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/StringRef.h" 15 #include "llvm/BinaryFormat/MachO.h" 16 #include "llvm/MC/MCExpr.h" 17 #include "llvm/MC/MCObjectWriter.h" 18 #include "llvm/MC/MCSection.h" 19 #include "llvm/MC/StringTableBuilder.h" 20 #include <cstdint> 21 #include <memory> 22 #include <string> 23 #include <vector> 24 25 namespace llvm { 26 27 class MachObjectWriter; 28 29 class MCMachObjectTargetWriter { 30 const unsigned Is64Bit : 1; 31 const uint32_t CPUType; 32 const uint32_t CPUSubtype; 33 unsigned LocalDifference_RIT; 34 35 protected: 36 MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, 37 uint32_t CPUSubtype_); 38 39 void setLocalDifferenceRelocationType(unsigned Type) { 40 LocalDifference_RIT = Type; 41 } 42 43 public: 44 virtual ~MCMachObjectTargetWriter(); 45 46 /// \name Lifetime Management 47 /// @{ 48 49 virtual void reset() {} 50 51 /// @} 52 53 /// \name Accessors 54 /// @{ 55 56 bool is64Bit() const { return Is64Bit; } 57 uint32_t getCPUType() const { return CPUType; } 58 uint32_t getCPUSubtype() const { return CPUSubtype; } 59 unsigned getLocalDifferenceRelocationType() const { 60 return LocalDifference_RIT; 61 } 62 63 /// @} 64 65 /// \name API 66 /// @{ 67 68 virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 69 const MCAsmLayout &Layout, 70 const MCFragment *Fragment, 71 const MCFixup &Fixup, MCValue Target, 72 uint64_t &FixedValue) = 0; 73 74 /// @} 75 }; 76 77 class MachObjectWriter : public MCObjectWriter { 78 /// Helper struct for containing some precomputed information on symbols. 79 struct MachSymbolData { 80 const MCSymbol *Symbol; 81 uint64_t StringIndex; 82 uint8_t SectionIndex; 83 84 // Support lexicographic sorting. 85 bool operator<(const MachSymbolData &RHS) const; 86 }; 87 88 /// The target specific Mach-O writer instance. 89 std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter; 90 91 /// \name Relocation Data 92 /// @{ 93 94 struct RelAndSymbol { 95 const MCSymbol *Sym; 96 MachO::any_relocation_info MRE; 97 RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE) 98 : Sym(Sym), MRE(MRE) {} 99 }; 100 101 DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations; 102 DenseMap<const MCSection *, unsigned> IndirectSymBase; 103 104 SectionAddrMap SectionAddress; 105 106 /// @} 107 /// \name Symbol Table Data 108 /// @{ 109 110 StringTableBuilder StringTable{StringTableBuilder::MachO}; 111 std::vector<MachSymbolData> LocalSymbolData; 112 std::vector<MachSymbolData> ExternalSymbolData; 113 std::vector<MachSymbolData> UndefinedSymbolData; 114 115 /// @} 116 117 MachSymbolData *findSymbolData(const MCSymbol &Sym); 118 119 public: 120 MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_pwrite_stream &OS, 121 bool IsLittleEndian) 122 : MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {} 123 124 const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const; 125 126 /// \name Lifetime management Methods 127 /// @{ 128 129 void reset() override; 130 131 /// @} 132 133 /// \name Utility Methods 134 /// @{ 135 136 bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 137 138 SectionAddrMap &getSectionAddressMap() { return SectionAddress; } 139 140 uint64_t getSectionAddress(const MCSection *Sec) const { 141 return SectionAddress.lookup(Sec); 142 } 143 uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const; 144 145 uint64_t getFragmentAddress(const MCFragment *Fragment, 146 const MCAsmLayout &Layout) const; 147 148 uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const; 149 150 bool doesSymbolRequireExternRelocation(const MCSymbol &S); 151 152 /// @} 153 154 /// \name Target Writer Proxy Accessors 155 /// @{ 156 157 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 158 bool isX86_64() const { 159 uint32_t CPUType = TargetObjectWriter->getCPUType(); 160 return CPUType == MachO::CPU_TYPE_X86_64; 161 } 162 163 /// @} 164 165 void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands, 166 unsigned LoadCommandsSize, bool SubsectionsViaSymbols); 167 168 /// Write a segment load command. 169 /// 170 /// \param NumSections The number of sections in this segment. 171 /// \param SectionDataSize The total size of the sections. 