在查找资料过程中，发现自己搭建虚拟的arm环境的话，有一个比较好的软件就是qemu了，当然还有其他的，大家各投所好就好。
接下来说一下qemu环境搭建过程。
其实搭建很简单，作为小白，我还是捣鼓了两三天才真正的安装成功，正在尝试着怎么使用。
上篇已经讲了安装Ubuntu系统后root密码的设置，这里就要用到root密码进行软件安装了。
可以在命令行模式下先进行update，输入：sudo apt-get update
在保证电脑联网的情况下，Ubuntu会自动进行文件更新，这个操作并不会更新整个文件系统，
他只是同步le /etc/apt/sources.list 和 /etc/apt/sources.list.d 中列出的源的索引，这样才能获取到最新的软件包。
并且只有在更新了资源列表后才能使用apt-get install进行成功安装（我当时就是没有update就去安装程序，失败了好多次，各种欲哭无泪，
另：一定要保证自己的网络环境良好，更新的文件都不大但是我想你不会想看着电脑以100B的速度去下载6000K+的文件的555555）
在update完成之后就可以进行qemu的安装了，输入指令：sudo apt-get install qemu（如果失败并提示你需要尝试修复什么文件的话用sudo apt-get -f install qemu代替）
在连着输入两个表示同意的‘y’之后等着系统自己安装就好了。
安装完毕，输入qemu并联系按几下table，就会显示当前qemu支持的架构（还是内核？不是很清楚这个概念）
qemu安装到此结束。
========================================和上方震惊体标题后脑残的内容划清界限，下面搭建Vexpress的qemu环境==========================================================================
1. 安装qemu，参考上方脑残内容，安装完毕后查看qemu版本可出现如下内容表示安装成功
sly@ubuntu:~/develop$ qemu-arm --version qemu-arm version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.19) Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
PS： 交叉编译工具链也需要安装 sudo apt-get install gcc-arm-linux-gnueabi
2. 编译Linux内核
sly@ubuntu:~/develop/linux-5.3.7$ make CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm vexpress_defconfig
#
# configuration written to .config
#
修改Makfile如下两个变量值
ARCH ?= arm CROSS_COMPILE ?= arm-linux-gnueabi-
编译：
sly@ubuntu:~/develop/linux-5.3.7$ make sly@ubuntu:~/develop/linux-5.3.7$ make modulessly@ubuntu:~/develop/linux-5.3.7$ make dtbs
生成的内核镱像位于arch/arm/boot/zImage， qemu启动时须要使用该镜像。
sly@ubuntu:~/develop/linux-5.3.7$ make scripts/kconfig/conf --syncconfig Kconfig CALL scripts/checksyscalls.sh CALL scripts/atomic/check-atomics.sh CHK include/generated/compile.h GZIP kernel/config_data.gz CC kernel/configs.o AR kernel/built-in.a GEN .version CHK include/generated/compile.h UPD include/generated/compile.h CC init/version.o AR init/built-in.a LD vmlinux.o MODPOST vmlinux.o MODINFO modules.builtin.modinfo- KSYM .tmp_kallsyms1.o KSYM .tmp_kallsyms2.o LD vmlinux SORTEX vmlinux SYSMAP System.map OBJCOPY arch/arm/boot/Image Kernel: arch/arm/boot/Image is ready GZIP arch/arm/boot/compressed/piggy_data AS arch/arm/boot/compressed/piggy.o LD arch/arm/boot/compressed/vmlinux OBJCOPY arch/arm/boot/zImage Kernel: arch/arm/boot/zImage is ready Building modules, stage 2. MODPOST 1 modules
3. 測试qemu和内核是否能执行成功
qemu已经安装好了。内核也编译成功了，到这里最好是測试一下，编译出来的内核是否OK，或者qemu对vexpress单板支持是否够友好。
执行命令：qemu-system-arm -M vexpress-a9 -m 512m -kernel /home/sly/develop/linux-5.3.7/arch/arm/boot/zImage -dtb linux-5.3.7/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -nographic -append "console=ttyAMA0"
sly@ubuntu:~/develop$ qemu-system-arm -M vexpress-a9 -m 512m -kernel /home/sly/develop/linux-5.3.7/arch/arm/boot/zImage -dtb linux-5.3.7/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 5.3.7 (sly@ubuntu) (gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)) #4 SMP Mon Dec 9 08:31:07 PST 2019
