linux-kernel - Re: [PATCH] tracing: fprobe-event: Fix to check tracepoint event and return

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Date:   Mon, 6 Nov 2023 17:28:11 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: fprobe-event: Fix to check tracepoint event
 and return

On Sat,  4 Nov 2023 01:05:34 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Fix to check the tracepoint event is not valid with $retval.
> The commit 08c9306fc2e3 ("tracing/fprobe-event: Assume fprobe is
> a return event by $retval") introduced automatic return probe
> conversion with $retval. But since tracepoint event does not
> support return probe, $retval is not acceptable.

Can you add the command that causes this to fail.

-- Steve

> 
> Fixes: 08c9306fc2e3 ("tracing/fprobe-event: Assume fprobe is a return event by $retval")
> Cc: stable@...r.kernel.org
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_fprobe.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
> index 8bfe23af9c73..7d2ddbcfa377 100644
> --- a/kernel/trace/trace_fprobe.c
> +++ b/kernel/trace/trace_fprobe.c
> @@ -927,11 +927,12 @@ static int parse_symbol_and_return(int argc, const char *argv[],
>  	for (i = 2; i < argc; i++) {
>  		tmp = strstr(argv[i], "$retval");
>  		if (tmp && !isalnum(tmp[7]) && tmp[7] != '_') {
> +			if (is_tracepoint) {
> +				trace_probe_log_set_index(i);
> +				trace_probe_log_err(tmp - argv[i], RETVAL_ON_PROBE);
> +				return -EINVAL;
> +			}
>  			*is_return = true;
> -			/*
> -			 * NOTE: Don't check is_tracepoint here, because it will
> -			 * be checked when the argument is parsed.
> -			 */
>  			break;
>  		}
>  	}