1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements ELF object file writer information.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/ADT/OwningPtr.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/ADT/StringMap.h"
20 #include "llvm/MC/MCAsmBackend.h"
21 #include "llvm/MC/MCAsmLayout.h"
22 #include "llvm/MC/MCAssembler.h"
23 #include "llvm/MC/MCContext.h"
24 #include "llvm/MC/MCELF.h"
25 #include "llvm/MC/MCELFSymbolFlags.h"
26 #include "llvm/MC/MCExpr.h"
27 #include "llvm/MC/MCFixupKindInfo.h"
28 #include "llvm/MC/MCObjectWriter.h"
29 #include "llvm/MC/MCSectionELF.h"
30 #include "llvm/MC/MCValue.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Support/ELF.h"
33 #include "llvm/Support/ErrorHandling.h"
38 #define DEBUG_TYPE "reloc-info"
41 class ELFObjectWriter : public MCObjectWriter {
44 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
45 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
46 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
47 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
48 bool Used, bool Renamed);
49 static bool isLocal(const MCSymbolData &Data, bool isSignature,
51 static bool IsELFMetaDataSection(const MCSectionData &SD);
52 static uint64_t DataSectionSize(const MCSectionData &SD);
53 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
54 const MCSectionData &SD);
55 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
56 const MCSectionData &SD);
58 void WriteDataSectionData(MCAssembler &Asm,
59 const MCAsmLayout &Layout,
60 const MCSectionELF &Section);
62 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
63 return Kind == X86::reloc_riprel_4byte ||
64 Kind == X86::reloc_riprel_4byte_movq_load;
67 /// ELFSymbolData - Helper struct for containing some precomputed
68 /// information on symbols.
69 struct ELFSymbolData {
70 MCSymbolData *SymbolData;
72 uint32_t SectionIndex;
74 // Support lexicographic sorting.
75 bool operator<(const ELFSymbolData &RHS) const {
76 return SymbolData->getSymbol().getName() <
77 RHS.SymbolData->getSymbol().getName();
81 /// The target specific ELF writer instance.
82 llvm::OwningPtr<MCELFObjectTargetWriter> TargetObjectWriter;
84 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
85 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
86 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
88 llvm::DenseMap<const MCSectionData*,
89 std::vector<ELFRelocationEntry> > Relocations;
90 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
93 /// @name Symbol Table Data
96 SmallString<256> StringTable;
97 std::vector<uint64_t> FileSymbolData;
98 std::vector<ELFSymbolData> LocalSymbolData;
99 std::vector<ELFSymbolData> ExternalSymbolData;
100 std::vector<ELFSymbolData> UndefinedSymbolData;
106 bool NeedsSymtabShndx;
108 // This holds the symbol table index of the last local symbol.
109 unsigned LastLocalSymbolIndex;
110 // This holds the .strtab section index.
111 unsigned StringTableIndex;
112 // This holds the .symtab section index.
113 unsigned SymbolTableIndex;
115 unsigned ShstrtabIndex;
118 const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
119 const MCValue &Target,
121 const MCFixup &Fixup,
124 // TargetObjectWriter wrappers.
125 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
126 const MCValue &Target,
128 const MCFixup &Fixup,
129 bool IsPCRel) const {
130 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
132 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
133 const MCFixup &Fixup,
134 bool IsPCRel) const {
135 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
139 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
140 bool hasRelocationAddend() const {
141 return TargetObjectWriter->hasRelocationAddend();
143 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
144 bool IsPCRel, bool IsRelocWithSymbol,
145 int64_t Addend) const {
146 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
147 IsRelocWithSymbol, Addend);
151 ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
152 raw_ostream &_OS, bool IsLittleEndian)
153 : MCObjectWriter(_OS, IsLittleEndian),
154 TargetObjectWriter(MOTW),
155 NeedsGOT(false), NeedsSymtabShndx(false) {
158 virtual ~ELFObjectWriter();
160 void WriteWord(uint64_t W) {
167 void StringLE16(char *buf, uint16_t Value) {
168 buf[0] = char(Value >> 0);
169 buf[1] = char(Value >> 8);
172 void StringLE32(char *buf, uint32_t Value) {
173 StringLE16(buf, uint16_t(Value >> 0));
174 StringLE16(buf + 2, uint16_t(Value >> 16));
177 void StringLE64(char *buf, uint64_t Value) {
178 StringLE32(buf, uint32_t(Value >> 0));
179 StringLE32(buf + 4, uint32_t(Value >> 32));
182 void StringBE16(char *buf ,uint16_t Value) {
183 buf[0] = char(Value >> 8);
184 buf[1] = char(Value >> 0);
187 void StringBE32(char *buf, uint32_t Value) {
188 StringBE16(buf, uint16_t(Value >> 16));
189 StringBE16(buf + 2, uint16_t(Value >> 0));
192 void StringBE64(char *buf, uint64_t Value) {
193 StringBE32(buf, uint32_t(Value >> 32));
194 StringBE32(buf + 4, uint32_t(Value >> 0));
197 void String8(MCDataFragment &F, uint8_t Value) {
200 F.getContents().append(&buf[0], &buf[1]);
