1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements ELF object file writer information.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/MC/MCAsmBackend.h"
20 #include "llvm/MC/MCAsmLayout.h"
21 #include "llvm/MC/MCAssembler.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCELF.h"
24 #include "llvm/MC/MCELFSymbolFlags.h"
25 #include "llvm/MC/MCExpr.h"
26 #include "llvm/MC/MCFixupKindInfo.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSectionELF.h"
29 #include "llvm/MC/MCValue.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/Endian.h"
32 #include "llvm/Support/ELF.h"
33 #include "llvm/Support/ErrorHandling.h"
38 #define DEBUG_TYPE "reloc-info"
41 class FragmentWriter {
45 FragmentWriter(bool IsLittleEndian);
46 template <typename T> void write(MCDataFragment &F, T Val);
49 typedef DenseMap<const MCSectionELF *, uint32_t> SectionIndexMapTy;
51 class SymbolTableWriter {
53 FragmentWriter &FWriter;
55 SectionIndexMapTy &SectionIndexMap;
57 // The symbol .symtab fragment we are writting to.
58 MCDataFragment *SymtabF;
60 // .symtab_shndx fragment we are writting to.
61 MCDataFragment *ShndxF;
63 // The numbel of symbols written so far.
66 void createSymtabShndx();
68 template <typename T> void write(MCDataFragment &F, T Value);
71 SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter, bool Is64Bit,
72 SectionIndexMapTy &SectionIndexMap,
73 MCDataFragment *SymtabF);
75 void writeSymbol(uint32_t name, uint8_t info, uint64_t value, uint64_t size,
76 uint8_t other, uint32_t shndx, bool Reserved);
79 class ELFObjectWriter : public MCObjectWriter {
80 FragmentWriter FWriter;
84 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
85 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
86 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
87 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
88 bool Used, bool Renamed);
89 static bool isLocal(const MCSymbolData &Data, bool isSignature,
91 static bool IsELFMetaDataSection(const MCSectionData &SD);
92 static uint64_t DataSectionSize(const MCSectionData &SD);
93 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
94 const MCSectionData &SD);
95 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
96 const MCSectionData &SD);
98 void WriteDataSectionData(MCAssembler &Asm,
99 const MCAsmLayout &Layout,
100 const MCSectionELF &Section);
102 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
103 return Kind == X86::reloc_riprel_4byte ||
104 Kind == X86::reloc_riprel_4byte_movq_load;
107 /// ELFSymbolData - Helper struct for containing some precomputed
108 /// information on symbols.
109 struct ELFSymbolData {
110 MCSymbolData *SymbolData;
111 uint64_t StringIndex;
112 uint32_t SectionIndex;
114 // Support lexicographic sorting.
115 bool operator<(const ELFSymbolData &RHS) const {
116 return SymbolData->getSymbol().getName() <
117 RHS.SymbolData->getSymbol().getName();
121 /// The target specific ELF writer instance.
122 std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
124 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
125 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
126 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
128 llvm::DenseMap<const MCSectionData*,
129 std::vector<ELFRelocationEntry> > Relocations;
130 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
133 /// @name Symbol Table Data
136 SmallString<256> StringTable;
137 std::vector<uint64_t> FileSymbolData;
138 std::vector<ELFSymbolData> LocalSymbolData;
139 std::vector<ELFSymbolData> ExternalSymbolData;
140 std::vector<ELFSymbolData> UndefinedSymbolData;
146 // This holds the symbol table index of the last local symbol.
147 unsigned LastLocalSymbolIndex;
148 // This holds the .strtab section index.
149 unsigned StringTableIndex;
150 // This holds the .symtab section index.
151 unsigned SymbolTableIndex;
153 unsigned ShstrtabIndex;
156 const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
157 const MCValue &Target,
159 const MCFixup &Fixup,
162 // TargetObjectWriter wrappers.
163 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
164 const MCValue &Target,
166 const MCFixup &Fixup,
167 bool IsPCRel) const {
168 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
170 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
171 const MCFixup &Fixup,
172 bool IsPCRel) const {
173 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
177 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
178 bool hasRelocationAddend() const {
179 return TargetObjectWriter->hasRelocationAddend();
181 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
182 bool IsPCRel, bool IsRelocWithSymbol,
183 int64_t Addend) const {
184 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
185 IsRelocWithSymbol, Addend);
189 ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_ostream &_OS,
191 : MCObjectWriter(_OS, IsLittleEndian), FWriter(IsLittleEndian),
192 TargetObjectWriter(MOTW), NeedsGOT(false) {}
194 virtual ~ELFObjectWriter();
196 void WriteWord(uint64_t W) {
203 template <typename T> void write(MCDataFragment &F, T Value) {
204 FWriter.write(F, Value);
207 void WriteHeader(const MCAssembler &Asm,
208 uint64_t SectionDataSize,
209 unsigned NumberOfSections);
211 void WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
212 const MCAsmLayout &Layout);
214 void WriteSymbolTable(MCDataFragment *SymtabF, MCAssembler &Asm,
215 const MCAsmLayout &Layout,
216 SectionIndexMapTy &SectionIndexMap);
218 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
219 const MCFragment *Fragment, const MCFixup &Fixup,
220 MCValue Target, uint64_t &FixedValue) override;
222 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
225 // Map from a group section to the signature symbol
226 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
227 // Map from a signature symbol to the group section
228 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
229 // Map from a section to the section with the relocations
230 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
231 // Map from a section to its offset
232 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
234 /// Compute the symbol table data
236 /// \param Asm - The assembler.
237 /// \param SectionIndexMap - Maps a section to its index.
238 /// \param RevGroupMap - Maps a signature symbol to the group section.
