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/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"
33 #include <cstdio>
34
35 using namespace llvm;
36
37 #define DEBUG_TYPE "WinCOFFObjectWriter"
38
39 namespace {
40 typedef SmallString<COFF::NameSize> name;
41
42 enum AuxiliaryType {
43 ATFunctionDefinition,
44 ATbfAndefSymbol,
45 ATWeakExternal,
46 ATFile,
47 ATSectionDefinition
48 };
49
50 struct AuxSymbol {
51 AuxiliaryType AuxType;
52 COFF::Auxiliary Aux;
53 };
54
55 class COFFSymbol;
56 class COFFSection;
57
58 class COFFSymbol {
59 public:
60 COFF::symbol Data;
61
62 typedef SmallVector<AuxSymbol, 1> AuxiliarySymbols;
63
64 name Name;
65 int Index;
66 AuxiliarySymbols Aux;
67 COFFSymbol *Other;
68 COFFSection *Section;
69 int Relocations;
70
71 MCSymbolData const *MCData;
72
73 COFFSymbol(StringRef name);
74 size_t size() const;
75 void set_name_offset(uint32_t Offset);
76
77 bool should_keep() const;
78 };
79
80 // This class contains staging data for a COFF relocation entry.
81 struct COFFRelocation {
82 COFF::relocation Data;
83 COFFSymbol *Symb;
84
COFFRelocation__anon79e664d50111::COFFRelocation85 COFFRelocation() : Symb(nullptr) {}
size__anon79e664d50111::COFFRelocation86 static size_t size() { return COFF::RelocationSize; }
87 };
88
89 typedef std::vector<COFFRelocation> relocations;
90
91 class COFFSection {
92 public:
93 COFF::section Header;
94
95 std::string Name;
96 int Number;
97 MCSectionData const *MCData;
98 COFFSymbol *Symbol;
99 relocations Relocations;
100
101 COFFSection(StringRef name);
102 static size_t size();
103 };
104
105 // This class holds the COFF string table.
106 class StringTable {
107 typedef StringMap<size_t> map;
108 map Map;
109
110 void update_length();
111 public:
112 std::vector<char> Data;
113
114 StringTable();
115 size_t size() const;
116 size_t insert(StringRef String);
117 };
118
119 class WinCOFFObjectWriter : public MCObjectWriter {
120 public:
121
122 typedef std::vector<std::unique_ptr<COFFSymbol>> symbols;
123 typedef std::vector<std::unique_ptr<COFFSection>> sections;
124
125 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
126 typedef DenseMap<MCSection const *, COFFSection *> section_map;
127
128 std::unique_ptr<MCWinCOFFObjectTargetWriter> TargetObjectWriter;
129
130 // Root level file contents.
131 COFF::header Header;
132 sections Sections;
133 symbols Symbols;
134 StringTable Strings;
135
136 // Maps used during object file creation.
137 section_map SectionMap;
138 symbol_map SymbolMap;
139
140 WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
141
142 COFFSymbol *createSymbol(StringRef Name);
143 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
144 COFFSection *createSection(StringRef Name);
145
146 template <typename object_t, typename list_t>
147 object_t *createCOFFEntity(StringRef Name, list_t &List);
148
149 void DefineSection(MCSectionData const &SectionData);
150 void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler,
151 const MCAsmLayout &Layout);
152
153 void MakeSymbolReal(COFFSymbol &S, size_t Index);
154 void MakeSectionReal(COFFSection &S, size_t Number);
155
156 bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
157
158 bool IsPhysicalSection(COFFSection *S);
159
160 // Entity writing methods.
161
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);
167
168 // MCObjectWriter interface implementation.
