From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f41.google.com (mail-pa0-f41.google.com [209.85.220.41]) by kanga.kvack.org (Postfix) with ESMTP id C89436B0032 for ; Fri, 30 Jan 2015 16:35:54 -0500 (EST) Received: by mail-pa0-f41.google.com with SMTP id kq14so57052831pab.0 for ; Fri, 30 Jan 2015 13:35:54 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id mz9si15007889pdb.205.2015.01.30.13.35.53 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 30 Jan 2015 13:35:53 -0800 (PST) Date: Fri, 30 Jan 2015 13:35:52 -0800 From: Andrew Morton Subject: Re: [PATCH v10 02/17] x86_64: add KASan support Message-Id: <20150130133552.580f73b97a9bd007979b5419@linux-foundation.org> In-Reply-To: <54CBAE2E.2030106@samsung.com> References: <1404905415-9046-1-git-send-email-a.ryabinin@samsung.com> <1422544321-24232-1-git-send-email-a.ryabinin@samsung.com> <1422544321-24232-3-git-send-email-a.ryabinin@samsung.com> <20150129151224.4e7947af78605c199763102c@linux-foundation.org> <54CBAE2E.2030106@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin Cc: linux-kernel@vger.kernel.org, Dmitry Vyukov , Konstantin Serebryany , Dmitry Chernenkov , Andrey Konovalov , Yuri Gribov , Konstantin Khlebnikov , Sasha Levin , Christoph Lameter , Joonsoo Kim , Dave Hansen , Andi Kleen , x86@kernel.org, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jonathan Corbet , Andy Lutomirski , "open list:DOCUMENTATION" On Fri, 30 Jan 2015 19:15:42 +0300 Andrey Ryabinin wrote: > >> --- a/lib/Kconfig.kasan > >> +++ b/lib/Kconfig.kasan > >> @@ -5,6 +5,7 @@ if HAVE_ARCH_KASAN > >> > >> config KASAN > >> bool "AddressSanitizer: runtime memory debugger" > >> + depends on !MEMORY_HOTPLUG > >> help > >> Enables address sanitizer - runtime memory debugger, > >> designed to find out-of-bounds accesses and use-after-free bugs. > > > > That's a significant restriction. It has obvious runtime implications. > > It also means that `make allmodconfig' and `make allyesconfig' don't > > enable kasan, so compile coverage will be impacted. > > > > This wasn't changelogged. What's the reasoning and what has to be done > > to fix it? > > > > Yes, this is runtime dependency. Hot adding memory won't work. > Since we don't have shadow for hotplugged memory, kernel will crash on the first access to it. > To fix this we need to allocate shadow for new memory. This definitely should be covered in the changelog. In general, please take most (all?) review questions as requests to add content to the changelog and/or to add code comments - if a reviewer didn't understand something then other readers are likely to be wondering the same thing. > Perhaps it would be better to have a runtime warning instead of Kconfig dependecy? mmm... yes, that sounds better. Maybe print a warning at startup and then disable memory hot-add? I expect that if the user has enabled kasan and mem-hotplug at the same time, he/she would prefer that hotplug be disabled than kasan. -- 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