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 const std::string &Name = SymbolData->getSymbol().getName();
68 return Name < 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 // This holds the current offset into the object file.
109 unsigned Is64Bit : 1;
111 bool HasRelocationAddend;
113 // This holds the symbol table index of the last local symbol.
114 unsigned LastLocalSymbolIndex;
115 // This holds the .strtab section index.
116 unsigned StringTableIndex;
118 unsigned ShstrtabIndex;
121 ELFObjectWriterImpl(ELFObjectWriter *_Writer, bool _Is64Bit,
123 : Writer(_Writer), OS(Writer->getStream()), FileOff(0),
124 Is64Bit(_Is64Bit), HasRelocationAddend(_HasRelAddend) {
127 void Write8(uint8_t Value) { Writer->Write8(Value); }
128 void Write16(uint16_t Value) { Writer->Write16(Value); }
129 void Write32(uint32_t Value) { Writer->Write32(Value); }
130 void Write64(uint64_t Value) { Writer->Write64(Value); }
131 void WriteZeros(unsigned N) { Writer->WriteZeros(N); }
132 void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
133 Writer->WriteBytes(Str, ZeroFillSize);
136 void WriteWord(uint64_t W) {
144 void String8(char *buf, uint8_t Value) {
148 void StringLE16(char *buf, uint16_t Value) {
149 buf[0] = char(Value >> 0);
150 buf[1] = char(Value >> 8);
153 void StringLE32(char *buf, uint32_t Value) {
154 buf[0] = char(Value >> 0);
155 buf[1] = char(Value >> 8);
156 buf[2] = char(Value >> 16);
157 buf[3] = char(Value >> 24);
160 void StringLE64(char *buf, uint64_t Value) {
161 buf[0] = char(Value >> 0);
162 buf[1] = char(Value >> 8);
163 buf[2] = char(Value >> 16);
164 buf[3] = char(Value >> 24);
165 buf[4] = char(Value >> 32);
166 buf[5] = char(Value >> 40);
167 buf[6] = char(Value >> 48);
168 buf[7] = char(Value >> 56);
171 void StringBE16(char *buf ,uint16_t Value) {
172 buf[0] = char(Value >> 8);
173 buf[1] = char(Value >> 0);
176 void StringBE32(char *buf, uint32_t Value) {
177 buf[0] = char(Value >> 24);
178 buf[1] = char(Value >> 16);
179 buf[2] = char(Value >> 8);
180 buf[3] = char(Value >> 0);
183 void StringBE64(char *buf, uint64_t Value) {
184 buf[0] = char(Value >> 56);
185 buf[1] = char(Value >> 48);
186 buf[2] = char(Value >> 40);
187 buf[3] = char(Value >> 32);
188 buf[4] = char(Value >> 24);
189 buf[5] = char(Value >> 16);
190 buf[6] = char(Value >> 8);
191 buf[7] = char(Value >> 0);
194 void String16(char *buf, uint16_t Value) {
195 if (Writer->isLittleEndian())
196 StringLE16(buf, Value);
198 StringBE16(buf, Value);
201 void String32(char *buf, uint32_t Value) {
202 if (Writer->isLittleEndian())
203 StringLE32(buf, Value);
205 StringBE32(buf, Value);
208 void String64(char *buf, uint64_t Value) {
209 if (Writer->isLittleEndian())
210 StringLE64(buf, Value);
212 StringBE64(buf, Value);
215 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
217 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
218 uint64_t value, uint64_t size,
219 uint8_t other, uint16_t shndx);
221 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
222 const MCAsmLayout &Layout);
224 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
225 const MCAsmLayout &Layout);
227 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
228 const MCFragment *Fragment, const MCFixup &Fixup,
229 MCValue Target, uint64_t &FixedValue);
231 // XXX-PERF: this should be cached
232 uint64_t getNumOfLocalSymbols(const MCAssembler &Asm) {
233 std::vector<const MCSymbol*> Local;
236 for (MCAssembler::const_symbol_iterator it = Asm.symbol_begin(),
237 ie = Asm.symbol_end(); it != ie; ++it) {
238 const MCSymbol &Symbol = it->getSymbol();
240 // Ignore non-linker visible symbols.
241 if (!Asm.isSymbolLinkerVisible(Symbol))
244 if (it->isExternal() || Symbol.isUndefined())
253 uint64_t getSymbolIndexInSymbolTable(MCAssembler &Asm, const MCSymbol *S);
255 /// ComputeSymbolTable - Compute the symbol table data
257 /// \param StringTable [out] - The string table data.
