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 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,
> 
>