rk/include/gdt.h

#ifndef RK_GDT_H_
#define RK_GDT_H_

#include <stdint.h>

#define GDT_NULL 0
#define GDT_KERNEL_CODE 1
#define GDT_KERNEL_DATA 2
#define GDT_SEGMENT_SELECTOR(i, p) ((i << 3) | p)

struct gdt_entry {
    uint16_t limit_low;
    uint16_t base_low;
    uint8_t base_middle;
    uint8_t access;
    uint8_t granularity;
    uint8_t base_high;
} __attribute__((packed));

struct tss_entry {
    uint32_t prev_tss;    // The previous TSS - with hardware task switching this is used
    uint32_t esp0;        // The stack pointer to load when we change to kernel mode
    uint32_t ss0;         // The stack segment to load when we change to kernel mode
    uint32_t esp1;        // Unused...
    uint32_t ss1;
    uint32_t esp2;
    uint32_t ss2;
    uint32_t cr3;
    uint32_t eip;
    uint32_t eflags;
    uint32_t eax;
    uint32_t ecx;
    uint32_t edx;
    uint32_t ebx;
    uint32_t esp;
    uint32_t ebp;
    uint32_t esi;
    uint32_t edi;
    uint32_t es;          // The value to load into ES when we change to kernel mode
    uint32_t cs;          // The value to load into CS when we change to kernel mode
    uint32_t ss;          // The value to load into SS when we change to kernel mode
    uint32_t ds;          // The value to load into DS when we change to kernel mode
    uint32_t fs;          // The value to load into FS when we change to kernel mode
    uint32_t gs;          // The value to load into GS when we change to kernel mode
    uint32_t ldt;         // Unused...
    uint16_t trap;
    uint16_t iomap_base;
} __attribute__((packed));

#endif