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/*
* FreeRTOS Kernel <DEVELOPMENT BRANCH>
* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* SPDX-License-Identifier: MIT
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* https://www.FreeRTOS.org
* https://github.com/FreeRTOS
*
*/
typedef void TCB_t;
extern volatile TCB_t * volatile pxCurrentTCB;
extern void vTaskSwitchContext( void );
/*
* Saves the stack pointer for one task into its TCB, calls
* vTaskSwitchContext() to update the TCB being used, then restores the stack
* from the new TCB read to run the task.
*/
void portSWITCH_CONTEXT( void );
/*
* Load the stack pointer from the TCB of the task which is going to be first
* to execute. Then force an IRET so the registers and IP are popped off the
* stack.
*/
void portFIRST_CONTEXT( void );
/* There are slightly different versions depending on whether you are building
* to include debugger information. If debugger information is used then there
* are a couple of extra bytes left of the ISR stack (presumably for use by the
* debugger). The true stack pointer is then stored in the bp register. We add
* 2 to the stack pointer to remove the extra bytes before we restore our context. */
#ifdef DEBUG_BUILD
#pragma aux portSWITCH_CONTEXT = "mov ax, seg pxCurrentTCB" \
"mov ds, ax" \
"les bx, pxCurrentTCB" /* Save the stack pointer into the TCB. */ \
"mov es:0x2[ bx ], ss" \
"mov es:[ bx ], sp" \
"call vTaskSwitchContext" /* Perform the switch. */ \
"mov ax, seg pxCurrentTCB" /* Restore the stack pointer from the TCB. */ \
"mov ds, ax" \
"les bx, dword ptr pxCurrentTCB" \
"mov ss, es:[ bx + 2 ]" \
"mov sp, es:[ bx ]" \
"mov bp, sp" /* Prepair the bp register for the restoration of the SP in the compiler generated portion of the ISR */ \
"add bp, 0x0002"
#pragma aux portFIRST_CONTEXT = "mov ax, seg pxCurrentTCB" \
"mov ds, ax" \
"les bx, dword ptr pxCurrentTCB" \
"mov ss, es:[ bx + 2 ]" \
"mov sp, es:[ bx ]" \
"add sp, 0x0002" /* Remove the extra bytes that exist in debug builds before restoring the context. */ \
"pop ax" \
"pop ax" \
"pop es" \
"pop ds" \
"popa" \
"iret"
#else /* ifdef DEBUG_BUILD */
#pragma aux portSWITCH_CONTEXT = "mov ax, seg pxCurrentTCB" \
"mov ds, ax" \
"les bx, pxCurrentTCB" /* Save the stack pointer into the TCB. */ \
"mov es:0x2[ bx ], ss" \
"mov es:[ bx ], sp" \
"call vTaskSwitchContext" /* Perform the switch. */ \
"mov ax, seg pxCurrentTCB" /* Restore the stack pointer from the TCB. */ \
"mov ds, ax" \
"les bx, dword ptr pxCurrentTCB" \
"mov ss, es:[ bx + 2 ]" \
"mov sp, es:[ bx ]"
#pragma aux portFIRST_CONTEXT = "mov ax, seg pxCurrentTCB" \
"mov ds, ax" \
"les bx, dword ptr pxCurrentTCB" \
"mov ss, es:[ bx + 2 ]" \
"mov sp, es:[ bx ]" \
"pop ax" \
"pop ax" \
"pop es" \
"pop ds" \
"popa" \
"iret"
#endif /* ifdef DEBUG_BUILD */
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