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=unavailable 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 1A94EC433DF for ; Fri, 29 May 2020 04:34:30 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C65E92075A for ; Fri, 29 May 2020 04:34:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C65E92075A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49YBYH5zHLzDqTd for ; Fri, 29 May 2020 14:34:27 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49YBKc1GSXzDqb9 for ; Fri, 29 May 2020 14:24:20 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au 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 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) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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