From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/7030 Path: news.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.comp.lib.glibc.alpha,gmane.linux.lib.musl.general,gmane.linux.kernel,gmane.linux.ports.arm.kernel Subject: Re: [PATCHv3 00/24] ILP32 support in ARM64 Date: Fri, 13 Feb 2015 13:37:07 -0500 Message-ID: <20150213183706.GF23507@brightrain.aerifal.cx> References: <20141002155217.GH32147@e104818-lin.cambridge.arm.com> <20150210181302.GA23886@brightrain.aerifal.cx> <20150211173919.GF9058@e104818-lin.cambridge.arm.com> <20150211192118.GC23507@brightrain.aerifal.cx> <20150212181735.GF25491@e104818-lin.cambridge.arm.com> <501530245.495972.1423767564997.JavaMail.open-xchange@oxbaltgw04.schlund.de> <20150213133355.GD3508@e104818-lin.cambridge.arm.com> <20150213163013.GE23507@brightrain.aerifal.cx> <20150213173345.GA26217@e104818-lin.cambridge.arm.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1423852660 9711 80.91.229.3 (13 Feb 2015 18:37:40 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 13 Feb 2015 18:37:40 +0000 (UTC) Cc: "libc-alpha@sourceware.org" , "arnd@arndb.de" , "pinskia@gmail.com" , "musl@lists.openwall.com" , "linux-kernel@vger.kernel.org" , Andrew Pinski , Marcus Shawcroft , "linux-arm-kernel@lists.infradead.org" To: Catalin Marinas Original-X-From: libc-alpha-return-56981-glibc-alpha=m.gmane.org@sourceware.org Fri Feb 13 19:37:39 2015 Return-path: Envelope-to: glibc-alpha@plane.gmane.org Original-Received: from server1.sourceware.org ([209.132.180.131] helo=sourceware.org) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YML7P-0003Dj-57 for glibc-alpha@plane.gmane.org; Fri, 13 Feb 2015 19:37:35 +0100 DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:cc:subject:message-id:references :mime-version:content-type:in-reply-to; q=dns; s=default; b=Nudz ESNkZofwXrC+RDBFyIrgUGSlUhxQaz+dAug7GFyQbwVEa+3Ohdb8srIZszOsTSbm wV6hyJnljCI+JeWMWLTHnotiLEzWfltmq9v8ew6U+Qb6LQiWP7WH8TgkvYE0xhvR mPr+sTWVoelDQtIelWYjysatHrnkbOIs1/cuaRA= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id :list-unsubscribe:list-subscribe:list-archive:list-post :list-help:sender:date:from:to:cc:subject:message-id:references :mime-version:content-type:in-reply-to; s=default; bh=G+zUOXKVTI ee5J7K/jO9F1J1u5M=; b=JBCRbF5xeUdU2P9inWV0xLxwPYV5L72Fk2hpQ62Y+6 y0+T/FRyLYTTjPOh8t8DiwGD4G00NSqIotxvQugT0TFd6Wg1kDNwUiYwStYV/r3g xcPhrSGSGFYj2gO4AfbcqdlY3yry9rx2lASmjy5JB0+Mt1v/3wjZLtriqx63VwTt M= Original-Received: (qmail 22960 invoked by alias); 13 Feb 2015 18:37:31 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Original-Sender: libc-alpha-owner@sourceware.org Original-Received: (qmail 22945 invoked by uid 89); 13 Feb 2015 18:37:30 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.8 required=5.0 tests=AWL,BAYES_00,RDNS_DYNAMIC,TVD_RCVD_IP autolearn=no version=3.3.2 X-HELO: brightrain.aerifal.cx Content-Disposition: inline In-Reply-To: <20150213173345.GA26217@e104818-lin.cambridge.arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Xref: news.gmane.org gmane.comp.lib.glibc.alpha:49273 gmane.linux.lib.musl.general:7030 gmane.linux.kernel:1887994 gmane.linux.ports.arm.kernel:393393 Archived-At: On Fri, Feb 13, 2015 at 05:33:46PM +0000, Catalin Marinas wrote: > > > > The data structure definition is a little bit fragile, as it depends on > > > > user space not using the __BIT_ENDIAN symbol in a conflicting way. So > > > > far we have managed to keep that outside of general purpose headers, but > > > > it should at least blow up in an obvious way if it does, rather than > > > > breaking silently. > > > > > > > > I still think it's more practical to keep the zeroing in user space though. > > > > In that case, we keep defining __kernel_timespec64 with a 'typedef long > > > > long __kernel_snseconds_t', and it's up to the libc to either use > > > > __kernel_timespec64 as its timespec, or to define a C11-compliant > > > > timespec itself and zero out the bits before passing the data to the kernel. > > > > > > The problem with doing this in user space is syscall(2). If we don't > > > allow it, then it's fine to do the padding in libc. > > > > It's already the case that callers have to tiptoe around syscall(2) > > usage on a per-arch basis for silly things like the convention for > > passing 64-bit arguments on 32-bit archs, different arg orders to work > > around 64-bit alignment and issues with too many args, and various > > legacy issues. So I think manual use of syscall(2) is a less-critical > > issue, though of course from a libc perspective I would very much like > > for the kernel to handle it right. > > I think there is another problem with sign-extending tv_nsec in libc. > The prototype for functions like clock_settime(2) take a const struct > timespec *. There isn't anything to prevent such structure being in a > read-only section, even though it is unlikely. So libc would have to > duplicate the structure rather than just sign-extending tv_nsec in > place. Yes, we already have to do this for x32 in musl. I'd rather not have to do the same for aarch64-ILP32. Rich