selftests/bpf: Test struct_ops maps with a large number of struct_ops program.

Create and load a struct_ops map with a large number of struct_ops
programs to generate trampolines taking a size over multiple pages. The
map includes 40 programs. Their trampolines takes 6.6k+, more than 1.5
pages, on x86.
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240224223418.526631-4-thinker.li@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h

@@ -43,6 +43,50 @@ struct bpf_testmod_ops {
 		int b;
 	} unsupported;
 	int data;
+
+	/* The following pointers are used to test the maps having multiple
+	 * pages of trampolines.
+	 */
+	int (*tramp_1)(int value);
+	int (*tramp_2)(int value);
+	int (*tramp_3)(int value);
+	int (*tramp_4)(int value);
+	int (*tramp_5)(int value);
+	int (*tramp_6)(int value);
+	int (*tramp_7)(int value);
+	int (*tramp_8)(int value);
+	int (*tramp_9)(int value);
+	int (*tramp_10)(int value);
+	int (*tramp_11)(int value);
+	int (*tramp_12)(int value);
+	int (*tramp_13)(int value);
+	int (*tramp_14)(int value);
+	int (*tramp_15)(int value);
+	int (*tramp_16)(int value);
+	int (*tramp_17)(int value);
+	int (*tramp_18)(int value);
+	int (*tramp_19)(int value);
+	int (*tramp_20)(int value);
+	int (*tramp_21)(int value);
+	int (*tramp_22)(int value);
+	int (*tramp_23)(int value);
+	int (*tramp_24)(int value);
+	int (*tramp_25)(int value);
+	int (*tramp_26)(int value);
+	int (*tramp_27)(int value);
+	int (*tramp_28)(int value);
+	int (*tramp_29)(int value);
+	int (*tramp_30)(int value);
+	int (*tramp_31)(int value);
+	int (*tramp_32)(int value);
+	int (*tramp_33)(int value);
+	int (*tramp_34)(int value);
+	int (*tramp_35)(int value);
+	int (*tramp_36)(int value);
+	int (*tramp_37)(int value);
+	int (*tramp_38)(int value);
+	int (*tramp_39)(int value);
+	int (*tramp_40)(int value);
 };
 
 #endif /* _BPF_TESTMOD_H */

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+
+#include "struct_ops_multi_pages.skel.h"
+
+static void do_struct_ops_multi_pages(void)
+{
+	struct struct_ops_multi_pages *skel;
+	struct bpf_link *link;
+
+	/* The size of all trampolines of skel->maps.multi_pages should be
+	 * over 1 page (at least for x86).
+	 */
+	skel = struct_ops_multi_pages__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "struct_ops_multi_pages_open_and_load"))
+		return;
+
+	link = bpf_map__attach_struct_ops(skel->maps.multi_pages);
+	ASSERT_OK_PTR(link, "attach_multi_pages");
+
+	bpf_link__destroy(link);
+	struct_ops_multi_pages__destroy(skel);
+}
+
+void test_struct_ops_multi_pages(void)
+{
+	if (test__start_subtest("multi_pages"))
+		do_struct_ops_multi_pages();
+}

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

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+#define TRAMP(x) \
+	SEC("struct_ops/tramp_" #x)		\
+	int BPF_PROG(tramp_ ## x, int a)	\
+	{					\
+		return a;			\
+	}
+
+TRAMP(1)
+TRAMP(2)
+TRAMP(3)
+TRAMP(4)
+TRAMP(5)
+TRAMP(6)
+TRAMP(7)
+TRAMP(8)
+TRAMP(9)
+TRAMP(10)
+TRAMP(11)
+TRAMP(12)
+TRAMP(13)
+TRAMP(14)
+TRAMP(15)
+TRAMP(16)
+TRAMP(17)
+TRAMP(18)
+TRAMP(19)
+TRAMP(20)
+TRAMP(21)
+TRAMP(22)
+TRAMP(23)
+TRAMP(24)
+TRAMP(25)
+TRAMP(26)
+TRAMP(27)
+TRAMP(28)
+TRAMP(29)
+TRAMP(30)
+TRAMP(31)
+TRAMP(32)
+TRAMP(33)
+TRAMP(34)
+TRAMP(35)
+TRAMP(36)
+TRAMP(37)
+TRAMP(38)
+TRAMP(39)
+TRAMP(40)
+
+#define F_TRAMP(x) .tramp_ ## x = (void *)tramp_ ## x
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops multi_pages = {
+	F_TRAMP(1),
+	F_TRAMP(2),
+	F_TRAMP(3),
+	F_TRAMP(4),
+	F_TRAMP(5),
+	F_TRAMP(6),
+	F_TRAMP(7),
+	F_TRAMP(8),
+	F_TRAMP(9),
+	F_TRAMP(10),
+	F_TRAMP(11),
+	F_TRAMP(12),
+	F_TRAMP(13),
+	F_TRAMP(14),
+	F_TRAMP(15),
+	F_TRAMP(16),
+	F_TRAMP(17),
+	F_TRAMP(18),
+	F_TRAMP(19),
+	F_TRAMP(20),
+	F_TRAMP(21),
+	F_TRAMP(22),
+	F_TRAMP(23),
+	F_TRAMP(24),
+	F_TRAMP(25),
+	F_TRAMP(26),
+	F_TRAMP(27),
+	F_TRAMP(28),
+	F_TRAMP(29),
+	F_TRAMP(30),
+	F_TRAMP(31),
+	F_TRAMP(32),
+	F_TRAMP(33),
+	F_TRAMP(34),
+	F_TRAMP(35),
+	F_TRAMP(36),
+	F_TRAMP(37),
+	F_TRAMP(38),
+	F_TRAMP(39),
+	F_TRAMP(40),
+};