6 ms·

Minimal Linux Bootloader (2018)

88 points by 1vuio0pswjnm7 2y ago

1vuio0pswjnm7 2y ago
This is Bootloader ID #11 with comments See: http://sebastian-plotz.blogspot.de http://sebastian-plotz.blogspot.de https://docs.kernel.org/arch/x86/boot.html https://docs.kernel.org/arch/x86/boot.html
- not_your_vase 2y ago
  > Blog nicht gefunden. Ahhh, after looking harder, I see the typo https://sebastian-plotz.blogspot.com/ https://sebastian-plotz.blogspot.com/
  - watermelon0 2y 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/
    - 1vuio0pswjnm7 2y ago
      "On Blogger since November 2020." https://www.blogger.com/profile/10975102234345772797 https://www.blogger.com/profile/10975102234345772797 Blog post is dated 2012. https://sebastian-plotz.blogspot.com/2012/07/1.html https://sebastian-plotz.blogspot.com/2012/07/1.html This is what happens when Google acquires potential competition. https://en.wikipedia.org/wiki/Blogger_(service) https://en.wikipedia.org/wiki/Blogger_(service) Unlikely that original Blogger service registered a "blogspot" domainname in myriad ccTLDs such as .de Blogger was not a surveillance-based advertising company
    - not_your_vase 2y ago
      When I wrote the comment the top comment's link had a typo in it: https://sebastion-plotz.blogspot.de https://sebastion-plotz.blogspot.de Since then it was edited, and in a cash-money style there isn't any note about it.
      - deleted 2y ago
        [deleted]
- secure 2y 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-bootloader-debugging-story/ https://michael.stapelberg.ch/posts/2024-02-11-minimal-linux...
D4ckard 2y ago
I love MBR hacking, it's so fun to see. Cf. sector lisp [1] and OSle [2]. [1]: https://github.com/jart/sectorlisp https://github.com/jart/sectorlisp [2]: https://news.ycombinator.com/item?id=43866585 https://news.ycombinator.com/item?id=43866585
micw 2y ago
Do I see it right that I need to recompile and reinstall it on each new kernel?
- paulannesley 2y 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 2y ago
I don't see how this is better than lilo.
- WalterGR 2y ago
  It’s not meant to be full-featured. It shows how to write a bootloader that’s smaller than 512 bytes.
- 6SixTy 2y 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.
6SixTy 2y ago
Kind of cool, but being exclusively for BIOS/MBR kind of kills my excitement.
- seba_dos1 2y ago
  With EFI, you can just boot straight into Linux without any bootloader.
  - NewJazz 2y ago
    Technically there's a pe shim, no?
    - cyberax 2y ago
      You can just package Linux as a PE executable.
      - deleted 2y ago
        [deleted]
      - NewJazz 2y ago
        I guess my point was that the package was in a way a very minimal bootloader. Equivocal, easily.
    - seba_dos1 2y ago
      Part of Linux: https://www.kernel.org/doc/html/latest/admin-guide/efi-stub.html https://www.kernel.org/doc/html/latest/admin-guide/efi-stub....
- nine_k 2y 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.
deleted 2y ago
[deleted]
gitroom 2y ago
yeah im always low key impressed this old boot stuff still works now - makes messing with it feel kinda worth it
1vuio0pswjnm7 2y 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://sebastian-plotz.blogspot.com/ https://web.archive.org/web/20130516162543if_/http://sebasti...

88 points by 1vuio0pswjnm7 2y ago

This is Bootloader ID #11 with comments See: http://sebastian-plotz.blogspot.de http://sebastian-plotz.blogspot.de https://docs.kernel.org/arch/x86/boot.html https://docs.kernel.org/arch/x86/boot.html

not_your_vase 2y ago
> Blog nicht gefunden. Ahhh, after looking harder, I see the typo https://sebastian-plotz.blogspot.com/ https://sebastian-plotz.blogspot.com/
- watermelon0 2y 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/
  - 1vuio0pswjnm7 2y ago
    "On Blogger since November 2020." https://www.blogger.com/profile/10975102234345772797 https://www.blogger.com/profile/10975102234345772797 Blog post is dated 2012. https://sebastian-plotz.blogspot.com/2012/07/1.html https://sebastian-plotz.blogspot.com/2012/07/1.html This is what happens when Google acquires potential competition. https://en.wikipedia.org/wiki/Blogger_(service) https://en.wikipedia.org/wiki/Blogger_(service) Unlikely that original Blogger service registered a "blogspot" domainname in myriad ccTLDs such as .de Blogger was not a surveillance-based advertising company
  - not_your_vase 2y ago
    When I wrote the comment the top comment's link had a typo in it: https://sebastion-plotz.blogspot.de https://sebastion-plotz.blogspot.de Since then it was edited, and in a cash-money style there isn't any note about it.
    - deleted 2y ago
      [deleted]
secure 2y 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-bootloader-debugging-story/ https://michael.stapelberg.ch/posts/2024-02-11-minimal-linux...

D4ckard 2y ago

I love MBR hacking, it's so fun to see. Cf. sector lisp [1] and OSle [2]. [1]: https://github.com/jart/sectorlisp https://github.com/jart/sectorlisp [2]: https://news.ycombinator.com/item?id=43866585 https://news.ycombinator.com/item?id=43866585

micw 2y ago

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

paulannesley 2y 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 2y ago

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

WalterGR 2y ago
It’s not meant to be full-featured. It shows how to write a bootloader that’s smaller than 512 bytes.
6SixTy 2y 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.

6SixTy 2y ago

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

seba_dos1 2y ago
With EFI, you can just boot straight into Linux without any bootloader.
- NewJazz 2y ago
  Technically there's a pe shim, no?
  - cyberax 2y ago
    You can just package Linux as a PE executable.
    - deleted 2y ago
      [deleted]
    - NewJazz 2y ago
      I guess my point was that the package was in a way a very minimal bootloader. Equivocal, easily.
  - seba_dos1 2y ago
    Part of Linux: https://www.kernel.org/doc/html/latest/admin-guide/efi-stub.html https://www.kernel.org/doc/html/latest/admin-guide/efi-stub....
nine_k 2y 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.

deleted 2y ago

[deleted]

gitroom 2y ago

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

1vuio0pswjnm7 2y 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://sebastian-plotz.blogspot.com/ https://web.archive.org/web/20130516162543if_/http://sebasti...