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

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//----------------------------------------------------------------------------//
// GNU GPL OS/K //
// //
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// Desc: GDT related functions //
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// //
// //
// 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/>. //
//----------------------------------------------------------------------------//
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#include <mm/gdt.h>
#include <mm/paging.h>
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#include <init/boot.h>
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GdtPtr_t gdtPtr;
GdtEntry_t gdt[4] __attribute__((__aligned__(KPAGESIZE)));
TssDescriptor_t tssDesc __attribute__((__aligned__(KPAGESIZE)));
Tss_t tss __attribute__((__aligned__(KPAGESIZE)));
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void MmInitGdt(void)
{
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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;
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gdt[2].lowLimit = 0xFFFF;
gdt[2].access = 0x98;
gdt[2].flags = 0x20;
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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);
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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
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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);
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}