From 94ca8c935fb089af62b50d076e0370f7d55cdbef Mon Sep 17 00:00:00 2001
From: Tom-on64 <kubecekt@gmail.com>
Date: Sun, 5 Jan 2025 18:20:15 +0100
Subject: [PATCH] Added AMAZING boot menu to KBOOT

---
 boot/stage1/bootsect.s |   7 +-
 boot/stage1/gdt.s      |   4 +-
 boot/stage2/attr.h     |   9 +++
 boot/stage2/disk.c     |  24 +++++++
 boot/stage2/disk.h     |  35 ++++++++++
 boot/stage2/entry.c    |  97 +++++++++++++++++++++++++++-
 boot/stage2/kbd.c      |  12 ++++
 boot/stage2/kbd.h      |  19 ++++++
 boot/stage2/linker.ld  |  13 ++--
 boot/stage2/menu.c     |  73 +++++++++++++++++++++
 boot/stage2/menu.h     |  33 ++++++++++
 boot/stage2/port.h     |  33 ++++++++++
 boot/stage2/stdarg.h   |  10 +++
 boot/stage2/stdint.h   |  22 +++++++
 boot/stage2/stdio.c    | 141 +++++++++++++++++++++++++++++++++++++++++
 boot/stage2/stdio.h    |  25 ++++++++
 boot/stage2/string.c   |  74 +++++++++++++++++++++
 boot/stage2/string.h   |  15 +++++
 defaults.mk            |   2 +-
 docs/coding-style.txt  |  16 +++++
 libc/string/itoa.c     |   1 +
 makefile               |   2 +-
 22 files changed, 651 insertions(+), 16 deletions(-)
 create mode 100644 boot/stage2/attr.h
 create mode 100644 boot/stage2/disk.c
 create mode 100644 boot/stage2/disk.h
 create mode 100644 boot/stage2/kbd.c
 create mode 100644 boot/stage2/kbd.h
 create mode 100644 boot/stage2/menu.c
 create mode 100644 boot/stage2/menu.h
 create mode 100644 boot/stage2/port.h
 create mode 100644 boot/stage2/stdarg.h
 create mode 100644 boot/stage2/stdint.h
 create mode 100644 boot/stage2/stdio.c
 create mode 100644 boot/stage2/stdio.h
 create mode 100644 boot/stage2/string.c
 create mode 100644 boot/stage2/string.h

diff --git a/boot/stage1/bootsect.s b/boot/stage1/bootsect.s
index 354f227..2de8a2f 100644
--- a/boot/stage1/bootsect.s
+++ b/boot/stage1/bootsect.s
@@ -11,6 +11,7 @@ jmp short .bpb_end
 nop
 
 ; FAT32 Bios Parameter Block
+; Some BIOSes mess with it so we just leave it blank
 .bpb:
 	.bpb_oem_id:		db "KERN    "
 	.bpb_sector_size:	dw 0
@@ -115,17 +116,17 @@ err:
 	[bits 32]
 	; Protected mode entry vector
 vector: 
-	mov eax, 0x10
+	mov ax, 0x10
 	mov ds, ax
 	mov es, ax
 	mov fs, ax
 	mov gs, ax
 	mov ss, ax
 
-	and edx, 0xff
+	and edx, 0xff	; Still should be boot drive number
 
 	; Call stage 2 bootloader
-	call 0x70000
+	call code_seg:0x70000
 
 ; Padding and boot signature
 times 510-($-$$) db 0
diff --git a/boot/stage1/gdt.s b/boot/stage1/gdt.s
index 192fde7..edade70 100644
--- a/boot/stage1/gdt.s
+++ b/boot/stage1/gdt.s
@@ -24,5 +24,5 @@ gdtp:
     dd gdt                  ; Pointer
 
