1//===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
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 contains an implementation of a Win32 COFF object file writer.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/MC/MCWinCOFFObjectWriter.h"
15#include "llvm/ADT/DenseMap.h"
16#include "llvm/ADT/StringMap.h"
17#include "llvm/ADT/StringRef.h"
18#include "llvm/ADT/STLExtras.h"
19#include "llvm/ADT/Twine.h"
20#include "llvm/MC/MCAsmLayout.h"
21#include "llvm/MC/MCAssembler.h"
22#include "llvm/MC/MCContext.h"
23#include "llvm/MC/MCExpr.h"
24#include "llvm/MC/MCObjectWriter.h"
25#include "llvm/MC/MCSection.h"
26#include "llvm/MC/MCSectionCOFF.h"
27#include "llvm/MC/MCSymbol.h"
28#include "llvm/MC/MCValue.h"
29#include "llvm/Support/COFF.h"
30#include "llvm/Support/Debug.h"
31#include "llvm/Support/ErrorHandling.h"
32#include "llvm/Support/TimeValue.h"
33#include <cstdio>
34
35using namespace llvm;
36
37#define DEBUG_TYPE "WinCOFFObjectWriter"
38
39namespace {
40typedef SmallString<COFF::NameSize> name;
41
42enum AuxiliaryType {
43  ATFunctionDefinition,
44  ATbfAndefSymbol,
45  ATWeakExternal,
46  ATFile,
47  ATSectionDefinition
48};
49
50struct AuxSymbol {
51  AuxiliaryType   AuxType;
52  COFF::Auxiliary Aux;
53};
54
55class COFFSymbol;
56class COFFSection;
57
58class COFFSymbol {
59public:
60  COFF::symbol Data;
61
62  typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
63
64  name             Name;
65  int              Index;
66  AuxiliarySymbols Aux;
67  COFFSymbol      *Other;
68  COFFSection     *Section;
69  int              Relocations;
70
71  MCSymbolData const *MCData;
72
73  COFFSymbol(StringRef name);
74  size_t size() const;
75  void set_name_offset(uint32_t Offset);
76
77  bool should_keep() const;
78};
79
80// This class contains staging data for a COFF relocation entry.
81struct COFFRelocation {
82  COFF::relocation Data;
83  COFFSymbol          *Symb;
84
85  COFFRelocation() : Symb(nullptr) {}
86  static size_t size() { return COFF::RelocationSize; }
87};
88
89typedef std::vector<COFFRelocation> relocations;
90
91class COFFSection {
92public:
93  COFF::section Header;
94
95  std::string          Name;
96  int                  Number;
97  MCSectionData const *MCData;
98  COFFSymbol          *Symbol;
99  relocations          Relocations;
100
101  COFFSection(StringRef name);
102  static size_t size();
103};
104
105// This class holds the COFF string table.
106class StringTable {
107  typedef StringMap<size_t> map;
108  map Map;
109
110  void update_length();
111public:
112  std::vector<char> Data;
113
114  StringTable();
115  size_t size() const;
116  size_t insert(StringRef String);
117};
118
119class WinCOFFObjectWriter : public MCObjectWriter {
120public:
121
122  typedef std::vector<std::unique_ptr<COFFSymbol>>  symbols;
123  typedef std::vector<std::unique_ptr<COFFSection>> sections;
124
125  typedef DenseMap<MCSymbol  const *, COFFSymbol *>   symbol_map;
126  typedef DenseMap<MCSection const *, COFFSection *> section_map;
127
128  std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
129
130  // Root level file contents.
131  COFF::header Header;
132  sections     Sections;
133  symbols      Symbols;
134  StringTable  Strings;
135
136  // Maps used during object file creation.
137  section_map SectionMap;
138  symbol_map  SymbolMap;
139
140  WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
141
142  COFFSymbol *createSymbol(StringRef Name);
143  COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
144  COFFSection *createSection(StringRef Name);
145
146  template <typename object_t, typename list_t>
147  object_t *createCOFFEntity(StringRef Name, list_t &List);
148
149  void DefineSection(MCSectionData const &SectionData);
150  void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
151                    const MCAsmLayout &Layout);
152
153  void MakeSymbolReal(COFFSymbol &S, size_t Index);
154  void MakeSectionReal(COFFSection &S, size_t Number);
155
156  bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
157
158  bool IsPhysicalSection(COFFSection *S);
159
160  // Entity writing methods.
