《操作系统》的实验代码。
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#include <stdio.h>
#define STS_IG32 0xE // 32-bit Interrupt Gate
#define STS_TG32 0xF // 32-bit Trap Gate
typedef unsigned uint32_t;
#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
};
int
main(void)
{
unsigned before;
unsigned intr;
unsigned after;
struct gatedesc gintr;
intr=8;
before=after=0;
gintr=*((struct gatedesc *)&intr);
SETGATE(gintr, 0,1,2,3);
intr=*(unsigned *)&(gintr);
printf("intr is 0x%x\n",intr);
printf("gintr is 0x%llx\n",gintr);
return 0;
}
// other examples
//ex1
#if 0
#include <stdlib.h>
#include <stdio.h>
#include <iostream>
#include <cstring>
#define STS_TG32 0xF
#define STS_IG32 0xE
#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; \
}
using namespace std;
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
};
int main()
{
gatedesc intr;
intr.gd_off_15_0 = 8;
intr.gd_ss = 0;
intr.gd_args = 0;
intr.gd_rsv1 = 0;
intr.gd_type = 0;
intr.gd_s = 0;
intr.gd_dpl = 0;
intr.gd_p = 0;
intr.gd_off_31_16 = 0;
SETGATE( intr, 0,1,2,3);
printf( "%u\n", intr);
printf( "%x", intr);
return 0;
}
#endif
//ex2
#if 0
#include "stdlib.h"
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
};
typedef struct gatedesc gatedesc;
typedef unsigned int uint32_t;
#define STS_IG32 0xE // 32-bit Interrupt Gate
#define STS_TG32 0xF // 32-bit Trap Gate
#define SETGATE(gate, istrap, sel, off, dpl) { \
((gatedesc*)(&gate))->gd_off_15_0 = (uint32_t)(off) & 0xffff; \
((gatedesc*)(&gate))->gd_ss = (sel); \
((gatedesc*)(&gate))->gd_args = 0; \
((gatedesc*)(&gate))->gd_rsv1 = 0; \
((gatedesc*)(&gate))->gd_type = (istrap) ? STS_TG32 : STS_IG32; \
((gatedesc*)(&gate))->gd_s = 0; \
((gatedesc*)(&gate))->gd_dpl = (dpl); \
((gatedesc*)(&gate))->gd_p = 1; \
((gatedesc*)(&gate))->gd_off_31_16 = (uint32_t)(off) >> 16; \
}
int main()
{
unsigned intr;
intr=8;
SETGATE(intr, 0,1,2,3);
printf("%d", intr);
return 0;
}
#endif