This is a stripped down version of Boundary device's 6x_bootscript for hab signed kernel

imx6_uboot_script.txt

# This is a stripped down version of Boundary device's 6x_bootscript
# which I used for learning and testing my hab images for imx6

# Prepare uboot script command
#u-boot-imx6$ ./tools/mkimage -A arm -O linux -T script -C none -a 0 -e 0 -n "my boot script" -d imx6_uboot_script.txt /tftpboot/imx6_uboot_script

setenv dtype mmc
setenv disk 0
setenv active_partition 1
# setenv kernel_img_name zImage
setenv kernel_img_name zImage_signed_10800000

setenv bootargs ''
setenv initrd_high 0xffffffff
m4=''
a_base=0x10000000

setexpr a_script  ${a_base} + 0x00800000
setexpr a_zImage  ${a_base} + 0x00800000
setexpr a_fdt     ${a_base} + 0x03000000
setexpr a_ramdisk ${a_base} + 0x03800000
setexpr a_initrd  ${a_base} + 0x03a00000
setexpr a_reset_cause_marker ${a_base} + 0x80
setexpr a_reset_cause	     ${a_base} + 0x84

dtbname=imx6q-${board}.dtb;

if itest.s x${bootpart} == x ; then
	bootpart=1
fi

if load ${dtype} ${disk}:${bootpart} ${a_script} uEnv.txt ; then
    env import -t ${a_script} ${filesize}
fi
setenv bootargs ${bootargs} console=${console},115200 vmalloc=400M consoleblank=0 rootwait fixrtc cpu=${cpu} board=${board}

if itest.s x == x${bootdir} ; then
	bootdir=/
fi

if load ${dtype} ${disk}:${bootpart} ${a_fdt} ${bootdir}${dtbname} ; then
	fdt addr ${a_fdt}
	setenv fdt_high 0xffffffff
else
	echo "!!!! Error loading ${bootdir}${dtbname}";
	exit;
fi

bpart=2

# Tell kernel where root partition is
if test "sata" = "${dtype}" ; then
	setenv bootargs "${bootargs} root=/dev/sda${bpart}" ;
elif test "usb" = "${dtype}" ; then
	setenv bootargs "${bootargs} root=/dev/sda${bpart}" ;
else
	setenv bootargs "${bootargs} root=/dev/mmcblk${disk}p${bpart}"
fi


if itest.s "x" != "x${show_fdt}" ; then
	fdt print /
fi

if itest.s "x" != "x${show_env}" ; then
	printenv
fi

# Boot kernel
# ===========
# TODO: Add check to ensure secure boot OTP fuse enabled

# location offset of ivt within img
ivt_offset=619000

# image_hex_len = includes kernel + padding + ivt + csf
image_hex_len=61a970
# TODO: verify possible bug. image_hex_len=619068 also passes hab_auth_img

if load ${dtype} ${disk}:${bootpart} ${a_zImage} /${kernel_img_name} ; then
    if hab_auth_img ${a_zImage} ${image_hex_len} ${ivt_offset}; then
        echo "Kernel signature verified.";
        bootz ${a_zImage} - ${a_fdt}
    else
        echo "Kernel signature failed.";
    fi
fi
echo "Error loading kernel image"