161
162  void WriteFileHeader(const COFF::header &Header);
163  void WriteSymbol(const COFFSymbol &S);
164  void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
165  void WriteSectionHeader(const COFF::section &S);
166  void WriteRelocation(const COFF::relocation &R);
167
168  // MCObjectWriter interface implementation.
169
170  void ExecutePostLayoutBinding(MCAssembler &Asm,
171                                const MCAsmLayout &Layout) override;
172
173  void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
174                        const MCFragment *Fragment, const MCFixup &Fixup,
175                        MCValue Target, bool &IsPCRel,
176                        uint64_t &FixedValue) override;
177
178  void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
179};
180}
181
182static inline void write_uint32_le(void *Data, uint32_t const &Value) {
183  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
184  Ptr[0] = (Value & 0x000000FF) >>  0;
185  Ptr[1] = (Value & 0x0000FF00) >>  8;
186  Ptr[2] = (Value & 0x00FF0000) >> 16;
187  Ptr[3] = (Value & 0xFF000000) >> 24;
188}
189
190//------------------------------------------------------------------------------
191// Symbol class implementation
192
193COFFSymbol::COFFSymbol(StringRef name)
194  : Name(name.begin(), name.end())
195  , Other(nullptr)
196  , Section(nullptr)
197  , Relocations(0)
198  , MCData(nullptr) {
199  memset(&Data, 0, sizeof(Data));
200}
201
202size_t COFFSymbol::size() const {
203  return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
204}
205
206// In the case that the name does not fit within 8 bytes, the offset
207// into the string table is stored in the last 4 bytes instead, leaving
208// the first 4 bytes as 0.
209void COFFSymbol::set_name_offset(uint32_t Offset) {
210  write_uint32_le(Data.Name + 0, 0);
211  write_uint32_le(Data.Name + 4, Offset);
212}
213
214/// logic to decide if the symbol should be reported in the symbol table
215bool COFFSymbol::should_keep() const {
216  // no section means its external, keep it
217  if (!Section)
218    return true;
219
220  // if it has relocations pointing at it, keep it
221  if (Relocations > 0)   {
222    assert(Section->Number != -1 && "Sections with relocations must be real!");
223    return true;
224  }
225
226  // if the section its in is being droped, drop it
227  if (Section->Number == -1)
228      return false;
229
230  // if it is the section symbol, keep it
231  if (Section->Symbol == this)
232    return true;
233
234  // if its temporary, drop it
235  if (MCData && MCData->getSymbol().isTemporary())
236      return false;
237
238  // otherwise, keep it
239  return true;
240}
241
242//------------------------------------------------------------------------------
243// Section class implementation
244
245COFFSection::COFFSection(StringRef name)
246  : Name(name)
247  , MCData(nullptr)
248  , Symbol(nullptr) {
249  memset(&Header, 0, sizeof(Header));
250}
251
252size_t COFFSection::size() {
253  return COFF::SectionSize;
254}
255
256//------------------------------------------------------------------------------
257// StringTable class implementation
258
259/// Write the length of the string table into Data.
260/// The length of the string table includes uint32 length header.
261void StringTable::update_length() {
262  write_uint32_le(&Data.front(), Data.size());
263}
264
265StringTable::StringTable() {
266  // The string table data begins with the length of the entire string table
267  // including the length header. Allocate space for this header.
268  Data.resize(4);
269  update_length();
270}
271
272size_t StringTable::size() const {
273  return Data.size();
274}
275
276/// Add String to the table iff it is not already there.
277/// @returns the index into the string table where the string is now located.
278size_t StringTable::insert(StringRef String) {
279  map::iterator i = Map.find(String);
280
281  if (i != Map.end())
282    return i->second;
283
284  size_t Offset = Data.size();
285
286  // Insert string data into string table.
