bpf: selftest: Add kfunc_call test

This patch adds two kernel function bpf_kfunc_call_test[12]() for the
selftest's test_run purpose.  They will be allowed for tc_cls prog.

The selftest calling the kernel function bpf_kfunc_call_test[12]()
is also added in this patch.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>

net/bpf/test_run.c

@@ -209,6 +209,17 @@ int noinline bpf_modify_return_test(int a, int *b)
 	*b += 1;
 	return a + *b;
 }
+
+u64 noinline bpf_kfunc_call_test1(struct sock *sk, u32 a, u64 b, u32 c, u64 d)
+{
+	return a + b + c + d;
+}
+
+int noinline bpf_kfunc_call_test2(struct sock *sk, u32 a, u32 b)
+{
+	return a + b;
+}
+
 __diag_pop();
 
 ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO);

net/core/filter.c

@@ -9799,12 +9799,23 @@ const struct bpf_prog_ops sk_filter_prog_ops = {
 	.test_run		= bpf_prog_test_run_skb,
 };
 
+BTF_SET_START(bpf_tc_cls_kfunc_ids)
+BTF_ID(func, bpf_kfunc_call_test1)
+BTF_ID(func, bpf_kfunc_call_test2)
+BTF_SET_END(bpf_tc_cls_kfunc_ids)
+
+static bool tc_cls_check_kern_func_call(u32 kfunc_id)
+{
+	return btf_id_set_contains(&bpf_tc_cls_kfunc_ids, kfunc_id);
+}
+
 const struct bpf_verifier_ops tc_cls_act_verifier_ops = {
 	.get_func_proto		= tc_cls_act_func_proto,
 	.is_valid_access	= tc_cls_act_is_valid_access,
 	.convert_ctx_access	= tc_cls_act_convert_ctx_access,
 	.gen_prologue		= tc_cls_act_prologue,
 	.gen_ld_abs		= bpf_gen_ld_abs,
+	.check_kern_func_call	= tc_cls_check_kern_func_call,
 };
 
 const struct bpf_prog_ops tc_cls_act_prog_ops = {

tools/testing/selftests/bpf/prog_tests/kfunc_call.c

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "kfunc_call_test.skel.h"
+#include "kfunc_call_test_subprog.skel.h"
+
+static __u32 duration;
+
+static void test_main(void)
+{
+	struct kfunc_call_test *skel;
+	int prog_fd, retval, err;
+
+	skel = kfunc_call_test__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		return;
+
+	prog_fd = bpf_program__fd(skel->progs.kfunc_call_test1);
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+				NULL, NULL, (__u32 *)&retval, &duration);
+
+	if (ASSERT_OK(err, "bpf_prog_test_run(test1)"))
+		ASSERT_EQ(retval, 12, "test1-retval");
+
+	prog_fd = bpf_program__fd(skel->progs.kfunc_call_test2);
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+				NULL, NULL, (__u32 *)&retval, &duration);
+	if (ASSERT_OK(err, "bpf_prog_test_run(test2)"))
+		ASSERT_EQ(retval, 3, "test2-retval");
+
+	kfunc_call_test__destroy(skel);
+}
+
+static void test_subprog(void)
+{
+	struct kfunc_call_test_subprog *skel;
+	int prog_fd, retval, err;
+
+	skel = kfunc_call_test_subprog__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel"))
+		return;
+
+	prog_fd = bpf_program__fd(skel->progs.kfunc_call_test1);
+	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+				NULL, NULL, (__u32 *)&retval, &duration);
+
+	if (ASSERT_OK(err, "bpf_prog_test_run(test1)"))
+		ASSERT_EQ(retval, 10, "test1-retval");
+
+	kfunc_call_test_subprog__destroy(skel);
+}
+
+void test_kfunc_call(void)
+{
+	if (test__start_subtest("main"))
+		test_main();
+
+	if (test__start_subtest("subprog"))
+		test_subprog();
+}

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

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
+
+extern __u64 bpf_kfunc_call_test1(struct sock *sk, __u32 a, __u64 b,
+				  __u32 c, __u64 d) __ksym;
+extern int bpf_kfunc_call_test2(struct sock *sk, __u32 a, __u32 b) __ksym;
+
+SEC("classifier/test2")
+int kfunc_call_test2(struct __sk_buff *skb)
+{
+	struct bpf_sock *sk = skb->sk;
+
+	if (!sk)
+		return -1;
+
+	sk = bpf_sk_fullsock(sk);
+	if (!sk)
+		return -1;
+
+	return bpf_kfunc_call_test2((struct sock *)sk, 1, 2);
+}
+
+SEC("classifier/test1")
+int kfunc_call_test1(struct __sk_buff *skb)
+{
+	struct bpf_sock *sk = skb->sk;
+	__u64 a = 1ULL << 32;
+	__u32 ret;
+
+	if (!sk)
+		return -1;
+
+	sk = bpf_sk_fullsock(sk);
+	if (!sk)
+		return -1;
+
+	a = bpf_kfunc_call_test1((struct sock *)sk, 1, a | 2, 3, a | 4);
+
+	ret = a >> 32;   /* ret should be 2 */
+	ret += (__u32)a; /* ret should be 12 */
+
+	return ret;
+}
+
+char _license[] SEC("license") = "GPL";

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

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_tcp_helpers.h"
+
+extern __u64 bpf_kfunc_call_test1(struct sock *sk, __u32 a, __u64 b,
+				  __u32 c, __u64 d) __ksym;
+
+__attribute__ ((noinline))
+int f1(struct __sk_buff *skb)
+{
+	struct bpf_sock *sk = skb->sk;
+
+	if (!sk)
+		return -1;
+
+	sk = bpf_sk_fullsock(sk);
+	if (!sk)
+		return -1;
+
+	return (__u32)bpf_kfunc_call_test1((struct sock *)sk, 1, 2, 3, 4);
+}
+
+SEC("classifier/test1_subprog")
+int kfunc_call_test1(struct __sk_buff *skb)
+{
+	return f1(skb);
+}
+
+char _license[] SEC("license") = "GPL";