239 /// \param NumRegularSections - Number of non-relocation sections.
240 void computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
241 const SectionIndexMapTy &SectionIndexMap,
242 RevGroupMapTy RevGroupMap,
243 unsigned NumRegularSections);
245 void ComputeIndexMap(MCAssembler &Asm,
246 SectionIndexMapTy &SectionIndexMap,
247 const RelMapTy &RelMap);
249 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
252 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
253 const RelMapTy &RelMap);
255 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
256 SectionIndexMapTy &SectionIndexMap,
257 const RelMapTy &RelMap);
259 // Create the sections that show up in the symbol table. Currently
260 // those are the .note.GNU-stack section and the group sections.
261 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
262 GroupMapTy &GroupMap,
263 RevGroupMapTy &RevGroupMap,
264 SectionIndexMapTy &SectionIndexMap,
265 const RelMapTy &RelMap);
267 void ExecutePostLayoutBinding(MCAssembler &Asm,
268 const MCAsmLayout &Layout) override;
270 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
271 const MCAsmLayout &Layout,
272 const SectionIndexMapTy &SectionIndexMap,
273 const SectionOffsetMapTy &SectionOffsetMap);
275 void ComputeSectionOrder(MCAssembler &Asm,
276 std::vector<const MCSectionELF*> &Sections);
278 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
279 uint64_t Address, uint64_t Offset,
280 uint64_t Size, uint32_t Link, uint32_t Info,
281 uint64_t Alignment, uint64_t EntrySize);
283 void WriteRelocationsFragment(const MCAssembler &Asm,
285 const MCSectionData *SD);
288 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
289 const MCSymbolData &DataA,
290 const MCFragment &FB,
292 bool IsPCRel) const override;
294 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
295 void WriteSection(MCAssembler &Asm,
296 const SectionIndexMapTy &SectionIndexMap,
297 uint32_t GroupSymbolIndex,
298 uint64_t Offset, uint64_t Size, uint64_t Alignment,
299 const MCSectionELF &Section);
303 FragmentWriter::FragmentWriter(bool IsLittleEndian)
304 : IsLittleEndian(IsLittleEndian) {}
306 template <typename T> void FragmentWriter::write(MCDataFragment &F, T Val) {
308 Val = support::endian::byte_swap<T, support::little>(Val);
310 Val = support::endian::byte_swap<T, support::big>(Val);
311 const char *Start = (const char *)&Val;
312 F.getContents().append(Start, Start + sizeof(T));
315 void SymbolTableWriter::createSymtabShndx() {
319 MCContext &Ctx = Asm.getContext();
320 const MCSectionELF *SymtabShndxSection =
321 Ctx.getELFSection(".symtab_shndxr", ELF::SHT_SYMTAB_SHNDX, 0,
322 SectionKind::getReadOnly(), 4, "");
323 MCSectionData *SymtabShndxSD =
324 &Asm.getOrCreateSectionData(*SymtabShndxSection);
325 SymtabShndxSD->setAlignment(4);
326 ShndxF = new MCDataFragment(SymtabShndxSD);
327 unsigned Index = SectionIndexMap.size() + 1;
328 SectionIndexMap[SymtabShndxSection] = Index;
330 for (unsigned I = 0; I < NumWritten; ++I)
331 write(*ShndxF, uint32_t(0));
334 template <typename T>
335 void SymbolTableWriter::write(MCDataFragment &F, T Value) {
336 FWriter.write(F, Value);
339 SymbolTableWriter::SymbolTableWriter(MCAssembler &Asm, FragmentWriter &FWriter,
341 SectionIndexMapTy &SectionIndexMap,
342 MCDataFragment *SymtabF)
343 : Asm(Asm), FWriter(FWriter), Is64Bit(Is64Bit),
344 SectionIndexMap(SectionIndexMap), SymtabF(SymtabF), ShndxF(nullptr),
347 void SymbolTableWriter::writeSymbol(uint32_t name, uint8_t info, uint64_t value,
348 uint64_t size, uint8_t other,
349 uint32_t shndx, bool Reserved) {
350 bool LargeIndex = shndx >= ELF::SHN_LORESERVE && !Reserved;
357 write(*ShndxF, shndx);
359 write(*ShndxF, uint32_t(0));
362 uint16_t Index = LargeIndex ? uint16_t(ELF::SHN_XINDEX) : shndx;
364 raw_svector_ostream OS(SymtabF->getContents());
367 write(*SymtabF, name); // st_name
368 write(*SymtabF, info); // st_info
369 write(*SymtabF, other); // st_other
370 write(*SymtabF, Index); // st_shndx
371 write(*SymtabF, value); // st_value
372 write(*SymtabF, size); // st_size
374 write(*SymtabF, name); // st_name
375 write(*SymtabF, uint32_t(value)); // st_value
376 write(*SymtabF, uint32_t(size)); // st_size
377 write(*SymtabF, info); // st_info
378 write(*SymtabF, other); // st_other
379 write(*SymtabF, Index); // st_shndx
385 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
386 const MCFixupKindInfo &FKI =
387 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
389 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
392 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
396 case MCSymbolRefExpr::VK_GOT:
397 case MCSymbolRefExpr::VK_PLT:
398 case MCSymbolRefExpr::VK_GOTPCREL:
399 case MCSymbolRefExpr::VK_GOTOFF:
400 case MCSymbolRefExpr::VK_TPOFF:
401 case MCSymbolRefExpr::VK_TLSGD:
402 case MCSymbolRefExpr::VK_GOTTPOFF:
403 case MCSymbolRefExpr::VK_INDNTPOFF:
404 case MCSymbolRefExpr::VK_NTPOFF:
405 case MCSymbolRefExpr::VK_GOTNTPOFF:
406 case MCSymbolRefExpr::VK_TLSLDM:
407 case MCSymbolRefExpr::VK_DTPOFF:
408 case MCSymbolRefExpr::VK_TLSLD:
413 ELFObjectWriter::~ELFObjectWriter()
416 // Emit the ELF header.
