From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0B5EBC43215 for ; Mon, 2 Dec 2019 08:07:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB84F2146E for ; Mon, 2 Dec 2019 08:07:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="NA9HB3/P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726330AbfLBIHf (ORCPT ); Mon, 2 Dec 2019 03:07:35 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:11699 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725977AbfLBIHf (ORCPT ); Mon, 2 Dec 2019 03:07:35 -0500 Received: from localhost (mailhub1-ext [192.168.12.233]) by localhost (Postfix) with ESMTP id 47RHlh4V2zz9txst; Mon, 2 Dec 2019 09:07:28 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=NA9HB3/P; dkim-adsp=pass; dkim-atps=neutral X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id jENeedGZyhzE; Mon, 2 Dec 2019 09:07:28 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 47RHlh3D7wz9txsq; Mon, 2 Dec 2019 09:07:28 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1575274048; bh=Pfkmv+6zl1ejxY4eGUsKi0YsAcRI6StbPSFCVUfcymU=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=NA9HB3/PUOD6nye920wQm+iK82PinDWNtTtkIOcwVa1Q+XpHLjn8keX59KuxuipNS YuhL54JKnZlUk7T5qR8Qwqgs0wSGG0sNjO5ZqcrZWty5f3leLyUVYXHDkyYS9c7jO2 JfJ/yrM/TCpcNOqje5a0VIbF206q2vfNm3DUNpsw= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 0FD2F8B79B; Mon, 2 Dec 2019 09:07:33 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id O4E_l5RfgFtW; Mon, 2 Dec 2019 09:07:32 +0100 (CET) Received: from [172.25.230.103] (po15451.idsi0.si.c-s.fr [172.25.230.103]) by messagerie.si.c-s.fr (Postfix) with ESMTP id C0DD68B770; Mon, 2 Dec 2019 09:07:32 +0100 (CET) Subject: Re: [PATCH v11 0/4] kasan: support backing vmalloc space with real shadow memory To: Daniel Axtens , kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org, aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, dvyukov@google.com Cc: linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com References: <20191031093909.9228-1-dja@axtens.net> From: Christophe Leroy Message-ID: <33b29093-5fbe-c648-a0b1-e3a8525c5631@c-s.fr> Date: Mon, 2 Dec 2019 09:07:31 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20191031093909.9228-1-dja@axtens.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 31/10/2019 à 10:39, Daniel Axtens a écrit : > Currently, vmalloc space is backed by the early shadow page. This > means that kasan is incompatible with VMAP_STACK. > > This series provides a mechanism to back vmalloc space with real, > dynamically allocated memory. I have only wired up x86, because that's > the only currently supported arch I can work with easily, but it's > very easy to wire up other architectures, and it appears that there is > some work-in-progress code to do this on arm64 and s390. There is also work for providing VMAP_STACK on powerpc32. There is a series waiting to be merged at https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=145109 Christophe > > This has been discussed before in the context of VMAP_STACK: > - https://bugzilla.kernel.org/show_bug.cgi?id=202009 > - https://lkml.org/lkml/2018/7/22/198 > - https://lkml.org/lkml/2019/7/19/822 > > In terms of implementation details: > > Most mappings in vmalloc space are small, requiring less than a full > page of shadow space. Allocating a full shadow page per mapping would > therefore be wasteful. Furthermore, to ensure that different mappings > use different shadow pages, mappings would have to be aligned to > KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE. > > Instead, share backing space across multiple mappings. Allocate a > backing page when a mapping in vmalloc space uses a particular page of > the shadow region. This page can be shared by other vmalloc mappings > later on. > > We hook in to the vmap infrastructure