120 lines
4.3 KiB
C
120 lines
4.3 KiB
C
/************************************************************************
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* up_initialstate.c
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*
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* Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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************************************************************************/
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/************************************************************************
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* Included Files
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************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <sched.h>
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#include "up_internal.h"
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/************************************************************************
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* Private Definitions
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************************************************************************/
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/************************************************************************
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* Private Data
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************************************************************************/
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/************************************************************************
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* Private Functions
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************************************************************************/
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/************************************************************************
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* Public Functions
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************************************************************************/
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/************************************************************************
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* Name: up_initial_state
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*
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* Description:
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* A new thread is being started and a new TCB
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* has been created. This function is called to initialize
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* the processor specific portions of the new TCB.
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*
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* This function must setup the intial architecture registers
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* and/or stack so that execution will begin at tcb->start
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* on the next context switch.
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*
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************************************************************************/
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void up_initial_state(FAR struct tcb_s *tcb)
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{
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FAR uint8_t *frame = tcb->xcp.stack;
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FAR uint8_t *regs = tcb->xcp.regs;
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/* This is the form of initial stack frame
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*
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* This initial stack frame will be configured to hold.
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* (1) The 16-bit return address of either:
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*
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* void task_start(void);
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* void pthread_start(void)
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*
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* The return address is stored at the top of stack.
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* so that the RETI instruction will work:
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*
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* PC15-8 <- ((SP))
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* (SP) <- (SP) -1
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* PC7-0 <- ((SP))
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* (SP) <- (SP) -1
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*/
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frame[FRAME_RETLS] = (((uint16_t)tcb->start) & 0xff);
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frame[FRAME_RETMS] = (((uint16_t)tcb->start) >> 8);
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/* The context save area for registers a, ie, and dpstr
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* follows the return address in the stack frame.
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*/
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frame[FRAME_IE] = 0x80;
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/* Save the number of bytes in the frame (which will be used
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* to initialize the stack pointer when the task is started).
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*/
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tcb->xcp.nbytes = FRAME_SIZE;
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/* Initialize the remaining register save area which is
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* outside of the stack save area.
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*/
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tcb->xcp.regs[REGS_PSW] = 0;
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}
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