linux-kernel - Re: [PATCH] x86/mm/ptdump: Fix soft lockup in page table walker.

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Date:   Fri, 10 Feb 2017 14:38:46 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        Tobias Regnery <tobias.regnery@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/mm/ptdump: Fix soft lockup in page table walker.

On Fri, Feb 10, 2017 at 02:02:19PM +0100, Dmitry Vyukov wrote:
> On Fri, Feb 10, 2017 at 1:15 PM, Andrey Ryabinin
> <aryabinin@...tuozzo.com> wrote:
> >
> >
> > On 02/10/2017 02:18 PM, Thomas Gleixner wrote:
> >> On Fri, 10 Feb 2017, Dmitry Vyukov wrote:

> >>> Could we default this rodata check to n under KASAN? Or at least print
> >>> some explanatory warning message before doing marking rodata (it
> >>> should be printed right before "hang", so if you stare at it for a
> >>> minute during each boot you realize that it may be related)?

Regardless of any optimisation work, I think it would make sense to both
log something in the debug_check_wx() and to default it off if KASAN is
selected.

That could be generic, so we don't have to alter each and every arch
port...

The WX check is a one-time boot check, and missing it for a KASAN kernel
isn't the end of the world, though I'd still like to be able to use the
userspace page table dumps.

Thanks,
Mark.