diff --git a/core/Makefile b/core/Makefile
index 5a13032..99df084 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -856,6 +856,23 @@
     --os_version $(PLATFORM_VERSION_LAST_STABLE) \
     --os_patch_level $(PLATFORM_SECURITY_PATCH)
 
+ifdef BOARD_GKI_SIGNING_KEY_PATH
+ifndef BOARD_GKI_SIGNING_ALGORITHM
+$(error BOARD_GKI_SIGNING_ALGORITHM should be defined with BOARD_GKI_SIGNING_KEY_PATH)
+endif
+INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS := \
+    --gki_signing_key $(BOARD_GKI_SIGNING_KEY_PATH) \
+    --gki_signing_algorithm $(BOARD_GKI_SIGNING_ALGORITHM) \
+    --gki_signing_avbtool_path $(AVBTOOL)
+endif
+
+# Using double quote to pass BOARD_GKI_SIGNING_SIGNATURE_ARGS as a single string
+# to MKBOOTIMG, although it may contain multiple args.
+ifdef BOARD_GKI_SIGNING_SIGNATURE_ARGS
+INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS += \
+    --gki_signing_signature_args "$(BOARD_GKI_SIGNING_SIGNATURE_ARGS)"
+endif
+
 # Define these only if we are building boot
 ifdef BUILDING_BOOT_IMAGE
 INSTALLED_BOOTIMAGE_TARGET := $(BUILT_BOOTIMAGE_TARGET)
@@ -870,7 +887,8 @@
 
 # $1: boot image target
 define build_boot_board_avb_enabled
-  $(MKBOOTIMG) --kernel $(call bootimage-to-kernel,$(1)) $(INTERNAL_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $(1)
+  $(MKBOOTIMG) --kernel $(call bootimage-to-kernel,$(1)) $(INTERNAL_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) \
+               $(INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $(1)
   $(call assert-max-image-size,$(1),$(call get-hash-image-max-size,$(call get-bootimage-partition-size,$(1),boot)))
   $(AVBTOOL) add_hash_footer \
           --image $(1) \
@@ -879,12 +897,12 @@
           $(BOARD_AVB_BOOT_ADD_HASH_FOOTER_ARGS)
 endef
 
-$(INSTALLED_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(AVBTOOL) $(INTERNAL_BOOTIMAGE_FILES) $(BOARD_AVB_BOOT_KEY_PATH)
+$(INSTALLED_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(AVBTOOL) $(INTERNAL_BOOTIMAGE_FILES) $(BOARD_AVB_BOOT_KEY_PATH) $(BOARD_GKI_SIGNING_KEY_PATH)
 	$(call pretty,"Target boot image: $@")
 	$(call build_boot_board_avb_enabled,$@)
 
 .PHONY: bootimage-nodeps
-bootimage-nodeps: $(MKBOOTIMG) $(AVBTOOL) $(BOARD_AVB_BOOT_KEY_PATH)
+bootimage-nodeps: $(MKBOOTIMG) $(AVBTOOL) $(BOARD_AVB_BOOT_KEY_PATH) $(BOARD_GKI_SIGNING_KEY_PATH)
 	@echo "make $@: ignoring dependencies"
 	$(foreach b,$(INSTALLED_BOOTIMAGE_TARGET),$(call build_boot_board_avb_enabled,$(b)))
 