417 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
418 uint64_t SectionDataSize,
419 unsigned NumberOfSections) {
425 // emitWord method behaves differently for ELF32 and ELF64, writing
426 // 4 bytes in the former and 8 in the latter.
428 Write8(0x7f); // e_ident[EI_MAG0]
429 Write8('E'); // e_ident[EI_MAG1]
430 Write8('L'); // e_ident[EI_MAG2]
431 Write8('F'); // e_ident[EI_MAG3]
433 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
436 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
438 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
440 Write8(TargetObjectWriter->getOSABI());
441 Write8(0); // e_ident[EI_ABIVERSION]
443 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
445 Write16(ELF::ET_REL); // e_type
447 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
449 Write32(ELF::EV_CURRENT); // e_version
450 WriteWord(0); // e_entry, no entry point in .o file
451 WriteWord(0); // e_phoff, no program header for .o
452 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
453 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
455 // e_flags = whatever the target wants
456 Write32(Asm.getELFHeaderEFlags());
458 // e_ehsize = ELF header size
459 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
461 Write16(0); // e_phentsize = prog header entry size
462 Write16(0); // e_phnum = # prog header entries = 0
464 // e_shentsize = Section header entry size
465 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
467 // e_shnum = # of section header ents
468 if (NumberOfSections >= ELF::SHN_LORESERVE)
469 Write16(ELF::SHN_UNDEF);
471 Write16(NumberOfSections);
473 // e_shstrndx = Section # of '.shstrtab'
474 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
475 Write16(ELF::SHN_XINDEX);
477 Write16(ShstrtabIndex);
480 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &OrigData,
481 const MCAsmLayout &Layout) {
482 MCSymbolData *Data = &OrigData;
483 if (Data->isCommon() && Data->isExternal())
484 return Data->getCommonAlignment();
486 const MCSymbol *Symbol = &Data->getSymbol();
487 bool IsThumbFunc = OrigData.getFlags() & ELF_Other_ThumbFunc;
490 if (Symbol->isVariable()) {
491 const MCExpr *Expr = Symbol->getVariableValue();
493 if (!Expr->EvaluateAsRelocatable(Value, &Layout))
494 llvm_unreachable("Invalid expression");
496 assert(!Value.getSymB());
498 Res = Value.getConstant();
500 if (const MCSymbolRefExpr *A = Value.getSymA()) {
501 Symbol = &A->getSymbol();
502 Data = &Layout.getAssembler().getSymbolData(*Symbol);
512 if (!Symbol || !Symbol->isInSection())
515 Res += Layout.getSymbolOffset(Data);
520 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
521 const MCAsmLayout &Layout) {
522 // The presence of symbol versions causes undefined symbols and
523 // versions declared with @@@ to be renamed.
525 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
526 ie = Asm.symbol_end(); it != ie; ++it) {
527 const MCSymbol &Alias = it->getSymbol();
528 const MCSymbol &Symbol = Alias.AliasedSymbol();
529 MCSymbolData &SD = Asm.getSymbolData(Symbol);
532 if (&Symbol == &Alias)
535 StringRef AliasName = Alias.getName();
536 size_t Pos = AliasName.find('@');
537 if (Pos == StringRef::npos)
540 // Aliases defined with .symvar copy the binding from the symbol they alias.
541 // This is the first place we are able to copy this information.
542 it->setExternal(SD.isExternal());
543 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
545 StringRef Rest = AliasName.substr(Pos);
546 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
549 // FIXME: produce a better error message.
550 if (Symbol.isUndefined() && Rest.startswith("@@") &&
551 !Rest.startswith("@@@"))
552 report_fatal_error("A @@ version cannot be undefined");
554 Renames.insert(std::make_pair(&Symbol, &Alias));
558 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
559 uint8_t Type = newType;
561 // Propagation rules:
562 // IFUNC > FUNC > OBJECT > NOTYPE
563 // TLS_OBJECT > OBJECT > NOTYPE
565 // dont let the new type degrade the old type
569 case ELF::STT_GNU_IFUNC:
570 if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
571 Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
572 Type = ELF::STT_GNU_IFUNC;
575 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
576 Type == ELF::STT_TLS)
577 Type = ELF::STT_FUNC;
579 case ELF::STT_OBJECT:
580 if (Type == ELF::STT_NOTYPE)
581 Type = ELF::STT_OBJECT;
584 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
585 Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
593 static const MCSymbol *getBaseSymbol(const MCAsmLayout &Layout,
594 const MCSymbol &Symbol) {
595 if (!Symbol.isVariable())
598 const MCExpr *Expr = Symbol.getVariableValue();
600 if (!Expr->EvaluateAsRelocatable(Value, &Layout))
601 llvm_unreachable("Invalid Expression");
602 assert(!Value.getSymB());
603 const MCSymbolRefExpr *A = Value.getSymA();
606 return getBaseSymbol(Layout, A->getSymbol());
609 void ELFObjectWriter::WriteSymbol(SymbolTableWriter &Writer, ELFSymbolData &MSD,
610 const MCAsmLayout &Layout) {
611 MCSymbolData &OrigData = *MSD.SymbolData;
613 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
615 const MCSymbol *Base = getBaseSymbol(Layout, OrigData.getSymbol());
617 // This has to be in sync with when computeSymbolTable uses SHN_ABS or
619 bool IsReserved = !Base || OrigData.isCommon();
621 // Binding and Type share the same byte as upper and lower nibbles
622 uint8_t Binding = MCELF::GetBinding(OrigData);
623 uint8_t Type = MCELF::GetType(OrigData);
625 MCSymbolData BaseSD = Layout.getAssembler().getSymbolData(*Base);
626 Type = mergeTypeForSet(Type, MCELF::GetType(BaseSD));
628 if (OrigData.getFlags() & ELF_Other_ThumbFunc)
629 Type = ELF::STT_FUNC;
630 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
632 // Other and Visibility share the same byte with Visibility using the lower
634 uint8_t Visibility = MCELF::GetVisibility(OrigData);
635 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
638 uint64_t Value = SymbolValue(OrigData, Layout);
639 if (OrigData.getFlags() & ELF_Other_ThumbFunc)
643 assert(!(Data.isCommon() && !Data.isExternal()));
645 const MCExpr *ESize = Data.getSize();
648 if (!ESize->EvaluateAsAbsolute(Res, Layout))
649 report_fatal_error("Size expression must be absolute.");
653 // Write out the symbol table entry
654 Writer.writeSymbol(MSD.StringIndex, Info, Value, Size, Other,
655 MSD.SectionIndex, IsReserved);
658 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
660 const MCAsmLayout &Layout,
661 SectionIndexMapTy &SectionIndexMap) {
662 // The string table must be emitted first because we need the index
663 // into the string table for all the symbol names.