 ; Segments
-code_seg equ gdt.code_desc - gdt
-data_seg equ gdt.data_desc - gdt
+code_seg: equ gdt.code_desc - gdt
+data_seg: equ gdt.data_desc - gdt
diff --git a/boot/stage2/attr.h b/boot/stage2/attr.h
new file mode 100644
index 0000000..870eeeb
--- /dev/null
+++ b/boot/stage2/attr.h
@@ -0,0 +1,9 @@
+#ifndef ATTR_H
+#define ATTR_H
+
+#define __packed 		__attribute__((packed))
+#define __naked			__attribute__((naked))
+#define __section(_sect) 	__attribute__((section(_sect)))
+#define noreturn 		__attribute__((noreturn))
+
+#endif
diff --git a/boot/stage2/disk.c b/boot/stage2/disk.c
new file mode 100644
index 0000000..b46267d
--- /dev/null
+++ b/boot/stage2/disk.c
@@ -0,0 +1,24 @@
+#include "stdint.h"
+#include "port.h"
+#include "disk.h"
+
+void readSectors(uint32_t lba, size_t count, void* dst) {
+	outb(PIO_PORT + 6, ((lba >> 24) & 0x0f) | 0xe0);
+	outb(PIO_PORT + 2, count);
+	outb(PIO_PORT + 3, lba & 0xff);
+	outb(PIO_PORT + 4, (lba >> 8) & 0xff);
+	outb(PIO_PORT + 5, (lba >> 16) & 0xff);
+	outb(PIO_PORT + 7, PIO_CMD_READ);
+
+	uint16_t* buf = (uint16_t*)dst;
+
+	for (size_t i = 0; i < count; i++) {
+		while (inb(PIO_PORT + 7) & (1 << 7));	// Wait until BSY is cleared
+		for (size_t j = 0; j < SECTOR_SIZE / 2; j++) *buf++ = inw(PIO_PORT);
+		for (uint8_t wait = 0; wait < 4; wait++) inb(PIO_ALT_STATUS);
+	}
+}
+
+/* TODO */
+void writeSectors(uint32_t lba, size_t count, void* src) {}
+
diff --git a/boot/stage2/disk.h b/boot/stage2/disk.h
new file mode 100644
index 0000000..0c36bab
--- /dev/null
+++ b/boot/stage2/disk.h
@@ -0,0 +1,35 @@
+#ifndef DISK_H
+#define DISK_H
+
+#include "stdint.h"
+#include "attr.h"
+
+#define SECTOR_SIZE	512
+#define PIO_PORT	0x1f0
+#define PIO_ALT_STATUS	0x3f6
+#define PIO_MASTER	0xa0
+#define PIO_CMD_READ	0x20
+#define PIO_CMD_WRITE	0x30
+#define PIO_CMD_FLUSH	0	// TODO
+
+#define BOOTABLE	0x80
+
+struct partition {
+	uint8_t bootable;
+	uint8_t startCHS[3];
+	uint8_t type;
+	uint8_t endCHS[3];
+	uint32_t startLBA;
+	uint32_t size;
+} __packed;
+
+struct MBR {
+	uint8_t bootstrap[446];
+	struct partition partitions[4];
+	uint16_t signature;
+} __packed;
+
+void readSectors(uint32_t lba, size_t count, void* buffer);
+void writeSectors(uint32_t lba, size_t count, void* buffer);
+
+#endif
diff --git a/boot/stage2/entry.c b/boot/stage2/entry.c
index b82e250..6e7c91d 100644
--- a/boot/stage2/entry.c
+++ b/boot/stage2/entry.c
@@ -1,3 +1,98 @@
-void entry() {
+#include "stdint.h"
+#include "stdio.h"
+#include "attr.h"
+#include "disk.h"
+#include "menu.h"
+#include "kbd.h"
+
+void drawPartitions(struct MBR* mbr, uint8_t sel);
+void partitonInfo(struct partition* part);
+
+__section("entry")
+noreturn void main() {
+	keyboardInit();
+
+	struct MBR mbr;
+	readSectors(0, 1, &mbr);
+
+	// Select bootable partition by default
+	uint8_t selected = 0;
+	for (size_t i = 0; i < 4; i++) {
+		if (mbr.partitions[i].bootable != BOOTABLE) continue;
+		selected = i;
+		break;
+	}
+	
