Esempio n. 1
0
uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
                                          const MCFragment &F) const {
  switch (F.getKind()) {
  case MCFragment::FT_Data:
  case MCFragment::FT_Relaxable:
  case MCFragment::FT_CompactEncodedInst:
    return cast<MCEncodedFragment>(F).getContents().size();
  case MCFragment::FT_Fill:
    return cast<MCFillFragment>(F).getSize();

  case MCFragment::FT_LEB:
    return cast<MCLEBFragment>(F).getContents().size();

  case MCFragment::FT_Align: {
    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
    unsigned Offset = Layout.getFragmentOffset(&AF);
    unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
    // If we are padding with nops, force the padding to be larger than the
    // minimum nop size.
    if (Size > 0 && AF.hasEmitNops()) {
      while (Size % getBackend().getMinimumNopSize())
        Size += AF.getAlignment();
    }
    if (Size > AF.getMaxBytesToEmit())
      return 0;
    return Size;
  }

  case MCFragment::FT_Org: {
    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
    int64_t TargetLocation;
    if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, Layout))
      report_fatal_error("expected assembly-time absolute expression");

    // FIXME: We need a way to communicate this error.
    uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
    int64_t Size = TargetLocation - FragmentOffset;
    if (Size < 0 || Size >= 0x40000000)
      report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
                         "' (at offset '" + Twine(FragmentOffset) + "')");
    return Size;
  }

  case MCFragment::FT_Dwarf:
    return cast<MCDwarfLineAddrFragment>(F).getContents().size();
  case MCFragment::FT_DwarfFrame:
    return cast<MCDwarfCallFrameFragment>(F).getContents().size();
  }

  llvm_unreachable("invalid fragment kind");
}
Esempio n. 2
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uint64_t MCCodePaddingPolicy::getNextFragmentOffset(const MCFragment *Fragment,
                                                    const MCAsmLayout &Layout) {
  assert(Fragment != nullptr && "Fragment cannot be null");
  MCFragment const *NextFragment = Fragment->getNextNode();
  return NextFragment == nullptr
             ? Layout.getSectionAddressSize(Fragment->getParent())
             : Layout.getFragmentOffset(NextFragment);
}
Esempio n. 3
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// Simple getSymbolOffset helper for the non-varibale case.
static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbol &S,
                           bool ReportError, uint64_t &Val) {
  if (!S.getFragment()) {
    if (ReportError)
      report_fatal_error("unable to evaluate offset to undefined symbol '" +
                         S.getName() + "'");
    return false;
  }
  Val = Layout.getFragmentOffset(S.getFragment()) + S.getOffset();
  return true;
}
Esempio n. 4
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void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer,
                                               const MCAssembler &Asm,
                                               const MCAsmLayout &Layout,
                                               const MCFragment *Fragment,
                                               const MCFixup &Fixup,
                                               MCValue Target,
                                               uint64_t &FixedValue) {
  assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
         !is64Bit() &&
         "Should only be called with a 32-bit TLVP relocation!");

  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
  uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
  unsigned IsPCRel = 0;

  // Get the symbol data.
  const MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
  unsigned Index = SD_A->getIndex();

  // We're only going to have a second symbol in pic mode and it'll be a
  // subtraction from the picbase. For 32-bit pic the addend is the difference
  // between the picbase and the next address.  For 32-bit static the addend is
  // zero.
  if (Target.getSymB()) {
    // If this is a subtraction then we're pcrel.
    uint32_t FixupAddress =
      Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
    const MCSymbolData *SD_B =
        &Asm.getSymbolData(Target.getSymB()->getSymbol());
    IsPCRel = 1;
    FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) +
                  Target.getConstant());
    FixedValue += 1ULL << Log2Size;
  } else {
    FixedValue = 0;
  }

  // struct relocation_info (8 bytes)
  MachO::any_relocation_info MRE;
  MRE.r_word0 = Value;
  MRE.r_word1 = ((Index                    <<  0) |
                 (IsPCRel                  << 24) |
                 (Log2Size                 << 25) |
                 (1                        << 27) | // r_extern
                 (MachO::GENERIC_RELOC_TLV << 28)); // r_type
  Writer->addRelocation(Fragment->getParent(), MRE);
}
Esempio n. 5
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void SVMMemoryLayout::RecordRelocation(const MCAssembler &Asm,
    const MCAsmLayout &Layout, const MCFragment *Fragment,
    const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue)
{
    SVM::Fixups kind = (SVM::Fixups) Fixup.getKind();
    switch (kind) {

        case SVM::fixup_fnstack: {
            /*
             * Function stack adjustment annotation. The adjustment amount is
             * stored in the first argument of a binary op.
             * (See SVMMCCodeEmitter::EncodeInstruction)
             *
             * We store this offset for later, in our FNStackMap, indexed
             * by the address of the FNStack pseudo-op itself.
             */
            FNStackMap[std::make_pair(Fragment->getParent(),
                Layout.getFragmentOffset(Fragment))] = (int)Target.getConstant();
            break;
        }
    
        default: {
            /*
             * All other fixups are applied later, in ApplyLateFixups().
             * This is necessary because other fixup types can depend on
             * the FNStack values collected above.
             */
            SVMLateFixup LF((MCFragment *) Fragment, Fixup, Target);
            LateFixupList.push_back(LF);

            // This gets OR'ed with the fixup later. Zero it.
            FixedValue = 0;
            break;
        }
    }
}
Esempio n. 6
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bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer,
                                                    const MCAssembler &Asm,
                                                    const MCAsmLayout &Layout,
                                                    const MCFragment *Fragment,
                                                    const MCFixup &Fixup,
                                                    MCValue Target,
                                                    unsigned Log2Size,
                                                    uint64_t &FixedValue) {
  uint64_t OriginalFixedValue = FixedValue;
  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
  unsigned Type = MachO::GENERIC_RELOC_VANILLA;

  // See <reloc.h>.
  const MCSymbol *A = &Target.getSymA()->getSymbol();
  const MCSymbolData *A_SD = &Asm.getSymbolData(*A);

  if (!A_SD->getFragment())
    report_fatal_error("symbol '" + A->getName() +
                       "' can not be undefined in a subtraction expression",
                       false);

  uint32_t Value = Writer->getSymbolAddress(A_SD, Layout);
  uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent());
  FixedValue += SecAddr;
  uint32_t Value2 = 0;

  if (const MCSymbolRefExpr *B = Target.getSymB()) {
    const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());

    if (!B_SD->getFragment())
      report_fatal_error("symbol '" + B->getSymbol().getName() +
                         "' can not be undefined in a subtraction expression",
                         false);

    // Select the appropriate difference relocation type.
    //
    // Note that there is no longer any semantic difference between these two
    // relocation types from the linkers point of view, this is done solely for
    // pedantic compatibility with 'as'.
    Type = A_SD->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF :
      (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF;
    Value2 = Writer->getSymbolAddress(B_SD, Layout);
    FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent());
  }

  // Relocations are written out in reverse order, so the PAIR comes first.
  if (Type == MachO::GENERIC_RELOC_SECTDIFF ||
      Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) {
    // If the offset is too large to fit in a scattered relocation,
    // we're hosed. It's an unfortunate limitation of the MachO format.
    if (FixupOffset > 0xffffff) {
      char Buffer[32];
      format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
      Asm.getContext().FatalError(Fixup.getLoc(),
                         Twine("Section too large, can't encode "
                                "r_address (") + Buffer +
                         ") into 24 bits of scattered "
                         "relocation entry.");
      llvm_unreachable("fatal error returned?!");
    }

    MachO::any_relocation_info MRE;
    MRE.r_word0 = ((0                         <<  0) | // r_address
                   (MachO::GENERIC_RELOC_PAIR << 24) | // r_type
                   (Log2Size                  << 28) |
                   (IsPCRel                   << 30) |
                   MachO::R_SCATTERED);
    MRE.r_word1 = Value2;
    Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
  } else {
    // If the offset is more than 24-bits, it won't fit in a scattered
    // relocation offset field, so we fall back to using a non-scattered
    // relocation. This is a bit risky, as if the offset reaches out of
    // the block and the linker is doing scattered loading on this
    // symbol, things can go badly.
    //
    // Required for 'as' compatibility.
    if (FixupOffset > 0xffffff) {
      FixedValue = OriginalFixedValue;
      return false;
    }
  }

