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=-8.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 8A8E8C433DF for ; Fri, 29 May 2020 04:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E66920DD4 for ; Fri, 29 May 2020 04:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728322AbgE2EYd (ORCPT ); Fri, 29 May 2020 00:24:33 -0400 Received: from bilbo.ozlabs.org ([203.11.71.1]:46907 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbgE2EYV (ORCPT ); Fri, 29 May 2020 00:24:21 -0400 Received: by ozlabs.org (Postfix, from userid 1034) id 49YBKb2VVkz9sT6; Fri, 29 May 2020 14:24:17 +1000 (AEST) X-powerpc-patch-notification: thanks X-powerpc-patch-commit: 17bc43367fc2a720400d21c745db641c654c1e6b In-Reply-To: To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , npiggin@gmail.com, segher@kernel.crashing.org From: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] powerpc/uaccess: Implement unsafe_copy_to_user() as a simple loop Message-Id: <49YBKb2VVkz9sT6@ozlabs.org> Date: Fri, 29 May 2020 14:24:17 +1000 (AEST) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2020-04-17 at 17:08:52 UTC, Christophe Leroy wrote: > At the time being, unsafe_copy_to_user() is based on > raw_copy_to_user() which calls __copy_tofrom_user(). > > __copy_tofrom_user() is a big optimised function to copy big amount > of data. It aligns destinations to cache line in order to use > dcbz instruction. > > Today unsafe_copy_to_user() is called only from filldir(). > It is used to mainly copy small amount of data like filenames, > so __copy_tofrom_user() is not fit. > > Also, unsafe_copy_to_user() is used within user_access_begin/end > sections. In those section, it is preferable to not call functions. > > Rewrite unsafe_copy_to_user() as a macro that uses __put_user_goto(). > We first perform a loop of long, then we finish with necessary > complements. > > unsafe_copy_to_user() might be used in the near future to copy > fixed-size data, like pt_regs structs during signal processing. > Having it as a macro allows GCC to optimise it for instead when > it knows the size in advance, it can unloop loops, drop complements > when the size is a multiple of longs, etc ... > > Signed-off-by: Christophe Leroy Applied to powerpc topic/uaccess-ppc, thanks. https://git.kernel.org/powerpc/c/17bc43367fc2a720400d21c745db641c654c1e6b cheers