@@ -2149,8 +2167,8 @@
                  $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(BOARD_RECOVERY_MKBOOTIMG_ARGS) \
                  --output $(1).unsigned, \
     $(MKBOOTIMG) $(if $(strip $(2)),--kernel $(strip $(2))) $(INTERNAL_RECOVERYIMAGE_ARGS) \
-                 $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(BOARD_RECOVERY_MKBOOTIMG_ARGS) \
-                 --output $(1))
+                 $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS) \
+                 $(BOARD_RECOVERY_MKBOOTIMG_ARGS) --output $(1))
   $(if $(filter true,$(PRODUCT_SUPPORTS_BOOT_SIGNER)),\
     $(if $(filter true,$(BOARD_USES_RECOVERY_AS_BOOT)),\
       $(BOOT_SIGNER) /boot $(1) $(PRODUCT_VERITY_SIGNING_KEY).pk8 $(PRODUCT_VERITY_SIGNING_KEY).x509.pem $(1),\
@@ -2178,6 +2196,9 @@
 ifeq (true,$(BOARD_AVB_ENABLE))
   recoveryimage-deps += $(AVBTOOL) $(BOARD_AVB_BOOT_KEY_PATH)
 endif
+ifdef BOARD_GKI_SIGNING_KEY_PATH
+  recoveryimage-deps += $(BOARD_GKI_SIGNING_KEY_PATH) $(AVBTOOL)
+endif
 ifdef BOARD_INCLUDE_RECOVERY_DTBO
   ifdef BOARD_PREBUILT_RECOVERY_DTBOIMAGE
     recoveryimage-deps += $(BOARD_PREBUILT_RECOVERY_DTBOIMAGE)
@@ -2353,17 +2374,18 @@
 # $(1): output file
 define build-debug-bootimage-target
   $(MKBOOTIMG) --kernel $(PRODUCT_OUT)/$(subst .img,,$(subst boot-debug,kernel,$(notdir $(1)))) \
-    $(INTERNAL_DEBUG_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $1
+    $(INTERNAL_DEBUG_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) \
+    $(INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $1
   $(if $(BOARD_AVB_BOOT_KEY_PATH),$(call test-key-sign-bootimage,$1,boot-debug))
 endef
 
 # Depends on original boot.img and ramdisk-debug.img, to build the new boot-debug.img
-$(INSTALLED_DEBUG_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INSTALLED_BOOTIMAGE_TARGET) $(INSTALLED_DEBUG_RAMDISK_TARGET)
+$(INSTALLED_DEBUG_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INSTALLED_BOOTIMAGE_TARGET) $(INSTALLED_DEBUG_RAMDISK_TARGET) $(BOARD_GKI_SIGNING_KEY_PATH) $(AVBTOOL)
 	$(call pretty,"Target boot debug image: $@")
 	$(call build-debug-bootimage-target, $@)
 
 .PHONY: bootimage_debug-nodeps
-bootimage_debug-nodeps: $(MKBOOTIMG)
+bootimage_debug-nodeps: $(MKBOOTIMG) $(BOARD_GKI_SIGNING_KEY_PATH) $(AVBTOOL)
 	echo "make $@: ignoring dependencies"
 	$(foreach b,$(INSTALLED_DEBUG_BOOTIMAGE_TARGET),$(call build-debug-bootimage-target,$b))
 
@@ -2528,17 +2550,19 @@
 # $(1): output file
 define build-boot-test-harness-target
   $(MKBOOTIMG) --kernel $(PRODUCT_OUT)/$(subst .img,,$(subst boot-test-harness,kernel,$(notdir $(1)))) \
-    $(INTERNAL_TEST_HARNESS_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $@
+    $(INTERNAL_TEST_HARNESS_BOOTIMAGE_ARGS) $(INTERNAL_MKBOOTIMG_VERSION_ARGS) \
+    $(INTERNAL_MKBOOTIMG_GKI_SINGING_ARGS) $(BOARD_MKBOOTIMG_ARGS) --output $@
   $(if $(BOARD_AVB_BOOT_KEY_PATH),$(call test-key-sign-bootimage,$@,boot-test-harness))
 endef
 
 # Build the new boot-test-harness.img, based on boot-debug.img and ramdisk-test-harness.img.
-$(INSTALLED_TEST_HARNESS_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INSTALLED_DEBUG_BOOTIMAGE_TARGET) $(INSTALLED_TEST_HARNESS_RAMDISK_TARGET)
+$(INSTALLED_TEST_HARNESS_BOOTIMAGE_TARGET): $(MKBOOTIMG) $(INSTALLED_DEBUG_BOOTIMAGE_TARGET) $(INSTALLED_TEST_HARNESS_RAMDISK_TARGET) \
+$(BOARD_GKI_SIGNING_KEY_PATH) $(AVBTOOL)
 	$(call pretty,"Target boot test harness image: $@")
 	$(call build-boot-test-harness-target,$@)
 
