Coverage Report

Created: 2018-01-17 21:32

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/tools/lld/COFF/Chunks.h
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//===- Chunks.h -------------------------------------------------*- C++ -*-===//
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//
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//                             The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_COFF_CHUNKS_H
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#define LLD_COFF_CHUNKS_H
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#include "Config.h"
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#include "InputFiles.h"
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#include "lld/Common/LLVM.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/iterator.h"
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#include "llvm/ADT/iterator_range.h"
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#include "llvm/Object/COFF.h"
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#include <utility>
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#include <vector>
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namespace lld {
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namespace coff {
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using llvm::COFF::ImportDirectoryTableEntry;
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using llvm::object::COFFSymbolRef;
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using llvm::object::SectionRef;
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using llvm::object::coff_relocation;
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using llvm::object::coff_section;
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class Baserel;
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class Defined;
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class DefinedImportData;
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class DefinedRegular;
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class ObjFile;
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class OutputSection;
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class Symbol;
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// Mask for section types (code, data, bss, disacardable, etc.)
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// and permissions (writable, readable or executable).
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const uint32_t PermMask = 0xFF0000F0;
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// A Chunk represents a chunk of data that will occupy space in the
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// output (if the resolver chose that). It may or may not be backed by
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// a section of an input file. It could be linker-created data, or
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// doesn't even have actual data (if common or bss).
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class Chunk {
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public:
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  enum Kind { SectionKind, OtherKind };
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  Kind kind() const { return ChunkKind; }
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  virtual ~Chunk() = default;
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  // Returns the size of this chunk (even if this is a common or BSS.)
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  virtual size_t getSize() const = 0;
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  // Write this chunk to a mmap'ed file, assuming Buf is pointing to
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  // beginning of the file. Because this function may use RVA values
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  // of other chunks for relocations, you need to set them properly
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  // before calling this function.
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  virtual void writeTo(uint8_t *Buf) const {}
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  // The writer sets and uses the addresses.
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  uint64_t getRVA() const { return RVA; }
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  void setRVA(uint64_t V) { RVA = V; }
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  // Returns true if this has non-zero data. BSS chunks return
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  // false. If false is returned, the space occupied by this chunk
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  // will be filled with zeros.
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  virtual bool hasData() const { return true; }
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  // Returns readable/writable/executable bits.
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  virtual uint32_t getPermissions() const { return 0; }
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  // Returns the section name if this is a section chunk.
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  // It is illegal to call this function on non-section chunks.
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  virtual StringRef getSectionName() const {
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    llvm_unreachable("unimplemented getSectionName");
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  }
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  // An output section has pointers to chunks in the section, and each
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  // chunk has a back pointer to an output section.
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  void setOutputSection(OutputSection *O) { Out = O; }
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  OutputSection *getOutputSection() const { return Out; }
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  // Windows-specific.
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  // Collect all locations that contain absolute addresses for base relocations.
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  virtual void getBaserels(std::vector<Baserel> *Res) {}
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  // Returns a human-readable name of this chunk. Chunks are unnamed chunks of
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  // bytes, so this is used only for logging or debugging.
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  virtual StringRef getDebugName() { return ""; }
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  // The alignment of this chunk. The writer uses the value.
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  uint32_t Alignment = 1;
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protected:
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  Chunk(Kind K = OtherKind) : ChunkKind(K) {}
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  const Kind ChunkKind;
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  // The RVA of this chunk in the output. The writer sets a value.
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  uint64_t RVA = 0;
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  // The output section for this chunk.
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  OutputSection *Out = nullptr;
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public:
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  // The offset from beginning of the output section. The writer sets a value.
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  uint64_t OutputSectionOff = 0;
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};
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// A chunk corresponding a section of an input file.
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class SectionChunk final : public Chunk {
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  // Identical COMDAT Folding feature accesses section internal data.