+	// Initial draw
+	setAttr(0x0f);
+	cls();
+	hideCursor();
+	rect(0, 0, COLS, ROWS);
+	hline(0, 2, COLS);
+	setAttr(0x02);
+	text(COLS / 2, 1, "KBOOT");
+	drawPartitions(&mbr, selected);
+	partitonInfo(&mbr.partitions[selected]);
+
+	while (1) {
+		// Check for up/down arrow keys or enter
+		uint8_t scancode = getScancode();
+		if (scancode == SC_ENTER) { // Boot selected
+			if (mbr.partitions[selected].type != 0) break;
+
+			// Don't allow booting an unused partition
+			setAttr(0x4f);
+			text(COLS / 2, ROWS / 2 + 6, "Unused Partition");
+		} else if (scancode != SC_EXTENDED) continue; // Not an arrow key
+		
+		scancode = getScancode();
+		if (scancode == SCE_ARROW_UP) selected--;
+		else if (scancode == SCE_ARROW_DOWN) selected++;
+		else continue;
+
+		if (selected == 0xff) selected = 3;
+		else if (selected == 4) selected = 0;
+
+		// Redraw
+		drawPartitions(&mbr, selected);
+		partitonInfo(&mbr.partitions[selected]);
+	}
+
+	setAttr(0x0f);
+	cls();
+	showCursor();
+	printf("Booting from Partition %d...", selected);
+
 	while (1);
 }
+
+void drawPartitions(struct MBR* mbr, uint8_t sel) {
+	uint32_t basey = ROWS / 2 - 2;
+	for (size_t i = 0; i < 4; i++) {
+		if (i == sel) setAttr(0xf0);
+		else if (mbr->partitions[i].type == 0) setAttr(0x04);
+		else setAttr(0x0f);
+
+		text(COLS / 2, basey + i, " [ Partition %d ] ", i+1);
+	}
+}
+
+void partitonInfo(struct partition* part) {
+	uint32_t basey = ROWS / 2 + 6;
+	setAttr(0x02);
+
+	// Clear previous text
+	fill(1, basey, COLS - 2, 3, '\0');
+
+	if (part->type == 0) {
+		text(COLS / 2, basey, "Unused Partition");
+		return;
+	}
+
+	text(COLS / 2, basey, "Type: %02x%s", part->type, 
+		(part->bootable == BOOTABLE) ? "  Bootable" : "");
+	text(COLS / 2, basey + 1, "Start LBA: %d; End LBA: %d", 
+		part->startLBA, part->startLBA + part->size);
+	text(COLS / 2, basey + 2, "Length: 0x%x", part->size);
+}
+
diff --git a/boot/stage2/kbd.c b/boot/stage2/kbd.c
new file mode 100644
index 0000000..111db1b
--- /dev/null
+++ b/boot/stage2/kbd.c
@@ -0,0 +1,12 @@
+#include "stdint.h"
+#include "port.h"
+#include "kbd.h"
+
+// TODO: Maybe do some setup?
+int keyboardInit() { return 0; }
+
+uint8_t getScancode() {
+	while (inb(PS2_STAT_PORT) & 0x01 == 0);
+	return inb(PS2_DATA_PORT);
+}
+
diff --git a/boot/stage2/kbd.h b/boot/stage2/kbd.h
new file mode 100644
index 0000000..f197099
--- /dev/null
+++ b/boot/stage2/kbd.h
@@ -0,0 +1,19 @@
+#ifndef _KBD_H
+#define _KBD_H
+
+#include "stdint.h"
+
+#define PS2_DATA_PORT	0x60
+#define PS2_STAT_PORT	0x64
+
+// Scancodes
+#define SC_ENTER	0x1C
+#define SC_EXTENDED	0xE0
+// Extended scancodes
+#define SCE_ARROW_UP	0x48
+#define SCE_ARROW_DOWN	0x50
+
+int keyboardInit();
+uint8_t getScancode();
+
+#endif
diff --git a/boot/stage2/linker.ld b/boot/stage2/linker.ld
index 55e53c4..6e83aea 100644
--- a/boot/stage2/linker.ld
+++ b/boot/stage2/linker.ld
@@ -1,27 +1,24 @@
 OUTPUT_FORMAT(binary)
-ENTRY(entry)
+OUTPUT_ARCH(i386)
 
