66 lines
1.7 KiB
C
Executable File
66 lines
1.7 KiB
C
Executable File
#include "gdt.h"
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#include "asm.h"
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#include "types.h"
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#define SIZEGDT 0x4 /* nombre de descripteurs */
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#define BASEGDT 0x00000800 /* addr de la GDT */
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/* registre gdt */
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static struct gdtr gdtreg;
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/* table de GDT */
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static gdtdes gdt[SIZEGDT];
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/*******************************************************************************/
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/* Initialise la GDT */
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void initgdt()
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{
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makegdtdes(0x0, 0x00000, 0x00, 0x00, &gdt[0]);
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makegdtdes(0x0, 0xFFFFF, 0x9B, 0x0D, &gdt[1]); /* code */
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makegdtdes(0x0, 0xFFFFF, 0x93, 0x0D, &gdt[2]); /* data */
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makegdtdes(0x0, 0x00000, 0x97, 0x0D, &gdt[3]); /* pile */
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/* initialise le registre gdt */
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gdtreg.limite = SIZEGDT * 8;
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gdtreg.base = BASEGDT;
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/* recopie de la GDT a son adresse */
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memcpy(&gdt, (u8 *) gdtreg.base, gdtreg.limite, 1);
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/* chargement du registre GDT */
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lgdt(&gdtreg);
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/* initialisation des segments */
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asm(" movw $0x10, %ax \n \
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movw %ax, %ds \n \
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movw %ax, %es \n \
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movw %ax, %fs \n \
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movw %ax, %gs \n \
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movl 0x0C(%esp), %ebx \n \
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movw $0x18, %ax \n \
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movw %ax, %ss \n \
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movl $0x20000, %esp \n \
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ljmp $0x08, $raz \n \
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raz: \n \
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pushl %ebx \n \
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ret\n");
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}
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/*******************************************************************************/
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/* Créé un descripteur GDT */
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void makegdtdes(u32 base, u32 limite, u8 acces, u8 flags, gdtdes *desc)
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{
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desc->lim0_15 = (limite & 0xffff);
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desc->base0_15 = (base & 0xffff);
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desc->base16_23 = (base & 0xff0000) >> 16;
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desc->acces = acces;
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desc->lim16_19 = (limite & 0xf0000) >> 16;
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desc->flags = (flags & 0xf);
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desc->base24_31 = (base & 0xff000000) >> 24;
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return;
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}
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