Re: [PATCH 6.1.y] tracing: Do not add length to print format in synthetic events

[Douglas Raillard <douglas.raillard@arm.com>]

Hi Sasha,

On 07-09-2025 23:25, Sasha Levin wrote:
>   1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index 385e9fbbfbe7c..c2817d0c05b69 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -383,13 +383,11 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter,
>   				str_field = (char *)entry + data_offset;
>   
>   				trace_seq_printf(s, print_fmt, se->fields[i]->name,
> -						 STR_VAR_LEN_MAX,
>   						 str_field,
>   						 i == se->n_fields - 1 ? "" : " ");
>   				n_u64++;
>   			} else {
>   				trace_seq_printf(s, print_fmt, se->fields[i]->name,
> -						 STR_VAR_LEN_MAX,
>   						 (char *)&entry->fields[n_u64],
>   						 i == se->n_fields - 1 ? "" : " ");
>   				n_u64 += STR_VAR_LEN_MAX / sizeof(u64);

This looks consistent to me with that patch:
[PATCH v2] tracing: Fix synth event printk format for str fields

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index e3f7d09e5512..f71e49cd35b0 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -305,7 +305,7 @@ static const char *synth_field_fmt(char *type)
         else if (strcmp(type, "gfp_t") == 0)
                 fmt = "%x";
         else if (synth_field_is_string(type))
-               fmt = "%.*s";
+               fmt = "%s";
         else if (synth_field_is_stack(type))
                 fmt = "%s";
  
I only tested the trace.dat route when writing it, thanks for catching this case.


Cheers,

Douglas