 SECTIONS {
-	/* Will be loaded at 0x70000 */
 	. = 0x70000;
 
 	.text : {
+		*(entry)
 		*(.text)
-		*(.text.*)
+	}
+
+	.rodata : {
 		*(.rodata)
-		*(.rodata.*)
 	}
 
 	.data : {
 		*(.data)
-		*(.data.*)
 	}
 
 	.bss : {
 		*(COMMON)
 		*(.bss)
-		*(.bss.*)
 	}
-
-	_end = .;
 }
diff --git a/boot/stage2/menu.c b/boot/stage2/menu.c
new file mode 100644
index 0000000..ff23a24
--- /dev/null
+++ b/boot/stage2/menu.c
@@ -0,0 +1,73 @@
+#include "stdarg.h"
+#include "stdint.h"
+#include "string.h"
+#include "stdio.h"
+#include "menu.h"
+
+/*
+ * The reason we subtract one from the width and height (or length) is because 
+ * we use the (in this example) width to offset from the (in this example) x 
+ * position. If something has a width of 1 character, the end of it should be 
+ * at 'x + w', so if 'w' were 1, it would be off by one. Therefore we subtract 
+ * one from the given dimensions.
+ */
+
+void rect(uint32_t x, uint32_t y, uint32_t _w, uint32_t _h) {
+	if (_w < 2 || _h < 2) return;
+	uint32_t w = _w - 1;
+	uint32_t h = _h - 1;
+	
+	// Top
+	putat(y, x, CORNER_TL);
+	for (size_t dx = 1; dx < w; dx++) putat(y, x + dx, LINE_H);
+	putat(y, x + w, CORNER_TR);
+
+	// Sides
+	for (size_t dy = 1; dy < h; dy++) {
+		putat(y + dy, x, LINE_V);
+		putat(y + dy, x + w, LINE_V);
+	}
+
+	// Bottom
+	putat(y + h, x, CORNER_BL);
+	for (size_t dx = 1; dx < w; dx++) putat(y + h, x + dx, LINE_H);
+	putat(y + h, x + w, CORNER_BR);
+}
+
+void fill(uint32_t x, uint32_t y, uint32_t w, uint32_t h, char c) {
+	// We don't add one to the dimensions here
+	for (size_t dy = 0; dy < h; dy++) {
+		for (size_t dx = 0; dx < w; dx++) {
+			putat(y + dy, x + dx, c);
+		}
+	}
+}
+
+void hline(uint32_t x, uint32_t y, uint32_t _len) {
+	uint32_t len = _len - 1;
+	putat(y, x, LINE_T_RIGHT);
+	for (size_t dx = 1; dx < len; dx++) putat(y, x + dx, LINE_H);
+	putat(y, x + len, LINE_T_LEFT);
+}
+
+void vline(uint32_t x, uint32_t y, uint32_t _len) {
+	uint32_t len = _len - 1;
+	putat(y, x, LINE_T_DOWN);
+	for (size_t dy = 1; dy < len; dy++) putat(y + dy, x, LINE_V);
+	putat(y + len, x, LINE_T_UP);
+}
+
+void text(uint32_t x, uint32_t y, char* fmt, ...) {
+	va_list args;
+	va_start(args, fmt);
+	char buf[256];
+	vsnprintf(buf, 256, fmt, args);
+	va_end(args);
+
+	uint32_t len = strlen(buf);
+	uint32_t basex = x - len / 2;
+
+	size_t i = 0;
+	while (buf[i] != '\0') putat(y, basex + i, buf[i++]);
+}
+
diff --git a/boot/stage2/menu.h b/boot/stage2/menu.h
new file mode 100644
index 0000000..b85b961
--- /dev/null
+++ b/boot/stage2/menu.h
@@ -0,0 +1,33 @@
+#ifndef _MENU_H
+#define _MENU_H
+
+// Box drawing characters
+#define SHADE_LIGHT	0xB0
+#define SHADE_MEDIUM	0xB1
+#define SHADE_DARK	0xB2
+#define LINE_V		0xB3
+#define LINE_T_LEFT	0xB4
+#define CORNER_TR	0xBF
+#define CORNER_BL	0xC0
+#define LINE_T_UP	0xC1
+#define LINE_T_DOWN	0xC2
+#define LINE_T_RIGHT	0xC3
