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Diffstat (limited to 'contrib/llvm/lib/MC/MachObjectWriter.cpp')
| -rw-r--r-- | contrib/llvm/lib/MC/MachObjectWriter.cpp | 1229 |
1 files changed, 1229 insertions, 0 deletions
diff --git a/contrib/llvm/lib/MC/MachObjectWriter.cpp b/contrib/llvm/lib/MC/MachObjectWriter.cpp new file mode 100644 index 0000000..7ca0951 --- /dev/null +++ b/contrib/llvm/lib/MC/MachObjectWriter.cpp @@ -0,0 +1,1229 @@ +//===- lib/MC/MachObjectWriter.cpp - Mach-O File Writer -------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "llvm/MC/MachObjectWriter.h" +#include "llvm/ADT/StringMap.h" +#include "llvm/ADT/Twine.h" +#include "llvm/MC/MCAssembler.h" +#include "llvm/MC/MCAsmLayout.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCObjectWriter.h" +#include "llvm/MC/MCSectionMachO.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/MC/MCMachOSymbolFlags.h" +#include "llvm/MC/MCValue.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/MachO.h" +#include "llvm/Target/TargetAsmBackend.h" + +// FIXME: Gross. +#include "../Target/X86/X86FixupKinds.h" + +#include <vector> +using namespace llvm; + +static unsigned getFixupKindLog2Size(unsigned Kind) { + switch (Kind) { + default: llvm_unreachable("invalid fixup kind!"); + case X86::reloc_pcrel_1byte: + case FK_Data_1: return 0; + case X86::reloc_pcrel_2byte: + case FK_Data_2: return 1; + case X86::reloc_pcrel_4byte: + case X86::reloc_riprel_4byte: + case X86::reloc_riprel_4byte_movq_load: + case FK_Data_4: return 2; + case FK_Data_8: return 3; + } +} + +static bool isFixupKindPCRel(unsigned Kind) { + switch (Kind) { + default: + return false; + case X86::reloc_pcrel_1byte: + case X86::reloc_pcrel_2byte: + case X86::reloc_pcrel_4byte: + case X86::reloc_riprel_4byte: + case X86::reloc_riprel_4byte_movq_load: + return true; + } +} + +static bool isFixupKindRIPRel(unsigned Kind) { + return Kind == X86::reloc_riprel_4byte || + Kind == X86::reloc_riprel_4byte_movq_load; +} + +static bool doesSymbolRequireExternRelocation(MCSymbolData *SD) { + // Undefined symbols are always extern. + if (SD->Symbol->isUndefined()) + return true; + + // References to weak definitions require external relocation entries; the + // definition may not always be the one in the same object file. + if (SD->getFlags() & SF_WeakDefinition) + return true; + + // Otherwise, we can use an internal relocation. + return false; +} + +namespace { + +class MachObjectWriterImpl { + // See <mach-o/loader.h>. + enum { + Header_Magic32 = 0xFEEDFACE, + Header_Magic64 = 0xFEEDFACF + }; + + enum { + Header32Size = 28, + Header64Size = 32, + SegmentLoadCommand32Size = 56, + SegmentLoadCommand64Size = 72, + Section32Size = 68, + Section64Size = 80, + SymtabLoadCommandSize = 24, + DysymtabLoadCommandSize = 80, + Nlist32Size = 12, + Nlist64Size = 16, + RelocationInfoSize = 8 + }; + + enum HeaderFileType { + HFT_Object = 0x1 + }; + + enum HeaderFlags { + HF_SubsectionsViaSymbols = 0x2000 + }; + + enum LoadCommandType { + LCT_Segment = 0x1, + LCT_Symtab = 0x2, + LCT_Dysymtab = 0xb, + LCT_Segment64 = 0x19 + }; + + // See <mach-o/nlist.h>. + enum SymbolTypeType { + STT_Undefined = 0x00, + STT_Absolute = 0x02, + STT_Section = 0x0e + }; + + enum SymbolTypeFlags { + // If any of these bits are set, then the entry is a stab entry number (see + // <mach-o/stab.h>. Otherwise the other masks apply. + STF_StabsEntryMask = 0xe0, + + STF_TypeMask = 0x0e, + STF_External = 0x01, + STF_PrivateExtern = 0x10 + }; + + /// IndirectSymbolFlags - Flags for encoding special values in the indirect + /// symbol entry. + enum IndirectSymbolFlags { + ISF_Local = 0x80000000, + ISF_Absolute = 0x40000000 + }; + + /// RelocationFlags - Special flags for addresses. + enum RelocationFlags { + RF_Scattered = 0x80000000 + }; + + enum RelocationInfoType { + RIT_Vanilla = 0, + RIT_Pair = 1, + RIT_Difference = 2, + RIT_PreboundLazyPointer = 3, + RIT_LocalDifference = 4, + RIT_TLV = 5 + }; + + /// X86_64 uses its own relocation types. + enum RelocationInfoTypeX86_64 { + RIT_X86_64_Unsigned = 0, + RIT_X86_64_Signed = 1, + RIT_X86_64_Branch = 2, + RIT_X86_64_GOTLoad = 3, + RIT_X86_64_GOT = 4, + RIT_X86_64_Subtractor = 5, + RIT_X86_64_Signed1 = 6, + RIT_X86_64_Signed2 = 7, + RIT_X86_64_Signed4 = 8, + RIT_X86_64_TLV = 9 + }; + + /// MachSymbolData - Helper struct for containing some precomputed information + /// on symbols. + struct MachSymbolData { + MCSymbolData *SymbolData; + uint64_t StringIndex; + uint8_t SectionIndex; + + // Support lexicographic sorting. + bool operator<(const MachSymbolData &RHS) const { + return SymbolData->getSymbol().getName() < + RHS.SymbolData->getSymbol().getName(); + } + }; + + /// @name Relocation Data + /// @{ + + struct MachRelocationEntry { + uint32_t Word0; + uint32_t Word1; + }; + + llvm::DenseMap<const