| ;/*
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| ; * FreeRTOS Kernel <DEVELOPMENT BRANCH>
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| ; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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| ; *
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| ; * SPDX-License-Identifier: MIT |
| ; * |
| ; * Permission is hereby granted, free of charge, to any person obtaining a copy of
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| ; * this software and associated documentation files (the "Software"), to deal in
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| ; * the Software without restriction, including without limitation the rights to
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| ; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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| ; * the Software, and to permit persons to whom the Software is furnished to do so,
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| ; * subject to the following conditions:
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| ; *
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| ; * The above copyright notice and this permission notice shall be included in all
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| ; * copies or substantial portions of the Software.
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| ; *
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| ; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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| ; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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| ; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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| ; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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| ; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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| ; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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| ; *
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| ; * https://www.FreeRTOS.org
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| ; * https://github.com/FreeRTOS
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| ; *
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| ; */
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|
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| #include "FreeRTOSConfig.h"
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|
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| SECTION .text:CODE:ROOT(2)
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| arm
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|
| /* Variables and functions. */
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| EXTERN pxCurrentTCB
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| EXTERN vTaskSwitchContext
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| EXTERN vApplicationIRQHandler
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| EXTERN ulPortInterruptNesting
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| EXTERN ulPortTaskHasFPUContext
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| EXTERN ulPortYieldRequired
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| EXTERN ulCriticalNesting
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|
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| PUBLIC FreeRTOS_IRQ_Handler
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| PUBLIC FreeRTOS_SVC_Handler
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| PUBLIC vPortRestoreTaskContext
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| SYS_MODE EQU 0x1f
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| SVC_MODE EQU 0x13
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| IRQ_MODE EQU 0x12
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|
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| portSAVE_CONTEXT MACRO
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|
|
| /* Save the LR and SPSR onto the system mode stack before switching to
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| system mode to save the remaining system mode registers. */
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| SRSDB sp!, #SYS_MODE
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| CPS #SYS_MODE
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| PUSH {R0-R12, R14}
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|
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| /* Push the critical nesting count. */
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| LDR R2, =ulCriticalNesting
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| LDR R1, [R2]
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| PUSH {R1}
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|
|
| /* Does the task have a floating point context that needs saving? If
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| ulPortTaskHasFPUContext is 0 then no. */
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| LDR R2, =ulPortTaskHasFPUContext
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| LDR R3, [R2]
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| CMP R3, #0
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|
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| /* Save the floating point context, if any. */
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| FMRXNE R1, FPSCR
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| VPUSHNE {D0-D15}
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| #if configFPU_D32 == 1
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| VPUSHNE {D16-D31}
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| #endif /* configFPU_D32 */
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| PUSHNE {R1}
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|
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| /* Save ulPortTaskHasFPUContext itself. */
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| PUSH {R3}
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|
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| /* Save the stack pointer in the TCB. */
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| LDR R0, =pxCurrentTCB
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| LDR R1, [R0]
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| STR SP, [R1]
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|
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| ENDM
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|
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| ; /**********************************************************************/
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| portRESTORE_CONTEXT MACRO
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|
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| /* Set the SP to point to the stack of the task being restored. */
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| LDR R0, =pxCurrentTCB
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| LDR R1, [R0]
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| LDR SP, [R1]
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|
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| /* Is there a floating point context to restore? If the restored
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| ulPortTaskHasFPUContext is zero then no. */
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| LDR R0, =ulPortTaskHasFPUContext
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| POP {R1}
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| STR R1, [R0]
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| CMP R1, #0
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|
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| /* Restore the floating point context, if any. */
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| POPNE {R0}
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| #if configFPU_D32 == 1
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| VPOPNE {D16-D31}
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| #endif /* configFPU_D32 */
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| VPOPNE {D0-D15}
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| VMSRNE FPSCR, R0
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|
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| /* Restore the critical section nesting depth. */
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| LDR R0, =ulCriticalNesting
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| POP {R1}
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| STR R1, [R0]
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|
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| /* Restore all system mode registers other than the SP (which is already
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| being used). */
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| POP {R0-R12, R14}
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|
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| /* Return to the task code, loading CPSR on the way. */
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| RFEIA sp!
