Re: [PATCH RFC v2 0/2] Handle UEFI NX-restricted page tables

[Matthew Garrett]

On Mon, Feb 28, 2022 at 05:45:53PM +0100, Ard Biesheuvel wrote:

> Given that this is a workaround for a very specific issue arising on
> PI based implementations of UEFI, I consider this a quirk, and so I
> think this approach is reasonable. I'd still like to gate it on some
> kind of identification, though - perhaps something related to DMI like
> the x86 core kernel does as well.

When the V1 patches were reviewed, you suggested allocating 
EFI_LOADER_CODE rather than EFI_LOADER_DATA. The example given for a 
failure case is when NxMemoryProtectionPolicy is set to 0x7fd4, in which 
case EFI_LOADER_CODE, EFI_BOOT_SERVICES_CODE and 
EFI_RUNTIEM_SERVICES_CODE should not have the nx policy applied. So it 
seems like your initial suggestion (s/LOADER_DATA/LOADER_CODE/) should 
have worked, even if there was disagreement about whether the spec 
required it to. Is this firmware applying a stricter policy?