diff --git a/core/Makefile b/core/Makefile
index 478c966..bbab48c 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -717,6 +717,9 @@
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SUPPORTS_VERITY),$(hide) echo "verity_signer_cmd=$(VERITY_SIGNER)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_VERITY_PARTITION),$(hide) echo "system_verity_block_device=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_SYSTEM_VERITY_PARTITION)" >> $(1))
 $(if $(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION),$(hide) echo "vendor_verity_block_device=$(PRODUCTS.$(INTERNAL_PRODUCT).PRODUCT_VENDOR_VERITY_PARTITION)" >> $(1))
+$(if $(filter true,$(BOARD_BUILD_SYSTEM_ROOT_IMAGE)),\
+    $(hide) echo "system_root_image=true" >> $(1);\
+    echo "ramdisk_dir=$(TARGET_ROOT_OUT)" >> $(1))
 $(if $(2),$(hide) $(foreach kv,$(2),echo "$(kv)" >> $(1);))
 endef
 
@@ -1417,7 +1420,7 @@
 	$(hide) mkdir -p $(zip_root)/META
 	$(hide) $(ACP) $(APKCERTS_FILE) $(zip_root)/META/apkcerts.txt
 	$(hide) if test -e $(tool_extensions)/releasetools.py; then $(ACP) $(tool_extensions)/releasetools.py $(zip_root)/META/; fi
-	$(hide)	echo "$(PRODUCT_OTA_PUBLIC_KEYS)" > $(zip_root)/META/otakeys.txt
+	$(hide) echo "$(PRODUCT_OTA_PUBLIC_KEYS)" > $(zip_root)/META/otakeys.txt
 	$(hide) echo "recovery_api_version=$(PRIVATE_RECOVERY_API_VERSION)" > $(zip_root)/META/misc_info.txt
 	$(hide) echo "fstab_version=$(PRIVATE_RECOVERY_FSTAB_VERSION)" >> $(zip_root)/META/misc_info.txt
 ifdef BOARD_FLASH_BLOCK_SIZE
@@ -1450,7 +1453,7 @@
 	$(hide) echo "oem_fingerprint_properties=$(OEM_THUMBPRINT_PROPERTIES)" >> $(zip_root)/META/misc_info.txt
 endif
 	$(call generate-userimage-prop-dictionary, $(zip_root)/META/misc_info.txt)
-	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH \
+	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH MKBOOTIMG=$(MKBOOTIMG) \
 	    ./build/tools/releasetools/make_recovery_patch $(zip_root) $(zip_root)
 	@# Zip everything up, preserving symlinks
 	$(hide) (cd $(zip_root) && zip -qry ../$(notdir $@) .)
@@ -1461,7 +1464,7 @@
 	$(hide) zipinfo -1 $@ | awk 'BEGIN { FS="BOOT/RAMDISK/" } /^BOOT\/RAMDISK\// {print $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/boot_filesystem_config.txt
 	$(hide) zipinfo -1 $@ | awk 'BEGIN { FS="RECOVERY/RAMDISK/" } /^RECOVERY\/RAMDISK\// {print $$2}' | $(HOST_OUT_EXECUTABLES)/fs_config -C -S $(SELINUX_FC) > $(zip_root)/META/recovery_filesystem_config.txt
 	$(hide) (cd $(zip_root) && zip -q ../$(notdir $@) META/*filesystem_config.txt)
-	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH \
+	$(hide) PATH=$(foreach p,$(INTERNAL_USERIMAGES_BINARY_PATHS),$(p):)$$PATH MKBOOTIMG=$(MKBOOTIMG) \
 	    ./build/tools/releasetools/add_img_to_target_files -p $(HOST_OUT) $@
 
 .PHONY: target-files-package
diff --git a/core/dex_preopt_libart.mk b/core/dex_preopt_libart.mk
index bee5d40..fb62e0c 100644
--- a/core/dex_preopt_libart.mk
+++ b/core/dex_preopt_libart.mk
@@ -62,7 +62,7 @@
 # $(1): the arch name.
 # $(2): the full path (including file name) of the corresponding .jar or .apk.
 define get-odex-file-path
-$(dir $(2))$(1)/$(basename $(notdir $(2))).odex
+$(dir $(2))oat/$(1)/$(basename $(notdir $(2))).odex
 endef
 
