On Tue, 3 Aug 2021 15:42:02 +0300
Yordan Karadzhov <y.karadz@xxxxxxxxx> wrote:
> On 2.08.21 г. 19:29, Steven Rostedt wrote:
> > What I was talking about is to change tep_print_field() to do something like:
> >
> > Take the current tep_print_field() and turn it into static _tep_print_field().
> >
> > [ Not even compiled tested ]
> >
>
> Hi Steven,
>
> I am not able to make sense from the code below.
>
> > void tep_print_field(struct trace_seq *s, void *data,
> > struct tep_format_field *field)
> > {
> > struct tep_event = field->event;
> > struct tep_print_parse = event->print_fmt.print_cache;
> > struct tep_handle *tep = event->tep;
> > unsigned int offset, len;
> >
> > if (event->flags & TEP_EVENT_FL_FAILED)
> > goto out;
> >
> > if (field->flags & TEP_FIELD_IS_DYNAMIC)
> > dynamic_offset(tep, field, data, &offset, &len);
> >
> > for (;parse; parse = parse->next) {
>
> You need
> if (!parse->arg)
> continue;
Sure. Like I said, I never even compiled this ;-)
>
> > if (parse->type == PRINT_FMT_STRING)
> > continue;
> > if (parse->arg->type != TEP_PRINT_FIELD)
> > continue;
>
> I can't understand the idea of those two checks. I printed the values and they don't seem to have any selective power.
Well, the print_cache stores portions of the print fmt format string. Where if you have something like:
print fmt: "fd: 0x%08lx, offset: 0x%08lx, count: 0x%08lx", ((unsigned long)(REC->fd)), ((unsigned long)(REC->offset)), ((unsigned long)(REC->count))
The "fd: " part is a PRINT_FMT_STRING. We don't want anything to do with that.
But the cache part that has fields, should be an arg of type
TEP_PRINT_FIELD, which should be mapped to some field to print. That
is, one of the REC->fd, REC->offset or REC->count.
That's what you are looking to see how to print it. As it also contains
how that field should be printed normally.
>
> > if (parse->arg->field.field->field != field)
> > continue;
> >
>
> This does not compile. I guess you mean
> if (parse->arg->field.field != field)
> continue;
>
> however "parse->arg->field.field" looks like unused memory (NULL or 0xffffffff) and this check always fails.
>
> Maybe we must call some of the process_XXX()static functions first in order to make your new version of
> tep_print_field() works?
How are you calling it? After loading the tep with tracefs_local_events()?
Because it should be loaded via tep_parse_event(), which calll
parse_args() and load the args to the event.
Basically we should be doing what print_event_cache() does, but only
for the field we are interested in.
-- Steve
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