linux-kernel - Re: [PATCH] x86, kasan: add KASAN checks to atomic operations

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Message-ID: <20170306203500.GR6500@twins.programming.kicks-ass.net>
Date:   Mon, 6 Mar 2017 21:35:00 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Ingo Molnar <mingo@...hat.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, will.deacon@....com
Subject: Re: [PATCH] x86, kasan: add KASAN checks to atomic operations

On Mon, Mar 06, 2017 at 04:20:18PM +0000, Mark Rutland wrote:
> > >> So the problem is doing load/stores from asm bits, and GCC
> > >> (traditionally) doesn't try and interpret APP asm bits.
> > >>
> > >> However, could we not write a GCC plugin that does exactly that?
> > >> Something that interprets the APP asm bits and generates these KASAN
> > >> bits that go with it?

> I don't think there's much you'll be able to do within the compiler,
> assuming you mean to derive this from the asm block inputs and outputs.

Nah, I was thinking about a full asm interpreter.

> Those can hide address-generation (e.g. with per-cpu stuff), which the
> compiler may erroneously be detected as racing.
> 
> Those may also take fake inputs (e.g. the sp input to arm64's
> __my_cpu_offset()) which may confuse matters.
> 
> Parsing the assembly itself will be *extremely* painful due to the way
> that's set up for run-time patching.

Argh, yah, completely forgot about all that alternative and similar
nonsense :/