  MachO::any_relocation_info MRE;
  MRE.r_word0 = ((FixupOffset <<  0) |
                 (Type        << 24) |
                 (Log2Size    << 28) |
                 (IsPCRel     << 30) |
                 MachO::R_SCATTERED);
  MRE.r_word1 = Value;
  Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
  return true;
}
Esempio n. 7
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uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment,
                                              const MCAsmLayout &Layout) const {
  return getSectionAddress(Fragment->getParent()) +
         Layout.getFragmentOffset(Fragment);
}
void ARMMachObjectWriter::
RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
                                 const MCAssembler &Asm,
                                 const MCAsmLayout &Layout,
                                 const MCFragment *Fragment,
                                 const MCFixup &Fixup,
                                 MCValue Target,
                                 uint64_t &FixedValue) {
  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
  unsigned Type = MachO::ARM_RELOC_HALF;

  // See <reloc.h>.
  const MCSymbol *A = &Target.getSymA()->getSymbol();
  const MCSymbolData *A_SD = &Asm.getSymbolData(*A);

  if (!A_SD->getFragment())
    Asm.getContext().FatalError(Fixup.getLoc(),
                       "symbol '" + A->getName() +
                       "' can not be undefined in a subtraction expression");

  uint32_t Value = Writer->getSymbolAddress(A_SD, Layout);
  uint32_t Value2 = 0;
  uint64_t SecAddr =
    Writer->getSectionAddress(A_SD->getFragment()->getParent());
  FixedValue += SecAddr;

  if (const MCSymbolRefExpr *B = Target.getSymB()) {
    const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());

    if (!B_SD->getFragment())
      Asm.getContext().FatalError(Fixup.getLoc(),
                         "symbol '" + B->getSymbol().getName() +
                         "' can not be undefined in a subtraction expression");

    // Select the appropriate difference relocation type.
    Type = MachO::ARM_RELOC_HALF_SECTDIFF;
    Value2 = Writer->getSymbolAddress(B_SD, Layout);
    FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent());
  }

  // Relocations are written out in reverse order, so the PAIR comes first.
  // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field:
  //
  // For these two r_type relocations they always have a pair following them and
  // the r_length bits are used differently.  The encoding of the r_length is as
  // follows:
  //   low bit of r_length:
  //      0 - :lower16: for movw instructions
  //      1 - :upper16: for movt instructions
  //   high bit of r_length:
  //      0 - arm instructions
  //      1 - thumb instructions
  // the other half of the relocated expression is in the following pair
  // relocation entry in the low 16 bits of r_address field.
  unsigned ThumbBit = 0;
  unsigned MovtBit = 0;
  switch ((unsigned)Fixup.getKind()) {
  default: break;
  case ARM::fixup_arm_movt_hi16:
    MovtBit = 1;
    // The thumb bit shouldn't be set in the 'other-half' bit of the
    // relocation, but it will be set in FixedValue if the base symbol
    // is a thumb function. Clear it out here.
    if (Asm.isThumbFunc(A))
      FixedValue &= 0xfffffffe;
    break;
  case ARM::fixup_t2_movt_hi16:
    if (Asm.isThumbFunc(A))
      FixedValue &= 0xfffffffe;
    MovtBit = 1;
    // Fallthrough
  case ARM::fixup_t2_movw_lo16:
    ThumbBit = 1;
    break;
  }

  if (Type == MachO::ARM_RELOC_HALF_SECTDIFF) {
    uint32_t OtherHalf = MovtBit
      ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16);

    MachO::any_relocation_info MRE;
    MRE.r_word0 = ((OtherHalf             <<  0) |
                   (MachO::ARM_RELOC_PAIR << 24) |
                   (MovtBit               << 28) |
                   (ThumbBit              << 29) |
                   (IsPCRel               << 30) |
                   MachO::R_SCATTERED);
    MRE.r_word1 = Value2;
    Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
  }
Esempio n. 9
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void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
                                      const MCAsmLayout &Layout) {
  // Assign symbol and section indexes and offsets.
  Header.NumberOfSections = 0;

  DenseMap<COFFSection *, uint16_t> SectionIndices;
  for (sections::iterator i = Sections.begin(),
                          e = Sections.end(); i != e; i++) {
    if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
      size_t Number = ++Header.NumberOfSections;
      SectionIndices[*i] = Number;
      MakeSectionReal(**i, Number);
    } else {
      (*i)->Number = -1;
    }
  }

  Header.NumberOfSymbols = 0;

  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
    COFFSymbol *coff_symbol = *i;
    MCSymbolData const *SymbolData = coff_symbol->MCData;

    // Update section number & offset for symbols that have them.
    if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
      assert(coff_symbol->Section != NULL);

      coff_symbol->Data.SectionNumber = coff_symbol->Section->Number;
      coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
                              + SymbolData->Offset;
    }

    if (coff_symbol->should_keep()) {
      MakeSymbolReal(*coff_symbol, Header.NumberOfSymbols++);

      // Update auxiliary symbol info.
      coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
      Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
    } else
      coff_symbol->Index = -1;
  }

  // Fixup weak external references.
  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
    COFFSymbol *coff_symbol = *i;
    if (coff_symbol->Other != NULL) {
      assert(coff_symbol->Index != -1);
      assert(coff_symbol->Aux.size() == 1 &&
             "Symbol must contain one aux symbol!");
      assert(coff_symbol->Aux[0].AuxType == ATWeakExternal &&
             "Symbol's aux symbol must be a Weak External!");
      coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = coff_symbol->Other->Index;
    }
  }

  // Fixup associative COMDAT sections.
  for (sections::iterator i = Sections.begin(),
                          e = Sections.end(); i != e; i++) {
    if ((*i)->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
        COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
      continue;

    const MCSectionCOFF &MCSec = static_cast<const MCSectionCOFF &>(
                                                    (*i)->MCData->getSection());

    COFFSection *Assoc = SectionMap.lookup(MCSec.getAssocSection());
    if (!Assoc) {
      report_fatal_error(Twine("Missing associated COMDAT section ") +
                         MCSec.getAssocSection()->getSectionName() +
                         " for section " + MCSec.getSectionName());
    }

    // Skip this section if the associated section is unused.
    if (Assoc->Number == -1)
      continue;

    (*i)->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
  }


  // Assign file offsets to COFF object file structures.

  unsigned offset = 0;

  offset += COFF::HeaderSize;
  offset += COFF::SectionSize * Header.NumberOfSections;

  for (MCAssembler::const_iterator i = Asm.begin(),
                                   e = Asm.end();
                                   i != e; i++) {
    COFFSection *Sec = SectionMap[&i->getSection()];

    if (Sec->Number == -1)
      continue;

    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);

    if (IsPhysicalSection(Sec)) {
      Sec->Header.PointerToRawData = offset;

      offset += Sec->Header.SizeOfRawData;
    }

    if (Sec->Relocations.size() > 0) {
      bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;

      if (RelocationsOverflow) {
        // Signal overflow by setting NumberOfSections to max value. Actual
        // size is found in reloc #0. Microsoft tools understand this.
        Sec->Header.NumberOfRelocations = 0xffff;
      } else {
        Sec->Header.NumberOfRelocations = Sec->Relocations.size();
      }
      Sec->Header.PointerToRelocations = offset;

      if (RelocationsOverflow) {
        // Reloc #0 will contain actual count, so make room for it.
        offset += COFF::RelocationSize;
      }

      offset += COFF::RelocationSize * Sec->Relocations.size();

      for (relocations::iterator cr = Sec->Relocations.begin(),
                                 er = Sec->Relocations.end();
                                 cr != er; ++cr) {
        assert((*cr).Symb->Index != -1);
        (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
      }
    }

    assert(Sec->Symbol->Aux.size() == 1
      && "Section's symbol must have one aux!");
    AuxSymbol &Aux = Sec->Symbol->Aux[0];
    assert(Aux.AuxType == ATSectionDefinition &&
           "Section's symbol's aux symbol must be a Section Definition!");
    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
    Aux.Aux.SectionDefinition.NumberOfRelocations =
                                                Sec->Header.NumberOfRelocations;
    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
                                                Sec->Header.NumberOfLineNumbers;
  }

