/usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp

Bug Summary

File:	src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp
Warning:	line 1914, column 29 Called C++ object pointer is null

Annotated Source Code

Press '?' to see keyboard shortcuts

Show analyzer invocation

clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name Writer.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model static -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/gnu/usr.bin/clang/liblldELF/obj -resource-dir /usr/local/lib/clang/13.0.0 -I /usr/src/gnu/usr.bin/clang/liblldELF/obj/../include/lld/ELF -I /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/include -I /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF -I /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/llvm/include -I /usr/src/gnu/usr.bin/clang/liblldELF/../include -I /usr/src/gnu/usr.bin/clang/liblldELF/obj -I /usr/src/gnu/usr.bin/clang/liblldELF/obj/../include -D NDEBUG -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D LLVM_PREFIX="/usr" -internal-isystem /usr/include/c++/v1 -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/usr/src/gnu/usr.bin/clang/liblldELF/obj -ferror-limit 19 -fvisibility-inlines-hidden -fwrapv -stack-protector 2 -fno-rtti -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c++ /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp

/usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp

→

1//===- Writer.cpp ---------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//

9#include "Writer.h"
10#include "AArch64ErrataFix.h"
11#include "ARMErrataFix.h"
12#include "CallGraphSort.h"
13#include "Config.h"
14#include "LinkerScript.h"
15#include "MapFile.h"
16#include "OutputSections.h"
17#include "Relocations.h"
18#include "SymbolTable.h"
19#include "Symbols.h"
20#include "SyntheticSections.h"
21#include "Target.h"
22#include "lld/Common/Arrays.h"
23#include "lld/Common/Filesystem.h"
24#include "lld/Common/Memory.h"
25#include "lld/Common/Strings.h"
26#include "llvm/ADT/StringMap.h"
27#include "llvm/ADT/StringSwitch.h"
28#include "llvm/Support/Parallel.h"
29#include "llvm/Support/RandomNumberGenerator.h"
30#include "llvm/Support/SHA1.h"
31#include "llvm/Support/TimeProfiler.h"
32#include "llvm/Support/xxhash.h"
33#include <climits>

35#define DEBUG_TYPE"lld" "lld"

37using namespace llvm;
38using namespace llvm::ELF;
39using namespace llvm::object;
40using namespace llvm::support;
41using namespace llvm::support::endian;
42using namespace lld;
43using namespace lld::elf;

45namespace {
46// The writer writes a SymbolTable result to a file.
47template <class ELFT> class Writer {
48public:
LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)using Elf_Addr = typename ELFT::Addr; using Elf_Off = typename
 ELFT::Off; using Elf_Half = typename ELFT::Half; using Elf_Word
 = typename ELFT::Word; using Elf_Sword = typename ELFT::Sword
; using Elf_Xword = typename ELFT::Xword; using Elf_Sxword = typename
 ELFT::Sxword; using uintX_t = typename ELFT::uint; using Elf_Ehdr
 = typename ELFT::Ehdr; using Elf_Shdr = typename ELFT::Shdr;
 using Elf_Sym = typename ELFT::Sym; using Elf_Dyn = typename
 ELFT::Dyn; using Elf_Phdr = typename ELFT::Phdr; using Elf_Rel
 = typename ELFT::Rel; using Elf_Rela = typename ELFT::Rela; using
 Elf_Relr = typename ELFT::Relr; using Elf_Verdef = typename ELFT
::Verdef; using Elf_Verdaux = typename ELFT::Verdaux; using Elf_Verneed
 = typename ELFT::Verneed; using Elf_Vernaux = typename ELFT::
Vernaux; using Elf_Versym = typename ELFT::Versym; using Elf_Hash
 = typename ELFT::Hash; using Elf_GnuHash = typename ELFT::GnuHash
; using Elf_Nhdr = typename ELFT::Nhdr; using Elf_Note = typename
 ELFT::Note; using Elf_Note_Iterator = typename ELFT::NoteIterator
; using Elf_CGProfile = typename ELFT::CGProfile; using Elf_BBAddrMap
 = typename ELFT::BBAddrMap; using Elf_Dyn_Range = typename ELFT
::DynRange; using Elf_Shdr_Range = typename ELFT::ShdrRange; using
 Elf_Sym_Range = typename ELFT::SymRange; using Elf_Rel_Range
 = typename ELFT::RelRange; using Elf_Rela_Range = typename ELFT
::RelaRange; using Elf_Relr_Range = typename ELFT::RelrRange;
 using Elf_Phdr_Range = typename ELFT::PhdrRange;

Writer() : buffer(errorHandler().outputBuffer) {}

void run();

55private:
void copyLocalSymbols();
void addSectionSymbols();
void forEachRelSec(llvm::function_ref<void(InputSectionBase &)> fn);
void sortSections();
void resolveShfLinkOrder();
void finalizeAddressDependentContent();
void optimizeBasicBlockJumps();
void sortInputSections();
void finalizeSections();
void checkExecuteOnly();
void setReservedSymbolSections();

std::vector<PhdrEntry *> createPhdrs(Partition &part);
void addPhdrForSection(Partition &part, unsigned shType, unsigned pType,
                       unsigned pFlags);
void assignFileOffsets();
void assignFileOffsetsBinary();
void setPhdrs(Partition &part);
void checkSections();
void fixSectionAlignments();
void openFile();
void writeTrapInstr();
void writeHeader();
void writeSections();
void writeSectionsBinary();
void writeBuildId();

std::unique_ptr<FileOutputBuffer> &buffer;

void addRelIpltSymbols();
void addStartEndSymbols();
void addStartStopSymbols(OutputSection *sec);

uint64_t fileSize;
uint64_t sectionHeaderOff;
91};
92} // anonymous namespace

94static bool isSectionPrefix(StringRef prefix, StringRef name) {
return name.startswith(prefix) || name == prefix.drop_back();
96}

98StringRef elf::getOutputSectionName(const InputSectionBase *s) {
if (config->relocatable)
  return s->name;

// This is for --emit-relocs. If .text.foo is emitted as .text.bar, we want
// to emit .rela.text.foo as .rela.text.bar for consistency (this is not
// technically required, but not doing it is odd). This code guarantees that.
if (auto *isec = dyn_cast<InputSection>(s)) {
  if (InputSectionBase *rel = isec->getRelocatedSection()) {
    OutputSection *out = rel->getOutputSection();
    if (s->type == SHT_RELA)
      return saver.save(".rela" + out->name);
    return saver.save(".rel" + out->name);
  }
}

// A BssSection created for a common symbol is identified as "COMMON" in
// linker scripts. It should go to .bss section.
if (s->name == "COMMON")
  return ".bss";

if (script->hasSectionsCommand)
  return s->name;

// When no SECTIONS is specified, emulate GNU ld's internal linker scripts
// by grouping sections with certain prefixes.

// GNU ld places text sections with prefix ".text.hot.", ".text.unknown.",
// ".text.unlikely.", ".text.startup." or ".text.exit." before others.
// We provide an option -z keep-text-section-prefix to group such sections
// into separate output sections. This is more flexible. See also
// sortISDBySectionOrder().
// ".text.unknown" means the hotness of the section is unknown. When
// SampleFDO is used, if a function doesn't have sample, it could be very
// cold or it could be a new function never being sampled. Those functions
// will be kept in the ".text.unknown" section.
// ".text.split." holds symbols which are split out from functions in other
// input sections. For example, with -fsplit-machine-functions, placing the
// cold parts in .text.split instead of .text.unlikely mitigates against poor
// profile inaccuracy. Techniques such as hugepage remapping can make
// conservative decisions at the section granularity.
if (config->zKeepTextSectionPrefix)
  for (StringRef v : {".text.hot.", ".text.unknown.", ".text.unlikely.",
                      ".text.startup.", ".text.exit.", ".text.split."})
    if (isSectionPrefix(v, s->name))
      return v.drop_back();

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.", ".ARM.extab.",
      ".openbsd.randomdata."})
  if (isSectionPrefix(v, s->name))
    return v.drop_back();

return s->name;
154}

156static bool needsInterpSection() {
return !config->relocatable && !config->shared &&
       !config->dynamicLinker.empty() && script->needsInterpSection();
159}

161template <class ELFT> void elf::writeResult() {
Writer<ELFT>().run();
163}

165static void removeEmptyPTLoad(std::vector<PhdrEntry *> &phdrs) {
auto it = std::stable_partition(
    phdrs.begin(), phdrs.end(), [&](const PhdrEntry *p) {
      if (p->p_type != PT_LOAD)
        return true;
      if (!p->firstSec)
        return false;
      uint64_t size = p->lastSec->addr + p->lastSec->size - p->firstSec->addr;
      return size != 0;
    });

// Clear OutputSection::ptLoad for sections contained in removed
// segments.
DenseSet<PhdrEntry *> removed(it, phdrs.end());
for (OutputSection *sec : outputSections)
  if (removed.count(sec->ptLoad))
    sec->ptLoad = nullptr;
phdrs.erase(it, phdrs.end());
183}

185void elf::copySectionsIntoPartitions() {
std::vector<InputSectionBase *> newSections;
for (unsigned part = 2; part != partitions.size() + 1; ++part) {
  for (InputSectionBase *s : inputSections) {
    if (!(s->flags & SHF_ALLOC) || !s->isLive())
      continue;
    InputSectionBase *copy;
    if (s->type == SHT_NOTE)
      copy = make<InputSection>(cast<InputSection>(*s));
    else if (auto *es = dyn_cast<EhInputSection>(s))
      copy = make<EhInputSection>(*es);
    else
      continue;
    copy->partition = part;
    newSections.push_back(copy);
  }
}

inputSections.insert(inputSections.end(), newSections.begin(),
                     newSections.end());
205}

207void elf::combineEhSections() {
llvm::TimeTraceScope timeScope("Combine EH sections");
for (InputSectionBase *&s : inputSections) {
  // Ignore dead sections and the partition end marker (.part.end),
  // whose partition number is out of bounds.
  if (!s->isLive() || s->partition == 255)
    continue;

  Partition &part = s->getPartition();
  if (auto *es = dyn_cast<EhInputSection>(s)) {
    part.ehFrame->addSection(es);
    s = nullptr;
  } else if (s->kind() == SectionBase::Regular && part.armExidx &&
             part.armExidx->addSection(cast<InputSection>(s))) {
    s = nullptr;
  }
}

std::vector<InputSectionBase *> &v = inputSections;
v.erase(std::remove(v.begin(), v.end(), nullptr), v.end());
227}

229static Defined *addOptionalRegular(StringRef name, SectionBase *sec,
                                 uint64_t val, uint8_t stOther = STV_HIDDEN,
                                 uint8_t binding = STB_GLOBAL) {
Symbol *s = symtab->find(name);
if (!s || s->isDefined())
  return nullptr;

s->resolve(Defined{/*file=*/nullptr, name, binding, stOther, STT_NOTYPE, val,
                   /*size=*/0, sec});
return cast<Defined>(s);
239}

241static Defined *addAbsolute(StringRef name) {
Symbol *sym = symtab->addSymbol(Defined{nullptr, name, STB_GLOBAL, STV_HIDDEN,
                                        STT_NOTYPE, 0, 0, nullptr});
return cast<Defined>(sym);
245}

247// The linker is expected to define some symbols depending on
248// the linking result. This function defines such symbols.
249void elf::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 = addAbsolute("_gp");

  // On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
  // start of function and 'gp' pointer into GOT.
  if (symtab->find("_gp_disp"))
    ElfSym::mipsGpDisp = addAbsolute("_gp_disp");

  // 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->find("__gnu_local_gp"))
    ElfSym::mipsLocalGp = addAbsolute("__gnu_local_gp");
} else if (config->emachine == EM_PPC) {
  // glibc *crt1.o has a undefined reference to _SDA_BASE_. Since we don't
  // support Small Data Area, define it arbitrarily as 0.
  addOptionalRegular("_SDA_BASE_", nullptr, 0, STV_HIDDEN);
} else if (config->emachine == EM_PPC64) {
  addPPC64SaveRestore();
}

// The Power Architecture 64-bit v2 ABI defines a TableOfContents (TOC) which
// combines the typical ELF GOT with the small data sections. It commonly
// includes .got .toc .sdata .sbss. The .TOC. symbol replaces both
// _GLOBAL_OFFSET_TABLE_ and _SDA_BASE_ from the 32-bit ABI. It is used to
// represent the TOC base which is offset by 0x8000 bytes from the start of
// the .got section.
// We do not allow _GLOBAL_OFFSET_TABLE_ to be defined by input objects as the
// correctness of some relocations depends on its value.
StringRef gotSymName =
    (config->emachine == EM_PPC64) ? ".TOC." : "_GLOBAL_OFFSET_TABLE_";

if (Symbol *s = symtab->find(gotSymName)) {
  if (s->isDefined()) {
    error(toString(s->file) + " cannot redefine linker defined symbol '" +
          gotSymName + "'");
    return;
  }

  uint64_t gotOff = 0;
  if (config->emachine == EM_PPC64)
    gotOff = 0x8000;

  s->resolve(Defined{/*file=*/nullptr, gotSymName, STB_GLOBAL, STV_HIDDEN,
                     STT_NOTYPE, gotOff, /*size=*/0, Out::elfHeader});
  ElfSym::globalOffsetTable = cast<Defined>(s);
}

// __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.
addOptionalRegular("__ehdr_start", Out::elfHeader, 0, STV_HIDDEN);

// __executable_start is not documented, but the expectation of at
// least the Android libc is that it points to the ELF header.
addOptionalRegular("__executable_start", Out::elfHeader, 0, STV_HIDDEN);

// __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.
addOptionalRegular("__dso_handle", Out::elfHeader, 0, STV_HIDDEN);

// If linker script do layout we do not need to create any standard symbols.
if (script->hasSectionsCommand)
  return;

auto add = [](StringRef s, int64_t pos) {
  return addOptionalRegular(s, Out::elfHeader, pos, STV_DEFAULT);
};

ElfSym::bss = add("__bss_start", 0);
ElfSym::data = add("__data_start", 0);
ElfSym::end1 = add("end", -1);
ElfSym::end2 = add("_end", -1);
ElfSym::etext1 = add("etext", -1);
ElfSym::etext2 = add("_etext", -1);
ElfSym::edata1 = add("edata", -1);
ElfSym::edata2 = add("_edata", -1);
335}

337static OutputSection *findSection(StringRef name, unsigned partition = 1) {
for (BaseCommand *base : script->sectionCommands)
  if (auto *sec = dyn_cast<OutputSection>(base))
    if (sec->name == name && sec->partition == partition)
      return sec;
return nullptr;
343}

345template <class ELFT> void elf::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));

// Add the .interp section first because it is not a SyntheticSection.
// The removeUnusedSyntheticSections() function relies on the
// SyntheticSections coming last.
if (needsInterpSection()) {
  for (size_t i = 1; i <= partitions.size(); ++i) {
    InputSection *sec = createInterpSection();
    sec->partition = i;
    inputSections.push_back(sec);
  }
}

auto add = [](SyntheticSection *sec) { inputSections.push_back(sec); };

in.shStrTab = make<StringTableSection>(".shstrtab", false);

