gdt.h

#ifndef GDT_H
#define GDT_H
#include "common.h"

typedef 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)) gdt_entry_t;

typedef struct gdt_ptr {
  uint16_t limit;
  uint32_t base;
} __attribute__((packed)) gdt_ptr_t;

// A struct describing a Task State Segment.
typedef struct tss_entry
{
   uint32_t prev_tss;   // The previous TSS - if we used hardware task switching this would form a linked list.
   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;
   // --- kernel mode values:
   uint32_t es;
   uint32_t cs;
   uint32_t ss;
   uint32_t ds;
   uint32_t fs;
   uint32_t gs;
   // ----
   uint32_t ldt;
   uint16_t trap;
   uint16_t iomap_base;
} __attribute__((packed)) tss_entry_t;

void init_gdt();

#endif