Index: projects/clang500-import/contrib/llvm/tools/lld/ELF/Writer.cpp
===================================================================
--- projects/clang500-import/contrib/llvm/tools/lld/ELF/Writer.cpp	(revision 320070)
+++ projects/clang500-import/contrib/llvm/tools/lld/ELF/Writer.cpp	(revision 320071)
@@ -1,1892 +1,1897 @@
 //===- Writer.cpp ---------------------------------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "Writer.h"
 #include "Config.h"
 #include "Filesystem.h"
 #include "LinkerScript.h"
 #include "MapFile.h"
 #include "Memory.h"
 #include "OutputSections.h"
 #include "Relocations.h"
 #include "Strings.h"
 #include "SymbolTable.h"
 #include "SyntheticSections.h"
 #include "Target.h"
 #include "Threads.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/FileOutputBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include <climits>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
 using namespace llvm::support;
 using namespace llvm::support::endian;
 
 using namespace lld;
 using namespace lld::elf;
 
 namespace {
 // The writer writes a SymbolTable result to a file.
 template <class ELFT> class Writer {
 public:
   typedef typename ELFT::Shdr Elf_Shdr;
   typedef typename ELFT::Ehdr Elf_Ehdr;
   typedef typename ELFT::Phdr Elf_Phdr;
 
   void run();
 
 private:
   void clearOutputSections();
   void createSyntheticSections();
   void copyLocalSymbols();
   void addSectionSymbols();
   void addReservedSymbols();
   void createSections();
   void forEachRelSec(std::function<void(InputSectionBase &)> Fn);
   void sortSections();
   void finalizeSections();
   void addPredefinedSections();
 
   std::vector<PhdrEntry> createPhdrs();
   void removeEmptyPTLoad();
   void addPtArmExid(std::vector<PhdrEntry> &Phdrs);
   void assignFileOffsets();
   void assignFileOffsetsBinary();
   void setPhdrs();
   void fixSectionAlignments();
   void fixPredefinedSymbols();
   void openFile();
   void writeHeader();
   void writeSections();
   void writeSectionsBinary();
   void writeBuildId();
 
   std::unique_ptr<FileOutputBuffer> Buffer;
 
   OutputSectionFactory Factory{OutputSections};
 
   void addRelIpltSymbols();
   void addStartEndSymbols();
   void addStartStopSymbols(OutputSection *Sec);
   uint64_t getEntryAddr();
   OutputSection *findSection(StringRef Name);
   OutputSection *findSectionInScript(StringRef Name);
   OutputSectionCommand *findSectionCommand(StringRef Name);
 
   std::vector<PhdrEntry> Phdrs;
 
   uint64_t FileSize;
   uint64_t SectionHeaderOff;
 };
 } // anonymous namespace
 
 StringRef elf::getOutputSectionName(StringRef Name) {
   // ".zdebug_" is a prefix for ZLIB-compressed sections.
   // Because we decompressed input sections, we want to remove 'z'.
   if (Name.startswith(".zdebug_"))
     return Saver.save("." + Name.substr(2));
 
   if (Config->Relocatable)
     return Name;
 
   for (StringRef V :
        {".text.", ".rodata.", ".data.rel.ro.", ".data.", ".bss.rel.ro.",
         ".bss.", ".init_array.", ".fini_array.", ".ctors.", ".dtors.", ".tbss.",
         ".gcc_except_table.", ".tdata.", ".ARM.exidx."}) {
     StringRef Prefix = V.drop_back();
     if (Name.startswith(V) || Name == Prefix)
       return Prefix;
   }
 
   // CommonSection is identified as "COMMON" in linker scripts.
   // By default, it should go to .bss section.
   if (Name == "COMMON")
     return ".bss";
 
   return Name;
 }
 
 template <class ELFT> static bool needsInterpSection() {
   return !Symtab<ELFT>::X->getSharedFiles().empty() &&
          !Config->DynamicLinker.empty() && !Script->ignoreInterpSection();
 }
 
 template <class ELFT> void elf::writeResult() { Writer<ELFT>().run(); }
 
 template <class ELFT> void Writer<ELFT>::removeEmptyPTLoad() {
   auto I = std::remove_if(Phdrs.begin(), Phdrs.end(), [&](const PhdrEntry &P) {
     if (P.p_type != PT_LOAD)
       return false;
     if (!P.First)
       return true;
     uint64_t Size = P.Last->Addr + P.Last->Size - P.First->Addr;
     return Size == 0;
   });
   Phdrs.erase(I, Phdrs.end());
 }
 
 template <class ELFT> static void combineEhFrameSections() {
   for (InputSectionBase *&S : InputSections) {
     EhInputSection *ES = dyn_cast<EhInputSection>(S);
     if (!ES || !ES->Live)
       continue;
 
     In<ELFT>::EhFrame->addSection(ES);
     S = nullptr;
   }
 
   std::vector<InputSectionBase *> &V = InputSections;
   V.erase(std::remove(V.begin(), V.end(), nullptr), V.end());
 }
 
 template <class ELFT> void Writer<ELFT>::clearOutputSections() {
   if (Script->Opt.HasSections)
     Script->createOrphanCommands();
   else
     Script->fabricateDefaultCommands();
   // Clear the OutputSections to make sure it is not used anymore. Any
   // code from this point on should be using the linker script
   // commands.
   for (OutputSection *Sec : OutputSections)
     Sec->Sections.clear();
   OutputSections.clear();
 }
 
 // The main function of the writer.
 template <class ELFT> void Writer<ELFT>::run() {
   // Create linker-synthesized sections such as .got or .plt.
   // Such sections are of type input section.
   createSyntheticSections();
 
   if (!Config->Relocatable)
     combineEhFrameSections<ELFT>();
 
   // We need to create some reserved symbols such as _end. Create them.
   if (!Config->Relocatable)
     addReservedSymbols();
 
   // Create output sections.
   if (Script->Opt.HasSections) {
     // If linker script contains SECTIONS commands, let it create sections.
     Script->processCommands(Factory);
 
     // Linker scripts may have left some input sections unassigned.
     // Assign such sections using the default rule.
     Script->addOrphanSections(Factory);
   } else {
     // If linker script does not contain SECTIONS commands, create
     // output sections by default rules. We still need to give the
     // linker script a chance to run, because it might contain
     // non-SECTIONS commands such as ASSERT.
     createSections();
     Script->processCommands(Factory);
   }
 
   if (Config->Discard != DiscardPolicy::All)
     copyLocalSymbols();
 
   if (Config->CopyRelocs)
     addSectionSymbols();
 
   // Now that we have a complete set of output sections. This function
   // completes section contents. For example, we need to add strings
   // to the string table, and add entries to .got and .plt.
   // finalizeSections does that.
   finalizeSections();
   if (ErrorCount)
     return;
 
   if (!Script->Opt.HasSections && !Config->Relocatable)
     fixSectionAlignments();
 
   // If -compressed-debug-sections is specified, we need to compress
   // .debug_* sections. Do it right now because it changes the size of
   // output sections.
   parallelForEach(
       OutputSectionCommands.begin(), OutputSectionCommands.end(),
       [](OutputSectionCommand *Cmd) { Cmd->maybeCompress<ELFT>(); });
 
   Script->assignAddresses(Phdrs);
 
   // Remove empty PT_LOAD to avoid causing the dynamic linker to try to mmap a
   // 0 sized region. This has to be done late since only after assignAddresses
   // we know the size of the sections.
   removeEmptyPTLoad();
 
   if (!Config->OFormatBinary)
     assignFileOffsets();
   else
     assignFileOffsetsBinary();
 
   setPhdrs();
 
   if (Config->Relocatable) {
     for (OutputSectionCommand *Cmd : OutputSectionCommands)
       Cmd->Sec->Addr = 0;
   } else {
     fixPredefinedSymbols();
   }
 
   // It does not make sense try to open the file if we have error already.
   if (ErrorCount)
     return;
   // Write the result down to a file.
   openFile();
   if (ErrorCount)
     return;
 
   if (!Config->OFormatBinary) {
     writeHeader();
     writeSections();
   } else {
     writeSectionsBinary();
   }
 
   // Backfill .note.gnu.build-id section content. This is done at last
   // because the content is usually a hash value of the entire output file.
   writeBuildId();
   if (ErrorCount)
     return;
 
 
   // Handle -Map option.
   writeMapFile<ELFT>(OutputSectionCommands);
   if (ErrorCount)
     return;
 
   if (auto EC = Buffer->commit())
     error("failed to write to the output file: " + EC.message());
 
   // Flush the output streams and exit immediately. A full shutdown
   // is a good test that we are keeping track of all allocated memory,
   // but actually freeing it is a waste of time in a regular linker run.
   if (Config->ExitEarly)
     exitLld(0);
 }
 
 // Initialize Out members.
 template <class ELFT> void Writer<ELFT>::createSyntheticSections() {
   // Initialize all pointers with NULL. This is needed because
   // you can call lld::elf::main more than once as a library.
   memset(&Out::First, 0, sizeof(Out));
 
   auto Add = [](InputSectionBase *Sec) { InputSections.push_back(Sec); };
 
   InX::DynStrTab = make<StringTableSection>(".dynstr", true);
   InX::Dynamic = make<DynamicSection<ELFT>>();
   In<ELFT>::RelaDyn = make<RelocationSection<ELFT>>(
       Config->IsRela ? ".rela.dyn" : ".rel.dyn", Config->ZCombreloc);
   InX::ShStrTab = make<StringTableSection>(".shstrtab", false);
 
