鸿蒙轻内核M核源码分析：中断Hwi

1、中断概念介

2、鸿蒙轻内核中断源代码

UINT32 g_intCount = 0;

inline UINT32 HalIsIntActive(VOID)
{
    return (g_intCount > 0);
}

我们在再看看中断向量表定义。⑴处代码为系统支持的中断定义了数组g_hwiForm[OS_VECTOR_CNT]，对于每一个中断号hwiNum，对应的数组元素g_hwiForm[hwiNum]表示每一个中断对应的中断处理执行入口程序。⑵处的宏OS_HWI_WITH_ARG表示中断处理程序是否支持参数传入，默认关闭。如果支持传参，定义⑶处的结构体HWI_HANDLER_FUNC来维护中断处理函数及其参数，还需要定义⑷处g_hwiHandlerForm数组。如果不支持传参，使用⑹处定义的g_hwiHandlerForm数组。对于每一个中断号hwiNum，对应的数组元素g_hwiHandlerForm[hwiNum]表示每一个中断对应的中断处理程序。⑸、⑺处定义个函数OsSetVector()用于设置指定中断号对应的中断处理执行入口程序和中断处理程序。中断处理执行入口程序和中断处理程序的关系是，当中断发生时，会执行中断处理执行入口程序，这个函数会进一步调用中断处理程序。

⑴  STATIC HWI_PROC_FUNC __attribute__((aligned(0x100))) g_hwiForm[OS_VECTOR_CNT] = {0};

⑵  #if (OS_HWI_WITH_ARG == 1)

⑶  typedef struct {
        HWI_PROC_FUNC pfnHandler;
        VOID *pParm;
    } HWI_HANDLER_FUNC;

⑷  STATIC HWI_HANDLER_FUNC g_hwiHandlerForm[OS_VECTOR_CNT] = {{ (HWI_PROC_FUNC)0, (HWI_ARG_T)0 }};
⑸  VOID OsSetVector(UINT32 num, HWI_PROC_FUNC vector, VOID *arg)
    {
        if ((num + OS_SYS_VECTOR_CNT) < OS_VECTOR_CNT) {
            g_hwiForm[num + OS_SYS_VECTOR_CNT] = (HWI_PROC_FUNC)HalInterrupt;
            g_hwiHandlerForm[num + OS_SYS_VECTOR_CNT].pfnHandler = vector;
            g_hwiHandlerForm[num + OS_SYS_VECTOR_CNT].pParm = arg;
        }
    }

    #else

⑹  STATIC HWI_PROC_FUNC g_hwiHandlerForm[OS_VECTOR_CNT] = {0};

⑺   VOID OsSetVector(UINT32 num, HWI_PROC_FUNC vector)
    {
        if ((num + OS_SYS_VECTOR_CNT) < OS_VECTOR_CNT) {
            g_hwiForm[num + OS_SYS_VECTOR_CNT] = HalInterrupt;
            g_hwiHandlerForm[num + OS_SYS_VECTOR_CNT] = vector;
        }
    }
    #endif

2.2 中断初始化HalHwiInit()

LITE_OS_SEC_TEXT_INIT VOID HalHwiInit()
{
#if (LOSCFG_USE_SYSTEM_DEFINED_INTERRUPT == 1)
    UINT32 index;
⑴  g_hwiForm[0] = 0;             /* [0] Top of Stack */
    g_hwiForm[1] = Reset_Handler; /* [1] reset */
⑵  for (index = 2; index < OS_VECTOR_CNT; index++) { /* 2: The starting position of the interrupt */
        g_hwiForm[index] = (HWI_PROC_FUNC)HalHwiDefaultHandler;
    }
    /* Exception handler register */
⑶  g_hwiForm[NonMaskableInt_IRQn + OS_SYS_VECTOR_CNT]   = HalExcNMI;
    g_hwiForm[HARDFAULT_IRQN + OS_SYS_VECTOR_CNT]        = HalExcHardFault;
    g_hwiForm[MemoryManagement_IRQn + OS_SYS_VECTOR_CNT] = HalExcMemFault;
    g_hwiForm[BusFault_IRQn + OS_SYS_VECTOR_CNT]         = HalExcBusFault;
    g_hwiForm[UsageFault_IRQn + OS_SYS_VECTOR_CNT]       = HalExcUsageFault;
    g_hwiForm[SVCall_IRQn + OS_SYS_VECTOR_CNT]           = HalExcSvcCall;
    g_hwiForm[PendSV_IRQn + OS_SYS_VECTOR_CNT]           = HalPendSV;
    g_hwiForm[SysTick_IRQn + OS_SYS_VECTOR_CNT]          = SysTick_Handler;

