cos2000v2/lib/gdt.c

95 lines
2.7 KiB
C
Executable File

#include "gdt.h"
#include "asm.h"
#include "types.h"
/* registre gdt */
static struct gdtr gdtreg;
/* table de GDT */
static gdtdes gdt[SIZEGDT];
/* TSS */
static struct tss tss0;
/*******************************************************************************/
/* Initialise la GDT */
void initgdt(u32 offset)
{
makegdtdes(0x0, 0x00000, 0x00, 0x00, &gdt[0]); /* descripteur nul */
makegdtdes(0x0, 0xFFFFF, 0x9B, 0x0D, &gdt[1]); /* code -> SEL_KERNEL_CODE */
makegdtdes(0x0, 0x00000, 0x97, 0x0D, &gdt[2]); /* pile -> SEL_KERNEL_STACK */
makegdtdes(0x0, 0xFFFFF, 0xFF, 0x0D, &gdt[3]); /* code -> SEL_USER_CODE */
makegdtdes(0x0, 0x00000, 0xF7, 0x0D, &gdt[4]); /* pile -> SEL_USER_STACK */
makegdtdes(0x0, 0xFFFFF, 0x93, 0x0D, &gdt[5]); /* data -> SEL_KERNEL_DATA */
makegdtdes(0x0, 0xFFFFF, 0xF3, 0x0D, &gdt[6]); /* data -> SEL_USER_DATA */
tss0.trapflag = 0x00;
tss0.iomap = 0x00;
tss0.esp0 = 0x1FFF0;
tss0.ss0 = SEL_TSS;
makegdtdes(&tss0, 0x67, 0xE9, 0x00, &gdt[7]); /* descripteur de tss */
/* initialise le registre gdt */
gdtreg.limite = SIZEGDT * 8;
gdtreg.base = BASEGDT;
/* recopie de la GDT a son adresse */
memcpy(&gdt, (u8 *) gdtreg.base, gdtreg.limite, 1);
/* chargement du registre GDT */
lgdt(&gdtreg);
/* initialisation des segments */
initselectors(offset);
}
/*******************************************************************************/
/* Initialise le registre de tâche (TSR) */
void inittr(void)
{
ltr(SEL_TSS);
}
/*******************************************************************************/
/* Initialise les selecteurs avec la GDT */
void initselectors(u32 executingoffset)
{
asm(" movw %[data], %%ax \n \
movw %%ax, %%ds \n \
movw %%ax, %%es \n \
movw %%ax, %%fs \n \
movw %%ax, %%gs \n \
movl %[offset], %%ebx \n \
movw %[stack], %%ax \n \
movw %%ax, %%ss \n \
movl %[stackoff], %%esp \n \
ljmp %[code], $raz \n \
raz: \n \
pushl %%ebx \n \
ret\n"::[data] "i"(SEL_KERNEL_DATA),[code] "i"(SEL_KERNEL_CODE), [stack] "i"(SEL_KERNEL_STACK), [stackoff] "i"(STACK_OFFSET), [offset] "m"(executingoffset));
}
/*******************************************************************************/
/* Créé un descripteur GDT */
void makegdtdes(u32 base, u32 limite, u8 acces, u8 flags, gdtdes *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->flags = (flags & 0xf);
desc->base24_31 = (base & 0xff000000) >> 24;
return;
}