selftests/bpf: fix test_cgroup_storage on s390

test_cgroup_storage fails on s390 with an assertion failure: packets are
dropped when they shouldn't. The problem is that BPF_DW packet count is
accessed as BPF_W with an offset of 0, which is not correct on
big-endian machines.

Since the point of this test is not to verify narrow loads/stores,
simply use BPF_DW when working with packet counts.

Fixes: 68cfa3a ("selftests/bpf: add a cgroup storage test")
Fixes: 919646d ("selftests/bpf: extend the storage test to test per-cpu cgroup storage")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/test_cgroup_storage.c

@@ -20,17 +20,17 @@ int main(int argc, char **argv)
 		BPF_MOV64_IMM(BPF_REG_2, 0), /* flags, not used */
 		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
 			     BPF_FUNC_get_local_storage),
-		BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_0, 0),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_0, 0),
 		BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 0x1),
-		BPF_STX_MEM(BPF_W, BPF_REG_0, BPF_REG_3, 0),
+		BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_3, 0),
 
 		BPF_LD_MAP_FD(BPF_REG_1, 0), /* map fd */
 		BPF_MOV64_IMM(BPF_REG_2, 0), /* flags, not used */
 		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
 			     BPF_FUNC_get_local_storage),
 		BPF_MOV64_IMM(BPF_REG_1, 1),
 		BPF_STX_XADD(BPF_DW, BPF_REG_0, BPF_REG_1, 0),
-		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_0, 0),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, 0),
 		BPF_ALU64_IMM(BPF_AND, BPF_REG_1, 0x1),
 		BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
 		BPF_EXIT_INSN(),