / Alignment * Alignment;
    TotalSize += AlignedSize;
  }
  return TotalSize;
}

static bool isRequiredForExecution(const SectionRef Section) {
  const ObjectFile *Obj = Section.getObject();
  if (isa<object::ELFObjectFileBase>(Obj))
    return ELFSectionRef(Section).getFlags() & ELF::SHF_ALLOC;
  if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj)) {
    const coff_section *CoffSection = COFFObj->getCOFFSection(Section);
    // Avoid loading zero-sized COFF sections.
    // In PE files, VirtualSize gives the section size, and SizeOfRawData
    // may be zero for sections with content. In Obj files, SizeOfRawData 
    // gives the section size, and VirtualSize is always zero. Hence
    // the need to check for both cases below.
    bool HasContent = (CoffSection->VirtualSize > 0) 
      || (CoffSection->SizeOfRawData > 0);
    bool IsDiscardable = CoffSection->Characteristics &
      (COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_LNK_INFO);
    return HasContent && !IsDiscardable;
  }
  
  assert(isa<MachOObjectFile>(Obj));
  return true;
}

static bool isReadOnlyData(const SectionRef Section) {
  const ObjectFile *Obj = Section.getObject();
  if (isa<object::ELFObjectFileBase>(Obj))
    return !(ELFSectionRef(Section).getFlags() &
             (ELF::SHF_WRITE | ELF::SHF_EXECINSTR));
  if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
    return ((COFFObj->getCOFFSection(Section)->Characteristics &
             (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
             | COFF::IMAGE_SCN_MEM_READ
             | COFF::IMAGE_SCN_MEM_WRITE))
             ==
             (COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
             | COFF::IMAGE_SCN_MEM_READ));

  assert(isa<MachOObjectFile>(Obj));
  return false;
}

static bool isZeroInit(const SectionRef Section) {
  const ObjectFile *Obj = Section.getObject();
  if (isa<object::ELFObjectFileBase>(Obj))
    return ELFSectionRef(Section).getType() == ELF::SHT_NOBITS;
  if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
    return COFFObj->getCOFFSection(Section)->Characteristics &
            COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;

  auto *MachO = cast<MachOObjectFile>(Obj);
  unsigned SectionType = MachO->getSectionType(Section);
  return SectionType == MachO::S_ZEROFILL ||
         SectionType == MachO::S_GB_ZEROFILL;
}

// Compute an upper bound of the memory size that is required to load all
// sections
void RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
                                            uint64_t &CodeSize,
                                            uint32_t &CodeAlign,
                                            uint64_t &RODataSize,
                                            uint32_t &RODataAlign,
                                            uint64_t &RWDataSize,
                                            uint32_t &RWDataAlign) {
  // Compute the size of all sections required for execution
  std::vector<uint64_t> CodeSectionSizes;
  std::vector<uint64_t> ROSectionSizes;
  std::vector<uint64_t> RWSectionSizes;

  // Collect sizes of all sections to be loaded;
  // also determine the max alignment of all sections
  for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
       SI != SE; ++SI) {
    const SectionRef &Section = *SI;

    bool IsRequired = isRequiredForExecution(Section);

    // Consider only the sections that are required to be loaded for execution
    if (IsRequired) {
      StringRef Name;
      uint64_t DataSize = Section.getSize();
      uint64_t Alignment64 = Section.getAlignment();
      bool IsCode = Section.isText();
      bool IsReadOnly = isReadOnlyData(Section);
      Check(Section.getName(Name));
      unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;

      uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
      uint64_t SectionSize = DataSize + StubBufSize;

      // The .eh_frame section (at least on Linux) needs an extra four bytes
      // padded
      // with zeroes added at the end.  For MachO objects, this section has a
      // slightly different name, so this won't have any effect for MachO
      // objects.
      if (Name == ".eh_frame")
        SectionSize += 4;

      if (!SectionSize)
        SectionSize = 1;

      if (IsCode) {
        CodeAlign = std::max(CodeAlign, Alignment);
        CodeSectionSizes.push_back(SectionSize);
      } else if (IsReadOnly) {
        RODataAlign = std::max(RODataAlign, Alignment);
        ROSectionSizes.push_back(SectionSize);
      } else {
        RWDataAlign = std::max(RWDataAlign, Alignment);
        RWSectionSizes.push_back(SectionSize);
      }
    }
  }

