From: Arnaldo Carvalho de Melo <acme@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, paulus@samba.org, hpa@zytor.com,
mingo@redhat.com, eranian@google.com, tzanussi@gmail.com,
penberg@cs.helsinki.fi, efault@gmx.de, peterz@infradead.org,
davej@redhat.com, davem@davemloft.net, fweisbec@gmail.com,
kees.cook@canonical.com, tglx@linutronix.de,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/urgent] perf symbols: Handle /proc/sys/kernel/kptr_restrict
Date: Fri, 27 May 2011 12:57:14 -0300 [thread overview]
Message-ID: <20110527155714.GD2349@ghostprotocols.net> (raw)
In-Reply-To: <BANLkTikiF8qUZL7tiVUgTyhiih0M=sQkpA@mail.gmail.com>
Em Fri, May 27, 2011 at 08:46:42AM -0700, Linus Torvalds escreveu:
> On Fri, May 27, 2011 at 1:35 AM, Ingo Molnar <mingo@elte.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.
I thought about that, ended up using the file not to rely on the values
on kallsyms, too much future proofing, I guess.
BTW, the problem reported by Ingo above (yelling even for root) is not a
bug, he ran 'perf record' as non root with kptr_restrict set and then
ran 'perf report' as root.
- Arnaldo
next prev parent reply other threads:[~2011-05-27 15:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-26 19:21 [tip:perf/urgent] perf symbols: Handle /proc/sys/kernel/kptr_restrict tip-bot for Arnaldo Carvalho de Melo
2011-05-26 19:39 ` Ingo Molnar
2011-05-26 21:20 ` Arnaldo Carvalho de Melo
2011-05-27 8:38 ` Ingo Molnar
2011-05-26 21:28 ` Arnaldo Carvalho de Melo
2011-05-27 8:35 ` Ingo Molnar
2011-05-27 15:46 ` Linus Torvalds
2011-05-27 15:57 ` Arnaldo Carvalho de Melo [this message]
2011-05-26 21:30 ` Arnaldo Carvalho de Melo
2011-05-27 8:42 ` Ingo Molnar
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