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先搭建必要的开发工具和下载源码

内核编译，使用的内核版本分支如下：

guang@guang-kylin:~/Develop/linux-stable$ git branch

* master

1 修改顶层目录下的makefile：

guang@guang-kylin:~/Develop/linux-stable$ vi Makefile

ARCH ?= $(SUBARCH)

CROSS_COMPILE ?= $(CONFIG_CROSS_COMPILE:”%”=%)

修改为： ARCH ?= arm CROSS_COMPILE ?= arm-linux-gnueabi-

2 配置对应的开发板，这里用的是vexpress-a9，如下：

make vexpress_defconfig

3 编译zImage，module以及dtb：

make zImage

make modules make dtbs zImage生成路径： arch/arm/boot/zImage modules生成路径： drivers/video/backlight/*.ko dtbs生成路径： arch/arm/boot/dts/vexpress-v2p-ca9.dtb

4 qemu启动内核，看看效果，由于还未挂载根文件系统，所以VFS会有报错

guang@guang-kylin:~/Develop/linux-stable$ qemu-system-arm -M vexpress-a9 -m 512M -kernel arch/arm/boot/zImage -dtb arch/arm/boot/dts/vexpress-v2p-ca9.dtb -nographic -append “console=ttyAMA0”

/****************************************************************/ pulseaudio: set_sink_input_volume() failed pulseaudio: Reason: Invalid argument pulseaudio: set_sink_input_mute() failed pulseaudio: Reason: Invalid argument Booting Linux on physical CPU 0x0 Linux version 4.17.0+ (guang@guang-kylin) (gcc version 7.3.0 (Ubuntu/Linaro 7.3.0-16ubuntu3)) #1 SMP Mon Jun 11 05:05:41 CST 2018 ……// 省略了很多打印信息 VFS: Cannot open root device “(null)” or unknown-block(0,0): error -6 Please append a correct “root=” boot option; here are the available partitions: 1f00 131072 mtdblock0 (driver?) 1f01 32768 mtdblock1 (driver?) Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0+ #1 Hardware name: ARM-Versatile Express [<8011074c>] (unwind_backtrace) from [<8010cd4c>] (show_stack+0x10/0x14) [<8010cd4c>] (show_stack) from [<80694dd4>] (dump_stack+0x88/0x9c) [<80694dd4>] (dump_stack) from [<8011ff6c>] (panic+0xf0/0x25c) [<8011ff6c>] (panic) from [<80901588>] (mount_block_root+0x1ec/0x2d8) [<80901588>] (mount_block_root) from [<809017b8>] (mount_root+0x144/0x160) [<809017b8>] (mount_root) from [<80901924>] (prepare_namespace+0x150/0x198) [<80901924>] (prepare_namespace) from [<80901174>] (kernel_init_freeable+0x340/0x350) [<80901174>] (kernel_init_freeable) from [<806a91f8>] (kernel_init+0x8/0x114) [<806a91f8>] (kernel_init) from [<801010e8>] (ret_from_fork+0x14/0x2c) Exception stack(0x9f48ffb0 to 0x9f48fff8) ffa0: 00000000 00000000 00000000 00000000 ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 —[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]—

用kill杀死对应的qemu-system-arm进程，咱们开始制作根文件系统

/****************************************************************/

5 busybox制作根文件系统

5.1 修改Makefile，新的busybox的makefile下面的选项是空配置的，需要修改如下：

CROSS_COMPILE ?= arm-linux-gnueabi-

ARCH ?= arm

5.2 配置

make defconfig或者make menuconfig

如果是menuconfig，下图选*： Settings —> — Build Options [ ] Build static binary (no shared libs)

可以看到生成的.config文件

guang@guang-kylin:~/Develop/busybox$ ls -al .config

-rw-rw-r– 1 guang guang 27083 6月 11 12:34 .config

参考文档：

5.3 编译 && 安装

make

make install

如下提示安装成功

*————————————————–

You will probably need to make your busybox binary setuid root to ensure all configured applets will work properly. *————————————————–

