selftests/bpf: Add test for bpf array map iterators

Two subtests are added.
$ ./test_progs -n 4
...
#4/20 bpf_array_map:OK
#4/21 bpf_percpu_array_map:OK
...

The bpf_array_map subtest also tested bpf program
changing array element values and send key/value
to user space through bpf_seq_write() interface.

Signed-off-by: Yonghong Song <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

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

···
 #include "bpf_iter_test_kern4.skel.h"
 #include "bpf_iter_bpf_hash_map.skel.h"
 #include "bpf_iter_bpf_percpu_hash_map.skel.h"
+#include "bpf_iter_bpf_array_map.skel.h"
+#include "bpf_iter_bpf_percpu_array_map.skel.h"
 
 static int duration;
 
···
 	bpf_iter_bpf_percpu_hash_map__destroy(skel);
 }
 
+static void test_bpf_array_map(void)
+{
+	__u64 val, expected_val = 0, res_first_val, first_val = 0;
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	__u32 expected_key = 0, res_first_key;
+	struct bpf_iter_bpf_array_map *skel;
+	int err, i, map_fd, iter_fd;
+	struct bpf_link *link;
+	char buf[64] = {};
+	int len, start;
+
+	skel = bpf_iter_bpf_array_map__open_and_load();
+	if (CHECK(!skel, "bpf_iter_bpf_array_map__open_and_load",
+		  "skeleton open_and_load failed\n"))
+		return;
+
+	map_fd = bpf_map__fd(skel->maps.arraymap1);
+	for (i = 0; i < bpf_map__max_entries(skel->maps.arraymap1); i++) {
+		val = i + 4;
+		expected_key += i;
+		expected_val += val;
+
+		if (i == 0)
+			first_val = val;
+
+		err = bpf_map_update_elem(map_fd, &i, &val, BPF_ANY);
+		if (CHECK(err, "map_update", "map_update failed\n"))
+			goto out;
+	}
+
+	opts.map_fd = map_fd;
+	link = bpf_program__attach_iter(skel->progs.dump_bpf_array_map, &opts);
+	if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+		goto out;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+		goto free_link;
+
+	/* do some tests */
+	start = 0;
+	while ((len = read(iter_fd, buf + start, sizeof(buf) - start)) > 0)
+		start += len;
+	if (CHECK(len < 0, "read", "read failed: %s\n", strerror(errno)))
+		goto close_iter;
+
+	/* test results */
+	res_first_key = *(__u32 *)buf;
+	res_first_val = *(__u64 *)(buf + sizeof(__u32));
+	if (CHECK(res_first_key != 0 || res_first_val != first_val,
+		  "bpf_seq_write",
+		  "seq_write failure: first key %u vs expected 0, "
+		  " first value %llu vs expected %llu\n",
+		  res_first_key, res_first_val, first_val))
+		goto close_iter;
+
+	if (CHECK(skel->bss->key_sum != expected_key,
+		  "key_sum", "got %u expected %u\n",
+		  skel->bss->key_sum, expected_key))
+		goto close_iter;
+	if (CHECK(skel->bss->val_sum != expected_val,
+		  "val_sum", "got %llu expected %llu\n",
+		  skel->bss->val_sum, expected_val))
+		goto close_iter;
+
+	for (i = 0; i < bpf_map__max_entries(skel->maps.arraymap1); i++) {
+		err = bpf_map_lookup_elem(map_fd, &i, &val);
+		if (CHECK(err, "map_lookup", "map_lookup failed\n"))
+			goto out;
+		if (CHECK(i != val, "invalid_val",
+			  "got value %llu expected %u\n", val, i))
+			goto out;
+	}
+
+close_iter:
+	close(iter_fd);
+free_link:
+	bpf_link__destroy(link);
+out:
+	bpf_iter_bpf_array_map__destroy(skel);
+}
+
+static void test_bpf_percpu_array_map(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+	struct bpf_iter_bpf_percpu_array_map *skel;
+	__u32 expected_key = 0, expected_val = 0;
+	int err, i, j, map_fd, iter_fd;
+	struct bpf_link *link;
+	char buf[64];
+	void *val;
+	int len;
+
+	val = malloc(8 * bpf_num_possible_cpus());
+
+	skel = bpf_iter_bpf_percpu_array_map__open();
+	if (CHECK(!skel, "bpf_iter_bpf_percpu_array_map__open",
+		  "skeleton open failed\n"))
+		return;
+
+	skel->rodata->num_cpus = bpf_num_possible_cpus();
+
+	err = bpf_iter_bpf_percpu_array_map__load(skel);
+	if (CHECK(!skel, "bpf_iter_bpf_percpu_array_map__load",
+		  "skeleton load failed\n"))
+		goto out;
+
+	/* update map values here */
+	map_fd = bpf_map__fd(skel->maps.arraymap1);
+	for (i = 0; i < bpf_map__max_entries(skel->maps.arraymap1); i++) {
+		expected_key += i;
+
+		for (j = 0; j < bpf_num_possible_cpus(); j++) {
+			*(__u32 *)(val + j * 8) = i + j;
+			expected_val += i + j;
+		}
+
+		err = bpf_map_update_elem(map_fd, &i, val, BPF_ANY);
+		if (CHECK(err, "map_update", "map_update failed\n"))
+			goto out;
+	}
+
+	opts.map_fd = map_fd;
+	link = bpf_program__attach_iter(skel->progs.dump_bpf_percpu_array_map, &opts);
+	if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+		goto out;
+
+	iter_fd = bpf_iter_create(bpf_link__fd(link));
+	if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+		goto free_link;
+
+	/* do some tests */
+	while ((len = read(iter_fd, buf, sizeof(buf))) > 0)
+		;
+	if (CHECK(len < 0, "read", "read failed: %s\n", strerror(errno)))
+		goto close_iter;
+
+	/* test results */
+	if (CHECK(skel->bss->key_sum != expected_key,
+		  "key_sum", "got %u expected %u\n",
+		  skel->bss->key_sum, expected_key))
+		goto close_iter;
+	if (CHECK(skel->bss->val_sum != expected_val,
+		  "val_sum", "got %u expected %u\n",
+		  skel->bss->val_sum, expected_val))
+		goto close_iter;
+
+close_iter:
+	close(iter_fd);
+free_link:
+	bpf_link__destroy(link);
+out:
+	bpf_iter_bpf_percpu_array_map__destroy(skel);
+}
+
 void test_bpf_iter(void)
 {
 	if (test__start_subtest("btf_id_or_null"))
···
 		test_bpf_hash_map();
 	if (test__start_subtest("bpf_percpu_hash_map"))
 		test_bpf_percpu_hash_map();
+	if (test__start_subtest("bpf_array_map"))
+		test_bpf_array_map();
+	if (test__start_subtest("bpf_percpu_array_map"))
+		test_bpf_percpu_array_map();
 }