203 void String16(MCDataFragment &F, uint16_t Value) {
205 if (isLittleEndian())
206 StringLE16(buf, Value);
208 StringBE16(buf, Value);
209 F.getContents().append(&buf[0], &buf[2]);
212 void String32(MCDataFragment &F, uint32_t Value) {
214 if (isLittleEndian())
215 StringLE32(buf, Value);
217 StringBE32(buf, Value);
218 F.getContents().append(&buf[0], &buf[4]);
221 void String64(MCDataFragment &F, uint64_t Value) {
223 if (isLittleEndian())
224 StringLE64(buf, Value);
226 StringBE64(buf, Value);
227 F.getContents().append(&buf[0], &buf[8]);
230 void WriteHeader(const MCAssembler &Asm,
231 uint64_t SectionDataSize,
232 unsigned NumberOfSections);
234 void WriteSymbolEntry(MCDataFragment *SymtabF,
235 MCDataFragment *ShndxF,
236 uint64_t name, uint8_t info,
237 uint64_t value, uint64_t size,
238 uint8_t other, uint32_t shndx,
241 void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
243 const MCAsmLayout &Layout);
245 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
246 void WriteSymbolTable(MCDataFragment *SymtabF,
247 MCDataFragment *ShndxF,
248 const MCAssembler &Asm,
249 const MCAsmLayout &Layout,
250 const SectionIndexMapTy &SectionIndexMap);
252 virtual void RecordRelocation(const MCAssembler &Asm,
253 const MCAsmLayout &Layout,
254 const MCFragment *Fragment,
255 const MCFixup &Fixup,
256 MCValue Target, uint64_t &FixedValue);
258 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
261 // Map from a group section to the signature symbol
262 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
263 // Map from a signature symbol to the group section
264 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
265 // Map from a section to the section with the relocations
266 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
267 // Map from a section to its offset
268 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
270 /// ComputeSymbolTable - Compute the symbol table data
272 /// \param Asm - The assembler.
273 /// \param SectionIndexMap - Maps a section to its index.
274 /// \param RevGroupMap - Maps a signature symbol to the group section.
275 /// \param NumRegularSections - Number of non-relocation sections.
276 void ComputeSymbolTable(MCAssembler &Asm,
277 const SectionIndexMapTy &SectionIndexMap,
278 RevGroupMapTy RevGroupMap,
279 unsigned NumRegularSections);
281 void ComputeIndexMap(MCAssembler &Asm,
282 SectionIndexMapTy &SectionIndexMap,
283 const RelMapTy &RelMap);
285 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
288 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
289 const RelMapTy &RelMap);
291 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
292 SectionIndexMapTy &SectionIndexMap,
293 const RelMapTy &RelMap);
295 // Create the sections that show up in the symbol table. Currently
296 // those are the .note.GNU-stack section and the group sections.
297 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
298 GroupMapTy &GroupMap,
299 RevGroupMapTy &RevGroupMap,
300 SectionIndexMapTy &SectionIndexMap,
301 const RelMapTy &RelMap);
303 virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
304 const MCAsmLayout &Layout);
306 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
307 const MCAsmLayout &Layout,
308 const SectionIndexMapTy &SectionIndexMap,
309 const SectionOffsetMapTy &SectionOffsetMap);
311 void ComputeSectionOrder(MCAssembler &Asm,
312 std::vector<const MCSectionELF*> &Sections);
314 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
315 uint64_t Address, uint64_t Offset,
316 uint64_t Size, uint32_t Link, uint32_t Info,
317 uint64_t Alignment, uint64_t EntrySize);
319 void WriteRelocationsFragment(const MCAssembler &Asm,
321 const MCSectionData *SD);
324 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
325 const MCSymbolData &DataA,
326 const MCFragment &FB,
330 virtual void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
331 void WriteSection(MCAssembler &Asm,
332 const SectionIndexMapTy &SectionIndexMap,
333 uint32_t GroupSymbolIndex,
334 uint64_t Offset, uint64_t Size, uint64_t Alignment,
335 const MCSectionELF &Section);
339 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
340 const MCFixupKindInfo &FKI =
341 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
343 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
346 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
350 case MCSymbolRefExpr::VK_GOT:
351 case MCSymbolRefExpr::VK_PLT:
352 case MCSymbolRefExpr::VK_GOTPCREL:
353 case MCSymbolRefExpr::VK_GOTOFF:
354 case MCSymbolRefExpr::VK_TPOFF:
355 case MCSymbolRefExpr::VK_TLSGD:
356 case MCSymbolRefExpr::VK_GOTTPOFF:
357 case MCSymbolRefExpr::VK_INDNTPOFF:
358 case MCSymbolRefExpr::VK_NTPOFF:
359 case MCSymbolRefExpr::VK_GOTNTPOFF:
360 case MCSymbolRefExpr::VK_TLSLDM:
361 case MCSymbolRefExpr::VK_DTPOFF:
362 case MCSymbolRefExpr::VK_TLSLD:
367 ELFObjectWriter::~ELFObjectWriter()
370 // Emit the ELF header.
371 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
372 uint64_t SectionDataSize,
373 unsigned NumberOfSections) {
379 // emitWord method behaves differently for ELF32 and ELF64, writing
380 // 4 bytes in the former and 8 in the latter.
