[RFC PATCH bpf-next 2/2] selftests/bpf: Add testcases for generic kfunc bpf_ffs64()

[Leon Hwang <hffilwlqm@gmail.com>]

Add a selftest to confirm the kfunc bpf_ffs64() runs OK.

./tools/testing/selftests/bpf/test_progs -t bitops
12/1    bitops/bitops_ffs64:OK
12      bitops:OK
Summary: 1/1 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
---
 .../testing/selftests/bpf/prog_tests/bitops.c | 54 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/bitops.c    | 21 ++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bitops.c
 create mode 100644 tools/testing/selftests/bpf/progs/bitops.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bitops.c b/tools/testing/selftests/bpf/prog_tests/bitops.c
new file mode 100644
index 0000000000000..e4c68da626280
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bitops.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include <test_progs.h>
+
+/* test_ffs64 tests the generic kfunc bpf_ffs64().
+ */
+static void test_ffs64(void)
+{
+	struct bpf_object *obj = NULL;
+	struct bpf_program *prog;
+	char buff[128] = {};
+	int err, prog_fd;
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		.data_in = buff,
+		.data_size_in = sizeof(buff),
+		.repeat = 1,
+	);
+
+	err = bpf_prog_test_load("bitops.bpf.o", BPF_PROG_TYPE_SCHED_CLS, &obj,
+				 &prog_fd);
+	if (!ASSERT_OK(err, "load obj"))
+		return;
+
+	prog = bpf_object__find_program_by_name(obj, "tc_ffs64");
+	if (!ASSERT_OK_PTR(prog, "find tc_ffs64"))
+		goto out;
+
+#define TEST_FFS(n)						\
+	do {							\
+		u64 __n = 1;					\
+								\
+		*(u64 *)(void *) buff = (u64) (__n << n);	\
+		err = bpf_prog_test_run_opts(prog_fd, &topts);	\
+		ASSERT_OK(err, "run prog");			\
+		ASSERT_EQ(topts.retval, n, "run prog");		\
+	} while (0)
+
+	TEST_FFS(0);
+	TEST_FFS(1);
+	TEST_FFS(31);
+	TEST_FFS(63);
+
+#undef TEST_FFS
+out:
+	bpf_object__close(obj);
+}
+
+void test_bitops(void)
+{
+	if (test__start_subtest("bitops_ffs64"))
+		test_ffs64();
+}
diff --git a/tools/testing/selftests/bpf/progs/bitops.c b/tools/testing/selftests/bpf/progs/bitops.c
new file mode 100644
index 0000000000000..0863d1392b3d4
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bitops.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+unsigned long bpf_ffs64(u64 word) __ksym;
+
+SEC("tc")
+int tc_ffs64(struct __sk_buff *skb)
+{
+	void *data_end = (void *)(long)skb->data_end;
+	u64 *data = (u64 *)(long)skb->data;
+
+	if ((void *)(u64)(data + 1) > data_end)
+		return -1;
+
+	return bpf_ffs64(*data);
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.42.1