s390: enable HAVE_FUNCTION_ERROR_INJECTION

This kernel feature is required for enabling BPF_KPROBE_OVERRIDE.

Define override_function_with_return() and regs_set_return_value()
functions, and fix compile errors in syscall_wrapper.h.

Signed-off-by: Ilya Leoshkevich <[email protected]>
Signed-off-by: Heiko Carstens <[email protected]>
diff --git a/arch/s390/lib/error-inject.c b/arch/s390/lib/error-inject.c
new file mode 100644
index 0000000..8c9d4da
--- /dev/null
+++ b/arch/s390/lib/error-inject.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <asm/ptrace.h>
+#include <linux/error-injection.h>
+#include <linux/kprobes.h>
+
+void override_function_with_return(struct pt_regs *regs)
+{
+	/*
+	 * Emulate 'br 14'. 'regs' is captured by kprobes on entry to some
+	 * kernel function.
+	 */
+	regs->psw.addr = regs->gprs[14];
+}
+NOKPROBE_SYMBOL(override_function_with_return);