   Out::ElfHeader = make<OutputSection>("", 0, SHF_ALLOC);
   Out::ElfHeader->Size = sizeof(Elf_Ehdr);
   Out::ProgramHeaders = make<OutputSection>("", 0, SHF_ALLOC);
   Out::ProgramHeaders->updateAlignment(Config->Wordsize);
 
   if (needsInterpSection<ELFT>()) {
     InX::Interp = createInterpSection();
     Add(InX::Interp);
   } else {
     InX::Interp = nullptr;
   }
 
   if (Config->Strip != StripPolicy::All) {
     InX::StrTab = make<StringTableSection>(".strtab", false);
     InX::SymTab = make<SymbolTableSection<ELFT>>(*InX::StrTab);
   }
 
   if (Config->BuildId != BuildIdKind::None) {
     InX::BuildId = make<BuildIdSection>();
     Add(InX::BuildId);
   }
 
   InX::Common = createCommonSection<ELFT>();
   if (InX::Common)
     Add(InX::Common);
 
   InX::Bss = make<BssSection>(".bss");
   Add(InX::Bss);
   InX::BssRelRo = make<BssSection>(".bss.rel.ro");
   Add(InX::BssRelRo);
 
   // Add MIPS-specific sections.
   bool HasDynSymTab = !Symtab<ELFT>::X->getSharedFiles().empty() ||
                       Config->Pic || Config->ExportDynamic;
   if (Config->EMachine == EM_MIPS) {
     if (!Config->Shared && HasDynSymTab) {
       InX::MipsRldMap = make<MipsRldMapSection>();
       Add(InX::MipsRldMap);
     }
     if (auto *Sec = MipsAbiFlagsSection<ELFT>::create())
       Add(Sec);
     if (auto *Sec = MipsOptionsSection<ELFT>::create())
       Add(Sec);
     if (auto *Sec = MipsReginfoSection<ELFT>::create())
       Add(Sec);
   }
 
   if (HasDynSymTab) {
     InX::DynSymTab = make<SymbolTableSection<ELFT>>(*InX::DynStrTab);
     Add(InX::DynSymTab);
 
     In<ELFT>::VerSym = make<VersionTableSection<ELFT>>();
     Add(In<ELFT>::VerSym);
 
     if (!Config->VersionDefinitions.empty()) {
       In<ELFT>::VerDef = make<VersionDefinitionSection<ELFT>>();
       Add(In<ELFT>::VerDef);
     }
 
     In<ELFT>::VerNeed = make<VersionNeedSection<ELFT>>();
     Add(In<ELFT>::VerNeed);
 
     if (Config->GnuHash) {
       InX::GnuHashTab = make<GnuHashTableSection>();
       Add(InX::GnuHashTab);
     }
 
     if (Config->SysvHash) {
       In<ELFT>::HashTab = make<HashTableSection<ELFT>>();
       Add(In<ELFT>::HashTab);
     }
 
     Add(InX::Dynamic);
     Add(InX::DynStrTab);
     Add(In<ELFT>::RelaDyn);
   }
 
   // Add .got. MIPS' .got is so different from the other archs,
   // it has its own class.
   if (Config->EMachine == EM_MIPS) {
     InX::MipsGot = make<MipsGotSection>();
     Add(InX::MipsGot);
   } else {
     InX::Got = make<GotSection>();
     Add(InX::Got);
   }
 
   InX::GotPlt = make<GotPltSection>();
   Add(InX::GotPlt);
   InX::IgotPlt = make<IgotPltSection>();
   Add(InX::IgotPlt);
 
   if (Config->GdbIndex) {
     InX::GdbIndex = make<GdbIndexSection>();
     Add(InX::GdbIndex);
   }
 
   // We always need to add rel[a].plt to output if it has entries.
   // Even for static linking it can contain R_[*]_IRELATIVE relocations.
   In<ELFT>::RelaPlt = make<RelocationSection<ELFT>>(
       Config->IsRela ? ".rela.plt" : ".rel.plt", false /*Sort*/);
   Add(In<ELFT>::RelaPlt);
 
   // The RelaIplt immediately follows .rel.plt (.rel.dyn for ARM) to ensure
   // that the IRelative relocations are processed last by the dynamic loader
   In<ELFT>::RelaIplt = make<RelocationSection<ELFT>>(
       (Config->EMachine == EM_ARM) ? ".rel.dyn" : In<ELFT>::RelaPlt->Name,
       false /*Sort*/);
   Add(In<ELFT>::RelaIplt);
 
   InX::Plt = make<PltSection>(Target->PltHeaderSize);
   Add(InX::Plt);
   InX::Iplt = make<PltSection>(0);
   Add(InX::Iplt);
 
   if (!Config->Relocatable) {
     if (Config->EhFrameHdr) {
       In<ELFT>::EhFrameHdr = make<EhFrameHeader<ELFT>>();
       Add(In<ELFT>::EhFrameHdr);
     }
     In<ELFT>::EhFrame = make<EhFrameSection<ELFT>>();
     Add(In<ELFT>::EhFrame);
   }
 
   if (InX::SymTab)
     Add(InX::SymTab);
   Add(InX::ShStrTab);
   if (InX::StrTab)
     Add(InX::StrTab);
 }
 
 static bool shouldKeepInSymtab(SectionBase *Sec, StringRef SymName,
                                const SymbolBody &B) {
   if (B.isFile() || B.isSection())
     return false;
 
   // If sym references a section in a discarded group, don't keep it.
   if (Sec == &InputSection::Discarded)
     return false;
 
   if (Config->Discard == DiscardPolicy::None)
     return true;
 
   // In ELF assembly .L symbols are normally discarded by the assembler.
   // If the assembler fails to do so, the linker discards them if
   // * --discard-locals is used.
   // * The symbol is in a SHF_MERGE section, which is normally the reason for
   //   the assembler keeping the .L symbol.
   if (!SymName.startswith(".L") && !SymName.empty())
     return true;
 
   if (Config->Discard == DiscardPolicy::Locals)
     return false;
 
   return !Sec || !(Sec->Flags & SHF_MERGE);
 }
 
 static bool includeInSymtab(const SymbolBody &B) {
   if (!B.isLocal() && !B.symbol()->IsUsedInRegularObj)
     return false;
 
   if (auto *D = dyn_cast<DefinedRegular>(&B)) {
     // Always include absolute symbols.
     SectionBase *Sec = D->Section;
     if (!Sec)
       return true;
     if (auto *IS = dyn_cast<InputSectionBase>(Sec)) {
       Sec = IS->Repl;
       IS = cast<InputSectionBase>(Sec);
       // Exclude symbols pointing to garbage-collected sections.
       if (!IS->Live)
         return false;
     }
     if (auto *S = dyn_cast<MergeInputSection>(Sec))
       if (!S->getSectionPiece(D->Value)->Live)
         return false;
   }
   return true;
 }
 
 // Local symbols are not in the linker's symbol table. This function scans
 // each object file's symbol table to copy local symbols to the output.
 template <class ELFT> void Writer<ELFT>::copyLocalSymbols() {
   if (!InX::SymTab)
     return;
   for (elf::ObjectFile<ELFT> *F : Symtab<ELFT>::X->getObjectFiles()) {
     for (SymbolBody *B : F->getLocalSymbols()) {
       if (!B->IsLocal)
         fatal(toString(F) +
               ": broken object: getLocalSymbols returns a non-local symbol");
       auto *DR = dyn_cast<DefinedRegular>(B);
 
       // No reason to keep local undefined symbol in symtab.
       if (!DR)
         continue;
       if (!includeInSymtab(*B))
         continue;
 
       SectionBase *Sec = DR->Section;
       if (!shouldKeepInSymtab(Sec, B->getName(), *B))
         continue;
       InX::SymTab->addSymbol(B);
     }
   }
 }
 
 template <class ELFT> void Writer<ELFT>::addSectionSymbols() {
   // Create one STT_SECTION symbol for each output section we might
   // have a relocation with.
   for (OutputSection *Sec : OutputSections) {
     if (Sec->Sections.empty())
       continue;
 
     InputSection *IS = Sec->Sections[0];
     if (isa<SyntheticSection>(IS) || IS->Type == SHT_REL ||
         IS->Type == SHT_RELA)
       continue;
 
     auto *Sym =
         make<DefinedRegular>("", /*IsLocal=*/true, /*StOther=*/0, STT_SECTION,
                              /*Value=*/0, /*Size=*/0, IS, nullptr);
     InX::SymTab->addSymbol(Sym);
   }
 }
 
 // Today's loaders have a feature to make segments read-only after
 // processing dynamic relocations to enhance security. PT_GNU_RELRO
 // is defined for that.
 //
 // This function returns true if a section needs to be put into a
 // PT_GNU_RELRO segment.
 bool elf::isRelroSection(const OutputSection *Sec) {
   if (!Config->ZRelro)
     return false;
 
   uint64_t Flags = Sec->Flags;
 
   // Non-allocatable or non-writable sections don't need RELRO because
   // they are not writable or not even mapped to memory in the first place.
   // RELRO is for sections that are essentially read-only but need to
   // be writable only at process startup to allow dynamic linker to
   // apply relocations.
   if (!(Flags & SHF_ALLOC) || !(Flags & SHF_WRITE))
     return false;
 
   // Once initialized, TLS data segments are used as data templates
   // for a thread-local storage. For each new thread, runtime
   // allocates memory for a TLS and copy templates there. No thread
   // are supposed to use templates directly. Thus, it can be in RELRO.
   if (Flags & SHF_TLS)
     return true;
 
