Index: test/tools/llvm-objcopy/weaken-all.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/weaken-all.test
@@ -0,0 +1,94 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy --weaken %t %t2
+# RUN: llvm-readobj -symbols %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Size:            64
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Info:            .text
+    Relocations:
+      - Offset: 0x1000
+        Symbol: undefGlobal
+        Type:   R_X86_64_PC32
+Symbols:
+  Local:
+    - Name:     Local
+      Type:     STT_FUNC
+      Section:  .text
+      Value:    0x1008
+      Size:     8
+  Weak:
+    - Name:     Weak
+      Type:     STT_FUNC
+      Size:     8
+      Section:  .text
+      Value:    0x1010
+  Global:
+    - Name:     Global
+      Type:     STT_FUNC
+      Size:     8
+      Section:  .text
+      Value:    0x1018
+    - Name:     undefGlobal
+      Type:     STT_FUNC
+      Size:     8
+
+#CHECK: Symbols [
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name:
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 0
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: None
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: Undefined
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Local
+#CHECK-NEXT:    Value: 0x1008
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Local
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Global
+#CHECK-NEXT:    Value: 0x1018
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Weak
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: undefGlobal
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Global
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section:
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: Weak
+#CHECK-NEXT:    Value: 0x1010
+#CHECK-NEXT:    Size: 8
+#CHECK-NEXT:    Binding: Weak
+#CHECK-NEXT:    Type: Function
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: .text
+#CHECK-NEXT:  }
+#CHECK-NEXT:]
Index: tools/llvm-objcopy/Opts.td
===================================================================
--- tools/llvm-objcopy/Opts.td
+++ tools/llvm-objcopy/Opts.td
@@ -72,3 +72,5 @@
                        HelpText<"Mark <symbol> as weak">;
 def W : JoinedOrSeparate<["-"], "W">,
         Alias<weaken_symbol>;
+def weaken : Flag<["-", "--"], "weaken">,
+                  HelpText<"Mark all global symbols as weak">;
Index: tools/llvm-objcopy/llvm-objcopy.cpp
===================================================================
--- tools/llvm-objcopy/llvm-objcopy.cpp
+++ tools/llvm-objcopy/llvm-objcopy.cpp
@@ -130,6 +130,7 @@
   bool StripDWO;
   bool ExtractDWO;
   bool LocalizeHidden;
+  bool Weaken;
 };
 
 using SectionPred = std::function<bool(const SectionBase &Sec)>;
@@ -334,6 +335,10 @@
           Sym.Binding == STB_GLOBAL)
         Sym.Binding = STB_WEAK;
 
+      if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
+          Sym.getShndx() != SHN_UNDEF)
+        Sym.Binding = STB_WEAK;
+
       const auto I = Config.SymbolsToRename.find(Sym.Name);
       if (I != Config.SymbolsToRename.end())
         Sym.Name = I->getValue();
@@ -423,6 +428,7 @@
   Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
   Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
   Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
+  Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
   for (auto Arg : InputArgs.filtered(OBJCOPY_localize_symbol))
     Config.SymbolsToLocalize.push_back(Arg->getValue());
   for (auto Arg : InputArgs.filtered(OBJCOPY_globalize_symbol))