1 //===-- llvm/MC/WinCOFFObjectWriter.cpp -------------------------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains an implementation of a Win32 COFF object file writer.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/MC/MCWinCOFFObjectWriter.h"
15 #include "llvm/ADT/DenseMap.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/StringMap.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Twine.h"
20 #include "llvm/Config/config.h"
21 #include "llvm/MC/MCAsmLayout.h"
22 #include "llvm/MC/MCAssembler.h"
23 #include "llvm/MC/MCContext.h"
24 #include "llvm/MC/MCExpr.h"
25 #include "llvm/MC/MCObjectFileInfo.h"
26 #include "llvm/MC/MCObjectWriter.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCSectionCOFF.h"
29 #include "llvm/MC/MCSymbolCOFF.h"
30 #include "llvm/MC/MCValue.h"
31 #include "llvm/MC/StringTableBuilder.h"
32 #include "llvm/Support/COFF.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/Endian.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/JamCRC.h"
37 #include "llvm/Support/TimeValue.h"
38 #include <cstdio>
39 #include <ctime>
40
41 using namespace llvm;
42
43 #define DEBUG_TYPE "WinCOFFObjectWriter"
44
45 namespace {
46 typedef SmallString<COFF::NameSize> name;
47
48 enum AuxiliaryType {
49 ATFunctionDefinition,
50 ATbfAndefSymbol,
51 ATWeakExternal,
52 ATFile,
53 ATSectionDefinition
54 };
55
56 struct AuxSymbol {
57 AuxiliaryType AuxType;
58 COFF::Auxiliary Aux;
59 };
60
61 class COFFSymbol;
62 class COFFSection;
63
64 class COFFSymbol {
65 public:
66 COFF::symbol Data;
67
68 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
69
70 name Name;
71 int Index;
72 AuxiliarySymbols Aux;
73 COFFSymbol *Other;
74 COFFSection *Section;
75 int Relocations;
76
77 const MCSymbol *MC;
78
79 COFFSymbol(StringRef name);
80 void set_name_offset(uint32_t Offset);
81
getIndex() const82 int64_t getIndex() const { return Index; }
setIndex(int Value)83 void setIndex(int Value) {
84 Index = Value;
85 if (MC)
86 MC->setIndex(static_cast<uint32_t>(Value));
87 }
88 };
89
90 // This class contains staging data for a COFF relocation entry.
91 struct COFFRelocation {
92 COFF::relocation Data;
93 COFFSymbol *Symb;
94
COFFRelocation__anon2c313f900111::COFFRelocation95 COFFRelocation() : Symb(nullptr) {}
size__anon2c313f900111::COFFRelocation96 static size_t size() { return COFF::RelocationSize; }
97 };
98
99 typedef std::vector<COFFRelocation> relocations;
100
101 class COFFSection {
102 public:
103 COFF::section Header;
104
105 std::string Name;
106 int Number;
107 MCSectionCOFF const *MCSection;
108 COFFSymbol *Symbol;
109 relocations Relocations;
110
111 COFFSection(StringRef name);
112 };
113
114 class WinCOFFObjectWriter : public MCObjectWriter {
115 public:
116 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
117 typedef std::vector<std::unique_ptr<COFFSection>> sections;
118
119 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
120 typedef DenseMap<MCSection const *, COFFSection *> section_map;
121
122 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
123
124 // Root level file contents.
125 COFF::header Header;
126 sections Sections;
127 symbols Symbols;
128 StringTableBuilder Strings{StringTableBuilder::WinCOFF};
129
130 // Maps used during object file creation.
131 section_map SectionMap;
132 symbol_map SymbolMap;
133
134 bool UseBigObj;
135
136 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS);
137
reset()138 void reset() override {
139 memset(&Header, 0, sizeof(Header));
140 Header.Machine = TargetObjectWriter->getMachine();
141 Sections.clear();
142 Symbols.clear();
143 Strings.clear();
144 SectionMap.clear();
145 SymbolMap.clear();
146 MCObjectWriter::reset();
147 }
148
149 COFFSymbol *createSymbol(StringRef Name);
150 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
151 COFFSection *createSection(StringRef Name);
152
153 template <typename object_t, typename list_t>
154 object_t *createCOFFEntity(StringRef Name, list_t &List);
155
156 void defineSection(MCSectionCOFF const &Sec);
157
158 COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
159 void DefineSymbol(const MCSymbol &Symbol, MCAssembler &Assembler,
160 const MCAsmLayout &Layout);
161
162 void SetSymbolName(COFFSymbol &S);
163 void SetSectionName(COFFSection &S);
164
165 bool IsPhysicalSection(COFFSection *S);
166
167 // Entity writing methods.
168
169 void WriteFileHeader(const COFF::header &Header);
170 void WriteSymbol(const COFFSymbol &S);
171 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
172 void writeSectionHeader(const COFF::section &S);
173 void WriteRelocation(const COFF::relocation &R);
174
175 // MCObjectWriter interface implementation.
