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 #define DEBUG_TYPE "WinCOFFObjectWriter"
15
16 #include "llvm/MC/MCWinCOFFObjectWriter.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/OwningPtr.h"
19 #include "llvm/ADT/StringMap.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/MC/MCAsmLayout.h"
23 #include "llvm/MC/MCAssembler.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCExpr.h"
26 #include "llvm/MC/MCObjectWriter.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCSectionCOFF.h"
29 #include "llvm/MC/MCSymbol.h"
30 #include "llvm/MC/MCValue.h"
31 #include "llvm/Support/COFF.h"
32 #include "llvm/Support/Debug.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TimeValue.h"
35 #include <cstdio>
36
37 using namespace llvm;
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__anona011415b0111::COFFRelocation85 COFFRelocation() : Symb(NULL) {}
size__anona011415b0111::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<COFFSymbol*> symbols;
123 typedef std::vector<COFFSection*> sections;
124
125 typedef DenseMap<MCSymbol const *, COFFSymbol *> symbol_map;
126 typedef DenseMap<MCSection const *, COFFSection *> section_map;
127
128 llvm::OwningPtr<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 ~WinCOFFObjectWriter();
142
143 COFFSymbol *createSymbol(StringRef Name);
144 COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol * Symbol);
145 COFFSection *createSection(StringRef Name);
146
147 template <typename object_t, typename list_t>
148 object_t *createCOFFEntity(StringRef Name, list_t &List);
149
150 void DefineSection(MCSectionData const &SectionData);
151 void DefineSymbol(MCSymbolData const &SymbolData,
152 MCAssembler &Assembler);
153
154 void MakeSymbolReal(COFFSymbol &S, size_t Index);
155 void MakeSectionReal(COFFSection &S, size_t Number);
156
157 bool ExportSection(COFFSection const *S);
158 bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
159
160 bool IsPhysicalSection(COFFSection *S);
161
162 // Entity writing methods.
163
164 void WriteFileHeader(const COFF::header &Header);
165 void WriteSymbol(const COFFSymbol *S);
166 void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
167 void WriteSectionHeader(const COFF::section &S);
168 void WriteRelocation(const COFF::relocation &R);
169
170 // MCObjectWriter interface implementation.
171
172 void ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout);
173
174 void RecordRelocation(const MCAssembler &Asm,
175 const MCAsmLayout &Layout,
176 const MCFragment *Fragment,
177 const MCFixup &Fixup,
178 MCValue Target,
179 uint64_t &FixedValue);
180
181 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
182 };
183 }
184
write_uint32_le(void * Data,uint32_t const & Value)185 static inline void write_uint32_le(void *Data, uint32_t const &Value) {
186 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
187 Ptr[0] = (Value & 0x000000FF) >> 0;
188 Ptr[1] = (Value & 0x0000FF00) >> 8;
189 Ptr[2] = (Value & 0x00FF0000) >> 16;
190 Ptr[3] = (Value & 0xFF000000) >> 24;
191 }
192
write_uint16_le(void * Data,uint16_t const & Value)193 static inline void write_uint16_le(void *Data, uint16_t const &Value) {
194 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
195 Ptr[0] = (Value & 0x00FF) >> 0;
196 Ptr[1] = (Value & 0xFF00) >> 8;
197 }
198
write_uint8_le(void * Data,uint8_t const & Value)199 static inline void write_uint8_le(void *Data, uint8_t const &Value) {
200 uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
201 Ptr[0] = (Value & 0xFF) >> 0;
202 }
203
204 //------------------------------------------------------------------------------
205 // Symbol class implementation
206
COFFSymbol(StringRef name)207 COFFSymbol::COFFSymbol(StringRef name)
208 : Name(name.begin(), name.end())
209 , Other(NULL)
210 , Section(NULL)
211 , Relocations(0)
212 , MCData(NULL) {
213 memset(&Data, 0, sizeof(Data));
214 }
215
size() const216 size_t COFFSymbol::size() const {
217 return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
218 }
219
220 // In the case that the name does not fit within 8 bytes, the offset
221 // into the string table is stored in the last 4 bytes instead, leaving
222 // the first 4 bytes as 0.
