diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 292f842..4224fda 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -75,6 +75,7 @@
 LOCAL_DX_FLAGS:=
 LOCAL_EMMA_COVERAGE_FILTER:=
 LOCAL_EMMA_INSTRUMENT:=
+LOCAL_ENFORCE_USES_LIBRARIES:=
 LOCAL_ERROR_PRONE_FLAGS:=
 LOCAL_EXPORT_CFLAGS:=
 LOCAL_EXPORT_C_INCLUDE_DEPS:=
@@ -180,6 +181,7 @@
 LOCAL_NOTICE_FILE:=
 LOCAL_ODM_MODULE:=
 LOCAL_OEM_MODULE:=
+LOCAL_OPTIONAL_USES_LIBRARIES:=
 LOCAL_OVERRIDES_PACKAGES:=
 LOCAL_OVERRIDES_MODULES:=
 LOCAL_PACKAGE_NAME:=
@@ -272,6 +274,7 @@
 LOCAL_USE_CLANG_LLD:=
 LOCAL_USE_R8:=
 LOCAL_USE_VNDK:=
+LOCAL_USES_LIBRARIES:=
 LOCAL_VENDOR_MODULE:=
 LOCAL_VINTF_FRAGMENTS:=
 LOCAL_VTSC_FLAGS:=
diff --git a/core/config.mk b/core/config.mk
index 713760f..506ce1a 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -1024,6 +1024,10 @@
 INTERNAL_PLATFORM_HIDDENAPI_DARK_GREYLIST := $(TARGET_OUT_COMMON_INTERMEDIATES)/PACKAGING/hiddenapi-dark-greylist.txt
 INTERNAL_PLATFORM_HIDDENAPI_BLACKLIST := $(TARGET_OUT_COMMON_INTERMEDIATES)/PACKAGING/hiddenapi-blacklist.txt
 
+# Missing optional uses-libraries so that the platform doesn't create build rules that depend on
+# them. See setup_one_odex.mk.
+INTERNAL_PLATFORM_MISSING_USES_LIBRARIES := com.google.android.ble com.google.android.wearable
+
 # This is the standard way to name a directory containing prebuilt target
 # objects. E.g., prebuilt/$(TARGET_PREBUILT_TAG)/libc.so
 TARGET_PREBUILT_TAG := android-$(TARGET_ARCH)
diff --git a/core/construct_context.sh b/core/construct_context.sh
new file mode 100755
index 0000000..b4ae519
--- /dev/null
+++ b/core/construct_context.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+#
+# Copyright (C) 2018 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.
+
+set -e
+
+# inputs:
+# $1 is PRIVATE_CONDITIONAL_USES_LIBRARIES_HOST
+# $2 is PRIVATE_CONDITIONAL_USES_LIBRARIES_TARGET
+
+# class_loader_context: library paths on the host
+# stored_class_loader_context_libs: library paths on device
+# these are both comma separated paths, example: lib1.jar:lib2.jar or /system/framework/lib1.jar:/system/framework/lib2.jar
+
+# target_sdk_version: parsed from manifest
+# my_conditional_host_libs: libraries conditionally added for non P
+# my_conditional_target_libs: target libraries conditionally added for non P
+#
+# outputs
+# class_loader_context_arg: final class loader conext arg
+# stored_class_loader_context_arg: final stored class loader context arg
+
+my_conditional_host_libs=$1
+my_conditional_target_libs=$2
+
+# Note that SDK 28 is P.
+if [[ "${target_sdk_version}" -lt "28" ]]; then
+  if [[ -z "${class_loader_context}" ]]; then
+    export class_loader_context="${my_conditional_host_libs}"
+  else
+    export class_loader_context="${my_conditional_host_libs}:${class_loader_context}"
+  fi
+  if [[ -z "${stored_class_loader_context_libs}" ]]; then
+    export stored_class_loader_context_libs="${my_conditional_target_libs}";
+  else
+    export stored_class_loader_context_libs="${my_conditional_target_libs}:${stored_class_loader_context_libs}";
+  fi
+fi
+
+# Generate the actual context string.