664 assert(StringTable.size() && "Missing string table");
666 // FIXME: Make sure the start of the symbol table is aligned.
668 SymbolTableWriter Writer(Asm, FWriter, is64Bit(), SectionIndexMap, SymtabF);
670 // The first entry is the undefined symbol entry.
671 Writer.writeSymbol(0, 0, 0, 0, 0, 0, false);
673 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
674 Writer.writeSymbol(FileSymbolData[i], ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
675 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
678 // Write the symbol table entries.
679 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
681 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
682 ELFSymbolData &MSD = LocalSymbolData[i];
683 WriteSymbol(Writer, MSD, Layout);
686 // Write out a symbol table entry for each regular section.
687 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
689 const MCSectionELF &Section =
690 static_cast<const MCSectionELF&>(i->getSection());
691 if (Section.getType() == ELF::SHT_RELA ||
692 Section.getType() == ELF::SHT_REL ||
693 Section.getType() == ELF::SHT_STRTAB ||
694 Section.getType() == ELF::SHT_SYMTAB ||
695 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
697 Writer.writeSymbol(0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT,
698 SectionIndexMap.lookup(&Section), false);
699 LastLocalSymbolIndex++;
702 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
703 ELFSymbolData &MSD = ExternalSymbolData[i];
704 MCSymbolData &Data = *MSD.SymbolData;
705 assert(((Data.getFlags() & ELF_STB_Global) ||
706 (Data.getFlags() & ELF_STB_Weak)) &&
707 "External symbol requires STB_GLOBAL or STB_WEAK flag");
708 WriteSymbol(Writer, MSD, Layout);
709 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
710 LastLocalSymbolIndex++;
713 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
714 ELFSymbolData &MSD = UndefinedSymbolData[i];
715 MCSymbolData &Data = *MSD.SymbolData;
716 WriteSymbol(Writer, MSD, Layout);
717 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
718 LastLocalSymbolIndex++;
722 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
723 const MCValue &Target,
725 const MCFixup &Fixup,
726 bool IsPCRel) const {
727 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
728 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
729 const MCSymbol *Renamed = Renames.lookup(&Symbol);
730 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
732 if (ASymbol.isUndefined()) {
735 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
738 if (SD.isExternal()) {
744 const MCSectionELF &Section =
745 static_cast<const MCSectionELF&>(ASymbol.getSection());
746 const SectionKind secKind = Section.getKind();
749 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
751 if (secKind.isThreadLocal()) {
757 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
758 const MCSectionELF &Sec2 =
759 static_cast<const MCSectionELF&>(F.getParent()->getSection());
761 if (&Sec2 != &Section &&
762 (Kind == MCSymbolRefExpr::VK_PLT ||
763 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
764 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
770 if (Section.getFlags() & ELF::SHF_MERGE) {
771 if (Target.getConstant() == 0)
772 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
778 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
783 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
784 const MCAsmLayout &Layout,
785 const MCFragment *Fragment,
786 const MCFixup &Fixup,
788 uint64_t &FixedValue) {
791 int64_t Value = Target.getConstant();
792 const MCSymbol *RelocSymbol = NULL;
794 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
795 if (!Target.isAbsolute()) {
796 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
797 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
798 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
800 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
801 const MCSymbol &SymbolB = RefB->getSymbol();
802 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
805 if (!SDB.getFragment())
806 Asm.getContext().FatalError(
808 Twine("symbol '") + SymbolB.getName() +
809 "' can not be undefined in a subtraction expression");
811 // Offset of the symbol in the section
812 int64_t a = Layout.getSymbolOffset(&SDB);
814 // Offset of the relocation in the section
815 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
820 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
821 MCFragment *F = SD.getFragment();
824 Index = F->getParent()->getOrdinal() + 1;
825 // Offset of the symbol in the section
826 Value += Layout.getSymbolOffset(&SD);
831 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_WEAKREF)
832 WeakrefUsedInReloc.insert(RelocSymbol);
834 UsedInReloc.insert(RelocSymbol);
838 if (hasRelocationAddend())
843 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
844 (RelocSymbol != 0), Addend);
845 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
846 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
847 if (RelocNeedsGOT(Modifier))
850 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
853 if (!hasRelocationAddend())
857 assert(isInt<64>(Addend));
859 assert(isInt<32>(Addend));
861 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
862 Relocations[Fragment->getParent()].push_back(ERE);
867 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
869 MCSymbolData &SD = Asm.getSymbolData(*S);
870 return SD.getIndex();