set_name_offset(uint32_t Offset)223 void COFFSymbol::set_name_offset(uint32_t Offset) {
224 write_uint32_le(Data.Name + 0, 0);
225 write_uint32_le(Data.Name + 4, Offset);
226 }
227
228 /// logic to decide if the symbol should be reported in the symbol table
should_keep() const229 bool COFFSymbol::should_keep() const {
230 // no section means its external, keep it
231 if (Section == NULL)
232 return true;
233
234 // if it has relocations pointing at it, keep it
235 if (Relocations > 0) {
236 assert(Section->Number != -1 && "Sections with relocations must be real!");
237 return true;
238 }
239
240 // if the section its in is being droped, drop it
241 if (Section->Number == -1)
242 return false;
243
244 // if it is the section symbol, keep it
245 if (Section->Symbol == this)
246 return true;
247
248 // if its temporary, drop it
249 if (MCData && MCData->getSymbol().isTemporary())
250 return false;
251
252 // otherwise, keep it
253 return true;
254 }
255
256 //------------------------------------------------------------------------------
257 // Section class implementation
258
COFFSection(StringRef name)259 COFFSection::COFFSection(StringRef name)
260 : Name(name)
261 , MCData(NULL)
262 , Symbol(NULL) {
263 memset(&Header, 0, sizeof(Header));
264 }
265
size()266 size_t COFFSection::size() {
267 return COFF::SectionSize;
268 }
269
270 //------------------------------------------------------------------------------
271 // StringTable class implementation
272
273 /// Write the length of the string table into Data.
274 /// The length of the string table includes uint32 length header.
update_length()275 void StringTable::update_length() {
276 write_uint32_le(&Data.front(), Data.size());
277 }
278
StringTable()279 StringTable::StringTable() {
280 // The string table data begins with the length of the entire string table
281 // including the length header. Allocate space for this header.
282 Data.resize(4);
283 update_length();
284 }
285
size() const286 size_t StringTable::size() const {
287 return Data.size();
288 }
289
290 /// Add String to the table iff it is not already there.
291 /// @returns the index into the string table where the string is now located.
insert(StringRef String)292 size_t StringTable::insert(StringRef String) {
293 map::iterator i = Map.find(String);
294
295 if (i != Map.end())
296 return i->second;
297
298 size_t Offset = Data.size();
299
300 // Insert string data into string table.
301 Data.insert(Data.end(), String.begin(), String.end());
302 Data.push_back('\0');
303
304 // Put a reference to it in the map.
305 Map[String] = Offset;
306
307 // Update the internal length field.
308 update_length();
309
310 return Offset;
311 }
312
313 //------------------------------------------------------------------------------
314 // WinCOFFObjectWriter class implementation
315
WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_ostream & OS)316 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
317 raw_ostream &OS)
318 : MCObjectWriter(OS, true)
319 , TargetObjectWriter(MOTW) {
320 memset(&Header, 0, sizeof(Header));
321
322 Header.Machine = TargetObjectWriter->getMachine();
323 }
324
~WinCOFFObjectWriter()325 WinCOFFObjectWriter::~WinCOFFObjectWriter() {
326 for (symbols::iterator I = Symbols.begin(), E = Symbols.end(); I != E; ++I)
327 delete *I;
328 for (sections::iterator I = Sections.begin(), E = Sections.end(); I != E; ++I)
329 delete *I;
330 }
331
createSymbol(StringRef Name)332 COFFSymbol *WinCOFFObjectWriter::createSymbol(StringRef Name) {
333 return createCOFFEntity<COFFSymbol>(Name, Symbols);
334 }
335
GetOrCreateCOFFSymbol(const MCSymbol * Symbol)336 COFFSymbol *WinCOFFObjectWriter::GetOrCreateCOFFSymbol(const MCSymbol * Symbol){
337 symbol_map::iterator i = SymbolMap.find(Symbol);
338 if (i != SymbolMap.end())
339 return i->second;
340 COFFSymbol *RetSymbol
341 = createCOFFEntity<COFFSymbol>(Symbol->getName(), Symbols);
342 SymbolMap[Symbol] = RetSymbol;
343 return RetSymbol;
344 }
345
createSection(StringRef Name)346 COFFSection *WinCOFFObjectWriter::createSection(StringRef Name) {
347 return createCOFFEntity<COFFSection>(Name, Sections);
348 }
349
350 /// A template used to lookup or create a symbol/section, and initialize it if
351 /// needed.
