1 //===- Object.cpp ---------------------------------------------------------===//
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 //===----------------------------------------------------------------------===//
11 #include "llvm-objcopy.h"
12 #include "llvm/ADT/ArrayRef.h"
13 #include "llvm/ADT/STLExtras.h"
14 #include "llvm/ADT/StringRef.h"
15 #include "llvm/ADT/Twine.h"
16 #include "llvm/ADT/iterator_range.h"
17 #include "llvm/BinaryFormat/ELF.h"
18 #include "llvm/MC/MCTargetOptions.h"
19 #include "llvm/Object/ELFObjectFile.h"
20 #include "llvm/Support/Compression.h"
21 #include "llvm/Support/ErrorHandling.h"
22 #include "llvm/Support/FileOutputBuffer.h"
23 #include "llvm/Support/Path.h"
35 using namespace object;
38 template <class ELFT> void ELFWriter<ELFT>::writePhdr(const Segment &Seg) {
39 uint8_t *B = Buf.getBufferStart();
40 B += Obj.ProgramHdrSegment.Offset + Seg.Index * sizeof(Elf_Phdr);
41 Elf_Phdr &Phdr = *reinterpret_cast<Elf_Phdr *>(B);
42 Phdr.p_type = Seg.Type;
43 Phdr.p_flags = Seg.Flags;
44 Phdr.p_offset = Seg.Offset;
45 Phdr.p_vaddr = Seg.VAddr;
46 Phdr.p_paddr = Seg.PAddr;
47 Phdr.p_filesz = Seg.FileSize;
48 Phdr.p_memsz = Seg.MemSize;
49 Phdr.p_align = Seg.Align;
52 void SectionBase::removeSectionReferences(const SectionBase *Sec) {}
53 void SectionBase::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {}
54 void SectionBase::initialize(SectionTableRef SecTable) {}
55 void SectionBase::finalize() {}
56 void SectionBase::markSymbols() {}
58 template <class ELFT> void ELFWriter<ELFT>::writeShdr(const SectionBase &Sec) {
59 uint8_t *B = Buf.getBufferStart();
60 B += Sec.HeaderOffset;
61 Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B);
62 Shdr.sh_name = Sec.NameIndex;
63 Shdr.sh_type = Sec.Type;
64 Shdr.sh_flags = Sec.Flags;
65 Shdr.sh_addr = Sec.Addr;
66 Shdr.sh_offset = Sec.Offset;
67 Shdr.sh_size = Sec.Size;
68 Shdr.sh_link = Sec.Link;
69 Shdr.sh_info = Sec.Info;
70 Shdr.sh_addralign = Sec.Align;
71 Shdr.sh_entsize = Sec.EntrySize;
74 template <class ELFT> void ELFSectionSizer<ELFT>::visit(Section &Sec) {}
77 void ELFSectionSizer<ELFT>::visit(OwnedDataSection &Sec) {}
80 void ELFSectionSizer<ELFT>::visit(StringTableSection &Sec) {}
83 void ELFSectionSizer<ELFT>::visit(DynamicRelocationSection &Sec) {}
86 void ELFSectionSizer<ELFT>::visit(SymbolTableSection &Sec) {
87 Sec.EntrySize = sizeof(Elf_Sym);
88 Sec.Size = Sec.Symbols.size() * Sec.EntrySize;
89 // Align to the largest field in Elf_Sym.
90 Sec.Align = ELFT::Is64Bits ? sizeof(Elf_Xword) : sizeof(Elf_Word);
94 void ELFSectionSizer<ELFT>::visit(RelocationSection &Sec) {
95 Sec.EntrySize = Sec.Type == SHT_REL ? sizeof(Elf_Rel) : sizeof(Elf_Rela);
96 Sec.Size = Sec.Relocations.size() * Sec.EntrySize;
97 // Align to the largest field in Elf_Rel(a).
98 Sec.Align = ELFT::Is64Bits ? sizeof(Elf_Xword) : sizeof(Elf_Word);
101 template <class ELFT>
102 void ELFSectionSizer<ELFT>::visit(GnuDebugLinkSection &Sec) {}
104 template <class ELFT> void ELFSectionSizer<ELFT>::visit(GroupSection &Sec) {}
106 template <class ELFT>
107 void ELFSectionSizer<ELFT>::visit(SectionIndexSection &Sec) {}
109 template <class ELFT>
110 void ELFSectionSizer<ELFT>::visit(CompressedSection &Sec) {}
112 template <class ELFT>
113 void ELFSectionSizer<ELFT>::visit(DecompressedSection &Sec) {}
115 void BinarySectionWriter::visit(const SectionIndexSection &Sec) {
116 error("Cannot write symbol section index table '" + Sec.Name + "' ");
119 void BinarySectionWriter::visit(const SymbolTableSection &Sec) {
120 error("Cannot write symbol table '" + Sec.Name + "' out to binary");
123 void BinarySectionWriter::visit(const RelocationSection &Sec) {
124 error("Cannot write relocation section '" + Sec.Name + "' out to binary");
127 void BinarySectionWriter::visit(const GnuDebugLinkSection &Sec) {
128 error("Cannot write '" + Sec.Name + "' out to binary");
131 void BinarySectionWriter::visit(const GroupSection &Sec) {
132 error("Cannot write '" + Sec.Name + "' out to binary");
135 void SectionWriter::visit(const Section &Sec) {
136 if (Sec.Type == SHT_NOBITS)
138 uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
139 llvm::copy(Sec.Contents, Buf);
142 void Section::accept(SectionVisitor &Visitor) const { Visitor.visit(*this); }
144 void Section::accept(MutableSectionVisitor &Visitor) { Visitor.visit(*this); }
146 void SectionWriter::visit(const OwnedDataSection &Sec) {
147 uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
148 llvm::copy(Sec.Data, Buf);
151 static const std::vector<uint8_t> ZlibGnuMagic = {'Z', 'L', 'I', 'B'};
153 static bool isDataGnuCompressed(ArrayRef<uint8_t> Data) {
154 return Data.size() > ZlibGnuMagic.size() &&
155 std::equal(ZlibGnuMagic.begin(), ZlibGnuMagic.end(), Data.data());
158 template <class ELFT>
159 static std::tuple<uint64_t, uint64_t>
160 getDecompressedSizeAndAlignment(ArrayRef<uint8_t> Data) {
161 const bool IsGnuDebug = isDataGnuCompressed(Data);
162 const uint64_t DecompressedSize =
164 ? support::endian::read64be(reinterpret_cast<const uint64_t *>(
165 Data.data() + ZlibGnuMagic.size()))
166 : reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())->ch_size;
167 const uint64_t DecompressedAlign =
169 : reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())
172 return std::make_tuple(DecompressedSize, DecompressedAlign);
175 template <class ELFT>
176 void ELFSectionWriter<ELFT>::visit(const DecompressedSection &Sec) {
177 uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
179 if (!zlib::isAvailable()) {
180 std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf);
184 const size_t DataOffset = isDataGnuCompressed(Sec.OriginalData)
185 ? (ZlibGnuMagic.size() + sizeof(Sec.Size))
186 : sizeof(Elf_Chdr_Impl<ELFT>);
188 StringRef CompressedContent(
189 reinterpret_cast<const char *>(Sec.OriginalData.data()) + DataOffset,
190 Sec.OriginalData.size() - DataOffset);
192 SmallVector<char, 128> DecompressedContent;
193 if (Error E = zlib::uncompress(CompressedContent, DecompressedContent,
194 static_cast<size_t>(Sec.Size)))
195 reportError(Sec.Name, std::move(E));
197 std::copy(DecompressedContent.begin(), DecompressedContent.end(), Buf);
200 void BinarySectionWriter::visit(const DecompressedSection &Sec) {
201 error("Cannot write compressed section '" + Sec.Name + "' ");
204 void DecompressedSection::accept(SectionVisitor &Visitor) const {
205 Visitor.visit(*this);
208 void DecompressedSection::accept(MutableSectionVisitor &Visitor) {
209 Visitor.visit(*this);
212 void OwnedDataSection::accept(SectionVisitor &Visitor) const {
213 Visitor.visit(*this);
216 void OwnedDataSection::accept(MutableSectionVisitor &Visitor) {
217 Visitor.visit(*this);
220 void BinarySectionWriter::visit(const CompressedSection &Sec) {
221 error("Cannot write compressed section '" + Sec.Name + "' ");
224 template <class ELFT>
