From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTP id 7988B5A026F for ; Wed, 27 Sep 2023 19:05:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1695834300; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jPyopISjGLIrxAY4dsNm7FkU5zNATELV/uAmo/lKwt0=; b=bQMO0kUWavfGiHug/kDgBoFpZ/Gf5Fbi8jB15w1FDZszYv2dvq8rRgCwzMRnDxazvzqHpI +kEzenOx0acmblFsowg4iJryK2me/6TbtunZeUbE8TJz0MBrVGKqgR1anZZlDoWjfGGoE9 2CWCKTHsrTAPlMet1GiClSr7IbnhChQ= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-13-xtiO3ZatOXqztQm67lzVcQ-1; Wed, 27 Sep 2023 13:04:57 -0400 X-MC-Unique: xtiO3ZatOXqztQm67lzVcQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E90C31C06E09; Wed, 27 Sep 2023 17:04:56 +0000 (UTC) Received: from elisabeth (unknown [10.39.208.37]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 17B6AC15BB8; Wed, 27 Sep 2023 17:04:55 +0000 (UTC) Date: Wed, 27 Sep 2023 19:04:50 +0200 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH 06/10] siphash: Use more hygienic state initialiser Message-ID: <20230927190450.6f827040@elisabeth> In-Reply-To: <20230922140630.3184256-7-david@gibson.dropbear.id.au> References: <20230922140630.3184256-1-david@gibson.dropbear.id.au> <20230922140630.3184256-7-david@gibson.dropbear.id.au> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: EGUWELP6KEVROGVJXMG74BXA4MH5LIQN X-Message-ID-Hash: EGUWELP6KEVROGVJXMG74BXA4MH5LIQN X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Sat, 23 Sep 2023 00:06:26 +1000 David Gibson wrote: > The PREAMBLE macro sets up the SipHash initial internal state. It also > defines that state as a variable, which isn't macro hygeinic. With > previous changes simplifying this premable, it's now possible to replace it > with a macro which simply expands to a C initialisedrfor that state. > > Signed-off-by: David Gibson > --- > siphash.c | 29 ++++++++++++----------------- > 1 file changed, 12 insertions(+), 17 deletions(-) > > diff --git a/siphash.c b/siphash.c > index 6932da2..21c560d 100644 > --- a/siphash.c > +++ b/siphash.c > @@ -58,15 +58,12 @@ > > #define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b)))) > > -#define PREAMBLE \ > - uint64_t v[4] = { 0x736f6d6570736575ULL, 0x646f72616e646f6dULL, \ > - 0x6c7967656e657261ULL, 0x7465646279746573ULL }; \ > - int __i; \ > - \ > - do { \ > - for (__i = sizeof(v) / sizeof(v[0]) - 1; __i >= 0; __i--) \ > - v[__i] ^= k[__i % 2]; \ > - } while (0) > +#define SIPHASH_INIT(k) { \ > + 0x736f6d6570736575ULL ^ (k)[0], \ > + 0x646f72616e646f6dULL ^ (k)[1], \ > + 0x6c7967656e657261ULL ^ (k)[0], \ > + 0x7465646279746573ULL ^ (k)[1] \ I don't think it actually matters (given the rationale for the choice of these constants given in the paper), but earlier this was equivalent to: 0x736f6d6570736575ULL ^ (k)[1], 0x646f72616e646f6dULL ^ (k)[0], 0x6c7967656e657261ULL ^ (k)[1], 0x7465646279746573ULL ^ (k)[0] and it matched both reference implementations linked in the file header. Anyway, the paper says: ...where k0 and k1 are the little-endian 64-bit words encoding the key k. without giving an order, so I guess either interpretation is fine. -- Stefano