linux-kernel - Re: Re: Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash

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Date:	Thu, 21 Mar 2013 22:23:33 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Timo Juhani Lindfors <timo.lindfors@....fi>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Nadia Yvette Chambers <nyc@...omorphy.com>,
	yrl.pp-manager.tt@...achi.com,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: Re: Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash_64() into
 .text.kprobe section

(2013/03/21 20:39), Ingo Molnar wrote:
> 
> * Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> 
>> (2013/03/19 5:57), Timo Juhani Lindfors wrote:
>>> Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> writes:
>>>> Thank you for reporting!!
>>>
>>> Thanks for fixing these! I spent some time trying to automate the
>>> process of finding sensitive functions and eventually resorted into
>>> booting a kvm instance with a minimal initrd to test every single
>>> function in a clean and reproducible environment.
>>>
>>> I found 7 more cases where calling register_kprobe() leads to an instant
>>> kernel panic:
>>>
>>> __flush_tlb_single
>>> native_flush_tlb
>>> native_safe_halt
>>> native_set_pgd
>>> native_set_pmd
>>> native_set_pud
>>> native_write_cr0
>>
>> Ah, right and Great! these native_* things are too fundamental one.
>> Hmm, curiously, those are defined as inline functions, and
>> I also couldn't find some of those symbols even with your previous
>> kconfig.
>>
>>> You can see full kernel console output for each function at
>>> http://lindi.iki.fi/lindi/linux/kprobes/panics_2013-03-18/
>>
>> As you can see, your panic messages, most of them caused GFP.
>> This may mean that int3 software exception must not happened
>> on those sites. Not the recursive call.
>>
>> Perhaps, I'd better add those native_* things into symbol-name
>> based blacklist, instead of adding __kprobes, because those
>> are not related to kprobes recursion.
> 
> Blacklists are not really good in general - it's easy for a symbol to be 
> renamed and the blacklist misses them silently ...

Ah, right.

> 
> symbol name and annotation should go hand in hand.

Thus, I think we'd better moving __kprobes into compiler.h first.

Anyway, I'm still waiting for the actual kconfig from Timo,
because I couldn't reproduce the problem yet (no such symbols).

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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