225 void ELFSectionWriter<ELFT>::visit(const CompressedSection &Sec) {
226 uint8_t *Buf = Out.getBufferStart();
229 if (Sec.CompressionType == DebugCompressionType::None) {
230 std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf);
234 if (Sec.CompressionType == DebugCompressionType::GNU) {
235 const char *Magic = "ZLIB";
236 memcpy(Buf, Magic, strlen(Magic));
237 Buf += strlen(Magic);
238 const uint64_t DecompressedSize =
239 support::endian::read64be(&Sec.DecompressedSize);
240 memcpy(Buf, &DecompressedSize, sizeof(DecompressedSize));
241 Buf += sizeof(DecompressedSize);
243 Elf_Chdr_Impl<ELFT> Chdr;
244 Chdr.ch_type = ELF::ELFCOMPRESS_ZLIB;
245 Chdr.ch_size = Sec.DecompressedSize;
246 Chdr.ch_addralign = Sec.DecompressedAlign;
247 memcpy(Buf, &Chdr, sizeof(Chdr));
251 std::copy(Sec.CompressedData.begin(), Sec.CompressedData.end(), Buf);
254 CompressedSection::CompressedSection(const SectionBase &Sec,
255 DebugCompressionType CompressionType)
256 : SectionBase(Sec), CompressionType(CompressionType),
257 DecompressedSize(Sec.OriginalData.size()), DecompressedAlign(Sec.Align) {
259 if (!zlib::isAvailable()) {
260 CompressionType = DebugCompressionType::None;
264 if (Error E = zlib::compress(
265 StringRef(reinterpret_cast<const char *>(OriginalData.data()),
266 OriginalData.size()),
268 reportError(Name, std::move(E));
271 if (CompressionType == DebugCompressionType::GNU) {
272 Name = ".z" + Sec.Name.substr(1);
273 ChdrSize = sizeof("ZLIB") - 1 + sizeof(uint64_t);
275 Flags |= ELF::SHF_COMPRESSED;
277 std::max(std::max(sizeof(object::Elf_Chdr_Impl<object::ELF64LE>),
278 sizeof(object::Elf_Chdr_Impl<object::ELF64BE>)),
279 std::max(sizeof(object::Elf_Chdr_Impl<object::ELF32LE>),
280 sizeof(object::Elf_Chdr_Impl<object::ELF32BE>)));
282 Size = ChdrSize + CompressedData.size();
286 CompressedSection::CompressedSection(ArrayRef<uint8_t> CompressedData,
287 uint64_t DecompressedSize,
288 uint64_t DecompressedAlign)
289 : CompressionType(DebugCompressionType::None),
290 DecompressedSize(DecompressedSize), DecompressedAlign(DecompressedAlign) {
291 OriginalData = CompressedData;
294 void CompressedSection::accept(SectionVisitor &Visitor) const {
295 Visitor.visit(*this);
298 void CompressedSection::accept(MutableSectionVisitor &Visitor) {
299 Visitor.visit(*this);
302 void StringTableSection::addString(StringRef Name) {
303 StrTabBuilder.add(Name);
304 Size = StrTabBuilder.getSize();
307 uint32_t StringTableSection::findIndex(StringRef Name) const {
308 return StrTabBuilder.getOffset(Name);
311 void StringTableSection::finalize() { StrTabBuilder.finalize(); }
313 void SectionWriter::visit(const StringTableSection &Sec) {
314 Sec.StrTabBuilder.write(Out.getBufferStart() + Sec.Offset);
317 void StringTableSection::accept(SectionVisitor &Visitor) const {
318 Visitor.visit(*this);
321 void StringTableSection::accept(MutableSectionVisitor &Visitor) {
322 Visitor.visit(*this);
325 template <class ELFT>
326 void ELFSectionWriter<ELFT>::visit(const SectionIndexSection &Sec) {
327 uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
328 auto *IndexesBuffer = reinterpret_cast<Elf_Word *>(Buf);
329 llvm::copy(Sec.Indexes, IndexesBuffer);
332 void SectionIndexSection::initialize(SectionTableRef SecTable) {
334 setSymTab(SecTable.getSectionOfType<SymbolTableSection>(
336 "Link field value " + Twine(Link) + " in section " + Name + " is invalid",
337 "Link field value " + Twine(Link) + " in section " + Name +
338 " is not a symbol table"));
339 Symbols->setShndxTable(this);
342 void SectionIndexSection::finalize() { Link = Symbols->Index; }
344 void SectionIndexSection::accept(SectionVisitor &Visitor) const {
345 Visitor.visit(*this);
348 void SectionIndexSection::accept(MutableSectionVisitor &Visitor) {
349 Visitor.visit(*this);
352 static bool isValidReservedSectionIndex(uint16_t Index, uint16_t Machine) {
358 if (Machine == EM_HEXAGON) {
360 case SHN_HEXAGON_SCOMMON:
361 case SHN_HEXAGON_SCOMMON_2:
362 case SHN_HEXAGON_SCOMMON_4:
363 case SHN_HEXAGON_SCOMMON_8:
370 // Large indexes force us to clarify exactly what this function should do. This
371 // function should return the value that will appear in st_shndx when written
373 uint16_t Symbol::getShndx() const {
374 if (DefinedIn != nullptr) {
375 if (DefinedIn->Index >= SHN_LORESERVE)
377 return DefinedIn->Index;
380 // This means that we don't have a defined section but we do need to
381 // output a legitimate section index.
382 case SYMBOL_SIMPLE_INDEX:
386 case SYMBOL_HEXAGON_SCOMMON:
387 case SYMBOL_HEXAGON_SCOMMON_2:
388 case SYMBOL_HEXAGON_SCOMMON_4:
389 case SYMBOL_HEXAGON_SCOMMON_8:
391 return static_cast<uint16_t>(ShndxType);
393 llvm_unreachable("Symbol with invalid ShndxType encountered");
396 bool Symbol::isCommon() const { return getShndx() == SHN_COMMON; }
398 void SymbolTableSection::assignIndices() {
400 for (auto &Sym : Symbols)
401 Sym->Index = Index++;
404 void SymbolTableSection::addSymbol(Twine Name, uint8_t Bind, uint8_t Type,
405 SectionBase *DefinedIn, uint64_t Value,
406 uint8_t Visibility, uint16_t Shndx,
409 Sym.Name = Name.str();
412 Sym.DefinedIn = DefinedIn;
413 if (DefinedIn != nullptr)
414 DefinedIn->HasSymbol = true;
415 if (DefinedIn == nullptr) {
416 if (Shndx >= SHN_LORESERVE)
417 Sym.ShndxType = static_cast<SymbolShndxType>(Shndx);
419 Sym.ShndxType = SYMBOL_SIMPLE_INDEX;
422 Sym.Visibility = Visibility;
424 Sym.Index = Symbols.size();
425 Symbols.emplace_back(llvm::make_unique<Symbol>(Sym));
426 Size += this->EntrySize;
429 void SymbolTableSection::removeSectionReferences(const SectionBase *Sec) {
430 if (SectionIndexTable == Sec)
431 SectionIndexTable = nullptr;
432 if (SymbolNames == Sec) {
433 error("String table " + SymbolNames->Name +
434 " cannot be removed because it is referenced by the symbol table " +
437 removeSymbols([Sec](const Symbol &Sym) { return Sym.DefinedIn == Sec; });
440 void SymbolTableSection::updateSymbols(function_ref<void(Symbol &)> Callable) {
441 std::for_each(std::begin(Symbols) + 1, std::end(Symbols),
442 [Callable](SymPtr &Sym) { Callable(*Sym); });
443 std::stable_partition(
444 std::begin(Symbols), std::end(Symbols),
445 [](const SymPtr &Sym) { return Sym->Binding == STB_LOCAL; });
449 void SymbolTableSection::removeSymbols(
450 function_ref<bool(const Symbol &)> ToRemove) {
452 std::remove_if(std::begin(Symbols) + 1, std::end(Symbols),
453 [ToRemove](const SymPtr &Sym) { return ToRemove(*Sym); }),
455 Size = Symbols.size() * EntrySize;
459 void SymbolTableSection::initialize(SectionTableRef SecTable) {
461 setStrTab(SecTable.getSectionOfType<StringTableSection>(
463 "Symbol table has link index of " + Twine(Link) +
464 " which is not a valid index",
465 "Symbol table has link index of " + Twine(Link) +
466 " which is not a string table"));
469 void SymbolTableSection::finalize() {
470 // Make sure SymbolNames is finalized before getting name indexes.
