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"
41 #define DEBUG_TYPE "WinCOFFObjectWriter"
44 typedef SmallString<COFF::NameSize> name;
55 AuxiliaryType AuxType;
66 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
77 COFFSymbol(StringRef name);
78 void set_name_offset(uint32_t Offset);
80 bool should_keep() const;
82 int64_t getIndex() const { return Index; }
83 void setIndex(int Value) {
86 MC->setIndex(static_cast<uint32_t>(Value));
90 // This class contains staging data for a COFF relocation entry.
91 struct COFFRelocation {
92 COFF::relocation Data;
95 COFFRelocation() : Symb(nullptr) {}
96 static size_t size() { return COFF::RelocationSize; }
99 typedef std::vector<COFFRelocation> relocations;
103 COFF::section Header;
107 MCSectionCOFF const *MCSection;
109 relocations Relocations;
111 COFFSection(StringRef name);
112 static size_t size();
115 class WinCOFFObjectWriter : public MCObjectWriter {
117 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
118 typedef std::vector<std::unique_ptr<COFFSection>> sections;
120 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
121 typedef DenseMap<MCSection const *, COFFSection *> section_map;
123 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
125 // Root level file contents.
129 StringTableBuilder Strings;
131 // Maps used during object file creation.
132 section_map SectionMap;
133 symbol_map SymbolMap;
137 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS);
139 void reset() override {
140 memset(&Header, 0, sizeof(Header));
141 Header.Machine = TargetObjectWriter->getMachine();
147 MCObjectWriter::reset();
150 COFFSymbol *createSymbol(StringRef Name);
151 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
152 COFFSection *createSection(StringRef Name);
154 template <typename object_t, typename list_t>
155 object_t *createCOFFEntity(StringRef Name, list_t &List);
157 void defineSection(MCSectionCOFF const &Sec);
158 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
159 const MCAsmLayout &Layout);
161 void SetSymbolName(COFFSymbol &S);
162 void SetSectionName(COFFSection &S);
164 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm);
166 bool IsPhysicalSection(COFFSection *S);
168 // Entity writing methods.
170 void WriteFileHeader(const COFF::header &Header);
171 void WriteSymbol(const COFFSymbol &S);
172 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
173 void writeSectionHeader(const COFF::section &S);
174 void WriteRelocation(const COFF::relocation &R);
176 // MCObjectWriter interface implementation.
178 void executePostLayoutBinding(MCAssembler &Asm,
179 const MCAsmLayout &Layout) override;
181 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
182 const MCSymbol &SymA,
183 const MCFragment &FB, bool InSet,
184 bool IsPCRel) const override;
186 bool isWeak(const MCSymbol &Sym) const override;
188 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
189 const MCFragment *Fragment, const MCFixup &Fixup,
190 MCValue Target, bool &IsPCRel,
191 uint64_t &FixedValue) override;
193 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
197 static inline void write_uint32_le(void *Data, uint32_t Value) {
198 support::endian::write<uint32_t, support::little, support::unaligned>(Data,
202 //------------------------------------------------------------------------------
203 // Symbol class implementation
205 COFFSymbol::COFFSymbol(StringRef name)
206 : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr),
207 Relocations(0), MC(nullptr) {
208 memset(&Data, 0, sizeof(Data));
211 // In the case that the name does not fit within 8 bytes, the offset
212 // into the string table is stored in the last 4 bytes instead, leaving
213 // the first 4 bytes as 0.
