hanchenye-llvm-project/lld/lib/ReaderWriter/CoreLinkingContext.cpp

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

#include "lld/ReaderWriter/CoreLinkingContext.h"

#include "lld/Core/Pass.h"
#include "lld/Core/PassManager.h"
#include "lld/Passes/LayoutPass.h"

#include "llvm/ADT/ArrayRef.h"

using namespace lld;

namespace {

/// \brief Simple atom created by the stubs pass.
class TestingStubAtom : public DefinedAtom {
public:
  TestingStubAtom(const File &F, const Atom &) : _file(F) {
    static uint32_t lastOrdinal = 0;
    _ordinal = lastOrdinal++;
  }

  virtual const File &file() const { return _file; }

  virtual StringRef name() const { return StringRef(); }

  virtual uint64_t ordinal() const { return _ordinal; }

  virtual uint64_t size() const { return 0; }

  virtual Scope scope() const { return DefinedAtom::scopeLinkageUnit; }

  virtual Interposable interposable() const { return DefinedAtom::interposeNo; }

  virtual Merge merge() const { return DefinedAtom::mergeNo; }

  virtual ContentType contentType() const { return DefinedAtom::typeStub; }

  virtual Alignment alignment() const { return Alignment(0, 0); }

  virtual SectionChoice sectionChoice() const {
    return DefinedAtom::sectionBasedOnContent;
  }

  virtual StringRef customSectionName() const { return StringRef(); }

  virtual SectionPosition sectionPosition() const { return sectionPositionAny; }

  virtual DeadStripKind deadStrip() const {
    return DefinedAtom::deadStripNormal;
  }

  virtual ContentPermissions permissions() const {
    return DefinedAtom::permR_X;
  }

  virtual bool isAlias() const { return false; }

  virtual ArrayRef<uint8_t> rawContent() const { return ArrayRef<uint8_t>(); }

  virtual reference_iterator begin() const {
    return reference_iterator(*this, nullptr);
  }

  virtual reference_iterator end() const {
    return reference_iterator(*this, nullptr);
  }

  virtual const Reference *derefIterator(const void *iter) const {
    return nullptr;
  }

  virtual void incrementIterator(const void *&iter) const {}

private:
  const File &_file;
  uint32_t _ordinal;
};

/// \brief Simple atom created by the GOT pass.
class TestingGOTAtom : public DefinedAtom {
public:
  TestingGOTAtom(const File &F, const Atom &) : _file(F) {
    static uint32_t lastOrdinal = 0;
    _ordinal = lastOrdinal++;
  }

  virtual const File &file() const { return _file; }

  virtual StringRef name() const { return StringRef(); }

  virtual uint64_t ordinal() const { return _ordinal; }

  virtual uint64_t size() const { return 0; }

  virtual Scope scope() const { return DefinedAtom::scopeLinkageUnit; }

  virtual Interposable interposable() const { return DefinedAtom::interposeNo; }

  virtual Merge merge() const { return DefinedAtom::mergeNo; }

  virtual ContentType contentType() const { return DefinedAtom::typeGOT; }

  virtual Alignment alignment() const { return Alignment(3, 0); }

  virtual SectionChoice sectionChoice() const {
    return DefinedAtom::sectionBasedOnContent;
  }

  virtual StringRef customSectionName() const { return StringRef(); }

  virtual SectionPosition sectionPosition() const { return sectionPositionAny; }

  virtual DeadStripKind deadStrip() const {
    return DefinedAtom::deadStripNormal;
  }

  virtual ContentPermissions permissions() const {
    return DefinedAtom::permRW_;
  }

  virtual bool isAlias() const { return false; }

  virtual ArrayRef<uint8_t> rawContent() const { return ArrayRef<uint8_t>(); }

  virtual reference_iterator begin() const {
    return reference_iterator(*this, nullptr);
  }

  virtual reference_iterator end() const {
    return reference_iterator(*this, nullptr);
  }

  virtual const Reference *derefIterator(const void *iter) const {
    return nullptr;
  }

  virtual void incrementIterator(const void *&iter) const {}

private:
  const File &_file;
  uint32_t _ordinal;
};

class TestingPassFile : public MutableFile {
public:
  TestingPassFile(const LinkingContext &ctx)
      : MutableFile(ctx, "Testing pass") {}

  virtual void addAtom(const Atom &atom) {
    if (const DefinedAtom *defAtom = dyn_cast<DefinedAtom>(&atom))
      _definedAtoms._atoms.push_back(defAtom);
    else
      llvm_unreachable("atom has unknown definition kind");
  }

  virtual DefinedAtomRange definedAtoms() {
    return range<std::vector<const DefinedAtom *>::iterator>(
        _definedAtoms._atoms.begin(), _definedAtoms._atoms.end());
  }

