1 //===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains an implementation of a Win32 COFF object file writer.
12 //===----------------------------------------------------------------------===//
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"
37 #define DEBUG_TYPE "WinCOFFObjectWriter"
40 typedef SmallString<COFF::NameSize> name;
51 AuxiliaryType AuxType;
62 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
71 MCSymbolData const *MCData;
73 COFFSymbol(StringRef name);
74 void set_name_offset(uint32_t Offset);
76 bool should_keep() const;
79 // This class contains staging data for a COFF relocation entry.
80 struct COFFRelocation {
81 COFF::relocation Data;
84 COFFRelocation() : Symb(nullptr) {}
85 static size_t size() { return COFF::RelocationSize; }
88 typedef std::vector<COFFRelocation> relocations;
96 MCSectionData const *MCData;
98 relocations Relocations;
100 COFFSection(StringRef name);
101 static size_t size();
104 // This class holds the COFF string table.
106 typedef StringMap<size_t> map;
109 void update_length();
111 std::vector<char> Data;
115 size_t insert(StringRef String);
118 class WinCOFFObjectWriter : public MCObjectWriter {
121 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
122 typedef std::vector<std::unique_ptr<COFFSection>> sections;
124 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
125 typedef DenseMap<MCSection const *, COFFSection *> section_map;
127 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
129 // Root level file contents.
135 // Maps used during object file creation.
136 section_map SectionMap;
137 symbol_map SymbolMap;
141 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
143 COFFSymbol *createSymbol(StringRef Name);
144 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
145 COFFSection *createSection(StringRef Name);
147 template <typename object_t, typename list_t>
148 object_t *createCOFFEntity(StringRef Name, list_t &List);
150 void DefineSection(MCSectionData const &SectionData);
151 void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
152 const MCAsmLayout &Layout);
154 void MakeSymbolReal(COFFSymbol &S, size_t Index);
155 void MakeSectionReal(COFFSection &S, size_t Number);
157 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm);
159 bool IsPhysicalSection(COFFSection *S);
161 // Entity writing methods.
163 void WriteFileHeader(const COFF::header &Header);
164 void WriteSymbol(const COFFSymbol &S);
165 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
166 void WriteSectionHeader(const COFF::section &S);
167 void WriteRelocation(const COFF::relocation &R);
169 // MCObjectWriter interface implementation.
171 void ExecutePostLayoutBinding(MCAssembler &Asm,
172 const MCAsmLayout &Layout) override;
174 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
175 const MCFragment *Fragment, const MCFixup &Fixup,
176 MCValue Target, bool &IsPCRel,
177 uint64_t &FixedValue) override;
179 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
183 static inline void write_uint32_le(void *Data, uint32_t const &Value) {
184 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
185 Ptr[0] = (Value & 0x000000FF) >> 0;
186 Ptr[1] = (Value & 0x0000FF00) >> 8;
187 Ptr[2] = (Value & 0x00FF0000) >> 16;
188 Ptr[3] = (Value & 0xFF000000) >> 24;
191 //------------------------------------------------------------------------------
192 // Symbol class implementation
194 COFFSymbol::COFFSymbol(StringRef name)
195 : Name(name.begin(), name.end())
200 memset(&Data, 0, sizeof(Data));
203 // In the case that the name does not fit within 8 bytes, the offset
204 // into the string table is stored in the last 4 bytes instead, leaving
205 // the first 4 bytes as 0.
206 void COFFSymbol::set_name_offset(uint32_t Offset) {
207 write_uint32_le(Data.Name + 0, 0);
208 write_uint32_le(Data.Name + 4, Offset);
211 /// logic to decide if the symbol should be reported in the symbol table
212 bool COFFSymbol::should_keep() const {
213 // no section means its external, keep it
217 // if it has relocations pointing at it, keep it
218 if (Relocations > 0) {
219 assert(Section->Number != -1 && "Sections with relocations must be real!");
223 // if the section its in is being droped, drop it
224 if (Section->Number == -1)
227 // if it is the section symbol, keep it
228 if (Section->Symbol == this)
231 // if its temporary, drop it
232 if (MCData && MCData->getSymbol().isTemporary())
235 // otherwise, keep it
239 //------------------------------------------------------------------------------
240 // Section class implementation
242 COFFSection::COFFSection(StringRef name)
246 memset(&Header, 0, sizeof(Header));
249 size_t COFFSection::size() {
250 return COFF::SectionSize;
253 //------------------------------------------------------------------------------
254 // StringTable class implementation
256 /// Write the length of the string table into Data.
