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 // 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 StringLE16(buf, uint16_t(Value >> 0));
155 StringLE16(buf + 2, uint16_t(Value >> 16));
158 void StringLE64(char *buf, uint64_t Value) {
159 StringLE32(buf, uint32_t(Value >> 0));
160 StringLE32(buf + 4, uint32_t(Value >> 32));
163 void StringBE16(char *buf ,uint16_t Value) {
164 buf[0] = char(Value >> 8);
165 buf[1] = char(Value >> 0);
168 void StringBE32(char *buf, uint32_t Value) {
169 StringBE16(buf, uint16_t(Value >> 16));
170 StringBE16(buf + 2, uint16_t(Value >> 0));
173 void StringBE64(char *buf, uint64_t Value) {
174 StringBE32(buf, uint32_t(Value >> 32));
175 StringBE32(buf + 4, uint32_t(Value >> 0));
178 void String16(char *buf, uint16_t Value) {
179 if (Writer->isLittleEndian())
180 StringLE16(buf, Value);
182 StringBE16(buf, Value);
185 void String32(char *buf, uint32_t Value) {
186 if (Writer->isLittleEndian())
187 StringLE32(buf, Value);
189 StringBE32(buf, Value);
192 void String64(char *buf, uint64_t Value) {
193 if (Writer->isLittleEndian())
194 StringLE64(buf, Value);
196 StringBE64(buf, Value);
199 void WriteHeader(uint64_t SectionDataSize, unsigned NumberOfSections);
201 void WriteSymbolEntry(MCDataFragment *F, uint64_t name, uint8_t info,
202 uint64_t value, uint64_t size,
203 uint8_t other, uint16_t shndx);
205 void WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
206 const MCAsmLayout &Layout);
208 void WriteSymbolTable(MCDataFragment *F, const MCAssembler &Asm,
209 const MCAsmLayout &Layout);
211 void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
212 const MCFragment *Fragment, const MCFixup &Fixup,
213 MCValue Target, uint64_t &FixedValue);
215 uint64_t getSymbolIndexInSymbolTable(const MCAssembler &Asm,
218 /// ComputeSymbolTable - Compute the symbol table data
220 /// \param StringTable [out] - The string table data.
221 /// \param StringIndexMap [out] - Map from symbol names to offsets in the
223 void ComputeSymbolTable(MCAssembler &Asm);
225 void WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
226 const MCSectionData &SD);
228 void WriteRelocations(MCAssembler &Asm, MCAsmLayout &Layout) {
229 for (MCAssembler::const_iterator it = Asm.begin(),
230 ie = Asm.end(); it != ie; ++it) {
231 WriteRelocation(Asm, Layout, *it);
235 void CreateMetadataSections(MCAssembler &Asm, MCAsmLayout &Layout);
237 void ExecutePostLayoutBinding(MCAssembler &Asm) {
238 // Compute symbol table information.
239 ComputeSymbolTable(Asm);
242 void WriteSecHdrEntry(uint32_t Name, uint32_t Type, uint64_t Flags,
243 uint64_t Address, uint64_t Offset,
244 uint64_t Size, uint32_t Link, uint32_t Info,
245 uint64_t Alignment, uint64_t EntrySize);
247 void WriteRelocationsFragment(const MCAssembler &Asm, MCDataFragment *F,
248 const MCSectionData *SD);
250 void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
255 // Emit the ELF header.
256 void ELFObjectWriterImpl::WriteHeader(uint64_t SectionDataSize,
257 unsigned NumberOfSections) {
263 // emitWord method behaves differently for ELF32 and ELF64, writing
264 // 4 bytes in the former and 8 in the latter.
