1 //===- llvm/MC/MCMachObjectWriter.h - Mach Object Writer --------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_MC_MCMACHOBJECTWRITER_H 10 #define LLVM_MC_MCMACHOBJECTWRITER_H 11 12 #include "llvm/ADT/DenseMap.h" 13 #include "llvm/ADT/StringRef.h" 14 #include "llvm/BinaryFormat/MachO.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCObjectWriter.h" 17 #include "llvm/MC/MCSection.h" 18 #include "llvm/MC/StringTableBuilder.h" 19 #include "llvm/Support/EndianStream.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 protected: 33 uint32_t CPUSubtype; 34 public: 35 unsigned LocalDifference_RIT = 0; 36 37 protected: 38 MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, 39 uint32_t CPUSubtype_); 40 41 void setLocalDifferenceRelocationType(unsigned Type) { 42 LocalDifference_RIT = Type; 43 } 44 45 public: 46 virtual ~MCMachObjectTargetWriter(); 47 48 Triple::ObjectFormatType getFormat() const override { return Triple::MachO; } 49 static bool classof(const MCObjectTargetWriter *W) { 50 return W->getFormat() == Triple::MachO; 51 } 52 53 /// \name Lifetime Management 54 /// @{ 55 56 virtual void reset() {} 57 58 /// @} 59 60 /// \name Accessors 61 /// @{ 62 63 bool is64Bit() const { return Is64Bit; } 64 uint32_t getCPUType() const { return CPUType; } 65 uint32_t getCPUSubtype() const { return CPUSubtype; } 66 unsigned getLocalDifferenceRelocationType() const { 67 return LocalDifference_RIT; 68 } 69 70 /// @} 71 72 /// \name API 73 /// @{ 74 75 virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 76 const MCAsmLayout &Layout, 77 const MCFragment *Fragment, 78 const MCFixup &Fixup, MCValue Target, 79 uint64_t &FixedValue) = 0; 80 81 /// @} 82 }; 83 84 class MachObjectWriter : public MCObjectWriter { 85 /// Helper struct for containing some precomputed information on symbols. 86 struct MachSymbolData { 87 const MCSymbol *Symbol; 88 uint64_t StringIndex; 89 uint8_t SectionIndex; 90 91 // Support lexicographic sorting. 92 bool operator<(const MachSymbolData &RHS) const; 93 }; 94 95 /// The target specific Mach-O writer instance. 96 std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter; 97 98 /// \name Relocation Data 99 /// @{ 100 101 struct RelAndSymbol { 102 const MCSymbol *Sym; 103 MachO::any_relocation_info MRE; 104 RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE) 105 : Sym(Sym), MRE(MRE) {} 106 }; 107 108 DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations; 109 DenseMap<const MCSection *, unsigned> IndirectSymBase; 110 111 SectionAddrMap SectionAddress; 112 113 /// @} 114 /// \name Symbol Table Data 115 /// @{ 116 117 StringTableBuilder StringTable; 118 std::vector<MachSymbolData> LocalSymbolData; 119 std::vector<MachSymbolData> ExternalSymbolData; 120 std::vector<MachSymbolData> UndefinedSymbolData; 121 122 /// @} 123 124 MachSymbolData *findSymbolData(const MCSymbol &Sym); 125 126 void writeWithPadding(StringRef Str, uint64_t Size); 127 128 public: 129 MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 130 raw_pwrite_stream &OS, bool IsLittleEndian) 131 : TargetObjectWriter(std::move(MOTW)), 132 StringTable(TargetObjectWriter->is64Bit() ? StringTableBuilder::MachO64 133 : StringTableBuilder::MachO), 134 W(OS, 135 IsLittleEndian ? llvm::endianness::little : llvm::endianness::big) {} 136 137 support::endian::Writer W; 138 139 const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const; 140 141 /// \name Lifetime management Methods 142 /// @{ 143 144 void reset() override; 145 146 /// @} 147 148 /// \name Utility Methods 149 /// @{ 150 151 bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 152 153 SectionAddrMap &getSectionAddressMap() { return SectionAddress; } 154 155 uint64_t getSectionAddress(const MCSection *Sec) const { 156 return SectionAddress.lookup(Sec); 157 } 158 uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const; 159 160 uint64_t getFragmentAddress(const MCFragment *Fragment, 161 const MCAsmLayout &Layout) const; 162 163 uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const; 164 165 bool doesSymbolRequireExternRelocation(const MCSymbol &S); 166 167 /// @} 168 169 /// \name Target Writer Proxy Accessors 170 /// @{ 171 172 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } 173 bool isX86_64() const { 174 uint32_t CPUType = TargetObjectWriter->getCPUType(); 175 return CPUType == MachO::CPU_TYPE_X86_64; 176 } 177 178 /// @} 179 180 void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands, 181 unsigned LoadCommandsSize, bool SubsectionsViaSymbols); 182 183 /// Write a segment load command. 