Used to be my personal blog. Now, it covers programming, low-level development, operating systems, and more.

Code Snippet: Part of the QEMU Debugcon Driver written in Assembly

The Probably Simplest x86 Driver Written in Assembly – Printing to QEMU’s debugcon-Device

This is an educational resource I wish I had when I started digging into low-level and operating systems during my early time of my studies at the university. However, dear past me, I got your back! Do you want to see a minimal way to communicate with (virtual) hardware and all of that written in pure assembly? Here you go. But at first, a few background information. How do we communicate with hardware? Read more…

By Philipp Schuster, ago

GNU ld Discards Section Containing Code – Section Flags are Important for ELF Files

Update: Since I published this article, I gained more knowledge from own research and hints from others. I adjusted the blog post. Thanks for the help! When it comes to low-level systems engineering and producing binaries, such as firmware or kernels, dealing with linkers and especially linker scripts feels like the end boss in a video game. Only very little (good) documentation can be found on the Web. This blog post is the Read more…

By Philipp Schuster, ago
Assembly Code Snippet: Use section flags if you need custom section names

Create a Bootable Image for a Custom Kernel with GRUB as Bootloader for Legacy x86 Boot (e.g. Multiboot2 Kernel)

In this blog post, I want to show you how you can boot your custom (i.e., self developed, non-linux) kernel with GRUB 2 in a legacy x86 boot flow. The tutorial is focused on Linux as build environment. A working example can be found on my GitHub. Introduction When you are an OS developer/low-level hacker and write your own kernels, you need a setup to boot your software stack (i.e., kernel and user Read more…

By Philipp Schuster, ago

Live Audio Visualization With Rust in a GUI Window

In early 2021 I had a closer look into several aspects of digital signal processing (DSP), including lowpass filters, frequency spectrum analysis, and audio visualization. I used Rust to experiment with this. The Rust ecosystem didn’t offer simple-to-use libraries for my use cases back then, or at least they were not easy to find. While I learned more about the topic, I created multiple crates, with the hope they may be helpful to Read more…

By Philipp Schuster, ago
Screeshot: Live Audio Visualization of Waveform (original vs lowpass filter)
Screenshot of Sourcecode

Direct Systemcalls to Linux from Rust Code (x86_64)

What I show in this blog post is nothing new or unique, but it is something I wish someone would have shown me in this simplicity in my second or third semester at university. In this post, I briefly explain how you can talk to Linux without the libc or the Rust standard library (which uses libc behind the scenes most probably). Furthermore, I give you pointers to the corresponding syscall code in Read more…

By Philipp Schuster, ago

Minimal GRUB Configuration To Boot A Multiboot2 Kernel With Boot Modules

TLDR: for Multiboot2 you use module2 and for Multiboot1 module in GRUB config files. One of my projects of the last months was to build a prototype setup for kernels written in Rust. The kernel is Multiboot2-compliant and boots on x86_64 with UEFI as firmware. To test everything, I create a standalone GRUB in a directory, which contains the kernel (an 64-bit ELF) and a minimal grub.conf. The “standalone GRUB” is a regular Read more…

By Philipp Schuster, ago