remove redundant readme command

.clang-format

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

.gitignore

@@ -1,2 +1 @@
-*.bin
-*.o
+.build

README.md

@@ -0,0 +1,23 @@
+# Nub OS
+
+## Dependencies
+
+- `make`
+- `grub`
+- `mtools`
+- `i386-elf-gcc`
+- `i386-elf-ld`
+
+## Building
+
+```sh
+make
+```
+
+## Running
+
+After building, run the following:
+
+```sh
+qemu-system-x86_64 -cdrom .build/nub-os.iso
+```

grub.cfg

@@ -0,0 +1,4 @@
+menuentry "nub-os" {
+    multiboot /boot/kernel.bin
+    boot
+}

makefile

@@ -1,26 +1,33 @@
-build: build/os.bin
-	@echo "Build succeded"
-	
-run: build/os.bin
-	qemu-system-x86_64 -drive file=build/os.bin,format=raw,index=0,media=disk
+CC = i386-elf-gcc
+LD = i386-elf-ld
 
-build/os.bin: build/boot.bin build/kernel.bin build/zeroes.bin
-	cat build/boot.bin build/kernel.bin build/zeroes.bin > build/os.bin
+CFLAGS = -ffreestanding -m32
 
-build/kernel.bin: build/kernel.o build/kernel_entry.o
-	i386-elf-ld -o build/kernel.bin -Ttext 0x1000 build/kernel_entry.o build/kernel.o --oformat binary
-
-build/kernel.o: src/kernel.c
-	i386-elf-gcc -ffreestanding -m32 -c -o build/kernel.o src/kernel.c
-
-build/kernel_entry.o: src/kernel_entry.asm
-	nasm -f elf -o build/kernel_entry.o src/kernel_entry.asm
-
-build/boot.bin: src/boot.asm
-	nasm -f bin -o build/boot.bin src/boot.asm
-
-build/zeroes.bin:
-	dd if=/dev/zero of=build/zeroes.bin bs=1 count=10240
+all: .build/nub-os.iso
 
 clean:
-	@rm build/* 2>/dev/null || true
+	@rm -r .build 2>/dev/null || true
+
+build-dir:
+	mkdir .build 2>/dev/null || true
+
+.build/nub-os.iso: build-dir .build/kernel.bin
+	mkdir -p .build/iso/boot/grub
+	cp grub.cfg .build/iso/boot/grub
+	cp .build/kernel.bin .build/iso/boot/
+	grub-mkrescue -o .build/nub-os.iso .build/iso/
+
+.build/kernel.bin: build-dir .build/entry.o .build/kernel.o .build/mem.o .build/print.o
+	$(LD) -Ttext 0x100000 -o .build/kernel.bin .build/entry.o .build/kernel.o .build/mem.o .build/print.o
+
+.build/kernel.o: build-dir src/kernel.c
+	$(CC) $(CFLAGS) -c -o .build/kernel.o src/kernel.c
+
+.build/mem.o: build-dir src/mem.c
+	$(CC) $(CFLAGS) -c -o .build/mem.o src/mem.c
+
+.build/print.o: build-dir src/print.c
+	$(CC) $(CFLAGS) -c -o .build/print.o src/print.c
+
+.build/entry.o: build-dir src/entry.asm
+	nasm -f elf -o .build/entry.o src/entry.asm

src/boot.asm

@@ -1,87 +0,0 @@
-[org 0x7c00]
-[bits 16]
-
-KERNEL_LOCATION equ 0x1000
-
-mov [BOOT_DISK], dl                 
-
-xor ax, ax                          
-mov es, ax
-mov ds, ax
-mov bp, 0x8000
-mov sp, bp
-
-mov bx, KERNEL_LOCATION
-mov dh, 2
-
-mov ah, 0x02
-mov al, dh 
-mov ch, 0x00
-mov dh, 0x00
-mov cl, 0x02
-mov dl, [BOOT_DISK]
-int 0x13
-
-                                    
-mov ah, 0x0
-mov al, 0x3
-int 0x10
-
-CODE_SEG equ gdt_code - gdt_start
-DATA_SEG equ gdt_data - gdt_start
-
-cli
-lgdt [gdt_descriptor]
-mov eax, cr0
-or eax, 1
-mov cr0, eax
-jmp CODE_SEG:start_protected_mode
-jmp $
-
-BOOT_DISK: db 0
-
-gdt_start:
-    gdt_null:
-        dd 0x0
-        dd 0x0
-
-    gdt_code:
-        dw 0xffff
-        dw 0x0
-        db 0x0
-        db 0b10011010
-        db 0b11001111
-        db 0x0
-
-    gdt_data:
-        dw 0xffff
-        dw 0x0
-        db 0x0
-        db 0b10010010
-        db 0b11001111
-        db 0x0
-
-gdt_end:
-
-gdt_descriptor:
-    dw gdt_end - gdt_start - 1
-    dd gdt_start
-
-[bits 32]
-start_protected_mode:
-    mov ax, DATA_SEG
-	mov ds, ax
-	mov ss, ax
-	mov es, ax
-	mov fs, ax
-	mov gs, ax
-	
-	mov ebp, 0x90000
-	mov esp, ebp
-
-    jmp KERNEL_LOCATION
-    jmp $
-
-
-times 510-($-$$) db 0
-dw 0xaa55

