BELK-AN-009: Using Visual Studio Code for remote debugging

Info Box Applies to Bora Applies to BORA Xpress

This application note was validated against specific versions of the kit only. It may not work with other versions. Supported versions are listed in the History section.

History

Version	Date	BELK/BXELK version	Notes
4.0.0/2.0.0	June 2019	4.0.0 / 2.0.0	First release

Introduction

Visual Studio Code (VSCode for short) is a powerful integrated development environment (IDE). In the last years, it has gotten growing popularity among software developers of any kind, thanks to its excellent flexibility. Numerous extensions, native git support, availability for all of the most common platforms are some of the features that have made it so successful.

Even though it was not designed for embedded software development specifically, it is so versatile that it can be used for this purpose as well. This application note shows, for instance, how to configure it in order to remotely debug an application running on the Bora/BoraX platform. As host machine, the Virtual Machine released along with the BELK/BXELK kit was used.

It assumed that the reader is familiar with BELK/BXELK kit and with VSCode.

Host configuration

The example here described allows compiling and debugging the application for the host machine too. For this reason, the procedure indicates to install the native gdb debugger as well.

In essence, the followings are the packages that have to be installed:

• Visual Studio Code with these extensions
  • C/C++
  • Native Debug
• sshpass (sudo apt install sshpass)
• gdb (sudo apt install gdb).

The two required extensions

Target configuration

The target has to be configured to mount the root file system over NFS. Please refer to link for more details.

The example project associated with this application note should be located in this directory of the host machine: /bora/rfs/belk-4.0.0/home/root/hello. This directory is seen by the target machine as /home/root/hello.

Please note that you need to change the permissions of the directory /bora/rfs/belk-4.0.0/home/root/hello in order to allow the user dvdk to access it without any restrictions:

dvdk@vagrant-ubuntu-trusty-64:~/bora/rfs/belk-4.0.0/home/root$ ll
total 16
drwxr-xr-x 3 root root 4096 Jun 12 16:27 ./
drwxr-xr-x 3 root root 4096 Jul 10  2017 ../
-rw------- 1 root root 1102 Jun 12 10:41 .bash_history
drwxr-xrwx 4 root root 4096 Jun 12 14:55 hello/

The example project

The example project is the umpteenth flavor of the world-famous "Hello, world!" program. Source code is available [ here] for download.

The example makes use of a simple Makefile for cross-building. This Makefile can be used either to build the application manually or to build it automatically as part of a VSCode-controlled debugging session.

The following image shows the files that the VSCode workspace consists of.

VSCode workspace

The most relevant are:

• hello.c
  • The source file of the program
• Makefile
  • This file allows building the program manually from the command line. It is also used by VSCode to build the program before starting a debug session.
• remote-debugging.sh
  • This script is invoked by VSCode to
    • Build the program for the embedded target
    • Start a remote debug session.
• cross-build.sh
  • This script is invoked in turn by remote-debugging.sh. The final command that triggers the actual building process is make hello, that is the same command used to build the program manually.
• start-gdbserver.sh
  • This script is invoked by remote-debugging.sh to start a gdbserver instance on the target.
• .gdbinit
  • In includes initialization scripts that are run by /home/dvdk/bora/sdk/belk-4.0.0/sysroots/x86_64-petalinux-linux/usr/bin/arm-xilinx-linux-gnueabi/arm-xilinx-linux-gnueabi-gdb upon startup. For more details, please see this page.
• launch.json
  • In this file two configurations are defined:
    • (gdb) Native launch
      • This is used to build and debug the application on the host machine
    • (gdb) Cross launch
      • This is used to cross build the application on the host machine and to debug it on the target machine
• tasks.json
  • In this file two tasks are defined:
    • native build
      • This is used to build the program for the host target. In this case, an explicit command is run (gcc -g -o hello.x86 hello.c)
    • build and start remote debugging
      • As stated before, this task invokes the remote-debugging.sh script.

Starting a debug session

In practice, once the target is up and running and the example project was copied onto the host machine, follow these steps to start a cross-debugging session:

• Open the VSCode workspace
• Select the (gdb) Cross launch configuration
• Click on the green Start Debugging or select the Debug->Start Debugging menu item. Alternatively, press F5. You should see something like the following picture. It is worth remembering that the scripts take care of killing any gdbserver instance running on the target before starting a new debugging session. This allows starting it with just one click.

Cross debugging session

For the sake of completeness, the native debugging session is illustrated as well.

Native debugging session