Gem5的基础知识（2）

一、安装交叉编译器

1、从网上下载arm-linux-gcc-4.4.3.tar.gz，解压到自己的目录下，我的目录结构/home/cyh/cyh/arm

2、建立目录

sudo mkdir /usr/local/arm

3、复制文件

sudo cp -r /home/cyh/cyh/arm/opt/FriendlyARM/toolschain/4.4.3 /usr/local/arm

4、添加环境变量
修改/etc/environment文件

sudo gedit /etc/environment

将原文件的PATH=”/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games“
修改为PATH=”/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/arm/4.4.3/bin”

5、重新启动电脑

6、检查路径是否添加到PATH中

echo $PATH
/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/arm/4.4.3/bin

7、测试是否安装成功
在终端中输入arm-linux-gcc -v，如果出现以下内容证明交叉编译器安装成功。

Using built-in specs.
Target: arm-none-linux-gnueabi
Configured with: /opt/FriendlyARM/mini2440/build-toolschain/working/src/gcc-4.4.3/configure --build=i386-build_redhat-linux-gnu --host=i386-build_redhat-linux-gnu --target=arm-none-linux-gnueabi --prefix=/opt/FriendlyARM/toolschain/4.4.3 --with-sysroot=/opt/FriendlyARM/toolschain/4.4.3/arm-none-linux-gnueabi//sys-root --enable-languages=c,c++ --disable-multilib --with-arch=armv4t --with-cpu=arm920t --with-tune=arm920t --with-float=soft --with-pkgversion=ctng-1.6.1 --disable-sjlj-exceptions --enable-__cxa_atexit --with-gmp=/opt/FriendlyARM/toolschain/4.4.3 --with-mpfr=/opt/FriendlyARM/toolschain/4.4.3 --with-ppl=/opt/FriendlyARM/toolschain/4.4.3 --with-cloog=/opt/FriendlyARM/toolschain/4.4.3 --with-mpc=/opt/FriendlyARM/toolschain/4.4.3 --with-local-prefix=/opt/FriendlyARM/toolschain/4.4.3/arm-none-linux-gnueabi//sys-root --disable-nls --enable-threads=posix --enable-symvers=gnu --enable-c99 --enable-long-long --enable-target-optspace
Thread model: posix
gcc version 4.4.3 (ctng-1.6.1) 

二、编写自己的程序进行测试

1、在/home/cyh/cyh/arm这个目录下写自己的测试程序hello.c

#include
int main(){
    printf("hello world!\nI am Fern.\n");
    return 0;
}

2、编译hello.c文件

arm-linux-gcc hello.c -o hello

如果出现以下的错误，说明本机是64位的，arm交叉编译环境是32位的，需要安装32位的兼容库。

error while loading shared libraries: libz.so.1: cannot open shared object file: No such file or directory

执行下面的命令：

apt-get install lib32ncurses5 ia32-libs

重新编译即可编译成功。

三、使用arm交叉编译器编译c文件并放入gem5中执行

1、建立自己的目录结构/home/cyh/cyh/gem5/gem5-stable/test

2、将上述编译过的hello文件拷贝到/home/cyh/cyh/gem5/gem5-stable/test这个目录下

3、在终端输入命令，运行hello程序

./build/ARM/gem5.opt ./configs/example/se.py -c test/hello

如果出现以下的错误，说明上述编译hello.c文件需要静态编译

gem5 Simulator System.  http://gem5.org
gem5 is copyrighted software; use the --copyright option for details.
gem5 compiled Dec 21 2016 17:39:13
gem5 started Dec 22 2016 09:48:24
gem5 executing on cyh-Lenovo
command line: ./build/ARM/gem5.opt ./configs/example/se.py -c test/hello
Global frequency set at 1000000000000 ticks per second
fatal: Object file is a dynamic executable however only static executables are supported!
       Please recompile your executable as a static binary and try again.
 @ cycle 0
[create:build/ARM/sim/process.cc, line 619]
Memory Usage: 635576 KBytes

4、重新编译hello.c文件

arm-linux-gcc hello.c -o hello -static

将hello替换原来/home/cyh/cyh/gem5/gem5-stable/test目录下的hello文件，在目录/home/cyh/cyh/gem5/gem5-stable下重新运行命令：./build/ARM/gem5.opt ./configs/example/se.py -c test/hello

5、运行结果：

cyh@cyh-Lenovo:~/cyh/gem5/gem5-stable$ ./build/ARM/gem5.opt ./configs/example/se.py -c test/hello 
gem5 Simulator System.  http://gem5.org
gem5 is copyrighted software; use the --copyright option for details.
gem5 compiled Dec 21 2016 17:39:13
gem5 started Dec 22 2016 10:20:47
gem5 executing on cyh-Lenovo
command line: ./build/ARM/gem5.opt ./configs/example/se.py -c test/hello
Global frequency set at 1000000000000 ticks per second
0: system.remote_gdb.listener: listening for remote gdb #0 on port 7000
**** REAL SIMULATION ****
info: Entering event queue @ 0.  Starting simulation...
hello world!
I am Fern.
hack: be nice to actually delete the event here
Exiting @ tick 3318500 because target called exit()

至此，使用arm交叉编译器编译的程序可以在gem5中执行。

注意：
1、这里gem5的编译应为：scons build/ARM/gem5.opt。
2、ARM: gem5 can model up to 64 (heterogeneous) cores of a Realview ARM platform, and boot unmodified Linux and Android with a combination of in-order and out-of-order CPUs. The ARM implementation supports 32 or 64-bit kernels and applications.
3、x86: The gem5 simulator supports a standard PC platform.