287  Data.insert(Data.end(), String.begin(), String.end());
288  Data.push_back('\0');
289
290  // Put a reference to it in the map.
291  Map[String] = Offset;
292
293  // Update the internal length field.
294  update_length();
295
296  return Offset;
297}
298
299//------------------------------------------------------------------------------
300// WinCOFFObjectWriter class implementation
301
302WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
303                                         raw_ostream &OS)
304  : MCObjectWriter(OS, true)
305  , TargetObjectWriter(MOTW) {
306  memset(&Header, 0, sizeof(Header));
307
308  Header.Machine = TargetObjectWriter->getMachine();
309}
310
311COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
312  return createCOFFEntity<COFFSymbol>(Name, Symbols);
313}
314
315COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
316  symbol_map::iterator i = SymbolMap.find(Symbol);
317  if (i != SymbolMap.end())
318    return i->second;
319  COFFSymbol *RetSymbol
320    = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
321  SymbolMap[Symbol] = RetSymbol;
322  return RetSymbol;
323}
324
325COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
326  return createCOFFEntity<COFFSection>(Name, Sections);
327}
328
329/// A template used to lookup or create a symbol/section, and initialize it if
330/// needed.
331template <typename object_t, typename list_t>
332object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
333                                                list_t &List) {
334  List.push_back(make_unique<object_t>(Name));
335
336  return List.back().get();
337}
338
339/// This function takes a section data object from the assembler
340/// and creates the associated COFF section staging object.
341void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
342  assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
343    && "Got non-COFF section in the COFF backend!");
344  // FIXME: Not sure how to verify this (at least in a debug build).
345  MCSectionCOFF const &Sec =
346    static_cast<MCSectionCOFF const &>(SectionData.getSection());
347
348  COFFSection *coff_section = createSection(Sec.getSectionName());
349  COFFSymbol  *coff_symbol = createSymbol(Sec.getSectionName());
350  if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
351    if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
352      COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
353      if (COMDATSymbol->Section)
354        report_fatal_error("two sections have the same comdat");
355      COMDATSymbol->Section = coff_section;
356    }
357  }
358
359  coff_section->Symbol = coff_symbol;
360  coff_symbol->Section = coff_section;
361  coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
362
363  // In this case the auxiliary symbol is a Section Definition.
364  coff_symbol->Aux.resize(1);
365  memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
366  coff_symbol->Aux[0].AuxType = ATSectionDefinition;
367  coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
368
369  coff_section->Header.Characteristics = Sec.getCharacteristics();
370
371  uint32_t &Characteristics = coff_section->Header.Characteristics;
372  switch (SectionData.getAlignment()) {
373  case 1:    Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;    break;
374  case 2:    Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;    break;
375  case 4:    Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;    break;
376  case 8:    Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;    break;
377  case 16:   Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;   break;
378  case 32:   Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;   break;
379  case 64:   Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;   break;
380  case 128:  Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;  break;
381  case 256:  Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;  break;
382  case 512:  Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;  break;
383  case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
384  case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
385  case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
386  case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
387  default:
388    llvm_unreachable("unsupported section alignment");
389  }
390
391  // Bind internal COFF section to MC section.
392  coff_section->MCData = &SectionData;
393  SectionMap[&SectionData.getSection()] = coff_section;
394}
395
396static uint64_t getSymbolValue(const MCSymbolData &Data,
397                               const MCAsmLayout &Layout) {
398  if (Data.isCommon() && Data.isExternal())
399    return Data.getCommonSize();
400
401  uint64_t Res;
402  if (!Layout.getSymbolOffset(&Data, Res))
403    return 0;
404
405  return Res;
406}
407
408/// This function takes a symbol data object from the assembler
409/// and creates the associated COFF symbol staging object.
410void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
411                                       MCAssembler &Assembler,
412                                       const MCAsmLayout &Layout) {
413  MCSymbol const &Symbol = SymbolData.getSymbol();
414  COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
415  SymbolMap[&Symbol] = coff_symbol;
416
417  if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
418    coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
419
420    if (Symbol.isVariable()) {
421      const MCSymbolRefExpr *SymRef =
422        dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
423
424      if (!SymRef)
425        report_fatal_error("Weak externals may only alias symbols");
426
427      coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
428    } else {
429      std::string WeakName = std::string(".weak.")
