1 //===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains an implementation of a Win32 COFF object file writer.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/MC/MCWinCOFFObjectWriter.h"
15 #include "llvm/ADT/DenseMap.h"
16 #include "llvm/ADT/StringMap.h"
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/ADT/STLExtras.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/MC/MCAsmLayout.h"
21 #include "llvm/MC/MCAssembler.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCObjectWriter.h"
25 #include "llvm/MC/MCSection.h"
26 #include "llvm/MC/MCSectionCOFF.h"
27 #include "llvm/MC/MCSymbol.h"
28 #include "llvm/MC/MCValue.h"
29 #include "llvm/Support/COFF.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ErrorHandling.h"
32 #include "llvm/Support/TimeValue.h"
37 #define DEBUG_TYPE "WinCOFFObjectWriter"
40 typedef SmallString<COFF::NameSize> name;
51 AuxiliaryType AuxType;
62 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
71 MCSymbolData const *MCData;
73 COFFSymbol(StringRef name);
74 void set_name_offset(uint32_t Offset);
76 bool should_keep() const;
79 // This class contains staging data for a COFF relocation entry.
80 struct COFFRelocation {
81 COFF::relocation Data;
84 COFFRelocation() : Symb(nullptr) {}
85 static size_t size() { return COFF::RelocationSize; }
88 typedef std::vector<COFFRelocation> relocations;
96 MCSectionData const *MCData;
98 relocations Relocations;
100 COFFSection(StringRef name);
101 static size_t size();
104 // This class holds the COFF string table.
106 typedef StringMap<size_t> map;
109 void update_length();
111 std::vector<char> Data;
115 size_t insert(StringRef String);
123 class WinCOFFObjectWriter : public MCObjectWriter {
126 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
127 typedef std::vector<std::unique_ptr<COFFSection>> sections;
129 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
130 typedef DenseMap<MCSection const *, COFFSection *> section_map;
132 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
134 // Root level file contents.
140 // Maps used during object file creation.
141 section_map SectionMap;
142 symbol_map SymbolMap;
146 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
148 void reset() override {
149 memset(&Header, 0, sizeof(Header));
150 Header.Machine = TargetObjectWriter->getMachine();
156 MCObjectWriter::reset();
159 COFFSymbol *createSymbol(StringRef Name);
160 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
161 COFFSection *createSection(StringRef Name);
163 template <typename object_t, typename list_t>
164 object_t *createCOFFEntity(StringRef Name, list_t &List);
166 void DefineSection(MCSectionData const &SectionData);
167 void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
168 const MCAsmLayout &Layout);
170 void MakeSymbolReal(COFFSymbol &S, size_t Index);
171 void MakeSectionReal(COFFSection &S, size_t Number);
173 bool ExportSymbol(const MCSymbol &Symbol, MCAssembler &Asm);
175 bool IsPhysicalSection(COFFSection *S);
177 // Entity writing methods.
179 void WriteFileHeader(const COFF::header &Header);
180 void WriteSymbol(const COFFSymbol &S);
181 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
182 void WriteSectionHeader(const COFF::section &S);
183 void WriteRelocation(const COFF::relocation &R);
185 // MCObjectWriter interface implementation.
187 void ExecutePostLayoutBinding(MCAssembler &Asm,
188 const MCAsmLayout &Layout) override;
190 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
191 const MCFragment *Fragment, const MCFixup &Fixup,
192 MCValue Target, bool &IsPCRel,
193 uint64_t &FixedValue) override;
195 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
199 static inline void write_uint32_le(void *Data, uint32_t const &Value) {
200 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
201 Ptr[0] = (Value & 0x000000FF) >> 0;
202 Ptr[1] = (Value & 0x0000FF00) >> 8;
203 Ptr[2] = (Value & 0x00FF0000) >> 16;
204 Ptr[3] = (Value & 0xFF000000) >> 24;
207 //------------------------------------------------------------------------------
208 // Symbol class implementation
210 COFFSymbol::COFFSymbol(StringRef name)
211 : Name(name.begin(), name.end())
216 memset(&Data, 0, sizeof(Data));
219 // In the case that the name does not fit within 8 bytes, the offset
220 // into the string table is stored in the last 4 bytes instead, leaving
221 // the first 4 bytes as 0.
