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#define DEBUG_TYPE "WinCOFFObjectWriter"
15
16#include "llvm/MC/MCObjectWriter.h"
17#include "llvm/MC/MCSection.h"
18#include "llvm/MC/MCContext.h"
19#include "llvm/MC/MCSymbol.h"
20#include "llvm/MC/MCExpr.h"
21#include "llvm/MC/MCValue.h"
22#include "llvm/MC/MCAssembler.h"
23#include "llvm/MC/MCAsmLayout.h"
24#include "llvm/MC/MCSectionCOFF.h"
25#include "llvm/MC/MCWinCOFFObjectWriter.h"
26
27#include "llvm/ADT/DenseMap.h"
28#include "llvm/ADT/OwningPtr.h"
29#include "llvm/ADT/StringMap.h"
30#include "llvm/ADT/StringRef.h"
31
32#include "llvm/Support/COFF.h"
33#include "llvm/Support/Debug.h"
34#include "llvm/Support/ErrorHandling.h"
35
36#include "llvm/Support/TimeValue.h"
37
38#include <cstdio>
39
40using namespace llvm;
41
42namespace {
43typedef llvm::SmallString<COFF::NameSize> name;
44
45enum AuxiliaryType {
46  ATFunctionDefinition,
47  ATbfAndefSymbol,
48  ATWeakExternal,
49  ATFile,
50  ATSectionDefinition
51};
52
53struct AuxSymbol {
54  AuxiliaryType   AuxType;
55  COFF::Auxiliary Aux;
56};
57
58class COFFSymbol;
59class COFFSection;
60
61class COFFSymbol {
62public:
63  COFF::symbol Data;
64
65  typedef llvm::SmallVector<AuxSymbol, 1> AuxiliarySymbols;
66
67  name             Name;
68  int              Index;
69  AuxiliarySymbols Aux;
70  COFFSymbol      *Other;
71  COFFSection     *Section;
72  int              Relocations;
73
74  MCSymbolData const *MCData;
75
76  COFFSymbol(llvm::StringRef name);
77  size_t size() const;
78  void set_name_offset(uint32_t Offset);
79
80  bool should_keep() const;
81};
82
83// This class contains staging data for a COFF relocation entry.
84struct COFFRelocation {
85  COFF::relocation Data;
86  COFFSymbol          *Symb;
87
88  COFFRelocation() : Symb(NULL) {}
89  static size_t size() { return COFF::RelocationSize; }
90};
91
92typedef std::vector<COFFRelocation> relocations;
93
94class COFFSection {
95public:
96  COFF::section Header;
97
98  std::string          Name;
99  int                  Number;
100  MCSectionData const *MCData;
101  COFFSymbol          *Symbol;
102  relocations          Relocations;
103
104  COFFSection(llvm::StringRef name);
105  static size_t size();
106};
107
108// This class holds the COFF string table.
109class StringTable {
110  typedef llvm::StringMap<size_t> map;
111  map Map;
112
113  void update_length();
114public:
115  std::vector<char> Data;
116
117  StringTable();
118  size_t size() const;
119  size_t insert(llvm::StringRef String);
120};
121
122class WinCOFFObjectWriter : public MCObjectWriter {
123public:
124
125  typedef std::vector<COFFSymbol*>  symbols;
126  typedef std::vector<COFFSection*> sections;
127
128  typedef DenseMap<MCSymbol  const *, COFFSymbol *>   symbol_map;
129  typedef DenseMap<MCSection const *, COFFSection *> section_map;
130
131  llvm::OwningPtr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
132
133  // Root level file contents.
134  COFF::header Header;
135  sections     Sections;
136  symbols      Symbols;
137  StringTable  Strings;
138
139  // Maps used during object file creation.
140  section_map SectionMap;
141  symbol_map  SymbolMap;
142
143  WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
144  ~WinCOFFObjectWriter();
145
146  COFFSymbol *createSymbol(StringRef Name);
147  COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
148  COFFSection *createSection(StringRef Name);
149
150  template <typename object_t, typename list_t>
151  object_t *createCOFFEntity(llvm::StringRef Name, list_t &List);
152
153  void DefineSection(MCSectionData const &SectionData);
154  void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler);
155
156  void MakeSymbolReal(COFFSymbol &S, size_t Index);
157  void MakeSectionReal(COFFSection &S, size_t Number);
158
159  bool ExportSection(COFFSection const *S);
160  bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
161
162  bool IsPhysicalSection(COFFSection *S);
163
164  // Entity writing methods.
