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/STLExtras.h"
17 #include "llvm/ADT/StringMap.h"
18 #include "llvm/ADT/StringRef.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/MCObjectFileInfo.h"
25 #include "llvm/MC/MCObjectWriter.h"
26 #include "llvm/MC/MCSection.h"
27 #include "llvm/MC/MCSectionCOFF.h"
28 #include "llvm/MC/MCSymbolCOFF.h"
29 #include "llvm/MC/MCValue.h"
30 #include "llvm/MC/StringTableBuilder.h"
31 #include "llvm/Support/COFF.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/Endian.h"
34 #include "llvm/Support/ErrorHandling.h"
35 #include "llvm/Support/JamCRC.h"
36 #include "llvm/Support/TimeValue.h"
42 #define DEBUG_TYPE "WinCOFFObjectWriter"
45 typedef SmallString<COFF::NameSize> name;
56 AuxiliaryType AuxType;
67 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
78 COFFSymbol(StringRef name);
79 void set_name_offset(uint32_t Offset);
81 bool should_keep() const;
83 int64_t getIndex() const { return Index; }
84 void setIndex(int Value) {
87 MC->setIndex(static_cast<uint32_t>(Value));
91 // This class contains staging data for a COFF relocation entry.
92 struct COFFRelocation {
93 COFF::relocation Data;
96 COFFRelocation() : Symb(nullptr) {}
97 static size_t size() { return COFF::RelocationSize; }
100 typedef std::vector<COFFRelocation> relocations;
104 COFF::section Header;
108 MCSectionCOFF const *MCSection;
110 relocations Relocations;
112 COFFSection(StringRef name);
113 static size_t size();
116 class WinCOFFObjectWriter : public MCObjectWriter {
118 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
119 typedef std::vector<std::unique_ptr<COFFSection>> sections;
121 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
122 typedef DenseMap<MCSection const *, COFFSection *> section_map;
124 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
126 // Root level file contents.
130 StringTableBuilder Strings;
132 // Maps used during object file creation.
133 section_map SectionMap;
134 symbol_map SymbolMap;
138 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS);
140 void reset() override {
141 memset(&Header, 0, sizeof(Header));
142 Header.Machine = TargetObjectWriter->getMachine();
148 MCObjectWriter::reset();
151 COFFSymbol *createSymbol(StringRef Name);
152 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
153 COFFSection *createSection(StringRef Name);
155 template <typename object_t, typename list_t>
156 object_t *createCOFFEntity(StringRef Name, list_t &List);
158 void defineSection(MCSectionCOFF const &Sec);
159 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
160 const MCAsmLayout &Layout);
162 void SetSymbolName(COFFSymbol &S);
163 void SetSectionName(COFFSection &S);
165 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm);
167 bool IsPhysicalSection(COFFSection *S);
169 // Entity writing methods.
171 void WriteFileHeader(const COFF::header &Header);
172 void WriteSymbol(const COFFSymbol &S);
173 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
174 void writeSectionHeader(const COFF::section &S);
175 void WriteRelocation(const COFF::relocation &R);
177 // MCObjectWriter interface implementation.
179 void executePostLayoutBinding(MCAssembler &Asm,
180 const MCAsmLayout &Layout) override;
182 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
183 const MCSymbol &SymA,
184 const MCFragment &FB, bool InSet,
185 bool IsPCRel) const override;
187 bool isWeak(const MCSymbol &Sym) const override;
189 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
190 const MCFragment *Fragment, const MCFixup &Fixup,
191 MCValue Target, bool &IsPCRel,
192 uint64_t &FixedValue) override;
194 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
198 static inline void write_uint32_le(void *Data, uint32_t Value) {
199 support::endian::write<uint32_t, support::little, support::unaligned>(Data,
203 //------------------------------------------------------------------------------
204 // Symbol class implementation
206 COFFSymbol::COFFSymbol(StringRef name)
207 : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr),
208 Relocations(0), MC(nullptr) {
209 memset(&Data, 0, sizeof(Data));
212 // In the case that the name does not fit within 8 bytes, the offset
213 // into the string table is stored in the last 4 bytes instead, leaving
214 // the first 4 bytes as 0.
