poky/meta/classes/uboot-sign.bbclass - mdmillerii/openbmc - Gitiles

 # This file is part of U-Boot verified boot support and is intended to be
 # inherited from u-boot recipe and from kernel-fitimage.bbclass.
 #
 # The signature procedure requires the user to generate an RSA key and
 # certificate in a directory and to define the following variable:
 #
 #   UBOOT_SIGN_KEYDIR = "/keys/directory"
 #   UBOOT_SIGN_KEYNAME = "dev" # keys name in keydir (eg. "dev.crt", "dev.key")
 #   UBOOT_MKIMAGE_DTCOPTS = "-I dts -O dtb -p 2000"
 #   UBOOT_SIGN_ENABLE = "1"
 #
 # As verified boot depends on fitImage generation, following is also required:
 #
 #   KERNEL_CLASSES ?= " kernel-fitimage "
 #   KERNEL_IMAGETYPE ?= "fitImage"
 #
 # The signature support is limited to the use of CONFIG_OF_SEPARATE in U-Boot.
 #
 # The tasks sequence is set as below, using DEPLOY_IMAGE_DIR as common place to
 # treat the device tree blob:
 #
 # * u-boot:do_install:append
 #   Install UBOOT_DTB_BINARY to datadir, so that kernel can use it for
 #   signing, and kernel will deploy UBOOT_DTB_BINARY after signs it.
 #
 # * virtual/kernel:do_assemble_fitimage
 #   Sign the image
 #
 # * u-boot:do_deploy[postfuncs]
 #   Deploy files like UBOOT_DTB_IMAGE, UBOOT_DTB_SYMLINK and others.
 #
 # For more details on signature process, please refer to U-Boot documentation.

 # We need some variables from u-boot-config
 inherit uboot-config

 # Enable use of a U-Boot fitImage
 UBOOT_FITIMAGE_ENABLE ?= "0"

 # Signature activation - these require their respective fitImages
 UBOOT_SIGN_ENABLE ?= "0"
 SPL_SIGN_ENABLE ?= "0"

 # Default value for deployment filenames.
 UBOOT_DTB_IMAGE ?= "u-boot-${MACHINE}-${PV}-${PR}.dtb"
 UBOOT_DTB_BINARY ?= "u-boot.dtb"
 UBOOT_DTB_SYMLINK ?= "u-boot-${MACHINE}.dtb"
 UBOOT_NODTB_IMAGE ?= "u-boot-nodtb-${MACHINE}-${PV}-${PR}.bin"
 UBOOT_NODTB_BINARY ?= "u-boot-nodtb.bin"
 UBOOT_NODTB_SYMLINK ?= "u-boot-nodtb-${MACHINE}.bin"
 UBOOT_ITS_IMAGE ?= "u-boot-its-${MACHINE}-${PV}-${PR}"
 UBOOT_ITS ?= "u-boot.its"
 UBOOT_ITS_SYMLINK ?= "u-boot-its-${MACHINE}"
 UBOOT_FITIMAGE_IMAGE ?= "u-boot-fitImage-${MACHINE}-${PV}-${PR}"
 UBOOT_FITIMAGE_BINARY ?= "u-boot-fitImage"
 UBOOT_FITIMAGE_SYMLINK ?= "u-boot-fitImage-${MACHINE}"
 SPL_DIR ?= "spl"
 SPL_DTB_IMAGE ?= "u-boot-spl-${MACHINE}-${PV}-${PR}.dtb"
 SPL_DTB_BINARY ?= "u-boot-spl.dtb"
 SPL_DTB_SYMLINK ?= "u-boot-spl-${MACHINE}.dtb"
 SPL_NODTB_IMAGE ?= "u-boot-spl-nodtb-${MACHINE}-${PV}-${PR}.bin"
 SPL_NODTB_BINARY ?= "u-boot-spl-nodtb.bin"
 SPL_NODTB_SYMLINK ?= "u-boot-spl-nodtb-${MACHINE}.bin"

 # U-Boot fitImage description
 UBOOT_FIT_DESC ?= "U-Boot fitImage for ${DISTRO_NAME}/${PV}/${MACHINE}"

 # Kernel / U-Boot fitImage Hash Algo
 FIT_HASH_ALG ?= "sha256"
 UBOOT_FIT_HASH_ALG ?= "sha256"

 # Kernel / U-Boot fitImage Signature Algo
 FIT_SIGN_ALG ?= "rsa2048"
 UBOOT_FIT_SIGN_ALG ?= "rsa2048"

 # Kernel / U-Boot fitImage Padding Algo
 FIT_PAD_ALG ?= "pkcs-1.5"

 # Generate keys for signing Kernel / U-Boot fitImage
 FIT_GENERATE_KEYS ?= "0"
 UBOOT_FIT_GENERATE_KEYS ?= "0"

 # Size of private keys in number of bits
 FIT_SIGN_NUMBITS ?= "2048"
 UBOOT_FIT_SIGN_NUMBITS ?= "2048"

 # args to openssl genrsa (Default is just the public exponent)
 FIT_KEY_GENRSA_ARGS ?= "-F4"
 UBOOT_FIT_KEY_GENRSA_ARGS ?= "-F4"

 # args to openssl req (Default is -batch for non interactive mode and
 # -new for new certificate)
 FIT_KEY_REQ_ARGS ?= "-batch -new"
 UBOOT_FIT_KEY_REQ_ARGS ?= "-batch -new"

 # Standard format for public key certificate
 FIT_KEY_SIGN_PKCS ?= "-x509"
 UBOOT_FIT_KEY_SIGN_PKCS ?= "-x509"

 # Functions on this bbclass can apply to either U-boot or Kernel,
 # depending on the scenario
 UBOOT_PN = "${@d.getVar('PREFERRED_PROVIDER_u-boot') or 'u-boot'}"
 KERNEL_PN = "${@d.getVar('PREFERRED_PROVIDER_virtual/kernel')}"