  Header.PointerToSymbolTable = offset;

  Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();

  // Write it all to disk...
  WriteFileHeader(Header);

  {
    sections::iterator i, ie;
    MCAssembler::const_iterator j, je;

    for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
      if ((*i)->Number != -1) {
        if ((*i)->Relocations.size() >= 0xffff) {
          (*i)->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
        }
        WriteSectionHeader((*i)->Header);
      }

    for (i = Sections.begin(), ie = Sections.end(),
         j = Asm.begin(), je = Asm.end();
         (i != ie) && (j != je); ++i, ++j) {

      if ((*i)->Number == -1)
        continue;

      if ((*i)->Header.PointerToRawData != 0) {
        assert(OS.tell() == (*i)->Header.PointerToRawData &&
               "Section::PointerToRawData is insane!");

        Asm.writeSectionData(j, Layout);
      }

      if ((*i)->Relocations.size() > 0) {
        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
               "Section::PointerToRelocations is insane!");

        if ((*i)->Relocations.size() >= 0xffff) {
          // In case of overflow, write actual relocation count as first
          // relocation. Including the synthetic reloc itself (+ 1).
          COFF::relocation r;
          r.VirtualAddress = (*i)->Relocations.size() + 1;
          r.SymbolTableIndex = 0;
          r.Type = 0;
          WriteRelocation(r);
        }

        for (relocations::const_iterator k = (*i)->Relocations.begin(),
                                               ke = (*i)->Relocations.end();
                                               k != ke; k++) {
          WriteRelocation(k->Data);
        }
      } else
        assert((*i)->Header.PointerToRelocations == 0 &&
               "Section::PointerToRelocations is insane!");
    }
  }

  assert(OS.tell() == Header.PointerToSymbolTable &&
         "Header::PointerToSymbolTable is insane!");

  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
    if ((*i)->Index != -1)
      WriteSymbol(*i);

  OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
}
Esempio n. 10
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void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
                                           const MCAsmLayout &Layout,
                                           const MCFragment *Fragment,
                                           const MCFixup &Fixup,
                                           MCValue Target,
                                           uint64_t &FixedValue) {
  assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");

  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
  const MCSymbol &A = Symbol.AliasedSymbol();
  MCSymbolData &A_SD = Asm.getSymbolData(A);

  MCSectionData const *SectionData = Fragment->getParent();

  // Mark this symbol as requiring an entry in the symbol table.
  assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
         "Section must already have been defined in ExecutePostLayoutBinding!");
  assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
         "Symbol must already have been defined in ExecutePostLayoutBinding!");

  COFFSection *coff_section = SectionMap[&SectionData->getSection()];
  COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
  const MCSymbolRefExpr *SymA = Target.getSymA();
  const MCSymbolRefExpr *SymB = Target.getSymB();
  const bool CrossSection = SymB &&
    &SymA->getSymbol().getSection() != &SymB->getSymbol().getSection();

  if (Target.getSymB()) {
    const MCSymbol *B = &Target.getSymB()->getSymbol();
    MCSymbolData &B_SD = Asm.getSymbolData(*B);

    // Offset of the symbol in the section
    int64_t a = Layout.getSymbolOffset(&B_SD);

    // Ofeset of the relocation in the section
    int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();

    FixedValue = b - a;
    // In the case where we have SymbA and SymB, we just need to store the delta
    // between the two symbols.  Update FixedValue to account for the delta, and
    // skip recording the relocation.
    if (!CrossSection)
      return;
  } else {
    FixedValue = Target.getConstant();
  }

  COFFRelocation Reloc;

  Reloc.Data.SymbolTableIndex = 0;
  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);

  // Turn relocations for temporary symbols into section relocations.
  if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
    Reloc.Symb = coff_symbol->Section->Symbol;
    FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
                + coff_symbol->MCData->getOffset();
  } else
    Reloc.Symb = coff_symbol;

  ++Reloc.Symb->Relocations;

  Reloc.Data.VirtualAddress += Fixup.getOffset();
  Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
                                                     CrossSection);

  // FIXME: Can anyone explain what this does other than adjust for the size
  // of the offset?
  if (Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32 ||
      Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)
    FixedValue += 4;

  coff_section->Relocations.push_back(Reloc);
}
void AArch64MachObjectWriter::RecordRelocation(
    MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
    const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
    uint64_t &FixedValue) {
    unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());

    // See <reloc.h>.
    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
    unsigned Log2Size = 0;
    int64_t Value = 0;
    unsigned Index = 0;
    unsigned Type = 0;
    unsigned Kind = Fixup.getKind();
    const MCSymbolData *RelSymbol = nullptr;

    FixupOffset += Fixup.getOffset();

    // AArch64 pcrel relocation addends do not include the section offset.
    if (IsPCRel)
        FixedValue += FixupOffset;

    // ADRP fixups use relocations for the whole symbol value and only
    // put the addend in the instruction itself. Clear out any value the
    // generic code figured out from the sybmol definition.
    if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
        FixedValue = 0;

    // imm19 relocations are for conditional branches, which require
    // assembler local symbols. If we got here, that's not what we have,
    // so complain loudly.
    if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
        Asm.getContext().FatalError(Fixup.getLoc(),
                                    "conditional branch requires assembler-local"
                                    " label. '" +
                                    Target.getSymA()->getSymbol().getName() +
                                    "' is external.");
        return;
    }

    // 14-bit branch relocations should only target internal labels, and so
    // should never get here.
    if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
        Asm.getContext().FatalError(Fixup.getLoc(),
                                    "Invalid relocation on conditional branch!");
        return;
    }

    if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
                                      Asm)) {
        Asm.getContext().FatalError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
        return;
    }

    Value = Target.getConstant();

    if (Target.isAbsolute()) { // constant
        // FIXME: Should this always be extern?
        // SymbolNum of 0 indicates the absolute section.
        Type = MachO::ARM64_RELOC_UNSIGNED;

        if (IsPCRel) {
            Asm.getContext().FatalError(Fixup.getLoc(),
                                        "PC relative absolute relocation!");

            // FIXME: x86_64 sets the type to a branch reloc here. Should we do
            // something similar?
        }
    } else if (Target.getSymB()) { // A - B + constant
        const MCSymbol *A = &Target.getSymA()->getSymbol();
        const MCSymbolData &A_SD = Asm.getSymbolData(*A);
        const MCSymbolData *A_Base = Asm.getAtom(&A_SD);

        const MCSymbol *B = &Target.getSymB()->getSymbol();
        const MCSymbolData &B_SD = Asm.getSymbolData(*B);
        const MCSymbolData *B_Base = Asm.getAtom(&B_SD);

        // Check for "_foo@got - .", which comes through here as:
        // Ltmp0:
        //    ... _foo@got - Ltmp0
        if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
                Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
                Layout.getSymbolOffset(&B_SD) ==
                Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
            // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
            Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
            IsPCRel = 1;
            MachO::any_relocation_info MRE;
            MRE.r_word0 = FixupOffset;
            MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
            Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
            return;
        } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
                   Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
            // Otherwise, neither symbol can be modified.
            Asm.getContext().FatalError(Fixup.getLoc(),
                                        "unsupported relocation of modified symbol");

        // We don't support PCrel relocations of differences.
        if (IsPCRel)
            Asm.getContext().FatalError(Fixup.getLoc(),
                                        "unsupported pc-relative relocation of "
                                        "difference");

        // AArch64 always uses external relocations. If there is no symbol to use as
        // a base address (a local symbol with no preceding non-local symbol),
        // error out.
        //
        // FIXME: We should probably just synthesize an external symbol and use
        // that.
        if (!A_Base)
            Asm.getContext().FatalError(
                Fixup.getLoc(),
                "unsupported relocation of local symbol '" + A->getName() +
                "'. Must have non-local symbol earlier in section.");
        if (!B_Base)
            Asm.getContext().FatalError(
                Fixup.getLoc(),
                "unsupported relocation of local symbol '" + B->getName() +
                "'. Must have non-local symbol earlier in section.");

        if (A_Base == B_Base && A_Base)
            Asm.getContext().FatalError(Fixup.getLoc(),
                                        "unsupported relocation with identical base");

