linux-kernel - Re: [RFC PATCH] UML: add support for KASAN under x86

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Message-ID: <CAKFsvUJu7NZpM0ER45zhSzte3ovkAvXBKx3Tppxci7O=0TwJMg@mail.gmail.com>
Date:   Thu, 6 Feb 2020 10:21:59 -0800
From:   Patricia Alfonso <trishalfonso@...gle.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     richard@....at, jdike@...toit.com,
        Brendan Higgins <brendanhiggins@...gle.com>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-um@...ts.infradead.org, David Gow <davidgow@...gle.com>,
        aryabinin@...tuozzo.com, Dmitry Vyukov <dvyukov@...gle.com>,
        anton.ivanov@...bridgegreys.com
Subject: Re: [RFC PATCH] UML: add support for KASAN under x86_64

On Thu, Jan 16, 2020 at 12:03 AM Johannes Berg
<johannes@...solutions.net> wrote:
>
> On Thu, 2020-01-16 at 08:57 +0100, Johannes Berg wrote:
> >
> > And if I remember from looking at KASAN, some of the constructors there
> > depended on initializing after the KASAN data structures were set up (or
> > at least allocated)? It may be that you solved that by allocating the
> > shadow so very early though.
>
> Actually, no ... it's still after main(), and the constructors run
> before.
>
> So I _think_ with the CONFIG_CONSTRUCTORS revert, this will no longer
> work (but happy to be proven wrong!), if so then I guess we do have to
> find a way to initialize the KASAN things from another (somehow
> earlier?) constructor ...
>
> Or find a way to fix CONFIG_CONSTRUCTORS and not revert, but I looked at
> it quite a bit and didn't.
>
> johannes

I've looked at this quite extensively over the past week or so. I was
able to initialize KASAN as one of the first things that gets executed
in main(), but constructors are, in fact, needed before main(). I
think it might be best to reintroduce constructors in a limited way to
allow KASAN to work in UML. I have done as much testing as I can on my
machine and this limited version seems to work, except when
STATIC_LINK is set. I will send some patches of what I have done so
far and we can talk more about it there. I would like to add your
name, Johannes, as a co-developed-by on that patch. If there is a
better way to give you credit for this, please let me know.

-- 
Patricia Alfonso