From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
x86@kernel.org, lkml <linux-kernel@vger.kernel.org>,
"Steven Rostedt (Red Hat)" <rostedt@goodmis.org>,
systemtap@sourceware.org, "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE_SYMBOL() and fixes crash bugs
Date: Fri, 06 Dec 2013 23:26:00 -0000 [thread overview]
Message-ID: <52A25CF0.9030706@hitachi.com> (raw)
In-Reply-To: <CA+b37P3BywWsuNgjVfvxxK2acAbV7qd6R5UJd1UEYdHHuQ56ag@mail.gmail.com>
(2013/12/06 15:54), Sandeepa Prabhu wrote:
>>> I am not sure if this question is related, uprobes or ftrace code does
>>> not define __kprobes, so is it safe to place kprobe on uprobes or
>>> ftrace code?
>>
>> Yes, it is "safe" in qualitative meaning. But for ftrace code, it could
>> give a performance impact by miss-hitting. Since uprobe is independent
>> from kprobe, it should work.
>>
>>> Is it expected from arch code to support such cases?
>>
>> Yes, the arch dependent implementation is the key. If it shares some
>> code which can be called from miss-hit path, it should be blacklisted.
> well, isn't the blacklist only for those routines that can not be
> handled or may crash kernel, like the code sections called from
> exception kprobes exception handlers etc?
Yes, that's why the blacklist is needed.
> suppose if the probe on routine can miss-hit (probes re-cursing) but
> can be handled, it's only a quantitative issue (i.e. performance
> impact) so it should be *user's* problem right? I mean, as you said
> earlier about having white-list or a performance gatekeeper
> (systemtap), one can avoid such cases by white list or removing
> miss-hit probes dynamically. But a blacklisting a symbol means
> placing a probe on that *can not be handled* and can crash the system,
> is it correct?
Yes, exactly that is what I meant. :)
The blacklist is only for avoiding such fundamental issue, therefore,
it strongly depends on the architecture code.
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2013-12-06 23:26 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-04 1:34 Masami Hiramatsu
2013-12-04 1:34 ` [PATCH -tip v4 1/6] kprobes: Prohibit probing on .entry.text code Masami Hiramatsu
2013-12-04 1:35 ` [PATCH -tip v4 2/6] kprobes: Introduce NOKPROBE_SYMBOL() macro for blacklist Masami Hiramatsu
2013-12-04 1:36 ` [PATCH -tip v4 4/6] [BUGFIX] x86: Prohibit probing on native_set_debugreg Masami Hiramatsu
2013-12-04 1:36 ` [PATCH -tip v4 6/6] [RFC] kprobes/x86: Call exception handlers directly from do_int3/do_debug Masami Hiramatsu
2013-12-04 2:39 ` Steven Rostedt
2013-12-11 13:31 ` Jiri Kosina
2013-12-12 4:40 ` Masami Hiramatsu
2013-12-12 9:59 ` Jiri Kosina
2013-12-12 10:31 ` Masami Hiramatsu
2013-12-04 1:36 ` [PATCH -tip v4 5/6] [BUGFIX] x86: Prohibit probing on thunk functions and restore Masami Hiramatsu
2013-12-04 1:36 ` [PATCH -tip v4 3/6] [BUGFIX] kprobes/x86: Prohibit probing on debug_stack_* Masami Hiramatsu
2013-12-04 2:54 ` [PATCH -tip v4 0/6] kprobes: introduce NOKPROBE_SYMBOL() and fixes crash bugs Sandeepa Prabhu
2013-12-04 7:39 ` Masami Hiramatsu
2013-12-04 8:46 ` Sandeepa Prabhu
2013-12-04 23:32 ` Masami Hiramatsu
2013-12-04 8:46 ` Ingo Molnar
2013-12-04 23:28 ` Masami Hiramatsu
2013-12-05 10:21 ` Ingo Molnar
2013-12-06 2:34 ` Masami Hiramatsu
2013-12-10 15:28 ` Ingo Molnar
2013-12-11 2:12 ` Masami Hiramatsu
2013-12-11 13:34 ` Ingo Molnar
2013-12-12 6:02 ` Masami Hiramatsu
2013-12-12 14:03 ` Ingo Molnar
2013-12-12 20:42 ` Josh Stone
2013-12-13 5:34 ` Masami Hiramatsu
2013-12-13 6:06 ` Masami Hiramatsu
2013-12-16 10:53 ` Masami Hiramatsu
2013-12-05 13:08 ` Sandeepa Prabhu
2013-12-06 6:23 ` Masami Hiramatsu
2013-12-06 6:54 ` Sandeepa Prabhu
2013-12-06 23:26 ` Masami Hiramatsu [this message]
2013-12-05 14:49 ` Frank Ch. Eigler
2013-12-06 6:13 ` Masami Hiramatsu
2013-12-06 19:08 ` Frank Ch. Eigler
2013-12-06 23:19 ` Masami Hiramatsu
2013-12-07 1:33 ` Frank Ch. Eigler
2013-12-07 2:35 ` Masami Hiramatsu
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