S32K144异常处理代码的编译问题分析
NXP S32 DS for ARM与MDK for ARM编译异常处理程序的不同
在实践嵌入式RTOS的代码编写过程中，发现在MDK下运行很好的任务切换代码，在NXP DS中运行就会莫名的死机，异常为3. 调试了几个星期，最后确定是编译引起。对比NXP DS下的FreeeRTOS代码（运行正常），感觉应该以下红色部分的不同。
FreeRTOS：
#define xPortPendSVHandler PendSV_Handler
void xPortPendSVHandler( void ) __attribute__ (( naked ));
void xPortPendSVHandler( void )
{
/* This is a naked function. */
__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. */
" \n"
" str r0, [r2] \n" /* Save the new top of stack into the first member of the TCB. */
" \n"
" stmdb sp!, {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!, {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 2 \n"
"pxCurrentTCBConst: .word pxCurrentTCB \n"
::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)
);
}
我的实验代码：
void PendSV_Handler(void)
{
__asm volatile(
"mrs r0, psp\n"
"cbz r0, PendSVHander_nosave\n"
"stmdb r0!, {r4-r11}\n"
"ldr r1, =currenttask\n"
"ldr r1, [r1]\n"
"str r0, [r1]\n"
"PendSVHander_nosave:\n"
"ldr r0, =currenttask\n"
"ldr r1, =nexttask\n"
"ldr r2, [r1]\n"
"str r2, [r0]\n"
"ldr r0, [r2]\n"
"ldmia r0!, {r4-r11}\n"
"msr psp, r0\n"
"orr lr, lr, #0x04\n"
"bx lr\n"
);
}
结果：大神的博客里说：“对于nake的不理解，查看了arm的文档。发现就是指定编译器不要产生序言和结尾。只能用__asm ”
加了 nake后，运行OK ：）。
https://download.csdn.net/download/holmes_sun5/11869848