[PATCH 22/35] arm64/mm: Implement map_shadow_stack()

[Mark Brown]

On Tue, Jul 18, 2023 at 10:10:04AM +0100, Szabolcs Nagy wrote:

>   uint64_t *p = map_shadow_stack(0, N*8, 0);

> i'd expect p[N-1] to be the end token and p[N-2] to be the cap token,
> not p[PAGE_ALIGN(N*8)/8-2].

Yes, that probably would be more helpful.

> if we allow misalligned size here (and in munmap) then i think it's
> better to not page align.  size%8!=0 || size<16 can be an error.

Honestly I'd be a lot happier to just not allow misalignment but that
raises the issue with binaries randomly not working when moved to a
kernel with a different page size.  I'll have a think but possibly the
safest thing would be requiring a multiple of 4K then rounding up to our
actual page size.
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