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/ELF.h"
32 #include "llvm/Support/ErrorHandling.h"
37 #define DEBUG_TYPE "reloc-info"
40 class ELFObjectWriter : public MCObjectWriter {
43 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
44 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
45 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
46 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
47 bool Used, bool Renamed);
48 static bool isLocal(const MCSymbolData &Data, bool isSignature,
50 static bool IsELFMetaDataSection(const MCSectionData &SD);
51 static uint64_t DataSectionSize(const MCSectionData &SD);
52 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
53 const MCSectionData &SD);
54 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
55 const MCSectionData &SD);
57 void WriteDataSectionData(MCAssembler &Asm,
58 const MCAsmLayout &Layout,
59 const MCSectionELF &Section);
61 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
62 return Kind == X86::reloc_riprel_4byte ||
63 Kind == X86::reloc_riprel_4byte_movq_load;
66 /// ELFSymbolData - Helper struct for containing some precomputed
67 /// information on symbols.
68 struct ELFSymbolData {
69 MCSymbolData *SymbolData;
71 uint32_t SectionIndex;
73 // Support lexicographic sorting.
74 bool operator<(const ELFSymbolData &RHS) const {
75 return SymbolData->getSymbol().getName() <
76 RHS.SymbolData->getSymbol().getName();
80 /// The target specific ELF writer instance.
81 std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
83 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
84 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
85 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
87 llvm::DenseMap<const MCSectionData*,
88 std::vector<ELFRelocationEntry> > Relocations;
89 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
92 /// @name Symbol Table Data
95 SmallString<256> StringTable;
96 std::vector<uint64_t> FileSymbolData;
97 std::vector<ELFSymbolData> LocalSymbolData;
98 std::vector<ELFSymbolData> ExternalSymbolData;
99 std::vector<ELFSymbolData> UndefinedSymbolData;
105 bool NeedsSymtabShndx;
107 // This holds the symbol table index of the last local symbol.
108 unsigned LastLocalSymbolIndex;
109 // This holds the .strtab section index.
110 unsigned StringTableIndex;
111 // This holds the .symtab section index.
112 unsigned SymbolTableIndex;
114 unsigned ShstrtabIndex;
117 const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
118 const MCValue &Target,
120 const MCFixup &Fixup,
123 // TargetObjectWriter wrappers.
124 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
125 const MCValue &Target,
127 const MCFixup &Fixup,
128 bool IsPCRel) const {
129 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
131 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
132 const MCFixup &Fixup,
133 bool IsPCRel) const {
134 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
138 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
139 bool hasRelocationAddend() const {
140 return TargetObjectWriter->hasRelocationAddend();
142 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
143 bool IsPCRel, bool IsRelocWithSymbol,
144 int64_t Addend) const {
145 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
146 IsRelocWithSymbol, Addend);
150 ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
151 raw_ostream &_OS, bool IsLittleEndian)
152 : MCObjectWriter(_OS, IsLittleEndian),
153 TargetObjectWriter(MOTW),
154 NeedsGOT(false), NeedsSymtabShndx(false) {
157 virtual ~ELFObjectWriter();
159 void WriteWord(uint64_t W) {
166 void StringLE16(char *buf, uint16_t Value) {
167 buf[0] = char(Value >> 0);
168 buf[1] = char(Value >> 8);
171 void StringLE32(char *buf, uint32_t Value) {
172 StringLE16(buf, uint16_t(Value >> 0));
173 StringLE16(buf + 2, uint16_t(Value >> 16));
176 void StringLE64(char *buf, uint64_t Value) {
177 StringLE32(buf, uint32_t(Value >> 0));
178 StringLE32(buf + 4, uint32_t(Value >> 32));
181 void StringBE16(char *buf ,uint16_t Value) {
182 buf[0] = char(Value >> 8);
183 buf[1] = char(Value >> 0);
186 void StringBE32(char *buf, uint32_t Value) {
187 StringBE16(buf, uint16_t(Value >> 16));
188 StringBE16(buf + 2, uint16_t(Value >> 0));
191 void StringBE64(char *buf, uint64_t Value) {
192 StringBE32(buf, uint32_t(Value >> 32));
193 StringBE32(buf + 4, uint32_t(Value >> 0));
196 void String8(MCDataFragment &F, uint8_t Value) {
199 F.getContents().append(&buf[0], &buf[1]);
202 void String16(MCDataFragment &F, uint16_t Value) {
204 if (isLittleEndian())
205 StringLE16(buf, Value);
207 StringBE16(buf, Value);
208 F.getContents().append(&buf[0], &buf[2]);
211 void String32(MCDataFragment &F, uint32_t Value) {
213 if (isLittleEndian())
214 StringLE32(buf, Value);
216 StringBE32(buf, Value);
217 F.getContents().append(&buf[0], &buf[4]);
220 void String64(MCDataFragment &F, uint64_t Value) {
222 if (isLittleEndian())
223 StringLE64(buf, Value);
225 StringBE64(buf, Value);
226 F.getContents().append(&buf[0], &buf[8]);
229 void WriteHeader(const MCAssembler &Asm,
230 uint64_t SectionDataSize,
231 unsigned NumberOfSections);
233 void WriteSymbolEntry(MCDataFragment *SymtabF,
234 MCDataFragment *ShndxF,
235 uint64_t name, uint8_t info,
236 uint64_t value, uint64_t size,
237 uint8_t other, uint32_t shndx,
240 void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
242 const MCAsmLayout &Layout);
244 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
245 void WriteSymbolTable(MCDataFragment *SymtabF,
246 MCDataFragment *ShndxF,
247 const MCAssembler &Asm,
248 const MCAsmLayout &Layout,
249 const SectionIndexMapTy &SectionIndexMap);
251 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
252 const MCFragment *Fragment, const MCFixup &Fixup,
253 MCValue Target, uint64_t &FixedValue) override;
255 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
258 // Map from a group section to the signature symbol
259 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
260 // Map from a signature symbol to the group section
261 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
262 // Map from a section to the section with the relocations
263 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
264 // Map from a section to its offset
265 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
267 /// ComputeSymbolTable - Compute the symbol table data
269 /// \param Asm - The assembler.
