dsctbl.c

/* GDT IDT descriptor table*/

#include "bootpack.h"

void init_gdtidt(void)
{
    struct SEGMENT_DESCRIPTOR* gdt = (struct SEGMENT_DESCRIPTOR*)ADR_GDT;
    struct GATE_DESCRIPTOR* idt = (struct GATE_DESCRIPTOR*)ADR_IDT;
    int i;

    /* GDT */
    for (i = 0; i <= LIMIT_GDT / 8; i++) {
        set_segmdesc(gdt + i, 0, 0, 0);
    }
    set_segmdesc(gdt + 1, 0xffffffff, 0x00000000, AR_DATA32_RW);
    set_segmdesc(gdt + 2, LIMIT_BOTPAK, ADR_BOTPAK, AR_CODE32_ER);
    load_gdtr(LIMIT_GDT, ADR_GDT);

    /* IDT */
    for (i = 0; i <= LIMIT_IDT / 8; i++) {
        set_gatedesc(idt + i, 0, 0, 0);
    }
    load_idtr(LIMIT_IDT, ADR_IDT);

    /* IDT */
    set_gatedesc(idt + 0x0c, (int)asm_inthandler0c, 2 * 8, AR_INTGATE32);
    set_gatedesc(idt + 0x0d, (int)asm_inthandler0d, 2 * 8, AR_INTGATE32);
    set_gatedesc(idt + 0x20, (int)asm_inthandler20, 2 * 8, AR_INTGATE32);
    set_gatedesc(idt + 0x21, (int)asm_inthandler21, 2 * 8, AR_INTGATE32);
    set_gatedesc(idt + 0x2c, (int)asm_inthandler2c, 2 * 8, AR_INTGATE32);
    set_gatedesc(idt + 0x40, (int)asm_hrb_api, 2 * 8, AR_INTGATE32 + 0x60);

    return;
}

void set_segmdesc(struct SEGMENT_DESCRIPTOR* sd, unsigned int limit, int base, int ar)
{
    if (limit > 0xfffff) {
        ar |= 0x8000; /* G_bit = 1 */
        limit /= 0x1000;
    }
    sd->limit_low = limit & 0xffff;
    sd->base_low = base & 0xffff;
    sd->base_mid = (base >> 16) & 0xff;
    sd->access_right = ar & 0xff;
    sd->limit_high = ((limit >> 16) & 0x0f) | ((ar >> 8) & 0xf0);
    sd->base_high = (base >> 24) & 0xff;
    return;
}

void set_gatedesc(struct GATE_DESCRIPTOR* gd, int offset, int selector, int ar)
{
    gd->offset_low = offset & 0xffff;
    gd->selector = selector;
    gd->dw_count = (ar >> 8) & 0xff;
    gd->access_right = ar & 0xff;
    gd->offset_high = (offset >> 16) & 0xffff;
    return;
}