Debug Linux kernel within Visual Studio Code
The following steps have to be performed in your Linux source directory.
Create a file called tasks.json in the directory .vscode and paste the following contents into it:
See https://go.microsoft.com/fwlink/?LinkId=733558 for the documentation about the tasks.json format
{
"version": "2.0.0",
"tasks": [
{
"label": "Build Kernel for ARM",
"type": "shell",
"command": "make",
"args": [
"ARCH=arm",
"CROSS_COMPILE=arm-linux-gnueabihf-",
"-j6"
],
"group": {
"kind": "build",
"isDefault": true
},
"problemMatcher": [
"$gcc"
]
},
{
"label": "Copy zImage",
"command": "cp",
"args": [
"arch/arm/boot/zImage",
"../emulation/boot/efi/boot/bootarm.efi"
],
"dependsOn":["Build Kernel for ARM"]
},
{
"label": "Run qemu",
"command": "/usr/bin/qemu-system-arm -m 1024 -cpu cortex-a15 -M virt -pflash flash0.img -pflash flash1.img -nographic -drive file=fat:rw:boot/ -smp '4' -s",
"options": {
"cwd": "${workspaceFolder}/../emulation"
},
"type": "shell",
"isBackground": true,
"problemMatcher": [
{
"pattern": [
{
"regexp": ".",
"file": 1,
"location": 2,
"message": 3
}
],
"background": {
"activeOnStart": true,
"beginsPattern": ".",
"endsPattern": ".",
}
}
],
"dependsOn":["Copy zImage"]
},
{
"label": "Terminate All Tasks",
"command": "echo ${input:terminate}",
"type": "shell",
"problemMatcher": []
}
],
"inputs": [
{
"id": "terminate",
"type": "command",
"command": "workbench.action.tasks.terminate",
"args": "terminateAll"
}
]
} Create a file called launch.json in the directory .vscode and paste the following contents into it:
Use IntelliSense to learn about possible attributes. Hover to view descriptions of existing attributes. For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
{
"version": "0.2.0",
"configurations": [
{
"name": "(gdb) Run",
"type": "cppdbg",
"request": "launch",
"program": "${workspaceRoot}/vmlinux",
"miDebuggerServerAddress": "localhost:1234",
"miDebuggerPath": "/usr/bin/gdb-multiarch",
"args": [],
"stopAtEntry": true,
"cwd": "${workspaceFolder}",
"environment": [],
"externalConsole": false,
"MIMode": "gdb",
"targetArchitecture": "arm",
"preLaunchTask": "Run qemu",
"postDebugTask": "Terminate All Tasks",
"setupCommands": [
{
"description": "Enable pretty-printing for gdb",
"text": "-enable-pretty-printing",
"ignoreFailures": true
}
]
}
]
}Create a file called c_cpp_properties.json in the directory .vscode and paste the following contents into it:
{
"configurations": [
{
"name": "Linux",
"includePath": [
"${workspaceFolder}",
"${workspaceFolder}/include",
"${workspaceFolder}/include/uapi",
"${workspaceFolder}/include/generated",
"${workspaceFolder}/arch/arm/include",
"${workspaceFolder}/arch/arm/include/uapi",
"${workspaceFolder}/arch/arm/include/generated"
],
"defines": [
"__KERNEL__"
],
"compilerPath": "/usr/bin/arm-linux-gnueabihf-gcc",
"cStandard": "gnu17",
"cppStandard": "c++17",
"intelliSenseMode": "linux-gcc-arm",
"browse": {
"path": [
"${workspaceFolder}",
"${workspaceFolder}/include",
"${workspaceFolder}/mm",
"${workspaceFolder}/fs",
"${workspaceFolder}/kernel"
],
"limitSymbolsToIncludedHeaders": true,
"databaseFilename": ""
}
}
],
"version": 4
}Press F5 to start debugging. The following steps will be performed:
Compile Kernel
Copy zImage to qemu EFI partition
Launch qemu
Start GDB debugging
The following keys are important:
F9 for creating a breakpoint
F10 for going a step forward
F11 for stepping into a function
F12 to step out of a function
Debug Linux kernel with GDB
Clone a Linux tree and run make ARCH=arm defconfig to make a generic kernel configuration suited for qemu. Now edit the kernel configuration (.config) and add the following lines at the bottom:
CONFIG_DEBUG_INFO=y
CONFIG_GDB_SCRIPTS=yNow run make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j$(nproc) to compile the kernel. If you get asked about anything, just press enter to use the standard value.
Copy the output zImage (arch/arm/boot/zImage) to efi/boot/bootarm.efi on your EFI partition folder in your qemu directory.
Run sudo apt-get install gdb-multiarch to install GDB on Ubuntu. gdb-mutliarch is required because normal gdb package doesn't have support for ARM.
Open up the terminal you want GDB to run in, and change directory to your Linux compilation directory. Then run gdb-multiarch vmlinux., it will open GDB you and you can now connect to a target with target remote localhost:1234. At this point GDB will wait for qemu to start. After that you can now debug with qemu, there are tutorials online to show you how to do this.
Go to the directory where your qemu files are located, start qemu as described in Qemu emulation, only change is that you need to add a -s parameter, this lets qemu know that it starts a GDB server.