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 #define DEBUG_TYPE "WinCOFFObjectWriter"
16 #include "llvm/MC/MCWinCOFFObjectWriter.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/MC/MCAsmLayout.h"
23 #include "llvm/MC/MCAssembler.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCExpr.h"
26 #include "llvm/MC/MCObjectWriter.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCSectionCOFF.h"
29 #include "llvm/MC/MCSymbol.h"
30 #include "llvm/MC/MCValue.h"
31 #include "llvm/Support/COFF.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TimeValue.h"
40 typedef SmallString<COFF::NameSize> name;
51 AuxiliaryType AuxType;
62 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
71 MCSymbolData const *MCData;
73 COFFSymbol(StringRef name);
75 void set_name_offset(uint32_t Offset);
77 bool should_keep() const;
80 // This class contains staging data for a COFF relocation entry.
81 struct COFFRelocation {
82 COFF::relocation Data;
85 COFFRelocation() : Symb(nullptr) {}
86 static size_t size() { return COFF::RelocationSize; }
89 typedef std::vector<COFFRelocation> relocations;
97 MCSectionData const *MCData;
99 relocations Relocations;
101 COFFSection(StringRef name);
102 static size_t size();
105 // This class holds the COFF string table.
107 typedef StringMap<size_t> map;
110 void update_length();
112 std::vector<char> Data;
116 size_t insert(StringRef String);
119 class WinCOFFObjectWriter : public MCObjectWriter {
122 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
123 typedef std::vector<std::unique_ptr<COFFSection>> sections;
125 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
126 typedef DenseMap<MCSection const *, COFFSection *> section_map;
128 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
130 // Root level file contents.
136 // Maps used during object file creation.
137 section_map SectionMap;
138 symbol_map SymbolMap;
140 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
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 MakeSymbolReal(COFFSymbol &S, size_t Index);
154 void MakeSectionReal(COFFSection &S, size_t Number);
156 bool ExportSymbol(MCSymbolData const &SymbolData, 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 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
174 const MCFragment *Fragment, const MCFixup &Fixup,
175 MCValue Target, bool &IsPCRel,
176 uint64_t &FixedValue) override;
178 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
182 static inline void write_uint32_le(void *Data, uint32_t const &Value) {
183 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
184 Ptr[0] = (Value & 0x000000FF) >> 0;
185 Ptr[1] = (Value & 0x0000FF00) >> 8;
186 Ptr[2] = (Value & 0x00FF0000) >> 16;
187 Ptr[3] = (Value & 0xFF000000) >> 24;
190 //------------------------------------------------------------------------------
191 // Symbol class implementation
193 COFFSymbol::COFFSymbol(StringRef name)
194 : Name(name.begin(), name.end())
199 memset(&Data, 0, sizeof(Data));
202 size_t COFFSymbol::size() const {
203 return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
206 // In the case that the name does not fit within 8 bytes, the offset
207 // into the string table is stored in the last 4 bytes instead, leaving
208 // the first 4 bytes as 0.
209 void COFFSymbol::set_name_offset(uint32_t Offset) {
210 write_uint32_le(Data.Name + 0, 0);
211 write_uint32_le(Data.Name + 4, Offset);
214 /// logic to decide if the symbol should be reported in the symbol table
215 bool COFFSymbol::should_keep() const {
216 // no section means its external, keep it
220 // if it has relocations pointing at it, keep it
221 if (Relocations > 0) {
222 assert(Section->Number != -1 && "Sections with relocations must be real!");
226 // if the section its in is being droped, drop it
227 if (Section->Number == -1)
230 // if it is the section symbol, keep it
231 if (Section->Symbol == this)
234 // if its temporary, drop it
235 if (MCData && MCData->getSymbol().isTemporary())
238 // otherwise, keep it
242 //------------------------------------------------------------------------------
243 // Section class implementation
245 COFFSection::COFFSection(StringRef name)
249 memset(&Header, 0, sizeof(Header));
252 size_t COFFSection::size() {
253 return COFF::SectionSize;
256 //------------------------------------------------------------------------------
257 // StringTable class implementation
259 /// Write the length of the string table into Data.
