[RFC PATCH bpf-next 2/2] selftests/bpf: Add a case to test global percpu data

[Leon Hwang <leon.hwang@linux.dev>]

If the arch, like s390x, does not support percpu insn, this case won't
test global percpu data by checking -EOPNOTSUPP when load prog.

cd tools/testing/selftests/bpf; ./test_progs -t global_percpu_data
124     global_percpu_data_init:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../bpf/prog_tests/global_data_init.c         | 83 ++++++++++++++++++-
 .../bpf/progs/test_global_percpu_data.c       | 21 +++++
 2 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/test_global_percpu_data.c

diff --git a/tools/testing/selftests/bpf/prog_tests/global_data_init.c b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
index 8466332d7406f..634ff531bf5a4 100644
--- a/tools/testing/selftests/bpf/prog_tests/global_data_init.c
+++ b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
+#include "test_global_percpu_data.skel.h"
 
 void test_global_data_init(void)
 {
@@ -8,7 +9,7 @@ void test_global_data_init(void)
 	__u8 *buff = NULL, *newval = NULL;
 	struct bpf_object *obj;
 	struct bpf_map *map;
-        __u32 duration = 0;
+	__u32 duration = 0;
 	size_t sz;
 
 	obj = bpf_object__open_file(file, NULL);
@@ -60,3 +61,83 @@ void test_global_data_init(void)
 	free(newval);
 	bpf_object__close(obj);
 }
+
+void test_global_percpu_data_init(void)
+{
+	struct test_global_percpu_data *skel = NULL;
+	u64 *percpu_data = NULL;
+	struct bpf_map *map;
+	size_t init_data_sz;
+	char buff[128] = {};
+	int init_value = 2;
+	int key, value_sz;
+	int prog_fd, err;
+	int *init_data;
+	int num_cpus;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = buff,
+		    .data_size_in = sizeof(buff),
+		    .repeat = 1,
+	);
+
+	num_cpus = libbpf_num_possible_cpus();
+	if (!ASSERT_GT(num_cpus, 0, "libbpf_num_possible_cpus"))
+		return;
+
+	percpu_data = calloc(num_cpus, sizeof(*percpu_data));
+	if (!ASSERT_FALSE(percpu_data == NULL, "calloc percpu_data"))
+		return;
+
+	value_sz = sizeof(*percpu_data) * num_cpus;
+	memset(percpu_data, 0, value_sz);
+
+	skel = test_global_percpu_data__open();
+	if (!ASSERT_OK_PTR(skel, "test_global_percpu_data__open"))
+		goto out;
+
+	map = skel->maps.data__percpu;
+	err = bpf_map__set_initial_value(map, &init_value,
+					 sizeof(init_value));
+	if (!ASSERT_OK(err, "bpf_map__set_initial_value"))
+		goto out;
+
+	init_data = bpf_map__initial_value(map, &init_data_sz);
+	if (!ASSERT_OK_PTR(init_data, "bpf_map__initial_value"))
+		goto out;
+
+	ASSERT_EQ(*init_data, init_value, "initial_value");
+	ASSERT_EQ(init_data_sz, sizeof(init_value), "initial_value size");
+
+	err = test_global_percpu_data__load(skel);
+	if (err == -EOPNOTSUPP)
+		goto out;
+	if (!ASSERT_OK(err, "test_global_percpu_data__load"))
+		goto out;
+
+	ASSERT_EQ(bpf_map__type(map), BPF_MAP_TYPE_PERCPU_ARRAY,
+		  "bpf_map__type");
+
+	prog_fd = bpf_program__fd(skel->progs.update_percpu_data);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "update_percpu_data");
+	ASSERT_EQ(topts.retval, 0, "update_percpu_data retval");
+
+	key = 0;
+	err = bpf_map__lookup_elem(map, &key, sizeof(key), percpu_data,
+				   value_sz, 0);
+	if (!ASSERT_OK(err, "bpf_map__lookup_elem"))
+		goto out;
+
+	if (!ASSERT_LT(skel->bss->curr_cpu, num_cpus, "curr_cpu"))
+		goto out;
+	ASSERT_EQ(percpu_data[skel->bss->curr_cpu], 1, "percpu_data");
+	if (num_cpus > 1)
+		ASSERT_EQ(percpu_data[(skel->bss->curr_cpu+1)%num_cpus],
+			  init_value, "init_value");
+
+out:
+	test_global_percpu_data__destroy(skel);
+	if (percpu_data)
+		free(percpu_data);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_global_percpu_data.c b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
new file mode 100644
index 0000000000000..2f01051b782c6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+
+#include <bpf/bpf_helpers.h>
+
+int percpu_data SEC(".data..percpu");
+int curr_cpu;
+
+SEC("tc")
+int update_percpu_data(struct __sk_buff *skb)
+{
+	curr_cpu = bpf_get_smp_processor_id();
+	percpu_data = 1;
+
+	return TC_ACT_OK;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.47.1