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/*
* libcaca Colour ASCII-Art library
* Copyright (c) 2006 Sam Hocevar <sam@hocevar.net>
* 2009 Jean-Yves Lamoureux <jylam@lnxscene.org>
* All Rights Reserved
*
* This library is free software. It comes without any warranty, to
* the extent permitted by applicable law. You can redistribute it
* and/or modify it under the terms of the Do What the Fuck You Want
* to Public License, Version 2, as published by Sam Hocevar. See
* http://www.wtfpl.net/ for more details.
*/
/*
*'freely' inspired by http://jojo.ouvaton.org/dossiers/boot_sector/tutorial02.html
* (actually, that's mostly copied, with minor compilation fixes)
*/
#include "kernel.h"
#include "klibc.h"
#define GDTBASE 0x800 /* Physical address of GDT */
#define GDTSIZE 0xFF /* Maximum table size (in entries) */
/* Segment descriptor */
struct gdtdesc
{
u16 lim0_15;
u16 base0_15;
u8 base16_23;
u8 acces;
u8 lim16_19:4;
u8 other:4;
u8 base24_31;
} __attribute__ ((packed));
/* GDTR register */
struct gdtr
{
u16 limite;
u32 base;
} __attribute__ ((packed));
struct gdtr kgdtr;
struct gdtdesc kgdt[GDTSIZE] = { {0, 0, 0, 0, 0, 0, 0} };
unsigned int kgdtptr = 1;
void init_code_desc(u32 base, u32 limite, struct gdtdesc *desc);
void init_data_desc(u32 base, u32 limite, struct gdtdesc *desc);
void add_gdt_desc(struct gdtdesc desc);
void init_gdt(void);
void init_gdt_desc(u32 base, u32 limite, u8 acces, u8 other,
struct gdtdesc *desc)
{
desc->lim0_15 = (limite & 0xffff);
desc->base0_15 = (base & 0xffff);
desc->base16_23 = (base & 0xff0000) >> 16;
desc->acces = acces;
desc->lim16_19 = (limite & 0xf0000) >> 16;
desc->other = (other & 0xf);
desc->base24_31 = (base & 0xff000000) >> 24;
return;
}
void init_code_desc(u32 base, u32 limite, struct gdtdesc *desc)
{
init_gdt_desc(base, limite, 0x9B, 0x0D, desc);
}
void init_data_desc(u32 base, u32 limite, struct gdtdesc *desc)
{
init_gdt_desc(base, limite, 0x93, 0x0D, desc);
}
void add_gdt_desc(struct gdtdesc desc)
{
kgdt[kgdtptr] = desc;
kgdtptr++;
}
void init_gdt(void)
{
struct gdtdesc code, data, stack;
/* initialisation des descripteurs de segment */
init_code_desc(0x0, 0xFFFFF, &code);
init_data_desc(0x0, 0xFFFFF, &data);
init_gdt_desc(0, 0x10, 0x97, 0x0D, &stack);
add_gdt_desc(code);
add_gdt_desc(data);
add_gdt_desc(stack);
/* initialisation de la structure pour GDTR */
kgdtr.limite = GDTSIZE * 8;
kgdtr.base = GDTBASE;
/* recopie de la GDT a son adresse */
memcpy((void *)kgdtr.base, kgdt, kgdtr.limite);
/* chargement du registre GDTR */
asm("lgdtl (kgdtr)");
/* initialisation des segments */
asm(" movw $0x10,%ax \n \
movw %ax, %ds \n \
movw %ax, %es \n \
movw %ax, %fs \n \
movw %ax, %gs \n \
movw $0x18,%ax \n \
movw %ax, %ss \n \
movl $0x1FFFF,%esp \n \
nop \n \
nop \n \
ljmp $0x08,$next \n \
next: \n");
}
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