diff options
Diffstat (limited to 'contrib/llvm/lib/MC/MachObjectWriter.cpp')
| -rw-r--r-- | contrib/llvm/lib/MC/MachObjectWriter.cpp | 958 |
1 files changed, 958 insertions, 0 deletions
diff --git a/contrib/llvm/lib/MC/MachObjectWriter.cpp b/contrib/llvm/lib/MC/MachObjectWriter.cpp new file mode 100644 index 000000000000..8234affc54da --- /dev/null +++ b/contrib/llvm/lib/MC/MachObjectWriter.cpp @@ -0,0 +1,958 @@ +//===- 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/MCMachObjectWriter.h" +#include "llvm/ADT/StringMap.h" +#include "llvm/ADT/Twine.h" +#include "llvm/MC/MCAsmBackend.h" +#include "llvm/MC/MCAsmLayout.h" +#include "llvm/MC/MCAssembler.h" +#include "llvm/MC/MCExpr.h" +#include "llvm/MC/MCFixupKindInfo.h" +#include "llvm/MC/MCMachOSymbolFlags.h" +#include "llvm/MC/MCObjectWriter.h" +#include "llvm/MC/MCSectionMachO.h" +#include "llvm/MC/MCSymbol.h" +#include "llvm/MC/MCValue.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/MachO.h" +#include <vector> +using namespace llvm; + +void MachObjectWriter::reset() { + Relocations.clear(); + IndirectSymBase.clear(); + StringTable.clear(); + LocalSymbolData.clear(); + ExternalSymbolData.clear(); + UndefinedSymbolData.clear(); + MCObjectWriter::reset(); +} + +bool MachObjectWriter:: +doesSymbolRequireExternRelocation(const 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; +} + +bool MachObjectWriter:: +MachSymbolData::operator<(const MachSymbolData &RHS) const { + return SymbolData->getSymbol().getName() < + RHS.SymbolData->getSymbol().getName(); +} + +bool MachObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) { + const MCFixupKindInfo &FKI = Asm.getBackend().getFixupKindInfo( + (MCFixupKind) Kind); + + return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel; +} + +uint64_t MachObjectWriter::getFragmentAddress(const MCFragment *Fragment, + const MCAsmLayout &Layout) const { + return getSectionAddress(Fragment->getParent()) + + Layout.getFragmentOffset(Fragment); +} + +uint64_t MachObjectWriter::getSymbolAddress(const MCSymbolData* SD, + const MCAsmLayout &Layout) const { + const MCSymbol &S = SD->getSymbol(); + + // If this is a variable, then recursively evaluate now. + if (S.isVariable()) { + if (const MCConstantExpr *C = + dyn_cast<const MCConstantExpr>(S.getVariableValue())) + return C->getValue(); + + + MCValue Target; + if (!S.getVariableValue()->EvaluateAsRelocatable(Target, Layout)) + report_fatal_error("unable to evaluate offset for variable '" + + S.getName() + "'"); + + // Verify that any used symbols are defined. + if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined()) + report_fatal_error("unable to evaluate offset to undefined symbol '" + + Target.getSymA()->getSymbol().getName() + "'"); + if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined()) + report_fatal_error("unable to evaluate offset to undefined symbol '" + + Target.getSymB()->getSymbol().getName() + "'"); + + uint64_t Address = Target.getConstant(); + if (Target.getSymA()) + Address += getSymbolAddress(&Layout.getAssembler().getSymbolData( + Target.getSymA()->getSymbol()), Layout); + if (Target.getSymB()) + Address += getSymbolAddress(&Layout.getAssembler().getSymbolData( + Target.getSymB()->getSymbol()), Layout); + return Address; + } + + return getSectionAddress(SD->getFragment()->getParent()) + + Layout.getSymbolOffset(SD); +} + +uint64_t MachObjectWriter::getPaddingSize(const MCSectionData *SD, + const MCAsmLayout &Layout) const { + uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD); + unsigned Next = SD->getLayoutOrder() + 1; + if (Next >= Layout.getSectionOrder().size()) + return 0; + + const MCSectionData &NextSD = *Layout.getSectionOrder()[Next]; + if (NextSD.getSection().isVirtualSection()) + return 0; + return OffsetToAlignment(EndAddr, NextSD.getAlignment()); +} + +void MachObjectWriter::WriteHeader(unsigned NumLoadCommands, + unsigned LoadCommandsSize, + bool