Out::programHeaders = make<OutputSection>("", 0, SHF_ALLOC);
Out::programHeaders->alignment = config->wordsize;

if (config->strip != StripPolicy::All) {
  in.strTab = make<StringTableSection>(".strtab", false);
  in.symTab = make<SymbolTableSection<ELFT>>(*in.strTab);
  in.symTabShndx = make<SymtabShndxSection>();
}

in.bss = make<BssSection>(".bss", 0, 1);
add(in.bss);

// If there is a SECTIONS command and a .data.rel.ro section name use name
// .data.rel.ro.bss so that we match in the .data.rel.ro output section.
// This makes sure our relro is contiguous.
bool hasDataRelRo =
    script->hasSectionsCommand && findSection(".data.rel.ro", 0);
in.bssRelRo =
    make<BssSection>(hasDataRelRo ? ".data.rel.ro.bss" : ".bss.rel.ro", 0, 1);
add(in.bssRelRo);

// Add MIPS-specific sections.
if (config->emachine == EM_MIPS) {
  if (!config->shared && config->hasDynSymTab) {
    in.mipsRldMap = make<MipsRldMapSection>();
    add(in.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);
}

StringRef relaDynName = config->isRela ? ".rela.dyn" : ".rel.dyn";

for (Partition &part : partitions) {
  auto add = [&](SyntheticSection *sec) {
    sec->partition = part.getNumber();
    inputSections.push_back(sec);
  };

  if (!part.name.empty()) {
    part.elfHeader = make<PartitionElfHeaderSection<ELFT>>();
    part.elfHeader->name = part.name;
    add(part.elfHeader);

    part.programHeaders = make<PartitionProgramHeadersSection<ELFT>>();
    add(part.programHeaders);
  }

  if (config->buildId != BuildIdKind::None) {
    part.buildId = make<BuildIdSection>();
    add(part.buildId);
  }

  part.dynStrTab = make<StringTableSection>(".dynstr", true);
  part.dynSymTab = make<SymbolTableSection<ELFT>>(*part.dynStrTab);
  part.dynamic = make<DynamicSection<ELFT>>();
  if (config->androidPackDynRelocs)
    part.relaDyn = make<AndroidPackedRelocationSection<ELFT>>(relaDynName);
  else
    part.relaDyn =
        make<RelocationSection<ELFT>>(relaDynName, config->zCombreloc);

  if (config->hasDynSymTab) {
    part.dynSymTab = make<SymbolTableSection<ELFT>>(*part.dynStrTab);
    add(part.dynSymTab);

    part.verSym = make<VersionTableSection>();
    add(part.verSym);

    if (!namedVersionDefs().empty()) {
      part.verDef = make<VersionDefinitionSection>();
      add(part.verDef);
    }

    part.verNeed = make<VersionNeedSection<ELFT>>();
    add(part.verNeed);

    if (config->gnuHash) {
      part.gnuHashTab = make<GnuHashTableSection>();
      add(part.gnuHashTab);
    }

    if (config->sysvHash) {
      part.hashTab = make<HashTableSection>();
      add(part.hashTab);
    }

    add(part.dynamic);
    add(part.dynStrTab);
    add(part.relaDyn);
  }

  if (config->relrPackDynRelocs) {
    part.relrDyn = make<RelrSection<ELFT>>();
    add(part.relrDyn);
  }

  if (!config->relocatable) {
    if (config->ehFrameHdr) {
      part.ehFrameHdr = make<EhFrameHeader>();
      add(part.ehFrameHdr);
    }
    part.ehFrame = make<EhFrameSection>();
    add(part.ehFrame);
  }

  if (config->emachine == EM_ARM && !config->relocatable) {
    // The ARMExidxsyntheticsection replaces all the individual .ARM.exidx
    // InputSections.
    part.armExidx = make<ARMExidxSyntheticSection>();
    add(part.armExidx);
  }
}

if (partitions.size() != 1) {
  // Create the partition end marker. This needs to be in partition number 255
  // so that it is sorted after all other partitions. It also has other
  // special handling (see createPhdrs() and combineEhSections()).
  in.partEnd = make<BssSection>(".part.end", config->maxPageSize, 1);
  in.partEnd->partition = 255;
  add(in.partEnd);

  in.partIndex = make<PartitionIndexSection>();
  addOptionalRegular("__part_index_begin", in.partIndex, 0);
  addOptionalRegular("__part_index_end", in.partIndex,
                     in.partIndex->getSize());
  add(in.partIndex);
}

// Add .got. MIPS' .got is so different from the other archs,
// it has its own class.
if (config->emachine == EM_MIPS) {
  in.mipsGot = make<MipsGotSection>();
  add(in.mipsGot);
} else {
  in.got = make<GotSection>();
  add(in.got);
}

if (config->emachine == EM_PPC) {
  in.ppc32Got2 = make<PPC32Got2Section>();
  add(in.ppc32Got2);
}

if (config->emachine == EM_PPC64) {
  in.ppc64LongBranchTarget = make<PPC64LongBranchTargetSection>();
  add(in.ppc64LongBranchTarget);
}

in.gotPlt = make<GotPltSection>();
add(in.gotPlt);
in.igotPlt = make<IgotPltSection>();
add(in.igotPlt);

// _GLOBAL_OFFSET_TABLE_ is defined relative to either .got.plt or .got. Treat
// it as a relocation and ensure the referenced section is created.
if (ElfSym::globalOffsetTable && config->emachine != EM_MIPS) {
  if (target->gotBaseSymInGotPlt)
    in.gotPlt->hasGotPltOffRel = true;
  else
    in.got->hasGotOffRel = true;
}

if (config->gdbIndex)
  add(GdbIndexSection::create<ELFT>());

// 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.relaPlt = make<RelocationSection<ELFT>>(
    config->isRela ? ".rela.plt" : ".rel.plt", /*sort=*/false);
add(in.relaPlt);

// The relaIplt immediately follows .rel[a].dyn to ensure that the IRelative
// relocations are processed last by the dynamic loader. We cannot place the
// iplt section in .rel.dyn when Android relocation packing is enabled because
// that would cause a section type mismatch. However, because the Android
// dynamic loader reads .rel.plt after .rel.dyn, we can get the desired
// behaviour by placing the iplt section in .rel.plt.
in.relaIplt = make<RelocationSection<ELFT>>(
    config->androidPackDynRelocs ? in.relaPlt->name : relaDynName,
    /*sort=*/false);
add(in.relaIplt);

if ((config->emachine == EM_386 || config->emachine == EM_X86_64) &&
    (config->andFeatures & GNU_PROPERTY_X86_FEATURE_1_IBT)) {
  in.ibtPlt = make<IBTPltSection>();
  add(in.ibtPlt);
}

in.plt = config->emachine == EM_PPC ? make<PPC32GlinkSection>()
                                    : make<PltSection>();
add(in.plt);
in.iplt = make<IpltSection>();
add(in.iplt);

if (config->andFeatures)
  add(make<GnuPropertySection>());

// .note.GNU-stack is always added when we are creating a re-linkable
// object file. Other linkers are using the presence of this marker
// section to control the executable-ness of the stack area, but that
// is irrelevant these days. Stack area should always be non-executable
// by default. So we emit this section unconditionally.
if (config->relocatable)
  add(make<GnuStackSection>());

if (in.symTab)
  add(in.symTab);
if (in.symTabShndx)
  add(in.symTabShndx);
add(in.shStrTab);
if (in.strTab)
  add(in.strTab);
582}

584// The main function of the writer.
585template <class ELFT> void Writer<ELFT>::run() {
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();
checkExecuteOnly();
if (errorCount())
  return;

// If -compressed-debug-sections is specified, we need to compress
// .debug_* sections. Do it right now because it changes the size of
// output sections.
for (OutputSection *sec : outputSections)
  sec->maybeCompress<ELFT>();

if (script->hasSectionsCommand)
  script->allocateHeaders(mainPart->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.
for (Partition &part : partitions)
  removeEmptyPTLoad(part.phdrs);

if (!config->oFormatBinary)
  assignFileOffsets();
else
  assignFileOffsetsBinary();

for (Partition &part : partitions)
  setPhdrs(part);

if (config->relocatable)
  for (OutputSection *sec : outputSections)
    sec->addr = 0;

// Handle --print-map(-M)/--Map, --cref and --print-archive-stats=. Dump them
// before checkSections() because the files may be useful in case
// checkSections() or openFile() fails, for example, due to an erroneous file
// size.
writeMapFile();
writeCrossReferenceTable();
writeArchiveStats();

if (config->checkSections)
  checkSections();

// It does not make sense try to open the file if we have error already.
if (errorCount())
  return;

{
  llvm::TimeTraceScope timeScope("Write output file");
  // Write the result down to a file.
  openFile();
  if (errorCount())
    return;

  if (!config->oFormatBinary) {
    if (config->zSeparate != SeparateSegmentKind::None)
      writeTrapInstr();
    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;

  if (auto e = buffer->commit())
    error("failed to write to the output file: " + toString(std::move(e)));
}
667}

669template <class ELFT, class RelTy>
670static void markUsedLocalSymbolsImpl(ObjFile<ELFT> *file,
                                   llvm::ArrayRef<RelTy> rels) {
for (const RelTy &rel : rels) {
  Symbol &sym = file->getRelocTargetSym(rel);
  if (sym.isLocal())
    sym.used = true;
}
677}

679// The function ensures that the "used" field of local symbols reflects the fact
680// that the symbol is used in a relocation from a live section.
681template <class ELFT> static void markUsedLocalSymbols() {
// With --gc-sections, the field is already filled.
// See MarkLive<ELFT>::resolveReloc().
if (config->gcSections)
  return;
// Without --gc-sections, the field is initialized with "true".
// Drop the flag first and then rise for symbols referenced in relocations.
for (InputFile *file : objectFiles) {
  ObjFile<ELFT> *f = cast<ObjFile<ELFT>>(file);
  for (Symbol *b : f->getLocalSymbols())
    b->used = false;
  for (InputSectionBase *s : f->getSections()) {
    InputSection *isec = dyn_cast_or_null<InputSection>(s);
    if (!isec)
      continue;
    if (isec->type == SHT_REL)
      markUsedLocalSymbolsImpl(f, isec->getDataAs<typename ELFT::Rel>());
    else if (isec->type == SHT_RELA)
      markUsedLocalSymbolsImpl(f, isec->getDataAs<typename ELFT::Rela>());
  }
}
702}

704static bool shouldKeepInSymtab(const Defined &sym) {
if (sym.isSection())
  return false;

// If --emit-reloc or -r is given, preserve symbols referenced by relocations
// from live sections.
if (config->copyRelocs && sym.used)
  return true;

// Exclude local symbols pointing to .ARM.exidx sections.
// They are probably mapping symbols "$d", which are optional for these
// sections. After merging the .ARM.exidx sections, some of these symbols
// may become dangling. The easiest way to avoid the issue is not to add
// them to the symbol table from the beginning.
if (config->emachine == EM_ARM && sym.section &&
    sym.section->type == SHT_ARM_EXIDX)
  return false;

if (config->discard == DiscardPolicy::None)
  return true;
if (config->discard == DiscardPolicy::All)
  return false;

// 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.
StringRef name = sym.getName();
bool isLocal = name.startswith(".L") || name.empty();
if (!isLocal)
  return true;

if (config->discard == DiscardPolicy::Locals)
  return false;

SectionBase *sec = sym.section;
return !sec || !(sec->flags & SHF_MERGE);
742}

744static bool includeInSymtab(const Symbol &b) {
if (!b.isLocal() && !b.isUsedInRegularObj)
  return false;

if (auto *d = dyn_cast<Defined>(&b)) {
  // Always include absolute symbols.
  SectionBase *sec = d->section;
  if (!sec)
    return true;
  sec = sec->repl;

  // Exclude symbols pointing to garbage-collected sections.
  if (isa<InputSectionBase>(sec) && !sec->isLive())
    return false;

  if (auto *s = dyn_cast<MergeInputSection>(sec))
    if (!s->getSectionPiece(d->value)->live)
      return false;
  return true;
}
return b.used;
765}

767// Local symbols are not in the linker's symbol table. This function scans
768// each object file's symbol table to copy local symbols to the output.
769template <class ELFT> void Writer<ELFT>::copyLocalSymbols() {
if (!in.symTab)
  return;
llvm::TimeTraceScope timeScope("Add local symbols");
if (config->copyRelocs && config->discard != DiscardPolicy::None)
  markUsedLocalSymbols<ELFT>();
for (InputFile *file : objectFiles) {
  ObjFile<ELFT> *f = cast<ObjFile<ELFT>>(file);
  for (Symbol *b : f->getLocalSymbols()) {
    assert(b->isLocal() && "should have been caught in initializeSymbols()")((void)0);
    auto *dr = dyn_cast<Defined>(b);

    // No reason to keep local undefined symbol in symtab.
    if (!dr)
      continue;
    if (!includeInSymtab(*b))
      continue;
    if (!shouldKeepInSymtab(*dr))
      continue;
    in.symTab->addSymbol(b);
  }
}
791}

793// Create a section symbol for each output section so that we can represent
794// relocations that point to the section. If we know that no relocation is
795// referring to a section (that happens if the section is a synthetic one), we
796// don't create a section symbol for that section.
797template <class ELFT> void Writer<ELFT>::addSectionSymbols() {
for (BaseCommand *base : script->sectionCommands) {
  auto *sec = dyn_cast<OutputSection>(base);
  if (!sec)
    continue;
  auto i = llvm::find_if(sec->sectionCommands, [](BaseCommand *base) {
    if (auto *isd = dyn_cast<InputSectionDescription>(base))
      return !isd->sections.empty();
    return false;
  });
  if (i == sec->sectionCommands.end())
    continue;
  InputSectionBase *isec = cast<InputSectionDescription>(*i)->sections[0];

  // Relocations are not using REL[A] section symbols.
  if (isec->type == SHT_REL || isec->type == SHT_RELA)
    continue;

  // Unlike other synthetic sections, mergeable output sections contain data
  // copied from input sections, and there may be a relocation pointing to its
  // contents if -r or -emit-reloc are given.
  if (isa<SyntheticSection>(isec) && !(isec->flags & SHF_MERGE))
    continue;

  // Set the symbol to be relative to the output section so that its st_value
  // equals the output section address. Note, there may be a gap between the
  // start of the output section and isec.
  auto *sym =
      make<Defined>(isec->file, "", STB_LOCAL, /*stOther=*/0, STT_SECTION,
                    /*value=*/0, /*size=*/0, isec->getOutputSection());
  in.symTab->addSymbol(sym);
}
829}

