| //===- 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 "EhFrame.h" |
| #include "Error.h" |
| #include "InputFiles.h" |
| #include "LinkerScript.h" |
| #include "Memory.h" |
| #include "OutputSections.h" |
| #include "Relocations.h" |
| #include "SyntheticSections.h" |
| #include "Target.h" |
| #include "Thunks.h" |
| #include "llvm/Object/Decompressor.h" |
| #include "llvm/Support/Compression.h" |
| #include "llvm/Support/Endian.h" |
| #include <mutex> |
| |
| using namespace llvm; |
| using namespace llvm::ELF; |
| using namespace llvm::object; |
| using namespace llvm::support; |
| using namespace llvm::support::endian; |
| |
| using namespace lld; |
| using namespace lld::elf; |
| |
| // Returns a string to construct an error message. |
| template <class ELFT> |
| std::string lld::toString(const InputSectionBase<ELFT> *Sec) { |
| // File can be absent if section is synthetic. |
| std::string FileName = |
| Sec->getFile() ? Sec->getFile()->getName() : "<internal>"; |
| return (FileName + ":(" + Sec->Name + ")").str(); |
| } |
| |
| template <class ELFT> |
| static ArrayRef<uint8_t> getSectionContents(elf::ObjectFile<ELFT> *File, |
| const typename ELFT::Shdr *Hdr) { |
| if (!File || Hdr->sh_type == SHT_NOBITS) |
| return makeArrayRef<uint8_t>(nullptr, Hdr->sh_size); |
| return check(File->getObj().getSectionContents(Hdr)); |
| } |
| |
| template <class ELFT> |
| InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File, |
| uintX_t Flags, uint32_t Type, |
| uintX_t Entsize, uint32_t Link, |
| uint32_t Info, uintX_t Addralign, |
| ArrayRef<uint8_t> Data, StringRef Name, |
| Kind SectionKind) |
| : InputSectionData(SectionKind, Name, Data, |
| !Config->GcSections || !(Flags & SHF_ALLOC)), |
| File(File), Flags(Flags), Entsize(Entsize), Type(Type), Link(Link), |
| Info(Info), Repl(this) { |
| NumRelocations = 0; |
| AreRelocsRela = false; |
| |
| // The ELF spec states that a value of 0 means the section has |
| // no alignment constraits. |
| uint64_t V = std::max<uint64_t>(Addralign, 1); |
| if (!isPowerOf2_64(V)) |
| fatal(toString(File) + ": section sh_addralign is not a power of 2"); |
| |
| // We reject object files having insanely large alignments even though |
| // they are allowed by the spec. I think 4GB is a reasonable limitation. |
| // We might want to relax this in the future. |
| if (V > UINT32_MAX) |
| fatal(toString(File) + ": section sh_addralign is too large"); |
| Alignment = V; |
| |
| // If it is not a mergeable section, overwrite the flag so that the flag |
| // is consistent with the class. This inconsistency could occur when |
| // string merging is disabled using -O0 flag. |
| if (!Config->Relocatable && !isa<MergeInputSection<ELFT>>(this)) |
| this->Flags &= ~(SHF_MERGE | SHF_STRINGS); |
| } |
| |
| // GNU assembler 2.24 and LLVM 4.0.0's MC (the newest release as of |
| // March 2017) fail to infer section types for sections starting with |
| // ".init_array." or ".fini_array.". They set SHT_PROGBITS instead of |
| // SHF_INIT_ARRAY. As a result, the following assembler directive |
| // creates ".init_array.100" with SHT_PROGBITS, for example. |
| // |
| // .section .init_array.100, "aw" |
| // |
| // This function forces SHT_{INIT,FINI}_ARRAY so that we can handle |
| // incorrect inputs as if they were correct from the beginning. |
| static uint64_t getType(uint64_t Type, StringRef Name) { |
| if (Type == SHT_PROGBITS && Name.startswith(".init_array.")) |