MCSectionData*, + std::vector<MachRelocationEntry> > Relocations; + llvm::DenseMap<const MCSectionData*, unsigned> IndirectSymBase; + + /// @} + /// @name Symbol Table Data + /// @{ + + SmallString<256> StringTable; + std::vector<MachSymbolData> LocalSymbolData; + std::vector<MachSymbolData> ExternalSymbolData; + std::vector<MachSymbolData> UndefinedSymbolData; + + /// @} + + MachObjectWriter *Writer; + + raw_ostream &OS; + + unsigned Is64Bit : 1; + +public: + MachObjectWriterImpl(MachObjectWriter *_Writer, bool _Is64Bit) + : Writer(_Writer), OS(Writer->getStream()), Is64Bit(_Is64Bit) { + } + + 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 WriteZeros(unsigned N) { Writer->WriteZeros(N); } + void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) { + Writer->WriteBytes(Str, ZeroFillSize); + } + + void WriteHeader(unsigned NumLoadCommands, unsigned LoadCommandsSize, + bool SubsectionsViaSymbols) { + uint32_t Flags = 0; + + if (SubsectionsViaSymbols) + Flags |= HF_SubsectionsViaSymbols; + + // struct mach_header (28 bytes) or + // struct mach_header_64 (32 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + Write32(Is64Bit ? Header_Magic64 : Header_Magic32); + + // FIXME: Support cputype. + Write32(Is64Bit ? MachO::CPUTypeX86_64 : MachO::CPUTypeI386); + // FIXME: Support cpusubtype. + Write32(MachO::CPUSubType_I386_ALL); + Write32(HFT_Object); + Write32(NumLoadCommands); // Object files have a single load command, the + // segment. + Write32(LoadCommandsSize); + Write32(Flags); + if (Is64Bit) + Write32(0); // reserved + + assert(OS.tell() - Start == Is64Bit ? Header64Size : Header32Size); + } + + /// WriteSegmentLoadCommand - Write a segment load command. + /// + /// \arg NumSections - The number of sections in this segment. + /// \arg SectionDataSize - The total size of the sections. + void WriteSegmentLoadCommand(unsigned NumSections, + uint64_t VMSize, + uint64_t SectionDataStartOffset, + uint64_t SectionDataSize) { + // struct segment_command (56 bytes) or + // struct segment_command_64 (72 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + unsigned SegmentLoadCommandSize = Is64Bit ? SegmentLoadCommand64Size : + SegmentLoadCommand32Size; + Write32(Is64Bit ? LCT_Segment64 : LCT_Segment); + Write32(SegmentLoadCommandSize + + NumSections * (Is64Bit ? Section64Size : Section32Size)); + + WriteBytes("", 16); + if (Is64Bit) { + Write64(0); // vmaddr + Write64(VMSize); // vmsize + Write64(SectionDataStartOffset); // file offset + Write64(SectionDataSize); // file size + } else { + Write32(0); // vmaddr + Write32(VMSize); // vmsize + Write32(SectionDataStartOffset); // file offset + Write32(SectionDataSize); // file size + } + Write32(0x7); // maxprot + Write32(0x7); // initprot + Write32(NumSections); + Write32(0); // flags + + assert(OS.tell() - Start == SegmentLoadCommandSize); + } + + void WriteSection(const MCAssembler &Asm, const MCAsmLayout &Layout, + const MCSectionData &SD, uint64_t FileOffset, + uint64_t RelocationsStart, unsigned NumRelocations) { + uint64_t SectionSize = Layout.getSectionSize(&SD); + + // The offset is unused for virtual sections. + if (Asm.getBackend().isVirtualSection(SD.getSection())) { + assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!"); + FileOffset = 0; + } + + // struct section (68 bytes) or + // struct section_64 (80 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection()); + WriteBytes(Section.getSectionName(), 16); + WriteBytes(Section.getSegmentName(), 16); + if (Is64Bit) { + Write64(Layout.getSectionAddress(&SD)); // address + Write64(SectionSize); // size + } else { + Write32(Layout.getSectionAddress(&SD)); // address + Write32(SectionSize); // size + } + Write32(FileOffset); + + unsigned Flags = Section.getTypeAndAttributes(); + if (SD.hasInstructions()) + Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS; + + assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!"); + Write32(Log2_32(SD.getAlignment())); + Write32(NumRelocations ? RelocationsStart : 0); + Write32(NumRelocations); + Write32(Flags); + Write32(IndirectSymBase.lookup(&SD)); // reserved1 + Write32(Section.getStubSize()); // reserved2 + if (Is64Bit) + Write32(0); // reserved3 + + assert(OS.tell() - Start == Is64Bit ? Section64Size : Section32Size); + } + + void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, + uint32_t StringTableOffset, + uint32_t StringTableSize) { + // struct symtab_command (24 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + Write32(LCT_Symtab); + Write32(SymtabLoadCommandSize); + Write32(SymbolOffset); + Write32(NumSymbols); + Write32(StringTableOffset); + Write32(StringTableSize); + + assert(OS.tell() - Start == SymtabLoadCommandSize); + } + + void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol, + uint32_t NumLocalSymbols, + uint32_t FirstExternalSymbol, + uint32_t