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);
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 static uint64_t getSymbolValue(const MCSymbolData &Data,
389 const MCAsmLayout &Layout) {
390 if (Data.isCommon() && Data.isExternal())
391 return Data.getCommonSize();
394 if (!Layout.getSymbolOffset(&Data, Res))
400 /// This function takes a symbol data object from the assembler
401 /// and creates the associated COFF symbol staging object.
402 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
403 MCAssembler &Assembler,
404 const MCAsmLayout &Layout) {
405 MCSymbol const &Symbol = SymbolData.getSymbol();
406 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
407 SymbolMap[&Symbol] = coff_symbol;
409 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
410 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
412 if (Symbol.isVariable()) {
413 const MCSymbolRefExpr *SymRef =
414 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
417 report_fatal_error("Weak externals may only alias symbols");
419 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
421 std::string WeakName = std::string(".weak.")
422 + Symbol.getName().str()
424 COFFSymbol *WeakDefault = createSymbol(WeakName);
425 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
426 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
427 WeakDefault->Data.Type = 0;
428 WeakDefault->Data.Value = 0;
429 coff_symbol->Other = WeakDefault;
432 // Setup the Weak External auxiliary symbol.
433 coff_symbol->Aux.resize(1);
434 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
435 coff_symbol->Aux[0].AuxType = ATWeakExternal;
436 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
437 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
438 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
440 coff_symbol->MCData = &SymbolData;
442 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
443 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
444 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
446 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
447 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
449 // If no storage class was specified in the streamer, define it here.
450 if (coff_symbol->Data.StorageClass == 0) {
451 bool external = ResSymData.isExternal() || !ResSymData.Fragment;
453 coff_symbol->Data.StorageClass =
454 external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
458 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
460 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
461 if (BaseData.Fragment)
462 coff_symbol->Section =
463 SectionMap[&BaseData.Fragment->getParent()->getSection()];
466 coff_symbol->MCData = &ResSymData;
470 // Maximum offsets for different string table entry encodings.
471 static const unsigned Max6DecimalOffset = 999999;
472 static const unsigned Max7DecimalOffset = 9999999;
473 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
475 // Encode a string table entry offset in base 64, padded to 6 chars, and
476 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
477 // Buffer must be at least 8 bytes large. No terminating null appended.
478 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
479 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
480 "Illegal section name encoding for value");
482 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
483 "abcdefghijklmnopqrstuvwxyz"
489 char* Ptr = Buffer + 7;
490 for (unsigned i = 0; i < 6; ++i) {
491 unsigned Rem = Value % 64;
493 *(Ptr--) = Alphabet[Rem];
497 /// making a section real involves assigned it a number and putting
498 /// name into the string table if needed
499 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
500 if (S.Name.size() > COFF::NameSize) {
501 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
503 if (StringTableEntry <= Max6DecimalOffset) {
504 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
505 } else if (StringTableEntry <= Max7DecimalOffset) {
506 // With seven digits, we have to skip the terminating null. Because
507 // sprintf always appends it, we use a larger temporary buffer.
508 char buffer[9] = { };
509 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
510 std::memcpy(S.Header.Name, buffer, 8);
511 } else if (StringTableEntry <= MaxBase64Offset) {
512 // Starting with 10,000,000, offsets are encoded as base64.
513 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
515 report_fatal_error("COFF string table is greater than 64 GB.");
518 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
521 S.Symbol->Data.SectionNumber = S.Number;
522 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
525 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
526 if (S.Name.size() > COFF::NameSize) {
527 size_t StringTableEntry = Strings.insert(S.Name.c_str());
529 S.set_name_offset(StringTableEntry);
531 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
535 bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
537 // This doesn't seem to be right. Strings referred to from the .data section
538 // need symbols so they can be linked to code in the .text section right?
540 // return Asm.isSymbolLinkerVisible (&SymbolData);
542 // For now, all non-variable symbols are exported,
543 // the linker will sort the rest out for us.
