On Fri, Oct 11, 2019 at 6:29 PM Alexei Starovoitov <ast@xxxxxx> wrote:
>
> On 10/11/19 5:40 PM, Alexei Starovoitov wrote:
> >> But even if kernel supports attach_btf_id, I think users still need to
> >> opt in into specifying attach_btf_id by libbpf. Think about existing
> >> raw_tp programs that are using bpf_probe_read() because they were not
> >> created with this kernel feature in mind. They will suddenly stop
> >> working without any of user's fault.
> >
> > This one is excellent catch.
> > loop1.c should have caught it, since it has
> > SEC("raw_tracepoint/kfree_skb")
> > {
> > int nested_loops(volatile struct pt_regs* ctx)
> > .. = PT_REGS_RC(ctx);
> >
> > and verifier would have rejected it.
> > But the way the test is written it's not using libbpf's autodetect
> > of program type, so everything is passing.
>
> With:
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> index 1c01ee2600a9..e27156dce10d 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> @@ -67,7 +67,7 @@ void test_bpf_verif_scale(void)
> */
> { "pyperf600_nounroll.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>
> - { "loop1.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
> + { "loop1.o", BPF_PROG_TYPE_UNSPEC},
> { "loop2.o", BPF_PROG_TYPE_RAW_TRACEPOINT },
>
> libbpf prog auto-detection kicks in and ...
> # ./test_progs -n 3/10
> libbpf: load bpf program failed: Permission denied
> libbpf: -- BEGIN DUMP LOG ---
> libbpf:
> raw_tp 'kfree_skb' doesn't have 10-th argument
> invalid bpf_context access off=80 size=8
>
> Good :) The verifier is doing its job.
oh, another super intuitive error from verifier ;) 10th argument, what?..