214 void COFFSymbol::set_name_offset(uint32_t Offset) {
215 write_uint32_le(Data.Name + 0, 0);
216 write_uint32_le(Data.Name + 4, Offset);
219 /// logic to decide if the symbol should be reported in the symbol table
220 bool COFFSymbol::should_keep() const {
221 // no section means its external, keep it
225 // if it has relocations pointing at it, keep it
226 if (Relocations > 0) {
227 assert(Section->Number != -1 && "Sections with relocations must be real!");
231 // if this is a safeseh handler, keep it
232 if (MC && (cast<MCSymbolCOFF>(MC)->isSafeSEH()))
235 // if the section its in is being droped, drop it
236 if (Section->Number == -1)
239 // if it is the section symbol, keep it
240 if (Section->Symbol == this)
243 // if its temporary, drop it
244 if (MC && MC->isTemporary())
247 // otherwise, keep it
251 //------------------------------------------------------------------------------
252 // Section class implementation
254 COFFSection::COFFSection(StringRef name)
255 : Name(name), MCSection(nullptr), Symbol(nullptr) {
256 memset(&Header, 0, sizeof(Header));
259 size_t COFFSection::size() { return COFF::SectionSize; }
261 //------------------------------------------------------------------------------
262 // WinCOFFObjectWriter class implementation
264 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
265 raw_pwrite_stream &OS)
266 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
267 memset(&Header, 0, sizeof(Header));
269 Header.Machine = TargetObjectWriter->getMachine();
272 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
273 return createCOFFEntity<COFFSymbol>(Name, Symbols);
276 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
277 symbol_map::iterator i = SymbolMap.find(Symbol);
278 if (i != SymbolMap.end())
280 COFFSymbol *RetSymbol =
281 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
282 SymbolMap[Symbol] = RetSymbol;
286 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
287 return createCOFFEntity<COFFSection>(Name, Sections);
290 /// A template used to lookup or create a symbol/section, and initialize it if
292 template <typename object_t, typename list_t>
293 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) {
294 List.push_back(make_unique<object_t>(Name));
296 return List.back().get();
299 /// This function takes a section data object from the assembler
300 /// and creates the associated COFF section staging object.
301 void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) {
302 COFFSection *coff_section = createSection(Sec.getSectionName());
303 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
304 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
305 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
306 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
307 if (COMDATSymbol->Section)
308 report_fatal_error("two sections have the same comdat");
309 COMDATSymbol->Section = coff_section;
313 coff_section->Symbol = coff_symbol;
314 coff_symbol->Section = coff_section;
315 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
317 // In this case the auxiliary symbol is a Section Definition.
318 coff_symbol->Aux.resize(1);
319 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
320 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
321 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
323 coff_section->Header.Characteristics = Sec.getCharacteristics();
325 uint32_t &Characteristics = coff_section->Header.Characteristics;
326 switch (Sec.getAlignment()) {
328 Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;
331 Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;
334 Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;
337 Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;
340 Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;
343 Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;
346 Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;
349 Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;
352 Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;
355 Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;
358 Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES;
361 Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES;
364 Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES;
367 Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES;
370 llvm_unreachable("unsupported section alignment");
373 // Bind internal COFF section to MC section.
374 coff_section->MCSection = &Sec;
375 SectionMap[&Sec] = coff_section;
378 static uint64_t getSymbolValue(const MCSymbol &Symbol,
379 const MCAsmLayout &Layout) {
380 if (Symbol.isCommon() && Symbol.isExternal())
381 return Symbol.getCommonSize();
384 if (!Layout.getSymbolOffset(Symbol, Res))
390 /// This function takes a symbol data object from the assembler
391 /// and creates the associated COFF symbol staging object.
392 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
393 MCAssembler &Assembler,
394 const MCAsmLayout &Layout) {
395 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
396 SymbolMap[&Symbol] = coff_symbol;
398 if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) {
399 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
401 if (Symbol.isVariable()) {
402 const MCSymbolRefExpr *SymRef =
403 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
406 report_fatal_error("Weak externals may only alias symbols");
408 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
410 std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
411 COFFSymbol *WeakDefault = createSymbol(WeakName);
412 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
413 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
414 WeakDefault->Data.Type = 0;
415 WeakDefault->Data.Value = 0;
416 coff_symbol->Other = WeakDefault;
419 // Setup the Weak External auxiliary symbol.
420 coff_symbol->Aux.resize(1);
421 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
422 coff_symbol->Aux[0].AuxType = ATWeakExternal;
423 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
424 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
425 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
427 coff_symbol->MC = &Symbol;
429 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
430 coff_symbol->Data.Value = getSymbolValue(Symbol, Layout);
432 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol);
433 coff_symbol->Data.Type = SymbolCOFF.getType();
434 coff_symbol->Data.StorageClass = SymbolCOFF.getClass();
436 // If no storage class was specified in the streamer, define it here.
