Building a custom Mach-O memory loader for macOS

In this blog we’ll look at what it takes to construct an in-memory loader for Mach-O bundles within MacOS Ventura without using dyld. We’ll walk through the lower-level details of what makes up a Mach-O file, how dyld processes load commands to map areas into memory, and how we can emulate this to avoid writing payloads to disk. I also recommend reading this post alongside the code published here to fully understand the individual areas called out.