selftests/bpf: Add custom SEC() handling selftest

Add a selftest validating various aspects of libbpf's handling of custom
SEC() handlers. It also demonstrates how libraries can ensure very early
callbacks registration and unregistration using
__attribute__((constructor))/__attribute__((destructor)) functions.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Alan Maguire <alan.maguire@oracle.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Link: https://lore.kernel.org/bpf/20220305010129.1549719-4-andrii@kernel.org

1 files changed, 63 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c b/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c
new file mode 100644
index 000000000000..4061f701ca50
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_custom_sec_handlers.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+const volatile int my_pid;
+
+bool abc1_called;
+bool abc2_called;
+bool custom1_called;
+bool custom2_called;
+bool kprobe1_called;
+bool xyz_called;
+
+SEC("abc")
+int abc1(void *ctx)
+{
+	abc1_called = true;
+	return 0;
+}
+
+SEC("abc/whatever")
+int abc2(void *ctx)
+{
+	abc2_called = true;
+	return 0;
+}
+
+SEC("custom")
+int custom1(void *ctx)
+{
+	custom1_called = true;
+	return 0;
+}
+
+SEC("custom/something")
+int custom2(void *ctx)
+{
+	custom2_called = true;
+	return 0;
+}
+
+SEC("kprobe")
+int kprobe1(void *ctx)
+{
+	kprobe1_called = true;
+	return 0;
+}
+
+SEC("xyz/blah")
+int xyz(void *ctx)
+{
+	int whatever;
+
+	/* use sleepable helper, custom handler should set sleepable flag */
+	bpf_copy_from_user(&whatever, sizeof(whatever), NULL);
+	xyz_called = true;
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";