1 //===- lib/MC/ELFObjectWriter.cpp - ELF File Writer -----------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements ELF object file writer information.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/ADT/SmallString.h"
18 #include "llvm/ADT/StringMap.h"
19 #include "llvm/MC/MCAsmBackend.h"
20 #include "llvm/MC/MCAsmLayout.h"
21 #include "llvm/MC/MCAssembler.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCELF.h"
24 #include "llvm/MC/MCELFSymbolFlags.h"
25 #include "llvm/MC/MCExpr.h"
26 #include "llvm/MC/MCFixupKindInfo.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSectionELF.h"
29 #include "llvm/MC/MCValue.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/ELF.h"
32 #include "llvm/Support/ErrorHandling.h"
37 #define DEBUG_TYPE "reloc-info"
40 class ELFObjectWriter : public MCObjectWriter {
43 static bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind);
44 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant);
45 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout);
46 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
47 bool Used, bool Renamed);
48 static bool isLocal(const MCSymbolData &Data, bool isSignature,
50 static bool IsELFMetaDataSection(const MCSectionData &SD);
51 static uint64_t DataSectionSize(const MCSectionData &SD);
52 static uint64_t GetSectionFileSize(const MCAsmLayout &Layout,
53 const MCSectionData &SD);
54 static uint64_t GetSectionAddressSize(const MCAsmLayout &Layout,
55 const MCSectionData &SD);
57 void WriteDataSectionData(MCAssembler &Asm,
58 const MCAsmLayout &Layout,
59 const MCSectionELF &Section);
61 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
62 return Kind == X86::reloc_riprel_4byte ||
63 Kind == X86::reloc_riprel_4byte_movq_load;
66 /// ELFSymbolData - Helper struct for containing some precomputed
67 /// information on symbols.
68 struct ELFSymbolData {
69 MCSymbolData *SymbolData;
71 uint32_t SectionIndex;
73 // Support lexicographic sorting.
74 bool operator<(const ELFSymbolData &RHS) const {
75 return SymbolData->getSymbol().getName() <
76 RHS.SymbolData->getSymbol().getName();
80 /// The target specific ELF writer instance.
81 std::unique_ptr<MCELFObjectTargetWriter> TargetObjectWriter;
83 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
84 SmallPtrSet<const MCSymbol *, 16> WeakrefUsedInReloc;
85 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
87 llvm::DenseMap<const MCSectionData*,
88 std::vector<ELFRelocationEntry> > Relocations;
89 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
92 /// @name Symbol Table Data
95 SmallString<256> StringTable;
96 std::vector<uint64_t> FileSymbolData;
97 std::vector<ELFSymbolData> LocalSymbolData;
98 std::vector<ELFSymbolData> ExternalSymbolData;
99 std::vector<ELFSymbolData> UndefinedSymbolData;
105 bool NeedsSymtabShndx;
107 // This holds the symbol table index of the last local symbol.
108 unsigned LastLocalSymbolIndex;
109 // This holds the .strtab section index.
110 unsigned StringTableIndex;
111 // This holds the .symtab section index.
112 unsigned SymbolTableIndex;
114 unsigned ShstrtabIndex;
117 const MCSymbol *SymbolToReloc(const MCAssembler &Asm,
118 const MCValue &Target,
120 const MCFixup &Fixup,
123 // TargetObjectWriter wrappers.
124 const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
125 const MCValue &Target,
127 const MCFixup &Fixup,
128 bool IsPCRel) const {
129 return TargetObjectWriter->ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
131 const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
132 const MCFixup &Fixup,
133 bool IsPCRel) const {
134 return TargetObjectWriter->undefinedExplicitRelSym(Target, Fixup,
138 bool is64Bit() const { return TargetObjectWriter->is64Bit(); }
139 bool hasRelocationAddend() const {
140 return TargetObjectWriter->hasRelocationAddend();
142 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
143 bool IsPCRel, bool IsRelocWithSymbol,
144 int64_t Addend) const {
145 return TargetObjectWriter->GetRelocType(Target, Fixup, IsPCRel,
146 IsRelocWithSymbol, Addend);
150 ELFObjectWriter(MCELFObjectTargetWriter *MOTW,
151 raw_ostream &_OS, bool IsLittleEndian)
152 : MCObjectWriter(_OS, IsLittleEndian),
153 TargetObjectWriter(MOTW),
154 NeedsGOT(false), NeedsSymtabShndx(false) {
157 virtual ~ELFObjectWriter();
159 void WriteWord(uint64_t W) {
166 void StringLE16(char *buf, uint16_t Value) {
167 buf[0] = char(Value >> 0);
168 buf[1] = char(Value >> 8);
171 void StringLE32(char *buf, uint32_t Value) {
172 StringLE16(buf, uint16_t(Value >> 0));
173 StringLE16(buf + 2, uint16_t(Value >> 16));
176 void StringLE64(char *buf, uint64_t Value) {
177 StringLE32(buf, uint32_t(Value >> 0));
178 StringLE32(buf + 4, uint32_t(Value >> 32));
181 void StringBE16(char *buf ,uint16_t Value) {
182 buf[0] = char(Value >> 8);
183 buf[1] = char(Value >> 0);
186 void StringBE32(char *buf, uint32_t Value) {
187 StringBE16(buf, uint16_t(Value >> 16));
188 StringBE16(buf + 2, uint16_t(Value >> 0));
191 void StringBE64(char *buf, uint64_t Value) {
192 StringBE32(buf, uint32_t(Value >> 32));
193 StringBE32(buf + 4, uint32_t(Value >> 0));
196 void String8(MCDataFragment &F, uint8_t Value) {
199 F.getContents().append(&buf[0], &buf[1]);
202 void String16(MCDataFragment &F, uint16_t Value) {
204 if (isLittleEndian())
205 StringLE16(buf, Value);
207 StringBE16(buf, Value);
208 F.getContents().append(&buf[0], &buf[2]);
211 void String32(MCDataFragment &F, uint32_t Value) {
213 if (isLittleEndian())
214 StringLE32(buf, Value);
216 StringBE32(buf, Value);
217 F.getContents().append(&buf[0], &buf[4]);
220 void String64(MCDataFragment &F, uint64_t Value) {
222 if (isLittleEndian())
223 StringLE64(buf, Value);
225 StringBE64(buf, Value);
226 F.getContents().append(&buf[0], &buf[8]);
229 void WriteHeader(const MCAssembler &Asm,
230 uint64_t SectionDataSize,
231 unsigned NumberOfSections);
233 void WriteSymbolEntry(MCDataFragment *SymtabF,
234 MCDataFragment *ShndxF,
235 uint64_t name, uint8_t info,
236 uint64_t value, uint64_t size,
237 uint8_t other, uint32_t shndx,
240 void WriteSymbol(MCDataFragment *SymtabF, MCDataFragment *ShndxF,
242 const MCAsmLayout &Layout);
244 typedef DenseMap<const MCSectionELF*, uint32_t> SectionIndexMapTy;
245 void WriteSymbolTable(MCDataFragment *SymtabF,
246 MCDataFragment *ShndxF,
247 const MCAssembler &Asm,
248 const MCAsmLayout &Layout,
249 const SectionIndexMapTy &SectionIndexMap);
251 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
252 const MCFragment *Fragment, const MCFixup &Fixup,
253 MCValue Target, uint64_t &FixedValue) override;
255 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
258 // Map from a group section to the signature symbol
259 typedef DenseMap<const MCSectionELF*, const MCSymbol*> GroupMapTy;
260 // Map from a signature symbol to the group section
261 typedef DenseMap<const MCSymbol*, const MCSectionELF*> RevGroupMapTy;
262 // Map from a section to the section with the relocations
263 typedef DenseMap<const MCSectionELF*, const MCSectionELF*> RelMapTy;
264 // Map from a section to its offset
265 typedef DenseMap<const MCSectionELF*, uint64_t> SectionOffsetMapTy;
267 /// ComputeSymbolTable - Compute the symbol table data
269 /// \param Asm - The assembler.
