On Wed, 21 Jun 2023 19:03:37 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Mon, 12 Jun 2023 20:58:57 +0900
> "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> wrote:
>
> > From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> >
> > To hide the first dummy 'data' argument on the tracepoint probe events,
> > the BTF argument array was modified (skip the first argument for tracepoint),
> > but the '$arg*' meta argument parser missed that.
> >
> > Fix to increment the argument index if it is tracepoint probe. And decrement
> > the index when searching the type of the argument.
>
> I'm curious. What if we want a variable that points to that data argument? ;-)
That is a dummy parameter which is passed when registering the callback, so
it is passed from trace_fprobe.c. Currently trace_fprobe.c passed NULL to
the data argument.
>
> Probably just add a new type I guess.
Yeah, if we get any idea to use it, it will be accessed by a new $-variable.
>
> Anyway,
>
> Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Thank you!
>
> -- Steve
>
> >
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> > ---
> > kernel/trace/trace_probe.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> > index 473e1c43bc57..643aa3a51d5a 100644
> > --- a/kernel/trace/trace_probe.c
> > +++ b/kernel/trace/trace_probe.c
> > @@ -456,7 +456,10 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code,
> >
> > if (name && !strcmp(name, varname)) {
> > code->op = FETCH_OP_ARG;
> > - code->param = i;
> > + if (ctx->flags & TPARG_FL_TPOINT)
> > + code->param = i + 1;
> > + else
> > + code->param = i;
> > return 0;
> > }
> > }
> > @@ -470,8 +473,11 @@ static const struct fetch_type *parse_btf_arg_type(int arg_idx,
> > struct btf *btf = traceprobe_get_btf();
> > const char *typestr = NULL;
> >
> > - if (btf && ctx->params)
> > + if (btf && ctx->params) {
> > + if (ctx->flags & TPARG_FL_TPOINT)
> > + arg_idx--;
> > typestr = type_from_btf_id(btf, ctx->params[arg_idx].type);
> > + }
> >
> > return find_fetch_type(typestr, ctx->flags);
> > }
>
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
