1 //===-- llvm/MC/MCMachObjectWriter.h - Mach Object Writer -------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef LLVM_MC_MCMACHOBJECTWRITER_H 11 #define LLVM_MC_MCMACHOBJECTWRITER_H 12 13 #include "llvm/ADT/DenseMap.h" 14 #include "llvm/ADT/SmallString.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCObjectWriter.h" 17 #include "llvm/MC/StringTableBuilder.h" 18 #include "llvm/Support/DataTypes.h" 19 #include "llvm/Support/MachO.h" 20 #include <vector> 21 22 namespace llvm { 23 24 class MachObjectWriter; 25 26 class MCMachObjectTargetWriter { 27 const unsigned Is64Bit : 1; 28 const uint32_t CPUType; 29 const uint32_t CPUSubtype; 30 unsigned LocalDifference_RIT; 31 32 protected: 33 MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, 34 uint32_t CPUSubtype_); 35 36 void setLocalDifferenceRelocationType(unsigned Type) { 37 LocalDifference_RIT = Type; 38 } 39 40 public: 41 virtual ~MCMachObjectTargetWriter(); 42 43 /// \name Lifetime Management 44 /// @{ 45 46 virtual void reset() {} 47 48 /// @} 49 50 /// \name Accessors 51 /// @{ 52 53 bool is64Bit() const { return Is64Bit; } 54 uint32_t getCPUType() const { return CPUType; } 55 uint32_t getCPUSubtype() const { return CPUSubtype; } 56 unsigned getLocalDifferenceRelocationType() const { 57 return LocalDifference_RIT; 58 } 59 60 /// @} 61 62 /// \name API 63 /// @{ 64 65 virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 66 const MCAsmLayout &Layout, 67 const MCFragment *Fragment, 68 const MCFixup &Fixup, MCValue Target, 69 uint64_t &FixedValue) = 0; 70 71 /// @} 72 }; 73 74 class MachObjectWriter : public MCObjectWriter { 75 /// Helper struct for containing some precomputed information on symbols. 76 struct MachSymbolData { 77 const MCSymbol *Symbol; 78 uint64_t StringIndex; 79 uint8_t SectionIndex; 80 81 // Support lexicographic sorting. 82 bool operator<(const MachSymbolData &RHS) const; 83 }; 84 85 /// The target specific Mach-O writer instance. 86 std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter; 87 88 /// \name Relocation Data 89 /// @{ 90 91 struct RelAndSymbol { 92 const MCSymbol *Sym; 93 MachO::any_relocation_info MRE; 94 RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE) 95 : Sym(Sym), MRE(MRE) {} 96 }; 97 98 llvm::DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations; 99 llvm::DenseMap<const MCSection *, unsigned> IndirectSymBase; 100 101 SectionAddrMap SectionAddress; 102 103 /// @} 104 /// \name Symbol Table Data 105 /// @{ 106 107 StringTableBuilder StringTable{StringTableBuilder::MachO}; 108 std::vector<MachSymbolData> LocalSymbolData; 109 std::vector<MachSymbolData> ExternalSymbolData; 110 std::vector<MachSymbolData> UndefinedSymbolData; 111 112 /// @} 113 114 MachSymbolData *findSymbolData(const MCSymbol &Sym); 115 116 public: 117 MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_pwrite_stream &OS, 118 bool IsLittleEndian) 119 : MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {} 120 121 const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const; 122 123 /// \name Lifetime management Methods 124 /// @{ 125 126 void reset() override; 127 128 /// @} 129 130 /// \name Utility Methods 131 /// @{ 132 133 bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 134 135 SectionAddrMap &getSectionAddressMap() { return SectionAddress; } 136 137 uint64_t getSectionAddress(const MCSection *Sec) const { 138 return SectionAddress.lookup(Sec); 139 } 140 uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const; 141 142 uint64_t getFragmentAddress(const MCFragment *Fragment, 143 const MCAsmLayout &Layout) const; 144 145 uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const; 146 147 bool doesSymbolRequireExternRelocation(const MCSymbol &S); 148 149 /// @} 150 151 /// \name Target Writer Proxy Accessors 152 /// @{ 153 154 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 155 bool isX86_64() const { 156 uint32_t CPUType = TargetObjectWriter->getCPUType(); 157 return CPUType == MachO::CPU_TYPE_X86_64; 158 } 159 160 /// @} 161 162 void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands, 163 unsigned LoadCommandsSize, bool SubsectionsViaSymbols); 164 165 /// Write a segment load command. 