OpenWrt fit 理解

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已于 2022-04-07 15:11:51 修改

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分类专栏： OpenWrt 文章标签： openwrt fit fit uimage

于 2022-04-07 15:09:04 首次发布

本文链接：https://blog.youkuaiyun.com/agave7/article/details/124017189

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OpenWrt fit 理解

开始

在 OpenWrt 中，常看到这样的写法:

在这里插入图片描述

fit 是做什么的呢？fit 的定义在 include/image-commands.mk 中

define Build/fit
        $(TOPDIR)/scripts/mkits.sh \
                -D $(DEVICE_NAME) -o $@.its -k $@ \
                -C $(word 1,$(1)) $(if $(word 2,$(1)),\
                $(if $(DEVICE_DTS_OVERLAY),-d $(KERNEL_BUILD_DIR)/image-$$(basename $(word 2,$(1))),\
                        -d $(word 2,$(1)))) \
                $(if $(findstring with-rootfs,$(word 3,$(1))),-r $(IMAGE_ROOTFS)) \
                $(if $(findstring with-initrd,$(word 3,$(1))), \
                        $(if $(CONFIG_TARGET_ROOTFS_INITRAMFS_SEPARATE), \
                                -i $(KERNEL_BUILD_DIR)/initrd.cpio$(strip $(call Build/initrd_compression)))) \
                -a $(KERNEL_LOADADDR) -e $(if $(KERNEL_ENTRY),$(KERNEL_ENTRY),$(KERNEL_LOADADDR)) \
                $(if $(DEVICE_FDT_NUM),-n $(DEVICE_FDT_NUM)) \
                $(if $(DEVICE_DTS_DELIMITER),-l $(DEVICE_DTS_DELIMITER)) \
                $(if $(DEVICE_DTS_OVERLAY),$(foreach dtso,$(DEVICE_DTS_OVERLAY), -O $(dtso):$(KERNEL_BUILD_DIR)/image-$(dtso).dtb)) \
                -c $(if $(DEVICE_DTS_CONFIG),$(DEVICE_DTS_CONFIG),"config-1") \
                -A $(LINUX_KARCH) -v $(LINUX_VERSION)
        PATH=$(LINUX_DIR)/scripts/dtc:$(PATH) mkimage $(if $(findstring external,$(word 3,$(1))),\
                -E -B 0x1000 $(if $(findstring static,$(word 3,$(1))),-p 0x1000)) -f $@.its $@.new
        @mv $@.new $@
endef

里面做了两件事情：

scripts/mkits.sh 生成 .its
mkimage 生成 fit

实例展开如下：

/home/my/openwrt/scripts/mkits.sh -D my -o /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin.its -k /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin -C none   -d /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/linux-5.15.31/arch/riscv/boot/dts/allwinner/my.dtb   -a 0x40200000 -e 0x40200000    -c "config-1" -A riscv -v 5.15.31

mkimage  -f /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin.its /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin.new

scripts/mkits.sh 理解

用法如下：

lql@debian:~/my/openwrt$ ./scripts/mkits.sh 
Usage: mkits.sh -A arch -C comp -a addr -e entry -v version -k kernel [-D name -n address -d dtb] -o its_file
        -A ==> set architecture to 'arch'
        -C ==> set compression type 'comp'
        -c ==> set config name 'config'
        -a ==> set load address to 'addr' (hex)
        -e ==> set entry point to 'entry' (hex)
        -f ==> set device tree compatible string
        -i ==> include initrd Blob 'initrd'
        -v ==> set kernel version to 'version'
        -k ==> include kernel image 'kernel'
        -D ==> human friendly Device Tree Blob 'name'
        -n ==> fdt unit-address 'address'
        -d ==> include Device Tree Blob 'dtb'
        -r ==> include RootFS blob 'rootfs'
        -H ==> specify hash algo instead of SHA1
        -l ==> legacy mode character (@ etc otherwise -)
        -o ==> create output file 'its_file'
        -O ==> create config with dt overlay 'name:dtb'
                (can be specified more than once)