生成的的_install文件如下，包含了各种shell命令：

guang@guang-kylin:~/Develop/busybox$ ls -al ./_install/

total 20

drwxrwxr-x 5 guang guang 4096 6月 11 12:49 . drwxrwxr-x 38 guang guang 4096 6月 11 12:48 .. drwxrwxr-x 2 guang guang 4096 6月 11 12:49 bin lrwxrwxrwx 1 root root 11 6月 11 12:49 linuxrc -> bin/busybox drwxrwxr-x 2 guang guang 4096 6月 11 12:49 sbin drwxrwxr-x 4 guang guang 4096 6月 11 12:48 usr

5.4 制作根文件系统

5.4.1 新建根目录

guang@guang-kylin:~/Develop$ mkdir trainning

guang@guang-kylin:~/Develop$ cd trainning/

guang@guang-kylin:~/Develop/trainning$ mkdir rootfs

guang@guang-kylin:~/Develop/trainning$ cd rootfs/

5.4.2 新建库文件目录，完成库文件的拷贝

guang@guang-kylin:~/Develop/trainning/rootfs$ mkdir lib

guang@guang-kylin:~/Develop/trainning/rootfs$ ls

lib

guang@guang-kylin:~/Develop/trainning/rootfs$ cp -r ../../busybox/_install/* ./

guang@guang-kylin:~/Develop/trainning/rootfs$ ls

bin lib linuxrc sbin usr

文件系统运行在arm平台，因此还需要arm-linux-gnueabi的库

guang@guang-kylin:~/Develop/trainning/rootfs$ cp -p /usr/arm-linux-gnueabi/lib/* ./lib

5.4.3 创建设备文件

guang@guang-kylin:~/Develop/trainning/rootfs$ mkdir dev

guang@guang-kylin:~/Develop/trainning/rootfs$ ls

bin dev lib linuxrc sbin usr

创建4个串口设备

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 tty1 c 4 1

[sudo] password for guang:

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 tty2 c 4 2

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 tty3 c 4 3

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 tty4 c 4 4

创建控制台

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 console c 5 1

创建null

guang@guang-kylin:~/Develop/trainning/rootfs/dev$ sudo mknod -m 666 null c 1 3

5.4.3 制作SD根文件系统镜像

生成虚拟sd卡并格式化为ext格式：

dd if=/dev/zero of=rootfs.ext3 bs=1M count=32

mkfs.ext3 rootfs.ext3

将虚拟sd卡挂载到/mnt，拷贝rootfs的所有文件到sd，卸载sd(块设备不能直接读写)

mount -t ext3 rootfs.ext3 /mnt/ -o loop

cp -r rootfs/* /mnt umount /mnt

5.4.4 启动内核，挂载rootfs

guang@guang-kylin:~/Develop/trainning$ qemu-system-arm -M vexpress-a9 -m 512M -dtb ../linux-stable/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -kernel ../linux-stable/arch/arm/boot/zImage -nographic -append “root=/dev/mmcblk0 rw console=ttyAMA0” -sd rootfs.ext3

不带lcd的启动效果：

带lcd的启动效果：

qemu-system-arm -M vexpress-a9 -m 512M -dtb ../linux-stable/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -kernel ../linux-stable/arch/arm/boot/zImage -append “root=/dev/mmcblk0 rw console=tty0” -sd rootfs.ext3

5.4.5 一个简单的ko测试程序

报错解决：写一个makefile，自动包含头文件路径

// qemu.c:#include 
   
    #include 
    
     static int __init qemu_init (void){    printk (KERN_INFO"[Info]Hello! Enter QEMU.");    return 0;}module_init (qemu_init);static void __exit qemu_exit (void){    printk (KERN_INFO"[Info]Hello! Exit QEMU.");}module_exit (qemu_exit);MODULE_AUTHOR ("Guang-kylin");MODULE_LICENSE ("GPL v2");MODULE_DESCRIPTION ("A simple qume test module");MODULE_ALIAS ("QEMU module");
    