437 if (coff_symbol->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
438 bool IsExternal = Symbol.isExternal() ||
439 (!Symbol.getFragment() && !Symbol.isVariable());
441 coff_symbol->Data.StorageClass = IsExternal
442 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
443 : COFF::IMAGE_SYM_CLASS_STATIC;
447 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
449 if (Base->getFragment()) {
450 COFFSection *Sec = SectionMap[Base->getFragment()->getParent()];
452 if (coff_symbol->Section && coff_symbol->Section != Sec)
453 report_fatal_error("conflicting sections for symbol");
455 coff_symbol->Section = Sec;
459 coff_symbol->MC = &Symbol;
463 // Maximum offsets for different string table entry encodings.
464 static const unsigned Max6DecimalOffset = 999999;
465 static const unsigned Max7DecimalOffset = 9999999;
466 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
468 // Encode a string table entry offset in base 64, padded to 6 chars, and
469 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
470 // Buffer must be at least 8 bytes large. No terminating null appended.
471 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
472 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
473 "Illegal section name encoding for value");
475 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
476 "abcdefghijklmnopqrstuvwxyz"
482 char *Ptr = Buffer + 7;
483 for (unsigned i = 0; i < 6; ++i) {
484 unsigned Rem = Value % 64;
486 *(Ptr--) = Alphabet[Rem];
490 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
491 if (S.Name.size() > COFF::NameSize) {
492 uint64_t StringTableEntry = Strings.getOffset(S.Name);
494 if (StringTableEntry <= Max6DecimalOffset) {
495 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
496 } else if (StringTableEntry <= Max7DecimalOffset) {
497 // With seven digits, we have to skip the terminating null. Because
498 // sprintf always appends it, we use a larger temporary buffer.
500 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
501 std::memcpy(S.Header.Name, buffer, 8);
502 } else if (StringTableEntry <= MaxBase64Offset) {
503 // Starting with 10,000,000, offsets are encoded as base64.
504 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
506 report_fatal_error("COFF string table is greater than 64 GB.");
509 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
512 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
513 if (S.Name.size() > COFF::NameSize)
514 S.set_name_offset(Strings.getOffset(S.Name));
516 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
519 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
521 // This doesn't seem to be right. Strings referred to from the .data section
522 // need symbols so they can be linked to code in the .text section right?
524 // return Asm.isSymbolLinkerVisible(Symbol);
526 // Non-temporary labels should always be visible to the linker.
527 if (!Symbol.isTemporary())
530 // Temporary variable symbols are invisible.
531 if (Symbol.isVariable())
534 // Absolute temporary labels are never visible.
