limine/common/sys/a20.s2.c
2022-02-03 10:38:43 +01:00

59 lines
1.1 KiB
C

#if bios == 1
#include <stdint.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/a20.h>
#include <sys/cpu.h>
#include <lib/real.h>
bool a20_check(void) {
if (mminw(0x7dfe) != mminw(0x7dfe + 0x100000))
return true;
mmoutw(0x7dfe, ~mminw(0x7dfe));
if (mminw(0x7dfe) != mminw(0x7dfe + 0x100000))
return true;
return false;
}
// Keyboard controller method code below taken from:
// https://wiki.osdev.org/A20_Line
bool a20_enable(void) {
if (a20_check())
return true;
// BIOS method
struct rm_regs r = {0};
r.eax = 0x2401;
rm_int(0x15, &r, &r);
if (a20_check())
return true;
// Keyboard controller method
while (inb(0x64) & 2);
outb(0x64, 0xad);
while (inb(0x64) & 2);
outb(0x64, 0xd0);
while (!(inb(0x64) & 1));
uint8_t b = inb(0x60);
while (inb(0x64) & 2);
outb(0x64, 0xd1);
while (inb(0x64) & 2);
outb(0x60, b | 2);
while (inb(0x64) & 2);
outb(0x64, 0xae);
while (inb(0x64) & 2);
if (a20_check())
return true;
return false;
}
#endif