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 MCAsmLayout &Layout,
275 const SectionIndexMapTy &SectionIndexMap,
276 RevGroupMapTy RevGroupMap,
277 unsigned NumRegularSections);
279 void ComputeIndexMap(MCAssembler &Asm,
280 SectionIndexMapTy &SectionIndexMap,
281 const RelMapTy &RelMap);
283 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
286 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
287 const RelMapTy &RelMap);
289 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
290 SectionIndexMapTy &SectionIndexMap,
291 const RelMapTy &RelMap);
293 // Create the sections that show up in the symbol table. Currently
294 // those are the .note.GNU-stack section and the group sections.
295 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
296 GroupMapTy &GroupMap,
297 RevGroupMapTy &RevGroupMap,
298 SectionIndexMapTy &SectionIndexMap,
299 const RelMapTy &RelMap);
301 void ExecutePostLayoutBinding(MCAssembler &Asm,
302 const MCAsmLayout &Layout) override;
304 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
305 const MCAsmLayout &Layout,
306 const SectionIndexMapTy &SectionIndexMap,
307 const SectionOffsetMapTy &SectionOffsetMap);
309 void ComputeSectionOrder(MCAssembler &Asm,
310 std::vector<const MCSectionELF*> &Sections);
312 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
313 uint64_t Address, uint64_t Offset,
314 uint64_t Size, uint32_t Link, uint32_t Info,
315 uint64_t Alignment, uint64_t EntrySize);
317 void WriteRelocationsFragment(const MCAssembler &Asm,
319 const MCSectionData *SD);
322 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
323 const MCSymbolData &DataA,
324 const MCFragment &FB,
326 bool IsPCRel) const override;
328 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
329 void WriteSection(MCAssembler &Asm,
330 const SectionIndexMapTy &SectionIndexMap,
331 uint32_t GroupSymbolIndex,
332 uint64_t Offset, uint64_t Size, uint64_t Alignment,
333 const MCSectionELF &Section);
337 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
338 const MCFixupKindInfo &FKI =
339 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
341 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
344 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
348 case MCSymbolRefExpr::VK_GOT:
349 case MCSymbolRefExpr::VK_PLT:
350 case MCSymbolRefExpr::VK_GOTPCREL:
351 case MCSymbolRefExpr::VK_GOTOFF:
352 case MCSymbolRefExpr::VK_TPOFF:
353 case MCSymbolRefExpr::VK_TLSGD:
354 case MCSymbolRefExpr::VK_GOTTPOFF:
355 case MCSymbolRefExpr::VK_INDNTPOFF:
356 case MCSymbolRefExpr::VK_NTPOFF:
357 case MCSymbolRefExpr::VK_GOTNTPOFF:
358 case MCSymbolRefExpr::VK_TLSLDM:
359 case MCSymbolRefExpr::VK_DTPOFF:
360 case MCSymbolRefExpr::VK_TLSLD:
365 ELFObjectWriter::~ELFObjectWriter()
368 // Emit the ELF header.
369 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
370 uint64_t SectionDataSize,
371 unsigned NumberOfSections) {
377 // emitWord method behaves differently for ELF32 and ELF64, writing
378 // 4 bytes in the former and 8 in the latter.
380 Write8(0x7f); // e_ident[EI_MAG0]
381 Write8('E'); // e_ident[EI_MAG1]
382 Write8('L'); // e_ident[EI_MAG2]
383 Write8('F'); // e_ident[EI_MAG3]
385 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
388 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
390 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
392 Write8(TargetObjectWriter->getOSABI());
393 Write8(0); // e_ident[EI_ABIVERSION]
395 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
397 Write16(ELF::ET_REL); // e_type
399 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
401 Write32(ELF::EV_CURRENT); // e_version
402 WriteWord(0); // e_entry, no entry point in .o file
403 WriteWord(0); // e_phoff, no program header for .o
404 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
405 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
407 // e_flags = whatever the target wants
408 Write32(Asm.getELFHeaderEFlags());
410 // e_ehsize = ELF header size
411 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
413 Write16(0); // e_phentsize = prog header entry size
414 Write16(0); // e_phnum = # prog header entries = 0
416 // e_shentsize = Section header entry size
417 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
419 // e_shnum = # of section header ents
420 if (NumberOfSections >= ELF::SHN_LORESERVE)
421 Write16(ELF::SHN_UNDEF);
423 Write16(NumberOfSections);
425 // e_shstrndx = Section # of '.shstrtab'
426 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
427 Write16(ELF::SHN_XINDEX);
429 Write16(ShstrtabIndex);
432 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
433 MCDataFragment *ShndxF,
435 uint8_t info, uint64_t value,
436 uint64_t size, uint8_t other,
440 if (shndx >= ELF::SHN_LORESERVE && !Reserved)
441 String32(*ShndxF, shndx);
443 String32(*ShndxF, 0);
446 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
447 uint16_t(ELF::SHN_XINDEX) : shndx;
