...

.clang-format

@@ -16,3 +16,5 @@ AllowShortLoopsOnASingleLine: false
 SeparateDefinitionBlocks: Always
 
 BreakBeforeBraces: Allman
+
+Cpp11BracedListStyle: false

src/boot/bootloader.asm

@@ -1,7 +1,7 @@
 [org 0x7c00]
 [bits 16]
 
-KERNEL_LOCATION equ 0x1000
+KERNEL_INIT equ 0x1000
 
 mov [BOOT_DISK], dl
 
@@ -11,7 +11,7 @@ mov ds, ax
 mov bp, 0x8000
 mov sp, bp
 
-mov bx, KERNEL_LOCATION
+mov bx, KERNEL_INIT
 mov dh, 2
 
 mov ah, 0x02
@@ -22,7 +22,6 @@ mov cl, 0x02
 mov dl, [BOOT_DISK]
 int 0x13
 
-                                    
 mov ah, 0x0
 mov al, 0x3
 int 0x10
@@ -41,7 +40,6 @@ jmp $
 BOOT_DISK: db 0
 
 gdt_start:
-    gdt_null:
     dd 0x0
     dd 0x0
 
@@ -79,9 +77,8 @@ start_protected_mode:
 	mov ebp, 0x90000
 	mov esp, ebp
 
-    jmp KERNEL_LOCATION
-    jmp $
-
+    jmp KERNEL_INIT
+    hlt
 
 times 510-($-$$) db 0
 dw 0xaa55

src/kernel/entry.asm

@@ -1,5 +1,4 @@
-section .text
-    [bits 32]
-    [extern init]
-    call init
-    jmp $
+[extern kernel_init]
+[bits 32]
+call kernel_init
+hlt

src/kernel/kernel.c

@@ -1,7 +1,52 @@
 #include "print.h"
 
-void init(void)
+/**
+ * C++ version 0.4 char* style "itoa":
+ * Written by Lukás Chmela
+ * Released under GPLv3.
+ */
+char* itoa(int value, char* result, int base)
 {
-    print_init();
-    println("Starting nub-os");
+    // check that the base if valid
+    if (base < 2 || base > 36)
+    {
+        *result = '\0';
+        return result;
+    }
+
+    char *ptr = result, *ptr1 = result, tmp_char;
+    int tmp_value;
+
+    do
+    {
+        tmp_value = value;
+        value /= base;
+        *ptr++ =
+            "zyxwvutsrqponmlkjihgfedcba9876543210123456789abcdefghijklmnopqrstuvwxyz"[35 + (tmp_value - value * base)];
+    } while (value);
+
+    // Apply negative sign
+    if (tmp_value < 0)
+        *ptr++ = '-';
+    *ptr-- = '\0';
+
+    // Reverse the string
+    while (ptr1 < ptr)
+    {
+        tmp_char = *ptr;
+        *ptr-- = *ptr1;
+        *ptr1++ = tmp_char;
+    }
+    return result;
+}
+
+void kernel_init(void)
+{
+    for (int i = 0; i < 100; i++)
+    {
+        // char buf[10];
+        // itoa(i, buf, 10);
+        // kernel_print(buf);
+        kernel_print("Starting nub-osStarting");
+    }
 }

src/kernel/linker.ld

@@ -0,0 +1,22 @@
+ENTRY(kernel_init)
+
+SECTIONS {
+    . = 0x1000;
+
+    .text : {
+        *(.text)
+    }
+
+    .rodata : {
+        *(.rodata)
+    }
+
+    .data : {
+        *(.data)
+    }
+
+    .bss : {
+        *(.bss)
+        *(COMMON)
+    }
+}

src/kernel/makefile

@@ -1,10 +1,7 @@
 CC = i386-elf-gcc -ffreestanding -m32
 
-kernel.bin: entry.o kernel.o mem.o print.o
-	i386-elf-ld -o kernel.bin -Ttext 0x1000 entry.o kernel.o mem.o print.o --oformat binary
-
-entry.o: entry.asm
-	nasm -f elf -o entry.o entry.asm
+kernel.bin: entry.o kernel.o linker.ld mem.o print.o
+	i386-elf-ld -o kernel.bin -T linker.ld entry.o kernel.o mem.o print.o --oformat binary
 
 kernel.o: kernel.c
 	$(CC) -c -o kernel.o kernel.c
@@ -15,5 +12,8 @@ mem.o: mem.c
 print.o: print.c
 	$(CC) -c -o print.o print.c
 
+entry.o: entry.asm
+	nasm -f elf entry.asm
+
 clean:
 	@rm *.o *.bin 2>/dev/null || true

src/kernel/print.c

@@ -1,41 +1,60 @@
 #include "print.h"
+#include <stdint.h>
+#include <string.h>
 
-#define VGA_WIDTH 80
-#define VGA_HEIGHT 25
+#define ROWS 25
+#define COLUMNS 80
+#define BUF_SIZE ((ROWS * COLUMNS) * 2)
 
