2 * FreeRTOS Kernel V10.2.1
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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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35 /* Hardware registers. */
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40 /* Variables and functions. */
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41 .extern ulMaxAPIPriorityMask
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42 .extern _freertos_vector_table
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43 .extern pxCurrentTCB
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44 .extern vTaskSwitchContext
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45 .extern vApplicationIRQHandler
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46 .extern ulPortInterruptNesting
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47 .extern ulPortTaskHasFPUContext
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49 .global FreeRTOS_IRQ_Handler
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50 .global FreeRTOS_SWI_Handler
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51 .global vPortRestoreTaskContext
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53 .macro portSAVE_CONTEXT
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55 /* Save the LR and SPSR onto the system mode stack before switching to
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56 system mode to save the remaining system mode registers. */
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57 SRSDB sp!, #SYS_MODE
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61 /* Push the critical nesting count. */
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62 LDR R2, ulCriticalNestingConst
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66 /* Does the task have a floating point context that needs saving? If
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67 ulPortTaskHasFPUContext is 0 then no. */
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68 LDR R2, ulPortTaskHasFPUContextConst
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72 /* Save the floating point context, if any. */
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75 /*VPUSHNE {D16-D31}*/
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78 /* Save ulPortTaskHasFPUContext itself. */
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81 /* Save the stack pointer in the TCB. */
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82 LDR R0, pxCurrentTCBConst
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88 ; /**********************************************************************/
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90 .macro portRESTORE_CONTEXT
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92 /* Set the SP to point to the stack of the task being restored. */
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93 LDR R0, pxCurrentTCBConst
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97 /* Is there a floating point context to restore? If the restored
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98 ulPortTaskHasFPUContext is zero then no. */
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99 LDR R0, ulPortTaskHasFPUContextConst
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104 /* Restore the floating point context, if any. */
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106 /*VPOPNE {D16-D31}*/
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110 /* Restore the critical section nesting depth. */
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111 LDR R0, ulCriticalNestingConst
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115 /* Ensure the priority mask is correct for the critical nesting depth. */
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116 LDR R2, ulICCPMRConst
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120 LDRNE R4, ulMaxAPIPriorityMaskConst
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124 /* Restore all system mode registers other than the SP (which is already
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128 /* Return to the task code, loading CPSR on the way. */
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136 /******************************************************************************
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137 * SVC handler is used to start the scheduler.
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138 *****************************************************************************/
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140 .type FreeRTOS_SWI_Handler, %function
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141 FreeRTOS_SWI_Handler:
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142 /* Save the context of the current task and select a new task to run. */
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144 LDR R0, vTaskSwitchContextConst
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146 portRESTORE_CONTEXT
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149 /******************************************************************************
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150 * vPortRestoreTaskContext is used to start the scheduler.
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151 *****************************************************************************/
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152 .type vPortRestoreTaskContext, %function
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153 vPortRestoreTaskContext:
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154 /* Switch to system mode. */
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156 portRESTORE_CONTEXT
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159 .type FreeRTOS_IRQ_Handler, %function
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160 FreeRTOS_IRQ_Handler:
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162 /* Return to the interrupted instruction. */
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165 /* Push the return address and SPSR. */
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170 /* Change to supervisor mode to allow reentry. */
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173 /* Push used registers. */
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176 /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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177 for future use. r1 holds the original ulPortInterruptNesting value for
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179 LDR r3, ulPortInterruptNestingConst
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184 /* Read value from the interrupt acknowledge register, which is stored in r0
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185 for future parameter and interrupt clearing use. */
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186 LDR r2, ulICCIARConst
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190 /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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191 future use. _RB_ Is this ever needed provided the start of the stack is
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192 alligned on an 8-byte boundary? */
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197 /* Call the interrupt handler. */
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199 LDR r1, vApplicationIRQHandlerConst
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208 /* Write the value read from ICCIAR to ICCEOIR. */
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209 LDR r4, ulICCEOIRConst
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213 /* Restore the old nesting count. */
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216 /* A context switch is never performed if the nesting count is not 0. */
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218 BNE exit_without_switch
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220 /* Did the interrupt request a context switch? r1 holds the address of
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221 ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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223 LDR r1, =ulPortYieldRequired
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226 BNE switch_before_exit
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228 exit_without_switch:
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229 /* No context switch. Restore used registers, LR_irq and SPSR before
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238 switch_before_exit:
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239 /* A context swtich is to be performed. Clear the context switch pending
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244 /* Restore used registers, LR-irq and SPSR before saving the context
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245 to the task stack. */
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253 /* Call the function that selects the new task to execute.
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254 vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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255 instructions, or 8 byte aligned stack allocated data. LR does not need
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256 saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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257 LDR R0, vTaskSwitchContextConst
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260 /* Restore the context of, and branch to, the task selected to execute
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262 portRESTORE_CONTEXT
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264 ulICCIARConst: .word ulICCIAR
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265 ulICCEOIRConst: .word ulICCEOIR
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266 ulICCPMRConst: .word ulICCPMR
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267 pxCurrentTCBConst: .word pxCurrentTCB
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268 ulCriticalNestingConst: .word ulCriticalNesting
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269 ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
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270 ulMaxAPIPriorityMaskConst: .word ulMaxAPIPriorityMask
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271 vTaskSwitchContextConst: .word vTaskSwitchContext
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272 vApplicationIRQHandlerConst: .word vApplicationIRQHandler
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273 ulPortInterruptNestingConst: .word ulPortInterruptNesting
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