169
170 void ExecutePostLayoutBinding(MCAssembler &Asm,
171 const MCAsmLayout &Layout) override;
172
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;
177
178 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
179 };
180 }
181
write_uint32_le(void * Data,uint32_t const & Value)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;
188 }
189
190 //------------------------------------------------------------------------------
191 // Symbol class implementation
192
COFFSymbol(StringRef name)193 COFFSymbol::COFFSymbol(StringRef name)
194 : Name(name.begin(), name.end())
195 , Other(nullptr)
196 , Section(nullptr)
197 , Relocations(0)
198 , MCData(nullptr) {
199 memset(&Data, 0, sizeof(Data));
200 }
201
size() const202 size_t COFFSymbol::size() const {
203 return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
204 }
205
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.
set_name_offset(uint32_t Offset)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);
212 }
213
214 /// logic to decide if the symbol should be reported in the symbol table
should_keep() const215 bool COFFSymbol::should_keep() const {
216 // no section means its external, keep it
217 if (!Section)
218 return true;
219
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!");
223 return true;
224 }
225
226 // if the section its in is being droped, drop it
227 if (Section->Number == -1)
228 return false;
229
230 // if it is the section symbol, keep it
231 if (Section->Symbol == this)
232 return true;
233
234 // if its temporary, drop it
235 if (MCData && MCData->getSymbol().isTemporary())
236 return false;
237
238 // otherwise, keep it
239 return true;
240 }
241
242 //------------------------------------------------------------------------------
243 // Section class implementation
244
COFFSection(StringRef name)245 COFFSection::COFFSection(StringRef name)
246 : Name(name)
247 , MCData(nullptr)
248 , Symbol(nullptr) {
249 memset(&Header, 0, sizeof(Header));
250 }
251
size()252 size_t COFFSection::size() {
253 return COFF::SectionSize;
254 }
255
256 //------------------------------------------------------------------------------
257 // StringTable class implementation
258
259 /// Write the length of the string table into Data.
260 /// The length of the string table includes uint32 length header.
update_length()261 void StringTable::update_length() {
262 write_uint32_le(&Data.front(), Data.size());
263 }
264
StringTable()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.
268 Data.resize(4);
269 update_length();
270 }
271
size() const272 size_t StringTable::size() const {
273 return Data.size();
274 }
275
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.
insert(StringRef String)278 size_t StringTable::insert(StringRef String) {
279 map::iterator i = Map.find(String);
280
281 if (i != Map.end())
282 return i->second;
283
284 size_t Offset = Data.size();
285
286 // Insert string data into string table.
287 Data.insert(Data.end(), String.begin(), String.end());
288 Data.push_back('\0');
289
290 // Put a reference to it in the map.
291 Map[String] = Offset;
292
293 // Update the internal length field.
294 update_length();
295
296 return Offset;
297 }
298
299 //------------------------------------------------------------------------------
300 // WinCOFFObjectWriter class implementation
301
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_ostream & OS)302 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
303 raw_ostream &OS)
304 : MCObjectWriter(OS, true)
305 , TargetObjectWriter(MOTW) {
306 memset(&Header, 0, sizeof(Header));
307
308 Header.Machine = TargetObjectWriter->getMachine();
309 }
310
createSymbol(StringRef Name)311 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
312 return createCOFFEntity<COFFSymbol>(Name, Symbols);
313 }
314
GetOrCreateCOFFSymbol(const MCSymbol * Symbol)315 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
316 symbol_map::iterator i = SymbolMap.find(Symbol);
317 if (i != SymbolMap.end())
318 return i->second;
319 COFFSymbol *RetSymbol
320 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
321 SymbolMap[Symbol] = RetSymbol;
322 return RetSymbol;
323 }
324
createSection(StringRef Name)325 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
326 return createCOFFEntity<COFFSection>(Name, Sections);
327 }
328
329 /// A template used to lookup or create a symbol/section, and initialize it if
330 /// needed.
331 template <typename object_t, typename list_t>
createCOFFEntity(StringRef Name,list_t & List)332 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
333 list_t &List) {
334 List.push_back(make_unique<object_t>(Name));
335
336 return List.back().get();
337 }
338
339 /// This function takes a section data object from the assembler
340 /// and creates the associated COFF section staging object.
