User Space Debugging Tools for Linux

The userspace is the area or space where all the applications executed by the user are located, such as the terminal, web browser, text editor, etc. In simple terms, the userspace is an area with resources for user processes to run.

This space has limited access to the hardware, a separate memory, and user privileges. It has its own components, such as:

• Shell ? The command-line interface.
• User Libraries ? Provide the interface for system calls.
• Daemons ? Background processes.
• Utilities and Tools ? Tools like grep and vim, which run inside the userspace.

Applications running in the userspace may encounter a lot of problems and issues, such as crashes, performance problems, bugs, or unexpected behaviors.

For these reasons, we need tools to help find and fix these problems, and we call these tools debuggers.

In Linux, there are many tools for this purpose, each with its own functionality and features. In this article, we will go through some of them.

GNU Debugger

In debugging, there are different tools and techniques depending on the situation that complement each other.
You cannot do everything with one tool. For example, you can fix bugs in software using print statements, but you may need to mix a few of them to fully resolve the problem.

GDB, or GNU Debugger, is a powerful tool that can handle many complex issues. It is also known for kernel debugging.

GDB has many features and is considered one of the top programs for debugging, mainly for software written in C and C++.

Some of the key characteristics of the GNU Debugger ?

• Interactive Debugging ? GDB allows us to debug programs at runtime and control their execution. We can start and stop program execution as needed. Alongside this, it can step through the code line by line or function by function.
• Inspect and Modify State ? GDB also allows us to inspect and modify the program's state during execution.

How to Use GDB?

GDB comes installed by default in Linux, and its usage is simple. To start a debugging session, use the command gdb followed by the name of the program ?

gdb ./name

Example ? Compile a C program with debug information using the -g flag. This will include debugging information to help GDB map the executable.

gcc -g -o main test.c

Open the compiled program with GDB ?

gdb ./test

The next step is to run the program using GDB ?

run

This stage will indicate the error, which is in element 5.

Valgrind

Another important tool that we can use alongside GDB is Valgrind, which also helps in debugging, especially if you are trying to find memory leaks in a program. One of the best areas where Valgrind excels is memory. It helps detect memory leaks and invalid memory access.

How Valgrind works is different from how GDB works. Valgrind operates as a virtual machine and executes the program inside it. This is what allows it to monitor memory usage and system interactions.

By default, Valgrind is not installed, so to work with it, you first need to install it using the following command ?

sudo apt install valgrind

This command is for Debian or Debian-based distributions like Ubuntu, Mint, etc.

For Red Hat/Fedora, use the following command ?

sudo dnf install valgrind

To use it, simply run Valgrind with the program you need to debug. For example ?

valgrind ./name

Strace

Another useful program for monitoring a program during execution is strace. It allows you to see the interaction between the program and the kernel. This will help find issues, network activities, and memory allocation.

strace is installed in Linux by default, and the usage is simple. To trace a program, you only need to run it with strace.

Example ? if you trace ls with strace, like this ?

strace ls

The output looks like this ?

This will show a bunch of information, such as system calls (execve), memory management, changes in memory, and a lot of other useful information.

Conclusion

Debugging is an important phase that helps fix problems and find issues. In this article, we learned about some of the tools that can be used to debug userspace in Linux. This was just an introduction and some simple tests to get you started in the world of debugging in Linux.