2 * FreeRTOS Kernel V10.0.0
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3 * Copyright (C) 2017 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. If you wish to use our Amazon
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14 * FreeRTOS name, please do so in a fair use way that does not cause confusion.
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16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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18 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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19 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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20 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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23 * http://www.FreeRTOS.org
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24 * http://aws.amazon.com/freertos
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26 * 1 tab == 4 spaces!
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29 #include "PriorityDefinitions.h"
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31 PUBLIC _prvStartFirstTask
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32 PUBLIC ___interrupt_27
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34 EXTERN _pxCurrentTCB
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35 EXTERN _vTaskSwitchContext
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41 /* When starting the scheduler there is nothing that needs moving to the
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42 interrupt stack because the function is not called from an interrupt.
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43 Just ensure the current stack is the user stack. */
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46 /* Obtain the location of the stack associated with which ever task
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47 pxCurrentTCB is currently pointing to. */
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48 MOV.L #_pxCurrentTCB, R15
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52 /* Restore the registers from the stack of the task pointed to by
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56 /* Accumulator low 32 bits. */
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60 /* Accumulator high 32 bits. */
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64 /* Floating point status word. */
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67 /* R1 to R15 - R0 is not included as it is the SP. */
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70 /* This pops the remaining registers. */
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75 /*-----------------------------------------------------------*/
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77 /* The software interrupt - overwrite the default 'weak' definition. */
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80 /* Re-enable interrupts. */
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83 /* Move the data that was automatically pushed onto the interrupt stack when
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84 the interrupt occurred from the interrupt stack to the user stack.
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86 R15 is saved before it is clobbered. */
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89 /* Read the user stack pointer. */
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92 /* Move the address down to the data being moved. */
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96 /* Copy the data across, R15, then PC, then PSW. */
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97 MOV.L [ R0 ], [ R15 ]
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98 MOV.L 4[ R0 ], 4[ R15 ]
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99 MOV.L 8[ R0 ], 8[ R15 ]
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101 /* Move the interrupt stack pointer to its new correct position. */
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104 /* All the rest of the registers are saved directly to the user stack. */
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107 /* Save the rest of the general registers (R15 has been saved already). */
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110 /* Save the FPSW and accumulator. */
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119 /* Shifted left as it is restored to the low order word. */
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123 /* Save the stack pointer to the TCB. */
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124 MOV.L #_pxCurrentTCB, R15
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128 /* Ensure the interrupt mask is set to the syscall priority while the kernel
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129 structures are being accessed. */
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130 MVTIPL #configMAX_SYSCALL_INTERRUPT_PRIORITY
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132 /* Select the next task to run. */
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133 BSR.A _vTaskSwitchContext
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135 /* Reset the interrupt mask as no more data structure access is required. */
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136 MVTIPL #configKERNEL_INTERRUPT_PRIORITY
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138 /* Load the stack pointer of the task that is now selected as the Running
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139 state task from its TCB. */
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140 MOV.L #_pxCurrentTCB,R15
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144 /* Restore the context of the new task. The PSW (Program Status Word) and
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145 PC will be popped by the RTE instruction. */
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157 /*-----------------------------------------------------------*/
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