535 return !Symbol.isAbsolute();
538 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
539 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
543 //------------------------------------------------------------------------------
544 // entity writing methods
546 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
548 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
550 writeLE16(COFF::BigObjHeader::MinBigObjectVersion);
551 writeLE16(Header.Machine);
552 writeLE32(Header.TimeDateStamp);
553 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic)));
558 writeLE32(Header.NumberOfSections);
559 writeLE32(Header.PointerToSymbolTable);
560 writeLE32(Header.NumberOfSymbols);
562 writeLE16(Header.Machine);
563 writeLE16(static_cast<int16_t>(Header.NumberOfSections));
564 writeLE32(Header.TimeDateStamp);
565 writeLE32(Header.PointerToSymbolTable);
566 writeLE32(Header.NumberOfSymbols);
567 writeLE16(Header.SizeOfOptionalHeader);
568 writeLE16(Header.Characteristics);
572 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
573 writeBytes(StringRef(S.Data.Name, COFF::NameSize));
574 writeLE32(S.Data.Value);
576 writeLE32(S.Data.SectionNumber);
578 writeLE16(static_cast<int16_t>(S.Data.SectionNumber));
579 writeLE16(S.Data.Type);
580 write8(S.Data.StorageClass);
581 write8(S.Data.NumberOfAuxSymbols);
582 WriteAuxiliarySymbols(S.Aux);
585 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
586 const COFFSymbol::AuxiliarySymbols &S) {
587 for (COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
589 switch (i->AuxType) {
590 case ATFunctionDefinition:
591 writeLE32(i->Aux.FunctionDefinition.TagIndex);
592 writeLE32(i->Aux.FunctionDefinition.TotalSize);
593 writeLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
594 writeLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
595 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
597 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
599 case ATbfAndefSymbol:
600 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
601 writeLE16(i->Aux.bfAndefSymbol.Linenumber);
602 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
603 writeLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
604 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
606 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
609 writeLE32(i->Aux.WeakExternal.TagIndex);
610 writeLE32(i->Aux.WeakExternal.Characteristics);
611 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
613 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
617 StringRef(reinterpret_cast<const char *>(&i->Aux),
618 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
620 case ATSectionDefinition:
621 writeLE32(i->Aux.SectionDefinition.Length);
622 writeLE16(i->Aux.SectionDefinition.NumberOfRelocations);
623 writeLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
624 writeLE32(i->Aux.SectionDefinition.CheckSum);
625 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
626 write8(i->Aux.SectionDefinition.Selection);
627 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
628 writeLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
630 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
636 void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) {
637 writeBytes(StringRef(S.Name, COFF::NameSize));
639 writeLE32(S.VirtualSize);
640 writeLE32(S.VirtualAddress);
641 writeLE32(S.SizeOfRawData);
642 writeLE32(S.PointerToRawData);
643 writeLE32(S.PointerToRelocations);
644 writeLE32(S.PointerToLineNumbers);
645 writeLE16(S.NumberOfRelocations);
646 writeLE16(S.NumberOfLineNumbers);
647 writeLE32(S.Characteristics);
650 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
651 writeLE32(R.VirtualAddress);
652 writeLE32(R.SymbolTableIndex);
656 ////////////////////////////////////////////////////////////////////////////////
657 // MCObjectWriter interface implementations
659 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
660 const MCAsmLayout &Layout) {
661 // "Define" each section & symbol. This creates section & symbol
662 // entries in the staging area.
663 for (const auto &Section : Asm)
664 defineSection(static_cast<const MCSectionCOFF &>(Section));
666 for (const MCSymbol &Symbol : Asm.symbols())
667 if (ExportSymbol(Symbol, Asm))
668 DefineSymbol(Symbol, Asm, Layout);
671 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
672 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
673 bool InSet, bool IsPCRel) const {
674 // MS LINK expects to be able to replace all references to a function with a
675 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
676 // away any relocations to functions.
677 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
678 if ((Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
680 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
684 bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const {
685 if (!Sym.isExternal())
688 if (!Sym.isInSection())
691 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection());
692 if (!Sec.getCOMDATSymbol())
695 // It looks like for COFF it is invalid to replace a reference to a global
696 // in a comdat with a reference to a local.
697 // FIXME: Add a specification reference if available.
701 void WinCOFFObjectWriter::recordRelocation(
702 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
703 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
704 assert(Target.getSymA() && "Relocation must reference a symbol!");
706 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
707 const MCSymbol &A = Symbol;
708 if (!A.isRegistered())
709 Asm.getContext().reportFatalError(Fixup.getLoc(),
710 Twine("symbol '") + A.getName() +
711 "' can not be undefined");
713 MCSection *Section = Fragment->getParent();
715 // Mark this symbol as requiring an entry in the symbol table.
