/************************************************************************************
 * arch/arm/src/armv6-m/up_saveusercontext.S
 *
 *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ************************************************************************************/

/************************************************************************************
 * Included Files
 ************************************************************************************/

#include <nuttx/config.h>
#include <arch/irq.h>

#include "nvic.h"
#include "svcall.h"

/************************************************************************************
 * Pre-processor Definitions
 ************************************************************************************/

/************************************************************************************
 * Global Symbols
 ************************************************************************************/

	.cpu	cortex-m0
	.file	"up_saveusercontext.S"

/************************************************************************************
 * Macros
 ************************************************************************************/

/************************************************************************************
 * Public Functions
 ************************************************************************************/

/************************************************************************************
 * Name: up_saveusercontext
 *
 * Description:
 *   Save the current thread context.  Full prototype is:
 *
 *   int  up_saveusercontext(uint32_t *saveregs);
 *
 * Return:
 *   0: Normal return
 *   1: Context switch return
 *
 ************************************************************************************/

	.text
	.align	2
	.code	16
	.thumb_func
	.globl	up_saveusercontext
	.type	up_saveusercontext, function
up_saveusercontext:

	/* Perform the System call with R0=0 and R1=regs */

	mov		r1, r0					/* R1: regs */
	mov		r0, #SYS_save_context	/* R0: save context (also return value) */
	svc		0						/* Force synchronous SVCall (or Hard Fault) */

	/* There are two return conditions.  On the first return, R0 (the
	 * return value will be zero.  On the second return we need to
	 * force R0 to be 1.
	 */

	mov		r3, #(4*REG_R0)			/* R3=Offset to R0 storage */
	add		r2, r1, r3				/* R2=Address of R0 storage */
	mov		r3, #1					/* R3=Return value of one */
	str		r3, [r2, #0]			/* Save return value */
	bx		lr						/* "normal" return with r0=0 or
									 * context switch with r0=1 */
	.size	up_saveusercontext, .-up_saveusercontext
	.end