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

Screenshot of the `paging-calculator` CLI utility

CLI Utility to Calculate Indices for Page Tables

I just want to drop a short notice that I created a small CLI utility that I think is helpful. paging-calculator helps you to calculate the indices for a given virtual address that are used for the physical address lookup at different page table levels. Paging is a mechanism that operating systems use for memory management. Check it out on crates.io or GitHub. You can install it with cargo install paging-calculator. It works Read more…

By Philipp Schuster, ago

Configure acpid From BusyBox in a Custom initrd

I have a setup with a Linux Kernel and a custom initrd, hence, no full Linux distribution. The initrd is meant to be as minimal as it can be. As a consequence, even basic things such as power-off on power-button pressed must be configured manually. There is no init system available – instead, I have to provide the init system. The initrd contains utilities from busybox. In this blog post, I show you Read more…

By Philipp Schuster, ago
acpid - Terminal Screenshot
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)