Re: [PATCH bpf-next 1/2] selftests/bpf: skip verifier tests that depend on CONFIG_CGROUP_BPF

[Stanislav Fomichev <sdf@fomichev.me>]

On 12/12, Alexei Starovoitov wrote:
> On Wed, Dec 12, 2018 at 10:59:13AM -0800, Stanislav Fomichev wrote:
> > On 12/12, Alexei Starovoitov wrote:
> > > On Wed, Dec 12, 2018 at 10:27:24AM -0800, Stanislav Fomichev wrote:
> > > > The following prog types don't make sense without bpf cgroup:
> > > > * BPF_PROG_TYPE_CGROUP_SKB
> > > > * BPF_PROG_TYPE_CGROUP_SOCK
> > > > * BPF_PROG_TYPE_CGROUP_SOCK_ADDR
> > > > 
> > > > Skip running verifier tests that exercise these prog types if
> > > > kernel is built without proper support.
> > > > 
> > > > See commit e5c504858a18 ("selftests/bpf: skip verifier sockmap tests
> > > > on kernels without support") for original motivation.
> > > > 
> > > > Signed-off-by: Stanislav Fomichev <sdf@google.com>
> > > > ---
> > > >  tools/testing/selftests/bpf/test_verifier.c | 35 +++++++++++++++++++++
> > > >  1 file changed, 35 insertions(+)
> > > > 
> > > > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > > > index f5015566ae1b..b5470a399996 100644
> > > > --- a/tools/testing/selftests/bpf/test_verifier.c
> > > > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > > > @@ -44,6 +44,7 @@
> > > >  /* fallback to all features enabled */
> > > >  # define CONFIG_BPF_STREAM_PARSER 1
> > > >  # define CONFIG_XDP_SOCKETS 1
> > > > +# define CONFIG_CGROUP_BPF 1
> > > 
> > > I really don't like where these is going.
> > > I think previous set should be reverted.
> > > This is not a scalable approach.
> > > Use libbpf probing approach to check whether feature is present instead.
> > I can probably add runtime probing instead of depending on compile-time
> > config, but I think that we would still need some per-test mechanism
> > to say that it depends on feature X (per-test .config_disabled or
> > similar).
> > Will moving these checks to runtime address your concern? (there is sill a
> > scalability issue though)
> 
> you said it youself. config_disabled doesn't scale.
> hence it's not a solution regardless of macro or runtime probing.
Let me see if I can use per-test prog_type for this type of probing.
Load 'return 0' program per-prog_type and use it as an indication of
runtime support. This should probably work in the majority of the cases.
I'll get back to you shortly.