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152 lines
4.8 KiB
ArmAsm
152 lines
4.8 KiB
ArmAsm
/*
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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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#include "PriorityDefinitions.h"
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PUBLIC _prvStartFirstTask
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PUBLIC ___interrupt_27
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EXTERN _pxCurrentTCB
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EXTERN _vTaskSwitchContext
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RSEG CODE:CODE(4)
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_prvStartFirstTask:
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/* When starting the scheduler there is nothing that needs moving to the
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interrupt stack because the function is not called from an interrupt.
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Just ensure the current stack is the user stack. */
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SETPSW U
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/* Obtain the location of the stack associated with which ever task
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pxCurrentTCB is currently pointing to. */
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MOV.L #_pxCurrentTCB, R15
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MOV.L [R15], R15
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MOV.L [R15], R0
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/* Restore the registers from the stack of the task pointed to by
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pxCurrentTCB. */
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POP R15
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/* Accumulator low 32 bits. */
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MVTACLO R15
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POP R15
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/* Accumulator high 32 bits. */
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MVTACHI R15
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/* R1 to R15 - R0 is not included as it is the SP. */
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POPM R1-R15
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/* This pops the remaining registers. */
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RTE
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NOP
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NOP
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/*-----------------------------------------------------------*/
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/* The software interrupt - overwrite the default 'weak' definition. */
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___interrupt_27:
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/* Re-enable interrupts. */
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SETPSW I
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/* Move the data that was automatically pushed onto the interrupt stack when
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the interrupt occurred from the interrupt stack to the user stack.
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R15 is saved before it is clobbered. */
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PUSH.L R15
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/* Read the user stack pointer. */
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MVFC USP, R15
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/* Move the address down to the data being moved. */
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SUB #12, R15
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MVTC R15, USP
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/* Copy the data across, R15, then PC, then PSW. */
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MOV.L [ R0 ], [ R15 ]
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MOV.L 4[ R0 ], 4[ R15 ]
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MOV.L 8[ R0 ], 8[ R15 ]
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/* Move the interrupt stack pointer to its new correct position. */
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ADD #12, R0
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/* All the rest of the registers are saved directly to the user stack. */
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SETPSW U
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/* Save the rest of the general registers (R15 has been saved already). */
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PUSHM R1-R14
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/* Save the accumulator. */
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MVFACHI R15
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PUSH.L R15
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/* Middle word. */
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MVFACMI R15
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/* Shifted left as it is restored to the low order word. */
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SHLL #16, R15
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PUSH.L R15
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/* Save the stack pointer to the TCB. */
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MOV.L #_pxCurrentTCB, R15
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MOV.L [ R15 ], R15
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MOV.L R0, [ R15 ]
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/* Ensure the interrupt mask is set to the syscall priority while the kernel
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structures are being accessed. */
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MVTIPL #configMAX_SYSCALL_INTERRUPT_PRIORITY
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/* Select the next task to run. */
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BSR.A _vTaskSwitchContext
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/* Reset the interrupt mask as no more data structure access is required. */
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MVTIPL #configKERNEL_INTERRUPT_PRIORITY
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/* Load the stack pointer of the task that is now selected as the Running
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state task from its TCB. */
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MOV.L #_pxCurrentTCB,R15
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MOV.L [ R15 ], R15
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MOV.L [ R15 ], R0
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/* Restore the context of the new task. The PSW (Program Status Word) and
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PC will be popped by the RTE instruction. */
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POP R15
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MVTACLO R15
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POP R15
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MVTACHI R15
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POPM R1-R15
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RTE
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NOP
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NOP
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/*-----------------------------------------------------------*/
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END
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