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 MCFragment &FB, bool InSet,
176 bool IsPCRel) const override;
178 void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
179 const MCFragment *Fragment, const MCFixup &Fixup,
180 MCValue Target, bool &IsPCRel,
181 uint64_t &FixedValue) override;
183 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
187 static inline void write_uint32_le(void *Data, uint32_t Value) {
188 support::endian::write<uint32_t, support::little, support::unaligned>(Data,
192 //------------------------------------------------------------------------------
193 // Symbol class implementation
195 COFFSymbol::COFFSymbol(StringRef name)
196 : Name(name.begin(), name.end())
201 memset(&Data, 0, sizeof(Data));
204 // In the case that the name does not fit within 8 bytes, the offset
205 // into the string table is stored in the last 4 bytes instead, leaving
206 // the first 4 bytes as 0.
207 void COFFSymbol::set_name_offset(uint32_t Offset) {
208 write_uint32_le(Data.Name + 0, 0);
209 write_uint32_le(Data.Name + 4, Offset);
212 /// logic to decide if the symbol should be reported in the symbol table
213 bool COFFSymbol::should_keep() const {
214 // no section means its external, keep it
218 // if it has relocations pointing at it, keep it
219 if (Relocations > 0) {
220 assert(Section->Number != -1 && "Sections with relocations must be real!");
224 // if the section its in is being droped, drop it
225 if (Section->Number == -1)
228 // if it is the section symbol, keep it
229 if (Section->Symbol == this)
232 // if its temporary, drop it
233 if (MCData && MCData->getSymbol().isTemporary())
236 // otherwise, keep it
240 //------------------------------------------------------------------------------
241 // Section class implementation
243 COFFSection::COFFSection(StringRef name)
247 memset(&Header, 0, sizeof(Header));
250 size_t COFFSection::size() {
251 return COFF::SectionSize;
254 //------------------------------------------------------------------------------
255 // WinCOFFObjectWriter class implementation
257 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
259 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
260 memset(&Header, 0, sizeof(Header));
262 Header.Machine = TargetObjectWriter->getMachine();
265 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
266 return createCOFFEntity<COFFSymbol>(Name, Symbols);
269 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
270 symbol_map::iterator i = SymbolMap.find(Symbol);
271 if (i != SymbolMap.end())
273 COFFSymbol *RetSymbol =
274 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
275 SymbolMap[Symbol] = RetSymbol;
279 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
280 return createCOFFEntity<COFFSection>(Name, Sections);
283 /// A template used to lookup or create a symbol/section, and initialize it if
285 template <typename object_t, typename list_t>
286 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
288 List.push_back(make_unique<object_t>(Name));
290 return List.back().get();
293 /// This function takes a section data object from the assembler
294 /// and creates the associated COFF section staging object.
295 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
296 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
297 && "Got non-COFF section in the COFF backend!");
298 // FIXME: Not sure how to verify this (at least in a debug build).
299 MCSectionCOFF const &Sec =
300 static_cast<MCSectionCOFF const &>(SectionData.getSection());
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 (SectionData.getAlignment()) {
327 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
328 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
329 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
330 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
331 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
332 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
333 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
334 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
335 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
336 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
337 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
338 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
339 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
340 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
342 llvm_unreachable("unsupported section alignment");
345 // Bind internal COFF section to MC section.
346 coff_section->MCData = &SectionData;
347 SectionMap[&SectionData.getSection()] = coff_section;
350 static uint64_t getSymbolValue(const MCSymbolData &Data,
351 const MCAsmLayout &Layout) {
352 if (Data.isCommon() && Data.isExternal())
353 return Data.getCommonSize();
356 if (!Layout.getSymbolOffset(&Data, Res))
362 /// This function takes a symbol data object from the assembler
363 /// and creates the associated COFF symbol staging object.
364 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
365 MCAssembler &Assembler,
366 const MCAsmLayout &Layout) {
367 MCSymbol const &Symbol = SymbolData.getSymbol();
368 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
369 SymbolMap[&Symbol] = coff_symbol;
371 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
372 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
374 if (Symbol.isVariable()) {
375 const MCSymbolRefExpr *SymRef =
376 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
379 report_fatal_error("Weak externals may only alias symbols");
381 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
383 std::string WeakName = std::string(".weak.")
384 + Symbol.getName().str()
386 COFFSymbol *WeakDefault = createSymbol(WeakName);
387 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
388 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
389 WeakDefault->Data.Type = 0;
390 WeakDefault->Data.Value = 0;
391 coff_symbol->Other = WeakDefault;
394 // Setup the Weak External auxiliary symbol.