382 Write8(0x7f); // e_ident[EI_MAG0]
383 Write8('E'); // e_ident[EI_MAG1]
384 Write8('L'); // e_ident[EI_MAG2]
385 Write8('F'); // e_ident[EI_MAG3]
387 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
390 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
392 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
394 Write8(TargetObjectWriter->getOSABI());
395 Write8(0); // e_ident[EI_ABIVERSION]
397 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
399 Write16(ELF::ET_REL); // e_type
401 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
403 Write32(ELF::EV_CURRENT); // e_version
404 WriteWord(0); // e_entry, no entry point in .o file
405 WriteWord(0); // e_phoff, no program header for .o
406 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
407 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
409 // e_flags = whatever the target wants
410 Write32(Asm.getELFHeaderEFlags());
412 // e_ehsize = ELF header size
413 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
415 Write16(0); // e_phentsize = prog header entry size
416 Write16(0); // e_phnum = # prog header entries = 0
418 // e_shentsize = Section header entry size
419 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
421 // e_shnum = # of section header ents
422 if (NumberOfSections >= ELF::SHN_LORESERVE)
423 Write16(ELF::SHN_UNDEF);
425 Write16(NumberOfSections);
427 // e_shstrndx = Section # of '.shstrtab'
428 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
429 Write16(ELF::SHN_XINDEX);
431 Write16(ShstrtabIndex);
434 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
435 MCDataFragment *ShndxF,
437 uint8_t info, uint64_t value,
438 uint64_t size, uint8_t other,
442 if (shndx >= ELF::SHN_LORESERVE && !Reserved)
443 String32(*ShndxF, shndx);
445 String32(*ShndxF, 0);
448 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
449 uint16_t(ELF::SHN_XINDEX) : shndx;
452 String32(*SymtabF, name); // st_name
453 String8(*SymtabF, info); // st_info
454 String8(*SymtabF, other); // st_other
455 String16(*SymtabF, Index); // st_shndx
456 String64(*SymtabF, value); // st_value
457 String64(*SymtabF, size); // st_size
459 String32(*SymtabF, name); // st_name
460 String32(*SymtabF, value); // st_value
461 String32(*SymtabF, size); // st_size
462 String8(*SymtabF, info); // st_info
463 String8(*SymtabF, other); // st_other
464 String16(*SymtabF, Index); // st_shndx
468 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
469 const MCAsmLayout &Layout) {
470 if (Data.isCommon() && Data.isExternal())
471 return Data.getCommonAlignment();
473 const MCSymbol &Symbol = Data.getSymbol();
475 if (Symbol.isAbsolute() && Symbol.isVariable()) {
476 if (const MCExpr *Value = Symbol.getVariableValue()) {
478 if (Value->EvaluateAsAbsolute(IntValue, Layout))
479 return (uint64_t)IntValue;
483 if (!Symbol.isInSection())
487 if (Data.getFragment()) {
488 if (Data.getFlags() & ELF_Other_ThumbFunc)
489 return Layout.getSymbolOffset(&Data)+1;
491 return Layout.getSymbolOffset(&Data);
497 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
498 const MCAsmLayout &Layout) {
499 // The presence of symbol versions causes undefined symbols and
500 // versions declared with @@@ to be renamed.
502 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
503 ie = Asm.symbol_end(); it != ie; ++it) {
504 const MCSymbol &Alias = it->getSymbol();
505 const MCSymbol &Symbol = Alias.AliasedSymbol();
506 MCSymbolData &SD = Asm.getSymbolData(Symbol);
509 if (&Symbol == &Alias)
512 StringRef AliasName = Alias.getName();
513 size_t Pos = AliasName.find('@');
514 if (Pos == StringRef::npos)
517 // Aliases defined with .symvar copy the binding from the symbol they alias.
518 // This is the first place we are able to copy this information.
519 it->setExternal(SD.isExternal());
520 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
522 StringRef Rest = AliasName.substr(Pos);
523 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
526 // FIXME: produce a better error message.
527 if (Symbol.isUndefined() && Rest.startswith("@@") &&
528 !Rest.startswith("@@@"))
529 report_fatal_error("A @@ version cannot be undefined");
531 Renames.insert(std::make_pair(&Symbol, &Alias));
535 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
536 MCDataFragment *ShndxF,
538 const MCAsmLayout &Layout) {
539 MCSymbolData &OrigData = *MSD.SymbolData;
541 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
543 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
544 Data.getSymbol().isVariable();
546 // Binding and Type share the same byte as upper and lower nibbles
547 uint8_t Binding = MCELF::GetBinding(OrigData);
548 uint8_t Type = MCELF::GetType(Data);
549 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
551 // Other and Visibility share the same byte with Visibility using the lower
553 uint8_t Visibility = MCELF::GetVisibility(OrigData);
554 uint8_t Other = MCELF::getOther(OrigData) <<
555 (ELF_Other_Shift - ELF_STV_Shift);
558 uint64_t Value = SymbolValue(Data, Layout);
561 assert(!(Data.isCommon() && !Data.isExternal()));
563 const MCExpr *ESize = Data.getSize();
566 if (!ESize->EvaluateAsAbsolute(Res, Layout))
567 report_fatal_error("Size expression must be absolute.");
571 // Write out the symbol table entry
572 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
573 Size, Other, MSD.SectionIndex, IsReserved);
576 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
577 MCDataFragment *ShndxF,
578 const MCAssembler &Asm,
579 const MCAsmLayout &Layout,
580 const SectionIndexMapTy &SectionIndexMap) {
581 // The string table must be emitted first because we need the index
582 // into the string table for all the symbol names.
