linux-kernel - Re: Re: [PATCH -tip v8 10/26] kprobes/x86: Allow probe on some kprobe preparation functions

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Date:	Thu, 27 Mar 2014 14:50:41 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org,
	fche@...hat.com, mingo@...hat.com, systemtap@...rceware.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: Re: [PATCH -tip v8 10/26] kprobes/x86: Allow probe on some
 kprobe preparation functions

(2014/03/25 4:35), Steven Rostedt wrote:
> On Wed, 05 Mar 2014 20:59:53 +0900
> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
>> There is no need to prohibit probing on the functions
>> used in preparation phase. Those are safely probed because
>> those are not invoked from breakpoint/fault/debug handlers,
>> there is no chance to cause recursive exceptions.
>>
>> Following functions are now removed from the kprobes blacklist.
>>  can_boost
>>  can_probe
>>  can_optimize
>>  is_IF_modifier
>>  __copy_instruction
>>  copy_optimized_instructions
>>  arch_copy_kprobe
>>  arch_prepare_kprobe
>>  arch_arm_kprobe
>>  arch_disarm_kprobe
>>  arch_remove_kprobe
> 
> Is there any possibility that the arm and disarm could cause issues if
> we have a probe in the middle of setting it?
> 
> I guess not, but I just wanted to ask, as your test only tested the
> start of function and not the middle of it.

OK, I've tested it by attached script which adds probes on every address
of the target function and run a testcase(register/unregister other probes),
and found no problem. :)

Thank you,


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




View attachment "kprobes_test.sh" of type "text/plain" (1867 bytes)