X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FMC%2FELFObjectWriter.cpp;h=ac8c250a8337fede05b5fdd92ccda563c7f2f687;hb=345ed9806a0ab5d680da1ff78fe3df7ebbc6107d;hp=8fb6ff60f8909d9af5d85f7ed602f5e33361a85b;hpb=2f6e0e68a455aa6bd6da74c3256470bd94c0b6f2;p=oota-llvm.git diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp index 8fb6ff60f89..ac8c250a833 100644 --- a/lib/MC/ELFObjectWriter.cpp +++ b/lib/MC/ELFObjectWriter.cpp @@ -12,6 +12,7 @@ //===----------------------------------------------------------------------===// #include "llvm/MC/ELFObjectWriter.h" +#include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/StringMap.h" #include "llvm/ADT/Twine.h" @@ -34,25 +35,59 @@ #include using namespace llvm; +static unsigned GetType(const MCSymbolData &SD) { + uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift; + assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT || + Type == ELF::STT_FUNC || Type == ELF::STT_SECTION || + Type == ELF::STT_FILE || Type == ELF::STT_COMMON || + Type == ELF::STT_TLS); + return Type; +} + +static unsigned GetBinding(const MCSymbolData &SD) { + uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift; + assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL || + Binding == ELF::STB_WEAK); + return Binding; +} + +static void SetBinding(MCSymbolData &SD, unsigned Binding) { + assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL || + Binding == ELF::STB_WEAK); + uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift); + SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift)); +} + +static bool isFixupKindX86PCRel(unsigned Kind) { + switch (Kind) { + default: + return false; + case X86::reloc_pcrel_1byte: + case X86::reloc_pcrel_4byte: + case X86::reloc_riprel_4byte: + case X86::reloc_riprel_4byte_movq_load: + return true; + } +} + +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 { - static bool isFixupKindX86PCRel(unsigned Kind) { - switch (Kind) { - default: - return false; - case X86::reloc_pcrel_1byte: - case X86::reloc_pcrel_4byte: - case X86::reloc_riprel_4byte: - case X86::reloc_riprel_4byte_movq_load: - return true; - } - } - - static bool isFixupKindX86RIPRel(unsigned Kind) { + /*static bool isFixupKindX86RIPRel(unsigned Kind) { return Kind == X86::reloc_riprel_4byte || Kind == X86::reloc_riprel_4byte_movq_load; - } + }*/ /// ELFSymbolData - Helper struct for containing some precomputed information @@ -64,6 +99,10 @@ namespace { // Support lexicographic sorting. bool operator<(const ELFSymbolData &RHS) const { + if (GetType(*SymbolData) == ELF::STT_FILE) + return true; + if (GetType(*RHS.SymbolData) == ELF::STT_FILE) + return false; return SymbolData->getSymbol().getName() < RHS.SymbolData->getSymbol().getName(); } @@ -75,7 +114,9 @@ namespace { struct ELFRelocationEntry { // Make these big enough for both 32-bit and 64-bit uint64_t r_offset; - uint64_t r_info; + int Index; + unsigned Type; + const MCSymbol *Symbol; uint64_t r_addend; // Support lexicographic sorting. @@ -84,6 +125,8 @@ namespace { } }; + SmallPtrSet UsedInReloc; + llvm::DenseMap > Relocations; DenseMap SectionStringTableIndex; @@ -99,17 +142,20 @@ namespace { /// @} + int NumRegularSections; + + bool NeedsGOT; + ELFObjectWriter *Writer; raw_ostream &OS; - // This holds the current offset into the object file. - size_t FileOff; - unsigned Is64Bit : 1; bool HasRelocationAddend; + Triple::OSType OSType; + // This holds the symbol table index of the last local symbol. unsigned LastLocalSymbolIndex; // This holds the .strtab section index. @@ -119,26 +165,26 @@ namespace { public: ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit, - bool _HasRelAddend) - : Writer(_Writer), OS(Writer->getStream()), FileOff(0), - Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend) { + bool _HasRelAddend, Triple::OSType _OSType) + : NeedsGOT(false), Writer(_Writer), OS(Writer->getStream()), + Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend), + OSType(_OSType) { } void Write8(uint8_t Value) { Writer->Write8(Value); } void Write16(uint16_t Value) { Writer->Write16(Value); } void Write32(uint32_t Value) { Writer->Write32(Value); } - void Write64(uint64_t Value) { Writer->Write64(Value); } + //void Write64(uint64_t Value) { Writer->Write64(Value); } void WriteZeros(unsigned