 # We need u-boot-tools-native if we're creating a U-Boot fitImage
 python() {
     if d.getVar('UBOOT_FITIMAGE_ENABLE') == '1':
         depends = d.getVar("DEPENDS")
         depends = "%s u-boot-tools-native dtc-native" % depends
         d.setVar("DEPENDS", depends)
 }

 concat_dtb_helper() {
 	if [ -e "${UBOOT_DTB_BINARY}" ]; then
 		ln -sf ${UBOOT_DTB_IMAGE} ${DEPLOYDIR}/${UBOOT_DTB_BINARY}
 		ln -sf ${UBOOT_DTB_IMAGE} ${DEPLOYDIR}/${UBOOT_DTB_SYMLINK}
 	fi

 	if [ -f "${UBOOT_NODTB_BINARY}" ]; then
 		install ${UBOOT_NODTB_BINARY} ${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}
 		ln -sf ${UBOOT_NODTB_IMAGE} ${DEPLOYDIR}/${UBOOT_NODTB_SYMLINK}
 		ln -sf ${UBOOT_NODTB_IMAGE} ${DEPLOYDIR}/${UBOOT_NODTB_BINARY}
 	fi

 	# If we're not using a signed u-boot fit, concatenate SPL w/o DTB & U-Boot DTB
 	# with public key (otherwise it will be deployed by the equivalent
 	# concat_spl_dtb_helper function - cf. kernel-fitimage.bbclass for more details)
 	if [ "${SPL_SIGN_ENABLE}" != "1" ] ; then
 		deployed_uboot_dtb_binary='${DEPLOY_DIR_IMAGE}/${UBOOT_DTB_IMAGE}'
 		if [ "x${UBOOT_SUFFIX}" = "ximg" -o "x${UBOOT_SUFFIX}" = "xrom" ] && \
 			[ -e "$deployed_uboot_dtb_binary" ]; then
 			oe_runmake EXT_DTB=$deployed_uboot_dtb_binary
 			install ${UBOOT_BINARY} ${DEPLOYDIR}/${UBOOT_IMAGE}
 		elif [ -e "${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}" -a -e "$deployed_uboot_dtb_binary" ]; then
 			cd ${DEPLOYDIR}
 			cat ${UBOOT_NODTB_IMAGE} $deployed_uboot_dtb_binary | tee ${B}/${CONFIG_B_PATH}/${UBOOT_BINARY} > ${UBOOT_IMAGE}

 			if [ -n "${UBOOT_CONFIG}" ]
 			then
 				i=0
 				j=0
 				for config in ${UBOOT_MACHINE}; do
 					i=$(expr $i + 1);
 					for type in ${UBOOT_CONFIG}; do
 						j=$(expr $j + 1);
 						if [ $j -eq $i ]
 						then
 							cp ${UBOOT_IMAGE} ${B}/${CONFIG_B_PATH}/u-boot-$type.${UBOOT_SUFFIX}
 						fi
 					done
 				done
 			fi
 		else
 			bbwarn "Failure while adding public key to u-boot binary. Verified boot won't be available."
 		fi
 	fi
 }

 concat_spl_dtb_helper() {

 	# We only deploy symlinks to the u-boot-spl.dtb,as the KERNEL_PN will
 	# be responsible for deploying the real file
 	if [ -e "${SPL_DIR}/${SPL_DTB_BINARY}" ] ; then
 		ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_SYMLINK}
 		ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_BINARY}
 	fi

 	# Concatenate the SPL nodtb binary and u-boot.dtb
 	deployed_spl_dtb_binary='${DEPLOY_DIR_IMAGE}/${SPL_DTB_IMAGE}'
 	if [ -e "${DEPLOYDIR}/${SPL_NODTB_IMAGE}" -a -e "$deployed_spl_dtb_binary" ] ; then
 		cd ${DEPLOYDIR}
 		cat ${SPL_NODTB_IMAGE} $deployed_spl_dtb_binary | tee ${B}/${CONFIG_B_PATH}/${SPL_BINARY} > ${SPL_IMAGE}
 	else
 		bbwarn "Failure while adding public key to spl binary. Verified U-Boot boot won't be available."
 	fi
 }


 concat_dtb() {
 	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${UBOOT_DTB_BINARY}" ]; then
 		mkdir -p ${DEPLOYDIR}
 		if [ -n "${UBOOT_CONFIG}" ]; then
 			for config in ${UBOOT_MACHINE}; do
 				CONFIG_B_PATH="$config"
 				cd ${B}/$config
 				concat_dtb_helper
 			done
 		else
 			CONFIG_B_PATH=""
 			cd ${B}
 			concat_dtb_helper
 		fi
 	fi
 }

 concat_spl_dtb() {
 	if [ "${SPL_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${SPL_DTB_BINARY}" ]; then
 		mkdir -p ${DEPLOYDIR}
 		if [ -n "${UBOOT_CONFIG}" ]; then
 			for config in ${UBOOT_MACHINE}; do
 				CONFIG_B_PATH="$config"
 				cd ${B}/$config
 				concat_spl_dtb_helper
 			done
 		else
 			CONFIG_B_PATH=""
 			cd ${B}
 			concat_spl_dtb_helper
 		fi
 	fi
 }


