Index: lld/MachO/InputFiles.cpp
===================================================================
--- lld/MachO/InputFiles.cpp
+++ lld/MachO/InputFiles.cpp
@@ -439,6 +439,12 @@
 static macho::Symbol *createDefined(const NList &sym, StringRef name,
                                     InputSection *isec, uint64_t value,
                                     uint64_t size) {
+  // LLVM's assembler isn't able to produce .o files with this set.
+  // If a tool ever appears that produces input files with this set,
+  // we'll have to add an `isReferencedDynamically` arg to Defined's
+  // constructor and pass this in.
+  assert(!(sym.n_desc & REFERENCED_DYNAMICALLY));
+
   // Symbol scope is determined by sym.n_type & (N_EXT | N_PEXT):
   // N_EXT: Global symbols. These go in the symbol table during the link,
   //        and also in the export table of the output so that the dynamic
Index: lld/MachO/Symbols.h
===================================================================
--- lld/MachO/Symbols.h
+++ lld/MachO/Symbols.h
@@ -115,8 +115,8 @@
           bool isThumb)
       : Symbol(DefinedKind, name, file), isec(isec), value(value), size(size),
         overridesWeakDef(false), privateExtern(isPrivateExtern),
-        includeInSymtab(true), thumb(isThumb), weakDef(isWeakDef),
-        external(isExternal) {
+        includeInSymtab(true), thumb(isThumb), referencedDynamically(false),
+        weakDef(isWeakDef), external(isExternal) {
     if (isec)
       isec->numRefs++;
   }
@@ -151,6 +151,11 @@
   bool includeInSymtab : 1;
   // Only relevant when compiling for Thumb-supporting arm32 archs.
   bool thumb : 1;
+  // Symbols marked referencedDynamically won't be removed from the output's
+  // symbol table by tools like strip. In theory, this could be set on arbitrary
+  // symbols in input object files. In practice, it's used solely for the
+  // synthetic __mh_execute_header symbol.
+  bool referencedDynamically : 1;
 
 private:
   const bool weakDef : 1;
Index: lld/MachO/SyntheticSections.cpp
===================================================================
--- lld/MachO/SyntheticSections.cpp
+++ lld/MachO/SyntheticSections.cpp
@@ -856,6 +856,8 @@
       }
       nList->n_desc |= defined->thumb ? N_ARM_THUMB_DEF : 0;
       nList->n_desc |= defined->isExternalWeakDef() ? N_WEAK_DEF : 0;
+      if (defined->referencedDynamically)
+        nList->n_desc |= REFERENCED_DYNAMICALLY;
     } else if (auto *dysym = dyn_cast<DylibSymbol>(entry.sym)) {
       uint16_t n_desc = nList->n_desc;
       int16_t ordinal = ordinalForDylibSymbol(*dysym);
@@ -1099,22 +1101,26 @@
   switch (config->outputType) {
     // FIXME: Assign the right address value for these symbols
     // (rather than 0). But we need to do that after assignAddresses().
-  case MH_EXECUTE:
+  case MH_EXECUTE: {
     // If linking PIE, __mh_execute_header is a defined symbol in
     //  __TEXT, __text)
     // Otherwise, it's an absolute symbol.
+    Defined *execHeader;
     if (config->isPic)
-      symtab->addSynthetic("__mh_execute_header", in.header->isec, /*value=*/0,
-                           /*privateExtern=*/false,
-                           /*includeInSymtab=*/true);
+      execHeader = symtab->addSynthetic("__mh_execute_header", in.header->isec,
+                                        /*value=*/0,
+                                        /*privateExtern=*/false,
+                                        /*includeInSymtab=*/true);
     else
-      symtab->addSynthetic("__mh_execute_header",
-                           /*isec*/ nullptr, /*value=*/0,
-                           /*privateExtern=*/false,
-                           /*includeInSymtab=*/true);
+      execHeader = symtab->addSynthetic("__mh_execute_header",
+                                        /*isec=*/nullptr, /*value=*/0,
+                                        /*privateExtern=*/false,
+                                        /*includeInSymtab=*/true);
+    execHeader->referencedDynamically = true;
     break;
+  }
 
-    // The following symbols are  N_SECT symbols, even though the header is not
+    // The following symbols are N_SECT symbols, even though the header is not
     // part of any section and that they are private to the bundle/dylib/object
     // they are part of.
   case MH_BUNDLE:
Index: lld/test/MachO/stabs.s
===================================================================
--- lld/test/MachO/stabs.s
+++ lld/test/MachO/stabs.s
@@ -78,7 +78,7 @@
 # CHECK-DAG:  (     SECT EXT) [[#%.2d,COMM_ID + 1]]      0000   [[#ZERO]]          '_zero'
 # CHECK-DAG:  (     SECT EXT) [[#%.2d,MORE_TEXT_ID + 1]] 0000   [[#FUN]]           '_fun'
 # CHECK-DAG:  (     SECT EXT) [[#%.2d,TEXT_ID + 1]]      0000   {{[0-9a-f]+}}      '_no_debug'
-# CHECK-DAG:  (       {{.*}}) {{[0-9]+}}                 0000   {{[0-9a-f]+}}      '__mh_execute_header'
+# CHECK-DAG:  (       {{.*}}) {{[0-9]+}}                 0010   {{[0-9a-f]+}}      '__mh_execute_header'
 # CHECK-EMPTY:
 
 ## Check that we don't attempt to emit rebase opcodes for the debug sections
Index: lld/test/MachO/symtab.s
===================================================================
--- lld/test/MachO/symtab.s
+++ lld/test/MachO/symtab.s
@@ -62,7 +62,8 @@
 # CHECK-NEXT:    Type: Section (0xE)
 # CHECK-NEXT:    Section: __text (0x1)
 # CHECK-NEXT:    RefType: UndefinedNonLazy (0x0)
-# CHECK-NEXT:    Flags [ (0x0)
+# CHECK-NEXT:    Flags [ (0x10)
+# CHECK-NEXT:      ReferencedDynamically (0x10)
 # CHECK-NEXT:    ]
 # CHECK-NEXT:    Value: 0x100000000
 # CHECK-NEXT:  }