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  friend class ICF;
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public:
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  class symbol_iterator : public llvm::iterator_adaptor_base<
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                              symbol_iterator, const coff_relocation *,
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                              std::random_access_iterator_tag, Symbol *> {
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    friend SectionChunk;
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    ObjFile *File;
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    symbol_iterator(ObjFile *File, const coff_relocation *I)
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        : symbol_iterator::iterator_adaptor_base(I), File(File) {}
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  public:
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    symbol_iterator() = default;
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    Symbol *operator*() const { return File->getSymbol(I->SymbolTableIndex); }
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  };
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  SectionChunk(ObjFile *File, const coff_section *Header);
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  static bool classof(const Chunk *C) { return C->kind() == SectionKind; }
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  size_t getSize() const override { return Header->SizeOfRawData; }
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  ArrayRef<uint8_t> getContents() const;
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  void writeTo(uint8_t *Buf) const override;
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  bool hasData() const override;
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  uint32_t getPermissions() const override;
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  StringRef getSectionName() const override { return SectionName; }
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  void getBaserels(std::vector<Baserel> *Res) override;
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  bool isCOMDAT() const;
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  void applyRelX64(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
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                   uint64_t P) const;
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  void applyRelX86(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
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                   uint64_t P) const;
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  void applyRelARM(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
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                   uint64_t P) const;
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  void applyRelARM64(uint8_t *Off, uint16_t Type, OutputSection *OS, uint64_t S,
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                     uint64_t P) const;
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  // Called if the garbage collector decides to not include this chunk
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  // in a final output. It's supposed to print out a log message to stdout.
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  void printDiscardedMessage() const;
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  // Adds COMDAT associative sections to this COMDAT section. A chunk
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  // and its children are treated as a group by the garbage collector.
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  void addAssociative(SectionChunk *Child);
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  StringRef getDebugName() override;
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  // Returns true if the chunk was not dropped by GC.
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  bool isLive() { return Live; }
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  // Used by the garbage collector.
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  void markLive() {
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    assert(Config->DoGC && "should only mark things live from GC");
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    assert(!isLive() && "Cannot mark an already live section!");
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    Live = true;
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  }
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  // True if this is a codeview debug info chunk. These will not be laid out in
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  // the image. Instead they will end up in the PDB, if one is requested.
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  bool isCodeView() const {
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    return SectionName == ".debug" || SectionName.startswith(".debug$");
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  }
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  // True if this is a DWARF debug info or exception handling chunk.
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  bool isDWARF() const {
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    return SectionName.startswith(".debug_") || SectionName == ".eh_frame";
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  }
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  // Allow iteration over the bodies of this chunk's relocated symbols.
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  llvm::iterator_range<symbol_iterator> symbols() const {
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    return llvm::make_range(symbol_iterator(File, Relocs.begin()),
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                            symbol_iterator(File, Relocs.end()));
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  }
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  // Allow iteration over the associated child chunks for this section.
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  ArrayRef<SectionChunk *> children() const { return AssocChildren; }
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  // A pointer pointing to a replacement for this chunk.
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  // Initially it points to "this" object. If this chunk is merged
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  // with other chunk by ICF, it points to another chunk,
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  // and this chunk is considrered as dead.
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  SectionChunk *Repl;
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  // The CRC of the contents as described in the COFF spec 4.5.5.
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  // Auxiliary Format 5: Section Definitions. Used for ICF.
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  uint32_t Checksum = 0;
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  const coff_section *Header;
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  // The file that this chunk was created from.
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  ObjFile *File;
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  // The COMDAT leader symbol if this is a COMDAT chunk.
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  DefinedRegular *Sym = nullptr;
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private:
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  StringRef SectionName;
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  std::vector<SectionChunk *> AssocChildren;
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  llvm::iterator_range<const coff_relocation *> Relocs;
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  size_t NumRelocs;
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  // Used by the garbage collector.
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  bool Live;
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  // Used for ICF (Identical COMDAT Folding)
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  void replace(SectionChunk *Other);
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  uint32_t Class[2] = {0, 0};
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};
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// A chunk for common symbols. Common chunks don't have actual data.
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class CommonChunk : public Chunk {
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public:
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  CommonChunk(const COFFSymbolRef Sym);
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  size_t getSize() const override { return Sym.getValue(); }
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  bool hasData() const override { return false; }
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  uint32_t getPermissions() const override;
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  StringRef getSectionName() const override { return ".bss"; }
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private:
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  const COFFSymbolRef Sym;
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};
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// A chunk for linker-created strings.