    /* Interrupt vector table location */
⑷  SCB->VTOR = (UINT32)(UINTPTR)g_hwiForm;
#endif
#if (__CORTEX_M >= 0x03U) /* only for Cortex-M3 and above */
⑸   NVIC_SetPriorityGrouping(OS_NVIC_AIRCR_PRIGROUP);
#endif

    /* Enable USGFAULT, BUSFAULT, MEMFAULT */
⑹   *(volatile UINT32 *)OS_NVIC_SHCSR |= (USGFAULT | BUSFAULT | MEMFAULT);
    /* Enable DIV 0 and unaligned exception */
    *(volatile UINT32 *)OS_NVIC_CCR |= DIV0FAULT;

    return;
}

2.3 创建中断UINT32 HalHwiCreate()

LITE_OS_SEC_TEXT_INIT UINT32 HalHwiCreate(HWI_HANDLE_T hwiNum,
                                          HWI_PRIOR_T hwiPrio,
                                          HWI_MODE_T mode,
                                          HWI_PROC_FUNC handler,
                                          HWI_ARG_T arg)
{
    UINTPTR intSave;

⑴  if (handler == NULL) {
        return OS_ERRNO_HWI_PROC_FUNC_NULL;
    }

    if (hwiNum >= OS_HWI_MAX_NUM) {
        return OS_ERRNO_HWI_NUM_INVALID;
    }

    if (g_hwiForm[hwiNum + OS_SYS_VECTOR_CNT] != (HWI_PROC_FUNC)HalHwiDefaultHandler) {
        return OS_ERRNO_HWI_ALREADY_CREATED;
    }

    if (hwiPrio > OS_HWI_PRIO_LOWEST) {
        return OS_ERRNO_HWI_PRIO_INVALID;
    }

    intSave = LOS_IntLock();
#if (OS_HWI_WITH_ARG == 1)
    OsSetVector(hwiNum, handler, arg);
#else
⑵   OsSetVector(hwiNum, handler);
#endif
⑶  NVIC_EnableIRQ((IRQn_Type)hwiNum);
    NVIC_SetPriority((IRQn_Type)hwiNum, hwiPrio);

    LOS_IntRestore(intSave);

    return LOS_OK;
}

2.4 删除中断UINT32 HalHwiDelete()

LITE_OS_SEC_TEXT_INIT UINT32 HalHwiDelete(HWI_HANDLE_T hwiNum)
{
    UINT32 intSave;

⑴  if (hwiNum >= OS_HWI_MAX_NUM) {
        return OS_ERRNO_HWI_NUM_INVALID;
    }

⑵  NVIC_DisableIRQ((IRQn_Type)hwiNum);

    intSave = LOS_IntLock();

⑶  g_hwiForm[hwiNum + OS_SYS_VECTOR_CNT] = (HWI_PROC_FUNC)HalHwiDefaultHandler;

    LOS_IntRestore(intSave);

    return LOS_OK;
}

2.5 中断处理执行入口程序

LITE_OS_SEC_TEXT_MINOR VOID HalHwiDefaultHandler(VOID)
{
    UINT32 irqNum = HalIntNumGet();
    PRINT_ERR("%s irqNum:%d\n", __FUNCTION__, irqNum);
    while (1) {}
}

继续来看中断处理执行入口程序HalInterrupt()，源码如下。

3、开关中断

    UINTPTR HalIntLock(VOID);
⑴  #define LOS_IntLock HalIntLock

    VOID HalIntRestore(UINTPTR intSave);
⑵  #define LOS_IntRestore HalIntRestore

    UINTPTR HalIntUnLock(VOID);
⑶  #define LOS_IntUnLock HalIntUnLock

可以看出，LOS_IntLock、LOS_IntRestore和LOS_IntUnLock是定义的宏，他们对应定义在文件kernel\arch\arm\cortex-m7\gcc\los_dispatch.S中的汇编函数，源码如下。我们分析下这些汇编函数。寄存器PRIMASK是单一bit位的寄存器，置为1后，就关掉所有可屏蔽异常，只剩下NMI和硬故障HardFault异常可以响应。默认值是0，表示没有关闭中断。汇编指令CPSID I会设置PRIMASK=1，关闭中断，指令CPSIE I设置PRIMASK=0，开启中断。

    .type HalIntLock, %function
    .global HalIntLock
HalIntLock:
    .fnstart
    .cantunwind

⑴  MRS R0, PRIMASK
    CPSID I
    BX LR
    .fnend

    .type HalIntUnLock, %function
    .global HalIntUnLock
HalIntUnLock:
    .fnstart
    .cantunwind

⑵  MRS R0, PRIMASK
    CPSIE I
    BX LR
    .fnend

    .type HalIntRestore, %function
    .global HalIntRestore
HalIntRestore:
    .fnstart
    .cantunwind

⑶  MSR PRIMASK, R0
    BX LR
    .fnend

小结