| //===- Symbols.cpp --------------------------------------------------------===// |
| // |
| // The LLVM Linker |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "Symbols.h" |
| #include "Error.h" |
| #include "InputFiles.h" |
| #include "InputSection.h" |
| #include "OutputSections.h" |
| #include "Target.h" |
| |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/Config/config.h" |
| |
| #ifdef HAVE_CXXABI_H |
| #include <cxxabi.h> |
| #endif |
| |
| using namespace llvm; |
| using namespace llvm::object; |
| using namespace llvm::ELF; |
| |
| using namespace lld; |
| using namespace lld::elf; |
| |
| template <class ELFT> |
| static typename ELFT::uint getSymVA(const SymbolBody &Body, |
| typename ELFT::uint &Addend) { |
| typedef typename ELFT::Sym Elf_Sym; |
| typedef typename ELFT::uint uintX_t; |
| |
| switch (Body.kind()) { |
| case SymbolBody::DefinedSyntheticKind: { |
| auto &D = cast<DefinedSynthetic<ELFT>>(Body); |
| return D.Section.getVA() + D.Value; |
| } |
| case SymbolBody::DefinedRegularKind: { |
| auto &D = cast<DefinedRegular<ELFT>>(Body); |
| InputSectionBase<ELFT> *SC = D.Section; |
| |
| // This is an absolute symbol. |
| if (!SC) |
| return D.Sym.st_value; |
| |
| const Elf_Sym &Sym = D.Sym; |
| uintX_t Offset = Sym.st_value; |
| if (Sym.getType() == STT_SECTION) { |
| Offset += Addend; |
| Addend = 0; |
| } |
| uintX_t VA = SC->OutSec->getVA() + SC->getOffset(Offset); |
| if (Sym.getType() == STT_TLS) |
| return VA - Out<ELFT>::TlsPhdr->p_vaddr; |
| return VA; |
| } |
| case SymbolBody::DefinedCommonKind: |
| return Out<ELFT>::Bss->getVA() + cast<DefinedCommon>(Body).OffsetInBss; |
| case SymbolBody::SharedKind: { |
| auto &SS = cast<SharedSymbol<ELFT>>(Body); |
| if (!SS.NeedsCopyOrPltAddr) |
| return 0; |
| if (SS.IsFunc) |
| return Body.getPltVA<ELFT>(); |
| return Out<ELFT>::Bss->getVA() + SS.OffsetInBss; |
| } |
| case SymbolBody::UndefinedElfKind: |
| case SymbolBody::UndefinedKind: |
| return 0; |
| case SymbolBody::LazyKind: |
| assert(Body.isUsedInRegularObj() && "lazy symbol reached writer"); |
| return 0; |
| case SymbolBody::DefinedBitcodeKind: |
| llvm_unreachable("should have been replaced"); |
| } |
| llvm_unreachable("invalid symbol kind"); |
| } |
| |
| // Returns true if a symbol can be replaced at load-time by a symbol |
| // with the same name defined in other ELF executable or DSO. |
| bool SymbolBody::isPreemptible() const { |
| if (isLocal()) |
| return false; |
| |
| if (isShared()) |
| return true; |
| |
| if (isUndefined()) { |
| if (!isWeak()) |
| return true; |
| |
| // Ideally the static linker should see a definition for every symbol, but |
| // shared object are normally allowed to have undefined references that the |
| // static linker never sees a definition for. |
| if (Config->Shared) |
| return true; |
| |
| // Otherwise, just resolve to 0. |
| return false; |
| } |
| |
| if (!Config->Shared) |
| return false; |
| if (getVisibility() != STV_DEFAULT) |
| return false; |
| if (Config->Bsymbolic || (Config->BsymbolicFunctions && IsFunc)) |
| return false; |
| return true; |
| } |
| |
| template <class ELFT> bool SymbolBody::isGnuIfunc() const { |
| if (auto *D = dyn_cast<DefinedElf<ELFT>>(this)) |
| return D->Sym.getType() == STT_GNU_IFUNC; |
| return false; |
| } |
| |
| template <class ELFT> |
| typename ELFT::uint SymbolBody::getVA(typename ELFT::uint Addend) const { |
| typename ELFT::uint OutVA = getSymVA<ELFT>(*this, Addend); |
| return OutVA + Addend; |
| } |
| |
| template <class ELFT> typename ELFT::uint SymbolBody::getGotVA() const { |
| return Out<ELFT>::Got->getVA() + |
| (Out<ELFT>::Got->getMipsLocalEntriesNum() + GotIndex) * |
| sizeof(typename ELFT::uint); |
| } |
| |
| template <class ELFT> typename ELFT::uint SymbolBody::getGotPltVA() const { |