257 /// The length of the string table includes uint32 length header.
258 void StringTable::update_length() {
259 write_uint32_le(&Data.front(), Data.size());
262 StringTable::StringTable() {
263 // The string table data begins with the length of the entire string table
264 // including the length header. Allocate space for this header.
269 size_t StringTable::size() const {
273 /// Add String to the table iff it is not already there.
274 /// @returns the index into the string table where the string is now located.
275 size_t StringTable::insert(StringRef String) {
276 map::iterator i = Map.find(String);
281 size_t Offset = Data.size();
283 // Insert string data into string table.
284 Data.insert(Data.end(), String.begin(), String.end());
285 Data.push_back('\0');
287 // Put a reference to it in the map.
288 Map[String] = Offset;
290 // Update the internal length field.
296 //------------------------------------------------------------------------------
297 // WinCOFFObjectWriter class implementation
299 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
301 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
302 memset(&Header, 0, sizeof(Header));
304 Header.Machine = TargetObjectWriter->getMachine();
307 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
308 return createCOFFEntity<COFFSymbol>(Name, Symbols);
311 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
312 symbol_map::iterator i = SymbolMap.find(Symbol);
313 if (i != SymbolMap.end())
315 COFFSymbol *RetSymbol
316 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
317 SymbolMap[Symbol] = RetSymbol;
321 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
322 return createCOFFEntity<COFFSection>(Name, Sections);
325 /// A template used to lookup or create a symbol/section, and initialize it if
327 template <typename object_t, typename list_t>
328 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
330 List.push_back(make_unique<object_t>(Name));
332 return List.back().get();
335 /// This function takes a section data object from the assembler
336 /// and creates the associated COFF section staging object.
337 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
338 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
339 && "Got non-COFF section in the COFF backend!");
340 // FIXME: Not sure how to verify this (at least in a debug build).
341 MCSectionCOFF const &Sec =
342 static_cast<MCSectionCOFF const &>(SectionData.getSection());
344 COFFSection *coff_section = createSection(Sec.getSectionName());
345 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
346 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
347 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
348 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
349 if (COMDATSymbol->Section)
350 report_fatal_error("two sections have the same comdat");
351 COMDATSymbol->Section = coff_section;
355 coff_section->Symbol = coff_symbol;
356 coff_symbol->Section = coff_section;
357 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
359 // In this case the auxiliary symbol is a Section Definition.
360 coff_symbol->Aux.resize(1);
361 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
362 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
363 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
365 coff_section->Header.Characteristics = Sec.getCharacteristics();
367 uint32_t &Characteristics = coff_section->Header.Characteristics;
368 switch (SectionData.getAlignment()) {
369 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
370 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
371 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
372 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
373 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
374 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
375 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
376 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
377 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
378 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
379 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
380 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
381 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
382 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
384 llvm_unreachable("unsupported section alignment");
387 // Bind internal COFF section to MC section.
388 coff_section->MCData = &SectionData;
389 SectionMap[&SectionData.getSection()] = coff_section;
392 static uint64_t getSymbolValue(const MCSymbolData &Data,
393 const MCAsmLayout &Layout) {
394 if (Data.isCommon() && Data.isExternal())
395 return Data.getCommonSize();
398 if (!Layout.getSymbolOffset(&Data, Res))
404 /// This function takes a symbol data object from the assembler
405 /// and creates the associated COFF symbol staging object.
406 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
407 MCAssembler &Assembler,
408 const MCAsmLayout &Layout) {
409 MCSymbol const &Symbol = SymbolData.getSymbol();
410 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
411 SymbolMap[&Symbol] = coff_symbol;
413 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
414 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
416 if (Symbol.isVariable()) {
417 const MCSymbolRefExpr *SymRef =
418 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
421 report_fatal_error("Weak externals may only alias symbols");
423 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
425 std::string WeakName = std::string(".weak.")
