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Re: map command for grub2 draft
From: |
Marco Gerards |
Subject: |
Re: map command for grub2 draft |
Date: |
Fri, 15 Jun 2007 20:56:00 +0200 |
User-agent: |
Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) |
Bean <address@hidden> writes:
> On Fri, Jun 15, 2007 at 08:22:16PM +0200, Marco Gerards wrote:
>> adrian15 <address@hidden> writes:
>>
>> > adrian15 escribió:
>> >> 1st) Where to save an array?
>> >> =============================
>> >>
>> >> If I mimic the grub legacy map command I need to save an array with
>> >> the
>> >> map definitions.
>> >>
>> >> static unsigned short bios_drive_map[DRIVE_MAP_SIZE + 1];
>> >> So that each time I call something like:
>> >> map (hd0) (hd1)
>> >> it modifies this vector.
>> >>
>> >> Any example on where should I define this vector so that I can use it
>> >> from each command ?
>> >
>> > I ask the question again.
>>
>> What is this vector supposed to do? Do you really need it outside
>> map.c?
>>
>> Can you describe the design of the map command?
>
> I happen to know something about the map command in GRUB Legacy, it works
> by hooking INT 13.
>
> It first reserves a small range of memory from the top of convensional
> memory by decreasing value at 0x413, then copy its INT 13 interrupt handler
> and the drive map to this area. Finally, it modifies the IVT table so that
> INT 13 points to the new handler.
>
> Inside the handler, it uses the drive map to translate the current drive
> stored in %dl to the real drive, then jump to the original handler.
Right, but the problem Adrian brought up was that he though he needs
to add a vector which describes the mapping as a global. I do not see
why this is required. So I wonder what he had in mind.
I think the main issue here is how to hook this into GRUB 2 so that
the hook becomes effective just before booting.
--
Marco