From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752830AbaEGXnL (ORCPT ); Wed, 7 May 2014 19:43:11 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:49196 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751620AbaEGXnI (ORCPT ); Wed, 7 May 2014 19:43:08 -0400 Date: Thu, 8 May 2014 05:12:56 +0530 From: Afzal Mohammed To: Andrey Ryabinin Cc: linux@arm.linux.org.uk, open list , "moderated list:ARM PORT" Subject: Re: [PATCH] arm: memset: zero out upper bytes in r1 Message-ID: <20140507234255.GA2050@afzal-ThinkPad-R50e> References: <1399273875-8403-1-git-send-email-a.ryabinin@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1399273875-8403-1-git-send-email-a.ryabinin@samsung.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andrey, On Mon, May 05, 2014 at 11:11:13AM +0400, Andrey Ryabinin wrote: > memset doesn't work right for following example: > > signed char c = 0xF0; > memset(addr, c, size); > > Variable c is signed, so after typcasting to int the value will be 0xFFFFFFF0. > This value will be passed through r1 regitster to memset function. > memset doesn't zero out upper bytes in r1, so memory will be filled > with 0xFFFFFFF0 instead of expected 0xF0F0F0F0. > --- a/arch/arm/lib/memset.S > +++ b/arch/arm/lib/memset.S > @@ -22,7 +22,8 @@ ENTRY(memset) > /* > * we know that the pointer in ip is aligned to a word boundary. > */ > -1: orr r1, r1, r1, lsl #8 > +1: and r1, r1, #0xff > + orr r1, r1, r1, lsl #8 int is to be converted to unsigned char in memset, would having above change immediately upon entry to memset rather than at a place where it won't always execute make intention clearer ? (although it doesn't make difference) ubfx r1, r1, #0, #8 would have given the needed typecasting, but seems it is available only on ARMv6T2 & above. Regards Afzal