54 lines
1.8 KiB
Markdown
54 lines
1.8 KiB
Markdown
#README
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Try below command
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```
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gcc -g -m32 lab0_ex3.c 2>&1|tee make.log
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```
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If you get gcc's error, try to read make.log and fix the bugs.
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If gcc successed, then you will get a.out.
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Try to answer below question.
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对于如下的代码段，
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```
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...
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#define STS_CG32 0xC // 32-bit Call Gate
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#define STS_IG32 0xE // 32-bit Interrupt Gate
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#define SETGATE(gate, istrap, sel, off, dpl) { \
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(gate).gd_off_15_0 = (uint32_t)(off) & 0xffff; \
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(gate).gd_ss = (sel); \
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(gate).gd_args = 0; \
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(gate).gd_rsv1 = 0; \
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(gate).gd_type = (istrap) ? STS_TG32 : STS_IG32; \
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(gate).gd_s = 0; \
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(gate).gd_dpl = (dpl); \
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(gate).gd_p = 1; \
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(gate).gd_off_31_16 = (uint32_t)(off) >> 16; \
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}
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/* Gate descriptors for interrupts and traps */
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struct gatedesc {
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unsigned gd_off_15_0 : 16; // low 16 bits of offset in segment
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unsigned gd_ss : 16; // segment selector
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unsigned gd_args : 5; // # args, 0 for interrupt/trap gates
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unsigned gd_rsv1 : 3; // reserved(should be zero I guess)
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unsigned gd_type : 4; // type(STS_{TG,IG32,TG32})
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unsigned gd_s : 1; // must be 0 (system)
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unsigned gd_dpl : 2; // descriptor(meaning new) privilege level
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unsigned gd_p : 1; // Present
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unsigned gd_off_31_16 : 16; // high bits of offset in segment
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};
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...
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```
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如果在其他代码段中有如下语句，
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```
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unsigned intr;
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intr=8;
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SETGATE(intr, 0,1,2,3);
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```
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请问执行上述指令后， intr的值是多少？
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