        Value += (!A_SD.getFragment() ? 0
                  : Writer->getSymbolAddress(&A_SD, Layout)) -
                 (!A_Base || !A_Base->getFragment()
                  ? 0
                  : Writer->getSymbolAddress(A_Base, Layout));
        Value -= (!B_SD.getFragment() ? 0
                  : Writer->getSymbolAddress(&B_SD, Layout)) -
                 (!B_Base || !B_Base->getFragment()
                  ? 0
                  : Writer->getSymbolAddress(B_Base, Layout));

        Type = MachO::ARM64_RELOC_UNSIGNED;

        MachO::any_relocation_info MRE;
        MRE.r_word0 = FixupOffset;
        MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
        Writer->addRelocation(A_Base, Fragment->getParent(), MRE);

        RelSymbol = B_Base;
        Type = MachO::ARM64_RELOC_SUBTRACTOR;
    } else { // A + constant
        const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
        const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
                                            Fragment->getParent()->getSection());

        bool CanUseLocalRelocation =
            canUseLocalRelocation(Section, *Symbol, Log2Size);
        if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
            const MCSection &Sec = Symbol->getSection();
            if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
                Asm.addLocalUsedInReloc(*Symbol);
        }

        const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
        const MCSymbolData *Base = Asm.getAtom(&SD);

        // If the symbol is a variable and we weren't able to get a Base for it
        // (i.e., it's not in the symbol table associated with a section) resolve
        // the relocation based its expansion instead.
        if (Symbol->isVariable() && !Base) {
            // If the evaluation is an absolute value, just use that directly
            // to keep things easy.
            int64_t Res;
            if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
                        Res, Layout, Writer->getSectionAddressMap())) {
                FixedValue = Res;
                return;
            }

            // FIXME: Will the Target we already have ever have any data in it
            // we need to preserve and merge with the new Target? How about
            // the FixedValue?
            if (!Symbol->getVariableValue()->EvaluateAsRelocatable(Target, &Layout,
                    &Fixup))
                Asm.getContext().FatalError(Fixup.getLoc(),
                                            "unable to resolve variable '" +
                                            Symbol->getName() + "'");
            return RecordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                                    FixedValue);
        }

        // Relocations inside debug sections always use local relocations when
        // possible. This seems to be done because the debugger doesn't fully
        // understand relocation entries and expects to find values that
        // have already been fixed up.
        if (Symbol->isInSection()) {
            if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
                Base = nullptr;
        }

        // AArch64 uses external relocations as much as possible. For debug
        // sections, and for pointer-sized relocations (.quad), we allow section
        // relocations.  It's code sections that run into trouble.
        if (Base) {
            RelSymbol = Base;

            // Add the local offset, if needed.
            if (Base != &SD)
                Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
        } else if (Symbol->isInSection()) {
            if (!CanUseLocalRelocation)
                Asm.getContext().FatalError(
                    Fixup.getLoc(),
                    "unsupported relocation of local symbol '" + Symbol->getName() +
                    "'. Must have non-local symbol earlier in section.");
            // Adjust the relocation to be section-relative.
            // The index is the section ordinal (1-based).
            const MCSectionData &SymSD =
                Asm.getSectionData(SD.getSymbol().getSection());
            Index = SymSD.getOrdinal() + 1;
            Value += Writer->getSymbolAddress(&SD, Layout);

            if (IsPCRel)
                Value -= Writer->getFragmentAddress(Fragment, Layout) +
                         Fixup.getOffset() + (1ULL << Log2Size);
        } else {
            // Resolve constant variables.
            if (SD.getSymbol().isVariable()) {
                int64_t Res;
                if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
                            Res, Layout, Writer->getSectionAddressMap())) {
                    FixedValue = Res;
                    return;
                }
            }
            Asm.getContext().FatalError(Fixup.getLoc(),
                                        "unsupported relocation of variable '" +
                                        Symbol->getName() + "'");
        }
    }

    // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
    // is represented via an Addend relocation, not encoded directly into
    // the instruction.
    if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
            Type == MachO::ARM64_RELOC_PAGE21 ||
            Type == MachO::ARM64_RELOC_PAGEOFF12) &&
            Value) {
        assert((Value & 0xff000000) == 0 && "Added relocation out of range!");

        MachO::any_relocation_info MRE;
        MRE.r_word0 = FixupOffset;
        MRE.r_word1 =
            (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
        Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);

        // Now set up the Addend relocation.
        Type = MachO::ARM64_RELOC_ADDEND;
        Index = Value;
        RelSymbol = nullptr;
        IsPCRel = 0;
        Log2Size = 2;

        // Put zero into the instruction itself. The addend is in the relocation.
        Value = 0;
    }

    // If there's any addend left to handle, encode it in the instruction.
    FixedValue = Value;

    // struct relocation_info (8 bytes)
    MachO::any_relocation_info MRE;
    MRE.r_word0 = FixupOffset;
    MRE.r_word1 =
        (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
    Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
}
Esempio n. 12
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void ELFObjectWriter::recordRelocation(MCAssembler &Asm,
                                       const MCAsmLayout &Layout,
                                       const MCFragment *Fragment,
                                       const MCFixup &Fixup, MCValue Target,
                                       uint64_t &FixedValue) {
  MCAsmBackend &Backend = Asm.getBackend();
  bool IsPCRel = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
                 MCFixupKindInfo::FKF_IsPCRel;
  const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent());
  uint64_t C = Target.getConstant();
  uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
  MCContext &Ctx = Asm.getContext();

  if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
    // Let A, B and C being the components of Target and R be the location of
    // the fixup. If the fixup is not pcrel, we want to compute (A - B + C).
    // If it is pcrel, we want to compute (A - B + C - R).

    // In general, ELF has no relocations for -B. It can only represent (A + C)
    // or (A + C - R). If B = R + K and the relocation is not pcrel, we can
    // replace B to implement it: (A - R - K + C)
    if (IsPCRel) {
      Ctx.reportError(
          Fixup.getLoc(),
          "No relocation available to represent this relative expression");
      return;
    }

    const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol());

    if (SymB.isUndefined()) {
      Ctx.reportError(Fixup.getLoc(),
                      Twine("symbol '") + SymB.getName() +
                          "' can not be undefined in a subtraction expression");
      return;
    }

    assert(!SymB.isAbsolute() && "Should have been folded");
    const MCSection &SecB = SymB.getSection();
    if (&SecB != &FixupSection) {
      Ctx.reportError(Fixup.getLoc(),
                      "Cannot represent a difference across sections");
      return;
    }

    uint64_t SymBOffset = Layout.getSymbolOffset(SymB);
    uint64_t K = SymBOffset - FixupOffset;
    IsPCRel = true;
    C -= K;
  }

  // We either rejected the fixup or folded B into C at this point.
  const MCSymbolRefExpr *RefA = Target.getSymA();
  const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr;

  bool ViaWeakRef = false;
  if (SymA && SymA->isVariable()) {
    const MCExpr *Expr = SymA->getVariableValue();
    if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) {
      if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) {
        SymA = cast<MCSymbolELF>(&Inner->getSymbol());
        ViaWeakRef = true;
      }
    }
  }

  unsigned Type = getRelocType(Ctx, Target, Fixup, IsPCRel);
  uint64_t OriginalC = C;
  bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type);
  if (!RelocateWithSymbol && SymA && !SymA->isUndefined())
    C += Layout.getSymbolOffset(*SymA);

  uint64_t Addend = 0;
  if (hasRelocationAddend()) {
    Addend = C;
    C = 0;
  }

