2 * FreeRTOS Kernel V10.2.0
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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.
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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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35 /* Variables and functions. */
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36 .extern ulMaxAPIPriorityMask
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37 .extern _freertos_vector_table
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38 .extern pxCurrentTCB
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39 .extern vTaskSwitchContext
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40 .extern vApplicationIRQHandler
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41 .extern ulPortInterruptNesting
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42 .extern ulPortTaskHasFPUContext
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44 .extern ulPortYieldRequired
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46 .global FreeRTOS_IRQ_Handler
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47 .global FreeRTOS_SVC_Handler
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48 .global vPortRestoreTaskContext
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51 .macro portSAVE_CONTEXT
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53 /* Save the LR and SPSR onto the system mode stack before switching to
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54 system mode to save the remaining system mode registers. */
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55 SRSDB sp!, #SYS_MODE
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59 /* Push the critical nesting count. */
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60 LDR R2, ulCriticalNestingConst
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64 /* Does the task have a floating point context that needs saving? If
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65 ulPortTaskHasFPUContext is 0 then no. */
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66 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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80 /* Save ulPortTaskHasFPUContext itself. */
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83 /* Save the stack pointer in the TCB. */
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84 LDR R0, pxCurrentTCBConst
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90 ; /**********************************************************************/
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92 .macro portRESTORE_CONTEXT
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94 /* Set the SP to point to the stack of the task being restored. */
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95 LDR R0, pxCurrentTCBConst
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99 /* Is there a floating point context to restore? If the restored
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100 ulPortTaskHasFPUContext is zero then no. */
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101 LDR R0, ulPortTaskHasFPUContextConst
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107 /* Restore the floating point context, if any. */
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109 #if configFPU_D32 == 1
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111 #endif /* configFPU_D32 */
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116 /* Restore the critical section nesting depth. */
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117 LDR R0, ulCriticalNestingConst
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121 /* Restore all system mode registers other than the SP (which is already
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125 /* Return to the task code, loading CPSR on the way. */
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133 /******************************************************************************
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134 * SVC handler is used to yield.
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135 *****************************************************************************/
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137 .type FreeRTOS_SVC_Handler, %function
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138 FreeRTOS_SVC_Handler:
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139 /* Save the context of the current task and select a new task to run. */
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141 LDR R0, vTaskSwitchContextConst
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143 portRESTORE_CONTEXT
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146 /******************************************************************************
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147 * vPortRestoreTaskContext is used to start the scheduler.
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148 *****************************************************************************/
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150 .type vPortRestoreTaskContext, %function
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151 vPortRestoreTaskContext:
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152 /* Switch to system mode. */
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154 portRESTORE_CONTEXT
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157 .type FreeRTOS_IRQ_Handler, %function
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158 FreeRTOS_IRQ_Handler:
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159 /* Return to the interrupted instruction. */
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162 /* Push the return address and SPSR. */
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167 /* Change to supervisor mode to allow reentry. */
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170 /* Push used registers. */
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173 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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174 for future use. r1 holds the original ulPortInterruptNesting value for
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176 LDR r3, ulPortInterruptNestingConst
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181 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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187 /* Call the interrupt handler. */
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189 LDR r1, vApplicationIRQHandlerConst
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198 /* Write to the EOI register. */
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199 LDR r0, ulICCEOIRConst
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203 /* Restore the old nesting count. */
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206 /* A context switch is never performed if the nesting count is not 0. */
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208 BNE exit_without_switch
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210 /* Did the interrupt request a context switch? r1 holds the address of
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211 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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213 LDR r1, ulPortYieldRequiredConst
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216 BNE switch_before_exit
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218 exit_without_switch:
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219 /* No context switch. Restore used registers, LR_irq and SPSR before
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228 switch_before_exit:
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229 /* A context swtich is to be performed. Clear the context switch pending
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234 /* Restore used registers, LR-irq and SPSR before saving the context
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235 to the task stack. */
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243 /* Call the function that selects the new task to execute.
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244 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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245 instructions, or 8 byte aligned stack allocated data. LR does not need
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246 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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247 LDR R0, vTaskSwitchContextConst
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250 /* Restore the context of, and branch to, the task selected to execute
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252 portRESTORE_CONTEXT
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254 ulICCEOIRConst: .word ulICCEOIR
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255 pxCurrentTCBConst: .word pxCurrentTCB
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256 ulCriticalNestingConst: .word ulCriticalNesting
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257 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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258 vTaskSwitchContextConst: .word vTaskSwitchContext
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259 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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260 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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261 ulPortYieldRequiredConst: .word ulPortYieldRequired
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