Self-referencing Page Tables for the x86-Architecture

https://0l.de/blog/2015/01/bachelor-thesis-abstract/

62•stv0g•1mo ago

Comments

cmpxchg8b•1mo ago

I'm confused, is this meant to be presented as new work? Windows has done this for a very long time.

protoman3000•1mo ago

It’s a bachelor’s thesis.

als0•1mo ago

"There is only a single reference5 dated to 2010 indicating that Microsoft might use a similar approach for its NT kernel."

cmpxchg8b•1mo ago

Googling for it brings up a ton of results.

raggi•1mo ago

I found it very opaquely worded the whole way through. I think the work being presented is simply an implementation of the technique in eduos, but short of going and reading the paper I don’t know.

no92•1mo ago

If I'm not mistaken, this is just fractal mapping, which is very common. See https://wiki.osdev.org/Fractal_Page_Mapping

userbinator•1mo ago

It's amusing to see a concept that is explained simply in a few lines, become an entire bachelor's thesis.

jdefr89•1mo ago

Isn't this just fractal page mappings? Am I missing something?

voidmain•1mo ago

I'm currently using recursive page tables for the OS I'm working on, but I'm probably going to change that. There are lots of different address spaces for different processes and (with IOMMU) devices, and it's nicer to be able to modify any of them rather than only the current one. I am leaning toward just assigning 2 MiB of memory to page tables at a time and keeping a mapping for these (I don't want to map all physical memory in the kernel for security reasons).

amluto•1mo ago

Don’t use recursive page tables.

- What if you want to port to an architecture that can’t do them?

- How sure are you that all the bonus bits in the entries line up right?

- What if you want to use huge pages of various sizes?

- What if you want to write-protect some page tables?

- What if you want to access a non-current page table? If you do that you need to write all the relevant logic anyway.

- What if a page table isn’t allocated? You probably don’t want to find out by trying to access it and getting a page fault in kernel mode.

- What if you don’t want user code to be able to trivially guess kernel addresses?

A Bid-Based NFT Advertising Grid

AI readability score for your documentation

NASA Study: Non-Biologic Processes Don't Explain Mars Organics

I inhaled traffic fumes to find out where air pollution goes in my body

X said it would give $1M to a user who had previously shared racist posts

155M US land parcel boundaries

Private Inference

Font Rendering from First Principles

Show HN: Seedance 2.0 AI video generator for creators and ecommerce

Wally: A fun, reliable voice assistant in the shape of a penguin

Rewriting Pycparser with the Help of an LLM

Lobsters Vibecoding Challenge

E-Commerce vs. Social Commerce

Avoiding Modern C++ – Anton Mikhailov [video]

Show HN: AegisMind–AI system with 12 brain regions modeled on human neuroscience

Zig – Package Management Workflow Enhancements

AI-powered text correction for macOS

AppSecMaster – Learn Application Security with hands on challenges

Fibonacci Number Certificates

AI Overviews are killing the web search, and there's nothing we can do about it

City skylines need an upgrade in the face of climate stress

1979: The Model World of Robert Symes [video]

Satellites Have a Lot of Room

1980s Farm Crisis

Show HN: FSID - Identifier for files and directories (like ISBN for Books)

Show HN: Holy Grail: Open-Source Autonomous Development Agent

Show HN: Minecraft Creeper meets 90s Tamagotchi

Show HN: Termiteam – Control center for multiple AI agent terminals

The only U.S. particle collider shuts down

Ask HN: Why do purchased B2B email lists still have such poor deliverability?