/* * File : context_gcc.S * This file is part of RT-Thread RTOS * COPYRIGHT (C) 2006 - 2018, RT-Thread Development Team * * The license and distribution terms for this file may be * found in the file LICENSE in this distribution or at * http://www.rt-thread.org/license/LICENSE * * Change Logs: * Date Author Notes * 2009-10-11 Bernard first version * 2012-01-01 aozima support context switch load/store FPU register. * 2013-06-18 aozima add restore MSP feature. * 2013-06-23 aozima support lazy stack optimized. * 2018-07-24 aozima enhancement hard fault exception handler. */ /** * @addtogroup cortex-m4 */ /*@{*/ .cpu cortex-m4 .syntax unified .thumb .text .equ SCB_VTOR, 0xE000ED08 /* Vector Table Offset Register */ .equ NVIC_INT_CTRL, 0xE000ED04 /* interrupt control state register */ .equ NVIC_SYSPRI2, 0xE000ED20 /* system priority register (2) */ .equ NVIC_PENDSV_PRI, 0x00FF0000 /* PendSV priority value (lowest) */ .equ NVIC_PENDSVSET, 0x10000000 /* value to trigger PendSV exception */ /* * rt_base_t rt_hw_interrupt_disable(); */ .global rt_hw_interrupt_disable .type rt_hw_interrupt_disable, %function rt_hw_interrupt_disable: MRS r0, PRIMASK CPSID I BX LR /* * void rt_hw_interrupt_enable(rt_base_t level); */ .global rt_hw_interrupt_enable .type rt_hw_interrupt_enable, %function rt_hw_interrupt_enable: MSR PRIMASK, r0 BX LR /* * void rt_hw_context_switch(rt_uint32 from, rt_uint32 to); * r0 --> from * r1 --> to */ .global rt_hw_context_switch_interrupt .type rt_hw_context_switch_interrupt, %function .global rt_hw_context_switch .type rt_hw_context_switch, %function rt_hw_context_switch_interrupt: rt_hw_context_switch: /* set rt_thread_switch_interrupt_flag to 1 */ LDR r2, =rt_thread_switch_interrupt_flag LDR r3, [r2] CMP r3, #1 BEQ _reswitch MOV r3, #1 STR r3, [r2] LDR r2, =rt_interrupt_from_thread /* set rt_interrupt_from_thread */ STR r0, [r2] _reswitch: LDR r2, =rt_interrupt_to_thread /* set rt_interrupt_to_thread */ STR r1, [r2] LDR r0, =NVIC_INT_CTRL /* trigger the PendSV exception (causes context switch) */ LDR r1, =NVIC_PENDSVSET STR r1, [r0] BX LR /* r0 --> switch from thread stack * r1 --> switch to thread stack * psr, pc, lr, r12, r3, r2, r1, r0 are pushed into [from] stack */ .global PendSV_Handler .type PendSV_Handler, %function PendSV_Handler: /* disable interrupt to protect context switch */ MRS r2, PRIMASK CPSID I /* get rt_thread_switch_interrupt_flag */ LDR r0, =rt_thread_switch_interrupt_flag LDR r1, [r0] CBZ r1, pendsv_exit /* pendsv already handled */ /* clear rt_thread_switch_interrupt_flag to 0 */ MOV r1, #0x00 STR r1, [r0] LDR r0, =rt_interrupt_from_thread LDR r1, [r0] CBZ r1, switch_to_thread /* skip register save at the first time */ MRS r1, psp /* get from thread stack pointer */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) TST lr, #0x10 /* if(!EXC_RETURN[4]) */ VSTMDBEQ r1!, {d8 - d15} /* push FPU register s16~s31 */ #endif STMFD r1!, {r4 - r11} /* push r4 - r11 register */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) MOV r4, #0x00 /* flag = 0 */ TST lr, #0x10 /* if(!EXC_RETURN[4]) */ MOVEQ r4, #0x01 /* flag = 1 */ STMFD r1!, {r4} /* push flag */ #endif LDR r0, [r0] STR r1, [r0] /* update from thread stack pointer */ switch_to_thread: LDR r1, =rt_interrupt_to_thread LDR r1, [r1] LDR r1, [r1] /* load thread stack pointer */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) LDMFD r1!, {r3} /* pop flag */ #endif LDMFD r1!, {r4 - r11} /* pop r4 - r11 register */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) CMP r3, #0 /* if(flag_r3 != 0) */ VLDMIANE r1!, {d8 - d15} /* pop FPU register s16~s31 */ #endif MSR psp, r1 /* update stack pointer */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) ORR lr, lr, #0x10 /* lr |= (1 << 4), clean FPCA. */ CMP r3, #0 /* if(flag_r3 != 0) */ BICNE lr, lr, #0x10 /* lr &= ~(1 << 4), set FPCA. */ #endif pendsv_exit: /* restore interrupt */ MSR PRIMASK, r2 ORR lr, lr, #0x04 BX lr /* * void rt_hw_context_switch_to(rt_uint32 to); * r0 --> to */ .global rt_hw_context_switch_to .type rt_hw_context_switch_to, %function rt_hw_context_switch_to: LDR r1, =rt_interrupt_to_thread STR r0, [r1] #if defined (__VFP_FP__) && !defined(__SOFTFP__) /* CLEAR CONTROL.FPCA */ MRS r2, CONTROL /* read */ BIC r2, #0x04 /* modify */ MSR CONTROL, r2 /* write-back */ #endif /* set from thread to 0 */ LDR r1, =rt_interrupt_from_thread MOV r0, #0x0 STR r0, [r1] /* set interrupt flag to 1 */ LDR r1, =rt_thread_switch_interrupt_flag MOV r0, #1 STR r0, [r1] /* set the PendSV exception priority */ LDR r0, =NVIC_SYSPRI2 LDR r1, =NVIC_PENDSV_PRI LDR.W r2, [r0,#0x00] /* read */ ORR r1,r1,r2 /* modify */ STR r1, [r0] /* write-back */ LDR r0, =NVIC_INT_CTRL /* trigger the PendSV exception (causes context switch) */ LDR r1, =NVIC_PENDSVSET STR r1, [r0] /* restore MSP */ LDR r0, =SCB_VTOR LDR r0, [r0] LDR r0, [r0] NOP MSR msp, r0 /* enable interrupts at processor level */ CPSIE F CPSIE I /* never reach here! */ /* compatible with old version */ .global rt_hw_interrupt_thread_switch .type rt_hw_interrupt_thread_switch, %function rt_hw_interrupt_thread_switch: BX lr NOP .global HardFault_Handler .type HardFault_Handler, %function HardFault_Handler: /* get current context */ MRS r0, msp /* get fault context from handler. */ TST lr, #0x04 /* if(!EXC_RETURN[2]) */ BEQ _get_sp_done MRS r0, psp /* get fault context from thread. */ _get_sp_done: STMFD r0!, {r4 - r11} /* push r4 - r11 register */ #if defined (__VFP_FP__) && !defined(__SOFTFP__) STMFD r0!, {lr} /* push dummy for flag */ #endif STMFD r0!, {lr} /* push exec_return register */ TST lr, #0x04 /* if(!EXC_RETURN[2]) */ BEQ _update_msp MSR psp, r0 /* update stack pointer to PSP. */ B _update_done _update_msp: MSR msp, r0 /* update stack pointer to MSP. */ _update_done: PUSH {LR} BL rt_hw_hard_fault_exception POP {LR} ORR lr, lr, #0x04 BX lr