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=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 A8445C433B4 for ; Wed, 12 May 2021 22:01:01 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 326CE613BD for ; Wed, 12 May 2021 22:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 326CE613BD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.126430.238001 (Exim 4.92) (envelope-from ) id 1lgwuE-0004LM-9C; Wed, 12 May 2021 22:00:38 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 126430.238001; Wed, 12 May 2021 22:00:38 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lgwuE-0004LF-5o; Wed, 12 May 2021 22:00:38 +0000 Received: by outflank-mailman (input) for mailman id 126430; Wed, 12 May 2021 22:00:36 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lgwuC-0004L9-Ro for xen-devel@lists.xenproject.org; Wed, 12 May 2021 22:00:36 +0000 Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 0dcb13c4-d187-4310-af71-02e1ea9606a3; Wed, 12 May 2021 22:00:36 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id AA374613BD; Wed, 12 May 2021 22:00:34 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 0dcb13c4-d187-4310-af71-02e1ea9606a3 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620856835; bh=uZq6wy4yE4KAlGFRiyHroM4bLsXCaJgs6J2sO/Z2u7I=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=KxcS5TBxEfCtc2xNmT7JxQF3oDdwUigV4axoiZpuy1phOYJpnG09y7His5vGGCFWb IxMSlbLNyQyzT1Zj3w0CAAup08JsI8anU+ec3zkaCN0JGHzPeGeORFHoMQ7zLLiJO7 JzRu5+UDDolVPM21JexGYC/PgOU57SgXM818rGXPpgsy55clelRzbYAZz1kkpXQoKR tb9anNKNZF3t5ig4tfN3G5gvT5pK/GQNfev4t5QKq7yN0KxjjyePrwKrIFpYV/OmHh wtBuWXsXGjaMvgXvtbJ05UXOBsOnGRsY2PvmtmHOH7oxahnKJ1gJzdENVgmjE6t/aw D+HLb5Rp3Ka/Q== Date: Wed, 12 May 2021 15:00:33 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: Julien Grall cc: xen-devel@lists.xenproject.org, Wei.Chen@arm.com, Henry.Wang@arm.com, Penny.Zheng@arm.com, Bertrand.Marquis@arm.com, Julien Grall , Stefano Stabellini , Volodymyr Babchuk Subject: Re: [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it In-Reply-To: <20210425201318.15447-9-julien@xen.org> Message-ID: References: <20210425201318.15447-1-julien@xen.org> <20210425201318.15447-9-julien@xen.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Sun, 25 Apr 2021, Julien Grall wrote: > From: Julien Grall > > Only the first 2GB of the virtual address space is shared between all > the page-tables on Arm32. > > There is a long outstanding TODO in xen_pt_update() stating that the > function is can only work with shared mapping. Nobody has ever called ^ remove > the function with private mapping, however as we add more callers > there is a risk to mess things up. > > Introduce a new define to mark the ened of the shared mappings and use ^end > it in xen_pt_update() to verify if the address is correct. > > Note that on Arm64, all the mappings are shared. Some compiler may > complain about an always true check, so the new define is not introduced > for arm64 and the code is protected with an #ifdef. On arm64 we could maybe define SHARED_VIRT_END to an arbitrarely large value, such as: #define SHARED_VIRT_END (1UL<<48) or: #define SHARED_VIRT_END DIRECTMAP_VIRT_END ? > Signed-off-by: Julien Grall > > --- > Changes in v2: > - New patch > --- > xen/arch/arm/mm.c | 11 +++++++++-- > xen/include/asm-arm/config.h | 4 ++++ > 2 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c > index 8fac24d80086..5c17cafff847 100644 > --- a/xen/arch/arm/mm.c > +++ b/xen/arch/arm/mm.c > @@ -1275,11 +1275,18 @@ static int xen_pt_update(unsigned long virt, > * For arm32, page-tables are different on each CPUs. Yet, they share > * some common mappings. It is assumed that only common mappings > * will be modified with this function. > - * > - * XXX: Add a check. > */ > const mfn_t root = virt_to_mfn(THIS_CPU_PGTABLE); > > +#ifdef SHARED_VIRT_END > + if ( virt > SHARED_VIRT_END || > + (SHARED_VIRT_END - virt) < nr_mfns ) The following would be sufficient, right? if ( virt + nr_mfns > SHARED_VIRT_END ) > + { > + mm_printk("Trying to map outside of the shared area.\n"); > + return -EINVAL; > + } > +#endif > + > /* > * The hardware was configured to forbid mapping both writeable and > * executable. > diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h > index c7b77912013e..85d4a510ce8a 100644 > --- a/xen/include/asm-arm/config.h > +++ b/xen/include/asm-arm/config.h > @@ -137,6 +137,10 @@ > > #define XENHEAP_VIRT_START _AT(vaddr_t,0x40000000) > #define XENHEAP_VIRT_END _AT(vaddr_t,0x7fffffff) > + > +/* The first 2GB is always shared between all the page-tables. */ > +#define SHARED_VIRT_END _AT(vaddr_t, 0x7fffffff) > + > #define DOMHEAP_VIRT_START _AT(vaddr_t,0x80000000) > #define DOMHEAP_VIRT_END _AT(vaddr_t,0xffffffff) > > -- > 2.17.1 >