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"
39 class ELFObjectWriterImpl {
40 static bool isFixupKindX86PCRel(unsigned Kind) {
44 case X86::reloc_pcrel_1byte:
45 case X86::reloc_pcrel_4byte:
46 case X86::reloc_riprel_4byte:
47 case X86::reloc_riprel_4byte_movq_load:
52 /*static bool isFixupKindX86RIPRel(unsigned Kind) {
53 return Kind == X86::reloc_riprel_4byte ||
54 Kind == X86::reloc_riprel_4byte_movq_load;
58 /// ELFSymbolData - Helper struct for containing some precomputed information
60 struct ELFSymbolData {
61 MCSymbolData *SymbolData;
63 uint32_t SectionIndex;
65 // Support lexicographic sorting.
66 bool operator<(const ELFSymbolData &RHS) const {
67 return SymbolData->getSymbol().getName() <
68 RHS.SymbolData->getSymbol().getName();
72 /// @name Relocation Data
75 struct ELFRelocationEntry {
76 // Make these big enough for both 32-bit and 64-bit
81 // Support lexicographic sorting.
82 bool operator<(const ELFRelocationEntry &RE) const {
83 return RE.r_offset < r_offset;
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<ELFSymbolData> LocalSymbolData;
97 std::vector<ELFSymbolData> ExternalSymbolData;
98 std::vector<ELFSymbolData> UndefinedSymbolData;
102 ELFObjectWriter *Writer;
106 unsigned Is64Bit : 1;
108 bool HasRelocationAddend;
110 // This holds the symbol table index of the last local symbol.
111 unsigned LastLocalSymbolIndex;
112 // This holds the .strtab section index.
113 unsigned StringTableIndex;
115 unsigned ShstrtabIndex;
118 ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
120 : Writer(_Writer), OS(Writer->getStream()),
121 Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend) {
124 void Write8(uint8_t Value) { Writer->Write8(Value); }
125 void Write16(uint16_t Value) { Writer->Write16(Value); }
126 void Write32(uint32_t Value) { Writer->Write32(Value); }
127 //void Write64(uint64_t Value) { Writer->Write64(Value); }
128 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
129 //void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
130 // Writer->WriteBytes(Str, ZeroFillSize);
133 void WriteWord(uint64_t W) {
140 void String8(char *buf, uint8_t Value) {
144 void StringLE16(char *buf, uint16_t Value) {
145 buf[0] = char(Value >> 0);
146 buf[1] = char(Value >> 8);
149 void StringLE32(char *buf, uint32_t Value) {
150 StringLE16(buf, uint16_t(Value >> 0));
151 StringLE16(buf + 2, uint16_t(Value >> 16));
154 void StringLE64(char *buf, uint64_t Value) {
155 StringLE32(buf, uint32_t(Value >> 0));
156 StringLE32(buf + 4, uint32_t(Value >> 32));
159 void StringBE16(char *buf ,uint16_t Value) {
160 buf[0] = char(Value >> 8);
161 buf[1] = char(Value >> 0);
164 void StringBE32(char *buf, uint32_t Value) {
165 StringBE16(buf, uint16_t(Value >> 16));
166 StringBE16(buf + 2, uint16_t(Value >> 0));
169 void StringBE64(char *buf, uint64_t Value) {
170 StringBE32(buf, uint32_t(Value >> 32));
171 StringBE32(buf + 4, uint32_t(Value >> 0));
174 void String16(char *buf, uint16_t Value) {
175 if (Writer->isLittleEndian())
176 StringLE16(buf, Value);
178 StringBE16(buf, Value);
181 void String32(char *buf, uint32_t Value) {
182 if (Writer->isLittleEndian())
183 StringLE32(buf, Value);
185 StringBE32(buf, Value);
188 void String64(char *buf, uint64_t Value) {
189 if (Writer->isLittleEndian())
190 StringLE64(buf, Value);
192 StringBE64(buf, Value);
195 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
197 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
198 uint64_t value, uint64_t size,
199 uint8_t other, uint16_t shndx);
201 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
202 const MCAsmLayout &Layout);
204 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
205 const MCAsmLayout &Layout);
207 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
208 const MCFragment *Fragment, const MCFixup &Fixup,
209 MCValue Target, uint64_t &FixedValue);
211 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
214 /// ComputeSymbolTable - Compute the symbol table data
216 /// \param StringTable [out] - The string table data.
