//----------------------------------------------------------------------------//
//                                OS on Kaleid                                //
//                                                                            //
//  Desc:         GDT related functions                                       //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2020 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/>.            //
//----------------------------------------------------------------------------//

#ifndef _KERNEL_H
#include <kernel.h>
#endif

#ifndef _MM_GDT_H
#define _MM_GDT_H

//----------------------------------------------------------------------------//

#define IOMAP_SIZE (8 * 1024)

//----------------------------------------------------------------------------//

// The gdt entry
struct GdtEntry_t
{
    ushort lowLimit;     // lower 16 bits
    ushort lowBase;      // lower 16 bits
    uchar  middleBase;   // next 8 bits
    uchar  access;       // determine what ring this segment can be used in
    uchar  flags;
    uchar  highBase;     // last 8 bits
} __attribute__((__packed__));

struct TssDescriptor_t
{
    ushort lowLimit;
    ushort lowBase;
    uchar middleBase;
    uchar access;
    uchar flags;
    uchar highBase;
    uint veryHighBase;
    uint reserved;
} __attribute__ ((packed));

struct Tss_t
{
    uint reserved1;

    // Stack pointers (RSP) for privilege levels 0-2
    ulong rsp0;
    ulong rsp1;
    ulong rsp2;
    ulong reserved2;

    // Interrupt stack table pointers
    ulong ist1;
    ulong ist2;
    ulong ist3;
    ulong ist4;
    ulong ist5;
    ulong ist6;
    ulong ist7;
    ulong reserved3;
    ushort reserved4;

    // Offset to the I/O permission bit map from the 64-bit TSS base
    ushort iomap_base;
    uchar iomap[IOMAP_SIZE];

} __attribute__ ((packed)) __attribute__((aligned(8)));

// The gdt pointer
struct GdtPtr_t
{
   ushort limit;         // upper 16 bits
   ulong base;          // address of the first entry
} __attribute__((__packed__));

//----------------------------------------------------------------------------//

//
// Initializes the descriptor table
//
void MmInitGdt(void);

//
// Loads the descriptor table
//
extern void MmLoadGdt(GdtPtr_t *gdtPtr, ushort tssOffset);


//
// Stores the descriptor table
//
extern void MmStoreGdt(void);

//----------------------------------------------------------------------------//

#endif