gdt.h

Go to the documentation of this file.

#pragma once
 
#include <kernel/cpu/tss.h>
#include <kernel/defs.h>
 
#include <stdint.h>
 
typedef enum
{
    GDT_RING0 = 0,
    GDT_RING1 = 1,
    GDT_RING2 = 2,
    GDT_RING3 = 3
} gdt_ring_t;
 
typedef enum
{
    GDT_NULL = 0,           
    GDT_KERNEL_CODE = 0x08, 
    GDT_KERNEL_DATA = 0x10, 
    GDT_USER_DATA = 0x18,   
    GDT_USER_CODE = 0x20,   
    GDT_TSS = 0x28,         
 
    GDT_CS_RING0 = GDT_KERNEL_CODE | GDT_RING0, 
    GDT_SS_RING0 = GDT_KERNEL_DATA | GDT_RING0, 
 
    GDT_CS_RING3 = GDT_USER_CODE | GDT_RING3, 
    GDT_SS_RING3 = GDT_USER_DATA | GDT_RING3, 
} gdt_segment_selector_t;
 
typedef enum
{
    GDT_ACCESS_ACCESSED = 1 << 0,   
    GDT_ACCESS_READ_WRITE = 1 << 1, 
    GDT_ACCESS_DIRECTION_CONFORMING = 1 << 2, 
    GDT_ACCESS_EXEC = 1 << 3,                 
    GDT_ACCESS_SYSTEM = 0 << 4,               
    GDT_ACCESS_DATA_CODE = 1 << 4,            
 
    GDT_ACCESS_TYPE_LDT = 0x2,           
    GDT_ACCESS_TYPE_TSS_AVAILABLE = 0x9, 
    GDT_ACCESS_TYPE_TSS_BUSY = 0xB,      
 
    GDT_ACCESS_RING0 = 0 << 5, 
    GDT_ACCESS_RING1 = 1 << 5, 
    GDT_ACCESS_RING2 = 2 << 5, 
    GDT_ACCESS_RING3 = 3 << 5, 
 
    GDT_ACCESS_PRESENT = 1 << 7, 
} gdt_access_t;
 
typedef enum
{
    GDT_FLAGS_NONE = 0,           
    GDT_FLAGS_RESERVED = 1 << 0,  
    GDT_FLAGS_LONG_MODE = 1 << 1, 
    GDT_FLAGS_SIZE = 1 << 2, 
    GDT_FLAGS_4KB = 1 << 3   
} gdt_flags_t;
 
typedef struct PACKED
{
    uint16_t size;   
    uint64_t offset; 
} gdt_desc_t;
 
typedef struct PACKED
{
    uint16_t limitLow;
    uint16_t baseLow;
    uint8_t baseMiddle;
    uint8_t access;
    uint8_t flagsAndLimitHigh;
    uint8_t baseHigh;
} gdt_segment_t;
 
typedef struct PACKED
{
    uint16_t limitLow;
    uint16_t baseLow;
    uint8_t baseLowerMiddle;
    uint8_t access;
    uint8_t flagsAndLimitHigh;
    uint8_t baseUpperMiddle;
    uint32_t baseHigh;
    uint32_t reserved;
} gdt_long_system_segment_t;
 
typedef struct PACKED
{
    gdt_segment_t null;
    gdt_segment_t kernelCode;
    gdt_segment_t kernelData;
    gdt_segment_t userData;
    gdt_segment_t userCode;
    gdt_long_system_segment_t tssDesc;
} gdt_t;
 
extern void gdt_load_descriptor(gdt_desc_t* descriptor);
 
void gdt_init(void);
 
void gdt_cpu_load(void);
 
void gdt_cpu_tss_load(tss_t* tss);