270 /// \param SectionIndexMap - Maps a section to its index.
271 /// \param RevGroupMap - Maps a signature symbol to the group section.
272 /// \param NumRegularSections - Number of non-relocation sections.
273 void ComputeSymbolTable(MCAssembler &Asm,
274 const SectionIndexMapTy &SectionIndexMap,
275 RevGroupMapTy RevGroupMap,
276 unsigned NumRegularSections);
278 void ComputeIndexMap(MCAssembler &Asm,
279 SectionIndexMapTy &SectionIndexMap,
280 const RelMapTy &RelMap);
282 void CreateRelocationSections(MCAssembler &Asm, MCAsmLayout &Layout,
285 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
286 const RelMapTy &RelMap);
288 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout,
289 SectionIndexMapTy &SectionIndexMap,
290 const RelMapTy &RelMap);
292 // Create the sections that show up in the symbol table. Currently
293 // those are the .note.GNU-stack section and the group sections.
294 void CreateIndexedSections(MCAssembler &Asm, MCAsmLayout &Layout,
295 GroupMapTy &GroupMap,
296 RevGroupMapTy &RevGroupMap,
297 SectionIndexMapTy &SectionIndexMap,
298 const RelMapTy &RelMap);
300 void ExecutePostLayoutBinding(MCAssembler &Asm,
301 const MCAsmLayout &Layout) override;
303 void WriteSectionHeader(MCAssembler &Asm, const GroupMapTy &GroupMap,
304 const MCAsmLayout &Layout,
305 const SectionIndexMapTy &SectionIndexMap,
306 const SectionOffsetMapTy &SectionOffsetMap);
308 void ComputeSectionOrder(MCAssembler &Asm,
309 std::vector<const MCSectionELF*> &Sections);
311 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
312 uint64_t Address, uint64_t Offset,
313 uint64_t Size, uint32_t Link, uint32_t Info,
314 uint64_t Alignment, uint64_t EntrySize);
316 void WriteRelocationsFragment(const MCAssembler &Asm,
318 const MCSectionData *SD);
321 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
322 const MCSymbolData &DataA,
323 const MCFragment &FB,
325 bool IsPCRel) const override;
327 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
328 void WriteSection(MCAssembler &Asm,
329 const SectionIndexMapTy &SectionIndexMap,
330 uint32_t GroupSymbolIndex,
331 uint64_t Offset, uint64_t Size, uint64_t Alignment,
332 const MCSectionELF &Section);
336 bool ELFObjectWriter::isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind) {
337 const MCFixupKindInfo &FKI =
338 Asm.getBackend().getFixupKindInfo((MCFixupKind) Kind);
340 return FKI.Flags & MCFixupKindInfo::FKF_IsPCRel;
343 bool ELFObjectWriter::RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
347 case MCSymbolRefExpr::VK_GOT:
348 case MCSymbolRefExpr::VK_PLT:
349 case MCSymbolRefExpr::VK_GOTPCREL:
350 case MCSymbolRefExpr::VK_GOTOFF:
351 case MCSymbolRefExpr::VK_TPOFF:
352 case MCSymbolRefExpr::VK_TLSGD:
353 case MCSymbolRefExpr::VK_GOTTPOFF:
354 case MCSymbolRefExpr::VK_INDNTPOFF:
355 case MCSymbolRefExpr::VK_NTPOFF:
356 case MCSymbolRefExpr::VK_GOTNTPOFF:
357 case MCSymbolRefExpr::VK_TLSLDM:
358 case MCSymbolRefExpr::VK_DTPOFF:
359 case MCSymbolRefExpr::VK_TLSLD:
364 ELFObjectWriter::~ELFObjectWriter()
367 // Emit the ELF header.
368 void ELFObjectWriter::WriteHeader(const MCAssembler &Asm,
369 uint64_t SectionDataSize,
370 unsigned NumberOfSections) {
376 // emitWord method behaves differently for ELF32 and ELF64, writing
377 // 4 bytes in the former and 8 in the latter.
379 Write8(0x7f); // e_ident[EI_MAG0]
380 Write8('E'); // e_ident[EI_MAG1]
381 Write8('L'); // e_ident[EI_MAG2]
382 Write8('F'); // e_ident[EI_MAG3]
384 Write8(is64Bit() ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
387 Write8(isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
389 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
391 Write8(TargetObjectWriter->getOSABI());
392 Write8(0); // e_ident[EI_ABIVERSION]
394 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
396 Write16(ELF::ET_REL); // e_type
398 Write16(TargetObjectWriter->getEMachine()); // e_machine = target
400 Write32(ELF::EV_CURRENT); // e_version
401 WriteWord(0); // e_entry, no entry point in .o file
402 WriteWord(0); // e_phoff, no program header for .o
403 WriteWord(SectionDataSize + (is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
404 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
406 // e_flags = whatever the target wants
407 Write32(Asm.getELFHeaderEFlags());
409 // e_ehsize = ELF header size
410 Write16(is64Bit() ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
412 Write16(0); // e_phentsize = prog header entry size
413 Write16(0); // e_phnum = # prog header entries = 0
415 // e_shentsize = Section header entry size
416 Write16(is64Bit() ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
418 // e_shnum = # of section header ents
419 if (NumberOfSections >= ELF::SHN_LORESERVE)
420 Write16(ELF::SHN_UNDEF);
422 Write16(NumberOfSections);
424 // e_shstrndx = Section # of '.shstrtab'
425 if (ShstrtabIndex >= ELF::SHN_LORESERVE)
426 Write16(ELF::SHN_XINDEX);
428 Write16(ShstrtabIndex);
431 void ELFObjectWriter::WriteSymbolEntry(MCDataFragment *SymtabF,
432 MCDataFragment *ShndxF,
434 uint8_t info, uint64_t value,
435 uint64_t size, uint8_t other,
439 if (shndx >= ELF::SHN_LORESERVE && !Reserved)
440 String32(*ShndxF, shndx);
442 String32(*ShndxF, 0);
445 uint16_t Index = (shndx >= ELF::SHN_LORESERVE && !Reserved) ?