450 String32(*SymtabF, name); // st_name
451 String8(*SymtabF, info); // st_info
452 String8(*SymtabF, other); // st_other
453 String16(*SymtabF, Index); // st_shndx
454 String64(*SymtabF, value); // st_value
455 String64(*SymtabF, size); // st_size
457 String32(*SymtabF, name); // st_name
458 String32(*SymtabF, value); // st_value
459 String32(*SymtabF, size); // st_size
460 String8(*SymtabF, info); // st_info
461 String8(*SymtabF, other); // st_other
462 String16(*SymtabF, Index); // st_shndx
466 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &OrigData,
467 const MCAsmLayout &Layout) {
468 MCSymbolData *Data = &OrigData;
469 if (Data->isCommon() && Data->isExternal())
470 return Data->getCommonAlignment();
472 const MCSymbol *Symbol = &Data->getSymbol();
473 const bool IsThumbFunc = OrigData.getFlags() & ELF_Other_ThumbFunc;
476 if (Symbol->isVariable()) {
477 const MCExpr *Expr = Symbol->getVariableValue();
479 if (!Expr->EvaluateAsRelocatable(Value, &Layout))
484 Res = Value.getConstant();
488 const MCSymbolRefExpr *A = Value.getSymA();
492 Symbol = &A->getSymbol();
493 Data = &Layout.getAssembler().getSymbolData(*Symbol);
496 if (!Symbol->isInSection())
499 if (!Data->getFragment())
502 Res += Layout.getSymbolOffset(Data);
503 if (IsThumbFunc || Data->getFlags() & ELF_Other_ThumbFunc)
509 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
510 const MCAsmLayout &Layout) {
511 // The presence of symbol versions causes undefined symbols and
512 // versions declared with @@@ to be renamed.
514 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
515 ie = Asm.symbol_end(); it != ie; ++it) {
516 const MCSymbol &Alias = it->getSymbol();
517 const MCSymbol &Symbol = Alias.AliasedSymbol();
518 MCSymbolData &SD = Asm.getSymbolData(Symbol);
521 if (&Symbol == &Alias)
524 StringRef AliasName = Alias.getName();
525 size_t Pos = AliasName.find('@');
526 if (Pos == StringRef::npos)
529 // Aliases defined with .symvar copy the binding from the symbol they alias.
530 // This is the first place we are able to copy this information.
531 it->setExternal(SD.isExternal());
532 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
534 StringRef Rest = AliasName.substr(Pos);
535 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
538 // FIXME: produce a better error message.
539 if (Symbol.isUndefined() && Rest.startswith("@@") &&
540 !Rest.startswith("@@@"))
541 report_fatal_error("A @@ version cannot be undefined");
543 Renames.insert(std::make_pair(&Symbol, &Alias));
547 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
548 uint8_t Type = newType;
550 // Propagation rules:
551 // IFUNC > FUNC > OBJECT > NOTYPE
552 // TLS_OBJECT > OBJECT > NOTYPE
554 // dont let the new type degrade the old type
558 case ELF::STT_GNU_IFUNC:
559 if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
560 Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
561 Type = ELF::STT_GNU_IFUNC;
564 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
565 Type == ELF::STT_TLS)
566 Type = ELF::STT_FUNC;
568 case ELF::STT_OBJECT:
569 if (Type == ELF::STT_NOTYPE)
570 Type = ELF::STT_OBJECT;
573 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
574 Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
582 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
583 MCDataFragment *ShndxF,
585 const MCAsmLayout &Layout) {
586 MCSymbolData &OrigData = *MSD.SymbolData;
587 const MCSymbol *Base = OrigData.getSymbol().getBaseSymbol(Layout);
588 const MCSymbolData &Data =
589 Base ? Layout.getAssembler().getSymbolData(*Base) : OrigData;
591 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
592 Data.getSymbol().isVariable();
594 // Binding and Type share the same byte as upper and lower nibbles
595 uint8_t Binding = MCELF::GetBinding(OrigData);
596 uint8_t Type = mergeTypeForSet(MCELF::GetType(OrigData), MCELF::GetType(Data));
597 if (OrigData.getFlags() & ELF_Other_ThumbFunc)
598 Type = ELF::STT_FUNC;
599 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
601 // Other and Visibility share the same byte with Visibility using the lower
603 uint8_t Visibility = MCELF::GetVisibility(OrigData);
604 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
607 uint64_t Value = SymbolValue(OrigData, Layout);
610 assert(!(Data.isCommon() && !Data.isExternal()));
612 const MCExpr *ESize = Data.getSize();
615 if (!ESize->EvaluateAsAbsolute(Res, Layout))
616 report_fatal_error("Size expression must be absolute.");
620 // Write out the symbol table entry
621 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
622 Size, Other, MSD.SectionIndex, IsReserved);
625 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
626 MCDataFragment *ShndxF,
627 const MCAssembler &Asm,
628 const MCAsmLayout &Layout,
629 const SectionIndexMapTy &SectionIndexMap) {
630 // The string table must be emitted first because we need the index
631 // into the string table for all the symbol names.