270 /// \param SectionIndexMap - Maps a section to its index.
271 /// \param RevGroupMap - Maps a signature symbol to the group section.
272 /// \param NumRegularSections - Number of non-relocation sections.
273 void ComputeSymbolTable(MCAssembler &Asm,
274 const SectionIndexMapTy &SectionIndexMap,
275 RevGroupMapTy RevGroupMap,
276 unsigned NumRegularSections);
278 void ComputeIndexMap(MCAssembler &Asm,
279 SectionIndexMapTy &SectionIndexMap,
280 const RelMapTy &RelMap);
282 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
285 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
286 const RelMapTy &RelMap);
288 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
289 SectionIndexMapTy &SectionIndexMap,
290 const RelMapTy &RelMap);
292 // Create the sections that show up in the symbol table. Currently
293 // those are the .note.GNU-stack section and the group sections.
294 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
295 GroupMapTy &GroupMap,
296 RevGroupMapTy &RevGroupMap,
297 SectionIndexMapTy &SectionIndexMap,
298 const RelMapTy &RelMap);
300 void ExecutePostLayoutBinding(MCAssembler &Asm,
301 const MCAsmLayout &Layout) override;
303 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
304 const MCAsmLayout &Layout,
305 const SectionIndexMapTy &SectionIndexMap,
306 const SectionOffsetMapTy &SectionOffsetMap);
308 void ComputeSectionOrder(MCAssembler &Asm,
309 std::vector<const MCSectionELF*> &Sections);
311 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
312 uint64_t Address, uint64_t Offset,
313 uint64_t Size, uint32_t Link, uint32_t Info,
314 uint64_t Alignment, uint64_t EntrySize);
316 void WriteRelocationsFragment(const MCAssembler &Asm,
318 const MCSectionData *SD);
321 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
322 const MCSymbolData &DataA,
323 const MCFragment &FB,
325 bool IsPCRel) const override;
327 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
328 void WriteSection(MCAssembler &Asm,
329 const SectionIndexMapTy &SectionIndexMap,
330 uint32_t GroupSymbolIndex,
331 uint64_t Offset, uint64_t Size, uint64_t Alignment,
332 const MCSectionELF &Section);
336 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
337 const MCFixupKindInfo &FKI =
338 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
340 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
343 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
347 case MCSymbolRefExpr::VK_GOT:
348 case MCSymbolRefExpr::VK_PLT:
349 case MCSymbolRefExpr::VK_GOTPCREL:
350 case MCSymbolRefExpr::VK_GOTOFF:
351 case MCSymbolRefExpr::VK_TPOFF:
352 case MCSymbolRefExpr::VK_TLSGD:
353 case MCSymbolRefExpr::VK_GOTTPOFF:
354 case MCSymbolRefExpr::VK_INDNTPOFF:
355 case MCSymbolRefExpr::VK_NTPOFF:
356 case MCSymbolRefExpr::VK_GOTNTPOFF:
357 case MCSymbolRefExpr::VK_TLSLDM:
358 case MCSymbolRefExpr::VK_DTPOFF:
359 case MCSymbolRefExpr::VK_TLSLD:
364 ELFObjectWriter::~ELFObjectWriter()
367 // Emit the ELF header.
368 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
369 uint64_t SectionDataSize,
370 unsigned NumberOfSections) {
376 // emitWord method behaves differently for ELF32 and ELF64, writing
377 // 4 bytes in the former and 8 in the latter.
