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
-
Arch Linux Available for Windows Subsystem for Linux
If you've ever wanted to use a rolling release distribution with WSL, now's your chance.
-
System76 Releases COSMIC Alpha 7
With scores of bug fixes and a really cool workspaces feature, COSMIC is looking to soon migrate from alpha to beta.
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.