176
177 void executePostLayoutBinding(MCAssembler &Asm,
178 const MCAsmLayout &Layout) override;
179
180 bool isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
181 const MCSymbol &SymA,
182 const MCFragment &FB, bool InSet,
183 bool IsPCRel) const override;
184
185 bool isWeak(const MCSymbol &Sym) const override;
186
187 void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
188 const MCFragment *Fragment, const MCFixup &Fixup,
189 MCValue Target, bool &IsPCRel,
190 uint64_t &FixedValue) override;
191
192 void writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
193 };
194 }
195
write_uint32_le(void * Data,uint32_t Value)196 static inline void write_uint32_le(void *Data, uint32_t Value) {
197 support::endian::write<uint32_t, support::little, support::unaligned>(Data,
198 Value);
199 }
200
201 //------------------------------------------------------------------------------
202 // Symbol class implementation
203
COFFSymbol(StringRef name)204 COFFSymbol::COFFSymbol(StringRef name)
205 : Name(name.begin(), name.end()), Other(nullptr), Section(nullptr),
206 Relocations(0), MC(nullptr) {
207 memset(&Data, 0, sizeof(Data));
208 }
209
210 // In the case that the name does not fit within 8 bytes, the offset
211 // into the string table is stored in the last 4 bytes instead, leaving
212 // the first 4 bytes as 0.
set_name_offset(uint32_t Offset)213 void COFFSymbol::set_name_offset(uint32_t Offset) {
214 write_uint32_le(Data.Name + 0, 0);
215 write_uint32_le(Data.Name + 4, Offset);
216 }
217
218 //------------------------------------------------------------------------------
219 // Section class implementation
220
COFFSection(StringRef name)221 COFFSection::COFFSection(StringRef name)
222 : Name(name), MCSection(nullptr), Symbol(nullptr) {
223 memset(&Header, 0, sizeof(Header));
224 }
225
226 //------------------------------------------------------------------------------
227 // WinCOFFObjectWriter class implementation
228
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_pwrite_stream & OS)229 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
230 raw_pwrite_stream &OS)
231 : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
232 memset(&Header, 0, sizeof(Header));
233
234 Header.Machine = TargetObjectWriter->getMachine();
235 }
236
createSymbol(StringRef Name)237 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
238 return createCOFFEntity<COFFSymbol>(Name, Symbols);
239 }
240
GetOrCreateCOFFSymbol(const MCSymbol * Symbol)241 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
242 symbol_map::iterator i = SymbolMap.find(Symbol);
243 if (i != SymbolMap.end())
244 return i->second;
245 COFFSymbol *RetSymbol =
246 createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
247 SymbolMap[Symbol] = RetSymbol;
248 return RetSymbol;
249 }
250
createSection(StringRef Name)251 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
252 return createCOFFEntity<COFFSection>(Name, Sections);
253 }
254
255 /// A template used to lookup or create a symbol/section, and initialize it if
256 /// needed.
257 template <typename object_t, typename list_t>
createCOFFEntity(StringRef Name,list_t & List)258 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name, list_t &List) {
259 List.push_back(make_unique<object_t>(Name));
260
261 return List.back().get();
262 }
263
264 /// This function takes a section data object from the assembler
265 /// and creates the associated COFF section staging object.
defineSection(MCSectionCOFF const & Sec)266 void WinCOFFObjectWriter::defineSection(MCSectionCOFF const &Sec) {
267 COFFSection *coff_section = createSection(Sec.getSectionName());
268 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
269 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
270 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
271 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
272 if (COMDATSymbol->Section)
273 report_fatal_error("two sections have the same comdat");
274 COMDATSymbol->Section = coff_section;
275 }
276 }
277
278 coff_section->Symbol = coff_symbol;
279 coff_symbol->Section = coff_section;
280 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
281
282 // In this case the auxiliary symbol is a Section Definition.
283 coff_symbol->Aux.resize(1);
284 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
285 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
286 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
287
288 coff_section->Header.Characteristics = Sec.getCharacteristics();
289
290 uint32_t &Characteristics = coff_section->Header.Characteristics;
291 switch (Sec.getAlignment()) {
292 case 1:
293 Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;
294 break;
295 case 2:
296 Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;
297 break;
298 case 4:
299 Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;
300 break;
301 case 8:
302 Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;
303 break;
304 case 16:
305 Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;
306 break;
307 case 32:
308 Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;
309 break;
310 case 64:
311 Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;
312 break;
313 case 128:
314 Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;
315 break;
316 case 256:
317 Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;
318 break;
319 case 512:
320 Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;
321 break;
322 case 1024:
323 Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES;
324 break;
325 case 2048:
326 Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES;
327 break;
328 case 4096:
329 Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES;
330 break;
331 case 8192:
332 Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES;
333 break;
334 default:
335 llvm_unreachable("unsupported section alignment");
336 }
337
338 // Bind internal COFF section to MC section.
