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/OwningPtr.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/ADT/StringMap.h"
20 #include "llvm/MC/MCAsmBackend.h"
21 #include "llvm/MC/MCAsmLayout.h"
22 #include "llvm/MC/MCAssembler.h"
23 #include "llvm/MC/MCContext.h"
24 #include "llvm/MC/MCELF.h"
25 #include "llvm/MC/MCELFSymbolFlags.h"
26 #include "llvm/MC/MCExpr.h"
27 #include "llvm/MC/MCFixupKindInfo.h"
28 #include "llvm/MC/MCObjectWriter.h"
29 #include "llvm/MC/MCSectionELF.h"
30 #include "llvm/MC/MCValue.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/ELF.h"
33 #include "llvm/Support/ErrorHandling.h"
38 #define DEBUG_TYPE "reloc-info"
41 class ELFObjectWriter : public MCObjectWriter {
44 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
45 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
46 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
47 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
48 bool Used, bool Renamed);
49 static bool isLocal(const MCSymbolData &Data, bool isSignature,
51 static bool IsELFMetaDataSection(const MCSectionData &SD);
52 static uint64_t DataSectionSize(const MCSectionData &SD);
53 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
54 const MCSectionData &SD);
55 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
56 const MCSectionData &SD);
58 void WriteDataSectionData(MCAssembler &Asm,
59 const MCAsmLayout &Layout,
60 const MCSectionELF &Section);
62 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
63 return Kind == X86::reloc_riprel_4byte ||
64 Kind == X86::reloc_riprel_4byte_movq_load;
67 /// ELFSymbolData - Helper struct for containing some precomputed
68 /// information on symbols.
69 struct ELFSymbolData {
70 MCSymbolData *SymbolData;
72 uint32_t SectionIndex;
74 // Support lexicographic sorting.
75 bool operator<(const ELFSymbolData &RHS) const {
76 return SymbolData->getSymbol().getName() <
77 RHS.SymbolData->getSymbol().getName();
81 /// The target specific ELF writer instance.
82 llvm::OwningPtr<MCELFObjectTargetWriter> TargetObjectWriter;
84 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
85 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
86 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
88 llvm::DenseMap<const MCSectionData*,
89 std::vector<ELFRelocationEntry> > Relocations;
90 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
93 /// @name Symbol Table Data
96 SmallString<256> StringTable;
97 std::vector<uint64_t> FileSymbolData;
98 std::vector<ELFSymbolData> LocalSymbolData;
99 std::vector<ELFSymbolData> ExternalSymbolData;
100 std::vector<ELFSymbolData> UndefinedSymbolData;
106 bool NeedsSymtabShndx;
108 // This holds the symbol table index of the last local symbol.
109 unsigned LastLocalSymbolIndex;
110 // This holds the .strtab section index.
111 unsigned StringTableIndex;
112 // This holds the .symtab section index.
113 unsigned SymbolTableIndex;
115 unsigned ShstrtabIndex;
118 const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
119 const MCValue &Target,
121 const MCFixup &Fixup,
124 // TargetObjectWriter wrappers.
125 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
126 const MCValue &Target,
128 const MCFixup &Fixup,
129 bool IsPCRel) const {
130 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
132 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
133 const MCFixup &Fixup,
134 bool IsPCRel) const {
135 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
139 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
140 bool hasRelocationAddend() const {
141 return TargetObjectWriter->hasRelocationAddend();
143 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
144 bool IsPCRel, bool IsRelocWithSymbol,
145 int64_t Addend) const {
146 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
147 IsRelocWithSymbol, Addend);
151 ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
152 raw_ostream &_OS, bool IsLittleEndian)
153 : MCObjectWriter(_OS, IsLittleEndian),
154 TargetObjectWriter(MOTW),
155 NeedsGOT(false), NeedsSymtabShndx(false) {
158 virtual ~ELFObjectWriter();
160 void WriteWord(uint64_t W) {
167 void StringLE16(char *buf, uint16_t Value) {
168 buf[0] = char(Value >> 0);
169 buf[1] = char(Value >> 8);
172 void StringLE32(char *buf, uint32_t Value) {
173 StringLE16(buf, uint16_t(Value >> 0));
174 StringLE16(buf + 2, uint16_t(Value >> 16));
177 void StringLE64(char *buf, uint64_t Value) {
178 StringLE32(buf, uint32_t(Value >> 0));
179 StringLE32(buf + 4, uint32_t(Value >> 32));
182 void StringBE16(char *buf ,uint16_t Value) {
183 buf[0] = char(Value >> 8);
184 buf[1] = char(Value >> 0);
187 void StringBE32(char *buf, uint32_t Value) {
188 StringBE16(buf, uint16_t(Value >> 16));
189 StringBE16(buf + 2, uint16_t(Value >> 0));
192 void StringBE64(char *buf, uint64_t Value) {
193 StringBE32(buf, uint32_t(Value >> 32));
194 StringBE32(buf + 4, uint32_t(Value >> 0));
197 void String8(MCDataFragment &F, uint8_t Value) {
200 F.getContents().append(&buf[0], &buf[1]);
203 void String16(MCDataFragment &F, uint16_t Value) {
205 if (isLittleEndian())