 # Install UBOOT_DTB_BINARY to datadir, so that kernel can use it for
 # signing, and kernel will deploy UBOOT_DTB_BINARY after signs it.
 install_helper() {
 	if [ -f "${UBOOT_DTB_BINARY}" ]; then
 		# UBOOT_DTB_BINARY is a symlink to UBOOT_DTB_IMAGE, so we
 		# need both of them.
 		install -Dm 0644 ${UBOOT_DTB_BINARY} ${D}${datadir}/${UBOOT_DTB_IMAGE}
 		ln -sf ${UBOOT_DTB_IMAGE} ${D}${datadir}/${UBOOT_DTB_BINARY}
 	else
 		bbwarn "${UBOOT_DTB_BINARY} not found"
 	fi
 }

 # Install SPL dtb and u-boot nodtb to datadir,
 install_spl_helper() {
 	if [ -f "${SPL_DIR}/${SPL_DTB_BINARY}" ]; then
 		install -Dm 0644 ${SPL_DIR}/${SPL_DTB_BINARY} ${D}${datadir}/${SPL_DTB_IMAGE}
 		ln -sf ${SPL_DTB_IMAGE} ${D}${datadir}/${SPL_DTB_BINARY}
 	else
 		bbwarn "${SPL_DTB_BINARY} not found"
 	fi
 	if [ -f "${UBOOT_NODTB_BINARY}" ] ; then
 		install -Dm 0644 ${UBOOT_NODTB_BINARY} ${D}${datadir}/${UBOOT_NODTB_IMAGE}
 		ln -sf ${UBOOT_NODTB_IMAGE} ${D}${datadir}/${UBOOT_NODTB_BINARY}
 	else
 		bbwarn "${UBOOT_NODTB_BINARY} not found"
 	fi

 	# We need to install a 'stub' u-boot-fitimage + its to datadir,
 	# so that the KERNEL_PN can use the correct filename when
 	# assembling and deploying them
 	touch ${D}/${datadir}/${UBOOT_FITIMAGE_IMAGE}
 	touch ${D}/${datadir}/${UBOOT_ITS_IMAGE}
 }

 do_install:append() {
 	if [ "${PN}" = "${UBOOT_PN}" ]; then
 		if [ -n "${UBOOT_CONFIG}" ]; then
 			for config in ${UBOOT_MACHINE}; do
 				cd ${B}/$config
 				if [ "${UBOOT_SIGN_ENABLE}" = "1" -o "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
 					[ -n "${UBOOT_DTB_BINARY}" ]; then
 					install_helper
 				fi
 				if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
 					install_spl_helper
 				fi
 			done
 		else
 			cd ${B}
 			if [ "${UBOOT_SIGN_ENABLE}" = "1" -o "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
 				[ -n "${UBOOT_DTB_BINARY}" ]; then
 				install_helper
 			fi
 			if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
 				install_spl_helper
 			fi
 		fi
 	fi
 }

 do_uboot_generate_rsa_keys() {
 	if [ "${SPL_SIGN_ENABLE}" = "0" ] && [ "${UBOOT_FIT_GENERATE_KEYS}" = "1" ]; then
 		bbwarn "UBOOT_FIT_GENERATE_KEYS is set to 1 eventhough SPL_SIGN_ENABLE is set to 0. The keys will not be generated as they won't be used."
 	fi

 	if [ "${SPL_SIGN_ENABLE}" = "1" ] && [ "${UBOOT_FIT_GENERATE_KEYS}" = "1" ]; then

 		# Generate keys only if they don't already exist
 		if [ ! -f "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key ] || \
 			[ ! -f "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".crt ]; then

 			# make directory if it does not already exist
 			mkdir -p "${SPL_SIGN_KEYDIR}"

 			echo "Generating RSA private key for signing U-Boot fitImage"
 			openssl genrsa ${UBOOT_FIT_KEY_GENRSA_ARGS} -out \
 				"${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key \
 				"${UBOOT_FIT_SIGN_NUMBITS}"

 			echo "Generating certificate for signing U-Boot fitImage"
 			openssl req ${FIT_KEY_REQ_ARGS} "${UBOOT_FIT_KEY_SIGN_PKCS}" \
 				-key "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key \
 				-out "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".crt
 		fi
 	fi

 }

 addtask uboot_generate_rsa_keys before do_uboot_assemble_fitimage after do_compile

 # Create a ITS file for the U-boot FIT, for use when
 # we want to sign it so that the SPL can verify it
 uboot_fitimage_assemble() {
 	uboot_its="$1"
 	uboot_nodtb_bin="$2"
 	uboot_dtb="$3"
 	uboot_bin="$4"
 	spl_dtb="$5"
 	uboot_csum="${UBOOT_FIT_HASH_ALG}"
 	uboot_sign_algo="${UBOOT_FIT_SIGN_ALG}"
 	uboot_sign_keyname="${SPL_SIGN_KEYNAME}"

 	rm -f $uboot_its $uboot_bin

 	# First we create the ITS script
 	cat << EOF >> $uboot_its
 /dts-v1/;

 / {
     description = "${UBOOT_FIT_DESC}";
     #address-cells = <1>;

     images {
         uboot {
             description = "U-Boot image";
             data = /incbin/("$uboot_nodtb_bin");
             type = "standalone";
             os = "u-boot";
             arch = "${UBOOT_ARCH}";
             compression = "none";
             load = <${UBOOT_LOADADDRESS}>;
             entry = <${UBOOT_ENTRYPOINT}>;
 EOF

 	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
 		cat << EOF >> $uboot_its
             signature {
                 algo = "$uboot_csum,$uboot_sign_algo";
                 key-name-hint = "$uboot_sign_keyname";
             };
 EOF
 	fi

 	cat << EOF >> $uboot_its
         };
         fdt {
             description = "U-Boot FDT";
             data = /incbin/("$uboot_dtb");
             type = "flat_dt";
             arch = "${UBOOT_ARCH}";
             compression = "none";
 EOF

