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	 > 嵌入式系統(tǒng) > 設(shè)計應(yīng)用 > GNU ARM匯編--(五)中斷匯編之嵌套中斷處理
          
    
          

          

          


	
	
	

          
	
          
		
          
			
          GNU ARM匯編--(五)中斷匯編之嵌套中斷處理
          
						
          
				作者：
				時間：2016-11-26
				來源：網(wǎng)絡(luò)
				
				
				
				
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			    在上篇《GNU ARM匯編--(四)中斷匯編之非嵌套中斷處理》中分析了最簡單的中斷處理的寫法,再看TQ2440啟動代碼中的中斷向量表的寫法就一目了然了.今天抽時間對嵌套中斷處理的學(xué)習(xí)做下整理.
              嵌套中斷處理的核心代碼如下:
          本文引用地址：http://www.ex-cimer.com/article/201611/321726.htm
          [cpp]view plaincopy
          1. ;/*
          2. ;*____________________________________________________________________
          3. ;*
          4. ;*Copyright(c)2004,AndrewN.Sloss,ChrisWrightandDominicSymes
          5. ;*Allrightsreserved.
          6. ;*____________________________________________________________________
          7. ;*
          8. ;*NON-COMMERCIALUSELicense
          9. ;*
          10. ;*Redistributionanduseinsourceandbinaryforms,withorwithout
          11. ;*modification,arepermittedprovidedthatthefollowingconditions
          12. ;*aremet:
          13. ;*
          14. ;*1.ForNON-COMMERCIALUSEonly.
          15. ;*
          16. ;*2.Redistributionsofsourcecodemustretaintheabovecopyright
          17. ;*notice,thislistofconditionsandthefollowingdisclaimer.
          18. ;*
          19. ;*3.Redistributionsinbinaryformmustreproducetheabove
          20. ;*copyrightnotice,thislistofconditionsandthefollowing
          21. ;*disclaimerinthedocumentationand/orothermaterialsprovided
          22. ;*withthedistribution.
          23. ;*
          24. ;*4.Alladvertisingmaterialsmentioningfeaturesoruseofthis
          25. ;*softwaremustdisplaythefollowingacknowledgement:
          26. ;*
          27. ;*ThisproductincludessoftwaredevelopedbyAndrewN.Sloss,
          28. ;*ChrisWrightandDominicSymes.
          29. ;*
          30. ;*THISSOFTWAREISPROVIDEDBYTHECONTRIBUTORS``ASISANDANY
          31. ;*EXPRESSORIMPLIEDWARRANTIES,INCLUDING,BUTNOTLIMITEDTO,THE
          32. ;*IMPLIEDWARRANTIESOFMERCHANTABILITYANDFITNESSFORAPARTICULAR
          33. ;*PURPOSEAREDISCLAIMED.INNOEVENTSHALLTHECONTRIBUTORSBE
          34. ;*LIABLEFORANYDIRECT,INDIRECT,INCIDENTAL,SPECIAL,EXEMPLARY,
          35. ;*ORCONSEQUENTIALDAMAGES(INCLUDING,BUTNOTLIMITEDTO,
          36. ;*PROCUREMENTOFSUBSTITUTEGOODSORSERVICES;LOSSOFUSE,DATA,
          37. ;*ORPROFITS;ORBUSINESSINTERRUPTION)HOWEVERCAUSEDANDONANY
          38. ;*THEORYOFLIABILITY,WHETHERINCONTRACT,STRICTLIABILITY,OR
          39. ;*TORT(INCLUDINGNEGLIGENCEOROTHERWISE)ARISINGINANYWAYOUT
          40. ;*OFTHEUSEOFTHISSOFTWARE,EVENIFADVISEDOFTHEPOSSIBILITY
          41. ;*OFSUCHDAMAGE.
          42. ;*
