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Re: Re: Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and general cleaning of kprobe blacklist
- From: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- To: Ingo Molnar <mingo at kernel dot org>
- Cc: "Frank Ch. Eigler" <fche at redhat dot com>, linux-arch at vger dot kernel dot org, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Sandeepa Prabhu <sandeepa dot prabhu at linaro dot org>, x86 at kernel dot org, lkml <linux-kernel at vger dot kernel dot org>, "Steven Rostedt (Red Hat)" <rostedt at goodmis dot org>, virtualization at lists dot linux-foundation dot org, systemtap at sourceware dot org, "David S. Miller" <davem at davemloft dot net>
- Date: Fri, 22 Nov 2013 20:46:14 +0900
- Subject: Re: Re: Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and general cleaning of kprobe blacklist
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- References: <20131120042148 dot 15296 dot 88360 dot stgit at kbuild-fedora dot novalocal> <y0mvbznxi6k dot fsf at fche dot csb> <20131120153801 dot GA9743 at gmail dot com> <20131120173600 dot GK8993 at redhat dot com> <528D6C9F dot 8050809 at hitachi dot com> <20131121072938 dot GA16912 at gmail dot com> <528EC2FF dot 30301 at hitachi dot com>
(2013/11/22 11:35), Masami Hiramatsu wrote:
> (2013/11/21 16:29), Ingo Molnar wrote:
>>
>> * Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> 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.
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.
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com