From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752836Ab3AVLYS (ORCPT ); Tue, 22 Jan 2013 06:24:18 -0500 Received: from nat28.tlf.novell.com ([130.57.49.28]:45601 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751988Ab3AVLYR convert rfc822-to-8bit (ORCPT ); Tue, 22 Jan 2013 06:24:17 -0500 Message-Id: <50FE84EC02000078000B83B7@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.1 Date: Tue, 22 Jan 2013 11:24:12 +0000 From: "Jan Beulich" To: , , Cc: , , Subject: [PATCH] ix86: tighten asmlinkage_protect() Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While the description of the commit that originally introduced asmlinkage_protect() validly says that this doesn't guarantee clobbering of the function arguments, using "m" constraints rather than "g" ones reduces the risk (by making it less attractive to the compiler to move those variables into registers) and generally results in better code (because we know the arguments are in memory anyway, and are frequently - if not always - used just once, with the second [compiler visible] use in asmlinkage_protect() itself being a fake one). Signed-off-by: Jan Beulich --- arch/x86/include/asm/linkage.h | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) --- 3.8-rc4/arch/x86/include/asm/linkage.h +++ 3.8-rc4-ix86-asmlinkage-protect/arch/x86/include/asm/linkage.h @@ -27,20 +27,20 @@ #define __asmlinkage_protect0(ret) \ __asmlinkage_protect_n(ret) #define __asmlinkage_protect1(ret, arg1) \ - __asmlinkage_protect_n(ret, "g" (arg1)) + __asmlinkage_protect_n(ret, "m" (arg1)) #define __asmlinkage_protect2(ret, arg1, arg2) \ - __asmlinkage_protect_n(ret, "g" (arg1), "g" (arg2)) + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2)) #define __asmlinkage_protect3(ret, arg1, arg2, arg3) \ - __asmlinkage_protect_n(ret, "g" (arg1), "g" (arg2), "g" (arg3)) + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3)) #define __asmlinkage_protect4(ret, arg1, arg2, arg3, arg4) \ - __asmlinkage_protect_n(ret, "g" (arg1), "g" (arg2), "g" (arg3), \ - "g" (arg4)) + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4)) #define __asmlinkage_protect5(ret, arg1, arg2, arg3, arg4, arg5) \ - __asmlinkage_protect_n(ret, "g" (arg1), "g" (arg2), "g" (arg3), \ - "g" (arg4), "g" (arg5)) + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4), "m" (arg5)) #define __asmlinkage_protect6(ret, arg1, arg2, arg3, arg4, arg5, arg6) \ - __asmlinkage_protect_n(ret, "g" (arg1), "g" (arg2), "g" (arg3), \ - "g" (arg4), "g" (arg5), "g" (arg6)) + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4), "m" (arg5), "m" (arg6)) #endif /* CONFIG_X86_32 */