 .PHONY: bootimage_test_harness-nodeps
-bootimage_test_harness-nodeps: $(MKBOOTIMG)
+bootimage_test_harness-nodeps: $(MKBOOTIMG) $(BOARD_GKI_SIGNING_KEY_PATH) $(AVBTOOL)
 	echo "make $@: ignoring dependencies"
 	$(foreach b,$(INSTALLED_TEST_HARNESS_BOOTIMAGE_TARGET),$(call build-boot-test-harness-target,$b))
 
@@ -4326,6 +4350,13 @@
 	$(hide) echo 'mkbootimg_args=$(BOARD_MKBOOTIMG_ARGS)' >> $@
 	$(hide) echo 'recovery_mkbootimg_args=$(BOARD_RECOVERY_MKBOOTIMG_ARGS)' >> $@
 	$(hide) echo 'mkbootimg_version_args=$(INTERNAL_MKBOOTIMG_VERSION_ARGS)' >> $@
+ifdef BOARD_GKI_SIGNING_KEY_PATH
+	$(hide) echo 'gki_signing_key_path=$(BOARD_GKI_SIGNING_KEY_PATH)' >> $@
+	$(hide) echo 'gki_signing_algorithm=$(BOARD_GKI_SIGNING_ALGORITHM)' >> $@
+endif
+ifdef BOARD_GKI_SIGNING_SIGNATURE_ARGS
+	$(hide) echo 'gki_signing_signature_args=$(BOARD_GKI_SIGNING_SIGNATURE_ARGS)' >> $@
+endif
 	$(hide) echo "multistage_support=1" >> $@
 	$(hide) echo "blockimgdiff_versions=3,4" >> $@
 ifeq ($(PRODUCT_BUILD_GENERIC_OTA_PACKAGE),true)
diff --git a/core/main.mk b/core/main.mk
index e2dde2d..56950ec 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -1870,7 +1870,7 @@
 ndk: $(SOONG_OUT_DIR)/ndk.timestamp
 .PHONY: ndk
 
-# Checks that build/soong/apex/allowed_deps.txt remains up to date
+# Checks that allowed_deps.txt remains up to date
 ifneq ($(UNSAFE_DISABLE_APEX_ALLOWED_DEPS_CHECK),true)
   droidcore: ${APEX_ALLOWED_DEPS_CHECK}
 endif
diff --git a/core/soong_config.mk b/core/soong_config.mk
index b4992fe..597ea78 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -199,6 +199,8 @@
 $(call add_json_list, BoardSepolicyM4Defs,               $(BOARD_SEPOLICY_M4DEFS))
 $(call add_json_str,  BoardSepolicyVers,                 $(BOARD_SEPOLICY_VERS))
 
+$(call add_json_str,  PlatformSepolicyVersion,           $(PLATFORM_SEPOLICY_VERSION))
+
 $(call add_json_bool, Flatten_apex,                      $(filter true,$(TARGET_FLATTEN_APEX)))
 $(call add_json_bool, ForceApexSymlinkOptimization,      $(filter true,$(TARGET_FORCE_APEX_SYMLINK_OPTIMIZATION)))
 