395 coff_symbol->Aux.resize(1);
396 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
397 coff_symbol->Aux[0].AuxType = ATWeakExternal;
398 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
399 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
400 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
402 coff_symbol->MCData = &SymbolData;
404 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
405 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
406 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
408 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
409 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
411 // If no storage class was specified in the streamer, define it here.
412 if (coff_symbol->Data.StorageClass == 0) {
414 ResSymData.isExternal() ||
415 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable());
417 coff_symbol->Data.StorageClass = IsExternal
418 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
419 : COFF::IMAGE_SYM_CLASS_STATIC;
423 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
425 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
426 if (BaseData.getFragment()) {
428 SectionMap[&BaseData.getFragment()->getParent()->getSection()];
430 if (coff_symbol->Section && coff_symbol->Section != Sec)
431 report_fatal_error("conflicting sections for symbol");
433 coff_symbol->Section = Sec;
437 coff_symbol->MCData = &ResSymData;
441 // Maximum offsets for different string table entry encodings.
442 static const unsigned Max6DecimalOffset = 999999;
443 static const unsigned Max7DecimalOffset = 9999999;
444 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
446 // Encode a string table entry offset in base 64, padded to 6 chars, and
447 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
448 // Buffer must be at least 8 bytes large. No terminating null appended.
449 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
450 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
451 "Illegal section name encoding for value");
453 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
454 "abcdefghijklmnopqrstuvwxyz"
460 char* Ptr = Buffer + 7;
461 for (unsigned i = 0; i < 6; ++i) {
462 unsigned Rem = Value % 64;
464 *(Ptr--) = Alphabet[Rem];
468 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
469 if (S.Name.size() > COFF::NameSize) {
470 uint64_t StringTableEntry = Strings.getOffset(S.Name);
472 if (StringTableEntry <= Max6DecimalOffset) {
473 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
474 } else if (StringTableEntry <= Max7DecimalOffset) {
475 // With seven digits, we have to skip the terminating null. Because
476 // sprintf always appends it, we use a larger temporary buffer.
477 char buffer[9] = { };
478 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
479 std::memcpy(S.Header.Name, buffer, 8);
480 } else if (StringTableEntry <= MaxBase64Offset) {
481 // Starting with 10,000,000, offsets are encoded as base64.
482 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
484 report_fatal_error("COFF string table is greater than 64 GB.");
487 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
490 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
491 if (S.Name.size() > COFF::NameSize)
492 S.set_name_offset(Strings.getOffset(S.Name));
494 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
497 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
499 // This doesn't seem to be right. Strings referred to from the .data section
500 // need symbols so they can be linked to code in the .text section right?
502 // return Asm.isSymbolLinkerVisible(Symbol);
504 // Non-temporary labels should always be visible to the linker.
505 if (!Symbol.isTemporary())
508 // Absolute temporary labels are never visible.
509 if (!Symbol.isInSection())
512 // For now, all non-variable symbols are exported,
513 // the linker will sort the rest out for us.
514 return !Symbol.isVariable();
517 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
518 return (S->Header.Characteristics
519 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
522 //------------------------------------------------------------------------------
523 // entity writing methods
525 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
527 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
529 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion);
530 WriteLE16(Header.Machine);
531 WriteLE32(Header.TimeDateStamp);
532 for (uint8_t MagicChar : COFF::BigObjMagic)
538 WriteLE32(Header.NumberOfSections);
539 WriteLE32(Header.PointerToSymbolTable);
540 WriteLE32(Header.NumberOfSymbols);
542 WriteLE16(Header.Machine);
543 WriteLE16(static_cast<int16_t>(Header.NumberOfSections));
544 WriteLE32(Header.TimeDateStamp);
545 WriteLE32(Header.PointerToSymbolTable);
546 WriteLE32(Header.NumberOfSymbols);
547 WriteLE16(Header.SizeOfOptionalHeader);
548 WriteLE16(Header.Characteristics);
552 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
553 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
554 WriteLE32(S.Data.Value);
556 WriteLE32(S.Data.SectionNumber);
558 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber));
559 WriteLE16(S.Data.Type);
560 Write8(S.Data.StorageClass);
561 Write8(S.Data.NumberOfAuxSymbols);
562 WriteAuxiliarySymbols(S.Aux);
565 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
566 const COFFSymbol::AuxiliarySymbols &S) {
567 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
570 case ATFunctionDefinition:
571 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
