selftests/bpf: Fix test_xdp_adjust_tail_grow2 selftest on powerpc

On powerpc cache line size is 128 bytes, so skb_shared_info must be
aligned accordingly.

Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20250110103109.3670793-1-skb99@linux.ibm.com

Author: Saket Kumar Bhaskar

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

@@ -82,6 +82,8 @@ static void test_xdp_adjust_tail_grow2(void)
 	/* SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) */
 #if defined(__s390x__)
 	int tailroom = 512;
+#elif defined(__powerpc__)
+	int tailroom = 384;
 #else
 	int tailroom = 320;
 #endif

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

@@ -10,6 +10,8 @@ int _xdp_adjust_tail_grow(struct xdp_md *xdp)
 	/* SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) */
 #if defined(__TARGET_ARCH_s390)
 	int tailroom = 512;
+#elif defined(__TARGET_ARCH_powerpc)
+	int tailroom = 384;
 #else
 	int tailroom = 320;
 #endif