 	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
 		cat << EOF >> $uboot_its
             signature {
                 algo = "$uboot_csum,$uboot_sign_algo";
                 key-name-hint = "$uboot_sign_keyname";
             };
 EOF
 	fi

 	cat << EOF >> $uboot_its
         };
     };

     configurations {
         default = "conf";
         conf {
             description = "Boot with signed U-Boot FIT";
             loadables = "uboot";
             fdt = "fdt";
         };
     };
 };
 EOF

 	#
 	# Assemble the U-boot FIT image
 	#
 	${UBOOT_MKIMAGE} \
 		${@'-D "${SPL_MKIMAGE_DTCOPTS}"' if len('${SPL_MKIMAGE_DTCOPTS}') else ''} \
 		-f $uboot_its \
 		$uboot_bin

 	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
 		#
 		# Sign the U-boot FIT image and add public key to SPL dtb
 		#
 		${UBOOT_MKIMAGE_SIGN} \
 			${@'-D "${SPL_MKIMAGE_DTCOPTS}"' if len('${SPL_MKIMAGE_DTCOPTS}') else ''} \
 			-F -k "${SPL_SIGN_KEYDIR}" \
 			-K "$spl_dtb" \
 			-r $uboot_bin \
 			${SPL_MKIMAGE_SIGN_ARGS}
 	fi

 }

 do_uboot_assemble_fitimage() {
 	# This function runs in KERNEL_PN context. The reason for that is that we need to
 	# support the scenario where UBOOT_SIGN_ENABLE is placing the Kernel fitImage's
 	# pubkey in the u-boot.dtb file, so that we can use it when building the U-Boot
 	# fitImage itself.
 	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
 	   [ -n "${SPL_DTB_BINARY}" -a "${PN}" = "${KERNEL_PN}" ] ; then
 		if [ "${UBOOT_SIGN_ENABLE}" != "1" ]; then
 			# If we're not signing the Kernel fitImage, that means
 			# we need to copy the u-boot.dtb from staging ourselves
 			cp -P ${STAGING_DATADIR}/u-boot*.dtb ${B}
 		fi
 		# As we are in the kernel context, we need to copy u-boot-spl.dtb from staging first.
 		# Unfortunately, need to glob on top of ${SPL_DTB_BINARY} since _IMAGE and _SYMLINK
 		# will contain U-boot's PV
 		# Similarly, we need to get the filename for the 'stub' u-boot-fitimage + its in
 		# staging so that we can use it for creating the image with the correct filename
 		# in the KERNEL_PN context.
 		# As for the u-boot.dtb (with fitimage's pubkey), it should come from the dependent
 		# do_assemble_fitimage task
 		cp -P ${STAGING_DATADIR}/u-boot-spl*.dtb ${B}
 		cp -P ${STAGING_DATADIR}/u-boot-nodtb*.bin ${B}
 		rm -rf ${B}/u-boot-fitImage-* ${B}/u-boot-its-*
 		kernel_uboot_fitimage_name=`basename ${STAGING_DATADIR}/u-boot-fitImage-*`
 		kernel_uboot_its_name=`basename ${STAGING_DATADIR}/u-boot-its-*`
 		cd ${B}
 		uboot_fitimage_assemble $kernel_uboot_its_name ${UBOOT_NODTB_BINARY} \
 					${UBOOT_DTB_BINARY} $kernel_uboot_fitimage_name \
 					${SPL_DTB_BINARY}
 	fi
 }

 addtask uboot_assemble_fitimage before do_deploy after do_compile

 do_deploy:prepend:pn-${UBOOT_PN}() {
 	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ] ; then
 		concat_dtb
 	fi

 	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] ; then
 	# Deploy the u-boot-nodtb binary and symlinks...
 		if [ -f "${SPL_DIR}/${SPL_NODTB_BINARY}" ] ; then
 			echo "Copying u-boot-nodtb binary..."
 			install -m 0644 ${SPL_DIR}/${SPL_NODTB_BINARY} ${DEPLOYDIR}/${SPL_NODTB_IMAGE}
 			ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_SYMLINK}
 			ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_BINARY}
 		fi


 		# We only deploy the symlinks to the uboot-fitImage and uboot-its
 		# images, as the KERNEL_PN will take care of deploying the real file
 		ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_FITIMAGE_BINARY}
 		ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_FITIMAGE_SYMLINK}
 		ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS}
 		ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS_SYMLINK}
 	fi

 	if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ] ; then
 		concat_spl_dtb
 	fi


 }

 do_deploy:append:pn-${UBOOT_PN}() {
 	# If we're creating a u-boot fitImage, point u-boot.bin
 	# symlink since it might get used by image recipes
 	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] ; then
 		ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_BINARY}
 		ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_SYMLINK}
 	fi
 }

 python () {
     if (   (d.getVar('UBOOT_SIGN_ENABLE') == '1'
             or d.getVar('UBOOT_FITIMAGE_ENABLE') == '1')
         and d.getVar('PN') == d.getVar('UBOOT_PN')
         and d.getVar('UBOOT_DTB_BINARY')):

         # Make "bitbake u-boot -cdeploy" deploys the signed u-boot.dtb
         # and/or the U-Boot fitImage
         d.appendVarFlag('do_deploy', 'depends', ' %s:do_deploy' % d.getVar('KERNEL_PN'))

     if d.getVar('UBOOT_FITIMAGE_ENABLE') == '1' and d.getVar('PN') == d.getVar('KERNEL_PN'):
         # As the U-Boot fitImage is created by the KERNEL_PN, we need
         # to make sure that the u-boot-spl.dtb and u-boot-spl-nodtb.bin
         # files are in the staging dir for it's use
         d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_populate_sysroot' % d.getVar('UBOOT_PN'))

