ELFObjectWriter.cpp revision 1261a2ff99299946952013f284615a06afa3dc50 
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/MC/ELFObjectWriter.h"
15#include "llvm/ADT/SmallPtrSet.h"
16#include "llvm/ADT/STLExtras.h"
17#include "llvm/ADT/StringMap.h"
18#include "llvm/ADT/Twine.h"
19#include "llvm/MC/MCAssembler.h"
20#include "llvm/MC/MCAsmLayout.h"
21#include "llvm/MC/MCContext.h"
22#include "llvm/MC/MCELFSymbolFlags.h"
23#include "llvm/MC/MCExpr.h"
24#include "llvm/MC/MCObjectWriter.h"
25#include "llvm/MC/MCSectionELF.h"
26#include "llvm/MC/MCSymbol.h"
27#include "llvm/MC/MCValue.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/ErrorHandling.h"
30#include "llvm/Support/ELF.h"
31#include "llvm/Target/TargetAsmBackend.h"
32
33#include "../Target/X86/X86FixupKinds.h"
34
35#include <vector>
36using namespace llvm;
37
38static unsigned GetType(const MCSymbolData &SD) {
39  uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
40  assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
41         Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
42         Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
43         Type == ELF::STT_TLS);
44  return Type;
45}
46
47static unsigned GetBinding(const MCSymbolData &SD) {
48  uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
49  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
50         Binding == ELF::STB_WEAK);
51  return Binding;
52}
53
54static void SetBinding(MCSymbolData &SD, unsigned Binding) {
55  assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
56         Binding == ELF::STB_WEAK);
57  uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
58  SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
59}
60
61static unsigned GetVisibility(MCSymbolData &SD) {
62  unsigned Visibility =
63    (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
64  assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
65         Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
66  return Visibility;
67}
68
69static bool isFixupKindX86PCRel(unsigned Kind) {
70  switch (Kind) {
71  default:
72    return false;
73  case X86::reloc_pcrel_1byte:
74  case X86::reloc_pcrel_4byte:
75  case X86::reloc_riprel_4byte:
76  case X86::reloc_riprel_4byte_movq_load:
77    return true;
78  }
79}
80
81static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
82  switch (Variant) {
83  default:
84    return false;
85  case MCSymbolRefExpr::VK_GOT:
86  case MCSymbolRefExpr::VK_PLT:
87  case MCSymbolRefExpr::VK_GOTPCREL:
88  case MCSymbolRefExpr::VK_TPOFF:
89  case MCSymbolRefExpr::VK_TLSGD:
90  case MCSymbolRefExpr::VK_GOTTPOFF:
91  case MCSymbolRefExpr::VK_INDNTPOFF:
92  case MCSymbolRefExpr::VK_NTPOFF:
93  case MCSymbolRefExpr::VK_GOTNTPOFF:
94  case MCSymbolRefExpr::VK_TLSLDM:
95  case MCSymbolRefExpr::VK_DTPOFF:
96  case MCSymbolRefExpr::VK_TLSLD:
97    return true;
98  }
99}
100
101namespace {
102
103  class ELFObjectWriterImpl {
104    /*static bool isFixupKindX86RIPRel(unsigned Kind) {
105      return Kind == X86::reloc_riprel_4byte ||
106        Kind == X86::reloc_riprel_4byte_movq_load;
107    }*/
108
109
110    /// ELFSymbolData - Helper struct for containing some precomputed information
111    /// on symbols.
112    struct ELFSymbolData {
113      MCSymbolData *SymbolData;
114      uint64_t StringIndex;
115      uint32_t SectionIndex;
116
117      // Support lexicographic sorting.
118      bool operator<(const ELFSymbolData &RHS) const {
119        if (GetType(*SymbolData) == ELF::STT_FILE)
120          return true;
121        if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
122          return false;
123        return SymbolData->getSymbol().getName() <
124               RHS.SymbolData->getSymbol().getName();
125      }
126    };
127
128    /// @name Relocation Data
129    /// @{
130
131    struct ELFRelocationEntry {
132      // Make these big enough for both 32-bit and 64-bit
133      uint64_t r_offset;
134      int Index;
135      unsigned Type;
136      const MCSymbol *Symbol;
137      uint64_t r_addend;
138
139      // Support lexicographic sorting.
140      bool operator<(const ELFRelocationEntry &RE) const {
141        return RE.r_offset < r_offset;
142      }
143    };
144
145    SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
146    SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
147    DenseMap<const MCSymbol *, const MCSymbol *> Renames;
148
149    llvm::DenseMap<const MCSectionData*,
150                   std::vector<ELFRelocationEntry> > Relocations;
151    DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
152
153    /// @}
154    /// @name Symbol Table Data
155    /// @{
156
157    SmallString<256> StringTable;
158    std::vector<ELFSymbolData> LocalSymbolData;
159    std::vector<ELFSymbolData> ExternalSymbolData;
160    std::vector<ELFSymbolData> UndefinedSymbolData;
161
162    /// @}
163
164    int NumRegularSections;
165
166    bool NeedsGOT;
167
168    bool NeedsSymtabShndx;
169
170    ELFObjectWriter *Writer;
171
172    raw_ostream &OS;
173
174    unsigned Is64Bit : 1;
175
176    bool HasRelocationAddend;
177
178    Triple::OSType OSType;
179
180    uint16_t EMachine;
181
182    // This holds the symbol table index of the last local symbol.
183    unsigned LastLocalSymbolIndex;
184    // This holds the .strtab section index.
185    unsigned StringTableIndex;
186    // This holds the .symtab section index.
