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/ELFObjectWriter.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/StringMap.h"
18 #include "llvm/ADT/Twine.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCAsmLayout.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCELFSymbolFlags.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCObjectWriter.h"
25 #include "llvm/MC/MCSectionELF.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/MC/MCValue.h"
28 #include "llvm/Support/Debug.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Support/ELF.h"
31 #include "llvm/Target/TargetAsmBackend.h"
33 #include "../Target/X86/X86FixupKinds.h"
38 static unsigned GetType(const MCSymbolData &SD) {
39 uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
40 assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
41 Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
42 Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
43 Type == ELF::STT_TLS);
47 static unsigned GetBinding(const MCSymbolData &SD) {
48 uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
49 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
50 Binding == ELF::STB_WEAK);
54 static void SetBinding(MCSymbolData &SD, unsigned Binding) {
55 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
56 Binding == ELF::STB_WEAK);
57 uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
58 SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
61 static unsigned GetVisibility(MCSymbolData &SD) {
63 (SD.getFlags() & (0xf << ELF_STV_Shift)) >> ELF_STV_Shift;
64 assert(Visibility == ELF::STV_DEFAULT || Visibility == ELF::STV_INTERNAL ||
65 Visibility == ELF::STV_HIDDEN || Visibility == ELF::STV_PROTECTED);
69 static bool isFixupKindX86PCRel(unsigned Kind) {
73 case X86::reloc_pcrel_1byte:
74 case X86::reloc_pcrel_4byte:
75 case X86::reloc_riprel_4byte:
76 case X86::reloc_riprel_4byte_movq_load:
81 static bool RelocNeedsGOT(MCSymbolRefExpr::VariantKind Variant) {
85 case MCSymbolRefExpr::VK_GOT:
86 case MCSymbolRefExpr::VK_PLT:
87 case MCSymbolRefExpr::VK_GOTPCREL:
88 case MCSymbolRefExpr::VK_TPOFF:
89 case MCSymbolRefExpr::VK_TLSGD:
90 case MCSymbolRefExpr::VK_GOTTPOFF:
91 case MCSymbolRefExpr::VK_INDNTPOFF:
92 case MCSymbolRefExpr::VK_NTPOFF:
93 case MCSymbolRefExpr::VK_GOTNTPOFF:
94 case MCSymbolRefExpr::VK_TLSLDM:
95 case MCSymbolRefExpr::VK_DTPOFF:
96 case MCSymbolRefExpr::VK_TLSLD:
103 class ELFObjectWriterImpl {
104 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
105 return Kind == X86::reloc_riprel_4byte ||
106 Kind == X86::reloc_riprel_4byte_movq_load;
110 /// ELFSymbolData - Helper struct for containing some precomputed information
112 struct ELFSymbolData {
113 MCSymbolData *SymbolData;
114 uint64_t StringIndex;
115 uint32_t SectionIndex;
117 // Support lexicographic sorting.
118 bool operator<(const ELFSymbolData &RHS) const {
119 if (GetType(*SymbolData) == ELF::STT_FILE)
121 if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
123 return SymbolData->getSymbol().getName() <
124 RHS.SymbolData->getSymbol().getName();
128 /// @name Relocation Data
131 struct ELFRelocationEntry {
132 // Make these big enough for both 32-bit and 64-bit
136 const MCSymbol *Symbol;
139 // Support lexicographic sorting.
140 bool operator<(const ELFRelocationEntry &RE) const {
141 return RE.r_offset < r_offset;
145 SmallPtrSet<const MCSymbol *, 16> UsedInReloc;
146 DenseMap<const MCSymbol *, const MCSymbol *> Renames;
148 llvm::DenseMap<const MCSectionData*,
149 std::vector<ELFRelocationEntry> > Relocations;
150 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
153 /// @name Symbol Table Data
156 SmallString<256> StringTable;
157 std::vector<ELFSymbolData> LocalSymbolData;
158 std::vector<ELFSymbolData> ExternalSymbolData;
159 std::vector<ELFSymbolData> UndefinedSymbolData;
163 int NumRegularSections;
167 ELFObjectWriter *Writer;
171 unsigned Is64Bit : 1;
173 bool HasRelocationAddend;
175 Triple::OSType OSType;
179 // This holds the symbol table index of the last local symbol.
180 unsigned LastLocalSymbolIndex;
181 // This holds the .strtab section index.
