ELFObjectWriter.cpp revision 25958730dffe0a16f9c251a1fa317799b8419a1f 
1//===- lib/MC/ELFObjectWriter.cpp - 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#include "llvm/ADT/SmallPtrSet.h"
15#include "llvm/ADT/STLExtras.h"
16#include "llvm/ADT/StringMap.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/MC/MCAssembler.h"
19#include "llvm/MC/MCAsmLayout.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCELFSymbolFlags.h"
22#include "llvm/MC/MCExpr.h"
23#include "llvm/MC/MCObjectWriter.h"
24#include "llvm/MC/MCSectionELF.h"
25#include "llvm/MC/MCSymbol.h"
26#include "llvm/MC/MCValue.h"
27#include "llvm/Support/Debug.h"
28#include "llvm/Support/ErrorHandling.h"
29#include "llvm/Support/ELF.h"
30#include "llvm/Target/TargetAsmBackend.h"
31
32#include "../Target/X86/X86FixupKinds.h"
33#include "../Target/ARM/ARMFixupKinds.h"
34#include "../Target/MBlaze/MBlazeFixupKinds.h"
35
36#include <vector>
37using namespace llvm;
38
39static unsigned GetType(const MCSymbolData &SD) {
40  uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
41  assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
42         Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
43         Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
44         Type == ELF::STT_TLS);
45  return Type;
46}
47
48static unsigned GetBinding(const MCSymbolData &SD) {
49  uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
50  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
51         Binding == ELF::STB_WEAK);
52  return Binding;
53}
54
55static void SetBinding(MCSymbolData &SD, unsigned Binding) {
56  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
57         Binding == ELF::STB_WEAK);
58  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
59  SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
60}
61
62static unsigned GetVisibility(MCSymbolData &SD) {
63  unsigned Visibility =
64    (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
65  assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
66         Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
67  return Visibility;
68}
69
70
71static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
72  switch (Variant) {
73  default:
74    return false;
75  case MCSymbolRefExpr::VK_GOT:
76  case MCSymbolRefExpr::VK_PLT:
77  case MCSymbolRefExpr::VK_GOTPCREL:
78  case MCSymbolRefExpr::VK_TPOFF:
79  case MCSymbolRefExpr::VK_TLSGD:
80  case MCSymbolRefExpr::VK_GOTTPOFF:
81  case MCSymbolRefExpr::VK_INDNTPOFF:
82  case MCSymbolRefExpr::VK_NTPOFF:
83  case MCSymbolRefExpr::VK_GOTNTPOFF:
84  case MCSymbolRefExpr::VK_TLSLDM:
85  case MCSymbolRefExpr::VK_DTPOFF:
86  case MCSymbolRefExpr::VK_TLSLD:
87    return true;
88  }
89}
90
91namespace {
92  class ELFObjectWriter : public MCObjectWriter {
93  protected:
94    /*static bool isFixupKindX86RIPRel(unsigned Kind) {
95      return Kind == X86::reloc_riprel_4byte ||
96        Kind == X86::reloc_riprel_4byte_movq_load;
97    }*/
98
99
100    /// ELFSymbolData - Helper struct for containing some precomputed information
101    /// on symbols.
102    struct ELFSymbolData {
103      MCSymbolData *SymbolData;
104      uint64_t StringIndex;
105      uint32_t SectionIndex;
106
107      // Support lexicographic sorting.
108      bool operator<(const ELFSymbolData &RHS) const {
109        if (GetType(*SymbolData) == ELF::STT_FILE)
110          return true;
111        if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
112          return false;
113        return SymbolData->getSymbol().getName() <
114               RHS.SymbolData->getSymbol().getName();
115      }
116    };
117
118    /// @name Relocation Data
119    /// @{
120
121    struct ELFRelocationEntry {
122      // Make these big enough for both 32-bit and 64-bit
123      uint64_t r_offset;
124      int Index;
125      unsigned Type;
126      const MCSymbol *Symbol;
127      uint64_t r_addend;
128
129      ELFRelocationEntry()
130        : r_offset(0), Index(0), Type(0), Symbol(0), r_addend(0) {}
131
132      ELFRelocationEntry(uint64_t RelocOffset, int Idx,
133                         unsigned RelType, const MCSymbol *Sym,
134                         uint64_t Addend)
135        : r_offset(RelocOffset), Index(Idx), Type(RelType),
136          Symbol(Sym), r_addend(Addend) {}
137
138      // Support lexicographic sorting.
139      bool operator<(const ELFRelocationEntry &RE) const {
140        return RE.r_offset < r_offset;
141      }
142    };
143
144    SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
145    SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
146    DenseMap<const MCSymbol *, const MCSymbol *> Renames;
147
148    llvm::DenseMap<const MCSectionData*,
149                   std::vector<ELFRelocationEntry> > Relocations;
150    DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
151
152    /// @}
153    /// @name Symbol Table Data
154    /// @{
155
156    SmallString<256> StringTable;
157    std::vector<ELFSymbolData> LocalSymbolData;
158    std::vector<ELFSymbolData> ExternalSymbolData;
159    std::vector<ELFSymbolData> UndefinedSymbolData;
160
161    /// @}
162
163    bool NeedsGOT;
164
165    bool NeedsSymtabShndx;
166
167    unsigned Is64Bit : 1;
168
169    bool HasRelocationAddend;
170
171    Triple::OSType OSType;
172
173    uint16_t EMachine;
174
175    // This holds the symbol table index of the last local symbol.
176    unsigned LastLocalSymbolIndex;
177    // This holds the .strtab section index.
178    unsigned StringTableIndex;
179    // This holds the .symtab section index.