   // .init_array, .preinit_array and .fini_array contain pointers to
   // functions that are executed on process startup or exit. These
   // pointers are set by the static linker, and they are not expected
   // to change at runtime. But if you are an attacker, you could do
   // interesting things by manipulating pointers in .fini_array, for
   // example. So they are put into RELRO.
   uint32_t Type = Sec->Type;
   if (Type == SHT_INIT_ARRAY || Type == SHT_FINI_ARRAY ||
       Type == SHT_PREINIT_ARRAY)
     return true;
 
   // .got contains pointers to external symbols. They are resolved by
   // the dynamic linker when a module is loaded into memory, and after
   // that they are not expected to change. So, it can be in RELRO.
   if (InX::Got && Sec == InX::Got->getParent())
     return true;
 
   // .got.plt contains pointers to external function symbols. They are
   // by default resolved lazily, so we usually cannot put it into RELRO.
   // However, if "-z now" is given, the lazy symbol resolution is
   // disabled, which enables us to put it into RELRO.
   if (Sec == InX::GotPlt->getParent())
     return Config->ZNow;
 
   // .dynamic section contains data for the dynamic linker, and
   // there's no need to write to it at runtime, so it's better to put
   // it into RELRO.
   if (Sec == InX::Dynamic->getParent())
     return true;
 
   // .bss.rel.ro is used for copy relocations for read-only symbols.
   // Since the dynamic linker needs to process copy relocations, the
   // section cannot be read-only, but once initialized, they shouldn't
   // change.
   if (Sec == InX::BssRelRo->getParent())
     return true;
 
   // Sections with some special names are put into RELRO. This is a
   // bit unfortunate because section names shouldn't be significant in
   // ELF in spirit. But in reality many linker features depend on
   // magic section names.
   StringRef S = Sec->Name;
   return S == ".data.rel.ro" || S == ".ctors" || S == ".dtors" || S == ".jcr" ||
          S == ".eh_frame" || S == ".openbsd.randomdata";
 }
 
 // We compute a rank for each section. The rank indicates where the
 // section should be placed in the file.  Instead of using simple
 // numbers (0,1,2...), we use a series of flags. One for each decision
 // point when placing the section.
 // Using flags has two key properties:
 // * It is easy to check if a give branch was taken.
 // * It is easy two see how similar two ranks are (see getRankProximity).
 enum RankFlags {
   RF_NOT_ADDR_SET = 1 << 16,
   RF_NOT_INTERP = 1 << 15,
   RF_NOT_ALLOC = 1 << 14,
   RF_WRITE = 1 << 13,
   RF_EXEC_WRITE = 1 << 12,
   RF_EXEC = 1 << 11,
   RF_NON_TLS_BSS = 1 << 10,
   RF_NON_TLS_BSS_RO = 1 << 9,
   RF_NOT_TLS = 1 << 8,
   RF_BSS = 1 << 7,
   RF_PPC_NOT_TOCBSS = 1 << 6,
   RF_PPC_OPD = 1 << 5,
   RF_PPC_TOCL = 1 << 4,
   RF_PPC_TOC = 1 << 3,
   RF_PPC_BRANCH_LT = 1 << 2,
   RF_MIPS_GPREL = 1 << 1,
   RF_MIPS_NOT_GOT = 1 << 0
 };
 
 static unsigned getSectionRank(const OutputSection *Sec) {
   unsigned Rank = 0;
 
   // We want to put section specified by -T option first, so we
   // can start assigning VA starting from them later.
   if (Config->SectionStartMap.count(Sec->Name))
     return Rank;
   Rank |= RF_NOT_ADDR_SET;
 
   // Put .interp first because some loaders want to see that section
   // on the first page of the executable file when loaded into memory.
   if (Sec->Name == ".interp")
     return Rank;
   Rank |= RF_NOT_INTERP;
 
   // Allocatable sections go first to reduce the total PT_LOAD size and
   // so debug info doesn't change addresses in actual code.
   if (!(Sec->Flags & SHF_ALLOC))
     return Rank | RF_NOT_ALLOC;
 
   // Sort sections based on their access permission in the following
   // order: R, RX, RWX, RW.  This order is based on the following
   // considerations:
   // * Read-only sections come first such that they go in the
   //   PT_LOAD covering the program headers at the start of the file.
   // * Read-only, executable sections come next, unless the
   //   -no-rosegment option is used.
   // * Writable, executable sections follow such that .plt on
   //   architectures where it needs to be writable will be placed
   //   between .text and .data.
   // * Writable sections come last, such that .bss lands at the very
   //   end of the last PT_LOAD.
   bool IsExec = Sec->Flags & SHF_EXECINSTR;
   bool IsWrite = Sec->Flags & SHF_WRITE;
 
   if (IsExec) {
     if (IsWrite)
       Rank |= RF_EXEC_WRITE;
     else if (!Config->SingleRoRx)
       Rank |= RF_EXEC;
   } else {
     if (IsWrite)
       Rank |= RF_WRITE;
   }
 
   // If we got here we know that both A and B are in the same PT_LOAD.
 
   bool IsTls = Sec->Flags & SHF_TLS;
   bool IsNoBits = Sec->Type == SHT_NOBITS;
 
   // The first requirement we have is to put (non-TLS) nobits sections last. The
   // reason is that the only thing the dynamic linker will see about them is a
   // p_memsz that is larger than p_filesz. Seeing that it zeros the end of the
   // PT_LOAD, so that has to correspond to the nobits sections.
   bool IsNonTlsNoBits = IsNoBits && !IsTls;
   if (IsNonTlsNoBits)
     Rank |= RF_NON_TLS_BSS;
 
   // We place nobits RelRo sections before plain r/w ones, and non-nobits RelRo
   // sections after r/w ones, so that the RelRo sections are contiguous.
   bool IsRelRo = isRelroSection(Sec);
   if (IsNonTlsNoBits && !IsRelRo)
     Rank |= RF_NON_TLS_BSS_RO;
   if (!IsNonTlsNoBits && IsRelRo)
     Rank |= RF_NON_TLS_BSS_RO;
 
   // The TLS initialization block needs to be a single contiguous block in a R/W
   // PT_LOAD, so stick TLS sections directly before the other RelRo R/W
   // sections. The TLS NOBITS sections are placed here as they don't take up
   // virtual address space in the PT_LOAD.
   if (!IsTls)
     Rank |= RF_NOT_TLS;
 
   // Within the TLS initialization block, the non-nobits sections need to appear
   // first.
   if (IsNoBits)
     Rank |= RF_BSS;
 
   // // Some architectures have additional ordering restrictions for sections
   // // within the same PT_LOAD.
   if (Config->EMachine == EM_PPC64) {
     // PPC64 has a number of special SHT_PROGBITS+SHF_ALLOC+SHF_WRITE sections
     // that we would like to make sure appear is a specific order to maximize
     // their coverage by a single signed 16-bit offset from the TOC base
     // pointer. Conversely, the special .tocbss section should be first among
     // all SHT_NOBITS sections. This will put it next to the loaded special
     // PPC64 sections (and, thus, within reach of the TOC base pointer).
     StringRef Name = Sec->Name;
     if (Name != ".tocbss")
       Rank |= RF_PPC_NOT_TOCBSS;
 
     if (Name == ".opd")
       Rank |= RF_PPC_OPD;
 
     if (Name == ".toc1")
       Rank |= RF_PPC_TOCL;
 
     if (Name == ".toc")
       Rank |= RF_PPC_TOC;
 
     if (Name == ".branch_lt")
       Rank |= RF_PPC_BRANCH_LT;
   }
   if (Config->EMachine == EM_MIPS) {
     // All sections with SHF_MIPS_GPREL flag should be grouped together
     // because data in these sections is addressable with a gp relative address.
     if (Sec->Flags & SHF_MIPS_GPREL)
       Rank |= RF_MIPS_GPREL;
 
     if (Sec->Name != ".got")
       Rank |= RF_MIPS_NOT_GOT;
   }
 
   return Rank;
 }
 
 static bool compareSections(const BaseCommand *ACmd, const BaseCommand *BCmd) {
   const OutputSection *A = cast<OutputSectionCommand>(ACmd)->Sec;
   const OutputSection *B = cast<OutputSectionCommand>(BCmd)->Sec;
   if (A->SortRank != B->SortRank)
     return A->SortRank < B->SortRank;
   if (!(A->SortRank & RF_NOT_ADDR_SET))
     return Config->SectionStartMap.lookup(A->Name) <
            Config->SectionStartMap.lookup(B->Name);
   return false;
 }
 
 void PhdrEntry::add(OutputSection *Sec) {
   Last = Sec;
   if (!First)
     First = Sec;
   p_align = std::max(p_align, Sec->Alignment);
   if (p_type == PT_LOAD)
     Sec->FirstInPtLoad = First;
 }
 
 template <class ELFT>
 static Symbol *addRegular(StringRef Name, SectionBase *Sec, uint64_t Value,
                           uint8_t StOther = STV_HIDDEN,
                           uint8_t Binding = STB_WEAK) {
   // The linker generated symbols are added as STB_WEAK to allow user defined
   // ones to override them.
   return Symtab<ELFT>::X->addRegular(Name, StOther, STT_NOTYPE, Value,
                                      /*Size=*/0, Binding, Sec,
                                      /*File=*/nullptr);
 }
 
 template <class ELFT>
 static DefinedRegular *
 addOptionalRegular(StringRef Name, SectionBase *Sec, uint64_t Val,
                    uint8_t StOther = STV_HIDDEN, uint8_t Binding = STB_GLOBAL) {
   SymbolBody *S = Symtab<ELFT>::X->find(Name);
   if (!S)
     return nullptr;
   if (S->isInCurrentDSO())
     return nullptr;
   return cast<DefinedRegular>(
       addRegular<ELFT>(Name, Sec, Val, StOther, Binding)->body());
 }
 
