selftests/bpf: Test multi_st_ops and calling kfuncs from different programs

Test multi_st_ops and demonstrate how different bpf programs can call
a kfuncs that refers to the struct_ops instance in the same source file
by id. The id is defined as a global vairable and initialized before
attaching the skeleton. Kfuncs that take the id can hide the argument
with a macro to make it almost transparent to bpf program developers.

The test involves two struct_ops returning different values from
.test_1. In syscall and tracing programs, check if the correct value is
returned by a kfunc that calls .test_1.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250806162540.681679-4-ameryhung@gmail.com

1 files changed, 59 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c b/tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c
new file mode 100644
index 000000000000..cea1a2f4b62f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+#include "../test_kmods/bpf_testmod.h"
+#include "../test_kmods/bpf_testmod_kfunc.h"
+
+char _license[] SEC("license") = "GPL";
+
+#define bpf_kfunc_multi_st_ops_test_1(args) bpf_kfunc_multi_st_ops_test_1(args, st_ops_id)
+int st_ops_id;
+
+int test_pid;
+int test_err;
+
+#define MAP2_MAGIC 4567
+
+SEC("struct_ops")
+int BPF_PROG(test_1, struct st_ops_args *args)
+{
+	return MAP2_MAGIC;
+}
+
+SEC("tp_btf/sys_enter")
+int BPF_PROG(sys_enter, struct pt_regs *regs, long id)
+{
+	struct st_ops_args args = {};
+	struct task_struct *task;
+	int ret;
+
+	task = bpf_get_current_task_btf();
+	if (!test_pid || task->pid != test_pid)
+		return 0;
+
+	ret = bpf_kfunc_multi_st_ops_test_1(&args);
+	if (ret != MAP2_MAGIC)
+		test_err++;
+
+	return 0;
+}
+
+SEC("syscall")
+int syscall_prog(void *ctx)
+{
+	struct st_ops_args args = {};
+	int ret;
+
+	ret = bpf_kfunc_multi_st_ops_test_1(&args);
+	if (ret != MAP2_MAGIC)
+		test_err++;
+
+	return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_multi_st_ops st_ops_map = {
+	.test_1 = (void *)test_1,
+};