linux-kernel - Re: [PATCH v19 00/15] arm64: untag user pointers passed to the kernel

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Message-ID: <96fd8da4-a912-f6cc-2b32-5791027dbbd5@intel.com>
Date:   Thu, 1 Aug 2019 08:36:47 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Kevin Brodsky <kevin.brodsky@....com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-rdma@...r.kernel.org, linux-media@...r.kernel.org,
        kvm@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Yishai Hadas <yishaih@...lanox.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Alexander Deucher <Alexander.Deucher@....com>,
        Christian Koenig <Christian.Koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Khalid Aziz <khalid.aziz@...cle.com>, enh <enh@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christoph Hellwig <hch@...radead.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH v19 00/15] arm64: untag user pointers passed to the kernel

On 8/1/19 5:48 AM, Andrey Konovalov wrote:
> On Thu, Aug 1, 2019 at 2:11 PM Kevin Brodsky <kevin.brodsky@....com> wrote:
>> On 31/07/2019 17:50, Dave Hansen wrote:
>>> On 7/23/19 10:58 AM, Andrey Konovalov wrote:
>>>> The mmap and mremap (only new_addr) syscalls do not currently accept
>>>> tagged addresses. Architectures may interpret the tag as a background
>>>> colour for the corresponding vma.
>>> What the heck is a "background colour"? :)
>> Good point, this is some jargon that we started using for MTE, the idea being that
>> the kernel could set a tag value (specified during mmap()) as "background colour" for
>> anonymous pages allocated in that range.
>>
>> Anyway, this patch series is not about MTE. Andrey, for v20 (if any), I think it's
>> best to drop this last sentence to avoid any confusion.
> Sure, thanks!

OK, but what does that mean for tagged addresses getting passed to
mmap/mremap?  That sentence read to me like "architectures might allow
tags for ...something...".  So do we accept tagged addresses into those
syscalls?