831// Today's loaders have a feature to make segments read-only after
832// processing dynamic relocations to enhance security. PT_GNU_RELRO
833// is defined for that.
834//
835// This function returns true if a section needs to be put into a
836// PT_GNU_RELRO segment.
837static bool 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 (in.got && sec == in.got->getParent())
  return true;

// .toc is a GOT-ish section for PowerPC64. Their contents are accessed
// through r2 register, which is reserved for that purpose. Since r2 is used
// for accessing .got as well, .got and .toc need to be close enough in the
// virtual address space. Usually, .toc comes just after .got. Since we place
// .got into RELRO, .toc needs to be placed into RELRO too.
if (sec->name.equals(".toc"))
  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 == in.gotPlt->getParent())
888#ifndef __OpenBSD__1
  return config->zNow;
890#else
  return true;	/* kbind(2) means we can always put these in RELRO */
892#endif

// .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->name == ".dynamic")
  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 == ".bss.rel.ro" || s == ".ctors" ||
       s == ".dtors" || s == ".jcr" || s == ".eh_frame" ||
       s == ".fini_array" || s == ".init_array" ||
       s == ".openbsd.randomdata" || s == ".preinit_array";
909}

911// We compute a rank for each section. The rank indicates where the
912// section should be placed in the file.  Instead of using simple
913// numbers (0,1,2...), we use a series of flags. One for each decision
914// point when placing the section.
915// Using flags has two key properties:
916// * It is easy to check if a give branch was taken.
917// * It is easy two see how similar two ranks are (see getRankProximity).
918enum RankFlags {
RF_NOT_ADDR_SET = 1 << 27,
RF_NOT_ALLOC = 1 << 26,
RF_PARTITION = 1 << 18, // Partition number (8 bits)
RF_NOT_PART_EHDR = 1 << 17,
RF_NOT_PART_PHDR = 1 << 16,
RF_NOT_INTERP = 1 << 15,
RF_NOT_NOTE = 1 << 14,
RF_WRITE = 1 << 13,
RF_EXEC_WRITE = 1 << 12,
RF_EXEC = 1 << 11,
RF_RODATA = 1 << 10,
RF_NOT_RELRO = 1 << 9,
RF_NOT_TLS = 1 << 8,
RF_BSS = 1 << 7,
RF_PPC_NOT_TOCBSS = 1 << 6,
RF_PPC_TOCL = 1 << 5,
RF_PPC_TOC = 1 << 4,
RF_PPC_GOT = 1 << 3,
RF_PPC_BRANCH_LT = 1 << 2,
RF_MIPS_GPREL = 1 << 1,
RF_MIPS_NOT_GOT = 1 << 0
940};

942static unsigned getSectionRank(const OutputSection *sec) {
unsigned rank = sec->partition * RF_PARTITION;

// 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;

// 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;

if (sec->type == SHT_LLVM_PART_EHDR)
  return rank;
rank |= RF_NOT_PART_EHDR;

if (sec->type == SHT_LLVM_PART_PHDR)
  return rank;
rank |= RF_NOT_PART_PHDR;

// 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;

// Put .note sections (which make up one PT_NOTE) at the beginning so that
// they are likely to be included in a core file even if core file size is
// limited. In particular, we want a .note.gnu.build-id and a .note.tag to be
// included in a core to match core files with executables.
if (sec->type == SHT_NOTE)
  return rank;
rank |= RF_NOT_NOTE;

// 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.
// * 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
    rank |= RF_EXEC;
} else if (isWrite) {
  rank |= RF_WRITE;
} else if (sec->type == SHT_PROGBITS) {
  // Make non-executable and non-writable PROGBITS sections (e.g .rodata
  // .eh_frame) closer to .text. They likely contain PC or GOT relative
  // relocations and there could be relocation overflow if other huge sections
  // (.dynstr .dynsym) were placed in between.
  rank |= RF_RODATA;
}

// Place RelRo sections first. After considering SHT_NOBITS below, the
// ordering is PT_LOAD(PT_GNU_RELRO(.data.rel.ro .bss.rel.ro) | .data .bss),
// where | marks where page alignment happens. An alternative ordering is
// PT_LOAD(.data | PT_GNU_RELRO( .data.rel.ro .bss.rel.ro) | .bss), but it may
// waste more bytes due to 2 alignment places.
if (!isRelroSection(sec))
  rank |= RF_NOT_RELRO;

// If we got here we know that both A and B are in the same PT_LOAD.

// 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. Since p_filesz can be less than p_memsz, place NOBITS sections
// after PROGBITS.
if (!(sec->flags & SHF_TLS))
  rank |= RF_NOT_TLS;

// Within TLS sections, or within other RelRo sections, or within non-RelRo
// sections, place non-NOBITS sections first.
if (sec->type == SHT_NOBITS)
  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 == ".toc1")
    rank |= RF_PPC_TOCL;

  if (name == ".toc")
    rank |= RF_PPC_TOC;

  if (name == ".got")
    rank |= RF_PPC_GOT;

  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;
1066}

1068static bool compareSections(const BaseCommand *aCmd, const BaseCommand *bCmd) {
const OutputSection *a = cast<OutputSection>(aCmd);
const OutputSection *b = cast<OutputSection>(bCmd);

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;
1079}

1081void PhdrEntry::add(OutputSection *sec) {
lastSec = sec;
if (!firstSec)
  firstSec = sec;
p_align = std::max(p_align, sec->alignment);
if (p_type == PT_LOAD)
  sec->ptLoad = this;
1088}

1090// The beginning and the ending of .rel[a].plt section are marked
1091// with __rel[a]_iplt_{start,end} symbols if it is a statically linked
1092// executable. The runtime needs these symbols in order to resolve
1093// all IRELATIVE relocs on startup. For dynamic executables, we don't
1094// need these symbols, since IRELATIVE relocs are resolved through GOT
1095// and PLT. For details, see http://www.airs.com/blog/archives/403.
1096template <class ELFT> void Writer<ELFT>::addRelIpltSymbols() {
if (config->relocatable || config->isPic)
  return;

// By default, __rela_iplt_{start,end} belong to a dummy section 0
// because .rela.plt might be empty and thus removed from output.
// We'll override Out::elfHeader with In.relaIplt later when we are
// sure that .rela.plt exists in output.
ElfSym::relaIpltStart = addOptionalRegular(
    config->isRela ? "__rela_iplt_start" : "__rel_iplt_start",
    Out::elfHeader, 0, STV_HIDDEN, STB_WEAK);

ElfSym::relaIpltEnd = addOptionalRegular(
    config->isRela ? "__rela_iplt_end" : "__rel_iplt_end",
    Out::elfHeader, 0, STV_HIDDEN, STB_WEAK);
1111}

1113template <class ELFT>
1114void Writer<ELFT>::forEachRelSec(
  llvm::function_ref<void(InputSectionBase &)> fn) {
// 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.
for (InputSectionBase *isec : inputSections)
  if (isec->isLive() && isa<InputSection>(isec) && (isec->flags & SHF_ALLOC))
    fn(*isec);
for (Partition &part : partitions) {
  for (EhInputSection *es : part.ehFrame->sections)
    fn(*es);
  if (part.armExidx && part.armExidx->isLive())
    for (InputSection *ex : part.armExidx->exidxSections)
      fn(*ex);
}
1131}

1133// This function generates assignments for predefined symbols (e.g. _end or
1134// _etext) and inserts them into the commands sequence to be processed at the
1135// appropriate time. This ensures that the value is going to be correct by the
1136// time any references to these symbols are processed and is equivalent to
1137// defining these symbols explicitly in the linker script.
1138template <class ELFT> void Writer<ELFT>::setReservedSymbolSections() {
if (ElfSym::globalOffsetTable) {
  // The _GLOBAL_OFFSET_TABLE_ symbol is defined by target convention usually
  // to the start of the .got or .got.plt section.
  InputSection *gotSection = in.gotPlt;
  if (!target->gotBaseSymInGotPlt)
    gotSection = in.mipsGot ? cast<InputSection>(in.mipsGot)
                            : cast<InputSection>(in.got);
  ElfSym::globalOffsetTable->section = gotSection;
}

// .rela_iplt_{start,end} mark the start and the end of in.relaIplt.
if (ElfSym::relaIpltStart && in.relaIplt->isNeeded()) {
  ElfSym::relaIpltStart->section = in.relaIplt;
  ElfSym::relaIpltEnd->section = in.relaIplt;
  ElfSym::relaIpltEnd->value = in.relaIplt->getSize();
}

PhdrEntry *last = nullptr;
PhdrEntry *lastRO = nullptr;

for (Partition &part : partitions) {
  for (PhdrEntry *p : part.phdrs) {
    if (p->p_type != PT_LOAD)
      continue;
    last = p;
    if (!(p->p_flags & PF_W))
      lastRO = p;
  }
}

if (lastRO) {
  // _etext is the first location after the last read-only loadable segment.
  if (ElfSym::etext1)
    ElfSym::etext1->section = lastRO->lastSec;
  if (ElfSym::etext2)
    ElfSym::etext2->section = lastRO->lastSec;
}

if (last) {
  // _edata points to the end of the last mapped initialized section.
  OutputSection *edata = nullptr;
  for (OutputSection *os : outputSections) {
    if (os->type != SHT_NOBITS)
      edata = os;
    if (os == last->lastSec)
      break;
  }

  if (ElfSym::edata1)
    ElfSym::edata1->section = edata;
  if (ElfSym::edata2)
    ElfSym::edata2->section = edata;

  // _end is the first location after the uninitialized data region.
  if (ElfSym::end1)
    ElfSym::end1->section = last->lastSec;
  if (ElfSym::end2)
    ElfSym::end2->section = last->lastSec;
}

if (ElfSym::bss)
  ElfSym::bss->section = findSection(".bss");

if (ElfSym::data)
  ElfSym::data->section = findSection(".data");

// Setup MIPS _gp_disp/__gnu_local_gp symbols which should
// be equal to the _gp symbol's value.
if (ElfSym::mipsGp) {
  // Find GP-relative section with the lowest address
  // and use this address to calculate default _gp value.
  for (OutputSection *os : outputSections) {
    if (os->flags & SHF_MIPS_GPREL) {
      ElfSym::mipsGp->section = os;
      ElfSym::mipsGp->value = 0x7ff0;
      break;
    }
  }
}
1218}

1220// We want to find how similar two ranks are.
1221// The more branches in getSectionRank that match, the more similar they are.
1222// Since each branch corresponds to a bit flag, we can just use
1223// countLeadingZeros.
1224static int getRankProximityAux(OutputSection *a, OutputSection *b) {
return countLeadingZeros(a->sortRank ^ b->sortRank);
1226}

1228static int getRankProximity(OutputSection *a, BaseCommand *b) {
auto *sec = dyn_cast<OutputSection>(b);
return (sec && sec->hasInputSections) ? getRankProximityAux(a, sec) : -1;
1231}

1233// When placing orphan sections, we want to place them after symbol assignments
1234// so that an orphan after
1235//   begin_foo = .;
1236//   foo : { *(foo) }
1237//   end_foo = .;
1238// doesn't break the intended meaning of the begin/end symbols.
1239// We don't want to go over sections since findOrphanPos is the
1240// one in charge of deciding the order of the sections.
1241// We don't want to go over changes to '.', since doing so in
1242//  rx_sec : { *(rx_sec) }
1243//  . = ALIGN(0x1000);
1244//  /* The RW PT_LOAD starts here*/
1245//  rw_sec : { *(rw_sec) }
1246// would mean that the RW PT_LOAD would become unaligned.
1247static bool shouldSkip(BaseCommand *cmd) {
if (auto *assign = dyn_cast<SymbolAssignment>(cmd))
  return assign->name != ".";
return false;
1251}

1253// We want to place orphan sections so that they share as much
1254// characteristics with their neighbors as possible. For example, if
1255// both are rw, or both are tls.
1256static std::vector<BaseCommand *>::iterator
1257findOrphanPos(std::vector<BaseCommand *>::iterator b,
            std::vector<BaseCommand *>::iterator e) {
OutputSection *sec = cast<OutputSection>(*e);

// 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 *curSec = dyn_cast<OutputSection>(*i);
  if (!curSec || !curSec->hasInputSections)
    continue;
  if (getRankProximity(sec, curSec) != proximity ||
      sec->sortRank < curSec->sortRank)
    break;
}

auto isOutputSecWithInputSections = [](BaseCommand *cmd) {
  auto *os = dyn_cast<OutputSection>(cmd);
  return os && os->hasInputSections;
};
auto j = std::find_if(llvm::make_reverse_iterator(i),
                      llvm::make_reverse_iterator(b),
                      isOutputSecWithInputSections);
i = j.base();

// As a special case, if the orphan section is the last section, put
// it at the very end, past any other commands.
// This matches bfd's behavior and is convenient when the linker script fully
// specifies the start of the file, but doesn't care about the end (the non
// alloc sections for example).
auto nextSec = std::find_if(i, e, isOutputSecWithInputSections);
if (nextSec == e)
  return e;

while (i != e && shouldSkip(*i))
  ++i;
return i;
1300}

1302// Adds random priorities to sections not already in the map.
1303static void maybeShuffle(DenseMap<const InputSectionBase *, int> &order) {
if (config->shuffleSections.empty())
  return;

std::vector<InputSectionBase *> matched, sections = inputSections;
matched.reserve(sections.size());
for (const auto &patAndSeed : config->shuffleSections) {
  matched.clear();
  for (InputSectionBase *sec : sections)
    if (patAndSeed.first.match(sec->name))
      matched.push_back(sec);
  const uint32_t seed = patAndSeed.second;
  if (seed == UINT32_MAX0xffffffffU) {
    // If --shuffle-sections <section-glob>=-1, reverse the section order. The
    // section order is stable even if the number of sections changes. This is
    // useful to catch issues like static initialization order fiasco
    // reliably.
    std::reverse(matched.begin(), matched.end());
  } else {
    std::mt19937 g(seed ? seed : std::random_device()());
    llvm::shuffle(matched.begin(), matched.end(), g);
  }
  size_t i = 0;
  for (InputSectionBase *&sec : sections)
    if (patAndSeed.first.match(sec->name))
      sec = matched[i++];
}

// Existing priorities are < 0, so use priorities >= 0 for the missing
// sections.
int prio = 0;
for (InputSectionBase *sec : sections) {
  if (order.try_emplace(sec, prio).second)
    ++prio;
}
1338}

1340// Builds section order for handling --symbol-ordering-file.
1341static DenseMap<const InputSectionBase *, int> buildSectionOrder() {
DenseMap<const InputSectionBase *, int> sectionOrder;
// Use the rarely used option -call-graph-ordering-file to sort sections.
if (!config->callGraphProfile.empty())
  return computeCallGraphProfileOrder();

if (config->symbolOrderingFile.empty())
  return sectionOrder;

struct SymbolOrderEntry {
  int priority;
  bool present;
};

// 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, SymbolOrderEntry> symbolOrder;
int priority = -config->symbolOrderingFile.size();
for (StringRef s : config->symbolOrderingFile)
  symbolOrder.insert({s, {priority++, false}});

