如何确读这些中断向量汇编指令？

-586 · 2011-1-8 16:39

最近学ARM，有如下的一段中断向量汇编指令，到最后，像
SWI_Handler
      B    SWI_Handler
这种最后不都是死循环了么？怎么执行中断服务程序？

      ENTRY
      LDR    PC, Reset_Addr
      LDR    PC, Undefined_Addr
      LDR    PC, SWI_Addr
      LDR    PC, Prefetch_Addr
      LDR    PC, Abort_Addr
      NOP                                     ; Reserved vector
      LDR    PC, IRQ_Addr
      LDR    PC, FIQ_Addr

      IMPORT  Reset_Handler          ; In init.s
      IMPORT IRQ_IntHandler


Reset_Addr       DCD    Reset_Handler
Undefined_Addr DCD    Undefined_Handler
SWI_Addr          DCD    SWI_Handler
Prefetch_Addr    DCD    Prefetch_Handler
Abort_Addr       DCD    Abort_Handler
IRQ_Addr          DCD    IRQ_IntHandler
FIQ_Addr          DCD    FIQ_Handler

; ************************
; Exception Handlers
; ************************
; The following dummy handlers do not do anything useful in this example.
; They are set up here for completeness.

Undefined_Handler
      B    Undefined_Handler
SWI_Handler
      B    SWI_Handler
Prefetch_Handler
      B    Prefetch_Handler
Abort_Handler
      B    Abort_Handler
IRQ_Handler
  B  IRQ_Handler

FIQ_Handler
      B    FIQ_Handler

END