selftests/bpf: Add field existence CO-RE relocs tests

Add a bunch of tests validating CO-RE is handling field existence
relocation. Relaxed CO-RE relocation mode is activated for these new
tests to prevent libbpf from rejecting BPF object for no-match
relocation, even though test BPF program is not going to use that
relocation, if field is missing.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191015182849.3922287-6-andriin@fb.com

1 files changed, 79 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_existence.c b/tools/testing/selftests/bpf/progs/test_core_reloc_existence.c
new file mode 100644
index 000000000000..c3cac95a19f1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_existence.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+#include "bpf_core_read.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+	char in[256];
+	char out[256];
+} data;
+
+struct core_reloc_existence_output {
+	int a_exists;
+	int a_value;
+	int b_exists;
+	int b_value;
+	int c_exists;
+	int c_value;
+	int arr_exists;
+	int arr_value;
+	int s_exists;
+	int s_value;
+};
+
+struct core_reloc_existence {
+	struct {
+		int x;
+	} s;
+	int arr[1];
+	int a;
+	struct {
+		int b;
+	};
+	int c;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_existence(void *ctx)
+{
+	struct core_reloc_existence *in = (void *)&data.in;
+	struct core_reloc_existence_output *out = (void *)&data.out;
+
+	out->a_exists = bpf_core_field_exists(in->a);
+	if (bpf_core_field_exists(in->a))
+		out->a_value = BPF_CORE_READ(in, a);
+	else
+		out->a_value = 0xff000001u;
+
+	out->b_exists = bpf_core_field_exists(in->b);
+	if (bpf_core_field_exists(in->b))
+		out->b_value = BPF_CORE_READ(in, b);
+	else
+		out->b_value = 0xff000002u;
+
+	out->c_exists = bpf_core_field_exists(in->c);
+	if (bpf_core_field_exists(in->c))
+		out->c_value = BPF_CORE_READ(in, c);
+	else
+		out->c_value = 0xff000003u;
+
+	out->arr_exists = bpf_core_field_exists(in->arr);
+	if (bpf_core_field_exists(in->arr))
+		out->arr_value = BPF_CORE_READ(in, arr[0]);
+	else
+		out->arr_value = 0xff000004u;
+
+	out->s_exists = bpf_core_field_exists(in->s);
+	if (bpf_core_field_exists(in->s))
+		out->s_value = BPF_CORE_READ(in, s.x);
+	else
+		out->s_value = 0xff000005u;
+
+	return 0;
+}
+