[PATCH 18/19] selftests/bpf: Add fentry/fexit multi func test

[Jiri Olsa <jolsa@kernel.org>]

Adding selftest for fentry/fexit multi func test that attaches
to bpf_fentry_test* functions and checks argument values based
on the processed function.

When multi_arg_check is used from 2 different places I'm getting
compilation fail, which I did not deciphered yet:

  $ CLANG=/opt/clang/bin/clang LLC=/opt/clang/bin/llc make
    CLNG-BPF [test_maps] fentry_fexit_multi_test.o
  progs/fentry_fexit_multi_test.c:18:2: error: too many args to t24: i64 = \
  GlobalAddress<void (i64, i64, i64, i64, i64, i64, i64, i64*)* @multi_arg_check> 0, \
  progs/fentry_fexit_multi_test.c:18:2 @[ progs/fentry_fexit_multi_test.c:16:5 ]
          multi_arg_check(ip, a, b, c, d, e, f, &test1_arg_result);
          ^
  progs/fentry_fexit_multi_test.c:25:2: error: too many args to t32: i64 = \
  GlobalAddress<void (i64, i64, i64, i64, i64, i64, i64, i64*)* @multi_arg_check> 0, \
  progs/fentry_fexit_multi_test.c:25:2 @[ progs/fentry_fexit_multi_test.c:23:5 ]
          multi_arg_check(ip, a, b, c, d, e, f, &test2_arg_result);
          ^
  In file included from progs/fentry_fexit_multi_test.c:5:
  /home/jolsa/linux-qemu/tools/testing/selftests/bpf/multi_check.h:9:6: error: defined with too many args
  void multi_arg_check(unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f, __u64 *test_result)
       ^
  /home/jolsa/linux-qemu/tools/testing/selftests/bpf/multi_check.h:9:6: error: defined with too many args
  /home/jolsa/linux-qemu/tools/testing/selftests/bpf/multi_check.h:9:6: error: defined with too many args
  5 errors generated.
  make: *** [Makefile:470: /home/jolsa/linux-qemu/tools/testing/selftests/bpf/fentry_fexit_multi_test.o] Error 1

I can fix that by defining 2 separate multi_arg_check functions
with different names, which I did in follow up temporaary patch.
Not sure I'm hitting some clang/bpf limitation in here?

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../bpf/prog_tests/fentry_fexit_multi_test.c  | 52 +++++++++++++++++++
 .../bpf/progs/fentry_fexit_multi_test.c       | 28 ++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/fentry_fexit_multi_test.c
 create mode 100644 tools/testing/selftests/bpf/progs/fentry_fexit_multi_test.c

diff --git a/tools/testing/selftests/bpf/prog_tests/fentry_fexit_multi_test.c b/tools/testing/selftests/bpf/prog_tests/fentry_fexit_multi_test.c
new file mode 100644
index 000000000000..76f917ad843d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/fentry_fexit_multi_test.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "fentry_fexit_multi_test.skel.h"
+
+void test_fentry_fexit_multi_test(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_link_update_opts, link_upd_opts);
+	struct fentry_fexit_multi_test *skel = NULL;
+	unsigned long long *bpf_fentry_test;
+	__u32 duration = 0, retval;
+	struct bpf_link *link;
+	int err, prog_fd;
+
+	skel = fentry_fexit_multi_test__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "fentry_multi_skel_load"))
+		goto cleanup;
+
+	bpf_fentry_test = &skel->bss->bpf_fentry_test[0];
+	ASSERT_OK(kallsyms_find("bpf_fentry_test1", &bpf_fentry_test[0]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test2", &bpf_fentry_test[1]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test3", &bpf_fentry_test[2]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test4", &bpf_fentry_test[3]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test5", &bpf_fentry_test[4]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test6", &bpf_fentry_test[5]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test7", &bpf_fentry_test[6]), "kallsyms_find");
+	ASSERT_OK(kallsyms_find("bpf_fentry_test8", &bpf_fentry_test[7]), "kallsyms_find");
+
+	link = bpf_program__attach(skel->progs.test1);
+	if (!ASSERT_OK_PTR(link, "attach_fentry_fexit"))
+		goto cleanup;
+
+	err = bpf_link_update(bpf_link__fd(link),
+			      bpf_program__fd(skel->progs.test2),
+			      NULL);
+	if (!ASSERT_OK(err, "bpf_link_update"))
+		goto cleanup_link;
+
+	prog_fd = bpf_program__fd(skel->progs.test1);
+	err = bpf_prog_test_run(prog_fd, 1, NULL, 0,
+				NULL, NULL, &retval, &duration);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(retval, 0, "test_run");
+
+	ASSERT_EQ(skel->bss->test1_arg_result, 8, "test1_arg_result");
+	ASSERT_EQ(skel->bss->test2_arg_result, 8, "test2_arg_result");
+	ASSERT_EQ(skel->bss->test2_ret_result, 8, "test2_ret_result");
+
+cleanup_link:
+	bpf_link__destroy(link);
+cleanup:
+	fentry_fexit_multi_test__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/fentry_fexit_multi_test.c b/tools/testing/selftests/bpf/progs/fentry_fexit_multi_test.c
new file mode 100644
index 000000000000..e25ab0085399
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/fentry_fexit_multi_test.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "multi_check.h"
+
+char _license[] SEC("license") = "GPL";
+
+unsigned long long bpf_fentry_test[8];
+
+__u64 test1_arg_result = 0;
+__u64 test2_arg_result = 0;
+__u64 test2_ret_result = 0;
+
+SEC("fentry.multi/bpf_fentry_test*")
+int BPF_PROG(test1, unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f)
+{
+	multi_arg_check(ip, a, b, c, d, e, f, &test1_arg_result);
+	return 0;
+}
+
+SEC("fexit.multi/")
+int BPF_PROG(test2, unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f, int ret)
+{
+	multi_arg_check(ip, a, b, c, d, e, f, &test2_arg_result);
+	multi_ret_check(ip, ret, &test2_ret_result);
+	return 0;
+}
-- 
2.31.1