From owner-freebsd-arm@FreeBSD.ORG Mon Apr 6 19:40:22 2015 Return-Path: Delivered-To: freebsd-arm@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id E95271B0 for ; Mon, 6 Apr 2015 19:40:22 +0000 (UTC) Received: from kanar.ci0.org (kanar.ci0.org [IPv6:2001:bc8:35e6::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7150A9D6 for ; Mon, 6 Apr 2015 19:40:22 +0000 (UTC) Received: from kanar.ci0.org (pluxor@localhost [127.0.0.1]) by kanar.ci0.org (8.14.8/8.14.8) with ESMTP id t36Je7D7064500; Mon, 6 Apr 2015 21:40:07 +0200 (CEST) (envelope-from mlfbsd@kanar.ci0.org) Received: (from mlfbsd@localhost) by kanar.ci0.org (8.14.8/8.14.8/Submit) id t36Je7fo064499; Mon, 6 Apr 2015 21:40:07 +0200 (CEST) (envelope-from mlfbsd) Date: Mon, 6 Apr 2015 21:40:07 +0200 From: Olivier Houchard To: Rui Paulo Subject: Re: remove broken lib/libc/arm/string/memcpy_xscale.S Message-ID: <20150406194007.GA64433@ci0.org> References: <20150405015245.GO51048@funkthat.com> <20150406171248.GV51048@funkthat.com> <20150406174130.GA63423@ci0.org> <3427080.JV46itjP9L@akita> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3427080.JV46itjP9L@akita> User-Agent: Mutt/1.5.23 (2014-03-12) 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 19:40:23 -0000 On Mon, Apr 06, 2015 at 11:32:25AM -0700, Rui Paulo wrote: > On Monday 06 April 2015 19:41:30 Olivier Houchard wrote: > > 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. > > Our implementation of memcpy() allows strings to overlap, so we really > shouldn't be special-casing armv4. > Any use of memcpy() with overlapping strings is a bug, I fail to see why we should make any effort to make it work. Olivier