/**************************************************************************************************

*

* File: paging.c

*

* Copyright (c) 2003, 2004 Erik Dubbelboer

*

* Contents: paging functions.

*

*************************************************************************************************/

#include "kernel.h"

#include "paging.h"

/**

* Set up the Boot Page-Directory and Tables, and enable Paging.

*

* This function is executed at the physicallKernel address.

* Therefore it can not use global variables or switch() statements.

**/

void paging_init(void)

{

uint index;

uint loop;

uint* table;

//

// Boot Page-Directory

//

uint* dir = (uint*)0x124000;

index = 0;

// The 1e Page-Table.

dir[index++] = 0x125000 | X86_PAGE_PRESENT | X86_PAGE_WRITE;

// The rest of the tables till 3GB are not present.

for (loop = 0; loop < 768 - 1; loop++)

dir[index++] = 0; // Not present.

// The 2e Page-Table.

dir[index++] = 0x126000 | X86_PAGE_PRESENT | X86_PAGE_WRITE;

// The rest of the tables is not present.

for (loop = 0; loop < 256 - 1; loop++)

dir[index++] = 0;

//

// Page-Table 1.

//

table = (uint*)0x125000;

index = 0;

// Map the First 2MB (512 Pages)

for (loop = 0; loop < 512; loop++)

table[index++] = (PAGE_SIZE * loop) | X86_PAGE_PRESENT | X86_PAGE_WRITE;

// The rest is not present.

for (loop = 0; loop < 512; loop++)

table[index++] = 0;

//

// Page-Table 2.

//

table = (uint*)0x126000;

index = 0;

// Map the First 2MB (512 Pages)

for (loop = 0; loop < 512; loop++)

table[index++] = (PAGE_SIZE * loop) | X86_PAGE_PRESENT | X86_PAGE_WRITE;

// The rest is not present.

for (loop = 0; loop < 512; loop++)

table[index++] = 0;

// load cr3 (Page-Directory Base Register) with the Page-Directory we are going to use,

// which is the Page-Directory from the Kernel process.

set_cr3((uint)dir);

//

// Enable paging.

//

set_cr0(get_cr0() | 0x80000000); // Set the paging bit.

}