471 SymbolNames->finalize();
473 uint32_t MaxLocalIndex = 0;
474 for (auto &Sym : Symbols) {
475 Sym->NameIndex = SymbolNames->findIndex(Sym->Name);
476 if (Sym->Binding == STB_LOCAL)
477 MaxLocalIndex = std::max(MaxLocalIndex, Sym->Index);
479 // Now we need to set the Link and Info fields.
480 Link = SymbolNames->Index;
481 Info = MaxLocalIndex + 1;
484 void SymbolTableSection::prepareForLayout() {
485 // Add all potential section indexes before file layout so that the section
486 // index section has the approprite size.
487 if (SectionIndexTable != nullptr) {
488 for (const auto &Sym : Symbols) {
489 if (Sym->DefinedIn != nullptr && Sym->DefinedIn->Index >= SHN_LORESERVE)
490 SectionIndexTable->addIndex(Sym->DefinedIn->Index);
492 SectionIndexTable->addIndex(SHN_UNDEF);
495 // Add all of our strings to SymbolNames so that SymbolNames has the right
496 // size before layout is decided.
497 for (auto &Sym : Symbols)
498 SymbolNames->addString(Sym->Name);
501 const Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) const {
502 if (Symbols.size() <= Index)
503 error("Invalid symbol index: " + Twine(Index));
504 return Symbols[Index].get();
507 Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) {
508 return const_cast<Symbol *>(
509 static_cast<const SymbolTableSection *>(this)->getSymbolByIndex(Index));
512 template <class ELFT>
513 void ELFSectionWriter<ELFT>::visit(const SymbolTableSection &Sec) {
514 uint8_t *Buf = Out.getBufferStart();
516 Elf_Sym *Sym = reinterpret_cast<Elf_Sym *>(Buf);
517 // Loop though symbols setting each entry of the symbol table.
518 for (auto &Symbol : Sec.Symbols) {
519 Sym->st_name = Symbol->NameIndex;
520 Sym->st_value = Symbol->Value;
521 Sym->st_size = Symbol->Size;
522 Sym->st_other = Symbol->Visibility;
523 Sym->setBinding(Symbol->Binding);
524 Sym->setType(Symbol->Type);
525 Sym->st_shndx = Symbol->getShndx();
530 void SymbolTableSection::accept(SectionVisitor &Visitor) const {
531 Visitor.visit(*this);
534 void SymbolTableSection::accept(MutableSectionVisitor &Visitor) {
535 Visitor.visit(*this);
538 template <class SymTabType>
539 void RelocSectionWithSymtabBase<SymTabType>::removeSectionReferences(
540 const SectionBase *Sec) {
541 if (Symbols == Sec) {
542 error("Symbol table " + Symbols->Name +
543 " cannot be removed because it is "
544 "referenced by the relocation "
550 template <class SymTabType>
551 void RelocSectionWithSymtabBase<SymTabType>::initialize(
552 SectionTableRef SecTable) {
553 if (Link != SHN_UNDEF)
554 setSymTab(SecTable.getSectionOfType<SymTabType>(
556 "Link field value " + Twine(Link) + " in section " + Name +
558 "Link field value " + Twine(Link) + " in section " + Name +
559 " is not a symbol table"));
561 if (Info != SHN_UNDEF)
562 setSection(SecTable.getSection(Info, "Info field value " + Twine(Info) +
563 " in section " + Name +
569 template <class SymTabType>
570 void RelocSectionWithSymtabBase<SymTabType>::finalize() {
571 this->Link = Symbols ? Symbols->Index : 0;
573 if (SecToApplyRel != nullptr)
574 this->Info = SecToApplyRel->Index;
577 template <class ELFT>
578 static void setAddend(Elf_Rel_Impl<ELFT, false> &Rel, uint64_t Addend) {}
580 template <class ELFT>
581 static void setAddend(Elf_Rel_Impl<ELFT, true> &Rela, uint64_t Addend) {
582 Rela.r_addend = Addend;
585 template <class RelRange, class T>
586 static void writeRel(const RelRange &Relocations, T *Buf) {
587 for (const auto &Reloc : Relocations) {
588 Buf->r_offset = Reloc.Offset;
589 setAddend(*Buf, Reloc.Addend);
590 Buf->setSymbolAndType(Reloc.RelocSymbol->Index, Reloc.Type, false);
595 template <class ELFT>
596 void ELFSectionWriter<ELFT>::visit(const RelocationSection &Sec) {
597 uint8_t *Buf = Out.getBufferStart() + Sec.Offset;
598 if (Sec.Type == SHT_REL)
599 writeRel(Sec.Relocations, reinterpret_cast<Elf_Rel *>(Buf));
601 writeRel(Sec.Relocations, reinterpret_cast<Elf_Rela *>(Buf));
604 void RelocationSection::accept(SectionVisitor &Visitor) const {
605 Visitor.visit(*this);
608 void RelocationSection::accept(MutableSectionVisitor &Visitor) {
609 Visitor.visit(*this);
612 void RelocationSection::removeSymbols(
613 function_ref<bool(const Symbol &)> ToRemove) {
614 for (const Relocation &Reloc : Relocations)
615 if (ToRemove(*Reloc.RelocSymbol))
616 error("not stripping symbol '" + Reloc.RelocSymbol->Name +
617 "' because it is named in a relocation");
620 void RelocationSection::markSymbols() {
621 for (const Relocation &Reloc : Relocations)
622 Reloc.RelocSymbol->Referenced = true;
625 void SectionWriter::visit(const DynamicRelocationSection &Sec) {
626 llvm::copy(Sec.Contents,
627 Out.getBufferStart() + Sec.Offset);
630 void DynamicRelocationSection::accept(SectionVisitor &Visitor) const {
631 Visitor.visit(*this);
634 void DynamicRelocationSection::accept(MutableSectionVisitor &Visitor) {
635 Visitor.visit(*this);
638 void Section::removeSectionReferences(const SectionBase *Sec) {
639 if (LinkSection == Sec) {
640 error("Section " + LinkSection->Name +
641 " cannot be removed because it is "
642 "referenced by the section " +
647 void GroupSection::finalize() {
648 this->Info = Sym->Index;
649 this->Link = SymTab->Index;
652 void GroupSection::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
653 if (ToRemove(*Sym)) {
654 error("Symbol " + Sym->Name +
655 " cannot be removed because it is "
656 "referenced by the section " +
657 this->Name + "[" + Twine(this->Index) + "]");
661 void GroupSection::markSymbols() {
663 Sym->Referenced = true;
666 void Section::initialize(SectionTableRef SecTable) {
667 if (Link != ELF::SHN_UNDEF) {
669 SecTable.getSection(Link, "Link field value " + Twine(Link) +
670 " in section " + Name + " is invalid");
671 if (LinkSection->Type == ELF::SHT_SYMTAB)
672 LinkSection = nullptr;
676 void Section::finalize() { this->Link = LinkSection ? LinkSection->Index : 0; }
678 void GnuDebugLinkSection::init(StringRef File, StringRef Data) {
679 FileName = sys::path::filename(File);
680 // The format for the .gnu_debuglink starts with the file name and is
681 // followed by a null terminator and then the CRC32 of the file. The CRC32
682 // should be 4 byte aligned. So we add the FileName size, a 1 for the null
683 // byte, and then finally push the size to alignment and add 4.
684 Size = alignTo(FileName.size() + 1, 4) + 4;
685 // The CRC32 will only be aligned if we align the whole section.
687 Type = ELF::SHT_PROGBITS;
688 Name = ".gnu_debuglink";
689 // For sections not found in segments, OriginalOffset is only used to
690 // establish the order that sections should go in. By using the maximum
691 // possible offset we cause this section to wind up at the end.
