| //===- lib/MC/MachObjectWriter.cpp - Mach-O File Writer -------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/ADT/iterator_range.h" |
| #include "llvm/BinaryFormat/MachO.h" |
| #include "llvm/MC/MCAsmBackend.h" |
| #include "llvm/MC/MCAsmLayout.h" |
| #include "llvm/MC/MCAssembler.h" |
| #include "llvm/MC/MCContext.h" |
| #include "llvm/MC/MCDirectives.h" |
| #include "llvm/MC/MCExpr.h" |
| #include "llvm/MC/MCFixupKindInfo.h" |
| #include "llvm/MC/MCFragment.h" |
| #include "llvm/MC/MCMachObjectWriter.h" |
| #include "llvm/MC/MCObjectWriter.h" |
| #include "llvm/MC/MCSection.h" |
| #include "llvm/MC/MCSectionMachO.h" |
| #include "llvm/MC/MCSymbol.h" |
| #include "llvm/MC/MCSymbolMachO.h" |
| #include "llvm/MC/MCValue.h" |
| #include "llvm/Support/Alignment.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <cstdint> |
| #include <string> |
| #include <utility> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "mc" |
| |
| void MachObjectWriter::reset() { |
| Relocations.clear(); |
| IndirectSymBase.clear(); |
| StringTable.clear(); |
| LocalSymbolData.clear(); |
| ExternalSymbolData.clear(); |
| UndefinedSymbolData.clear(); |
| MCObjectWriter::reset(); |
| } |
| |
| bool MachObjectWriter::doesSymbolRequireExternRelocation(const MCSymbol &S) { |
| // Undefined symbols are always extern. |
| if (S.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 (cast<MCSymbolMachO>(S).isWeakDefinition()) |
| return true; |
| |
| // Otherwise, we can use an internal relocation. |
| return false; |
| } |
| |
| bool MachObjectWriter:: |
| MachSymbolData::operator<(const MachSymbolData &RHS) const { |
| return Symbol->getName() < RHS.Symbol->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 MCSymbol &S, |
| const MCAsmLayout &Layout) const { |
| // 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, nullptr)) |
| 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(Target.getSymA()->getSymbol(), Layout); |
| if (Target.getSymB()) |
| Address += getSymbolAddress(Target.getSymB()->getSymbol(), Layout); |
| return Address; |
| } |
| |
| return getSectionAddress(S.getFragment()->getParent()) + |
| Layout.getSymbolOffset(S); |
| } |
| |
| uint64_t MachObjectWriter::getPaddingSize(const MCSection *Sec, |
| const MCAsmLayout &Layout) const { |
| uint64_t EndAddr = getSectionAddress(Sec) + Layout.getSectionAddressSize(Sec); |
| unsigned Next = Sec->getLayoutOrder() + 1; |
| if (Next >= Layout.getSectionOrder().size()) |
| return 0; |
| |
| const MCSection &NextSec = *Layout.getSectionOrder()[Next]; |
| if (NextSec.isVirtualSection()) |
| return 0; |
| return offsetToAlignment(EndAddr, Align(NextSec.getAlignment())); |
| } |
| |
| void MachObjectWriter::writeHeader(MachO::HeaderFileType Type, |
| 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 = W.OS.tell(); |
| (void) Start; |
| |
| W.write<uint32_t>(is64Bit() ? MachO::MH_MAGIC_64 : MachO::MH_MAGIC); |
| |
| W.write<uint32_t>(TargetObjectWriter->getCPUType()); |
| W.write<uint32_t>(TargetObjectWriter->getCPUSubtype()); |
| |
| W.write<uint32_t>(Type); |
| W.write<uint32_t>(NumLoadCommands); |
| W.write<uint32_t>(LoadCommandsSize); |
| W.write<uint32_t>(Flags); |
| if (is64Bit()) |
| W.write<uint32_t>(0); // reserved |
| |
| assert(W.OS.tell() - Start == (is64Bit() ? sizeof(MachO::mach_header_64) |