187    unsigned SymbolTableIndex;
188
189    unsigned ShstrtabIndex;
190
191  public:
192    ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
193                        uint16_t _EMachine, bool _HasRelAddend,
194                        Triple::OSType _OSType)
195      : NeedsGOT(false), NeedsSymtabShndx(false), Writer(_Writer),
196        OS(Writer->getStream()),
197        Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
198        OSType(_OSType), EMachine(_EMachine) {
199    }
200
201    void Write8(uint8_t Value) { Writer->Write8(Value); }
202    void Write16(uint16_t Value) { Writer->Write16(Value); }
203    void Write32(uint32_t Value) { Writer->Write32(Value); }
204    //void Write64(uint64_t Value) { Writer->Write64(Value); }
205    void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
206    //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
207    //  Writer->WriteBytes(Str, ZeroFillSize);
208    //}
209
210    void WriteWord(uint64_t W) {
211      if (Is64Bit)
212        Writer->Write64(W);
213      else
214        Writer->Write32(W);
215    }
216
217    void StringLE16(char *buf, uint16_t Value) {
218      buf[0] = char(Value >> 0);
219      buf[1] = char(Value >> 8);
220    }
221
222    void StringLE32(char *buf, uint32_t Value) {
223      StringLE16(buf, uint16_t(Value >> 0));
224      StringLE16(buf + 2, uint16_t(Value >> 16));
225    }
226
227    void StringLE64(char *buf, uint64_t Value) {
228      StringLE32(buf, uint32_t(Value >> 0));
229      StringLE32(buf + 4, uint32_t(Value >> 32));
230    }
231
232    void StringBE16(char *buf ,uint16_t Value) {
233      buf[0] = char(Value >> 8);
234      buf[1] = char(Value >> 0);
235    }
236
237    void StringBE32(char *buf, uint32_t Value) {
238      StringBE16(buf, uint16_t(Value >> 16));
239      StringBE16(buf + 2, uint16_t(Value >> 0));
240    }
241
242    void StringBE64(char *buf, uint64_t Value) {
243      StringBE32(buf, uint32_t(Value >> 32));
244      StringBE32(buf + 4, uint32_t(Value >> 0));
245    }
246
247    void String8(MCDataFragment &F, uint8_t Value) {
248      char buf[1];
249      buf[0] = Value;
250      F.getContents() += StringRef(buf, 1);
251    }
252
253    void String16(MCDataFragment &F, uint16_t Value) {
254      char buf[2];
255      if (Writer->isLittleEndian())
256        StringLE16(buf, Value);
257      else
258        StringBE16(buf, Value);
259      F.getContents() += StringRef(buf, 2);
260    }
261
262    void String32(MCDataFragment &F, uint32_t Value) {
263      char buf[4];
264      if (Writer->isLittleEndian())
265        StringLE32(buf, Value);
266      else
267        StringBE32(buf, Value);
268      F.getContents() += StringRef(buf, 4);
269    }
270
271    void String64(MCDataFragment &F, uint64_t Value) {
272      char buf[8];
273      if (Writer->isLittleEndian())
274        StringLE64(buf, Value);
275      else
276        StringBE64(buf, Value);
277      F.getContents() += StringRef(buf, 8);
278    }
279
280    void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
281
282    void WriteSymbolEntry(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
283                          uint64_t name, uint8_t info,
284                          uint64_t value, uint64_t size,
285                          uint8_t other, uint32_t shndx,
286                          bool Reserved);
287
288    void WriteSymbol(MCDataFragment *SymtabF,  MCDataFragment *ShndxF,
289                     ELFSymbolData &MSD,
290                     const MCAsmLayout &Layout);
291
292    typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
293    void WriteSymbolTable(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
294                          const MCAssembler &Asm,
295                          const MCAsmLayout &Layout,
296                          const SectionIndexMapTy &SectionIndexMap);
297
298    void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
299                          const MCFragment *Fragment, const MCFixup &Fixup,
300                          MCValue Target, uint64_t &FixedValue);
301
302    uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
303                                         const MCSymbol *S);
304
305    /// ComputeSymbolTable - Compute the symbol table data
306    ///
307    /// \param StringTable [out] - The string table data.
308    /// \param StringIndexMap [out] - Map from symbol names to offsets in the
309    /// string table.
310    void ComputeSymbolTable(MCAssembler &Asm,
311                            const SectionIndexMapTy &SectionIndexMap);
312
313    void ComputeIndexMap(MCAssembler &Asm,
314                         SectionIndexMapTy &SectionIndexMap);
315
316    void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
317                         const MCSectionData &SD);
318
319    void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
320      for (MCAssembler::const_iterator it = Asm.begin(),
321             ie = Asm.end(); it != ie; ++it) {
322        WriteRelocation(Asm, Layout, *it);
323      }
324    }
325
326    void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
327                                const SectionIndexMapTy &SectionIndexMap);
328
329    // Map from a group section to the signature symbol
330    typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
331    void CreateGroupSections(MCAssembler &Asm, MCAsmLayout &Layout,
332                             GroupMapTy &GroupMap);
333
334    void ExecutePostLayoutBinding(MCAssembler &Asm);
335
336    void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
337                          uint64_t Address, uint64_t Offset,
338                          uint64_t Size, uint32_t Link, uint32_t Info,
339                          uint64_t Alignment, uint64_t EntrySize);
340
341    void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
342                                  const MCSectionData *SD);
343
344    bool IsFixupFullyResolved(const MCAssembler &Asm,
345                              const MCValue Target,
346                              bool IsPCRel,
347                              const MCFragment *DF) const;
348
349    void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
350    void WriteSection(MCAssembler &Asm,
351                      const SectionIndexMapTy &SectionIndexMap,
352                      uint32_t GroupSymbolIndex,
353                      uint64_t Offset, uint64_t Size, uint64_t Alignment,
354                      const MCSectionELF &Section);
355  };
356
357}
358
359// Emit the ELF header.
360void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
361                                      unsigned NumberOfSections) {
362  // ELF Header
363  // ----------
364  //
365  // Note
366  // ----
367  // emitWord method behaves differently for ELF32 and ELF64, writing
368  // 4 bytes in the former and 8 in the latter.
369
370  Write8(0x7f); // e_ident[EI_MAG0]
371  Write8('E');  // e_ident[EI_MAG1]
372  Write8('L');  // e_ident[EI_MAG2]
373  Write8('F');  // e_ident[EI_MAG3]
374
375  Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
376
377  // e_ident[EI_DATA]
378  Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
379
380  Write8(ELF::EV_CURRENT);        // e_ident[EI_VERSION]
381  // e_ident[EI_OSABI]
382  switch (OSType) {
383    case Triple::FreeBSD:  Write8(ELF::ELFOSABI_FREEBSD); break;
384    case Triple::Linux:    Write8(ELF::ELFOSABI_LINUX); break;
385    default:               Write8(ELF::ELFOSABI_NONE); break;
386  }
387  Write8(0);                  // e_ident[EI_ABIVERSION]
388
389  WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
390
391  Write16(ELF::ET_REL);             // e_type
392
393  Write16(EMachine); // e_machine = target
394
395  Write32(ELF::EV_CURRENT);         // e_version
396  WriteWord(0);                    // e_entry, no entry point in .o file
397  WriteWord(0);                    // e_phoff, no program header for .o
398  WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
399            sizeof(ELF::Elf32_Ehdr)));  // e_shoff = sec hdr table off in bytes
400
401  // FIXME: Make this configurable.