  // Compute the size of all common symbols
  uint64_t CommonSize = 0;
  for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
       ++I) {
    uint32_t Flags = I->getFlags();
    if (Flags & SymbolRef::SF_Common) {
      // Add the common symbols to a list.  We'll allocate them all below.
      uint64_t Size = I->getCommonSize();
      CommonSize += Size;
    }
  }
  if (CommonSize != 0) {
    RWSectionSizes.push_back(CommonSize);
  }

  // Compute the required allocation space for each different type of sections
  // (code, read-only data, read-write data) assuming that all sections are
  // allocated with the max alignment. Note that we cannot compute with the
  // individual alignments of the sections, because then the required size
  // depends on the order, in which the sections are allocated.
  CodeSize = computeAllocationSizeForSections(CodeSectionSizes, CodeAlign);
  RODataSize = computeAllocationSizeForSections(ROSectionSizes, RODataAlign);
  RWDataSize = computeAllocationSizeForSections(RWSectionSizes, RWDataAlign);
}

// compute stub buffer size for the given section
unsigned RuntimeDyldImpl::computeSectionStubBufSize(const ObjectFile &Obj,
                                                    const SectionRef &Section) {
  unsigned StubSize = getMaxStubSize();
  if (StubSize == 0) {
    return 0;
  }
  // FIXME: this is an inefficient way to handle this. We should computed the
  // necessary section allocation size in loadObject by walking all the sections
  // once.
  unsigned StubBufSize = 0;
  for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
       SI != SE; ++SI) {
    section_iterator RelSecI = SI->getRelocatedSection();
    if (!(RelSecI == Section))
      continue;

    for (const RelocationRef &Reloc : SI->relocations())
      if (relocationNeedsStub(Reloc))
        StubBufSize += StubSize;
  }

  // Get section data size and alignment
  uint64_t DataSize = Section.getSize();
  uint64_t Alignment64 = Section.getAlignment();

  // Add stubbuf size alignment
  unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
  unsigned StubAlignment = getStubAlignment();
  unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
  if (StubAlignment > EndAlignment)
    StubBufSize += StubAlignment - EndAlignment;
  return StubBufSize;
}

uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
                                             unsigned Size) const {
  uint64_t Result = 0;
  if (IsTargetLittleEndian) {
    Src += Size - 1;
    while (Size--)
      Result = (Result << 8) | *Src--;
  } else
    while (Size--)
      Result = (Result << 8) | *Src++;

  return Result;
}

void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
                                          unsigned Size) const {
  if (IsTargetLittleEndian) {
    while (Size--) {
      *Dst++ = Value & 0xFF;
      Value >>= 8;
    }
  } else {
    Dst += Size - 1;
    while (Size--) {
      *Dst-- = Value & 0xFF;
      Value >>= 8;
    }
  }
}

void RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
                                        CommonSymbolList &CommonSymbols) {
  if (CommonSymbols.empty())
    return;

  uint64_t CommonSize = 0;
  CommonSymbolList SymbolsToAllocate;

  DEBUG(dbgs() << "Processing common symbols...\n");

  for (const auto &Sym : CommonSymbols) {
    ErrorOr<StringRef> NameOrErr = Sym.getName();
    Check(NameOrErr.getError());
    StringRef Name = *NameOrErr;

    // Skip common symbols already elsewhere.
    if (GlobalSymbolTable.count(Name) ||
        Resolver.findSymbolInLogicalDylib(Name)) {
      DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
                   << "'\n");
      continue;
    }

    uint32_t Align = Sym.getAlignment();
    uint64_t Size = Sym.getCommonSize();