   

// MakefileKVERS = $(shell uname -r)# Kernel modulesobj-m += qemu.o#EXTRA_CFLAGS=-g -O0build: kernel_moduleskernel_modules:        make -C /lib/modules/$(KVERS)/build M=$(CURDIR) modulesclean:        make -C /lib/modules/$(KVERS)/build M=$(CURDIR) clean

rootfs根文件系统下面创建一个test目录用来存放ko文件

拷贝rootfs的内容到rootfs.ext3虚拟SD中

mount -t ext3 rootfs.ext3 /mnt/ -o loop

cp -r rootfs/* /mnt umount /mnt

启动开发板，加载KO，报错

检查一下ko的类型，发现是x86的ko，Makefile还得再修改一下，ko必须是arm-linux-gnueabi交叉编译器生成的，和生成zImage的编译器版本一致

修改过后的Makefile:

KDIR=/home/guang/Develop/linux-stable #linux代码路径，没有详细研究依赖了那些文件，全部包含了PWD=$(shell pwd)# Kernel modulesobj-m += qemu.omodule-objs = qemu.oARCH=armCROSS_COMPILE=arm-linux-gnueabi-CC := $(CROSS_COMPILE)gccLD := $(CROSS_COMPILE)ld#EXTRA_CFLAGS=-g -O0default:    make -C $(KDIR) M=$(PWD) modulesclean:    rm -f *.ko *.o *.mod.c *.symvers *.order

查看ko，拷贝rootfs的内容到rootfs.ext3，查看加载效果

把zImage和dtb文件都拷贝到同一个目录了，在当前目录敲命令行省事，也可以写成一个shell脚本，后面再搞

/*****/ qemu-system-arm -M vexpress-a9 -m 512M -dtb ./vexpress-v2p-ca9.dtb -kernel ./zImage -nographic -append “root=/dev/mmcblk0 rw console=ttyAMA0” -sd rootfs.ext3 /*****/

加载还是报错，rcS找不到，文件系统还没有制作完成，还得继续

5.4.6 创建etc，进一步完善根文件系统

guang@guang-ubuntu:~/Develop/trainning/rootfs$ mkdir etc

guang@guang-ubuntu:~/Develop/trainning/rootfs$ cd etc

创建inittab

::sysinit:/etc/init.d/rcS#::respawn:-/bin/sh#tty2::askfirst:-/bin/sh#::ctrlaltdel:/bin/umount -a -rconsole::askfirst:-/bin/sh::ctrlaltdel:/sbin/reboot::shutdown:/bin/umount -a -r

创建fstab

proc            /proc           proc    defaults                0       0tmpfs           /tmp            tmpfs   defaults                0       0sysfs           /sys            sysfs   defaults                0       0tmpfs           /dev            tmpfs   defaults                0       0var             /dev            tmpfs   defaults                0       0ramfs           /dev            ramfs   defaults                0       0

创建profile

PS1='guang@arm-vexpress:\w # ' export PS1

创建init.d/rcS

#! /bin/shPATH=/sbin:/bin:/usr/sbin:/usr/binLD_LIBRARY_PATH=/libexport PATH LD_LIBRARY_PATHmount -amkdir -p /dev/ptsmount -t devpts devpts /dev/ptsmdev -smkdir -p /var/lockecho "-----------------------------------"echo " welcome to A9 vexpress board"echo "-----------------------------------"

5.4.7 用最新的rootfs覆盖rootfs.ext3虚拟SD卡，启动开发板验证，效果如下，还有问题，待调试：

以上问题换了linux kernel得到解决，疑是内核污染的问题，版本4.17.0+

6 使用u-boot加载linux kernel

6.1 修改顶层Makefile，指定交叉编译器

CROSS_COMPILE ?= arm-linux-gnueabi-

6.2 修改顶层config.mk，指定ARM架构

ARCH := arm

6.3 配置开发板

make vexpress_ca9x4_defconfig

6.4 编译u-boot

make –j4

6.5 运行u-boot

qemu-system-arm -M vexpress-a9 -kernel u-boot -nographic -m 512M

6.5 配置QEMU的网络功能

采用桥接(bridge)的网络连接与Host通信

需要主机内核tun/tap模块支持(linux17.04以后的版本都支持了，不支持的老版本需要自己创建，我安装的ubuntu是18.04，故已经有了这个模块)

