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 <cstdint> 20 #include <memory> 21 #include <string> 22 #include <vector> 23 24 namespace llvm { 25 26 class MachObjectWriter; 27 28 class MCMachObjectTargetWriter : public MCObjectTargetWriter { 29 const unsigned Is64Bit : 1; 30 const uint32_t CPUType; 31 protected: 32 uint32_t CPUSubtype; 33 public: 34 unsigned LocalDifference_RIT; 35 36 protected: 37 MCMachObjectTargetWriter(bool Is64Bit_, uint32_t CPUType_, 38 uint32_t CPUSubtype_); 39 setLocalDifferenceRelocationType(unsigned Type)40 void setLocalDifferenceRelocationType(unsigned Type) { 41 LocalDifference_RIT = Type; 42 } 43 44 public: 45 virtual ~MCMachObjectTargetWriter(); 46 getFormat()47 virtual Triple::ObjectFormatType getFormat() const { return Triple::MachO; } classof(const MCObjectTargetWriter * W)48 static bool classof(const MCObjectTargetWriter *W) { 49 return W->getFormat() == Triple::MachO; 50 } 51 52 /// \name Lifetime Management 53 /// @{ 54 reset()55 virtual void reset() {} 56 57 /// @} 58 59 /// \name Accessors 60 /// @{ 61 is64Bit()62 bool is64Bit() const { return Is64Bit; } getCPUType()63 uint32_t getCPUType() const { return CPUType; } getCPUSubtype()64 uint32_t getCPUSubtype() const { return CPUSubtype; } getLocalDifferenceRelocationType()65 unsigned getLocalDifferenceRelocationType() const { 66 return LocalDifference_RIT; 67 } 68 69 /// @} 70 71 /// \name API 72 /// @{ 73 74 virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, 75 const MCAsmLayout &Layout, 76 const MCFragment *Fragment, 77 const MCFixup &Fixup, MCValue Target, 78 uint64_t &FixedValue) = 0; 79 80 /// @} 81 }; 82 83 class MachObjectWriter : public MCObjectWriter { 84 /// Helper struct for containing some precomputed information on symbols. 85 struct MachSymbolData { 86 const MCSymbol *Symbol; 87 uint64_t StringIndex; 88 uint8_t SectionIndex; 89 90 // Support lexicographic sorting. 91 bool operator<(const MachSymbolData &RHS) const; 92 }; 93 94 /// The target specific Mach-O writer instance. 95 std::unique_ptr<MCMachObjectTargetWriter> TargetObjectWriter; 96 97 /// \name Relocation Data 98 /// @{ 99 100 struct RelAndSymbol { 101 const MCSymbol *Sym; 102 MachO::any_relocation_info MRE; RelAndSymbolRelAndSymbol103 RelAndSymbol(const MCSymbol *Sym, const MachO::any_relocation_info &MRE) 104 : Sym(Sym), MRE(MRE) {} 105 }; 106 107 DenseMap<const MCSection *, std::vector<RelAndSymbol>> Relocations; 108 DenseMap<const MCSection *, unsigned> IndirectSymBase; 109 110 SectionAddrMap SectionAddress; 111 112 /// @} 113 /// \name Symbol Table Data 114 /// @{ 115 116 StringTableBuilder StringTable{StringTableBuilder::MachO}; 117 std::vector<MachSymbolData> LocalSymbolData; 118 std::vector<MachSymbolData> ExternalSymbolData; 119 std::vector<MachSymbolData> UndefinedSymbolData; 120 121 /// @} 122 123 MachSymbolData *findSymbolData(const MCSymbol &Sym); 124 125 void writeWithPadding(StringRef Str, uint64_t Size); 126 127 public: MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW,raw_pwrite_stream & OS,bool IsLittleEndian)128 MachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 129 raw_pwrite_stream &OS, bool IsLittleEndian) 130 : TargetObjectWriter(std::move(MOTW)), 131 W(OS, IsLittleEndian ? support::little : support::big) {} 132 133 support::endian::Writer W; 134 135 const MCSymbol &findAliasedSymbol(const MCSymbol &Sym) const; 136 137 /// \name Lifetime management Methods 138 /// @{ 139 140 void reset() override; 141 142 /// @} 143 144 /// \name Utility Methods 145 /// @{ 146 147 bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind); 148 getSectionAddressMap()149 SectionAddrMap &getSectionAddressMap() { return SectionAddress; } 150 getSectionAddress(const MCSection * Sec)151 uint64_t getSectionAddress(const MCSection *Sec) const { 152 return SectionAddress.lookup(Sec); 153 } 154 uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const; 155 156 uint64_t getFragmentAddress(const MCFragment *Fragment, 157 const MCAsmLayout &Layout) const; 158 159 uint64_t getPaddingSize(const MCSection *SD, const MCAsmLayout &Layout) const; 160 161 bool doesSymbolRequireExternRelocation(const MCSymbol &S); 162 163 /// @} 164 165 /// \name Target Writer Proxy Accessors 166 /// @{ 167 is64Bit()168 bool is64Bit() const { return TargetObjectWriter->is64Bit(); } isX86_64()169 bool isX86_64() const { 170 uint32_t CPUType = TargetObjectWriter->getCPUType(); 171 return CPUType == MachO::CPU_TYPE_X86_64; 172 } 173 174 /// @} 175 176 void writeHeader(MachO::HeaderFileType Type, unsigned NumLoadCommands, 177 unsigned LoadCommandsSize, bool SubsectionsViaSymbols); 178 179 /// Write a segment load command. 