N) { Writer->WriteZeros(N); } - void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) { - Writer->WriteBytes(Str, ZeroFillSize); - } + //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) { + // Writer->WriteBytes(Str, ZeroFillSize); + //} void WriteWord(uint64_t W) { - if (Is64Bit) { + if (Is64Bit) Writer->Write64(W); - } else { + else Writer->Write32(W); - } } void String8(char *buf, uint8_t Value) { @@ -206,7 +252,8 @@ namespace { const MCAsmLayout &Layout); void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm, - const MCAsmLayout &Layout); + const MCAsmLayout &Layout, + unsigned NumRegularSections); void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, @@ -235,8 +282,6 @@ namespace { void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout); void ExecutePostLayoutBinding(MCAssembler &Asm) { - // Compute symbol table information. - ComputeSymbolTable(Asm); } void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags, @@ -247,7 +292,12 @@ namespace { void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F, const MCSectionData *SD); - void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout); + bool IsFixupFullyResolved(const MCAssembler &Asm, + const MCValue Target, + bool IsPCRel, + const MCFragment *DF) const; + + void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout); }; } @@ -274,7 +324,12 @@ void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize, Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB); Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION] - Write8(ELF::ELFOSABI_LINUX); // e_ident[EI_OSABI] + // e_ident[EI_OSABI] + switch (OSType) { + case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break; + case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break; + default: Write8(ELF::ELFOSABI_NONE); break; + } Write8(0); // e_ident[EI_ABIVERSION] WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD); @@ -356,17 +411,32 @@ void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name, } } +static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) { + if (Data.isCommon() && Data.isExternal()) + return Data.getCommonAlignment(); + + const MCSymbol &Symbol = Data.getSymbol(); + if (!Symbol.isInSection()) + return 0; + + if (!Data.isCommon() && !(Data.getFlags() & ELF_STB_Weak)) + if (MCFragment *FF = Data.getFragment()) + return Layout.getSymbolAddress(&Data) - + Layout.getSectionAddress(FF->getParent()); + + return 0; +} + void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD, const MCAsmLayout &Layout) { MCSymbolData &Data = *MSD.SymbolData; uint8_t Info = (Data.getFlags() & 0xff); uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift); - uint64_t Value = 0; + uint64_t Value = SymbolValue(Data, Layout); uint64_t Size = 0; const MCExpr *ESize; - if (Data.isCommon() && Data.isExternal()) - Value = Data.getCommonAlignment(); + assert(!(Data.isCommon() && !Data.isExternal())); ESize = Data.getSize(); if (Data.getSize()) { @@ -375,13 +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()); - - Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B); - Value = Layout.getSymbolAddress(&Data); + 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); + } + + 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(); @@ -397,7 +476,8 @@ void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD, void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm, - const MCAsmLayout &Layout) { + const MCAsmLayout &Layout, + unsigned NumRegularSections) { // The string table must be emitted first because we need the index // into the string table for all the symbol names. assert(StringTable.size() && "Missing string table"); @@ -415,20 +495,16 @@ void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F, WriteSymbol(F, MSD, Layout); } - // Write out a symbol table entry for each section. - // leaving out the just added .symtab which is at - // the very end + // Write out a symbol table entry for each regular section. unsigned Index = 1; - for (MCAssembler::const_iterator it = Asm.begin(), - ie = Asm.end(); it != ie; ++it, ++Index) { + for (MCAssembler::const_iterator it = Asm.begin(); + Index <= NumRegularSections; ++it, ++Index) { const MCSectionELF &Section = static_cast(it->getSection()); // Leave out relocations so we don't have indexes within // the relocations messed up if (Section.getType() == ELF::SHT_RELA || Section.getType() == ELF::SHT_REL) continue; - if (Index == Asm.size()) - continue; WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index); LastLocalSymbolIndex++; } @@ -436,23 +512,50 @@ 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 (Data.getFlags() & ELF_STB_Local) + if (GetBinding(Data) == ELF::STB_LOCAL) LastLocalSymbolIndex++; } for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) { ELFSymbolData &MSD = UndefinedSymbolData[i]; MCSymbolData &Data = *MSD.SymbolData; - Data.setFlags(Data.getFlags() | ELF_STB_Global); WriteSymbol(F, MSD, Layout); - if (Data.getFlags() & ELF_STB_Local) + if (GetBinding(Data) == ELF::STB_LOCAL) LastLocalSymbolIndex++; } } +static bool ShouldRelocOnSymbol(const MCSymbolData &SD, + const MCValue &Target, + const MCFragment &F) { + const MCSymbol &Symbol = SD.getSymbol(); + if (Symbol.isUndefined()) + return true; + + const MCSectionELF &Section = + static_cast(Symbol.getSection()); + + if (SD.isExternal()) + return true; + + if (Section.getFlags() & MCSectionELF::SHF_MERGE) + return Target.getConstant() != 0; + + 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; +} + // FIXME: this is currently X86/X86_64 only void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, @@ -460,65 +563,101 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue) { - unsigned IsPCRel = isFixupKindX86PCRel(Fixup.getKind()); - - uint64_t FixupOffset = - Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); - int64_t Value; int64_t Addend = 0; - unsigned Index = 0; - unsigned Type; - - Value = Target.getConstant(); + int Index = 0; + int64_t Value = Target.getConstant(); + const MCSymbol *Symbol = 0; + bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind()); if (!Target.isAbsolute()) { - const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); + Symbol = &Target.getSymA()->getSymbol(); MCSymbolData &SD = Asm.getSymbolData(*Symbol); - const MCSymbolData *Base = Asm.getAtom(Layout, &SD); - - if (Base) { - MCFragment *F = SD.getFragment(); - if (F && (!Symbol->isInSection() || SD.isCommon())) { - Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1; - Value += Layout.getSymbolAddress(&SD); - } else - Index = getSymbolIndexInSymbolTable(Asm, Symbol); - if (Base != &SD) - Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base); - Addend = Value; - Value = 0; + MCFragment *F = SD.getFragment(); + + if (const MCSymbolRefExpr *RefB = Target.getSymB()) { + const MCSymbol &SymbolB = RefB->getSymbol(); + MCSymbolData &SDB = Asm.getSymbolData(SymbolB); + IsPCRel = true; + MCSectionData *Sec = Fragment->getParent(); + + // Offset of the symbol in the section + int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec); + + // Ofeset of the relocation in the section + int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); + Value += b - a; + } + + // Check that this case has already been fully resolved before we get + // here. + if (Symbol->isDefined() && !SD.isExternal() && + IsPCRel && + &Fragment->getParent()->getSection() == &Symbol->getSection()) { + llvm_unreachable("We don't need a relocation in this case."); + return; + } + + bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target, *Fragment); + if (!RelocOnSymbol) { + Index = F->getParent()->getOrdinal(); + + MCSectionData *FSD = F->getParent(); + // Offset of the symbol in the section + Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD); } else { - MCFragment *F = SD.getFragment(); - if (F) { - // Index of the section in .symtab against this symbol - // is being relocated + 2 (empty section + abs. symbols). - Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1; - - MCSectionData *FSD = F->getParent(); - // Offset of the symbol in the section - Addend = Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD); - } else { - FixedValue = Value; - return; - } + UsedInReloc.insert(Symbol); + Index = -1; } + Addend = Value; + // Compensate for the addend on i386. + if (Is64Bit) + Value = 0; } + FixedValue = Value; + // determine the type of the relocation + + MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); + unsigned Type; if (Is64Bit) { if (IsPCRel) { - Type = ELF::R_X86_64_PC32; + switch (Modifier) { + case MCSymbolRefExpr::VK_None: + Type = ELF::R_X86_64_PC32; + break; + case MCSymbolRefExpr::VK_PLT: + Type = ELF::R_X86_64_PLT32; + break; + case llvm::MCSymbolRefExpr::VK_GOTPCREL: + Type = ELF::R_X86_64_GOTPCREL; + break; + default: + llvm_unreachable("Unimplemented"); + } } else { switch ((unsigned)Fixup.getKind()) { default: llvm_unreachable("invalid fixup kind!"); case FK_Data_8: Type = ELF::R_X86_64_64; break; + case X86::reloc_signed_4byte: case X86::reloc_pcrel_4byte: - case FK_Data_4: - // check that the offset fits within a signed long - if (isInt<32>(Target.getConstant())) + assert(isInt<32>(Target.getConstant())); + switch (Modifier) { + case MCSymbolRefExpr::VK_None: Type = ELF::R_X86_64_32S; - else - Type = ELF::R_X86_64_32; + break; + 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"); + } + break; + case FK_Data_4: + Type = ELF::R_X86_64_32; break; case FK_Data_2: Type = ELF::R_X86_64_16; break; case X86::reloc_pcrel_1byte: @@ -531,6 +670,10 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, } else { switch ((unsigned)Fixup.getKind()) { default: llvm_unreachable("invalid fixup kind!"); + + // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode + // instead? + case X86::reloc_signed_4byte: case X86::reloc_pcrel_4byte: case FK_Data_4: Type = ELF::R_386_32; break; case FK_Data_2: Type = ELF::R_386_16; break; @@ -540,21 +683,16 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, } } - FixedValue = Value; + if (RelocNeedsGOT(Type)) + NeedsGOT = true; ELFRelocationEntry ERE; - if (Is64Bit) { - struct ELF::Elf64_Rela ERE64; - ERE64.setSymbolAndType(Index, Type); - ERE.r_info = ERE64.r_info; - } else { - struct ELF::Elf32_Rela ERE32; - ERE32.setSymbolAndType(Index, Type); - ERE.r_info = ERE32.r_info; - } + ERE.Index = Index; + ERE.Type = Type; + ERE.Symbol = Symbol; - ERE.r_offset = FixupOffset; + ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); if (HasRelocationAddend) ERE.r_addend = Addend; @@ -567,23 +705,51 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, uint64_t ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm, const MCSymbol *S) { - for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) - if (&LocalSymbolData[i].SymbolData->getSymbol() == S) - return i + /* empty symbol */ 1; - for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) - if (&ExternalSymbolData[i].SymbolData->getSymbol() == S) - return i + LocalSymbolData.size() + Asm.size() + /* empty symbol */ 1; - for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) - if (&UndefinedSymbolData[i].SymbolData->getSymbol() == S) - return i + LocalSymbolData.size() + ExternalSymbolData.size() + - Asm.size() + /* empty symbol */ 1; + MCSymbolData &SD = Asm.getSymbolData(*S); + + // Local symbol. + if (!SD.isExternal() && !S->isUndefined()) + return SD.getIndex() + /* empty symbol */ 1; + + // External or undefined symbol. + 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; - llvm_unreachable("Cannot find symbol which should exist!"); + 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. - DenseMap SectionIndexMap; + NumRegularSections = Asm.size(); + DenseMap SectionIndexMap; unsigned Index = 1; for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it, ++Index) @@ -598,11 +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)) + if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol))) continue; - if (it->isExternal() || Symbol.isUndefined()) + if (!isLocal(*it)) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; @@ -620,7 +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); } @@ -631,11 +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)) + if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol))) continue; - if (!it->isExternal() && !Symbol.isUndefined()) + if (isLocal(*it)) continue; uint64_t &Entry = StringIndexMap[Symbol.getName()]; @@ -649,17 +820,30 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { MSD.SymbolData = it; MSD.StringIndex = Entry; - if (Symbol.isUndefined()) { + // 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; - // XXX: for some reason we dont Emit* this - it->setFlags(it->getFlags() | ELF_STB_Global); + // FIXME: Undefined symbols are global, but this is the first place we + // are able to set it. + if (GetBinding(*it) == ELF::STB_LOCAL) + SetBinding(*it, ELF::STB_GLOBAL); UndefinedSymbolData.push_back(MSD); } else if (Symbol.isAbsolute()) { MSD.SectionIndex = ELF::SHN_ABS; ExternalSymbolData.push_back(MSD); - } else if (it->isCommon()) { - MSD.SectionIndex = ELF::SHN_COMMON; - ExternalSymbolData.push_back(MSD); } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); @@ -707,13 +891,13 @@ void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout, false, EntrySize); MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection); - RelaSD.setAlignment(1); + RelaSD.setAlignment(Is64Bit ? 