352 template <typename object_t, typename list_t>
createCOFFEntity(StringRef Name,list_t & List)353 object_t *WinCOFFObjectWriter::createCOFFEntity(StringRef Name,
354 list_t &List) {
355 object_t *Object = new object_t(Name);
356
357 List.push_back(Object);
358
359 return Object;
360 }
361
362 /// This function takes a section data object from the assembler
363 /// and creates the associated COFF section staging object.
DefineSection(MCSectionData const & SectionData)364 void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
365 assert(SectionData.getSection().getVariant() == MCSection::SV_COFF
366 && "Got non COFF section in the COFF backend!");
367 // FIXME: Not sure how to verify this (at least in a debug build).
368 MCSectionCOFF const &Sec =
369 static_cast<MCSectionCOFF const &>(SectionData.getSection());
370
371 COFFSection *coff_section = createSection(Sec.getSectionName());
372 COFFSymbol *coff_symbol = createSymbol(Sec.getSectionName());
373
374 coff_section->Symbol = coff_symbol;
375 coff_symbol->Section = coff_section;
376 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
377
378 // In this case the auxiliary symbol is a Section Definition.
379 coff_symbol->Aux.resize(1);
380 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
381 coff_symbol->Aux[0].AuxType = ATSectionDefinition;
382 coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
383
384 coff_section->Header.Characteristics = Sec.getCharacteristics();
385
386 uint32_t &Characteristics = coff_section->Header.Characteristics;
387 switch (SectionData.getAlignment()) {
388 case 1: Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES; break;
389 case 2: Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES; break;
390 case 4: Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES; break;
391 case 8: Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES; break;
392 case 16: Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES; break;
393 case 32: Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES; break;
394 case 64: Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES; break;
395 case 128: Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES; break;
396 case 256: Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES; break;
397 case 512: Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES; break;
398 case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
399 case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
400 case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
401 case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
402 default:
403 llvm_unreachable("unsupported section alignment");
404 }
405
406 // Bind internal COFF section to MC section.
407 coff_section->MCData = &SectionData;
408 SectionMap[&SectionData.getSection()] = coff_section;
409 }
410
411 /// This function takes a section data object from the assembler
412 /// and creates the associated COFF symbol staging object.
DefineSymbol(MCSymbolData const & SymbolData,MCAssembler & Assembler)413 void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
414 MCAssembler &Assembler) {
415 MCSymbol const &Symbol = SymbolData.getSymbol();
416 COFFSymbol *coff_symbol = GetOrCreateCOFFSymbol(&Symbol);
417 SymbolMap[&Symbol] = coff_symbol;
418
419 if (SymbolData.getFlags() & COFF::SF_WeakExternal) {
420 coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
421
422 if (Symbol.isVariable()) {
423 const MCSymbolRefExpr *SymRef =
424 dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
425
426 if (!SymRef)
427 report_fatal_error("Weak externals may only alias symbols");
428
429 coff_symbol->Other = GetOrCreateCOFFSymbol(&SymRef->getSymbol());
430 } else {
431 std::string WeakName = std::string(".weak.")
432 + Symbol.getName().str()
433 + ".default";
434 COFFSymbol *WeakDefault = createSymbol(WeakName);
435 WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
436 WeakDefault->Data.StorageClass = COFF::IMAGE_SYM_CLASS_EXTERNAL;
437 WeakDefault->Data.Type = 0;
438 WeakDefault->Data.Value = 0;
439 coff_symbol->Other = WeakDefault;
440 }
441
442 // Setup the Weak External auxiliary symbol.
443 coff_symbol->Aux.resize(1);
444 memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
445 coff_symbol->Aux[0].AuxType = ATWeakExternal;
446 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
447 coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
448 COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
449
450 coff_symbol->MCData = &SymbolData;
451 } else {
452 const MCSymbolData &ResSymData =
453 Assembler.getSymbolData(Symbol.AliasedSymbol());
454
455 coff_symbol->Data.Type = (ResSymData.getFlags() & 0x0000FFFF) >> 0;
456 coff_symbol->Data.StorageClass = (ResSymData.getFlags() & 0x00FF0000) >> 16;
457
458 // If no storage class was specified in the streamer, define it here.
