gdt.h

一个微型操作系统源码

/*
 * OSV
 * Copyright (C) 2002 Ciprian DOSOFTEI <[e-mail]>
 * All rights reserved.
 * 
 * http://backster.free.fr/osv
 *
 * This file is part of the OSV project. OSV is free software, also known as
 * "open source"; you can redistribute it and/or modify it under the terms 
 * of the GNU General Public License (GPL), version 2, as published by the Free
 * Software Foundation (FSF). To explore alternate licensing terms, contact 
 * the author at [e-mail] or [phone].
 * 
 * OSV is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GPL for more details.  You should have
 * received a copy of the GPL along with OSV; see the file COPYING.  If
 * not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
 */

#ifndef INCGDT
#define INCGDT

#include <sys/params.h>
#include <types.h>
#include <string.h>

typedef struct descriptor
{
  /* segment limit 15:00 */
  word limit0_15;
  /* base address 15:00 */
  word base0_15;
  /* base address 23:16 */
  byte base16_23;
  /* segment type */
  byte type : 4;
  /* descriptor type */
  byte s : 1;
  /* descriptor privilege level - aka Ring */
  byte dpl : 2;
  /* segment present */
  byte p : 1;
  /* segment limit 19:16 */
  byte limit16_19 : 4;
  /* available for use by system software */
  byte avl : 1;
  /* always 0 */
  byte zero : 1;
  /* default operation size */
  byte db : 1;
  /* granularity */
  byte g : 1;
  /* base address 31:24 */
  byte base24_31;
} __attribute__ ((packed)) descriptor;

extern descriptor *GDT;
extern void setupGDT(void);
extern void setupDescriptor(descriptor *d, dword base, dword limit, byte type, byte dpl, byte s, byte db);

#endif