luxos/SysCore/hal/gdt/gdt.h

39 lines
1.2 KiB
C

/******************************************************************
* gdt.h - GLOBAL DESCRIPTOR TABLE *
* Contains structures and function declarations for GDT *
******************************************************************/
#ifndef __GDT_H
#define __GDT_H
/* Defines a GDT entry. We say packed, because it prevents the
* compiler from doing things that it thinks is best: Prevent
* compiler "optimization" by packing */
struct gdt_entry
{
unsigned short limit_low;
unsigned short base_low;
unsigned char base_middle;
unsigned char access;
unsigned char granularity;
unsigned char base_high;
} __attribute__((packed));
/* Special pointer which includes the limit: The max bytes
* taken up by the GDT, minus 1. Again, this NEEDS to be packed */
struct gdt_ptr
{
unsigned short limit;
unsigned int base;
} __attribute__((packed));
/* This will be a function in start.asm. We use this to properly
* reload the new segment registers */
extern void i86_gdt_flush();
extern void i86_gdt_set_gate(int num, unsigned long base, unsigned long limit, unsigned char access, unsigned char gran);
extern struct gdt_entry* i86_gdt_get_gate(int num);
extern void i86_gdt_install();
#endif