165
166  void WriteFileHeader(const COFF::header &Header);
167  void WriteSymbol(const COFFSymbol *S);
168  void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
169  void WriteSectionHeader(const COFF::section &S);
170  void WriteRelocation(const COFF::relocation &R);
171
172  // MCObjectWriter interface implementation.
173
174  void ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout);
175
176  void RecordRelocation(const MCAssembler &Asm,
177                        const MCAsmLayout &Layout,
178                        const MCFragment *Fragment,
179                        const MCFixup &Fixup,
180                        MCValue Target,
181                        uint64_t &FixedValue);
182
183  void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
184};
185}
186
187static inline void write_uint32_le(void *Data, uint32_t const &Value) {
188  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
189  Ptr[0] = (Value & 0x000000FF) >>  0;
190  Ptr[1] = (Value & 0x0000FF00) >>  8;
191  Ptr[2] = (Value & 0x00FF0000) >> 16;
192  Ptr[3] = (Value & 0xFF000000) >> 24;
193}
194
195static inline void write_uint16_le(void *Data, uint16_t const &Value) {
196  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
197  Ptr[0] = (Value & 0x00FF) >> 0;
198  Ptr[1] = (Value & 0xFF00) >> 8;
199}
200
201static inline void write_uint8_le(void *Data, uint8_t const &Value) {
202  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
203  Ptr[0] = (Value & 0xFF) >> 0;
204}
205
206//------------------------------------------------------------------------------
207// Symbol class implementation
208
209COFFSymbol::COFFSymbol(llvm::StringRef name)
210  : Name(name.begin(), name.end())
211  , Other(NULL)
212  , Section(NULL)
213  , Relocations(0)
214  , MCData(NULL) {
215  memset(&Data, 0, sizeof(Data));
216}
217
218size_t COFFSymbol::size() const {
219  return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
220}
221
222// In the case that the name does not fit within 8 bytes, the offset
223// into the string table is stored in the last 4 bytes instead, leaving
224// the first 4 bytes as 0.
225void COFFSymbol::set_name_offset(uint32_t Offset) {
226  write_uint32_le(Data.Name + 0, 0);
227  write_uint32_le(Data.Name + 4, Offset);
228}
229
230/// logic to decide if the symbol should be reported in the symbol table
231bool COFFSymbol::should_keep() const {
232  // no section means its external, keep it
233  if (Section == NULL)
234    return true;
235
236  // if it has relocations pointing at it, keep it
237  if (Relocations > 0)   {
238    assert(Section->Number != -1 && "Sections with relocations must be real!");
239    return true;
240  }
241
242  // if the section its in is being droped, drop it
243  if (Section->Number == -1)
244      return false;
245
246  // if it is the section symbol, keep it
247  if (Section->Symbol == this)
248    return true;
249
250  // if its temporary, drop it
251  if (MCData && MCData->getSymbol().isTemporary())
252      return false;
253
254  // otherwise, keep it
255  return true;
256}
257
258//------------------------------------------------------------------------------
259// Section class implementation
260
261COFFSection::COFFSection(llvm::StringRef name)
262  : Name(name)
263  , MCData(NULL)
264  , Symbol(NULL) {
265  memset(&Header, 0, sizeof(Header));
266}
267
268size_t COFFSection::size() {
269  return COFF::SectionSize;
270}
271
272//------------------------------------------------------------------------------
273// StringTable class implementation
274
275/// Write the length of the string table into Data.
276/// The length of the string table includes uint32 length header.
277void StringTable::update_length() {
278  write_uint32_le(&Data.front(), Data.size());
279}
280
281StringTable::StringTable() {
282  // The string table data begins with the length of the entire string table
283  // including the length header. Allocate space for this header.