426 + Symbol.getName().str()
428 COFFSymbol *WeakDefault = createSymbol(WeakName);
429 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
430 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
431 WeakDefault->Data.Type = 0;
432 WeakDefault->Data.Value = 0;
433 coff_symbol->Other = WeakDefault;
436 // Setup the Weak External auxiliary symbol.
437 coff_symbol->Aux.resize(1);
438 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
439 coff_symbol->Aux[0].AuxType = ATWeakExternal;
440 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
441 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
442 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
444 coff_symbol->MCData = &SymbolData;
446 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
447 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
448 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
450 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
451 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
453 // If no storage class was specified in the streamer, define it here.
454 if (coff_symbol->Data.StorageClass == 0) {
456 ResSymData.isExternal() ||
457 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable());
459 coff_symbol->Data.StorageClass = IsExternal
460 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
461 : COFF::IMAGE_SYM_CLASS_STATIC;
465 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
467 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
468 if (BaseData.Fragment) {
470 SectionMap[&BaseData.Fragment->getParent()->getSection()];
472 if (coff_symbol->Section && coff_symbol->Section != Sec)
473 report_fatal_error("conflicting sections for symbol");
475 coff_symbol->Section = Sec;
479 coff_symbol->MCData = &ResSymData;
483 // Maximum offsets for different string table entry encodings.
484 static const unsigned Max6DecimalOffset = 999999;
485 static const unsigned Max7DecimalOffset = 9999999;
486 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
488 // Encode a string table entry offset in base 64, padded to 6 chars, and
489 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
490 // Buffer must be at least 8 bytes large. No terminating null appended.
491 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
492 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
493 "Illegal section name encoding for value");
495 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
496 "abcdefghijklmnopqrstuvwxyz"
502 char* Ptr = Buffer + 7;
503 for (unsigned i = 0; i < 6; ++i) {
504 unsigned Rem = Value % 64;
506 *(Ptr--) = Alphabet[Rem];
510 /// making a section real involves assigned it a number and putting
511 /// name into the string table if needed
512 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
513 if (S.Name.size() > COFF::NameSize) {
514 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
516 if (StringTableEntry <= Max6DecimalOffset) {
517 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
518 } else if (StringTableEntry <= Max7DecimalOffset) {
519 // With seven digits, we have to skip the terminating null. Because
520 // sprintf always appends it, we use a larger temporary buffer.
521 char buffer[9] = { };
522 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
523 std::memcpy(S.Header.Name, buffer, 8);
524 } else if (StringTableEntry <= MaxBase64Offset) {
525 // Starting with 10,000,000, offsets are encoded as base64.
526 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
528 report_fatal_error("COFF string table is greater than 64 GB.");
531 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
534 S.Symbol->Data.SectionNumber = S.Number;
535 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
538 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
539 if (S.Name.size() > COFF::NameSize) {
540 size_t StringTableEntry = Strings.insert(S.Name.c_str());
542 S.set_name_offset(StringTableEntry);
544 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
548 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
550 // This doesn't seem to be right. Strings referred to from the .data section
551 // need symbols so they can be linked to code in the .text section right?
553 // return Asm.isSymbolLinkerVisible(Symbol);
555 // Non-temporary labels should always be visible to the linker.
556 if (!Symbol.isTemporary())
559 // Absolute temporary labels are never visible.
560 if (!Symbol.isInSection())
563 // For now, all non-variable symbols are exported,
564 // the linker will sort the rest out for us.
