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

A test case is added for hashmap and percpu hashmap. The test
also exercises nested bpf_for_each_map_elem() calls like
    bpf_prog:
      bpf_for_each_map_elem(func1)
    func1:
      bpf_for_each_map_elem(func2)
    func2:

  $ ./test_progs -n 45
  #45/1 hash_map:OK
  #45 for_each:OK
  Summary: 1/1 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/20210226204933.3885657-1-yhs@fb.com

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

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "for_each_hash_map_elem.skel.h"
+
+static unsigned int duration;
+
+static void test_hash_map(void)
+{
+ int i, err, hashmap_fd, max_entries, percpu_map_fd;
+ struct for_each_hash_map_elem *skel;
+ __u64 *percpu_valbuf = NULL;
+ __u32 key, num_cpus, retval;
+ __u64 val;
+
+ skel = for_each_hash_map_elem__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "for_each_hash_map_elem__open_and_load"))
+ return;
+
+ hashmap_fd = bpf_map__fd(skel->maps.hashmap);
+ max_entries = bpf_map__max_entries(skel->maps.hashmap);
+ for (i = 0; i < max_entries; i++) {
+ key = i;
+ val = i + 1;
+ err = bpf_map_update_elem(hashmap_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 = 1;
+ 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->hashmap_output, 4, "hashmap_output");
+ ASSERT_EQ(skel->bss->hashmap_elems, max_entries, "hashmap_elems");
+
+ key = 1;
+ err = bpf_map_lookup_elem(hashmap_fd, &key, &val);
+ ASSERT_ERR(err, "hashmap_lookup");
+
+ ASSERT_EQ(skel->bss->percpu_called, 1, "percpu_called");
+ ASSERT_LT(skel->bss->cpu, num_cpus, "num_cpus");
+ ASSERT_EQ(skel->bss->percpu_map_elems, 1, "percpu_map_elems");
+ ASSERT_EQ(skel->bss->percpu_key, 1, "percpu_key");
+ ASSERT_EQ(skel->bss->percpu_val, skel->bss->cpu + 1, "percpu_val");
+ ASSERT_EQ(skel->bss->percpu_output, 100, "percpu_output");
+out:
+ free(percpu_valbuf);
+ for_each_hash_map_elem__destroy(skel);
+}
+
+void test_for_each(void)
+{
+ if (test__start_subtest("hash_map"))
+ test_hash_map();
+}

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

@@ -0,0 +1,95 @@
+// 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_HASH);
+ __uint(max_entries, 3);
+ __type(key, __u32);
+ __type(value, __u64);
+} hashmap SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_HASH);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, __u64);
+} percpu_map SEC(".maps");
+
+struct callback_ctx {
+ struct __sk_buff *ctx;
+ int input;
+ int output;
+};
+
+static __u64
+check_hash_elem(struct bpf_map *map, __u32 *key, __u64 *val,
+ struct callback_ctx *data)
+{
+ struct __sk_buff *skb = data->ctx;
+ __u32 k;
+ __u64 v;
+
+ if (skb) {
+ k = *key;
+ v = *val;
+ if (skb->len == 10000 && k == 10 && v == 10)
+ data->output = 3; /* impossible path */
+ else
+ data->output = 4;
+ } else {
+ data->output = data->input;
+ bpf_map_delete_elem(map, key);
+ }
+
+ return 0;
+}
+
+__u32 cpu = 0;
+__u32 percpu_called = 0;
+__u32 percpu_key = 0;
+__u64 percpu_val = 0;
+int percpu_output = 0;
+
+static __u64
+check_percpu_elem(struct bpf_map *map, __u32 *key, __u64 *val,
+ struct callback_ctx *unused)
+{
+ struct callback_ctx data;
+
+ percpu_called++;
+ cpu = bpf_get_smp_processor_id();
+ percpu_key = *key;
+ percpu_val = *val;
+
+ data.ctx = 0;
+ data.input = 100;
+ data.output = 0;
+ bpf_for_each_map_elem(&hashmap, check_hash_elem, &data, 0);
+ percpu_output = data.output;
+
+ return 0;
+}
+
+int hashmap_output = 0;
+int hashmap_elems = 0;
+int percpu_map_elems = 0;
+
+SEC("classifier")
+int test_pkt_access(struct __sk_buff *skb)
+{
+ struct callback_ctx data;
+
+ data.ctx = skb;
+ data.input = 10;
+ data.output = 0;
+ hashmap_elems = bpf_for_each_map_elem(&hashmap, check_hash_elem, &data, 0);
+ hashmap_output = data.output;
+
+ percpu_map_elems = bpf_for_each_map_elem(&percpu_map, check_percpu_elem,
+ (void *)0, 0);
+ return 0;
+}

tools/testing/selftests/bpf/test_progs.h

@@ -152,6 +152,17 @@ extern int test__join_cgroup(const char *path);
  ___ok; \
 })
 
+#define ASSERT_LT(actual, expected, name) ({ \
+ static int duration = 0; \
+ typeof(actual) ___act = (actual); \
+ typeof(expected) ___exp = (expected); \
+ bool ___ok = ___act < ___exp; \
+ CHECK(!___ok, (name), \
+ "unexpected %s: actual %lld >= expected %lld\n", \
+ (name), (long long)(___act), (long long)(___exp)); \
+ ___ok; \
+})
+
 #define ASSERT_STREQ(actual, expected, name) ({ \
  static int duration = 0; \
  const char *___act = actual; \