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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Wed, 24 Jul 2019 16:16:49 +0200
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Subject: Re: [PATCH v19 00/15] arm64: untag user pointers passed to the kernel
To:     Will Deacon <will@kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
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On Wed, Jul 24, 2019 at 4:02 PM Will Deacon <will@kernel.org> wrote:
>
> Hi Andrey,
>
> On Tue, Jul 23, 2019 at 08:03:29PM +0200, Andrey Konovalov wrote:
> > On Tue, Jul 23, 2019 at 7:59 PM Andrey Konovalov <andreyknvl@google.com> wrote:
> > >
> > > === Overview
> > >
> > > arm64 has a feature called Top Byte Ignore, which allows to embed pointer
> > > tags into the top byte of each pointer. Userspace programs (such as
> > > HWASan, a memory debugging tool [1]) might use this feature and pass
> > > tagged user pointers to the kernel through syscalls or other interfaces.
> > >
> > > Right now the kernel is already able to handle user faults with tagged
> > > pointers, due to these patches:
> > >
> > > 1. 81cddd65 ("arm64: traps: fix userspace cache maintenance emulation on a
> > >              tagged pointer")
> > > 2. 7dcd9dd8 ("arm64: hw_breakpoint: fix watchpoint matching for tagged
> > >               pointers")
> > > 3. 276e9327 ("arm64: entry: improve data abort handling of tagged
> > >               pointers")
> > >
> > > This patchset extends tagged pointer support to syscall arguments.
>
> [...]
>
> > Do you think this is ready to be merged?
> >
> > Should this go through the mm or the arm tree?
>
> I would certainly prefer to take at least the arm64 bits via the arm64 tree
> (i.e. patches 1, 2 and 15). We also need a Documentation patch describing
> the new ABI.

Sounds good! Should I post those patches together with the
Documentation patches from Vincenzo as a separate patchset?

Vincenzo, could you share the last version of the Documentation patches?

Thanks!

>
> Will