selftests/bpf: Add test to access integer type of variable array

Add prog test for accessing integer type of variable array in tracing
program.
In addition, hook load_balance function to access sd->span[0], only
to confirm whether the load is successful. Because there is no direct
way to trigger load_balance call.

Co-developed-by: Chengming Zhou <[email protected]>
Signed-off-by: Chengming Zhou <[email protected]>
Signed-off-by: Feng Zhou <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

1 files changed, 19 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_access_variable_array.c b/tools/testing/selftests/bpf/progs/test_access_variable_array.c
new file mode 100644
index 000000000000..808c49b79889
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_access_variable_array.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Bytedance */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+unsigned long span = 0;
+
+SEC("fentry/load_balance")
+int BPF_PROG(fentry_fentry, int this_cpu, struct rq *this_rq,
+		struct sched_domain *sd)
+{
+	span = sd->span[0];
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";