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142 lines
4.7 KiB
C
142 lines
4.7 KiB
C
/*
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* FreeRTOS Kernel <DEVELOPMENT BRANCH>
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* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* SPDX-License-Identifier: MIT
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* https://www.FreeRTOS.org
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* https://github.com/FreeRTOS
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*
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*/
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/*
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Changes from V1.00:
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+ pxPortInitialiseStack() now initialises the stack of new tasks to the
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same format used by the compiler. This allows the compiler generated
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interrupt mechanism to be used for context switches.
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Changes from V2.4.2:
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+ pvPortMalloc and vPortFree have been removed. The projects now use
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the definitions from the source/portable/MemMang directory.
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Changes from V2.6.1:
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+ usPortCheckFreeStackSpace() has been moved to tasks.c.
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*/
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#include <stdlib.h>
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#include "FreeRTOS.h"
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/*-----------------------------------------------------------*/
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/* See header file for description. */
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StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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{
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StackType_t DS_Reg = 0;
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StackType_t * pxOriginalSP;
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/* Place a few bytes of known values on the bottom of the stack.
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This is just useful for debugging. */
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*pxTopOfStack = 0x1111;
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pxTopOfStack--;
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*pxTopOfStack = 0x2222;
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pxTopOfStack--;
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*pxTopOfStack = 0x3333;
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pxTopOfStack--;
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*pxTopOfStack = 0x4444;
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pxTopOfStack--;
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*pxTopOfStack = 0x5555;
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pxTopOfStack--;
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/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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/* We are going to start the scheduler using a return from interrupt
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instruction to load the program counter, so first there would be the
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status register and interrupt return address. We make this the start
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of the task. */
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*pxTopOfStack = portINITIAL_SW;
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pxTopOfStack--;
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*pxTopOfStack = FP_SEG( pxCode );
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pxTopOfStack--;
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*pxTopOfStack = FP_OFF( pxCode );
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pxTopOfStack--;
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/* We are going to setup the stack for the new task to look like
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the stack frame was setup by a compiler generated ISR. We need to know
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the address of the existing stack top to place in the SP register within
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the stack frame. pxOriginalSP holds SP before (simulated) pusha was
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called. */
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pxOriginalSP = pxTopOfStack;
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/* The remaining registers would be pushed on the stack by our context
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switch function. These are loaded with values simply to make debugging
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easier. */
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*pxTopOfStack = FP_OFF( pvParameters ); /* AX */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0xCCCC; /* CX */
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pxTopOfStack--;
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*pxTopOfStack = FP_SEG( pvParameters ); /* DX */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0xBBBB; /* BX */
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pxTopOfStack--;
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*pxTopOfStack = FP_OFF( pxOriginalSP ); /* SP */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0xBBBB; /* BP */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0x0123; /* SI */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0xDDDD; /* DI */
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/* We need the true data segment. */
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__asm{ MOV DS_Reg, DS };
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pxTopOfStack--;
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*pxTopOfStack = DS_Reg; /* DS */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) 0xEEEE; /* ES */
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/* The AX register is pushed again twice - don't know why. */
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pxTopOfStack--;
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*pxTopOfStack = FP_OFF( pvParameters ); /* AX */
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pxTopOfStack--;
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*pxTopOfStack = FP_OFF( pvParameters ); /* AX */
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#ifdef DEBUG_BUILD
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/* The compiler adds space to each ISR stack if building to
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include debug information. Presumably this is used by the
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debugger - we don't need to initialise it to anything just
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make sure it is there. */
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pxTopOfStack--;
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#endif
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/*lint +e950 +e611 +e923 */
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return pxTopOfStack;
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}
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/*-----------------------------------------------------------*/
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