| : sizeof(MachO::mach_header))); |
| } |
| |
| void MachObjectWriter::writeWithPadding(StringRef Str, uint64_t Size) { |
| assert(Size >= Str.size()); |
| W.OS << Str; |
| W.OS.write_zeros(Size - Str.size()); |
| } |
| |
| /// 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( |
| StringRef Name, unsigned NumSections, uint64_t VMAddr, uint64_t VMSize, |
| uint64_t SectionDataStartOffset, uint64_t SectionDataSize, uint32_t MaxProt, |
| uint32_t InitProt) { |
| // struct segment_command (56 bytes) or |
| // struct segment_command_64 (72 bytes) |
| |
| uint64_t Start = W.OS.tell(); |
| (void) Start; |
| |
| unsigned SegmentLoadCommandSize = |
| is64Bit() ? sizeof(MachO::segment_command_64): |
| sizeof(MachO::segment_command); |
| W.write<uint32_t>(is64Bit() ? MachO::LC_SEGMENT_64 : MachO::LC_SEGMENT); |
| W.write<uint32_t>(SegmentLoadCommandSize + |
| NumSections * (is64Bit() ? sizeof(MachO::section_64) : |
| sizeof(MachO::section))); |
| |
| writeWithPadding(Name, 16); |
| if (is64Bit()) { |
| W.write<uint64_t>(VMAddr); // vmaddr |
| W.write<uint64_t>(VMSize); // vmsize |
| W.write<uint64_t>(SectionDataStartOffset); // file offset |
| W.write<uint64_t>(SectionDataSize); // file size |
| } else { |
| W.write<uint32_t>(VMAddr); // vmaddr |
| W.write<uint32_t>(VMSize); // vmsize |
| W.write<uint32_t>(SectionDataStartOffset); // file offset |
| W.write<uint32_t>(SectionDataSize); // file size |
| } |
| // maxprot |
| W.write<uint32_t>(MaxProt); |
| // initprot |
| W.write<uint32_t>(InitProt); |
| W.write<uint32_t>(NumSections); |
| W.write<uint32_t>(0); // flags |
| |
| assert(W.OS.tell() - Start == SegmentLoadCommandSize); |
| } |
| |
| void MachObjectWriter::writeSection(const MCAsmLayout &Layout, |
| const MCSection &Sec, uint64_t VMAddr, |
| uint64_t FileOffset, unsigned Flags, |
| uint64_t RelocationsStart, |
| unsigned NumRelocations) { |
| uint64_t SectionSize = Layout.getSectionAddressSize(&Sec); |
| const MCSectionMachO &Section = cast<MCSectionMachO>(Sec); |
| |
| // The offset is unused for virtual sections. |
| if (Section.isVirtualSection()) { |
| assert(Layout.getSectionFileSize(&Sec) == 0 && "Invalid file size!"); |
| FileOffset = 0; |
| } |
| |
| // struct section (68 bytes) or |
| // struct section_64 (80 bytes) |
| |
| uint64_t Start = W.OS.tell(); |
| (void) Start; |
| |
| writeWithPadding(Section.getSectionName(), 16); |
| writeWithPadding(Section.getSegmentName(), 16); |
| if (is64Bit()) { |
| W.write<uint64_t>(VMAddr); // address |
| W.write<uint64_t>(SectionSize); // size |
| } else { |
| W.write<uint32_t>(VMAddr); // address |
| W.write<uint32_t>(SectionSize); // size |
| } |
| W.write<uint32_t>(FileOffset); |
| |
| assert(isPowerOf2_32(Section.getAlignment()) && "Invalid alignment!"); |
| W.write<uint32_t>(Log2_32(Section.getAlignment())); |
| W.write<uint32_t>(NumRelocations ? RelocationsStart : 0); |
| W.write<uint32_t>(NumRelocations); |
| W.write<uint32_t>(Flags); |
| W.write<uint32_t>(IndirectSymBase.lookup(&Sec)); // reserved1 |
| W.write<uint32_t>(Section.getStubSize()); // reserved2 |
| if (is64Bit()) |
| W.write<uint32_t>(0); // reserved3 |
| |
| assert(W.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 = W.OS.tell(); |
| (void) Start; |
| |
| W.write<uint32_t>(MachO::LC_SYMTAB); |
| W.write<uint32_t>(sizeof(MachO::symtab_command)); |
