# gdt.h

    00001
    00002
    00003
    00004 /**************************************************************************************
    00005  Copyright (c) 2002 The UbixOS Project
    00006  All rights reserved.
    00007
    00008 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
    00009
    00010 Redistributions of source code must retain the above copyright notice, this list of conditions, the following disclaimer and the list of authors.
    00011 Redistributions in binary form must reproduce the above copyright notice, this list of conditions, the following disclaimer and the list of authors
    00012 in the documentation and/or other materials provided with the distribution. Neither the name of the UbixOS Project nor the names of its
    00013 contributors may be used to endorse or promote products derived from this software without specific prior written permission.
    00014
    00015 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
    00016 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
    00017 PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
    00018 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
    00019 GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
    00020 OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    00021 OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    00022
    00023  $Id$
    00024
    00025 **************************************************************************************/
    00026
    00027 #ifndef _GDT_H
    00028 #define _GDT_H
    00029
    00030 /* Descriptor Definitions */
    00031 #define dCall 0x0C00 /* 386 Call Gate                */
    00032 #define dCode 0x1800 /* Code Segment                 */
    00033 #define dData 0x1000 /* Data Segment                 */
    00034 #define dInt  0x0E00 /* 386 Interrupt Gate           */
    00035 #define dLdt  0x200  /* Local Descriptor Table (LDT) */
    00036 #define dTask 0x500  /* Task gate                    */
    00037 #define dTrap 0x0F00 /* 386 Trap Gate                */
    00038 #define dTss  0x900  /* Task State Segment (TSS)     */
    00039
    00040 /* Descriptor Options */
    00041 #define dDpl3     0x6000 /* DPL3 or mask for DPL             */
    00042 #define dDpl2     0x4000 /* DPL2 or mask for DPL             */
    00043 #define dDpl1     0x2000 /* DPL1 or mask for DPL             */
    00044 #define dPresent  0x8000 /* Present                          */
    00045 #define dNpresent 0x8000 /* Not Present                      */
    00046 #define dAcc      0x100  /* Accessed (Data or Code)          */
    00047 #define dWrite    0x200  /* Writable (Data segments only)    */
    00048 #define dRead     0x200  /* Readable (Code segments only)    */
    00049 #define dBusy     0xB00  /* Busy (TSS only)    was 200       */
    00050 #define dEexdown  0x400  /* Expand down (Data segments only) */
    00051 #define dConform  0x400  /* Conforming (Code segments only)  */
    00052 #define dBig      0x40   /* Default to 32 bit mode           */
    00053 #define dBiglim   0x80   /* Limit is in 4K units             */
    00054
    00055 /* GDT Descriptor */
    00056 struct gdtDescriptor {
    00057   unsigned short limitLow;      /* Limit 0..15    */
    00058   unsigned short baseLow;       /* Base  0..15    */
    00059   unsigned char  baseMed;       /* Base  16..23   */
    00060   unsigned char  access;        /* Access Byte    */
    00061   unsigned int   limitHigh:4;   /* Limit 16..19   */
    00062   unsigned int   granularity:4; /* Granularity    */
    00063   unsigned char  baseHigh;      /* Base 24..31    */
    00064   } __attribute__ ((packed));
    00065
    00066 struct gdtGate {
    00067   unsigned short offsetLow;  /* Offset 0..15  */
    00068   unsigned short selector;   /* Selector      */
    00069   unsigned short access;     /* Access Flags  */
    00070   unsigned short offsetHigh; /* Offset 16..31 */
    00071   } __attribute__ ((packed));
    00072
    00073 union descriptorTableunion {
    00074   struct gdtDescriptor descriptor; /* Normal descriptor */
    00075   struct gdtGate gate;             /* Gate descriptor   */
    00076   unsigned long dummy;             /* Any other info    */
    00077   };
    00078
    00079
    00080 #define descriptorTable(name,length) union descriptorTableunion name[length] =
    00081 #define standardDescriptor(base, limit, control) {descriptor: {(limit & 0xffff), (base & 0xffff), ((base >> 16) & 0xff), \
    00082                                                ((control+dPresent) >> 8), (limit >> 16), \
    00083                                                ((control & 0xff) >> 4), (base >> 24)}}
    00084 #define gateDescriptor(offset, selector, control) {gate: {(offset & 0xffff), selector, \
    00085                                                      (control+dPresent), (offset >> 16) }}
    00086
    00087 #endif
    00088