  FixedValue = C;

  if (!RelocateWithSymbol) {
    const MCSection *SecA =
        (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr;
    auto *ELFSec = cast_or_null<MCSectionELF>(SecA);
    const auto *SectionSymbol =
        ELFSec ? cast<MCSymbolELF>(ELFSec->getBeginSymbol()) : nullptr;
    if (SectionSymbol)
      SectionSymbol->setUsedInReloc();
    ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA,
                           OriginalC);
    Relocations[&FixupSection].push_back(Rec);
    return;
  }

  const auto *RenamedSymA = SymA;
  if (SymA) {
    if (const MCSymbolELF *R = Renames.lookup(SymA))
      RenamedSymA = R;

    if (ViaWeakRef)
      RenamedSymA->setIsWeakrefUsedInReloc();
    else
      RenamedSymA->setUsedInReloc();
  }
  ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA,
                         OriginalC);
  Relocations[&FixupSection].push_back(Rec);
}
void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
                                           const MCAsmLayout &Layout,
                                           const MCFragment *Fragment,
                                           const MCFixup &Fixup,
                                           MCValue Target,
                                           uint64_t &FixedValue) {
  assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");

  const MCSymbol *A = &Target.getSymA()->getSymbol();
  MCSymbolData &A_SD = Asm.getSymbolData(*A);

  MCSectionData const *SectionData = Fragment->getParent();

  // Mark this symbol as requiring an entry in the symbol table.
  assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
         "Section must already have been defined in ExecutePostLayoutBinding!");
  assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
         "Symbol must already have been defined in ExecutePostLayoutBinding!");

  COFFSection *coff_section = SectionMap[&SectionData->getSection()];
  COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];

  if (Target.getSymB()) {
    if (&Target.getSymA()->getSymbol().getSection()
     != &Target.getSymB()->getSymbol().getSection()) {
      llvm_unreachable("Symbol relative relocations are only allowed between "
                       "symbols in the same section");
    }
    const MCSymbol *B = &Target.getSymB()->getSymbol();
    MCSymbolData &B_SD = Asm.getSymbolData(*B);

    FixedValue = Layout.getSymbolOffset(&A_SD) - Layout.getSymbolOffset(&B_SD);

    // In the case where we have SymbA and SymB, we just need to store the delta
    // between the two symbols.  Update FixedValue to account for the delta, and
    // skip recording the relocation.
    return;
  } else {
    FixedValue = Target.getConstant();
  }

  COFFRelocation Reloc;

  Reloc.Data.SymbolTableIndex = 0;
  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);

  // Turn relocations for temporary symbols into section relocations.
  if (coff_symbol->MCData->getSymbol().isTemporary()) {
    Reloc.Symb = coff_symbol->Section->Symbol;
    FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
                + coff_symbol->MCData->getOffset();
  } else
    Reloc.Symb = coff_symbol;

  ++Reloc.Symb->Relocations;

  Reloc.Data.VirtualAddress += Fixup.getOffset();

  switch ((unsigned)Fixup.getKind()) {
  case FK_PCRel_4:
  case X86::reloc_riprel_4byte:
  case X86::reloc_riprel_4byte_movq_load:
    Reloc.Data.Type = Is64Bit ? COFF::IMAGE_REL_AMD64_REL32
                              : COFF::IMAGE_REL_I386_REL32;
    // FIXME: Can anyone explain what this does other than adjust for the size
    // of the offset?
    FixedValue += 4;
    break;
  case FK_Data_4:
  case X86::reloc_signed_4byte:
    Reloc.Data.Type = Is64Bit ? COFF::IMAGE_REL_AMD64_ADDR32
                              : COFF::IMAGE_REL_I386_DIR32;
    break;
  case FK_Data_8:
    if (Is64Bit)
      Reloc.Data.Type = COFF::IMAGE_REL_AMD64_ADDR64;
    else
      llvm_unreachable("unsupported relocation type");
    break;
  default:
    llvm_unreachable("unsupported relocation type");
  }

  coff_section->Relocations.push_back(Reloc);
}
Esempio n. 14
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void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
                                              const MCAssembler &Asm,
                                              const MCAsmLayout &Layout,
                                              const MCFragment *Fragment,
                                              const MCFixup &Fixup,
                                              MCValue Target,
                                              uint64_t &FixedValue) {
  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());

  // If this is a 32-bit TLVP reloc it's handled a bit differently.
  if (Target.getSymA() &&
      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
    RecordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                         FixedValue);
    return;
  }

  // If this is a difference or a defined symbol plus an offset, then we need a
  // scattered relocation entry. Differences always require scattered
  // relocations.
  if (Target.getSymB()) {
    RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
                              Target, Log2Size, FixedValue);
    return;
  }

  // Get the symbol data, if any.
  const MCSymbolData *SD = nullptr;
  if (Target.getSymA())
    SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());

  // If this is an internal relocation with an offset, it also needs a scattered
  // relocation entry.
  uint32_t Offset = Target.getConstant();
  if (IsPCRel)
    Offset += 1 << Log2Size;
  // Try to record the scattered relocation if needed. Fall back to non
  // scattered if necessary (see comments in RecordScatteredRelocation()
  // for details).
  if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD) &&
      RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
                                Target, Log2Size, FixedValue))
    return;

  // See <reloc.h>.
  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
  unsigned Index = 0;
  unsigned Type = 0;
  const MCSymbol *RelSymbol = nullptr;

  if (Target.isAbsolute()) { // constant
    // SymbolNum of 0 indicates the absolute section.
    //
    // FIXME: Currently, these are never generated (see code below). I cannot
    // find a case where they are actually emitted.
    Type = MachO::GENERIC_RELOC_VANILLA;
  } else {
    // Resolve constant variables.
    if (SD->getSymbol().isVariable()) {
      int64_t Res;
      if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
            Res, Layout, Writer->getSectionAddressMap())) {
        FixedValue = Res;
        return;
      }
    }

    // Check whether we need an external or internal relocation.
    if (Writer->doesSymbolRequireExternRelocation(SD)) {
      RelSymbol = &SD->getSymbol();
      // For external relocations, make sure to offset the fixup value to
      // compensate for the addend of the symbol address, if it was
      // undefined. This occurs with weak definitions, for example.
      if (!SD->getSymbol().isUndefined())
        FixedValue -= Layout.getSymbolOffset(SD);
    } else {
      // The index is the section ordinal (1-based).
      const MCSectionData &SymSD = Asm.getSectionData(
        SD->getSymbol().getSection());
      Index = SymSD.getOrdinal() + 1;
      FixedValue += Writer->getSectionAddress(&SymSD);
    }
    if (IsPCRel)
      FixedValue -= Writer->getSectionAddress(Fragment->getParent());

    Type = MachO::GENERIC_RELOC_VANILLA;
  }

  // struct relocation_info (8 bytes)
  MachO::any_relocation_info MRE;
  MRE.r_word0 = FixupOffset;
  MRE.r_word1 =
      (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
  Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
}
Esempio n. 15
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uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
                                          const MCFragment &F) const {
  switch (F.getKind()) {
  case MCFragment::FT_Data:
    return cast<MCDataFragment>(F).getContents().size();
  case MCFragment::FT_Relaxable:
    return cast<MCRelaxableFragment>(F).getContents().size();
  case MCFragment::FT_CompactEncodedInst:
    return cast<MCCompactEncodedInstFragment>(F).getContents().size();
  case MCFragment::FT_Fill:
    return cast<MCFillFragment>(F).getSize();

  case MCFragment::FT_LEB:
    return cast<MCLEBFragment>(F).getContents().size();

  case MCFragment::FT_SafeSEH:
    return 4;

  case MCFragment::FT_Align: {
    const MCAlignFragment &AF = cast<MCAlignFragment>(F);
    unsigned Offset = Layout.getFragmentOffset(&AF);
    unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
    // If we are padding with nops, force the padding to be larger than the
    // minimum nop size.
    if (Size > 0 && AF.hasEmitNops()) {
      while (Size % getBackend().getMinimumNopSize())
        Size += AF.getAlignment();
    }
    if (Size > AF.getMaxBytesToEmit())
      return 0;
    return Size;
  }

  case MCFragment::FT_Org: {
    const MCOrgFragment &OF = cast<MCOrgFragment>(F);
    MCValue Value;
    if (!OF.getOffset().evaluateAsValue(Value, Layout)) {
      getContext().reportError(OF.getLoc(),
                               "expected assembly-time absolute expression");
        return 0;
    }

    uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
    int64_t TargetLocation = Value.getConstant();
    if (const MCSymbolRefExpr *A = Value.getSymA()) {
      uint64_t Val;
      if (!Layout.getSymbolOffset(A->getSymbol(), Val)) {
        getContext().reportError(OF.getLoc(), "expected absolute expression");
        return 0;
      }
      TargetLocation += Val;
    }
    int64_t Size = TargetLocation - FragmentOffset;
    if (Size < 0 || Size >= 0x40000000) {
      getContext().reportError(
          OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
                           "' (at offset '" + Twine(FragmentOffset) + "')");
      return 0;
    }
    return Size;
  }

  case MCFragment::FT_Dwarf:
    return cast<MCDwarfLineAddrFragment>(F).getContents().size();
  case MCFragment::FT_DwarfFrame:
    return cast<MCDwarfCallFrameFragment>(F).getContents().size();
  case MCFragment::FT_CVInlineLines:
    return cast<MCCVInlineLineTableFragment>(F).getContents().size();
  case MCFragment::FT_CVDefRange:
    return cast<MCCVDefRangeFragment>(F).getContents().size();
  case MCFragment::FT_Dummy:
    llvm_unreachable("Should not have been added");
  }

  llvm_unreachable("invalid fragment kind");
}
void SVMELFProgramWriter::rwCompress(MCAssembler &Asm, const MCAsmLayout &Layout, SVMMemoryLayout &ML)
{
    /*
     * Look for all segments with initialized data for RAM, flatten them, and
     * compress the resulting data. Create a new segment with the compressed
     * RWDATA. This segment will always be included in the binary. The originals
     * are considered debug-only sections, since they are no longer needed
     * at runtime.
     */

    // Flattened binary contents of RAM
    std::vector<uint8_t> plaintext;

    // Iterate over SPS_RW sections
    for (MCAssembler::const_iterator IS = Asm.begin(), ES = Asm.end(); IS != ES; ++IS) {
        const MCSectionData *SD = &*IS;
        if (ML.getSectionKind(SD) != SPS_RW_PLAIN)
            continue;

        int offset = ML.getSectionMemAddress(SD) - SVMTargetMachine::getRAMBase();
        int limit = SVMTargetMachine::getRAMSize();

        // Iterate over fragments, pasting them into 'plaintext'
        for (MCSectionData::const_iterator IF = SD->begin(), EF = SD->end(); IF != EF; ++IF) {
            const MCFragment *F = &*IF;
            if (F->getKind() == MCFragment::FT_Data) {
                const MCDataFragment *DF = cast<MCDataFragment>(F);
                int fragmentOffset = Layout.getFragmentOffset(F);
                for (unsigned i = 0; i < DF->getContents().size(); i++) {
                    int totalOffset = fragmentOffset + offset + i;
                    if (totalOffset < limit) {
                        while (totalOffset >= int(plaintext.size()))
                            plaintext.push_back(0);
                        plaintext[totalOffset] = DF->getContents()[i];
                    }
                }
            }
        }
    }

    // FastLZ requires a minimum of 16 bytes to compress. Pad our section data.
    while (plaintext.size() < 16)
        plaintext.push_back(0);

    // Compress using FastLZ level 1
    std::vector<uint8_t> compressed(plaintext.size() * 2);
    compressed.resize(fastlz_compress_level(1, &plaintext[0], plaintext.size(), &compressed[0]));

    // Create the new section
    const MCSectionELF *LZSection =
        Asm.getContext().getELFSection(".rwdata.lz", ELF::SHT_NOTE,
                                       0, SectionKind::getDataNoRel());
    MCSectionData &LZSectionSD = Asm.getOrCreateSectionData(*LZSection);
    LZSectionSD.setAlignment(1);

    // Force it to be interpreted as SPS_RW, and set the decompressed size
    ML.setSectionKind(&LZSectionSD, SPS_RW_Z);
    ML.setSectionMemSize(&LZSectionSD, plaintext.size());

    // Add compressed data
    MCDataFragment *F = new MCDataFragment(&LZSectionSD);
    F->getContents().append(compressed.begin(), compressed.end());
}
void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
                                           const MCAsmLayout &Layout,
                                           const MCFragment *Fragment,
                                           const MCFixup &Fixup,
                                           MCValue Target,
                                           bool &IsPCRel,
                                           uint64_t &FixedValue) {
  assert(Target.getSymA() && "Relocation must reference a symbol!");

  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
  const MCSymbol &A = Symbol.AliasedSymbol();
  if (!Asm.hasSymbolData(A))
    Asm.getContext().FatalError(
        Fixup.getLoc(),
        Twine("symbol '") + A.getName() + "' can not be undefined");

  const MCSymbolData &A_SD = Asm.getSymbolData(A);

  MCSectionData const *SectionData = Fragment->getParent();

  // Mark this symbol as requiring an entry in the symbol table.
  assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
         "Section must already have been defined in ExecutePostLayoutBinding!");
  assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
         "Symbol must already have been defined in ExecutePostLayoutBinding!");

  COFFSection *coff_section = SectionMap[&SectionData->getSection()];
  COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
  const MCSymbolRefExpr *SymB = Target.getSymB();
  bool CrossSection = false;

  if (SymB) {
    const MCSymbol *B = &SymB->getSymbol();
    const MCSymbolData &B_SD = Asm.getSymbolData(*B);
    if (!B_SD.getFragment())
      Asm.getContext().FatalError(
          Fixup.getLoc(),
          Twine("symbol '") + B->getName() +
              "' can not be undefined in a subtraction expression");

    if (!A_SD.getFragment())
      Asm.getContext().FatalError(
          Fixup.getLoc(),
          Twine("symbol '") + Symbol.getName() +
              "' can not be undefined in a subtraction expression");

    CrossSection = &Symbol.getSection() != &B->getSection();

    // Offset of the symbol in the section
    int64_t a = Layout.getSymbolOffset(&B_SD);

    // Ofeset of the relocation in the section
    int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();

    FixedValue = b - a;
    // In the case where we have SymbA and SymB, we just need to store the delta
    // between the two symbols.  Update FixedValue to account for the delta, and
    // skip recording the relocation.
    if (!CrossSection)
      return;
  } else {
    FixedValue = Target.getConstant();
  }

  COFFRelocation Reloc;

  Reloc.Data.SymbolTableIndex = 0;
  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);

  // Turn relocations for temporary symbols into section relocations.
  if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
    Reloc.Symb = coff_symbol->Section->Symbol;
    FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
                + coff_symbol->MCData->getOffset();
  } else
    Reloc.Symb = coff_symbol;

  ++Reloc.Symb->Relocations;

  Reloc.Data.VirtualAddress += Fixup.getOffset();
  Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
                                                     CrossSection);

  // FIXME: Can anyone explain what this does other than adjust for the size
  // of the offset?
  if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
       Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
      (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
       Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
    FixedValue += 4;

  if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
    switch (Reloc.Data.Type) {
    case COFF::IMAGE_REL_ARM_ABSOLUTE:
    case COFF::IMAGE_REL_ARM_ADDR32:
    case COFF::IMAGE_REL_ARM_ADDR32NB:
    case COFF::IMAGE_REL_ARM_TOKEN:
    case COFF::IMAGE_REL_ARM_SECTION:
    case COFF::IMAGE_REL_ARM_SECREL:
      break;
    case COFF::IMAGE_REL_ARM_BRANCH11:
    case COFF::IMAGE_REL_ARM_BLX11:
      // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
      // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
      // for Windows CE).
    case COFF::IMAGE_REL_ARM_BRANCH24:
    case COFF::IMAGE_REL_ARM_BLX24:
    case COFF::IMAGE_REL_ARM_MOV32A:
      // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
      // only used for ARM mode code, which is documented as being unsupported
      // by Windows on ARM.  Emperical proof indicates that masm is able to
      // generate the relocations however the rest of the MSVC toolchain is
      // unable to handle it.
      llvm_unreachable("unsupported relocation");
      break;
    case COFF::IMAGE_REL_ARM_MOV32T:
      break;
    case COFF::IMAGE_REL_ARM_BRANCH20T:
    case COFF::IMAGE_REL_ARM_BRANCH24T:
    case COFF::IMAGE_REL_ARM_BLX23T:
      // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
      // perform a 4 byte adjustment to the relocation.  Relative branches are
      // offset by 4 on ARM, however, because there is no RELA relocations, all
      // branches are offset by 4.
      FixedValue = FixedValue + 4;
      break;
    }
  }

  coff_section->Relocations.push_back(Reloc);
}
Esempio n. 18
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void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
                                      const MCAsmLayout &Layout) {
  // Assign symbol and section indexes and offsets.
  Header.NumberOfSections = 0;

  for (sections::iterator i = Sections.begin(),
                          e = Sections.end(); i != e; i++) {
    if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
      MakeSectionReal(**i, ++Header.NumberOfSections);
    } else {
      (*i)->Number = -1;
    }
  }