182 unsigned StringTableIndex;
184 unsigned ShstrtabIndex;
187 ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
188 uint16_t _EMachine, bool _HasRelAddend,
189 Triple::OSType _OSType)
190 : NeedsGOT(false), Writer(_Writer), OS(Writer->getStream()),
191 Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
192 OSType(_OSType), EMachine(_EMachine) {
195 void Write8(uint8_t Value) { Writer->Write8(Value); }
196 void Write16(uint16_t Value) { Writer->Write16(Value); }
197 void Write32(uint32_t Value) { Writer->Write32(Value); }
198 //void Write64(uint64_t Value) { Writer->Write64(Value); }
199 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
200 //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
201 // Writer->WriteBytes(Str, ZeroFillSize);
204 void WriteWord(uint64_t W) {
211 void String8(char *buf, uint8_t Value) {
215 void StringLE16(char *buf, uint16_t Value) {
216 buf[0] = char(Value >> 0);
217 buf[1] = char(Value >> 8);
220 void StringLE32(char *buf, uint32_t Value) {
221 StringLE16(buf, uint16_t(Value >> 0));
222 StringLE16(buf + 2, uint16_t(Value >> 16));
225 void StringLE64(char *buf, uint64_t Value) {
226 StringLE32(buf, uint32_t(Value >> 0));
227 StringLE32(buf + 4, uint32_t(Value >> 32));
230 void StringBE16(char *buf ,uint16_t Value) {
231 buf[0] = char(Value >> 8);
232 buf[1] = char(Value >> 0);
235 void StringBE32(char *buf, uint32_t Value) {
236 StringBE16(buf, uint16_t(Value >> 16));
237 StringBE16(buf + 2, uint16_t(Value >> 0));
240 void StringBE64(char *buf, uint64_t Value) {
241 StringBE32(buf, uint32_t(Value >> 32));
242 StringBE32(buf + 4, uint32_t(Value >> 0));
245 void String16(char *buf, uint16_t Value) {
246 if (Writer->isLittleEndian())
247 StringLE16(buf, Value);
249 StringBE16(buf, Value);
252 void String32(char *buf, uint32_t Value) {
253 if (Writer->isLittleEndian())
254 StringLE32(buf, Value);
256 StringBE32(buf, Value);
259 void String64(char *buf, uint64_t Value) {
260 if (Writer->isLittleEndian())
261 StringLE64(buf, Value);
263 StringBE64(buf, Value);
266 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
268 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
269 uint64_t value, uint64_t size,
270 uint8_t other, uint16_t shndx);
272 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
273 const MCAsmLayout &Layout);
275 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
276 const MCAsmLayout &Layout,
277 unsigned NumRegularSections);
279 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
280 const MCFragment *Fragment, const MCFixup &Fixup,
281 MCValue Target, uint64_t &FixedValue);
283 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
286 /// ComputeSymbolTable - Compute the symbol table data
288 /// \param StringTable [out] - The string table data.
289 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
291 void ComputeSymbolTable(MCAssembler &Asm);
293 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
294 const MCSectionData &SD);
296 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
297 for (MCAssembler::const_iterator it = Asm.begin(),
298 ie = Asm.end(); it != ie; ++it) {
299 WriteRelocation(Asm, Layout, *it);
303 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
305 void ExecutePostLayoutBinding(MCAssembler &Asm);
307 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
308 uint64_t Address, uint64_t Offset,
309 uint64_t Size, uint32_t Link, uint32_t Info,
310 uint64_t Alignment, uint64_t EntrySize);
312 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
313 const MCSectionData *SD);
315 bool IsFixupFullyResolved(const MCAssembler &Asm,
316 const MCValue Target,
318 const MCFragment *DF) const;
320 void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
325 // Emit the ELF header.
326 void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
327 unsigned NumberOfSections) {
333 // emitWord method behaves differently for ELF32 and ELF64, writing
334 // 4 bytes in the former and 8 in the latter.
336 Write8(0x7f); // e_ident[EI_MAG0]
337 Write8('E'); // e_ident[EI_MAG1]
338 Write8('L'); // e_ident[EI_MAG2]
339 Write8('F'); // e_ident[EI_MAG3]
341 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
344 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
346 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
349 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break;
350 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break;
351 default: Write8(ELF::ELFOSABI_NONE); break;
353 Write8(0); // e_ident[EI_ABIVERSION]
355 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
357 Write16(ELF::ET_REL); // e_type
359 Write16(EMachine); // e_machine = target
361 Write32(ELF::EV_CURRENT); // e_version
362 WriteWord(0); // e_entry, no entry point in .o file
363 WriteWord(0); // e_phoff, no program header for .o
364 WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
365 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
367 // FIXME: Make this configurable.