379 Write8(0x7f); // e_ident[EI_MAG0]
380 Write8('E'); // e_ident[EI_MAG1]
381 Write8('L'); // e_ident[EI_MAG2]
382 Write8('F'); // e_ident[EI_MAG3]
384 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
387 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
389 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
391 Write8(TargetObjectWriter->getOSABI());
392 Write8(0); // e_ident[EI_ABIVERSION]
394 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
396 Write16(ELF::ET_REL); // e_type
398 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
400 Write32(ELF::EV_CURRENT); // e_version
401 WriteWord(0); // e_entry, no entry point in .o file
402 WriteWord(0); // e_phoff, no program header for .o
403 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
404 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
406 // e_flags = whatever the target wants
407 Write32(Asm.getELFHeaderEFlags());
409 // e_ehsize = ELF header size
410 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
412 Write16(0); // e_phentsize = prog header entry size
413 Write16(0); // e_phnum = # prog header entries = 0
415 // e_shentsize = Section header entry size
416 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
418 // e_shnum = # of section header ents
419 if (NumberOfSections >= ELF::SHN_LORESERVE)
420 Write16(ELF::SHN_UNDEF);
422 Write16(NumberOfSections);
424 // e_shstrndx = Section # of '.shstrtab'
425 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
426 Write16(ELF::SHN_XINDEX);
428 Write16(ShstrtabIndex);
431 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
432 MCDataFragment *ShndxF,
434 uint8_t info, uint64_t value,
435 uint64_t size, uint8_t other,
439 if (shndx >= ELF::SHN_LORESERVE && !Reserved)
440 String32(*ShndxF, shndx);
442 String32(*ShndxF, 0);
445 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
446 uint16_t(ELF::SHN_XINDEX) : shndx;
449 String32(*SymtabF, name); // st_name
450 String8(*SymtabF, info); // st_info
451 String8(*SymtabF, other); // st_other
452 String16(*SymtabF, Index); // st_shndx
453 String64(*SymtabF, value); // st_value
454 String64(*SymtabF, size); // st_size
456 String32(*SymtabF, name); // st_name
457 String32(*SymtabF, value); // st_value
458 String32(*SymtabF, size); // st_size
459 String8(*SymtabF, info); // st_info
460 String8(*SymtabF, other); // st_other
461 String16(*SymtabF, Index); // st_shndx
465 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &OrigData,
466 const MCAsmLayout &Layout) {
467 MCSymbolData *Data = &OrigData;
468 if (Data->isCommon() && Data->isExternal())
469 return Data->getCommonAlignment();
471 const MCSymbol *Symbol = &Data->getSymbol();
472 bool IsThumbFunc = OrigData.getFlags() & ELF_Other_ThumbFunc;
475 if (Symbol->isVariable()) {
476 const MCExpr *Expr = Symbol->getVariableValue();
478 if (!Expr->EvaluateAsRelocatable(Value, &Layout))
479 llvm_unreachable("Invalid expression");
481 assert(!Value.getSymB());
483 Res = Value.getConstant();
485 if (const MCSymbolRefExpr *A = Value.getSymA()) {
486 Symbol = &A->getSymbol();
487 Data = &Layout.getAssembler().getSymbolData(*Symbol);
497 if (!Symbol || !Symbol->isInSection())
500 Res += Layout.getSymbolOffset(Data);
505 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
506 const MCAsmLayout &Layout) {
507 // The presence of symbol versions causes undefined symbols and
508 // versions declared with @@@ to be renamed.
510 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
511 ie = Asm.symbol_end(); it != ie; ++it) {
512 const MCSymbol &Alias = it->getSymbol();
513 const MCSymbol &Symbol = Alias.AliasedSymbol();
514 MCSymbolData &SD = Asm.getSymbolData(Symbol);
517 if (&Symbol == &Alias)
520 StringRef AliasName = Alias.getName();
521 size_t Pos = AliasName.find('@');
522 if (Pos == StringRef::npos)
525 // Aliases defined with .symvar copy the binding from the symbol they alias.
526 // This is the first place we are able to copy this information.
527 it->setExternal(SD.isExternal());
528 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
530 StringRef Rest = AliasName.substr(Pos);
531 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
534 // FIXME: produce a better error message.
535 if (Symbol.isUndefined() && Rest.startswith("@@") &&
536 !Rest.startswith("@@@"))
537 report_fatal_error("A @@ version cannot be undefined");
539 Renames.insert(std::make_pair(&Symbol, &Alias));
543 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
544 uint8_t Type = newType;
546 // Propagation rules:
547 // IFUNC > FUNC > OBJECT > NOTYPE
548 // TLS_OBJECT > OBJECT > NOTYPE
550 // dont let the new type degrade the old type
554 case ELF::STT_GNU_IFUNC:
555 if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
556 Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
557 Type = ELF::STT_GNU_IFUNC;
560 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
561 Type == ELF::STT_TLS)
562 Type = ELF::STT_FUNC;
564 case ELF::STT_OBJECT:
565 if (Type == ELF::STT_NOTYPE)
566 Type = ELF::STT_OBJECT;
569 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
570 Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
578 static const MCSymbol *getBaseSymbol(const MCAsmLayout &Layout,
579 const MCSymbol &Symbol) {
580 if (!Symbol.isVariable())
583 const MCExpr *Expr = Symbol.getVariableValue();
585 if (!Expr->EvaluateAsRelocatable(Value, &Layout))
586 llvm_unreachable("Invalid Expression");
587 assert(!Value.getSymB());
588 const MCSymbolRefExpr *A = Value.getSymA();
591 return getBaseSymbol(Layout, A->getSymbol());
594 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
595 MCDataFragment *ShndxF,
597 const MCAsmLayout &Layout) {
598 MCSymbolData &OrigData = *MSD.SymbolData;
600 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
602 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
603 Data.getSymbol().isVariable();
605 // Binding and Type share the same byte as upper and lower nibbles
606 uint8_t Binding = MCELF::GetBinding(OrigData);
607 uint8_t Type = MCELF::GetType(OrigData);
608 const MCSymbol *Base = getBaseSymbol(Layout, OrigData.getSymbol());
610 MCSymbolData BaseSD = Layout.getAssembler().getSymbolData(*Base);
611 Type = mergeTypeForSet(Type, MCELF::GetType(BaseSD));
613 if (OrigData.getFlags() & ELF_Other_ThumbFunc)
614 Type = ELF::STT_FUNC;
615 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
617 // Other and Visibility share the same byte with Visibility using the lower
619 uint8_t Visibility = MCELF::GetVisibility(OrigData);
620 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
623 uint64_t Value = SymbolValue(OrigData, Layout);
624 if (OrigData.getFlags() & ELF_Other_ThumbFunc)
628 assert(!(Data.isCommon() && !Data.isExternal()));
630 const MCExpr *ESize = Data.getSize();
633 if (!ESize->EvaluateAsAbsolute(Res, Layout))
634 report_fatal_error("Size expression must be absolute.");
638 // Write out the symbol table entry
639 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
640 Size, Other, MSD.SectionIndex, IsReserved);
643 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
644 MCDataFragment *ShndxF,
645 const MCAssembler &Asm,
646 const MCAsmLayout &Layout,
647 const SectionIndexMapTy &SectionIndexMap) {
648 // The string table must be emitted first because we need the index
649 // into the string table for all the symbol names.