544 return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
547 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
548 return (S->Header.Characteristics
549 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
552 //------------------------------------------------------------------------------
553 // entity writing methods
555 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
556 WriteLE16(Header.Machine);
557 WriteLE16(Header.NumberOfSections);
558 WriteLE32(Header.TimeDateStamp);
559 WriteLE32(Header.PointerToSymbolTable);
560 WriteLE32(Header.NumberOfSymbols);
561 WriteLE16(Header.SizeOfOptionalHeader);
562 WriteLE16(Header.Characteristics);
565 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
566 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
567 WriteLE32(S.Data.Value);
568 WriteLE16(S.Data.SectionNumber);
569 WriteLE16(S.Data.Type);
570 Write8(S.Data.StorageClass);
571 Write8(S.Data.NumberOfAuxSymbols);
572 WriteAuxiliarySymbols(S.Aux);
575 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
576 const COFFSymbol::AuxiliarySymbols &S) {
577 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
580 case ATFunctionDefinition:
581 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
582 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
583 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
584 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
585 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
587 case ATbfAndefSymbol:
588 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
589 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
590 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
591 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
592 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
595 WriteLE32(i->Aux.WeakExternal.TagIndex);
596 WriteLE32(i->Aux.WeakExternal.Characteristics);
597 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
600 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
601 sizeof(i->Aux.File.FileName)));
603 case ATSectionDefinition:
604 WriteLE32(i->Aux.SectionDefinition.Length);
605 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
606 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
607 WriteLE32(i->Aux.SectionDefinition.CheckSum);
608 WriteLE16(i->Aux.SectionDefinition.Number);
609 Write8(i->Aux.SectionDefinition.Selection);
610 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
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.
644 static_assert(sizeof(((COFF::AuxiliaryFile *)nullptr)->FileName) == COFF::SymbolSize,
645 "size mismatch for COFF::AuxiliaryFile::FileName");
646 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
648 // round up to calculate the number of auxiliary symbols required
649 unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize;
651 COFFSymbol *file = createSymbol(".file");
652 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
653 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
654 file->Aux.resize(Count);
657 unsigned Length = FI->size();
658 for (auto & Aux : file->Aux) {
659 Aux.AuxType = ATFile;
661 if (Length > COFF::SymbolSize) {
662 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize);
663 Length = Length - COFF::SymbolSize;
665 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length);
666 memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length);
670 Offset = Offset + COFF::SymbolSize;
674 for (const auto & Section : Asm)
675 DefineSection(Section);
677 for (MCSymbolData &SD : Asm.symbols())
678 if (ExportSymbol(SD, Asm))
679 DefineSymbol(SD, Asm, Layout);
682 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
683 const MCAsmLayout &Layout,
684 const MCFragment *Fragment,
685 const MCFixup &Fixup,
688 uint64_t &FixedValue) {
689 assert(Target.getSymA() && "Relocation must reference a symbol!");
691 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
692 const MCSymbol &A = Symbol.AliasedSymbol();
693 if (!Asm.hasSymbolData(A))
694 Asm.getContext().FatalError(
696 Twine("symbol '") + A.getName() + "' can not be undefined");
698 const MCSymbolData &A_SD = Asm.getSymbolData(A);
700 MCSectionData const *SectionData = Fragment->getParent();
702 // Mark this symbol as requiring an entry in the symbol table.
703 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
704 "Section must already have been defined in ExecutePostLayoutBinding!");
705 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
706 "Symbol must already have been defined in ExecutePostLayoutBinding!");
708 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
709 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
710 const MCSymbolRefExpr *SymB = Target.getSymB();
711 bool CrossSection = false;
714 const MCSymbol *B = &SymB->getSymbol();
715 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
716 if (!B_SD.getFragment())
717 Asm.getContext().FatalError(
719 Twine("symbol '") + B->getName() +
720 "' can not be undefined in a subtraction expression");
722 if (!A_SD.getFragment())
723 Asm.getContext().FatalError(
725 Twine("symbol '") + Symbol.getName() +
726 "' can not be undefined in a subtraction expression");
728 CrossSection = &Symbol.getSection() != &B->getSection();
730 // Offset of the symbol in the section
731 int64_t a = Layout.getSymbolOffset(&B_SD);
733 // Ofeset of the relocation in the section
734 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
737 // In the case where we have SymbA and SymB, we just need to store the delta
738 // between the two symbols. Update FixedValue to account for the delta, and
739 // skip recording the relocation.