873 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
874 const MCSymbolData &Data,
875 bool Used, bool Renamed) {
876 const MCSymbol &Symbol = Data.getSymbol();
877 if (Symbol.isVariable()) {
878 const MCExpr *Expr = Symbol.getVariableValue();
879 if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
880 if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
891 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
894 const MCSymbol &A = Symbol.AliasedSymbol();
895 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
898 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
899 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
902 if (Symbol.isTemporary())
908 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
909 bool isUsedInReloc) {
910 if (Data.isExternal())
913 const MCSymbol &Symbol = Data.getSymbol();
914 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
916 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
917 if (isSignature && !isUsedInReloc)
926 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
927 SectionIndexMapTy &SectionIndexMap,
928 const RelMapTy &RelMap) {
930 for (MCAssembler::iterator it = Asm.begin(),
931 ie = Asm.end(); it != ie; ++it) {
932 const MCSectionELF &Section =
933 static_cast<const MCSectionELF &>(it->getSection());
934 if (Section.getType() != ELF::SHT_GROUP)
936 SectionIndexMap[&Section] = Index++;
939 for (MCAssembler::iterator it = Asm.begin(),
940 ie = Asm.end(); it != ie; ++it) {
941 const MCSectionELF &Section =
942 static_cast<const MCSectionELF &>(it->getSection());
943 if (Section.getType() == ELF::SHT_GROUP ||
944 Section.getType() == ELF::SHT_REL ||
945 Section.getType() == ELF::SHT_RELA)
947 SectionIndexMap[&Section] = Index++;
948 const MCSectionELF *RelSection = RelMap.lookup(&Section);
950 SectionIndexMap[RelSection] = Index++;
955 ELFObjectWriter::computeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
956 const SectionIndexMapTy &SectionIndexMap,
957 RevGroupMapTy RevGroupMap,
958 unsigned NumRegularSections) {
959 // FIXME: Is this the correct place to do this?
960 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
962 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
963 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
964 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
965 Data.setExternal(true);
966 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
969 // Index 0 is always the empty string.
970 StringMap<uint64_t> StringIndexMap;
971 StringTable += '\x00';
973 // FIXME: We could optimize suffixes in strtab in the same way we
974 // optimize them in shstrtab.
976 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
977 ie = Asm.file_names_end();
980 StringRef Name = *it;
981 uint64_t &Entry = StringIndexMap[Name];
983 Entry = StringTable.size();
985 StringTable += '\x00';
987 FileSymbolData.push_back(Entry);
990 // Add the data for the symbols.
991 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
992 ie = Asm.symbol_end(); it != ie; ++it) {
993 const MCSymbol &Symbol = it->getSymbol();
995 bool Used = UsedInReloc.count(&Symbol);
996 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
997 bool isSignature = RevGroupMap.count(&Symbol);
999 if (!isInSymtab(Asm, *it,
1000 Used || WeakrefUsed || isSignature,
1001 Renames.count(&Symbol)))
1005 MSD.SymbolData = it;
1006 const MCSymbol *BaseSymbol = getBaseSymbol(Layout, Symbol);
1008 // Undefined symbols are global, but this is the first place we
1009 // are able to set it.
1010 bool Local = isLocal(*it, isSignature, Used);
1011 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
1013 MCSymbolData &SD = Asm.getSymbolData(*BaseSymbol);
1014 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
1015 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
1019 MSD.SectionIndex = ELF::SHN_ABS;
1020 } else if (it->isCommon()) {
1022 MSD.SectionIndex = ELF::SHN_COMMON;
1023 } else if (BaseSymbol->isUndefined()) {
1024 if (isSignature && !Used)
1025 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
1027 MSD.SectionIndex = ELF::SHN_UNDEF;
1028 if (!Used && WeakrefUsed)
1029 MCELF::SetBinding(*it, ELF::STB_WEAK);
1031 const MCSectionELF &Section =
1032 static_cast<const MCSectionELF&>(BaseSymbol->getSection());
1033 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
1034 assert(MSD.SectionIndex && "Invalid section index!");
1037 // The @@@ in symbol version is replaced with @ in undefined symbols and
1038 // @@ in defined ones.
1039 StringRef Name = Symbol.getName();
1040 SmallString<32> Buf;
1042 size_t Pos = Name.find("@@@");
1043 if (Pos != StringRef::npos) {
1044 Buf += Name.substr(0, Pos);
1045 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
1046 Buf += Name.substr(Pos + Skip);
1050 uint64_t &Entry = StringIndexMap[Name];
1052 Entry = StringTable.size();
1053 StringTable += Name;
1054 StringTable += '\x00';
1056 MSD.StringIndex = Entry;
1057 if (MSD.SectionIndex == ELF::SHN_UNDEF)
1058 UndefinedSymbolData.push_back(MSD);
1060 LocalSymbolData.push_back(MSD);
1062 ExternalSymbolData.push_back(MSD);
1065 // Symbols are required to be in lexicographic order.
1066 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1067 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1068 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1070 // Set the symbol indices. Local symbols must come before all other
1071 // symbols with non-local bindings.