446 uint16_t(ELF::SHN_XINDEX) : shndx;
449 String32(*SymtabF, name); // st_name
450 String8(*SymtabF, info); // st_info
451 String8(*SymtabF, other); // st_other
452 String16(*SymtabF, Index); // st_shndx
453 String64(*SymtabF, value); // st_value
454 String64(*SymtabF, size); // st_size
456 String32(*SymtabF, name); // st_name
457 String32(*SymtabF, value); // st_value
458 String32(*SymtabF, size); // st_size
459 String8(*SymtabF, info); // st_info
460 String8(*SymtabF, other); // st_other
461 String16(*SymtabF, Index); // st_shndx
465 uint64_t ELFObjectWriter::SymbolValue(MCSymbolData &Data,
466 const MCAsmLayout &Layout) {
467 if (Data.isCommon() && Data.isExternal())
468 return Data.getCommonAlignment();
470 const MCSymbol &Symbol = Data.getSymbol();
472 if (Symbol.isAbsolute() && Symbol.isVariable()) {
473 if (const MCExpr *Value = Symbol.getVariableValue()) {
475 if (Value->EvaluateAsAbsolute(IntValue, Layout))
476 return (uint64_t)IntValue;
480 if (!Symbol.isInSection())
484 if (Data.getFragment()) {
485 if (Data.getFlags() & ELF_Other_ThumbFunc)
486 return Layout.getSymbolOffset(&Data)+1;
488 return Layout.getSymbolOffset(&Data);
494 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm,
495 const MCAsmLayout &Layout) {
496 // The presence of symbol versions causes undefined symbols and
497 // versions declared with @@@ to be renamed.
499 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
500 ie = Asm.symbol_end(); it != ie; ++it) {
501 const MCSymbol &Alias = it->getSymbol();
502 const MCSymbol &Symbol = Alias.AliasedSymbol();
503 MCSymbolData &SD = Asm.getSymbolData(Symbol);
506 if (&Symbol == &Alias)
509 StringRef AliasName = Alias.getName();
510 size_t Pos = AliasName.find('@');
511 if (Pos == StringRef::npos)
514 // Aliases defined with .symvar copy the binding from the symbol they alias.
515 // This is the first place we are able to copy this information.
516 it->setExternal(SD.isExternal());
517 MCELF::SetBinding(*it, MCELF::GetBinding(SD));
519 StringRef Rest = AliasName.substr(Pos);
520 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
523 // FIXME: produce a better error message.
524 if (Symbol.isUndefined() && Rest.startswith("@@") &&
525 !Rest.startswith("@@@"))
526 report_fatal_error("A @@ version cannot be undefined");
528 Renames.insert(std::make_pair(&Symbol, &Alias));
532 static uint8_t mergeTypeForSet(uint8_t origType, uint8_t newType) {
533 uint8_t Type = newType;
535 // Propagation rules:
536 // IFUNC > FUNC > OBJECT > NOTYPE
537 // TLS_OBJECT > OBJECT > NOTYPE
539 // dont let the new type degrade the old type
543 case ELF::STT_GNU_IFUNC:
544 if (Type == ELF::STT_FUNC || Type == ELF::STT_OBJECT ||
545 Type == ELF::STT_NOTYPE || Type == ELF::STT_TLS)
546 Type = ELF::STT_GNU_IFUNC;
549 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
550 Type == ELF::STT_TLS)
551 Type = ELF::STT_FUNC;
553 case ELF::STT_OBJECT:
554 if (Type == ELF::STT_NOTYPE)
555 Type = ELF::STT_OBJECT;
558 if (Type == ELF::STT_OBJECT || Type == ELF::STT_NOTYPE ||
559 Type == ELF::STT_GNU_IFUNC || Type == ELF::STT_FUNC)
567 void ELFObjectWriter::WriteSymbol(MCDataFragment *SymtabF,
568 MCDataFragment *ShndxF,
570 const MCAsmLayout &Layout) {
571 MCSymbolData &OrigData = *MSD.SymbolData;
573 Layout.getAssembler().getSymbolData(OrigData.getSymbol().AliasedSymbol());
575 bool IsReserved = Data.isCommon() || Data.getSymbol().isAbsolute() ||
576 Data.getSymbol().isVariable();
578 // Binding and Type share the same byte as upper and lower nibbles
579 uint8_t Binding = MCELF::GetBinding(OrigData);
580 uint8_t Type = mergeTypeForSet(MCELF::GetType(OrigData), MCELF::GetType(Data));
581 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
583 // Other and Visibility share the same byte with Visibility using the lower
585 uint8_t Visibility = MCELF::GetVisibility(OrigData);
586 uint8_t Other = MCELF::getOther(OrigData) << (ELF_STO_Shift - ELF_STV_Shift);
589 uint64_t Value = SymbolValue(Data, Layout);
592 assert(!(Data.isCommon() && !Data.isExternal()));
594 const MCExpr *ESize = Data.getSize();
597 if (!ESize->EvaluateAsAbsolute(Res, Layout))
598 report_fatal_error("Size expression must be absolute.");
602 // Write out the symbol table entry
603 WriteSymbolEntry(SymtabF, ShndxF, MSD.StringIndex, Info, Value,
604 Size, Other, MSD.SectionIndex, IsReserved);
607 void ELFObjectWriter::WriteSymbolTable(MCDataFragment *SymtabF,
608 MCDataFragment *ShndxF,
609 const MCAssembler &Asm,
610 const MCAsmLayout &Layout,
611 const SectionIndexMapTy &SectionIndexMap) {
612 // The string table must be emitted first because we need the index
613 // into the string table for all the symbol names.
614 assert(StringTable.size() && "Missing string table");
616 // FIXME: Make sure the start of the symbol table is aligned.
618 // The first entry is the undefined symbol entry.
619 WriteSymbolEntry(SymtabF, ShndxF, 0, 0, 0, 0, 0, 0, false);
621 for (unsigned i = 0, e = FileSymbolData.size(); i != e; ++i) {
622 WriteSymbolEntry(SymtabF, ShndxF, FileSymbolData[i],
623 ELF::STT_FILE | ELF::STB_LOCAL, 0, 0,
624 ELF::STV_DEFAULT, ELF::SHN_ABS, true);
627 // Write the symbol table entries.
628 LastLocalSymbolIndex = FileSymbolData.size() + LocalSymbolData.size() + 1;
630 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
631 ELFSymbolData &MSD = LocalSymbolData[i];
632 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
635 // Write out a symbol table entry for each regular section.
