k-chow/k/gdt.h

#ifndef GDT_H
#define GDT_H

#include <stdint.h>

#define GDT_NB_ENTRIES 3
#define GDT_SIZE (GDT_NB_ENTRIES * sizeof(struct gdt_entry))

#define KERNEL_CS_INDEX 1
#define KERNEL_DS_INDEX 2

struct gdt_entry
{
    uint16_t limit_1    : 16;
    uint16_t base_1     : 16;
    uint8_t base_2      : 8;
    uint8_t accessed    : 1;
    uint8_t rw          : 1;
    uint8_t dc          : 1;
    uint8_t ex          : 1;
    uint8_t desc_type   : 1;
    uint8_t desc_priv   : 2;
    uint8_t present     : 1;
    uint8_t limit_2     : 4;
    uint8_t available   : 1;
    uint8_t l           : 1;
    uint8_t db          : 1;
    uint8_t granularity : 1;
    uint8_t base_3      : 8;
} __attribute__ ((packed));

struct gdt
{
    struct gdt_entry entries[GDT_NB_ENTRIES];
};

struct gdt_r
{
    uint16_t limit;
    uint32_t addr;
} __attribute__ ((packed));

struct segment_selector
{
    uint8_t rpl             : 2;
    uint8_t table_indicator : 1;
    uint16_t index          : 13;
} __attribute__ ((packed));

void init_gdt();

#endif  /* !GDT_H */