How to detect EFI and get the EFI memory map?

From a pre-OS environment, meaning immediately after BIOS POST, what is the
method to detect an EFI enabled BIOS, and to get the EFI memory map as
opposed to the BIOS E820 memory map?  The problem I am running into is that
the E820 map lists some portions of memory as user accessible, but as soon
as I write to them I get protection errors.  My suspicion is that EFI has
data storage in these particular areas and that EFI would have told me these
areas are reserved.  How would I go about accessing the EFI routines to get
an EFI map, before any OS loader?

Thanks,

whodunit wrote:
> From a pre-OS environment, meaning immediately after BIOS POST, what is th
e
> method to detect an EFI enabled BIOS, and to get the EFI memory map as
> opposed to the BIOS E820 memory map?  The problem I am running into is tha
t
> the E820 map lists some portions of memory as user accessible, but as soon
> as I write to them I get protection errors.  My suspicion is that EFI has
> data storage in these particular areas and that EFI would have told me the
se
> areas are reserved.  How would I go about accessing the EFI routines to ge
t
> an EFI map, before any OS loader?
>
> Thanks,
>
>
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