260 /// The length of the string table includes uint32 length header.
261 void StringTable::update_length() {
262 write_uint32_le(&Data.front(), Data.size());
265 StringTable::StringTable() {
266 // The string table data begins with the length of the entire string table
267 // including the length header. Allocate space for this header.
272 size_t StringTable::size() const {
276 /// Add String to the table iff it is not already there.
277 /// @returns the index into the string table where the string is now located.
278 size_t StringTable::insert(StringRef String) {
279 map::iterator i = Map.find(String);
284 size_t Offset = Data.size();
286 // Insert string data into string table.
287 Data.insert(Data.end(), String.begin(), String.end());
288 Data.push_back('\0');
290 // Put a reference to it in the map.
291 Map[String] = Offset;
293 // Update the internal length field.
299 //------------------------------------------------------------------------------
300 // WinCOFFObjectWriter class implementation
302 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
304 : MCObjectWriter(OS, true)
305 , TargetObjectWriter(MOTW) {
306 memset(&Header, 0, sizeof(Header));
308 Header.Machine = TargetObjectWriter->getMachine();
311 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
312 return createCOFFEntity<COFFSymbol>(Name, Symbols);
315 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
316 symbol_map::iterator i = SymbolMap.find(Symbol);
317 if (i != SymbolMap.end())
319 COFFSymbol *RetSymbol
320 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
321 SymbolMap[Symbol] = RetSymbol;
325 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
326 return createCOFFEntity<COFFSection>(Name, Sections);
329 /// A template used to lookup or create a symbol/section, and initialize it if
331 template <typename object_t, typename list_t>
332 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
334 List.push_back(make_unique<object_t>(Name));
336 return List.back().get();
339 /// This function takes a section data object from the assembler
340 /// and creates the associated COFF section staging object.
341 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
342 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
343 && "Got non-COFF section in the COFF backend!");
344 // FIXME: Not sure how to verify this (at least in a debug build).
345 MCSectionCOFF const &Sec =
346 static_cast<MCSectionCOFF const &>(SectionData.getSection());
348 COFFSection *coff_section = createSection(Sec.getSectionName());
349 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
351 coff_section->Symbol = coff_symbol;
352 coff_symbol->Section = coff_section;
353 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
355 // In this case the auxiliary symbol is a Section Definition.
356 coff_symbol->Aux.resize(1);
357 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
358 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
359 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
361 coff_section->Header.Characteristics = Sec.getCharacteristics();
363 uint32_t &Characteristics = coff_section->Header.Characteristics;
364 switch (SectionData.getAlignment()) {
365 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
366 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
367 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
368 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
369 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
370 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
371 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
372 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
373 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
374 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
375 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
376 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
377 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
378 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
380 llvm_unreachable("unsupported section alignment");
383 // Bind internal COFF section to MC section.
384 coff_section->MCData = &SectionData;
385 SectionMap[&SectionData.getSection()] = coff_section;
388 /// This function takes a symbol data object from the assembler
389 /// and creates the associated COFF symbol staging object.
390 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
391 MCAssembler &Assembler,
392 const MCAsmLayout &Layout) {
393 MCSymbol const &Symbol = SymbolData.getSymbol();
394 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
395 SymbolMap[&Symbol] = coff_symbol;
397 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
398 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
400 if (Symbol.isVariable()) {
401 const MCSymbolRefExpr *SymRef =
402 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
405 report_fatal_error("Weak externals may only alias symbols");
407 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
409 std::string WeakName = std::string(".weak.")
410 + Symbol.getName().str()
412 COFFSymbol *WeakDefault = createSymbol(WeakName);
413 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
414 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
415 WeakDefault->Data.Type = 0;
416 WeakDefault->Data.Value = 0;
417 coff_symbol->Other = WeakDefault;
420 // Setup the Weak External auxiliary symbol.
