On Sun, Nov 10, 2019 at 09:04:58AM -0800, Andrii Nakryiko wrote:
> On Thu, Nov 7, 2019 at 10:43 PM Alexei Starovoitov <ast@xxxxxxxxxx> wrote:
> >
> > Add a test that attaches one FEXIT program to main sched_cls networking program
> > and two other FEXIT programs to subprograms. All three tracing programs
> > access return values and skb->len of networking program and subprograms.
> >
> > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> > ---
>
> Acked-by: Andrii Nakryiko <andriin@xxxxxx>
>
> > .../selftests/bpf/prog_tests/fexit_bpf2bpf.c | 76 ++++++++++++++++
> > .../selftests/bpf/progs/fexit_bpf2bpf.c | 91 +++++++++++++++++++
> > 2 files changed, 167 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
> > create mode 100644 tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c
> >
>
> [...]
>
> > +SEC("fexit/test_pkt_access_subprog2")
> > +int test_subprog2(struct args_subprog2 *ctx)
> > +{
> > + struct sk_buff *skb = (void *)ctx->args[0];
> > + __u64 ret;
> > + int len;
> > +
> > + bpf_probe_read(&len, sizeof(len),
> > + __builtin_preserve_access_index(&skb->len));
>
> nit: we have bpf_core_read() for this, but I suspect you may have
> wanted __builtin spelled out explicitly
exactly. it should have been bpf_probe_read_kernel though. will fix.
