diff options
Diffstat (limited to 'llvm/tools/llvm-objcopy/ELF/Object.cpp')
| -rw-r--r-- | llvm/tools/llvm-objcopy/ELF/Object.cpp | 1621 |
1 files changed, 1621 insertions, 0 deletions
diff --git a/llvm/tools/llvm-objcopy/ELF/Object.cpp b/llvm/tools/llvm-objcopy/ELF/Object.cpp new file mode 100644 index 00000000000..5b2138436d5 --- /dev/null +++ b/llvm/tools/llvm-objcopy/ELF/Object.cpp @@ -0,0 +1,1621 @@ +//===- Object.cpp ---------------------------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#include "Object.h" +#include "llvm-objcopy.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/ADT/Twine.h" +#include "llvm/ADT/iterator_range.h" +#include "llvm/BinaryFormat/ELF.h" +#include "llvm/MC/MCTargetOptions.h" +#include "llvm/Object/ELFObjectFile.h" +#include "llvm/Support/Compression.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/FileOutputBuffer.h" +#include "llvm/Support/Path.h" +#include <algorithm> +#include <cstddef> +#include <cstdint> +#include <iterator> +#include <utility> +#include <vector> + +namespace llvm { +namespace objcopy { +namespace elf { + +using namespace object; +using namespace ELF; + +template <class ELFT> void ELFWriter<ELFT>::writePhdr(const Segment &Seg) { + uint8_t *B = Buf.getBufferStart(); + B += Obj.ProgramHdrSegment.Offset + Seg.Index * sizeof(Elf_Phdr); + Elf_Phdr &Phdr = *reinterpret_cast<Elf_Phdr *>(B); + Phdr.p_type = Seg.Type; + Phdr.p_flags = Seg.Flags; + Phdr.p_offset = Seg.Offset; + Phdr.p_vaddr = Seg.VAddr; + Phdr.p_paddr = Seg.PAddr; + Phdr.p_filesz = Seg.FileSize; + Phdr.p_memsz = Seg.MemSize; + Phdr.p_align = Seg.Align; +} + +void SectionBase::removeSectionReferences(const SectionBase *Sec) {} +void SectionBase::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) {} +void SectionBase::initialize(SectionTableRef SecTable) {} +void SectionBase::finalize() {} +void SectionBase::markSymbols() {} + +template <class ELFT> void ELFWriter<ELFT>::writeShdr(const SectionBase &Sec) { + uint8_t *B = Buf.getBufferStart(); + B += Sec.HeaderOffset; + Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B); + Shdr.sh_name = Sec.NameIndex; + Shdr.sh_type = Sec.Type; + Shdr.sh_flags = Sec.Flags; + Shdr.sh_addr = Sec.Addr; + Shdr.sh_offset = Sec.Offset; + Shdr.sh_size = Sec.Size; + Shdr.sh_link = Sec.Link; + Shdr.sh_info = Sec.Info; + Shdr.sh_addralign = Sec.Align; + Shdr.sh_entsize = Sec.EntrySize; +} + +SectionVisitor::~SectionVisitor() {} + +void BinarySectionWriter::visit(const SectionIndexSection &Sec) { + error("Cannot write symbol section index table '" + Sec.Name + "' "); +} + +void BinarySectionWriter::visit(const SymbolTableSection &Sec) { + error("Cannot write symbol table '" + Sec.Name + "' out to binary"); +} + +void BinarySectionWriter::visit(const RelocationSection &Sec) { + error("Cannot write relocation section '" + Sec.Name + "' out to binary"); +} + +void BinarySectionWriter::visit(const GnuDebugLinkSection &Sec) { + error("Cannot write '" + Sec.Name + "' out to binary"); +} + +void BinarySectionWriter::visit(const GroupSection &Sec) { + error("Cannot write '" + Sec.Name + "' out to binary"); +} + +void SectionWriter::visit(const Section &Sec) { + if (Sec.Type == SHT_NOBITS) + return; + uint8_t *Buf = Out.getBufferStart() + Sec.Offset; + std::copy(std::begin(Sec.Contents), std::end(Sec.Contents), Buf); +} + +void Section::accept(SectionVisitor &Visitor) const { Visitor.visit(*this); } + +void SectionWriter::visit(const OwnedDataSection &Sec) { + uint8_t *Buf = Out.getBufferStart() + Sec.Offset; + std::copy(std::begin(Sec.Data), std::end(Sec.Data), Buf); +} + +static const std::vector<uint8_t> ZlibGnuMagic = {'Z', 'L', 'I', 'B'}; + +static bool isDataGnuCompressed(ArrayRef<uint8_t> Data) { + return Data.size() > ZlibGnuMagic.size() && + std::equal(ZlibGnuMagic.begin(), ZlibGnuMagic.end(), Data.data()); +} + +template <class ELFT> +static std::tuple<uint64_t, uint64_t> +getDecompressedSizeAndAlignment(ArrayRef<uint8_t> Data) { + const bool IsGnuDebug = isDataGnuCompressed(Data); + const uint64_t DecompressedSize = + IsGnuDebug + ? support::endian::read64be(reinterpret_cast<const uint64_t *>( + Data.data() + ZlibGnuMagic.size())) + : reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data())->ch_size; + const uint64_t DecompressedAlign = + IsGnuDebug ? 1 + : reinterpret_cast<const Elf_Chdr_Impl<ELFT> *>(Data.data()) + ->ch_addralign; + + return std::make_tuple(DecompressedSize, DecompressedAlign); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const DecompressedSection &Sec) { + uint8_t *Buf = Out.getBufferStart() + Sec.Offset; + + if (!zlib::isAvailable()) { + std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf); + return; + } + + const size_t DataOffset = isDataGnuCompressed(Sec.OriginalData) + ? (ZlibGnuMagic.size() + sizeof(Sec.Size)) + : sizeof(Elf_Chdr_Impl<ELFT>); + + StringRef CompressedContent( + reinterpret_cast<const char *>(Sec.OriginalData.data()) + DataOffset, + Sec.OriginalData.size() - DataOffset); + + SmallVector<char, 128> DecompressedContent; + if (Error E = zlib::uncompress(CompressedContent, DecompressedContent, + static_cast<size_t>(Sec.Size))) + reportError(Sec.Name, std::move(E)); + + std::copy(DecompressedContent.begin(), DecompressedContent.end(), Buf); +} + +void BinarySectionWriter::visit(const DecompressedSection &Sec) { + error("Cannot write compressed section '" + Sec.Name + "' "); +} + +void DecompressedSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +void OwnedDataSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +void BinarySectionWriter::visit(const CompressedSection &Sec) { + error("Cannot write compressed section '" + Sec.Name + "' "); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const CompressedSection &Sec) { + uint8_t *Buf = Out.getBufferStart(); + Buf += Sec.Offset; + + if (Sec.CompressionType == DebugCompressionType::None) { + std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(), Buf); + return; + } + + if (Sec.CompressionType == DebugCompressionType::GNU) { + const char *Magic = "ZLIB"; + memcpy(Buf, Magic, strlen(Magic)); + Buf += strlen(Magic); + const uint64_t DecompressedSize = + support::endian::read64be(&Sec.DecompressedSize); + memcpy(Buf, &DecompressedSize, sizeof(DecompressedSize)); + Buf += sizeof(DecompressedSize); + } else { + Elf_Chdr_Impl<ELFT> Chdr; + Chdr.ch_type = ELF::ELFCOMPRESS_ZLIB; + Chdr.ch_size = Sec.DecompressedSize; + Chdr.ch_addralign = Sec.DecompressedAlign; + memcpy(Buf, &Chdr, sizeof(Chdr)); + Buf += sizeof(Chdr); + } + + std::copy(Sec.CompressedData.begin(), Sec.CompressedData.end(), Buf); +} + +CompressedSection::CompressedSection(const SectionBase &Sec, + DebugCompressionType CompressionType) + : SectionBase(Sec), CompressionType(CompressionType), + DecompressedSize(Sec.OriginalData.size()), DecompressedAlign(Sec.Align) { + + if (!zlib::isAvailable()) { + CompressionType = DebugCompressionType::None; + return; + } + + if (Error E = zlib::compress( + StringRef(reinterpret_cast<const char *>(OriginalData.data()), + OriginalData.size()), + CompressedData)) + reportError(Name, std::move(E)); + + size_t ChdrSize; + if (CompressionType == DebugCompressionType::GNU) { + Name = ".z" + Sec.Name.substr(1); + ChdrSize = sizeof("ZLIB") - 1 + sizeof(uint64_t); + } else { + Flags |= ELF::SHF_COMPRESSED; + ChdrSize = + std::max(std::max(sizeof(object::Elf_Chdr_Impl<object::ELF64LE>), + sizeof(object::Elf_Chdr_Impl<object::ELF64BE>)), + std::max(sizeof(object::Elf_Chdr_Impl<object::ELF32LE>), + sizeof(object::Elf_Chdr_Impl<object::ELF32BE>))); + } + Size = ChdrSize + CompressedData.size(); + Align = 8; +} + +CompressedSection::CompressedSection(ArrayRef<uint8_t> CompressedData, + uint64_t DecompressedSize, + uint64_t DecompressedAlign) + : CompressionType(DebugCompressionType::None), + DecompressedSize(DecompressedSize), DecompressedAlign(DecompressedAlign) { + OriginalData = CompressedData; +} + +void CompressedSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +void StringTableSection::addString(StringRef Name) { + StrTabBuilder.add(Name); + Size = StrTabBuilder.getSize(); +} + +uint32_t StringTableSection::findIndex(StringRef Name) const { + return StrTabBuilder.getOffset(Name); +} + +void StringTableSection::finalize() { StrTabBuilder.finalize(); } + +void SectionWriter::visit(const StringTableSection &Sec) { + Sec.StrTabBuilder.write(Out.getBufferStart() + Sec.Offset); +} + +void StringTableSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const SectionIndexSection &Sec) { + uint8_t *Buf = Out.getBufferStart() + Sec.Offset; + auto *IndexesBuffer = reinterpret_cast<Elf_Word *>(Buf); + std::copy(std::begin(Sec.Indexes), std::end(Sec.Indexes), IndexesBuffer); +} + +void SectionIndexSection::initialize(SectionTableRef SecTable) { + Size = 0; + setSymTab(SecTable.getSectionOfType<SymbolTableSection>( + Link, + "Link field value " + Twine(Link) + " in section " + Name + " is invalid", + "Link field value " + Twine(Link) + " in section " + Name + + " is not a symbol table")); + Symbols->setShndxTable(this); +} + +void SectionIndexSection::finalize() { Link = Symbols->Index; } + +void SectionIndexSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +static bool isValidReservedSectionIndex(uint16_t Index, uint16_t Machine) { + switch (Index) { + case SHN_ABS: + case SHN_COMMON: + return true; + } + if (Machine == EM_HEXAGON) { + switch (Index) { + case SHN_HEXAGON_SCOMMON: + case SHN_HEXAGON_SCOMMON_2: + case SHN_HEXAGON_SCOMMON_4: + case SHN_HEXAGON_SCOMMON_8: + return true; + } + } + return false; +} + +// Large indexes force us to clarify exactly what this function should do. This +// function should return the value that will appear in st_shndx when written +// out. +uint16_t Symbol::getShndx() const { + if (DefinedIn != nullptr) { + if (DefinedIn->Index >= SHN_LORESERVE) + return SHN_XINDEX; + return DefinedIn->Index; + } + switch (ShndxType) { + // This means that we don't have a defined section but we do need to + // output a legitimate section index. + case SYMBOL_SIMPLE_INDEX: + return SHN_UNDEF; + case SYMBOL_ABS: + case SYMBOL_COMMON: + case SYMBOL_HEXAGON_SCOMMON: + case SYMBOL_HEXAGON_SCOMMON_2: + case SYMBOL_HEXAGON_SCOMMON_4: + case SYMBOL_HEXAGON_SCOMMON_8: + case SYMBOL_XINDEX: + return static_cast<uint16_t>(ShndxType); + } + llvm_unreachable("Symbol with invalid ShndxType encountered"); +} + +void SymbolTableSection::assignIndices() { + uint32_t Index = 0; + for (auto &Sym : Symbols) + Sym->Index = Index++; +} + +void SymbolTableSection::addSymbol(Twine Name, uint8_t Bind, uint8_t Type, + SectionBase *DefinedIn, uint64_t Value, + uint8_t Visibility, uint16_t Shndx, + uint64_t Size) { + Symbol Sym; + Sym.Name = Name.str(); + Sym.Binding = Bind; + Sym.Type = Type; + Sym.DefinedIn = DefinedIn; + if (DefinedIn != nullptr) + DefinedIn->HasSymbol = true; + if (DefinedIn == nullptr) { + if (Shndx >= SHN_LORESERVE) + Sym.ShndxType = static_cast<SymbolShndxType>(Shndx); + else + Sym.ShndxType = SYMBOL_SIMPLE_INDEX; + } + Sym.Value = Value; + Sym.Visibility = Visibility; + Sym.Size = Size; + Sym.Index = Symbols.size(); + Symbols.emplace_back(llvm::make_unique<Symbol>(Sym)); + Size += this->EntrySize; +} + +void SymbolTableSection::removeSectionReferences(const SectionBase *Sec) { + if (SectionIndexTable == Sec) + SectionIndexTable = nullptr; + if (SymbolNames == Sec) { + error("String table " + SymbolNames->Name + + " cannot be removed because it is referenced by the symbol table " + + this->Name); + } + removeSymbols([Sec](const Symbol &Sym) { return Sym.DefinedIn == Sec; }); +} + +void SymbolTableSection::updateSymbols(function_ref<void(Symbol &)> Callable) { + std::for_each(std::begin(Symbols) + 1, std::end(Symbols), + [Callable](SymPtr &Sym) { Callable(*Sym); }); + std::stable_partition( + std::begin(Symbols), std::end(Symbols), + [](const SymPtr &Sym) { return Sym->Binding == STB_LOCAL; }); + assignIndices(); +} + +void SymbolTableSection::removeSymbols( + function_ref<bool(const Symbol &)> ToRemove) { + Symbols.erase( + std::remove_if(std::begin(Symbols) + 1, std::end(Symbols), + [ToRemove](const SymPtr &Sym) { return ToRemove(*Sym); }), + std::end(Symbols)); + Size = Symbols.size() * EntrySize; + assignIndices(); +} + +void SymbolTableSection::initialize(SectionTableRef SecTable) { + Size = 0; + setStrTab(SecTable.getSectionOfType<StringTableSection>( + Link, + "Symbol table has link index of " + Twine(Link) + + " which is not a valid index", + "Symbol table has link index of " + Twine(Link) + + " which is not a string table")); +} + +void SymbolTableSection::finalize() { + // Make sure SymbolNames is finalized before getting name indexes. + SymbolNames->finalize(); + + uint32_t MaxLocalIndex = 0; + for (auto &Sym : Symbols) { + Sym->NameIndex = SymbolNames->findIndex(Sym->Name); + if (Sym->Binding == STB_LOCAL) + MaxLocalIndex = std::max(MaxLocalIndex, Sym->Index); + } + // Now we need to set the Link and Info fields. + Link = SymbolNames->Index; + Info = MaxLocalIndex + 1; +} + +void SymbolTableSection::prepareForLayout() { + // Add all potential section indexes before file layout so that the section + // index section has the approprite size. + if (SectionIndexTable != nullptr) { + for (const auto &Sym : Symbols) { + if (Sym->DefinedIn != nullptr && Sym->DefinedIn->Index >= SHN_LORESERVE) + SectionIndexTable->addIndex(Sym->DefinedIn->Index); + else + SectionIndexTable->addIndex(SHN_UNDEF); + } + } + // Add all of our strings to SymbolNames so that SymbolNames has the right + // size before layout is decided. + for (auto &Sym : Symbols) + SymbolNames->addString(Sym->Name); +} + +const Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) const { + if (Symbols.size() <= Index) + error("Invalid symbol index: " + Twine(Index)); + return Symbols[Index].get(); +} + +Symbol *SymbolTableSection::getSymbolByIndex(uint32_t