Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753350AbcCGSXe (ORCPT ); Mon, 7 Mar 2016 13:23:34 -0500 Received: from aserp1040.oracle.com ([141.146.126.69]:44301 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752082AbcCGSXX (ORCPT ); Mon, 7 Mar 2016 13:23:23 -0500 Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI) To: Andy Lutomirski References: <1456951177-23579-1-git-send-email-khalid.aziz@oracle.com> <20160305.230702.1325379875282120281.davem@davemloft.net> <56DD9949.1000106@oracle.com> <20160307.115626.807716799249471744.davem@davemloft.net> <56DDC2B6.6020009@oracle.com> Cc: David Miller , Jonathan Corbet , Andrew Morton , dingel@linux.vnet.ibm.com, bob.picco@oracle.com, "Kirill A. Shutemov" , "Aneesh Kumar K.V" , Andrea Arcangeli , Arnd Bergmann , sparclinux@vger.kernel.org, Rob Gardner , Michal Hocko , chris.hyser@oracle.com, Richard Weinberger , Vlastimil Babka , Konstantin Khlebnikov , Oleg Nesterov , Greg Thelen , Jan Kara , xiexiuqi@huawei.com, Vineet.Gupta1@synopsys.com, Andrew Lutomirski , "Eric W. Biederman" , Benjamin Segall , Geert Uytterhoeven , Davidlohr Bueso , Alexey Dobriyan , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , linux-arch , Linux API From: Khalid Aziz Organization: Oracle Corp Message-ID: <56DDC6E0.4000907@oracle.com> Date: Mon, 7 Mar 2016 11:22:24 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2009 Lines: 58 On 03/07/2016 11:08 AM, Andy Lutomirski wrote: > On Mon, Mar 7, 2016 at 10:04 AM, Khalid Aziz wrote: >> On 03/07/2016 09:56 AM, David Miller wrote: >>> >>> From: Khalid Aziz >>> Date: Mon, 7 Mar 2016 08:07:53 -0700 >>> >>>> PR_GET_SPARC_ADICAPS >>> >>> >>> Put this into a new ELF auxiliary vector entry via ARCH_DLINFO. >>> >>> So now all that's left is supposedly the TAG stuff, please explain >>> that to me so I can direct you to the correct existing interface to >>> provide that as well. >>> >>> Really, try to avoid prtctl, it's poorly typed and almost worse than >>> ioctl(). >>> >> >> The two remaining operations I am looking at are: >> >> 1. Is PSTATE.mcde bit set for the process? PR_SET_SPARC_ADI provides this in >> its return value in the patch I sent. >> >> 2. Is TTE.mcd set for a given virtual address? PR_GET_SPARC_ADI_STATUS >> provides this function in the patch I sent. >> >> Setting and clearing version tags can be done entirely from userspace: >> >> while (addr < end) { >> asm volatile( >> "stxa %1, [%0]ASI_MCD_PRIMARY\n\t" >> : >> : "r" (addr), "r" (version)); >> addr += adicap.blksz; >> } >> so I do not have to add any kernel code for tags. > > Is the effect of that to change the tag associated with a page to > which the caller has write access? No, it changes the tag associated with the virtual address for the caller. Physical page backing this virtual address is unaffected. Tag checking is done for virtual addresses. The one restriction where physical address is relevant is when two processes map the same physical page, they both have to use the same tag for the virtual addresses that map on to the shared physical pages. > > I sense DoS issues in your future. > Are you concerned about DoS even if the tag is associated with virtual address, not physical address? Thanks, Khalid