+export class_loader_context_arg="--class-loader-context=PCL[${class_loader_context}]"
+export stored_class_loader_context_arg="--stored-class-loader-context=PCL[${stored_class_loader_context_libs}]"
diff --git a/core/dex_preopt_libart.mk b/core/dex_preopt_libart.mk
index 10522ac..45ec6ee 100644
--- a/core/dex_preopt_libart.mk
+++ b/core/dex_preopt_libart.mk
@@ -163,12 +163,26 @@
 
 # $(1): the input .jar or .apk file
 # $(2): the output .odex file
+# In the case where LOCAL_ENFORCE_USES_LIBRARIES is true, PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT
+# contains the normalized path list of the libraries. This makes it easier to conditionally prepend
+# org.apache.http.legacy.boot based on the SDK level if required.
 define dex2oat-one-file
 $(hide) rm -f $(2)
 $(hide) mkdir -p $(dir $(2))
-$(hide) ANDROID_LOG_TAGS="*:e" $(DEX2OAT) \
+stored_class_loader_context_libs=$(PRIVATE_DEX2OAT_STORED_CLASS_LOADER_CONTEXT_LIBS) && \
+class_loader_context_arg=--class-loader-context=$(PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT) && \
+class_loader_context=$(PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT) && \
+stored_class_loader_context_arg="" && \
+uses_library_names="$(PRIVATE_USES_LIBRARY_NAMES)" && \
+optional_uses_library_names="$(PRIVATE_OPTIONAL_USES_LIBRARY_NAMES)" && \
+$(if $(PRIVATE_ENFORCE_USES_LIBRARIES), \
+source build/make/core/verify_uses_libraries.sh "$(1)" && \
+source build/make/core/construct_context.sh "$(PRIVATE_CONDITIONAL_USES_LIBRARIES_HOST)" "$(PRIVATE_CONDITIONAL_USES_LIBRARIES_TARGET)" && \
+,) \
+ANDROID_LOG_TAGS="*:e" $(DEX2OAT) \
 	--runtime-arg -Xms$(DEX2OAT_XMS) --runtime-arg -Xmx$(DEX2OAT_XMX) \
-	--class-loader-context=$(PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT) \
+	$${class_loader_context_arg} \
+	$${stored_class_loader_context_arg} \
 	--boot-image=$(PRIVATE_DEX_PREOPT_IMAGE_LOCATION) \
 	--dex-file=$(1) \
 	--dex-location=$(PRIVATE_DEX_LOCATION) \
diff --git a/core/setup_one_odex.mk b/core/setup_one_odex.mk
index e0d9926..51df43e 100644
--- a/core/setup_one_odex.mk
+++ b/core/setup_one_odex.mk
@@ -25,17 +25,89 @@
 my_dex_preopt_image_location := $($(my_2nd_arch_prefix)DEFAULT_DEX_PREOPT_BUILT_IMAGE_LOCATION)
 endif
 my_dex_preopt_image_filename := $(call get-image-file-path,$($(my_2nd_arch_prefix)DEX2OAT_TARGET_ARCH),$(my_dex_preopt_image_location))
+
+# If LOCAL_ENFORCE_USES_LIBRARIES is not set, default to true if either of LOCAL_USES_LIBRARIES or
+# LOCAL_OPTIONAL_USES_LIBRARIES are specified.
+ifeq (,$(LOCAL_ENFORCE_USES_LIBRARIES))
+# Will change the default to true unconditionally in the future.
+ifneq (,$(LOCAL_OPTIONAL_USES_LIBRARIES))
+LOCAL_ENFORCE_USES_LIBRARIES := true
+endif
+ifneq (,$(LOCAL_USES_LIBRARIES))
+LOCAL_ENFORCE_USES_LIBRARIES := true
+endif
+endif
+
+my_uses_libraries := $(LOCAL_USES_LIBRARIES)
+my_optional_uses_libraries := $(LOCAL_OPTIONAL_USES_LIBRARIES)
+my_missing_uses_libraries := $(INTERNAL_PLATFORM_MISSING_USES_LIBRARIES)
+
+# If we have either optional or required uses-libraries, set up the class loader context
+# accordingly.