402  Write32(0);   // e_flags = whatever the target wants
403
404  // e_ehsize = ELF header size
405  Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
406
407  Write16(0);                  // e_phentsize = prog header entry size
408  Write16(0);                  // e_phnum = # prog header entries = 0
409
410  // e_shentsize = Section header entry size
411  Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
412
413  // e_shnum     = # of section header ents
414  if (NumberOfSections >= ELF::SHN_LORESERVE)
415    Write16(0);
416  else
417    Write16(NumberOfSections);
418
419  // e_shstrndx  = Section # of '.shstrtab'
420  if (NumberOfSections >= ELF::SHN_LORESERVE)
421    Write16(ELF::SHN_XINDEX);
422  else
423    Write16(ShstrtabIndex);
424}
425
426void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *SymtabF,
427                                           MCDataFragment *ShndxF,
428                                           uint64_t name,
429                                           uint8_t info, uint64_t value,
430                                           uint64_t size, uint8_t other,
431                                           uint32_t shndx,
432                                           bool Reserved) {
433  if (ShndxF) {
434    if (shndx >= ELF::SHN_LORESERVE && !Reserved)
435      String32(*ShndxF, shndx);
436    else
437      String32(*ShndxF, 0);
438  }
439
440  uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
441    uint16_t(ELF::SHN_XINDEX) : shndx;
442
443  if (Is64Bit) {
444    String32(*SymtabF, name);  // st_name
445    String8(*SymtabF, info);   // st_info
446    String8(*SymtabF, other);  // st_other
447    String16(*SymtabF, Index); // st_shndx
448    String64(*SymtabF, value); // st_value
449    String64(*SymtabF, size);  // st_size
450  } else {
451    String32(*SymtabF, name);  // st_name
452    String32(*SymtabF, value); // st_value
453    String32(*SymtabF, size);  // st_size
454    String8(*SymtabF, info);   // st_info
455    String8(*SymtabF, other);  // st_other
456    String16(*SymtabF, Index); // st_shndx
457  }
458}
459
460static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) {
461  if (Data.isCommon() && Data.isExternal())
462    return Data.getCommonAlignment();
463
464  const MCSymbol &Symbol = Data.getSymbol();
465  if (!Symbol.isInSection())
466    return 0;
467
468  if (MCFragment *FF = Data.getFragment())
469    return Layout.getSymbolAddress(&Data) -
470      Layout.getSectionAddress(FF->getParent());
471
472  return 0;
473}
474
475static const MCSymbol &AliasedSymbol(const MCSymbol &Symbol) {
476  const MCSymbol *S = &Symbol;
477  while (S->isVariable()) {
478    const MCExpr *Value = S->getVariableValue();
479    MCExpr::ExprKind Kind = Value->getKind();
480    switch (Kind) {
481    case MCExpr::SymbolRef: {
482      const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Value);
483      S = &Ref->getSymbol();
484      break;
485    }
486    case MCExpr::Target: {
487      const MCTargetExpr *TExp = static_cast<const MCTargetExpr*>(Value);
488      MCValue Res;
489      TExp->EvaluateAsRelocatableImpl(Res, NULL);
490      S = &Res.getSymA()->getSymbol();
491      break;
492    }
493    default:
494      return *S;
495    }
496  }
497  return *S;
498}
499
500void ELFObjectWriterImpl::ExecutePostLayoutBinding(MCAssembler &Asm) {
501  // The presence of symbol versions causes undefined symbols and
502  // versions declared with @@@ to be renamed.
503
504  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
505         ie = Asm.symbol_end(); it != ie; ++it) {
506    const MCSymbol &Alias = it->getSymbol();
507    const MCSymbol &Symbol = AliasedSymbol(Alias);
508    MCSymbolData &SD = Asm.getSymbolData(Symbol);
509
510    // Undefined symbols are global, but this is the first place we
511    // are able to set it.
512    if (Symbol.isUndefined() && !Symbol.isVariable()) {
513      if (GetBinding(SD) == ELF::STB_LOCAL) {
514        SetBinding(SD, ELF::STB_GLOBAL);
515        SetBinding(*it, ELF::STB_GLOBAL);
516      }
517    }
518
519    // Not an alias.
520    if (&Symbol == &Alias)
521      continue;
522
523    StringRef AliasName = Alias.getName();
524    size_t Pos = AliasName.find('@');
525    if (Pos == StringRef::npos)
526      continue;
527
528    // Aliases defined with .symvar copy the binding from the symbol they alias.
529    // This is the first place we are able to copy this information.
530    it->setExternal(SD.isExternal());
531    SetBinding(*it, GetBinding(SD));
532
533    StringRef Rest = AliasName.substr(Pos);
534    if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
535      continue;
536
537    // FIXME: produce a better error message.
538    if (Symbol.isUndefined() && Rest.startswith("@@") &&
539        !Rest.startswith("@@@"))
540      report_fatal_error("A @@ version cannot be undefined");
541
542    Renames.insert(std::make_pair(&Symbol, &Alias));
543  }
544}
545
546void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *SymtabF,
547                                      MCDataFragment *ShndxF,
548                                      ELFSymbolData &MSD,
549                                      const MCAsmLayout &Layout) {
550  MCSymbolData &OrigData = *MSD.SymbolData;
551  MCSymbolData &Data =
552    Layout.getAssembler().getSymbolData(AliasedSymbol(OrigData.getSymbol()));
553
554  bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
555    Data.getSymbol().isVariable();
556
557  uint8_t Binding = GetBinding(OrigData);
558  uint8_t Visibility = GetVisibility(OrigData);
559  uint8_t Type = GetType(Data);
560
561  uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
562  uint8_t Other = Visibility;
563
564  uint64_t Value = SymbolValue(Data, Layout);
565  uint64_t Size = 0;
566  const MCExpr *ESize;
567
568  assert(!(Data.isCommon() && !Data.isExternal()));
569
570  ESize = Data.getSize();
571  if (Data.getSize()) {
572    MCValue Res;
573    if (ESize->getKind() == MCExpr::Binary) {
574      const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
575
576      if (BE->EvaluateAsRelocatable(Res, &Layout)) {
577        assert(!Res.getSymA() || !Res.getSymA()->getSymbol().isDefined());
578        assert(!Res.getSymB() || !Res.getSymB()->getSymbol().isDefined());
579        Size = Res.getConstant();
580      }
581    } else if (ESize->getKind() == MCExpr::Constant) {
582      Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
583    } else {
584      assert(0 && "Unsupported size expression");
585    }
586  }
587
588  // Write out the symbol table entry
589  WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
590                   Size, Other, MSD.SectionIndex, IsReserved);
591}
592
593void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *SymtabF,
594                                           MCDataFragment *ShndxF,
595                                           const MCAssembler &Asm,
596                                           const MCAsmLayout &Layout,
597                                     const SectionIndexMapTy &SectionIndexMap) {
598  // The string table must be emitted first because we need the index
599  // into the string table for all the symbol names.