284  Data.resize(4);
285  update_length();
286}
287
288size_t StringTable::size() const {
289  return Data.size();
290}
291
292/// Add String to the table iff it is not already there.
293/// @returns the index into the string table where the string is now located.
294size_t StringTable::insert(llvm::StringRef String) {
295  map::iterator i = Map.find(String);
296
297  if (i != Map.end())
298    return i->second;
299
300  size_t Offset = Data.size();
301
302  // Insert string data into string table.
303  Data.insert(Data.end(), String.begin(), String.end());
304  Data.push_back('\0');
305
306  // Put a reference to it in the map.
307  Map[String] = Offset;
308
309  // Update the internal length field.
310  update_length();
311
312  return Offset;
313}
314
315//------------------------------------------------------------------------------
316// WinCOFFObjectWriter class implementation
317
318WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
319                                         raw_ostream &OS)
320  : MCObjectWriter(OS, true)
321  , TargetObjectWriter(MOTW) {
322  memset(&Header, 0, sizeof(Header));
323
324  Header.Machine = TargetObjectWriter->getMachine();
325}
326
327WinCOFFObjectWriter::~WinCOFFObjectWriter() {
328  for (symbols::iterator I = Symbols.begin(), E = Symbols.end(); I != E; ++I)
329    delete *I;
330  for (sections::iterator I = Sections.begin(), E = Sections.end(); I != E; ++I)
331    delete *I;
332}
333
334COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
335  return createCOFFEntity<COFFSymbol>(Name, Symbols);
336}
337
338COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
339  symbol_map::iterator i = SymbolMap.find(Symbol);
340  if (i != SymbolMap.end())
341    return i->second;
342  COFFSymbol *RetSymbol
343    = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
344  SymbolMap[Symbol] = RetSymbol;
345  return RetSymbol;
346}
347
348COFFSection *WinCOFFObjectWriter::createSection(llvm::StringRef Name) {
349  return createCOFFEntity<COFFSection>(Name, Sections);
350}
351
352/// A template used to lookup or create a symbol/section, and initialize it if
353/// needed.
354template <typename object_t, typename list_t>
355object_t *WinCOFFObjectWriter::createCOFFEntity(llvm::StringRef Name,
356                                                list_t &List) {
357  object_t *Object = new object_t(Name);
358
359  List.push_back(Object);
360
361  return Object;
362}
363
364/// This function takes a section data object from the assembler
365/// and creates the associated COFF section staging object.
366void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
367  assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
368    && "Got non COFF section in the COFF backend!");
369  // FIXME: Not sure how to verify this (at least in a debug build).
370  MCSectionCOFF const &Sec =
371    static_cast<MCSectionCOFF const &>(SectionData.getSection());
372
373  COFFSection *coff_section = createSection(Sec.getSectionName());
374  COFFSymbol  *coff_symbol = createSymbol(Sec.getSectionName());
375
376  coff_section->Symbol = coff_symbol;
377  coff_symbol->Section = coff_section;
378  coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
379
380  // In this case the auxiliary symbol is a Section Definition.
381  coff_symbol->Aux.resize(1);
382  memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
383  coff_symbol->Aux[0].AuxType = ATSectionDefinition;
384  coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
385
386  coff_section->Header.Characteristics = Sec.getCharacteristics();
387
388  uint32_t &Characteristics = coff_section->Header.Characteristics;
389  switch (SectionData.getAlignment()) {
390  case 1:    Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;    break;
391  case 2:    Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;    break;
392  case 4:    Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;    break;
393  case 8:    Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;    break;
394  case 16:   Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;   break;
395  case 32:   Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;   break;
396  case 64:   Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;   break;
397  case 128:  Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;  break;
398  case 256:  Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;  break;
399  case 512:  Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;  break;
400  case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
401  case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
402  case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
403  case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
404  default:
405    llvm_unreachable("unsupported section alignment");
406  }
407
408  // Bind internal COFF section to MC section.
409  coff_section->MCData = &SectionData;
410  SectionMap[&SectionData.getSection()] = coff_section;
411}
412
413/// This function takes a section data object from the assembler
414/// and creates the associated COFF symbol staging object.