DefineSection(MCSectionData const & SectionData)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());
347
348 COFFSection *coff_section = createSection(Sec.getSectionName());
349 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
350 if (Sec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
351 if (const MCSymbol *S = Sec.getCOMDATSymbol()) {
352 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
353 if (COMDATSymbol->Section)
354 report_fatal_error("two sections have the same comdat");
355 COMDATSymbol->Section = coff_section;
356 }
357 }
358
359 coff_section->Symbol = coff_symbol;
360 coff_symbol->Section = coff_section;
361 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
362
363 // In this case the auxiliary symbol is a Section Definition.
364 coff_symbol->Aux.resize(1);
365 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
366 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
367 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
368
369 coff_section->Header.Characteristics = Sec.getCharacteristics();
370
371 uint32_t &Characteristics = coff_section->Header.Characteristics;
372 switch (SectionData.getAlignment()) {
373 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
374 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
375 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
376 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
377 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
378 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
379 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
380 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
381 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
382 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
383 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
384 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
385 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
386 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
387 default:
388 llvm_unreachable("unsupported section alignment");
389 }
390
391 // Bind internal COFF section to MC section.
392 coff_section->MCData = &SectionData;
393 SectionMap[&SectionData.getSection()] = coff_section;
394 }
395
getSymbolValue(const MCSymbolData & Data,const MCAsmLayout & Layout)396 static uint64_t getSymbolValue(const MCSymbolData &Data,
397 const MCAsmLayout &Layout) {
398 if (Data.isCommon() && Data.isExternal())
399 return Data.getCommonSize();
400
401 uint64_t Res;
402 if (!Layout.getSymbolOffset(&Data, Res))
403 return 0;
404
405 return Res;
406 }
407
408 /// This function takes a symbol data object from the assembler
409 /// and creates the associated COFF symbol staging object.
DefineSymbol(MCSymbolData const & SymbolData,MCAssembler & Assembler,const MCAsmLayout & Layout)410 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
411 MCAssembler &Assembler,
412 const MCAsmLayout &Layout) {
413 MCSymbol const &Symbol = SymbolData.getSymbol();
414 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
415 SymbolMap[&Symbol] = coff_symbol;
416
417 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
418 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
419
420 if (Symbol.isVariable()) {
421 const MCSymbolRefExpr *SymRef =
422 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
423
424 if (!SymRef)
425 report_fatal_error("Weak externals may only alias symbols");
426
427 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
428 } else {
429 std::string WeakName = std::string(".weak.")
430 + Symbol.getName().str()
431 + ".default";
432 COFFSymbol *WeakDefault = createSymbol(WeakName);
433 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
434 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
435 WeakDefault->Data.Type = 0;
436 WeakDefault->Data.Value = 0;
437 coff_symbol->Other = WeakDefault;
438 }
439
440 // Setup the Weak External auxiliary symbol.
441 coff_symbol->Aux.resize(1);
442 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
443 coff_symbol->Aux[0].AuxType = ATWeakExternal;
444 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
445 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
446 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
447
448 coff_symbol->MCData = &SymbolData;
449 } else {
450 const MCSymbolData &ResSymData = Assembler.getSymbolData(Symbol);
451 const MCSymbol *Base = Layout.getBaseSymbol(Symbol);
452 coff_symbol->Data.Value = getSymbolValue(ResSymData, Layout);
453
454 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
455 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
456
457 // If no storage class was specified in the streamer, define it here.
458 if (coff_symbol->Data.StorageClass == 0) {
459 bool external = ResSymData.isExternal() || !ResSymData.Fragment;
460
461 coff_symbol->Data.StorageClass =
462 external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
463 }
464
465 if (!Base) {
466 coff_symbol->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
467 } else {
468 const MCSymbolData &BaseData = Assembler.getSymbolData(*Base);
469 if (BaseData.Fragment) {
470 COFFSection *Sec =
471 SectionMap[&BaseData.Fragment->getParent()->getSection()];
472
473 if (coff_symbol->Section && coff_symbol->Section != Sec)
474 report_fatal_error("conflicting sections for symbol");
475
476 coff_symbol->Section = Sec;
477 }
478 }
479
480 coff_symbol->MCData = &ResSymData;
481 }
482 }
483
484 // Maximum offsets for different string table entry encodings.
