On Tue, Jun 08, 2021 at 12:30:33PM -0700, John Fastabend wrote:
> This adds some extra noise to the tailcall_bpf2bpf4 tests that will cause
> verifier to patch insns. This then moves around subprog start/end insn
> index and poke descriptor insn index to ensure that verify and JIT will
> continue to track these correctly.
This test is the most complicated one where I tried to document the scope
of it on the side of prog_tests/tailcalls.c. I feel that it would make it
more difficult to debug it if under any circumstances something would have
been broken with that logic.
Maybe a separate test scenario? Or is this an overkill? If so, I would
vote for moving it to tailcall_bpf2bpf1.c and have a little comment that
testing other bpf helpers mixed in is in scope of that test.
>
> Reviewed-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
> ---
> .../selftests/bpf/progs/tailcall_bpf2bpf4.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf4.c b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf4.c
> index 9a1b166b7fbe..0d70de5f97e2 100644
> --- a/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf4.c
> +++ b/tools/testing/selftests/bpf/progs/tailcall_bpf2bpf4.c
> @@ -2,6 +2,13 @@
> #include <linux/bpf.h>
> #include <bpf/bpf_helpers.h>
>
> +struct {
> + __uint(type, BPF_MAP_TYPE_ARRAY);
> + __uint(max_entries, 1);
> + __uint(key_size, sizeof(__u32));
> + __uint(value_size, sizeof(__u32));
> +} nop_table SEC(".maps");
> +
> struct {
> __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
> __uint(max_entries, 3);
> @@ -11,9 +18,19 @@ struct {
>
> static volatile int count;
>
> +__noinline
> +int subprog_noise(struct __sk_buff *skb)
> +{
> + __u32 key = 0;
> +
> + bpf_map_lookup_elem(&nop_table, &key);
> + return 0;
> +}
> +
> __noinline
> int subprog_tail_2(struct __sk_buff *skb)
> {
> + subprog_noise(skb);
> bpf_tail_call_static(skb, &jmp_table, 2);
> return skb->len * 3;
> }
>
>