743 FixedValue = Target.getConstant();
746 COFFRelocation Reloc;
748 Reloc.Data.SymbolTableIndex = 0;
749 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
751 // Turn relocations for temporary symbols into section relocations.
752 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
753 Reloc.Symb = coff_symbol->Section->Symbol;
754 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
755 + coff_symbol->MCData->getOffset();
757 Reloc.Symb = coff_symbol;
759 ++Reloc.Symb->Relocations;
761 Reloc.Data.VirtualAddress += Fixup.getOffset();
762 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
765 // FIXME: Can anyone explain what this does other than adjust for the size
767 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
768 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
769 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
770 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
773 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
774 switch (Reloc.Data.Type) {
775 case COFF::IMAGE_REL_ARM_ABSOLUTE:
776 case COFF::IMAGE_REL_ARM_ADDR32:
777 case COFF::IMAGE_REL_ARM_ADDR32NB:
778 case COFF::IMAGE_REL_ARM_TOKEN:
779 case COFF::IMAGE_REL_ARM_SECTION:
780 case COFF::IMAGE_REL_ARM_SECREL:
782 case COFF::IMAGE_REL_ARM_BRANCH11:
783 case COFF::IMAGE_REL_ARM_BLX11:
784 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
785 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
787 case COFF::IMAGE_REL_ARM_BRANCH24:
788 case COFF::IMAGE_REL_ARM_BLX24:
789 case COFF::IMAGE_REL_ARM_MOV32A:
790 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
791 // only used for ARM mode code, which is documented as being unsupported
792 // by Windows on ARM. Emperical proof indicates that masm is able to
793 // generate the relocations however the rest of the MSVC toolchain is
794 // unable to handle it.
795 llvm_unreachable("unsupported relocation");
797 case COFF::IMAGE_REL_ARM_MOV32T:
799 case COFF::IMAGE_REL_ARM_BRANCH20T:
800 case COFF::IMAGE_REL_ARM_BRANCH24T:
801 case COFF::IMAGE_REL_ARM_BLX23T:
802 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
803 // perform a 4 byte adjustment to the relocation. Relative branches are
804 // offset by 4 on ARM, however, because there is no RELA relocations, all
805 // branches are offset by 4.
806 FixedValue = FixedValue + 4;
811 coff_section->Relocations.push_back(Reloc);
814 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
815 const MCAsmLayout &Layout) {
816 // Assign symbol and section indexes and offsets.
817 Header.NumberOfSections = 0;
819 DenseMap<COFFSection *, uint16_t> SectionIndices;
820 for (auto & Section : Sections) {
821 if (Layout.getSectionAddressSize(Section->MCData) > 0) {
822 size_t Number = ++Header.NumberOfSections;
823 SectionIndices[Section.get()] = Number;
824 MakeSectionReal(*Section, Number);
826 Section->Number = -1;
830 Header.NumberOfSymbols = 0;
832 for (auto & Symbol : Symbols) {
833 // Update section number & offset for symbols that have them.
835 Symbol->Data.SectionNumber = Symbol->Section->Number;
837 if (Symbol->should_keep()) {
838 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++);
840 // Update auxiliary symbol info.
841 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
842 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
847 // Fixup weak external references.
848 for (auto & Symbol : Symbols) {
850 assert(Symbol->Index != -1);
851 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
852 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
853 "Symbol's aux symbol must be a Weak External!");
854 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
858 // Fixup associative COMDAT sections.
859 for (auto & Section : Sections) {
860 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
861 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
864 const MCSectionCOFF &MCSec =
865 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
867 COFFSection *Assoc = SectionMap.lookup(MCSec.getAssocSection());
869 report_fatal_error(Twine("Missing associated COMDAT section ") +
870 MCSec.getAssocSection()->getSectionName() +
871 " for section " + MCSec.getSectionName());
873 // Skip this section if the associated section is unused.