692 OriginalOffset = std::numeric_limits<uint64_t>::max();
694 CRC.update(ArrayRef<char>(Data.data(), Data.size()));
695 // The CRC32 value needs to be complemented because the JamCRC dosn't
696 // finalize the CRC32 value. It also dosn't negate the initial CRC32 value
697 // but it starts by default at 0xFFFFFFFF which is the complement of zero.
698 CRC32 = ~CRC.getCRC();
701 GnuDebugLinkSection::GnuDebugLinkSection(StringRef File) : FileName(File) {
702 // Read in the file to compute the CRC of it.
703 auto DebugOrErr = MemoryBuffer::getFile(File);
705 error("'" + File + "': " + DebugOrErr.getError().message());
706 auto Debug = std::move(*DebugOrErr);
707 init(File, Debug->getBuffer());
710 template <class ELFT>
711 void ELFSectionWriter<ELFT>::visit(const GnuDebugLinkSection &Sec) {
712 auto Buf = Out.getBufferStart() + Sec.Offset;
713 char *File = reinterpret_cast<char *>(Buf);
715 reinterpret_cast<Elf_Word *>(Buf + Sec.Size - sizeof(Elf_Word));
717 llvm::copy(Sec.FileName, File);
720 void GnuDebugLinkSection::accept(SectionVisitor &Visitor) const {
721 Visitor.visit(*this);
724 void GnuDebugLinkSection::accept(MutableSectionVisitor &Visitor) {
725 Visitor.visit(*this);
728 template <class ELFT>
729 void ELFSectionWriter<ELFT>::visit(const GroupSection &Sec) {
730 ELF::Elf32_Word *Buf =
731 reinterpret_cast<ELF::Elf32_Word *>(Out.getBufferStart() + Sec.Offset);
732 *Buf++ = Sec.FlagWord;
733 for (const auto *S : Sec.GroupMembers)
734 support::endian::write32<ELFT::TargetEndianness>(Buf++, S->Index);
737 void GroupSection::accept(SectionVisitor &Visitor) const {
738 Visitor.visit(*this);
741 void GroupSection::accept(MutableSectionVisitor &Visitor) {
742 Visitor.visit(*this);
745 // Returns true IFF a section is wholly inside the range of a segment
746 static bool sectionWithinSegment(const SectionBase &Section,
747 const Segment &Segment) {
748 // If a section is empty it should be treated like it has a size of 1. This is
749 // to clarify the case when an empty section lies on a boundary between two
750 // segments and ensures that the section "belongs" to the second segment and
752 uint64_t SecSize = Section.Size ? Section.Size : 1;
753 return Segment.Offset <= Section.OriginalOffset &&
754 Segment.Offset + Segment.FileSize >= Section.OriginalOffset + SecSize;
757 // Returns true IFF a segment's original offset is inside of another segment's
759 static bool segmentOverlapsSegment(const Segment &Child,
760 const Segment &Parent) {
762 return Parent.OriginalOffset <= Child.OriginalOffset &&
763 Parent.OriginalOffset + Parent.FileSize > Child.OriginalOffset;
766 static bool compareSegmentsByOffset(const Segment *A, const Segment *B) {
767 // Any segment without a parent segment should come before a segment
768 // that has a parent segment.
769 if (A->OriginalOffset < B->OriginalOffset)
771 if (A->OriginalOffset > B->OriginalOffset)
773 return A->Index < B->Index;
776 static bool compareSegmentsByPAddr(const Segment *A, const Segment *B) {
777 if (A->PAddr < B->PAddr)
779 if (A->PAddr > B->PAddr)
781 return A->Index < B->Index;
784 void BinaryELFBuilder::initFileHeader() {
787 Obj->OSABI = ELFOSABI_NONE;
790 Obj->Machine = EMachine;
794 void BinaryELFBuilder::initHeaderSegment() { Obj->ElfHdrSegment.Index = 0; }
796 StringTableSection *BinaryELFBuilder::addStrTab() {
797 auto &StrTab = Obj->addSection<StringTableSection>();
798 StrTab.Name = ".strtab";
800 Obj->SectionNames = &StrTab;
804 SymbolTableSection *BinaryELFBuilder::addSymTab(StringTableSection *StrTab) {
805 auto &SymTab = Obj->addSection<SymbolTableSection>();
807 SymTab.Name = ".symtab";
808 SymTab.Link = StrTab->Index;
810 // The symbol table always needs a null symbol
811 SymTab.addSymbol("", 0, 0, nullptr, 0, 0, 0, 0);
813 Obj->SymbolTable = &SymTab;
817 void BinaryELFBuilder::addData(SymbolTableSection *SymTab) {
818 auto Data = ArrayRef<uint8_t>(
819 reinterpret_cast<const uint8_t *>(MemBuf->getBufferStart()),
820 MemBuf->getBufferSize());
821 auto &DataSection = Obj->addSection<Section>(Data);
822 DataSection.Name = ".data";
823 DataSection.Type = ELF::SHT_PROGBITS;
824 DataSection.Size = Data.size();
825 DataSection.Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
827 std::string SanitizedFilename = MemBuf->getBufferIdentifier().str();
828 std::replace_if(std::begin(SanitizedFilename), std::end(SanitizedFilename),
829 [](char C) { return !isalnum(C); }, '_');
830 Twine Prefix = Twine("_binary_") + SanitizedFilename;
832 SymTab->addSymbol(Prefix + "_start", STB_GLOBAL, STT_NOTYPE, &DataSection,
833 /*Value=*/0, STV_DEFAULT, 0, 0);
834 SymTab->addSymbol(Prefix + "_end", STB_GLOBAL, STT_NOTYPE, &DataSection,
835 /*Value=*/DataSection.Size, STV_DEFAULT, 0, 0);
836 SymTab->addSymbol(Prefix + "_size", STB_GLOBAL, STT_NOTYPE, nullptr,
837 /*Value=*/DataSection.Size, STV_DEFAULT, SHN_ABS, 0);
840 void BinaryELFBuilder::initSections() {
841 for (auto &Section : Obj->sections()) {
842 Section.initialize(Obj->sections());
846 std::unique_ptr<Object> BinaryELFBuilder::build() {
849 StringTableSection *StrTab = addStrTab();
850 SymbolTableSection *SymTab = addSymTab(StrTab);
854 return std::move(Obj);
857 template <class ELFT> void ELFBuilder<ELFT>::setParentSegment(Segment &Child) {
858 for (auto &Parent : Obj.segments()) {
859 // Every segment will overlap with itself but we don't want a segment to
860 // be it's own parent so we avoid that situation.
861 if (&Child != &Parent && segmentOverlapsSegment(Child, Parent)) {
862 // We want a canonical "most parental" segment but this requires
863 // inspecting the ParentSegment.
864 if (compareSegmentsByOffset(&Parent, &Child))
865 if (Child.ParentSegment == nullptr ||
866 compareSegmentsByOffset(&Parent, Child.ParentSegment)) {
867 Child.ParentSegment = &Parent;
873 template <class ELFT> void ELFBuilder<ELFT>::readProgramHeaders() {
875 for (const auto &Phdr : unwrapOrError(ElfFile.program_headers())) {
876 ArrayRef<uint8_t> Data{ElfFile.base() + Phdr.p_offset,
877 (size_t)Phdr.p_filesz};
878 Segment &Seg = Obj.addSegment(Data);
879 Seg.Type = Phdr.p_type;
880 Seg.Flags = Phdr.p_flags;
881 Seg.OriginalOffset = Phdr.p_offset;
882 Seg.Offset = Phdr.p_offset;
883 Seg.VAddr = Phdr.p_vaddr;
884 Seg.PAddr = Phdr.p_paddr;
885 Seg.FileSize = Phdr.p_filesz;
886 Seg.MemSize = Phdr.p_memsz;
887 Seg.Align = Phdr.p_align;
889 for (auto &Section : Obj.sections()) {
890 if (sectionWithinSegment(Section, Seg)) {
891 Seg.addSection(&Section);
892 if (!Section.ParentSegment ||
893 Section.ParentSegment->Offset > Seg.Offset) {
894 Section.ParentSegment = &Seg;
900 auto &ElfHdr = Obj.ElfHdrSegment;
901 ElfHdr.Index = Index++;
903 const auto &Ehdr = *ElfFile.getHeader();
904 auto &PrHdr = Obj.ProgramHdrSegment;
905 PrHdr.Type = PT_PHDR;
907 // The spec requires us to have p_vaddr % p_align == p_offset % p_align.
