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Re: Re: Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and general cleaning of kprobe blacklist
- From: Ingo Molnar <mingo at kernel dot org>
- To: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- 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: Wed, 27 Nov 2013 14:30:45 +0100
- 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> <528F4406 dot 3090309 at hitachi dot com>
* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
> (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.
assembler symbols shouldn't be particular hard either, just put them
into the noprobes section.
> 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.
Thanks,
Ingo