485 static const unsigned Max6DecimalOffset = 999999;
486 static const unsigned Max7DecimalOffset = 9999999;
487 static const uint64_t MaxBase64Offset = 0xFFFFFFFFFULL; // 64^6, including 0
488
489 // Encode a string table entry offset in base 64, padded to 6 chars, and
490 // prefixed with a double slash: '//AAAAAA', '//AAAAAB', ...
491 // Buffer must be at least 8 bytes large. No terminating null appended.
encodeBase64StringEntry(char * Buffer,uint64_t Value)492 static void encodeBase64StringEntry(char* Buffer, uint64_t Value) {
493 assert(Value > Max7DecimalOffset && Value <= MaxBase64Offset &&
494 "Illegal section name encoding for value");
495
496 static const char Alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
497 "abcdefghijklmnopqrstuvwxyz"
498 "0123456789+/";
499
500 Buffer[0] = '/';
501 Buffer[1] = '/';
502
503 char* Ptr = Buffer + 7;
504 for (unsigned i = 0; i < 6; ++i) {
505 unsigned Rem = Value % 64;
506 Value /= 64;
507 *(Ptr--) = Alphabet[Rem];
508 }
509 }
510
511 /// making a section real involves assigned it a number and putting
512 /// name into the string table if needed
MakeSectionReal(COFFSection & S,size_t Number)513 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
514 if (S.Name.size() > COFF::NameSize) {
515 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
516
517 if (StringTableEntry <= Max6DecimalOffset) {
518 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
519 } else if (StringTableEntry <= Max7DecimalOffset) {
520 // With seven digits, we have to skip the terminating null. Because
521 // sprintf always appends it, we use a larger temporary buffer.
522 char buffer[9] = { };
523 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
524 std::memcpy(S.Header.Name, buffer, 8);
525 } else if (StringTableEntry <= MaxBase64Offset) {
526 // Starting with 10,000,000, offsets are encoded as base64.
527 encodeBase64StringEntry(S.Header.Name, StringTableEntry);
528 } else {
529 report_fatal_error("COFF string table is greater than 64 GB.");
530 }
531 } else
532 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
533
534 S.Number = Number;
535 S.Symbol->Data.SectionNumber = S.Number;
536 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
537 }
538
MakeSymbolReal(COFFSymbol & S,size_t Index)539 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
540 if (S.Name.size() > COFF::NameSize) {
541 size_t StringTableEntry = Strings.insert(S.Name.c_str());
542
543 S.set_name_offset(StringTableEntry);
544 } else
545 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
546 S.Index = Index;
547 }
548
ExportSymbol(MCSymbolData const & SymbolData,MCAssembler & Asm)549 bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
550 MCAssembler &Asm) {
551 // This doesn't seem to be right. Strings referred to from the .data section
552 // need symbols so they can be linked to code in the .text section right?
553
554 // return Asm.isSymbolLinkerVisible(SymbolData.getSymbol());
555
556 // For now, all non-variable symbols are exported,
557 // the linker will sort the rest out for us.
