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/STLExtras.h"
16 #include "llvm/ADT/StringMap.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/MC/MCAssembler.h"
19 #include "llvm/MC/MCAsmLayout.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCELFSymbolFlags.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCObjectWriter.h"
24 #include "llvm/MC/MCSectionELF.h"
25 #include "llvm/MC/MCSymbol.h"
26 #include "llvm/MC/MCValue.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/ELF.h"
30 #include "llvm/Target/TargetAsmBackend.h"
32 #include "../Target/X86/X86FixupKinds.h"
37 static unsigned GetType(const MCSymbolData &SD) {
38 uint32_t Type = (SD.getFlags() & (0xf << ELF_STT_Shift)) >> ELF_STT_Shift;
39 assert(Type == ELF::STT_NOTYPE || Type == ELF::STT_OBJECT ||
40 Type == ELF::STT_FUNC || Type == ELF::STT_SECTION ||
41 Type == ELF::STT_FILE || Type == ELF::STT_COMMON ||
42 Type == ELF::STT_TLS);
46 static unsigned GetBinding(const MCSymbolData &SD) {
47 uint32_t Binding = (SD.getFlags() & (0xf << ELF_STB_Shift)) >> ELF_STB_Shift;
48 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
49 Binding == ELF::STB_WEAK);
53 static void SetBinding(MCSymbolData &SD, unsigned Binding) {
54 assert(Binding == ELF::STB_LOCAL || Binding == ELF::STB_GLOBAL ||
55 Binding == ELF::STB_WEAK);
56 uint32_t OtherFlags = SD.getFlags() & ~(0xf << ELF_STB_Shift);
57 SD.setFlags(OtherFlags | (Binding << ELF_STB_Shift));
62 class ELFObjectWriterImpl {
63 static bool isFixupKindX86PCRel(unsigned Kind) {
67 case X86::reloc_pcrel_1byte:
68 case X86::reloc_pcrel_4byte:
69 case X86::reloc_riprel_4byte:
70 case X86::reloc_riprel_4byte_movq_load:
75 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
76 return Kind == X86::reloc_riprel_4byte ||
77 Kind == X86::reloc_riprel_4byte_movq_load;
81 /// ELFSymbolData - Helper struct for containing some precomputed information
83 struct ELFSymbolData {
84 MCSymbolData *SymbolData;
86 uint32_t SectionIndex;
88 // Support lexicographic sorting.
89 bool operator<(const ELFSymbolData &RHS) const {
90 if (GetType(*SymbolData) == ELF::STT_FILE)
92 if (GetType(*RHS.SymbolData) == ELF::STT_FILE)
94 return SymbolData->getSymbol().getName() <
95 RHS.SymbolData->getSymbol().getName();
99 /// @name Relocation Data
102 struct ELFRelocationEntry {
103 // Make these big enough for both 32-bit and 64-bit
108 // Support lexicographic sorting.
109 bool operator<(const ELFRelocationEntry &RE) const {
110 return RE.r_offset < r_offset;
114 llvm::DenseMap<const MCSectionData*,
115 std::vector<ELFRelocationEntry> > Relocations;
116 DenseMap<const MCSection*, uint64_t> SectionStringTableIndex;
119 /// @name Symbol Table Data
122 SmallString<256> StringTable;
123 std::vector<ELFSymbolData> LocalSymbolData;
124 std::vector<ELFSymbolData> ExternalSymbolData;
125 std::vector<ELFSymbolData> UndefinedSymbolData;
129 ELFObjectWriter *Writer;
133 unsigned Is64Bit : 1;
135 bool HasRelocationAddend;
137 Triple::OSType OSType;
139 // This holds the symbol table index of the last local symbol.
140 unsigned LastLocalSymbolIndex;
141 // This holds the .strtab section index.