632 assert(StringTable.size() && "Missing string table");
634 // FIXME: Make sure the start of the symbol table is aligned.
636 // The first entry is the undefined symbol entry.
637 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
639 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
640 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i],
641 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
642 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
645 // Write the symbol table entries.
646 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
648 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
649 ELFSymbolData &MSD = LocalSymbolData[i];
650 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
653 // Write out a symbol table entry for each regular section.
654 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
656 const MCSectionELF &Section =
657 static_cast<const MCSectionELF&>(i->getSection());
658 if (Section.getType() == ELF::SHT_RELA ||
659 Section.getType() == ELF::SHT_REL ||
660 Section.getType() == ELF::SHT_STRTAB ||
661 Section.getType() == ELF::SHT_SYMTAB ||
662 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
664 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
665 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
667 LastLocalSymbolIndex++;
670 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
671 ELFSymbolData &MSD = ExternalSymbolData[i];
672 MCSymbolData &Data = *MSD.SymbolData;
673 assert(((Data.getFlags() & ELF_STB_Global) ||
674 (Data.getFlags() & ELF_STB_Weak)) &&
675 "External symbol requires STB_GLOBAL or STB_WEAK flag");
676 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
677 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
678 LastLocalSymbolIndex++;
681 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
682 ELFSymbolData &MSD = UndefinedSymbolData[i];
683 MCSymbolData &Data = *MSD.SymbolData;
684 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
685 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
686 LastLocalSymbolIndex++;
690 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
691 const MCValue &Target,
693 const MCFixup &Fixup,
694 bool IsPCRel) const {
695 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
696 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
697 const MCSymbol *Renamed = Renames.lookup(&Symbol);
698 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
700 if (ASymbol.isUndefined()) {
703 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
706 if (SD.isExternal()) {
712 const MCSectionELF &Section =
713 static_cast<const MCSectionELF&>(ASymbol.getSection());
714 const SectionKind secKind = Section.getKind();
717 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
719 if (secKind.isThreadLocal()) {
725 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
726 const MCSectionELF &Sec2 =
727 static_cast<const MCSectionELF&>(F.getParent()->getSection());
729 if (&Sec2 != &Section &&
730 (Kind == MCSymbolRefExpr::VK_PLT ||
731 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
732 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
738 if (Section.getFlags() & ELF::SHF_MERGE) {
739 if (Target.getConstant() == 0)
740 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
746 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
751 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
752 const MCAsmLayout &Layout,
753 const MCFragment *Fragment,
754 const MCFixup &Fixup,
756 uint64_t &FixedValue) {
759 int64_t Value = Target.getConstant();
760 const MCSymbol *RelocSymbol = NULL;
762 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
763 if (!Target.isAbsolute()) {
764 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
765 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
766 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
768 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
769 const MCSymbol &SymbolB = RefB->getSymbol();
770 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
773 if (!SDB.getFragment())
774 Asm.getContext().FatalError(
776 Twine("symbol '") + SymbolB.getName() +
777 "' can not be undefined in a subtraction expression");
779 // Offset of the symbol in the section
780 int64_t a = Layout.getSymbolOffset(&SDB);
782 // Offset of the relocation in the section
783 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
788 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
789 MCFragment *F = SD.getFragment();
792 Index = F->getParent()->getOrdinal() + 1;
793 // Offset of the symbol in the section
794 Value += Layout.getSymbolOffset(&SD);
799 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
800 WeakrefUsedInReloc.insert(RelocSymbol);
802 UsedInReloc.insert(RelocSymbol);
806 if (hasRelocationAddend())
811 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
812 (RelocSymbol != 0), Addend);
