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

//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:         GDT 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 <mm/gdt.h>
#include <mm/paging.h>
#include <init/boot.h>

GdtPtr_t gdtPtr;
GdtEntry_t gdt[4] __attribute__((__aligned__(KPAGESIZE)));
TssDescriptor_t tssDesc __attribute__((__aligned__(KPAGESIZE)));
Tss_t tss __attribute__((__aligned__(KPAGESIZE)));

void MmInitGdt(void)
{
    ushort tssOffset = (ushort)((ulong)(&gdt[2]) - (ulong)(&gdt[0]));

    gdtPtr.base = (ulong)&gdt[0];
    gdtPtr.limit = sizeof(gdt) - 1;

    memzero((void *)&gdt[0], sizeof(gdt));
    memzero((void *)&tssDesc, sizeof(tssDesc));
    memzero((void *)&tss, sizeof(tss));

    gdt[1].lowLimit     = 0xFFFF;
    gdt[1].access       = 0x98;
    gdt[1].flags        = 0x20;

    gdt[2].lowLimit     = 0xFFFF;
    gdt[2].access       = 0x98;
    gdt[2].flags        = 0x20;

    tssDesc.access          = 0x89;
    tssDesc.flags           = 0x40;
    tssDesc.lowBase         = (ulong)&tss & 0xFFFF;
    tssDesc.middleBase      = ((ulong)&tss >> 16) & 0xFF;
    tssDesc.highBase        = ((ulong)&tss >> 24) & 0xFF;
    tssDesc.veryHighBase    = ((ulong)&tss >> 32) & 0xFFFFFFFF;
    tssDesc.lowLimit        = sizeof(tss);

    tss.ist1 = (ulong)0x00007BFF;  // ISR RESCUE STACK, GARANTIED FREE FOR USE BY OSDEV.ORG
    tss.ist2 = (ulong)0x00043F00;  // ISR STACK, GARANTIED FREE FOR USE BY OSDEV.ORG
    tss.ist3 = (ulong)0x0007FFFF;  // ISR STACK, GARANTIED FREE FOR USE BY OSDEV.ORG
    tss.iomap_base = sizeof(tss);

    memmove(&gdt[2], &tssDesc, sizeof(TssDescriptor_t));

    /* DebugLog("TSS\n" */
    /*          "gdt[0]        %#x\n" */
    /*          "gdt[2]        %#x\n" */
    /*          "access :      %#x\n" */
    /*          "flags  :      %#x\n" */
    /*          "lowBase  :    %#x\n" */
    /*          "middleBase  : %#x\n" */
    /*          "highBase  :   %#x\n" */
    /*          "veryHighBase: %#x\n" */
    /*          "lowLimit  :   %#x\n" */
    /*          "ist  :        %#x\n" */
    /*          "iomap_base  : %#x\n" */
    /*          "offset  :     %#x\n", */
    /*          &gdt[0], */
    /*          &gdt[2], */
    /*          tssDesc.access, */
    /*          tssDesc.flags, */
    /*          tssDesc.lowBase, */
    /*          tssDesc.middleBase, */
    /*          tssDesc.highBase, */
    /*          tssDesc.veryHighBase, */
    /*          tssDesc.lowLimit, */
    /*          tss.ist1, */
    /*          tss.iomap_base, */
    /*          tssOffset */
    /* ); */

    MmLoadGdt(&gdtPtr, tssOffset);
}