142 unsigned StringTableIndex;
144 unsigned ShstrtabIndex;
147 ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
148 bool _HasRelAddend, Triple::OSType _OSType)
149 : Writer(_Writer), OS(Writer->getStream()),
150 Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend),
154 void Write8(uint8_t Value) { Writer->Write8(Value); }
155 void Write16(uint16_t Value) { Writer->Write16(Value); }
156 void Write32(uint32_t Value) { Writer->Write32(Value); }
157 //void Write64(uint64_t Value) { Writer->Write64(Value); }
158 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
159 //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
160 // Writer->WriteBytes(Str, ZeroFillSize);
163 void WriteWord(uint64_t W) {
170 void String8(char *buf, uint8_t Value) {
174 void StringLE16(char *buf, uint16_t Value) {
175 buf[0] = char(Value >> 0);
176 buf[1] = char(Value >> 8);
179 void StringLE32(char *buf, uint32_t Value) {
180 StringLE16(buf, uint16_t(Value >> 0));
181 StringLE16(buf + 2, uint16_t(Value >> 16));
184 void StringLE64(char *buf, uint64_t Value) {
185 StringLE32(buf, uint32_t(Value >> 0));
186 StringLE32(buf + 4, uint32_t(Value >> 32));
189 void StringBE16(char *buf ,uint16_t Value) {
190 buf[0] = char(Value >> 8);
191 buf[1] = char(Value >> 0);
194 void StringBE32(char *buf, uint32_t Value) {
195 StringBE16(buf, uint16_t(Value >> 16));
196 StringBE16(buf + 2, uint16_t(Value >> 0));
199 void StringBE64(char *buf, uint64_t Value) {
200 StringBE32(buf, uint32_t(Value >> 32));
201 StringBE32(buf + 4, uint32_t(Value >> 0));
204 void String16(char *buf, uint16_t Value) {
205 if (Writer->isLittleEndian())
206 StringLE16(buf, Value);
208 StringBE16(buf, Value);
211 void String32(char *buf, uint32_t Value) {
212 if (Writer->isLittleEndian())
213 StringLE32(buf, Value);
215 StringBE32(buf, Value);
218 void String64(char *buf, uint64_t Value) {
219 if (Writer->isLittleEndian())
220 StringLE64(buf, Value);
222 StringBE64(buf, Value);
225 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
227 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
228 uint64_t value, uint64_t size,
229 uint8_t other, uint16_t shndx);
231 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
232 const MCAsmLayout &Layout);
234 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
235 const MCAsmLayout &Layout,
236 unsigned NumRegularSections);
238 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
239 const MCFragment *Fragment, const MCFixup &Fixup,
240 MCValue Target, uint64_t &FixedValue);
242 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
245 /// ComputeSymbolTable - Compute the symbol table data
247 /// \param StringTable [out] - The string table data.
248 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
250 void ComputeSymbolTable(MCAssembler &Asm);
252 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
253 const MCSectionData &SD);
255 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
256 for (MCAssembler::const_iterator it = Asm.begin(),
257 ie = Asm.end(); it != ie; ++it) {
258 WriteRelocation(Asm, Layout, *it);
262 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
264 void ExecutePostLayoutBinding(MCAssembler &Asm) {
265 // Compute symbol table information.
266 ComputeSymbolTable(Asm);
269 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
270 uint64_t Address, uint64_t Offset,
271 uint64_t Size, uint32_t Link, uint32_t Info,
272 uint64_t Alignment, uint64_t EntrySize);
274 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
275 const MCSectionData *SD);
277 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
282 // Emit the ELF header.
283 void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
284 unsigned NumberOfSections) {
290 // emitWord method behaves differently for ELF32 and ELF64, writing
291 // 4 bytes in the former and 8 in the latter.
293 Write8(0x7f); // e_ident[EI_MAG0]
294 Write8('E'); // e_ident[EI_MAG1]
295 Write8('L'); // e_ident[EI_MAG2]
296 Write8('F'); // e_ident[EI_MAG3]
298 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
301 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
303 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
306 case Triple::FreeBSD: Write8(ELF::ELFOSABI_FREEBSD); break;
307 case Triple::Linux: Write8(ELF::ELFOSABI_LINUX); break;
308 default: Write8(ELF::ELFOSABI_NONE); break;
310 Write8(0); // e_ident[EI_ABIVERSION]
312 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
314 Write16(ELF::ET_REL); // e_type
316 // FIXME: Make this configurable
317 Write16(Is64Bit ? ELF::EM_X86_64 : ELF::EM_386); // e_machine = target
319 Write32(ELF::EV_CURRENT); // e_version
320 WriteWord(0); // e_entry, no entry point in .o file
321 WriteWord(0); // e_phoff, no program header for .o
322 WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
323 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
325 // FIXME: Make this configurable.
