[PATCH bpf-next v1 5/8] selftests/bpf: bad_struct_ops test

[Eduard Zingerman <eddyz87@gmail.com>]

When loading struct_ops programs kernel requires BTF id of the
struct_ops type and member index for attachment point inside that
type. This makes it not possible to have same BPF program used in
struct_ops maps that have different struct_ops type.
Check if libbpf rejects such BPF objects files.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   | 24 +++++++++++
 .../selftests/bpf/bpf_testmod/bpf_testmod.h   |  4 ++
 .../selftests/bpf/prog_tests/bad_struct_ops.c | 42 +++++++++++++++++++
 .../selftests/bpf/progs/bad_struct_ops.c      | 17 ++++++++
 4 files changed, 87 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
 create mode 100644 tools/testing/selftests/bpf/progs/bad_struct_ops.c

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 0d8437e05f64..69f5eb9ad546 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -601,6 +601,29 @@ struct bpf_struct_ops bpf_bpf_testmod_ops = {
 	.owner = THIS_MODULE,
 };
 
+static int bpf_dummy_reg2(void *kdata)
+{
+	struct bpf_testmod_ops2 *ops = kdata;
+
+	ops->test_1();
+	return 0;
+}
+
+static struct bpf_testmod_ops2 __bpf_testmod_ops2 = {
+	.test_1 = bpf_testmod_test_1,
+};
+
+struct bpf_struct_ops bpf_testmod_ops2 = {
+	.verifier_ops = &bpf_testmod_verifier_ops,
+	.init = bpf_testmod_ops_init,
+	.init_member = bpf_testmod_ops_init_member,
+	.reg = bpf_dummy_reg2,
+	.unreg = bpf_dummy_unreg,
+	.cfi_stubs = &__bpf_testmod_ops2,
+	.name = "bpf_testmod_ops2",
+	.owner = THIS_MODULE,
+};
+
 extern int bpf_fentry_test1(int a);
 
 static int bpf_testmod_init(void)
@@ -612,6 +635,7 @@ static int bpf_testmod_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
+	ret = ret ?: register_bpf_struct_ops(&bpf_testmod_ops2, bpf_testmod_ops2);
 	if (ret < 0)
 		return ret;
 	if (bpf_fentry_test1(0) < 0)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
index c3b0cf788f9f..3183fff7f246 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h
@@ -37,4 +37,8 @@ struct bpf_testmod_ops {
 	int (*test_maybe_null)(int dummy, struct task_struct *task);
 };
 
+struct bpf_testmod_ops2 {
+	int (*test_1)(void);
+};
+
 #endif /* _BPF_TESTMOD_H */
diff --git a/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c b/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
new file mode 100644
index 000000000000..9c689db4b05b
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/bad_struct_ops.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "bad_struct_ops.skel.h"
+
+#define EXPECTED_MSG "libbpf: struct_ops reloc"
+
+static libbpf_print_fn_t old_print_cb;
+static bool msg_found;
+
+static int print_cb(enum libbpf_print_level level, const char *fmt, va_list args)
+{
+	old_print_cb(level, fmt, args);
+	if (level == LIBBPF_WARN && strncmp(fmt, EXPECTED_MSG, strlen(EXPECTED_MSG)) == 0)
+		msg_found = true;
+
+	return 0;
+}
+
+static void test_bad_struct_ops(void)
+{
+	struct bad_struct_ops *skel;
+	int err;
+
+	old_print_cb = libbpf_set_print(print_cb);
+	skel = bad_struct_ops__open_and_load();
+	err = errno;
+	libbpf_set_print(old_print_cb);
+	if (!ASSERT_NULL(skel, "bad_struct_ops__open_and_load"))
+		return;
+
+	ASSERT_EQ(err, EINVAL, "errno should be EINVAL");
+	ASSERT_TRUE(msg_found, "expected message");
+
+	bad_struct_ops__destroy(skel);
+}
+
+void serial_test_bad_struct_ops(void)
+{
+	if (test__start_subtest("test_bad_struct_ops"))
+		test_bad_struct_ops();
+}
diff --git a/tools/testing/selftests/bpf/progs/bad_struct_ops.c b/tools/testing/selftests/bpf/progs/bad_struct_ops.c
new file mode 100644
index 000000000000..9c103afbfdb1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bad_struct_ops.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("struct_ops/test_1")
+int BPF_PROG(test_1) { return 0; }
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_1 = { .test_1 = (void *)test_1 };
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops2 testmod_2 = { .test_1 = (void *)test_1 };
-- 
2.43.0