217 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
219 void ComputeSymbolTable(MCAssembler &Asm);
221 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
222 const MCSectionData &SD);
224 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
225 for (MCAssembler::const_iterator it = Asm.begin(),
226 ie = Asm.end(); it != ie; ++it) {
227 WriteRelocation(Asm, Layout, *it);
231 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
233 void ExecutePostLayoutBinding(MCAssembler &Asm) {
234 // Compute symbol table information.
235 ComputeSymbolTable(Asm);
238 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
239 uint64_t Address, uint64_t Offset,
240 uint64_t Size, uint32_t Link, uint32_t Info,
241 uint64_t Alignment, uint64_t EntrySize);
243 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
244 const MCSectionData *SD);
246 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
251 // Emit the ELF header.
252 void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
253 unsigned NumberOfSections) {
259 // emitWord method behaves differently for ELF32 and ELF64, writing
260 // 4 bytes in the former and 8 in the latter.
262 Write8(0x7f); // e_ident[EI_MAG0]
263 Write8('E'); // e_ident[EI_MAG1]
264 Write8('L'); // e_ident[EI_MAG2]
265 Write8('F'); // e_ident[EI_MAG3]
267 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
270 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
272 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
273 Write8(ELF::ELFOSABI_LINUX); // e_ident[EI_OSABI]
274 Write8(0); // e_ident[EI_ABIVERSION]
276 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
278 Write16(ELF::ET_REL); // e_type
280 // FIXME: Make this configurable
281 Write16(Is64Bit ? ELF::EM_X86_64 : ELF::EM_386); // e_machine = target
283 Write32(ELF::EV_CURRENT); // e_version
284 WriteWord(0); // e_entry, no entry point in .o file
285 WriteWord(0); // e_phoff, no program header for .o
286 WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
287 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
289 // FIXME: Make this configurable.
290 Write32(0); // e_flags = whatever the target wants
292 // e_ehsize = ELF header size
293 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
295 Write16(0); // e_phentsize = prog header entry size
296 Write16(0); // e_phnum = # prog header entries = 0
298 // e_shentsize = Section header entry size
299 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
301 // e_shnum = # of section header ents
302 Write16(NumberOfSections);
304 // e_shstrndx = Section # of '.shstrtab'
305 Write16(ShstrtabIndex);
308 void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
309 uint8_t info, uint64_t value,
310 uint64_t size, uint8_t other,
316 F->getContents() += StringRef(buf, 4); // st_name
319 F->getContents() += StringRef(buf, 1); // st_info
322 F->getContents() += StringRef(buf, 1); // st_other
324 String16(buf, shndx);
325 F->getContents() += StringRef(buf, 2); // st_shndx
327 String64(buf, value);
328 F->getContents() += StringRef(buf, 8); // st_value
331 F->getContents() += StringRef(buf, 8); // st_size
336 F->getContents() += StringRef(buf, 4); // st_name
338 String32(buf, value);
339 F->getContents() += StringRef(buf, 4); // st_value
342 F->getContents() += StringRef(buf, 4); // st_size
345 F->getContents() += StringRef(buf, 1); // st_info
348 F->getContents() += StringRef(buf, 1); // st_other
350 String16(buf, shndx);
351 F->getContents() += StringRef(buf, 2); // st_shndx
355 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
356 const MCAsmLayout &Layout) {
357 MCSymbolData &Data = *MSD.SymbolData;
358 uint8_t Info = (Data.getFlags() & 0xff);
359 uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift);
364 if (Data.isCommon() && Data.isExternal())
365 Value = Data.getCommonAlignment();
367 if (!Data.isCommon() && !(Data.getFlags() & ELF_STB_Weak))
368 if (MCFragment *FF = Data.getFragment())
369 Value = Layout.getSymbolAddress(&Data) -
370 Layout.getSectionAddress(FF->getParent());
372 ESize = Data.getSize();
373 if (Data.getSize()) {
375 if (ESize->getKind() == MCExpr::Binary) {
376 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
378 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
380 Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol());
382 Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol());
384 Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B);
386 } else if (ESize->getKind() == MCExpr::Constant) {
387 Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
389 assert(0 && "Unsupported size expression");
393 // Write out the symbol table entry
394 WriteSymbolEntry(F, MSD.StringIndex, Info, Value,
395 Size, Other, MSD.SectionIndex);
398 void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F,
399 const MCAssembler &Asm,
400 const MCAsmLayout &Layout) {
401 // The string table must be emitted first because we need the index
402 // into the string table for all the symbol names.
