Re: [PATCH v3] aarch64: enforce >=64K guard size

[Florian Weimer <fweimer at redhat dot com>]

On 01/16/2018 05:04 PM, James Greenhalgh wrote:
> The GCC requirements from non-glibc targets remain unclear to me. Rich
> said:
>
> https://sourceware.org/ml/libc-alpha/2017-12/msg00682.html
>
>    For what it's worth, I would prefer having the assumed minimum guard
>    size be 4k for musl targets. Even if we do increase the default guard
>    to 64k for 64-bit archs (seems likely), applications that manually set
>    it lower for whatever reason should still be handled safely.
>
> So, for me, that makes the GCC path clear - the compromise/consensus proposal
> to have two modes is the only way to unify the glibc and musl requirements.

Currently, musl and glibc requirements are completely aligned: Both 
provide a 4 KiB guard region and thus require a 4 KiB probe interval and 
a caller/callee probing regime compatible with that.

There is *nothing* in glibc which currently favors a 64 KiB guard 
region.  4 KiB is strongly preferred because that's how the ABI started out.

Thanks,
Florian