 # Returns the path to the image file (such as "/system/framework/<arch>/boot.art"
diff --git a/core/dpi_specific_apk.mk b/core/dpi_specific_apk.mk
index 0e8cbdf..06e498d 100644
--- a/core/dpi_specific_apk.mk
+++ b/core/dpi_specific_apk.mk
@@ -47,7 +47,10 @@
 ifneq ($(jni_shared_libraries),)
 	$(add-jni-shared-libs-to-package)
 endif
-ifneq ($(full_classes_jar),)
+ifeq ($(full_classes_jar),)
+# We don't build jar, need to add the Java resources here.
+	$(if $(PRIVATE_EXTRA_JAR_ARGS),$(call add-java-resources-to,$@))
+else
 	$(add-dex-to-package)
 endif
 	$(add-carried-java-resources)
diff --git a/core/package_internal.mk b/core/package_internal.mk
index e389b04..5dac455 100644
--- a/core/package_internal.mk
+++ b/core/package_internal.mk
@@ -396,7 +396,10 @@
 ifneq ($(jni_shared_libraries),)
 	$(add-jni-shared-libs-to-package)
 endif
-ifneq ($(full_classes_jar),)
+ifeq ($(full_classes_jar),)
+# We don't build jar, need to add the Java resources here.
+	$(if $(PRIVATE_EXTRA_JAR_ARGS),$(call add-java-resources-to,$@))
+else
 	$(add-dex-to-package)
 endif
 	$(sign-package)
diff --git a/core/tasks/check_boot_jars/check_boot_jars.py b/core/tasks/check_boot_jars/check_boot_jars.py
index 89d9ee8..5a0ec40 100755
--- a/core/tasks/check_boot_jars/check_boot_jars.py
+++ b/core/tasks/check_boot_jars/check_boot_jars.py
@@ -64,10 +64,10 @@
 def main(argv):
   if len(argv) < 2:
     print __doc__
-    sys.exit(1)
+    return 1
 
   if not LoadWhitelist(argv[0]):
-    sys.exit(1)
+    return 1
 
   passed = True
   for jar in argv[1:]:
@@ -80,4 +80,4 @@
 
 
 if __name__ == '__main__':
-  main(sys.argv[1:])
+  sys.exit(main(sys.argv[1:]))
diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 97ed873..7984ad6 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -137,11 +137,20 @@
   if not os.path.exists(fc_config):
     fc_config = None
 
+  # Override values loaded from info_dict.
+  if fs_config:
+    image_props["fs_config"] = fs_config
+  if fc_config:
+    image_props["selinux_fc"] = fc_config
+  if block_list:
+    image_props["block_list"] = block_list
+  if image_props.get("system_root_image") == "true":
+    image_props["ramdisk_dir"] = os.path.join(input_dir, "BOOT/RAMDISK")
+    image_props["ramdisk_fs_config"] = os.path.join(
+        input_dir, "META/boot_filesystem_config.txt")
+
   succ = build_image.BuildImage(os.path.join(input_dir, what),
-                                image_props, img,
-                                fs_config=fs_config,
-                                fc_config=fc_config,
-                                block_list=block_list)
+                                image_props, img)
   assert succ, "build " + what + ".img image failed"
 
   return img
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 359489f..4e78acb 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -194,25 +194,39 @@
   shutil.rmtree(tempdir_name, ignore_errors=True)
   return True
 
-def BuildImage(in_dir, prop_dict, out_file,
-               fs_config=None,
-               fc_config=None,
-               block_list=None):
+def BuildImage(in_dir, prop_dict, out_file):
   """Build an image to out_file from in_dir with property prop_dict.
 
   Args:
     in_dir: path of input directory.
     prop_dict: property dictionary.
     out_file: path of the output image file.
-    fs_config: path to the fs_config file (typically
-      META/filesystem_config.txt).  If None then the configuration in
-      the local client will be used.
-    fc_config: path to the SELinux file_contexts file.  If None then
-      the value from prop_dict['selinux_fc'] will be used.
 
