Index: ELF/Driver.cpp
===================================================================
--- ELF/Driver.cpp
+++ ELF/Driver.cpp
@@ -877,6 +877,37 @@
   return V;
 }
 
+// Function used to handle --defsym= option. It can be one of 3:
+// 1) --defsym=name=alias
+// 2) --defsym=name=integer
+// 3) --defsym=name=expression
+// We support first two. Alias implemented very similar to --wrap option,
+// second form simply creates an absolute symbol. We do not support
+// expressions with math for simplicity.
+template <class ELFT> static void handleDefsym(opt::InputArgList &Args) {
+  std::vector<std::pair<StringRef, StringRef>> Ret;
+  for (auto *Arg : Args.filtered(OPT_defsym)) {
+    StringRef Name;
+    StringRef Expr;
+    std::tie(Name, Expr) = StringRef(Arg->getValue()).split('=');
+
+    if (isValidCIdentifier(Expr)) {
+      Symtab<ELFT>::X->alias(Name, Expr);
+      continue;
+    }
+
+    uint64_t Val;
+    if (!Expr.getAsInteger(0, Val)) {
+      DefinedRegular *DR =
+          Symtab<ELFT>::X->addAbsolute(Name, STV_DEFAULT, STB_GLOBAL);
+      DR->Value = Val;
+      continue;
+    }
+
+    error("--defsym=: number expected, but got " + Expr);
+  }
+}
+
 // Do actual linking. Note that when this function is called,
 // all linker scripts have already been parsed.
 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
@@ -942,6 +973,9 @@
   for (auto *Arg : Args.filtered(OPT_wrap))
     Symtab.wrap(Arg->getValue());
 
+  // Handle --defsym=sym=expr option.
+  handleDefsym<ELFT>(Args);
+
   // Now that we have a complete list of input files.
   // Beyond this point, no new files are added.
   // Aggregate all input sections into one place.
Index: ELF/Options.td
===================================================================
--- ELF/Options.td
+++ ELF/Options.td
@@ -25,6 +25,8 @@
 def compress_debug_sections : J<"compress-debug-sections=">,
   HelpText<"Compress DWARF debug sections">;
 
+def defsym: J<"defsym=">, HelpText<"Create a global symbol alias or absolute symbol">;
+
 def L: JoinedOrSeparate<["-"], "L">, MetaVarName<"<dir>">,
   HelpText<"Add a directory to the library search path">;
 
Index: ELF/SymbolTable.h
===================================================================
--- ELF/SymbolTable.h
+++ ELF/SymbolTable.h
@@ -86,6 +86,7 @@
 
   void trace(StringRef Name);
   void wrap(StringRef Name);
+  void alias(StringRef Alias, StringRef Name);
 
 private:
   std::vector<SymbolBody *> findByVersion(SymbolVersion Ver);
Index: ELF/SymbolTable.cpp
===================================================================
--- ELF/SymbolTable.cpp
+++ ELF/SymbolTable.cpp
@@ -168,6 +168,19 @@
   memcpy(Sym->Body.buffer, Wrap->Body.buffer, sizeof(Wrap->Body));
 }
 
+// Creates alias for symbol. Used to implement --defsym=SYM=ALIAS
+template <class ELFT>
+void SymbolTable<ELFT>::alias(StringRef Alias, StringRef Name) {
+  SymbolBody *B = find(Name);
+  if (!B) {
+    error("undefined symbol '" + Name + "' used in --defsym= expression");
+    return;
+  }
+  Symbol *Sym = B->symbol();
+  Symbol *AliasSym = addUndefined(Alias);
+  memcpy(AliasSym->Body.buffer, Sym->Body.buffer, sizeof(AliasSym->Body));
+}
+
 static uint8_t getMinVisibility(uint8_t VA, uint8_t VB) {
   if (VA == STV_DEFAULT)
     return VB;
Index: test/ELF/defsym.s
===================================================================
--- test/ELF/defsym.s
+++ test/ELF/defsym.s
@@ -0,0 +1,41 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld -o %t %t.o --defsym=foo2=foo1 --defsym=foo3=0x456
+# RUN: llvm-readobj -t -s %t | FileCheck %s
+
+# CHECK:      Symbol {
+# CHECK:        Name: foo1
+# CHECK-NEXT:   Value: [[ADDR:.*]]
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Binding: Global
+# CHECK-NEXT:   Type:
+# CHECK-NEXT:   Other:
+# CHECK-NEXT:   Section: Absolute
+# CHECK-NEXT: }
+# CHECK-NEXT: Symbol {
+# CHECK-NEXT:   Name: foo1
+# CHECK-NEXT:   Value: [[ADDR]]
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Binding: Global
+# CHECK-NEXT:   Type:
+# CHECK-NEXT:   Other:
+# CHECK-NEXT:   Section: Absolute
+# CHECK-NEXT: }
+# CHECK-NEXT: Symbol {
+# CHECK-NEXT:   Name: foo3
+# CHECK-NEXT:   Value: 0x456
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Binding: Global
+# CHECK-NEXT:   Type:
+# CHECK-NEXT:   Other:
+# CHECK-NEXT:   Section: Absolute
+# CHECK-NEXT: }
+
+# RUN: not ld.lld -o %t %t.o --defsym=foo2=foo1+1 2>&1 | FileCheck %s -check-prefix=ERR1
+# ERR1: error: --defsym=: number expected, but got foo1+1
+
+# RUN: not ld.lld -o %t %t.o --defsym=foo2=und 2>&1 | FileCheck %s -check-prefix=ERR2
+# ERR2: error: undefined symbol 'und' used in --defsym= expression
+
+.globl foo1
+ foo1 = 0x123