95 lines
2.7 KiB
C
Executable File
95 lines
2.7 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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/* 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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/* TSS */
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static struct tss tss0;
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/*******************************************************************************/
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/* Initialise la GDT */
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void initgdt(u32 offset)
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{
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makegdtdes(0x0, 0x00000, 0x00, 0x00, &gdt[0]); /* descripteur nul */
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makegdtdes(0x0, 0xFFFFF, 0x9B, 0x0D, &gdt[1]); /* code -> SEL_KERNEL_CODE */
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makegdtdes(0x0, 0x00000, 0x97, 0x0D, &gdt[2]); /* pile -> SEL_KERNEL_STACK */
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makegdtdes(0x0, 0xFFFFF, 0xFF, 0x0D, &gdt[3]); /* code -> SEL_USER_CODE */
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makegdtdes(0x0, 0x00000, 0xF7, 0x0D, &gdt[4]); /* pile -> SEL_USER_STACK */
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makegdtdes(0x0, 0xFFFFF, 0x93, 0x0D, &gdt[5]); /* data -> SEL_KERNEL_DATA */
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makegdtdes(0x0, 0xFFFFF, 0xF3, 0x0D, &gdt[6]); /* data -> SEL_USER_DATA */
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tss0.trapflag = 0x00;
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tss0.iomap = 0x00;
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tss0.esp0 = 0x1FFF0;
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tss0.ss0 = SEL_TSS;
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makegdtdes(&tss0, 0x67, 0xE9, 0x00, &gdt[7]); /* descripteur de tss */
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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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initselectors(offset);
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}
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/*******************************************************************************/
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/* Initialise le registre de tâche (TSR) */
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void inittr(void)
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{
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ltr(SEL_TSS);
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}
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/*******************************************************************************/
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/* Initialise les selecteurs avec la GDT */
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void initselectors(u32 executingoffset)
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{
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asm(" movw %[data], %%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 %[offset], %%ebx \n \
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movw %[stack], %%ax \n \
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movw %%ax, %%ss \n \
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movl %[stackoff], %%esp \n \
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ljmp %[code], $raz \n \
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raz: \n \
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pushl %%ebx \n \
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ret\n"::[data] "i"(SEL_KERNEL_DATA),[code] "i"(SEL_KERNEL_CODE), [stack] "i"(SEL_KERNEL_STACK), [stackoff] "i"(STACK_OFFSET), [offset] "m"(executingoffset));
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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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