565 return !Symbol.isVariable();
568 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
569 return (S->Header.Characteristics
570 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
573 //------------------------------------------------------------------------------
574 // entity writing methods
576 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
578 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
580 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion);
581 WriteLE16(Header.Machine);
582 WriteLE32(Header.TimeDateStamp);
583 for (uint8_t MagicChar : COFF::BigObjMagic)
589 WriteLE32(Header.NumberOfSections);
590 WriteLE32(Header.PointerToSymbolTable);
591 WriteLE32(Header.NumberOfSymbols);
593 WriteLE16(Header.Machine);
594 WriteLE16(static_cast<int16_t>(Header.NumberOfSections));
595 WriteLE32(Header.TimeDateStamp);
596 WriteLE32(Header.PointerToSymbolTable);
597 WriteLE32(Header.NumberOfSymbols);
598 WriteLE16(Header.SizeOfOptionalHeader);
599 WriteLE16(Header.Characteristics);
603 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
604 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
605 WriteLE32(S.Data.Value);
607 WriteLE32(S.Data.SectionNumber);
609 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber));
610 WriteLE16(S.Data.Type);
611 Write8(S.Data.StorageClass);
612 Write8(S.Data.NumberOfAuxSymbols);
613 WriteAuxiliarySymbols(S.Aux);
616 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
617 const COFFSymbol::AuxiliarySymbols &S) {
618 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
621 case ATFunctionDefinition:
622 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
623 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
624 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
625 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
626 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
628 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
630 case ATbfAndefSymbol:
631 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
632 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
633 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
634 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
635 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
637 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
640 WriteLE32(i->Aux.WeakExternal.TagIndex);
641 WriteLE32(i->Aux.WeakExternal.Characteristics);
642 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
644 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
648 StringRef(reinterpret_cast<const char *>(&i->Aux),
649 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
651 case ATSectionDefinition:
652 WriteLE32(i->Aux.SectionDefinition.Length);
653 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
654 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
655 WriteLE32(i->Aux.SectionDefinition.CheckSum);
656 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
657 Write8(i->Aux.SectionDefinition.Selection);
658 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
659 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
661 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
667 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
668 WriteBytes(StringRef(S.Name, COFF::NameSize));
670 WriteLE32(S.VirtualSize);
671 WriteLE32(S.VirtualAddress);
672 WriteLE32(S.SizeOfRawData);
673 WriteLE32(S.PointerToRawData);
674 WriteLE32(S.PointerToRelocations);
675 WriteLE32(S.PointerToLineNumbers);
676 WriteLE16(S.NumberOfRelocations);
677 WriteLE16(S.NumberOfLineNumbers);
678 WriteLE32(S.Characteristics);
681 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
682 WriteLE32(R.VirtualAddress);
683 WriteLE32(R.SymbolTableIndex);
687 ////////////////////////////////////////////////////////////////////////////////
688 // MCObjectWriter interface implementations
690 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
691 const MCAsmLayout &Layout) {
692 // "Define" each section & symbol. This creates section & symbol
693 // entries in the staging area.
694 for (const auto & Section : Asm)
695 DefineSection(Section);
697 for (MCSymbolData &SD : Asm.symbols())
698 if (ExportSymbol(SD.getSymbol(), Asm))
699 DefineSymbol(SD, Asm, Layout);
702 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
703 const MCAsmLayout &Layout,
704 const MCFragment *Fragment,
705 const MCFixup &Fixup,
708 uint64_t &FixedValue) {
709 assert(Target.getSymA() && "Relocation must reference a symbol!");
711 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
712 const MCSymbol &A = Symbol.AliasedSymbol();
713 if (!Asm.hasSymbolData(A))
714 Asm.getContext().FatalError(
716 Twine("symbol '") + A.getName() + "' can not be undefined");
718 const MCSymbolData &A_SD = Asm.getSymbolData(A);
720 MCSectionData const *SectionData = Fragment->getParent();
722 // Mark this symbol as requiring an entry in the symbol table.
723 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
724 "Section must already have been defined in ExecutePostLayoutBinding!");
725 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
726 "Symbol must already have been defined in ExecutePostLayoutBinding!");
728 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
729 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
730 const MCSymbolRefExpr *SymB = Target.getSymB();
731 bool CrossSection = false;
734 const MCSymbol *B = &SymB->getSymbol();
735 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
736 if (!B_SD.getFragment())
737 Asm.getContext().FatalError(
739 Twine("symbol '") + B->getName() +
740 "' can not be undefined in a subtraction expression");
742 if (!A_SD.getFragment())
743 Asm.getContext().FatalError(
745 Twine("symbol '") + Symbol.getName() +
746 "' can not be undefined in a subtraction expression");
748 CrossSection = &Symbol.getSection() != &B->getSection();
750 // Offset of the symbol in the section
751 int64_t a = Layout.getSymbolOffset(&B_SD);
753 // Ofeset of the relocation in the section
754 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
757 // In the case where we have SymbA and SymB, we just need to store the delta
758 // between the two symbols. Update FixedValue to account for the delta, and
759 // skip recording the relocation.