180    unsigned SymbolTableIndex;
181
182    unsigned ShstrtabIndex;
183
184
185    const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
186                                  const MCValue &Target,
187                                  const MCFragment &F) const;
188
189  public:
190    ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
191                    uint16_t _EMachine, bool _HasRelAddend,
192                    Triple::OSType _OSType)
193      : MCObjectWriter(_OS, IsLittleEndian),
194        NeedsGOT(false), NeedsSymtabShndx(false),
195        Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
196        OSType(_OSType), EMachine(_EMachine) {
197    }
198
199    virtual ~ELFObjectWriter();
200
201    void WriteWord(uint64_t W) {
202      if (Is64Bit)
203        Write64(W);
204      else
205        Write32(W);
206    }
207
208    void StringLE16(char *buf, uint16_t Value) {
209      buf[0] = char(Value >> 0);
210      buf[1] = char(Value >> 8);
211    }
212
213    void StringLE32(char *buf, uint32_t Value) {
214      StringLE16(buf, uint16_t(Value >> 0));
215      StringLE16(buf + 2, uint16_t(Value >> 16));
216    }
217
218    void StringLE64(char *buf, uint64_t Value) {
219      StringLE32(buf, uint32_t(Value >> 0));
220      StringLE32(buf + 4, uint32_t(Value >> 32));
221    }
222
223    void StringBE16(char *buf ,uint16_t Value) {
224      buf[0] = char(Value >> 8);
225      buf[1] = char(Value >> 0);
226    }
227
228    void StringBE32(char *buf, uint32_t Value) {
229      StringBE16(buf, uint16_t(Value >> 16));
230      StringBE16(buf + 2, uint16_t(Value >> 0));
231    }
232
233    void StringBE64(char *buf, uint64_t Value) {
234      StringBE32(buf, uint32_t(Value >> 32));
235      StringBE32(buf + 4, uint32_t(Value >> 0));
236    }
237
238    void String8(MCDataFragment &F, uint8_t Value) {
239      char buf[1];
240      buf[0] = Value;
241      F.getContents() += StringRef(buf, 1);
242    }
243
244    void String16(MCDataFragment &F, uint16_t Value) {
245      char buf[2];
246      if (isLittleEndian())
247        StringLE16(buf, Value);
248      else
249        StringBE16(buf, Value);
250      F.getContents() += StringRef(buf, 2);
251    }
252
253    void String32(MCDataFragment &F, uint32_t Value) {
254      char buf[4];
255      if (isLittleEndian())
256        StringLE32(buf, Value);
257      else
258        StringBE32(buf, Value);
259      F.getContents() += StringRef(buf, 4);
260    }
261
262    void String64(MCDataFragment &F, uint64_t Value) {
263      char buf[8];
264      if (isLittleEndian())
265        StringLE64(buf, Value);
266      else
267        StringBE64(buf, Value);
268      F.getContents() += StringRef(buf, 8);
269    }
270
271    virtual void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
272
273    virtual void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
274                          uint64_t name, uint8_t info,
275                          uint64_t value, uint64_t size,
276                          uint8_t other, uint32_t shndx,
277                          bool Reserved);
278
279    virtual void WriteSymbol(MCDataFragment *SymtabF,  MCDataFragment *ShndxF,
280                     ELFSymbolData &MSD,
281                     const MCAsmLayout &Layout);
282
283    typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
284    virtual void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
285                          const MCAssembler &Asm,
286                          const MCAsmLayout &Layout,
287                          const SectionIndexMapTy &SectionIndexMap);
288
289    virtual void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
290                          const MCFragment *Fragment, const MCFixup &Fixup,
291                                  MCValue Target, uint64_t &FixedValue) {
292      assert(0 && "RecordRelocation is not specific enough");
293    }
294
295    virtual uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
296                                         const MCSymbol *S);
297
298    // Map from a group section to the signature symbol
299    typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
300    // Map from a signature symbol to the group section
301    typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
302
303    /// ComputeSymbolTable - Compute the symbol table data
304    ///
305    /// \param StringTable [out] - The string table data.
306    /// \param StringIndexMap [out] - Map from symbol names to offsets in the
307    /// string table.
308    virtual void ComputeSymbolTable(MCAssembler &Asm,
309                            const SectionIndexMapTy &SectionIndexMap,
310                            RevGroupMapTy RevGroupMap);
311
312    virtual void ComputeIndexMap(MCAssembler &Asm,
313                         SectionIndexMapTy &SectionIndexMap);
314
315    virtual void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
316                         const MCSectionData &SD);
317
318    virtual void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
319      for (MCAssembler::const_iterator it = Asm.begin(),
320             ie = Asm.end(); it != ie; ++it) {
321        WriteRelocation(Asm, Layout, *it);
322      }
323    }
324
325    virtual void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
326                                const SectionIndexMapTy &SectionIndexMap);
327
328    virtual void CreateGroupSections(MCAssembler &Asm, MCAsmLayout &Layout,
329                             GroupMapTy &GroupMap, RevGroupMapTy &RevGroupMap);
330
331    virtual void ExecutePostLayoutBinding(MCAssembler &Asm);
332
333    virtual void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
334                          uint64_t Address, uint64_t Offset,
335                          uint64_t Size, uint32_t Link, uint32_t Info,
336                          uint64_t Alignment, uint64_t EntrySize);
337
338    virtual void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
339                                  const MCSectionData *SD);
340
341    virtual bool IsFixupFullyResolved(const MCAssembler &Asm,
342                              const MCValue Target,
343                              bool IsPCRel,
344                              const MCFragment *DF) const;
345
346    virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
347    virtual void WriteSection(MCAssembler &Asm,
348                      const SectionIndexMapTy &SectionIndexMap,
349                      uint32_t GroupSymbolIndex,
350                      uint64_t Offset, uint64_t Size, uint64_t Alignment,
351                      const MCSectionELF &Section);
352  };
353
354  //===- X86ELFObjectWriter -------------------------------------------===//
355
356  class X86ELFObjectWriter : public ELFObjectWriter {
357  public:
358    X86ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
359                       uint16_t _EMachine, bool _HasRelAddend,
360                       Triple::OSType _OSType);
361
362    virtual ~X86ELFObjectWriter();
363    virtual void RecordRelocation(const MCAssembler &Asm,
364                                  const MCAsmLayout &Layout,
365                                  const MCFragment *Fragment,
366                                  const MCFixup &Fixup, MCValue Target,
367                                  uint64_t &FixedValue);
368
369  private:
370    static bool isFixupKindPCRel(unsigned Kind) {
371      switch (Kind) {
372      default:
373        return false;
374      case X86::reloc_pcrel_1byte:
375      case X86::reloc_pcrel_4byte:
376      case X86::reloc_riprel_4byte:
377      case X86::reloc_riprel_4byte_movq_load:
378        return true;
379      }
380    }
381  };
382
383
384  //===- ARMELFObjectWriter -------------------------------------------===//
385
386  class ARMELFObjectWriter : public ELFObjectWriter {
387  public:
388    ARMELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
389                       uint16_t _EMachine, bool _HasRelAddend,
390                       Triple::OSType _OSType);
391
392    virtual ~ARMELFObjectWriter();
393    virtual void RecordRelocation(const MCAssembler &Asm,
394                                  const MCAsmLayout &Layout,
395                                  const MCFragment *Fragment,
396                                  const MCFixup &Fixup, MCValue Target,
397                                  uint64_t &FixedValue);
398
399  private:
400    static bool isFixupKindPCRel(unsigned Kind) {
401      switch (Kind) {
402      default:
403        return false;
404      case ARM::fixup_arm_pcrel_12:
405      case ARM::fixup_arm_vfp_pcrel_12:
406      case ARM::fixup_arm_branch:
407        return true;
408      }
409    }
410  };
411
412  //===- MBlazeELFObjectWriter -------------------------------------------===//
413
414  class MBlazeELFObjectWriter : public ELFObjectWriter {
415  public:
416    MBlazeELFObjectWriter(raw_ostream &_OS, bool _Is64Bit, bool IsLittleEndian,
417                          uint16_t _EMachine, bool _HasRelAddend,
418                          Triple::OSType _OSType);
419
420    virtual ~MBlazeELFObjectWriter();
421    virtual void RecordRelocation(const MCAssembler &Asm,
422                                  const MCAsmLayout &Layout,
423                                  const MCFragment *Fragment,
424                                  const MCFixup &Fixup, MCValue Target,
425                                  uint64_t &FixedValue);
426
427  private:
428    static bool isFixupKindPCRel(unsigned Kind) {
429      switch (Kind) {
430      default:
431        return false;
432      case MBlaze::reloc_pcrel_2byte:
433      case MBlaze::reloc_pcrel_4byte:
434        return true;
435      }
436    }
437  };
438}
439
440ELFObjectWriter::~ELFObjectWriter()
441{}
442
443// Emit the ELF header.
444void ELFObjectWriter::WriteHeader(uint64_t SectionDataSize,
445                                  unsigned NumberOfSections) {
446  // ELF Header
447  // ----------
448  //
449  // Note
450  // ----
451  // emitWord method behaves differently for ELF32 and ELF64, writing
452  // 4 bytes in the former and 8 in the latter.
