;/* ; * FreeRTOS Kernel V10.2.0 ; * 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" 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