  Header.NumberOfSymbols = 0;

  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
    COFFSymbol *coff_symbol = *i;
    MCSymbolData const *SymbolData = coff_symbol->MCData;

    // Update section number & offset for symbols that have them.
    if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
      assert(coff_symbol->Section != NULL);

      coff_symbol->Data.SectionNumber = coff_symbol->Section->Number;
      coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
                              + SymbolData->Offset;
    }

    if (coff_symbol->should_keep()) {
      MakeSymbolReal(*coff_symbol, Header.NumberOfSymbols++);

      // Update auxiliary symbol info.
      coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
      Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
    } else
      coff_symbol->Index = -1;
  }

  // Fixup weak external references.
  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
    COFFSymbol *coff_symbol = *i;
    if (coff_symbol->Other != NULL) {
      assert(coff_symbol->Index != -1);
      assert(coff_symbol->Aux.size() == 1 &&
             "Symbol must contain one aux symbol!");
      assert(coff_symbol->Aux[0].AuxType == ATWeakExternal &&
             "Symbol's aux symbol must be a Weak External!");
      coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = coff_symbol->Other->Index;
    }
  }

  // Assign file offsets to COFF object file structures.

  unsigned offset = 0;

  offset += COFF::HeaderSize;
  offset += COFF::SectionSize * Header.NumberOfSections;

  for (MCAssembler::const_iterator i = Asm.begin(),
                                   e = Asm.end();
                                   i != e; i++) {
    COFFSection *Sec = SectionMap[&i->getSection()];

    if (Sec->Number == -1)
      continue;

    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);

    if (IsPhysicalSection(Sec)) {
      Sec->Header.PointerToRawData = offset;

      offset += Sec->Header.SizeOfRawData;
    }

    if (Sec->Relocations.size() > 0) {
      Sec->Header.NumberOfRelocations = Sec->Relocations.size();
      Sec->Header.PointerToRelocations = offset;

      offset += COFF::RelocationSize * Sec->Relocations.size();

      for (relocations::iterator cr = Sec->Relocations.begin(),
                                 er = Sec->Relocations.end();
                                 cr != er; ++cr) {
        assert((*cr).Symb->Index != -1);
        (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
      }
    }

    assert(Sec->Symbol->Aux.size() == 1
      && "Section's symbol must have one aux!");
    AuxSymbol &Aux = Sec->Symbol->Aux[0];
    assert(Aux.AuxType == ATSectionDefinition &&
           "Section's symbol's aux symbol must be a Section Definition!");
    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
    Aux.Aux.SectionDefinition.NumberOfRelocations =
                                                Sec->Header.NumberOfRelocations;
    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
                                                Sec->Header.NumberOfLineNumbers;
  }

  Header.PointerToSymbolTable = offset;

  Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();

  // Write it all to disk...
  WriteFileHeader(Header);

  {
    sections::iterator i, ie;
    MCAssembler::const_iterator j, je;

    for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
      if ((*i)->Number != -1)
        WriteSectionHeader((*i)->Header);

    for (i = Sections.begin(), ie = Sections.end(),
         j = Asm.begin(), je = Asm.end();
         (i != ie) && (j != je); ++i, ++j) {

      if ((*i)->Number == -1)
        continue;

      if ((*i)->Header.PointerToRawData != 0) {
        assert(OS.tell() == (*i)->Header.PointerToRawData &&
               "Section::PointerToRawData is insane!");

        Asm.writeSectionData(j, Layout);
      }

      if ((*i)->Relocations.size() > 0) {
        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
               "Section::PointerToRelocations is insane!");

        for (relocations::const_iterator k = (*i)->Relocations.begin(),
                                               ke = (*i)->Relocations.end();
                                               k != ke; k++) {
          WriteRelocation(k->Data);
        }
      } else
        assert((*i)->Header.PointerToRelocations == 0 &&
               "Section::PointerToRelocations is insane!");
    }
  }

  assert(OS.tell() == Header.PointerToSymbolTable &&
         "Header::PointerToSymbolTable is insane!");

  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
    if ((*i)->Index != -1)
      WriteSymbol(*i);

  OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
}
Esempio n. 19
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void X86MachObjectWriter::RecordX86_64Relocation(
    MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
    const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
    uint64_t &FixedValue) {
  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
  unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());

  // See <reloc.h>.
  uint32_t FixupOffset =
    Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
  uint32_t FixupAddress =
    Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
  int64_t Value = 0;
  unsigned Index = 0;
  unsigned IsExtern = 0;
  unsigned Type = 0;
  const MCSymbol *RelSymbol = nullptr;

  Value = Target.getConstant();

  if (IsPCRel) {
    // Compensate for the relocation offset, Darwin x86_64 relocations only have
    // the addend and appear to have attempted to define it to be the actual
    // expression addend without the PCrel bias. However, instructions with data
    // following the relocation are not accommodated for (see comment below
    // regarding SIGNED{1,2,4}), so it isn't exactly that either.
    Value += 1LL << Log2Size;
  }

  if (Target.isAbsolute()) { // constant
    // SymbolNum of 0 indicates the absolute section.
    Type = MachO::X86_64_RELOC_UNSIGNED;

    // FIXME: I believe this is broken, I don't think the linker can understand
    // it. I think it would require a local relocation, but I'm not sure if that
    // would work either. The official way to get an absolute PCrel relocation
    // is to use an absolute symbol (which we don't support yet).
    if (IsPCRel) {
      IsExtern = 1;
      Type = MachO::X86_64_RELOC_BRANCH;
    }
  } else if (Target.getSymB()) { // A - B + constant
    const MCSymbol *A = &Target.getSymA()->getSymbol();
    if (A->isTemporary())
      A = &Writer->findAliasedSymbol(*A);
    const MCSymbolData &A_SD = Asm.getSymbolData(*A);
    const MCSymbol *A_Base = Asm.getAtom(&A_SD);

    const MCSymbol *B = &Target.getSymB()->getSymbol();
    if (B->isTemporary())
      B = &Writer->findAliasedSymbol(*B);
    const MCSymbolData &B_SD = Asm.getSymbolData(*B);
    const MCSymbol *B_Base = Asm.getAtom(&B_SD);

    // Neither symbol can be modified.
    if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
        Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
      report_fatal_error("unsupported relocation of modified symbol", false);

    // We don't support PCrel relocations of differences. Darwin 'as' doesn't
    // implement most of these correctly.
    if (IsPCRel)
      report_fatal_error("unsupported pc-relative relocation of difference",
                         false);

    // The support for the situation where one or both of the symbols would
    // require a local relocation is handled just like if the symbols were
    // external.  This is certainly used in the case of debug sections where the
    // section has only temporary symbols and thus the symbols don't have base
    // symbols.  This is encoded using the section ordinal and non-extern
    // relocation entries.

