Almost fourteen months ago, I started working on my bachelor thesis. Although I finished it half a year ago, it’s still part of my work as a student research assistant.
During my initial work, most of the code was written for an internal research kernel. I’m now happy that we were able to port it to an open source kernel called eduOS: /RWTH-OS/eduOS ). This minimal operating system is used for practical demo’s and assignments during the OS course at my university. There’s much more I could write about. So this will probably be another separate blog post.
The motive for this article is an abstract I wrote for the student research competition of the ASPLOS conference which is held this year in Istanbul, Turkey. Unfortunately my submission got rejected. But as a nice side-effect, I’ve now the chance to present my work to an English audience as well:
Self-referencing Page Tables for the x86-Architecture Section titled “Self-referencing Page Tables for the x86-Architecture”
A simple Paging Implementation for a minimalistic Operating System Section titled “A simple Paging Implementation for a minimalistic Operating System”
Steffen Vogel
Academic advisor: Dr. rer nat. Stefan Lankes Institute for Automation of Complex Power Systems E.ON Energy Research Center, RWTH Aachen University Mathieustr. 10, 52074 Aachen, Germany
This was a submission for ASPLOS Student Research Competition ’15 Istanbul, Turkey1.
The adoption of 64 bit architectures went along with an extension of the virtual address space (VAS). To cope with this growth, the memory management unit (MMU) had to be extended as well. For paging-based systems like Intel’s x86-architecture this was realized by adding more levels of indirection to the page table walk.
This walk translates virtual pages to physical page frames (PF) by performing look-ups in a radix / prefix tree in which every node represents a page table (Figure 1a). Since the tables are part of the translation process, they must be referenced by physical page frame numbers (PFN, blue line). As the operating system is only eligible to access the VAS, it cannot follow the path of a walk. In order to allow the manipulation of page tables, it must provide:
... continue reading