459 if (coff_symbol->Data.StorageClass == 0) {
460 bool external = ResSymData.isExternal() || (ResSymData.Fragment == NULL);
461
462 coff_symbol->Data.StorageClass =
463 external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
464 }
465
466 if (ResSymData.Fragment != NULL)
467 coff_symbol->Section =
468 SectionMap[&ResSymData.Fragment->getParent()->getSection()];
469
470 coff_symbol->MCData = &ResSymData;
471 }
472 }
473
474 /// making a section real involves assigned it a number and putting
475 /// name into the string table if needed
MakeSectionReal(COFFSection & S,size_t Number)476 void WinCOFFObjectWriter::MakeSectionReal(COFFSection &S, size_t Number) {
477 if (S.Name.size() > COFF::NameSize) {
478 const unsigned Max6DecimalSize = 999999;
479 const unsigned Max7DecimalSize = 9999999;
480 uint64_t StringTableEntry = Strings.insert(S.Name.c_str());
481
482 if (StringTableEntry <= Max6DecimalSize) {
483 std::sprintf(S.Header.Name, "/%d", unsigned(StringTableEntry));
484 } else if (StringTableEntry <= Max7DecimalSize) {
485 // With seven digits, we have to skip the terminating null. Because
486 // sprintf always appends it, we use a larger temporary buffer.
487 char buffer[9] = { };
488 std::sprintf(buffer, "/%d", unsigned(StringTableEntry));
489 std::memcpy(S.Header.Name, buffer, 8);
490 } else {
491 report_fatal_error("COFF string table is greater than 9,999,999 bytes.");
492 }
493 } else
494 std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
495
496 S.Number = Number;
497 S.Symbol->Data.SectionNumber = S.Number;
498 S.Symbol->Aux[0].Aux.SectionDefinition.Number = S.Number;
499 }
500
MakeSymbolReal(COFFSymbol & S,size_t Index)501 void WinCOFFObjectWriter::MakeSymbolReal(COFFSymbol &S, size_t Index) {
502 if (S.Name.size() > COFF::NameSize) {
503 size_t StringTableEntry = Strings.insert(S.Name.c_str());
504
505 S.set_name_offset(StringTableEntry);
506 } else
507 std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
508 S.Index = Index;
509 }
510
ExportSection(COFFSection const * S)511 bool WinCOFFObjectWriter::ExportSection(COFFSection const *S) {
512 return !S->MCData->getFragmentList().empty();
513 }
514
ExportSymbol(MCSymbolData const & SymbolData,MCAssembler & Asm)515 bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
516 MCAssembler &Asm) {
517 // This doesn't seem to be right. Strings referred to from the .data section
518 // need symbols so they can be linked to code in the .text section right?
519
520 // return Asm.isSymbolLinkerVisible (&SymbolData);
521
522 // For now, all non-variable symbols are exported,
523 // the linker will sort the rest out for us.
524 return SymbolData.isExternal() || !SymbolData.getSymbol().isVariable();
525 }
526
IsPhysicalSection(COFFSection * S)527 bool WinCOFFObjectWriter::IsPhysicalSection(COFFSection *S) {
528 return (S->Header.Characteristics
529 & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
530 }
531
532 //------------------------------------------------------------------------------
533 // entity writing methods
534
WriteFileHeader(const COFF::header & Header)535 void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
536 WriteLE16(Header.Machine);
537 WriteLE16(Header.NumberOfSections);
538 WriteLE32(Header.TimeDateStamp);
539 WriteLE32(Header.PointerToSymbolTable);
540 WriteLE32(Header.NumberOfSymbols);
541 WriteLE16(Header.SizeOfOptionalHeader);
542 WriteLE16(Header.Characteristics);
543 }
544
WriteSymbol(const COFFSymbol * S)545 void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol *S) {
546 WriteBytes(StringRef(S->Data.Name, COFF::NameSize));
547 WriteLE32(S->Data.Value);
548 WriteLE16(S->Data.SectionNumber);
549 WriteLE16(S->Data.Type);
550 Write8(S->Data.StorageClass);
551 Write8(S->Data.NumberOfAuxSymbols);
552 WriteAuxiliarySymbols(S->Aux);
553 }
554
WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols & S)555 void WinCOFFObjectWriter::WriteAuxiliarySymbols(
556 const COFFSymbol::AuxiliarySymbols &S) {
557 for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
558 i != e; ++i) {
559 switch(i->AuxType) {
560 case ATFunctionDefinition:
561 WriteLE32(i->Aux.FunctionDefinition.TagIndex);
562 WriteLE32(i->Aux.FunctionDefinition.TotalSize);
563 WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
564 WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
565 WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
