[PATCH bpf-next 1/5] bpf: add dummy BPF STRUCT_OPS for test purpose

[Hou Tao <houtao1@huawei.com>]

Currently the test of BPF STRUCT_OPS depends on the specific bpf
implementation of tcp_congestion_ops, but it can not cover all
basic functionalities (e.g, return value handling), so introduce
a dummy BPF STRUCT_OPS for test purpose.

Loading a bpf_dummy_ops implementation from userspace is prohibited,
and its only purpose is to run BPF_PROG_TYPE_STRUCT_OPS program
through bpf(BPF_PROG_TEST_RUN).

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 include/linux/bpf_dummy_ops.h     | 14 ++++++++++
 kernel/bpf/bpf_struct_ops_types.h |  2 ++
 net/bpf/Makefile                  |  3 +++
 net/bpf/bpf_dummy_struct_ops.c    | 44 +++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)
 create mode 100644 include/linux/bpf_dummy_ops.h
 create mode 100644 net/bpf/bpf_dummy_struct_ops.c

diff --git a/include/linux/bpf_dummy_ops.h b/include/linux/bpf_dummy_ops.h
new file mode 100644
index 000000000000..a594ae830eba
--- /dev/null
+++ b/include/linux/bpf_dummy_ops.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021. Huawei Technologies Co., Ltd
+ */
+#ifndef _BPF_DUMMY_OPS_H
+#define _BPF_DUMMY_OPS_H
+
+typedef int (*bpf_dummy_ops_init_t)(void);
+
+struct bpf_dummy_ops {
+	bpf_dummy_ops_init_t init;
+};
+
+#endif
diff --git a/kernel/bpf/bpf_struct_ops_types.h b/kernel/bpf/bpf_struct_ops_types.h
index 066d83ea1c99..02c86cf9c207 100644
--- a/kernel/bpf/bpf_struct_ops_types.h
+++ b/kernel/bpf/bpf_struct_ops_types.h
@@ -2,6 +2,8 @@
 /* internal file - do not include directly */
 
 #ifdef CONFIG_BPF_JIT
+#include <linux/bpf_dummy_ops.h>
+BPF_STRUCT_OPS_TYPE(bpf_dummy_ops)
 #ifdef CONFIG_INET
 #include <net/tcp.h>
 BPF_STRUCT_OPS_TYPE(tcp_congestion_ops)
diff --git a/net/bpf/Makefile b/net/bpf/Makefile
index 1c0a98d8c28f..1ebe270bde23 100644
--- a/net/bpf/Makefile
+++ b/net/bpf/Makefile
@@ -1,2 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_BPF_SYSCALL)	:= test_run.o
+ifeq ($(CONFIG_BPF_JIT),y)
+obj-$(CONFIG_BPF_SYSCALL)	+= bpf_dummy_struct_ops.o
+endif
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
new file mode 100644
index 000000000000..1249e4bb4ccb
--- /dev/null
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021. Huawei Technologies Co., Ltd
+ */
+#include <linux/kernel.h>
+#include <linux/bpf_verifier.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/bpf_dummy_ops.h>
+
+extern struct bpf_struct_ops bpf_bpf_dummy_ops;
+
+static int bpf_dummy_init(struct btf *btf)
+{
+	return 0;
+}
+
+static const struct bpf_verifier_ops bpf_dummy_verifier_ops = {
+};
+
+static int bpf_dummy_init_member(const struct btf_type *t,
+				 const struct btf_member *member,
+				 void *kdata, const void *udata)
+{
+	return -EOPNOTSUPP;
+}
+
+static int bpf_dummy_reg(void *kdata)
+{
+	return -EOPNOTSUPP;
+}
+
+static void bpf_dummy_unreg(void *kdata)
+{
+}
+
+struct bpf_struct_ops bpf_bpf_dummy_ops = {
+	.verifier_ops = &bpf_dummy_verifier_ops,
+	.init = bpf_dummy_init,
+	.init_member = bpf_dummy_init_member,
+	.reg = bpf_dummy_reg,
+	.unreg = bpf_dummy_unreg,
+	.name = "bpf_dummy_ops",
+};
-- 
2.29.2