一.qemu模拟x86
1.1 qemu的安装
ubuntu 12.04下安装qemu很简单,
sudo apt-get install qemu
1.2 linux内核的编译
下载内核, 以linux-3.0.1为例
sun@ubuntu:/work/x86/kernel$ tar xf ./linux-3.0.1.tar.bz2
sun@ubuntu:/work/x86/kernel$ cd linux-3.0.1/
sun@ubuntu:/work/x86/kernel/linux-3.0.1$ make menuconfig
sun@ubuntu:/work/x86/kernel/linux-3.0.1$ make bzImage
这样就会生成内核文件 arch/x86/boot/bzImage
1.3 busybox的编译
下载busybox, 以busybox-1.21.1.tar.bz2为例
sun@ubuntu:/work/x86/kernel$ tar xv busybox-1.21.1.tar.bz2
sun@ubuntu:/work/x86/kernel$ cd busybox-1.21.1/
sun@ubuntu:/work/x86/kernel/busybox-1.21.1$ make menuconfig
Busybox Settings --->
Build Options --->
[*] Build BusyBox as a static binary (no shared libs)
//静态方式编译
Networking Utilities --->
[ ] inetd
//去掉inetd
sun@ubuntu:/work/x86/kernel/busybox-1.21.1$ make install
这会生成 _install目录
1.4 最小文件系统的建立
只用一个脚本creatfs.sh就可以生成cramfs文件系统
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#!/bin/sh
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KERNEL=$(pwd)
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BUSYBOX=$(find busybox* -maxdepth 0)
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LINUX=$(find linux* -maxdepth 0)
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#create filesystem
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cd $BUSYBOX
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mkdir -pv proc sys dev etc etc/init.d //先创建系统目录
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cat << EOF > etc/init.d/rcS //生成rcS文件
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#!/bin/sh
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mount -t proc none /proc
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mount -t sysfs none /sys
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/sbin/mdev -s
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EOF
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chmod 777 ./etc/init.d/rcS //修改rcS权限
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cd -
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#create cpio img
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cd $BUSYBOX/_install
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find . | cpio -o --format=newc > $KERNEL/rootfs.img
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cd -
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#create zip img
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cd $KERNEL
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gzip -c rootfs.img > rootfs.img.gz
1.5 启动qemu
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#!/bin/sh
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LINUX=$(find linux* -maxdepth 0)
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#启动qemu
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if [ $# = 0 ] ; then
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qemu-system-i386 -kernel $LINUX/arch/i386/boot/bzImage -initrd rootfs.img.gz -append "root=/dev/ram rdinit=sbin/init noapic"
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fi
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if [ "$1" = "s" ] ; then
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qemu-system-i386 -s -S -kernel $LINUX/arch/i386/boot/bzImage -initrd rootfs.img.gz -append "root=/dev/ram rdinit=sbin/init noapic"
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fi
如果没有参数直接运行qemu, 如果有参数s, 则进入调试模式
qemu参数:
-s : 在1234接受gdb调试连接
-S : 虚拟机启动后立即暂停,等侍gdb连接
最后所有文件如下:
sun@ubuntu:/work/x86/kernel$ tree -L 1
.