+#define LINE_H		0xC4
+#define LINE_CROSS	0xC5
+#define CORNER_BR	0xD9
+#define CORNER_TL	0xDA
+#define BLOCK		0xDB
+#define BLOCK_UPPER	0xDC
+#define BLOCK_LEFT	0xDD
+#define BLOCK_RIGHT	0xDE
+#define BLOCK_LOWER	0xDF
+#define INT_UPPER	0xF4
+#define INT_LOWER	0xF5
+
+void rect(uint32_t x, uint32_t y, uint32_t w, uint32_t h);
+void fill(uint32_t x, uint32_t y, uint32_t w, uint32_t h, char c);
+void hline(uint32_t x, uint32_t y, uint32_t len);
+void vline(uint32_t x, uint32_t y, uint32_t len);
+void text(uint32_t x, uint32_t y, char* fmt, ...);
+
+#endif
diff --git a/boot/stage2/port.h b/boot/stage2/port.h
new file mode 100644
index 0000000..789fe07
--- /dev/null
+++ b/boot/stage2/port.h
@@ -0,0 +1,33 @@
+#ifndef PORT_H
+#define PORT_H
+
+#include "stdint.h"
+
+inline uint8_t inb(uint16_t port) {
+    uint8_t result;
+    __asm__ volatile("inb %1, %0" : "=a"(result) : "Nd"(port));
+    return result;
+}
+inline void outb(uint16_t port, uint8_t data) { 
+    __asm__ volatile("outb %0, %1" :: "a"(data), "Nd"(port));
+}
+
+inline uint16_t inw(uint16_t port) {
+    uint16_t result;
+    __asm__ volatile("inw %1, %0" : "=a"(result) : "Nd"(port));
+    return result;
+}
+inline void outw(uint16_t port, uint16_t data) {
+    __asm__ volatile("outw %0, %1" :: "a"(data), "Nd"(port));
+}
+
+inline uint32_t inl(uint16_t port) {
+    uint32_t result;
+    __asm__ volatile("inl %1, %0" : "=a"(result) : "Nd"(port));
+    return result;
+}
+inline void outl(uint16_t port, uint32_t data) {
+    __asm__ volatile("outl %0, %1" :: "a"(data), "Nd"(port));
+}
+
+#endif
diff --git a/boot/stage2/stdarg.h b/boot/stage2/stdarg.h
new file mode 100644
index 0000000..4d1e8ac
--- /dev/null
+++ b/boot/stage2/stdarg.h
@@ -0,0 +1,10 @@
+#ifndef _STDARG_H
+#define _STDARG_H
+
+typedef char* va_list;
+#define va_start(ap, paramn) (void)((ap) = (char*)(&(paramn) + 1))
+#define va_end(ap) (void)((ap) = 0)
+#define va_arg(ap, type) (((type*)((ap) = ((ap) + sizeof(type))))[-1])
+
+#endif
+
diff --git a/boot/stage2/stdint.h b/boot/stage2/stdint.h
new file mode 100644
index 0000000..cb6d964
--- /dev/null
+++ b/boot/stage2/stdint.h
@@ -0,0 +1,22 @@
+#ifndef _STDINT_H
+#define _STDINT_H
+
+#define NULL ((void*)0)
+
+// Naitive size
+typedef unsigned int size_t;
+typedef signed int ssize_t;
+
+// Signed ints
+typedef signed char int8_t;
+typedef signed short int16_t;
+typedef signed int int32_t;
+typedef signed long long int64_t;
+
+// Unsigned ints
+typedef unsigned char uint8_t;
+typedef unsigned short uint16_t;
+typedef unsigned int uint32_t;
+typedef unsigned long long uint64_t;
+
+#endif
diff --git a/boot/stage2/stdio.c b/boot/stage2/stdio.c
new file mode 100644
index 0000000..3b75ee6
--- /dev/null
+++ b/boot/stage2/stdio.c
@@ -0,0 +1,141 @@
+#include "stdarg.h"
+#include "stdint.h"
+#include "string.h"
+#include "stdio.h"
+#include "port.h"