| return SHT_INIT_ARRAY; |
| if (Type == SHT_PROGBITS && Name.startswith(".fini_array.")) |
| return SHT_FINI_ARRAY; |
| return Type; |
| } |
| |
| template <class ELFT> |
| InputSectionBase<ELFT>::InputSectionBase(elf::ObjectFile<ELFT> *File, |
| const Elf_Shdr *Hdr, StringRef Name, |
| Kind SectionKind) |
| : InputSectionBase(File, Hdr->sh_flags & ~SHF_INFO_LINK, |
| getType(Hdr->sh_type, Name), Hdr->sh_entsize, |
| Hdr->sh_link, Hdr->sh_info, Hdr->sh_addralign, |
| getSectionContents(File, Hdr), Name, SectionKind) { |
| this->Offset = Hdr->sh_offset; |
| } |
| |
| template <class ELFT> size_t InputSectionBase<ELFT>::getSize() const { |
| if (auto *S = dyn_cast<SyntheticSection<ELFT>>(this)) |
| return S->getSize(); |
| |
| if (auto *D = dyn_cast<InputSection<ELFT>>(this)) |
| if (D->getThunksSize() > 0) |
| return D->getThunkOff() + D->getThunksSize(); |
| |
| return Data.size(); |
| } |
| |
| template <class ELFT> |
| typename ELFT::uint InputSectionBase<ELFT>::getOffset(uintX_t Offset) const { |
| switch (kind()) { |
| case Regular: |
| return cast<InputSection<ELFT>>(this)->OutSecOff + Offset; |
| case Synthetic: |
| // For synthetic sections we treat offset -1 as the end of the section. |
| // The same approach is used for synthetic symbols (DefinedSynthetic). |
| return cast<InputSection<ELFT>>(this)->OutSecOff + |
| (Offset == uintX_t(-1) ? getSize() : Offset); |
| case EHFrame: |
| // 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. |
| return Offset; |
| case Merge: |
| return cast<MergeInputSection<ELFT>>(this)->getOffset(Offset); |
| } |
| llvm_unreachable("invalid section kind"); |
| } |
| |
| // Uncompress section contents. Note that this function is called |
| // from parallel_for_each, so it must be thread-safe. |
| template <class ELFT> void InputSectionBase<ELFT>::uncompress() { |
| Decompressor Decompressor = check(Decompressor::create( |
| Name, toStringRef(Data), ELFT::TargetEndianness == llvm::support::little, |
| ELFT::Is64Bits)); |
| |
| size_t Size = Decompressor.getDecompressedSize(); |
| char *OutputBuf; |
| { |
| static std::mutex Mu; |
| std::lock_guard<std::mutex> Lock(Mu); |
| OutputBuf = BAlloc.Allocate<char>(Size); |
| } |
| |
| if (Error E = Decompressor.decompress({OutputBuf, Size})) |
| fatal(E, toString(this)); |
| Data = ArrayRef<uint8_t>((uint8_t *)OutputBuf, Size); |
| } |
| |
| template <class ELFT> |
| typename ELFT::uint |
| InputSectionBase<ELFT>::getOffset(const DefinedRegular<ELFT> &Sym) const { |
| return getOffset(Sym.Value); |
| } |
| |
| template <class ELFT> |
| InputSectionBase<ELFT> *InputSectionBase<ELFT>::getLinkOrderDep() const { |
| if ((Flags & SHF_LINK_ORDER) && Link != 0) |
| return getFile()->getSections()[Link]; |
| return nullptr; |
| } |
| |
| // Returns a source location string. Used to construct an error message. |
| template <class ELFT> |
| std::string InputSectionBase<ELFT>::getLocation(typename ELFT::uint Offset) { |
| // First check if we can get desired values from debugging information. |
| std::string LineInfo = File->getLineInfo(this, Offset); |
| if (!LineInfo.empty()) |
| return LineInfo; |
| |
| // File->SourceFile contains STT_FILE symbol that contains a |
| // source file name. If it's missing, we use an object file name. |
| std::string SrcFile = File->SourceFile; |
| if (SrcFile.empty()) |
| SrcFile = toString(File); |
| |
| // Find a function symbol that encloses a given location. |
