Sashiko commented:
> > + }
> > + *close = '\0';
> >
> > - ctx->offset += 1; /* for the '(' */
> > - /* We need to parse the nested one */
> > - ret = parse_probe_arg(tmp + 1, find_fetch_type(NULL,
> > ctx->flags),
> > - pcode, end, ctx);
> > - if (ret < 0)
> > - return ret;
> > - ctx->nested_level--;
> > - clear_struct_btf(ctx);
> > + /* We need to parse the nested one */
> > + ret = parse_probe_arg(tmp, find_fetch_type(NULL, ctx->flags),
> > + pcode, end, ctx);
>
> Does routing the nested argument through parse_probe_arg() instead of
> parse_btf_arg() break the documented eprobe syntax (STRUCT)FIELD->MEMBER?
> Since this patch removes the TPARG_FL_TEVENT handling block from
> parse_btf_arg(), and handle_typecast() now recursively invokes
> parse_probe_arg() on the extracted FIELD name, a bare eprobe FIELD name
> that does not start with a '$' prefix will hit the default case in
> parse_probe_arg().
> This causes it to be unconditionally rejected with -EINVAL (NOSUP_BTFARG)
> because eprobe flags (TPARG_FL_TEVENT) do not satisfy
> tparg_is_function_entry() or tparg_is_function_return(). This acts as an
> ABI breakage for existing user-space scripts relying on this eprobe syntax.
Wait... Did the type-casting support patch accidentally allow access to
event fields without the "$"?
Hmm, if so, it should be documented, and need to support correctly
with/without typecast.
Thank you,
--
Masami Hiramatsu (Google) <[email protected]>
