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/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/MC/StringTableBuilder.h"
30 #include "llvm/Support/COFF.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/Endian.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TimeValue.h"
39 #define DEBUG_TYPE "WinCOFFObjectWriter"
42 typedef SmallString<COFF::NameSize> name;
53 AuxiliaryType AuxType;
64 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
73 MCSymbolData const *MCData;
75 COFFSymbol(StringRef name);
76 void set_name_offset(uint32_t Offset);
78 bool should_keep() const;
81 // This class contains staging data for a COFF relocation entry.
82 struct COFFRelocation {
83 COFF::relocation Data;
86 COFFRelocation() : Symb(nullptr) {}
87 static size_t size() { return COFF::RelocationSize; }
90 typedef std::vector<COFFRelocation> relocations;
98 MCSectionData const *MCData;
100 relocations Relocations;
102 COFFSection(StringRef name);
103 static size_t size();
106 class WinCOFFObjectWriter : public MCObjectWriter {
109 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
110 typedef std::vector<std::unique_ptr<COFFSection>> sections;
112 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
113 typedef DenseMap<MCSection const *, COFFSection *> section_map;
115 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
117 // Root level file contents.
121 StringTableBuilder Strings;
123 // Maps used during object file creation.
124 section_map SectionMap;
125 symbol_map SymbolMap;
129 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
131 void reset() override {
132 memset(&Header, 0, sizeof(Header));
133 Header.Machine = TargetObjectWriter->getMachine();
139 MCObjectWriter::reset();
142 COFFSymbol *createSymbol(StringRef Name);
143 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
144 COFFSection *createSection(StringRef Name);
146 template <typename object_t, typename list_t>
147 object_t *createCOFFEntity(StringRef Name, list_t &List);
149 void DefineSection(MCSectionData const &SectionData);
150 void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
151 const MCAsmLayout &Layout);
153 void SetSymbolName(COFFSymbol &S);
154 void SetSectionName(COFFSection &S);
156 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm);
158 bool IsPhysicalSection(COFFSection *S);
160 // Entity writing methods.
162 void WriteFileHeader(const COFF::header &Header);
163 void WriteSymbol(const COFFSymbol &S);
164 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
165 void WriteSectionHeader(const COFF::section &S);
166 void WriteRelocation(const COFF::relocation &R);
168 // MCObjectWriter interface implementation.
170 void ExecutePostLayoutBinding(MCAssembler &Asm,
171 const MCAsmLayout &Layout) override;
173 bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
174 const MCSymbolData &DataA,
175 const MCSymbolData *DataB,
176 const MCFragment &FB, bool InSet,
177 bool IsPCRel) const override;
179 bool isWeak(const MCSymbolData &SD) const override;
181 void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
182 const MCFragment *Fragment, const MCFixup &Fixup,
183 MCValue Target, bool &IsPCRel,
184 uint64_t &FixedValue) override;
186 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
190 static inline void write_uint32_le(void *Data, uint32_t Value) {
191 support::endian::write<uint32_t, support::little, support::unaligned>(Data,
195 //------------------------------------------------------------------------------
196 // Symbol class implementation
198 COFFSymbol::COFFSymbol(StringRef name)
199 : Name(name.begin(), name.end())
204 memset(&Data, 0, sizeof(Data));
207 // In the case that the name does not fit within 8 bytes, the offset
208 // into the string table is stored in the last 4 bytes instead, leaving
209 // the first 4 bytes as 0.
