linux-kernel - RE: [PATCH v5 00/18] Rework READ

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Message-ID: <9ba9552bd68a4461bb346dc3bae71d7a@AcuMS.aculab.com>
Date:   Wed, 13 May 2020 13:21:06 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Will Deacon' <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
CC:     Marco Elver <elver@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: RE: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen

From: Will Deacon
> Sent: 13 May 2020 13:40
> On Wed, May 13, 2020 at 02:32:43PM +0200, Peter Zijlstra wrote:
> > On Wed, May 13, 2020 at 01:48:41PM +0200, Marco Elver wrote:
> >
> > > Disabling most instrumentation for arch/x86 is reasonable. Also fine
> > > with the __READ_ONCE/__WRITE_ONCE changes (your improved
> > > compiler-friendlier version).
> > >
> > > We likely can't have both: still instrument __READ_ONCE/__WRITE_ONCE
> > > (as Will suggested) *and* avoid double-instrumentation in arch_atomic.
> > > If most use-cases of __READ_ONCE/__WRITE_ONCE are likely to use
> > > data_race() or KCSAN_SANITIZE := n anyway, I'd say it's reasonable for
> > > now.
> 
> I agree that Peter's patch is the right thing to do for now. I was hoping we
> could instrument __{READ,WRITE}_ONCE(), but that we before I realised that
> __no_sanitize_or_inline doesn't seem to do anything.

Could something be done that put the addresses of the instructions
into a separate segment and have KASAN check that table before
reporting an actual error?

	David

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