uefi-rs VS builder-hex0

Hi, did you know that you can write UEFI-code with Rust? You can, using uefi-rs!

Thanks for pointing that out. I've filed https://github.com/rust-osdev/uefi-rs/issues/685

I'm extremely confused as to what's going on here. I think it might be related to Line 129: https://github.com/rust-osdev/uefi-rs/blob/main/src/table/system.rs

First off I don't recommend implementing the specification from scratch. It is big, and there are implementations already in various languages: for C you can use GNU-UEFI, for example, and for Rust you can use uefi-rs. Zig even has it in its standard library! These take care of the fiddly details of interacting with the UEFI firmware's services.

There's tutorial type articles for these around: for C there's https://wiki.osdev.org/UEFI_App_Bare_Bones, for Rust there's this template https://github.com/rust-osdev/uefi-rs/tree/main/template and the crate's documentation.

A few people have made some progress into working with UEFI in Rust, and the results are here: https://github.com/rust-osdev/uefi-rs

use uefi::prelude::Handle; points to uefi-rs/src/prelude.rs found here: https://github.com/rust-osdev/uefi-rs/blob/master/src/prelude.rs

Here is an UEFI app/example that should show you how to write a UEFI bootloader.

Isn't that what builder-hex0 does?

https://github.com/ironmeld/builder-hex0

They literally create a file system and whole operating system in 4KB of text and it is good enough to bootstrap GCC/Linux ( https://github.com/ironmeld/builder-hex0 )

"It is true: in our quest to make full use of the CPU, we must abandon all of those helpful routines provided by BIOS. As we will see when we look in more detail at the 32-bit protected mode switch-over, BIOS routines, having been coded to work only in 16-bit real mode, are no longer valid in 32-bit protected mode; indeed, attempting to use them would likely crash the machine.

"So what this means is that a 32-bit operating system must provide its own drivers for all hardware of the machine (e.g. the keybaord, screen, disk drives, mouse, etc). Actually, it is possible for a 32-bit protected mode operating system to switch temporarily back into 16-bit mode whereupon it may utilise BIOS, but this teachnique can be more trouble than it is worth, especially in terms of performance."

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In the toy 32-bit OS I am currently writing, having easy disk access and text output was more important to me than performance, so I decided to implement this technique to access the disk and screen via the BIOS instead of writing an ATA disk driver.

Although I could not find any minimal yet complete working examples of dropping to 16 bit and later resuming 32 bit mode, I was able to piece it together and write assembly functions called enter_16bit_real and resume_32bit_mode. See https://github.com/ironmeld/builder-hex0/blob/main/builder-h.... Those routines are working well but beware the project is a volatile work in progress and is coded in hex for bootstrapping reasons.