368 Write32(0); // e_flags = whatever the target wants
370 // e_ehsize = ELF header size
371 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
373 Write16(0); // e_phentsize = prog header entry size
374 Write16(0); // e_phnum = # prog header entries = 0
376 // e_shentsize = Section header entry size
377 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
379 // e_shnum = # of section header ents
380 Write16(NumberOfSections);
382 // e_shstrndx = Section # of '.shstrtab'
383 Write16(ShstrtabIndex);
386 void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
387 uint8_t info, uint64_t value,
388 uint64_t size, uint8_t other,
394 F->getContents() += StringRef(buf, 4); // st_name
397 F->getContents() += StringRef(buf, 1); // st_info
400 F->getContents() += StringRef(buf, 1); // st_other
402 String16(buf, shndx);
403 F->getContents() += StringRef(buf, 2); // st_shndx
405 String64(buf, value);
406 F->getContents() += StringRef(buf, 8); // st_value
409 F->getContents() += StringRef(buf, 8); // st_size
414 F->getContents() += StringRef(buf, 4); // st_name
416 String32(buf, value);
417 F->getContents() += StringRef(buf, 4); // st_value
420 F->getContents() += StringRef(buf, 4); // st_size
423 F->getContents() += StringRef(buf, 1); // st_info
426 F->getContents() += StringRef(buf, 1); // st_other
428 String16(buf, shndx);
429 F->getContents() += StringRef(buf, 2); // st_shndx
433 static uint64_t SymbolValue(MCSymbolData &Data, const MCAsmLayout &Layout) {
434 if (Data.isCommon() && Data.isExternal())
435 return Data.getCommonAlignment();
437 const MCSymbol &Symbol = Data.getSymbol();
438 if (!Symbol.isInSection())
441 if (!Data.isCommon() && !(Data.getFlags() & ELF_STB_Weak))
442 if (MCFragment *FF = Data.getFragment())
443 return Layout.getSymbolAddress(&Data) -
444 Layout.getSectionAddress(FF->getParent());
449 static const MCSymbol &AliasedSymbol(const MCSymbol &Symbol) {
450 const MCSymbol *S = &Symbol;
451 while (S->isVariable()) {
452 const MCExpr *Value = S->getVariableValue();
453 if (Value->getKind() != MCExpr::SymbolRef)
455 const MCSymbolRefExpr *Ref = static_cast<const MCSymbolRefExpr*>(Value);
456 S = &Ref->getSymbol();
461 void ELFObjectWriterImpl::ExecutePostLayoutBinding(MCAssembler &Asm) {
462 // The presence of symbol versions causes undefined symbols and
463 // versions declared with @@@ to be renamed.
465 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
466 ie = Asm.symbol_end(); it != ie; ++it) {
467 const MCSymbol &Alias = it->getSymbol();
468 if (!Alias.isVariable())
470 const MCSymbol &Symbol = AliasedSymbol(Alias);
471 StringRef AliasName = Alias.getName();
472 size_t Pos = AliasName.find('@');
473 if (Pos == StringRef::npos)
476 StringRef Rest = AliasName.substr(Pos);
477 if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
480 // FIXME: produce a better error message.
481 if (Symbol.isUndefined() && Rest.startswith("@@") &&
482 !Rest.startswith("@@@"))
483 report_fatal_error("A @@ version cannot be undefined");
485 Renames.insert(std::make_pair(&Symbol, &Alias));
489 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
490 const MCAsmLayout &Layout) {
491 MCSymbolData &OrigData = *MSD.SymbolData;
493 Layout.getAssembler().getSymbolData(AliasedSymbol(OrigData.getSymbol()));
495 uint8_t Binding = GetBinding(OrigData);
496 uint8_t Visibility = GetVisibility(OrigData);
497 uint8_t Type = GetType(Data);
499 uint8_t Info = (Binding << ELF_STB_Shift) | (Type << ELF_STT_Shift);
500 uint8_t Other = Visibility;
502 uint64_t Value = SymbolValue(Data, Layout);
506 assert(!(Data.isCommon() && !Data.isExternal()));
508 ESize = Data.getSize();
509 if (Data.getSize()) {
511 if (ESize->getKind() == MCExpr::Binary) {
512 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
514 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
515 assert(!Res.getSymA() || !Res.getSymA()->getSymbol().isDefined());
516 assert(!Res.getSymB() || !Res.getSymB()->getSymbol().isDefined());
517 Size = Res.getConstant();
519 } else if (ESize->getKind() == MCExpr::Constant) {
520 Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
522 assert(0 && "Unsupported size expression");
526 // Write out the symbol table entry
527 WriteSymbolEntry(F, MSD.StringIndex, Info, Value,
528 Size, Other, MSD.SectionIndex);
531 void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F,
532 const MCAssembler &Asm,
533 const MCAsmLayout &Layout,
534 unsigned NumRegularSections) {
535 // The string table must be emitted first because we need the index
536 // into the string table for all the symbol names.
537 assert(StringTable.size() && "Missing string table");
539 // FIXME: Make sure the start of the symbol table is aligned.
541 // The first entry is the undefined symbol entry.
542 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
543 F->getContents().append(EntrySize, '\x00');
545 // Write the symbol table entries.
