void init_gdt()
{
gdt_desc.limit = (sizeof(struct s_gdt_entry) * 6) - 1;
gdt_desc.base = (unsigned int)&gdt;
/* Null segment */
init_segment(0, 0, 0, 0, 0);
/*Ring 0*/
/* Code segment */
init_segment(1, BASE, LIMIT, 0xC, 0x9A);
/* Data segment */
init_segment(2, BASE, LIMIT, 0xC, 0x92);
/*Ring 3*/
/* Code segment */
init_segment(3, BASE, LIMIT, 0xC, 0xFA);
/* Data segment */
init_segment(4, BASE, LIMIT, 0xC, 0xF2);
/*TSS*/
write_tss(5, 0x10, 0);
flush_gdt();
flush_tss();
}
void gdt_install(){
// null desc
set_gdt_desc(0, 0, 0, 0, 0);
// code descriptor, full 4 gigs and 4 kilobyte granularity
set_gdt_desc(1, 0, 0xFFFFFFFF, 0x9A, 0xCF);
// data descriptor, same as above
set_gdt_desc(2, 0, 0xFFFFFFFF, 0x92, 0xCF);
// user code and data descriptors
set_gdt_desc(3, 0, 0xFFFFFFFF, 0xFA, 0xCF);
set_gdt_desc(4, 0, 0xFFFFFFFF, 0xF2, 0xCF);
// flush the gdt into memory
flush_gdt();
}
extern "C" void init_gdt() {
create_gdt_entry(0, 0, 0, 0, gdt);
create_gdt_entry(0, 0xFFFFFFFF, 0x9A, 0xCF, gdt + 1);
create_gdt_entry(0, 0xFFFFFFFF, 0x92, 0xCF, gdt + 2);
flush_gdt(gdt, 3 * (sizeof *gdt) - 1);
}
