interrupt-vectors_2.htm

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align=left>由于IDT最多会有256个实体，所以我们可以定义：</P>
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align=left>&nbsp;</P>
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align=left>const int &nbsp;MAX_INTR_DESC_ENTITY = 256;</P>
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align=left>descriptor_s idt[MAX_INTR_DESC_ENTITY];</P>
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align=left>&nbsp;</P>
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align=left>设置Interrupt Gate Descriptor和Trap Gate 
Descriptor，我们可以通过下面的C++代码实现：</P>
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align=left>&nbsp;</P>
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align=left>typedef unsigned long addr_t;</P>
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align=left>typedef unsigned short selector_t;</P>
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align=left>&nbsp;</P>
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align=left>inline void set_gate(descriptor_s&amp; __gate_addr,&nbsp; \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
unsigned int __type,&nbsp;\</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
unsigned int __dpl, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
addr_t __addr, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
selector_t __sel)</P>
<P class=MsoNormal 
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align=left>{</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; __gate_addr.low_dw = 
(__sel &lt;&lt; 16) | (__addr&amp;0xffff);</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; __gate_addr.high_dw 
= (__addr&amp;0xffff0000) | 0x8000 | (__dpl &lt;&lt; 13) | (__type &lt;&lt; 8 
);</P>
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align=left>}</P>
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align=left>&nbsp;</P>
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align=left>如果想更加高效，可以使用汇编：</P>
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align=left>&nbsp;</P>
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align=left>inline void set_gate(descriptor_s&amp; __gate_addr, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
unsigned int __type, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
unsigned int __dpl, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
addr_t __addr, \</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
selector_t __sel)</P>
<P class=MsoNormal 
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align=left>{</P>
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align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; __asm__ __volatile__ 
("movw %%dx,%%ax\n\t"&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
"movw %2,%%dx\n\t"&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
"movl %%eax,%0\n\t"&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
"movl %%edx,%1"&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :"=m" 
(*((long *) 
(__gate_addr))),&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
"=m" (*(1+(long *) 
(__gate_addr)))&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :"i" 
((short) 
(0x8000+(__dpl&lt;&lt;13)+(__type&lt;&lt;8))),&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
"d" ((char *) (__addr)),"a"&nbsp;(__sel &lt;&lt; 
16)&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; :"ax","dx");</P>
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align=left>}</P>
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align=left>&nbsp;</P>
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align=left>下面的C++代码实现了设置Interrupt Gate和Trap 
Gate的3个Function。函数set_intr_gate/set_trap_gate只能被在CPL=0时调用，对于一个OS来说，只能被内核所引起的中断调用。对于只使用特权等级为0和3的OS来说，set_system_gate既可以被OS 
Kernel调用，又可以被Application调用。</P>
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align=left>&nbsp;</P>
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align=left>const unsigned int INTR_GATE_TYPE = 0x0e;</P>
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align=left>const unsigned int TRAP_GATE_TYPE = 0x0f;</P>
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align=left>&nbsp;</P>
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align=left>inline void set_intr_gate(unsigned int __n, addr_t __addr, selector_t 
__sel)</P>
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align=left>{<BR>&nbsp;set_gate(idt[__n], INTR_GATE_TYPE, 0, __addr, __sel);</P>
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align=left>}</P>
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align=left>&nbsp;</P>
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align=left>inline void set_trap_gate(unsigned int __n, addr_t __addr, selector_t 
__sel)</P>
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align=left>{<BR>&nbsp;set_gate(idt[__n], TRAP_GATE_TYPE, 0, __addr, __sel);</P>
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align=left>}</P>
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align=left>&nbsp;</P>
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align=left>&nbsp;</P>
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align=left>inline void set_system_gate(unsigned int __n, addr_t __addr, 
selector_t __sel)</P>
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align=left>{<BR>&nbsp;set_gate(idt[__n], TRAP_GATE_TYPE, 3, __addr, __sel);</P>
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align=left>}</P>
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align=left>&nbsp;</P>
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align=left>&nbsp;</P>
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