453
454  Write8(0x7f); // e_ident[EI_MAG0]
455  Write8('E');  // e_ident[EI_MAG1]
456  Write8('L');  // e_ident[EI_MAG2]
457  Write8('F');  // e_ident[EI_MAG3]
458
459  Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
460
461  // e_ident[EI_DATA]
462  Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
463
464  Write8(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
465  // e_ident[EI_OSABI]
466  switch (OSType) {
467    case Triple::FreeBSD:  Write8(ELF::ELFOSABI_FREEBSD); break;
468    case Triple::Linux:    Write8(ELF::ELFOSABI_LINUX); break;
469    default:               Write8(ELF::ELFOSABI_NONE); break;
470  }
471  Write8(0);                  // e_ident[EI_ABIVERSION]
472
473  WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
474
475  Write16(ELF::ET_REL);             // e_type
476
477  Write16(EMachine); // e_machine = target
478
479  Write32(ELF::EV_CURRENT);         // e_version
480  WriteWord(0);                    // e_entry, no entry point in .o file
481  WriteWord(0);                    // e_phoff, no program header for .o
482  WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
483            sizeof(ELF::Elf32_Ehdr)));  // e_shoff = sec hdr table off in bytes
484
485  // FIXME: Make this configurable.
486  Write32(0);   // e_flags = whatever the target wants
487
488  // e_ehsize = ELF header size
489  Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
490
491  Write16(0);                  // e_phentsize = prog header entry size
492  Write16(0);                  // e_phnum = # prog header entries = 0
493
494  // e_shentsize = Section header entry size
495  Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
496
497  // e_shnum     = # of section header ents
498  if (NumberOfSections >= ELF::SHN_LORESERVE)
499    Write16(0);
500  else
501    Write16(NumberOfSections);
502
503  // e_shstrndx  = Section # of '.shstrtab'
504  if (NumberOfSections >= ELF::SHN_LORESERVE)
505    Write16(ELF::SHN_XINDEX);
506  else
507    Write16(ShstrtabIndex);
508}
509
510void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
511                                       MCDataFragment *ShndxF,
512                                       uint64_t name,
513                                       uint8_t info, uint64_t value,
514                                       uint64_t size, uint8_t other,
515                                       uint32_t shndx,
516                                       bool Reserved) {
517  if (ShndxF) {
518    if (shndx >= ELF::SHN_LORESERVE && !Reserved)
519      String32(*ShndxF, shndx);
520    else
521      String32(*ShndxF, 0);
522  }
523
524  uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
525    uint16_t(ELF::SHN_XINDEX) : shndx;
526
527  if (Is64Bit) {
528    String32(*SymtabF, name);  // st_name
529    String8(*SymtabF, info);   // st_info
530    String8(*SymtabF, other);  // st_other
531    String16(*SymtabF, Index); // st_shndx
532    String64(*SymtabF, value); // st_value
533    String64(*SymtabF, size);  // st_size
534  } else {
535    String32(*SymtabF, name);  // st_name
536    String32(*SymtabF, value); // st_value
537    String32(*SymtabF, size);  // st_size
538    String8(*SymtabF, info);   // st_info
539    String8(*SymtabF, other);  // st_other
540    String16(*SymtabF, Index); // st_shndx
541  }
542}
543
544static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) {
545  if (Data.isCommon() && Data.isExternal())
546    return Data.getCommonAlignment();
547
548  const MCSymbol &Symbol = Data.getSymbol();
549  if (!Symbol.isInSection())
550    return 0;
551
552  if (MCFragment *FF = Data.getFragment())
553    return Layout.getSymbolAddress(&Data) -
554      Layout.getSectionAddress(FF->getParent());
555
556  return 0;
557}
558
559void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
560  // The presence of symbol versions causes undefined symbols and
561  // versions declared with @@@ to be renamed.
562
563  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
564         ie = Asm.symbol_end(); it != ie; ++it) {
565    const MCSymbol &Alias = it->getSymbol();
566    const MCSymbol &Symbol = Alias.AliasedSymbol();
567    MCSymbolData &SD = Asm.getSymbolData(Symbol);
568
569    // Not an alias.
570    if (&Symbol == &Alias)
571      continue;
572
573    StringRef AliasName = Alias.getName();
574    size_t Pos = AliasName.find('@');
575    if (Pos == StringRef::npos)
576      continue;
577
578    // Aliases defined with .symvar copy the binding from the symbol they alias.
579    // This is the first place we are able to copy this information.
580    it->setExternal(SD.isExternal());
581    SetBinding(*it, GetBinding(SD));
582
583    StringRef Rest = AliasName.substr(Pos);
584    if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
585      continue;
586
587    // FIXME: produce a better error message.
588    if (Symbol.isUndefined() && Rest.startswith("@@") &&
589        !Rest.startswith("@@@"))
590      report_fatal_error("A @@ version cannot be undefined");
591
592    Renames.insert(std::make_pair(&Symbol, &Alias));
593  }
594}
595
596void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
597                                  MCDataFragment *ShndxF,
598                                  ELFSymbolData &MSD,
599                                  const MCAsmLayout &Layout) {
600  MCSymbolData &OrigData = *MSD.SymbolData;
601  MCSymbolData &Data =
602    Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
603
604  bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
605    Data.getSymbol().isVariable();
606
607  uint8_t Binding = GetBinding(OrigData);
608  uint8_t Visibility = GetVisibility(OrigData);
609  uint8_t Type = GetType(Data);
610
611  uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
612  uint8_t Other = Visibility;
613
614  uint64_t Value = SymbolValue(Data, Layout);
615  uint64_t Size = 0;
616  const MCExpr *ESize;
617
618  assert(!(Data.isCommon() && !Data.isExternal()));
619
620  ESize = Data.getSize();
621  if (Data.getSize()) {
622    MCValue Res;
623    if (ESize->getKind() == MCExpr::Binary) {
624      const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
625
626      if (BE->EvaluateAsRelocatable(Res, &Layout)) {
627        assert(!Res.getSymA() || !Res.getSymA()->getSymbol().isDefined());
628        assert(!Res.getSymB() || !Res.getSymB()->getSymbol().isDefined());
629        Size = Res.getConstant();
630      }
631    } else if (ESize->getKind() == MCExpr::Constant) {
632      Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
633    } else {
634      assert(0 && "Unsupported size expression");
635    }
636  }
637
638  // Write out the symbol table entry
639  WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
640                   Size, Other, MSD.SectionIndex, IsReserved);
641}
642
643void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
644                                       MCDataFragment *ShndxF,
645                                       const MCAssembler &Asm,
646                                       const MCAsmLayout &Layout,
647                                     const SectionIndexMapTy &SectionIndexMap) {
648  // The string table must be emitted first because we need the index
649  // into the string table for all the symbol names.
650  assert(StringTable.size() && "Missing string table");
651
652  // FIXME: Make sure the start of the symbol table is aligned.
653
654  // The first entry is the undefined symbol entry.
655  WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
656
657  // Write the symbol table entries.
658  LastLocalSymbolIndex = LocalSymbolData.size() + 1;
659  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
660    ELFSymbolData &MSD = LocalSymbolData[i];
661    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
662  }
663
664  // Write out a symbol table entry for each regular section.