908 // Whereas this works automatically for ElfHdr, here OriginalOffset is
909 // always non-zero and to ensure the equation we assign the same value to
911 PrHdr.OriginalOffset = PrHdr.Offset = PrHdr.VAddr = Ehdr.e_phoff;
913 PrHdr.FileSize = PrHdr.MemSize = Ehdr.e_phentsize * Ehdr.e_phnum;
914 // The spec requires us to naturally align all the fields.
915 PrHdr.Align = sizeof(Elf_Addr);
916 PrHdr.Index = Index++;
918 // Now we do an O(n^2) loop through the segments in order to match up
920 for (auto &Child : Obj.segments())
921 setParentSegment(Child);
922 setParentSegment(ElfHdr);
923 setParentSegment(PrHdr);
926 template <class ELFT>
927 void ELFBuilder<ELFT>::initGroupSection(GroupSection *GroupSec) {
928 auto SecTable = Obj.sections();
929 auto SymTab = SecTable.template getSectionOfType<SymbolTableSection>(
931 "Link field value " + Twine(GroupSec->Link) + " in section " +
932 GroupSec->Name + " is invalid",
933 "Link field value " + Twine(GroupSec->Link) + " in section " +
934 GroupSec->Name + " is not a symbol table");
935 auto Sym = SymTab->getSymbolByIndex(GroupSec->Info);
937 error("Info field value " + Twine(GroupSec->Info) + " in section " +
938 GroupSec->Name + " is not a valid symbol index");
939 GroupSec->setSymTab(SymTab);
940 GroupSec->setSymbol(Sym);
941 if (GroupSec->Contents.size() % sizeof(ELF::Elf32_Word) ||
942 GroupSec->Contents.empty())
943 error("The content of the section " + GroupSec->Name + " is malformed");
944 const ELF::Elf32_Word *Word =
945 reinterpret_cast<const ELF::Elf32_Word *>(GroupSec->Contents.data());
946 const ELF::Elf32_Word *End =
947 Word + GroupSec->Contents.size() / sizeof(ELF::Elf32_Word);
948 GroupSec->setFlagWord(*Word++);
949 for (; Word != End; ++Word) {
950 uint32_t Index = support::endian::read32<ELFT::TargetEndianness>(Word);
951 GroupSec->addMember(SecTable.getSection(
952 Index, "Group member index " + Twine(Index) + " in section " +
953 GroupSec->Name + " is invalid"));
957 template <class ELFT>
958 void ELFBuilder<ELFT>::initSymbolTable(SymbolTableSection *SymTab) {
959 const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index));
960 StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr));
961 ArrayRef<Elf_Word> ShndxData;
963 auto Symbols = unwrapOrError(ElfFile.symbols(&Shdr));
964 for (const auto &Sym : Symbols) {
965 SectionBase *DefSection = nullptr;
966 StringRef Name = unwrapOrError(Sym.getName(StrTabData));
968 if (Sym.st_shndx == SHN_XINDEX) {
969 if (SymTab->getShndxTable() == nullptr)
970 error("Symbol '" + Name +
971 "' has index SHN_XINDEX but no SHT_SYMTAB_SHNDX section exists.");
972 if (ShndxData.data() == nullptr) {
973 const Elf_Shdr &ShndxSec =
974 *unwrapOrError(ElfFile.getSection(SymTab->getShndxTable()->Index));
975 ShndxData = unwrapOrError(
976 ElfFile.template getSectionContentsAsArray<Elf_Word>(&ShndxSec));
977 if (ShndxData.size() != Symbols.size())
978 error("Symbol section index table does not have the same number of "
979 "entries as the symbol table.");
981 Elf_Word Index = ShndxData[&Sym - Symbols.begin()];
982 DefSection = Obj.sections().getSection(
984 "Symbol '" + Name + "' has invalid section index " + Twine(Index));
985 } else if (Sym.st_shndx >= SHN_LORESERVE) {
986 if (!isValidReservedSectionIndex(Sym.st_shndx, Obj.Machine)) {
989 "' has unsupported value greater than or equal to SHN_LORESERVE: " +
990 Twine(Sym.st_shndx));
992 } else if (Sym.st_shndx != SHN_UNDEF) {
993 DefSection = Obj.sections().getSection(
994 Sym.st_shndx, "Symbol '" + Name +
995 "' is defined has invalid section index " +
996 Twine(Sym.st_shndx));
999 SymTab->addSymbol(Name, Sym.getBinding(), Sym.getType(), DefSection,
1000 Sym.getValue(), Sym.st_other, Sym.st_shndx, Sym.st_size);
1004 template <class ELFT>
1005 static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, false> &Rel) {}
1007 template <class ELFT>
1008 static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, true> &Rela) {
1009 ToSet = Rela.r_addend;
1013 static void initRelocations(RelocationSection *Relocs,
1014 SymbolTableSection *SymbolTable, T RelRange) {
1015 for (const auto &Rel : RelRange) {
1017 ToAdd.Offset = Rel.r_offset;
1018 getAddend(ToAdd.Addend, Rel);
1019 ToAdd.Type = Rel.getType(false);
1020 ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Rel.getSymbol(false));
1021 Relocs->addRelocation(ToAdd);
1025 SectionBase *SectionTableRef::getSection(uint32_t Index, Twine ErrMsg) {
1026 if (Index == SHN_UNDEF || Index > Sections.size())
1028 return Sections[Index - 1].get();
1032 T *SectionTableRef::getSectionOfType(uint32_t Index, Twine IndexErrMsg,
1034 if (T *Sec = dyn_cast<T>(getSection(Index, IndexErrMsg)))
1039 template <class ELFT>
1040 SectionBase &ELFBuilder<ELFT>::makeSection(const Elf_Shdr &Shdr) {
1041 ArrayRef<uint8_t> Data;
1042 switch (Shdr.sh_type) {
1045 if (Shdr.sh_flags & SHF_ALLOC) {
1046 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1047 return Obj.addSection<DynamicRelocationSection>(Data);
1049 return Obj.addSection<RelocationSection>();
1051 // If a string table is allocated we don't want to mess with it. That would
1052 // mean altering the memory image. There are no special link types or
1053 // anything so we can just use a Section.
1054 if (Shdr.sh_flags & SHF_ALLOC) {
1055 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1056 return Obj.addSection<Section>(Data);
1058 return Obj.addSection<StringTableSection>();
1061 // Hash tables should refer to SHT_DYNSYM which we're not going to change.
1062 // Because of this we don't need to mess with the hash tables either.
