M kernel/os_main.c → kernel/os_main.c

@@ -1,9 +1,23 @@
 #include "os_text.h"
 
 int main(void) {
+    const char* string[] = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
     clear();
-    write("Welcome!");
-    backspace();
+    for (int i = 0; i < 50; i++) {
+        write("LINE ");
+        write(string[i / 10]);
+        write(string[i % 10]);
+        write("\n");
+    }
+
+    write(  "SOMEBODY ONCE TOLD ME "
+            "THE WORLD IS GONNA ROLL ME "
+            "I AINT THE SHARPEST TOOL IN THE SHED "
+            "SHE WAS LOOKING KINDA DUMB "
+            "WITH HER FINGER AND HER THUMB "
+            "IN THE SHAPE OF AN L ON HER FOREHEAD"
+        );
+    //backspace();
 
     return 0;
 }

A kernel/os_string.c

@@ -0,0 +1,21 @@
+#include "os_string.h"
+
+void *memcpy (void *destination, const void *source, size_t num) {
+    if (destination >= source) {
+        for (uint32_t i = 0; i < num; i++) {
+            ((uint8_t*)destination)[num - 1 - i] = ((uint8_t*)source)[num - 1 - i];
+        }
+    } else {
+        for (uint32_t i = 0; i < num; i++) {
+            ((uint8_t*)destination)[i] = ((uint8_t*)source)[i];
+        }
+    }
+    return destination;
+}
+
+void *memset (void *ptr, int value, size_t num) {
+    for (uint32_t i = 0; i < num; i++) {
+        ((uint8_t*)ptr)[i] = (uint8_t)value;
+    }
+    return ptr;
+}

A kernel/os_string.h

@@ -0,0 +1,33 @@
+/*! \file
+ * Defines several functions to manipulate C strings and arrays.
+ */
+#ifndef OS_STRING_H
+#define OS_STRING_H
+
+#include <stdint.h>
+
+/*!
+ * Unsigned integral type.
+ */
+typedef uint32_t size_t;
+
+/*!
+ * Copies a block of memory.
+ * \param destination Pointer to the destination array where the content is to be copied.
+ * \param source Pointer to the source of the data to be copied.
+ * \param num Number of bytes to be copied.
+ * \return \p destination is returned.
+ */
+void *memcpy (void *destination, const void *source, size_t num);
+
+/*!
+ * Sets the \p num first bytes of the block of memory pointed to by \p ptr 
+ * to the specified \p value
+ * \param ptr Pointer to the block of memory to be filled.
+ * \param value Value to be set (Passed as int, but converted to unsigned char)
+ * \param num Number of bytes to set to \p value.
+ * \return \p ptr is returned.
+ */
+void *memset (void *ptr, int value, size_t num);
+
+#endif

M kernel/os_text.c → kernel/os_text.c

@@ -1,13 +1,18 @@
 #include "linker.h"
 #include "assembly.h"
+#include "os_string.h"
 
 #define VGA_TEXTMODE_COLUMNS 80
 #define VGA_TEXTMODE_LINES 25
+#define VGA_TEXTMODE_BPC 2
+#define VGA_TEXTMODE_LINE_WIDTH (VGA_TEXTMODE_COLUMNS * VGA_TEXTMODE_BPC)
 #define VGA_TEXTMODE_CELLS (VGA_TEXTMODE_COLUMNS * VGA_TEXTMODE_LINES)
-#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_MEM_VALUE(line, column) (VGA_TEXTMODE_MEM[VGA_MEM_POS((line), (column))])
+#define VGA_MEM_COLOR(line, column) (VGA_TEXTMODE_MEM[VGA_MEM_POS((line), (column)) + 1])
+#define VGA_MEM_ADDR(line, column) (&(VGA_MEM_VALUE((line), (column))))
 
 #define VGA_INDEX_REG ((uint16_t)0x3D4)
 #define VGA_DATA_REG ((uint16_t)0x3D5)
@@ -17,23 +22,36 @@ uint32_t column = 0;
 uint8_t color = 0x0F;
 
 __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;
+    VGA_MEM_VALUE(line, column) = value;
+    VGA_MEM_COLOR(line, column) = color;
 }
 
 __attribute((always_inline)) inline void lfcr() {
-    if (line < VGA_TEXTMODE_LINES) {
-        line++;
-    } else {
+    line++;
+    column = 0;
+    
+    if (line >= VGA_TEXTMODE_LINES) {
+        memcpy(
+                VGA_MEM_ADDR(0, 0), 
+                VGA_MEM_ADDR(1, 0), 
+                VGA_TEXTMODE_LINE_WIDTH * (VGA_TEXTMODE_LINES - 1)
+            );
+        memset(
+                VGA_MEM_ADDR(VGA_TEXTMODE_LINES - 1, 0), 
+                0, 
+                VGA_TEXTMODE_LINE_WIDTH
+            );
         line = VGA_TEXTMODE_LINES - 1;
     }
-    column = 0;
 }
 
 __attribute((always_inline)) inline void write_char(char value) {
+    if (column >= VGA_TEXTMODE_COLUMNS  || value == '\n') {
+        lfcr();
+    }
+    
     switch (value) {
         case '\n':
-            lfcr();
             break;
         case '\0':
             break;
@@ -41,10 +59,6 @@ default:
             set_char(value);
             column++;
             break;
-    }
-
-    if (column >= VGA_TEXTMODE_COLUMNS) {
-        lfcr();
     }
 }
 

M second_stage/entry.s → second_stage/entry.s

@@ -21,12 +21,4 @@ ljmp $8, $__KERNEL_VMA
 
   # loop until the heat death of the universe
 loop:
-  jmp loop
-  
-
-.section .data
-low_kernel_welcome:
-  .ascii "Welcome to the low kernel!"
-  .byte 13
-  .byte 10
-  .byte 0
+  jmp loop