206 StringLE16(buf, Value);
208 StringBE16(buf, Value);
209 F.getContents().append(&buf[0], &buf[2]);
212 void String32(MCDataFragment &F, uint32_t Value) {
214 if (isLittleEndian())
215 StringLE32(buf, Value);
217 StringBE32(buf, Value);
218 F.getContents().append(&buf[0], &buf[4]);
221 void String64(MCDataFragment &F, uint64_t Value) {
223 if (isLittleEndian())
224 StringLE64(buf, Value);
226 StringBE64(buf, Value);
227 F.getContents().append(&buf[0], &buf[8]);
230 void WriteHeader(const MCAssembler &Asm,
231 uint64_t SectionDataSize,
232 unsigned NumberOfSections);
234 void WriteSymbolEntry(MCDataFragment *SymtabF,
235 MCDataFragment *ShndxF,
236 uint64_t name, uint8_t info,
237 uint64_t value, uint64_t size,
238 uint8_t other, uint32_t shndx,
241 void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
243 const MCAsmLayout &Layout);
245 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
246 void WriteSymbolTable(MCDataFragment *SymtabF,
247 MCDataFragment *ShndxF,
248 const MCAssembler &Asm,
249 const MCAsmLayout &Layout,
250 const SectionIndexMapTy &SectionIndexMap);
252 virtual void RecordRelocation(const MCAssembler &Asm,
253 const MCAsmLayout &Layout,
254 const MCFragment *Fragment,
255 const MCFixup &Fixup,
256 MCValue Target, uint64_t &FixedValue);
258 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
261 // Map from a group section to the signature symbol
262 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
263 // Map from a signature symbol to the group section
264 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
265 // Map from a section to the section with the relocations
266 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
267 // Map from a section to its offset
268 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
270 /// ComputeSymbolTable - Compute the symbol table data
272 /// \param Asm - The assembler.
273 /// \param SectionIndexMap - Maps a section to its index.
274 /// \param RevGroupMap - Maps a signature symbol to the group section.
275 /// \param NumRegularSections - Number of non-relocation sections.
276 void ComputeSymbolTable(MCAssembler &Asm,
277 const SectionIndexMapTy &SectionIndexMap,
278 RevGroupMapTy RevGroupMap,
279 unsigned NumRegularSections);
281 void ComputeIndexMap(MCAssembler &Asm,
282 SectionIndexMapTy &SectionIndexMap,
283 const RelMapTy &RelMap);
285 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
288 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
289 const RelMapTy &RelMap);
291 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
292 SectionIndexMapTy &SectionIndexMap,
293 const RelMapTy &RelMap);
295 // Create the sections that show up in the symbol table. Currently
296 // those are the .note.GNU-stack section and the group sections.
297 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
298 GroupMapTy &GroupMap,
299 RevGroupMapTy &RevGroupMap,
300 SectionIndexMapTy &SectionIndexMap,
301 const RelMapTy &RelMap);
303 virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
304 const MCAsmLayout &Layout);
306 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
307 const MCAsmLayout &Layout,
308 const SectionIndexMapTy &SectionIndexMap,
309 const SectionOffsetMapTy &SectionOffsetMap);
311 void ComputeSectionOrder(MCAssembler &Asm,
312 std::vector<const MCSectionELF*> &Sections);
314 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
315 uint64_t Address, uint64_t Offset,
316 uint64_t Size, uint32_t Link, uint32_t Info,
317 uint64_t Alignment, uint64_t EntrySize);
319 void WriteRelocationsFragment(const MCAssembler &Asm,
321 const MCSectionData *SD);
324 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
325 const MCSymbolData &DataA,
326 const MCFragment &FB,
330 virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
331 void WriteSection(MCAssembler &Asm,
332 const SectionIndexMapTy &SectionIndexMap,
333 uint32_t GroupSymbolIndex,
334 uint64_t Offset, uint64_t Size, uint64_t Alignment,
335 const MCSectionELF &Section);
339 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
340 const MCFixupKindInfo &FKI =
341 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
343 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
346 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
350 case MCSymbolRefExpr::VK_GOT:
351 case MCSymbolRefExpr::VK_PLT:
352 case MCSymbolRefExpr::VK_GOTPCREL:
353 case MCSymbolRefExpr::VK_GOTOFF:
354 case MCSymbolRefExpr::VK_TPOFF:
355 case MCSymbolRefExpr::VK_TLSGD:
356 case MCSymbolRefExpr::VK_GOTTPOFF:
357 case MCSymbolRefExpr::VK_INDNTPOFF:
358 case MCSymbolRefExpr::VK_NTPOFF:
359 case MCSymbolRefExpr::VK_GOTNTPOFF:
360 case MCSymbolRefExpr::VK_TLSLDM:
361 case MCSymbolRefExpr::VK_DTPOFF:
362 case MCSymbolRefExpr::VK_TLSLD:
367 ELFObjectWriter::~ELFObjectWriter()
370 // Emit the ELF header.
371 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
372 uint64_t SectionDataSize,
373 unsigned NumberOfSections) {
379 // emitWord method behaves differently for ELF32 and ELF64, writing
380 // 4 bytes in the former and 8 in the latter.
