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

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0240437@AcuExch.aculab.com>
Date:   Thu, 15 Dec 2016 13:56:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Hannes Frederic Sowa' <hannes@...essinduktion.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>
CC:     Netdev <netdev@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Linux Crypto Mailing List" <linux-crypto@...r.kernel.org>,
        "Daniel J . Bernstein" <djb@...yp.to>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Eric Biggers <ebiggers3@...il.com>
Subject: RE: [PATCH v2 1/4] siphash: add cryptographically secure hashtable
 function

From: Hannes Frederic Sowa
> Sent: 15 December 2016 12:50
> On 15.12.2016 13:28, David Laight wrote:
> > From: Hannes Frederic Sowa
> >> Sent: 15 December 2016 12:23
> > ...
> >> Hmm? Even the Intel ABI expects alignment of unsigned long long to be 8
> >> bytes on 32 bit. Do you question that?
> >
> > Yes.
> >
> > The linux ABI for x86 (32 bit) only requires 32bit alignment for u64 (etc).
> 
> Hmm, u64 on 32 bit is unsigned long long and not unsigned long. Thus I
> am actually not sure if the ABI would say anything about that (sorry
> also for my wrong statement above).
> 
> Alignment requirement of unsigned long long on gcc with -m32 actually
> seem to be 8.

It depends on the architecture.
For x86 it is definitely 4.
It might be 8 for sparc, ppc and/or alpha.

	David