-char* vga_text_pos;
+#define BUF_START 0xb8000
+#define BUF_END (BUF_START + BUF_SIZE)
 
-void print_init(void)
+enum FG_COLOR
 {
-    vga_text_pos = (char*)0xb8000;
-}
+    FG_BLACK = 0x0,
+    FG_BLUE = 0x1,
+    FG_GREEN = 0x2,
+    FG_CYAN = 0x3,
+    FG_RED = 0x4,
+    FG_MAGENTA = 0x5,
+    FG_BROWN = 0x6,
+    FG_LIGHT_GRAY = 0x7,
+    FG_DARK_GRAY = 0x8,
+    FG_LIGHT_BLUE = 0x9,
+    FG_LIGHT_GREEN = 0xA,
+    FG_LIGHT_CYAN = 0xB,
+    FG_LIGHT_RED = 0xC,
+    FG_LIGHT_MAGENTA = 0xD,
+    FG_YELLOW = 0xE,
+    FG_WHITE = 0xF,
+};
 
-void print_newline(void)
+enum BG_COLOR
 {
-    vga_text_pos += 160 - ((vga_text_pos - (char*)0xb8000) % 160);
-}
+    BG_BLACK = 0x0,
+    BG_BLUE = 0x1,
+    BG_GREEN = 0x2,
+    BG_CYAN = 0x3,
+    BG_RED = 0x4,
+    BG_MAGENTA = 0x5,
+    BG_BROWN = 0x6,
+    BG_LIGHT_GRAY = 0x7,
+};
 
-void print_clr(const char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color)
+typedef struct
+{
+    uint8_t character;
+    uint8_t color;
+} vga_char;
+
+static vga_char* print_buf = (vga_char*)BUF_START;
+
+void kernel_print(const char* string)
 {
     for (int i = 0; string[i]; i++)
     {
-        *vga_text_pos++ = string[i];
-        *vga_text_pos++ = (bg_color << 4) | fg_color;
+        // todo(nub): scroll if overflowing
+
+        *print_buf++ = (vga_char){ string[i], FG_WHITE | BG_BLACK << 4 };
     }
 }
-
-void println_clr(const char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color)
-{
-    print_clr(string, fg_color, bg_color);
-    print_newline();
-}
-
-void print(const char* string)
-{
-    print_clr(string, VGA_FG_WHITE, VGA_BG_BLACK);
-}
-
-void println(const char* string)
-{
-    println_clr(string, VGA_FG_WHITE, VGA_BG_BLACK);
-}

src/kernel/print.h

@@ -1,41 +1 @@
-enum VGA_FG_COLOR
-{
-    VGA_FG_BLACK = 0x0,
-    VGA_FG_BLUE = 0x1,
-    VGA_FG_GREEN = 0x2,
-    VGA_FG_CYAN = 0x3,
-    VGA_FG_RED = 0x4,
-    VGA_FG_MAGENTA = 0x5,
-    VGA_FG_BROWN = 0x6,
-    VGA_FG_LIGHT_GRAY = 0x7,
-    VGA_FG_DARK_GRAY = 0x8,
-    VGA_FG_LIGHT_BLUE = 0x9,
-    VGA_FG_LIGHT_GREEN = 0xA,
-    VGA_FG_LIGHT_CYAN = 0xB,
-    VGA_FG_LIGHT_RED = 0xC,
-    VGA_FG_LIGHT_MAGENTA = 0xD,
-    VGA_FG_YELLOW = 0xE,
-    VGA_FG_WHITE = 0xF,
-};
-
-enum VGA_BG_COLOR
-{
-    VGA_BG_BLACK = 0x0,
-    VGA_BG_BLUE = 0x1,
-    VGA_BG_GREEN = 0x2,
-    VGA_BG_CYAN = 0x3,
-    VGA_BG_RED = 0x4,
-    VGA_BG_MAGENTA = 0x5,
-    VGA_BG_BROWN = 0x6,
-    VGA_BG_LIGHT_GRAY = 0x7,
-};
-
-void print_init(void);
-
-void print_newline(void);
-
-void print(const char* string);
-void println(const char* string);
-
-void print_clr(const char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color);
-void println_clr(const char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color);
+void kernel_print(const char* string);

src/makefile

@@ -1,4 +1,7 @@
-os.bin: boot/bootloader.bin kernel/kernel.bin zeroes.bin
+.PHONY: kernel/kernel.bin boot/bootloader.bin
+
+os.bin: boot/bootloader.bin kernel/kernel.bin
+	dd if=/dev/zero of=zeroes.bin bs=1 count=10240
 	cat boot/bootloader.bin kernel/kernel.bin zeroes.bin > os.bin
 
 kernel/kernel.bin:
@@ -7,9 +10,6 @@ kernel/kernel.bin:
 boot/bootloader.bin:
 	pushd boot; make bootloader.bin; popd
 
-zeroes.bin:
-	dd if=/dev/zero of=zeroes.bin bs=1 count=10240
-
 run: os.bin
 	qemu-system-x86_64 -drive file=os.bin,format=raw,index=0,media=disk