+my_lib_names :=
+my_optional_lib_names :=
+my_filtered_optional_uses_libraries :=
+my_system_dependencies :=
+my_stored_preopt_class_loader_context_libs :=
+my_conditional_uses_libraries_host :=
+my_conditional_uses_libraries_target :=
+
+ifneq (true,$(LOCAL_ENFORCE_USES_LIBRARIES))
+  # Pass special class loader context to skip the classpath and collision check.
+  # This will get removed once LOCAL_USES_LIBRARIES is enforced.
+  # Right now LOCAL_USES_LIBRARIES is opt in, for the case where it's not specified we still default
+  # to the &.
+  my_dex_preopt_class_loader_context := \&
+else
+  # Compute the filtered optional uses libraries by removing ones that are not supposed to exist.
+  my_filtered_optional_uses_libraries := \
+      $(filter-out $(my_missing_uses_libraries), $(my_optional_uses_libraries))
+  my_filtered_uses_libraries := $(my_uses_libraries) $(my_filtered_optional_uses_libraries)
+
+  # These are the ones we are verifying in the make rule, use the unfiltered libraries.
+  my_lib_names := $(my_uses_libraries)
+  my_optional_lib_names := $(my_optional_uses_libraries)
+
+  # Calculate system build dependencies based on the filtered libraries.
+  my_intermediate_libs := $(foreach lib_name, $(my_lib_names) $(my_filtered_optional_uses_libraries), \
+    $(call intermediates-dir-for,JAVA_LIBRARIES,$(lib_name),,COMMON)/javalib.jar)
+  my_dex_preopt_system_dependencies := $(my_intermediate_libs)
+  my_dex_preopt_class_loader_context := $(call normalize-path-list,$(my_intermediate_libs))
+
+  # The class loader context checksums are filled in by dex2oat.
+  my_stored_preopt_class_loader_context_libs := $(call normalize-path-list, \
+      $(foreach lib_name,$(my_filtered_uses_libraries),/system/framework/$(lib_name).jar))
+
+  # Fix up org.apache.http.legacy.boot since it should be org.apache.http.legacy in the manifest.
+  my_lib_names := $(patsubst org.apache.http.legacy.boot,org.apache.http.legacy,$(my_lib_names))
+  my_optional_lib_names := $(patsubst org.apache.http.legacy.boot,org.apache.http.legacy,$(my_optional_lib_names))
+  ifeq (,$(filter org.apache.http.legacy,$(my_lib_names) $(my_optional_lib_names)))
+    my_conditional_uses_libraries_host := $(call intermediates-dir-for,JAVA_LIBRARIES,org.apache.http.legacy.boot,,COMMON)/javalib.jar
+    my_conditional_uses_libraries_target := /system/framework/org.apache.http.legacy.boot.jar
+  endif
+endif
+
+# Always depend on org.apache.http.legacy.boot since it may get used by dex2oat-one-file for apps
+# targetting <SDK 28(P).