665  for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
666       ++i) {
667    const MCSectionELF &Section =
668      static_cast<const MCSectionELF&>(i->getSection());
669    if (Section.getType() == ELF::SHT_RELA ||
670        Section.getType() == ELF::SHT_REL ||
671        Section.getType() == ELF::SHT_STRTAB ||
672        Section.getType() == ELF::SHT_SYMTAB)
673      continue;
674    WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
675                     ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false);
676    LastLocalSymbolIndex++;
677  }
678
679  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
680    ELFSymbolData &MSD = ExternalSymbolData[i];
681    MCSymbolData &Data = *MSD.SymbolData;
682    assert(((Data.getFlags() & ELF_STB_Global) ||
683            (Data.getFlags() & ELF_STB_Weak)) &&
684           "External symbol requires STB_GLOBAL or STB_WEAK flag");
685    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
686    if (GetBinding(Data) == ELF::STB_LOCAL)
687      LastLocalSymbolIndex++;
688  }
689
690  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
691    ELFSymbolData &MSD = UndefinedSymbolData[i];
692    MCSymbolData &Data = *MSD.SymbolData;
693    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
694    if (GetBinding(Data) == ELF::STB_LOCAL)
695      LastLocalSymbolIndex++;
696  }
697}
698
699const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
700                                               const MCValue &Target,
701                                               const MCFragment &F) const {
702  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
703  const MCSymbol &ASymbol = Symbol.AliasedSymbol();
704  const MCSymbol *Renamed = Renames.lookup(&Symbol);
705  const MCSymbolData &SD = Asm.getSymbolData(Symbol);
706
707  if (ASymbol.isUndefined()) {
708    if (Renamed)
709      return Renamed;
710    return &ASymbol;
711  }
712
713  if (SD.isExternal()) {
714    if (Renamed)
715      return Renamed;
716    return &Symbol;
717  }
718
719  const MCSectionELF &Section =
720    static_cast<const MCSectionELF&>(ASymbol.getSection());
721  const SectionKind secKind = Section.getKind();
722
723  if (secKind.isBSS())
724    return NULL;
725
726  if (secKind.isThreadLocal()) {
727    if (Renamed)
728      return Renamed;
729    return &Symbol;
730  }
731
732  MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
733  const MCSectionELF &Sec2 =
734    static_cast<const MCSectionELF&>(F.getParent()->getSection());
735
736  if (&Sec2 != &Section &&
737      (Kind == MCSymbolRefExpr::VK_PLT ||
738       Kind == MCSymbolRefExpr::VK_GOTPCREL ||
739       Kind == MCSymbolRefExpr::VK_GOTOFF)) {
740    if (Renamed)
741      return Renamed;
742    return &Symbol;
743  }
744
745  if (Section.getFlags() & MCSectionELF::SHF_MERGE) {
746    if (Target.getConstant() == 0)
747      return NULL;
748    if (Renamed)
749      return Renamed;
750    return &Symbol;
751  }
752
753  return NULL;
754}
755
756
757uint64_t
758ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
759                                             const MCSymbol *S) {
760  MCSymbolData &SD = Asm.getSymbolData(*S);
761  return SD.getIndex();
762}
763
764static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
765                       bool Used, bool Renamed) {
766  if (Data.getFlags() & ELF_Other_Weakref)
767    return false;
768
769  if (Used)
770    return true;
771
772  if (Renamed)
773    return false;
774
775  const MCSymbol &Symbol = Data.getSymbol();
776
777  if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
778    return true;
779
780  const MCSymbol &A = Symbol.AliasedSymbol();
781  if (!A.isVariable() && A.isUndefined() && !Data.isCommon())
782    return false;
783
784  if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
785    return false;
786
787  if (Symbol.isTemporary())
788    return false;
789
790  return true;
791}
792
793static bool isLocal(const MCSymbolData &Data, bool isSignature,
794                    bool isUsedInReloc) {
795  if (Data.isExternal())
796    return false;
797
798  const MCSymbol &Symbol = Data.getSymbol();
799  const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
800
801  if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
802    if (isSignature && !isUsedInReloc)
803      return true;
804
805    return false;
806  }
807
808  return true;
809}
810
811void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
812                                      SectionIndexMapTy &SectionIndexMap) {
813  unsigned Index = 1;
814  for (MCAssembler::iterator it = Asm.begin(),
815         ie = Asm.end(); it != ie; ++it) {
816    const MCSectionELF &Section =
817      static_cast<const MCSectionELF &>(it->getSection());
818    if (Section.getType() != ELF::SHT_GROUP)
819      continue;
820    SectionIndexMap[&Section] = Index++;
821  }
822
823  for (MCAssembler::iterator it = Asm.begin(),
824         ie = Asm.end(); it != ie; ++it) {
825    const MCSectionELF &Section =
826      static_cast<const MCSectionELF &>(it->getSection());
827    if (Section.getType() == ELF::SHT_GROUP)
828      continue;
829    SectionIndexMap[&Section] = Index++;
830  }
831}
832
833void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
834                                      const SectionIndexMapTy &SectionIndexMap,
835                                      RevGroupMapTy RevGroupMap) {
836  // FIXME: Is this the correct place to do this?
837  if (NeedsGOT) {
838    llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_";
839    MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
840    MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
841    Data.setExternal(true);
842    SetBinding(Data, ELF::STB_GLOBAL);
843  }
844
845  // Build section lookup table.
846  int NumRegularSections = Asm.size();
847
848  // Index 0 is always the empty string.
849  StringMap<uint64_t> StringIndexMap;
850  StringTable += '\x00';
851
852  // Add the data for the symbols.
853  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
854         ie = Asm.symbol_end(); it != ie; ++it) {
855    const MCSymbol &Symbol = it->getSymbol();
856
857    bool Used = UsedInReloc.count(&Symbol);
858    bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
859    bool isSignature = RevGroupMap.count(&Symbol);
860
861    if (!isInSymtab(Asm, *it,
862                    Used || WeakrefUsed || isSignature,
863                    Renames.count(&Symbol)))
864      continue;
865
866    ELFSymbolData MSD;
867    MSD.SymbolData = it;
868    const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
869
870    // Undefined symbols are global, but this is the first place we
871    // are able to set it.
872    bool Local = isLocal(*it, isSignature, Used);
873    if (!Local && GetBinding(*it) == ELF::STB_LOCAL) {
874      MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
875      SetBinding(*it, ELF::STB_GLOBAL);
876      SetBinding(SD, ELF::STB_GLOBAL);
877    }
878
879    if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
880      SetBinding(*it, ELF::STB_WEAK);
881
882    if (it->isCommon()) {
883      assert(!Local);
884      MSD.SectionIndex = ELF::SHN_COMMON;
885    } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
886      MSD.SectionIndex = ELF::SHN_ABS;
887    } else if (RefSymbol.isUndefined()) {
888      if (isSignature && !Used)
889        MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
890      else
891        MSD.SectionIndex = ELF::SHN_UNDEF;
892    } else {
893      const MCSectionELF &Section =
894        static_cast<const MCSectionELF&>(RefSymbol.getSection());
895      MSD.SectionIndex = SectionIndexMap.lookup(&Section);
896      if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
897        NeedsSymtabShndx = true;
898      assert(MSD.SectionIndex && "Invalid section index!");
899    }
900
901    // The @@@ in symbol version is replaced with @ in undefined symbols and
902    // @@ in defined ones.