166 /// 167 /// \param NumSections The number of sections in this segment. 168 /// \param SectionDataSize The total size of the sections. 169 void writeSegmentLoadCommand(StringRef Name, unsigned NumSections, 170 uint64_t VMAddr, uint64_t VMSize, 171 uint64_t SectionDataStartOffset, 172 uint64_t SectionDataSize, uint32_t MaxProt, 173 uint32_t InitProt); 174 175 void writeSection(const MCAsmLayout &Layout, const MCSection &Sec, 176 uint64_t VMAddr, uint64_t FileOffset, unsigned Flags, 177 uint64_t RelocationsStart, unsigned NumRelocations); 178 179 void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, 180 uint32_t StringTableOffset, 181 uint32_t StringTableSize); 182 183 void writeDysymtabLoadCommand( 184 uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols, 185 uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols, 186 uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols, 187 uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols); 188 189 void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout); 190 191 void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset, 192 uint32_t DataSize); 193 194 void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options); 195 196 // FIXME: We really need to improve the relocation validation. Basically, we 197 // want to implement a separate computation which evaluates the relocation 198 // entry as the linker would, and verifies that the resultant fixup value is 199 // exactly what the encoder wanted. This will catch several classes of 200 // problems: 201 // 202 // - Relocation entry bugs, the two algorithms are unlikely to have the same 203 // exact bug. 204 // 205 // - Relaxation issues, where we forget to relax something. 206 // 207 // - Input errors, where something cannot be correctly encoded. 'as' allows 208 // these through in many cases. 209 210 // Add a relocation to be output in the object file. At the time this is 211 // called, the symbol indexes are not know, so if the relocation refers 212 // to a symbol it should be passed as \p RelSymbol so that it can be updated 213 // afterwards. If the relocation doesn't refer to a symbol, nullptr should be 214 // used. 215 void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, 216 MachO::any_relocation_info &MRE) { 217 RelAndSymbol P(RelSymbol, MRE); 218 Relocations[Sec].push_back(P); 219 } 220 221 void recordScatteredRelocation(const MCAssembler &Asm, 222 const MCAsmLayout &Layout, 223 const MCFragment *Fragment, 224 const MCFixup &Fixup, MCValue Target, 225 unsigned Log2Size, uint64_t &FixedValue); 226 227 void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 228 const MCFragment *Fragment, const MCFixup &Fixup, 229 MCValue Target, uint64_t &FixedValue); 230 231 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 232 const MCFragment *Fragment, const MCFixup &Fixup, 233 MCValue Target, bool &IsPCRel, 234 uint64_t &FixedValue) override; 235 236 void bindIndirectSymbols(MCAssembler &Asm); 237 238 /// Compute the symbol table data. 239 void computeSymbolTable(MCAssembler &Asm, 240 std::vector<MachSymbolData> &LocalSymbolData, 241 std::vector<MachSymbolData> &ExternalSymbolData, 242 std::vector<MachSymbolData> &UndefinedSymbolData); 243 244 void computeSectionAddresses(const MCAssembler &Asm, 245 const MCAsmLayout &Layout); 246 247 void executePostLayoutBinding(MCAssembler &Asm, 248 const MCAsmLayout &Layout) override; 249 250 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 251 const MCSymbol &A, 252 const MCSymbol &B, 253 bool InSet) const override; 254 255 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 256 const MCSymbol &SymA, 257 const MCFragment &FB, bool InSet, 258 bool IsPCRel) const override; 259 260 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 261 }; 262 263 /// Construct a new Mach-O writer instance. 264 /// 265 /// This routine takes ownership of the target writer subclass. 266 /// 267 /// \param MOTW - The target specific Mach-O writer subclass. 268 /// \param OS - The stream to write to. 269 /// \returns The constructed object writer. 270 MCObjectWriter *createMachObjectWriter(MCMachObjectTargetWriter *MOTW, 271 raw_pwrite_stream &OS, 272 bool IsLittleEndian); 273 274 } // End llvm namespace 275 276 #endif 277
