X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FMC%2FELFObjectWriter.cpp;h=d249c92dad594557f4605331eba89ace27c9cdaa;hb=138abae2a2149b2bda3c5e28d3c4db97e3c82663;hp=94251d76b285edf8cdfca8e08bc0b3810f89259b;hpb=7070387f08f7dc797b554ed8013cba9f8b74121a;p=oota-llvm.git diff --git a/lib/MC/ELFObjectWriter.cpp b/lib/MC/ELFObjectWriter.cpp index 94251d76b28..d249c92dad5 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" @@ -57,21 +58,40 @@ static void SetBinding(MCSymbolData &SD, unsigned Binding) { SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift)); } +static unsigned GetVisibility(MCSymbolData &SD) { + unsigned Visibility = + (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift; + assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL || + Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED); + return Visibility; +} + +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) { return Kind == X86::reloc_riprel_4byte || Kind == X86::reloc_riprel_4byte_movq_load; @@ -102,7 +122,9 @@ 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. @@ -111,6 +133,8 @@ namespace { } }; + SmallPtrSet UsedInReloc; + llvm::DenseMap > Relocations; DenseMap SectionStringTableIndex; @@ -126,6 +150,10 @@ namespace { /// @} + int NumRegularSections; + + bool NeedsGOT; + ELFObjectWriter *Writer; raw_ostream &OS; @@ -146,7 +174,7 @@ 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) { } @@ -262,8 +290,6 @@ 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, @@ -279,7 +305,7 @@ namespace { bool IsPCRel, const MCFragment *DF) const; - void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout); + void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout); }; } @@ -409,11 +435,30 @@ static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) { return 0; } +static const MCSymbol &AliasedSymbol(const MCSymbol &Symbol) { + const MCSymbol *S = &Symbol; + while (S->isVariable()) { + const MCExpr *Value = S->getVariableValue(); + assert (Value->getKind() == MCExpr::SymbolRef && "Unimplemented"); + const MCSymbolRefExpr *Ref = static_cast(Value); + S = &Ref->getSymbol(); + } + return *S; +} + 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); + MCSymbolData &OrigData = *MSD.SymbolData; + MCSymbolData &Data = + Layout.getAssembler().getSymbolData(AliasedSymbol(OrigData.getSymbol())); + + uint8_t Binding = GetBinding(OrigData); + uint8_t Visibility = GetVisibility(OrigData); + uint8_t Type = GetType(Data); + + uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift); + uint8_t Other = Visibility; + uint64_t Value = SymbolValue(Data, Layout); uint64_t Size = 0; const MCExpr *ESize; @@ -427,12 +472,22 @@ 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); + } + + if (SymB.isDefined()) { + MCSymbolData &B = Layout.getAssembler().getSymbolData(SymB); + AddressB = Layout.getSymbolAddress(&B); + } - Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B); + Size = AddressA - AddressB; } } else if (ESize->getKind() == MCExpr::Constant) { Size = static_cast(ESize)->getValue(); @@ -484,8 +539,9 @@ 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++; @@ -500,11 +556,31 @@ void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F, } } -static const MCSymbolData *getAtom(const MCSymbolData &SD) { - if (!SD.getFragment()) - return 0; +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; - return SD.getFragment()->getAtom(); + 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 @@ -515,79 +591,101 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, MCValue Target, uint64_t &FixedValue) { int64_t Addend = 0; - unsigned Index = 0; + 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 = &AliasedSymbol(Target.getSymA()->getSymbol()); MCSymbolData &SD = Asm.getSymbolData(*Symbol); - const MCSymbolData *Base = getAtom(SD); MCFragment *F = SD.getFragment(); - // Avoid relocations for cases like jumps and calls in the same file. + 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()) { - uint64_t FixupAddr = Layout.getFragmentAddress(Fragment) + Fixup.getOffset(); - FixedValue = Layout.getSymbolAddress(&SD) + Target.getConstant() - FixupAddr; + llvm_unreachable("We don't need a relocation in this case."); return; } - if (Base) { - if (Base != &SD) { - Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1; - - MCSectionData *FSD = F->getParent(); - // Offset of the symbol in the section - Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD); - } else - Index = getSymbolIndexInSymbolTable(Asm, Symbol); - Addend = Value; - // Compensate for the addend on i386. - if (Is64Bit) - Value = 0; + 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 { - 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 - Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD); - } else { - Index = getSymbolIndexInSymbolTable(Asm, Symbol); - } - Addend = Value; - // Compensate for the addend on i386. - if (Is64Bit) - Value = 0; + 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 (Target.getConstant() < 0) { - assert(isInt<32>(Target.getConstant())); + assert(isInt<32>(Target.getConstant())); + switch (Modifier) { + case MCSymbolRefExpr::VK_None: Type = ELF::R_X86_64_32S; - } else { - assert(isUInt<32>(Target.getConstant())); - 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: case FK_Data_1: Type = ELF::R_X86_64_8; break; @@ -599,6 +697,10 @@ 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; @@ -608,17 +710,14 @@ void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm, } } + 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 = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); @@ -640,12 +739,44 @@ ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm, return SD.getIndex() + /* empty symbol */ 1; // External or undefined symbol. - return SD.getIndex() + Asm.size() + /* empty symbol */ 1; + 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. - DenseMap SectionIndexMap; + NumRegularSections = Asm.size(); + DenseMap SectionIndexMap; unsigned Index = 1; for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it, ++Index) @@ -655,82 +786,61 @@ void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) { StringMap StringIndexMap; StringTable += '\x00'; - // Add the data for local symbols. - for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), - 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()) - continue; - - uint64_t &Entry = StringIndexMap[Symbol.getName()]; - if (!Entry) { - Entry = StringTable.size(); - StringTable += Symbol.getName(); - StringTable += '\x00'; - } - - ELFSymbolData MSD; - MSD.SymbolData = it; - MSD.StringIndex = Entry; - - if (Symbol.isAbsolute()) { - MSD.SectionIndex = ELF::SHN_ABS; - LocalSymbolData.push_back(MSD); - } else { - MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); - assert(MSD.SectionIndex && "Invalid section index!"); - LocalSymbolData.push_back(MSD); - } - } - - // Now add non-local symbols. + // Add the data for the symbols. for (MCAssembler::symbol_iterator it = Asm.symbol_begin(), ie = Asm.symbol_end(); it != ie; ++it) { const MCSymbol &Symbol = it->getSymbol(); - // Ignore non-linker visible symbols. - if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined()) - continue; - - if (!it->isExternal() && !Symbol.isUndefined()) - continue; - - if (Symbol.isVariable()) + if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol))) continue; - uint64_t &Entry = StringIndexMap[Symbol.getName()]; - if (!Entry) { - Entry = StringTable.size(); - StringTable += Symbol.getName(); - StringTable += '\x00'; - } - ELFSymbolData MSD; MSD.SymbolData = it; - MSD.StringIndex = Entry; + bool Local = isLocal(*it); + bool Add = false; if (it->isCommon()) { + assert(!Local); MSD.SectionIndex = ELF::SHN_COMMON; - ExternalSymbolData.push_back(MSD); + Add = true; + } else if (Symbol.isAbsolute()) { + MSD.SectionIndex = ELF::SHN_ABS; + Add = true; + } else if (Symbol.isVariable()) { + const MCSymbol &RefSymbol = AliasedSymbol(Symbol); + if (RefSymbol.isDefined()) { + MSD.SectionIndex = SectionIndexMap.lookup(&RefSymbol.getSection()); + assert(MSD.SectionIndex && "Invalid section index!"); + Add = true; + } } else if (Symbol.isUndefined()) { + assert(!Local); MSD.SectionIndex = ELF::SHN_UNDEF; // 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); + Add = true; } else { MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); assert(MSD.SectionIndex && "Invalid section index!"); - ExternalSymbolData.push_back(MSD); + Add = true; + } + + if (Add) { + uint64_t &Entry = StringIndexMap[Symbol.getName()]; + if (!Entry) { + Entry = StringTable.size(); + StringTable += Symbol.getName(); + StringTable += '\x00'; + } + MSD.StringIndex = Entry; + if (MSD.SectionIndex == ELF::SHN_UNDEF) + UndefinedSymbolData.push_back(MSD); + else if (Local) + LocalSymbolData.push_back(MSD); + else + ExternalSymbolData.push_back(MSD); } } @@ -812,13 +922,19 @@ void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm, for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { ELFRelocationEntry entry = Relocs[e - i - 1]; + if (entry.Index < 0) + entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol); + else + entry.Index += LocalSymbolData.size() + 1; if (Is64Bit) { char buf[8]; String64(buf, entry.r_offset); F->getContents() += StringRef(buf, 8); - String64(buf, entry.r_info); + struct ELF::Elf64_Rela ERE64; + ERE64.setSymbolAndType(entry.Index, entry.Type); + String64(buf, ERE64.r_info); F->getContents() += StringRef(buf, 8); if (HasRelocationAddend) { @@ -831,7 +947,9 @@ void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm, String32(buf, entry.r_offset); F->getContents() += StringRef(buf, 4); - String32(buf, entry.r_info); + struct ELF::Elf32_Rela ERE32; + ERE32.setSymbolAndType(entry.Index, entry.Type); + String32(buf, ERE32.r_info); F->getContents() += StringRef(buf, 4); if (HasRelocationAddend) { @@ -945,8 +1063,11 @@ bool ELFObjectWriterImpl::IsFixupFullyResolved(const MCAssembler &Asm, 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)); @@ -978,7 +1099,7 @@ void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm, // ... then all of the sections ... DenseMap SectionOffsetMap; - DenseMap SectionIndexMap; + DenseMap SectionIndexMap; unsigned Index = 1; for (MCAssembler::const_iterator it = Asm.begin(), @@ -1111,7 +1232,7 @@ bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm, IsPCRel, DF); } -void ELFObjectWriter::WriteObject(const MCAssembler &Asm, +void ELFObjectWriter::WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) { ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout); }