558 return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
559 }
560
IsPhysicalSection(COFFSection * S)561 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
562 return (S->Header.Characteristics
563 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
564 }
565
566 //------------------------------------------------------------------------------
567 // entity writing methods
568
WriteFileHeader(const COFF::header & Header)569 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
570 WriteLE16(Header.Machine);
571 WriteLE16(Header.NumberOfSections);
572 WriteLE32(Header.TimeDateStamp);
573 WriteLE32(Header.PointerToSymbolTable);
574 WriteLE32(Header.NumberOfSymbols);
575 WriteLE16(Header.SizeOfOptionalHeader);
576 WriteLE16(Header.Characteristics);
577 }
578
WriteSymbol(const COFFSymbol & S)579 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol &S) {
580 WriteBytes(StringRef(S.Data.Name, COFF::NameSize));
581 WriteLE32(S.Data.Value);
582 WriteLE16(S.Data.SectionNumber);
583 WriteLE16(S.Data.Type);
584 Write8(S.Data.StorageClass);
585 Write8(S.Data.NumberOfAuxSymbols);
586 WriteAuxiliarySymbols(S.Aux);
587 }
588
WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols & S)589 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
590 const COFFSymbol::AuxiliarySymbols &S) {
591 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
592 i != e; ++i) {
593 switch(i->AuxType) {
594 case ATFunctionDefinition:
595 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
596 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
597 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
598 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
599 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
600 break;
601 case ATbfAndefSymbol:
602 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
603 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
604 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
605 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
606 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
607 break;
608 case ATWeakExternal:
609 WriteLE32(i->Aux.WeakExternal.TagIndex);
610 WriteLE32(i->Aux.WeakExternal.Characteristics);
611 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
612 break;
613 case ATFile:
614 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
615 sizeof(i->Aux.File.FileName)));
616 break;
617 case ATSectionDefinition:
618 WriteLE32(i->Aux.SectionDefinition.Length);
619 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
620 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
621 WriteLE32(i->Aux.SectionDefinition.CheckSum);
622 WriteLE16(i->Aux.SectionDefinition.Number);
623 Write8(i->Aux.SectionDefinition.Selection);
624 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
625 break;
626 }
627 }
628 }
629
WriteSectionHeader(const COFF::section & S)630 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
631 WriteBytes(StringRef(S.Name, COFF::NameSize));
632
633 WriteLE32(S.VirtualSize);
634 WriteLE32(S.VirtualAddress);
635 WriteLE32(S.SizeOfRawData);
636 WriteLE32(S.PointerToRawData);
637 WriteLE32(S.PointerToRelocations);
638 WriteLE32(S.PointerToLineNumbers);
639 WriteLE16(S.NumberOfRelocations);
640 WriteLE16(S.NumberOfLineNumbers);
641 WriteLE32(S.Characteristics);
642 }
643
WriteRelocation(const COFF::relocation & R)644 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
645 WriteLE32(R.VirtualAddress);
646 WriteLE32(R.SymbolTableIndex);
647 WriteLE16(R.Type);
648 }
649
650 ////////////////////////////////////////////////////////////////////////////////
651 // MCObjectWriter interface implementations
652
ExecutePostLayoutBinding(MCAssembler & Asm,const MCAsmLayout & Layout)653 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
654 const MCAsmLayout &Layout) {
655 // "Define" each section & symbol. This creates section & symbol
656 // entries in the staging area.
657
658 static_assert(sizeof(((COFF::AuxiliaryFile *)nullptr)->FileName) == COFF::SymbolSize,
659 "size mismatch for COFF::AuxiliaryFile::FileName");
660 for (auto FI = Asm.file_names_begin(), FE = Asm.file_names_end();
661 FI != FE; ++FI) {
662 // round up to calculate the number of auxiliary symbols required
663 unsigned Count = (FI->size() + COFF::SymbolSize - 1) / COFF::SymbolSize;
664
665 COFFSymbol *file = createSymbol(".file");
666 file->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
667 file->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
668 file->Aux.resize(Count);
669
670 unsigned Offset = 0;
671 unsigned Length = FI->size();
672 for (auto & Aux : file->Aux) {
673 Aux.AuxType = ATFile;
674
675 if (Length > COFF::SymbolSize) {
676 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, COFF::SymbolSize);
677 Length = Length - COFF::SymbolSize;
678 } else {
679 memcpy(Aux.Aux.File.FileName, FI->c_str() + Offset, Length);
680 memset(&Aux.Aux.File.FileName[Length], 0, COFF::SymbolSize - Length);
681 Length = 0;
682 }
683
684 Offset = Offset + COFF::SymbolSize;
685 }
686 }
687
688 for (const auto & Section : Asm)
689 DefineSection(Section);
690
691 for (MCSymbolData &SD : Asm.symbols())
692 if (ExportSymbol(SD, Asm))
693 DefineSymbol(SD, Asm, Layout);
694 }
695
RecordRelocation(const MCAssembler & Asm,const MCAsmLayout & Layout,const MCFragment * Fragment,const MCFixup & Fixup,MCValue Target,bool & IsPCRel,uint64_t & FixedValue)696 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
697 const MCAsmLayout &Layout,
698 const MCFragment *Fragment,
699 const MCFixup &Fixup,
700 MCValue Target,
701 bool &IsPCRel,
702 uint64_t &FixedValue) {
703 assert(Target.getSymA() && "Relocation must reference a symbol!");
704
705 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
706 const MCSymbol &A = Symbol.AliasedSymbol();
707 if (!Asm.hasSymbolData(A))
708 Asm.getContext().FatalError(
709 Fixup.getLoc(),
710 Twine("symbol '") + A.getName() + "' can not be undefined");
711
712 const MCSymbolData &A_SD = Asm.getSymbolData(A);
713
714 MCSectionData const *SectionData = Fragment->getParent();
715
716 // Mark this symbol as requiring an entry in the symbol table.
