Re: gPXE scripts and boot module order

Hi,

On Thu, Aug 13, 2009 at 12:11:41PM +0100, Stefan Hajnoczi wrote:
> Have you tried fetching modules in the reverse order?

Yes, that works fine.

> When gPXE downloads an image, memory is handed out from the top of
> memory towards lower addresses.  The first image you download will
> have a higher memory address than the second image you download.
> (Details: core/downloader.c uses urealloc() to reserve memory for the
> image being downloaded, arch/i386/interface/pcbios/memtop_umalloc.c
> implements the umalloc() heap by growing it downwards.)
> 
> The multiboot code in gPXE will sort modules in ascending memory order
> for OS compatibility reasons, therefore the last module you downloaded
> is first in the list.  (Details: You will see a comment in
> arch/i386/image/multiboot.c that says:
> /* At least some OSes expect the multiboot modules to
>  * be in ascending order, so we have to support it.
>  */)

Thank you for the explanation. It would be cool to see this fixed in
future versions as it seems a bit weird to declare boot modules
bottom-up while all other loaders do it top-down. I like gPXE and
appreciate your work.

Regards
-- 
Christian Helmuth
Genode Labs

http://www.genode-labs.com/ · http://genode.org/

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