430                           +  Symbol.getName().str()
431                           + ".default";
432      COFFSymbol *WeakDefault = createSymbol(WeakName);
433      WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
434      WeakDefault->Data.StorageClass  = COFF::IMAGE_SYM_CLASS_EXTERNAL;
435      WeakDefault->Data.Type          = 0;
436      WeakDefault->Data.Value         = 0;
437      coff_symbol->Other = WeakDefault;
438    }
439
440    // Setup the Weak External auxiliary symbol.
441    coff_symbol->Aux.resize(1);
442    memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
443    coff_symbol->Aux[0].AuxType = ATWeakExternal;
444    coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
445    coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
446      COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
447
448    coff_symbol->MCData = &SymbolData;
449  } else {
450    const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
451    const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
452    coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
453
454    coff_symbol->Data.Type         = (ResSymData.getFlags() & 0x0000FFFF) >>  0;
455    coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
456
457    // If no storage class was specified in the streamer, define it here.
458    if (coff_symbol->Data.StorageClass == 0) {
459      bool external = ResSymData.isExternal() || !ResSymData.Fragment;
460
461      coff_symbol->Data.StorageClass =
462       external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
463    }
464
465    if (!Base) {
466      coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
467    } else {
468      const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
469      if (BaseData.Fragment) {
470        COFFSection *Sec =
471            SectionMap[&BaseData.Fragment->getParent()->getSection()];
472
473        if (coff_symbol->Section && coff_symbol->Section != Sec)
474          report_fatal_error("conflicting sections for symbol");
475
476        coff_symbol->Section = Sec;
477      }
478    }
479
480    coff_symbol->MCData = &ResSymData;
481  }
482}
483
484// Maximum offsets for different string table entry encodings.
485static const unsigned Max6DecimalOffset = 999999;
486static const unsigned Max7DecimalOffset = 9999999;
487static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
488
489// Encode a string table entry offset in base 64, padded to 6 chars, and
490// prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
491// Buffer must be at least 8 bytes large. No terminating null appended.
492static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
493  assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
494         "Illegal section name encoding for value");
495
496  static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
497                                 "abcdefghijklmnopqrstuvwxyz"
498                                 "0123456789+/";
499
500  Buffer[0] = '/';
501  Buffer[1] = '/';
502
503  char* Ptr = Buffer + 7;
504  for (unsigned i = 0; i < 6; ++i) {
505    unsigned Rem = Value % 64;
506    Value /= 64;
507    *(Ptr--) = Alphabet[Rem];
508  }
509}
510
511/// making a section real involves assigned it a number and putting
512/// name into the string table if needed
513void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
514  if (S.Name.size() > COFF::NameSize) {
515    uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
516
517    if (StringTableEntry <= Max6DecimalOffset) {
518      std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
519    } else if (StringTableEntry <= Max7DecimalOffset) {
520      // With seven digits, we have to skip the terminating null. Because
521      // sprintf always appends it, we use a larger temporary buffer.
522      char buffer[9] = { };
523      std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
524      std::memcpy(S.Header.Name, buffer, 8);
525    } else if (StringTableEntry <= MaxBase64Offset) {
526      // Starting with 10,000,000, offsets are encoded as base64.
527      encodeBase64StringEntry(S.Header.Name, StringTableEntry);
528    } else {
529      report_fatal_error("COFF string table is greater than 64 GB.");
530    }
531  } else
532    std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
533
534  S.Number = Number;
535  S.Symbol->Data.SectionNumber = S.Number;
536  S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
537}
538
539void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
540  if (S.Name.size() > COFF::NameSize) {
541    size_t StringTableEntry = Strings.insert(S.Name.c_str());
542
543    S.set_name_offset(StringTableEntry);
544  } else
545    std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
546  S.Index = Index;
547}
548
549bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
550                                       MCAssembler &Asm) {
551  // This doesn't seem to be right. Strings referred to from the .data section
552  // need symbols so they can be linked to code in the .text section right?