546 LastLocalSymbolIndex = LocalSymbolData.size() + 1;
547 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
548 ELFSymbolData &MSD = LocalSymbolData[i];
549 WriteSymbol(F, MSD, Layout);
552 // Write out a symbol table entry for each regular section.
554 for (MCAssembler::const_iterator it = Asm.begin();
555 Index <= NumRegularSections; ++it, ++Index) {
556 const MCSectionELF &Section =
557 static_cast<const MCSectionELF&>(it->getSection());
558 // Leave out relocations so we don't have indexes within
559 // the relocations messed up
560 if (Section.getType() == ELF::SHT_RELA || Section.getType() == ELF::SHT_REL)
562 WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index);
563 LastLocalSymbolIndex++;
566 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
567 ELFSymbolData &MSD = ExternalSymbolData[i];
568 MCSymbolData &Data = *MSD.SymbolData;
569 assert(((Data.getFlags() & ELF_STB_Global) ||
570 (Data.getFlags() & ELF_STB_Weak)) &&
571 "External symbol requires STB_GLOBAL or STB_WEAK flag");
572 WriteSymbol(F, MSD, Layout);
573 if (GetBinding(Data) == ELF::STB_LOCAL)
574 LastLocalSymbolIndex++;
577 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
578 ELFSymbolData &MSD = UndefinedSymbolData[i];
579 MCSymbolData &Data = *MSD.SymbolData;
580 WriteSymbol(F, MSD, Layout);
581 if (GetBinding(Data) == ELF::STB_LOCAL)
582 LastLocalSymbolIndex++;
586 static bool ShouldRelocOnSymbol(const MCSymbolData &SD,
587 const MCValue &Target,
588 const MCFragment &F) {
589 const MCSymbol &Symbol = SD.getSymbol();
590 if (Symbol.isUndefined())
593 const MCSectionELF &Section =
594 static_cast<const MCSectionELF&>(Symbol.getSection());
599 MCSymbolRefExpr::VariantKind Kind = Target.getSymA()->getKind();
600 const MCSectionELF &Sec2 =
601 static_cast<const MCSectionELF&>(F.getParent()->getSection());
603 if (Section.getKind().isBSS())
606 if (&Sec2 != &Section &&
607 (Kind == MCSymbolRefExpr::VK_PLT ||
608 Kind == MCSymbolRefExpr::VK_GOTPCREL ||
609 Kind == MCSymbolRefExpr::VK_GOTOFF))
612 if (Section.getFlags() & MCSectionELF::SHF_MERGE)
613 return Target.getConstant() != 0;
618 // FIXME: this is currently X86/X86_64 only
619 void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
620 const MCAsmLayout &Layout,
621 const MCFragment *Fragment,
622 const MCFixup &Fixup,
624 uint64_t &FixedValue) {
627 int64_t Value = Target.getConstant();
628 const MCSymbol *Symbol = 0;
630 bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
631 if (!Target.isAbsolute()) {
632 Symbol = &AliasedSymbol(Target.getSymA()->getSymbol());
633 const MCSymbol *Renamed = Renames.lookup(Symbol);
636 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
637 MCFragment *F = SD.getFragment();
639 if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
640 const MCSymbol &SymbolB = RefB->getSymbol();
641 MCSymbolData &SDB = Asm.getSymbolData(SymbolB);
643 MCSectionData *Sec = Fragment->getParent();
645 // Offset of the symbol in the section
646 int64_t a = Layout.getSymbolAddress(&SDB) - Layout.getSectionAddress(Sec);
648 // Ofeset of the relocation in the section
649 int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
653 // Check that this case has already been fully resolved before we get
655 if (Symbol->isDefined() && !SD.isExternal() &&
657 &Fragment->getParent()->getSection() == &Symbol->getSection()) {
658 llvm_unreachable("We don't need a relocation in this case.");
662 bool RelocOnSymbol = ShouldRelocOnSymbol(SD, Target, *Fragment);
663 if (!RelocOnSymbol) {
664 Index = F->getParent()->getOrdinal();
666 MCSectionData *FSD = F->getParent();
667 // Offset of the symbol in the section
668 Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
670 UsedInReloc.insert(Symbol);
674 // Compensate for the addend on i386.
