lld/ELF/InputSection.cpp - toolchain/llvm-project - Gitiles

 //===- InputSection.cpp ---------------------------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//

 #include "InputSection.h"
 #include "Config.h"
 #include "Error.h"
 #include "InputFiles.h"
 #include "OutputSections.h"
 #include "Target.h"

 #include "llvm/Support/Endian.h"

 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::support::endian;

 using namespace lld;
 using namespace lld::elf;

 template <class ELFT>
 InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File,
                                          const Elf_Shdr *Header,
                                          Kind SectionKind)
     : Header(Header), File(File), SectionKind(SectionKind), Repl(this) {
   // The garbage collector sets sections' Live bits.
   // If GC is disabled, all sections are considered live by default.
   Live = !Config->GcSections;

   // The ELF spec states that a value of 0 means the section has
   // no alignment constraits.
   Align = std::max<uintX_t>(Header->sh_addralign, 1);
 }

 template <class ELFT> size_t InputSectionBase<ELFT>::getSize() const {
   if (auto *D = dyn_cast<InputSection<ELFT>>(this))
     if (D->getThunksSize() > 0)
       return D->getThunkOff() + D->getThunksSize();
   return Header->sh_size;
 }

 template <class ELFT> StringRef InputSectionBase<ELFT>::getSectionName() const {
   return check(File->getObj().getSectionName(this->Header));
 }

 template <class ELFT>
 ArrayRef<uint8_t> InputSectionBase<ELFT>::getSectionData() const {
   return check(this->File->getObj().getSectionContents(this->Header));
 }

 template <class ELFT>
 typename ELFT::uint InputSectionBase<ELFT>::getOffset(uintX_t Offset) {
   switch (SectionKind) {
   case Regular:
     return cast<InputSection<ELFT>>(this)->OutSecOff + Offset;
   case EHFrame:
     return cast<EHInputSection<ELFT>>(this)->getOffset(Offset);
   case Merge:
     return cast<MergeInputSection<ELFT>>(this)->getOffset(Offset);
   case MipsReginfo:
     // MIPS .reginfo sections are consumed by the linker,
     // so it should never be copied to output.
     llvm_unreachable("MIPS .reginfo reached writeTo().");
   }
   llvm_unreachable("invalid section kind");
 }

 template <class ELFT>
 typename ELFT::uint InputSectionBase<ELFT>::getOffset(const Elf_Sym &Sym) {
   return getOffset(Sym.st_value);
 }

 // Returns a section that Rel relocation is pointing to.
 template <class ELFT>
 InputSectionBase<ELFT> *
 InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) const {
   // Global symbol
   uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
   SymbolBody &B = File->getSymbolBody(SymIndex).repl();
   if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B))
     if (D->Section)
       return D->Section->Repl;
   return nullptr;
 }

 template <class ELFT>
 InputSectionBase<ELFT> *
 InputSectionBase<ELFT>::getRelocTarget(const Elf_Rela &Rel) const {
   return getRelocTarget(reinterpret_cast<const Elf_Rel &>(Rel));
 }

 template <class ELFT>
 InputSection<ELFT>::InputSection(elf::ObjectFile<ELFT> *F,
                                  const Elf_Shdr *Header)
     : InputSectionBase<ELFT>(F, Header, Base::Regular) {}

 template <class ELFT>
 bool InputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
   return S->SectionKind == Base::Regular;
 }

 template <class ELFT>
 InputSectionBase<ELFT> *InputSection<ELFT>::getRelocatedSection() {
   assert(this->Header->sh_type == SHT_RELA || this->Header->sh_type == SHT_REL);
   ArrayRef<InputSectionBase<ELFT> *> Sections = this->File->getSections();
   return Sections[this->Header->sh_info];
 }

 template <class ELFT> void InputSection<ELFT>::addThunk(SymbolBody &Body) {
   Body.ThunkIndex = Thunks.size();
   Thunks.push_back(&Body);
 }

 template <class ELFT> uint64_t InputSection<ELFT>::getThunkOff() const {
   return this->Header->sh_size;
 }

 template <class ELFT> uint64_t InputSection<ELFT>::getThunksSize() const {
   return Thunks.size() * Target->ThunkSize;
 }

 // This is used for -r. We can't use memcpy to copy relocations because we need
 // to update symbol table offset and section index for each relocation. So we
 // copy relocations one by one.
 template <class ELFT>
 template <class RelTy>
 void InputSection<ELFT>::copyRelocations(uint8_t *Buf,
                                          iterator_range<const RelTy *> Rels) {
   InputSectionBase<ELFT> *RelocatedSection = getRelocatedSection();

   for (const RelTy &Rel : Rels) {
     uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
     uint32_t Type = Rel.getType(Config->Mips64EL);
     SymbolBody &Body = this->File->getSymbolBody(SymIndex).repl();

     RelTy *P = reinterpret_cast<RelTy *>(Buf);
     Buf += sizeof(RelTy);