215 void COFFSymbol::set_name_offset(uint32_t Offset) {
216 write_uint32_le(Data.Name + 0, 0);
217 write_uint32_le(Data.Name + 4, Offset);
220 /// logic to decide if the symbol should be reported in the symbol table
221 bool COFFSymbol::should_keep() const {
222 // no section means its external, keep it
226 // if it has relocations pointing at it, keep it
227 if (Relocations > 0) {
228 assert(Section->Number != -1 && "Sections with relocations must be real!");
232 // if this is a safeseh handler, keep it
233 if (MC && (cast<MCSymbolCOFF>(MC)->isSafeSEH()))
236 // if the section its in is being droped, drop it
237 if (Section->Number == -1)
240 // if it is the section symbol, keep it
241 if (Section->Symbol == this)
244 // if its temporary, drop it
245 if (MC && MC->isTemporary())
248 // otherwise, keep it
252 //------------------------------------------------------------------------------
253 // Section class implementation
255 COFFSection::COFFSection(StringRef name)
256 : Name(name), MCSection(nullptr), Symbol(nullptr) {
257 memset(&Header, 0, sizeof(Header));
260 size_t COFFSection::size() { return COFF::SectionSize; }
262 //------------------------------------------------------------------------------
263 // WinCOFFObjectWriter class implementation
265 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
266 raw_pwrite_stream &OS)
267 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
268 memset(&Header, 0, sizeof(Header));
270 Header.Machine = TargetObjectWriter->getMachine();
273 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
274 return createCOFFEntity<COFFSymbol>(Name, Symbols);
277 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
278 symbol_map::iterator i = SymbolMap.find(Symbol);
279 if (i != SymbolMap.end())
281 COFFSymbol *RetSymbol =
282 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
283 SymbolMap[Symbol] = RetSymbol;
287 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
288 return createCOFFEntity<COFFSection>(Name, Sections);
291 /// A template used to lookup or create a symbol/section, and initialize it if
293 template <typename object_t, typename list_t>
294 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) {
295 List.push_back(make_unique<object_t>(Name));
297 return List.back().get();
300 /// This function takes a section data object from the assembler
301 /// and creates the associated COFF section staging object.
302 void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) {
303 COFFSection *coff_section = createSection(Sec.getSectionName());
304 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
305 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
306 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
307 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
308 if (COMDATSymbol->Section)
309 report_fatal_error("two sections have the same comdat");
310 COMDATSymbol->Section = coff_section;
314 coff_section->Symbol = coff_symbol;
315 coff_symbol->Section = coff_section;
316 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
318 // In this case the auxiliary symbol is a Section Definition.
319 coff_symbol->Aux.resize(1);
320 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
321 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
322 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
324 coff_section->Header.Characteristics = Sec.getCharacteristics();
326 uint32_t &Characteristics = coff_section->Header.Characteristics;
327 switch (Sec.getAlignment()) {
329 Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;
332 Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;
335 Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;
338 Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;
341 Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;
344 Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;
347 Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;
350 Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;
353 Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;
356 Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;
359 Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES;
362 Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES;
365 Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES;
368 Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES;
371 llvm_unreachable("unsupported section alignment");
374 // Bind internal COFF section to MC section.
375 coff_section->MCSection = &Sec;
376 SectionMap[&Sec] = coff_section;
379 static uint64_t getSymbolValue(const MCSymbol &Symbol,
380 const MCAsmLayout &Layout) {
381 if (Symbol.isCommon() && Symbol.isExternal())
382 return Symbol.getCommonSize();
385 if (!Layout.getSymbolOffset(Symbol, Res))
391 /// This function takes a symbol data object from the assembler
392 /// and creates the associated COFF symbol staging object.
393 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
394 MCAssembler &Assembler,
395 const MCAsmLayout &Layout) {
396 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
397 SymbolMap[&Symbol] = coff_symbol;
399 if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) {
400 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
402 if (Symbol.isVariable()) {
403 const MCSymbolRefExpr *SymRef =
404 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
407 report_fatal_error("Weak externals may only alias symbols");
409 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
411 std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
412 COFFSymbol *WeakDefault = createSymbol(WeakName);
413 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
414 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
415 WeakDefault->Data.Type = 0;
416 WeakDefault->Data.Value = 0;
417 coff_symbol->Other = WeakDefault;
420 // Setup the Weak External auxiliary symbol.