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|
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| ENDM
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|
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| /******************************************************************************
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| * SVC handler is used to yield.
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| *****************************************************************************/
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| FreeRTOS_SVC_Handler:
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| /* Save the context of the current task and select a new task to run. */
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| portSAVE_CONTEXT
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| LDR R0, =vTaskSwitchContext
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| BLX R0
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| portRESTORE_CONTEXT
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|
|
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| /******************************************************************************
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| * vPortRestoreTaskContext is used to start the scheduler.
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| *****************************************************************************/
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| vPortRestoreTaskContext:
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| /* Switch to system mode. */
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| CPS #SYS_MODE
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| portRESTORE_CONTEXT
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|
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| FreeRTOS_IRQ_Handler:
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| /* Return to the interrupted instruction. */
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| SUB lr, lr, #4
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|
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| /* Push the return address and SPSR. */
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| PUSH {lr}
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| MRS lr, SPSR
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| PUSH {lr}
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|
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| /* Change to supervisor mode to allow reentry. */
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| CPS #SVC_MODE
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|
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| /* Push used registers. */
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| PUSH {r0-r3, r12}
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|
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| /* Increment nesting count. r3 holds the address of ulPortInterruptNesting
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| for future use. r1 holds the original ulPortInterruptNesting value for
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| future use. */
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| LDR r3, =ulPortInterruptNesting
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| LDR r1, [r3]
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| ADD r0, r1, #1
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| STR r0, [r3]
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|
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| /* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
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| future use. */
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| MOV r0, sp
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| AND r2, r0, #4
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| SUB sp, sp, r2
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|
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| /* Call the interrupt handler. */
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| PUSH {r0-r3, lr}
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| LDR r1, =vApplicationIRQHandler
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| BLX r1
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| POP {r0-r3, lr}
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| ADD sp, sp, r2
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|
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| CPSID i
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| DSB
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| ISB
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| /* Write to the EOI register. */
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| LDR r2, =configEOI_ADDRESS
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| STR r0, [r2]
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|
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| /* Restore the old nesting count. */
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| STR r1, [r3]
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|
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| /* A context switch is never performed if the nesting count is not 0. */
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| CMP r1, #0
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| BNE exit_without_switch
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|
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| /* Did the interrupt request a context switch? r1 holds the address of
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| ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
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| use. */
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| LDR r1, =ulPortYieldRequired
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| LDR r0, [r1]
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| CMP r0, #0
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| BNE switch_before_exit
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|
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| exit_without_switch:
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| /* No context switch. Restore used registers, LR_irq and SPSR before
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| returning. */
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| POP {r0-r3, r12}
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| CPS #IRQ_MODE
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| POP {LR}
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| MSR SPSR_cxsf, LR
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| POP {LR}
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| MOVS PC, LR
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|
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| switch_before_exit:
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| /* A context swtich is to be performed. Clear the context switch pending
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| flag. */
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| MOV r0, #0
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| STR r0, [r1]
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|
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| /* Restore used registers, LR-irq and SPSR before saving the context
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| to the task stack. */
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| POP {r0-r3, r12}
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| CPS #IRQ_MODE
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| POP {LR}
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| MSR SPSR_cxsf, LR
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| POP {LR}
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| portSAVE_CONTEXT
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|
|
| /* Call the function that selects the new task to execute.
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| vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
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| instructions, or 8 byte aligned stack allocated data. LR does not need
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| saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
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| LDR R0, =vTaskSwitchContext
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| BLX R0
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|
|
| /* Restore the context of, and branch to, the task selected to execute
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| next. */
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| portRESTORE_CONTEXT
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|
|
| END
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