     P->r_offset = RelocatedSection->getOffset(Rel.r_offset);
     P->setSymbolAndType(Body.DynsymIndex, Type, Config->Mips64EL);
   }
 }

 template <class RelTy>
 static uint32_t getMipsPairType(const RelTy *Rel, const SymbolBody &Sym) {
   switch (Rel->getType(Config->Mips64EL)) {
   case R_MIPS_HI16:
     return R_MIPS_LO16;
   case R_MIPS_GOT16:
     return Sym.isLocal() ? R_MIPS_LO16 : R_MIPS_NONE;
   case R_MIPS_PCHI16:
     return R_MIPS_PCLO16;
   case R_MICROMIPS_HI16:
     return R_MICROMIPS_LO16;
   default:
     return R_MIPS_NONE;
   }
 }

 template <endianness E> static int16_t readSignedLo16(uint8_t *Loc) {
   return read32<E>(Loc) & 0xffff;
 }

 template <class ELFT>
 template <class RelTy>
 int32_t
 InputSectionBase<ELFT>::findMipsPairedAddend(uint8_t *Buf, uint8_t *BufLoc,
                                              SymbolBody &Sym, const RelTy *Rel,
                                              const RelTy *End) {
   uint32_t SymIndex = Rel->getSymbol(Config->Mips64EL);
   uint32_t Type = getMipsPairType(Rel, Sym);

   // Some MIPS relocations use addend calculated from addend of the relocation
   // itself and addend of paired relocation. ABI requires to compute such
   // combined addend in case of REL relocation record format only.
   // See p. 4-17 at ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
   if (RelTy::IsRela || Type == R_MIPS_NONE)
     return 0;

   for (const RelTy *RI = Rel; RI != End; ++RI) {
     if (RI->getType(Config->Mips64EL) != Type)
       continue;
     if (RI->getSymbol(Config->Mips64EL) != SymIndex)
       continue;
     uintX_t Offset = getOffset(RI->r_offset);
     if (Offset == (uintX_t)-1)
       break;
     const endianness E = ELFT::TargetEndianness;
     return ((read32<E>(BufLoc) & 0xffff) << 16) +
            readSignedLo16<E>(Buf + Offset);
   }
   unsigned OldType = Rel->getType(Config->Mips64EL);
   StringRef OldName = getELFRelocationTypeName(Config->EMachine, OldType);
   StringRef NewName = getELFRelocationTypeName(Config->EMachine, Type);
   warning("can't find matching " + NewName + " relocation for " + OldName);
   return 0;
 }

 template <class ELFT, class uintX_t>
 static uintX_t adjustMipsSymVA(uint32_t Type, const elf::ObjectFile<ELFT> &File,
                                const SymbolBody &Body, uintX_t AddrLoc,
                                uintX_t SymVA) {
   if (Type == R_MIPS_HI16 && &Body == Config->MipsGpDisp)
     return getMipsGpAddr<ELFT>() - AddrLoc;
   if (Type == R_MIPS_LO16 && &Body == Config->MipsGpDisp)
     return getMipsGpAddr<ELFT>() - AddrLoc + 4;
   if (&Body == Config->MipsLocalGp)
     return getMipsGpAddr<ELFT>();
   if (Body.isLocal() && (Type == R_MIPS_GPREL16 || Type == R_MIPS_GPREL32))
     // We need to adjust SymVA value in case of R_MIPS_GPREL16/32
     // relocations because they use the following expression to calculate
     // the relocation's result for local symbol: S + A + GP0 - G.
     return SymVA + File.getMipsGp0();
   return SymVA;
 }

 template <class ELFT, class uintX_t>
 static uintX_t getMipsGotVA(const SymbolBody &Body, uintX_t SymVA,
                             uint8_t *BufLoc) {
   if (Body.isLocal())
     // If relocation against MIPS local symbol requires GOT entry, this entry
     // should be initialized by 'page address'. This address is high 16-bits
     // of sum the symbol's value and the addend.
     return Out<ELFT>::Got->getMipsLocalPageAddr(SymVA);
   if (!Body.isPreemptible())
     // For non-local symbols GOT entries should contain their full
     // addresses. But if such symbol cannot be preempted, we do not
     // have to put them into the "global" part of GOT and use dynamic
     // linker to determine their actual addresses. That is why we
     // create GOT entries for them in the "local" part of GOT.
     return Out<ELFT>::Got->getMipsLocalFullAddr(Body);
   return Body.getGotVA<ELFT>();
 }

 template <class ELFT>
 template <class RelTy>
 void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd,
                                       iterator_range<const RelTy *> Rels) {
   size_t Num = Rels.end() - Rels.begin();
   for (size_t I = 0; I < Num; ++I) {
     const RelTy &RI = *(Rels.begin() + I);
     uintX_t Offset = getOffset(RI.r_offset);
     if (Offset == (uintX_t)-1)
       continue;

     uintX_t A = getAddend<ELFT>(RI);
     uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
     uint32_t Type = RI.getType(Config->Mips64EL);
     uint8_t *BufLoc = Buf + Offset;
     uintX_t AddrLoc = OutSec->getVA() + Offset;

     if (Target->pointsToLocalDynamicGotEntry(Type) &&
         !Target->canRelaxTls(Type, nullptr)) {
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
                           Out<ELFT>::Got->getTlsIndexVA() + A);
       continue;
     }