650 assert(StringTable.size() && "Missing string table");
652 // FIXME: Make sure the start of the symbol table is aligned.
654 // The first entry is the undefined symbol entry.
655 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
657 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
658 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i],
659 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
660 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
663 // Write the symbol table entries.
664 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
666 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
667 ELFSymbolData &MSD = LocalSymbolData[i];
668 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
671 // Write out a symbol table entry for each regular section.
672 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
674 const MCSectionELF &Section =
675 static_cast<const MCSectionELF&>(i->getSection());
676 if (Section.getType() == ELF::SHT_RELA ||
677 Section.getType() == ELF::SHT_REL ||
678 Section.getType() == ELF::SHT_STRTAB ||
679 Section.getType() == ELF::SHT_SYMTAB ||
680 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
682 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
683 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
685 LastLocalSymbolIndex++;
688 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
689 ELFSymbolData &MSD = ExternalSymbolData[i];
690 MCSymbolData &Data = *MSD.SymbolData;
691 assert(((Data.getFlags() & ELF_STB_Global) ||
692 (Data.getFlags() & ELF_STB_Weak)) &&
693 "External symbol requires STB_GLOBAL or STB_WEAK flag");
694 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
695 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
696 LastLocalSymbolIndex++;
699 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
700 ELFSymbolData &MSD = UndefinedSymbolData[i];
701 MCSymbolData &Data = *MSD.SymbolData;
702 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
703 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
704 LastLocalSymbolIndex++;
708 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
709 const MCValue &Target,
711 const MCFixup &Fixup,
712 bool IsPCRel) const {
713 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
714 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
715 const MCSymbol *Renamed = Renames.lookup(&Symbol);
716 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
718 if (ASymbol.isUndefined()) {
721 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
724 if (SD.isExternal()) {
730 const MCSectionELF &Section =
731 static_cast<const MCSectionELF&>(ASymbol.getSection());
732 const SectionKind secKind = Section.getKind();
735 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
737 if (secKind.isThreadLocal()) {
743 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
744 const MCSectionELF &Sec2 =
745 static_cast<const MCSectionELF&>(F.getParent()->getSection());
747 if (&Sec2 != &Section &&
748 (Kind == MCSymbolRefExpr::VK_PLT ||
749 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
750 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
756 if (Section.getFlags() & ELF::SHF_MERGE) {
757 if (Target.getConstant() == 0)
758 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
764 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
769 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
770 const MCAsmLayout &Layout,
771 const MCFragment *Fragment,
772 const MCFixup &Fixup,
774 uint64_t &FixedValue) {
777 int64_t Value = Target.getConstant();
778 const MCSymbol *RelocSymbol = NULL;
780 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
781 if (!Target.isAbsolute()) {
782 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
783 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
784 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
786 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
787 const MCSymbol &SymbolB = RefB->getSymbol();
788 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
791 if (!SDB.getFragment())
792 Asm.getContext().FatalError(
794 Twine("symbol '") + SymbolB.getName() +
795 "' can not be undefined in a subtraction expression");
797 // Offset of the symbol in the section
798 int64_t a = Layout.getSymbolOffset(&SDB);
800 // Offset of the relocation in the section
801 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
806 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
807 MCFragment *F = SD.getFragment();
810 Index = F->getParent()->getOrdinal() + 1;
811 // Offset of the symbol in the section
812 Value += Layout.getSymbolOffset(&SD);
817 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_WEAKREF)
818 WeakrefUsedInReloc.insert(RelocSymbol);
820 UsedInReloc.insert(RelocSymbol);
824 if (hasRelocationAddend())
829 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
830 (RelocSymbol != 0), Addend);
831 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
832 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
833 if (RelocNeedsGOT(Modifier))
836 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
839 if (!hasRelocationAddend())
843 assert(isInt<64>(Addend));
845 assert(isInt<32>(Addend));
847 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
848 Relocations[Fragment->getParent()].push_back(ERE);
853 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
855 MCSymbolData &SD = Asm.getSymbolData(*S);
856 return SD.getIndex();
859 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
860 const MCSymbolData &Data,
861 bool Used, bool Renamed) {
862 const MCSymbol &Symbol = Data.getSymbol();
863 if (Symbol.isVariable()) {
864 const MCExpr *Expr = Symbol.getVariableValue();
865 if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
866 if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
877 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
880 const MCSymbol &A = Symbol.AliasedSymbol();
881 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
884 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
885 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
888 if (Symbol.isTemporary())
894 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
895 bool isUsedInReloc) {
896 if (Data.isExternal())
899 const MCSymbol &Symbol = Data.getSymbol();
900 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
902 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
903 if (isSignature && !isUsedInReloc)
912 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
913 SectionIndexMapTy &SectionIndexMap,
914 const RelMapTy &RelMap) {
916 for (MCAssembler::iterator it = Asm.begin(),
917 ie = Asm.end(); it != ie; ++it) {
918 const MCSectionELF &Section =
919 static_cast<const MCSectionELF &>(it->getSection());
920 if (Section.getType() != ELF::SHT_GROUP)
922 SectionIndexMap[&Section] = Index++;
925 for (MCAssembler::iterator it = Asm.begin(),
926 ie = Asm.end(); it != ie; ++it) {
927 const MCSectionELF &Section =
928 static_cast<const MCSectionELF &>(it->getSection());
929 if (Section.getType() == ELF::SHT_GROUP ||
930 Section.getType() == ELF::SHT_REL ||
931 Section.getType() == ELF::SHT_RELA)
933 SectionIndexMap[&Section] = Index++;
934 const MCSectionELF *RelSection = RelMap.lookup(&Section);
936 SectionIndexMap[RelSection] = Index++;
940 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
941 const SectionIndexMapTy &SectionIndexMap,
942 RevGroupMapTy RevGroupMap,
943 unsigned NumRegularSections) {
944 // FIXME: Is this the correct place to do this?
