selftests/bpf: Add testcases for tailcall infinite loop fixing

Add 4 test cases to confirm the tailcall infinite loop bug has been fixed.

Like tailcall_bpf2bpf cases, do fentry/fexit on the bpf2bpf, and then
check the final count result.

tools/testing/selftests/bpf/test_progs -t tailcalls
226/13 tailcalls/tailcall_bpf2bpf_fentry:OK
226/14 tailcalls/tailcall_bpf2bpf_fexit:OK
226/15 tailcalls/tailcall_bpf2bpf_fentry_fexit:OK
226/16 tailcalls/tailcall_bpf2bpf_fentry_entry:OK
226 tailcalls:OK
Summary: 1/16 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Leon Hwang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/prog_tests/tailcalls.c

···
 	bpf_object__close(obj);
 }
 
-static void test_tailcall_count(const char *which)
+static void test_tailcall_count(const char *which, bool test_fentry,
+				bool test_fexit)
 {
+	struct bpf_object *obj = NULL, *fentry_obj = NULL, *fexit_obj = NULL;
+	struct bpf_link *fentry_link = NULL, *fexit_link = NULL;
 	int err, map_fd, prog_fd, main_fd, data_fd, i, val;
 	struct bpf_map *prog_array, *data_map;
 	struct bpf_program *prog;
-	struct bpf_object *obj;
 	char buff[128] = {};
 	LIBBPF_OPTS(bpf_test_run_opts, topts,
 		.data_in = buff,
···
 	if (CHECK_FAIL(err))
 		goto out;
 
+	if (test_fentry) {
+		fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_fentry.bpf.o",
+						   NULL);
+		if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file"))
+			goto out;
+
+		prog = bpf_object__find_program_by_name(fentry_obj, "fentry");
+		if (!ASSERT_OK_PTR(prog, "find fentry prog"))
+			goto out;
+
+		err = bpf_program__set_attach_target(prog, prog_fd,
+						     "subprog_tail");
+		if (!ASSERT_OK(err, "set_attach_target subprog_tail"))
+			goto out;
+
+		err = bpf_object__load(fentry_obj);
+		if (!ASSERT_OK(err, "load fentry_obj"))
+			goto out;
+
+		fentry_link = bpf_program__attach_trace(prog);
+		if (!ASSERT_OK_PTR(fentry_link, "attach_trace"))
+			goto out;
+	}
+
+	if (test_fexit) {
+		fexit_obj = bpf_object__open_file("tailcall_bpf2bpf_fexit.bpf.o",
+						  NULL);
+		if (!ASSERT_OK_PTR(fexit_obj, "open fexit_obj file"))
+			goto out;
+
+		prog = bpf_object__find_program_by_name(fexit_obj, "fexit");
+		if (!ASSERT_OK_PTR(prog, "find fexit prog"))
+			goto out;
+
+		err = bpf_program__set_attach_target(prog, prog_fd,
+						     "subprog_tail");
+		if (!ASSERT_OK(err, "set_attach_target subprog_tail"))
+			goto out;
+
+		err = bpf_object__load(fexit_obj);
+		if (!ASSERT_OK(err, "load fexit_obj"))
+			goto out;
+
+		fexit_link = bpf_program__attach_trace(prog);
+		if (!ASSERT_OK_PTR(fexit_link, "attach_trace"))
+			goto out;
+	}
+
 	err = bpf_prog_test_run_opts(main_fd, &topts);
 	ASSERT_OK(err, "tailcall");
 	ASSERT_EQ(topts.retval, 1, "tailcall retval");
···
 	ASSERT_OK(err, "tailcall count");
 	ASSERT_EQ(val, 33, "tailcall count");
 
