From owner-freebsd-arm@FreeBSD.ORG Mon Apr 6 19:09:16 2015 Return-Path: Delivered-To: freebsd-arm@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id F29F6936 for ; Mon, 6 Apr 2015 19:09:15 +0000 (UTC) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "gold.funkthat.com", Issuer "gold.funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id C33C868F for ; Mon, 6 Apr 2015 19:09:15 +0000 (UTC) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.14.5/8.14.5) with ESMTP id t36J91RY008691 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 6 Apr 2015 12:09:01 -0700 (PDT) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.14.5/8.14.5/Submit) id t36J918t008690; Mon, 6 Apr 2015 12:09:01 -0700 (PDT) (envelope-from jmg) Date: Mon, 6 Apr 2015 12:09:01 -0700 From: John-Mark Gurney To: Olivier Houchard Subject: Re: remove broken lib/libc/arm/string/memcpy_xscale.S Message-ID: <20150406190901.GW51048@funkthat.com> References: <20150405015245.GO51048@funkthat.com> <20150406171248.GV51048@funkthat.com> <20150406174130.GA63423@ci0.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150406174130.GA63423@ci0.org> X-Operating-System: FreeBSD 9.1-PRERELEASE amd64 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (gold.funkthat.com [127.0.0.1]); Mon, 06 Apr 2015 12:09:01 -0700 (PDT) Cc: freebsd-arm@FreeBSD.org X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 06 Apr 2015 19:09:16 -0000 Olivier Houchard wrote this message on Mon, Apr 06, 2015 at 19:41 +0200: > On Mon, Apr 06, 2015 at 10:12:48AM -0700, John-Mark Gurney wrote: > > Warner Losh wrote this message on Mon, Apr 06, 2015 at 09:58 -0600: > > > > On Apr 4, 2015, at 7:52 PM, John-Mark Gurney wrote: > > > > > > > > I would like to remove this file as it does not implement our defined > > > > memcpy. Per POSIX, overlapping regions passed to memcpy is undefined > > > > behavior. We have defined it to have the same symatics as memmove. > > > > > > > > Sample test program: > > > > #include > > > > #include > > > > > > > > char bufa[512] = "this is a test buffer that should be copied fine."; > > > > int > > > > main() > > > > { > > > > > > > > memcpy(&bufa[10], &bufa[0], strlen(&bufa[10])); > > > > printf("%s\n", bufa); > > > > > > > > return 0; > > > > } > > > > > > > > Output on amd64 HEAD: > > > > this is a this is a test buffer that should be co > > > > > > > > Output on old armv4 from 9.x: > > > > this is a this is a thst buffethst bufhould beufh > > > > > > > > If you just look at the file, it is clear that the implementation does > > > > not adjust the copy direction based upon pointers. We imported the > > > > code from NetBSD, and NetBSD does apparently require memcpy's arguments > > > > to be non-overlapping. > > > > > > > > I'll remove the file shortly unless someone can prove to me that all > > > > uses of memcpy in our tree do not depend upon our defined behavior > > > > per memcpy(3)'s man page. > > > > > > Any chance you can fix this implementation instead? > > > > I don't know arm assembly well enough, nor do I have the time to fix > > it.. I am willing to test any implementations as I have access to > > hardware... > > > > I guess I should add a test to verify that memcpy behavese like memmove > > to our test suite... > > > > I think the bug is in the manpage, not the code, and we should fix it the way > NetBSD did. Have you audited all of our code base to confirm that such a change will not break anything? The man page has been like this since r1573, so it's very possible that code has been written to depend upon this behavior... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."