403 assert(StringTable.size() && "Missing string table");
405 // FIXME: Make sure the start of the symbol table is aligned.
407 // The first entry is the undefined symbol entry.
408 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
409 F->getContents().append(EntrySize, '\x00');
411 // Write the symbol table entries.
412 LastLocalSymbolIndex = LocalSymbolData.size() + 1;
413 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
414 ELFSymbolData &MSD = LocalSymbolData[i];
415 WriteSymbol(F, MSD, Layout);
418 // Write out a symbol table entry for each section.
419 // leaving out the just added .symtab which is at
422 for (MCAssembler::const_iterator it = Asm.begin(),
423 ie = Asm.end(); it != ie; ++it, ++Index) {
424 const MCSectionELF &Section =
425 static_cast<const MCSectionELF&>(it->getSection());
426 // Leave out relocations so we don't have indexes within
427 // the relocations messed up
428 if (Section.getType() == ELF::SHT_RELA || Section.getType() == ELF::SHT_REL)
430 if (Index == Asm.size())
432 WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index);
433 LastLocalSymbolIndex++;
436 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
437 ELFSymbolData &MSD = ExternalSymbolData[i];
438 MCSymbolData &Data = *MSD.SymbolData;
439 assert((Data.getFlags() & ELF_STB_Global) &&
440 "External symbol requires STB_GLOBAL flag");
441 WriteSymbol(F, MSD, Layout);
442 if (Data.getFlags() & ELF_STB_Local)
443 LastLocalSymbolIndex++;
446 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
447 ELFSymbolData &MSD = UndefinedSymbolData[i];
448 MCSymbolData &Data = *MSD.SymbolData;
449 Data.setFlags(Data.getFlags() | ELF_STB_Global);
450 WriteSymbol(F, MSD, Layout);
451 if (Data.getFlags() & ELF_STB_Local)
452 LastLocalSymbolIndex++;
456 // FIXME: this is currently X86/X86_64 only
457 void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
458 const MCAsmLayout &Layout,
459 const MCFragment *Fragment,
460 const MCFixup &Fixup,
462 uint64_t &FixedValue) {
465 int64_t Value = Target.getConstant();
467 if (!Target.isAbsolute()) {
468 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
469 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
470 const MCSymbolData *Base = Asm.getAtom(Layout, &SD);
471 MCFragment *F = SD.getFragment();
474 if (F && (!Symbol->isInSection() || SD.isCommon()) && !SD.isExternal()) {
475 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
476 Value += Layout.getSymbolAddress(&SD);
478 Index = getSymbolIndexInSymbolTable(Asm, Symbol);
480 Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
482 // Compensate for the addend on i386.
487 // Index of the section in .symtab against this symbol
488 // is being relocated + 2 (empty section + abs. symbols).
489 Index = F->getParent()->getOrdinal() + LocalSymbolData.size() + 1;
491 MCSectionData *FSD = F->getParent();
492 // Offset of the symbol in the section
493 Addend = Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
503 // determine the type of the relocation
504 bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
508 Type = ELF::R_X86_64_PC32;
510 switch ((unsigned)Fixup.getKind()) {
511 default: llvm_unreachable("invalid fixup kind!");
512 case FK_Data_8: Type = ELF::R_X86_64_64; break;
513 case X86::reloc_pcrel_4byte:
515 // check that the offset fits within a signed long
516 if (isInt<32>(Target.getConstant()))
517 Type = ELF::R_X86_64_32S;
519 Type = ELF::R_X86_64_32;
521 case FK_Data_2: Type = ELF::R_X86_64_16; break;
522 case X86::reloc_pcrel_1byte:
523 case FK_Data_1: Type = ELF::R_X86_64_8; break;
528 Type = ELF::R_386_PC32;
530 switch ((unsigned)Fixup.getKind()) {
531 default: llvm_unreachable("invalid fixup kind!");
532 case X86::reloc_pcrel_4byte:
533 case FK_Data_4: Type = ELF::R_386_32; break;
534 case FK_Data_2: Type = ELF::R_386_16; break;
535 case X86::reloc_pcrel_1byte:
536 case FK_Data_1: Type = ELF::R_386_8; break;
541 ELFRelocationEntry ERE;
544 struct ELF::Elf64_Rela ERE64;
545 ERE64.setSymbolAndType(Index, Type);
546 ERE.r_info = ERE64.r_info;
548 struct ELF::Elf32_Rela ERE32;
549 ERE32.setSymbolAndType(Index, Type);
550 ERE.r_info = ERE32.r_info;
553 ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
555 if (HasRelocationAddend)
