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/************************************************************************
* up_initialstate.c
*
* Copyright (C) 2007, 2009 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 <stdint.h>
#include <sched.h>
#include "up_internal.h"
/************************************************************************
* Private Definitions
************************************************************************/
/************************************************************************
* Private Data
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: up_initial_state
*
* Description:
* A new thread is being started and a new TCB
* has been created. This function is called to initialize
* the processor specific portions of the new TCB.
*
* This function must setup the intial architecture registers
* and/or stack so that execution will begin at tcb->start
* on the next context switch.
*
************************************************************************/
void up_initial_state(FAR struct tcb_s *tcb)
{
FAR uint8_t *frame = tcb->xcp.stack;
FAR uint8_t *regs = tcb->xcp.regs;
/* This is the form of initial stack frame
*
* This initial stack frame will be configured to hold.
* (1) The 16-bit return address of either:
*
* void task_start(void);
* void pthread_start(void)
*
* The return address is stored at the top of stack.
* so that the RETI instruction will work:
*
* PC15-8 <- ((SP))
* (SP) <- (SP) -1
* PC7-0 <- ((SP))
* (SP) <- (SP) -1
*/
frame[FRAME_RETLS] = (((uint16_t)tcb->start) & 0xff);
frame[FRAME_RETMS] = (((uint16_t)tcb->start) >> 8);
/* The context save area for registers a, ie, and dpstr
* follows the return address in the stack frame.
*/
frame[FRAME_IE] = 0x80;
/* Save the number of bytes in the frame (which will be used
* to initialize the stack pointer when the task is started).
*/
tcb->xcp.nbytes = FRAME_SIZE;
/* Initialize the remaining register save area which is
* outside of the stack save area.
*/
tcb->xcp.regs[REGS_PSW] = 0;
}
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