selftests/bpf: BPF task work scheduling tests

Introducing selftests that check BPF task work scheduling mechanism.
Validate that verifier does not accepts incorrect calls to
bpf_task_work_schedule kfunc.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250923112404.668720-9-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 150 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/test_task_work.c b/tools/testing/selftests/bpf/prog_tests/test_task_work.c
new file mode 100644
index 000000000000..666585270fbf
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/test_task_work.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <string.h>
+#include <stdio.h>
+#include "task_work.skel.h"
+#include "task_work_fail.skel.h"
+#include <linux/bpf.h>
+#include <linux/perf_event.h>
+#include <sys/syscall.h>
+#include <time.h>
+
+static int perf_event_open(__u32 type, __u64 config, int pid)
+{
+	struct perf_event_attr attr = {
+		.type = type,
+		.config = config,
+		.size = sizeof(struct perf_event_attr),
+		.sample_period = 100000,
+	};
+
+	return syscall(__NR_perf_event_open, &attr, pid, -1, -1, 0);
+}
+
+struct elem {
+	char data[128];
+	struct bpf_task_work tw;
+};
+
+static int verify_map(struct bpf_map *map, const char *expected_data)
+{
+	int err;
+	struct elem value;
+	int processed_values = 0;
+	int k, sz;
+
+	sz = bpf_map__max_entries(map);
+	for (k = 0; k < sz; ++k) {
+		err = bpf_map__lookup_elem(map, &k, sizeof(int), &value, sizeof(struct elem), 0);
+		if (err)
+			continue;
+		if (!ASSERT_EQ(strcmp(expected_data, value.data), 0, "map data")) {
+			fprintf(stderr, "expected '%s', found '%s' in %s map", expected_data,
+				value.data, bpf_map__name(map));
+			return 2;
+		}
+		processed_values++;
+	}
+
+	return processed_values == 0;
+}
+
+static void task_work_run(const char *prog_name, const char *map_name)
+{
+	struct task_work *skel;
+	struct bpf_program *prog;
+	struct bpf_map *map;
+	struct bpf_link *link;
+	int err, pe_fd = 0, pid, status, pipefd[2];
+	char user_string[] = "hello world";
+
+	if (!ASSERT_NEQ(pipe(pipefd), -1, "pipe"))
+		return;
+
+	pid = fork();
+	if (pid == 0) {
+		__u64 num = 1;
+		int i;
+		char buf;
+
+		close(pipefd[1]);
+		read(pipefd[0], &buf, sizeof(buf));
+		close(pipefd[0]);
+
+		for (i = 0; i < 10000; ++i)
+			num *= time(0) % 7;
+		(void)num;
+		exit(0);
+	}
+	ASSERT_GT(pid, 0, "fork() failed");
+
+	skel = task_work__open();
+	if (!ASSERT_OK_PTR(skel, "task_work__open"))
+		return;
+
+	bpf_object__for_each_program(prog, skel->obj) {
+		bpf_program__set_autoload(prog, false);
+	}
+
+	prog = bpf_object__find_program_by_name(skel->obj, prog_name);
+	if (!ASSERT_OK_PTR(prog, "prog_name"))
+		goto cleanup;
+	bpf_program__set_autoload(prog, true);
+	skel->bss->user_ptr = (char *)user_string;
+
+	err = task_work__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	pe_fd = perf_event_open(PERF_TYPE_HARDWARE, PERF_COUNT_HW_CPU_CYCLES, pid);
+	if (pe_fd == -1 && (errno == ENOENT || errno == EOPNOTSUPP)) {
+		printf("%s:SKIP:no PERF_COUNT_HW_CPU_CYCLES\n", __func__);
+		test__skip();
+		goto cleanup;
+	}
+	if (!ASSERT_NEQ(pe_fd, -1, "pe_fd")) {
+		fprintf(stderr, "perf_event_open errno: %d, pid: %d\n", errno, pid);
+		goto cleanup;
+	}
+
+	link = bpf_program__attach_perf_event(prog, pe_fd);
+	if (!ASSERT_OK_PTR(link, "attach_perf_event"))
+		goto cleanup;
+
+	close(pipefd[0]);
+	write(pipefd[1], user_string, 1);
+	close(pipefd[1]);
+	/* Wait to collect some samples */
+	waitpid(pid, &status, 0);
+	pid = 0;
+	map = bpf_object__find_map_by_name(skel->obj, map_name);
+	if (!ASSERT_OK_PTR(map, "find map_name"))
+		goto cleanup;
+	if (!ASSERT_OK(verify_map(map, user_string), "verify map"))
+		goto cleanup;
+cleanup:
+	if (pe_fd >= 0)
+		close(pe_fd);
+	task_work__destroy(skel);
+	if (pid) {
+		close(pipefd[0]);
+		write(pipefd[1], user_string, 1);
+		close(pipefd[1]);
+		waitpid(pid, &status, 0);
+	}
+}
+
+void test_task_work(void)
+{
+	if (test__start_subtest("test_task_work_hash_map"))
+		task_work_run("oncpu_hash_map", "hmap");
+
+	if (test__start_subtest("test_task_work_array_map"))
+		task_work_run("oncpu_array_map", "arrmap");
+
+	if (test__start_subtest("test_task_work_lru_map"))
+		task_work_run("oncpu_lru_map", "lrumap");
+
+	RUN_TESTS(task_work_fail);
+}