[RFCv2] arm64: support HAVE_ARCH_RARE_WRITE and HAVE_ARCH_RARE_WRITE_MEMCPY

[Russell King - ARM Linux]

On Thu, Mar 30, 2017 at 12:38:15PM -0700, Kees Cook wrote:
> Great work! I think this will need some further changes, though, since
> it doesn't look to me like this would pass LKDTM's tests if it was
> built as a module. (This is missing from my ARM attempt too... I
> haven't figured out how to set the domain on the kernel modules...)

You're not going to be able to do it very easily.  The only way I can
think of achieving it would be to split the module area into one
chunk for text, one chunk for write-rare and one chunk for data.

I still think that using domains is a mistake for this - it's a good
solution for things that are contiguous and big (like userspace), but
not for small amounts of data (like module sections.)

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