SubsectionsViaSymbols) { + uint32_t Flags = 0; + + if (SubsectionsViaSymbols) + Flags |= MachO::MH_SUBSECTIONS_VIA_SYMBOLS; + + // struct mach_header (28 bytes) or + // struct mach_header_64 (32 bytes) + + uint64_t Start = OS.tell(); + (void) Start; + + Write32(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC); + + Write32(TargetObjectWriter->getCPUType()); + Write32(TargetObjectWriter->getCPUSubtype()); + + Write32(MachO::MH_OBJECT); + Write32(NumLoadCommands); + Write32(LoadCommandsSize); + Write32(Flags); + if (is64Bit()) + Write32(0); // reserved + + assert(OS.tell() - Start == + (is64Bit()?sizeof(MachO::mach_header_64): sizeof(MachO::mach_header))); +} + +/// WriteSegmentLoadCommand - Write a segment load command. +/// +/// \param NumSections The number of sections in this segment. +/// \param SectionDataSize The total size of the sections. +void MachObjectWriter::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() ? sizeof(MachO::segment_command_64): + sizeof(MachO::segment_command); + Write32(is64Bit() ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT); + Write32(SegmentLoadCommandSize + + NumSections * (is64Bit() ? sizeof(MachO::section_64) : + sizeof(MachO::section))); + + 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 + } + // maxprot + Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE); + // initprot + Write32(MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE); + Write32(NumSections); + Write32(0); // flags + + assert(OS.tell() - Start == SegmentLoadCommandSize); +} + +void MachObjectWriter::WriteSection(const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCSectionData &SD, + uint64_t FileOffset, + uint64_t RelocationsStart, + unsigned NumRelocations) { + uint64_t SectionSize = Layout.getSectionAddressSize(&SD); + + // The offset is unused for virtual sections. + if (SD.getSection().isVirtualSection()) { + 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(getSectionAddress(&SD)); // address + Write64(SectionSize); // size + } else { + Write32(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() ? sizeof(MachO::section_64) : + sizeof(MachO::section))); +} + +void MachObjectWriter::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(MachO::LC_SYMTAB); + Write32(sizeof(MachO::symtab_command)); + Write32(SymbolOffset); + Write32(NumSymbols); + Write32(StringTableOffset); + Write32(StringTableSize); + + assert(OS.tell() - Start == sizeof(MachO::symtab_command)); +} + +void MachObjectWriter::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(MachO::LC_DYSYMTAB); + Write32(sizeof(MachO::dysymtab_command)); + 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 == sizeof(MachO::dysymtab_command)); +} + +void MachObjectWriter::WriteNlist(MachSymbolData &MSD, + const MCAsmLayout &Layout) { + MCSymbolData &Data = *MSD.SymbolData; + const MCSymbol &Symbol = Data.getSymbol(); + uint8_t Type = 0; + uint16_t Flags = Data.getFlags(); + uint64_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 = MachO::N_UNDF; + else if (Symbol.isAbsolute()) + Type = MachO::N_ABS; + else + Type = MachO::N_SECT; + + // FIXME: Set STAB bits. + + if (Data.isPrivateExtern()) + Type |= MachO::N_PEXT; + + // Set external bit. + if (Data.isExternal() || Symbol.isUndefined()) + Type |= MachO::N_EXT; + + // Compute the symbol address. + if (Symbol.isDefined()) { + Address = getSymbolAddress(&Data, Layout); + } 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) + "' for '" + Symbol.getName() + "'", + false); + // 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); +} + +void MachObjectWriter::WriteLinkeditLoadCommand(uint32_t Type, + uint32_t DataOffset, + uint32_t DataSize) { + uint64_t Start = OS.tell(); + (void) Start; + + Write32(Type); + Write32(sizeof(MachO::linkedit_data_command)); + Write32(DataOffset); + Write32(DataSize); + + assert(OS.tell() - Start == sizeof(MachO::linkedit_data_command)); +} + +static unsigned ComputeLinkerOptionsLoadCommandSize( + const std::vector<std::string> &Options, bool is64Bit) +{ + unsigned Size = sizeof(MachO::linker_options_command); + for (unsigned i = 0, e = Options.size(); i != e; ++i) + Size += Options[i].size() + 1; + return RoundUpToAlignment(Size, is64Bit ? 