[PATCH bpf-next v3 2/2] selftests: bpf: Add tests for void global subprogs

[Emil Tsalapatis <emil@etsalapatis.com>]

Add additional testing for void global functions. The tests
ensure that calls to void global functions properly keep
R0 invalid. Also make sure that exception callbacks still
require a return value.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
---
 .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  | 24 +++++++++++++++++++
 .../bpf/prog_tests/test_global_funcs.c        |  2 ++
 .../selftests/bpf/progs/exceptions_fail.c     | 19 ++++++++++++---
 .../bpf/progs/freplace_int_with_void.c        | 14 +++++++++++
 .../selftests/bpf/progs/freplace_void.c       | 14 +++++++++++
 .../selftests/bpf/progs/test_global_func18.c  | 23 ++++++++++++++++++
 6 files changed, 93 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/freplace_int_with_void.c
 create mode 100644 tools/testing/selftests/bpf/progs/freplace_void.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_global_func18.c

diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
index f29fc789c14b..23d933f1aec6 100644
--- a/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
@@ -347,6 +347,17 @@ static void test_func_sockmap_update(void)
 				  prog_name, false, NULL);
 }
 
+static void test_func_replace_void(void)
+{
+	const char *prog_name[] = {
+		"freplace/foo",
+	};
+	test_fexit_bpf2bpf_common("./freplace_void.bpf.o",
+				  "./test_global_func7.bpf.o",
+				  ARRAY_SIZE(prog_name),
+				  prog_name, false, NULL);
+}
+
 static void test_obj_load_failure_common(const char *obj_file,
 					 const char *target_obj_file,
 					 const char *exp_msg)
@@ -432,6 +443,15 @@ static void test_func_replace_global_func(void)
 				  prog_name, false, NULL);
 }
 
+static void test_func_replace_int_with_void(void)
+{
+	/* Make sure we can't freplace with the wrong type */
+	test_obj_load_failure_common("freplace_int_with_void.bpf.o",
+				     "./test_global_func2.bpf.o",
+				     "Return type UNKNOWN of test_freplace_int_with_void()"
+				     " doesn't match type INT of global_func2()");
+}
+
 static int find_prog_btf_id(const char *name, __u32 attach_prog_fd)
 {
 	struct bpf_prog_info info = {};
@@ -597,4 +617,8 @@ void serial_test_fexit_bpf2bpf(void)
 		test_fentry_to_cgroup_bpf();
 	if (test__start_subtest("func_replace_progmap"))
 		test_func_replace_progmap();
+	if (test__start_subtest("freplace_int_with_void"))
+		test_func_replace_int_with_void();
+	if (test__start_subtest("freplace_void"))
+		test_func_replace_void();
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
index e905cbaf6b3d..45854cbcbfcf 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
@@ -18,6 +18,7 @@
 #include "test_global_func15.skel.h"
 #include "test_global_func16.skel.h"
 #include "test_global_func17.skel.h"
+#include "test_global_func18.skel.h"
 #include "test_global_func_ctx_args.skel.h"
 
 #include "bpf/libbpf_internal.h"
@@ -155,6 +156,7 @@ void test_test_global_funcs(void)
 	RUN_TESTS(test_global_func15);
 	RUN_TESTS(test_global_func16);
 	RUN_TESTS(test_global_func17);
+	RUN_TESTS(test_global_func18);
 	RUN_TESTS(test_global_func_ctx_args);
 
 	if (test__start_subtest("ctx_arg_rewrite"))
diff --git a/tools/testing/selftests/bpf/progs/exceptions_fail.c b/tools/testing/selftests/bpf/progs/exceptions_fail.c
index d28ecc4ee2d0..691c16001952 100644
--- a/tools/testing/selftests/bpf/progs/exceptions_fail.c
+++ b/tools/testing/selftests/bpf/progs/exceptions_fail.c
@@ -29,11 +29,15 @@ struct {
 private(A) struct bpf_spin_lock lock;
 private(A) struct bpf_rb_root rbtree __contains(foo, node);
 
-__noinline void *exception_cb_bad_ret_type(u64 cookie)
+__noinline void *exception_cb_bad_ret_type1(u64 cookie)
 {
 	return NULL;
 }
 
+__noinline void exception_cb_bad_ret_type2(u64 cookie)
+{
+}
+
 __noinline int exception_cb_bad_arg_0(void)
 {
 	return 0;
@@ -50,8 +54,8 @@ __noinline int exception_cb_ok_arg_small(int a)
 }
 
 SEC("?tc")
-__exception_cb(exception_cb_bad_ret_type)
-__failure __msg("Global function exception_cb_bad_ret_type() return value not void or scalar.")
+__exception_cb(exception_cb_bad_ret_type1)
+__failure __msg("Global function exception_cb_bad_ret_type1() return value not void or scalar.")
 int reject_exception_cb_type_1(struct __sk_buff *ctx)
 {
 	bpf_throw(0);
@@ -85,6 +89,15 @@ int reject_exception_cb_type_4(struct __sk_buff *ctx)
 	return 0;
 }
 
+SEC("?tc")
+__exception_cb(exception_cb_bad_ret_type2)
+__failure __msg("exception cb cannot return void")
+int reject_exception_cb_type_5(struct __sk_buff *ctx)
+{
+	bpf_throw(0);
+	return 0;
+}
+
 __noinline
 static int timer_cb(void *map, int *key, struct bpf_timer *timer)
 {
diff --git a/tools/testing/selftests/bpf/progs/freplace_int_with_void.c b/tools/testing/selftests/bpf/progs/freplace_int_with_void.c
new file mode 100644
index 000000000000..8b6f5776cf0f
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/freplace_int_with_void.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+#include <bpf/bpf_helpers.h>
+
+volatile int data;
+
+SEC("freplace/global_func2")
+void test_freplace_int_with_void(struct __sk_buff *skb)
+{
+	data = 1;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/freplace_void.c b/tools/testing/selftests/bpf/progs/freplace_void.c
new file mode 100644
index 000000000000..76707b29dc6a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/freplace_void.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+volatile int data;
+
+SEC("freplace/foo")
+__weak
+void test_freplace_void(struct __sk_buff *skb)
+{
+	data = 1;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_global_func18.c b/tools/testing/selftests/bpf/progs/test_global_func18.c
new file mode 100644
index 000000000000..3dafb0dc2342
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_global_func18.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+__weak
+void foo(void)
+{
+}
+
+SEC("tc")
+__failure __msg("!read_ok")
+int global_func18(struct __sk_buff *skb)
+{
+	foo();
+
+	asm volatile(
+		"r1 = r0;"
+		:::
+	);
+
+	return 0;
+}
-- 
2.49.0