566 break;
567 case ATbfAndefSymbol:
568 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
569 WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
570 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
571 WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
572 WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
573 break;
574 case ATWeakExternal:
575 WriteLE32(i->Aux.WeakExternal.TagIndex);
576 WriteLE32(i->Aux.WeakExternal.Characteristics);
577 WriteZeros(sizeof(i->Aux.WeakExternal.unused));
578 break;
579 case ATFile:
580 WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
581 sizeof(i->Aux.File.FileName)));
582 break;
583 case ATSectionDefinition:
584 WriteLE32(i->Aux.SectionDefinition.Length);
585 WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
586 WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
587 WriteLE32(i->Aux.SectionDefinition.CheckSum);
588 WriteLE16(i->Aux.SectionDefinition.Number);
589 Write8(i->Aux.SectionDefinition.Selection);
590 WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
591 break;
592 }
593 }
594 }
595
WriteSectionHeader(const COFF::section & S)596 void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
597 WriteBytes(StringRef(S.Name, COFF::NameSize));
598
599 WriteLE32(S.VirtualSize);
600 WriteLE32(S.VirtualAddress);
601 WriteLE32(S.SizeOfRawData);
602 WriteLE32(S.PointerToRawData);
603 WriteLE32(S.PointerToRelocations);
604 WriteLE32(S.PointerToLineNumbers);
605 WriteLE16(S.NumberOfRelocations);
606 WriteLE16(S.NumberOfLineNumbers);
607 WriteLE32(S.Characteristics);
608 }
609
WriteRelocation(const COFF::relocation & R)610 void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
611 WriteLE32(R.VirtualAddress);
612 WriteLE32(R.SymbolTableIndex);
613 WriteLE16(R.Type);
614 }
615
616 ////////////////////////////////////////////////////////////////////////////////
617 // MCObjectWriter interface implementations
618
ExecutePostLayoutBinding(MCAssembler & Asm,const MCAsmLayout & Layout)619 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
620 const MCAsmLayout &Layout) {
621 // "Define" each section & symbol. This creates section & symbol
622 // entries in the staging area.
623
624 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; i++)
625 DefineSection(*i);
626
627 for (MCAssembler::const_symbol_iterator i = Asm.symbol_begin(),
628 e = Asm.symbol_end(); i != e; i++) {
629 if (ExportSymbol(*i, Asm)) {
630 DefineSymbol(*i, Asm);
631 }
632 }
633 }
634
RecordRelocation(const MCAssembler & Asm,const MCAsmLayout & Layout,const MCFragment * Fragment,const MCFixup & Fixup,MCValue Target,uint64_t & FixedValue)635 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
636 const MCAsmLayout &Layout,
637 const MCFragment *Fragment,
638 const MCFixup &Fixup,
639 MCValue Target,
640 uint64_t &FixedValue) {
641 assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");
642
643 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
644 const MCSymbol &A = Symbol.AliasedSymbol();
645 MCSymbolData &A_SD = Asm.getSymbolData(A);
646
647 MCSectionData const *SectionData = Fragment->getParent();
648
649 // Mark this symbol as requiring an entry in the symbol table.
650 assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() &&
651 "Section must already have been defined in ExecutePostLayoutBinding!");
652 assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() &&
653 "Symbol must already have been defined in ExecutePostLayoutBinding!");
654
655 COFFSection *coff_section = SectionMap[&SectionData->getSection()];
656 COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()];
657 const MCSymbolRefExpr *SymA = Target.getSymA();
658 const MCSymbolRefExpr *SymB = Target.getSymB();
659 const bool CrossSection = SymB &&
660 &SymA->getSymbol().getSection() != &SymB->getSymbol().getSection();
661
662 if (Target.getSymB()) {
663 const MCSymbol *B = &Target.getSymB()->getSymbol();
664 MCSymbolData &B_SD = Asm.getSymbolData(*B);
665
666 // Offset of the symbol in the section
667 int64_t a = Layout.getSymbolOffset(&B_SD);
668
669 // Ofeset of the relocation in the section
670 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
671
672 FixedValue = b - a;
673 // In the case where we have SymbA and SymB, we just need to store the delta
674 // between the two symbols. Update FixedValue to account for the delta, and
675 // skip recording the relocation.