   Returns:
     True iff the image is built successfully.
   """
+  # system_root_image=true: build a system.img that combines the contents of /system
+  # and the ramdisk, and can be mounted at the root of the file system.
+  origin_in = in_dir
+  fs_config = prop_dict.get("fs_config")
+  if (prop_dict.get("system_root_image") == "true"
+      and prop_dict["mount_point"] == "system"):
+    in_dir = tempfile.mkdtemp()
+    # Change the mount point to "/"
+    prop_dict["mount_point"] = "/"
+    if fs_config:
+      # We need to merge the fs_config files of system and ramdisk.
+      fd, merged_fs_config = tempfile.mkstemp(prefix="root_fs_config",
+                                              suffix=".txt")
+      os.close(fd)
+      with open(merged_fs_config, "w") as fw:
+        if "ramdisk_fs_config" in prop_dict:
+          with open(prop_dict["ramdisk_fs_config"]) as fr:
+            fw.writelines(fr.readlines())
+        with open(fs_config) as fr:
+          fw.writelines(fr.readlines())
+      fs_config = merged_fs_config
+
   build_command = []
   fs_type = prop_dict.get("fs_type", "")
   run_fsck = False
@@ -241,22 +255,18 @@
       build_command.extend(["-j", prop_dict["journal_size"]])
     if "timestamp" in prop_dict:
       build_command.extend(["-T", str(prop_dict["timestamp"])])
-    if fs_config is not None:
+    if fs_config:
       build_command.extend(["-C", fs_config])
-    if block_list is not None:
-      build_command.extend(["-B", block_list])
+    if "block_list" in prop_dict:
+      build_command.extend(["-B", prop_dict["block_list"]])
     build_command.extend(["-L", prop_dict["mount_point"]])
-    if fc_config is not None:
-      build_command.append(fc_config)
-    elif "selinux_fc" in prop_dict:
+    if "selinux_fc" in prop_dict:
       build_command.append(prop_dict["selinux_fc"])
   elif fs_type.startswith("squash"):
     build_command = ["mksquashfsimage.sh"]
     build_command.extend([in_dir, out_file])
     build_command.extend(["-m", prop_dict["mount_point"]])
-    if fc_config is not None:
-      build_command.extend(["-c", fc_config])
-    elif "selinux_fc" in prop_dict:
+    if "selinux_fc" in prop_dict:
       build_command.extend(["-c", prop_dict["selinux_fc"]])
   elif fs_type.startswith("f2fs"):
     build_command = ["mkf2fsuserimg.sh"]
@@ -271,7 +281,23 @@
       build_command.append(prop_dict["selinux_fc"])
       build_command.append(prop_dict["mount_point"])
 
-  exit_code = RunCommand(build_command)
+  if in_dir != origin_in:
+    # Construct a staging directory of the root file system.
+    ramdisk_dir = prop_dict.get("ramdisk_dir")
+    if ramdisk_dir:
+      shutil.rmtree(in_dir)
+      shutil.copytree(ramdisk_dir, in_dir, symlinks=True)
+    staging_system = os.path.join(in_dir, "system")
+    shutil.rmtree(staging_system, ignore_errors=True)
+    shutil.copytree(origin_in, staging_system, symlinks=True)
+  try:
+    exit_code = RunCommand(build_command)
+  finally:
+    if in_dir != origin_in:
+      # Clean up temporary directories and files.
+      shutil.rmtree(in_dir, ignore_errors=True)
+      if fs_config:
+        os.remove(fs_config)
   if exit_code != 0:
     return False
 
@@ -332,6 +358,8 @@
     copy_prop("system_size", "partition_size")
     copy_prop("system_journal_size", "journal_size")
     copy_prop("system_verity_block_device", "verity_block_device")
+    copy_prop("system_root_image","system_root_image")
+    copy_prop("ramdisk_dir","ramdisk_dir")
   elif mount_point == "data":
     # Copy the generic fs type first, override with specific one if available.
     copy_prop("fs_type", "fs_type")