421 coff_symbol->Aux.resize(1);
422 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
423 coff_symbol->Aux[0].AuxType = ATWeakExternal;
424 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
425 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
426 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
428 coff_symbol->MCData = &SymbolData;
430 const MCSymbolData &ResSymData =
431 Assembler.getSymbolData(Symbol.AliasedSymbol());
433 if (Symbol.isVariable()) {
435 if (Symbol.getVariableValue()->EvaluateAsAbsolute(Addr, Layout))
436 coff_symbol->Data.Value = Addr;
437 } else if (SymbolData.isExternal() && SymbolData.isCommon()) {
438 coff_symbol->Data.Value = SymbolData.getCommonSize();
441 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
442 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
444 // If no storage class was specified in the streamer, define it here.
445 if (coff_symbol->Data.StorageClass == 0) {
446 bool external = ResSymData.isExternal() || !ResSymData.Fragment;
448 coff_symbol->Data.StorageClass =
449 external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
452 if (Symbol.isAbsolute() || Symbol.AliasedSymbol().isVariable())
453 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
454 else if (ResSymData.Fragment)
455 coff_symbol->Section =
456 SectionMap[&ResSymData.Fragment->getParent()->getSection()];
458 coff_symbol->MCData = &ResSymData;
462 // Maximum offsets for different string table entry encodings.
463 static const unsigned Max6DecimalOffset = 999999;
464 static const unsigned Max7DecimalOffset = 9999999;
465 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
467 // Encode a string table entry offset in base 64, padded to 6 chars, and
468 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
469 // Buffer must be at least 8 bytes large. No terminating null appended.
470 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
471 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
472 "Illegal section name encoding for value");
474 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
475 "abcdefghijklmnopqrstuvwxyz"
481 char* Ptr = Buffer + 7;
482 for (unsigned i = 0; i < 6; ++i) {
483 unsigned Rem = Value % 64;
485 *(Ptr--) = Alphabet[Rem];
489 /// making a section real involves assigned it a number and putting
490 /// name into the string table if needed
491 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
492 if (S.Name.size() > COFF::NameSize) {
493 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
495 if (StringTableEntry <= Max6DecimalOffset) {
496 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
497 } else if (StringTableEntry <= Max7DecimalOffset) {
498 // With seven digits, we have to skip the terminating null. Because
499 // sprintf always appends it, we use a larger temporary buffer.
500 char buffer[9] = { };
501 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
502 std::memcpy(S.Header.Name, buffer, 8);
503 } else if (StringTableEntry <= MaxBase64Offset) {
504 // Starting with 10,000,000, offsets are encoded as base64.
505 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
507 report_fatal_error("COFF string table is greater than 64 GB.");
510 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
513 S.Symbol->Data.SectionNumber = S.Number;
514 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
517 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
518 if (S.Name.size() > COFF::NameSize) {
519 size_t StringTableEntry = Strings.insert(S.Name.c_str());
521 S.set_name_offset(StringTableEntry);
523 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
527 bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
529 // This doesn't seem to be right. Strings referred to from the .data section
530 // need symbols so they can be linked to code in the .text section right?
532 // return Asm.isSymbolLinkerVisible (&SymbolData);
534 // For now, all non-variable symbols are exported,
535 // the linker will sort the rest out for us.
536 return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
539 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
540 return (S->Header.Characteristics
541 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
544 //------------------------------------------------------------------------------
545 // entity writing methods
547 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
548 WriteLE16(Header.Machine);
549 WriteLE16(Header.NumberOfSections);
550 WriteLE32(Header.TimeDateStamp);
551 WriteLE32(Header.PointerToSymbolTable);
552 WriteLE32(Header.NumberOfSymbols);
553 WriteLE16(Header.SizeOfOptionalHeader);
554 WriteLE16(Header.Characteristics);
557 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
558 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
559 WriteLE32(S.Data.Value);
560 WriteLE16(S.Data.SectionNumber);
561 WriteLE16(S.Data.Type);
562 Write8(S.Data.StorageClass);
563 Write8(S.Data.NumberOfAuxSymbols);
564 WriteAuxiliarySymbols(S.Aux);
567 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
568 const COFFSymbol::AuxiliarySymbols &S) {
569 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
572 case ATFunctionDefinition:
573 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
574 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
575 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
576 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
577 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
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));
587 WriteLE32(i->Aux.WeakExternal.TagIndex);
588 WriteLE32(i->Aux.WeakExternal.Characteristics);
589 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
592 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
593 sizeof(i->Aux.File.FileName)));
595 case ATSectionDefinition:
596 WriteLE32(i->Aux.SectionDefinition.Length);
597 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
598 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
599 WriteLE32(i->Aux.SectionDefinition.CheckSum);
600 WriteLE16(i->Aux.SectionDefinition.Number);
601 Write8(i->Aux.SectionDefinition.Selection);
602 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
608 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
609 WriteBytes(StringRef(S.Name, COFF::NameSize));
611 WriteLE32(S.VirtualSize);
612 WriteLE32(S.VirtualAddress);
613 WriteLE32(S.SizeOfRawData);
614 WriteLE32(S.PointerToRawData);
615 WriteLE32(S.PointerToRelocations);
616 WriteLE32(S.PointerToLineNumbers);
617 WriteLE16(S.NumberOfRelocations);
618 WriteLE16(S.NumberOfLineNumbers);
619 WriteLE32(S.Characteristics);
622 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
623 WriteLE32(R.VirtualAddress);
624 WriteLE32(R.SymbolTableIndex);
628 ////////////////////////////////////////////////////////////////////////////////
629 // MCObjectWriter interface implementations
631 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
632 const MCAsmLayout &Layout) {
633 // "Define" each section & symbol. This creates section & symbol
634 // entries in the staging area.
636 static_assert(sizeof(COFF::AuxiliaryFile::FileName) == COFF::SymbolSize,
637 "size mismatch for COFF::AuxiliaryFile::FileName");
638 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
640 // round up to calculate the number of auxiliary symbols required
641 unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize;
643 COFFSymbol *file = createSymbol(".file");
644 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
645 file->Aux.resize(Count);
648 unsigned Length = FI->size();
649 for (auto & Aux : file->Aux) {
650 Aux.AuxType = ATFile;
652 if (Length > COFF::SymbolSize) {
653 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize);
654 Length = Length - COFF::SymbolSize;
656 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length);
657 memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length);
661 Offset = Offset + COFF::SymbolSize;
665 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; i++)
668 for (MCAssembler::const_symbol_iterator i = Asm.symbol_begin(),
669 e = Asm.symbol_end();
671 if (ExportSymbol(*i, Asm)) {
672 DefineSymbol(*i, Asm, Layout);
677 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
678 const MCAsmLayout &Layout,
679 const MCFragment *Fragment,
680 const MCFixup &Fixup,
683 uint64_t &FixedValue) {
684 assert(Target.getSymA() && "Relocation must reference a symbol!");
686 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
687 const MCSymbol &A = Symbol.AliasedSymbol();
688 if (!Asm.hasSymbolData(A))
689 Asm.getContext().FatalError(
691 Twine("symbol '") + A.getName() + "' can not be undefined");
693 MCSymbolData &A_SD = Asm.getSymbolData(A);
695 MCSectionData const *SectionData = Fragment->getParent();
697 // Mark this symbol as requiring an entry in the symbol table.