600  assert(StringTable.size() && "Missing string table");
601
602  // FIXME: Make sure the start of the symbol table is aligned.
603
604  // The first entry is the undefined symbol entry.
605  WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
606
607  // Write the symbol table entries.
608  LastLocalSymbolIndex = LocalSymbolData.size() + 1;
609  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
610    ELFSymbolData &MSD = LocalSymbolData[i];
611    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
612  }
613
614  // Write out a symbol table entry for each regular section.
615  for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
616       ++i) {
617    const MCSectionELF &Section =
618      static_cast<const MCSectionELF&>(i->getSection());
619    if (Section.getType() == ELF::SHT_RELA ||
620        Section.getType() == ELF::SHT_REL ||
621        Section.getType() == ELF::SHT_STRTAB ||
622        Section.getType() == ELF::SHT_SYMTAB)
623      continue;
624    WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
625                     ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section), false);
626    LastLocalSymbolIndex++;
627  }
628
629  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
630    ELFSymbolData &MSD = ExternalSymbolData[i];
631    MCSymbolData &Data = *MSD.SymbolData;
632    assert(((Data.getFlags() & ELF_STB_Global) ||
633            (Data.getFlags() & ELF_STB_Weak)) &&
634           "External symbol requires STB_GLOBAL or STB_WEAK flag");
635    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
636    if (GetBinding(Data) == ELF::STB_LOCAL)
637      LastLocalSymbolIndex++;
638  }
639
640  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
641    ELFSymbolData &MSD = UndefinedSymbolData[i];
642    MCSymbolData &Data = *MSD.SymbolData;
643    WriteSymbol(SymtabF, ShndxF, MSD, Layout);
644    if (GetBinding(Data) == ELF::STB_LOCAL)
645      LastLocalSymbolIndex++;
646  }
647}
648
649static bool ShouldRelocOnSymbol(const MCSymbolData &SD,
650                                const MCValue &Target,
651                                const MCFragment &F) {
652  const MCSymbol &Symbol = SD.getSymbol();
653  if (Symbol.isUndefined())
654    return true;
655
656  const MCSectionELF &Section =
657    static_cast<const MCSectionELF&>(Symbol.getSection());
658
659  if (SD.isExternal())
660    return true;
661
662  MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
663  const MCSectionELF &Sec2 =
664    static_cast<const MCSectionELF&>(F.getParent()->getSection());
665
666  if (Section.getKind().isBSS())
667    return false;
668
669  if (&Sec2 != &Section &&
670      (Kind == MCSymbolRefExpr::VK_PLT ||
671       Kind == MCSymbolRefExpr::VK_GOTPCREL ||
672       Kind == MCSymbolRefExpr::VK_GOTOFF))
673    return true;
674
675  if (Section.getFlags() & MCSectionELF::SHF_MERGE)
676    return Target.getConstant() != 0;
677
678  return false;
679}
680
681// FIXME: this is currently X86/X86_64 only
682void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
683                                           const MCAsmLayout &Layout,
684                                           const MCFragment *Fragment,
685                                           const MCFixup &Fixup,
686                                           MCValue Target,
687                                           uint64_t &FixedValue) {
688  int64_t Addend = 0;
689  int Index = 0;
690  int64_t Value = Target.getConstant();
691  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
692  const MCSymbol &ASymbol = AliasedSymbol(Symbol);
693  const MCSymbol *RenamedP = Renames.lookup(&Symbol);
694  if (!RenamedP)
695    RenamedP = &ASymbol;
696  const MCSymbol &Renamed = *RenamedP;
697
698  bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
699  if (!Target.isAbsolute()) {
700    MCSymbolData &SD = Asm.getSymbolData(Symbol);
701    MCFragment *F = SD.getFragment();
702
703    if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
704      const MCSymbol &SymbolB = RefB->getSymbol();
705      MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
706      IsPCRel = true;
707      MCSectionData *Sec = Fragment->getParent();
708
709      // Offset of the symbol in the section
710      int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec);
711
712      // Ofeset of the relocation in the section
713      int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
714      Value += b - a;
715    }
716
717    bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target, *Fragment);
718    if (!RelocOnSymbol) {
719      Index = F->getParent()->getOrdinal();
720
721      MCSectionData *FSD = F->getParent();
722      // Offset of the symbol in the section
723      Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
724    } else {
725      if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
726        WeakrefUsedInReloc.insert(&Renamed);
727      else
728        UsedInReloc.insert(&Renamed);
729      Index = -1;
730    }
731    Addend = Value;
732    // Compensate for the addend on i386.
