From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f71.google.com (mail-oi0-f71.google.com [209.85.218.71]) by kanga.kvack.org (Postfix) with ESMTP id CE92C6B029C for ; Tue, 7 Nov 2017 06:26:18 -0500 (EST) Received: by mail-oi0-f71.google.com with SMTP id s185so12573733oif.16 for ; Tue, 07 Nov 2017 03:26:18 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id i203si436872oib.234.2017.11.07.03.26.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Nov 2017 03:26:17 -0800 (PST) Subject: Re: POWER: Unexpected fault when writing to brk-allocated memory References: <20171105231850.5e313e46@roar.ozlabs.ibm.com> <871slcszfl.fsf@linux.vnet.ibm.com> <20171106174707.19f6c495@roar.ozlabs.ibm.com> <24b93038-76f7-33df-d02e-facb0ce61cd2@redhat.com> <20171106192524.12ea3187@roar.ozlabs.ibm.com> <546d4155-5b7c-6dba-b642-29c103e336bc@redhat.com> <20171107160705.059e0c2b@roar.ozlabs.ibm.com> <20171107111543.ep57evfxxbwwlhdh@node.shutemov.name> From: Florian Weimer Message-ID: Date: Tue, 7 Nov 2017 12:26:12 +0100 MIME-Version: 1.0 In-Reply-To: <20171107111543.ep57evfxxbwwlhdh@node.shutemov.name> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" , Nicholas Piggin Cc: "Aneesh Kumar K.V" , "Kirill A. Shutemov" , linuxppc-dev@lists.ozlabs.org, linux-mm , Andrew Morton , Andy Lutomirski , Dave Hansen , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , linux-arch@vger.kernel.org, Ingo Molnar , Linux Kernel Mailing List On 11/07/2017 12:15 PM, Kirill A. Shutemov wrote: >> First of all, using addr and MAP_FIXED to develop our heuristic can >> never really give unchanged ABI. It's an in-band signal. brk() is a >> good example that steadily keeps incrementing address, so depending >> on malloc usage and address space randomization, you will get a brk() >> that ends exactly at 128T, then the next one will be > >> DEFAULT_MAP_WINDOW, and it will switch you to 56 bit address space. > > No, it won't. You will hit stack first. That's not actually true on POWER in some cases. See the process maps I posted here: Thanks, Florian -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org