准备环境

•运行环境：Ubuntu 16.04

•需要的虚拟机：Qemu

•交叉编译环境：ARM GCC

•内核源码：Linux 4.7.3

•u-boot源码：u-boot-2016.09

安装 Qemu 、 ARM GCC

$ sudo add-apt-repository ppa:linaro-maintainers/tools

$ sudo apt-get install linaro-image-tools qemu-user-static qemu-system

$ sudo apt-get install gcc-arm-linux-gnueabi g++-arm-linux-gnueabi

$ sudo apt install bridge-utils

下载、编译 U-BOOT 源码

•下载源码

$ wget -c ftp://ftp.denx.de/pub/u-boot/u-boot-2016.09.tar.bz2$ tar xvf u-boot-2016.09.tar.bz2

$ cd u-boot-2016.09

•修改配置文件 include/configs/vexpress_common.h

#define V2M_BASE        0x80000000#define CONFIG_SYS_TEXT_BASE    0x80800000#endif/* 添加如下三行代码 */#define CONFIG_IPADDR   192.168.0.5#define CONFIG_NETMASK  255.255.255.0#define CONFIG_SERVERIP 192.168.0.3/*

 * Physical addresses, offset from V2M_PA_CS0-3 */#define V2M_NOR0        (V2M_PA_CS0)#define V2M_NOR1        (V2M_PA_CS1)........

........

......../* 对如下 CONFIG_BOOTCOMMAND 作出修改 *//* Basic environment settings */#define CONFIG_BOOTCOMMAND     "run distro_bootcmd; "     "run bootflash; "#undef CONFIG_BOOTCOMMAND#define CONFIG_BOOTCOMMAND "tftp 0x62008000 kernel; setenv bootargs 'root=/dev/mmcblk0 console=ttyAMA0,38400n8'; bootz 0x62008000"#define BOOT_TARGET_DEVICES(func)

        func(MMC, mmc, 1)

        func(MMC, mmc, 0)

        func(PXE, pxe, na)

        func(DHCP, dhcp, na)

#include <config_distro_bootcmd.h>

•编译源码

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- vexpress_ca9x4_defconfig

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-$ mkdir -p ~/tftp

$ ln -sf $PWD/u-boot ~/tftp

准备内核镜像文件

•下载源码

$ wget -c https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.7.3.tar.xz$ tar xvf linux-4.7.3.tar.xz

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- vexpress_defconfig

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- menuconfig

•编译，一个漫长的过程

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- all

$ ln -sf arch/arm/boot/dts/vexpress-v2p-ca9.dtb ~/tftp

$ ln -sf arch/arm/boot/zImage ~/tftp

准备 Qemu 网络

•qemu-ifup 内容如下。

#!/bin/sh#

#cript to bring up the tun device in QEMU in bridged mode

# first parameter is name of tap device (e.g. tap0)

# some constants specific to the local host - change to suit your host

ETH0IPADDR=192.168.0.3MASK=255.255.255.0GATEWAY=192.168.0.1BROADCAST=192.168.0.255ETH=enp0s3 # 根据自己的网络接口修改。

# First take eth0 down, then bring it up with IP address 0.0.0.0 #

ifdown $ETHifconfig $ETH 0.0.0.0 promisc up

# Bring up the tap device (name specified as first argument, by QEMU)

#/usr/sbin/openvpn --mktun --dev $1 --user `id -un`ifconfig $1 0.0.0.0 promisc up

# create the bridge between eth0 and the tap device

brctl addbr br0

brctl addif br0 $ETH

brctl addif br0 $1#

# only a single bridge so loops are not possible, turn off spanning tree protocol

brctl stp br0 off

# Bring up the bridge with ETH0IPADDR and add the default route

#ifconfig br0 $ETH0IPADDR netmask $MASK broadcast $BROADCAST

route add default gw $GATEWAY

# stop firewall - comment this out if you don't use Firestarter#

#service firestarter stop

•qemu-ifdown

#!/bin/sh #

# Script to bring down and delete bridge br0 when QEMU exits

# Bring down eth0 and br0

ETH=enp0s3

ifdown $ETH

ifdown br0ifconfig br0 down

# Delete the bridge

brctl delbr br0

# bring up eth0 in "normal" mode

#ifconfig $ETH -promisc

ifup $ETH

# delete the tap device

#/usr/sbin/openvpn --rmtun --dev $1#

# start firewall again

#service firestarter start

•复制到 /etc 目录

$ sudo cp qemu-if* /etc

$ sudo chmod +x /etc/qemu-if*

搭建 TFTP 服务

•本文中设置的 TFTP 服务的根目录为 ～/tftp 。

•参考如下文章，配置 TFTP 服务。

•How do I install and run a TFTP server?

准备启动 U-BOOT

•append 设备树到 zImage

$ cd ~/tftp && cp zImage kernel

$ cat express-v2p-ca9.dtb >> kernel

•启动 U-BOOT

$ sudo qemu-system-arm -M vexpress-a9 

-m 128M -nographic                 -net nic -net tap,ifname=tap0                 -kernel u-boot                 -dtb vexpress-v2p-ca9.dtb

•如果中间没有出现问题，则能成功启动内核。

U-Boot 2016.07 (Sep 16 2016 - 11:18:06 +0800)

DRAM:  128 MiB

WARNING: Caches not enabled

Flash: 128 MiB

MMC:   MMC: 0*** Warning - bad CRC, using default environment

In:    serial

Out:   serial

Err:   serial

Net:   smc911x-0Hit any key to stop autoboot:  0 smc911x: MAC 52:54:00:12:34:56smc911x: detected LAN9118 controller

smc911x: phy initialized

smc911x: MAC 52:54:00:12:34:56Using smc911x-0 device

TFTP from server 192.168.0.3; our IP address is 192.168.0.5Filename 'kernel'.

Load address: 0x62008000Loading: #################################################################

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     ################################################     2 MiB/sdoneBytes transferred = 3571036 (367d5c hex)

smc911x: MAC 52:54:00:12:34:56Kernel image @ 0x62008000 [ 0x000000 - 0x3643e8 ]

Starting kernel ...

Uncompressing Linux... done, booting the kernel.

Booting Linux on physical CPU 0x0Linux version 4.7.3 (rain@rain-pc) (gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.1) ) #7 SMP Fri Sep 16 11:11:23 CST 2016CPU: ARMv7 Processor [410fc090] revision 0 (ARMv7), cr=10c5387d

CPU: PIPT / VIPT nonaliasing data cache, VIPT nonaliasing instruction cache

Machine model: V2P-CA9

Memory policy: Data cache writeback

CPU: All CPU(s) started in SVC mode.