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#define INDEX_FROM_BIT(b) (b/(8*sizeof(DWORD)))
#define OFFSET_FROM_BIT(b) (b%(8*sizeof(DWORD)))

//extern DWORD end;

DWORD mem_size = 1024 * 1024;
//DWORD used_mem = (DWORD) &end;

DWORD pages_directory[1024]__attribute__((aligned (4096)));
DWORD kernel_page_table[1024]__attribute__((aligned (4096)));

void page_fault_handler(REGISTERS *regs) {
	DWORD address = GetFaultingPageAddress();
	print_str("PAGE FAULT AT ADDRESS : ", 4);
	print_int(address, 4);
}

void initMemoryManager() {

	char *mem_check = (char *) 0x0;
	while (1) {
		mem_check[mem_size] = 0x0f;
		if (mem_check[mem_size] != 0x0f)
			break;
		mem_size += 1024 * 1024;
	}

	pages_directory[0]=(DWORD)kernel_page_table;
	pages_directory[0]=pages_directory[0] | 3;

	for (int i=0;i<1024;i++)
	{
		pages_directory[i]= 0 | 2;
	}

	DWORD address=0x0000;

	for(int i=0;i<1024;i++){
		kernel_page_table[i]=address | 3;
		address+=4096;
	}

	RegisterInterruptHandler(14, page_fault_handler);
	SwitchPageDirectory((DWORD)pages_directory);
}

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;===============================================================
;	PAGING FUNCTIONS
;===============================================================
GetFaultingPageAddress:
    push    ebp
    mov     ebp,esp
    sub     esp,0x40

    mov eax,cr2

    leave
    ret

EnablePaging:
	mov eax,cr0
	or eax,0x80000000 ;enable paging flag
	mov cr0,eax
	ret

SwitchPageDirectory:
	push    ebp
        mov     ebp,esp
        sub     esp,0x40
	mov eax,[ebp+8]
	mov cr3,eax
	call EnablePaging

	leave
	ret