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Re: Multiboot2 header


From: Tomáš Ebenlendr
Subject: Re: Multiboot2 header
Date: Wed, 5 Nov 2008 18:40:32 +0100 (CET)
User-agent: SquirrelMail/1.5.1

Dne 4 Listopad 2008, 21:36, Robert Millan napsal(a):
>

> The Multiboot2 draft says a Multiboot2 header must be included in the OS
> image.  However, our code assumes (in code itself and in comments) that
> for MB2 this is optional.
>
>
> As a consequence, if you feed GRUB's multiboot loader any ELF, it will
> attempt to load it.  I think this is very confusing for those developing a
> Multiboot _1_ OS.  If they happen to make a mistake and put the MB1
> header too high or unaligned, GRUB won't tell them about it but instead
> fail in a very confusing way.

Those developers will appretiate if grub will be VERBOSE when loading an
OS image. I.e., it should tell what header it found and where. Then the
developer will be able to get know that his MBR1 was not found, no matter
how much another headers were tried after.

> So I assume (I'd like to!) that the correct one is the draft, and it's
> the code that should be changed to reject executables that don't have
> either MB1 or MB2 headers?

But you are true, that the user should have control what headers are
tried. There may be some os image (binary, proprietary, thus not
repairable by
user) that would need specific way of loading (e.g. the elf-way). Such
image may fail in ambiguous way when booted other way (I mean, the image
fails, grub's part of bootloading will be okay).

> --
> Robert Millan
-- 
.                           Tomas Ebenlendr
.                           http://drak.ucw.cz/~ebik





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