Add first attempt of a MBR

boot/mbr.asm

@@ -0,0 +1,77 @@
+; Memory layout:
+%define self      0x00600 ; 1 sector
+%define prog      0x07C00 ; 1 sector
+
+org self
+cpu 8086
+
+init:
+  cli
+
+  ; Stack grows down from PSP + 64k
+  xor ax, ax
+  mov ss, ax
+  mov sp, ax
+
+  push dx
+
+  ; Relocate from [prog] to [self]
+  mov ds, ax
+  mov es, ax
+  mov si, prog
+  mov di, self
+  mov cx, 0x100
+  rep movsw
+
+  jmp 0:main
+
+main:
+  mov bp, 0x0035
+  mov WORD [dap.blocknum], 1
+  mov si, dap
+  mov ah, 0x42
+  stc
+  int 0x13
+  jc error
+  mov cx, [dap.blocknum]
+  int3
+
+error:
+  mov ax, bp
+  mov ah, 0x0e
+  mov bx, 7
+  int 0x10
+  mov al, 0x21
+  int 0x10
+  xor ax, ax
+  int 0x16
+  int 0x19
+
+dap:
+.size:
+  db 0
+  db 0
+.count:
+  dw 1
+.buffer:
+  dw prog
+  dw 0
+.blocknum:
+  dq 0
+
+times (0x1BE - ($-$$)) db 0
+part1:
+  db 0x80
+.chs_start:
+  db 0xFF, 0xFF, 0xFF
+.type:
+  db 0x01
+.chs_end:
+  db 0xFF, 0xFF, 0xFF
+.begin:
+  dd 1
+.end:
+  dd (FLOPPY * 2)
+
+times (0x1FE - ($-$$)) db 0
+dw 0xAA55