698 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
699 "Section must already have been defined in ExecutePostLayoutBinding!");
700 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
701 "Symbol must already have been defined in ExecutePostLayoutBinding!");
703 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
704 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
705 const MCSymbolRefExpr *SymB = Target.getSymB();
706 bool CrossSection = false;
709 const MCSymbol *B = &SymB->getSymbol();
710 MCSymbolData &B_SD = Asm.getSymbolData(*B);
711 if (!B_SD.getFragment())
712 Asm.getContext().FatalError(
714 Twine("symbol '") + B->getName() +
715 "' can not be undefined in a subtraction expression");
717 if (!A_SD.getFragment())
718 Asm.getContext().FatalError(
720 Twine("symbol '") + Symbol.getName() +
721 "' can not be undefined in a subtraction expression");
723 CrossSection = &Symbol.getSection() != &B->getSection();
725 // Offset of the symbol in the section
726 int64_t a = Layout.getSymbolOffset(&B_SD);
728 // Ofeset of the relocation in the section
729 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
732 // In the case where we have SymbA and SymB, we just need to store the delta
733 // between the two symbols. Update FixedValue to account for the delta, and
734 // skip recording the relocation.
738 FixedValue = Target.getConstant();
741 COFFRelocation Reloc;
743 Reloc.Data.SymbolTableIndex = 0;
744 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
746 // Turn relocations for temporary symbols into section relocations.
747 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
748 Reloc.Symb = coff_symbol->Section->Symbol;
749 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
750 + coff_symbol->MCData->getOffset();
752 Reloc.Symb = coff_symbol;
754 ++Reloc.Symb->Relocations;
756 Reloc.Data.VirtualAddress += Fixup.getOffset();
757 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
760 // FIXME: Can anyone explain what this does other than adjust for the size
762 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
763 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
764 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
765 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
768 coff_section->Relocations.push_back(Reloc);
771 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
772 const MCAsmLayout &Layout) {
773 // Assign symbol and section indexes and offsets.
774 Header.NumberOfSections = 0;
776 DenseMap<COFFSection *, uint16_t> SectionIndices;
777 for (sections::iterator i = Sections.begin(),
778 e = Sections.end(); i != e; i++) {
779 if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
780 size_t Number = ++Header.NumberOfSections;
781 SectionIndices[i->get()] = Number;
782 MakeSectionReal(**i, Number);
788 Header.NumberOfSymbols = 0;
790 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
791 COFFSymbol &coff_symbol = **i;
792 MCSymbolData const *SymbolData = coff_symbol.MCData;
794 // Update section number & offset for symbols that have them.
795 if (SymbolData && SymbolData->Fragment) {
796 assert(coff_symbol.Section != nullptr);
798 coff_symbol.Data.SectionNumber = coff_symbol.Section->Number;
799 coff_symbol.Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
800 + SymbolData->Offset;
803 if (coff_symbol.should_keep()) {
804 MakeSymbolReal(coff_symbol, Header.NumberOfSymbols++);
806 // Update auxiliary symbol info.
807 coff_symbol.Data.NumberOfAuxSymbols = coff_symbol.Aux.size();
808 Header.NumberOfSymbols += coff_symbol.Data.NumberOfAuxSymbols;
810 coff_symbol.Index = -1;
813 // Fixup weak external references.
814 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
815 COFFSymbol &coff_symbol = **i;
816 if (coff_symbol.Other) {
817 assert(coff_symbol.Index != -1);
818 assert(coff_symbol.Aux.size() == 1 &&
819 "Symbol must contain one aux symbol!");
820 assert(coff_symbol.Aux[0].AuxType == ATWeakExternal &&
821 "Symbol's aux symbol must be a Weak External!");
822 coff_symbol.Aux[0].Aux.WeakExternal.TagIndex = coff_symbol.Other->Index;
826 // Fixup associative COMDAT sections.
827 for (sections::iterator i = Sections.begin(),
828 e = Sections.end(); i != e; i++) {
829 if ((*i)->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
830 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
833 const MCSectionCOFF &MCSec = static_cast<const MCSectionCOFF &>(
834 (*i)->MCData->getSection());
836 COFFSection *Assoc = SectionMap.lookup(MCSec.getAssocSection());
838 report_fatal_error(Twine("Missing associated COMDAT section ") +
839 MCSec.getAssocSection()->getSectionName() +
840 " for section " + MCSec.getSectionName());
843 // Skip this section if the associated section is unused.