         # If the Kernel fitImage is being signed, we need to
         # create the U-Boot fitImage after it
         if d.getVar('UBOOT_SIGN_ENABLE') == '1':
             d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_assemble_fitimage' % d.getVar('KERNEL_PN'))
             d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_assemble_fitimage_initramfs' % d.getVar('KERNEL_PN'))

 }
	# This file is part of U-Boot verified boot support and is intended to be
	# inherited from u-boot recipe and from kernel-fitimage.bbclass.
	#
	# The signature procedure requires the user to generate an RSA key and
	# certificate in a directory and to define the following variable:
	#
	# UBOOT_SIGN_KEYDIR = "/keys/directory"
	# UBOOT_SIGN_KEYNAME = "dev" # keys name in keydir (eg. "dev.crt", "dev.key")
	# UBOOT_MKIMAGE_DTCOPTS = "-I dts -O dtb -p 2000"
	# UBOOT_SIGN_ENABLE = "1"
	#
	# As verified boot depends on fitImage generation, following is also required:
	#
	# KERNEL_CLASSES ?= " kernel-fitimage "
	# KERNEL_IMAGETYPE ?= "fitImage"
	#
	# The signature support is limited to the use of CONFIG_OF_SEPARATE in U-Boot.
	#
	# The tasks sequence is set as below, using DEPLOY_IMAGE_DIR as common place to
	# treat the device tree blob:
	#
	# * u-boot:do_install:append
	# Install UBOOT_DTB_BINARY to datadir, so that kernel can use it for
	# signing, and kernel will deploy UBOOT_DTB_BINARY after signs it.
	#
	# * virtual/kernel:do_assemble_fitimage
	# Sign the image
	#
	# * u-boot:do_deploy[postfuncs]
	# Deploy files like UBOOT_DTB_IMAGE, UBOOT_DTB_SYMLINK and others.
	#
	# For more details on signature process, please refer to U-Boot documentation.

	# We need some variables from u-boot-config
	inherit uboot-config

	# Enable use of a U-Boot fitImage
	UBOOT_FITIMAGE_ENABLE ?= "0"

	# Signature activation - these require their respective fitImages
	UBOOT_SIGN_ENABLE ?= "0"
	SPL_SIGN_ENABLE ?= "0"

	# Default value for deployment filenames.
	UBOOT_DTB_IMAGE ?= "u-boot-${MACHINE}-${PV}-${PR}.dtb"
	UBOOT_DTB_BINARY ?= "u-boot.dtb"
	UBOOT_DTB_SYMLINK ?= "u-boot-${MACHINE}.dtb"
	UBOOT_NODTB_IMAGE ?= "u-boot-nodtb-${MACHINE}-${PV}-${PR}.bin"
	UBOOT_NODTB_BINARY ?= "u-boot-nodtb.bin"
	UBOOT_NODTB_SYMLINK ?= "u-boot-nodtb-${MACHINE}.bin"
	UBOOT_ITS_IMAGE ?= "u-boot-its-${MACHINE}-${PV}-${PR}"
	UBOOT_ITS ?= "u-boot.its"
	UBOOT_ITS_SYMLINK ?= "u-boot-its-${MACHINE}"
	UBOOT_FITIMAGE_IMAGE ?= "u-boot-fitImage-${MACHINE}-${PV}-${PR}"
	UBOOT_FITIMAGE_BINARY ?= "u-boot-fitImage"
	UBOOT_FITIMAGE_SYMLINK ?= "u-boot-fitImage-${MACHINE}"
	SPL_DIR ?= "spl"
	SPL_DTB_IMAGE ?= "u-boot-spl-${MACHINE}-${PV}-${PR}.dtb"
	SPL_DTB_BINARY ?= "u-boot-spl.dtb"
	SPL_DTB_SYMLINK ?= "u-boot-spl-${MACHINE}.dtb"
	SPL_NODTB_IMAGE ?= "u-boot-spl-nodtb-${MACHINE}-${PV}-${PR}.bin"
	SPL_NODTB_BINARY ?= "u-boot-spl-nodtb.bin"
	SPL_NODTB_SYMLINK ?= "u-boot-spl-nodtb-${MACHINE}.bin"

	# U-Boot fitImage description
	UBOOT_FIT_DESC ?= "U-Boot fitImage for ${DISTRO_NAME}/${PV}/${MACHINE}"

	# Kernel / U-Boot fitImage Hash Algo
	FIT_HASH_ALG ?= "sha256"
	UBOOT_FIT_HASH_ALG ?= "sha256"

	# Kernel / U-Boot fitImage Signature Algo
	FIT_SIGN_ALG ?= "rsa2048"
	UBOOT_FIT_SIGN_ALG ?= "rsa2048"

	# Kernel / U-Boot fitImage Padding Algo
	FIT_PAD_ALG ?= "pkcs-1.5"

	# Generate keys for signing Kernel / U-Boot fitImage
	FIT_GENERATE_KEYS ?= "0"
	UBOOT_FIT_GENERATE_KEYS ?= "0"

	# Size of private keys in number of bits
	FIT_SIGN_NUMBITS ?= "2048"
	UBOOT_FIT_SIGN_NUMBITS ?= "2048"

	# args to openssl genrsa (Default is just the public exponent)
	FIT_KEY_GENRSA_ARGS ?= "-F4"
	UBOOT_FIT_KEY_GENRSA_ARGS ?= "-F4"

	# args to openssl req (Default is -batch for non interactive mode and
	# -new for new certificate)
	FIT_KEY_REQ_ARGS ?= "-batch -new"
	UBOOT_FIT_KEY_REQ_ARGS ?= "-batch -new"

	# Standard format for public key certificate
	FIT_KEY_SIGN_PKCS ?= "-x509"
	UBOOT_FIT_KEY_SIGN_PKCS ?= "-x509"

	# Functions on this bbclass can apply to either U-boot or Kernel,
	# depending on the scenario
	UBOOT_PN = "${@d.getVar('PREFERRED_PROVIDER_u-boot') or 'u-boot'}"
	KERNEL_PN = "${@d.getVar('PREFERRED_PROVIDER_virtual/kernel')}"

