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Re: Loading boot image retrieved from CD-ROM

From: Vesa Jääskeläinen
Subject: Re: Loading boot image retrieved from CD-ROM
Date: Sun, 24 Jun 2007 10:53:56 +0300
User-agent: Thunderbird (Windows/20070604)

Alex Roman wrote:
> Hello,
> As you may recall, I'm working on the Google Summer of Code project to
> enable GRUB2 to boot off CDs.
> I can now read boot images from CDs using int 13h BIOS calls :) And
> I've confirmed I'm actually reading the ISOLINUX image because I can
> perform some manual disassembly and it matches what I see in the
> ISOLINUX source code :)

> The problem is that QEMU freezes when I call the asm function. Was
> wondering if anyone could take a quick look at the function to see if
> I'm doing anything wrong, or if someone could suggest how to best
> debug this issue...

Sorry not having the time to test out PXE boot in vmware. Actually I
didn't event discover way to do PXE boot without setting up required
server software.... Anyway please provide floppy disk image next time ;)

Back to your issue. What BIOS call did you use? I am asking this because
if you did end up using packet calls then it might not work for ISOLINUX
as it most likely uses emulated reads. And might need drive remapping. I
have faint memory that some register needs to contain drive number being
booted. And now you have zeroed almost everything. Anyway. Best to make
custom image so that you know that you have booted it and not to quess
that perhaps something is happening :) You could easily make 512 bytes
image that does something like printing something to screen or so.

Here is a wiki link about memory map:

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