vxWorks系统中(MIPS架构)的中断分发分析

这里单独分析中断分发函数，大部分是基于汇编，初始化过程在另一个博客单独分析。

首先当中断来了之后硬件会自动跳转到函数：

(这里进行了部分删减，方便进行查看过程。)

.entexcNormVmVec.setnoatFUNC_LABEL(excNormVmVec).setnoreorder#ifdef _WRS_MIPS_VR4131_ERRATAnop/* 延时作用 */#endif/* _WRS_MIPS_VR4131_ERRATA */mfc0k0, C0_CAUSE/*取cause寄存器的值*/HAZARD_CP_READandk0, CAUSE_EXCMASK/*取cause code码 */bnek0, zero, 1f/*如果code码==0说明是中断 */noplak0, excIntVmStubjk0/*中断跳转到excIntVmStub函数，进行具体的分发 */nopexcNormVmVecEnd:.setat.setreorderFUNC_END(excNormVmVec).endexcNormVmVec        .sdata        .align    4excNormVmVecSize:    .word    excNormVmVecEnd-excNormVmVec    .text

这是excIntVmStub函数：

.globlexcIntVmStub.entexcIntVmStubFUNC_LABEL(excIntVmStub)//保存相关的寄存器值SWAT, EXCPAGE_EXCSTUB_AT(zero)SWt7, EXCPAGE_EXCSTUB_T7(zero)SWt8, EXCPAGE_EXCSTUB_T8(zero)SWt9, EXCPAGE_EXCSTUB_T9(zero).setnoreordermfc0t7, C0_EPC/*读取epc的值*/mfc0t8, C0_SR/*读取SR寄存器*/mfc0t9, C0_CAUSE/*读取cause寄存器*/HAZARD_CP_READ.setreorderswt7, EXCPAGE_EXCSTUB_PC(zero) /*保存epc*/swt8, EXCPAGE_EXCSTUB_SR(zero) /*保存SR*/swt9, EXCPAGE_EXCSTUB_CR(zero) /*保存cause*//*关中断，并清楚exl*注意：在清中断前清楚exl，interrupts could be re-enabled here* for one or more cycles。所以在做完其他操作后，在去清楚exl位*/and  t9, t8, ~(SR_KSUMASK|SR_IE) /*关中断，并清除用户权限位进入特权级 */.setnoreordermtc0t9, C0_SR  HAZARD_INTERRUPT.setreorderandt9, ~SR_EXL/*清除exl */.setnoreordermtc0t9, C0_SRHAZARD_CP_WRITE.setreorder /*检查是否在中断栈中，增加areWeNested的值并保存 */_MIPS_PER_CPU_ARCH_VALUE_AND_ADRS_GET(t7,t8,areWeNested).set noreorderbnez    t7, nestedVm            /* if in isr don't reset sp      */move    t9, sp.set reorder/*如果没有在中断栈上，获取中断栈的值 */_MIPS_PER_CPU_VALUE_GET(t9,vxIntStackBase)nestedVm:subu    t9, ESTKSIZE            /* make room for frame           */SW      sp, E_STK_SP(t9)        /* save sp on int stack          */move    sp, t9                  /* init new int stack ptr        *//* save areWeNested */add     t9, t7, 1sw      t9, 0(t8)SW      gp, E_STK_GP(sp)lagp, _gp#ifdef _WRS_CONFIG_SMP_MIPS_PER_CPU_VALUE_GET(t8,errno)#else /* _WRS_CONFIG_SMP */lwt8, _WRS_MIPS_SDA_OFFSET(errno)#endif /* _WRS_CONFIG_SMP */swt8, E_ERRNO(sp)/*保存必要的值*/LWt9, EXCPAGE_EXCSTUB_AT(zero)SWt9, E_STK_AT(sp)LWt7, EXCPAGE_EXCSTUB_T7(zero)LWt8, EXCPAGE_EXCSTUB_T8(zero)LWt9, EXCPAGE_EXCSTUB_T9(zero)SWt7, E_STK_T7(sp)SWt8, E_STK_T8(sp)SWt9, E_STK_T9(sp)SWt0, E_STK_T0(sp)/* t0 saved here so a sputious int * won't lead it possibly getting * corrupted */SWzero, E_STK_K0(sp)/* dummy value to k0 */SWzero, E_STK_K1(sp)/* dummy value to k1 */SWv0, E_STK_V0(sp)/* save func return 0, used *//* to hold cause    */lwt9, EXCPAGE_EXCSTUB_PC(zero)lwt8, EXCPAGE_EXCSTUB_SR(zero)lwv0, EXCPAGE_EXCSTUB_CR(zero)swt9, E_STK_EPC(sp)/* save EPC on stack*/swt8, E_STK_SR(sp)/* save status on stack*/swv0, E_STK_CAUSE(sp)/* save cause on stack*/bcommonExcIntStubCode  /*跳转到正常中断处理函数中*/FUNC_END(excIntVmStub).endexcIntVmStub