	# We need u-boot-tools-native if we're creating a U-Boot fitImage
	python() {
	if d.getVar('UBOOT_FITIMAGE_ENABLE') == '1':
	depends = d.getVar("DEPENDS")
	depends = "%s u-boot-tools-native dtc-native" % depends
	d.setVar("DEPENDS", depends)
	}

	concat_dtb_helper() {
	if [ -e "${UBOOT_DTB_BINARY}" ]; then
	ln -sf ${UBOOT_DTB_IMAGE} ${DEPLOYDIR}/${UBOOT_DTB_BINARY}
	ln -sf ${UBOOT_DTB_IMAGE} ${DEPLOYDIR}/${UBOOT_DTB_SYMLINK}
	fi

	if [ -f "${UBOOT_NODTB_BINARY}" ]; then
	install ${UBOOT_NODTB_BINARY} ${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}
	ln -sf ${UBOOT_NODTB_IMAGE} ${DEPLOYDIR}/${UBOOT_NODTB_SYMLINK}
	ln -sf ${UBOOT_NODTB_IMAGE} ${DEPLOYDIR}/${UBOOT_NODTB_BINARY}
	fi

	# If we're not using a signed u-boot fit, concatenate SPL w/o DTB & U-Boot DTB
	# with public key (otherwise it will be deployed by the equivalent
	# concat_spl_dtb_helper function - cf. kernel-fitimage.bbclass for more details)
	if [ "${SPL_SIGN_ENABLE}" != "1" ] ; then
	deployed_uboot_dtb_binary='${DEPLOY_DIR_IMAGE}/${UBOOT_DTB_IMAGE}'
	if [ "x${UBOOT_SUFFIX}" = "ximg" -o "x${UBOOT_SUFFIX}" = "xrom" ] && \
	[ -e "$deployed_uboot_dtb_binary" ]; then
	oe_runmake EXT_DTB=$deployed_uboot_dtb_binary
	install ${UBOOT_BINARY} ${DEPLOYDIR}/${UBOOT_IMAGE}
	elif [ -e "${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}" -a -e "$deployed_uboot_dtb_binary" ]; then
	cd ${DEPLOYDIR}
	cat ${UBOOT_NODTB_IMAGE} $deployed_uboot_dtb_binary \| tee ${B}/${CONFIG_B_PATH}/${UBOOT_BINARY} > ${UBOOT_IMAGE}

	if [ -n "${UBOOT_CONFIG}" ]
	then
	i=0
	j=0
	for config in ${UBOOT_MACHINE}; do
	i=$(expr $i + 1);
	for type in ${UBOOT_CONFIG}; do
	j=$(expr $j + 1);
	if [ $j -eq $i ]
	then
	cp ${UBOOT_IMAGE} ${B}/${CONFIG_B_PATH}/u-boot-$type.${UBOOT_SUFFIX}
	fi
	done
	done
	fi
	else
	bbwarn "Failure while adding public key to u-boot binary. Verified boot won't be available."
	fi
	fi
	}

	concat_spl_dtb_helper() {

	# We only deploy symlinks to the u-boot-spl.dtb,as the KERNEL_PN will
	# be responsible for deploying the real file
	if [ -e "${SPL_DIR}/${SPL_DTB_BINARY}" ] ; then
	ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_SYMLINK}
	ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_BINARY}
	fi

	# Concatenate the SPL nodtb binary and u-boot.dtb
	deployed_spl_dtb_binary='${DEPLOY_DIR_IMAGE}/${SPL_DTB_IMAGE}'
	if [ -e "${DEPLOYDIR}/${SPL_NODTB_IMAGE}" -a -e "$deployed_spl_dtb_binary" ] ; then
	cd ${DEPLOYDIR}
	cat ${SPL_NODTB_IMAGE} $deployed_spl_dtb_binary \| tee ${B}/${CONFIG_B_PATH}/${SPL_BINARY} > ${SPL_IMAGE}
	else
	bbwarn "Failure while adding public key to spl binary. Verified U-Boot boot won't be available."
	fi
	}


	concat_dtb() {
	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${UBOOT_DTB_BINARY}" ]; then
	mkdir -p ${DEPLOYDIR}
	if [ -n "${UBOOT_CONFIG}" ]; then
	for config in ${UBOOT_MACHINE}; do
	CONFIG_B_PATH="$config"
	cd ${B}/$config
	concat_dtb_helper
	done
	else
	CONFIG_B_PATH=""
	cd ${B}
	concat_dtb_helper
	fi
	fi
	}

	concat_spl_dtb() {
	if [ "${SPL_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${SPL_DTB_BINARY}" ]; then
	mkdir -p ${DEPLOYDIR}
	if [ -n "${UBOOT_CONFIG}" ]; then
	for config in ${UBOOT_MACHINE}; do
	CONFIG_B_PATH="$config"
	cd ${B}/$config
	concat_spl_dtb_helper
	done
	else
	CONFIG_B_PATH=""
	cd ${B}
	concat_spl_dtb_helper
	fi
	fi
	}


	# Install UBOOT_DTB_BINARY to datadir, so that kernel can use it for
	# signing, and kernel will deploy UBOOT_DTB_BINARY after signs it.
	install_helper() {
	if [ -f "${UBOOT_DTB_BINARY}" ]; then
	# UBOOT_DTB_BINARY is a symlink to UBOOT_DTB_IMAGE, so we
	# need both of them.
	install -Dm 0644 ${UBOOT_DTB_BINARY} ${D}${datadir}/${UBOOT_DTB_IMAGE}
	ln -sf ${UBOOT_DTB_IMAGE} ${D}${datadir}/${UBOOT_DTB_BINARY}
	else
	bbwarn "${UBOOT_DTB_BINARY} not found"
	fi
	}