339 coff_section->MCSection = &Sec;
340 SectionMap[&Sec] = coff_section;
341 }
342
getSymbolValue(const MCSymbol & Symbol,const MCAsmLayout & Layout)343 static uint64_t getSymbolValue(const MCSymbol &Symbol,
344 const MCAsmLayout &Layout) {
345 if (Symbol.isCommon() && Symbol.isExternal())
346 return Symbol.getCommonSize();
347
348 uint64_t Res;
349 if (!Layout.getSymbolOffset(Symbol, Res))
350 return 0;
351
352 return Res;
353 }
354
getLinkedSymbol(const MCSymbol & Symbol)355 COFFSymbol *WinCOFFObjectWriter::getLinkedSymbol(const MCSymbol &Symbol) {
356 if (!Symbol.isVariable())
357 return nullptr;
358
359 const MCSymbolRefExpr *SymRef =
360 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
361 if (!SymRef)
362 return nullptr;
363
364 const MCSymbol &Aliasee = SymRef->getSymbol();
365 if (!Aliasee.isUndefined())
366 return nullptr;
367 return GetOrCreateCOFFSymbol(&Aliasee);
368 }
369
370 /// This function takes a symbol data object from the assembler
371 /// and creates the associated COFF symbol staging object.
DefineSymbol(const MCSymbol & Symbol,MCAssembler & Assembler,const MCAsmLayout & Layout)372 void WinCOFFObjectWriter::DefineSymbol(const MCSymbol &Symbol,
373 MCAssembler &Assembler,
374 const MCAsmLayout &Layout) {
375 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
376 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
377 COFFSection *Sec = nullptr;
378 if (Base && Base->getFragment()) {
379 Sec = SectionMap[Base->getFragment()->getParent()];
380 if (coff_symbol->Section && coff_symbol->Section != Sec)
381 report_fatal_error("conflicting sections for symbol");
382 }
383
384 COFFSymbol *Local = nullptr;
385 if (cast<MCSymbolCOFF>(Symbol).isWeakExternal()) {
386 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
387
388 COFFSymbol *WeakDefault = getLinkedSymbol(Symbol);
389 if (!WeakDefault) {
390 std::string WeakName = (".weak." + Symbol.getName() + ".default").str();
391 WeakDefault = createSymbol(WeakName);
392 if (!Sec)
393 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
394 else
395 WeakDefault->Section = Sec;
396 Local = WeakDefault;
397 }
398
399 coff_symbol->Other = WeakDefault;
400
401 // Setup the Weak External auxiliary symbol.
402 coff_symbol->Aux.resize(1);
403 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
404 coff_symbol->Aux[0].AuxType = ATWeakExternal;
405 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
406 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
407 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
408 } else {
409 if (!Base)
410 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
411 else
412 coff_symbol->Section = Sec;
413 Local = coff_symbol;
414 }
415
416 if (Local) {
417 Local->Data.Value = getSymbolValue(Symbol, Layout);
418
419 const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(Symbol);
420 Local->Data.Type = SymbolCOFF.getType();
421 Local->Data.StorageClass = SymbolCOFF.getClass();
422
423 // If no storage class was specified in the streamer, define it here.
424 if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
425 bool IsExternal = Symbol.isExternal() ||
426 (!Symbol.getFragment() && !Symbol.isVariable());
427
428 Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
429 : COFF::IMAGE_SYM_CLASS_STATIC;
430 }
431 }
432
433 coff_symbol->MC = &Symbol;
434 }
435
436 // Maximum offsets for different string table entry encodings.
437 enum : unsigned { Max7DecimalOffset = 9999999U };
438 enum : uint64_t { MaxBase64Offset = 0xFFFFFFFFFULL }; // 64^6, including 0
439
440 // Encode a string table entry offset in base 64, padded to 6 chars, and
441 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
442 // Buffer must be at least 8 bytes large. No terminating null appended.
encodeBase64StringEntry(char * Buffer,uint64_t Value)443 static void encodeBase64StringEntry(char *Buffer, uint64_t Value) {
444 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
445 "Illegal section name encoding for value");
446
447 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
448 "abcdefghijklmnopqrstuvwxyz"
449 "0123456789+/";
450
451 Buffer[0] = '/';
452 Buffer[1] = '/';
453
454 char *Ptr = Buffer + 7;
455 for (unsigned i = 0; i < 6; ++i) {
456 unsigned Rem = Value % 64;
457 Value /= 64;
458 *(Ptr--) = Alphabet[Rem];
459 }
460 }
461
SetSectionName(COFFSection & S)462 void WinCOFFObjectWriter::SetSectionName(COFFSection &S) {
463 if (S.Name.size() > COFF::NameSize) {
464 uint64_t StringTableEntry = Strings.getOffset(S.Name);
465
466 if (StringTableEntry <= Max7DecimalOffset) {
467 SmallVector<char, COFF::NameSize> Buffer;
468 Twine('/').concat(Twine(StringTableEntry)).toVector(Buffer);
469 assert(Buffer.size() <= COFF::NameSize && Buffer.size() >= 2);
470
471 std::memcpy(S.Header.Name, Buffer.data(), Buffer.size());
472 } else if (StringTableEntry <= MaxBase64Offset) {
473 // Starting with 10,000,000, offsets are encoded as base64.