733    if (Is64Bit)
734      Value = 0;
735  }
736
737  FixedValue = Value;
738
739  // determine the type of the relocation
740
741  MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
742  unsigned Type;
743  if (Is64Bit) {
744    if (IsPCRel) {
745      switch (Modifier) {
746      default:
747        llvm_unreachable("Unimplemented");
748      case MCSymbolRefExpr::VK_None:
749        Type = ELF::R_X86_64_PC32;
750        break;
751      case MCSymbolRefExpr::VK_PLT:
752        Type = ELF::R_X86_64_PLT32;
753        break;
754      case MCSymbolRefExpr::VK_GOTPCREL:
755        Type = ELF::R_X86_64_GOTPCREL;
756        break;
757      case MCSymbolRefExpr::VK_GOTTPOFF:
758        Type = ELF::R_X86_64_GOTTPOFF;
759        break;
760      case MCSymbolRefExpr::VK_TLSGD:
761        Type = ELF::R_X86_64_TLSGD;
762        break;
763      case MCSymbolRefExpr::VK_TLSLD:
764        Type = ELF::R_X86_64_TLSLD;
765        break;
766      }
767    } else {
768      switch ((unsigned)Fixup.getKind()) {
769      default: llvm_unreachable("invalid fixup kind!");
770      case FK_Data_8: Type = ELF::R_X86_64_64; break;
771      case X86::reloc_signed_4byte:
772      case X86::reloc_pcrel_4byte:
773        assert(isInt<32>(Target.getConstant()));
774        switch (Modifier) {
775        default:
776          llvm_unreachable("Unimplemented");
777        case MCSymbolRefExpr::VK_None:
778          Type = ELF::R_X86_64_32S;
779          break;
780        case MCSymbolRefExpr::VK_GOT:
781          Type = ELF::R_X86_64_GOT32;
782          break;
783        case MCSymbolRefExpr::VK_GOTPCREL:
784          Type = ELF::R_X86_64_GOTPCREL;
785          break;
786        case MCSymbolRefExpr::VK_TPOFF:
787          Type = ELF::R_X86_64_TPOFF32;
788          break;
789        case MCSymbolRefExpr::VK_DTPOFF:
790          Type = ELF::R_X86_64_DTPOFF32;
791          break;
792        }
793        break;
794      case FK_Data_4:
795        Type = ELF::R_X86_64_32;
796        break;
797      case FK_Data_2: Type = ELF::R_X86_64_16; break;
798      case X86::reloc_pcrel_1byte:
799      case FK_Data_1: Type = ELF::R_X86_64_8; break;
800      }
801    }
802  } else {
803    if (IsPCRel) {
804      switch (Modifier) {
805      default:
806        llvm_unreachable("Unimplemented");
807      case MCSymbolRefExpr::VK_None:
808        Type = ELF::R_386_PC32;
809        break;
810      case MCSymbolRefExpr::VK_PLT:
811        Type = ELF::R_386_PLT32;
812        break;
813      }
814    } else {
815      switch ((unsigned)Fixup.getKind()) {
816      default: llvm_unreachable("invalid fixup kind!");
817
818      case X86::reloc_global_offset_table:
819        Type = ELF::R_386_GOTPC;
820        break;
821
822      // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode
823      // instead?
824      case X86::reloc_signed_4byte:
825      case X86::reloc_pcrel_4byte:
826      case FK_Data_4:
827        switch (Modifier) {
828        default:
829          llvm_unreachable("Unimplemented");
830        case MCSymbolRefExpr::VK_None:
831          Type = ELF::R_386_32;
832          break;
833        case MCSymbolRefExpr::VK_GOT:
834          Type = ELF::R_386_GOT32;
835          break;
836        case MCSymbolRefExpr::VK_GOTOFF:
837          Type = ELF::R_386_GOTOFF;
838          break;
839        case MCSymbolRefExpr::VK_TLSGD:
840          Type = ELF::R_386_TLS_GD;
841          break;
842        case MCSymbolRefExpr::VK_TPOFF:
843          Type = ELF::R_386_TLS_LE_32;
844          break;
845        case MCSymbolRefExpr::VK_INDNTPOFF:
846          Type = ELF::R_386_TLS_IE;
847          break;
848        case MCSymbolRefExpr::VK_NTPOFF:
849          Type = ELF::R_386_TLS_LE;
850          break;
851        case MCSymbolRefExpr::VK_GOTNTPOFF:
852          Type = ELF::R_386_TLS_GOTIE;
853          break;
854        case MCSymbolRefExpr::VK_TLSLDM:
855          Type = ELF::R_386_TLS_LDM;
856          break;
857        case MCSymbolRefExpr::VK_DTPOFF:
858          Type = ELF::R_386_TLS_LDO_32;
859          break;
860        }
861        break;
862      case FK_Data_2: Type = ELF::R_386_16; break;
863      case X86::reloc_pcrel_1byte:
864      case FK_Data_1: Type = ELF::R_386_8; break;
865      }
866    }
867  }
868
869  if (RelocNeedsGOT(Modifier))
870    NeedsGOT = true;
871
872  ELFRelocationEntry ERE;
873
874  ERE.Index = Index;
875  ERE.Type = Type;
876  ERE.Symbol = &Renamed;
877
878  ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
879
880  if (HasRelocationAddend)
881    ERE.r_addend = Addend;
882  else
883    ERE.r_addend = 0; // Silence compiler warning.
884
885  Relocations[Fragment->getParent()].push_back(ERE);
886}
887
888uint64_t
889ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
890                                                 const MCSymbol *S) {
891  MCSymbolData &SD = Asm.getSymbolData(*S);
892
893  // Local symbol.
894  if (!SD.isExternal() && !S->isUndefined())
895    return SD.getIndex() + /* empty symbol */ 1;
896
897  // External or undefined symbol.
898  return SD.getIndex() + NumRegularSections + /* empty symbol */ 1;
899}
900
901static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
902                       bool Used, bool Renamed) {
903  if (Data.getFlags() & ELF_Other_Weakref)
904    return false;
905
906  if (Used)
907    return true;
908
909  if (Renamed)
910    return false;
911
912  const MCSymbol &Symbol = Data.getSymbol();
913
914  if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
915    return true;
916
917  const MCSymbol &A = AliasedSymbol(Symbol);
918  if (!A.isVariable() && A.isUndefined() && !Data.isCommon())
919    return false;
920
921  if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
922    return false;
923
924  if (Symbol.isTemporary())
925    return false;
926
927  return true;
928}
929
930static bool isLocal(const MCSymbolData &Data) {
931  if (Data.isExternal())
932    return false;
933
934  const MCSymbol &Symbol = Data.getSymbol();
935  if (Symbol.isUndefined() && !Symbol.isVariable())
936    return false;
937
938  return true;
939}
940
941void ELFObjectWriterImpl::ComputeIndexMap(MCAssembler &Asm,
942                                          SectionIndexMapTy &SectionIndexMap) {
943  unsigned Index = 1;
944  for (MCAssembler::iterator it = Asm.begin(),
945         ie = Asm.end(); it != ie; ++it) {
946    const MCSectionELF &Section =
947      static_cast<const MCSectionELF &>(it->getSection());
948    if (Section.getType() != ELF::SHT_GROUP)
949      continue;
950    SectionIndexMap[&Section] = Index++;
951  }
952
953  for (MCAssembler::iterator it = Asm.begin(),
954         ie = Asm.end(); it != ie; ++it) {
955    const MCSectionELF &Section =
956      static_cast<const MCSectionELF &>(it->getSection());
957    if (Section.getType() == ELF::SHT_GROUP)
958      continue;
959    SectionIndexMap[&Section] = Index++;
960  }
961}
962
963void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm,
964                                     const SectionIndexMapTy &SectionIndexMap) {
965  // FIXME: Is this the correct place to do this?
966  if (NeedsGOT) {
967    llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_";
968    MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
969    MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
970    Data.setExternal(true);
971    SetBinding(Data, ELF::STB_GLOBAL);
972  }
973
974  // Build section lookup table.
975  NumRegularSections = Asm.size();
976
977  // Index 0 is always the empty string.
