| ;/* |
| ; * FreeRTOS Kernel <DEVELOPMENT BRANCH> |
| ; * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
| ; * |
| ; * SPDX-License-Identifier: MIT |
| ; * |
| ; * 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. |
| ; * |
| ; * https://www.FreeRTOS.org |
| ; * https://github.com/FreeRTOS |
| ; * |
| ; */ |
| |
| #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 switch 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 |