421 coff_symbol->Aux.resize(1);
422 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
423 coff_symbol->Aux[0].AuxType = ATWeakExternal;
424 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
425 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
426 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
428 coff_symbol->MC = &Symbol;
430 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
431 coff_symbol->Data.Value = getSymbolValue(Symbol, Layout);
433 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol);
434 coff_symbol->Data.Type = SymbolCOFF.getType();
435 coff_symbol->Data.StorageClass = SymbolCOFF.getClass();
437 // If no storage class was specified in the streamer, define it here.
438 if (coff_symbol->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
439 bool IsExternal = Symbol.isExternal() ||
440 (!Symbol.getFragment() && !Symbol.isVariable());
442 coff_symbol->Data.StorageClass = IsExternal
443 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
444 : COFF::IMAGE_SYM_CLASS_STATIC;
448 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
450 if (Base->getFragment()) {
451 COFFSection *Sec = SectionMap[Base->getFragment()->getParent()];
453 if (coff_symbol->Section && coff_symbol->Section != Sec)
454 report_fatal_error("conflicting sections for symbol");
456 coff_symbol->Section = Sec;
460 coff_symbol->MC = &Symbol;
464 // Maximum offsets for different string table entry encodings.
465 static const unsigned Max6DecimalOffset = 999999;
466 static const unsigned Max7DecimalOffset = 9999999;
467 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
469 // Encode a string table entry offset in base 64, padded to 6 chars, and
470 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
471 // Buffer must be at least 8 bytes large. No terminating null appended.
472 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
473 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
474 "Illegal section name encoding for value");
476 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
477 "abcdefghijklmnopqrstuvwxyz"
483 char *Ptr = Buffer + 7;
484 for (unsigned i = 0; i < 6; ++i) {
485 unsigned Rem = Value % 64;
487 *(Ptr--) = Alphabet[Rem];
491 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
492 if (S.Name.size() > COFF::NameSize) {
493 uint64_t StringTableEntry = Strings.getOffset(S.Name);
495 if (StringTableEntry <= Max6DecimalOffset) {
496 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
497 } else if (StringTableEntry <= Max7DecimalOffset) {
498 // With seven digits, we have to skip the terminating null. Because
499 // sprintf always appends it, we use a larger temporary buffer.
501 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
502 std::memcpy(S.Header.Name, buffer, 8);
503 } else if (StringTableEntry <= MaxBase64Offset) {
504 // Starting with 10,000,000, offsets are encoded as base64.
505 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
507 report_fatal_error("COFF string table is greater than 64 GB.");
510 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
513 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
514 if (S.Name.size() > COFF::NameSize)
515 S.set_name_offset(Strings.getOffset(S.Name));
517 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
520 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
522 // This doesn't seem to be right. Strings referred to from the .data section
523 // need symbols so they can be linked to code in the .text section right?
525 // return Asm.isSymbolLinkerVisible(Symbol);
527 // Non-temporary labels should always be visible to the linker.
528 if (!Symbol.isTemporary())
531 // Temporary variable symbols are invisible.
532 if (Symbol.isVariable())
535 // Absolute temporary labels are never visible.