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

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct key_t {
+	int a;
+	int b;
+	int c;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 3);
+	__type(key, __u32);
+	__type(value, __u64);
+} arraymap1 SEC(".maps");
+
+__u32 key_sum = 0;
+__u64 val_sum = 0;
+
+SEC("iter/bpf_map_elem")
+int dump_bpf_array_map(struct bpf_iter__bpf_map_elem *ctx)
+{
+	__u32 *key = ctx->key;
+	__u64 *val = ctx->value;
+
+	if (key == (void *)0 || val == (void *)0)
+		return 0;
+
+	bpf_seq_write(ctx->meta->seq, key, sizeof(__u32));
+	bpf_seq_write(ctx->meta->seq, val, sizeof(__u64));
+	key_sum += *key;
+	val_sum += *val;
+	*val = *key;
+	return 0;
+}

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

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct key_t {
+	int a;
+	int b;
+	int c;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, 3);
+	__type(key, __u32);
+	__type(value, __u32);
+} arraymap1 SEC(".maps");
+
+/* will set before prog run */
+volatile const __u32 num_cpus = 0;
+
+__u32 key_sum = 0, val_sum = 0;
+
+SEC("iter/bpf_map_elem")
+int dump_bpf_percpu_array_map(struct bpf_iter__bpf_map_elem *ctx)
+{
+	__u32 *key = ctx->key;
+	void *pptr = ctx->value;
+	__u32 step;
+	int i;
+
+	if (key == (void *)0 || pptr == (void *)0)
+		return 0;
+
+	key_sum += *key;
+
+	step = 8;
+	for (i = 0; i < num_cpus; i++) {
+		val_sum += *(__u32 *)pptr;
+		pptr += step;
+	}
+	return 0;
+}