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Subject: Re: GSoC: CD-ROM booting options
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Alex Roman wrote:
> On 05/06/07, adrian15 <adrian15@raulete.net> wrote:
>> GRUB 2 needs to support both cases, but I prefer to see something not
>> present in GRUB Legacy implemented in GRUB 2 first.
> 
> Good point... In any case there's some commonality between the two
> cases and for now I'm working to see if I can read some ElTorito data
> structures from a bootable CD... Which brings me to the question:
> 
> Is it possible to call int 13h functions from a GRUB2 module? If yes,
> what is the (preferred?) way to do it?

You need to add new kernel thunk(s) to grub2/kern/i386/pc/startup.S and
then make them jump to 16b real mode and then return back to protected
mode. There are lots of examples in that file. Then make proper include
file for your calls (most likely you can add it to existing one in this
include file grub2/include/grub/i386/pc/biosdisk.h).

I would suggest to make testing command that accesses those kernel
thunks. This way it is easier to test out those API calls.