+
+static uint32_t xpos;
+static uint32_t ypos;
+static uint8_t attr;
+
+void setAttr(uint8_t newattr) {
+	attr = newattr;
+}
+
+void setCursor(uint32_t row, uint32_t col) {
+	xpos = col;
+	ypos = row;
+	updateCursor();
+}
+
+void updateCursor() {
+	uint16_t pos = xpos + ypos * COLS;
+
+	outb(0x3d4, 0x0f);
+	outb(0x3d5, pos & 0xff);
+	outb(0x3d4, 0x0e);
+	outb(0x3d5, (pos >> 8) & 0xff);
+}
+
+void hideCursor() {
+	outb(0x3d4, 0x0a);
+	outb(0x3d5, 0x20);
+}
+
+void showCursor() {
+	uint8_t start 	= 0;
+	uint8_t end 	= 15;
+
+	outb(0x3d4, 0x0a);
+	outb(0x3d5, (inb(0x3d5) & 0xc0) | start);
+	outb(0x3d4, 0x0b);
+	outb(0x3d5, (inb(0x3d5) & 0xe0) | end);
+}
+
+void cls() {
+	uint8_t* vidmem = (uint8_t*)VIDMEM;
+
+	for (size_t i = 0; i < ROWS * COLS; i++) {
+		vidmem[i * 2] = 0;
+		vidmem[i * 2 + 1] = attr;
+	}
+	
+	xpos = 0;
+	ypos = 0;
+	updateCursor();
+}
+
+void putat(uint32_t row, uint32_t col, int c) {
+	uint8_t* vidmem = (uint8_t*)VIDMEM;
+	vidmem[(col + row * COLS) * 2] = c & 0xFF;
+	vidmem[(col + row * COLS) * 2 + 1] = attr;
+}
+
+void newline() {
+	xpos = 0;
+	ypos++;
+	if (ypos >= ROWS) ypos = 0;
+	updateCursor();
+}
+
+void putc(int c) {
+	putat(ypos, xpos, c);
+	xpos++;
+	if (xpos >= COLS) newline();
+	updateCursor();
+}
+
+void puts(char* s) {
+	while (*s != '\0') {
+		if (*s == '\n' || *s == '\r') {
+			newline();
+			s++;
+		} else putc(*s++);
+	}
+}
+
+int vsnprintf(void* buf, size_t len, char* fmt, va_list args) {
+	char* str = (char*)buf;
+	size_t pos = 0;
+
+	while (*fmt != '\0') {
+		if (*fmt != '%') {
+			if (pos < len - 1) str[pos++] = *fmt++;
+			continue;
+		}
+
+		fmt++;
+		char pad = ' ';
+		int width = 0;
+
+		// TODO: padding
+		if (*fmt == '0') pad = '0';
+		while (*fmt >= '0' && *fmt <= '9') {
+			width *= 10;
+			width += *fmt++ - '0';
+		}
+
+		// DO NOT TALK ABOUT THIS ABOMINATION
+		char* s;
+		switch (*fmt++) {
+		case 'd': s = itoa(va_arg(args, int), 10); goto string;
+		case 'x': s = itoa(va_arg(args, int), 16); goto string;
+		case 's': s = va_arg(args, char*);
+		string: while (*s != '\0' && pos < len - 1) str[pos++] = *s++; break;
+		case 'c': if (pos < len - 1) str[pos++] = va_arg(args, char); break;
+		case '%': if (pos < len - 1) str[pos++] = '%'; break;
+		default:
+			if (pos < len - 1) str[pos++] = '%';
+			if (pos < len - 1) str[pos++] = *(fmt - 1);
+			break;
+		}
+	}
+
+	if (len > 0) {
+		if (pos < len) str[pos++] = '\0';
+		else str[len - 1] = '\0';	// Shouldn't be able to be reached, but who knows
+	}
+
+	return pos;
+}
+
+int printf(char* fmt, ...) {
+	va_list args;
+	va_start(args, fmt);
+	char buf[256];
+	int ret = vsnprintf(buf, 256, fmt, args);
+	va_end(args);
+	puts(buf);
+	return ret;
+}
+
diff --git a/boot/stage2/stdio.h b/boot/stage2/stdio.h
new file mode 100644
index 0000000..9ce4b05
--- /dev/null
+++ b/boot/stage2/stdio.h
@@ -0,0 +1,25 @@
+#ifndef _STDIO_H
