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SubjectRe: [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE_SYMBOL() and fixes crash bugs
(2013/12/05 19:21), Ingo Molnar wrote:
> * Masami Hiramatsu <> wrote:
>>> So we need both a maintainable and a sane/safe solution, and I'd
>>> like to apply the whole thing at once and be at ease that the
>>> solution is round. We should have done this years ago.
>> For the safeness of kprobes, I have an idea; introduce a whitelist
>> for dynamic events. AFAICS, the biggest unstable issue of kprobes
>> comes from putting *many* probes on the functions called from
>> tracers.
> If the number of 'noprobe' annotations is expected to explode then
> maybe another approach should be considered.

No, since this is a "quantitative" issue, the annotation helps us.

> For example in perf we detect recursion. Could kprobes do that and
> detect hitting a probe while running kprobes code, and ignore it [do
> an early return]?

Yes, the kprobe itself already has recursion detector and it rejects
calling handler.

> That way most of the annotations could be removed and kprobes would
> become inherently safe. Is there any complication I'm missing?

That is actually what I'm doing with cleanup patches. :)

Thank you,

IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory

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