  virtual const atom_collection<DefinedAtom> &defined() const {
    return _definedAtoms;
  }
  virtual const atom_collection<UndefinedAtom> &undefined() const {
    return _undefinedAtoms;
  }
  virtual const atom_collection<SharedLibraryAtom> &sharedLibrary() const {
    return _sharedLibraryAtoms;
  }
  virtual const atom_collection<AbsoluteAtom> &absolute() const {
    return _absoluteAtoms;
  }

private:
  atom_collection_vector<DefinedAtom> _definedAtoms;
  atom_collection_vector<UndefinedAtom> _undefinedAtoms;
  atom_collection_vector<SharedLibraryAtom> _sharedLibraryAtoms;
  atom_collection_vector<AbsoluteAtom> _absoluteAtoms;
};

struct TestingKindMapping {
  const char *string;
  int32_t value;
  bool isBranch;
  bool isGotLoad;
  bool isGotUse;
};

//
// Table of fixup kinds in YAML documents used for testing
//
const TestingKindMapping sKinds[] = {
  { "in-group", -3, false, false, false },
  { "layout-after", -2, false, false, false },
  { "layout-before", -1, false, false, false },
  { "call32", 2, true, false, false }, { "pcrel32", 3, false, false, false },
  { "gotLoad32", 7, false, true, true }, { "gotUse32", 9, false, false, true },
  { "lea32wasGot", 8, false, false, false }, { nullptr, 0, false, false, false }
};

class TestingStubsPass : public StubsPass {
public:
  TestingStubsPass(const LinkingContext &ctx) : _file(TestingPassFile(ctx)) {}

  virtual bool noTextRelocs() { return true; }

  virtual bool isCallSite(int32_t kind) {
    for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
      if (kind == p->value)
        return p->isBranch;
    }
    return false;
  }

  virtual const DefinedAtom *getStub(const Atom &target) {
    const DefinedAtom *result = new TestingStubAtom(_file, target);
    _file.addAtom(*result);
    return result;
  }

  virtual void addStubAtoms(MutableFile &mergedFile) {
    for (const DefinedAtom *stub : _file.defined()) {
      mergedFile.addAtom(*stub);
    }
  }

private:
  TestingPassFile _file;
};

class TestingGOTPass : public GOTPass {
public:
  TestingGOTPass(const LinkingContext &ctx) : _file(TestingPassFile(ctx)) {}

  virtual bool noTextRelocs() { return true; }

  virtual bool isGOTAccess(int32_t kind, bool &canBypassGOT) {
    for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
      if (kind == p->value) {
        canBypassGOT = p->isGotLoad;
        return p->isGotUse || p->isGotLoad;
      }
    }
    return false;
  }

  virtual void updateReferenceToGOT(const Reference *ref, bool targetIsNowGOT) {
    if (targetIsNowGOT)
      const_cast<Reference *>(ref)->setKind(3); // pcrel32
    else
      const_cast<Reference *>(ref)->setKind(8); // lea32wasGot
  }

  virtual const DefinedAtom *makeGOTEntry(const Atom &target) {
    return new TestingGOTAtom(_file, target);
  }

private:
  TestingPassFile _file;
};

} // anonymous namespace

CoreLinkingContext::CoreLinkingContext() {}

bool CoreLinkingContext::validateImpl(raw_ostream &diagnostics) {
  _reader = createReaderYAML(*this);
  return true;
}

void CoreLinkingContext::addPasses(PassManager &pm) const {
  for (StringRef name : _passNames) {
    if (name.equals("layout"))
      pm.add(std::unique_ptr<Pass>((new LayoutPass())));
    else if (name.equals("GOT"))
      pm.add(std::unique_ptr<Pass>(new TestingGOTPass(*this)));
    else if (name.equals("stubs"))
      pm.add(std::unique_ptr<Pass>(new TestingStubsPass(*this)));
    else
      llvm_unreachable("bad pass name");
  }
}

Writer &CoreLinkingContext::writer() const {
  if (!_writer)
    _writer = createWriterYAML(*this);
  return *_writer;
}

ErrorOr<Reference::Kind>
CoreLinkingContext::relocKindFromString(StringRef str) const {
  for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
    if (str.equals(p->string))
      return p->value;
  }
  return make_error_code(yaml_reader_error::illegal_value);
}

ErrorOr<std::string>
CoreLinkingContext::stringFromRelocKind(Reference::Kind kind) const {
  for (const TestingKindMapping *p = sKinds; p->string != nullptr; ++p) {
    if (kind == p->value)
      return std::string(p->string);
  }
  return make_error_code(yaml_reader_error::illegal_value);
}