linux-kernel - Re: [PATCH] tracing/selftests: Fix kprobe event name test for .isra. functions

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Date: Tue, 21 May 2024 10:49:19 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH] tracing/selftests: Fix kprobe event name test for
 .isra. functions

On Mon, 20 May 2024 20:57:37 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> The kprobe_eventname.tc test checks if a function with .isra. can have a
> kprobe attached to it. It loops through the kallsyms file for all the
> functions that have the .isra. name, and checks if it exists in the
> available_filter_functions file, and if it does, it uses it to attach a
> kprobe to it.
> 
> The issue is that kprobes can not attach to functions that are listed more
> than once in available_filter_functions. With the latest kernel, the
> function that is found is: rapl_event_update.isra.0
> 
>   # grep rapl_event_update.isra.0 /sys/kernel/tracing/available_filter_functions
>   rapl_event_update.isra.0
>   rapl_event_update.isra.0
> 
> It is listed twice. This causes the attached kprobe to it to fail which in
> turn fails the test. Instead of just picking the function function that is
> found in available_filter_functions, pick the first one that is listed
> only once in available_filter_functions.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> Cc: stable@...r.kernel.org
> Fixes: 604e3548236de ("selftests/ftrace: Select an existing function in kprobe_eventname test")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  .../testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
> index 1f6981ef7afa..ba19b81cef39 100644
> --- a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
> +++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
> @@ -30,7 +30,8 @@ find_dot_func() {
>  	fi
>  
>  	grep " [tT] .*\.isra\..*" /proc/kallsyms | cut -f 3 -d " " | while read f; do
> -		if grep -s $f available_filter_functions; then
> +		cnt=`grep -s $f available_filter_functions | wc -l`;
> +		if [ $cnt -eq 1 ]; then
>  			echo $f
>  			break
>  		fi
> -- 
> 2.43.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>