636 for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e;
638 const MCSectionELF &Section =
639 static_cast<const MCSectionELF&>(i->getSection());
640 if (Section.getType() == ELF::SHT_RELA ||
641 Section.getType() == ELF::SHT_REL ||
642 Section.getType() == ELF::SHT_STRTAB ||
643 Section.getType() == ELF::SHT_SYMTAB ||
644 Section.getType() == ELF::SHT_SYMTAB_SHNDX)
646 WriteSymbolEntry(SymtabF, ShndxF, 0, ELF::STT_SECTION, 0, 0,
647 ELF::STV_DEFAULT, SectionIndexMap.lookup(&Section),
649 LastLocalSymbolIndex++;
652 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
653 ELFSymbolData &MSD = ExternalSymbolData[i];
654 MCSymbolData &Data = *MSD.SymbolData;
655 assert(((Data.getFlags() & ELF_STB_Global) ||
656 (Data.getFlags() & ELF_STB_Weak)) &&
657 "External symbol requires STB_GLOBAL or STB_WEAK flag");
658 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
659 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
660 LastLocalSymbolIndex++;
663 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
664 ELFSymbolData &MSD = UndefinedSymbolData[i];
665 MCSymbolData &Data = *MSD.SymbolData;
666 WriteSymbol(SymtabF, ShndxF, MSD, Layout);
667 if (MCELF::GetBinding(Data) == ELF::STB_LOCAL)
668 LastLocalSymbolIndex++;
672 const MCSymbol *ELFObjectWriter::SymbolToReloc(const MCAssembler &Asm,
673 const MCValue &Target,
675 const MCFixup &Fixup,
676 bool IsPCRel) const {
677 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
678 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
679 const MCSymbol *Renamed = Renames.lookup(&Symbol);
680 const MCSymbolData &SD = Asm.getSymbolData(Symbol);
682 if (ASymbol.isUndefined()) {
685 return undefinedExplicitRelSym(Target, Fixup, IsPCRel);
688 if (SD.isExternal()) {
694 const MCSectionELF &Section =
695 static_cast<const MCSectionELF&>(ASymbol.getSection());
696 const SectionKind secKind = Section.getKind();
699 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
701 if (secKind.isThreadLocal()) {
707 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
708 const MCSectionELF &Sec2 =
709 static_cast<const MCSectionELF&>(F.getParent()->getSection());
711 if (&Sec2 != &Section &&
712 (Kind == MCSymbolRefExpr::VK_PLT ||
713 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
714 Kind == MCSymbolRefExpr::VK_GOTOFF)) {
720 if (Section.getFlags() & ELF::SHF_MERGE) {
721 if (Target.getConstant() == 0)
722 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
728 return ExplicitRelSym(Asm, Target, F, Fixup, IsPCRel);
733 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
734 const MCAsmLayout &Layout,
735 const MCFragment *Fragment,
736 const MCFixup &Fixup,
738 uint64_t &FixedValue) {
741 int64_t Value = Target.getConstant();
742 const MCSymbol *RelocSymbol = NULL;
744 bool IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
745 if (!Target.isAbsolute()) {
746 const MCSymbol &Symbol = Target.getSymA()->getSymbol();
747 const MCSymbol &ASymbol = Symbol.AliasedSymbol();
748 RelocSymbol = SymbolToReloc(Asm, Target, *Fragment, Fixup, IsPCRel);
750 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
751 const MCSymbol &SymbolB = RefB->getSymbol();
752 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
755 if (!SDB.getFragment())
756 Asm.getContext().FatalError(
758 Twine("symbol '") + SymbolB.getName() +
759 "' can not be undefined in a subtraction expression");
761 // Offset of the symbol in the section
762 int64_t a = Layout.getSymbolOffset(&SDB);
764 // Offset of the relocation in the section
765 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
770 MCSymbolData &SD = Asm.getSymbolData(ASymbol);
771 MCFragment *F = SD.getFragment();
774 Index = F->getParent()->getOrdinal() + 1;
775 // Offset of the symbol in the section
776 Value += Layout.getSymbolOffset(&SD);
781 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_WEAKREF)
782 WeakrefUsedInReloc.insert(RelocSymbol);
784 UsedInReloc.insert(RelocSymbol);
788 if (hasRelocationAddend())
793 unsigned Type = GetRelocType(Target, Fixup, IsPCRel,
794 (RelocSymbol != 0), Addend);
795 MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
796 MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
797 if (RelocNeedsGOT(Modifier))
800 uint64_t RelocOffset = Layout.getFragmentOffset(Fragment) +
803 if (!hasRelocationAddend())
807 assert(isInt<64>(Addend));
809 assert(isInt<32>(Addend));
811 ELFRelocationEntry ERE(RelocOffset, Index, Type, RelocSymbol, Addend, Fixup);
812 Relocations[Fragment->getParent()].push_back(ERE);
817 ELFObjectWriter::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
819 MCSymbolData &SD = Asm.getSymbolData(*S);
820 return SD.getIndex();
823 bool ELFObjectWriter::isInSymtab(const MCAssembler &Asm,
824 const MCSymbolData &Data,
825 bool Used, bool Renamed) {
826 const MCSymbol &Symbol = Data.getSymbol();
827 if (Symbol.isVariable()) {
828 const MCExpr *Expr = Symbol.getVariableValue();
829 if (const MCSymbolRefExpr *Ref = dyn_cast<MCSymbolRefExpr>(Expr)) {
830 if (Ref->getKind() == MCSymbolRefExpr::VK_WEAKREF)
841 if (Symbol.getName() == "_GLOBAL_OFFSET_TABLE_")
844 const MCSymbol &A = Symbol.AliasedSymbol();
845 if (Symbol.isVariable() && !A.isVariable() && A.isUndefined())
848 bool IsGlobal = MCELF::GetBinding(Data) == ELF::STB_GLOBAL;
849 if (!Symbol.isVariable() && Symbol.isUndefined() && !IsGlobal)
852 if (Symbol.isTemporary())
858 bool ELFObjectWriter::isLocal(const MCSymbolData &Data, bool isSignature,
859 bool isUsedInReloc) {
860 if (Data.isExternal())
863 const MCSymbol &Symbol = Data.getSymbol();
864 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
866 if (RefSymbol.isUndefined() && !RefSymbol.isVariable()) {
867 if (isSignature && !isUsedInReloc)
876 void ELFObjectWriter::ComputeIndexMap(MCAssembler &Asm,
877 SectionIndexMapTy &SectionIndexMap,
878 const RelMapTy &RelMap) {
880 for (MCAssembler::iterator it = Asm.begin(),
881 ie = Asm.end(); it != ie; ++it) {
882 const MCSectionELF &Section =
883 static_cast<const MCSectionELF &>(it->getSection());
884 if (Section.getType() != ELF::SHT_GROUP)
886 SectionIndexMap[&Section] = Index++;
889 for (MCAssembler::iterator it = Asm.begin(),
890 ie = Asm.end(); it != ie; ++it) {
891 const MCSectionELF &Section =
892 static_cast<const MCSectionELF &>(it->getSection());
893 if (Section.getType() == ELF::SHT_GROUP ||
894 Section.getType() == ELF::SHT_REL ||
895 Section.getType() == ELF::SHT_RELA)
897 SectionIndexMap[&Section] = Index++;
898 const MCSectionELF *RelSection = RelMap.lookup(&Section);
900 SectionIndexMap[RelSection] = Index++;
904 void ELFObjectWriter::ComputeSymbolTable(MCAssembler &Asm,
905 const SectionIndexMapTy &SectionIndexMap,
906 RevGroupMapTy RevGroupMap,
907 unsigned NumRegularSections) {
908 // FIXME: Is this the correct place to do this?
