Re: Corrupted EFI region

From: Borislav Petkov
Date: Thu Aug 01 2013 - 12:51:57 EST

On Wed, Jul 31, 2013 at 10:54:23PM +0100, Matthew Garrett wrote:
> On Wed, Jul 31, 2013 at 11:51:30PM +0200, Borislav Petkov wrote:
> > But the problem is, something messes up the upper boundary of the region
> > and it is an EFI_BOOT_SERVICES_DATA region which we need for the runtime
> > services mapping and if we can't map it properly, we're probably going
> > to miss functionality or not have runtime at all.
> "Easiest" way around this would probably be to stash the address map
> after ExitBootServices() and compare it at SetVirtualAddressMap()
> time, then take the widest boundaries and trim the e820 map to match.
> This is obviously dependent upon the system not allocating anything
> further after that, but it seems safest. The worst case is finding the
> firmware writing over bits of the kernel.

Actually, with UEFI impl. f*ckup like that, I'd rather kick it back to
the curb and simply not init runtime services instead of fixing stuff
around it. SetVirtualAddressMap in itself is a f*ckup as it is already.

Oh well, let's see what edk2 guys would say first.


Sent from a fat crate under my desk. Formatting is fine.
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