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//===- llvm/MC/MCMachObjectWriter.h - Mach Object Writer --------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/StringTableBuilder.h"
#include <cstdint>
#include <memory>
#include <string>
#include <vector>
namespace llvm {
class MachObjectWriter;
class MCMachObjectTargetWriter : public MCObjectTargetWriter {
const unsigned Is64Bit : 1;
const uint32_t CPUType;
const uint32_t CPUSubtype;
unsigned LocalDifference_RIT;
MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_,
uint32_t CPUSubtype_);
void setLocalDifferenceRelocationType(unsigned Type) {
LocalDifference_RIT = Type;
virtual ~MCMachObjectTargetWriter();
virtual Triple::ObjectFormatType getFormat() const { return Triple::MachO; }
static bool classof(const MCObjectTargetWriter *W) {
return W->getFormat() == Triple::MachO;
/// \name Lifetime Management
/// @{
virtual void reset() {}
/// @}
/// \name Accessors
/// @{
bool is64Bit() const { return Is64Bit; }
uint32_t getCPUType() const { return CPUType; }
uint32_t getCPUSubtype() const { return CPUSubtype; }
unsigned getLocalDifferenceRelocationType() const {
return LocalDifference_RIT;
/// @}
/// \name API
/// @{
virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) = 0;
/// @}
class MachObjectWriter : public MCObjectWriter {
/// Helper struct for containing some precomputed information on symbols.
struct MachSymbolData {
const MCSymbol *Symbol;
uint64_t StringIndex;
uint8_t SectionIndex;
// Support lexicographic sorting.
bool operator<(const MachSymbolData &RHS) const;
/// The target specific Mach-O writer instance.
std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter;
/// \name Relocation Data
/// @{
struct RelAndSymbol {
const MCSymbol *Sym;
MachO::any_relocation_info MRE;
RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE)
: Sym(Sym), MRE(MRE) {}
DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations;
DenseMap<const MCSection *, unsigned> IndirectSymBase;
SectionAddrMap SectionAddress;
/// @}
/// \name Symbol Table Data
/// @{
StringTableBuilder StringTable{StringTableBuilder::MachO};
std::vector<MachSymbolData> LocalSymbolData;
std::vector<MachSymbolData> ExternalSymbolData;
std::vector<MachSymbolData> UndefinedSymbolData;
/// @}
MachSymbolData *findSymbolData(const MCSymbol &Sym);
void writeWithPadding(StringRef Str, uint64_t Size);
MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
raw_pwrite_stream &OS, bool IsLittleEndian)
: TargetObjectWriter(std::move(MOTW)),
W(OS, IsLittleEndian ? support::little : support::big) {}
support::endian::Writer W;
const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const;
/// \name Lifetime management Methods
/// @{
void reset() override;
/// @}
/// \name Utility Methods
/// @{
bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
SectionAddrMap &getSectionAddressMap() { return SectionAddress; }
uint64_t getSectionAddress(const MCSection *Sec) const {
return SectionAddress.lookup(Sec);
uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const;
uint64_t getFragmentAddress(const MCFragment *Fragment,
const MCAsmLayout &Layout) const;
uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const;
bool doesSymbolRequireExternRelocation(const MCSymbol &S);
/// @}
/// \name Target Writer Proxy Accessors
/// @{
bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
bool isX86_64() const {
uint32_t CPUType = TargetObjectWriter->getCPUType();
return CPUType == MachO::CPU_TYPE_X86_64;
/// @}
void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands,
unsigned LoadCommandsSize, bool SubsectionsViaSymbols);
/// Write a segment load command.
/// \param NumSections The number of sections in this segment.
/// \param SectionDataSize The total size of the sections.
void writeSegmentLoadCommand(StringRef Name, unsigned NumSections,
uint64_t VMAddr, uint64_t VMSize,
uint64_t SectionDataStartOffset,
uint64_t SectionDataSize, uint32_t MaxProt,
uint32_t InitProt);
void writeSection(const MCAsmLayout &Layout, const MCSection &Sec,
uint64_t VMAddr, uint64_t FileOffset, unsigned Flags,
uint64_t RelocationsStart, unsigned NumRelocations);
void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
uint32_t StringTableOffset,
uint32_t StringTableSize);
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);
void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout);
void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset,
uint32_t DataSize);
void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options);
// 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.
// Add a relocation to be output in the object file. At the time this is
// called, the symbol indexes are not know, so if the relocation refers
// to a symbol it should be passed as \p RelSymbol so that it can be updated
// afterwards. If the relocation doesn't refer to a symbol, nullptr should be
// used.
void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec,
MachO::any_relocation_info &MRE) {
RelAndSymbol P(RelSymbol, MRE);
void recordScatteredRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target,
unsigned Log2Size, uint64_t &FixedValue);
void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup,
MCValue Target, uint64_t &FixedValue);
void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup,
MCValue Target, uint64_t &FixedValue) override;
void bindIndirectSymbols(MCAssembler &Asm);
/// Compute the symbol table data.
void computeSymbolTable(MCAssembler &Asm,
std::vector<MachSymbolData> &LocalSymbolData,
std::vector<MachSymbolData> &ExternalSymbolData,
std::vector<MachSymbolData> &UndefinedSymbolData);
void computeSectionAddresses(const MCAssembler &Asm,
const MCAsmLayout &Layout);
void executePostLayoutBinding(MCAssembler &Asm,
const MCAsmLayout &Layout) override;
bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
const MCSymbol &A,
const MCSymbol &B,
bool InSet) const override;
bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
const MCSymbol &SymA,
const MCFragment &FB, bool InSet,
bool IsPCRel) const override;
uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
/// Construct a new Mach-O writer instance.
/// This routine takes ownership of the target writer subclass.
/// \param MOTW - The target specific Mach-O writer subclass.
/// \param OS - The stream to write to.
/// \returns The constructed object writer.
createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,
raw_pwrite_stream &OS, bool IsLittleEndian);
} // end namespace llvm