717 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
718 "Section must already have been defined in ExecutePostLayoutBinding!");
719 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
720 "Symbol must already have been defined in ExecutePostLayoutBinding!");
721
722 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
723 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
724 const MCSymbolRefExpr *SymB = Target.getSymB();
725 bool CrossSection = false;
726
727 if (SymB) {
728 const MCSymbol *B = &SymB->getSymbol();
729 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
730 if (!B_SD.getFragment())
731 Asm.getContext().FatalError(
732 Fixup.getLoc(),
733 Twine("symbol '") + B->getName() +
734 "' can not be undefined in a subtraction expression");
735
736 if (!A_SD.getFragment())
737 Asm.getContext().FatalError(
738 Fixup.getLoc(),
739 Twine("symbol '") + Symbol.getName() +
740 "' can not be undefined in a subtraction expression");
741
742 CrossSection = &Symbol.getSection() != &B->getSection();
743
744 // Offset of the symbol in the section
745 int64_t a = Layout.getSymbolOffset(&B_SD);
746
747 // Ofeset of the relocation in the section
748 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
749
750 FixedValue = b - a;
751 // In the case where we have SymbA and SymB, we just need to store the delta
752 // between the two symbols. Update FixedValue to account for the delta, and
753 // skip recording the relocation.
754 if (!CrossSection)
755 return;
756 } else {
757 FixedValue = Target.getConstant();
758 }
759
760 COFFRelocation Reloc;
761
762 Reloc.Data.SymbolTableIndex = 0;
763 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
764
765 // Turn relocations for temporary symbols into section relocations.
766 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
767 Reloc.Symb = coff_symbol->Section->Symbol;
768 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
769 + coff_symbol->MCData->getOffset();
770 } else
771 Reloc.Symb = coff_symbol;
772
773 ++Reloc.Symb->Relocations;
774
775 Reloc.Data.VirtualAddress += Fixup.getOffset();
776 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
777 CrossSection);
778
779 // FIXME: Can anyone explain what this does other than adjust for the size
780 // of the offset?
781 if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
782 Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
783 (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
784 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32))
785 FixedValue += 4;
786
787 if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
788 switch (Reloc.Data.Type) {
789 case COFF::IMAGE_REL_ARM_ABSOLUTE:
790 case COFF::IMAGE_REL_ARM_ADDR32:
791 case COFF::IMAGE_REL_ARM_ADDR32NB:
792 case COFF::IMAGE_REL_ARM_TOKEN:
793 case COFF::IMAGE_REL_ARM_SECTION:
794 case COFF::IMAGE_REL_ARM_SECREL:
795 break;
796 case COFF::IMAGE_REL_ARM_BRANCH11:
797 case COFF::IMAGE_REL_ARM_BLX11:
798 // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
799 // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
800 // for Windows CE).
