gdt.h

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// Copyright (c) 2014, 임경현 (dlarudgus20)
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
//   list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
//   this list of conditions and the following disclaimer in the documentation
//   and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef GDT_H_
#define GDT_H_

#include <stddef.h>
#include <stdint.h>

#include "memory_map.h"

#define NULL_SEGMENT 0

#define KERNEL_DATA_SEGMENT (1 * 8)

#define KERNEL_CODE_SEGMENT (2 * 8)

#define MAKE_GDT_TYPE1(SegmentType,S,DPL,P) \
    ((((P) << 7) & 0x80) | (((DPL) << 5) & 0x60) | (((S) << 4) & 0x10) | ((SegmentType) & 0x0f))

#define MAKE_DATA_SEGMENT(expdown,writable) \
    (((((expdown) << 2) & 0x04) | (((writable) << 1) & 0x02)) & 0x06)

#define MAKE_CODE_SEGMENT(conforming,readable) \
    ((((((conforming) << 2) & 0x04) | (((readable) << 1) & 0x02)) | 0x08) & 0x0e)

#define DATA_SEGMENT_TYPE MAKE_DATA_SEGMENT(0,1)

#define CODE_SEGMENT_TYPE MAKE_CODE_SEGMENT(0,1)

typedef uint8_t GdtType1;
typedef uint8_t GdtType2;

typedef struct tagGdt
{
    uint16_t Size_0_15, Address_0_15;

    uint8_t Address_16_23;

    union
    {
        struct
        {
            unsigned SegmentType:4, S:1, DPL:2, P:1;
        };
        GdtType1 type1;
    };

    union
    {
        struct
        {
            unsigned Size_16_19:4;
            unsigned AVL:1, reserved:1, D:1, G:1;
        };
        GdtType2 type2;
    };

    uint8_t Address_24_32;
} Gdt;

static Gdt * const g_pGdtTable = (Gdt *)GDT_TABLE_ADDRESS;

void ckGdtInit(Gdt *pGdt, uint32_t address, uint32_t size, GdtType1 type1);

static inline void ckGdtInitNull(Gdt *pGdt)
{
    ((int *)pGdt)[1] = ((int *)pGdt)[0] = 0;
}

void ckGdtLoad(uint16_t size, Gdt *address);

void ckGdtTableInitialize(void);

#endif /* GDT_H_ */