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

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Date:	Tue, 25 Mar 2014 18:20:26 +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>
Subject: 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?

No problem at least on x86, since we need to take a text_mutex for
arm/disarm, those must not be called from int3/debug interrupts.

> I guess not, but I just wanted to ask, as your test only tested the
> start of function and not the middle of it.

No I've not tested yet. OK, I'll test it and report.

Thank you,

> 
> -- Steve
> 
> 
>>  arch_trampoline_kprobe
>>  arch_prepare_kprobe_ftrace
>>  arch_prepare_optimized_kprobe
>>  arch_check_optimized_kprobe
>>  arch_within_optimized_kprobe
>>  __arch_remove_optimized_kprobe
>>  arch_remove_optimized_kprobe
>>  arch_optimize_kprobes
>>  arch_unoptimize_kprobe
>>
> 
> 


-- 
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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