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#include <system.h>
#include <gdt.h>
extern void gdt_flush();

gdt_entry_struct gdt[6];
gdt_ptr_struct gp;

void gdt_set(unsigned int index, unsigned long base, unsigned long limit, unsigned char access, unsigned char granularity)
{
	setBase(index, base);
	gdt[index].limit_low   = limit & 0xFFFF;
	gdt[index].granularity = granularity;
	gdt[index].access      = access;
}

void gdt_install()
{
   	// Setup the GDT pointer and limit 
	gp.limit = (sizeof(gdt_entry_struct) * 6) - 1;
	gp.base  = (unsigned int)&gdt;

   	gdt_set(0, 0, 0, 0, 0);
   	gdt_set(1, 0, 0xFFFFFFFF, 0x9A, 0xCF);
   	gdt_set(2, 0, 0xFFFFFFFF, 0x92, 0xCF);
	//thanks to Bran's Kernel Development for these access and granularity values!	

   	//Flush out the old GDT and install the new changes!
   	gdt_flush();
}

void setBase(unsigned int index, unsigned long base)
{
	gdt[index].base_low    = base;
	gdt[index].base_middle = base >> BASE_MIDDLE_SHIFT;
	gdt[index].base_high   = base >> BASE_HIGH_SHIFT;
}