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From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC][PATCH 0/3] kprobes/ftrace/x86: Function graph trace jprobes
Date: Thu, 29 Jan 2015 08:48:02 -0500	[thread overview]
Message-ID: <20150129084802.77431788@gandalf.local.home> (raw)
In-Reply-To: <54C9CD7C.3030402@hitachi.com>

On Thu, 29 Jan 2015 15:04:44 +0900
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
 
> Hmm, could you make this more generic? Maybe we can directly call
> ftrace_return_to_handler() from longjmp_break_handler().

I tried that, but because the longjump handlers can also be traced (and
I still want them to be :-) It makes things even more complicated to
get the stacks right. It's best to deal with the stack when you can.

> Actually, current implementation seems just skipping one return
> address, however, there may be possible to call jprobe_return() in
> the nested functions, like below;
> 
> void test_exit(int flag)
> {
> 	if (!flag)
> 		jprobe_return();
> }
> int jdo_fork(...)
> {
> 	...
> 	test_exit(something_to_test);
> 	...
> 	jprobe_return();
> 	return 0;
> }
> 
> I've tested similar code on this series and it crashed kernel.
> (I also checked that the above example can work safely without graph tracer)
> 

Ah yes, I missed this. I have a way to solve this but it's not going to
get done before the merge window. Thanks for the test case. I'll use
this and more complicated ones for future changes.

Thanks!

-- Steve


      reply	other threads:[~2015-01-29 13:48 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-28  4:30 Steven Rostedt
2015-01-28  4:30 ` [RFC][PATCH 1/3] ftrace/jprobes/x86: Allow jprobes to be graph traced if using fentry Steven Rostedt
2015-01-28  4:30 ` [RFC][PATCH 2/3] ftrace/jprobes/x86: Have function being probed be graph traced Steven Rostedt
2015-01-28  4:30 ` [RFC][PATCH 3/3] ftrace: Rename variable from old_hash_ops to old_ops_hash Steven Rostedt
2015-01-29  6:04 ` [RFC][PATCH 0/3] kprobes/ftrace/x86: Function graph trace jprobes Masami Hiramatsu
2015-01-29 13:48   ` Steven Rostedt [this message]

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