415void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
416                                       MCAssembler &Assembler) {
417  COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&SymbolData.getSymbol());
418
419  coff_symbol->Data.Type         = (SymbolData.getFlags() & 0x0000FFFF) >>  0;
420  coff_symbol->Data.StorageClass = (SymbolData.getFlags() & 0x00FF0000) >> 16;
421
422  if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
423    coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
424
425    if (SymbolData.getSymbol().isVariable()) {
426      coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
427      const MCExpr *Value = SymbolData.getSymbol().getVariableValue();
428
429      // FIXME: This assert message isn't very good.
430      assert(Value->getKind() == MCExpr::SymbolRef &&
431              "Value must be a SymbolRef!");
432
433      const MCSymbolRefExpr *SymbolRef =
434        static_cast<const MCSymbolRefExpr *>(Value);
435      coff_symbol->Other = GetOrCreateCOFFSymbol(&SymbolRef->getSymbol());
436    } else {
437      std::string WeakName = std::string(".weak.")
438                           +  SymbolData.getSymbol().getName().str()
439                           + ".default";
440      COFFSymbol *WeakDefault = createSymbol(WeakName);
441      WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
442      WeakDefault->Data.StorageClass  = COFF::IMAGE_SYM_CLASS_EXTERNAL;
443      WeakDefault->Data.Type          = 0;
444      WeakDefault->Data.Value         = 0;
445      coff_symbol->Other = WeakDefault;
446    }
447
448    // Setup the Weak External auxiliary symbol.
449    coff_symbol->Aux.resize(1);
450    memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
451    coff_symbol->Aux[0].AuxType = ATWeakExternal;
452    coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
453    coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
454      COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
455  }
456
457  // If no storage class was specified in the streamer, define it here.
458  if (coff_symbol->Data.StorageClass == 0) {
459    bool external = SymbolData.isExternal() || (SymbolData.Fragment == NULL);
460
461    coff_symbol->Data.StorageClass =
462      external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
463  }
464
465  if (SymbolData.Fragment != NULL)
466    coff_symbol->Section =
467      SectionMap[&SymbolData.Fragment->getParent()->getSection()];
468
469  // Bind internal COFF symbol to MC symbol.
470  coff_symbol->MCData = &SymbolData;
471  SymbolMap[&SymbolData.getSymbol()] = coff_symbol;
472}
473
474/// making a section real involves assigned it a number and putting
475/// name into the string table if needed
476void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
477  if (S.Name.size() > COFF::NameSize) {
478    size_t StringTableEntry = Strings.insert(S.Name.c_str());
479
480    // FIXME: Why is this number 999999? This number is never mentioned in the
481    // spec. I'm assuming this is due to the printed value needing to fit into
482    // the S.Header.Name field. In which case why not 9999999 (7 9's instead of
483    // 6)? The spec does not state if this entry should be null terminated in
484    // this case, and thus this seems to be the best way to do it. I think I
485    // just solved my own FIXME...
486    if (StringTableEntry > 999999)
487      report_fatal_error("COFF string table is greater than 999999 bytes.");
488
489    std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
490  } else
491    std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
492
493  S.Number = Number;
494  S.Symbol->Data.SectionNumber = S.Number;
495  S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
496}
497
498void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
499  if (S.Name.size() > COFF::NameSize) {
500    size_t StringTableEntry = Strings.insert(S.Name.c_str());
501
502    S.set_name_offset(StringTableEntry);
503  } else
504    std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
505  S.Index = Index;
506}
507
508bool WinCOFFObjectWriter::ExportSection(COFFSection const *S) {
509  return !S->MCData->getFragmentList().empty();
510}
511
512bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
513                                       MCAssembler &Asm) {
514  // This doesn't seem to be right. Strings referred to from the .data section
515  // need symbols so they can be linked to code in the .text section right?
516
517  // return Asm.isSymbolLinkerVisible (&SymbolData);
518
519  // For now, all non-variable symbols are exported,
520  // the linker will sort the rest out for us.
