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8cdf1cca41
* ELFTypes.h contains template magic for defining types based on endianess, size, and alignment. * ELFFile.h defines the ELFFile class which provides low level ELF specific access. * ELFObjectFile.h contains ELFObjectFile which uses ELFFile to implement the ObjectFile interface. llvm-svn: 188022
400 lines
13 KiB
C++
400 lines
13 KiB
C++
//===- yaml2elf - Convert YAML to a ELF object file -----------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// \brief The ELF component of yaml2obj.
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///
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//===----------------------------------------------------------------------===//
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#include "yaml2obj.h"
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#include "llvm/Object/ELFObjectFile.h"
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#include "llvm/Object/ELFYAML.h"
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#include "llvm/Support/ELF.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/YAMLTraits.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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// There is similar code in yaml2coff, but with some slight COFF-specific
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// variations like different initial state. Might be able to deduplicate
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// some day, but also want to make sure that the Mach-O use case is served.
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//
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// This class has a deliberately small interface, since a lot of
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// implementation variation is possible.
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//
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// TODO: Use an ordered container with a suffix-based comparison in order
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// to deduplicate suffixes. std::map<> with a custom comparator is likely
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// to be the simplest implementation, but a suffix trie could be more
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// suitable for the job.
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namespace {
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class StringTableBuilder {
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/// \brief Indices of strings currently present in `Buf`.
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StringMap<unsigned> StringIndices;
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/// \brief The contents of the string table as we build it.
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std::string Buf;
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public:
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StringTableBuilder() {
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Buf.push_back('\0');
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}
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/// \returns Index of string in string table.
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unsigned addString(StringRef S) {
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StringMapEntry<unsigned> &Entry = StringIndices.GetOrCreateValue(S);
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unsigned &I = Entry.getValue();
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if (I != 0)
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return I;
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I = Buf.size();
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Buf.append(S.begin(), S.end());
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Buf.push_back('\0');
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return I;
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}
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size_t size() const {
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return Buf.size();
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}
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void writeToStream(raw_ostream &OS) {
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OS.write(Buf.data(), Buf.size());
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}
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};
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} // end anonymous namespace
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// This class is used to build up a contiguous binary blob while keeping
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// track of an offset in the output (which notionally begins at
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// `InitialOffset`).
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namespace {
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class ContiguousBlobAccumulator {
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const uint64_t InitialOffset;
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SmallVector<char, 128> Buf;
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raw_svector_ostream OS;
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/// \returns The new offset.
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uint64_t padToAlignment(unsigned Align) {
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uint64_t CurrentOffset = InitialOffset + OS.tell();
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uint64_t AlignedOffset = RoundUpToAlignment(CurrentOffset, Align);
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for (; CurrentOffset != AlignedOffset; ++CurrentOffset)
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OS.write('\0');
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return AlignedOffset; // == CurrentOffset;
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}
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public:
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ContiguousBlobAccumulator(uint64_t InitialOffset_)
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: InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
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template <class Integer>
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raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align = 16) {
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Offset = padToAlignment(Align);
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return OS;
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}
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void writeBlobToStream(raw_ostream &Out) { Out << OS.str(); }
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};
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} // end anonymous namespace
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// Used to keep track of section names, so that in the YAML file sections
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// can be referenced by name instead of by index.
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namespace {
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class SectionNameToIdxMap {
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StringMap<int> Map;
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public:
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/// \returns true if name is already present in the map.
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bool addName(StringRef SecName, unsigned i) {
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StringMapEntry<int> &Entry = Map.GetOrCreateValue(SecName, -1);
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if (Entry.getValue() != -1)
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return true;
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Entry.setValue((int)i);
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return false;
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}
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/// \returns true if name is not present in the map
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bool lookupSection(StringRef SecName, unsigned &Idx) const {
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StringMap<int>::const_iterator I = Map.find(SecName);
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if (I == Map.end())
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return true;
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Idx = I->getValue();
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return false;
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}
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};
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} // end anonymous namespace
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template <class T>
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static size_t vectorDataSize(const std::vector<T> &Vec) {
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return Vec.size() * sizeof(T);
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}
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template <class T>
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static void writeVectorData(raw_ostream &OS, const std::vector<T> &Vec) {
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OS.write((const char *)Vec.data(), vectorDataSize(Vec));
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}
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template <class T>
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static void zero(T &Obj) {
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memset(&Obj, 0, sizeof(Obj));
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}
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/// \brief Create a string table in `SHeader`, which we assume is already
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/// zero'd.