1063 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1064 return Obj.addSection<Section>(Data);
1066 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1067 return Obj.addSection<GroupSection>(Data);
1069 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1070 return Obj.addSection<DynamicSymbolTableSection>(Data);
1072 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1073 return Obj.addSection<DynamicSection>(Data);
1075 auto &SymTab = Obj.addSection<SymbolTableSection>();
1076 Obj.SymbolTable = &SymTab;
1079 case SHT_SYMTAB_SHNDX: {
1080 auto &ShndxSection = Obj.addSection<SectionIndexSection>();
1081 Obj.SectionIndexTable = &ShndxSection;
1082 return ShndxSection;
1085 return Obj.addSection<Section>(Data);
1087 Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
1089 if (isDataGnuCompressed(Data) || (Shdr.sh_flags & ELF::SHF_COMPRESSED)) {
1090 uint64_t DecompressedSize, DecompressedAlign;
1091 std::tie(DecompressedSize, DecompressedAlign) =
1092 getDecompressedSizeAndAlignment<ELFT>(Data);
1093 return Obj.addSection<CompressedSection>(Data, DecompressedSize,
1097 return Obj.addSection<Section>(Data);
1102 template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() {
1104 for (const auto &Shdr : unwrapOrError(ElfFile.sections())) {
1109 auto &Sec = makeSection(Shdr);
1110 Sec.Name = unwrapOrError(ElfFile.getSectionName(&Shdr));
1111 Sec.Type = Shdr.sh_type;
1112 Sec.Flags = Shdr.sh_flags;
1113 Sec.Addr = Shdr.sh_addr;
1114 Sec.Offset = Shdr.sh_offset;
1115 Sec.OriginalOffset = Shdr.sh_offset;
1116 Sec.Size = Shdr.sh_size;
1117 Sec.Link = Shdr.sh_link;
1118 Sec.Info = Shdr.sh_info;
1119 Sec.Align = Shdr.sh_addralign;
1120 Sec.EntrySize = Shdr.sh_entsize;
1121 Sec.Index = Index++;
1123 ArrayRef<uint8_t>(ElfFile.base() + Shdr.sh_offset,
1124 (Shdr.sh_type == SHT_NOBITS) ? 0 : Shdr.sh_size);
1127 // If a section index table exists we'll need to initialize it before we
1128 // initialize the symbol table because the symbol table might need to
1130 if (Obj.SectionIndexTable)
1131 Obj.SectionIndexTable->initialize(Obj.sections());
1133 // Now that all of the sections have been added we can fill out some extra
1134 // details about symbol tables. We need the symbol table filled out before
1136 if (Obj.SymbolTable) {
1137 Obj.SymbolTable->initialize(Obj.sections());
1138 initSymbolTable(Obj.SymbolTable);
1141 // Now that all sections and symbols have been added we can add
1142 // relocations that reference symbols and set the link and info fields for
1143 // relocation sections.
1144 for (auto &Section : Obj.sections()) {
1145 if (&Section == Obj.SymbolTable)
1147 Section.initialize(Obj.sections());
1148 if (auto RelSec = dyn_cast<RelocationSection>(&Section)) {
1149 auto Shdr = unwrapOrError(ElfFile.sections()).begin() + RelSec->Index;
1150 if (RelSec->Type == SHT_REL)
1151 initRelocations(RelSec, Obj.SymbolTable,
1152 unwrapOrError(ElfFile.rels(Shdr)));
1154 initRelocations(RelSec, Obj.SymbolTable,
1155 unwrapOrError(ElfFile.relas(Shdr)));
1156 } else if (auto GroupSec = dyn_cast<GroupSection>(&Section)) {
1157 initGroupSection(GroupSec);
1162 template <class ELFT> void ELFBuilder<ELFT>::build() {
1163 const auto &Ehdr = *ElfFile.getHeader();
1165 Obj.OSABI = Ehdr.e_ident[EI_OSABI];
1166 Obj.ABIVersion = Ehdr.e_ident[EI_ABIVERSION];
1167 Obj.Type = Ehdr.e_type;
1168 Obj.Machine = Ehdr.e_machine;
1169 Obj.Version = Ehdr.e_version;
1170 Obj.Entry = Ehdr.e_entry;
1171 Obj.Flags = Ehdr.e_flags;
1173 readSectionHeaders();
1174 readProgramHeaders();
1176 uint32_t ShstrIndex = Ehdr.e_shstrndx;
1177 if (ShstrIndex == SHN_XINDEX)
1178 ShstrIndex = unwrapOrError(ElfFile.getSection(0))->sh_link;
1181 Obj.sections().template getSectionOfType<StringTableSection>(
1183 "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) +
1184 " in elf header " + " is invalid",
1185 "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) +
1186 " in elf header " + " is not a string table");
1189 // A generic size function which computes sizes of any random access range.
1190 template <class R> size_t size(R &&Range) {
1191 return static_cast<size_t>(std::end(Range) - std::begin(Range));
1194 Writer::~Writer() {}
1196 Reader::~Reader() {}
1198 std::unique_ptr<Object> BinaryReader::create() const {
1199 return BinaryELFBuilder(MInfo.EMachine, MemBuf).build();
1202 std::unique_ptr<Object> ELFReader::create() const {
1203 auto Obj = llvm::make_unique<Object>();
1204 if (auto *O = dyn_cast<ELFObjectFile<ELF32LE>>(Bin)) {
1205 ELFBuilder<ELF32LE> Builder(*O, *Obj);
1208 } else if (auto *O = dyn_cast<ELFObjectFile<ELF64LE>>(Bin)) {
1209 ELFBuilder<ELF64LE> Builder(*O, *Obj);
1212 } else if (auto *O = dyn_cast<ELFObjectFile<ELF32BE>>(Bin)) {
1213 ELFBuilder<ELF32BE> Builder(*O, *Obj);
1216 } else if (auto *O = dyn_cast<ELFObjectFile<ELF64BE>>(Bin)) {
1217 ELFBuilder<ELF64BE> Builder(*O, *Obj);
1221 error("Invalid file type");
1224 template <class ELFT> void ELFWriter<ELFT>::writeEhdr() {
1225 uint8_t *B = Buf.getBufferStart();
1226 Elf_Ehdr &Ehdr = *reinterpret_cast<Elf_Ehdr *>(B);
1227 std::fill(Ehdr.e_ident, Ehdr.e_ident + 16, 0);
1228 Ehdr.e_ident[EI_MAG0] = 0x7f;
1229 Ehdr.e_ident[EI_MAG1] = 'E';
1230 Ehdr.e_ident[EI_MAG2] = 'L';
1231 Ehdr.e_ident[EI_MAG3] = 'F';
1232 Ehdr.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
1233 Ehdr.e_ident[EI_DATA] =
1234 ELFT::TargetEndianness == support::big ? ELFDATA2MSB : ELFDATA2LSB;
1235 Ehdr.e_ident[EI_VERSION] = EV_CURRENT;
1236 Ehdr.e_ident[EI_OSABI] = Obj.OSABI;
1237 Ehdr.e_ident[EI_ABIVERSION] = Obj.ABIVersion;
1239 Ehdr.e_type = Obj.Type;
1240 Ehdr.e_machine = Obj.Machine;
1241 Ehdr.e_version = Obj.Version;
1242 Ehdr.e_entry = Obj.Entry;
1243 // We have to use the fully-qualified name llvm::size
1244 // since some compilers complain on ambiguous resolution.
1245 Ehdr.e_phnum = llvm::size(Obj.segments());
1246 Ehdr.e_phoff = (Ehdr.e_phnum != 0) ? Obj.ProgramHdrSegment.Offset : 0;
1247 Ehdr.e_phentsize = (Ehdr.e_phnum != 0) ? sizeof(Elf_Phdr) : 0;
1248 Ehdr.e_flags = Obj.Flags;
1249 Ehdr.e_ehsize = sizeof(Elf_Ehdr);
1250 if (WriteSectionHeaders && size(Obj.sections()) != 0) {
1251 Ehdr.e_shentsize = sizeof(Elf_Shdr);
1252 Ehdr.e_shoff = Obj.SHOffset;
1254 // If the number of sections is greater than or equal to
1255 // SHN_LORESERVE (0xff00), this member has the value zero and the actual
1256 // number of section header table entries is contained in the sh_size field
1257 // of the section header at index 0.
1259 auto Shnum = size(Obj.sections()) + 1;
1260 if (Shnum >= SHN_LORESERVE)
1263 Ehdr.e_shnum = Shnum;
1265 // If the section name string table section index is greater than or equal
1266 // to SHN_LORESERVE (0xff00), this member has the value SHN_XINDEX (0xffff)
1267 // and the actual index of the section name string table section is
1268 // contained in the sh_link field of the section header at index 0.
1270 if (Obj.SectionNames->Index >= SHN_LORESERVE)
1271 Ehdr.e_shstrndx = SHN_XINDEX;
1273 Ehdr.e_shstrndx = Obj.SectionNames->Index;
1275 Ehdr.e_shentsize = 0;
1278 Ehdr.e_shstrndx = 0;
1282 template <class ELFT> void ELFWriter<ELFT>::writePhdrs() {
1283 for (auto &Seg : Obj.segments())
1287 template <class ELFT> void ELFWriter<ELFT>::writeShdrs() {
1288 uint8_t *B = Buf.getBufferStart() + Obj.SHOffset;
1289 // This reference serves to write the dummy section header at the begining
1290 // of the file. It is not used for anything else
1291 Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B);
1293 Shdr.sh_type = SHT_NULL;
1297 // See writeEhdr for why we do this.