521  return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
522}
523
524bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
525  return (S->Header.Characteristics
526         & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
527}
528
529//------------------------------------------------------------------------------
530// entity writing methods
531
532void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
533  WriteLE16(Header.Machine);
534  WriteLE16(Header.NumberOfSections);
535  WriteLE32(Header.TimeDateStamp);
536  WriteLE32(Header.PointerToSymbolTable);
537  WriteLE32(Header.NumberOfSymbols);
538  WriteLE16(Header.SizeOfOptionalHeader);
539  WriteLE16(Header.Characteristics);
540}
541
542void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol *S) {
543  WriteBytes(StringRef(S->Data.Name, COFF::NameSize));
544  WriteLE32(S->Data.Value);
545  WriteLE16(S->Data.SectionNumber);
546  WriteLE16(S->Data.Type);
547  Write8(S->Data.StorageClass);
548  Write8(S->Data.NumberOfAuxSymbols);
549  WriteAuxiliarySymbols(S->Aux);
550}
551
552void WinCOFFObjectWriter::WriteAuxiliarySymbols(
553                                        const COFFSymbol::AuxiliarySymbols &S) {
554  for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
555      i != e; ++i) {
556    switch(i->AuxType) {
557    case ATFunctionDefinition:
558      WriteLE32(i->Aux.FunctionDefinition.TagIndex);
559      WriteLE32(i->Aux.FunctionDefinition.TotalSize);
560      WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
561      WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
562      WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
563      break;
564    case ATbfAndefSymbol:
565      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
566      WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
567      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
568      WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
569      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
570      break;
571    case ATWeakExternal:
572      WriteLE32(i->Aux.WeakExternal.TagIndex);
573      WriteLE32(i->Aux.WeakExternal.Characteristics);
574      WriteZeros(sizeof(i->Aux.WeakExternal.unused));
575      break;
576    case ATFile:
577      WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
578                 sizeof(i->Aux.File.FileName)));
579      break;
580    case ATSectionDefinition:
581      WriteLE32(i->Aux.SectionDefinition.Length);
582      WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
583      WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
584      WriteLE32(i->Aux.SectionDefinition.CheckSum);
585      WriteLE16(i->Aux.SectionDefinition.Number);
586      Write8(i->Aux.SectionDefinition.Selection);
587      WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
588      break;
589    }
590  }
591}
592
593void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
594  WriteBytes(StringRef(S.Name, COFF::NameSize));
595
596  WriteLE32(S.VirtualSize);
597  WriteLE32(S.VirtualAddress);
598  WriteLE32(S.SizeOfRawData);
599  WriteLE32(S.PointerToRawData);
600  WriteLE32(S.PointerToRelocations);
601  WriteLE32(S.PointerToLineNumbers);
602  WriteLE16(S.NumberOfRelocations);
603  WriteLE16(S.NumberOfLineNumbers);
604  WriteLE32(S.Characteristics);
605}
606
607void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
608  WriteLE32(R.VirtualAddress);
609  WriteLE32(R.SymbolTableIndex);
610  WriteLE16(R.Type);
611}
612
613////////////////////////////////////////////////////////////////////////////////
614// MCObjectWriter interface implementations
615
616void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
617                                                   const MCAsmLayout &Layout) {
618  // "Define" each section & symbol. This creates section & symbol
619  // entries in the staging area.
620
621  for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; i++)
622    DefineSection(*i);
623
624  for (MCAssembler::const_symbol_iterator i = Asm.symbol_begin(),
625                                          e = Asm.symbol_end(); i != e; i++) {
626    if (ExportSymbol(*i, Asm))
627      DefineSymbol(*i, Asm);
628  }
629}
630
631void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
632                                           const MCAsmLayout &Layout,
633                                           const MCFragment *Fragment,
634                                           const MCFixup &Fixup,
635                                           MCValue Target,
636                                           uint64_t &FixedValue) {
637  assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");
638
639  const MCSymbol *A = &Target.getSymA()->getSymbol();
640  MCSymbolData &A_SD = Asm.getSymbolData(*A);
641
642  MCSectionData const *SectionData = Fragment->getParent();
643
644  // Mark this symbol as requiring an entry in the symbol table.
