lib/MC/ELFObjectWriter.h

   1 //===- lib/MC/ELFObjectWriter.h - ELF File Writer -------------------------===//
   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 // This file implements ELF object file writer information.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_MC_ELFOBJECTWRITER_H
  15 #define LLVM_MC_ELFOBJECTWRITER_H
  16
  17 #include "MCELF.h"
  18 #include "llvm/ADT/OwningPtr.h"
  19 #include "llvm/ADT/SmallPtrSet.h"
  20 #include "llvm/ADT/SmallString.h"
  21 #include "llvm/ADT/STLExtras.h"
  22 #include "llvm/MC/MCAssembler.h"
  23 #include "llvm/MC/MCELFObjectWriter.h"
  24 #include "llvm/MC/MCELFSymbolFlags.h"
  25 #include "llvm/MC/MCObjectWriter.h"
  26 #include "llvm/MC/MCExpr.h"
  27 #include "llvm/MC/MCSymbol.h"
  28
  29 #include <vector>
  30
  31 namespace llvm {
  32
  33 class MCSection;
  34 class MCDataFragment;
  35 class MCSectionELF;
  36
  37 class ELFObjectWriter : public MCObjectWriter {
  38   protected:
  39
  40     static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
  41     static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
  42     static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
  43     static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
  44                            bool Used, bool Renamed);
  45     static bool isLocal(const MCSymbolData &Data, bool isSignature,
  46                         bool isUsedInReloc);
  47     static bool IsELFMetaDataSection(const MCSectionData &SD);
  48     static uint64_t DataSectionSize(const MCSectionData &SD);
  49     static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
  50                                        const MCSectionData &SD);
  51     static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
  52                                           const MCSectionData &SD);
  53
  54     void WriteDataSectionData(MCAssembler &Asm,
  55                               const MCAsmLayout &Layout,
  56                               const MCSectionELF &Section);
  57
  58     /*static bool isFixupKindX86RIPRel(unsigned Kind) {
  59       return Kind == X86::reloc_riprel_4byte ||
  60         Kind == X86::reloc_riprel_4byte_movq_load;
  61     }*/
  62
  63     /// ELFSymbolData - Helper struct for containing some precomputed
  64     /// information on symbols.
  65     struct ELFSymbolData {
  66       MCSymbolData *SymbolData;
  67       uint64_t StringIndex;
  68       uint32_t SectionIndex;
  69
  70       // Support lexicographic sorting.
  71       bool operator<(const ELFSymbolData &RHS) const {
  72         if (MCELF::GetType(*SymbolData) == ELF::STT_FILE)
  73           return true;
  74         if (MCELF::GetType(*RHS.SymbolData) == ELF::STT_FILE)
  75           return false;
  76         return SymbolData->getSymbol().getName() <
  77                RHS.SymbolData->getSymbol().getName();
  78       }
  79     };
  80
  81     /// @name Relocation Data
  82     /// @{
  83
  84     struct ELFRelocationEntry {
  85       // Make these big enough for both 32-bit and 64-bit
  86       uint64_t r_offset;
  87       int Index;
  88       unsigned Type;
  89       const MCSymbol *Symbol;
  90       uint64_t r_addend;
  91
  92       ELFRelocationEntry()
  93         : r_offset(0), Index(0), Type(0), Symbol(0), r_addend(0) {}
  94
  95       ELFRelocationEntry(uint64_t RelocOffset, int Idx,
  96                          unsigned RelType, const MCSymbol *Sym,
  97                          uint64_t Addend)
  98         : r_offset(RelocOffset), Index(Idx), Type(RelType),
  99           Symbol(Sym), r_addend(Addend) {}
 100
 101       // Support lexicographic sorting.
 102       bool operator<(const ELFRelocationEntry &RE) const {
 103         return RE.r_offset < r_offset;
 104       }
 105     };
 106
 107     /// The target specific ELF writer instance.
 108     llvm::OwningPtr<MCELFObjectTargetWriter> TargetObjectWriter;
 109
 110     SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
 111     SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
 112     DenseMap<const MCSymbol *, const MCSymbol *> Renames;
 113
 114     llvm::DenseMap<const MCSectionData*,
 115                    std::vector<ELFRelocationEntry> > Relocations;
 116     DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
 117
 118     /// @}
 119     /// @name Symbol Table Data
 120     /// @{
 121
 122     SmallString<256> StringTable;
 123     std::vector<ELFSymbolData> LocalSymbolData;
 124     std::vector<ELFSymbolData> ExternalSymbolData;
 125     std::vector<ELFSymbolData> UndefinedSymbolData;
 126
 127     /// @}
 128
 129     bool NeedsGOT;
 130
 131     bool NeedsSymtabShndx;
 132
 133     // This holds the symbol table index of the last local symbol.