    CommonSize += Align + Size;
    SymbolsToAllocate.push_back(Sym);
  }

  // Allocate memory for the section
  unsigned SectionID = Sections.size();
  uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, sizeof(void *),
                                             SectionID, StringRef(), false);
  if (!Addr)
    report_fatal_error("Unable to allocate memory for common symbols!");
  uint64_t Offset = 0;
  Sections.push_back(
      SectionEntry("<common symbols>", Addr, CommonSize, CommonSize, 0));
  memset(Addr, 0, CommonSize);

  DEBUG(dbgs() << "emitCommonSection SectionID: " << SectionID << " new addr: "
               << format("%p", Addr) << " DataSize: " << CommonSize << "\n");

  // Assign the address of each symbol
  for (auto &Sym : SymbolsToAllocate) {
    uint32_t Align = Sym.getAlignment();
    uint64_t Size = Sym.getCommonSize();
    ErrorOr<StringRef> NameOrErr = Sym.getName();
    Check(NameOrErr.getError());
    StringRef Name = *NameOrErr;
    if (Align) {
      // This symbol has an alignment requirement.
      uint64_t AlignOffset = OffsetToAlignment((uint64_t)Addr, Align);
      Addr += AlignOffset;
      Offset += AlignOffset;
    }
    uint32_t Flags = Sym.getFlags();
    JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
    if (Flags & SymbolRef::SF_Weak)
      RTDyldSymFlags |= JITSymbolFlags::Weak;
    if (Flags & SymbolRef::SF_Exported)
      RTDyldSymFlags |= JITSymbolFlags::Exported;
    DEBUG(dbgs() << "Allocating common symbol " << Name << " address "
                 << format("%p", Addr) << "\n");
    GlobalSymbolTable[Name] =
      SymbolTableEntry(SectionID, Offset, RTDyldSymFlags);
    Offset += Size;
    Addr += Size;
  }

  if (Checker)
    Checker->registerSection(Obj.getFileName(), SectionID);
}

unsigned RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
                                      const SectionRef &Section, bool IsCode) {

  StringRef data;
  uint64_t Alignment64 = Section.getAlignment();

  unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
  unsigned PaddingSize = 0;
  unsigned StubBufSize = 0;
  StringRef Name;
  bool IsRequired = isRequiredForExecution(Section);
  bool IsVirtual = Section.isVirtual();
  bool IsZeroInit = isZeroInit(Section);
  bool IsReadOnly = isReadOnlyData(Section);
  uint64_t DataSize = Section.getSize();
  Check(Section.getName(Name));

  StubBufSize = computeSectionStubBufSize(Obj, Section);

  // The .eh_frame section (at least on Linux) needs an extra four bytes padded
  // with zeroes added at the end.  For MachO objects, this section has a
  // slightly different name, so this won't have any effect for MachO objects.
  if (Name == ".eh_frame")
    PaddingSize = 4;

  uintptr_t Allocate;
  unsigned SectionID = Sections.size();
  uint8_t *Addr;
  const char *pData = nullptr;

  // If this section contains any bits (i.e. isn't a virtual or bss section),
  // grab a reference to them.
  if (!IsVirtual && !IsZeroInit) {
    // In either case, set the location of the unrelocated section in memory,
    // since we still process relocations for it even if we're not applying them.
    Check(Section.getContents(data));
    pData = data.data();
  }

  // Code section alignment needs to be at least as high as stub alignment or
  // padding calculations may by incorrect when the section is remapped to a
  // higher alignment.
  if (IsCode)
    Alignment = std::max(Alignment, getStubAlignment());

  // Some sections, such as debug info, don't need to be loaded for execution.
  // Leave those where they are.
  if (IsRequired) {
    Allocate = DataSize + PaddingSize + StubBufSize;
    if (!Allocate)
      Allocate = 1;
    Addr = IsCode ? MemMgr.allocateCodeSection(Allocate, Alignment, SectionID,
                                               Name)
                  : MemMgr.allocateDataSection(Allocate, Alignment, SectionID,
                                               Name, IsReadOnly);
    if (!Addr)
      report_fatal_error("Unable to allocate section memory!");

