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/*
* FreeRTOS Kernel V10.2.1
* Copyright (C) 2019 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"
#define portCONTEXT_SIZE 132
#define portEPC_STACK_LOCATION 124
#define portSTATUS_STACK_LOCATION 128
/******************************************************************/
.macro portSAVE_CONTEXT
/* Make room for the context. First save the current status so it can be
manipulated, and the cause and EPC registers so their original values are
captured. */
mfc0 k0, _CP0_CAUSE
addiu sp, sp, -portCONTEXT_SIZE
mfc0 k1, _CP0_STATUS
/* Also save s6 and s5 so they can be used. Any nesting interrupts should
maintain the values of these registers across the ISR. */
sw s6, 44(sp)
sw s5, 40(sp)
sw k1, portSTATUS_STACK_LOCATION(sp)
/* Prepare to enable interrupts above the current priority. */
srl k0, k0, 0xa
ins k1, k0, 10, 6
ins k1, zero, 1, 4
/* s5 is used as the frame pointer. */
add s5, zero, sp
/* Check the nesting count value. */
la k0, uxInterruptNesting
lw s6, (k0)
/* If the nesting count is 0 then swap to the the system stack, otherwise
the system stack is already being used. */
bne s6, zero, 1f
nop
/* Swap to the system stack. */
la sp, xISRStackTop
lw sp, (sp)
/* Increment and save the nesting count. */
1: addiu s6, s6, 1
sw s6, 0(k0)
/* s6 holds the EPC value, this is saved after interrupts are re-enabled. */
mfc0 s6, _CP0_EPC
/* Re-enable interrupts. */
mtc0 k1, _CP0_STATUS
/* Save the context into the space just created. s6 is saved again
here as it now contains the EPC value. No other s registers need be
saved. */
sw ra, 120(s5)
sw s8, 116(s5)
sw t9, 112(s5)
sw t8, 108(s5)
sw t7, 104(s5)
sw t6, 100(s5)
sw t5, 96(s5)
sw t4, 92(s5)
sw t3, 88(s5)
sw t2, 84(s5)
sw t1, 80(s5)
sw t0, 76(s5)
sw a3, 72(s5)
sw a2, 68(s5)
sw a1, 64(s5)
sw a0, 60(s5)
sw v1, 56(s5)
sw v0, 52(s5)
sw s6, portEPC_STACK_LOCATION(s5)
sw $1, 16(s5)
/* s6 is used as a scratch register. */
mfhi s6
sw s6, 12(s5)
mflo s6
sw s6, 8(s5)
/* Update the task stack pointer value if nesting is zero. */
la s6, uxInterruptNesting
lw s6, (s6)
addiu s6, s6, -1
bne s6, zero, 1f
nop
/* Save the stack pointer. */
la s6, uxSavedTaskStackPointer
sw s5, (s6)
1:
.endm
/******************************************************************/
.macro portRESTORE_CONTEXT
/* Restore the stack pointer from the TCB. This is only done if the
nesting count is 1. */
la s6, uxInterruptNesting
lw s6, (s6)
addiu s6, s6, -1
bne s6, zero, 1f
nop
la s6, uxSavedTaskStackPointer
lw s5, (s6)
/* Restore the context. */
1: lw s6, 8(s5)
mtlo s6
lw s6, 12(s5)
mthi s6
lw $1, 16(s5)
/* s6 is loaded as it was used as a scratch register and therefore saved
as part of the interrupt context. */
lw s6, 44(s5)
lw v0, 52(s5)
lw v1, 56(s5)
lw a0, 60(s5)
lw a1, 64(s5)
lw a2, 68(s5)
lw a3, 72(s5)
lw t0, 76(s5)
lw t1, 80(s5)
lw t2, 84(s5)
lw t3, 88(s5)
lw t4, 92(s5)
lw t5, 96(s5)
lw t6, 100(s5)
lw t7, 104(s5)
lw t8, 108(s5)
lw t9, 112(s5)
lw s8, 116(s5)
lw ra, 120(s5)
/* Protect access to the k registers, and others. */
di
ehb
/* Decrement the nesting count. */
la k0, uxInterruptNesting
lw k1, (k0)
addiu k1, k1, -1
sw k1, 0(k0)
lw k0, portSTATUS_STACK_LOCATION(s5)
lw k1, portEPC_STACK_LOCATION(s5)
/* Leave the stack in its original state. First load sp from s5, then
restore s5 from the stack. */
add sp, zero, s5
lw s5, 40(sp)
addiu sp, sp, portCONTEXT_SIZE
mtc0 k0, _CP0_STATUS
mtc0 k1, _CP0_EPC
ehb
eret
nop
.endm
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