583 assert(StringTable.size() && "Missing string table");
585 // FIXME: Make sure the start of the symbol table is aligned.
587 // The first entry is the undefined symbol entry.
588 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
590 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
591 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i],
592 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
593 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
596 // Write the symbol table entries.
597 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
599 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
600 ELFSymbolData &MSD = LocalSymbolData[i];
601 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
604 // Write out a symbol table entry for each regular section.
605 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
607 const MCSectionELF &Section =
608 static_cast<const MCSectionELF&>(i->getSection());
609 if (Section.getType() == ELF::SHT_RELA ||
610 Section.getType() == ELF::SHT_REL ||
611 Section.getType() == ELF::SHT_STRTAB ||
612 Section.getType() == ELF::SHT_SYMTAB ||
613 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
615 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
616 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
618 LastLocalSymbolIndex++;
621 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
622 ELFSymbolData &MSD = ExternalSymbolData[i];
623 MCSymbolData &Data = *MSD.SymbolData;
624 assert(((Data.getFlags() & ELF_STB_Global) ||
625 (Data.getFlags() & ELF_STB_Weak)) &&
626 "External symbol requires STB_GLOBAL or STB_WEAK flag");
627 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
628 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
629 LastLocalSymbolIndex++;
632 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
633 ELFSymbolData &MSD = UndefinedSymbolData[i];
634 MCSymbolData &Data = *MSD.SymbolData;
635 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
636 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
637 LastLocalSymbolIndex++;
641 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
642 const MCValue &Target,
644 const MCFixup &Fixup,
645 bool IsPCRel) const {
646 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
647 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
648 const MCSymbol *Renamed = Renames.lookup(&Symbol);
649 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
651 if (ASymbol.isUndefined()) {
654 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
657 if (SD.isExternal()) {
663 const MCSectionELF &Section =
664 static_cast<const MCSectionELF&>(ASymbol.getSection());
665 const SectionKind secKind = Section.getKind();
668 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
670 if (secKind.isThreadLocal()) {
676 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
677 const MCSectionELF &Sec2 =
678 static_cast<const MCSectionELF&>(F.getParent()->getSection());
680 if (&Sec2 != &Section &&
681 (Kind == MCSymbolRefExpr::VK_PLT ||
682 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
683 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
689 if (Section.getFlags() & ELF::SHF_MERGE) {
690 if (Target.getConstant() == 0)
691 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
697 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
702 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
703 const MCAsmLayout &Layout,
704 const MCFragment *Fragment,
705 const MCFixup &Fixup,
707 uint64_t &FixedValue) {
710 int64_t Value = Target.getConstant();
711 const MCSymbol *RelocSymbol = NULL;
713 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
714 if (!Target.isAbsolute()) {
715 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
716 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
717 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
719 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
720 const MCSymbol &SymbolB = RefB->getSymbol();
721 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
724 // Offset of the symbol in the section
725 int64_t a = Layout.getSymbolOffset(&SDB);
727 // Offset of the relocation in the section
728 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
733 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
734 MCFragment *F = SD.getFragment();
737 Index = F->getParent()->getOrdinal() + 1;
738 // Offset of the symbol in the section
739 Value += Layout.getSymbolOffset(&SD);
744 if (Asm.getSymbolData(Symbol).getFlags() & ELF_Other_Weakref)
745 WeakrefUsedInReloc.insert(RelocSymbol);
747 UsedInReloc.insert(RelocSymbol);
751 if (hasRelocationAddend())
756 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
757 (RelocSymbol != 0), Addend);
758 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
759 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
760 if (RelocNeedsGOT(Modifier))
763 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
766 if (!hasRelocationAddend())
770 assert(isInt<64>(Addend));
772 assert(isInt<32>(Addend));
774 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
775 Relocations[Fragment->getParent()].push_back(ERE);
780 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
782 MCSymbolData &SD = Asm.getSymbolData(*S);
783 return SD.getIndex();
786 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
787 const MCSymbolData &Data,
788 bool Used, bool Renamed) {
789 if (Data.getFlags() & ELF_Other_Weakref)
798 const MCSymbol &Symbol = Data.getSymbol();
800 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
803 const MCSymbol &A = Symbol.AliasedSymbol();
804 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
807 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
808 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
811 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
814 if (Symbol.isTemporary())
820 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
821 bool isUsedInReloc) {
822 if (Data.isExternal())
825 const MCSymbol &Symbol = Data.getSymbol();
826 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
828 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
829 if (isSignature && !isUsedInReloc)
838 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
839 SectionIndexMapTy &SectionIndexMap,
840 const RelMapTy &RelMap) {
842 for (MCAssembler::iterator it = Asm.begin(),
843 ie = Asm.end(); it != ie; ++it) {
844 const MCSectionELF &Section =
845 static_cast<const MCSectionELF &>(it->getSection());
846 if (Section.getType() != ELF::SHT_GROUP)
848 SectionIndexMap[&Section] = Index++;
851 for (MCAssembler::iterator it = Asm.begin(),
852 ie = Asm.end(); it != ie; ++it) {
853 const MCSectionELF &Section =
854 static_cast<const MCSectionELF &>(it->getSection());
855 if (Section.getType() == ELF::SHT_GROUP ||
856 Section.getType() == ELF::SHT_REL ||
857 Section.getType() == ELF::SHT_RELA)
859 SectionIndexMap[&Section] = Index++;
860 const MCSectionELF *RelSection = RelMap.lookup(&Section);
862 SectionIndexMap[RelSection] = Index++;
866 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
867 const SectionIndexMapTy &SectionIndexMap,
868 RevGroupMapTy RevGroupMap,
869 unsigned NumRegularSections) {
870 // FIXME: Is this the correct place to do this?