6.5.1 主机安装工具包：

apt install uml-utilities bridge-utils

6.5.2 创建tun设备文件：/dev/net/tun（如果没有）

6.5.3 修改/etc/network/interfaces文件，文件最后添加如下内容并保存，enp0s3字段是ifconfig查到的虚拟网卡的名称

auto enp0s3

auto br0 iface br0 inet dhcp bridge_ports enp0s3

6.5.4 reboot，如下br0已经生成， ip是10.0.2.15：

guang@guang-ubuntu:~$ ifconfigbr0: flags=4163
   
      mtu 1500        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255        inet6 fe80::a00:27ff:fe6e:98c6  prefixlen 64  scopeid 0x20
            ether 08:00:27:6e:98:c6  txqueuelen 1000  (Ethernet)        RX packets 156  bytes 346295 (346.2 KB)        RX errors 0  dropped 0  overruns 0  frame 0        TX packets 229  bytes 27996 (27.9 KB)        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0enp0s3: flags=4163
    
       mtu 1500        ether 08:00:27:6e:98:c6  txqueuelen 1000  (Ethernet)        RX packets 374  bytes 360251 (360.2 KB)        RX errors 0  dropped 0  overruns 0  frame 0        TX packets 229  bytes 28436 (28.4 KB)        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0lo: flags=73
     
        mtu 65536        inet 127.0.0.1  netmask 255.0.0.0        inet6 ::1  prefixlen 128  scopeid 0x10
      
               loop  txqueuelen 1000  (Local Loopback)        RX packets 62  bytes 5127 (5.1 KB)        RX errors 0  dropped 0  overruns 0  frame 0        TX packets 62  bytes 5127 (5.1 KB)        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0guang@guang-ubuntu:~$
      
     
    
   

6.5.5 编译uImage

make LOADADDR=0x60003000 uImage -j4

6.5.6 主机TFTP工具安装

apt-get install tftp-hpa tftpd-hpa xinetd

6.5.7 修改配置文件：/etc/default/tftpd-hpa

# /etc/default/tftpd-hpaTFTP_USERNAME="tftp"TFTP_DIRECTORY="/home/guang/Develop/trainning/tftpboot"TFTP_ADDRESS="0.0.0.0:69"# TFTP_OPTIONS="--secure"TFTP_OPTIONS="-l -c -s"

6.5.8 创建tftpboot目录

guang@guang-ubuntu:~/Develop/trainning$ mkdir tftpbootguang@guang-ubuntu:~/Develop/trainning$ chmod +rwx tftpbootguang@guang-ubuntu:~/Develop/trainning$ cd tftpboot/guang@guang-ubuntu:~/Develop/trainning/tftpboot$ pwd/home/guang/Develop/trainning/tftpboot

6.5.8 重启tftp服务

guang@guang-ubuntu:~/Develop/trainning$ sudo /etc/init.d/tftpd-hpa restart[ ok ] Restarting tftpd-hpa (via systemctl): tftpd-hpa.service.

6.5.8 修改u-boot文件：include/configs/vexpress_common.h

/*config qemu' network
   
    */                                                                                                                                 #define CONFIG_BOOTCOMMAND \        "tftp 0x60003000 uImage;tftp 0x60500000 vexpress-v2p-ca9.dtb; \        setenv bootargs 'root=/dev/mmcblk0 console=tty0'; \        bootm 0x60003000 - 0x60500000;"#define CONFIG_IPADDR 10.0.2.14#define CONFIG_NETMASK 255.255.255.0#define CONFIG_SERVERIP 10.0.2.15
   

6.5.9 编译u-boot

6.5.8 创建tftpboot目录