382 Write8(0x7f); // e_ident[EI_MAG0]
383 Write8('E'); // e_ident[EI_MAG1]
384 Write8('L'); // e_ident[EI_MAG2]
385 Write8('F'); // e_ident[EI_MAG3]
387 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
390 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
392 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
394 Write8(TargetObjectWriter->getOSABI());
395 Write8(0); // e_ident[EI_ABIVERSION]
397 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
399 Write16(ELF::ET_REL); // e_type
401 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
403 Write32(ELF::EV_CURRENT); // e_version
404 WriteWord(0); // e_entry, no entry point in .o file
405 WriteWord(0); // e_phoff, no program header for .o
406 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
407 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
409 // e_flags = whatever the target wants
410 Write32(Asm.getELFHeaderEFlags());
412 // e_ehsize = ELF header size
413 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
415 Write16(0); // e_phentsize = prog header entry size
416 Write16(0); // e_phnum = # prog header entries = 0
418 // e_shentsize = Section header entry size
419 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
421 // e_shnum = # of section header ents
422 if (NumberOfSections >= ELF::SHN_LORESERVE)
423 Write16(ELF::SHN_UNDEF);
425 Write16(NumberOfSections);
427 // e_shstrndx = Section # of '.shstrtab'
428 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
429 Write16(ELF::SHN_XINDEX);
431 Write16(ShstrtabIndex);
434 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
435 MCDataFragment *ShndxF,
437 uint8_t info, uint64_t value,
438 uint64_t size, uint8_t other,
442 if (shndx >= ELF::SHN_LORESERVE && !Reserved)
443 String32(*ShndxF, shndx);
445 String32(*ShndxF, 0);
448 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
449 uint16_t(ELF::SHN_XINDEX) : shndx;
452 String32(*SymtabF, name); // st_name
453 String8(*SymtabF, info); // st_info
454 String8(*SymtabF, other); // st_other
455 String16(*SymtabF, Index); // st_shndx
456 String64(*SymtabF, value); // st_value
457 String64(*SymtabF, size); // st_size
459 String32(*SymtabF, name); // st_name
460 String32(*SymtabF, value); // st_value
461 String32(*SymtabF, size); // st_size
462 String8(*SymtabF, info); // st_info
463 String8(*SymtabF, other); // st_other
464 String16(*SymtabF, Index); // st_shndx
468 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
469 const MCAsmLayout &Layout) {
470 if (Data.isCommon() && Data.isExternal())
471 return Data.getCommonAlignment();
473 const MCSymbol &Symbol = Data.getSymbol();
475 if (Symbol.isAbsolute() && Symbol.isVariable()) {
476 if (const MCExpr *Value = Symbol.getVariableValue()) {
478 if (Value->EvaluateAsAbsolute(IntValue, Layout))
479 return (uint64_t)IntValue;
483 if (!Symbol.isInSection())
487 if (Data.getFragment()) {
488 if (Data.getFlags() & ELF_Other_ThumbFunc)
489 return Layout.getSymbolOffset(&Data)+1;
491 return Layout.getSymbolOffset(&Data);
497 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
498 const MCAsmLayout &Layout) {
499 // The presence of symbol versions causes undefined symbols and
500 // versions declared with @@@ to be renamed.
502 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
503 ie = Asm.symbol_end(); it != ie; ++it) {
504 const MCSymbol &Alias = it->getSymbol();
505 const MCSymbol &Symbol = Alias.AliasedSymbol();
506 MCSymbolData &SD = Asm.getSymbolData(Symbol);
509 if (&Symbol == &Alias)
512 StringRef AliasName = Alias.getName();
513 size_t Pos = AliasName.find('@');
514 if (Pos == StringRef::npos)
517 // Aliases defined with .symvar copy the binding from the symbol they alias.
518 // This is the first place we are able to copy this information.
519 it->setExternal(SD.isExternal());
520 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
522 StringRef Rest = AliasName.substr(Pos);
523 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
526 // FIXME: produce a better error message.
527 if (Symbol.isUndefined() && Rest.startswith("@@") &&
528 !Rest.startswith("@@@"))
529 report_fatal_error("A @@ version cannot be undefined");
531 Renames.insert(std::make_pair(&Symbol, &Alias));
535 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
536 uint8_t Type = newType;
538 // Propagation rules:
539 // IFUNC > FUNC > OBJECT > NOTYPE
540 // TLS_OBJECT > OBJECT > NOTYPE
542 // dont let the new type degrade the old type
546 case ELF::STT_GNU_IFUNC:
547 if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
548 Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
549 Type = ELF::STT_GNU_IFUNC;
552 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
553 Type == ELF::STT_TLS)
554 Type = ELF::STT_FUNC;
556 case ELF::STT_OBJECT:
557 if (Type == ELF::STT_NOTYPE)
558 Type = ELF::STT_OBJECT;
561 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
562 Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
570 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
571 MCDataFragment *ShndxF,
573 const MCAsmLayout &Layout) {
574 MCSymbolData &OrigData = *MSD.SymbolData;
576 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
578 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
579 Data.getSymbol().isVariable();
581 // Binding and Type share the same byte as upper and lower nibbles
582 uint8_t Binding = MCELF::GetBinding(OrigData);
583 uint8_t Type = mergeTypeForSet(MCELF::GetType(OrigData), MCELF::GetType(Data));
584 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
586 // Other and Visibility share the same byte with Visibility using the lower
588 uint8_t Visibility = MCELF::GetVisibility(OrigData);
589 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
592 uint64_t Value = SymbolValue(Data, Layout);
595 assert(!(Data.isCommon() && !Data.isExternal()));
597 const MCExpr *ESize = Data.getSize();
600 if (!ESize->EvaluateAsAbsolute(Res, Layout))
601 report_fatal_error("Size expression must be absolute.");
605 // Write out the symbol table entry
606 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
607 Size, Other, MSD.SectionIndex, IsReserved);
610 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
611 MCDataFragment *ShndxF,
612 const MCAssembler &Asm,
613 const MCAsmLayout &Layout,
614 const SectionIndexMapTy &SectionIndexMap) {
615 // The string table must be emitted first because we need the index
616 // into the string table for all the symbol names.