210 void COFFSymbol::set_name_offset(uint32_t Offset) {
211 write_uint32_le(Data.Name + 0, 0);
212 write_uint32_le(Data.Name + 4, Offset);
215 /// logic to decide if the symbol should be reported in the symbol table
216 bool COFFSymbol::should_keep() const {
217 // no section means its external, keep it
221 // if it has relocations pointing at it, keep it
222 if (Relocations > 0) {
223 assert(Section->Number != -1 && "Sections with relocations must be real!");
227 // if the section its in is being droped, drop it
228 if (Section->Number == -1)
231 // if it is the section symbol, keep it
232 if (Section->Symbol == this)
235 // if its temporary, drop it
236 if (MCData && MCData->getSymbol().isTemporary())
239 // otherwise, keep it
243 //------------------------------------------------------------------------------
244 // Section class implementation
246 COFFSection::COFFSection(StringRef name)
250 memset(&Header, 0, sizeof(Header));
253 size_t COFFSection::size() {
254 return COFF::SectionSize;
257 //------------------------------------------------------------------------------
258 // WinCOFFObjectWriter class implementation
260 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
262 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
263 memset(&Header, 0, sizeof(Header));
265 Header.Machine = TargetObjectWriter->getMachine();
268 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
269 return createCOFFEntity<COFFSymbol>(Name, Symbols);
272 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
273 symbol_map::iterator i = SymbolMap.find(Symbol);
274 if (i != SymbolMap.end())
276 COFFSymbol *RetSymbol =
277 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
278 SymbolMap[Symbol] = RetSymbol;
282 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
283 return createCOFFEntity<COFFSection>(Name, Sections);
286 /// A template used to lookup or create a symbol/section, and initialize it if
288 template <typename object_t, typename list_t>
289 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
291 List.push_back(make_unique<object_t>(Name));
293 return List.back().get();
296 /// This function takes a section data object from the assembler
297 /// and creates the associated COFF section staging object.
298 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
299 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
300 && "Got non-COFF section in the COFF backend!");
301 // FIXME: Not sure how to verify this (at least in a debug build).
302 MCSectionCOFF const &Sec =
303 static_cast<MCSectionCOFF const &>(SectionData.getSection());
305 COFFSection *coff_section = createSection(Sec.getSectionName());
306 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
307 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
308 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
309 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
310 if (COMDATSymbol->Section)
311 report_fatal_error("two sections have the same comdat");
312 COMDATSymbol->Section = coff_section;
316 coff_section->Symbol = coff_symbol;
317 coff_symbol->Section = coff_section;
318 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
320 // In this case the auxiliary symbol is a Section Definition.
321 coff_symbol->Aux.resize(1);
322 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
323 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
324 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
326 coff_section->Header.Characteristics = Sec.getCharacteristics();
328 uint32_t &Characteristics = coff_section->Header.Characteristics;
329 switch (SectionData.getAlignment()) {
330 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
331 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
332 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
333 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
334 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
335 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
336 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
337 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
338 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
339 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
340 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
341 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
342 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
343 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
345 llvm_unreachable("unsupported section alignment");
348 // Bind internal COFF section to MC section.
349 coff_section->MCData = &SectionData;
350 SectionMap[&SectionData.getSection()] = coff_section;
353 static uint64_t getSymbolValue(const MCSymbolData &Data,
354 const MCAsmLayout &Layout) {
355 if (Data.isCommon() && Data.isExternal())
356 return Data.getCommonSize();
359 if (!Layout.getSymbolOffset(&Data, Res))
365 /// This function takes a symbol data object from the assembler
366 /// and creates the associated COFF symbol staging object.
367 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
368 MCAssembler &Assembler,
369 const MCAsmLayout &Layout) {
370 MCSymbol const &Symbol = SymbolData.getSymbol();
371 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
372 SymbolMap[&Symbol] = coff_symbol;
374 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
375 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
377 if (Symbol.isVariable()) {
378 const MCSymbolRefExpr *SymRef =
379 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
382 report_fatal_error("Weak externals may only alias symbols");
384 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
386 std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
387 COFFSymbol *WeakDefault = createSymbol(WeakName);
388 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
389 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
390 WeakDefault->Data.Type = 0;
391 WeakDefault->Data.Value = 0;
392 coff_symbol->Other = WeakDefault;
395 // Setup the Weak External auxiliary symbol.
396 coff_symbol->Aux.resize(1);
397 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
398 coff_symbol->Aux[0].AuxType = ATWeakExternal;
399 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
400 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
401 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
403 coff_symbol->MCData = &SymbolData;
405 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
406 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
407 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
409 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
410 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
412 // If no storage class was specified in the streamer, define it here.
413 if (coff_symbol->Data.StorageClass == 0) {
415 ResSymData.isExternal() ||
416 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable());
418 coff_symbol->Data.StorageClass = IsExternal
419 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
420 : COFF::IMAGE_SYM_CLASS_STATIC;
424 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
426 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
427 if (BaseData.getFragment()) {
429 SectionMap[&BaseData.getFragment()->getParent()->getSection()];
431 if (coff_symbol->Section && coff_symbol->Section != Sec)
432 report_fatal_error("conflicting sections for symbol");
434 coff_symbol->Section = Sec;
438 coff_symbol->MCData = &ResSymData;
442 // Maximum offsets for different string table entry encodings.