266 Write8(0x7f); // e_ident[EI_MAG0]
267 Write8('E'); // e_ident[EI_MAG1]
268 Write8('L'); // e_ident[EI_MAG2]
269 Write8('F'); // e_ident[EI_MAG3]
271 Write8(Is64Bit ? ELF::ELFCLASS64 : ELF::ELFCLASS32); // e_ident[EI_CLASS]
274 Write8(Writer->isLittleEndian() ? ELF::ELFDATA2LSB : ELF::ELFDATA2MSB);
276 Write8(ELF::EV_CURRENT); // e_ident[EI_VERSION]
277 Write8(ELF::ELFOSABI_LINUX); // e_ident[EI_OSABI]
278 Write8(0); // e_ident[EI_ABIVERSION]
280 WriteZeros(ELF::EI_NIDENT - ELF::EI_PAD);
282 Write16(ELF::ET_REL); // e_type
284 // FIXME: Make this configurable
285 Write16(Is64Bit ? ELF::EM_X86_64 : ELF::EM_386); // e_machine = target
287 Write32(ELF::EV_CURRENT); // e_version
288 WriteWord(0); // e_entry, no entry point in .o file
289 WriteWord(0); // e_phoff, no program header for .o
290 WriteWord(SectionDataSize + (Is64Bit ? sizeof(ELF::Elf64_Ehdr) :
291 sizeof(ELF::Elf32_Ehdr))); // e_shoff = sec hdr table off in bytes
293 // FIXME: Make this configurable.
294 Write32(0); // e_flags = whatever the target wants
296 // e_ehsize = ELF header size
297 Write16(Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr));
299 Write16(0); // e_phentsize = prog header entry size
300 Write16(0); // e_phnum = # prog header entries = 0
302 // e_shentsize = Section header entry size
303 Write16(Is64Bit ? sizeof(ELF::Elf64_Shdr) : sizeof(ELF::Elf32_Shdr));
305 // e_shnum = # of section header ents
306 Write16(NumberOfSections);
308 // e_shstrndx = Section # of '.shstrtab'
309 Write16(ShstrtabIndex);
312 void ELFObjectWriterImpl::WriteSymbolEntry(MCDataFragment *F, uint64_t name,
313 uint8_t info, uint64_t value,
314 uint64_t size, uint8_t other,
320 F->getContents() += StringRef(buf, 4); // st_name
323 F->getContents() += StringRef(buf, 1); // st_info
326 F->getContents() += StringRef(buf, 1); // st_other
328 String16(buf, shndx);
329 F->getContents() += StringRef(buf, 2); // st_shndx
331 String64(buf, value);
332 F->getContents() += StringRef(buf, 8); // st_value
335 F->getContents() += StringRef(buf, 8); // st_size
340 F->getContents() += StringRef(buf, 4); // st_name
342 String32(buf, value);
343 F->getContents() += StringRef(buf, 4); // st_value
346 F->getContents() += StringRef(buf, 4); // st_size
349 F->getContents() += StringRef(buf, 1); // st_info
352 F->getContents() += StringRef(buf, 1); // st_other
354 String16(buf, shndx);
355 F->getContents() += StringRef(buf, 2); // st_shndx
359 void ELFObjectWriterImpl::WriteSymbol(MCDataFragment *F, ELFSymbolData &MSD,
360 const MCAsmLayout &Layout) {
361 MCSymbolData &Data = *MSD.SymbolData;
362 uint8_t Info = (Data.getFlags() & 0xff);
363 uint8_t Other = ((Data.getFlags() & 0xf00) >> ELF_STV_Shift);
368 if (Data.isCommon() && Data.isExternal())
369 Value = Data.getCommonAlignment();
371 ESize = Data.getSize();
372 if (Data.getSize()) {
374 if (ESize->getKind() == MCExpr::Binary) {
375 const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(ESize);
377 if (BE->EvaluateAsRelocatable(Res, &Layout)) {
379 Layout.getAssembler().getSymbolData(Res.getSymA()->getSymbol());
381 Layout.getAssembler().getSymbolData(Res.getSymB()->getSymbol());
383 Size = Layout.getSymbolAddress(&A) - Layout.getSymbolAddress(&B);
384 Value = Layout.getSymbolAddress(&Data);
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) {
466 if (!Target.isAbsolute()) {
467 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