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template <class Elf_Shdr>
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static void createStringTableSectionHeader(Elf_Shdr &SHeader,
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StringTableBuilder &STB,
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ContiguousBlobAccumulator &CBA) {
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SHeader.sh_type = ELF::SHT_STRTAB;
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STB.writeToStream(CBA.getOSAndAlignedOffset(SHeader.sh_offset));
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SHeader.sh_size = STB.size();
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SHeader.sh_addralign = 1;
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}
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namespace {
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/// \brief "Single point of truth" for the ELF file construction.
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/// TODO: This class still has a ways to go before it is truly a "single
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/// point of truth".
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template <class ELFT>
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class ELFState {
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/// \brief The future ".strtab" section.
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StringTableBuilder DotStrtab;
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/// \brief The section number of the ".strtab" section.
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unsigned DotStrtabSecNo;
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/// \brief The accumulated contents of all sections so far.
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ContiguousBlobAccumulator &SectionContentAccum;
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typedef typename object::ELFFile<ELFT>::Elf_Ehdr Elf_Ehdr;
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/// \brief The ELF file header.
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Elf_Ehdr &Header;
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SectionNameToIdxMap &SN2I;
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public:
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ELFState(Elf_Ehdr &Header_, ContiguousBlobAccumulator &Accum,
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unsigned DotStrtabSecNo_, SectionNameToIdxMap &SN2I_)
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: DotStrtab(), DotStrtabSecNo(DotStrtabSecNo_),
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SectionContentAccum(Accum), Header(Header_), SN2I(SN2I_) {}
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unsigned getDotStrTabSecNo() const { return DotStrtabSecNo; }
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StringTableBuilder &getStringTable() { return DotStrtab; }
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ContiguousBlobAccumulator &getSectionContentAccum() {
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return SectionContentAccum;
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}
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SectionNameToIdxMap &getSN2I() { return SN2I; }
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};
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} // end anonymous namespace
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// FIXME: At this point it is fairly clear that we need to refactor these
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// static functions into methods of a class sharing some typedefs. These
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// ELF type names are insane.
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template <class ELFT>
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static void
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addSymbols(const std::vector<ELFYAML::Symbol> &Symbols, ELFState<ELFT> &State,
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std::vector<typename object::ELFFile<ELFT>::Elf_Sym> &Syms,
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unsigned SymbolBinding) {
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typedef typename object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
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for (unsigned i = 0, e = Symbols.size(); i != e; ++i) {
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const ELFYAML::Symbol &Sym = Symbols[i];
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Elf_Sym Symbol;
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zero(Symbol);
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if (!Sym.Name.empty())
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Symbol.st_name = State.getStringTable().addString(Sym.Name);
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Symbol.setBindingAndType(SymbolBinding, Sym.Type);
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if (!Sym.Section.empty()) {
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unsigned Index;
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if (State.getSN2I().lookupSection(Sym.Section, Index)) {
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errs() << "error: Unknown section referenced: '" << Sym.Section
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<< "' by YAML symbol " << Sym.Name << ".\n";
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exit(1);
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}
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Symbol.st_shndx = Index;
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} // else Symbol.st_shndex == SHN_UNDEF (== 0), since it was zero'd earlier.
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Symbol.st_value = Sym.Value;
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Symbol.st_size = Sym.Size;
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Syms.push_back(Symbol);
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}
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}
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template <class ELFT>
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static void
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handleSymtabSectionHeader(const ELFYAML::LocalGlobalWeakSymbols &Symbols,
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ELFState<ELFT> &State,
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typename object::ELFFile<ELFT>::Elf_Shdr &SHeader) {
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typedef typename object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
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SHeader.sh_type = ELF::SHT_SYMTAB;
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SHeader.sh_link = State.getDotStrTabSecNo();
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// One greater than symbol table index of the last local symbol.
