Index: ELF/Config.h
===================================================================
--- ELF/Config.h
+++ ELF/Config.h
@@ -42,6 +42,7 @@
   llvm::StringRef Sysroot;
   std::string RPath;
   std::vector<llvm::StringRef> SearchPaths;
+  std::vector<llvm::StringRef> Undefined;
   bool AllowMultipleDefinition;
   bool AsNeeded = false;
   bool Bsymbolic;
Index: ELF/Driver.cpp
===================================================================
--- ELF/Driver.cpp
+++ ELF/Driver.cpp
@@ -189,6 +189,9 @@
     }
   }
 
+  for (auto *Arg : Args.filtered(OPT_undefined))
+    Config->Undefined.push_back(Arg->getValue());
+
   if (Files.empty())
     error("no input files.");
 }
@@ -225,8 +228,8 @@
   for (std::unique_ptr<InputFile> &F : Files)
     Symtab.addFile(std::move(F));
 
-  for (auto *Arg : Args.filtered(OPT_undefined))
-    Symtab.addUndefinedOpt(Arg->getValue());
+  for (auto &U : Config->Undefined)
+    Symtab.addUndefinedOpt(U);
 
   if (Config->OutputFile.empty())
     Config->OutputFile = "a.out";
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -43,6 +43,7 @@
 
   void readAsNeeded();
   void readEntry();
+  void readExtern();
   void readGroup();
   void readInclude();
   void readOutput();
@@ -63,6 +64,8 @@
       continue;
     if (Tok == "ENTRY") {
       readEntry();
+    } else if (Tok == "EXTERN") {
+      readExtern();
     } else if (Tok == "GROUP" || Tok == "INPUT") {
       readGroup();
     } else if (Tok == "INCLUDE") {
@@ -181,6 +184,16 @@
   expect(")");
 }
 
+void LinkerScript::readExtern() {
+  expect("(");
+  for (;;) {
+    StringRef Tok = next();
+    if (Tok == ")")
+      return;
+    Config->Undefined.push_back(Tok);
+  }
+}
+
 void LinkerScript::readGroup() {
   expect("(");
   for (;;) {
Index: test/elf2/linkerscript.s
===================================================================
--- test/elf2/linkerscript.s
+++ test/elf2/linkerscript.s
@@ -6,6 +6,10 @@
 # RUN: rm -f %t.dir/libxyz.a
 # RUN: llvm-ar rcs %t.dir/libxyz.a %t2.o
 
+# RUN: echo "EXTERN( undef undef2 )" > %t.script
+# RUN: ld.lld2 %t -o %t2 %t.script
+# RUN: llvm-readobj %t2 > /dev/null
+
 # RUN: echo "GROUP(" %t ")" > %t.script
 # RUN: ld.lld2 -o %t2 %t.script
 # RUN: llvm-readobj %t2 > /dev/null