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From: Andy Lutomirski <luto@amacapital.net>
Date: Mon, 7 Mar 2016 10:08:24 -0800
Message-ID: <CALCETrXN43nT4zq2MpO90VrgK3k+DKHjOHWf7iOhS7TSBmdCPQ@mail.gmail.com>
Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: David Miller <davem@davemloft.net>, Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>, dingel@linux.vnet.ibm.com,
        bob.picco@oracle.com,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        sparclinux@vger.kernel.org, Rob Gardner <rob.gardner@oracle.com>,
        Michal Hocko <mhocko@suse.cz>, chris.hyser@oracle.com,
        Richard Weinberger <richard@nod.at>, Vlastimil Babka <vbabka@suse.cz>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Greg Thelen <gthelen@google.com>,
        Jan Kara <jack@suse.cz>, xiexiuqi@huawei.com,
        Vineet.Gupta1@synopsys.com, Andrew Lutomirski <luto@kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Benjamin Segall <bsegall@google.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>
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On Mon, Mar 7, 2016 at 10:04 AM, Khalid Aziz <khalid.aziz@oracle.com> wrote:
> On 03/07/2016 09:56 AM, David Miller wrote:
>>
>> From: Khalid Aziz <khalid.aziz@oracle.com>
>> 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?

I sense DoS issues in your future.