如何从Cortex-M3硬/使用/总线故障中返回？

Question

我正在为cortex-m3开发微内核。 我创建了一个小型测试应用程序，有意导致故障。

现在我不确定如何从故障中恢复。 我了解堆栈可能需要使用其他函数的地址进行更新。 我也理解从错误中恢复可能在某些情况下是个坏主意，但我的内核是按照相应的方式编写的。

这是一些示例代码：

#include "core_cm3.h"

// PSR flags

// EPSR flags
#define TFLG (1<<24)
#define puts printk
#define printf printk
#define error printk
// APSR flags
#define NFLG (1<<31)
#define ZFLG (1<<30)
#define CFLG (1<<29)
#define VFLG (1<<28)
#define QFLG (1<<27)
// IPSR flags
#define ISR_THREADMODE  0
#define ISR_NMI         2
#define ISR_HARDFAULT   3
#define ISR_MEMMANAGE   4
#define ISR_BUSFAULT    5
#define ISR_USAGEFAULT  6
#define ISR_SVCALL      11
#define ISR_PENDSV      14
#define ISR_SYSTICK     15
#define ISR_IRQ0        16

// HFSR flags
#define VECTTBL     (1<<1)
#define FORCED      (1<<30)
#define DEBUGEVT    (1<<31)

// CFSR flags

// BFSR flags
#define IBUSERR     (1<<0)
#define PRECISERR   (1<<1)
#define IMPRECISERR (1<<2)
#define UNSTKERR    (1<<3)
#define STKERR      (1<<4)
#define BFARVALID   (1<<7)

// UFSR flags
#define UNDEFINSTR  (1<<0)
#define INVSTATE    (1<<1)
#define INVPC       (1<<2)
#define NOCP        (1<<3)
#define UNALIGNED   (1<<8)
#define DIVBYZERO   (1<<9)

// MMFSR flags
#define IACCVIOL    (1<<0)
#define DACCVIOL    (1<<1)
#define MUNSTKERR   (1<<3)
#define MSTKERR     (1<<4)
#define MMARVALID   (1<<7)

// DFSR
#define EXTERNAL    (1<<4)
#define VCATCH      (1<<3)
#define DWTTRAP     (1<<2)
#define BKPT        (1<<1)
#define HALTED      (1<<0)

/** Hard Fault Handler code comes from these spots:
 *
 * http://blog.frankvh.com/2011/12/07/cortex-m3-m4-hard-fault-handler/
 * http://blog.feabhas.com/2013/02/developing-a-generic-hard-fault-handler-for-arm-cortex-m3cortex-m4/
 */

/**
 * This is the actual handler, which sets up the data to be used by the C function, then calls it.
 */
void __attribute__((naked)) HardFault_Handler(void)
{
    __asm__(
            ".thumb                                 \n"
            "   tst     lr, #4                      \n" // for priv/non-priv, test for msp or psp in return (thread or handler mode)
            "   ite     eq                          \n"
            "   mrseq   r0, MSP                     \n" // move main stack pointer into r0
            "   mrsne   r0, PSP                     \n" // move process stack pointer into r0
            "   b       hard_fault_handler          \n" // jump to the c function
            :
            :
            :
            );
}

/**
 * Here we print out the junk in the stack and some special registers to help with debugging.
 */
void hard_fault_handler(unsigned int *hardfault_args)
{
      unsigned int stacked_r0;
      unsigned int stacked_r1;
      unsigned int stacked_r2;
      unsigned int stacked_r3;
      unsigned int stacked_r12;
      unsigned int stacked_lr;
      unsigned int stacked_pc;
      unsigned int stacked_psr;
      unsigned int cfsr, bfsr, ufsr, mmfsr;
      //unsigned int control;

      stacked_r0 = ((unsigned long) hardfault_args[0]);
      stacked_r1 = ((unsigned long) hardfault_args[1]);
      stacked_r2 = ((unsigned long) hardfault_args[2]);
      stacked_r3 = ((unsigned long) hardfault_args[3]);

      stacked_r12 = ((unsigned long) hardfault_args[4]);
      stacked_lr = ((unsigned long) hardfault_args[5]);
      stacked_pc = ((unsigned long) hardfault_args[6]);
      stacked_psr = ((unsigned long) hardfault_args[7]);
      //control = __get_CONTROL();

      // TODO 2: Eliminate printf

      puts("\n\n[Hard fault]\n");
      printf("R0 = 0x%08x\n", stacked_r0);
      printf("R1 = 0x%08x\n", stacked_r1);
      printf("R2 = 0x%08x\n", stacked_r2);
      printf("R3 = 0x%08x\n", stacked_r3);
      printf("R12 = 0x%08x\n", stacked_r12);
      printf("LR [R14] = 0x%08x  subroutine call return address.\n", stacked_lr);
      printf("PC [R15] = 0x%08x  program counter\n", stacked_pc);

      // PSR
      printf("PSR = 0x%04x ", stacked_psr);
      if (stacked_psr & NFLG) printf("N");
      if (stacked_psr & ZFLG) printf("Z");
      if (stacked_psr & CFLG) printf("C");
      if (stacked_psr & VFLG) printf("V");
      if (stacked_psr & QFLG) printf("Q");
      puts(" ");
      unsigned int isrnum = (stacked_psr & 0xff);
      switch (isrnum) {
      case ISR_THREADMODE:
          puts("Thread mode ");
          break;
      case ISR_NMI:
          puts("NMI ");
          break;
      case ISR_HARDFAULT:
          puts("HardFault ");
          break;
      case ISR_MEMMANAGE:
          puts("MemManage ");
          break;
      case ISR_BUSFAULT:
          puts("BusFault ");
          break;
      case ISR_USAGEFAULT:
          puts("UsageFault ");
          break;
      case ISR_SVCALL:
          puts("SVCall ");
          break;
      case ISR_PENDSV:
          puts("PendSV ");
          break;
      case ISR_SYSTICK:
          puts("SysTick ");
          break;
      case ISR_IRQ0:
          puts("IRQ0 ");
          break;
      }
      printf(" ");
      if (stacked_psr & TFLG)
          printf("thumb");
      else
          printf("non-thumb");
      puts("\n");