474 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
475 } else {
476 report_fatal_error("COFF string table is greater than 64 GB.");
477 }
478 } else {
479 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
480 }
481 }
482
SetSymbolName(COFFSymbol & S)483 void WinCOFFObjectWriter::SetSymbolName(COFFSymbol &S) {
484 if (S.Name.size() > COFF::NameSize)
485 S.set_name_offset(Strings.getOffset(S.Name));
486 else
487 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
488 }
489
IsPhysicalSection(COFFSection * S)490 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
491 return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
492 0;
493 }
494
495 //------------------------------------------------------------------------------
496 // entity writing methods
497
WriteFileHeader(const COFF::header & Header)498 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
499 if (UseBigObj) {
500 writeLE16(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
501 writeLE16(0xFFFF);
502 writeLE16(COFF::BigObjHeader::MinBigObjectVersion);
503 writeLE16(Header.Machine);
504 writeLE32(Header.TimeDateStamp);
505 writeBytes(StringRef(COFF::BigObjMagic, sizeof(COFF::BigObjMagic)));
506 writeLE32(0);
507 writeLE32(0);
508 writeLE32(0);
509 writeLE32(0);
510 writeLE32(Header.NumberOfSections);
511 writeLE32(Header.PointerToSymbolTable);
512 writeLE32(Header.NumberOfSymbols);
513 } else {
514 writeLE16(Header.Machine);
515 writeLE16(static_cast<int16_t>(Header.NumberOfSections));
516 writeLE32(Header.TimeDateStamp);
517 writeLE32(Header.PointerToSymbolTable);
518 writeLE32(Header.NumberOfSymbols);
519 writeLE16(Header.SizeOfOptionalHeader);
520 writeLE16(Header.Characteristics);
521 }
522 }
523
WriteSymbol(const COFFSymbol & S)524 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
525 writeBytes(StringRef(S.Data.Name, COFF::NameSize));
526 writeLE32(S.Data.Value);
527 if (UseBigObj)
528 writeLE32(S.Data.SectionNumber);
529 else
530 writeLE16(static_cast<int16_t>(S.Data.SectionNumber));
531 writeLE16(S.Data.Type);
532 write8(S.Data.StorageClass);
533 write8(S.Data.NumberOfAuxSymbols);
534 WriteAuxiliarySymbols(S.Aux);
535 }
536
WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols & S)537 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
538 const COFFSymbol::AuxiliarySymbols &S) {
539 for (const AuxSymbol &i : S) {
540 switch (i.AuxType) {
541 case ATFunctionDefinition:
542 writeLE32(i.Aux.FunctionDefinition.TagIndex);
543 writeLE32(i.Aux.FunctionDefinition.TotalSize);
544 writeLE32(i.Aux.FunctionDefinition.PointerToLinenumber);
545 writeLE32(i.Aux.FunctionDefinition.PointerToNextFunction);
546 WriteZeros(sizeof(i.Aux.FunctionDefinition.unused));
547 if (UseBigObj)
548 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
549 break;
550 case ATbfAndefSymbol:
551 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused1));
552 writeLE16(i.Aux.bfAndefSymbol.Linenumber);
553 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused2));
554 writeLE32(i.Aux.bfAndefSymbol.PointerToNextFunction);
555 WriteZeros(sizeof(i.Aux.bfAndefSymbol.unused3));
556 if (UseBigObj)
557 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
558 break;
559 case ATWeakExternal:
560 writeLE32(i.Aux.WeakExternal.TagIndex);
561 writeLE32(i.Aux.WeakExternal.Characteristics);
562 WriteZeros(sizeof(i.Aux.WeakExternal.unused));
563 if (UseBigObj)
564 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
565 break;
566 case ATFile:
567 writeBytes(
568 StringRef(reinterpret_cast<const char *>(&i.Aux),
569 UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size));
570 break;
571 case ATSectionDefinition:
572 writeLE32(i.Aux.SectionDefinition.Length);
573 writeLE16(i.Aux.SectionDefinition.NumberOfRelocations);
574 writeLE16(i.Aux.SectionDefinition.NumberOfLinenumbers);
575 writeLE32(i.Aux.SectionDefinition.CheckSum);
576 writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number));
577 write8(i.Aux.SectionDefinition.Selection);
578 WriteZeros(sizeof(i.Aux.SectionDefinition.unused));
579 writeLE16(static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16));
580 if (UseBigObj)
581 WriteZeros(COFF::Symbol32Size - COFF::Symbol16Size);
582 break;
583 }
584 }
585 }
586
writeSectionHeader(const COFF::section & S)587 void WinCOFFObjectWriter::writeSectionHeader(const COFF::section &S) {
588 writeBytes(StringRef(S.Name, COFF::NameSize));
589
590 writeLE32(S.VirtualSize);
591 writeLE32(S.VirtualAddress);