813 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
814 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
815 if (RelocNeedsGOT(Modifier))
818 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
821 if (!hasRelocationAddend())
825 assert(isInt<64>(Addend));
827 assert(isInt<32>(Addend));
829 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
830 Relocations[Fragment->getParent()].push_back(ERE);
835 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
837 MCSymbolData &SD = Asm.getSymbolData(*S);
838 return SD.getIndex();
841 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
842 const MCSymbolData &Data,
843 bool Used, bool Renamed) {
844 if (Data.getFlags() & ELF_Other_Weakref)
853 const MCSymbol &Symbol = Data.getSymbol();
855 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
858 const MCSymbol &A = Symbol.AliasedSymbol();
859 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
862 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
863 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
866 if (Symbol.isTemporary())
872 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
873 bool isUsedInReloc) {
874 if (Data.isExternal())
877 const MCSymbol &Symbol = Data.getSymbol();
878 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
880 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
881 if (isSignature && !isUsedInReloc)
890 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
891 SectionIndexMapTy &SectionIndexMap,
892 const RelMapTy &RelMap) {
894 for (MCAssembler::iterator it = Asm.begin(),
895 ie = Asm.end(); it != ie; ++it) {
896 const MCSectionELF &Section =
897 static_cast<const MCSectionELF &>(it->getSection());
898 if (Section.getType() != ELF::SHT_GROUP)
900 SectionIndexMap[&Section] = Index++;
903 for (MCAssembler::iterator it = Asm.begin(),
904 ie = Asm.end(); it != ie; ++it) {
905 const MCSectionELF &Section =
906 static_cast<const MCSectionELF &>(it->getSection());
907 if (Section.getType() == ELF::SHT_GROUP ||
908 Section.getType() == ELF::SHT_REL ||
909 Section.getType() == ELF::SHT_RELA)
911 SectionIndexMap[&Section] = Index++;
912 const MCSectionELF *RelSection = RelMap.lookup(&Section);
914 SectionIndexMap[RelSection] = Index++;
919 ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm, const MCAsmLayout &Layout,
920 const SectionIndexMapTy &SectionIndexMap,
921 RevGroupMapTy RevGroupMap,
922 unsigned NumRegularSections) {
923 // FIXME: Is this the correct place to do this?
924 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
926 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
927 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
928 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
929 Data.setExternal(true);
930 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
933 // Index 0 is always the empty string.
934 StringMap<uint64_t> StringIndexMap;
935 StringTable += '\x00';
937 // FIXME: We could optimize suffixes in strtab in the same way we
938 // optimize them in shstrtab.
940 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
941 ie = Asm.file_names_end();
944 StringRef Name = *it;
945 uint64_t &Entry = StringIndexMap[Name];
947 Entry = StringTable.size();
949 StringTable += '\x00';
951 FileSymbolData.push_back(Entry);
954 // Add the data for the symbols.
955 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
956 ie = Asm.symbol_end(); it != ie; ++it) {
957 const MCSymbol &Symbol = it->getSymbol();
959 bool Used = UsedInReloc.count(&Symbol);
960 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
961 bool isSignature = RevGroupMap.count(&Symbol);
963 if (!isInSymtab(Asm, *it,
964 Used || WeakrefUsed || isSignature,
965 Renames.count(&Symbol)))
970 const MCSymbol *BaseSymbol = Symbol.getBaseSymbol(Layout);
972 // Undefined symbols are global, but this is the first place we
973 // are able to set it.
974 bool Local = isLocal(*it, isSignature, Used);
975 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
977 MCSymbolData &SD = Asm.getSymbolData(*BaseSymbol);
978 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
979 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
983 MSD.SectionIndex = ELF::SHN_ABS;
984 } else if (it->isCommon()) {
986 MSD.SectionIndex = ELF::SHN_COMMON;
987 } else if (BaseSymbol->isUndefined()) {
988 if (isSignature && !Used)
989 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
991 MSD.SectionIndex = ELF::SHN_UNDEF;
992 if (!Used && WeakrefUsed)
993 MCELF::SetBinding(*it, ELF::STB_WEAK);
995 const MCSectionELF &Section =
996 static_cast<const MCSectionELF&>(BaseSymbol->getSection());
997 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
998 if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
999 NeedsSymtabShndx = true;
1000 assert(MSD.SectionIndex && "Invalid section index!");
1003 // The @@@ in symbol version is replaced with @ in undefined symbols and
1004 // @@ in defined ones.