909 // FIXME: Why is an undefined reference to _GLOBAL_OFFSET_TABLE_ needed?
911 StringRef Name = "_GLOBAL_OFFSET_TABLE_";
912 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
913 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
914 Data.setExternal(true);
915 MCELF::SetBinding(Data, ELF::STB_GLOBAL);
918 // Index 0 is always the empty string.
919 StringMap<uint64_t> StringIndexMap;
920 StringTable += '\x00';
922 // FIXME: We could optimize suffixes in strtab in the same way we
923 // optimize them in shstrtab.
925 for (MCAssembler::const_file_name_iterator it = Asm.file_names_begin(),
926 ie = Asm.file_names_end();
929 StringRef Name = *it;
930 uint64_t &Entry = StringIndexMap[Name];
932 Entry = StringTable.size();
934 StringTable += '\x00';
936 FileSymbolData.push_back(Entry);
939 // Add the data for the symbols.
940 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
941 ie = Asm.symbol_end(); it != ie; ++it) {
942 const MCSymbol &Symbol = it->getSymbol();
944 bool Used = UsedInReloc.count(&Symbol);
945 bool WeakrefUsed = WeakrefUsedInReloc.count(&Symbol);
946 bool isSignature = RevGroupMap.count(&Symbol);
948 if (!isInSymtab(Asm, *it,
949 Used || WeakrefUsed || isSignature,
950 Renames.count(&Symbol)))
955 const MCSymbol &RefSymbol = Symbol.AliasedSymbol();
957 // Undefined symbols are global, but this is the first place we
958 // are able to set it.
959 bool Local = isLocal(*it, isSignature, Used);
960 if (!Local && MCELF::GetBinding(*it) == ELF::STB_LOCAL) {
961 MCSymbolData &SD = Asm.getSymbolData(RefSymbol);
962 MCELF::SetBinding(*it, ELF::STB_GLOBAL);
963 MCELF::SetBinding(SD, ELF::STB_GLOBAL);
966 if (RefSymbol.isUndefined() && !Used && WeakrefUsed)
967 MCELF::SetBinding(*it, ELF::STB_WEAK);
969 if (it->isCommon()) {
971 MSD.SectionIndex = ELF::SHN_COMMON;
972 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
973 MSD.SectionIndex = ELF::SHN_ABS;
974 } else if (RefSymbol.isUndefined()) {
975 if (isSignature && !Used)
976 MSD.SectionIndex = SectionIndexMap.lookup(RevGroupMap[&Symbol]);
978 MSD.SectionIndex = ELF::SHN_UNDEF;
980 const MCSectionELF &Section =
981 static_cast<const MCSectionELF&>(RefSymbol.getSection());
982 MSD.SectionIndex = SectionIndexMap.lookup(&Section);
983 if (MSD.SectionIndex >= ELF::SHN_LORESERVE)
984 NeedsSymtabShndx = true;
985 assert(MSD.SectionIndex && "Invalid section index!");
988 // The @@@ in symbol version is replaced with @ in undefined symbols and
989 // @@ in defined ones.
990 StringRef Name = Symbol.getName();
993 size_t Pos = Name.find("@@@");
994 if (Pos != StringRef::npos) {
995 Buf += Name.substr(0, Pos);
996 unsigned Skip = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
997 Buf += Name.substr(Pos + Skip);
1001 uint64_t &Entry = StringIndexMap[Name];
1003 Entry = StringTable.size();
1004 StringTable += Name;
1005 StringTable += '\x00';
1007 MSD.StringIndex = Entry;
1008 if (MSD.SectionIndex == ELF::SHN_UNDEF)
1009 UndefinedSymbolData.push_back(MSD);
1011 LocalSymbolData.push_back(MSD);
1013 ExternalSymbolData.push_back(MSD);
1016 // Symbols are required to be in lexicographic order.
1017 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
1018 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
1019 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
1021 // Set the symbol indices. Local symbols must come before all other
1022 // symbols with non-local bindings.
1023 unsigned Index = FileSymbolData.size() + 1;
1024 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
1025 LocalSymbolData[i].SymbolData->setIndex(Index++);
1027 Index += NumRegularSections;
1029 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
1030 ExternalSymbolData[i].SymbolData->setIndex(Index++);
1031 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
1032 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
1034 if (Index >= ELF::SHN_LORESERVE)
1035 NeedsSymtabShndx = true;
1038 void ELFObjectWriter::CreateRelocationSections(MCAssembler &Asm,
1039 MCAsmLayout &Layout,
1041 for (MCAssembler::const_iterator it = Asm.begin(),
1042 ie = Asm.end(); it != ie; ++it) {
1043 const MCSectionData &SD = *it;
1044 if (Relocations[&SD].empty())
1047 MCContext &Ctx = Asm.getContext();
1048 const MCSectionELF &Section =
1049 static_cast<const MCSectionELF&>(SD.getSection());
1051 const StringRef SectionName = Section.getSectionName();
1052 std::string RelaSectionName = hasRelocationAddend() ? ".rela" : ".rel";
1053 RelaSectionName += SectionName;
1056 if (hasRelocationAddend())
1057 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
1059 EntrySize = is64Bit() ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
1062 StringRef Group = "";
1063 if (Section.getFlags() & ELF::SHF_GROUP) {
1064 Flags = ELF::SHF_GROUP;
1065 Group = Section.getGroup()->getName();
1068 const MCSectionELF *RelaSection =
1069 Ctx.getELFSection(RelaSectionName, hasRelocationAddend() ?
1070 ELF::SHT_RELA : ELF::SHT_REL, Flags,
1071 SectionKind::getReadOnly(),
1073 RelMap[&Section] = RelaSection;
1074 Asm.getOrCreateSectionData(*RelaSection);
1078 void ELFObjectWriter::WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout,
1079 const RelMapTy &RelMap) {
1080 for (MCAssembler::const_iterator it = Asm.begin(),
1081 ie = Asm.end(); it != ie; ++it) {
1082 const MCSectionData &SD = *it;
1083 const MCSectionELF &Section =
1084 static_cast<const MCSectionELF&>(SD.getSection());
1086 const MCSectionELF *RelaSection = RelMap.lookup(&Section);
1089 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
1090 RelaSD.setAlignment(is64Bit() ? 8 : 4);
1092 MCDataFragment *F = new MCDataFragment(&RelaSD);
1093 WriteRelocationsFragment(Asm, F, &*it);
1097 void ELFObjectWriter::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1098 uint64_t Flags, uint64_t Address,
1099 uint64_t Offset, uint64_t Size,
1100 uint32_t Link, uint32_t Info,
1102 uint64_t EntrySize) {
1103 Write32(Name); // sh_name: index into string table
1104 Write32(Type); // sh_type
1105 WriteWord(Flags); // sh_flags
1106 WriteWord(Address); // sh_addr
1107 WriteWord(Offset); // sh_offset
1108 WriteWord(Size); // sh_size
1109 Write32(Link); // sh_link
1110 Write32(Info); // sh_info
1111 WriteWord(Alignment); // sh_addralign
1112 WriteWord(EntrySize); // sh_entsize
1115 void ELFObjectWriter::WriteRelocationsFragment(const MCAssembler &Asm,
1117 const MCSectionData *SD) {
1118 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1120 // Sort the relocation entries. Most targets just sort by r_offset, but some
1121 // (e.g., MIPS) have additional constraints.