468 MCSymbolData &SD = Asm.getSymbolData(*Symbol);
469 const MCSymbolData *Base = Asm.getAtom(Layout, &SD);
470 MCFragment *F = SD.getFragment();
471 int64_t Value = Target.getConstant();
474 if (F && (!Symbol->isInSection() || SD.isCommon())) {
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);
502 // determine the type of the relocation
503 bool IsPCRel = isFixupKindX86PCRel(Fixup.getKind());
507 Type = ELF::R_X86_64_PC32;
509 switch ((unsigned)Fixup.getKind()) {
510 default: llvm_unreachable("invalid fixup kind!");
511 case FK_Data_8: Type = ELF::R_X86_64_64; break;
512 case X86::reloc_pcrel_4byte:
514 // check that the offset fits within a signed long
515 if (isInt<32>(Target.getConstant()))
516 Type = ELF::R_X86_64_32S;
518 Type = ELF::R_X86_64_32;
520 case FK_Data_2: Type = ELF::R_X86_64_16; break;
521 case X86::reloc_pcrel_1byte:
522 case FK_Data_1: Type = ELF::R_X86_64_8; break;
527 Type = ELF::R_386_PC32;
529 switch ((unsigned)Fixup.getKind()) {
530 default: llvm_unreachable("invalid fixup kind!");
531 case X86::reloc_pcrel_4byte:
532 case FK_Data_4: Type = ELF::R_386_32; break;
533 case FK_Data_2: Type = ELF::R_386_16; break;
534 case X86::reloc_pcrel_1byte:
535 case FK_Data_1: Type = ELF::R_386_8; break;
540 ELFRelocationEntry ERE;
543 struct ELF::Elf64_Rela ERE64;
544 ERE64.setSymbolAndType(Index, Type);
545 ERE.r_info = ERE64.r_info;
547 struct ELF::Elf32_Rela ERE32;
548 ERE32.setSymbolAndType(Index, Type);
549 ERE.r_info = ERE32.r_info;
552 ERE.r_offset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
554 if (HasRelocationAddend)
555 ERE.r_addend = Addend;
557 ERE.r_addend = 0; // Silence compiler warning.
559 Relocations[Fragment->getParent()].push_back(ERE);
563 ELFObjectWriterImpl::getSymbolIndexInSymbolTable(const MCAssembler &Asm,
565 MCSymbolData &SD = Asm.getSymbolData(*S);
568 if (!SD.isExternal() && !S->isUndefined())
569 return SD.getIndex() + /* empty symbol */ 1;
571 // External or undefined symbol.
572 return SD.getIndex() + Asm.size() + /* empty symbol */ 1;
575 void ELFObjectWriterImpl::ComputeSymbolTable(MCAssembler &Asm) {
576 // Build section lookup table.
577 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
579 for (MCAssembler::iterator it = Asm.begin(),
580 ie = Asm.end(); it != ie; ++it, ++Index)
581 SectionIndexMap[&it->getSection()] = Index;
583 // Index 0 is always the empty string.
584 StringMap<uint64_t> StringIndexMap;
585 StringTable += '\x00';
587 // Add the data for local symbols.
588 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
589 ie = Asm.symbol_end(); it != ie; ++it) {
590 const MCSymbol &Symbol = it->getSymbol();
592 // Ignore non-linker visible symbols.
593 if (!Asm.isSymbolLinkerVisible(Symbol))
596 if (it->isExternal() || Symbol.isUndefined())
599 uint64_t &Entry = StringIndexMap[Symbol.getName()];
601 Entry = StringTable.size();
602 StringTable += Symbol.getName();
603 StringTable += '\x00';
608 MSD.StringIndex = Entry;
610 if (Symbol.isAbsolute()) {
611 MSD.SectionIndex = ELF::SHN_ABS;
612 LocalSymbolData.push_back(MSD);
614 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
615 assert(MSD.SectionIndex && "Invalid section index!");
616 LocalSymbolData.push_back(MSD);
620 // Now add non-local symbols.
621 for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
622 ie = Asm.symbol_end(); it != ie; ++it) {
623 const MCSymbol &Symbol = it->getSymbol();
625 // Ignore non-linker visible symbols.