 // The beginning and the ending of .rel[a].plt section are marked
 // with __rel[a]_iplt_{start,end} symbols if it is a statically linked
 // executable. The runtime needs these symbols in order to resolve
 // all IRELATIVE relocs on startup. For dynamic executables, we don't
 // need these symbols, since IRELATIVE relocs are resolved through GOT
 // and PLT. For details, see http://www.airs.com/blog/archives/403.
 template <class ELFT> void Writer<ELFT>::addRelIpltSymbols() {
   if (InX::DynSymTab)
     return;
   StringRef S = Config->IsRela ? "__rela_iplt_start" : "__rel_iplt_start";
   addOptionalRegular<ELFT>(S, In<ELFT>::RelaIplt, 0, STV_HIDDEN, STB_WEAK);
 
   S = Config->IsRela ? "__rela_iplt_end" : "__rel_iplt_end";
   addOptionalRegular<ELFT>(S, In<ELFT>::RelaIplt, -1, STV_HIDDEN, STB_WEAK);
 }
 
 // The linker is expected to define some symbols depending on
 // the linking result. This function defines such symbols.
 template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
   if (Config->EMachine == EM_MIPS) {
     // Define _gp for MIPS. st_value of _gp symbol will be updated by Writer
     // so that it points to an absolute address which by default is relative
     // to GOT. Default offset is 0x7ff0.
     // See "Global Data Symbols" in Chapter 6 in the following document:
     // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
     ElfSym::MipsGp = Symtab<ELFT>::X->addAbsolute("_gp", STV_HIDDEN, STB_LOCAL);
 
     // On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
     // start of function and 'gp' pointer into GOT.
     if (Symtab<ELFT>::X->find("_gp_disp"))
       ElfSym::MipsGpDisp =
           Symtab<ELFT>::X->addAbsolute("_gp_disp", STV_HIDDEN, STB_LOCAL);
 
     // The __gnu_local_gp is a magic symbol equal to the current value of 'gp'
     // pointer. This symbol is used in the code generated by .cpload pseudo-op
     // in case of using -mno-shared option.
     // https://sourceware.org/ml/binutils/2004-12/msg00094.html
     if (Symtab<ELFT>::X->find("__gnu_local_gp"))
       ElfSym::MipsLocalGp =
           Symtab<ELFT>::X->addAbsolute("__gnu_local_gp", STV_HIDDEN, STB_LOCAL);
   }
 
   // In the assembly for 32 bit x86 the _GLOBAL_OFFSET_TABLE_ symbol
   // is magical and is used to produce a R_386_GOTPC relocation.
   // The R_386_GOTPC relocation value doesn't actually depend on the
   // symbol value, so it could use an index of STN_UNDEF which, according
   // to the spec, means the symbol value is 0.
   // Unfortunately both gas and MC keep the _GLOBAL_OFFSET_TABLE_ symbol in
   // the object file.
   // The situation is even stranger on x86_64 where the assembly doesn't
   // need the magical symbol, but gas still puts _GLOBAL_OFFSET_TABLE_ as
   // an undefined symbol in the .o files.
   // Given that the symbol is effectively unused, we just create a dummy
   // hidden one to avoid the undefined symbol error.
   Symtab<ELFT>::X->addIgnored("_GLOBAL_OFFSET_TABLE_");
 
   // __tls_get_addr is defined by the dynamic linker for dynamic ELFs. For
   // static linking the linker is required to optimize away any references to
   // __tls_get_addr, so it's not defined anywhere. Create a hidden definition
   // to avoid the undefined symbol error.
   if (!InX::DynSymTab)
     Symtab<ELFT>::X->addIgnored("__tls_get_addr");
 
   // __ehdr_start is the location of ELF file headers. Note that we define
   // this symbol unconditionally even when using a linker script, which
   // differs from the behavior implemented by GNU linker which only define
   // this symbol if ELF headers are in the memory mapped segment.
   // __executable_start is not documented, but the expectation of at
   // least the android libc is that it points to the elf header too.
   // __dso_handle symbol is passed to cxa_finalize as a marker to identify
   // each DSO. The address of the symbol doesn't matter as long as they are
   // different in different DSOs, so we chose the start address of the DSO.
   for (const char *Name :
        {"__ehdr_start", "__executable_start", "__dso_handle"})
     addOptionalRegular<ELFT>(Name, Out::ElfHeader, 0, STV_HIDDEN);
 
   // If linker script do layout we do not need to create any standart symbols.
   if (Script->Opt.HasSections)
     return;
 
   auto Add = [](StringRef S) {
     return addOptionalRegular<ELFT>(S, Out::ElfHeader, 0, STV_DEFAULT);
   };
 
   ElfSym::Bss = Add("__bss_start");
   ElfSym::End1 = Add("end");
   ElfSym::End2 = Add("_end");
   ElfSym::Etext1 = Add("etext");
   ElfSym::Etext2 = Add("_etext");
   ElfSym::Edata1 = Add("edata");
   ElfSym::Edata2 = Add("_edata");
 }
 
 // Sort input sections by section name suffixes for
 // __attribute__((init_priority(N))).
 static void sortInitFini(OutputSection *S) {
   if (S)
     reinterpret_cast<OutputSection *>(S)->sortInitFini();
 }
 
 // Sort input sections by the special rule for .ctors and .dtors.
 static void sortCtorsDtors(OutputSection *S) {
   if (S)
     reinterpret_cast<OutputSection *>(S)->sortCtorsDtors();
 }
 
 // Sort input sections using the list provided by --symbol-ordering-file.
 template <class ELFT>
 static void sortBySymbolsOrder(ArrayRef<OutputSection *> OutputSections) {
   if (Config->SymbolOrderingFile.empty())
     return;
 
   // Build a map from symbols to their priorities. Symbols that didn't
   // appear in the symbol ordering file have the lowest priority 0.
   // All explicitly mentioned symbols have negative (higher) priorities.
   DenseMap<StringRef, int> SymbolOrder;
   int Priority = -Config->SymbolOrderingFile.size();
   for (StringRef S : Config->SymbolOrderingFile)
     SymbolOrder.insert({S, Priority++});
 
   // Build a map from sections to their priorities.
   DenseMap<SectionBase *, int> SectionOrder;
   for (elf::ObjectFile<ELFT> *File : Symtab<ELFT>::X->getObjectFiles()) {
     for (SymbolBody *Body : File->getSymbols()) {
       auto *D = dyn_cast<DefinedRegular>(Body);
       if (!D || !D->Section)
         continue;
       int &Priority = SectionOrder[D->Section];
       Priority = std::min(Priority, SymbolOrder.lookup(D->getName()));
     }
   }
 
   // Sort sections by priority.
   for (OutputSection *Base : OutputSections)
     if (auto *Sec = dyn_cast<OutputSection>(Base))
       Sec->sort([&](InputSectionBase *S) { return SectionOrder.lookup(S); });
 }
 
 template <class ELFT>
 void Writer<ELFT>::forEachRelSec(std::function<void(InputSectionBase &)> Fn) {
   for (InputSectionBase *IS : InputSections) {
     if (!IS->Live)
       continue;
     // Scan all relocations. Each relocation goes through a series
     // of tests to determine if it needs special treatment, such as
     // creating GOT, PLT, copy relocations, etc.
     // Note that relocations for non-alloc sections are directly
     // processed by InputSection::relocateNonAlloc.
     if (!(IS->Flags & SHF_ALLOC))
       continue;
     if (isa<InputSection>(IS) || isa<EhInputSection>(IS))
       Fn(*IS);
   }
 
   if (!Config->Relocatable) {
     for (EhInputSection *ES : In<ELFT>::EhFrame->Sections)
       Fn(*ES);
   }
 }
 
 template <class ELFT> void Writer<ELFT>::createSections() {
   for (InputSectionBase *IS : InputSections)
     if (IS)
       Factory.addInputSec(IS, getOutputSectionName(IS->Name));
 
   sortBySymbolsOrder<ELFT>(OutputSections);
   sortInitFini(findSection(".init_array"));
   sortInitFini(findSection(".fini_array"));
   sortCtorsDtors(findSection(".ctors"));
   sortCtorsDtors(findSection(".dtors"));
 }
 
 // We want to find how similar two ranks are.
 // The more branches in getSectionRank that match, the more similar they are.
 // Since each branch corresponds to a bit flag, we can just use
 // countLeadingZeros.
 static int getRankProximity(OutputSection *A, OutputSection *B) {
   return countLeadingZeros(A->SortRank ^ B->SortRank);
 }
 
 static int getRankProximity(OutputSection *A, BaseCommand *B) {
   if (auto *Cmd = dyn_cast<OutputSectionCommand>(B))
     if (Cmd->Sec)
       return getRankProximity(A, Cmd->Sec);
   return -1;
 }
 
 // When placing orphan sections, we want to place them after symbol assignments
 // so that an orphan after
 //   begin_foo = .;
 //   foo : { *(foo) }
 //   end_foo = .;
 // doesn't break the intended meaning of the begin/end symbols.
 // We don't want to go over sections since findOrphanPos is the
 // one in charge of deciding the order of the sections.
 // We don't want to go over changes to '.', since doing so in
 //  rx_sec : { *(rx_sec) }
 //  . = ALIGN(0x1000);
 //  /* The RW PT_LOAD starts here*/
 //  rw_sec : { *(rw_sec) }
 // would mean that the RW PT_LOAD would become unaligned.
 static bool shouldSkip(BaseCommand *Cmd) {
   if (isa<OutputSectionCommand>(Cmd))
     return false;
   if (auto *Assign = dyn_cast<SymbolAssignment>(Cmd))
     return Assign->Name != ".";
   return true;
 }
 
