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 : public MCObjectTargetWriter { 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 setLocalDifferenceRelocationType(unsigned Type)39 void setLocalDifferenceRelocationType(unsigned Type) { 40 LocalDifference_RIT = Type; 41 } 42 43 public: 44 virtual ~MCMachObjectTargetWriter(); 45 getFormat()46 virtual Triple::ObjectFormatType getFormat() const { return Triple::MachO; } classof(const MCObjectTargetWriter * W)47 static bool classof(const MCObjectTargetWriter *W) { 48 return W->getFormat() == Triple::MachO; 49 } 50 51 /// \name Lifetime Management 52 /// @{ 53 reset()54 virtual void reset() {} 55 56 /// @} 57 58 /// \name Accessors 59 /// @{ 60 is64Bit()61 bool is64Bit() const { return Is64Bit; } getCPUType()62 uint32_t getCPUType() const { return CPUType; } getCPUSubtype()63 uint32_t getCPUSubtype() const { return CPUSubtype; } getLocalDifferenceRelocationType()64 unsigned getLocalDifferenceRelocationType() const { 65 return LocalDifference_RIT; 66 } 67 68 /// @} 69 70 /// \name API 71 /// @{ 72 73 virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 74 const MCAsmLayout &Layout, 75 const MCFragment *Fragment, 76 const MCFixup &Fixup, MCValue Target, 77 uint64_t &FixedValue) = 0; 78 79 /// @} 80 }; 81 82 class MachObjectWriter : public MCObjectWriter { 83 /// Helper struct for containing some precomputed information on symbols. 84 struct MachSymbolData { 85 const MCSymbol *Symbol; 86 uint64_t StringIndex; 87 uint8_t SectionIndex; 88 89 // Support lexicographic sorting. 90 bool operator<(const MachSymbolData &RHS) const; 91 }; 92 93 /// The target specific Mach-O writer instance. 94 std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter; 95 96 /// \name Relocation Data 97 /// @{ 98 99 struct RelAndSymbol { 100 const MCSymbol *Sym; 101 MachO::any_relocation_info MRE; RelAndSymbolRelAndSymbol102 RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE) 103 : Sym(Sym), MRE(MRE) {} 104 }; 105 106 DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations; 107 DenseMap<const MCSection *, unsigned> IndirectSymBase; 108 109 SectionAddrMap SectionAddress; 110 111 /// @} 112 /// \name Symbol Table Data 113 /// @{ 114 115 StringTableBuilder StringTable{StringTableBuilder::MachO}; 116 std::vector<MachSymbolData> LocalSymbolData; 117 std::vector<MachSymbolData> ExternalSymbolData; 118 std::vector<MachSymbolData> UndefinedSymbolData; 119 120 /// @} 121 122 MachSymbolData *findSymbolData(const MCSymbol &Sym); 123 124 void writeWithPadding(StringRef Str, uint64_t Size); 125 126 public: MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,raw_pwrite_stream & OS,bool IsLittleEndian)127 MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 128 raw_pwrite_stream &OS, bool IsLittleEndian) 129 : TargetObjectWriter(std::move(MOTW)), 130 W(OS, IsLittleEndian ? support::little : support::big) {} 131 132 support::endian::Writer W; 133 134 const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const; 135 136 /// \name Lifetime management Methods 137 /// @{ 138 139 void reset() override; 140 141 /// @} 142 143 /// \name Utility Methods 144 /// @{ 145 146 bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 147 getSectionAddressMap()148 SectionAddrMap &getSectionAddressMap() { return SectionAddress; } 149 getSectionAddress(const MCSection * Sec)150 uint64_t getSectionAddress(const MCSection *Sec) const { 151 return SectionAddress.lookup(Sec); 152 } 153 uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const; 154 155 uint64_t getFragmentAddress(const MCFragment *Fragment, 156 const MCAsmLayout &Layout) const; 157 158 uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const; 159 160 bool doesSymbolRequireExternRelocation(const MCSymbol &S); 161 162 /// @} 163 164 /// \name Target Writer Proxy Accessors 165 /// @{ 166 is64Bit()167 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } isX86_64()168 bool isX86_64() const { 169 uint32_t CPUType = TargetObjectWriter->getCPUType(); 170 return CPUType == MachO::CPU_TYPE_X86_64; 171 } 172 173 /// @} 174 175 void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands, 176 unsigned LoadCommandsSize, bool SubsectionsViaSymbols); 177 178 /// Write a segment load command. 179 /// 180 /// \param NumSections The number of sections in this segment. 