          43. ;*Ifyouhavequestionsaboutthislicenseorwouldlikeadifferent
          44. ;*licensepleaseemail:
          45. ;*
          46. ;*andrew@sloss.net
          47. ;*
          48. ;*
          49. ;*/
          51. ;/***********************************************************************
          52. ;*
          53. ;*Module:nih9_9.s
          54. ;*Descriptions:NestedInterruptHandler
          55. ;*Example:9.9
          56. ;*OS:generic
          57. ;*Platform:generic
          58. ;*History:
          59. ;*
          60. ;*31thDecember2003
          61. ;*-addedheader
          62. ;*
          63. ;***********************************************************************/
          65. EXPORTnestedInterruptHandler
          67. MaskmdEQU0x1f;processormodemask
          68. SVC32mdEQU0x13;SVCmode
          69. I_BitEQU0x80;IRQbit
          71. FRAME_R0EQU0x00
          72. FRAME_R1EQUFRAME_R0+4
          73. FRAME_R2EQUFRAME_R1+4
          74. FRAME_R3EQUFRAME_R2+4
          75. FRAME_R4EQUFRAME_R3+4
          76. FRAME_R5EQUFRAME_R4+4
          77. FRAME_R6EQUFRAME_R5+4
          78. FRAME_R7EQUFRAME_R6+4
          79. FRAME_R8EQUFRAME_R7+4
          80. FRAME_R9EQUFRAME_R8+4
          81. FRAME_R10EQUFRAME_R9+4
          82. FRAME_R11EQUFRAME_R10+4
          83. FRAME_R12EQUFRAME_R11+4
          84. FRAME_PSREQUFRAME_R12+4
          85. FRAME_LREQUFRAME_PSR+4
          86. FRAME_PCEQUFRAME_LR+4
          87. FRAME_SIZEEQUFRAME_PC+4
          89. AREAnih9_9,CODE,readonly
          91. nestedInterruptHandler;instructionstate:comment
          92. SUBr14,r14,#4;2:
          93. STMDBr13!,{r0-r3,r12,r14};2:savecontext
          94. ;
          95. BLread_RescheduleFlag;3:moreprocessing
          96. CMPr0,#0;3:ifprocessing?
          97. LDMNEIAr13!,{r0-r3,r12,pc}^;4:thenreturn
          98. MRSr2,SPSR;5:copySPSR_irq
          99. MOVr0,r13;5:copyr13_irq
          100. ADDr13,r13,#6*4;5:resetstack
          101. MRSr1,CPSR;6:copyCPSR
          102. BICr1,r1,#Maskmd;6:
          103. ORRr1,r1,#SVC32md;6:
          104. MSRCPSR_c,r1;6:changeSVCmode
          105. SUBr13,r13,#FRAME_SIZE-FRAME_R4;7:makestackspace
          106. STMIAr13,{r4-r11};7:saver4-r11
          107. LDMIAr0,{r4-r9};7:r4-r9IRQstack
          108. BICr1,r1,#I_Bit;8:
          109. MSRCPSR_c,r1;8:enableint
          110. STMDBr13!,{r4-r7};9:saver4-r7SVC
          111. STRr2,[r13,#FRAME_PSR];9:savePSR
          112. STRr8,[r13,#FRAME_R12];9:saver12
          113. STRr9,[r13,#FRAME_PC];9:savepc
          114. STRr14,[r13,#FRAME_LR];9:savelr
          115. ;
          116. LDMIAr13!,{r0-r12,r14};11:restorecontext
          117. MSRSPSR_cxsf,r14;11:restoreSPSR
          118. LDMIAr13!,{r14,pc}^;11:return
          121. read_RescheduleFlag
          122. ;
          123. MOVr0,#0;moreprocessing
          124. MOVpc,r14;return
          126. END