903    StringRef Name = Symbol.getName();
904    SmallString<32> Buf;
905
906    size_t Pos = Name.find("@@@");
907    if (Pos != StringRef::npos) {
908      Buf += Name.substr(0, Pos);
909      unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
910      Buf += Name.substr(Pos + Skip);
911      Name = Buf;
912    }
913
914    uint64_t &Entry = StringIndexMap[Name];
915    if (!Entry) {
916      Entry = StringTable.size();
917      StringTable += Name;
918      StringTable += '\x00';
919    }
920    MSD.StringIndex = Entry;
921    if (MSD.SectionIndex == ELF::SHN_UNDEF)
922      UndefinedSymbolData.push_back(MSD);
923    else if (Local)
924      LocalSymbolData.push_back(MSD);
925    else
926      ExternalSymbolData.push_back(MSD);
927  }
928
929  // Symbols are required to be in lexicographic order.
930  array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
931  array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
932  array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
933
934  // Set the symbol indices. Local symbols must come before all other
935  // symbols with non-local bindings.
936  unsigned Index = 1;
937  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
938    LocalSymbolData[i].SymbolData->setIndex(Index++);
939
940  Index += NumRegularSections;
941
942  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
943    ExternalSymbolData[i].SymbolData->setIndex(Index++);
944  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
945    UndefinedSymbolData[i].SymbolData->setIndex(Index++);
946}
947
948void ELFObjectWriter::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
949                                      const MCSectionData &SD) {
950  if (!Relocations[&SD].empty()) {
951    MCContext &Ctx = Asm.getContext();
952    const MCSectionELF *RelaSection;
953    const MCSectionELF &Section =
954      static_cast<const MCSectionELF&>(SD.getSection());
955
956    const StringRef SectionName = Section.getSectionName();
957    std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
958    RelaSectionName += SectionName;
959
960    unsigned EntrySize;
961    if (HasRelocationAddend)
962      EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
963    else
964      EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
965
966    RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
967                                    ELF::SHT_RELA : ELF::SHT_REL, 0,
968                                    SectionKind::getReadOnly(),
969                                    EntrySize, "");
970
971    MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
972    RelaSD.setAlignment(Is64Bit ? 8 : 4);
973
974    MCDataFragment *F = new MCDataFragment(&RelaSD);
975
976    WriteRelocationsFragment(Asm, F, &SD);
977
978    Asm.AddSectionToTheEnd(*this, RelaSD, Layout);
979  }
980}
981
982void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
983                                       uint64_t Flags, uint64_t Address,
984                                       uint64_t Offset, uint64_t Size,
985                                       uint32_t Link, uint32_t Info,
986                                       uint64_t Alignment,
987                                       uint64_t EntrySize) {
988  Write32(Name);        // sh_name: index into string table
989  Write32(Type);        // sh_type
990  WriteWord(Flags);     // sh_flags
991  WriteWord(Address);   // sh_addr
992  WriteWord(Offset);    // sh_offset
993  WriteWord(Size);      // sh_size
994  Write32(Link);        // sh_link
995  Write32(Info);        // sh_info
996  WriteWord(Alignment); // sh_addralign
997  WriteWord(EntrySize); // sh_entsize
998}
999
1000void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1001                                               MCDataFragment *F,
1002                                               const MCSectionData *SD) {
1003  std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1004  // sort by the r_offset just like gnu as does
1005  array_pod_sort(Relocs.begin(), Relocs.end());
1006
1007  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1008    ELFRelocationEntry entry = Relocs[e - i - 1];
1009
1010    if (!entry.Index)
1011      ;
1012    else if (entry.Index < 0)
1013      entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1014    else
1015      entry.Index += LocalSymbolData.size();
1016    if (Is64Bit) {
1017      String64(*F, entry.r_offset);
1018
1019      struct ELF::Elf64_Rela ERE64;
1020      ERE64.setSymbolAndType(entry.Index, entry.Type);
1021      String64(*F, ERE64.r_info);
1022
1023      if (HasRelocationAddend)
1024        String64(*F, entry.r_addend);
1025    } else {
1026      String32(*F, entry.r_offset);
1027
1028      struct ELF::Elf32_Rela ERE32;
1029      ERE32.setSymbolAndType(entry.Index, entry.Type);
1030      String32(*F, ERE32.r_info);
1031
1032      if (HasRelocationAddend)
1033        String32(*F, entry.r_addend);
1034    }
1035  }
1036}
1037
1038void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1039                                             MCAsmLayout &Layout,
1040                                    const SectionIndexMapTy &SectionIndexMap) {
1041  MCContext &Ctx = Asm.getContext();
1042  MCDataFragment *F;
1043
1044  unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1045
1046  // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1047  const MCSectionELF *ShstrtabSection =
1048    Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1049                      SectionKind::getReadOnly());
1050  MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1051  ShstrtabSD.setAlignment(1);
1052  ShstrtabIndex = Asm.size();
1053
1054  const MCSectionELF *SymtabSection =
1055    Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1056                      SectionKind::getReadOnly(),
1057                      EntrySize, "");
1058  MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1059  SymtabSD.setAlignment(Is64Bit ? 8 : 4);
1060  SymbolTableIndex = Asm.size();
1061
1062  MCSectionData *SymtabShndxSD = NULL;
1063
1064  if (NeedsSymtabShndx) {
1065    const MCSectionELF *SymtabShndxSection =
1066      Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1067                        SectionKind::getReadOnly(), 4, "");
1068    SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1069    SymtabShndxSD->setAlignment(4);
1070  }
1071
1072  const MCSection *StrtabSection;
1073  StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1074                                    SectionKind::getReadOnly());
1075  MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1076  StrtabSD.setAlignment(1);
1077  StringTableIndex = Asm.size();
1078
1079  WriteRelocations(Asm, Layout);
1080
1081  // Symbol table
1082  F = new MCDataFragment(&SymtabSD);
1083  MCDataFragment *ShndxF = NULL;
1084  if (NeedsSymtabShndx) {
1085    ShndxF = new MCDataFragment(SymtabShndxSD);
1086    Asm.AddSectionToTheEnd(*this, *SymtabShndxSD, Layout);
1087  }
1088  WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1089  Asm.AddSectionToTheEnd(*this, SymtabSD, Layout);
1090
1091  F = new MCDataFragment(&StrtabSD);
1092  F->getContents().append(StringTable.begin(), StringTable.end());
1093  Asm.AddSectionToTheEnd(*this, StrtabSD, Layout);
1094
1095  F = new MCDataFragment(&ShstrtabSD);
1096
1097  // Section header string table.
1098  //
1099  // The first entry of a string table holds a null character so skip
1100  // section 0.
1101  uint64_t Index = 1;
1102  F->getContents() += '\x00';
1103
1104  StringMap<uint64_t> SecStringMap;
1105  for (MCAssembler::const_iterator it = Asm.begin(),
1106         ie = Asm.end(); it != ie; ++it) {
1107    const MCSectionELF &Section =
1108      static_cast<const MCSectionELF&>(it->getSection());
1109    // FIXME: We could merge suffixes like in .text and .rela.text.
1110
1111    StringRef Name = Section.getSectionName();
1112    if (SecStringMap.count(Name)) {
1113      SectionStringTableIndex[&Section] =  SecStringMap[Name];
1114      continue;
1115    }
1116    // Remember the index into the string table so we can write it
1117    // into the sh_name field of the section header table.
1118    SectionStringTableIndex[&Section] = Index;
1119    SecStringMap[Name] = Index;
1120
1121    Index += Name.size() + 1;
1122    F->getContents() += Name;
1123    F->getContents() += '\x00';
1124  }
1125
1126  Asm.AddSectionToTheEnd(*this, ShstrtabSD, Layout);
1127}
1128
1129bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm,
1130                                           const MCValue Target,
1131                                           bool IsPCRel,
1132                                           const MCFragment *DF) const {
1133  // If this is a PCrel relocation, find the section this fixup value is
1134  // relative to.