1005 StringRef Name = Symbol.getName();
1006 SmallString<32> Buf;
1008 size_t Pos = Name.find("@@@");
1009 if (Pos != StringRef::npos) {
1010 Buf += Name.substr(0, Pos);
1011 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
1012 Buf += Name.substr(Pos + Skip);
1016 uint64_t &Entry = StringIndexMap[Name];
1018 Entry = StringTable.size();
1019 StringTable += Name;
1020 StringTable += '\x00';
1022 MSD.StringIndex = Entry;
1023 if (MSD.SectionIndex == ELF::SHN_UNDEF)
1024 UndefinedSymbolData.push_back(MSD);
1026 LocalSymbolData.push_back(MSD);
1028 ExternalSymbolData.push_back(MSD);
1031 // Symbols are required to be in lexicographic order.
1032 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1033 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1034 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1036 // Set the symbol indices. Local symbols must come before all other
1037 // symbols with non-local bindings.
1038 unsigned Index = FileSymbolData.size() + 1;
1039 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1040 LocalSymbolData[i].SymbolData->setIndex(Index++);
1042 Index += NumRegularSections;
1044 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1045 ExternalSymbolData[i].SymbolData->setIndex(Index++);
1046 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1047 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1049 if (Index >= ELF::SHN_LORESERVE)
1050 NeedsSymtabShndx = true;
1053 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1054 MCAsmLayout &Layout,
1056 for (MCAssembler::const_iterator it = Asm.begin(),
1057 ie = Asm.end(); it != ie; ++it) {
1058 const MCSectionData &SD = *it;
1059 if (Relocations[&SD].empty())
1062 MCContext &Ctx = Asm.getContext();
1063 const MCSectionELF &Section =
1064 static_cast<const MCSectionELF&>(SD.getSection());
1066 const StringRef SectionName = Section.getSectionName();
1067 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1068 RelaSectionName += SectionName;
1071 if (hasRelocationAddend())
1072 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1074 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1077 StringRef Group = "";
1078 if (Section.getFlags() & ELF::SHF_GROUP) {
1079 Flags = ELF::SHF_GROUP;
1080 Group = Section.getGroup()->getName();
1083 const MCSectionELF *RelaSection =
1084 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1085 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1086 SectionKind::getReadOnly(),
1088 RelMap[&Section] = RelaSection;
1089 Asm.getOrCreateSectionData(*RelaSection);
1093 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1094 const RelMapTy &RelMap) {
1095 for (MCAssembler::const_iterator it = Asm.begin(),
1096 ie = Asm.end(); it != ie; ++it) {
1097 const MCSectionData &SD = *it;
1098 const MCSectionELF &Section =
1099 static_cast<const MCSectionELF&>(SD.getSection());
1101 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1104 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1105 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1107 MCDataFragment *F = new MCDataFragment(&RelaSD);
1108 WriteRelocationsFragment(Asm, F, &*it);
1112 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1113 uint64_t Flags, uint64_t Address,
1114 uint64_t Offset, uint64_t Size,
1115 uint32_t Link, uint32_t Info,
1117 uint64_t EntrySize) {
1118 Write32(Name); // sh_name: index into string table
1119 Write32(Type); // sh_type
1120 WriteWord(Flags); // sh_flags
1121 WriteWord(Address); // sh_addr
1122 WriteWord(Offset); // sh_offset
1123 WriteWord(Size); // sh_size
1124 Write32(Link); // sh_link
1125 Write32(Info); // sh_info
1126 WriteWord(Alignment); // sh_addralign
1127 WriteWord(EntrySize); // sh_entsize
1130 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1132 const MCSectionData *SD) {
1133 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1135 // Sort the relocation entries. Most targets just sort by r_offset, but some
1136 // (e.g., MIPS) have additional constraints.
