[PATCH bpf v3 2/2] selftests/bpf: add a test for subprogram extables

[Krister Johansen <kjlx@xxxxxxxxxxxxxxxxxx>]

In certain situations a program with subprograms may have a NULL
extable entry.  This should not happen, and when it does, it turns a
single trap into multiple.  Add a test case for further debugging and to
prevent regressions.  N.b: without any other patches this can panic or
oops a kernel.

Signed-off-by: Krister Johansen <kjlx@xxxxxxxxxxxxxxxxxx>
---
 .../bpf/prog_tests/subprogs_extable.c         | 31 +++++++++++++
 .../bpf/progs/test_subprogs_extable.c         | 46 +++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_subprogs_extable.c

diff --git a/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c b/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
new file mode 100644
index 000000000000..2201988274a4
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/subprogs_extable.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include "test_subprogs_extable.skel.h"
+
+void test_subprogs_extable(void)
+{
+	const int READ_SZ = 456;
+	struct test_subprogs_extable *skel;
+	int err;
+
+	skel = test_subprogs_extable__open();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		return;
+
+	err = test_subprogs_extable__load(skel);
+	if (!ASSERT_OK(err, "skel_load"))
+		goto cleanup;
+
+	err = test_subprogs_extable__attach(skel);
+	if (!ASSERT_OK(err, "skel_attach"))
+		goto cleanup;
+
+	/* trigger tracepoint */
+	ASSERT_OK(trigger_module_test_read(READ_SZ), "trigger_read");
+
+	test_subprogs_extable__detach(skel);
+
+cleanup:
+	test_subprogs_extable__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_subprogs_extable.c b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
new file mode 100644
index 000000000000..c3ff66bf4cbe
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 8);
+	__type(key, __u32);
+	__type(value, __u64);
+} test_array SEC(".maps");
+
+static __u64 test_cb(struct bpf_map *map, __u32 *key, __u64 *val, void *data)
+{
+	return 1;
+}
+
+SEC("fexit/bpf_testmod_return_ptr")
+int BPF_PROG(handle_fexit_ret_subprogs, int arg, struct file *ret)
+{
+	*(volatile long *)ret;
+	*(volatile int *)&ret->f_mode;
+	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
+	return 0;
+}
+
+SEC("fexit/bpf_testmod_return_ptr")
+int BPF_PROG(handle_fexit_ret_subprogs2, int arg, struct file *ret)
+{
+	*(volatile long *)ret;
+	*(volatile int *)&ret->f_mode;
+	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
+	return 0;
+}
+
+SEC("fexit/bpf_testmod_return_ptr")
+int BPF_PROG(handle_fexit_ret_subprogs3, int arg, struct file *ret)
+{
+	*(volatile long *)ret;
+	*(volatile int *)&ret->f_mode;
+	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.25.1