os-k/kaleid/kernel/mm/gdt.c

//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:         Mapping and checking memory related functions               //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K 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             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <kernel/mm.h>

GdtEntry_t gdtEntries[5] = { 0 };
TssEntry_t tssEntry = { 0 };
GdtPtr_t gdtPtr;

static void SetGdtEntry(int index, uint base, uint limit, uchar access)
{
    gdtEntries[index].lowBase      = (base & 0xFFFF);
    gdtEntries[index].middleBase   = (base >> 16) & 0xFF;
    gdtEntries[index].highBase     = (base >> 24) & 0xFF;

    gdtEntries[index].lowLimit     = (limit & 0xFFFF);
    gdtEntries[index].granularity  = (limit >> 16) & 0x0F;

    gdtEntries[index].granularity |= 0xA0;

    // 0x10 is system
    // 0x80 is present
    gdtEntries[index].access       = access | 0x10 | 0x80;
}

static void SetTssEntry(uchar index, ulong base, ulong limit)
{
    TssDescriptor_t tssDesc = { 0 };

    tssDesc.limitLow = limit & 0xffff;
    tssDesc.size = (limit >> 16) & 0xf;

    tssDesc.base00 = base & 0xffff;
    tssDesc.base16 = (base >> 16) & 0xff;
    tssDesc.base24 = (base >> 24) & 0xff;
    tssDesc.base32 = (base >> 32) & 0xffffffff;
    tssDesc.reserved = 0;

    tssDesc.access = 0x01 | 0x08 | 0x10 | 0x80;

    memmove(&gdtEntries[index], &tssDesc, sizeof(TssDescriptor_t));
}


void MmInitGdt(void)
{
    gdtPtr.limit = (sizeof(GdtEntry_t) * 5) - 1;
    gdtPtr.base  = (uint)(ullong)&gdtEntries;

    MmStoreGdt();

    /* SetGdtEntry(1, 0x0, 0xfffff, 0x02 | 0x08); */

    /* tssEntry.ioMapOffset = sizeof(TssEntry_t); */

    /* SetTssEntry(2, (ulong)&tssEntry, sizeof(TssEntry_t)); */

    /* MmLoadGdt(0x8, 0x0, 2 << 3); */
}