netdev - Re: [PATCH bpf-next 2/2] tools/bpf: selftests: add map lookup to test_map_in

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Date:   Wed, 27 Feb 2019 15:36:22 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 2/2] tools/bpf: selftests: add map lookup to
 test_map_in_map bpf prog

On Wed, Feb 27, 2019 at 1:24 PM Yonghong Song <yhs@...com> wrote:
>
> The bpf_map_lookup_elem is added in the bpf program.
> Without previous patch, the test change will trigger the
> following error:
>   $ ./test_maps
>   ...
>   ; value_p = bpf_map_lookup_elem(map, &key);
>   20: (bf) r1 = r7
>   21: (bf) r2 = r8
>   22: (85) call bpf_map_lookup_elem#1
>   ; if (!value_p || *value_p != 123)
>   23: (15) if r0 == 0x0 goto pc+16
>    R0=map_value(id=2,off=0,ks=4,vs=4,imm=0) R6=inv1 R7=map_ptr(id=0,off=0,ks=4,vs=4,imm=0)
>    R8=fp-8,call_-1 R10=fp0,call_-1 fp-8=mmmmmmmm
>   ; if (!value_p || *value_p != 123)
>   24: (61) r1 = *(u32 *)(r0 +0)
>    R0=map_value(id=2,off=0,ks=4,vs=4,imm=0) R6=inv1 R7=map_ptr(id=0,off=0,ks=4,vs=4,imm=0)
>    R8=fp-8,call_-1 R10=fp0,call_-1 fp-8=mmmmmmmm
>   bpf_spin_lock cannot be accessed directly by load/store
>
> With the kernel fix in the previous commit, the error goes away.
>
> Signed-off-by: Yonghong Song <yhs@...com>
> ---
>  tools/testing/selftests/bpf/progs/test_map_in_map.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/test_map_in_map.c b/tools/testing/selftests/bpf/progs/test_map_in_map.c
> index ce923e67e08e..2985f262846e 100644
> --- a/tools/testing/selftests/bpf/progs/test_map_in_map.c
> +++ b/tools/testing/selftests/bpf/progs/test_map_in_map.c
> @@ -27,6 +27,7 @@ SEC("xdp_mimtest")
>  int xdp_mimtest0(struct xdp_md *ctx)
>  {
>         int value = 123;
> +       int *value_p;
>         int key = 0;
>         void *map;
>
> @@ -35,6 +36,9 @@ int xdp_mimtest0(struct xdp_md *ctx)
>                 return XDP_DROP;
>
>         bpf_map_update_elem(map, &key, &value, 0);
> +       value_p = bpf_map_lookup_elem(map, &key);
> +       if (!value_p || *value_p != 123)
> +               return XDP_DROP;
>
>         map = bpf_map_lookup_elem(&mim_hash, &key);
>         if (!map)
> --
> 2.17.1
>

LGTM.

Acked-by: Andrii Nakryiko <andriin@...com>