443 static const unsigned Max6DecimalOffset = 999999;
444 static const unsigned Max7DecimalOffset = 9999999;
445 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
447 // Encode a string table entry offset in base 64, padded to 6 chars, and
448 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
449 // Buffer must be at least 8 bytes large. No terminating null appended.
450 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
451 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
452 "Illegal section name encoding for value");
454 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
455 "abcdefghijklmnopqrstuvwxyz"
461 char* Ptr = Buffer + 7;
462 for (unsigned i = 0; i < 6; ++i) {
463 unsigned Rem = Value % 64;
465 *(Ptr--) = Alphabet[Rem];
469 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
470 if (S.Name.size() > COFF::NameSize) {
471 uint64_t StringTableEntry = Strings.getOffset(S.Name);
473 if (StringTableEntry <= Max6DecimalOffset) {
474 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
475 } else if (StringTableEntry <= Max7DecimalOffset) {
476 // With seven digits, we have to skip the terminating null. Because
477 // sprintf always appends it, we use a larger temporary buffer.
478 char buffer[9] = { };
479 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
480 std::memcpy(S.Header.Name, buffer, 8);
481 } else if (StringTableEntry <= MaxBase64Offset) {
482 // Starting with 10,000,000, offsets are encoded as base64.
483 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
485 report_fatal_error("COFF string table is greater than 64 GB.");
488 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
491 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
492 if (S.Name.size() > COFF::NameSize)
493 S.set_name_offset(Strings.getOffset(S.Name));
495 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
498 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
500 // This doesn't seem to be right. Strings referred to from the .data section
501 // need symbols so they can be linked to code in the .text section right?
503 // return Asm.isSymbolLinkerVisible(Symbol);
505 // Non-temporary labels should always be visible to the linker.
506 if (!Symbol.isTemporary())
509 // Absolute temporary labels are never visible.
510 if (!Symbol.isInSection())
513 // For now, all non-variable symbols are exported,
514 // the linker will sort the rest out for us.
515 return !Symbol.isVariable();
518 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
519 return (S->Header.Characteristics
520 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
523 //------------------------------------------------------------------------------
524 // entity writing methods
526 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
528 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
530 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion);
531 WriteLE16(Header.Machine);
532 WriteLE32(Header.TimeDateStamp);
533 for (uint8_t MagicChar : COFF::BigObjMagic)
539 WriteLE32(Header.NumberOfSections);
540 WriteLE32(Header.PointerToSymbolTable);
541 WriteLE32(Header.NumberOfSymbols);
543 WriteLE16(Header.Machine);
544 WriteLE16(static_cast<int16_t>(Header.NumberOfSections));
545 WriteLE32(Header.TimeDateStamp);
546 WriteLE32(Header.PointerToSymbolTable);
547 WriteLE32(Header.NumberOfSymbols);
548 WriteLE16(Header.SizeOfOptionalHeader);
549 WriteLE16(Header.Characteristics);
553 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
554 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
555 WriteLE32(S.Data.Value);
557 WriteLE32(S.Data.SectionNumber);
559 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber));
560 WriteLE16(S.Data.Type);
561 Write8(S.Data.StorageClass);
562 Write8(S.Data.NumberOfAuxSymbols);
563 WriteAuxiliarySymbols(S.Aux);
566 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
567 const COFFSymbol::AuxiliarySymbols &S) {
568 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
571 case ATFunctionDefinition:
572 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
573 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
574 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
575 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
576 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
578 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
580 case ATbfAndefSymbol:
581 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
582 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
583 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
584 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
585 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
587 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
590 WriteLE32(i->Aux.WeakExternal.TagIndex);
591 WriteLE32(i->Aux.WeakExternal.Characteristics);
592 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
594 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
598 StringRef(reinterpret_cast<const char *>(&i->Aux),
599 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
601 case ATSectionDefinition:
602 WriteLE32(i->Aux.SectionDefinition.Length);
603 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
604 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
605 WriteLE32(i->Aux.SectionDefinition.CheckSum);
606 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
607 Write8(i->Aux.SectionDefinition.Selection);
608 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
609 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
611 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
617 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
618 WriteBytes(StringRef(S.Name, COFF::NameSize));
620 WriteLE32(S.VirtualSize);
621 WriteLE32(S.VirtualAddress);
622 WriteLE32(S.SizeOfRawData);
623 WriteLE32(S.PointerToRawData);
624 WriteLE32(S.PointerToRelocations);
625 WriteLE32(S.PointerToLineNumbers);
626 WriteLE16(S.NumberOfRelocations);
627 WriteLE16(S.NumberOfLineNumbers);
628 WriteLE32(S.Characteristics);
631 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
632 WriteLE32(R.VirtualAddress);
633 WriteLE32(R.SymbolTableIndex);
637 ////////////////////////////////////////////////////////////////////////////////
638 // MCObjectWriter interface implementations
640 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
641 const MCAsmLayout &Layout) {
642 // "Define" each section & symbol. This creates section & symbol
643 // entries in the staging area.