874 if (Assoc->Number == -1)
877 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
881 // Assign file offsets to COFF object file structures.
885 offset += COFF::HeaderSize;
886 offset += COFF::SectionSize * Header.NumberOfSections;
888 for (const auto & Section : Asm) {
889 COFFSection *Sec = SectionMap[&Section.getSection()];
891 if (Sec->Number == -1)
894 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
896 if (IsPhysicalSection(Sec)) {
897 Sec->Header.PointerToRawData = offset;
899 offset += Sec->Header.SizeOfRawData;
902 if (Sec->Relocations.size() > 0) {
903 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
905 if (RelocationsOverflow) {
906 // Signal overflow by setting NumberOfSections to max value. Actual
907 // size is found in reloc #0. Microsoft tools understand this.
908 Sec->Header.NumberOfRelocations = 0xffff;
910 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
912 Sec->Header.PointerToRelocations = offset;
914 if (RelocationsOverflow) {
915 // Reloc #0 will contain actual count, so make room for it.
916 offset += COFF::RelocationSize;
919 offset += COFF::RelocationSize * Sec->Relocations.size();
921 for (auto & Relocation : Sec->Relocations) {
922 assert(Relocation.Symb->Index != -1);
923 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
927 assert(Sec->Symbol->Aux.size() == 1 &&
928 "Section's symbol must have one aux!");
929 AuxSymbol &Aux = Sec->Symbol->Aux[0];
930 assert(Aux.AuxType == ATSectionDefinition &&
931 "Section's symbol's aux symbol must be a Section Definition!");
932 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
933 Aux.Aux.SectionDefinition.NumberOfRelocations =
934 Sec->Header.NumberOfRelocations;
935 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
936 Sec->Header.NumberOfLineNumbers;
939 Header.PointerToSymbolTable = offset;
941 // We want a deterministic output. It looks like GNU as also writes 0 in here.
942 Header.TimeDateStamp = 0;
944 // Write it all to disk...
945 WriteFileHeader(Header);
948 sections::iterator i, ie;
949 MCAssembler::const_iterator j, je;
951 for (auto & Section : Sections) {
952 if (Section->Number != -1) {
953 if (Section->Relocations.size() >= 0xffff)
954 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
955 WriteSectionHeader(Section->Header);
959 for (i = Sections.begin(), ie = Sections.end(),
960 j = Asm.begin(), je = Asm.end();
961 (i != ie) && (j != je); ++i, ++j) {
963 if ((*i)->Number == -1)
966 if ((*i)->Header.PointerToRawData != 0) {
967 assert(OS.tell() == (*i)->Header.PointerToRawData &&
968 "Section::PointerToRawData is insane!");
970 Asm.writeSectionData(j, Layout);
973 if ((*i)->Relocations.size() > 0) {
974 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
975 "Section::PointerToRelocations is insane!");
977 if ((*i)->Relocations.size() >= 0xffff) {
978 // In case of overflow, write actual relocation count as first
979 // relocation. Including the synthetic reloc itself (+ 1).
981 r.VirtualAddress = (*i)->Relocations.size() + 1;
982 r.SymbolTableIndex = 0;
987 for (const auto & Relocation : (*i)->Relocations)
988 WriteRelocation(Relocation.Data);
990 assert((*i)->Header.PointerToRelocations == 0 &&
991 "Section::PointerToRelocations is insane!");
995 assert(OS.tell() == Header.PointerToSymbolTable &&
996 "Header::PointerToSymbolTable is insane!");
998 for (auto & Symbol : Symbols)
999 if (Symbol->Index != -1)
1000 WriteSymbol(*Symbol);
1002 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
1005 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1009 // Pin the vtable to this file.
1010 void MCWinCOFFObjectTargetWriter::anchor() {}
1012 //------------------------------------------------------------------------------
1013 // WinCOFFObjectWriter factory function
1016 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1018 return new WinCOFFObjectWriter(MOTW, OS);