871 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
873 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
874 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
875 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
876 Data.setExternal(true);
877 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
880 // Index 0 is always the empty string.
881 StringMap<uint64_t> StringIndexMap;
882 StringTable += '\x00';
884 // FIXME: We could optimize suffixes in strtab in the same way we
885 // optimize them in shstrtab.
887 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
888 ie = Asm.file_names_end();
891 StringRef Name = *it;
892 uint64_t &Entry = StringIndexMap[Name];
894 Entry = StringTable.size();
896 StringTable += '\x00';
898 FileSymbolData.push_back(Entry);
901 // Add the data for the symbols.
902 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
903 ie = Asm.symbol_end(); it != ie; ++it) {
904 const MCSymbol &Symbol = it->getSymbol();
906 bool Used = UsedInReloc.count(&Symbol);
907 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
908 bool isSignature = RevGroupMap.count(&Symbol);
910 if (!isInSymtab(Asm, *it,
911 Used || WeakrefUsed || isSignature,
912 Renames.count(&Symbol)))
917 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
919 // Undefined symbols are global, but this is the first place we
920 // are able to set it.
921 bool Local = isLocal(*it, isSignature, Used);
922 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
923 MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
924 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
925 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
928 if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
929 MCELF::SetBinding(*it, ELF::STB_WEAK);
931 if (it->isCommon()) {
933 MSD.SectionIndex = ELF::SHN_COMMON;
934 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
935 MSD.SectionIndex = ELF::SHN_ABS;
936 } else if (RefSymbol.isUndefined()) {
937 if (isSignature && !Used)
938 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
940 MSD.SectionIndex = ELF::SHN_UNDEF;
942 const MCSectionELF &Section =
943 static_cast<const MCSectionELF&>(RefSymbol.getSection());
944 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
945 if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
946 NeedsSymtabShndx = true;
947 assert(MSD.SectionIndex && "Invalid section index!");
950 // The @@@ in symbol version is replaced with @ in undefined symbols and
951 // @@ in defined ones.
952 StringRef Name = Symbol.getName();
955 size_t Pos = Name.find("@@@");
956 if (Pos != StringRef::npos) {
957 Buf += Name.substr(0, Pos);
958 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
959 Buf += Name.substr(Pos + Skip);
963 uint64_t &Entry = StringIndexMap[Name];
965 Entry = StringTable.size();
967 StringTable += '\x00';
969 MSD.StringIndex = Entry;
970 if (MSD.SectionIndex == ELF::SHN_UNDEF)
971 UndefinedSymbolData.push_back(MSD);
973 LocalSymbolData.push_back(MSD);
975 ExternalSymbolData.push_back(MSD);
978 // Symbols are required to be in lexicographic order.
979 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
980 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
981 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
983 // Set the symbol indices. Local symbols must come before all other
984 // symbols with non-local bindings.
985 unsigned Index = FileSymbolData.size() + 1;
986 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
987 LocalSymbolData[i].SymbolData->setIndex(Index++);
989 Index += NumRegularSections;
991 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
992 ExternalSymbolData[i].SymbolData->setIndex(Index++);
993 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
994 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
996 if (Index >= ELF::SHN_LORESERVE)
997 NeedsSymtabShndx = true;
1000 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1001 MCAsmLayout &Layout,
1003 for (MCAssembler::const_iterator it = Asm.begin(),
1004 ie = Asm.end(); it != ie; ++it) {
1005 const MCSectionData &SD = *it;
1006 if (Relocations[&SD].empty())
1009 MCContext &Ctx = Asm.getContext();
1010 const MCSectionELF &Section =
1011 static_cast<const MCSectionELF&>(SD.getSection());
1013 const StringRef SectionName = Section.getSectionName();
1014 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1015 RelaSectionName += SectionName;
1018 if (hasRelocationAddend())
1019 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1021 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1024 StringRef Group = "";
1025 if (Section.getFlags() & ELF::SHF_GROUP) {
1026 Flags = ELF::SHF_GROUP;
1027 Group = Section.getGroup()->getName();
1030 const MCSectionELF *RelaSection =
1031 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1032 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1033 SectionKind::getReadOnly(),
1035 RelMap[&Section] = RelaSection;
1036 Asm.getOrCreateSectionData(*RelaSection);
1040 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1041 const RelMapTy &RelMap) {
1042 for (MCAssembler::const_iterator it = Asm.begin(),
1043 ie = Asm.end(); it != ie; ++it) {
1044 const MCSectionData &SD = *it;
1045 const MCSectionELF &Section =
1046 static_cast<const MCSectionELF&>(SD.getSection());
1048 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1051 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1052 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1054 MCDataFragment *F = new MCDataFragment(&RelaSD);
1055 WriteRelocationsFragment(Asm, F, &*it);
1059 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1060 uint64_t Flags, uint64_t Address,
1061 uint64_t Offset, uint64_t Size,
1062 uint32_t Link, uint32_t Info,
1064 uint64_t EntrySize) {
1065 Write32(Name); // sh_name: index into string table
1066 Write32(Type); // sh_type
1067 WriteWord(Flags); // sh_flags
1068 WriteWord(Address); // sh_addr
1069 WriteWord(Offset); // sh_offset
1070 WriteWord(Size); // sh_size
1071 Write32(Link); // sh_link
1072 Write32(Info); // sh_info
1073 WriteWord(Alignment); // sh_addralign
1074 WriteWord(EntrySize); // sh_entsize
1077 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1079 const MCSectionData *SD) {
1080 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1082 // Sort the relocation entries. Most targets just sort by r_offset, but some
1083 // (e.g., MIPS) have additional constraints.
