/**************************************************************************************
 Copyright (c) 2002 The UbixOS Project
 All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions, the following disclaimer and the list of authors.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions, the following disclaimer and the list of authors
in the documentation and/or other materials provided with the distribution. Neither the name of the UbixOS Project nor the names of its
contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 $Id$

**************************************************************************************/

#ifndef _GDT_H
#define _GDT_H

/* Descriptor Definitions */
#define dCall 0x0C00 /* 386 Call Gate                */
#define dCode 0x1800 /* Code Segment                 */
#define dData 0x1000 /* Data Segment                 */
#define dInt  0x0E00 /* 386 Interrupt Gate           */
#define dLdt  0x200  /* Local Descriptor Table (LDT) */
#define dTask 0x500  /* Task gate                    */
#define dTrap 0x0F00 /* 386 Trap Gate                */
#define dTss  0x900  /* Task State Segment (TSS)     */

/* Descriptor Options */
#define dDpl3     0x6000 /* DPL3 or mask for DPL             */
#define dDpl2     0x4000 /* DPL2 or mask for DPL             */
#define dDpl1     0x2000 /* DPL1 or mask for DPL             */
#define dPresent  0x8000 /* Present                          */
#define dNpresent 0x8000 /* Not Present                      */
#define dAcc      0x100  /* Accessed (Data or Code)          */
#define dWrite    0x200  /* Writable (Data segments only)    */
#define dRead     0x200  /* Readable (Code segments only)    */
#define dBusy     0xB00  /* Busy (TSS only)    was 200       */
#define dEexdown  0x400  /* Expand down (Data segments only) */
#define dConform  0x400  /* Conforming (Code segments only)  */
#define dBig      0x40   /* Default to 32 bit mode           */
#define dBiglim   0x80   /* Limit is in 4K units             */

/* GDT Descriptor */
struct gdtDescriptor {
  unsigned short limitLow;      /* Limit 0..15    */
  unsigned short baseLow;       /* Base  0..15    */
  unsigned char  baseMed;       /* Base  16..23   */
  unsigned char  access;        /* Access Byte    */
  unsigned int   limitHigh:4;   /* Limit 16..19   */
  unsigned int   granularity:4; /* Granularity    */
  unsigned char  baseHigh;      /* Base 24..31    */
  } __attribute__ ((packed));

struct gdtGate {
  unsigned short offsetLow;  /* Offset 0..15  */
  unsigned short selector;   /* Selector      */
  unsigned short access;     /* Access Flags  */
  unsigned short offsetHigh; /* Offset 16..31 */
  } __attribute__ ((packed));

union descriptorTableunion {
  struct gdtDescriptor descriptor; /* Normal descriptor */
  struct gdtGate gate;             /* Gate descriptor   */
  unsigned long dummy;             /* Any other info    */
  };


#define descriptorTable(name,length) union descriptorTableunion name[length] =
#define standardDescriptor(base, limit, control) {descriptor: {(limit & 0xffff), (base & 0xffff), ((base >> 16) & 0xff), \
                                               ((control+dPresent) >> 8), (limit >> 16), \
                                               ((control & 0xff) >> 4), (base >> 24)}}
#define gateDescriptor(offset, selector, control) {gate: {(offset & 0xffff), selector, \
                                                     (control+dPresent), (offset >> 16) }}

#endif