diff --git a/target/product/OWNERS b/target/product/OWNERS
index 259c8f4..82e6e88 100644
--- a/target/product/OWNERS
+++ b/target/product/OWNERS
@@ -1 +1,5 @@
 per-file runtime_libart.mk = calin@google.com, mast@google.com, ngeoffray@google.com, oth@google.com, rpl@google.com, vmarko@google.com
+
+# GSI
+per-file gsi_release.mk = file:/target/product/gsi/OWNERS
+per-file gsi_keys.mk = file:/target/product/gsi/OWNERS
diff --git a/target/product/gsi/OWNERS b/target/product/gsi/OWNERS
index 3fdd5af..39f97de 100644
--- a/target/product/gsi/OWNERS
+++ b/target/product/gsi/OWNERS
@@ -1,3 +1,6 @@
+bowgotsai@google.com
 jiyong@google.com
 justinyun@google.com
 smoreland@google.com
+szuweilin@google.com
+yochiang@google.com
diff --git a/target/product/gsi/current.txt b/target/product/gsi/current.txt
index c753e6c..550ae7c 100644
--- a/target/product/gsi/current.txt
+++ b/target/product/gsi/current.txt
@@ -14,6 +14,7 @@
 LLNDK: libmediandk.so
 LLNDK: libnativewindow.so
 LLNDK: libneuralnetworks.so
+LLNDK: libneuralnetworks_shim.so
 LLNDK: libselinux.so
 LLNDK: libsync.so
 LLNDK: libvndksupport.so
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 0061819..414ab97 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1339,6 +1339,35 @@
   RunAndCheckOutput(verify_cmd)
 
 
+def AppendGkiSigningArgs(cmd):
+  """Append GKI signing arguments for mkbootimg."""
+  # e.g., --gki_signing_key path/to/signing_key
+  #       --gki_signing_algorithm SHA256_RSA4096"
+
+  key_path = OPTIONS.info_dict.get("gki_signing_key_path")
+  # It's fine that a non-GKI boot.img has no gki_signing_key_path.
+  if not key_path:
+    return
+
+  if not os.path.exists(key_path) and OPTIONS.search_path:
+    new_key_path = os.path.join(OPTIONS.search_path, key_path)
+    if os.path.exists(new_key_path):
+      key_path = new_key_path
+
+  # Checks key_path exists, before appending --gki_signing_* args.
+  if not os.path.exists(key_path):
+    raise ExternalError('gki_signing_key_path: "{}" not found'.format(key_path))
+
+  algorithm = OPTIONS.info_dict.get("gki_signing_algorithm")
+  if key_path and algorithm:
+    cmd.extend(["--gki_signing_key", key_path,
+                "--gki_signing_algorithm", algorithm])
+
+    signature_args = OPTIONS.info_dict.get("gki_signing_signature_args")
+    if signature_args:
+      cmd.extend(["--gki_signing_signature_args", signature_args])
+
+
 def BuildVBMeta(image_path, partitions, name, needed_partitions):
   """Creates a VBMeta image.
 
@@ -1520,6 +1549,8 @@
   if has_ramdisk:
     cmd.extend(["--ramdisk", ramdisk_img.name])
 
+  AppendGkiSigningArgs(cmd)
+
   img_unsigned = None
   if info_dict.get("vboot"):
     img_unsigned = tempfile.NamedTemporaryFile()
diff --git a/tools/releasetools/sign_target_files_apks.py b/tools/releasetools/sign_target_files_apks.py
index 00acd98..3db5559 100755
--- a/tools/releasetools/sign_target_files_apks.py
+++ b/tools/releasetools/sign_target_files_apks.py
@@ -123,6 +123,17 @@
       mounted on the partition (e.g. "--signing_helper /path/to/helper"). The
       args will be appended to the existing ones in info dict.
 
