X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FMC%2FELFObjectWriter.cpp;h=ac8c250a8337fede05b5fdd92ccda563c7f2f687;hb=345ed9806a0ab5d680da1ff78fe3df7ebbc6107d;hp=b9d2acea4612fb74d880eebc289f1baf3b3d022f;hpb=8f413fa9c00dbaea000ddfe265ab5edd285ea3ab;p=oota-llvm.git diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp index b9d2acea461..ac8c250a833 100644 --- a/lib/MC/ELFObjectWriter.cpp +++ b/lib/MC/ELFObjectWriter.cpp @@ -70,6 +70,17 @@ static bool isFixupKindX86PCRel(unsigned Kind) { } } +static bool RelocNeedsGOT(unsigned Type) { + switch (Type) { + default: + return false; + case ELF::R_X86_64_GOT32: + case ELF::R_X86_64_PLT32: + case ELF::R_X86_64_GOTPCREL: + return true; + } +} + namespace { class ELFObjectWriterImpl { @@ -133,6 +144,8 @@ namespace { int NumRegularSections; + bool NeedsGOT; + ELFObjectWriter *Writer; raw_ostream &OS; @@ -153,7 +166,7 @@ namespace { public: ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit, bool _HasRelAddend, Triple::OSType _OSType) - : Writer(_Writer), OS(Writer->getStream()), + : NeedsGOT(false), Writer(_Writer), OS(Writer->getStream()), Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend), OSType(_OSType) { } @@ -432,12 +445,22 @@ void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD, const MCBinaryExpr *BE = static_cast(ESize); if (BE->EvaluateAsRelocatable(Res, &Layout)) { - MCSymbolData &A = - Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol()); - MCSymbolData &B = - Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol()); + uint64_t AddressA = 0; + uint64_t AddressB = 0; + const MCSymbol &SymA = Res.getSymA()->getSymbol(); + const MCSymbol &SymB = Res.getSymB()->getSymbol(); + + if (SymA.isDefined()) { + MCSymbolData &A = Layout.getAssembler().getSymbolData(SymA); + AddressA = Layout.getSymbolAddress(&A); + } - Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B); + if (SymB.isDefined()) { + MCSymbolData &B = Layout.getAssembler().getSymbolData(SymB); + AddressB = Layout.getSymbolAddress(&B); + } + + Size = AddressA - AddressB; } } else if (ESize->getKind() == MCExpr::Constant) { Size = static_cast(ESize)->getValue(); @@ -489,8 +512,9 @@ void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F, for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) { ELFSymbolData &MSD = ExternalSymbolData[i]; MCSymbolData &Data = *MSD.SymbolData; - assert((Data.getFlags() & ELF_STB_Global) && - "External symbol requires STB_GLOBAL flag"); + assert(((Data.getFlags() & ELF_STB_Global) || + (Data.getFlags() & ELF_STB_Weak)) && + "External symbol requires STB_GLOBAL or STB_WEAK flag"); WriteSymbol(F, MSD, Layout); if (GetBinding(Data) == ELF::STB_LOCAL) LastLocalSymbolIndex++; @@ -506,7 +530,8 @@ void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F, } static bool ShouldRelocOnSymbol(const MCSymbolData &SD, - const MCValue &Target) { + const MCValue &Target, + const MCFragment &F) { const MCSymbol &Symbol = SD.getSymbol(); if (Symbol.isUndefined()) return true; @@ -514,10 +539,18 @@ static bool ShouldRelocOnSymbol(const MCSymbolData &SD, const MCSectionELF &Section = static_cast(Symbol.getSection()); + if (SD.isExternal()) + return true; + if (Section.getFlags() & MCSectionELF::SHF_MERGE) return Target.getConstant() != 0; - if (SD.isExternal()) + MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind(); + const MCSectionELF &Sec2 = + static_cast(F.getParent()->getSection()); + + if (&Sec2 != &Section && + (Kind == MCSymbolRefExpr::VK_PLT || Kind == MCSymbolRefExpr::VK_GOTPCREL)) return true; return false; @@ -564,7 +597,7 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, return; } - bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target); + bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target, *Fragment); if (!RelocOnSymbol) { Index = F->getParent()->getOrdinal(); @@ -616,6 +649,9 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, case MCSymbolRefExpr::VK_GOT: Type = ELF::R_X86_64_GOT32; break; + case llvm::MCSymbolRefExpr::VK_GOTPCREL: + Type = ELF::R_X86_64_GOTPCREL; + break; default: llvm_unreachable("Unimplemented"); } @@ -647,6 +683,9 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, } } + if (RelocNeedsGOT(Type)) + NeedsGOT = true; + ELFRelocationEntry ERE; ERE.Index = Index; @@ -676,10 +715,41 @@ ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm, return SD.getIndex() + NumRegularSections + /* empty symbol */ 1; } +static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data, + bool Used) { + const MCSymbol &Symbol = Data.getSymbol(); + if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) + return false; + + if (!Used && Symbol.isTemporary()) + return false; + + return true; +} + +static bool isLocal(const MCSymbolData &Data) { + if (Data.isExternal()) + return false; + + const MCSymbol &Symbol = Data.getSymbol(); + if (Symbol.isUndefined() && !Symbol.isVariable()) + return false; + + return true; +} + void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { + // FIXME: Is this the correct place to do this? + if (NeedsGOT) { + llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_"; + MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name); + MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym); + Data.setExternal(true); + } + // Build section lookup table. NumRegularSections = Asm.size(); - DenseMap SectionIndexMap; + DenseMap SectionIndexMap; unsigned Index = 1; for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it, ++Index) @@ -694,14 +764,10 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { ie = Asm.symbol_end(); it != ie; ++it) { const MCSymbol &Symbol = it->getSymbol(); - // Ignore non-linker visible symbols. - if (!Asm.isSymbolLinkerVisible(Symbol)) - continue; - - if (it->isExternal() || Symbol.isUndefined()) + if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol))) continue; - if (Symbol.isTemporary() && !UsedInReloc.count(&Symbol)) + if (!isLocal(*it)) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; @@ -719,7 +785,14 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { MSD.SectionIndex = ELF::SHN_ABS; LocalSymbolData.push_back(MSD); } else { - MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); + const MCSymbol *SymbolP = &Symbol; + if (Symbol.isVariable()) { + const MCExpr *Value = Symbol.getVariableValue(); + assert (Value->getKind() == MCExpr::SymbolRef && "Unimplemented"); + const MCSymbolRefExpr *Ref = static_cast(Value); + SymbolP = &Ref->getSymbol(); + } + MSD.SectionIndex = SectionIndexMap.lookup(&SymbolP->getSection()); assert(MSD.SectionIndex && "Invalid section index!"); LocalSymbolData.push_back(MSD); } @@ -730,18 +803,10 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { ie = Asm.symbol_end(); it != ie; ++it) { const MCSymbol &Symbol = it->getSymbol(); - // Ignore non-linker visible symbols. - if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) + if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol))) continue; - if (!it->isExternal() && !Symbol.isUndefined()) - continue; - - if (Symbol.isVariable()) - continue; - - if (Symbol.isUndefined() && !UsedInReloc.count(&Symbol) - && Symbol.isTemporary()) + if (isLocal(*it)) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; @@ -755,9 +820,20 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { MSD.SymbolData = it; MSD.StringIndex = Entry; + // FIXME: There is duplicated code with the local case. if (it->isCommon()) { MSD.SectionIndex = ELF::SHN_COMMON; ExternalSymbolData.push_back(MSD); + } else if (Symbol.isVariable()) { + const MCExpr *Value = Symbol.getVariableValue(); + assert (Value->getKind() == MCExpr::SymbolRef && "Unimplemented"); + const MCSymbolRefExpr *Ref = static_cast(Value); + const MCSymbol &RefSymbol = Ref->getSymbol(); + if (RefSymbol.isDefined()) { + MSD.SectionIndex = SectionIndexMap.lookup(&RefSymbol.getSection()); + assert(MSD.SectionIndex && "Invalid section index!"); + ExternalSymbolData.push_back(MSD); + } } else if (Symbol.isUndefined()) { MSD.SectionIndex = ELF::SHN_UNDEF; // FIXME: Undefined symbols are global, but this is the first place we