--省略甚多log----------
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.3.7 #4
Hardware name: ARM-Versatile Express
[<80110808>] (unwind_backtrace) from [<8010c680>] (show_stack+0x10/0x14)
[<8010c680>] (show_stack) from [<8074c7cc>] (dump_stack+0x88/0x9c)
[<8074c7cc>] (dump_stack) from [<80120e64>] (panic+0x110/0x310)
[<80120e64>] (panic) from [<80a01640>] (mount_block_root+0x1e8/0x2d4)
[<80a01640>] (mount_block_root) from [<80a01870>] (mount_root+0x144/0x160)
[<80a01870>] (mount_root) from [<80a019dc>] (prepare_namespace+0x150/0x198)
[<80a019dc>] (prepare_namespace) from [<80763874>] (kernel_init+0x8/0x114)
[<80763874>] (kernel_init) from [<801010e8>] (ret_from_fork+0x14/0x2c)
Exception stack(0x9e4a1fb0 to 0x9e4a1ff8)
1fa0: 00000000 00000000 00000000 00000000
1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---
假设看到内核启动过程中的打印，说明前的搭建是成功的。
这里简介下qemu命令的參数：
-M vexpress-a9 模拟vexpress-a9单板，你能够使用-M ?參数来获取该qemu版本号支持的全部单板 -m 512M 单板执行物理内存512M -kernel /home/ivan/kernel_git/linux/arch/arm/boot/zImage 告诉qemu单板执行内核镜像路径 -nographic 不使用图形化界面，仅仅使用串口 -append "console=ttyAMA0" 内核启动參数。这里告诉内核vexpress单板执行。串口设备是哪个tty。从生成的.config文件CONFIG_CONSOLE宏找到
4. 利用busybox构建最小文件系统（下载地址：https://busybox.net/）
不加载文件系统穷的那个qemu会产生上面贴的log中的panic信息，下面先制作一个可用的最小文件系统。
a. 编译busybox
a1. 下载源文件后进行配置
sly@ubuntu:~/develop$ cd busybox-1.24.2/ sly@ubuntu:~/develop/busybox-1.24.2$ export ARCH=arm sly@ubuntu:~/develop/busybox-1.24.2$ export CROSS_COMPILE=arm-linux-gnueabi- sly@ubuntu:~/develop/busybox-1.24.2$ make menuconfig
a2.menuconfig配置成静态
Busybox Settings ---> Build Options ---> [*] Build BusyBox as a static binary (no shared libs)
a3. 开始编译, 编译完成后会在busybox目录下生成一个_install的目录，该目录是编译好的文件系统需要使用的一些命令集合。
sly@ubuntu:~/develop/busybox-1.24.2$ make defconfigsly@ubuntu:~/develop/busybox-1.24.2$ make CROSS_COMPILE=arm-linux-gnueabi-sly@ubuntu:~/develop/busybox-1.24.2$ make install CROSS_COMPILE=arm-linux-gnueabi-
生成的_install目录包含如下内容
sly@ubuntu:~/develop/busybox-1.24.2/_install$ ll total 20 drwxrwxr-x 5 sly sly 4096 Dec 9 08:14 ./ drwxr-xr-x 36 sly sly 4096 Dec 9 21:08 ../ drwxrwxr-x 2 sly sly 4096 Dec 9 08:14 bin/ lrwxrwxrwx 1 sly sly 11 Dec 9 08:14 linuxrc -> bin/busybox* drwxrwxr-x 2 sly sly 4096 Dec 9 08:14 sbin/ drwxrwxr-x 4 sly sly 4096 Oct 30 22:18 usr/
b. 制作根文件系统
b1. 新建一个根文件系统的文件夹
sly@ubuntu:~/develop$ mkdir rootfssly@ubuntu:~/develop$ cd rootfs/
b2. 拷贝install目录的命令集到文件夹中
sly@ubuntu:~/develop/rootfs$ cp -rf ../busybox-1.24.2/_install/* . sly@ubuntu:~/develop/rootfs$ ls bin dev lib linuxrc sbin usr
b3. 新建lib目录，从工具链中拷贝执行库到lib文件夹下
sly@ubuntu:~/develop/rootfs$ mkdir libsly@ubuntu:~/develop/rootfs$ cp -p /usr/arm-linux-gnueabi/lib/* ./lib
b4. 创建设备文件, 创建4个串口设备,和控制台
sly@ubuntu:~/develop/rootfs$ sudo mknod dev/tty1 c 4 1 sly@ubuntu:~/develop/rootfs$ sudo mknod dev/tty2 c 4 2 sly@ubuntu:~/develop/rootfs$ sudo mknod dev/tty3 c 4 3 sly@ubuntu:~/develop/rootfs$ sudo mknod dev/tty4 c 4 4 sly@ubuntu:~/develop/rootfs$sudo mknod -m 666 console c 5 1