172 void writeSegmentLoadCommand(StringRef Name, unsigned NumSections, 173 uint64_t VMAddr, uint64_t VMSize, 174 uint64_t SectionDataStartOffset, 175 uint64_t SectionDataSize, uint32_t MaxProt, 176 uint32_t InitProt); 177 178 void writeSection(const MCAsmLayout &Layout, const MCSection &Sec, 179 uint64_t VMAddr, uint64_t FileOffset, unsigned Flags, 180 uint64_t RelocationsStart, unsigned NumRelocations); 181 182 void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, 183 uint32_t StringTableOffset, 184 uint32_t StringTableSize); 185 186 void writeDysymtabLoadCommand( 187 uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols, 188 uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols, 189 uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols, 190 uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols); 191 192 void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout); 193 194 void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset, 195 uint32_t DataSize); 196 197 void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options); 198 199 // FIXME: We really need to improve the relocation validation. Basically, we 200 // want to implement a separate computation which evaluates the relocation 201 // entry as the linker would, and verifies that the resultant fixup value is 202 // exactly what the encoder wanted. This will catch several classes of 203 // problems: 204 // 205 // - Relocation entry bugs, the two algorithms are unlikely to have the same 206 // exact bug. 207 // 208 // - Relaxation issues, where we forget to relax something. 209 // 210 // - Input errors, where something cannot be correctly encoded. 'as' allows 211 // these through in many cases. 212 213 // Add a relocation to be output in the object file. At the time this is 214 // called, the symbol indexes are not know, so if the relocation refers 215 // to a symbol it should be passed as \p RelSymbol so that it can be updated 216 // afterwards. If the relocation doesn't refer to a symbol, nullptr should be 217 // used. 218 void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, 219 MachO::any_relocation_info &MRE) { 220 RelAndSymbol P(RelSymbol, MRE); 221 Relocations[Sec].push_back(P); 222 } 223 224 void recordScatteredRelocation(const MCAssembler &Asm, 225 const MCAsmLayout &Layout, 226 const MCFragment *Fragment, 227 const MCFixup &Fixup, MCValue Target, 228 unsigned Log2Size, uint64_t &FixedValue); 229 230 void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 231 const MCFragment *Fragment, const MCFixup &Fixup, 232 MCValue Target, uint64_t &FixedValue); 233 234 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 235 const MCFragment *Fragment, const MCFixup &Fixup, 236 MCValue Target, bool &IsPCRel, 237 uint64_t &FixedValue) override; 238 239 void bindIndirectSymbols(MCAssembler &Asm); 240 241 /// Compute the symbol table data. 242 void computeSymbolTable(MCAssembler &Asm, 243 std::vector<MachSymbolData> &LocalSymbolData, 244 std::vector<MachSymbolData> &ExternalSymbolData, 245 std::vector<MachSymbolData> &UndefinedSymbolData); 246 247 void computeSectionAddresses(const MCAssembler &Asm, 248 const MCAsmLayout &Layout); 249 250 void executePostLayoutBinding(MCAssembler &Asm, 251 const MCAsmLayout &Layout) override; 252 253 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 254 const MCSymbol &A, 255 const MCSymbol &B, 256 bool InSet) const override; 257 258 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 259 const MCSymbol &SymA, 260 const MCFragment &FB, bool InSet, 261 bool IsPCRel) const override; 262 263 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 264 }; 265 266 /// Construct a new Mach-O writer instance. 267 /// 268 /// This routine takes ownership of the target writer subclass. 269 /// 270 /// \param MOTW - The target specific Mach-O writer subclass. 271 /// \param OS - The stream to write to. 272 /// \returns The constructed object writer. 273 MCObjectWriter *createMachObjectWriter(MCMachObjectTargetWriter *MOTW, 274 raw_pwrite_stream &OS, 275 bool IsLittleEndian); 276 277 } // end namespace llvm 278 279 #endif // LLVM_MC_MCMACHOBJECTWRITER_H 280
