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;

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)
{
   struct Gate *theGate = (struct Gate *)IDT + intNo;

   theGate->offsetlo  = (unsigned short)(offset & 0xFFFF);
   theGate->segselect = selector;
   theGate->ist       = 0;
   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)
{
   struct Gate *theGate = (struct Gate *)IDT + intNo;

   theGate->offsetlo  = (unsigned short)(offset & 0xFFFF);
   theGate->segselect = selector;
   theGate->ist       = 0;
   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);
   }
   CreateTrapGate(code64, (long)&gpf, 13);
   CreateTrapGate(code64, (long)&pf, 14);
   CreateTrapGate(code64, (long)&SwitchTasks, 20);
   CreateTrapGate(code64, (long)&SpecificSwitchTasks, 22);
   CreateTrapGate(code64, (long)&TimerInt, 32);
   CreateIntGate(code64, (long)&KbInt, 33);
   CreateIntGate(code64, (long)&HdInt, 46);
}


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);
}