c - ARM Cortex M4 处理器中耗时的测试 C 代码中出现错误 SEGV

Question

我正在为我的 stm32f429 板编写嵌入式操作系统代码。我正在测试这段代码的运行时间:

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h> 
#include <fcntl.h>
#include <time.h>
#include <stdint.h>


#define DEFAULT_DELAY   1

uint32_t m_nStart;               //DEBUG Stopwatch start cycle counter value
uint32_t m_nStop;   //DEBUG Stopwatch stop cycle counter value             
#define DEMCR_TRCENA    0x01000000

/* Core Debug registers */
#define DEMCR           (*((volatile uint32_t *)0xE000EDFC))
#define DWT_CTRL        (*(volatile uint32_t *)0xE0001000)
#define CYCCNTENA       (1<<0)
#define DWT_CYCCNT      ((volatile uint32_t *)0xE0001004)
#define CPU_CYCLES      *DWT_CYCCNT



#define STOPWATCH_START { m_nStart = *(*(volatile unsigned int*)0xE0001004);}//DWT_CYCCNT;}
#define STOPWATCH_STOP  { m_nStop = *(*(volatile unsigned int *)0xE0001004);}




static inline void stopwatch_reset(void)
{
    /* Enable DWT */
    DEMCR |= DEMCR_TRCENA; 
    *DWT_CYCCNT = 0;             
    /* Enable CPU cycle counter */
    DWT_CTRL |= CYCCNTENA;
}

static inline uint32_t stopwatch_getticks()
{
    return CPU_CYCLES;
}

static inline void stopwatch_delay(uint32_t ticks)
{
    stopwatch_reset();
    while(1)
    {
        if (stopwatch_getticks() >= ticks)
                break;
    }
}

uint32_t CalcNanosecondsFromStopwatch(uint32_t nStart, uint32_t nStop)
{
    uint32_t nTemp;
    uint32_t n;
    uint32_t SystemCoreClock = 180000000;
    nTemp = nStop - nStart;

    nTemp *= 1000;                          // Scale cycles by 1000.
    n = SystemCoreClock / 1000000;          // Convert Hz to MHz
   nTemp = nTemp / n;                      // nanosec = (Cycles * 1000) / (Cycles/microsec)

   return nTemp;
} 



int main( int argc, char **argv )
{
    int delay = DEFAULT_DELAY;  // Initial value for the delay

    int timeDiff = 0;

    STOPWATCH_START;
    printf("Try\n\n");
    STOPWATCH_STOP;
    timeDiff = CalcNanosecondsFromStopwatch(m_nStart, m_nStop);
    printf("My function took %d nanoseconds\n", timeDiff);  


   return( 0 );
}

它编译时没有错误，但是当我在 stm32f429 上运行这个程序时，我收到一个 SEGV 错误，可能是在 #define STOPWATCH_START 中。也许我的寄存器有问题(？)。

代码是http://pastebin.com/qr6sF9eU (它删除了我使用的系统调用的调用)

make的输出是:http://pastebin.com/Q14xTaXH

我在 stm32f429 板上运行测试时的输出是:http://pastebin.com/sGmjZjxj

你能帮我吗？

Answer 1

NVIC 寄存器很可能受 MPU 保护，并且用户代码无法访问。使用操作系统时，你不能搞乱一切。