+  --gki_signing_algorithm <algorithm>
+  --gki_signing_key <key>
+      Use the specified algorithm (e.g. SHA256_RSA4096) and the key to generate
+      'boot signature' in a v4 boot.img. Otherwise it uses the existing values
+      in info dict.
+
+  --gki_signing_extra_args <args>
+      Specify any additional args that are needed to generate 'boot signature'
+      (e.g. --prop foo:bar). The args will be appended to the existing ones
+      in info dict.
+
   --android_jar_path <path>
       Path to the android.jar to repack the apex file.
 """
@@ -174,6 +185,9 @@
 OPTIONS.avb_keys = {}
 OPTIONS.avb_algorithms = {}
 OPTIONS.avb_extra_args = {}
+OPTIONS.gki_signing_key = None
+OPTIONS.gki_signing_algorithm = None
+OPTIONS.gki_signing_extra_args = None
 OPTIONS.android_jar_path = None
 
 
@@ -677,6 +691,9 @@
   if misc_info.get('avb_enable') == 'true':
     RewriteAvbProps(misc_info)
 
+  # Replace the GKI signing key for boot.img, if any.
+  ReplaceGkiSigningKey(misc_info)
+
   # Write back misc_info with the latest values.
   ReplaceMiscInfoTxt(input_tf_zip, output_tf_zip, misc_info)
 
@@ -995,6 +1012,28 @@
       misc_info[args_key] = result
 
 
+def ReplaceGkiSigningKey(misc_info):
+  """Replaces the GKI signing key."""
+
+  key = OPTIONS.gki_signing_key
+  if not key:
+    return
+
+  algorithm = OPTIONS.gki_signing_algorithm
+  if not algorithm:
+    raise ValueError("Missing --gki_signing_algorithm")
+
+  print('Replacing GKI signing key with "%s" (%s)' % (key, algorithm))
+  misc_info["gki_signing_algorithm"] = algorithm
+  misc_info["gki_signing_key_path"] = key
+
+  extra_args = OPTIONS.gki_signing_extra_args
+  if extra_args:
+    print('Setting extra GKI signing args: "%s"' % (extra_args))
+    misc_info["gki_signing_signature_args"] = (
+        misc_info.get("gki_signing_signature_args", '') + ' ' + extra_args)
+
+
 def BuildKeyMap(misc_info, key_mapping_options):
   for s, d in key_mapping_options:
     if s is None:   # -d option
@@ -1226,6 +1265,12 @@
       # 'oem=--signing_helper_with_files=/tmp/avbsigner.sh'.
       partition, extra_args = a.split("=", 1)
       OPTIONS.avb_extra_args[partition] = extra_args
+    elif o == "--gki_signing_key":
+      OPTIONS.gki_signing_key = a
+    elif o == "--gki_signing_algorithm":
+      OPTIONS.gki_signing_algorithm = a
+    elif o == "--gki_signing_extra_args":
+      OPTIONS.gki_signing_extra_args = a
     else:
       return False
     return True
@@ -1273,6 +1318,9 @@
           "avb_extra_custom_image_key=",
           "avb_extra_custom_image_algorithm=",
           "avb_extra_custom_image_extra_args=",
+          "gki_signing_key=",
+          "gki_signing_algorithm=",
+          "gki_signing_extra_args=",
       ],
       extra_option_handler=option_handler)
 
diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
index ecd759c..a516366 100644
--- a/tools/releasetools/test_common.py
+++ b/tools/releasetools/test_common.py
@@ -1670,6 +1670,127 @@
                   common.OPTIONS.aftl_key_path]
     common.RunAndCheckOutput(verify_cmd)
 