553
554  // return Asm.isSymbolLinkerVisible(SymbolData.getSymbol());
555
556  // For now, all non-variable symbols are exported,
557  // the linker will sort the rest out for us.
558  return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
559}
560
561bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
562  return (S->Header.Characteristics
563         & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
564}
565
566//------------------------------------------------------------------------------
567// entity writing methods
568
569void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
570  WriteLE16(Header.Machine);
571  WriteLE16(Header.NumberOfSections);
572  WriteLE32(Header.TimeDateStamp);
573  WriteLE32(Header.PointerToSymbolTable);
574  WriteLE32(Header.NumberOfSymbols);
575  WriteLE16(Header.SizeOfOptionalHeader);
576  WriteLE16(Header.Characteristics);
577}
578
579void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
580  WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
581  WriteLE32(S.Data.Value);
582  WriteLE16(S.Data.SectionNumber);
583  WriteLE16(S.Data.Type);
584  Write8(S.Data.StorageClass);
585  Write8(S.Data.NumberOfAuxSymbols);
586  WriteAuxiliarySymbols(S.Aux);
587}
588
589void WinCOFFObjectWriter::WriteAuxiliarySymbols(
590                                        const COFFSymbol::AuxiliarySymbols &S) {
591  for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
592      i != e; ++i) {
593    switch(i->AuxType) {
594    case ATFunctionDefinition:
595      WriteLE32(i->Aux.FunctionDefinition.TagIndex);
596      WriteLE32(i->Aux.FunctionDefinition.TotalSize);
597      WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
598      WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
599      WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
600      break;
601    case ATbfAndefSymbol:
602      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
603      WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
604      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
605      WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
606      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
607      break;
608    case ATWeakExternal:
609      WriteLE32(i->Aux.WeakExternal.TagIndex);
610      WriteLE32(i->Aux.WeakExternal.Characteristics);
611      WriteZeros(sizeof(i->Aux.WeakExternal.unused));
612      break;
613    case ATFile:
614      WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
615                 sizeof(i->Aux.File.FileName)));
616      break;
617    case ATSectionDefinition:
618      WriteLE32(i->Aux.SectionDefinition.Length);
619      WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
620      WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
621      WriteLE32(i->Aux.SectionDefinition.CheckSum);
622      WriteLE16(i->Aux.SectionDefinition.Number);
623      Write8(i->Aux.SectionDefinition.Selection);
624      WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
625      break;
626    }
627  }
628}
629
630void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
631  WriteBytes(StringRef(S.Name, COFF::NameSize));
632
633  WriteLE32(S.VirtualSize);
634  WriteLE32(S.VirtualAddress);
635  WriteLE32(S.SizeOfRawData);
636  WriteLE32(S.PointerToRawData);
637  WriteLE32(S.PointerToRelocations);
638  WriteLE32(S.PointerToLineNumbers);
639  WriteLE16(S.NumberOfRelocations);
640  WriteLE16(S.NumberOfLineNumbers);
641  WriteLE32(S.Characteristics);
642}
643
644void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
645  WriteLE32(R.VirtualAddress);
646  WriteLE32(R.SymbolTableIndex);
647  WriteLE16(R.Type);
648}
649
650////////////////////////////////////////////////////////////////////////////////
651// MCObjectWriter interface implementations
652
653void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
654                                                   const MCAsmLayout &Layout) {
655  // "Define" each section & symbol. This creates section & symbol
656  // entries in the staging area.