326 Write32(0); // e_flags = whatever the target wants
328 // e_ehsize = ELF header size
329 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
331 Write16(0); // e_phentsize = prog header entry size
332 Write16(0); // e_phnum = # prog header entries = 0
334 // e_shentsize = Section header entry size
335 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
337 // e_shnum = # of section header ents
338 Write16(NumberOfSections);
340 // e_shstrndx = Section # of '.shstrtab'
341 Write16(ShstrtabIndex);
344 void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
345 uint8_t info, uint64_t value,
346 uint64_t size, uint8_t other,
352 F->getContents() += StringRef(buf, 4); // st_name
355 F->getContents() += StringRef(buf, 1); // st_info
358 F->getContents() += StringRef(buf, 1); // st_other
360 String16(buf, shndx);
361 F->getContents() += StringRef(buf, 2); // st_shndx
363 String64(buf, value);
364 F->getContents() += StringRef(buf, 8); // st_value
367 F->getContents() += StringRef(buf, 8); // st_size
372 F->getContents() += StringRef(buf, 4); // st_name
374 String32(buf, value);
375 F->getContents() += StringRef(buf, 4); // st_value
378 F->getContents() += StringRef(buf, 4); // st_size
381 F->getContents() += StringRef(buf, 1); // st_info
384 F->getContents() += StringRef(buf, 1); // st_other
386 String16(buf, shndx);
387 F->getContents() += StringRef(buf, 2); // st_shndx
391 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
392 const MCAsmLayout &Layout) {
393 MCSymbolData &Data = *MSD.SymbolData;
394 uint8_t Info = (Data.getFlags() & 0xff);
395 uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift);
400 if (Data.isCommon() && Data.isExternal())
401 Value = Data.getCommonAlignment();
403 assert(!(Data.isCommon() && !Data.isExternal()));
405 if (!Data.isCommon() && !(Data.getFlags() & ELF_STB_Weak))
406 if (MCFragment *FF = Data.getFragment())
407 Value = Layout.getSymbolAddress(&Data) -
408 Layout.getSectionAddress(FF->getParent());
410 ESize = Data.getSize();
411 if (Data.getSize()) {
413 if (ESize->getKind() == MCExpr::Binary) {
414 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
416 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
418 Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol());
420 Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol());
422 Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B);
424 } else if (ESize->getKind() == MCExpr::Constant) {
425 Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
427 assert(0 && "Unsupported size expression");
431 // Write out the symbol table entry
432 WriteSymbolEntry(F, MSD.StringIndex, Info, Value,
433 Size, Other, MSD.SectionIndex);
436 void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F,
437 const MCAssembler &Asm,
438 const MCAsmLayout &Layout,
439 unsigned NumRegularSections) {
440 // The string table must be emitted first because we need the index
441 // into the string table for all the symbol names.
442 assert(StringTable.size() && "Missing string table");
444 // FIXME: Make sure the start of the symbol table is aligned.
446 // The first entry is the undefined symbol entry.
447 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
448 F->getContents().append(EntrySize, '\x00');
450 // Write the symbol table entries.
451 LastLocalSymbolIndex = LocalSymbolData.size() + 1;
452 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
453 ELFSymbolData &MSD = LocalSymbolData[i];
454 WriteSymbol(F, MSD, Layout);
457 // Write out a symbol table entry for each regular section.