676 if (!CrossSection)
677 return;
678 } else {
679 FixedValue = Target.getConstant();
680 }
681
682 COFFRelocation Reloc;
683
684 Reloc.Data.SymbolTableIndex = 0;
685 Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
686
687 // Turn relocations for temporary symbols into section relocations.
688 if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) {
689 Reloc.Symb = coff_symbol->Section->Symbol;
690 FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment)
691 + coff_symbol->MCData->getOffset();
692 } else
693 Reloc.Symb = coff_symbol;
694
695 ++Reloc.Symb->Relocations;
696
697 Reloc.Data.VirtualAddress += Fixup.getOffset();
698 Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup,
699 CrossSection);
700
701 // FIXME: Can anyone explain what this does other than adjust for the size
702 // of the offset?
703 if (Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32 ||
704 Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)
705 FixedValue += 4;
706
707 coff_section->Relocations.push_back(Reloc);
708 }
709
WriteObject(MCAssembler & Asm,const MCAsmLayout & Layout)710 void WinCOFFObjectWriter::WriteObject(MCAssembler &Asm,
711 const MCAsmLayout &Layout) {
712 // Assign symbol and section indexes and offsets.
713 Header.NumberOfSections = 0;
714
715 DenseMap<COFFSection *, uint16_t> SectionIndices;
716 for (sections::iterator i = Sections.begin(),
717 e = Sections.end(); i != e; i++) {
718 if (Layout.getSectionAddressSize((*i)->MCData) > 0) {
719 size_t Number = ++Header.NumberOfSections;
720 SectionIndices[*i] = Number;
721 MakeSectionReal(**i, Number);
722 } else {
723 (*i)->Number = -1;
724 }
725 }
726
727 Header.NumberOfSymbols = 0;
728
729 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
730 COFFSymbol *coff_symbol = *i;
731 MCSymbolData const *SymbolData = coff_symbol->MCData;
732
733 // Update section number & offset for symbols that have them.
734 if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
735 assert(coff_symbol->Section != NULL);
736
737 coff_symbol->Data.SectionNumber = coff_symbol->Section->Number;
738 coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment)
739 + SymbolData->Offset;
740 }
741
742 if (coff_symbol->should_keep()) {
743 MakeSymbolReal(*coff_symbol, Header.NumberOfSymbols++);
744
745 // Update auxiliary symbol info.
746 coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
747 Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
748 } else
749 coff_symbol->Index = -1;
750 }
751
752 // Fixup weak external references.
753 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
754 COFFSymbol *coff_symbol = *i;
755 if (coff_symbol->Other != NULL) {
756 assert(coff_symbol->Index != -1);
757 assert(coff_symbol->Aux.size() == 1 &&
758 "Symbol must contain one aux symbol!");
759 assert(coff_symbol->Aux[0].AuxType == ATWeakExternal &&
760 "Symbol's aux symbol must be a Weak External!");
761 coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = coff_symbol->Other->Index;
762 }
763 }
764
765 // Fixup associative COMDAT sections.
766 for (sections::iterator i = Sections.begin(),
767 e = Sections.end(); i != e; i++) {
768 if ((*i)->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
769 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
770 continue;
771
772 const MCSectionCOFF &MCSec = static_cast<const MCSectionCOFF &>(
773 (*i)->MCData->getSection());
774
775 COFFSection *Assoc = SectionMap.lookup(MCSec.getAssocSection());
776 if (!Assoc) {
777 report_fatal_error(Twine("Missing associated COMDAT section ") +
778 MCSec.getAssocSection()->getSectionName() +
779 " for section " + MCSec.getSectionName());
780 }
781
782 // Skip this section if the associated section is unused.
783 if (Assoc->Number == -1)
784 continue;
785
786 (*i)->Symbol->Aux[0].Aux.SectionDefinition.Number = SectionIndices[Assoc];
787 }
788
789
790 // Assign file offsets to COFF object file structures.
791
792 unsigned offset = 0;
793
794 offset += COFF::HeaderSize;
795 offset += COFF::SectionSize * Header.NumberOfSections;
796
797 for (MCAssembler::const_iterator i = Asm.begin(),
798 e = Asm.end();
799 i != e; i++) {
800 COFFSection *Sec = SectionMap[&i->getSection()];
801
802 if (Sec->Number == -1)
803 continue;
804
805 Sec->Header.SizeOfRawData = Layout.getSectionAddressSize(i);
806
807 if (IsPhysicalSection(Sec)) {
808 Sec->Header.PointerToRawData = offset;
809
810 offset += Sec->Header.SizeOfRawData;
811 }
812
813 if (Sec->Relocations.size() > 0) {
814 bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
815
816 if (RelocationsOverflow) {
817 // Signal overflow by setting NumberOfSections to max value. Actual
818 // size is found in reloc #0. Microsoft tools understand this.
