High Assurance Boot (HAB) for i.MX6 CPUs
  
  To authenticate U-Boot only by the CPU there is no code required in
  U-Boot itself. However, the U-Boot image to be programmed into the
  boot media needs to be properly constructed, i.e. it must contain a
  proper Command Sequence File (CSF).
  
  The Initial Vector Table contains a pointer to the CSF. Please see
  doc/README.imximage for how to prepare u-boot.imx.
  
  The CSF itself is being generated by Freescale HAB tools.
  
  mkimage will output additional information about "HAB Blocks"
  which can be used in the Freescale tooling to authenticate U-Boot
  (entries in the CSF file).
  
  Image Type:   Freescale IMX Boot Image
  Image Ver:    2 (i.MX53/6 compatible)
  Data Size:    327680 Bytes = 320.00 kB = 0.31 MB
  Load Address: 177ff420
  Entry Point:  17800000
  HAB Blocks:   177ff400 00000000 0004dc00

  	      ^^^^^^^^ ^^^^^^^^ ^^^^^^^^

  		|	|	   |
  		|	|	   -------- (1)
  		|	|
  		|	------------------- (2)
  		|
  		--------------------------- (3)
  
  (1)	Size of area in file u-boot.imx to sign
  	This area should include the IVT, the Boot Data the DCD
  	and U-Boot itself.
  (2)	Start of area in u-boot.imx to sign
  (3)	Start of area in RAM to authenticate
  
  CONFIG_SECURE_BOOT currently enables only an additional command
  'hab_status' in U-Boot to retrieve the HAB status and events. This
  can be useful while developing and testing HAB.
  
  Commands to generate a signed U-Boot using Freescale HAB tools:
  cst --o U-Boot_CSF.bin < U-Boot.CSF
  objcopy -I binary -O binary --pad-to 0x2000 --gap-fill=0x00 \
  	U-Boot_CSF.bin U-Boot_CSF_pad.bin
  cat u-boot.imx U-Boot_CSF_pad.bin > u-boot-signed.imx
  
  NOTE: U-Boot_CSF.bin needs to be padded to the value specified in
  the imximage.cfg file.