     SymbolBody &Body = File->getSymbolBody(SymIndex).repl();

     if (Target->canRelaxTls(Type, &Body)) {
       uintX_t SymVA;
       if (Target->needsGot(Type, Body))
         SymVA = Body.getGotVA<ELFT>();
       else
         SymVA = Body.getVA<ELFT>();
       // By optimizing TLS relocations, it is sometimes needed to skip
       // relocations that immediately follow TLS relocations. This function
       // knows how many slots we need to skip.
       I += Target->relaxTls(BufLoc, BufEnd, Type, AddrLoc, SymVA, Body);
       continue;
     }

     // PPC64 has a special relocation representing the TOC base pointer
     // that does not have a corresponding symbol.
     if (Config->EMachine == EM_PPC64 && RI.getType(false) == R_PPC64_TOC) {
       uintX_t SymVA = getPPC64TocBase() + A;
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA);
       continue;
     }

     if (Target->isTlsGlobalDynamicRel(Type) &&
         !Target->canRelaxTls(Type, &Body)) {
       Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
                           Out<ELFT>::Got->getGlobalDynAddr(Body) + A);
       continue;
     }

     if (!RelTy::IsRela)
       A += Target->getImplicitAddend(BufLoc, Type);
     if (Config->EMachine == EM_MIPS)
       A += findMipsPairedAddend(Buf, BufLoc, Body, &RI, Rels.end());
     uintX_t SymVA = Body.getVA<ELFT>(A);

     if (Target->needsPlt(Type, Body)) {
       SymVA = Body.getPltVA<ELFT>() + A;
     } else if (Target->needsGot(Type, Body)) {
       if (Config->EMachine == EM_MIPS)
         SymVA = getMipsGotVA<ELFT>(Body, SymVA, BufLoc);
       else
         SymVA = Body.getGotVA<ELFT>() + A;
       if (Body.IsTls)
         Type = Target->getTlsGotRel(Type);
     } else if (Target->isSizeRel(Type) && Body.isPreemptible()) {
       // A SIZE relocation is supposed to set a symbol size, but if a symbol
       // can be preempted, the size at runtime may be different than link time.
       // If that's the case, we leave the field alone rather than filling it
       // with a possibly incorrect value.
       continue;
     } else if (Target->needsThunk(Type, *this->getFile(), Body)) {
       // Get address of a thunk code related to the symbol.
       SymVA = Body.getThunkVA<ELFT>();
     } else if (Config->EMachine == EM_MIPS) {
       SymVA = adjustMipsSymVA<ELFT>(Type, *File, Body, AddrLoc, SymVA);
     } else if (!Target->needsCopyRel<ELFT>(Type, Body) &&
                Body.isPreemptible()) {
       continue;
     }
     if (Target->isSizeRel(Type))
       SymVA = Body.getSize<ELFT>() + A;

     Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA);
   }
 }

 template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) {
   if (this->Header->sh_type == SHT_NOBITS)
     return;
   ELFFile<ELFT> &EObj = this->File->getObj();

   // If -r is given, then an InputSection may be a relocation section.
   if (this->Header->sh_type == SHT_RELA) {
     copyRelocations(Buf + OutSecOff, EObj.relas(this->Header));
     return;
   }
   if (this->Header->sh_type == SHT_REL) {
     copyRelocations(Buf + OutSecOff, EObj.rels(this->Header));
     return;
   }

   // Copy section contents from source object file to output file.
   ArrayRef<uint8_t> Data = this->getSectionData();
   memcpy(Buf + OutSecOff, Data.data(), Data.size());

   // Iterate over all relocation sections that apply to this section.
   uint8_t *BufEnd = Buf + OutSecOff + Data.size();
   for (const Elf_Shdr *RelSec : this->RelocSections) {
     if (RelSec->sh_type == SHT_RELA)
       this->relocate(Buf, BufEnd, EObj.relas(RelSec));
     else
       this->relocate(Buf, BufEnd, EObj.rels(RelSec));
   }

   // The section might have a data/code generated by the linker and need
   // to be written after the section. Usually these are thunks - small piece
   // of code used to jump between "incompatible" functions like PIC and non-PIC
   // or if the jump target too far and its address does not fit to the short
   // jump istruction.
   if (!Thunks.empty()) {
     Buf += OutSecOff + getThunkOff();
     for (const SymbolBody *S : Thunks) {
       Target->writeThunk(Buf, S->getVA<ELFT>());
       Buf += Target->ThunkSize;
     }
   }
 }

 template <class ELFT>
 void InputSection<ELFT>::replace(InputSection<ELFT> *Other) {
   this->Align = std::max(this->Align, Other->Align);
   Other->Repl = this->Repl;
   Other->Live = false;
 }

 template <class ELFT>
 SplitInputSection<ELFT>::SplitInputSection(
     elf::ObjectFile<ELFT> *File, const Elf_Shdr *Header,
     typename InputSectionBase<ELFT>::Kind SectionKind)
     : InputSectionBase<ELFT>(File, Header, SectionKind) {}

