Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934538AbcCNPhv (ORCPT ); Mon, 14 Mar 2016 11:37:51 -0400 Received: from kanga.kvack.org ([205.233.56.17]:50480 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752773AbcCNPhs (ORCPT ); Mon, 14 Mar 2016 11:37:48 -0400 Date: Mon, 14 Mar 2016 11:37:47 -0400 From: Benjamin LaHaise To: "H. Peter Anvin" Cc: Ingo Molnar , Russell King , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86_32: add support for 64 bit __get_user() v3 Message-ID: <20160314153747.GH17923@kvack.org> References: <20160309172225.GN12913@kvack.org> <20160309175016.GO12913@kvack.org> <56E069FA.7070700@zytor.com> <20160309193035.GS12913@kvack.org> <20160309200556.GT12913@kvack.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160309200556.GT12913@kvack.org> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2324 Lines: 65 Any more comments/feedback on this? Can this be merged for 4.6? -ben On Wed, Mar 09, 2016 at 03:05:56PM -0500, Benjamin LaHaise wrote: > The existing __get_user() implementation does not support fetching > 64 bit values on 32 bit x86. Implement this in a way that does not > generate any incorrect warnings as cautioned by Russell King. Test > code available at http://www.kvack.org/~bcrl/x86_32-get_user.tar . > > v2: use __inttype() as suggested by H. Peter Anvin, which cleans the > code up nicely, and fix things to work on x86_64 as well. > > v3: fix undefined behaviour on 32 bit x86 caused by multiple expansion > of ptr in the 64 bit case. > > Signed-off-by: Benjamin LaHaise > > diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h > index a4a30e4..8743552 100644 > --- a/arch/x86/include/asm/uaccess.h > +++ b/arch/x86/include/asm/uaccess.h > @@ -333,7 +333,26 @@ do { \ > } while (0) > > #ifdef CONFIG_X86_32 > -#define __get_user_asm_u64(x, ptr, retval, errret) (x) = __get_user_bad() > +#define __get_user_asm_u64(x, ptr, retval, errret) \ > +({ \ > + __typeof__(ptr) __ptr = (ptr); \ > + asm volatile(ASM_STAC "\n" \ > + "1: movl %2,%%eax\n" \ > + "2: movl %3,%%edx\n" \ > + "3: " ASM_CLAC "\n" \ > + ".section .fixup,\"ax\"\n" \ > + "4: mov %4,%0\n" \ > + " xorl %%eax,%%eax\n" \ > + " xorl %%edx,%%edx\n" \ > + " jmp 3b\n" \ > + ".previous\n" \ > + _ASM_EXTABLE(1b, 4b) \ > + _ASM_EXTABLE(2b, 4b) \ > + : "=r" (retval), "=A"(x) \ > + : "m" (__m(__ptr)), "m" __m(((u32 *)(__ptr)) + 1), \ > + "i" (errret), "0" (retval)); \ > +}) > + > #define __get_user_asm_ex_u64(x, ptr) (x) = __get_user_bad() > #else > #define __get_user_asm_u64(x, ptr, retval, errret) \ > @@ -420,7 +439,7 @@ do { \ > #define __get_user_nocheck(x, ptr, size) \ > ({ \ > int __gu_err; \ > - unsigned long __gu_val; \ > + __inttype(*(ptr)) __gu_val; \ > __uaccess_begin(); \ > __get_user_size(__gu_val, (ptr), (size), __gu_err, -EFAULT); \ > __uaccess_end(); \ > > -- > "Thought is the essence of where you are now." -- "Thought is the essence of where you are now."