626 if (!Asm.isSymbolLinkerVisible(Symbol))
629 if (!it->isExternal() && !Symbol.isUndefined())
632 uint64_t &Entry = StringIndexMap[Symbol.getName()];
634 Entry = StringTable.size();
635 StringTable += Symbol.getName();
636 StringTable += '\x00';
641 MSD.StringIndex = Entry;
643 if (Symbol.isUndefined()) {
644 MSD.SectionIndex = ELF::SHN_UNDEF;
645 // XXX: for some reason we dont Emit* this
646 it->setFlags(it->getFlags() | ELF_STB_Global);
647 UndefinedSymbolData.push_back(MSD);
648 } else if (Symbol.isAbsolute()) {
649 MSD.SectionIndex = ELF::SHN_ABS;
650 ExternalSymbolData.push_back(MSD);
651 } else if (it->isCommon()) {
652 MSD.SectionIndex = ELF::SHN_COMMON;
653 ExternalSymbolData.push_back(MSD);
655 MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
656 assert(MSD.SectionIndex && "Invalid section index!");
657 ExternalSymbolData.push_back(MSD);
661 // Symbols are required to be in lexicographic order.
662 array_pod_sort(LocalSymbolData.begin(), LocalSymbolData.end());
663 array_pod_sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
664 array_pod_sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
666 // Set the symbol indices. Local symbols must come before all other
667 // symbols with non-local bindings.
669 for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
670 LocalSymbolData[i].SymbolData->setIndex(Index++);
671 for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
672 ExternalSymbolData[i].SymbolData->setIndex(Index++);
673 for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
674 UndefinedSymbolData[i].SymbolData->setIndex(Index++);
677 void ELFObjectWriterImpl::WriteRelocation(MCAssembler &Asm, MCAsmLayout &Layout,
678 const MCSectionData &SD) {
679 if (!Relocations[&SD].empty()) {
680 MCContext &Ctx = Asm.getContext();
681 const MCSection *RelaSection;
682 const MCSectionELF &Section =
683 static_cast<const MCSectionELF&>(SD.getSection());
685 const StringRef SectionName = Section.getSectionName();
686 std::string RelaSectionName = HasRelocationAddend ? ".rela" : ".rel";
687 RelaSectionName += SectionName;
690 if (HasRelocationAddend)
691 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rela) : sizeof(ELF::Elf32_Rela);
693 EntrySize = Is64Bit ? sizeof(ELF::Elf64_Rel) : sizeof(ELF::Elf32_Rel);
695 RelaSection = Ctx.getELFSection(RelaSectionName, HasRelocationAddend ?
696 ELF::SHT_RELA : ELF::SHT_REL, 0,
697 SectionKind::getReadOnly(),
700 MCSectionData &RelaSD = Asm.getOrCreateSectionData(*RelaSection);
701 RelaSD.setAlignment(1);
703 MCDataFragment *F = new MCDataFragment(&RelaSD);
705 WriteRelocationsFragment(Asm, F, &SD);
707 Asm.AddSectionToTheEnd(RelaSD, Layout);
711 void ELFObjectWriterImpl::WriteSecHdrEntry(uint32_t Name, uint32_t Type,
712 uint64_t Flags, uint64_t Address,
713 uint64_t Offset, uint64_t Size,
714 uint32_t Link, uint32_t Info,
716 uint64_t EntrySize) {
717 Write32(Name); // sh_name: index into string table
718 Write32(Type); // sh_type
719 WriteWord(Flags); // sh_flags
720 WriteWord(Address); // sh_addr
721 WriteWord(Offset); // sh_offset
722 WriteWord(Size); // sh_size
723 Write32(Link); // sh_link
724 Write32(Info); // sh_info
725 WriteWord(Alignment); // sh_addralign
726 WriteWord(EntrySize); // sh_entsize
729 void ELFObjectWriterImpl::WriteRelocationsFragment(const MCAssembler &Asm,
731 const MCSectionData *SD) {
732 std::vector<ELFRelocationEntry> &Relocs = Relocations[SD];
733 // sort by the r_offset just like gnu as does
