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//===- lib/ReaderWriter/PECOFF/LinkerGeneratedSymbolFile.cpp --------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "Atoms.h"
#include "GroupedSectionsPass.h"
#include "IdataPass.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Path.h"
#include "lld/Core/ArchiveLibraryFile.h"
#include "lld/Core/InputFiles.h"
#include "lld/Core/PassManager.h"
#include "lld/Passes/LayoutPass.h"
#include "lld/ReaderWriter/PECOFFLinkingContext.h"
#include "lld/ReaderWriter/Reader.h"
#include "lld/ReaderWriter/Simple.h"
#include "lld/ReaderWriter/Writer.h"
namespace lld {
namespace coff {
namespace {
// The symbol __ImageBase is a linker generated symbol. No standard library
// files define it, but the linker is expected to prepare it as if it was read
// from a file. The content of the atom is a 4-byte integer equal to the image
// base address. Note that because the name is prefixed by an underscore on x86
// Win32, the actual symbol name will be ___ImageBase (three underscores).
class ImageBaseAtom : public COFFLinkerInternalAtom {
public:
ImageBaseAtom(const PECOFFLinkingContext &context, const File &file,
uint32_t imageBase)
: COFFLinkerInternalAtom(file, assembleRawContent(imageBase)),
_name(context.decorateSymbol("__ImageBase")) {}
virtual StringRef name() const { return _name; }
virtual uint64_t ordinal() const { return 0; }
virtual ContentType contentType() const { return typeData; }
virtual ContentPermissions permissions() const { return permRW_; }
virtual DeadStripKind deadStrip() const { return deadStripAlways; }
private:
std::vector<uint8_t> assembleRawContent(uint32_t imageBase) {
std::vector<uint8_t> data = std::vector<uint8_t>(4);
*(reinterpret_cast<uint32_t *>(&data[0])) = imageBase;
return data;
}
StringRef _name;
};
// The file to wrap ImageBaseAtom. This is the only member file of
// LinkerGeneratedSymbolFile.
class MemberFile : public SimpleFile {
public:
MemberFile(const PECOFFLinkingContext &context)
: SimpleFile(context, "Member of the Linker Internal File"),
_atom(context, *this, context.getBaseAddress()) {
addAtom(_atom);
};
bool contains(StringRef name) const {
return _atom.name() == name;
}
private:
ImageBaseAtom _atom;
};
} // anonymous namespace
// A pseudo library file to wrap MemberFile, which in turn wraps ImageBaseAtom.
// The file the core linker handle is this.
//
// The reason why we don't pass MemberFile to the core linker is because, if we
// did so, ImageBaseAtom would always be emit to the resultant executable. By
// wrapping the file by a library file, we made it to emit ImageBaseAtom only
// when the atom is really referenced.
class LinkerGeneratedSymbolFile : public ArchiveLibraryFile {
public:
LinkerGeneratedSymbolFile(const PECOFFLinkingContext &context)
: ArchiveLibraryFile(context, "Linker Internal File"),
_memberFile(context) {};
virtual const File *find(StringRef name, bool dataSymbolOnly) const {
if (_memberFile.contains(name))
return &_memberFile;
return nullptr;
}
virtual const atom_collection<DefinedAtom> &defined() const {
return _noDefinedAtoms;
}
virtual const atom_collection<UndefinedAtom> &undefined() const {
return _noUndefinedAtoms;
}
virtual const atom_collection<SharedLibraryAtom> &sharedLibrary() const {
return _noSharedLibraryAtoms;
}
virtual const atom_collection<AbsoluteAtom> &absolute() const {
return _noAbsoluteAtoms;
}
private:
MemberFile _memberFile;
};
} // end namespace coff
} // end namespace lld
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