184 /// 185 /// \param NumSections The number of sections in this segment. 186 /// \param SectionDataSize The total size of the sections. 187 void writeSegmentLoadCommand(StringRef Name, unsigned NumSections, 188 uint64_t VMAddr, uint64_t VMSize, 189 uint64_t SectionDataStartOffset, 190 uint64_t SectionDataSize, uint32_t MaxProt, 191 uint32_t InitProt); 192 193 void writeSection(const MCAsmLayout &Layout, const MCSection &Sec, 194 uint64_t VMAddr, uint64_t FileOffset, unsigned Flags, 195 uint64_t RelocationsStart, unsigned NumRelocations); 196 197 void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, 198 uint32_t StringTableOffset, 199 uint32_t StringTableSize); 200 201 void writeDysymtabLoadCommand( 202 uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols, 203 uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols, 204 uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols, 205 uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols); 206 207 void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout); 208 209 void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset, 210 uint32_t DataSize); 211 212 void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options); 213 214 // FIXME: We really need to improve the relocation validation. Basically, we 215 // want to implement a separate computation which evaluates the relocation 216 // entry as the linker would, and verifies that the resultant fixup value is 217 // exactly what the encoder wanted. This will catch several classes of 218 // problems: 219 // 220 // - Relocation entry bugs, the two algorithms are unlikely to have the same 221 // exact bug. 222 // 223 // - Relaxation issues, where we forget to relax something. 224 // 225 // - Input errors, where something cannot be correctly encoded. 'as' allows 226 // these through in many cases. 227 228 // Add a relocation to be output in the object file. At the time this is 229 // called, the symbol indexes are not know, so if the relocation refers 230 // to a symbol it should be passed as \p RelSymbol so that it can be updated 231 // afterwards. If the relocation doesn't refer to a symbol, nullptr should be 232 // used. 233 void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, 234 MachO::any_relocation_info &MRE) { 235 RelAndSymbol P(RelSymbol, MRE); 236 Relocations[Sec].push_back(P); 237 } 238 239 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 240 const MCFragment *Fragment, const MCFixup &Fixup, 241 MCValue Target, uint64_t &FixedValue) override; 242 243 void bindIndirectSymbols(MCAssembler &Asm); 244 245 /// Compute the symbol table data. 246 void computeSymbolTable(MCAssembler &Asm, 247 std::vector<MachSymbolData> &LocalSymbolData, 248 std::vector<MachSymbolData> &ExternalSymbolData, 249 std::vector<MachSymbolData> &UndefinedSymbolData); 250 251 void computeSectionAddresses(const MCAssembler &Asm, 252 const MCAsmLayout &Layout); 253 254 void executePostLayoutBinding(MCAssembler &Asm, 255 const MCAsmLayout &Layout) override; 256 257 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 258 const MCSymbol &A, 259 const MCSymbol &B, 260 bool InSet) const override; 261 262 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 263 const MCSymbol &SymA, 264 const MCFragment &FB, bool InSet, 265 bool IsPCRel) const override; 266 267 void populateAddrSigSection(MCAssembler &Asm); 268 269 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 270 }; 271 272 /// Construct a new Mach-O writer instance. 273 /// 274 /// This routine takes ownership of the target writer subclass. 275 /// 276 /// \param MOTW - The target specific Mach-O writer subclass. 277 /// \param OS - The stream to write to. 278 /// \returns The constructed object writer. 279 std::unique_ptr<MCObjectWriter> 280 createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 281 raw_pwrite_stream &OS, bool IsLittleEndian); 282 283 } // end namespace llvm 284 285 #endif // LLVM_MC_MCMACHOBJECTWRITER_H 286