    // Zero-initialize or copy the data from the image
    if (IsZeroInit || IsVirtual)
      memset(Addr, 0, DataSize);
    else
      memcpy(Addr, pData, DataSize);

    // Fill in any extra bytes we allocated for padding
    if (PaddingSize != 0) {
      memset(Addr + DataSize, 0, PaddingSize);
      // Update the DataSize variable so that the stub offset is set correctly.
      DataSize += PaddingSize;
    }

    DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
                 << " obj addr: " << format("%p", pData)
                 << " new addr: " << format("%p", Addr)
                 << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate << "\n");
  } else {
    // Even if we didn't load the section, we need to record an entry for it
    // to handle later processing (and by 'handle' I mean don't do anything
    // with these sections).
    Allocate = 0;
    Addr = nullptr;
    DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
                 << " obj addr: " << format("%p", data.data()) << " new addr: 0"
                 << " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
                 << " Allocate: " << Allocate << "\n");
  }

  Sections.push_back(
      SectionEntry(Name, Addr, DataSize, Allocate, (uintptr_t)pData));

  if (Checker)
    Checker->registerSection(Obj.getFileName(), SectionID);

  return SectionID;
}

unsigned RuntimeDyldImpl::findOrEmitSection(const ObjectFile &Obj,
                                            const SectionRef &Section,
                                            bool IsCode,
                                            ObjSectionToIDMap &LocalSections) {

  unsigned SectionID = 0;
  ObjSectionToIDMap::iterator i = LocalSections.find(Section);
  if (i != LocalSections.end())
    SectionID = i->second;
  else {
    SectionID = emitSection(Obj, Section, IsCode);
    LocalSections[Section] = SectionID;
  }
  return SectionID;
}

void RuntimeDyldImpl::addRelocationForSection(const RelocationEntry &RE,
                                              unsigned SectionID) {
  Relocations[SectionID].push_back(RE);
}

void RuntimeDyldImpl::addRelocationForSymbol(const RelocationEntry &RE,
                                             StringRef SymbolName) {
  // Relocation by symbol.  If the symbol is found in the global symbol table,
  // create an appropriate section relocation.  Otherwise, add it to
  // ExternalSymbolRelocations.
  RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(SymbolName);
  if (Loc == GlobalSymbolTable.end()) {
    ExternalSymbolRelocations[SymbolName].push_back(RE);
  } else {
    // Copy the RE since we want to modify its addend.
    RelocationEntry RECopy = RE;
    const auto &SymInfo = Loc->second;
    RECopy.Addend += SymInfo.getOffset();
    Relocations[SymInfo.getSectionID()].push_back(RECopy);
  }
}

uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr,
                                             unsigned AbiVariant) {
  if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be) {
    // This stub has to be able to access the full address space,
    // since symbol lookup won't necessarily find a handy, in-range,
    // PLT stub for functions which could be anywhere.
    // Stub can use ip0 (== x16) to calculate address
    writeBytesUnaligned(0xd2e00010, Addr,    4); // movz ip0, #:abs_g3:<addr>
    writeBytesUnaligned(0xf2c00010, Addr+4,  4); // movk ip0, #:abs_g2_nc:<addr>
    writeBytesUnaligned(0xf2a00010, Addr+8,  4); // movk ip0, #:abs_g1_nc:<addr>
    writeBytesUnaligned(0xf2800010, Addr+12, 4); // movk ip0, #:abs_g0_nc:<addr>
    writeBytesUnaligned(0xd61f0200, Addr+16, 4); // br ip0