+	if (test_fentry) {
+		data_map = bpf_object__find_map_by_name(fentry_obj, ".bss");
+		if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+				  "find tailcall_bpf2bpf_fentry.bss map"))
+			goto out;
+
+		data_fd = bpf_map__fd(data_map);
+		if (!ASSERT_FALSE(data_fd < 0,
+				  "find tailcall_bpf2bpf_fentry.bss map fd"))
+			goto out;
+
+		i = 0;
+		err = bpf_map_lookup_elem(data_fd, &i, &val);
+		ASSERT_OK(err, "fentry count");
+		ASSERT_EQ(val, 33, "fentry count");
+	}
+
+	if (test_fexit) {
+		data_map = bpf_object__find_map_by_name(fexit_obj, ".bss");
+		if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+				  "find tailcall_bpf2bpf_fexit.bss map"))
+			goto out;
+
+		data_fd = bpf_map__fd(data_map);
+		if (!ASSERT_FALSE(data_fd < 0,
+				  "find tailcall_bpf2bpf_fexit.bss map fd"))
+			goto out;
+
+		i = 0;
+		err = bpf_map_lookup_elem(data_fd, &i, &val);
+		ASSERT_OK(err, "fexit count");
+		ASSERT_EQ(val, 33, "fexit count");
+	}
+
 	i = 0;
 	err = bpf_map_delete_elem(map_fd, &i);
 	if (CHECK_FAIL(err))
···
 	ASSERT_OK(err, "tailcall");
 	ASSERT_OK(topts.retval, "tailcall retval");
 out:
+	bpf_link__destroy(fentry_link);
+	bpf_link__destroy(fexit_link);
+	bpf_object__close(fentry_obj);
+	bpf_object__close(fexit_obj);
 	bpf_object__close(obj);
 }
 
···
  */
 static void test_tailcall_3(void)
 {
-	test_tailcall_count("tailcall3.bpf.o");
+	test_tailcall_count("tailcall3.bpf.o", false, false);
 }
 
 /* test_tailcall_6 checks that the count value of the tail call limit
···
  */
 static void test_tailcall_6(void)
 {
-	test_tailcall_count("tailcall6.bpf.o");
+	test_tailcall_count("tailcall6.bpf.o", false, false);
 }
 
 /* test_tailcall_4 checks that the kernel properly selects indirect jump
···
 	tailcall_bpf2bpf6__destroy(obj);
 }
 