222 void COFFSymbol::set_name_offset(uint32_t Offset) {
223 write_uint32_le(Data.Name + 0, 0);
224 write_uint32_le(Data.Name + 4, Offset);
227 /// logic to decide if the symbol should be reported in the symbol table
228 bool COFFSymbol::should_keep() const {
229 // no section means its external, keep it
233 // if it has relocations pointing at it, keep it
234 if (Relocations > 0) {
235 assert(Section->Number != -1 && "Sections with relocations must be real!");
239 // if the section its in is being droped, drop it
240 if (Section->Number == -1)
243 // if it is the section symbol, keep it
244 if (Section->Symbol == this)
247 // if its temporary, drop it
248 if (MCData && MCData->getSymbol().isTemporary())
251 // otherwise, keep it
255 //------------------------------------------------------------------------------
256 // Section class implementation
258 COFFSection::COFFSection(StringRef name)
262 memset(&Header, 0, sizeof(Header));
265 size_t COFFSection::size() {
266 return COFF::SectionSize;
269 //------------------------------------------------------------------------------
270 // StringTable class implementation
272 /// Write the length of the string table into Data.
273 /// The length of the string table includes uint32 length header.
274 void StringTable::update_length() {
275 write_uint32_le(&Data.front(), Data.size());
278 StringTable::StringTable() {
279 // The string table data begins with the length of the entire string table
280 // including the length header. Allocate space for this header.
285 size_t StringTable::size() const {
289 /// Add String to the table iff it is not already there.
290 /// @returns the index into the string table where the string is now located.
291 size_t StringTable::insert(StringRef String) {
292 map::iterator i = Map.find(String);
297 size_t Offset = Data.size();
299 // Insert string data into string table.
300 Data.insert(Data.end(), String.begin(), String.end());
301 Data.push_back('\0');
303 // Put a reference to it in the map.
304 Map[String] = Offset;
306 // Update the internal length field.
312 //------------------------------------------------------------------------------
313 // WinCOFFObjectWriter class implementation
315 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
317 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
318 memset(&Header, 0, sizeof(Header));
320 Header.Machine = TargetObjectWriter->getMachine();
323 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
324 return createCOFFEntity<COFFSymbol>(Name, Symbols);
327 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
328 symbol_map::iterator i = SymbolMap.find(Symbol);
329 if (i != SymbolMap.end())
331 COFFSymbol *RetSymbol
332 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
333 SymbolMap[Symbol] = RetSymbol;
337 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
338 return createCOFFEntity<COFFSection>(Name, Sections);
341 /// A template used to lookup or create a symbol/section, and initialize it if
343 template <typename object_t, typename list_t>
344 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
346 List.push_back(make_unique<object_t>(Name));
348 return List.back().get();
351 /// This function takes a section data object from the assembler
352 /// and creates the associated COFF section staging object.
353 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
354 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
355 && "Got non-COFF section in the COFF backend!");
356 // FIXME: Not sure how to verify this (at least in a debug build).
357 MCSectionCOFF const &Sec =
358 static_cast<MCSectionCOFF const &>(SectionData.getSection());
360 COFFSection *coff_section = createSection(Sec.getSectionName());
361 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
362 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
363 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
364 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
365 if (COMDATSymbol->Section)
366 report_fatal_error("two sections have the same comdat");
367 COMDATSymbol->Section = coff_section;
371 coff_section->Symbol = coff_symbol;
372 coff_symbol->Section = coff_section;
373 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
375 // In this case the auxiliary symbol is a Section Definition.
