selftests/bpf: Add struct_ops prog private stack tests

Add three tests for struct_ops using private stack.
  ./test_progs -t struct_ops_private_stack
  #336/1   struct_ops_private_stack/private_stack:OK
  #336/2   struct_ops_private_stack/private_stack_fail:OK
  #336/3   struct_ops_private_stack/private_stack_recur:OK
  #336     struct_ops_private_stack:OK

The following is a snippet of a struct_ops check_member() implementation:

	u32 moff = __btf_member_bit_offset(t, member) / 8;
	switch (moff) {
	case offsetof(struct bpf_testmod_ops3, test_1):
        	prog->aux->priv_stack_requested = true;
                prog->aux->recursion_detected = test_1_recursion_detected;
        	fallthrough;
	default:
        	break;
	}
	return 0;

The first test is with nested two different callback functions where the
first prog has more than 512 byte stack size (including subprogs) with
private stack enabled.

The second test is a negative test where the second prog has more than 512
byte stack size without private stack enabled.

The third test is the same callback function recursing itself. At run time,
the jit trampoline recursion check kicks in to prevent the recursion. The
recursion_detected() callback function is implemented by the bpf_testmod,
the following message in dmesg
  bpf_testmod: oh no, recursing into test_1, recursion_misses 1
demonstrates the callback function is indeed triggered when recursion miss
happens.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20241112163938.2225528-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 106 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c b/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c
new file mode 100644
index 000000000000..4006879ca3fe
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/struct_ops_private_stack.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "struct_ops_private_stack.skel.h"
+#include "struct_ops_private_stack_fail.skel.h"
+#include "struct_ops_private_stack_recur.skel.h"
+
+static void test_private_stack(void)
+{
+	struct struct_ops_private_stack *skel;
+	struct bpf_link *link;
+	int err;
+
+	skel = struct_ops_private_stack__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_private_stack__open"))
+		return;
+
+	if (skel->data->skip) {
+		test__skip();
+		goto cleanup;
+	}
+
+	err = struct_ops_private_stack__load(skel);
+	if (!ASSERT_OK(err, "struct_ops_private_stack__load"))
+		goto cleanup;
+
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+	if (!ASSERT_OK_PTR(link, "attach_struct_ops"))
+		goto cleanup;
+
+	ASSERT_OK(trigger_module_test_read(256), "trigger_read");
+
+	ASSERT_EQ(skel->bss->val_i, 3, "val_i");
+	ASSERT_EQ(skel->bss->val_j, 8, "val_j");
+
+	bpf_link__destroy(link);
+
+cleanup:
+	struct_ops_private_stack__destroy(skel);
+}
+
+static void test_private_stack_fail(void)
+{
+	struct struct_ops_private_stack_fail *skel;
+	int err;
+
+	skel = struct_ops_private_stack_fail__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_private_stack_fail__open"))
+		return;
+
+	if (skel->data->skip) {
+		test__skip();
+		goto cleanup;
+	}
+
+	err = struct_ops_private_stack_fail__load(skel);
+	if (!ASSERT_ERR(err, "struct_ops_private_stack_fail__load"))
+		goto cleanup;
+	return;
+
+cleanup:
+	struct_ops_private_stack_fail__destroy(skel);
+}
+
+static void test_private_stack_recur(void)
+{
+	struct struct_ops_private_stack_recur *skel;
+	struct bpf_link *link;
+	int err;
+
+	skel = struct_ops_private_stack_recur__open();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_private_stack_recur__open"))
+		return;
+
+	if (skel->data->skip) {
+		test__skip();
+		goto cleanup;
+	}
+
+	err = struct_ops_private_stack_recur__load(skel);
+	if (!ASSERT_OK(err, "struct_ops_private_stack_recur__load"))
+		goto cleanup;
+
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+	if (!ASSERT_OK_PTR(link, "attach_struct_ops"))
+		goto cleanup;
+
+	ASSERT_OK(trigger_module_test_read(256), "trigger_read");
+
+	ASSERT_EQ(skel->bss->val_j, 3, "val_j");
+
+	bpf_link__destroy(link);
+
+cleanup:
+	struct_ops_private_stack_recur__destroy(skel);
+}
+
+void test_struct_ops_private_stack(void)
+{
+	if (test__start_subtest("private_stack"))
+		test_private_stack();
+	if (test__start_subtest("private_stack_fail"))
+		test_private_stack_fail();
+	if (test__start_subtest("private_stack_recur"))
+		test_private_stack_recur();
+}