556 ERE.r_addend = Addend;
558 ERE.r_addend = 0; // Silence compiler warning.
560 Relocations[Fragment->getParent()].push_back(ERE);
564 ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
566 MCSymbolData &SD = Asm.getSymbolData(*S);
569 if (!SD.isExternal() && !S->isUndefined())
570 return SD.getIndex() + /* empty symbol */ 1;
572 // External or undefined symbol.
573 return SD.getIndex() + Asm.size() + /* empty symbol */ 1;
576 void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
577 // Build section lookup table.
578 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
580 for (MCAssembler::iterator it = Asm.begin(),
581 ie = Asm.end(); it != ie; ++it, ++Index)
582 SectionIndexMap[&it->getSection()] = Index;
584 // Index 0 is always the empty string.
585 StringMap<uint64_t> StringIndexMap;
586 StringTable += '\x00';
588 // Add the data for local symbols.
589 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
590 ie = Asm.symbol_end(); it != ie; ++it) {
591 const MCSymbol &Symbol = it->getSymbol();
593 // Ignore non-linker visible symbols.
594 if (!Asm.isSymbolLinkerVisible(Symbol))
597 if (it->isExternal() || Symbol.isUndefined())
600 uint64_t &Entry = StringIndexMap[Symbol.getName()];
602 Entry = StringTable.size();
603 StringTable += Symbol.getName();
604 StringTable += '\x00';
609 MSD.StringIndex = Entry;
611 if (Symbol.isAbsolute()) {
612 MSD.SectionIndex = ELF::SHN_ABS;
613 LocalSymbolData.push_back(MSD);
615 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
616 assert(MSD.SectionIndex && "Invalid section index!");
617 LocalSymbolData.push_back(MSD);
621 // Now add non-local symbols.
622 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
623 ie = Asm.symbol_end(); it != ie; ++it) {
624 const MCSymbol &Symbol = it->getSymbol();
626 // Ignore non-linker visible symbols.
627 if (!Asm.isSymbolLinkerVisible(Symbol))
630 if (!it->isExternal() && !Symbol.isUndefined())
633 uint64_t &Entry = StringIndexMap[Symbol.getName()];
635 Entry = StringTable.size();
636 StringTable += Symbol.getName();
637 StringTable += '\x00';
642 MSD.StringIndex = Entry;
644 if (Symbol.isUndefined()) {
645 MSD.SectionIndex = ELF::SHN_UNDEF;
646 // XXX: for some reason we dont Emit* this
647 it->setFlags(it->getFlags() | ELF_STB_Global);
648 UndefinedSymbolData.push_back(MSD);
649 } else if (Symbol.isAbsolute()) {
650 MSD.SectionIndex = ELF::SHN_ABS;
651 ExternalSymbolData.push_back(MSD);
652 } else if (it->isCommon()) {
653 MSD.SectionIndex = ELF::SHN_COMMON;
654 ExternalSymbolData.push_back(MSD);
656 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
657 assert(MSD.SectionIndex && "Invalid section index!");
658 ExternalSymbolData.push_back(MSD);
662 // Symbols are required to be in lexicographic order.
663 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
664 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
665 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
667 // Set the symbol indices. Local symbols must come before all other
668 // symbols with non-local bindings.