459 for (MCAssembler::const_iterator it = Asm.begin();
460 Index <= NumRegularSections; ++it, ++Index) {
461 const MCSectionELF &Section =
462 static_cast<const MCSectionELF&>(it->getSection());
463 // Leave out relocations so we don't have indexes within
464 // the relocations messed up
465 if (Section.getType() == ELF::SHT_RELA || Section.getType() == ELF::SHT_REL)
467 WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index);
468 LastLocalSymbolIndex++;
471 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
472 ELFSymbolData &MSD = ExternalSymbolData[i];
473 MCSymbolData &Data = *MSD.SymbolData;
474 assert((Data.getFlags() & ELF_STB_Global) &&
475 "External symbol requires STB_GLOBAL flag");
476 WriteSymbol(F, MSD, Layout);
477 if (GetBinding(Data) == ELF::STB_LOCAL)
478 LastLocalSymbolIndex++;
481 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
482 ELFSymbolData &MSD = UndefinedSymbolData[i];
483 MCSymbolData &Data = *MSD.SymbolData;
484 WriteSymbol(F, MSD, Layout);
485 if (GetBinding(Data) == ELF::STB_LOCAL)
486 LastLocalSymbolIndex++;
490 static const MCSymbolData *getAtom(const MCSymbolData &SD) {
491 if (!SD.getFragment())
494 return SD.getFragment()->getAtom();
497 // FIXME: this is currently X86/X86_64 only
498 void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
499 const MCAsmLayout &Layout,
500 const MCFragment *Fragment,
501 const MCFixup &Fixup,
503 uint64_t &FixedValue) {
506 int64_t Value = Target.getConstant();
508 bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
509 if (!Target.isAbsolute()) {
510 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
511 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
512 const MCSymbolData *Base = getAtom(SD);
513 MCFragment *F = SD.getFragment();
515 // Avoid relocations for cases like jumps and calls in the same file.
516 if (Symbol->isDefined() && !SD.isExternal() &&
518 &Fragment->getParent()->getSection() == &Symbol->getSection()) {
519 uint64_t FixupAddr = Layout.getFragmentAddress(Fragment) + Fixup.getOffset();
520 FixedValue = Layout.getSymbolAddress(&SD) + Target.getConstant() - FixupAddr;
526 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
528 MCSectionData *FSD = F->getParent();
529 // Offset of the symbol in the section
530 Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
532 Index = getSymbolIndexInSymbolTable(Asm, Symbol);
534 // Compensate for the addend on i386.
539 // Index of the section in .symtab against this symbol
540 // is being relocated + 2 (empty section + abs. symbols).
541 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
543 MCSectionData *FSD = F->getParent();
544 // Offset of the symbol in the section
545 Value += Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
547 Index = getSymbolIndexInSymbolTable(Asm, Symbol);
550 // Compensate for the addend on i386.
558 // determine the type of the relocation
562 Type = ELF::R_X86_64_PC32;
564 switch ((unsigned)Fixup.getKind()) {
565 default: llvm_unreachable("invalid fixup kind!");
566 case FK_Data_8: Type = ELF::R_X86_64_64; break;
567 case X86::reloc_pcrel_4byte:
569 // check that the offset fits within a signed long
570 if (Target.getConstant() < 0) {
571 assert(isInt<32>(Target.getConstant()));
572 Type = ELF::R_X86_64_32S;
574 assert(isUInt<32>(Target.getConstant()));
575 Type = ELF::R_X86_64_32;
578 case FK_Data_2: Type = ELF::R_X86_64_16; break;
579 case X86::reloc_pcrel_1byte:
580 case FK_Data_1: Type = ELF::R_X86_64_8; break;
585 Type = ELF::R_386_PC32;
587 switch ((unsigned)Fixup.getKind()) {
588 default: llvm_unreachable("invalid fixup kind!");
589 case X86::reloc_pcrel_4byte:
590 case FK_Data_4: Type = ELF::R_386_32; break;
591 case FK_Data_2: Type = ELF::R_386_16; break;
592 case X86::reloc_pcrel_1byte:
593 case FK_Data_1: Type = ELF::R_386_8; break;
598 ELFRelocationEntry ERE;
601 struct ELF::Elf64_Rela ERE64;
602 ERE64.setSymbolAndType(Index, Type);
603 ERE.r_info = ERE64.r_info;
605 struct ELF::Elf32_Rela ERE32;
606 ERE32.setSymbolAndType(Index, Type);
607 ERE.r_info = ERE32.r_info;
610 ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
612 if (HasRelocationAddend)
613 ERE.r_addend = Addend;
615 ERE.r_addend = 0; // Silence compiler warning.
617 Relocations[Fragment->getParent()].push_back(ERE);
621 ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
623 MCSymbolData &SD = Asm.getSymbolData(*S);
626 if (!SD.isExternal() && !S->isUndefined())
627 return SD.getIndex() + /* empty symbol */ 1;
629 // External or undefined symbol.