945 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
947 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
948 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
949 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
950 Data.setExternal(true);
951 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
954 // Index 0 is always the empty string.
955 StringMap<uint64_t> StringIndexMap;
956 StringTable += '\x00';
958 // FIXME: We could optimize suffixes in strtab in the same way we
959 // optimize them in shstrtab.
961 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
962 ie = Asm.file_names_end();
965 StringRef Name = *it;
966 uint64_t &Entry = StringIndexMap[Name];
968 Entry = StringTable.size();
970 StringTable += '\x00';
972 FileSymbolData.push_back(Entry);
975 // Add the data for the symbols.
976 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
977 ie = Asm.symbol_end(); it != ie; ++it) {
978 const MCSymbol &Symbol = it->getSymbol();
980 bool Used = UsedInReloc.count(&Symbol);
981 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
982 bool isSignature = RevGroupMap.count(&Symbol);
984 if (!isInSymtab(Asm, *it,
985 Used || WeakrefUsed || isSignature,
986 Renames.count(&Symbol)))
991 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
993 // Undefined symbols are global, but this is the first place we
994 // are able to set it.
995 bool Local = isLocal(*it, isSignature, Used);
996 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
997 MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
998 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
999 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
1002 if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
1003 MCELF::SetBinding(*it, ELF::STB_WEAK);
1005 if (it->isCommon()) {
1007 MSD.SectionIndex = ELF::SHN_COMMON;
1008 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
1009 MSD.SectionIndex = ELF::SHN_ABS;
1010 } else if (RefSymbol.isUndefined()) {
1011 if (isSignature && !Used)
1012 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
1014 MSD.SectionIndex = ELF::SHN_UNDEF;
1016 const MCSectionELF &Section =
1017 static_cast<const MCSectionELF&>(RefSymbol.getSection());
1018 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
1019 if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
1020 NeedsSymtabShndx = true;
1021 assert(MSD.SectionIndex && "Invalid section index!");
1024 // The @@@ in symbol version is replaced with @ in undefined symbols and
1025 // @@ in defined ones.
1026 StringRef Name = Symbol.getName();
1027 SmallString<32> Buf;
1029 size_t Pos = Name.find("@@@");
1030 if (Pos != StringRef::npos) {
1031 Buf += Name.substr(0, Pos);
1032 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
1033 Buf += Name.substr(Pos + Skip);
1037 uint64_t &Entry = StringIndexMap[Name];
1039 Entry = StringTable.size();
1040 StringTable += Name;
1041 StringTable += '\x00';
1043 MSD.StringIndex = Entry;
1044 if (MSD.SectionIndex == ELF::SHN_UNDEF)
1045 UndefinedSymbolData.push_back(MSD);
1047 LocalSymbolData.push_back(MSD);
1049 ExternalSymbolData.push_back(MSD);
1052 // Symbols are required to be in lexicographic order.
1053 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1054 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1055 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1057 // Set the symbol indices. Local symbols must come before all other
1058 // symbols with non-local bindings.
