2 ; * FreeRTOS Kernel V10.2.0
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3 ; * Copyright (C) 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 ; * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 ; * this software and associated documentation files (the "Software"), to deal in
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7 ; * the Software without restriction, including without limitation the rights to
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8 ; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 ; * the Software, and to permit persons to whom the Software is furnished to do so,
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10 ; * subject to the following conditions:
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12 ; * The above copyright notice and this permission notice shall be included in all
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13 ; * copies or substantial portions of the Software.
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15 ; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 ; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 ; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 ; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 ; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 ; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 ; * http://www.FreeRTOS.org
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23 ; * http://aws.amazon.com/freertos
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25 ; * 1 tab == 4 spaces!
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28 INCLUDE FreeRTOSConfig.h
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31 EXTERN vTaskSwitchContext
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32 EXTERN ulPortYieldRequired
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33 EXTERN ulPortInterruptNesting
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34 EXTERN vApplicationIRQHandler
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36 PUBLIC FreeRTOS_SWI_Handler
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37 PUBLIC FreeRTOS_IRQ_Handler
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38 PUBLIC vPortRestoreTaskContext
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44 SECTION .text:CODE:ROOT(2)
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49 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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50 ; SVC handler is used to yield a task.
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51 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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52 FreeRTOS_SWI_Handler
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56 ; Save the context of the current task and select a new task to run.
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58 LDR R0, =vTaskSwitchContext
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62 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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63 ; vPortRestoreTaskContext is used to start the scheduler.
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64 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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65 vPortRestoreTaskContext
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69 ; Switch to system mode
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73 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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74 ; IRQ interrupt handler used when individual priorities cannot be masked
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75 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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76 FreeRTOS_IRQ_Handler
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80 ; Return to the interrupted instruction.
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83 ; Push the return address and SPSR
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88 ; Change to supervisor mode to allow reentry.
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91 ; Push used registers.
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94 ; Increment nesting count. r3 holds the address of ulPortInterruptNesting
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95 ; for future use. r1 holds the original ulPortInterruptNesting value for
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97 LDR r3, =ulPortInterruptNesting
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102 ; Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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110 ; Call the port part specific handler.
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111 LDR r0, =vApplicationIRQHandler
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118 ; Write to the EOI register.
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119 LDR r4, =configEOI_ADDRESS
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122 ; Restore the old nesting count
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125 ; A context switch is never performed if the nesting count is not 0.
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127 BNE exit_without_switch
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129 ; Did the interrupt request a context switch? r1 holds the address of
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130 ; ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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132 LDR r1, =ulPortYieldRequired
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135 BNE switch_before_exit
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137 exit_without_switch
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138 ; No context switch. Restore used registers, LR_irq and SPSR before
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148 ; A context switch is to be performed. Clear the context switch pending
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153 ; Restore used registers, LR-irq and SPSR before saving the context
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154 ; to the task stack.
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162 ; Call the function that selects the new task to execute.
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163 ; vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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164 ; instructions, or 8 byte aligned stack allocated data. LR does not need
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165 ; saving as a new LR will be loaded by portRESTORE_CONTEXT anyway.
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166 LDR r0, =vTaskSwitchContext
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169 ; Restore the context of, and branch to, the task selected to execute next.
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170 portRESTORE_CONTEXT
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