| for (SymbolBody *B : File->getSymbols()) |
| if (auto *D = dyn_cast<DefinedRegular<ELFT>>(B)) |
| if (D->Section == this && D->Type == STT_FUNC) |
| if (D->Value <= Offset && Offset < D->Value + D->Size) |
| return SrcFile + ":(function " + toString(*D) + ")"; |
| |
| // If there's no symbol, print out the offset in the section. |
| return (SrcFile + ":(" + Name + "+0x" + utohexstr(Offset) + ")").str(); |
| } |
| |
| template <class ELFT> |
| InputSection<ELFT>::InputSection() : InputSectionBase<ELFT>() {} |
| |
| template <class ELFT> |
| InputSection<ELFT>::InputSection(uintX_t Flags, uint32_t Type, |
| uintX_t Addralign, ArrayRef<uint8_t> Data, |
| StringRef Name, Kind K) |
| : InputSectionBase<ELFT>(nullptr, Flags, Type, |
| /*Entsize*/ 0, /*Link*/ 0, /*Info*/ 0, Addralign, |
| Data, Name, K) {} |
| |
| template <class ELFT> |
| InputSection<ELFT>::InputSection(elf::ObjectFile<ELFT> *F, |
| const Elf_Shdr *Header, StringRef Name) |
| : InputSectionBase<ELFT>(F, Header, Name, Base::Regular) {} |
| |
| template <class ELFT> |
| bool InputSection<ELFT>::classof(const InputSectionData *S) { |
| return S->kind() == Base::Regular || S->kind() == Base::Synthetic; |
| } |
| |
| template <class ELFT> |
| InputSectionBase<ELFT> *InputSection<ELFT>::getRelocatedSection() { |
| assert(this->Type == SHT_RELA || this->Type == SHT_REL); |
| ArrayRef<InputSectionBase<ELFT> *> Sections = this->File->getSections(); |
| return Sections[this->Info]; |
| } |
| |
| template <class ELFT> void InputSection<ELFT>::addThunk(const Thunk<ELFT> *T) { |
| Thunks.push_back(T); |
| } |
| |
| template <class ELFT> uint64_t InputSection<ELFT>::getThunkOff() const { |
| return this->Data.size(); |
| } |
| |
| template <class ELFT> uint64_t InputSection<ELFT>::getThunksSize() const { |
| uint64_t Total = 0; |
| for (const Thunk<ELFT> *T : Thunks) |
| Total += T->size(); |
| return Total; |
| } |
| |
| // 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, ArrayRef<RelTy> Rels) { |
| InputSectionBase<ELFT> *RelocatedSection = getRelocatedSection(); |
| |
| for (const RelTy &Rel : Rels) { |
| uint32_t Type = Rel.getType(Config->Mips64EL); |
| SymbolBody &Body = this->File->getRelocTargetSym(Rel); |
| |
| Elf_Rela *P = reinterpret_cast<Elf_Rela *>(Buf); |
| Buf += sizeof(RelTy); |
| |
| if (Config->Rela) |
| P->r_addend = getAddend<ELFT>(Rel); |
| P->r_offset = RelocatedSection->getOffset(Rel.r_offset); |
| P->setSymbolAndType(In<ELFT>::SymTab->getSymbolIndex(&Body), Type, |
| Config->Mips64EL); |
| } |
| } |
| |
| static uint32_t getARMUndefinedRelativeWeakVA(uint32_t Type, uint32_t A, |
| uint32_t P) { |
| switch (Type) { |
| case R_ARM_THM_JUMP11: |
| return P + 2; |
| case R_ARM_CALL: |
| case R_ARM_JUMP24: |
| case R_ARM_PC24: |
| case R_ARM_PLT32: |
| case R_ARM_PREL31: |
| case R_ARM_THM_JUMP19: |
| case R_ARM_THM_JUMP24: |
| return P + 4; |
| case R_ARM_THM_CALL: |
| // We don't want an interworking BLX to ARM |
| return P + 5; |
| default: |
| return A; |
| } |
| } |
| |
| static uint64_t getAArch64UndefinedRelativeWeakVA(uint64_t Type, uint64_t A, |
| uint64_t P) { |
| switch (Type) { |
| case R_AARCH64_CALL26: |
| case R_AARCH64_CONDBR19: |
| case R_AARCH64_JUMP26: |
| case R_AARCH64_TSTBR14: |
| return P + 4; |
| default: |
| return A; |
| } |
| } |
| |
| template <class ELFT> |
| static typename ELFT::uint |
| getRelocTargetVA(uint32_t Type, typename ELFT::uint A, typename ELFT::uint P, |