592 writeLE32(S.SizeOfRawData);
593 writeLE32(S.PointerToRawData);
594 writeLE32(S.PointerToRelocations);
595 writeLE32(S.PointerToLineNumbers);
596 writeLE16(S.NumberOfRelocations);
597 writeLE16(S.NumberOfLineNumbers);
598 writeLE32(S.Characteristics);
599 }
600
WriteRelocation(const COFF::relocation & R)601 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
602 writeLE32(R.VirtualAddress);
603 writeLE32(R.SymbolTableIndex);
604 writeLE16(R.Type);
605 }
606
607 ////////////////////////////////////////////////////////////////////////////////
608 // MCObjectWriter interface implementations
609
executePostLayoutBinding(MCAssembler & Asm,const MCAsmLayout & Layout)610 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm,
611 const MCAsmLayout &Layout) {
612 // "Define" each section & symbol. This creates section & symbol
613 // entries in the staging area.
614 for (const auto &Section : Asm)
615 defineSection(static_cast<const MCSectionCOFF &>(Section));
616
617 for (const MCSymbol &Symbol : Asm.symbols())
618 if (!Symbol.isTemporary())
619 DefineSymbol(Symbol, Asm, Layout);
620 }
621
isSymbolRefDifferenceFullyResolvedImpl(const MCAssembler & Asm,const MCSymbol & SymA,const MCFragment & FB,bool InSet,bool IsPCRel) const622 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
623 const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
624 bool InSet, bool IsPCRel) const {
625 // MS LINK expects to be able to replace all references to a function with a
626 // thunk to implement their /INCREMENTAL feature. Make sure we don't optimize
627 // away any relocations to functions.
628 uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
629 if (Asm.isIncrementalLinkerCompatible() &&
630 (Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
631 return false;
632 return MCObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(Asm, SymA, FB,
633 InSet, IsPCRel);
634 }
635
isWeak(const MCSymbol & Sym) const636 bool WinCOFFObjectWriter::isWeak(const MCSymbol &Sym) const {
637 if (!Sym.isExternal())
638 return false;
639
640 if (!Sym.isInSection())
641 return false;
642
643 const auto &Sec = cast<MCSectionCOFF>(Sym.getSection());
644 if (!Sec.getCOMDATSymbol())
645 return false;
646
647 // It looks like for COFF it is invalid to replace a reference to a global
648 // in a comdat with a reference to a local.
649 // FIXME: Add a specification reference if available.
650 return true;
651 }
652
recordRelocation(MCAssembler & Asm,const MCAsmLayout & Layout,const MCFragment * Fragment,const MCFixup & Fixup,MCValue Target,bool & IsPCRel,uint64_t & FixedValue)653 void WinCOFFObjectWriter::recordRelocation(
654 MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment,
655 const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) {
656 assert(Target.getSymA() && "Relocation must reference a symbol!");
657
658 const MCSymbol &A = Target.getSymA()->getSymbol();
659 if (!A.isRegistered()) {
660 Asm.getContext().reportError(Fixup.getLoc(),
661 Twine("symbol '") + A.getName() +
662 "' can not be undefined");
663 return;
664 }
665 if (A.isTemporary() && A.isUndefined()) {
666 Asm.getContext().reportError(Fixup.getLoc(),
667 Twine("assembler label '") + A.getName() +
668 "' can not be undefined");
669 return;
670 }
671
672 MCSection *Section = Fragment->getParent();
673
674 // Mark this symbol as requiring an entry in the symbol table.
675 assert(SectionMap.find(Section) != SectionMap.end() &&
676 "Section must already have been defined in executePostLayoutBinding!");
677
678 COFFSection *coff_section = SectionMap[Section];
679 const MCSymbolRefExpr *SymB = Target.getSymB();
680 bool CrossSection = false;
681
682 if (SymB) {
683 const MCSymbol *B = &SymB->getSymbol();
684 if (!B->getFragment()) {
685 Asm.getContext().reportError(
686 Fixup.getLoc(),
687 Twine("symbol '") + B->getName() +
688 "' can not be undefined in a subtraction expression");
689 return;
690 }
691
692 if (!A.getFragment()) {
693 Asm.getContext().reportError(
694 Fixup.getLoc(),
695 Twine("symbol '") + A.getName() +
696 "' can not be undefined in a subtraction expression");
697 return;
698 }
699
700 CrossSection = &A.getSection() != &B->getSection();
701
702 // Offset of the symbol in the section
703 int64_t OffsetOfB = Layout.getSymbolOffset(*B);
704
705 // In the case where we have SymbA and SymB, we just need to store the delta
706 // between the two symbols. Update FixedValue to account for the delta, and
707 // skip recording the relocation.