 134     unsigned LastLocalSymbolIndex;
 135     // This holds the .strtab section index.
 136     unsigned StringTableIndex;
 137     // This holds the .symtab section index.
 138     unsigned SymbolTableIndex;
 139
 140     unsigned ShstrtabIndex;
 141
 142
 143     const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
 144                                   const MCValue &Target,
 145                                   const MCFragment &F) const;
 146
 147     // For arch-specific emission of explicit reloc symbol
 148     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
 149                                            const MCValue &Target,
 150                                            const MCFragment &F,
 151                                            bool IsBSS) const {
 152       return NULL;
 153     }
 154
 155     bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
 156     bool hasRelocationAddend() const {
 157       return TargetObjectWriter->hasRelocationAddend();
 158     }
 159
 160   public:
 161     ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
 162                     raw_ostream &_OS, bool IsLittleEndian)
 163       : MCObjectWriter(_OS, IsLittleEndian),
 164         TargetObjectWriter(MOTW),
 165         NeedsGOT(false), NeedsSymtabShndx(false){
 166     }
 167
 168     virtual ~ELFObjectWriter();
 169
 170     void WriteWord(uint64_t W) {
 171       if (is64Bit())
 172         Write64(W);
 173       else
 174         Write32(W);
 175     }
 176
 177     void StringLE16(char *buf, uint16_t Value) {
 178       buf[0] = char(Value >> 0);
 179       buf[1] = char(Value >> 8);
 180     }
 181
 182     void StringLE32(char *buf, uint32_t Value) {
 183       StringLE16(buf, uint16_t(Value >> 0));
 184       StringLE16(buf + 2, uint16_t(Value >> 16));
 185     }
 186
 187     void StringLE64(char *buf, uint64_t Value) {
 188       StringLE32(buf, uint32_t(Value >> 0));
 189       StringLE32(buf + 4, uint32_t(Value >> 32));
 190     }
 191
 192     void StringBE16(char *buf ,uint16_t Value) {
 193       buf[0] = char(Value >> 8);
 194       buf[1] = char(Value >> 0);
 195     }
 196
 197     void StringBE32(char *buf, uint32_t Value) {
 198       StringBE16(buf, uint16_t(Value >> 16));
 199       StringBE16(buf + 2, uint16_t(Value >> 0));
 200     }
 201
 202     void StringBE64(char *buf, uint64_t Value) {
 203       StringBE32(buf, uint32_t(Value >> 32));
 204       StringBE32(buf + 4, uint32_t(Value >> 0));
 205     }
 206
 207     void String8(MCDataFragment &F, uint8_t Value) {
 208       char buf[1];
 209       buf[0] = Value;
 210       F.getContents() += StringRef(buf, 1);
 211     }
 212
 213     void String16(MCDataFragment &F, uint16_t Value) {
 214       char buf[2];
 215       if (isLittleEndian())
 216         StringLE16(buf, Value);
 217       else
 218         StringBE16(buf, Value);
 219       F.getContents() += StringRef(buf, 2);
 220     }
 221
 222     void String32(MCDataFragment &F, uint32_t Value) {
 223       char buf[4];
 224       if (isLittleEndian())
 225         StringLE32(buf, Value);
 226       else
 227         StringBE32(buf, Value);
 228       F.getContents() += StringRef(buf, 4);
 229     }
 230
 231     void String64(MCDataFragment &F, uint64_t Value) {
 232       char buf[8];
 233       if (isLittleEndian())
 234         StringLE64(buf, Value);
 235       else
 236         StringBE64(buf, Value);
 237       F.getContents() += StringRef(buf, 8);
 238     }
 239
 240     virtual void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
 241
 242     /// Default e_flags = 0
 243     virtual void WriteEFlags() { Write32(0); }
 244
 245     virtual void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
 246                           uint64_t name, uint8_t info,
 247                           uint64_t value, uint64_t size,
 248                           uint8_t other, uint32_t shndx,
 249                           bool Reserved);
 250
 251     virtual void WriteSymbol(MCDataFragment *SymtabF,  MCDataFragment *ShndxF,
 252                      ELFSymbolData &MSD,
 253                      const MCAsmLayout &Layout);
 254
 255     typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
 256     virtual void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
 257                           const MCAssembler &Asm,
 258                           const MCAsmLayout &Layout,
 259                           const SectionIndexMapTy &SectionIndexMap);
 260
 261     virtual void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
 262                                   const MCFragment *Fragment, const MCFixup &Fixup,
 263                                   MCValue Target, uint64_t &FixedValue);
 264
 265     virtual uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
 266                                          const MCSymbol *S);
 267
 268     // Map from a group section to the signature symbol
 269     typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
 270     // Map from a signature symbol to the group section
 271     typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
 272     // Map from a section to the section with the relocations
 273     typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
 274     // Map from a section to its offset
 275     typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
 276
 277     /// ComputeSymbolTable - Compute the symbol table data
 278     ///
 279     /// \param StringTable [out] - The string table data.
