Buggy screen driver.

kernel/kernel.c

@@ -1,10 +1,6 @@
+#include "../drivers/screen.h"
+
 void main() {
-	/*
-	 * point to first text cell of the video memory
-	 */
-	char *video_memory = (char*) 0xb8000;
-	/*
-	 * store the character 'X' there
-	 */
-	*video_memory = 'X';
+	/*clear_screen();
+	print_at("This is a test.", 0, 0);*/
 }

kernel/ports.c

@@ -1,4 +1,4 @@
-unsigned char port_byte_in(unsigned char port) {
+unsigned char port_byte_in(unsigned short port) {
 	unsigned char res;
 	/*
 	 * `"=a" (res)' means: put result of `al' into `res' variable
@@ -8,7 +8,7 @@ unsigned char port_byte_in(unsigned char port) {
 	return res;
 }
 
-void port_byte_out(unsigned char port, unsigned char data) {
+void port_byte_out(unsigned short port, unsigned char data) {
 	__asm__("out %%al, %%dx" : : "a" (data), "d" (port));
 }
 

kernel/ports.h

@@ -3,11 +3,11 @@
 /*
  * return a byte from a port.
  */
-unsigned char port_byte_in(unsigned char port);
+unsigned char port_byte_in(unsigned short port);
 /*
  * write a byte of data to a port.
  */
-void port_byte_out(unsigned char port, unsigned char data);
+void port_byte_out(unsigned short port, unsigned char data);
 /*
  * return a word of data from a port.
  */

kernel/util.c

@@ -0,0 +1,7 @@
+void memory_copy(char *src, char *dest, unsigned int n) {
+	unsigned int i;
+	for(i = 0; i < n; ++i)
+	{
+		dest[i] = src[i];
+	}
+}

kernel/util.h

@@ -0,0 +1,2 @@
+#pragma once
+void memory_copy(char *src, char *dest, unsigned int n);