376 coff_symbol->Aux.resize(1);
377 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
378 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
379 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
381 coff_section->Header.Characteristics = Sec.getCharacteristics();
383 uint32_t &Characteristics = coff_section->Header.Characteristics;
384 switch (SectionData.getAlignment()) {
385 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
386 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
387 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
388 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
389 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
390 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
391 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
392 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
393 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
394 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
395 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
396 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
397 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
398 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
400 llvm_unreachable("unsupported section alignment");
403 // Bind internal COFF section to MC section.
404 coff_section->MCData = &SectionData;
405 SectionMap[&SectionData.getSection()] = coff_section;
408 static uint64_t getSymbolValue(const MCSymbolData &Data,
409 const MCAsmLayout &Layout) {
410 if (Data.isCommon() && Data.isExternal())
411 return Data.getCommonSize();
414 if (!Layout.getSymbolOffset(&Data, Res))
420 /// This function takes a symbol data object from the assembler
421 /// and creates the associated COFF symbol staging object.
422 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
423 MCAssembler &Assembler,
424 const MCAsmLayout &Layout) {
425 MCSymbol const &Symbol = SymbolData.getSymbol();
426 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
427 SymbolMap[&Symbol] = coff_symbol;
429 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
430 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
432 if (Symbol.isVariable()) {
433 const MCSymbolRefExpr *SymRef =
434 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
437 report_fatal_error("Weak externals may only alias symbols");
439 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
441 std::string WeakName = std::string(".weak.")
442 + Symbol.getName().str()
444 COFFSymbol *WeakDefault = createSymbol(WeakName);
445 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
446 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
447 WeakDefault->Data.Type = 0;
448 WeakDefault->Data.Value = 0;
449 coff_symbol->Other = WeakDefault;
452 // Setup the Weak External auxiliary symbol.
453 coff_symbol->Aux.resize(1);
454 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
455 coff_symbol->Aux[0].AuxType = ATWeakExternal;
456 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
457 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
458 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
460 coff_symbol->MCData = &SymbolData;
462 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
463 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
464 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
466 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
467 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
469 // If no storage class was specified in the streamer, define it here.
470 if (coff_symbol->Data.StorageClass == 0) {
472 ResSymData.isExternal() ||
473 (!ResSymData.getFragment() && !ResSymData.getSymbol().isVariable());
475 coff_symbol->Data.StorageClass = IsExternal
476 ? COFF::IMAGE_SYM_CLASS_EXTERNAL
477 : COFF::IMAGE_SYM_CLASS_STATIC;
481 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
483 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
484 if (BaseData.Fragment) {
486 SectionMap[&BaseData.Fragment->getParent()->getSection()];
488 if (coff_symbol->Section && coff_symbol->Section != Sec)
489 report_fatal_error("conflicting sections for symbol");
491 coff_symbol->Section = Sec;
495 coff_symbol->MCData = &ResSymData;
499 // Maximum offsets for different string table entry encodings.
500 static const unsigned Max6DecimalOffset = 999999;
501 static const unsigned Max7DecimalOffset = 9999999;
502 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
504 // Encode a string table entry offset in base 64, padded to 6 chars, and
505 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
506 // Buffer must be at least 8 bytes large. No terminating null appended.
507 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
508 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
509 "Illegal section name encoding for value");
511 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
512 "abcdefghijklmnopqrstuvwxyz"
518 char* Ptr = Buffer + 7;
519 for (unsigned i = 0; i < 6; ++i) {
520 unsigned Rem = Value % 64;
522 *(Ptr--) = Alphabet[Rem];
526 /// making a section real involves assigned it a number and putting
527 /// name into the string table if needed
528 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
529 if (S.Name.size() > COFF::NameSize) {
530 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
532 if (StringTableEntry <= Max6DecimalOffset) {
533 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
534 } else if (StringTableEntry <= Max7DecimalOffset) {
535 // With seven digits, we have to skip the terminating null. Because
536 // sprintf always appends it, we use a larger temporary buffer.