1072 unsigned Index = FileSymbolData.size() + 1;
1073 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1074 LocalSymbolData[i].SymbolData->setIndex(Index++);
1076 Index += NumRegularSections;
1078 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1079 ExternalSymbolData[i].SymbolData->setIndex(Index++);
1080 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1081 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1084 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1085 MCAsmLayout &Layout,
1087 for (MCAssembler::const_iterator it = Asm.begin(),
1088 ie = Asm.end(); it != ie; ++it) {
1089 const MCSectionData &SD = *it;
1090 if (Relocations[&SD].empty())
1093 MCContext &Ctx = Asm.getContext();
1094 const MCSectionELF &Section =
1095 static_cast<const MCSectionELF&>(SD.getSection());
1097 const StringRef SectionName = Section.getSectionName();
1098 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1099 RelaSectionName += SectionName;
1102 if (hasRelocationAddend())
1103 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1105 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1108 StringRef Group = "";
1109 if (Section.getFlags() & ELF::SHF_GROUP) {
1110 Flags = ELF::SHF_GROUP;
1111 Group = Section.getGroup()->getName();
1114 const MCSectionELF *RelaSection =
1115 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1116 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1117 SectionKind::getReadOnly(),
1119 RelMap[&Section] = RelaSection;
1120 Asm.getOrCreateSectionData(*RelaSection);
1124 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1125 const RelMapTy &RelMap) {
1126 for (MCAssembler::const_iterator it = Asm.begin(),
1127 ie = Asm.end(); it != ie; ++it) {
1128 const MCSectionData &SD = *it;
1129 const MCSectionELF &Section =
1130 static_cast<const MCSectionELF&>(SD.getSection());
1132 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1135 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1136 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1138 MCDataFragment *F = new MCDataFragment(&RelaSD);
1139 WriteRelocationsFragment(Asm, F, &*it);
1143 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1144 uint64_t Flags, uint64_t Address,
1145 uint64_t Offset, uint64_t Size,
1146 uint32_t Link, uint32_t Info,
1148 uint64_t EntrySize) {
1149 Write32(Name); // sh_name: index into string table
1150 Write32(Type); // sh_type
1151 WriteWord(Flags); // sh_flags
1152 WriteWord(Address); // sh_addr
1153 WriteWord(Offset); // sh_offset
1154 WriteWord(Size); // sh_size
1155 Write32(Link); // sh_link
1156 Write32(Info); // sh_info
1157 WriteWord(Alignment); // sh_addralign
1158 WriteWord(EntrySize); // sh_entsize
1161 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1163 const MCSectionData *SD) {
1164 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1166 // Sort the relocation entries. Most targets just sort by r_offset, but some
1167 // (e.g., MIPS) have additional constraints.
1168 TargetObjectWriter->sortRelocs(Asm, Relocs);
1170 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1171 ELFRelocationEntry entry = Relocs[e - i - 1];
1175 // FIXME: this is most likely a bug if index overflows.
1176 else if (entry.Index < 0)
1177 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1179 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1181 write(*F, entry.r_offset);
1182 if (TargetObjectWriter->isN64()) {
1183 write(*F, uint32_t(entry.Index));
1185 write(*F, TargetObjectWriter->getRSsym(entry.Type));
1186 write(*F, TargetObjectWriter->getRType3(entry.Type));
1187 write(*F, TargetObjectWriter->getRType2(entry.Type));
1188 write(*F, TargetObjectWriter->getRType(entry.Type));
1191 struct ELF::Elf64_Rela ERE64;
1192 ERE64.setSymbolAndType(entry.Index, entry.Type);
1193 write(*F, ERE64.r_info);
1195 if (hasRelocationAddend())
1196 write(*F, entry.r_addend);
1198 write(*F, uint32_t(entry.r_offset));
1200 struct ELF::Elf32_Rela ERE32;
1201 ERE32.setSymbolAndType(entry.Index, entry.Type);
1202 write(*F, ERE32.r_info);
1204 if (hasRelocationAddend())
1205 write(*F, uint32_t(entry.r_addend));
1210 static int compareBySuffix(const MCSectionELF *const *a,
1211 const MCSectionELF *const *b) {
1212 const StringRef &NameA = (*a)->getSectionName();
1213 const StringRef &NameB = (*b)->getSectionName();
1214 const unsigned sizeA = NameA.size();
1215 const unsigned sizeB = NameB.size();
1216 const unsigned len = std::min(sizeA, sizeB);
1217 for (unsigned int i = 0; i < len; ++i) {
1218 char ca = NameA[sizeA - i - 1];
1219 char cb = NameB[sizeB - i - 1];
1224 return sizeB - sizeA;
1227 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1228 MCAsmLayout &Layout,
1229 SectionIndexMapTy &SectionIndexMap,
1230 const RelMapTy &RelMap) {
1231 MCContext &Ctx = Asm.getContext();
1234 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1236 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1237 const MCSectionELF *ShstrtabSection =
1238 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1239 SectionKind::getReadOnly());
1240 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1241 ShstrtabSD.setAlignment(1);
1243 const MCSectionELF *SymtabSection =
1244 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1245 SectionKind::getReadOnly(),
1247 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1248 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1250 const MCSectionELF *StrtabSection;
1251 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1252 SectionKind::getReadOnly());
1253 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1254 StrtabSD.setAlignment(1);
1256 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1258 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1259 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1260 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1263 F = new MCDataFragment(&SymtabSD);
1264 WriteSymbolTable(F, Asm, Layout, SectionIndexMap);
1266 F = new MCDataFragment(&StrtabSD);
1267 F->getContents().append(StringTable.begin(), StringTable.end());
1269 F = new MCDataFragment(&ShstrtabSD);
1271 std::vector<const MCSectionELF*> Sections;
1272 for (MCAssembler::const_iterator it = Asm.begin(),
1273 ie = Asm.end(); it != ie; ++it) {
1274 const MCSectionELF &Section =
1275 static_cast<const MCSectionELF&>(it->getSection());
1276 Sections.push_back(&Section);
1278 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1280 // Section header string table.
