selftests/bpf: Fix test_xdp_adjust_tail_grow2 on s390x

s390x cache line size is 256 bytes, so skb_shared_info must be aligned
on a much larger boundary than for x86.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-17-iii@linux.ibm.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -76,10 +76,15 @@ static void test_xdp_adjust_tail_grow2(void)
 {
 	const char *file = "./test_xdp_adjust_tail_grow.bpf.o";
 	char buf[4096]; /* avoid segfault: large buf to hold grow results */
-	int tailroom = 320; /* SKB_DATA_ALIGN(sizeof(struct skb_shared_info))*/;
 	struct bpf_object *obj;
 	int err, cnt, i;
 	int max_grow, prog_fd;
+	/* SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) */
+#if defined(__s390x__)
+	int tailroom = 512;
+#else
+	int tailroom = 320;
+#endif
 
 	LIBBPF_OPTS(bpf_test_run_opts, tattr,
 		.repeat		= 1,

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

@@ -9,6 +9,12 @@ int _xdp_adjust_tail_grow(struct xdp_md *xdp)
 	void *data = (void *)(long)xdp->data;
 	int data_len = bpf_xdp_get_buff_len(xdp);
 	int offset = 0;
+	/* SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) */
+#if defined(__TARGET_ARCH_s390)
+	int tailroom = 512;
+#else
+	int tailroom = 320;
+#endif
 
 	/* Data length determine test case */
 
@@ -20,7 +26,7 @@ int _xdp_adjust_tail_grow(struct xdp_md *xdp)
 		offset = 128;
 	} else if (data_len == 128) {
 		/* Max tail grow 3520 */
-		offset = 4096 - 256 - 320 - data_len;
+		offset = 4096 - 256 - tailroom - data_len;
 	} else if (data_len == 9000) {
 		offset = 10;
 	} else if (data_len == 9001) {