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class StringChunk : public Chunk {
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public:
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  explicit StringChunk(StringRef S) : Str(S) {}
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  size_t getSize() const override { return Str.size() + 1; }
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  void writeTo(uint8_t *Buf) const override;
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private:
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  StringRef Str;
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};
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static const uint8_t ImportThunkX86[] = {
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    0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // JMP *0x0
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};
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static const uint8_t ImportThunkARM[] = {
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    0x40, 0xf2, 0x00, 0x0c, // mov.w ip, #0
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    0xc0, 0xf2, 0x00, 0x0c, // mov.t ip, #0
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    0xdc, 0xf8, 0x00, 0xf0, // ldr.w pc, [ip]
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};
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static const uint8_t ImportThunkARM64[] = {
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    0x10, 0x00, 0x00, 0x90, // adrp x16, #0
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    0x10, 0x02, 0x40, 0xf9, // ldr  x16, [x16]
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    0x00, 0x02, 0x1f, 0xd6, // br   x16
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};
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// Windows-specific.
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// A chunk for DLL import jump table entry. In a final output, it's
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// contents will be a JMP instruction to some __imp_ symbol.
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class ImportThunkChunkX64 : public Chunk {
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public:
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  explicit ImportThunkChunkX64(Defined *S);
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  size_t getSize() const override { return sizeof(ImportThunkX86); }
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  void writeTo(uint8_t *Buf) const override;
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private:
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  Defined *ImpSymbol;
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};
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class ImportThunkChunkX86 : public Chunk {
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public:
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  explicit ImportThunkChunkX86(Defined *S) : ImpSymbol(S) {}
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  size_t getSize() const override { return sizeof(ImportThunkX86); }
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  void getBaserels(std::vector<Baserel> *Res) override;
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  void writeTo(uint8_t *Buf) const override;
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private:
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  Defined *ImpSymbol;
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};
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class ImportThunkChunkARM : public Chunk {
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public:
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  explicit ImportThunkChunkARM(Defined *S) : ImpSymbol(S) {}
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  size_t getSize() const override { return sizeof(ImportThunkARM); }
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  void getBaserels(std::vector<Baserel> *Res) override;
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  void writeTo(uint8_t *Buf) const override;
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private:
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  Defined *ImpSymbol;
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};
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class ImportThunkChunkARM64 : public Chunk {
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public:
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  explicit ImportThunkChunkARM64(Defined *S) : ImpSymbol(S) {}
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  size_t getSize() const override { return sizeof(ImportThunkARM64); }
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  void writeTo(uint8_t *Buf) const override;
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private:
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  Defined *ImpSymbol;
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};
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// Windows-specific.
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// See comments for DefinedLocalImport class.
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class LocalImportChunk : public Chunk {
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public:
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  explicit LocalImportChunk(Defined *S) : Sym(S) {}
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  size_t getSize() const override;
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  void getBaserels(std::vector<Baserel> *Res) override;
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  void writeTo(uint8_t *Buf) const override;
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private:
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  Defined *Sym;
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};
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// Windows-specific.
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// A chunk for SEH table which contains RVAs of safe exception handler
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// functions. x86-only.
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class SEHTableChunk : public Chunk {
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public:
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  explicit SEHTableChunk(std::set<Defined *> S) : Syms(std::move(S)) {}
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  size_t getSize() const override { return Syms.size() * 4; }
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  void writeTo(uint8_t *Buf) const override;
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private:
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  std::set<Defined *> Syms;
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};
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// Windows-specific.
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// This class represents a block in .reloc section.
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// See the PE/COFF spec 5.6 for details.
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class BaserelChunk : public Chunk {
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public:
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  BaserelChunk(uint32_t Page, Baserel *Begin, Baserel *End);
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  size_t getSize() const override { return Data.size(); }
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  void writeTo(uint8_t *Buf) const override;
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private:
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  std::vector<uint8_t> Data;
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};
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class Baserel {
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public:
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  Baserel(uint32_t V, uint8_t Ty) : RVA(V), Type(Ty) {}
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  explicit Baserel(uint32_t V) : Baserel(V, getDefaultType()) {}
Unexecuted instantiation: lld::coff::Baserel::Baserel(unsigned int)
Unexecuted instantiation: lld::coff::Baserel::Baserel(unsigned int)
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  uint8_t getDefaultType();
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  uint32_t RVA;
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  uint8_t Type;
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};
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void applyMOV32T(uint8_t *Off, uint32_t V);
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void applyBranch24T(uint8_t *Off, int32_t V);
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} // namespace coff
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} // namespace lld
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#endif