1137 TargetObjectWriter->sortRelocs(Asm, Relocs);
1139 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1140 ELFRelocationEntry entry = Relocs[e - i - 1];
1144 else if (entry.Index < 0)
1145 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1147 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1149 String64(*F, entry.r_offset);
1150 if (TargetObjectWriter->isN64()) {
1151 String32(*F, entry.Index);
1153 String8(*F, TargetObjectWriter->getRSsym(entry.Type));
1154 String8(*F, TargetObjectWriter->getRType3(entry.Type));
1155 String8(*F, TargetObjectWriter->getRType2(entry.Type));
1156 String8(*F, TargetObjectWriter->getRType(entry.Type));
1159 struct ELF::Elf64_Rela ERE64;
1160 ERE64.setSymbolAndType(entry.Index, entry.Type);
1161 String64(*F, ERE64.r_info);
1163 if (hasRelocationAddend())
1164 String64(*F, entry.r_addend);
1166 String32(*F, entry.r_offset);
1168 struct ELF::Elf32_Rela ERE32;
1169 ERE32.setSymbolAndType(entry.Index, entry.Type);
1170 String32(*F, ERE32.r_info);
1172 if (hasRelocationAddend())
1173 String32(*F, entry.r_addend);
1178 static int compareBySuffix(const MCSectionELF *const *a,
1179 const MCSectionELF *const *b) {
1180 const StringRef &NameA = (*a)->getSectionName();
1181 const StringRef &NameB = (*b)->getSectionName();
1182 const unsigned sizeA = NameA.size();
1183 const unsigned sizeB = NameB.size();
1184 const unsigned len = std::min(sizeA, sizeB);
1185 for (unsigned int i = 0; i < len; ++i) {
1186 char ca = NameA[sizeA - i - 1];
1187 char cb = NameB[sizeB - i - 1];
1192 return sizeB - sizeA;
1195 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1196 MCAsmLayout &Layout,
1197 SectionIndexMapTy &SectionIndexMap,
1198 const RelMapTy &RelMap) {
1199 MCContext &Ctx = Asm.getContext();
1202 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1204 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1205 const MCSectionELF *ShstrtabSection =
1206 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1207 SectionKind::getReadOnly());
1208 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1209 ShstrtabSD.setAlignment(1);
1211 const MCSectionELF *SymtabSection =
1212 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1213 SectionKind::getReadOnly(),
1215 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1216 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1218 MCSectionData *SymtabShndxSD = NULL;
1220 if (NeedsSymtabShndx) {
1221 const MCSectionELF *SymtabShndxSection =
1222 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1223 SectionKind::getReadOnly(), 4, "");
1224 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1225 SymtabShndxSD->setAlignment(4);
1228 const MCSectionELF *StrtabSection;
1229 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1230 SectionKind::getReadOnly());
1231 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1232 StrtabSD.setAlignment(1);
1234 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1236 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1237 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1238 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1241 F = new MCDataFragment(&SymtabSD);
1242 MCDataFragment *ShndxF = NULL;
1243 if (NeedsSymtabShndx) {
1244 ShndxF = new MCDataFragment(SymtabShndxSD);
1246 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1248 F = new MCDataFragment(&StrtabSD);
1249 F->getContents().append(StringTable.begin(), StringTable.end());
1251 F = new MCDataFragment(&ShstrtabSD);
1253 std::vector<const MCSectionELF*> Sections;
1254 for (MCAssembler::const_iterator it = Asm.begin(),
1255 ie = Asm.end(); it != ie; ++it) {
1256 const MCSectionELF &Section =
1257 static_cast<const MCSectionELF&>(it->getSection());
1258 Sections.push_back(&Section);
1260 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1262 // Section header string table.
1264 // The first entry of a string table holds a null character so skip
1267 F->getContents().push_back('\x00');
1269 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1270 const MCSectionELF &Section = *Sections[I];
1272 StringRef Name = Section.getSectionName();
1274 StringRef PreviousName = Sections[I - 1]->getSectionName();
1275 if (PreviousName.endswith(Name)) {
1276 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1280 // Remember the index into the string table so we can write it
1281 // into the sh_name field of the section header table.
1282 SectionStringTableIndex[&Section] = Index;
1284 Index += Name.size() + 1;
1285 F->getContents().append(Name.begin(), Name.end());
1286 F->getContents().push_back('\x00');
1290 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1291 MCAsmLayout &Layout,
1292 GroupMapTy &GroupMap,
1293 RevGroupMapTy &RevGroupMap,
1294 SectionIndexMapTy &SectionIndexMap,
1295 const RelMapTy &RelMap) {
1296 // Create the .note.GNU-stack section if needed.
