[PATCH bpf-next v3 3/3] selftests/bpf: Add testcases for callback with tailcall

[Pu Lehui]

From: Pu Lehui <pulehui@xxxxxxxxxx>

Add 2 testcases for callback with tailcall:
1. failure case: callback->subprog->tailcall.
2. success case: subprog with tailcall do not affect
   no-tailcall callback.

Signed-off-by: Pu Lehui <pulehui@xxxxxxxxxx>
---
 .../selftests/bpf/prog_tests/tailcalls.c      |  7 ++
 .../selftests/bpf/progs/tailcall_callback.c   | 81 +++++++++++++++++++
 2 files changed, 88 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/tailcall_callback.c

diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
index a5a226d0104c..c66037162da5 100644
--- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
+++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
@@ -12,6 +12,7 @@
 #include "tailcall_cgrp_storage_no_storage.skel.h"
 #include "tailcall_cgrp_storage.skel.h"
 #include "tailcall_sleepable.skel.h"
+#include "tailcall_callback.skel.h"
 
 /* test_tailcall_1 checks basic functionality by patching multiple locations
  * in a single program for a single tail call slot with nop->jmp, jmp->nop
@@ -1901,6 +1902,11 @@ static void test_tailcall_sleepable(void)
 	tailcall_sleepable__destroy(skel);
 }
 
+static void test_tailcall_callback(void)
+{
+	RUN_TESTS(tailcall_callback);
+}
+
 void test_tailcalls(void)
 {
 	if (test__start_subtest("tailcall_1"))
@@ -1967,4 +1973,5 @@ void test_tailcalls(void)
 		test_tailcall_cgrp_storage_no_storage_leaf();
 	if (test__start_subtest("tailcall_cgrp_storage_no_storage_bridge"))
 		test_tailcall_cgrp_storage_no_storage_bridge();
+	test_tailcall_callback();
 }
diff --git a/tools/testing/selftests/bpf/progs/tailcall_callback.c b/tools/testing/selftests/bpf/progs/tailcall_callback.c
new file mode 100644
index 000000000000..c41632cf423b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_callback.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "bpf_test_utils.h"
+
+int classifier_0(struct __sk_buff *skb);
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(__u32));
+	__array(values, void (void));
+} jmp_table SEC(".maps") = {
+	.values = {
+		[0] = (void *) &classifier_0,
+	},
+};
+
+__auxiliary
+SEC("tc")
+int classifier_0(struct __sk_buff *skb)
+{
+	return 0;
+}
+
+static __noinline
+int subprog_tail0(struct __sk_buff *skb)
+{
+	int ret = 0;
+
+	bpf_tail_call_static(skb, &jmp_table, 0);
+	barrier_var(ret);
+	return ret;
+}
+
+static __noinline
+int callback_loop(int index, void **cb_ctx)
+{
+	int ret;
+
+	ret = subprog_tail0(*cb_ctx);
+	barrier_var(ret);
+	return ret ? 1 : 0;
+}
+
+static __noinline
+int callback_empty(int index, void *data)
+{
+	return 0;
+}
+
+/* callback involving subprog with tail call is rejected */
+SEC("tc")
+__failure __msg("cannot tail call within callback")
+int tailcall_callback_1(struct __sk_buff *skb)
+{
+	clobber_regs_stack();
+
+	bpf_loop(1, callback_loop, &skb, 0);
+	return 0;
+}
+
+/* subprogs with tailcall do not affect no-tailcall callback */
+SEC("tc")
+__success
+__retval(0)
+int tailcall_callback_2(struct __sk_buff *skb)
+{
+	int ret;
+
+	clobber_regs_stack();
+
+	ret = subprog_tail0(skb);
+	__sink(ret);
+
+	bpf_loop(1, callback_empty, NULL, 0);
+	return 0;
+}
+
+char __license[] SEC("license") = "GPL";
-- 
2.34.1