1059 unsigned Index = FileSymbolData.size() + 1;
1060 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1061 LocalSymbolData[i].SymbolData->setIndex(Index++);
1063 Index += NumRegularSections;
1065 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1066 ExternalSymbolData[i].SymbolData->setIndex(Index++);
1067 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1068 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1070 if (Index >= ELF::SHN_LORESERVE)
1071 NeedsSymtabShndx = true;
1074 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1075 MCAsmLayout &Layout,
1077 for (MCAssembler::const_iterator it = Asm.begin(),
1078 ie = Asm.end(); it != ie; ++it) {
1079 const MCSectionData &SD = *it;
1080 if (Relocations[&SD].empty())
1083 MCContext &Ctx = Asm.getContext();
1084 const MCSectionELF &Section =
1085 static_cast<const MCSectionELF&>(SD.getSection());
1087 const StringRef SectionName = Section.getSectionName();
1088 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1089 RelaSectionName += SectionName;
1092 if (hasRelocationAddend())
1093 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1095 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1098 StringRef Group = "";
1099 if (Section.getFlags() & ELF::SHF_GROUP) {
1100 Flags = ELF::SHF_GROUP;
1101 Group = Section.getGroup()->getName();
1104 const MCSectionELF *RelaSection =
1105 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1106 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1107 SectionKind::getReadOnly(),
1109 RelMap[&Section] = RelaSection;
1110 Asm.getOrCreateSectionData(*RelaSection);
1114 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1115 const RelMapTy &RelMap) {
1116 for (MCAssembler::const_iterator it = Asm.begin(),
1117 ie = Asm.end(); it != ie; ++it) {
1118 const MCSectionData &SD = *it;
1119 const MCSectionELF &Section =
1120 static_cast<const MCSectionELF&>(SD.getSection());
1122 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1125 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1126 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1128 MCDataFragment *F = new MCDataFragment(&RelaSD);
1129 WriteRelocationsFragment(Asm, F, &*it);
1133 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1134 uint64_t Flags, uint64_t Address,
1135 uint64_t Offset, uint64_t Size,
1136 uint32_t Link, uint32_t Info,
1138 uint64_t EntrySize) {
1139 Write32(Name); // sh_name: index into string table
1140 Write32(Type); // sh_type
1141 WriteWord(Flags); // sh_flags
1142 WriteWord(Address); // sh_addr
1143 WriteWord(Offset); // sh_offset
1144 WriteWord(Size); // sh_size
1145 Write32(Link); // sh_link
1146 Write32(Info); // sh_info
1147 WriteWord(Alignment); // sh_addralign
1148 WriteWord(EntrySize); // sh_entsize
1151 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1153 const MCSectionData *SD) {
1154 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1156 // Sort the relocation entries. Most targets just sort by r_offset, but some
1157 // (e.g., MIPS) have additional constraints.
1158 TargetObjectWriter->sortRelocs(Asm, Relocs);
1160 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1161 ELFRelocationEntry entry = Relocs[e - i - 1];
1165 else if (entry.Index < 0)
1166 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1168 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1170 String64(*F, entry.r_offset);
1171 if (TargetObjectWriter->isN64()) {
1172 String32(*F, entry.Index);
1174 String8(*F, TargetObjectWriter->getRSsym(entry.Type));
1175 String8(*F, TargetObjectWriter->getRType3(entry.Type));
1176 String8(*F, TargetObjectWriter->getRType2(entry.Type));
1177 String8(*F, TargetObjectWriter->getRType(entry.Type));
1180 struct ELF::Elf64_Rela ERE64;
1181 ERE64.setSymbolAndType(entry.Index, entry.Type);
1182 String64(*F, ERE64.r_info);
1184 if (hasRelocationAddend())
1185 String64(*F, entry.r_addend);
1187 String32(*F, entry.r_offset);
1189 struct ELF::Elf32_Rela ERE32;
1190 ERE32.setSymbolAndType(entry.Index, entry.Type);
1191 String32(*F, ERE32.r_info);
1193 if (hasRelocationAddend())
1194 String32(*F, entry.r_addend);
1199 static int compareBySuffix(const MCSectionELF *const *a,
1200 const MCSectionELF *const *b) {
1201 const StringRef &NameA = (*a)->getSectionName();
1202 const StringRef &NameB = (*b)->getSectionName();
1203 const unsigned sizeA = NameA.size();
1204 const unsigned sizeB = NameB.size();
1205 const unsigned len = std::min(sizeA, sizeB);
1206 for (unsigned int i = 0; i < len; ++i) {
1207 char ca = NameA[sizeA - i - 1];
1208 char cb = NameB[sizeB - i - 1];
1213 return sizeB - sizeA;
1216 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1217 MCAsmLayout &Layout,
1218 SectionIndexMapTy &SectionIndexMap,
1219 const RelMapTy &RelMap) {
1220 MCContext &Ctx = Asm.getContext();
1223 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1225 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1226 const MCSectionELF *ShstrtabSection =
1227 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1228 SectionKind::getReadOnly());
1229 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1230 ShstrtabSD.setAlignment(1);
1232 const MCSectionELF *SymtabSection =
1233 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1234 SectionKind::getReadOnly(),
1236 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1237 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1239 MCSectionData *SymtabShndxSD = NULL;
1241 if (NeedsSymtabShndx) {
1242 const MCSectionELF *SymtabShndxSection =
1243 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1244 SectionKind::getReadOnly(), 4, "");
1245 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1246 SymtabShndxSD->setAlignment(4);
1249 const MCSectionELF *StrtabSection;
1250 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1251 SectionKind::getReadOnly());
1252 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1253 StrtabSD.setAlignment(1);
1255 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1257 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1258 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1259 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1262 F = new MCDataFragment(&SymtabSD);
1263 MCDataFragment *ShndxF = NULL;
1264 if (NeedsSymtabShndx) {
1265 ShndxF = new MCDataFragment(SymtabShndxSD);
1267 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1269 F = new MCDataFragment(&StrtabSD);
1270 F->getContents().append(StringTable.begin(), StringTable.end());
1272 F = new MCDataFragment(&ShstrtabSD);
1274 std::vector<const MCSectionELF*> Sections;
1275 for (MCAssembler::const_iterator it = Asm.begin(),
1276 ie = Asm.end(); it != ie; ++it) {
1277 const MCSectionELF &Section =
1278 static_cast<const MCSectionELF&>(it->getSection());
1279 Sections.push_back(&Section);
1281 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1283 // Section header string table.
1285 // The first entry of a string table holds a null character so skip
1288 F->getContents().push_back('\x00');
1290 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1291 const MCSectionELF &Section = *Sections[I];
1293 StringRef Name = Section.getSectionName();
1295 StringRef PreviousName = Sections[I - 1]->getSectionName();
1296 if (PreviousName.endswith(Name)) {
1297 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1301 // Remember the index into the string table so we can write it
1302 // into the sh_name field of the section header table.