src/entry.asm

@@ -0,0 +1,21 @@
+extern kernel_init
+
+section .multiboot
+align 4
+    dd 0x1BADB002          ; multiboot magic number
+    dd 0x0                 ; flags
+    dd -(0x1BADB002+0x0)   ; checksum
+
+section .text
+global _start
+_start:
+    cli
+    mov esp, stack_top
+    call kernel_init
+.hang:
+    hlt
+    jmp .hang
+
+section .bss
+resb 8192
+stack_top:

src/kernel.c

@@ -1,5 +1,6 @@
-int main(void)
+#include "print.h"
+
+void kernel_init(void)
 {
-    *(char*)0xb8000 = 'A';
-    return 0;
-}
+    print("Starting nub-os\n");
+}

src/kernel_entry.asm

@@ -1,5 +0,0 @@
-section .text
-    [bits 32]
-    [extern main]
-    call main
-    jmp $

src/mem.c

@@ -0,0 +1,26 @@
+#include "mem.h"
+
+void* memcpy(void* dest, const void* src, long n)
+{
+    char* d = dest;
+    const char* s = src;
+    for (long i = 0; i < n; i++)
+        d[i] = s[i];
+    return dest;
+}
+
+void* memset(void* dest, int val, long n)
+{
+    char* d = dest;
+    for (long i = 0; i < n; i++)
+        d[i] = val;
+    return dest;
+}
+
+long strlen(const char* str)
+{
+    long len = 0;
+    while (str[len])
+        len++;
+    return len;
+}

src/mem.h

@@ -0,0 +1,3 @@
+void* memcpy(void* dest, const void* src, long n);
+void* memset(void* dest, int val, long n);
+long strlen(const char* str);

src/print.c

@@ -0,0 +1,125 @@
+#include "print.h"
+#include <stdint.h>
+
+#define ROWS 25
+#define COLUMNS 80
+#define BUF_SIZE ((ROWS * COLUMNS) * 2)
+
+#define BUF_START 0xb8000
+#define BUF_END (BUF_START + BUF_SIZE)
+
+enum FG_COLOR
+{
+    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,
+};
+
+enum BG_COLOR
+{
+    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,
+};
+
+typedef struct
+{
+    uint8_t character;
+    uint8_t color;
+} vga_char;
+
+static vga_char* vga_buffer = (vga_char*)BUF_START;
+static int cursor_row = 0;
+static int cursor_col = 0;
+
+void scroll(void)
+{
+    for (int row = 1; row < ROWS; row++)
+    {
+        for (int col = 0; col < COLUMNS; col++)
+        {
+            vga_buffer[(row - 1) * COLUMNS + col] = vga_buffer[row * COLUMNS + col];
+        }
+    }
+
+    for (int col = 0; col < COLUMNS; col++)
+    {
+        vga_buffer[(ROWS - 1) * COLUMNS + col] = (vga_char){ ' ', FG_WHITE | BG_BLACK << 4 };
+    }
+}
+
+void put_char(char c, uint8_t color)
+{
+    if (c == '\n')
+    {
+        cursor_col = 0;
+        cursor_row++;
+    }
+    else
+    {
+        vga_buffer[cursor_row * COLUMNS + cursor_col] = (vga_char){ c, color };
+        cursor_col++;
+    }
+
+    if (cursor_col >= COLUMNS)
+    {
+        cursor_col = 0;
+        cursor_row++;
+    }
+
+    if (cursor_row >= ROWS)
+    {
+        scroll();
+        cursor_row = ROWS - 1;
+    }
+}
+
+void print(const char* string)
+{
+    uint8_t color = FG_WHITE | BG_BLACK << 4;
+
+    for (int i = 0; string[i]; i++)
+    {
+        put_char(string[i], color);
+    }
+}
+
+void clear_screen(void)
+{
+    uint8_t color = FG_WHITE | BG_BLACK << 4;
+
+    for (int i = 0; i < ROWS * COLUMNS; i++)
+    {
+        vga_buffer[i] = (vga_char){ ' ', color };
+    }
+
+    cursor_row = 0;
+    cursor_col = 0;
+}
+
+void set_cursor_position(int row, int col)
+{
+    if (row >= 0 && row < ROWS && col >= 0 && col < COLUMNS)
+    {
+        cursor_row = row;
+        cursor_col = col;
+    }
+}

src/print.h

@@ -0,0 +1,8 @@
+#include <stdint.h>
+
+void kernel_print(const char* string);
+
+void put_char(char c, uint8_t color);
+void print(const char* string);
+void clear_screen(void);
+void set_cursor_position(int row, int col);