 280     /// \param StringIndexMap [out] - Map from symbol names to offsets in the
 281     /// string table.
 282     virtual void ComputeSymbolTable(MCAssembler &Asm,
 283                             const SectionIndexMapTy &SectionIndexMap,
 284                                     RevGroupMapTy RevGroupMap,
 285                                     unsigned NumRegularSections);
 286
 287     virtual void ComputeIndexMap(MCAssembler &Asm,
 288                                  SectionIndexMapTy &SectionIndexMap,
 289                                  const RelMapTy &RelMap);
 290
 291     void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
 292                                   RelMapTy &RelMap);
 293
 294     void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
 295                           const RelMapTy &RelMap);
 296
 297     virtual void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
 298                                         SectionIndexMapTy &SectionIndexMap,
 299                                         const RelMapTy &RelMap);
 300
 301     // Create the sections that show up in the symbol table. Currently
 302     // those are the .note.GNU-stack section and the group sections.
 303     virtual void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
 304                                        GroupMapTy &GroupMap,
 305                                        RevGroupMapTy &RevGroupMap,
 306                                        SectionIndexMapTy &SectionIndexMap,
 307                                        const RelMapTy &RelMap);
 308
 309     virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
 310                                           const MCAsmLayout &Layout);
 311
 312     void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
 313                             const MCAsmLayout &Layout,
 314                             const SectionIndexMapTy &SectionIndexMap,
 315                             const SectionOffsetMapTy &SectionOffsetMap);
 316
 317     void ComputeSectionOrder(MCAssembler &Asm,
 318                              std::vector<const MCSectionELF*> &Sections);
 319
 320     virtual void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
 321                           uint64_t Address, uint64_t Offset,
 322                           uint64_t Size, uint32_t Link, uint32_t Info,
 323                           uint64_t Alignment, uint64_t EntrySize);
 324
 325     virtual void WriteRelocationsFragment(const MCAssembler &Asm,
 326                                           MCDataFragment *F,
 327                                           const MCSectionData *SD);
 328
 329     virtual bool
 330     IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
 331                                            const MCSymbolData &DataA,
 332                                            const MCFragment &FB,
 333                                            bool InSet,
 334                                            bool IsPCRel) const;
 335
 336     virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
 337     virtual void WriteSection(MCAssembler &Asm,
 338                       const SectionIndexMapTy &SectionIndexMap,
 339                       uint32_t GroupSymbolIndex,
 340                       uint64_t Offset, uint64_t Size, uint64_t Alignment,
 341                       const MCSectionELF &Section);
 342
 343   protected:
 344     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 345                                   bool IsPCRel, bool IsRelocWithSymbol,
 346                                   int64_t Addend) = 0;
 347   };
 348
 349   //===- X86ELFObjectWriter -------------------------------------------===//
 350
 351   class X86ELFObjectWriter : public ELFObjectWriter {
 352   public:
 353     X86ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
 354                        raw_ostream &_OS,
 355                        bool IsLittleEndian);
 356
 357     virtual ~X86ELFObjectWriter();
 358   protected:
 359     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 360                                   bool IsPCRel, bool IsRelocWithSymbol,
 361                                   int64_t Addend);
 362   };
 363
 364
 365   //===- ARMELFObjectWriter -------------------------------------------===//
 366
 367   class ARMELFObjectWriter : public ELFObjectWriter {
 368   public:
 369     // FIXME: MCAssembler can't yet return the Subtarget,
 370     enum { DefaultEABIVersion = 0x05000000U };
 371
 372     ARMELFObjectWriter(MCELFObjectTargetWriter *MOTW,
 373                        raw_ostream &_OS,
 374                        bool IsLittleEndian);
 375
 376     virtual ~ARMELFObjectWriter();
 377
 378     virtual void WriteEFlags();
 379   protected:
 380     virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
 381                                            const MCValue &Target,
 382                                            const MCFragment &F,
 383                                            bool IsBSS) const;
 384
 385     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 386                                   bool IsPCRel, bool IsRelocWithSymbol,
 387                                   int64_t Addend);
 388   };
 389
 390   //===- MBlazeELFObjectWriter -------------------------------------------===//
 391
 392   class MBlazeELFObjectWriter : public ELFObjectWriter {
 393   public:
 394     MBlazeELFObjectWriter(MCELFObjectTargetWriter *MOTW,
 395                           raw_ostream &_OS,
 396                           bool IsLittleEndian);
 397
 398     virtual ~MBlazeELFObjectWriter();
 399   protected:
 400     virtual unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
 401                                   bool IsPCRel, bool IsRelocWithSymbol,
 402                                   int64_t Addend);
 403   };
 404 }
 405
 406 #endif