[PATCH bpf-next 2/2] tools/bpf: selftests: add map lookup to test_map_in_map bpf prog

[Yonghong Song]

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 <y...@fb.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