linux-kernel - Re: [BUG -tip] kmemleak and stacktrace cause page faul

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Message-ID: <20191023134413.GI12121@uranus.lan>
Date:   Wed, 23 Oct 2019 16:44:13 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, linux-mm@...ck.org,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [BUG -tip] kmemleak and stacktrace cause page faul

On Wed, Oct 23, 2019 at 03:38:40PM +0200, Thomas Gleixner wrote:
> > > 
> > > [0,2,4,5,6,8,10,12] are guard pages so 0 is not that crappy at all
> > 
> > Wait, Thomas, I might be wrong, but per-cpu is initialized to the pointer,
> > the memory for this estack_pages has not yet been allocated, no?
> 
> static const
> struct estack_pages estack_pages[CEA_ESTACK_PAGES] ____cacheline_aligned = {
>         EPAGERANGE(DF),
> 	EPAGERANGE(NMI),
> 	EPAGERANGE(DB1),
> 	EPAGERANGE(DB),
>         EPAGERANGE(MCE),
> };
> 
> It's statically allocated. So it's available from the very beginning.

Indeed, thanks! I happened to overlooked this moment.
...
> And as I explained to you properly decoded the values _ARE_ correct and
> make sense.

Yes, just posted the diff itself to be sure. Thanks a huge for
explanation, Thomas!