//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:  Memory manager 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/>.            //
//----------------------------------------------------------------------------//

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

#ifndef _MM_MM_H
#define _MM_MM_H

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

#define MINIMUM_RAM_SIZE  16    // Mio, the minimum RAM size.
#define IOMAP_SIZE (8 * 1024)

#define AVAILABLE_ZONE    1     // Fully usable RAM zone
#define RESERVED_ZONE     2     // Used by the firmware
#define ACPI_ZONE         3     // Used by ACPI but can be freed
#define NVS_ZONE          4     // Dunno
#define BADRAM_ZONE       5     // Invalid zone because material problem...
#define MAX_ENTRIES       2048  // Max number of memory map entries

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

// The entry structure of the map
struct MapEntry_t {
    void *addr;
    size_t length;  // in bytes
    uint type;      // reserved or not
} __attribute__((__packed__));

// the map structure
struct MemoryMap_t {
    size_t length;
    size_t freeRamSize;
    size_t nonfreeRamSize;
    MapEntry_t entry[MAX_ENTRIES];
} __attribute__((__packed__));

// 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;
    unsigned middleLimit: 4;
    unsigned flags: 4;
    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));



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

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

//
// Initializes the memory map structure
//
void MmInitMemoryMap(void);

//
// Initializes the memory map structure
//
void MmPrintMemoryMap(void);

//
// Returns the size of the first available memory zone
// from the start address pointer
//
size_t MmGetAvailZoneSize(void *start);

//
// Returns the first available memory zone from the start address pointer
//
void *MmGetFirstAvailZone(void *start);

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

//
// Loads the descriptor table
//
extern void MmLoadGdt();


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

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

#endif