selftests/bpf: Add arraymap test for bpf_for_each_map_elem() helper

A test is added for arraymap and percpu arraymap. The test also
exercises the early return for the helper which does not
traverse all elements.
    $ ./test_progs -n 45
    #45/1 hash_map:OK
    #45/2 array_map:OK
    #45 for_each:OK
    Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204934.3885756-1-yhs@fb.com

tools/testing/selftests/bpf/prog_tests/for_each.c

@@ -3,6 +3,7 @@
 #include <test_progs.h>
 #include <network_helpers.h>
 #include "for_each_hash_map_elem.skel.h"
+#include "for_each_array_map_elem.skel.h"
 
 static unsigned int duration;
 
@@ -66,8 +67,64 @@ out:
 	for_each_hash_map_elem__destroy(skel);
 }
 
+static void test_array_map(void)
+{
+	__u32 key, num_cpus, max_entries, retval;
+	int i, arraymap_fd, percpu_map_fd, err;
+	struct for_each_array_map_elem *skel;
+	__u64 *percpu_valbuf = NULL;
+	__u64 val, expected_total;
+
+	skel = for_each_array_map_elem__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "for_each_array_map_elem__open_and_load"))
+		return;
+
+	arraymap_fd = bpf_map__fd(skel->maps.arraymap);
+	expected_total = 0;
+	max_entries = bpf_map__max_entries(skel->maps.arraymap);
+	for (i = 0; i < max_entries; i++) {
+		key = i;
+		val = i + 1;
+		/* skip the last iteration for expected total */
+		if (i != max_entries - 1)
+			expected_total += val;
+		err = bpf_map_update_elem(arraymap_fd, &key, &val, BPF_ANY);
+		if (!ASSERT_OK(err, "map_update"))
+			goto out;
+	}
+
+	num_cpus = bpf_num_possible_cpus();
+	percpu_map_fd = bpf_map__fd(skel->maps.percpu_map);
+	percpu_valbuf = malloc(sizeof(__u64) * num_cpus);
+	if (!ASSERT_OK_PTR(percpu_valbuf, "percpu_valbuf"))
+		goto out;
+
+	key = 0;
+	for (i = 0; i < num_cpus; i++)
+		percpu_valbuf[i] = i + 1;
+	err = bpf_map_update_elem(percpu_map_fd, &key, percpu_valbuf, BPF_ANY);
+	if (!ASSERT_OK(err, "percpu_map_update"))
+		goto out;
+
+	err = bpf_prog_test_run(bpf_program__fd(skel->progs.test_pkt_access),
+				1, &pkt_v4, sizeof(pkt_v4), NULL, NULL,
+				&retval, &duration);
+	if (CHECK(err || retval, "ipv4", "err %d errno %d retval %d\n",
+		  err, errno, retval))
+		goto out;
+
+	ASSERT_EQ(skel->bss->arraymap_output, expected_total, "array_output");
+	ASSERT_EQ(skel->bss->cpu + 1, skel->bss->percpu_val, "percpu_val");
+
+out:
+	free(percpu_valbuf);
+	for_each_array_map_elem__destroy(skel);
+}
+
 void test_for_each(void)
 {
 	if (test__start_subtest("hash_map"))
 		test_hash_map();
+	if (test__start_subtest("array_map"))
+		test_array_map();
 }

tools/testing/selftests/bpf/progs/for_each_array_map_elem.c

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#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_PERCPU_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u64);
+} percpu_map SEC(".maps");
+
+struct callback_ctx {
+	int output;
+};
+
+static __u64
+check_array_elem(struct bpf_map *map, __u32 *key, __u64 *val,
+		 struct callback_ctx *data)
+{
+	data->output += *val;
+	if (*key == 1)
+		return 1; /* stop the iteration */
+	return 0;
+}
+
+__u32 cpu = 0;
+__u64 percpu_val = 0;
+
+static __u64
+check_percpu_elem(struct bpf_map *map, __u32 *key, __u64 *val,
+		  struct callback_ctx *data)
+{
+	cpu = bpf_get_smp_processor_id();
+	percpu_val = *val;
+	return 0;
+}
+
+u32 arraymap_output = 0;
+
+SEC("classifier")
+int test_pkt_access(struct __sk_buff *skb)
+{
+	struct callback_ctx data;
+
+	data.output = 0;
+	bpf_for_each_map_elem(&arraymap, check_array_elem, &data, 0);
+	arraymap_output = data.output;
+
+	bpf_for_each_map_elem(&percpu_map, check_percpu_elem, (void *)0, 0);
+	return 0;
+}