On Fri, 11 Jul 2025 14:37:03 +0900
Masami Hiramatsu (Google) <mhira...@kernel.org> wrote:
> I investigated this but it is not possible to use update_event_fields()
> because that function is only used if the
> CONFIG_TRACE_EVAL_MAP_FILE=y.
That had better *not* be true, otherwise all the TRACE_DEFINE_ENUM() in
include/trace/events/*.h would be useless and those events would not
parse. Note, I usually run without that config enabled, so it would
most definitely break on me if this was true.
In the code we have:
----------------------8<----------------------
#else /* CONFIG_TRACE_EVAL_MAP_FILE */
static inline void trace_create_eval_file(struct dentry *d_tracer) { }
static inline void trace_insert_eval_map_file(struct module *mod,
struct trace_eval_map **start, int len) { }
#endif /* !CONFIG_TRACE_EVAL_MAP_FILE */
static void trace_insert_eval_map(struct module *mod,
struct trace_eval_map **start, int len)
{
struct trace_eval_map **map;
if (len <= 0)
return;
map = start;
trace_event_eval_update(map, len);
trace_insert_eval_map_file(mod, start, len);
}
---------------------->8----------------------
Notice the "#endif". The trace_insert_eval_map_file() is a nop, but the
trace_event_eval_update() is not. That has the call to
update_event_printk() and update_event_fields().
So it can most definitely be used when that config is not defined. That
config only creates a file to show you *what* was replaced. It doesn't
stop the replacing.
-- Steve