844 if (Assoc->Number == -1)
847 (*i)->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
851 // Assign file offsets to COFF object file structures.
855 offset += COFF::HeaderSize;
856 offset += COFF::SectionSize * Header.NumberOfSections;
858 for (MCAssembler::const_iterator i = Asm.begin(),
861 COFFSection *Sec = SectionMap[&i->getSection()];
863 if (Sec->Number == -1)
866 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);
868 if (IsPhysicalSection(Sec)) {
869 Sec->Header.PointerToRawData = offset;
871 offset += Sec->Header.SizeOfRawData;
874 if (Sec->Relocations.size() > 0) {
875 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
877 if (RelocationsOverflow) {
878 // Signal overflow by setting NumberOfSections to max value. Actual
879 // size is found in reloc #0. Microsoft tools understand this.
880 Sec->Header.NumberOfRelocations = 0xffff;
882 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
884 Sec->Header.PointerToRelocations = offset;
886 if (RelocationsOverflow) {
887 // Reloc #0 will contain actual count, so make room for it.
888 offset += COFF::RelocationSize;
891 offset += COFF::RelocationSize * Sec->Relocations.size();
893 for (relocations::iterator cr = Sec->Relocations.begin(),
894 er = Sec->Relocations.end();
896 assert((*cr).Symb->Index != -1);
897 (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
901 assert(Sec->Symbol->Aux.size() == 1
902 && "Section's symbol must have one aux!");
903 AuxSymbol &Aux = Sec->Symbol->Aux[0];
904 assert(Aux.AuxType == ATSectionDefinition &&
905 "Section's symbol's aux symbol must be a Section Definition!");
906 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
907 Aux.Aux.SectionDefinition.NumberOfRelocations =
908 Sec->Header.NumberOfRelocations;
909 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
910 Sec->Header.NumberOfLineNumbers;
913 Header.PointerToSymbolTable = offset;
915 // We want a deterministic output. It looks like GNU as also writes 0 in here.
916 Header.TimeDateStamp = 0;
918 // Write it all to disk...
919 WriteFileHeader(Header);
922 sections::iterator i, ie;
923 MCAssembler::const_iterator j, je;
925 for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
926 if ((*i)->Number != -1) {
927 if ((*i)->Relocations.size() >= 0xffff) {
928 (*i)->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
930 WriteSectionHeader((*i)->Header);
933 for (i = Sections.begin(), ie = Sections.end(),
934 j = Asm.begin(), je = Asm.end();
935 (i != ie) && (j != je); ++i, ++j) {
937 if ((*i)->Number == -1)
940 if ((*i)->Header.PointerToRawData != 0) {
941 assert(OS.tell() == (*i)->Header.PointerToRawData &&
942 "Section::PointerToRawData is insane!");
944 Asm.writeSectionData(j, Layout);
947 if ((*i)->Relocations.size() > 0) {
948 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
949 "Section::PointerToRelocations is insane!");
951 if ((*i)->Relocations.size() >= 0xffff) {
952 // In case of overflow, write actual relocation count as first
953 // relocation. Including the synthetic reloc itself (+ 1).
955 r.VirtualAddress = (*i)->Relocations.size() + 1;
956 r.SymbolTableIndex = 0;
961 for (relocations::const_iterator k = (*i)->Relocations.begin(),
962 ke = (*i)->Relocations.end();
964 WriteRelocation(k->Data);
967 assert((*i)->Header.PointerToRelocations == 0 &&
968 "Section::PointerToRelocations is insane!");
972 assert(OS.tell() == Header.PointerToSymbolTable &&
973 "Header::PointerToSymbolTable is insane!");
975 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
976 if ((*i)->Index != -1)
979 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
982 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
986 // Pin the vtable to this file.
987 void MCWinCOFFObjectTargetWriter::anchor() {}
989 //------------------------------------------------------------------------------
990 // WinCOFFObjectWriter factory function
993 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
995 return new WinCOFFObjectWriter(MOTW, OS);