801 case COFF::IMAGE_REL_ARM_BRANCH24:
802 case COFF::IMAGE_REL_ARM_BLX24:
803 case COFF::IMAGE_REL_ARM_MOV32A:
804 // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
805 // only used for ARM mode code, which is documented as being unsupported
806 // by Windows on ARM. Empirical proof indicates that masm is able to
807 // generate the relocations however the rest of the MSVC toolchain is
808 // unable to handle it.
809 llvm_unreachable("unsupported relocation");
810 break;
811 case COFF::IMAGE_REL_ARM_MOV32T:
812 break;
813 case COFF::IMAGE_REL_ARM_BRANCH20T:
814 case COFF::IMAGE_REL_ARM_BRANCH24T:
815 case COFF::IMAGE_REL_ARM_BLX23T:
816 // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
817 // perform a 4 byte adjustment to the relocation. Relative branches are
818 // offset by 4 on ARM, however, because there is no RELA relocations, all
819 // branches are offset by 4.
820 FixedValue = FixedValue + 4;
821 break;
822 }
823 }
824
825 if (TargetObjectWriter->recordRelocation(Fixup))
826 coff_section->Relocations.push_back(Reloc);
827 }
828
WriteObject(MCAssembler & Asm,const MCAsmLayout & Layout)829 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
830 const MCAsmLayout &Layout) {
831 // Assign symbol and section indexes and offsets.
832 Header.NumberOfSections = 0;
833
834 DenseMap<COFFSection *, uint16_t> SectionIndices;
835 for (auto & Section : Sections) {
836 size_t Number = ++Header.NumberOfSections;
837 SectionIndices[Section.get()] = Number;
838 MakeSectionReal(*Section, Number);
839 }
840
841 Header.NumberOfSymbols = 0;
842
843 for (auto & Symbol : Symbols) {
844 // Update section number & offset for symbols that have them.
845 if (Symbol->Section)
846 Symbol->Data.SectionNumber = Symbol->Section->Number;
847
848 if (Symbol->should_keep()) {
849 MakeSymbolReal(*Symbol, Header.NumberOfSymbols++);
850
851 // Update auxiliary symbol info.
852 Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
853 Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
854 } else
855 Symbol->Index = -1;
856 }
857
858 // Fixup weak external references.
859 for (auto & Symbol : Symbols) {
860 if (Symbol->Other) {
861 assert(Symbol->Index != -1);
862 assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
863 assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
864 "Symbol's aux symbol must be a Weak External!");
865 Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->Index;
866 }
867 }
868
869 // Fixup associative COMDAT sections.
870 for (auto & Section : Sections) {
871 if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
872 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
873 continue;
874
875 const MCSectionCOFF &MCSec =
876 static_cast<const MCSectionCOFF &>(Section->MCData->getSection());
877
878 const MCSymbol *COMDAT = MCSec.getCOMDATSymbol();
879 assert(COMDAT);
880 COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(COMDAT);
881 assert(COMDATSymbol);
882 COFFSection *Assoc = COMDATSymbol->Section;
883 if (!Assoc)
884 report_fatal_error(
885 Twine("Missing associated COMDAT section for section ") +
886 MCSec.getSectionName());
887
888 // Skip this section if the associated section is unused.
889 if (Assoc->Number == -1)
890 continue;
891
892 Section->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
893 }
894
895
896 // Assign file offsets to COFF object file structures.
897
898 unsigned offset = 0;
899
900 offset += COFF::HeaderSize;
901 offset += COFF::SectionSize * Header.NumberOfSections;
902
903 for (const auto & Section : Asm) {
904 COFFSection *Sec = SectionMap[&Section.getSection()];
905
906 if (Sec->Number == -1)
907 continue;
908
909 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(&Section);
910
911 if (IsPhysicalSection(Sec)) {
912 Sec->Header.PointerToRawData = offset;
913
914 offset += Sec->Header.SizeOfRawData;
915 }
916
917 if (Sec->Relocations.size() > 0) {
918 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
919
920 if (RelocationsOverflow) {
921 // Signal overflow by setting NumberOfSections to max value. Actual
922 // size is found in reloc #0. Microsoft tools understand this.