Index) { + return const_cast<Symbol *>( + static_cast<const SymbolTableSection *>(this)->getSymbolByIndex(Index)); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const SymbolTableSection &Sec) { + uint8_t *Buf = Out.getBufferStart(); + Buf += Sec.Offset; + Elf_Sym *Sym = reinterpret_cast<Elf_Sym *>(Buf); + // Loop though symbols setting each entry of the symbol table. + for (auto &Symbol : Sec.Symbols) { + Sym->st_name = Symbol->NameIndex; + Sym->st_value = Symbol->Value; + Sym->st_size = Symbol->Size; + Sym->st_other = Symbol->Visibility; + Sym->setBinding(Symbol->Binding); + Sym->setType(Symbol->Type); + Sym->st_shndx = Symbol->getShndx(); + ++Sym; + } +} + +void SymbolTableSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +template <class SymTabType> +void RelocSectionWithSymtabBase<SymTabType>::removeSectionReferences( + const SectionBase *Sec) { + if (Symbols == Sec) { + error("Symbol table " + Symbols->Name + + " cannot be removed because it is " + "referenced by the relocation " + "section " + + this->Name); + } +} + +template <class SymTabType> +void RelocSectionWithSymtabBase<SymTabType>::initialize( + SectionTableRef SecTable) { + if (Link != SHN_UNDEF) + setSymTab(SecTable.getSectionOfType<SymTabType>( + Link, + "Link field value " + Twine(Link) + " in section " + Name + + " is invalid", + "Link field value " + Twine(Link) + " in section " + Name + + " is not a symbol table")); + + if (Info != SHN_UNDEF) + setSection(SecTable.getSection(Info, "Info field value " + Twine(Info) + + " in section " + Name + + " is invalid")); + else + setSection(nullptr); +} + +template <class SymTabType> +void RelocSectionWithSymtabBase<SymTabType>::finalize() { + this->Link = Symbols ? Symbols->Index : 0; + + if (SecToApplyRel != nullptr) + this->Info = SecToApplyRel->Index; +} + +template <class ELFT> +static void setAddend(Elf_Rel_Impl<ELFT, false> &Rel, uint64_t Addend) {} + +template <class ELFT> +static void setAddend(Elf_Rel_Impl<ELFT, true> &Rela, uint64_t Addend) { + Rela.r_addend = Addend; +} + +template <class RelRange, class T> +static void writeRel(const RelRange &Relocations, T *Buf) { + for (const auto &Reloc : Relocations) { + Buf->r_offset = Reloc.Offset; + setAddend(*Buf, Reloc.Addend); + Buf->setSymbolAndType(Reloc.RelocSymbol->Index, Reloc.Type, false); + ++Buf; + } +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const RelocationSection &Sec) { + uint8_t *Buf = Out.getBufferStart() + Sec.Offset; + if (Sec.Type == SHT_REL) + writeRel(Sec.Relocations, reinterpret_cast<Elf_Rel *>(Buf)); + else + writeRel(Sec.Relocations, reinterpret_cast<Elf_Rela *>(Buf)); +} + +void RelocationSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +void RelocationSection::removeSymbols( + function_ref<bool(const Symbol &)> ToRemove) { + for (const Relocation &Reloc : Relocations) + if (ToRemove(*Reloc.RelocSymbol)) + error("not stripping symbol '" + Reloc.RelocSymbol->Name + + "' because it is named in a relocation"); +} + +void RelocationSection::markSymbols() { + for (const Relocation &Reloc : Relocations) + Reloc.RelocSymbol->Referenced = true; +} + +void SectionWriter::visit(const DynamicRelocationSection &Sec) { + std::copy(std::begin(Sec.Contents), std::end(Sec.Contents), + Out.getBufferStart() + Sec.Offset); +} + +void DynamicRelocationSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +void Section::removeSectionReferences(const SectionBase *Sec) { + if (LinkSection == Sec) { + error("Section " + LinkSection->Name + + " cannot be removed because it is " + "referenced by the section " + + this->Name); + } +} + +void GroupSection::finalize() { + this->Info = Sym->Index; + this->Link = SymTab->Index; +} + +void GroupSection::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) { + if (ToRemove(*Sym)) { + error("Symbol " + Sym->Name + + " cannot be removed because it is " + "referenced by the section " + + this->Name + "[" + Twine(this->Index) + "]"); + } +} + +void GroupSection::markSymbols() { + if (Sym) + Sym->Referenced = true; +} + +void Section::initialize(SectionTableRef SecTable) { + if (Link != ELF::SHN_UNDEF) { + LinkSection = + SecTable.getSection(Link, "Link field value " + Twine(Link) + + " in section " + Name + " is invalid"); + if (LinkSection->Type == ELF::SHT_SYMTAB) + LinkSection = nullptr; + } +} + +void Section::finalize() { this->Link = LinkSection ? LinkSection->Index : 0; } + +void GnuDebugLinkSection::init(StringRef File, StringRef Data) { + FileName = sys::path::filename(File); + // The format for the .gnu_debuglink starts with the file name and is + // followed by a null terminator and then the CRC32 of the file. The CRC32 + // should be 4 byte aligned. So we add the FileName size, a 1 for the null + // byte, and then finally push the size to alignment and add 4. + Size = alignTo(FileName.size() + 1, 4) + 4; + // The CRC32 will only be aligned if we align the whole section. + Align = 4; + Type = ELF::SHT_PROGBITS; + Name = ".gnu_debuglink"; + // For sections not found in segments, OriginalOffset is only used to + // establish the order that sections should go in. By using the maximum + // possible offset we cause this section to wind up at the end. + OriginalOffset = std::numeric_limits<uint64_t>::max(); + JamCRC crc; + crc.update(ArrayRef<char>(Data.data(), Data.size())); + // The CRC32 value needs to be complemented because the JamCRC dosn't + // finalize the CRC32 value. It also dosn't negate the initial CRC32 value + // but it starts by default at 0xFFFFFFFF which is the complement of zero. + CRC32 = ~crc.getCRC(); +} + +GnuDebugLinkSection::GnuDebugLinkSection(StringRef File) : FileName(File) { + // Read in the file to compute the CRC of it. + auto DebugOrErr = MemoryBuffer::getFile(File); + if (!DebugOrErr) + error("'" + File + "': " + DebugOrErr.getError().message()); + auto Debug = std::move(*DebugOrErr); + init(File, Debug->getBuffer()); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const GnuDebugLinkSection &Sec) { + auto Buf = Out.getBufferStart() + Sec.Offset; + char *File = reinterpret_cast<char *>(Buf); + Elf_Word *CRC = + reinterpret_cast<Elf_Word *>(Buf + Sec.Size - sizeof(Elf_Word)); + *CRC = Sec.CRC32; + std::copy(std::begin(Sec.FileName), std::end(Sec.FileName), File); +} + +void GnuDebugLinkSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +template <class ELFT> +void ELFSectionWriter<ELFT>::visit(const GroupSection &Sec) { + ELF::Elf32_Word *Buf = + reinterpret_cast<ELF::Elf32_Word *>(Out.getBufferStart() + Sec.Offset); + *Buf++ = Sec.FlagWord; + for (const auto *S : Sec.GroupMembers) + support::endian::write32<ELFT::TargetEndianness>(Buf++, S->Index); +} + +void GroupSection::accept(SectionVisitor &Visitor) const { + Visitor.visit(*this); +} + +// Returns true IFF a section is wholly inside the range of a segment +static bool sectionWithinSegment(const SectionBase &Section, + const Segment &Segment) { + // If