// Build a map from sections to their priorities.
auto addSym = [&](Symbol &sym) {
  auto it = symbolOrder.find(sym.getName());
  if (it == symbolOrder.end())
    return;
  SymbolOrderEntry &ent = it->second;
  ent.present = true;

  maybeWarnUnorderableSymbol(&sym);

  if (auto *d = dyn_cast<Defined>(&sym)) {
    if (auto *sec = dyn_cast_or_null<InputSectionBase>(d->section)) {
      int &priority = sectionOrder[cast<InputSectionBase>(sec->repl)];
      priority = std::min(priority, ent.priority);
    }
  }
};

// We want both global and local symbols. We get the global ones from the
// symbol table and iterate the object files for the local ones.
for (Symbol *sym : symtab->symbols())
  if (!sym->isLazy())
    addSym(*sym);

for (InputFile *file : objectFiles)
  for (Symbol *sym : file->getSymbols()) {
    if (!sym->isLocal())
      break;
    addSym(*sym);
  }

if (config->warnSymbolOrdering)
  for (auto orderEntry : symbolOrder)
    if (!orderEntry.second.present)
      warn("symbol ordering file: no such symbol: " + orderEntry.first);

return sectionOrder;
1400}

1402// Sorts the sections in ISD according to the provided section order.
1403static void
1404sortISDBySectionOrder(InputSectionDescription *isd,
                    const DenseMap<const InputSectionBase *, int> &order) {
std::vector<InputSection *> unorderedSections;
std::vector<std::pair<InputSection *, int>> orderedSections;
uint64_t unorderedSize = 0;

for (InputSection *isec : isd->sections) {
  auto i = order.find(isec);
  if (i == order.end()) {
    unorderedSections.push_back(isec);
    unorderedSize += isec->getSize();
    continue;
  }
  orderedSections.push_back({isec, i->second});
}
llvm::sort(orderedSections, llvm::less_second());

// Find an insertion point for the ordered section list in the unordered
// section list. On targets with limited-range branches, this is the mid-point
// of the unordered section list. This decreases the likelihood that a range
// extension thunk will be needed to enter or exit the ordered region. If the
// ordered section list is a list of hot functions, we can generally expect
// the ordered functions to be called more often than the unordered functions,
// making it more likely that any particular call will be within range, and
// therefore reducing the number of thunks required.
//
// For example, imagine that you have 8MB of hot code and 32MB of cold code.
// If the layout is:
//
// 8MB hot
// 32MB cold
//
// only the first 8-16MB of the cold code (depending on which hot function it
// is actually calling) can call the hot code without a range extension thunk.
// However, if we use this layout:
//
// 16MB cold
// 8MB hot
// 16MB cold
//
// both the last 8-16MB of the first block of cold code and the first 8-16MB
// of the second block of cold code can call the hot code without a thunk. So
// we effectively double the amount of code that could potentially call into
// the hot code without a thunk.
size_t insPt = 0;
if (target->getThunkSectionSpacing() && !orderedSections.empty()) {
  uint64_t unorderedPos = 0;
  for (; insPt != unorderedSections.size(); ++insPt) {
    unorderedPos += unorderedSections[insPt]->getSize();
    if (unorderedPos > unorderedSize / 2)
      break;
  }
}

isd->sections.clear();
for (InputSection *isec : makeArrayRef(unorderedSections).slice(0, insPt))
  isd->sections.push_back(isec);
for (std::pair<InputSection *, int> p : orderedSections)
  isd->sections.push_back(p.first);
for (InputSection *isec : makeArrayRef(unorderedSections).slice(insPt))
  isd->sections.push_back(isec);
1465}

1467static void sortSection(OutputSection *sec,
                      const DenseMap<const InputSectionBase *, int> &order) {
StringRef name = sec->name;

// Never sort these.
if (name == ".init" || name == ".fini")
  return;

// IRelative relocations that usually live in the .rel[a].dyn section should
// be processed last by the dynamic loader. To achieve that we add synthetic
// sections in the required order from the beginning so that the in.relaIplt
// section is placed last in an output section. Here we just do not apply
// sorting for an output section which holds the in.relaIplt section.
if (in.relaIplt->getParent() == sec)
  return;

// Sort input sections by priority using the list provided by
// --symbol-ordering-file or --shuffle-sections=. This is a least significant
// digit radix sort. The sections may be sorted stably again by a more
// significant key.
if (!order.empty())
  for (BaseCommand *b : sec->sectionCommands)
    if (auto *isd = dyn_cast<InputSectionDescription>(b))
      sortISDBySectionOrder(isd, order);

// Sort input sections by section name suffixes for
// __attribute__((init_priority(N))).
if (name == ".init_array" || name == ".fini_array") {
  if (!script->hasSectionsCommand)
    sec->sortInitFini();
  return;
}

// Sort input sections by the special rule for .ctors and .dtors.
if (name == ".ctors" || name == ".dtors") {
  if (!script->hasSectionsCommand)
    sec->sortCtorsDtors();
  return;
}

// .toc is allocated just after .got and is accessed using GOT-relative
// relocations. Object files compiled with small code model have an
// addressable range of [.got, .got + 0xFFFC] for GOT-relative relocations.
// To reduce the risk of relocation overflow, .toc contents are sorted so that
// sections having smaller relocation offsets are at beginning of .toc
if (config->emachine == EM_PPC64 && name == ".toc") {
  if (script->hasSectionsCommand)
    return;
  assert(sec->sectionCommands.size() == 1)((void)0);
  auto *isd = cast<InputSectionDescription>(sec->sectionCommands[0]);
  llvm::stable_sort(isd->sections,
                    [](const InputSection *a, const InputSection *b) -> bool {
                      return a->file->ppc64SmallCodeModelTocRelocs &&
                             !b->file->ppc64SmallCodeModelTocRelocs;
                    });
  return;
}
1524}

1526// If no layout was provided by linker script, we want to apply default
1527// sorting for special input sections. This also handles --symbol-ordering-file.
1528template <class ELFT> void Writer<ELFT>::sortInputSections() {
// Build the order once since it is expensive.
DenseMap<const InputSectionBase *, int> order = buildSectionOrder();
maybeShuffle(order);
for (BaseCommand *base : script->sectionCommands)
  if (auto *sec = dyn_cast<OutputSection>(base))
    sortSection(sec, order);
1535}

1537template <class ELFT> void Writer<ELFT>::sortSections() {
llvm::TimeTraceScope timeScope("Sort sections");
script->adjustSectionsBeforeSorting();

// 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;

sortInputSections();

for (BaseCommand *base : script->sectionCommands) {
  auto *os = dyn_cast<OutputSection>(base);
  if (!os)
    continue;
  os->sortRank = getSectionRank(os);

  // We want to assign rude approximation values to outSecOff fields
  // to know the relative order of the input sections. We use it for
  // sorting SHF_LINK_ORDER sections. See resolveShfLinkOrder().
  uint64_t i = 0;
  for (InputSection *sec : getInputSections(os))
    sec->outSecOff = i++;
}

if (!script->hasSectionsCommand) {
  // We know that all the OutputSections are contiguous in this case.
  auto isSection = [](BaseCommand *base) { return isa<OutputSection>(base); };
  std::stable_sort(
      llvm::find_if(script->sectionCommands, isSection),
      llvm::find_if(llvm::reverse(script->sectionCommands), isSection).base(),
      compareSections);

  // Process INSERT commands. From this point onwards the order of
  // script->sectionCommands is fixed.
  script->processInsertCommands();
  return;
}

script->processInsertCommands();

// 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 can share
//    a PT_LOAD.
//
// There is some ambiguity as to where exactly a new entry should be
// inserted, because 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->sectionCommands.begin();
auto e = script->sectionCommands.end();
auto nonScriptI = std::find_if(i, e, [](BaseCommand *base) {
  if (auto *sec = dyn_cast<OutputSection>(base))
    return sec->sectionIndex == UINT32_MAX0xffffffffU;
  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(i, nonScriptI);
  OutputSection *orphan = cast<OutputSection>(*nonScriptI);

  // 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<OutputSection>(cmd)->sortRank != rank;
  });
  std::rotate(pos, nonScriptI, end);
  nonScriptI = end;
}

script->adjustSectionsAfterSorting();
1654}

1656static bool compareByFilePosition(InputSection *a, InputSection *b) {
InputSection *la = a->flags & SHF_LINK_ORDER ? a->getLinkOrderDep() : nullptr;
InputSection *lb = b->flags & SHF_LINK_ORDER ? b->getLinkOrderDep() : nullptr;
// SHF_LINK_ORDER sections with non-zero sh_link are ordered before
// non-SHF_LINK_ORDER sections and SHF_LINK_ORDER sections with zero sh_link.
if (!la || !lb)
  return la && !lb;
OutputSection *aOut = la->getParent();
OutputSection *bOut = lb->getParent();

if (aOut != bOut)
  return aOut->addr < bOut->addr;
return la->outSecOff < lb->outSecOff;
1669}

1671template <class ELFT> void Writer<ELFT>::resolveShfLinkOrder() {
llvm::TimeTraceScope timeScope("Resolve SHF_LINK_ORDER");
for (OutputSection *sec : outputSections) {
  if (!(sec->flags & SHF_LINK_ORDER))
    continue;

  // The ARM.exidx section use SHF_LINK_ORDER, but we have consolidated
  // this processing inside the ARMExidxsyntheticsection::finalizeContents().
  if (!config->relocatable && config->emachine == EM_ARM &&
      sec->type == SHT_ARM_EXIDX)
    continue;

  // Link order may be distributed across several InputSectionDescriptions.
  // Sorting is performed separately.
  std::vector<InputSection **> scriptSections;
  std::vector<InputSection *> sections;
  for (BaseCommand *base : sec->sectionCommands) {
    auto *isd = dyn_cast<InputSectionDescription>(base);
    if (!isd)
      continue;
    bool hasLinkOrder = false;
    scriptSections.clear();
    sections.clear();
    for (InputSection *&isec : isd->sections) {
      if (isec->flags & SHF_LINK_ORDER) {
        InputSection *link = isec->getLinkOrderDep();
        if (link && !link->getParent())
          error(toString(isec) + ": sh_link points to discarded section " +
                toString(link));
        hasLinkOrder = true;
      }
      scriptSections.push_back(&isec);
      sections.push_back(isec);
    }
    if (hasLinkOrder && errorCount() == 0) {
      llvm::stable_sort(sections, compareByFilePosition);
      for (int i = 0, n = sections.size(); i != n; ++i)
        *scriptSections[i] = sections[i];
    }
  }
}
1712}

1714static void finalizeSynthetic(SyntheticSection *sec) {
if (sec && sec->isNeeded() && sec->getParent()) {
  llvm::TimeTraceScope timeScope("Finalize synthetic sections", sec->name);
  sec->finalizeContents();
}
1719}

1721// We need to generate and finalize the content that depends on the address of
1722// InputSections. As the generation of the content may also alter InputSection
1723// addresses we must converge to a fixed point. We do that here. See the comment
1724// in Writer<ELFT>::finalizeSections().
1725template <class ELFT> void Writer<ELFT>::finalizeAddressDependentContent() {
llvm::TimeTraceScope timeScope("Finalize address dependent content");
ThunkCreator tc;
AArch64Err843419Patcher a64p;
ARMErr657417Patcher a32p;
script->assignAddresses();
// .ARM.exidx and SHF_LINK_ORDER do not require precise addresses, but they
// do require the relative addresses of OutputSections because linker scripts
// can assign Virtual Addresses to OutputSections that are not monotonically
// increasing.
for (Partition &part : partitions)
  finalizeSynthetic(part.armExidx);
resolveShfLinkOrder();

// Converts call x@GDPLT to call __tls_get_addr
if (config->emachine == EM_HEXAGON)
  hexagonTLSSymbolUpdate(outputSections);

int assignPasses = 0;
for (;;) {
  bool changed = target->needsThunks && tc.createThunks(outputSections);

  // With Thunk Size much smaller than branch range we expect to
  // converge quickly; if we get to 15 something has gone wrong.
  if (changed && tc.pass >= 15) {
    error("thunk creation not converged");
    break;
  }

  if (config->fixCortexA53Errata843419) {
    if (changed)
      script->assignAddresses();
    changed |= a64p.createFixes();
  }
  if (config->fixCortexA8) {
    if (changed)
      script->assignAddresses();
    changed |= a32p.createFixes();
  }

  if (in.mipsGot)
    in.mipsGot->updateAllocSize();

  for (Partition &part : partitions) {
    changed |= part.relaDyn->updateAllocSize();
    if (part.relrDyn)
      changed |= part.relrDyn->updateAllocSize();
  }

  const Defined *changedSym = script->assignAddresses();
  if (!changed) {
    // Some symbols may be dependent on section addresses. When we break the
    // loop, the symbol values are finalized because a previous
    // assignAddresses() finalized section addresses.
    if (!changedSym)
      break;
    if (++assignPasses == 5) {
      errorOrWarn("assignment to symbol " + toString(*changedSym) +
                  " does not converge");
      break;
    }
  }
}

// If addrExpr is set, the address may not be a multiple of the alignment.
// Warn because this is error-prone.
for (BaseCommand *cmd : script->sectionCommands)
  if (auto *os = dyn_cast<OutputSection>(cmd))
    if (os->addr % os->alignment != 0)
      warn("address (0x" + Twine::utohexstr(os->addr) + ") of section " +
           os->name + " is not a multiple of alignment (" +
           Twine(os->alignment) + ")");
1797}

1799// If Input Sections have been shrunk (basic block sections) then
1800// update symbol values and sizes associated with these sections.  With basic
1801// block sections, input sections can shrink when the jump instructions at
1802// the end of the section are relaxed.
1803static void fixSymbolsAfterShrinking() {
for (InputFile *File : objectFiles) {
  parallelForEach(File->getSymbols(), [&](Symbol *Sym) {
    auto *def = dyn_cast<Defined>(Sym);
    if (!def)
      return;

    const SectionBase *sec = def->section;
    if (!sec)
      return;

    const InputSectionBase *inputSec = dyn_cast<InputSectionBase>(sec->repl);
    if (!inputSec || !inputSec->bytesDropped)
      return;

    const size_t OldSize = inputSec->data().size();
    const size_t NewSize = OldSize - inputSec->bytesDropped;

    if (def->value > NewSize && def->value <= OldSize) {
      LLVM_DEBUG(llvm::dbgs()do { } while (false)
                 << "Moving symbol " << Sym->getName() << " from "do { } while (false)
                 << def->value << " to "do { } while (false)
                 << def->value - inputSec->bytesDropped << " bytes\n")do { } while (false);
      def->value -= inputSec->bytesDropped;
      return;
    }

    if (def->value + def->size > NewSize && def->value <= OldSize &&
        def->value + def->size <= OldSize) {
      LLVM_DEBUG(llvm::dbgs()do { } while (false)
                 << "Shrinking symbol " << Sym->getName() << " from "do { } while (false)
                 << def->size << " to " << def->size - inputSec->bytesDroppeddo { } while (false)
                 << " bytes\n")do { } while (false);
      def->size -= inputSec->bytesDropped;
    }
  });
}
1840}