681 // determine the type of the relocation
683 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
689 llvm_unreachable("Unimplemented");
690 case MCSymbolRefExpr::VK_None:
691 Type = ELF::R_X86_64_PC32;
693 case MCSymbolRefExpr::VK_PLT:
694 Type = ELF::R_X86_64_PLT32;
696 case MCSymbolRefExpr::VK_GOTPCREL:
697 Type = ELF::R_X86_64_GOTPCREL;
699 case MCSymbolRefExpr::VK_GOTTPOFF:
700 Type = ELF::R_X86_64_GOTTPOFF;
702 case MCSymbolRefExpr::VK_TLSGD:
703 Type = ELF::R_X86_64_TLSGD;
705 case MCSymbolRefExpr::VK_TLSLD:
706 Type = ELF::R_X86_64_TLSLD;
710 switch ((unsigned)Fixup.getKind()) {
711 default: llvm_unreachable("invalid fixup kind!");
712 case FK_Data_8: Type = ELF::R_X86_64_64; break;
713 case X86::reloc_signed_4byte:
714 case X86::reloc_pcrel_4byte:
715 assert(isInt<32>(Target.getConstant()));
718 llvm_unreachable("Unimplemented");
719 case MCSymbolRefExpr::VK_None:
720 Type = ELF::R_X86_64_32S;
722 case MCSymbolRefExpr::VK_GOT:
723 Type = ELF::R_X86_64_GOT32;
725 case MCSymbolRefExpr::VK_GOTPCREL:
726 Type = ELF::R_X86_64_GOTPCREL;
728 case MCSymbolRefExpr::VK_TPOFF:
729 Type = ELF::R_X86_64_TPOFF32;
734 Type = ELF::R_X86_64_32;
736 case FK_Data_2: Type = ELF::R_X86_64_16; break;
737 case X86::reloc_pcrel_1byte:
738 case FK_Data_1: Type = ELF::R_X86_64_8; break;
745 llvm_unreachable("Unimplemented");
746 case MCSymbolRefExpr::VK_None:
747 Type = ELF::R_386_PC32;
749 case MCSymbolRefExpr::VK_PLT:
750 Type = ELF::R_386_PLT32;
754 switch ((unsigned)Fixup.getKind()) {
755 default: llvm_unreachable("invalid fixup kind!");
757 case X86::reloc_global_offset_table:
758 Type = ELF::R_386_GOTPC;
761 // FIXME: Should we avoid selecting reloc_signed_4byte in 32 bit mode
763 case X86::reloc_signed_4byte:
764 case X86::reloc_pcrel_4byte:
768 llvm_unreachable("Unimplemented");
769 case MCSymbolRefExpr::VK_None:
770 Type = ELF::R_386_32;
772 case MCSymbolRefExpr::VK_GOT:
773 Type = ELF::R_386_GOT32;
775 case MCSymbolRefExpr::VK_GOTOFF:
776 Type = ELF::R_386_GOTOFF;
778 case MCSymbolRefExpr::VK_TLSGD:
779 Type = ELF::R_386_TLS_GD;
781 case MCSymbolRefExpr::VK_TPOFF:
782 Type = ELF::R_386_TLS_LE_32;
784 case MCSymbolRefExpr::VK_INDNTPOFF:
785 Type = ELF::R_386_TLS_IE;
787 case MCSymbolRefExpr::VK_NTPOFF:
788 Type = ELF::R_386_TLS_LE;
790 case MCSymbolRefExpr::VK_GOTNTPOFF:
791 Type = ELF::R_386_TLS_GOTIE;
793 case MCSymbolRefExpr::VK_TLSLDM:
794 Type = ELF::R_386_TLS_LDM;
796 case MCSymbolRefExpr::VK_DTPOFF:
797 Type = ELF::R_386_TLS_LDO_32;
801 case FK_Data_2: Type = ELF::R_386_16; break;
802 case X86::reloc_pcrel_1byte:
803 case FK_Data_1: Type = ELF::R_386_8; break;
808 if (RelocNeedsGOT(Modifier))
811 ELFRelocationEntry ERE;
817 ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
819 if (HasRelocationAddend)
820 ERE.r_addend = Addend;
822 ERE.r_addend = 0; // Silence compiler warning.
824 Relocations[Fragment->getParent()].push_back(ERE);
828 ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
830 MCSymbolData &SD = Asm.getSymbolData(*S);
833 if (!SD.isExternal() && !S->isUndefined())
834 return SD.getIndex() + /* empty symbol */ 1;
836 // External or undefined symbol.
837 return SD.getIndex() + NumRegularSections + /* empty symbol */ 1;
840 static bool isInSymtab(const MCAssembler &Asm, const MCSymbolData &Data,
841 bool Used, bool Renamed) {
848 const MCSymbol &Symbol = Data.getSymbol();
850 const MCSymbol &A = AliasedSymbol(Symbol);
851 if (&A != &Symbol && A.isUndefined())
854 if (!Asm.isSymbolLinkerVisible(Symbol) && !Symbol.isUndefined())
857 if (Symbol.isTemporary())
863 static bool isLocal(const MCSymbolData &Data) {
864 if (Data.isExternal())
867 const MCSymbol &Symbol = Data.getSymbol();
868 if (Symbol.isUndefined() && !Symbol.isVariable())
874 void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
875 // FIXME: Is this the correct place to do this?