670 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
671 LocalSymbolData[i].SymbolData->setIndex(Index++);
672 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
673 ExternalSymbolData[i].SymbolData->setIndex(Index++);
674 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
675 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
678 void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
679 const MCSectionData &SD) {
680 if (!Relocations[&SD].empty()) {
681 MCContext &Ctx = Asm.getContext();
682 const MCSection *RelaSection;
683 const MCSectionELF &Section =
684 static_cast<const MCSectionELF&>(SD.getSection());
686 const StringRef SectionName = Section.getSectionName();
687 std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
688 RelaSectionName += SectionName;
691 if (HasRelocationAddend)
692 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
694 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
696 RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
697 ELF::SHT_RELA : ELF::SHT_REL, 0,
698 SectionKind::getReadOnly(),
701 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
702 RelaSD.setAlignment(Is64Bit ? 8 : 4);
704 MCDataFragment *F = new MCDataFragment(&RelaSD);
706 WriteRelocationsFragment(Asm, F, &SD);
708 Asm.AddSectionToTheEnd(RelaSD, Layout);
712 void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
713 uint64_t Flags, uint64_t Address,
714 uint64_t Offset, uint64_t Size,
715 uint32_t Link, uint32_t Info,
717 uint64_t EntrySize) {
718 Write32(Name); // sh_name: index into string table
719 Write32(Type); // sh_type
720 WriteWord(Flags); // sh_flags
721 WriteWord(Address); // sh_addr
722 WriteWord(Offset); // sh_offset
723 WriteWord(Size); // sh_size
724 Write32(Link); // sh_link
725 Write32(Info); // sh_info
726 WriteWord(Alignment); // sh_addralign
727 WriteWord(EntrySize); // sh_entsize
730 void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
732 const MCSectionData *SD) {
733 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
734 // sort by the r_offset just like gnu as does
735 array_pod_sort(Relocs.begin(), Relocs.end());
737 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
738 ELFRelocationEntry entry = Relocs[e - i - 1];
740 unsigned WordSize = Is64Bit ? 8 : 4;
741 F->getContents() += StringRef((const char *)&entry.r_offset, WordSize);
742 F->getContents() += StringRef((const char *)&entry.r_info, WordSize);
744 if (HasRelocationAddend)
745 F->getContents() += StringRef((const char *)&entry.r_addend, WordSize);
749 void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
750 MCAsmLayout &Layout) {
751 MCContext &Ctx = Asm.getContext();
754 WriteRelocations(Asm, Layout);
756 const MCSection *SymtabSection;
757 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
759 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
760 SectionKind::getReadOnly(),
763 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
765 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
767 F = new MCDataFragment(&SymtabSD);
770 WriteSymbolTable(F, Asm, Layout);
771 Asm.AddSectionToTheEnd(SymtabSD, Layout);
773 const MCSection *StrtabSection;
774 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
775 SectionKind::getReadOnly(), false);
777 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
778 StrtabSD.setAlignment(1);
780 // FIXME: This isn't right. If the sections get rearranged this will
781 // be wrong. We need a proper lookup.
782 StringTableIndex = Asm.size();
784 F = new MCDataFragment(&StrtabSD);
785 F->getContents().append(StringTable.begin(), StringTable.end());
786 Asm.AddSectionToTheEnd(StrtabSD, Layout);
788 const MCSection *ShstrtabSection;
789 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
790 SectionKind::getReadOnly(), false);
792 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
793 ShstrtabSD.setAlignment(1);
795 F = new MCDataFragment(&ShstrtabSD);
797 // FIXME: This isn't right. If the sections get rearranged this will
798 // be wrong. We need a proper lookup.
799 ShstrtabIndex = Asm.size();
801 // Section header string table.
803 // The first entry of a string table holds a null character so skip
806 F->getContents() += '\x00';
808 for (MCAssembler::const_iterator it = Asm.begin(),
809 ie = Asm.end(); it != ie; ++it) {
810 const MCSectionELF &Section =
811 static_cast<const MCSectionELF&>(it->getSection());
813 // Remember the index into the string table so we can write it
814 // into the sh_name field of the section header table.
815 SectionStringTableIndex[&it->getSection()] = Index;
817 Index += Section.getSectionName().size() + 1;
818 F->getContents() += Section.getSectionName();
819 F->getContents() += '\x00';
822 Asm.AddSectionToTheEnd(ShstrtabSD, Layout);
825 void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm,
826 const MCAsmLayout &Layout) {
827 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
828 const_cast<MCAsmLayout&>(Layout));
830 // Add 1 for the null section.
