Re: What Bios data is sent to the Bootloader/OS ?

[Igor Skochinsky <skochinsky@gmail.com>]

Hi Rafael,

It's certainly possible although not trivial.
One possible approach is DUET which can emulate UEFI environment on top of
the legacy BIOS. So you could have your legacy bootloader load DUET, which
would in turn load and boot the UEFI-compatible OS. This page may be of
use: http://www.rodsbooks.com/bios2uefi/index.html

AFAIK GRUB already supports both BIOS and UEFI booting, so you may not have
to do anything except set it up correctly.

On Fri, Aug 11, 2017 at 3:00 PM, Rafael Machado <
rafaelrodrigues.machado@gmail.com> wrote:

> Hi everyone
>
> I have a question that probably some guys here can help.
> The scenario I have, is that I need to create a OS image that must be able
> to boot at a UEFI system (with no csm module), and at a legacy bios system.
> My fist thought is that this is not possible.
>
> The first thing I see that is different is the what the memory map is
> presented to the Bootloader/OS. At legacy bios the int15/0xE820 is used,
> and at a UEFI bios the GetMemoryMap() from the boot service is used. Is my
> understanding correct?
>
> Besides that. Is there any other change that could not make it possible to
> create a single BootloaderLoader/OS image able to boot on a UEFI BIOS(with
> no CSM) and on a Legacy Bios ?
>
> I would like to create a list or arguments to talk with my client that
> requested this, in case this is really not possible.
>
> The OS in this case is Linux, and the bootloader is Grub or Syslinux.
>
> Thanks and Regards
> Rafael R. Machado
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-- 
WBR, Igor