linux-kernel - Re: [PATCH] ftrace: distinguish kretprobe'd functions in trace logs

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Message-ID: <863e9df20810311233j13f996b8qa185cceddbd90849@mail.gmail.com>
Date:	Fri, 31 Oct 2008 15:33:00 -0400
From:	"Abhishek Sagar" <sagar.abhishek@...il.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Al Viro" <viro@...iv.linux.org.uk>, ananth@...ibm.com,
	jkenisto@...ibm.com, mhiramat@...hat.com
Subject: Re: [PATCH] ftrace: distinguish kretprobe'd functions in trace logs

On Fri, Oct 31, 2008 at 11:50 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> From: Steven Rostedt <srostedt@...hat.com>
> Subject: ftrace: use kretprobe trampoline name to test in output
>
> When a function is kprobed, the return address is set to the
> kprobe_trampoline, or something similar. This caused the output
> of the trace to look confusing when the parent seemed to be this
> "kprobe_trampoline" function.
>
> To fix this, Abhishek Sagar added a test of the instruction pointer
> of the parent to see if it matched the kprobe_trampoline. If it
> did, the output would print a "[unknown/kretprobe'd]" instead.
>
> Unfortunately, not all archs do this the same way, and the trampoline
> function may not be exported, which causes failures in builds.
>
> This patch will compare the name instead of the pointer to see
> if it matches. This prevents us from depending on a function from
> being exported, and should work on all archs. The worst that can
> happen is that an arch might use a different name and then we
> go back to the confusing output. At least the arch will still build.
>
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
>  kernel/trace/trace.c |   39 +++++++++++++++++++++------------------
>  1 file changed, 21 insertions(+), 18 deletions(-)

Looks good, and worked on x86-32.

Acked-by: Abhishek Sagar <sagar.abhishek@...il.com>
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