537 char buffer[9] = { };
538 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
539 std::memcpy(S.Header.Name, buffer, 8);
540 } else if (StringTableEntry <= MaxBase64Offset) {
541 // Starting with 10,000,000, offsets are encoded as base64.
542 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
544 report_fatal_error("COFF string table is greater than 64 GB.");
547 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
550 S.Symbol->Data.SectionNumber = S.Number;
551 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
554 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
555 if (S.Name.size() > COFF::NameSize) {
556 size_t StringTableEntry = Strings.insert(S.Name.c_str());
558 S.set_name_offset(StringTableEntry);
560 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
564 bool WinCOFFObjectWriter::ExportSymbol(const MCSymbol &Symbol,
566 // This doesn't seem to be right. Strings referred to from the .data section
567 // need symbols so they can be linked to code in the .text section right?
569 // return Asm.isSymbolLinkerVisible(Symbol);
571 // Non-temporary labels should always be visible to the linker.
572 if (!Symbol.isTemporary())
575 // Absolute temporary labels are never visible.
576 if (!Symbol.isInSection())
579 // For now, all non-variable symbols are exported,
580 // the linker will sort the rest out for us.
581 return !Symbol.isVariable();
584 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
585 return (S->Header.Characteristics
586 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
589 //------------------------------------------------------------------------------
590 // entity writing methods
592 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
594 WriteLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
596 WriteLE16(COFF::BigObjHeader::MinBigObjectVersion);
597 WriteLE16(Header.Machine);
598 WriteLE32(Header.TimeDateStamp);
599 for (uint8_t MagicChar : COFF::BigObjMagic)
605 WriteLE32(Header.NumberOfSections);
606 WriteLE32(Header.PointerToSymbolTable);
607 WriteLE32(Header.NumberOfSymbols);
609 WriteLE16(Header.Machine);
610 WriteLE16(static_cast<int16_t>(Header.NumberOfSections));
611 WriteLE32(Header.TimeDateStamp);
612 WriteLE32(Header.PointerToSymbolTable);
613 WriteLE32(Header.NumberOfSymbols);
614 WriteLE16(Header.SizeOfOptionalHeader);
615 WriteLE16(Header.Characteristics);
619 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
620 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
621 WriteLE32(S.Data.Value);
623 WriteLE32(S.Data.SectionNumber);
625 WriteLE16(static_cast<int16_t>(S.Data.SectionNumber));
626 WriteLE16(S.Data.Type);
627 Write8(S.Data.StorageClass);
628 Write8(S.Data.NumberOfAuxSymbols);
629 WriteAuxiliarySymbols(S.Aux);
632 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
633 const COFFSymbol::AuxiliarySymbols &S) {
634 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
637 case ATFunctionDefinition:
638 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
639 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
640 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
641 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
642 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
644 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
646 case ATbfAndefSymbol:
647 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
648 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
649 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
650 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
651 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
653 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
656 WriteLE32(i->Aux.WeakExternal.TagIndex);
657 WriteLE32(i->Aux.WeakExternal.Characteristics);
658 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
660 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
664 StringRef(reinterpret_cast<const char *>(&i->Aux),
665 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
667 case ATSectionDefinition:
668 WriteLE32(i->Aux.SectionDefinition.Length);
669 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
670 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
671 WriteLE32(i->Aux.SectionDefinition.CheckSum);
672 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number));
673 Write8(i->Aux.SectionDefinition.Selection);
674 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
675 WriteLE16(static_cast<int16_t>(i->Aux.SectionDefinition.Number >> 16));
677 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
683 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
684 WriteBytes(StringRef(S.Name, COFF::NameSize));
686 WriteLE32(S.VirtualSize);
687 WriteLE32(S.VirtualAddress);
688 WriteLE32(S.SizeOfRawData);
689 WriteLE32(S.PointerToRawData);
690 WriteLE32(S.PointerToRelocations);
691 WriteLE32(S.PointerToLineNumbers);
692 WriteLE16(S.NumberOfRelocations);
693 WriteLE16(S.NumberOfLineNumbers);
694 WriteLE32(S.Characteristics);
697 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
698 WriteLE32(R.VirtualAddress);
699 WriteLE32(R.SymbolTableIndex);
703 ////////////////////////////////////////////////////////////////////////////////
704 // MCObjectWriter interface implementations
706 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
707 const MCAsmLayout &Layout) {
708 // "Define" each section & symbol. This creates section & symbol
709 // entries in the staging area.
