ex-scall.S

// 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]
	addi	$p1, $r0, #THREAD_CPU_CONTEXT
	smw.bi 	$r6, [$p1], $r14, #0xb		! push r6~r14, fp, lp, sp
	move	$r25, $r1
#if defined(CONFIG_FPU)
	call	_switch_fpu
#endif
	addi	$r1, $r25, #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)