1842// If basic block sections exist, there are opportunities to delete fall thru
1843// jumps and shrink jump instructions after basic block reordering.  This
1844// relaxation pass does that.  It is only enabled when --optimize-bb-jumps
1845// option is used.
1846template <class ELFT> void Writer<ELFT>::optimizeBasicBlockJumps() {
assert(config->optimizeBBJumps)((void)0);

script->assignAddresses();
// For every output section that has executable input sections, this
// does the following:
//   1. Deletes all direct jump instructions in input sections that
//      jump to the following section as it is not required.
//   2. If there are two consecutive jump instructions, it checks
//      if they can be flipped and one can be deleted.
for (OutputSection *os : outputSections) {
  if (!(os->flags & SHF_EXECINSTR))
    continue;
  std::vector<InputSection *> sections = getInputSections(os);
  std::vector<unsigned> result(sections.size());
  // Delete all fall through jump instructions.  Also, check if two
  // consecutive jump instructions can be flipped so that a fall
  // through jmp instruction can be deleted.
  parallelForEachN(0, sections.size(), [&](size_t i) {
    InputSection *next = i + 1 < sections.size() ? sections[i + 1] : nullptr;
    InputSection &is = *sections[i];
    result[i] =
        target->deleteFallThruJmpInsn(is, is.getFile<ELFT>(), next) ? 1 : 0;
  });
  size_t numDeleted = std::count(result.begin(), result.end(), 1);
  if (numDeleted > 0) {
    script->assignAddresses();
    LLVM_DEBUG(llvm::dbgs()do { } while (false)
               << "Removing " << numDeleted << " fall through jumps\n")do { } while (false);
  }
}

fixSymbolsAfterShrinking();

for (OutputSection *os : outputSections) {
  std::vector<InputSection *> sections = getInputSections(os);
  for (InputSection *is : sections)
    is->trim();
}
1885}

1887// In order to allow users to manipulate linker-synthesized sections,
1888// we had to add synthetic sections to the input section list early,
1889// even before we make decisions whether they are needed. This allows
1890// users to write scripts like this: ".mygot : { .got }".
1891//
1892// Doing it has an unintended side effects. If it turns out that we
1893// don't need a .got (for example) at all because there's no
1894// relocation that needs a .got, we don't want to emit .got.
1895//
1896// To deal with the above problem, this function is called after
1897// scanRelocations is called to remove synthetic sections that turn
1898// out to be empty.
1899static void removeUnusedSyntheticSections() {
// All input synthetic sections that can be empty are placed after
// all regular ones. Reverse iterate to find the first synthetic section
// after a non-synthetic one which will be our starting point.
auto start = std::find_if(inputSections.rbegin(), inputSections.rend(),
                          [](InputSectionBase *s) {
                            return !isa<SyntheticSection>(s);
                          })
                 .base();

DenseSet<InputSectionDescription *> isdSet;
// Mark unused synthetic sections for deletion
auto end = std::stable_partition(
20
←
Calling 'stable_partition<std::__wrap_iter<lld::elf::InputSectionBase **>, (lambda at /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp:1912:35)>'→
    start, inputSections.end(), [&](InputSectionBase *s) {
      SyntheticSection *ss = dyn_cast<SyntheticSection>(s);
25
←
Assuming 's' is not a 'SyntheticSection'→
26
←
'ss' initialized to a null pointer value→
      OutputSection *os = ss->getParent();
27
←
Called C++ object pointer is null
      if (!os || ss->isNeeded())
        return true;

      // If we reach here, then ss is an unused synthetic section and we want
      // to remove it from the corresponding input section description, and
      // orphanSections.
      for (BaseCommand *b : os->sectionCommands)
        if (auto *isd = dyn_cast<InputSectionDescription>(b))
          isdSet.insert(isd);

      llvm::erase_if(
          script->orphanSections,
          [=](const InputSectionBase *isec) { return isec == ss; });

      return false;
    });

DenseSet<InputSectionBase *> unused(end, inputSections.end());
for (auto *isd : isdSet)
  llvm::erase_if(isd->sections,
                 [=](InputSection *isec) { return unused.count(isec); });

// Erase unused synthetic sections.
inputSections.erase(end, inputSections.end());
1939}

1941// Create output section objects and add them to OutputSections.
1942template <class ELFT> void Writer<ELFT>::finalizeSections() {
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) {
1
Assuming field 'relocatable' is true→
2
←
Taking false branch→
  addStartEndSymbols();
  for (BaseCommand *base : script->sectionCommands)
    if (auto *sec = dyn_cast<OutputSection>(base))
      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 (mainPart->dynamic->parent)
3
←
Assuming field 'parent' is null→
4
←
Taking false branch→
  symtab->addSymbol(Defined{/*file=*/nullptr, "_DYNAMIC", STB_WEAK,
                            STV_HIDDEN, STT_NOTYPE,
                            /*value=*/0, /*size=*/0, mainPart->dynamic});

// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();

// RISC-V's gp can address +/- 2 KiB, set it to .sdata + 0x800. This symbol
// should only be defined in an executable. If .sdata does not exist, its
// value/section does not matter but it has to be relative, so set its
// st_shndx arbitrarily to 1 (Out::elfHeader).
if (config->emachine == EM_RISCV && !config->shared) {
5
←
Assuming field 'emachine' is not equal to EM_RISCV→
  OutputSection *sec = findSection(".sdata");
  ElfSym::riscvGlobalPointer =
      addOptionalRegular("__global_pointer$", sec ? sec : Out::elfHeader,
                         0x800, STV_DEFAULT, STB_GLOBAL);
}

if (config->emachine == EM_X86_64) {
6
←
Assuming field 'emachine' is not equal to EM_X86_64→
7
←
Taking false branch→
  // On targets that support TLSDESC, _TLS_MODULE_BASE_ is defined in such a
  // way that:
  //
  // 1) Without relaxation: it produces a dynamic TLSDESC relocation that
  // computes 0.
  // 2) With LD->LE relaxation: _TLS_MODULE_BASE_@tpoff = 0 (lowest address in
  // the TLS block).
  //
  // 2) is special cased in @tpoff computation. To satisfy 1), we define it as
  // an absolute symbol of zero. This is different from GNU linkers which
  // define _TLS_MODULE_BASE_ relative to the first TLS section.
  Symbol *s = symtab->find("_TLS_MODULE_BASE_");
  if (s && s->isUndefined()) {
    s->resolve(Defined{/*file=*/nullptr, s->getName(), STB_GLOBAL, STV_HIDDEN,
                       STT_TLS, /*value=*/0, 0,
                       /*section=*/nullptr});
    ElfSym::tlsModuleBase = cast<Defined>(s);
  }
}

{
  llvm::TimeTraceScope timeScope("Finalize .eh_frame");
  // This responsible for splitting up .eh_frame section into
  // pieces. The relocation scan uses those pieces, so this has to be
  // earlier.
  for (Partition &part : partitions)
    finalizeSynthetic(part.ehFrame);
}

for (Symbol *sym : symtab->symbols())
  sym->isPreemptible = computeIsPreemptible(*sym);

// Change values of linker-script-defined symbols from placeholders (assigned
// by declareSymbols) to actual definitions.
script->processSymbolAssignments();

{
  llvm::TimeTraceScope timeScope("Scan relocations");
  // Scan relocations. This must be done after every symbol is declared so
  // that we can correctly decide if a dynamic relocation is needed. This is
  // called after processSymbolAssignments() because it needs to know whether
  // a linker-script-defined symbol is absolute.
  ppc64noTocRelax.clear();
  if (!config->relocatable) {
8
←
Assuming field 'relocatable' is true→
9
←
Taking false branch→
    forEachRelSec(scanRelocations<ELFT>);
    reportUndefinedSymbols<ELFT>();
  }
}

if (in.plt && in.plt->isNeeded())
10
←
Assuming field 'plt' is null→
  in.plt->addSymbols();
if (in.iplt && in.iplt->isNeeded())
11
←
Assuming field 'iplt' is null→
  in.iplt->addSymbols();

if (config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore) {
12
←
Assuming field 'unresolvedSymbolsInShlib' is equal to Ignore→
13
←
Taking false branch→
  auto diagnose =
      config->unresolvedSymbolsInShlib == UnresolvedPolicy::ReportError
          ? errorOrWarn
          : warn;
  // Error on undefined symbols in a shared object, if all of its DT_NEEDED
  // entries are seen. These cases would otherwise lead to runtime errors
  // reported by the dynamic linker.
  //
  // ld.bfd traces all DT_NEEDED to emulate the logic of the dynamic linker to
  // catch more cases. That is too much for us. Our approach resembles the one
  // used in ld.gold, achieves a good balance to be useful but not too smart.
  for (SharedFile *file : sharedFiles) {
    bool allNeededIsKnown =
        llvm::all_of(file->dtNeeded, [&](StringRef needed) {
          return symtab->soNames.count(needed);
        });
    if (!allNeededIsKnown)
      continue;
    for (Symbol *sym : file->requiredSymbols)
      if (sym->isUndefined() && !sym->isWeak())
        diagnose(toString(file) + ": undefined reference to " +
                 toString(*sym) + " [--no-allow-shlib-undefined]");
  }
}

{
  llvm::TimeTraceScope timeScope("Add symbols to symtabs");
  // Now that we have defined all possible global symbols including linker-
  // synthesized ones. Visit all symbols to give the finishing touches.
  for (Symbol *sym : symtab->symbols()) {
    if (!includeInSymtab(*sym))
      continue;
    if (in.symTab)
      in.symTab->addSymbol(sym);

    if (sym->includeInDynsym()) {
      partitions[sym->partition - 1].dynSymTab->addSymbol(sym);
      if (auto *file = dyn_cast_or_null<SharedFile>(sym->file))
        if (file->isNeeded && !sym->isUndefined())
          addVerneed(sym);
    }
  }

  // We also need to scan the dynamic relocation tables of the other
  // partitions and add any referenced symbols to the partition's dynsym.
  for (Partition &part : MutableArrayRef<Partition>(partitions).slice(1)) {
14
←
Assuming '__begin2' is equal to '__end2'→
    DenseSet<Symbol *> syms;
    for (const SymbolTableEntry &e : part.dynSymTab->getSymbols())
      syms.insert(e.sym);
    for (DynamicReloc &reloc : part.relaDyn->relocs)
      if (reloc.sym && reloc.needsDynSymIndex() &&
          syms.insert(reloc.sym).second)
        part.dynSymTab->addSymbol(reloc.sym);
  }
}

// Do not proceed if there was an undefined symbol.
if (errorCount())
15
←
Assuming the condition is false→
16
←
Taking false branch→
  return;

if (in.mipsGot)
17
←
Assuming field 'mipsGot' is null→
18
←
Taking false branch→
  in.mipsGot->build();

removeUnusedSyntheticSections();
19
←
Calling 'removeUnusedSyntheticSections'→
script->diagnoseOrphanHandling();

sortSections();

// Now that we have the final list, create a list of all the
// OutputSections for convenience.
for (BaseCommand *base : script->sectionCommands)
  if (auto *sec = dyn_cast<OutputSection>(base))
    outputSections.push_back(sec);

// Prefer command line supplied address over other constraints.
for (OutputSection *sec : outputSections) {
  auto i = config->sectionStartMap.find(sec->name);
  if (i != config->sectionStartMap.end())
    sec->addrExpr = [=] { return i->second; };
}

// With the outputSections available check for GDPLT relocations
// and add __tls_get_addr symbol if needed.
if (config->emachine == EM_HEXAGON && hexagonNeedsTLSSymbol(outputSections)) {
  Symbol *sym = symtab->addSymbol(Undefined{
      nullptr, "__tls_get_addr", STB_GLOBAL, STV_DEFAULT, STT_NOTYPE});
  sym->isPreemptible = true;
  partitions[0].dynSymTab->addSymbol(sym);
}

// This is a bit of a hack. A value of 0 means undef, so we set it
// to 1 to make __ehdr_start defined. The section number is not
// particularly relevant.
Out::elfHeader->sectionIndex = 1;

for (size_t i = 0, e = outputSections.size(); i != e; ++i) {
  OutputSection *sec = outputSections[i];
  sec->sectionIndex = i + 1;
  sec->shName = in.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) {
  for (Partition &part : partitions) {
    part.phdrs = script->hasPhdrsCommands() ? script->createPhdrs()
                                            : createPhdrs(part);
    if (config->emachine == EM_ARM) {
      // PT_ARM_EXIDX is the ARM EHABI equivalent of PT_GNU_EH_FRAME
      addPhdrForSection(part, SHT_ARM_EXIDX, PT_ARM_EXIDX, PF_R);
    }
    if (config->emachine == EM_MIPS) {
      // Add separate segments for MIPS-specific sections.
      addPhdrForSection(part, SHT_MIPS_REGINFO, PT_MIPS_REGINFO, PF_R);
      addPhdrForSection(part, SHT_MIPS_OPTIONS, PT_MIPS_OPTIONS, PF_R);
      addPhdrForSection(part, SHT_MIPS_ABIFLAGS, PT_MIPS_ABIFLAGS, PF_R);
    }
  }
  Out::programHeaders->size = sizeof(Elf_Phdr) * mainPart->phdrs.size();

  // Find the TLS segment. This happens before the section layout loop so that
  // Android relocation packing can look up TLS symbol addresses. We only need
  // to care about the main partition here because all TLS symbols were moved
  // to the main partition (see MarkLive.cpp).
  for (PhdrEntry *p : mainPart->phdrs)
    if (p->p_type == PT_TLS)
      Out::tlsPhdr = p;
}

// Some symbols are defined in term of program headers. Now that we
// have the headers, we can find out which sections they point to.
setReservedSymbolSections();

{
  llvm::TimeTraceScope timeScope("Finalize synthetic sections");

  finalizeSynthetic(in.bss);
  finalizeSynthetic(in.bssRelRo);
  finalizeSynthetic(in.symTabShndx);
  finalizeSynthetic(in.shStrTab);
  finalizeSynthetic(in.strTab);
  finalizeSynthetic(in.got);
  finalizeSynthetic(in.mipsGot);
  finalizeSynthetic(in.igotPlt);
  finalizeSynthetic(in.gotPlt);
  finalizeSynthetic(in.relaIplt);
  finalizeSynthetic(in.relaPlt);
  finalizeSynthetic(in.plt);
  finalizeSynthetic(in.iplt);
  finalizeSynthetic(in.ppc32Got2);
  finalizeSynthetic(in.partIndex);