644 for (const auto &Section : Asm)
645 DefineSection(Section);
647 for (MCSymbolData &SD : Asm.symbols())
648 if (ExportSymbol(SD.getSymbol(), Asm))
649 DefineSymbol(SD, Asm, Layout);
652 bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
653 const MCAssembler &Asm, const MCSymbolData &DataA,
654 const MCSymbolData *DataB, const MCFragment &FB, bool InSet,
655 bool IsPCRel) const {
656 // MS LINK expects to be able to replace all references to a function with a
657 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
658 // away any relocations to functions.
659 if ((((DataA.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift) >>
660 COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
662 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
663 Asm, DataA, DataB, FB, InSet, IsPCRel);
666 bool WinCOFFObjectWriter::isWeak(const MCSymbolData &SD) const {
667 // FIXME: this is for PR23025. Write a good description on
668 // why this is needed.
669 return SD.isExternal();
672 void WinCOFFObjectWriter::RecordRelocation(
673 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
674 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
675 assert(Target.getSymA() && "Relocation must reference a symbol!");
677 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
678 const MCSymbol &A = Symbol.AliasedSymbol();
679 if (!Asm.hasSymbolData(A))
680 Asm.getContext().FatalError(
682 Twine("symbol '") + A.getName() + "' can not be undefined");
684 const MCSymbolData &A_SD = Asm.getSymbolData(A);
686 MCSectionData const *SectionData = Fragment->getParent();
688 // Mark this symbol as requiring an entry in the symbol table.
689 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
690 "Section must already have been defined in ExecutePostLayoutBinding!");
691 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
692 "Symbol must already have been defined in ExecutePostLayoutBinding!");
694 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
695 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
696 const MCSymbolRefExpr *SymB = Target.getSymB();
697 bool CrossSection = false;
700 const MCSymbol *B = &SymB->getSymbol();
701 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
702 if (!B_SD.getFragment())
703 Asm.getContext().FatalError(
705 Twine("symbol '") + B->getName() +
706 "' can not be undefined in a subtraction expression");
708 if (!A_SD.getFragment())
709 Asm.getContext().FatalError(
711 Twine("symbol '") + Symbol.getName() +
712 "' can not be undefined in a subtraction expression");
714 CrossSection = &Symbol.getSection() != &B->getSection();
716 // Offset of the symbol in the section
717 int64_t OffsetOfB = Layout.getSymbolOffset(&B_SD);
719 // In the case where we have SymbA and SymB, we just need to store the delta
720 // between the two symbols. Update FixedValue to account for the delta, and
721 // skip recording the relocation.
723 int64_t OffsetOfA = Layout.getSymbolOffset(&A_SD);
724 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
728 // Offset of the relocation in the section
729 int64_t OffsetOfRelocation =
730 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
732 FixedValue = OffsetOfRelocation - OffsetOfB;
734 FixedValue = Target.getConstant();
737 COFFRelocation Reloc;
739 Reloc.Data.SymbolTableIndex = 0;
740 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
742 // Turn relocations for temporary symbols into section relocations.