| W.write<uint32_t>(SymbolOffset); |
| W.write<uint32_t>(NumSymbols); |
| W.write<uint32_t>(StringTableOffset); |
| W.write<uint32_t>(StringTableSize); |
| |
| assert(W.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 = W.OS.tell(); |
| (void) Start; |
| |
| W.write<uint32_t>(MachO::LC_DYSYMTAB); |
| W.write<uint32_t>(sizeof(MachO::dysymtab_command)); |
| W.write<uint32_t>(FirstLocalSymbol); |
| W.write<uint32_t>(NumLocalSymbols); |
| W.write<uint32_t>(FirstExternalSymbol); |
| W.write<uint32_t>(NumExternalSymbols); |
| W.write<uint32_t>(FirstUndefinedSymbol); |
| W.write<uint32_t>(NumUndefinedSymbols); |
| W.write<uint32_t>(0); // tocoff |
| W.write<uint32_t>(0); // ntoc |
| W.write<uint32_t>(0); // modtaboff |
| W.write<uint32_t>(0); // nmodtab |
| W.write<uint32_t>(0); // extrefsymoff |
| W.write<uint32_t>(0); // nextrefsyms |
| W.write<uint32_t>(IndirectSymbolOffset); |
| W.write<uint32_t>(NumIndirectSymbols); |
| W.write<uint32_t>(0); // extreloff |
| W.write<uint32_t>(0); // nextrel |
| W.write<uint32_t>(0); // locreloff |
| W.write<uint32_t>(0); // nlocrel |
| |
| assert(W.OS.tell() - Start == sizeof(MachO::dysymtab_command)); |
| } |
| |
| MachObjectWriter::MachSymbolData * |
| MachObjectWriter::findSymbolData(const MCSymbol &Sym) { |
| for (auto *SymbolData : |
| {&LocalSymbolData, &ExternalSymbolData, &UndefinedSymbolData}) |
| for (MachSymbolData &Entry : *SymbolData) |
| if (Entry.Symbol == &Sym) |
| return &Entry; |
| |
| return nullptr; |
| } |
| |
| const MCSymbol &MachObjectWriter::findAliasedSymbol(const MCSymbol &Sym) const { |
| const MCSymbol *S = &Sym; |
| while (S->isVariable()) { |
| const MCExpr *Value = S->getVariableValue(); |
| const auto *Ref = dyn_cast<MCSymbolRefExpr>(Value); |
| if (!Ref) |
| return *S; |
| S = &Ref->getSymbol(); |
| } |
| return *S; |
| } |
| |
| void MachObjectWriter::writeNlist(MachSymbolData &MSD, |
| const MCAsmLayout &Layout) { |
| const MCSymbol *Symbol = MSD.Symbol; |
| const MCSymbol &Data = *Symbol; |
| const MCSymbol *AliasedSymbol = &findAliasedSymbol(*Symbol); |
| uint8_t SectionIndex = MSD.SectionIndex; |
| uint8_t Type = 0; |
| uint64_t Address = 0; |
| bool IsAlias = Symbol != AliasedSymbol; |
| |
| const MCSymbol &OrigSymbol = *Symbol; |
| MachSymbolData *AliaseeInfo; |
| if (IsAlias) { |
| AliaseeInfo = findSymbolData(*AliasedSymbol); |
| if (AliaseeInfo) |
| SectionIndex = AliaseeInfo->SectionIndex; |
| Symbol = AliasedSymbol; |
| // FIXME: Should this update Data as well? |
| } |
| |
| // Set the N_TYPE bits. See <mach-o/nlist.h>. |
| // |
| // FIXME: Are the prebound or indirect fields possible here? |
| if (IsAlias && Symbol->isUndefined()) |
| Type = MachO::N_INDR; |
| else 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() || (!IsAlias && Symbol->isUndefined())) |
| Type |= MachO::N_EXT; |
| |
| // Compute the symbol address. |
| if (IsAlias && Symbol->isUndefined()) |
| Address = AliaseeInfo->StringIndex; |
| else if (Symbol->isDefined()) |
| Address = getSymbolAddress(OrigSymbol, Layout); |
| else if (Symbol->isCommon()) { |
| // Common symbols are encoded with the size in the address |
| // field, and their alignment in the flags. |
| Address = Symbol->getCommonSize(); |
| } |
| |
| // struct nlist (12 bytes) |
| |
| W.write<uint32_t>(MSD.StringIndex); |