536 return !Symbol.isAbsolute();
539 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
540 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
544 //------------------------------------------------------------------------------
545 // entity writing methods
547 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
549 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
551 writeLE16(COFF::BigObjHeader::MinBigObjectVersion);
552 writeLE16(Header.Machine);
553 writeLE32(Header.TimeDateStamp);
554 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic)));
559 writeLE32(Header.NumberOfSections);
560 writeLE32(Header.PointerToSymbolTable);
561 writeLE32(Header.NumberOfSymbols);
563 writeLE16(Header.Machine);
564 writeLE16(static_cast<int16_t>(Header.NumberOfSections));
565 writeLE32(Header.TimeDateStamp);
566 writeLE32(Header.PointerToSymbolTable);
567 writeLE32(Header.NumberOfSymbols);
568 writeLE16(Header.SizeOfOptionalHeader);
569 writeLE16(Header.Characteristics);
573 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
574 writeBytes(StringRef(S.Data.Name, COFF::NameSize));
575 writeLE32(S.Data.Value);
577 writeLE32(S.Data.SectionNumber);
579 writeLE16(static_cast<int16_t>(S.Data.SectionNumber));
580 writeLE16(S.Data.Type);
581 write8(S.Data.StorageClass);
582 write8(S.Data.NumberOfAuxSymbols);
583 WriteAuxiliarySymbols(S.Aux);
586 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
587 const COFFSymbol::AuxiliarySymbols &S) {
588 for (COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
590 switch (i->AuxType) {
591 case ATFunctionDefinition:
592 writeLE32(i->Aux.FunctionDefinition.TagIndex);
593 writeLE32(i->Aux.FunctionDefinition.TotalSize);
594 writeLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
595 writeLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
596 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
598 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
600 case ATbfAndefSymbol:
601 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
602 writeLE16(i->Aux.bfAndefSymbol.Linenumber);
603 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
604 writeLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
605 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
607 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
610 writeLE32(i->Aux.WeakExternal.TagIndex);
611 writeLE32(i->Aux.WeakExternal.Characteristics);
612 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
614 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
618 StringRef(reinterpret_cast<const char *>(&i->Aux),
619 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
621 case ATSectionDefinition:
622 writeLE32(i->Aux.SectionDefinition.Length);
623 writeLE16(i->Aux.SectionDefinition.NumberOfRelocations);
624 writeLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
625 writeLE32(i->Aux.SectionDefinition.CheckSum);
626 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
627 write8(i->Aux.SectionDefinition.Selection);
628 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
629 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
631 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
637 void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) {
638 writeBytes(StringRef(S.Name, COFF::NameSize));
640 writeLE32(S.VirtualSize);
641 writeLE32(S.VirtualAddress);
642 writeLE32(S.SizeOfRawData);
643 writeLE32(S.PointerToRawData);
644 writeLE32(S.PointerToRelocations);
645 writeLE32(S.PointerToLineNumbers);
646 writeLE16(S.NumberOfRelocations);
647 writeLE16(S.NumberOfLineNumbers);
648 writeLE32(S.Characteristics);
651 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
652 writeLE32(R.VirtualAddress);
653 writeLE32(R.SymbolTableIndex);
657 ////////////////////////////////////////////////////////////////////////////////
658 // MCObjectWriter interface implementations
660 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
661 const MCAsmLayout &Layout) {
662 // "Define" each section & symbol. This creates section & symbol
663 // entries in the staging area.
664 for (const auto &Section : Asm)
665 defineSection(static_cast<const MCSectionCOFF &>(Section));
667 for (const MCSymbol &Symbol : Asm.symbols())
668 if (ExportSymbol(Symbol, Asm))
669 DefineSymbol(Symbol, Asm, Layout);
672 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
673 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
674 bool InSet, bool IsPCRel) const {
675 // MS LINK expects to be able to replace all references to a function with a
676 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
677 // away any relocations to functions.
678 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
679 if ((Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
681 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
685 bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const {
686 if (!Sym.isExternal())
689 if (!Sym.isInSection())
692 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection());
693 if (!Sec.getCOMDATSymbol())
696 // It looks like for COFF it is invalid to replace a reference to a global
697 // in a comdat with a reference to a local.
698 // FIXME: Add a specification reference if available.
702 void WinCOFFObjectWriter::recordRelocation(
703 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
704 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
705 assert(Target.getSymA() && "Relocation must reference a symbol!");
707 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
708 const MCSymbol &A = Symbol;
709 if (!A.isRegistered())
710 Asm.getContext().reportFatalError(Fixup.getLoc(),
711 Twine("symbol '") + A.getName() +
712 "' can not be undefined");
713 if (A.isTemporary() && A.isUndefined()) {
714 Asm.getContext().reportFatalError(Fixup.getLoc(),
715 Twine("assembler label '") + A.getName() +
716 "' can not be undefined");
719 MCSection *Section = Fragment->getParent();
721 // Mark this symbol as requiring an entry in the symbol table.
