v4.19.13 snapshot.
diff --git a/arch/nds32/kernel/ex-scall.S b/arch/nds32/kernel/ex-scall.S
new file mode 100644
index 0000000..36aa87e
--- /dev/null
+++ b/arch/nds32/kernel/ex-scall.S
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/linkage.h>
+#include <asm/unistd.h>
+#include <asm/assembler.h>
+#include <asm/nds32.h>
+#include <asm/asm-offsets.h>
+#include <asm/thread_info.h>
+#include <asm/current.h>
+
+/*
+ * $r0 = previous task_struct,
+ * $r1 = next task_struct,
+ * previous and next are guaranteed not to be the same.
+ */
+
+ENTRY(__switch_to)
+
+ la $p0, __entry_task
+ sw $r1, [$p0]
+ move $p1, $r0
+ addi $p1, $p1, #THREAD_CPU_CONTEXT
+ smw.bi $r6, [$p1], $r14, #0xb ! push r6~r14, fp, lp, sp
+ move $r25, $r1
+ addi $r1, $r1, #THREAD_CPU_CONTEXT
+ lmw.bi $r6, [$r1], $r14, #0xb ! pop r6~r14, fp, lp, sp
+ ret
+
+
+#define tbl $r8
+
+/*
+ * $r7 will be writen as syscall nr
+ */
+ .macro get_scno
+ lwi $r7, [$sp + R15_OFFSET]
+ swi $r7, [$sp + SYSCALLNO_OFFSET]
+ .endm
+
+ .macro updateipc
+ addi $r17, $r13, #4 ! $r13 is $IPC
+ swi $r17, [$sp + IPC_OFFSET]
+ .endm
+
+ENTRY(eh_syscall)
+ updateipc
+
+ get_scno
+ gie_enable
+
+ lwi $p0, [tsk+#TSK_TI_FLAGS] ! check for syscall tracing
+
+ andi $p1, $p0, #_TIF_WORK_SYSCALL_ENTRY ! are we tracing syscalls?
+ bnez $p1, __sys_trace
+
+ la $lp, ret_fast_syscall ! return address
+jmp_systbl:
+ addi $p1, $r7, #-__NR_syscalls ! syscall number of syscall instruction is guarded by addembler
+ bgez $p1, _SCNO_EXCEED ! call sys_* routine
+ la tbl, sys_call_table ! load syscall table pointer
+ slli $p1, $r7, #2
+ add $p1, tbl, $p1
+ lwi $p1, [$p1]
+ jr $p1 ! no return
+
+_SCNO_EXCEED:
+ ori $r0, $r7, #0
+ ori $r1, $sp, #0
+ b bad_syscall
+
+/*
+ * This is the really slow path. We're going to be doing
+ * context switches, and waiting for our parent to respond.
+ */
+__sys_trace:
+ move $r0, $sp
+ bal syscall_trace_enter
+ move $r7, $r0
+ la $lp, __sys_trace_return ! return address
+
+ addi $p1, $r7, #1
+ beqz $p1, ret_slow_syscall ! fatal signal is pending
+
+ addi $p1, $sp, #R0_OFFSET ! pointer to regs
+ lmw.bi $r0, [$p1], $r5 ! have to reload $r0 - $r5
+ b jmp_systbl
+
+__sys_trace_return:
+ swi $r0, [$sp+#R0_OFFSET] ! T: save returned $r0
+ move $r0, $sp ! set pt_regs for syscall_trace_leave
+ bal syscall_trace_leave
+ b ret_slow_syscall
+
+ENTRY(sys_rt_sigreturn_wrapper)
+ addi $r0, $sp, #0
+ b sys_rt_sigreturn
+ENDPROC(sys_rt_sigreturn_wrapper)