Change kernel blob format to be option rom compatible

boot/floppy.asm

@@ -48,10 +48,6 @@ _startup:
   ; setup stack area growing down from 0x10000
   mov ss, ax
   mov sp, ax
-  ; backup important values
-  push bx
-  push cx
-  push dx
   ; adjust CS
   jmp 0x07C0:main
 
@@ -63,6 +59,11 @@ rootdir:
   dw 0
 
 main:
+  ; backup important values
+  push bx
+  push cx
+  push dx
+
   ; setup buffer area directly at 4k
   mov ax, 0x0100
   mov ds, ax
@@ -78,13 +79,16 @@ main:
 
   ; restore important variables
   xor ax, ax
-  mov bp, ax
-  mov si, ax
-  mov di, ax
   pop dx
   pop cx
   pop bx
-  jmp 0x0100:0000
+  mov di, [0x001A]
+  mov ax, [di+0x1A]
+  push ds
+  push ax
+  retf
+  call error
+  db "ROM ERROR", 0
 
 ; Write AX, a string and bail out
 ; Return pointer is the string start
@@ -228,9 +232,9 @@ loadblk:
 times (0x1F0 - ($-$$)) db 0
 
 bootfilename:
-  db "BOOT"
+  db "KERNEL"
   times (0x1F8 - ($-$$)) db " "
-  db "BIN"
+  db "ROM"
 
 times (0x1FE - ($-$$)) db 0