[v2,1/1] linux: Add support for FIT image

The FIT (Flattened Image Tree) image format is a much more advanced and
flexible format compared to regular uImage, let alone zImage.

The FIT image format allows for storing multiple kernel images, multiple
device tree blobs and even multiple configurations for their combinations
in a single image.

Furthermore, it enhances integrity protection of images with sha1, sha256
and md5 checksums as well as signature verification against a public key.

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
---
Changes in v2:
  - build the device tree blob prior to the FIT image
  - add error message if file path is missing
---
 linux/Config.in | 13 +++++++++++++
 linux/linux.mk  | 21 ++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

Hi Jörg,

Le 29/05/2015 21:32, Jörg Krause a écrit :
> The FIT (Flattened Image Tree) image format is a much more advanced and
> flexible format compared to regular uImage, let alone zImage.
> 
> The FIT image format allows for storing multiple kernel images, multiple
> device tree blobs and even multiple configurations for their combinations
> in a single image.
> 
> Furthermore, it enhances integrity protection of images with sha1, sha256
> and md5 checksums as well as signature verification against a public key.
> 
> Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
> ---
> Changes in v2:
>   - build the device tree blob prior to the FIT image
>   - add error message if file path is missing
> ---
>  linux/Config.in | 13 +++++++++++++
>  linux/linux.mk  | 21 ++++++++++++++++++++-
>  2 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/linux/Config.in b/linux/Config.in
> index 457ada6..03ce8cf 100644
> --- a/linux/Config.in
> +++ b/linux/Config.in
> @@ -174,6 +174,13 @@ config BR2_LINUX_KERNEL_UBOOT_IMAGE
>  choice
>  	prompt "Kernel binary format"
>  
> +config BR2_LINUX_KERNEL_FITIMAGE
> +	bool "fitImage"
> +	depends on BR2_arc || BR2_arm || BR2_armeb || BR2_bfin || \
> +		   BR2_powerpc || BR2_avr32 || BR2_sh || BR2_sh64 || \

avr32 support has been removed since 2015.05 Buildroot release.

> +		   BR2_mips || BR2_mipsel || BR2_mips64 || BR2_mips64el

I don't know much about FIT image format, is it really architecture dependent ?
There is an example in uboot documentation for booting an x86 (32bit) system
with a FIT image format.

http://git.denx.de/?p=u-boot.git;a=blob;f=doc/uImage.FIT/x86-fit-boot.txt

> +	select BR2_LINUX_KERNEL_UBOOT_IMAGE
> +
>  config BR2_LINUX_KERNEL_UIMAGE
>  	bool "uImage"
>  	depends on BR2_arc || BR2_arm || BR2_armeb || BR2_bfin || \
> @@ -248,6 +255,12 @@ config BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM
>  
>  endchoice
>  
> +config BR2_LINUX_KERNEL_FITIMAGE_ITS_FILE
> +	string "FIT image device tree descriptor file path"
> +	depends on BR2_LINUX_KERNEL_FITIMAGE
> +	help
> +	  Path to the FIT image device tree descriptor.

Maybe say that a FIT image device tree descriptor is an *.its file ?

> +
>  config BR2_LINUX_KERNEL_IMAGE_TARGET_NAME
>  	string "Kernel image target name"
>  	depends on BR2_LINUX_KERNEL_IMAGE_TARGET_CUSTOM
> diff --git a/linux/linux.mk b/linux/linux.mk
> index c765954..a4fbe47 100644
> --- a/linux/linux.mk
> +++ b/linux/linux.mk
> @@ -108,6 +108,9 @@ LINUX_TARGET_NAME = $(call qstrip,$(BR2_LINUX_KERNEL_IMAGE_TARGET_NAME))
>  ifeq ($(LINUX_IMAGE_NAME),)
>  LINUX_IMAGE_NAME = $(LINUX_TARGET_NAME)
>  endif
> +else ifeq ($(BR2_LINUX_KERNEL_FITIMAGE),y)
> +LINUX_IMAGE_NAME = fitImage
> +LINUX_TARGET_NAME = zImage
>  else
>  ifeq ($(BR2_LINUX_KERNEL_UIMAGE),y)
>  LINUX_IMAGE_NAME = uImage
> @@ -155,7 +158,9 @@ else
>  KERNEL_ARCH_PATH = $(LINUX_DIR)/arch/$(KERNEL_ARCH)
>  endif
>  
> -ifeq ($(BR2_LINUX_KERNEL_VMLINUX),y)
> +ifeq ($(BR2_LINUX_KERNEL_FITIMAGE),y)
> +LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)
> +else ifeq ($(BR2_LINUX_KERNEL_VMLINUX),y)
>  LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)

This can be factorized with:
ifeq ($(BR2_LINUX_KERNEL_VMLINUX)$(BR2_LINUX_KERNEL_FITIMAGE),y)
LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)

>  else ifeq ($(BR2_LINUX_KERNEL_VMLINUZ),y)
>  LINUX_IMAGE_PATH = $(LINUX_DIR)/$(LINUX_IMAGE_NAME)
> @@ -277,6 +282,13 @@ LINUX_APPEND_DTB += $(sep) MKIMAGE_ARGS=`$(MKIMAGE) -l $(LINUX_IMAGE_PATH) |\
>  endif
>  endif
>  

For consistency with the coding style, define LINUX_BUILD_FITIMAGE only when
BR2_LINUX_KERNEL_FITIMAGE is selected:

ifeq ($(BR2_LINUX_KERNEL_FITIMAGE),y)
> +define LINUX_BUILD_FITIMAGE
> +	$(LINUX_INSTALL_HOST_TOOLS)
> +	cp $(call qstrip,$(BR2_LINUX_KERNEL_FITIMAGE_ITS_FILE)) $(@D)/fit-image.its
> +	$(TARGET_MAKE_ENV) $(MKIMAGE) -f $(@D)/fit-image.its $(@D)/$(LINUX_IMAGE_NAME)
> +	rm $(@D)/fit-image.its
> +endef

endif

> +
>  # Compilation. We make sure the kernel gets rebuilt when the
>  # configuration has changed.
>  define LINUX_BUILD_CMDS
> @@ -288,6 +300,7 @@ define LINUX_BUILD_CMDS
>  	fi
>  	$(LINUX_BUILD_DTB)
>  	$(LINUX_APPEND_DTB)
> +	$(if $(BR2_LINUX_KERNEL_FITIMAGE), $(LINUX_BUILD_FITIMAGE))

Then simply use:
	$(LINUX_BUILD_FITIMAGE)
>  endef
>  

Best regards,
Romain Naour

>  
> @@ -374,4 +387,10 @@ $(error No kernel configuration file specified, check your BR2_LINUX_KERNEL_CUST
>  endif
>  endif
>  
> +ifeq ($(BR2_LINUX_KERNEL_FITIMAGE),y)
> +ifeq ($(call qstrip,$(BR2_LINUX_KERNEL_FITIMAGE_ITS_FILE)),)
> +$(error No FIT image device tree descriptor file specified, check your BR2_LINUX_KERNEL_FITIMAGE_ITS_FILE setting)
> +endif
> +endif
> +
>  endif
>