Use COM-based format, get bootloader working

kernel/main.asm

@@ -1,60 +1,5 @@
 cpu 8086
-org 0x0000
-rom:
-  db 0x55, 0xAA
-.sectors:
-  db 0x00
-.init:
-  push cs
-  pop es
-
-  mov di, start
-  mov ax, 0x18
-  call intr_register
-
-  retf
-.name:
-  db "ROM DOS", 0
-
-  times (0x18 - ($-$$)) db 0
-.pcir_ptr:
-  dw 0
-
-  times (0x1A - ($-$$)) db 0
-.pnp_ptr:
-  dw pnp
-
-pnp:
-  db "$PnP"
-.version:
-  db 1 ; version 1
-.length:
-  db 2 ; 2 * 16 length
-  dw 0 ; offset of next header
-  db 0
-.checksum:
-  db 0 ; checksum (filled by fix-rom)
-  dd 0 ; device identifier
-  dw 0 ; manufacturer string
-  dw rom.name ; product name string
-  db 0,0,0 ; device type string
-  db 0x20 ; device indicator, bit for "read cacheable" set
-  dw 0 ; boot connection vector
-  dw 0 ; boot disconnect vector
-  dw start ; bootstrap entry point
-  dw 0 ; reserved
-  dw 0
-
-start:
-  xor ax, ax
-  mov ds, ax
-  mov es, ax
-  mov ss, ax
-  mov sp, 0x800
-  mov di, sp
-
-  call drvtab_create
-
+org 0x0100
   push cs
   pop es
   mov di, isr_dos_main
@@ -64,7 +9,6 @@ start:
 .loop:
   mov ah, 0x01
   int 0x21
-  int3
   jmp .loop
 
   cli
@@ -91,4 +35,4 @@ isr_return:
 
 %include "chario.asm"
 
-align 512
+times 1000 db 0xEA