From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS3215 2.6.0.0/16 X-Spam-Status: No, score=-3.5 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_PASS, T_SCC_BODY_TEXT_LINE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by dcvr.yhbt.net (Postfix) with ESMTP id B0A201F8C4 for ; Mon, 21 Mar 2022 21:26:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229534AbiCUVVy (ORCPT ); Mon, 21 Mar 2022 17:21:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229898AbiCUVVx (ORCPT ); Mon, 21 Mar 2022 17:21:53 -0400 Received: from ring.crustytoothpaste.net (ring.crustytoothpaste.net [172.105.110.227]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2AEAE192344 for ; Mon, 21 Mar 2022 14:19:53 -0700 (PDT) Received: from camp.crustytoothpaste.net (unknown [IPv6:2001:470:b056:101:a6ae:7d13:8741:9028]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by ring.crustytoothpaste.net (Postfix) with ESMTPSA id 9482B5A0C8; Mon, 21 Mar 2022 21:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=crustytoothpaste.net; s=default; t=1647897591; bh=NtBk8SYM1Hjj//dhDjEfeamznc0l/vAx8WKXWd9FCpk=; h=Date:From:To:Cc:Subject:References:Content-Type: Content-Disposition:In-Reply-To:From:Reply-To:Subject:Date:To:CC: Resent-Date:Resent-From:Resent-To:Resent-Cc:In-Reply-To:References: Content-Type:Content-Disposition; b=MWKXDAt/i4u14oC3r28UQU5IPe05RAUQDS8b2jl3vzlRIX7Jrw8QwCeHDS8EpMLgz Pc06SNOQydNIPT/1FyCCHZhTzMyAdGlodMsG+F3Iyf6BlUtE76pyEHL1RO6LeTu9QP lF4zahEC88NJ37QNHluSJTvOS+r+HS1iy9VE0Gh2OpPzScznjrLr/1JYowy9NCV5tT 24ANMeQaxhReG72qJoI5fyVWX+xioj6DRd92NEeBHFPu242e/O2pjYJ02n/B+VeiyD DIb7nJA8HzLNDBUQtGEEnFwGpClMPhU8fOCwmjOufJ8YvpN1QLIiCW6kVEzHzOCzqj HynwK9bI7BZcW82iFXnmZgIigyiQN2BV2ulZ4/r+uB1mLLoTBaMZVAyp2MzxktY5Wk ky1Q/YzfuWixevv7jTpWG7487z+uwseM+KrvsnO/sC5h/RYMOcPKm4uFnBBGU11qLv BS3Jb/5XfXf0R4/9V25L6EbXbanNHzyPNPQXwFKLVodq4i5USHb Date: Mon, 21 Mar 2022 21:19:49 +0000 From: "brian m. carlson" To: =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason Cc: git@vger.kernel.org, Junio C Hamano , Mike Hommey , Carlo Marcelo Arenas =?utf-8?B?QmVsw7Nu?= , Taylor Blau Subject: Re: [PATCH v2] ppc: remove custom SHA-1 implementation Message-ID: Mail-Followup-To: "brian m. carlson" , =?utf-8?B?w4Z2YXIgQXJuZmrDtnLDsA==?= Bjarmason , git@vger.kernel.org, Junio C Hamano , Mike Hommey , Carlo Marcelo Arenas =?utf-8?B?QmVsw7Nu?= , Taylor Blau References: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="JiyWO78N0HaVYDHI" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.1.4 (2021-12-11) Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org --JiyWO78N0HaVYDHI Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2022-03-21 at 17:06:12, =C3=86var Arnfj=C3=B6r=C3=B0 Bjarmason wrote: > Remove the PPC_SHA1 implementation added in a6ef3518f9a ([PATCH] PPC > assembly implementation of SHA1, 2005-04-22). When this was added > Apple consumer hardware used the PPC architecture, and the > implementation was intended to improve SHA-1 speed there. >=20 > Since it was added we've moved to DC_SHA1 by default, and anyone > wanting hard-rolled non-DC SHA-1 implementation can use OpenSSL's via > the OPENSSL_SHA1 knob. >=20 > I'm unsure if this was ever supposed to work on 64-bit PPC. It clearly > originally targeted 32 bit PPC, but there's some mailing list > references to this being tried on G5 (PPC 970). I can't get it to do > anything but segfault on the BE POWER8 machine in the GCC compile > farm. Anyone caring about speed on PPC these days is likely to be > using IBM's POWER, not PPC 970. >=20 > There have been proposals to entirely remove non-DC_SHA1 > implementations from the tree[1]. I think per [2] that would be a bit > overzealous. I.e. there are various set-ups git's speed is going to be > more important than the relatively implausible SHA-1 collision attack, > or where such attacks are entirely mitigated by other means (e.g. by > incoming objects being checked with DC_SHA1). >=20 > The main reason for doing so at this point is to simplify follow-up > Makefile change. Since PPC_SHA1 included the only in-tree *.S assembly > file we needed to keep around special support for building objects > from it. By getting rid of it we know we'll always build *.o from *.c > files, which makes the build process simpler. >=20 > As an aside the code being removed here was also throwing warnings > with the "-pedantic" flag, but let's remove it instead of fixing it, > as 544d93bc3b4 (block-sha1: remove use of obsolete x86 assembly, > 2022-03-10) did for block-sha1/*. While I don't agree that we shouldn't remove the other non-DC SHA-1 implementations, I do agree that we should remove this one. Given the testing you've done and the fact that almost everyone desiring speed is using a 64-bit machine these days, I think it's unlikely that anyone is using this in the real world. --=20 brian m. carlson (he/him or they/them) Toronto, Ontario, CA --JiyWO78N0HaVYDHI Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.3.1 (GNU/Linux) iHUEABYKAB0WIQQILOaKnbxl+4PRw5F8DEliiIeigQUCYjjr9AAKCRB8DEliiIei gcmtAQDm5cGmnnH98i3lJWi7tcIf2+hase37QBQfAM9XkDvDUQEAwhq7X4mTSmvw Sn6irZbnji2YfVlumNTQrd/1fL/T4wQ= =Txe4 -----END PGP SIGNATURE----- --JiyWO78N0HaVYDHI--