I’ve seen my fair share of bugs in Springboard, the ubiquitous program which controls the iOS home screen — from cloning app icons to immortal ghost apps to catastrophic rendering fails.
But what exactly is Springboard?
First, let’s dip our toe into computer science theory.
Operating Systems & The Kernel
An OS manages a computer’s resources. Operating Systems typically have 2 components; the Kernel and Userland.
The Kernel creates and manages abstractions on top of hardware — converting CPU, RAM, and SSD into threads, heap memory, and file systems. It also makes basic system functionality available to the software that constitutes Userland.
Want to see the iOS Kernel? It’s right here, on Github. If you spot a way to perform no-click kernel code execution, Apple may just give you $1m.
Now we’ve tested the temperature, let’s caaarefully lower our foot.
Userland
We typically interact with Userland applications (a.k.a. “user space”) when we use any computer — an OS is software programs all the way down.
Userland apps interact with the Kernel via syscalls. These are functions with elevated permissions, not available to third-party apps, which can bypass security protections like memory virtualisation and app sandboxing.
Now we’re primed to paddle in with both feet. Watch your trousers!