923 Sec->Header.NumberOfRelocations = 0xffff;
924 } else {
925 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
926 }
927 Sec->Header.PointerToRelocations = offset;
928
929 if (RelocationsOverflow) {
930 // Reloc #0 will contain actual count, so make room for it.
931 offset += COFF::RelocationSize;
932 }
933
934 offset += COFF::RelocationSize * Sec->Relocations.size();
935
936 for (auto & Relocation : Sec->Relocations) {
937 assert(Relocation.Symb->Index != -1);
938 Relocation.Data.SymbolTableIndex = Relocation.Symb->Index;
939 }
940 }
941
942 assert(Sec->Symbol->Aux.size() == 1 &&
943 "Section's symbol must have one aux!");
944 AuxSymbol &Aux = Sec->Symbol->Aux[0];
945 assert(Aux.AuxType == ATSectionDefinition &&
946 "Section's symbol's aux symbol must be a Section Definition!");
947 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
948 Aux.Aux.SectionDefinition.NumberOfRelocations =
949 Sec->Header.NumberOfRelocations;
950 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
951 Sec->Header.NumberOfLineNumbers;
952 }
953
954 Header.PointerToSymbolTable = offset;
955
956 // We want a deterministic output. It looks like GNU as also writes 0 in here.
957 Header.TimeDateStamp = 0;
958
959 // Write it all to disk...
960 WriteFileHeader(Header);
961
962 {
963 sections::iterator i, ie;
964 MCAssembler::const_iterator j, je;
965
966 for (auto & Section : Sections) {
967 if (Section->Number != -1) {
968 if (Section->Relocations.size() >= 0xffff)
969 Section->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
970 WriteSectionHeader(Section->Header);
971 }
972 }
973
974 for (i = Sections.begin(), ie = Sections.end(),
975 j = Asm.begin(), je = Asm.end();
976 (i != ie) && (j != je); ++i, ++j) {
977
978 if ((*i)->Number == -1)
979 continue;
980
981 if ((*i)->Header.PointerToRawData != 0) {
982 assert(OS.tell() == (*i)->Header.PointerToRawData &&
983 "Section::PointerToRawData is insane!");
984
985 Asm.writeSectionData(j, Layout);
986 }
987
988 if ((*i)->Relocations.size() > 0) {
989 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
990 "Section::PointerToRelocations is insane!");
991
992 if ((*i)->Relocations.size() >= 0xffff) {
993 // In case of overflow, write actual relocation count as first
994 // relocation. Including the synthetic reloc itself (+ 1).
995 COFF::relocation r;
996 r.VirtualAddress = (*i)->Relocations.size() + 1;
997 r.SymbolTableIndex = 0;
998 r.Type = 0;
999 WriteRelocation(r);
1000 }
1001
1002 for (const auto & Relocation : (*i)->Relocations)
1003 WriteRelocation(Relocation.Data);
1004 } else
1005 assert((*i)->Header.PointerToRelocations == 0 &&
1006 "Section::PointerToRelocations is insane!");
1007 }
1008 }
1009
1010 assert(OS.tell() == Header.PointerToSymbolTable &&
1011 "Header::PointerToSymbolTable is insane!");
1012
1013 for (auto & Symbol : Symbols)
1014 if (Symbol->Index != -1)
1015 WriteSymbol(*Symbol);
1016
1017 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
1018 }
1019
MCWinCOFFObjectTargetWriter(unsigned Machine_)1020 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
1021 Machine(Machine_) {
1022 }
1023
1024 // Pin the vtable to this file.
anchor()1025 void MCWinCOFFObjectTargetWriter::anchor() {}
1026
1027 //------------------------------------------------------------------------------
1028 // WinCOFFObjectWriter factory function
1029
1030 namespace llvm {
createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_ostream & OS)1031 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
1032 raw_ostream &OS) {
1033 return new WinCOFFObjectWriter(MOTW, OS);
1034 }
1035 }
1036