617 assert(StringTable.size() && "Missing string table");
619 // FIXME: Make sure the start of the symbol table is aligned.
621 // The first entry is the undefined symbol entry.
622 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
624 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
625 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i],
626 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
627 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
630 // Write the symbol table entries.
631 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
633 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
634 ELFSymbolData &MSD = LocalSymbolData[i];
635 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
638 // Write out a symbol table entry for each regular section.
639 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
641 const MCSectionELF &Section =
642 static_cast<const MCSectionELF&>(i->getSection());
643 if (Section.getType() == ELF::SHT_RELA ||
644 Section.getType() == ELF::SHT_REL ||
645 Section.getType() == ELF::SHT_STRTAB ||
646 Section.getType() == ELF::SHT_SYMTAB ||
647 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
649 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
650 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
652 LastLocalSymbolIndex++;
655 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
656 ELFSymbolData &MSD = ExternalSymbolData[i];
657 MCSymbolData &Data = *MSD.SymbolData;
658 assert(((Data.getFlags() & ELF_STB_Global) ||
659 (Data.getFlags() & ELF_STB_Weak)) &&
660 "External symbol requires STB_GLOBAL or STB_WEAK flag");
661 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
662 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
663 LastLocalSymbolIndex++;
666 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
667 ELFSymbolData &MSD = UndefinedSymbolData[i];
668 MCSymbolData &Data = *MSD.SymbolData;
669 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
670 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
671 LastLocalSymbolIndex++;
675 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
676 const MCValue &Target,
678 const MCFixup &Fixup,
679 bool IsPCRel) const {
680 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
681 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
682 const MCSymbol *Renamed = Renames.lookup(&Symbol);
683 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
685 if (ASymbol.isUndefined()) {
688 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
691 if (SD.isExternal()) {
697 const MCSectionELF &Section =
698 static_cast<const MCSectionELF&>(ASymbol.getSection());
699 const SectionKind secKind = Section.getKind();
702 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
704 if (secKind.isThreadLocal()) {
710 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
711 const MCSectionELF &Sec2 =
712 static_cast<const MCSectionELF&>(F.getParent()->getSection());
714 if (&Sec2 != &Section &&
715 (Kind == MCSymbolRefExpr::VK_PLT ||
716 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
717 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
723 if (Section.getFlags() & ELF::SHF_MERGE) {
724 if (Target.getConstant() == 0)
725 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
731 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
736 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
737 const MCAsmLayout &Layout,
738 const MCFragment *Fragment,
739 const MCFixup &Fixup,
741 uint64_t &FixedValue) {
744 int64_t Value = Target.getConstant();
745 const MCSymbol *RelocSymbol = NULL;
747 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
748 if (!Target.isAbsolute()) {
749 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
750 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
751 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
753 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
754 const MCSymbol &SymbolB = RefB->getSymbol();
755 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
758 if (!SDB.getFragment())
759 Asm.getContext().FatalError(
761 Twine("symbol '") + SymbolB.getName() +
762 "' can not be undefined in a subtraction expression");
764 // Offset of the symbol in the section
765 int64_t a = Layout.getSymbolOffset(&SDB);
767 // Offset of the relocation in the section
768 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
773 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
774 MCFragment *F = SD.getFragment();
777 Index = F->getParent()->getOrdinal() + 1;
778 // Offset of the symbol in the section
779 Value += Layout.getSymbolOffset(&SD);
784 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
785 WeakrefUsedInReloc.insert(RelocSymbol);
787 UsedInReloc.insert(RelocSymbol);
791 if (hasRelocationAddend())
796 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
797 (RelocSymbol != 0), Addend);
798 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
799 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
800 if (RelocNeedsGOT(Modifier))
803 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
806 if (!hasRelocationAddend())
810 assert(isInt<64>(Addend));
812 assert(isInt<32>(Addend));
814 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
815 Relocations[Fragment->getParent()].push_back(ERE);
820 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
822 MCSymbolData &SD = Asm.getSymbolData(*S);
823 return SD.getIndex();
826 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
827 const MCSymbolData &Data,
828 bool Used, bool Renamed) {
829 if (Data.getFlags() & ELF_Other_Weakref)
838 const MCSymbol &Symbol = Data.getSymbol();
840 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
843 const MCSymbol &A = Symbol.AliasedSymbol();
844 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
847 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
848 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
851 if (Symbol.isTemporary())
857 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
858 bool isUsedInReloc) {
859 if (Data.isExternal())
862 const MCSymbol &Symbol = Data.getSymbol();
863 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
865 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
866 if (isSignature && !isUsedInReloc)
875 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
876 SectionIndexMapTy &SectionIndexMap,
877 const RelMapTy &RelMap) {
879 for (MCAssembler::iterator it = Asm.begin(),
880 ie = Asm.end(); it != ie; ++it) {
881 const MCSectionELF &Section =
882 static_cast<const MCSectionELF &>(it->getSection());
883 if (Section.getType() != ELF::SHT_GROUP)
885 SectionIndexMap[&Section] = Index++;
888 for (MCAssembler::iterator it = Asm.begin(),
889 ie = Asm.end(); it != ie; ++it) {
890 const MCSectionELF &Section =
891 static_cast<const MCSectionELF &>(it->getSection());
892 if (Section.getType() == ELF::SHT_GROUP ||
893 Section.getType() == ELF::SHT_REL ||
894 Section.getType() == ELF::SHT_RELA)
896 SectionIndexMap[&Section] = Index++;
897 const MCSectionELF *RelSection = RelMap.lookup(&Section);
899 SectionIndexMap[RelSection] = Index++;
903 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
904 const SectionIndexMapTy &SectionIndexMap,
905 RevGroupMapTy RevGroupMap,
906 unsigned NumRegularSections) {
907 // FIXME: Is this the correct place to do this?
