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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 4445AC46464 for ; Tue, 14 Aug 2018 12:34:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6CC42170F for ; Tue, 14 Aug 2018 12:34:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kXuS6usS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E6CC42170F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1732563AbeHNPV4 (ORCPT ); Tue, 14 Aug 2018 11:21:56 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:36056 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732396AbeHNPVz (ORCPT ); Tue, 14 Aug 2018 11:21:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3uTet5jZ820jJsV7crh8eqqWPnUji4A9TGfrWDwMoB4=; b=kXuS6usSTzcByj9w0vy/pLek6 tWYHIzOWH2v0wVvoj82IpNsHQzEa7d4kW0fIu/vCCctA4kns/HcI7mmRQAeUlMEF9wn9OR+GyYSOL E9ClQBHd+xUMUDF0ysLeSqVLqSsISA6b2h1+GN77lISdisbi5+rc6KLIHYnsJKIvBHa49JJjNSqxl IstxFFaLsFPtH/CXyqP2D9mOxsCNsUkUotRTqrfF6j7uFsuGyMrLU1nVtnwhLmoKtH6rA7j2Ssrqz /ChHOuGLF4aWJTOAAGTgM6FU5WMYR+XxmGh4L6NxtoHdQWfEs2zhCuU9BdJA5KysTX8wFemNUkwxD QaUd6Ntvg==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fpYXG-0004Ja-RW; Tue, 14 Aug 2018 12:34:54 +0000 Date: Tue, 14 Aug 2018 05:34:54 -0700 From: Matthew Wilcox To: Xiaofeng Yuan Cc: keescook@chromium.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] usercopy: optimize stack check flow when the Message-ID: <20180814123454.GA25328@bombadil.infradead.org> References: <1534249051-56879-1-git-send-email-yuanxiaofeng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1534249051-56879-1-git-send-email-yuanxiaofeng1@huawei.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 14, 2018 at 08:17:31PM +0800, Xiaofeng Yuan wrote: > The check_heap_object() checks the spanning multiple pages and slab. > When the page-spanning test is disabled, the check_heap_object() is > redundant for spanning multiple pages. However, the kernel stacks are > multiple pages under certain conditions: CONFIG_ARCH_THREAD_STACK_ALLOCATOR > is not defined and (THREAD_SIZE >= PAGE_SIZE). At this point, We can skip > the check_heap_object() for kernel stacks to improve performance. > Similarly, the virtually-mapped stack can skip check_heap_object() also, > beacause virt_addr_valid() will return. Why not just check_stack_object() first, then check_heap_object() second?