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AppendGkiSigningArgs_NoSigningKeyPath(self):
+    # A non-GKI boot.img has no gki_signing_key_path.
+    common.OPTIONS.info_dict = {
+        # 'gki_signing_key_path': pubkey,
+        'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+
+    # Tests no --gki_signing_* args are appended if there is no
+    # gki_signing_key_path.
+    cmd = ['mkbootimg', '--header_version', '4']
+    expected_cmd = ['mkbootimg', '--header_version', '4']
+    common.AppendGkiSigningArgs(cmd)
+    self.assertEqual(cmd, expected_cmd)
+
+  def test_AppendGkiSigningArgs_NoSigningAlgorithm(self):
+    pubkey = os.path.join(self.testdata_dir, 'testkey_gki.pem')
+    with open(pubkey, 'wb') as f:
+      f.write(b'\x00' * 100)
+    self.assertTrue(os.path.exists(pubkey))
+
+    # Tests no --gki_signing_* args are appended if there is no
+    # gki_signing_algorithm.
+    common.OPTIONS.info_dict = {
+        'gki_signing_key_path': pubkey,
+        # 'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+
+    cmd = ['mkbootimg', '--header_version', '4']
+    expected_cmd = ['mkbootimg', '--header_version', '4']
+    common.AppendGkiSigningArgs(cmd)
+    self.assertEqual(cmd, expected_cmd)
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AppendGkiSigningArgs(self):
+    pubkey = os.path.join(self.testdata_dir, 'testkey_gki.pem')
+    with open(pubkey, 'wb') as f:
+      f.write(b'\x00' * 100)
+    self.assertTrue(os.path.exists(pubkey))
+
+    common.OPTIONS.info_dict = {
+        'gki_signing_key_path': pubkey,
+        'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+    cmd = ['mkbootimg', '--header_version', '4']
+    common.AppendGkiSigningArgs(cmd)
+
+    expected_cmd = [
+      'mkbootimg', '--header_version', '4',
+      '--gki_signing_key', pubkey,
+      '--gki_signing_algorithm', 'SHA256_RSA4096',
+      '--gki_signing_signature_args', '--prop foo:bar'
+    ]
+    self.assertEqual(cmd, expected_cmd)
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AppendGkiSigningArgs_KeyPathNotFound(self):
+    pubkey = os.path.join(self.testdata_dir, 'no_testkey_gki.pem')
+    self.assertFalse(os.path.exists(pubkey))
+
+    common.OPTIONS.info_dict = {
+        'gki_signing_key_path': pubkey,
+        'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+    cmd = ['mkbootimg', '--header_version', '4']
+    self.assertRaises(common.ExternalError, common.AppendGkiSigningArgs, cmd)
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AppendGkiSigningArgs_SearchKeyPath(self):
+    pubkey = 'testkey_gki.pem'
+    self.assertFalse(os.path.exists(pubkey))
+
+    # Tests it should replace the pubkey with an existed key under
+    # OPTIONS.search_path, i.e., os.path.join(OPTIONS.search_path, pubkey).
+    search_path_dir = common.MakeTempDir()
+    search_pubkey = os.path.join(search_path_dir, pubkey)
+    with open(search_pubkey, 'wb') as f:
+      f.write(b'\x00' * 100)
+    self.assertTrue(os.path.exists(search_pubkey))
+
+    common.OPTIONS.search_path = search_path_dir
+    common.OPTIONS.info_dict = {
+        'gki_signing_key_path': pubkey,
+        'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+    cmd = ['mkbootimg', '--header_version', '4']
+    common.AppendGkiSigningArgs(cmd)
+
+    expected_cmd = [
+      'mkbootimg', '--header_version', '4',
+      '--gki_signing_key', search_pubkey,
+      '--gki_signing_algorithm', 'SHA256_RSA4096',
+      '--gki_signing_signature_args', '--prop foo:bar'
+    ]
+    self.assertEqual(cmd, expected_cmd)
+
+  @test_utils.SkipIfExternalToolsUnavailable()
+  def test_AppendGkiSigningArgs_SearchKeyPathNotFound(self):
+    pubkey = 'no_testkey_gki.pem'
+    self.assertFalse(os.path.exists(pubkey))
+
+    # Tests it should raise ExternalError if no key found under
+    # OPTIONS.search_path.
+    search_path_dir = common.MakeTempDir()
+    search_pubkey = os.path.join(search_path_dir, pubkey)
+    self.assertFalse(os.path.exists(search_pubkey))
+
+    common.OPTIONS.search_path = search_path_dir
+    common.OPTIONS.info_dict = {
+        'gki_signing_key_path': pubkey,
+        'gki_signing_algorithm': 'SHA256_RSA4096',
+        'gki_signing_signature_args': '--prop foo:bar',
+    }
+    cmd = ['mkbootimg', '--header_version', '4']
+    self.assertRaises(common.ExternalError, common.AppendGkiSigningArgs, cmd)
+
 
