Luna/kernel/src/gdt/GDT.cpp

#define MODULE "gdt"

#include "gdt/GDT.h"
#include "log/Log.h"
#include <stdint.h>

struct GDTR
{
    uint16_t size;
    uint64_t offset;
} __attribute__((packed));

struct GDTEntry
{
    uint16_t limit0;
    uint16_t base0;
    uint8_t base1;
    uint8_t access;
    uint8_t limit1_flags;
    uint8_t base2;
} __attribute__((packed));

struct InternalGDT
{
    GDTEntry null;
    GDTEntry kernel_code;
    GDTEntry kernel_data;
    GDTEntry user_null;
    GDTEntry user_code;
    GDTEntry user_data;
} __attribute__((packed)) __attribute((aligned(0x1000)));

__attribute__((aligned(0x1000))) static InternalGDT internal_gdt = {
    {0x0000, 0x0000, 0x00, 0x00, 0x00, 0x00}, {0xffff, 0x0000, 0x00, 0x9a, 0xaf, 0x00},
    {0xffff, 0x0000, 0x00, 0x92, 0xcf, 0x00}, {0x0000, 0x0000, 0x00, 0x00, 0x00, 0x00},
    {0xffff, 0x0000, 0x00, 0xfa, 0xaf, 0x00}, {0xffff, 0x0000, 0x00, 0xf2, 0xcf, 0x00}};

extern "C" void load_gdt(GDTR* gdtr);

void GDT::load()
{
    static GDTR gdtr;
    gdtr.offset = (uint64_t)&internal_gdt;
    gdtr.size = sizeof(InternalGDT);
    kdbgln("Loading GDT at offset %lx, size %d", gdtr.offset, gdtr.size);
    load_gdt(&gdtr);
}