1303 SectionStringTableIndex[&Section] = Index;
1305 Index += Name.size() + 1;
1306 F->getContents().append(Name.begin(), Name.end());
1307 F->getContents().push_back('\x00');
1311 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1312 MCAsmLayout &Layout,
1313 GroupMapTy &GroupMap,
1314 RevGroupMapTy &RevGroupMap,
1315 SectionIndexMapTy &SectionIndexMap,
1316 const RelMapTy &RelMap) {
1317 // Create the .note.GNU-stack section if needed.
1318 MCContext &Ctx = Asm.getContext();
1319 if (Asm.getNoExecStack()) {
1320 const MCSectionELF *GnuStackSection =
1321 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1322 SectionKind::getReadOnly());
1323 Asm.getOrCreateSectionData(*GnuStackSection);
1327 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1329 const MCSectionELF &Section =
1330 static_cast<const MCSectionELF&>(it->getSection());
1331 if (!(Section.getFlags() & ELF::SHF_GROUP))
1334 const MCSymbol *SignatureSymbol = Section.getGroup();
1335 Asm.getOrCreateSymbolData(*SignatureSymbol);
1336 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1338 Group = Ctx.CreateELFGroupSection();
1339 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1340 Data.setAlignment(4);
1341 MCDataFragment *F = new MCDataFragment(&Data);
1342 String32(*F, ELF::GRP_COMDAT);
1344 GroupMap[Group] = SignatureSymbol;
1347 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1349 // Add sections to the groups
1350 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1352 const MCSectionELF &Section =
1353 static_cast<const MCSectionELF&>(it->getSection());
1354 if (!(Section.getFlags() & ELF::SHF_GROUP))
1356 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1357 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1358 // FIXME: we could use the previous fragment
1359 MCDataFragment *F = new MCDataFragment(&Data);
1360 unsigned Index = SectionIndexMap.lookup(&Section);
1361 String32(*F, Index);
1365 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1366 const SectionIndexMapTy &SectionIndexMap,
1367 uint32_t GroupSymbolIndex,
1368 uint64_t Offset, uint64_t Size,
1370 const MCSectionELF &Section) {
1371 uint64_t sh_link = 0;
1372 uint64_t sh_info = 0;
1374 switch(Section.getType()) {
1375 case ELF::SHT_DYNAMIC:
1376 sh_link = SectionStringTableIndex[&Section];
1381 case ELF::SHT_RELA: {
1382 const MCSectionELF *SymtabSection;
1383 const MCSectionELF *InfoSection;
1384 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1386 SectionKind::getReadOnly());
1387 sh_link = SectionIndexMap.lookup(SymtabSection);
1388 assert(sh_link && ".symtab not found");
1390 // Remove ".rel" and ".rela" prefixes.
1391 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1392 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1393 StringRef GroupName =
1394 Section.getGroup() ? Section.getGroup()->getName() : "";
1396 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1397 0, SectionKind::getReadOnly(),
1399 sh_info = SectionIndexMap.lookup(InfoSection);
1403 case ELF::SHT_SYMTAB:
1404 case ELF::SHT_DYNSYM:
1405 sh_link = StringTableIndex;
1406 sh_info = LastLocalSymbolIndex;
1409 case ELF::SHT_SYMTAB_SHNDX:
1410 sh_link = SymbolTableIndex;
1413 case ELF::SHT_PROGBITS:
1414 case ELF::SHT_STRTAB:
1415 case ELF::SHT_NOBITS:
1418 case ELF::SHT_ARM_ATTRIBUTES:
1419 case ELF::SHT_INIT_ARRAY:
1420 case ELF::SHT_FINI_ARRAY:
1421 case ELF::SHT_PREINIT_ARRAY:
1422 case ELF::SHT_X86_64_UNWIND:
1423 case ELF::SHT_MIPS_REGINFO:
1424 case ELF::SHT_MIPS_OPTIONS:
1428 case ELF::SHT_GROUP:
1429 sh_link = SymbolTableIndex;
1430 sh_info = GroupSymbolIndex;
1434 assert(0 && "FIXME: sh_type value not supported!");
1438 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1439 Section.getType() == ELF::SHT_ARM_EXIDX) {
1440 StringRef SecName(Section.getSectionName());
1441 if (SecName == ".ARM.exidx") {
1442 sh_link = SectionIndexMap.lookup(
1443 Asm.getContext().getELFSection(".text",
1445 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1446 SectionKind::getText()));
1447 } else if (SecName.startswith(".ARM.exidx")) {
1448 StringRef GroupName =
1449 Section.getGroup() ? Section.getGroup()->getName() : "";
1450 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1451 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1452 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1457 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1458 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1459 Alignment, Section.getEntrySize());
1462 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1463 return SD.getOrdinal() == ~UINT32_C(0) &&
1464 !SD.getSection().isVirtualSection();
1467 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1469 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1471 const MCFragment &F = *i;
1472 assert(F.getKind() == MCFragment::FT_Data);
1473 Ret += cast<MCDataFragment>(F).getContents().size();
1478 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1479 const MCSectionData &SD) {
1480 if (IsELFMetaDataSection(SD))
1481 return DataSectionSize(SD);
1482 return Layout.getSectionFileSize(&SD);
1485 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1486 const MCSectionData &SD) {
1487 if (IsELFMetaDataSection(SD))
1488 return DataSectionSize(SD);
1489 return Layout.getSectionAddressSize(&SD);
1492 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1493 const MCAsmLayout &Layout,
1494 const MCSectionELF &Section) {
1495 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1497 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1498 WriteZeros(Padding);
1500 if (IsELFMetaDataSection(SD)) {
1501 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1503 const MCFragment &F = *i;
1504 assert(F.getKind() == MCFragment::FT_Data);
1505 WriteBytes(cast<MCDataFragment>(F).getContents());
1508 Asm.writeSectionData(&SD, Layout);
1512 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1513 const GroupMapTy &GroupMap,
1514 const MCAsmLayout &Layout,
1515 const SectionIndexMapTy &SectionIndexMap,
1516 const SectionOffsetMapTy &SectionOffsetMap) {
1517 const unsigned NumSections = Asm.size() + 1;
1519 std::vector<const MCSectionELF*> Sections;
1520 Sections.resize(NumSections - 1);
1522 for (SectionIndexMapTy::const_iterator i=
1523 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1524 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1525 Sections[p.second - 1] = p.first;
1528 // Null section first.