1135  const MCSection *BaseSection = 0;
1136  if (IsPCRel) {
1137    BaseSection = &DF->getParent()->getSection();
1138    assert(BaseSection);
1139  }
1140
1141  const MCSection *SectionA = 0;
1142  const MCSymbol *SymbolA = 0;
1143  if (const MCSymbolRefExpr *A = Target.getSymA()) {
1144    SymbolA = &A->getSymbol();
1145    SectionA = &SymbolA->AliasedSymbol().getSection();
1146  }
1147
1148  const MCSection *SectionB = 0;
1149  const MCSymbol *SymbolB = 0;
1150  if (const MCSymbolRefExpr *B = Target.getSymB()) {
1151    SymbolB = &B->getSymbol();
1152    SectionB = &SymbolB->AliasedSymbol().getSection();
1153  }
1154
1155  if (!BaseSection)
1156    return SectionA == SectionB;
1157
1158  if (SymbolB)
1159    return false;
1160
1161  // Absolute address but PCrel instruction, so we need a relocation.
1162  if (!SymbolA)
1163    return false;
1164
1165  // FIXME: This is in here just to match gnu as output. If the two ends
1166  // are in the same section, there is nothing that the linker can do to
1167  // break it.
1168  const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA);
1169  if (DataA.isExternal())
1170    return false;
1171
1172  return BaseSection == SectionA;
1173}
1174
1175void ELFObjectWriter::CreateGroupSections(MCAssembler &Asm,
1176                                          MCAsmLayout &Layout,
1177                                          GroupMapTy &GroupMap,
1178                                          RevGroupMapTy &RevGroupMap) {
1179  // Build the groups
1180  for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1181       it != ie; ++it) {
1182    const MCSectionELF &Section =
1183      static_cast<const MCSectionELF&>(it->getSection());
1184    if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1185      continue;
1186
1187    const MCSymbol *SignatureSymbol = Section.getGroup();
1188    Asm.getOrCreateSymbolData(*SignatureSymbol);
1189    const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1190    if (!Group) {
1191      Group = Asm.getContext().CreateELFGroupSection();
1192      MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1193      Data.setAlignment(4);
1194      MCDataFragment *F = new MCDataFragment(&Data);
1195      String32(*F, ELF::GRP_COMDAT);
1196    }
1197    GroupMap[Group] = SignatureSymbol;
1198  }
1199
1200  // Add sections to the groups
1201  unsigned Index = 1;
1202  unsigned NumGroups = RevGroupMap.size();
1203  for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1204       it != ie; ++it, ++Index) {
1205    const MCSectionELF &Section =
1206      static_cast<const MCSectionELF&>(it->getSection());
1207    if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1208      continue;
1209    const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1210    MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1211    // FIXME: we could use the previous fragment
1212    MCDataFragment *F = new MCDataFragment(&Data);
1213    String32(*F, NumGroups + Index);
1214  }
1215
1216  for (RevGroupMapTy::const_iterator i = RevGroupMap.begin(),
1217         e = RevGroupMap.end(); i != e; ++i) {
1218    const MCSectionELF *Group = i->second;
1219    MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1220    Asm.AddSectionToTheEnd(*this, Data, Layout);
1221  }
1222}
1223
1224void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1225                                   const SectionIndexMapTy &SectionIndexMap,
1226                                   uint32_t GroupSymbolIndex,
1227                                   uint64_t Offset, uint64_t Size,
1228                                   uint64_t Alignment,
1229                                   const MCSectionELF &Section) {
1230  uint64_t sh_link = 0;
1231  uint64_t sh_info = 0;
1232
1233  switch(Section.getType()) {
1234  case ELF::SHT_DYNAMIC:
1235    sh_link = SectionStringTableIndex[&Section];
1236    sh_info = 0;
1237    break;
1238
1239  case ELF::SHT_REL:
1240  case ELF::SHT_RELA: {
1241    const MCSectionELF *SymtabSection;
1242    const MCSectionELF *InfoSection;
1243    SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1244                                                   0,
1245                                                   SectionKind::getReadOnly());
1246    sh_link = SectionIndexMap.lookup(SymtabSection);
1247    assert(sh_link && ".symtab not found");
1248
1249    // Remove ".rel" and ".rela" prefixes.
1250    unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1251    StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1252
1253    InfoSection = Asm.getContext().getELFSection(SectionName,
1254                                                 ELF::SHT_PROGBITS, 0,
1255                                                 SectionKind::getReadOnly());
1256    sh_info = SectionIndexMap.lookup(InfoSection);
1257    break;
1258  }
1259
1260  case ELF::SHT_SYMTAB:
1261  case ELF::SHT_DYNSYM:
1262    sh_link = StringTableIndex;
1263    sh_info = LastLocalSymbolIndex;
1264    break;
1265
1266  case ELF::SHT_SYMTAB_SHNDX:
1267    sh_link = SymbolTableIndex;
1268    break;
1269
1270  case ELF::SHT_PROGBITS:
1271  case ELF::SHT_STRTAB:
1272  case ELF::SHT_NOBITS:
1273  case ELF::SHT_NULL:
1274  case ELF::SHT_ARM_ATTRIBUTES:
1275    // Nothing to do.
1276    break;
1277
1278  case ELF::SHT_GROUP: {
1279    sh_link = SymbolTableIndex;
1280    sh_info = GroupSymbolIndex;
1281    break;
1282  }
1283
1284  default:
1285    assert(0 && "FIXME: sh_type value not supported!");
1286    break;
1287  }
1288
1289  WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1290                   Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1291                   Alignment, Section.getEntrySize());
1292}
1293
1294void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1295                                  const MCAsmLayout &Layout) {
1296  GroupMapTy GroupMap;
1297  RevGroupMapTy RevGroupMap;
1298  CreateGroupSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1299                      RevGroupMap);
1300
1301  SectionIndexMapTy SectionIndexMap;
1302
1303  ComputeIndexMap(Asm, SectionIndexMap);
1304
1305  // Compute symbol table information.
1306  ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap);
1307
1308  CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1309                         const_cast<MCAsmLayout&>(Layout),
1310                         SectionIndexMap);
1311
1312  // Update to include the metadata sections.
1313  ComputeIndexMap(Asm, SectionIndexMap);
1314
1315  // Add 1 for the null section.
1316  unsigned NumSections = Asm.size() + 1;
1317  uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
1318  uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
1319  uint64_t FileOff = HeaderSize;
1320
1321  std::vector<const MCSectionELF*> Sections;
1322  Sections.resize(NumSections);
1323
1324  for (SectionIndexMapTy::const_iterator i=
1325         SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1326    const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1327    Sections[p.second] = p.first;
1328  }
1329
1330  for (unsigned i = 1; i < NumSections; ++i) {
1331    const MCSectionELF &Section = *Sections[i];
1332    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1333
1334    FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1335
1336    // Get the size of the section in the output file (including padding).
1337    uint64_t Size = Layout.getSectionFileSize(&SD);
1338
1339    FileOff += Size;
1340  }
1341
1342  FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1343
1344  // Write out the ELF header ...
1345  WriteHeader(FileOff - HeaderSize, NumSections);
1346
1347  FileOff = HeaderSize;
1348
1349  // ... then all of the sections ...