181 /// \param SectionDataSize The total size of the sections. 182 void writeSegmentLoadCommand(StringRef Name, unsigned NumSections, 183 uint64_t VMAddr, uint64_t VMSize, 184 uint64_t SectionDataStartOffset, 185 uint64_t SectionDataSize, uint32_t MaxProt, 186 uint32_t InitProt); 187 188 void writeSection(const MCAsmLayout &Layout, const MCSection &Sec, 189 uint64_t VMAddr, uint64_t FileOffset, unsigned Flags, 190 uint64_t RelocationsStart, unsigned NumRelocations); 191 192 void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, 193 uint32_t StringTableOffset, 194 uint32_t StringTableSize); 195 196 void writeDysymtabLoadCommand( 197 uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols, 198 uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols, 199 uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols, 200 uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols); 201 202 void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout); 203 204 void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset, 205 uint32_t DataSize); 206 207 void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options); 208 209 // FIXME: We really need to improve the relocation validation. Basically, we 210 // want to implement a separate computation which evaluates the relocation 211 // entry as the linker would, and verifies that the resultant fixup value is 212 // exactly what the encoder wanted. This will catch several classes of 213 // problems: 214 // 215 // - Relocation entry bugs, the two algorithms are unlikely to have the same 216 // exact bug. 217 // 218 // - Relaxation issues, where we forget to relax something. 219 // 220 // - Input errors, where something cannot be correctly encoded. 'as' allows 221 // these through in many cases. 222 223 // Add a relocation to be output in the object file. At the time this is 224 // called, the symbol indexes are not know, so if the relocation refers 225 // to a symbol it should be passed as \p RelSymbol so that it can be updated 226 // afterwards. If the relocation doesn't refer to a symbol, nullptr should be 227 // used. addRelocation(const MCSymbol * RelSymbol,const MCSection * Sec,MachO::any_relocation_info & MRE)228 void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, 229 MachO::any_relocation_info &MRE) { 230 RelAndSymbol P(RelSymbol, MRE); 231 Relocations[Sec].push_back(P); 232 } 233 234 void recordScatteredRelocation(const MCAssembler &Asm, 235 const MCAsmLayout &Layout, 236 const MCFragment *Fragment, 237 const MCFixup &Fixup, MCValue Target, 238 unsigned Log2Size, uint64_t &FixedValue); 239 240 void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 241 const MCFragment *Fragment, const MCFixup &Fixup, 242 MCValue Target, uint64_t &FixedValue); 243 244 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 245 const MCFragment *Fragment, const MCFixup &Fixup, 246 MCValue Target, uint64_t &FixedValue) override; 247 248 void bindIndirectSymbols(MCAssembler &Asm); 249 250 /// Compute the symbol table data. 251 void computeSymbolTable(MCAssembler &Asm, 252 std::vector<MachSymbolData> &LocalSymbolData, 253 std::vector<MachSymbolData> &ExternalSymbolData, 254 std::vector<MachSymbolData> &UndefinedSymbolData); 255 256 void computeSectionAddresses(const MCAssembler &Asm, 257 const MCAsmLayout &Layout); 258 259 void executePostLayoutBinding(MCAssembler &Asm, 260 const MCAsmLayout &Layout) override; 261 262 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 263 const MCSymbol &A, 264 const MCSymbol &B, 265 bool InSet) const override; 266 267 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 268 const MCSymbol &SymA, 269 const MCFragment &FB, bool InSet, 270 bool IsPCRel) const override; 271 272 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 273 }; 274 275 /// Construct a new Mach-O writer instance. 276 /// 277 /// This routine takes ownership of the target writer subclass. 278 /// 279 /// \param MOTW - The target specific Mach-O writer subclass. 280 /// \param OS - The stream to write to. 281 /// \returns The constructed object writer. 282 std::unique_ptr<MCObjectWriter> 283 createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 284 raw_pwrite_stream &OS, bool IsLittleEndian); 285 286 } // end namespace llvm 287 288 #endif // LLVM_MC_MCMACHOBJECTWRITER_H 289