657
658  static_assert(sizeof(((COFF::AuxiliaryFile *)nullptr)->FileName) == COFF::SymbolSize,
659                "size mismatch for COFF::AuxiliaryFile::FileName");
660  for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
661       FI != FE; ++FI) {
662    // round up to calculate the number of auxiliary symbols required
663    unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize;
664
665    COFFSymbol *file = createSymbol(".file");
666    file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
667    file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
668    file->Aux.resize(Count);
669
670    unsigned Offset = 0;
671    unsigned Length = FI->size();
672    for (auto & Aux : file->Aux) {
673      Aux.AuxType = ATFile;
674
675      if (Length > COFF::SymbolSize) {
676        memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize);
677        Length = Length - COFF::SymbolSize;
678      } else {
679        memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length);
680        memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length);
681        Length = 0;
682      }
683
684      Offset = Offset + COFF::SymbolSize;
685    }
686  }
687
688  for (const auto & Section : Asm)
689    DefineSection(Section);
690
691  for (MCSymbolData &SD : Asm.symbols())
692    if (ExportSymbol(SD, Asm))
693      DefineSymbol(SD, Asm, Layout);
694}
695
696void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
697                                           const MCAsmLayout &Layout,
698                                           const MCFragment *Fragment,
699                                           const MCFixup &Fixup,
700                                           MCValue Target,
701                                           bool &IsPCRel,
702                                           uint64_t &FixedValue) {
703  assert(Target.getSymA() && "Relocation must reference a symbol!");
704
705  const MCSymbol &Symbol = Target.getSymA()->getSymbol();
706  const MCSymbol &A = Symbol.AliasedSymbol();
707  if (!Asm.hasSymbolData(A))
708    Asm.getContext().FatalError(
709        Fixup.getLoc(),
710        Twine("symbol '") + A.getName() + "' can not be undefined");
711
712  const MCSymbolData &A_SD = Asm.getSymbolData(A);
713
714  MCSectionData const *SectionData = Fragment->getParent();
715
716  // Mark this symbol as requiring an entry in the symbol table.
717  assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
718         "Section must already have been defined in ExecutePostLayoutBinding!");
719  assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
720         "Symbol must already have been defined in ExecutePostLayoutBinding!");
721
722  COFFSection *coff_section = SectionMap[&SectionData->getSection()];
723  COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
724  const MCSymbolRefExpr *SymB = Target.getSymB();
725  bool CrossSection = false;
726
727  if (SymB) {
728    const MCSymbol *B = &SymB->getSymbol();
729    const MCSymbolData &B_SD = Asm.getSymbolData(*B);
730    if (!B_SD.getFragment())
731      Asm.getContext().FatalError(
732          Fixup.getLoc(),
733          Twine("symbol '") + B->getName() +
734              "' can not be undefined in a subtraction expression");
735
736    if (!A_SD.getFragment())
737      Asm.getContext().FatalError(
738          Fixup.getLoc(),
739          Twine("symbol '") + Symbol.getName() +
740              "' can not be undefined in a subtraction expression");
741
742    CrossSection = &Symbol.getSection() != &B->getSection();
743
744    // Offset of the symbol in the section
745    int64_t a = Layout.getSymbolOffset(&B_SD);
746
747    // Ofeset of the relocation in the section
748    int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
749
750    FixedValue = b - a;
751    // In the case where we have SymbA and SymB, we just need to store the delta
752    // between the two symbols.  Update FixedValue to account for the delta, and
753    // skip recording the relocation.
754    if (!CrossSection)
755      return;
756  } else {
757    FixedValue = Target.getConstant();
758  }
759
760  COFFRelocation Reloc;
761
762  Reloc.Data.SymbolTableIndex = 0;
763  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
764
765  // Turn relocations for temporary symbols into section relocations.
766  if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
767    Reloc.Symb = coff_symbol->Section->Symbol;
768    FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
769                + coff_symbol->MCData->getOffset();
770  } else
771    Reloc.Symb = coff_symbol;
772
773  ++Reloc.Symb->Relocations;
774
775  Reloc.Data.VirtualAddress += Fixup.getOffset();
776  Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
777                                                     CrossSection);
778
779  // FIXME: Can anyone explain what this does other than adjust for the size
780  // of the offset?
