Use vscode to remotely debug the Linux kernel

Preface

The previous article introduced the use of QEMU GDB to debug the Linux kernel. However, sometimes it is not very convenient to directly use GDB to debug and view the code. Therefore, on such an important occasion, how can the artifact of vscode be missing? This article introduces how to use vscode to remotely debug the kernel.

Environment of this article:

• windows10
• vscode
• ubuntu 20.04

I personally use Tencent Cloud Server, so I save the process of installing a virtual machine. Start directly from vscode configuration.

vscode plug-in installation

remote-ssh

Find the Remote-SSH plug-in in the plug-in library and install it.

After the installation is complete, there will be an additional function on the right toolbar

Press F1 to call out the dialog box, enter remote-ssh, and select open ssh configuration file.

Select the first configuration file

# Read more about SSH config files: https://linux.die.net/man/5/ssh_config
Host ubuntu
    HostName 服务器IP地址
    User 用户名
    IdentityFile 私钥路径

I am using the private key method to log in to the server, and IdentityFile fills in the absolute path of the private key.

After configuration, click the plus button to log in to the server

Error: Setting up SSH Host XX:Copying VS Code Server to host with scp

I got stuck while connecting and have been waiting for Setting up SSH Host XX:Copying VS Code Server to host with scp.

reason

It’s because the home directory ~/.vscode-server/bin/commit_id/vscode-servlet.tar.gz is not downloaded under the remote server.

commit_id can be viewed in vscode [Help]->[Terminal].

Solution

Then we will download vscode-servlet.tar.gz manually. Download via the link below.

#注意把:${commit_id}替换成对应的Commit ID
https://update.code.visualstudio.com/commit:${commit_id}/server-linux-x64/stable

Run the following line of command. Delete everything in the ~/.vscode-server/bin directory.

rm ~/.vscode-server/bin/* -rf

If there is no ~/.vscode-server/bin directory, create it. If there is, please ignore this step*.

mkdir -p ~/.vscode-server/bin

Place the downloaded compressed package vscode-server-linux-x64.tar.gz in the ~/.vscode-server/bin directory.

Run the following three lines of commands, where ${commit_id} needs to be replaced with the commit_id recorded in step 2.

cd ~/.vscode-server/bin
tar -zxf vscode-server-linux-x64.tar.gz
mv vscode-server-linux-x64 ${commit_id}

报错：Permissions for ‘vscode_rsa’ are too open.

然后就可以在原来的文件浏览界面，打开远程的文件夹。但是在配置好进行连接的时候，VScode的终端报错了:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@     WARNING: UNPROTECTED PRIVATE KEY FILE!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions for 'vscode_rsa' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
Load key "vscode_rsa": bad permissions

根本原因是私钥的权限问题。这要是在Linux里，直接使用chmod，就可以修改，修改为644即可，但是windows，就稍微麻烦点。

在私钥上右击选择属性，然后选择【安全】选项卡，然后点击下面的【高级】按钮，然后在新弹出的窗口下方点击【禁用继承】，然后点击继承那个按钮上面的【添加】按钮重新将当前window登录用户设置为私钥的所有者，并勾选所有权限。最后跟下面一样即可：

这时再次打开VScode远程连接，就没有问题了。

C/C++

安装C/C++插件

依次点击【运行】->【打开配置】，将以下配置复制到launch.json中。

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "kernel-debug",
            "type": "cppdbg",
            "request": "launch",
            "miDebuggerServerAddress": "127.0.0.1:1234",
            "program": "${workspaceFolder}/vmlinux",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "logging": {
                "engineLogging": false
            },
            "MIMode": "gdb",
        }
    ]
}

然后在main函数中，打上两个断点，在服务器上开启QEMU，F5即可开启调试。

在vscode中调试内核，和正常的在windows调试代码是一样的，侧边栏可以看到变量，监视变量，调用堆栈等，非常方便。

大功告成，以后就可以在可视化界面调试内核了！

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