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