630 return SD.getIndex() + Asm.size() + /* empty symbol */ 1;
633 void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
634 // Build section lookup table.
635 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
637 for (MCAssembler::iterator it = Asm.begin(),
638 ie = Asm.end(); it != ie; ++it, ++Index)
639 SectionIndexMap[&it->getSection()] = Index;
641 // Index 0 is always the empty string.
642 StringMap<uint64_t> StringIndexMap;
643 StringTable += '\x00';
645 // Add the data for local symbols.
646 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
647 ie = Asm.symbol_end(); it != ie; ++it) {
648 const MCSymbol &Symbol = it->getSymbol();
650 // Ignore non-linker visible symbols.
651 if (!Asm.isSymbolLinkerVisible(Symbol))
654 if (it->isExternal() || Symbol.isUndefined())
657 uint64_t &Entry = StringIndexMap[Symbol.getName()];
659 Entry = StringTable.size();
660 StringTable += Symbol.getName();
661 StringTable += '\x00';
666 MSD.StringIndex = Entry;
668 if (Symbol.isAbsolute()) {
669 MSD.SectionIndex = ELF::SHN_ABS;
670 LocalSymbolData.push_back(MSD);
672 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
673 assert(MSD.SectionIndex && "Invalid section index!");
674 LocalSymbolData.push_back(MSD);
678 // Now add non-local symbols.
679 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
680 ie = Asm.symbol_end(); it != ie; ++it) {
681 const MCSymbol &Symbol = it->getSymbol();
683 // Ignore non-linker visible symbols.
684 if (!Asm.isSymbolLinkerVisible(Symbol))
687 if (!it->isExternal() && !Symbol.isUndefined())
690 uint64_t &Entry = StringIndexMap[Symbol.getName()];
692 Entry = StringTable.size();
693 StringTable += Symbol.getName();
694 StringTable += '\x00';
699 MSD.StringIndex = Entry;
701 if (it->isCommon()) {
702 MSD.SectionIndex = ELF::SHN_COMMON;
703 ExternalSymbolData.push_back(MSD);
704 } else if (Symbol.isUndefined()) {
705 MSD.SectionIndex = ELF::SHN_UNDEF;
706 // FIXME: Undefined symbols are global, but this is the first place we
707 // are able to set it.
708 if (GetBinding(*it) == ELF::STB_LOCAL)
709 SetBinding(*it, ELF::STB_GLOBAL);
710 UndefinedSymbolData.push_back(MSD);
711 } else if (Symbol.isAbsolute()) {
712 MSD.SectionIndex = ELF::SHN_ABS;
713 ExternalSymbolData.push_back(MSD);
715 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
716 assert(MSD.SectionIndex && "Invalid section index!");
717 ExternalSymbolData.push_back(MSD);
721 // Symbols are required to be in lexicographic order.
722 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
723 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
724 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
726 // Set the symbol indices. Local symbols must come before all other
727 // symbols with non-local bindings.