1297 MCContext &Ctx = Asm.getContext();
1298 if (Asm.getNoExecStack()) {
1299 const MCSectionELF *GnuStackSection =
1300 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1301 SectionKind::getReadOnly());
1302 Asm.getOrCreateSectionData(*GnuStackSection);
1306 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1308 const MCSectionELF &Section =
1309 static_cast<const MCSectionELF&>(it->getSection());
1310 if (!(Section.getFlags() & ELF::SHF_GROUP))
1313 const MCSymbol *SignatureSymbol = Section.getGroup();
1314 Asm.getOrCreateSymbolData(*SignatureSymbol);
1315 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1317 Group = Ctx.CreateELFGroupSection();
1318 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1319 Data.setAlignment(4);
1320 MCDataFragment *F = new MCDataFragment(&Data);
1321 String32(*F, ELF::GRP_COMDAT);
1323 GroupMap[Group] = SignatureSymbol;
1326 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1328 // Add sections to the groups
1329 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1331 const MCSectionELF &Section =
1332 static_cast<const MCSectionELF&>(it->getSection());
1333 if (!(Section.getFlags() & ELF::SHF_GROUP))
1335 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1336 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1337 // FIXME: we could use the previous fragment
1338 MCDataFragment *F = new MCDataFragment(&Data);
1339 unsigned Index = SectionIndexMap.lookup(&Section);
1340 String32(*F, Index);
1344 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1345 const SectionIndexMapTy &SectionIndexMap,
1346 uint32_t GroupSymbolIndex,
1347 uint64_t Offset, uint64_t Size,
1349 const MCSectionELF &Section) {
1350 uint64_t sh_link = 0;
1351 uint64_t sh_info = 0;
1353 switch(Section.getType()) {
1354 case ELF::SHT_DYNAMIC:
1355 sh_link = SectionStringTableIndex[&Section];
1360 case ELF::SHT_RELA: {
1361 const MCSectionELF *SymtabSection;
1362 const MCSectionELF *InfoSection;
1363 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1365 SectionKind::getReadOnly());
1366 sh_link = SectionIndexMap.lookup(SymtabSection);
1367 assert(sh_link && ".symtab not found");
1369 // Remove ".rel" and ".rela" prefixes.
1370 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1371 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1372 StringRef GroupName =
1373 Section.getGroup() ? Section.getGroup()->getName() : "";
1375 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1376 0, SectionKind::getReadOnly(),
1378 sh_info = SectionIndexMap.lookup(InfoSection);
1382 case ELF::SHT_SYMTAB:
1383 case ELF::SHT_DYNSYM:
1384 sh_link = StringTableIndex;
1385 sh_info = LastLocalSymbolIndex;
1388 case ELF::SHT_SYMTAB_SHNDX:
1389 sh_link = SymbolTableIndex;
1392 case ELF::SHT_PROGBITS:
1393 case ELF::SHT_STRTAB:
1394 case ELF::SHT_NOBITS:
1397 case ELF::SHT_ARM_ATTRIBUTES:
1398 case ELF::SHT_INIT_ARRAY:
1399 case ELF::SHT_FINI_ARRAY:
1400 case ELF::SHT_PREINIT_ARRAY:
1401 case ELF::SHT_X86_64_UNWIND:
1402 case ELF::SHT_MIPS_REGINFO:
1403 case ELF::SHT_MIPS_OPTIONS:
1407 case ELF::SHT_GROUP:
1408 sh_link = SymbolTableIndex;
1409 sh_info = GroupSymbolIndex;
1413 assert(0 && "FIXME: sh_type value not supported!");
1417 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1418 Section.getType() == ELF::SHT_ARM_EXIDX) {
1419 StringRef SecName(Section.getSectionName());
1420 if (SecName == ".ARM.exidx") {
1421 sh_link = SectionIndexMap.lookup(
1422 Asm.getContext().getELFSection(".text",
1424 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1425 SectionKind::getText()));
1426 } else if (SecName.startswith(".ARM.exidx")) {
1427 StringRef GroupName =
1428 Section.getGroup() ? Section.getGroup()->getName() : "";
1429 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1430 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1431 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1436 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1437 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1438 Alignment, Section.getEntrySize());
1441 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1442 return SD.getOrdinal() == ~UINT32_C(0) &&
1443 !SD.getSection().isVirtualSection();
1446 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1448 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1450 const MCFragment &F = *i;
1451 assert(F.getKind() == MCFragment::FT_Data);
1452 Ret += cast<MCDataFragment>(F).getContents().size();
1457 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1458 const MCSectionData &SD) {
1459 if (IsELFMetaDataSection(SD))
1460 return DataSectionSize(SD);
1461 return Layout.getSectionFileSize(&SD);
1464 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1465 const MCSectionData &SD) {
1466 if (IsELFMetaDataSection(SD))
1467 return DataSectionSize(SD);
1468 return Layout.getSectionAddressSize(&SD);
1471 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1472 const MCAsmLayout &Layout,
1473 const MCSectionELF &Section) {
1474 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1476 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1477 WriteZeros(Padding);
1479 if (IsELFMetaDataSection(SD)) {
1480 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1482 const MCFragment &F = *i;
1483 assert(F.getKind() == MCFragment::FT_Data);
1484 WriteBytes(cast<MCDataFragment>(F).getContents());
1487 Asm.writeSectionData(&SD, Layout);
1491 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1492 const GroupMapTy &GroupMap,
1493 const MCAsmLayout &Layout,
1494 const SectionIndexMapTy &SectionIndexMap,
1495 const SectionOffsetMapTy &SectionOffsetMap) {
1496 const unsigned NumSections = Asm.size() + 1;
1498 std::vector<const MCSectionELF*> Sections;
1499 Sections.resize(NumSections - 1);
1501 for (SectionIndexMapTy::const_iterator i=
1502 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1503 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1504 Sections[p.second - 1] = p.first;
1507 // Null section first.
