I have always wondered what happens when we enter the kernel from userspace: what preparations does the hardware meet when the userspace to kernel space switch instructions are executed and back, and what does the kernel do when it executes a system call. There are also a bunch of things it does before it executes the actual syscall so I try to look at those too.
This talk is an attempt to demystify some of the aspects of the cryptic x86 entry code in arch/x86/entry/ written in assembly and how does that all fit with software-visible architecture of x86, what hardware features are being used and how.
With the hope to get more people excited about this funky piece of the kernel and maybe have the same fun we’re having.
Borislav Petkov, SUSE