1084 TargetObjectWriter->sortRelocs(Asm, Relocs);
1086 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1087 ELFRelocationEntry entry = Relocs[e - i - 1];
1091 else if (entry.Index < 0)
1092 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1094 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1096 String64(*F, entry.r_offset);
1097 if (TargetObjectWriter->isN64()) {
1098 String32(*F, entry.Index);
1100 String8(*F, TargetObjectWriter->getRSsym(entry.Type));
1101 String8(*F, TargetObjectWriter->getRType3(entry.Type));
1102 String8(*F, TargetObjectWriter->getRType2(entry.Type));
1103 String8(*F, TargetObjectWriter->getRType(entry.Type));
1106 struct ELF::Elf64_Rela ERE64;
1107 ERE64.setSymbolAndType(entry.Index, entry.Type);
1108 String64(*F, ERE64.r_info);
1110 if (hasRelocationAddend())
1111 String64(*F, entry.r_addend);
1113 String32(*F, entry.r_offset);
1115 struct ELF::Elf32_Rela ERE32;
1116 ERE32.setSymbolAndType(entry.Index, entry.Type);
1117 String32(*F, ERE32.r_info);
1119 if (hasRelocationAddend())
1120 String32(*F, entry.r_addend);
1125 static int compareBySuffix(const MCSectionELF *const *a,
1126 const MCSectionELF *const *b) {
1127 const StringRef &NameA = (*a)->getSectionName();
1128 const StringRef &NameB = (*b)->getSectionName();
1129 const unsigned sizeA = NameA.size();
1130 const unsigned sizeB = NameB.size();
1131 const unsigned len = std::min(sizeA, sizeB);
1132 for (unsigned int i = 0; i < len; ++i) {
1133 char ca = NameA[sizeA - i - 1];
1134 char cb = NameB[sizeB - i - 1];
1139 return sizeB - sizeA;
1142 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1143 MCAsmLayout &Layout,
1144 SectionIndexMapTy &SectionIndexMap,
1145 const RelMapTy &RelMap) {
1146 MCContext &Ctx = Asm.getContext();
1149 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1151 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1152 const MCSectionELF *ShstrtabSection =
1153 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1154 SectionKind::getReadOnly());
1155 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1156 ShstrtabSD.setAlignment(1);
1158 const MCSectionELF *SymtabSection =
1159 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1160 SectionKind::getReadOnly(),
1162 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1163 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1165 MCSectionData *SymtabShndxSD = NULL;
1167 if (NeedsSymtabShndx) {
1168 const MCSectionELF *SymtabShndxSection =
1169 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1170 SectionKind::getReadOnly(), 4, "");
1171 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1172 SymtabShndxSD->setAlignment(4);
1175 const MCSectionELF *StrtabSection;
1176 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1177 SectionKind::getReadOnly());
1178 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1179 StrtabSD.setAlignment(1);
1181 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1183 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1184 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1185 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1188 F = new MCDataFragment(&SymtabSD);
1189 MCDataFragment *ShndxF = NULL;
1190 if (NeedsSymtabShndx) {
1191 ShndxF = new MCDataFragment(SymtabShndxSD);
1193 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1195 F = new MCDataFragment(&StrtabSD);
1196 F->getContents().append(StringTable.begin(), StringTable.end());
1198 F = new MCDataFragment(&ShstrtabSD);
1200 std::vector<const MCSectionELF*> Sections;
1201 for (MCAssembler::const_iterator it = Asm.begin(),
1202 ie = Asm.end(); it != ie; ++it) {
1203 const MCSectionELF &Section =
1204 static_cast<const MCSectionELF&>(it->getSection());
1205 Sections.push_back(&Section);
1207 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1209 // Section header string table.
1211 // The first entry of a string table holds a null character so skip
1214 F->getContents().push_back('\x00');
1216 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1217 const MCSectionELF &Section = *Sections[I];
1219 StringRef Name = Section.getSectionName();
1221 StringRef PreviousName = Sections[I - 1]->getSectionName();
1222 if (PreviousName.endswith(Name)) {
1223 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1227 // Remember the index into the string table so we can write it
1228 // into the sh_name field of the section header table.
