Minimal Linux Bootloader (2018)

https://raw.githubusercontent.com/Stefan20162016/linux-insides-code/master/bootloader.asm

by 1vuio0pswjnm7 • 1 year ago

88 27 1 year ago

raw.githubusercontent.com

1vuio0pswjnm73• 1 year ago

This is Bootloader ID #11 with comments

See:

http://sebastian-plotz.blogspot.de

https://docs.kernel.org/arch/x86/boot.html

not_your_vase2• 1 year ago

  > Blog nicht gefunden.

Ahhh, after looking harder, I see the typo

https://sebastian-plotz.blogspot.com/

watermelon0• 1 year ago

.de redirects me to .com.

Maybe this is somehow geolocked in a weird way, to return not found error for you.

  > GET / HTTP/1.1
  > Host: sebastian-plotz.blogspot.de
  > User-Agent: curl/8.7.1
  > Accept: */*
  >
  * Request completely sent off
  < HTTP/1.1 302 Moved Temporarily
  < Location: http://sebastian-plotz.blogspot.com/

secure• 1 year ago

I use this bootloader in gokrazy and blogged about debugging a limitation in it a while ago: https://michael.stapelberg.ch/posts/2024-02-11-minimal-linux...

D4ckard• 1 year ago

I love MBR hacking, it's so fun to see. Cf. sector lisp [1] and OSle [2].

[1] https://github.com/jart/sectorlisp

[2] https://news.ycombinator.com/item?id=43866585

micw• 1 year ago

Do I see it right that I need to recompile and reinstall it on each new kernel?

paulannesley• 1 year ago

Yeah it looks like it needs to be assembled and written any time the kernel file's position on disk changes (`current_lba`), or different kernel cmdline is required.

I seem to remember having to do something similar with lilo… not hand-editing assembly, but running a command to rewrite the boot sector when the kernel moves on disk.

M95D• 1 year ago

I don't see how this is better than lilo.

WalterGR• 1 year ago

It’s not meant to be full-featured. It shows how to write a bootloader that’s smaller than 512 bytes.

6SixTy2• 1 year ago

It's not supposed to be better than lilo, just code golf. Limine is pretty much the only serious bootloader gunning for the spot lilo/elilo was going for.

6SixTy2• 1 year ago

Kind of cool, but being exclusively for BIOS/MBR kind of kills my excitement.

seba_dos12• 1 year ago

With EFI, you can just boot straight into Linux without any bootloader.

NewJazz2• 1 year ago

Technically there's a pe shim, no?

nine_k• 1 year ago

Yes. BIOS. Real mode. Not that I've been missing them these 30 years, and they are still in place. It gives a weird feeling.

I mean, if you target ancient baroque hardware like e.g. ZX Spectrum, you specifically target an ancient machine. But this is expected to work on any modern x86 hardware, while it feels like code for a 80286, and likely would run there. And this ancient stuff is still supported and actively used.

musicale2• 1 year ago

this ancient stuff is still supported and actively used.

It sort of warms my heart that code for the IBM 360 (now IBM Z) and the IBM PC (now x86 PC) can still run on modern hardware decades later.

On one hand, we're stuck with the legacy of the past. But on the other hand, we can build on things and don't need to reinvent them unnecessarily.

raxxorraxor• 1 year ago

Yes. BIOS. Real mode.

  ; 0x20000 - 0x2fdff temporal space to load ; size: 63.5Kb is the max.

wasn't there an inofficial unreal mode that increased the adressable space? Otherwise there aren't too many options as to stay minimal in the first place.

gitroom• 1 year ago

yeah im always low key impressed this old boot stuff still works now - makes messing with it feel kinda worth it

1vuio0pswjnm73• 1 year ago

HN has added "(2018)" to the title but the source for this bootloader was originally uploaded to Google six years earlier in 2012. The version uploaded to Github in 2018 added comments.

https://web.archive.org/web/20130516162543if_/http://sebasti...

Minimal Linux Bootloader (2018)

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