763 FixedValue = Target.getConstant();
766 COFFRelocation Reloc;
768 Reloc.Data.SymbolTableIndex = 0;
769 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
771 // Turn relocations for temporary symbols into section relocations.
772 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
773 Reloc.Symb = coff_symbol->Section->Symbol;
774 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
775 + coff_symbol->MCData->getOffset();
777 Reloc.Symb = coff_symbol;
779 ++Reloc.Symb->Relocations;
781 Reloc.Data.VirtualAddress += Fixup.getOffset();
782 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
785 // FIXME: Can anyone explain what this does other than adjust for the size
787 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
788 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
789 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
790 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
793 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
794 switch (Reloc.Data.Type) {
795 case COFF::IMAGE_REL_ARM_ABSOLUTE:
796 case COFF::IMAGE_REL_ARM_ADDR32:
797 case COFF::IMAGE_REL_ARM_ADDR32NB:
798 case COFF::IMAGE_REL_ARM_TOKEN:
799 case COFF::IMAGE_REL_ARM_SECTION:
800 case COFF::IMAGE_REL_ARM_SECREL:
802 case COFF::IMAGE_REL_ARM_BRANCH11:
803 case COFF::IMAGE_REL_ARM_BLX11:
804 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
805 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
807 case COFF::IMAGE_REL_ARM_BRANCH24:
808 case COFF::IMAGE_REL_ARM_BLX24:
809 case COFF::IMAGE_REL_ARM_MOV32A:
810 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
811 // only used for ARM mode code, which is documented as being unsupported
812 // by Windows on ARM. Empirical proof indicates that masm is able to
813 // generate the relocations however the rest of the MSVC toolchain is
814 // unable to handle it.
815 llvm_unreachable("unsupported relocation");
817 case COFF::IMAGE_REL_ARM_MOV32T:
819 case COFF::IMAGE_REL_ARM_BRANCH20T:
820 case COFF::IMAGE_REL_ARM_BRANCH24T:
821 case COFF::IMAGE_REL_ARM_BLX23T:
822 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
823 // perform a 4 byte adjustment to the relocation. Relative branches are
824 // offset by 4 on ARM, however, because there is no RELA relocations, all
825 // branches are offset by 4.
826 FixedValue = FixedValue + 4;
831 if (TargetObjectWriter->recordRelocation(Fixup))
832 coff_section->Relocations.push_back(Reloc);
835 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
836 const MCAsmLayout &Layout) {
837 size_t SectionsSize = Sections.size();
838 if (SectionsSize > static_cast<size_t>(INT32_MAX))
840 "PE COFF object files can't have more than 2147483647 sections");
842 // Assign symbol and section indexes and offsets.
843 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
845 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
847 DenseMap<COFFSection *, int32_t> SectionIndices(
848 NextPowerOf2(NumberOfSections));
850 for (const auto &Section : Sections) {
851 SectionIndices[Section.get()] = Number;
852 MakeSectionReal(*Section, Number);
856 Header.NumberOfSections = NumberOfSections;
857 Header.NumberOfSymbols = 0;
859 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
861 // round up to calculate the number of auxiliary symbols required
862 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
863 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize;
865 COFFSymbol *file = createSymbol(".file");
866 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
867 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
868 file->Aux.resize(Count);
871 unsigned Length = FI->size();
872 for (auto & Aux : file->Aux) {
873 Aux.AuxType = ATFile;
875 if (Length > SymbolSize) {
876 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize);
877 Length = Length - SymbolSize;
879 memcpy(&Aux.Aux, FI->c_str() + Offset, Length);
880 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
884 Offset += SymbolSize;
888 for (auto &Symbol : Symbols) {
889 // Update section number & offset for symbols that have them.
891 Symbol->Data.SectionNumber = Symbol->Section->Number;
893 if (Symbol->should_keep()) {
894 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++);
896 // Update auxiliary symbol info.
897 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
898 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
903 // Fixup weak external references.
904 for (auto & Symbol : Symbols) {
906 assert(Symbol->Index != -1);
907 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
908 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
909 "Symbol's aux symbol must be a Weak External!");
910 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
914 // Fixup associative COMDAT sections.