908 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
910 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
911 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
912 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
913 Data.setExternal(true);
914 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
917 // Index 0 is always the empty string.
918 StringMap<uint64_t> StringIndexMap;
919 StringTable += '\x00';
921 // FIXME: We could optimize suffixes in strtab in the same way we
922 // optimize them in shstrtab.
924 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
925 ie = Asm.file_names_end();
928 StringRef Name = *it;
929 uint64_t &Entry = StringIndexMap[Name];
931 Entry = StringTable.size();
933 StringTable += '\x00';
935 FileSymbolData.push_back(Entry);
938 // Add the data for the symbols.
939 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
940 ie = Asm.symbol_end(); it != ie; ++it) {
941 const MCSymbol &Symbol = it->getSymbol();
943 bool Used = UsedInReloc.count(&Symbol);
944 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
945 bool isSignature = RevGroupMap.count(&Symbol);
947 if (!isInSymtab(Asm, *it,
948 Used || WeakrefUsed || isSignature,
949 Renames.count(&Symbol)))
954 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
956 // Undefined symbols are global, but this is the first place we
957 // are able to set it.
958 bool Local = isLocal(*it, isSignature, Used);
959 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
960 MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
961 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
962 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
965 if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
966 MCELF::SetBinding(*it, ELF::STB_WEAK);
968 if (it->isCommon()) {
970 MSD.SectionIndex = ELF::SHN_COMMON;
971 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
972 MSD.SectionIndex = ELF::SHN_ABS;
973 } else if (RefSymbol.isUndefined()) {
974 if (isSignature && !Used)
975 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
977 MSD.SectionIndex = ELF::SHN_UNDEF;
979 const MCSectionELF &Section =
980 static_cast<const MCSectionELF&>(RefSymbol.getSection());
981 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
982 if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
983 NeedsSymtabShndx = true;
984 assert(MSD.SectionIndex && "Invalid section index!");
987 // The @@@ in symbol version is replaced with @ in undefined symbols and
988 // @@ in defined ones.
989 StringRef Name = Symbol.getName();
992 size_t Pos = Name.find("@@@");
993 if (Pos != StringRef::npos) {
994 Buf += Name.substr(0, Pos);
995 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
996 Buf += Name.substr(Pos + Skip);
1000 uint64_t &Entry = StringIndexMap[Name];
1002 Entry = StringTable.size();
1003 StringTable += Name;
1004 StringTable += '\x00';
1006 MSD.StringIndex = Entry;
1007 if (MSD.SectionIndex == ELF::SHN_UNDEF)
1008 UndefinedSymbolData.push_back(MSD);
1010 LocalSymbolData.push_back(MSD);
1012 ExternalSymbolData.push_back(MSD);
1015 // Symbols are required to be in lexicographic order.
1016 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1017 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1018 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1020 // Set the symbol indices. Local symbols must come before all other
1021 // symbols with non-local bindings.
1022 unsigned Index = FileSymbolData.size() + 1;
1023 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1024 LocalSymbolData[i].SymbolData->setIndex(Index++);
1026 Index += NumRegularSections;
1028 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1029 ExternalSymbolData[i].SymbolData->setIndex(Index++);
1030 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1031 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1033 if (Index >= ELF::SHN_LORESERVE)
1034 NeedsSymtabShndx = true;
1037 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1038 MCAsmLayout &Layout,
1040 for (MCAssembler::const_iterator it = Asm.begin(),
1041 ie = Asm.end(); it != ie; ++it) {
1042 const MCSectionData &SD = *it;
1043 if (Relocations[&SD].empty())
1046 MCContext &Ctx = Asm.getContext();
1047 const MCSectionELF &Section =
1048 static_cast<const MCSectionELF&>(SD.getSection());
1050 const StringRef SectionName = Section.getSectionName();
1051 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1052 RelaSectionName += SectionName;
1055 if (hasRelocationAddend())
1056 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1058 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1061 StringRef Group = "";
1062 if (Section.getFlags() & ELF::SHF_GROUP) {
1063 Flags = ELF::SHF_GROUP;
1064 Group = Section.getGroup()->getName();
1067 const MCSectionELF *RelaSection =
1068 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1069 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1070 SectionKind::getReadOnly(),
1072 RelMap[&Section] = RelaSection;
1073 Asm.getOrCreateSectionData(*RelaSection);
1077 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1078 const RelMapTy &RelMap) {
1079 for (MCAssembler::const_iterator it = Asm.begin(),
1080 ie = Asm.end(); it != ie; ++it) {
1081 const MCSectionData &SD = *it;
1082 const MCSectionELF &Section =
1083 static_cast<const MCSectionELF&>(SD.getSection());
1085 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1088 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1089 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1091 MCDataFragment *F = new MCDataFragment(&RelaSD);
1092 WriteRelocationsFragment(Asm, F, &*it);
1096 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1097 uint64_t Flags, uint64_t Address,
1098 uint64_t Offset, uint64_t Size,
1099 uint32_t Link, uint32_t Info,
1101 uint64_t EntrySize) {
1102 Write32(Name); // sh_name: index into string table
1103 Write32(Type); // sh_type
1104 WriteWord(Flags); // sh_flags
1105 WriteWord(Address); // sh_addr
1106 WriteWord(Offset); // sh_offset
1107 WriteWord(Size); // sh_size
1108 Write32(Link); // sh_link
1109 Write32(Info); // sh_info
1110 WriteWord(Alignment); // sh_addralign
1111 WriteWord(EntrySize); // sh_entsize
1114 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1116 const MCSectionData *SD) {
1117 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1119 // Sort the relocation entries. Most targets just sort by r_offset, but some
1120 // (e.g., MIPS) have additional constraints.
