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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 3C221C4CECE for ; Mon, 14 Oct 2019 15:44:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F56521882 for ; Mon, 14 Oct 2019 15:44:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387669AbfJNPoG (ORCPT ); Mon, 14 Oct 2019 11:44:06 -0400 Received: from foss.arm.com ([217.140.110.172]:47290 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731441AbfJNPoG (ORCPT ); Mon, 14 Oct 2019 11:44:06 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 60DE228; Mon, 14 Oct 2019 08:44:03 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C9CCC3F718; Mon, 14 Oct 2019 08:44:01 -0700 (PDT) Date: Mon, 14 Oct 2019 16:43:59 +0100 From: Mark Rutland To: Daniel Axtens Cc: 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, dvyukov@google.com, christophe.leroy@c-s.fr, linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory Message-ID: <20191014154359.GC20438@lakrids.cambridge.arm.com> References: <20191001065834.8880-1-dja@axtens.net> <20191001065834.8880-2-dja@axtens.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191001065834.8880-2-dja@axtens.net> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 01, 2019 at 04:58:30PM +1000, Daniel Axtens wrote: > Hook into vmalloc and vmap, and dynamically allocate real shadow > memory to back the mappings. > > 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. > > To avoid the difficulties around swapping mappings around, this code > expects that the part of the shadow region that covers the vmalloc > space will not be covered by the early shadow page, but will be left > unmapped. This will require changes in arch-specific code. > > This allows KASAN with VMAP_STACK, and may be helpful for architectures > that do not have a separate module space (e.g. powerpc64, which I am > currently working on). It also allows relaxing the module alignment > back to PAGE_SIZE. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202009 > Acked-by: Vasily Gorbik > Signed-off-by: Daniel Axtens > [Mark: rework shadow allocation] > Signed-off-by: Mark Rutland Sorry to point this out so late, but your S-o-B should come last in the chain per Documentation/process/submitting-patches.rst. Judging by the rest of that, I think you want something like: Co-developed-by: Mark Rutland Signed-off-by: Mark Rutland [shadow rework] Signed-off-by: Daniel Axtens ... leaving yourself as the Author in the headers. Sorry to have made that more complicated! [...] > +static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, > + void *unused) > +{ > + unsigned long page; > + > + page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT); > + > + spin_lock(&init_mm.page_table_lock); > + > + if (likely(!pte_none(*ptep))) { > + pte_clear(&init_mm, addr, ptep); > + free_page(page); > + } There should be TLB maintenance between clearing the PTE and freeing the page here. Thanks, Mark. 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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 1B68EECE587 for ; Mon, 14 Oct 2019 15:46:31 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 86F622133F for ; Mon, 14 Oct 2019 15:46:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 86F622133F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46sNFw1jdWzDqt0 for ; Tue, 15 Oct 2019 02:46:28 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=mark.rutland@arm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=arm.com Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 46sNCC0LghzDqnM for ; Tue, 15 Oct 2019 02:44:05 +1100 (AEDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 60DE228; Mon, 14 Oct 2019 08:44:03 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C9CCC3F718; Mon, 14 Oct 2019 08:44:01 -0700 (PDT) Date: Mon, 14 Oct 2019 16:43:59 +0100 From: Mark Rutland To: Daniel Axtens Subject: Re: [PATCH v8 1/5] kasan: support backing vmalloc space with real shadow memory Message-ID: <20191014154359.GC20438@lakrids.cambridge.arm.com> References: <20191001065834.8880-1-dja@axtens.net> <20191001065834.8880-2-dja@axtens.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191001065834.8880-2-dja@axtens.net> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: gor@linux.ibm.com, x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, glider@google.com, luto@kernel.org, aryabinin@virtuozzo.com, linuxppc-dev@lists.ozlabs.org, dvyukov@google.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Oct 01, 2019 at 04:58:30PM +1000, Daniel Axtens wrote: > Hook into vmalloc and vmap, and dynamically allocate real shadow > memory to back the mappings. > > 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. > > To avoid the difficulties around swapping mappings around, this code > expects that the part of the shadow region that covers the vmalloc > space will not be covered by the early shadow page, but will be left > unmapped. This will require changes in arch-specific code. > > This allows KASAN with VMAP_STACK, and may be helpful for architectures > that do not have a separate module space (e.g. powerpc64, which I am > currently working on). It also allows relaxing the module alignment > back to PAGE_SIZE. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202009 > Acked-by: Vasily Gorbik > Signed-off-by: Daniel Axtens > [Mark: rework shadow allocation] > Signed-off-by: Mark Rutland Sorry to point this out so late, but your S-o-B should come last in the chain per Documentation/process/submitting-patches.rst. Judging by the rest of that, I think you want something like: Co-developed-by: Mark Rutland Signed-off-by: Mark Rutland [shadow rework] Signed-off-by: Daniel Axtens ... leaving yourself as the Author in the headers. Sorry to have made that more complicated! [...] > +static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, > + void *unused) > +{ > + unsigned long page; > + > + page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT); > + > + spin_lock(&init_mm.page_table_lock); > + > + if (likely(!pte_none(*ptep))) { > + pte_clear(&init_mm, addr, ptep); > + free_page(page); > + } There should be TLB maintenance between clearing the PTE and freeing the page here. Thanks, Mark.