+my_always_depend_libraries := $(call intermediates-dir-for,JAVA_LIBRARIES,org.apache.http.legacy.boot,,COMMON)/javalib.jar
+
+$(my_built_odex): $(AAPT)
+$(my_built_odex): $(my_always_depend_libraries)
+$(my_built_odex): $(my_dex_preopt_system_dependencies)
+$(my_built_odex): PRIVATE_ENFORCE_USES_LIBRARIES := $(LOCAL_ENFORCE_USES_LIBRARIES)
+$(my_built_odex): PRIVATE_CONDITIONAL_USES_LIBRARIES_HOST := $(my_conditional_uses_libraries_host)
+$(my_built_odex): PRIVATE_CONDITIONAL_USES_LIBRARIES_TARGET := $(my_conditional_uses_libraries_target)
+$(my_built_odex): PRIVATE_USES_LIBRARY_NAMES := $(my_lib_names)
+$(my_built_odex): PRIVATE_OPTIONAL_USES_LIBRARY_NAMES := $(my_optional_lib_names)
 $(my_built_odex): PRIVATE_2ND_ARCH_VAR_PREFIX := $(my_2nd_arch_prefix)
 $(my_built_odex): PRIVATE_DEX_LOCATION := $(patsubst $(PRODUCT_OUT)%,%,$(LOCAL_INSTALLED_MODULE))
 $(my_built_odex): PRIVATE_DEX_PREOPT_IMAGE_LOCATION := $(my_dex_preopt_image_location)
+$(my_built_odex): PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT := $(my_dex_preopt_class_loader_context)
+$(my_built_odex): PRIVATE_DEX2OAT_STORED_CLASS_LOADER_CONTEXT_LIBS := $(my_stored_preopt_class_loader_context_libs)
 $(my_built_odex) : $($(my_2nd_arch_prefix)DEXPREOPT_ONE_FILE_DEPENDENCY_BUILT_BOOT_PREOPT) \
     $(DEXPREOPT_ONE_FILE_DEPENDENCY_TOOLS) \
     $(my_dex_preopt_image_filename)
 
-# Pass special class loader context to skip the classpath and collision check.
-# Should modify build system to pass used libraries properly later.
-$(my_built_odex): PRIVATE_DEX2OAT_CLASS_LOADER_CONTEXT := \&
-
 my_installed_odex := $(call get-odex-installed-file-path,$($(my_2nd_arch_prefix)DEX2OAT_TARGET_ARCH),$(LOCAL_INSTALLED_MODULE))
 
 my_built_vdex := $(patsubst %.odex,%.vdex,$(my_built_odex))
diff --git a/core/verify_uses_libraries.sh b/core/verify_uses_libraries.sh
new file mode 100755
index 0000000..8135be6
--- /dev/null
+++ b/core/verify_uses_libraries.sh
@@ -0,0 +1,45 @@
+#!/bin/bash
+#
+# Copyright (C) 2018 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.
+
+
+# Parse sdk, targetSdk, and uses librares in the APK, then cross reference against build specified ones.
+
+set -e
+local_apk=$1
+badging=$(aapt dump badging "${local_apk}")
+export sdk_version=$(echo "${badging}" | grep "sdkVersion" | sed -n "s/sdkVersion:'\(.*\)'/\1/p")
+# Export target_sdk_version to the caller.
+export target_sdk_version=$(echo "${badging}" | grep "targetSdkVersion" | sed -n "s/targetSdkVersion:'\(.*\)'/\1/p")
+uses_libraries=$(echo "${badging}" | grep "uses-library" | sed -n "s/uses-library:'\(.*\)'/\1/p")
+optional_uses_libraries=$(echo "${badging}" | grep "uses-library-not-required" | sed -n "s/uses-library-not-required:'\(.*\)'/\1/p")
+
+# Verify that the uses libraries match exactly.
+# Currently we validate the ordering of the libraries since it matters for resolution.
+single_line_libs=$(echo "${uses_libraries}" | tr '\n' ' ' | awk '{$1=$1}1')
+if [[ "${single_line_libs}" != "${uses_library_names}" ]]; then
+  echo "LOCAL_USES_LIBRARIES (${uses_library_names})" \
+       "do not match (${single_line_libs}) in manifest for ${local_apk}"
+  exit 1
+fi
+
+# Verify that the optional uses libraries match exactly.
+single_line_optional_libs=$(echo "${optional_uses_libraries}" | tr '\n' ' ' | awk '{$1=$1}1')
+if [[ "${single_line_optional_libs}" != "${optional_uses_library_names}" ]]; then
+  echo "LOCAL_OPTIONAL_USES_LIBRARIES (${optional_uses_library_names}) " \
+       "do not match (${single_line_optional_libs}) in manifest for ${local_apk}"
+  exit 1
+fi
+