1 files changed, 73 insertions, 0 deletions
diff --git a/lld/lib/ReaderWriter/ELF/File.h b/lld/lib/ReaderWriter/ELF/File.h
index 33d925067b2..7e0a07691b2 100644
--- a/lld/lib/ReaderWriter/ELF/File.h
+++ b/lld/lib/ReaderWriter/ELF/File.h
@@ -737,6 +737,79 @@ private:
   /// \brief the cached options relevant while reading the ELF File
   bool _doStringsMerge : 1;
 };
+
+/// \brief All atoms are owned by a File. To add linker specific atoms
+/// the atoms need to be inserted to a file called (CRuntimeFile) which
+/// are basically additional symbols required by libc and other runtime
+/// libraries part of executing a program. This class provides support
+/// for adding absolute symbols and undefined symbols
+template <class ELFT> class CRuntimeFile : public ELFFile<ELFT> {
+public:
+  typedef llvm::object::Elf_Sym_Impl<ELFT> Elf_Sym;
+  CRuntimeFile(const ELFLinkingContext &context, StringRef name = "C runtime")
+      : ELFFile<ELFT>(context, name) {}
+
+  /// \brief add a global absolute atom
+  virtual Atom *addAbsoluteAtom(StringRef symbolName) {
+    assert(!symbolName.empty() && "AbsoluteAtoms must have a name");
+    Elf_Sym *symbol = new (_allocator) Elf_Sym;
+    symbol->st_name = 0;
+    symbol->st_value = 0;
+    symbol->st_shndx = llvm::ELF::SHN_ABS;
+    symbol->setBindingAndType(llvm::ELF::STB_GLOBAL, llvm::ELF::STT_OBJECT);
+    symbol->st_other = llvm::ELF::STV_DEFAULT;
+    symbol->st_size = 0;
+    auto *newAtom =
+        new (_allocator) ELFAbsoluteAtom<ELFT>(*this, symbolName, symbol, -1);
+    _absoluteAtoms._atoms.push_back(newAtom);
+    return newAtom;
+  }
+
+  /// \brief add an undefined atom
+  virtual Atom *addUndefinedAtom(StringRef symbolName) {
+    assert(!symbolName.empty() && "UndefinedAtoms must have a name");
+    Elf_Sym *symbol = new (_allocator) Elf_Sym;
+    symbol->st_name = 0;
+    symbol->st_value = 0;
+    symbol->st_shndx = llvm::ELF::SHN_UNDEF;
+    symbol->st_other = llvm::ELF::STV_DEFAULT;
+    symbol->st_size = 0;
+    auto *newAtom =
+        new (_allocator) ELFUndefinedAtom<ELFT>(*this, symbolName, symbol);
+    _undefinedAtoms._atoms.push_back(newAtom);
+    return newAtom;
+  }
+
+  virtual const File::atom_collection<DefinedAtom> &defined() const {
+    return _definedAtoms;
+  }
+
+  virtual const File::atom_collection<UndefinedAtom> &undefined() const {
+    return _undefinedAtoms;
+  }
+
+  virtual const File::atom_collection<SharedLibraryAtom> &
+  sharedLibrary() const {
+    return _sharedLibraryAtoms;
+  }
+
+  virtual const File::atom_collection<AbsoluteAtom> &absolute() const {
+    return _absoluteAtoms;
+  }
+
+  // cannot add atoms to C Runtime file
+  virtual void addAtom(const Atom &) {
+    llvm_unreachable("cannot add atoms to Runtime files");
+  }
+
+protected:
+  llvm::BumpPtrAllocator _allocator;
+  File::atom_collection_vector<DefinedAtom> _definedAtoms;
+  File::atom_collection_vector<UndefinedAtom> _undefinedAtoms;
+  File::atom_collection_vector<SharedLibraryAtom> _sharedLibraryAtoms;
+  File::atom_collection_vector<AbsoluteAtom> _absoluteAtoms;
+};
+
 } // end namespace elf
 } // end namespace lld