1298 uint64_t Shnum = size(Obj.sections()) + 1;
1299 if (Shnum >= SHN_LORESERVE)
1300 Shdr.sh_size = Shnum;
1303 // See writeEhdr for why we do this.
1304 if (Obj.SectionNames != nullptr && Obj.SectionNames->Index >= SHN_LORESERVE)
1305 Shdr.sh_link = Obj.SectionNames->Index;
1309 Shdr.sh_addralign = 0;
1310 Shdr.sh_entsize = 0;
1312 for (auto &Sec : Obj.sections())
1316 template <class ELFT> void ELFWriter<ELFT>::writeSectionData() {
1317 for (auto &Sec : Obj.sections())
1318 Sec.accept(*SecWriter);
1321 void Object::removeSections(std::function<bool(const SectionBase &)> ToRemove) {
1323 auto Iter = std::stable_partition(
1324 std::begin(Sections), std::end(Sections), [=](const SecPtr &Sec) {
1327 if (auto RelSec = dyn_cast<RelocationSectionBase>(Sec.get())) {
1328 if (auto ToRelSec = RelSec->getSection())
1329 return !ToRemove(*ToRelSec);
1333 if (SymbolTable != nullptr && ToRemove(*SymbolTable))
1334 SymbolTable = nullptr;
1335 if (SectionNames != nullptr && ToRemove(*SectionNames))
1336 SectionNames = nullptr;
1337 if (SectionIndexTable != nullptr && ToRemove(*SectionIndexTable))
1338 SectionIndexTable = nullptr;
1339 // Now make sure there are no remaining references to the sections that will
1340 // be removed. Sometimes it is impossible to remove a reference so we emit
1341 // an error here instead.
1342 for (auto &RemoveSec : make_range(Iter, std::end(Sections))) {
1343 for (auto &Segment : Segments)
1344 Segment->removeSection(RemoveSec.get());
1345 for (auto &KeepSec : make_range(std::begin(Sections), Iter))
1346 KeepSec->removeSectionReferences(RemoveSec.get());
1348 // Now finally get rid of them all togethor.
1349 Sections.erase(Iter, std::end(Sections));
1352 void Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {
1356 for (const SecPtr &Sec : Sections)
1357 Sec->removeSymbols(ToRemove);
1360 void Object::sortSections() {
1361 // Put all sections in offset order. Maintain the ordering as closely as
1362 // possible while meeting that demand however.
1363 auto CompareSections = [](const SecPtr &A, const SecPtr &B) {
1364 return A->OriginalOffset < B->OriginalOffset;
1366 std::stable_sort(std::begin(this->Sections), std::end(this->Sections),
1370 static uint64_t alignToAddr(uint64_t Offset, uint64_t Addr, uint64_t Align) {
1371 // Calculate Diff such that (Offset + Diff) & -Align == Addr & -Align.
1375 static_cast<int64_t>(Addr % Align) - static_cast<int64_t>(Offset % Align);
1376 // We only want to add to Offset, however, so if Diff < 0 we can add Align and
1377 // (Offset + Diff) & -Align == Addr & -Align will still hold.
1380 return Offset + Diff;
1383 // Orders segments such that if x = y->ParentSegment then y comes before x.
1384 static void orderSegments(std::vector<Segment *> &Segments) {
1385 std::stable_sort(std::begin(Segments), std::end(Segments),
1386 compareSegmentsByOffset);
1389 // This function finds a consistent layout for a list of segments starting from
1390 // an Offset. It assumes that Segments have been sorted by OrderSegments and
1391 // returns an Offset one past the end of the last segment.
1392 static uint64_t LayoutSegments(std::vector<Segment *> &Segments,
1394 assert(std::is_sorted(std::begin(Segments), std::end(Segments),
1395 compareSegmentsByOffset));
1396 // The only way a segment should move is if a section was between two
1397 // segments and that section was removed. If that section isn't in a segment
1398 // then it's acceptable, but not ideal, to simply move it to after the
1399 // segments. So we can simply layout segments one after the other accounting
1401 for (auto &Segment : Segments) {
1402 // We assume that segments have been ordered by OriginalOffset and Index
1403 // such that a parent segment will always come before a child segment in
1404 // OrderedSegments. This means that the Offset of the ParentSegment should
1405 // already be set and we can set our offset relative to it.
1406 if (Segment->ParentSegment != nullptr) {
1407 auto Parent = Segment->ParentSegment;
1409 Parent->Offset + Segment->OriginalOffset - Parent->OriginalOffset;
1411 Offset = alignToAddr(Offset, Segment->VAddr, Segment->Align);
1412 Segment->Offset = Offset;
1414 Offset = std::max(Offset, Segment->Offset + Segment->FileSize);
1419 // This function finds a consistent layout for a list of sections. It assumes
1420 // that the ->ParentSegment of each section has already been laid out. The
1421 // supplied starting Offset is used for the starting offset of any section that
1422 // does not have a ParentSegment. It returns either the offset given if all
1423 // sections had a ParentSegment or an offset one past the last section if there
1424 // was a section that didn't have a ParentSegment.
1425 template <class Range>
1426 static uint64_t layoutSections(Range Sections, uint64_t Offset) {
1427 // Now the offset of every segment has been set we can assign the offsets
1428 // of each section. For sections that are covered by a segment we should use
1429 // the segment's original offset and the section's original offset to compute
1430 // the offset from the start of the segment. Using the offset from the start
1431 // of the segment we can assign a new offset to the section. For sections not
1432 // covered by segments we can just bump Offset to the next valid location.
1434 for (auto &Section : Sections) {
1435 Section.Index = Index++;
1436 if (Section.ParentSegment != nullptr) {
1437 auto Segment = *Section.ParentSegment;
1439 Segment.Offset + (Section.OriginalOffset - Segment.OriginalOffset);
1441 Offset = alignTo(Offset, Section.Align == 0 ? 1 : Section.Align);
1442 Section.Offset = Offset;
1443 if (Section.Type != SHT_NOBITS)
1444 Offset += Section.Size;
1450 template <class ELFT> void ELFWriter<ELFT>::initEhdrSegment() {
1451 auto &ElfHdr = Obj.ElfHdrSegment;
1452 ElfHdr.Type = PT_PHDR;
1454 ElfHdr.OriginalOffset = ElfHdr.Offset = 0;
1457 ElfHdr.FileSize = ElfHdr.MemSize = sizeof(Elf_Ehdr);
1461 template <class ELFT> void ELFWriter<ELFT>::assignOffsets() {
1462 // We need a temporary list of segments that has a special order to it
1463 // so that we know that anytime ->ParentSegment is set that segment has
1464 // already had its offset properly set.
1465 std::vector<Segment *> OrderedSegments;
1466 for (auto &Segment : Obj.segments())
1467 OrderedSegments.push_back(&Segment);
1468 OrderedSegments.push_back(&Obj.ElfHdrSegment);
1469 OrderedSegments.push_back(&Obj.ProgramHdrSegment);
1470 orderSegments(OrderedSegments);
1471 // Offset is used as the start offset of the first segment to be laid out.
1472 // Since the ELF Header (ElfHdrSegment) must be at the start of the file,
1473 // we start at offset 0.
1474 uint64_t Offset = 0;
1475 Offset = LayoutSegments(OrderedSegments, Offset);
1476 Offset = layoutSections(Obj.sections(), Offset);
1477 // If we need to write the section header table out then we need to align the
1478 // Offset so that SHOffset is valid.
1479 if (WriteSectionHeaders)
1480 Offset = alignTo(Offset, sizeof(Elf_Addr));
1481 Obj.SHOffset = Offset;
1484 template <class ELFT> size_t ELFWriter<ELFT>::totalSize() const {
1485 // We already have the section header offset so we can calculate the total
1486 // size by just adding up the size of each section header.