+#define _STDIO_H
+
+#include "stdarg.h"
+#include "stdint.h"
+
+#define VIDMEM	0xb8000
+#define COLS	80
+#define ROWS	25
+
+void setAttr(uint8_t attr);
+void setCursor(uint32_t row, uint32_t col);
+void updateCursor();
+void hideCursor();
+void showCursor();
+
+void cls();
+void newline();
+void putc(int c);
+void puts(char* s);
+int printf(char* fmt, ...);
+int vsnprintf(void* buf, size_t len, char* fmt, va_list args);
+void putat(uint32_t row, uint32_t col, int c);
+
+#endif
diff --git a/boot/stage2/string.c b/boot/stage2/string.c
new file mode 100644
index 0000000..3d67650
--- /dev/null
+++ b/boot/stage2/string.c
@@ -0,0 +1,74 @@
+#include "stdint.h"
+#include "string.h"
+
+char* itoa(size_t val, int base) {
+	static char buf[32] = { 0 };
+
+	if (base == 0 || base > 16) return NULL; 
+
+	if (val == 0) {
+		buf[0] = '0';
+		buf[1] = '\0';
+		return buf;
+	}
+
+	int i;
+	buf[31] = '\0';
+	for (i = 30; val && i; i--, val /= base) {
+		buf[i] = "0123456789abcdef"[val % base];
+	}
+
+	return &buf[i + 1];
+}
+
+void* memcpy(void* src, void* dst, size_t length) {
+	uint8_t* p = dst;
+	size_t i = 0;
+	while (i < length) p[i] = *(uint8_t*)(src + i);
+	return dst;
+}
+
+void* memset(void* dst, uint8_t val, size_t length) {
+	uint8_t* p = dst;
+	size_t i = 0;
+	while (i < length) p[i++] = val;
+	return dst;
+}
+
+char* strcpy(char* str1, const char* str2) {
+	char* p = str1;
+	while (*str2 != '\0') *p++ = *str2++;
+	return str1;
+}
+
+char* strcat(char* str1, const char* str2) {
+	char* p = str1;
+	while (*str2++ != '\0');
+	while (*str2 != '\0') *p++ = *str2++;
+	return str1;
+}
+
+char* strchr(const char* str, char c) {
+	char* p = (char*)str;
+	while (*p != '\0' && *p != c) p++;
+    	return (*p == c) ? p : NULL;
+}
+
+int strcmp(const char* str1, const char* str2) {
+    while (*str1 != '\0' && *str1 == *str2) {
+        str1++;
+        str2++;
+    }
+
+    uint8_t c1 = (*(uint8_t*)str1);
+    uint8_t c2 = (*(uint8_t*)str2);
+
+    return ((c1 < c2) ? -1 : (c1 > c2));
+}
+
+size_t strlen(const char* str) {
+	size_t len = 0;
+	while (str[len++] != '\0');
+	return len;
+}
+
diff --git a/boot/stage2/string.h b/boot/stage2/string.h
new file mode 100644
index 0000000..7f65eaf
--- /dev/null
+++ b/boot/stage2/string.h
@@ -0,0 +1,15 @@
+#ifndef _STRING_H
+#define _STRING_H
+
+#include "stdint.h"
+
+char* itoa(size_t val, int base);
+void* memcpy(void* src, void* dst, size_t length);
+void* memset(void* dst, uint8_t value, size_t length);
+char* strcpy(char* str1, const char* str2);
+char* strcat(char* str1, const char* str2);
+char* strchr(const char* str, char c);
+int strcmp(const char* str1, const char* str2);
+size_t strlen(const char* str);
+
+#endif
diff --git a/defaults.mk b/defaults.mk
index 9c85750..d808bbf 100644
--- a/defaults.mk
+++ b/defaults.mk
@@ -8,7 +8,7 @@ OBJCOPY = i686-elf-objcopy
 MAKE = make
 