1282 // The first entry of a string table holds a null character so skip
1285 F->getContents().push_back('\x00');
1287 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1288 const MCSectionELF &Section = *Sections[I];
1290 StringRef Name = Section.getSectionName();
1292 StringRef PreviousName = Sections[I - 1]->getSectionName();
1293 if (PreviousName.endswith(Name)) {
1294 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1298 // Remember the index into the string table so we can write it
1299 // into the sh_name field of the section header table.
1300 SectionStringTableIndex[&Section] = Index;
1302 Index += Name.size() + 1;
1303 F->getContents().append(Name.begin(), Name.end());
1304 F->getContents().push_back('\x00');
1308 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1309 MCAsmLayout &Layout,
1310 GroupMapTy &GroupMap,
1311 RevGroupMapTy &RevGroupMap,
1312 SectionIndexMapTy &SectionIndexMap,
1313 const RelMapTy &RelMap) {
1314 // Create the .note.GNU-stack section if needed.
1315 MCContext &Ctx = Asm.getContext();
1316 if (Asm.getNoExecStack()) {
1317 const MCSectionELF *GnuStackSection =
1318 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1319 SectionKind::getReadOnly());
1320 Asm.getOrCreateSectionData(*GnuStackSection);
1324 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1326 const MCSectionELF &Section =
1327 static_cast<const MCSectionELF&>(it->getSection());
1328 if (!(Section.getFlags() & ELF::SHF_GROUP))
1331 const MCSymbol *SignatureSymbol = Section.getGroup();
1332 Asm.getOrCreateSymbolData(*SignatureSymbol);
1333 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1335 Group = Ctx.CreateELFGroupSection();
1336 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1337 Data.setAlignment(4);
1338 MCDataFragment *F = new MCDataFragment(&Data);
1339 write(*F, uint32_t(ELF::GRP_COMDAT));
1341 GroupMap[Group] = SignatureSymbol;
1344 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1346 // Add sections to the groups
1347 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1349 const MCSectionELF &Section =
1350 static_cast<const MCSectionELF&>(it->getSection());
1351 if (!(Section.getFlags() & ELF::SHF_GROUP))
1353 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1354 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1355 // FIXME: we could use the previous fragment
1356 MCDataFragment *F = new MCDataFragment(&Data);
1357 uint32_t Index = SectionIndexMap.lookup(&Section);
1362 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1363 const SectionIndexMapTy &SectionIndexMap,
1364 uint32_t GroupSymbolIndex,
1365 uint64_t Offset, uint64_t Size,
1367 const MCSectionELF &Section) {
1368 uint64_t sh_link = 0;
1369 uint64_t sh_info = 0;
1371 switch(Section.getType()) {
1372 case ELF::SHT_DYNAMIC:
1373 sh_link = SectionStringTableIndex[&Section];
1378 case ELF::SHT_RELA: {
1379 const MCSectionELF *SymtabSection;
1380 const MCSectionELF *InfoSection;
1381 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1383 SectionKind::getReadOnly());
1384 sh_link = SectionIndexMap.lookup(SymtabSection);
1385 assert(sh_link && ".symtab not found");
1387 // Remove ".rel" and ".rela" prefixes.
1388 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1389 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1390 StringRef GroupName =
1391 Section.getGroup() ? Section.getGroup()->getName() : "";
1393 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1394 0, SectionKind::getReadOnly(),
1396 sh_info = SectionIndexMap.lookup(InfoSection);
1400 case ELF::SHT_SYMTAB:
1401 case ELF::SHT_DYNSYM:
1402 sh_link = StringTableIndex;
1403 sh_info = LastLocalSymbolIndex;
1406 case ELF::SHT_SYMTAB_SHNDX:
1407 sh_link = SymbolTableIndex;
1410 case ELF::SHT_PROGBITS:
1411 case ELF::SHT_STRTAB:
1412 case ELF::SHT_NOBITS:
1415 case ELF::SHT_ARM_ATTRIBUTES:
1416 case ELF::SHT_INIT_ARRAY:
1417 case ELF::SHT_FINI_ARRAY:
1418 case ELF::SHT_PREINIT_ARRAY:
1419 case ELF::SHT_X86_64_UNWIND:
1420 case ELF::SHT_MIPS_REGINFO:
1421 case ELF::SHT_MIPS_OPTIONS:
1425 case ELF::SHT_GROUP:
1426 sh_link = SymbolTableIndex;
1427 sh_info = GroupSymbolIndex;
1431 assert(0 && "FIXME: sh_type value not supported!");
1435 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1436 Section.getType() == ELF::SHT_ARM_EXIDX) {
1437 StringRef SecName(Section.getSectionName());
1438 if (SecName == ".ARM.exidx") {
1439 sh_link = SectionIndexMap.lookup(
1440 Asm.getContext().getELFSection(".text",
1442 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1443 SectionKind::getText()));
1444 } else if (SecName.startswith(".ARM.exidx")) {
1445 StringRef GroupName =
1446 Section.getGroup() ? Section.getGroup()->getName() : "";
1447 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1448 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1449 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1454 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1455 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1456 Alignment, Section.getEntrySize());
1459 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1460 return SD.getOrdinal() == ~UINT32_C(0) &&
1461 !SD.getSection().isVirtualSection();
1464 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1466 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1468 const MCFragment &F = *i;
1469 assert(F.getKind() == MCFragment::FT_Data);
1470 Ret += cast<MCDataFragment>(F).getContents().size();
1475 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1476 const MCSectionData &SD) {
1477 if (IsELFMetaDataSection(SD))
1478 return DataSectionSize(SD);
1479 return Layout.getSectionFileSize(&SD);
1482 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1483 const MCSectionData &SD) {
1484 if (IsELFMetaDataSection(SD))
1485 return DataSectionSize(SD);
1486 return Layout.getSectionAddressSize(&SD);
1489 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1490 const MCAsmLayout &Layout,
1491 const MCSectionELF &Section) {
1492 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1494 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1495 WriteZeros(Padding);
1497 if (IsELFMetaDataSection(SD)) {
1498 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1500 const MCFragment &F = *i;
1501 assert(F.getKind() == MCFragment::FT_Data);
1502 WriteBytes(cast<MCDataFragment>(F).getContents());
1505 Asm.writeSectionData(&SD, Layout);
1509 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1510 const GroupMapTy &GroupMap,
1511 const MCAsmLayout &Layout,
1512 const SectionIndexMapTy &SectionIndexMap,
1513 const SectionOffsetMapTy &SectionOffsetMap) {
1514 const unsigned NumSections = Asm.size() + 1;
1516 std::vector<const MCSectionELF*> Sections;
1517 Sections.resize(NumSections - 1);
1519 for (SectionIndexMapTy::const_iterator i=
1520 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1521 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1522 Sections[p.second - 1] = p.first;
1525 // Null section first.