| return Out<ELFT>::GotPlt->getVA() + GotPltIndex * sizeof(typename ELFT::uint); |
| } |
| |
| template <class ELFT> typename ELFT::uint SymbolBody::getPltVA() const { |
| return Out<ELFT>::Plt->getVA() + Target->PltZeroSize + |
| PltIndex * Target->PltEntrySize; |
| } |
| |
| template <class ELFT> typename ELFT::uint SymbolBody::getSize() const { |
| if (auto *B = dyn_cast<DefinedElf<ELFT>>(this)) |
| return B->Sym.st_size; |
| return 0; |
| } |
| |
| static uint8_t getMinVisibility(uint8_t VA, uint8_t VB) { |
| if (VA == STV_DEFAULT) |
| return VB; |
| if (VB == STV_DEFAULT) |
| return VA; |
| return std::min(VA, VB); |
| } |
| |
| static int compareCommons(DefinedCommon *A, DefinedCommon *B) { |
| if (Config->WarnCommon) |
| warning("multiple common of " + A->getName()); |
| A->Alignment = B->Alignment = std::max(A->Alignment, B->Alignment); |
| if (A->Size < B->Size) |
| return -1; |
| return 1; |
| } |
| |
| // Returns 1, 0 or -1 if this symbol should take precedence |
| // over the Other, tie or lose, respectively. |
| template <class ELFT> int SymbolBody::compare(SymbolBody *Other) { |
| assert(!isLazy() && !Other->isLazy()); |
| std::tuple<bool, bool, bool> L(isDefined(), !isShared(), !isWeak()); |
| std::tuple<bool, bool, bool> R(Other->isDefined(), !Other->isShared(), |
| !Other->isWeak()); |
| |
| // Normalize |
| if (L > R) |
| return -Other->compare<ELFT>(this); |
| |
| Visibility = Other->Visibility = |
| getMinVisibility(Visibility, Other->Visibility); |
| |
| if (IsUsedInRegularObj || Other->IsUsedInRegularObj) |
| IsUsedInRegularObj = Other->IsUsedInRegularObj = true; |
| |
| // We want to export all symbols that exist both in the executable |
| // and in DSOs, so that the symbols in the executable can interrupt |
| // symbols in the DSO at runtime. |
| if (isShared() != Other->isShared()) |
| if (isa<DefinedRegular<ELFT>>(isShared() ? Other : this)) |
| MustBeInDynSym = Other->MustBeInDynSym = true; |
| |
| if (L != R) |
| return -1; |
| if (!isDefined() || isShared() || isWeak()) |
| return 1; |
| if (!isCommon() && !Other->isCommon()) |
| return 0; |
| if (isCommon() && Other->isCommon()) |
| return compareCommons(cast<DefinedCommon>(this), |
| cast<DefinedCommon>(Other)); |
| if (Config->WarnCommon) |
| warning("common " + this->getName() + " is overridden"); |
| return isCommon() ? -1 : 1; |
| } |
| |
| Defined::Defined(Kind K, StringRef Name, bool IsWeak, bool IsLocal, |
| uint8_t Visibility, uint8_t Type) |
| : SymbolBody(K, Name, IsWeak, IsLocal, Visibility, Type) {} |
| |
| DefinedBitcode::DefinedBitcode(StringRef Name, bool IsWeak, uint8_t Visibility) |
| : Defined(DefinedBitcodeKind, Name, IsWeak, false, Visibility, |
| 0 /* Type */) {} |
| |
| bool DefinedBitcode::classof(const SymbolBody *S) { |
| return S->kind() == DefinedBitcodeKind; |
| } |
| |
| Undefined::Undefined(SymbolBody::Kind K, StringRef N, bool IsWeak, |
| uint8_t Visibility, uint8_t Type) |
| : SymbolBody(K, N, IsWeak, false, Visibility, Type), |
| CanKeepUndefined(false) {} |
| |
| Undefined::Undefined(StringRef N, bool IsWeak, uint8_t Visibility, |
| bool CanKeepUndefined) |
| : Undefined(SymbolBody::UndefinedKind, N, IsWeak, Visibility, 0 /* Type */) { |
| this->CanKeepUndefined = CanKeepUndefined; |
| } |
| |
| template <typename ELFT> |
| UndefinedElf<ELFT>::UndefinedElf(StringRef N, const Elf_Sym &Sym) |
| : Undefined(SymbolBody::UndefinedElfKind, N, |
| Sym.getBinding() == llvm::ELF::STB_WEAK, Sym.getVisibility(), |
| Sym.getType()), |
| Sym(Sym) {} |
| |
| template <typename ELFT> |
| DefinedSynthetic<ELFT>::DefinedSynthetic(StringRef N, uintX_t Value, |
| OutputSectionBase<ELFT> &Section, |
| uint8_t Visibility) |
| : Defined(SymbolBody::DefinedSyntheticKind, N, false, false, Visibility, |
| 0 /* Type */), |
| Value(Value), Section(Section) {} |
