From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id 4107F6B0038 for ; Mon, 16 Nov 2015 11:51:07 -0500 (EST) Received: by padhx2 with SMTP id hx2so180294937pad.1 for ; Mon, 16 Nov 2015 08:51:07 -0800 (PST) Received: from foss.arm.com (foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id zo6si51578263pbc.29.2015.11.16.08.51.06 for ; Mon, 16 Nov 2015 08:51:06 -0800 (PST) Date: Mon, 16 Nov 2015 16:51:00 +0000 From: Catalin Marinas Subject: Re: [PATCH v7 0/4] KASAN for arm64 Message-ID: <20151116165100.GE6556@e104818-lin.cambridge.arm.com> References: <1444665180-301-1-git-send-email-ryabinin.a.a@gmail.com> <20151013083432.GG6320@e104818-lin.cambridge.arm.com> <5649BAFD.6030005@arm.com> <5649F783.40109@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5649F783.40109@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin Cc: "Suzuki K. Poulose" , Yury , Arnd Bergmann , linux-mm@kvack.org, Linus Walleij , Ard Biesheuvel , Will Deacon , linux-kernel@vger.kernel.org, kasan-dev , Alexey Klimov , Alexander Potapenko , Dmitry Vyukov , Andrey Konovalov , David Keitel , linux-arm-kernel@lists.infradead.org On Mon, Nov 16, 2015 at 06:34:27PM +0300, Andrey Ryabinin wrote: > On 11/16/2015 02:16 PM, Suzuki K. Poulose wrote: > > On 13/10/15 09:34, Catalin Marinas wrote: > >> On Mon, Oct 12, 2015 at 06:52:56PM +0300, Andrey Ryabinin wrote: > >>> Andrey Ryabinin (3): > >>> arm64: move PGD_SIZE definition to pgalloc.h > >>> arm64: add KASAN support > >>> Documentation/features/KASAN: arm64 supports KASAN now > >>> > >>> Linus Walleij (1): > >>> ARM64: kasan: print memory assignment > >> > >> Patches queued for 4.4. Thanks. > > > > I get the following failure with KASAN + 16K_PAGES + 48BIT_VA, with 4.4-rc1: > > > > arch/arm64/mm/kasan_init.c: In function a??kasan_early_inita??: > > include/linux/compiler.h:484:38: error: call to a??__compiletime_assert_95a?? declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE) > > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > > ^ > > include/linux/compiler.h:467:4: note: in definition of macro a??__compiletime_asserta?? > > prefix ## suffix(); \ > > ^ > > include/linux/compiler.h:484:2: note: in expansion of macro a??_compiletime_asserta?? > > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > > ^ > > include/linux/bug.h:50:37: note: in expansion of macro a??compiletime_asserta?? > > #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > > ^ > > include/linux/bug.h:74:2: note: in expansion of macro a??BUILD_BUG_ON_MSGa?? > > BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > > ^ > > arch/arm64/mm/kasan_init.c:95:2: note: in expansion of macro a??BUILD_BUG_ONa?? > > BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE)); > > > > The problem is that the PGDIR_SIZE is (1UL << 47) with 16K+48bit, which makes > > the KASAN_SHADOW_END unaligned(which is aligned to (1UL << (48 - 3)) ). Is the > > alignment really needed ? Thoughts on how best we could fix this ? > > Yes, it's really needed, because some code relies on this (e.g. > clear_pgs() and kasan_init()). But it should be possible to get rid of > this requirement. I don't think clear_pgds() and kasan_init() are the only problems. IIUC, kasan_populate_zero_shadow() also assumes that KASan shadow covers multiple pgds. You need some kind of recursive writing which avoids populating an entry which is not empty (like kasan_early_pud_populate). -- Catalin -- 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