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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 AF533C4338F for ; Tue, 17 Aug 2021 07:07:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 92F76600D4 for ; Tue, 17 Aug 2021 07:07:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238270AbhHQHIP (ORCPT ); Tue, 17 Aug 2021 03:08:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234741AbhHQHII (ORCPT ); Tue, 17 Aug 2021 03:08:08 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6DB7C061764; Tue, 17 Aug 2021 00:07:35 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1629184053; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=M5vEOrmUZ/7iiA0ok5cYoWGZ9p/fqiIXSRXLn17nevs=; b=st61vqpH3pL+9MJflwlR7TQy0tnRliq2uR+V9XK3bBqW9Z9jdsXF3/FbX5bVIVws6GTMzb uiESRbTZhFdXKGJ9SMI7nJJBVMMKYetWA+ygAE0TVYrtYrCr11K7vKEcyJITXTiZD3e5Vg jAMnRi4J486RYRod6n3P94oRcNvINos1qCAbwud1JxkW28NB7zFLbihmlJ/ZSfjcDYk7Q+ iEKLa6WDZYH9bBcRhsuTa0jiaUORj9nhB7tGdaPKvtTFZSXWM6tGgqYHf9SBaFwdBRGAL8 aIKNxiyKTQ/devHkMZjTyiz7ncInKxgWH9avXmNmGdNiODKmzXNn/dtZOT+nQQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1629184053; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=M5vEOrmUZ/7iiA0ok5cYoWGZ9p/fqiIXSRXLn17nevs=; b=NY81Fugu1nR0drMuAiGUREJu1drIDB4eyyd2n5uuMm7itDE9MilnIxHWx10ykWH3/4Xs1i Oq/Qfmc58i0DTPAw== To: Huacai Chen Cc: Davidlohr Bueso , Huacai Chen , Ingo Molnar , Peter Zijlstra , Darren Hart , Thomas Bogendoerfer , "open list:MIPS" , LKML , Xuefeng Li , Jiaxun Yang , Hongchen Zhang Subject: Re: [PATCH] futex: Fix fault_in_user_writeable() In-Reply-To: References: <20210816065417.3987596-1-chenhuacai@loongson.cn> <20210816182750.26i535ilc6nef5k6@offworld> <874kbpp5zd.ffs@tglx> Date: Tue, 17 Aug 2021 09:07:32 +0200 Message-ID: <871r6spn0r.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 17 2021 at 09:53, Huacai Chen wrote: > On Tue, Aug 17, 2021 at 3:03 AM Thomas Gleixner wrote: >> That's surely one way to fix that. If that does not work for whatever >> reason, then we really don't want this find_vma() hack there, but rather >> something like: > I don't know why find_vma() is unacceptable here, there is also > find_vma() in fixup_user_fault(). Wrong. find_extend_vma() != find_vma(). Aside of that fixup_user_fault() does way more than that. >> if (IS_ENABLED(CONFIG_ARCH_USER_FAULT_VOODOO) && get_user(&tmp, uaddr)) >> return -EFAULT; > > get_user() may be better than find_vma(), but can we drop > CONFIG_ARCH_USER_FAULT_VOODOO here? On those "W implies R" archs, > get_user() always success, this can simplify the logic. For architectures which imply R fixup_user_fault() is way more effinicient than taking the fault on get_user() and then invoking fixup_user_fault() to ensure that the mapping is writeable. No, we are not making stuff less efficient just because of MIPS. Thanks, tglx