selftests/bpf: Test auto-load disabling logic for BPF programs

Validate that BPF object with broken (in multiple ways) BPF program can still
be successfully loaded, if that broken BPF program is disabled.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200625232629.3444003-3-andriin@fb.com

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

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+bool prog1_called = false;
+bool prog2_called = false;
+bool prog3_called = false;
+
+SEC("raw_tp/sys_enter")
+int prog1(const void *ctx)
+{
+	prog1_called = true;
+	return 0;
+}
+
+SEC("raw_tp/sys_exit")
+int prog2(const void *ctx)
+{
+	prog2_called = true;
+	return 0;
+}
+
+struct fake_kernel_struct {
+	int whatever;
+} __attribute__((preserve_access_index));
+
+SEC("fentry/unexisting-kprobe-will-fail-if-loaded")
+int prog3(const void *ctx)
+{
+	struct fake_kernel_struct *fake = (void *)ctx;
+	fake->whatever = 123;
+	prog3_called = true;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";