On Mon, Oct 26, 2020 at 3:14 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > On Fri, Oct 23, 2020 at 11:22:05AM -0700, Andrii Nakryiko wrote: > > On Thu, Oct 22, 2020 at 11:58 PM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > > > > > On Fri, Oct 23, 2020 at 07:36:57AM +0200, Jiri Olsa wrote: > > > > On Thu, Oct 22, 2020 at 01:00:19PM -0700, Andrii Nakryiko wrote: > > > > > > > > SNIP > > > > > > > > > > > > > > > > hi, > > > > > > FYI there's still no solution yet, so far the progress is: > > > > > > > > > > > > the proposed workaround was to use the negation -> we don't have > > > > > > DW_AT_declaration tag, so let's find out instead which DW_TAG_subprogram > > > > > > tags have attached code and skip them if they don't have any: > > > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060#c10 > > > > > > > > > > > > the attached patch is doing that, but the resulting BTF is missing > > > > > > several functions due to another bug in dwarf: > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1890107 > > > > > > > > > > It seems fine if there are only few functions (especially if those are > > > > > unlikely to be traced). Do you have an estimate of how many functions > > > > > have this second DWARF bug? > > > > > > > > it wasn't that many, I'll recheck > > > > > > 127 functions missing if the workaround is applied, list attached > > > > > > > some of those seem pretty useful... I guess the quick workaround in > > pahole would be to just remember function names that were emitted > > already. The problem with that is that we can pick a version without > > parameter names, which is not the end of the world, but certainly > > annoying. > > with the change below I seem to get all argument names > > the change assumes that we can skip dwarf functions with > no argument names, because if the function is defined in > the object, it needs to have argument names I'd love it if it was that simple, but I learn time and time again that DWARF and compilers tend to always have some bugs and gotchas with type information. But let's try and see, of course. > > so there will be eventualy dwarf definition of that function > with full argument names > > I wonder we could use this code as a check that the function > is present in the object ;-) but I think we need to keep > the symbols check as well > > I'll send that out together with the rest of the changes > > jirka > > > --- > diff --git a/btf_encoder.c b/btf_encoder.c > index 7e370eb48174..0c14ac210425 100644 > --- a/btf_encoder.c > +++ b/btf_encoder.c > @@ -397,6 +397,19 @@ static int config(struct btf_elf *btfe, bool do_percpu_vars) > return 0; > } > > +static bool has_arg_names(struct cu *cu, struct ftype *ftype) > +{ > + struct parameter *param; > + const char *name; > + > + ftype__for_each_parameter(ftype, param) { > + name = dwarves__active_loader->strings__ptr(cu, param->name); > + if (name == NULL) > + return false; > + } > + return true; > +} > + > int cu__encode_btf(struct cu *cu, int verbose, bool force, > bool skip_encoding_vars) > { > @@ -472,6 +485,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > int btf_fnproto_id, btf_fn_id; > const char *name; > > + if (!has_arg_names(cu, &fn->proto)) > + continue; > + > if (!generate_func(btfe, function__name(fn, cu))) > continue; > >