| const SymbolBody &Body, RelExpr Expr) { |
| switch (Expr) { |
| case R_HINT: |
| case R_TLSDESC_CALL: |
| llvm_unreachable("cannot relocate hint relocs"); |
| case R_TLSLD: |
| return In<ELFT>::Got->getTlsIndexOff() + A - In<ELFT>::Got->getSize(); |
| case R_TLSLD_PC: |
| return In<ELFT>::Got->getTlsIndexVA() + A - P; |
| case R_THUNK_ABS: |
| return Body.getThunkVA<ELFT>() + A; |
| case R_THUNK_PC: |
| case R_THUNK_PLT_PC: |
| return Body.getThunkVA<ELFT>() + A - P; |
| case R_PPC_TOC: |
| return getPPC64TocBase() + A; |
| case R_TLSGD: |
| return In<ELFT>::Got->getGlobalDynOffset(Body) + A - |
| In<ELFT>::Got->getSize(); |
| case R_TLSGD_PC: |
| return In<ELFT>::Got->getGlobalDynAddr(Body) + A - P; |
| case R_TLSDESC: |
| return In<ELFT>::Got->getGlobalDynAddr(Body) + A; |
| case R_TLSDESC_PAGE: |
| return getAArch64Page(In<ELFT>::Got->getGlobalDynAddr(Body) + A) - |
| getAArch64Page(P); |
| case R_PLT: |
| return Body.getPltVA<ELFT>() + A; |
| case R_PLT_PC: |
| case R_PPC_PLT_OPD: |
| return Body.getPltVA<ELFT>() + A - P; |
| case R_SIZE: |
| return Body.getSize<ELFT>() + A; |
| case R_GOTREL: |
| return Body.getVA<ELFT>(A) - In<ELFT>::Got->getVA(); |
| case R_GOTREL_FROM_END: |
| return Body.getVA<ELFT>(A) - In<ELFT>::Got->getVA() - |
| In<ELFT>::Got->getSize(); |
| case R_RELAX_TLS_GD_TO_IE_END: |
| case R_GOT_FROM_END: |
| return Body.getGotOffset<ELFT>() + A - In<ELFT>::Got->getSize(); |
| case R_RELAX_TLS_GD_TO_IE_ABS: |
| case R_GOT: |
| return Body.getGotVA<ELFT>() + A; |
| case R_RELAX_TLS_GD_TO_IE_PAGE_PC: |
| case R_GOT_PAGE_PC: |
| return getAArch64Page(Body.getGotVA<ELFT>() + A) - getAArch64Page(P); |
| case R_RELAX_TLS_GD_TO_IE: |
| case R_GOT_PC: |
| return Body.getGotVA<ELFT>() + A - P; |
| case R_GOTONLY_PC: |
| return In<ELFT>::Got->getVA() + A - P; |
| case R_GOTONLY_PC_FROM_END: |
| return In<ELFT>::Got->getVA() + A - P + In<ELFT>::Got->getSize(); |
| case R_RELAX_TLS_LD_TO_LE: |
| case R_RELAX_TLS_IE_TO_LE: |
| case R_RELAX_TLS_GD_TO_LE: |
| case R_TLS: |
| // A weak undefined TLS symbol resolves to the base of the TLS |
| // block, i.e. gets a value of zero. If we pass --gc-sections to |
| // lld and .tbss is not referenced, it gets reclaimed and we don't |
| // create a TLS program header. Therefore, we resolve this |
| // statically to zero. |
| if (Body.isTls() && (Body.isLazy() || Body.isUndefined()) && |
| Body.symbol()->isWeak()) |
| return 0; |
| if (Target->TcbSize) |
| return Body.getVA<ELFT>(A) + |
| alignTo(Target->TcbSize, Out<ELFT>::TlsPhdr->p_align); |
| return Body.getVA<ELFT>(A) - Out<ELFT>::TlsPhdr->p_memsz; |
| case R_RELAX_TLS_GD_TO_LE_NEG: |
| case R_NEG_TLS: |
| return Out<ELF32LE>::TlsPhdr->p_memsz - Body.getVA<ELFT>(A); |
| case R_ABS: |
| case R_RELAX_GOT_PC_NOPIC: |
| return Body.getVA<ELFT>(A); |
| case R_GOT_OFF: |
| return Body.getGotOffset<ELFT>() + A; |
| case R_MIPS_GOT_LOCAL_PAGE: |
| // 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 In<ELFT>::MipsGot->getVA() + |
| In<ELFT>::MipsGot->getPageEntryOffset(Body, A) - |
| In<ELFT>::MipsGot->getGp(); |
| case R_MIPS_GOT_OFF: |
| case R_MIPS_GOT_OFF32: |
| // In case of MIPS if a GOT relocation has non-zero addend this addend |
| // should be applied to the GOT entry content not to the GOT entry offset. |
| // That is why we use separate expression type. |
| return In<ELFT>::MipsGot->getVA() + |
| In<ELFT>::MipsGot->getBodyEntryOffset(Body, A) - |
| In<ELFT>::MipsGot->getGp(); |
