x86/efistub: Prefer EFI memory attributes protocol over DXE services

From: Ard Biesheuvel <ardb@kernel.org>

[ Commit 11078876

 upstream ]

Currently, the EFI stub relies on DXE services in some cases to clear
non-execute restrictions from page allocations that need to be
executable. This is dodgy, because DXE services are not specified by
UEFI but by PI, and they are not intended for consumption by OS loaders.
However, no alternative existed at the time.

Now, there is a new UEFI protocol that should be used instead, so if it
exists, prefer it over the DXE services calls.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-18-ardb@kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>