path: root/lib/MC/MachObjectWriter.cpp

//===- 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/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.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 FK_Data_2: return 1;
  case X86::reloc_pcrel_4byte:
  case X86::reloc_riprel_4byte:
  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_4byte:
  case X86::reloc_riprel_4byte:
    return true;
  }
}

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
  };

  /// 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 {
      const std::string &Name = SymbolData->getSymbol().getName();
      return Name < RHS.SymbolData->getSymbol().getName();
    }
  };

  /// @name Relocation Data
  /// @{

  struct MachRelocationEntry {
    uint32_t Word0;
    uint32_t Word1;
  };

  llvm::DenseMap<const MCSectionData*,
                 std::vector<MachRelocationEntry> > Relocations;

  /// @}
  /// @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_Subsect