831 unsigned NumSections = Asm.size() + 1;
832 uint64_t NaturalAlignment = Is64Bit ? 8 : 4;
833 uint64_t HeaderSize = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
834 uint64_t FileOff = HeaderSize;
836 for (MCAssembler::const_iterator it = Asm.begin(),
837 ie = Asm.end(); it != ie; ++it) {
838 const MCSectionData &SD = *it;
840 FileOff = RoundUpToAlignment(FileOff, SD.getAlignment());
842 // Get the size of the section in the output file (including padding).
843 uint64_t Size = Layout.getSectionFileSize(&SD);
848 FileOff = RoundUpToAlignment(FileOff, NaturalAlignment);
850 // Write out the ELF header ...
851 WriteHeader(FileOff - HeaderSize, NumSections);
853 FileOff = HeaderSize;
855 // ... then all of the sections ...
856 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
858 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
861 for (MCAssembler::const_iterator it = Asm.begin(),
862 ie = Asm.end(); it != ie; ++it) {
863 const MCSectionData &SD = *it;
865 uint64_t Padding = OffsetToAlignment(FileOff, SD.getAlignment());
869 // Remember the offset into the file for this section.
870 SectionOffsetMap[&it->getSection()] = FileOff;
871 SectionIndexMap[&it->getSection()] = Index++;
873 FileOff += Layout.getSectionFileSize(&SD);
875 Asm.WriteSectionData(it, Layout, Writer);
878 uint64_t Padding = OffsetToAlignment(FileOff, NaturalAlignment);
882 // ... and then the section header table.
883 // Should we align the section header table?
885 // Null section first.
886 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
888 for (MCAssembler::const_iterator it = Asm.begin(),
889 ie = Asm.end(); it != ie; ++it) {
890 const MCSectionData &SD = *it;
891 const MCSectionELF &Section =
892 static_cast<const MCSectionELF&>(SD.getSection());
894 uint64_t sh_link = 0;
895 uint64_t sh_info = 0;
897 switch(Section.getType()) {
898 case ELF::SHT_DYNAMIC:
899 sh_link = SectionStringTableIndex[&it->getSection()];
904 case ELF::SHT_RELA: {
905 const MCSection *SymtabSection;
906 const MCSection *InfoSection;
908 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
909 SectionKind::getReadOnly(),
911 sh_link = SectionIndexMap[SymtabSection];
913 // Remove ".rel" and ".rela" prefixes.
914 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
915 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
917 InfoSection = Asm.getContext().getELFSection(SectionName,
918 ELF::SHT_PROGBITS, 0,
919 SectionKind::getReadOnly(),
921 sh_info = SectionIndexMap[InfoSection];
925 case ELF::SHT_SYMTAB:
926 case ELF::SHT_DYNSYM:
927 sh_link = StringTableIndex;
928 sh_info = LastLocalSymbolIndex;
931 case ELF::SHT_PROGBITS:
932 case ELF::SHT_STRTAB:
933 case ELF::SHT_NOBITS:
940 case ELF::SHT_SYMTAB_SHNDX:
942 assert(0 && "FIXME: sh_type value not supported!");
946 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
947 Section.getType(), Section.getFlags(),
948 Layout.getSectionAddress(&SD),
949 SectionOffsetMap.lookup(&SD.getSection()),
950 Layout.getSectionSize(&SD), sh_link,
951 sh_info, SD.getAlignment(),
952 Section.getEntrySize());
956 ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
959 bool HasRelocationAddend)
960 : MCObjectWriter(OS, IsLittleEndian)
962 Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend);
965 ELFObjectWriter::~ELFObjectWriter() {
966 delete (ELFObjectWriterImpl*) Impl;
969 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
970 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
973 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
974 const MCAsmLayout &Layout,
975 const MCFragment *Fragment,
976 const MCFixup &Fixup, MCValue Target,
977 uint64_t &FixedValue) {
978 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
982 void ELFObjectWriter::WriteObject(const MCAssembler &Asm,
983 const MCAsmLayout &Layout) {
984 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);