 // We want to place orphan sections so that they share as much
 // characteristics with their neighbors as possible. For example, if
 // both are rw, or both are tls.
 template <typename ELFT>
 static std::vector<BaseCommand *>::iterator
 findOrphanPos(std::vector<BaseCommand *>::iterator B,
               std::vector<BaseCommand *>::iterator E) {
   OutputSection *Sec = cast<OutputSectionCommand>(*E)->Sec;
 
   // Find the first element that has as close a rank as possible.
   auto I = std::max_element(B, E, [=](BaseCommand *A, BaseCommand *B) {
     return getRankProximity(Sec, A) < getRankProximity(Sec, B);
   });
   if (I == E)
     return E;
 
   // Consider all existing sections with the same proximity.
   int Proximity = getRankProximity(Sec, *I);
   for (; I != E; ++I) {
     auto *Cmd = dyn_cast<OutputSectionCommand>(*I);
     if (!Cmd || !Cmd->Sec)
       continue;
     if (getRankProximity(Sec, Cmd->Sec) != Proximity ||
         Sec->SortRank < Cmd->Sec->SortRank)
       break;
   }
   auto J = std::find_if(
       llvm::make_reverse_iterator(I), llvm::make_reverse_iterator(B),
       [](BaseCommand *Cmd) { return isa<OutputSectionCommand>(Cmd); });
   I = J.base();
   while (I != E && shouldSkip(*I))
     ++I;
   return I;
 }
 
 template <class ELFT> void Writer<ELFT>::sortSections() {
   // Don't sort if using -r. It is not necessary and we want to preserve the
   // relative order for SHF_LINK_ORDER sections.
   if (Config->Relocatable)
     return;
 
   if (Script->Opt.HasSections)
     Script->adjustSectionsBeforeSorting();
 
   for (BaseCommand *Base : Script->Opt.Commands)
     if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       if (OutputSection *Sec = Cmd->Sec)
         Sec->SortRank = getSectionRank(Sec);
 
   if (!Script->Opt.HasSections) {
     // We know that all the OutputSectionCommands are contiguous in
     // this case.
     auto E = Script->Opt.Commands.end();
     auto I = Script->Opt.Commands.begin();
     auto IsSection = [](BaseCommand *Base) {
       return isa<OutputSectionCommand>(Base);
     };
     I = std::find_if(I, E, IsSection);
     E = std::find_if(llvm::make_reverse_iterator(E),
                      llvm::make_reverse_iterator(I), IsSection)
             .base();
     std::stable_sort(I, E, compareSections);
     return;
   }
 
   // Orphan sections are sections present in the input files which are
   // not explicitly placed into the output file by the linker script.
   //
   // The sections in the linker script are already in the correct
   // order. We have to figuere out where to insert the orphan
   // sections.
   //
   // The order of the sections in the script is arbitrary and may not agree with
   // compareSections. This means that we cannot easily define a strict weak
   // ordering. To see why, consider a comparison of a section in the script and
   // one not in the script. We have a two simple options:
   // * Make them equivalent (a is not less than b, and b is not less than a).
   //   The problem is then that equivalence has to be transitive and we can
   //   have sections a, b and c with only b in a script and a less than c
   //   which breaks this property.
   // * Use compareSectionsNonScript. Given that the script order doesn't have
   //   to match, we can end up with sections a, b, c, d where b and c are in the
   //   script and c is compareSectionsNonScript less than b. In which case d
   //   can be equivalent to c, a to b and d < a. As a concrete example:
   //   .a (rx) # not in script
   //   .b (rx) # in script
   //   .c (ro) # in script
   //   .d (ro) # not in script
   //
   // The way we define an order then is:
   // *  Sort only the orphan sections. They are in the end right now.
   // *  Move each orphan section to its preferred position. We try
   //    to put each section in the last position where it it can share
   //    a PT_LOAD.
   //
   // There is some ambiguity as to where exactly a new entry should be
   // inserted, because Opt.Commands contains not only output section
   // commands but also other types of commands such as symbol assignment
   // expressions. There's no correct answer here due to the lack of the
   // formal specification of the linker script. We use heuristics to
   // determine whether a new output command should be added before or
   // after another commands. For the details, look at shouldSkip
   // function.
 
   auto I = Script->Opt.Commands.begin();
   auto E = Script->Opt.Commands.end();
   auto NonScriptI = std::find_if(I, E, [](BaseCommand *Base) {
     if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       return Cmd->Sec && Cmd->Sec->SectionIndex == INT_MAX;
     return false;
   });
 
   // Sort the orphan sections.
   std::stable_sort(NonScriptI, E, compareSections);
 
   // As a horrible special case, skip the first . assignment if it is before any
   // section. We do this because it is common to set a load address by starting
   // the script with ". = 0xabcd" and the expectation is that every section is
   // after that.
   auto FirstSectionOrDotAssignment =
       std::find_if(I, E, [](BaseCommand *Cmd) { return !shouldSkip(Cmd); });
   if (FirstSectionOrDotAssignment != E &&
       isa<SymbolAssignment>(**FirstSectionOrDotAssignment))
     ++FirstSectionOrDotAssignment;
   I = FirstSectionOrDotAssignment;
 
   while (NonScriptI != E) {
     auto Pos = findOrphanPos<ELFT>(I, NonScriptI);
     OutputSection *Orphan = cast<OutputSectionCommand>(*NonScriptI)->Sec;
 
     // As an optimization, find all sections with the same sort rank
     // and insert them with one rotate.
     unsigned Rank = Orphan->SortRank;
     auto End = std::find_if(NonScriptI + 1, E, [=](BaseCommand *Cmd) {
       return cast<OutputSectionCommand>(Cmd)->Sec->SortRank != Rank;
     });
     std::rotate(Pos, NonScriptI, End);
     NonScriptI = End;
   }
 
   Script->adjustSectionsAfterSorting();
 }
 
 static void applySynthetic(const std::vector<SyntheticSection *> &Sections,
                            std::function<void(SyntheticSection *)> Fn) {
   for (SyntheticSection *SS : Sections)
     if (SS && SS->getParent() && !SS->empty())
       Fn(SS);
 }
 
 // We need to add input synthetic sections early in createSyntheticSections()
 // to make them visible from linkescript side. But not all sections are always
 // required to be in output. For example we don't need dynamic section content
 // sometimes. This function filters out such unused sections from the output.
 static void removeUnusedSyntheticSections(std::vector<OutputSection *> &V) {
   // All input synthetic sections that can be empty are placed after
   // all regular ones. We iterate over them all and exit at first
   // non-synthetic.
   for (InputSectionBase *S : llvm::reverse(InputSections)) {
     SyntheticSection *SS = dyn_cast<SyntheticSection>(S);
     if (!SS)
       return;
     OutputSection *OS = SS->getParent();
     if (!SS->empty() || !OS)
       continue;
     OS->Sections.erase(std::find(OS->Sections.begin(), OS->Sections.end(), SS));
     SS->Live = false;
     // If there are no other sections in the output section, remove it from the
     // output.
     if (OS->Sections.empty())
       V.erase(std::find(V.begin(), V.end(), OS));
   }
 }
 
 // Create output section objects and add them to OutputSections.
 template <class ELFT> void Writer<ELFT>::finalizeSections() {
   Out::DebugInfo = findSection(".debug_info");
   Out::PreinitArray = findSection(".preinit_array");
   Out::InitArray = findSection(".init_array");
   Out::FiniArray = findSection(".fini_array");
 
   // The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
   // symbols for sections, so that the runtime can get the start and end
   // addresses of each section by section name. Add such symbols.
   if (!Config->Relocatable) {
     addStartEndSymbols();
     for (OutputSection *Sec : OutputSections)
       addStartStopSymbols(Sec);
   }
 
   // Add _DYNAMIC symbol. Unlike GNU gold, our _DYNAMIC symbol has no type.
   // It should be okay as no one seems to care about the type.
   // Even the author of gold doesn't remember why gold behaves that way.
   // https://sourceware.org/ml/binutils/2002-03/msg00360.html
   if (InX::DynSymTab)
     addRegular<ELFT>("_DYNAMIC", InX::Dynamic, 0);
 
   // Define __rel[a]_iplt_{start,end} symbols if needed.
   addRelIpltSymbols();
 
   // This responsible for splitting up .eh_frame section into
   // pieces. The relocation scan uses those pieces, so this has to be
   // earlier.
   applySynthetic({In<ELFT>::EhFrame},
                  [](SyntheticSection *SS) { SS->finalizeContents(); });
 
   // Scan relocations. This must be done after every symbol is declared so that
   // we can correctly decide if a dynamic relocation is needed.
   forEachRelSec(scanRelocations<ELFT>);
 
   if (InX::Plt && !InX::Plt->empty())
     InX::Plt->addSymbols();
   if (InX::Iplt && !InX::Iplt->empty())
     InX::Iplt->addSymbols();
 
