[coreboot] ADLO for buildrom

[Rudolf Marek]

> The main question is who holds the know how on how to enable/disable
> write protection and shadowing of the e and f segment.

Well this is chipset specific (memory controller).

> And: Whether we need to care at all. Can't we just leave that space
> writable and rely on the OS not trying to overwrite the machine's BIOS?
> I would be surprised if any OS really tried that.

This is what I did exactly with the K8T890/VT8237. The chipset has the shadow 
ram prot bits even if the memory controller is in K8. But hey wrong setup of 
this caused DMA from HDD to fail if the physical memory target for DMA was in 
"shadow" memory range.

To sum it up. Coreboot should handle this. ADLO/LegacyBIOS whatever should not 
touch this. We can unprotect  the shadows regions in coreboot. All we need is 
just sane memory map.

Rudolf