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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH 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 DCEE0C32789 for ; Fri, 2 Nov 2018 20:12:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C09A2082E for ; Fri, 2 Nov 2018 20:12:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="lQJGiYaW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C09A2082E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1726707AbeKCFUi (ORCPT ); Sat, 3 Nov 2018 01:20:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:52636 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725728AbeKCFUi (ORCPT ); Sat, 3 Nov 2018 01:20:38 -0400 Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com [209.85.221.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EF01B20847 for ; Fri, 2 Nov 2018 20:12:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1541189525; bh=u4p1RNF3EEbbDEWjYtGvYoNaHMDvEfPPCmImjEVWqXA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=lQJGiYaW/jp3aPRvfE0C7E3XIiQ28OXdITbO7OkuGAvEAxO+mFGK4L2ZHBOsikBEO V2FYCsfFGsaCWhOnudWHZk2XhWSTl5ScYh3DhZ7etiETVOPlYgY3QzIuDPFuq7XCY9 DTkSHQJ0uxNadLmorKggcElC2WHosiuU1SU3TQPk= Received: by mail-wr1-f45.google.com with SMTP id k15-v6so191956wre.12 for ; Fri, 02 Nov 2018 13:12:04 -0700 (PDT) X-Gm-Message-State: AGRZ1gKs8YubcwxnLmkCWh262ncnd5daDzGYTv8AKGKevpj8dSsg7UyC a/tqwe7v+1iPgBzQE4PE91RkuZ9+A7cZ5Mb1FxxMwA== X-Google-Smtp-Source: AJdET5c7xd2e6tbeJdpW3GC7CDGfUfeaTs7ZRXsCktAtWRPWypad1Jz9rOzDjSYcmhu8ndL2WsVeSTclhUydSXJdZcY= X-Received: by 2002:adf:97d3:: with SMTP id t19-v6mr11959807wrb.283.1541189523387; Fri, 02 Nov 2018 13:12:03 -0700 (PDT) MIME-Version: 1.0 References: <1541187610-5322-1-git-send-email-longman@redhat.com> In-Reply-To: From: Andy Lutomirski Date: Fri, 2 Nov 2018 13:11:50 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH] x86/mm/fault: Allow stack access below %rsp To: Waiman Long Cc: Dave Hansen , Dave Hansen , Andrew Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , X86 ML , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 2, 2018 at 12:50 PM Waiman Long wrote: > > On 11/02/2018 03:44 PM, Dave Hansen wrote: > > On 11/2/18 12:40 PM, Waiman Long wrote: > >> The 64k+ limit check is kind of arbitrary. So the check is now removed > >> to just let expand_stack() decide if a segmentation fault should happen. > > With the 64k check removed, what's the next limit that we bump into? Is > > it just the stack_guard_gap space above the next-lowest VMA? > > I think it is both the stack_guard_gap space above the next lowest VMA > and the rlimit(RLIMIT_STACK). > Did the non-working programs ever work? Because, if not, I say let them fail.