| W.OS << char(Type); |
| W.OS << char(SectionIndex); |
| |
| // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc' |
| // value. |
| bool EncodeAsAltEntry = |
| IsAlias && cast<MCSymbolMachO>(OrigSymbol).isAltEntry(); |
| W.write<uint16_t>(cast<MCSymbolMachO>(Symbol)->getEncodedFlags(EncodeAsAltEntry)); |
| if (is64Bit()) |
| W.write<uint64_t>(Address); |
| else |
| W.write<uint32_t>(Address); |
| } |
| |
| void MachObjectWriter::writeLinkeditLoadCommand(uint32_t Type, |
| uint32_t DataOffset, |
| uint32_t DataSize) { |
| uint64_t Start = W.OS.tell(); |
| (void) Start; |
| |
| W.write<uint32_t>(Type); |
| W.write<uint32_t>(sizeof(MachO::linkedit_data_command)); |
| W.write<uint32_t>(DataOffset); |
| W.write<uint32_t>(DataSize); |
| |
| assert(W.OS.tell() - Start == sizeof(MachO::linkedit_data_command)); |
| } |
| |
| static unsigned ComputeLinkerOptionsLoadCommandSize( |
| const std::vector<std::string> &Options, bool is64Bit) |
| { |
| unsigned Size = sizeof(MachO::linker_option_command); |
| for (const std::string &Option : Options) |
| Size += Option.size() + 1; |
| return alignTo(Size, is64Bit ? 8 : 4); |
| } |
| |
| void MachObjectWriter::writeLinkerOptionsLoadCommand( |
| const std::vector<std::string> &Options) |
| { |
| unsigned Size = ComputeLinkerOptionsLoadCommandSize(Options, is64Bit()); |
| uint64_t Start = W.OS.tell(); |
| (void) Start; |
| |
| W.write<uint32_t>(MachO::LC_LINKER_OPTION); |
| W.write<uint32_t>(Size); |
| W.write<uint32_t>(Options.size()); |
| uint64_t BytesWritten = sizeof(MachO::linker_option_command); |
| for (const std::string &Option : Options) { |
| // Write each string, including the null byte. |
| W.OS << Option << '\0'; |
| BytesWritten += Option.size() + 1; |
| } |
| |
| // Pad to a multiple of the pointer size. |
| W.OS.write_zeros( |
| offsetToAlignment(BytesWritten, is64Bit() ? Align(8) : Align(4))); |
| |
| assert(W.OS.tell() - Start == Size); |
| } |
| |
| static bool isFixupTargetValid(const MCValue &Target) { |
| // Target is (LHS - RHS + cst). |
| // We don't support the form where LHS is null: -RHS + cst |
| if (!Target.getSymA() && Target.getSymB()) |
| return false; |
| return true; |
| } |
| |
| void MachObjectWriter::recordRelocation(MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, MCValue Target, |
| uint64_t &FixedValue) { |
| if (!isFixupTargetValid(Target)) { |
| Asm.getContext().reportError(Fixup.getLoc(), |
| "unsupported relocation expression"); |
| return; |
| } |
| |
| 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->Section); |
| |
| if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS && |
| Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS && |
| Section.getType() != MachO::S_THREAD_LOCAL_VARIABLE_POINTERS && |
| Section.getType() != MachO::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->Section); |
| |
| if (Section.getType() != MachO::S_NON_LAZY_SYMBOL_POINTERS && |
| Section.getType() != MachO::S_THREAD_LOCAL_VARIABLE_POINTERS) |
| continue; |
| |
| // Initialize the section indirect symbol base, if necessary. |
| IndirectSymBase.insert(std::make_pair(it->Section, IndirectIndex)); |
| |
| Asm.registerSymbol(*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->Section); |
| |
| if (Section.getType() != MachO::S_LAZY_SYMBOL_POINTERS && |
