selftests/bpf: add file dynptr tests

Introducing selftests for validating file-backed dynptr works as
expected.
 * validate implementation supports dynptr slice and read operations
 * validate destructors should be paired with initializers
 * validate sleepable progs can page in.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251026203853.135105-11-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/file_reader_fail.c b/tools/testing/selftests/bpf/progs/file_reader_fail.c
new file mode 100644
index 000000000000..32fe28ed2439
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/file_reader_fail.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <string.h>
+#include <stdbool.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+
+char _license[] SEC("license") = "GPL";
+
+int err;
+void *user_ptr;
+
+SEC("lsm/file_open")
+__failure
+__msg("Unreleased reference id=")
+int on_nanosleep_unreleased_ref(void *ctx)
+{
+	struct task_struct *task = bpf_get_current_task_btf();
+	struct file *file = bpf_get_task_exe_file(task);
+	struct bpf_dynptr dynptr;
+
+	if (!file)
+		return 0;
+
+	err = bpf_dynptr_from_file(file, 0, &dynptr);
+	return err ? 1 : 0;
+}
+
+SEC("xdp")
+__failure
+__msg("Expected a dynptr of type file as arg #0")
+int xdp_wrong_dynptr_type(struct xdp_md *xdp)
+{
+	struct bpf_dynptr dynptr;
+
+	bpf_dynptr_from_xdp(xdp, 0, &dynptr);
+	bpf_dynptr_file_discard(&dynptr);
+	return 0;
+}
+
+SEC("xdp")
+__failure
+__msg("Expected an initialized dynptr as arg #0")
+int xdp_no_dynptr_type(struct xdp_md *xdp)
+{
+	struct bpf_dynptr dynptr;
+
+	bpf_dynptr_file_discard(&dynptr);
+	return 0;
+}