Re: [PATCH bpf-next] bpf: add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

[Jiri Olsa <olsajiri@gmail.com>]

On Thu, Mar 09, 2023 at 09:16:53AM +0100, Jiri Olsa wrote:
> On Wed, Mar 08, 2023 at 10:53:51PM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Mon, Feb 13, 2023 at 10:09:21PM -0800, Alexei Starovoitov escreveu:
> > > On Mon, Feb 13, 2023 at 7:12 PM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
> > > > On Thu, Feb 9, 2023 at 5:29 AM Alan Maguire <alan.maguire@oracle.com> wrote:
> > > > > +++ b/scripts/pahole-flags.sh
> > > > > @@ -23,5 +23,8 @@ if [ "${pahole_ver}" -ge "124" ]; then
> > > > >         # see PAHOLE_HAS_LANG_EXCLUDE
> > > > >         extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
> > > > >  fi
> > > > > +if [ "${pahole_ver}" -ge "125" ]; then
> > > > > +       extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_inconsistent_proto --btf_gen_optimized"
> > > > > +fi
> > > >
> > > > We landed this too soon.
> > > > #229     tracing_struct:FAIL
> > > > is failing now.
> > > > since bpf_testmod.ko is missing a bunch of functions though they're global.
> > > >
> > > > I've tried a bunch of different flags and attributes, but none of them
> > > > helped.
> > > > The only thing that works is:
> > > > diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > > > b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > > > index 46500636d8cd..5fd0f75d5d20 100644
> > > > --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > > > +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> > > > @@ -28,6 +28,7 @@ struct bpf_testmod_struct_arg_2 {
> > > >         long b;
> > > >  };
> > > >
> > > > +__attribute__((optimize("-O0")))
> > > >  noinline int
> > > >  bpf_testmod_test_struct_arg_1(struct bpf_testmod_struct_arg_2 a, int
> > > > b, int c) {
> > > >
> > > > We cannot do:
> > > > --- a/tools/testing/selftests/bpf/bpf_testmod/Makefile
> > > > +++ b/tools/testing/selftests/bpf/bpf_testmod/Makefile
> > > > @@ -10,7 +10,7 @@ endif
> > > >  MODULES = bpf_testmod.ko
> > > >
> > > >  obj-m += bpf_testmod.o
> > > > -CFLAGS_bpf_testmod.o = -I$(src)
> > > > +CFLAGS_bpf_testmod.o = -I$(src) -O0
> > > >
> > > > The build fails due to asm stuff.
> > > >
> > > > Maybe we should make scripts/pahole-flags.sh selective
> > > > and don't apply skip_encoding_btf_inconsiste to bpf_testmod ?
> > > >
> > > > Thoughts?
> > > 
> > > It's even worse with clang compiled kernel:
> > 
> > I tested what is now in the master branch with both gcc and clang, on
> > fedora:37, Alan also tested it, Jiri, it would be great if you could
> > check if reverting the revert works for you as well.
> 
> ok, will check your master branch

looks good.. got no duplicates and passing bpf tests for both
gcc and clang setups

jirka