Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752281AbbKPPd7 (ORCPT ); Mon, 16 Nov 2015 10:33:59 -0500 Received: from mail-lf0-f41.google.com ([209.85.215.41]:35572 "EHLO mail-lf0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751606AbbKPPd5 (ORCPT ); Mon, 16 Nov 2015 10:33:57 -0500 Subject: Re: [PATCH v7 0/4] KASAN for arm64 To: "Suzuki K. Poulose" References: <1444665180-301-1-git-send-email-ryabinin.a.a@gmail.com> <20151013083432.GG6320@e104818-lin.cambridge.arm.com> <5649BAFD.6030005@arm.com> Cc: Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, Yury , Alexey Klimov , Arnd Bergmann , linux-mm@kvack.org, Andrey Konovalov , Linus Walleij , Ard Biesheuvel , linux-kernel@vger.kernel.org, kasan-dev , David Keitel , Alexander Potapenko , Dmitry Vyukov From: Andrey Ryabinin Message-ID: <5649F783.40109@gmail.com> Date: Mon, 16 Nov 2015 18:34:27 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <5649BAFD.6030005@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3198 Lines: 80 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. >> > > Hi, > > I get the following failure with KASAN + 16K_PAGES + 48BIT_VA, with 4.4-rc1: > > > arch/arm64/mm/kasan_init.c: In function ?kasan_early_init?: > include/linux/compiler.h:484:38: error: call to ?__compiletime_assert_95? 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 ?__compiletime_assert? > prefix ## suffix(); \ > ^ > include/linux/compiler.h:484:2: note: in expansion of macro ?_compiletime_assert? > _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) > ^ > include/linux/bug.h:50:37: note: in expansion of macro ?compiletime_assert? > #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) > ^ > include/linux/bug.h:74:2: note: in expansion of macro ?BUILD_BUG_ON_MSG? > BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) > ^ > arch/arm64/mm/kasan_init.c:95:2: note: in expansion of macro ?BUILD_BUG_ON? > 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. At first we need to rework clear_pgs(). The purpose of clear_pgs() is to remove kasan shadow from swapper_pg_dir. So clear_pgs() should clear the top most kasan_zero_* entries from page tables. Previously it was enough to clear PGDs, in case of 16K_PAGES + 48BIT_VA we probably need to clear PMDs We also have to change following part of kasan_init() ... /* * We are going to perform proper setup of shadow memory. * At first we should unmap early shadow (clear_pgds() call bellow). * However, instrumented code couldn't execute without shadow memory. * tmp_pg_dir used to keep early shadow mapped until full shadow * setup will be finished. */ memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir)); Besides tmp_pg_dir we will need one more temporary page table to store those entries which later will be removed from swapper_pg_dir by clear_pgds(). > Cheers > Suzuki > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/