Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -104,6 +104,9 @@
   bool Provide = false;
   bool Hidden = false;
 
+  // Flag shows if this command is -defsym assignment.
+  bool IsDefsym = false;
+
   // Holds file name and line number for error reporting.
   std::string Location;
 };
@@ -206,6 +209,7 @@
 
   llvm::DenseMap<StringRef, OutputSection *> NameToOutputSection;
 
+  void addDefSymbol(SymbolAssignment *Cmd);
   void addSymbol(SymbolAssignment *Cmd);
   void assignSymbol(SymbolAssignment *Cmd, bool InSec);
   void setDot(Expr E, const Twine &Loc, bool InSec);
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -153,6 +153,38 @@
   Cmd->Sym = cast<Defined>(Sym);
 }
 
+void LinkerScript::addDefSymbol(SymbolAssignment *Cmd) {
+  ExprValue Value = Cmd->Expression();
+  SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
+  uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
+  uint64_t SymValue = Value.Sec ? 0 : Value.getValue();
+
+  switch (Config->EKind) {
+  case ELF32LEKind:
+    Symtab->addRegular<ELF32LE>(Cmd->Name, Visibility, STT_NOTYPE, SymValue,
+                                /*Size=*/0, STB_GLOBAL, Sec,
+                                /*File=*/nullptr);
+    return;
+  case ELF32BEKind:
+    Symtab->addRegular<ELF32BE>(Cmd->Name, Visibility, STT_NOTYPE, SymValue,
+                                /*Size=*/0, STB_GLOBAL, Sec,
+                                /*File=*/nullptr);
+    return;
+  case ELF64LEKind:
+    Symtab->addRegular<ELF64LE>(Cmd->Name, Visibility, STT_NOTYPE, SymValue,
+                                /*Size=*/0, STB_GLOBAL, Sec,
+                                /*File=*/nullptr);
+    return;
+  case ELF64BEKind:
+    Symtab->addRegular<ELF64BE>(Cmd->Name, Visibility, STT_NOTYPE, SymValue,
+                                /*Size=*/0, STB_GLOBAL, Sec,
+                                /*File=*/nullptr);
+    return;
+  default:
+    llvm_unreachable("unknown Config->EKind");
+  }
+}
+
 // This function is called from assignAddresses, while we are
 // fixing the output section addresses. This function is supposed
 // to set the final value for a given symbol assignment.
@@ -364,7 +396,10 @@
   for (BaseCommand *Base : SectionCommands) {
     // Handle symbol assignments outside of any output section.
     if (auto *Cmd = dyn_cast<SymbolAssignment>(Base)) {
-      addSymbol(Cmd);
+      if (Cmd->IsDefsym)
+        addDefSymbol(Cmd);
+      else
+        addSymbol(Cmd);
       continue;
     }
 
Index: ELF/ScriptParser.cpp
===================================================================
--- ELF/ScriptParser.cpp
+++ ELF/ScriptParser.cpp
@@ -275,6 +275,7 @@
   if (!atEOF())
     setError("EOF expected, but got " + next());
   SymbolAssignment *Cmd = make<SymbolAssignment>(Name, E, getCurrentLocation());
+  Cmd->IsDefsym = true;
   Script->SectionCommands.push_back(Cmd);
 }
 
Index: test/ELF/linkerscript/symbol-multiple-defs.s
===================================================================
--- test/ELF/linkerscript/symbol-multiple-defs.s
+++ test/ELF/linkerscript/symbol-multiple-defs.s
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+
+# RUN: echo "foo = 0x3;" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -t %t1 | FileCheck %s --check-prefix=SCRIPT
+# SCRIPT: 0000000000000003 *ABS* 00000000 foo
+
+# RUN: not ld.lld --defsym=foo=0x3 -o %t2 %t 2>&1 \
+# RUN:  | FileCheck %s --check-prefix=ERR
+# ERR: duplicate symbol: foo
+
+.global foo
+foo: