Linux异常体系之vector_stub宏解析

ARM-Linux汇编的宏定义语法说明如下：

使用注意：

1.宏定义以.macro开始，以.endm结束

2.可带参数，参数可有默认值

3.直接使用参数的名字\arg

vector_stub宏的功能：

计算处理完异常的返回地址；

保存寄存器(r0，lr，spsr)

进入管理模式；

最后根据进入异常前的模式跳转到相应的某个分支。

 /*
  * Vector stubs.
  *
  * This code is copied to 0xffff0200 so we can use branches in the
  * vectors, rather than ldr's.  Note that this code must not
  * exceed 0x300 bytes.
  *
  * Common stub entry macro:
  *   Enter in IRQ mode, spsr = SVC/USR CPSR, lr = SVC/USR PC
  *
  * SP points to a minimal amount of processor-private memory, the address
  * of which is copied into r0 for the mode specific abort handler.
  */
     .macro    vector_stub, name, mode, correction=
     .align    

 vector_\name:
     .if \correction
     sub    lr, lr, #\correction
     .endif

     @
     @ Save r0, lr_<exception> (parent PC) and spsr_<exception>
     @ (parent CPSR)
     @
     stmia    sp, {r0, lr}        @ save r0, lr
     mrs    lr, spsr
     str    lr, [sp, #]        @ save spsr

     @
     @ Prepare for SVC32 mode.  IRQs remain disabled.
     @
     mrs    r0, cpsr
     eor    r0, r0, #(\mode ^ SVC_MODE)
     msr    spsr_cxsf, r0

     @
     @ the branch table must immediately follow this code
     @
     and    lr, lr, #0x0f
     mov    r0, sp
     ldr    lr, [pc, lr, lsl #]
     movs    pc, lr            @ branch to handler in SVC mode
     .endm

展开

 /*
  * Interrupt dispatcher
  */
     vector_stub    irq, IRQ_MODE, 

     .long    __irq_usr            @    (USR_26 / USR_32)
     .long    __irq_invalid            @    (FIQ_26 / FIQ_32)
     .long    __irq_invalid            @    (IRQ_26 / IRQ_32)
     .long    __irq_svc            @    (SVC_26 / SVC_32)
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @  a
     .long    __irq_invalid            @  b
     .long    __irq_invalid            @  c
     .long    __irq_invalid            @  d
     .long    __irq_invalid            @  e
     .long    __irq_invalid            @  f

后得到

 /*
  * Interrupt dispatcher
  */
     .align    

 vector_irq:
     sub    lr, lr, #               //保存irq返回地址

     @
     @ Save r0, lr_<exception> (parent PC) and spsr_<exception>
     @ (parent CPSR)
     @
     stmia    sp, {r0, lr}        @ save r0, lr
     mrs    lr, spsr
     str    lr, [sp, #]        @ save spsr

     @
     @ Prepare for SVC32 mode.  IRQs remain disabled.
     @
     mrs    r0, cpsr
     eor    r0, r0, #(\mode ^ SVC_MODE)
     msr    spsr_cxsf, r0 //对spsr的所有控制位进行写操作,将r0的值全部注入spsr，进入svc模式

     @
     @ the branch table must immediately follow this code
     @
     and    lr, lr, #0x0f  //根据进入中断前的模式跳转到相应的中断处理函数
     mov    r0, sp
     ldr    lr, [pc, lr, lsl #]
     movs    pc, lr            @ branch to handler in SVC mode

     .long    __irq_usr            @    (USR_26 / USR_32)
     .long    __irq_invalid            @    (FIQ_26 / FIQ_32)
     .long    __irq_invalid            @    (IRQ_26 / IRQ_32)
     .long    __irq_svc            @    (SVC_26 / SVC_32)
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @
     .long    __irq_invalid            @  a
     .long    __irq_invalid            @  b
     .long    __irq_invalid            @  c
     .long    __irq_invalid            @  d
     .long    __irq_invalid            @  e
     .long    __irq_invalid            @  f