b5. 制作SD根文件系统镜像, 生成虚拟sd卡并格式化为ext格式：
dd if=/dev/zero of=rootfs.ext3 bs=1M count=32mkfs.ext3 rootfs.ext3
sly@ubuntu:~/develop$ dd if=/dev/zero of=rootfs.ext3 bs=1M count=32
32+0 records in
32+0 records out
33554432 bytes (34 MB, 32 MiB) copied, 0.0941612 s, 356 MB/s
sly@ubuntu:~/develop$ mkfs.ext3 rootfs.ext3
mke2fs 1.44.1 (24-Mar-2018)
Discarding device blocks: done
Creating filesystem with 32768 1k blocks and 8192 inodes
Filesystem UUID: fe2c8081-588f-4e0c-b0c7-09489d0fded5
Superblock backups stored on blocks:
8193, 24577
Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
sly@ubuntu:~/develop$ ls
busybox-1.24.2 linux-5.3.7 linux-5.3.7.tar rootfs rootfs.ext3 tmpfs
b6. 将虚拟sd卡挂载到/tmpfs，拷贝rootfs的所有文件到sd，卸载sd(块设备不能直接读写)
sudo mkdir tmpfssudo mount -t ext3 rootfs.ext3 tmpfs/ -o loop
sudo cp -r rootfs/* tmpfs/
sudo umount tmpfs
sly@ubuntu:~/develop$ sudo mount -t ext3 rootfs.ext3 tmpfs/ -o loop
sly@ubuntu:~/develop$ sudo cp -r rootfs/* tmpfs/
sly@ubuntu:~/develop$ ls tmpfs/
bin dev lib linuxrc lost+found sbin usr
sly@ubuntu:~/develop$ sudo umount tmpfs
sly@ubuntu:~/develop$ ls tmpfs/
sly@ubuntu:~/develop$
5. 启动内核，挂载rootfs
qemu-system-arm -M vexpress-a9 -m 512m -kernel /home/sly/develop/linux-5.3.7/arch/arm/boot/zImage -dtb linux-5.3.7/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -nographic -append "root=/dev/mmcblk0 console=ttyAMA0" -sd rootfs.ext3
sly@ubuntu:~/develop$ qemu-system-arm -M vexpress-a9 -m 512m -kernel /home/sly/develop/linux-5.3.7/arch/arm/boot/zImage -dtb linux-5.3.7/arch/arm/boot/dts/vexpress-v2p-ca9.dtb -nographic -append "root=/dev/mmcblk0 console=ttyAMA0" -sd rootfs.ext3
WARNING: Image format was not specified for 'rootfs.ext3' and probing guessed raw.
Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted.
Specify the 'raw' format explicitly to remove the restrictions.
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 5.3.7 (sly@ubuntu) (gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)) #4 SMP Mon Dec 9 08:31:07 PST 2019=====================================================......=========================================================================
ALSA device list:
#0: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24
input: ImExPS/2 Generic Explorer Mouse as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10007000.kmi/serio1/input/input2
Error: Driver 'vexpress-muxfpga' is already registered, aborting...
drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111
drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD
EXT4-fs (mmcblk0): mounting ext3 file system using the ext4 subsystem
random: fast init done
EXT4-fs (mmcblk0): mounted filesystem with ordered data mode. Opts: (null)
VFS: Mounted root (ext3 filesystem) readonly on device 179:0.
Freeing unused kernel memory: 1024K
Run /sbin/init as init process
random: crng init done
can't run '/etc/init.d/rcS': No such file or directory
Please press Enter to activate this console.