8 : 4); MCDataFragment *F = new MCDataFragment(&RelaSD); WriteRelocationsFragment(Asm, F, &SD); - Asm.AddSectionToTheEnd(RelaSD, Layout); + Asm.AddSectionToTheEnd(*Writer, RelaSD, Layout); } } @@ -745,12 +929,41 @@ void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm, for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { ELFRelocationEntry entry = Relocs[e - i - 1]; - unsigned WordSize = Is64Bit ? 8 : 4; - F->getContents() += StringRef((const char *)&entry.r_offset, WordSize); - F->getContents() += StringRef((const char *)&entry.r_info, WordSize); + if (entry.Index < 0) + entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); + else + entry.Index += LocalSymbolData.size() + 1; + if (Is64Bit) { + char buf[8]; - if (HasRelocationAddend) - F->getContents() += StringRef((const char *)&entry.r_addend, WordSize); + String64(buf, entry.r_offset); + F->getContents() += StringRef(buf, 8); + + struct ELF::Elf64_Rela ERE64; + ERE64.setSymbolAndType(entry.Index, entry.Type); + String64(buf, ERE64.r_info); + F->getContents() += StringRef(buf, 8); + + if (HasRelocationAddend) { + String64(buf, entry.r_addend); + F->getContents() += StringRef(buf, 8); + } + } else { + char buf[4]; + + String32(buf, entry.r_offset); + F->getContents() += StringRef(buf, 4); + + struct ELF::Elf32_Rela ERE32; + ERE32.setSymbolAndType(entry.Index, entry.Type); + String32(buf, ERE32.r_info); + F->getContents() += StringRef(buf, 4); + + if (HasRelocationAddend) { + String32(buf, entry.r_addend); + F->getContents() += StringRef(buf, 4); + } + } } } @@ -759,53 +972,45 @@ void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm, MCContext &Ctx = Asm.getContext(); MCDataFragment *F; - WriteRelocations(Asm, Layout); - const MCSection *SymtabSection; unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32; + unsigned NumRegularSections = Asm.size(); + + // We construct .shstrtab, .symtab and .strtab in this order to match gnu as. + const MCSection *ShstrtabSection; + ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, + SectionKind::getReadOnly(), false); + MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); + ShstrtabSD.setAlignment(1); + ShstrtabIndex = Asm.size(); + SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0, SectionKind::getReadOnly(), false, EntrySize); - MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection); - SymtabSD.setAlignment(Is64Bit ? 8 : 4); - F = new MCDataFragment(&SymtabSD); - - // Symbol table - WriteSymbolTable(F, Asm, Layout); - Asm.AddSectionToTheEnd(SymtabSD, Layout); - const MCSection *StrtabSection; StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0, SectionKind::getReadOnly(), false); - MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection); StrtabSD.setAlignment(1); - - // FIXME: This isn't right. If the sections get rearranged this will - // be wrong. We need a proper lookup. StringTableIndex = Asm.size(); - F = new MCDataFragment(&StrtabSD); - F->getContents().append(StringTable.begin(), StringTable.end()); - Asm.AddSectionToTheEnd(StrtabSD, Layout); + WriteRelocations(Asm, Layout); - const MCSection *ShstrtabSection; - ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0, - SectionKind::getReadOnly(), false); + // Symbol table + F = new MCDataFragment(&SymtabSD); + WriteSymbolTable(F, Asm, Layout, NumRegularSections); + Asm.AddSectionToTheEnd(*Writer, SymtabSD, Layout); - MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection); - ShstrtabSD.setAlignment(1); + F = new MCDataFragment(&StrtabSD); + F->getContents().append(StringTable.begin(), StringTable.end()); + Asm.AddSectionToTheEnd(*Writer, StrtabSD, Layout); F = new MCDataFragment(&ShstrtabSD); - // FIXME: This isn't right. If the sections get rearranged this will - // be wrong. We need a proper lookup. - ShstrtabIndex = Asm.size(); - // Section header string table. // // The first entry of a string table holds a null character so skip @@ -817,6 +1022,7 @@ void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm, ie = Asm.end(); it != ie; ++it) { const MCSectionELF &Section = static_cast(it->getSection()); + // FIXME: We could merge suffixes like in .text and .rela.text. // Remember the index into the string table so we can write it // into the sh_name field of the section header table. @@ -827,31 +1033,75 @@ void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm, F->getContents() += '\x00'; } - Asm.AddSectionToTheEnd(ShstrtabSD, Layout); + Asm.AddSectionToTheEnd(*Writer, ShstrtabSD, Layout); +} + +bool ELFObjectWriterImpl::IsFixupFullyResolved(const MCAssembler &Asm, + const MCValue Target, + bool IsPCRel, + const MCFragment *DF) const { + // If this is a PCrel relocation, find the section this fixup value is + // relative to. + const MCSection *BaseSection = 0; + if (IsPCRel) { + BaseSection = &DF->getParent()->getSection(); + assert(BaseSection); + } + + const MCSection *SectionA = 0; + const MCSymbol *SymbolA = 0; + if (const MCSymbolRefExpr *A = Target.getSymA()) { + SymbolA = &A->getSymbol(); + SectionA = &SymbolA->getSection(); + } + + const MCSection *SectionB = 0; + if (const MCSymbolRefExpr *B = Target.getSymB()) { + SectionB = &B->getSymbol().getSection(); + } + + if (!BaseSection) + return SectionA == SectionB; + + const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA); + if (DataA.isExternal()) + return false; + + return !SectionB && BaseSection == SectionA; } -void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, +void ELFObjectWriterImpl::WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) { + // Compute symbol table information. + ComputeSymbolTable(Asm); + CreateMetadataSections(const_cast(Asm), const_cast(Layout)); // Add 1 for the null section. unsigned NumSections = Asm.size() + 1; - - uint64_t SectionDataSize = 0; + uint64_t NaturalAlignment = Is64Bit ? 8 : 4; + uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr); + uint64_t FileOff = HeaderSize; for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) { const MCSectionData &SD = *it; + FileOff = RoundUpToAlignment(FileOff, SD.getAlignment()); + // Get the size of the section in the output file (including padding). uint64_t Size = Layout.getSectionFileSize(&SD); - SectionDataSize += Size; + + FileOff += Size; } + FileOff = RoundUpToAlignment(FileOff, NaturalAlignment); + // Write out the ELF header ... - WriteHeader(SectionDataSize, NumSections); - FileOff = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr); + WriteHeader(FileOff - HeaderSize, NumSections); + + FileOff = HeaderSize; // ... then all of the sections ... DenseMap SectionOffsetMap; @@ -861,17 +1111,25 @@ void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, unsigned Index = 1; for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it) { + const MCSectionData &SD = *it; + + uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment()); + WriteZeros(Padding); + FileOff += Padding; + // Remember the offset into the file for this section. SectionOffsetMap[&it->getSection()] = FileOff; - SectionIndexMap[&it->getSection()] = Index++; - const MCSectionData &SD = *it; FileOff += Layout.getSectionFileSize(&SD); Asm.WriteSectionData(it, Layout, Writer); } + uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment); + WriteZeros(Padding); + FileOff += Padding; + // ... and then the section header table. // Should we align the section header table? // @@ -924,6 +1182,7 @@ void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, case ELF::SHT_PROGBITS: case ELF::SHT_STRTAB: case ELF::SHT_NOBITS: + case ELF::SHT_NULL: // Nothing to do. break; @@ -937,7 +1196,7 @@ void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()], Section.getType(), Section.getFlags(), - Layout.getSectionAddress(&SD), + 0, SectionOffsetMap.lookup(&SD.getSection()), Layout.getSectionSize(&SD), sh_link, sh_info, SD.getAlignment(), @@ -947,11 +1206,12 @@ void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, ELFObjectWriter::ELFObjectWriter(raw_ostream &OS, bool Is64Bit, + Triple::OSType OSType, bool IsLittleEndian, bool HasRelocationAddend) : MCObjectWriter(OS, IsLittleEndian) { - Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend); + Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend, OSType); } ELFObjectWriter::~ELFObjectWriter() { @@ -971,7 +1231,15 @@ void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm, Target, FixedValue); } -void ELFObjectWriter::WriteObject(const MCAssembler &Asm, +bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm, + const MCValue Target, + bool IsPCRel, + const MCFragment *DF) const { + return ((ELFObjectWriterImpl*) Impl)->IsFixupFullyResolved(Asm, Target, + IsPCRel, DF); +} + +void ELFObjectWriter::WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) { ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout); }