luxos/Kernel/hal/cpu/gdt.h

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/******************************************************************
* 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 */
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struct GdtEntry
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{
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 */
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struct GdtPointer
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{
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 GdtInstall();
extern void GdtFlush();
extern void GdtSetGate(int num, unsigned long base, unsigned long limit, unsigned char access, unsigned char gran);
extern struct GdtEntry* GdtGetGate(int num);
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#endif