/ #
/ # ls
bin dev lib linuxrc lost+found sbin usr
6. 编写简单的模块进行加载
文件目录结构如下
sly@ubuntu:~/develop/module/first$ ls first.c Makefile
编写源文件
#include <linux/module.h>
#include <linux/kernel.h>
int init_hello_module(void)
{
printk("init hello_moudle\n");
return 0;
}
void exit_hello_module(void)
{
printk("exit hello_module\n");
}
module_init(init_hello_module);
module_exit(exit_hello_module);
MODULE_LICENSE("GPL");
makefile文件
KERN_DIR=../../linux-5.3.7
all:
make -C $(KERN_DIR) M=`pwd` modules
clean:
make -C $(KERN_DIR) M=`pwd` modules clean
rm -rf modules.order
obj-m += first.o
执行编译，编译出ko文件
sly@ubuntu:~/develop/module/first$ make make -C ../../linux-5.3.7 M=`pwd` modules make[1]: Entering directory '/home/sly/develop/linux-5.3.7' CC [M] /home/sly/develop/module/first/first.o Building modules, stage 2. MODPOST 1 modules CC /home/sly/develop/module/first/first.mod.o LD [M] /home/sly/develop/module/first/first.ko make[1]: Leaving directory '/home/sly/develop/linux-5.3.7' sly@ubuntu:~/develop/module/first$ ls first.c first.ko first.mod first.mod.c first.mod.o first.o Makefile modules.order Module.symvers
rootfs根文件系统下面创建一个modules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
/ # ls bin lib lost+found sbin dev linuxrc modules usr / # cd te -/bin/sh: cd: can't cd to te / # cd modules/ /modules # ls first.ko /modules # insmod first.ko first: loading out-of-tree module taints kernel. init hello_moudle /modules # rmmod first.ko rmmod: can't change directory to '/lib/modules': No such file or directory /lib # lsmod lsmod: can't open '/proc/modules': No such file or directory
7. 继续完善文件系统
a. 创建etc及inittable文件，语句含义参考： https://blog.csdn.net/u014089899/article/details/80622607
sly@ubuntu:~/develop/rootfs$ mkdir etc sly@ubuntu:~/develop/rootfs$ cd etc/ sly@ubuntu:~/develop/rootfs/etc$ sudo vi inittab
inittab内容如下
::sysinit:/etc/init.d/rcS #::respawn:-/bin/sh #tty2::askfirst:-/bin/sh #::ctrlaltdel:/bin/umount -a -r console::askfirst:-/bin/sh ::ctrlaltdel:/sbin/reboot ::shutdown:/bin/umount -a -r
创建fstab，相应文件夹需要自行创建好 含义参考：https://blog.csdn.net/xyajia/article/details/79165655
sly@ubuntu:~/develop/rootfs/etc$ sudo vi fstab # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sda1 during installation proc /proc proc defaults 0 0 tmpfs /tmp tmpfs defaults 0 0 sysfs /sys sysfs defaults 0 0 tmpfs /dev tmpfs defaults 0 0 var /dev tmpfs defaults 0 0 ramfs /dev ramfs defaults 0 0
创建init.d/rcS
sly@ubuntu:~/develop/rootfs/etc$ sudo mkdir init.d sly@ubuntu:~/develop/rootfs/etc$ cd init.d/ sly@ubuntu:~/develop/rootfs/etc/init.d$ sudo vi rcS #! /bin/sh PATH=/sbin:/bin:/usr/sbin:/usr/bin LD_LIBRARY_PATH=/lib export PATH LD_LIBRARY_PATH mount -a mkdir -p /dev/pts mount -t devpts devpts /dev/pts mdev -s mkdir -p /var/lock echo "----------------------------------------" echo " welcome debugging on A9 vexpress board" echo "----------------------------------------"
sly@ubuntu:~/develop/rootfs/etc/init.d$ sudo chmod 777 rcS
用最新的rootfs覆盖rootfs.ext3虚拟SD卡，启动开发板验证，效果如下：（出错部分不知道问什么挂在到mnt后在mnt中没有可执行权限，添加下可执行权限就行）
Error: Driver 'vexpress-muxfpga' is already registered, aborting... drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111 drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD input: AT Raw Set 2 keyboard as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10006000.kmi/serio0/input/input0 mmc0: new SD card at address 4567 Error: Driver 'vexpress-muxfpga' is already registered, aborting... drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111 drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD mmcblk0: mmc0:4567 QEMU! 32.0 MiB Error: Driver 'vexpress-muxfpga' is already registered, aborting... drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111 drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD Error: Driver 'vexpress-muxfpga' is already registered, aborting... drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111 drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD rtc-pl031 10017000.rtc: setting system clock to 2019-12-24T05:46:23 UTC (1577166383) ALSA device list: #0: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24 input: ImExPS/2 Generic Explorer Mouse as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10007000.kmi/serio1/input/input2 Error: Driver 'vexpress-muxfpga' is already registered, aborting... drm-clcd-pl111 10020000.clcd: initializing Versatile Express PL111 drm-clcd-pl111 10020000.clcd: DVI muxed to daughterboard 1 (core tile) CLCD EXT4-fs (mmcblk0): mounting ext3 file system using the ext4 subsystem random: fast init done EXT4-fs (mmcblk0): mounted filesystem with ordered data mode. Opts: (null) VFS: Mounted root (ext3 filesystem) readonly on device 179:0. Freeing unused kernel memory: 1024K Run /sbin/init as init process random: crng init done can't run '/etc/init.d/rcS': Permission denied Please press Enter to activate this console.
/ # ls
bin etc linuxrc proc sys usr
dev lib modules sbin tmp var
进行insmod和rmmod操作，发现还需要创建几个文件夹，根据提示在lib下创建lib/modules和lib/modules/5.3.7，就此告一段落
/modules # ls first.ko hello /modules # cat hello hello /modules # vi hello /modules #
来源：https://www.cnblogs.com/edver/p/6001786.html