1508 uint64_t FirstSectionSize =
1509 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1510 uint32_t FirstSectionLink =
1511 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1512 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1514 for (unsigned i = 0; i < NumSections - 1; ++i) {
1515 const MCSectionELF &Section = *Sections[i];
1516 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1517 uint32_t GroupSymbolIndex;
1518 if (Section.getType() != ELF::SHT_GROUP)
1519 GroupSymbolIndex = 0;
1521 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1522 GroupMap.lookup(&Section));
1524 uint64_t Size = GetSectionAddressSize(Layout, SD);
1526 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1527 SectionOffsetMap.lookup(&Section), Size,
1528 SD.getAlignment(), Section);
1532 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1533 std::vector<const MCSectionELF*> &Sections) {
1534 for (MCAssembler::iterator it = Asm.begin(),
1535 ie = Asm.end(); it != ie; ++it) {
1536 const MCSectionELF &Section =
1537 static_cast<const MCSectionELF &>(it->getSection());
1538 if (Section.getType() == ELF::SHT_GROUP)
1539 Sections.push_back(&Section);
1542 for (MCAssembler::iterator it = Asm.begin(),
1543 ie = Asm.end(); it != ie; ++it) {
1544 const MCSectionELF &Section =
1545 static_cast<const MCSectionELF &>(it->getSection());
1546 if (Section.getType() != ELF::SHT_GROUP &&
1547 Section.getType() != ELF::SHT_REL &&
1548 Section.getType() != ELF::SHT_RELA)
1549 Sections.push_back(&Section);
1552 for (MCAssembler::iterator it = Asm.begin(),
1553 ie = Asm.end(); it != ie; ++it) {
1554 const MCSectionELF &Section =
1555 static_cast<const MCSectionELF &>(it->getSection());
1556 if (Section.getType() == ELF::SHT_REL ||
1557 Section.getType() == ELF::SHT_RELA)
1558 Sections.push_back(&Section);
1562 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1563 const MCAsmLayout &Layout) {
1564 GroupMapTy GroupMap;
1565 RevGroupMapTy RevGroupMap;
1566 SectionIndexMapTy SectionIndexMap;
1568 unsigned NumUserSections = Asm.size();
1570 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1571 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1573 const unsigned NumUserAndRelocSections = Asm.size();
1574 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1575 RevGroupMap, SectionIndexMap, RelMap);
1576 const unsigned AllSections = Asm.size();
1577 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1579 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1581 // Compute symbol table information.
1582 ComputeSymbolTable(Asm, Layout, SectionIndexMap, RevGroupMap,
1583 NumRegularSections);
1585 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1587 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1588 const_cast<MCAsmLayout&>(Layout),
1592 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1593 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1594 sizeof(ELF::Elf32_Ehdr);
1595 uint64_t FileOff = HeaderSize;
1597 std::vector<const MCSectionELF*> Sections;
1598 ComputeSectionOrder(Asm, Sections);
1599 unsigned NumSections = Sections.size();
1600 SectionOffsetMapTy SectionOffsetMap;
1601 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1602 const MCSectionELF &Section = *Sections[i];
1603 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1605 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1607 // Remember the offset into the file for this section.
1608 SectionOffsetMap[&Section] = FileOff;
1610 // Get the size of the section in the output file (including padding).
1611 FileOff += GetSectionFileSize(Layout, SD);
1614 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1616 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1618 uint64_t SectionHeaderEntrySize = is64Bit() ?
1619 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1620 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1622 for (unsigned i = NumRegularSections + 1; i < NumSections; ++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 // Write out the ELF header ...
1636 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1638 // ... then the regular sections ...
1639 // + because of .shstrtab
1640 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1641 WriteDataSectionData(Asm, Layout, *Sections[i]);
1643 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1644 WriteZeros(Padding);
1646 // ... then the section header table ...
1647 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1650 // ... and then the remaining sections ...
1651 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1652 WriteDataSectionData(Asm, Layout, *Sections[i]);
1656 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1657 const MCSymbolData &DataA,
1658 const MCFragment &FB,
1660 bool IsPCRel) const {
1661 if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
1663 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1664 Asm, DataA, FB,InSet, IsPCRel);
1667 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1669 bool IsLittleEndian) {
1670 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);