Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754818AbYLJR5I (ORCPT ); Wed, 10 Dec 2008 12:57:08 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752371AbYLJR44 (ORCPT ); Wed, 10 Dec 2008 12:56:56 -0500 Received: from ocean.emcraft.com ([213.221.7.182]:40595 "EHLO ocean.emcraft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751408AbYLJR4z convert rfc822-to-8bit (ORCPT ); Wed, 10 Dec 2008 12:56:55 -0500 Date: Wed, 10 Dec 2008 20:56:51 +0300 From: Yuri Tikhonov Organization: EmCraft X-Priority: 3 (Normal) Message-ID: <527599002.20081210205651@emcraft.com> To: Scott Wood CC: Al Viro , Wolfgang Denk , Detlev Zundel , , Milton Miller , , Geert Uytterhoeven , Ilya Yanok Subject: Re[2]: [PATCH] fork_init: fix division by zero In-Reply-To: <20081210172512.GA19584@ld0162-tx32.am.freescale.net> References: <200812092044.40649.yur@emcraft.com> <503391615.20081210130113@emcraft.com> <20081210101745.GG28946@ZenIV.linux.org.uk> <1795455197.20081210132912@emcraft.com> <20081210172512.GA19584@ld0162-tx32.am.freescale.net> MIME-Version: 1.0 Content-Type: text/plain; charset=windows-1251 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 45 Hello Scott, On Wednesday, December 10, 2008 you wrote: > On Wed, Dec 10, 2008 at 01:29:12PM +0300, Yuri Tikhonov wrote: >> On Wednesday, December 10, 2008 you wrote: >> > x * y / z is parsed as (x * y) / z, not x * (y / z). >> >> Here we believe in preprocessor: since all PAGE_SIZE, 8, and >> THREAD_SIZE are the constants we expect it will calculate this. >> >> E.g. here is the result from this line as produced by cross-gcc >> 4.2.2: >> >> lis r9,0 >> rlwinm r29,r29,2,16,29 >> stw r29,0(r9) >> >> As you see - only rotate-left, i.e. multiplication to the constant. > Yes, and also note that it is masking the result by 0xfffc, to preserve > the effect of any overflow in (x * y). Right, such a mask was the result of missed brackets. Now (see "[PATCH][v2] fork_init: fix division by zero" I've just posted) the situation is better: lis r9,0 rlwinm r29,r29,2,0,29 stw r29,0(r9) I.e. the mask is 0xFFFFFFFC. Regards, Yuri -- Yuri Tikhonov, Senior Software Engineer Emcraft Systems, www.emcraft.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/