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llvm-project/lld/ELF/Symbols.cpp

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//===- 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>
typename ELFFile<ELFT>::uintX_t SymbolBody::getVA() const {
switch (kind()) {
case DefinedSyntheticKind: {
auto *D = cast<DefinedSynthetic<ELFT>>(this);
return D->Section.getVA() + D->Value;
}
case DefinedRegularKind: {
auto *D = cast<DefinedRegular<ELFT>>(this);
InputSectionBase<ELFT> *SC = D->Section;
// This is an absolute symbol.
if (!SC)
return D->Sym.st_value;
assert(SC->Live);
// Symbol offsets for AMDGPU are the offsets in bytes of the symbols
// from the beginning of the section. Note that this part of AMDGPU's
// ELF spec is odd and not in line with the standard ELF.
if (Config->EMachine == EM_AMDGPU)
return SC->getOffset(D->Sym);
if (D->Sym.getType() == STT_TLS)
return SC->OutSec->getVA() + SC->getOffset(D->Sym) -
Out<ELFT>::TlsPhdr->p_vaddr;
return SC->OutSec->getVA() + SC->getOffset(D->Sym);
}
case DefinedCommonKind:
return Out<ELFT>::Bss->getVA() + cast<DefinedCommon>(this)->OffsetInBss;
case SharedKind: {
auto *SS = cast<SharedSymbol<ELFT>>(this);
if (!SS->NeedsCopyOrPltAddr)
return 0;
if (SS->IsFunc)
return getPltVA<ELFT>();
else
return Out<ELFT>::Bss->getVA() + SS->OffsetInBss;
}
case UndefinedElfKind:
case UndefinedKind:
return 0;
case LazyKind:
assert(isUsedInRegularObj() && "Lazy symbol reached writer");
return 0;
case DefinedBitcodeKind:
llvm_unreachable("Should have been replaced");
}
llvm_unreachable("Invalid symbol kind");
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t SymbolBody::getGotVA() const {
return Out<ELFT>::Got->getVA() +
(Out<ELFT>::Got->getMipsLocalEntriesNum() + GotIndex) *
sizeof(typename ELFFile<ELFT>::uintX_t);
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t SymbolBody::getGotPltVA() const {
return Out<ELFT>::GotPlt->getVA() +
GotPltIndex * sizeof(typename ELFFile<ELFT>::uintX_t);
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t SymbolBody::getPltVA() const {
return Out<ELFT>::Plt->getVA() + Target->PltZeroSize +
PltIndex * Target->PltEntrySize;
}
template <class ELFT>
typename ELFFile<ELFT>::uintX_t 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);
}
// 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) {
typedef typename ELFFile<ELFT>::uintX_t uintX_t;
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 (!std::get<0>(L) || !std::get<1>(L) || !std::get<2>(L))
return 1;
if (isCommon()) {
if (!Other->isCommon())
return -1;
auto *ThisC = cast<DefinedCommon>(this);
auto *OtherC = cast<DefinedCommon>(Other);
uintX_t Align = std::max(ThisC->MaxAlignment, OtherC->MaxAlignment);
if (ThisC->Size >= OtherC->Size) {
ThisC->MaxAlignment = Align;
return 1;
}
OtherC->MaxAlignment = Align;
return -1;
}
if (Other->isCommon())
return 1;
return 0;
}
Defined::Defined(Kind K, StringRef Name, bool IsWeak, uint8_t Visibility,
bool IsTls, bool IsFunction)
: SymbolBody(K, Name, IsWeak, Visibility, IsTls, IsFunction) {}
DefinedBitcode::DefinedBitcode(StringRef Name, bool IsWeak)
: Defined(DefinedBitcodeKind, Name, IsWeak, STV_DEFAULT, false, false) {}
bool DefinedBitcode::classof(const SymbolBody *S) {
return S->kind() == DefinedBitcodeKind;
}
Undefined::Undefined(SymbolBody::Kind K, StringRef N, bool IsWeak,
uint8_t Visibility, bool IsTls)
: SymbolBody(K, N, IsWeak, Visibility, IsTls, /*IsFunction*/ false),
CanKeepUndefined(false) {}
Undefined::Undefined(StringRef N, bool IsWeak, uint8_t Visibility,
bool CanKeepUndefined)
: Undefined(SymbolBody::UndefinedKind, N, IsWeak, Visibility,
/*IsTls*/ false) {
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() == llvm::ELF::STT_TLS),
Sym(Sym) {}
template <typename ELFT>
DefinedSynthetic<ELFT>::DefinedSynthetic(StringRef N, uintX_t Value,
OutputSectionBase<ELFT> &Section,
uint8_t Visibility)
: Defined(SymbolBody::DefinedSyntheticKind, N, false, Visibility,
/*IsTls*/ false, /*IsFunction*/ false),
Value(Value), Section(Section) {}
DefinedCommon::DefinedCommon(StringRef N, uint64_t Size, uint64_t Alignment,
bool IsWeak, uint8_t Visibility)
: Defined(SymbolBody::DefinedCommonKind, N, IsWeak, Visibility,
/*IsTls*/ false, /*IsFunction*/ false) {
MaxAlignment = Alignment;
this->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());
}
template <class ELFT> static void doInitSymbols() {
ElfSym<ELFT>::Etext.setBinding(STB_GLOBAL);
ElfSym<ELFT>::Edata.setBinding(STB_GLOBAL);
ElfSym<ELFT>::End.setBinding(STB_GLOBAL);
ElfSym<ELFT>::Ignored.setBinding(STB_WEAK);
ElfSym<ELFT>::Ignored.setVisibility(STV_HIDDEN);
}
void elf::initSymbols() {
doInitSymbols<ELF32LE>();
doInitSymbols<ELF32BE>();
doInitSymbols<ELF64LE>();
doInitSymbols<ELF64BE>();
}
// 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 uint32_t SymbolBody::template getVA<ELF32LE>() const;
template uint32_t SymbolBody::template getVA<ELF32BE>() const;
template uint64_t SymbolBody::template getVA<ELF64LE>() const;
template uint64_t SymbolBody::template getVA<ELF64BE>() 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>;
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