blob: b256b74efbafbca22cbf617bbd7b4d4b01a7b834 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
#include"../include/types.h"
extern void loadPageDirectory(uint32_t*);
extern void enablePaging();
uint32_t page_directory[1024] __attribute__((aligned(4096)));
void set_pd()
{
//set each entry to not present
for(size_t i=0;i<1024;i++)
{
// This sets the following flags to the pages:
// Supervisor: Only kernel-mode can access them
// Write Enabled: It can be both read from and written to
// Not Present: The page table is not present
page_directory[i] = 0x00000002;
}
}
uint32_t first_page_table[1024] __attribute__((aligned(4096)));
void set_pt()
{
// holds the physical address where we want to start mapping these pages to.
// in this case, we want to map these pages to the very beginning of memory.
unsigned int i;
//we will fill all 1024 entries in the table, mapping 4 megabytes
for(i = 0; i < 1024; i++)
{
// As the address is page aligned, it will always leave 12 bits zeroed.
// Those bits are used by the attributes ;)
first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
}
}
void put_pt()
{
// attributes: supervisor level, read/write, present
page_directory[0] = ((uint32_t)first_page_table) | 3;
}
void set_paging()
{
set_pd();
set_pt();
put_pt();
loadPageDirectory(page_directory);
enablePaging();
}
|
