Add first steps for VBR bootloader

Makefile

@@ -1,7 +1,14 @@
 default: kernel.com
 
 kernel.com: kernel/*.asm
-	nasm -s -o kernel.com -I kernel kernel/main.asm
+	nasm -s -o $@ -I kernel kernel/main.asm
+
+vbr.bin: boot/vbr.asm
+	nasm -s -o $@ -I lib $<
+
+fdimage.img: vbr.bin kernel.com
+	dd if=/dev/zero bs=512 count=720 of=$@
+	dd if=vbr.bin bs=512 count=1 conv=notrunc of=$@
 
 clean:
 	rm -f *.com

boot/vbr.asm

@@ -0,0 +1,49 @@
+org 0x7C00
+
+bpb:
+  jmp _startup ; 2 bytes
+  nop ; 1 byte
+.oem:
+  db "2A      "	; OEM
+.bps:
+  dw 0x200	; bytes per sector
+.spc:
+  db 1		; sectors per cluster
+.rsectors:
+  dw 2		; number of reserved sectors
+.fatcnt:
+  db 2		; number of file allocation tables
+.dirents:
+  dw 2		; Number of directory entries
+.seccnt:
+  dw 720	; total number of sectors
+.mtd:		; media descriptor type
+  db 0xFD	; 5.25-inch Double sided, 40 tracks per side, 9 sectors per track (360 KB)
+.spfat:		; sectors per fat
+  dw 0
+.spt:
+  dw 9		; sectors per track
+.headcnt:
+  dw 2		; number of heads
+.hidseccnt:
+  dd 0		; number of hidden sectors
+.lrgseccnt:
+  dd 0		; large sector count
+
+times (0x3E - ($-$$)) nop
+
+_startup:
+  mov ah, 0x08
+  mov dl, 0x00
+  int 0x13
+  mov ax, cx
+  and ax, 0x003F
+  call print16
+.end:
+  hlt
+  jmp .end
+
+%include "print.asm"
+
+times (0x1FE - ($-$$)) nop
+dw 0xAA55

run-floppy.sh

@@ -0,0 +1,2 @@
+#!/bin/sh
+exec qemu-system-x86_64 -fda fdimage.img