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SHeader.sh_info = Symbols.Local.size() + 1;
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SHeader.sh_entsize = sizeof(Elf_Sym);
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std::vector<Elf_Sym> Syms;
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{
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// Ensure STN_UNDEF is present
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Elf_Sym Sym;
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zero(Sym);
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Syms.push_back(Sym);
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}
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addSymbols(Symbols.Local, State, Syms, ELF::STB_LOCAL);
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addSymbols(Symbols.Global, State, Syms, ELF::STB_GLOBAL);
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addSymbols(Symbols.Weak, State, Syms, ELF::STB_WEAK);
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ContiguousBlobAccumulator &CBA = State.getSectionContentAccum();
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writeVectorData(CBA.getOSAndAlignedOffset(SHeader.sh_offset), Syms);
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SHeader.sh_size = vectorDataSize(Syms);
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}
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template <class ELFT>
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static int writeELF(raw_ostream &OS, const ELFYAML::Object &Doc) {
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using namespace llvm::ELF;
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typedef typename object::ELFFile<ELFT>::Elf_Ehdr Elf_Ehdr;
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typedef typename object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
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const ELFYAML::FileHeader &Hdr = Doc.Header;
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Elf_Ehdr Header;
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zero(Header);
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Header.e_ident[EI_MAG0] = 0x7f;
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Header.e_ident[EI_MAG1] = 'E';
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Header.e_ident[EI_MAG2] = 'L';
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Header.e_ident[EI_MAG3] = 'F';
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Header.e_ident[EI_CLASS] = ELFT::Is64Bits ? ELFCLASS64 : ELFCLASS32;
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bool IsLittleEndian = ELFT::TargetEndianness == support::little;
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Header.e_ident[EI_DATA] = IsLittleEndian ? ELFDATA2LSB : ELFDATA2MSB;
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Header.e_ident[EI_VERSION] = EV_CURRENT;
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Header.e_ident[EI_OSABI] = Hdr.OSABI;
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Header.e_ident[EI_ABIVERSION] = 0;
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Header.e_type = Hdr.Type;
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Header.e_machine = Hdr.Machine;
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Header.e_version = EV_CURRENT;
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Header.e_entry = Hdr.Entry;
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Header.e_ehsize = sizeof(Elf_Ehdr);
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// TODO: Flesh out section header support.
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// TODO: Program headers.
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Header.e_shentsize = sizeof(Elf_Shdr);
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// Immediately following the ELF header.
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Header.e_shoff = sizeof(Header);
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const std::vector<ELFYAML::Section> &Sections = Doc.Sections;
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// "+ 4" for
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// - SHT_NULL entry (placed first, i.e. 0'th entry)
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// - symbol table (.symtab) (placed third to last)
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// - string table (.strtab) (placed second to last)
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// - section header string table. (placed last)
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Header.e_shnum = Sections.size() + 4;
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// Place section header string table last.
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Header.e_shstrndx = Header.e_shnum - 1;
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const unsigned DotStrtabSecNo = Header.e_shnum - 2;
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// XXX: This offset is tightly coupled with the order that we write
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// things to `OS`.
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const size_t SectionContentBeginOffset =
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Header.e_ehsize + Header.e_shentsize * Header.e_shnum;
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ContiguousBlobAccumulator CBA(SectionContentBeginOffset);
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SectionNameToIdxMap SN2I;
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for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
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StringRef Name = Sections[i].Name;
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if (Name.empty())
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continue;
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// "+ 1" to take into account the SHT_NULL entry.