708 if (!CrossSection) {
709 int64_t OffsetOfA = Layout.getSymbolOffset(A);
710 FixedValue = (OffsetOfA - OffsetOfB) + Target.getConstant();
711 return;
712 }
713
714 // Offset of the relocation in the section
715 int64_t OffsetOfRelocation =
716 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
717
718 FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
719 } else {
720 FixedValue = Target.getConstant();
721 }
722
723 COFFRelocation Reloc;
724
725 Reloc.Data.SymbolTableIndex = 0;
726 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
727
728 // Turn relocations for temporary symbols into section relocations.
729 if (A.isTemporary() || CrossSection) {
730 MCSection *TargetSection = &A.getSection();
731 assert(
732 SectionMap.find(TargetSection) != SectionMap.end() &&
733 "Section must already have been defined in executePostLayoutBinding!");
734 Reloc.Symb = SectionMap[TargetSection]->Symbol;
735 FixedValue += Layout.getSymbolOffset(A);
736 } else {
737 assert(
738 SymbolMap.find(&A) != SymbolMap.end() &&
739 "Symbol must already have been defined in executePostLayoutBinding!");
740 Reloc.Symb = SymbolMap[&A];
741 }
742
743 ++Reloc.Symb->Relocations;
744
745 Reloc.Data.VirtualAddress += Fixup.getOffset();
746 Reloc.Data.Type = TargetObjectWriter->getRelocType(
747 Target, Fixup, CrossSection, Asm.getBackend());
748
749 // FIXME: Can anyone explain what this does other than adjust for the size
750 // of the offset?
751 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
752 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
753 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
754 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
755 FixedValue += 4;
756
757 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
758 switch (Reloc.Data.Type) {
759 case COFF::IMAGE_REL_ARM_ABSOLUTE:
760 case COFF::IMAGE_REL_ARM_ADDR32:
761 case COFF::IMAGE_REL_ARM_ADDR32NB:
762 case COFF::IMAGE_REL_ARM_TOKEN:
763 case COFF::IMAGE_REL_ARM_SECTION:
764 case COFF::IMAGE_REL_ARM_SECREL:
765 break;
766 case COFF::IMAGE_REL_ARM_BRANCH11:
767 case COFF::IMAGE_REL_ARM_BLX11:
768 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
769 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
770 // for Windows CE).
771 case COFF::IMAGE_REL_ARM_BRANCH24:
772 case COFF::IMAGE_REL_ARM_BLX24:
773 case COFF::IMAGE_REL_ARM_MOV32A:
774 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
775 // only used for ARM mode code, which is documented as being unsupported
776 // by Windows on ARM. Empirical proof indicates that masm is able to
777 // generate the relocations however the rest of the MSVC toolchain is
778 // unable to handle it.
779 llvm_unreachable("unsupported relocation");
780 break;
781 case COFF::IMAGE_REL_ARM_MOV32T:
782 break;
783 case COFF::IMAGE_REL_ARM_BRANCH20T:
784 case COFF::IMAGE_REL_ARM_BRANCH24T:
785 case COFF::IMAGE_REL_ARM_BLX23T:
786 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
787 // perform a 4 byte adjustment to the relocation. Relative branches are
788 // offset by 4 on ARM, however, because there is no RELA relocations, all
789 // branches are offset by 4.
790 FixedValue = FixedValue + 4;
791 break;
792 }
793 }
794
795 // The fixed value never makes sense for section indicies, ignore it.
796 if (Fixup.getKind() == FK_SecRel_2)
797 FixedValue = 0;
798
799 if (TargetObjectWriter->recordRelocation(Fixup))
800 coff_section->Relocations.push_back(Reloc);
801 }
802
writeObject(MCAssembler & Asm,const MCAsmLayout & Layout)803 void WinCOFFObjectWriter::writeObject(MCAssembler &Asm,
804 const MCAsmLayout &Layout) {
805 size_t SectionsSize = Sections.size();
806 if (SectionsSize > static_cast<size_t>(INT32_MAX))
807 report_fatal_error(
808 "PE COFF object files can't have more than 2147483647 sections");
809
810 // Assign symbol and section indexes and offsets.
811 int32_t NumberOfSections = static_cast<int32_t>(SectionsSize);
812
813 UseBigObj = NumberOfSections > COFF::MaxNumberOfSections16;
814
815 // Assign section numbers.
