up_createstack.c

這是一個實時嵌入式作業系統 實作了MCS51 ARM等MCU

/************************************************************
 * common/up_createstack.c
 *
 *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <[e-mail]>
 *
 * 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 Gregory Nutt 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 <sys/types.h>
#include <sched.h>
#include <debug.h>
#include <nuttx/kmalloc.h>
#include <nuttx/arch.h>
#include "up_arch.h"
#include "up_internal.h"

/************************************************************
 * Private Types
 ************************************************************/

/************************************************************
 * Private Function Prototypes
 ************************************************************/

/************************************************************
 * Global Functions
 ************************************************************/

/************************************************************
 * Name: up_create_stack
 *
 * Description:
 *   Allocate a stack for a new thread and setup
 *   up stack-related information in the TCB.
 *
 *   The following TCB fields must be initialized:
 *   adj_stack_size: Stack size after adjustment for hardware,
 *     processor, etc.  This value is retained only for debug
 *     purposes.
 *   stack_alloc_ptr: Pointer to allocated stack
 *   adj_stack_ptr: Adjusted stack_alloc_ptr for HW.  The
 *     initial value of the stack pointer.
 *
 * Inputs:
 *   tcb: The TCB of new task
 *   stack_size:  The requested stack size.  At least this much
 *     must be allocated.
 ************************************************************/

STATUS up_create_stack(_TCB *tcb, size_t stack_size)
{
  if (tcb->stack_alloc_ptr &&
      tcb->adj_stack_size != stack_size)
    {
      sched_free(tcb->stack_alloc_ptr);
      tcb->stack_alloc_ptr = NULL;
    }

   if (!tcb->stack_alloc_ptr)
     {
       tcb->stack_alloc_ptr = (uint32 *)kzmalloc(stack_size);
     }

   if (tcb->stack_alloc_ptr)
     {
       size_t top_of_stack;
       size_t size_of_stack;

       /* The Arm7Tdmi uses a push-down stack:  the stack grows
	* toward loweraddresses in memory.  The stack pointer
	* register, points to the lowest, valid work address
	* (the "top" of the stack).  Items on the stack are
	* referenced as positive word offsets from sp.
	*/

       top_of_stack = (uint32)tcb->stack_alloc_ptr + stack_size - 4;

       /* The Arm7Tdmi stack must be aligned at word (4 byte)
	* boundaries. If necessary top_of_stack must be rounded
	* down to the next boundary
	*/

       top_of_stack &= ~3;
       size_of_stack = top_of_stack - (uint32)tcb->stack_alloc_ptr + 4;

       /* Save the adjusted stack values in the _TCB */

       tcb->adj_stack_ptr  = (uint32*)top_of_stack;
       tcb->adj_stack_size = size_of_stack;

       up_ledon(LED_STACKCREATED);
       return OK;
     }

   return ERROR;
}