| case R_MIPS_GOTREL: |
| return Body.getVA<ELFT>(A) - In<ELFT>::MipsGot->getGp(); |
| case R_MIPS_TLSGD: |
| return In<ELFT>::MipsGot->getVA() + In<ELFT>::MipsGot->getTlsOffset() + |
| In<ELFT>::MipsGot->getGlobalDynOffset(Body) - |
| In<ELFT>::MipsGot->getGp(); |
| case R_MIPS_TLSLD: |
| return In<ELFT>::MipsGot->getVA() + In<ELFT>::MipsGot->getTlsOffset() + |
| In<ELFT>::MipsGot->getTlsIndexOff() - In<ELFT>::MipsGot->getGp(); |
| case R_PPC_OPD: { |
| uint64_t SymVA = Body.getVA<ELFT>(A); |
| // If we have an undefined weak symbol, we might get here with a symbol |
| // address of zero. That could overflow, but the code must be unreachable, |
| // so don't bother doing anything at all. |
| if (!SymVA) |
| return 0; |
| if (Out<ELF64BE>::Opd) { |
| // If this is a local call, and we currently have the address of a |
| // function-descriptor, get the underlying code address instead. |
| uint64_t OpdStart = Out<ELF64BE>::Opd->Addr; |
| uint64_t OpdEnd = OpdStart + Out<ELF64BE>::Opd->Size; |
| bool InOpd = OpdStart <= SymVA && SymVA < OpdEnd; |
| if (InOpd) |
| SymVA = read64be(&Out<ELF64BE>::OpdBuf[SymVA - OpdStart]); |
| } |
| return SymVA - P; |
| } |
| case R_PC: |
| if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak()) { |
| // On ARM and AArch64 a branch to an undefined weak resolves to the |
| // next instruction, otherwise the place. |
| if (Config->EMachine == EM_ARM) |
| return getARMUndefinedRelativeWeakVA(Type, A, P); |
| if (Config->EMachine == EM_AARCH64) |
| return getAArch64UndefinedRelativeWeakVA(Type, A, P); |
| } |
| case R_RELAX_GOT_PC: |
| return Body.getVA<ELFT>(A) - P; |
| case R_PLT_PAGE_PC: |
| case R_PAGE_PC: |
| if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak()) |
| return getAArch64Page(A); |
| return getAArch64Page(Body.getVA<ELFT>(A)) - getAArch64Page(P); |
| } |
| llvm_unreachable("Invalid expression"); |
| } |
| |
| // This function applies relocations to sections without SHF_ALLOC bit. |
| // Such sections are never mapped to memory at runtime. Debug sections are |
| // an example. Relocations in non-alloc sections are much easier to |
| // handle than in allocated sections because it will never need complex |
| // treatement such as GOT or PLT (because at runtime no one refers them). |
| // So, we handle relocations for non-alloc sections directly in this |
| // function as a performance optimization. |
| template <class ELFT> |
| template <class RelTy> |
| void InputSection<ELFT>::relocateNonAlloc(uint8_t *Buf, ArrayRef<RelTy> Rels) { |
| for (const RelTy &Rel : Rels) { |
| uint32_t Type = Rel.getType(Config->Mips64EL); |
| uintX_t Offset = this->getOffset(Rel.r_offset); |
| uint8_t *BufLoc = Buf + Offset; |
| uintX_t Addend = getAddend<ELFT>(Rel); |
| if (!RelTy::IsRela) |
| Addend += Target->getImplicitAddend(BufLoc, Type); |
| |
| SymbolBody &Sym = this->File->getRelocTargetSym(Rel); |
| if (Target->getRelExpr(Type, Sym) != R_ABS) { |
| error(this->getLocation(Offset) + ": has non-ABS reloc"); |
| return; |
| } |
| |
| uintX_t AddrLoc = this->OutSec->Addr + Offset; |
| uint64_t SymVA = 0; |
| if (!Sym.isTls() || Out<ELFT>::TlsPhdr) |
| SymVA = SignExtend64<sizeof(uintX_t) * 8>( |
| getRelocTargetVA<ELFT>(Type, Addend, AddrLoc, Sym, R_ABS)); |
| Target->relocateOne(BufLoc, Type, SymVA); |
| } |
| } |
| |
| template <class ELFT> |
| void InputSectionBase<ELFT>::relocate(uint8_t *Buf, uint8_t *BufEnd) { |