572 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
573 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
574 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
575 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
577 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
579 case ATbfAndefSymbol:
580 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
581 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
582 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
583 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
584 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
586 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
589 WriteLE32(i->Aux.WeakExternal.TagIndex);
590 WriteLE32(i->Aux.WeakExternal.Characteristics);
591 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
593 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
597 StringRef(reinterpret_cast<const char *>(&i->Aux),
598 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
600 case ATSectionDefinition:
601 WriteLE32(i->Aux.SectionDefinition.Length);
602 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
603 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
604 WriteLE32(i->Aux.SectionDefinition.CheckSum);
605 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
606 Write8(i->Aux.SectionDefinition.Selection);
607 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
608 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
610 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
616 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
617 WriteBytes(StringRef(S.Name, COFF::NameSize));
619 WriteLE32(S.VirtualSize);
620 WriteLE32(S.VirtualAddress);
621 WriteLE32(S.SizeOfRawData);
622 WriteLE32(S.PointerToRawData);
623 WriteLE32(S.PointerToRelocations);
624 WriteLE32(S.PointerToLineNumbers);
625 WriteLE16(S.NumberOfRelocations);
626 WriteLE16(S.NumberOfLineNumbers);
627 WriteLE32(S.Characteristics);
630 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
631 WriteLE32(R.VirtualAddress);
632 WriteLE32(R.SymbolTableIndex);
636 ////////////////////////////////////////////////////////////////////////////////
637 // MCObjectWriter interface implementations
639 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
640 const MCAsmLayout &Layout) {
641 // "Define" each section & symbol. This creates section & symbol
642 // entries in the staging area.
643 for (const auto &Section : Asm)
644 DefineSection(Section);
646 for (MCSymbolData &SD : Asm.symbols())
647 if (ExportSymbol(SD.getSymbol(), Asm))
648 DefineSymbol(SD, Asm, Layout);
651 bool WinCOFFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
652 const MCAssembler &Asm, const MCSymbolData &DataA, const MCFragment &FB,
653 bool InSet, bool IsPCRel) const {
654 // MS LINK expects to be able to replace all references to a function with a
655 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
656 // away any relocations to functions.
657 if ((((DataA.getFlags() & COFF::SF_TypeMask) >> COFF::SF_TypeShift) >>
658 COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
660 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA, FB,
664 void WinCOFFObjectWriter::RecordRelocation(
665 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
666 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
667 assert(Target.getSymA() && "Relocation must reference a symbol!");
669 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
670 const MCSymbol &A = Symbol.AliasedSymbol();
671 if (!Asm.hasSymbolData(A))
672 Asm.getContext().FatalError(
674 Twine("symbol '") + A.getName() + "' can not be undefined");
676 const MCSymbolData &A_SD = Asm.getSymbolData(A);
678 MCSectionData const *SectionData = Fragment->getParent();
680 // Mark this symbol as requiring an entry in the symbol table.
681 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
682 "Section must already have been defined in ExecutePostLayoutBinding!");
683 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
684 "Symbol must already have been defined in ExecutePostLayoutBinding!");
686 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
687 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
688 const MCSymbolRefExpr *SymB = Target.getSymB();
689 bool CrossSection = false;
692 const MCSymbol *B = &SymB->getSymbol();
693 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
694 if (!B_SD.getFragment())
695 Asm.getContext().FatalError(
697 Twine("symbol '") + B->getName() +
698 "' can not be undefined in a subtraction expression");
700 if (!A_SD.getFragment())
701 Asm.getContext().FatalError(
703 Twine("symbol '") + Symbol.getName() +
704 "' can not be undefined in a subtraction expression");
706 CrossSection = &Symbol.getSection() != &B->getSection();
708 // Offset of the symbol in the section
709 int64_t OffsetOfB = Layout.getSymbolOffset(&B_SD);
711 // In the case where we have SymbA and SymB, we just need to store the delta
712 // between the two symbols. Update FixedValue to account for the delta, and
713 // skip recording the relocation.
715 int64_t OffsetOfA = Layout.getSymbolOffset(&A_SD);
716 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
720 // Offset of the relocation in the section
721 int64_t OffsetOfRelocation =
722 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
724 FixedValue = OffsetOfRelocation - OffsetOfB;
726 FixedValue = Target.getConstant();
729 COFFRelocation Reloc;
731 Reloc.Data.SymbolTableIndex = 0;
732 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
734 // Turn relocations for temporary symbols into section relocations.