  // Dynamic section must be the last one in this list and dynamic
  // symbol table section (dynSymTab) must be the first one.
  for (Partition &part : partitions) {
    finalizeSynthetic(part.dynSymTab);
    finalizeSynthetic(part.gnuHashTab);
    finalizeSynthetic(part.hashTab);
    finalizeSynthetic(part.verDef);
    finalizeSynthetic(part.relaDyn);
    finalizeSynthetic(part.relrDyn);
    finalizeSynthetic(part.ehFrameHdr);
    finalizeSynthetic(part.verSym);
    finalizeSynthetic(part.verNeed);
    finalizeSynthetic(part.dynamic);
  }
}

if (!script->hasSectionsCommand && !config->relocatable)
  fixSectionAlignments();

// This is used to:
// 1) Create "thunks":
//    Jump instructions in many ISAs have small displacements, and therefore
//    they cannot jump to arbitrary addresses in memory. For example, RISC-V
//    JAL instruction can target only +-1 MiB from PC. It is a linker's
//    responsibility to create and insert small pieces of code between
//    sections to extend the ranges if jump targets are out of range. Such
//    code pieces are called "thunks".
//
//    We add thunks at this stage. We couldn't do this before this point
//    because this is the earliest point where we know sizes of sections and
//    their layouts (that are needed to determine if jump targets are in
//    range).
//
// 2) Update the sections. We need to generate content that depends on the
//    address of InputSections. For example, MIPS GOT section content or
//    android packed relocations sections content.
//
// 3) Assign the final values for the linker script symbols. Linker scripts
//    sometimes using forward symbol declarations. We want to set the correct
//    values. They also might change after adding the thunks.
finalizeAddressDependentContent();
if (errorCount())
  return;

{
  llvm::TimeTraceScope timeScope("Finalize synthetic sections");
  // finalizeAddressDependentContent may have added local symbols to the
  // static symbol table.
  finalizeSynthetic(in.symTab);
  finalizeSynthetic(in.ppc64LongBranchTarget);
}

// Relaxation to delete inter-basic block jumps created by basic block
// sections. Run after in.symTab is finalized as optimizeBasicBlockJumps
// can relax jump instructions based on symbol offset.
if (config->optimizeBBJumps)
  optimizeBasicBlockJumps();

// 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 (OutputSection *sec : outputSections)
  sec->finalize();
2252}

2254// Ensure data sections are not mixed with executable sections when
2255// -execute-only is used. -execute-only is a feature to make pages executable
2256// but not readable, and the feature is currently supported only on AArch64.
2257template <class ELFT> void Writer<ELFT>::checkExecuteOnly() {
if (!config->executeOnly)
  return;

for (OutputSection *os : outputSections)
  if (os->flags & SHF_EXECINSTR)
    for (InputSection *isec : getInputSections(os))
      if (!(isec->flags & SHF_EXECINSTR))
        error("cannot place " + toString(isec) + " into " + toString(os->name) +
              ": -execute-only does not support intermingling data and code");
2267}

2269// The linker is expected to define SECNAME_start and SECNAME_end
2270// symbols for a few sections. This function defines them.
2271template <class ELFT> void Writer<ELFT>::addStartEndSymbols() {
// If a section does not exist, there's ambiguity as to how we
// define _start and _end symbols for an init/fini section. Since
// the loader assume that the symbols are always defined, we need to
// always define them. But what value? The loader iterates over all
// pointers between _start and _end to run global ctors/dtors, so if
// the section is empty, their symbol values don't actually matter
// as long as _start and _end point to the same location.
//
// That said, we don't want to set the symbols to 0 (which is
// probably the simplest value) because that could cause some
// program to fail to link due to relocation overflow, if their
// program text is above 2 GiB. We use the address of the .text
// section instead to prevent that failure.
//
// In rare situations, the .text section may not exist. If that's the
// case, use the image base address as a last resort.
OutputSection *Default = findSection(".text");
if (!Default)
  Default = Out::elfHeader;

auto define = [=](StringRef start, StringRef end, OutputSection *os) {
  if (os) {
    addOptionalRegular(start, os, 0);
    addOptionalRegular(end, os, -1);
  } else {
    addOptionalRegular(start, Default, 0);
    addOptionalRegular(end, Default, 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);
2308}

2310// If a section name is valid as a C identifier (which is rare because of
2311// the leading '.'), linkers are expected to define __start_<secname> and
2312// __stop_<secname> symbols. They are at beginning and end of the section,
2313// respectively. This is not requested by the ELF standard, but GNU ld and
2314// gold provide the feature, and used by many programs.
2315template <class ELFT>
2316void Writer<ELFT>::addStartStopSymbols(OutputSection *sec) {
StringRef s = sec->name;
if (!isValidCIdentifier(s))
  return;
addOptionalRegular(saver.save("__start_" + s), sec, 0,
                   config->zStartStopVisibility);
addOptionalRegular(saver.save("__stop_" + s), sec, -1,
                   config->zStartStopVisibility);
2324}

2326static 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;
2336}

2338// Linker scripts are responsible for aligning addresses. Unfortunately, most
2339// linker scripts are designed for creating two PT_LOADs only, one RX and one
2340// RW. This means that there is no alignment in the RO to RX transition and we
2341// cannot create a PT_LOAD there.
2342static uint64_t computeFlags(uint64_t flags) {
if (config->omagic)
  return PF_R | PF_W | PF_X;
if (config->executeOnly && (flags & PF_X))
  return flags & ~PF_R;
if (config->singleRoRx && !(flags & PF_W))
  return flags | PF_X;
return flags;
2350}

2352// Decide which program headers to create and which sections to include in each
2353// one.
2354template <class ELFT>
2355std::vector<PhdrEntry *> Writer<ELFT>::createPhdrs(Partition &part) {
std::vector<PhdrEntry *> ret;
auto addHdr = [&](unsigned type, unsigned flags) -> PhdrEntry * {
  ret.push_back(make<PhdrEntry>(type, flags));
  return ret.back();
};

unsigned partNo = part.getNumber();
bool isMain = partNo == 1;

// Add the first PT_LOAD segment for regular output sections.
uint64_t flags = computeFlags(PF_R);
PhdrEntry *load = nullptr;

// nmagic or omagic output does not have PT_PHDR, PT_INTERP, or the readonly
// PT_LOAD.
if (!config->nmagic && !config->omagic) {
  // The first phdr entry is PT_PHDR which describes the program header
  // itself.
  if (isMain)
    addHdr(PT_PHDR, PF_R)->add(Out::programHeaders);
  else
    addHdr(PT_PHDR, PF_R)->add(part.programHeaders->getParent());

  // PT_INTERP must be the second entry if exists.
  if (OutputSection *cmd = findSection(".interp", partNo))
    addHdr(PT_INTERP, cmd->getPhdrFlags())->add(cmd);

  // Add the headers. We will remove them if they don't fit.
  // In the other partitions the headers are ordinary sections, so they don't
  // need to be added here.
  if (isMain) {
    load = addHdr(PT_LOAD, flags);
    load->add(Out::elfHeader);
    load->add(Out::programHeaders);
  }
}

// PT_GNU_RELRO includes all sections that should be marked as
// read-only by dynamic linker after processing relocations.
// Current dynamic loaders only support one PT_GNU_RELRO PHDR, give
// an error message if more than one PT_GNU_RELRO PHDR is required.
PhdrEntry *relRo = make<PhdrEntry>(PT_GNU_RELRO, PF_R);
bool inRelroPhdr = false;
OutputSection *relroEnd = nullptr;
for (OutputSection *sec : outputSections) {
  if (sec->partition != partNo || !needsPtLoad(sec))
    continue;
  if (isRelroSection(sec)) {
    inRelroPhdr = true;
    if (!relroEnd)
      relRo->add(sec);
    else
      error("section: " + sec->name + " is not contiguous with other relro" +
            " sections");
  } else if (inRelroPhdr) {
    inRelroPhdr = false;
    relroEnd = sec;
  }
}

for (OutputSection *sec : outputSections) {
  if (!needsPtLoad(sec))
    continue;

  // Normally, sections in partitions other than the current partition are
  // ignored. But partition number 255 is a special case: it contains the
  // partition end marker (.part.end). It needs to be added to the main
  // partition so that a segment is created for it in the main partition,
  // which will cause the dynamic loader to reserve space for the other
  // partitions.
  if (sec->partition != partNo) {
    if (isMain && sec->partition == 255)
      addHdr(PT_LOAD, computeFlags(sec->getPhdrFlags()))->add(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 or memory
  // region using AT or AT> linker script command, respectively. At the same
  // time, we don't want to create a separate load segment for the headers,
  // even if the first output section has an AT or AT> attribute.
  uint64_t newFlags = computeFlags(sec->getPhdrFlags());
  bool sameLMARegion =
      load && !sec->lmaExpr && sec->lmaRegion == load->firstSec->lmaRegion;
  if (!(load && newFlags == flags && sec != relroEnd &&
        sec->memRegion == load->firstSec->memRegion &&
        (sameLMARegion || load->lastSec == Out::programHeaders))) {
    load = addHdr(PT_LOAD, newFlags);
    flags = newFlags;
  }

  load->add(sec);
}

// Add a TLS segment if any.
PhdrEntry *tlsHdr = make<PhdrEntry>(PT_TLS, PF_R);
for (OutputSection *sec : outputSections)
  if (sec->partition == partNo && sec->flags & SHF_TLS)
    tlsHdr->add(sec);
if (tlsHdr->firstSec)
  ret.push_back(tlsHdr);

// Add an entry for .dynamic.
if (OutputSection *sec = part.dynamic->getParent())
  addHdr(PT_DYNAMIC, sec->getPhdrFlags())->add(sec);

if (relRo->firstSec)
  ret.push_back(relRo);

// PT_GNU_EH_FRAME is a special section pointing on .eh_frame_hdr.
if (part.ehFrame->isNeeded() && part.ehFrameHdr &&
    part.ehFrame->getParent() && part.ehFrameHdr->getParent())
  addHdr(PT_GNU_EH_FRAME, part.ehFrameHdr->getParent()->getPhdrFlags())
      ->add(part.ehFrameHdr->getParent());

// PT_OPENBSD_RANDOMIZE is an OpenBSD-specific feature. That makes
// the dynamic linker fill the segment with random data.
if (OutputSection *cmd = findSection(".openbsd.randomdata", partNo))
  addHdr(PT_OPENBSD_RANDOMIZE, cmd->getPhdrFlags())->add(cmd);

if (config->zGnustack != GnuStackKind::None) {
  // 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 = PF_R | PF_W;
  if (config->zGnustack == GnuStackKind::Exec)
    perm |= PF_X;
  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);

if (OutputSection *cmd = findSection(".note.gnu.property", partNo))
  addHdr(PT_GNU_PROPERTY, PF_R)->add(cmd);

// Create one PT_NOTE per a group of contiguous SHT_NOTE sections with the
// same alignment.
PhdrEntry *note = nullptr;
for (OutputSection *sec : outputSections) {
  if (sec->partition != partNo)
    continue;
  if (sec->type == SHT_NOTE && (sec->flags & SHF_ALLOC)) {
    if (!note || sec->lmaExpr || note->lastSec->alignment != sec->alignment)
      note = addHdr(PT_NOTE, PF_R);
    note->add(sec);
  } else {
    note = nullptr;
  }
}
return ret;
2514}

2516template <class ELFT>
2517void Writer<ELFT>::addPhdrForSection(Partition &part, unsigned shType,
                                   unsigned pType, unsigned pFlags) {
unsigned partNo = part.getNumber();
auto i = llvm::find_if(outputSections, [=](OutputSection *cmd) {
  return cmd->partition == partNo && cmd->type == shType;
});
if (i == outputSections.end())
  return;

PhdrEntry *entry = make<PhdrEntry>(pType, pFlags);
entry->add(*i);
part.phdrs.push_back(entry);
2529}

2531// Place the first section of each PT_LOAD to a different page (of maxPageSize).
2532// This is achieved by assigning an alignment expression to addrExpr of each
2533// such section.
2534template <class ELFT> void Writer<ELFT>::fixSectionAlignments() {
const PhdrEntry *prev;
auto pageAlign = [&](const PhdrEntry *p) {
  OutputSection *cmd = p->firstSec;
  if (!cmd)
    return;
  cmd->alignExpr = [align = cmd->alignment]() { return align; };
  if (!cmd->addrExpr) {
    // Prefer advancing to align(dot, maxPageSize) + dot%maxPageSize to avoid
    // padding in the file contents.
    //
    // When -z separate-code is used we must not have any overlap in pages
    // between an executable segment and a non-executable segment. We align to
    // the next maximum page size boundary on transitions between executable
    // and non-executable segments.
    //
    // SHT_LLVM_PART_EHDR marks the start of a partition. The partition
    // sections will be extracted to a separate file. Align to the next
    // maximum page size boundary so that we can find the ELF header at the
    // start. We cannot benefit from overlapping p_offset ranges with the
    // previous segment anyway.
    if (config->zSeparate == SeparateSegmentKind::Loadable ||
        (config->zSeparate == SeparateSegmentKind::Code && prev &&
         (prev->p_flags & PF_X) != (p->p_flags & PF_X)) ||
        cmd->type == SHT_LLVM_PART_EHDR)
      cmd->addrExpr = [] {
        return alignTo(script->getDot(), config->maxPageSize);
      };
    // PT_TLS is at the start of the first RW PT_LOAD. If `p` includes PT_TLS,
    // it must be the RW. Align to p_align(PT_TLS) to make sure
    // p_vaddr(PT_LOAD)%p_align(PT_LOAD) = 0. Otherwise, if
    // sh_addralign(.tdata) < sh_addralign(.tbss), we will set p_align(PT_TLS)
    // to sh_addralign(.tbss), while p_vaddr(PT_TLS)=p_vaddr(PT_LOAD) may not
    // be congruent to 0 modulo p_align(PT_TLS).
    //
    // Technically this is not required, but as of 2019, some dynamic loaders
    // don't handle p_vaddr%p_align != 0 correctly, e.g. glibc (i386 and
    // x86-64) doesn't make runtime address congruent to p_vaddr modulo
    // p_align for dynamic TLS blocks (PR/24606), FreeBSD rtld has the same
    // bug, musl (TLS Variant 1 architectures) before 1.1.23 handled TLS
    // blocks correctly. We need to keep the workaround for a while.
    else if (Out::tlsPhdr && Out::tlsPhdr->firstSec == p->firstSec)
      cmd->addrExpr = [] {
        return alignTo(script->getDot(), config->maxPageSize) +
               alignTo(script->getDot() % config->maxPageSize,
                       Out::tlsPhdr->p_align);
      };
    else
      cmd->addrExpr = [] {
        return alignTo(script->getDot(), config->maxPageSize) +
               script->getDot() % config->maxPageSize;
      };
  }
};

