rt-thread-official/bsp/qemu-vexpress-a9/cpu/stack.c

/*
 * File      : stack.c
 * This file is part of RT-Thread RTOS
 * COPYRIGHT (C) 2011, RT-Thread Development Team
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rt-thread.org/license/LICENSE
 *
 * Change Logs:
 * Date           Author       Notes
 * 2011-09-23     Bernard      the first version
 * 2011-10-05     Bernard      add thumb mode
 */
#include <rtthread.h>
#include <board.h>

/**
 * @addtogroup AM33xx
 */
/*@{*/

/**
 * This function will initialize thread stack
 *
 * @param tentry the entry of thread
 * @param parameter the parameter of entry 
 * @param stack_addr the beginning stack address
 * @param texit the function will be called when thread exit
 *
 * @return stack address
 */
rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter,
        rt_uint8_t *stack_addr, void *texit)
{
    rt_uint32_t *stk;

    stack_addr += sizeof(rt_uint32_t);
    stack_addr  = (rt_uint8_t *)RT_ALIGN_DOWN((rt_uint32_t)stack_addr, 8);
    stk 	 = (rt_uint32_t*)stack_addr;
    *(--stk) = (rt_uint32_t)tentry;			/* entry point */
    *(--stk) = (rt_uint32_t)texit;			/* lr */
    *(--stk) = 0;							/* r12 */
    *(--stk) = 0;							/* r11 */
    *(--stk) = 0;							/* r10 */
    *(--stk) = 0;							/* r9 */
    *(--stk) = 0;							/* r8 */
    *(--stk) = 0;							/* r7 */
    *(--stk) = 0;							/* r6 */
    *(--stk) = 0;							/* r5 */
    *(--stk) = 0;							/* r4 */
    *(--stk) = 0;							/* r3 */
    *(--stk) = 0;							/* r2 */
    *(--stk) = 0;							/* r1 */
    *(--stk) = (rt_uint32_t)parameter;		/* r0 : argument */
    /* cpsr */
    if ((rt_uint32_t)tentry & 0x01)
        *(--stk) = SVCMODE | 0x20;			/* thumb mode */
    else
        *(--stk) = SVCMODE;					/* arm mode   */

#ifdef RT_USING_LWP
    *(--stk) = 0;		/* user lr */
    *(--stk) = 0;		/* user sp*/
#endif

    /* return task's current stack address */
    return (rt_uint8_t *)stk;
}

/*@}*/