    return Addr;
  } else if (Arch == Triple::arm || Arch == Triple::armeb) {
    // TODO: There is only ARM far stub now. We should add the Thumb stub,
    // and stubs for branches Thumb - ARM and ARM - Thumb.
    writeBytesUnaligned(0xe51ff004, Addr, 4); // ldr pc,<label>
    return Addr + 4;
  } else if (IsMipsO32ABI) {
    // 0:   3c190000        lui     t9,%hi(addr).
    // 4:   27390000        addiu   t9,t9,%lo(addr).
    // 8:   03200008        jr      t9.
    // c:   00000000        nop.
    const unsigned LuiT9Instr = 0x3c190000, AdduiT9Instr = 0x27390000;
    const unsigned JrT9Instr = 0x03200008, NopInstr = 0x0;

    writeBytesUnaligned(LuiT9Instr, Addr, 4);
    writeBytesUnaligned(AdduiT9Instr, Addr+4, 4);
    writeBytesUnaligned(JrT9Instr, Addr+8, 4);
    writeBytesUnaligned(NopInstr, Addr+12, 4);
    return Addr;
  } else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
    // Depending on which version of the ELF ABI is in use, we need to
    // generate one of two variants of the stub.  They both start with
    // the same sequence to load the target address into r12.
    writeInt32BE(Addr,    0x3D800000); // lis   r12, highest(addr)
    writeInt32BE(Addr+4,  0x618C0000); // ori   r12, higher(addr)
    writeInt32BE(Addr+8,  0x798C07C6); // sldi  r12, r12, 32
    writeInt32BE(Addr+12, 0x658C0000); // oris  r12, r12, h(addr)
    writeInt32BE(Addr+16, 0x618C0000); // ori   r12, r12, l(addr)
    if (AbiVariant == 2) {
      // PowerPC64 stub ELFv2 ABI: The address points to the function itself.
      // The address is already in r12 as required by the ABI.  Branch to it.
      writeInt32BE(Addr+20, 0xF8410018); // std   r2,  24(r1)
      writeInt32BE(Addr+24, 0x7D8903A6); // mtctr r12
      writeInt32BE(Addr+28, 0x4E800420); // bctr
    } else {
      // PowerPC64 stub ELFv1 ABI: The address points to a function descriptor.
      // Load the function address on r11 and sets it to control register. Also
      // loads the function TOC in r2 and environment pointer to r11.
      writeInt32BE(Addr+20, 0xF8410028); // std   r2,  40(r1)
      writeInt32BE(Addr+24, 0xE96C0000); // ld    r11, 0(r12)
      writeInt32BE(Addr+28, 0xE84C0008); // ld    r2,  0(r12)
      writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
      writeInt32BE(Addr+36, 0xE96C0010); // ld    r11, 16(r2)
      writeInt32BE(Addr+40, 0x4E800420); // bctr
    }
    return Addr;
  } else if (Arch == Triple::systemz) {
    writeInt16BE(Addr,    0xC418);     // lgrl %r1,.+8
    writeInt16BE(Addr+2,  0x0000);
    writeInt16BE(Addr+4,  0x0004);
    writeInt16BE(Addr+6,  0x07F1);     // brc 15,%r1
    // 8-byte address stored at Addr + 8
    return Addr;
  } else if (Arch == Triple::x86_64) {
    *Addr      = 0xFF; // jmp
    *(Addr+1)  = 0x25; // rip
    // 32-bit PC-relative address of the GOT entry will be stored at Addr+2
  } else if (Arch == Triple::x86) {
    *Addr      = 0xE9; // 32-bit pc-relative jump.
  }
  return Addr;
}

// Assign an address to a symbol name and resolve all the relocations
// associated with it.
void RuntimeDyldImpl::reassignSectionAddress(unsigned SectionID,
                                             uint64_t Addr) {
  // The address to use for relocation resolution is not
  // the address of the local section buffer. We must be doing
  // a remote execution environment of some sort. Relocations can't
  // be applied until all the sections have been moved.  The client must
  // trigger this with a call to MCJIT::finalize() or
  // RuntimeDyld::resolveRelocations().
  //
  // Addr is a uint64_t because we can't assume the pointer width
  // of the target is the same as that of the host. Just use a generic
  // "big enough" type.
  DEBUG(dbgs() << "Reassigning address for section " << SectionID << " ("
               << Sections[SectionID].getName() << "): "
               << format("0x%016" PRIx64, Sections[SectionID].getLoadAddress())
               << " -> " << format("0x%016" PRIx64, Addr) << "\n");
  Sections[SectionID].setLoadAddress(Addr);
}