1350  DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
1351
1352  for (unsigned i = 1; i < NumSections; ++i) {
1353    const MCSectionELF &Section = *Sections[i];
1354    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1355
1356    uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
1357    WriteZeros(Padding);
1358    FileOff += Padding;
1359
1360    // Remember the offset into the file for this section.
1361    SectionOffsetMap[&Section] = FileOff;
1362
1363    FileOff += Layout.getSectionFileSize(&SD);
1364
1365    Asm.WriteSectionData(&SD, Layout, this);
1366  }
1367
1368  uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
1369  WriteZeros(Padding);
1370  FileOff += Padding;
1371
1372  // ... and then the section header table.
1373  // Should we align the section header table?
1374  //
1375  // Null section first.
1376  uint64_t FirstSectionSize =
1377    NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1378  uint32_t FirstSectionLink =
1379    ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1380  WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1381
1382  for (unsigned i = 1; i < NumSections; ++i) {
1383    const MCSectionELF &Section = *Sections[i];
1384    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1385    uint32_t GroupSymbolIndex;
1386    if (Section.getType() != ELF::SHT_GROUP)
1387      GroupSymbolIndex = 0;
1388    else
1389      GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, GroupMap[&Section]);
1390
1391    WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1392                 SectionOffsetMap[&Section], Layout.getSectionSize(&SD),
1393                 SD.getAlignment(), Section);
1394  }
1395}
1396
1397MCObjectWriter *llvm::createELFObjectWriter(raw_ostream &OS,
1398                                            bool Is64Bit,
1399                                            Triple::OSType OSType,
1400                                            uint16_t EMachine,
1401                                            bool IsLittleEndian,
1402                                            bool HasRelocationAddend) {
1403  switch (EMachine) {
1404    case ELF::EM_386:
1405    case ELF::EM_X86_64:
1406      return new X86ELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1407                                    HasRelocationAddend, OSType); break;
1408    case ELF::EM_ARM:
1409      return new ARMELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1410                                    HasRelocationAddend, OSType); break;
1411    case ELF::EM_MBLAZE:
1412      return new MBlazeELFObjectWriter(OS, Is64Bit, IsLittleEndian, EMachine,
1413                                       HasRelocationAddend, OSType); break;
1414    default: llvm_unreachable("Unsupported architecture"); break;
1415  }
1416}
1417
1418
1419/// START OF SUBCLASSES for ELFObjectWriter
1420//===- ARMELFObjectWriter -------------------------------------------===//
1421
1422ARMELFObjectWriter::ARMELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1423                                       bool _IsLittleEndian,
1424                                       uint16_t _EMachine, bool _HasRelocationAddend,
1425                                       Triple::OSType _OSType)
1426  : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1427                    _HasRelocationAddend, _OSType)
1428{}
1429
1430ARMELFObjectWriter::~ARMELFObjectWriter()
1431{}
1432
1433void ARMELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1434                                          const MCAsmLayout &Layout,
1435                                          const MCFragment *Fragment,
1436                                          const MCFixup &Fixup,
1437                                          MCValue Target,
1438                                          uint64_t &FixedValue) {
1439  assert(0 && "ARMELFObjectWriter::RecordRelocation() unimplemented");
1440}
1441
1442//===- MBlazeELFObjectWriter -------------------------------------------===//
1443
1444MBlazeELFObjectWriter::MBlazeELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1445                                             bool _IsLittleEndian,
1446                                             uint16_t _EMachine,
1447                                             bool _HasRelocationAddend,
1448                                             Triple::OSType _OSType)
1449  : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1450                    _HasRelocationAddend, _OSType) {
1451}
1452
1453MBlazeELFObjectWriter::~MBlazeELFObjectWriter() {
1454}
1455
1456void MBlazeELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1457                                             const MCAsmLayout &Layout,
1458                                             const MCFragment *Fragment,
1459                                             const MCFixup &Fixup,
1460                                             MCValue Target,
1461                                             uint64_t &FixedValue) {
1462  int64_t Addend = 0;
1463  int Index = 0;
1464  int64_t Value = Target.getConstant();
1465  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
1466  const MCSymbol &ASymbol = Symbol.AliasedSymbol();
1467  const MCSymbol *RelocSymbol = SymbolToReloc(Asm, Target, *Fragment);
1468
1469  bool IsPCRel = isFixupKindPCRel(Fixup.getKind());
1470  if (!Target.isAbsolute()) {
1471    if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
1472      const MCSymbol &SymbolB = RefB->getSymbol();
1473      MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
1474      IsPCRel = true;
1475      MCSectionData *Sec = Fragment->getParent();
1476
1477      // Offset of the symbol in the section
1478      int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec);
1479
1480      // Ofeset of the relocation in the section
1481      int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
1482      Value += b - a;
1483    }
1484
1485    if (!RelocSymbol) {
1486      MCSymbolData &SD = Asm.getSymbolData(ASymbol);
1487      MCFragment *F = SD.getFragment();
1488
1489      Index = F->getParent()->getOrdinal();
1490
1491      MCSectionData *FSD = F->getParent();
1492      // Offset of the symbol in the section
1493      Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
1494    } else {
1495      if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
1496        WeakrefUsedInReloc.insert(RelocSymbol);
1497      else
1498        UsedInReloc.insert(RelocSymbol);
1499      Index = -1;
1500    }
1501    Addend = Value;
1502  }
1503
1504  FixedValue = Value;
1505
1506  // determine the type of the relocation
1507  unsigned Type;
1508  if (IsPCRel) {
1509    switch ((unsigned)Fixup.getKind()) {
1510    default:
1511      llvm_unreachable("Unimplemented");
1512    case MBlaze::reloc_pcrel_4byte:
1513      Type = ELF::R_MICROBLAZE_64_PCREL;
1514      break;
1515    case MBlaze::reloc_pcrel_2byte:
1516      Type = ELF::R_MICROBLAZE_32_PCREL;
1517      break;
1518    }
1519  } else {
1520    switch ((unsigned)Fixup.getKind()) {
1521    default: llvm_unreachable("invalid fixup kind!");
1522    case FK_Data_4:
1523      Type = (RelocSymbol || Addend !=0) ? ELF::R_MICROBLAZE_32
1524                                         : ELF::R_MICROBLAZE_64;
1525      break;
1526    case FK_Data_2:
1527      Type = ELF::R_MICROBLAZE_32;
1528      break;
1529    }
1530  }
1531
1532  MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
1533  if (RelocNeedsGOT(Modifier))
1534    NeedsGOT = true;
1535
1536  uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
1537    Fixup.getOffset();
1538
1539  if (!HasRelocationAddend) Addend = 0;
1540  ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend);
1541  Relocations[Fragment->getParent()].push_back(ERE);
1542}
1543
1544//===- X86ELFObjectWriter -------------------------------------------===//
1545
1546
1547X86ELFObjectWriter::X86ELFObjectWriter(raw_ostream &_OS, bool _Is64Bit,
1548                                       bool _IsLittleEndian,
1549                                       uint16_t _EMachine, bool _HasRelocationAddend,
1550                                       Triple::OSType _OSType)
1551  : ELFObjectWriter(_OS, _Is64Bit, _IsLittleEndian, _EMachine,
1552                    _HasRelocationAddend, _OSType)
1553{}
1554
1555X86ELFObjectWriter::~X86ELFObjectWriter()
1556{}
1557
1558void X86ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1559                                       const MCAsmLayout &Layout,
1560                                       const MCFragment *Fragment,
1561                                       const MCFixup &Fixup,
1562                                       MCValue Target,
1563                                       uint64_t &FixedValue) {
1564  int64_t Addend = 0;
1565  int Index = 0;
1566  int64_t Value = Target.getConstant();
1567  const MCSymbol *RelocSymbol = NULL;
1568
1569  bool IsPCRel = isFixupKindPCRel(Fixup.getKind());
1570  if (!Target.isAbsolute()) {
1571    const MCSymbol &Symbol = Target.getSymA()->getSymbol();
1572    const MCSymbol &ASymbol = Symbol.AliasedSymbol();
1573    RelocSymbol = SymbolToReloc(Asm, Target, *Fragment);
1574
1575    if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
1576      const MCSymbol &SymbolB = RefB->getSymbol();
1577      MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
1578      IsPCRel = true;
1579      MCSectionData *Sec = Fragment->getParent();
1580
1581      // Offset of the symbol in the section
1582      int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec);
1583
1584      // Ofeset of the relocation in the section
1585      int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
1586      Value += b - a;
1587    }
1588
1589    if (!RelocSymbol) {
1590      MCSymbolData &SD = Asm.getSymbolData(ASymbol);
1591      MCFragment *F = SD.getFragment();
1592
1593      Index = F->getParent()->getOrdinal() + 1;
1594
1595      MCSectionData *FSD = F->getParent();
1596      // Offset of the symbol in the section
1597      Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
1598    } else {
1599      if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
1600        WeakrefUsedInReloc.insert(RelocSymbol);
1601      else
1602        UsedInReloc.insert(RelocSymbol);
1603      Index = -1;
1604    }
1605    Addend = Value;
1606    // Compensate for the addend on i386.