722 assert(SectionMap.find(Section) != SectionMap.end() &&
723 "Section must already have been defined in executePostLayoutBinding!");
724 assert(SymbolMap.find(&A) != SymbolMap.end() &&
725 "Symbol must already have been defined in executePostLayoutBinding!");
727 COFFSection *coff_section = SectionMap[Section];
728 COFFSymbol *coff_symbol = SymbolMap[&A];
729 const MCSymbolRefExpr *SymB = Target.getSymB();
730 bool CrossSection = false;
733 const MCSymbol *B = &SymB->getSymbol();
734 if (!B->getFragment())
735 Asm.getContext().reportFatalError(
737 Twine("symbol '") + B->getName() +
738 "' can not be undefined in a subtraction expression");
740 if (!A.getFragment())
741 Asm.getContext().reportFatalError(
743 Twine("symbol '") + Symbol.getName() +
744 "' can not be undefined in a subtraction expression");
746 CrossSection = &Symbol.getSection() != &B->getSection();
748 // Offset of the symbol in the section
749 int64_t OffsetOfB = Layout.getSymbolOffset(*B);
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.
755 int64_t OffsetOfA = Layout.getSymbolOffset(A);
756 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
760 // Offset of the relocation in the section
761 int64_t OffsetOfRelocation =
762 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
764 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
766 FixedValue = Target.getConstant();
769 COFFRelocation Reloc;
771 Reloc.Data.SymbolTableIndex = 0;
772 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
774 // Turn relocations for temporary symbols into section relocations.
775 if (coff_symbol->MC->isTemporary() || CrossSection) {
776 Reloc.Symb = coff_symbol->Section->Symbol;
777 FixedValue += Layout.getFragmentOffset(coff_symbol->MC->getFragment()) +
778 coff_symbol->MC->getOffset();
780 Reloc.Symb = coff_symbol;
782 ++Reloc.Symb->Relocations;
784 Reloc.Data.VirtualAddress += Fixup.getOffset();
785 Reloc.Data.Type = TargetObjectWriter->getRelocType(
786 Target, Fixup, CrossSection, Asm.getBackend());
788 // FIXME: Can anyone explain what this does other than adjust for the size
790 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
791 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
792 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
793 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
796 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
797 switch (Reloc.Data.Type) {
798 case COFF::IMAGE_REL_ARM_ABSOLUTE:
799 case COFF::IMAGE_REL_ARM_ADDR32:
800 case COFF::IMAGE_REL_ARM_ADDR32NB:
801 case COFF::IMAGE_REL_ARM_TOKEN:
802 case COFF::IMAGE_REL_ARM_SECTION:
803 case COFF::IMAGE_REL_ARM_SECREL:
805 case COFF::IMAGE_REL_ARM_BRANCH11:
806 case COFF::IMAGE_REL_ARM_BLX11:
807 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
808 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
810 case COFF::IMAGE_REL_ARM_BRANCH24:
811 case COFF::IMAGE_REL_ARM_BLX24:
812 case COFF::IMAGE_REL_ARM_MOV32A:
813 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
814 // only used for ARM mode code, which is documented as being unsupported
815 // by Windows on ARM. Empirical proof indicates that masm is able to
816 // generate the relocations however the rest of the MSVC toolchain is
817 // unable to handle it.
818 llvm_unreachable("unsupported relocation");
820 case COFF::IMAGE_REL_ARM_MOV32T:
822 case COFF::IMAGE_REL_ARM_BRANCH20T:
823 case COFF::IMAGE_REL_ARM_BRANCH24T:
824 case COFF::IMAGE_REL_ARM_BLX23T:
825 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
826 // perform a 4 byte adjustment to the relocation. Relative branches are
827 // offset by 4 on ARM, however, because there is no RELA relocations, all
828 // branches are offset by 4.
829 FixedValue = FixedValue + 4;
834 if (TargetObjectWriter->recordRelocation(Fixup))
835 coff_section->Relocations.push_back(Reloc);
838 void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
839 const MCAsmLayout &Layout) {
840 size_t SectionsSize = Sections.size();
841 if (SectionsSize > static_cast<size_t>(INT32_MAX))
843 "PE COFF object files can't have more than 2147483647 sections");
845 // Assign symbol and section indexes and offsets.
846 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
848 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
850 // Assign section numbers.
