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|
;/*
; * FreeRTOS Kernel V10.3.0
; * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
; *
; * Permission is hereby granted, free of charge, to any person obtaining a copy of
; * this software and associated documentation files (the "Software"), to deal in
; * the Software without restriction, including without limitation the rights to
; * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
; * the Software, and to permit persons to whom the Software is furnished to do so,
; * subject to the following conditions:
; *
; * The above copyright notice and this permission notice shall be included in all
; * copies or substantial portions of the Software.
; *
; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
; * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
; * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
; * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
; * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
; *
; * http://www.FreeRTOS.org
; * http://aws.amazon.com/freertos
; *
; * 1 tab == 4 spaces!
; */
#include "FreeRTOSConfig.h"
SECTION .text:CODE:ROOT(2)
arm
/* Variables and functions. */
EXTERN pxCurrentTCB
EXTERN vTaskSwitchContext
EXTERN vApplicationIRQHandler
EXTERN ulPortInterruptNesting
EXTERN ulPortTaskHasFPUContext
EXTERN ulPortYieldRequired
EXTERN ulCriticalNesting
PUBLIC FreeRTOS_IRQ_Handler
PUBLIC FreeRTOS_SVC_Handler
PUBLIC vPortRestoreTaskContext
SYS_MODE EQU 0x1f
SVC_MODE EQU 0x13
IRQ_MODE EQU 0x12
portSAVE_CONTEXT MACRO
/* Save the LR and SPSR onto the system mode stack before switching to
system mode to save the remaining system mode registers. */
SRSDB sp!, #SYS_MODE
CPS #SYS_MODE
PUSH {R0-R12, R14}
/* Push the critical nesting count. */
LDR R2, =ulCriticalNesting
LDR R1, [R2]
PUSH {R1}
/* Does the task have a floating point context that needs saving? If
ulPortTaskHasFPUContext is 0 then no. */
LDR R2, =ulPortTaskHasFPUContext
LDR R3, [R2]
CMP R3, #0
/* Save the floating point context, if any. */
FMRXNE R1, FPSCR
VPUSHNE {D0-D15}
#if configFPU_D32 == 1
VPUSHNE {D16-D31}
#endif /* configFPU_D32 */
PUSHNE {R1}
/* Save ulPortTaskHasFPUContext itself. */
PUSH {R3}
/* Save the stack pointer in the TCB. */
LDR R0, =pxCurrentTCB
LDR R1, [R0]
STR SP, [R1]
ENDM
; /**********************************************************************/
portRESTORE_CONTEXT MACRO
/* Set the SP to point to the stack of the task being restored. */
LDR R0, =pxCurrentTCB
LDR R1, [R0]
LDR SP, [R1]
/* Is there a floating point context to restore? If the restored
ulPortTaskHasFPUContext is zero then no. */
LDR R0, =ulPortTaskHasFPUContext
POP {R1}
STR R1, [R0]
CMP R1, #0
/* Restore the floating point context, if any. */
POPNE {R0}
#if configFPU_D32 == 1
VPOPNE {D16-D31}
#endif /* configFPU_D32 */
VPOPNE {D0-D15}
VMSRNE FPSCR, R0
/* Restore the critical section nesting depth. */
LDR R0, =ulCriticalNesting
POP {R1}
STR R1, [R0]
/* Restore all system mode registers other than the SP (which is already
being used). */
POP {R0-R12, R14}
/* Return to the task code, loading CPSR on the way. */
RFEIA sp!
ENDM
/******************************************************************************
* SVC handler is used to yield.
*****************************************************************************/
FreeRTOS_SVC_Handler:
/* Save the context of the current task and select a new task to run. */
portSAVE_CONTEXT
LDR R0, =vTaskSwitchContext
BLX R0
portRESTORE_CONTEXT
/******************************************************************************
* vPortRestoreTaskContext is used to start the scheduler.
*****************************************************************************/
vPortRestoreTaskContext:
/* Switch to system mode. */
CPS #SYS_MODE
portRESTORE_CONTEXT
FreeRTOS_IRQ_Handler:
/* Return to the interrupted instruction. */
SUB lr, lr, #4
/* Push the return address and SPSR. */
PUSH {lr}
MRS lr, SPSR
PUSH {lr}
/* Change to supervisor mode to allow reentry. */
CPS #SVC_MODE
/* Push used registers. */
PUSH {r0-r3, r12}
/* Increment nesting count. r3 holds the address of ulPortInterruptNesting
for future use. r1 holds the original ulPortInterruptNesting value for
future use. */
LDR r3, =ulPortInterruptNesting
LDR r1, [r3]
ADD r0, r1, #1
STR r0, [r3]
/* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
future use. */
MOV r0, sp
AND r2, r0, #4
SUB sp, sp, r2
/* Call the interrupt handler. */
PUSH {r0-r3, lr}
LDR r1, =vApplicationIRQHandler
BLX r1
POP {r0-r3, lr}
ADD sp, sp, r2
CPSID i
DSB
ISB
/* Write to the EOI register. */
LDR r2, =configEOI_ADDRESS
STR r0, [r2]
/* Restore the old nesting count. */
STR r1, [r3]
/* A context switch is never performed if the nesting count is not 0. */
CMP r1, #0
BNE exit_without_switch
/* Did the interrupt request a context switch? r1 holds the address of
ulPortYieldRequired and r0 the value of ulPortYieldRequired for future
use. */
LDR r1, =ulPortYieldRequired
LDR r0, [r1]
CMP r0, #0
BNE switch_before_exit
exit_without_switch:
/* No context switch. Restore used registers, LR_irq and SPSR before
returning. */
POP {r0-r3, r12}
CPS #IRQ_MODE
POP {LR}
MSR SPSR_cxsf, LR
POP {LR}
MOVS PC, LR
switch_before_exit:
/* A context swtich is to be performed. Clear the context switch pending
flag. */
MOV r0, #0
STR r0, [r1]
/* Restore used registers, LR-irq and SPSR before saving the context
to the task stack. */
POP {r0-r3, r12}
CPS #IRQ_MODE
POP {LR}
MSR SPSR_cxsf, LR
POP {LR}
portSAVE_CONTEXT
/* Call the function that selects the new task to execute.
vTaskSwitchContext() if vTaskSwitchContext() uses LDRD or STRD
instructions, or 8 byte aligned stack allocated data. LR does not need
saving as a new LR will be loaded by portRESTORE_CONTEXT anyway. */
LDR R0, =vTaskSwitchContext
BLX R0
/* Restore the context of, and branch to, the task selected to execute
next. */
portRESTORE_CONTEXT
END
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