258 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
260 void ComputeSymbolTable(MCAssembler &Asm);
262 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
263 const MCSectionData &SD);
265 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
266 for (MCAssembler::const_iterator it = Asm.begin(),
267 ie = Asm.end(); it != ie; ++it) {
268 WriteRelocation(Asm, Layout, *it);
272 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
274 void ExecutePostLayoutBinding(MCAssembler &Asm) {}
276 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
277 uint64_t Address, uint64_t Offset,
278 uint64_t Size, uint32_t Link, uint32_t Info,
279 uint64_t Alignment, uint64_t EntrySize);
281 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
282 const MCSectionData *SD);
284 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
289 // Emit the ELF header.
290 void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
291 unsigned NumberOfSections) {
297 // emitWord method behaves differently for ELF32 and ELF64, writing
298 // 4 bytes in the former and 8 in the latter.
300 Write8(0x7f); // e_ident[EI_MAG0]
301 Write8('E'); // e_ident[EI_MAG1]
302 Write8('L'); // e_ident[EI_MAG2]
303 Write8('F'); // e_ident[EI_MAG3]
305 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
308 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
310 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
311 Write8(ELF::ELFOSABI_LINUX); // e_ident[EI_OSABI]
312 Write8(0); // e_ident[EI_ABIVERSION]
314 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
316 Write16(ELF::ET_REL); // e_type
318 // FIXME: Make this configurable
319 Write16(ELF::EM_X86_64); // e_machine = target
321 Write32(ELF::EV_CURRENT); // e_version
322 WriteWord(0); // e_entry, no entry point in .o file
323 WriteWord(0); // e_phoff, no program header for .o
324 WriteWord(SectionDataSize + 64); // e_shoff = sec hdr table off in bytes
326 // FIXME: Make this configurable.
327 Write32(0); // e_flags = whatever the target wants
329 // e_ehsize = ELF header size
330 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
332 Write16(0); // e_phentsize = prog header entry size
333 Write16(0); // e_phnum = # prog header entries = 0
335 // e_shentsize = Section header entry size
336 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
338 // e_shnum = # of section header ents
339 Write16(NumberOfSections);
341 // e_shstrndx = Section # of '.shstrtab'
342 Write16(ShstrtabIndex);
345 void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
346 uint8_t info, uint64_t value,
347 uint64_t size, uint8_t other,
353 F->getContents() += StringRef(buf, 4); // st_name
356 F->getContents() += StringRef(buf, 1); // st_info
359 F->getContents() += StringRef(buf, 1); // st_other
361 String16(buf, shndx);
362 F->getContents() += StringRef(buf, 2); // st_shndx
364 String64(buf, value);
365 F->getContents() += StringRef(buf, 8); // st_value
368 F->getContents() += StringRef(buf, 8); // st_size
373 F->getContents() += StringRef(buf, 4); // st_name
375 String32(buf, value);
376 F->getContents() += StringRef(buf, 4); // st_value
379 F->getContents() += StringRef(buf, 4); // st_size
382 F->getContents() += StringRef(buf, 1); // st_info
385 F->getContents() += StringRef(buf, 1); // st_other
387 String16(buf, shndx);
388 F->getContents() += StringRef(buf, 2); // st_shndx
392 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
393 const MCAsmLayout &Layout) {
394 MCSymbolData &Data = *MSD.SymbolData;
395 uint8_t Info = (Data.getFlags() & 0xff);
396 uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift);
401 if (Data.isCommon() && Data.isExternal())
402 Value = Data.getCommonAlignment();
404 ESize = Data.getSize();
405 if (Data.getSize()) {
407 if (ESize->getKind() == MCExpr::Binary) {
408 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
410 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
412 Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol());
414 Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol());
416 Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B);
417 Value = Layout.getSymbolAddress(&Data);
419 } else if (ESize->getKind() == MCExpr::Constant) {
420 Size = static_cast<const MCConstantExpr *>(ESize)->getValue();
422 assert(0 && "Unsupported size expression");
426 // Write out the symbol table entry
427 WriteSymbolEntry(F, MSD.StringIndex, Info, Value,
428 Size, Other, MSD.SectionIndex);
431 void ELFObjectWriterImpl::WriteSymbolTable(MCDataFragment *F,
432 const MCAssembler &Asm,
433 const MCAsmLayout &Layout) {
434 // The string table must be emitted first because we need the index
435 // into the string table for all the symbol names.
