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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36 /* Variables and functions. */
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37 .extern ulMaxAPIPriorityMask
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38 .extern _freertos_vector_table
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39 .extern pxCurrentTCB
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40 .extern vTaskSwitchContext
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41 .extern vApplicationIRQHandler
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42 .extern ulPortInterruptNesting
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43 .extern ulPortTaskHasFPUContext
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45 .extern ulPortYieldRequired
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47 .global FreeRTOS_IRQ_Handler
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48 .global FreeRTOS_SVC_Handler
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49 .global vPortRestoreTaskContext
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52 .macro portSAVE_CONTEXT
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54 /* Save the LR and SPSR onto the system mode stack before switching to
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55 system mode to save the remaining system mode registers. */
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56 SRSDB sp!, #SYS_MODE
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60 /* Push the critical nesting count. */
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61 LDR R2, ulCriticalNestingConst
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65 /* Does the task have a floating point context that needs saving? If
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66 ulPortTaskHasFPUContext is 0 then no. */
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67 LDR R2, ulPortTaskHasFPUContextConst
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71 /* Save the floating point context, if any. */
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74 #if configFPU_D32 == 1
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76 #endif /* configFPU_D32 */
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79 /* Save ulPortTaskHasFPUContext itself. */
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82 /* Save the stack pointer in the TCB. */
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83 LDR R0, pxCurrentTCBConst
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89 ; /**********************************************************************/
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91 .macro portRESTORE_CONTEXT
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93 /* Set the SP to point to the stack of the task being restored. */
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94 LDR R0, pxCurrentTCBConst
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98 /* Is there a floating point context to restore? If the restored
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99 ulPortTaskHasFPUContext is zero then no. */
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100 LDR R0, ulPortTaskHasFPUContextConst
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105 /* Restore the floating point context, if any. */
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107 #if configFPU_D32 == 1
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109 #endif /* configFPU_D32 */
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113 /* Restore the critical section nesting depth. */
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114 LDR R0, ulCriticalNestingConst
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118 /* Restore all system mode registers other than the SP (which is already
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122 /* Return to the task code, loading CPSR on the way. */
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130 /******************************************************************************
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131 * SVC handler is used to yield.
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132 *****************************************************************************/
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134 .type FreeRTOS_SVC_Handler, %function
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135 FreeRTOS_SVC_Handler:
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136 /* Save the context of the current task and select a new task to run. */
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138 LDR R0, vTaskSwitchContextConst
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140 portRESTORE_CONTEXT
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143 /******************************************************************************
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144 * vPortRestoreTaskContext is used to start the scheduler.
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145 *****************************************************************************/
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147 .type vPortRestoreTaskContext, %function
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148 vPortRestoreTaskContext:
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149 /* Switch to system mode. */
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151 portRESTORE_CONTEXT
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154 .type FreeRTOS_IRQ_Handler, %function
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155 FreeRTOS_IRQ_Handler:
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156 /* Return to the interrupted instruction. */
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159 /* Push the return address and SPSR. */
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164 /* Change to supervisor mode to allow reentry. */
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167 /* Push used registers. */
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170 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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171 for future use. r1 holds the original ulPortInterruptNesting value for
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173 LDR r3, ulPortInterruptNestingConst
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178 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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184 /* Call the interrupt handler. */
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186 LDR r1, vApplicationIRQHandlerConst
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195 /* Write to the EOI register. */
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196 LDR r0, ulICCEOIRConst
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200 /* Restore the old nesting count. */
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203 /* A context switch is never performed if the nesting count is not 0. */
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205 BNE exit_without_switch
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207 /* Did the interrupt request a context switch? r1 holds the address of
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208 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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210 LDR r1, ulPortYieldRequiredConst
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213 BNE switch_before_exit
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215 exit_without_switch:
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216 /* No context switch. Restore used registers, LR_irq and SPSR before
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225 switch_before_exit:
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226 /* A context swtich is to be performed. Clear the context switch pending
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231 /* Restore used registers, LR-irq and SPSR before saving the context
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232 to the task stack. */
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240 /* Call the function that selects the new task to execute.
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241 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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242 instructions, or 8 byte aligned stack allocated data. LR does not need
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243 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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244 LDR R0, vTaskSwitchContextConst
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247 /* Restore the context of, and branch to, the task selected to execute
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249 portRESTORE_CONTEXT
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251 ulICCEOIRConst: .word ulICCEOIR
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252 pxCurrentTCBConst: .word pxCurrentTCB
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253 ulCriticalNestingConst: .word ulCriticalNesting
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254 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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255 vTaskSwitchContextConst: .word vTaskSwitchContext
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256 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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257 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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258 ulPortYieldRequiredConst: .word ulPortYieldRequired
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