root/gates.c

DEFINITIONS

1. CreateTrapGate
2. CreateIntGate
3. InitIDT
4. CreateTssDesc

#include "memory.h"

extern intr;
extern gpf;
extern pf;
extern SwitchTasks;
extern SpecificSwitchTasks;
extern TimerInt;
extern KbInt;
extern HdInt;
extern div0;
extern i1;
extern i2;
extern i3;
extern i4;
extern i5;
extern i6;
extern i7;
extern df;
extern i9;
extern ia;
extern ib;
extern ic;

struct Gate {
    unsigned short offsetlo;    //   : 16;
    unsigned short segselect;   //   : 16;
    unsigned ist:3;
    unsigned:1;
    unsigned:1;
    unsigned:3;
    unsigned type:4;
    unsigned:1;
    unsigned dpl:2;
    unsigned p:1;
    unsigned short offsetmid;   //    : 16;
    unsigned int offsethi;  //       : 32;
    unsigned int reserved;  //       : 32;
};

struct TSSDescriptor {
    unsigned short limitlo;
    unsigned short baselo;
    unsigned basemid1:8;
    unsigned type:4;
    unsigned:1;
    unsigned dpl:2;
    unsigned p:1;
    unsigned limithi:4;
    unsigned avl:1;
    unsigned:1;
    unsigned:1;
    unsigned g:1;
    unsigned basemid2:8;
    unsigned int basehi;
    unsigned:32;
};

void CreateTrapGate(short selector, long offset, long intNo, unsigned char ist)
{
    struct Gate *theGate = (struct Gate *)IDT + intNo;

    theGate->offsetlo = (unsigned short)(offset & 0xFFFF);
    theGate->segselect = selector;
    theGate->ist = ist;
    theGate->type = 0xF;
    theGate->p = 1;
    theGate->offsetmid = (unsigned short)((offset >> 16) & 0xFFFF);
    theGate->offsethi = (unsigned int)((offset >> 32) & 0xFFFFFFFF);
    theGate->reserved = 0;
}

void CreateIntGate(short selector, long offset, long intNo, unsigned char ist)
{
    struct Gate *theGate = (struct Gate *)IDT + intNo;

    theGate->offsetlo = (unsigned short)(offset & 0xFFFF);
    theGate->segselect = selector;
    theGate->ist = ist;
    theGate->type = 0xE;
    theGate->p = 1;
    theGate->offsetmid = (unsigned short)((offset >> 16) & 0xFFFF);
    theGate->offsethi = (unsigned int)((offset >> 32) & 0xFFFFFFFF);
    theGate->reserved = 0;
}

void InitIDT(void)
{
    int i;

    for (i = 0; i < 48; i++) {
        CreateTrapGate(code64, (long)&intr, i, 0);
    }
    CreateTrapGate(code64, (long)&div0, 0, 1);
    CreateTrapGate(code64, (long)&i1, 1, 1);
    CreateTrapGate(code64, (long)&i2, 2, 1);
    CreateTrapGate(code64, (long)&i3, 3, 1);
    CreateTrapGate(code64, (long)&i4, 4, 1);
    CreateTrapGate(code64, (long)&i5, 5, 1);
    CreateTrapGate(code64, (long)&i6, 6, 1);
    CreateTrapGate(code64, (long)&i7, 7, 1);
    CreateTrapGate(code64, (long)&df, 8, 1);
    CreateTrapGate(code64, (long)&i9, 9, 1);
    CreateTrapGate(code64, (long)&ia, 10, 1);
    CreateTrapGate(code64, (long)&ib, 11, 1);
    CreateTrapGate(code64, (long)&ic, 12, 1);
    CreateTrapGate(code64, (long)&gpf, 13, 1);
    CreateTrapGate(code64, (long)&pf, 14, 1);
    CreateTrapGate(code64, (long)&SwitchTasks, 20, 0);
    CreateTrapGate(code64, (long)&SpecificSwitchTasks, 22, 0);
    CreateTrapGate(code64, (long)&TimerInt, 32, 0);
    CreateIntGate(code64, (long)&KbInt, 33, 0);
    CreateIntGate(code64, (long)&HdInt, 46, 0);
}

void CreateTssDesc(long base, int selector)
{
    long *l;
    struct TSSDescriptor *desc = (struct TSSDescriptor *)(GDT + selector);

    l = (long *)desc;
    l[0] = 0;
    l[1] = 0;
    desc->limitlo = tsslength;
    desc->limithi = 0;
    desc->type = 9;
    desc->dpl = 0;
    desc->p = 1;
    desc->baselo = (unsigned short)(base & 0xFFFF);
    desc->basemid1 = (unsigned char)((base >> 16) & 0xFF);
    desc->basemid2 = (unsigned char)((base >> 20) & 0xFF);
    desc->basehi = (unsigned int)((base >> 24) & 0xFFFFFFFF);
}