u-boot: basic support of dtb append for verified boot

This introduces a new uboot-sign.class to support U-Boot verified boot.

This part delivers the new class file, with related environment variables, and
a new task intended to run before do_install task and which performs the
concatenation of the u-boot-nodtb.bin and the device tree blob. The 'cat'
command used overrides the u-boot.bin in both DEPLOYDIR & build dir to
propagate the changes in later tasks (do_install, do_package, etc.)

Signed-off-by: Yannick Gicquel <yannick.gicquel@iot.bzh>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/meta/classes/uboot-sign.bbclass b/meta/classes/uboot-sign.bbclass
new file mode 100644
index 0000000000..ad84c44c22
--- /dev/null
+++ b/meta/classes/uboot-sign.bbclass
@@ -0,0 +1,67 @@
+# 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_deploy_dtb
+#   u-boot:do_deploy
+#   virtual/kernel:do_assemble_fitimage
+#   u-boot:do_concat_dtb
+#   u-boot:do_install
+#
+# For more details on signature process, please refer to U-boot documentation.
+
+# Signature activation.
+UBOOT_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}-${PR}.${UBOOT_SUFFIX}"
+UBOOT_NODTB_BINARY ?= "u-boot-nodtb.${UBOOT_SUFFIX}"
+UBOOT_NODTB_SYMLINK ?= "u-boot-nodtb-${MACHINE}.${UBOOT_SUFFIX}"
+
+#
+# Following is relevant only for u-boot recipes:
+#
+
+do_concat_dtb () {
+	# Concatenate U-Boot w/o DTB & DTB with public key
+	# (cf. kernel-fitimage.bbclass for more details)
+	cd ${DEPLOYDIR}
+	if [ "x${UBOOT_SIGN_ENABLE}" = "x1" ]; then
+		if [ -e "${UBOOT_NODTB_IMAGE}" -a -e "${UBOOT_DTB_IMAGE}" ]; then
+			cat ${UBOOT_NODTB_IMAGE} ${UBOOT_DTB_IMAGE} | tee ${B}/${UBOOT_BINARY} > ${UBOOT_IMAGE}
+		else
+			bbwarn "Failure while adding public key to u-boot binary. Verified boot won't be available."
+		fi
+	fi
+}
+
+python () {
+	uboot_pn = d.getVar('PREFERRED_PROVIDER_u-boot', True) or 'u-boot'
+	if d.getVar('UBOOT_SIGN_ENABLE', True) == '1' and d.getVar('PN', True) == uboot_pn:
+		kernel_pn = d.getVar('PREFERRED_PROVIDER_virtual/kernel', True)
+
+		# do_concat_dtb is scheduled _before_ do_install as it overwrite the
+		# u-boot.bin in both DEPLOYDIR and DEPLOY_IMAGE_DIR.
+		bb.build.addtask('do_concat_dtb', 'do_install', None, d)
+		d.appendVarFlag('do_concat_dtb', 'depends', ' %s:do_assemble_fitimage' % kernel_pn)
+}