   // Now that we have defined all possible global symbols including linker-
   // synthesized ones. Visit all symbols to give the finishing touches.
   for (Symbol *S : Symtab<ELFT>::X->getSymbols()) {
     SymbolBody *Body = S->body();
 
     if (!includeInSymtab(*Body))
       continue;
     if (InX::SymTab)
       InX::SymTab->addSymbol(Body);
 
     if (InX::DynSymTab && S->includeInDynsym()) {
       InX::DynSymTab->addSymbol(Body);
       if (auto *SS = dyn_cast<SharedSymbol>(Body))
         if (cast<SharedFile<ELFT>>(SS->File)->isNeeded())
           In<ELFT>::VerNeed->addSymbol(SS);
     }
   }
 
   // Do not proceed if there was an undefined symbol.
   if (ErrorCount)
     return;
 
   addPredefinedSections();
   removeUnusedSyntheticSections(OutputSections);
 
   clearOutputSections();
   sortSections();
 
   // Now that we have the final list, create a list of all the
   // OutputSectionCommands for convenience.
   for (BaseCommand *Base : Script->Opt.Commands)
     if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
       OutputSectionCommands.push_back(Cmd);
 
   // This is a bit of a hack. A value of 0 means undef, so we set it
   // to 1 t make __ehdr_start defined. The section number is not
   // particularly relevant.
   Out::ElfHeader->SectionIndex = 1;
 
   unsigned I = 1;
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     Sec->SectionIndex = I++;
     Sec->ShName = InX::ShStrTab->addString(Sec->Name);
   }
 
   // Binary and relocatable output does not have PHDRS.
   // The headers have to be created before finalize as that can influence the
   // image base and the dynamic section on mips includes the image base.
   if (!Config->Relocatable && !Config->OFormatBinary) {
     Phdrs = Script->hasPhdrsCommands() ? Script->createPhdrs() : createPhdrs();
     addPtArmExid(Phdrs);
     Out::ProgramHeaders->Size = sizeof(Elf_Phdr) * Phdrs.size();
   }
 
   // Compute the size of .rela.dyn and .rela.plt early since we need
   // them to populate .dynamic.
   for (SyntheticSection *SS : {In<ELFT>::RelaDyn, In<ELFT>::RelaPlt})
     if (SS->getParent() && !SS->empty())
       SS->getParent()->assignOffsets();
 
   // Dynamic section must be the last one in this list and dynamic
   // symbol table section (DynSymTab) must be the first one.
   applySynthetic({InX::DynSymTab,    InX::Bss,           InX::BssRelRo,
                   InX::GnuHashTab,   In<ELFT>::HashTab,  InX::SymTab,
                   InX::ShStrTab,     InX::StrTab,        In<ELFT>::VerDef,
                   InX::DynStrTab,    InX::GdbIndex,      InX::Got,
                   InX::MipsGot,      InX::IgotPlt,       InX::GotPlt,
                   In<ELFT>::RelaDyn, In<ELFT>::RelaIplt, In<ELFT>::RelaPlt,
                   InX::Plt,          InX::Iplt,          In<ELFT>::EhFrameHdr,
                   In<ELFT>::VerSym,  In<ELFT>::VerNeed,  InX::Dynamic},
                  [](SyntheticSection *SS) { SS->finalizeContents(); });
 
   // Some architectures use small displacements for jump instructions.
   // It is linker's responsibility to create thunks containing long
   // jump instructions if jump targets are too far. Create thunks.
   if (Target->NeedsThunks) {
     // FIXME: only ARM Interworking and Mips LA25 Thunks are implemented,
     // these
     // do not require address information. To support range extension Thunks
     // we need to assign addresses so that we can tell if jump instructions
     // are out of range. This will need to turn into a loop that converges
     // when no more Thunks are added
     ThunkCreator TC;
     if (TC.createThunks(OutputSectionCommands)) {
       applySynthetic({InX::MipsGot},
                      [](SyntheticSection *SS) { SS->updateAllocSize(); });
       if (TC.createThunks(OutputSectionCommands))
         fatal("All non-range thunks should be created in first call");
     }
   }
 
   // Fill other section headers. The dynamic table is finalized
   // at the end because some tags like RELSZ depend on result
   // of finalizing other sections.
   for (OutputSectionCommand *Cmd : OutputSectionCommands)
     Cmd->finalize<ELFT>();
 
   // createThunks may have added local symbols to the static symbol table
   applySynthetic({InX::SymTab, InX::ShStrTab, InX::StrTab},
                  [](SyntheticSection *SS) { SS->postThunkContents(); });
 }
 
 template <class ELFT> void Writer<ELFT>::addPredefinedSections() {
   // ARM ABI requires .ARM.exidx to be terminated by some piece of data.
   // We have the terminater synthetic section class. Add that at the end.
   auto *OS = dyn_cast_or_null<OutputSection>(findSection(".ARM.exidx"));
   if (!OS || OS->Sections.empty() || Config->Relocatable)
     return;
 
   auto *Sentinel = make<ARMExidxSentinelSection>();
   OS->addSection(Sentinel);
   // If there are linker script commands existing at this point then add the
   // sentinel to the last of these too.
   if (OutputSectionCommand *C = Script->getCmd(OS)) {
     auto ISD = std::find_if(C->Commands.rbegin(), C->Commands.rend(),
                             [](const BaseCommand *Base) {
                               return isa<InputSectionDescription>(Base);
                             });
     cast<InputSectionDescription>(*ISD)->Sections.push_back(Sentinel);
   }
 }
 
 // The linker is expected to define SECNAME_start and SECNAME_end
 // symbols for a few sections. This function defines them.
 template <class ELFT> void Writer<ELFT>::addStartEndSymbols() {
   auto Define = [&](StringRef Start, StringRef End, OutputSection *OS) {
     // These symbols resolve to the image base if the section does not exist.
     // A special value -1 indicates end of the section.
     if (OS) {
       addOptionalRegular<ELFT>(Start, OS, 0);
       addOptionalRegular<ELFT>(End, OS, -1);
     } else {
       if (Config->Pic)
         OS = Out::ElfHeader;
       addOptionalRegular<ELFT>(Start, OS, 0);
       addOptionalRegular<ELFT>(End, OS, 0);
     }
   };
 
   Define("__preinit_array_start", "__preinit_array_end", Out::PreinitArray);
   Define("__init_array_start", "__init_array_end", Out::InitArray);
   Define("__fini_array_start", "__fini_array_end", Out::FiniArray);
 
   if (OutputSection *Sec = findSection(".ARM.exidx"))
     Define("__exidx_start", "__exidx_end", Sec);
 }
 
 // If a section name is valid as a C identifier (which is rare because of
 // the leading '.'), linkers are expected to define __start_<secname> and
 // __stop_<secname> symbols. They are at beginning and end of the section,
 // respectively. This is not requested by the ELF standard, but GNU ld and
 // gold provide the feature, and used by many programs.
 template <class ELFT>
 void Writer<ELFT>::addStartStopSymbols(OutputSection *Sec) {
   StringRef S = Sec->Name;
   if (!isValidCIdentifier(S))
     return;
   addOptionalRegular<ELFT>(Saver.save("__start_" + S), Sec, 0, STV_DEFAULT);
   addOptionalRegular<ELFT>(Saver.save("__stop_" + S), Sec, -1, STV_DEFAULT);
 }
 
 template <class ELFT>
 OutputSectionCommand *Writer<ELFT>::findSectionCommand(StringRef Name) {
   for (OutputSectionCommand *Cmd : OutputSectionCommands)
     if (Cmd->Name == Name)
       return Cmd;
   return nullptr;
 }
 
 template <class ELFT> OutputSection *Writer<ELFT>::findSectionInScript(StringRef Name) {
   if (OutputSectionCommand *Cmd = findSectionCommand(Name))
     return Cmd->Sec;
   return nullptr;
 }
 
 template <class ELFT> OutputSection *Writer<ELFT>::findSection(StringRef Name) {
   for (OutputSection *Sec : OutputSections)
     if (Sec->Name == Name)
       return Sec;
   return nullptr;
 }
 
 static bool needsPtLoad(OutputSection *Sec) {
   if (!(Sec->Flags & SHF_ALLOC))
     return false;
 
   // Don't allocate VA space for TLS NOBITS sections. The PT_TLS PHDR is
   // responsible for allocating space for them, not the PT_LOAD that
   // contains the TLS initialization image.
   if (Sec->Flags & SHF_TLS && Sec->Type == SHT_NOBITS)
     return false;
   return true;
 }
 
 // Linker scripts are responsible for aligning addresses. Unfortunately, most
 // linker scripts are designed for creating two PT_LOADs only, one RX and one
 // RW. This means that there is no alignment in the RO to RX transition and we
 // cannot create a PT_LOAD there.
 static uint64_t computeFlags(uint64_t Flags) {
   if (Config->Omagic)
     return PF_R | PF_W | PF_X;
   if (Config->SingleRoRx && !(Flags & PF_W))
     return Flags | PF_X;
   return Flags;
 }
 
 // Decide which program headers to create and which sections to include in each
 // one.
 template <class ELFT> std::vector<PhdrEntry> Writer<ELFT>::createPhdrs() {
   std::vector<PhdrEntry> Ret;
   auto AddHdr = [&](unsigned Type, unsigned Flags) -> PhdrEntry * {
     Ret.emplace_back(Type, Flags);
     return &Ret.back();
   };
 
   // The first phdr entry is PT_PHDR which describes the program header itself.
   AddHdr(PT_PHDR, PF_R)->add(Out::ProgramHeaders);
 
   // PT_INTERP must be the second entry if exists.
   if (OutputSection *Sec = findSectionInScript(".interp"))
     AddHdr(PT_INTERP, Sec->getPhdrFlags())->add(Sec);
 
   // Add the first PT_LOAD segment for regular output sections.
   uint64_t Flags = computeFlags(PF_R);
   PhdrEntry *Load = AddHdr(PT_LOAD, Flags);
 