1487 auto NullSectionSize = WriteSectionHeaders ? sizeof(Elf_Shdr) : 0;
1488 return Obj.SHOffset + size(Obj.sections()) * sizeof(Elf_Shdr) +
1492 template <class ELFT> void ELFWriter<ELFT>::write() {
1496 if (WriteSectionHeaders)
1498 if (auto E = Buf.commit())
1499 reportError(Buf.getName(), errorToErrorCode(std::move(E)));
1502 template <class ELFT> void ELFWriter<ELFT>::finalize() {
1503 // It could happen that SectionNames has been removed and yet the user wants
1504 // a section header table output. We need to throw an error if a user tries
1506 if (Obj.SectionNames == nullptr && WriteSectionHeaders)
1507 error("Cannot write section header table because section header string "
1508 "table was removed.");
1512 // We need to assign indexes before we perform layout because we need to know
1513 // if we need large indexes or not. We can assign indexes first and check as
1514 // we go to see if we will actully need large indexes.
1515 bool NeedsLargeIndexes = false;
1516 if (size(Obj.sections()) >= SHN_LORESERVE) {
1517 auto Sections = Obj.sections();
1519 std::any_of(Sections.begin() + SHN_LORESERVE, Sections.end(),
1520 [](const SectionBase &Sec) { return Sec.HasSymbol; });
1521 // TODO: handle case where only one section needs the large index table but
1522 // only needs it because the large index table hasn't been removed yet.
1525 if (NeedsLargeIndexes) {
1526 // This means we definitely need to have a section index table but if we
1527 // already have one then we should use it instead of making a new one.
1528 if (Obj.SymbolTable != nullptr && Obj.SectionIndexTable == nullptr) {
1529 // Addition of a section to the end does not invalidate the indexes of
1530 // other sections and assigns the correct index to the new section.
1531 auto &Shndx = Obj.addSection<SectionIndexSection>();
1532 Obj.SymbolTable->setShndxTable(&Shndx);
1533 Shndx.setSymTab(Obj.SymbolTable);
1536 // Since we don't need SectionIndexTable we should remove it and all
1537 // references to it.
1538 if (Obj.SectionIndexTable != nullptr) {
1539 Obj.removeSections([this](const SectionBase &Sec) {
1540 return &Sec == Obj.SectionIndexTable;
1545 // Make sure we add the names of all the sections. Importantly this must be
1546 // done after we decide to add or remove SectionIndexes.
1547 if (Obj.SectionNames != nullptr)
1548 for (const auto &Section : Obj.sections()) {
1549 Obj.SectionNames->addString(Section.Name);
1554 // Before we can prepare for layout the indexes need to be finalized.
1555 // Also, the output arch may not be the same as the input arch, so fix up
1556 // size-related fields before doing layout calculations.
1558 auto SecSizer = llvm::make_unique<ELFSectionSizer<ELFT>>();
1559 for (auto &Sec : Obj.sections()) {
1560 Sec.Index = Index++;
1561 Sec.accept(*SecSizer);
1564 // The symbol table does not update all other sections on update. For
1565 // instance, symbol names are not added as new symbols are added. This means
1566 // that some sections, like .strtab, don't yet have their final size.
1567 if (Obj.SymbolTable != nullptr)
1568 Obj.SymbolTable->prepareForLayout();
1572 // Finalize SectionNames first so that we can assign name indexes.
1573 if (Obj.SectionNames != nullptr)
1574 Obj.SectionNames->finalize();
1575 // Finally now that all offsets and indexes have been set we can finalize any
1576 // remaining issues.
1577 uint64_t Offset = Obj.SHOffset + sizeof(Elf_Shdr);
1578 for (auto &Section : Obj.sections()) {
1579 Section.HeaderOffset = Offset;
1580 Offset += sizeof(Elf_Shdr);
1581 if (WriteSectionHeaders)
1582 Section.NameIndex = Obj.SectionNames->findIndex(Section.Name);
1586 Buf.allocate(totalSize());
1587 SecWriter = llvm::make_unique<ELFSectionWriter<ELFT>>(Buf);
1590 void BinaryWriter::write() {
1591 for (auto &Section : Obj.sections()) {
1592 if ((Section.Flags & SHF_ALLOC) == 0)
1594 Section.accept(*SecWriter);
1596 if (auto E = Buf.commit())
1597 reportError(Buf.getName(), errorToErrorCode(std::move(E)));
1600 void BinaryWriter::finalize() {
1601 // TODO: Create a filter range to construct OrderedSegments from so that this
1602 // code can be deduped with assignOffsets above. This should also solve the
1603 // todo below for LayoutSections.
1604 // We need a temporary list of segments that has a special order to it
1605 // so that we know that anytime ->ParentSegment is set that segment has
1606 // already had it's offset properly set. We only want to consider the segments
1607 // that will affect layout of allocated sections so we only add those.
1608 std::vector<Segment *> OrderedSegments;
1609 for (auto &Section : Obj.sections()) {
1610 if ((Section.Flags & SHF_ALLOC) != 0 && Section.ParentSegment != nullptr) {
1611 OrderedSegments.push_back(Section.ParentSegment);
1615 // For binary output, we're going to use physical addresses instead of
1616 // virtual addresses, since a binary output is used for cases like ROM
1617 // loading and physical addresses are intended for ROM loading.
1618 // However, if no segment has a physical address, we'll fallback to using
1619 // virtual addresses for all.
1620 if (all_of(OrderedSegments,
1621 [](const Segment *Seg) { return Seg->PAddr == 0; }))
1622 for (Segment *Seg : OrderedSegments)
1623 Seg->PAddr = Seg->VAddr;
1625 std::stable_sort(std::begin(OrderedSegments), std::end(OrderedSegments),
1626 compareSegmentsByPAddr);
1628 // Because we add a ParentSegment for each section we might have duplicate
1629 // segments in OrderedSegments. If there were duplicates then LayoutSegments
1630 // would do very strange things.
1632 std::unique(std::begin(OrderedSegments), std::end(OrderedSegments));
1633 OrderedSegments.erase(End, std::end(OrderedSegments));
1635 uint64_t Offset = 0;
1637 // Modify the first segment so that there is no gap at the start. This allows
1638 // our layout algorithm to proceed as expected while not writing out the gap
1640 if (!OrderedSegments.empty()) {
1641 auto Seg = OrderedSegments[0];
1642 auto Sec = Seg->firstSection();
1643 auto Diff = Sec->OriginalOffset - Seg->OriginalOffset;
1644 Seg->OriginalOffset += Diff;
1645 // The size needs to be shrunk as well.
1646 Seg->FileSize -= Diff;
1647 // The PAddr needs to be increased to remove the gap before the first
1650 uint64_t LowestPAddr = Seg->PAddr;
1651 for (auto &Segment : OrderedSegments) {
1652 Segment->Offset = Segment->PAddr - LowestPAddr;
1653 Offset = std::max(Offset, Segment->Offset + Segment->FileSize);
1657 // TODO: generalize LayoutSections to take a range. Pass a special range
1658 // constructed from an iterator that skips values for which a predicate does
1659 // not hold. Then pass such a range to LayoutSections instead of constructing
1660 // AllocatedSections here.
1661 std::vector<SectionBase *> AllocatedSections;
1662 for (auto &Section : Obj.sections()) {
1663 if ((Section.Flags & SHF_ALLOC) == 0)
1665 AllocatedSections.push_back(&Section);
1667 layoutSections(make_pointee_range(AllocatedSections), Offset);
1669 // Now that every section has been laid out we just need to compute the total
1670 // file size. This might not be the same as the offset returned by
1671 // LayoutSections, because we want to truncate the last segment to the end of
1672 // its last section, to match GNU objcopy's behaviour.
1674 for (const auto &Section : AllocatedSections) {
1675 if (Section->Type != SHT_NOBITS)
1676 TotalSize = std::max(TotalSize, Section->Offset + Section->Size);
1679 Buf.allocate(TotalSize);
1680 SecWriter = llvm::make_unique<BinarySectionWriter>(Buf);
1683 template class ELFBuilder<ELF64LE>;
1684 template class ELFBuilder<ELF64BE>;
1685 template class ELFBuilder<ELF32LE>;
1686 template class ELFBuilder<ELF32BE>;
1688 template class ELFWriter<ELF64LE>;
1689 template class ELFWriter<ELF64BE>;
1690 template class ELFWriter<ELF32LE>;
1691 template class ELFWriter<ELF32BE>;
1693 } // end namespace elf
1694 } // end namespace objcopy
1695 } // end namespace llvm