1526 uint64_t FirstSectionSize =
1527 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1528 uint32_t FirstSectionLink =
1529 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1530 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1532 for (unsigned i = 0; i < NumSections - 1; ++i) {
1533 const MCSectionELF &Section = *Sections[i];
1534 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1535 uint32_t GroupSymbolIndex;
1536 if (Section.getType() != ELF::SHT_GROUP)
1537 GroupSymbolIndex = 0;
1539 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1540 GroupMap.lookup(&Section));
1542 uint64_t Size = GetSectionAddressSize(Layout, SD);
1544 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1545 SectionOffsetMap.lookup(&Section), Size,
1546 SD.getAlignment(), Section);
1550 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1551 std::vector<const MCSectionELF*> &Sections) {
1552 for (MCAssembler::iterator it = Asm.begin(),
1553 ie = Asm.end(); it != ie; ++it) {
1554 const MCSectionELF &Section =
1555 static_cast<const MCSectionELF &>(it->getSection());
1556 if (Section.getType() == ELF::SHT_GROUP)
1557 Sections.push_back(&Section);
1560 for (MCAssembler::iterator it = Asm.begin(),
1561 ie = Asm.end(); it != ie; ++it) {
1562 const MCSectionELF &Section =
1563 static_cast<const MCSectionELF &>(it->getSection());
1564 if (Section.getType() != ELF::SHT_GROUP &&
1565 Section.getType() != ELF::SHT_REL &&
1566 Section.getType() != ELF::SHT_RELA)
1567 Sections.push_back(&Section);
1570 for (MCAssembler::iterator it = Asm.begin(),
1571 ie = Asm.end(); it != ie; ++it) {
1572 const MCSectionELF &Section =
1573 static_cast<const MCSectionELF &>(it->getSection());
1574 if (Section.getType() == ELF::SHT_REL ||
1575 Section.getType() == ELF::SHT_RELA)
1576 Sections.push_back(&Section);
1580 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1581 const MCAsmLayout &Layout) {
1582 GroupMapTy GroupMap;
1583 RevGroupMapTy RevGroupMap;
1584 SectionIndexMapTy SectionIndexMap;
1586 unsigned NumUserSections = Asm.size();
1588 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1589 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1591 const unsigned NumUserAndRelocSections = Asm.size();
1592 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1593 RevGroupMap, SectionIndexMap, RelMap);
1594 const unsigned AllSections = Asm.size();
1595 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1597 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1599 // Compute symbol table information.
1600 computeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
1601 NumRegularSections);
1603 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1605 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1606 const_cast<MCAsmLayout&>(Layout),
1610 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1611 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1612 sizeof(ELF::Elf32_Ehdr);
1613 uint64_t FileOff = HeaderSize;
1615 std::vector<const MCSectionELF*> Sections;
1616 ComputeSectionOrder(Asm, Sections);
1617 unsigned NumSections = Sections.size();
1618 SectionOffsetMapTy SectionOffsetMap;
1619 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1620 const MCSectionELF &Section = *Sections[i];
1621 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1623 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1625 // Remember the offset into the file for this section.
1626 SectionOffsetMap[&Section] = FileOff;
1628 // Get the size of the section in the output file (including padding).
1629 FileOff += GetSectionFileSize(Layout, SD);
1632 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1634 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1636 uint64_t SectionHeaderEntrySize = is64Bit() ?
1637 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1638 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1640 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
1641 const MCSectionELF &Section = *Sections[i];
1642 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1644 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1646 // Remember the offset into the file for this section.
1647 SectionOffsetMap[&Section] = FileOff;
1649 // Get the size of the section in the output file (including padding).
1650 FileOff += GetSectionFileSize(Layout, SD);
1653 // Write out the ELF header ...
1654 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1656 // ... then the regular sections ...
1657 // + because of .shstrtab
1658 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1659 WriteDataSectionData(Asm, Layout, *Sections[i]);
1661 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1662 WriteZeros(Padding);
1664 // ... then the section header table ...
1665 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1668 // ... and then the remaining sections ...
1669 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1670 WriteDataSectionData(Asm, Layout, *Sections[i]);
1674 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1675 const MCSymbolData &DataA,
1676 const MCFragment &FB,
1678 bool IsPCRel) const {
1679 if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
1681 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1682 Asm, DataA, FB,InSet, IsPCRel);
1685 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1687 bool IsLittleEndian) {
1688 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);