645  assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
646         "Section must already have been defined in ExecutePostLayoutBinding!");
647  assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
648         "Symbol must already have been defined in ExecutePostLayoutBinding!");
649
650  COFFSection *coff_section = SectionMap[&SectionData->getSection()];
651  COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
652  const MCSymbolRefExpr *SymA = Target.getSymA();
653  const MCSymbolRefExpr *SymB = Target.getSymB();
654  const bool CrossSection = SymB &&
655    &SymA->getSymbol().getSection() != &SymB->getSymbol().getSection();
656
657  if (Target.getSymB()) {
658    const MCSymbol *B = &Target.getSymB()->getSymbol();
659    MCSymbolData &B_SD = Asm.getSymbolData(*B);
660
661    // Offset of the symbol in the section
662    int64_t a = Layout.getSymbolOffset(&B_SD);
663
664    // Ofeset of the relocation in the section
665    int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
666
667    FixedValue = b - a;
668    // In the case where we have SymbA and SymB, we just need to store the delta
669    // between the two symbols.  Update FixedValue to account for the delta, and
670    // skip recording the relocation.
671    if (!CrossSection)
672      return;
673  } else {
674    FixedValue = Target.getConstant();
675  }
676
677  COFFRelocation Reloc;
678
679  Reloc.Data.SymbolTableIndex = 0;
680  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
681
682  // Turn relocations for temporary symbols into section relocations.
683  if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
684    Reloc.Symb = coff_symbol->Section->Symbol;
685    FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
686                + coff_symbol->MCData->getOffset();
687  } else
688    Reloc.Symb = coff_symbol;
689
690  ++Reloc.Symb->Relocations;
691
692  Reloc.Data.VirtualAddress += Fixup.getOffset();
693
694  unsigned FixupKind = Fixup.getKind();
695
696  if (CrossSection)
697    FixupKind = FK_PCRel_4;
698
699  Reloc.Data.Type = TargetObjectWriter->getRelocType(FixupKind);
700
701  // FIXME: Can anyone explain what this does other than adjust for the size
702  // of the offset?
703  if (Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32 ||
704      Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)
705    FixedValue += 4;
706
707  coff_section->Relocations.push_back(Reloc);
708}
709
710void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
711                                      const MCAsmLayout &Layout) {
712  // Assign symbol and section indexes and offsets.
713  Header.NumberOfSections = 0;
714
715  for (sections::iterator i = Sections.begin(),
716                          e = Sections.end(); i != e; i++) {
717    if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
718      MakeSectionReal(**i, ++Header.NumberOfSections);
719    } else {
720      (*i)->Number = -1;
721    }
722  }
723
724  Header.NumberOfSymbols = 0;
725
726  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
727    COFFSymbol *coff_symbol = *i;
728    MCSymbolData const *SymbolData = coff_symbol->MCData;
729
730    // Update section number & offset for symbols that have them.
731    if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
732      assert(coff_symbol->Section != NULL);
733
734      coff_symbol->Data.SectionNumber = coff_symbol->Section->Number;
735      coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
736                              + SymbolData->Offset;
737    }
738
739    if (coff_symbol->should_keep()) {
740      MakeSymbolReal(*coff_symbol, Header.NumberOfSymbols++);
741
742      // Update auxiliary symbol info.
743      coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
744      Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
745    } else
746      coff_symbol->Index = -1;
747  }
748
749  // Fixup weak external references.
750  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
751    COFFSymbol *coff_symbol = *i;
752    if (coff_symbol->Other != NULL) {
753      assert(coff_symbol->Index != -1);
754      assert(coff_symbol->Aux.size() == 1 &&
755             "Symbol must contain one aux symbol!");
756      assert(coff_symbol->Aux[0].AuxType == ATWeakExternal &&
757             "Symbol's aux symbol must be a Weak External!");
758      coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = coff_symbol->Other->Index;
759    }
760  }
761
762  // Assign file offsets to COFF object file structures.