710 for (const auto & Section : Asm)
711 DefineSection(Section);
713 for (MCSymbolData &SD : Asm.symbols())
714 if (ExportSymbol(SD.getSymbol(), Asm))
715 DefineSymbol(SD, Asm, Layout);
718 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
719 const MCAsmLayout &Layout,
720 const MCFragment *Fragment,
721 const MCFixup &Fixup,
724 uint64_t &FixedValue) {
725 assert(Target.getSymA() && "Relocation must reference a symbol!");
727 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
728 const MCSymbol &A = Symbol.AliasedSymbol();
729 if (!Asm.hasSymbolData(A))
730 Asm.getContext().FatalError(
732 Twine("symbol '") + A.getName() + "' can not be undefined");
734 const MCSymbolData &A_SD = Asm.getSymbolData(A);
736 MCSectionData const *SectionData = Fragment->getParent();
738 // Mark this symbol as requiring an entry in the symbol table.
739 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
740 "Section must already have been defined in ExecutePostLayoutBinding!");
741 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
742 "Symbol must already have been defined in ExecutePostLayoutBinding!");
744 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
745 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
746 const MCSymbolRefExpr *SymB = Target.getSymB();
747 bool CrossSection = false;
750 const MCSymbol *B = &SymB->getSymbol();
751 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
752 if (!B_SD.getFragment())
753 Asm.getContext().FatalError(
755 Twine("symbol '") + B->getName() +
756 "' can not be undefined in a subtraction expression");
758 if (!A_SD.getFragment())
759 Asm.getContext().FatalError(
761 Twine("symbol '") + Symbol.getName() +
762 "' can not be undefined in a subtraction expression");
764 CrossSection = &Symbol.getSection() != &B->getSection();
766 // Offset of the symbol in the section
767 int64_t a = Layout.getSymbolOffset(&B_SD);
769 // Ofeset of the relocation in the section
770 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
773 // In the case where we have SymbA and SymB, we just need to store the delta
774 // between the two symbols. Update FixedValue to account for the delta, and
775 // skip recording the relocation.
779 FixedValue = Target.getConstant();
782 COFFRelocation Reloc;
784 Reloc.Data.SymbolTableIndex = 0;
785 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
787 // Turn relocations for temporary symbols into section relocations.
788 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
789 Reloc.Symb = coff_symbol->Section->Symbol;
790 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
791 + coff_symbol->MCData->getOffset();
793 Reloc.Symb = coff_symbol;
795 ++Reloc.Symb->Relocations;
797 Reloc.Data.VirtualAddress += Fixup.getOffset();
798 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
801 // FIXME: Can anyone explain what this does other than adjust for the size
803 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
804 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
805 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
806 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
809 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
810 switch (Reloc.Data.Type) {
811 case COFF::IMAGE_REL_ARM_ABSOLUTE:
812 case COFF::IMAGE_REL_ARM_ADDR32:
813 case COFF::IMAGE_REL_ARM_ADDR32NB:
814 case COFF::IMAGE_REL_ARM_TOKEN:
815 case COFF::IMAGE_REL_ARM_SECTION:
816 case COFF::IMAGE_REL_ARM_SECREL:
818 case COFF::IMAGE_REL_ARM_BRANCH11:
819 case COFF::IMAGE_REL_ARM_BLX11:
820 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
821 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
823 case COFF::IMAGE_REL_ARM_BRANCH24:
824 case COFF::IMAGE_REL_ARM_BLX24:
825 case COFF::IMAGE_REL_ARM_MOV32A:
826 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
827 // only used for ARM mode code, which is documented as being unsupported
828 // by Windows on ARM. Empirical proof indicates that masm is able to
829 // generate the relocations however the rest of the MSVC toolchain is
830 // unable to handle it.
