| ;/*
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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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| INCLUDE portmacro.h
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| EXTERN vApplicationIRQHandler
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| EXTERN vTaskSwitchContext
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| EXTERN ulPortYieldRequired
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| EXTERN ulPortInterruptNesting
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| PUBLIC FreeRTOS_SWI_Handler
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| PUBLIC FreeRTOS_IRQ_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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| SECTION .text:CODE:ROOT(2)
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| ARM
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| INCLUDE portASM.h
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| ; SVC handler is used to yield a task.
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| FreeRTOS_SWI_Handler
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|
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| PRESERVE8
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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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| ; 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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| ; PL390 GIC interrupt handler
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| ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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| FreeRTOS_IRQ_Handler
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|
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| ; Return to the interrupted instruction.
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| SUB lr, lr, #4
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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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| ; Push used registers.
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| PUSH {r0-r4, r12}
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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 r4, r1, #1
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| STR r4, [r3]
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|
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| ; Read value from the interrupt acknowledge register, which is stored in r0
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| ; for future parameter and interrupt clearing use.
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| LDR r2, =portICCIAR_INTERRUPT_ACKNOWLEDGE_REGISTER_ADDRESS
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| LDR r0, [r2]
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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. _RB_ Is this ever necessary if start of stack is 8-byte aligned?
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| MOV r2, sp
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| AND r2, r2, #4
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| SUB sp, sp, r2
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|
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| ; Call the interrupt handler. r4 is pushed to maintain alignment.
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| PUSH {r0-r4, lr}
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| LDR r1, =vApplicationIRQHandler
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| BLX r1
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| POP {r0-r4, lr}
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| ADD sp, sp, r2
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|
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| CPSID i
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| ; Write the value read from ICCIAR to ICCEOIR
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| LDR r4, =portICCEOIR_END_OF_INTERRUPT_REGISTER_ADDRESS
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| STR r0, [r4]
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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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| ; 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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| 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-r4, 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 switch 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-r4, 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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|
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| ; Restore the context of, and branch to, the task selected to execute next.
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| portRESTORE_CONTEXT
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| END
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