	# Install SPL dtb and u-boot nodtb to datadir,
	install_spl_helper() {
	if [ -f "${SPL_DIR}/${SPL_DTB_BINARY}" ]; then
	install -Dm 0644 ${SPL_DIR}/${SPL_DTB_BINARY} ${D}${datadir}/${SPL_DTB_IMAGE}
	ln -sf ${SPL_DTB_IMAGE} ${D}${datadir}/${SPL_DTB_BINARY}
	else
	bbwarn "${SPL_DTB_BINARY} not found"
	fi
	if [ -f "${UBOOT_NODTB_BINARY}" ] ; then
	install -Dm 0644 ${UBOOT_NODTB_BINARY} ${D}${datadir}/${UBOOT_NODTB_IMAGE}
	ln -sf ${UBOOT_NODTB_IMAGE} ${D}${datadir}/${UBOOT_NODTB_BINARY}
	else
	bbwarn "${UBOOT_NODTB_BINARY} not found"
	fi

	# We need to install a 'stub' u-boot-fitimage + its to datadir,
	# so that the KERNEL_PN can use the correct filename when
	# assembling and deploying them
	touch ${D}/${datadir}/${UBOOT_FITIMAGE_IMAGE}
	touch ${D}/${datadir}/${UBOOT_ITS_IMAGE}
	}

	do_install:append() {
	if [ "${PN}" = "${UBOOT_PN}" ]; then
	if [ -n "${UBOOT_CONFIG}" ]; then
	for config in ${UBOOT_MACHINE}; do
	cd ${B}/$config
	if [ "${UBOOT_SIGN_ENABLE}" = "1" -o "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
	[ -n "${UBOOT_DTB_BINARY}" ]; then
	install_helper
	fi
	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
	install_spl_helper
	fi
	done
	else
	cd ${B}
	if [ "${UBOOT_SIGN_ENABLE}" = "1" -o "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
	[ -n "${UBOOT_DTB_BINARY}" ]; then
	install_helper
	fi
	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
	install_spl_helper
	fi
	fi
	fi
	}

	do_uboot_generate_rsa_keys() {
	if [ "${SPL_SIGN_ENABLE}" = "0" ] && [ "${UBOOT_FIT_GENERATE_KEYS}" = "1" ]; then
	bbwarn "UBOOT_FIT_GENERATE_KEYS is set to 1 eventhough SPL_SIGN_ENABLE is set to 0. The keys will not be generated as they won't be used."
	fi

	if [ "${SPL_SIGN_ENABLE}" = "1" ] && [ "${UBOOT_FIT_GENERATE_KEYS}" = "1" ]; then

	# Generate keys only if they don't already exist
	if [ ! -f "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key ] \|\| \
	[ ! -f "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".crt ]; then

	# make directory if it does not already exist
	mkdir -p "${SPL_SIGN_KEYDIR}"

	echo "Generating RSA private key for signing U-Boot fitImage"
	openssl genrsa ${UBOOT_FIT_KEY_GENRSA_ARGS} -out \
	"${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key \
	"${UBOOT_FIT_SIGN_NUMBITS}"

	echo "Generating certificate for signing U-Boot fitImage"
	openssl req ${FIT_KEY_REQ_ARGS} "${UBOOT_FIT_KEY_SIGN_PKCS}" \
	-key "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".key \
	-out "${SPL_SIGN_KEYDIR}/${SPL_SIGN_KEYNAME}".crt
	fi
	fi

	}

	addtask uboot_generate_rsa_keys before do_uboot_assemble_fitimage after do_compile

	# Create a ITS file for the U-boot FIT, for use when
	# we want to sign it so that the SPL can verify it
	uboot_fitimage_assemble() {
	uboot_its="$1"
	uboot_nodtb_bin="$2"
	uboot_dtb="$3"
	uboot_bin="$4"
	spl_dtb="$5"
	uboot_csum="${UBOOT_FIT_HASH_ALG}"
	uboot_sign_algo="${UBOOT_FIT_SIGN_ALG}"
	uboot_sign_keyname="${SPL_SIGN_KEYNAME}"

	rm -f $uboot_its $uboot_bin

	# First we create the ITS script
	cat << EOF >> $uboot_its
	/dts-v1/;

	/ {
	description = "${UBOOT_FIT_DESC}";
	#address-cells = <1>;

	images {
	uboot {
	description = "U-Boot image";
	data = /incbin/("$uboot_nodtb_bin");
	type = "standalone";
	os = "u-boot";
	arch = "${UBOOT_ARCH}";
	compression = "none";
	load = <${UBOOT_LOADADDRESS}>;
	entry = <${UBOOT_ENTRYPOINT}>;
	EOF

	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
	cat << EOF >> $uboot_its
	signature {
	algo = "$uboot_csum,$uboot_sign_algo";
	key-name-hint = "$uboot_sign_keyname";
	};
	EOF
	fi

	cat << EOF >> $uboot_its
	};
	fdt {
	description = "U-Boot FDT";
	data = /incbin/("$uboot_dtb");
	type = "flat_dt";
	arch = "${UBOOT_ARCH}";
	compression = "none";
	EOF

	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
	cat << EOF >> $uboot_its
	signature {
	algo = "$uboot_csum,$uboot_sign_algo";
	key-name-hint = "$uboot_sign_keyname";
	};
	EOF
	fi

	cat << EOF >> $uboot_its
	};
	};

	configurations {
	default = "conf";
	conf {
	description = "Boot with signed U-Boot FIT";
	loadables = "uboot";
	fdt = "fdt";
	};
	};
	};
	EOF