436 assert(StringTable.size() && "Missing string table");
438 // FIXME: Make sure the start of the symbol table is aligned.
440 // The first entry is the undefined symbol entry.
441 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
442 F->getContents().append(EntrySize, '\x00');
444 // Write the symbol table entries.
445 LastLocalSymbolIndex = LocalSymbolData.size() + 1;
446 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i) {
447 ELFSymbolData &MSD = LocalSymbolData[i];
448 WriteSymbol(F, MSD, Layout);
451 // Write out a symbol table entry for each section.
452 // leaving out the just added .symtab which is at
455 for (MCAssembler::const_iterator it = Asm.begin(),
456 ie = Asm.end(); it != ie; ++it, ++Index) {
457 const MCSectionELF &Section =
458 static_cast<const MCSectionELF&>(it->getSection());
459 // Leave out relocations so we don't have indexes within
460 // the relocations messed up
461 if (Section.getType() == ELF::SHT_RELA)
463 if (Index == Asm.size())
465 WriteSymbolEntry(F, 0, ELF::STT_SECTION, 0, 0, ELF::STV_DEFAULT, Index);
466 LastLocalSymbolIndex++;
469 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i) {
470 ELFSymbolData &MSD = ExternalSymbolData[i];
471 MCSymbolData &Data = *MSD.SymbolData;
472 assert((Data.getFlags() & ELF_STB_Global) &&
473 "External symbol requires STB_GLOBAL flag");
474 WriteSymbol(F, MSD, Layout);
475 if (Data.getFlags() & ELF_STB_Local)
476 LastLocalSymbolIndex++;
479 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i) {
480 ELFSymbolData &MSD = UndefinedSymbolData[i];
481 MCSymbolData &Data = *MSD.SymbolData;
482 Data.setFlags(Data.getFlags() | ELF_STB_Global);
483 WriteSymbol(F, MSD, Layout);
484 if (Data.getFlags() & ELF_STB_Local)
485 LastLocalSymbolIndex++;
489 // FIXME: this is currently X86_64 only
490 void ELFObjectWriterImpl::RecordRelocation(const MCAssembler &Asm,
491 const MCAsmLayout &Layout,
492 const MCFragment *Fragment,
493 const MCFixup &Fixup,
495 uint64_t &FixedValue) {
496 unsigned IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
497 ELFRelocationEntry ERE;
498 struct ELF::Elf64_Rela ERE64;
500 uint64_t FixupOffset =
501 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
507 Value = Target.getConstant();
509 if (Target.isAbsolute()) {
510 Type = ELF::R_X86_64_NONE;
513 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
514 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
515 const MCSymbolData *Base = Asm.getAtom(Layout, &SD);
518 Index = getSymbolIndexInSymbolTable(const_cast<MCAssembler &>(Asm), &Base->getSymbol());
520 Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
524 MCFragment *F = SD.getFragment();
526 // Index of the section in .symtab against this symbol
527 // is being relocated + 2 (empty section + abs. symbols).
528 Index = SD.getFragment()->getParent()->getOrdinal() +
529 getNumOfLocalSymbols(Asm) + 1;
531 MCSectionData *FSD = F->getParent();
532 // Offset of the symbol in the section
533 Addend = Layout.getSymbolAddress(&SD) - Layout.getSectionAddress(FSD);
541 // determine the type of the relocation
543 Type = ELF::R_X86_64_PC32;
545 switch ((unsigned)Fixup.getKind()) {
546 default: llvm_unreachable("invalid fixup kind!");
547 case FK_Data_8: Type = ELF::R_X86_64_64; break;
548 case X86::reloc_pcrel_4byte:
550 // check that the offset fits within a signed long
551 if (isInt<32>(Target.getConstant()))
552 Type = ELF::R_X86_64_32S;
554 Type = ELF::R_X86_64_32;
556 case FK_Data_2: Type = ELF::R_X86_64_16; break;
557 case X86::reloc_pcrel_1byte:
559 Type = ELF::R_X86_64_8;
566 ERE64.setSymbolAndType(Index, Type);
568 ERE.r_offset = FixupOffset;
569 ERE.r_info = ERE64.r_info;
570 if (HasRelocationAddend)
571 ERE.r_addend = Addend;
573 ERE.r_addend = 0; // Silence compiler warning.
575 Relocations[Fragment->getParent()].push_back(ERE);
578 // XXX-PERF: this should be cached
579 uint64_t ELFObjectWriterImpl::getSymbolIndexInSymbolTable(MCAssembler &Asm,
581 std::vector<ELFSymbolData> Local;
582 std::vector<ELFSymbolData> External;
583 std::vector<ELFSymbolData> Undefined;
585 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
586 ie = Asm.symbol_end(); it != ie; ++it) {
587 const MCSymbol &Symbol = it->getSymbol();
589 // Ignore non-linker visible symbols.