2589#ifdef __OpenBSD__1
// On i386, produce binaries that are compatible with our W^X implementation
if (config->emachine == EM_386) {
  auto NXAlign = [](OutputSection *Cmd) {
    if (Cmd && !Cmd->addrExpr)
      Cmd->addrExpr = [=] {
        return alignTo(script->getDot(), 0x20000000);
      };
  };

  for (Partition &part : partitions) {
    PhdrEntry *firstRW = nullptr;
    for (PhdrEntry *P : part.phdrs) {
      if (P->p_type == PT_LOAD && (P->p_flags & PF_W)) {
        firstRW = P;
        break;
      }
    }

    if (firstRW)
      NXAlign(firstRW->firstSec);
  }
}
2612#endif

for (Partition &part : partitions) {
  prev = nullptr;
  for (const PhdrEntry *p : part.phdrs)
    if (p->p_type == PT_LOAD && p->firstSec) {
      pageAlign(p);
      prev = p;
    }
}
2622}

2624// Compute an in-file position for a given section. The file offset must be the
2625// same with its virtual address modulo the page size, so that the loader can
2626// load executables without any address adjustment.
2627static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {
// The first section in a PT_LOAD has to have congruent offset and address
// modulo the maximum page size.
if (os->ptLoad && os->ptLoad->firstSec == os)
  return alignTo(off, os->ptLoad->p_align, os->addr);

// File offsets are not significant for .bss sections other than the first one
// in a PT_LOAD. By convention, we keep section offsets monotonically
// increasing rather than setting to zero.
 if (os->type == SHT_NOBITS)
   return off;

// If the section is not in a PT_LOAD, we just have to align it.
if (!os->ptLoad)
  return alignTo(off, os->alignment);

// If two sections share the same PT_LOAD the file offset is calculated
// using this formula: Off2 = Off1 + (VA2 - VA1).
OutputSection *first = os->ptLoad->firstSec;
return first->offset + os->addr - first->addr;
2647}

2649// Set an in-file position to a given section and returns the end position of
2650// the section.
2651static uint64_t setFileOffset(OutputSection *os, uint64_t off) {
off = computeFileOffset(os, off);
os->offset = off;

if (os->type == SHT_NOBITS)
  return off;
return off + os->size;
2658}

2660template <class ELFT> void Writer<ELFT>::assignFileOffsetsBinary() {
// Compute the minimum LMA of all non-empty non-NOBITS sections as minAddr.
auto needsOffset = [](OutputSection &sec) {
  return sec.type != SHT_NOBITS && (sec.flags & SHF_ALLOC) && sec.size > 0;
};
uint64_t minAddr = UINT64_MAX0xffffffffffffffffULL;
for (OutputSection *sec : outputSections)
  if (needsOffset(*sec)) {
    sec->offset = sec->getLMA();
    minAddr = std::min(minAddr, sec->offset);
  }

// Sections are laid out at LMA minus minAddr.
fileSize = 0;
for (OutputSection *sec : outputSections)
  if (needsOffset(*sec)) {
    sec->offset -= minAddr;
    fileSize = std::max(fileSize, sec->offset + sec->size);
  }
2679}

2681static std::string rangeToString(uint64_t addr, uint64_t len) {
return "[0x" + utohexstr(addr) + ", 0x" + utohexstr(addr + len - 1) + "]";
2683}

2685// Assign file offsets to output sections.
2686template <class ELFT> void Writer<ELFT>::assignFileOffsets() {
uint64_t off = 0;
off = setFileOffset(Out::elfHeader, off);
off = setFileOffset(Out::programHeaders, off);

PhdrEntry *lastRX = nullptr;
for (Partition &part : partitions)
  for (PhdrEntry *p : part.phdrs)
    if (p->p_type == PT_LOAD && (p->p_flags & PF_X))
      lastRX = p;

// Layout SHF_ALLOC sections before non-SHF_ALLOC sections. A non-SHF_ALLOC
// will not occupy file offsets contained by a PT_LOAD.
for (OutputSection *sec : outputSections) {
  if (!(sec->flags & SHF_ALLOC))
    continue;
  off = setFileOffset(sec, off);

  // If this is a last section of the last executable segment and that
  // segment is the last loadable segment, align the offset of the
  // following section to avoid loading non-segments parts of the file.
  if (config->zSeparate != SeparateSegmentKind::None && lastRX &&
      lastRX->lastSec == sec)
    off = alignTo(off, config->commonPageSize);
}
for (OutputSection *sec : outputSections)
  if (!(sec->flags & SHF_ALLOC))
    off = setFileOffset(sec, off);

sectionHeaderOff = alignTo(off, config->wordsize);
fileSize = sectionHeaderOff + (outputSections.size() + 1) * sizeof(Elf_Shdr);

// Our logic assumes that sections have rising VA within the same segment.
// With use of linker scripts it is possible to violate this rule and get file
// offset overlaps or overflows. That should never happen with a valid script
// which does not move the location counter backwards and usually scripts do
// not do that. Unfortunately, there are apps in the wild, for example, Linux
// kernel, which control segment distribution explicitly and move the counter
// backwards, so we have to allow doing that to support linking them. We
// perform non-critical checks for overlaps in checkSectionOverlap(), but here
// we want to prevent file size overflows because it would crash the linker.
for (OutputSection *sec : outputSections) {
  if (sec->type == SHT_NOBITS)
    continue;
  if ((sec->offset > fileSize) || (sec->offset + sec->size > fileSize))
    error("unable to place section " + sec->name + " at file offset " +
          rangeToString(sec->offset, sec->size) +
          "; check your linker script for overflows");
}
2735}

2737// Finalize the program headers. We call this function after we assign
2738// file offsets and VAs to all sections.
2739template <class ELFT> void Writer<ELFT>::setPhdrs(Partition &part) {
for (PhdrEntry *p : part.phdrs) {
  OutputSection *first = p->firstSec;
  OutputSection *last = p->lastSec;

  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;

    // File offsets in partitions other than the main partition are relative
    // to the offset of the ELF headers. Perform that adjustment now.
    if (part.elfHeader)
      p->p_offset -= part.elfHeader->getParent()->offset;

    if (!p->hasLMA)
      p->p_paddr = first->getLMA();
  }

  if (p->p_type == PT_GNU_RELRO) {
    p->p_align = 1;
    // musl/glibc ld.so 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_offset + p->p_memsz, config->commonPageSize) -
                 p->p_offset;
  }
}
2771}

2773// A helper struct for checkSectionOverlap.
2774namespace {
2775struct SectionOffset {
OutputSection *sec;
uint64_t offset;
2778};
2779} // namespace

2781// Check whether sections overlap for a specific address range (file offsets,
2782// load and virtual addresses).
2783static void checkOverlap(StringRef name, std::vector<SectionOffset> &sections,
                       bool isVirtualAddr) {
llvm::sort(sections, [=](const SectionOffset &a, const SectionOffset &b) {
  return a.offset < b.offset;
});

// Finding overlap is easy given a vector is sorted by start position.
// If an element starts before the end of the previous element, they overlap.
for (size_t i = 1, end = sections.size(); i < end; ++i) {
  SectionOffset a = sections[i - 1];
  SectionOffset b = sections[i];
  if (b.offset >= a.offset + a.sec->size)
    continue;

  // If both sections are in OVERLAY we allow the overlapping of virtual
  // addresses, because it is what OVERLAY was designed for.
  if (isVirtualAddr && a.sec->inOverlay && b.sec->inOverlay)
    continue;

  errorOrWarn("section " + a.sec->name + " " + name +
              " range overlaps with " + b.sec->name + "\n>>> " + a.sec->name +
              " range is " + rangeToString(a.offset, a.sec->size) + "\n>>> " +
              b.sec->name + " range is " +
              rangeToString(b.offset, b.sec->size));
}
2808}

2810// Check for overlapping sections and address overflows.
2811//
2812// In this function we check that none of the output sections have overlapping
2813// file offsets. For SHF_ALLOC sections we also check that the load address
2814// ranges and the virtual address ranges don't overlap
2815template <class ELFT> void Writer<ELFT>::checkSections() {
// First, check that section's VAs fit in available address space for target.
for (OutputSection *os : outputSections)
  if ((os->addr + os->size < os->addr) ||
      (!ELFT::Is64Bits && os->addr + os->size > UINT32_MAX0xffffffffU))
    errorOrWarn("section " + os->name + " at 0x" + utohexstr(os->addr) +
                " of size 0x" + utohexstr(os->size) +
                " exceeds available address space");

// Check for overlapping file offsets. In this case we need to skip any
// section marked as SHT_NOBITS. These sections don't actually occupy space in
// the file so Sec->Offset + Sec->Size can overlap with others. If --oformat
// binary is specified only add SHF_ALLOC sections are added to the output
// file so we skip any non-allocated sections in that case.
std::vector<SectionOffset> fileOffs;
for (OutputSection *sec : outputSections)
  if (sec->size > 0 && sec->type != SHT_NOBITS &&
      (!config->oFormatBinary || (sec->flags & SHF_ALLOC)))
    fileOffs.push_back({sec, sec->offset});
checkOverlap("file", fileOffs, false);

// When linking with -r there is no need to check for overlapping virtual/load
// addresses since those addresses will only be assigned when the final
// executable/shared object is created.
if (config->relocatable)
  return;

// Checking for overlapping virtual and load addresses only needs to take
// into account SHF_ALLOC sections since others will not be loaded.
// Furthermore, we also need to skip SHF_TLS sections since these will be
// mapped to other addresses at runtime and can therefore have overlapping
// ranges in the file.
std::vector<SectionOffset> vmas;
for (OutputSection *sec : outputSections)
  if (sec->size > 0 && (sec->flags & SHF_ALLOC) && !(sec->flags & SHF_TLS))
    vmas.push_back({sec, sec->addr});
checkOverlap("virtual address", vmas, true);

// Finally, check that the load addresses don't overlap. This will usually be
// the same as the virtual addresses but can be different when using a linker
// script with AT().
std::vector<SectionOffset> lmas;
for (OutputSection *sec : outputSections)
  if (sec->size > 0 && (sec->flags & SHF_ALLOC) && !(sec->flags & SHF_TLS))
    lmas.push_back({sec, sec->getLMA()});
checkOverlap("load address", lmas, false);
2861}

2863// The entry point address is chosen in the following ways.
2864//
2865// 1. the '-e' entry command-line option;
2866// 2. the ENTRY(symbol) command in a linker control script;
2867// 3. the value of the symbol _start, if present;
2868// 4. the number represented by the entry symbol, if it is a number;
2869// 5. the address of the first byte of the .text section, if present;
2870// 6. the address 0.
2871static uint64_t getEntryAddr() {
// Case 1, 2 or 3
if (Symbol *b = symtab->find(config->entry))
  return b->getVA();

// Case 4
uint64_t addr;
if (to_integer(config->entry, addr))
  return addr;

// Case 5
if (OutputSection *sec = findSection(".text")) {
  if (config->warnMissingEntry)
    warn("cannot find entry symbol " + config->entry + "; defaulting to 0x" +
         utohexstr(sec->addr));
  return sec->addr;
}

// Case 6
if (config->warnMissingEntry)
  warn("cannot find entry symbol " + config->entry +
       "; not setting start address");
return 0;
2894}

2896static uint16_t getELFType() {
if (config->isPic)
  return ET_DYN;
if (config->relocatable)
  return ET_REL;
return ET_EXEC;
2902}

2904template <class ELFT> void Writer<ELFT>::writeHeader() {
writeEhdr<ELFT>(Out::bufferStart, *mainPart);
writePhdrs<ELFT>(Out::bufferStart + sizeof(Elf_Ehdr), *mainPart);

auto *eHdr = reinterpret_cast<Elf_Ehdr *>(Out::bufferStart);
eHdr->e_type = getELFType();
eHdr->e_entry = getEntryAddr();
eHdr->e_shoff = sectionHeaderOff;

// Write the section header table.
//
// The ELF header can only store numbers up to SHN_LORESERVE in the e_shnum
// and e_shstrndx fields. When the value of one of these fields exceeds
// SHN_LORESERVE ELF requires us to put sentinel values in the ELF header and
// use fields in the section header at index 0 to store
// the value. The sentinel values and fields are:
// e_shnum = 0, SHdrs[0].sh_size = number of sections.
// e_shstrndx = SHN_XINDEX, SHdrs[0].sh_link = .shstrtab section index.
auto *sHdrs = reinterpret_cast<Elf_Shdr *>(Out::bufferStart + eHdr->e_shoff);
size_t num = outputSections.size() + 1;
if (num >= SHN_LORESERVE)
  sHdrs->sh_size = num;
else
  eHdr->e_shnum = num;

uint32_t strTabIndex = in.shStrTab->getParent()->sectionIndex;
if (strTabIndex >= SHN_LORESERVE) {
  sHdrs->sh_link = strTabIndex;
  eHdr->e_shstrndx = SHN_XINDEX;
} else {
  eHdr->e_shstrndx = strTabIndex;
}

for (OutputSection *sec : outputSections)
  sec->writeHeaderTo<ELFT>(++sHdrs);
2939}

2941// Open a result file.
2942template <class ELFT> void Writer<ELFT>::openFile() {
uint64_t maxSize = config->is64 ? INT64_MAX0x7fffffffffffffffLL : UINT32_MAX0xffffffffU;
if (fileSize != size_t(fileSize) || maxSize < fileSize) {
  std::string msg;
  raw_string_ostream s(msg);
  s << "output file too large: " << Twine(fileSize) << " bytes\n"
    << "section sizes:\n";
  for (OutputSection *os : outputSections)
    s << os->name << ' ' << os->size << "\n";
  error(s.str());
  return;
}

unlinkAsync(config->outputFile);
unsigned flags = 0;
if (!config->relocatable)
  flags |= FileOutputBuffer::F_executable;
if (!config->mmapOutputFile)
  flags |= FileOutputBuffer::F_no_mmap;
Expected<std::unique_ptr<FileOutputBuffer>> bufferOrErr =
    FileOutputBuffer::create(config->outputFile, fileSize, flags);

if (!bufferOrErr) {
  error("failed to open " + config->outputFile + ": " +
        llvm::toString(bufferOrErr.takeError()));
  return;
}
buffer = std::move(*bufferOrErr);
Out::bufferStart = buffer->getBufferStart();
2971}

2973template <class ELFT> void Writer<ELFT>::writeSectionsBinary() {
for (OutputSection *sec : outputSections)
  if (sec->flags & SHF_ALLOC)
    sec->writeTo<ELFT>(Out::bufferStart + sec->offset);
2977}

2979static void fillTrap(uint8_t *i, uint8_t *end) {
for (; i + 4 <= end; i += 4)
  memcpy(i, &target->trapInstr, 4);
2982}

2984// Fill the last page of executable segments with trap instructions
2985// instead of leaving them as zero. Even though it is not required by any
2986// standard, it is in general a good thing to do for security reasons.
2987//
2988// We'll leave other pages in segments as-is because the rest will be
2989// overwritten by output sections.
2990template <class ELFT> void Writer<ELFT>::writeTrapInstr() {
for (Partition &part : partitions) {
  // Fill the last page.
  for (PhdrEntry *p : part.phdrs)
    if (p->p_type == PT_LOAD && (p->p_flags & PF_X))
      fillTrap(Out::bufferStart + alignDown(p->firstSec->offset + p->p_filesz,
                                            config->commonPageSize),
               Out::bufferStart + alignTo(p->firstSec->offset + p->p_filesz,
                                          config->commonPageSize));

