Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861AbaKDKo3 (ORCPT ); Tue, 4 Nov 2014 05:44:29 -0500 Received: from casper.infradead.org ([85.118.1.10]:35914 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752661AbaKDKo0 (ORCPT ); Tue, 4 Nov 2014 05:44:26 -0500 Date: Tue, 4 Nov 2014 11:44:14 +0100 From: Peter Zijlstra To: Maxime COQUELIN Cc: gong.chen@linux.intel.com, Ingo Molnar , " Paul E. McKenney" , tytso@mit.edu, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel@stlinux.com, eric.paire@st.com Subject: Re: [PATCH v2] bitops: Fix shift overflow in GENMASK macros Message-ID: <20141104104414.GL3337@twins.programming.kicks-ass.net> References: <1415095437-28723-1-git-send-email-maxime.coquelin@st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415095437-28723-1-git-send-email-maxime.coquelin@st.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 04, 2014 at 11:03:57AM +0100, Maxime COQUELIN wrote: > -#define GENMASK(h, l) (((U32_C(1) << ((h) - (l) + 1)) - 1) << (l)) > -#define GENMASK_ULL(h, l) (((U64_C(1) << ((h) - (l) + 1)) - 1) << (l)) > +#define GENMASK(h, l) ((~0UL >> (BITS_PER_LONG - (h - l + 1))) << l) > +#define GENMASK_ULL(h, l) ((~0ULL >> (BITS_PER_LONG_LONG - (h - l + 1))) << l) OK, so you need to keep the (h) and (l) bits, macro arguments should be wrapped in seemingly superfluous braces in order to preserve precedence on expansion. My bad for not explicitly doing that when suggesting the alternative. -- 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/