Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762984Ab3IDPcj (ORCPT ); Wed, 4 Sep 2013 11:32:39 -0400 Received: from mail-ee0-f45.google.com ([74.125.83.45]:52644 "EHLO mail-ee0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762970Ab3IDPci (ORCPT ); Wed, 4 Sep 2013 11:32:38 -0400 MIME-Version: 1.0 In-Reply-To: References: <52210D34.5030807@infradead.org> <52212128.3000100@infradead.org> <1377905319.2070.38.camel@joe-AO722> Date: Wed, 4 Sep 2013 08:32:37 -0700 Message-ID: Subject: Re: do_div() silently truncates "base" to 32bit From: Anatol Pomozov To: Joe Perches Cc: Randy Dunlap , LKML , Tejun Heo , bernie@develer.com, Geert Uytterhoeven Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1460 Lines: 35 Hi On Fri, Aug 30, 2013 at 5:50 PM, Anatol Pomozov wrote: > Hi, Joe > > On Fri, Aug 30, 2013 at 4:28 PM, Joe Perches wrote: >> On Fri, 2013-08-30 at 15:48 -0700, Randy Dunlap wrote: >>> On 08/30/13 15:14, Anatol Pomozov wrote: >>> > But another question still remains: why compiler does not warn that >>> > size truncation happens? How to prevent bugs like CFQ one in the >>> > future? Should we add a compile-time assert to do_div() to prevent >>> > passing 64 numbers in "base" macro parameter? >>> That sounds like a fine idea to me. >> >> Geert thought so too and submitted a patch >> >> http://www.spinics.net/lists/linux-btrfs/msg26788.html > > Thanks it works! > > block/cfq-iosched.c: In function 'cfqg_prfill_avg_queue_size': > block/cfq-iosched.c:4423:3: error: size of unnamed array is negative > make[2]: *** [block/gfq-iosched.s] Error 1 > make[1]: *** [block/gfq-iosched.s] Error 2 > I see a number of other truncation errors. We need to fix them as well. I looked at the places where do_div() passes incorrect parameters and it is quite a lot of them. It would be better to warn users until all the places are fixed. Is there any BUILD_WARN_ON() macro? -- 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/