selftests/bpf: Skip test_bpf_syscall_macro's syscall_arg1 on arm64 and s390

These architectures can provide access to the first syscall argument
only through PT_REGS_PARM1_CORE_SYSCALL().
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220209021745.2215452-8-iii@linux.ibm.com

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

@@ -33,7 +33,11 @@ void test_bpf_syscall_macro(void)
 
 	/* check whether args of syscall are copied correctly */
 	prctl(exp_arg1, exp_arg2, exp_arg3, exp_arg4, exp_arg5);
+#if defined(__aarch64__) || defined(__s390__)
+	ASSERT_NEQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
+#else
 	ASSERT_EQ(skel->bss->arg1, exp_arg1, "syscall_arg1");
+#endif
 	ASSERT_EQ(skel->bss->arg2, exp_arg2, "syscall_arg2");
 	ASSERT_EQ(skel->bss->arg3, exp_arg3, "syscall_arg3");
 	/* it cannot copy arg4 when uses PT_REGS_PARM4 on x86_64 */

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

@@ -28,7 +28,7 @@ int BPF_KPROBE(handle_sys_prctl)
 {
 	struct pt_regs *real_regs;
 	pid_t pid = bpf_get_current_pid_tgid() >> 32;
-	unsigned long tmp;
+	unsigned long tmp = 0;
 
 	if (pid != filter_pid)
 		return 0;
@@ -37,7 +37,9 @@ int BPF_KPROBE(handle_sys_prctl)
 
 	/* test for PT_REGS_PARM */
 
+#if !defined(bpf_target_arm64) && !defined(bpf_target_s390)
 	bpf_probe_read_kernel(&tmp, sizeof(tmp), &PT_REGS_PARM1_SYSCALL(real_regs));
+#endif
 	arg1 = tmp;
 	bpf_probe_read_kernel(&arg2, sizeof(arg2), &PT_REGS_PARM2_SYSCALL(real_regs));
 	bpf_probe_read_kernel(&arg3, sizeof(arg3), &PT_REGS_PARM3_SYSCALL(real_regs));