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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!
*/
.text
.arm
.set SYS_MODE, 0x1f
.set SVC_MODE, 0x13
.set IRQ_MODE, 0x12
/* Hardware registers. */
.extern ulICCIAR
.extern ulICCEOIR
.extern ulICCPMR
/* Variables and functions. */
.extern ulMaxAPIPriorityMask
.extern _freertos_vector_table
.extern pxCurrentTCB
.extern vTaskSwitchContext
.extern vApplicationIRQHandler
.extern ulPortInterruptNesting
.extern ulPortTaskHasFPUContext
.global FreeRTOS_IRQ_Handler
.global FreeRTOS_SWI_Handler
.global vPortRestoreTaskContext
.macro portSAVE_CONTEXT
/* 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, ulCriticalNestingConst
LDR R1, [R2]
PUSH {R1}
/* Does the task have a floating point context that needs saving? If
ulPortTaskHasFPUContext is 0 then no. */
LDR R2, ulPortTaskHasFPUContextConst
LDR R3, [R2]
CMP R3, #0
/* Save the floating point context, if any. */
FMRXNE R1, FPSCR
VPUSHNE {D0-D15}
/*VPUSHNE {D16-D31}*/
PUSHNE {R1}
/* Save ulPortTaskHasFPUContext itself. */
PUSH {R3}
/* Save the stack pointer in the TCB. */
LDR R0, pxCurrentTCBConst
LDR R1, [R0]
STR SP, [R1]
.endm
; /**********************************************************************/
.macro portRESTORE_CONTEXT
/* Set the SP to point to the stack of the task being restored. */
LDR R0, pxCurrentTCBConst
LDR R1, [R0]
LDR SP, [R1]
/* Is there a floating point context to restore? If the restored
ulPortTaskHasFPUContext is zero then no. */
LDR R0, ulPortTaskHasFPUContextConst
POP {R1}
STR R1, [R0]
CMP R1, #0
/* Restore the floating point context, if any. */
POPNE {R0}
/*VPOPNE {D16-D31}*/
VPOPNE {D0-D15}
VMSRNE FPSCR, R0
/* Restore the critical section nesting depth. */
LDR R0, ulCriticalNestingConst
POP {R1}
STR R1, [R0]
/* Ensure the priority mask is correct for the critical nesting depth. */
LDR R2, ulICCPMRConst
LDR R2, [R2]
CMP R1, #0
MOVEQ R4, #255
LDRNE R4, ulMaxAPIPriorityMaskConst
LDRNE R4, [R4]
STR R4, [R2]
/* 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 start the scheduler.
*****************************************************************************/
.align 4
.type FreeRTOS_SWI_Handler, %function
FreeRTOS_SWI_Handler:
/* Save the context of the current task and select a new task to run. */
portSAVE_CONTEXT
LDR R0, vTaskSwitchContextConst
BLX R0
portRESTORE_CONTEXT
/******************************************************************************
* vPortRestoreTaskContext is used to start the scheduler.
*****************************************************************************/
.type vPortRestoreTaskContext, %function
vPortRestoreTaskContext:
/* Switch to system mode. */
CPS #SYS_MODE
portRESTORE_CONTEXT
.align 4
.type FreeRTOS_IRQ_Handler, %function
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-r4, r12}
/* Increment nesting count. r3 holds the address of ulPortInterruptNesting
for future use. r1 holds the original ulPortInterruptNesting value for
future use. */
LDR r3, ulPortInterruptNestingConst
LDR r1, [r3]
ADD r4, r1, #1
STR r4, [r3]
/* Read value from the interrupt acknowledge register, which is stored in r0
for future parameter and interrupt clearing use. */
LDR r2, ulICCIARConst
LDR r2, [r2]
LDR r0, [r2]
/* Ensure bit 2 of the stack pointer is clear. r2 holds the bit 2 value for
future use. _RB_ Is this ever needed provided the start of the stack is
alligned on an 8-byte boundary? */
MOV r2, sp
AND r2, r2, #4
SUB sp, sp, r2
/* Call the interrupt handler. */
PUSH {r0-r4, lr}
LDR r1, vApplicationIRQHandlerConst
BLX r1
POP {r0-r4, lr}
ADD sp, sp, r2
CPSID i
DSB
ISB
/* Write the value read from ICCIAR to ICCEOIR. */
LDR r4, ulICCEOIRConst
LDR r4, [r4]
STR r0, [r4]
/* 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-r4, 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-r4, 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, vTaskSwitchContextConst
BLX R0
/* Restore the context of, and branch to, the task selected to execute
next. */
portRESTORE_CONTEXT
ulICCIARConst: .word ulICCIAR
ulICCEOIRConst: .word ulICCEOIR
ulICCPMRConst: .word ulICCPMR
pxCurrentTCBConst: .word pxCurrentTCB
ulCriticalNestingConst: .word ulCriticalNesting
ulPortTaskHasFPUContextConst: .word ulPortTaskHasFPUContext
ulMaxAPIPriorityMaskConst: .word ulMaxAPIPriorityMask
vTaskSwitchContextConst: .word vTaskSwitchContext
vApplicationIRQHandlerConst: .word vApplicationIRQHandler
ulPortInterruptNestingConst: .word ulPortInterruptNesting
.end
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