selftests/bpf: add CO-RE relocs testing setup

Add CO-RE relocation test runner. Add one simple test validating that
libbpf's logic for searching for kernel image and loading BTF out of it
works.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
new file mode 100644
index 000000000000..37e02aa3f0c8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_core_reloc_kernel.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Facebook
+
+#include <linux/bpf.h>
+#include <stdint.h>
+#include "bpf_helpers.h"
+
+char _license[] SEC("license") = "GPL";
+
+static volatile struct data {
+	char in[256];
+	char out[256];
+} data;
+
+struct task_struct {
+	int pid;
+	int tgid;
+};
+
+SEC("raw_tracepoint/sys_enter")
+int test_core_kernel(void *ctx)
+{
+	struct task_struct *task = (void *)bpf_get_current_task();
+	uint64_t pid_tgid = bpf_get_current_pid_tgid();
+	int pid, tgid;
+
+	if (BPF_CORE_READ(&pid, &task->pid) ||
+	    BPF_CORE_READ(&tgid, &task->tgid))
+		return 1;
+
+	/* validate pid + tgid matches */
+	data.out[0] = (((uint64_t)pid << 32) | tgid) == pid_tgid;
+
+	return 0;
+}
+