arm64: boot: Support Flat Image Tree

Add a script which produces a Flat Image Tree (FIT), a single file
containing the built kernel and associated devicetree files.
Compression defaults to gzip which gives a good balance of size and
performance.

The files compress from about 86MB to 24MB using this approach.

The FIT can be used by bootloaders which support it, such as U-Boot
and Linuxboot. It permits automatic selection of the correct
devicetree, matching the compatible string of the running board with
the closest compatible string in the FIT. There is no need for
filenames or other workarounds.

Add a 'make image.fit' build target for arm64, as well.

The FIT can be examined using 'dumpimage -l'.

This uses the 'dtbs-list' file but processes only .dtb files, ignoring
the overlay .dtbo files.

This features requires pylibfdt (use 'pip install libfdt'). It also
requires compression utilities for the algorithm being used. Supported
compression options are the same as the Image.xxx files. Use
FIT_COMPRESSION to select an algorithm other than gzip.

While FIT supports a ramdisk / initrd, no attempt is made to support
this here, since it must be built separately from the Linux build.

Signed-off-by: Simon Glass <[email protected]>
Acked-by: Masahiro Yamada <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: sjg20

Documentation/process/changes.rst

@@ -62,6 +62,7 @@ Sphinx\ [#f1]_         2.4.4            sphinx-build --version
 cpio                   any              cpio --version
 GNU tar                1.28             tar --version
 gtags (optional)       6.6.5            gtags --version
+mkimage (optional)     2017.01          mkimage --version
 ====================== ===============  ========================================
 
 .. [#f1] Sphinx is needed only to build the Kernel documentation
@@ -189,6 +190,14 @@ The kernel build requires GNU GLOBAL version 6.6.5 or later to generate
 tag files through ``make gtags``.  This is due to its use of the gtags
 ``-C (--directory)`` flag.
 
+mkimage
+-------
+
+This tool is used when building a Flat Image Tree (FIT), commonly used on ARM
+platforms. The tool is available via the ``u-boot-tools`` package or can be
+built from the U-Boot source code. See the instructions at
+https://docs.u-boot.org/en/latest/build/tools.html#building-tools-for-linux
+
 System utilities
 ****************
 

MAINTAINERS

@@ -3051,6 +3051,13 @@ F:	drivers/mmc/host/sdhci-of-arasan.c
 N:	zynq
 N:	xilinx
 
+ARM64 FIT SUPPORT
+M:	Simon Glass <[email protected]>
+L:	[email protected] (moderated for non-subscribers)
+S:	Maintained
+F:	arch/arm64/boot/Makefile
+F:	scripts/make_fit.py
+
 ARM64 PORT (AARCH64 ARCHITECTURE)
 M:	Catalin Marinas <[email protected]>
 M:	Will Deacon <[email protected]>

arch/arm64/Makefile

@@ -154,7 +154,7 @@ libs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 # Default target when executing plain make
 boot		:= arch/arm64/boot
 
-BOOT_TARGETS	:= Image vmlinuz.efi
+BOOT_TARGETS	:= Image vmlinuz.efi image.fit
 
 PHONY += $(BOOT_TARGETS)
 
@@ -166,7 +166,9 @@ endif
 
 all:	$(notdir $(KBUILD_IMAGE))
 
-vmlinuz.efi: Image
+image.fit: dtbs
+
+vmlinuz.efi image.fit: Image
 $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
 
@@ -219,6 +221,7 @@ virtconfig:
 define archhelp
   echo  '* Image.gz      - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
   echo  '  Image         - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
+  echo  '  image.fit     - Flat Image Tree (arch/$(ARCH)/boot/image.fit)'
   echo  '  install       - Install uncompressed kernel'
   echo  '  zinstall      - Install compressed kernel'
   echo  '                  Install using (your) ~/bin/installkernel or'

arch/arm64/boot/.gitignore

@@ -2,3 +2,4 @@
 Image
 Image.gz
 vmlinuz*
+image.fit

arch/arm64/boot/Makefile

@@ -16,7 +16,8 @@
 
 OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
 
-targets := Image Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo Image.zst
+targets := Image Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo \
+	Image.zst image.fit
 
 $(obj)/Image: vmlinux FORCE
 	$(call if_changed,objcopy)
@@ -39,6 +40,9 @@ $(obj)/Image.lzo: $(obj)/Image FORCE
 $(obj)/Image.zst: $(obj)/Image FORCE
 	$(call if_changed,zstd)
 
+$(obj)/image.fit: $(obj)/Image $(obj)/dts/dtbs-list FORCE
+	$(call if_changed,fit)
+
 EFI_ZBOOT_PAYLOAD	:= Image
 EFI_ZBOOT_BFD_TARGET	:= elf64-littleaarch64
 EFI_ZBOOT_MACH_TYPE	:= ARM64

scripts/Makefile.lib

@@ -504,6 +504,22 @@ quiet_cmd_uimage = UIMAGE  $@
 			-a $(UIMAGE_LOADADDR) -e $(UIMAGE_ENTRYADDR) \
 			-n '$(UIMAGE_NAME)' -d $< $@
 
+# Flat Image Tree (FIT)
+# This allows for packaging of a kernel and all devicetrees files, using
+# compression.
+# ---------------------------------------------------------------------------
+
+MAKE_FIT := $(srctree)/scripts/make_fit.py
+
+# Use this to override the compression algorithm
+FIT_COMPRESSION ?= gzip
+
+quiet_cmd_fit = FIT     $@
+      cmd_fit = $(MAKE_FIT) -o $@ --arch $(UIMAGE_ARCH) --os linux \
+		--name '$(UIMAGE_NAME)' \
+		$(if $(findstring 1,$(KBUILD_VERBOSE)),-v) \
+		--compress $(FIT_COMPRESSION) -k $< @$(word 2,$^)
+
 # XZ
 # ---------------------------------------------------------------------------
 # Use xzkern to compress the kernel image and xzmisc to compress other things.