729 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
730 LocalSymbolData[i].SymbolData->setIndex(Index++);
731 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
732 ExternalSymbolData[i].SymbolData->setIndex(Index++);
733 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
734 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
737 void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
738 const MCSectionData &SD) {
739 if (!Relocations[&SD].empty()) {
740 MCContext &Ctx = Asm.getContext();
741 const MCSection *RelaSection;
742 const MCSectionELF &Section =
743 static_cast<const MCSectionELF&>(SD.getSection());
745 const StringRef SectionName = Section.getSectionName();
746 std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
747 RelaSectionName += SectionName;
750 if (HasRelocationAddend)
751 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
753 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
755 RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
756 ELF::SHT_RELA : ELF::SHT_REL, 0,
757 SectionKind::getReadOnly(),
760 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
761 RelaSD.setAlignment(Is64Bit ? 8 : 4);
763 MCDataFragment *F = new MCDataFragment(&RelaSD);
765 WriteRelocationsFragment(Asm, F, &SD);
767 Asm.AddSectionToTheEnd(RelaSD, Layout);
771 void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
772 uint64_t Flags, uint64_t Address,
773 uint64_t Offset, uint64_t Size,
774 uint32_t Link, uint32_t Info,
776 uint64_t EntrySize) {
777 Write32(Name); // sh_name: index into string table
778 Write32(Type); // sh_type
779 WriteWord(Flags); // sh_flags
780 WriteWord(Address); // sh_addr
781 WriteWord(Offset); // sh_offset
782 WriteWord(Size); // sh_size
783 Write32(Link); // sh_link
784 Write32(Info); // sh_info
785 WriteWord(Alignment); // sh_addralign
786 WriteWord(EntrySize); // sh_entsize
789 void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
791 const MCSectionData *SD) {
792 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
793 // sort by the r_offset just like gnu as does
794 array_pod_sort(Relocs.begin(), Relocs.end());
796 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
797 ELFRelocationEntry entry = Relocs[e - i - 1];
802 String64(buf, entry.r_offset);
803 F->getContents() += StringRef(buf, 8);
805 String64(buf, entry.r_info);
806 F->getContents() += StringRef(buf, 8);
808 if (HasRelocationAddend) {
809 String64(buf, entry.r_addend);
810 F->getContents() += StringRef(buf, 8);
815 String32(buf, entry.r_offset);
816 F->getContents() += StringRef(buf, 4);
818 String32(buf, entry.r_info);
819 F->getContents() += StringRef(buf, 4);
821 if (HasRelocationAddend) {
822 String32(buf, entry.r_addend);
823 F->getContents() += StringRef(buf, 4);
829 void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
830 MCAsmLayout &Layout) {
831 MCContext &Ctx = Asm.getContext();
834 WriteRelocations(Asm, Layout);
836 const MCSection *SymtabSection;
837 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
839 unsigned NumRegularSections = Asm.size();
841 // We construct .shstrtab, .symtab and .strtab in this order to match gnu as.
842 const MCSection *ShstrtabSection;
843 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
844 SectionKind::getReadOnly(), false);
845 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
846 ShstrtabSD.setAlignment(1);
847 ShstrtabIndex = Asm.size();
849 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
850 SectionKind::getReadOnly(),
852 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
853 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
855 const MCSection *StrtabSection;
856 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
857 SectionKind::getReadOnly(), false);
858 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
859 StrtabSD.setAlignment(1);
860 StringTableIndex = Asm.size();
864 F = new MCDataFragment(&SymtabSD);
865 WriteSymbolTable(F, Asm, Layout, NumRegularSections);
866 Asm.AddSectionToTheEnd(SymtabSD, Layout);
868 F = new MCDataFragment(&StrtabSD);
869 F->getContents().append(StringTable.begin(), StringTable.end());
870 Asm.AddSectionToTheEnd(StrtabSD, Layout);
872 F = new MCDataFragment(&ShstrtabSD);
874 // Section header string table.
876 // The first entry of a string table holds a null character so skip
879 F->getContents() += '\x00';
881 for (MCAssembler::const_iterator it = Asm.begin(),
882 ie = Asm.end(); it != ie; ++it) {
883 const MCSectionELF &Section =
884 static_cast<const MCSectionELF&>(it->getSection());
885 // FIXME: We could merge suffixes like in .text and .rela.text.
887 // Remember the index into the string table so we can write it
888 // into the sh_name field of the section header table.