1121 TargetObjectWriter->sortRelocs(Asm, Relocs);
1123 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1124 ELFRelocationEntry entry = Relocs[e - i - 1];
1128 else if (entry.Index < 0)
1129 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1131 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1133 String64(*F, entry.r_offset);
1134 if (TargetObjectWriter->isN64()) {
1135 String32(*F, entry.Index);
1137 String8(*F, TargetObjectWriter->getRSsym(entry.Type));
1138 String8(*F, TargetObjectWriter->getRType3(entry.Type));
1139 String8(*F, TargetObjectWriter->getRType2(entry.Type));
1140 String8(*F, TargetObjectWriter->getRType(entry.Type));
1143 struct ELF::Elf64_Rela ERE64;
1144 ERE64.setSymbolAndType(entry.Index, entry.Type);
1145 String64(*F, ERE64.r_info);
1147 if (hasRelocationAddend())
1148 String64(*F, entry.r_addend);
1150 String32(*F, entry.r_offset);
1152 struct ELF::Elf32_Rela ERE32;
1153 ERE32.setSymbolAndType(entry.Index, entry.Type);
1154 String32(*F, ERE32.r_info);
1156 if (hasRelocationAddend())
1157 String32(*F, entry.r_addend);
1162 static int compareBySuffix(const MCSectionELF *const *a,
1163 const MCSectionELF *const *b) {
1164 const StringRef &NameA = (*a)->getSectionName();
1165 const StringRef &NameB = (*b)->getSectionName();
1166 const unsigned sizeA = NameA.size();
1167 const unsigned sizeB = NameB.size();
1168 const unsigned len = std::min(sizeA, sizeB);
1169 for (unsigned int i = 0; i < len; ++i) {
1170 char ca = NameA[sizeA - i - 1];
1171 char cb = NameB[sizeB - i - 1];
1176 return sizeB - sizeA;
1179 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1180 MCAsmLayout &Layout,
1181 SectionIndexMapTy &SectionIndexMap,
1182 const RelMapTy &RelMap) {
1183 MCContext &Ctx = Asm.getContext();
1186 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1188 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1189 const MCSectionELF *ShstrtabSection =
1190 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1191 SectionKind::getReadOnly());
1192 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1193 ShstrtabSD.setAlignment(1);
1195 const MCSectionELF *SymtabSection =
1196 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1197 SectionKind::getReadOnly(),
1199 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1200 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1202 MCSectionData *SymtabShndxSD = NULL;
1204 if (NeedsSymtabShndx) {
1205 const MCSectionELF *SymtabShndxSection =
1206 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1207 SectionKind::getReadOnly(), 4, "");
1208 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1209 SymtabShndxSD->setAlignment(4);
1212 const MCSectionELF *StrtabSection;
1213 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1214 SectionKind::getReadOnly());
1215 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1216 StrtabSD.setAlignment(1);
1218 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1220 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1221 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1222 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1225 F = new MCDataFragment(&SymtabSD);
1226 MCDataFragment *ShndxF = NULL;
1227 if (NeedsSymtabShndx) {
1228 ShndxF = new MCDataFragment(SymtabShndxSD);
1230 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1232 F = new MCDataFragment(&StrtabSD);
1233 F->getContents().append(StringTable.begin(), StringTable.end());
1235 F = new MCDataFragment(&ShstrtabSD);
1237 std::vector<const MCSectionELF*> Sections;
1238 for (MCAssembler::const_iterator it = Asm.begin(),
1239 ie = Asm.end(); it != ie; ++it) {
1240 const MCSectionELF &Section =
1241 static_cast<const MCSectionELF&>(it->getSection());
1242 Sections.push_back(&Section);
1244 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1246 // Section header string table.
1248 // The first entry of a string table holds a null character so skip
1251 F->getContents().push_back('\x00');
1253 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1254 const MCSectionELF &Section = *Sections[I];
1256 StringRef Name = Section.getSectionName();
1258 StringRef PreviousName = Sections[I - 1]->getSectionName();
1259 if (PreviousName.endswith(Name)) {
1260 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1264 // Remember the index into the string table so we can write it
1265 // into the sh_name field of the section header table.
