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 <[e-mail]>
Signed-off-by: Martin KaFai Lau <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

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

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "struct_ops_id_ops_mapping1.skel.h"
+#include "struct_ops_id_ops_mapping2.skel.h"
+
+static void test_st_ops_id_ops_mapping(void)
+{
+	struct struct_ops_id_ops_mapping1 *skel1 = NULL;
+	struct struct_ops_id_ops_mapping2 *skel2 = NULL;
+	struct bpf_map_info info = {};
+	__u32 len = sizeof(info);
+	int err, pid, prog1_fd, prog2_fd;
+
+	skel1 = struct_ops_id_ops_mapping1__open_and_load();
+	if (!ASSERT_OK_PTR(skel1, "struct_ops_id_ops_mapping1__open"))
+		goto out;
+
+	skel2 = struct_ops_id_ops_mapping2__open_and_load();
+	if (!ASSERT_OK_PTR(skel2, "struct_ops_id_ops_mapping2__open"))
+		goto out;
+
+	err = bpf_map_get_info_by_fd(bpf_map__fd(skel1->maps.st_ops_map),
+				     &info, &len);
+	if (!ASSERT_OK(err, "bpf_map_get_info_by_fd"))
+		goto out;
+
+	skel1->bss->st_ops_id = info.id;
+
+	err = bpf_map_get_info_by_fd(bpf_map__fd(skel2->maps.st_ops_map),
+				     &info, &len);
+	if (!ASSERT_OK(err, "bpf_map_get_info_by_fd"))
+		goto out;
+
+	skel2->bss->st_ops_id = info.id;
+
+	err = struct_ops_id_ops_mapping1__attach(skel1);
+	if (!ASSERT_OK(err, "struct_ops_id_ops_mapping1__attach"))
+		goto out;
+
+	err = struct_ops_id_ops_mapping2__attach(skel2);
+	if (!ASSERT_OK(err, "struct_ops_id_ops_mapping2__attach"))
+		goto out;
+
+	/* run tracing prog that calls .test_1 and checks return */
+	pid = getpid();
+	skel1->bss->test_pid = pid;
+	skel2->bss->test_pid = pid;
+	sys_gettid();
+	skel1->bss->test_pid = 0;
+	skel2->bss->test_pid = 0;
+
+	/* run syscall_prog that calls .test_1 and checks return */
+	prog1_fd = bpf_program__fd(skel1->progs.syscall_prog);
+	err = bpf_prog_test_run_opts(prog1_fd, NULL);
+	ASSERT_OK(err, "bpf_prog_test_run_opts");
+
+	prog2_fd = bpf_program__fd(skel2->progs.syscall_prog);
+	err = bpf_prog_test_run_opts(prog2_fd, NULL);
+	ASSERT_OK(err, "bpf_prog_test_run_opts");
+
+	ASSERT_EQ(skel1->bss->test_err, 0, "skel1->bss->test_err");
+	ASSERT_EQ(skel2->bss->test_err, 0, "skel2->bss->test_err");
+
+out:
+	struct_ops_id_ops_mapping1__destroy(skel1);
+	struct_ops_id_ops_mapping2__destroy(skel2);
+}
+
+void test_struct_ops_id_ops_mapping(void)
+{
+	if (test__start_subtest("st_ops_id_ops_mapping"))
+		test_st_ops_id_ops_mapping();
+}

tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping1.c

···
+// 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 MAP1_MAGIC 1234
+
+SEC("struct_ops")
+int BPF_PROG(test_1, struct st_ops_args *args)
+{
+	return MAP1_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 != MAP1_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 != MAP1_MAGIC)
+		test_err++;
+
+	return 0;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_multi_st_ops st_ops_map = {
+	.test_1 = (void *)test_1,
+};

tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c

···
+// 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,
+};