 template <class ELFT>
 EHInputSection<ELFT>::EHInputSection(elf::ObjectFile<ELFT> *F,
                                      const Elf_Shdr *Header)
     : SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::EHFrame) {
   // Mark .eh_frame sections as live by default because there are
   // usually no relocations that point to .eh_frames. Otherwise,
   // the garbage collector would drop all .eh_frame sections.
   this->Live = true;
 }

 template <class ELFT>
 bool EHInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
   return S->SectionKind == InputSectionBase<ELFT>::EHFrame;
 }

 template <class ELFT>
 typename ELFT::uint EHInputSection<ELFT>::getOffset(uintX_t Offset) {
   // The file crtbeginT.o has relocations pointing to the start of an empty
   // .eh_frame that is known to be the first in the link. It does that to
   // identify the start of the output .eh_frame. Handle this special case.
   if (this->getSectionHdr()->sh_size == 0)
     return Offset;
   std::pair<uintX_t, uintX_t> *I = this->getRangeAndSize(Offset).first;
   uintX_t Base = I->second;
   if (Base == uintX_t(-1))
     return -1; // Not in the output

   uintX_t Addend = Offset - I->first;
   return Base + Addend;
 }

 template <class ELFT>
 MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F,
                                            const Elf_Shdr *Header)
     : SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::Merge) {}

 template <class ELFT>
 bool MergeInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
   return S->SectionKind == InputSectionBase<ELFT>::Merge;
 }

 template <class ELFT>
 std::pair<std::pair<typename ELFT::uint, typename ELFT::uint> *,
           typename ELFT::uint>
 SplitInputSection<ELFT>::getRangeAndSize(uintX_t Offset) {
   ArrayRef<uint8_t> D = this->getSectionData();
   StringRef Data((const char *)D.data(), D.size());
   uintX_t Size = Data.size();
   if (Offset >= Size)
     fatal("entry is past the end of the section");

   // Find the element this offset points to.
   auto I = std::upper_bound(
       Offsets.begin(), Offsets.end(), Offset,
       [](const uintX_t &A, const std::pair<uintX_t, uintX_t> &B) {
         return A < B.first;
       });
   uintX_t End = I == Offsets.end() ? Data.size() : I->first;
   --I;
   return std::make_pair(&*I, End);
 }

 template <class ELFT>
 typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) {
   std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
       this->getRangeAndSize(Offset);
   std::pair<uintX_t, uintX_t> *I = T.first;
   uintX_t End = T.second;
   uintX_t Start = I->first;

   // Compute the Addend and if the Base is cached, return.
   uintX_t Addend = Offset - Start;
   uintX_t &Base = I->second;
   if (Base != uintX_t(-1))
     return Base + Addend;

   // Map the base to the offset in the output section and cache it.
   ArrayRef<uint8_t> D = this->getSectionData();
   StringRef Data((const char *)D.data(), D.size());
   StringRef Entry = Data.substr(Start, End - Start);
   Base =
       static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Entry);
   return Base + Addend;
 }

 template <class ELFT>
 MipsReginfoInputSection<ELFT>::MipsReginfoInputSection(elf::ObjectFile<ELFT> *F,
                                                        const Elf_Shdr *Hdr)
     : InputSectionBase<ELFT>(F, Hdr, InputSectionBase<ELFT>::MipsReginfo) {
   // Initialize this->Reginfo.
   ArrayRef<uint8_t> D = this->getSectionData();
   if (D.size() != sizeof(Elf_Mips_RegInfo<ELFT>))
     fatal("invalid size of .reginfo section");
   Reginfo = reinterpret_cast<const Elf_Mips_RegInfo<ELFT> *>(D.data());
 }

 template <class ELFT>
 bool MipsReginfoInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
   return S->SectionKind == InputSectionBase<ELFT>::MipsReginfo;
 }

 template class elf::InputSectionBase<ELF32LE>;
 template class elf::InputSectionBase<ELF32BE>;
 template class elf::InputSectionBase<ELF64LE>;
 template class elf::InputSectionBase<ELF64BE>;

 template class elf::InputSection<ELF32LE>;
 template class elf::InputSection<ELF32BE>;
 template class elf::InputSection<ELF64LE>;
 template class elf::InputSection<ELF64BE>;

 template class elf::EHInputSection<ELF32LE>;
 template class elf::EHInputSection<ELF32BE>;
 template class elf::EHInputSection<ELF64LE>;
 template class elf::EHInputSection<ELF64BE>;

 template class elf::MergeInputSection<ELF32LE>;
 template class elf::MergeInputSection<ELF32BE>;
 template class elf::MergeInputSection<ELF64LE>;
 template class elf::MergeInputSection<ELF64BE>;

 template class elf::MipsReginfoInputSection<ELF32LE>;
 template class elf::MipsReginfoInputSection<ELF32BE>;
 template class elf::MipsReginfoInputSection<ELF64LE>;
 template class elf::MipsReginfoInputSection<ELF64BE>;
	//===- InputSection.cpp ---------------------------------------------------===//
	//
	// The LLVM Linker
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//

	#include "InputSection.h"
	#include "Config.h"
	#include "Error.h"
	#include "InputFiles.h"
	#include "OutputSections.h"
	#include "Target.h"