8 : 4); +} + +void MachObjectWriter::WriteLinkerOptionsLoadCommand( + const std::vector<std::string> &Options) +{ + unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit()); + uint64_t Start = OS.tell(); + (void) Start; + + Write32(MachO::LC_LINKER_OPTIONS); + Write32(Size); + Write32(Options.size()); + uint64_t BytesWritten = sizeof(MachO::linker_options_command); + for (unsigned i = 0, e = Options.size(); i != e; ++i) { + // Write each string, including the null byte. + const std::string &Option = Options[i]; + WriteBytes(Option.c_str(), Option.size() + 1); + BytesWritten += Option.size() + 1; + } + + // Pad to a multiple of the pointer size. + WriteBytes("", OffsetToAlignment(BytesWritten, is64Bit() ? 8 : 4)); + + assert(OS.tell() - Start == Size); +} + + +void MachObjectWriter::RecordRelocation(const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, + MCValue Target, + uint64_t &FixedValue) { + TargetObjectWriter->RecordRelocation(this, Asm, Layout, Fragment, Fixup, + Target, FixedValue); +} + +void MachObjectWriter::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. + + // Report errors for use of .indirect_symbol not in a symbol pointer section + // or stub section. + for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(), + ie = Asm.indirect_symbol_end(); it != ie; ++it) { + const MCSectionMachO &Section = + cast<MCSectionMachO>(it->SectionData->getSection()); + + if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS && + Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS && + Section.getType() != MCSectionMachO::S_SYMBOL_STUBS) { + MCSymbol &Symbol = *it->Symbol; + report_fatal_error("indirect symbol '" + Symbol.getName() + + "' not in a symbol pointer or stub section"); + } + } + + // 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. + IndirectSymBase.insert(std::make_pair(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. + IndirectSymBase.insert(std::make_pair(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 MachObjectWriter:: +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 MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm, + const MCAsmLayout &Layout) { + uint64_t StartAddress = 0; + const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder(); + for (int i = 0, n = Order.size(); i != n ; ++i) { + const MCSectionData *SD = Order[i]; + StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment()); + SectionAddress[SD] = StartAddress; + StartAddress += Layout.getSectionAddressSize(SD); + + // Explicitly pad the section to match the alignment requirements of the + // following one. This is for 'gas' compatibility, it shouldn't + /// strictly be necessary. + StartAddress += getPaddingSize(SD, Layout); + } +} + +void MachObjectWriter::markAbsoluteVariableSymbols(MCAssembler &Asm, + const MCAsmLayout &Layout) { + for (MCAssembler::symbol_iterator i = Asm.symbol_begin(), + e = Asm.symbol_end(); + i != e; ++i) { + MCSymbolData &SD = *i; + if (!SD.getSymbol().isVariable()) + continue; + + // Is the variable is a symbol difference (SA - SB + C) expression, + // and neither symbol is external, mark the variable as absolute. + const MCExpr *Expr = SD.getSymbol().getVariableValue(); + MCValue Value; + if (Expr->EvaluateAsRelocatable(Value, Layout)) { + if (Value.getSymA() && Value.getSymB()) + const_cast<MCSymbol*>(&SD.getSymbol())->setAbsolute(); + } + } +} + +void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, + const MCAsmLayout &Layout) { + computeSectionAddresses(Asm, Layout); + + // Create symbol data for any indirect symbols. + BindIndirectSymbols(Asm); + + // Mark symbol