889 SectionStringTableIndex[&it->getSection()] = Index;
891 Index += Section.getSectionName().size() + 1;
892 F->getContents() += Section.getSectionName();
893 F->getContents() += '\x00';
896 Asm.AddSectionToTheEnd(ShstrtabSD, Layout);
899 void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm,
900 const MCAsmLayout &Layout) {
901 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
902 const_cast<MCAsmLayout&>(Layout));
904 // Add 1 for the null section.
905 unsigned NumSections = Asm.size() + 1;
906 uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
907 uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
908 uint64_t FileOff = HeaderSize;
910 for (MCAssembler::const_iterator it = Asm.begin(),
911 ie = Asm.end(); it != ie; ++it) {
912 const MCSectionData &SD = *it;
914 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
916 // Get the size of the section in the output file (including padding).
917 uint64_t Size = Layout.getSectionFileSize(&SD);
922 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
924 // Write out the ELF header ...
925 WriteHeader(FileOff - HeaderSize, NumSections);
927 FileOff = HeaderSize;
929 // ... then all of the sections ...
930 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
932 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
935 for (MCAssembler::const_iterator it = Asm.begin(),
936 ie = Asm.end(); it != ie; ++it) {
937 const MCSectionData &SD = *it;
939 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
943 // Remember the offset into the file for this section.
944 SectionOffsetMap[&it->getSection()] = FileOff;
945 SectionIndexMap[&it->getSection()] = Index++;
947 FileOff += Layout.getSectionFileSize(&SD);
949 Asm.WriteSectionData(it, Layout, Writer);
952 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
956 // ... and then the section header table.
957 // Should we align the section header table?
959 // Null section first.
960 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
962 for (MCAssembler::const_iterator it = Asm.begin(),
963 ie = Asm.end(); it != ie; ++it) {
964 const MCSectionData &SD = *it;
965 const MCSectionELF &Section =
966 static_cast<const MCSectionELF&>(SD.getSection());
968 uint64_t sh_link = 0;
969 uint64_t sh_info = 0;
971 switch(Section.getType()) {
972 case ELF::SHT_DYNAMIC:
973 sh_link = SectionStringTableIndex[&it->getSection()];
978 case ELF::SHT_RELA: {
979 const MCSection *SymtabSection;
980 const MCSection *InfoSection;
982 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
983 SectionKind::getReadOnly(),
985 sh_link = SectionIndexMap[SymtabSection];
987 // Remove ".rel" and ".rela" prefixes.
988 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
989 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
991 InfoSection = Asm.getContext().getELFSection(SectionName,
992 ELF::SHT_PROGBITS, 0,
993 SectionKind::getReadOnly(),
995 sh_info = SectionIndexMap[InfoSection];
999 case ELF::SHT_SYMTAB:
1000 case ELF::SHT_DYNSYM:
1001 sh_link = StringTableIndex;
1002 sh_info = LastLocalSymbolIndex;
1005 case ELF::SHT_PROGBITS:
1006 case ELF::SHT_STRTAB:
1007 case ELF::SHT_NOBITS:
1013 case ELF::SHT_GROUP:
1014 case ELF::SHT_SYMTAB_SHNDX:
1016 assert(0 && "FIXME: sh_type value not supported!");
1020 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
1021 Section.getType(), Section.getFlags(),
1023 SectionOffsetMap.lookup(&SD.getSection()),
1024 Layout.getSectionSize(&SD), sh_link,
1025 sh_info, SD.getAlignment(),
1026 Section.getEntrySize());
1030 ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
1032 Triple::OSType OSType,
1033 bool IsLittleEndian,
1034 bool HasRelocationAddend)
1035 : MCObjectWriter(OS, IsLittleEndian)
1037 Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend, OSType);
1040 ELFObjectWriter::~ELFObjectWriter() {
1041 delete (ELFObjectWriterImpl*) Impl;
1044 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
1045 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
1048 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1049 const MCAsmLayout &Layout,
1050 const MCFragment *Fragment,
1051 const MCFixup &Fixup, MCValue Target,
1052 uint64_t &FixedValue) {
1053 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
1054 Target, FixedValue);
1057 void ELFObjectWriter::WriteObject(const MCAssembler &Asm,
1058 const MCAsmLayout &Layout) {
1059 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);