877 llvm::StringRef Name = "_GLOBAL_OFFSET_TABLE_";
878 MCSymbol *Sym = Asm.getContext().GetOrCreateSymbol(Name);
879 MCSymbolData &Data = Asm.getOrCreateSymbolData(*Sym);
880 Data.setExternal(true);
883 // Build section lookup table.
884 NumRegularSections = Asm.size();
885 DenseMap<const MCSection*, uint32_t> SectionIndexMap;
887 for (MCAssembler::iterator it = Asm.begin(),
888 ie = Asm.end(); it != ie; ++it, ++Index)
889 SectionIndexMap[&it->getSection()] = Index;
891 // Index 0 is always the empty string.
892 StringMap<uint64_t> StringIndexMap;
893 StringTable += '\x00';
895 // Add the data for the symbols.
896 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
897 ie = Asm.symbol_end(); it != ie; ++it) {
898 const MCSymbol &Symbol = it->getSymbol();
900 if (!isInSymtab(Asm, *it, UsedInReloc.count(&Symbol),
901 Renames.count(&Symbol)))
906 bool Local = isLocal(*it);
907 const MCSymbol &RefSymbol = AliasedSymbol(Symbol);
909 if (it->isCommon()) {
911 MSD.SectionIndex = ELF::SHN_COMMON;
912 } else if (Symbol.isAbsolute() || RefSymbol.isVariable()) {
913 MSD.SectionIndex = ELF::SHN_ABS;
914 } else if (RefSymbol.isUndefined()) {
915 MSD.SectionIndex = ELF::SHN_UNDEF;
916 // FIXME: Undefined symbols are global, but this is the first place we
917 // are able to set it.
918 if (GetBinding(*it) == ELF::STB_LOCAL)
919 SetBinding(*it, ELF::STB_GLOBAL);
921 MSD.SectionIndex = SectionIndexMap.lookup(&RefSymbol.getSection());
922 assert(MSD.SectionIndex && "Invalid section index!");
925 // The @@@ in symbol version is replaced with @ in undefined symbols and
926 // @@ in defined ones.
927 StringRef Name = Symbol.getName();
928 size_t Pos = Name.find("@@@");
929 std::string FinalName;
930 if (Pos != StringRef::npos) {
931 StringRef Prefix = Name.substr(0, Pos);
932 unsigned n = MSD.SectionIndex == ELF::SHN_UNDEF ? 2 : 1;
933 StringRef Suffix = Name.substr(Pos + n);
934 FinalName = Prefix.str() + Suffix.str();
936 FinalName = Name.str();
939 uint64_t &Entry = StringIndexMap[FinalName];
941 Entry = StringTable.size();
942 StringTable += FinalName;
943 StringTable += '\x00';
945 MSD.StringIndex = Entry;
946 if (MSD.SectionIndex == ELF::SHN_UNDEF)
947 UndefinedSymbolData.push_back(MSD);
949 LocalSymbolData.push_back(MSD);
951 ExternalSymbolData.push_back(MSD);
954 // Symbols are required to be in lexicographic order.
955 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
956 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
957 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
959 // Set the symbol indices. Local symbols must come before all other
960 // symbols with non-local bindings.
962 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
963 LocalSymbolData[i].SymbolData->setIndex(Index++);
964 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
965 ExternalSymbolData[i].SymbolData->setIndex(Index++);
966 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
967 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
970 void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
971 const MCSectionData &SD) {
972 if (!Relocations[&SD].empty()) {
973 MCContext &Ctx = Asm.getContext();
974 const MCSection *RelaSection;
975 const MCSectionELF &Section =
976 static_cast<const MCSectionELF&>(SD.getSection());
978 const StringRef SectionName = Section.getSectionName();
979 std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
980 RelaSectionName += SectionName;
983 if (HasRelocationAddend)
984 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
986 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
988 RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
989 ELF::SHT_RELA : ELF::SHT_REL, 0,
990 SectionKind::getReadOnly(),
993 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
994 RelaSD.setAlignment(Is64Bit ? 8 : 4);
996 MCDataFragment *F = new MCDataFragment(&RelaSD);
998 WriteRelocationsFragment(Asm, F, &SD);
1000 Asm.AddSectionToTheEnd(*Writer, RelaSD, Layout);
1004 void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
1005 uint64_t Flags, uint64_t Address,
1006 uint64_t Offset, uint64_t Size,
1007 uint32_t Link, uint32_t Info,
1009 uint64_t EntrySize) {
1010 Write32(Name); // sh_name: index into string table
1011 Write32(Type); // sh_type
1012 WriteWord(Flags); // sh_flags
1013 WriteWord(Address); // sh_addr
1014 WriteWord(Offset); // sh_offset
1015 WriteWord(Size); // sh_size
1016 Write32(Link); // sh_link
1017 Write32(Info); // sh_info
1018 WriteWord(Alignment); // sh_addralign