├── busybox-1.21.1
//busbyox及_install
├── creatfs.sh
//文件系统生成脚本
├── linux-3.0.1
//Linux源码,及 bzImage
└── start.sh
//启动qemu
注意：
a. 将linux启动信息打印到串口
在qemu启动时加上:
qemu-system-i386 -kernel $LINUX/arch/i386/boot/bzImage -initrd
rootfs.img.gz -append "root=/dev/ram rdinit=sbin/init noapic
console=ttyS0"
-serial file:/tmp/serial.out
就会在/tmp/serial.out中出现系统的信息
b. 将linux启动信息直接打印到控制台
加入 -nographic 和stdio,则会在当前运行的terminal中把linux启动信息打印出来
qemu-system-i386 -kernel $LINUX/arch/i386/boot/bzImage -initrd
rootfs.img.gz -append "root=/dev/ram rdinit=sbin/init console=ttyS0"
-nographic
c. qemu的快捷键
C-a h print this help
C-a x exit emulator
C-a s save disk data back to file (if -snapshot)
C-a t toggle console timestamps
C-a b send break (magic sysrq)
C-a c switch between console and monitor
C-a C-a sends C-a
二.qemu模拟ARM
2.1 qemu-system-arm的安装
如果只是apt-get install qemu,不会安装qemu-system-arm
sun@ubuntu:/work/qemu$ sudo apt-get install qemu qemu-system qemu-utils
sun@ubuntu:/work/qemu$ qemu-system-arm --version
QEMU emulator version 1.0.50 (Debian 1.0.50-2012.03-0ubuntu2.1), Copyright (c) 2003-2008 Fabrice Bellard
注意： 编译工具链可以不用apt-get install 来安装，试过6410自带的交叉编译工具链是完全可用的。
2.2 编译u-boot, kernel, busybox
这儿的编译跟x86的不同之处是：
不论是编译u-boot 还是 linux-3.0.1 还是busybox都需要个改Makefile中的ARCH与CROSS_COMPILE两个变量ｃ
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ARCH ?= arm
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CROSS_COMPILE ?= /opt/6410/4.3.2/bin/arm-none-linux-gnueabi-
编译u-boot时是用的make ca9x4_ct_vxp_config
编译Linux-3.0.1时是用的 arch/arm/configs/vexpress_defconfig
内核编译命令: make vexpress_defconfig && make -j16
a.copy zImage
在arch/arm/Makefile中
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278 zImage Image xipImage bootpImage uImage: vmlinux
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279 $(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
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280 echo "$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@"
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281 cp $(boot)/$@ ../
其中$(boot)/$@是zImage的路径
../ 是linux-3.01源码的上一层
2.3 用ext3系统启动
编译完成busybox， make install 后，用mkfs.sh脚本生成文件系统，只是生成，不用打包成其它格式
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#!/bin/sh
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KERNEL=$(pwd)
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BUSYBOX=$(find busybox* -maxdepth 0)
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LINUX=$(find linux* -maxdepth 0)
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#create filesystem
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cd $BUSYBOX
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mkdir -pv proc sys dev etc etc/init.d //先创建系统目录
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cat << EOF > etc/init.d/rcS //生成rcS文件
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#!/bin/sh
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mount -t proc none /proc
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mount -t sysfs none /sys
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/sbin/mdev -s
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EOF
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chmod 777 ./etc/init.d/rcS //修改rcS权限
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cd -
用ext3.sh脚本创建ext3文件系统
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#!/bin/sh
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#创建一个32M的空文件
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dd if=/dev/zero of=a9rootfs.ext3 bs=1M count=32
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#格式化为EXT3
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sudo mkfs.ext3 a9rootfs.ext3
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# 挂载到a9rootdir目录
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mkdir -pv /tmp/a9rootdir
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sudo mount -t ext3 a9rootfs.ext3 /tmp/a9rootdir/ -o loop
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#拷贝文件到该目录，相对于放到a9rootfs.ext3里面
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sudo cp /work/qemu/rootfs/* /tmp/a9rootdir/ -Rf
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sudo umount /tmp/a9rootdir
2.3.1文件系统的目录结构
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cong@msi:/tmp/a9rootdir$ tree
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.
