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#include <stdint.h>
#include <print.h>
#include <compiler.h>
#include <mem.h>


#define PAGE_SIZE	4096

/* PDE */
typedef struct pde_structure {
	uint32_t present 	:	1;
	uint32_t rw		:	1;
	uint32_t us		:	1;
	uint32_t pwt		:	1;
        uint32_t pcd		:	1;
        uint32_t accessed	:	1;
        uint32_t unused		:	6;
	uint32_t address	:	20;
} pde_t;

/* PTE */
typedef struct pte_structure {
	uint32_t present	:	1;
	uint32_t rw		:	1;
	uint32_t us		:	1;
	uint32_t pwt		:	1;
	uint32_t pcd		:	1;
	uint32_t accessed	:	1;
	uint32_t dirty		:	1;
	uint32_t unused		:	5;
	uint32_t address	:	20;
} pte_t;

/* page directory */
pde_t current_pd[1024] __ALIGNED(PAGE_SIZE);

/* page table */
pte_t current_pt[1024] __ALIGNED(PAGE_SIZE);

void install_handler();

void init_paging()
{
	int i;
	uint32_t address = 0;

	memset(current_pt, 0, sizeof(current_pt));
	memset(current_pd, 0, sizeof(current_pd));

	install_handler(14, page_fault_handler);

	address = (uint32_t)&current_pt>>12;

	/* set kernel PD */
	current_pd[0].present = 1;
	current_pd[0].rw = 1;
	current_pd[0].us = 1;
	current_pd[0].address = address;

	address = 0;

	/* first 4MB identity mapped */
	for (i = 0; i != 1024; i++) {
		current_pt[i].present = 1;
		current_pt[i].rw = 1;
		current_pt[i].address = address>>12;
		address += PAGE_SIZE;
	}

	init_msg(Initializing paging);

	/*
	 * Intel, Vol 3a, ch. 19.30.3
	 */
	asm volatile("movl %0, %%eax; movl %%eax, %%cr3;"
		::"r"(&current_pd):);

	asm volatile(
		"movl %cr0, %eax;"
		"orl $0x80000000, %eax;"
		"movl %eax, %cr0;"
		"jmp 1f; 1:"
		);
}