最后会跳转到C函数进行分发：、

commonExcIntStubCode:SWra, E_STK_RA(sp)/* save RA on stack*/SWt0, E_STK_T0(sp)/* save temp reg 0 (early) */SWt1, E_STK_T1(sp)/* save temp reg 1 (early) */SWt2, E_STK_T2(sp)/* save temp reg 2 (early) */SWt3, E_STK_T3(sp)/* save temp reg 3 (early) */_MIPS_PER_CPU_VALUE_AND_ADRS_GET(t2,t1,intCnt)addu    t2, 1                   /* increment intCnt */sw      t2, 0(t1)excIntStubNormal:/* now t8 has STATUS and v0 has CAUSE */and     t2, v0, SR_IMASK        /* check for spurious interrupt  */and     v0, t8, t2              /* v0 = ints enabled and pending */.set noreorderbeqz    v0, restoreVolatile     /* return if no interrupt */movet1, zero/* flag only volatile restore * if branch is taken *//* vxbus interrupt handler processing */sllt1, 4/* mult by Prio table size       */lwt2, intPrioTable+8(t1)/* get user mask                 */  orv0, v0, t2/* add user mask                 */notv0/* invert interrupt mask         */andt8, v0, t8/* apply interrupt mask to t8    */excIntStubCommonExit:andv0, t8, ~(SR_KSUMASK|SR_EXL|SR_IE).setnoreordermtc0v0, C0_SRHAZARD_INTERRUPT.setreorderand t8, ~(SR_KSUMASK|SR_EXL)mtc0t8, C0_SR/* enable interrupts w/ new mask */HAZARD_CP_WRITE/* * Begin state save */intStateSave:SWzero,E_STK_ZERO(sp)/* init zero reg storage */SWv1,E_STK_V1(sp)/* save func return 1 */SWa0,E_STK_A0(sp)/* save passed param 0         */SWa1,E_STK_A1(sp)/* save passed param 1 */SWa2,E_STK_A2(sp)/* save passed param 2 */SWa3,E_STK_A3(sp)/* save passed param 3 */SWt0,E_STK_T0(sp)/* save temp reg 0 *//* save temp reg 1 (above) *//* save temp reg 2 (above) *//* save temp reg 3 (above) */SWt4,E_STK_T4(sp)/* save temp reg 4 */SWt5,E_STK_T5(sp)/* save temp reg 5 */SWt6,E_STK_T6(sp)/* save temp reg 6 *//* save temp reg 7 (above)       *//* save temp reg 8 (above)       *//* save temp reg 9 (above)       *//* save return address (above)   */mflot2/* read int mult lo reg */SWt2,E_STK_LO(sp)/* save int mult lo reg         */mfhit2/* read int mult hi reg */SWt2,E_STK_HI(sp)/* save int mult hi reg */        /* flag full context is being saved */        sw      zero, E_STK_ULEXTRA1(sp)MFC0t2,C0_TLBHI/* read tlb entryHi reg */HAZARD_CP_READSWt2,E_STK_TLBHI(sp)/* save tlb entryHi reg *//*进入C函数，进行中断的分发*/lwt2, _WRS_MIPS_SDA_OFFSET(_func_vxBusIntHdlr)beq     t2, zero, 1fmove    a0, t9          /* pass pin number of interrupt */.set noreorderjalt2/* call registered vxBus ISR */movea1, sp          /* pass exc stack frame */bRestore

在vxbMipsIntCtlrInstInit函数中对_func_vxBusIntHdlr进行了赋值操作： _func_vxBusIntHdlr = vxbMipsIntCtlrISR。也就是说真正的分发函数是：vxbMipsIntCtlrISRvoid vxbMipsIntCtlrISR     (    int pinNum,    ESFMIPS * pEsf    )    {#ifdef _WRS_CONFIG_SMP    int cpunum = vxCpuIndexGet ();#else    int cpunum = 0; /* UP and AMP always use zero cpu number */#endif /* _WRS_CONFIG_SMP */    struct vxbIntCtlrPin * pPin = vxbIntCtlrPinEntryGet(                    &(pVxbMipsIntCtlrDrvCtrl [cpunum]->isrHandle), pinNum);    (*pPin->isr) ((void *)(pPin->pArg), (int)pEsf);    }

在对中断进行初始化时，每个引脚对初始化为一个结构体，这个结构体包含了中断处理函数，所有最后分发时，只需要得到对应引脚的机构体，也就找到了具体的中断函数。

当然了每个中断函数的挂接，都是在中断初始化时所做的工作。后面对中断初始化分析时，会详细说明中断的挂接，以及相关结构体的初始化。