linux-kernel - Re: [PATCH v2 sl-b 2/5] mm: Make mem_dump_obj() handle NULL and zero-sized pointers

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Date:   Wed, 9 Dec 2020 19:25:35 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, mingo@...nel.org, jiangshanlai@...il.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        iamjoonsoo.kim@....com, andrii@...nel.org,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org
Subject: Re: [PATCH v2 sl-b 2/5] mm: Make mem_dump_obj() handle NULL and
 zero-sized pointers

On Wed, Dec 09, 2020 at 06:48:47PM +0100, Vlastimil Babka wrote:
> On 12/9/20 2:13 AM, paulmck@...nel.org wrote:
> > From: "Paul E. McKenney" <paulmck@...nel.org>
> > 
> > This commit makes mem_dump_obj() call out NULL and zero-sized pointers
> > specially instead of classifying them as non-paged memory.
> > 
> > Cc: Christoph Lameter <cl@...ux.com>
> > Cc: Pekka Enberg <penberg@...nel.org>
> > Cc: David Rientjes <rientjes@...gle.com>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: <linux-mm@...ck.org>
> > Reported-by: Andrii Nakryiko <andrii@...nel.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Applied, thank you!

						Thanx, Paul

> > ---
> >  mm/util.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/mm/util.c b/mm/util.c
> > index d0e60d2..8c2449f 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -985,7 +985,12 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
> >  void mem_dump_obj(void *object)
> >  {
> >  	if (!virt_addr_valid(object)) {
> > -		pr_cont(" non-paged (local) memory.\n");
> > +		if (object == NULL)
> > +			pr_cont(" NULL pointer.\n");
> > +		else if (object == ZERO_SIZE_PTR)
> > +			pr_cont(" zero-size pointer.\n");
> > +		else
> > +			pr_cont(" non-paged (local) memory.\n");
> >  		return;
> >  	}
> >  	if (kmem_valid_obj(object)) {
> > 
>