gdt.h

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#pragma once
 
#include <stdint.h>
 
struct gdt
{
    uint16_t segment;
    uint16_t base_first;
    uint8_t base;
    uint8_t access;
    uint8_t high_flags;
    uint8_t base_24_31_bits;
} __attribute__((packed));
 
struct gdt_structured
{
    uint32_t base;
    uint32_t limit;
    uint8_t type;
};
 
struct gdt_descriptor 
{
    uint16_t size;
    uint32_t start_address;
} __attribute__((packed));
 
void gdt_load(struct gdt *gdt, unsigned int size);
void gdt_read(struct gdt_descriptor *target);
void gdt_structured_to_gdt(struct gdt *gdt, struct gdt_structured *structured_gdt, unsigned int total_entries);
 
#define TOTAL_GDT_SEGMENTS 6
 
#define KERNEL_CODE_SELECTOR 0x08
#define KERNEL_DATA_SELECTOR 0x10
 
#define USER_CODE_SELECTOR 0x1b
#define USER_DATA_SELECTOR 0x23