	#include "llvm/Support/Endian.h"

	using namespace llvm;
	using namespace llvm::ELF;
	using namespace llvm::object;
	using namespace llvm::support::endian;

	using namespace lld;
	using namespace lld::elf;

	template <class ELFT>
	InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File,
	const Elf_Shdr *Header,
	Kind SectionKind)
	: Header(Header), File(File), SectionKind(SectionKind), Repl(this) {
	// The garbage collector sets sections' Live bits.
	// If GC is disabled, all sections are considered live by default.
	Live = !Config->GcSections;

	// The ELF spec states that a value of 0 means the section has
	// no alignment constraits.
	Align = std::max<uintX_t>(Header->sh_addralign, 1);
	}

	template <class ELFT> size_t InputSectionBase<ELFT>::getSize() const {
	if (auto *D = dyn_cast<InputSection<ELFT>>(this))
	if (D->getThunksSize() > 0)
	return D->getThunkOff() + D->getThunksSize();
	return Header->sh_size;
	}

	template <class ELFT> StringRef InputSectionBase<ELFT>::getSectionName() const {
	return check(File->getObj().getSectionName(this->Header));
	}

	template <class ELFT>
	ArrayRef<uint8_t> InputSectionBase<ELFT>::getSectionData() const {
	return check(this->File->getObj().getSectionContents(this->Header));
	}

	template <class ELFT>
	typename ELFT::uint InputSectionBase<ELFT>::getOffset(uintX_t Offset) {
	switch (SectionKind) {
	case Regular:
	return cast<InputSection<ELFT>>(this)->OutSecOff + Offset;
	case EHFrame:
	return cast<EHInputSection<ELFT>>(this)->getOffset(Offset);
	case Merge:
	return cast<MergeInputSection<ELFT>>(this)->getOffset(Offset);
	case MipsReginfo:
	// MIPS .reginfo sections are consumed by the linker,
	// so it should never be copied to output.
	llvm_unreachable("MIPS .reginfo reached writeTo().");
	}
	llvm_unreachable("invalid section kind");
	}

	template <class ELFT>
	typename ELFT::uint InputSectionBase<ELFT>::getOffset(const Elf_Sym &Sym) {
	return getOffset(Sym.st_value);
	}

	// Returns a section that Rel relocation is pointing to.
	template <class ELFT>
	InputSectionBase<ELFT> *
	InputSectionBase<ELFT>::getRelocTarget(const Elf_Rel &Rel) const {
	// Global symbol
	uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
	SymbolBody &B = File->getSymbolBody(SymIndex).repl();
	if (auto *D = dyn_cast<DefinedRegular<ELFT>>(&B))
	if (D->Section)
	return D->Section->Repl;
	return nullptr;
	}

	template <class ELFT>
	InputSectionBase<ELFT> *
	InputSectionBase<ELFT>::getRelocTarget(const Elf_Rela &Rel) const {
	return getRelocTarget(reinterpret_cast<const Elf_Rel &>(Rel));
	}

	template <class ELFT>
	InputSection<ELFT>::InputSection(elf::ObjectFile<ELFT> *F,
	const Elf_Shdr *Header)
	: InputSectionBase<ELFT>(F, Header, Base::Regular) {}

	template <class ELFT>
	bool InputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
	return S->SectionKind == Base::Regular;
	}

	template <class ELFT>
	InputSectionBase<ELFT> *InputSection<ELFT>::getRelocatedSection() {
	assert(this->Header->sh_type == SHT_RELA \|\| this->Header->sh_type == SHT_REL);
	ArrayRef<InputSectionBase<ELFT> *> Sections = this->File->getSections();
	return Sections[this->Header->sh_info];
	}

	template <class ELFT> void InputSection<ELFT>::addThunk(SymbolBody &Body) {
	Body.ThunkIndex = Thunks.size();
	Thunks.push_back(&Body);
	}

	template <class ELFT> uint64_t InputSection<ELFT>::getThunkOff() const {
	return this->Header->sh_size;
	}

	template <class ELFT> uint64_t InputSection<ELFT>::getThunksSize() const {
	return Thunks.size() * Target->ThunkSize;
	}

	// This is used for -r. We can't use memcpy to copy relocations because we need
	// to update symbol table offset and section index for each relocation. So we
	// copy relocations one by one.
	template <class ELFT>
	template <class RelTy>
	void InputSection<ELFT>::copyRelocations(uint8_t *Buf,
	iterator_range<const RelTy *> Rels) {
	InputSectionBase<ELFT> *RelocatedSection = getRelocatedSection();

	for (const RelTy &Rel : Rels) {
	uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
	uint32_t Type = Rel.getType(Config->Mips64EL);
	SymbolBody &Body = this->File->getSymbolBody(SymIndex).repl();

	RelTy P = reinterpret_cast<RelTy >(Buf);
	Buf += sizeof(RelTy);

