325 lines
7.7 KiB
C++
325 lines
7.7 KiB
C++
/*****************************************************************************
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* *
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* B I O S *
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* *
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*---------------------------------------------------------------------------*
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* Beschreibung: BIOS-Schnittstelle *
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* *
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* Autor: Michael Schoettner, 29.11.2018 *
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*****************************************************************************/
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#include "kernel/BIOS.h"
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#include "kernel/Globals.h"
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// 16-Bit Code aufrufen, siehe Konstruktor und Aufruf in startup.asm
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extern "C" {
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void bios_call();
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}
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// in startup.asm im GDT-Eintrag so festgeschrieben!
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constexpr const unsigned int BIOS16_CODE_MEMORY_START = 0x24000;
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// Parameter fuer BIOS-Aufrufe (Register)
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constexpr const unsigned int BIOS16_PARAM_BASE = 0x26000;
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// Zeiger auf Speichbereich fuer Parameter fuer BIOS-Aufruf (siehe BIOS.h)
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BIOScall_params* BC_params = reinterpret_cast<BIOScall_params*>(BIOS16_PARAM_BASE);
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/*****************************************************************************
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* Methode: BIOS::BIOS *
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*---------------------------------------------------------------------------*
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* Beschreibung: Konstruktor. Baut manuell ein 16-Bit Code Segment fuer *
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* den BIOS-Aufruf. Startadresse dieser Funktion steht *
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* im 4. GDT-Eintrag (siehe startup.asm). *
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*****************************************************************************/
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BIOS::BIOS() {
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unsigned char* codeAddr = reinterpret_cast<unsigned char*>(BIOS16_CODE_MEMORY_START);
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// mov eax, 25000 (Adresse wohin aktuelles esp gesichert wird)
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0xB8;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x50;
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codeAddr++;
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*codeAddr = 0x02;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// mov [eax], esp (esp abspeichern)
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x67;
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codeAddr++;
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*codeAddr = 0x89;
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codeAddr++;
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*codeAddr = 0x20;
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codeAddr++;
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// mov eax,cr0 (cr0 auslesen)
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*codeAddr = 0x0F;
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codeAddr++;
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*codeAddr = 0x20;
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codeAddr++;
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*codeAddr = 0xC0;
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codeAddr++;
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// and eax, 7FFEFFFE (Bitmaske zum Abschlaten des Protected-Mode)
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x25;
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codeAddr++;
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*codeAddr = 0xFE;
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codeAddr++;
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*codeAddr = 0xFF;
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codeAddr++;
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*codeAddr = 0xFE;
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codeAddr++;
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*codeAddr = 0x7F;
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codeAddr++;
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// mov cr0, eax (cr0 syetzen um den Protected-Mode auszuschalten)
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*codeAddr = 0x0F;
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codeAddr++;
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*codeAddr = 0x22;
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codeAddr++;
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*codeAddr = 0xC0;
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codeAddr++;
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// jmp 2400:001B Instruktions-Pipeline leeren und Dekodierungseinheit auf 16-Bit code umschalten
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// Wir springen hier zur naechsten Instruktion (*)
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// 2400:001B (2400<<4 = 24000 + 1B)
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*codeAddr = 0xEA;
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codeAddr++;
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*codeAddr = 0x1B;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x24;
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codeAddr++;
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// (*) mov dx,2400 (Lade 0x2400 nach dx (fuer Parameter-Zugriff -> BIOS16_PARAM_BAS)
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*codeAddr = 0xBA;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x24;
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codeAddr++;
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// mov ss,dx (Lade Stack-Segment-Register)
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xD2;
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codeAddr++;
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// mov gs,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xEA;
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codeAddr++;
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// mov esp,2000 -> BIOS16_PARAM_BASE 0x260000 (= 0x2400:2000)
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0xBC;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x20;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// Register laden (stehen in BIOS16_PARAM_BASE, ab 0x260000)
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// (pop erhöht die Adressen)
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// pop ds
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*codeAddr = 0x1F;
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codeAddr++;
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// pop es
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*codeAddr = 0x07;
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codeAddr++;
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// pop fs
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*codeAddr = 0x0f;
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codeAddr++;
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*codeAddr = 0xa1;
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codeAddr++;
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// pop ax
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*codeAddr = 0x58;
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codeAddr++;
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// popad
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x61;
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codeAddr++;
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// int(nr)
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*codeAddr = 0xCD;
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codeAddr++; // 'int' Instruktion
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*codeAddr = 0x00;
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codeAddr++; // Nummer (wird direkt von BIOS::Int direkt hier reingeschrieben)
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// Register speichern in BIOS16_PARAM_BASE (ab 0x260000)
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// pushad
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x60;
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codeAddr++;
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// pushf
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*codeAddr = 0x9C;
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codeAddr++;
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// push fs
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*codeAddr = 0x0f;
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codeAddr++;
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*codeAddr = 0xa0;
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codeAddr++;
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// push es
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*codeAddr = 0x06;
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codeAddr++;
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// push ds
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*codeAddr = 0x1E;
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codeAddr++;
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// mov eax,cr0
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*codeAddr = 0x0F;
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codeAddr++;
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*codeAddr = 0x20;
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codeAddr++;
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*codeAddr = 0xC0;
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codeAddr++;
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// or eax, 00010001 (protected mode without paging)
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x0D;
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codeAddr++;
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*codeAddr = 0x01;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x01;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// mov cr0, eax
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*codeAddr = 0x0F;
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codeAddr++;
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*codeAddr = 0x22;
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codeAddr++;
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*codeAddr = 0xC0;
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codeAddr++;
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// jmp 0018:0049, flush pipeline & switch decoding (active 32 Bit PM)
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// 0018:0049
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*codeAddr = 0xEA;
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codeAddr++;
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*codeAddr = 0x49;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x18;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// mov dx,0010
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*codeAddr = 0xBA;
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codeAddr++;
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*codeAddr = 0x10;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// mov ds,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xDA;
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codeAddr++;
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// mov es,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xC2;
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codeAddr++;
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// mov es,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xE2;
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codeAddr++;
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// mov fs,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xEA;
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codeAddr++;
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// mov ss,dx
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*codeAddr = 0x8E;
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codeAddr++;
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*codeAddr = 0xD2;
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codeAddr++;
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// mov eax, 25000
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0xB8;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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*codeAddr = 0x50;
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codeAddr++;
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*codeAddr = 0x02;
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codeAddr++;
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*codeAddr = 0x00;
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codeAddr++;
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// mov esp, [eax]
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0x67;
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codeAddr++;
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*codeAddr = 0x8B;
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codeAddr++;
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*codeAddr = 0x20;
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codeAddr++;
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// far ret
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*codeAddr = 0x66;
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codeAddr++;
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*codeAddr = 0xCB;
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}
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/*****************************************************************************
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* Methode: BIOS::Int *
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*---------------------------------------------------------------------------*
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* Beschreibung: Fuehrt einen BIOS-Aufruf per Software-Interrupt durch. *
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*****************************************************************************/
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void BIOS::Int(int inter) {
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unsigned char* ptr = reinterpret_cast<unsigned char*>(BIOS16_CODE_MEMORY_START);
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// Interrupt-Nummer in 16-Bit Code-Segment schreiben (unschoen, aber ...)
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*(ptr + 48) = static_cast<unsigned char>(inter);
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CPU::disable_int(); // Interrupts abschalten
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bios_call();
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CPU::enable_int();
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}
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