763
764  unsigned offset = 0;
765
766  offset += COFF::HeaderSize;
767  offset += COFF::SectionSize * Header.NumberOfSections;
768
769  for (MCAssembler::const_iterator i = Asm.begin(),
770                                   e = Asm.end();
771                                   i != e; i++) {
772    COFFSection *Sec = SectionMap[&i->getSection()];
773
774    if (Sec->Number == -1)
775      continue;
776
777    Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);
778
779    if (IsPhysicalSection(Sec)) {
780      Sec->Header.PointerToRawData = offset;
781
782      offset += Sec->Header.SizeOfRawData;
783    }
784
785    if (Sec->Relocations.size() > 0) {
786      bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
787
788      if (RelocationsOverflow) {
789        // Signal overflow by setting NumberOfSections to max value. Actual
790        // size is found in reloc #0. Microsoft tools understand this.
791        Sec->Header.NumberOfRelocations = 0xffff;
792      } else {
793        Sec->Header.NumberOfRelocations = Sec->Relocations.size();
794      }
795      Sec->Header.PointerToRelocations = offset;
796
797      if (RelocationsOverflow) {
798        // Reloc #0 will contain actual count, so make room for it.
799        offset += COFF::RelocationSize;
800      }
801
802      offset += COFF::RelocationSize * Sec->Relocations.size();
803
804      for (relocations::iterator cr = Sec->Relocations.begin(),
805                                 er = Sec->Relocations.end();
806                                 cr != er; ++cr) {
807        assert((*cr).Symb->Index != -1);
808        (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
809      }
810    }
811
812    assert(Sec->Symbol->Aux.size() == 1
813      && "Section's symbol must have one aux!");
814    AuxSymbol &Aux = Sec->Symbol->Aux[0];
815    assert(Aux.AuxType == ATSectionDefinition &&
816           "Section's symbol's aux symbol must be a Section Definition!");
817    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
818    Aux.Aux.SectionDefinition.NumberOfRelocations =
819                                                Sec->Header.NumberOfRelocations;
820    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
821                                                Sec->Header.NumberOfLineNumbers;
822  }
823
824  Header.PointerToSymbolTable = offset;
825
826  Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();
827
828  // Write it all to disk...
829  WriteFileHeader(Header);
830
831  {
832    sections::iterator i, ie;
833    MCAssembler::const_iterator j, je;
834
835    for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
836      if ((*i)->Number != -1) {
837        if ((*i)->Relocations.size() >= 0xffff) {
838          (*i)->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
839        }
840        WriteSectionHeader((*i)->Header);
841      }
842
843    for (i = Sections.begin(), ie = Sections.end(),
844         j = Asm.begin(), je = Asm.end();
845         (i != ie) && (j != je); ++i, ++j) {
846
847      if ((*i)->Number == -1)
848        continue;
849
850      if ((*i)->Header.PointerToRawData != 0) {
851        assert(OS.tell() == (*i)->Header.PointerToRawData &&
852               "Section::PointerToRawData is insane!");
853
854        Asm.writeSectionData(j, Layout);
855      }
856
857      if ((*i)->Relocations.size() > 0) {
858        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
859               "Section::PointerToRelocations is insane!");
860
861        if ((*i)->Relocations.size() >= 0xffff) {
862          // In case of overflow, write actual relocation count as first
863          // relocation. Including the synthetic reloc itself (+ 1).
864          COFF::relocation r;
865          r.VirtualAddress = (*i)->Relocations.size() + 1;
866          r.SymbolTableIndex = 0;
867          r.Type = 0;
868          WriteRelocation(r);
869        }
870
871        for (relocations::const_iterator k = (*i)->Relocations.begin(),
872                                               ke = (*i)->Relocations.end();
873                                               k != ke; k++) {
874          WriteRelocation(k->Data);
875        }
876      } else
877        assert((*i)->Header.PointerToRelocations == 0 &&
878               "Section::PointerToRelocations is insane!");
879    }
880  }
881
882  assert(OS.tell() == Header.PointerToSymbolTable &&
883         "Header::PointerToSymbolTable is insane!");
884
885  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
886    if ((*i)->Index != -1)
887      WriteSymbol(*i);
888
889  OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
890}
891
892MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
893  Machine(Machine_) {
894}
895
896//------------------------------------------------------------------------------
897// WinCOFFObjectWriter factory function
898
899namespace llvm {
900  MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
901                                            raw_ostream &OS) {
902    return new WinCOFFObjectWriter(MOTW, OS);
903  }
904}
905