netdev - Re: [PATCH v2 bpf-next] selftests/bpf: fix "alu with different scalars 1" on s390

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Message-ID: <CAADnVQ+H9bOW+EY6=AKt7mqgdEgaPhc1Wk_o=Ez43CracLCaiA@mail.gmail.com>
Date:   Mon, 15 Jul 2019 15:13:05 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Ilya Leoshkevich <iii@...ux.ibm.com>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Y Song <ys114321@...il.com>
Subject: Re: [PATCH v2 bpf-next] selftests/bpf: fix "alu with different
 scalars 1" on s390

On Thu, Jul 4, 2019 at 1:53 AM Ilya Leoshkevich <iii@...ux.ibm.com> wrote:
>
> BPF_LDX_MEM is used to load the least significant byte of the retrieved
> test_val.index, however, on big-endian machines it ends up retrieving
> the most significant byte.
>
> Use the correct least significant byte offset on big-endian machines.
>
> Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
> ---
>
> v1->v2:
> - use __BYTE_ORDER instead of __BYTE_ORDER__.
>
>  tools/testing/selftests/bpf/verifier/value_ptr_arith.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/verifier/value_ptr_arith.c b/tools/testing/selftests/bpf/verifier/value_ptr_arith.c
> index c3de1a2c9dc5..e5940c4e8b8f 100644
> --- a/tools/testing/selftests/bpf/verifier/value_ptr_arith.c
> +++ b/tools/testing/selftests/bpf/verifier/value_ptr_arith.c
> @@ -183,7 +183,11 @@
>         BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
>         BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 1),
>         BPF_EXIT_INSN(),
> +#if __BYTE_ORDER == __LITTLE_ENDIAN
>         BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, 0),
> +#else
> +       BPF_LDX_MEM(BPF_B, BPF_REG_1, BPF_REG_0, sizeof(int) - 1),
> +#endif

I think tests should be arch and endian independent where possible.
In this case test_val.index is 4 byte and 4 byte load should work just as well.