   // Add the headers. We will remove them if they don't fit.
   Load->add(Out::ElfHeader);
   Load->add(Out::ProgramHeaders);
 
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (!(Sec->Flags & SHF_ALLOC))
       break;
     if (!needsPtLoad(Sec))
       continue;
 
     // Segments are contiguous memory regions that has the same attributes
     // (e.g. executable or writable). There is one phdr for each segment.
     // Therefore, we need to create a new phdr when the next section has
     // different flags or is loaded at a discontiguous address using AT linker
     // script command.
     uint64_t NewFlags = computeFlags(Sec->getPhdrFlags());
     if (Script->hasLMA(Sec) || Flags != NewFlags) {
       Load = AddHdr(PT_LOAD, NewFlags);
       Flags = NewFlags;
     }
 
     Load->add(Sec);
   }
 
   // Add a TLS segment if any.
   PhdrEntry TlsHdr(PT_TLS, PF_R);
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec->Flags & SHF_TLS)
       TlsHdr.add(Sec);
   }
   if (TlsHdr.First)
     Ret.push_back(std::move(TlsHdr));
 
   // Add an entry for .dynamic.
   if (InX::DynSymTab)
     AddHdr(PT_DYNAMIC, InX::Dynamic->getParent()->getPhdrFlags())
         ->add(InX::Dynamic->getParent());
 
   // PT_GNU_RELRO includes all sections that should be marked as
   // read-only by dynamic linker after proccessing relocations.
   PhdrEntry RelRo(PT_GNU_RELRO, PF_R);
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (needsPtLoad(Sec) && isRelroSection(Sec))
       RelRo.add(Sec);
   }
   if (RelRo.First)
     Ret.push_back(std::move(RelRo));
 
   // PT_GNU_EH_FRAME is a special section pointing on .eh_frame_hdr.
   if (!In<ELFT>::EhFrame->empty() && In<ELFT>::EhFrameHdr &&
       In<ELFT>::EhFrame->getParent() && In<ELFT>::EhFrameHdr->getParent())
     AddHdr(PT_GNU_EH_FRAME, In<ELFT>::EhFrameHdr->getParent()->getPhdrFlags())
         ->add(In<ELFT>::EhFrameHdr->getParent());
 
   // PT_OPENBSD_RANDOMIZE is an OpenBSD-specific feature. That makes
   // the dynamic linker fill the segment with random data.
   if (OutputSection *Sec = findSectionInScript(".openbsd.randomdata"))
     AddHdr(PT_OPENBSD_RANDOMIZE, Sec->getPhdrFlags())->add(Sec);
 
   // PT_GNU_STACK is a special section to tell the loader to make the
   // pages for the stack non-executable. If you really want an executable
   // stack, you can pass -z execstack, but that's not recommended for
   // security reasons.
   unsigned Perm;
   if (Config->ZExecstack)
     Perm = PF_R | PF_W | PF_X;
   else
     Perm = PF_R | PF_W;
   AddHdr(PT_GNU_STACK, Perm)->p_memsz = Config->ZStackSize;
 
   // PT_OPENBSD_WXNEEDED is a OpenBSD-specific header to mark the executable
   // is expected to perform W^X violations, such as calling mprotect(2) or
   // mmap(2) with PROT_WRITE | PROT_EXEC, which is prohibited by default on
   // OpenBSD.
   if (Config->ZWxneeded)
     AddHdr(PT_OPENBSD_WXNEEDED, PF_X);
 
   // Create one PT_NOTE per a group of contiguous .note sections.
   PhdrEntry *Note = nullptr;
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec->Type == SHT_NOTE) {
       if (!Note || Script->hasLMA(Sec))
         Note = AddHdr(PT_NOTE, PF_R);
       Note->add(Sec);
     } else {
       Note = nullptr;
     }
   }
   return Ret;
 }
 
 template <class ELFT>
 void Writer<ELFT>::addPtArmExid(std::vector<PhdrEntry> &Phdrs) {
   if (Config->EMachine != EM_ARM)
     return;
   auto I =
       std::find_if(OutputSectionCommands.begin(), OutputSectionCommands.end(),
                    [](OutputSectionCommand *Cmd) {
                      return Cmd->Sec->Type == SHT_ARM_EXIDX;
                    });
   if (I == OutputSectionCommands.end())
     return;
 
   // PT_ARM_EXIDX is the ARM EHABI equivalent of PT_GNU_EH_FRAME
   PhdrEntry ARMExidx(PT_ARM_EXIDX, PF_R);
   ARMExidx.add((*I)->Sec);
   Phdrs.push_back(ARMExidx);
 }
 
 // The first section of each PT_LOAD, the first section in PT_GNU_RELRO and the
 // first section after PT_GNU_RELRO have to be page aligned so that the dynamic
 // linker can set the permissions.
 template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
   auto PageAlign = [](OutputSection *Sec) {
     OutputSectionCommand *Cmd = Script->getCmd(Sec);
     if (Cmd && !Cmd->AddrExpr)
       Cmd->AddrExpr = [=] {
         return alignTo(Script->getDot(), Config->MaxPageSize);
       };
   };
 
   for (const PhdrEntry &P : Phdrs)
     if (P.p_type == PT_LOAD && P.First)
       PageAlign(P.First);
 
   for (const PhdrEntry &P : Phdrs) {
     if (P.p_type != PT_GNU_RELRO)
       continue;
     if (P.First)
       PageAlign(P.First);
     // Find the first section after PT_GNU_RELRO. If it is in a PT_LOAD we
     // have to align it to a page.
     auto End = OutputSectionCommands.end();
     auto I =
         std::find(OutputSectionCommands.begin(), End, Script->getCmd(P.Last));
     if (I == End || (I + 1) == End)
       continue;
     OutputSection *Sec = (*(I + 1))->Sec;
     if (needsPtLoad(Sec))
       PageAlign(Sec);
   }
 }
 
 // Adjusts the file alignment for a given output section and returns
 // its new file offset. The file offset must be the same with its
 // virtual address (modulo the page size) so that the loader can load
 // executables without any address adjustment.
 static uint64_t getFileAlignment(uint64_t Off, OutputSection *Sec) {
   OutputSection *First = Sec->FirstInPtLoad;
   // If the section is not in a PT_LOAD, we just have to align it.
   if (!First)
     return alignTo(Off, Sec->Alignment);
 
   // The first section in a PT_LOAD has to have congruent offset and address
   // module the page size.
   if (Sec == First)
     return alignTo(Off, Config->MaxPageSize, Sec->Addr);
 
   // If two sections share the same PT_LOAD the file offset is calculated
   // using this formula: Off2 = Off1 + (VA2 - VA1).
   return First->Offset + Sec->Addr - First->Addr;
 }
 
 static uint64_t setOffset(OutputSection *Sec, uint64_t Off) {
   if (Sec->Type == SHT_NOBITS) {
     Sec->Offset = Off;
     return Off;
   }
 
   Off = getFileAlignment(Off, Sec);
   Sec->Offset = Off;
   return Off + Sec->Size;
 }
 
 template <class ELFT> void Writer<ELFT>::assignFileOffsetsBinary() {
   uint64_t Off = 0;
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec->Flags & SHF_ALLOC)
       Off = setOffset(Sec, Off);
   }
   FileSize = alignTo(Off, Config->Wordsize);
 }
 
 // Assign file offsets to output sections.
 template <class ELFT> void Writer<ELFT>::assignFileOffsets() {
   uint64_t Off = 0;
   Off = setOffset(Out::ElfHeader, Off);
   Off = setOffset(Out::ProgramHeaders, Off);
 
   for (OutputSectionCommand *Cmd : OutputSectionCommands)
     Off = setOffset(Cmd->Sec, Off);
 
   SectionHeaderOff = alignTo(Off, Config->Wordsize);
   FileSize =
       SectionHeaderOff + (OutputSectionCommands.size() + 1) * sizeof(Elf_Shdr);
 }
 
 // Finalize the program headers. We call this function after we assign
 // file offsets and VAs to all sections.
 template <class ELFT> void Writer<ELFT>::setPhdrs() {
   for (PhdrEntry &P : Phdrs) {
     OutputSection *First = P.First;
     OutputSection *Last = P.Last;
     if (First) {
       P.p_filesz = Last->Offset - First->Offset;
       if (Last->Type != SHT_NOBITS)
         P.p_filesz += Last->Size;
       P.p_memsz = Last->Addr + Last->Size - First->Addr;
       P.p_offset = First->Offset;
       P.p_vaddr = First->Addr;
       if (!P.HasLMA)
         P.p_paddr = First->getLMA();
     }
     if (P.p_type == PT_LOAD)
       P.p_align = Config->MaxPageSize;
-    else if (P.p_type == PT_GNU_RELRO)
+    else if (P.p_type == PT_GNU_RELRO) {
       P.p_align = 1;
+      // The glibc dynamic loader rounds the size down, so we need to round up
+      // to protect the last page. This is a no-op on FreeBSD which always
+      // rounds up.
+      P.p_memsz = alignTo(P.p_memsz, Target->PageSize);
+    }
 
     // The TLS pointer goes after PT_TLS. At least glibc will align it,
     // so round up the size to make sure the offsets are correct.
     if (P.p_type == PT_TLS) {
       Out::TlsPhdr = &P;
       if (P.p_memsz)
         P.p_memsz = alignTo(P.p_memsz, P.p_align);
     }
   }
 }
 