978  StringMap<uint64_t> StringIndexMap;
979  StringTable += '\x00';
980
981  // Add the data for the symbols.
982  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
983         ie = Asm.symbol_end(); it != ie; ++it) {
984    const MCSymbol &Symbol = it->getSymbol();
985
986    bool Used = UsedInReloc.count(&Symbol);
987    bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
988    if (!isInSymtab(Asm, *it, Used || WeakrefUsed,
989                    Renames.count(&Symbol)))
990      continue;
991
992    ELFSymbolData MSD;
993    MSD.SymbolData = it;
994    bool Local = isLocal(*it);
995    const MCSymbol &RefSymbol = AliasedSymbol(Symbol);
996
997    if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
998      SetBinding(*it, ELF::STB_WEAK);
999
1000    if (it->isCommon()) {
1001      assert(!Local);
1002      MSD.SectionIndex = ELF::SHN_COMMON;
1003    } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
1004      MSD.SectionIndex = ELF::SHN_ABS;
1005    } else if (RefSymbol.isUndefined()) {
1006      MSD.SectionIndex = ELF::SHN_UNDEF;
1007    } else {
1008      const MCSectionELF &Section =
1009        static_cast<const MCSectionELF&>(RefSymbol.getSection());
1010      MSD.SectionIndex = SectionIndexMap.lookup(&Section);
1011      if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
1012        NeedsSymtabShndx = true;
1013      assert(MSD.SectionIndex && "Invalid section index!");
1014    }
1015
1016    // The @@@ in symbol version is replaced with @ in undefined symbols and
1017    // @@ in defined ones.
1018    StringRef Name = Symbol.getName();
1019    SmallString<32> Buf;
1020
1021    size_t Pos = Name.find("@@@");
1022    if (Pos != StringRef::npos) {
1023      Buf += Name.substr(0, Pos);
1024      unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
1025      Buf += Name.substr(Pos + Skip);
1026      Name = Buf;
1027    }
1028
1029    uint64_t &Entry = StringIndexMap[Name];
1030    if (!Entry) {
1031      Entry = StringTable.size();
1032      StringTable += Name;
1033      StringTable += '\x00';
1034    }
1035    MSD.StringIndex = Entry;
1036    if (MSD.SectionIndex == ELF::SHN_UNDEF)
1037      UndefinedSymbolData.push_back(MSD);
1038    else if (Local)
1039      LocalSymbolData.push_back(MSD);
1040    else
1041      ExternalSymbolData.push_back(MSD);
1042  }
1043
1044  // Symbols are required to be in lexicographic order.
1045  array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1046  array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1047  array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1048
1049  // Set the symbol indices. Local symbols must come before all other
1050  // symbols with non-local bindings.
1051  unsigned Index = 0;
1052  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1053    LocalSymbolData[i].SymbolData->setIndex(Index++);
1054  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1055    ExternalSymbolData[i].SymbolData->setIndex(Index++);
1056  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1057    UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1058}
1059
1060void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
1061                                          const MCSectionData &SD) {
1062  if (!Relocations[&SD].empty()) {
1063    MCContext &Ctx = Asm.getContext();
1064    const MCSectionELF *RelaSection;
1065    const MCSectionELF &Section =
1066      static_cast<const MCSectionELF&>(SD.getSection());
1067
1068    const StringRef SectionName = Section.getSectionName();
1069    std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
1070    RelaSectionName += SectionName;
1071
1072    unsigned EntrySize;
1073    if (HasRelocationAddend)
1074      EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1075    else
1076      EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1077
1078    RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
1079                                    ELF::SHT_RELA : ELF::SHT_REL, 0,
1080                                    SectionKind::getReadOnly(),
1081                                    EntrySize, "");
1082
1083    MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1084    RelaSD.setAlignment(Is64Bit ? 8 : 4);
1085
1086    MCDataFragment *F = new MCDataFragment(&RelaSD);
1087
1088    WriteRelocationsFragment(Asm, F, &SD);
1089
1090    Asm.AddSectionToTheEnd(*Writer, RelaSD, Layout);
1091  }
1092}
1093
1094void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1095                                           uint64_t Flags, uint64_t Address,
1096                                           uint64_t Offset, uint64_t Size,
1097                                           uint32_t Link, uint32_t Info,
1098                                           uint64_t Alignment,
1099                                           uint64_t EntrySize) {
1100  Write32(Name);        // sh_name: index into string table
1101  Write32(Type);        // sh_type
1102  WriteWord(Flags);     // sh_flags
1103  WriteWord(Address);   // sh_addr
1104  WriteWord(Offset);    // sh_offset
1105  WriteWord(Size);      // sh_size
1106  Write32(Link);        // sh_link
1107  Write32(Info);        // sh_info
1108  WriteWord(Alignment); // sh_addralign
1109  WriteWord(EntrySize); // sh_entsize
1110}
1111
1112void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
1113                                                   MCDataFragment *F,
1114                                                   const MCSectionData *SD) {
1115  std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1116  // sort by the r_offset just like gnu as does
1117  array_pod_sort(Relocs.begin(), Relocs.end());
1118
1119  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1120    ELFRelocationEntry entry = Relocs[e - i - 1];
1121
1122    if (entry.Index < 0)
1123      entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1124    else
1125      entry.Index += LocalSymbolData.size() + 1;
1126    if (Is64Bit) {
1127      String64(*F, entry.r_offset);
1128
1129      struct ELF::Elf64_Rela ERE64;
1130      ERE64.setSymbolAndType(entry.Index, entry.Type);
1131      String64(*F, ERE64.r_info);
1132
1133      if (HasRelocationAddend)
1134        String64(*F, entry.r_addend);
1135    } else {
1136      String32(*F, entry.r_offset);
1137
1138      struct ELF::Elf32_Rela ERE32;
1139      ERE32.setSymbolAndType(entry.Index, entry.Type);
1140      String32(*F, ERE32.r_info);
1141
1142      if (HasRelocationAddend)
1143        String32(*F, entry.r_addend);
1144    }
1145  }
1146}
1147
1148void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
1149                                                 MCAsmLayout &Layout,
1150                                    const SectionIndexMapTy &SectionIndexMap) {
1151  MCContext &Ctx = Asm.getContext();
1152  MCDataFragment *F;
1153
1154  unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1155
1156  // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1157  const MCSectionELF *ShstrtabSection =
1158    Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1159                      SectionKind::getReadOnly());
1160  MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1161  ShstrtabSD.setAlignment(1);
1162  ShstrtabIndex = Asm.size();
1163
1164  const MCSectionELF *SymtabSection =
1165    Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1166                      SectionKind::getReadOnly(),
1167                      EntrySize, "");
1168  MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1169  SymtabSD.setAlignment(Is64Bit ? 8 : 4);
1170  SymbolTableIndex = Asm.size();
1171
1172  MCSectionData *SymtabShndxSD = NULL;
1173
1174  if (NeedsSymtabShndx) {
1175    const MCSectionELF *SymtabShndxSection =
1176      Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1177                        SectionKind::getReadOnly(), 4, "");
1178    SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1179    SymtabShndxSD->setAlignment(4);
1180  }
1181
1182  const MCSection *StrtabSection;
1183  StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1184                                    SectionKind::getReadOnly());
1185  MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1186  StrtabSD.setAlignment(1);
1187  StringTableIndex = Asm.size();
1188
1189  WriteRelocations(Asm, Layout);
1190
1191  // Symbol table
1192  F = new MCDataFragment(&SymtabSD);
1193  MCDataFragment *ShndxF = NULL;
1194  if (NeedsSymtabShndx) {
1195    ShndxF = new MCDataFragment(SymtabShndxSD);
1196    Asm.AddSectionToTheEnd(*Writer, *SymtabShndxSD, Layout);
1197  }
1198  WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1199  Asm.AddSectionToTheEnd(*Writer, SymtabSD, Layout);
1200
1201  F = new MCDataFragment(&StrtabSD);
1202  F->getContents().append(StringTable.begin(), StringTable.end());
1203  Asm.AddSectionToTheEnd(*Writer, StrtabSD, Layout);
1204
1205  F = new MCDataFragment(&ShstrtabSD);
1206
1207  // Section header string table.
1208  //
1209  // The first entry of a string table holds a null character so skip
1210  // section 0.
1211  uint64_t Index = 1;
1212  F->getContents() += '\x00';
1213
1214  StringMap<uint64_t> SecStringMap;
1215  for (MCAssembler::const_iterator it = Asm.begin(),
1216         ie = Asm.end(); it != ie; ++it) {
1217    const MCSectionELF &Section =
1218      static_cast<const MCSectionELF&>(it->getSection());
1219    // FIXME: We could merge suffixes like in .text and .rela.text.
1220
1221    StringRef Name = Section.getSectionName();
1222    if (SecStringMap.count(Name)) {
1223      SectionStringTableIndex[&Section] =  SecStringMap[Name];
1224      continue;
1225    }
1226    // Remember the index into the string table so we can write it
1227    // into the sh_name field of the section header table.
1228    SectionStringTableIndex[&Section] = Index;
1229    SecStringMap[Name] = Index;
1230
1231    Index += Name.size() + 1;
1232    F->getContents() += Name;
1233    F->getContents() += '\x00';
1234  }
1235
1236  Asm.AddSectionToTheEnd(*Writer, ShstrtabSD, Layout);
1237}
1238
1239bool ELFObjectWriterImpl::IsFixupFullyResolved(const MCAssembler &Asm,
1240                                               const MCValue Target,
1241                                               bool IsPCRel,
1242                                               const MCFragment *DF) const {
1243  // If this is a PCrel relocation, find the section this fixup value is
1244  // relative to.
1245  const MCSection *BaseSection = 0;
1246  if (IsPCRel) {
1247    BaseSection = &DF->getParent()->getSection();
1248    assert(BaseSection);
1249  }
1250
1251  const MCSection *SectionA = 0;
1252  const MCSymbol *SymbolA = 0;
1253  if (const MCSymbolRefExpr *A = Target.getSymA()) {
1254    SymbolA = &A->getSymbol();
1255    SectionA = &SymbolA->getSection();
1256  }
1257
1258  const MCSection *SectionB = 0;
1259  if (const MCSymbolRefExpr *B = Target.getSymB()) {
1260    SectionB = &B->getSymbol().getSection();
1261  }
1262
1263  if (!BaseSection)
1264    return SectionA == SectionB;
1265
1266  const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA);
1267  if (DataA.isExternal())
1268    return false;
1269
1270  return !SectionB && BaseSection == SectionA;
1271}
1272
1273void ELFObjectWriterImpl::CreateGroupSections(MCAssembler &Asm,
1274                                              MCAsmLayout &Layout,
1275                                              GroupMapTy &GroupMap) {
1276  typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
1277  // Build the groups
1278  RevGroupMapTy Groups;
1279  for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1280       it != ie; ++it) {
1281    const MCSectionELF &Section =
1282      static_cast<const MCSectionELF&>(it->getSection());
1283    if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1284      continue;
1285
1286    const MCSymbol *SignatureSymbol = Section.getGroup();
1287    Asm.getOrCreateSymbolData(*SignatureSymbol);
1288    const MCSectionELF *&Group = Groups[SignatureSymbol];
1289    if (!Group) {
1290      Group = Asm.getContext().CreateELFGroupSection();
1291      MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1292      Data.setAlignment(4);
1293      MCDataFragment *F = new MCDataFragment(&Data);
1294      String32(*F, ELF::GRP_COMDAT);
1295    }
1296    GroupMap[Group] = SignatureSymbol;
1297  }
1298
1299  // Add sections to the groups
1300  unsigned Index = 1;
1301  unsigned NumGroups = Groups.size();
1302  for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1303       it != ie; ++it, ++Index) {
1304    const MCSectionELF &Section =
1305      static_cast<const MCSectionELF&>(it->getSection());
1306    if (!(Section.getFlags() & MCSectionELF::SHF_GROUP))
1307      continue;
1308    const MCSectionELF *Group = Groups[Section.getGroup()];
1309    MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1310    // FIXME: we could use the previous fragment
1311    MCDataFragment *F = new MCDataFragment(&Data);
1312    String32(*F, NumGroups + Index);
1313  }
1314
1315  for (RevGroupMapTy::const_iterator i = Groups.begin(), e = Groups.end();
1316       i != e; ++i) {
1317    const MCSectionELF *Group = i->second;
1318    MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1319    Asm.AddSectionToTheEnd(*Writer, Data, Layout);
1320  }
1321}
1322
1323void ELFObjectWriterImpl::WriteSection(MCAssembler &Asm,
1324                                       const SectionIndexMapTy &SectionIndexMap,
1325                                       uint32_t GroupSymbolIndex,
1326                                       uint64_t Offset, uint64_t Size,
1327                                       uint64_t Alignment,
1328                                       const MCSectionELF &Section) {
1329  uint64_t sh_link = 0;
1330  uint64_t sh_info = 0;
1331
1332  switch(Section.getType()) {
1333  case ELF::SHT_DYNAMIC:
1334    sh_link = SectionStringTableIndex[&Section];
1335    sh_info = 0;
1336    break;
1337
1338  case ELF::SHT_REL:
1339  case ELF::SHT_RELA: {
1340    const MCSectionELF *SymtabSection;
1341    const MCSectionELF *InfoSection;
1342    SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1343                                                   0,
1344                                                   SectionKind::getReadOnly());
1345    sh_link = SectionIndexMap.lookup(SymtabSection);
1346    assert(sh_link && ".symtab not found");
1347
1348    // Remove ".rel" and ".rela" prefixes.