1607    if (Is64Bit)
1608      Value = 0;
1609  }
1610
1611  FixedValue = Value;
1612
1613  // determine the type of the relocation
1614
1615  MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
1616    MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
1617  unsigned Type;
1618  if (Is64Bit) {
1619    if (IsPCRel) {
1620      switch (Modifier) {
1621      default:
1622        llvm_unreachable("Unimplemented");
1623      case MCSymbolRefExpr::VK_None:
1624        Type = ELF::R_X86_64_PC32;
1625        break;
1626      case MCSymbolRefExpr::VK_PLT:
1627        Type = ELF::R_X86_64_PLT32;
1628        break;
1629      case MCSymbolRefExpr::VK_GOTPCREL:
1630        Type = ELF::R_X86_64_GOTPCREL;
1631        break;
1632      case MCSymbolRefExpr::VK_GOTTPOFF:
1633        Type = ELF::R_X86_64_GOTTPOFF;
1634        break;
1635      case MCSymbolRefExpr::VK_TLSGD:
1636        Type = ELF::R_X86_64_TLSGD;
1637        break;
1638      case MCSymbolRefExpr::VK_TLSLD:
1639        Type = ELF::R_X86_64_TLSLD;
1640        break;
1641      }
1642    } else {
1643      switch ((unsigned)Fixup.getKind()) {
1644      default: llvm_unreachable("invalid fixup kind!");
1645      case FK_Data_8: Type = ELF::R_X86_64_64; break;
1646      case X86::reloc_signed_4byte:
1647      case X86::reloc_pcrel_4byte:
1648        assert(isInt<32>(Target.getConstant()));
1649        switch (Modifier) {
1650        default:
1651          llvm_unreachable("Unimplemented");
1652        case MCSymbolRefExpr::VK_None:
1653          Type = ELF::R_X86_64_32S;
1654          break;
1655        case MCSymbolRefExpr::VK_GOT:
1656          Type = ELF::R_X86_64_GOT32;
1657          break;
1658        case MCSymbolRefExpr::VK_GOTPCREL:
1659          Type = ELF::R_X86_64_GOTPCREL;
1660          break;
1661        case MCSymbolRefExpr::VK_TPOFF:
1662          Type = ELF::R_X86_64_TPOFF32;
1663          break;
1664        case MCSymbolRefExpr::VK_DTPOFF:
1665          Type = ELF::R_X86_64_DTPOFF32;
1666          break;
1667        }
1668        break;
1669      case FK_Data_4:
1670        Type = ELF::R_X86_64_32;
1671        break;
1672      case FK_Data_2: Type = ELF::R_X86_64_16; break;
1673      case X86::reloc_pcrel_1byte:
1674      case FK_Data_1: Type = ELF::R_X86_64_8; break;
1675      }
1676    }
1677  } else {
1678    if (IsPCRel) {
1679      switch (Modifier) {
1680      default:
1681        llvm_unreachable("Unimplemented");
1682      case MCSymbolRefExpr::VK_None:
1683        Type = ELF::R_386_PC32;
1684        break;
1685      case MCSymbolRefExpr::VK_PLT:
1686        Type = ELF::R_386_PLT32;
1687        break;
1688      }
1689    } else {
1690      switch ((unsigned)Fixup.getKind()) {
1691      default: llvm_unreachable("invalid fixup kind!");
1692
1693      case X86::reloc_global_offset_table:
1694        Type = ELF::R_386_GOTPC;
1695        break;
1696
1697      // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode
1698      // instead?
1699      case X86::reloc_signed_4byte:
1700      case X86::reloc_pcrel_4byte:
1701      case FK_Data_4:
1702        switch (Modifier) {
1703        default:
1704          llvm_unreachable("Unimplemented");
1705        case MCSymbolRefExpr::VK_None:
1706          Type = ELF::R_386_32;
1707          break;
1708        case MCSymbolRefExpr::VK_GOT:
1709          Type = ELF::R_386_GOT32;
1710          break;
1711        case MCSymbolRefExpr::VK_GOTOFF:
1712          Type = ELF::R_386_GOTOFF;
1713          break;
1714        case MCSymbolRefExpr::VK_TLSGD:
1715          Type = ELF::R_386_TLS_GD;
1716          break;
1717        case MCSymbolRefExpr::VK_TPOFF:
1718          Type = ELF::R_386_TLS_LE_32;
1719          break;
1720        case MCSymbolRefExpr::VK_INDNTPOFF:
1721          Type = ELF::R_386_TLS_IE;
1722          break;
1723        case MCSymbolRefExpr::VK_NTPOFF:
1724          Type = ELF::R_386_TLS_LE;
1725          break;
1726        case MCSymbolRefExpr::VK_GOTNTPOFF:
1727          Type = ELF::R_386_TLS_GOTIE;
1728          break;
1729        case MCSymbolRefExpr::VK_TLSLDM:
1730          Type = ELF::R_386_TLS_LDM;
1731          break;
1732        case MCSymbolRefExpr::VK_DTPOFF:
1733          Type = ELF::R_386_TLS_LDO_32;
1734          break;
1735        }
1736        break;
1737      case FK_Data_2: Type = ELF::R_386_16; break;
1738      case X86::reloc_pcrel_1byte:
1739      case FK_Data_1: Type = ELF::R_386_8; break;
1740      }
1741    }
1742  }
1743
1744  if (RelocNeedsGOT(Modifier))
1745    NeedsGOT = true;
1746
1747
1748  uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
1749    Fixup.getOffset();
1750
1751  if (!HasRelocationAddend) Addend = 0;
1752  ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend);
1753  Relocations[Fragment->getParent()].push_back(ERE);
1754}
1755