734 array_pod_sort(Relocs.begin(), Relocs.end());
736 for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
737 ELFRelocationEntry entry = Relocs[e - i - 1];
739 unsigned WordSize = Is64Bit ? 8 : 4;
740 F->getContents() += StringRef((const char *)&entry.r_offset, WordSize);
741 F->getContents() += StringRef((const char *)&entry.r_info, WordSize);
743 if (HasRelocationAddend)
744 F->getContents() += StringRef((const char *)&entry.r_addend, WordSize);
748 void ELFObjectWriterImpl::CreateMetadataSections(MCAssembler &Asm,
749 MCAsmLayout &Layout) {
750 MCContext &Ctx = Asm.getContext();
753 WriteRelocations(Asm, Layout);
755 const MCSection *SymtabSection;
756 unsigned EntrySize = Is64Bit ? ELF::SYMENTRY_SIZE64 : ELF::SYMENTRY_SIZE32;
758 SymtabSection = Ctx.getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
759 SectionKind::getReadOnly(),
762 MCSectionData &SymtabSD = Asm.getOrCreateSectionData(*SymtabSection);
764 SymtabSD.setAlignment(Is64Bit ? 8 : 4);
766 F = new MCDataFragment(&SymtabSD);
769 WriteSymbolTable(F, Asm, Layout);
770 Asm.AddSectionToTheEnd(SymtabSD, Layout);
772 const MCSection *StrtabSection;
773 StrtabSection = Ctx.getELFSection(".strtab", ELF::SHT_STRTAB, 0,
774 SectionKind::getReadOnly(), false);
776 MCSectionData &StrtabSD = Asm.getOrCreateSectionData(*StrtabSection);
777 StrtabSD.setAlignment(1);
779 // FIXME: This isn't right. If the sections get rearranged this will
780 // be wrong. We need a proper lookup.
781 StringTableIndex = Asm.size();
783 F = new MCDataFragment(&StrtabSD);
784 F->getContents().append(StringTable.begin(), StringTable.end());
785 Asm.AddSectionToTheEnd(StrtabSD, Layout);
787 const MCSection *ShstrtabSection;
788 ShstrtabSection = Ctx.getELFSection(".shstrtab", ELF::SHT_STRTAB, 0,
789 SectionKind::getReadOnly(), false);
791 MCSectionData &ShstrtabSD = Asm.getOrCreateSectionData(*ShstrtabSection);
792 ShstrtabSD.setAlignment(1);
794 F = new MCDataFragment(&ShstrtabSD);
796 // FIXME: This isn't right. If the sections get rearranged this will
797 // be wrong. We need a proper lookup.
798 ShstrtabIndex = Asm.size();
800 // Section header string table.
802 // The first entry of a string table holds a null character so skip
805 F->getContents() += '\x00';
807 for (MCAssembler::const_iterator it = Asm.begin(),
808 ie = Asm.end(); it != ie; ++it) {
809 const MCSectionELF &Section =
810 static_cast<const MCSectionELF&>(it->getSection());
812 // Remember the index into the string table so we can write it
813 // into the sh_name field of the section header table.
814 SectionStringTableIndex[&it->getSection()] = Index;
816 Index += Section.getSectionName().size() + 1;
817 F->getContents() += Section.getSectionName();
818 F->getContents() += '\x00';
821 Asm.AddSectionToTheEnd(ShstrtabSD, Layout);
824 void ELFObjectWriterImpl::WriteObject(const MCAssembler &Asm,
825 const MCAsmLayout &Layout) {
826 CreateMetadataSections(const_cast<MCAssembler&>(Asm),
827 const_cast<MCAsmLayout&>(Layout));
829 // Add 1 for the null section.
830 unsigned NumSections = Asm.size() + 1;
832 uint64_t SectionDataSize = 0;
834 for (MCAssembler::const_iterator it = Asm.begin(),
835 ie = Asm.end(); it != ie; ++it) {
836 const MCSectionData &SD = *it;
838 // Get the size of the section in the output file (including padding).
839 uint64_t Size = Layout.getSectionFileSize(&SD);
840 SectionDataSize += Size;
843 // Write out the ELF header ...