1266 SectionStringTableIndex[&Section] = Index;
1268 Index += Name.size() + 1;
1269 F->getContents().append(Name.begin(), Name.end());
1270 F->getContents().push_back('\x00');
1274 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1275 MCAsmLayout &Layout,
1276 GroupMapTy &GroupMap,
1277 RevGroupMapTy &RevGroupMap,
1278 SectionIndexMapTy &SectionIndexMap,
1279 const RelMapTy &RelMap) {
1280 // Create the .note.GNU-stack section if needed.
1281 MCContext &Ctx = Asm.getContext();
1282 if (Asm.getNoExecStack()) {
1283 const MCSectionELF *GnuStackSection =
1284 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1285 SectionKind::getReadOnly());
1286 Asm.getOrCreateSectionData(*GnuStackSection);
1290 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1292 const MCSectionELF &Section =
1293 static_cast<const MCSectionELF&>(it->getSection());
1294 if (!(Section.getFlags() & ELF::SHF_GROUP))
1297 const MCSymbol *SignatureSymbol = Section.getGroup();
1298 Asm.getOrCreateSymbolData(*SignatureSymbol);
1299 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1301 Group = Ctx.CreateELFGroupSection();
1302 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1303 Data.setAlignment(4);
1304 MCDataFragment *F = new MCDataFragment(&Data);
1305 String32(*F, ELF::GRP_COMDAT);
1307 GroupMap[Group] = SignatureSymbol;
1310 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1312 // Add sections to the groups
1313 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1315 const MCSectionELF &Section =
1316 static_cast<const MCSectionELF&>(it->getSection());
1317 if (!(Section.getFlags() & ELF::SHF_GROUP))
1319 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1320 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1321 // FIXME: we could use the previous fragment
1322 MCDataFragment *F = new MCDataFragment(&Data);
1323 unsigned Index = SectionIndexMap.lookup(&Section);
1324 String32(*F, Index);
1328 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1329 const SectionIndexMapTy &SectionIndexMap,
1330 uint32_t GroupSymbolIndex,
1331 uint64_t Offset, uint64_t Size,
1333 const MCSectionELF &Section) {
1334 uint64_t sh_link = 0;
1335 uint64_t sh_info = 0;
1337 switch(Section.getType()) {
1338 case ELF::SHT_DYNAMIC:
1339 sh_link = SectionStringTableIndex[&Section];
1344 case ELF::SHT_RELA: {
1345 const MCSectionELF *SymtabSection;
1346 const MCSectionELF *InfoSection;
1347 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1349 SectionKind::getReadOnly());
1350 sh_link = SectionIndexMap.lookup(SymtabSection);
1351 assert(sh_link && ".symtab not found");
1353 // Remove ".rel" and ".rela" prefixes.
1354 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1355 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1356 StringRef GroupName =
1357 Section.getGroup() ? Section.getGroup()->getName() : "";
1359 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1360 0, SectionKind::getReadOnly(),
1362 sh_info = SectionIndexMap.lookup(InfoSection);
1366 case ELF::SHT_SYMTAB:
1367 case ELF::SHT_DYNSYM:
1368 sh_link = StringTableIndex;
1369 sh_info = LastLocalSymbolIndex;
1372 case ELF::SHT_SYMTAB_SHNDX:
1373 sh_link = SymbolTableIndex;
1376 case ELF::SHT_PROGBITS:
1377 case ELF::SHT_STRTAB:
1378 case ELF::SHT_NOBITS:
1381 case ELF::SHT_ARM_ATTRIBUTES:
1382 case ELF::SHT_INIT_ARRAY:
1383 case ELF::SHT_FINI_ARRAY:
1384 case ELF::SHT_PREINIT_ARRAY:
1385 case ELF::SHT_X86_64_UNWIND:
1386 case ELF::SHT_MIPS_REGINFO:
1387 case ELF::SHT_MIPS_OPTIONS:
1391 case ELF::SHT_GROUP:
1392 sh_link = SymbolTableIndex;
1393 sh_info = GroupSymbolIndex;
1397 assert(0 && "FIXME: sh_type value not supported!");
1401 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1402 Section.getType() == ELF::SHT_ARM_EXIDX) {
1403 StringRef SecName(Section.getSectionName());
1404 if (SecName == ".ARM.exidx") {
1405 sh_link = SectionIndexMap.lookup(
1406 Asm.getContext().getELFSection(".text",
1408 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1409 SectionKind::getText()));
1410 } else if (SecName.startswith(".ARM.exidx")) {
1411 StringRef GroupName =
1412 Section.getGroup() ? Section.getGroup()->getName() : "";
1413 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1414 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1415 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1420 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1421 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1422 Alignment, Section.getEntrySize());
1425 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1426 return SD.getOrdinal() == ~UINT32_C(0) &&
1427 !SD.getSection().isVirtualSection();
1430 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1432 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1434 const MCFragment &F = *i;
1435 assert(F.getKind() == MCFragment::FT_Data);
1436 Ret += cast<MCDataFragment>(F).getContents().size();
1441 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1442 const MCSectionData &SD) {
1443 if (IsELFMetaDataSection(SD))
1444 return DataSectionSize(SD);
1445 return Layout.getSectionFileSize(&SD);
1448 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1449 const MCSectionData &SD) {
1450 if (IsELFMetaDataSection(SD))
1451 return DataSectionSize(SD);
1452 return Layout.getSectionAddressSize(&SD);
1455 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1456 const MCAsmLayout &Layout,
1457 const MCSectionELF &Section) {
1458 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1460 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1461 WriteZeros(Padding);
1463 if (IsELFMetaDataSection(SD)) {
1464 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1466 const MCFragment &F = *i;
1467 assert(F.getKind() == MCFragment::FT_Data);
1468 WriteBytes(cast<MCDataFragment>(F).getContents());
1471 Asm.writeSectionData(&SD, Layout);
1475 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1476 const GroupMapTy &GroupMap,
1477 const MCAsmLayout &Layout,
1478 const SectionIndexMapTy &SectionIndexMap,
1479 const SectionOffsetMapTy &SectionOffsetMap) {
1480 const unsigned NumSections = Asm.size() + 1;
1482 std::vector<const MCSectionELF*> Sections;
1483 Sections.resize(NumSections - 1);
1485 for (SectionIndexMapTy::const_iterator i=
1486 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1487 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1488 Sections[p.second - 1] = p.first;
1491 // Null section first.