716 assert(SectionMap.find(Section) != SectionMap.end() &&
717 "Section must already have been defined in executePostLayoutBinding!");
718 assert(SymbolMap.find(&A) != SymbolMap.end() &&
719 "Symbol must already have been defined in executePostLayoutBinding!");
721 COFFSection *coff_section = SectionMap[Section];
722 COFFSymbol *coff_symbol = SymbolMap[&A];
723 const MCSymbolRefExpr *SymB = Target.getSymB();
724 bool CrossSection = false;
727 const MCSymbol *B = &SymB->getSymbol();
728 if (!B->getFragment())
729 Asm.getContext().reportFatalError(
731 Twine("symbol '") + B->getName() +
732 "' can not be undefined in a subtraction expression");
734 if (!A.getFragment())
735 Asm.getContext().reportFatalError(
737 Twine("symbol '") + Symbol.getName() +
738 "' can not be undefined in a subtraction expression");
740 CrossSection = &Symbol.getSection() != &B->getSection();
742 // Offset of the symbol in the section
743 int64_t OffsetOfB = Layout.getSymbolOffset(*B);
745 // In the case where we have SymbA and SymB, we just need to store the delta
746 // between the two symbols. Update FixedValue to account for the delta, and
747 // skip recording the relocation.
749 int64_t OffsetOfA = Layout.getSymbolOffset(A);
750 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
754 // Offset of the relocation in the section
755 int64_t OffsetOfRelocation =
756 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
758 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
760 FixedValue = Target.getConstant();
763 COFFRelocation Reloc;
765 Reloc.Data.SymbolTableIndex = 0;
766 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
768 // Turn relocations for temporary symbols into section relocations.
769 if (coff_symbol->MC->isTemporary() || CrossSection) {
770 Reloc.Symb = coff_symbol->Section->Symbol;
771 FixedValue += Layout.getFragmentOffset(coff_symbol->MC->getFragment()) +
772 coff_symbol->MC->getOffset();
774 Reloc.Symb = coff_symbol;
776 ++Reloc.Symb->Relocations;
778 Reloc.Data.VirtualAddress += Fixup.getOffset();
779 Reloc.Data.Type = TargetObjectWriter->getRelocType(
780 Target, Fixup, CrossSection, Asm.getBackend());
782 // FIXME: Can anyone explain what this does other than adjust for the size
784 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
785 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
786 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
787 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
790 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
791 switch (Reloc.Data.Type) {
792 case COFF::IMAGE_REL_ARM_ABSOLUTE:
793 case COFF::IMAGE_REL_ARM_ADDR32:
794 case COFF::IMAGE_REL_ARM_ADDR32NB:
795 case COFF::IMAGE_REL_ARM_TOKEN:
796 case COFF::IMAGE_REL_ARM_SECTION:
797 case COFF::IMAGE_REL_ARM_SECREL:
799 case COFF::IMAGE_REL_ARM_BRANCH11:
800 case COFF::IMAGE_REL_ARM_BLX11:
801 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
802 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
804 case COFF::IMAGE_REL_ARM_BRANCH24:
805 case COFF::IMAGE_REL_ARM_BLX24:
806 case COFF::IMAGE_REL_ARM_MOV32A:
807 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
808 // only used for ARM mode code, which is documented as being unsupported
809 // by Windows on ARM. Empirical proof indicates that masm is able to
810 // generate the relocations however the rest of the MSVC toolchain is
811 // unable to handle it.
812 llvm_unreachable("unsupported relocation");
814 case COFF::IMAGE_REL_ARM_MOV32T:
816 case COFF::IMAGE_REL_ARM_BRANCH20T:
817 case COFF::IMAGE_REL_ARM_BRANCH24T:
818 case COFF::IMAGE_REL_ARM_BLX23T:
819 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
820 // perform a 4 byte adjustment to the relocation. Relative branches are
821 // offset by 4 on ARM, however, because there is no RELA relocations, all
822 // branches are offset by 4.
823 FixedValue = FixedValue + 4;
828 if (TargetObjectWriter->recordRelocation(Fixup))
829 coff_section->Relocations.push_back(Reloc);
832 void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
833 const MCAsmLayout &Layout) {
834 size_t SectionsSize = Sections.size();
835 if (SectionsSize > static_cast<size_t>(INT32_MAX))
837 "PE COFF object files can't have more than 2147483647 sections");
839 // Assign symbol and section indexes and offsets.
