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
> +
> + ret = ctx->ret;
> + /* bpf_prog_load() loads "test_pkt_access.o" with BPF_F_TEST_RND_HI32
> + * which randomizes upper 32 bits after BPF_ALU32 insns.
> + * Hence after 'w0 <<= 1' upper bits of $rax are random.
> + * That is expected and correct. Trim them.
> + */
> + ret = (__u32) ret;
> + if (len != 74 || ret != 148)
> + return 0;
> + test_result_subprog2 = 1;
> + return 0;
> +}
> +char _license[] SEC("license") = "GPL";
> --
> 2.23.0
>