1349    unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1350    StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1351
1352    InfoSection = Asm.getContext().getELFSection(SectionName,
1353                                                 ELF::SHT_PROGBITS, 0,
1354                                                 SectionKind::getReadOnly());
1355    sh_info = SectionIndexMap.lookup(InfoSection);
1356    break;
1357  }
1358
1359  case ELF::SHT_SYMTAB:
1360  case ELF::SHT_DYNSYM:
1361    sh_link = StringTableIndex;
1362    sh_info = LastLocalSymbolIndex;
1363    break;
1364
1365  case ELF::SHT_SYMTAB_SHNDX:
1366    sh_link = SymbolTableIndex;
1367    break;
1368
1369  case ELF::SHT_PROGBITS:
1370  case ELF::SHT_STRTAB:
1371  case ELF::SHT_NOBITS:
1372  case ELF::SHT_NULL:
1373  case ELF::SHT_ARM_ATTRIBUTES:
1374    // Nothing to do.
1375    break;
1376
1377  case ELF::SHT_GROUP: {
1378    sh_link = SymbolTableIndex;
1379    sh_info = GroupSymbolIndex;
1380    break;
1381  }
1382
1383  default:
1384    assert(0 && "FIXME: sh_type value not supported!");
1385    break;
1386  }
1387
1388  WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1389                   Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1390                   Alignment, Section.getEntrySize());
1391}
1392
1393void ELFObjectWriterImpl::WriteObject(MCAssembler &Asm,
1394                                      const MCAsmLayout &Layout) {
1395
1396  GroupMapTy GroupMap;
1397  CreateGroupSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap);
1398
1399  SectionIndexMapTy SectionIndexMap;
1400
1401  ComputeIndexMap(Asm, SectionIndexMap);
1402
1403  // Compute symbol table information.
1404  ComputeSymbolTable(Asm, SectionIndexMap);
1405
1406  CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1407                         const_cast<MCAsmLayout&>(Layout),
1408                         SectionIndexMap);
1409
1410  // Update to include the metadata sections.
1411  ComputeIndexMap(Asm, SectionIndexMap);
1412
1413  // Add 1 for the null section.
1414  unsigned NumSections = Asm.size() + 1;
1415  uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
1416  uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
1417  uint64_t FileOff = HeaderSize;
1418
1419  std::vector<const MCSectionELF*> Sections;
1420  Sections.resize(NumSections);
1421
1422  for (SectionIndexMapTy::const_iterator i=
1423         SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1424    const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1425    Sections[p.second] = p.first;
1426  }
1427
1428  for (unsigned i = 1; i < NumSections; ++i) {
1429    const MCSectionELF &Section = *Sections[i];
1430    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1431
1432    FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1433
1434    // Get the size of the section in the output file (including padding).
1435    uint64_t Size = Layout.getSectionFileSize(&SD);
1436
1437    FileOff += Size;
1438  }
1439
1440  FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1441
1442  // Write out the ELF header ...
1443  WriteHeader(FileOff - HeaderSize, NumSections);
1444
1445  FileOff = HeaderSize;
1446
1447  // ... then all of the sections ...
1448  DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
1449
1450  for (unsigned i = 1; i < NumSections; ++i) {
1451    const MCSectionELF &Section = *Sections[i];
1452    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1453
1454    uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
1455    WriteZeros(Padding);
1456    FileOff += Padding;
1457
1458    // Remember the offset into the file for this section.
1459    SectionOffsetMap[&Section] = FileOff;
1460
1461    FileOff += Layout.getSectionFileSize(&SD);
1462
1463    Asm.WriteSectionData(&SD, Layout, Writer);
1464  }
1465
1466  uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
1467  WriteZeros(Padding);
1468  FileOff += Padding;
1469
1470  // ... and then the section header table.
1471  // Should we align the section header table?
1472  //
1473  // Null section first.
1474  uint64_t FirstSectionSize =
1475    NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1476  uint32_t FirstSectionLink =
1477    ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1478  WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1479
1480  for (unsigned i = 1; i < NumSections; ++i) {
1481    const MCSectionELF &Section = *Sections[i];
1482    const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1483    uint32_t GroupSymbolIndex;
1484    if (Section.getType() != ELF::SHT_GROUP)
1485      GroupSymbolIndex = 0;
1486    else
1487      GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm, GroupMap[&Section]);
1488
1489    WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1490                 SectionOffsetMap[&Section], Layout.getSectionSize(&SD),
1491                 SD.getAlignment(), Section);
1492  }
1493}
1494
1495ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
1496                                 bool Is64Bit,
1497                                 Triple::OSType OSType,
1498                                 uint16_t EMachine,
1499                                 bool IsLittleEndian,
1500                                 bool HasRelocationAddend)
1501  : MCObjectWriter(OS, IsLittleEndian)
1502{
1503  Impl = new ELFObjectWriterImpl(this, Is64Bit, EMachine,
1504                                 HasRelocationAddend, OSType);
1505}
1506
1507ELFObjectWriter::~ELFObjectWriter() {
1508  delete (ELFObjectWriterImpl*) Impl;
1509}
1510
1511void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
1512  ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
1513}
1514
1515void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1516                                       const MCAsmLayout &Layout,
1517                                       const MCFragment *Fragment,
1518                                       const MCFixup &Fixup, MCValue Target,
1519                                       uint64_t &FixedValue) {
1520  ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
1521                                                  Target, FixedValue);
1522}
1523
1524bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm,
1525                                           const MCValue Target,
1526                                           bool IsPCRel,
1527                                           const MCFragment *DF) const {
1528  return ((ELFObjectWriterImpl*) Impl)->IsFixupFullyResolved(Asm, Target,
1529                                                             IsPCRel, DF);
1530}
1531
1532void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1533                                  const MCAsmLayout &Layout) {
1534  ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);
1535}
1536