NumExternalSymbols, + uint32_t FirstUndefinedSymbol, + uint32_t NumUndefinedSymbols, + uint32_t IndirectSymbolOffset, + uint32_t NumIndirectSymbols) { + // struct dysymtab_command (80 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + Write32(LCT_Dysymtab); + Write32(DysymtabLoadCommandSize); + Write32(FirstLocalSymbol); + Write32(NumLocalSymbols); + Write32(FirstExternalSymbol); + Write32(NumExternalSymbols); + Write32(FirstUndefinedSymbol); + Write32(NumUndefinedSymbols); + Write32(0); // tocoff + Write32(0); // ntoc + Write32(0); // modtaboff + Write32(0); // nmodtab + Write32(0); // extrefsymoff + Write32(0); // nextrefsyms + Write32(IndirectSymbolOffset); + Write32(NumIndirectSymbols); + Write32(0); // extreloff + Write32(0); // nextrel + Write32(0); // locreloff + Write32(0); // nlocrel + + assert(OS.tell() - Start == DysymtabLoadCommandSize); + } + + void WriteNlist(MachSymbolData &MSD, const MCAsmLayout &Layout) { + MCSymbolData &Data = *MSD.SymbolData; + const MCSymbol &Symbol = Data.getSymbol(); + uint8_t Type = 0; + uint16_t Flags = Data.getFlags(); + uint32_t Address = 0; + + // Set the N_TYPE bits. See <mach-o/nlist.h>. + // + // FIXME: Are the prebound or indirect fields possible here? + if (Symbol.isUndefined()) + Type = STT_Undefined; + else if (Symbol.isAbsolute()) + Type = STT_Absolute; + else + Type = STT_Section; + + // FIXME: Set STAB bits. + + if (Data.isPrivateExtern()) + Type |= STF_PrivateExtern; + + // Set external bit. + if (Data.isExternal() || Symbol.isUndefined()) + Type |= STF_External; + + // Compute the symbol address. + if (Symbol.isDefined()) { + if (Symbol.isAbsolute()) { + Address = cast<MCConstantExpr>(Symbol.getVariableValue())->getValue(); + } else { + Address = Layout.getSymbolAddress(&Data); + } + } else if (Data.isCommon()) { + // Common symbols are encoded with the size in the address + // field, and their alignment in the flags. + Address = Data.getCommonSize(); + + // Common alignment is packed into the 'desc' bits. + if (unsigned Align = Data.getCommonAlignment()) { + unsigned Log2Size = Log2_32(Align); + assert((1U << Log2Size) == Align && "Invalid 'common' alignment!"); + if (Log2Size > 15) + report_fatal_error("invalid 'common' alignment '" + + Twine(Align) + "'"); + // FIXME: Keep this mask with the SymbolFlags enumeration. + Flags = (Flags & 0xF0FF) | (Log2Size << 8); + } + } + + // struct nlist (12 bytes) + + Write32(MSD.StringIndex); + Write8(Type); + Write8(MSD.SectionIndex); + + // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc' + // value. + Write16(Flags); + if (Is64Bit) + Write64(Address); + else + Write32(Address); + } + + // FIXME: We really need to improve the relocation validation. Basically, we + // want to implement a separate computation which evaluates the relocation + // entry as the linker would, and verifies that the resultant fixup value is + // exactly what the encoder wanted. This will catch several classes of + // problems: + // + // - Relocation entry bugs, the two algorithms are unlikely to have the same + // exact bug. + // + // - Relaxation issues, where we forget to relax something. + // + // - Input errors, where something cannot be correctly encoded. 'as' allows + // these through in many cases. + + void RecordX86_64Relocation(const MCAssembler &Asm, const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, + uint64_t &FixedValue) { + unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind()); + unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); + unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); + + // See <reloc.h>. + uint32_t FixupOffset = + Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); + uint32_t FixupAddress = + Layout.getFragmentAddress(Fragment) + Fixup.getOffset(); + int64_t Value = 0; + unsigned Index = 0; + unsigned IsExtern = 0; + unsigned Type = 0; + + Value = Target.getConstant(); + + if (IsPCRel) { + // Compensate for the relocation offset, Darwin x86_64 relocations only + // have the addend and appear to have attempted to define it to be the + // actual expression addend without the PCrel bias. However, instructions + // with data following the relocation are not accomodated for (see comment + // below regarding SIGNED{1,2,4}), so it isn't exactly that either. + Value += 1LL << Log2Size; + } + + if (Target.isAbsolute()) { // constant + // SymbolNum of 0 indicates the absolute section. + Type = RIT_X86_64_Unsigned; + Index = 0; + + // FIXME: I believe this is broken, I don't think the linker can + // understand it. I think it would require a local relocation, but I'm not + // sure if that would work either. The official way to get an absolute + // PCrel relocation is to use an absolute symbol (which we don't support + // yet). + if (IsPCRel) { + IsExtern = 1; + Type = RIT_X86_64_Branch; + } + } else