590 if (!Asm.isSymbolLinkerVisible(Symbol))
593 if (it->isExternal() || Symbol.isUndefined())
599 Local.push_back(MSD);
601 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
602 ie = Asm.symbol_end(); it != ie; ++it) {
603 const MCSymbol &Symbol = it->getSymbol();
605 // Ignore non-linker visible symbols.
606 if (!Asm.isSymbolLinkerVisible(Symbol))
609 if (!it->isExternal() && !Symbol.isUndefined())
615 if (Symbol.isUndefined())
616 Undefined.push_back(MSD);
618 External.push_back(MSD);
621 array_pod_sort(Local.begin(), Local.end());
622 array_pod_sort(External.begin(), External.end());
623 array_pod_sort(Undefined.begin(), Undefined.end());
625 for (unsigned i = 0, e = Local.size(); i != e; ++i)
626 if (&Local[i].SymbolData->getSymbol() == S)
627 return i + /* empty symbol */ 1;
628 for (unsigned i = 0, e = External.size(); i != e; ++i)
629 if (&External[i].SymbolData->getSymbol() == S)
630 return i + Local.size() + Asm.size() + /* empty symbol */ 1;
631 for (unsigned i = 0, e = Undefined.size(); i != e; ++i)
632 if (&Undefined[i].SymbolData->getSymbol() == S)
633 return i + Local.size() + External.size() + Asm.size() + /* empty symbol */ 1;
635 llvm_unreachable("Cannot find symbol which should exist!");
638 void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
639 // Build section lookup table.
640 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
642 for (MCAssembler::iterator it = Asm.begin(),
643 ie = Asm.end(); it != ie; ++it, ++Index)
644 SectionIndexMap[&it->getSection()] = Index;
646 // Index 0 is always the empty string.
647 StringMap<uint64_t> StringIndexMap;
648 StringTable += '\x00';
650 // Add the data for local symbols.
651 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
652 ie = Asm.symbol_end(); it != ie; ++it) {
653 const MCSymbol &Symbol = it->getSymbol();
655 // Ignore non-linker visible symbols.
656 if (!Asm.isSymbolLinkerVisible(Symbol))
659 if (it->isExternal() || Symbol.isUndefined())
662 uint64_t &Entry = StringIndexMap[Symbol.getName()];
664 Entry = StringTable.size();
665 StringTable += Symbol.getName();
666 StringTable += '\x00';
671 MSD.StringIndex = Entry;
673 if (Symbol.isAbsolute()) {
674 MSD.SectionIndex = ELF::SHN_ABS;
675 LocalSymbolData.push_back(MSD);
677 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
678 assert(MSD.SectionIndex && "Invalid section index!");
679 LocalSymbolData.push_back(MSD);
683 // Now add non-local symbols.
684 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
685 ie = Asm.symbol_end(); it != ie; ++it) {
686 const MCSymbol &Symbol = it->getSymbol();
688 // Ignore non-linker visible symbols.
689 if (!Asm.isSymbolLinkerVisible(Symbol))
692 if (!it->isExternal() && !Symbol.isUndefined())
695 uint64_t &Entry = StringIndexMap[Symbol.getName()];
697 Entry = StringTable.size();
698 StringTable += Symbol.getName();
699 StringTable += '\x00';
704 MSD.StringIndex = Entry;
706 if (Symbol.isUndefined()) {
707 MSD.SectionIndex = ELF::SHN_UNDEF;
708 // XXX: for some reason we dont Emit* this
709 it->setFlags(it->getFlags() | ELF_STB_Global);
710 UndefinedSymbolData.push_back(MSD);
711 } else if (Symbol.isAbsolute()) {
712 MSD.SectionIndex = ELF::SHN_ABS;
713 ExternalSymbolData.push_back(MSD);
714 } else if (it->isCommon()) {
715 MSD.SectionIndex = ELF::SHN_COMMON;
716 ExternalSymbolData.push_back(MSD);
718 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
719 assert(MSD.SectionIndex && "Invalid section index!");
720 ExternalSymbolData.push_back(MSD);
724 // Symbols are required to be in lexicographic order.