+/* test_tailcall_bpf2bpf_fentry checks that the count value of the tail call
+ * limit enforcement matches with expectations when tailcall is preceded with
+ * bpf2bpf call, and the bpf2bpf call is traced by fentry.
+ */
+static void test_tailcall_bpf2bpf_fentry(void)
+{
+	test_tailcall_count("tailcall_bpf2bpf2.bpf.o", true, false);
+}
+
+/* test_tailcall_bpf2bpf_fexit checks that the count value of the tail call
+ * limit enforcement matches with expectations when tailcall is preceded with
+ * bpf2bpf call, and the bpf2bpf call is traced by fexit.
+ */
+static void test_tailcall_bpf2bpf_fexit(void)
+{
+	test_tailcall_count("tailcall_bpf2bpf2.bpf.o", false, true);
+}
+
+/* test_tailcall_bpf2bpf_fentry_fexit checks that the count value of the tail
+ * call limit enforcement matches with expectations when tailcall is preceded
+ * with bpf2bpf call, and the bpf2bpf call is traced by both fentry and fexit.
+ */
+static void test_tailcall_bpf2bpf_fentry_fexit(void)
+{
+	test_tailcall_count("tailcall_bpf2bpf2.bpf.o", true, true);
+}
+
+/* test_tailcall_bpf2bpf_fentry_entry checks that the count value of the tail
+ * call limit enforcement matches with expectations when tailcall is preceded
+ * with bpf2bpf call, and the bpf2bpf caller is traced by fentry.
+ */
+static void test_tailcall_bpf2bpf_fentry_entry(void)
+{
+	struct bpf_object *tgt_obj = NULL, *fentry_obj = NULL;
+	int err, map_fd, prog_fd, data_fd, i, val;
+	struct bpf_map *prog_array, *data_map;
+	struct bpf_link *fentry_link = NULL;
+	struct bpf_program *prog;
+	char buff[128] = {};
+
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		.data_in = buff,
+		.data_size_in = sizeof(buff),
+		.repeat = 1,
+	);
+
+	err = bpf_prog_test_load("tailcall_bpf2bpf2.bpf.o",
+				 BPF_PROG_TYPE_SCHED_CLS,
+				 &tgt_obj, &prog_fd);
+	if (!ASSERT_OK(err, "load tgt_obj"))
+		return;
+
+	prog_array = bpf_object__find_map_by_name(tgt_obj, "jmp_table");
+	if (!ASSERT_OK_PTR(prog_array, "find jmp_table map"))
+		goto out;
+
+	map_fd = bpf_map__fd(prog_array);
+	if (!ASSERT_FALSE(map_fd < 0, "find jmp_table map fd"))
+		goto out;
+
+	prog = bpf_object__find_program_by_name(tgt_obj, "classifier_0");
+	if (!ASSERT_OK_PTR(prog, "find classifier_0 prog"))
+		goto out;
+
+	prog_fd = bpf_program__fd(prog);
+	if (!ASSERT_FALSE(prog_fd < 0, "find classifier_0 prog fd"))
+		goto out;
+
+	i = 0;
+	err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
+	if (!ASSERT_OK(err, "update jmp_table"))
+		goto out;
+
+	fentry_obj = bpf_object__open_file("tailcall_bpf2bpf_fentry.bpf.o",
+					   NULL);
+	if (!ASSERT_OK_PTR(fentry_obj, "open fentry_obj file"))
+		goto out;
+
+	prog = bpf_object__find_program_by_name(fentry_obj, "fentry");
+	if (!ASSERT_OK_PTR(prog, "find fentry prog"))
+		goto out;
+
+	err = bpf_program__set_attach_target(prog, prog_fd, "classifier_0");
+	if (!ASSERT_OK(err, "set_attach_target classifier_0"))
+		goto out;
+
+	err = bpf_object__load(fentry_obj);
+	if (!ASSERT_OK(err, "load fentry_obj"))
+		goto out;
+
+	fentry_link = bpf_program__attach_trace(prog);
+	if (!ASSERT_OK_PTR(fentry_link, "attach_trace"))
+		goto out;
+
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "tailcall");
+	ASSERT_EQ(topts.retval, 1, "tailcall retval");
+
+	data_map = bpf_object__find_map_by_name(tgt_obj, "tailcall.bss");
+	if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+			  "find tailcall.bss map"))
+		goto out;
+
+	data_fd = bpf_map__fd(data_map);
+	if (!ASSERT_FALSE(data_fd < 0, "find tailcall.bss map fd"))
+		goto out;
+
+	i = 0;
+	err = bpf_map_lookup_elem(data_fd, &i, &val);
+	ASSERT_OK(err, "tailcall count");
+	ASSERT_EQ(val, 34, "tailcall count");
+
+	data_map = bpf_object__find_map_by_name(fentry_obj, ".bss");
+	if (!ASSERT_FALSE(!data_map || !bpf_map__is_internal(data_map),
+			  "find tailcall_bpf2bpf_fentry.bss map"))
+		goto out;
+
+	data_fd = bpf_map__fd(data_map);
+	if (!ASSERT_FALSE(data_fd < 0,
+			  "find tailcall_bpf2bpf_fentry.bss map fd"))
+		goto out;
+
+	i = 0;
+	err = bpf_map_lookup_elem(data_fd, &i, &val);
+	ASSERT_OK(err, "fentry count");
+	ASSERT_EQ(val, 1, "fentry count");
+
+out:
+	bpf_link__destroy(fentry_link);
+	bpf_object__close(fentry_obj);
+	bpf_object__close(tgt_obj);
+}
+
 void test_tailcalls(void)
 {
 	if (test__start_subtest("tailcall_1"))
···
 		test_tailcall_bpf2bpf_4(true);
 	if (test__start_subtest("tailcall_bpf2bpf_6"))
 		test_tailcall_bpf2bpf_6();
+	if (test__start_subtest("tailcall_bpf2bpf_fentry"))
+		test_tailcall_bpf2bpf_fentry();
+	if (test__start_subtest("tailcall_bpf2bpf_fexit"))
+		test_tailcall_bpf2bpf_fexit();
+	if (test__start_subtest("tailcall_bpf2bpf_fentry_fexit"))
+		test_tailcall_bpf2bpf_fentry_fexit();
+	if (test__start_subtest("tailcall_bpf2bpf_fentry_entry"))
+		test_tailcall_bpf2bpf_fentry_entry();
 }

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fentry.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+int count = 0;
+
+SEC("fentry/subprog_tail")
+int BPF_PROG(fentry, struct sk_buff *skb)
+{
+	count++;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_fexit.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Leon Hwang */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+int count = 0;
+
+SEC("fexit/subprog_tail")
+int BPF_PROG(fexit, struct sk_buff *skb)
+{
+	count++;
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";