selftests/bpf: Improve percpu_alloc test robustness

Make these non-serial tests filter BPF programs by intended PID of
a test runner process. This makes it isolated from other parallel tests
that might interfere accidentally.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20231011223728.3188086-2-andrii@kernel.org

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

@@ -19,6 +19,7 @@ static void test_array(void)
 	bpf_program__set_autoload(skel->progs.test_array_map_3, true);
 	bpf_program__set_autoload(skel->progs.test_array_map_4, true);
 
+	skel->bss->my_pid = getpid();
 	skel->rodata->nr_cpus = libbpf_num_possible_cpus();
 
 	err = percpu_alloc_array__load(skel);
@@ -51,6 +52,7 @@ static void test_array_sleepable(void)
 
 	bpf_program__set_autoload(skel->progs.test_array_map_10, true);
 
+	skel->bss->my_pid = getpid();
 	skel->rodata->nr_cpus = libbpf_num_possible_cpus();
 
 	err = percpu_alloc_array__load(skel);
@@ -85,6 +87,7 @@ static void test_cgrp_local_storage(void)
 	if (!ASSERT_OK_PTR(skel, "percpu_alloc_cgrp_local_storage__open"))
 		goto close_fd;
 
+	skel->bss->my_pid = getpid();
 	skel->rodata->nr_cpus = libbpf_num_possible_cpus();
 
 	err = percpu_alloc_cgrp_local_storage__load(skel);

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

@@ -71,6 +71,7 @@ int BPF_PROG(test_array_map_2)
 }
 
 int cpu0_field_d, sum_field_c;
+int my_pid;
 
 /* Summarize percpu data */
 SEC("?fentry/bpf_fentry_test3")
@@ -81,6 +82,9 @@ int BPF_PROG(test_array_map_3)
 	struct val_t *v;
 	struct elem *e;
 
+	if ((bpf_get_current_pid_tgid() >> 32) != my_pid)
+		return 0;
+
 	e = bpf_map_lookup_elem(&array, &index);
 	if (!e)
 		return 0;
@@ -130,6 +134,9 @@ int BPF_PROG(test_array_map_10)
 	struct val_t *v;
 	struct elem *e;
 
+	if ((bpf_get_current_pid_tgid() >> 32) != my_pid)
+		return 0;
+
 	e = bpf_map_lookup_elem(&array, &index);
 	if (!e)
 		return 0;

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

@@ -70,6 +70,7 @@ int BPF_PROG(test_cgrp_local_storage_2)
 }
 
 int cpu0_field_d, sum_field_c;
+int my_pid;
 
 /* Summarize percpu data collection */
 SEC("fentry/bpf_fentry_test3")
@@ -81,6 +82,9 @@ int BPF_PROG(test_cgrp_local_storage_3)
 	struct elem *e;
 	int i;
 
+	if ((bpf_get_current_pid_tgid() >> 32) != my_pid)
+		return 0;
+
 	task = bpf_get_current_task_btf();
 	e = bpf_cgrp_storage_get(&cgrp, task->cgroups->dfl_cgrp, 0, 0);
 	if (!e)