 # Flags
-HOSTCFLAGS = -Wall -Wextra -Wpedantic -O2 -std=c17 -g
+HOSTCFLAGS = -Wall -Wextra -Wpedantic -Os -std=c17 -g
 CFLAGS = -Wall -Wextra -Wpedantic -Wno-pointer-arith\
 	 -ffreestanding -fno-stack-protector -fno-builtin -fno-pie -fcommon\
 	 -O2 -std=c17 -nostdinc -nostdlib -z notext -march=i386 -g
diff --git a/docs/coding-style.txt b/docs/coding-style.txt
index e51e283..56a5a98 100644
--- a/docs/coding-style.txt
+++ b/docs/coding-style.txt
@@ -196,3 +196,19 @@ The prefered way of ordering '#include' directives is as so:
 Directives should be ordered by lenght, descending. If two or more includes
 have the same length, order alphabetically.
 
+Header Guards
+*************
+`#ifndef X #define X` header guards are preffered. To avoid conflicts they 
+should follow this format:
+`#define _PATH_TO_HEADER_H`
+
+For example `drivers/fat32.h would have this guard:
+```
+#ifndef _DRIVERS_FAT32_H
+#define _DRIVERS_FAT32_H
+
+/* Header stuff */
+
+#endif
+```
+
diff --git a/libc/string/itoa.c b/libc/string/itoa.c
index 478e5e1..55c8098 100644
--- a/libc/string/itoa.c
+++ b/libc/string/itoa.c
@@ -8,6 +8,7 @@ char* itoa(size_t val, int base) {
 
     if (val == 0) {
         buf[0] = '0';
+	buf[1] = '\0';
         return buf;
     }
  
diff --git a/makefile b/makefile
index 7966e1b..1832629 100644
--- a/makefile
+++ b/makefile
@@ -29,7 +29,7 @@ clean:
 qemu:
 	qemu-system-x86_64\
 		-drive format=raw,file=$(IMG),index=0,media=disk\
-		-m 256M -accel tcg -monitor stdio\
+		-m 256M -accel tcg -monitor stdio -net none\
 		-rtc base=localtime,clock=host,driftfix=slew\
 		-audiodev coreaudio,id=audio0 -machine pcspk-audiodev=audio0