819 Sec->Header.NumberOfRelocations = 0xffff;
820 } else {
821 Sec->Header.NumberOfRelocations = Sec->Relocations.size();
822 }
823 Sec->Header.PointerToRelocations = offset;
824
825 if (RelocationsOverflow) {
826 // Reloc #0 will contain actual count, so make room for it.
827 offset += COFF::RelocationSize;
828 }
829
830 offset += COFF::RelocationSize * Sec->Relocations.size();
831
832 for (relocations::iterator cr = Sec->Relocations.begin(),
833 er = Sec->Relocations.end();
834 cr != er; ++cr) {
835 assert((*cr).Symb->Index != -1);
836 (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
837 }
838 }
839
840 assert(Sec->Symbol->Aux.size() == 1
841 && "Section's symbol must have one aux!");
842 AuxSymbol &Aux = Sec->Symbol->Aux[0];
843 assert(Aux.AuxType == ATSectionDefinition &&
844 "Section's symbol's aux symbol must be a Section Definition!");
845 Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
846 Aux.Aux.SectionDefinition.NumberOfRelocations =
847 Sec->Header.NumberOfRelocations;
848 Aux.Aux.SectionDefinition.NumberOfLinenumbers =
849 Sec->Header.NumberOfLineNumbers;
850 }
851
852 Header.PointerToSymbolTable = offset;
853
854 Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();
855
856 // Write it all to disk...
857 WriteFileHeader(Header);
858
859 {
860 sections::iterator i, ie;
861 MCAssembler::const_iterator j, je;
862
863 for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
864 if ((*i)->Number != -1) {
865 if ((*i)->Relocations.size() >= 0xffff) {
866 (*i)->Header.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
867 }
868 WriteSectionHeader((*i)->Header);
869 }
870
871 for (i = Sections.begin(), ie = Sections.end(),
872 j = Asm.begin(), je = Asm.end();
873 (i != ie) && (j != je); ++i, ++j) {
874
875 if ((*i)->Number == -1)
876 continue;
877
878 if ((*i)->Header.PointerToRawData != 0) {
879 assert(OS.tell() == (*i)->Header.PointerToRawData &&
880 "Section::PointerToRawData is insane!");
881
882 Asm.writeSectionData(j, Layout);
883 }
884
885 if ((*i)->Relocations.size() > 0) {
886 assert(OS.tell() == (*i)->Header.PointerToRelocations &&
887 "Section::PointerToRelocations is insane!");
888
889 if ((*i)->Relocations.size() >= 0xffff) {
890 // In case of overflow, write actual relocation count as first
891 // relocation. Including the synthetic reloc itself (+ 1).
892 COFF::relocation r;
893 r.VirtualAddress = (*i)->Relocations.size() + 1;
894 r.SymbolTableIndex = 0;
895 r.Type = 0;
896 WriteRelocation(r);
897 }
898
899 for (relocations::const_iterator k = (*i)->Relocations.begin(),
900 ke = (*i)->Relocations.end();
901 k != ke; k++) {
902 WriteRelocation(k->Data);
903 }
904 } else
905 assert((*i)->Header.PointerToRelocations == 0 &&
906 "Section::PointerToRelocations is insane!");
907 }
908 }
909
910 assert(OS.tell() == Header.PointerToSymbolTable &&
911 "Header::PointerToSymbolTable is insane!");
912
913 for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
914 if ((*i)->Index != -1)
915 WriteSymbol(*i);
916
917 OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
918 }
919
MCWinCOFFObjectTargetWriter(unsigned Machine_)920 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_) :
921 Machine(Machine_) {
922 }
923
924 //------------------------------------------------------------------------------
925 // WinCOFFObjectWriter factory function
926
927 namespace llvm {
createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter * MOTW,raw_ostream & OS)928 MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
929 raw_ostream &OS) {
930 return new WinCOFFObjectWriter(MOTW, OS);
931 }
932 }
933