  // Round up the file size of the last segment to the page boundary iff it is
  // an executable segment to ensure that other tools don't accidentally
  // trim the instruction padding (e.g. when stripping the file).
  PhdrEntry *last = nullptr;
  for (PhdrEntry *p : part.phdrs)
    if (p->p_type == PT_LOAD)
      last = p;

  if (last && (last->p_flags & PF_X))
    last->p_memsz = last->p_filesz =
        alignTo(last->p_filesz, config->commonPageSize);
}
3012}

3014// Write section contents to a mmap'ed file.
3015template <class ELFT> void Writer<ELFT>::writeSections() {
// 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 (OutputSection *sec : outputSections)
  if (sec->type == SHT_REL || sec->type == SHT_RELA)
    sec->writeTo<ELFT>(Out::bufferStart + sec->offset);

for (OutputSection *sec : outputSections)
  if (sec->type != SHT_REL && sec->type != SHT_RELA)
    sec->writeTo<ELFT>(Out::bufferStart + sec->offset);

// Finally, check that all dynamic relocation addends were written correctly.
if (config->checkDynamicRelocs && config->writeAddends) {
  for (OutputSection *sec : outputSections)
    if (sec->type == SHT_REL || sec->type == SHT_RELA)
      sec->checkDynRelAddends(Out::bufferStart);
}
3033}

3035// Computes a hash value of Data using a given hash function.
3036// In order to utilize multiple cores, we first split data into 1MB
3037// chunks, compute a hash for each chunk, and then compute a hash value
3038// of the hash values.
3039static void
3040computeHash(llvm::MutableArrayRef<uint8_t> hashBuf,
          llvm::ArrayRef<uint8_t> data,
          std::function<void(uint8_t *dest, ArrayRef<uint8_t> arr)> hashFn) {
std::vector<ArrayRef<uint8_t>> chunks = split(data, 1024 * 1024);
std::vector<uint8_t> hashes(chunks.size() * hashBuf.size());

// Compute hash values.
parallelForEachN(0, chunks.size(), [&](size_t i) {
  hashFn(hashes.data() + i * hashBuf.size(), chunks[i]);
});

// Write to the final output buffer.
hashFn(hashBuf.data(), hashes);
3053}

3055template <class ELFT> void Writer<ELFT>::writeBuildId() {
if (!mainPart->buildId || !mainPart->buildId->getParent())
  return;

if (config->buildId == BuildIdKind::Hexstring) {
  for (Partition &part : partitions)
    part.buildId->writeBuildId(config->buildIdVector);
  return;
}

// Compute a hash of all sections of the output file.
size_t hashSize = mainPart->buildId->hashSize;
std::vector<uint8_t> buildId(hashSize);
llvm::ArrayRef<uint8_t> buf{Out::bufferStart, size_t(fileSize)};

switch (config->buildId) {
case BuildIdKind::Fast:
  computeHash(buildId, buf, [](uint8_t *dest, ArrayRef<uint8_t> arr) {
    write64le(dest, xxHash64(arr));
  });
  break;
case BuildIdKind::Md5:
  computeHash(buildId, buf, [&](uint8_t *dest, ArrayRef<uint8_t> arr) {
    memcpy(dest, MD5::hash(arr).data(), hashSize);
  });
  break;
case BuildIdKind::Sha1:
  computeHash(buildId, buf, [&](uint8_t *dest, ArrayRef<uint8_t> arr) {
    memcpy(dest, SHA1::hash(arr).data(), hashSize);
  });
  break;
case BuildIdKind::Uuid:
  if (auto ec = llvm::getRandomBytes(buildId.data(), hashSize))
    error("entropy source failure: " + ec.message());
  break;
default:
  llvm_unreachable("unknown BuildIdKind")__builtin_unreachable();
}
for (Partition &part : partitions)
  part.buildId->writeBuildId(buildId);
3095}

3097template void elf::createSyntheticSections<ELF32LE>();
3098template void elf::createSyntheticSections<ELF32BE>();
3099template void elf::createSyntheticSections<ELF64LE>();
3100template void elf::createSyntheticSections<ELF64BE>();

3102template void elf::writeResult<ELF32LE>();
3103template void elf::writeResult<ELF32BE>();
3104template void elf::writeResult<ELF64LE>();
3105template void elf::writeResult<ELF64BE>();

←

/usr/include/c++/v1/__algorithm/stable_partition.h

1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//

9#ifndef _LIBCPP___ALGORITHM_STABLE_PARTITION_H
10#define _LIBCPP___ALGORITHM_STABLE_PARTITION_H

12#include <__config>
13#include <__algorithm/rotate.h>
14#include <__iterator/iterator_traits.h>
15#include <__utility/swap.h>
16#include <memory>

18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19#pragma GCC system_header
20#endif

22_LIBCPP_PUSH_MACROSpush_macro("min")
 push_macro("max")
23#include <__undef_macros>

25_LIBCPP_BEGIN_NAMESPACE_STDnamespace std { inline namespace __1 {

27template <class _Predicate, class _ForwardIterator, class _Distance, class _Pair>
28_ForwardIterator
29__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
                 _Distance __len, _Pair __p, forward_iterator_tag __fit)
31{
  // *__first is known to be false
  // __len >= 1
  if (__len == 1)
      return __first;
  if (__len == 2)
  {
      _ForwardIterator __m = __first;
      if (__pred(*++__m))
      {
          swap(*__first, *__m);
          return __m;
      }
      return __first;
  }
  if (__len <= __p.second)
  {   // The buffer is big enough to use
      typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
      __destruct_n __d(0);
      unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
      // Move the falses into the temporary buffer, and the trues to the front of the line
      // Update __first to always point to the end of the trues
      value_type* __t = __p.first;
      ::new ((void*)__t) value_type(_VSTDstd::__1::move(*__first));
      __d.template __incr<value_type>();
      ++__t;
      _ForwardIterator __i = __first;
      while (++__i != __last)
      {
          if (__pred(*__i))
          {
              *__first = _VSTDstd::__1::move(*__i);
              ++__first;
          }
          else
          {
              ::new ((void*)__t) value_type(_VSTDstd::__1::move(*__i));
              __d.template __incr<value_type>();
              ++__t;
          }
      }
      // All trues now at start of range, all falses in buffer
      // Move falses back into range, but don't mess up __first which points to first false
      __i = __first;
      for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
          *__i = _VSTDstd::__1::move(*__t2);
      // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
      return __first;
  }
  // Else not enough buffer, do in place
  // __len >= 3
  _ForwardIterator __m = __first;
  _Distance __len2 = __len / 2;  // __len2 >= 2
  _VSTDstd::__1::advance(__m, __len2);
  // recurse on [__first, __m), *__first know to be false
  // F?????????????????
  // f       m         l
  typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
  _ForwardIterator __first_false = _VSTDstd::__1::__stable_partition<_PredRef>(__first, __m, __pred, __len2, __p, __fit);
  // TTTFFFFF??????????
  // f  ff   m         l
  // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
  _ForwardIterator __m1 = __m;
  _ForwardIterator __second_false = __last;
  _Distance __len_half = __len - __len2;
  while (__pred(*__m1))
  {
      if (++__m1 == __last)
          goto __second_half_done;
      --__len_half;
  }
  // TTTFFFFFTTTF??????
  // f  ff   m  m1     l
  __second_false = _VSTDstd::__1::__stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __fit);
105__second_half_done:
  // TTTFFFFFTTTTTFFFFF
  // f  ff   m    sf   l
  return _VSTDstd::__1::rotate(__first_false, __m, __second_false);
  // TTTTTTTTFFFFFFFFFF
  //         |
111}

113template <class _Predicate, class _ForwardIterator>
114_ForwardIterator
115__stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred,
                 forward_iterator_tag)
117{
  const unsigned __alloc_limit = 3;  // might want to make this a function of trivial assignment
  // Either prove all true and return __first or point to first false
  while (true)
  {
      if (__first == __last)
          return __first;
      if (!__pred(*__first))
          break;
      ++__first;
  }
  // We now have a reduced range [__first, __last)
  // *__first is known to be false
  typedef typename iterator_traits<_ForwardIterator>::difference_type difference_type;
  typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
  difference_type __len = _VSTDstd::__1::distance(__first, __last);
  pair<value_type*, ptrdiff_t> __p(0, 0);
  unique_ptr<value_type, __return_temporary_buffer> __h;
  if (__len >= __alloc_limit)
  {
      __p = _VSTDstd::__1::get_temporary_buffer<value_type>(__len);
      __h.reset(__p.first);
  }
  return _VSTDstd::__1::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
                           (__first, __last, __pred, __len, __p, forward_iterator_tag());
142}

144template <class _Predicate, class _BidirectionalIterator, class _Distance, class _Pair>
145_BidirectionalIterator
146__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
                 _Distance __len, _Pair __p, bidirectional_iterator_tag __bit)
148{
  // *__first is known to be false
  // *__last is known to be true
  // __len >= 2
  if (__len == 2)
  {
      swap(*__first, *__last);
      return __last;
  }
  if (__len == 3)
  {
      _BidirectionalIterator __m = __first;
      if (__pred(*++__m))
      {
          swap(*__first, *__m);
          swap(*__m, *__last);
          return __last;
      }
      swap(*__m, *__last);
      swap(*__first, *__m);
      return __m;
  }
  if (__len <= __p.second)
  {   // The buffer is big enough to use
      typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
      __destruct_n __d(0);
      unique_ptr<value_type, __destruct_n&> __h(__p.first, __d);
      // Move the falses into the temporary buffer, and the trues to the front of the line
      // Update __first to always point to the end of the trues
      value_type* __t = __p.first;
      ::new ((void*)__t) value_type(_VSTDstd::__1::move(*__first));
      __d.template __incr<value_type>();
      ++__t;
      _BidirectionalIterator __i = __first;
      while (++__i != __last)
      {
          if (__pred(*__i))
          {
              *__first = _VSTDstd::__1::move(*__i);
              ++__first;
          }
          else
          {
              ::new ((void*)__t) value_type(_VSTDstd::__1::move(*__i));
              __d.template __incr<value_type>();
              ++__t;
          }
      }
      // move *__last, known to be true
      *__first = _VSTDstd::__1::move(*__i);
      __i = ++__first;
      // All trues now at start of range, all falses in buffer
      // Move falses back into range, but don't mess up __first which points to first false
      for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
          *__i = _VSTDstd::__1::move(*__t2);
      // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
      return __first;
  }
  // Else not enough buffer, do in place
  // __len >= 4
  _BidirectionalIterator __m = __first;
  _Distance __len2 = __len / 2;  // __len2 >= 2
  _VSTDstd::__1::advance(__m, __len2);
  // recurse on [__first, __m-1], except reduce __m-1 until *(__m-1) is true, *__first know to be false
  // F????????????????T
  // f       m        l
  _BidirectionalIterator __m1 = __m;
  _BidirectionalIterator __first_false = __first;
  _Distance __len_half = __len2;
  while (!__pred(*--__m1))
  {
      if (__m1 == __first)
          goto __first_half_done;
      --__len_half;
  }
  // F???TFFF?????????T
  // f   m1  m        l
  typedef typename add_lvalue_reference<_Predicate>::type _PredRef;
  __first_false = _VSTDstd::__1::__stable_partition<_PredRef>(__first, __m1, __pred, __len_half, __p, __bit);
227__first_half_done:
  // TTTFFFFF?????????T
  // f  ff   m        l
  // recurse on [__m, __last], except increase __m until *(__m) is false, *__last know to be true
  __m1 = __m;
  _BidirectionalIterator __second_false = __last;
  ++__second_false;
  __len_half = __len - __len2;
  while (__pred(*__m1))
  {
      if (++__m1 == __last)
          goto __second_half_done;
      --__len_half;
  }
  // TTTFFFFFTTTF?????T
  // f  ff   m  m1    l
  __second_false = _VSTDstd::__1::__stable_partition<_PredRef>(__m1, __last, __pred, __len_half, __p, __bit);
244__second_half_done:
  // TTTFFFFFTTTTTFFFFF
  // f  ff   m    sf  l
  return _VSTDstd::__1::rotate(__first_false, __m, __second_false);
  // TTTTTTTTFFFFFFFFFF
  //         |
250}

252template <class _Predicate, class _BidirectionalIterator>
253_BidirectionalIterator
254__stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last, _Predicate __pred,
                 bidirectional_iterator_tag)
256{
  typedef typename iterator_traits<_BidirectionalIterator>::difference_type difference_type;
  typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
  const difference_type __alloc_limit = 4;  // might want to make this a function of trivial assignment
  // Either prove all true and return __first or point to first false
  while (true)
22
←
Loop condition is true.  Entering loop body→
  {
      if (__first == __last)
23
←
Taking false branch→
          return __first;
      if (!__pred(*__first))
24
←
Calling 'operator()'→
          break;
      ++__first;
  }
  // __first points to first false, everything prior to __first is already set.
  // Either prove [__first, __last) is all false and return __first, or point __last to last true
  do
  {
      if (__first == --__last)
          return __first;
  } while (!__pred(*__last));
  // We now have a reduced range [__first, __last]
  // *__first is known to be false
  // *__last is known to be true
  // __len >= 2
  difference_type __len = _VSTDstd::__1::distance(__first, __last) + 1;
  pair<value_type*, ptrdiff_t> __p(0, 0);
  unique_ptr<value_type, __return_temporary_buffer> __h;
  if (__len >= __alloc_limit)
  {
      __p = _VSTDstd::__1::get_temporary_buffer<value_type>(__len);
      __h.reset(__p.first);
  }
  return _VSTDstd::__1::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
                           (__first, __last, __pred, __len, __p, bidirectional_iterator_tag());
290}

292template <class _ForwardIterator, class _Predicate>
293inline _LIBCPP_INLINE_VISIBILITY__attribute__ ((__visibility__("hidden"))) __attribute__ ((__exclude_from_explicit_instantiation__
))
294_ForwardIterator
295stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate __pred)
296{
  return _VSTDstd::__1::__stable_partition<typename add_lvalue_reference<_Predicate>::type>
21
←
Calling '__stable_partition<(lambda at /usr/src/gnu/usr.bin/clang/liblldELF/../../../llvm/lld/ELF/Writer.cpp:1912:35) &, std::__wrap_iter<lld::elf::InputSectionBase **>>'→
                           (__first, __last, __pred, typename iterator_traits<_ForwardIterator>::iterator_category());
299}

301_LIBCPP_END_NAMESPACE_STD} }

303_LIBCPP_POP_MACROSpop_macro("min")
 pop_macro("max")

305#endif // _LIBCPP___ALGORITHM_STABLE_PARTITION_H