1529 uint64_t FirstSectionSize =
1530 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1531 uint32_t FirstSectionLink =
1532 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1533 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1535 for (unsigned i = 0; i < NumSections - 1; ++i) {
1536 const MCSectionELF &Section = *Sections[i];
1537 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1538 uint32_t GroupSymbolIndex;
1539 if (Section.getType() != ELF::SHT_GROUP)
1540 GroupSymbolIndex = 0;
1542 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1543 GroupMap.lookup(&Section));
1545 uint64_t Size = GetSectionAddressSize(Layout, SD);
1547 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1548 SectionOffsetMap.lookup(&Section), Size,
1549 SD.getAlignment(), Section);
1553 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1554 std::vector<const MCSectionELF*> &Sections) {
1555 for (MCAssembler::iterator it = Asm.begin(),
1556 ie = Asm.end(); it != ie; ++it) {
1557 const MCSectionELF &Section =
1558 static_cast<const MCSectionELF &>(it->getSection());
1559 if (Section.getType() == ELF::SHT_GROUP)
1560 Sections.push_back(&Section);
1563 for (MCAssembler::iterator it = Asm.begin(),
1564 ie = Asm.end(); it != ie; ++it) {
1565 const MCSectionELF &Section =
1566 static_cast<const MCSectionELF &>(it->getSection());
1567 if (Section.getType() != ELF::SHT_GROUP &&
1568 Section.getType() != ELF::SHT_REL &&
1569 Section.getType() != ELF::SHT_RELA)
1570 Sections.push_back(&Section);
1573 for (MCAssembler::iterator it = Asm.begin(),
1574 ie = Asm.end(); it != ie; ++it) {
1575 const MCSectionELF &Section =
1576 static_cast<const MCSectionELF &>(it->getSection());
1577 if (Section.getType() == ELF::SHT_REL ||
1578 Section.getType() == ELF::SHT_RELA)
1579 Sections.push_back(&Section);
1583 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1584 const MCAsmLayout &Layout) {
1585 GroupMapTy GroupMap;
1586 RevGroupMapTy RevGroupMap;
1587 SectionIndexMapTy SectionIndexMap;
1589 unsigned NumUserSections = Asm.size();
1591 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1592 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1594 const unsigned NumUserAndRelocSections = Asm.size();
1595 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1596 RevGroupMap, SectionIndexMap, RelMap);
1597 const unsigned AllSections = Asm.size();
1598 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1600 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1602 // Compute symbol table information.
1603 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections);
1606 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1608 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1609 const_cast<MCAsmLayout&>(Layout),
1613 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1614 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1615 sizeof(ELF::Elf32_Ehdr);
1616 uint64_t FileOff = HeaderSize;
1618 std::vector<const MCSectionELF*> Sections;
1619 ComputeSectionOrder(Asm, Sections);
1620 unsigned NumSections = Sections.size();
1621 SectionOffsetMapTy SectionOffsetMap;
1622 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1623 const MCSectionELF &Section = *Sections[i];
1624 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1626 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1628 // Remember the offset into the file for this section.
1629 SectionOffsetMap[&Section] = FileOff;
1631 // Get the size of the section in the output file (including padding).
1632 FileOff += GetSectionFileSize(Layout, SD);
1635 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1637 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1639 uint64_t SectionHeaderEntrySize = is64Bit() ?
1640 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1641 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1643 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
1644 const MCSectionELF &Section = *Sections[i];
1645 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1647 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1649 // Remember the offset into the file for this section.
1650 SectionOffsetMap[&Section] = FileOff;
1652 // Get the size of the section in the output file (including padding).
1653 FileOff += GetSectionFileSize(Layout, SD);
1656 // Write out the ELF header ...
1657 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1659 // ... then the regular sections ...
1660 // + because of .shstrtab
1661 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1662 WriteDataSectionData(Asm, Layout, *Sections[i]);
1664 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1665 WriteZeros(Padding);
1667 // ... then the section header table ...
1668 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1671 // ... and then the remaining sections ...
1672 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1673 WriteDataSectionData(Asm, Layout, *Sections[i]);
1677 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1678 const MCSymbolData &DataA,
1679 const MCFragment &FB,
1681 bool IsPCRel) const {
1682 if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
1684 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1685 Asm, DataA, FB,InSet, IsPCRel);
1688 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1690 bool IsLittleEndian) {
1691 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);