if (Target.getSymB()) { // A - B + constant + const MCSymbol *A = &Target.getSymA()->getSymbol(); + MCSymbolData &A_SD = Asm.getSymbolData(*A); + const MCSymbolData *A_Base = Asm.getAtom(Layout, &A_SD); + + const MCSymbol *B = &Target.getSymB()->getSymbol(); + MCSymbolData &B_SD = Asm.getSymbolData(*B); + const MCSymbolData *B_Base = Asm.getAtom(Layout, &B_SD); + + // Neither symbol can be modified. + if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || + Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) + report_fatal_error("unsupported relocation of modified symbol"); + + // We don't support PCrel relocations of differences. Darwin 'as' doesn't + // implement most of these correctly. + if (IsPCRel) + report_fatal_error("unsupported pc-relative relocation of difference"); + + // We don't currently support any situation where one or both of the + // symbols would require a local relocation. This is almost certainly + // unused and may not be possible to encode correctly. + if (!A_Base || !B_Base) + report_fatal_error("unsupported local relocations in difference"); + + // Darwin 'as' doesn't emit correct relocations for this (it ends up with + // a single SIGNED relocation); reject it for now. + if (A_Base == B_Base) + report_fatal_error("unsupported relocation with identical base"); + + Value += Layout.getSymbolAddress(&A_SD) - Layout.getSymbolAddress(A_Base); + Value -= Layout.getSymbolAddress(&B_SD) - Layout.getSymbolAddress(B_Base); + + Index = A_Base->getIndex(); + IsExtern = 1; + Type = RIT_X86_64_Unsigned; + + MachRelocationEntry MRE; + MRE.Word0 = FixupOffset; + MRE.Word1 = ((Index << 0) | + (IsPCRel << 24) | + (Log2Size << 25) | + (IsExtern << 27) | + (Type << 28)); + Relocations[Fragment->getParent()].push_back(MRE); + + Index = B_Base->getIndex(); + IsExtern = 1; + Type = RIT_X86_64_Subtractor; + } else { + const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); + MCSymbolData &SD = Asm.getSymbolData(*Symbol); + const MCSymbolData *Base = Asm.getAtom(Layout, &SD); + + // Relocations inside debug sections always use local relocations when + // possible. This seems to be done because the debugger doesn't fully + // understand x86_64 relocation entries, and expects to find values that + // have already been fixed up. + if (Symbol->isInSection()) { + const MCSectionMachO &Section = static_cast<const MCSectionMachO&>( + Fragment->getParent()->getSection()); + if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG)) + Base = 0; + } + + // x86_64 almost always uses external relocations, except when there is no + // symbol to use as a base address (a local symbol with no preceeding + // non-local symbol). + if (Base) { + Index = Base->getIndex(); + IsExtern = 1; + + // Add the local offset, if needed. + if (Base != &SD) + Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base); + } else if (Symbol->isInSection()) { + // The index is the section ordinal (1-based). + Index = SD.getFragment()->getParent()->getOrdinal() + 1; + IsExtern = 0; + Value += Layout.getSymbolAddress(&SD); + + if (IsPCRel) + Value -= FixupAddress + (1 << Log2Size); + } else { + report_fatal_error("unsupported relocation of undefined symbol '" + + Symbol->getName() + "'"); + } + + MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); + if (IsPCRel) { + if (IsRIPRel) { + if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { + // x86_64 distinguishes movq foo@GOTPCREL so that the linker can + // rewrite the movq to an leaq at link time if the symbol ends up in + // the same linkage unit. + if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) + Type = RIT_X86_64_GOTLoad; + else + Type = RIT_X86_64_GOT; + } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { + Type = RIT_X86_64_TLV; + } else if (Modifier != MCSymbolRefExpr::VK_None) { + report_fatal_error("unsupported symbol modifier in relocation"); + } else { + Type = RIT_X86_64_Signed; + + // The Darwin x86_64 relocation format has a problem where it cannot + // encode an address (L<foo> + <constant>) which is outside the atom + // containing L<foo>. Generally, this shouldn't occur but it does + // happen when we have a RIPrel instruction with data following the + // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel + // adjustment Darwin x86_64 uses, the offset is still negative and + // the linker has no way to recognize this. + // + // To work around this, Darwin uses several special relocation types + // to indicate the offsets. However, the specification or + // implementation of these seems to also be incomplete; they should + // adjust the addend as well based on the actual encoded instruction + // (the additional bias), but instead appear to just look at the + // final offset. + switch (-(Target.getConstant() + (1LL << Log2Size))) { + case 1: Type = RIT_X86_64_Signed1; break; + case 2: Type = RIT_X86_64_Signed2; break; + case 4: Type = RIT_X86_64_Signed4; break; + } + } + } else { + if (Modifier != MCSymbolRefExpr::VK_None) + report_fatal_error("unsupported symbol modifier in branch " + "relocation"); + + Type = RIT_X86_64_Branch; + } + } else { + if (Modifier == MCSymbolRefExpr::VK_GOT) { + Type = RIT_X86_64_GOT; + } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { + // GOTPCREL is allowed as a modifier on non-PCrel instructions, in + // which case all we do is set the PCrel bit in the relocation entry; + // this is used with exception handling, for example. The source is + // required to include any necessary offset directly. + Type = RIT_X86_64_GOT; + IsPCRel = 1; + } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { + report_fatal_error("TLVP symbol modifier should have been rip-rel"); + } else if (Modifier != MCSymbolRefExpr::VK_None) + report_fatal_error("unsupported symbol modifier in relocation"); + else + Type = RIT_X86_64_Unsigned; + } + } + + // x86_64 always writes custom values into the fixups. + FixedValue = Value; + + // struct relocation_info (8 bytes) + MachRelocationEntry MRE; + MRE.Word0 = FixupOffset; + MRE.Word1 = ((Index << 0) | + (IsPCRel << 24) | + (Log2Size << 25) | + (IsExtern << 27) | + (Type << 28)); + Relocations[Fragment->getParent()].push_back(MRE); + } + + void RecordScatteredRelocation(const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, + uint64_t &FixedValue) { + uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); + unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind()); + unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); + unsigned Type = RIT_Vanilla; + + // See <reloc.h>. + const MCSymbol *A = &Target.getSymA()->getSymbol(); + MCSymbolData *A_SD = &Asm.getSymbolData(*A); + + if (!A_SD->getFragment()) + report_fatal_error("symbol '" + A->getName() + + "' can not be undefined in a subtraction expression"); + + uint32_t Value = Layout.getSymbolAddress(A_SD); + uint32_t Value2 = 0; + + if (const MCSymbolRefExpr *B = Target.getSymB()) { + MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol()); + + if (!B_SD->getFragment()) + report_fatal_error("symbol '" + B->getSymbol().getName() + + "' can not be undefined in a subtraction expression"); + + // Select the appropriate difference relocation type. + // + // Note that there is no longer any semantic difference between these two + // relocation types from the linkers point of view, this is done solely + // for pedantic compatibility with 'as'. + Type = A_SD->isExternal() ? RIT_Difference : RIT_LocalDifference; + Value2 = Layout.getSymbolAddress(B_SD); + } + + // Relocations are written out in reverse order, so the PAIR comes first. + if (Type == RIT_Difference || Type == RIT_LocalDifference) { + MachRelocationEntry MRE; + MRE.Word0 = ((0 << 0) | + (RIT_Pair << 24) | + (Log2Size << 28) | + (IsPCRel << 30) | + RF_Scattered); + MRE.Word1 = Value2; + Relocations[Fragment->getParent()].push_back(MRE); + } + + MachRelocationEntry MRE; + MRE.Word0 = ((FixupOffset << 0) | + (Type << 24) | + (Log2Size << 28) | + (IsPCRel << 30) | + RF_Scattered); + MRE.Word1 = Value; + Relocations[Fragment->getParent()].push_back(MRE); + } + + void RecordTLVPRelocation(const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, + uint64_t &FixedValue) { + assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && + !Is64Bit && + "Should only be called with a 32-bit TLVP relocation!"); + + unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); + uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); + unsigned IsPCRel = 0; + + // Get the symbol data. + MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol()); + unsigned Index = SD_A->getIndex(); + + // We're only going to have a second symbol in pic mode and it'll be a + // subtraction from the picbase. For 32-bit pic the addend is the difference + // between the picbase and the next address. For 32-bit static the addend + // is zero. + if (Target.getSymB()) { + // If this is a subtraction then we're pcrel. + uint32_t FixupAddress = + Layout.getFragmentAddress(Fragment) + Fixup.getOffset(); + MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol()); + IsPCRel = 1; + FixedValue = (FixupAddress - Layout.getSymbolAddress(SD_B) + + Target.getConstant()); + FixedValue += 1 << Log2Size; + } else { + FixedValue = 0; + } + + // struct relocation_info (8 bytes) + MachRelocationEntry MRE; + MRE.Word0 = Value; + MRE.Word1 = ((Index << 0) | + (IsPCRel << 24) | + (Log2Size << 25) | + (1 << 27) | // Extern + (RIT_TLV << 28)); // Type + Relocations[Fragment->getParent()].push_back(MRE); + } + + void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, + const MCFragment *Fragment, const MCFixup &Fixup, + MCValue Target, uint64_t &FixedValue) { + if (Is64Bit) { + RecordX86_64Relocation(Asm, Layout, Fragment, Fixup, Target, FixedValue); + return; + } + + unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind()); + unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); + + // If this is a 32-bit TLVP reloc it's handled a bit differently. + if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) { + RecordTLVPRelocation(Asm, Layout, Fragment, Fixup, Target, FixedValue); + return; + } + + // If this is a difference or a defined symbol plus an offset, then we need + // a scattered relocation entry. + // Differences always require scattered relocations. + if (Target.getSymB()) + return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup, + Target, FixedValue); + + // Get the symbol data, if any. + MCSymbolData *SD = 0; + if (Target.getSymA()) + SD = &Asm.getSymbolData(Target.getSymA()->getSymbol()); + + // If this is an internal relocation with an offset, it also needs a + // scattered relocation entry. + uint32_t Offset = Target.getConstant(); + if (IsPCRel) + Offset += 1 << Log2Size; + if (Offset && SD && !doesSymbolRequireExternRelocation(SD)) + return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup, + Target, FixedValue); + + // See <reloc.h>. + uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); + unsigned Index = 0; + unsigned IsExtern = 0; + unsigned Type = 0; + + if (Target.isAbsolute()) { // constant + // SymbolNum of 0 indicates the absolute section. + // + // FIXME: Currently, these are never generated (see code below). I cannot + // find a case where they are actually emitted. + Type = RIT_Vanilla; + } else { + // Check whether we need an external or internal relocation. + if (doesSymbolRequireExternRelocation(SD)) { + IsExtern = 1; + Index = SD->getIndex(); + // For external relocations, make sure to offset the fixup value to + // compensate for the addend of the symbol address, if it was + // undefined. This occurs with weak definitions, for example. + if (!SD->Symbol->isUndefined()) + FixedValue -= Layout.getSymbolAddress(SD); + } else { + // The index is the section ordinal (1-based). + Index = SD->getFragment()->getParent()->getOrdinal() + 1; + } + + Type = RIT_Vanilla; + } + + // struct relocation_info (8 bytes) + MachRelocationEntry MRE; + MRE.Word0 = FixupOffset; + MRE.Word1 = ((Index << 0) | + (IsPCRel << 24) | + (Log2Size << 25) | + (IsExtern << 27) | + (Type << 28)); + Relocations[Fragment->getParent()].push_back(MRE); + } + + void BindIndirectSymbols(MCAssembler &Asm) { + // This is the point where 'as' creates actual symbols for indirect symbols + // (in the following two passes). It would be easier for us to do this + // sooner when we see the attribute, but that makes getting the order in the + // symbol table much more complicated than it is worth. + // + // FIXME: Revisit this when the dust settles. + + // Bind non lazy symbol pointers first. + unsigned IndirectIndex = 0; + for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(), + ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) { + const MCSectionMachO &Section = + cast<MCSectionMachO>(it->SectionData->getSection()); + + if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) + continue; + + // Initialize the section indirect symbol base, if necessary. + if (!IndirectSymBase.count(it->SectionData)) + IndirectSymBase[it->SectionData] = IndirectIndex; + + Asm.getOrCreateSymbolData(*it->Symbol); + } + + // Then lazy symbol pointers and symbol stubs. + IndirectIndex = 0; + for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(), + ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) { + const MCSectionMachO &Section = + cast<MCSectionMachO>(it->SectionData->getSection()); + + if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS && + Section.getType() != MCSectionMachO::S_SYMBOL_STUBS) + continue; + + // Initialize the section indirect symbol base, if necessary. + if (!IndirectSymBase.count(it->SectionData)) + IndirectSymBase[it->SectionData] = IndirectIndex; + + // Set the symbol type to undefined lazy, but only on construction. + // + // FIXME: Do not hardcode. + bool Created; + MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created); + if (Created) + Entry.setFlags(Entry.getFlags() | 0x0001); + } + } + + /// ComputeSymbolTable - Compute the symbol table data + /// + /// \param StringTable [out] - The string table data. + /// \param StringIndexMap [out] - Map from symbol names to offsets in the + /// string table. + void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable, + std::vector<MachSymbolData> &LocalSymbolData, + std::vector<MachSymbolData> &ExternalSymbolData, + std::vector<MachSymbolData> &UndefinedSymbolData) { + // Build section lookup table. + DenseMap<const MCSection*, uint8_t> SectionIndexMap; + unsigned Index = 1; + for (MCAssembler::iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it, ++Index) + SectionIndexMap[&it->getSection()] = Index; + assert(Index <= 256 && "Too many sections!"); + + // Index 0 is always the empty string. + StringMap<uint64_t> StringIndexMap; + StringTable += '\x00'; + + // Build the symbol arrays and the string table, but only for non-local + // symbols. + // + // The particular order that we collect the symbols and create the string + // table, then sort the symbols is chosen to match 'as'. Even though it + // doesn't matter for correctness, this is important for letting us diff .o + // files. + 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(it->getSymbol())) + continue; + + if (!it->isExternal() && !Symbol.isUndefined()) + continue; + + uint64_t &Entry = StringIndexMap[Symbol.getName()]; + if (!Entry) { + Entry = StringTable.size(); + StringTable += Symbol.getName(); + StringTable += '\x00'; + } + + MachSymbolData MSD; + MSD.SymbolData = it; + MSD.StringIndex = Entry; + + if (Symbol.isUndefined()) { + MSD.SectionIndex = 0; + UndefinedSymbolData.push_back(MSD); + } else if (Symbol.isAbsolute()) { + MSD.SectionIndex = 0; + ExternalSymbolData.push_back(MSD); + } else { + MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); + assert(MSD.SectionIndex && "Invalid section index!"); + ExternalSymbolData.push_back(MSD); + } + } + + // Now 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(it->getSymbol())) + continue; + + if (it->isExternal() || Symbol.isUndefined()) + continue; + + uint64_t &Entry = StringIndexMap[Symbol.getName()]; + if (!Entry) { + Entry = StringTable.size(); + StringTable += Symbol.getName(); + StringTable += '\x00'; + } + + MachSymbolData MSD; + MSD.SymbolData = it; + MSD.StringIndex = Entry; + + if (Symbol.isAbsolute()) { + MSD.SectionIndex = 0; + LocalSymbolData.push_back(MSD); + } else { + MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection()); + assert(MSD.SectionIndex && "Invalid section index!"); + LocalSymbolData.push_back(MSD); + } + } + + // External and undefined symbols are required to be in lexicographic order. + std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end()); + std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end()); + + // Set the symbol indices. + Index = 0; + for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) + LocalSymbolData[i].SymbolData->setIndex(Index++); + for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) + ExternalSymbolData[i].SymbolData->setIndex(Index++); + for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) + UndefinedSymbolData[i].SymbolData->setIndex(Index++); + + // The string table is padded to a multiple of 4. + while (StringTable.size() % 4) + StringTable += '\x00'; + } + + void ExecutePostLayoutBinding(MCAssembler &Asm) { + // Create symbol data for any indirect symbols. + BindIndirectSymbols(Asm); + + // Compute symbol table information and bind symbol indices. + ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData, + UndefinedSymbolData); + } + + void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout) { + unsigned NumSections = Asm.size(); + + // The section data starts after the header, the segment load command (and + // section headers) and the symbol table. + unsigned NumLoadCommands = 1; + uint64_t LoadCommandsSize = Is64Bit ? + SegmentLoadCommand64Size + NumSections * Section64Size : + SegmentLoadCommand32Size + NumSections * Section32Size; + + // Add the symbol table load command sizes, if used. + unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() + + UndefinedSymbolData.size(); + if (NumSymbols) { + NumLoadCommands += 2; + LoadCommandsSize += SymtabLoadCommandSize + DysymtabLoadCommandSize; + } + + // Compute the total size of the section data, as well as its file size and + // vm size. + uint64_t SectionDataStart = (Is64Bit ? Header64Size : Header32Size) + + LoadCommandsSize; + uint64_t SectionDataSize = 0; + uint64_t SectionDataFileSize = 0; + uint64_t VMSize = 0; + for (MCAssembler::const_iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it) { + const MCSectionData &SD = *it; + uint64_t Address = Layout.getSectionAddress(&SD); + uint64_t Size = Layout.getSectionSize(&SD); + uint64_t FileSize = Layout.getSectionFileSize(&SD); + + VMSize = std::max(VMSize, Address + Size); + + if (Asm.getBackend().isVirtualSection(SD.getSection())) + continue; + + SectionDataSize = std::max(SectionDataSize, Address + Size); + SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize); + } + + // The section data is padded to 4 bytes. + // + // FIXME: Is this machine dependent? + unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4); + SectionDataFileSize += SectionDataPadding; + + // Write the prolog, starting with the header and load