52 lines
No EOL
1.8 KiB
C
52 lines
No EOL
1.8 KiB
C
#ifndef GDT_H
|
|
#define GDT_H
|
|
|
|
#include <stdint.h>
|
|
|
|
// GDT Access Flags
|
|
#define GDT_ACCESS_PRESENT 0x80 // Segment is present
|
|
#define GDT_ACCESS_RING0 0x00 // Privilege Level 0 (Kernel)
|
|
#define GDT_ACCESS_RING3 0x60 // Privilege Level 3 (User)
|
|
#define GDT_ACCESS_SYSTEM 0x00 // System segment (e.g., TSS)
|
|
#define GDT_ACCESS_CODE 0x18 // Code segment (Executable)
|
|
#define GDT_ACCESS_DATA 0x10 // Data segment (Readable/Writable)
|
|
#define GDT_ACCESS_DIRECTION 0x04 // Direction bit (0 = Grows up, 1 = Grows down)
|
|
#define GDT_ACCESS_EXECUTABLE 0x08 // Executable segment
|
|
#define GDT_ACCESS_RW 0x02 // Readable for code, Writable for data
|
|
#define GDT_ACCESS_ACCESSED 0x01 // CPU sets this when accessed
|
|
|
|
// Common Access Flags
|
|
#define GDT_KERNEL_CODE (GDT_ACCESS_PRESENT | GDT_ACCESS_RING0 | GDT_ACCESS_CODE | GDT_ACCESS_EXECUTABLE | GDT_ACCESS_RW)
|
|
#define GDT_KERNEL_DATA (GDT_ACCESS_PRESENT | GDT_ACCESS_RING0 | GDT_ACCESS_DATA | GDT_ACCESS_RW)
|
|
#define GDT_USER_CODE (GDT_ACCESS_PRESENT | GDT_ACCESS_RING3 | GDT_ACCESS_CODE | GDT_ACCESS_EXECUTABLE | GDT_ACCESS_RW)
|
|
#define GDT_USER_DATA (GDT_ACCESS_PRESENT | GDT_ACCESS_RING3 | GDT_ACCESS_DATA | GDT_ACCESS_RW)
|
|
#define GDT_TSS 0xE9
|
|
|
|
// Granularity Flags
|
|
#define GDT_GRANULARITY_4K 0x80
|
|
#define GDT_GRANULARITY_32B 0x40
|
|
#define GDT_GRANULARITY_LONG_MODE 0x20
|
|
#define GDT_GRANULARITY_FLAT (GDT_GRANULARITY_4K | GDT_GRANULARITY_LONG_MODE)
|
|
|
|
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;
|
|
uint64_t base;
|
|
} __attribute__((packed)) gdt_ptr_t;
|
|
|
|
extern gdt_ptr_t gdt_ptr;
|
|
|
|
void gdt_init();
|
|
void gdt_flush(gdt_ptr_t gdt_ptr);
|
|
|
|
#endif // GDT_H
|