1019 WriteWord(EntrySize); // sh_entsize
1022 void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
1024 const MCSectionData *SD) {
1025 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
1026 // sort by the r_offset just like gnu as does
1027 array_pod_sort(Relocs.begin(), Relocs.end());
1029 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
1030 ELFRelocationEntry entry = Relocs[e - i - 1];
1032 if (entry.Index < 0)
1033 entry.Index = getSymbolIndexInSymbolTable(Asm, entry.Symbol);
1035 entry.Index += LocalSymbolData.size() + 1;
1039 String64(buf, entry.r_offset);
1040 F->getContents() += StringRef(buf, 8);
1042 struct ELF::Elf64_Rela ERE64;
1043 ERE64.setSymbolAndType(entry.Index, entry.Type);
1044 String64(buf, ERE64.r_info);
1045 F->getContents() += StringRef(buf, 8);
1047 if (HasRelocationAddend) {
1048 String64(buf, entry.r_addend);
1049 F->getContents() += StringRef(buf, 8);
1054 String32(buf, entry.r_offset);
1055 F->getContents() += StringRef(buf, 4);
1057 struct ELF::Elf32_Rela ERE32;
1058 ERE32.setSymbolAndType(entry.Index, entry.Type);
1059 String32(buf, ERE32.r_info);
1060 F->getContents() += StringRef(buf, 4);
1062 if (HasRelocationAddend) {
1063 String32(buf, entry.r_addend);
1064 F->getContents() += StringRef(buf, 4);
1070 void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
1071 MCAsmLayout &Layout) {
1072 MCContext &Ctx = Asm.getContext();
1075 const MCSection *SymtabSection;
1076 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
1078 unsigned NumRegularSections = Asm.size();
1080 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
1081 const MCSection *ShstrtabSection;
1082 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
1083 SectionKind::getReadOnly(), false);
1084 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
1085 ShstrtabSD.setAlignment(1);
1086 ShstrtabIndex = Asm.size();
1088 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1089 SectionKind::getReadOnly(),
1091 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
1092 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
1094 const MCSection *StrtabSection;
1095 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
1096 SectionKind::getReadOnly(), false);
1097 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
1098 StrtabSD.setAlignment(1);
1099 StringTableIndex = Asm.size();
1101 WriteRelocations(Asm, Layout);
1104 F = new MCDataFragment(&SymtabSD);
1105 WriteSymbolTable(F, Asm, Layout, NumRegularSections);
1106 Asm.AddSectionToTheEnd(*Writer, SymtabSD, Layout);
1108 F = new MCDataFragment(&StrtabSD);
1109 F->getContents().append(StringTable.begin(), StringTable.end());
1110 Asm.AddSectionToTheEnd(*Writer, StrtabSD, Layout);
1112 F = new MCDataFragment(&ShstrtabSD);
1114 // Section header string table.
1116 // The first entry of a string table holds a null character so skip
1119 F->getContents() += '\x00';
1121 for (MCAssembler::const_iterator it = Asm.begin(),
1122 ie = Asm.end(); it != ie; ++it) {
1123 const MCSectionELF &Section =
1124 static_cast<const MCSectionELF&>(it->getSection());
1125 // FIXME: We could merge suffixes like in .text and .rela.text.
1127 // Remember the index into the string table so we can write it
1128 // into the sh_name field of the section header table.
1129 SectionStringTableIndex[&it->getSection()] = Index;
1131 Index += Section.getSectionName().size() + 1;
1132 F->getContents() += Section.getSectionName();
1133 F->getContents() += '\x00';
1136 Asm.AddSectionToTheEnd(*Writer, ShstrtabSD, Layout);
1139 bool ELFObjectWriterImpl::IsFixupFullyResolved(const MCAssembler &Asm,
1140 const MCValue Target,
1142 const MCFragment *DF) const {
1143 // If this is a PCrel relocation, find the section this fixup value is
1145 const MCSection *BaseSection = 0;
1147 BaseSection = &DF->getParent()->getSection();
1148 assert(BaseSection);
1151 const MCSection *SectionA = 0;
1152 const MCSymbol *SymbolA = 0;
1153 if (const MCSymbolRefExpr *A = Target.getSymA()) {
1154 SymbolA = &A->getSymbol();
1155 SectionA = &SymbolA->getSection();
1158 const MCSection *SectionB = 0;
1159 if (const MCSymbolRefExpr *B = Target.getSymB()) {
1160 SectionB = &B->getSymbol().getSection();
1164 return SectionA == SectionB;
1166 const MCSymbolData &DataA = Asm.getSymbolData(*SymbolA);
1167 if (DataA.isExternal())
1170 return !SectionB && BaseSection == SectionA;
1173 void ELFObjectWriterImpl::WriteObject(MCAssembler &Asm,
1174 const MCAsmLayout &Layout) {
1175 // Compute symbol table information.