 // The entry point address is chosen in the following ways.
 //
 // 1. the '-e' entry command-line option;
 // 2. the ENTRY(symbol) command in a linker control script;
 // 3. the value of the symbol start, if present;
 // 4. the address of the first byte of the .text section, if present;
 // 5. the address 0.
 template <class ELFT> uint64_t Writer<ELFT>::getEntryAddr() {
   // Case 1, 2 or 3. As a special case, if the symbol is actually
   // a number, we'll use that number as an address.
   if (SymbolBody *B = Symtab<ELFT>::X->find(Config->Entry))
     return B->getVA();
   uint64_t Addr;
   if (to_integer(Config->Entry, Addr))
     return Addr;
 
   // Case 4
   if (OutputSection *Sec = findSectionInScript(".text")) {
     if (Config->WarnMissingEntry)
       warn("cannot find entry symbol " + Config->Entry + "; defaulting to 0x" +
            utohexstr(Sec->Addr));
     return Sec->Addr;
   }
 
   // Case 5
   if (Config->WarnMissingEntry)
     warn("cannot find entry symbol " + Config->Entry +
          "; not setting start address");
   return 0;
 }
 
 static uint16_t getELFType() {
   if (Config->Pic)
     return ET_DYN;
   if (Config->Relocatable)
     return ET_REL;
   return ET_EXEC;
 }
 
 // This function is called after we have assigned address and size
 // to each section. This function fixes some predefined
 // symbol values that depend on section address and size.
 template <class ELFT> void Writer<ELFT>::fixPredefinedSymbols() {
   // _etext is the first location after the last read-only loadable segment.
   // _edata is the first location after the last read-write loadable segment.
   // _end is the first location after the uninitialized data region.
   PhdrEntry *Last = nullptr;
   PhdrEntry *LastRO = nullptr;
   PhdrEntry *LastRW = nullptr;
   for (PhdrEntry &P : Phdrs) {
     if (P.p_type != PT_LOAD)
       continue;
     Last = &P;
     if (P.p_flags & PF_W)
       LastRW = &P;
     else
       LastRO = &P;
   }
 
   auto Set = [](DefinedRegular *S, OutputSection *Sec, uint64_t Value) {
     if (S) {
       S->Section = Sec;
       S->Value = Value;
     }
   };
 
   if (Last) {
     Set(ElfSym::End1, Last->First, Last->p_memsz);
     Set(ElfSym::End2, Last->First, Last->p_memsz);
   }
   if (LastRO) {
     Set(ElfSym::Etext1, LastRO->First, LastRO->p_filesz);
     Set(ElfSym::Etext2, LastRO->First, LastRO->p_filesz);
   }
   if (LastRW) {
     Set(ElfSym::Edata1, LastRW->First, LastRW->p_filesz);
     Set(ElfSym::Edata2, LastRW->First, LastRW->p_filesz);
   }
 
   if (ElfSym::Bss)
     ElfSym::Bss->Section = findSectionInScript(".bss");
 
   // Setup MIPS _gp_disp/__gnu_local_gp symbols which should
   // be equal to the _gp symbol's value.
   if (Config->EMachine == EM_MIPS && !ElfSym::MipsGp->Value) {
     // Find GP-relative section with the lowest address
     // and use this address to calculate default _gp value.
     for (const OutputSectionCommand *Cmd : OutputSectionCommands) {
       OutputSection *OS = Cmd->Sec;
       if (OS->Flags & SHF_MIPS_GPREL) {
         ElfSym::MipsGp->Value = OS->Addr + 0x7ff0;
         break;
       }
     }
   }
 }
 
 template <class ELFT> void Writer<ELFT>::writeHeader() {
   uint8_t *Buf = Buffer->getBufferStart();
   memcpy(Buf, "\177ELF", 4);
 
   // Write the ELF header.
   auto *EHdr = reinterpret_cast<Elf_Ehdr *>(Buf);
   EHdr->e_ident[EI_CLASS] = Config->Is64 ? ELFCLASS64 : ELFCLASS32;
   EHdr->e_ident[EI_DATA] = Config->IsLE ? ELFDATA2LSB : ELFDATA2MSB;
   EHdr->e_ident[EI_VERSION] = EV_CURRENT;
   EHdr->e_ident[EI_OSABI] = Config->OSABI;
   EHdr->e_type = getELFType();
   EHdr->e_machine = Config->EMachine;
   EHdr->e_version = EV_CURRENT;
   EHdr->e_entry = getEntryAddr();
   EHdr->e_shoff = SectionHeaderOff;
   EHdr->e_ehsize = sizeof(Elf_Ehdr);
   EHdr->e_phnum = Phdrs.size();
   EHdr->e_shentsize = sizeof(Elf_Shdr);
   EHdr->e_shnum = OutputSectionCommands.size() + 1;
   EHdr->e_shstrndx = InX::ShStrTab->getParent()->SectionIndex;
 
   if (Config->EMachine == EM_ARM)
     // We don't currently use any features incompatible with EF_ARM_EABI_VER5,
     // but we don't have any firm guarantees of conformance. Linux AArch64
     // kernels (as of 2016) require an EABI version to be set.
     EHdr->e_flags = EF_ARM_EABI_VER5;
   else if (Config->EMachine == EM_MIPS)
     EHdr->e_flags = getMipsEFlags<ELFT>();
 
   if (!Config->Relocatable) {
     EHdr->e_phoff = sizeof(Elf_Ehdr);
     EHdr->e_phentsize = sizeof(Elf_Phdr);
   }
 
   // Write the program header table.
   auto *HBuf = reinterpret_cast<Elf_Phdr *>(Buf + EHdr->e_phoff);
   for (PhdrEntry &P : Phdrs) {
     HBuf->p_type = P.p_type;
     HBuf->p_flags = P.p_flags;
     HBuf->p_offset = P.p_offset;
     HBuf->p_vaddr = P.p_vaddr;
     HBuf->p_paddr = P.p_paddr;
     HBuf->p_filesz = P.p_filesz;
     HBuf->p_memsz = P.p_memsz;
     HBuf->p_align = P.p_align;
     ++HBuf;
   }
 
   // Write the section header table. Note that the first table entry is null.
   auto *SHdrs = reinterpret_cast<Elf_Shdr *>(Buf + EHdr->e_shoff);
   for (OutputSectionCommand *Cmd : OutputSectionCommands)
     Cmd->Sec->writeHeaderTo<ELFT>(++SHdrs);
 }
 
 // Open a result file.
 template <class ELFT> void Writer<ELFT>::openFile() {
   if (!Config->Is64 && FileSize > UINT32_MAX) {
     error("output file too large: " + Twine(FileSize) + " bytes");
     return;
   }
 
   unlinkAsync(Config->OutputFile);
   ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
       FileOutputBuffer::create(Config->OutputFile, FileSize,
                                FileOutputBuffer::F_executable);
 
   if (auto EC = BufferOrErr.getError())
     error("failed to open " + Config->OutputFile + ": " + EC.message());
   else
     Buffer = std::move(*BufferOrErr);
 }
 
 template <class ELFT> void Writer<ELFT>::writeSectionsBinary() {
   uint8_t *Buf = Buffer->getBufferStart();
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec->Flags & SHF_ALLOC)
       Cmd->writeTo<ELFT>(Buf + Sec->Offset);
   }
 }
 
 // Write section contents to a mmap'ed file.
 template <class ELFT> void Writer<ELFT>::writeSections() {
   uint8_t *Buf = Buffer->getBufferStart();
 
   // PPC64 needs to process relocations in the .opd section
   // before processing relocations in code-containing sections.
   if (auto *OpdCmd = findSectionCommand(".opd")) {
     Out::Opd = OpdCmd->Sec;
     Out::OpdBuf = Buf + Out::Opd->Offset;
     OpdCmd->template writeTo<ELFT>(Buf + Out::Opd->Offset);
   }
 
   OutputSection *EhFrameHdr =
       (In<ELFT>::EhFrameHdr && !In<ELFT>::EhFrameHdr->empty())
           ? In<ELFT>::EhFrameHdr->getParent()
           : nullptr;
 
   // In -r or -emit-relocs mode, write the relocation sections first as in
   // ELf_Rel targets we might find out that we need to modify the relocated
   // section while doing it.
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec->Type == SHT_REL || Sec->Type == SHT_RELA)
       Cmd->writeTo<ELFT>(Buf + Sec->Offset);
   }
 
   for (OutputSectionCommand *Cmd : OutputSectionCommands) {
     OutputSection *Sec = Cmd->Sec;
     if (Sec != Out::Opd && Sec != EhFrameHdr && Sec->Type != SHT_REL &&
         Sec->Type != SHT_RELA)
       Cmd->writeTo<ELFT>(Buf + Sec->Offset);
   }
 
   // The .eh_frame_hdr depends on .eh_frame section contents, therefore
   // it should be written after .eh_frame is written.
   if (EhFrameHdr) {
     OutputSectionCommand *Cmd = Script->getCmd(EhFrameHdr);
     Cmd->writeTo<ELFT>(Buf + EhFrameHdr->Offset);
   }
 }
 
 template <class ELFT> void Writer<ELFT>::writeBuildId() {
   if (!InX::BuildId || !InX::BuildId->getParent())
     return;
 
   // Compute a hash of all sections of the output file.
   uint8_t *Start = Buffer->getBufferStart();
   uint8_t *End = Start + FileSize;
   InX::BuildId->writeBuildId({Start, End});
 }
 
 template void elf::writeResult<ELF32LE>();
 template void elf::writeResult<ELF32BE>();
 template void elf::writeResult<ELF64LE>();
 template void elf::writeResult<ELF64BE>();