[PATCH bpf-next v6 09/12] selftests/bpf: Add test to verify accessing rdonly percpu_array

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

Since percpu_array supports direct-read, it should not break accessing
rdonly percpu_array.

Add a test to verify that adding '.map_direct_value_addr' to percpu_array
won't break the case.

Assisted-by: Codex:gpt-5.5-xhigh
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 .../bpf/prog_tests/global_data_init.c         | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

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 ea7e4e3d91cf..f59d83919058 100644
--- a/tools/testing/selftests/bpf/prog_tests/global_data_init.c
+++ b/tools/testing/selftests/bpf/prog_tests/global_data_init.c
@@ -232,6 +232,48 @@ static void test_global_percpu_data_lskel(void)
 	free(online);
 }
 
+static void test_global_percpu_data_rdonly_direct_read(void)
+{
+	LIBBPF_OPTS(bpf_map_create_opts, map_opts,
+		    .map_flags = BPF_F_RDONLY_PROG,
+	);
+	struct bpf_insn insns[] = {
+		BPF_ST_MEM(BPF_W, BPF_REG_10, -8, 0),
+		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+		BPF_LD_MAP_FD(BPF_REG_1, 0),
+		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+		BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	int key = 0, map_fd, prog_fd = -1, err;
+	__u64 value = 0;
+
+	map_fd = bpf_map_create(BPF_MAP_TYPE_PERCPU_ARRAY, "percpu_ro_map", sizeof(int),
+				sizeof(__u64), 1, &map_opts);
+	if (!ASSERT_GE(map_fd, 0, "bpf_map_create"))
+		return;
+
+	err = bpf_map_update_elem(map_fd, &key, &value, BPF_F_ALL_CPUS);
+	if (!ASSERT_OK(err, "bpf_map_update_elem"))
+		goto out;
+
+	err = bpf_map_freeze(map_fd);
+	if (!ASSERT_OK(err, "bpf_map_freeze"))
+		goto out;
+
+	insns[3].imm = map_fd;
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "percpu_ro_prog", "GPL", insns,
+				ARRAY_SIZE(insns), NULL);
+	ASSERT_GE(prog_fd, 0, "bpf_prog_load");
+
+out:
+	if (prog_fd >= 0)
+		close(prog_fd);
+	close(map_fd);
+}
+
 void test_global_percpu_data(void)
 {
 	if (!feat_supported(NULL, FEAT_PERCPU_DATA)) {
@@ -243,4 +285,6 @@ void test_global_percpu_data(void)
 		test_global_percpu_data_init();
 	if (test__start_subtest("lskel"))
 		test_global_percpu_data_lskel();
+	if (test__start_subtest("rdonly_direct_read"))
+		test_global_percpu_data_rdonly_direct_read();
 }
-- 
2.54.0