1229 SectionStringTableIndex[&Section] = Index;
1231 Index += Name.size() + 1;
1232 F->getContents().append(Name.begin(), Name.end());
1233 F->getContents().push_back('\x00');
1237 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1238 MCAsmLayout &Layout,
1239 GroupMapTy &GroupMap,
1240 RevGroupMapTy &RevGroupMap,
1241 SectionIndexMapTy &SectionIndexMap,
1242 const RelMapTy &RelMap) {
1243 // Create the .note.GNU-stack section if needed.
1244 MCContext &Ctx = Asm.getContext();
1245 if (Asm.getNoExecStack()) {
1246 const MCSectionELF *GnuStackSection =
1247 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1248 SectionKind::getReadOnly());
1249 Asm.getOrCreateSectionData(*GnuStackSection);
1253 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1255 const MCSectionELF &Section =
1256 static_cast<const MCSectionELF&>(it->getSection());
1257 if (!(Section.getFlags() & ELF::SHF_GROUP))
1260 const MCSymbol *SignatureSymbol = Section.getGroup();
1261 Asm.getOrCreateSymbolData(*SignatureSymbol);
1262 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1264 Group = Ctx.CreateELFGroupSection();
1265 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1266 Data.setAlignment(4);
1267 MCDataFragment *F = new MCDataFragment(&Data);
1268 String32(*F, ELF::GRP_COMDAT);
1270 GroupMap[Group] = SignatureSymbol;
1273 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1275 // Add sections to the groups
1276 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1278 const MCSectionELF &Section =
1279 static_cast<const MCSectionELF&>(it->getSection());
1280 if (!(Section.getFlags() & ELF::SHF_GROUP))
1282 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1283 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1284 // FIXME: we could use the previous fragment
1285 MCDataFragment *F = new MCDataFragment(&Data);
1286 unsigned Index = SectionIndexMap.lookup(&Section);
1287 String32(*F, Index);
1291 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1292 const SectionIndexMapTy &SectionIndexMap,
1293 uint32_t GroupSymbolIndex,
1294 uint64_t Offset, uint64_t Size,
1296 const MCSectionELF &Section) {
1297 uint64_t sh_link = 0;
1298 uint64_t sh_info = 0;
1300 switch(Section.getType()) {
1301 case ELF::SHT_DYNAMIC:
1302 sh_link = SectionStringTableIndex[&Section];
1307 case ELF::SHT_RELA: {
1308 const MCSectionELF *SymtabSection;
1309 const MCSectionELF *InfoSection;
1310 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1312 SectionKind::getReadOnly());
1313 sh_link = SectionIndexMap.lookup(SymtabSection);
1314 assert(sh_link && ".symtab not found");
1316 // Remove ".rel" and ".rela" prefixes.
1317 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1318 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1319 StringRef GroupName =
1320 Section.getGroup() ? Section.getGroup()->getName() : "";
1322 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1323 0, SectionKind::getReadOnly(),
1325 sh_info = SectionIndexMap.lookup(InfoSection);
1329 case ELF::SHT_SYMTAB:
1330 case ELF::SHT_DYNSYM:
1331 sh_link = StringTableIndex;
1332 sh_info = LastLocalSymbolIndex;
1335 case ELF::SHT_SYMTAB_SHNDX:
1336 sh_link = SymbolTableIndex;
1339 case ELF::SHT_PROGBITS:
1340 case ELF::SHT_STRTAB:
1341 case ELF::SHT_NOBITS:
1344 case ELF::SHT_ARM_ATTRIBUTES:
1345 case ELF::SHT_INIT_ARRAY:
1346 case ELF::SHT_FINI_ARRAY:
1347 case ELF::SHT_PREINIT_ARRAY:
1348 case ELF::SHT_X86_64_UNWIND:
1349 case ELF::SHT_MIPS_REGINFO:
1350 case ELF::SHT_MIPS_OPTIONS:
1354 case ELF::SHT_GROUP:
1355 sh_link = SymbolTableIndex;
1356 sh_info = GroupSymbolIndex;
1360 assert(0 && "FIXME: sh_type value not supported!");
1364 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1365 Section.getType() == ELF::SHT_ARM_EXIDX) {
1366 StringRef SecName(Section.getSectionName());
1367 if (SecName == ".ARM.exidx") {
1368 sh_link = SectionIndexMap.lookup(
1369 Asm.getContext().getELFSection(".text",
1371 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1372 SectionKind::getText()));
1373 } else if (SecName.startswith(".ARM.exidx")) {
1374 StringRef GroupName =
1375 Section.getGroup() ? Section.getGroup()->getName() : "";
1376 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1377 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1378 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1383 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1384 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1385 Alignment, Section.getEntrySize());
1388 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1389 return SD.getOrdinal() == ~UINT32_C(0) &&
1390 !SD.getSection().isVirtualSection();
1393 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1395 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1397 const MCFragment &F = *i;
1398 assert(F.getKind() == MCFragment::FT_Data);
1399 Ret += cast<MCDataFragment>(F).getContents().size();
1404 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1405 const MCSectionData &SD) {
1406 if (IsELFMetaDataSection(SD))
1407 return DataSectionSize(SD);
1408 return Layout.getSectionFileSize(&SD);
1411 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1412 const MCSectionData &SD) {
1413 if (IsELFMetaDataSection(SD))
1414 return DataSectionSize(SD);
1415 return Layout.getSectionAddressSize(&SD);
1418 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1419 const MCAsmLayout &Layout,
1420 const MCSectionELF &Section) {
1421 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1423 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1424 WriteZeros(Padding);
1426 if (IsELFMetaDataSection(SD)) {
1427 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1429 const MCFragment &F = *i;
1430 assert(F.getKind() == MCFragment::FT_Data);
1431 WriteBytes(cast<MCDataFragment>(F).getContents());
1434 Asm.writeSectionData(&SD, Layout);
1438 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1439 const GroupMapTy &GroupMap,
1440 const MCAsmLayout &Layout,
1441 const SectionIndexMapTy &SectionIndexMap,
1442 const SectionOffsetMapTy &SectionOffsetMap) {
1443 const unsigned NumSections = Asm.size() + 1;
1445 std::vector<const MCSectionELF*> Sections;
1446 Sections.resize(NumSections - 1);
1448 for (SectionIndexMapTy::const_iterator i=
1449 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1450 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1451 Sections[p.second - 1] = p.first;
1454 // Null section first.
