ecos中断分析.docx
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ecos中断分析
eCos学习笔记之中断处理代码分析
2006-07-2411:
06
中断处理代码分析:
.macro hal_vectors_init//中断向量初始化,packages/hal/mips/ref4955/v2_0/include/platform.inc
#Ifwedon~tplaynicewithaROMmonitor,copytherequired
#vectorsintotheproperlocation.
la t0,0x80000000 #destaddr//有些MIPS变种不需要处理tlb的异常
la t1,utlb_vector #sourceaddr
la t3,utlb_vector_end #enddestaddr
1:
lw v0,0(t1) #getword
addi t1,t1,4
sw v0,0(t0) #writeword
addi t0,t0,4
bne t1,t3,1b
nop
la t0,0x80000180 #destaddr//将other_vector拷贝到0x80000180处,完成中断向量的安装
la t1,other_vector #sourceaddr
la t3,other_vector_end #enddestaddr
1:
lw v0,0(t1) #getword
addi t1,t1,4
sw v0,0(t0) #writeword
addi t0,t0,4
bne t1,t3,1b
nop
.endm
.section".other_vector","ax"//中断处理代码安装的位置
#Commonvectorat0x80000080or0xBFC00180
FUNC_START(other_vector)//MIPS异常处理程序的入口,packages/hal/mips/arch/v2_0/src/vectors.S
mfc0 k0,cause #K0=exceptioncause//读取cause寄存器
nop
andi k0,k0,0x7F #isolateexceptioncode//取cause寄存器中的ExcCode值
la k1,hal_vsr_table #addressofVSRtable//取VSR表的基地址
add k1,k1,k0 #offsetofVSRentry//根据ExcCode值取得VSR表的入口地址
lw k1,0(k1) #k1=pointertoVSR//取得VSR表中对应处理程序的地址
jr k1 #gothere//跳转执行
nop #(delayslot)
FUNC_END(other_vector)
##VSRtable.
##ThemaininterruptcodeindirectsthroughheretofindtheVSR
##toexecuteforeacharchitecturedefinedinterrupt.
##Thisisonlyusedforsimulatedtargets,onrealtargetsafixedlocationVSR
##tableisnowallocatedat0x80000100.
#ifndefCYG_HAL_MIPS_VSR_TABLE_DEFINED
## .section".vsr_table","a"//VSR表
.data//VSR表在data段中
.globl hal_vsr_table
hal_vsr_table:
.long __default_interrupt_vsr //定义了64个interrupt入口
.rept 63
.long __default_exception_vsr
.endr
#endif
##DefaultinterruptVSR.
##SavesmachinestateandcallsappropriateISR.Whendone,calls
##interrupt_end()tofinishupandpossiblyreschedule.
FUNC_START(__default_interrupt_vsr)//缺省的中断处理程序
#WeenterherewithalloftheCPUstatestill
#initsregistersexcept:
#K0=vectorindex
#K1=addressofthisfunction
move k1,sp #K1=originalSP//保存原始SP
addi sp,sp,-mips_exception_decrement//分配stack空间
#spaceforregisters+safetymargin
sw k0,mipsreg_vector(sp) #storevector//将异常类型(即ExcCode值)存入堆栈
#storeGPRs//保存通用寄存器
.set noat
sgpr 0,sp
sgpr 1,sp
sgpr 2,sp
sgpr 3,sp
sgpr 4,sp
sgpr 5,sp
sgpr 6,sp
sgpr 7,sp
sgpr 8,sp
sgpr 9,sp
sgpr 10,sp
sgpr 11,sp
sgpr 12,sp
sgpr 13,sp
sgpr 14,sp
sgpr 15,sp
sgpr 16,sp
sgpr 17,sp
sgpr 18,sp
sgpr 19,sp
sgpr 20,sp
sgpr 21,sp
sgpr 22,sp
sgpr 23,sp
sgpr 24,sp
sgpr 25,sp
# sgpr 26,sp #==K0
# sgpr 27,sp #==K1
sgpr 28,sp #==GP
# sgpr 29,sp #==SP
sgpr 30,sp #==FP
sgpr 31,sp #==RA
.set at
mfhi a0//保存hi和lo寄存器
mflo a1
shi a0,sp
slo a1,sp
#K1containsoriginalSP
ssp k1,sp #storeinregdump //保存原始SP到新的stack中的特殊位置上
mfc0 t1,status//保存status,cachectrl和epc寄存器
mfc0 t2,cachectrl
mvafc0 t3,epc
sw t1,mipsreg_sr(sp)
sw t2,mipsreg_cachectrl(sp)
sva t3,mipsreg_pc(sp)//epc寄存器
hal_fpu_savesp//保存浮点寄存器,packages/hal/mips/arch/v2_0/include/arch.inc,如果处理器没有fpu则该宏为空,Lupine没有浮点寄存器
//到此为止处理器的状态已经保存到栈上了
#Themachinestateisnowallsavedonthestack.
#LoadGlobalPointerregister.
la gp,_gp//加载gp指针
#ifdefCYGFUN_HAL_COMMON_KERNEL_SUPPORT
.extern cyg_scheduler_sched_lock
la v0,cyg_scheduler_sched_lock//锁住调度器
lw a0,0(v0)
addi a0,a0,1
sw a0,0(v0)
#endif
move s0,sp #savepointertosavedstate//取sp指针,留做后用
#ifdefCYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK//如果中断使用独立堆栈
la a0,__interrupt_stack #a0=stacktop//栈顶指针
la a1,__interrupt_stack_base #a1=stackbase//栈基址,定义如下:
.bss
.balign16
.globalcyg_interrupt_stack_base
cyg_interrupt_stack_base
__interrupt_stack_base:
.reptCYGNUM_HAL_COMMON_INTERRUPTS_STACK_SIZE//stack的大小
.byte0
.endr
sub a3,sp,a1 #a3=sp-base//现在的sp是否比__interrupt_stack_base小
bltz a3,1f #notonistackif<0
nop #delayslot
sub t0,a0,sp #t0=top-sp//现在的sp是否比__interrupt_stack大
bgtz t0,8f #alreadyonistackif>0
nop #delayslot
1:
move sp,a0 #switchtoistack//notonistack
8:
addi sp,sp,-8 #spaceforoldSP//onistack,为保存现在的sp留出空间
#(8tokeepdwordalignment!
