From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D1A8C5ACCC for ; Thu, 18 Oct 2018 08:58:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E7CA208E4 for ; Thu, 18 Oct 2018 08:58:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2E7CA208E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727881AbeJRQ6J (ORCPT ); Thu, 18 Oct 2018 12:58:09 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:49274 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727461AbeJRQ6J (ORCPT ); Thu, 18 Oct 2018 12:58:09 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07684846|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e02c03298;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=16;RT=16;SR=0;TI=SMTPD_---.D3txbJc_1539853072; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.D3txbJc_1539853072) by smtp.aliyun-inc.com(10.147.41.178); Thu, 18 Oct 2018 16:57:52 +0800 Date: Thu, 18 Oct 2018 16:57:52 +0800 From: Guo Ren To: Arnd Bergmann Cc: Andrew Morton , Daniel Lezcano , David Miller , gregkh , Christoph Hellwig , Marc Zyngier , Mark Rutland , Peter Zijlstra , Rob Herring , Thomas Gleixner , Linux Kernel Mailing List , linux-arch , DTML , Rob Herring , c-sky_gcc_upstream@c-sky.com Subject: Re: [PATCH V9 21/21] csky: support dword access for get_user_size() Message-ID: <20181018085751.GA21934@guoren-Inspiron-7460> References: <4bc11ff0cff5960892a464189605f9bc808383fc.1539655732.git.ren_guo@c-sky.com> <20181018034117.GD15088@guoren-Inspiron-7460> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 18, 2018 at 10:34:00AM +0200, Arnd Bergmann wrote: > On Thu, Oct 18, 2018 at 5:41 AM Guo Ren wrote: > > > > On Wed, Oct 17, 2018 at 05:44:17PM +0200, Arnd Bergmann wrote: > > > On Tue, Oct 16, 2018 at 5:33 AM Guo Ren wrote: > > > > > > > > Support dword access for get_user_size and redesign put_user_size with > > > > the same style of get_user_size. It's Ok to use xxx_user_asm_common for > > > > all size of variable with ldb, ldh, ldw, ld.d > > > > > > > > ld.d rx, (addr, 0) could "rx <= addr" "and r(x+1) <= addr+4" and this also > > > > follow abiv2 gcc ABI for dword access. > > > > > > Are you sure this is correct for this? > > > > > > static inline u32 get_64_to_32(__u64 __user *p) > > > { > > > u32 ret; > > > get_user(ret, p); > > > return ret; > > > } > > > > > > If I read __get_user_asm_common() right, the ld.d would overwrite > > > two registers, but the caller only expects one, so it clobbers one > > > that might be in use. > > Ah... BUG! I only consider the get_user(u64, u64 *) :P > > > > Change to: > > case 8: \ > > __get_user_asm_dword((x), ptr, "ld.d", retval); \ > > break; > > > > #define __get_user_asm_dword(x, ptr, err) \ > > do { \ > > u64 tmp; \ > > __get_user_asm_common(tmp, ptr, "ld.d", err); \ > > x = typeof(x) tmp; \ > > } while(0) > > > > #define __put_user_asm_dword(x, ptr, err) \ > > do { \ > > u64 tmp = (u64) x; \ > > __put_user_asm_common(tmp, ptr, "st.d", err); \ > > } while(0) > > > > I think this will cause warnings for code that passes a pointer. > > The 64-bit __get_user() is really hard, and most 32-bit architectures don't > implement it at all. If you really want to add it, have a look at what > x86 and arm do. IIRC they both use __builtin_choose_expr(), Thx for the tips and I'll drop the patch first for the upstream. I want to implement it because of make allmodconfig and drivers/android/binder.c need it. I'll learn __builtin_choose_expr() and prepare patch next. Best Regards Guo Ren