844 WriteHeader(SectionDataSize, NumSections);
845 FileOff = Is64Bit ? sizeof(ELF::Elf64_Ehdr) : sizeof(ELF::Elf32_Ehdr);
847 // ... then all of the sections ...
848 DenseMap<const MCSection*, uint64_t> SectionOffsetMap;
850 DenseMap<const MCSection*, uint8_t> SectionIndexMap;
853 for (MCAssembler::const_iterator it = Asm.begin(),
854 ie = Asm.end(); it != ie; ++it) {
855 // Remember the offset into the file for this section.
856 SectionOffsetMap[&it->getSection()] = FileOff;
858 SectionIndexMap[&it->getSection()] = Index++;
860 const MCSectionData &SD = *it;
861 FileOff += Layout.getSectionFileSize(&SD);
863 Asm.WriteSectionData(it, Layout, Writer);
866 // ... and then the section header table.
867 // Should we align the section header table?
869 // Null section first.
870 WriteSecHdrEntry(0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
872 for (MCAssembler::const_iterator it = Asm.begin(),
873 ie = Asm.end(); it != ie; ++it) {
874 const MCSectionData &SD = *it;
875 const MCSectionELF &Section =
876 static_cast<const MCSectionELF&>(SD.getSection());
878 uint64_t sh_link = 0;
879 uint64_t sh_info = 0;
881 switch(Section.getType()) {
882 case ELF::SHT_DYNAMIC:
883 sh_link = SectionStringTableIndex[&it->getSection()];
888 case ELF::SHT_RELA: {
889 const MCSection *SymtabSection;
890 const MCSection *InfoSection;
892 SymtabSection = Asm.getContext().getELFSection(".symtab", ELF::SHT_SYMTAB, 0,
893 SectionKind::getReadOnly(),
895 sh_link = SectionIndexMap[SymtabSection];
897 // Remove ".rel" and ".rela" prefixes.
898 unsigned SecNameLen = (Section.getType() == ELF::SHT_REL) ? 4 : 5;
899 StringRef SectionName = Section.getSectionName().substr(SecNameLen);
901 InfoSection = Asm.getContext().getELFSection(SectionName,
902 ELF::SHT_PROGBITS, 0,
903 SectionKind::getReadOnly(),
905 sh_info = SectionIndexMap[InfoSection];
909 case ELF::SHT_SYMTAB:
910 case ELF::SHT_DYNSYM:
911 sh_link = StringTableIndex;
912 sh_info = LastLocalSymbolIndex;
915 case ELF::SHT_PROGBITS:
916 case ELF::SHT_STRTAB:
917 case ELF::SHT_NOBITS:
923 case ELF::SHT_SYMTAB_SHNDX:
925 assert(0 && "FIXME: sh_type value not supported!");
929 WriteSecHdrEntry(SectionStringTableIndex[&it->getSection()],
930 Section.getType(), Section.getFlags(),
931 Layout.getSectionAddress(&SD),
932 SectionOffsetMap.lookup(&SD.getSection()),
933 Layout.getSectionSize(&SD), sh_link,
934 sh_info, SD.getAlignment(),
935 Section.getEntrySize());
939 ELFObjectWriter::ELFObjectWriter(raw_ostream &OS,
942 bool HasRelocationAddend)
943 : MCObjectWriter(OS, IsLittleEndian)
945 Impl = new ELFObjectWriterImpl(this, Is64Bit, HasRelocationAddend);
948 ELFObjectWriter::~ELFObjectWriter() {
949 delete (ELFObjectWriterImpl*) Impl;
952 void ELFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
953 ((ELFObjectWriterImpl*) Impl)->ExecutePostLayoutBinding(Asm);
956 void ELFObjectWriter::RecordRelocation(const MCAssembler &Asm,
957 const MCAsmLayout &Layout,
958 const MCFragment *Fragment,
959 const MCFixup &Fixup, MCValue Target,
960 uint64_t &FixedValue) {
961 ((ELFObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
965 void ELFObjectWriter::WriteObject(const MCAssembler &Asm,
966 const MCAsmLayout &Layout) {
967 ((ELFObjectWriterImpl*) Impl)->WriteObject(Asm, Layout);