Delve into ELF Binary Magic
Delve into ELF Binary Magic
Discover what goes on inside executable files, how to reverse-engineer them, and how to make them as small as possible.
Back in the good old days, you could leave your door unlocked at night, music made sense, and writing computer programs was simply a case of putting some CPU instructions in the right order. Today, we have a mammoth range of libraries, toolkits, abstraction layers, and other things that make writing large programs easier – but it's increasingly difficult to understand what the CPU is actually doing. Open up LibreOffice, for example, and type a dot (period) character. What exactly happens here? How many CPU instructions are being executed between your finger hitting the key and that dot appearing on the screen?
Now, we don't want to sound like old codgers who think that everything should be written in assembly language. There's a reason why we have these layers of abstraction, to make software safer, easier to understand, and more portable. But sometimes it's good to go low-level and interact more closely with the CPU and operating system, to better understand what's going on. So, in this article, we'll get down and dirty with CPU instructions, the ELF executable format, and reverse-engineering binary files so you can see what they do.
I Can C Clearly Now
Let's start by writing a very simple C program. Put this into a file called test.c in your home directory:
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
The Bullet-Proof KDE Software Initiative Is Coming
KDE, Techpaladin, and Kubuntu Focus have announced a new initiative that will provide at least three years of support for KDE Plasma 6.6 LTS and related software.
-
Linux Mint Shares a Possible Kernel Cleanup Solution
For those on Linux Mint who like to keep multiple kernels around but don't want them to take up too much space, you might be getting a new automated tool.
-
CachyOS Gets an Update
CachyOS August 2026 release is now available with the latest version of KDE, some new features, and plenty of improvements.
-
The Linux Kernel Dev Staging Area Now Rejects AI-Generated Patches
Unless a kernel patch is a valid security fix, it will be rejected if it was created using AI.
-
Linux Surpasses Double-Digit Market Share
According to two sources, the Linux operating system has hit a major milestone in market share that naysayers thought would never happen.
-
AI Helped Develop a Linux Exploit
A use-after-free race exploit was discovered and exploited on CentOS Stream 9.
-
Yet Another Linux Kernel Vulnerability Discovered
Affecting millions of systems, a kernel flaw discovered by Qualys could allow users to gain root privileges.
-
Ubuntu 26.10 to Include Ubuntu Certified Hardware Check
If you've ever wondered if your laptop or PC is officially certified to run Ubuntu, that curiosity will soon be met.
-
Substantial Update to IPFire Now Available
The lastest version of IPFire features a fundamental change to how the system handles DNS.
-
Gnome Working on Test Center App to Make Testing Easier
It's now possible to test experimental features on the Gnome desktop without worrying that you'll break things.