Re: [kernel-hardening] Re: [PATCH v2 1/4] siphash: add cryptographically secure hashtable function

Jason A. Donenfeld
2016-12-15T21:11:30Z

On Thu, Dec 15, 2016 at 10:09 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Dec 15, 2016 at 07:50:36PM +0100, Jason A. Donenfeld wrote:
>> There's no 32-bit platform
>> that will trap on a 64-bit unaligned access because there's no such
>> thing as a 64-bit access there. In short, we're fine.
>
> ARMv7 LPAE is a 32bit architecture that has 64bit load/stores IIRC.
>
> x86 has cmpxchg8b that can do 64bit things and very much wants the u64
> aligned.
>
> Also, IIRC we have a few platforms where u64 doesn't carry 8 byte
> alignment, m68k or something like that, but yes, you likely don't care.

Indeed, I stand corrected. But in any case, the use of __aligned(8) in
the patchset ensures that things are fixed and that we don't have this
issue.