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
|
#include<source/gdt.h>
#include<types.h>
extern void load_gdt(struct gdt_pointer *gdtp);
struct gdt_entry gdt[5];
struct gdt_pointer gdtp;
void init_gdt_entry(size_t num, uint16_t limit, uint32_t base, uint8_t access,
uint8_t limit_flags)
{
gdt[num].limit=limit;
gdt[num].base1=(base & 0xffff);
gdt[num].base2=(uint8_t)((base & 0xff0000) >> 16);
gdt[num].access=access;
gdt[num].limit_flags=limit_flags;
gdt[num].base3=(uint8_t)((base & 0xff000000) >> 24);
}
void init_gdt_table(void)
{
gdtp.size=sizeof(gdt)-1;
gdtp.offset=(uint32_t)&gdt;
init_gdt_entry(0,0,0,0,0); // null segment
init_gdt_entry(1,0xffff,0,0x9a,0xcf); // code segment
init_gdt_entry(2,0xffff,0,0x92,0xcf); // data segment
init_gdt_entry(3,0xffff,0,0xfa,0xcf); // user mode code segment
init_gdt_entry(4,0xffff,0,0xf2,0xcf); // user mode data segment
load_gdt(&gdtp);
}
|
