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uboot - bootcmd简单分析

Posted May 24, 2022
By Prejoy
7 min read

uboot - based on 2022.1

默认启动命令

Hit any key to stop autoboot: 2

默认会执行 run bootcmd ，相关变量和命令：

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bootcmd=run distro_bootcmd
distro_bootcmd=scsi_need_init=; for target in ${boot_targets}; do run bootcmd_${target}; done
boot_targets=mmc0 jtag mmc0 mmc1 qspi0 nand0 usb0 usb1 scsi0 pxe dhcp 
bootcmd_dhcp=devtype=dhcp; run boot_net_usb_start; if dhcp ${scriptaddr} ${boot_script_dhcp}; then source ${scriptaddr}; fi;setenv efi_fdtfile ${fdtfile}; setenv efi_old_vci ${bootp_vci};setenv efi_old_arch ${bootp_arch};setenv bootp_vci PXEClient:Arch:00011:UNDI:003000;setenv bootp_arch 0xb;if dhcp ${kernel_addr_r}; then tftpboot ${fdt_addr_r} dtb/${efi_fdtfile};if fdt addr ${fdt_addr_r}; then bootefi ${kernel_addr_r} ${fdt_addr_r}; else bootefi ${kernel_addr_r} ${fdtcontroladdr};fi;fi;setenv bootp_vci ${efi_old_vci};setenv bootp_arch ${efi_old_arch};setenv efi_fdtfile;setenv efi_old_arch;setenv efi_old_vci;

bootcmd_jtag=echo JTAG: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo JTAG: SCRIPT FAILED: continuing...;
bootcmd_mmc0=devnum=0; run mmc_boot
bootcmd_mmc1=devnum=1; run mmc_boot
bootcmd_nand0= nand info && nand read $scriptaddr $script_offset_f $script_size_f && echo NAND: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo NAND: SCRIPT FAILED: continuing...;
bootcmd_pxe=run boot_net_usb_start; dhcp; if pxe get; then pxe boot; fi
bootcmd_qspi0=sf probe 0 0 0 && sf read $scriptaddr $script_offset_f $script_size_f && echo QSPI: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo QSPI: SCRIPT FAILED: continuing...;
bootcmd_scsi0=devnum=0; run scsi_boot
bootcmd_usb0=devnum=0; run usb_boot
bootcmd_usb1=devnum=1; run usb_boot
bootcmd_usb_dfu0=setenv dfu_alt_info boot.scr ram $scriptaddr $script_size_f && dfu 0 ram 0 60 && echo DFU0: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo DFU0: SCRIPT FAILED: continuing...;
bootcmd_usb_dfu1=setenv dfu_alt_info boot.scr ram $scriptaddr $script_size_f && dfu 1 ram 1 60 && echo DFU1: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo DFU1: SCRIPT FAILED: continuing...;
bootcmd_usb_thor0=setenv dfu_alt_info boot.scr ram $scriptaddr $script_size_f && thordown 0 ram 0 && echo THOR0: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo THOR0: SCRIPT FAILED: continuing...;
bootcmd_usb_thor1=setenv dfu_alt_info boot.scr ram $scriptaddr $script_size_f && thordown 1 ram 1 && echo THOR1: Trying to boot script at ${scriptaddr} && source ${scriptaddr}; echo THOR1: SCRIPT FAILED: continuing...;

sd/mmc boot

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bootcmd_mmc0=devnum=0; run mmc_boot

mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi
scan_dev_for_boot_part=part list ${devtype} ${devnum} -bootable devplist; env exists devplist || setenv devplist 1; for distro_bootpart in ${devplist}; do if fstype ${devtype} ${devnum}:${distro_bootpart} bootfstype; then run scan_dev_for_boot; fi; done; setenv devplist

scan_dev_for_boot=echo Scanning ${devtype} ${devnum}:${distro_bootpart}...; for prefix in ${boot_prefixes}; do run scan_dev_for_extlinux; run scan_dev_for_scripts; done;run scan_dev_for_efi;

########################################################################

boot_prefixes=/ /boot/

scan_dev_for_extlinux=if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${boot_syslinux_conf}; then echo Found ${prefix}${boot_syslinux_conf}; run boot_extlinux; echo SCRIPT FAILED: continuing...; fi

boot_extlinux=sysboot ${devtype} ${devnum}:${distro_bootpart} any ${scriptaddr} ${prefix}${boot_syslinux_conf}

########################################################################

boot_scripts=boot.scr.uimg boot.scr
script_offset_f=3e80000 //这个是给无文件系统的Nand或Qspi flash 用的，没在这里用（这里是mmc boot，和qspi boot和nand boot的操作有些差别，主要就是这个地方，一个带文件系统，一个不带，直接操作MTD地址）
script_size_f=0x80000   //这个也是给无文件系统的Nand或Qspi flash 用的，没在这里用（这里是mmc boot，和qspi boot和nand boot的操作有些差别，主要就是这个地方一个带文件系统，一个不带，直接操作MTD地址）
scriptaddr=20000000     //这个是脚本的目标加载地址

scan_dev_for_scripts=for script in ${boot_scripts}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${script}; then echo Found U-Boot script ${prefix}${script}; run boot_a_script; echo SCRIPT FAILED: continuing...; fi; done

boot_a_script=load ${devtype} ${devnum}:${distro_bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr}