1122 TargetObjectWriter->sortRelocs(Asm, Relocs);
1124 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1125 ELFRelocationEntry entry = Relocs[e - i - 1];
1129 else if (entry.Index < 0)
1130 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1132 entry.Index += FileSymbolData.size() + LocalSymbolData.size();
1134 String64(*F, entry.r_offset);
1135 if (TargetObjectWriter->isN64()) {
1136 String32(*F, entry.Index);
1138 String8(*F, TargetObjectWriter->getRSsym(entry.Type));
1139 String8(*F, TargetObjectWriter->getRType3(entry.Type));
1140 String8(*F, TargetObjectWriter->getRType2(entry.Type));
1141 String8(*F, TargetObjectWriter->getRType(entry.Type));
1144 struct ELF::Elf64_Rela ERE64;
1145 ERE64.setSymbolAndType(entry.Index, entry.Type);
1146 String64(*F, ERE64.r_info);
1148 if (hasRelocationAddend())
1149 String64(*F, entry.r_addend);
1151 String32(*F, entry.r_offset);
1153 struct ELF::Elf32_Rela ERE32;
1154 ERE32.setSymbolAndType(entry.Index, entry.Type);
1155 String32(*F, ERE32.r_info);
1157 if (hasRelocationAddend())
1158 String32(*F, entry.r_addend);
1163 static int compareBySuffix(const MCSectionELF *const *a,
1164 const MCSectionELF *const *b) {
1165 const StringRef &NameA = (*a)->getSectionName();
1166 const StringRef &NameB = (*b)->getSectionName();
1167 const unsigned sizeA = NameA.size();
1168 const unsigned sizeB = NameB.size();
1169 const unsigned len = std::min(sizeA, sizeB);
1170 for (unsigned int i = 0; i < len; ++i) {
1171 char ca = NameA[sizeA - i - 1];
1172 char cb = NameB[sizeB - i - 1];
1177 return sizeB - sizeA;
1180 void ELFObjectWriter::CreateMetadataSections(MCAssembler &Asm,
1181 MCAsmLayout &Layout,
1182 SectionIndexMapTy &SectionIndexMap,
1183 const RelMapTy &RelMap) {
1184 MCContext &Ctx = Asm.getContext();
1187 unsigned EntrySize = is64Bit() ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1189 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1190 const MCSectionELF *ShstrtabSection =
1191 Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1192 SectionKind::getReadOnly());
1193 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1194 ShstrtabSD.setAlignment(1);
1196 const MCSectionELF *SymtabSection =
1197 Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1198 SectionKind::getReadOnly(),
1200 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1201 SymtabSD.setAlignment(is64Bit() ? 8 : 4);
1203 MCSectionData *SymtabShndxSD = NULL;
1205 if (NeedsSymtabShndx) {
1206 const MCSectionELF *SymtabShndxSection =
1207 Ctx.getELFSection(".symtab_shndx", ELF::SHT_SYMTAB_SHNDX, 0,
1208 SectionKind::getReadOnly(), 4, "");
1209 SymtabShndxSD = &Asm.getOrCreateSectionData(*SymtabShndxSection);
1210 SymtabShndxSD->setAlignment(4);
1213 const MCSectionELF *StrtabSection;
1214 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1215 SectionKind::getReadOnly());
1216 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1217 StrtabSD.setAlignment(1);
1219 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1221 ShstrtabIndex = SectionIndexMap.lookup(ShstrtabSection);
1222 SymbolTableIndex = SectionIndexMap.lookup(SymtabSection);
1223 StringTableIndex = SectionIndexMap.lookup(StrtabSection);
1226 F = new MCDataFragment(&SymtabSD);
1227 MCDataFragment *ShndxF = NULL;
1228 if (NeedsSymtabShndx) {
1229 ShndxF = new MCDataFragment(SymtabShndxSD);
1231 WriteSymbolTable(F, ShndxF, Asm, Layout, SectionIndexMap);
1233 F = new MCDataFragment(&StrtabSD);
1234 F->getContents().append(StringTable.begin(), StringTable.end());
1236 F = new MCDataFragment(&ShstrtabSD);
1238 std::vector<const MCSectionELF*> Sections;
1239 for (MCAssembler::const_iterator it = Asm.begin(),
1240 ie = Asm.end(); it != ie; ++it) {
1241 const MCSectionELF &Section =
1242 static_cast<const MCSectionELF&>(it->getSection());
1243 Sections.push_back(&Section);
1245 array_pod_sort(Sections.begin(), Sections.end(), compareBySuffix);
1247 // Section header string table.
1249 // The first entry of a string table holds a null character so skip
1252 F->getContents().push_back('\x00');
1254 for (unsigned int I = 0, E = Sections.size(); I != E; ++I) {
1255 const MCSectionELF &Section = *Sections[I];
1257 StringRef Name = Section.getSectionName();
1259 StringRef PreviousName = Sections[I - 1]->getSectionName();
1260 if (PreviousName.endswith(Name)) {
1261 SectionStringTableIndex[&Section] = Index - Name.size() - 1;
1265 // Remember the index into the string table so we can write it
1266 // into the sh_name field of the section header table.
1267 SectionStringTableIndex[&Section] = Index;
1269 Index += Name.size() + 1;
1270 F->getContents().append(Name.begin(), Name.end());
1271 F->getContents().push_back('\x00');
1275 void ELFObjectWriter::CreateIndexedSections(MCAssembler &Asm,
1276 MCAsmLayout &Layout,
1277 GroupMapTy &GroupMap,
1278 RevGroupMapTy &RevGroupMap,
1279 SectionIndexMapTy &SectionIndexMap,
1280 const RelMapTy &RelMap) {
1281 // Create the .note.GNU-stack section if needed.