781  if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
782       Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
783      (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
784       Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
785    FixedValue += 4;
786
787  if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
788    switch (Reloc.Data.Type) {
789    case COFF::IMAGE_REL_ARM_ABSOLUTE:
790    case COFF::IMAGE_REL_ARM_ADDR32:
791    case COFF::IMAGE_REL_ARM_ADDR32NB:
792    case COFF::IMAGE_REL_ARM_TOKEN:
793    case COFF::IMAGE_REL_ARM_SECTION:
794    case COFF::IMAGE_REL_ARM_SECREL:
795      break;
796    case COFF::IMAGE_REL_ARM_BRANCH11:
797    case COFF::IMAGE_REL_ARM_BLX11:
798      // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
799      // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
800      // for Windows CE).
801    case COFF::IMAGE_REL_ARM_BRANCH24:
802    case COFF::IMAGE_REL_ARM_BLX24:
803    case COFF::IMAGE_REL_ARM_MOV32A:
804      // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
805      // only used for ARM mode code, which is documented as being unsupported
806      // by Windows on ARM.  Empirical proof indicates that masm is able to
807      // generate the relocations however the rest of the MSVC toolchain is
808      // unable to handle it.
809      llvm_unreachable("unsupported relocation");
810      break;
811    case COFF::IMAGE_REL_ARM_MOV32T:
812      break;
813    case COFF::IMAGE_REL_ARM_BRANCH20T:
814    case COFF::IMAGE_REL_ARM_BRANCH24T:
815    case COFF::IMAGE_REL_ARM_BLX23T:
816      // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
817      // perform a 4 byte adjustment to the relocation.  Relative branches are
818      // offset by 4 on ARM, however, because there is no RELA relocations, all
819      // branches are offset by 4.
820      FixedValue = FixedValue + 4;
821      break;
822    }
823  }
824
825  if (TargetObjectWriter->recordRelocation(Fixup))
826    coff_section->Relocations.push_back(Reloc);
827}
828
829void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
830                                      const MCAsmLayout &Layout) {
831  // Assign symbol and section indexes and offsets.
832  Header.NumberOfSections = 0;
833
834  DenseMap<COFFSection *, uint16_t> SectionIndices;
835  for (auto & Section : Sections) {
836    size_t Number = ++Header.NumberOfSections;
837    SectionIndices[Section.get()] = Number;
838    MakeSectionReal(*Section, Number);
839  }
840
841  Header.NumberOfSymbols = 0;
842
843  for (auto & Symbol : Symbols) {
844    // Update section number & offset for symbols that have them.
845    if (Symbol->Section)
846      Symbol->Data.SectionNumber = Symbol->Section->Number;
847
848    if (Symbol->should_keep()) {
849      MakeSymbolReal(*Symbol, Header.NumberOfSymbols++);
850
851      // Update auxiliary symbol info.
852      Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
853      Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
854    } else
855      Symbol->Index = -1;
856  }
857
858  // Fixup weak external references.
859  for (auto & Symbol : Symbols) {
860    if (Symbol->Other) {
861      assert(Symbol->Index != -1);
862      assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
863      assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
864             "Symbol's aux symbol must be a Weak External!");
865      Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
866    }
867  }
868
869  // Fixup associative COMDAT sections.
870  for (auto & Section : Sections) {
871    if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
872        COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
873      continue;
874
875    const MCSectionCOFF &MCSec =
876      static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
877
878    const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
879    assert(COMDAT);
880    COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
881    assert(COMDATSymbol);
882    COFFSection *Assoc = COMDATSymbol->Section;
883    if (!Assoc)
884      report_fatal_error(
885          Twine("Missing associated COMDAT section for section ") +
886          MCSec.getSectionName());
887
888    // Skip this section if the associated section is unused.
889    if (Assoc->Number == -1)
890      continue;
891
892    Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
893  }
894
895
896  // Assign file offsets to COFF object file structures.
897
898  unsigned offset = 0;
899
900  offset += COFF::HeaderSize;
901  offset += COFF::SectionSize * Header.NumberOfSections;
902
903  for (const auto & Section : Asm) {
904    COFFSection *Sec = SectionMap[&Section.getSection()];
905
906    if (Sec->Number == -1)
907      continue;
908
909    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
910
911    if (IsPhysicalSection(Sec)) {
912      Sec->Header.PointerToRawData = offset;
913
914      offset += Sec->Header.SizeOfRawData;
915    }
916
917    if (Sec->Relocations.size() > 0) {
918      bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
919
920      if (RelocationsOverflow) {
921        // Signal overflow by setting NumberOfSections to max value. Actual
922        // size is found in reloc #0. Microsoft tools understand this.
