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From: Christopher Lameter <cl@linux.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Tobin C . Harding" <me@tobin.cc>, linux-mm <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
Date: Mon, 11 Dec 2017 06:00:40 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1712110558560.19414@nuc-kabylake> (raw)
In-Reply-To: <CA+55aFzE0Z98KRT4rk3f3R0BcMqGMrHWHsaB9Aq02etwWm_hjg@mail.gmail.com>

On Sun, 10 Dec 2017, Linus Torvalds wrote:

> On Thu, Dec 7, 2017 at 2:17 AM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> >         if (cachep->flags & SLAB_STORE_USER) {
> > -               pr_err("Last user: [<%p>](%pSR)\n",
> > +               pr_err("Last user: [<%px>](%pSR)\n",
> >                        *dbg_userword(cachep, objp),
> >                        *dbg_userword(cachep, objp));
>
> Is there actually any point to the %px at all?
>
> Why not remove it? the _real_ information is printed out by %pSR, and
> that's both sufficient and useful in ways %px isn't.

This pointer refers to code so we can remove it.

>
> > -                               pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
> > +                               pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
> >                                        print_tainted(), cachep->name,
> >                                        realobj, size);
>
> and here, is the pointer actually interesting, or should we just give
> the offset to the allocation?
>
> But if the pointer is interesting, then ack.

The pointer here is to an slab object which could be important if one
wants to find the pointer value  in a hexdump of another object (f.e.
listhead) or other pointer information that is being inspected
in a debugging session.

WARNING: multiple messages have this Message-ID
From: Christopher Lameter <cl@linux.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
	Pekka Enberg <penberg@kernel.org>,
	David Rientjes <rientjes@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Tobin C . Harding" <me@tobin.cc>, linux-mm <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/slab: Do not hash pointers when debugging slab
Date: Mon, 11 Dec 2017 06:00:40 -0600 (CST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1712110558560.19414@nuc-kabylake> (raw)
In-Reply-To: <CA+55aFzE0Z98KRT4rk3f3R0BcMqGMrHWHsaB9Aq02etwWm_hjg@mail.gmail.com>

On Sun, 10 Dec 2017, Linus Torvalds wrote:

> On Thu, Dec 7, 2017 at 2:17 AM, Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> >         if (cachep->flags & SLAB_STORE_USER) {
> > -               pr_err("Last user: [<%p>](%pSR)\n",
> > +               pr_err("Last user: [<%px>](%pSR)\n",
> >                        *dbg_userword(cachep, objp),
> >                        *dbg_userword(cachep, objp));
>
> Is there actually any point to the %px at all?
>
> Why not remove it? the _real_ information is printed out by %pSR, and
> that's both sufficient and useful in ways %px isn't.

This pointer refers to code so we can remove it.

>
> > -                               pr_err("Slab corruption (%s): %s start=%p, len=%d\n",
> > +                               pr_err("Slab corruption (%s): %s start=%px, len=%d\n",
> >                                        print_tainted(), cachep->name,
> >                                        realobj, size);
>
> and here, is the pointer actually interesting, or should we just give
> the offset to the allocation?
>
> But if the pointer is interesting, then ack.

The pointer here is to an slab object which could be important if one
wants to find the pointer value  in a hexdump of another object (f.e.
listhead) or other pointer information that is being inspected
in a debugging session.

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  parent reply	other threads:[~2017-12-11 12:00 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-07 10:17 Geert Uytterhoeven
2017-12-07 11:13 ` Christopher Lameter
2017-12-07 11:13   ` Christopher Lameter
2017-12-07 18:43   ` Kees Cook
2017-12-07 18:43     ` Kees Cook
2017-12-07 20:15     ` Christopher Lameter
2017-12-07 20:15       ` Christopher Lameter
2017-12-10 20:45 ` Linus Torvalds
2017-12-10 20:45   ` Linus Torvalds
2017-12-11  8:08   ` Geert Uytterhoeven
2017-12-11  8:08     ` Geert Uytterhoeven
2017-12-11 12:00   ` Christopher Lameter [this message]
2017-12-11 12:00     ` Christopher Lameter

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