831 llvm_unreachable("unsupported relocation");
833 case COFF::IMAGE_REL_ARM_MOV32T:
835 case COFF::IMAGE_REL_ARM_BRANCH20T:
836 case COFF::IMAGE_REL_ARM_BRANCH24T:
837 case COFF::IMAGE_REL_ARM_BLX23T:
838 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
839 // perform a 4 byte adjustment to the relocation. Relative branches are
840 // offset by 4 on ARM, however, because there is no RELA relocations, all
841 // branches are offset by 4.
842 FixedValue = FixedValue + 4;
847 if (TargetObjectWriter->recordRelocation(Fixup))
848 coff_section->Relocations.push_back(Reloc);
851 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
852 const MCAsmLayout &Layout) {
853 size_t SectionsSize = Sections.size();
854 if (SectionsSize > static_cast<size_t>(INT32_MAX))
856 "PE COFF object files can't have more than 2147483647 sections");
858 // Assign symbol and section indexes and offsets.
859 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
861 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
863 DenseMap<COFFSection *, int32_t> SectionIndices(
864 NextPowerOf2(NumberOfSections));
866 for (const auto &Section : Sections) {
867 SectionIndices[Section.get()] = Number;
868 MakeSectionReal(*Section, Number);
872 Header.NumberOfSections = NumberOfSections;
873 Header.NumberOfSymbols = 0;
875 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
877 // round up to calculate the number of auxiliary symbols required
878 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
879 unsigned Count = (FI->size() + SymbolSize - 1) / SymbolSize;
881 COFFSymbol *file = createSymbol(".file");
882 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
883 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
884 file->Aux.resize(Count);
887 unsigned Length = FI->size();
888 for (auto & Aux : file->Aux) {
889 Aux.AuxType = ATFile;
891 if (Length > SymbolSize) {
892 memcpy(&Aux.Aux, FI->c_str() + Offset, SymbolSize);
893 Length = Length - SymbolSize;
895 memcpy(&Aux.Aux, FI->c_str() + Offset, Length);
896 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
900 Offset += SymbolSize;
904 for (auto &Symbol : Symbols) {
905 // Update section number & offset for symbols that have them.
907 Symbol->Data.SectionNumber = Symbol->Section->Number;
909 if (Symbol->should_keep()) {
910 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++);
912 // Update auxiliary symbol info.
913 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
914 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
919 // Fixup weak external references.
920 for (auto & Symbol : Symbols) {
922 assert(Symbol->Index != -1);
923 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
924 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
925 "Symbol's aux symbol must be a Weak External!");
926 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
930 // Fixup associative COMDAT sections.
931 for (auto & Section : Sections) {
932 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
933 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
936 const MCSectionCOFF &MCSec =
937 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
939 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
941 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
942 assert(COMDATSymbol);
943 COFFSection *Assoc = COMDATSymbol->Section;
946 Twine("Missing associated COMDAT section for section ") +
947 MCSec.getSectionName());
949 // Skip this section if the associated section is unused.
950 if (Assoc->Number == -1)
953 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
957 // Assign file offsets to COFF object file structures.