1282 MCContext &Ctx = Asm.getContext();
1283 if (Asm.getNoExecStack()) {
1284 const MCSectionELF *GnuStackSection =
1285 Ctx.getELFSection(".note.GNU-stack", ELF::SHT_PROGBITS, 0,
1286 SectionKind::getReadOnly());
1287 Asm.getOrCreateSectionData(*GnuStackSection);
1291 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1293 const MCSectionELF &Section =
1294 static_cast<const MCSectionELF&>(it->getSection());
1295 if (!(Section.getFlags() & ELF::SHF_GROUP))
1298 const MCSymbol *SignatureSymbol = Section.getGroup();
1299 Asm.getOrCreateSymbolData(*SignatureSymbol);
1300 const MCSectionELF *&Group = RevGroupMap[SignatureSymbol];
1302 Group = Ctx.CreateELFGroupSection();
1303 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1304 Data.setAlignment(4);
1305 MCDataFragment *F = new MCDataFragment(&Data);
1306 String32(*F, ELF::GRP_COMDAT);
1308 GroupMap[Group] = SignatureSymbol;
1311 ComputeIndexMap(Asm, SectionIndexMap, RelMap);
1313 // Add sections to the groups
1314 for (MCAssembler::const_iterator it = Asm.begin(), ie = Asm.end();
1316 const MCSectionELF &Section =
1317 static_cast<const MCSectionELF&>(it->getSection());
1318 if (!(Section.getFlags() & ELF::SHF_GROUP))
1320 const MCSectionELF *Group = RevGroupMap[Section.getGroup()];
1321 MCSectionData &Data = Asm.getOrCreateSectionData(*Group);
1322 // FIXME: we could use the previous fragment
1323 MCDataFragment *F = new MCDataFragment(&Data);
1324 unsigned Index = SectionIndexMap.lookup(&Section);
1325 String32(*F, Index);
1329 void ELFObjectWriter::WriteSection(MCAssembler &Asm,
1330 const SectionIndexMapTy &SectionIndexMap,
1331 uint32_t GroupSymbolIndex,
1332 uint64_t Offset, uint64_t Size,
1334 const MCSectionELF &Section) {
1335 uint64_t sh_link = 0;
1336 uint64_t sh_info = 0;
1338 switch(Section.getType()) {
1339 case ELF::SHT_DYNAMIC:
1340 sh_link = SectionStringTableIndex[&Section];
1345 case ELF::SHT_RELA: {
1346 const MCSectionELF *SymtabSection;
1347 const MCSectionELF *InfoSection;
1348 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB,
1350 SectionKind::getReadOnly());
1351 sh_link = SectionIndexMap.lookup(SymtabSection);
1352 assert(sh_link && ".symtab not found");
1354 // Remove ".rel" and ".rela" prefixes.
1355 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1356 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1357 StringRef GroupName =
1358 Section.getGroup() ? Section.getGroup()->getName() : "";
1360 InfoSection = Asm.getContext().getELFSection(SectionName, ELF::SHT_PROGBITS,
1361 0, SectionKind::getReadOnly(),
1363 sh_info = SectionIndexMap.lookup(InfoSection);
1367 case ELF::SHT_SYMTAB:
1368 case ELF::SHT_DYNSYM:
1369 sh_link = StringTableIndex;
1370 sh_info = LastLocalSymbolIndex;
1373 case ELF::SHT_SYMTAB_SHNDX:
1374 sh_link = SymbolTableIndex;
1377 case ELF::SHT_PROGBITS:
1378 case ELF::SHT_STRTAB:
1379 case ELF::SHT_NOBITS:
1382 case ELF::SHT_ARM_ATTRIBUTES:
1383 case ELF::SHT_INIT_ARRAY:
1384 case ELF::SHT_FINI_ARRAY:
1385 case ELF::SHT_PREINIT_ARRAY:
1386 case ELF::SHT_X86_64_UNWIND:
1387 case ELF::SHT_MIPS_REGINFO:
1388 case ELF::SHT_MIPS_OPTIONS:
1392 case ELF::SHT_GROUP:
1393 sh_link = SymbolTableIndex;
1394 sh_info = GroupSymbolIndex;
1398 assert(0 && "FIXME: sh_type value not supported!");
1402 if (TargetObjectWriter->getEMachine() == ELF::EM_ARM &&
1403 Section.getType() == ELF::SHT_ARM_EXIDX) {
1404 StringRef SecName(Section.getSectionName());
1405 if (SecName == ".ARM.exidx") {
1406 sh_link = SectionIndexMap.lookup(
1407 Asm.getContext().getELFSection(".text",
1409 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC,
1410 SectionKind::getText()));
1411 } else if (SecName.startswith(".ARM.exidx")) {
1412 StringRef GroupName =
1413 Section.getGroup() ? Section.getGroup()->getName() : "";
1414 sh_link = SectionIndexMap.lookup(Asm.getContext().getELFSection(
1415 SecName.substr(sizeof(".ARM.exidx") - 1), ELF::SHT_PROGBITS,
1416 ELF::SHF_EXECINSTR | ELF::SHF_ALLOC, SectionKind::getText(), 0,
1421 WriteSecHdrEntry(SectionStringTableIndex[&Section], Section.getType(),
1422 Section.getFlags(), 0, Offset, Size, sh_link, sh_info,
1423 Alignment, Section.getEntrySize());
1426 bool ELFObjectWriter::IsELFMetaDataSection(const MCSectionData &SD) {
1427 return SD.getOrdinal() == ~UINT32_C(0) &&
1428 !SD.getSection().isVirtualSection();
1431 uint64_t ELFObjectWriter::DataSectionSize(const MCSectionData &SD) {
1433 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1435 const MCFragment &F = *i;
1436 assert(F.getKind() == MCFragment::FT_Data);
1437 Ret += cast<MCDataFragment>(F).getContents().size();
1442 uint64_t ELFObjectWriter::GetSectionFileSize(const MCAsmLayout &Layout,
1443 const MCSectionData &SD) {
1444 if (IsELFMetaDataSection(SD))
1445 return DataSectionSize(SD);
1446 return Layout.getSectionFileSize(&SD);
1449 uint64_t ELFObjectWriter::GetSectionAddressSize(const MCAsmLayout &Layout,
1450 const MCSectionData &SD) {
1451 if (IsELFMetaDataSection(SD))
1452 return DataSectionSize(SD);
1453 return Layout.getSectionAddressSize(&SD);
1456 void ELFObjectWriter::WriteDataSectionData(MCAssembler &Asm,
1457 const MCAsmLayout &Layout,
1458 const MCSectionELF &Section) {
1459 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1461 uint64_t Padding = OffsetToAlignment(OS.tell(), SD.getAlignment());
1462 WriteZeros(Padding);
1464 if (IsELFMetaDataSection(SD)) {
1465 for (MCSectionData::const_iterator i = SD.begin(), e = SD.end(); i != e;
1467 const MCFragment &F = *i;
1468 assert(F.getKind() == MCFragment::FT_Data);
1469 WriteBytes(cast<MCDataFragment>(F).getContents());
1472 Asm.writeSectionData(&SD, Layout);
1476 void ELFObjectWriter::WriteSectionHeader(MCAssembler &Asm,
1477 const GroupMapTy &GroupMap,
1478 const MCAsmLayout &Layout,
1479 const SectionIndexMapTy &SectionIndexMap,
1480 const SectionOffsetMapTy &SectionOffsetMap) {
1481 const unsigned NumSections = Asm.size() + 1;
1483 std::vector<const MCSectionELF*> Sections;
1484 Sections.resize(NumSections - 1);
1486 for (SectionIndexMapTy::const_iterator i=
1487 SectionIndexMap.begin(), e = SectionIndexMap.end(); i != e; ++i) {
1488 const std::pair<const MCSectionELF*, uint32_t> &p = *i;
1489 Sections[p.second - 1] = p.first;
1492 // Null section first.
