Lab Three: Trace analysis of the boot process of the Linux kernel-----20135108 li Zeyuan

Experimental requirements:

• Booting from Start_kernel to init process using GDB trace debug kernel

• Detailed analysis of the process initiated from Start_kernel to Init process and the combination of experiments to write a signed blog, and in the blog post "real name (and the name of the final application certificate must be consistent) + Original works reproduced please specify the source +" Linux kernel Analysis "MOOC Course/http mooc.study.163.com/course/ustc-1000029000 ", the specific requirements of the blog content are as follows:

• Topic self-proposed, the content revolves around the Linux kernel boot process, namely starts from Start_kernel to the INIT process;

• You need to use an experiment in your blog

• The execution of the Start_kernel function needs to be carefully analyzed in the blog content

• The summary section needs to clarify its understanding of the "Linux system startup process", especially how the idle process, process 1th is coming.

• 3) Please submit the blog post URL to the NetEase cloud classroom MOOC Platform Linux kernel Analysis Mooc course, edited into a link can be directly clicked open.

Open the shell with a virtual machine in the lab building

cd LinuxKernel/qemu -kernel linux-3.18.6/arch/x86/boot/bzImage -initrd rootfs.img

After the kernel boot is completed, enter the menu program, support three commands help, version and quit, you can add more commands, for elective "Software Engineering C Coding practice" of children's shoes should be a piece of cake.

Debug kernel with GDB trace

The help command I chose here

qemu -kernel linux-3.18.6/arch/x86/boot/bzImage -initrd rootfs.img -s -S # 关于-s和-S选项的说明： -S freeze CPU at startup (use ’c’ to start execution) -s shorthand for -gdb tcp::1234 若不想使用1234端口，则可以使用-gdb tcp:xxxx来取代-s选项
冻结qemu

Open another Shell window

输入 gdb

（gdb）file linux-3.18.6/vmlinux # 在gdb界面中targe remote之前加载符号表
（gdb）target remote:1234 # 建立gdb和gdbserver之间的连接,按c 让qemu上的Linux继续运行
起初一直出现连接超时的问题

（gdb）break start_kernel # 断点的设置可以在target remote之前，也可以在之后

设置断点 程序执行到断点处


实验结束。

Lab Three: Trace analysis of the boot process of the Linux kernel-----20135108 li Zeyuan