743 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
744 Reloc.Symb = coff_symbol->Section->Symbol;
745 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->getFragment()) +
746 coff_symbol->MCData->getOffset();
748 Reloc.Symb = coff_symbol;
750 ++Reloc.Symb->Relocations;
752 Reloc.Data.VirtualAddress += Fixup.getOffset();
754 TargetObjectWriter->getRelocType(Target, Fixup, CrossSection,
757 // FIXME: Can anyone explain what this does other than adjust for the size
759 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
760 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
761 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
762 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
765 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
766 switch (Reloc.Data.Type) {
767 case COFF::IMAGE_REL_ARM_ABSOLUTE:
768 case COFF::IMAGE_REL_ARM_ADDR32:
769 case COFF::IMAGE_REL_ARM_ADDR32NB:
770 case COFF::IMAGE_REL_ARM_TOKEN:
771 case COFF::IMAGE_REL_ARM_SECTION:
772 case COFF::IMAGE_REL_ARM_SECREL:
774 case COFF::IMAGE_REL_ARM_BRANCH11:
775 case COFF::IMAGE_REL_ARM_BLX11:
776 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
777 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
779 case COFF::IMAGE_REL_ARM_BRANCH24:
780 case COFF::IMAGE_REL_ARM_BLX24:
781 case COFF::IMAGE_REL_ARM_MOV32A:
782 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
783 // only used for ARM mode code, which is documented as being unsupported
784 // by Windows on ARM. Empirical proof indicates that masm is able to
785 // generate the relocations however the rest of the MSVC toolchain is
786 // unable to handle it.
787 llvm_unreachable("unsupported relocation");
789 case COFF::IMAGE_REL_ARM_MOV32T:
791 case COFF::IMAGE_REL_ARM_BRANCH20T:
792 case COFF::IMAGE_REL_ARM_BRANCH24T:
793 case COFF::IMAGE_REL_ARM_BLX23T:
794 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
795 // perform a 4 byte adjustment to the relocation. Relative branches are
796 // offset by 4 on ARM, however, because there is no RELA relocations, all
797 // branches are offset by 4.
798 FixedValue = FixedValue + 4;
803 if (TargetObjectWriter->recordRelocation(Fixup))
804 coff_section->Relocations.push_back(Reloc);
807 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
808 const MCAsmLayout &Layout) {
809 size_t SectionsSize = Sections.size();
810 if (SectionsSize > static_cast<size_t>(INT32_MAX))
812 "PE COFF object files can't have more than 2147483647 sections");
814 // Assign symbol and section indexes and offsets.
815 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
817 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
819 DenseMap<COFFSection *, int32_t> SectionIndices(
820 NextPowerOf2(NumberOfSections));
822 // Assign section numbers.
824 for (const auto &Section : Sections) {
825 SectionIndices[Section.get()] = Number;
826 Section->Number = Number;
827 Section->Symbol->Data.SectionNumber = Number;
828 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
832 Header.NumberOfSections = NumberOfSections;
833 Header.NumberOfSymbols = 0;
835 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
837 // round up to calculate the number of auxiliary symbols required
838 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
839 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize;
841 COFFSymbol *file = createSymbol(".file");
842 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
843 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
844 file->Aux.resize(Count);
847 unsigned Length = FI->size();
848 for (auto &Aux : file->Aux) {
849 Aux.AuxType = ATFile;
851 if (Length > SymbolSize) {
852 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize);
853 Length = Length - SymbolSize;
855 memcpy(&Aux.Aux, FI->c_str() + Offset, Length);
856 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
860 Offset += SymbolSize;
864 for (auto &Symbol : Symbols) {
865 // Update section number & offset for symbols that have them.
867 Symbol->Data.SectionNumber = Symbol->Section->Number;
868 if (Symbol->should_keep()) {
869 Symbol->Index = Header.NumberOfSymbols++;
870 // Update auxiliary symbol info.
871 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
872 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
877 // Build string table.
878 for (const auto &S : Sections)
879 if (S->Name.size() > COFF::NameSize)
880 Strings.add(S->Name);
881 for (const auto &S : Symbols)
882 if (S->should_keep() && S->Name.size() > COFF::NameSize)
883 Strings.add(S->Name);
884 Strings.finalize(StringTableBuilder::WinCOFF);
887 for (const auto &S : Sections)
889 for (auto &S : Symbols)
890 if (S->should_keep())
893 // Fixup weak external references.
894 for (auto &Symbol : Symbols) {
896 assert(Symbol->Index != -1);
897 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
898 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
899 "Symbol's aux symbol must be a Weak External!");
900 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
904 // Fixup associative COMDAT sections.
905 for (auto &Section : Sections) {
906 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
907 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
910 const MCSectionCOFF &MCSec =
911 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
913 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
915 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
916 assert(COMDATSymbol);
917 COFFSection *Assoc = COMDATSymbol->Section;
920 Twine("Missing associated COMDAT section for section ") +
921 MCSec.getSectionName());
923 // Skip this section if the associated section is unused.
924 if (Assoc->Number == -1)
927 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
931 // Assign file offsets to COFF object file structures.