852 for (const auto &Section : Sections) {
853 Section->Number = Number;
854 Section->Symbol->Data.SectionNumber = Number;
855 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
859 Header.NumberOfSections = NumberOfSections;
860 Header.NumberOfSymbols = 0;
862 for (const std::string &Name : Asm.getFileNames()) {
863 // round up to calculate the number of auxiliary symbols required
864 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
865 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
867 COFFSymbol *file = createSymbol(".file");
868 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
869 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
870 file->Aux.resize(Count);
873 unsigned Length = Name.size();
874 for (auto &Aux : file->Aux) {
875 Aux.AuxType = ATFile;
877 if (Length > SymbolSize) {
878 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
879 Length = Length - SymbolSize;
881 memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
882 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
886 Offset += SymbolSize;
890 for (auto &Symbol : Symbols) {
891 // Update section number & offset for symbols that have them.
893 Symbol->Data.SectionNumber = Symbol->Section->Number;
894 if (Symbol->should_keep()) {
895 Symbol->setIndex(Header.NumberOfSymbols++);
896 // Update auxiliary symbol info.
897 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
898 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
900 Symbol->setIndex(-1);
904 // Build string table.
905 for (const auto &S : Sections)
906 if (S->Name.size() > COFF::NameSize)
907 Strings.add(S->Name);
908 for (const auto &S : Symbols)
909 if (S->should_keep() && S->Name.size() > COFF::NameSize)
910 Strings.add(S->Name);
911 Strings.finalize(StringTableBuilder::WinCOFF);
914 for (const auto &S : Sections)
916 for (auto &S : Symbols)
917 if (S->should_keep())
920 // Fixup weak external references.
921 for (auto &Symbol : Symbols) {
923 assert(Symbol->getIndex() != -1);
924 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
925 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
926 "Symbol's aux symbol must be a Weak External!");
927 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
931 // Fixup associative COMDAT sections.
932 for (auto &Section : Sections) {
933 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
934 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
937 const MCSectionCOFF &MCSec = *Section->MCSection;
939 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
941 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
942 assert(COMDATSymbol);
943 COFFSection *Assoc = COMDATSymbol->Section;
946 Twine("Missing associated COMDAT section for section ") +
947 MCSec.getSectionName());
949 // Skip this section if the associated section is unused.
950 if (Assoc->Number == -1)
953 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
956 // Assign file offsets to COFF object file structures.
961 offset += COFF::Header32Size;
963 offset += COFF::Header16Size;
964 offset += COFF::SectionSize * Header.NumberOfSections;
966 for (const auto &Section : Asm) {
967 COFFSection *Sec = SectionMap[&Section];
969 if (Sec->Number == -1)
972 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
974 if (IsPhysicalSection(Sec)) {
975 // Align the section data to a four byte boundary.
976 offset = RoundUpToAlignment(offset, 4);
977 Sec->Header.PointerToRawData = offset;
979 offset += Sec->Header.SizeOfRawData;
982 if (Sec->Relocations.size() > 0) {
983 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
985 if (RelocationsOverflow) {
986 // Signal overflow by setting NumberOfRelocations to max value. Actual
987 // size is found in reloc #0. Microsoft tools understand this.
988 Sec->Header.NumberOfRelocations = 0xffff;
990 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
992 Sec->Header.PointerToRelocations = offset;
994 if (RelocationsOverflow) {
995 // Reloc #0 will contain actual count, so make room for it.
996 offset += COFF::RelocationSize;
999 offset += COFF::RelocationSize * Sec->Relocations.size();
1001 for (auto &Relocation : Sec->Relocations) {
1002 assert(Relocation.Symb->getIndex() != -1);
1003 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
1007 assert(Sec->Symbol->Aux.size() == 1 &&
1008 "Section's symbol must have one aux!");
1009 AuxSymbol &Aux = Sec->Symbol->Aux[0];
1010 assert(Aux.AuxType == ATSectionDefinition &&
1011 "Section's symbol's aux symbol must be a Section Definition!");
1012 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
1013 Aux.Aux.SectionDefinition.NumberOfRelocations =
1014 Sec->Header.NumberOfRelocations;
1015 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
1016 Sec->Header.NumberOfLineNumbers;
1019 Header.PointerToSymbolTable = offset;
1021 #if (ENABLE_TIMESTAMPS == 1)
1022 // MS LINK expects to be able to use this timestamp to implement their
1023 // /INCREMENTAL feature.