a section is empty it should be treated like it has a size of 1. This is + // to clarify the case when an empty section lies on a boundary between two + // segments and ensures that the section "belongs" to the second segment and + // not the first. + uint64_t SecSize = Section.Size ? Section.Size : 1; + return Segment.Offset <= Section.OriginalOffset && + Segment.Offset + Segment.FileSize >= Section.OriginalOffset + SecSize; +} + +// Returns true IFF a segment's original offset is inside of another segment's +// range. +static bool segmentOverlapsSegment(const Segment &Child, + const Segment &Parent) { + + return Parent.OriginalOffset <= Child.OriginalOffset && + Parent.OriginalOffset + Parent.FileSize > Child.OriginalOffset; +} + +static bool compareSegmentsByOffset(const Segment *A, const Segment *B) { + // Any segment without a parent segment should come before a segment + // that has a parent segment. + if (A->OriginalOffset < B->OriginalOffset) + return true; + if (A->OriginalOffset > B->OriginalOffset) + return false; + return A->Index < B->Index; +} + +static bool compareSegmentsByPAddr(const Segment *A, const Segment *B) { + if (A->PAddr < B->PAddr) + return true; + if (A->PAddr > B->PAddr) + return false; + return A->Index < B->Index; +} + +template <class ELFT> void BinaryELFBuilder<ELFT>::initFileHeader() { + Obj->Flags = 0x0; + Obj->Type = ET_REL; + Obj->Entry = 0x0; + Obj->Machine = EMachine; + Obj->Version = 1; +} + +template <class ELFT> void BinaryELFBuilder<ELFT>::initHeaderSegment() { + Obj->ElfHdrSegment.Index = 0; +} + +template <class ELFT> StringTableSection *BinaryELFBuilder<ELFT>::addStrTab() { + auto &StrTab = Obj->addSection<StringTableSection>(); + StrTab.Name = ".strtab"; + + Obj->SectionNames = &StrTab; + return &StrTab; +} + +template <class ELFT> +SymbolTableSection * +BinaryELFBuilder<ELFT>::addSymTab(StringTableSection *StrTab) { + auto &SymTab = Obj->addSection<SymbolTableSection>(); + + SymTab.Name = ".symtab"; + SymTab.Link = StrTab->Index; + // TODO: Factor out dependence on ElfType here. + SymTab.EntrySize = sizeof(Elf_Sym); + + // The symbol table always needs a null symbol + SymTab.addSymbol("", 0, 0, nullptr, 0, 0, 0, 0); + + Obj->SymbolTable = &SymTab; + return &SymTab; +} + +template <class ELFT> +void BinaryELFBuilder<ELFT>::addData(SymbolTableSection *SymTab) { + auto Data = ArrayRef<uint8_t>( + reinterpret_cast<const uint8_t *>(MemBuf->getBufferStart()), + MemBuf->getBufferSize()); + auto &DataSection = Obj->addSection<Section>(Data); + DataSection.Name = ".data"; + DataSection.Type = ELF::SHT_PROGBITS; + DataSection.Size = Data.size(); + DataSection.Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE; + + std::string SanitizedFilename = MemBuf->getBufferIdentifier().str(); + std::replace_if(std::begin(SanitizedFilename), std::end(SanitizedFilename), + [](char c) { return !isalnum(c); }, '_'); + Twine Prefix = Twine("_binary_") + SanitizedFilename; + + SymTab->addSymbol(Prefix + "_start", STB_GLOBAL, STT_NOTYPE, &DataSection, + /*Value=*/0, STV_DEFAULT, 0, 0); + SymTab->addSymbol(Prefix + "_end", STB_GLOBAL, STT_NOTYPE, &DataSection, + /*Value=*/DataSection.Size, STV_DEFAULT, 0, 0); + SymTab->addSymbol(Prefix + "_size", STB_GLOBAL, STT_NOTYPE, nullptr, + /*Value=*/DataSection.Size, STV_DEFAULT, SHN_ABS, 0); +} + +template <class ELFT> void BinaryELFBuilder<ELFT>::initSections() { + for (auto &Section : Obj->sections()) { + Section.initialize(Obj->sections()); + } +} + +template <class ELFT> std::unique_ptr<Object> BinaryELFBuilder<ELFT>::build() { + initFileHeader(); + initHeaderSegment(); + StringTableSection *StrTab = addStrTab(); + SymbolTableSection *SymTab = addSymTab(StrTab); + initSections(); + addData(SymTab); + + return std::move(Obj); +} + +template <class ELFT> void ELFBuilder<ELFT>::setParentSegment(Segment &Child) { + for (auto &Parent : Obj.segments()) { + // Every segment will overlap with itself but we don't want a segment to + // be it's own parent so we avoid that situation. + if (&Child != &Parent && segmentOverlapsSegment(Child, Parent)) { + // We want a canonical "most parental" segment but this requires + // inspecting the ParentSegment. + if (compareSegmentsByOffset(&Parent, &Child)) + if (Child.ParentSegment == nullptr || + compareSegmentsByOffset(&Parent, Child.ParentSegment)) { + Child.ParentSegment = &Parent; + } + } + } +} + +template <class ELFT> void ELFBuilder<ELFT>::readProgramHeaders() { + uint32_t Index = 0; + for (const auto &Phdr : unwrapOrError(ElfFile.program_headers())) { + ArrayRef<uint8_t> Data{ElfFile.base() + Phdr.p_offset, + (size_t)Phdr.p_filesz}; + Segment &Seg = Obj.addSegment(Data); + Seg.Type = Phdr.p_type; + Seg.Flags = Phdr.p_flags; + Seg.OriginalOffset = Phdr.p_offset; + Seg.Offset = Phdr.p_offset; + Seg.VAddr = Phdr.p_vaddr; + Seg.PAddr = Phdr.p_paddr; + Seg.FileSize = Phdr.p_filesz; + Seg.MemSize = Phdr.p_memsz; + Seg.Align = Phdr.p_align; + Seg.Index = Index++; + for (auto &Section : Obj.sections()) { + if (sectionWithinSegment(Section, Seg)) { + Seg.addSection(&Section); + if (!Section.ParentSegment || + Section.ParentSegment->Offset > Seg.Offset) { + Section.ParentSegment = &Seg; + } + } + } + } + + auto &ElfHdr = Obj.ElfHdrSegment; + ElfHdr.Index = Index++; + + const auto &Ehdr = *ElfFile.getHeader(); + auto &PrHdr = Obj.ProgramHdrSegment; + PrHdr.Type = PT_PHDR; + PrHdr.Flags = 0; + // The spec requires us to have p_vaddr % p_align == p_offset % p_align. + // Whereas this works automatically for ElfHdr, here OriginalOffset is + // always non-zero and to ensure the equation we assign the same value to + // VAddr as well. + PrHdr.OriginalOffset = PrHdr.Offset = PrHdr.VAddr = Ehdr.e_phoff; + PrHdr.PAddr = 0; + PrHdr.FileSize = PrHdr.MemSize = Ehdr.e_phentsize * Ehdr.e_phnum; + // The spec requires us to naturally align all the fields. + PrHdr.Align = sizeof(Elf_Addr); + PrHdr.Index = Index++; + + // Now we do an O(n^2) loop through the segments in order to match up + // segments. + for (auto &Child : Obj.segments()) + setParentSegment(Child); + setParentSegment(ElfHdr); + setParentSegment(PrHdr); +} + +template <class ELFT> +void ELFBuilder<ELFT>::initGroupSection(GroupSection *GroupSec) { + auto SecTable = Obj.sections(); + auto SymTab = SecTable.template getSectionOfType<SymbolTableSection>( + GroupSec->Link, + "Link field value " + Twine(GroupSec->Link) + " in section " + + GroupSec->Name + " is invalid", + "Link field value " + Twine(GroupSec->Link) + " in section " + + GroupSec->Name + " is not a symbol table"); + auto Sym = SymTab->getSymbolByIndex(GroupSec->Info); + if (!Sym) + error("Info field value " + Twine(GroupSec->Info) + " in section " + + GroupSec->Name + " is not a valid symbol index"); + GroupSec->setSymTab(SymTab); + GroupSec->setSymbol(Sym); + if (GroupSec->Contents.size() % sizeof(ELF::Elf32_Word) || + GroupSec->Contents.empty()) + error("The content of the section " + GroupSec->Name + " is malformed"); + const ELF::Elf32_Word *Word = + reinterpret_cast<const ELF::Elf32_Word *>(GroupSec->Contents.data()); + const ELF::Elf32_Word *End = + Word + GroupSec->Contents.size() / sizeof(ELF::Elf32_Word); + GroupSec->setFlagWord(*Word++); + for (; Word != End; ++Word) { + uint32_t Index = support::endian::read32<ELFT::TargetEndianness>(Word); + GroupSec->addMember(SecTable.getSection( + Index, "Group member index " + Twine(Index) + " in section " + + GroupSec->Name + " is invalid")); + } +} + +template <class ELFT> +void ELFBuilder<ELFT>::initSymbolTable(SymbolTableSection *SymTab) { + const Elf_Shdr &Shdr = *unwrapOrError(ElfFile.getSection(SymTab->Index)); + StringRef StrTabData = unwrapOrError(ElfFile.getStringTableForSymtab(Shdr)); + ArrayRef<Elf_Word> ShndxData; + + auto Symbols = unwrapOrError(ElfFile.symbols(&Shdr)); + for (const auto &Sym : Symbols) { + SectionBase *DefSection = nullptr; + StringRef Name = unwrapOrError(Sym.getName(StrTabData)); + + if (Sym.st_shndx == SHN_XINDEX) { + if (SymTab->getShndxTable() == nullptr) + error("Symbol '" + Name + + "' has index SHN_XINDEX but no SHT_SYMTAB_SHNDX section exists."); + if (ShndxData.data() == nullptr) { + const Elf_Shdr &ShndxSec = + *unwrapOrError(ElfFile.getSection(SymTab->getShndxTable()->Index)); + ShndxData = unwrapOrError( + ElfFile.template getSectionContentsAsArray<Elf_Word>(&ShndxSec)); + if (ShndxData.size() != Symbols.size()) + error("Symbol section index table does not have the same number of " + "entries as the symbol table."); + } + Elf_Word Index = ShndxData[&Sym - Symbols.begin()]; + DefSection = Obj.sections().getSection( + Index, + "Symbol '" + Name + "' has invalid section index " + Twine(Index)); + } else if (Sym.st_shndx >= SHN_LORESERVE) { + if (!isValidReservedSectionIndex(Sym.st_shndx, Obj.Machine)) { + error( + "Symbol '" + Name + + "' has unsupported value greater than or equal to SHN_LORESERVE: " + + Twine(Sym.st_shndx)); + } + } else if (Sym.st_shndx != SHN_UNDEF) { + DefSection = Obj.sections().getSection( + Sym.st_shndx, "Symbol '" + Name + + "' is defined has invalid section index " + + Twine(Sym.st_shndx)); + } + + SymTab->addSymbol(Name, Sym.getBinding(), Sym.getType(), DefSection, + Sym.getValue(), Sym.st_other, Sym.st_shndx, Sym.st_size); + } +} + +template <class ELFT> +static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, false> &Rel) {} + +template <class ELFT> +static void getAddend(uint64_t &ToSet, const Elf_Rel_Impl<ELFT, true> &Rela) { + ToSet = Rela.r_addend; +} + +template <class T> +static void initRelocations(RelocationSection *Relocs, + SymbolTableSection *SymbolTable, T RelRange) { + for (const auto &Rel : RelRange) { + Relocation ToAdd; + ToAdd.Offset = Rel.r_offset; + getAddend(ToAdd.Addend, Rel); + ToAdd.Type = Rel.getType(false); + ToAdd.RelocSymbol = SymbolTable->getSymbolByIndex(Rel.getSymbol(false)); + Relocs->addRelocation(ToAdd); + } +} + +SectionBase *SectionTableRef::getSection(uint32_t Index, Twine ErrMsg) { + if (Index == SHN_UNDEF || Index > Sections.size()) + error(ErrMsg); + return Sections[Index - 1].get(); +} + +template <class T> +T *SectionTableRef::getSectionOfType(uint32_t Index, Twine IndexErrMsg, + Twine TypeErrMsg) { + if (T *Sec = dyn_cast<T>(getSection(Index, IndexErrMsg))) + return Sec; + error(TypeErrMsg); +} + +template <class ELFT> +SectionBase &ELFBuilder<ELFT>::makeSection(const Elf_Shdr &Shdr) { + ArrayRef<uint8_t> Data; + switch (Shdr.sh_type) { + case SHT_REL: + case SHT_RELA: + if (Shdr.sh_flags & SHF_ALLOC) { + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<DynamicRelocationSection>(Data); + } + return Obj.addSection<RelocationSection>(); + case SHT_STRTAB: + // If a string table is allocated we don't want to mess with it. That would + // mean altering the memory image. There are no special link types or + // anything so we can just use a Section. + if (Shdr.sh_flags & SHF_ALLOC) { + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<Section>(Data); + } + return Obj.addSection<StringTableSection>(); + case SHT_HASH: + case SHT_GNU_HASH: + // Hash tables should refer to SHT_DYNSYM which we're not going to change. + // Because of this we don't need to mess with the hash tables either. + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<Section>(Data); + case SHT_GROUP: + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<GroupSection>(Data); + case SHT_DYNSYM: + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<DynamicSymbolTableSection>(Data); + case SHT_DYNAMIC: + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + return Obj.addSection<DynamicSection>(Data); + case SHT_SYMTAB: { + auto &SymTab = Obj.addSection<SymbolTableSection>(); + Obj.SymbolTable = &SymTab; + return SymTab; + } + case SHT_SYMTAB_SHNDX: { + auto &ShndxSection = Obj.addSection<SectionIndexSection>(); + Obj.SectionIndexTable = &ShndxSection; + return ShndxSection; + } + case SHT_NOBITS: + return Obj.addSection<Section>(Data); + default: { + Data = unwrapOrError(ElfFile.getSectionContents(&Shdr)); + + if (isDataGnuCompressed(Data) || (Shdr.sh_flags & ELF::SHF_COMPRESSED)) { + uint64_t DecompressedSize, DecompressedAlign; + std::tie(DecompressedSize, DecompressedAlign) = + getDecompressedSizeAndAlignment<ELFT>(Data); + return Obj.addSection<CompressedSection>(Data, DecompressedSize, + DecompressedAlign); + } + + return Obj.addSection<Section>(Data); + } + } +} + +template <class ELFT> void ELFBuilder<ELFT>::readSectionHeaders() { + uint32_t Index = 0; + for (const auto &Shdr : unwrapOrError(ElfFile.sections())) { + if (Index == 0) { + ++Index; + continue; + } + auto &Sec = makeSection(Shdr); + Sec.Name = unwrapOrError(ElfFile.getSectionName(&Shdr)); + Sec.Type = Shdr.sh_type; + Sec.Flags = Shdr.sh_flags; + Sec.Addr = Shdr.sh_addr; + Sec.Offset = Shdr.sh_offset; + Sec.OriginalOffset = Shdr.sh_offset; + Sec.Size = Shdr.sh_size; + Sec.Link = Shdr.sh_link; + Sec.Info = Shdr.sh_info; + Sec.Align = Shdr.sh_addralign; + Sec.EntrySize = Shdr.sh_entsize; + Sec.Index = Index++; + Sec.OriginalData = + ArrayRef<uint8_t>(ElfFile.base() + Shdr.sh_offset, + (Shdr.sh_type == SHT_NOBITS) ? 