command... + WriteHeader(NumLoadCommands, LoadCommandsSize, + Asm.getSubsectionsViaSymbols()); + WriteSegmentLoadCommand(NumSections, VMSize, + SectionDataStart, SectionDataSize); + + // ... and then the section headers. + uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize; + for (MCAssembler::const_iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it) { + std::vector<MachRelocationEntry> &Relocs = Relocations[it]; + unsigned NumRelocs = Relocs.size(); + uint64_t SectionStart = SectionDataStart + Layout.getSectionAddress(it); + WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs); + RelocTableEnd += NumRelocs * RelocationInfoSize; + } + + // Write the symbol table load command, if used. + if (NumSymbols) { + unsigned FirstLocalSymbol = 0; + unsigned NumLocalSymbols = LocalSymbolData.size(); + unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols; + unsigned NumExternalSymbols = ExternalSymbolData.size(); + unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols; + unsigned NumUndefinedSymbols = UndefinedSymbolData.size(); + unsigned NumIndirectSymbols = Asm.indirect_symbol_size(); + unsigned NumSymTabSymbols = + NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols; + uint64_t IndirectSymbolSize = NumIndirectSymbols * 4; + uint64_t IndirectSymbolOffset = 0; + + // If used, the indirect symbols are written after the section data. + if (NumIndirectSymbols) + IndirectSymbolOffset = RelocTableEnd; + + // The symbol table is written after the indirect symbol data. + uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize; + + // The string table is written after symbol table. + uint64_t StringTableOffset = + SymbolTableOffset + NumSymTabSymbols * (Is64Bit ? Nlist64Size : + Nlist32Size); + WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols, + StringTableOffset, StringTable.size()); + + WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols, + FirstExternalSymbol, NumExternalSymbols, + FirstUndefinedSymbol, NumUndefinedSymbols, + IndirectSymbolOffset, NumIndirectSymbols); + } + + // Write the actual section data. + for (MCAssembler::const_iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it) + Asm.WriteSectionData(it, Layout, Writer); + + // Write the extra padding. + WriteZeros(SectionDataPadding); + + // Write the relocation entries. + for (MCAssembler::const_iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it) { + // Write the section relocation entries, in reverse order to match 'as' + // (approximately, the exact algorithm is more complicated than this). + std::vector<MachRelocationEntry> &Relocs = Relocations[it]; + for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { + Write32(Relocs[e - i - 1].Word0); + Write32(Relocs[e - i - 1].Word1); + } + } + + // Write the symbol table data, if used. + if (NumSymbols) { + // Write the indirect symbol entries. + for (MCAssembler::const_indirect_symbol_iterator + it = Asm.indirect_symbol_begin(), + ie = Asm.indirect_symbol_end(); it != ie; ++it) { + // Indirect symbols in the non lazy symbol pointer section have some + // special handling. + const MCSectionMachO &Section = + static_cast<const MCSectionMachO&>(it->SectionData->getSection()); + if (Section.getType() == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) { + // If this symbol is defined and internal, mark it as such. + if (it->Symbol->isDefined() && + !Asm.getSymbolData(*it->Symbol).isExternal()) { + uint32_t Flags = ISF_Local; + if (it->Symbol->isAbsolute()) + Flags |= ISF_Absolute; + Write32(Flags); + continue; + } + } + + Write32(Asm.getSymbolData(*it->Symbol).getIndex()); + } + + // FIXME: Check that offsets match computed ones. + + // Write the symbol table entries. + for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) + WriteNlist(LocalSymbolData[i], Layout); + for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) + WriteNlist(ExternalSymbolData[i], Layout); + for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) + WriteNlist(UndefinedSymbolData[i], Layout); + + // Write the string table. + OS << StringTable.str(); + } + } +}; + +} + +MachObjectWriter::MachObjectWriter(raw_ostream &OS, + bool Is64Bit, + bool IsLittleEndian) + : MCObjectWriter(OS, IsLittleEndian) +{ + Impl = new MachObjectWriterImpl(this, Is64Bit); +} + +MachObjectWriter::~MachObjectWriter() { + delete (MachObjectWriterImpl*) Impl; +} + +void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) { + ((MachObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm); +} + +void MachObjectWriter::RecordRelocation(const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, + uint64_t &FixedValue) { + ((MachObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup, + Target, FixedValue); +} + +void MachObjectWriter::WriteObject(const MCAssembler &Asm, + const MCAsmLayout &Layout) { + ((MachObjectWriterImpl*) Impl)->WriteObject(Asm, Layout); +} |
