diff --git a/NativeCode.mk b/NativeCode.mk
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index 0000000..0dfad3b
--- /dev/null
+++ b/NativeCode.mk
@@ -0,0 +1,121 @@
+# Copyright (C) 2007 The Android Open Source Project
+#
+# 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.
+
+#
+# Definitions for building the native code needed for the core library.
+#
+
+#
+# Common definitions for host and target.
+#
+
+# Get the list of all native directories that contain sub.mk files.
+# We're using "sub.mk" to make it clear that these are not typical
+# android makefiles.
+define all-core-native-dirs
+$(patsubst %/sub.mk,%,$(shell cd $(LOCAL_PATH) && ls -d */src/$(1)/native/sub.mk 2> /dev/null))
+endef
+
+# These two definitions are used to help sanity check what's put in
+# sub.mk. See, the "error" directives immediately below.
+core_magic_local_target := ...//::default:://...
+core_local_path := $(LOCAL_PATH)
+
+# Include a submakefile, resolve its source file locations,
+# and stick them on core_src_files.  The submakefiles are
+# free to append to LOCAL_SRC_FILES, LOCAL_C_INCLUDES,
+# LOCAL_SHARED_LIBRARIES, or LOCAL_STATIC_LIBRARIES, but nothing
+# else. All other LOCAL_* variables will be ignored.
+#
+# $(1): directory containing the makefile to include
+define include-core-native-dir
+    LOCAL_SRC_FILES :=
+    include $(LOCAL_PATH)/$(1)/sub.mk
+    ifneq ($$(LOCAL_MODULE),$(core_magic_local_target))
+        $$(error $(LOCAL_PATH)/$(1)/sub.mk should not include CLEAR_VARS \
+            or define LOCAL_MODULE)
+    endif
+    ifneq ($$(LOCAL_PATH),$(core_local_path))
+        $$(error $(LOCAL_PATH)/$(1)/sub.mk should not define LOCAL_PATH)
+    endif
+    core_src_files += $$(addprefix $(1)/,$$(LOCAL_SRC_FILES))
+    LOCAL_SRC_FILES :=
+endef
+
+# Find any native directories containing sub.mk files.
+core_native_dirs := $(strip $(call all-core-native-dirs,main))
+ifeq ($(core_native_dirs),)
+    $(error No native code defined for libcore)
+endif
+
+# Set up the default state. Note: We use CLEAR_VARS here, even though
+# we aren't quite defining a new rule yet, to make sure that the
+# sub.mk files don't see anything stray from the last rule that was
+# set up.
+include $(CLEAR_VARS)
+LOCAL_MODULE := $(core_magic_local_target)
+core_src_files :=
+
+# Include the sub.mk files.
+$(foreach dir, \
+    $(core_native_dirs), \
+    $(eval $(call include-core-native-dir,$(dir))))
+
+# Extract out the allowed LOCAL_* variables. Note: $(sort) also
+# removes duplicates.
+core_c_includes := $(sort $(LOCAL_C_INCLUDES) $(JNI_H_INCLUDE))
+core_shared_libraries := $(sort $(LOCAL_SHARED_LIBRARIES))
+core_static_libraries := $(sort $(LOCAL_STATIC_LIBRARIES))
+
+
+#
+# Build for the target (device).
+#
+
+include $(CLEAR_VARS)
+
+# Define the rules.
+LOCAL_SRC_FILES := $(core_src_files)
+LOCAL_C_INCLUDES := $(core_c_includes)
+LOCAL_SHARED_LIBRARIES := $(core_shared_libraries)
+LOCAL_STATIC_LIBRARIES := $(core_static_libraries)
+LOCAL_MODULE := libjavacore
+include $(BUILD_STATIC_LIBRARY)
+
+# Deal with keystores required for security. Note: The path to this file
+# is hardcoded in TrustManagerFactoryImpl.java.
+ALL_PREBUILT += $(TARGET_OUT)/etc/security/cacerts.bks
+$(TARGET_OUT)/etc/security/cacerts.bks : $(LOCAL_PATH)/security/src/main/files/cacerts.bks | $(ACP)
+	$(transform-prebuilt-to-target)
+
+
+#
+# Build for the host.
+#
+
+ifeq ($(WITH_HOST_DALVIK),true)
+
+    include $(CLEAR_VARS)
+
+    # Define the rules.
+    LOCAL_SRC_FILES := $(core_src_files)
+    LOCAL_C_INCLUDES := $(core_c_includes)
+    LOCAL_SHARED_LIBRARIES := $(core_shared_libraries)
+    LOCAL_STATIC_LIBRARIES := $(core_static_libraries)
+    LOCAL_MODULE := libjavacore-host
+    include $(BUILD_HOST_STATIC_LIBRARY)
+
+    # TODO: Figure out cacerts.bks for the host.
+
+endif
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