725 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
726 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
727 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
729 // Set the symbol indices. Local symbols must come before all other
730 // symbols with non-local bindings.
732 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
733 LocalSymbolData[i].SymbolData->setIndex(Index++);
734 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
735 ExternalSymbolData[i].SymbolData->setIndex(Index++);
736 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
737 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
740 void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
741 const MCSectionData &SD) {
742 if (!Relocations[&SD].empty()) {
743 MCContext &Ctx = Asm.getContext();
744 const MCSection *RelaSection;
745 const MCSectionELF &Section =
746 static_cast<const MCSectionELF&>(SD.getSection());
748 const StringRef SectionName = Section.getSectionName();
749 std::string RelaSectionName = ".rela";
751 RelaSectionName += SectionName;
752 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
754 RelaSection = Ctx.getELFSection(RelaSectionName, ELF::SHT_RELA, 0,
755 SectionKind::getReadOnly(),
758 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
759 RelaSD.setAlignment(1);
761 MCDataFragment *F = new MCDataFragment(&RelaSD);
763 WriteRelocationsFragment(Asm, F, &SD);
765 Asm.AddSectionToTheEnd(RelaSD, Layout);
769 void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
770 uint64_t Flags, uint64_t Address,
771 uint64_t Offset, uint64_t Size,
772 uint32_t Link, uint32_t Info,
774 uint64_t EntrySize) {
775 Write32(Name); // sh_name: index into string table
776 Write32(Type); // sh_type
777 WriteWord(Flags); // sh_flags
778 WriteWord(Address); // sh_addr
779 WriteWord(Offset); // sh_offset
780 WriteWord(Size); // sh_size
781 Write32(Link); // sh_link
782 Write32(Info); // sh_info
783 WriteWord(Alignment); // sh_addralign
784 WriteWord(EntrySize); // sh_entsize
787 void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
789 const MCSectionData *SD) {
790 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
791 // sort by the r_offset just like gnu as does
792 array_pod_sort(Relocs.begin(), Relocs.end());
794 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
795 ELFRelocationEntry entry = Relocs[e - i - 1];
797 unsigned WordSize = Is64Bit ? 8 : 4;
798 F->getContents() += StringRef((const char *)&entry.r_offset, WordSize);
799 F->getContents() += StringRef((const char *)&entry.r_info, WordSize);
801 if (HasRelocationAddend)
802 F->getContents() += StringRef((const char *)&entry.r_addend, WordSize);
806 void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
807 MCAsmLayout &Layout) {
808 MCContext &Ctx = Asm.getContext();
811 WriteRelocations(Asm, Layout);
813 const MCSection *SymtabSection;
814 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
816 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
817 SectionKind::getReadOnly(),
820 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
822 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
824 F = new MCDataFragment(&SymtabSD);
827 WriteSymbolTable(F, Asm, Layout);
828 Asm.AddSectionToTheEnd(SymtabSD, Layout);
830 const MCSection *StrtabSection;
831 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
832 SectionKind::getReadOnly(), false);
834 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
835 StrtabSD.setAlignment(1);
837 // FIXME: This isn't right. If the sections get rearranged this will
838 // be wrong. We need a proper lookup.
839 StringTableIndex = Asm.size();
841 F = new MCDataFragment(&StrtabSD);
842 F->getContents().append(StringTable.begin(), StringTable.end());
843 Asm.AddSectionToTheEnd(StrtabSD, Layout);
845 const MCSection *ShstrtabSection;
846 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
847 SectionKind::getReadOnly(), false);
849 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
850 ShstrtabSD.setAlignment(1);
852 F = new MCDataFragment(&ShstrtabSD);
854 // FIXME: This isn't right. If the sections get rearranged this will
855 // be wrong. We need a proper lookup.
856 ShstrtabIndex = Asm.size();
858 // Section header string table.
860 // The first entry of a string table holds a null character so skip
863 F->getContents() += '\x00';
865 for (MCAssembler::const_iterator it = Asm.begin(),
866 ie = Asm.end(); it != ie; ++it) {
867 const MCSectionELF &Section =
868 static_cast<const MCSectionELF&>(it->getSection());
870 // Remember the index into the string table so we can write it
871 // into the sh_name field of the section header table.