816 size_t Number = 1;
817 for (const auto &Section : Sections) {
818 Section->Number = Number;
819 Section->Symbol->Data.SectionNumber = Number;
820 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Number;
821 ++Number;
822 }
823
824 Header.NumberOfSections = NumberOfSections;
825 Header.NumberOfSymbols = 0;
826
827 for (const std::string &Name : Asm.getFileNames()) {
828 // round up to calculate the number of auxiliary symbols required
829 unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
830 unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
831
832 COFFSymbol *file = createSymbol(".file");
833 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
834 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
835 file->Aux.resize(Count);
836
837 unsigned Offset = 0;
838 unsigned Length = Name.size();
839 for (auto &Aux : file->Aux) {
840 Aux.AuxType = ATFile;
841
842 if (Length > SymbolSize) {
843 memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
844 Length = Length - SymbolSize;
845 } else {
846 memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
847 memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
848 break;
849 }
850
851 Offset += SymbolSize;
852 }
853 }
854
855 for (auto &Symbol : Symbols) {
856 // Update section number & offset for symbols that have them.
857 if (Symbol->Section)
858 Symbol->Data.SectionNumber = Symbol->Section->Number;
859 Symbol->setIndex(Header.NumberOfSymbols++);
860 // Update auxiliary symbol info.
861 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
862 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
863 }
864
865 // Build string table.
866 for (const auto &S : Sections)
867 if (S->Name.size() > COFF::NameSize)
868 Strings.add(S->Name);
869 for (const auto &S : Symbols)
870 if (S->Name.size() > COFF::NameSize)
871 Strings.add(S->Name);
872 Strings.finalize();
873
874 // Set names.
875 for (const auto &S : Sections)
876 SetSectionName(*S);
877 for (auto &S : Symbols)
878 SetSymbolName(*S);
879
880 // Fixup weak external references.
881 for (auto &Symbol : Symbols) {
882 if (Symbol->Other) {
883 assert(Symbol->getIndex() != -1);
884 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
885 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
886 "Symbol's aux symbol must be a Weak External!");
887 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
888 }
889 }
890
891 // Fixup associative COMDAT sections.
892 for (auto &Section : Sections) {
893 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
894 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
895 continue;
896
897 const MCSectionCOFF &MCSec = *Section->MCSection;
898
899 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
900 assert(COMDAT);
901 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
902 assert(COMDATSymbol);
903 COFFSection *Assoc = COMDATSymbol->Section;
904 if (!Assoc)
905 report_fatal_error(
906 Twine("Missing associated COMDAT section for section ") +
907 MCSec.getSectionName());
908
909 // Skip this section if the associated section is unused.
910 if (Assoc->Number == -1)
911 continue;
912
913 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = Assoc->Number;
914 }
915
916 // Assign file offsets to COFF object file structures.
917
918 unsigned offset = getInitialOffset();
919
920 if (UseBigObj)
921 offset += COFF::Header32Size;
922 else
923 offset += COFF::Header16Size;
924 offset += COFF::SectionSize * Header.NumberOfSections;
925
926 for (const auto &Section : Asm) {
927 COFFSection *Sec = SectionMap[&Section];
928
929 if (Sec->Number == -1)
930 continue;
931
932 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
933
934 if (IsPhysicalSection(Sec)) {
935 // Align the section data to a four byte boundary.
936 offset = alignTo(offset, 4);
937 Sec->Header.PointerToRawData = offset;
938
939 offset += Sec->Header.SizeOfRawData;
940 }
941
942 if (Sec->Relocations.size() > 0) {
943 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
944
945 if (RelocationsOverflow) {
946 // Signal overflow by setting NumberOfRelocations to max value. Actual
947 // size is found in reloc #0. Microsoft tools understand this.
948 Sec->Header.NumberOfRelocations = 0xffff;
949 } else {
950 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
951 }
952 Sec->Header.PointerToRelocations = offset;
953
954 if (RelocationsOverflow) {
955 // Reloc #0 will contain actual count, so make room for it.
956 offset += COFF::RelocationSize;
957 }
958
959 offset += COFF::RelocationSize * Sec->Relocations.size();
960
961 for (auto &Relocation : Sec->Relocations) {
962 assert(Relocation.Symb->getIndex() != -1);
963 Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
964 }
965 }
966
967 assert(Sec->Symbol->Aux.size() == 1 &&
968 "Section's symbol must have one aux!");
969 AuxSymbol &Aux = Sec->Symbol->Aux[0];
970 assert(Aux.AuxType == ATSectionDefinition &&
971 "Section's symbol's aux symbol must be a Section Definition!");
972 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
973 Aux.Aux.SectionDefinition.NumberOfRelocations =
974 Sec->Header.NumberOfRelocations;
975 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
976 Sec->Header.NumberOfLineNumbers;
977 }
978
979 Header.PointerToSymbolTable = offset;
980
981 // MS LINK expects to be able to use this timestamp to implement their
982 // /INCREMENTAL feature.
