GNU ARM汇编--(五)中断汇编之嵌套中断处理

在上篇《GNU ARM汇编--(四)中断汇编之非嵌套中断处理》中分析了最简单的中断处理的写法,再看TQ2440启动代码中的中断向量表的写法就一目了然了.今天抽时间对嵌套中断处理的学习做下整理.

嵌套中断处理的核心代码如下:

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1. ;/*
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4. ;*Copyright(c)2004,AndrewN.Sloss,ChrisWrightandDominicSymes
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28. ;*ChrisWrightandDominicSymes.
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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

代码的关键就是在中断后切换到SVC模式下,利用svc mode的stack来实现中断嵌套过程的备份以及恢复操作.从