상황 Windows11 CubeIDE STM32F429 + FreeRTOS 포팅 context switch(이하 문맥전환) 수업 시간에 각 태스크에서 led를 켜고, delay 시 led를 끄도록 위 코드와 같이 작성함 디버깅 시 첫번째, 두번째 문맥 전환에서는 정상 동작 세번째 문맥 전환 발생 시 Bus Fault 발생 소스 코드 void xPortPendSVHandler( void ) { /* This is a naked function. */ ledoff(); __asm volatile ( " mrs r0, psp \n" " isb \n" " \n" " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */ " ldr r2, [r3] \n" " \n" " tst r14, #0x10 \n" /* Is the task using the FPU context? If so, push high vfp registers. */ " it eq \n" " vstmdbeq r0!, {s16-s31} \n" " \n" " stmdb r0!, {r4-r11, r14} \n" /* Save the core registers. */ " str r0, [r2] \n" /* Save the new top of stack into the first member of the TCB. */ " \n" " stmdb sp!, {r0, r3} \n" " mov r0, %0 \n" " msr basepri, r0 \n" " dsb \n" " isb \n" " bl vTaskSwitchContext \n" " mov r0, #0 \n" " msr basepri, r0 \n" " ldmia sp!, {r0, r3} \n" " \n" " ldr r1, [r3] \n" /* The first item in pxCurrentTCB is the task top of stack. */ " ldr r0, [r1] \n" " \n" " ldmia r0!, {r4-r11, r14} \n" /* Pop the core registers. */ " \n" " tst r14, #0x10 \n" /* Is the task using the FPU context? If so, pop the high vfp registers too. */ " it eq \n" " vldmiaeq r0!, {s16-s31} \n" " \n" " msr psp, r0 \n" " isb \n" " \n" #ifdef WORKAROUND_PMU_CM001 /* XMC4000 specific errata workaround. */ #if WORKAROUND_PMU_CM001 == 1 " push { r14 } \n" " pop { pc } \n" #endif #endif " \n" " bx r14 \n" " \n" " .align 4 \n" "pxCurrentTCBConst: .word pxCurrentTCB \n" ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY) ); } /*-----------------------------------------------------------*/ 원인(요약) xPortPendSVHandler()는 naked 함수로 선언되어 있음
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