983 if (Asm.isIncrementalLinkerCompatible()) {
984 std::time_t Now = time(nullptr);
985 if (Now < 0 || !isUInt<32>(Now))
986 Now = UINT32_MAX;
987 Header.TimeDateStamp = Now;
988 } else {
989 // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
990 Header.TimeDateStamp = 0;
991 }
992
993 // Write it all to disk...
994 WriteFileHeader(Header);
995
996 {
997 sections::iterator i, ie;
998 MCAssembler::iterator j, je;
999
1000 for (auto &Section : Sections) {
1001 if (Section->Number != -1) {
1002 if (Section->Relocations.size() >= 0xffff)
1003 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
1004 writeSectionHeader(Section->Header);
1005 }
1006 }
1007
1008 SmallVector<char, 128> SectionContents;
1009 for (i = Sections.begin(), ie = Sections.end(), j = Asm.begin(),
1010 je = Asm.end();
1011 (i != ie) && (j != je); ++i, ++j) {
1012
1013 if ((*i)->Number == -1)
1014 continue;
1015
1016 if ((*i)->Header.PointerToRawData != 0) {
1017 assert(getStream().tell() <= (*i)->Header.PointerToRawData &&
1018 "Section::PointerToRawData is insane!");
1019
1020 unsigned SectionDataPadding =
1021 (*i)->Header.PointerToRawData - getStream().tell();
1022 assert(SectionDataPadding < 4 &&
1023 "Should only need at most three bytes of padding!");
1024
1025 WriteZeros(SectionDataPadding);
1026
1027 // Save the contents of the section to a temporary buffer, we need this
1028 // to CRC the data before we dump it into the object file.
1029 SectionContents.clear();
1030 raw_svector_ostream VecOS(SectionContents);
1031 raw_pwrite_stream &OldStream = getStream();
1032 // Redirect the output stream to our buffer.
1033 setStream(VecOS);
1034 // Fill our buffer with the section data.
1035 Asm.writeSectionData(&*j, Layout);
1036 // Reset the stream back to what it was before.
1037 setStream(OldStream);
1038
1039 // Calculate our CRC with an initial value of '0', this is not how
1040 // JamCRC is specified but it aligns with the expected output.
1041 JamCRC JC(/*Init=*/0x00000000U);
1042 JC.update(SectionContents);
1043
1044 // Write the section contents to the object file.
1045 getStream() << SectionContents;
1046
1047 // Update the section definition auxiliary symbol to record the CRC.
1048 COFFSection *Sec = SectionMap[&*j];
1049 COFFSymbol::AuxiliarySymbols &AuxSyms = Sec->Symbol->Aux;
1050 assert(AuxSyms.size() == 1 &&
1051 AuxSyms[0].AuxType == ATSectionDefinition);
1052 AuxSymbol &SecDef = AuxSyms[0];
1053 SecDef.Aux.SectionDefinition.CheckSum = JC.getCRC();
1054 }
1055
1056 if ((*i)->Relocations.size() > 0) {
1057 assert(getStream().tell() == (*i)->Header.PointerToRelocations &&
1058 "Section::PointerToRelocations is insane!");
1059
1060 if ((*i)->Relocations.size() >= 0xffff) {
1061 // In case of overflow, write actual relocation count as first
1062 // relocation. Including the synthetic reloc itself (+ 1).
1063 COFF::relocation r;
1064 r.VirtualAddress = (*i)->Relocations.size() + 1;
1065 r.SymbolTableIndex = 0;
1066 r.Type = 0;
1067 WriteRelocation(r);
1068 }
1069
1070 for (const auto &Relocation : (*i)->Relocations)
1071 WriteRelocation(Relocation.Data);
1072 } else
1073 assert((*i)->Header.PointerToRelocations == 0 &&
1074 "Section::PointerToRelocations is insane!");
1075 }
1076 }
1077
1078 assert(getStream().tell() == Header.PointerToSymbolTable &&
1079 "Header::PointerToSymbolTable is insane!");
1080
1081 for (auto &Symbol : Symbols)
1082 if (Symbol->getIndex() != -1)
1083 WriteSymbol(*Symbol);
1084
1085 getStream().write(Strings.data().data(), Strings.data().size());
1086 }
1087
MCWinCOFFObjectTargetWriter(unsigned Machine_)1088 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1089 : Machine(Machine_) {}
1090
1091 // Pin the vtable to this file.
anchor()1092 void MCWinCOFFObjectTargetWriter::anchor() {}
1093
1094 //------------------------------------------------------------------------------
1095 // WinCOFFObjectWriter factory function
1096
1097 MCObjectWriter *
createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_pwrite_stream & OS)1098 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1099 raw_pwrite_stream &OS) {
1100 return new WinCOFFObjectWriter(MOTW, OS);
1101 }
1102