| Section.getType() != MachO::S_SYMBOL_STUBS) |
| continue; |
| |
| // Initialize the section indirect symbol base, if necessary. |
| IndirectSymBase.insert(std::make_pair(it->Section, IndirectIndex)); |
| |
| // Set the symbol type to undefined lazy, but only on construction. |
| // |
| // FIXME: Do not hardcode. |
| bool Created; |
| Asm.registerSymbol(*it->Symbol, &Created); |
| if (Created) |
| cast<MCSymbolMachO>(it->Symbol)->setReferenceTypeUndefinedLazy(true); |
| } |
| } |
| |
| /// computeSymbolTable - Compute the symbol table data |
| void MachObjectWriter::computeSymbolTable( |
| MCAssembler &Asm, 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] = Index; |
| assert(Index <= 256 && "Too many sections!"); |
| |
| // Build the string table. |
| for (const MCSymbol &Symbol : Asm.symbols()) { |
| if (!Asm.isSymbolLinkerVisible(Symbol)) |
| continue; |
| |
| StringTable.add(Symbol.getName()); |
| } |
| StringTable.finalize(); |
| |
| // Build the symbol arrays but only for non-local symbols. |
| // |
| // The particular order that we collect and 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 (const MCSymbol &Symbol : Asm.symbols()) { |
| // Ignore non-linker visible symbols. |
| if (!Asm.isSymbolLinkerVisible(Symbol)) |
| continue; |
| |
| if (!Symbol.isExternal() && !Symbol.isUndefined()) |
| continue; |
| |
| MachSymbolData MSD; |
| MSD.Symbol = &Symbol; |
| MSD.StringIndex = StringTable.getOffset(Symbol.getName()); |
| |
| 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 (const MCSymbol &Symbol : Asm.symbols()) { |
| // Ignore non-linker visible symbols. |
| if (!Asm.isSymbolLinkerVisible(Symbol)) |
| continue; |
| |
| if (Symbol.isExternal() || Symbol.isUndefined()) |
| continue; |
| |
| MachSymbolData MSD; |
| MSD.Symbol = &Symbol; |
| MSD.StringIndex = StringTable.getOffset(Symbol.getName()); |
| |
| 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. |
| llvm::sort(ExternalSymbolData); |
| llvm::sort(UndefinedSymbolData); |
| |
| // Set the symbol indices. |
| Index = 0; |
| for (auto *SymbolData : |
| {&LocalSymbolData, &ExternalSymbolData, &UndefinedSymbolData}) |
| for (MachSymbolData &Entry : *SymbolData) |
| Entry.Symbol->setIndex(Index++); |
| |
| for (const MCSection &Section : Asm) { |
| for (RelAndSymbol &Rel : Relocations[&Section]) { |
| if (!Rel.Sym) |
| continue; |
| |
| // Set the Index and the IsExtern bit. |
| unsigned Index = Rel.Sym->getIndex(); |
| assert(isInt<24>(Index)); |
| if (W.Endian == support::little) |
| Rel.MRE.r_word1 = (Rel.MRE.r_word1 & (~0U << 24)) | Index | (1 << 27); |
| else |
| Rel.MRE.r_word1 = (Rel.MRE.r_word1 & 0xff) | Index << 8 | (1 << 4); |
| } |
| } |
| } |
| |
| void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| uint64_t StartAddress = 0; |
| for (const MCSection *Sec : Layout.getSectionOrder()) { |
| StartAddress = alignTo(StartAddress, Sec->getAlignment()); |
| SectionAddress[Sec] = StartAddress; |
| StartAddress += Layout.getSectionAddressSize(Sec); |
| |
| // 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(Sec, Layout); |
| } |
| } |
| |
| void MachObjectWriter::executePostLayoutBinding(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| computeSectionAddresses(Asm, Layout); |
| |
| // Create symbol data for any indirect symbols. |
| bindIndirectSymbols(Asm); |
| } |
