December 25, 2025
Been there, paged that
Self-referencing Page Tables for the x86-Architecture
Student’s memory trick hits the web and sparks a 'this isn’t new' pile-on
TLDR: A student ported a classic memory trick to a teaching OS so it can edit its own memory map more easily. Commenters say it’s old news—known as “fractal mapping”—and debate whether it’s still useful, with one dev arguing it breaks down when juggling many processes and devices.
A student shows off a neat memory “hack” for a tiny teaching operating system, using a self-referencing page table—basically a way for the computer to see and edit its own map of memory without extra fuss. It’s now in the open-source eduOS, and the author even tried to present it at a big conference (rejected!). But the internet’s first reaction? Deja vu.
Top commenters rushed in with “We’ve seen this before!” energy. One points out Windows did this ages ago. Another says it’s literally fractal mapping, a well-known trick where the map includes itself. A third piles on with, “Am I missing something?” The vibe: not a scam, just not new—more “classic move” than “plot twist.”
Then the mood shifts from dunking to practical debate. A developer using recursive tables says they’re switching away because it’s a pain with many processes and devices. Translation: this trick is clever for one sandbox, but gets awkward when you juggle many sandboxes at once. Meanwhile, the peanut gallery spins memes about “reinventing the wheel,” while others cheer the educational value. Bottom line: the technique is smart and handy, but the drama is all about novelty vs. teaching value, with bonus points for naming wars—recursive, fractal, or just “been there, paged that.”
Key Points
- •The thesis proposes self-referencing page tables on x86 by adding a self-reference in the root table (PML4/PGD).
- •This enables access to all page tables from the virtual address space, removing the need for manual mappings.
- •The implementation is compatible with both 32-bit protected mode and 64-bit long mode, consolidating separate code bases.
- •Ported to the open-source teaching OS eduOS, which is used in RWTH Aachen’s OS course.
- •The abstract was submitted to the ASPLOS 2015 Student Research Competition in Istanbul but was rejected.