脚本理解：

#!/bin/sh
#
# Licensed under the terms of the GNU GPL License version 2 or later.
#
# Author: Peter Tyser <ptyser@xes-inc.com>
#
# U-Boot firmware supports the booting of images in the Flattened Image
# Tree (FIT) format.  The FIT format uses a device tree structure to
# describe a kernel image, device tree blob, ramdisk, etc.  This script
# creates an Image Tree Source (.its file) which can be passed to the
# 'mkimage' utility to generate an Image Tree Blob (.itb file).  The .itb
# file can then be booted by U-Boot (or other bootloaders which support
# FIT images).  See doc/uImage.FIT/howto.txt in U-Boot source code for
# additional information on FIT images.
#

脚本的开头注释说明了一切：

fit 是指 Flattened ImageTree (FIT)
mkits.sh目的是生成 Image Tree Source (.its file)
.its 文件是给 mkimage 用的，用于生成 Image Tree Blob (.itb file)
更多关于FIT请看u-boot 源码中的 doc/uImage.FIT/howto.txt

生成的目标文件 .its 如下：

/dts-v1/;

/ {
	description = "RISCV OpenWrt FIT (Flattened Image Tree)";
	#address-cells = <1>;

	images {
		kernel-1 {
			description = "RISCV OpenWrt Linux-5.15.31";
			data = /incbin/("/home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin");
			type = "kernel";
			arch = "riscv";
			os = "linux";
			compression = "none";
			load = <0x40200000>;
			entry = <0x40200000>;
			hash@1 {
				algo = "crc32";
			};
			hash@2 {
				algo = "sha1";
			};
		};


		fdt-1 {
			description = "RISCV OpenWrt my device tree blob";
			
			data = /incbin/("/home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/linux-5.15.31/arch/riscv/boot/dts/allwinner/my.dtb");
			type = "flat_dt";
			
			arch = "riscv";
			compression = "none";
			hash@1 {
				algo = "crc32";
			};
			hash@2 {
				algo = "sha1";
			};
		};



	};

	configurations {
		default = "config-1";
		config-1 {
			description = "OpenWrt my";
			kernel = "kernel-1";
			fdt = "fdt-1";
			
			
			
		};
		
	};
};

mkimage

关于 mkimage ，并不陌生，常规用法如下，用于生成 uImage

define Build/uImage
        mkimage \
                -A $(LINUX_KARCH) \
                -O linux \
                -T kernel \
                -C $(word 1,$(1)) \
                -a $(KERNEL_LOADADDR) \
                -e $(if $(KERNEL_ENTRY),$(KERNEL_ENTRY),$(KERNEL_LOADADDR)) \
                -n '$(if $(UIMAGE_NAME),$(UIMAGE_NAME),$(call toupper,$(LINUX_KARCH)) $(VERSION_DIST) Linux-$(LINUX_VERSION))' \
                $(if $(UIMAGE_MAGIC),-M $(UIMAGE_MAGIC)) \
                $(wordlist 2,$(words $(1)),$(1)) \
                -d $@ $@.new
        mv $@.new $@
ende

mkimage -h 查看 usage

lql@debian:~/my/openwrt$ mkimage -h
mkimage: invalid option -- 'h'
Error: Invalid option
Usage: mkimage -l image
          -l ==> list image header information
       mkimage [-x] -A arch -O os -T type -C comp -a addr -e ep -n name -d data_file[:data_file...] image
          -A ==> set architecture to 'arch'
          -O ==> set operating system to 'os'
          -T ==> set image type to 'type'
          -C ==> set compression type 'comp'
          -a ==> set load address to 'addr' (hex)
          -e ==> set entry point to 'ep' (hex)
          -n ==> set image name to 'name'
          -d ==> use image data from 'datafile'
          -x ==> set XIP (execute in place)
       mkimage [-D dtc_options] [-f fit-image.its|-f auto|-F] [-b <dtb> [-b <dtb>]] [-i <ramdisk.cpio.gz>] fit-image
           <dtb> file is used with -f auto, it may occur multiple times.
          -D => set all options for device tree compiler
          -f => input filename for FIT source
          -i => input filename for ramdisk file
Signing / verified boot not supported (CONFIG_FIT_SIGNATURE undefined)
       mkimage -V ==> print version information and exit
Use -T to see a list of available image types

这里我们看到另一种用法：用 -f 指定 FIT 文件。

mkimage  -f /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin.its /home/my/openwrt/build_dir/target-riscv64_riscv64_musl/linux-sunxid1/my-kernel.bin.new

输入文件和各项参数都在 .its 中指定了。相比第一种用法，更适用于多个文件的拼接。