selftests/bpf: Add test for missed counts of perf event link kprobe

Adding test that puts kprobe on bpf_fentry_test1 that calls
bpf_kfunc_common_test kfunc, which has also kprobe on.

The latter won't get triggered due to kprobe recursion check
and kprobe missed counter is incremented.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/bpf/20230920213145.1941596-8-jolsa@kernel.org

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

@@ -138,6 +138,10 @@ __bpf_kfunc void bpf_iter_testmod_seq_destroy(struct bpf_iter_testmod_seq *it)
 	it->cnt = 0;
 }
 
+__bpf_kfunc void bpf_kfunc_common_test(void)
+{
+}
+
 struct bpf_testmod_btf_type_tag_1 {
 	int a;
 };
@@ -343,6 +347,7 @@ BTF_SET8_START(bpf_testmod_common_kfunc_ids)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_new, KF_ITER_NEW)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_destroy, KF_ITER_DESTROY)
+BTF_ID_FLAGS(func, bpf_kfunc_common_test)
 BTF_SET8_END(bpf_testmod_common_kfunc_ids)
 
 static const struct btf_kfunc_id_set bpf_testmod_common_kfunc_set = {

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h

@@ -104,4 +104,6 @@ void bpf_kfunc_call_test_fail1(struct prog_test_fail1 *p);
 void bpf_kfunc_call_test_fail2(struct prog_test_fail2 *p);
 void bpf_kfunc_call_test_fail3(struct prog_test_fail3 *p);
 void bpf_kfunc_call_test_mem_len_fail1(void *mem, int len);
+
+void bpf_kfunc_common_test(void) __ksym;
 #endif /* _BPF_TESTMOD_KFUNC_H */

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

+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "missed_kprobe.skel.h"
+
+/*
+ * Putting kprobe on bpf_fentry_test1 that calls bpf_kfunc_common_test
+ * kfunc, which has also kprobe on. The latter won't get triggered due
+ * to kprobe recursion check and kprobe missed counter is incremented.
+ */
+static void test_missed_perf_kprobe(void)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct bpf_link_info info = {};
+	struct missed_kprobe *skel;
+	__u32 len = sizeof(info);
+	int err, prog_fd;
+
+	skel = missed_kprobe__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "missed_kprobe__open_and_load"))
+		goto cleanup;
+
+	err = missed_kprobe__attach(skel);
+	if (!ASSERT_OK(err, "missed_kprobe__attach"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.trigger);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "test_run");
+	ASSERT_EQ(topts.retval, 0, "test_run");
+
+	err = bpf_link_get_info_by_fd(bpf_link__fd(skel->links.test2), &info, &len);
+	if (!ASSERT_OK(err, "bpf_link_get_info_by_fd"))
+		goto cleanup;
+
+	ASSERT_EQ(info.type, BPF_LINK_TYPE_PERF_EVENT, "info.type");
+	ASSERT_EQ(info.perf_event.type, BPF_PERF_EVENT_KPROBE, "info.perf_event.type");
+	ASSERT_EQ(info.perf_event.kprobe.missed, 1, "info.perf_event.kprobe.missed");
+
+cleanup:
+	missed_kprobe__destroy(skel);
+}
+
+void test_missed(void)
+{
+	if (test__start_subtest("perf_kprobe"))
+		test_missed_perf_kprobe();
+}

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

+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod_kfunc.h"
+
+char _license[] SEC("license") = "GPL";
+
+/*
+ * No tests in here, just to trigger 'bpf_fentry_test*'
+ * through tracing test_run
+ */
+SEC("fentry/bpf_modify_return_test")
+int BPF_PROG(trigger)
+{
+	return 0;
+}
+
+SEC("kprobe/bpf_fentry_test1")
+int test1(struct pt_regs *ctx)
+{
+	bpf_kfunc_common_test();
+	return 0;
+}
+
+SEC("kprobe/bpf_kfunc_common_test")
+int test2(struct pt_regs *ctx)
+{
+	return 0;
+}