| // scanReloc function in Writer.cpp constructs Relocations |
| // vector only for SHF_ALLOC'ed sections. For other sections, |
| // we handle relocations directly here. |
| auto *IS = dyn_cast<InputSection<ELFT>>(this); |
| if (IS && !(IS->Flags & SHF_ALLOC)) { |
| if (IS->AreRelocsRela) |
| IS->relocateNonAlloc(Buf, IS->relas()); |
| else |
| IS->relocateNonAlloc(Buf, IS->rels()); |
| return; |
| } |
| |
| const unsigned Bits = sizeof(uintX_t) * 8; |
| for (const Relocation &Rel : Relocations) { |
| uintX_t Offset = getOffset(Rel.Offset); |
| uint8_t *BufLoc = Buf + Offset; |
| uint32_t Type = Rel.Type; |
| uintX_t A = Rel.Addend; |
| |
| uintX_t AddrLoc = OutSec->Addr + Offset; |
| RelExpr Expr = Rel.Expr; |
| uint64_t TargetVA = SignExtend64<Bits>( |
| getRelocTargetVA<ELFT>(Type, A, AddrLoc, *Rel.Sym, Expr)); |
| |
| switch (Expr) { |
| case R_RELAX_GOT_PC: |
| case R_RELAX_GOT_PC_NOPIC: |
| Target->relaxGot(BufLoc, TargetVA); |
| break; |
| case R_RELAX_TLS_IE_TO_LE: |
| Target->relaxTlsIeToLe(BufLoc, Type, TargetVA); |
| break; |
| case R_RELAX_TLS_LD_TO_LE: |
| Target->relaxTlsLdToLe(BufLoc, Type, TargetVA); |
| break; |
| case R_RELAX_TLS_GD_TO_LE: |
| case R_RELAX_TLS_GD_TO_LE_NEG: |
| Target->relaxTlsGdToLe(BufLoc, Type, TargetVA); |
| break; |
| case R_RELAX_TLS_GD_TO_IE: |
| case R_RELAX_TLS_GD_TO_IE_ABS: |
| case R_RELAX_TLS_GD_TO_IE_PAGE_PC: |
| case R_RELAX_TLS_GD_TO_IE_END: |
| Target->relaxTlsGdToIe(BufLoc, Type, TargetVA); |
| break; |
| case R_PPC_PLT_OPD: |
| // Patch a nop (0x60000000) to a ld. |
| if (BufLoc + 8 <= BufEnd && read32be(BufLoc + 4) == 0x60000000) |
| write32be(BufLoc + 4, 0xe8410028); // ld %r2, 40(%r1) |
| // fallthrough |
| default: |
| Target->relocateOne(BufLoc, Type, TargetVA); |
| break; |
| } |
| } |
| } |
| |
| template <class ELFT> void InputSection<ELFT>::writeTo(uint8_t *Buf) { |
| if (this->Type == SHT_NOBITS) |
| return; |
| |
| if (auto *S = dyn_cast<SyntheticSection<ELFT>>(this)) { |
| S->writeTo(Buf + OutSecOff); |
| return; |
| } |
| |
| // If -r is given, then an InputSection may be a relocation section. |
| if (this->Type == SHT_RELA) { |
| copyRelocations(Buf + OutSecOff, this->template getDataAs<Elf_Rela>()); |
| return; |
| } |
| if (this->Type == SHT_REL) { |
| copyRelocations(Buf + OutSecOff, this->template getDataAs<Elf_Rel>()); |
| return; |
| } |
| |
| // Copy section contents from source object file to output file. |
| ArrayRef<uint8_t> Data = this->Data; |
| memcpy(Buf + OutSecOff, Data.data(), Data.size()); |
| |
| // Iterate over all relocation sections that apply to this section. |
| uint8_t *BufEnd = Buf + OutSecOff + Data.size(); |
| this->relocate(Buf, BufEnd); |
| |
| // 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 Thunk<ELFT> *T : Thunks) { |
| T->writeTo(Buf); |
| Buf += T->size(); |
| } |
| } |
| } |
| |
| template <class ELFT> |
| void InputSection<ELFT>::replace(InputSection<ELFT> *Other) { |
| this->Alignment = std::max(this->Alignment, Other->Alignment); |
| Other->Repl = this->Repl; |
| Other->Live = false; |
| } |
| |
| template <class ELFT> |
| EhInputSection<ELFT>::EhInputSection(elf::ObjectFile<ELFT> *F, |
| const Elf_Shdr *Header, StringRef Name) |
| : InputSectionBase<ELFT>(F, Header, Name, 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 InputSectionData *S) { |
| return S->kind() == InputSectionBase<ELFT>::EHFrame; |
| } |
| |
| // Returns the index of the first relocation that points to a region between |
