Re: [edk2] Corrupted EFI region

From: Matthew Garrett
Date: Wed Aug 07 2013 - 17:23:30 EST

On Wed, Aug 07, 2013 at 02:10:28PM -0700, Andrew Fish wrote:

> Well the issue I see is I don't think OS X or Windows are doing this.
> So I'm guessing there is some unique thing beings done on the Linux
> side and we don't have good tests to catch bugs in the EFI
> implementations. If the Linux loader hides the bugs and we don't hit
> them with other operating systems they are never going to get fixed.
> It would be good if we could track down some of these issues and make
> a request for some tests that can help catch these issues. The tests
> would be part of, but since some of us play in both worlds we
> can forward the known issues to the UEFI test work group.

Linux enables NX before calling SetVirtualAddressMap(). If other OSes
don't do that, you probably won't see the bug.

> Is it possible to have a switch to turn off the not required behavior
> (hiding EFI implementation bugs) so that bad platforms could be
> detected? This would be a good thing to try on platforms at the
> upcoming UEFI Plugfest hosted by the Linux Foundation and the UEFI
> Forum, so the bad behavior can be detected and the vendors can fix the
> issue.

It's behaviour that we already have to work around due to shipping
hardware exhibiting it, so while we could certainly develop a test,
Linux is always going to need to include the workaround code.

That being said, some of what we do with the memory map in Linux right
now is probably unnecessary - we're modifying the memory map because
that's a convenient place to store the information, rather than because
the memory map actually needs to be modified. We could do a better job
of that.

Matthew Garrett | mjg59@xxxxxxxxxxxxx
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