915 for (auto & Section : Sections) {
916 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
917 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
920 const MCSectionCOFF &MCSec =
921 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
923 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
925 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
926 assert(COMDATSymbol);
927 COFFSection *Assoc = COMDATSymbol->Section;
930 Twine("Missing associated COMDAT section for section ") +
931 MCSec.getSectionName());
933 // Skip this section if the associated section is unused.
934 if (Assoc->Number == -1)
937 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
941 // Assign file offsets to COFF object file structures.
946 offset += COFF::Header32Size;
948 offset += COFF::Header16Size;
949 offset += COFF::SectionSize * Header.NumberOfSections;
951 for (const auto & Section : Asm) {
952 COFFSection *Sec = SectionMap[&Section.getSection()];
954 if (Sec->Number == -1)
957 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
959 if (IsPhysicalSection(Sec)) {
960 Sec->Header.PointerToRawData = offset;
962 offset += Sec->Header.SizeOfRawData;
965 if (Sec->Relocations.size() > 0) {
966 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
968 if (RelocationsOverflow) {
969 // Signal overflow by setting NumberOfRelocations to max value. Actual
970 // size is found in reloc #0. Microsoft tools understand this.
971 Sec->Header.NumberOfRelocations = 0xffff;
973 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
975 Sec->Header.PointerToRelocations = offset;
977 if (RelocationsOverflow) {
978 // Reloc #0 will contain actual count, so make room for it.
979 offset += COFF::RelocationSize;
982 offset += COFF::RelocationSize * Sec->Relocations.size();
984 for (auto & Relocation : Sec->Relocations) {
985 assert(Relocation.Symb->Index != -1);
986 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
990 assert(Sec->Symbol->Aux.size() == 1 &&
991 "Section's symbol must have one aux!");
992 AuxSymbol &Aux = Sec->Symbol->Aux[0];
993 assert(Aux.AuxType == ATSectionDefinition &&
994 "Section's symbol's aux symbol must be a Section Definition!");
995 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
996 Aux.Aux.SectionDefinition.NumberOfRelocations =
997 Sec->Header.NumberOfRelocations;
998 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
999 Sec->Header.NumberOfLineNumbers;
1002 Header.PointerToSymbolTable = offset;
1004 // We want a deterministic output. It looks like GNU as also writes 0 in here.
1005 Header.TimeDateStamp = 0;
1007 // Write it all to disk...
1008 WriteFileHeader(Header);
1011 sections::iterator i, ie;
1012 MCAssembler::const_iterator j, je;
1014 for (auto & Section : Sections) {
1015 if (Section->Number != -1) {
1016 if (Section->Relocations.size() >= 0xffff)
1017 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1018 WriteSectionHeader(Section->Header);
1022 for (i = Sections.begin(), ie = Sections.end(),
1023 j = Asm.begin(), je = Asm.end();
1024 (i != ie) && (j != je); ++i, ++j) {
1026 if ((*i)->Number == -1)
1029 if ((*i)->Header.PointerToRawData != 0) {
1030 assert(OS.tell() == (*i)->Header.PointerToRawData &&
1031 "Section::PointerToRawData is insane!");
1033 Asm.writeSectionData(j, Layout);
1036 if ((*i)->Relocations.size() > 0) {
1037 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
1038 "Section::PointerToRelocations is insane!");
1040 if ((*i)->Relocations.size() >= 0xffff) {
1041 // In case of overflow, write actual relocation count as first
1042 // relocation. Including the synthetic reloc itself (+ 1).
1044 r.VirtualAddress = (*i)->Relocations.size() + 1;
1045 r.SymbolTableIndex = 0;
1050 for (const auto & Relocation : (*i)->Relocations)
1051 WriteRelocation(Relocation.Data);
1053 assert((*i)->Header.PointerToRelocations == 0 &&
1054 "Section::PointerToRelocations is insane!");
1058 assert(OS.tell() == Header.PointerToSymbolTable &&
1059 "Header::PointerToSymbolTable is insane!");
1061 for (auto & Symbol : Symbols)
1062 if (Symbol->Index != -1)
1063 WriteSymbol(*Symbol);
1065 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
1068 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1072 // Pin the vtable to this file.
1073 void MCWinCOFFObjectTargetWriter::anchor() {}
1075 //------------------------------------------------------------------------------
1076 // WinCOFFObjectWriter factory function
1079 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1081 return new WinCOFFObjectWriter(MOTW, OS);