1024 std::time_t Now = time(nullptr);
1025 if (Now < 0 || !isUInt<32>(Now))
1027 Header.TimeDateStamp = Now;
1029 // We want a deterministic output. It looks like GNU as also writes 0 in here.
1030 Header.TimeDateStamp = 0;
1033 // Write it all to disk...
1034 WriteFileHeader(Header);
1037 sections::iterator i, ie;
1038 MCAssembler::iterator j, je;
1040 for (auto &Section : Sections) {
1041 if (Section->Number != -1) {
1042 if (Section->Relocations.size() >= 0xffff)
1043 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1044 writeSectionHeader(Section->Header);
1048 SmallVector<char, 128> SectionContents;
1049 for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(),
1051 (i != ie) && (j != je); ++i, ++j) {
1053 if ((*i)->Number == -1)
1056 if ((*i)->Header.PointerToRawData != 0) {
1057 assert(getStream().tell() <= (*i)->Header.PointerToRawData &&
1058 "Section::PointerToRawData is insane!");
1060 unsigned SectionDataPadding =
1061 (*i)->Header.PointerToRawData - getStream().tell();
1062 assert(SectionDataPadding < 4 &&
1063 "Should only need at most three bytes of padding!");
1065 WriteZeros(SectionDataPadding);
1067 // Save the contents of the section to a temporary buffer, we need this
1068 // to CRC the data before we dump it into the object file.
1069 SectionContents.clear();
1070 raw_svector_ostream VecOS(SectionContents);
1071 raw_pwrite_stream &OldStream = getStream();
1072 // Redirect the output stream to our buffer.
1074 // Fill our buffer with the section data.
1075 Asm.writeSectionData(&*j, Layout);
1076 // Reset the stream back to what it was before.
1077 setStream(OldStream);
1079 // Calculate our CRC with an initial value of '0', this is not how
1080 // JamCRC is specified but it aligns with the expected output.
1081 JamCRC JC(/*Init=*/0x00000000U);
1082 JC.update(SectionContents);
1084 // Write the section contents to the object file.
1085 getStream() << SectionContents;
1087 // Update the section definition auxiliary symbol to record the CRC.
1088 COFFSection *Sec = SectionMap[&*j];
1089 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
1090 assert(AuxSyms.size() == 1 &&
1091 AuxSyms[0].AuxType == ATSectionDefinition);
1092 AuxSymbol &SecDef = AuxSyms[0];
1093 SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC();
1096 if ((*i)->Relocations.size() > 0) {
1097 assert(getStream().tell() == (*i)->Header.PointerToRelocations &&
1098 "Section::PointerToRelocations is insane!");
1100 if ((*i)->Relocations.size() >= 0xffff) {
1101 // In case of overflow, write actual relocation count as first
1102 // relocation. Including the synthetic reloc itself (+ 1).
1104 r.VirtualAddress = (*i)->Relocations.size() + 1;
1105 r.SymbolTableIndex = 0;
1110 for (const auto &Relocation : (*i)->Relocations)
1111 WriteRelocation(Relocation.Data);
1113 assert((*i)->Header.PointerToRelocations == 0 &&
1114 "Section::PointerToRelocations is insane!");
1118 assert(getStream().tell() == Header.PointerToSymbolTable &&
1119 "Header::PointerToSymbolTable is insane!");
1121 for (auto &Symbol : Symbols)
1122 if (Symbol->getIndex() != -1)
1123 WriteSymbol(*Symbol);
1125 getStream().write(Strings.data().data(), Strings.data().size());
1128 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1129 : Machine(Machine_) {}
1131 // Pin the vtable to this file.
1132 void MCWinCOFFObjectTargetWriter::anchor() {}
1134 //------------------------------------------------------------------------------
1135 // WinCOFFObjectWriter factory function
1138 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1139 raw_pwrite_stream &OS) {
1140 return new WinCOFFObjectWriter(MOTW, OS);