962 offset += COFF::Header32Size;
964 offset += COFF::Header16Size;
965 offset += COFF::SectionSize * Header.NumberOfSections;
967 for (const auto & Section : Asm) {
968 COFFSection *Sec = SectionMap[&Section.getSection()];
970 if (Sec->Number == -1)
973 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
975 if (IsPhysicalSection(Sec)) {
976 Sec->Header.PointerToRawData = offset;
978 offset += Sec->Header.SizeOfRawData;
981 if (Sec->Relocations.size() > 0) {
982 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
984 if (RelocationsOverflow) {
985 // Signal overflow by setting NumberOfRelocations to max value. Actual
986 // size is found in reloc #0. Microsoft tools understand this.
987 Sec->Header.NumberOfRelocations = 0xffff;
989 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
991 Sec->Header.PointerToRelocations = offset;
993 if (RelocationsOverflow) {
994 // Reloc #0 will contain actual count, so make room for it.
995 offset += COFF::RelocationSize;
998 offset += COFF::RelocationSize * Sec->Relocations.size();
1000 for (auto & Relocation : Sec->Relocations) {
1001 assert(Relocation.Symb->Index != -1);
1002 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
1006 assert(Sec->Symbol->Aux.size() == 1 &&
1007 "Section's symbol must have one aux!");
1008 AuxSymbol &Aux = Sec->Symbol->Aux[0];
1009 assert(Aux.AuxType == ATSectionDefinition &&
1010 "Section's symbol's aux symbol must be a Section Definition!");
1011 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
1012 Aux.Aux.SectionDefinition.NumberOfRelocations =
1013 Sec->Header.NumberOfRelocations;
1014 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
1015 Sec->Header.NumberOfLineNumbers;
1018 Header.PointerToSymbolTable = offset;
1020 // We want a deterministic output. It looks like GNU as also writes 0 in here.
1021 Header.TimeDateStamp = 0;
1023 // Write it all to disk...
1024 WriteFileHeader(Header);
1027 sections::iterator i, ie;
1028 MCAssembler::const_iterator j, je;
1030 for (auto & Section : Sections) {
1031 if (Section->Number != -1) {
1032 if (Section->Relocations.size() >= 0xffff)
1033 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1034 WriteSectionHeader(Section->Header);
1038 for (i = Sections.begin(), ie = Sections.end(),
1039 j = Asm.begin(), je = Asm.end();
1040 (i != ie) && (j != je); ++i, ++j) {
1042 if ((*i)->Number == -1)
1045 if ((*i)->Header.PointerToRawData != 0) {
1046 assert(OS.tell() == (*i)->Header.PointerToRawData &&
1047 "Section::PointerToRawData is insane!");
1049 Asm.writeSectionData(j, Layout);
1052 if ((*i)->Relocations.size() > 0) {
1053 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
1054 "Section::PointerToRelocations is insane!");
1056 if ((*i)->Relocations.size() >= 0xffff) {
1057 // In case of overflow, write actual relocation count as first
1058 // relocation. Including the synthetic reloc itself (+ 1).
1060 r.VirtualAddress = (*i)->Relocations.size() + 1;
1061 r.SymbolTableIndex = 0;
1066 for (const auto & Relocation : (*i)->Relocations)
1067 WriteRelocation(Relocation.Data);
1069 assert((*i)->Header.PointerToRelocations == 0 &&
1070 "Section::PointerToRelocations is insane!");
1074 assert(OS.tell() == Header.PointerToSymbolTable &&
1075 "Header::PointerToSymbolTable is insane!");
1077 for (auto & Symbol : Symbols)
1078 if (Symbol->Index != -1)
1079 WriteSymbol(*Symbol);
1081 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
1084 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1088 // Pin the vtable to this file.
1089 void MCWinCOFFObjectTargetWriter::anchor() {}
1091 //------------------------------------------------------------------------------
1092 // WinCOFFObjectWriter factory function
1095 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1097 return new WinCOFFObjectWriter(MOTW, OS);