872 SectionStringTableIndex[&it->getSection()] = Index;
874 Index += Section.getSectionName().size() + 1;
875 F->getContents() += Section.getSectionName();
876 F->getContents() += '\x00';
879 Asm.AddSectionToTheEnd(ShstrtabSD, Layout);
882 void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm,
883 const MCAsmLayout &Layout) {
884 // Compute symbol table information.
885 ComputeSymbolTable(const_cast<MCAssembler&>(Asm));
887 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
888 const_cast<MCAsmLayout&>(Layout));
890 // Add 1 for the null section.
891 unsigned NumSections = Asm.size() + 1;
893 uint64_t SectionDataSize = 0;
895 for (MCAssembler::const_iterator it = Asm.begin(),
896 ie = Asm.end(); it != ie; ++it) {
897 const MCSectionData &SD = *it;
899 // Get the size of the section in the output file (including padding).
900 uint64_t Size = Layout.getSectionFileSize(&SD);
901 SectionDataSize += Size;
904 // Write out the ELF header ...
905 WriteHeader(SectionDataSize, NumSections);
906 FileOff = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
908 // ... then all of the sections ...
909 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
911 for (MCAssembler::const_iterator it = Asm.begin(),
912 ie = Asm.end(); it != ie; ++it) {
913 // Remember the offset into the file for this section.
914 SectionOffsetMap[&it->getSection()] = FileOff;
916 const MCSectionData &SD = *it;
917 FileOff += Layout.getSectionFileSize(&SD);
919 Asm.WriteSectionData(it, Layout, Writer);
922 // ... and then the section header table.
923 // Should we align the section header table?
925 // Null section first.
926 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
928 for (MCAssembler::const_iterator it = Asm.begin(),
929 ie = Asm.end(); it != ie; ++it) {
930 const MCSectionData &SD = *it;
931 const MCSectionELF &Section =
932 static_cast<const MCSectionELF&>(SD.getSection());
934 uint64_t sh_link = 0;
935 uint64_t sh_info = 0;
937 switch(Section.getType()) {
938 case ELF::SHT_DYNAMIC:
939 sh_link = SectionStringTableIndex[&it->getSection()];
944 case ELF::SHT_RELA: {
945 const MCSection *SymtabSection;
946 const MCSection *InfoSection;
947 StringRef SectionName;
948 const MCSectionData *SymtabSD;
949 const MCSectionData *InfoSD;
951 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
952 SectionKind::getReadOnly(),
954 SymtabSD = &Asm.getSectionData(*SymtabSection);
955 // we have to count the empty section in too
956 sh_link = SymtabSD->getLayoutOrder() + 1;
958 SectionName = Section.getSectionName();
959 SectionName = SectionName.slice(5, SectionName.size());
960 InfoSection = Asm.getContext().getELFSection(SectionName,
961 ELF::SHT_PROGBITS, 0,
962 SectionKind::getReadOnly(),
964 InfoSD = &Asm.getSectionData(*InfoSection);
965 sh_info = InfoSD->getLayoutOrder() + 1;
969 case ELF::SHT_SYMTAB:
970 case ELF::SHT_DYNSYM:
971 sh_link = StringTableIndex;
972 sh_info = LastLocalSymbolIndex;
975 case ELF::SHT_PROGBITS:
976 case ELF::SHT_STRTAB:
977 case ELF::SHT_NOBITS:
983 case ELF::SHT_SYMTAB_SHNDX:
985 assert(0 && "FIXME: sh_type value not supported!");
989 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
990 Section.getType(), Section.getFlags(),
991 Layout.getSectionAddress(&SD),
992 SectionOffsetMap.lookup(&SD.getSection()),
993 Layout.getSectionSize(&SD), sh_link,
994 sh_info, SD.getAlignment(),
995 Section.getEntrySize());
999 ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
1001 bool IsLittleEndian,
1002 bool HasRelocationAddend)
1003 : MCObjectWriter(OS, IsLittleEndian)
1005 Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend);
1008 ELFObjectWriter::~ELFObjectWriter() {
1009 delete (ELFObjectWriterImpl*) Impl;
1012 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
1013 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
1016 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
1017 const MCAsmLayout &Layout,
1018 const MCFragment *Fragment,
1019 const MCFixup &Fixup, MCValue Target,
1020 uint64_t &FixedValue) {
1021 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
1022 Target, FixedValue);
1025 void ELFObjectWriter::WriteObject(const MCAssembler &Asm,
1026 const MCAsmLayout &Layout) {
1027 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);