From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756433Ab2ICM6Z (ORCPT ); Mon, 3 Sep 2012 08:58:25 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:44128 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756412Ab2ICM6X (ORCPT ); Mon, 3 Sep 2012 08:58:23 -0400 Date: Mon, 3 Sep 2012 13:58:11 +0100 From: Catalin Marinas To: Arnd Bergmann Cc: "linux-arch@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Will Deacon , Marc Zyngier Subject: Re: [PATCH v2 20/31] arm64: User access library function Message-ID: <20120903125810.GB3313@mbp> References: <1344966752-16102-1-git-send-email-catalin.marinas@arm.com> <1344966752-16102-21-git-send-email-catalin.marinas@arm.com> <201208151449.54834.arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201208151449.54834.arnd@arndb.de> 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 On Wed, Aug 15, 2012 at 03:49:54PM +0100, Arnd Bergmann wrote: > On Tuesday 14 August 2012, Catalin Marinas wrote: > > > +/* > > + * Single-value transfer routines. They automatically use the right > > + * size if we just have the right pointer type. Note that the functions > > + * which read from user space (*get_*) need to take care not to leak > > + * kernel data even if the calling code is buggy and fails to check > > + * the return value. This means zeroing out the destination variable > > + * or buffer on error. Normally this is done out of line by the > > + * fixup code, but there are a few places where it intrudes on the > > + * main code path. When we only write to user space, there is no > > + * problem. > > + */ > > +extern long __get_user_1(void *); > > +extern long __get_user_2(void *); > > +extern long __get_user_4(void *); > > +extern long __get_user_8(void *); > > + > > +#define __get_user_x(__r2,__p,__e,__s,__i...) \ > > + asm volatile( \ > > + __asmeq("%0", "x0") __asmeq("%1", "x2") \ > > + "bl __get_user_" #__s \ > > + : "=&r" (__e), "=r" (__r2) \ > > + : "0" (__p) \ > > + : __i, "cc") > > + > > +#define get_user(x,p) \ > > + ({ \ > > + register const typeof(*(p)) __user *__p asm("x0") = (p);\ > > + register unsigned long __r2 asm("x2"); \ > > + register long __e asm("x0"); \ > > + switch (sizeof(*(__p))) { \ > > + case 1: \ > > + __get_user_x(__r2, __p, __e, 1, "x30"); \ > > + break; \ > > + case 2: \ > > + __get_user_x(__r2, __p, __e, 2, "x3", "x30"); \ > > + break; \ > > + case 4: \ > > + __get_user_x(__r2, __p, __e, 4, "x30"); \ > > + break; \ > > + case 8: \ > > + __get_user_x(__r2, __p, __e, 8, "x30"); \ > > + break; \ > > + default: __e = __get_user_bad(); break; \ > > + } \ > > + x = (typeof(*(p))) __r2; \ > > + __e; \ > > + }) > > It's fairly unusual to have out of line get_user/put_user functions. > What is the reason for this, other than copying from ARM? I changed these to inline asm. The only reason which I don't think matters much in this case is a few KB increase in Image size. -- Catalin