What Bios data is sent to the Bootloader/OS ?

[Rafael Machado <rafaelrodrigues.machado@gmail.com>]

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