linux-kernel - Re: [tip:perf/urgent] perf symbols: Handle /proc/sys/kernel/kptr

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Message-ID: <BANLkTikiF8qUZL7tiVUgTyhiih0M=sQkpA@mail.gmail.com>
Date:	Fri, 27 May 2011 08:46:42 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
	mingo@...hat.com, eranian@...gle.com, tzanussi@...il.com,
	penberg@...helsinki.fi, efault@....de, peterz@...radead.org,
	davej@...hat.com, davem@...emloft.net, fweisbec@...il.com,
	kees.cook@...onical.com, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/urgent] perf symbols: Handle /proc/sys/kernel/kptr_restrict

On Fri, May 27, 2011 at 1:35 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> I think the biggest problem is that it is yelling at us even when i'm
> root - and root can access all the pointer values just fine:

Instead of looking at the kptr_restrict file, please just look at the
addresses in the kallsyms file, and if they are all zero, you know
that it's not a usable kallsyms file (and you can pretty much assume
that it's due to kptr_restrict).

So I think the whole symbol__read_kptr_restrict() thing is just
pointless. Don't do it.

                     Linus
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