 class InstallRecoveryScriptFormatTest(test_utils.ReleaseToolsTestCase):
   """Checks the format of install-recovery.sh.
diff --git a/tools/releasetools/test_sign_target_files_apks.py b/tools/releasetools/test_sign_target_files_apks.py
index 18e4858..64e27a2 100644
--- a/tools/releasetools/test_sign_target_files_apks.py
+++ b/tools/releasetools/test_sign_target_files_apks.py
@@ -23,8 +23,8 @@
 import test_utils
 from sign_target_files_apks import (
     CheckApkAndApexKeysAvailable, EditTags, GetApkFileInfo, ReadApexKeysInfo,
-    ReplaceCerts, ReplaceVerityKeyId, RewriteAvbProps, RewriteProps,
-    WriteOtacerts)
+    ReplaceCerts, ReplaceGkiSigningKey, ReplaceVerityKeyId, RewriteAvbProps,
+    RewriteProps, WriteOtacerts)
 
 
 class SignTargetFilesApksTest(test_utils.ReleaseToolsTestCase):
@@ -588,3 +588,52 @@
             'system/apex/apexd/apexd_testdata/com.android.apex.test_package_2.pem',
             'build/make/target/product/security/testkey'),
         }, keys_info)
+
+  def test_ReplaceGkiSigningKey(self):
+    common.OPTIONS.gki_signing_key = 'release_gki_key'
+    common.OPTIONS.gki_signing_algorithm = 'release_gki_algorithm'
+    common.OPTIONS.gki_signing_extra_args = 'release_gki_signature_extra_args'
+
+    misc_info = {
+        'gki_signing_key_path': 'default_gki_key',
+        'gki_signing_algorithm': 'default_gki_algorithm',
+        'gki_signing_signature_args': 'default_gki_signature_args',
+    }
+    expected_dict = {
+        'gki_signing_key_path': 'release_gki_key',
+        'gki_signing_algorithm': 'release_gki_algorithm',
+        'gki_signing_signature_args': 'default_gki_signature_args release_gki_signature_extra_args',
+    }
+    ReplaceGkiSigningKey(misc_info)
+    self.assertDictEqual(expected_dict, misc_info)
+
+  def test_ReplaceGkiSigningKey_MissingSigningAlgorithm(self):
+    common.OPTIONS.gki_signing_key = 'release_gki_key'
+    common.OPTIONS.gki_signing_algorithm = None
+    common.OPTIONS.gki_signing_extra_args = 'release_gki_signature_extra_args'
+
+    misc_info = {
+        'gki_signing_key_path': 'default_gki_key',
+        'gki_signing_algorithm': 'default_gki_algorithm',
+        'gki_signing_signature_args': 'default_gki_signature_args',
+    }
+    self.assertRaises(ValueError, ReplaceGkiSigningKey, misc_info)
+
+  def test_ReplaceGkiSigningKey_MissingSigningKeyNop(self):
+    common.OPTIONS.gki_signing_key = None
+    common.OPTIONS.gki_signing_algorithm = 'release_gki_algorithm'
+    common.OPTIONS.gki_signing_extra_args = 'release_gki_signature_extra_args'
+
+    # No change to misc_info if common.OPTIONS.gki_signing_key is missing.
+    misc_info = {
+        'gki_signing_key_path': 'default_gki_key',
+        'gki_signing_algorithm': 'default_gki_algorithm',
+        'gki_signing_signature_args': 'default_gki_signature_args',
+    }
+    expected_dict = {
+        'gki_signing_key_path': 'default_gki_key',
+        'gki_signing_algorithm': 'default_gki_algorithm',
+        'gki_signing_signature_args': 'default_gki_signature_args',
+    }
+    ReplaceGkiSigningKey(misc_info)
+    self.assertDictEqual(expected_dict, misc_info)