180 /// 181 /// \param NumSections The number of sections in this segment. 182 /// \param SectionDataSize The total size of the sections. 183 void writeSegmentLoadCommand(StringRef Name, unsigned NumSections, 184 uint64_t VMAddr, uint64_t VMSize, 185 uint64_t SectionDataStartOffset, 186 uint64_t SectionDataSize, uint32_t MaxProt, 187 uint32_t InitProt); 188 189 void writeSection(const MCAsmLayout &Layout, const MCSection &Sec, 190 uint64_t VMAddr, uint64_t FileOffset, unsigned Flags, 191 uint64_t RelocationsStart, unsigned NumRelocations); 192 193 void writeSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols, 194 uint32_t StringTableOffset, 195 uint32_t StringTableSize); 196 197 void writeDysymtabLoadCommand( 198 uint32_t FirstLocalSymbol, uint32_t NumLocalSymbols, 199 uint32_t FirstExternalSymbol, uint32_t NumExternalSymbols, 200 uint32_t FirstUndefinedSymbol, uint32_t NumUndefinedSymbols, 201 uint32_t IndirectSymbolOffset, uint32_t NumIndirectSymbols); 202 203 void writeNlist(MachSymbolData &MSD, const MCAsmLayout &Layout); 204 205 void writeLinkeditLoadCommand(uint32_t Type, uint32_t DataOffset, 206 uint32_t DataSize); 207 208 void writeLinkerOptionsLoadCommand(const std::vector<std::string> &Options); 209 210 // FIXME: We really need to improve the relocation validation. Basically, we 211 // want to implement a separate computation which evaluates the relocation 212 // entry as the linker would, and verifies that the resultant fixup value is 213 // exactly what the encoder wanted. This will catch several classes of 214 // problems: 215 // 216 // - Relocation entry bugs, the two algorithms are unlikely to have the same 217 // exact bug. 218 // 219 // - Relaxation issues, where we forget to relax something. 220 // 221 // - Input errors, where something cannot be correctly encoded. 'as' allows 222 // these through in many cases. 223 224 // Add a relocation to be output in the object file. At the time this is 225 // called, the symbol indexes are not know, so if the relocation refers 226 // to a symbol it should be passed as \p RelSymbol so that it can be updated 227 // afterwards. If the relocation doesn't refer to a symbol, nullptr should be 228 // used. addRelocation(const MCSymbol * RelSymbol,const MCSection * Sec,MachO::any_relocation_info & MRE)229 void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, 230 MachO::any_relocation_info &MRE) { 231 RelAndSymbol P(RelSymbol, MRE); 232 Relocations[Sec].push_back(P); 233 } 234 235 void recordScatteredRelocation(const MCAssembler &Asm, 236 const MCAsmLayout &Layout, 237 const MCFragment *Fragment, 238 const MCFixup &Fixup, MCValue Target, 239 unsigned Log2Size, uint64_t &FixedValue); 240 241 void recordTLVPRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, 242 const MCFragment *Fragment, const MCFixup &Fixup, 243 MCValue Target, uint64_t &FixedValue); 244 245 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, 246 const MCFragment *Fragment, const MCFixup &Fixup, 247 MCValue Target, uint64_t &FixedValue) override; 248 249 void bindIndirectSymbols(MCAssembler &Asm); 250 251 /// Compute the symbol table data. 252 void computeSymbolTable(MCAssembler &Asm, 253 std::vector<MachSymbolData> &LocalSymbolData, 254 std::vector<MachSymbolData> &ExternalSymbolData, 255 std::vector<MachSymbolData> &UndefinedSymbolData); 256 257 void computeSectionAddresses(const MCAssembler &Asm, 258 const MCAsmLayout &Layout); 259 260 void executePostLayoutBinding(MCAssembler &Asm, 261 const MCAsmLayout &Layout) override; 262 263 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 264 const MCSymbol &A, 265 const MCSymbol &B, 266 bool InSet) const override; 267 268 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm, 269 const MCSymbol &SymA, 270 const MCFragment &FB, bool InSet, 271 bool IsPCRel) const override; 272 273 uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override; 274 }; 275 276 /// Construct a new Mach-O writer instance. 277 /// 278 /// This routine takes ownership of the target writer subclass. 279 /// 280 /// \param MOTW - The target specific Mach-O writer subclass. 281 /// \param OS - The stream to write to. 282 /// \returns The constructed object writer. 283 std::unique_ptr<MCObjectWriter> 284 createMachObjectWriter(std::unique_ptr<MCMachObjectTargetWriter> MOTW, 285 raw_pwrite_stream &OS, bool IsLittleEndian); 286 287 } // end namespace llvm 288 289 #endif // LLVM_MC_MCMACHOBJECTWRITER_H 290