	P->r_offset = RelocatedSection->getOffset(Rel.r_offset);
	P->setSymbolAndType(Body.DynsymIndex, Type, Config->Mips64EL);
	}
	}

	template <class RelTy>
	static uint32_t getMipsPairType(const RelTy *Rel, const SymbolBody &Sym) {
	switch (Rel->getType(Config->Mips64EL)) {
	case R_MIPS_HI16:
	return R_MIPS_LO16;
	case R_MIPS_GOT16:
	return Sym.isLocal() ? R_MIPS_LO16 : R_MIPS_NONE;
	case R_MIPS_PCHI16:
	return R_MIPS_PCLO16;
	case R_MICROMIPS_HI16:
	return R_MICROMIPS_LO16;
	default:
	return R_MIPS_NONE;
	}
	}

	template <endianness E> static int16_t readSignedLo16(uint8_t *Loc) {
	return read32<E>(Loc) & 0xffff;
	}

	template <class ELFT>
	template <class RelTy>
	int32_t
	InputSectionBase<ELFT>::findMipsPairedAddend(uint8_t Buf, uint8_t BufLoc,
	SymbolBody &Sym, const RelTy *Rel,
	const RelTy *End) {
	uint32_t SymIndex = Rel->getSymbol(Config->Mips64EL);
	uint32_t Type = getMipsPairType(Rel, Sym);

	// Some MIPS relocations use addend calculated from addend of the relocation
	// itself and addend of paired relocation. ABI requires to compute such
	// combined addend in case of REL relocation record format only.
	// See p. 4-17 at ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
	if (RelTy::IsRela \|\| Type == R_MIPS_NONE)
	return 0;

	for (const RelTy *RI = Rel; RI != End; ++RI) {
	if (RI->getType(Config->Mips64EL) != Type)
	continue;
	if (RI->getSymbol(Config->Mips64EL) != SymIndex)
	continue;
	uintX_t Offset = getOffset(RI->r_offset);
	if (Offset == (uintX_t)-1)
	break;
	const endianness E = ELFT::TargetEndianness;
	return ((read32<E>(BufLoc) & 0xffff) << 16) +
	readSignedLo16<E>(Buf + Offset);
	}
	unsigned OldType = Rel->getType(Config->Mips64EL);
	StringRef OldName = getELFRelocationTypeName(Config->EMachine, OldType);
	StringRef NewName = getELFRelocationTypeName(Config->EMachine, Type);
	warning("can't find matching " + NewName + " relocation for " + OldName);
	return 0;
	}

	template <class ELFT, class uintX_t>
	static uintX_t adjustMipsSymVA(uint32_t Type, const elf::ObjectFile<ELFT> &File,
	const SymbolBody &Body, uintX_t AddrLoc,
	uintX_t SymVA) {
	if (Type == R_MIPS_HI16 && &Body == Config->MipsGpDisp)
	return getMipsGpAddr<ELFT>() - AddrLoc;
	if (Type == R_MIPS_LO16 && &Body == Config->MipsGpDisp)
	return getMipsGpAddr<ELFT>() - AddrLoc + 4;
	if (&Body == Config->MipsLocalGp)
	return getMipsGpAddr<ELFT>();
	if (Body.isLocal() && (Type == R_MIPS_GPREL16 \|\| Type == R_MIPS_GPREL32))
	// We need to adjust SymVA value in case of R_MIPS_GPREL16/32
	// relocations because they use the following expression to calculate
	// the relocation's result for local symbol: S + A + GP0 - G.
	return SymVA + File.getMipsGp0();
	return SymVA;
	}

	template <class ELFT, class uintX_t>
	static uintX_t getMipsGotVA(const SymbolBody &Body, uintX_t SymVA,
	uint8_t *BufLoc) {
	if (Body.isLocal())
	// If relocation against MIPS local symbol requires GOT entry, this entry
	// should be initialized by 'page address'. This address is high 16-bits
	// of sum the symbol's value and the addend.
	return Out<ELFT>::Got->getMipsLocalPageAddr(SymVA);
	if (!Body.isPreemptible())
	// For non-local symbols GOT entries should contain their full
	// addresses. But if such symbol cannot be preempted, we do not
	// have to put them into the "global" part of GOT and use dynamic
	// linker to determine their actual addresses. That is why we
	// create GOT entries for them in the "local" part of GOT.
	return Out<ELFT>::Got->getMipsLocalFullAddr(Body);
	return Body.getGotVA<ELFT>();
	}

	template <class ELFT>
	template <class RelTy>
	void InputSectionBase<ELFT>::relocate(uint8_t Buf, uint8_t BufEnd,
	iterator_range<const RelTy *> Rels) {
	size_t Num = Rels.end() - Rels.begin();
	for (size_t I = 0; I < Num; ++I) {
	const RelTy &RI = *(Rels.begin() + I);
	uintX_t Offset = getOffset(RI.r_offset);
	if (Offset == (uintX_t)-1)
	continue;

	uintX_t A = getAddend<ELFT>(RI);
	uint32_t SymIndex = RI.getSymbol(Config->Mips64EL);
	uint32_t Type = RI.getType(Config->Mips64EL);
	uint8_t *BufLoc = Buf + Offset;
	uintX_t AddrLoc = OutSec->getVA() + Offset;

	if (Target->pointsToLocalDynamicGotEntry(Type) &&
	!Target->canRelaxTls(Type, nullptr)) {
	Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
	Out<ELFT>::Got->getTlsIndexVA() + A);
	continue;
	}

