[PATCH bpf-next v3 08/10] selftests/bpf: Add BPF iterator tests for resizable hash map

Mykyta Yatsenko
2026-04-24T19:51:22Z

From: Mykyta Yatsenko <yatsenko@meta.com>

Test basic BPF iterator functionality for BPF_MAP_TYPE_RHASH,
verifying all elements are visited.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
---
tools/testing/selftests/bpf/prog_tests/rhash.c | 63 ++++++++++++++++++++++
.../selftests/bpf/progs/bpf_iter_bpf_rhash_map.c | 34 ++++++++++++
2 files changed, 97 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/rhash.c b/tools/testing/selftests/bpf/prog_tests/rhash.c
index 0f6eec4fe1fe..7e5a5fbd70c2 100644
--- a/tools/testing/selftests/bpf/prog_tests/rhash.c
+++ b/tools/testing/selftests/bpf/prog_tests/rhash.c
@@ -4,6 +4,7 @@
#include <string.h>
#include <stdio.h>
#include "rhash.skel.h"
+#include "bpf_iter_bpf_rhash_map.skel.h"
#include <linux/bpf.h>
#include <linux/perf_event.h>
#include <sys/syscall.h>
@@ -39,6 +40,65 @@ static void rhash_run(const char *prog_name)
rhash__destroy(skel);
}

+static void rhash_iter_test(void)
+{
+ DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
+ struct bpf_iter_bpf_rhash_map *skel;
+ int err, i, len, map_fd, iter_fd;
+ union bpf_iter_link_info linfo;
+ u32 expected_key_sum = 0, key;
+ struct bpf_link *link;
+ u64 val = 0;
+ char buf[64];
+
+ skel = bpf_iter_bpf_rhash_map__open();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_bpf_rhash_map__open"))
+ return;
+
+ err = bpf_iter_bpf_rhash_map__load(skel);
+ if (!ASSERT_OK(err, "bpf_iter_bpf_rhash_map__load"))
+ goto out;
+
+ map_fd = bpf_map__fd(skel->maps.rhashmap);
+
+ /* Populate map with test data */
+ for (i = 0; i < 64; i++) {
+ key = i + 1;
+ expected_key_sum += key;
+
+ err = bpf_map_update_elem(map_fd, &key, &val, BPF_NOEXIST);
+ if (!ASSERT_OK(err, "map_update"))
+ goto out;
+ }
+
+ memset(&linfo, 0, sizeof(linfo));
+ linfo.map.map_fd = map_fd;
+ opts.link_info = &linfo;
+ opts.link_info_len = sizeof(linfo);
+
+ link = bpf_program__attach_iter(skel->progs.dump_bpf_rhash_map, &opts);
+ if (!ASSERT_OK_PTR(link, "attach_iter"))
+ goto out;
+
+ iter_fd = bpf_iter_create(bpf_link__fd(link));
+ if (!ASSERT_GE(iter_fd, 0, "create_iter"))
+ goto free_link;
+
+ do {
+ len = read(iter_fd, buf, sizeof(buf));
+ } while (len > 0);
+
+ ASSERT_EQ(skel->bss->key_sum, expected_key_sum, "key_sum");
+ ASSERT_EQ(skel->bss->elem_count, 64, "elem_count");
+
+ close(iter_fd);
+
+free_link:
+ bpf_link__destroy(link);
+out:
+ bpf_iter_bpf_rhash_map__destroy(skel);
+}
+
void test_rhash(void)
{
if (test__start_subtest("test_rhash_lookup_update"))
@@ -61,4 +121,7 @@ void test_rhash(void)

if (test__start_subtest("test_rhash_delete_nonexistent"))
rhash_run("test_rhash_delete_nonexistent");
+
+ if (test__start_subtest("test_rhash_iter"))
+ rhash_iter_test();
}
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_bpf_rhash_map.c b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_rhash_map.c
new file mode 100644
index 000000000000..86f6c0d5eadb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_bpf_rhash_map.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+ __uint(type, BPF_MAP_TYPE_RHASH);
+ __uint(map_flags, BPF_F_NO_PREALLOC);
+ __uint(max_entries, 64);
+ __type(key, __u32);
+ __type(value, __u64);
+} rhashmap SEC(".maps");
+
+__u32 key_sum = 0;
+__u64 val_sum = 0;
+__u32 elem_count = 0;
+__u32 err = 0;
+
+SEC("iter/bpf_map_elem")
+int dump_bpf_rhash_map(struct bpf_iter__bpf_map_elem *ctx)
+{
+ __u32 *key = ctx->key;
+ __u64 *val = ctx->value;
+
+ if (!key || !val)
+ return 0;
+
+ key_sum += *key;
+ val_sum += *val;
+ elem_count++;
+ return 0;
+}

--
2.52.0