1, .LCvectors                        @ set up the vectors
           ldmia r1, {r1, r2, r3, r4, r5, r6, ip, lr}
           stmia r0, {r1, r2, r3, r4, r5, r6, ip, lr}
           add    r2, r0, #0x200
           adr    r0, __stubs_start          @ copy stubs to 0x200
           adr    r1, __stubs_end
1:                 ldr     r3, [r0], #4
           str     r3, [r2], #4
           cmp  r0, r1
           blt     1b
           LOADREGS(fd, sp!, {r4 - r6, pc}) 

以上可以看出這個函數(shù)初始化了中斷向量，實際上把相應的跳轉指令拷貝到了對應的地址。
當發(fā)生中斷時，不管是從用戶模式還是管理模式調(diào)用的，最終都要調(diào)用do_IRQ()：

__irq_usr:    sub    sp, sp, #S_FRAME_SIZE
           stmia sp, {r0 - r12}                         @ save r0 - r12
           ldr     r4, .LCirq
           add    r8, sp, #S_PC
           ldmia r4, {r5 - r7}                           @ get saved PC, SPSR
           stmia r8, {r5 - r7}                           @ save pc, psr, old_r0
           stmdb         r8, {sp, lr}^
           alignment_trap r4, r7, __temp_irq
           zero_fp
1:                 get_irqnr_and_base r0, r6, r5, lr
           movne