	#
	# Assemble the U-boot FIT image
	#
	${UBOOT_MKIMAGE} \
	${@'-D "${SPL_MKIMAGE_DTCOPTS}"' if len('${SPL_MKIMAGE_DTCOPTS}') else ''} \
	-f $uboot_its \
	$uboot_bin

	if [ "${SPL_SIGN_ENABLE}" = "1" ] ; then
	#
	# Sign the U-boot FIT image and add public key to SPL dtb
	#
	${UBOOT_MKIMAGE_SIGN} \
	${@'-D "${SPL_MKIMAGE_DTCOPTS}"' if len('${SPL_MKIMAGE_DTCOPTS}') else ''} \
	-F -k "${SPL_SIGN_KEYDIR}" \
	-K "$spl_dtb" \
	-r $uboot_bin \
	${SPL_MKIMAGE_SIGN_ARGS}
	fi

	}

	do_uboot_assemble_fitimage() {
	# This function runs in KERNEL_PN context. The reason for that is that we need to
	# support the scenario where UBOOT_SIGN_ENABLE is placing the Kernel fitImage's
	# pubkey in the u-boot.dtb file, so that we can use it when building the U-Boot
	# fitImage itself.
	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] && \
	[ -n "${SPL_DTB_BINARY}" -a "${PN}" = "${KERNEL_PN}" ] ; then
	if [ "${UBOOT_SIGN_ENABLE}" != "1" ]; then
	# If we're not signing the Kernel fitImage, that means
	# we need to copy the u-boot.dtb from staging ourselves
	cp -P ${STAGING_DATADIR}/u-boot*.dtb ${B}
	fi
	# As we are in the kernel context, we need to copy u-boot-spl.dtb from staging first.
	# Unfortunately, need to glob on top of ${SPL_DTB_BINARY} since _IMAGE and _SYMLINK
	# will contain U-boot's PV
	# Similarly, we need to get the filename for the 'stub' u-boot-fitimage + its in
	# staging so that we can use it for creating the image with the correct filename
	# in the KERNEL_PN context.
	# As for the u-boot.dtb (with fitimage's pubkey), it should come from the dependent
	# do_assemble_fitimage task
	cp -P ${STAGING_DATADIR}/u-boot-spl*.dtb ${B}
	cp -P ${STAGING_DATADIR}/u-boot-nodtb*.bin ${B}
	rm -rf ${B}/u-boot-fitImage-* ${B}/u-boot-its-*
	kernel_uboot_fitimage_name=`basename ${STAGING_DATADIR}/u-boot-fitImage-*`
	kernel_uboot_its_name=`basename ${STAGING_DATADIR}/u-boot-its-*`
	cd ${B}
	uboot_fitimage_assemble $kernel_uboot_its_name ${UBOOT_NODTB_BINARY} \
	${UBOOT_DTB_BINARY} $kernel_uboot_fitimage_name \
	${SPL_DTB_BINARY}
	fi
	}

	addtask uboot_assemble_fitimage before do_deploy after do_compile

	do_deploy:prepend:pn-${UBOOT_PN}() {
	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ] ; then
	concat_dtb
	fi

	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] ; then
	# Deploy the u-boot-nodtb binary and symlinks...
	if [ -f "${SPL_DIR}/${SPL_NODTB_BINARY}" ] ; then
	echo "Copying u-boot-nodtb binary..."
	install -m 0644 ${SPL_DIR}/${SPL_NODTB_BINARY} ${DEPLOYDIR}/${SPL_NODTB_IMAGE}
	ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_SYMLINK}
	ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_BINARY}
	fi


	# We only deploy the symlinks to the uboot-fitImage and uboot-its
	# images, as the KERNEL_PN will take care of deploying the real file
	ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_FITIMAGE_BINARY}
	ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_FITIMAGE_SYMLINK}
	ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS}
	ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS_SYMLINK}
	fi

	if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ] ; then
	concat_spl_dtb
	fi


	}

	do_deploy:append:pn-${UBOOT_PN}() {
	# If we're creating a u-boot fitImage, point u-boot.bin
	# symlink since it might get used by image recipes
	if [ "${UBOOT_FITIMAGE_ENABLE}" = "1" ] ; then
	ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_BINARY}
	ln -sf ${UBOOT_FITIMAGE_IMAGE} ${DEPLOYDIR}/${UBOOT_SYMLINK}
	fi
	}

	python () {
	if ( (d.getVar('UBOOT_SIGN_ENABLE') == '1'
	or d.getVar('UBOOT_FITIMAGE_ENABLE') == '1')
	and d.getVar('PN') == d.getVar('UBOOT_PN')
	and d.getVar('UBOOT_DTB_BINARY')):

	# Make "bitbake u-boot -cdeploy" deploys the signed u-boot.dtb
	# and/or the U-Boot fitImage
	d.appendVarFlag('do_deploy', 'depends', ' %s:do_deploy' % d.getVar('KERNEL_PN'))

	if d.getVar('UBOOT_FITIMAGE_ENABLE') == '1' and d.getVar('PN') == d.getVar('KERNEL_PN'):
	# As the U-Boot fitImage is created by the KERNEL_PN, we need
	# to make sure that the u-boot-spl.dtb and u-boot-spl-nodtb.bin
	# files are in the staging dir for it's use
	d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_populate_sysroot' % d.getVar('UBOOT_PN'))

	# If the Kernel fitImage is being signed, we need to
	# create the U-Boot fitImage after it
	if d.getVar('UBOOT_SIGN_ENABLE') == '1':
	d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_assemble_fitimage' % d.getVar('KERNEL_PN'))
	d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_assemble_fitimage_initramfs' % d.getVar('KERNEL_PN'))

	}