)
sw s0,0(sp) #saveoldSPonstack//保存现在的sp
#endif
subu sp,sp,mips_stack_frame_size #makeanullframe //做一个空的栈帧(32bytes)
#Needtosetupbackpointersetc.?
?
?
#Decodeexternalinterruptviainterruptcontroller
hal_intc_decode s2//根据cause寄存器的IP位解码,返回IP号,packages/hal/mips/tx39/v2_0/include/variant.inc
#Here,s2containsthenumberoftheinterruptbeingserviced,
#weneedtoderivefromthatthevectornumbertocallintheISR
#table.
hal_intc_translates2,s1//packages/hal/mips/tx39/v2_0/include/variant.inc
#Heres1isthenumberofthevectortobecalledands2is
#thenumberoftheinterruptbeingserviced.
hal_diag_intr_start//中断诊断程序,可以不实现,packages/hal/mips/vrc437x/v2_0/include/platform.inc
#ifdefined(CYGPKG_KERNEL_INSTRUMENT)&&defined(CYGDBG_KERNEL_INSTRUMENT_INTR)
#Callcyg_instrumenttorecordthatthisinterruptisbeingraised.//记录程序
li a0,0x0301 #a0=type=INTR,RAISE
move a1,s1 #a1=vectornumber
jal cyg_instrument #callinstrumentfunction
move a2,s2 #a2=interruptnumber
#endif
#ifdefined(CYGDBG_HAL_MIPS_DEBUG_GDB_CTRLC_SUPPORT)
#IfwearesupportingCtrl-CinterruptsfromGDB,wemustsquirrel
#awayapointertothesaveinterruptstateheresothatwecan
#plantabreakpointatsomelatertime.
.extern hal_saved_interrupt_state//使用GDBstub调试时,用于保存中断状态
la v0,hal_saved_interrupt_state
sw s0,0(v0)//s0是sp指针
#endif
sll s1,s1,2 #s1=byteoffsetofvector//根据中断向量号计算中断向量偏移
//在此之前都是禁用中断的
hal_cpu_except_enable #reenableexceptions//启用中断,packages/hal/mips/arch/v2_0/include/arch.inc
la t2,hal_interrupt_handlers #handlertable//加载中断处理程序表,如果未定以CYG_HAL_MIPS_ISR_TABLES_DEFINED,该表在packages/hal/mips/arch/v2_0/src/vectors.S中,否则根据platform不同有不同定义,如packages/hal/mips/tx39/v2_0/src/variant.S
add t2,t2,s1 #addressofISRptr//根据中断向量号计算在中断处理程序表中的偏移
lw t2,0(t2) #ISRpointer//取中断处理程序地址
la a1,hal_interrupt_data #datatable//加载中断处理程序数据表,定义位置与hal_interrupts_handlers一样
add a1,a1,s1 #addressofdataptr//计算中断处理程序数据偏移
lw a1,0(a1) #Datapointer//将中断处理程序数据地址存入a1,作为参数
move a0,s2 #passinterruptnumber//将中断号存入a0寄存器,作为参数
jalr t2 #callISRviat2//调用具体的中断处理程序,有两个参数,分别是中断向量号和中断处理程序数据
nop #(delayslot)
#ifdefCYGIMP_HAL_COMMON_INTERRUPTS_USE_INTERRUPT_STACK
#Ifwearereturningfromthelastnestedinterrupt,moveback
#tothethreadstack.interrupt_end()mustbecalledonthe
#threadstacksinceitpotentiallycausesacontextswitch.
#Sincewehavearrangedforthetopofstacklocationto
#containthespweneedtogobacktohere,justpopitoff
#andputitinSP.
lw sp,mips_stack_frame_size(sp) #sp=*sp
subu sp,sp,mips_stack_frame_size #makeanullframe
#endif
#ifdefCYGFUN_HAL_COMMON_KERNEL_SUPPORT
#Weonlyneedtocall_interrupt_end()whenthereisakernel
#presenttodoanytidyingup.
#Onreturnv0bit1willindicatewhetheraDSRis
#tobeposted.Passthistogetherwithapointerto
#theinterruptobjectwehavejustusedtothe
#interrupttidyuproutine.
#Notethats0,s1ands2aredefinedtobepreservedacross
#callsbythecallingconvention,sotheystillcontain
#theregisterdump,thevectoroffsetandtheinterruptnumber
#respectively.
move s2,v0//临时保存中断处理程序的返回值
la a1,hal_interrupt_objects #interruptobjecttable//取中断对象,定义位置与hal_interrupt_handlers一样,将地址存入a1,用作参数
add a1,a1,s1 #addressofobjectptr
lw a1,0(a1) #a1=objectptr
move a2,s0 #arg3=savedregisterdump//堆栈指针存入a2,作为参数
.extern interrupt_end
jal interrupt_end #callintoCtofinishoff//调用interrupt_end做后面的处理(挂起DSR,解锁调度器,执行DSR),有三个参数,分别是ISR返回值,中断对象,堆栈指针,此处可能导致线程上下文切换