| // Begin and Begin+Size. |
| template <class IntTy, class RelTy> |
| static unsigned getReloc(IntTy Begin, IntTy Size, const ArrayRef<RelTy> &Rels, |
| unsigned &RelocI) { |
| // Start search from RelocI for fast access. That works because the |
| // relocations are sorted in .eh_frame. |
| for (unsigned N = Rels.size(); RelocI < N; ++RelocI) { |
| const RelTy &Rel = Rels[RelocI]; |
| if (Rel.r_offset < Begin) |
| continue; |
| |
| if (Rel.r_offset < Begin + Size) |
| return RelocI; |
| return -1; |
| } |
| return -1; |
| } |
| |
| // .eh_frame is a sequence of CIE or FDE records. |
| // This function splits an input section into records and returns them. |
| template <class ELFT> void EhInputSection<ELFT>::split() { |
| // Early exit if already split. |
| if (!this->Pieces.empty()) |
| return; |
| |
| if (this->NumRelocations) { |
| if (this->AreRelocsRela) |
| split(this->relas()); |
| else |
| split(this->rels()); |
| return; |
| } |
| split(makeArrayRef<typename ELFT::Rela>(nullptr, nullptr)); |
| } |
| |
| template <class ELFT> |
| template <class RelTy> |
| void EhInputSection<ELFT>::split(ArrayRef<RelTy> Rels) { |
| ArrayRef<uint8_t> Data = this->Data; |
| unsigned RelI = 0; |
| for (size_t Off = 0, End = Data.size(); Off != End;) { |
| size_t Size = readEhRecordSize<ELFT>(this, Off); |
| this->Pieces.emplace_back(Off, this, Size, getReloc(Off, Size, Rels, RelI)); |
| // The empty record is the end marker. |
| if (Size == 4) |
| break; |
| Off += Size; |
| } |
| } |
| |
| static size_t findNull(ArrayRef<uint8_t> A, size_t EntSize) { |
| // Optimize the common case. |
| StringRef S((const char *)A.data(), A.size()); |
| if (EntSize == 1) |
| return S.find(0); |
| |
| for (unsigned I = 0, N = S.size(); I != N; I += EntSize) { |
| const char *B = S.begin() + I; |
| if (std::all_of(B, B + EntSize, [](char C) { return C == 0; })) |
| return I; |
| } |
| return StringRef::npos; |
| } |
| |
| // Split SHF_STRINGS section. Such section is a sequence of |
| // null-terminated strings. |
| template <class ELFT> |
| void MergeInputSection<ELFT>::splitStrings(ArrayRef<uint8_t> Data, |
| size_t EntSize) { |
| size_t Off = 0; |
| bool IsAlloc = this->Flags & SHF_ALLOC; |
| while (!Data.empty()) { |
| size_t End = findNull(Data, EntSize); |
| if (End == StringRef::npos) |
| fatal(toString(this) + ": string is not null terminated"); |
| size_t Size = End + EntSize; |
| Pieces.emplace_back(Off, !IsAlloc); |
| Hashes.push_back(hash_value(toStringRef(Data.slice(0, Size)))); |
| Data = Data.slice(Size); |
| Off += Size; |
| } |
| } |
| |
| // Split non-SHF_STRINGS section. Such section is a sequence of |
| // fixed size records. |
| template <class ELFT> |
| void MergeInputSection<ELFT>::splitNonStrings(ArrayRef<uint8_t> Data, |
| size_t EntSize) { |
| size_t Size = Data.size(); |
| assert((Size % EntSize) == 0); |
| bool IsAlloc = this->Flags & SHF_ALLOC; |
| for (unsigned I = 0, N = Size; I != N; I += EntSize) { |
| Hashes.push_back(hash_value(toStringRef(Data.slice(I, EntSize)))); |
| Pieces.emplace_back(I, !IsAlloc); |
| } |
| } |
| |
| template <class ELFT> |
| MergeInputSection<ELFT>::MergeInputSection(elf::ObjectFile<ELFT> *F, |
| const Elf_Shdr *Header, |
| StringRef Name) |
| : InputSectionBase<ELFT>(F, Header, Name, InputSectionBase<ELFT>::Merge) {} |
| |
| // This function is called after we obtain a complete list of input sections |
| // that need to be linked. This is responsible to split section contents |