difference expressions in variables (from .set or = directives) + // as absolute. + markAbsoluteVariableSymbols(Asm, Layout); + + // Compute symbol table information and bind symbol indices. + ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData, + UndefinedSymbolData); +} + +bool MachObjectWriter:: +IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, + const MCSymbolData &DataA, + const MCFragment &FB, + bool InSet, + bool IsPCRel) const { + if (InSet) + return true; + + // The effective address is + // addr(atom(A)) + offset(A) + // - addr(atom(B)) - offset(B) + // and the offsets are not relocatable, so the fixup is fully resolved when + // addr(atom(A)) - addr(atom(B)) == 0. + const MCSymbolData *A_Base = 0, *B_Base = 0; + + const MCSymbol &SA = DataA.getSymbol().AliasedSymbol(); + const MCSection &SecA = SA.getSection(); + const MCSection &SecB = FB.getParent()->getSection(); + + if (IsPCRel) { + // The simple (Darwin, except on x86_64) way of dealing with this was to + // assume that any reference to a temporary symbol *must* be a temporary + // symbol in the same atom, unless the sections differ. Therefore, any PCrel + // relocation to a temporary symbol (in the same section) is fully + // resolved. This also works in conjunction with absolutized .set, which + // requires the compiler to use .set to absolutize the differences between + // symbols which the compiler knows to be assembly time constants, so we + // don't need to worry about considering symbol differences fully resolved. + // + // If the file isn't using sub-sections-via-symbols, we can make the + // same assumptions about any symbol that we normally make about + // assembler locals. + + if (!Asm.getBackend().hasReliableSymbolDifference()) { + if (!SA.isInSection() || &SecA != &SecB || + (!SA.isTemporary() && + FB.getAtom() != Asm.getSymbolData(SA).getFragment()->getAtom() && + Asm.getSubsectionsViaSymbols())) + return false; + return true; + } + // For Darwin x86_64, there is one special case when the reference IsPCRel. + // If the fragment with the reference does not have a base symbol but meets + // the simple way of dealing with this, in that it is a temporary symbol in + // the same atom then it is assumed to be fully resolved. This is needed so + // a relocation entry is not created and so the static linker does not + // mess up the reference later. + else if(!FB.getAtom() && + SA.isTemporary() && SA.isInSection() && &SecA == &SecB){ + return true; + } + } else { + if (!TargetObjectWriter->useAggressiveSymbolFolding()) + return false; + } + + const MCFragment *FA = Asm.getSymbolData(SA).getFragment(); + + // Bail if the symbol has no fragment. + if (!FA) + return false; + + A_Base = FA->getAtom(); + if (!A_Base) + return false; + + B_Base = FB.getAtom(); + if (!B_Base) + return false; + + // If the atoms are the same, they are guaranteed to have the same address. + if (A_Base == B_Base) + return true; + + // Otherwise, we can't prove this is fully resolved. + return false; +} + +void MachObjectWriter::WriteObject(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() ? + sizeof(MachO::segment_command_64) + NumSections * sizeof(MachO::section_64): + sizeof(MachO::segment_command) + NumSections * sizeof(MachO::section); + + // Add the data-in-code load command size, if used. + unsigned NumDataRegions = Asm.getDataRegions().size(); + if (NumDataRegions) { + ++NumLoadCommands; + LoadCommandsSize += sizeof(MachO::linkedit_data_command); + } + + // Add the symbol table load command sizes, if used. + unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() + + UndefinedSymbolData.size(); + if (NumSymbols) { + NumLoadCommands += 2; + LoadCommandsSize += (sizeof(MachO::symtab_command) + + sizeof(MachO::dysymtab_command)); + } + + // Add the linker option load commands sizes. + const std::vector<std::vector<std::string> > &LinkerOptions = + Asm.getLinkerOptions(); + for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) { + ++NumLoadCommands; + LoadCommandsSize += ComputeLinkerOptionsLoadCommandSize(LinkerOptions[i], + is64Bit()); + } + + // Compute the total size of the section data, as well as its file size and vm + // size. + uint64_t SectionDataStart = (is64Bit() ? sizeof(MachO::mach_header_64) : + sizeof(MachO::mach_header)) + 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 = getSectionAddress(&SD); + uint64_t Size = Layout.getSectionAddressSize(&SD); + uint64_t FileSize = Layout.getSectionFileSize(&SD); + FileSize += getPaddingSize(&SD, Layout); + + VMSize = std::max(VMSize, Address + Size); + + if (SD.getSection().isVirtualSection()) + 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<MachO::any_relocation_info> &Relocs = Relocations[it]; + unsigned NumRelocs = Relocs.size(); + uint64_t SectionStart = SectionDataStart + getSectionAddress(it); + WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs); + RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info); + } + + // Write the data-in-code load command, if used. + uint64_t DataInCodeTableEnd = RelocTableEnd + NumDataRegions * 8; + if (NumDataRegions) { + uint64_t DataRegionsOffset = RelocTableEnd; + uint64_t DataRegionsSize = NumDataRegions * 8; + WriteLinkeditLoadCommand(MachO::LC_DATA_IN_CODE, DataRegionsOffset, + DataRegionsSize); + } + + // 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 = DataInCodeTableEnd; + + // The symbol table is written after the indirect symbol data. + uint64_t SymbolTableOffset = DataInCodeTableEnd + IndirectSymbolSize; + + // The string table is written after symbol table. + uint64_t StringTableOffset = + SymbolTableOffset + NumSymTabSymbols * (is64Bit() ? + sizeof(MachO::nlist_64) : + sizeof(MachO::nlist)); + WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols, + StringTableOffset, StringTable.size()); + + WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols, + FirstExternalSymbol, NumExternalSymbols, + FirstUndefinedSymbol, NumUndefinedSymbols, + IndirectSymbolOffset, NumIndirectSymbols); + } + + // Write the linker options load commands. + for (unsigned i = 0, e = LinkerOptions.size(); i != e; ++i) { + WriteLinkerOptionsLoadCommand(LinkerOptions[i]); + } + + // Write the actual section data. + for (MCAssembler::const_iterator it = Asm.begin(), + ie = Asm.end(); it != ie; ++it) { + Asm.writeSectionData(it, Layout); + + uint64_t Pad = getPaddingSize(it, Layout); + for (unsigned int i = 0; i < Pad; ++i) + Write8(0); + } + + // 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<MachO::any_relocation_info> &Relocs = Relocations[it]; + for (unsigned i = 0, e = Relocs.size(); i != e; ++i) { + Write32(Relocs[e - i - 1].r_word0); + Write32(Relocs[e - i - 1].r_word1); + } + } + + // Write out the data-in-code region payload, if there is one. + for (MCAssembler::const_data_region_iterator + it = Asm.data_region_begin(), ie = Asm.data_region_end(); + it != ie; ++it) { + const DataRegionData *Data = &(*it); + uint64_t Start = + getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->Start), + Layout); + uint64_t End = + getSymbolAddress(&Layout.getAssembler().getSymbolData(*Data->End), + Layout); + DEBUG(dbgs() << "data in code region-- kind: " << Data->Kind + << " start: " << Start << "(" << Data->Start->getName() << ")" + << " end: " << End << "(" << Data->End->getName() << ")" + << " size: " << End - Start + << "\n"); + Write32(Start); + Write16(End - Start); + Write16(Data->Kind); + } + + // 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 = MachO::INDIRECT_SYMBOL_LOCAL; + if (it->Symbol->isAbsolute()) + Flags |= MachO::INDIRECT_SYMBOL_ABS; + 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(); + } +} + +MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW, + raw_ostream &OS, + bool IsLittleEndian) { + return new MachObjectWriter(MOTW, OS, IsLittleEndian); +} |