              代碼的關(guān)鍵就是在中斷后切換到SVC模式下,利用svc mode的stack來實現(xiàn)中斷嵌套過程的備份以及恢復(fù)操作.從代碼中可以看到,從R0到PC都在棧中有備份,這里我們叫棧幀.記得《深入理解計算機(jī)系統(tǒng)》一書在講x86匯編的函數(shù)調(diào)用時也是棧幀的概念.這點上中斷嵌套和函數(shù)調(diào)用有相似之處.有了這個棧幀,利用壓棧出棧操作就一切ok了.
              剛看這個代碼,對有個地方有疑問,就是覺得中斷開早了:
            BIC   r1,r1,#I_Bit        ; 8 :
            MSR   CPSR_c,r1         ; 8 : enable int
            STMDB  r13!,{r4-r7}        ; 9 : save r4-r7 SVC
            STR   r2,[r13,#FRAME_PSR]    ; 9 : save PSR
            STR   r8,[r13,#FRAME_R12]    ; 9 : save r12
            STR   r9,[r13,#FRAME_PC]     ; 9 : save pc   
            STR   r14,[r13,#FRAME_LR]    ; 9 : save lr
              覺得開中斷的代碼應(yīng)該放在后面,這樣才能保證svc mode下的stack frame不會被破壞.但在草稿紙上畫一下irq和svc下的stack圖,就發(fā)現(xiàn)堆棧操作并沒有問題.可以假設(shè)剛開中斷立馬就有新的中斷了,r4-r7 r8 r9都有在STMIA  r13,{r4-r11} 中保存到svc的stack中,LDMIA  r0,{r4-r9} 和STMDB  r13!,{r4-r7} 保證了最初的r0-r3在棧中,而LDMIA  r0,{r4-r9}和STR   r8,[r13,#FRAME_R12] 以及STR   r9,[r13,#FRAME_PC] 保證了R12和PC,保證正確返回.(這里的r9裝的是r14_irq,所以pc就是r14_irq,這樣就保證了從中斷服務(wù)例程中返回).至于STR   r14,[r13,#FRAME_LR]中的r14是r14_svc,將其壓入svc的stack中,中斷例程用bl就不會出現(xiàn)錯誤了,在最后LDMIA  r13!,{r14,pc}^ 中r14得到恢復(fù).而r2保存的是spsr,也就是svc模式的狀態(tài),一直不變,不用擔(dān)心會被覆蓋.
              最后,再看了一遍圖,覺得r10和r11的幀可以省去,因為r4-r9是用來存atpcs的r0-r3,r12,r14,而r10和r11用不到.貌似可以省點空間和時間,具體的待會實驗一下.
           下面給出實際的嵌套中斷處理,利用r10來保存INTOFFSET的值,根據(jù)該值來判定是什么中斷,從而做不同的處理.具體的效果是:代碼會做流水燈的動作,Key1代表INT1,中斷處理動作是4個燈全全亮然后全滅,Key4代表代表INT0,中斷處理動作是第一個燈和第三個燈亮,然后第二個燈和第四個燈亮.
          [cpp]view plaincopy
          1. /*
          2. simpleinterruption
          3. copyleft@dndxhej@gmail.com
          4. */
          6. .equMaskmd,0x1f@processormodemask
          7. .equSVC32md,0x13@SVCmode
          8. .equI_Bit,0x80@IRQbit
          10. .equFRAME_R0,0x00
          11. .equFRAME_R1,FRAME_R0+4
          12. .equFRAME_R2,FRAME_R1+4
          13. .equFRAME_R3,FRAME_R2+4
          14. .equFRAME_R4,FRAME_R3+4
          15. .equFRAME_R5,FRAME_R4+4
          16. .equFRAME_R6,FRAME_R5+4
          17. .equFRAME_R7,FRAME_R6+4
          18. .equFRAME_R8,FRAME_R7+4
          19. .equFRAME_R9,FRAME_R8+4
          20. .equFRAME_R10,FRAME_R9+4
          21. .equFRAME_R11,FRAME_R10+4
          22. .equFRAME_R12,FRAME_R11+4
          23. .equFRAME_PSR,FRAME_R12+4
          24. .equFRAME_LR,FRAME_PSR+4
          25. .equFRAME_PC,FRAME_LR+4
          26. .equFRAME_SIZE,FRAME_PC+4
          30. .equNOINT,0xc0
          31. .equWTCON,0x53000000
          32. .equGPBCON,0x56000010@led
          33. .equGPBDAT,0x56000014@led
          34. .equGPBUP,0x56000018@led
          35. .equGPFCON,0x56000050@interruptconfig
          36. .equEINTMASK,0x560000a4
          37. .equEXTINT0,0x56000088
          38. .equEXTINT1,0x5600008c
          39. .equEXTINT2,0x56000090
          40. .equINTMSK,0x4A000008
          41. .equEINTPEND,0x560000a8
          43. .equINTSUBMSK,0X4A00001C
          45. .equSRCPND,0X4A000000
          46. .equINTPND,0X4A000010
          48. .equINTOFFSET,0x4A000014
          50. .global_start
          51. _start:breset
          52. ldrpc,_undefined_instruction
          53. ldrpc,_software_interrupt
          54. ldrpc,_prefetch_abort
          55. ldrpc,_data_abort
          56. ldrpc,_not_used
          57. @birq
          58. ldrpc,_irq
          59. ldrpc,_fiq
          63. _undefined_instruction:.wordundefined_instruction
          64. _software_interrupt:.wordsoftware_interrupt
          65. _prefetch_abort:.wordprefetch_abort
          66. _data_abort:.worddata_abort
          67. _not_used:.wordnot_used
          68. _irq:.wordirq
          69. _fiq:.wordfiq
          71. .balignl16,0xdeadbeef
          73. reset:
          76. ldrr3,=WTCON
          77. movr4,#0x0
          78. strr4,[r3]@disablewatchdog
          80. ldrr0,=GPBCON
          81. ldrr1,=0x15400
          82. strr1,[r0]
          84. ldrr2,=GPBDAT
          85. ldrr1,=0x160
          86. strr1,[r2]
          88. bldelay
          91. msrcpsr_c,#0xd2@進(jìn)入中斷模式
          92. ldrsp,=0xc00@中斷模式的棧指針定義
          94. msrcpsr_c,#0xd3@進(jìn)入svc模式
          95. ldrsp,=0xfff@設(shè)置svc模式的棧指針
          97. @--------------------------------------------
          99. ldrr0,=GPBUP
          100. ldrr1,=0x03f0
          101. strr1,[r0]
          102. 				   
				
            
                
			
							
            
                
			            
            
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            			            ARM匯編中斷匯編中斷處
                        
            
          
            
			
          
		
          	
		

	

          
	
	
          
		
          
			
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