selftests/bpf: add test for bpf_for_each_map_elem() with different maps

A test is added for bpf_for_each_map_elem() with either an arraymap or a
hashmap.
$ tools/testing/selftests/bpf/test_progs -t for_each
 #93/1    for_each/hash_map:OK
 #93/2    for_each/array_map:OK
 #93/3    for_each/write_map_key:OK
 #93/4    for_each/multi_maps:OK
 #93      for_each:OK
Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240405025536.18113-4-lulie@linux.alibaba.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 49 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/for_each_multi_maps.c b/tools/testing/selftests/bpf/progs/for_each_multi_maps.c
new file mode 100644
index 000000000000..ff0bed7d4459
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/for_each_multi_maps.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 3);
+	__type(key, __u32);
+	__type(value, __u64);
+} arraymap SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 5);
+	__type(key, __u32);
+	__type(value, __u64);
+} hashmap SEC(".maps");
+
+struct callback_ctx {
+	int output;
+};
+
+u32 data_output = 0;
+int use_array = 0;
+
+static __u64
+check_map_elem(struct bpf_map *map, __u32 *key, __u64 *val,
+	       struct callback_ctx *data)
+{
+	data->output += *val;
+	return 0;
+}
+
+SEC("tc")
+int test_pkt_access(struct __sk_buff *skb)
+{
+	struct callback_ctx data;
+
+	data.output = 0;
+	if (use_array)
+		bpf_for_each_map_elem(&arraymap, check_map_elem, &data, 0);
+	else
+		bpf_for_each_map_elem(&hashmap, check_map_elem, &data, 0);
+	data_output = data.output;
+
+	return 0;
+}