1176 ComputeSymbolTable(Asm);
1178 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
1179 const_cast<MCAsmLayout&>(Layout));
1181 // Add 1 for the null section.
1182 unsigned NumSections = Asm.size() + 1;
1183 uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
1184 uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
1185 uint64_t FileOff = HeaderSize;
1187 for (MCAssembler::const_iterator it = Asm.begin(),
1188 ie = Asm.end(); it != ie; ++it) {
1189 const MCSectionData &SD = *it;
1191 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
1193 // Get the size of the section in the output file (including padding).
1194 uint64_t Size = Layout.getSectionFileSize(&SD);
1199 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
1201 // Write out the ELF header ...
1202 WriteHeader(FileOff - HeaderSize, NumSections);
1204 FileOff = HeaderSize;
1206 // ... then all of the sections ...
1207 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
1209 DenseMap<const MCSection*, uint32_t> SectionIndexMap;
1212 for (MCAssembler::const_iterator it = Asm.begin(),
1213 ie = Asm.end(); it != ie; ++it) {
1214 const MCSectionData &SD = *it;
1216 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
1217 WriteZeros(Padding);
1220 // Remember the offset into the file for this section.
1221 SectionOffsetMap[&it->getSection()] = FileOff;
1222 SectionIndexMap[&it->getSection()] = Index++;
1224 FileOff += Layout.getSectionFileSize(&SD);
1226 Asm.WriteSectionData(it, Layout, Writer);
1229 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
1230 WriteZeros(Padding);
1233 // ... and then the section header table.
1234 // Should we align the section header table?
1236 // Null section first.
1237 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
1239 for (MCAssembler::const_iterator it = Asm.begin(),
1240 ie = Asm.end(); it != ie; ++it) {
1241 const MCSectionData &SD = *it;
1242 const MCSectionELF &Section =
1243 static_cast<const MCSectionELF&>(SD.getSection());
1245 uint64_t sh_link = 0;
1246 uint64_t sh_info = 0;
1248 switch(Section.getType()) {
1249 case ELF::SHT_DYNAMIC:
1250 sh_link = SectionStringTableIndex[&it->getSection()];
1255 case ELF::SHT_RELA: {
1256 const MCSection *SymtabSection;
1257 const MCSection *InfoSection;
1259 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
1260 SectionKind::getReadOnly(),
1262 sh_link = SectionIndexMap[SymtabSection];
1264 // Remove ".rel" and ".rela" prefixes.
1265 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
1266 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
1268 InfoSection = Asm.getContext().getELFSection(SectionName,
1269 ELF::SHT_PROGBITS, 0,
1270 SectionKind::getReadOnly(),
1272 sh_info = SectionIndexMap[InfoSection];
1276 case ELF::SHT_SYMTAB:
1277 case ELF::SHT_DYNSYM:
1278 sh_link = StringTableIndex;
1279 sh_info = LastLocalSymbolIndex;
1282 case ELF::SHT_PROGBITS:
1283 case ELF::SHT_STRTAB:
1284 case ELF::SHT_NOBITS:
1286 case ELF::SHT_ARM_ATTRIBUTES:
1291 assert(0 && "FIXME: sh_type value not supported!");
1295 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
1296 Section.getType(), Section.getFlags(),
1298 SectionOffsetMap.lookup(&SD.getSection()),
1299 Layout.getSectionSize(&SD), sh_link,
1300 sh_info, SD.getAlignment(),
1301 Section.getEntrySize());
1305 ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
1307 Triple::OSType OSType,
1309 bool IsLittleEndian,
1310 bool HasRelocationAddend)
1311 : MCObjectWriter(OS, IsLittleEndian)
1313 Impl = new ELFObjectWriterImpl(this, Is64Bit, EMachine,
1314 HasRelocationAddend, OSType);
1317 ELFObjectWriter::~ELFObjectWriter() {
1318 delete (ELFObjectWriterImpl*) Impl;
1321 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
1322 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
1325 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1326 const MCAsmLayout &Layout,
1327 const MCFragment *Fragment,
1328 const MCFixup &Fixup, MCValue Target,
1329 uint64_t &FixedValue) {
1330 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
1331 Target, FixedValue);
1334 bool ELFObjectWriter::IsFixupFullyResolved(const MCAssembler &Asm,
1335 const MCValue Target,
1337 const MCFragment *DF) const {
1338 return ((ELFObjectWriterImpl*) Impl)->IsFixupFullyResolved(Asm, Target,
1342 void ELFObjectWriter::WriteObject(MCAssembler &Asm,
1343 const MCAsmLayout &Layout) {
1344 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);