1492 uint64_t FirstSectionSize =
1493 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1494 uint32_t FirstSectionLink =
1495 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1496 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1498 for (unsigned i = 0; i < NumSections - 1; ++i) {
1499 const MCSectionELF &Section = *Sections[i];
1500 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1501 uint32_t GroupSymbolIndex;
1502 if (Section.getType() != ELF::SHT_GROUP)
1503 GroupSymbolIndex = 0;
1505 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1506 GroupMap.lookup(&Section));
1508 uint64_t Size = GetSectionAddressSize(Layout, SD);
1510 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1511 SectionOffsetMap.lookup(&Section), Size,
1512 SD.getAlignment(), Section);
1516 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1517 std::vector<const MCSectionELF*> &Sections) {
1518 for (MCAssembler::iterator it = Asm.begin(),
1519 ie = Asm.end(); it != ie; ++it) {
1520 const MCSectionELF &Section =
1521 static_cast<const MCSectionELF &>(it->getSection());
1522 if (Section.getType() == ELF::SHT_GROUP)
1523 Sections.push_back(&Section);
1526 for (MCAssembler::iterator it = Asm.begin(),
1527 ie = Asm.end(); it != ie; ++it) {
1528 const MCSectionELF &Section =
1529 static_cast<const MCSectionELF &>(it->getSection());
1530 if (Section.getType() != ELF::SHT_GROUP &&
1531 Section.getType() != ELF::SHT_REL &&
1532 Section.getType() != ELF::SHT_RELA)
1533 Sections.push_back(&Section);
1536 for (MCAssembler::iterator it = Asm.begin(),
1537 ie = Asm.end(); it != ie; ++it) {
1538 const MCSectionELF &Section =
1539 static_cast<const MCSectionELF &>(it->getSection());
1540 if (Section.getType() == ELF::SHT_REL ||
1541 Section.getType() == ELF::SHT_RELA)
1542 Sections.push_back(&Section);
1546 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1547 const MCAsmLayout &Layout) {
1548 GroupMapTy GroupMap;
1549 RevGroupMapTy RevGroupMap;
1550 SectionIndexMapTy SectionIndexMap;
1552 unsigned NumUserSections = Asm.size();
1554 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1555 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1557 const unsigned NumUserAndRelocSections = Asm.size();
1558 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1559 RevGroupMap, SectionIndexMap, RelMap);
1560 const unsigned AllSections = Asm.size();
1561 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1563 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1565 // Compute symbol table information.
1566 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections);
1569 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1571 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1572 const_cast<MCAsmLayout&>(Layout),
1576 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1577 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1578 sizeof(ELF::Elf32_Ehdr);
1579 uint64_t FileOff = HeaderSize;
1581 std::vector<const MCSectionELF*> Sections;
1582 ComputeSectionOrder(Asm, Sections);
1583 unsigned NumSections = Sections.size();
1584 SectionOffsetMapTy SectionOffsetMap;
1585 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1586 const MCSectionELF &Section = *Sections[i];
1587 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1589 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1591 // Remember the offset into the file for this section.
1592 SectionOffsetMap[&Section] = FileOff;
1594 // Get the size of the section in the output file (including padding).
1595 FileOff += GetSectionFileSize(Layout, SD);
1598 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1600 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1602 uint64_t SectionHeaderEntrySize = is64Bit() ?
1603 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1604 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1606 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
1607 const MCSectionELF &Section = *Sections[i];
1608 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1610 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1612 // Remember the offset into the file for this section.
1613 SectionOffsetMap[&Section] = FileOff;
1615 // Get the size of the section in the output file (including padding).
1616 FileOff += GetSectionFileSize(Layout, SD);
1619 // Write out the ELF header ...
1620 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1622 // ... then the regular sections ...
1623 // + because of .shstrtab
1624 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1625 WriteDataSectionData(Asm, Layout, *Sections[i]);
1627 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1628 WriteZeros(Padding);
1630 // ... then the section header table ...
1631 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1634 // ... and then the remaining sections ...
1635 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1636 WriteDataSectionData(Asm, Layout, *Sections[i]);
1640 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1641 const MCSymbolData &DataA,
1642 const MCFragment &FB,
1644 bool IsPCRel) const {
1645 if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
1647 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1648 Asm, DataA, FB,InSet, IsPCRel);
1651 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1653 bool IsLittleEndian) {
1654 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);