1455 uint64_t FirstSectionSize =
1456 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1457 uint32_t FirstSectionLink =
1458 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1459 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1461 for (unsigned i = 0; i < NumSections - 1; ++i) {
1462 const MCSectionELF &Section = *Sections[i];
1463 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1464 uint32_t GroupSymbolIndex;
1465 if (Section.getType() != ELF::SHT_GROUP)
1466 GroupSymbolIndex = 0;
1468 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1469 GroupMap.lookup(&Section));
1471 uint64_t Size = GetSectionAddressSize(Layout, SD);
1473 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1474 SectionOffsetMap.lookup(&Section), Size,
1475 SD.getAlignment(), Section);
1479 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1480 std::vector<const MCSectionELF*> &Sections) {
1481 for (MCAssembler::iterator it = Asm.begin(),
1482 ie = Asm.end(); it != ie; ++it) {
1483 const MCSectionELF &Section =
1484 static_cast<const MCSectionELF &>(it->getSection());
1485 if (Section.getType() == ELF::SHT_GROUP)
1486 Sections.push_back(&Section);
1489 for (MCAssembler::iterator it = Asm.begin(),
1490 ie = Asm.end(); it != ie; ++it) {
1491 const MCSectionELF &Section =
1492 static_cast<const MCSectionELF &>(it->getSection());
1493 if (Section.getType() != ELF::SHT_GROUP &&
1494 Section.getType() != ELF::SHT_REL &&
1495 Section.getType() != ELF::SHT_RELA)
1496 Sections.push_back(&Section);
1499 for (MCAssembler::iterator it = Asm.begin(),
1500 ie = Asm.end(); it != ie; ++it) {
1501 const MCSectionELF &Section =
1502 static_cast<const MCSectionELF &>(it->getSection());
1503 if (Section.getType() == ELF::SHT_REL ||
1504 Section.getType() == ELF::SHT_RELA)
1505 Sections.push_back(&Section);
1509 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1510 const MCAsmLayout &Layout) {
1511 GroupMapTy GroupMap;
1512 RevGroupMapTy RevGroupMap;
1513 SectionIndexMapTy SectionIndexMap;
1515 unsigned NumUserSections = Asm.size();
1517 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1518 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1520 const unsigned NumUserAndRelocSections = Asm.size();
1521 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1522 RevGroupMap, SectionIndexMap, RelMap);
1523 const unsigned AllSections = Asm.size();
1524 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1526 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1528 // Compute symbol table information.
1529 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections);
1532 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1534 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1535 const_cast<MCAsmLayout&>(Layout),
1539 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1540 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1541 sizeof(ELF::Elf32_Ehdr);
1542 uint64_t FileOff = HeaderSize;
1544 std::vector<const MCSectionELF*> Sections;
1545 ComputeSectionOrder(Asm, Sections);
1546 unsigned NumSections = Sections.size();
1547 SectionOffsetMapTy SectionOffsetMap;
1548 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1549 const MCSectionELF &Section = *Sections[i];
1550 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1552 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1554 // Remember the offset into the file for this section.
1555 SectionOffsetMap[&Section] = FileOff;
1557 // Get the size of the section in the output file (including padding).
1558 FileOff += GetSectionFileSize(Layout, SD);
1561 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1563 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1565 uint64_t SectionHeaderEntrySize = is64Bit() ?
1566 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1567 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1569 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
1570 const MCSectionELF &Section = *Sections[i];
1571 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1573 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1575 // Remember the offset into the file for this section.
1576 SectionOffsetMap[&Section] = FileOff;
1578 // Get the size of the section in the output file (including padding).
1579 FileOff += GetSectionFileSize(Layout, SD);
1582 // Write out the ELF header ...
1583 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1585 // ... then the regular sections ...
1586 // + because of .shstrtab
1587 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1588 WriteDataSectionData(Asm, Layout, *Sections[i]);
1590 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1591 WriteZeros(Padding);
1593 // ... then the section header table ...
1594 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1597 // ... and then the remaining sections ...
1598 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1599 WriteDataSectionData(Asm, Layout, *Sections[i]);
1603 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1604 const MCSymbolData &DataA,
1605 const MCFragment &FB,
1607 bool IsPCRel) const {
1608 if (DataA.getFlags() & ELF_STB_Weak)
1610 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1611 Asm, DataA, FB,InSet, IsPCRel);
1614 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1616 bool IsLittleEndian) {
1617 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);