Recently I’ve finished the Practical Malware Analysis book and I’ve wanted to familiarise myself a bit more with the Win32 API. After spending a good amount of time on setting up Visual Studio C++ for MASM (Microsoft Macro Assembler) I wanted to stab myself in the eye with a rusty fork due to the overload of visual clutter. Alas, running plain MASM on Windows 10 seems to be a no-go these days.
Recently I decided to study for the SLAE64 course from Pentester Academy to work on my assembly knowledge, specifically on x86_64. Through the course does focus on Linux I want to apply the knowledge to OpenBSD/amd64 too and thus I installed NASM and looked at what I needed to adjust on my Linux samples to get it working on OpenBSD. Turns out, not that much actually! Both operating systems use same calling convention, namely the System V AMD64 ABI.