1493 uint64_t FirstSectionSize =
1494 NumSections >= ELF::SHN_LORESERVE ? NumSections : 0;
1495 uint32_t FirstSectionLink =
1496 ShstrtabIndex >= ELF::SHN_LORESERVE ? ShstrtabIndex : 0;
1497 WriteSecHdrEntry(0, 0, 0, 0, 0, FirstSectionSize, FirstSectionLink, 0, 0, 0);
1499 for (unsigned i = 0; i < NumSections - 1; ++i) {
1500 const MCSectionELF &Section = *Sections[i];
1501 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1502 uint32_t GroupSymbolIndex;
1503 if (Section.getType() != ELF::SHT_GROUP)
1504 GroupSymbolIndex = 0;
1506 GroupSymbolIndex = getSymbolIndexInSymbolTable(Asm,
1507 GroupMap.lookup(&Section));
1509 uint64_t Size = GetSectionAddressSize(Layout, SD);
1511 WriteSection(Asm, SectionIndexMap, GroupSymbolIndex,
1512 SectionOffsetMap.lookup(&Section), Size,
1513 SD.getAlignment(), Section);
1517 void ELFObjectWriter::ComputeSectionOrder(MCAssembler &Asm,
1518 std::vector<const MCSectionELF*> &Sections) {
1519 for (MCAssembler::iterator it = Asm.begin(),
1520 ie = Asm.end(); it != ie; ++it) {
1521 const MCSectionELF &Section =
1522 static_cast<const MCSectionELF &>(it->getSection());
1523 if (Section.getType() == ELF::SHT_GROUP)
1524 Sections.push_back(&Section);
1527 for (MCAssembler::iterator it = Asm.begin(),
1528 ie = Asm.end(); it != ie; ++it) {
1529 const MCSectionELF &Section =
1530 static_cast<const MCSectionELF &>(it->getSection());
1531 if (Section.getType() != ELF::SHT_GROUP &&
1532 Section.getType() != ELF::SHT_REL &&
1533 Section.getType() != ELF::SHT_RELA)
1534 Sections.push_back(&Section);
1537 for (MCAssembler::iterator it = Asm.begin(),
1538 ie = Asm.end(); it != ie; ++it) {
1539 const MCSectionELF &Section =
1540 static_cast<const MCSectionELF &>(it->getSection());
1541 if (Section.getType() == ELF::SHT_REL ||
1542 Section.getType() == ELF::SHT_RELA)
1543 Sections.push_back(&Section);
1547 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1548 const MCAsmLayout &Layout) {
1549 GroupMapTy GroupMap;
1550 RevGroupMapTy RevGroupMap;
1551 SectionIndexMapTy SectionIndexMap;
1553 unsigned NumUserSections = Asm.size();
1555 DenseMap<const MCSectionELF*, const MCSectionELF*> RelMap;
1556 CreateRelocationSections(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1558 const unsigned NumUserAndRelocSections = Asm.size();
1559 CreateIndexedSections(Asm, const_cast<MCAsmLayout&>(Layout), GroupMap,
1560 RevGroupMap, SectionIndexMap, RelMap);
1561 const unsigned AllSections = Asm.size();
1562 const unsigned NumIndexedSections = AllSections - NumUserAndRelocSections;
1564 unsigned NumRegularSections = NumUserSections + NumIndexedSections;
1566 // Compute symbol table information.
1567 ComputeSymbolTable(Asm, SectionIndexMap, RevGroupMap, NumRegularSections);
1570 WriteRelocations(Asm, const_cast<MCAsmLayout&>(Layout), RelMap);
1572 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1573 const_cast<MCAsmLayout&>(Layout),
1577 uint64_t NaturalAlignment = is64Bit() ? 8 : 4;
1578 uint64_t HeaderSize = is64Bit() ? sizeof(ELF::Elf64_Ehdr) :
1579 sizeof(ELF::Elf32_Ehdr);
1580 uint64_t FileOff = HeaderSize;
1582 std::vector<const MCSectionELF*> Sections;
1583 ComputeSectionOrder(Asm, Sections);
1584 unsigned NumSections = Sections.size();
1585 SectionOffsetMapTy SectionOffsetMap;
1586 for (unsigned i = 0; i < NumRegularSections + 1; ++i) {
1587 const MCSectionELF &Section = *Sections[i];
1588 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1590 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1592 // Remember the offset into the file for this section.
1593 SectionOffsetMap[&Section] = FileOff;
1595 // Get the size of the section in the output file (including padding).
1596 FileOff += GetSectionFileSize(Layout, SD);
1599 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1601 const unsigned SectionHeaderOffset = FileOff - HeaderSize;
1603 uint64_t SectionHeaderEntrySize = is64Bit() ?
1604 sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr);
1605 FileOff += (NumSections + 1) * SectionHeaderEntrySize;
1607 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i) {
1608 const MCSectionELF &Section = *Sections[i];
1609 const MCSectionData &SD = Asm.getOrCreateSectionData(Section);
1611 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1613 // Remember the offset into the file for this section.
1614 SectionOffsetMap[&Section] = FileOff;
1616 // Get the size of the section in the output file (including padding).
1617 FileOff += GetSectionFileSize(Layout, SD);
1620 // Write out the ELF header ...
1621 WriteHeader(Asm, SectionHeaderOffset, NumSections + 1);
1623 // ... then the regular sections ...
1624 // + because of .shstrtab
1625 for (unsigned i = 0; i < NumRegularSections + 1; ++i)
1626 WriteDataSectionData(Asm, Layout, *Sections[i]);
1628 uint64_t Padding = OffsetToAlignment(OS.tell(), NaturalAlignment);
1629 WriteZeros(Padding);
1631 // ... then the section header table ...
1632 WriteSectionHeader(Asm, GroupMap, Layout, SectionIndexMap,
1635 // ... and then the remaining sections ...
1636 for (unsigned i = NumRegularSections + 1; i < NumSections; ++i)
1637 WriteDataSectionData(Asm, Layout, *Sections[i]);
1641 ELFObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
1642 const MCSymbolData &DataA,
1643 const MCFragment &FB,
1645 bool IsPCRel) const {
1646 if (DataA.getFlags() & ELF_STB_Weak || MCELF::GetType(DataA) == ELF::STT_GNU_IFUNC)
1648 return MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(
1649 Asm, DataA, FB,InSet, IsPCRel);
1652 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
1654 bool IsLittleEndian) {
1655 return new ELFObjectWriter(MOTW, OS, IsLittleEndian);