VS Code调试Linux内核环境

Ubuntu 20.04 Linux主机/虚拟机或WSL环境下使用说明

在Linux终端命令行上执行如下：

```
git clone https://gitee.com/mengning997/linuxkernel.git
cd linuxkernel/kerneldebuging
sudo ./auto-tasks.sh
# 执行如下命令会弹出QEMU窗口运行Linux内核+Alpine mini rootfs系统
qemu-system-x86_64 -kernel linux-5.4.34/arch/x86/boot/bzImage -initrd rootfs.img
# 纯命令行下启动虚拟机
qemu-system-x86_64 -kernel linux-5.4.34/arch/x86/boot/bzImage -initrd rootfs.img -nographic -append "console=ttyS0"
...
[    2.650661] Write protecting the kernel read-only data: 20480k
[    2.653933] Freeing unused kernel image memory: 2004K
[    2.655225] Freeing unused kernel image memory: 860K
[    2.655516] Run /init as init process
            --------------------               
                                                
            Wellcome MengningOS!               
                                                
            --------------------               
/home #
```

在Dev Container容器环境下使用说明

1. Windows下安装 Docker Desktop

2. 自主安装 Git 、VS Code, 并在 VS Code 中安装 Dev Container 插件。

3. 克隆本仓库，在VS Code中打开项目，然后点击左下角远程开发，选择在容器中重新打开；最后在Terminal中执行：

   cd ~
   git clone https://gitee.com/mengning997/linuxkernel.git # 注意：如果要编译Linux内核一定要在Linux文件系统环境下，克隆到Windows文件系统下编译过程中会有问题！
   cd linuxkernel/kerneldebuging
   sudo apt-get update
   sudo apt-get install -y global build-essential qemu qemu-system-x86 libncurses5-dev bison flex libssl-dev libelf-dev git wget bc cpio python gdb
   make
   ...
   [    2.650661] Write protecting the kernel read-only data: 20480k
   [    2.653933] Freeing unused kernel image memory: 2004K
   [    2.655225] Freeing unused kernel image memory: 860K
   [    2.655516] Run /init as init process
               --------------------               
                                                   
               Wellcome MengningOS!               
                                                   
               --------------------               
   /home #
   

调试Linux内核

4. 为了调试重新配置内核选项。

   make defconfig # Default configuration is based on 'x86_64_defconfig'
   make menuconfig
   # 打开debug相关选项
   Kernel hacking  --->
       Compile-time checks and compiler options  --->
           [*] Compile the kernel with debug info
           [*]   Provide GDB scripts for kernel debugging
    [*] Kernel debugging
   # 关闭KASLR，否则会导致打断点失败
   Processor type and features ---->
       [] Randomize the address of the kernel image (KASLR)
   

5. 重新编译内核。

   make -j$(nproc)
   

6. VS Code调试内核

todo: .vscode/launch.json中的preLaunchTask一直处于启动过程中，似乎没有调用起来gdb？

• 手工启动Terminal -> Run task... 选择"run MengningOS as Debug mode"
• 然后F5启动调试

7. 命令行模式调试内核

• 启动内核命令

  qemu-system-x86_64 -kernel linux-5.4.34/arch/x86/boot/bzImage -initrd rootfs.img -S -s
  # 纯命令行下启动虚拟机
  qemu-system-x86_64 -kernel linux-5.4.34/arch/x86/boot/bzImage -initrd rootfs.img -S -s -nographic -append "console=ttyS0"
  

• 启动gdb

  gdb linux-5.4.34/vmlinux
  (gdb) target remote:1234
  (gdb) b start_kernel
  (gdb) c、bt、list、next、step....
  

参考

• https://gitee.com/mengning997/linuxkerneldebug
• Linux源码阅读、编译调试和启动过程.pptx