| // into small chunks for further processing. |
| // |
| // Note that this function is called from parallel_for_each. This must be |
| // thread-safe (i.e. no memory allocation from the pools). |
| template <class ELFT> void MergeInputSection<ELFT>::splitIntoPieces() { |
| ArrayRef<uint8_t> Data = this->Data; |
| uintX_t EntSize = this->Entsize; |
| if (this->Flags & SHF_STRINGS) |
| splitStrings(Data, EntSize); |
| else |
| splitNonStrings(Data, EntSize); |
| |
| if (Config->GcSections && (this->Flags & SHF_ALLOC)) |
| for (uintX_t Off : LiveOffsets) |
| this->getSectionPiece(Off)->Live = true; |
| } |
| |
| template <class ELFT> |
| bool MergeInputSection<ELFT>::classof(const InputSectionData *S) { |
| return S->kind() == InputSectionBase<ELFT>::Merge; |
| } |
| |
| // Do binary search to get a section piece at a given input offset. |
| template <class ELFT> |
| SectionPiece *MergeInputSection<ELFT>::getSectionPiece(uintX_t Offset) { |
| auto *This = static_cast<const MergeInputSection<ELFT> *>(this); |
| return const_cast<SectionPiece *>(This->getSectionPiece(Offset)); |
| } |
| |
| template <class It, class T, class Compare> |
| static It fastUpperBound(It First, It Last, const T &Value, Compare Comp) { |
| size_t Size = std::distance(First, Last); |
| assert(Size != 0); |
| while (Size != 1) { |
| size_t H = Size / 2; |
| const It MI = First + H; |
| Size -= H; |
| First = Comp(Value, *MI) ? First : First + H; |
| } |
| return Comp(Value, *First) ? First : First + 1; |
| } |
| |
| template <class ELFT> |
| const SectionPiece * |
| MergeInputSection<ELFT>::getSectionPiece(uintX_t Offset) const { |
| uintX_t Size = this->Data.size(); |
| if (Offset >= Size) |
| fatal(toString(this) + ": entry is past the end of the section"); |
| |
| // Find the element this offset points to. |
| auto I = fastUpperBound( |
| Pieces.begin(), Pieces.end(), Offset, |
| [](const uintX_t &A, const SectionPiece &B) { return A < B.InputOff; }); |
| --I; |
| return &*I; |
| } |
| |
| // Returns the offset in an output section for a given input offset. |
| // Because contents of a mergeable section is not contiguous in output, |
| // it is not just an addition to a base output offset. |
| template <class ELFT> |
| typename ELFT::uint MergeInputSection<ELFT>::getOffset(uintX_t Offset) const { |
| // Initialize OffsetMap lazily. |
| std::call_once(InitOffsetMap, [&] { |
| OffsetMap.reserve(Pieces.size()); |
| for (const SectionPiece &Piece : Pieces) |
| OffsetMap[Piece.InputOff] = Piece.OutputOff; |
| }); |
| |
| // Find a string starting at a given offset. |
| auto It = OffsetMap.find(Offset); |
| if (It != OffsetMap.end()) |
| return It->second; |
| |
| if (!this->Live) |
| return 0; |
| |
| // If Offset is not at beginning of a section piece, it is not in the map. |
| // In that case we need to search from the original section piece vector. |
| const SectionPiece &Piece = *this->getSectionPiece(Offset); |
| if (!Piece.Live) |
| return 0; |
| |
| uintX_t Addend = Offset - Piece.InputOff; |
| return Piece.OutputOff + Addend; |
| } |
| |
| 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 std::string lld::toString(const InputSectionBase<ELF32LE> *); |
| template std::string lld::toString(const InputSectionBase<ELF32BE> *); |
| template std::string lld::toString(const InputSectionBase<ELF64LE> *); |
| template std::string lld::toString(const InputSectionBase<ELF64BE> *); |