0 : Shdr.sh_size); + } + + // If a section index table exists we'll need to initialize it before we + // initialize the symbol table because the symbol table might need to + // reference it. + if (Obj.SectionIndexTable) + Obj.SectionIndexTable->initialize(Obj.sections()); + + // Now that all of the sections have been added we can fill out some extra + // details about symbol tables. We need the symbol table filled out before + // any relocations. + if (Obj.SymbolTable) { + Obj.SymbolTable->initialize(Obj.sections()); + initSymbolTable(Obj.SymbolTable); + } + + // Now that all sections and symbols have been added we can add + // relocations that reference symbols and set the link and info fields for + // relocation sections. + for (auto &Section : Obj.sections()) { + if (&Section == Obj.SymbolTable) + continue; + Section.initialize(Obj.sections()); + if (auto RelSec = dyn_cast<RelocationSection>(&Section)) { + auto Shdr = unwrapOrError(ElfFile.sections()).begin() + RelSec->Index; + if (RelSec->Type == SHT_REL) + initRelocations(RelSec, Obj.SymbolTable, + unwrapOrError(ElfFile.rels(Shdr))); + else + initRelocations(RelSec, Obj.SymbolTable, + unwrapOrError(ElfFile.relas(Shdr))); + } else if (auto GroupSec = dyn_cast<GroupSection>(&Section)) { + initGroupSection(GroupSec); + } + } +} + +template <class ELFT> void ELFBuilder<ELFT>::build() { + const auto &Ehdr = *ElfFile.getHeader(); + + Obj.Type = Ehdr.e_type; + Obj.Machine = Ehdr.e_machine; + Obj.Version = Ehdr.e_version; + Obj.Entry = Ehdr.e_entry; + Obj.Flags = Ehdr.e_flags; + + readSectionHeaders(); + readProgramHeaders(); + + uint32_t ShstrIndex = Ehdr.e_shstrndx; + if (ShstrIndex == SHN_XINDEX) + ShstrIndex = unwrapOrError(ElfFile.getSection(0))->sh_link; + + Obj.SectionNames = + Obj.sections().template getSectionOfType<StringTableSection>( + ShstrIndex, + "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) + + " in elf header " + " is invalid", + "e_shstrndx field value " + Twine(Ehdr.e_shstrndx) + + " in elf header " + " is not a string table"); +} + +// A generic size function which computes sizes of any random access range. +template <class R> size_t size(R &&Range) { + return static_cast<size_t>(std::end(Range) - std::begin(Range)); +} + +Writer::~Writer() {} + +Reader::~Reader() {} + +std::unique_ptr<Object> BinaryReader::create() const { + if (MInfo.Is64Bit) + return MInfo.IsLittleEndian + ? BinaryELFBuilder<ELF64LE>(MInfo.EMachine, MemBuf).build() + : BinaryELFBuilder<ELF64BE>(MInfo.EMachine, MemBuf).build(); + else + return MInfo.IsLittleEndian + ? BinaryELFBuilder<ELF32LE>(MInfo.EMachine, MemBuf).build() + : BinaryELFBuilder<ELF32BE>(MInfo.EMachine, MemBuf).build(); +} + +std::unique_ptr<Object> ELFReader::create() const { + auto Obj = llvm::make_unique<Object>(); + if (auto *o = dyn_cast<ELFObjectFile<ELF32LE>>(Bin)) { + ELFBuilder<ELF32LE> Builder(*o, *Obj); + Builder.build(); + return Obj; + } else if (auto *o = dyn_cast<ELFObjectFile<ELF64LE>>(Bin)) { + ELFBuilder<ELF64LE> Builder(*o, *Obj); + Builder.build(); + return Obj; + } else if (auto *o = dyn_cast<ELFObjectFile<ELF32BE>>(Bin)) { + ELFBuilder<ELF32BE> Builder(*o, *Obj); + Builder.build(); + return Obj; + } else if (auto *o = dyn_cast<ELFObjectFile<ELF64BE>>(Bin)) { + ELFBuilder<ELF64BE> Builder(*o, *Obj); + Builder.build(); + return Obj; + } + error("Invalid file type"); +} + +template <class ELFT> void ELFWriter<ELFT>::writeEhdr() { + uint8_t *B = Buf.getBufferStart(); + Elf_Ehdr &Ehdr = *reinterpret_cast<Elf_Ehdr *>(B); + std::fill(Ehdr.e_ident, Ehdr.e_ident + 16, 0); + Ehdr.e_ident[EI_MAG0] = 0x7f; + Ehdr.e_ident[EI_MAG1] = 'E'; + Ehdr.e_ident[EI_MAG2] = 'L'; + Ehdr.e_ident[EI_MAG3] = 'F'; + Ehdr.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32; + Ehdr.e_ident[EI_DATA] = + ELFT::TargetEndianness == support::big ? ELFDATA2MSB : ELFDATA2LSB; + Ehdr.e_ident[EI_VERSION] = EV_CURRENT; + Ehdr.e_ident[EI_OSABI] = ELFOSABI_NONE; + Ehdr.e_ident[EI_ABIVERSION] = 0; + + Ehdr.e_type = Obj.Type; + Ehdr.e_machine = Obj.Machine; + Ehdr.e_version = Obj.Version; + Ehdr.e_entry = Obj.Entry; + // We have to use the fully-qualified name llvm::size + // since some compilers complain on ambiguous resolution. + Ehdr.e_phnum = llvm::size(Obj.segments()); + Ehdr.e_phoff = (Ehdr.e_phnum != 0) ? Obj.ProgramHdrSegment.Offset : 0; + Ehdr.e_phentsize = (Ehdr.e_phnum != 0) ? sizeof(Elf_Phdr) : 0; + Ehdr.e_flags = Obj.Flags; + Ehdr.e_ehsize = sizeof(Elf_Ehdr); + if (WriteSectionHeaders && size(Obj.sections()) != 0) { + Ehdr.e_shentsize = sizeof(Elf_Shdr); + Ehdr.e_shoff = Obj.SHOffset; + // """ + // If the number of sections is greater than or equal to + // SHN_LORESERVE (0xff00), this member has the value zero and the actual + // number of section header table entries is contained in the sh_size field + // of the section header at index 0. + // """ + auto Shnum = size(Obj.sections()) + 1; + if (Shnum >= SHN_LORESERVE) + Ehdr.e_shnum = 0; + else + Ehdr.e_shnum = Shnum; + // """ + // If the section name string table section index is greater than or equal + // to SHN_LORESERVE (0xff00), this member has the value SHN_XINDEX (0xffff) + // and the actual index of the section name string table section is + // contained in the sh_link field of the section header at index 0. + // """ + if (Obj.SectionNames->Index >= SHN_LORESERVE) + Ehdr.e_shstrndx = SHN_XINDEX; + else + Ehdr.e_shstrndx = Obj.SectionNames->Index; + } else { + Ehdr.e_shentsize = 0; + Ehdr.e_shoff = 0; + Ehdr.e_shnum = 0; + Ehdr.e_shstrndx = 0; + } +} + +template <class ELFT> void ELFWriter<ELFT>::writePhdrs() { + for (auto &Seg : Obj.segments()) + writePhdr(Seg); +} + +template <class ELFT> void ELFWriter<ELFT>::writeShdrs() { + uint8_t *B = Buf.getBufferStart() + Obj.SHOffset; + // This reference serves to write the dummy section header at the begining + // of the file. It is not used for anything else + Elf_Shdr &Shdr = *reinterpret_cast<Elf_Shdr *>(B); + Shdr.sh_name = 0; + Shdr.sh_type = SHT_NULL; + Shdr.sh_flags = 0; + Shdr.sh_addr = 0; + Shdr.sh_offset = 0; + // See writeEhdr for why we do this. + uint64_t Shnum = size(Obj.sections()) + 1; + if (Shnum >= SHN_LORESERVE) + Shdr.sh_size = Shnum; + else + Shdr.sh_size = 0; + // See writeEhdr for why we do this. + if (Obj.SectionNames != nullptr && Obj.SectionNames->Index >= SHN_LORESERVE) + Shdr.sh_link = Obj.SectionNames->Index; + else + Shdr.sh_link = 0; + Shdr.sh_info = 0; + Shdr.sh_addralign = 0; + Shdr.sh_entsize = 0; + + for (auto &Sec : Obj.sections()) + writeShdr(Sec); +} + +template <class ELFT> void ELFWriter<ELFT>::writeSectionData() { + for (auto &Sec : Obj.sections()) + Sec.accept(*SecWriter); +} + +void Object::removeSections(std::function<bool(const SectionBase &)> ToRemove) { + + auto Iter = std::stable_partition( + std::begin(Sections), std::end(Sections), [=](const SecPtr &Sec) { + if (ToRemove(*Sec)) + return false; + if (auto RelSec = dyn_cast<RelocationSectionBase>(Sec.get())) { + if (auto ToRelSec = RelSec->getSection()) + return !ToRemove(*ToRelSec); + } + return true; + }); + if (SymbolTable != nullptr && ToRemove(*SymbolTable)) + SymbolTable = nullptr; + if (SectionNames != nullptr && ToRemove(*SectionNames)) + SectionNames = nullptr; + if (SectionIndexTable != nullptr && ToRemove(*SectionIndexTable)) + SectionIndexTable = nullptr; + // Now make sure there are no remaining references to the sections that will + // be removed. Sometimes it is impossible to remove a reference so we emit + // an error here instead. + for (auto &RemoveSec : make_range(Iter, std::end(Sections))) { + for (auto &Segment : Segments) + Segment->removeSection(RemoveSec.get()); + for (auto &KeepSec : make_range(std::begin(Sections), Iter)) + KeepSec->removeSectionReferences(RemoveSec.get()); + } + // Now finally get rid of them all togethor. + Sections.erase(Iter, std::end(Sections)); +} + +void Object::removeSymbols(function_ref<bool(const Symbol &)> ToRemove) { + if (!SymbolTable) + return; + + for (const SecPtr &Sec : Sections) + Sec->removeSymbols(ToRemove); +} + +void Object::sortSections() { + // Put all sections in offset order. Maintain the ordering as closely as + // possible while meeting that demand however. + auto CompareSections = [](const SecPtr &A, const SecPtr &B) { + return A->OriginalOffset < B->OriginalOffset; + }; + std::stable_sort(std::begin(this->Sections), std::end(this->Sections), + CompareSections); +} + +static uint64_t alignToAddr(uint64_t Offset, uint64_t Addr, uint64_t Align) { + // Calculate Diff such that (Offset + Diff) & -Align == Addr & -Align. + if (Align == 0) + Align = 1; + auto Diff = + static_cast<int64_t>(Addr % Align) - static_cast<int64_t>(Offset % Align); + // We only want to add to Offset, however, so if Diff < 0 we can add Align and + // (Offset + Diff) & -Align == Addr & -Align will still hold. + if (Diff < 0) + Diff += Align; + return Offset + Diff; +} + +// Orders segments such that if x = y->ParentSegment then y comes before x. +static void OrderSegments(std::vector<Segment *> &Segments) { + std::stable_sort(std::begin(Segments), std::end(Segments), + compareSegmentsByOffset); +} + +// This function finds a consistent layout for a list of segments starting from +// an Offset. It assumes that Segments have been sorted by OrderSegments and +// returns an Offset one past the end of the last segment. +static uint64_t LayoutSegments(std::vector<Segment *> &Segments, + uint64_t Offset) { + assert(std::is_sorted(std::begin(Segments), std::end(Segments), + compareSegmentsByOffset)); + // The only way a segment should move is if a section was between two + // segments and that section was removed. If that section isn't in a segment + // then it's acceptable, but not ideal, to simply move it to after the + // segments. So we can simply layout segments one after the other accounting + // for alignment. + for (auto &Segment : Segments) { + // We assume that segments have been ordered by OriginalOffset and Index + // such that a parent segment will always come before a child segment in + // OrderedSegments. This means that the Offset of the ParentSegment should + // already be set and we can set our offset relative to it. + if (Segment->ParentSegment != nullptr) { + auto Parent = Segment->ParentSegment; + Segment->Offset = + Parent->Offset + Segment->OriginalOffset - Parent->OriginalOffset; + } else { + Offset = alignToAddr(Offset, Segment->VAddr, Segment->Align); + Segment->Offset = Offset; + } + Offset = std::max(Offset, Segment->Offset + Segment->FileSize); + } + return Offset; +} + +// This function finds a consistent layout for a list of sections. It assumes +// that the ->ParentSegment of each section has already been laid out. The +// supplied starting Offset is used for the starting offset of any section that +// does not have a ParentSegment. It returns either the offset given if all +// sections had a ParentSegment or an offset one past the last section if there +// was a section that didn't have a ParentSegment. +template <class Range> +static uint64_t LayoutSections(Range Sections, uint64_t Offset) { + // Now the offset of every segment has been set we can assign the offsets + // of each section. For sections that are covered by a segment we should use + // the segment's original offset and the section's original offset to compute + // the offset from the start of the segment. Using the offset from the start + // of the segment we can assign a new offset to the section. For sections not + // covered by segments we can just bump Offset to the next valid location. + uint32_t Index = 1; + for (auto &Section : Sections) { + Section.Index = Index++; + if (Section.ParentSegment != nullptr) { + auto Segment = *Section.ParentSegment; + Section.Offset = + Segment.Offset + (Section.OriginalOffset - Segment.OriginalOffset); + } else { + Offset = alignTo(Offset, Section.Align == 0 ? 1 : Section.Align); + Section.Offset = Offset; + if (Section.Type != SHT_NOBITS) + Offset += Section.Size; + } + } + return Offset; +} + +template <class ELFT> void ELFWriter<ELFT>::initEhdrSegment() { + auto &ElfHdr = Obj.ElfHdrSegment; + ElfHdr.Type = PT_PHDR; + ElfHdr.Flags = 0; + ElfHdr.OriginalOffset = ElfHdr.Offset = 0; + ElfHdr.VAddr = 0; + ElfHdr.PAddr = 0; + ElfHdr.FileSize = ElfHdr.MemSize = sizeof(Elf_Ehdr); + ElfHdr.Align = 0; +} + +template <class ELFT> void ELFWriter<ELFT>::assignOffsets() { + // We need a temporary list of segments that has a special order to it + // so that we know that anytime ->ParentSegment is set that segment has + // already had its offset properly set. + std::vector<Segment *> OrderedSegments; + for (auto &Segment : Obj.segments()) + OrderedSegments.push_back(&Segment); + OrderedSegments.push_back(&Obj.ElfHdrSegment); + OrderedSegments.push_back(&Obj.ProgramHdrSegment); + OrderSegments(OrderedSegments); + // Offset is used as the start offset of the first segment to be laid out. + // Since the ELF Header (ElfHdrSegment) must be at the start of the file, + // we start at offset 0. + uint64_t Offset = 0; + Offset = LayoutSegments(OrderedSegments, Offset); + Offset = LayoutSections(Obj.sections(), Offset); + // If we need to write the section header table out then we need to align the + // Offset so that SHOffset is valid. + if (WriteSectionHeaders) + Offset = alignTo(Offset, sizeof(Elf_Addr)); + Obj.SHOffset = Offset; +} + +template <class ELFT> size_t ELFWriter<ELFT>::totalSize() const { + // We already have the section header offset so we can calculate the total + // size by just adding up the size of each section header. + auto NullSectionSize = WriteSectionHeaders ? sizeof(Elf_Shdr) : 0; + return Obj.SHOffset + size(Obj.sections()) * sizeof(Elf_Shdr) + + NullSectionSize; +} + +template <class ELFT> void ELFWriter<ELFT>::write() { + writeEhdr(); + writePhdrs(); + writeSectionData(); + if (WriteSectionHeaders) + writeShdrs(); + if (auto E = Buf.commit()) + reportError(Buf.getName(), errorToErrorCode(std::move(E))); +} + +template <class ELFT> void ELFWriter<ELFT>::finalize() { + // It could happen that SectionNames has been removed and yet the user wants + // a section header table output. We need to throw an error if a user tries + // to do that. + if (Obj.SectionNames == nullptr && WriteSectionHeaders) + error("Cannot write section header table because section header string " + "table was removed."); + + Obj.sortSections(); + + // We need to assign indexes before we perform layout because we need to know + // if we need large indexes or not. We can assign indexes first and check as + // we go to see if we will actully need large indexes. + bool NeedsLargeIndexes = false; + if (size(Obj.sections()) >= SHN_LORESERVE) { + auto Sections = Obj.sections(); + NeedsLargeIndexes = + std::any_of(Sections.begin() + SHN_LORESERVE, Sections.end(), + [](const SectionBase &Sec) { return Sec.HasSymbol; }); + // TODO: handle case where only one section needs the large index table but + // only needs it because the large index table hasn't been removed yet. + } + + if (NeedsLargeIndexes) { + // This means we definitely need to have a section index table but if we + // already have one then we should use it instead of making a new one. + if (Obj.SymbolTable != nullptr && Obj.SectionIndexTable == nullptr) { + // Addition of a section to the end does not invalidate the indexes of + // other sections and assigns the correct index to the new section. + auto &Shndx = Obj.addSection<SectionIndexSection>(); + Obj.SymbolTable->setShndxTable(&Shndx); + Shndx.setSymTab(Obj.SymbolTable); + } + } else { + // Since we don't need SectionIndexTable we should remove it and all + // references to it. + if (Obj.SectionIndexTable != nullptr) { + Obj.removeSections([this](const SectionBase &Sec) { + return &Sec == Obj.SectionIndexTable; + }); + } + } + + // Make sure we add the names of all the sections. Importantly this must be + // done after we decide to add or remove SectionIndexes. + if (Obj.SectionNames != nullptr) + for (const auto &Section : Obj.sections()) { + Obj.SectionNames->addString(Section.Name); + } + + initEhdrSegment(); + // Before we can prepare for layout the indexes need to be finalized. + uint64_t Index = 0; + for (auto &Sec : Obj.sections()) + Sec.Index = Index++; + + // The symbol table does not update all other sections on update. For + // instance, symbol names are not added as new symbols are added. This means + // that some sections, like .strtab, don't yet have their final size. + if (Obj.SymbolTable != nullptr) + Obj.SymbolTable->prepareForLayout(); + + assignOffsets(); + + // Finalize SectionNames first so that we can assign name indexes. + if (Obj.SectionNames != nullptr) + Obj.SectionNames->finalize(); + // Finally now that all offsets and indexes have been set we can finalize any + // remaining issues. + uint64_t Offset = Obj.SHOffset + sizeof(Elf_Shdr); + for (auto &Section : Obj.sections()) { + Section.HeaderOffset = Offset; + Offset += sizeof(Elf_Shdr); + if (WriteSectionHeaders) + Section.NameIndex = Obj.SectionNames->findIndex(Section.Name); + Section.finalize(); + } + + Buf.allocate(totalSize()); + SecWriter = llvm::make_unique<ELFSectionWriter<ELFT>>(Buf); +} + +void BinaryWriter::write() { + for (auto &Section : Obj.sections()) { + if ((Section.Flags & SHF_ALLOC) == 0) + continue; + Section.accept(*SecWriter); + } + if (auto E = Buf.commit()) + reportError(Buf.getName(), errorToErrorCode(std::move(E))); +} + +void BinaryWriter::finalize() { + // TODO: Create a filter range to construct OrderedSegments from so that this + // code can be deduped with assignOffsets above. This should also solve the + // todo below for LayoutSections. + // We need a temporary list of segments that has a special order to it + // so that we know that anytime ->ParentSegment is set that segment has + // already had it's offset properly set. We only want to consider the segments + // that will affect layout of allocated sections so we only add those. + std::vector<Segment *> OrderedSegments; + for (auto &Section : Obj.sections()) { + if ((Section.Flags & SHF_ALLOC) != 0 && Section.ParentSegment != nullptr) { + OrderedSegments.push_back(Section.ParentSegment); + } + } + + // For binary output, we're going to use physical addresses instead of + // virtual addresses, since a binary output is used for cases like ROM + // loading and physical addresses are intended for ROM loading. + // However, if no segment has a physical address, we'll fallback to using + // virtual addresses for all. + if (std::all_of(std::begin(OrderedSegments), std::end(OrderedSegments), + [](const Segment *Segment) { return Segment->PAddr == 0; })) + for (const auto &Segment : OrderedSegments) + Segment->PAddr = Segment->VAddr; + + std::stable_sort(std::begin(OrderedSegments), std::end(OrderedSegments), + compareSegmentsByPAddr); + + // Because we add a ParentSegment for each section we might have duplicate + // segments in OrderedSegments. If there were duplicates then LayoutSegments + // would do very strange things. + auto End = + std::unique(std::begin(OrderedSegments), std::end(OrderedSegments)); + OrderedSegments.erase(End, std::end(OrderedSegments)); + + uint64_t Offset = 0; + + // Modify the first segment so that there is no gap at the start. This allows + // our layout algorithm to proceed as expected while not out writing out the + // gap at the start. + if (!OrderedSegments.empty()) { + auto Seg = OrderedSegments[0]; + auto Sec = Seg->firstSection(); + auto Diff = Sec->OriginalOffset - Seg->OriginalOffset; + Seg->OriginalOffset += Diff; + // The size needs to be shrunk as well. + Seg->FileSize -= Diff; + // The PAddr needs to be increased to remove the gap before the first + // section. + Seg->PAddr += Diff; + uint64_t LowestPAddr = Seg->PAddr; + for (auto &Segment : OrderedSegments) { + Segment->Offset = Segment->PAddr - LowestPAddr; + Offset = std::max(Offset, Segment->Offset + Segment->FileSize); + } + } + + // TODO: generalize LayoutSections to take a range. Pass a special range + // constructed from an iterator that skips values for which a predicate does + // not hold. Then pass such a range to LayoutSections instead of constructing + // AllocatedSections here. + std::vector<SectionBase *> AllocatedSections; + for (auto &Section : Obj.sections()) { + if ((Section.Flags & SHF_ALLOC) == 0) + continue; + AllocatedSections.push_back(&Section); + } + LayoutSections(make_pointee_range(AllocatedSections), Offset); + + // Now that every section has been laid out we just need to compute the total + // file size. This might not be the same as the offset returned by + // LayoutSections, because we want to truncate the last segment to the end of + // its last section, to match GNU objcopy's behaviour. + TotalSize = 0; + for (const auto &Section : AllocatedSections) { + if (Section->Type != SHT_NOBITS) + TotalSize = std::max(TotalSize, Section->Offset + Section->Size); + } + + Buf.allocate(TotalSize); + SecWriter = llvm::make_unique<BinarySectionWriter>(Buf); +} + +template class BinaryELFBuilder<ELF64LE>; +template class BinaryELFBuilder<ELF64BE>; +template class BinaryELFBuilder<ELF32LE>; +template class BinaryELFBuilder<ELF32BE>; + +template class ELFBuilder<ELF64LE>; +template class ELFBuilder<ELF64BE>; +template class ELFBuilder<ELF32LE>; +template class ELFBuilder<ELF32BE>; + +template class ELFWriter<ELF64LE>; +template class ELFWriter<ELF64BE>; +template class ELFWriter<ELF32LE>; +template class ELFWriter<ELF32BE>; + +} // end namespace elf +} // end namespace objcopy +} // end namespace llvm |