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├── bin
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│ ├── busybox
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│ ├── init -> busybox
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│ ├── ls -> busybox
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│ ├── mount -> busybox
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│ └── sh -> busybox
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├── dev
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│ ├── console
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│ ├── null
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│ └── tty1
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├── etc
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│ ├── fstab
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│ ├── init.d
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│ │ └── rcS
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│ └── inittab
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├── lib
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│ ├── ld-2.8.so -->解释器
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│ ├── ld-linux.so.3 -> ld-2.8.so
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│ ├── libc-2.8.so -->libc库运行时必需
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│ ├── libcrypt-2.8.so -->libcrypt是busybox需要用的
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│ ├── libcrypt.so.1 -> libcrypt-2.8.so
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│ ├── libc.so.6 -> libc-2.8.so
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│ ├── libgcc_s.so -> libgcc_s.so.1
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│ ├── libgcc_s.so.1 -->运行时必需
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│ ├── libm-2.8.so -->libm是busybox需要用的
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│ └── libm.so.6 -> libm-2.8.so
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├── linuxrc -> ./bin/busybox
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├── lost+found [error opening dir]
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├── proc
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├── sbin
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│ └── mdev -> ../bin/busybox
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└── sys
2.3.2启动的流程
kernel-->/bin/init -->/etc/inittab--> /etc/init.d/rcS --> mount 会用到/etc/fstab
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cong@msi:/tmp/a9rootdir$ cat etc/inittab
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::sysinit:/etc/init.d/rcS
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ttyAMA0::askfirst:-/bin/sh
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#console::askfirst:-/bin/sh
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cong@msi:/tmp/a9rootdir$ cat etc/init.d/rcS
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#!/bin/sh
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mount -a
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/sbin/mdev -s
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cong@msi:/tmp/a9rootdir$ cat etc/fstab
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proc /proc proc defaults 0 0
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sysfs /sys sysfs defaults 0 0
2.3.3启动：
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qemu-system-arm -kernel zImage -M vexpress-a9 -append "root=/dev/mmcblk0 console=ttyAMA0 console=tty0" -sd a9rootfs.ext3 -serial stdio
2.4 用NFS启动
编译完成busybox， make install 后，用mkfs.sh脚本生成文件系统，只是生成，不用打包成其它格式
启动：
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qemu-system-arm -m 256 -kernel zImage -serial stdio -M vexpress-a9 -append root="/dev/nfs console=ttyAMA0 console=tty0 nfsroot=10.0.0.1:/work/qemu/rootfs rw ip=10.0.0.2:10.0.0.1:10.0.0.1:255.255.255.0 " -net nic,vlan=0 -net tap,vlan=0,ifname=tap0,script=qemu-ifup &
qemu-ifup脚本如下：
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#!/bin/sh
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echo "Executing /etc/qemu-ifup"
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sudo ifconfig $1 10.0.0.1
前提是主机上的nfs-server己配置好
三. qemu调试linux系统
3.1 启动调试模式下的qemu
sun@ubuntu:/work/x86/kernel$ sh start.sh s
3.2 另起一个terminal
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sun@ubuntu:/work/x86/kernel/linux-3.0.1$ gdb vmlinux
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Reading symbols from /work/x86/kernel/linux-3.0.1/vmlinux...done.
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(gdb) target remote localhost:1234
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Remote debugging using localhost:1234
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0x0000fff0 in ?? ()
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(gdb) b kernel_init
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Breakpoint 1 at 0xc15c7786: file init/main.c, line 781.
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(gdb) c
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Continuing.
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Breakpoint 1, kernel_init (unused=0x0) at init/main.c:781
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781 {
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(gdb) l
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776 panic("No init found. Try passing init= option to kernel. "
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777 "See Linux Documentation/init.txt for guidance.");
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778 }
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779
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780 static int __init kernel_init(void * unused)
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781 {
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782 /*
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783 * Wait until kthreadd is all set-up.
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784 */
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785 wait_for_completion(&kthreadd_done);
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(gdb)
3.3 每次都这么操作比较麻烦,可以建立一个gdbinit脚本
sun@ubuntu:/work/x86/kernel/linux-3.0.1$ vi .gdbinit
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target remote localhost:1234
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b kernel_init
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c
然后下次运行时就可以
sun@ubuntu:/work/x86/kernel/linux-3.0.1$ gdb vmlinux
注意,如果用gdbinit脚本时出现以下问题:
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warning: File "/work/x86/kernel/linux-3.0.1/.gdbinit" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
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To enable execution of this file add
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add-auto-load-safe-path /work/x86/kernel/linux-3.0.1/.gdbinit
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line to your configuration file "/home/sun/.gdbinit".
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To completely disable this security protection add
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set auto-load safe-path /
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line to your configuration file "/home/sun/.gdbinit".
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For more information about this security protection see the
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"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
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info "(gdb)Auto-loading safe path"
sun@ubuntu:/work/x86/kernel/linux-3.0.1$ vi ~/.gdbinit
set auto-load safe-path /
在~/.gdbini中加入上面这一行,取消掉
[参]:
以QEMU模拟Linux,学习linux内核
http://www.cnblogs.com/senix/archive/2013/02/21/2921221.html
使用qemu调试linux内核
http://blog.csdn.net/aero_boy/article/details/6262609
使用qemu模拟Coretex-A9运行u-boot和Linux
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