	SymbolBody &Body = File->getSymbolBody(SymIndex).repl();

	if (Target->canRelaxTls(Type, &Body)) {
	uintX_t SymVA;
	if (Target->needsGot(Type, Body))
	SymVA = Body.getGotVA<ELFT>();
	else
	SymVA = Body.getVA<ELFT>();
	// By optimizing TLS relocations, it is sometimes needed to skip
	// relocations that immediately follow TLS relocations. This function
	// knows how many slots we need to skip.
	I += Target->relaxTls(BufLoc, BufEnd, Type, AddrLoc, SymVA, Body);
	continue;
	}

	// PPC64 has a special relocation representing the TOC base pointer
	// that does not have a corresponding symbol.
	if (Config->EMachine == EM_PPC64 && RI.getType(false) == R_PPC64_TOC) {
	uintX_t SymVA = getPPC64TocBase() + A;
	Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA);
	continue;
	}

	if (Target->isTlsGlobalDynamicRel(Type) &&
	!Target->canRelaxTls(Type, &Body)) {
	Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc,
	Out<ELFT>::Got->getGlobalDynAddr(Body) + A);
	continue;
	}

	if (!RelTy::IsRela)
	A += Target->getImplicitAddend(BufLoc, Type);
	if (Config->EMachine == EM_MIPS)
	A += findMipsPairedAddend(Buf, BufLoc, Body, &RI, Rels.end());
	uintX_t SymVA = Body.getVA<ELFT>(A);

	if (Target->needsPlt(Type, Body)) {
	SymVA = Body.getPltVA<ELFT>() + A;
	} else if (Target->needsGot(Type, Body)) {
	if (Config->EMachine == EM_MIPS)
	SymVA = getMipsGotVA<ELFT>(Body, SymVA, BufLoc);
	else
	SymVA = Body.getGotVA<ELFT>() + A;
	if (Body.IsTls)
	Type = Target->getTlsGotRel(Type);
	} else if (Target->isSizeRel(Type) && Body.isPreemptible()) {
	// A SIZE relocation is supposed to set a symbol size, but if a symbol
	// can be preempted, the size at runtime may be different than link time.
	// If that's the case, we leave the field alone rather than filling it
	// with a possibly incorrect value.
	continue;
	} else if (Target->needsThunk(Type, *this->getFile(), Body)) {
	// Get address of a thunk code related to the symbol.
	SymVA = Body.getThunkVA<ELFT>();
	} else if (Config->EMachine == EM_MIPS) {
	SymVA = adjustMipsSymVA<ELFT>(Type, *File, Body, AddrLoc, SymVA);
	} else if (!Target->needsCopyRel<ELFT>(Type, Body) &&
	Body.isPreemptible()) {
	continue;
	}
	if (Target->isSizeRel(Type))
	SymVA = Body.getSize<ELFT>() + A;

	Target->relocateOne(BufLoc, BufEnd, Type, AddrLoc, SymVA);
	}
	}

	template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) {
	if (this->Header->sh_type == SHT_NOBITS)
	return;
	ELFFile<ELFT> &EObj = this->File->getObj();

	// If -r is given, then an InputSection may be a relocation section.
	if (this->Header->sh_type == SHT_RELA) {
	copyRelocations(Buf + OutSecOff, EObj.relas(this->Header));
	return;
	}
	if (this->Header->sh_type == SHT_REL) {
	copyRelocations(Buf + OutSecOff, EObj.rels(this->Header));
	return;
	}

	// Copy section contents from source object file to output file.
	ArrayRef<uint8_t> Data = this->getSectionData();
	memcpy(Buf + OutSecOff, Data.data(), Data.size());

	// Iterate over all relocation sections that apply to this section.
	uint8_t *BufEnd = Buf + OutSecOff + Data.size();
	for (const Elf_Shdr *RelSec : this->RelocSections) {
	if (RelSec->sh_type == SHT_RELA)
	this->relocate(Buf, BufEnd, EObj.relas(RelSec));
	else
	this->relocate(Buf, BufEnd, EObj.rels(RelSec));
	}

	// The section might have a data/code generated by the linker and need
	// to be written after the section. Usually these are thunks - small piece
	// of code used to jump between "incompatible" functions like PIC and non-PIC
	// or if the jump target too far and its address does not fit to the short
	// jump istruction.
	if (!Thunks.empty()) {
	Buf += OutSecOff + getThunkOff();
	for (const SymbolBody *S : Thunks) {
	Target->writeThunk(Buf, S->getVA<ELFT>());
	Buf += Target->ThunkSize;
	}
	}
	}

	template <class ELFT>
	void InputSection<ELFT>::replace(InputSection<ELFT> *Other) {
	this->Align = std::max(this->Align, Other->Align);
	Other->Repl = this->Repl;
	Other->Live = false;
	}

	template <class ELFT>
	SplitInputSection<ELFT>::SplitInputSection(
	elf::ObjectFile<ELFT> File, const Elf_Shdr Header,
	typename InputSectionBase<ELFT>::Kind SectionKind)
	: InputSectionBase<ELFT>(File, Header, SectionKind) {}