| |
| bool MachObjectWriter::isSymbolRefDifferenceFullyResolvedImpl( |
| const MCAssembler &Asm, const MCSymbol &A, const MCSymbol &B, |
| bool InSet) const { |
| // FIXME: We don't handle things like |
| // foo = . |
| // creating atoms. |
| if (A.isVariable() || B.isVariable()) |
| return false; |
| return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, A, B, |
| InSet); |
| } |
| |
| bool MachObjectWriter::isSymbolRefDifferenceFullyResolvedImpl( |
| const MCAssembler &Asm, const MCSymbol &SymA, 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 MCSymbol &SA = findAliasedSymbol(SymA); |
| const MCSection &SecA = SA.getSection(); |
| const MCSection &SecB = *FB.getParent(); |
| |
| 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. |
| |
| bool hasReliableSymbolDifference = isX86_64(); |
| if (!hasReliableSymbolDifference) { |
| if (!SA.isInSection() || &SecA != &SecB || |
| (!SA.isTemporary() && FB.getAtom() != 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; |
| } |
| } |
| |
| // If they are not in the same section, we can't compute the diff. |
| if (&SecA != &SecB) |
| return false; |
| |
| const MCFragment *FA = SA.getFragment(); |
| |
| // Bail if the symbol has no fragment. |
| if (!FA) |
| return false; |
| |
| // If the atoms are the same, they are guaranteed to have the same address. |
| if (FA->getAtom() == FB.getAtom()) |
| return true; |
| |
| // Otherwise, we can't prove this is fully resolved. |
| return false; |
| } |
| |
| static MachO::LoadCommandType getLCFromMCVM(MCVersionMinType Type) { |
| switch (Type) { |
| case MCVM_OSXVersionMin: return MachO::LC_VERSION_MIN_MACOSX; |
| case MCVM_IOSVersionMin: return MachO::LC_VERSION_MIN_IPHONEOS; |
| case MCVM_TvOSVersionMin: return MachO::LC_VERSION_MIN_TVOS; |
| case MCVM_WatchOSVersionMin: return MachO::LC_VERSION_MIN_WATCHOS; |
| } |
| llvm_unreachable("Invalid mc version min type"); |
| } |
| |
| uint64_t MachObjectWriter::writeObject(MCAssembler &Asm, |
| const MCAsmLayout &Layout) { |
| uint64_t StartOffset = W.OS.tell(); |
| |
| // Compute symbol table information and bind symbol indices. |
| computeSymbolTable(Asm, LocalSymbolData, ExternalSymbolData, |
| UndefinedSymbolData); |
| |
| unsigned NumSections = Asm.size(); |
| const MCAssembler::VersionInfoType &VersionInfo = |
| Layout.getAssembler().getVersionInfo(); |
| |
| // 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 deployment target version info load command size, if used. |
| if (VersionInfo.Major != 0) { |
| ++NumLoadCommands; |
| if (VersionInfo.EmitBuildVersion) |
| LoadCommandsSize += sizeof(MachO::build_version_command); |
| else |
| LoadCommandsSize += sizeof(MachO::version_min_command); |
| } |
| |
| // 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 loh load command size, if used. |
| uint64_t LOHRawSize = Asm.getLOHContainer().getEmitSize(*this, Layout); |
| uint64_t LOHSize = alignTo(LOHRawSize, is64Bit() ? 8 : 4); |
| if (LOHSize) { |
| ++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. |
| for (const auto &Option : Asm.getLinkerOptions()) { |
| ++NumLoadCommands; |
| LoadCommandsSize += ComputeLinkerOptionsLoadCommandSize(Option, 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 (const MCSection &Sec : Asm) { |
| uint64_t Address = getSectionAddress(&Sec); |
