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

[Masami Hiramatsu]

(2013/11/27 22:30), Ingo Molnar wrote:
> 
> * Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx> wrote:
> 
>> (2013/11/22 11:35), Masami Hiramatsu wrote:
>>> (2013/11/21 16:29), Ingo Molnar wrote:
>>>>
>>>> * Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx> wrote:
>>>>
>>>>> (2013/11/21 2:36), Frank Ch. Eigler wrote:
>>>>
>>>> [ ... ]
>>>>>> 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. [...]
>>>>
>>>> Then it needs to be fixed ASAP!
>>>
>>> OK, I see. At least the two patches included this series
>>> should be fixed. :)
>>>
>>> And more, I need to test all symbols and drills down.
>>
>> OK, what I've found was;
>>  - The functions which can be ftraced look good.
>>    (see tracing/available_filter_functions)
>>  - following functions should not be able to be probed.
>>    - memcpy, memset
>>    - native_load_sp0 and some other native functions (need to be clear)
>>    - restore
>>    - trace_graph_return
>>    - trace_hardirqs_off_thunk, trace_hardirqs_on_thunk
>>    - This list still be not perfect. I just enabled/disabled kprobes
>>      one by one. There might be combined bugs (combination of several
>>      kprobes).
>>  - Some of them are hard to specify by NOKPROBE_SYMBOL because they are
>>    defined in assembly file.
>>
>> Anyway, to fix all of them, I think we need file-based blacklist
>> especially for assembler symbols.
> 
> assembler symbols shouldn't be particular hard either, just put them 
> into the noprobes section.

Would you mean .kprobes.text? Hmm, I hope not to use it anymore,
but yeah, bugfix is more important. Agreed.

>> For example, we can get all text symbols by below command;
>>  nm some-file.o | grep -i " t " | cut -f3 -d" "
>> so that we can make a blacklisted-symbol list for the file.
>> I need to look the Kbuild for how I can do that in Makefile.
> 
> I think it's generally better to add explicit annotations to the code.

OK, thus I'll add annotations first.

Thank you!

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


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