	template <class ELFT>
	EHInputSection<ELFT>::EHInputSection(elf::ObjectFile<ELFT> *F,
	const Elf_Shdr *Header)
	: SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::EHFrame) {
	// Mark .eh_frame sections as live by default because there are
	// usually no relocations that point to .eh_frames. Otherwise,
	// the garbage collector would drop all .eh_frame sections.
	this->Live = true;
	}

	template <class ELFT>
	bool EHInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
	return S->SectionKind == InputSectionBase<ELFT>::EHFrame;
	}

	template <class ELFT>
	typename ELFT::uint EHInputSection<ELFT>::getOffset(uintX_t Offset) {
	// The file crtbeginT.o has relocations pointing to the start of an empty
	// .eh_frame that is known to be the first in the link. It does that to
	// identify the start of the output .eh_frame. Handle this special case.
	if (this->getSectionHdr()->sh_size == 0)
	return Offset;
	std::pair<uintX_t, uintX_t> *I = this->getRangeAndSize(Offset).first;
	uintX_t Base = I->second;
	if (Base == uintX_t(-1))
	return -1; // Not in the output

	uintX_t Addend = Offset - I->first;
	return Base + Addend;
	}

	template <class ELFT>
	MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F,
	const Elf_Shdr *Header)
	: SplitInputSection<ELFT>(F, Header, InputSectionBase<ELFT>::Merge) {}

	template <class ELFT>
	bool MergeInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
	return S->SectionKind == InputSectionBase<ELFT>::Merge;
	}

	template <class ELFT>
	std::pair<std::pair<typename ELFT::uint, typename ELFT::uint> *,
	typename ELFT::uint>
	SplitInputSection<ELFT>::getRangeAndSize(uintX_t Offset) {
	ArrayRef<uint8_t> D = this->getSectionData();
	StringRef Data((const char *)D.data(), D.size());
	uintX_t Size = Data.size();
	if (Offset >= Size)
	fatal("entry is past the end of the section");

	// Find the element this offset points to.
	auto I = std::upper_bound(
	Offsets.begin(), Offsets.end(), Offset,
	[](const uintX_t &A, const std::pair<uintX_t, uintX_t> &B) {
	return A < B.first;
	});
	uintX_t End = I == Offsets.end() ? Data.size() : I->first;
	--I;
	return std::make_pair(&*I, End);
	}

	template <class ELFT>
	typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) {
	std::pair<std::pair<uintX_t, uintX_t> *, uintX_t> T =
	this->getRangeAndSize(Offset);
	std::pair<uintX_t, uintX_t> *I = T.first;
	uintX_t End = T.second;
	uintX_t Start = I->first;

	// Compute the Addend and if the Base is cached, return.
	uintX_t Addend = Offset - Start;
	uintX_t &Base = I->second;
	if (Base != uintX_t(-1))
	return Base + Addend;

	// Map the base to the offset in the output section and cache it.
	ArrayRef<uint8_t> D = this->getSectionData();
	StringRef Data((const char *)D.data(), D.size());
	StringRef Entry = Data.substr(Start, End - Start);
	Base =
	static_cast<MergeOutputSection<ELFT> *>(this->OutSec)->getOffset(Entry);
	return Base + Addend;
	}

	template <class ELFT>
	MipsReginfoInputSection<ELFT>::MipsReginfoInputSection(elf::ObjectFile<ELFT> *F,
	const Elf_Shdr *Hdr)
	: InputSectionBase<ELFT>(F, Hdr, InputSectionBase<ELFT>::MipsReginfo) {
	// Initialize this->Reginfo.
	ArrayRef<uint8_t> D = this->getSectionData();
	if (D.size() != sizeof(Elf_Mips_RegInfo<ELFT>))
	fatal("invalid size of .reginfo section");
	Reginfo = reinterpret_cast<const Elf_Mips_RegInfo<ELFT> *>(D.data());
	}

	template <class ELFT>
	bool MipsReginfoInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
	return S->SectionKind == InputSectionBase<ELFT>::MipsReginfo;
	}

	template class elf::InputSectionBase<ELF32LE>;
	template class elf::InputSectionBase<ELF32BE>;
	template class elf::InputSectionBase<ELF64LE>;
	template class elf::InputSectionBase<ELF64BE>;

	template class elf::InputSection<ELF32LE>;
	template class elf::InputSection<ELF32BE>;
	template class elf::InputSection<ELF64LE>;
	template class elf::InputSection<ELF64BE>;

	template class elf::EHInputSection<ELF32LE>;
	template class elf::EHInputSection<ELF32BE>;
	template class elf::EHInputSection<ELF64LE>;
	template class elf::EHInputSection<ELF64BE>;

	template class elf::MergeInputSection<ELF32LE>;
	template class elf::MergeInputSection<ELF32BE>;
	template class elf::MergeInputSection<ELF64LE>;
	template class elf::MergeInputSection<ELF64BE>;

	template class elf::MipsReginfoInputSection<ELF32LE>;
	template class elf::MipsReginfoInputSection<ELF32BE>;
	template class elf::MipsReginfoInputSection<ELF64LE>;
	template class elf::MipsReginfoInputSection<ELF64BE>;