840 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
842 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
844 // Assign section numbers.
846 for (const auto &Section : Sections) {
847 Section->Number = Number;
848 Section->Symbol->Data.SectionNumber = Number;
849 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
853 Header.NumberOfSections = NumberOfSections;
854 Header.NumberOfSymbols = 0;
856 for (const std::string &Name : Asm.getFileNames()) {
857 // round up to calculate the number of auxiliary symbols required
858 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
859 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
861 COFFSymbol *file = createSymbol(".file");
862 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
863 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
864 file->Aux.resize(Count);
867 unsigned Length = Name.size();
868 for (auto &Aux : file->Aux) {
869 Aux.AuxType = ATFile;
871 if (Length > SymbolSize) {
872 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
873 Length = Length - SymbolSize;
875 memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
876 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
880 Offset += SymbolSize;
884 for (auto &Symbol : Symbols) {
885 // Update section number & offset for symbols that have them.
887 Symbol->Data.SectionNumber = Symbol->Section->Number;
888 if (Symbol->should_keep()) {
889 Symbol->setIndex(Header.NumberOfSymbols++);
890 // Update auxiliary symbol info.
891 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
892 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
894 Symbol->setIndex(-1);
898 // Build string table.
899 for (const auto &S : Sections)
900 if (S->Name.size() > COFF::NameSize)
901 Strings.add(S->Name);
902 for (const auto &S : Symbols)
903 if (S->should_keep() && S->Name.size() > COFF::NameSize)
904 Strings.add(S->Name);
905 Strings.finalize(StringTableBuilder::WinCOFF);
908 for (const auto &S : Sections)
910 for (auto &S : Symbols)
911 if (S->should_keep())
914 // Fixup weak external references.
915 for (auto &Symbol : Symbols) {
917 assert(Symbol->getIndex() != -1);
918 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
919 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
920 "Symbol's aux symbol must be a Weak External!");
921 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
925 // Fixup associative COMDAT sections.
926 for (auto &Section : Sections) {
927 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
928 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
931 const MCSectionCOFF &MCSec = *Section->MCSection;
933 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
935 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
936 assert(COMDATSymbol);
937 COFFSection *Assoc = COMDATSymbol->Section;
940 Twine("Missing associated COMDAT section for section ") +
941 MCSec.getSectionName());
943 // Skip this section if the associated section is unused.
944 if (Assoc->Number == -1)
947 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
950 // Assign file offsets to COFF object file structures.
955 offset += COFF::Header32Size;
957 offset += COFF::Header16Size;
958 offset += COFF::SectionSize * Header.NumberOfSections;
960 for (const auto &Section : Asm) {
961 COFFSection *Sec = SectionMap[&Section];
963 if (Sec->Number == -1)
966 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
968 if (IsPhysicalSection(Sec)) {
969 // Align the section data to a four byte boundary.
970 offset = RoundUpToAlignment(offset, 4);
971 Sec->Header.PointerToRawData = offset;
973 offset += Sec->Header.SizeOfRawData;
976 if (Sec->Relocations.size() > 0) {
977 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
979 if (RelocationsOverflow) {
980 // Signal overflow by setting NumberOfRelocations to max value. Actual
981 // size is found in reloc #0. Microsoft tools understand this.
982 Sec->Header.NumberOfRelocations = 0xffff;
984 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
986 Sec->Header.PointerToRelocations = offset;
988 if (RelocationsOverflow) {
989 // Reloc #0 will contain actual count, so make room for it.
990 offset += COFF::RelocationSize;
993 offset += COFF::RelocationSize * Sec->Relocations.size();
995 for (auto &Relocation : Sec->Relocations) {
996 assert(Relocation.Symb->getIndex() != -1);
997 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
1001 assert(Sec->Symbol->Aux.size() == 1 &&
1002 "Section's symbol must have one aux!");
1003 AuxSymbol &Aux = Sec->Symbol->Aux[0];
1004 assert(Aux.AuxType == ATSectionDefinition &&
1005 "Section's symbol's aux symbol must be a Section Definition!");
1006 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
1007 Aux.Aux.SectionDefinition.NumberOfRelocations =
1008 Sec->Header.NumberOfRelocations;
1009 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
1010 Sec->Header.NumberOfLineNumbers;
1013 Header.PointerToSymbolTable = offset;
1015 // We want a deterministic output. It looks like GNU as also writes 0 in here.
