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/**
* Copyright (c) 2026 Alexey Gavrilov <alexey.gavrilov@mail.com>
*
* This file is part of ObjectiveOS.
*
* ObjectiveOS 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 (at your option) any later
* version.
*
* ObjectiveOS 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
* ObjectiveOS. If not, see <https://www.gnu.org/licenses/>.
*/
#include "Gdt.h"
uint64 MngGdt::gdt[MngGdt::size];
bool MngGdt::isInitialize = false;
bool MngGdt::gdtLoaded = false;
MngGdt mngGdt;
MngGdt::MngGdt()
{
if(!isInitialize)
{
MemoryOperations::set(gdt, 0, sizeof(uint64) * size);
currIdx = 1;
gdtLoaded = false;
isInitialize = true;
codeSegmentKern = NULL;
}
};
DescSeg32::DescSeg32(uint32 base, uint32 limit, uint8 access, uint8 flags)
{
this->baseLow = base & 0x0000FFFF;
this->baseMiddle = (base & 0x00FF0000) >> 16;
this->baseHight = (base & 0xFF000000) >> 24;
this->limitLow = limit & 0x0000FFFF;
this->limitMiddle = (limit & 0x000F0000) >> 16;
this->access = access;
this->flags = flags & 0x000E;
};
uint64 DescSeg32::getDescriptor()
{
uint64 descriptor = 0;
descriptor |= (uint64)limitLow;
descriptor |= (uint64)baseLow << 16;
descriptor |= (uint64)baseMiddle << 32;
descriptor |= (uint64)access << 40;
descriptor |= (uint64)limitMiddle << 48;
descriptor |= (uint64)flags << 52;
descriptor |= (uint64)baseHight << 56;
return descriptor;
};
uint64 DescSeg32::flatCodeKernel()
{
return DescSeg32(0, 0xFFFFF, CODE_ER | PRESENT | NSYSTEMSEG
, PAGEGRAN | HIGHSIZE).getDescriptor();
};
uint64 DescSeg32::flatDataKernel()
{
return DescSeg32(0, 0xFFFFF, DATA_RW | PRESENT | NSYSTEMSEG
, PAGEGRAN | HIGHSIZE).getDescriptor();
}
uint64 DescSeg32::flatCodeUser()
{
return DescSeg32(0, 0xFFFFF, CODE_ER | PRESENT | NSYSTEMSEG | USER
, PAGEGRAN | HIGHSIZE).getDescriptor();
};
uint64 DescSeg32::flatDataUser()
{
return DescSeg32(0, 0xFFFFF, DATA_RW | PRESENT | NSYSTEMSEG | USER
, PAGEGRAN | HIGHSIZE).getDescriptor();
};
bool MngGdt::addDescriptor(uint64 desc)
{
if(currIdx >= size or currIdx == 0 or gdtLoaded)
{
return false;
}
if(desc == DescSeg32::flatCodeKernel()) codeSegmentKern = currIdx * 8;
this->gdt[currIdx++] = desc;
return true;
};
bool MngGdt::loadGdt()
{
if(gdtLoaded)
{
return false;
}
// Set pointer
uint64 descriptor = 0;
uint16 size = sizeof(uint64) * this->size - 1;
uint32 offset = (uint32)(&gdt);
descriptor |= offset;
descriptor <<= 16;
descriptor |= size;
SWITCHTOGDT(descriptor);
gdtLoaded = 1;
return true;
};
// Get static instance of MngGdt initialized once
MngGdt &MngGdt::getInstance()
{
if(!isInitialize) mngGdt = MngGdt();
return mngGdt;
};
uint16 MngGdt::getCodeSegmentKernel()
{
return codeSegmentKern;
};
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