A include/assembly.h

@@ -0,0 +1,16 @@
+#ifndef ASSEMBLY_H
+#define ASSEMBLY_H
+
+#include <stdint.h>
+
+__attribute((always_inline)) inline void outb(uint8_t msg, uint16_t port) {
+    __asm__ volatile ("outb %0, %1" : "=a" (msg), "=Nd" (port));
+}
+
+__attribute((always_inline)) inline uint8_t inb(uint16_t port) {
+    uint8_t msg;
+    __asm__ volatile ("inb %1, %0" : "=a" (msg) : "Nd" (port));
+    return msg;
+}
+
+#endif

M kernel/main.c → kernel/main.c

@@ -3,6 +3,7 @@
 int main(void) {
     clear();
     write("Welcome!");
+    backspace();
 
     return 0;
 }

M kernel/text.c → kernel/text.c

@@ -1,4 +1,5 @@
 #include "linker.h"
+#include "assembly.h"
 
 #define VGA_TEXTMODE_COLUMNS 80
 #define VGA_TEXTMODE_LINES 25
@@ -7,17 +8,25 @@ #define VGA_TEXTMODE_BPC 2
 #define VGA_MEM_POS(line, column) ((line) * VGA_TEXTMODE_COLUMNS * VGA_TEXTMODE_BPC + (column) * VGA_TEXTMODE_BPC)
 
 #define VGA_TEXTMODE_MEM ((uint8_t*)0xB8000)
+
+#define VGA_INDEX_REG ((uint16_t)0x3D4)
+#define VGA_DATA_REG ((uint16_t)0x3D5)
 
 uint32_t line = 0;
 uint32_t column = 0;
 uint8_t color = 0x0F;
 
-void lfcr() {
+__attribute((always_inline)) inline void set_char(char value) {
+    VGA_TEXTMODE_MEM[VGA_MEM_POS(line, column)] = value;
+    VGA_TEXTMODE_MEM[VGA_MEM_POS(line, column) + 1] = color;
+}
+
+__attribute((always_inline)) inline void lfcr() {
     line++;
     column = 0;
 }
 
-void write_char(char value) {
+__attribute((always_inline)) inline void write_char(char value) {
     switch (value) {
         case '\n':
             lfcr();
@@ -25,8 +34,7 @@ break;
         case '\0':
             break;
         default:
-            VGA_TEXTMODE_MEM[VGA_MEM_POS(line, column)] = value;
-            VGA_TEXTMODE_MEM[VGA_MEM_POS(line, column) + 1] = color;
+            set_char(value);
             column++;
             break;
     }
@@ -36,19 +44,53 @@ lfcr();
     }
 }
 
+__attribute((always_inline)) inline void set_cursor(uint16_t line, uint16_t column) {
+    uint16_t pos = line * VGA_TEXTMODE_COLUMNS + column;
+    outb(0x0F, VGA_INDEX_REG);
+    outb((uint8_t)(pos & 0xFF), VGA_DATA_REG);
+    outb(0x0E, VGA_INDEX_REG);
+    outb((uint8_t)(pos >> 8), VGA_DATA_REG);
+}
+
+void backspace(void) {
+    if (column == 0 && line > 0) {
+        line--;
+        column = VGA_TEXTMODE_COLUMNS - 1;
+    } else if (column > 0) {
+        column--;
+    }
+
+    set_char(0);
+    set_cursor(line, column);
+}
+
 void write_n(const char *string, uint32_t num) {
     for (uint32_t i = 0; i < num; i++) {
         write_char(string[0]);
     }
+    set_cursor(line, column);
 }
 
 void write(const char *string) {
     while (*string) {
         write_char(*(string++));
     }
+    set_cursor(line, column);
 }
 
-void clear() {
+void write_c(const char c) {
+    write_char(c);
+    set_cursor(line, column);
+}
+
+void enable_cursor(void) {
+    outb(0x0A, VGA_INDEX_REG);
+    outb((inb(VGA_DATA_REG) & 0x0C) | 0x00, VGA_DATA_REG);
+    outb(0x0B, VGA_INDEX_REG);
+    outb((inb(VGA_DATA_REG) & 0xE0) | 0x0F, VGA_DATA_REG);
+}
+
+void clear(void) {
     for (int i = 0; i < VGA_TEXTMODE_CELLS; i++) {
         VGA_TEXTMODE_MEM[2 * i] = 0;
         VGA_TEXTMODE_MEM[2 * i + 1] = 0;
@@ -56,4 +98,6 @@ }
 
     line = 0;
     column = 0;
-}+    enable_cursor();
+    set_cursor(line, column);
+}

M kernel/text.h → kernel/text.h

@@ -7,5 +7,6 @@ void write_n(const char *string, uint32_t num);
 void write(const char *string);
 
 void clear();
+void backspace(void);
 
 #endif

M makefile → makefile

@@ -6,7 +6,8 @@ export INCLUDE_DIR		= $(CURRENT_DIR)/include
 export DEBUG_DIR		= $(CURRENT_DIR)/debug
 
 export GCC_PREFIX		= $(HOME)/opt/cross/i686-elf-/bin/i686-elf-
-export GCC_OPTIONS		= -O0 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding
+export GCC_OPTIONS		= -O1 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding
+
 
 # OBJ_FILES = $(wildcard obj/asm/*.o) $(wildcard obj/cpp/*.o)