923        Sec->Header.NumberOfRelocations = 0xffff;
924      } else {
925        Sec->Header.NumberOfRelocations = Sec->Relocations.size();
926      }
927      Sec->Header.PointerToRelocations = offset;
928
929      if (RelocationsOverflow) {
930        // Reloc #0 will contain actual count, so make room for it.
931        offset += COFF::RelocationSize;
932      }
933
934      offset += COFF::RelocationSize * Sec->Relocations.size();
935
936      for (auto & Relocation : Sec->Relocations) {
937        assert(Relocation.Symb->Index != -1);
938        Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
939      }
940    }
941
942    assert(Sec->Symbol->Aux.size() == 1 &&
943           "Section's symbol must have one aux!");
944    AuxSymbol &Aux = Sec->Symbol->Aux[0];
945    assert(Aux.AuxType == ATSectionDefinition &&
946           "Section's symbol's aux symbol must be a Section Definition!");
947    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
948    Aux.Aux.SectionDefinition.NumberOfRelocations =
949                                                Sec->Header.NumberOfRelocations;
950    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
951                                                Sec->Header.NumberOfLineNumbers;
952  }
953
954  Header.PointerToSymbolTable = offset;
955
956  // We want a deterministic output. It looks like GNU as also writes 0 in here.
957  Header.TimeDateStamp = 0;
958
959  // Write it all to disk...
960  WriteFileHeader(Header);
961
962  {
963    sections::iterator i, ie;
964    MCAssembler::const_iterator j, je;
965
966    for (auto & Section : Sections) {
967      if (Section->Number != -1) {
968        if (Section->Relocations.size() >= 0xffff)
969          Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
970        WriteSectionHeader(Section->Header);
971      }
972    }
973
974    for (i = Sections.begin(), ie = Sections.end(),
975         j = Asm.begin(), je = Asm.end();
976         (i != ie) && (j != je); ++i, ++j) {
977
978      if ((*i)->Number == -1)
979        continue;
980
981      if ((*i)->Header.PointerToRawData != 0) {
982        assert(OS.tell() == (*i)->Header.PointerToRawData &&
983               "Section::PointerToRawData is insane!");
984
985        Asm.writeSectionData(j, Layout);
986      }
987
988      if ((*i)->Relocations.size() > 0) {
989        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
990               "Section::PointerToRelocations is insane!");
991
992        if ((*i)->Relocations.size() >= 0xffff) {
993          // In case of overflow, write actual relocation count as first
994          // relocation. Including the synthetic reloc itself (+ 1).
995          COFF::relocation r;
996          r.VirtualAddress = (*i)->Relocations.size() + 1;
997          r.SymbolTableIndex = 0;
998          r.Type = 0;
999          WriteRelocation(r);
1000        }
1001
1002        for (const auto & Relocation : (*i)->Relocations)
1003          WriteRelocation(Relocation.Data);
1004      } else
1005        assert((*i)->Header.PointerToRelocations == 0 &&
1006               "Section::PointerToRelocations is insane!");
1007    }
1008  }
1009
1010  assert(OS.tell() == Header.PointerToSymbolTable &&
1011         "Header::PointerToSymbolTable is insane!");
1012
1013  for (auto & Symbol : Symbols)
1014    if (Symbol->Index != -1)
1015      WriteSymbol(*Symbol);
1016
1017  OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
1018}
1019
1020MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1021  Machine(Machine_) {
1022}
1023
1024// Pin the vtable to this file.
1025void MCWinCOFFObjectTargetWriter::anchor() {}
1026
1027//------------------------------------------------------------------------------
1028// WinCOFFObjectWriter factory function
1029
1030namespace llvm {
1031  MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1032                                            raw_ostream &OS) {
1033    return new WinCOFFObjectWriter(MOTW, OS);
1034  }
1035}
1036