linux-kernel - Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and general cleaning of kprobe blacklist

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Message-ID: <528D6C9F.8050809@hitachi.com>
Date:	Thu, 21 Nov 2013 11:14:55 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-arch@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>, x86@...nel.org,
	lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	virtualization@...ts.linux-foundation.org,
	systemtap@...rceware.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and
 general cleaning of kprobe blacklist

(2013/11/21 2:36), Frank Ch. Eigler wrote:
> Hi -
> 
>>> Does this new blacklist cover enough that the kernel now survives a 
>>> broadly wildcarded perf-probe, e.g. over e.g. all of its kallsyms?
>>
>> That's generally the purpose of the annotations - if it doesn't then 
>> that's a bug.
> 
> AFAIK, no kernel since kprobes was introduced has ever stood up to
> that test.  perf probe lacks the wildcarding powers of systemtap, so
> one needs to resort to something like:
> 
> # cat /proc/kallsyms | grep ' [tT] ' | while read addr type symbol; do
>    perf probe $symbol
> done
> 
> then wait for a few hours for that to finish. Then, or while the loop
> is still running, run
> 
> # perf record -e 'probe:*' -aR sleep 1
> 
> to take a kernel down.

Um, indeed, current blacklist is not perfect. As I reported in this
series, I've found 2 more patterns. I guess there still have some
others.

But anyway, I don't think it is good to fix all such bugs
in this series.
This is just the first step to do it. :)

Thank you,

-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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