diff --git a/cc/sdk.go b/cc/sdk.go
new file mode 100644
index 0000000..d05a04a
--- /dev/null
+++ b/cc/sdk.go
@@ -0,0 +1,65 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cc
+
+import (
+	"android/soong/android"
+	"android/soong/genrule"
+)
+
+// sdkMutator sets a creates a platform and an SDK variant for modules
+// that set sdk_version, and ignores sdk_version for the platform
+// variant.  The SDK variant will be used for embedding in APKs
+// that may be installed on older platforms.  Apexes use their own
+// variants that enforce backwards compatibility.
+func sdkMutator(ctx android.BottomUpMutatorContext) {
+	if ctx.Os() != android.Android {
+		return
+	}
+
+	switch m := ctx.Module().(type) {
+	case LinkableInterface:
+		if m.AlwaysSdk() {
+			if !m.UseSdk() {
+				ctx.ModuleErrorf("UseSdk() must return true when AlwaysSdk is set, did the factory forget to set Sdk_version?")
+			}
+			ctx.CreateVariations("sdk")
+		} else if m.UseSdk() {
+			modules := ctx.CreateVariations("", "sdk")
+			modules[0].(*Module).Properties.Sdk_version = nil
+			modules[1].(*Module).Properties.IsSdkVariant = true
+
+			if ctx.Config().UnbundledBuild() {
+				modules[0].(*Module).Properties.HideFromMake = true
+			} else {
+				modules[1].(*Module).Properties.SdkAndPlatformVariantVisibleToMake = true
+				modules[1].(*Module).Properties.PreventInstall = true
+			}
+			ctx.AliasVariation("")
+		} else {
+			ctx.CreateVariations("")
+			ctx.AliasVariation("")
+		}
+	case *genrule.Module:
+		if p, ok := m.Extra.(*GenruleExtraProperties); ok {
+			if String(p.Sdk_version) != "" {
+				ctx.CreateVariations("", "sdk")
+			} else {
+				ctx.CreateVariations("")
+			}
+			ctx.AliasVariation("")
+		}
+	}
+}