735 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
736 Reloc.Symb = coff_symbol->Section->Symbol;
737 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->getFragment()) +
738 coff_symbol->MCData->getOffset();
740 Reloc.Symb = coff_symbol;
742 ++Reloc.Symb->Relocations;
744 Reloc.Data.VirtualAddress += Fixup.getOffset();
746 TargetObjectWriter->getRelocType(Target, Fixup, CrossSection,
749 // FIXME: Can anyone explain what this does other than adjust for the size
751 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
752 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
753 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
754 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
757 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
758 switch (Reloc.Data.Type) {
759 case COFF::IMAGE_REL_ARM_ABSOLUTE:
760 case COFF::IMAGE_REL_ARM_ADDR32:
761 case COFF::IMAGE_REL_ARM_ADDR32NB:
762 case COFF::IMAGE_REL_ARM_TOKEN:
763 case COFF::IMAGE_REL_ARM_SECTION:
764 case COFF::IMAGE_REL_ARM_SECREL:
766 case COFF::IMAGE_REL_ARM_BRANCH11:
767 case COFF::IMAGE_REL_ARM_BLX11:
768 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
769 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
771 case COFF::IMAGE_REL_ARM_BRANCH24:
772 case COFF::IMAGE_REL_ARM_BLX24:
773 case COFF::IMAGE_REL_ARM_MOV32A:
774 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
775 // only used for ARM mode code, which is documented as being unsupported
776 // by Windows on ARM. Empirical proof indicates that masm is able to
777 // generate the relocations however the rest of the MSVC toolchain is
778 // unable to handle it.
779 llvm_unreachable("unsupported relocation");
781 case COFF::IMAGE_REL_ARM_MOV32T:
783 case COFF::IMAGE_REL_ARM_BRANCH20T:
784 case COFF::IMAGE_REL_ARM_BRANCH24T:
785 case COFF::IMAGE_REL_ARM_BLX23T:
786 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
787 // perform a 4 byte adjustment to the relocation. Relative branches are
788 // offset by 4 on ARM, however, because there is no RELA relocations, all
789 // branches are offset by 4.
790 FixedValue = FixedValue + 4;
795 if (TargetObjectWriter->recordRelocation(Fixup))
796 coff_section->Relocations.push_back(Reloc);
799 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
800 const MCAsmLayout &Layout) {
801 size_t SectionsSize = Sections.size();
802 if (SectionsSize > static_cast<size_t>(INT32_MAX))
804 "PE COFF object files can't have more than 2147483647 sections");
806 // Assign symbol and section indexes and offsets.
807 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
809 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
811 DenseMap<COFFSection *, int32_t> SectionIndices(
812 NextPowerOf2(NumberOfSections));
814 // Assign section numbers.
816 for (const auto &Section : Sections) {
817 SectionIndices[Section.get()] = Number;
818 Section->Number = Number;
819 Section->Symbol->Data.SectionNumber = Number;
820 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
824 Header.NumberOfSections = NumberOfSections;
825 Header.NumberOfSymbols = 0;
827 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
829 // round up to calculate the number of auxiliary symbols required
830 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
831 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize;
833 COFFSymbol *file = createSymbol(".file");
834 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
835 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
836 file->Aux.resize(Count);
839 unsigned Length = FI->size();
840 for (auto &Aux : file->Aux) {
841 Aux.AuxType = ATFile;
843 if (Length > SymbolSize) {
844 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize);
845 Length = Length - SymbolSize;
847 memcpy(&Aux.Aux, FI->c_str() + Offset, Length);
848 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
852 Offset += SymbolSize;
856 for (auto &Symbol : Symbols) {
857 // Update section number & offset for symbols that have them.
859 Symbol->Data.SectionNumber = Symbol->Section->Number;
860 if (Symbol->should_keep()) {
861 Symbol->Index = Header.NumberOfSymbols++;
862 // Update auxiliary symbol info.
863 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
864 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
869 // Build string table.
870 for (const auto &S : Sections)
871 if (S->Name.size() > COFF::NameSize)
872 Strings.add(S->Name);
873 for (const auto &S : Symbols)
874 if (S->should_keep() && S->Name.size() > COFF::NameSize)
875 Strings.add(S->Name);
876 Strings.finalize(StringTableBuilder::WinCOFF);
879 for (const auto &S : Sections)
881 for (auto &S : Symbols)
882 if (S->should_keep())
885 // Fixup weak external references.
886 for (auto &Symbol : Symbols) {
888 assert(Symbol->Index != -1);
889 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
890 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
891 "Symbol's aux symbol must be a Weak External!");
892 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
896 // Fixup associative COMDAT sections.
897 for (auto &Section : Sections) {
898 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
899 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
902 const MCSectionCOFF &MCSec =
903 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
905 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
907 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
908 assert(COMDATSymbol);
909 COFFSection *Assoc = COMDATSymbol->Section;
912 Twine("Missing associated COMDAT section for section ") +
913 MCSec.getSectionName());
915 // Skip this section if the associated section is unused.