    // Darwin 'as' doesn't emit correct relocations for this (it ends up with a
    // single SIGNED relocation); reject it for now.  Except the case where both
    // symbols don't have a base, equal but both NULL.
    if (A_Base == B_Base && A_Base)
      report_fatal_error("unsupported relocation with identical base", false);

    // A subtraction expression where either symbol is undefined is a
    // non-relocatable expression.
    if (A->isUndefined() || B->isUndefined()) {
      StringRef Name = A->isUndefined() ? A->getName() : B->getName();
      Asm.getContext().FatalError(Fixup.getLoc(),
        "unsupported relocation with subtraction expression, symbol '" +
        Name + "' can not be undefined in a subtraction expression");
    }

    Value +=
        Writer->getSymbolAddress(&A_SD, Layout) -
        (!A_Base ? 0 : Writer->getSymbolAddress(&A_Base->getData(), Layout));
    Value -=
        Writer->getSymbolAddress(&B_SD, Layout) -
        (!B_Base ? 0 : Writer->getSymbolAddress(&B_Base->getData(), Layout));

    if (!A_Base)
      Index = A_SD.getFragment()->getParent()->getOrdinal() + 1;
    Type = MachO::X86_64_RELOC_UNSIGNED;

    MachO::any_relocation_info MRE;
    MRE.r_word0 = FixupOffset;
    MRE.r_word1 =
        (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
    Writer->addRelocation(A_Base, Fragment->getParent(), MRE);

    if (B_Base)
      RelSymbol = B_Base;
    else
      Index = B_SD.getFragment()->getParent()->getOrdinal() + 1;
    Type = MachO::X86_64_RELOC_SUBTRACTOR;
  } else {
    const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
    if (Symbol->isTemporary() && Value) {
      const MCSection &Sec = Symbol->getSection();
      if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
        Asm.addLocalUsedInReloc(*Symbol);
    }
    const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
    RelSymbol = Asm.getAtom(&SD);

    // Relocations inside debug sections always use local relocations when
    // possible. This seems to be done because the debugger doesn't fully
    // understand x86_64 relocation entries, and expects to find values that
    // have already been fixed up.
    if (Symbol->isInSection()) {
      const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
        Fragment->getParent()->getSection());
      if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
        RelSymbol = nullptr;
    }

    // x86_64 almost always uses external relocations, except when there is no
    // symbol to use as a base address (a local symbol with no preceding
    // non-local symbol).
    if (RelSymbol) {
      // Add the local offset, if needed.
      if (&RelSymbol->getData() != &SD)
        Value += Layout.getSymbolOffset(&SD) -
                 Layout.getSymbolOffset(&RelSymbol->getData());
    } else if (Symbol->isInSection() && !Symbol->isVariable()) {
      // The index is the section ordinal (1-based).
      Index = SD.getFragment()->getParent()->getOrdinal() + 1;
      Value += Writer->getSymbolAddress(&SD, Layout);

      if (IsPCRel)
        Value -= FixupAddress + (1 << Log2Size);
    } else if (Symbol->isVariable()) {
      const MCExpr *Value = Symbol->getVariableValue();
      int64_t Res;
      bool isAbs = Value->EvaluateAsAbsolute(Res, Layout,
                                             Writer->getSectionAddressMap());
      if (isAbs) {
        FixedValue = Res;
        return;
      } else {
        report_fatal_error("unsupported relocation of variable '" +
                           Symbol->getName() + "'", false);
      }
    } else {
      report_fatal_error("unsupported relocation of undefined symbol '" +
                         Symbol->getName() + "'", false);
    }

    MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
    if (IsPCRel) {
      if (IsRIPRel) {
        if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
          // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
          // rewrite the movq to an leaq at link time if the symbol ends up in
          // the same linkage unit.
          if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
            Type = MachO::X86_64_RELOC_GOT_LOAD;
          else
            Type = MachO::X86_64_RELOC_GOT;
        }  else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
          Type = MachO::X86_64_RELOC_TLV;
        }  else if (Modifier != MCSymbolRefExpr::VK_None) {
          report_fatal_error("unsupported symbol modifier in relocation",
                             false);
        } else {
          Type = MachO::X86_64_RELOC_SIGNED;

          // The Darwin x86_64 relocation format has a problem where it cannot
          // encode an address (L<foo> + <constant>) which is outside the atom
          // containing L<foo>. Generally, this shouldn't occur but it does
          // happen when we have a RIPrel instruction with data following the
          // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
          // adjustment Darwin x86_64 uses, the offset is still negative and the
          // linker has no way to recognize this.
          //
          // To work around this, Darwin uses several special relocation types
          // to indicate the offsets. However, the specification or
          // implementation of these seems to also be incomplete; they should
          // adjust the addend as well based on the actual encoded instruction
          // (the additional bias), but instead appear to just look at the final
          // offset.
          switch (-(Target.getConstant() + (1LL << Log2Size))) {
          case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break;
          case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break;
          case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break;
          }
        }
      } else {
        if (Modifier != MCSymbolRefExpr::VK_None)
          report_fatal_error("unsupported symbol modifier in branch "
                             "relocation", false);

        Type = MachO::X86_64_RELOC_BRANCH;
      }
    } else {
      if (Modifier == MCSymbolRefExpr::VK_GOT) {
        Type = MachO::X86_64_RELOC_GOT;
      } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
        // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which
        // case all we do is set the PCrel bit in the relocation entry; this is
        // used with exception handling, for example. The source is required to
        // include any necessary offset directly.
        Type = MachO::X86_64_RELOC_GOT;
        IsPCRel = 1;
      } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
        report_fatal_error("TLVP symbol modifier should have been rip-rel",
                           false);
      } else if (Modifier != MCSymbolRefExpr::VK_None)
        report_fatal_error("unsupported symbol modifier in relocation", false);
      else {
        Type = MachO::X86_64_RELOC_UNSIGNED;
        unsigned Kind = Fixup.getKind();
        if (Kind == X86::reloc_signed_4byte)
          report_fatal_error("32-bit absolute addressing is not supported in "
                             "64-bit mode", false);
      }
    }
  }

  // x86_64 always writes custom values into the fixups.
  FixedValue = Value;

  // struct relocation_info (8 bytes)
  MachO::any_relocation_info MRE;
  MRE.r_word0 = FixupOffset;
  MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
                (IsExtern << 27) | (Type << 28);
  Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
}
Esempio n. 20
0
bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
                                const MCFixup &Fixup, const MCFragment *DF,
                                MCValue &Target, uint64_t &Value) const {
  ++stats::evaluateFixup;

  // FIXME: This code has some duplication with recordRelocation. We should
  // probably merge the two into a single callback that tries to evaluate a
  // fixup and records a relocation if one is needed.
  const MCExpr *Expr = Fixup.getValue();
  if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup))
    getContext().reportFatalError(Fixup.getLoc(), "expected relocatable expression");

  bool IsPCRel = Backend.getFixupKindInfo(
    Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;

  bool IsResolved;
  if (IsPCRel) {
    if (Target.getSymB()) {
      IsResolved = false;
    } else if (!Target.getSymA()) {
      IsResolved = false;
    } else {
      const MCSymbolRefExpr *A = Target.getSymA();
      const MCSymbol &SA = A->getSymbol();
      if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
        IsResolved = false;
      } else {
        IsResolved = getWriter().isSymbolRefDifferenceFullyResolvedImpl(
            *this, SA, *DF, false, true);
      }
    }
  } else {
    IsResolved = Target.isAbsolute();
  }

  Value = Target.getConstant();

  if (const MCSymbolRefExpr *A = Target.getSymA()) {
    const MCSymbol &Sym = A->getSymbol();
    if (Sym.isDefined())
      Value += Layout.getSymbolOffset(Sym);
  }
  if (const MCSymbolRefExpr *B = Target.getSymB()) {
    const MCSymbol &Sym = B->getSymbol();
    if (Sym.isDefined())
      Value -= Layout.getSymbolOffset(Sym);
  }


  bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags &
                         MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
  assert((ShouldAlignPC ? IsPCRel : true) &&
    "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");

  if (IsPCRel) {
    uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();

    // A number of ARM fixups in Thumb mode require that the effective PC
    // address be determined as the 32-bit aligned version of the actual offset.
    if (ShouldAlignPC) Offset &= ~0x3;
    Value -= Offset;
  }

  // Let the backend adjust the fixup value if necessary, including whether
  // we need a relocation.
  Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value,
                            IsResolved);

  return IsResolved;
}