to lazily clean up unused shadow > memory. > > Testing with test_vmalloc.sh on an x86 VM with 2 vCPUs shows that: > > - Turning on KASAN, inline instrumentation, without vmalloc, introuduces > a 4.1x-4.2x slowdown in vmalloc operations. > > - Turning this on introduces the following slowdowns over KASAN: > * ~1.76x slower single-threaded (test_vmalloc.sh performance) > * ~2.18x slower when both cpus are performing operations > simultaneously (test_vmalloc.sh sequential_test_order=1) > > This is unfortunate but given that this is a debug feature only, not > the end of the world. The benchmarks are also a stress-test for the > vmalloc subsystem: they're not indicative of an overall 2x slowdown! > > > v1: https://lore.kernel.org/linux-mm/20190725055503.19507-1-dja@axtens.net/ > v2: https://lore.kernel.org/linux-mm/20190729142108.23343-1-dja@axtens.net/ > Address review comments: > - Patch 1: use kasan_unpoison_shadow's built-in handling of > ranges that do not align to a full shadow byte > - Patch 3: prepopulate pgds rather than faulting things in > v3: https://lore.kernel.org/linux-mm/20190731071550.31814-1-dja@axtens.net/ > Address comments from Mark Rutland: > - kasan_populate_vmalloc is a better name > - handle concurrency correctly > - various nits and cleanups > - relax module alignment in KASAN_VMALLOC case > v4: https://lore.kernel.org/linux-mm/20190815001636.12235-1-dja@axtens.net/ > Changes to patch 1 only: > - Integrate Mark's rework, thanks Mark! > - handle the case where kasan_populate_shadow might fail > - poision shadow on free, allowing the alloc path to just > unpoision memory that it uses > v5: https://lore.kernel.org/linux-mm/20190830003821.10737-1-dja@axtens.net/ > Address comments from Christophe Leroy: > - Fix some issues with my descriptions in commit messages and docs > - Dynamically free unused shadow pages by hooking into the vmap book-keeping > - Split out the test into a separate patch > - Optional patch to track the number of pages allocated > - minor checkpatch cleanups > v6: https://lore.kernel.org/linux-mm/20190902112028.23773-1-dja@axtens.net/ > Properly guard freeing pages in patch 1, drop debugging code. > v7: https://lore.kernel.org/linux-mm/20190903145536.3390-1-dja@axtens.net/ > Add a TLB flush on freeing, thanks Mark Rutland. > Explain more clearly how I think freeing is concurrency-safe. > v8: https://lore.kernel.org/linux-mm/20191001065834.8880-1-dja@axtens.net/ > rename kasan_vmalloc/shadow_pages to kasan/vmalloc_shadow_pages > v9: https://lore.kernel.org/linux-mm/20191017012506.28503-1-dja@axtens.net/ > (attempt to) address a number of review comments for patch 1. > v10: https://lore.kernel.org/linux-mm/20191029042059.28541-1-dja@axtens.net/ > - rebase on linux-next, pulling in Vlad's new work on splitting the > vmalloc locks. > - after much discussion of barriers, document where I think they > are needed and why. Thanks Mark and Andrey. > - clean up some TLB flushing and checkpatch bits > v11: Address review comments from Andrey and Vlad, drop patch 5, add benchmarking > results. > > Daniel Axtens (4): > kasan: support backing vmalloc space with real shadow memory > kasan: add test for vmalloc > fork: support VMAP_STACK with KASAN_VMALLOC > x86/kasan: support KASAN_VMALLOC > > Documentation/dev-tools/kasan.rst | 63 ++++++++ > arch/Kconfig | 9 +- > arch/x86/Kconfig | 1 + > arch/x86/mm/kasan_init_64.c | 61 ++++++++ > include/linux/kasan.h | 31 ++++ > include/linux/moduleloader.h | 2 +- > include/linux/vmalloc.h | 12 ++ > kernel/fork.c | 4 + > lib/Kconfig.kasan | 16 +++ > lib/test_kasan.c | 26 ++++ > mm/kasan/common.c | 231 ++++++++++++++++++++++++++++++ > mm/kasan/generic_report.c | 3 + > mm/kasan/kasan.h | 1 + > mm/vmalloc.c | 53 +++++-- > 14 files changed, 500 insertions(+), 13 deletions(-) >