      // CONTROL (not sure this works...)
      //printf("CONTROL = 0x%04x ", control);
      //printf("\n");

      // HFSR
      printf("HFSR = 0x%08x ", SCB->HFSR);
      if (SCB->HFSR & DEBUGEVT) printf("DEBUGEVT ");
      if (SCB->HFSR & FORCED) printf("Forced Hard fault ");
      if (SCB->HFSR & VECTTBL) printf("VECTTBL ");
      puts("\n");
      // CFSR
      printf("CFSR = 0x%08x\n", SCB->CFSR);
      cfsr = SCB->CFSR;
      ufsr = (cfsr>>16);
      printf("UFSR = 0x%04x ", ufsr);
      if (ufsr & DIVBYZERO) printf("Divide by zero UsageFault ");
      if (ufsr & UNALIGNED) printf("Unaligned access UsageFault ");
      if (ufsr & NOCP) printf("No coprocessor UsageFault ");
      if (ufsr & INVPC) printf("Invalid PC load UsageFault ");
      if (ufsr & INVSTATE) printf("Invalid state UsageFault ");
      if (ufsr & UNDEFINSTR) printf("Undefined instruction UsageFault ");
      puts("\n");

      // BFSR
      bfsr = ((cfsr >> 8) & 0xff);
      printf("BFSR = 0x%02x ", bfsr);
      if ((bfsr & IBUSERR) != 0) printf("IBUSERR ");
      if ((bfsr & PRECISERR) != 0) printf("Precise Data Bus Error ");
      if ((bfsr & IMPRECISERR) != 0) printf("Imprecise Data Bus Error ");
      if (bfsr & UNSTKERR) printf("Unstacking Error ");
      if (bfsr & STKERR) printf("Stacking error ");
      if (bfsr & BFARVALID) printf("Bus Fault Address Register Valid ");
      printf("\n");
      // BFAR
      //The value of SCB->BFAR indicates the memory address that caused a Bus Fault and is valid if the bit BFARVALID in the
      //SCB->CFSR register is set.
      puts("BFAR = ");
      if (bfsr & BFARVALID) {
          printf("0x%08x\n", SCB->BFAR);
      } else {
          puts("invalid\n");
      }

      // MMFSR
      mmfsr = (cfsr & 0xff);
      printf("MMFSR = 0x%02x ", mmfsr);
      if (mmfsr & IACCVIOL) printf("Instruction Access Violation ");
      if (mmfsr & DACCVIOL) printf("Data Access Violation ");
      if (mmfsr & MUNSTKERR) printf("Memory Unstacking Error ");
      if (mmfsr & MSTKERR) printf("Memory Stacking Error ");
      if (mmfsr & MMARVALID) printf("MMARVALID ");
      puts("\n");
      // MMFAR
      // The value of SCB->MMFAR indicates the memory address that caused a Memory Management Fault and is valid if the bit
      // MMARVALID in the SCB->CFSR register is set.
      puts("MMFAR = ");
      if (mmfsr & MMARVALID) {
          printf("0x%08x ", SCB->MMFAR);
      } else {
          printf("invalid\n");
      }

      // DFSR
      printf("DFSR = 0x%08lx ", SCB->DFSR);
      if (SCB->DFSR & EXTERNAL) printf("EXTERNAL ");
      if (SCB->DFSR & VCATCH) printf("VCATCH ");
      if (SCB->DFSR & DWTTRAP) printf("DWTTRAP ");
      if (SCB->DFSR & BKPT) printf("BKPT ");
      if (SCB->DFSR & HALTED) printf("HALTED ");
      puts("\n");

      printf("AFSR = 0x%08lx\n", SCB->AFSR);
      printf("SHCSR = 0x%08lx\n", SCB->SHCSR);
      __asm volatile("BKPT #01\n"); // <-- **I want to return here**
      while (1); 
}

/*
void HardFault_Handler(void) {
    while(1);
    error("\n\n%% Hard Fault %%\n");
}
*/

void UsageFault_Handler(void) {
    error("\n\n%% Usage Fault %%\n");
}

void BusFault_Handler() {
    error("\n\n%% Bus Fault %%\n");
}

void MemMang_Handler() {
    error("\n\n%% MemMang Fault %%\n");
}

我已标记要返回的行。 我目前已禁用“用法/总线/内存”故障，但可以根据需要启用它们。

帮助将不胜感激。

Answer 1

您需要的所有信息都可以在《 ARM cortex M3技术参考手册》中找到。

您可以查询发出了引起故障的指令的PC，引起故障的读取地址，原因等。您可以在发生故障之前重建确切的处理器状态。 例如，这就是完成按需寻呼的方式。

但是，如果您遇到“硬故障”，则不能保证系统的其余部分（包括硬件外围设备和总线基础结构）都能够以任何有意义的方式继续运行。 您的总线仲裁器可能被锁定； 您的内存控制器可能被锁定，您的代码内存可能已损坏。 您可能经历了电力不足的情况，并且有些逻辑已经失效。 有不计其数的事情可能是错误的，您不知道并且无法真正从中恢复。