916 if (Assoc->Number == -1)
919 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
923 // Assign file offsets to COFF object file structures.
928 offset += COFF::Header32Size;
930 offset += COFF::Header16Size;
931 offset += COFF::SectionSize * Header.NumberOfSections;
933 for (const auto &Section : Asm) {
934 COFFSection *Sec = SectionMap[&Section.getSection()];
936 if (Sec->Number == -1)
939 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
941 if (IsPhysicalSection(Sec)) {
942 // Align the section data to a four byte boundary.
943 Sec->Header.PointerToRawData = RoundUpToAlignment(offset, 4);
945 offset += Sec->Header.SizeOfRawData;
948 if (Sec->Relocations.size() > 0) {
949 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
951 if (RelocationsOverflow) {
952 // Signal overflow by setting NumberOfRelocations to max value. Actual
953 // size is found in reloc #0. Microsoft tools understand this.
954 Sec->Header.NumberOfRelocations = 0xffff;
956 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
958 Sec->Header.PointerToRelocations = offset;
960 if (RelocationsOverflow) {
961 // Reloc #0 will contain actual count, so make room for it.
962 offset += COFF::RelocationSize;
965 offset += COFF::RelocationSize * Sec->Relocations.size();
967 for (auto &Relocation : Sec->Relocations) {
968 assert(Relocation.Symb->Index != -1);
969 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
973 assert(Sec->Symbol->Aux.size() == 1 &&
974 "Section's symbol must have one aux!");
975 AuxSymbol &Aux = Sec->Symbol->Aux[0];
976 assert(Aux.AuxType == ATSectionDefinition &&
977 "Section's symbol's aux symbol must be a Section Definition!");
978 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
979 Aux.Aux.SectionDefinition.NumberOfRelocations =
980 Sec->Header.NumberOfRelocations;
981 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
982 Sec->Header.NumberOfLineNumbers;
985 Header.PointerToSymbolTable = offset;
987 // We want a deterministic output. It looks like GNU as also writes 0 in here.
988 Header.TimeDateStamp = 0;
990 // Write it all to disk...
991 WriteFileHeader(Header);
994 sections::iterator i, ie;
995 MCAssembler::const_iterator j, je;
997 for (auto &Section : Sections) {
998 if (Section->Number != -1) {
999 if (Section->Relocations.size() >= 0xffff)
1000 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1001 WriteSectionHeader(Section->Header);
1005 for (i = Sections.begin(), ie = Sections.end(),
1006 j = Asm.begin(), je = Asm.end();
1007 (i != ie) && (j != je); ++i, ++j) {
1009 if ((*i)->Number == -1)
1012 if ((*i)->Header.PointerToRawData != 0) {
1013 assert(OS.tell() <= (*i)->Header.PointerToRawData &&
1014 "Section::PointerToRawData is insane!");
1016 unsigned SectionDataPadding = (*i)->Header.PointerToRawData - OS.tell();
1017 assert(SectionDataPadding < 4 &&
1018 "Should only need at most three bytes of padding!");
1020 WriteZeros(SectionDataPadding);
1022 Asm.writeSectionData(j, Layout);
1025 if ((*i)->Relocations.size() > 0) {
1026 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
1027 "Section::PointerToRelocations is insane!");
1029 if ((*i)->Relocations.size() >= 0xffff) {
1030 // In case of overflow, write actual relocation count as first
1031 // relocation. Including the synthetic reloc itself (+ 1).
1033 r.VirtualAddress = (*i)->Relocations.size() + 1;
1034 r.SymbolTableIndex = 0;
1039 for (const auto &Relocation : (*i)->Relocations)
1040 WriteRelocation(Relocation.Data);
1042 assert((*i)->Header.PointerToRelocations == 0 &&
1043 "Section::PointerToRelocations is insane!");
1047 assert(OS.tell() == Header.PointerToSymbolTable &&
1048 "Header::PointerToSymbolTable is insane!");
1050 for (auto &Symbol : Symbols)
1051 if (Symbol->Index != -1)
1052 WriteSymbol(*Symbol);
1054 OS.write(Strings.data().data(), Strings.data().size());
1057 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1061 // Pin the vtable to this file.
1062 void MCWinCOFFObjectTargetWriter::anchor() {}
1064 //------------------------------------------------------------------------------
1065 // WinCOFFObjectWriter factory function
1068 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1070 return new WinCOFFObjectWriter(MOTW, OS);