936 offset += COFF::Header32Size;
938 offset += COFF::Header16Size;
939 offset += COFF::SectionSize * Header.NumberOfSections;
941 for (const auto &Section : Asm) {
942 COFFSection *Sec = SectionMap[&Section.getSection()];
944 if (Sec->Number == -1)
947 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
949 if (IsPhysicalSection(Sec)) {
950 // Align the section data to a four byte boundary.
951 offset = RoundUpToAlignment(offset, 4);
952 Sec->Header.PointerToRawData = offset;
954 offset += Sec->Header.SizeOfRawData;
957 if (Sec->Relocations.size() > 0) {
958 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
960 if (RelocationsOverflow) {
961 // Signal overflow by setting NumberOfRelocations to max value. Actual
962 // size is found in reloc #0. Microsoft tools understand this.
963 Sec->Header.NumberOfRelocations = 0xffff;
965 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
967 Sec->Header.PointerToRelocations = offset;
969 if (RelocationsOverflow) {
970 // Reloc #0 will contain actual count, so make room for it.
971 offset += COFF::RelocationSize;
974 offset += COFF::RelocationSize * Sec->Relocations.size();
976 for (auto &Relocation : Sec->Relocations) {
977 assert(Relocation.Symb->Index != -1);
978 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
982 assert(Sec->Symbol->Aux.size() == 1 &&
983 "Section's symbol must have one aux!");
984 AuxSymbol &Aux = Sec->Symbol->Aux[0];
985 assert(Aux.AuxType == ATSectionDefinition &&
986 "Section's symbol's aux symbol must be a Section Definition!");
987 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
988 Aux.Aux.SectionDefinition.NumberOfRelocations =
989 Sec->Header.NumberOfRelocations;
990 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
991 Sec->Header.NumberOfLineNumbers;
994 Header.PointerToSymbolTable = offset;
996 // We want a deterministic output. It looks like GNU as also writes 0 in here.
997 Header.TimeDateStamp = 0;
999 // Write it all to disk...
1000 WriteFileHeader(Header);
1003 sections::iterator i, ie;
1004 MCAssembler::const_iterator j, je;
1006 for (auto &Section : Sections) {
1007 if (Section->Number != -1) {
1008 if (Section->Relocations.size() >= 0xffff)
1009 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1010 WriteSectionHeader(Section->Header);
1014 for (i = Sections.begin(), ie = Sections.end(),
1015 j = Asm.begin(), je = Asm.end();
1016 (i != ie) && (j != je); ++i, ++j) {
1018 if ((*i)->Number == -1)
1021 if ((*i)->Header.PointerToRawData != 0) {
1022 assert(OS.tell() <= (*i)->Header.PointerToRawData &&
1023 "Section::PointerToRawData is insane!");
1025 unsigned SectionDataPadding = (*i)->Header.PointerToRawData - OS.tell();
1026 assert(SectionDataPadding < 4 &&
1027 "Should only need at most three bytes of padding!");
1029 WriteZeros(SectionDataPadding);
1031 Asm.writeSectionData(j, Layout);
1034 if ((*i)->Relocations.size() > 0) {
1035 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
1036 "Section::PointerToRelocations is insane!");
1038 if ((*i)->Relocations.size() >= 0xffff) {
1039 // In case of overflow, write actual relocation count as first
1040 // relocation. Including the synthetic reloc itself (+ 1).
1042 r.VirtualAddress = (*i)->Relocations.size() + 1;
1043 r.SymbolTableIndex = 0;
1048 for (const auto &Relocation : (*i)->Relocations)
1049 WriteRelocation(Relocation.Data);
1051 assert((*i)->Header.PointerToRelocations == 0 &&
1052 "Section::PointerToRelocations is insane!");
1056 assert(OS.tell() == Header.PointerToSymbolTable &&
1057 "Header::PointerToSymbolTable is insane!");
1059 for (auto &Symbol : Symbols)
1060 if (Symbol->Index != -1)
1061 WriteSymbol(*Symbol);
1063 OS.write(Strings.data().data(), Strings.data().size());
1066 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1070 // Pin the vtable to this file.
1071 void MCWinCOFFObjectTargetWriter::anchor() {}
1073 //------------------------------------------------------------------------------
1074 // WinCOFFObjectWriter factory function
1077 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1079 return new WinCOFFObjectWriter(MOTW, OS);