void RuntimeDyldImpl::resolveRelocationList(const RelocationList &Relocs,
                                            uint64_t Value) {
  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
    const RelocationEntry &RE = Relocs[i];
    // Ignore relocations for sections that were not loaded
    if (Sections[RE.SectionID].getAddress() == nullptr)
      continue;
    resolveRelocation(RE, Value);
  }
}

void RuntimeDyldImpl::resolveExternalSymbols() {
  while (!ExternalSymbolRelocations.empty()) {
    StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();

    StringRef Name = i->first();
    if (Name.size() == 0) {
      // This is an absolute symbol, use an address of zero.
      DEBUG(dbgs() << "Resolving absolute relocations."
                   << "\n");
      RelocationList &Relocs = i->second;
      resolveRelocationList(Relocs, 0);
    } else {
      uint64_t Addr = 0;
      RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(Name);
      if (Loc == GlobalSymbolTable.end()) {
        // This is an external symbol, try to get its address from the symbol
        // resolver.
        Addr = Resolver.findSymbol(Name.data()).getAddress();
        // The call to getSymbolAddress may have caused additional modules to
        // be loaded, which may have added new entries to the
        // ExternalSymbolRelocations map.  Consquently, we need to update our
        // iterator.  This is also why retrieval of the relocation list
        // associated with this symbol is deferred until below this point.
        // New entries may have been added to the relocation list.
        i = ExternalSymbolRelocations.find(Name);
      } else {
        // We found the symbol in our global table.  It was probably in a
        // Module that we loaded previously.
        const auto &SymInfo = Loc->second;
        Addr = getSectionLoadAddress(SymInfo.getSectionID()) +
               SymInfo.getOffset();
      }

      // FIXME: Implement error handling that doesn't kill the host program!
      if (!Addr)
        report_fatal_error("Program used external function '" + Name +
                           "' which could not be resolved!");

      // If Resolver returned UINT64_MAX, the client wants to handle this symbol
      // manually and we shouldn't resolve its relocations.
      if (Addr != UINT64_MAX) {
        DEBUG(dbgs() << "Resolving relocations Name: " << Name << "\t"
                     << format("0x%lx", Addr) << "\n");
        // This list may have been updated when we called getSymbolAddress, so
        // don't change this code to get the list earlier.
        RelocationList &Relocs = i->second;
        resolveRelocationList(Relocs, Addr);
      }
    }

    ExternalSymbolRelocations.erase(i);
  }
}

//===----------------------------------------------------------------------===//
// RuntimeDyld class implementation

uint64_t RuntimeDyld::LoadedObjectInfo::getSectionLoadAddress(
                                          const object::SectionRef &Sec) const {

  auto I = ObjSecToIDMap.find(Sec);
  if (I != ObjSecToIDMap.end())
    return RTDyld.Sections[I->second].getLoadAddress();

  return 0;
}

void RuntimeDyld::MemoryManager::anchor() {}
void RuntimeDyld::SymbolResolver::anchor() {}

RuntimeDyld::RuntimeDyld(RuntimeDyld::MemoryManager &MemMgr,
                         RuntimeDyld::SymbolResolver &Resolver)
    : MemMgr(MemMgr), Resolver(Resolver) {
  // FIXME: There's a potential issue lurking here if a single instance of
  // RuntimeDyld is used to load multiple objects.  The current implementation
  // associates a single memory manager with a RuntimeDyld instance.  Even
  // though the public class spawns a new 'impl' instance for each load,
  // they share a single memory manager.  This can become a problem when page
  // permissions are applied.
  Dyld = nullptr;
  ProcessAllSections = false;
  Checker = nullptr;
}