1016 Header.TimeDateStamp = 0;
1018 // Write it all to disk...
1019 WriteFileHeader(Header);
1022 sections::iterator i, ie;
1023 MCAssembler::iterator j, je;
1025 for (auto &Section : Sections) {
1026 if (Section->Number != -1) {
1027 if (Section->Relocations.size() >= 0xffff)
1028 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1029 writeSectionHeader(Section->Header);
1033 SmallVector<char, 128> SectionContents;
1034 for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(),
1036 (i != ie) && (j != je); ++i, ++j) {
1038 if ((*i)->Number == -1)
1041 if ((*i)->Header.PointerToRawData != 0) {
1042 assert(getStream().tell() <= (*i)->Header.PointerToRawData &&
1043 "Section::PointerToRawData is insane!");
1045 unsigned SectionDataPadding =
1046 (*i)->Header.PointerToRawData - getStream().tell();
1047 assert(SectionDataPadding < 4 &&
1048 "Should only need at most three bytes of padding!");
1050 WriteZeros(SectionDataPadding);
1052 // Save the contents of the section to a temporary buffer, we need this
1053 // to CRC the data before we dump it into the object file.
1054 SectionContents.clear();
1055 raw_svector_ostream VecOS(SectionContents);
1056 raw_pwrite_stream &OldStream = getStream();
1057 // Redirect the output stream to our buffer.
1059 // Fill our buffer with the section data.
1060 Asm.writeSectionData(&*j, Layout);
1061 // Reset the stream back to what it was before.
1062 setStream(OldStream);
1064 // Calculate our CRC with an initial value of '0', this is not how
1065 // JamCRC is specified but it aligns with the expected output.
1066 JamCRC JC(/*Init=*/0x00000000U);
1067 JC.update(SectionContents);
1069 // Write the section contents to the object file.
1070 getStream() << SectionContents;
1072 // Update the section definition auxiliary symbol to record the CRC.
1073 COFFSection *Sec = SectionMap[&*j];
1074 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
1075 assert(AuxSyms.size() == 1 &&
1076 AuxSyms[0].AuxType == ATSectionDefinition);
1077 AuxSymbol &SecDef = AuxSyms[0];
1078 SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC();
1081 if ((*i)->Relocations.size() > 0) {
1082 assert(getStream().tell() == (*i)->Header.PointerToRelocations &&
1083 "Section::PointerToRelocations is insane!");
1085 if ((*i)->Relocations.size() >= 0xffff) {
1086 // In case of overflow, write actual relocation count as first
1087 // relocation. Including the synthetic reloc itself (+ 1).
1089 r.VirtualAddress = (*i)->Relocations.size() + 1;
1090 r.SymbolTableIndex = 0;
1095 for (const auto &Relocation : (*i)->Relocations)
1096 WriteRelocation(Relocation.Data);
1098 assert((*i)->Header.PointerToRelocations == 0 &&
1099 "Section::PointerToRelocations is insane!");
1103 assert(getStream().tell() == Header.PointerToSymbolTable &&
1104 "Header::PointerToSymbolTable is insane!");
1106 for (auto &Symbol : Symbols)
1107 if (Symbol->getIndex() != -1)
1108 WriteSymbol(*Symbol);
1110 getStream().write(Strings.data().data(), Strings.data().size());
1113 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1114 : Machine(Machine_) {}
1116 // Pin the vtable to this file.
1117 void MCWinCOFFObjectTargetWriter::anchor() {}
1119 //------------------------------------------------------------------------------
1120 // WinCOFFObjectWriter factory function
1123 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1124 raw_pwrite_stream &OS) {
1125 return new WinCOFFObjectWriter(MOTW, OS);