llvm-project/lld/lib/ReaderWriter/MachO/ExecutableAtoms.h

//===- lib/ReaderWriter/MachO/ExecutableAtoms.h ---------------------------===//
//
//                             The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H
#define LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H

#include "Atoms.h"
#include "File.h"

#include "llvm/BinaryFormat/MachO.h"

#include "lld/Core/DefinedAtom.h"
#include "lld/Core/File.h"
#include "lld/Core/LinkingContext.h"
#include "lld/Core/Reference.h"
#include "lld/Core/Simple.h"
#include "lld/Core/UndefinedAtom.h"
#include "lld/ReaderWriter/MachOLinkingContext.h"

namespace lld {
namespace mach_o {


//
// CEntryFile adds an UndefinedAtom for "_main" so that the Resolving
// phase will fail if "_main" is undefined.
//
class CEntryFile : public SimpleFile {
public:
  CEntryFile(const MachOLinkingContext &context)
      : SimpleFile("C entry", kindCEntryObject),
       _undefMain(*this, context.entrySymbolName()) {
    this->addAtom(_undefMain);
  }

private:
  SimpleUndefinedAtom   _undefMain;
};


//
// StubHelperFile adds an UndefinedAtom for "dyld_stub_binder" so that
// the Resolveing phase will fail if "dyld_stub_binder" is undefined.
//
class StubHelperFile : public SimpleFile {
public:
  StubHelperFile(const MachOLinkingContext &context)
      : SimpleFile("stub runtime", kindStubHelperObject),
        _undefBinder(*this, context.binderSymbolName()) {
    this->addAtom(_undefBinder);
  }

private:
  SimpleUndefinedAtom   _undefBinder;
};


//
// MachHeaderAliasFile lazily instantiates the magic symbols that mark the start
// of the mach_header for final linked images.
//
class MachHeaderAliasFile : public SimpleFile {
public:
  MachHeaderAliasFile(const MachOLinkingContext &context)
    : SimpleFile("mach_header symbols", kindHeaderObject) {
    StringRef machHeaderSymbolName;
    DefinedAtom::Scope symbolScope = DefinedAtom::scopeLinkageUnit;
    StringRef dsoHandleName;
    switch (context.outputMachOType()) {
    case llvm::MachO::MH_OBJECT:
      machHeaderSymbolName = "__mh_object_header";
      break;
    case llvm::MachO::MH_EXECUTE:
      machHeaderSymbolName = "__mh_execute_header";
      symbolScope = DefinedAtom::scopeGlobal;
      dsoHandleName = "___dso_handle";
      break;
    case llvm::MachO::MH_FVMLIB:
      llvm_unreachable("no mach_header symbol for file type");
    case llvm::MachO::MH_CORE:
      llvm_unreachable("no mach_header symbol for file type");
    case llvm::MachO::MH_PRELOAD:
      llvm_unreachable("no mach_header symbol for file type");
    case llvm::MachO::MH_DYLIB:
      machHeaderSymbolName = "__mh_dylib_header";
      dsoHandleName = "___dso_handle";
      break;
    case llvm::MachO::MH_DYLINKER:
      machHeaderSymbolName = "__mh_dylinker_header";
      dsoHandleName = "___dso_handle";
      break;
    case llvm::MachO::MH_BUNDLE:
      machHeaderSymbolName = "__mh_bundle_header";
      dsoHandleName = "___dso_handle";
      break;
    case llvm::MachO::MH_DYLIB_STUB:
      llvm_unreachable("no mach_header symbol for file type");
    case llvm::MachO::MH_DSYM:
      llvm_unreachable("no mach_header symbol for file type");
    case llvm::MachO::MH_KEXT_BUNDLE:
      dsoHandleName = "___dso_handle";
      break;
    }
    if (!machHeaderSymbolName.empty())
      _definedAtoms.push_back(new (allocator()) MachODefinedAtom(
          *this, machHeaderSymbolName, symbolScope,
          DefinedAtom::typeMachHeader, DefinedAtom::mergeNo, false,
          true /* noDeadStrip */,
          ArrayRef<uint8_t>(), DefinedAtom::Alignment(4096)));

    if (!dsoHandleName.empty())
      _definedAtoms.push_back(new (allocator()) MachODefinedAtom(
          *this, dsoHandleName, DefinedAtom::scopeLinkageUnit,
          DefinedAtom::typeDSOHandle, DefinedAtom::mergeNo, false,
          true /* noDeadStrip */,
          ArrayRef<uint8_t>(), DefinedAtom::Alignment(1)));
  }

  const AtomRange<DefinedAtom> defined() const override {
    return _definedAtoms;
  }
  const AtomRange<UndefinedAtom> undefined() const override {
    return _noUndefinedAtoms;
  }

  const AtomRange<SharedLibraryAtom> sharedLibrary() const override {
    return _noSharedLibraryAtoms;
  }

  const AtomRange<AbsoluteAtom> absolute() const override {
    return _noAbsoluteAtoms;
  }

  void clearAtoms() override {
    _definedAtoms.clear();
    _noUndefinedAtoms.clear();
    _noSharedLibraryAtoms.clear();
    _noAbsoluteAtoms.clear();
  }


private:
  mutable AtomVector<DefinedAtom> _definedAtoms;
};

} // namespace mach_o
} // namespace lld

#endif // LLD_READER_WRITER_MACHO_EXECUTABLE_ATOMS_H