//补充：
//(boot.scr 是一个二进制 和 文本混合文件，头部有一个二进制头，后面跟了文本形式的脚本内容)
//mmc(SD卡)启动，和qspi/nand启动不一样，SD卡启动是在FAT文件系统中放 BOOT.BIN ，image.ub 和 boot.scr ，qspi/nand 直接是烧到配置的地址上面。
//image.ub 是xilinx自己定义的后缀，uboot官方应该叫 itb ，由its源文件指定生成itb
//uboot的环境变量saveenv，一般保存在qspi flash，的一个分区上，环境变量分区，和boot.scr 不是一个分区
########################################################################

fdtfile=xilinx/zynqmp-zcu104-revC.dtb
efi_dtb_prefixes=/ /dtb/ /dtb/current/


scan_dev_for_efi=setenv efi_fdtfile ${fdtfile}; for prefix in ${efi_dtb_prefixes}; do if test -e ${devtype} ${devnum}:${distro_bootpart} ${prefix}${efi_fdtfile}; then run load_efi_dtb; fi;done;run boot_efi_bootmgr;if test -e ${devtype} ${devnum}:${distro_bootpart} efi/boot/bootaa64.efi; then echo Found EFI removable media binary efi/boot/bootaa64.efi; run boot_efi_binary; echo EFI LOAD FAILED: continuing...; fi; setenv efi_fdtfile

//关于efi启动，可能在arm64 服务器中会使用，uefi启动要求固件符合uefi接口规范，然后OS要为UEFI建立EFI分区。嵌入式环境应该还用不到。另外，UEFI是支持设备树的。
########################################################################

scan_dev_for_boot_part:检测可以启动的分区，使用的命令：

  • part - disk partition related commands
  • env - environment handling commands
  • setenv - set environment variables
  • fstype - Look up a filesystem type

boot.scr 参考

boot.scr是二进制+文本的文件，开头一段二进制数据，后面接脚本文本。截取文本部分

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xxxx
xxxx
xxxx （二进制部分）
# This is a boot script for U-Boot
# Generate boot.scr:
# mkimage -c none -A arm -T script -d boot.cmd.default boot.scr
#
################
fitimage_name=image.ub
kernel_name=Image
ramdisk_name=ramdisk.cpio.gz.u-boot
rootfs_name=rootfs.cpio.gz.u-boot


for boot_target in ${boot_targets};
do
	echo "Trying to load boot images from ${boot_target}"
	if test "${boot_target}" = "jtag" ; then
		booti 0x00200000 0x04000000 0x00100000
	fi
	if test "${boot_target}" = "mmc0" || test "${boot_target}" = "mmc1" || test "${boot_target}" = "usb0" || test "${boot_target}" = "usb1"; then
		if test -e ${devtype} ${devnum}:${distro_bootpart} /uEnv.txt; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x00200000 uEnv.txt;
			echo "Importing environment(uEnv.txt) from ${boot_target}..."
			env import -t 0x00200000 $filesize
			if test -n $uenvcmd; then
				echo "Running uenvcmd ...";
				run uenvcmd;
			fi
		fi
		if test -e ${devtype} ${devnum}:${distro_bootpart} /${fitimage_name}; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x10000000 ${fitimage_name};
			bootm 0x10000000;
                fi
		if test -e ${devtype} ${devnum}:${distro_bootpart} /${kernel_name}; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x00200000 ${kernel_name};
		fi
		if test -e ${devtype} ${devnum}:${distro_bootpart} /system.dtb; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x00100000 system.dtb;
		fi
		if test -e ${devtype} ${devnum}:${distro_bootpart} /${ramdisk_name} && test "${skip_tinyramdisk}" != "yes"; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x04000000 ${ramdisk_name};
			booti 0x00200000 0x04000000 0x00100000
		fi
		if test -e ${devtype} ${devnum}:${distro_bootpart} /${rootfs_name} && test "${skip_ramdisk}" != "yes"; then
			fatload ${devtype} ${devnum}:${distro_bootpart} 0x04000000 ${rootfs_name};
			booti 0x00200000 0x04000000 0x00100000
		fi
		booti 0x00200000 - 0x00100000
	fi
	if test "${boot_target}" = "xspi0" || test "${boot_target}" = "qspi" || test "${boot_target}" = "qspi0"; then
		sf probe 0 0 0;
		sf read 0x10000000 0xF40000 0x6400000
		bootm 0x10000000;
		echo "Booting using Fit image failed"

		sf read 0x00200000 0xF00000 0x1D00000
		sf read 0x04000000 0x4000000 0x4000000
		booti 0x00200000 0x04000000 0x00100000;
		echo "Booting using Separate images failed"
	fi
	if test "${boot_target}" = "nand" || test "${boot_target}" = "nand0"; then
		nand info;
		nand read 0x10000000 0x4180000 0x6400000
		bootm 0x10000000;
		echo "Booting using Fit image failed"

		nand read 0x00200000 0x4100000 0x3200000
		nand read 0x04000000 0x7800000 0x3200000
		booti 0x00200000 0x04000000 0x00100000;
		echo "Booting using Separate images failed"
	fi
done
BootLoader, U-Boot
uboot
This post is licensed under CC BY 4.0 by the author.
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