RuntimeDyld::~RuntimeDyld() {}

static std::unique_ptr<RuntimeDyldCOFF>
createRuntimeDyldCOFF(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
                      RuntimeDyld::SymbolResolver &Resolver,
                      bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
  std::unique_ptr<RuntimeDyldCOFF> Dyld =
    RuntimeDyldCOFF::create(Arch, MM, Resolver);
  Dyld->setProcessAllSections(ProcessAllSections);
  Dyld->setRuntimeDyldChecker(Checker);
  return Dyld;
}

static std::unique_ptr<RuntimeDyldELF>
createRuntimeDyldELF(RuntimeDyld::MemoryManager &MM,
                     RuntimeDyld::SymbolResolver &Resolver,
                     bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
  std::unique_ptr<RuntimeDyldELF> Dyld(new RuntimeDyldELF(MM, Resolver));
  Dyld->setProcessAllSections(ProcessAllSections);
  Dyld->setRuntimeDyldChecker(Checker);
  return Dyld;
}

static std::unique_ptr<RuntimeDyldMachO>
createRuntimeDyldMachO(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
                       RuntimeDyld::SymbolResolver &Resolver,
                       bool ProcessAllSections,
                       RuntimeDyldCheckerImpl *Checker) {
  std::unique_ptr<RuntimeDyldMachO> Dyld =
    RuntimeDyldMachO::create(Arch, MM, Resolver);
  Dyld->setProcessAllSections(ProcessAllSections);
  Dyld->setRuntimeDyldChecker(Checker);
  return Dyld;
}

std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
RuntimeDyld::loadObject(const ObjectFile &Obj) {
  if (!Dyld) {
    if (Obj.isELF())
      Dyld = createRuntimeDyldELF(MemMgr, Resolver, ProcessAllSections, Checker);
    else if (Obj.isMachO())
      Dyld = createRuntimeDyldMachO(
               static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
               ProcessAllSections, Checker);
    else if (Obj.isCOFF())
      Dyld = createRuntimeDyldCOFF(
               static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
               ProcessAllSections, Checker);
    else
      report_fatal_error("Incompatible object format!");
  }

  if (!Dyld->isCompatibleFile(Obj))
    report_fatal_error("Incompatible object format!");

  auto LoadedObjInfo = Dyld->loadObject(Obj);
  MemMgr.notifyObjectLoaded(*this, Obj);
  return LoadedObjInfo;
}

void *RuntimeDyld::getSymbolLocalAddress(StringRef Name) const {
  if (!Dyld)
    return nullptr;
  return Dyld->getSymbolLocalAddress(Name);
}

RuntimeDyld::SymbolInfo RuntimeDyld::getSymbol(StringRef Name) const {
  if (!Dyld)
    return nullptr;
  return Dyld->getSymbol(Name);
}

void RuntimeDyld::resolveRelocations() { Dyld->resolveRelocations(); }

void RuntimeDyld::reassignSectionAddress(unsigned SectionID, uint64_t Addr) {
  Dyld->reassignSectionAddress(SectionID, Addr);
}

void RuntimeDyld::mapSectionAddress(const void *LocalAddress,
                                    uint64_t TargetAddress) {
  Dyld->mapSectionAddress(LocalAddress, TargetAddress);
}

bool RuntimeDyld::hasError() { return Dyld->hasError(); }

StringRef RuntimeDyld::getErrorString() { return Dyld->getErrorString(); }

void RuntimeDyld::finalizeWithMemoryManagerLocking() {
  bool MemoryFinalizationLocked = MemMgr.FinalizationLocked;
  MemMgr.FinalizationLocked = true;
  resolveRelocations();
  registerEHFrames();
  if (!MemoryFinalizationLocked) {
    MemMgr.finalizeMemory();
    MemMgr.FinalizationLocked = false;
  }
}

void RuntimeDyld::registerEHFrames() {
  if (Dyld)
    Dyld->registerEHFrames();
}

void RuntimeDyld::deregisterEHFrames() {
  if (Dyld)
    Dyld->deregisterEHFrames();
}

} // end namespace llvm