From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id 9EA306B0010 for ; Mon, 5 Mar 2018 09:36:38 -0500 (EST) Received: by mail-oi0-f72.google.com with SMTP id u68so8831532oia.0 for ; Mon, 05 Mar 2018 06:36:38 -0800 (PST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id b13si3707072oih.300.2018.03.05.06.36.37 for ; Mon, 05 Mar 2018 06:36:37 -0800 (PST) Date: Mon, 5 Mar 2018 14:36:26 +0000 From: Mark Rutland Subject: Re: [RFC PATCH 06/14] khwasan: enable top byte ignore for the kernel Message-ID: <20180305143625.vtrfvsbw7loxngaj@lakrids.cambridge.arm.com> References: <739eecf573b6342fc41c4f89d7f64eb8c183e312.1520017438.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <739eecf573b6342fc41c4f89d7f64eb8c183e312.1520017438.git.andreyknvl@google.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Jonathan Corbet , Catalin Marinas , Will Deacon , Theodore Ts'o , Jan Kara , Christopher Li , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Masahiro Yamada , Michal Marek , Ard Biesheuvel , Yury Norov , Nick Desaulniers , Marc Zyngier , Bob Picco , Suzuki K Poulose , Kristina Martsenko , Punit Agrawal , Dave Martin , James Morse , Julien Thierry , Michael Weiser , Steve Capper , Ingo Molnar , Thomas Gleixner , Sandipan Das , Paul Lawrence , David Woodhouse , Kees Cook , Geert Uytterhoeven , Josh Poimboeuf , Arnd Bergmann , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ext4@vger.kernel.org, linux-sparse@vger.kernel.org, linux-mm@kvack.org, linux-kbuild@vger.kernel.org, Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Kees Cook , Jann Horn , Mark Brand On Fri, Mar 02, 2018 at 08:44:25PM +0100, Andrey Konovalov wrote: > KHWASAN uses the Top Byte Ignore feature of arm64 CPUs to store a pointer > tag in the top byte of each pointer. This commit enables the TCR_TBI1 bit, > which enables Top Byte Ignore for the kernel, when KHWASAN is used. > --- > arch/arm64/include/asm/pgtable-hwdef.h | 1 + > arch/arm64/mm/proc.S | 8 +++++++- > 2 files changed, 8 insertions(+), 1 deletion(-) Before it's safe to do this, I also think you'll need to fix up at least: * virt_to_phys() * access_ok() ... and potentially others which assume that bits [63:56] of kernel addresses are 0xff. For example, bits of the fault handling logic might need fixups. Thanks, Mark. -- 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