在AOSP中使用libcryptsetup编译ramdisk时，需要在BoardConfig.mk文件中添加相应的配置项，以解决编译失败的问题。具体步骤如下：

1. 在BoardConfig.mk文件中添加以下配置项：

BOARD_BUILD_RAMDISK_WITH_CRYPTO := true
CRYPTO_TYPE := cryptsetup

2. 修改mkbootfs源文件，需要添加libcryptsetup库，例如Android 9.0源码中路径为external/sepolicy/tools/mkbootfs。

LOCAL_CFLAGS := \
        -DSYSTEM_ROOT_IMAGE='"$(PRODUCT_OUT)/system.img"' \
        -DOVERRIDE_ANDROID_FILESYSTEM_CONFIG \
        -DANDROID_FILESYSTEM_CONFIG=\"$(COMMON_OUT_DIR)/etc/filesystems_config.h\" \
        -DSHORT_VERSION='"$(PLATFORM_VERSION)"' \
        -DPLATFORM_VERSION_UNSIGNED=$(PLATFORM_VERSION_UNSIGNED) \
        -DPLATFORM_SDK_VERSION=$(PLATFORM_SDK_VERSION) \
        -DSYSTEM_DEFAULT_PROPERTIES_PATH=\"$(COMMON_OUT_DIR)/etc/system.default.prop\" \
        -DSYSTEM_ENCRYPTED_PROPERTIES_PATH=\"$(COMMON_OUT_DIR)/etc/system.encrypted.props\" \
        -DSYSTEM_SERVER_CONFIG_PATH=\"$(COMMON_OUT_DIR)/etc/server_config.xml\" \
        -DSYSTEM_SECURE_PROPERTIES_PATH=\"$(COMMON_OUT_DIR)/etc/security.config\" \
        -DANDROID_RAMDISK_SOURCE_PREFIX=\"$(TARGET_PREBUILT_KERNEL_RAMDISK_DIR)/\" \
        -I$(PRIVATE) \
        -I$(PRIVATE)/include \
        -I$(PRIVATE)/../sepolicy/include \
        -I$(PRIVATE)/../libcryptfs/include
        // 添加上面最后一行，引入libcryptfs库

3. 在BoardConfig.mk文件中添加以下配置项：

BOARD_PREBUILT_RAMDISK_DIR := $(PRODUCT_OUT)/ramdisk_encrypt
# if ramdisk encrypt is true, the key is generated from
# the 32byte long CRYPTO_PASSWORD_ANDROID, otherwise a randomly
# generated key is used.

BOARD_RECOVERYIMAGE_PARTITION_SIZE := 128M
BOARD_RECOVERYRAMDISK_PARTITION_SIZE := 32M

ifeq ($(BOARD_BUILD_RAMDISK_WITH_CRYPTO), true)
  ifneq ($(CRYPTO_TYPE),cryptfs)
    $(error Invalid CRYPTO_TYPE=$(CRYPTO_TYPE), supported values: cryptfs)
  endif
  PRODUCT_BUILD_WITH_ENCRYPTED_RAMDISK := true
  PRODUCT_SYSTEM_RAMDISK_ENCRYPT := true
  # first 16 bytes of crypto key will be reserved
  PRODUCT_ENCRYPTED_RAMDISK_EXTRA_ARGS := "--crypto_keyspace 32 --crypto_blkdev nodev --crypto_type cryptfs"
  CRYPTO_ALGORITHM := aes-cbc-essiv:sha256
  CRYPTO_KEYSIZE := 256
  ENCRYPT_IN_KERNEL := true
  TARGET_PROVIDES_INIT := true

  # Include libcryptfs libraries in the target
  PRODUCT_PACKAGES += libcryptfs libcryptfs-utils

  ifeq ($(TARGET_INIT_VENDOR),)
    TARGET_INIT_VENDOR := $(LOCAL_PATH)/../../init/init_vendor
  endif
endif

4. 添加init.rc配置启动ramdisk加密：

# Property indicating the presence of a prebuilt encrypted ramdisk
# image. This is set by the build system when building an OTA for a
# device with encrypted ramdisk support.
#
# After checking the initial state to see if ramdisk encryption is
# enabled, the script at /init.encrypted-ramdisk will be executed,
# which will ensure that the device can mount the encrypted partitions
# required for decrypting the ramdisk. The actual encryption of the
# ram