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if (SN2I.addName(Name, i + 1)) {
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errs() << "error: Repeated section name: '" << Name
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<< "' at YAML section number " << i << ".\n";
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return 1;
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}
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}
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ELFState<ELFT> State(Header, CBA, DotStrtabSecNo, SN2I);
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StringTableBuilder SHStrTab;
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std::vector<Elf_Shdr> SHeaders;
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{
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// Ensure SHN_UNDEF entry is present. An all-zero section header is a
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// valid SHN_UNDEF entry since SHT_NULL == 0.
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Elf_Shdr SHdr;
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zero(SHdr);
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SHeaders.push_back(SHdr);
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}
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for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
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const ELFYAML::Section &Sec = Sections[i];
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Elf_Shdr SHeader;
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zero(SHeader);
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SHeader.sh_name = SHStrTab.addString(Sec.Name);
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SHeader.sh_type = Sec.Type;
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SHeader.sh_flags = Sec.Flags;
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SHeader.sh_addr = Sec.Address;
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Sec.Content.writeAsBinary(CBA.getOSAndAlignedOffset(SHeader.sh_offset));
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SHeader.sh_size = Sec.Content.binary_size();
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if (!Sec.Link.empty()) {
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unsigned Index;
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if (SN2I.lookupSection(Sec.Link, Index)) {
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errs() << "error: Unknown section referenced: '" << Sec.Link
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<< "' at YAML section number " << i << ".\n";
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return 1;
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}
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SHeader.sh_link = Index;
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}
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SHeader.sh_info = 0;
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SHeader.sh_addralign = Sec.AddressAlign;
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SHeader.sh_entsize = 0;
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SHeaders.push_back(SHeader);
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}
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// .symtab section.
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Elf_Shdr SymtabSHeader;
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zero(SymtabSHeader);
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SymtabSHeader.sh_name = SHStrTab.addString(StringRef(".symtab"));
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handleSymtabSectionHeader<ELFT>(Doc.Symbols, State, SymtabSHeader);
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SHeaders.push_back(SymtabSHeader);
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// .strtab string table header.
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Elf_Shdr DotStrTabSHeader;
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zero(DotStrTabSHeader);
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DotStrTabSHeader.sh_name = SHStrTab.addString(StringRef(".strtab"));
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createStringTableSectionHeader(DotStrTabSHeader, State.getStringTable(), CBA);
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SHeaders.push_back(DotStrTabSHeader);
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// Section header string table header.
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Elf_Shdr SHStrTabSHeader;
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zero(SHStrTabSHeader);
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createStringTableSectionHeader(SHStrTabSHeader, SHStrTab, CBA);
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SHeaders.push_back(SHStrTabSHeader);
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OS.write((const char *)&Header, sizeof(Header));
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writeVectorData(OS, SHeaders);
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CBA.writeBlobToStream(OS);
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return 0;
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}
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static bool is64Bit(const ELFYAML::Object &Doc) {
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return Doc.Header.Class == ELFYAML::ELF_ELFCLASS(ELF::ELFCLASS64);
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}
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static bool isLittleEndian(const ELFYAML::Object &Doc) {
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return Doc.Header.Data == ELFYAML::ELF_ELFDATA(ELF::ELFDATA2LSB);
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}
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int yaml2elf(llvm::raw_ostream &Out, llvm::MemoryBuffer *Buf) {
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yaml::Input YIn(Buf->getBuffer());
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ELFYAML::Object Doc;
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YIn >> Doc;
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if (YIn.error()) {
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errs() << "yaml2obj: Failed to parse YAML file!\n";
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return 1;
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}
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using object::ELFType;
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typedef ELFType<support::little, 8, true> LE64;
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typedef ELFType<support::big, 8, true> BE64;
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typedef ELFType<support::little, 4, false> LE32;
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typedef ELFType<support::big, 4, false> BE32;
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if (is64Bit(Doc)) {
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if (isLittleEndian(Doc))
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return writeELF<LE64>(outs(), Doc);
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else
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return writeELF<BE64>(outs(), Doc);
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} else {
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if (isLittleEndian(Doc))
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return writeELF<LE32>(outs(), Doc);
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else
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return writeELF<BE32>(outs(), Doc);
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}
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}
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