| uint64_t Size = Layout.getSectionAddressSize(&Sec); |
| uint64_t FileSize = Layout.getSectionFileSize(&Sec); |
| FileSize += getPaddingSize(&Sec, Layout); |
| |
| VMSize = std::max(VMSize, Address + Size); |
| |
| if (Sec.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, Align(4)); |
| SectionDataFileSize += SectionDataPadding; |
| |
| // Write the prolog, starting with the header and load command... |
| writeHeader(MachO::MH_OBJECT, NumLoadCommands, LoadCommandsSize, |
| Asm.getSubsectionsViaSymbols()); |
| uint32_t Prot = |
| MachO::VM_PROT_READ | MachO::VM_PROT_WRITE | MachO::VM_PROT_EXECUTE; |
| writeSegmentLoadCommand("", NumSections, 0, VMSize, SectionDataStart, |
| SectionDataSize, Prot, Prot); |
| |
| // ... and then the section headers. |
| uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize; |
| for (const MCSection &Section : Asm) { |
| const auto &Sec = cast<MCSectionMachO>(Section); |
| std::vector<RelAndSymbol> &Relocs = Relocations[&Sec]; |
| unsigned NumRelocs = Relocs.size(); |
| uint64_t SectionStart = SectionDataStart + getSectionAddress(&Sec); |
| unsigned Flags = Sec.getTypeAndAttributes(); |
| if (Sec.hasInstructions()) |
| Flags |= MachO::S_ATTR_SOME_INSTRUCTIONS; |
| writeSection(Layout, Sec, getSectionAddress(&Sec), SectionStart, Flags, |
| RelocTableEnd, NumRelocs); |
| RelocTableEnd += NumRelocs * sizeof(MachO::any_relocation_info); |
| } |
| |
| // Write out the deployment target information, if it's available. |
| if (VersionInfo.Major != 0) { |
| auto EncodeVersion = [](VersionTuple V) -> uint32_t { |
| assert(!V.empty() && "empty version"); |
| unsigned Update = V.getSubminor() ? *V.getSubminor() : 0; |
| unsigned Minor = V.getMinor() ? *V.getMinor() : 0; |
| assert(Update < 256 && "unencodable update target version"); |
| assert(Minor < 256 && "unencodable minor target version"); |
| assert(V.getMajor() < 65536 && "unencodable major target version"); |
| return Update | (Minor << 8) | (V.getMajor() << 16); |
| }; |
| uint32_t EncodedVersion = EncodeVersion( |
| VersionTuple(VersionInfo.Major, VersionInfo.Minor, VersionInfo.Update)); |
| uint32_t SDKVersion = !VersionInfo.SDKVersion.empty() |
| ? EncodeVersion(VersionInfo.SDKVersion) |
| : 0; |
| if (VersionInfo.EmitBuildVersion) { |
| // FIXME: Currently empty tools. Add clang version in the future. |
| W.write<uint32_t>(MachO::LC_BUILD_VERSION); |
| W.write<uint32_t>(sizeof(MachO::build_version_command)); |
| W.write<uint32_t>(VersionInfo.TypeOrPlatform.Platform); |
| W.write<uint32_t>(EncodedVersion); |
| W.write<uint32_t>(SDKVersion); |
| W.write<uint32_t>(0); // Empty tools list. |
| } else { |
| MachO::LoadCommandType LCType |
| = getLCFromMCVM(VersionInfo.TypeOrPlatform.Type); |
| W.write<uint32_t>(LCType); |
| W.write<uint32_t>(sizeof(MachO::version_min_command)); |
| W.write<uint32_t>(EncodedVersion); |
| W.write<uint32_t>(SDKVersion); |
| } |
| } |
| |
| // 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 loh load command, if used. |
| uint64_t LOHTableEnd = DataInCodeTableEnd + LOHSize; |
| if (LOHSize) |
| writeLinkeditLoadCommand(MachO::LC_LINKER_OPTIMIZATION_HINT, |
| DataInCodeTableEnd, LOHSize); |
| |
| // 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 = LOHTableEnd; |
| |
| // The symbol table is written after the indirect symbol data. |
