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

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Message-ID: <20131120125649.40ca99c3@gandalf.local.home>
Date:	Wed, 20 Nov 2013 12:56:49 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Frank Ch. Eigler" <fche@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	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>,
	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

On Wed, 20 Nov 2013 12:36:00 -0500
"Frank Ch. Eigler" <fche@...hat.com> 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

I'm curious to why one would do that. IIUC, perf now has function
tracing support.

-- Steve

> 
> 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.
> 
> 
> - FChE

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