| |
| DefinedCommon::DefinedCommon(StringRef N, uint64_t Size, uint64_t Alignment, |
| bool IsWeak, uint8_t Visibility) |
| : Defined(SymbolBody::DefinedCommonKind, N, IsWeak, false, Visibility, |
| 0 /* Type */), |
| Alignment(Alignment), Size(Size) {} |
| |
| std::unique_ptr<InputFile> Lazy::getMember() { |
| MemoryBufferRef MBRef = File->getMember(&Sym); |
| |
| // getMember returns an empty buffer if the member was already |
| // read from the library. |
| if (MBRef.getBuffer().empty()) |
| return std::unique_ptr<InputFile>(nullptr); |
| return createObjectFile(MBRef, File->getName()); |
| } |
| |
| // Returns the demangled C++ symbol name for Name. |
| std::string elf::demangle(StringRef Name) { |
| #if !defined(HAVE_CXXABI_H) |
| return Name; |
| #else |
| if (!Config->Demangle) |
| return Name; |
| |
| // __cxa_demangle can be used to demangle strings other than symbol |
| // names which do not necessarily start with "_Z". Name can be |
| // either a C or C++ symbol. Don't call __cxa_demangle if the name |
| // does not look like a C++ symbol name to avoid getting unexpected |
| // result for a C symbol that happens to match a mangled type name. |
| if (!Name.startswith("_Z")) |
| return Name; |
| |
| char *Buf = |
| abi::__cxa_demangle(Name.str().c_str(), nullptr, nullptr, nullptr); |
| if (!Buf) |
| return Name; |
| std::string S(Buf); |
| free(Buf); |
| return S; |
| #endif |
| } |
| |
| template bool SymbolBody::template isGnuIfunc<ELF32LE>() const; |
| template bool SymbolBody::template isGnuIfunc<ELF32BE>() const; |
| template bool SymbolBody::template isGnuIfunc<ELF64LE>() const; |
| template bool SymbolBody::template isGnuIfunc<ELF64BE>() const; |
| |
| template uint32_t SymbolBody::template getVA<ELF32LE>(uint32_t) const; |
| template uint32_t SymbolBody::template getVA<ELF32BE>(uint32_t) const; |
| template uint64_t SymbolBody::template getVA<ELF64LE>(uint64_t) const; |
| template uint64_t SymbolBody::template getVA<ELF64BE>(uint64_t) const; |
| |
| template uint32_t SymbolBody::template getGotVA<ELF32LE>() const; |
| template uint32_t SymbolBody::template getGotVA<ELF32BE>() const; |
| template uint64_t SymbolBody::template getGotVA<ELF64LE>() const; |
| template uint64_t SymbolBody::template getGotVA<ELF64BE>() const; |
| |
| template uint32_t SymbolBody::template getGotPltVA<ELF32LE>() const; |
| template uint32_t SymbolBody::template getGotPltVA<ELF32BE>() const; |
| template uint64_t SymbolBody::template getGotPltVA<ELF64LE>() const; |
| template uint64_t SymbolBody::template getGotPltVA<ELF64BE>() const; |
| |
| template uint32_t SymbolBody::template getPltVA<ELF32LE>() const; |
| template uint32_t SymbolBody::template getPltVA<ELF32BE>() const; |
| template uint64_t SymbolBody::template getPltVA<ELF64LE>() const; |
| template uint64_t SymbolBody::template getPltVA<ELF64BE>() const; |
| |
| template uint32_t SymbolBody::template getSize<ELF32LE>() const; |
| template uint32_t SymbolBody::template getSize<ELF32BE>() const; |
| template uint64_t SymbolBody::template getSize<ELF64LE>() const; |
| template uint64_t SymbolBody::template getSize<ELF64BE>() const; |
| |
| template int SymbolBody::compare<ELF32LE>(SymbolBody *Other); |
| template int SymbolBody::compare<ELF32BE>(SymbolBody *Other); |
| template int SymbolBody::compare<ELF64LE>(SymbolBody *Other); |
| template int SymbolBody::compare<ELF64BE>(SymbolBody *Other); |
| |
| template class elf::UndefinedElf<ELF32LE>; |
| template class elf::UndefinedElf<ELF32BE>; |
| template class elf::UndefinedElf<ELF64LE>; |
| template class elf::UndefinedElf<ELF64BE>; |
| |
| template class elf::DefinedSynthetic<ELF32LE>; |
| template class elf::DefinedSynthetic<ELF32BE>; |
| template class elf::DefinedSynthetic<ELF64LE>; |
| template class elf::DefinedSynthetic<ELF64BE>; |