| uint64_t SymbolTableOffset = LOHTableEnd + 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.getSize()); |
| |
| writeDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols, |
| FirstExternalSymbol, NumExternalSymbols, |
| FirstUndefinedSymbol, NumUndefinedSymbols, |
| IndirectSymbolOffset, NumIndirectSymbols); |
| } |
| |
| // Write the linker options load commands. |
| for (const auto &Option : Asm.getLinkerOptions()) |
| writeLinkerOptionsLoadCommand(Option); |
| |
| // Write the actual section data. |
| for (const MCSection &Sec : Asm) { |
| Asm.writeSectionData(W.OS, &Sec, Layout); |
| |
| uint64_t Pad = getPaddingSize(&Sec, Layout); |
| W.OS.write_zeros(Pad); |
| } |
| |
| // Write the extra padding. |
| W.OS.write_zeros(SectionDataPadding); |
| |
| // Write the relocation entries. |
| for (const MCSection &Sec : Asm) { |
| // Write the section relocation entries, in reverse order to match 'as' |
| // (approximately, the exact algorithm is more complicated than this). |
| std::vector<RelAndSymbol> &Relocs = Relocations[&Sec]; |
| for (const RelAndSymbol &Rel : make_range(Relocs.rbegin(), Relocs.rend())) { |
| W.write<uint32_t>(Rel.MRE.r_word0); |
| W.write<uint32_t>(Rel.MRE.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(*Data->Start, Layout); |
| uint64_t End; |
| if (Data->End) |
| End = getSymbolAddress(*Data->End, Layout); |
| else |
| report_fatal_error("Data region not terminated"); |
| |
| LLVM_DEBUG(dbgs() << "data in code region-- kind: " << Data->Kind |
| << " start: " << Start << "(" << Data->Start->getName() |
| << ")" |
| << " end: " << End << "(" << Data->End->getName() << ")" |
| << " size: " << End - Start << "\n"); |
| W.write<uint32_t>(Start); |
| W.write<uint16_t>(End - Start); |
| W.write<uint16_t>(Data->Kind); |
| } |
| |
| // Write out the loh commands, if there is one. |
| if (LOHSize) { |
| #ifndef NDEBUG |
| unsigned Start = W.OS.tell(); |
| #endif |
| Asm.getLOHContainer().emit(*this, Layout); |
| // Pad to a multiple of the pointer size. |
| W.OS.write_zeros( |
| offsetToAlignment(LOHRawSize, is64Bit() ? Align(8) : Align(4))); |
| assert(W.OS.tell() - Start == LOHSize); |
| } |
| |
| // 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->Section); |
| if (Section.getType() == MachO::S_NON_LAZY_SYMBOL_POINTERS) { |
| // If this symbol is defined and internal, mark it as such. |
| if (it->Symbol->isDefined() && !it->Symbol->isExternal()) { |
| uint32_t Flags = MachO::INDIRECT_SYMBOL_LOCAL; |
| if (it->Symbol->isAbsolute()) |
| Flags |= MachO::INDIRECT_SYMBOL_ABS; |
| W.write<uint32_t>(Flags); |
| continue; |
| } |
| } |
| |
| W.write<uint32_t>(it->Symbol->getIndex()); |
| } |
| |
| // FIXME: Check that offsets match computed ones. |
| |
| // Write the symbol table entries. |
| for (auto *SymbolData : |
| {&LocalSymbolData, &ExternalSymbolData, &UndefinedSymbolData}) |
| for (MachSymbolData &Entry : *SymbolData) |
| writeNlist(Entry, Layout); |
| |
| // Write the string table. |
| StringTable.write(W.OS); |
| } |
| |
| return W.OS.tell() - StartOffset; |
| } |
| |
| std::unique_ptr<MCObjectWriter> |
| llvm::createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, |
| raw_pwrite_stream &OS, bool IsLittleEndian) { |
| return std::make_unique<MachObjectWriter>(std::move(MOTW), OS, |
| IsLittleEndian); |
| } |
