linux-kernel - Re: [PATCH] synthetic tracing: Fix trace

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Date: Thu, 15 Feb 2024 22:37:31 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Thorsten Blum <thorsten.blum@...lux.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] synthetic tracing: Fix trace_string() return value

On Wed, 14 Feb 2024 23:05:56 +0100
Thorsten Blum <thorsten.blum@...lux.com> wrote:

> Fix trace_string() by assigning the string length to the return variable
> which got lost in commit ddeea494a16f ("tracing/synthetic: Use union
> instead of casts") and caused trace_string() to always return 0.
> 

Good catch!

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

Fixes: ddeea494a16f ("tracing/synthetic: Use union instead of casts")
Cc: stable@...r.kernel.org

Thanks!

> Signed-off-by: Thorsten Blum <thorsten.blum@...lux.com>
> ---
>  kernel/trace/trace_events_synth.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index e7af286af4f1..c82b401a294d 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -441,8 +441,9 @@ static unsigned int trace_string(struct synth_trace_event *entry,
>  	if (is_dynamic) {
>  		union trace_synth_field *data = &entry->fields[*n_u64];
>  
> +		len = fetch_store_strlen((unsigned long)str_val);
>  		data->as_dynamic.offset = struct_size(entry, fields, event->n_u64) + data_size;
> -		data->as_dynamic.len = fetch_store_strlen((unsigned long)str_val);
> +		data->as_dynamic.len = len;
>  
>  		ret = fetch_store_string((unsigned long)str_val, &entry->fields[*n_u64], entry);
>  
> -- 
> 2.39.2
> 


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